Book of Abstracts

ICTCA2019 Beijing

14th International Conference on

Theoretical and Computational Acoustics

Book of Abstracts

Beijing, China, July 28 – August 1, 2019

Organizer:

Key Laboratory of Underwater Acoustic Environment,

Institute of Acoustics, Chinese Academy of Sciences

Co-organizers:

Department of Engineering Science and Ocean Engineering, Taiwan

University

State Key Laboratory of Acoustics, Institute of Acoustics, Chinese

Academy of Sciences

Sponsors:

Acoustical Society of China

Institute of Acoustics, Chinese Academy of Sciences

Office of Naval Research Global

Editors:

Juan Zeng

Dayong Peng

Published by:

Institute of Acoustics, Chinese Academy of Sciences http://www.ictca2019.com

Contents

Welcome to ICTCA2019 ...... 1

General Information ...... 3

Honorary Co-Chairmen ...... 3

Conference Co-Chairmen ...... 3

Student Awards Committee ...... 3

Local Organizing Committee ...... 3

Technical Committee ...... 4

Practical Information ...... 5

Sites of Events ...... 5

Conference Calendar ...... 9

Information for Presenters ...... 10

Coffee & Meals ...... 10

WiFi at the Venue ...... 10

Welcome Reception ...... 10

Banquet ...... 10

Mu Tian Yu Great Wall Sight Seeing ...... 10

Outline of the Time and Sites of Structured Sessions ...... 11

Scientific Program ...... 14

Monday, July 29...... 14

Tuesday, July 30 ...... 23

Wednesday, July 31 ...... 32

Abstracts ...... 37

Plenary Lectures ...... 38

The Inversion of Seismic Wave ...... 48

Underwater Acoustic Communication and Network ...... 54

Numerical Simulation and Vibroacoustical Prediction Technique ...... 61

Theoretical and Numerical Modeling of the Elastic-Wave in Dynamics ...... 65

Seismo-Acoustics, Electromagnetics, and Multiphysics Coupling ...... 71

Signal Processing in Shallow Water ...... 89

Ambient Noise and Its Effect on Aquatic Animals ...... 100

Nonlinear Ultrasonic Theory and Modeling ...... 109

Microacoustic Materials, Propagation, Devices and Application ...... 114

Inverse problems of acoustic wave ...... 119

Acoustical Propagation and Signal Processing in Internal Wave Environment ... 129

Acoustic Field in Deep Water ...... 144

Theory and Applications of Reservoir Acoustics ...... 151

Boundary Element Methods ...... 167

Seismic Data Analysis and Parameter Inversion (Machine Learning Approaches) ...... 181

Structural Vibration and Sound Radiation ...... 199

Geoacoustics and Ultra-Low-Frequency (ULF) Underwater Acoustics ...... 210

Acoustics in Ice-Covered Environment and Interface Reverberation ...... 220

Ultrasonic Nondestructive Testing ...... 230

Sound-structure Interaction ...... 242

Authors Index ...... 250

Welcome to ICTCA2019

Dear Colleagues,

With all of your contributions, again ICTCA is turning to a new historic page in Beijing, the capital city of China after 18 years have been passed since 2001 ICTCA in Beijing. On behalf of the organizing committee, we would like to welcome all of you who give supports and helps to the 14th International Conference on Theoretical and Computational Acoustics held at the Beijing International Convention Center. With the total of 202 papers, 6 plenary talks, and 20 structured sessions, ICTCA2019 is a technic forum for active scientists in various fields of acoustics to share with state-of-the-art research results in their work, to exchange ideas, as well as to stimulate future research in the jointed acoustic fields. The authors who present their research work on this conference are encouraged to submit the corresponding manuscripts to the Journal of Theoretical and Computational Acoustics (JTCA) so that they will be considered for publications in the Special Issues on topics specified by the Guest Editors. The ICTCA2019 will be selecting four best papers from those presented by graduate students during the conference, with a reward of 3000 RMB Yuan. Several scientists engaged in their respective acoustical research areas will be invited to form the review committee to be co-chaired by Prof. Yuefeng Sun, Prof. Xiuming Wang and Prof. Juan Zeng. The review committee will be responsible for the evaluation, and later for the reward presentation at the Banquet on Wednesday evening, 31 July, 2019. We would like to extend our appreciation to the Office of Naval Research Global (ONRG) for its supports and contributions of the past and present ICTCAs. We also would like to acknowledge the supports of the Acoustical Society of China (ASC) and the Institute of Acoustics in Chinese Academy of Sciences (IACAS). We would like to give the great thanks to the plenary speakers, the Structured Session Organizers, and all of the people who enthusiastically participate in the conference. Without their efforts and hard work, ICTCA2019 would never happens. Just like an old Chinese saying, a great cooker could do nothing without the food supplies, or one cannot make bricks without straw.

Finally, we would like to express our deepest gratitude to the local organizing committee for countless hours and tremendous efforts in making this conference come true. Wish you a fruitful ICTCA2019 and an enjoyable staying in Beijing.

Co-chairman of the Conference Co-chairman of the Conference Juan Zeng Xiuming Wang

General Information

Honorary Co-Chairmen Er-Chang Shang Institute of Acoustics, CAS, China Yu-Chiung Teng Columbia University, USA

Conference Co-Chairmen Juan Zeng Institute of Acoustics, CAS, China Xiuming Wang Institute of Acoustics, CAS, China Li Ma Institute of Acoustics, CAS, China Chi-Fang Chen National Taiwan University, Taiwan

Student Awards Committee Yuefeng Sun Texas A&M University, USA Juan Zeng Institute of Acoustics, CAS, China Xiuming Wang Institute of Acoustics, CAS, China

Local Organizing Committee Juan Zeng Institute of Acoustics, CAS, China Xiuming Wang Institute of Acoustics, CAS, China Li Ma Institute of Acoustics, CAS, China Haibin Wang Institute of Acoustics, CAS, China Dayong Peng Institute of Acoustics, CAS, China Qunyan Ren Institute of Acoustics, CAS, China Zhendong Zhao Institute of Acoustics, CAS, China Fan Li Institute of Acoustics, CAS, China Yihan Geng Institute of Acoustics, CAS, China Zhenbang Hu Institute of Acoustics, CAS, China Ying Li Institute of Acoustics, CAS, China

Technical Committee Desen Yang Harbin Engineering University, China Xiuming Wang Institute of Acoustics, CAS, China Juan Zeng Institute of Acoustics, CAS, China Li Ma Institute of Acoustics, CAS, China Chi-Fang Chen National Taiwan University, Taiwan Jeffrey Simmen Office of Naval Research Global (ONRG) T.C. Yang Zhejiang University, China Geza Seriani Institute National di Oceanografia e di Geofisica Sperimentale, Italy Qing Huo Liu Duke University, USA Steffen Marburg Technical University of Munich, Germany Gabard Gwenael Le Mans University, France Yuefeng Sun Texas A&M University, USA Sean Feng Wu Wayne State University, USA Daniel Rouseff University of Washington, USA Jea-soo Kim College of Ocean Science and Technology, Korea Tomonari Akamatsu Fisheries Research and Education Agency, Japan Wen Xu Zhejiang University, China Jinghuai Gao Xi’an Jiaotong University, China Gang Qiao Harbin Engineering University, China Ning Wang Ocean University of China, China Xiaozhou Liu Nanjing university, China Zhenglin Li Institute of Acoustics, CAS, China N.Ross Chapman University of Victoria, Canada Manfred Kaltenbacher TU Wien, Austria Piotr Borejko TU Wien, Austria Ching-Sang Chiu Naval Postgraduate School, USA Marcia Isakson ARL, University of Texas at Austin, USA Hefeng Dong Norwegian University of Science and Technology, Norway Megan Ballard ARL, University of Texas at Austin, USA Linus Chiu National Sun Yat-sen University, Taiwan Jun Yang Institute of Acoustics, CAS, China

Practical Information

Sites of Events

Conference Venue: Beijing International Convention Center (BICC) The conference will be held at Beijing International Convention Center. It is next to the Birds nest (Beijing national stadium) and Olympic Village, with access to convenient transportation that makes getting there and back simple. Beijing Continental Grand Hotel There are interior walkways between 1st floor of Beijing Continental Grand Hotel and 2nd floor of Beijing International Convention Center, which brings your event under one roof. Register Site: Lobby of the 3rd floor of BICC Conference Sites: Room 303, 305, 310, 311A-C, 3rd floor of BICC Welcome Reception Site: Grand Ballroom, 2nd floor of Beijing Continental Grand Hotel Optional Free Lunch Site: Grand Ballroom, 2nd floor of Beijing Continental Grand Hotel Banquet Site: Zhengyuan Restaurant There will be shuttle buses between the restaurant and BICC.

Surroundings of the conference venue

3rd floor of Beijing International Convention Center

2nd floor of Beijing Continental Grand Hotel

Conference Calendar

Time/Date July 28 (Sun) July 29 (Mon) July 30 (Tue) July 31 (Wed) August 1 (Thu) 08:00-18:00 Registration Registration Registration 08:00-08:15 Opening Ceremony 08:15-09:45 Plenary Lectures Plenary Lectures Plenary Lectures 09:45-10:05 Coffee Break Coffee Break Coffee Break Mu Tian Yu 10:05-12:05 Structured Sessions Structured Sessions Structured Sessions Great-Wall Sight 12:05-13:30 Lunch Lunch Lunch Seeing 13:30-15:30 Structured Sessions Structured Sessions Structured Sessions 15:30-15:50 Registration Coffee Break Coffee Break 15:50-17:50 Structured Sessions Structured Sessions 18:00-20:00 Welcome Reception Banquet

Information for Presenters All lecture rooms are equipped with projectors. A laptop computer and laser pointer will be provided by the conference organization. Our lecture room staff will assist you. Please copy your presentation (PDF or PowerPoint) to the provided computer before the start of each session, and test if everything is working well.

Coffee & Meals During the coffee breaks, there will be drinks, coffee and snacks provided. Optional Free Lunch will be provided.

WiFi at the Venue WiFi is available in the Beijing International Convention Center. Conference participants can get access to Internet anywhere in BICC.

Welcome Reception The welcome reception (icebreaker) will be held at Grand Ballroom, 2nd floor of Beijing Continental Grand Hotel, 18:00-20:00, July 28, 2019.

Banquet The banquet will be held at a Chinese traditional restaurant (Zhengyuan Restaurant), 18:00-20:00, July 31, 2019. There will be shuttle buses between the restaurant and BICC.

From BICC to Restaurant: 17:30 From Restaurant to BICC: 20:20

Mu Tian Yu Great Wall Sight Seeing The participants who want to attend this tour have to register in advance and send their relative information to the local committee by July 20, 2019. It will start from the Beijing International Convention Center at 08:00, August 1, 2019, and back to BICC at about 14:00.

Outline of the Time and Sites of Structured Sessions

1. Title: The Inversion of Seismic Wave Chairs: Jianwei Ma, Wenlong Wang, Pengliang Yang and Siwei Yu Time: 10:05-12:05, July 29 Site: Room 303

2. Title: Underwater Acoustic Communication and Network Chairs: Kim Jeasoo and Gang Qiao Time: 10:05-12:05, July 29 Site: Room 310

3. Title: Numerical Simulation and Vibroacoustical Prediction Technique Chairs: Fusheng Sui and Xianhui Li Time: 10:05-12:05, July 29 Site: Room 311A

4. Title: Theoretical and Numerical Modeling of the Elastic-Wave in Dynamics Chairs: Géza Seriani, Saulo P. Oliveira and Guo-shuang Shui Time: 10:05-12:05, July 29 Site: Room 311B

5. Title: Seismo-Acoustics, Electromagnetics, and Multiphysics Coupling Chairs: Yuefeng Sun, Qing Huo Liu and Hao Chen Time: 10:05-12:05, 13:30-15:30, 15:50-17:50, July 29 Site: Room 311C

6. Title: Signal Processing in Shallow Water Chair: T. C. Yang Time: 13:30-15:30, 15:50-17:50, July 29 Site: Room 303

7. Title: Ambient Noise and Its Effect on Aquatic Animals Chairs: Tomonari Akamatsu and Matthew Pine Time: 13:30-15:30, 15:50-17:50, July 29 Site: Room 310

8. Title: Nonlinear Ultrasonic Theory and Modeling Chairs: Zhiwu An and Mingxi Deng Time: 13:30-15:30, July 29 Site: Room 311A

9. Title: Microacoustic Materials, Propagation, Devices and Application Chairs: Wen Wang and Xiaozhou Liu Time: 15:50-17:50, July 29 Site: Room 311A

10. Title: Inverse Problems of Acoustic Wave Chairs: Haijun Wu and Weikang Jiang Time: 13:30-15:30, 15:50-17:50, July 29 Site: Room 311B

11. Title: Acoustical Propagation and Signal Processing in Internal Wave Environment Chairs: Daniel Rouseff and Ning Wang Time: 10:05-12:05, 13:30-15:30, 15:50-17:50, July 30 Site: Room 303

12. Title: Acoustic Field in Deep Water Chairs: Ting Zhang and Zhenglin Li Time: 10:05-12:05, July 30 Site: Room 310

13. Title: Theory and Applications of Reservoir Acoustics Chairs: Xiumei Zhang, Jing Ba and Tongcheng Han Time: 10:05-12:05, 13:30-15:30, 15:50-17:50, July 30 Site: Room 311A

14. Title: Boundary Element Methods Chairs: Steffen Marburg and Haibo Chen Time: 10:05-12:05, 13:30-15:30, 15:50-17:50, July 30 Site: Room 311B

15. Title: Seismic Data Analysis and Parameter Inversion (Machine Learning Approaches) Chairs: Yu-Chiung Teng, Jinghuai Gao and Guangming Zhu Time: 10:05-12:05, 13:30-15:30, 15:50-17:50, July 30 Site: Room 311C

16. Title: Structural Vibration and Sound Radiation Chair: Dejiang Shang Time: 13:30-15:30, 15:50-17:50, July 30 Site: Room 310

17. Title: Geoacoustics and Ultra-Low-Frequency (ULF) Underwater Acoustics Chairs: Shihong Zhou and Chi-Fang Chen Time: 10:05-12:05, 13:30-15:30, July 31 Site: Room 303

18. Title: Acoustics in Ice-Covered Environment and Interface Reverberation Chairs: Xueli Sheng and Jinrong Wu Time: 10:05-12:05, 13:30-15:30, July 31 Site: Room 310

19. Title: Ultrasonic Nondestructive Testing Chairs: Jie Mao and Bixing Zhang Time: 10:05-12:05, 13:30-15:30, July 31 Site: Room 311A

20. Title: Sound-Structure Interaction Chairs: Hongling Sun Time: 10:05-12:05, 13:30-15:30, July 31 Site: Room 311B

Scientific Program

Monday, July 29 08:00-08:15 Opening Ceremony Room305 Welcome speeches

08:15-09:00 Plenary Lecture Room305 Effect of Ocean Internal Waves on Acoustic Array Processing Daniel Rouseff, University of Washington, USA 09:00-09:45 Plenary Lecture Room305 Visualization of Distribution and Diversity of Aquatic Animals Based on Long Term Recording Data Sets Tomonari Akamatsu, Japan Fisheries Research and Education Agency, Japan Chaired by Juan Zeng

09:45-10:05 Coffee Break

10:05-12:05 Structured Session Room303 The Inversion of Seismic Wave Chaired by Jianwei Ma, Wenlong Wang, Pengliang Yang and Siwei Yu 10:05-10:25 The Adaptive Distributed Acoustic Sensing Coupling Noise Removal Method Jianyou Chen, Wenchao Chen, Peng Xu, Debao Wang 10:25-10:45 Adaptive Multiple Subtraction Based on Support Vector Regression Zhongxiao Li, Bingluo Gu, Zhenchun Li 10:45-11:05 Full Waveform Inversion of SH-wave and its Application in Prospecting for Anomaly in Near-surface Hang Duan, Peimin Zhu 11:05-11:25 Advanced Geological Prediction in Soft Soil Tunnel Based on Seismic Wave Reflection Technology Xingmeng Dong, Fangqing Deng, Yuwen Zhai, Zhiqiang Yang 11:25-11:45 Random Noise Attenuation via Group Sparsity Residual Constraint Dictionary Learning Xiaojing Wang, Jianwei Ma 14

Structured Sessions, Monday 11:45-12:05 Structure-guided Blind Sparse Spike Deconvolution Yuhan Sui, Jianwei Ma

10:05-12:25 Structured Session Room310 Underwater Acoustic Communication and Network Chaired by Kim Jeasoo and Gang Qiao 10:05-10:25 Interleaved Hybrid Spread Spectrum Underwater Acoustic Communication on Long-delay-spread Multipath Channel Ning Jia, Yan Li, Jianchun Huang, Zhongyuan Guo, Biao Liu 10:25-10:45 A Pattern Recognition-aware Spread Spectrum Signal Classification Model for Underwater Acoustic Communications Chao Li, Haibin Wang, Yannick Benezeth, Fan Yang 10:45-11:05 Non-Uniform Hybrid Norm Constraint Based Underwater Acoustic Channel Adaptive Estimation ZHANG YongLin, WANG HaiBin, TAI YuPeng, WANG Jun, CHEN Xi 11:05-11:25 An Underwater Acoustics Network Positioning Algorithm Combined with Its Protocol Yixuan Feng, Dong Xiao, Yan Chen, Liping Wei, Min Zhao, Li Ma 11:25-11:45 Overview of Turbo Equalization in Underwater Acoustic Communication Xuan Yu, Xuan Geng 11:45-12:05 Channel Equalization Algorithm Based on Sparse Source Reconstruction CHEN Yang, ZHOU Menglin, PEI Ming, ZHU Yanping 12:05-12:25 Bionic Morse Coding Mimicking Humpback Whale Song for Covert Underwater Communication Muhammad Bilal, Songzuo Liu, Gang Qiao

10:05-11:25 Structured Session Room311A Numerical Simulation and Vibroacoustical Prediction Technique Chaired by Fusheng Sui and Xianhui Li 10:05-10:25 Spectral Stochastic Infinite Element Method in Vibroacoustics Felix Kronowetter, Lennart Moheit, Kheirollah Sepahvand, Steffen Marburg 10:25-10:45 Numerical Study of Acoustic Source in Vortical Flows: Direct Simulation and Modal Analysis Feng Feng, Qiang Wang 15

Structured Sessions, Monday 10:45-11:05 Numerical Simulation and Performance Prediction of a High Intensity Air-modulated Speaker Yun Zhao, Xinwu Zeng, Changchao Gong, Zhangfu Tian 11:05-11:25 A Numerical Investigation of the Mass Redistributed Edge-based Smoothed Finite Element Method for 3D Acoustic Radiation Problems Tengfei Dai, Xia Jin, Huaze Yang, Tianran Lin, Yuantong Gu

10:05-12:05 Structured Session Room311B Theoretical and Numerical Modeling of the Elastic-Wave in Dynamics Chaired by Géza Seriani, Saulo P. Oliveira and Guo-shuang Shui 10:05-10:25 Solving 2D Linear Isotropic Elastodynamics by Means of Scalar Potentials: a New Challenge for Finite Elements Jorge Albella Martínez, Sébastien Imperia, Patrick Joly, Jerónimo Rodríguez 10:25-10:45 Propagation of Transient Elastic Wave in Periodically Layered Time-space Modulated Media Subjected to Anti-plane Loading Xiang Zhou, Yi-Ze Wang, Guo-Shuang Shui, Yue-Sheng Wang 10:45-11:05 The Research on the Acoustic Propagation in Ideal Drill strings Yuwen Zhai, Fangqing Deng, Xingmeng Dong, Zhiqiang Yang 11:05-11:25 Retrieving the Characteristics of Elastic Scatterers from FFP Measurements Rabia Djellouli 11:25-11:45 Theoretical Study and Simulation of Ultrasonic Multi-wave Focusing Imaging DAI Yu-xiang, YAN Shou-guo, HUANG Juan, ZHANG Bi-xing 11:45-12:05 Asymptotic Ray Tracing with Velocity Models Based on Sigmoidal Shape Functions for Wave Propagation Modeling S. P. Oliveira

10:05-12:05 Structured Session Room311C Seismo-Acoustics, Electromagnetics, and Multiphysics Coupling Chaired by Yuefeng Sun, Qing Huo Liu and Hao Chen 10:05-10:25 Improved Fast Iterative Method for Higher Calculation Accuracy of Travel-time (Invited) Wei Cai, Peimin Zhu

Structured Sessions, Monday 10:25-10:45 An Adaptive High-Order Solver for Anisotropic Poroelastic/Elastic/Fluid Coupling (Invited) Qiwei Zhan, Mingwei Zhuang, Qing Huo Liu 10:45-11:05 Simulation of Seismoelectric Waves using Finite-Difference Frequency-Space Method: 2-D PSVTM Mode Dongdong Wang, Yongxin Gao 11:05-11:25 Discrete Differential Forms for the Numerical Solution of Helmholtz Equations (Invited) Georg Wimmer, Sebastian Lange 11:25-11:45 The Effect of Window Length on the Uncertainty of RJMCMC Inversion for Electromagnetic LWD Jian Wang, Lei Zhang, Hao Chen 11:45-12:05 Simulation and Analysis of the Seismoelectric Logging Wavefield (Invited) Hengshan Hu, Yunda Duan, Wei Guan

12:05-13:30 Lunch Break

13:30-17:10 Structured Session Room303 Signal Processing in Shallow Water Chaired by T. C. Yang 13:30-13:50 Research on Low-Frequency Underwater Locator Beacon for Aviation Wen-Yang Liu, Richard Jih, Chi-Fang Chen 13:50-14:10 The Motion Compensation Method of the Side Scan Sonar Liu Jia, Ma Ming yang, Xu Feng 14:10-14:30 Improved Robust Adaptive Beamforming Based on Correlated Projection and Reconstruction for Imaging Sonar Lu Yan, Shengchun Piao, Tian Chen, Feng Xu 14:30-14:50 Multi-mode Excitation of Frequency Modulated Signals in Shallow water Xiaofeng Yi, Dayong Peng, Juan Zeng, Li Ma 14:50-15:10 Time Domain Electromagnetic Modeling Capability for Shallow Water Buried Targets Yue Zhao, Feng Xu, Jia Liu, Lijun Jiang 15:10-15:30 The Sequential Source Localization Using Unscented Particle Filter Lin Su, Shengming Guo, Yuqing Jia, Li Ma 17

Structured Sessions, Monday 15:30-15:50 Coffee Break 15:50-16:10 Two Methods Adaptive Interference Suppression for Underwater Target Estimation Suiling Ren, Lianrong Chen, Yanli Chen, Dong Wang 16:10-16:30 Source Depth Determination Through Improved Depth-based Signal Separation in the Deep Sea Wenbo Wang, Lin Su, Tao Hu, Li Ma, Qunyan Ren 16:30-16:50 Source Depth Estimation Based on Mode Phase Matching in Shallow Water Huaigang Cao, Zhendong Zhao, Shengming Guo, Li Ma 16:50-17:10 Fast Recursive Updating the Eigenvalue and Eigenvector Decomposition for Array Signal Processing Chao Yan, Lianghao Guo, Weiyu Zhang, Peng Xu

13:30-16:50 Structured Session Room310 Ambient Noise and Its Effect on Aquatic Animals Chaired by Tomonari Akamatsu and Matthew Pine 13:30-13:50 Assessing Underwater Noise Impacts on Chinese White Dolphins within Hong Kong waters (Invited) Matthew K. Pine, Ding Wang, Kexiong Wang 13:50-14:10 Influence of Deep-sea Surface Duct on Ocean Ambient Noise Distribution Xinyi Guo, Li Ma 14:10-14:30 Statistical Model of High-density Ships and its Application in Ambient Noise Regional Differences Analysis Guoli Song, Xinyi Guo, He Li, Li Ma 14:30-14:50 Underwater Noise Simulation of Impact Pile Driving with the Noise Mitigation Technology for Offshore Wind Farm in Taiwan Chiu-Kuan Shih, Yin-Ying Fang, Wei-Chun Hu, Chi-Fang Chen 14:50-15:10 Broadband Ship Noise and Its Potential Impacts on Indo-Pacific Humpback Dolphins Songhai Li, Mingming Liu, Lijun Dong, and Mingli Lin 15:10-15:30 Role of Acoustic Indices in Assessment of Impact of Noise on Marine Mammals Siddagangaiah Shashidhara, Chen Chi-Fang 15:30-15:50 Coffee Break

Structured Sessions, Monday 15:50-16:10 Detection and Localization of Indo-Pacific Humpback Dolphin with Multiple PAM Stations in the Vicinity of Taichung Harbor Wei-Yen Chu, Chi-Fang Chen 16:10-16:30 Study on Estimation of Fish School Number Density with Acoustic Statistical Echoes Chun Zhang, Feng Xu, QiaoHua Zhang 16:30-16:50 On-line Monitoring System for Metro Noise Hongbin Xu, Gaoxiang Lin, Wenfa Zhu, Xingjie Chen

13:30-15:10 Structured Session Room311A Nonlinear Ultrasonic Theory and Modeling Chaired by Zhiwu An and Mingxi Deng 13:30-13:50 Excitation of Nonlinear Rayleigh Waves on a Layered Half-space Surface Lu Jia, Shouguo Yan, Bixing Zhang 13:50-14:10 Numerical Perspective of Nonlinear Frequency Response of Lamb Waves Mixing Weibin Li, Mingxi Deng, Bingyao Chen 14:10-14:30 Nonlinear Guided Waves Mixing for Location and Assessment of Damage in Pipes Weibin Li, Zifeng Lan,Mingxi Deng 14:30-14:50 High-order Solution of Nonlinear Acoustic Wave Equation in Isotropic Solids Using Perturbation and Finite Difference Methods Wenhan Lyu, Xianmei Wu, Weijiang Xu, Jiayi Chen 14:50-15:10 Nonlinear Ultrasonic Testing by Coaxial Longitudinal- Transverse Transducers Hui Zhang

15:50-17:30 Structured Session Room311A Microacoustic Materials, Propagation, Devices and Application Chaired by Wen Wang and Xiaozhou Liu 15:50-16:10 Stabilizing Hypersonic Boundary-layer Flow with Impedance- near-zero Acoustic Metasurface (Invited) Tuo Liu, Rui Zhao, Chih-yung Wen, Li Cheng, Jie Zhu 16:10-16:30 Influence of Shear Modulus of the Guiding Layer on the Sensitivity of a Surface Acoustics Wave Gas Sensor based on ST- 90°X Quartz/SiO2 Structure Li Hong, Jiuling Liu, Shitang He 19

Structured Sessions, Monday 16:30-16:50 Optimization of LGS based Surface Acoustic Wave Device for Sensing High Temperature Xueling Li, Wen Wang, Shuyao Fan 16:50-17:10 Optimal Design on SAW Strain Sensing Device at High Temperature Employing AlN Piezoelectric Thin-film Shuyao Fan, Wen Wang, Xueling Li 17:10-17:30 Sensing Mechanism of Love Wave Based Ice Sensor Employing Structure of SiO2/36°YX-LiTaO3 Yi-ning Yin, Wen Wang, Ya-na Jia

13:30-17:10 Structured Session Room311B Inverse Problems of Acoustic Wave Chaired by Haijun Wu and Weikang Jiang 13:30-13:50 An Investigation on the Regressive Discrete Fourier Series for Sparse Reconstruction of Sound Field Man-Ying Zhang, Ding-Yu Hu, Tao Wang 13:50-14:10 A Weighted Acoustic Radiation Modes Based Method for Reconstructing the Surface Velocity of Vibrating Structure Ding-Yu Hu, Man-Ying Zhang, Wen-Fa Zhu 14:10-14:30 3D Temperature Distribution Reconstruction Based on Acoustics Tomography Qian Kong, Genshan Jiang, Yuechao Liu, Jianhao Sun 14:30-14:50 Non-synchronous Microphone Array Measurements ： An Alternative Way of Compressive Sensing Measurements in Acoustics (Invited) Liang Yu, Haijun Wu, Weikang Jiang 14:50-15:10 A Contribution to the Source Identification in Aeroacoustics Utilizing Galbrun’s Equation. Marcus Maeder, Andrew Peplow, Steffen Marburg 15:10-15:30 A Beamforming Method in Localization of Rotating Sources Using Virtual Array Jianzheng Gao, Haijun Wu, Weikang Jiang 15:30-15:50 Coffee Break 15:50-16:10 OMP-SVD Algorithm for Acoustic Imaging in Low Signal-to- Noise Ratio Environments (Invited) Fangli Ning, Feng Pan

Structured Sessions, Monday 16:10-16:30 Determination of Propagation Matrix of Inverse Model Method Based on Generalized Cross-Correlationfor Wideband Sound Source Localization (Invited) Weng Jing, Chu Zhigang, Yang Yang 16:30-16:50 Laser-assisted Reconstruction – A holistic View of the Entire Vibro-acoustic Behaviors of a Complex Vibrating Structure (Invited) Sean F. Wu, Lingguang Chen, Antonio Figueroa, Michael Telenko, Jr. 16:50-17:10 Geometrical Full Waveform Inversion of Defects Fan Shi, Peter Huthewaite

13:30-17:50 Structured Session Room311C Seismo-Acoustics, Electromagnetics, and Multiphysics Coupling Chaired by Yuefeng Sun, Qing Huo Liu and Hao Chen 13:30-13:50 A Method for Estimation of Acoustic-to-Seismic Transfer Function under Complex Noise Field Tao Jiang, Jing-Ye Wang, Yun-Feng Chao, Qi Zhou, Jing-Han Zheng, Da-Peng Yang 13:50-14:10 Estimation and Comparison of Three-Component Acoustic-to- Seismic Coupling Transfer Function of Sound Source near the Surface Jing-Ye Wang, Tao Jiang, Yun-Feng Chao, Qi Zhou, Xin Wang, Fan Zheng 14:10-14:30 Localization and Tracking of Low-flying Target Using Single Geophone Array Yunfeng Chao, Guangda Liu, Tao Jiang, Jingye Wang, Xin Wang 14:30-14:50 Microseismic Location Based on Interferometric Imaging and Hilbert-Huang Transform (Invited) Tingting Zhan, Hao Chen 14:50-15:10 Analytical Solutions of Borehole Acoustic Fields for an Eccentric Drill Collar in the Monopole Acoustic LWD Yunjia Ji, Xiao He, Zhifeng Sun, Hao Chen 15:10-15:30 Simulation of Reflection and Scattering Waves in Acoustic Logging While Drilling Pan Yue, He Xiao, Chen Hao 15:30-15:50 Coffee Break

Structured Sessions, Monday 15:50-16:10 Anisotropy Inversion using a Small-diameter Acoustic Logging Tool with Separated Cross-dipole Sources Chao Li, Hao Chen, Xiao He, Xiu-Ming Wang, Fu-Qiang Zeng 16:10-16:30 Digital Rock Physics-based Acoustic Properties Modelling of Carbonate Rocks (Invited) Jianguo Zhao, Yangming Hu, Langqiu Sun, Fang Ouyang, Zhi Li, Zengjia Xiao 16:30-16:50 Digital Rock Physics Based Pore Structure Characterization of Carbonate Rocks Yangming Hu, Jianguo Zhao, Langqiu Sun, Fang Ouyang 16:50-17:10 Estimation of Acoustic Properties of Rock Samples in the Low Frequency Range (Invited) Jianguo Zhao, Yangming Hu, Langqiu Sun, Fang Ouyang, Zhi Li, Zengjia Xiao 17:10-17:30 A Combined Model for Predicting Frequency-dependent Elastic Properties in Sandstones Fang Ouyang, Jianguo Zhao, Zhi Li, Zengjia Xiao 17:30-17:50 Seismic Waveform and Its Spectrum (Invited) Yuefeng Sun

Structured Sessions, Tuesday Tuesday, July 30 08:15-09:00 Plenary Lecture Room305 A Review on Methods and Applications of Wave Propagation Numerical Modeling Géza Seriani, Istituto Nazionale di Oceanografia e Geofisica Sperimentale, Italy 09:00-09:45 Plenary Lecture Room305 Super-resolution Inversion of Seismic Wavelet and Reflectivity for Non-stationary Seismic Trace Using Deep Learning Jinghuai Gao, Xi’an Jiaotong University, China Chaired by Xiuming Wang

09:45-10:05 Coffee Break

10:05-11:45 Structured Session Room303 Acoustical Propagation and Signal Processing in Internal Wave Environment Chaired by Daniel Rouseff and Ning Wang 10:05-10:25 Estimating the Solitary Internal Wave Parameters Using Distributed Sensors Tongchen Wang, T.C. Yang, Wen Xu 10:25-10:45 Statistical Analysis of Sound Propagation in Shallow Water with Solitary Internal Waves Hu Ping, Peng Zhaohui 10:45-11:05 Sound Intensity Fluctuations as Evidence of Mode Coupling Due to Moving Nonlinear Internal Waves in Shallow Water Yun Ren, Boris Katsnelson 11:05-11:25 Analysis of Periodic Sound Fluctuations Caused by Internal Waves in the Yellow Sea Zhen Wang, Tao Hu, Shengming Guo, Li Ma 11:25-11:45 Effects of the Linear Internal Waves on Sound Propagation in the South China Sea Zhang Qing-qing, Li Zheng-lin, Ren Yun

10:05-12:25 Structured Session Room310 Acoustic Field in Deep Water Chaired by Ting Zhang and Zhenglin Li 10:05-10:25 Effect of Emission angle on Acoustic transmission (Invited) Yanyang Lu, Kunde Yang

Structured Sessions, Tuesday 10:25-10:45 Modeling of Acoustic Effects Induced by Subaqueous Sand Dune Field Andrea Chang, Linus Chiu, Ching-Sang Chiu, Chi-Fang Chen 10:45-11:05 Spatial Coherence of Sound Field on the Seafloor Surface in Continental Slope Area Bo Zhang, Fenghua Li, Jin Liu, Wen Li 11:05-11:25 Anomalous Transmission Loss Due to Bathymetry Variation Licheng Lu, Qunyan Ren, Shengming Guo, Li Ma 11:25-11:45 Combined Estimation of Range and Depth for Underwater Source in the Direct Zone in Deep Water Wang Meng-yuan, Li Zheng-lin, Qin Ji-xing, Wu Shuang-lin 11:45-12:05 A Simulation Study on the Depth Dependence of Ambient Noise Characteristics in Deep Ocean Kai Zhang, TC Yang, Wen Xu 12:05-12:25 Simulation of Ocean Ambient Noise Field’s Three-dimensional Effect in Seamount area Shan Yuanchun, Lin Jianheng, Yi Xuejuan, Jiang Pengfei, Sun Junping, Li Na

10:05-12:05 Structured Session Room311A Theory and Applications of Reservoir Acoustics Chaired by Xiumei Zhang, Jing Ba and Tongcheng Han 10:05-10:25 Assessing Cement Leak Paths by Analysis Borehole Wavefield Modes (Invited) Hua Wang, Michael Fehler, Aimé Fournier, Guo Tao 10:25-10:45 Integrated Application of Seismic Reservoir Prediction Technology in Deep Dolomite Reservoir: A Case Study of Cambrian Longwangmiao Formation, Gaoshiti-Moxi Area, Sichuan Basin, China (Invited) Jiang Ren, Liu Chenglin, Zhang Jing, He Pei, Huang Jiaqiang, He WeiWei, Du Bingyi 10:45-11:05 The Application of a New Segment Cement Bond Evaluation Tool in Horizontal Well Deng Fangqing, Dong Xingmeng, Zhai Yuwen, Xia Hui, Fu Rui 11:05-11:25 Application of Near-borehole Structures Imaging using Directional Reflected P-wave Jianlin Ben, Wenxiao Qiao, Xiaohua Che, Xiaodong Ju, Junqiang Lu, Baiyong Men 24

Structured Sessions, Tuesday 11:25-11:45 Pre-stack Seismic Inversion of Tight Sandstone Reservoirs based on Levenberg- Marquardt Algorithm Shuang Xiao, Jing Ba, Qiang Guo, Tiansheng Chen 11:45-12:05 Acoustic Relaxation Spectra Gas Detection Based on Deep Learning Wei Zheng, Xue Wang, Junyu Ren, Ming Zhu

10:05-11:45 Structured Session Room311B Boundary Element Methods Chaired by Steffen Marburg and Haibo Chen 10:05-10:25 Acoustic Shape Optimization based on Fast Multipole Isogeometric BEM with Adjoint Variable Method (Invited) Haibo Chen, Jie Wang, WenchangZhao, Changjun Zheng, Leilei Chen 10:25-10:45 Towards Large-scale Acoustic Shape Optimization Including Viscous and Thermal Losses (Invited) Peter Risby Andersen, Vicente Cutanda Henríquez, Niels Aage 10:45-11:05 Shape and Topology Optimization of Three Dimensional Acoustic Problems with Isogeometric Boundary Element Method (Invited) L.L. Chen, C. Lu, W.C. Zhao, H.B. Chen, S. Marburg 11:05-11:25 Design of Damping Layer by Topology Optimization and Non- Negative Intensity (Invited) Wen-Chang Zhao, Hai-Bo Chen, Steffen Marburg 11:25-11:45 On the Choice of Solution Schemes for the Acoustic Boundary Element Method with many Right-Hand Sides (Invited) Christopher Jelich, Steffen Marburg

10:05-12:05 Structured Session Room311C Seismic Data Analysis and Parameter Inversion (Machine Learning Approaches) Chaired by Yu-Chiung Teng, Jinghuai Gao and Guangming Zhu 10:05-10:25 The Importance of Strain Energy Field for Interpretation in Exploration Geophysics (Invited) Yu-Chiung Teng, Zhenxiang Fan, Guihua Li 10:25-10:45 Seismic Impedance Inversion via Residual Learning Networks (Invited) Lingling Wang, Delin Meng, Weirong Qiu, and Bangyu Wu 25

Structured Sessions, Tuesday 10:45-11:05 Generalized Beta Wavelet Transform of 3-D Seismic Data For Horizontal Well Placement in Tight Reservoirs (Invited) Zhiguo Wang, Jinghuai Gao, Bing Zhang 11:05-11:25 A Method of Coherence Attribute for Seismic Data Based on the Renyi Divergence Yang Tao, Gao Jinghuai, Zhang Bing, Gao zhaoqi 11:25-11:45 Dispersion Estimation Using the Generalized S-Transform Zhi Hu, Jinghuai Gao 11:45-12:05 Seismic Super Resolution Inversion Based on Model-driven Deep Learning Hongling Chen, Jinghuai Gao, Yan Yang

12:05-13:30 Lunch Break

13:30-17:10 Structured Session Room303 Acoustical Propagation and Signal Processing in Internal Wave Environment Chaired by Daniel Rouseff and Ning Wang 13:30-13:50 Acoustic Intensity Fluctuation Due to Internal Tide in the Yellow Sea Fan Li, Tao Hu, Sheng-ming Guo 13:50-14:10 Diurnal Fluctuation of Shallow-Water Acoustic Propagation in the Cold Dome Off Northeastern Taiwan in Spring Chen Cheng, Bo Lei, Yuanliang Ma, Liu Ying, Yang Wang 14:10-14:30 Mesoscale Eddies on Underwater Sound Propagation Zhu fengqin, Qu ke, Zhang minghui 14:30-14:50 Sound Propagation through an Eddy Using the Parabolic Approach in Moving Media CHEN Yuchen, ZHANG Haigang, MA Jun 14:50-15:10 Deep Anti-Decoherence: A Deep Network for Acoustic Interference Striation Recovery Based on Random Mode-coupling Matrix Xiaolei Li, Wenhua Song, Dazhi Gao, Wei Gao, Haozhong Wang 15:10-15:30 Multipath Compensation in Shallow Water Environments: A Propagation Invariant Approach Pengyu Wang, Wenhua Song 15:30-15:50 Coffee Break

Structured Sessions, Tuesday 15:50-16:10 Source Localization in Uncertain Environments Using Deep Learning with One Sensor Haiqiang Niu, Zaixiao Gong, Emma Ozanich, Peter Gerstoft, Zhenglin Li 16:10-16:30 Matched-field Processing Geoacoustic Inversion Using Propagation Invariant in Range-dependent Environments Wenhua Song, Pengyu Wang 16:30-16:50 Numerical Modeling of Sound Propagation Under Rough Sea Surface of PM Spectrum Meijuan Yao, Licheng Lu, Shengming Guo, Li Ma 16:50-17:10 Deep Argo Data Analysis Salinity, Temperature, and Sound Speed Profiles Extrapolation & Subsequent Rectifications Kashif Iqbal, Minghui Zhang, Shengchun Piao, He Ge

13:30-17:30 Structured Session Room310 Structural Vibration and Sound Radiation Chaired by Dejiang Shang 13:30-13:50 Study on a Low Frequency Narrow Beam Transducer with Quasi- Periodic Structure Zhiqiang Dai, Guangbin Zhang 13:50-14:10 Finite Element Model Coupled with Lumped Parameter Elements Daniel Gert Nielsen, Jakob Søndergaard Jensen, Vicente Cutanda Henriquez, Finn Thomas Agerkvist 14:10-14:30 Effects of Carbon Nanotube Thermal Conductivity on Optoacoustic Transducer Performance Jiapu Li, Xuekai Lan, Shuang Lei, Jun Ou-Yang, Xiaofei Yang, Benpeng Zhu 14:30-14:50 Analysis of Acoustic Radiation Characteristics of Three- Dimensional Elastic Structure in Shallow Water by FEM-NM Method Bu-chao An, Chao Zhang, De-jiang Shang, Yi-hao Liu 14:50-15:10 Research on Sound Radiation Characteristics of Elastic Structure in Shallow Water Based on Wave Superposition and Acoustic Ray Theory Yi-hao Liu, Chao Zhang, De-jiang Shang, Bu-chao An 15:10-15:30 Directivity Pattern of the Acoustic Field for a Propeller Shaft-hull Coupled System Li-Bo Qi, Ming-Song Zou 27

Structured Sessions, Tuesday 15:30-15:50 Coffee Break 15:50-16:10 Flexural Wave Bandgap Property in Thin Plates with Designed Periodic Partial-Constrained-Layer Damping Qi Qin, Meiping Sheng, Fan Zhao, Zheng Fang 16:10-16:30 Uncertainty Quantification in Sound Radiation due to Three- dimensional Vibration of Ring Zhe Liu, Kheirollah Sepahvand, Yintao Wei, Steffen Marburg 16:30-16:50 Discipline of Different Structures on Cylindrical Shells’ Vibration and Sound Radiation under Inner Noise Source Fang Ji, Huadong Zhang, Meiping Sheng, Guonan Li, Jiangtao Liu 16:50-17:10 Underwater Coupled Sound Field Characteristics of Cylindrical Shells under Complex Excitation of Mechanical Force and Acoustic Motivation Fang Ji, Huadong Zhang, Meiping Sheng, Guonan Li, Jiangtao Liu 17:10-17:30 The Noise Reduction Mechanism of Different Microstructures on the Superhydrophobic Surfaces Chen Niu, Yong-wei Liu, De-jiang Shang

13:30-17:10 Structured Session Room311A Theory and Applications of Reservoir Acoustics Chaired by Xiumei Zhang, Jing Ba and Tongcheng Han 13:30-13:50 Estimation of Formation Shear Attenuation using Dipole Acoustic Waveform Data (Invited) Qiaomu Qi, Arthur Cheng, Yunyue Elita Li 13:50-14:10 Effects of Background Anisotropy on Effective Elastic Properties of Fractured Rocks (Invited) Junxin Guo, Tongcheng Han, Li-Yun Fu, Denghui Xu, Xinding Fang 14:10-14:30 Carbonate Reservoir Characterization by Using Joint Seismic Attributes Fan Li, Jing Ba, Cun Yu, Jian Zhou 14:30-14:50 Using Finite-Difference Method to Simulate the Radiation Wavefield of a Double-Couple Point Source Induced by Hydraulic Fracturing Chengwei Zhang, Wenxiao Qiao, Xiaohua Che 14:50-15:10 Rock Physics Template of a Crack-Pore System of Tight Sandstone Reservoirs Runfa He, Jing Ba, Cong Luo, Rupeng Ma 28

Structured Sessions, Tuesday 15:10-15:30 Poro-acoustoelasticity Theoretical Model with Embedded Microcracks for Saturated Carbonates Wenchang Ling, Jing Ba, Qiang Guo 15:30-15:50 Coffee Break 15:50-16:10 Effect of Aligned Inclined Cracks on Elastics on Properties of Transversely Isotropic Rocks Denghui Xu, Tongcheng Han 16:10-16:30 Characteristics of Waves in Gas Hydrate-Bearing Sediments Lin Liu, Xiu-mei Zhang, Xiu-ming Wang 16:30-16:50 Theoretical Modeling on Compressional Wave Velocity Variation with Temperature in Fluid-saturated Rocks Hui Qi, Jing Ba, Cong Luo, Rupeng Ma 16:50-17:10 Finite Difference Modeling of Wave Fields in Fluid- Filled Boreholes Excited by Linear Phased Array Acoustic Transmitters Shubo Yang, Wenxiao Qiao, Xiaohua Che, Xiaodong Ju

13:30-16:50 Structured Session Room311B Boundary Element Methods Chaired by Steffen Marburg and Haibo Chen 13:30-13:50 Combined Optimization of Structural Shape and Absorbing Material Distribution for Sound Barrier (Invited) Fuhan Jiang, Zhenyun Wu, Wenchang Zhao, Leilei Chen, Haibo Chen 13:50-14:10 Topology Optimization of Sound Absorbing Materials Using Subdivision Surface Boundary Element Method (Invited) C. Lu, L.L. Chen, W.C. Zhao, H.B. Chen 14:10-14:30 Evaluation of a Hybrid FEM-BEM Implementation of Acoustics with Visco-Thermal Losses (Invited) Vicente Cutanda Henriquez 14:30-14:50 A Half-space FMBEM for the Simulation of Sound Propagation Above an Impedance Plane (Invited) Chang-Jun Zheng, Hai-Bo Chen 14:50-15:10 Non-Negative Intensity for Elementary Acoustic Sources (Invited) Daipei Liu, Paul Croaker, Steffen Marburg, Nicole Kessissoglou 15:10-15:30 Evaluating Acoustic Properties for Interior Problems Based on the Sound Energy (Invited) Caglar Guerbuez, Steffen Marburg 15:30-15:50 Coffee Break 29

Structured Sessions, Tuesday 15:50-16:10 Lamb Wave Surface Detection of Flat Plate by Boundary Element Method (Invited) Xianhui Wang, Yujian Liu, Xiaoming Zhang 16:10-16:30 The Adaptive Cross Approximation Boundary Element Method for Acoustic Radiation Problems (Invited) Xiujuan Liu 16:30-16:50 Acoustic-vibration Coupling Response of Shell Structure by a Coupling Solver (Invited) Qiang Xi, Zhuo-jia Fu

13:30-17:50 Structured Session Room311C Seismic Data Analysis and Parameter Inversion (Machine Learning Approaches) Chaired by Yu-Chiung Teng, Jinghuai Gao and Guangming Zhu 13:30-13:50 Comparison of the Static and Dynamic Properties of Dand-clay Sediments (Invited) Hui Li, Jinghuai Gao 13:50-14:10 Deep Learning Based Global Optimization Scheme for High- dimensional Seismic inversion (Invited) Zhaoqi Gao, Zhibin Pan, Jinghuai Gao, Zongben Xu 14:10-14:30 Sedimentary Cycle Distribution Prediction Method Based on Alternating Iterative Depth Neural Network Yajun Tian, Jinghuai Gao 14:30-14:50 A Deep Learning Based Data-driven Method for Seismic High Resolution Inversion Daoyu Chen, Jinghuai Gao 14:50-15:10 Extraction of Effective Events Based on Phase-only Correction for Noised Microseismic Data Yinting Wu, Guangming Zhu 15:10-15:30 A Method of Seismic Data Denoising Based on Mathematical Morphology J. T. Wu 15:30-15:50 Coffee Break 15:50-16:10 Characterizing Channel Sand Bodies Using a Self-adaptive Generalized S-transform (Invited) Naihao Liu, Jinghuai Gao, Bo Zhang, Hao Wu

Structured Sessions, Tuesday 16:10-16:30 Enhancing Subsurface Scatters Using Reflection Damped Plane- Wave Least-Squares Migration (Invited) Chuang Li, Jinghuai Gao 16:30-16:50 Behavioral Characteristic of Seismic Modulus with Ultrasonic Surface Wave in Pavement Structures (Invited) J. T. Wu, X. H. Wu, S. M. Li 16:50-17:10 Effect of Thin Layer Thickness on Peak Frequency of Thin Layer Seismic Activities Huan Cao, Shuhong Zhao 17:10-17:30 Physical Analysis of Seismic Source Wave Field and Wavelet Reservoir Identification Hongjuan Quan, Guangming Zhu, Yuefeng Sun 17:30-17:50 The CMP Stack Processing Method Based on Statistical Properties of Seismic Random Noise Guihua Li, Jingqi Wang, Yun Xu

Structured Sessions, Wednesday Wednesday, July 31 08:15-09:00 Plenary Lecture Room305 Computational Modelling of Noise Radiation from Aircraft Engines Gwénaël Gabard, Le Mans University, France 09:00-09:45 Plenary Lecture Room305 Controlling Sound Directivity with Acoustic Metamaterials Xiaozhou Liu, Nanjing University, China Chaired by Chi-Fang Chen

09:45-10:05 Coffee Break

10:05-11:45 Structured Session Room303 Geoacoustics and Ultra-Low-Frequency (ULF) Underwater Acoustics Chaired by Shihong Zhou and Chi-Fang Chen 10:05-10:25 Criteria For Evaluating the Inverted Geoacoustic Parameters of Sea-bottom Zhendong Zhao, Juan Zeng, Li Ma and Er-Chang Shang 10:25-10:45 Development of the Predictive Geoacoustic Model Linus Chiu, Andrea Chang, Ching-Sang Chiu, Jian-Yuh Lou 10:45-11:05 Sediment Characterization from Acoustic Echo-sounding Using Artificial Neural Networks: Preliminary Results from at-sea Data Haiyan Ni, Wenbo Wang, Li Ma, Jinrong Wu, Qunyan Ren 11:05-11:25 The Analysis of Multi-layered Effect for Elastic Sea Bottom on Geoacoustic Propagation Yaxiao Mo, LiCheng Lu, Bingwen Sun, Chaojin Zhang, Shengming Guo 11:25-11:45 Characterizing the Stress Interactions Influenced by the Wave- induced Fluid Flow Cheng-Hao Cao, Li-Yun Fu, Tong-Cheng Han, Jing Ba

10:05-11:45 Structured Session Room310 Acoustics in Ice-Covered Environment and Interface Reverberation Chaired by Xueli Sheng and Jinrong Wu 10:05-10:25 Polar Acoustics & Information Tech (Invited) Xueli Sheng

Structured Sessions, Wednesday 10:25-10:45 Ice Acoustic Parameter Measurement Based on Polarization Filtering Jiahui Gao, Yuxiang Zhang, Zhinan Xie, Dingyi Ma, Xiukun Li, Jingwei Yin 10:45-11:05 Study on Acoustic Inversion Method of Sound Velocity Profile in Ice Jing Yan, Zhu Guangping, Yin Jingwei, Liu Jianshe, Song Zelin 11:05-11:25 Reflection of Acoustic Wave from Rough Sea Ices Qianqian Li, Juan Shi, Pingshou Ming, Fanlin Yang, Kai Zhang 11:25-11:45 Sea-ice Thickness Measurement Based on Ice Layer Waveguide Theory Dingyi Ma, Zhinan Xie,Yuxiang Zhang，Jiahui Gao, Jingwei Yin

10:05-12:05 Structured Session Room311A Ultrasonic Nondestructive Testing Chaired by Jie Mao and Bixing Zhang 10:05-10:25 Probability Imaging for Damage Location via Time Reversal Lamb Waves under the Baseline-free Signal Hanfei Zhang, Shiwei Ma, YanyanLiu, Haiyan Zhang 10:25-10:45 Experimental Verification of Acoustic Source Localization Technique in Heterogeneous Plates Shenxin Yin, Jia Fu, Tribikram Kundu, Zhiwen Cui 10:45-11:05 The Wavenumber Method for Characterizing a Delamination in Ballastless Slab Track Guopeng Fan, Haiyan Zhang,Hui Zhang, Wenfa Zhu, Xiaodong Chai 11:05-11:25 Study of Sound Velocity under Simulated Martian Environmental Conditions Rushan Shen, Hanyin Cui, Weijun Lin 11:25-11:45 Improved SAFT for Internal Defects of CA Mortar Layer of Ballastless Track Xiangzhen Meng，Wenfa Zhu，Haiyan Zhang，Hui Zhang，Yujie Zhang 11:45-12:05 Quantitative Characterization of Axial Defects in Pipes Based on Circumferential SH Guided Waves Jiuhong Jia , Tianyang Liu, Xuecheng Liu, Yun Tu, Shandong Tu

Structured Sessions, Wednesday 10:05-11:45 Structured Session Room311B Sound-structure Interaction Chaired by Hongling Sun 10:05-10:25 Acoustic Energy Harvesting Based on Phononic Crystals Tianyu Zhang, Han Zhang, Xiaoxing Su 10:25-10:45 Multilayer Structure Qptimization of Pentamode Acoustic Cloaking based on PSO Algorithm Chao Sun, Han Zhang, Jun Yang 10:45-11:05 Vortex Beams Formed with An Annular Acoustic Sources Hongzhen Bi, Han Zhang, Jun Yang, Muguang Wang 11:05-11:25 Acoustic Vortex Beam Generation by a Piezoelectric Transducer Using Spiral Electrodes (Invited) Han Zhang, Hongzhen Bi, Tianyu Zhang 11:25-11:45 Numerical Simulation and Analysis of Flow Field and Sound Field of Hydraulic Vortex Whistle Xiaopin Wang, Yu Liu, Mingduo Zhang, Anqian Tan

12:05-13:30 Lunch Break

13:30-15:10 Structured Session Room303 Geoacoustics and Ultra-Low-Frequency (ULF) Underwater Acoustics Chaired by Shihong Zhou and Chi-Fang Chen 13:30-13:50 Simulations of VLF Underwater- and Seismo-acoustic Propagation Fields in the Wedge Coast and the Borehole Onshore Shuyuan Du, Shihong Zhou,Yubo Qi 13:50-14:10 At-sea Observation and Theoretical Simulation on Very-low- frequency Sound Propagation in Shallow Water Jingpu Cao, Shuyuan Du, Shihong Zhou, Yubo Qi 14:10-14:30 Analysis on the Sound Propagation Caused by Very Low Frequency Sound Source near the Sloped Seabed Liang Xu, Haigang Zhang 14:30-14:50 Effect of Sediment Layer on Scholte Wave Dispersion Characteristics Xiayun Luo, Jun Yuan, Guangli Cheng, Luwen Meng, Mingmin Zhang 14:50-15:10 The Influence of Periodic Corrugated Surfaces on the Generation and Propagation of Scholte Waves Minshuai Liang, Gaokun Yu, Linhui Peng 34

Structured Sessions, Wednesday 13:30-15:10 Structured Session Room310 Acoustics in Ice-Covered Environment and Interface Reverberation Chaired by Xueli Sheng and Jinrong Wu 13:30-13:50 A Practical Bottom Rough Surface Reverberation Model in Shallow Water Jinrong Wu, Peng Li, Er-Chang Shang, Zhendong Zhao 13:50-14:10 Modeling Reverberation Time Series Based on Full Wave Reverberation Theory Jianlan Zhang, Jinrong Wu 14:10-14:30 Extracting Bottom Roughness Parameters Using Reverberation data in shallow water Qiannan Hou, Er-Chang Shang, Jinrong Wu, Chaojin Zhang, Lijun Yin 14:30-14:50 Characteristics of Bottom Reverberation Intensity in Deep Water Lijun Yin, Jinrong Wu, Qiannan Hou 14:50-15:10 Reverberation Time Measurement Method Based on Time- Frequency Analysis Yang liuqing, Chen Yi, Huang Yongjun, Shang Dajing

13:30-15:30 Structured Session Room311A Ultrasonic Nondestructive Testing Chaired by Jie Mao and Bixing Zhang 13:30-13:50 Wavenumber Imaging Using Diffuse Field Full Matrix for Near- surface Defects in Rails Hui Zhang, Haiyan Zhang, Jianquan Liu, Guopeng Fan, Wenfa Zhu 13:50-14:10 Ultrasonic Transducer Acoustic Pressure Measurement Method Based on Laser Reflection Tomography Weiyin Wang, Yi Chen, Shiquan Wang, Liuqing Yang 14:10-14:30 Interface Defects Detection of Steel-Concrete Structure Based on Ultrasonic Guided Waves Yujie Zhang, Wenfa Zhu, Haiyan Zhang, Hui Zhang, Xiangzhen Meng 14:30-14:50 Focused Sound Field in Austenitic Stainless Steel Weld by Ultrasonic Phased Array Shouguo Yan, Zhongcun Guo, Bixing Zhang

Structured Sessions, Wednesday 14:50-15:10 Ultrasound Beam Engineering via a Programmable Transducer Array Yaxi Shen, Xuefeng Zhu, Feiyan Cai, Teng Ma, Jie Zhu, and Hairong Zheng 15:10-15:30 Defect Localization in Fiber Reinforced Polymer Composites with Diffuse Ultrasonic Waves Qi Zhu, Yuxuan Ding, Dawei Tu, Haiyan Zhang

13:30-14:30 Structured Session Room311B Sound-structure Interaction Chaired by Hongling Sun 13:30-13:50 A Benchmark Study on Fluid-loaded Structural Modes Martin Eser, Stefan Schneider, Suhaib Koji Baydoun, Felix Kronowetter, Steffen Marburg 13:50-14:10 Energy Transmission Analysis of A Water-Filled Pipe Baffled with A Finite Elastic Plate Yajun Li, Hongling Sun, Luyang Sun, Jun Yang 14:10-14:30 Vibro-acoustic Analysis of a Rectangular Enclosure Bounded by a Ribbed Flexible Wall Yuan Wang, Nai-Fei Ren, Zheng-Wei Qiu

Abstracts

Plenary Lectures Effect of Ocean Internal Waves on Acoustic Array Processing Daniel Rouseff Applied Physics Laboratory, University of Washington, Seattle, WA USA

Internal waves arise in the ocean because the water density is not constant with depth. Often there is a near-constant density mixed layer between the sea surface and the denser water below. External forces like tides and currents cause internal waves to propagate along the interfaces between these waters of different density. Internal waves can propagate long distances and “break” similar to the more familiar waves on the sea surface. Breaking internal waves create turbulence that affects ocean circulation. Besides being interesting in their own right, internal waves are important for how they affect acoustic propagation. The internal waves perturb the speed of sound, causing acoustic focusing and defocusing. As the internal waves propagate, the temporal and spatial coherence of acoustic signals will change accordingly. In the present talk, the effects of internal waves on acoustic array processing are surveyed. Both non-linear and nearly linear internal waves in shallow water are considered. In predicting the output of the array processor, it is imperative that the acoustic model be compatible with both the oceanographic phenomena and array geometry of interest. Four specific cases are considered that involve different combinations of acoustic models (parabolic equation, adiabatic modes, coupled modes, rays), oceanographic phenomena (linear and non-linear internal waves, turbulence), and array geometry (horizontal, vertical). Modeling and experimental results are compared. Biographical Sketch: Daniel Rouseff received the Ph.D. degree in electrical engineering from the University of Washington in 1989. After working at the Johns Hopkins University, he returned in 1992 to the University of Washington where he is currently an Affiliate Scientist at the Applied Physics Laboratory. Since 2012, he has also been an Adjunct Professor at Portland State University in the Department of Electrical and Computer Engineering. He has held visiting positions at the Naval Research Laboratory, Washington DC, and the Department of Applied Mathematics and Theoretical Physics, Cambridge University, Cambridge, U.K. Dr. Rouseff was Chief Scientist on the 2009 Cooperative Array Performance Experiment (CAPEx09), a joint China-USA underwater acoustics experiment. His primary technical interest is in how oceanographic variability affects underwater acoustic signal processing. Dr. Rouseff is a Senior Member of IEEE and a Fellow of the Acoustical Society of America.

Plenary Lectures Visualization of Distribution and Diversity of Aquatic Animals Based on Long Term Recording Data Sets Tomonari Akamatsu National Research Institute of Fisheries Science, Japan Fisheries Research and Education Agency, Yokohama, Japan

Big data has been extensively used to visualize social and biological activities in these years. Changes of tropical forests, traffic jam and international communication can be shown on maps by using big data obtained from satellites, live camera, smartphone and the internet. Visual, audio and other numerical information obtained by those systems should be annotated to a specific meaning such as chlorophyll density, license plate and words. Unlike terrestrial world, underwater objects have been unexplored because the available number of sensors are limited, light and radio waves does not travel long distance and access to the ocean is not easy. In these years, significant number of acoustic sensors have been deployed for different purpose. Autonomous recorders were submerged to monitor vocalization of whales and other animals. Cable networks with hydrophone keep recording seismic activities on seabed. Moving platforms such as sea gliders or drifting buoys are ideal means for acoustic monitoring due to its silent operation. If the annotated database is available in addition to the big acoustic data in the water, various objects will be identified and localized. Two examples to visualize phonating aquatic animals are introduced. Over 20 recording stations deployed approximately 110 km along the coastal water of Japan collected vocalizations of silver croakers, finless porpoises and snapping shrimps. Three different type of sounds were counted automatically by a newly developed feature extraction algorism. Using density estimation model, received number of sounds were converted to the existing individual density of animals. The density map drawn by the passive acoustic monitoring showed high density hots spots. The second example is the phenology of underwater soundscape obtained in a coral reef in Okinawa, Japan. The entire 13 months recordings were divided into each 3 minutes segment. Dominant sound type for each segment was classified by unsupervised k-means clustering. Results shows clear seasonal and diurnal change of sound types, which represent phenology of soundscape in the coral reef. The soundscape in shallow (<2 m in depth) and deep (20m in depth) waters showed completely different pattern, which could cause sound propagation characteristics or composition of sound sources. Shannon indexes calculated by using the number and types of sounds was high in the deeper waters than that in the shallow water. The various type of sounds co-exist in deep water that might suggest the higher biodiversity in deep coral. Increasing numerical audio information in the water will aid underwater remote sensing of sounding objects. Annotated database of each 39

Plenary Lectures sound source is important for identification. This work was supported by JST CREST Grant Number JPMJCR11A1, Grant- in-Aid for Scientific Research on Innovative Areas (A) 17H00799 and Grant-in-Aid for Challenging Exploratory Research 16K14518. Many of collaborators in these projects contributed field works, data collections and analysis. Biographical Sketch: Dr. Tomonari Akamatsu graduated Physics department of Tohoku University in 1987 and received PhD in Agriculture in 1996 from Nihon University. His research subjects are biosonar behavior of dolphins and porpoises, passive acoustic monitoring of aquatic animals. He developed a biomimetic broadband sonar and underwater autonomous recorders, which is used world-widely. He is a member of IEEE/OES Japan chapter, IUCN cetacean and sirenian specialists groups, and ISO/TC43. He was a visiting scholar of National Institute of Polar Research (1997) and University of Kentucky (1999). Currently he is a senior researcher of Japan Fisheries Research and Education Agency.

Plenary Lectures A Review on Methods and Applications of Wave Propagation Numerical Modeling Géza Seriani Istituto Nazionale di Oceanografia e Geofisica Sperimentale, Trieste, Italy

Numerical simulation techniques are sophisticated tools that play a key role in the study of complex physical phenomena when analytical or semi-analytical methods are insufficient to their assessment. This is the case of elastic wave propagation phenomena that arise in complex heterogeneous geological structures having, for example, anisotropic, viscoelastic, or poroelastic rheologies. Due to the complexity of these realistic media, wave propagation occurs with reflection, refraction, diffraction and scattering phenomena that are difficult to quantify. So, numerical full-wave-equation-based methods are needed for wave modeling in full 3D models that are of great interest in exploration geophysics, seismology and volcanology. An overview of the most used numerical methods for solving elastic wave equations is presented. These can be divided into two main categories: “strong” and “weak.” Strong methods are based on the differential form of wave equations with suitable boundary conditions. The equations should to be verified specifically on discrete points of a grid on which the continuum is interpolated. Examples of strong methods are the finite-difference and the pseudospectral methods. Weak methods are based on an integral form of the wave equations that contains implicitly the boundary conditions. The equations should to be globally verified over elements that use a discrete norm for the solution. Examples of weak methods are the finite-element, spectral-element and discontinuous-Galerkin methods. Accuracy and efficiency will be discussed. Indeed, for large scale modeling, the challenge is to find the maximum efficiency for a specific required accuracy.

References [1] J.O.A. Robertsson, et al. (eds), Numerical Modeling of Seismic Wave Propagation: Gridded Two-Way Wave-Equation Methods, Geophysics Reprint Series No. 28 (2012). [2] R.-S. Wu, V. Maupin (eds), Advances in Wave Propagation in Heterogeneous Earth, Advances in Geophysics Vol. 48 (2007), Elsevier–Academic Press, London. [3] EU-funded projects in Computational Seismology, SPICE and QUEST Biographical Sketch: Géza Seriani received the“Laurea in Scienze Fisiche” degree in 1970 with a theoretical thesis from Institute of Physics, Università degli Studi di Trieste, Italy. He joined Istituto Nazionale di Oceanografia e di Geofisica Sperimentale (OGS) in 41

Plenary Lectures Trieste, Italy as a Tenure researcher in 1981; became a Tenure senior researcher in 1992, and Affiliated senior researcher in 2014. His research areas include Generation, propagation and simulation of acoustic and elastic wave propagation in realistic media and complex geological structures, Numerical modelling methods for wave propagation such as pseudospectral techniques, finite element analysis, spectral element methods and massive parallel computing, Application to Rock physics, Geophysical prospecting, Seismology and Earthquake engineering. He participated as Leader Scientist to many research projects funded by EU on seismic wave modelling and inversion, the most recent are SPICE (Seismic wave Propagation and Imaging in Complex media: a European network) and QUEST (QUantitative Estimation of Earth's Seismic Sources and STructure). He was an Invited Visiting Scientist (at IACAS, Beijing) in September 2011, granted by the Chinese Academy of Sciences Visiting Professorship for Senior International Scientists. He is the Editor of the book Theoretical and Computational Acoustics ICTCA'99: Proceedings of the 4th International Conference Stazione Marittima, Trieste, Italy.

Plenary Lectures Super-resolution Inversion of Seismic Wavelet and Reflectivity for Non-stationary Seismic Trace Using Deep Learning Jinghuai Gao1,2, Daoyu Chen1,2, Zhaoqi Gao1,2, Hongling Chen1,2, Zongben Xu3 1National Engineering Laboratory for Offshore Oil Exploration, Xi’an Jiaotong University, Xi’an, CHINA 2Faculty of Electronic and Information Engineering, Xi’an Jiaotong University, Xi’an, CHINA 3School of Mathematics and Statistics, Xi’an Jiaotong University, Xi’an, CHINA

Common methods for super-resolution inversion of the seismic trace are based on the convolution model, which assumes that the seismic wavelet does not vary with the propagation of seismic wave. However, this hypothesis fails under many conditions. As a matter of fact, the seismic trace satisfies the varying-wavelet model that also called non-stationary convolution model. In this talk, we propose a method for the super-resolution inversion of non-stationary seismic traces. The proposed method consists of two parts. In Part I, we devoted to transform the non-stationary seismic trace into a stationary one. In Part II, we propose an alternating inversion method to simultaneously estimate seismic wavelet and reflectivity using deep learning. The detailed information of these two parts are as follows: In Part I, we first propose a data-driven representation method for non-stationary convolution seismic trace. The proposed method contains two steps. Step 1: Splitting the nonstationary seismic trace into several segments, each of which is stationary. To this end, we propose two approaches, which are the deterministic approach and the statistics one. Step 2: Constructing molecular frame transform, which has an exact inverse transform, based on the segments. Then, based on the data-driven representation, the non-stationary seismic trace is transformed into a stationary one by Q compensation with the Q factor estimated from the seismic trace. To accurately estimate the Q factor, we build a constructive operator to obtain the amplitude spectrum of the “equivalent wavelet” for each molecular. In Part II, we propose a deep learning based data-driven method for super- resolution inversion of stationary seismic trace. The method splits the inversion into two subproblems: one inverts for the seismic wavelet and the other for reflectivity. Using a partially learned approach, the proposed method simultaneously estimates the wavelet and reflectivity in an alternative way, and the estimation is realized using deep neural networks (DNN). Both synthetic and field data examples clearly demonstrate the advantages of the proposed method in reducing the prediction error, ensuring the sparsity of the reflectivity and improving the lateral stability. Biographical Sketch: Jinghuai Gao received the M.S. degree in applied geophysics from Chang’an University, Xi’an, China, in 1991 and the Ph.D. degree in electromagnetic field and microwave technology from Xi’an Jiaotong University, Xi’an, in 1997. From 1997 to 2000, he was a Postdoctoral with the Institute of Geology and Geophysics, Chinese 43

Plenary Lectures Academy of Sciences, Beijing, China. In 1999, he was a Visiting Scientist with the Modeling and Imaging Laboratory, University of California, Santa Cruz, CA, USA. He is currently a Professor with the School of Electronic and Information Engineering and the School of Mathematics and Statistics, Xi’an Jiaotong University. He is also the Associate Director of the National Engineering Laboratory for Offshore Oil Exploration. His research interests include unconventional oil and gas exploration, seismic signal processing, seismic wave propagation theory and seismic imaging and inversion theory and application. Prof. Gao is the Project Leader of the Fundamental Theory and Method for Geophysical Exploration and Development of Unconventional Oil and Gas, which is a major program of the National Natural Science Foundation of China (No. 41390454). He is an Editorial Board Member of the Chinese Journal of Geophysics, Applied Geophysics and Chinese Science Bulletin. He was a recipient of the Chen Zongqi Geophysical Best Paper Award in 2013.

Plenary Lectures Computational Modelling of Noise Radiation from Aircraft Engines Gwénaël Gabard LAUM, Le Mans Université, France

Computational acoustics plays a central role in the design of various components of aircraft engines, from the fan, the intake and bypass ducts, to the compressor, combustor, etc. It is also used for the acoustic design of other elements of the aircraft, in particular the landing gears. The objective is not only to reduce acoustic emissions to meet certification targets, but also to minimize cabin noise to improve passenger comfort. This presentation aims to highlight the challenges of applying computational acoustics to this type of problems, with a particular focus on sound propagation from aircraft engines. A typical example of application is the optimization of an acoustic treatment on the intake of an aircraft engine. This problem involves complex geometries, a non-uniform background mean flow, sound radiation to the far field and scattering by large objects (e.g. wing and fuselage). In addition, there is some uncertainty on the noise sources and the environment (temperature, wind profile, flight conditions). For the computational aspects, this involves very large models that one has to solve many times for different frequencies, flight conditions and design parameters. Various computational techniques have been proposed to address these challenges and a number of those will be presented in some detail. They include the use of high- order finite elements to reduce the computational costs, in particular the development of an anisotropic adaptive scheme to automatically adjust the numerical resolution. We will also consider domain-decomposition methods to provide more scalable numerical models. Finally, the coupling of different propagation models will be presented to describe the underlying physics in an efficient manner. To provide potential directions for further research in this field, we will outline a number of remaining challenges, in terms of physical modelling or computational simulations. Biographical Sketch: Gwénaël Gabard is a senior researcher at the LAUM, the acoustics lab at Le Mans Université, France. Before the LAUM he was associate professor at the Institute of Sound and Vibration Research (ISVR) at the University of Southampton, UK. His research area is computational aero-acoustics with a particular emphasis on the prediction of aircraft noise and the modelling of acoustic treatments for aerospace applications. He also teaches aero-acoustics and computational methods to graduate students. In 2000, he completed the Master in Acoustics from the University of Technology 45

Plenary Lectures of Compiegne where is then conducted his doctoral research on computational aeroacoustics. He was awarded his PhD 2003. Between 2005 and 2017 he was part of the Rolls-Royce University Technology Centre in gas turbine noise at the University of Southampton, working on modelling and simulation methods to support the development of low-noise technologies at Rolls-Royce. Since 2017 he is the recipient of an Industrial Chair, funded by the Safran group and the French government, to work on novel acoustic treatments for aircraft engines. In parallel, since 2009, he collaborates with Siemens PLM to develop more efficient computational methods for sound propagation problems.

Plenary Lectures Controlling Sound Directivity with Acoustic Metamaterials Xiaozhou Liu Key Lab of Modern Acoustics, Institute of Acoustics, Nanjing University, Nanjing , China

How to realize the directional propagation of low frequency acoustic waves in space is an important scientific issue. From the perspective of adjusting boundary conditions, acoustic radiation pattern based on acoustic metasurface is studied. By changing the locations of the periodic Helmholtz resonators (HRs),we can obtain dipole-like radiation pattern with arbitrary direction in the semi-infinite plane area, the scheme also has wide working band. A finite array of dipole sources is also reported, which is used to enhance the directivity and radiation gains of sound in the meantime, it is demonstrated that this idea can be realized as several sub-wavelength slits in a plate with periodic Helmholtz resonators. Moreover, the array gain of this structure can be further improved by adjusting the effective boundary impedance. The directivity of the dipole array is compared with that of a point array, and the advantages of the dipole array are revealed. A method of using the Mie resonance structure to realize the efficient directional propagation and the collimating beam of the sound wave is proposed. The relationship between the Mie resonance characteristics and the geometric parameters is discussed. We also use the Mie resonance structure to suppress the characteristics of the wave vector, and propose a method to achieve the collimation of the sound wave. Biographical Sketch: Xiaozhou Liu was graduated from Department of Science and Engineering, Nanjing University, Nanjing, China in 1998. He received his Ph.D degree in acoustics from Nanjing University in 1999. He was a postdoctor in Shanghai Jiaotong University from 1999 to 2000. In 2009, he was a visiting professor at the Institute of Materials, Pennsylvania State University. Now he is a professor in Nanjing University. Over the past 30 years, he has conducted both theoretical and experimental research in the area of acoustics. He current interests including nonlinear effects in solids, ultrasound transducer designer, medical ultrasonic imaging, ultrasonic nondestructive evaluation (NDE) and signal processing. More than 120 papers have been published in academic journals and international conferences, including Nature Communications, Physics Review B, Physics Review E, Applied Physics Letters and Journal of the Acoustical Society of America. Nine national invention patents have been granted.

The Inversion of Seismic Wave The Adaptive Distributed Acoustic Sensing Coupling Noise Removal Method Jianyou Chen1, Wenchao Chen1, Peng Xu2, Debao Wang2

1)National Engineering Laboratory for Offshore Oil Exploration, Xi'an Jiaotong University, Xi’an, China 2)Jiuquan Satellite Launch Center, Jiuquan, China

The VSP (Vertical Seismic Profiling) data acquired from the DAS (Distributed Acoustic Sensing) system has wide application. However, the DAS data suffers from strong coherent noise such as cable slapping and ringing due to the physical placement of the wireline in the well [1]. A novel method based on sparse optimization is a useful method to suppress the coupling noise. We choose the continuous wavelet transform (CWT) and discrete cosine transform (DCT) as two transform dictionaries to sparsely represent desired signal and DAS coupling noise [2]. However, when processing the whole data in the same work area, if we do not consider the noise intensity in different trace, we may not suppress the DAS coupling noise completely or damage the useful signal information. The DCT threshold weighting efficient in BCR algorithm can be expressed as following: P    P 100 , (1) DCTi i where， P is the DCT threshold weighting efficient of the jth trace data, is DCTi  a constant modificatory gene, and Pi is the amplitude spectrum kurtosis of the jth trace data. We also propose an amplitude mean method to get the last step fundamental threshold parameter.

N k Tmin j | ( x j,i ) N |, (2) i1

k where, Tmin j is the minimum fundamental threshold value of the jth trace data, x j,i is the ith sampling point value in the jth trace, and N is the sampling point length of each trace. The denoising results demonstrate that our method can effectively remove optical cable coupling noise very well without causing impairment for the desired signal. References [1] Mateeva, A., Lopez, J., Potters H., Distributed acoustic sensing for reservoir monitoring with vertical seismic profiling, Geophysical Prospecting 62 (2014), no. 4, 679-692. [2] Wang, W., Gao, J., Chen, W., Xu, J., Data adaptive ground-roll attenuation via sparsity promotion, Journal of Applied Geophysics 83 (2012), no. 6, 19-28. 48

The Inversion of Seismic Wave Adaptive Multiple Subtraction Based on Support Vector Regression Zhongxiao Li1, Bingluo Gu2, Zhenchun Li2 1)School of Electronic Information, Qingdao University, Qingdao, China 2)School of Geosciences, China University of Petroleum (East China), Qingdao, China After multiple prediction, adaptive multiple subtraction is an important step for the success of multiple removal [1]. Generally, adaptive multiple subtraction is posed as a problem of linear regression, in which the filter coefficients linearly combine sampling points of the predicted multiples to match with the original data. In general, the iterative reweighted least-squares (IRLS) algorithm is used to solve the optimization problem of linear regression, which includes an L1-norm minimization constraint of primaries [1]. The complicated discrepancies between the predicted multiples and the true multiples can be very challenging. How to balance multiple removal and primary preservation is very important for adaptive multiple subtraction. For the IRLS-based method, the mathematical model of linear regression has limitations to express the complicated discrepancies between the predicted multiples and the true multiples. Additionally, the IRLS algorithm may not obtain the optimal solution to the L1-norm minimization problem. Therefore, the IRLS- based adaptive multiple subtraction may cause the residual multiples or distorted primaries, especially in the case of complex media. As an important part of the artificial-intelligence technology, the machine- learning algorithm is widely used for data classification, regression, cluster, anomaly detection, and so on. Support vector machines (SVMs) are supervised learning models for support vector regression (SVR) with continuous outputs. In seismic-data processing, SVR has been used to interpolate missing seismic traces [2]. As a state- of-the-art tool of machine learning, SVR can transform a nonlinear regression problem into a linear regression problem, which can be solved easily. Motivated by the SVR research for interpolation [2], we propose to introduce SVR into adaptive multiple subtraction. We express adaptive multiple subtraction as a problem of SVR in this paper. It firstly estimates a regression function to represent the relationship between the predicted multiples and the true multiples, then estimates multiples by inputting feature vectors of the predicted multiples into the regression function, and finally obtains multiple-removal results by subtracting the estimated multiples from the original data directly. The SVR-based method can estimate a SVR function to express the complicated discrepancies between the predicted multiples and the true multiples effectively. Furthermore, the optimization algorithm used in the SVR-based method is effective in solving the corresponding optimization problem. Synthetic and field data examples demonstrate that the SVR- based method can separate primaries and multiples better than the IRLS-based method. References [1] Guitton, and D. J. Verschuur, Adaptive subtraction of multiples using the L1- norm, Geophysical Prospecting 52 (2004), no. 1, 27-38. [2] Y. Jia, and J. Ma, What can machine learning do for seismic data processing? An interpolation application, Geophysics 83 (2017), no. 3, V163-V177. 49

The Inversion of Seismic Wave Full Waveform Inversion of SH-wave and its Application in Prospecting for Anomaly in Near-surface Hang Duan, Peimin Zhu Institute of Geophysics & Geomatics China University of Geosciences, Wuhan

The conventional SH-wave seismic exploration has the disadvantage of insufficient resolution for small anomaly prospecting. A 2D full waveform inversion of SH-wave (SH-FWI) method is proposed and applied to image the small size of anomaly, for instance, various sizes and shapes of boulders which are the barriers of tunnel boring machine (TBM) in tunnel engineering. The 2D SH-FWI method is assumed to fit the isotropic elastic media and SH-wave propagation can be described as a stress-velocity formulation of coupled, linear partial differential equation. This SH-FWI works in time domain with LBFGS to inverse physical parameters, velocity and density, of underground earth media. To demonstrate the feasibility of SH-FWI for detecting small anomalous bodies in near-surface, a synthetic SH-wave seismic data is used to test the accuracy of inverted results. Experimental results show that proposed method can clearly distinguish the various small sizes of anomalous bodies in inverted results, in which inverted result of velocity is better than that of density.

The Inversion of Seismic Wave Advanced Geological Prediction in Soft Soil Tunnel Based on Seismic Wave Reflection Technology Xingmeng Dong, Fangqing Deng, Yuwen Zhai, Zhiqiang Yang The 22th Research Institute of China Electronics Technology Corporation, Xinxiang, China

During the construction of shield tunnels, it is necessary to use advanced geological prediction system to detect the geological conditions in front of the tunnel face and to warn the abnormal geology. Based on seismic reflection technology, this paper studies a set of advanced geological prediction system for shield tunnel construction, which can effectively detect stratum information and distribution of unfavorable geological bodies in front of the tunnel face. In this paper, two aspects of wave field forward simulation and imaging are studied. Firstly, two- dimensional numerical simulation of seismic wave field in Sonic Softground Probing (SSP) tunnel is carried out by using finite element numerical simulation method. The propagation characteristics of seismic wave when encountering solitary rocks and holes, as well as source excitation parameters and geophone arrangement suitable for SSP tunnel detection are studied. Based on forward modeling, seismic reflection wave extraction technology and migration imaging technology suitable for SSP system geological exploration are studied. Combining numerical simulation with experimental simulation, a set of shield tunnel geological prediction method based on seismic reflection imaging technology is formed, and the effective detection range of the prediction system is discussed. References G. Kneib, A. Kassel, and K. Lorenz, Automatic seismic prediction ahead of the tunnel boring machine, First Break 18 (2010), no. 7, 295–302.

The Inversion of Seismic Wave Random Noise Attenuation via Group Sparsity Residual Constraint Dictionary Learning Xiaojing Wang, Jianwei Ma Center of Geophysics and Department of Mathematics, Harbin Institute of Technology, Harbin, China

The attenuation of random noise plays a significant role in the seismic data processing. Local-sparsity based dictionary learning method has been applied widely in seismic data denoising problem. However, the existing dictionary learning method[1] only considers the local sparsity, ignoring the correlation of the underlying data. To overcome this disadvantage, the group-based sparse representation [2] is proposed to exploit the group sparsity of similar patches in the dictionary domain which has shown great advantage in various image restorations, such as denoising, interpolation, deblurring. Inspired by this, in this abstract, we apply the group sparsity residual constraint dictionary learning method [3] (GSRCDL) for the random noise attenuation. The cost function of GSRCDL method is given as follow: N 2 min {||Yi  Di Ai ||F  || Ai  Bi ||1} (1) D ,A  i i i1 th where Y denotes the two-dimensional noisy seismic data, Yi denotes the i group data with similar structures extracted from Y ,  is the trade-off between the fidelity function and regularization. Di is the dictionary and Ai is the sparse coding of the noisy data under the dictionary Di . Bi represents the true sparse coding of the clean data.

As we do not have original clean data, the original Bi is unknown. Thus, we need to estimate the Bi in Equation (1). There are plentiful algorithms to estimated Bi , which can exploit the priori information of the clean data. These algorithms such as BM3D method, GMM method are either not accurate or slow. We use the nonlocal samples in each group data to estimate the original Bi . Then the dictionary Di and sparse coding Ai of noisy data, sparse coding Bi of estimated data are updated alternatively to solve Equation (1). References [1] M. Aharon, M. Elad, A. Bruckstein, et al., K-svd: An algorithm for designing overcomplete dictionaries for sparse representation, IEEE Transactions on signal processing 54 (2006), no. 11, 4311. [2] J. Zhang, D. Zhao, W. Gao, Group-based sparse representation for image restoration, IEEE Transactions on Image Processing 8 (2014), no. 23, 3336- 3351. [3] Z. Zha, X. Zhang, Q. Wang, et al., Group sparsity residual with non-local samples for image denoising, 2018 IEEE International Conference on Acoustics, Speech and Signal Processing (ICASSP). IEEE (2018), 1353-1357. 52

The Inversion of Seismic Wave Structure-guided Blind Sparse Spike Deconvolution Yuhan Sui, Jianwei Ma Center of Geophysics and Department of Mathematics, Harbin Institute of Technology, Harbin, China Seismic wavelet estimation and deconvolution are essential for high-resolution seismic processing. One of the classical approaches is blind sparse spike deconvolution which obtain the seismic wavelet and reflectivity in the shape of spikes based on convolution model. Conventionally, Toeplitz-sparse matrix factorization [1] (TSMF) is applied. It is a bilinear decomposition of a matrix into the product of a Toeplitz matrix and a sparse matrix, then optimizes reflectivity and matrix elements as the same time. However, TSMF is implemented trace-by-trace, it is important problem to preserve the lateral continuous of the reflectivity. In geophysical inversion, a structural regularization [2] is proposed to obtain an accurate impedance and interval velocity. We propose a structure-guided blind sparse spike deconvolution based on TSMF and structural regularization. The cost function of TSMF is n1 2 1 (1) min Y  ( k Ik )R   || Ri ||1  1 || ω ||1 2 (k1  k )  3 || ω ||2 ω,R    2 kn1 2 where Y is seismogram, R is the reflectivity and ω is the vector which is the first column and first row of the wavelet matrix. The structural regularization needs to be built by the structure tensor of the seismic data. The structure tensors are computed as smoothed outer products of the image gradients, and the eigenvectors of the tensors provide estimations of seismic structural and stratigraphic orientations. The details of structural regularization are in [2]. The cost function of our proposed method is n1 2 1 T T min Y  ( k Ik )R   || Ri ||  B(ω), s.t. vv R  0 uu R  0 (2) ω,R   2 kn1 2 To solve the cost function (2), we use the fast iterative shrinkage-thresholding algorithm [3] (FISTA). Consider the structural regularization of the reflectivity in our approach, we are able to preserve the lateral continuous of the reflectivity and to observe the structure of the data much more clearly. References [1] L.Wang, Q. Zhao, J. Gao, Z. Xu, M. Fehler, and X. Jiang, Seismic sparse-spike deconvolution via toeplitz-sparse matrix factorization, Geophysics, 81(2016), no.3, V169–V182 [2] X. Wu, Structure-, stratigraphy- and fault-guided regularization in geophysical inversion, Geophysical Journal International, 210(2017), no. 1, 184–195. [3] Beck and M. Teboulle, A fast iterative shrinkage-thresholding algorithm for linear inverse problems, SIAM Journal on Imaging Sciences, 2(2009), no. 1, 183–202. 53

Underwater Acoustic Communication and Network Interleaved Hybrid Spread Spectrum Underwater Acoustic Communication on Long-delay-spread Multipath Channel Ning Jia1,2, Yan Li1,2,3, Jianchun Huang1,2, Zhongyuan Guo1,2, Biao Liu1,2,3 1 Key Laboratory of Underwater Acoustic Environment, Institute of Acoustics, CAS, Beijing, China 2 Institute of Acoustics, CAS, Beijing, China 3 University Chinese Academy of Sciences, Beijing, China

Spread spectrum is widely used in underwater acoustic communication systems, which is usually implemented by direct sequence spread spectrum (DSSS), cyclic shift spread spectrum, M-ary parallel combinatory spread spectrum, etc. These approaches have demonstrated can perform well when the symbol duration is much longer than the delays due to the effect of multipath. However, for long-delay-spread multipath channel, deep sea long-distance horizontal channel for instance, their performances degrade tremendously because of the coherent interference among the symbols. To tackle this, an interleaved hybrid spread spectrum method for long- delay-spread underwater acoustic channel is proposed in this paper. This method adapts the cyclic shifting and parallel combinatory spread spectrum jointly to improve bandwidth utilization, afterwards, chip level interleaving for adjacent symbols is implemented to convert the coherent interference among symbols into non-coherent interference. The performance of the proposed method is analyzed and verified through synthetic tests and sea trial data in long-delay-spread multipath channel, which both demonstrate the proposed method has better performance than traditional spread spectrum methods

Underwater Acoustic Communication and Network A Pattern Recognition-aware Spread Spectrum Signal Classification Model for Underwater Acoustic Communications Chao Li1,2, Haibin Wang1, Yannick Benezeth2, Fan Yang2 1 State Key Laboratory of Acoustics, Institute of Acoustics, CAS, Beijing, China 2 Laboratory of ImViA, University of Burgundy-Franche-Comte, Dijon, France 3 Institute of Acoustics, CAS, Beijing, China

Spread spectrum communication is always a crucial research topic in the field of acoustic engineering for its benefit of high reliability. Spread spectrum demodulation is one of the key components of the underwater acoustic communication (UAC) modalities. Its goal is to map the received symbol signals to the correct code sequences via some matching procedure. Yet, this job is far from easy with the signal distortions caused by the time and space variations of the underwater environment, reverberation, multi-path effect, low signal-to-noise ratio, etc. Most of today’s spread spectrum demodulators are based on the matched filter (MF), which is oriented by optimizing the SNR of the filter output [1]. It is well known that the output gain of the matched filter is constrained by the time-bandwidth product of the communication signals. The UAC modalities necessitate low bandwidth for the purpose of low attenuation ratios, whereas the length of the symbol signals is constrained by the time-varying sound channels and the communication rates, resulting in the bottleneck of the MF output gains. Our work focuses on the high-performance UAC studies. We address the issue of the spread spectrum demodulation by abstracting it as a pattern recognition problem, which allows the machine learning methods. Despite of some exciting experiment results in the previous works, the fundamental principal of the family of these methods are not explained satisfactorily. Consequently, our recent work gets back to the very beginning of the research in order to find out why the machine learning demodulators can achieve more output gains than MFs. This report presents a linear spread spectrum signal classification model as well as its optimizing procedure. According to this new model, the advantages of the machine learning demodulators are further explored. All the hypotheses of this work are verified within simulation experiments.

References [1] Turin G. L., An introduction to matched filters, Information Theory Ire Transactions on 1960, 6, 311–329. [2] Li C., Wang H. B., Wang J., Tai Y. P., Yang F., Multicollinearity problem of CPM communication signals and its suppression method with PLS algorithm, the 13th ACM International Conference on Underwater Networks & Systems (WUWNet'18), Shenzhen China, Dec. 3-5, 2018. [3] Li C., Marzani F., Yang F., Demodulation of Chaos Phase Modulation Spread Spectrum Signals Using Machine Learning Methods and Its Evaluation for Underwater Acoustic Communication, Sensors, 2018, 18 55

Underwater Acoustic Communication and Network Non-Uniform Hybrid Norm Constraint based Underwater Acoustic Channel Adaptive Estimation ZHANG YongLin1,2, WANG HaiBin1, TAI YuPeng1, WANG Jun1, CHEN Xi1 1State Key Laboratory of Acoustics, Institute of Acoustics, CAS, Beijing, China 2University of Chinese Academy of Sciences, Beijing, China It is known that underwater acoustic channels(UAC) exhibit cluster-sparse characteristics in nature[1], meaning that the impulse response of the sparse channel typically consists of a large number of near-zero taps and with only a few none-zero ones assemble in clusters in a structured manner. Moreover, the cluster structure is unevenly distributed on the time domain, especially in the deep ocean environment. Compared with traditional ones, the existing sparse adaptive algorithms have already been improved in the UAC estimation accuracy. However, the non-uniform cluster sparse distribution of the channel impulse responses is still not fully exploited. In this paper, an improved proportionate affine projection algorithm (IPAPA) with the non-uniform hybrid norm constraint is proposed for underwater acoustic channel estimation. Prior to commencing the process, the channel partition and related parameters are initialized according to the channel priori information obtained by deep ocean acoustic wave propagation theory. Then the proposed algorithm penalizes a mixed 푙푙21-norm on IPAPA to enforce the cluster-sparsity of the UAC: it encourages correlation among coefficients inside each group via the 푙푙2 norm and facilitates sparsity across all groups using the 푙푙1 norm. Besides, the method can perform non- uniform updating of the channel partition during each iteration adaptively. In general, the proposed method can reach a good adaptive estimation effect by the non-uniform mixed norm constraint of the UAC cluster structure. Numerical simulation results are shown in Fig. 1(a), and the experimental results obtained in physical long range deep-water acoustic channels are shown in Fig. 1(b). It shows that the proposed UAC estimation algorithm can achieve a better performance in terms of Mean Square Error (MSE) compared to existing sparse channel estimation methods.

(a) Numerical simulations (b) At-sea experiment Fig. 1 Numerical simulations and at-sea experiment References [1] Wang Z, Zhou S, Presig J. C, Pattipati K R, Willett P, Clustered adaptation for estimation of time-varying underwater acoustic channels, IEEE Transaction on Signal Processing 58 (2012), no. 6, 3042-3054. 56

Underwater Acoustic Communication and Network An Underwater Acoustic Network Positioning Algorithm Combined with Its Protocol Yi-Xuan Feng1,2, Dong Xiao1, Yan Chen1, Li-Ping Wei1, Min Zhao3, Li Ma1 1Institute of Acoustics, CAS, Beijing, China 2 University of CAS, Beijing, China 3 Economic Research Institute, State Grid Jibei Electric Power Company Limited Beijing, China

Global positioning system (GPS) cannot be used in underwater acoustic sensor network (UASN), because radio waves suffer severe absorption in water. Although the node can be positioned accurately above water, water flow always washes it away after it is deployed underwater. And the offset is hard to calculate, so the node needs to be positioned after deployment. The traditional method consumes considerable energy in the node positioning process. Because the battery in the node is quite limited and hard to replace, network lifetime is curtailed to some degree. An underwater network node positioning algorithm combined with the network protocol is proposed in this paper. Before each node is deployed into water, it is initiated with a GPS value. Then, the nodes are deployed according to certain rules, which are each node must have two other nodes in its communication range and the two other nodes can also communication with each other. Combined with our network self- organization protocol, the distances between two nodes are ranged by time of arrival algorithm. The initial GPS values are correcting according to the distances. Simulations show that the offset can be reduced to 50% or less averagely if the directions of all the offset are random, and the energy consumption is lower than the traditional method. This algorithm makes an attempt in underwater network node positioning combined with protocol, simplifies the positioning process and saves the energy. It may promote underwater network development and accelerate ocean exploitation and utilization.

Underwater Acoustic Communication and Network Overview of Turbo Equalization in Underwater Acoustic Communication Xuan Yu, Xuan Geng School of Information Engineering, Shanghai Maritime University, Shanghai, China

Due to Turbo equalization plays an important role in the realization of the hydroacoustic communication physical layer, the paper analyzes and summarizes the existing Turbo equalization. First, according to the signal processing process, it is divided into time-domain equalization and frequency-domain equalization. The realization and characteristics of linear and decision feedback structures under two kinds of equalization are summarized. Then the Turbo equalization in frequency time domain is introduced. Finally, the complexity and antiinterference performance of different algorithms are analyzed. The analysis shows that in the time domain and frequency domain, the computational complexity of the linear equalization based on the minimum mean square error criterion is relatively high, and the decision feedback equalization will cause a certain amount of error propagation. The time-frequency domain Turbo equalization not only retains the performance of the time-domain bit error rate, but also has a low computational complexity, which is a better technology in the current Turbo equalization field and has a very good development space in the future.

Underwater Acoustic Communication and Network Channel Equalization Algorithm Based on Sparse Source Reconstruction CHEN Yang, ZHOU Menglin, PEI Ming, ZHU Yanping School of Information Science & Engineering, Changzhou University, Changzhou, Jiangsu 213164, China

A channel equalization algorithm that is based on compressed sensing theory is proposed. When the source is sparse in a certain linear transform domain, the reception in a communication channel can be modeled as a weighted summation of a dictionary by the sparse source on the basis of compressed sensing theory. The channel can be equalized through source reconfiguration with a reconfiguring algorithm. Given that the source is directly reconfigured, the proposed equalizer outperforms the conventional linear transversal equalizer (LTE) and decision feedback equalizer (DFE) and lacks the problems of noise amplification and error propagation. The Basis Pursuit De-Noising algorithm is adopted to reconfigure the source when additive Gaussian white noise is present in the communication channel. Simulation studies showed that the proposed equalizer has better equalizing performance than LTE and DFE and similar robustness as LTE and DFE. Furthermore, the proposed equalizer retains its excellent equalization performance even under deteriorating channel conditions.

Underwater Acoustic Communication and Network Bionic Morse Coding Mimicking Humpback Whale Song for Covert Underwater Communication Muhammad Bilal1,2.3, Songzuo Liu1,2,3, Gang Qiao1,2,3 1 Acoustic Science and Technology Laboratory, Harbin Engineering University, Harbin150001, China. 2 Key Laboratory of Marine Information Acquisition and Security (Harbin Engineering University), Ministry of Industry and Information Technology, Harbin 150001, China. 3 College of Underwater Acoustic Engineering, Harbin Engineering University, Harbin 150001, China A novel method of bionic Morse coding mimicking humpback whale vocal is presented. Mimicry is an innovative approach for covert communication where the secret information is transmitted in presence of enemy [1]. The communication signal is structured akin to the natural sea noise. The signal can be detected by intruder but it is excluded from the process of recognition due to natural sound signature. It gives excellent Low Probability of Recognition characteristics [2]. A standardized cetacean codes based on Morse theory has been presented. Male humpback whales are famous for emitting loud and long duration vocal termed as song. The complex humpback whale song is translated as cetacean Morse codes based on information entropy as shown in figure. The communication signal is made analogous to the natural singing of male humpback whales. A flawless stealthy underwater acoustic communication has been established which has negligible chances of deciphered with high imperceptibility. A standard mimicry Morse codes has been researched for characters of English language and compared with traditional methods of coding. Proposed method results high covert data rate with less complexity. Transmission rate of 1 character per second can be achieved with stealthy and clandestine communication.

Fig.1: Representation of word COVERT using Bionic Morse codes using humpback whale song. References [1] R. Diamand and L. Lampe, Low Probability of Detection for Underwater Acoustic Communication: A Review, IEEE Access 6 (2018), 19099 – 19112 [2] G. Qiao, M. Bilal, S. Liu, Z. Babar, T. Ma, Biologically inspired covert underwater acoustic communication-A review, Physical Communication 30 (2018), 107-114 60

Numerical Simulation and Vibroacoustical Prediction Technique Spectral Stochastic Infinite Element Method in Vibroacoustics Felix Kronowetter1, Lennart Moheit, Kheirollah Sepahvand1, Steffen Marburg1 1Chair of Vibroacoustics of Vehicles and Machines, Technical University Munich, Garching, Germany

A new method to solve exterior Helmholtz problems in the case of monopole excitations and random input data is developed. The infinite element method (IFEM) is chosen to solve exterior Helmholtz problems and an infinite element code is self- implemented. To prove the accuracy of the code, it is validated for full-space and half-space domains. The consideration of the random input data leads to a stochastic infinite element (SIFEM) formulation. The generalized polynomial chaos (gPC) expansion of the random data results in the spectral stochastic infinite element (SSIFEM) formulation. As a solution technique, the non-intrusive collocation method is chosen. According to that the IFEM code can be treated as black-box and the uncertainty quantification is implemented as a stochastic framework. The model of a two-dimensional convertible car with an open roof is selected as a test case for the SSIFEM. This test case is considered to be an half-space exterior Helmholtz problem, with the street bounding the problem. The excitation of the front window due to vibrations as well as the admittance of the seat cushion is considered random. An evaluation point is defined, representing the ear of the driver. A random sound pressure response function is defined to analyze the influence of the excitation of the front window on the sound pressure level at the ear of the driver. The SSIFEM is compared to the Monte Carlo method (MCM) to show its accuracy. The results approve the stochastic infinite element method to be an accurate and efficient method to solve exterior Helmholtz problems with random input data.

Numerical Simulation and Vibroacoustical Prediction Technique Numerical Study of Acoustic Source in Vortical Flows: Direct Simulation and Modal Analysis Feng Feng, Qiang Wang China Academy of Aerospace Aerodynamics, Beijing, People’s Republic of China

The mechanism of sound generation by the aerodynamic source in unsteady flows has challenged investigators for many years. In classic acoustic analogies (AA)[1], the acoustic source comprises as a spatio-temporal correlation of fluctuating quantities, which is difficult to represent the dynamics of flow-generated sound in an intuitive way. The vortex sound theory [2, 3] emphasizes the role of vorticity as the sound source for low Mach number flows, which provides physical insight into acoustic sources. Nevertheless, it is still difficult to explain the underlying mechanism of acoustic source in vortical flows. Two issues are waiting to be addressed. First, the true source in the hydrodynamic field responsible for sound generation need be determined. Second, the dynamics transferred the energy from hydrodynamics into acoustics need to be clarified. Two-dimensional compressible vortices and their sound field are directly computed by the numerical simulation of the unsteady compressible Navier-Stokes equations in the present work. Then, a modal analysis method, POD (proper orthogonal decomposition), is employed to decompose the hydrodynamic field into plenty of flow modes and to explore the true sources of the vortical flows. It is found that each hydrodynamic component potentially contributes to the sound generation. Particularly, in the modal view, each acoustic component is correspondingly produced by the interaction between its counterpart hydrodynamic mode and the base-flow mode. This mechanism of sound generation by the aerodynamic source dominates the vortical flow, which possesses distinct large-scale vortex structures. References [1] M. J. Lighthill, On sound generated aerodynamically: I. General theory, Proceedings of the Royal Society of London A, 211 (1952), no. 1107, 564-587. [2] A. Powell, Theory of vortex sound, Journal of the Acoustical Society of America, 36 (1964), 177-195. [3] M. S. Howe, Contributions to the theory of aerodynamic sound, with applications to excess jet noise and the theory of the flute, Journal of Fluid Mechanics,.71 (1975), no. 4, 625-673.

Numerical Simulation and Vibroacoustical Prediction Technique Numerical Simulation and Performance Prediction of a High Intensity Air-modulated Speaker Yun Zhao, Xinwu Zeng, Changchao Gong, Zhangfu Tian College of Meteorology and Oceanography, National University of Defense Technology, Changsha, China The air-modulated speaker (AMS) [1][2] is a typical wide-frequency, high-power, high-intensity sound source, which is widely used in long-distance broadcasting, noise environment testing and acoustic agglomeration. High intensity sound radiation is generated by large amplitude pressure disturbances in the transient aerodynamic flow. The classical theoretical prediction model [1][3] is based on the quasi-steady or frequency-independent assumption. It is generally considered that the theoretical deviation is not ignorable at high frequency and low flow speed conditions. As details of the source structure and internal flow are simplified, the classical model is not suitable for the detailed source mechanism research and optimization of the device design. Numerical simulation model of AMS is based on a finite volume compressible flow solver. The high-speed jet modulation is modeled by the moving mesh method. The electromagnetic vibration of the moving parts for the modulation realization is calculated by a finite element model. Parameter selection of the compressible flow solver, moving mesh, geometric boundary and mesh generation is discussed. Performance prediction of the model includes pneumatic power consumption and high intensity acoustic radiation for different source designs and working conditions. The complex transient flow inside an axial symmetric source is analyzed at typical working condition. Dependencies of the internal unsteady flow characteristics on chamber pressure are studied. Flow field snapshots, time signals of static pressure and mass flow rate are presented for low frequency (100Hz) and high frequency modulation (500Hz). Root-mean-square sound pressure levels at different locations in the vocal tract are given while the chamber pressure increases from 0.2 to 0.6 MPa. Prediction results of flow field in the source are consistent with the experimental results with particle image velocimetry (PIV). Source performance predicted by the model is consistent with the quasi-steady theory under different working conditions. Primary physical factors and main components of the source device are considered by the model, which provides an ideal method for the further study of source mechanism and improvement of the source design. Vortex shedding, pressure gap and local high pressure region are discovered inside the source, which changes the source characteristics under high chamber pressure and high frequency modulation. References [1] C. J. Chapman, A. G. Glendinning, A theoretical analysis of a compressed air loudspeaker, Journal of Sound and Vibration 138 (1990), no. 493–499. [2] A. G. Glendinning, P. A. Nelson, and S. J. Elliott, Experiments on a compressed air loudspeaker, Journal of Sound and Vibration 138(1990) , no. 479–491. [3] W. A. Meyer, Theoretical analysis of the performance of an air-modulated speaker, Journal of Acoustical Society of America 45 (1969), no. 957-965. 63

Numerical Simulation and Vibroacoustical Prediction Technique A Numerical Investigation of the Mass Redistributed Edge-based Smoothed Finite Element Method for 3D Acoustic Radiation Problems Tengfei Dai1, Xia Jin1, Huaze Yang1, Tianran Lin1, Yuantong Gu2 1Qingdao University of Technology, Qingdao 266520, P.R. China 2Queensland University of Technology, Brisbane 4001, Australia

Both finite element method (FEM) and boundary element method (BEM) have limitations in solving the acoustic radiation problem in the mid to high frequency range. Mass redistributed edge-based smoothed finite element method (MR-ES- FEM) can moderately soften the stiffness matrix of the traditional FEM by the edge based generalized technology and adjust the balance of the stiffness and mass matrices by the mass redistribution technique to improve the calculation accuracy of the traditional FEM. The method was successfully applied in solving a three- dimensional (3D) acoustic problem of an enclosed sound field in the mid to high frequency region in a previous study by the same authors [1]. To testify the feasibility of MR-ES-FEM in solving 3D acoustic radiation problems, the technique is applied on a 3D sound propagation problem where the infinite external acoustic domain is transformed into a finite one by introducing an artificial boundary condition and the Dirichlet-to-Neumann (DtN) map into MR-ES-FEM in the study. The result from a numerical example shows that MR-ES-FEM can effectively reduce the dispersion error of the traditional FEM, which confirms that the numerical technique can be used for 3D acoustic radiation problems.

Reference [1] T.F. Dai; X. Jin, H.Z. Yang, T.R. Lin, Y.T. Gu, Smoothed Finite Element Methods for predicting the mid to high frequency acoustic response in the cylinder-head chamber of a diesel engine. (submitted)

Theoretical and Numerical Modeling of the Elastic-Wave in Dynamics Solving 2D Linear Isotropic Elastodynamics by Means of Scalar Potentials: A New Challenge for Finite Elements Jorge Albella Martínez1, Sébastien Imperial,2,3, Patrick Joly2,4, Jerónimo Rodríguez1,5,6 1Dpto. de Matemática Aplicada, Universidade de Santiago de Compostela, 15706 Santiago de Compostela, Spain 2INRIA, Université Paris-Saclay, France 3LMS, Ecole Polytechnique, CNRS, Université Paris-Saclay, France 4UMA, ENSTA, CNRS, Université Paris-Saclay, France 5IMAT, Universidade de Santiago de Compostela, 15706 Santiago de Compostela, Spain 6ITMATI, Campus Sur, 15706 Santiago de Compostela, Spain

When solving 2D linear elastodynamic equations in a homogeneous isotropic media, a Helmholtz decomposition of the displacement field decouples the equations into two scalar wave equations that only interact on the boundary. It is then natural to look for numerical schemes that solve independently the scalar waves problem and are recoupled at the boundary. In [1, 2] the case of rigid boundary condition was treated without any specific difficulty. However in [3] the case of free surface boundary condition was proven to be unstable if a straightforward approach is used. Then an adequate functional framework as well as a time domain mixed formulation to circumvent these issues was presented. In this work we first review the method presented in [3] to then describe in more detail the subsequent stabilized numerical scheme.

References [1] Burel A., Imperiale S., Joly P. Solving the homogeneous isotropic linear elastodynamics equations using potentials and finite elements. The case of the rigid boundary condition. Numerical Analysis and Applications, 5(2):136-143, 2012. [2] Burel A. Contributions à la simulation numérique en élastodynamique: découplage des ondes P et S, modéles asymptotiques pour la traversée de couches minces. PhD thesis, Université Paris Sud-Paris XI, 2014. [3] Albella J., Imperiale S., Joly P., Rodríguez J. Solving 2d linear isotropic elastodynamics by means of scalar potentials: a new challenge for finite elements. Journal of Scientific Computing, 2018.

Theoretical and Numerical Modeling of the Elastic-Wave in Dynamics Propagation of Transient Elastic Wave in Periodically Layered Time-space Modulated Media Subjected to Anti-plane Loading Xiang Zhou1, Yi-Ze Wang2*, Guo-Shuang Shui1, Yue-Sheng Wang2 1Institute of Engineering Mechanics, Beijing Jiaotong University, Beijing 100044, China 2Department of Mechanics, Tianjin University, Tianjin 300350, China *E-mail: [email protected]

In recent years, there is a great attention on elastic metamaterials which can show superior mechanical properties. On the other hand, the transient elastic wave in the elastic metamaterials and phononic crystals is also an interesting and challenging topic. In this work, the propagation of the transient wave in a time-space modulated metamaterials is studied. We consider the interaction of the transient wave in a one- dimensional a periodically layered structure which is subjected to the anti-plane loading. Numerical calculations are performed to show some interesting phenomena.

Acknowledgements The authors acknowledge the supports by the National Natural Science Foundation of China (Grant No. 11532001), the Joint Sino-German Research Project (Grant No. GZ 1355) and the German Research Foundation (DFG, Grant No. ZH 15/27-1) for this research work.

Theoretical and Numerical Modeling of the Elastic-Wave in Dynamics The Research on the Acoustic Propagation in Ideal Drill Strings Yuwen Zhai, Fangqing Deng, Xingmeng Dong, Zhiqiang Yang The 22th Research Institute of China Electronics Technology Corporation, Xinxiang, China

The transmission characteristics of acoustic waves in drill strings have not yet been studied fully. Therefore, the transmission mechanism and property of acoustic waves in the string were analysis firstly. Finite-difference method is used to simulate and analysis the unit impulse function acoustic signal propagation in periodic tube structure. Based on the obtained time domain and frequency domain distribution of the signals, the following conclusions are given. As for the periodical drill string structure, drill string channel structure is the comb filter structure, band pass exists resonant peak, the number of peak is associated with the number of drill string and joint, rational number of the sectional area of drill string and tool joint determine the frequency band of drill string, the decrease of the rational number narrows the band pass.

Theoretical and Numerical Modeling of the Elastic-Wave in Dynamics Retrieving the Characteristics of Elastic Scatterers from FFP Measurements Rabia Djellouli Department of Mathematics & Interdisciplinary Research Institute for the Science (IRIS) California State University Northridge,

We have designed a solution methodology for determining all the parameters characterizing an elastic scatterer (the shape, the material properties, and the location) from its corresponding FFP measurements. To the best of our knowledge, this is the first attempt to solve numerically this challenging inverse scattering problem that is relevant to various real world applications. The proposed numerical approach is a multistage iterative procedure in which a carefully designed regularized Newton algorithm plays a central role. Numerical results will be reported to highlight the computational effectiveness of the proposed multistage strategy.

Theoretical and Numerical Modeling of the Elastic-Wave in Dynamics Theoretical Study and Simulation of Ultrasonic Multi-wave Focusing Imaging DAI Yu-xiang1,2, YAN Shou-guo2, HUANG Juan2, ZHANG Bi-xing1,2 1University of Chinese Academy of Sciences, Beijing, China 2State Key Laboratory of Acoustics, Institute of Acoustics, CAS, Beijing, China

In the traditional phased-array ultrasonic testing, only a single wave (such as P wave) is focused, which results in a low signal-to-noise ratio and poor image resolution. In this paper, a new ultrasonic testing method based on 'multi-wave focusing' is studied: a short pulse emitted by a source inside a solid medium are recorded by the transducers on the surface of medium. Then the time-reversed signals are reemitted by the corresponding transducers respectively. A set of theoretical formulations are proposed to describe this multi-wave focusing process. It is shown that the multiple types of wave such as P wave and S wave can be focused at the source at the same time. Additional, the ultrasonic imaging of internal defects in a semi-infinite solid medium is simulated. The results show that the focusing quality of the multi-wave is related to their respective wavelengths. Compared with the traditional ultrasonic imaging focused by the P wave, the multi-wave containing SV wave can be better focused. So the ultrasonic image obtained by multi-wave focusing has obvious improvement in image resolution and detection signal-to-noise ratio.

Theoretical and Numerical Modeling of the Elastic-Wave in Dynamics Asymptotic Ray Tracing with Velocity Models Based on Sigmoidal Shape Functions for Wave Propagation Modeling S. P. Oliveira Universidade Federal do Paraná, Brazil

Numerical methods based on asymptotic ray theory have been widely applied in seismology, seismic exploration, and acoustics for qualitatively modeling of wave propagation phenomena (see, e.g., [1, 2]). These methods usually have a lower computational cost than others based on a full wave-equation, such as finite- difference and finite-element methods, but have some limitations as well. One of these limitations is the assumption of continuity of the material properties, which can be very restrictive for wave modeling in complex media. One can introduce discontinuities in the model through domain decomposition with reflection/transmission conditions at the interfaces between blocks [4]. In this work, the domain decomposition is avoided (i.e., the ray tracing algorithm operates over the entire domain) with the use of a sigmoidal representation [3] of the material properties, which allow sharp variations without loosing continuity and smoothness. The representation follows the formalism of finite element and Haar wavelet bases. Numerical experiments illustrate the performance of the method in nearly discontinuous models. This work is carried out in collaboration with R. A. Guimarães, A. de Oliveira, and W. J. Silva from Federal University of Paraná (Brazil), and J. S. Azevedo and W. M. Figueiró from Universidade Federal da Bahia (Brazil).

References [1] A. H. Andersen and A. C. Kak, Digital ray tracing in two-dimensional refractive fields, Journal of the Acoustic Society of America 72 (1982), no. 5, 1593–1606. [2] V. Cˇ ervený, Seismic ray theory, Cambridge University Press, Cambridge, 2001. [3] D. Costarelli and R. Spigler, Constructive approximation by superposition of sigmoidal functions, Analysis in Theory and Applications 29 (2013), no. 2, 169– 196. [4] C. A. Zelt and R. B. Smith, Seismic traveltime inversion for 2-D crustal velocity structure, Geophysical Journal International 108 (1992), no. 1, 16–34.

Seismo-Acoustics, Electromagnetics, and Multiphysics Coupling Improved Fast Iterative Method for Higher Calculation Accuracy of Travel-time Wei Cai and Peimin Zhu Institute of Geophysics & Geomatics, China University of Geosciences, Wuhan

Fast Iterative Method (FIM)[1,2] is a new ray tracing method based on the grid for SIMD architecture parallel computing. Compared with the traditional serial fast marching method (FMM), the computing speed has been significantly improved. However, in the classic FIM, the finite-difference scheme usually adopts the first- order Godunov upwind difference scheme, so its calculation accuracy is insufficient. In view of this, this study introduces second-order, mixed-order difference schemes and diagonal point calculation in 2D and 3D Cartesian grids for FIM, and uses double-grid method to improve the accuracy of the near-source region. The model tests show that the new difference schemes and double-grid method can significantly improve the travel-time calculation accuracy and enhance the applicability of FIM. References [1] W. K Jeong, R T. Whitaker. A fast iterative method for eikonal equations, Society for Industrial and Applied Mathematics, 2008, 30(5): 2512-2534. [2] W. K Jeong, S Hong. A group-ordered fast iterative method for eikonal equations, IEEE Transactions on Parallel & Distributed Systems, 2017, 28(2): 318-331.

Seismo-Acoustics, Electromagnetics, and Multiphysics Coupling An Adaptive High-Order Solver for Anisotropic Poroelastic Elastic Fluid Coupling Qiwei Zhan1, Mingwei Zhuang2, Qing Huo Liu1 1)Department of Electrical & Computer Engineering, Duke University, Durham, NC, 27708, USA 2)Institute of Electromagnetics and Acoustics, Xiamen University, Xiamen, Fujian, 361005, China

Porous materials are ubiquitous in the applications for biomedical imaging, soil mechanics, reservoir interpretation, and electrical foamed materials. However, the wave-field coupling between the poroelastic, elastic, and fluid is still a challenging work, especially for anisotropic materials. In the framework of an adaptive high- order discontinuous Galerkin method, a generalized anisotropic wave impedance is proposed, to succinctly solve the Riemann problem for 3-D full-anisotropic poroelastic/elastic/fluid wave propagation [1, 2]. Even though governing equations and dependent physical variables are vastly distinct in poroelastic, elastic, and fluid regions, we introduce a dimension matching matrix, helping unify all the formulations. Numerical results are verified and validated with analytical and numerical solutions. In addition, the long- time stability issue, resolved by the Riemann solver, for anisotropic material interfaces is corroborated. References [1] Q. Zhan, Q. Ren, M. Zhuang, Q. Sun, Q. H. Liu, An exact Riemann solver for wave propagation in arbitrary anisotropic elastic media with fluid coupling. Computer Methods in Applied Mechanics and Engineering 329, 24-39 (2018). [2] Q. Zhan et al., Full-anisotropic poroelastic wave modeling: A discontinuous Galerkin algorithm with a generalized wave impedance. Computer Methods in Applied Mechanics and Engineering 346, 288-311 (2019).

Seismo-Acoustics, Electromagnetics, and Multiphysics Coupling Simulation of Seismoelectric Waves using Finite-Difference Frequency- Space Method: 2-D PSVTM Mode Dongdong Wang, Yongxin Gao School of Civil Engineering, Hefei University of Technology, Hefei, China

We develop a finite-difference frequency-domain (FDFD) method to simulate the 2D PSVTM-mode seismoelectric waves. The method approximates the second-order derivatives and non-derivatives terms of the wave equations using averaged weighting finite-difference operators in a 25-point computational stencil. To suppress the reflections of the seismic and EM waves from the truncated boundaries, we apply the perfectly match layers surrounding the modeled area to absorb the seismic waves, and add several additional layers out of the perfectly matched layers to absorb the EM waves. We validate the FDFD technique by comparing the FDFD solutions in a two- layer model with the solutions from an analytically-base method. The results show that the FDFD solutions agree excellently with analytical solutions in both the seismic and EM signals, proving that the FDFD method is an efficient and powerful tool in modeling the seismoelectric waves. The FDFD method proposed in this paper requires no quasi-static approximation, and thus can be used to accurately model and interpret the seismoelecettric responses in a complex stratum. References [1] Yang Q, Mao W. (2017). Simulation of seismic wave propagation in 2-D poroelastic media using weighted-averaging finite difference stencils in the frequency–space domain. Geophysical Journal International, 208(1), 148-161. [2] Min, D.-J., Shin, C., Kwon, B.-D., & Chung, S. (2000). Improved frequency- domain elastic wave modeling using weighted-averaging difference operators. Geophysics, 65(3), 884-895. [3] Min, D.-J., Shin, C., & Yoo, H. S. (2004). Free-Surface Boundary Condition in Finite-Difference Elastic Wave Modeling. Bulletin of the Seismological Society of America, 94(1), 237-250.

Seismo-Acoustics, Electromagnetics, and Multiphysics Coupling Discrete Differential Forms for the Numerical Solution of Helmholtz Equations Georg Wimmer1, Sebastian Lange2 1)University of Applied Sciences Würzburg-Schweinfurt, Germany 2)Bundeswehr Research Institute for Protective Technologies and CBRN Protection, Munster, Germany

Time harmonic solutions of the wave equation known as Helmholtz type equations occur in computational acoustics and electromagnetics and can be written as 2 2 curl curl E  k E  0 in 3D or Ez  k Ez  0 in 2D (1) 2 2 p  k p  0 in 3D or p  k p  0 in 2D (2) In a 3-dimensional or 2-dimensional bounded domain with smooth boundary

3D or 2D . E denotes the electric field, Ez the z- component of the electric field for electromagnetic applications as an accelerator induction cell and p denotes the pressure in acoustic applications. These equations are well investigated from a theoretical point of view and numerical techniques as the Finite Element method has been used for the numerical solution. However it is important to understand that the electric field E is a vector quantity related to a line. However Ez and p are E quantities related to a vertex. Mathematically speaking is a 1-form and Ez and p are 0-forms. Using differential forms eq. (1) and (2) can be uniformly written as m (1) d * du  * u . Here d denotes the exterior derivative which maps m to (3 m)  forms, * and * denote Hodge-star operators converting m to (3 m)  forms usually containing material properties. Galerkin techniques can applied using the wedge product for multiplication of differential forms. A software implementation based on discrete differential forms is presented in [1] for 3D applications. Stiffness and mass matrices are available for 0-, 1-, 2-forms on different 3D geometries as tetrahedron, hexahedron. We show that the same methodology is available for 2D-problems and investigate the convergence of the eigenfunctions and eigenvalues of (1) and (2) using different refined meshes (h-adaptivity) and Lagrange type interpolatory basis functions of different degree (p-adaptivity) which can be efficiently computed with 1-dimensional Silvester polynomials [2]. References [1] P. Castillo, J. Koning, R. Rieben, M. Stowell and D. White, Discrete Differential Forms: A Novel Methodology for Robust Computational Electromagnetics, Lawrence Livermore National Laboratory, UCRL-ID-151522, 2003. [2] R. D. Graglia and A. F. Peterson, Higher Order Techniques in Computational Electromagnetics (Mario Boella Series on Electromagnetism in Information and Communication), SciTech Publishing, Edison, NJ, 2016, ISBN: 978-1-61353- 016-0. 74

Seismo-Acoustics, Electromagnetics, and Multiphysics Coupling The Effect of Window Length on the Uncertainty of RJMCMC Inversion for Electromagnetic LWD Jian Wang1,2, Lei Zhang1,2, Hao Chen1,2 1)Institute of Acoustics, CAS, Beijing, China 2)Engineering Research Center of sea deep drilling and exploration, Beijing, China Since the ultra-deep directional resistivity logging while drilling (LWD) tool was first introduced a few years ago, it has been widely used in the well placement, the reservoir mapping, the geo-stopping, etc. (Dupuis, 2015). The long spacing exceeding 30 m significantly improves the ability of look-ahead and look-around, which is crucial to reduce drilling risk and maximize reservoir exposure. However, the severe nonlinearity of the responses makes it difficult to invert and interpret. The quality of inversion results depends on the choice of the initial model, and because the tool can detect multiple interfaces, the dimension of model space cannot be fixed in priori. Moreover, low-resolution seismic and shallow-detection depth logging data as model constraints also bring uncertainties to the initial model. For these reasons, an automatic inversion method based on reversible jump Markov chain Monte Carlo (RJ- MCMC) algorithm is recently adopted in the ultra-deep directional resistivity LWD inversion (Wang et al., 2018). The mainly feature of the method is completely data-driven without any bias, and it is also easier to evaluate the uncertainty which is sometimes more important for guiding the drilling. The slipping inversion window technique is usually adopted to satisfy the real-time requirements, and the length of window could affect the computational efficiency and the accuracy of inversion, especially for RJ-MCMC method. However, the choice of the window is usually empirical, though it could be affected by many factors. In this work, we applied the RJ-MCMC algorithm to the inversion of the ultra-deep directional resistivity LWD data. Rather than a best-fit model, the result is a gather of acceptable models, the spread of which gives insights into sensitivities and depths of investigation. Based on the numerical experiments, it is shown that the length of the window has a great influence on the inversion results. Short window is more sensitive to deep layer but tends to lead to a huge uncertainty of model, while the long window could play an important role in getting a good result in shallow layer, though it may not applicable in the deep layer, even obtains an incorrect result. Therefore, only reasonable window length can fully excavate the information contained in the data. However, the window length is a complex function of formation resistivity and investigation depth of tool, the quantitative relationship between them remains to be further studied. References [1] C. Dupuis and J M. Denichou, Automatic inversion of deep-directional- resistivity measurements for well placement and reservoir description. The Leading Edge, (2015), 34(5), 504-512. [2] H. Wang, Q. Shen and J. Chen, Sensitivity Study and Uncertainty Quantification of Azimuthal Propagation Resistivity Measurements. 59th Annual Logging Symposium, SPWLA, (2018). 75

Seismo-Acoustics, Electromagnetics, and Multiphysics Coupling Simulation and Analysis of the Seismoelectric Logging Wavefield Hengshan Hu, Yunda Duan, Wei Guan Department of Astronautics and Mechanics, Harbin Institute of Technology, Harbin, China

Due to the existence of surplus ions in pore channels in rocks, elastic waves in porous rock are usually coupled to electromagnetic field. The coupling equations were given by Pride[1]. Seismologists explained the coseismic electric and magnetic signals when an earthquake occurs[2]. Borehole geophysists wonder if the seismoelectric conversion signals can be used to characterize the porous formation. It this study, we are interested in the simulation of the wavefield generated in seismoelectric well logging, followed by analyses of the each wave component in a full waveform. Let an acoustic transducer be located in the fluid-filled borehole. The porous formation is assumed to be of Biot type and permits Darcy flow. By solving the Pride equations under the borehole wall boundary conditions, expressions are obtained in integral forms for acoustic and electromagnetic waves in both the borehole and the formation. The calculated full waveform of the electric signal at a point on the borehole axis consists of wave groups with acoustic velocities (AE) and a group with electromagnetic (EM) wave velocity. Traveling mechanism for separate waves are analyzed in detail by considering branch-cut integrals and residue contributions. The AE waves includes electric signals accompanying the compressional wave, the shear and pseudo Rayleigh wave, and the Stoneley wave, each with a different acoustic to electric conversion ratio. The EM signal is usually much smaller than the AE signals, but there are exceptions. These exceptions occurs when the salinity changes abruptly from the borehole to the formation. This explains the large EM to AE amplitude ratio in the full waveforms recently recorded in a field test by another research group. References [1] S.R. Pride, Governing equations for the coupled electro-magnetics and acoustics of porous media, Phys.Rev.B, 50 (1994), 15678–15696. [2] H. Hu and Y. Gao, Electromagnetic field generated by a finite fault due to electrokinetic effect, Journal of Geophysical Research-Solid Earth. 116(2011), B08302, doi: 10.1029/2010JB007958.

Seismo-Acoustics, Electromagnetics, and Multiphysics Coupling A Method for Estimation of Acoustic-to-Seismic Transfer Function under Complex Noise Field Tao Jiang1,2, Jing-Ye Wang1,2, Yun-Feng Chao1,2, Qi Zhou1,2, Jing-Han Zheng1,2, Da-Peng Yang1,2 1Jilin University, Key Laboratory of Geophysical Exploration Equipment, Ministry of Education, Changchun, China 2Jilin University, College of Instrumentation & Electrical Engineer, Changchun, China

Air disturbances caused by meteor explosions, explosives and airborne flight caused ground vibrations, which provided a good basis for studying the theory of acoustic-to-seismic coupling. At present, the research on acoustic coupling theory is still in its infancy, mainly because of the lack of reliable observation data. The high impedance of the air-ground interface, complex environmental noise and coupling mechanism of the sensor and the earth make the detection data signal very weak and difficult to detect. In response to this problem, we used the omnidirectional sound source to perform the acoustic-to-seismic coupling experiment of the near-field continuous sound source on a piece of frozen soil in winter. The standard sound source output has a maximum sound pressure level of 90 dB and an ambient noise of approximately 60 dB. As the distance from the sound source increases, the vertical component of the same test point is inconsistent with the frequency bands of the acoustic-to-seismic transfer function peak of a single component signal. After the seismic data is correlated with the standard output signal, the detection signal at a distance is completely submerged by the noise and cannot be identified accurately. Analyze the characteristics of complex environmental noise such as single frequency of power supply and its harmonic interference, wind sound, human walking, air plane and vehicle passing, etc. A single- frequency noise suppression method based on Synchrosqueezing-principal component analysis (SS-PCA) and a spike suppression method based on energy recognition are proposed and combined with random noise characteristics to improve signal quality. The continuous seismic signal is convolved with the output sound source signal and the transfer function is calculated in the frequency domain. The results showed that the acoustic-to-seismic transfer function of the single component signal exhibits a uniform law. The frequency band of the peak of the transfer function narrows as the propagation distance increases, and the lower limit band of the peak band is always around 60 Hz. As the propagation distance continues to increase, the peak band continues to narrow but the number increases. This is not the same as the acoustic-to-seismic coupling transfer function based on plane wave approximation, the possible reasons of this difference are analyzed and simulated, and it is showed that the theory of plane wave approximation in the near field can leads to critical errors.

Seismo-Acoustics, Electromagnetics, and Multiphysics Coupling Estimation and Comparison of Three-Component Acoustic-to- Seismic Coupling Transfer Function of Sound Source near the Surface Jing-Ye Wang1,2, Tao Jiang1,2, Yun-Feng Chao1,2, Qi Zhou1,2, Xin Wang1,2, Fan Zheng1,2 1)Jilin University, Key Laboratory of Geophysical Exploration Equipment, Ministry of Education, Changchun, China 2)Jilin University, College of Instrumentation & Electrical Engineer, Changchun, China

When estimating the amplitude of seismic wave excited by sound sources near the surface, it usually focuses on the vibration projected in the vertical direction. However, solid particles actually have different displacement components in all directions, so the three-component seismic data carries more information about the acoustic-to-seismic coupling process than the single-component data. Field experiments on nearfield continuous sound sources using omnidirectional sound sources on frozen soils show that seismic data with different components in the same three-component seismic station have inconsistent characteristics with frequency attenuation. At the nearest seismic station, the peak frequency band of its vertical component transfer function is 60~150 Hz, and the peak frequency band of the horizontal components is broader, with a range of 50~200 Hz. The radial component has no obvious peak frequency band and appears as multiple frequency points. In addition, by observing the signal after each component is decomposed with the standard output, it is found that the continuation of the signal of the radial components is significantly longer than the other two components. As the distance between the station and the source increases, the energy of radial components is stronger than that of vertical components, while that of horizontal components is the weakest, before that, the energy of vertical components is the strongest, and the horizontal component is similar to the radial component energy. By observing the vibration law of particle based on three component data and simulation, it is believed that the difference of energy is due to the particle vibration first starts to move vertically downward after the acoustic wave is coupled to the underground. The vertical component is the most energetic at this time, and then the retrograde motion rolls forward with the ellipse, which is the most energetic in the direction of the radial.

Seismo-Acoustics, Electromagnetics, and Multiphysics Coupling Localization and Tracking of Low-flying Target Using Single Geophone Array Yunfeng Chao1,2, Guangda Liu1,2, Tao Jiang1,2, Jingye Wang1,2, Xin Wang1,2 1)Jilin University, Key Laboratory of Geophysical Exploration Equipment, Ministry of Education, Changchun, China 2)Jilin University, College of Instrumentation & Electrical Engineer, Changchun, China

Traditionally, arrays of microphones are used to determine the location of acoustic sources, but acoustic arrays are usually disturbed by background noise, such as rain, wind or other natural or artificial source. A method of localization and tracking of low-altitude flying target that only requires a stationary geophone array is proposed. When an airborne target fly at low altitude, the acoustic waves it produces will cause the ground to resonate to form Rayleigh waves. The properties of Rayleigh waves related to air waves can be used for finding the position of a low-flying target as a strong acoustic wave source by a geophone array. The geophone array is a cross array consist of five geophones. The paper analyses low-flying target position localization principle by a cross array. Due to the low sampling rate of seismic system, we present the improved passive location algorithm related to TDOA (Time Difference of Arrival) based on cubic spline interpolation. Combining these locations, this algorithm provides a total least square estimate of the target trajectory. Compared to acoustic array system, the elastic properties of the environment where the geophone is placed efficiently suppress background noise interference, and thanks to their passive principle they provide the users with the advantages of hidden positioning and difficult discovery with reconnaissance tools. The effect and uniqueness of proposed algorithm is also validated by processing the data collected in field experiments.

Seismo-Acoustics, Electromagnetics, and Multiphysics Coupling Microseismic Location Based on Interferometric Imaging and Hilbert-Huang Transform Tingting Zhan1,2,3, Hao Chen1,2,3 1)State Key Laboratory of Acoustics, Institute of Acoustics, Chinese Academy of Sciences, Beijing, China 2)University of Chinese Academy of Sciences, Beijing, China 3)Beijing Engineering Research Center of Sea Deep Drilling and Exploration, Institute of Acoustics, Chinese Academy of Sciences, Beijing, China

For microseismic monitoring, the inaccurate microseismic source location will inevitably lead to misjudgment of the fracture geometry, thus reducing the reliability of microseismic monitoring. The location accuracy is greatly affected by the noise. Therefore, it is necessary and important to improve the location accuracy and the robustness of the source location algorithm under the low SNR condition. Considering the non-stationarity of microseismic signals with strong random noise, a new microseismic event location approach based on interferometric imaging and Hilbert-Huang transform (HHT) is proposed[1]. First, the synthetic microseismic signals are processed to the instantaneous energy spectrums and the Hilbert spectrums by HHT. Then, these two spectrums are respectively used as the characteristic functions of interferometric imaging method for microseismic source location and two different location methods are obtained[2,3]. Finally, in homogeneous medium, the imaging results of the traditional approach and the proposed approach on synthetic low SNR datasets are analyzed and compared. The results demonstrate that the proposed approach can effectively suppress random noise and improves the location accuracy under the low SNR condition. Moreover, the intrinsic mode function (IMF) components and the marginal spectrums of the microseismic signals, obtained by HHT, will be further discussed in detail to improve the location accuracy. These studies are of great significance to real time microseismic monitoring, especially for surface method. References [1] G. T. Schuster, J. Yu and J. Sheng, Interferometric/daylight seismic imaging, Geophysical Journal International 157(2004), no. 2, 838–852. [2] N. Li, B. X. Huang, X. Zhang, et al., Characteristics of microseismic waveforms induced by hydraulic fracturing in coal seam for coal rock dynamic disasters prevention, Safety Science 115(2019), 188-198. [3] L. Q. Huang, H. Hao, X. B. Li, et al., Source identification of microseismic events in underground mines with interferometric imaging and cross wavelet transform, Tunnelling and Underground Space Technology 71(2018), 318–328.

Seismo-Acoustics, Electromagnetics, and Multiphysics Coupling Analytical Solutions of Borehole Acoustic Fields for an Eccentric Drill Collar in the Monopole Acoustic LWD Yunjia Ji1,2,3, Xiao He1,2,3, Zhifeng Sun4, Hao Chen1,2,3 1)State Key Laboratory of Acoustics, Institute of Acoustics, Chinese Academy of Sciences, Beijing, China 2)University of Chinese Academy of Sciences, Beijing, China 3)Beijing Engineering Research Center of Sea Deep Drilling and Exploration, Institute of Acoustics, Chinese Academy of Sciences, Beijing, China 4)China Oilfield Services Limited, Beijing, China Analytical solutions of acoustic fields are derived for the case of an eccentric drill collar inside a fluid-filled borehole, which often troubles us a lot during logging while drilling (LWD) due to complex string movements [1, 2]. The formations are derived from both the Navier’s equations of linear elasticity for solid materials and the wave equations for fluids through the typical means of separation of variables [3]. Two cylindrical coordinate systems are employed to describe the wave fields, which are related by Graf’s addition theorem for Bessel functions. The exact boundary conditions are applied to relate the elasto-acoustic fields in each layer [4]. The solutions of the fields are obtained in the frequency-wavenumber domain by solving an infinite system of linear equations. With this method, the borehole wave fields of such condition are investigated excited by a monopole source with the center frequency of 8 kHz in fast formations. The effects on the waveforms at different azimuths and for different orders, caused by an off-center drill collar with varying tool offsets, are analyzed. The results show that the full waveforms in the direction of the tool offset have the maximum amplitude; while in the opposite azimuth appears the minimum. This feature can be partly explained by the characteristics of the waveforms for different orders, that is, waveforms of adjacent orders have contrary phases. Moreover, in the case of severe eccentricity, some interesting phenomena about Stoneley wave are featured, which need to be discussed in detail. These studies will be helpful for tool design and data processing. References [1] S. M. Haugland, Analytical Solution for an Eccentric Mandrel in a Fluid-Filled Borehole: The Acoustic Case, SEG, Denver, 2004. [2] S. M. Haugland, Mandrel Eccentricity Effects on Acoustic Borehole-Guided Waves, SEG, Denver, 2004. [3] X. He, X. M. Wang, H. Chen, Theoretical simulations of wave field variation excited by a monopole within collar for acoustic logging while drilling, Wave Motion 72 (2017), 287- 302. [4] S. M. Hasheminejad, H. Mousavi-Akbarzadeh, Three dimensional non- axisymmetric transient acoustic radiation from an eccentric hollow cylinder, Wave Motion 50 (2013), no. 4, 723-738.

Seismo-Acoustics, Electromagnetics, and Multiphysics Coupling Simulation of Reflection and Scattering Waves in Acoustic Logging While Drilling Pan Yue1,2,3, He Xiao1,2,3, Chen Hao1,2,3 1)State Key Laboratory of Acoustics, Institute of Acoustics, Chinese Academy of Sciences, Beijing 100190, China 2)University of Chinese Academy of Sciences, Beijing 100049, China 3)Beijing Engineering Research Center of sea deep drilling and exploration, Beijing 100190, China

To extract the reflection signals from the logging while drilling (LWD) data for the goal of geo-steering, it is significant to investigate the propagation of those arrivals separately. Yet the medium discontinuity at the drill bit and the bottom of borehole produces reflection responses, which can cover the effective signals. In this work, we investigate the wave fields generated by the scattering effect, which confirmed the collar and Stoneley waves will each produce a powerful reflection of Stoneley and collar waves at the bottom of the well, by simulation result of the finite difference modeling[1,2,3]. In the model of the heterogeneous formation outside the borehole, scattered waves from the bottom of the well are generally much stronger than the reflected waves from the formation boundary. By means of numerical simulation and ray analysis, propagation mechanisms of two kinds of reflection waves in the LWD models are revealed[2]. The first kind is the direct waves, which radiates into the formation and then reflects back to the borehole and propagates along the collar. Their phase velocity obtained from the arrays matches well with the theoretical speed of the collar wave. Second, either the collar or the Stoneley wave transmits to the borehole bottom and scatters outward. And those radiation waves can also reflect at the bed boundary. The arrival time of the reflected wave of each component in the numerical simulation results is consistent with the expected result of the ray theory. These reflected and converted waves make the full wave signals more complicated, which will surely bring new challenges to data processing and imaging of remote acoustic logging while drilling. References [1] Chen X L, Wei Z T, Numerical simulation of single-pole acoustic reflection logging while drilling, Journal of Petroleum, 2012, 33(5): 835-840. [2] He X , Wang X , Chen H, Theoretical simulations of wave field variation excited by a monopole within collar for acoustic logging while drilling, Wave Motion, 2017, 72:287- 302. [3] Wang T, Tang X M. 2003. LWD Finite-difference Modeling of elastic wave propagation: A nonsplitting perfectly matched layer approach. Geophysics, 68(5):1749-1755.

Seismo-Acoustics, Electromagnetics, and Multiphysics Coupling Anisotropy Inversion using a Small-diameter Acoustic Logging Tool with Separated Cross-dipole Sources Chao Li1,2, Hao Chen1,2, Xiao He1,2, Xiu-Ming Wang1,2, Fu-Qiang Zeng3 1)Beijing Engineering and Technology Research Center for Deep Drilling Exploration and Measurement, Beijing, China 2)State Key Laboratory of Acoustics, Institute of Acoustics, Chinese Academy of Sciences, Beijing, China 3)State Key Laboratory of Petroleum Resources and Prospecting, China University of Petroleum-Beijing, Beijing, China

Anisotropy is widely existing in the sedimentary rocks. Cross-dipole acoustic logging is commonly used to obtain the azimuth anisotropy in the HTI (Horizontal Transverse Isotropy) formation. Since slim hole drilling technology has been utilized in oil and mining industry, the corresponding diameter of logging devices should also be reduced. In such cases, it would be a challenge to design a cross-dipole acoustic logging tool with the two dipole sources assembling in the same position. We develop an anisotropy inversion method for a small-diameter acoustic logging tool with separated cross-dipole sources. Additionally, the unmatched property of the fast and slow flexural waves caused by the transmitter and formation is considered. An objective function in frequency domain in consideration of the source-receiver spacing and wave amplitude difference is constructed. Firstly, four- component cross-dipole acoustic logging responses with different source-receiver spacing and source signals are simulated in HTI medium. Then the fast and slow flexural wave slowness and azimuth are inverted with a single dipole source and two separated cross-dipole sources respectively. The results using a single dipole source show that it can acquire anisotropy under favorable conditions. The inversion with two separated cross-dipole sources can achieve more accurate results. Finally, the method is used in field data processing which further testify its effectiveness. Therefore, an anisotropy inversion method for separated cross-dipole sources is developed, which could be used both for small-diameter tool and other tools without requiring the cross-dipole sources are collocated. References [1] Alford, R. M., Shear data in the presence of azimuthal anisotropy, 56th Annual International Meeting, SEG Technical Program Expanded Abstracts (1986), 476–479. [2] Bose, S., Sinha, B.K., Sunaga, S., Endo, T., and Valero, H.P., Anisotropy processing without matched cross-dipole transmitters, 77th Annual International Meeting, SEG Technical Program Expanded Abstracts (2007), 114-118. [3] Tang, X. M., and R. K. Chunduru, Simultaneous inversion of formation shear- wave anisotropy parameters from cross-dipole acoustic-array waveform data, Geophysics 64 (1999), 1502–1511. [4] Zeng F., Yue W., Li C., Anisotropy inversion in the frequency domain for flexural waves with unmatched sources, IEEE Geoscience and Remote Sensing Letters 15 (2018), no.10, 1530-1534. 83

Seismo-Acoustics, Electromagnetics, and Multiphysics Coupling Digital Rock Physics-based Acoustic Properties Modelling of Carbonate Rocks Jianguo Zhao, Yangming Hu, Langqiu Sun, Fang Ouyang, Zhi Li, Zengjia Xiao China University of Petroleum (Beijing), State Key Laboratory of Petroleum Resources and Prospecting, Key Laboratory of Geophysical Prospecting, ChangPing, Beijing The digital rock physics (DRP) works on the real rock models that can provide physical properties of rocks quantitatively for further study, and effectively simulate the real rock model with complicated pore structures and lithological characters. The DRP workflow primarily consists of three steps: three-dimensional image acquisition, raw image processing and physical properties simulation. Linear elastic finite element method (FEM) solver based on microstructure images was utilized to estimate the elastic properties. We first verified FEM results by those from ultrasonic measurements, then derived cross-property correlations for acoustic velocity and porosity. Without consideration of pore type diversity, most of model used to explain the relationship between rock acoustic properties and reservoir parameters usually does not work. A frame flexibility factor (γ) used in carbonate rock physics model can quantify the effect of pore type changes on seismic velocity. We find that for a certain porosity, the lower γ, the higher the acoustic velocity. The samples with low γ (γ <3) represents the moldic pores in dolomite, and the medium γ (3<γ<6) stand for the dissolved intercrystalline pores, while high γ (γ>6) characterize fractures or microcrack. The -φ can be effectively classified with γ according to different pore type that helps to improve the accuracy of porosity prediction.

References [1] Garboczi, E.J., and Day, A.R. An algorithm for computing the effective linear elastic properties of heterogeneous materials: three-dimensional results for composites with equal phase poisson ratios. J. Mech. Phys. Solids 43 (1995), 1349–1362. [2] Sun, Y. F., Effects of pore structure on elastic wave propagation in rocks, AVO modeling, Journal of Geophysics and Engineering, 1(2004), 268 – 276. 84

Seismo-Acoustics, Electromagnetics, and Multiphysics Coupling Digital Rock Physics Based Pore Structure Characterization of Carbonate Rocks Yangming Hu, Jianguo Zhao, Langqiu Sun, Fang Ouyang Department of Geophysics, China University of Petroleum, Beijing, P.R.China Finding the exact correlation between pore structure and elastic properties of carbonate rocks is always a difficult problem remained to be solved in oil and gas industry. This paper tried to explore a way to address this problem by digital rock physics. The digital rock physics (DRP) works on real rock models that can provide physical properties of rocks quantitatively for further study, and effectively simulate the real rock model with complicated pore structures and lithological characters. The most critical step in the application of digital rock physics in carbonate rock is image processing to build accurate and reliable digital rock models. This paper proposed a set of image processing methods which forms an effective workflow to solve this problem. We first examined and evaluated crucial parameters of anisotropic diffusion filtering, and then made the image achieved best level of smoothing [1]. After that, the phase edge of matrix and pores was extracted through a gradient kernel edge detector, thus we got phase edge enhanced images. On this basis, we then chose Otsu’s algorithm to implement the segmentation of pre-processed images, which showed in Figure 1 (a-b) [2]. From the rigorous workflow mentioned above, we successfully got the digital rock model (Figure (c-d)), and we verified its accuracy by helium porosity measured in laboratory. The digital rock model was then used to simulate the elastic properties with FEM solver. Based on 3D porous structure of each digital rock model, we classified such FEM data points into several groups by different pore type indicator calculated from Sun’s model[3]. Through the classification approach in terms of pore type, one can obtain better correlations between acoustic velocity and porosity concerning with different pore-type carbonate.

(a) (b) (c) (d) Fig 1. (a) Original CT image after filtering. (b) Segmentation results from (a). (c) Rock frame after segmentation. (d) Pore structure after segmentation. References [1] P. Perona, J. Malik, Scale space and edge detection using anisotropic diffusion [J]. IEEE Transactions on Image Processing 12 (8) (1990) 629–639. [2] Otsu N. A Threshold Selection Method from Gray-Level Histograms [J]. IEEE Transactions on Systems, Man, and Cybernetics, 1979, 9(1):62-66. [3] Sun, Y.F., On the foundations of the dynamical theory of fractured porous media and the gravity variations caused by dilatancies [D]. Columbia Univ., New York, 1994. 85

Seismo-Acoustics, Electromagnetics, and Multiphysics Coupling Estimation of Acoustic Properties of Rock Samples in the Low Frequency Range Jianguo Zhao, Yangming Hu, Langqiu Sun, Fang Ouyang, Zhi Li, Zengjia Xiao China University of Petroleum (Beijing), State Key Laboratory of Petroleum Resources and Prospecting, Key Laboratory of Geophysical Prospecting, ChangPing, Beijing Many theories have been developed to predict and interpret the seismic wave dispersion in fluid-saturated reservoir rocks. These theoretical models play important roles in understanding the dispersion mechanism on seismic wave propagation, however, still remain unconstrained by experimental data due to the scarcity of laboratory measurements, especially at low seismic frequency range. At present, the ultrasonic transmission method is the mostly used laboratory measurement technique to determine the acoustic properties of fluid-saturated reservoir rocks, and further dispersion studies are implemented via the ultrasonic method-based measurements. However, considerable efforts have to be made to reconcile high-frequency (ultrasonic method, MHz) measurement results to low-frequency (seismic frequency, <100Hz) applications. To obtain the direct laboratory-scale dispersion measurements, especially at the low seismic frequency range, we laboratory have developed systematic measurement techniques to investigate the elastic properties of partially fluid-saturated rock, which cover frequency bands from seismic frequency range to ultrasonic range. The multi- band measurement techniques provide great potential to clarify the features of wave dispersion and attenuation in the reservoir rocks from seismic to ultrasonic frequency range, especially due to the presence of fluid. Two devices involved in the direct low-frequency measurement techniques are differential acoustic resonance spectroscopy (DARS) and stress-strain measurement system based on the forced oscillation method, respectively. It proves that the two measurement techniques, in conjunction with traditional ultrasonic method, form the Multi-band direct laboratory measurement methodology relative to dispersion studies on reservoir rocks. Meanwhile, μ-CT scanning-based digital rock technique makes possible to investigate the influence of pore structures and shapes on the seismic wave dispersion. In conclusion, systematic measurement techniques have been developed to investigate the elastic properties of partially fluid-saturated rock, which cover frequency bands from seismic to ultrasonic range. Two devices involved in the study are DARS and stress-strain systems, respectively. It proves that the two measurement techniques, in conjunction with traditional ultrasonic method, form the Multi-band direct laboratory measurement methodology of dispersion studies on reservoir rocks. Meanwhile, μ-CT scanning based digital rock technique makes possible to further investigate the influence of pore structures and shapes on the seismic wave dispersion. References [1] Garboczi, E.J., and Day, A.R. An algorithm for computing the effective linear elastic properties of heterogeneous materials: three-dimensional results for composites with equal phase poisson ratios. J. Mech. Phys. Solids 43 (1995), 1349–1362. [2] Sun, Y. F., Effects of pore structure on elastic wave propagation in rocks, AVO modeling, Journal of Geo-physics and Engineering, 1(2004), 268 – 276. 86

Seismo-Acoustics, Electromagnetics, and Multiphysics Coupling A Combined Model for Predicting Frequency-dependent Elastic Properties in Sandstones Fang Ouyang, Jianguo Zhao, Zhi Li, Zengjia Xiao Department of Geophysics, China University of Petroleum Beijing, China A procedure based on rock physics models is presented for estimating the frequency- dependent elastic properties in fluid-filled sandstones. In the study, the pore space of the sandstones is assumed to contain a distribution of penny-shaped crack (soft pores) aspect ratios, along with one family of stiff pores having an aspect ratio lying somewhere between 0.01 and 1. In general, the procedure consists of five steps (Figure1): I. Minerals present in the rock are mixed by mixing law (e.g., the Reuss-Voigt-Hill average). We start with a solid rock matrix having the properties of this mixture. II. The pore structure (e.g., pore aspect ratio distribution and crack porosity distribution) in the rock is extracted from the pressure dependence of dry velocities, following the idea provided by David and Zimmermann [1]. III. All pores including cracks and stiff pores are added into the solid matrix using the effective medium theory to provide the effective elastic properties. IV. Only the cracks are saturated with liquid to obtain a “wet frame” of the rock. In the “wet frame”, the fluid flow between cracks and stiff pores is described using a simple squirt flow model [2]. Therefore, the resultant “wet frame moduli” is a function of frequency and pressure. V. White’s patchy-saturation model[3] is used as the dispersion and attenuation scheme to account for the mesoscopic-loss mechanism. The proposed model can be used to estimate the velocity dispersion and attenuation as functions of frequency, saturation and pressure in a broad frequency range. The study has potential to bring large convenience for seismic velocity prediction.

Fig 1. Procedure for prediction of frequency-dependent properties References [1] E. C. David, and R. W. Zimmerman, Pore structure model for elastic wave velocities in fluid-saturated sandstones, Journal of Geophysical Research 117 (2012), B07210, 1–15. [2] B. Gurevich, D. Makarynska, O. Bastos de Paula, and M. Pervukhina, A simple model for squirt-flow dispersion and attenuation in fluid-saturated granular rocks, Geophydiscs 76 (2010), no. 6, N109–N120. [3] J. E. White, Computed seismic speeds and attenuation in rocks with partial gas saturation, Geophydiscs 40 (1975), no. 2, 224–232. 87

Seismo-Acoustics, Electromagnetics, and Multiphysics Coupling Seismic Waveform and Its Spectrum Yuefeng Sun Department of Geology and Geophysics, Texas A&M University, USA

Seismic, acoustic or electromagnetic disturbance changes its amplitude, frequency and phase as it propagates in corporeal composites, resulting in different waveforms in space and time. The waveforms thus carry or encode important information or characteristics of the source and the medium in which they propagate. The spectrum of a waveform has been studied most often than its temporal wavelet. For example, studies of absorption of electromagnetic radiation by a blackbody gave rise to the Planck's law which reveals or implies the energy quantization with frequency. For seismic disturbance, Norman Hurd Ricker applied the Stokes equation to elastic solid considering the internal friction or viscosity and formulated the wavelet spectrum in a closed form, of which its temporal waveform being referred to as the "Ricker wavelet" has been rather widely known. In this report, we estimate time-varying waveforms from field seismic data and analyze their spectra using Ricker wavelet spectrum and analogous Wien's law and Planck's law. Results show that when frequency is less than the dominant frequency of the wavelet which is about 30 Hz for the studied time interval, Ricker wavelet spectrum is close to that calculated from the Wien's law. When frequency is greater than the dominant frequency of the wavelet, calculated spectra from the Wien's law and the Planck's law agrees with each other. When frequency is very low, for example, < 10 Hz, both Ricker spectrum and Wien's Law overestimate the energy absorption and the spectrum calculated from the Planck's law fits the field data better. However, when frequency is greater than the dominant frequency of the wavelet, all three theoretical wavelet spectra severely underestimate the absorption.

Signal Processing in Shallow Water

Research on Low-Frequency Underwater Locator Beacon for Aviation Wen-Yang Liu1, Richard Jih2, Chi-Fang Chen1 1 Department of Engineering Science and Ocean Engineering, National Taiwan University 2 Investigation Lab, Aviation Safety Council, Republic of China

Flight recorder is placed in an aircraft, which is also known by the “black box”, but its actual color is bright orange to aid in its recovery after accident. Thus if the airplane crashes and plumps into water, the underwater locater beacon (ULB) will be activated and emit supersonic sound at 37.5 kHz for 30 days. After 30 days, the signal will be lost due to insufficient power, which highlights the urgency of the investigation and positioning of the flight recorder. In order to improve this problem, a new Low Frequency Underwater Locator Device (L-F ULD) has been recommended by ICAO for overwater operations as of January 1, 2018. EASA has adopted this requirement and demands compliance from January 1, 2019. Other countries have similar regulations. The L-F ULD itself will transmit an 8.8 kHz acoustic signal (pinger) for a minimum of 90 days. Its low frequency will increase the detection range at 13-22 km (7-12 NM) over the standard ULB (37.5 kHz). The main goal of this work is to explore the underwater sound propagation of ULB and help improve search and location methods.

Signal Processing in Shallow Water The Motion Compensation Method of the Side Scan Sonar Liu Jia, Ma Ming yang, Xu Feng Institute of Acoustic, Chinese Academy of sciences, Beijing, China [email protected]

Side-scan sonar is an important tool in ocean survey and marine objects detection. Side-scan sonar has a high imaging rate and provides high resolution images of the seabed. This imagery technique has long been a field of intense research interest for both military and civilian applications. They can provide the users with images which have high resolution and long ranges of hundreds of meters, even in turbid waters. These advantages make it widely used on AUV, USV and ships. While conventional side-scan systems will be influenced duo to the motion of vehicle, including rolling, pitching and yawing, especially when the vehicle is used in the shallow water. The image of side scan sonar will be distorted, and the image of seafloor does not guarantee to provide full bottom coverage. To solve the problem, a new side scan sonar system is introduced. The motion compensation method of sonar is applied in the sonar system. The attitude and heading information of vehicle was got by the navigation system. Then the beamforming is compensated with the parameters. The real-time pixels are calculated at each frame. So the sonar will focus at every single pixel in the images. At last, the high quality images could be obtained. The simulation result shows the proposed motion compensation method is validity.

Signal Processing in Shallow Water Improved Robust Adaptive Beamforming Based on Correlated Projection and Reconstruction for Imaging Sonar Lu Yan1,2, Shengchun Piao1, Tian Chen2, Feng Xu2, 1 College of Underwater Acoustic Engineering, Harbin Engineering University, Harbin, China 2 Institute of Acoustics, CAS, Beijing, China

Robust adaptive beamforming has recently been proposed as an attractive alternative to conventional beamforming in imaging sonar. Compared to conventional beamforming methods, adaptive beamforming is often able to improve image quality in radar, ultrasound, imaging sonar. However, adaptive beamforming is not inherently robust, and may suffer from a phenomenon called desired signal cancellation in active systems. The performance of adaptive beamforming approach degrades severely in presence of signal model mismatch, especially when the desired signal is present in the training snapshots, since the desired signal is considered as interference to be suppressed. Therefore, an improved robust adaptive beamforming for imaging sonar system is proposed based on correlated projection and matrix reconstruction to eliminate the desired signal cancellation effect and improve robustness. In the proposed method, the desired signal corresponding eigenvector is estimated firstly utilizing the correlated projection. Then the interference-plus-noise covariance matrix is accurately reconstructed to remove desire signal from sample covariance matrix. Afterwards, the weighted vector is corrected by using the adaptive beamforming to eliminate the noise perturbation and improve robustness. Simulation results demonstrate that the performance of proposed approach is enhanced in many scenarios. In addition, at-lake experiments using sector-scan imaging sonar also demonstrate the proposed approach could eliminate the desired signal cancellation effect and improve image quality.

Signal Processing in Shallow Water Multi-mode Excitation of Frequency Modulated Signals in Shallow Water Xiaofeng Yi1,2,3, Dayong Peng1,2, Juan Zeng1,2, Li Ma1,2 1 Institute of Acoustics, CAS, Beijing, China 2 Key Laboratory of Underwater Acoustic Environment, CAS, Beijing, China 3 University of Chinese Academy of Sciences, Beijing, China

A multi-mode sound field excitation method of linear frequency modulated (LFM) and hyperbolic frequency modulated (HFM) signals using a vertical source array (VSA) in shallow water is proposed. The eigenvalues and modal functions of the low-order modes are calculated using the carrier frequency based on normal mode theory. Then by adjusting the weight coefficient of VSA to stack the low-order modes in same phase at specific position, the sound field focusing effect can be realized within a certain space around the specific position. Because the lower-order modes have relatively lower sensitivity to environment parameters compared to the higher-order modes, the environment mismatch has less influence on multi-mode excitation. The simulations of multi-mode excitation of LFM and HFM signals in Pekeris waveguide show that using the first three modes can realize a robust multi- mode focusing effect at most water depths when the bandwidth is much less than the carrier frequency. And by scanning the focusing depth using the multi-mode excitation method, the target depth discrimination can be realized according to the target echo strength of different focusing depths, which indicates that the multi-mode excitation method of frequency-modulated signals has a broad application prospect in active detection.

Signal Processing in Shallow Water Time Domain Electromagnetic Modeling Capability for Shallow Water Buried Targets Yue Zhao, Feng Xu, Jia Liu, Lijun Jiang Institute of Acoustics, Chinese Academy of Sciences, Beijing, China

It is an ongoing challenge to detect and recognize the underwater buried targets, especially in the very shallow water region. Recently, several sensor technologies have been made in detecting and identifying underwater small targets, including the use of imaging sonar (SLS, FLS, SAS et al.), magnetometers (total-field and gradiometers), various types of time-domain and frequency-domain electromagnetic induction (EMI). However, the shallow water environment presents an especially difficult challenge for conventional high frequency sonars to be effective. Interfering reverberations from the air/sea and sea/bottom interfaces, bottom topographical features, and debris clutter may lead to a high false-alarm rate using conventional imaging sonar approach. In addition, the use of non-ferrous materials will limit the effectiveness of magnetometers. In this study, we develop a new approach based on the principle of EMI as a supplement of conventional imaging sonars. Time domain electromagnetic (TEM) is a time domain EMI method and has been successfully applied in the detection of the land UXO (Unexploded Ordnance). In the TEM method a time varying magnetic field is used to illuminate a conducting target. The magnetic field decay with time, the rate of decay and the spatial behavior of the magnetic field is determined by the target's conductivity, magnetic permeability, shape, and size. Since the shallow water TEM is still in its infancy, it is necessary to study its exploration capability and select the best system parameters for the undersea system. Detection and location of different kinds of undersea buried targets are crucial strategic tasks. For this purpose, we using vector finite element (VFEM) algorithm to simulate the TEM response of 3D underwater structure. Then, we can analyze the influence of various parameters (seawater depth, configuration size and seafloor conductivity) on TEM detection capability. Finally, we acquire the information of position and conductivity of buried targets by using nonlinear inversion algorithm.

Signal Processing in Shallow Water Underwater Target High-frequency Acoustics Scattering Simulation with High Performances Computing Lian-hui Jia, Yang Zhang, Gui-juan Li, Jin Bai Science and Technology on Underwater Test and Control Laboratory, Dalian, China

Numerical simulation is one of the most important methods for predicting the acoustic scattering characteristics of underwater targets. Finite element method (FEM), boundary element method (BEM) and Kirchhoff approximation (KA) are commonly used numerical methods for underwater target acoustic scattering prediction. KA method is generally more suitable for high-frequency acoustic scattering characteristics prediction, since FEM and BEM are too expensive under such conditions. KA method needs to differentiate light domain and shadow domain in monostatic scattering, and half-shadow domain in bistatic scattering extra. This distinction calculation takes a lot of time sometimes, especially when the target geometry is complex and multiple objects scattering interactions. This paper established a fast distinguishing algorithm based on the linked list search (LLS) method to solve the problem. Through the projection transformation, the underwater target surface elements are projected onto the incident wave plane or the receiving plane, and the background mesh cell is divided on the projection plane. The fast distinction of light domain and shadow domain implement by dividing calculation areas and planning a reasonable computing order, while using OpenMP parallel technology. Taking an underwater vehicle as an example, target strength (TS) under the condition of 0 to 180 degree in monostatic scattering is calculated by traditional method and the fast distinguishing algorithm. And parallel computational speedup and efficiency are discussed. Results are good and show that this method can effectively improve the computing speed without reducing the accuracy on underwater target high-frequency acoustic scattering TS prediction.

Signal Processing in Shallow Water The Sequential Source Localization Using Unscented Particle Filter Lin Su1,2, Shengming Guo1,2, Yuqing Jia1,2,3, Li Ma 1,2 1 Key laboratory of underwater Acoustics Environment CAS, Beijing, China 2 Institute of Acoustics, CAS, Beijing, China 3 University of Chinese Academy of Sciences, Beijing, China

Ocean dynamic processes such as sea waves, rainfall and internal waves will lead to the modeling mismatch and influence the performance of source localization of matched filed processor (MFP). Based on the empirical orthogonal functions (EOFs) and the state-space model which describe the evolution characteristics of sound speed profile (SSP), source range and depth are estimated via the acoustic array data simulated by the measured SSPs and prior seabed acoustic properties. In consideration of the characteristics of nonlinear systems and non-Gaussian distributions in the underwater acoustic channel, an algorithm of the unscented particle filter (UPF) is implemented for the tracking of moving source under the circumstances of time-evolving sound speed profiles. The validity and practicality are demonstrated by the simulation, which indicates that the proposed scheme enables the continuous tracking of the moving source.

References [1] Yardim C, Gerstoft P, and Hodgkiss W S. Tracking of geoacoustic parameters using Kalman and particle filter. J Acoust Soc Am.，125(2009), no.2, 746-760. [2] Carriere O, Hermand J P, and Candy J V. Inversion for time-evolving soundspeed field in a shallow ocean by ensemble Kalman filtering. IEEE J. Ocean. Eng., 34(2009), no.4, 586-602. [3] T Lin, Michalopoulou Z H. Sound speed estimation and source localization with linearization and particle filtering. J Acoust Soc Am., 135(2014), no.5, 1115- 1126

Signal Processing in Shallow Water Two Methods Adaptive Interference Suppression for Underwater Target Estimation Suiling Ren, Lianrong Chen, Yanli Chen, Dong Wang State Key Laboratory of Acoustics, Institute of Acoustics, Chinese Academy of Sciences

It is generally difficult for a passive sonar system to localize a weak source due to the complexity and variability of the ocean environment, especially in the presence of strong interferences. Two methods, an eigenanalysis-based adaptive interference suppression (EAAIS) method [1] and a sparse-representation-based adaptive interference suppression (SRAIS) method [2], have been proposed for estimating the weak source bearing, which are always mutually complementary. The EAAIS method can provide much more robust interference rejection capability but not work effectively when the input powers of the target signal and the interferences are at the almost same level. Instead, the SRAIS method can reduce the power loss of the target signal and has more accurate DOA estimates when the input powers of the target signal and the interferences are at the almost same level or even the TOI and the interferences are closely spaced. In this paper, we mainly compared the interference rejection capability of these two methods for different signal to noise ratio (SNR) and signal to interference ratio (SIR). Simulation and experimental results demonstrate the performance of the proposed methods.

References [1] Suiling Ren, Feng-Xiang Ge, Xin Guo, and Lianghao Guo. Eigenanalysis-Based Adaptive Interference Suppression and Its Application in Acoustic Source Range Estimation, IEEE J. Ocean. Eng., October 2015, 40(4): 903–916. [2] Yishu Shi, Suiling Ren, F. X. Ge and Ying Chen. Sparse-representation-based adaptive interference suppression, in Proc. Oceans. IEEE, 2015.

Signal Processing in Shallow Water Source Depth Determination Through Improved Depth-based Signal Separation in the Deep Sea Wenbo Wang1,2,3, Lin Su 1,2, Tao Hu 1,2, Li Ma 1,2, Qunyan Ren 1,2 1Key Laboratory of Underwater Acoustic Environment, Beijing, China 2 Institute of Acoustics, CAS, Beijing, China 3 University of Chinese Academy of Science, Beijing, China

In deep-sea environment, the interference with distance and frequency can be observed on the receiving path. However, source depth separated from distance interference depends on horizontal aperture of array or horizontal information of source movement. The frequency interference structure of broadband sound source receiving at fixed point is very sensitive to source depth, but it is easily submerged by noise. In this paper, an improved depth-based signal separation method is proposed to process broadband signals received by short vertical linear arrays, which can estimate the depth of deep-sea submerged target in the complex environment of low SNR or multi-target environment. The simulation results show that this method does not need environmental information, nor does it need to acquire the distance and velocity of the source. The effectiveness of this method is also proved by actual sea trial data.

References [1] R. McCargar and L. M. Zurk, Depth-based signal separation with vertical line arrays in the deep ocean, J. Acoust. Soc. Am. (2013), 133(4), EL320–EL325. [2] G. P. Kniffin, J. K. Boyle, L. M. Zurk and M. SideriusZHM, Performance metrics for depth-based signal separation using deep vertical line arrays, J. Acoust. Soc. Am. (2016), 139(1), 418–425

Signal Processing in Shallow Water Source Depth Estimation Based on Mode Phase Matching in Shallow Water Huaigang Cao1,2,3, Zhendong Zhao1,2, Shengming Guo1,2, Li Ma1,2 1 Institute of Acoustics, Chinese Academy of Science, Beijing, China 2 Key Laboratory of Underwater Acoustics Environment, Chinese Academy of Sciences, Beijing, China 3 University of Chinese Academy of Science, Beijing, China

Aiming at the problem of passive continuous source depth estimation in shallow water waveguides, a passive source depth estimation method with a vertical line array processing is proposed in this paper. The method estimates the source depth through matching the phase of modes. In this method, the signal received from a vertical line array is used to get normal mode coefficients by mode decomposition processing which relies on a normal-mode propagation model, and thus requires prior knowledge of the mode characteristics. After mode decomposition processing, the phase relation can be obtained from the specific value of adjacent normal mode coefficient. According to phase relation of different modes, the depth of source can be estimated. Comparing with traditional matched mode processing, this method has lower requirements for the hydrophone spacing of the vertical line array. Simulation and experimental results show that the depth of the source can be estimated even if the depth sampling is not sufficient and the decomposition of normal waves is not ideal.

Signal Processing in Shallow Water Fast Recursive Updating the Eigenvalue and Eigenvector Decomposition for Array Signal Processing Chao Yan, Lianghao Guo, Weiyu Zhang, Peng Xu State Key Laboratory of Acoustics, Institute of Acoustics, Chinese Academy of Sciences

In this paper, first we analyze the compute architecture of the adaptive beamformer. And we find that in most cases, the eigenvalue and eigenvector decomposition take the most compute resources, such as MUSIC, ESPRIT and some robust MVDR algorithm. In general speaking, there are two methods to form the input data covariance matrix: sliding window and forgetting factor, and both of them just update a little data to form the covariance matrix. We propose a matched framework and method for recursive updating the eigenvalue and the eigenvetor decomposition. And the analysis shows that the complexity of the method we proposed reduces computational complexity from O(M3) to O(M2) successfully. With the software optimization, some algorithm can run in real time on the original processing system.

References [1] Kai-Bor Yu, Recursive Updating the Eigenvalue Decomposition of a Covariance Matrix, IEEE Trans. Signal Process., May 1991, 39(5): 1136~1144.

Ambient Noise and Its Effect on Aquatic Animals Assessing Underwater Noise Impacts on Chinese White Dolphins within Hong Kong Waters Matthew K. Pine*1,2, Ding Wang3, Kexiong Wang3 1Department of Biology, University of Victoria, British Columbia Canada 2Ocean Acoustics Limited, Auckland, New Zealand 3Institute of Hydrobiology, Chinese Academy of Sciences, Wuhan, PR China. *Telephone: +64-22-695-8957 *Email: [email protected]

The ability for dolphins to communicate and sense their environment using sound underwater is highly reliant on their ambient acoustic environment, as biologically-important signals must be audible over the background sound level. Hong Kong has been the site for several large-scale projects and high shipping activity for many years. These activities are capable of generating high levels of underwater noise that, within some range, can lead to physiological impacts and interfere with a cetacean’s ability to perceive biologically-important signals. Percussive piling is a major source of anthropogenic noise associated with many offshore developments in Hong Kong, yet very few studies have investigated this noise source in the region. Here, we discuss the potential noise impacts of percussive piling associated with the proposed construction of a liquefied natural gas platform near the Soko Islands. This assessment was done using advanced acoustic propagation models, as well as empirical data on the dolphin’s hearing biology and ambient soundscape. Based on the United States National Marine Fisheries Service (NMFS) 2018 harassment guidance, noise from percussive piling works is capable of having short-term auditory masking, behavioural and physiological effects within a limited radius around the source, even with mitigation put in place. Of particular concern is the potential occurrence of those impacts within a proposed marine protected area designed to protect an important Chinese white dolphin habitat. Consequently, an acoustic monitoring programme has been put into place to determine the risk of acoustic disturbance on Chinese white dolphins in a real-world scenario, as well as monitor any changes in the dolphins’ presence in the area during the construction. This study was funded by the World Wide Fund for Nature – Hong Kong and Ocean Acoustics Limited.

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Ambient Noise and Its Effect on Aquatic Animals Influence of Deep-sea Surface Duct on Ocean Ambient Noise Distribution Xinyi Guo1,2, Li Ma1,2 1Key Laboratory of Underwater Acoustic Environment, CAS, Beijing 2Institute of Acoustics, CAS, Beijing, China

Because the sea surface noise source exists in the surface duct, the excited sound field has good propagation environment. In the experiment, it was observed that the spectrum level of ocean ambient noise received by the hydrophone located in the surface duct was higher than that of the hydrophone below the surface waveguide in some frequency bands, even if the distance between these hydrophones was only within tens of meters, the spectrum level difference was obvious. Through the analysis of underwater wave theory, this paper studies the main mode of noise source propagation in the surface duct and the influence of the surface duct on the vertical distribution of the deep sea noise field. By comparing the experimental data with the theoretical analysis results, the main physical mechanism of the vertical spatial distribution of the noise field under the environment of deep-sea surface duct is obtained.

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Ambient Noise and Its Effect on Aquatic Animals Statistical Model of High-density Ships and its Application in Ambient Noise Regional Differences Analysis Guoli Song1, Xinyi Guo1, He Li1,2, Li Ma1 1Institute of Acoustics, Chinese Academy of Sciences, Beijing, China 2University of Chinese Academy of Sciences, Beijing, China

This paper presents a statistical model of high-density ships in port and based on which studying on the spatial distribution of ocean ambient noise. Firstly, the average acoustic energy is analyzed under statistical conditions to illustrate the significance of statistical average processing, which indicates that the sectional average method makes the acoustic energy tend to a stable value. Then a statistical model of high-density ship noise sources is established using the same technology as the former. Under far-field and statistical average conditions, the ships in port can be approximately equivalent to a single source with high intensity. After that, a method is proposed to study spatial distribution difference of ambient noise affected mainly by high-density ships. Based on the simplified model presented before, the noise level difference of two stations is linearly correlated with the transmission loss difference. Finally, the validity of this method is verified by both numerical simulations and relevant experimentations. The simulated result shows a negative linear correlation with a coefficient of -0.95 about the two mentioned above. At the same time, the validation test conducted in the South China Sea also presents a correlation coefficient about 0.78 at the band of 50Hz~500Hz.

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Ambient Noise and Its Effect on Aquatic Animals Underwater Noise Simulation of Iimpact Pile Driving with the Noise Mitigation Technology for Offshore Wind Farm in Taiwan Chiu-Kuan Shih*, Yin-Ying Fang, Wei-Chun Hu, Chi-Fang Chen Department of engineering Science and Ocean Engineering, National Taiwan University *[email protected]

In recent years, International community has actively promoted green energy. Due to the wind power has become one of major development projects, pile driving noise also become an important study issue. Most of the study which use the Finite Element method following acoustic theory treat the sediment as a fluid. In this study, we treat sediment as solid medium and utilize Finite Element (FE) to get the pile driving noise in the sound field. Then using the Inverse Fourier Transform to get the time series sound pressure and calculating sound pressure level. However, the place where are suitable for developing the offshore wind energy in Taiwan is surrounded by endangered marine mammals. Pile driving generates huge low-frequency noise, which may seriously affect the ecology of marine mammals. In addition to this, there are some underwater noise regulations and standards in the building period. In order to comply with the regulations, we combined the simulation results with noise mitigation technology (balloon curtain) to build a full system of pile driving noise prediction and reduction. To verify the reliability of the simulation of our study, we use bottom-mounted hydrophones and ship-measurements to record the noise created during the piling when Swancor Renewable Energy Co., Ltd constructed the offshore wind turbine, off the western coast of Miaoli, northern Taiwan. These measurement data can be comparing with our prediction results. From the comparison, the energy of pile driving are center from 100 Hz to 500 Hz. And our result shows that adding the noise mitigation system to the Finite Element (FE) model cannot only successfully predict the pile driving noise but also can simulate the effect of the noise mitigation system in the real sea.

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Ambient Noise and Its Effect on Aquatic Animals Broadband Ship Noise and Its Potential Impacts on Indo-Pacific Humpback Dolphins Songhai Li, Mingming Liu, Lijun Dong, and Mingli Lin Sanya Key Laboratory of Marine Mammal and Marine Bioacoustics, Institute of Deep-sea Science and Engineering, Chinese Academy of Sciences, Sanya, 572000, China, email: [email protected]

Ship noise pollution has raised considerable concerns among regulatory agencies and cetacean researchers worldwide. There is an urgent need to quantify ship noise in coastal areas and assess its potential biological impacts. In this study, underwater broadband noise from commercial ships in a critical habitat of Indo- Pacific humpback dolphins was recorded and analyzed. Data analysis indicated that the ship noise caused by the investigated commercial ships with an average length of 134±81 m, traveling at 18.8±2.5 km/h [mean±standard deviation (SD), n=21] comprises mid-to-high components with frequencies approaching and exceeding 100 kHz, and the ship noise could be sensed auditorily by Indo-Pacific humpback dolphins within most of their sensitive frequency range. The contributions of ship noise to ambient noise were highest in two third-octave bands with center frequencies of 8 and 50 kHz, which are within the sensitive hearing range of Indo- Pacific humpback dolphins and overlap the frequency of sounds that are biologically significant to the dolphins. It is estimated that ship noise in these third-octave bands can be auditorily sensed by and potentially affect the dolphins within 2290±1172m and 848±358m (mean±SD, n=21), respectively.

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Ambient Noise and Its Effect on Aquatic Animals Role of Acoustic Indices in Sssessment of Impact of Noise on Marine Mammals Siddagangaiah Shashidhara, Chen Chi-Fang Underwater acoustic laboratory, Department of engineering sciences and ocean engineering, National Taiwan University, Taipei, Taiwan (R.O.C.) a [email protected]

Increasing anthropogenic noise around the world oceans is affecting the marine ecology. Recent deployment of Passive Acoustic Monitoring (PAM) has resulted in large datasets, which has enabled to study the marine soundscapes and to explore the both broad and fine-scale ecological patterns. These long-term passive acoustics datasets are utilized to extract the species biophony trends in the marine soundscape. Usually this is done by computing the accumulated energy at chorusing frequency through power spectral density (PSD), long-term spectral average (LTSA), root mean square (RMS) and percentile sound pressure level (SPL). However, these methods rely on average energy method to quantify the chorusing trends at the frequency where it is necessary to make sure that most of the energy is from the focal species. If any other noise source contributes significantly to the energy within the given frequency band during the analysis, then it is difficult to assess the contribution of the focal species. To overcome this, recently, Acoustic Indices (AI) were utilized to localize and quantify the biophony in the marine soundscape. Nevertheless, AIs employed in complex marine environments, dominated by several anthropogenic and geophonic sources, have yet to be understood fully. In this study, we introduce a method based on Complexity-Entropy (C-H) for detection of biophonic sounds originating from fish choruses. The fish chorus detection performance of C-H was compared with AIs, such as the Acoustic Complexity Index (ACI), the Acoustic Diversity Index (ADI) and the Bioacoustic Index (BI). Fish chorusing was found to be well correlated with the introduced Complexity (C) and Entropy (H), thus yielding Pearson’s correlation, |r| > 0.95, whereas the AIs, such as ACI, ADI and BI, overlooked the fish chorusing, resulting in lower |r|. This study suggest that C-H method can effectively utilized to quantify the biophony. Therefore, can be utilized as a reliable index for the monitoring of the marine biodiversity any impact of noise on the marine fauna.

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Ambient Noise and Its Effect on Aquatic Animals Detection and Localization of Indo-Pacific Humpback Dolphin with Multiple PAM Stations in the Vicinity of Taichung Harbor Wei-Yen Chu, Chi-Fang Chen Department of Engineering Science and Ocean Engineering, National Taiwan University

Nowadays, most of Taiwan's energy raw materials rely on imports, and it has made huge and immediate impact on the environment. Therefore, the government is developing green energy positively, and offshore wind farms have been established. However, the site of offshore wind farms overlapped with the Indo-Pacific Humpback Dolphin reservation zone. In order to avoid the noise impact to the cetaceans caused by the construction and operation of the wind turbine, the establishment of a monitoring system is a priority. PAM (Passive Acoustic Monitoring) is widely used and its efficiency is much higher, so the use of PAM to monitor the ocean background noise and the cetacean call, in addition to make up for the defects of the visual method, it also can understand the relationship between the two. This study deployed several stations of PAM stations in the vicinity of Taichung harbor and recorded the cetaceans call. Moreover, trying to localize its position. In order to simulate the cetaceans call, this study launched artificial chirp signal on the ship in the real ocean. Each PAM station received the chirp signals at different time and used TDOA (Time Difference of Arrival) to localize the position of the sound source. Furthermore, achieve the localization of the real cetaceans call.

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Ambient Noise and Its Effect on Aquatic Animals Study on Estimation of Fish School Number Density with Acoustic Statistical Echos Chun Zhang, Feng Xu, QiaoHua Zhang Institute of Acoustics, CAS, Beijing, China

Statistical characteristics of echo amplitude of random scatterers in ocean are often used to estimate important information of scatterers from which the echoes present will fluctuate from ping to ping due to various interference phenomena and statistical processes. Observations of these fluctuations can be used to infer properties of the scatterers such as numerical density. In the detection resolution cell with single-beam echosounder systems, when the number of random scatterers in a certain medium is large enough, the probability density function of echo amplitude statistics tends to Rayleigh distribution. When the number of scatterers is small, the distribution presents obvious non-Rayleigh characteristics, which is related to the numerical density of scatterers. The probability density functions (pdfs) of echo envelopes in such cases can be highly non-Rayleigh and possess heavy tails, and the shape of the pdf curves contains information of the number density of scatterers. In this paper, the feasibility of estimating the density of fishery resources by using the statistical model of echo amplitude under low-density fish school was studied. The results of the evaluation of the statistical echo model were compared with those of the echo integral method, and the results were basically consistent. By designing measurement experiment of fish school, the statistical curves of echo amplitude of fish school with different number density conditions were obtained, which directly related to the number density of fish school. The research result show that using echo statistical models to estimate the number density of fish school will have a good prospect in application of Investigation and assessment of fishery resources. Compared with the traditional echo integration of energy, the advantage of echo statistical method in the numbers density estimation of fish school is that absolute calibration of detection system is not needed.

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Ambient Noise and Its Effect on Aquatic Animals On-line Monitoring System for Metro Noise Hongbin Xu, Gaoxiang Lin, Wenfa Zhu, Xingjie Chen School of Urban Railway Transportation, Shanghai University of Engineering Science, Shanghai, China

According to the problem that noise has severely affected the surrounding environment and the work, life and health of residents along the line during the operation of Metro, an on-line monitoring system for Metro noise is specially developed. The system mainly aims at carrying out data acquisition, data processing, data analysis, data communication and storage for monitoring the signal during the operation of Metro, and adopts the signal processing technology of time-domain analysis and frequency-domain analysis to extract the characteristic evaluation parameters which can reflect the level of Metro noise, so as to solve the problem that the existing general monitoring equipment cannot meet the monitoring requirements during Metro operation. As for the packet loss problem of noise data in the process of wireless network transmission, it puts forward a sparse compression and reconstruction algorithm of data in the process of transmission, based on compressed sensing theory, aiming at reducing the load pressure and flow consumption of network, so as to achieve efficient and accurate transmission of monitoring data. Finally, LabVIEW software is adopted to develop the on-line monitoring system of Metro noise, and that will be verified by examples along the actual Metro line. The system mainly provides noise evaluation data for the Department of Metro Engineering and Department of Environment Protection, and provides scientific research methods for the reduction of vibration and noise of urban rail transit.

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Nonlinear Ultrasonic Theory and Modeling Excitation of Nonlinear Rayleigh Waves on a Layered Half-space Surface Lu Jia1,2, Shouguo Yan1, BixingZhang1,2 1)State Key Laboratory of Acoustics, Institute of Acoustics, CAS, Beijing, China 2)University of Chinese Academy of Sciences, Beijing, China

The excitation and propagation laws of the second harmonic of Rayleigh wave are studied in the elastic layered half-space structure. The second harmonic of Rayleigh wave in the layered half-space model is written as a linear combination of Rayleigh wave modes by using the perturbation technique and the modal decomposition. The phase velocity matching points of the primary wave and the double-frequency wave are found by the dispersion curve, and in the case of exciting by the normal force on the surface, the excitation mechanism of the fundamental wave and the double frequency wave near the matching frequency are analyzed. It shows that there always has a non-zero energy flux between the double frequency wave and the primary wave, so in this case of approximate phase velocity matching, the phase-matched double-frequency mode grows at a linear rate with propagation distance, while other double-frequency modes oscillate with the propagation distance. And the second harmonic amplitude with cumulative effect is related to the excitation intensity and energy transfer parameters of the double frequency wave. This result is not only beneficial to select matching points with obvious nonlinear effects, but also provides theory for practical nonlinear Rayleigh wave detection.

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Nonlinear Ultrasonic Theory and Modeling Numerical Perspective of Nonlinear Frequency Response of Lamb Waves Mixing Weibin Li1, Mingxi Deng2, Bingyao Chen1 1)School of Aerospace Engineering, Xiamen University, Xiamen, China 2)College of Aerospace Engineering, Chongqing University, Chongqing, China

Physical insight of frequency mixing response caused by the cross-interactions of two Lamb waves is theoretically and experimentally studied in our previous work [1]. In this study, systematical studies on the characteristics of nonlinear frequency response for Lamb waves mixing are examined numerically in an isotropic plate. The effect of synchronism between primary Lamb waves and generated combined harmonics at mixing frequencies is explored in a numerical perspective manner. The magnitudes of second-order combined harmonic waves bounded and oscillated with the spatial periodicity are clearly illustrated, under the condition of approximate satisfaction of synchronism. Nonlinear frequency mixing responses of two Lamb waves with different symmetric property are provided systematically. Results indicate that the synchronism and symmetric property of selection of primary Lamb wave mode pair significantly affect the generation of combined harmonic waves at mixing frequencies. These numerical investigations clearly illustrate the physical process and nonlinear feature of Lamb waves mixing. It is shown that the controllable potential of mode pair selection for Lamb waves mixing, which is of practical significance for nonlinear acoustic scanning in large specimen. References [1] W. Li, M. Deng, N. Hu and Y. Xiang, Theoretical analysis and experimental observation of frequency mixing response of ultrasonic Lamb waves, Journal of Applied Physics 124 (2018), no. 4, 44901.

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Nonlinear Ultrasonic Theory and Modeling Nonlinear Guided Waves Mixing for Location and Assessment of Damage in Pipes Weibin Li1, Zifeng Lan1, Mingxi Deng2 1)School of Aerospace Engineering, Xiamen University, Xiamen, China 2)College of Aerospace Engineering, Chongqing University, Chongqing, China

Nonlinear ultrasonic waves have been recognized as a potential technique to characterize the state of material micro-structure in solids. However, in the case of second harmonic generation approaches, the measured nonlinearity is holistic value that contains nonlinearity from instrument, material, transducers and couplant [1]. Consequently, we are not able to locate damage and distinguish material nonlinearity from other distractions. Only qualitative assessment and detection of material can be performed. The second combined harmonic generated by mixing different waves can successfully overcome this drawback [2, 3]. In this paper, numerical simulations have been conducted on axial guided wave propagating in pipes. On the one hand, cumulative effect of sum and difference harmonics induced by the collinear cross-interaction of two primary longitudinal guided waves with different frequencies is explored. On the other hand, the feasibility of using back wave, which is generated by two homodromous longitudinal guided waves, to quantificationally locate and evaluate damage is investigated. The results indicate that the cumulative effect of combined harmonics could enhance the amplitude of material nonlinearity and the back wave generation can quantificationally locate and evaluate damage in pipes by controlling the mixing position of two homodromous primary longitudinal guided waves. This study can provide a promising reference for experimental research on the assessment of damage in pipes. References [1] M. Sun, Y. Xiang, M. Deng, B. Tang, W. Zhu, and F. Xuan, Experimental and numerical investigations of nonlinear interaction of counter-propagating Lamb waves, Applied Physics Letters, 114.1 (2019): 011902. [2] W. Li, M. Deng, N. Hu, and Y. Xiang, Theoretical analysis and experimental observation of frequency mixing response of ultrasonic Lamb waves, Journal of Applied Physics 124.4 (2018): 044901. [3] M. Hasanian, and C. J. Lissenden, Second order harmonic guided wave mutual interactions in plate: Vector analysis, numerical simulation, and experimental results, Journal of Applied Physics 122.8(2017):084901.

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Nonlinear Ultrasonic Theory and Modeling High-order Solution of Nonlinear Acoustic Wave Equation in Isotropic Solids Using Perturbation and Finite Difference Methods Wenhan Lyu1,2, Xianmei Wu1,2, Weijiang Xu3, Jiayi Chen1,2 1)State Key Laboratory of Acoustics, Institute of Acoustics, Chinese Academy of Sciences, Beijing, P.R. China 2)University of Chinese Academy of Sciences, Beijing, P.R. China 3)Université Polytechnique Hauts-de-France, CNRS, Univ. Lille, YNCREA, Centrale Lille, UMR 8520IEMN- DOAE, F-59313 Valenciennes CEDEX 9, France

Nonlinear acoustic wave equation with Murnaghan parameters in isotropic solids is usually resolved by perturbation method [1-3]. High-order harmonics are obtained by expanding the equation in one linear and a series of nonlinear equations. It is found that errors in harmonics will be accumulated when the order is increased. To estimate these errors at high-order harmonics, numerical method of finite difference in time domain (FDTD) was employed and the solutions were compared to those obtained by perturbation method. Computational parameters from steel were used as an example. Results show that perturbation solutions of fundamental wave and the second-order harmonics are in good agreements with the solutions in FDTD, relative errors are no more than 10%. While for higher order harmonics, relative errors increase heavily, especially for solutions at longer propagation distance or with higher driving amplitude, the difference is up to 50%, or even higher. References [1] H. Khelladi, F. Rahmi. Perturbation methods for the spectral analysis of a weakly nonlinear acoustic field generated by a transient insonation, Journal of the Acoustical Society of America, 2013, 133(1):3555-3555. [2] G. Liu, P. G. Jayathilake, B. C. Khoo. Perturbation method for the second-order nonlinear effect of focused acoustic field around a scatterer in an ideal fluid. Ultrasonics, 2014, 54(2):576-585. [3] G. Ren, J. Kim, K. Y. Jhang. Relationship between second- and third-order acoustic nonlinear parameters in relative measurement. Ultrasonics, 2015, 56:539-544.

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Nonlinear Ultrasonic Theory and Modeling Nonlinear Ultrasonic Testing by Coaxial Longitudinal- Transverse Transducers Hui Zhang Jiangsu Key Laboratory for Design and Manufacture of Micro-Nano Biomedical Instruments, School of Mechanical Engineering, Southeast University, Nanjing, China

The nonlinear mechanical properties are difficult to detect by linear ultrasonic testing. Therefore, it is an important issue to reveal nonlinear ultrasound testing for early defects. Here, the coaxial longitudinal-transverse waves for nonlinear ultrasound testing are investigated, in which transverse effect of a longitudinal wave has been used for designing a coaxial longitudinal-transverse transducer. Theoretically, the effects of two chip shapes for exciting the longitudinal and transverse waves are investigated. The exciting longitudinal wave and transverse wave generate a nonlinear mixing resonance in the defect formation zone, in which the amplitude of the nonlinear mixing wave is in association with the level of stress concentration or plastic deformation. Meanwhile, the results of finite element method (FEM) show that the designed coaxial longitudinal-transverse transducer can effectively excite coaxial longitudinal-transverse ultrasonic waves, which can enhance the nonlinear mixing resonance due to the high sound field coupling in the coaxial direction. In applications, the enhanced nonlinear mixing resonance can be used for improving testing accuracy of early defects. References [1] Z. Chen, G. Tang, Y. Zhao, L. J. Jacobs, and J. Qu, Mixing of collinear plane wave pulses in elastic solids with quadratic nonlinearity, J. Acoust. Soc. Am. 136 (2014), no.5, 2389-2404. [2] H. Zhang, S. Y. Zhang, L. Fan, and Y. R. Wang, Characteristics of thickness- shear modes excited by two-layer piezoelectric film in acoustic sensors, J. Appl. Phys.111(2012), no. 3, 033504.

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Microacoustic Materials, Propagation, Devices and Application Stabilizing Hypersonic Boundary-layer Flow with Impedance- near-zero Acoustic Metasurface Tuo Liu1,2, Rui Zhao3, Chih-yung Wen1, Li Cheng1, Jie Zhu1,2 1)Department of Mechanical Engineering, The Hong Kong Polytechnic University, Kowloon, Hong Kong SAR, China 2)The Hong Kong Polytechnic University Shenzhen Research Institute, Shenzhen, China 3)School of Aerospace Engineering, Beijing Institute of Technology, Beijing, China

In hypersonic environment, the amplified Mack second mode propagating along cool and smooth surfaces is the dominant instability that triggers the boundary-layer transition from laminar to turbulent flow [1]. Although the underlying physics behind the annoying phenomenon is yet to be completely unearthed, it has been realized that this type of unstable disturbance behaves like a trapped acoustic mode and can thus be stabilized by introducing wave energy absorption [2]. Contrary to the dissipation- based conventional strategy, our linear stability analysis shows that the amplification of the Mack second mode may still be effectively reduced, and even better, by employing an almost non-dissipative artificial boundary that possesses near-zero surface acoustic impedance [3]. Such a counter-intuitive behavior results from the minimized coupling between the particle velocity and pressure disturbance, enabled by the impedance-near-zero boundary positioned at the pressure amplitude maximum of the Mack second mode. This fundamentally inhibits the flow-acoustic interaction within the boundary layer and accordingly the excitation of the surface- wave-like mode. A grooved acoustic metasurface capable of providing near-zero surface acoustic impedance at resonance is subsequently proposed and validated in numerical simulations. The vicinity of effective zero impedance is a result of the out- of-phase reflection due to the quarter-wavelength resonance. Our study reveals an important physical characteristics of the Mack second mode that has not been noticed in previous works, which indicates an alternative stabilization mechanism. It also confirms the new possibilities brought by acoustic metasurface to the full control of hypersonic boundary-layer transition. References [1] L. Mack, Boundary-layer stability theory, Jet Propulsion Lab Report No. 900- 277. Rev. A, California Institute of Technology, Pasadena, CA, USA, (1969) [2] Fedorov, A. Shiplyuk, A. Maslov, E. Burov, and N. Malmuth, Stabilization of a hypersonic boundary layer using an ultrasonically absorptive coating, Journal of Fluid Mechanics 479 (2003), 99. [3] R. Zhao, T. Liu, C. Wen, J. Zhu, and L. Cheng, Impedance-near-zero acoustic metasurface for hypersonic boundary-layer flow stabilization, Physical Review Applied 11 (2019), no. 4, 044015

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Microacoustic Materials, Propagation, Devices and Application Influence of Shear Modulus of the Guiding Layer on the Sensitivity of a Surface Acoustics Wave Gas Sensor based on ST-90°X

Quartz/SiO2 Structure 1,2 1 1 Li Hong , Jiuling Liu ,Shitang He 1)Institute of Acoustics, CAS, Beijing, China 2)University of Chinese Academy of Sciences, Beijing, China

Surface acoustic wave (SAW) gas sensor with Love wave mode has the advantages of long service life and high sensitivity. In order to meet the requirement of high sensitivity for surface acoustic wave gas sensor, the influence of the shear modulus of the SiO2 guiding layer on the sensitivity of the gas sensor based on ST- 90°X quartz/SiO2 structure is studied in this paper by solving the dispersion equation. The relationship between the sensitivity of the sensor and the shear modulus and thickness of the SiO2 waveguide layer is analyzed. And the optimum sensitivity and the corresponding thickness of waveguide layer under different shear modulus are extracted. The results show that the SiO2 guiding layer with smaller shear modulus can obtain higher device sensitivity under ST-90°X quartz/ SiO2 structure. This work provides a theoretical basis for optimizing the thickness of guiding layers with different shear modulus in the design of Love mode SAW gas sensors.

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Microacoustic Materials, Propagation, Devices and Application Optimization of LGS based Surface Acoustic Wave Device for Sensing High Temperature Xueling Li1,2, Wen Wang1, Shuyao Fan1,2 1)Institute of Acoustics, CAS, Beijing, China 2)University of Chinese Academy of Sciences, Beijing, China

This work contributes a theoretical optimization of LGS based surface acoustic wave (SAW) device structured by Al2O3/IDTs/LGS for sensing extreme high temperature in the fields of aerospace vehicles. Referring to the FEM, the SAW transmission characteristics in the layered structure was investigated, and the generation and suppression of parasitic/clutter modes was explored, and corresponding suppression method was advised. Moreover, the computation parameters for coupling of modes (COM) simulation were extracted. The optimal design parameters of LGS based SAW device employing one-port resonator configuration were determined, leading to significant improvement of Q-value, the key indicator for high temperature sensing. The optimization conducted in this work provides theoretical guidance for development of extreme high temperature sensor.

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Microacoustic Materials, Propagation, Devices and Application Optimal Design on SAW Strain Sensing Device at High Temperature Employing AlN Piezoelectric Thin-film Shuyao Fan1,2, Wen Wang1, Xueling Li1,2 1)Institute of Acoustics, Chinese Academy of Sciences, Beijing, 100190, China; 2)University of Chinese Academy of Sciences, Beijing, 100190, China;

Sensing strain of high-temperature components in the fields of aerospace and nuclear power is of great significance to ensure accurate operation and safe production of equipment. To obtain strain information at extreme high temperature environment, a SAW strain sensing device employing composite structure of Al2O3/IDTs/AlN/Metal/Support layer. Al2O3 is filled between the IDT electrodes to increase electrode reflectivity, reduce acoustic losses, and improve device temperature stability. The SAW propagation characteristics in multi-layered composite structures was analyzed by using finite element method (FEM). The effects of support layer materials as Al2O3, Si and Diamond on the acoustic propagation characteristics was studied, and corresponding simulation parameters in coupling of modes (COM) model was extracted theoretically. High Q-value and excellent temperature stability were achieved from the proposed SAW sensing device by using the determined design parameters.

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Microacoustic Materials, Propagation, Devices and Application Sensing Mechanism of Love wave based Ice Sensor Employing

Structure of SiO2/36°YX-LiTaO3 Yi-ning Yin1,2, Wen Wang1, Ya-na Jia1 1)Institute of Acoustics, CAS, Beijing, China 2)University of Chinese Academy of Sciences, Beijing, China

Road icing will bring huge safety hazards to aircraft flight and road safety. Therefore, it is of great significance to use icing sensors to realize early warning of road icing. In this work, a Love wave based icing sensor configuration was proposed, and corresponding response mechanism was analysed theoretically. The mass loading induced by the icing process modulate the acoustic wave propagation. By solving the acoustic propagation in layered media, the sensing mechanism of the Love wave device employing waveguide structure of SiO2/36o YX LiTaO3 was investigated. Interesting results were found in the theoretical analysis, that is, in the initial status of icing process with ice-water mixture, a sudden drop was observed in the acoustic wave velocity. While the acoustic wave velocity increases with the completion of the icing process. Obviously, the phenomenon described above provides an effective way to monitor the icing process.

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Inverse Problems of Acoustic Wave An Investigation on the Regressive Discrete Fourier Series for Sparse Reconstruction of Sound Field Man-Ying Zhang, Ding-Yu Hu, Tao Wang Department of Urban Rail Transportation, Shanghai University of Engineering science, Shanghai, China

Reconstructing sound field with sparse measurement has received much attention recently, as it can greatly reduce the measurement cost. In this study, a sparse reconstruction method based on regressive discrete Fourier series (RDFS) is proposed. The RDFS-based method has been proven to be an effective method for patch nearfield acoustic holography. And its performance for sparse reconstruction of sound field is investigated. Different from the original RDFS-based patch nearfield acoustic holography, in which the pressure on the measurement plane is decomposed into discrete Fourier series, the reconstruction model is reformulated by decomposing the particle velocity on the reconstruction plane, which will enhance the robustness of the method. Meanwhile, the problem is solved by using sparse regularization. The method is applied to reconstructing the sound field of a vibrating plate, and the results show that the method can effectively reconstruct the sound field with reduced measurement.

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Inverse Problems of Acoustic Wave A Weighted Acoustic Radiation Modes based method for Reconstructing the Surface Velocity of Vibrating Structure Ding-Yu Hu, Man-Ying Zhang, Wen-Fa Zhu School of Urban Rail Transportation, Shanghai University of Engineering science, Shanghai, China

The acoustic radiation mode (ARM) based method has been proven to be an effective method for reconstructing the surface velocity. The method can also be implemented in the framework of compressive sensing as the velocity can be sparsely represented with the ARMs, which will greatly reduce the measurement cost. However, the ARMs must be truncated as the reconstruction problem is ill- posed. Till now, determination of the cut-off order remains an open issue. In this study, a weighted ARMs based method is proposed. The method utilizes the matching pursuit to iteratively select the candidate ARMs to yield a sparse solution. And the low-order ARMs will be preferred in the reconstruction as they have larger weights. Both numerical and experimental results demonstrate the advantages of weighting the ARMs and the validity of the proposed method.

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Inverse Problems of Acoustic Wave 3D Temperature Distribution Reconstruction Based on Acoustics Tomography Qian Kong, Genshan Jiang, Yuechao Liu, Jianhao Sun North China Electric Power University, Baoding, China

3D temperature field measurement based on acoustic tomography (AT) calculates temperature distributions of the measurement region through multi-path acoustic time of flight (TOF) data. And with the advantages of wide measuring range, non- contacting measurement and large measurement space, AT technology provides an effective means for temperature distribution visualization. Due to the complexity of 3D temperature distribution and computational difficulty, 3D temperature field reconstruction is discussed by only few researchers. In this paper, a new 3D temperature field reconstruction model based on RBF approximation with polynomial reproduction (RBF-PR) is proposed for solving the AT inverse problem and improving the accuracy and stability of present RBF model. In addition, Discretization of temperature reconstruction inverse problems generally gives rise to very ill- posed systems of algebraic equations, the modified reconstruction method that integrates the advantage of the TSVD and Tikhonov regularization method is presented to improve the reconstruction quality (RQ) and the anti-noise ability. Numerical simulations are implemented to evaluate the feasibility and effectiveness of the proposed reconstruction model and method using 3D different temperature distribution models, which include the one-peak symmetry distribution, one-peak asymmetry distribution and two-peak symmetry one. To study the anti- noise ability of the modified method, noises are also added to the value of TOF. 3D display of reconstructed temperature fields and reconstruction errors are given. The results indicate that our new model and method can reconstruct temperature distribution with higher accuracy and better anti-noise ability compared with other popular methods. Besides that, the modified method can determine the hot spot position with higher precision and the temperature error of the hot spot is lower than the other compared methods. As a result, a useful approach is introduced for solving the 3D AT inverse problem in this paper.

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Inverse Problems of Acoustic Wave Non-synchronous Microphone Array Measurements：An Alternative Way of Compressive Sensing Measurements in Acoustics Liang Yu, Haijun Wu, Weikang Jiang Institute of Vibration, Shock and Noise, School of Mechanical Engineering, Shanghai Jiao Tong University, P.R. China

A fundamental limitation of the acoustic imaging is determined by the size of the array and the microphone density. A solution to achieve large array and/or high microphone density is to scan the object of interest by moving sequentially a small prototype array, which is referred to as non-synchronous measurements. The non- synchronous microphone array measurements may be considered as an alternative way of compressive sensing measurements in acoustics. The main issue of non- synchronous measurements is that the phase information is missing between consecutive positions. In this talk, these problems are tried to be solved based on the Empirical Bayes theory and low dimensional models. First, the physical sources are modeled as the low dimensional source of statistical representation; second, the statistical representation of acoustical source, propagation function and the non- synchronous measurements are modeled as the forward problem; last, the acoustical sources are reconstructed based on the Empirical Bayes theory. The proposed methodology has been validated both in simulation and laboratory experiment.

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Inverse Problems of Acoustic Wave A Contribution to the Source Identification in Aeroacoustics Utilizing Galbrun’s Equation. Marcus Maeder1, Andrew Peplow2, Steffen Marburg1 1)Chair of Vibroacoustics of Vehicles and Machines, TU-Munich, Munich, Germany 2)College of Natural and Health Sciences, Zayed University, Abu Dhabi, UAE

In recent years, flow induced noise problems have gained remarkable interest in the engineering field of aeroacoustics. Despite the difficult topic of convected sound propagation in nonuniform flow, the source identification in such an environment has not been fully understood up to the present time. Since the famous work of Lighthill in 1952 [3], various attempts have been published to give an insight to the mechanisms of acoustic sources in turbulent flow and possible methods on how to model these acoustic sources, cf. Ewert and Schröder [2]. A still rather unknow approach was presented by Galbrun in 1932. Therein, Galbrun used a Lagrangian- Eulerian frame to describe the propagation of perturbations of flow quantities, leading to a displacement-based formulation of aeroacoustics. His ideas and the proposed method have been investigated with respect to the stability when utilizing numerical methods such as the finite element method, cf [1,5]. Minotti et al. [3] derived a nonlinear version of Galbrun’s equation. In this paper, the authors take Minotti’s derivation of Galbrun’s equation and extend it to possible source terms. The rigorous derivation based on continuum mechanics will give an insight to possible sources in turbulent flow. Finally, these terms are further discussed in the frame of linear acoustics. References [1] A.-S. Bonnet-Ben Dhia, È. -M. Duclairoir, G. Legendre, J.-F. Mercier, Time- harmonic acoustic propagation in the presence of a shear flow, Journal of Computational and Applied Mathematics 204 (2007), 428–439. [2] R. Ewert, W. Schröder, Acoustic perturbation equations based on flow decomposition via source filtering, Journal of Computational Physics 188 (2003), 365–398. [3] M.J. Lighthill, On sound generated aerodynamically I. General theory, The Royal Society [4] 211 (1952), nr. 1107, 564–587 [5] Minotti, J.-Ph. Brazier, F. Simon, Extension of the Eulerian-Lagrangian description to nonlinear perturbations in an arbitrary inviscid flow, Journal of Sound and Vibration, 331 (2012), 4537–4553. [6] F. Treyssède, G. Gabard, M. Ben Tahar, A mixed finite element method for acoustic wave propagation in moving fluids based on an Eulerian-Lagrangian description, The Journal of Acoustical Society of America 113 (2003), 705–716.

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Inverse Problems of Acoustic Wave A Beamforming Method in Localization of Rotating Sources Using Virtual Array Jianzheng Gao1,2, Haijun Wu1,2, Weikang Jiang1,2 1State Key Laboratory of Mechanical System and Vibration, Shanghai Jiao Tong University, Shanghai 200240, China 2Institute of Vibration, Shock and Noise, Collaborative Innovation Center for Advanced Ship and Deep-Sea Exploration, Shanghai Jiao Tong University, Shanghai 200240, China

Beamforming method has been applied in localization of either static or moving sources. In localization of static sources there exists a lot of advanced beamforming methods like deconvolution, SEM, etc., but few improvements proposed for rotating sources. Besides, some of the advanced methods for rotating sources are performed in the vicinity of a limited emission time interval, which would lead to an insufficient averaging in time domain. In this work, the rotating sources can be located using a planar array, which does not need to be parallel to the rotating plane. Signal radiated from rotating sources are sampled by a static array and transferred into a virtual rotating array that rotates with the sources. A cross-spectral matrix can be achieved for rotating sources directly like the static source. With the fully averaged cross- spectral matrix, the advanced methods like deconvolution and SEM used in static source beamforming could then be applied to the rotating sources. The method has been validated by numerical simulations and experimentally results. The peak frequency of rotating sources was appeared correctly, and mapping results was presented for rotating sources.

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Inverse Problems of Acoustic Wave OMP-SVD Algorithm for Acoustic Imaging in Low Signal-to-Noise Ratio Environments Fangli Ning, Feng Pan Northwestern Polytechnical University, Xi’an, China, 710072

Acoustic imaging has been an indispensable technique for locating acoustic sources for many engineering applications. Many methods have been applied to acoustic imaging, such as the CBF (Conventional Beamformer) method, the l1-SVD (l1-norm combined with singular value decomposition) method, the OMP (orthogonal matching pursuit of CS algorithm) method and so on. However, each of these methods has inherent disadvantages. For example, the CBF method suffers from poor spatial resolution and side lobes contamination; the l1-SVD method has high computational costs especially for three-dimensional acoustic imaging; the OMP method could not get accurate results in low SNR (signal-to-noise ratio) environments. The OMP-SVD method, which combines the OMP method and SVD, was proposed in our work. The OMP-SVD method not only has the advantages of super resolution and high computational efficiency of the OMP method, but also is robust in low SNR environments. The OMP-SVD method can locate all sources exactly for the SNR as low as -10dB, while the above three methods can only locate for the SNR greater than 5 dB. Furthermore, the target sparsity is overestimated but no extra reconstructed source appears in the locating maps. In addition, we study the performance of the OMP-SVD method for three- dimensional acoustic imaging and the method still performs well. For practical application, we conducted gas leakage experiment to verify the performance. The OMP-SVD method can locate the sources in strong air compressor noise (-10 dB) in both two dimensional and three- dimensional acoustic imaging. Besides, we applied the OMP-SVD method to noise source localization of aircraft landing gear in wind tunnel. The results show the OMP-SVD method can accurately locate the main source of noise for different frequencies.

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Inverse Problems of Acoustic Wave Determination of Propagation Matrix of Inverse Model Method Based on Generalized Cross-Correlationfor Wideband Sound Source Localization Weng Jing1,2, Chu Zhigang1,2, Yang Yang1,2 1)State Key Laboratory of Mechanical Transmissions, Chongqing University, Chongqing 400044, PR China 2)College of Automotive Engineering, Chongqing University, Chongqing 400044, PR China

The performance of acoustic source localization with inverse model based on generalized cross-correlation depends on propagation matrix which relies on time threshold. However, the optimized time threshold varies with the test configurations and lacks for unity, which affects the practical application of the inverse model. Therefore, two methods are proposed to determine the matrix in this work. One: the relationship between the performance of the inverse method and the cumulative probability of the travel time difference from all focus pairs to all microphone pairs is established by a large number of simulations to determine the optimal and uniform cumulative probability. The time threshold is then determined by the relationship between cumulative probability and the time threshold. Finally, the matrix can be computed. Another: a new propagation matrix with self-adaptability to test configurations is derived, which can shun the time threshold. Both simulations and experiments show that the propagation matrix established by the two methods can adapt to different configurations, and the latter has slightly better localization performance.

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Inverse Problems of Acoustic Wave Laser-assisted Reconstruction – A holistic View of the Entire Vibro-acoustic Behaviors of a Complex Vibrating Structure Sean F. Wu1, Lingguang Chen1, Antonio Figueroa2, Michael Telenko, Jr.2 Department of Mechanical Engineering, Wayne State University Detroit, MI 48202 Shiloh Industries 47632 Halyard Drive Plymouth, MI 48170

This keynote speech presents a new technology – laser-assisted reconstruction of vibro-acoustic characteristics of an arbitrarily shaped vibrating structure. The underlying principle of this new technology is the modified Helmholtz Equation Least Squares (HELS) method. The input data to the modified HELS formulations are the normal surface velocity, and the field acoustic pressure. These data are easy to acquire by aiming a laser vibrometer to the accessible areas of a target structure and by mounting an array of six microphones in front of the structure. The output data, however, encompass all the vibro-acoustic characteristics of the vibrating structure such as the normal surface velocity distributions, operational deflection shapes at the resonance frequencies, the acoustic pressure distributions, the normal surface acoustic intensity vector distributions, the time-averaged acoustic power spectrum, the sound transmission paths, the dimensionless structural damping ratios, etc. Examples of using this technology to acquire an in- depth understanding of the vibro-acoustic characteristics of an automobile front dash panel are presented.

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Inverse Problems of Acoustic Wave Geometrical Full Waveform Inversion of Defects Fan Shi1, Peter Huthewaite2 1)Department of Mechanical and Aerospace Engineering, Hongkong University of Science and Technology, Hongkong, China 2)Department of Mechanical Engineering, Imperial College London, London, UK

Ultrasonic characterization of internal defects, such as cracks and voids, provides vital information for evaluating the remaining lifetime of critical engineering components used in the nuclear and aerospace industry. Various inverse and imaging methods have been applied including total focusing method (TFM) [1], diffraction tomography[2] and parametric manifold mapping[3]. In this study, we propose a different methodology, which utilizes measured full waveforms to achieve an automatic inversion of the defects. The new method, which we call geometrical full waveform inversion (GFWI), is developed in the light of full waveform inversion (FWI), which originated from the geophysical community[4]. Different from conventional FWI aiming to recover a spatial map of material properties of the subsurface medium, GFWI seeks to recover the true shape of internal defects by minimizing the cost function between the synthetic and measurement data. GFWI is based on a carefully designed formulation to calculate the deformation of the defect’s boundary, following its negative geometrical boundary gradient. The defect will gradually evolve to the true shape after a few iterations. Multiple GPUs are executed to significantly enhance the efficiency of inversion. In addition, defects are often found located near the boundary of the engineering component where the stresses are highly concentrated. We will show that the very strong multiple scattering raised can be utilized automatically during the optimization to significantly enhance the inversion. References [1] Drinkwater, B.W. and Wilcox, P.D., 2006, “Ultrasonic array for non-destructive evaluation: A review’’, NDT&E International, 39, pp.525-541. [2] Belanger, P., Cawley, P. and Simonetti, F., 2010, “Guided wave diffraction tomography within the born approximation”, IEEE UFFC, 57, pp.1405-1418. [3] Velichko, A., Bai, L. and Drinkwater, B. W., 2017, “Ultrasonic defect characterization using parametric-manifold mapping”, Proc. Roy. Soc. London A, 473, 20170056 [4] Pratt, R.G., Shin, C. and Hick, G. J., 1998, “Gauss–Newton and full Newton methods in frequency–space seismic waveform inversion’’, Geophys J. Int., 133, pp. 341-362.

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Acoustical Propagation and Signal Processing in Internal Wave Environment Estimating the Solitary Internal Wave Parameters Using Distributed Sensors Tongchen Wang1,2, T.C. Yang1,2, Wen Xu1,2 1 College of Information Science and Electronic Engineering, Zhejiang University, Hangzhou, China 2 Zhejiang Provincal Key Laboratory of Ocean Observation-Imaging Testbed of, Zhoushan, China

Nonlinear internal waves, also known as solitary internal waves (SIWs), are widely found in continental shelf areas around the world. As SIWs move toward the coast, they change the sound speed profile in both depth and range, which not only affects the sound speed propagation but also impacts navigation of the vehicle encountering the SIWs. Therefore, knowing the tracks of the SIWs are of practical importance. Currently, measurements of their positions are based on satellite images which are limited by the satellite trajectory and also the weather conditions. In addition, the sound speed changes caused by the SIWs are measured based on temperature data collected on thermistor strings - such data fail to provide direct information on the spatial distribution of SIWs. It is envisioned that in the future many inexpensive sensors will be available and will be deployed as distributed sensors forming a network which can be used to transmit the data back to the base station. We propose to use acoustic data collected on the distributed sensors to (1) determine when the SIWs pass by, thereby to predict their positions later in time and (2) estimate the parameters of SIWs based on acoustic inversion methods. In this paper, we use simulated acoustic data to conduct the inversion. The sound speed perturbation caused by SIWs are modeled as a function of SIW parameters assuming the conventional model for SIWs. Together with the unperturbed sound speed profile (SSP), one can model the acoustic wave propagation from sound transmitted from one sensor node to another. Given multiple transmissions between the sensor nodes, one can study the propagation characteristics of acoustic signals traveling through the SIWs and estimate the SIW parameters using acoustic tomographic methods. In this paper, matched-field inversion will be used to estimate the SIW parameters such as the position, direction of travel, and width of the SIWs. Several transducers and hydrophones are placed on the sea floor to obtain acoustic signals passing through the water. The change in signal intensity and multipath arrival time before and after the SIWs pass through the SIWS will be used to detect the presence of SIWs. After the SIWs are detected, matched-field inversion is applied to invert for the SIW parameters. To validate the approach proposed, simulation analyses are carried out for point-to-point measurement data for single-parameter inversion and multi-parameter integrated inversion of SIWs, based on measured SSP and modelled SIWs . The analysis results show the approach can effectively inverse the SIW parameters, and still keep reasonable accuracy under low signal-to-noise ratio conditions. 129

Acoustical Propagation and Signal Processing in Internal Wave Environment Statistical Analysis of Sound Propagation in Shallow Water with Solitary Internal Waves Hu Ping1,2, Peng Zhaohui1 1 State Key Laboratory of Acoustics, Institute of Acoustics, CAS, Beijing, China 2 University of Chinese Academy of Sciences, Beijing, China

Acoustic signals propagating through the internal waves in time-varying shallow water environment will fluctuate seriously with time. In order to study the statistical characteristics of sound propagation in shallow water with solitary internal wave packets exist, an experiment was conducted in the north of the South China Sea in 2015. The sound propagation data were collected by a 16-hydrophone vertical linear array. The source was a linear frequency modulation signal with band range from 175Hz to 225Hz, which was 14.72 kilometers from received array. Three temperature sensor arrays composed a triangle to detect solitary internal wave packets. Great fluctuations of sound transmission loss due to nonlinear solitary internal wave packets were observed. The statistical analysis proposed that the statistical variance was obviously greater and the mode of such fluctuation increased by 2dB. Then, the sound transmission loss was simulated based on the temperature data during such experiment with a two-dimensional advective model. The simulation was well agreement with the experimental data.

References [1] Li Zhenglin, Zhang Renhe, Mohsen Badiey, Jing Luo, Arrival time fluctuation of higher order normal modes caused by solitary internal waves, Acta Acustica., 36(2011), no.6, 559-567 [2] Timothy F. Duda, Acoustic Mode Coupling by Nonlinear Internal Wave Packets in a Shelfbreak Front Area, IEEE Journal of Ocean Eng., 29(2004), no.1, 118- 125. [3] Zhang Haiqing, Research on acoustic field fluctuation caused by Shallow water Internal waves in 2005 Acoustics Experiment of Yellow Sea oceanic front and internal waves, PHD, Ocean University of China,2005 [4] Ji-xun Zhou and Xue-zhen Zhang, Resonant interaction of sound wave with internal solitons in the coastal zone, J. Acoust. Soc. Am., 90(1991), no. 4, 2042- 2054

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Acoustical Propagation and Signal Processing in Internal Wave Environment Sound Intensity Fluctuations as Evidence of Mode Coupling Due to Moving Nonlinear Internal Waves in Shallow Water Yun Ren1, Boris Katsnelson2 1State Key Laboratory of Acoustics, Institute of Acoustics CAS, Beijing, China 2Department of Marine Geosciences, University of Haifa, Haifa, Israel

On the base of experimental data of ASIAEX2001, it is shown that the sound intensity fluctuates at predominating frequencies in the presence of nonlinear internal waves moving along acoustic track. By theoretical analysis, the sound intensity fluctuation are caused by mode coupling due to nonlinear internal waves and the corresponding predominating frequency is determined by both the speed of internal waves and scales of interference beating of waveguide modes. The mentioned frequency is in a good correspondence with modal theory and experiment.

131

Acoustical Propagation and Signal Processing in Internal Wave Environment Analysis of Periodic Sound Fluctuations Caused by Internal Waves in the Yellow Sea Zhen Wang1,2,3, Tao Hu1,2, Shengming Guo1,2, Li Ma1,2 1Key Laboratory of Underwater Acoustic Environment, Institute of Acoustics, CAS, Beijing, China 2Institute of Acoustics, CAS, Beijing, China 3University of Chinese Academy of Sciences, Beijing, China

An acoustic fluctuation experiment was carried out in the Yellow Sea in the summer of 2009, where the water depth is about 32 m to 36 m from the position of source to receivers. The sound source emitted 260 Hz single-frequency pulse signal at a depth of 11.2 m, and the signal was received by a 16-element vertical array about 11 km away. During the sound signal propagation, the periodic fluctuation of the thermocline caused by internal waves (mainly semi-diurnal tide) was monitored by temperature chains moored at the positions of the sound source and receiving array. Sound signal fluctuations with a period of several hours are found in the received signals, and acoustical energy fluctuation at the offshore surface and the offshore bottom depth is just the opposite. Using the data of temperature chain and CTD measurements, RAM successfully simulates similar periodic fluctuations when the sound velocity profiles are taken as a function of distance and fluctuation of the sea floor is taken into account. The modal analysis of the simulated sound fields shows such sound fluctuations are due to the variation of the second and third order modes with distance at different time. And the differences in modal shape and ratio are partly due to the change in sound velocity profiles over time, which is obviously caused by internal waves.

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Acoustical Propagation and Signal Processing in Internal Wave Environment Effects of the Linear Internal Waves on Sound Propagation in the South China Sea Zhang Qing-qing1,2, Li Zheng-lin1, Ren Yun1 1 Institute of Acoustics, CAS, Beijing, China 2 University of Chinese Academy of Sciences, Beijing, China

The internal wave characteristic parameters and the internal wave spectrum are analyzed extracted from the ocean environment measurements of a shallow-water experiment conducted in the northern South China Sea. The Monte Carlo method is applied to investigate the influences of the randomly linear internal waves on transmission loss (TL) in the shallow water. The probability distributions of TLs at different linear internal wave conditions are analyzed. It is shown that the TL statistical characteristics are related to the average energy flow density, source frequency, source position, range, and sound speed profile. Distribution of the TLs can be measured by the dispersion widths and maximal probabilities of the TLs. The probability distributions of TLs are more dispersive with the increase of the source frequency and the average energy flow density of linear internal waves. When the source is located above the thermocline, the probability distributions of TLs are more dispersive than the case that the source is located below the thermocline. The interval width of the probability distribution becomes wider with the increase of the ranges.

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Acoustical Propagation and Signal Processing in Internal Wave Environment Acoustic Intensity Fluctuation Due to Internal Tide in the Yellow Sea Fan Li, Tao Hu, Shengming Guo Key Laboratory of Underwater Acoustic Environment, Institute of Acoustics, Chinese Academy of Sciences, Beijing, China

In the paper, harmonic analysis method of tidal current was used to study characteristics of the tide in Yellow Sea. A simplified tidal current propagation modal was built and used to simulate horizontal distribution of sound speed profile along the acoustic propagation path. Using the modal, the acoustic intensity fluctuation for 500 minutes was gotten. We compared the prediction result with experiment data and depth integral of acoustic intensity fluctuation was coincided with experiment results. The result show that internal tide in the Yellow Sea was the primary cause of acoustic intensity fluctuation and the dynamic prediction of the acoustic field in Yellow Sea was achieved.

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Acoustical Propagation and Signal Processing in Internal Wave Environment Diurnal Fluctuation of Shallow-Water Acoustic Propagation in the Cold Dome Off Northeastern Taiwan in Spring Chen Cheng1, Bo Lei2, Yuanliang Ma2, Liu Ying2, Yang Wang2 1School of Information Science and Engineering, Harbin Institute of Technology, Weihai, China 2School of Marine Science and Technology, Northwestern Polytechnical University, Xi’an, China

The diurnal fluctuation of acoustic propagation in a cold dome region was studied by using the output of the high-resolution Finite Volume Coastal Ocean Model (FVCOM). The three-dimensional acoustic propagation in this region was studied first, and the results suggest that the diurnal fluctuation of the ocean environment results in the fluctuation of acoustic propagation. However, the variation pattern cannot be determined with only few outputs, and comprehensive analysis was needed. Then, a feature model for the thermal front on the edge of the cold dome was proposed. By analyzing the output of the ocean model, fluctuations were found to mainly occur in the two aspects of the feature model: (a) horizontal excursion of the thermal front and (b) vertical motion of the isothermal lines in cold dome. The variation pattern of acoustic propagation over the two kinds of fluctuations was quantified. Results suggest that both kinds of fluctuations of model parameters result in great TL variation in some cases. Typically, acoustic propagation with high frequency and deep source experience great influence from the fluctuations. The transmission loss versus range usually experience influence from the fluctuations of the first kind from an approximately 40 km range and from the start for the second kind. The reason is that the vertical motion of the isothermal lines of the cold dome induces variation over the temperature profile from the start till the end, whereas the horizontal excursion of the thermal front brings influence mainly over the temperature profiles near the thermal front.

Fig.1 Sketch map for the front feature model; the front feature model consists of three parts: shelf water, upwelling water and the interacting front; the range fluctuation and the depth fluctuation corresponds to the fluctuation of front position and the fluctuation of the isothermal lines in the upwelling water region, respectively.

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Acoustical Propagation and Signal Processing in Internal Wave Environment Mesoscale Eddies on Underwater Sound Propagation Zhu fengqin1,2,3,4 ,Qu ke4, Zhang minghui1,2,3 1 Acoustic Science and Technology Laboratory, Harbin Engineering University, Harbin 150001, China 2 Key Laboratory of Marine Information Acquisition and Security (Harbin Engineering University), Ministry of Industry and Information Technology, Harbin 150001, China 3 College of Underwater Acoustic Engineering, Harbin Engineering University, Harbin 150001, China 4 College of Electronic and Information Engineering, Guangdong Ocean University, Zhanjiang 524088, China

As important mesoscale phenomena in the ocean environment, mesoscale eddies have been considered to be one of the main contributions of spatial variation in the actual ocean environment. They directly influence the structure of sound velocity profile, and further make an impact on sound propagation. The Kuroshio region is the key region in mid-latitude ocean atmosphere interaction where mesoscale eddies can achieve their largest magnitude. The results of sound propagation through an anticyclonic mesoscale eddy in the region of Kuroshio at the Northwest Pacific are investigated. The eddy lies at about 21° N. Horizontal size of the eddy was about 300 km, vertical size was more than 1600 m. An analytical approach is used to obtain an approximate solution for deep-ocean mesoscale eddies by Henrick[1,2] and Jian[3]. The transmission loss of acoustic energy through the cross section of the warm-core ring center is simulated using BELLHOP model. When the sound source is located at different position, and the receiving hydrophone is located different depth. The sound field changes obviously.

Reference [1] Henrick R F, Siegmann W L, Jacobson M J. General analysis of ocean eddy effects for sound transmission applications. J.Acoust.Soc.Am (1977), 62:860– 70. [2] Henrick RF, Jacobson MJ, Siegmann WL. General effects of currents and soundspeed variations on short-range acoustic transmission in cyclonic eddies. J. Acoust. Soc. Am (1980),67:121–34. [3] Y.J. Jian, J. Zhang, Q.S. Liu, Y.F. Wang. Effect of Mesoscale eddies on underwater sound propagation. Applied Acoustics (2009), 70:432–440

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Acoustical Propagation and Signal Processing in Internal Wave Environment Sound Propagation through an Eddy Using the Parabolic Approach in Moving Media CHEN Yuchen1, ZHANG Haigang1,2,3, MA Jun1 1College of Underwater Acoustic Engineering, Harbin Engineering University, Harbin 150001, China 2Acoustic Science and Technology Laboratory, Harbin Engineering University, Harbin 150001, China 3Key Laboratory of Marine Information Acquisition and Security (Harbin Engineering University), Ministry of Industry and Information Technology; Harbin 150001, China

Oceanic eddies are ubiquitous in global ocean and have a significant effect on sound propagation. The effects of eddies on sound propagation by changing the sound-speed profile has been widely studied and some profound results has been achieved. However, the current speed has rarely been considered. In this paper, sound propagation through an ocean region characterized by a current-speed distribution produced by an eddy is investigated. A wide-angle parabolic equation for sound propagation in inhomogeneous moving media is applied to simulate the sound propagation through a Gaussian cold eddy. The numerical results show that the current speed can make the sound field change greatly.

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Acoustical Propagation and Signal Processing in Internal Wave Environment Deep Anti-Decoherence: A Deep Network for Acoustic Interference Striation Recovery Based on Random Mode-coupling Matrix Xiaolei Li1, Wenhua Song2, Dazhi Gao1, Wei Gao1, Haozhong Wang1 1Department of Marine Technology, Ocean University of China, Qingdao, China 2Department of Physics, Ocean University of China, Qingdao, China

As an important underwater acoustic parameter, waveguide invariant β has been used in source ranging, de-dispersion transform, geoacoustic inversion and etc. The value of β is closely related to acoustic interference striation (AIS) and can be extracted from AIS by Hough transform or Radon transform. However, AIS will be distorted when a soliton internal wave (SIW) exists in the ocean waveguide because of mode coupling, which impedes the applications of waveguide invariant. If AIS can be recovered from distorted interference striation (DIS), the application scenarios of waveguide invariant will be expanded. For example, source ranging can be realized by waveguide invariant in an ocean waveguide with SIW. To achieve this goal, a deep network is trained to recover AIS from DIS when a SIW exists in the ocean waveguide. Because of the variety of SIWs, it is difficult to establish an accurate acoustic model for all SIWs. Note that mode coupling induced by a SIW can be described by mode-coupling matrix and the distortion of AIS is mainly caused by the non-diagonal elements of mode-coupling matrix, a random mode-coupling matrix model, whose non-diagonal elements are random numbers, is introduced to model the mode coupling induced by a SIW. Based on the random mode-coupling matrix model, 4500 pairs of AIS and DIS are computed as training data to train the deep network. From the point of view of extracting β distribution, the trained deep network achieves state-of-the-art results in AIS recovery. It is turned out that the trained deep network is robust not only to the amplitude, width and shape of ISW but also to signal to noise ratio.

Acknowledgments The authors wish to thank Ning Wang for useful discussions and suggestions.

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Acoustical Propagation and Signal Processing in Internal Wave Environment Multipath Compensation in Shallow Water Environments: A Propagation Invariant Approach Pengyu Wang, Wenhua Song Ocean University of China, 238 Songling Rd. Qingdao, P. R. China

A method for compensation of signal distortion and propagation loss is developed. To compensate the deformation of signal, a vertical array to receive both the signal from a guide source and an unknown objective source which propagates over a partially shared path. We introduce a notion referred to as the propagation/transmission invariant (PTI), which is certain field transformation of sound field data of the guided and unknown sources. By employing the PTI, many of the distorting effects of an unknown propagation region can be removed, including propagation loss, mode coupling and multi-paths. As a result, the output approximates the signal that the unknown source would be received at the location of the guide source, a virtual receiver array. Results are given for several numerical experiments in the frequency domains. The numerical simulations are used to illustrate the approach in range-dependent shallow water environments exhibiting lossy propagation and the mode coupling in ocean environments with nonlinear internal wave and slope. We also compare the difference between the PTI and the passive phase conjugation (PHC) approach, the PTI outperforms than the PHC for long range propagation problem.

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Acoustical Propagation and Signal Processing in Internal Wave Environment Source Localization in Uncertain Environments Using Deep Learning with One Sensor Haiqiang Niu1, Zaixiao Gong1, Emma Ozanich2, Peter Gerstoft2, Zhenglin Li1 1Institute of Acoustics, Chinese Academy of Sciences, Beijing 100190, People’s Republic of China 2Scripps Institution of Oceanography, University of California San Diego, California 92093-0238, USA

A challenging task in a real application is to locate a source in uncertain ocean environments. Different from the matched-field processing (MFP) methods, a deep learning approach is proposed to locate a broadband acoustic source with one hydrophone in uncertain ocean environments. To handle the environmental uncertainty, several 50-layer residual neural networks are trained on a large data set that is generated by an acoustic propagation model. A two-stage training strategy is presented to facilitate the training of deep learning models. In the first stage, the source is determined within coarse grids (5 km). Secondly, the source range and depth are estimated on a finer grid. The proposed method is tested on simulated data in uncertain environments and then on experimental data. The localization results demonstrate that the proposed approach is able to adapt to a variety of environments in source localization problems.

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Acoustical Propagation and Signal Processing in Internal Wave Environment Matched-field Processing Geoacoustic Inversion Using Propagation Invariant in Range-dependent Environments Wenhua Song, Pengyu Wang College of Information Science and Engineering, Ocean University of China, Qingdao, China

Matched-field processing (MFP) has been applied successfully in geoacoustic inversion for the seabed parameters. However, the prediction capability of the matched-field processor can be destroyed by variabilities in the environment, such as changes in bathymetry, variability in the water column, or abrupt changes in the seabed properties. It is impossible to include all these variabilities in the numerical modeling required for the MFP inversion. In this paper a field transformation of acoustic data is proposed, referred to as propagation invariant (PI). PI is purely data- driven and most importantly can eliminate the effect of the intermediate propagation variability, which means that the received acoustic data is same as that propagated through a range independent waveguide. Therefore, propagation invariant can provide the matched-field processor with ideal acoustic data. A towed sound source is used with a moored VLA in the simulation, and results show good performance of MFP geoacoustic inversion even in a highly range-dependent waveguide

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Acoustical Propagation and Signal Processing in Internal Wave Environment Numerical Modeling of Sound Propagation under Rough Sea Surface of PM Spectrum Meijuan Yao1,2, Licheng Lu1,2, Shengming Guo1,2, Li Ma1,2 1Institute of Acoustics, Chinese Academy of Sciences, Beijing, China 2Key Laboratory of Underwater Acoustics Environment, Chinese Academy of Sciences, Beijing, China

Sea surface, acting as the top boundary of the waveguide, can significantly affects underwater acoustic propagation. The rough sea surface has, not only reflection effect, but also scattering effect on acoustic wave, which lead to reflection loss. Based on Kirchhoff Approximation scattering theory and Small Slope Approximation scattering theory, Krakenc-KA(Kirchhoff Approximation，KA) and Krakenc-SSA (Small Slope Approximation，SSA) sound propagation models are put forward. The numerical simulation result shows that the horizontal locations of the interference peak and trough of acoustic field are changed when Krakenc-SSA model is used as the reflection coefficient calculated using SSA theory can change the phase of the field, while it is not like that when Krakenc-KA model is used. Moreover, using Monte-Carlo method to generate one-dimension rough sea surface, Ramsurf sound propagation models are compared with Krakenc-KA and Krakenc-SSA models under rough sea surface of PM spectrum.

References [1] E. I. Thorsos and S. L. Broschat, An investigation of the small slope approximation for scattering from rough surfaces. Part I. Theory, J.Acoust. Soc. Am. 1995; 97(4):2082–2093 [2] K.L. Williams, E.I. Thorsos, and W.T. Elam, “Examination of coherent surface reflection coefficient (CSRC) approximations in shallow water propagation”, J. Acoust. Soc. America, 2004; 116 (4): 1975 –1984.

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Acoustical Propagation and Signal Processing in Internal Wave Environment Deep Argo Data Analysis Salinity, Temperature, and Sound Speed Profiles Extrapolation & Subsequent Rectifications Kashif Iqbal, Minghui Zhang, Shengchun Piao, He Ge College of Underwater Acoustics, Harbin Engineering University, Harbin, China

Both R. Davis & D. Webb were able to develop Argo float technology during early 1990s. A profiling array comprising of 3300 such floats was proposed to cover the oceans globally in 1998 by the Argo’s Science Team. The first Argo profiling float came into existence in the year 1999. By the year 2007, Argo had achieved its target of 3000 active floats covering the desired global ocean. The conventional depth for obtaining Argo data has been 0 - 2000 meters. As a giant leap forward, by the middle of 2014, a workshop named, “Deep Argo Implementation Workshop”, was held in Hobart. In this conference, Johnson et al. proposed an array of 1228 floats providing coverage of 5° × 5° × 15-day cycles. Deployment of pilot arrays for covering particular regions has already been executed. Deep Ninja and Deep Arvor from Japan and France simultaneously cover depths of 0 - 4000, while Apex & Solo of Unites States are developed to cover 0 - 6000 meters. This study is focused on obtaining in-situ data from varying deep Argo buoys and then, compares their salinity, temperature, and sound speed's in-situ values with the extrapolated ones. Prior to availability of deep Argo, the data in depth was usually extrapolated for various parameter calculations. The literature presents numerous methods and examples for extrapolation of vertical profiles for salinity, temperature, and sound speed profiles. The measured temperature and salinity parameters with the pressure were converted to sound speed profile. The conversions were done by employing varying formulas i.e. Mackenzie, Chen & Millero, Del Grosso’s Equation, and UNESCO Chen & Millero Equations. These converted sound speed profiles along with both salinity and temperature were extrapolated below 2000 meters depth in order to cover deeper oceans. The extrapolation was carried out using MATLAB’s polyfit and polyval functions. The comparative analysis among in-situ data and the extrapolated one illustrates deviation in deeper vertical profiles especially after 2500 meters. The analysis results are presented in the form of graphs and marked accordingly for both in-situ and extrapolated curves. In addition, the study focuses on varying factors responsible for the typical anomalies especially in deeper oceans. The anomalies suggest that for deeper depth calculations, the real measured values present more accurate results instead of mere extrapolations.

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Acoustic Field in Deep Water Effect of Emission Angle on Acoustic Transmission Yanyang Lu, Kunde Yang School of Marine Science and Technology, Northwestern Polytechnical University, Xi’an, 710072, China; [email protected] In this study, the effect of the emission angle of a source array on acoustic transmission is simulated and analyzed. Firstly, we derive the formula of the received signal based on the Normal Mode. 푁 푌(휃) = 푆(휔) ∙ ∑푛=1((퐵푛) ∙ 휓푛(푧)) (1) 푆(휔) is the source signal; Bn is the beamform on the nth mode of all of the source elements; 휓푛(푧) is the sampling of the nth mode at the receiving depth; 푌(휃)is the received signal. The formula indicates that the signal is determined by the beamform on the modes of all sources and the samplings of all modes at the receiving depth. Two characteristics of the optimal emission angle (OEA) are obtained from the simulation: (1) The transmission loss (TL) distribution exhibits alternating dark and bright streaks with the changes of receiving depth. (2) In some shallow depths, the OEA is shown to deviate further from 0° with an increasing source depth. We explained the characteristics utilizing the aforementioned formula. The observed distribution of TL for different sources and receivers are consistent with the obtained characteristics. Then the article analyses the different influences of the emission angle on the sound propagation in the shallow sea and the deep sea respectively. Due to the existence of convergence zone and shadow sound zone (SSZ), there have also been some different phenomena in deep sea: (1) First of all, due to the existence of the SSZ, regardless of the emission angle, the sound signal is always weak at close distance, that is, the change of the emission angle has almost no influence on the SSZ. (2) The distance of the convergence zone will change with the emission angle. The larger the emission angle deviates from 0°, the closer the convergence zone appears. (3) The energy of the convergence zone with emission angle 0° is strongest. The biggest difference between the deep sea and the shallow sea is obviously the depth. The large depth can provide a more complete acoustic environment for sound propagation, and also provide a more complete SSP. The specific difference is that the sound rays have more contact with the sea surface and the sea floor in shallow sea. This process not only consumes most of the sound energy, but also changes the structure of sound rays. In contrast, the deep-sea sound speed structure can retain most of the sound energy in the water. The article shows that emission angle under certain condition is valuable to practical engineering. In addition, simulation in deep sea shows that the emission angle has little effect on the SSZ but can change the distance of convergence zone. This all can be applied to active sonar detection to increase the detection range. References [1] Zhang, T.W., Yang, K.D., et al. A robust localization method for source localization based on the auto-correlation function of wideband signal. Acta Phys. Sin. 64 (2015), no.2, 276–282. [2] F. B. Jensen, W. A. Kuperman, M. B. Porter et al., Computational Ocean Acoustics,2.ed., Springer, New York, 1994,ISBN:978-1-4419-8677-1 144

Acoustic Field in Deep Water Modeling of Acoustic Effects Induced by Subaqueous Sand Dune Field Andrea Chang1, Linus Chiu2, Ching-Sang Chiu3, Chi-Fang Chen4 1 Center of Marine Technology, National Sun Yat-sen University, Kaohsiung, Taiwan 2Institute of Undersea Technology, National Sun Yat-sen University, Kaohsiung, Taiwan 3Department of Oceanography, Naval Postgraduate School, Monterey, USA 4 Department of Ocean Engineering and Engineering Science, National Taiwan University, Taipei, Taiwan

Large-amplitude sand dunes and sand waves are discovered in the sea area around the northeastern South China Sea. The amplitude and width of sand dunes are much larger than acoustic wave length and will have significant impact on sound propagation, but few results are published. This research is motivated by the need of applying underwater mobile acoustic system in subaqueous sand dune waveguide and is to study the acoustic propagation effects and the variations resulted by various sand dunes. In this research, numerical modeling is applied to study the variations of impulse response and the vertical distribution of sound intensity by changing the sand dune wave high. Also, the resonant interaction between acoustic propagating modes and subaqueous sand dunes are numerically investigated as a function of sand dune wavelength, acoustic frequency and sand dune packet length. The results demonstrate that sand dune wavelength impacts acoustic mode coupling behavior, with the principal transfer of energy occurring between acoustic modes whose eigenvalue difference is equal to the peak value in the sand dune wavenumber spectrum. The observed effect of wavelength is greater than that of acoustic frequency and sand dune packet length. Finally, the joint effects of the nonlinear internal waves and the sand dunes on acoustic propagation are analyzed and discussed in this research. [This research was supported by the Ministry of Science and Technology of Taiwan with project number: MOST 108-2623-E-110-002 -D].

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Acoustic Field in Deep Water Anomalous Transmission Loss Due to Bathymetry Variation Licheng Lu1,2, Qunyan Ren1,2, Shengming Guo1,2, Li Ma1,2 1Key Laboratory of Underwater Acoustic Environment, Institute of Acoustics, CAS, Beijing, China 2Institute of Acoustics, CAS, Beijing, China

An acoustic propagation experiment was conducted in the East Sea in July 2017, two types of explosive source detonated at depths of 25 m and 50 m were used to calculate the transmission loss (TL) along range. The TL at the depth of 50 m explosive source are found slightly anomalous in the frequency band of 300 Hz - 500 Hz at range about 40 km, while only minor anomalous of the TL at the depth of 25 m is observed. It is well known that, the sound propagation in shallow water is greatly influenced by the properties of seabed, such as bathymetry and sediment acoustic parameters, which may cause anomalous TL. This paper compares the results of the experiment with the prediction using a range-dependent sound propagation model. Numerous synthetic simulations have been calculated to replicate the experimental results, from these simulations, the bathymetry variation has been demonstrated can affect the TL in specific frequency band.

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Acoustic Field in Deep Water Combined Estimation of Range and Depth for Underwater Source in the Direct Zone in Deep Water Wang Meng-yuan1,2, Li Zheng-lin1, Qin Ji-xing1, Wu Shuang-lin1 1 State Key Laboratory of Acoustics, Institute of Acoustics, Chinese Academy of Sciences, Beijing, China 2 University of Chinese Academy of Sciences, Beijing, China

The sound field of direct zone in deep water has obvious multi-path structure, which can be used for passive localization of underwater sound source. Using the data obtained from an experiment in the South China Sea, a combined source localization method for underwater target in deep water is proposed, which estimates the range based on the cross-correlation function of signals received by two vertical hydrophones and depth from the autocorrelation function of signals received by a single hydrophone. Firstly, the arrival time of the direct wave is extracted from the cross-correlation function to estimate the source range by assuming the source depth range from 50 m to 300 m. Then, the delay time between direct wave and surface reflect wave is extracted from the auto-correlation function of one receiver to estimate the sound source depth combining the range estimation result. Finally, a more accurate range estimation can be derived by combing the average value of the depth estimation result and the cross-correlation function. The results show that the relative error of range estimation is within 10.5%, and the relative error of sound source depth estimation is within 13.3%.

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Acoustic Field in Deep Water Spatial Coherence of Sound Field on the Seafloor Surface in Continental Slope Area Bo Zhang1, Fenghua Li1, Jin Liu1, Wen Li1,2 1 State Key Laboratory of Acoustics, Institute of Acoustics, CAS, Beijing, China 2University of Chinese Academy of Sciences, Beijing, China

For convenience of deployment, horizontal arrays are often laid on the seafloor. In continental slope area, the seafloor surface has a grazing angle, and the hydrophones of a bottom-mounted horizontal array are not at the same depth in general. As a result, the spatial coherence of sound field on the seafloor surface is synthetically affected by both horizontal and vertical separation between hydrophones. In the present study, the seafloor-surface spatial cross-coherence was measured experimentally by bottom-mounted receiver arrays using explosive sources in Northern South China Sea, where the mean water depth is 1000m and the bottom has a slope angle of about 2.3°. Expressed in terms of wavelengths, the transverse horizontal spatial coherence length is measured to be only 5λ ~ 20λ at 100Hz with the array bottom-mounted at 1000m depth. Besides, the spatial coherence of sound field on the seafloor surface has been simulated numerically. The preliminary conclusion is that the spatial difference of normal mode interferences induced by internal waves and the sloping bottom lead to the spatial coherence degradation in continental slope area during our experiment.

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Acoustic Field in Deep Water A Simulation Study on the Depth Dependence of Ambient Noise Characteristics in Deep Ocean Kai Zhang1, TC Yang1,2, Wen Xu1,2 1 School of Information Science and Electronic Engineering, Zhejiang University, Hangzhou, China 2 Zhejiang Provincial Key Laboratory of Ocean Observation-Imaging Testbed Zhoushan, China Wind and shipping noises are the predominant sources of ocean ambient noise at the frequency band of 20-500 Hz[1]. In the 1960s-1970s, many experiments were carried out in deep oceans for noise measurements. In 2007, Gaul et al. presented detailed analyses of the acoustic data from one of those experiments, known as CHURCH OPAL, performed in the Northeast Pacific[2]. An important objective of the experiment was to understand the nature of ambient noise in a deep-ocean environment. Since then there were scattered experiments to study the noise in the deep ocean including the recent experiment using ARAP array[3]. While the general nature of the ambient noise data was understood, it is noted that experimental data are inherently tied to the environmental condition under which the data are collected. In water deep enough, there exists a critical depth at which the sound speed equals the speed at surface. The ambient noise level below the critical depth is expected to be significantly lower than above the critical depth since distant wind and shipping noises are refracted back and/or blocked by bottom bathymetry and other effects. The properties of the ambient noise, such as noise intensity level, noise vertical coherence, and directionality are of great interest for acoustic detection applications. In an earlier paper[4], we studied the depth dependence of noise intensity at 50 Hz using simulation data in a general and systematic way. Most of previous simulation work were focused on noise below the critical depth. Our interest was to compare the noise properties (intensities, coherence, directionality etc.) below the critical depth to that above the critical depth for different environmental conditions. The approach we adopted is similar to the study carried out in shallow water using the Kuperman-Ingenito (KI) model[5], but for deep water the physics involved is different below and above the critical depth. Our objective is to understand how the depth dependence of noise intensity is influenced by various environmental conditions including (a) local wind and near/distant shipping noises, (b) noise source depth, (c) variation of sound speed profile (SSP) and in future studies, (d) bathymetry effects. The environment model adopted in the simulation is similar to the conditions under which the Church Opal measurements took place. The parabolic equation model RAM is used for field calculation. Some of the main conclusions drawn from the simulations include (1) the local wind and near shipping noises contribute equally to the noise intensity for below and above the critical depth, while distant shipping noises cause an intensity decrease below that point; (2) a lower source depth motivates higher ambient noise level in the water column; (3) the blocking of seamounts significantly changes the shape and tendency of the intensity curve versus water depth while the variations of SSP we explored cause just moderate changes other than its principal shape. Reference [1] G. M. Wenz, Acoustic ambient noise in the ocean: Spectra and sources, The Journal of the Acoustical Society of America 34.12 (1962): 1936-1956. [2] R. D. Gaul, D. P. Knobles, J. A. Shooter, et al., Ambient noise analysis of deep-ocean measurements in the Northeast Pacific, IEEE Journal of Oceanic Engineering, 32.2 (2007): 497-512. [3] J. F. McEachern, et al., ARAP-deep ocean vector sensor research array, Proceedings of OCEANS 2006, IEEE, 2006: 1-5. [4] K. Zhang, TC Yang, and W. Xu, Influence of Wind and Shipping Noises on the Depth Dependence and Spatial Coherence of Ambient Noise in the Deep Ocean: A Simulation Study, IEEE OCEANS 2019 Marseille. [5] W. A. Kuperman, and F. Ingenito, Spatial correlation of surface generated noise in a stratified ocean, The Journal of the Acoustical Society of America, 67.6 (1980): 1988-1996. 149

Acoustic Field in Deep Water Simulation of Ocean Ambient Noise Field’s Three-dimensional Effect in Seamount Area Shan Yuanchun1,3, Lin Jianheng1,2, Yi Xuejuan1, Jiang Pengfei1, Sun Junping1, Li Na1 1Qingdao Laboratory of Institute of Acoustics, Chinese Academy of Sciences, Qingdao, China 2 Key Laboratory of Underwater Acoustics Environment, Chinese Academy of Sciences, Beijing, China 3University of Chinese Academy of Sciences, Beijing, China

The three-dimensional effect of is a key point of ambient noise research, because it can have an obvious influence the performance of sonars. As a typical seabed of complicated sea area, seamount is a significant, cause of three-dimensional effect of ocean ambient noise. This article use large scale seamount, with ray method[1][2] and sources randomly distributing on an infinite plane under ocean surface. It simulated and compared some character of ambient noise field in two conditions: one considered horizontal refraction and the other not. The results showed that the energy diffuses around seamount when ray horizontal refraction is considered, so the ambient noise level was higher than the condition without consideration of ray horizontal refractions. The difference of ambient noise level caused by horizontal refraction is more obvious, especially in different orientation and range.

References [1] Yang Jia-xuan, Shuai Chang-geng, He Ling, Wang Zhan-you, Acoustic simulation and application based on Bellhop model using different alpha grazing angles, Technical Acoustics,34(2015),No.4,136-139. [2] Chen Xiao-long, Fan Jun, Tang Wei-lin, Ray method for predicting ambient noise field in stratified shallow water. Technical Acoustics,23(2004),No.2,79-84

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Theory and Applications of Reservoir Acoustics Assessing Cement Leak Paths by Analysis Borehole Wavefield Modes Hua Wang1, Michael Fehler2, Aimé Fournier2, Guo Tao3 1)School of Resources and Environment, University of Electronic Science and Technology of China, Chengdu, China; 2)Earth Resources Laboratory, Massachusetts Institute of Technology, Cambridge, MA, United States; 3)Department of Petroleum Geosciences, Khalifa University of Science and Technology, Abu Dhabi, UAE

Evaluation of possible cement leakage pathways is essential for successful Carbon Capture and Storage (CCS), geothermal engineering, groundwater development, and oil/gas development. A channel in the borehole cement, which secures the borehole casing to the formation, may allow fluid to escape. Risk assessment and remediation decisions about the presence of such channels depend on channel parameters: radial position from the center of the borehole r; channel thickness d; azimuthal position of the channel φ; and azimuthal extent of the channel θ. Conditional cement bond log, which uses only the first arrival at a centralized borehole receiver, cannot diagnose details of cement leak channels. To accurately characterize the possible cement leak paths, we use a 3-dimensional finite-difference method to investigate the use of the abundant data collected by a modernized monopole sonic tool that contains an array of azimuthally distributed receivers in a singly-cased borehole with different bonding conditions. We also investigate how to improve the tool design to acquire even more useful information. We investigate various receiver geometries, multi-modal analyses of multifrequency data to discover the type of logging tool that provides the best information for cement bond evaluation. Modal dispersion curves and dispersion analysis facilitate the identification of propagation modes. We find that the casing modes are strong when interface I (interface between casing and cement) is partially or fully replaced with fluid. The amplitude dependence on fluid thickness is small which could lead to ambiguity in interpretation. The casing modes are different when interface II (interface between cement and formation) is partially replaced with fluid, because the modes propagate in the mixed material of steel pipe and cement and the velocities are highly dependent on the cement thickness. It would highly possibly misjudge cement quality because the amplitudes of these modes are very small and they propagate with nearly the formation P velocity. However, it is possible to use the amplitude to estimate the thickness of the cement sheath because the variation of amplitude with thickness is very clear. We find that an appropriate choice of wave modes, source frequencies, source polarities, and receiver locations and offsets provide sensitivity to d, φ, θ. The amplitude of the first arrival from a monopole source is sensitive to θ. Amplitudes at receivers at different azimuths are sensitive to φ. While the Stoneley mode (ST1) propagates in the borehole fluid, a slow Stoneley mode (ST2) appears in the fluid column outside the casing when cement is partially or fully replaced with fluid. The slow Stoneley mode (ST2) velocity is sensitive to d, but ST2 is not easy to pick when θ and d are small. Further improvement is necessary to provide comprehensive information about possible flow channels in casing cement. Machine learning methods are also anticipated to be used to pick the specified modes and to calculate dispersion curves from field data, which will speed up the data processing in field. 151

Theory and Applications of Reservoir Acoustics Integrated Application of Seismic Reservoir Prediction Technology in Deep Dolomite Reservoir: A Case Study of Cambrian Longwangmiao Formation, Gaoshiti-Moxi Area, Sichuan Basin, China Jiang Ren1,2, Liu Chenglin1, Zhang Jing2, He Pei2, Huang Jiaqiang2, He WeiWei2, Du Bingyi2 1)College of Geosciences, China University of Petroleum, Beijing, PR China 2)Petrochina Company Limited, Research Institute of Petroleum Exploration and Development, Beijing, PR China Anyue gas field is located in the middle Sichuan paleo-uplift of Sichuan Basin, and its reservoir is mainly composed of large-scale shallow high-energy granular beach deposits of Lower Cambrian Longwangmiao Formation (LWM fm.). Reservoir heterogeneity is strong, and gas-water relationship is complex. It is restricted to develope LWM reservoir efficiently for its strong heterogeneity and complex gas-water relationship of reservoir. In recent years, many researchers have done a lot of work on reservoir prediction of LWM fm., mainly focusing on reservoir prediction using amplitude attribute [1-3], and the method of post-stack seismic attributes has ambiguity in fluid prediction. An effective reservoir prediction method is selected to improve the accuracy and reliability of interpretation guiding by rock physics analysis and forward modeling. The purpose of rock physics analysis is to find the most sensitive rock physical parameters to porosity and gas saturation, thereby reducing ambiguity of seismic interpretation. The crossplot of multi-well rock physical parameters shows that gas reservoirs have the feature of low density and P-wave impedance compared with tight and water layers. Therefore, P-wave impedance can be used to predict the porosity of reservoirs and the parameter of density can be utilized to detect gas saturation. Forward modeling shows that the waveform can be used to delineate the favorable facies of reservoirs. Firstly, the waveform classification of 3D seismic data is carried out by using the neural network method, and then explain the waveform according to the above-mentioned favorable waveform characteristics to obtain qualitatively the favorable zone of the plane. P wave impedance, retrieved by sparse spike inversion, is used to predict the porosity of the reservoir. It is the key to get the accurate inversion result on the basis of accurate wavelet extraction by fine seismic-well. Finally, the gas saturation was indicated by the density inversion. The reason for difficulty in obtaining the density parameters by traditional prestack inversion is that the coefficient matrix of density solution is an ill- conditioned matrix with small determinant. Solving the equation directly will lead to the wrong solution affected by noise, and the inversion results are not practical. To solve this problem, we modify the objective function and replace Euclidean distance with Mohr distance to quantitatively balance the contribution of these two terms to the objective function so that we can obtain the most objective and reasonable solution. The application of synthetic data and case study shows that the inversion method is reliable. References [1] Zhang Guangrong, Liao Qi, Yu Yi, et al. Seismic prediction on the favorable efficient development areas of the Longwang-miao Fm has reservoir in the Gaoshiti-Moxi area, Sichuan Basin. Natural Gas Industry, 2017, 37(1): 66-75 [2] application to seismic exploration of the deep marine carbonate reservoirs in the Leshan-Longnvsi Paleouplift. Natural Gas Industry, 2014, 34(3): 67-73 [3] Li Yalin, Wu Furong, Liu Dingjin, et al. Distribution rule and exploration prospect of the Longwangmiao Fm reservoirs in the Leshan-Longniisi Paleouplift， Sichuan Basin. Natural Gas Industry, 2014, 34(3): 61-66L 152

Theory and Applications of Reservoir Acoustics The Application of a New Segment Cement Bond Evaluation Tool in Horizontal Well Deng Fangqing1, Dong Xingmeng1, Zhai Yuwen1, Xia Hui2, Fu Rui2 1)The 22th Research Institute of China Electronics Technology Corporation, Xinxiang 453003, China) 2)XinJiang company of CNPC Logging Group, Kelamayi 834000, China)

A new segment bond evaluation tool is designed to provide an evaluation of cement quality and integrity around the casing. This tool measures the quality of cement effectiveness, vertically and laterally around the circumference of the casing. The tool provides cement bond amplitude, attenuation, and variable density for evaluation of a cemented casing in deviated/horizontal well. Through reasonable acoustic transducers and receivers design, compared with traditional segment cementing instruments, many factors that affect the logging quality such as decentralization and temperature can be eliminated cleverly. Perfect logging data was obtained in horizontal well.

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Theory and Applications of Reservoir Acoustics Application of Near-borehole Structures Imaging using Directional Reflected P-wave Jianlin Ben1,2, Wenxiao Qiao1,2, Xiaohua Che1,2, Xiaodong Ju1,2, Junqiang Lu1,2, Baiyong Men1,2 1)State Key Laboratory of Petroleum Resources and Prospecting, China University of Petroleum-Beijing, Beijing, China 2)Key Laboratory of Earth Prospecting and Information Technology, Beijing, China

Formation structures are not only important reservoir spaces but also excellent fluid flow passages. Therefore, the priority of reservoirs exploration is to seek favorable structures, such as fractures and faults. Logging information can be used to describe the formation structures, including the identifications of structure zones and the quantitative calculations of attitudes. However, the conventional logging can only evaluate structures within a few meters, which is limited by the relatively patchy radial detection zone, and it is difficult to accurately describe the longitudinal penetration depths and the lateral extension lengths. Acoustic reflection imaging logging usually measures structures with abnormal acoustic impedances, increasing the investigation range from one meter to dozens of meters, and leads a visual display. P-wave imaging has long been used to measure the distances between fractures and borehole, which is based on the symmetrical vibration modes of the transmitters and receivers [1]. And S-wave imaging obtains the relevant strike angles because of the directivity of transmitting and receiving transducers [2]. A newly developed azimuthal acoustic receiver sonde for a downhole tool based on phased-arc arrays records the acoustic signal individually [3]. Consequently, the directional reflected P-wave contains the azimuthal information and permits accurate measurements for structures. The application of the new method is demonstrated with an eight-direction data set measured in a borehole. Using the directionality of the reflected P-wave, the method successfully obtains the near-borehole structure boundaries and azimuths. In addition, the shorter wavelength of the reflected P-wave allows for imaging the smaller formation structures。 References [1] Hornby, B. E., Imaging of near-borehole structure using full-waveform sonic data, Geophysics 54 (1989), no. 6, 747-757. [2] Tang,X. M., Imaging near-borehole structure using directional acoustic-wave measurement, Geophysics69 (2004), no. 6, 1378-1386. [3] Che, X. H., Qiao, W. X., and Ju, X. D., Experimental study on the performance of an azimuthal acoustic receiver sonde for a downhole tool. Geophysical Prospecting 65 (2016), 1-12.

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Theory and Applications of Reservoir Acoustics Pre-stack Seismic Inversion of Tight Sandstone Reservoirs based on Levenberg-Marquardt Algorithm Shuang Xiao1, Jing Ba1, Qiang Guo1, Tiansheng Chen2 1)School of Earth Sciences and Engineering, Hohai University, Nanjing, China 2)Sinopec Petroleum Exploration and Production Research Institute, Beijing, China

The original seismic information may be affected by the post-stack processing, which in turn affects the following seismic interpretation and reservoir prediction. The pre-stack seismic data preserves the full characteristic information of amplitude versus offset or incident angle (AVO). The compressional wave, shear wave and density information can be computed by the AVO inversion of pre-stack data. The sensitivities of compressional wave and shear wave to fluid are different, and the different elastic parameters can be calculated by the combinations of three parameters (P- and S-wave velocities and density), which can effectively describe the underground rock physical properties. Aki-Richards equation directly relates the pre-stack seismic trace data to the angles. It is used in calculating reflection coefficients and forward modeling. In acquiring the highly non-linear model parameters, the iterative method is normally used due to the larger error resulted from linear approximation. The Levenberg-Marquardt (LM) algorithm is an optimization method which is widely used in geophysics. It achieves the convergence by adaptively adjusting the damping factor and has a higher iterative convergence rate. The iterative formula based on LM algorithm is as follows:

T 1 T xk 1  xk  (Ak Ak  K I) Ak fk （1）

Where x is the model parameter matrix, Ak is Jacobian matrix, f is the residual matrix and k is the damping factor. The LM algorithm has a strict requirement on the initial model value. The conventional initial model is given by the extrapolation method with log data, and the lack of log data may lead to large errors between the initial model and the true value. In this paper, the Simulate Annealing (SA) algorithm is used to generate the initial value for LM algorithm, which decreases the dependence of the algorithm on initial value. Then the algorithm is used iteratively to find the global optimal solution. This paper uses the pre-stack data to invert the compressional and shear wave velocity and density terms of the tight sandstone reservoirs from western Sichuan Basin. The inversion results are basically consistent with the log data, indicating that the proposed method can be well applied to the elastic parameter pre-stack inversion of tight sandstone reservoirs.

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Theory and Applications of Reservoir Acoustics Acoustic Relaxation Spectra Gas Detection Based on Deep Learning Wei Zheng2, Xue Wang1, Junyu Ren1, Ming Zhu1 1)Department of Information, HuaZhong University, Wuhan, China 2)State Grid Corporation of China Australia Representative Office

Traditional gas detection method of analyzing acoustic gas spectra mathematically is not practical for complicated components due to its complexity. A one-dimensional convolutional neural network (1D CNN) was established for acoustic spectra classification. The goal of this work was to extract small amount of representative acoustic spectrum points that can specify gas mixture components, since intensive sampling is quite expensive in practice. We verified that the 1D CNN extracted acoustic spectrum characteristic automatically and classified these characteristic frequency points with high accuracy. Furthermore, an acoustic relaxation gas detection Web application has been designed and tested. We provide an interactive and visualized simulation platform for acoustic relaxation spectra gas detection.

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Theory and Applications of Reservoir Acoustics Estimation of Formation Shear Attenuation using Dipole Acoustic Waveform Data Qiaomu Qi1, Arthur Cheng2, Yunyue Elita Li2 1)College of Geophysics, Chengdu University of Technology, Chengdu, China

2)National University of Singapore, Singapore

Formation S-wave attenuation, when combined with compressional attenuation, serves as a potential hydrocarbon indicator for seismic reservoir characterization (Klimentos, 1995). Sonic flexural wave measurements provide a direct means for obtaining the in-situ S-wave attenuation at log scale. The key characteristic of the flexural wave is that it propagates at the formation shear slowness and experiences shear attenuation at low frequency. However, in a fast formation, the dipole log consists of refracted P- and S-waves in addition to the flexural wave. The refracted P-wave arrives early and can be removed from the dipole waveforms through time windowing. However, the refracted S-wave, which is often embedded in the flexural wave packet, is difficult to separate from the dipole waveforms. The additional energy loss associated with the refracted S-wave results in the estimated dipole attenuation being higher than the shear attenuation at low frequency. To address this issue, we have developed a new method for accurately determining the formation shear attenuation from the dipole acoustic waveform data. The method uses a multifrequency inversion of the frequency-dependent flexural wave attenuation based on energy partitioning. We first developed our method using synthetic data. Application to field data results in a shear attenuation log that is consistent with lithologic interpretation of other available logs. Examples will be shown to illustrate the usefulness of sonic log attenuation in evaluating gas potential in shale reservoirs. References [1] T. Klimentos, Attenuation of P- and S-waves as a method of distinguishing gas and condensate from oil and water, Geophysics 60 (1995), 447–458.

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Theory and Applications of Reservoir Acoustics Effects of Background Anisotropy on Effective Elastic Properties of Fractured Rocks

Junxin Guo1,2, Tongcheng Han2, Li-Yun Fu2, Denghui Xu2, Xinding Fang1 1)Department of Earth and Space Sciences, Southern University of Science and Technology, Shenzhen, China 2)School of Geosciences, China University of Petroleum (East China), Qingdao, China

Seismic characterization of fractures is of great importance in many disciplines, for which rock physics models provide the basis to link fracture properties to seismic attributes. However, to date, most rock physics models neglect the background anisotropy which may exist in many fractured formations. Hence, in this work, we developed a theoretical model for rock effective elastic properties with penny-shaped cracks embedded in the transversely isotropic (TI) background medium. We first derived analytical solutions for the case with dry or fluid-filled penny-shaped cracks parallel to the isotropic plane of TI background medium. Further, the results were extended to the case with cracks inclined to the isotropic plane with any angles. We then studied, based on the developed theoretical model, two tight sand samples with TI and isotropic background, respectively to illustrate effects of background anisotropy on effective elastic properties of fractured rocks. The results show that the background anisotropy has significant influence on P- and S- wave velocity anisotropy, as well as on shear wave splitting. The background anisotropy can either increase or decrease P- and SH- wave velocity anisotropy depending on crack inclination angles, whereas it has relatively small influence on SV-wave velocity anisotropy. To further illustrate the important effects of background anisotropy, we compared theoretical predictions to ultrasonic measurements on a synthetic fractured sandstone sample with TI background medium. The results show notable improvement of the agreement between theoretical predictions and experimental results after considering background anisotropy.

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Theory and Applications of Reservoir Acoustics Carbonate Reservoir Characterization by Using Joint Seismic Attributes Fan Li, Jing Ba, Cun Yu, Jian Zhou School of Earth Sciences and Engineering, Hohai University, Nanjing, China

Conventional interpretation methods face difficulties to effectively identify carbonate oil/gas reservoirs in China, because those carbonate reservoirs generally have the characteristics of deep burial, complex sedimentary environment, low porosity, low permeability and strong heterogeneity. In this paper, a new prediction method based on joint seismic attributes is proposed, which combines seismic attenuation properties and seismic instantaneous phase properties to construct a joint indicator. It can be used to characterize the pore-permeability features and gas- bearing potential in carbonates. The theoretical assumption of the improved frequency shift method suggest that seismically estimated Q can effectively reduce the effect of noise. The quality factor Q is estimated as follows: 2  tf c2 fc1 Q  2 2 (1) 16( fc1  fc2 ) where, t is the travel time, fc1 is the centroid frequency of the signal before attenuation, and fc2 is the centroid frequency of the signal after attenuation. The instantaneous phase property is affected by the fluid content in reservoir rocks. Generally, when the seismic signal transmits through a reservoir interface, the seismic reflection parameters changes and phase features were reversed. Therefore, the instantaneous phase is used to detect the lithologic boundary to achieve a good recognition effect. The estimation equation is: g(t) IP(t)  arctan (2) f (t) where, g(t) is the imaginary part of the Hilbert transform of the original seismic record, and f (t) is the real part. The normalized attenuation attribute and instantaneous phase attribute are combined to construct the indicator Qx , and the expression is:

Qx  mQg  (1 m)IPg (3) where, m is the weight coefficient, Qg is the normalized parameter of Q , IPg is the normalized parameter of IP , which will be decided based on vertical resolution of target reservoir and the actual reservoir thickness. The Qx indicator not only preserves the horizontal distinguishing ability of the attenuation attribute for the stratum, but also incorporates the vertical resolution, therefore it can be used for a relatively complete prediction for reservoir quality. The new joint attribute is used for characterizing complex carbonate reservoirs from west China. Qx is shown to identify the reservoirs, which reflects the true thickness of the reservoir, and simultaneously distinguishes hydrocarbon-bearing rocks from brine-saturate ones. 159

Theory and Applications of Reservoir Acoustics Using Finite-Difference Method to Simulate the Radiation Wavefield of A Double-Couple Point Source Induced by Hydraulic Fracturing Chengwei Zhang1,2, Wenxiao Qiao1,2, Xiaohua Che1,2 1)State Key Laboratory of Petroleum Resources and Prospecting, China University of Petroleum, Beijing, China 2)Key Laboratory of Earth Prospecting and Information Technology, Beijing, China

Hydraulic fracturing is an essential technology for oil and gas development and production. Study of a fracturing-induced microseismic source mechanism is valuable for understanding fracture growth, wavefield characteristics and stress-field evolution within a reservoir, knowledge of which can help to increase production and reduce earthquake risk. Seismic moment tensor, which is a matrix of nine force couples, was most commonly used to describe the seismic source. According to different rupture characteristics, the focal mechanism has three different mathematical representations: isotropic (ISO), double couple (DC), and compensated linear vector dipole (CLVD). The pure ISO source is usually used to indicate pure expansion or implosive force, the pure DC source is caused by shear faulting, which is the most common case in fracturing-induced seismicity, the CLVD source is accompanied by the ISO source but is more complicated than pure ISO source. In this study, we use the staggered-grid finite-difference method to simulate the radiation wavefield of a hydrofracturing-induced double-coupled source in a 3D isotropic media. Considering the spatial distribution of stress and velocity nodes in staggered grid, we apply a single forces onto the velocity nodes along the horizontal direction to construct a double-couple source model. According to the simulated solutions, in the far field, the P-waves have only a radial component and the S-waves have transverse components only. Both the radiation patterns for the P- and S-waves have four lobes. For the longitudinal wave radiation lobes, the particle motion alternately changes in the adjacent lobes, and the initial movement of the particle is positive (outward) for the lobes corresponding to the compressive stress, and the initial movement of the particle for the lobes corresponding to the tensile stress is negative (inward). For the shear wave radiation lobes, the particle motion is also alternately changed between adjacent lobes. The direction of particle motion is either clockwise or counter-clockwise, while the radiation direction with the maximum waveform amplitude is the horizontal and vertical direction. The numerical simulation is consistent with the analytical solution, which indicates that the finite- difference method is an effective tool for microseismic double-couple source simulation. References [1] K. Aki, P. G. Richards, Quantitative seismology, 2. ed., University Science Books, 2009, ISBN: 978-1-891-38963-4.

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Theory and Applications of Reservoir Acoustics Rock Physics Template of a Crack-Pore System of Tight Sandstone Reservoirs Runfa He, Jing Ba, Cong Luo, Rupeng Ma 1School of Earth Sciences and Engineering, Hohai University, Nanjing, China

Tight sandstone generally has the geological characteristics of low porosity, low permeability, containing developed micro-crack, and presents a strong heterogeneity. The rock physical model can be used to connect reservoir physical parameters with seismic data information. Conventional rock physics models are built based on the simplified assumptions (for instance, inhomogeneity, single- porosity, single-scale, etc.). Hence the established rock physics template by such rock physics models is not suitable for complexed tight sandstone reservoirs. In this abstract, based on the Biot-Rayleigh equation of wave propagation in double- porosity rocks, a rock physical model is established to predict the reservoirs by considering crack parameters. Based on the theoretical models, this abstract presents the process of rock physical modeling for tight sandstones. The specific steps are as follows: (1) The Voigt- Reuss-Hill (VRH) model is used to calculate the elastic modulus of the rock matrix according to the mineral compositions and contents of reservoir rocks in the geological data; (2) The differential elastic medium (DEM) model is used to calculate the elastic modulus of the main rock skeleton containing cracks; (3) The P- wave velocity and S-wave velocity are obtained by the fluid substitution with the Biot- Rayleigh equation. According to the rock elastic parameters calculated by the model, the elastic parameter combination, which is sensitive to the pore and crack content, is preferably selected to construct the crack-pore rock physical template, and the experimental and logging data are used to correct the template. Taking the tight sandstone gas reservoirs of the western Sichuan Basin as an example, based on the calibrated template, the reservoir porosity and crack content are inverted with the pre- stack seismic data, and the inversion results near borehole are compared with the estimated porosity curves by well logs and gas production reports. The results show that the crack content and porosity are consistent well with the estimated curves and production reports. It shows the effectiveness of the proposed template in quantitative interpretation of gas reservoirs.

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Theory and Applications of Reservoir Acoustics Poro-acoustoelasticity Theoretical Model with Embedded Microcracks for Saturated Carbonates Wenchang Ling, Jing Ba, Qiang Guo School of Earth Sciences and Engineering, Hohai University, Nanjing, China.

Variations of pore pressure and tectonic stresses play an important role in triggering earthquakes, enabling safe drilling, and efficiently exploiting reservoirs. Elastic wave velocities or elastic moduli are strongly affected by subsurface pore pressure and tectonic stresses, which, in turn, are used to monitor variation in the stresses. Stress-induced influences on elastic wave velocities include elastic and inelastic behaviors. In general, deformation of rocks is primarily linear to small- magnitude stresses. The conventional poro-acoustoelasticity combines the kinetic and strain energy functions via the Lagrange equation. The theory reveals the strain energy transformation of the stiff pores and rock grains for velocity variations. This theory assumes a homogeneous rock structure and neglects the microcracks. In this paper, we assume that the development of microcracks is classified into the three stages as external load increases: closing, stable, and developing, which are respectively responsible for three stages of deformation. Hence, a continuum model derived from the mechanics of tensile microcracks is presented which describes the deformation of saturated rocks. Based on the microcrack models of effective medium theories [1], the criterion for the initiation of damage (crack growth) is derived from the analysis of individual cracks. Then the evolution of a population of microcracks in a material element is specified by generalizing the behavior of a single fracture to that of a random ensemble of microcracks. The correlation between the mineral matrix modulus and stress is predicted by the model. We incorporate the microcrack model into the conventional poro- acoustoelasticity theory accounting for linear and nonlinear elastic deformations. Application of the proposed model to ultrasonic measurements under different differential stresses for the five cylindrical carbonate samples shows that the poro- acoustoelasticity with microcracks can provide predictions for stress-induced velocity variations with better accuracy. In this paper, we also discuss on the errors between theoretical predictions and measurements by examining the influence of local flows and microstructures. References [1] G. Mavko, T. Mukerji, J. Dvorkin, The rock physics handbook: Tools for seismic analysis of porous media, 2. Ed., Cambridge university press, New York, 2009, ISBN: 978-0-521-86136-6

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Theory and Applications of Reservoir Acoustics Effect of Aligned Inclined Cracks on Elastics on Properties of Transversely Isotropic Rocks Denghui Xu, Tongcheng Han School of Geosciences, China University of Petroleum (East China), Qingdao, China

Natural rocks normally contain a lot of cracks, which are not parallel to the layers. Assuming that the X-Y plane is the isotropic plane, there are two angles between a randomly orienting crack and the planes in the three-dimensional (3D) coordinate system, i.e., the angles to the X-Y plane and to the Y-Z plane, respectively. In this work, we first derived the analytical solutions for the case with the penny-shaped cracks parallel to the isotropic plane of the TI background medium. Further, the results were extended to the case where the cracks are inclined to the isotropic plane with any angles. Finally, based on the definition of the compliance tensor (e.g., Kachanov, 1992) and the expressions for normal and shear fracture weakness (Schoenberg and Sayers, 1995), we derive equations for the compliance matrix of the 3D inclined cracks by changing the normal vector of the inclined cracks. Based on the derived models, we study the effect of varying θ and φ on the elastic properties of transversely isotropic media, where, θ and φ are the angles between cracks and the X-Y plane (the isotropic plane) and the Y-Z plane, respectively. It is found that both inclined angle of the cracks have significant influence on the elastic coefficients, among which C11, C22 , C33 are sensitive to the variation of φ and θ because of the change of P-wave velocity travelling along the x, y and z axis. To validate our theoretical model, we compared the theoretical predictions of our results to other models. The results show good agreement between them. The theoretical model proposed in this paper is convenient to use, and can be applied to simulate the effects of random cracks on the elastic properties of the fractured formations. References [1] Kachanov, M. (1992). Effective elastic properties of cracked solids: critical review of some basic concepts. Applied Mechanics Reviews, 45, 304-335. [2] Schoenberg, M., & Sayers, C. M. (1995). Seismic anisotropy of fractured rock. Geophysics, 60, 204–211. [3] Guo, J., Han, T., Fu, L., Xu, D., & Fang, X. (2019). Effective elastic properties of transversely isotropic rocks permeated by aligned penny-shaped cracks. Journal of Geophysical Research: Solid Earth, 124, 400-424.

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Theory and Applications of Reservoir Acoustics Characteristics of Waves in Gas Hydrate-Bearing Sediments Lin Liu1,2,3, Xiu-mei Zhang1,3, Xiu-ming Wang1,3 1)State Key Laboratory of Acoustics, Institute of Acoustics, Chinese Academy of Sciences, Beijing, China 2)University of Chinese Academy of Sciences, Beijing, China 3)Beijing Engineering Research Center of Sea Deep Drilling and Exploration, Beijing, China In this paper, based on Carcione’s extention[1] of a Biot-type three-phase theory[2,3] in frozen porous media, combined with physically based components such as friction between two solid phase components by Geurin[4], applying an improved method for calculating elastic modulus of skeleton by Lee[5], the propagation characteristics of elastic waves in gas hydrate-bearing sediments are studied. Variations of phase velocities and attenuation of different type of body waves with frequencies, gas hydrate saturation, porosity, etc. are analyzed. The investigations give comprehensive relations of the velocity and attenuation with varies parameters. In particular, the features of these waves in the frequency range of seismic exploration and acoustic logging are studied. The analyses show that there is no dispersion of P1 and S1 waves in seismic exploration and acoustic logging frequency range, the phase velocities of these two waves increase linearly with the increase of gas hydrate saturation. In seismic exploration frequency range, P2, S2, and P3 waves are dispersive, and the attenuation of them is large. In acoustic logging frequency range, however, P2, S2, and P3 waves are nondispersive when the gas hydrate saturation and porosity are low, the phase velocities increase linearly with the increase of porosity, and the attenuation of them is small. Clay reduces the phase velocities of P1 and S1 waves significantly and has almost no effect on phase velocities of S2 and P3 waves. In the frequency range of seismic exploration, clay has little impact on the phase velocity of P2 wave, while clay reduces the phase velocity of P2 wave obviously in the frequency range of acoustic logging. Clay increases the attenuation of P1 wave, and the attenuation of S1, P2, S2 and P3 waves is not affected by clay content basically. Under the influence of the squirt-flow mechanism[6], the phase velocity of P1 wave is almost unaffected, while the velocities of P2 and P3 waves are influenced. This study has provided the foundation for our further research of the determination of gas hydrate saturation based on velocity and attenuation under different cases. References [1] J M. Carcione, J E. Santos, and C L. Ravazzoli, Wave Simulation in Frozen Porous Media, Journal of Computational Physics 170 (2012), no. 2, 676-695. [2] M A. Biot, Mechanics of Deformation and Acoustic Propagation in Porous Media, Journal of Applied Physics 33 (2004), no. 4, 1482-1498. [3] Ph. Leclaire, Extension of Biot’s theory of wave propagation to frozen porous media, The Journal of the Acoustical Society of America 96 (1994), no. 3, 3753. [4] G. Guerin, D. Goldberg, Modeling of acoustic wave dissipation in gas hydrate- bearing sediments, Geochemistry Geophysics Geosystems 6 (2005), no. 7, 1-16. [5] M W. Lee, W F. Waite, Estimating pore-space gas hydrate saturations from well log acoustic data, Geochemistry Geophysics Geosystems 9 (2008), no. 7, 1-8. [6] J. Dvorkin, R. Nolen-Hoeksema, and A. Nur, The Squirt-flow mechanism: Macroscopic description, Geophysics 59 (1994), no. 3, 428-438. 164

Theory and Applications of Reservoir Acoustics Theoretical Modeling on Compressional Wave Velocity Variation with Temperature in Fluid-saturated Rocks Hui Qi, Jing Ba, Cong Luo, Rupeng Ma School of Earth Sciences and Engineering, Hohai University, Nanjing , China The influences of pressure and temperature on the physical and mechanical properties of rocks have been an essential topic in rock mechanics. High pressure and temperature affect the thermal stress, mineral expansion, physical and mineralogical properties of rock. However, at present, the research is rare in the temperature dependence of ultrasonic wave velocities in saturated rocks. In this work, we analyze the variations of the P-wave velocities with the temperature in saturated rocks. In this paper, based on the Biot-Rayleigh double-porosity model (BR) and Batzle- Wang formulas (BW), we propose a model to characterize the relationship between seismic properties and reservoir temperature. We use the BW formulas to calculate the fluid parameters in different temperature conditions. And the P-wave velocities of the saturated rock are given by plane wave analysis method. Besides the proposed model also considers the heterogeneity of rocks. The P-wave velocity variation with temperature is simulated by this model. When the temperature is below 150 ℃, the P-wave velocities slightly decrease with the increasing temperature. However, the P-wave velocities sharply drop when the temperature is more than 150 ℃. Because the effect of temperature on seismic velocities is closely related to the thermophysical properties of the pore fluid. The temperature increase causes the thermal expansion of rock minerals, promotes the development of micro- fractures in rocks, and then leads to the rapid decreases of P-wave velocities. The basalt and hyaloclastite rock samples are collected in Krafla and Hengill, Iceland. The porosities and densities of samples are 20% and 20.7%, 2.37g/cm3 and 2.15g/cm3, respectively. The experimental measurements are carried out by Jaya [1] on the samples at the temperature range of 0~300℃. We analyze these experimental data of the water-saturated rock samples by using the proposed model. The predicted P-wave velocities fit well with the experimental data, which indicates that the model, to some extent, can effectively describe the variation rule of P- wave velocity with the temperature of basalt and hyaloclastite. The predicted results of the model are also compared with that of the modified Gassmann equation (MG) [1]. The MG results have relatively lower consistency, especially at high temperature. Because of the hard texture of basalt and hyaloclastite, the hard pores within the rock gradually soften with the temperature increases, which causes the pore structure change of the rock and further changes the fluid flow channel. Therefore, compared with our model, the MG method ignores the changes in the complex pore structure at high temperature. References [1] M.S. Jaya, et al, Temperature dependence of seismic properties in geothermal rocks at reservoir conditions, Geothermics 39 (2010), no.1, 115–123. 165

Theory and Applications of Reservoir Acoustics Finite Difference Modeling of Wave Fields in Fluid- Filled Boreholes Excited by Linear Phased Array Acoustic Transmitters Shubo Yang1,2, Wenxiao Qiao1,2, Xiaohua Che1,2, Xiaodong Ju1,2 1)State Key Laboratory of Petroleum Resources and Prospecting, China University of Petroleum, Beijing, China 2)Key Laboratory of Earth Prospecting and Information Technology, Beijing, China

The investigation depth and the measurement resolution of conventional monopole acoustic logging tools are limited for the following two shortcomings of monopole acoustic transmitters. First, only a small amount of energy is radiated to the formation on the receiver side, with most energy forming useless waves. Second, the energy distributions in fluid-filled boreholes cannot be controlled. In this study, a method is proposed to enhance the amplitudes of refracted compressional (P) and shear (S) waves under wireline-logging (WL) and logging-while-drilling (LWD) conditions, based on the directional radiation technology of linear phased array (LPA) acoustic transmitters. Waveforms in the fluid-filled boreholes generated by the monopole and LPA acoustic transmitters under WL and LWD conditions are numerically simulated using the finite-difference time-domain (FDTD) method. Moreover, the influences of LPA parameters on the refracted P and S waves are also analyzed. The simulation results show that, the guided waves in the borehole generated by the LPA acoustic transmitter have the same type but different relative amplitudes compared to those generated by the monopole acoustic transmitter, whether under WL condition or LWD condition. The angular width and deflection angle of the main radiated acoustic beam in the borehole can be controlled by adjusting the LPA parameters. As the delay time between the excitation signals applied to adjacent elements increases, the deflection angle satisfies the generation conditions for the refracted P and S waves, successively. When the deflection angle is equal to the first (or second) critical angle of the formation, the amplitudes of the refracted P (or S) waves are greatly enhanced, and the multiples increase linearly as the element number increases. Therefore, compared to the monopole acoustic transmitter, the LPA acoustic transmitter can be utilized to effectively improve the reliability of acoustic logging tools in measuring formation velocities. This study establishes a theoretical foundation for the development of next-generation acoustic WL and LWD tools. References [1] J. Wu, W. Qiao, X. Che, X. Ju, J. Lu, and W. Wu, Experimental study on the radiation characteristics of downhole acoustic phased combined arc array transmitter, Geophysics 78 (2013), no. 1, D1-D9. [2] X. Che, W. Qiao, X. Ju, J. Lu, J. Wu, and M. Cai, Experimental study of the azimuthal performance of 3D acoustic transmitter stations, Petroleum Science 13 (2016), no. 1, 52-63.

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Boundary Element Methods Acoustic Shape Optimization based on Fast Multipole Isogeometric BEM with Adjoint Variable Method Haibo Chen1, Jie Wang1, Wenchang Zhao1, Changjun Zheng2, Leilei Chen3 1)CAS Key Laboratory of Mechanical Behavior and Design of Materials, Department of Modern Mechanics, University of Science and Technology of China, Hefei, China 2)Institute of Sound and Vibration Research, HFUT, Hefei, China 3)College of Civil Engineering, Xinyang Normal University, Xinyang, China

According to the concept of isogeometric analysis (IGA), Non-Uniform Rational B-splines (NURBS) are used to describe the geometry and approximate the physical fields. This treatment circumvents the requirement of mesh regeneration, which is a significant progress in reducing the gap between engineering design and analysis. In this work, we introduce the fast multipole method (FMM) to the IGA boundary element method (BEM) of two dimensional(2D) acoustic problems to improve its numerical efficiency. Furthermore, we apply the FMM IGA BEM to acoustic shape optimization. The key treatment is the acoustic sensitivity analysis using the adjoint variable method (AVM). Compared with the direct differentiation method (DDM), the AVM is more suitable for problems with a large number of design variables. The gradient-based optimization solver is applied for updating the design variables during the optimization iteration process and the Burton-Miller method is adopted to conquer the fictitious eigen-frequency problem in solving exterior acoustic problems. An example of scattering by an infinite rigid cylinder is presented to demonstrate the acceleration and the improved accuracy of FMM IGA BEM. Then we verify the efficiency of the developed sensitivity algorithm through the same model and demonstrate its potential in solving large-scale engineering problems. Finally, an optimization example is provided to validate the proposed optimization procedure. Numerical tests also show that the optimal results are strongly frequency dependent. References [1] Zhao WC,Chen LL, Chen HB, Marburg S. Topology optimization of exterior acoustic-structure interaction systems using the coupled FEM-BEM method,International Journal for Numerical Methods in Engineering,2019: 1- 28. [2] Zhao WC, Zheng CJ, Liu C, Chen HB. Minimization of sound radiation in fully coupled structural-acoustic systems using topology optimization, Structural and Multidisciplinary Optimization, 2018,58(1): 115-128. [3] Liu C., Chen LL., Zhao WC., Chen HB., Shape optimization of sound barrier using an isogeometric fast multipole boundary element method in two dimensions, Engineering Analysis with Boundary Elements 85(2017): 142–157.

167

Boundary Element Methods Towards Large-scale Acoustic Shape Optimization Including Viscous and Thermal Losses Peter Risby Andersen1,a, Vicente Cutanda Henríquez1,a, Niels Aage1,b 1)Centre for Acoustic-Mechanical Micro Systems, Technical University of Denmark, Kgs. Lyngby, Denmark a)Department of Electrical Engineering b)Department of Mechanical Engineering

Accurate modeling of acoustic viscous and thermal dissipation effects is necessary for the study of the behavior of many acoustic devices. It is therefore crucial that acoustic devices, such as acoustic absorbers, transducers and hearing aids are designed with dissipative effects in mind. Shape and topology optimization techniques based on numerical models have gained interest because they open the door to new improved designs with better performance. However, often the modeling of acoustic viscous and thermal dissipation is neglected or simplified [1,2]. The importance of acoustic viscous and thermal losses in combination with gradient- based shape optimization was recently demonstrated by the design of acoustic quarter-wave and Helmholtz resonator absorbers [3]. However, the efficiency of the current shape optimization technique is restricted by a simple finite difference sensitivity analysis limiting the approach to small problems with few design variables. Different and more efficient shape optimization implementation techniques are needed in order to attack large-scale problems with many design variables. Therefore, in this work, we discuss the implementation and performance of a semi- analytical discrete adjoint sensitivity analysis approach applied in combination with gradient- based viscothermal Boundary Element Method shape optimization. This includes several optimization examples showcasing the potential of the shape optimization technique for developing new high performing acoustic devices where losses can be included in the design process. References [1] R. Udawalpola, E. Wadbro, M. Berggren, Optimization of a variable mouth acoustic horn, International Journal for Numerical Methods in Engineering 84 (2011), no. 5, 591-606 [2] R. E. Christensen, E. Fernandez-Grande, Experimental validation of a topology optimized acoustic cavity, Journal of the Acoustical Society of America 138 (2015), 3470-3474 [3] P. R. Andersen, V. Cutanda Henriquez, N. Aage, Shape optimization of microacoustic devices including viscous and thermal losses, Journal of Sound and Vibration 447 (2019), 120-136

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Boundary Element Methods Shape and Topology Optimization of Three Dimensional Acoustic Problems with Isogeometric Boundary Element Method L.L. Chen1, C. Lu1, W.C. Zhao2, H.B. Chen2, S. Marburg3 1)College of architecture and civil engineering, Xinyang Normal University, Xinyang, China 2)Department of Modern Mechanics, University of Science and Technology of China, Hefei, China 3)Institute of Vibroacoustics of Vehicles and Machines, Faculty of Mechanical Engineering, Technical University of Munich, Garching bei München, Germany

The isogeometric boundary element method (IGABEM) is a recent progress in the category of boundary element approaches, which is inspired by the concept of isogeometric analysis (IGA) and employs the spline functions of CAD as basis functions to discretize unknown physical fields. The advantage of IGABEM: (1) the geometry and the analysis can be interacted, (2) remeshing with shape morphing can be avoided, and (3) an optimized solution returns a CAD geometry directly without postprocessing steps [1]. In the present paper, we apply the IGABEM to structural shape and topology optimization of three dimensional exterior acoustic problems, fully exploiting the strength of IGABEM in addressing infinite domain problems and integrating CAD and numerical analysis. Shape optimization using NURBS to obtain optimal structural design scheme, and topology optimization approach based on subdivision surfaces is proposed for the optimal distribution of sound absorbing material on structural surfaces [2]. The spline interpolation was used for both geometric interpolation and physical interpolation, achieving high-order approximation of the structural surface and physical field. We employ the Burton-Miller formulation to overcome fictitious frequency problems, in which hyper-singular integrals are evaluated explicitly. The gradient-based optimizer is adopted, where shape sensitivity analysis is conducted with implicit differentiation methods and topology sensitivity analysis is applied to adjoint variable methods. The design variables are set to be the positions of control points which directly determine the shape of structures. The proposed algorithm is then applied to some numerical examples to illustrate the potential for engineering optimization design. References [1] Liu Z, Majeed M, Cirak F, et al. Isogeometric FEM-BEM coupled structural- acoustic analysis of shells using subdivision surfaces[J]. International Journal for Numerical Methods in Engineering, 2018, 113(9): 1507-1530. [2] Zhao W, Chen L, Zheng C, et al. Design of absorbing material distribution for sound barrier using topology optimization[J]. Structural and Multidisciplinary Optimization, 2017, 56(2): 315-329.

169

Boundary Element Methods Design of Damping Layer by Topology Optimization and Non-negative Intensity Wen-Chang Zhao1,2, Hai-Bo Chen1, Steffen Marburg2 1)CAS Key Laboratory of Mechanical Behavior and Design of Materials, Department of Modern Mechanics, University of Science and Technology of China, Hefei, Anhui, 230027, China 2)Chair of Vibroacoustics of Vehicles and Machines, Faculty of Mechanical Engineering, Technical University of Munich, 85748 Munich, Germany

Non-Negative Intensity (NNI) is a quantity which avoids near-field cancellation effects in sound intensity and provides direct visualization of the surface contributions to the radiated sound power. Hence, minimizing the sum of NNI on predefined surfaces is implemented to be the design objective of topology optimization for damping layer design in this work. NNI can be easily computed based on the radiation modes and the particle velocity on the surfaces of interest. Regarding the radiation modes, an eigenvalue analysis for the acoustic impedance matrix is required. This can be performed by combining the boundary element method (BEM) and the implicitly restarted Arnoldi method (IRAM). Furthermore, the fast multipole method (FMM) is adopted to improve the efficiency of BEM. To compute the particle velocity on structural surfaces, a two-way coupling of the finite element method (FEM) and the BEM is established. After evaluating the objective function, the gradients of the objective function are computed by an adjoint variable method. These gradients enable the optimization to be solved by the method of moving asymptotes (MMA). Finally, some numerical examples are presented to validate the proposed optimization approach.

170

Boundary Element Methods On the Choice of Solution Schemes for the Acoustic Boundary Element Method with many Right-Hand Sides

Christopher Jelich, Steffen Marburg 1)Chair of Vibroacoustics of Vehicles and Machines, Technical University Munich, Garching, Germany

Today’s design processes in engineering are heavily relying on numerical computations. This is especially true in the early design stages at which the cost of assessing the products’ behavior and properties experimentally is unreasonably high. Here, numerical analyses are the method of choice. Analyzing a design numerically can be brought down to solving partial differential equations (PDE). Contemporary numerical models are large-scale and thus, discretizing the PDE yields large systems of linear equations. Since solving the corresponding systems is very time consuming and needs to be done repeatedly during the design process, developing more efficient solution schemes has been an extensive field of research over the last decades. In the recent past, the engineers’ need for evaluating the products’ performance for many different load cases or for uncertain parameters has become imminent. Mathematically speaking, this often implies solving systems of linear equations with many right-hand sides. Fortunately, efficient solution techniques already exist for those system types. However, in many cases, and especially in the field of acoustics, it is still unclear which scheme performs best under certain circumstances. This question will be addressed in this talk. The general focus is set on time- harmonic acoustic problems with a particular emphasize on systems of linear equations arising from boundary element discretizations. Based on a numerical study using academic examples, the most promising solution techniques for systems with many right-hand sides are compared. Among others, these include the block variants of well-known Krylov subspace methods [2] and the block IDR(s) method [1]. A general recommendation on which solution scheme to pick will be given. Keywords: Boundary Element Methods, Krylov Subspace Methods, Many Right- Hand Sides, Helmholtz Equation, Iterative Solvers References [1] L. Du, T. Sogabe, B. Yu, Y. Yamamoto and S.-L. Zhang, A block IDR(s) method for nonsymmetric linear systems with multiple right-hand sides, Journal of Computational and Applied Mathematics 235 (2012), no. 14, 3–11. [2] M. H. Gutknecht, Block Krylov space methods for linear systems with multiple right-hand side: An introduction, In: “Modern mathematical models, methods and algorithms for real world systems”, Anshan, 2007, ISBN: 1- 904798-64-0.

171

Boundary Element Methods Combined Optimization of Structural Shape and Absorbing Material Distribution for Sound Barrier

Fuhan Jiang1, Zhenyun Wu1, Wenchang Zhao1, Leilei Chen2, Haibo Chen1 1)CAS Key Laboratory of Mechanical Behavior and Design of Materials,Department of Modern Mechanics, University of Science and Technology of China, Hefei, China 2)College of Architecture and Civil Engineering, Xinyang Normal University, PR China

Reducing noise level in human surroundings is an important issue in engineering. A combined optimization algorithm is developed in this work to devise high performance sound barrier by means of a concurrent optimization of structural shape and absorbing material distribution. The boundary element method (BEM) is used for acoustic analysis and sensitivity evaluation of objective function. The method of moving asymptotes (MMA) is used for the optimization procedure. A topology optimization model is set up based on continuous material interpolation function for the absorbing material. The shape optimization method is established by selecting elements as design variables and volumes of sound barrier as constraints. The objective function of the shape and topology method is the sound pressure at reference surface. We also introduce the Burton-Miller method to avoid the non- uniqueness problem of the solution in solving the semi-infinite acoustic problem by the conventional boundary integral equation method. Numerical tests are provided to illustrate the validity of the proposed algorithm, which also show that the combined optimization algorithm performs better than using shape or topology optimization alone in the design of sound barrier. References [1] Zhao W, Chen L, Zheng C, et al. Design of absorbing material distribution for sound barrier using topology optimization, Structural and Multidisciplinary Optimization, 56(2017), no. 2, 315-329. [2] Liu C, Chen L, Zhao W, et al. Shape optimization of sound barrier using an isogeometric fast multipole boundary element method in two dimensions, Engineering Analysis with Boundary Elements, 85(2017), 142-157.

172

Boundary Element Methods Topology Optimization of Sound Absorbing Materials Using Subdivision Surface Boundary Element Method C. Lu1, L.L. Chen1, W.C. Zhao2, H.B. Chen2 1)College of architecture and civil engineering, Xinyang Normal University, Xinyang, China 2)Department of Modern Mechanics, University of Science and Technology of China, Hefei, China

The subdivision surface overcomes the difficulty of the gap in the surface slice splicing of NURBS, and can express the geometric with arbitrary free-form topology, so as to construct the smooth and continuous overall surfaces. This method has the following advantages: 1). It is suitable for any topological structure; 2). The numerical calculation is stable; 3). It is simple to implement; 4). Local refinement and continuity control. In the acoustic field, the higher the frequency, the shorter the wavelength and the larger the number of meshes required. Combining the Loop subdivision surface with the boundary element method, the high-order box-splines interpolation is superior to the traditional Lagrangian interpolation in the calculation accuracy. In the present paper, a topology optimization approach is proposed for find optimal distribution of sound absorbing material for a given subdivision structural mesh. The densities of the sound absorbing material are used as the design variables. A minimum volume of the sound absorbing material is used as the optimizing constraint. The optimization problem is solved by using the method of moving asymptotes algorithm. Subdivision surfaces begin with a coarse polygon mesh and applies a certain subdivision algorithm to recursively refine this polygon mesh until refined meshes eventually converge to a smooth limit surface[1]. Cirak[2] implemented Loop subdivision surfaces for Krichhoff-Love shell analysis in 2000. A topology optimization approach based on the boundary element method is proposed for the optimal design of sound absorbing material distribution[3]. References [1] Liu Z, Majeed M, Cirak F, et al. Isogeometric FEM-BEM coupled structural- acoustic analysis of shells using subdivision surfaces[J]. International Journal for Numerical Methods in Engineering, 2018, 113(9): 1507-1530. [2] Cirak F, Ortiz M, Schroder P, et al. Subdivision surfaces: a new paradigm for thin‐shell finite‐element analysis[J]. International Journal for Numerical Methods in Engineering, 2000, 47(12): 2039-2072. [3] Zhao W, Chen L, Zheng C, et al. Design of absorbing material distribution for sound barrier using topology optimization[J]. Structural and Multidisciplinary Optimization, 2017, 56(2): 315-329.

173

Boundary Element Methods Evaluation of a Hybrid FEM-BEM Implementation of Acoustics with Visco-Thermal Losses Vicente Cutanda Henriquez Centre for Acoustic-Mechanical Micro Systems (CAMM), Technical University of Denmark, Kgs. Lyngby, Denmark

The modeling of acoustic setups including viscous and thermal losses is of particular relevance for devices where narrow features in the millimeter/micrometer range are present. Most of these losses take place in the so-called viscous and thermal boundary layers, which for the audible frequencies have thicknesses ranging from a few micrometers to a fraction of a millimeter. When these thicknesses are comparable to the dimensions of the acoustic domain, the effect of losses can be very relevant and should be accounted for. This is the case of many acoustic transducers, couplers, absorbing materials and acoustic metamaterials. The available tools for acoustic modeling with losses include analytical models for simplified geometries, numerical models with simplifying assumptions and full numerical models. In the latter class, the linearized Navier-Stokes equations with no flow are discretized by means of the Finite Element Method (FEM) or the Boundary Element Method (BEM). In BEM, the Kirchhoff decomposition is employed to split the sound field into three modes: acoustic, thermal and viscous, which are then discretized independently and coupled at the boundary. Recently, new implementations where FEM is employed for the acoustic mode and BEM for the viscous and thermal modes have been proposed [1,2]. In both cases, the FEM and BEM matrices are sparse: FEM already produces sparse matrices, while BEM is only used for the thermal and viscous modes, which die out at a short distance, making most BEM matrix coefficients negligible. In this work, the hybrid FEM-BEM with losses is analyzed in terms of stability, convergence, and computational load. The goal is defining the class of problems where the new method can be advantageous in terms of size, geometrical complexity and frequency range. References [1] Cutanda Henriquez, V., Juhl, P. M. & Barrera Figueroa, S., Modeling of measurement condenser microphones at low frequencies: numerical issues, Proceedings of Inter-noise 2019. Madrid, Spain, 2019. [2] Andersen, P. R., Cutanda Henriquez, V., Aage, N. & Marburg, S., Numerical Acoustic Models Including Viscous and Thermal losses: Review of Existing and New Methods, Proceedings of DAGA 2017. Deutsche Gesellschaft für Akustik e.V., Kiel, Germany, 2017.

174

Boundary Element Methods A Half-space FMBEM for the Simulation of Sound Propagation Above an Impedance Plane Chang-Jun Zheng1, Hai-Bo Chen2 1)Institute of Sound and Vibration Research, Hefei University of Technology, Hefei, China 2)Department of Modern Mechanics, University of Science and Technology of China, Hefei, China

Half-space acoustic problems are of great importance, since sound fields caused by radiation or scattering from structures are seldom found in the boundless free space. In many cases, a flat ground with certain surface impedance confines the acoustic space as it encounters for instance when treating the problems of outdoor sound propagation. Although the boundary element method (BEM) is a mighty tool for predicting sound fields, the conventional method is restricted to small models at low frequencies because of the high solution cost. In this paper, a half-space fast multipole BEM (FMBEM) is presented for 3D acoustic wave problems over an infinite impedance plane. The half-space impedance Green’s function based on the complex images [1] is used, so that both mass-like and spring-like impedance boundary conditions on the infinite plane can be explicitly satisfied and the infinite plane does not have to be discretized. The Burton-Miller method [2] is employed to tackle the fictitious eigenfrequency problem involved in the conventional boundary integral equation method[3,4]. Image relations of the multipole expansion coefficients[5] are used and the half-space impedance Green’s function is modified for the purpose of applying such relations to avoid calculating, translating and saving the multipole/local expansion coefficients of the image domain. Numerical examples are presented to demonstrate the accuracy and efficiency of the method. Good solutions and high acceleration ratios compared with the conventional BEM clearly show the potential of the developed method for large-scale 3D acoustic wave problems over an infinite impedance plane. References [1] M. Ochmann, The complex equivalent source method for sound propagation over an impedance plane, Journal of Acoustical Society of America 116 (2004), no. 6, 3304-11. [2] A.J. Burton, G.F. Miller, The application of integral equation methods to the numerical solution of some exterior boundary-value problems, Proceedings of the Royal Society of London. Series A, Mathematical and Physical Sciences 323 (1971), no. 1553, 201-10. [3] S. Marburg, B. Nolte, Computational acoustics of noise propagation in fluids- finite and boundary element methods, Springer, Berlin, 2008, ISBN: 978-3-540- 77447-1. [4] C.J. Zheng, C.X. Bi, C. Zhang, Y.B. Zhang, H.B. Chen, Fictitious eigenfrequencies in the BEM for interior acoustic problems, Engineering Analysis with Boundary Elements 104 (2019), 170-82. [5] C.J. Zheng, H.B. Chen, L.L. Chen, A wideband fast multipole boundary element method for half-space/plane-symmetric acoustic wave problems, Acta Mechanica Sinica 29 (2013), no. 2, 219-32. 175

Boundary Element Methods

Non-Negative Intensity for Elementary Acoustic Sources Daipei Liu1, Paul Croaker1, Steffen Marburg2, Nicole Kessissoglou1 1)School of Mechanical and Manufacturing Engineering, The University of New South Wales, Sydney, Australia 2)Vibroacoustics of Vehicles and Machines, Technische Universität München, München, Germany

Non-negative intensity is implemented to identify individual elementary acoustic sources that contribute to far-field sound power. Lateral and longitudinal quadrupole sources are chosen to illustrate the numerical technique, whereby each type of quadrupole source is modelled using four individual monopole sources. Non- negative intensity for four monopole sources, which collectively comprise a quadrupole source, are calculated from eigenvalue decomposition of the acoustic impedance matrix obtained on a far-field receiver surface area. The radiated sound power is then obtained by integrating non-negative intensity over the surface area of the monopole sources. For comparison with the sound power predicted using non- negative intensity, the sound power of the original quadrupole source is obtained numerically from the acoustic intensity integrated over the far-field area as well as from an analytical solution. Results show that the sound power calculated using the three approaches are in excellent agreement. Non-negative intensity is shown to successfully identify the contributions of the individual monopole sources to the radiated sound power of the quadrupole sources.

176

Boundary Element Methods Evaluating Acoustic Properties for Interior Problems Based on the Sound Energy Caglar Guerbuez, Steffen Marburg Chair of Vibroacoustics of Vehicles and Machines, Technical University Munich, Garching, Germany

The analysis of sound radiation of vibrating structures is of great importance in order to develop quite structures. For exterior problems, it was shown that the non- negative intensity should be considered in order to evaluate the acoustic properties of a structure, since this method accounts for acoustic short circuiting. This phenomenon is not taken into account by common sound intensity measures. For interior problems, the sound pressure level is commonly analyzed to characterize the acoustic behavior. However, the sound pressure level is strongly dependent on the location where it is evaluated, i.e. the position of the field point. Thus, the analysis of the sound pressure level is highly sensitive to deviations of the field point position. This contribution introduces the sound energy as an appropriate quality criterion for interior problems. The sound energy quantities are compared with the sound pressure level for numerical benchmark examples and real world applications. Based on the time harmonic problem formulation, the acoustic interior problem is solved with the boundary element method (BEM).

177

Boundary Element Methods Lamb Wave Surface Detection of Flat Plate by Boundary Element Method Xianhui Wang, Yujian Liu, Xiaoming Zhang School of Mechanical and Power Engineering, Henan Polytechnic University, Jiaozuo, China

It is a suitable choice to solve the scattering field problem by the boundary element method as the integral equation of the boundary element method can automatically satisfy the Sommerfield condition at infinity. Based on the boundary element method of boundary element method and eigenmode expansion method, the Lamb wave is used to detect the defect on the flat surface in this paper. The eigenmode expansion method is mainly used to establish the boundary conditions of the left and right non-free virtual boundary. A new matrix transformation method to reduce the solution scale of simultaneous equations. Numerical examples demonstrate the effectiveness of the presented method. The research has a certain guiding significance for the detection of flat defects using Lamb wave. References [1] Y. Cho, J. L. Rose. An elastodynamic hybrid boundary element study for elastic guided wave interactions with a surface breaking defect. International Journal of Solids & Structures 37(2000), no.30, 4103-4124. [2] X. L. Zhao, J. L. Rose. Boundary element modeling for defect characterization potential in a wave guide. International Journal of Solids and Structures 40(2003), no. 11, 2645-2658.

178

Boundary Element Methods The Adaptive Cross Approximation Boundary Element Method for Acoustic Radiation Problems Xiujuan Liu School of Mechanical Engineering, Ningxia University, Yinchuan, China

The coeﬃcient matrices of conventional boundary element method (CBEM) are dense and fully populated. Special techniques such as hierarchical matrices (H- matrices) format are required to extent its ability of handling large-scale problems. Adaptive cross approximation (ACA) algorithm is a widely adopted algorithm to obtain the H-matrices. In this paper, the convergence and accuracy of the ACA boundary element method for acoustic radiation problems are verified by solving a pulsating sphere model. The results indicate that ACA boundary element method is convergent. It can almost achieve the same accuracy as the CBEM. The adaptability of ACA boundary element method is also analyzed in different frequency bands. Finally, the step need to be noticed and the condition choosing row indexes of ACA algorithm are also discussed.

179

Boundary Element Methods Acoustic-vibration Coupling Response of Shell Structure by a

Coupling Solver

Qiang Xi12, Zhuo-jia Fu123 1)Key Laboratory of Coastal Disaster and Defence, Ministry of Education, Hohai University, Nanjing 210098, China 2) Center for Numerical Simulation Software in Engineering and Sciences, College of Mechanics and Materials, Hohai University, Nanjing 211100, China 3)Institute of Continuum Mechanics, Leibniz University Hannover Appelstraße 11, 30167 Hannover, Germany

This paper presents a novel coupled computational solver by combining the singular boundary method [1] (SBM) and the finite element method (FEM), which is adopted to analyze the acoustic-vibration coupling response of three-dimensional shell structure excited by simple harmonic force in shallow water. In this coupling solver, the FEM is employed to obtain the vibration response of shell structure, and the SBM with Pekeris waveguide Green function [2] is used to calculate the external acoustic field of shell structure. To facilitate the FEM–SBM coupling, the fluid-solid coupled boundary conditions are adopted on the surface of shell structure. Several numerical examples are carried out to demonstrate the accuracy and efficiency of the proposed coupling solver in the solution of acoustic-vibration coupling response of shell structure. References [1] Z. J. Fu, W. Chen, P. H. Wen, et al. Singular boundary method for wave propagation analysis in periodic structures, Journal of Sound and Vibration, 425 (2018), 170-188. [2] M. S. Zou, Y. S. Wu, S. X. Liu. A three-dimensional sono-elastic method of ships in finite depth water with experimental validation, Ocean Engineering, 164 (2018), 238- 247.

180

Seismic Data Analysis and Parameter Inversion (Machine Learning Approaches) The Importance of Strain Energy Field for Interpretation in Exploration Geophysics Yu-Chiung Teng1, Zhenxiang Fan2, Guihua Li3 1)Aldridge Laboratory of Applied Geophysics, School of Mines, Columbia University, New York, NY 10027, USA 2)Geophysical Research Institute, Geophysical Prospecting Ministry of Petroleum Industry Zhou Zhou , Hebei, China 3)ShanDong University of Science and Technology, Qingdau, Shandong, China

The most powerful application of the finite element modeling technology is to simulate the problems for the oil-gas bearing strata with very complex geological structure, particularly for those with high contrast wave velocities between media. In this paper, with the incorporation of the input parameters provided by well-logged measurements, we study the numerical results of the two-dimensional finite element models which simulate the buried reef problems. We also present the synthetic seismograms on free surface and in the vertical seismic profile (VSP) of the displacements. From the two components of the displacement field, several physical quantities such as dilatation, rotation, strain energy, and kinetic energy can be deduced. Each of these physical quantities lends its support to the others. We found that the magnitudes of the strain energy at the interface of two different media are at least 100 times greater than those in regions of proximity of the interface. Therefore, the snapshot view of wave pattern of the strain energy can sharply delineate the interface of the media. It is just as the stress concentration at the interface of two different materials, except that it is of a lower order. The display of both the strain energy and the kinetic energy possesses higher resolution than that of the displacement fields. The high resolution feature of kinetic energy is particularly shown up for the transverse waves SS. SP. Therefore, the display for the two different kinds of energy complements each other in identifying wave fields. Through this analysis, we may have a better understanding of the seismic wave propagation mechanism for the oil-gas bearing strata quantitatively.

181

Seismic Data Analysis and Parameter Inversion (Machine Learning Approaches) Seismic Impedance Inversion via Residual Learning Networks Lingling Wang1, Delin Meng2, Weirong Qiu2, Bangyu Wu2 1)Institute of Geophysics and Geomatics, China University of Geosciences, Wuhan, Hubei, China 2)School of Mathematics and Statistics, Xi’an Jiaotong University, Xi’an, Shaanxi, China The Convolutional Neural Network (CNN) is a kind of mapping from input to output in essence. It can obtain the mapping relations between plenty of inputs and outputs without knowing any exact mathematic expression between them. Thus, if we take the seismic traces as inputs and the corresponding impedance traces as outputs to train a designed CNN, we can predict the impedance traces from seismic traces directly by the appropriately trained CNN[1]. The convolution kernel size and the number of the layers of CNN determine the degree of fineness for charactering the data. When the size of the convolution kernel is big, the CNN can characterize the main features of the data with few layers, but it may lead to the loss of some local features. When the size of the convolution kernel is small, the CNN needs more layers to depict the overall characteristics, but the deep model is prone to the problem of gradient dissipation. In order to solve the above problems, we propose to use a Residual Learning Networks (ResNets) [2] for seismic impedance inversion, where the Residual Block and Batch Normalization (BN) are introduced into 1D CNN. The ResNets we used has 8 layers, includes three ResNets Block between two 1D CNNs. The convolution kernel size of the first layer and the last layer is 300 and 3 samples with strides as 1 sample respectively. Residual Block contains two 1D convolution layers. Batch Normalization is added after each convolution layer in the block to prevent gradient dissipation, and improve the training speed and generalization ability of the network. Each convolution layer is activated by a Rectified Linear Unit (ReLU). Tests on the synthetic seismic data from the Marmousi model with complex stratigraphic structure demonstrate that the proposed method (1) is less sensitive to the stratigraphic medium model; (2) has a certain degree of tolerance to the phase error of wavelet; (3) is not able to predict either the training set or any of the testing sets in the presence of various domain frequencies of source wavelet, showing the importance of knowing a-priori the value of the domain frequency of the source wavelet when using this method; (4) can depict the local characteristics of the seismic data finer, and get higher precision impedance compared with the CNN based method. Acknowledgments: We would like to thank the National Natural Science Foundation of China (41874154, 41404107, 41604106) for funding this work. References [1] Vishal Das, Ahinoam Pollack, Uri Wollner, and Tapan Mukerji, Convolutional neural network for seismic impedance inversion, SEG International Exposition and 88th Annual Meeting, 2071-2075. [2] He K , Zhang X , Ren S, Sun J, Deep Residual Learning for Image Recognition, 2016 IEEE Conference on Computer Vision and Pattern Recognition,2016, no. 1, 770-778. 182

Seismic Data Analysis and Parameter Inversion (Machine Learning Approaches) Generalized Beta Wavelet Transform of 3-D Seismic Data For Horizontal Well Placement in Tight Reservoirs Zhiguo Wang1, Jinghuai Gao2, Bing Zhang2 1)School of Mathematics and Statistics, Xi’an Jiaotong University, Xi’an, China 2)School of Electronic and Information Engineering., Xi’an Jiaotong University, Xi’an, China

The Sulige gas field in central Ordos Basin is the largest gas fields in China [1]. So far, more than 1000 horizontal wells have produced gas. Thus, it is important to better map and predict the horizontal distribution of economic tight sandstones. The continuous wavelet transform (CWT) is a powerful tool due to the thickness- frequency tuning [2]. In this study, we proposed a workflow based on the CWT with generalized Beta wavelets (GBWs) to assist the 3-D seismic interpretation in tight gas reservoirs. we proposed the generalized Beta wavelets (GBWs), which are a two- parameter family of analytic wavelets:

  , () U()a, (F()) (1 F()) (1)

2arctan() F()  (2)  where，U() is the unit step function, a , is a normalization constant, and  and  are two parameters controlling the shape of the wavelet. To be a valid wavelet, one must have   0 and   0 . Because of , (0)  0 , the GBWs have zero-mean and finite energy, and satisfy the “admissibility condition”. For the 3D volume in the Ordos Basin, 71 spectral components at 1-Hz intervals were calculated in a frequency window of 10 - 80 Hz. We applied the PCA and the RGB blending technique to the spectrally decomposed components. In the geological P h interpretation in 1 8 reservoir, the different color areas can be interpreted as the P h sedimentary facies of the 1 8 reservoir. In the production phase of a tight gas reservoir, the delineation of horizontal sandstones distribution is important to reduce the risk of well placement. We applied the spectral attributes by CWT to improve the delineation of horizontal sandstones distribution in the Lower Permian Xiashihezi Formation, Ordos Basin, China. References [1] J. Dai, W. Wu, C. Fang, and D. Liu, Exploration and development of large gas fields in China since 2000: Natural Gas Industry B 2 (2015), no.1, 1-9. [2] Chakraborty, and D. Okaya, Frequency-time decomposition of seismic data using wavelet-based methods: Geophysics 60 (1995), no. 6, 1906–1916.

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Seismic Data Analysis and Parameter Inversion (Machine Learning Approaches) A Method of Coherence Attribute for Seismic Data Based on the Renyi Divergence Yang Tao1,2, Gao Jinghuai1,2, Zhang Bing1,2, Gao zhaoqi1,2 1)School of Electronic and Information Engineering, Xi’an Jiaotong University, Xi’an, China 2)National Engineering Laboratory for Offshore Oil Exploration, China

Attribute of seismic data has been an important tools for seismic interpretation. The coherence attribute is one of them. This paper proposed an improved method of seismic attribute extraction based on Renyi divergence for representing geological discontinuities of seismic data. The coherence attribute is widely used to geological feature imaging, such as faults, channels, karst collapse, and submarine canyons in petroleum exploration and development. There are various coherence algorithms, this method was first proposed by Bahorich and Farmer in 1995, they used the cross- correlation coefficients of seismic traces in-line and cross-line directions to estimate the coherence attribute, named as the first-generation coherence (C1) algorithm [1]. Next, there are many methods by other researcher, Gersztenkorn and Marfurt developed an eigenstructure-based coherence algorithm, e.g., the third-generation coherence (C3) algorithm[2] which has been widely applied to practical industry, but this algorithm often use the linear correlation measurement to measure the relationship between two seismic traces, and it does not work well because seismic data do not obey the normal distribution. In this paper, introduced the theory of Renyi divergence to overcome the limitation of do not obey the normal distribution, due to the Renyi divergence have be using for measuring the distance between two distributions, combining with existing measure criterion by information divergence[3] for extraction of seismic data. References [1] Bahorich, M., Farmer, S., 1995. 3-D seismic discontinuity for faults and stratigraphic features: the coherence cube. Lead. Edge 14, 1053–1058. [2] Gersztenkorn, A., Marfurt, K.J., 1999. Eigenstructure-based coherence computations as an aid to 3-D structural and stratigraphic mapping. Geophysics 64, 1468–1479.. [3] Yang T, Zhang B, Gao J. A fast algorithm for coherency estimation in seismic data based on information divergence[J]. Journal of Applied Geophysics, 2015, 115:140-144.

184

Seismic Data Analysis and Parameter Inversion (Machine Learning Approaches) Dispersion Estimation Using the Generalized S-Transform Zhi Hu1,2 and Jinghuai Gao1,2 1)School of Electronic and Information Engineering, Xi’an Jiaotong University, Xi’an, China 2)National Engineering Laboratory for Offshore Oil Exploration, Xi’an, China When a wave propagates, the phenomenon that different frequency components have different velocities is called dispersion.Dispersion and attenuation must occur simultaneously, which can be explained by the plane wave propagation equation: U( z , t ) U exp( z )exp( i (  t  z )) (1) 0 where  2/fvp contains dispersion information. The dispersion relation can be expressed by phase velocityv fp k f / ( ) and group velocity vg d f d k f / ( ) which are related to frequency. In order to get the frequency information, seismic signals should be analyzed in the TF domain. The generalized S-transform (GST) may be an optimal method to analyze seismic signals, because the modified Gaussian function with three parameters is employed to match the seismic wavelet[1]. There are many researches on calculating group velocity with instantaneous frequency[2], but we find that calculating group velocity with group delay time has more definite physical significance[3]. With the help of the GST and group delay time, we can calculate the transmission time of different frequency components between the two receivers, so as to fit the dispersion curve (group velocity).

The dispersion estimation relies on four steps. Firstly, the seismic signal stn () and stm () received by the n th and the m th receiver could be transformed to be

Sfn ( , ) and Sfm (,) in the TF domain by GST. Secondly, we can extract the group delay time  n ()f and  m ()f , which contain the transmission time of different frequency components. Then, for each frequency, the distance between the two receivers should be divided by the corresponding group delay time difference and the velocity could be figured out. Finally, the velocity corresponding to different frequencies can be simulated to the group velocity. We apply the GST and group delay time to the synthetic data with Kolsky’s dispersion model to estimate the group velocity. Numerical examples demonstrate the dispersion estimated by the above method fit the theoretical Kolsky’s dispersion well. References [1] J. Gao, W. Chen, Y. Li, and F. Tian, Generalized S transform and seismic response analysis of thin interbeds surrounding regions by GPS, Chinese Journal of Geophysics46(2003), no. 4, 526–532. [2] R. Askari, andS. Hejazi,Estimation of surface-wave group velocity using slant stack in the generalized S-transform domain, Geophysics, 80(2015), no.4, 83- 92. [3] K. Kodera, R.Gendrin, and C.Villedary,Analysis of time-varying signals with small BT values, IEEE Transactions on Acoustics, Speech, and Signal Processing, 26 (1978), no.1, 64-76. 185

Seismic Data Analysis and Parameter Inversion (Machine Learning Approaches) Seismic Super Resolution Inversion Based on Model-driven Deep Learning Hongling Chen1,2, Jinghuai Gao1,2, Yan Yang3 1)School of Electronic and Information Engineering, Xi'an Jiaotong University, Xi’an, China 2)National Engineering Laboratory for Offshore Oil Exploration, Xi’an Jiaotong University, Xi’an, China 3)School of Mathematics and Statistics, Xi’an Jiaotong University, Xi’an, China

Super resolution inversion based on the sparse constraint plays a significant role in seismic exploration [3-5], which can make some composite waves separated to clearly characterize the stratigraphic structure. However, the performance of the conventional sparse inversion method depends on the selection of regularization parameters and the algorithm. In order to address these shortcomings, deep learning has been an effective tool for solving inversion problem [2]. In this paper, a model- driven deep-learning approach called ADMM-CSNet proposed by Yang et al [1] is applied to implement the super resolution inversion. This network is established by combining the traditional iterative optimization algorithm and data-driven deep learning method, which turns each iteration into a layer of a network. All the parameters, such as regularization parameters and shrinkage functions, in this network can be discriminatively learned from training data sets. Based on the advantage of this network, we modify the network to adapt it to seismic super resolution inversion where the forward matrix is Toeplitz matrix different from measurement matrix in compressive sensing [1]. Therefore, the modified network is called ADMM-SRINet. Finally, synthetic and field data examples are tested to demonstrate the effectiveness of the ADMM- SRINet, which achieves higher accuracy and takes comparable computational time. References [1] Yang Y, Sun J, Li H, et al. ADMM-CSNet: A Deep Learning Approach for Image Compressive Sensing[J]. IEEE Transactions on Pattern Analysis and Machine Intelligence, 2018:1-1. [2] Xu Z, Sun J. Model-driven deep-learning[J]. National Science Review, 2018, v.5(01):26- 28. [3] H. Chen, J. Gao, N. Liu and Y. Yang, "Multitrace Semiblind Nonstationary Deconvoluti on," IEEE Geoscience and Remote Sensing Letters, p1-5, 2019. [4] Chen, H., S. Cao, S. Yuan, X. Pan, S. Chen, and S. Shen, 2017a, Nonstationary sparse reflectivity inversion with EADTV regularization: Eage Conference and Exhibition. [5] Wang, L., J. Gao, Z. Wei, and X. Jiang, 2012, Enhancing resolution of nonstationary seismic data by molecular-gabor transform: Geophysics, 78, 31.

186

Seismic Data Analysis and Parameter Inversion (Machine Learning Approaches) Comparison of the Static and Dynamic Properties of Dand-clay Sediments Hui Li1,2, Jinghuai Gao1,2 1)National Engineering Laboratory for Offshore Oil Exploration, Xi’an Jiaotong University, Xi’an, P. R. China. 2)School of Electronic and Information Engineering, Xi'an Jiaotong University, Shaanxi, China

Improved understanding the elastic, mechanical properties of loose, compressible sand packs and sand-clay mixtures are significant to characterize the features of unconsolidated reservoir and sea floor sedimentary. A series of laboratory measurements on sand-clay mixture with clay content ranging from 0% to 100% by weight are conducted to investigate the pressure loading histories of 2 MPa-50 MPa and clay content effects on porosity variation, P-, S- wave velocity, and static moduli. The measured results show that the elastic, mechanical properties of sand-clay mixture behave differently under both varying pressure loading histories and clay content. The sand-clay mixtures show a high permanent compaction under pressure loading. Overall, for the pressure uploading, the reduction of porosity is increasingly fast with increasing clay content. For the pressure downloading, the porosity change with pressure follows a different track from uploading. Correspondingly, there is a large difference in P-wave velocities between the up- and down-loading processes.

187

Seismic Data Analysis and Parameter Inversion (Machine Learning Approaches) Deep Learning Based Global Optimization Scheme for High- dimensional Seismic inversion Zhaoqi Gao1,2, Zhibin Pan2, Jinghuai Gao1,2, Zongben Xu3 1)National Engineering Laboratory for Offshore Oil Exploration, Xi’an Jiaotong University, Xi’an, CHINA 2)School of Electronic and Information Engineering, Xi’an Jiaotong University, Xi’an, CHINA 3)School of Mathematics and Statistics, Xi’an Jiaotong University, Xi’an, CHINA

In seismic inversion, unknown model parameters are usually estimated by minimizing a misﬁt function, which measures the discrepancy between observed and calculated data. Because data and model are nonlinearly related, the misﬁt function usually has several local minima. As a consequence, global optimization algorithms, which do not require an accurate initial model and can jump out of the local minimum, are suitable for seismic inversion. However, global optimizations are well-known to be inefficient in solving seismic inversion problem especially for high-dimensional problem. In this paper, we propose a new global optimization scheme for high-dimensional seismic inversion. Specifically, we first propose a new global optimization method that has two operations, i.e., recombination and selection. Then, we use a deep network to represent these two operations with network layers and learn their hyper-parameters using a network training procedure. Finally, we apply the trained network in solving seismic inversion problem. We use both numerical examples based on both synthetic and field dataset to verify the effectiveness of the proposed method. It is clearly demonstrated by these numerical results that the proposed deep learning based global optimization scheme has obvious advantages over conventional global optimization method in efficiency.

188

Seismic Data Analysis and Parameter Inversion (Machine Learning Approaches) Sedimentary Cycle Distribution Prediction Method Based on Alternating Iterative Depth Neural Network Yajun Tian1,2, Jinghuai Gao1,2 1)School of Electronic and Information Engineering, Xi’an Jiaotong University, Xi’an, China 2)National Engineering Laboratory for Offshore Oil Exploration, Xi’an, China The discussion of cyclicity in sedimentary records has a long history. Seismic data, as a response of the lithology and physical properties of geological strata, contain a lot of information related to sedimentary cycles. It is significant to extract the information reflecting cycles effectively, which is the basis for further pointing out bedding structure, restoring paleogeomorphology and developing fine reservoir description [1]. Time-frequency analysis is a widely used method for the division of the sedimentary cycles. In the early 1980s, Л Ю .Бродов and И .АМУ цин first applied the time-frequency analysis for the discrimination of sedimentary cycles. Since then, the windowed Fourier transform, continuous wavelet analysis, generalized S transform, and Hilbert-Huang transform have been developed to identify sedimentary cycles. The time-frequency analysis based methods can be used for the pattern recognition of sedimentary cycles is due to the frequency-increasing and amplitude- decreasing effect in the time-frequency response mechanism of thin layers. Increasing (positive sedimentary cycle) or decreasing (reverse sedimentary cycle) the thicknesses of small beds in cyclic thin interbeds will correspondingly cause the main frequency component of the instantaneous spectrum to decrease or increase gradually. These laws lay a theoretical foundation for the application of time-frequency analysis to discriminate sedimentary cycle patterns[2]. In this paper, the model test proves that the time-frequency analysis method can describe the time-frequency characteristics of sedimentary cycles more accurately when the time-frequency base atom matches the seismic wavelet waveform optimally. Based on this understanding, we propose an alternating iterative depth neural network method to retrieve the wavelet of actual seismic data, and then obtain the time-frequency basis atom (three-parameter wavelet) which can best match the seismic wavelet by parameter fitting method[3]. Furthermore, the operation of synchrosqueezing is used to improve the aggregation of time-frequency spectrum, which makes the sedimentary cycle more interpretable. Finally, based on the time- frequency analysis results of actual seismic data of braided river delta sedimentary facies in the target stratum, the distribution range of sedimentary cycle units is traced. The actual tracing results are consistent with the well interpretation results at the well point, which proves the effectiveness of the proposed method. References [1] J. H. Zhang, Y. G. Wang, G. Q. Yang, Seismic cycles and application of the concept, Oil Geophysical Prospecting, 38, (2003), no.3, 281-284. [2] Y. J. Tian, X. Y. Li, Y. Cheng, Comparison result of several time-frequency analysis methods on identifying sedimentary cycle, Mathematics in Practice & Theory, 48, (2018), no.4, 206-214. [3] J. H. Gao, T. Wan, W. Chen, J. Mao, Three parameter wavelet and its applications to seismic data processing, Chinese Journal of Geophysics, 49, (2006), no.6, 337-347. 189

Seismic Data Analysis and Parameter Inversion (Machine Learning Approaches) A Deep Learning Based Data-driven Method for Seismic High Resolution Inversion Daoyu Chen1,2, Jinghuai Gao1,2 1)School of Electronic and Information Engineering, Xi’an Jiaotong University, Xi’an, China 2)National Engineering Laboratory for Offshore Oil Exploration, Xi’an Jiaotong University, Xi’an, China

The common used method in seismic high resolution inversion is based on the assumption that the seismic wavelet has the minimum-phase property, which is unreasonable. In this work, we propose a deep learning based data-driven method for seismic high resolution inversion without the minimum-phase assumption. The proposed method simultaneously estimates wavelet and reflectivity in an alternative way, and the estimation of wavelet or reflectivity is realized by a deep neural network. Synthetic and field data examples clearly demonstrate the advantages of the proposed method in reducing the prediction error, ensuring the sparsity of the reflectivity and improving the lateral stability. According to the convolutional model [1], the seismic records can be presented as: s  Gr  n (1) where r represents the reflectivity, n is the additive noise and G is a Toeplitz matrix consisting of seismic wavelet w . The objective of seismic high resolution inversion is to solve for an optimal reflectivity of r , which is often realized through an optimization problem that minimizes an objective function: 1 Jˆ  min || s  Gr |||2 (r)  (w) (2) 2 2 where, (r) is a convex regularization function for r and (w) is a convex regularization function for w . It is difficult to solve equation (2) directly. To simplify the problem, we propose a method to alternatively invert the wavelet and reflectivity, i.e., we decompose the inversion to two sub-problems[2]. Based on such recognition, we introduce a partially learned approach[3] into seismic high resolution inversion to realize the estimation of seismic reflectivity and wavelet in a data-driven manner. References [1] Robinson, E. A., Seismic time-invariant convolutional model, GEOPHYSICS (1985), 50(12):2742-2751. [2] Wang, L., Q. Zhao, J. Gao, Z. Xu, M. Fehler, and X. Jiang, Seismic sparse-spike deconvolution via toeplitz-sparse matrix factorization, GEOPHYSICS (2016), 81, V169–V182. [3] Adler, J., and O. Öktem, Solving ill-posed inverse problems using iterative deep neural networks, Inverse Problems (2017), 33.

190

Seismic Data Analysis and Parameter Inversion (Machine Learning Approaches) Extraction of Effective Events Based on Phase-only Correction for Noised Microseismic Data Yinting Wu1,2, Guangming Zhu1 1)School of Geology Engineering and Geomatics, Chang’an University, Xi’an, China 2)School of Electronics and Information Engineering, Xi’an Jiaotong University, Xi’an, China

The existence of an unknown number of microseismic events with the characteristics of weak energy is usually quite large and concentrated in a certain period. In order to meet the requirements of real-time and on-site processing, it is important to study the automatic picking up and identification of events under strong noise background [1-2]. This research is focused on depicting extractions of effective events based on phase-only correction algorithm [3-5]. (1) Two images of a fingerprint and Lena with 445*356 points were studied and tested. Compared to the traditional correction method, the phase-only correlation has better discrimination ability, and the peak height can be used as the measurement of signal similarity. (2) Moreover, two synthetic microseismic signals are introduced and tested to reveal the influence of noise. The phase-only autocorrelation of one signal and the phase-only correlation of two signals are carried out. In order to find the peak change under different S/N ratio of infinity (no noise), 20, 10 and 5, contrastive study of various levels are made. From the tests, the degree of similarity and the displacement can be determined by the correlation coefficient even in the face of extraction of weak signals in strong noise background. For this reason, phase-only correlation method is recommended to the automatic acquisition of arrival time for practical application. (3) We applied this method to a field microseismic data for extraction of arrival time. For this test, noise is present in the original record at almost every point. While, when the arrival time of one event is nested on the seismogram, we can see that they are consistent with each other. The experimental results are reliable. References [1] Gu H. M., H. Q. Zhou and X. Q. Zhang, 1992. The auto pick up for first breaking arrivals: Physical prospection and chemical prospection, 16, no.2, 130-136. [2] Molyneux J. B., 1999. Schmitt D R. First-break timing: Arrival onset times by direct correlation: Geophysics, 64, no.5, 1492-1501. [3] Foroosh H., J. B. Zeubia, M. Berthod, 2002. Extension of phase correlation to subject Registration: IEEE Transactions on Image Processing, 11, no.3, 188- 200. [4] Kuglin C. D., D. C. Hines, 1975. The phase correlation image alignment method: Proceedings of IEEE International Conference on Cybernetics and Society, New York, 163-165. [5] Zheng Z. B., Z. F. Ye, 2006. Image matching Algorithm based on phase only correction: Data acquisition and processing, 21, no.4, 444-449.

191

Seismic Data Analysis and Parameter Inversion (Machine Learning Approaches) A Method of Seismic Data Denoising Based on Mathematical Morphology J. T. Wu College of Civil Engineering, Ningbo Institute of Technology, Zhejiang University, Ningbo, Zhejiang, P. R. China

Mathematical morphology [1] has become the basis of theoretical presupposition and visual detection system [2]. Seismic data processing can draw lessons from the advantages of mathematical morphology on the morphological structure [3-5], and it can be applied on the seismic data denoising[6]. In this study, we analyzed the composition of the mathematical morphology filters, and proposed a hybrid filter by the average combination of OC and CO filters as follow: OC  CO b  2 where OC filter is to do the opening operation first and then do the closing operation to the result, meanwhile the CO filter is in reverse order. By subtracting the filtered data from the original data, it is believed a satisfactory result can be obtained easily. The analogue signal is made denoising processing and comparison analysis of the filtering effect was done, as well as it was applied in the actual microseismic and ground seismic data. The influence of shape (semiellipse and flat) and size (7, 21, 49, and 99ms) of different structure elements was discussed. We believe that relative to the shape, the size of structure element has a greater impact on filtering results. The applications to the field data of mircroseismic and stack record of ground seismic show our method is a simple but an effective method in seismic data denoising. References [1] Serra J. Image analysis and mathematical morphology: Academic Press, 1982. [2] Chanda B., M. Kundu, Y. Padamaja. A multi-scale morphologic edge detector. Pattern Recognition, 1998, 31: 1469-1478. [3] Chen H, Guo K, Hu Y. Application of mathematical morphology to seismic data processing. Process in Exploration Geophysics, 2009, 24: 1995-2002. [4] Faucon T., E. Decenciere, C. Magneron. Morphological segmentation applied to 3D seismic data. Mathematical Morphology: 40 Years on Computational Imaging and Vision, 2005: 475- 484. [5] Zheng, G., R. Wang. Application of mathematical morphology in seismic data processing. Process in Exploration Geophysics, 2003, 26: 277-281. [6] Li Huijian, W. Runqiu, C. Siyuan. A method for low-frequency noise suppression based on mathematical morphology in microseismic monitoring. Geophysics, 2016, 18: 159-167.

192

Seismic Data Analysis and Parameter Inversion (Machine Learning Approaches) Characterizing Channel Sand Bodies Using a Self-adaptive Generalized S-transform Naihao Liu1,2, Jinghuai Gao1,2, Bo Zhang3, Hao Wu3 1)School of Electronic and Information Engineering, Xi’an Jiaotong University, Xi’an, Shaanxi, China 2)National Engineering Laboratory for Offshore Oil Exploration, Xi’an, Shaanxi, China 3)Department of Geological Sciences, College of Arts and Sciences, University of Alabama, Tuscaloosa, Alabama, United States

Achieving a proper time-frequency (TF) resolution is the key to extract information from seismic data using time-frequency algorithms and characterize channel sand bodies using decomposed frequency components. The generalized S- transform (GST) is one of the most widely used TF algorithms [1]. However, it is difficult to choose an optimized parameter set for the whole seismic data set. In this paper, we propose to set the parameters of the GST adaptively using the instantaneous frequency (IF) of seismic traces. The proposed workflow begins with building a relationship between the parameter set of the GST and IF using a synthetic wedge model. We use the IF as an indicator for the time thickness of each trace in the wedge model [2]. We then compute the time-frequency spectrum of each trace using the GST with different parameter sets and compare the similarity between the computed TF spectrum and theory TF spectrum. The parameter set with the largest similarity is regarded as the best parameter set for each trace in the wedge model. In this manner, we build a relationship between the parameter set and IF value. We can finally choose the optimum parameter set for the GST according to the IF values of seismic traces. We name the proposed workflow as the self- adaptive generalized S-transform (SAGST). To demonstrate the validity and effectiveness of the proposed SAGST, we apply it to synthetic seismic traces and field data. Both synthetic and real data examples illustrate that the SAGST can obtain a time-frequency representation with a high time-frequency resolution, which contributes to characterize channel sand bodies. References [1] N. Liu, J. Gao, B. Zhang, F. Li, Q. Wang, Time-frequency analysis of seismic data using a three parameter S-transform, IEEE Geoscience and Remote Sensing Letters 15 (2018), no. 1, 142-146. [2] N. Liu, J. Gao, X. Jiang, Z. Zhang, P. Wang, Seismic instantaneous frequency extraction based on the SST-MAW, Journal of Geophysics and Engineering 15 (2018), no. 3, 995- 1007.

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Seismic Data Analysis and Parameter Inversion (Machine Learning Approaches) Enhancing Subsurface Scatters Using Reflection Damped Plane- Wave Least-Squares Migration Chuang Li1,2, Jinghuai Gao1,2 1)School of Electronics and Information Engineering, Xi'an Jiaotong University, Xi'an, China 2)The National Engineering Laboratory for Offshore Oil Exploration, Xi'an Jiaotong University, Xi'an, China

Subsurface scatters are always masked by reflectors in seismic reverse time migration [1] images because the diffractions are much weaker in energy than the reflections. We propose a novel imaging method, named as reflection damped plane- wave least-squares reverse time migration (RD_PLSRTM), to enhance the scatters in the migration image. We formulate seismic imaging as an inverse problem that minimizes a weighted residual between the modelled and observed seismic data. In the proposed approach, we use the plane-wave destruction filter [1] to separate the diffractions from the reflections in the data residual. A reflection damped weighting matrix is then used to govern the fitting of the diffractions and reflections, and therefore emphasis the updates of the scatters. The misfit function is formulated as 1 J (m)  [W (Lm  d )]T [W (Lm  d )] (1) RD 2 RD obs RD obs

WRD  S  wr (I  S) (2)

where J RD (m) is the new misfit function of RD_PLSRTM; WRD is a weighting matrix which governs the data fitting and guides the gradient to enhance the updates of subsurface scatters; S is the plane-wave destruction filter; I is unit matrix; 0  wr 1 is the damping operator for reflections. The inverse problem is finally solved by using an iteratively reweighted least- squares (IRLS) algorithm[2]. The proposed method provides a generalized formulation which could be reduced to conventional plane-wave least-squares reverse time migration (PLSRTM) and PLSRTM of diffractions (PLSRTM_D) by using specific damping operators. We conduct numerical tests on a karst caverns model and the Sigsbee2A salt model that prove the superiority of the proposed method over PLSRTM in imaging deep scatters and subsalt scatters. Compared with PLSRTM_D, the proposed method could produce high-quality images of not only the scatters but also the reflectors. References [1] E. Baysal, D. Kosloff, and J. Sherwood, Reverse time migration, Geophysics, 48 (1983), no. 11, 1514-1524. [2] S. Fomel, Applications of plane-wave destruction filters, Geophysics 67 (2002), no. 6, 1946−1960.

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Seismic Data Analysis and Parameter Inversion (Machine Learning Approaches) Behavioral Characteristic of Seismic Modulus with Ultrasonic Surface Wave in Pavement Structures J. T. Wu1, X. H. Wu2 and S. M. Li2 1)College of Civil Engineering, Ningbo Institute of Technology, Zhejiang University, Ningbo, Zhejiang, P. R. China 2)Key Laboratory of Road and Traffic Engineering of the Ministry of Education, Tongji University, Shanghai, P. R. China

Seismic technology application in road engineering, belongs to the shallow seismic exploration. Ultrasonic surface wave (USW) is used in the modulus measurement of pavement structure with the portable seismic property analyzer (PSPA) [1-3]. During the exciting and receiving process of seismic wave, the method of repeated shock is employed, that is, the superposition of multiple excitation approach is applied to enhance the effective wave and suppress interference wave. This paper analyzed the influence of pavement structure specimen size, the bottom support materials and the interlayer bonding situations on the measured seismic modulus experimentally [4-6]. Moreover, the measured values were compared with the actual dynamic modulus and splitting tensile strength. References [1] S. Nazarian, M. Baker, and K. Crain. Development and testing of a seismic pavement analyzer.(1993) Washington, D.C. SHRP. National Research Council, Report SHRP-H-375. [2] N. Gucunski and A. Maher, 2002. Evaluation of seismic pavement analyzer for pavement condition monitoring. Final Report FHWA-NJ-2002-012. Piscataway, NJ: Department of Civil & Environmental Engineering at Rutgers University. [3] Nazarian, S., et al., 2005. Quality management of flexible pavement layers by seismic methods; Research Report 0-1735-3. El Paso, TX: Center for Transportation Infrastructure Systems. [4] J. Wu, F. Ye, and Y. Wu. Modulus Evolution of Asphalt Pavement Based on Full-scale Accelerated Pavement Testing with Mobile Load Simulator 66. International Journal of Pavement Engineering, 16 (2015), no. 7, 609-619. [5] X. Wu. Design and Research on the Calibration Object for Portable Seismic Pavement Analyzer. (2016). Shanghai: Tongji University. [6] J. Wu, F. Ye, J. Li. Seismic Modulus Response of Asphalt Pavement in Accelerated Loading Tests with Rayleigh Wave.13th International Conference on Theoretical and Computational Acoustics. 30 July- 3 August. Vienna, Austria, 2017:161.

195

Seismic Data Analysis and Parameter Inversion (Machine Learning Approaches) Effect of Thin Layer Thickness on Peak Frequency of Thin Layer Seismic Activities Huan Cao, Shuhong Zhao School of Geology Engineering and Geomatics, Chang’an University, Xi’an, China

Thin reservoir exploration is the emphasis and difficulty of seismic exploration. Based on the thin layer’s ratio of the reflection coefficient, the thin layer is divided into four types. When the seismic wave is incident vertically, derivation of the relationship between seismic peak frequency and thin layer thickness using a three- layer dual interface time domain model is achieved. And the high order approximation is suitable for different types of thin layer expression. Then the characteristic curves of peak frequency changing with thickness of these four kinds of thin layers are discussed respectively. And the measuring plate of peak frequency changing with thickness is obtained by combining the ratio of reflection coefficient. The thickness of thin layer can be read from the measuring plate according to the seismic peak frequency, which provides certain practical reference value for predicting the thickness of thin layer. Finally, the model is tested to show the accuracy and credibility of the model.

196

Seismic Data Analysis and Parameter Inversion (Machine Learning Approaches) Physical Analysis of Seismic Source Wave Field and Wavelet Reservoir Identification Hongjuan Quan1, Guangming Zhu2, Yuefeng Sun3 1)College of Science, Chang’an University, Xi’an,China 2)School of Geological and Surveying Engineering, Chang’an University, Xi’an, China 3)College of Geoscience, Texas A&M University, College Station, USA

Seismic source simulation is a good way to improve the development efficiency of oil and gas reservoirs and to save exploration cost. This paper discusses the wave fields from physical point of view with different sources to analyze the formation mechanism of seismic waves. Moreover it simulates numerically propagation characteristics of source wavelet in different media. After lots of tests, several conclusions are drawn: (1) According to the direction of the force, the direction of propagation of the wave and the polarization direction of the wave, the components of the seismic wave field can be physically analyzed and judged; (2) The wavelet of seismic source has changes not only in the amplitude but also in the shape during wave propagation；(3) It is feasible to determine reservoir properties and degree of anisotropy with different seismic wave responses to reservoirs based on wavelets change; (4) Propagation medium, source force, observation system and polarization direction are the comprehensive factors for observing the phenomenon of shear wave splitting.

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Seismic Data Analysis and Parameter Inversion (Machine Learning Approaches) The CMP Stack Processing Method Based on Statistical Properties of Seismic Random Noise Guihua Li1, Jingqi Wang2, Yun Xu3 1)College of Earth Science and Engineering, Shandong University of Science and Technology,Qingdao, China, 266590 2)College of Earth Science and Engineering, Shandong University of Science and Technology,Qingdao, China, 266590 3)Retirement office, China University of Geosciences, Beijing, China, 100083

At present, the mountainous areas in Western China are the most potential oil and gas exploration and development zones in China. Complex surface conditions and geological structures make seismic records have low signal-to-noise ratio, complex wave fields and difficult to identify effective information, which makes seismic data processing and interpretation difficult. In the field seismic records, some white noises which are not related to the records can be basically eliminated by superposition, but some random interference backgrounds have the characteristics of coherence with CMP gathers, which cannot be eliminated only by simple CMP superposition. According to the probability and statistic characteristics and judgment criteria of random disturbance background of seismic records, we analyzed the CMP stacking processing method. The method was applied to simulate the records with random noise which is correlated with seismic records, and the CMP stacking processing of data was carried out, and the ideal results were obtained. References [1] Wintercheer, Е. С. (Soviet Union), translated by Mingqi Cui et al. Probability Theory, Science and Technology Press, 1961.05 [2] Dong mei Wang. Study on Temporal and Spatial Characteristics of Random Noise in Land Seismic Exploration [Ph. D. thesis] (in Chinese). Changchun: Jilin University, 2016.

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Structural Vibration and Sound Radiation Study on a Low Frequency Narrow Beam Transducer with Quasi- Periodic Structure Zhiqiang Dai, Guangbin Zhang Shaanxi Key Laboratory of Ultrasonics, College of Physics and Information Technology, Shaanxi Normal University, Xi’an, China

In this paper, we present a quasi-periodic structure transducer, which can adjust the resonant frequency by replacing nonadjacent piezoelectric pieces with non- piezoelectric materials. Finite element model of the transducer is setup to analysis its performance. Simulation results shows that the resonant frequency of the transducer will drop from 20 kHz to 15460 Hz when half of the ten piezoelectric pieces which are nonadjacent but with equal interval are replaced by metal lead. The resonant frequency of the transducer will drop from 20 kHz to 7455.6 Hz when half of the ten piezoelectric pieces which are nonadjacent but with equal interval are replaced by nylon. However, the transmitting voltage response of the transducer decreased by 14.8 dB, and the beam width of the transducer is found to be 180 degrees. In order to improve the transmitting voltage response and reduce the beam width of the quasi-periodic structure transducer, a thin circular plate with thickness of 2 mm is added to the radiation end of the transducer, and the influence of the thin circular plate on the transmitting voltage response and beam width of the transducer is analyzed. Simulation results indicate that when the diameter of the thin circular plate is 60 mm, the transmitting voltage response of the transducer is 168.7 dB, which is 12.6 dB higher than that of the 20 kHz transducer and 27.4 dB higher than that of the quasi-periodic structure transducer without thin circular plate. The beam width can drop to 57.585 degrees. The study has certain significance for the design of low frequency narrow beam underwater acoustic transducer

199

Structural Vibration and Sound Radiation Finite Element Model Coupled with Lumped Parameter Elements Daniel Gert Nielsen1, Jakob Søndergaard Jensen2, Vicente Cutanda Henriquez2, Finn Thomas Agerkvist1 1 Acoustic Technology, Department of Electrical Engineering Technical University of Denmark, Kgs. Lyngby, Denmark 2 Centre for Acoustic-Mechanical Micro Systems, Technical University of Denmark, Kgs. Lyngby, Denmark

Numerical modelling of loudspeakers is a challenging task due to the multidisciplinary nature of the problem. If one wants to model all physical domains of a loudspeaker one needs to consider acoustics, solid mechanics and electronic circuits. Finite element modelling is often used for the modelling of the behaviour of the diaphragm at high frequencies, beyond its piston range. If a high degree of accuracy is required from the numerical approximations the computational time can be unfeasible. Simplifications are therefore in many cases a necessity. This work presents a modelling technique that utilizes lumped components of the electrical system and parts of the mechanical system of a loudspeaker. The lumped component model is coupled with a finite element model of the exterior acoustic domain and the loudspeaker diaphragm and surround. Lumped components are widely used as a modelling technique for low frequencies[1] and also for measuring the performance of transducers[2]. The advantage of partly lumping the loudspeaker is that we achieve a reduction in computational time while maintaining accuracy at higher frequencies.

References [1] W. M Leach Jr, Introduction to Electroacoustics & Audio Amplifier Design, Kendal/Hunt Publishing Company, 3rd edition, 2003. [2] W. Klippel, Tutorial: Loudspeaker Nonlinearities – Causes, Parameters, Symptoms, J. Audio Eng. Soc., Vol. 54, No. 19, 2006.

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Structural Vibration and Sound Radiation Effects of carbon nanotube thermal conductivity on optoacoustic transducer performance Jiapu Li1, Xuekai Lan1, Shuang Lei1, Jun Ou-Yang1, Xiaofei Yang1, Benpeng Zhu1,2,3 1School of Optical and Electronic Information, Huazhong University of Science and Technology, Wuhan, 430074, China 2Engineering Research Center for Functional Ceramics, Ministry of Education, Huazhong University of Science and Technology, Wuhan, 430074, China 3State Key Laboratory of Transducer Technology, Chinese Academy of Sciences, Shanghai, 200050, China

CNT-PDMS composite is regarded as a promising candidate for optoacoustic transducer application[1,2]. However, the relationship between the CNT thermal conductivity and optoacoustic transducer performance is still undefined. To explore this relationship, four types of CNTs with different diameters and lengths were employed to successfully fabricate four types of optoacoustic transducers. The thermal properties of CNTs were analyzed and discussed in this paper; the laser- generated ultrasound and optoacoustic conversion efficiency of the transducers were experimentally and theoretically investigated[3,4]. Results of comparison revealed the CNT with a diameter and length of 8nm and 10-30μm, respectively, to have the highest thermal conductivity. With this type of CNT/PDMS composite, the optoacoustic conversion efficiency reached as high as 9.59×103. Overall, the results demonstrate that higher CNT thermal conductivity corresponds to better optoacoustic transducer performance. References [1] Z. Chen, Y. Wu, Y. Yang, J.P. Li, B.S. Xie, X.J. Li, S. Lei, J.O. Yang, X.F. Yang, Q.F. Zhou, B.P. Zhu, Multilayered carbon nanotube yarn based optoacoustic transducer with high energy conversion efficiency for ultrasound application, Nanomater. Energy.2018, 46 (6),314-321. [2] I.N. Kholmanov, C.W. Magnuson, R. Piner, J.Y. Kim, A.E. Aliev, Y.K. Cheng, A.A. Zakhidov, G. Sberveglieri, R.H. Baughman, R.S. Ruoff, Optical,Electrical and electromechanical properties of hybrid graphene/carbon nanotube films, Adv. Mater. 2015,27 (19),3053-3059. [3] N. Mingo, D.A. Broido, Length dependence of carbon nanotube thermal conductivity and the problem of long waves, Nano Lett. 2005,5 (7),1221-1225. [4] A. Rosencwaig, A. Gersho, Theory of the photoacoustic effect with solids. J. Appl. Phys. 1976,47 (1) , 64-69.

201

Structural Vibration and Sound Radiation Analysis of Acoustic Radiation Characteristics of Three- Dimensional Elastic Structure in Shallow Water by FEM-NM Method Bu-chao An1,2,3, Chao Zhang1,2,3, De-jiang Shang1,2,3, Yi-hao Liu1,2,3 1 Acoustic Science and Technology Laboratory, Harbin Engineering University, Harbin 150001, China 2 Key Laboratory of Marine Information Acquisition and Security(Harbin Engineering University), Ministry of Industry and Information Technology;Harbin 150001,China 3 College of Underwater Acoustic Engineering, Harbin Engineering University, Harbin 150001, China

A method of combining finite element and normal modes (FEM-NM) is proposed to predict acoustic radiation from elastic structures in shallow water. Different from the classical method that regards the structure as a point source, FEMNM is a complete three-dimensional method considering the elastic structure and the sound field environment. Firstly, FEM is used to calculate the acoustic near field region of the structural source, then the eigen function expansion is performed at the depth direction and the azimuth direction, and the coefficients of modes can be obtained by using the orthogonality of the eigen function. Therefore, we can calculate the acoustic field at any range. This method avoids the process of solving inverse matrix of a large complex matrix and is very efficient to calculate the far field. The simulation results of FEM-NM in typical waveguide environment are compared with those of using FEM directly, which proves the reliability of FEM- NM method. Aiming at the acoustic radiation from an elastic cylindrical shell in shallow water, the simulation analysis is carried out to study the vertical distribution and horizontal propagation characteristics of the acoustic field under different sound velocities of seawater and different parameters of seabed. The results of the study are helpful to understand the radiation laws of the elastic structure in shallow water and to guide the measurement of sound radiation field in shallow water.

202

Structural Vibration and Sound Radiation Research on Sound Radiation Characteristics of Elastic Structure in Shallow Water Based on Wave Superposition and Acoustic Ray Theory Yi-hao Liu1,2,3, Chao Zhang1,2,3, De-jiang Shang1,2,3, Bu-chao An1,2,3 1Acoustic Science and Technology Laboratory, Harbin Engineering University, Harbin 150001, China 2Key Laboratory of Marine Information Acquisition and Security (Harbin Engineering University), Ministry of Industry and Information Technology, Harbin 150001, China 3College of Underwater Acoustic Engineering, Harbin Engineering University, Harbin 150001, China

The propagation of acoustic radiated from the elastic structure in the shallow water is greatly affected by the channel environment. Due to the sound reflection on the upper and lower boundary surfaces, the traditional free-field analysis method is severely limited, making the radiation acoustic prediction in the shallow sea channel difficult, especially at high frequencies. A method combining ray theory, wave superposition theory and finite element theory is established in this paper to analyse the high-frequency acoustic radiation characteristics of elastic structures in shallow water, and to predict the high-frequency acoustic radiation in shallow water. Based on the distribution of virtual source inside the structure derived from the normal velocity matrix on structural surface and the eigenrays given by ray theory, the shallow water channel acoustic transfer function suitable for the high frequency to calculate the acoustic field is established in this paper. The method Takes into account the effect of channel boundaries on the acoustic field and has good adaptability to complex channel environments. The accuracy of the calculated acoustic field is verified by comparing the reconstructed acoustic field of the virtual source with the radiated acoustic field numerical method. Finally, the acoustic radiation characteristics of elastic structures in shallow water channels are analysed considering the variation of the sound speed profile, depth of shallow water and frequency.

203

Structural Vibration and Sound Radiation Directivity pattern of the acoustic field for a propellershaft-hull coupled system Li-Bo Qi1,2, Ming-Song Zou1,2 1 China Ship Scientific Research Center, Wuxi, China 2 State Key Laboratory of Deep-sea Manned Vehicles, Wuxi, China

In this paper, the directivity pattern of the acoustic field radiated from the longitudinal and transverse modes of a propeller-shaft-hull coupled system are investigated based on the threedimensional sono-elasticity software Thafts-Acoustic 1.0. The measurement characteristics of acoustic radiation of different modes for the coupled system are summarized by comparing the sound pressure of different modes at different field points in different directions. The results show that the acoustic radiation of longitudinal modes of the propeller-shaft-hull coupled system has a directivity characteristic that the bow and tail direction is significantly stronger than the left and right direction, while the acoustic radiation of transverse modes has a directivity characteristic that the left and right direction is slightly stronger than the bow and tail direction. The conclusions of this paper can provide technical support for the measurement of the acoustic radiation of a ship.

204

Structural Vibration and Sound Radiation Flexural Wave Bandgap Property in Thin Plates with Designed Periodic Partial-Constrained-Layer Damping Qi Qin1,2, Meiping Sheng1,2, Fan Zhao1,2, Zheng Fang1,2 1School of Marine Science and Technology, Northwestern Polytechnical University, 127 Youyixilu, 710072 Xi’an, China 2Research & Development Institute of Northwestern Polytechnical University in Shenzhen, 25 Gaoxin Nan Sidao, 518057 Shenzhen, China

Traditional theory on partial-constrained-layer damping (PCLD) is mainly focused on vibration damping and system loss factors. The bandgap analysis is introduced in thin plates with designed periodic PCLD. The behavior of wave propagation in a thin plate with designed periodic PCLD is investigated analytically. The bandgap dispersion relation is studied first, with the periodic cell consisting of a rectangular plate and the attached structure of certain scales. Each attached structure includes constraining layer and the viscoelastic layer, of which the damping characteristics are not considered to exactly find how the periodicity acts on wave propagation. It is found that, multiple resonant modes of the attached structure make the band-structure curves abundant, and there appear bandgaps within which flexural waves are forbidden to propagate into the infinite plate with designed periodic PCLD. Vibration transmission response in the finite structure is also calculated, and the transmission gaps are in good agreement with the bandgaps. Furthermore, by applying the damping characteristic to viscoelastic layers, it is observed that the vibration attenuation band can be broadened. To illustrate vibration suppression effects of designed periodic PCLD, together with another two finite models, the vibration responses are compared, including a plate attached with periodic lumped resonant elements, and a sandwich plate with monolithic viscoelastic core. The results show that much broader attenuation gaps are achieved in the plate with designed periodic PCLD. The bandgap analysis in plates with designed periodic PCLD can give guidance on suppression of structural vibration.

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Structural Vibration and Sound Radiation Uncertainty Quantification in Sound Radiation due to Three- dimensional Vibration of Ring Zhe Liu1, Kheirollah Sepahvand1, Yintao Wei2, Steffen Marburg1 1 Department of Mechanical Engineering, Technical University of Munich, Garching, Germany 2 Department of Automotive Engineering, State Key Lab Automotive Safety and Energy, Tsinghua University, Beijing, China

Material and geometrical parameters of some ring-like engineering structures, such as tire, involve some degree of uncertainty due to the production process. This will result in uncertainty of the system responses. In this study, a theoretical model is studied to describe the impact of uncertainty in elastic and geometrical parameters of ring on the sound radiation created by the three-dimensional surface vibration of the ring model. The generalized Polynomial Chaos (gPC) expansion with unknown coefficients is adopted to approximate the uncertain parameters of the ring and as well as the sound power density. The in-plane and out-of-plane bending and torsional vibrations of the ring are treated as the source of noise generation. The non-intrusive probabilistic collocation method is employed in order to obtain the unknown coefficients. Based on linearly independent condition, the number of selected collocation points is reduced as much as possible. This yields an efficient simulation in terms of computational time. Numerical results of sound power due to free and forced vibrations under concentrated line forces are compared in this paper.

206

Structural Vibration and Sound Radiation Discipline of Different Structures on Cylindrical Shells’ Vibration and Sound Radiation under Inner Noise Source Fang Ji1, Huadong Zhang1,2, Meiping Sheng2, Guonan Li1,3, Jiangtao Liu1 1China Ship Research and Development Academy, 100192 Beijing, China 2School of Marine Science and Technology, Northwestern Polytechnical University, 127 Youyixilu, 710072 Xi’an, China 3College of Power and Energy Engineering, Harbin Engineering University, 145 Nantongdajie, 150001 Harbin, China

To address sound radiation from an underwater vehicle due to inner intense noise source (including intense transient noise source), a scale model experiment was carried out in order to study the influence of inner noise from 100Hz to 1500Hz on the shell vibration and sound radiation. Take single, double and cone-cylinder combined ring-stiffened shells as objects, the discipline of different structures on cylindrical shells’ vibration and sound radiation under inner noise source is discussed. The result shows that overall sound pressure level of double shell is the lowest while cone-cylinder takes second place. The sound pressure level of single and conecylinder shells are lower than double shell from 100Hz to 350Hz; acoustic modes are the major factor of sound radiation below 400Hz; from 400Hz to 1500Hz, sound radiation is controlled by structure modes and acoustic modes.

207

Structural Vibration and Sound Radiation Underwater Coupled Sound Field Characteristics of Cylindrical Shells under Complex Excitation of Mechanical Force and Acoustic Motivation Fang Ji1, Huadong Zhang1,2, Meiping Sheng2, Guonan Li1,3, Jiangtao Liu1 1China Ship Research and Development Academy, 100192 Beijing, China 2School of Marine Science and Technology, Northwestern Polytechnical University, 127 Youyixilu, 710072 Xi’an, China 3College of Power and Energy Engineering, Harbin Engineering University, 145 Nantongdajie, 150001 Harbin, China

To study the coupled problem of sound transmission and radiation under the united excitation of mechanical force and acoustic motivation, a scale model experiment was carried out in order to study the influence of united excitation from 100Hz to 1500Hz on the shell vibration and sound radiation. Take single, double and cone-cylinder combined ring-stiffened shells as objects, the discipline of cylindrical shells’ vibration and sound radiation between different structures under this united excitation is discussed. The result shows, under the united excitation, the major factor of sound radiation below 400Hz is the acoustic motivation; sound radiation is controlled by the mechanical force, but acoustic-structural coupled phenomenon leads to peaks at 566Hz(double shell), 742Hz(single shell) and 966Hz(cone-cylinder combined shell) , and the sound transmission is non-resonant.

208

Structural Vibration and Sound Radiation The Noise Reduction Mechanism of Different Microstructures on the Superhydrophobic Surfaces Chen Niu1,2, Yong-wei Liu1,2, De-jiang Shang1,2 1Acoustic Science and Technology Laboratory, Harbin Engineering University, Harbin 150001,China 2Key Laboratory of Marine Information Acquisition and Security(Harbin Engineering University),Ministry of Industry and Information Technology; Harbin 150001,China 3College of Underwater Acoustic Engineering, Harbin Engineering University, Harbin 150001,China

Since the fluid boundary layer can be changed by the micro-structures, the skin friction can be reduced by the superhydrophobic surfaces in the laminar and turbulent flows. However, the noise reduction mechanism from these superhydrophobic surfaces has less been focused on. To investigate the noise reduction effect from the superhydrophobic surfaces, we have established three simulation models, which have different characteristics of superhydrophobic surfaces including square, cylinder, and cone to control the flow and reduce the hydrodynamic noise. Water flows through the micro-structure on surface at a rate of 3m/s and the length of fluid field is 2mm. The simulated results show that when water flows through the model’s surface, different micro-structures on the superhydrophobic surfaces can create a Cassie state and the slip flow can be formed. Then, the vortexes formed near the microstructure have changed the turbulent kinetic energy and the Reynolds stress in the boundary layer, reduced the fluctuation pressure. That’s the reason why the superhydrophobic surfaces can reduce the drag and the hydrodynamic noise. Therefore, our results can provide important reference value for acoustic stealth performance of underwater vehicles

209

Geoacoustics and Ultra-Low-Frequency (ULF) Underwater Acoustics Criteria for Evaluating the Inverted Geoacoustic Parameters of Sea-bottom Zhendong Zhao, Juan Zeng, Li Ma and Er-Chang Shang Key Laboratory of Underwater Acoustic Environment, Institute of Acoustics, Chinese Academy of Sciences, Beijing, China

Inverting Geoacoustic parameters of sea-bottom from acoustic data has been a very active research area over the past four decades. However, the approaches are model based. For model-based approach, the model-mismatching problem has to be eff resolved. If vector mR represents the real bottom parameters and vector mA represents the inverted bottom parameters of the assumed model, then we are facing eff eff a critical question: how to evaluate mA ? In other words: to what extent mA is close to mR ? In this paper, based on data-model comparison approach we use the eff “data difference” – DD ≡ Dataobs(mR) – Datamod(mA ) - as the criterion for eff evaluating mA . Then, with case study, we discuss the following two important issues for a satisfied parameter evaluating: 1) Data selection, and 2) frequency selection.

210

Geoacoustics and Ultra-Low-Frequency (ULF) Underwater Acoustics Development of the Predictive Geoacoustic Model Linus Chiu1, Andrea Chang2, Ching-Sang Chiu3, Jiann-Yuh Lou4 1Institute of Undersea Technology, National Sun Yat-sen University, Kaohsiung, Taiwan 2 Center of Marine Technology, National Sun Yat-sen University, Kaohsiung, Taiwan 3Department of Oceanography, Naval Postgraduate School, Monterey, USA 4 Department of Marine Science, R.O.C. Naval Academy, Kaohsiung, Taiwan

Normal incidence echo data can provide acoustic reflectivity estimates that can be further used to predict sediment properties using seabed sediment models. There are several models describing the properties of seabed sediments. Among these models, the Biot model shows high accuracy in estimating geoacoustic parameters of sediment and has been extensively verified. Thus, geoacoustic inversion techniques that utilize normal incidence reflection measurements with the Biot model to determine the sound speed, density, and attenuation of surficial sediments are developed [1-2]. In the inversion process, several empirical equations are applied to estimate sediment properties, including the equation that estimating the mean grain size by giving the porosity. In this research, coring data collected in the South China Sea is analyzed and used to verify the empirical equation for the porosity and the mean grain size. The errors between the measured and estimated mean grain size and also the inversion results are analyzed. Additionally, a predictive geoacoustic model that incorporate the coring data is developed and presented, which can predict the geoacoustic properties based on the coring data. [This research is supported by the Ministry of Science and Technology of Taiwan with project number: MOST 108- 2623-E-110-001 –D, MOS 107-2218-E-110 -004 -, and MOST 107-2218-E-110 - 006 -]

References [1] S. Schock, A method for estimating the physical and acoustic properties of the seabed using chirp sonar data, IEEE J. Ocean. Eng., 29(2004), 1200–1217. [2] L. Chiu, A. Chang, Y. Lin, and C. Liu, Estimating geoacoustic properties of surficial sediments in the North Mien-Hua Canyon region with a chirp sonar profiler, IEEE J. Ocean. Eng., 40(2015), 222–236.

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Geoacoustics and Ultra-Low-Frequency (ULF) Underwater Acoustics Sediment Characterization from Acoustic Echo-sounding Using Artificial Neural Networks: Preliminary Results from at-sea Data Haiyan Ni1,2,3, Wenbo Wang1,2,3, Li Ma1,2, Jinrong Wu1,2, Qunyan Ren1,2 1 Key Laboratory of Underwater Acoustic Environment, Chinese Academy of Sciences, Beijing , China 2Institute of Acoustics, Chinese Academy of Sciences, Beijing, China 3University of Chinese Academy of Sciences, Beijing, China

The feasibility of artificial neural networks in sediment classification and parameter estimation is discussed. Two experiments have been conducted simultaneously in the same ship track using singlebeam echosounder and multibeam sonar system offshore the coast of Qingdao, 2018. The mean angular response extracted from multibeam backscattered data have been exploited as inputting parameters in the Back Propagation neural networks (BPNN) and convolutional neural networks (CNN) to estimate the mean grain size (푀푧) of surface sediment. As for training label corresponding to inputted multibeam data in neural networks, the estimated index of mean grain size acquired from the singlebeam data inversion is utilized, which is basically consist with the ground-truth information obtained by previously core samples. Thereafter, the neural network intelligently mines the connection between the inputting parameters and the label information during the training of the neural network, and therefore is competent to predict the 푀푧value of surface sediment. Preliminary results demonstrate that the prediction accuracy of neural network-based method could up to 94 percent within the absolute error tolerance of 0.5 in terms of 푀푧 prediction. The factors affecting the prediction accuracy will be discussed.

212

Geoacoustics and Ultra-Low-Frequency (ULF) Underwater Acoustics The Analysis of Multi-layered Effect for Elastic Sea Bottom on Geoacoustic Propagation Yaxiao Mo1, Licheng Lu1, Bingwen Sun1, Chaojin Zhang1,2, Shengming Guo1 1 Key Laboratory of Underwater Acoustic Environment, Institute of Acoustics, Chinese Academy of Sciences, Beijing, China 2 University of Chinese Academy of Sciences, Beijing, China

Geoacoustic propagation is the mean approach of transmission in low frequency and ultra-low-frequency in shallow or inshore area, which is generated by the coupling from water to bottom. The geoacoutic field is transmitted by the sea bottom. In low frequency sound propagation, shear wave in sea bottom and the submarine stratification are both non-negligible factors. However, compared with the effect caused by the bottom shear wave, how the layered structure affects the propagation is not as explicit. A geoacoustic propagation model for the multi-layered elastic sea bottom is developed based on mapping approach in parabolic equation method. Interface conditions between multi-layered elastic medias are accurately handled by using proper physics fields. Simulated results under shallow and inshore environment indicate that geoacoutic signal is not only transmitted as interface wave between the water and the sea bottom, but also propagated more efficiently in the wave guide made up of multi-layered bottom. Meanwhile, the intensity of interface wave between the elastic layers is higher than that between liquid-elastic layers.

References [1] Shi-e Yang, Theory of underwater sound propagation., Harbin Engineering University Press, Harbin, 2009, ISBN: 978-7-81133-556-9 [2] M. D. Collins, D. K. Dacol, A mapping approach for handing sloping interface, J. Acoust. Soc. Am, 107(2000), no. 4, 1937-1942 [3] Licheng Lu, Li Ma, Acoustic characteristics of the seabed, Physics, 43(2014), no. 11, 717-722 [4] Haigang Zhang, Shengchun Piao, Shi-e Yang, Propagation of seismic waves caused by underwater infrasound, J. Harb. Eng. Univ, 31(2010), no. 7, 879-887 [5] M. D. Collins, W. L. Siegmann, Treatment of a sloping fluid-solid interface and sediment layering with the seismo-acoustic parabolic equation, J. Acoust. Soc. Am, 137(2015), no. 1, 492-497

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Geoacoustics and Ultra-Low-Frequency (ULF) Underwater Acoustics Characterizing the Stress Interactions Influenced by the Wave- induced Fluid Flow Cheng-Hao Cao1,3, Li-Yun Fu2, Tong-Cheng Han2, Jing Ba4 1 Key Laboratory of Petroleum Resource Research, Institute of Geology and Geophysic, Chinese Academy of Sciences, No. 19, Beitucheng Western Road, Beijing 100029, China 2 Key Laboratory of Deep Oil and Gas, China University of Petroleum (East China),Shandong 266580, China [email protected] 3 Institutions of Earth Science, Chinese Academy of Sciences, 19 Beitucheng Western Road, Chaoyang District, Beijing 100029, China 4 School of Earth Sciences and Engineering, Hohai University, Nanjing, 211100, China. As the crack density in rocks exceeds the limit of dilute assumption, interactions between the cracks will significantly affect the local stress distribution and the corresponding effective elasticity. This will be complicated by the wave-induced- fluid-flow. Based on the quasi-static Biot’s equation of consolidation, two kinds of synthetic rock samples: stacked cracked media where the crack interaction is caused in the form of stress shielding; and coplanar cracked media where the crack interaction is caused in the form of stress amplification, are considered. We then perform an exhaustive analysis to study the role played by two kinds of stress interactions on the seismic attenuation and dispersion respectively. Numerical outputs show that the shielding effect will lead to a smaller value of attenuation with a greater peak frequency corresponding to the largest attenuation. On the other side, the larger amplification effect will lead to the smaller attenuation but negligible peak frequency shift. This suggests that frequency-dependent characteristics could be to distinguish different stress interactions, providing an effective tool to explore the detailed structure information of the rock samples. Meanwhile, due to the excluded energy outside of the model, attenuation fluctuation is obvious for smaller incidence angles in low frequency band (0.1Hz- 20Hz). However, for a continuously increasing angles, the attenuation will increase, and stress amplification will also be enhanced, leading to greater attenuation. In addition, since the two kinds of stress interactions have opposite effects on the properties of the model, it is expected a cancelation of stress interactions as the two stress interactions coexist simultaneously. And our results fit well with the analytical ones excluding the stress interactions, validating the cancelation of stress interactions. References [1] Ba, J, Carcione J M, and Nie J X., Biot-Rayleigh theory of wave propagation in double-porosity media[J]. Journal of Geophysical Research Atmospheres, 116(2011), no.B6, 309-311. [2] Guo, J, Rubino J G, Barbosa N D, et al., Seismic dispersion and attenuation in saturated porous rocks with aligned fractures of finite thickness: Theory and numerical simulations —Part 2: Frequency-dependent anisotropy. Geophysics, 83(2018): no.1, WA63-WA71

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Geoacoustics and Ultra-Low-Frequency (ULF) Underwater Acoustics Simulations of VLF Underwater- and Seismo-acoustic Propagation Fields in the Wedge Coast and the Borehole Onshore Shuyuan Du, Shihong Zhou, Yubo Qi State Key Laboratory of Acoustics Institute of Acoustics, Chinese Academy of Sciences, Beijing, China

The coastal continental shelf area is a wedge-shaped shallow-water waveguide consisting of water column and a layered elastic bottom. In this kind of environment, it is necessary to learn the propagation physics of the very-low-frequency (VLF) underwater-acoustic or seismo-acoustic field, which is radiated from the underwater source, propagates through the water media, propagates over a sloping layered elastic bottom and is received in the wedge coast and the borehole onshore. In the process of wave propagation, there occurs the mode conversion and the mode cutoff in the wedge-shaped duct, energy coupling and leakage into the bottom in terms of longitudinal, transverse and interface waves. Generally, Scholte wave as a kind of interface waves converted from the modes in the shallow duct are important, which might be weak due to the thick and soft sediment in the coast and be stronger in the borehole onshore. So it is of interests to research the propagation mechanism and the energy distribution of the very-low-frequency underwater-acoustic or seismo- acoustic field in the coastal continental shelf area. Considering the effects of elastic sea-bottom, the full wave fields covering underwater-acoustics and seismo-acoustics below 20 Hz both in water and in borehole onshore are calculated using the 2-D Spectral Element Method (SPECFEM-2D)[1]and the mesh tool CUBIT. Waveform and spatial energy distribution at different frequencies are predicted. The results show that the very low frequency acoustic filed can be coupled to seabed in form of Scholte wave propagating through the upper interface of the rock layer and it is better to capture it in the borehole onshore at the boundary depth of rock layer than on the seafloor in the duct.

References [1] Komatitsch D., Tromp J., Spectral-element simulations of global seismic wave propagation- I．Validation．Geophys．J．Int. (2002) , no.149(2) , 390–412

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Geoacoustics and Ultra-Low-Frequency (ULF) Underwater Acoustics At-sea Observation and Theoretical Simulation on Very-low- Frequency Sound Propagation in Shallow Water Jingpu Cao1,2, Shuyuan Du1, Shihong Zhou1, Yubo Qi1 1 State Key Laboratory of Acoustics, Institute of Acoustics, Chinese Academy of Sciences, Beijing 100190, China 2 University of Chinese Academy of Sciences, Beijing 100049, China

The very-low-frequency (VLF) sound has significant potential for developing underwater detection and sea-bottom inversion. Due to the effect of layered elastic sea-bottom on the VLF sound propagation, it is necessary to understand the propagation principle and characteristics of VLF underwater- and seismo-acoustic fields. The typical seismo-acoustic fields include generally head-waves, interface waves, reflected shear-waves and wide-angle reflected/refracted seismic phases. In this paper, the experiment conducted in May 2018 in shallow water is introduced. In this experiment, the Ocean Bottom Seismometer (OBS) was used to receive the low-frequency signals excited by a towed air-gun at depth of 10 meters. The water depth is about 126 meters in the experiment area. Except for the head waves and the wide-angle seismic phase corresponding to the multiple-layer bottom and the deep basement respectively, the obvious Scholte waves are also observed within offset 5 km and frequency band 1.5-3 Hz at the horizontal and vertical geophones. The Scholte wave dominates the wave field below the waveguide cut-off frequency and the horizontal component has stronger signal-to-noise ratio than the vertical component but no response on the hydrophone. The dispersion analysis using phase shift method[1] from the common receive gathers shows that at least 4 Scholte wave modes are excited with the dispersive phase velocity between 200m/s and 800m/s. Based on the extracted P wave velocities from the head waves and the estimated S wave velocities from the Scholte waves, the full wave filed simulations using the 2-D Spectral Element Method (SPECFEM-2D)[2] in the case of layered elastic bottom medium are carried out to explain the physical mechanism of all the types of seismo- and underwater-acoustic components. The simulated full waveform basically matches the measured.

References [1] Park C. B., Miller R. D. and Xia J. H., Imaging dispersion curves of surface waves on multichannel records, SEG Expanded Abstracts, 17(1998), 1377-1380. [2] Komatitsch D., Tromp J., Spectral-element simulations of global seismic wave propagation- I．Validation．Geophys．J．Int. (2002), 149(2), 390–412.

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Geoacoustics and Ultra-Low-Frequency (ULF) Underwater Acoustics Analysis on the Sound Propagation Caused by Very Low Frequency Sound Source near the Sloped Seabed Liang Xu3, Haigang Zhang1,2,3 1 Acoustic Science and Technology Laboratory, Harbin Engineering University, Harbin, China 2 Key Laboratory of Marine Information Acquisition and Security, Ministry of Industry and Information Technology, Harbin, China 3 College of Underwater Acoustic Engineering, Harbin Engineering University, Harbin, China

In order to obtain the propagation features of ocean seismo-acoustics near the seabed, this paper introduces an algorithm for synthetic acoustic vector field and seismic wave fields[1] aroused by Very-Low-Frequency(VLF) sound source based on RAMs[2][3]. Numerical calculation of synthetic sound field in seafloor was carried out at a sloped seabed. According to the results of numerical examples and experiment, surface waves can be excited again and spread in the sloped seabed.

References [1] Haigang Zhang. Research on modeling and rule of infrasound propagation in shallow sea [D]. Harbin Engineering University, 2010. [2] Sanders, W.M. and M.D. Collins, Nonuniform depth grids in parabolic equation solutions. The Journal of the Acoustical Society of America, 2013. 133(4): p. 1953-1958. [3] Collins, M.D., H. Schmidt and W.L. Siegmann, An energy-conserving spectral solution. J Acoust Soc Am, 2000. 107(4): p. 1964-6. [4] Jensen, F. B., Kuperman, W. A., Porter, M. B., & Schmidt, H. (2011). Computational ocean acoustics. Springer Science & Business

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Geoacoustics and Ultra-Low-Frequency (ULF) Underwater Acoustics Effect of Sediment Layer on Scholte Wave Dispersion Characteristics Xiayun Luo1, Jun Yuan1, Guangli Cheng1, Luwen Meng2, Mingmin Zhang1 1Electronics Engineering College, Naval University of Engineering, Wuhan , China; 2National Innovation Institute of Defense Technology, Beijing, China;

In order to study the effect of sediment layer on Scholte wave dispersion characteristics, the characteristic equation of all wave modes in the acoustic field model is derived based on the ocean acoustic field model with solid sediment. The phase velocity dispersion curve of Scholte wave is obtained by numerical calculation. The results show that the phase velocity of Scholte wave increases with the increase of seabed S-wave velocity at the same frequency, the cutoff frequency moves upward gradually, and the frequency band area with obvious dispersion decreases gradually; the phase velocity of Scholte wave increases with the increase of P-wave velocity and density of the seabed, but the trend of the dispersion curve, the cutoff frequency and the frequency band area with obvious dispersion almost unchanged; with the increase of sea depth, the cutoff frequency of Scholte wave moves downward gradually, however, with the increase of frequency, the limit value of phase velocity tends to be stable and remains unchanged. The role of sediment thickness change is mainly to determine the position of the dispersion curve moving horizontally, in extreme cases, when the thickness of the sediment becomes infinite, the cutoff frequency is zero. When the thickness of sediment layer becomes thinner, the dispersion curve will gradually shift to the right, and the cutoff frequency will increase. If the thickness trends to zero, the Scholte wave on the surface of sediment layer will disappear, at this time, the Love surface wave which originally existed at the interface between sediment and underlying media is transformed into Scholte wave. High-order staggered grid finite difference method is used to simulate the Scholte wave excited by pulse source, and the effect of sediment thickness and type on Scholte wave is analyzed. The results show that the Scholte wave only appears weak dispersion at very low frequency without cutoff frequency when no sediment layer is added. With the increase of sediment layer, the dispersion increase and cutoff frequency appears. With the decrease of the thickness of sediment layer, the dispersion and the cutoff frequency increase gradually, which is the same as the numerical results of the characteristic equation. The structure of Scholte wave time domain signal waveform becomes more complex after adding sediment layer. The thinner the sediment layer is, the more complex the received signal waveform is, and the larger the signal amplitude is. With the increase of sediment layer thickness, the received signal waveform tends to increase the waveform of the signal without adding the sediment layer.

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Geoacoustics and Ultra-Low-Frequency (ULF) Underwater Acoustics The Influence of Periodic Corrugated Surfaces on the Generation and Propagation of Scholte Waves Minshuai Liang, Gaokun Yu, Linhui Peng Department of Marine Technology, Ocean University of China, Qingdao, China

This paper studies the influence of periodic corrugated surfaces on the generation and propagation of Scholte waves. The relationship between parameters of periodic surfaces and the generation frequency of Scholte waves is studied by theoretical derivations of the Scholte wave velocity dispersion equations and the scattering coefficient of periodic corrugated surfaces, and the coupling relationship between the two factors is obtained. At the same time, the finite element method is used to establish the calculation model, and numerical calculations prove the above theory is correct. Through comparing theoretical calculations and numerical simulation results, we can get conclusions: (1). periodic corrugated surfaces contribute to the generation of Scholte waves. (2). the finite length of periodic corrugated surfaces and the hard seafloor are the key factors for generating long- range Scholte waves.

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Acoustics in Ice-Covered Environment and Interface Reverberation Polar Acoustics & Information Tech Xueli Sheng1,2,3 1 Acoustic science and Technology laboratory, Harbin Engineering University, Harbin, China 2 College of Underwater Acoustic Engineering, Harbin Engineering University, Harbin, China 3 Key Laboratory of Marine Information Acquisition and Security （Harbin Engineering University），Ministry of Industry and Information Technology; Harbin, China

China's Arctic Policy, the first white paper on the Arctic, makes it clear that China will become an active participant, builder and contributor in Arctic affairs. More and more underwater manned and unmanned submarines are participating in the polar science examination and resource survey. However, due to the wide range of ice sheets, underwater vehicles can not surf the water surface to establish links with other air-space or offshore platforms, which making underwater acoustic technology become an important or even the only means of information acquisition and transmission under ice in the Arctic. Moreover, due to the existence of ice interface, the special marine environment under ice brings new scientific problems to the physical model of sound propagation and new challenges to the application efficiency of sonar technology. The United States and the former Soviet Union have done a lot of research on underwater acoustic technology in the Arctic sea ice area, but with the end of the Cold War, it has faded out of sight. In 2014, the Office of Naval Research (U.S.) relisted polar acoustics as one of the three major research directions. However, polar acoustics is still in its infancy in China, and many research directions are almost blank. Since 2014, Harbin Engineering University has been conducting underwater acoustic research in the Songhua River, Bohai Bay area and Vladivostok Sea Ice Area with Far Eastern Federal University (Russian). And it has participated in the eighth and ninth Chinese National Arctic Research Expeditions. Focusing on the adaptive technical requirements of underwater acoustic technology in sea ice area, Harbin Engineering University carried out the basic research of polar acoustics and the research on acquisition and transmission of information under ice, and proposed the corresponding technical solutions.

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Acoustics in Ice-Covered Environment and Interface Reverberation Ice Acoustic Parameter Measurement Based on Polarization Filtering Jiahui Gao1,2,3, Yuxiang Zhang1,2,3, Zhinan Xie1,2,3, Dingyi Ma1,2,3, Xiukun Li1,2,3,Jingwei Yin1,2,3 1 Acoustic science and Technology laboratory, Harbin Engineering University, Harbin, China; 2 College of Underwater Acoustic Engineering, Harbin Engineering University, Harbin, China; 3 Key Laboratory of Marine Information Acquisition and Security （Harbin Engineering University）， Ministry of Industry and Information Technology; Harbin, China

Acoustic parameters of ice are important as they feature the mechanical properties of ice, their determination is, however, sophisticated. Conventional methods, e.g. time-of-flight (TOF) test or resonant frequency measurement, are often off-line and complicated as they require extraction and preservation of ice core. In 1993, T.C. Yang simplified the ice layer to a flat plate and tried to determine its acoustic parameters in-situ by measuring the velocities of P-wave and S-wave through TOF tests. However, due to the inhomogeneity and anisotropy of ice, different types of wave are severely couple in recorded signal, which impairs the results in term of precision. On this basis, polarization filtering is proposed here for reducing error and increasing precision in acoustic velocity assessment. Using 3- component seismometer as receiver and impact from metal object as source, experiments have been conducted on the Songhua River for validation. Results show that, without polarization filtering, signals of S-wave and flexure-wave interfere with each other. Their respective propagation velocities can thus not be obtained with satisfactory precision. With polarization filtering, the arrivals of different types of waves become more distinct in recorded signals. Having them correctly separated, the precision of obtained propagation velocity of different types of wave are considerably improved.

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Acoustics in Ice-Covered Environment and Interface Reverberation Study on Acoustic Inversion Method of Sound Velocity Profile in Ice Jing Yan1,2,3, Zhu Guangping1,2,3, Yin Jingwei1,2,3, Liu Jianshe1,2,3, Song Zelin1,2,3 1 Acoustic Science and Technology Laboratory, Harbin Engineering University, Harbin 150001，China; 2 Key Laboratory of Marine Information Acquisition and Security (Harbin Engineering University), Harbin 150001, China; 3 College of Underwater Acoustic Engineering, Harbin Engineering University, Harbin 150001, China

The harsh environment in the Arctic has made it difficult to measure the temperature profile of the polar sea ice. In this paper, an acoustic measurement method is studied, and the temperature profile curve in ice is obtained by inversion. First, in the field test, the transducer is used to measure the average sound velocity of the Songhua River ice; then, the temperature profile curve in the ice is inversed by the relevant mathematical physical methods, the sound velocity empirical formula and the iterative method. Finally, compared with the measured temperature profile of the field, the error is calculated and the feasibility of this method is tested. Acoustic measurement methods can effectively ensure the safety of polar researchers and reduce the cost of polar research activities.

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Acoustics in Ice-Covered Environment and Interface Reverberation Reflection of Acoustic Wave from Rough Sea Ices Qianqian Li1,2, Juan Shi1, Pingshou Ming1, Fanlin Yang1, Kai Zhang1 1 College of Geomrtics, Shandong University of Science and Technology, Qingdao, China 2 State Key Laboratory of Acoustics, Institute of Acoustics, CAS, Beijing, China

In order to build an efficient underwater acoustic sensor network in the Arctic Ocean environment, transmission characteristics of under-ice acoustic channels need comprehensive understanding. The reflecting and scattering of acoustic waves from sea ices have great influences on under-ice acoustic channels. Both topology and structure of sea surface ices are very complex and variable. The physical dimension, acoustic property and interface roughness of sea ices depend not only on local environment, but also on climate and formation time. Therefore, it is of great significance to develop a model of reflecting and scattering of acoustic waves from sea ices for investigating the sound propagation in the under-ice environment. Assuming that sea ice is an elastic solid medium and the ice-water interface is rough, we develop a geometrical model of the rough sea ice. The sea ice thickness data over the years were trained to determine the distribution of the ridge height. It is found that the ridge height obeys gamma distribution, and the number of ridges/km are 18. Then, the rough sea ice geometrical model (RSIGM) is created, and the ice thicknesses over distance are generated randomly. Here, we selected some measured ice thickness out of training data as the test group. The reflection coefficient of ice layer is calculated based on the physical acoustic parameters of ice. The sound field propagation loss under the ice cover is obtained using the Bellhop ocean acoustic propagation model, and the influences of the model ice and the measured ice on the reflection coefficient are analyzed. The results show that the difference between the propagation of sound fields under the model ice and measured ice are less than 3dB within 40 km.

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Acoustics in Ice-Covered Environment and Interface Reverberation Sea-ice Thickness Measurement Based on Ice Layer Waveguide Theory Dingyi Ma1,2,3, Zhinan Xie1,2,3, Yuxiang Zhang1,2,3, Jiahui Gao1,2,3, Jingwei Yin1,2,3 1 Acoustic science and Technology laboratory, Harbin Engineering University, Harbin, China 2 College of Underwater Acoustic Engineering, Harbin Engineering University, Harbin, China 3 Key Laboratory of Marine Information Acquisition and Security （Harbin Engineering University），Ministry of Industry and Information Technology; Harbin, China

Sea ice is a sensitive indicator of global climate changing, of which the studies are of particular significance from both scientific and practical point of views. Therefore, researches on sea ice become a focus in its respective area. The thickness is one of the most important parameters of sea ice. It is, however, also one of the geophysical parameters that are most difficult to acquire. In this letter, an acoustic method for measuring sea-ice thickness is described and discussed. Sea ice is firstly simplified into an infinite layer with a constant thickness, the dependence between its thickness and its dispersion behavior is deduced by studying low-order waveguide modes of the layer. To further take into account the energy leakage at its interfaces, it is then modeled with a multi-layer structure as air-ice-water. The leaking dispersion behaviors are then studied in a similar manner. The results show that, for either model, the waveguide modes become less distinct between one another with the increase of thickness. Comparing the two models side by side, the effect from leakage mode at the icewater interface is as well revealed. In long term, this study lays a good foundation for the further researches as it helps building a reliable forward model of the acoustic waveguide within sea ice, which could in turn render an acoustic imaging technique for probing the inner structure of sea ice from above or underwater. As for more immediate perspectives, a discussion on extending results from this study into modeling multi-year sea ice and sea ice with varying thickness is included at the end.

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Acoustics in Ice-Covered Environment and Interface Reverberation A Practical Bottom Rough Surface Reverberation Model in Shallow Water Jinrong Wu1,2, Peng Li1,2, Er-Chang Shang1,2, Zhendong Zhao1,2 1 Key Laboratory of Underwater Acoustic Environment, Institute of Acoustics, CAS, Beijing, China 2 Institute of Acoustics, CAS, Beijing, China

Bottom rough surface scattering is the dominating source of low to mid frequency reverberation in shallow water. It is difficult to test the traditional full wave reverberation model using experiment data because many environmental parameters in the model are not easy to get. A three parameters model of shallow water waveguide reverberation based on full wave reverberation model was proposed. The three unknown environmental parameters in the new model include: bottom reflection attenuation parameter P, bottom reflection phase parameter Q, and bottom backscattering parameter . These parameters can be measured or inversed easily, and have clear physical pictures. This new practical shallow water reverberation model was compared with the Yellow Sea low frequency reverberation experiment data. The results show that the new proposed model can explain low frequency shallow water reverberation well. [This work was supported by the National Natural Science Foundation of China under No. 11774375].

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Acoustics in Ice-Covered Environment and Interface Reverberation Modeling Reverberation Time Series Based on Full Wave Reverberation Theory Jianlan Zhang1,2, Jinrong Wu1,2 1 Key Laboratory of Underwater Acoustic Environment, Institute of Acoustics, CAS, Beijing, China 2 Institute of Acoustics, CAS, Beijing, China

Traditionally, reverberation time series was simulated by cell-scatter model, point-scatter model, linear prediction model, or nonlinear prediction model. A new method to simulate reverberation time series has been proposed in this talk. The reverberation time series was simulated based on the full wave reverberation model we developed. The rough surface of scattering area was simulated firstly, then the initial signal was convolved with the effect scattering area to get the scattering kernel, finally, forward and backward sound propagation factors were included in the method. Numerical analysis shows: the new reverberation time series simulation model is faster than the cell-scatter model, point-scatter model and other traditional reverberation time series prediction models. At the same time, this new method has the clear physical picture, and can be used for reverberation time series simulation in sonar model. [This work was supported by the National Natural Science Foundation of China under No. 11774375].

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Acoustics in Ice-Covered Environment and Interface Reverberation Extracting Bottom Roughness Parameters Using Reverberation Data in Shallow Water Qiannan Hou 1, Er-Chang Shang 1, Jinrong Wu 1, Chaojin Zhang 1, 2, Lijun Yin 1, 2 1 Key Laboratory of Underwater Acoustic Environment, Institute of Acoustics, Chinese Academy of Sciences, Beijing, China 2 University of Chinese Academy of Sciences, Beijing, China

Though reverberation is an exceptive interfering signal for sonar, it contains lots of information of bottom rough interface, especially in shallow water. So extracting such roughness from reverberation data is an effective means of remote sensing and proves a new ways to fast assessment of marine environment. The traditional reverberation model, which is based on empirical scattering theory, is severely limited when analyzing the contribution of roughness to reverberation field. So the reverberation model based on scattering which has clear physical mechanism is made. The full-wave reverberation model is based on Bass perturbation theory proposes that roughness is considered as "scattering source" in wave function, then solves it and gets sound scattering field and reverberation field. In this model, the bottom roughness is narrated as spectrum and characterizes backscattering strength, which provides the theory basis for extracting of bottom roughness. This research is based on the full-wave reverberation theory and obtained frequency dependency of backscattering strength due to bottom roughness in according with the frequency dependency of reverberation average strength and two-way propagation loss. Thereafter, the parameters of bottom roughness spectrum are extracted based on clear and definite numerical relationship between bottom roughness spectrum and backscattering strength. Numerical simulation and experiment on sea will both give the proofs of the rationality of such method and the accuracy of the result.

References [1] E.C. Shang, T. F. Gao, J.R. Wu, A shallow-water reverberation model based on perturbation theory, IEEE. J. Ocean Eng., 33(2008), no. 4, 451-461. [2] T. F. Gao, Relation between waveguide and non-waveguide scattering from a rough interface, Acta Acoust., 14(1989), no. 2, 126-132 [3] E.C.Shang, The averaged intensity structure determined by the parameters of the Bottom-Reflection-Loss, Acta Oceanologia Sinica, 1(1979), no. 1, 58-64 [4] J. R. Wu, E. C. Shang, T. F. Gao, A new energy-flue model of waveguide reverberation based on pertubation theory, J. Acoust. Soc. Am., 18(2010), no. 3, 209-225

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Acoustics in Ice-Covered Environment and Interface Reverberation Characteristics of Bottom Reverberation Intensity in Deep Water Lijun Yin1,2,3, Jinrong Wu2,3, Qiannan Hou2,3 1Institute of Acoustics, CAS, Beijing, China 2Key Laboratory of Underwater Acoustic Environment, CAS, Beijing, China 3University of Chinese Academy of Science, Beijing, China

Bottom reverberation intensity as a function of frequency varied as bottom conditions. In order fully to understand the relationship between bottom reverberation intensity and frequency, the model of reverberation due to rough bottom sediment-water interface and sea-surface in deep water base on the classical ray theory was provided. The empirical scattering model presented by Ogden and Erskine was used for computing the sea-surface backscattering and the small slope approximation for the bottom interface backscattering. The frequency characteristics of reverberation intensify was obtained through numerical simulation. The results also demonstrated that the sea-surface reverberation intensity attenuated faster than bottom interface reverberation intensity, which gave a suggestion that the influence of sea-surface reverberation could be ignored in the analysis of bottom reverberation. And reverberation intensity had no remarkable relation with the depth of source. Moreover, the conclusion had also been verified according to the data from sea trials with explosive source in deep water.

References [1] P. Mourad, D. Jackson, A model/data comparison for low-frequency bottom backscattering, J Acoust Soc Am (1993), no. 94, 344–358. [2] H. Merklinger, Bottom reverberation measured with explosive charges fired deep in the ocean, J Acoust Soc Am (1968), no. 44, 508–513. [3] R. Gauss, R. Gragg, D. Wurmser, J. Fialkowski, Broadband Models for Predicting Bistatic Bottom, Surface, and Volume Scattering Strengths, Nasa Sti/recon Technical Report N, Washington, 2002, OMB: 0704-0188. [4] H. Zhou, Reverberation intensity pssrediction in deep ocean based on ray theory, Harbin Engineering University(2016), 12-26.

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Acoustics in Ice-Covered Environment and Interface Reverberation Reverberation Time Measurement Method Based on Time-frequency Analysis Yang liuqing1, Chen Yi1, Huang Yongjun1, Shang Dajing2 1 HangZhou Applied Acoustics Research Institute, 311400, Hangzhou 2 College of Underwater Acoustic Engineering, Harbin Engineering University,150001,Harbin

The traditional method of measuring reverberation time cannot measure the reverberation time of multiple frequency points at the same time, which affects the test efficiency. Therefore, this paper proposes a reverberation time measurement method based on time-frequency analysis. Based on the interrupted sound source method, the method changes the emission to a broadband noise signal, and uses time- frequency analysis to calculate reverberation time of different frequency points. In this paper, the reverberation time measurement experiment is carried out in a reverberant pool with a size of 15×9×6, and the reverberation time in the 200 Hz~10 kHz band is calculated by time-frequency analysis methods such as short-time Fourier transform and wavelet transform. And compare the calculated results with the reverberation time measurements in the B&K pulse, which are basically the same. This shows that using this method to measure reverberation time is correct and effective, and can greatly improve the test efficiency of reverberation time.

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Ultrasonic Nondestructive Testing Probability Imaging for Damage Location via Time Reversal Lamb Waves under the Baseline-free Signal Hanfei Zhang1, Shiwei Ma1, YanyanLiu1, Haiyan Zhang2 1)School of Mechatronic Engineering and Automation, Shanghai University, Shanghai, China 2)School of Communication and Information Engineering, Shanghai University, Shanghai, China

Aiming at the problem of poor practicability of extracting damage scattering signal from baseline signal, a baseline-free time reversal probabilistic imaging algorithm is proposed in this paper based on ultrasound guided waves time reversal theory and probability statistics principle. Firstly, the time reversal of signal and the adaptive focusing mechanism of wave source are used to eliminate the dispersion effect of Lamb wave. Secondly, the energy characteristic difference coefficient between the reconstructed Lamb wave signal and the original excitation signal, is taken as the damage factor. Finally, the relative distance between the damage and the direct path of the sensor-actuator channel is used to adjust the weight distribution function. The weighted probabilistic values of each sensor path in the sensor network are mapped to the discrete coordinates in the detection area, and the probabilistic imaging of the damage appearing on these discrete coordinates is constructed for multiple damages imaging and location. Experiments on aluminium sheets show that the method can clearly separate the damage scattering signals without baseline signals, achieve the focus of the original excitation signal, and obtain the damage probability images of structure. Compared to traditional probability distribution function method, it has better imaging accuracy and imaging quality. This method can accurately identify and locate multiple damages in aluminium sheet, which verifies the validity of this method and has certain engineering application value. References [1] C. Stefano, N. Francesco, and S. Gennaro,Finite difference model of wave motion for structural health monitoring of single lap joints, International Journal of Solids and Structures 161(2019), 219- 227. [2] Z. Ahmad, K. Sungwon, and A. Daniel, Lamb wave mode decomposition based on cross-Wigner-Ville distribution and its application to anomaly imaging for structural health monitoring, IEEE transactions on ultrasonics, ferroelectrics, and frequency control 3(2019), 193- 208. [3] J Y. Park, J R. Lee, Application of the ultrasonic propagation imaging system to an immersed metallic structure with a crack under a randomly oscillating water surface, Journal of Mechanical Science and Technology 31(2017), no. 9, 4099- 4108.

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Ultrasonic Nondestructive Testing Experimental Verification of Acoustic Source Localization Technique in Heterogeneous Plates Shenxin Yin1,2, Jia Fu1, Tribikram Kundu2, Zhiwen Cui1 1)Department of Acoustics and Microwave Physics, College of Physics, Jilin University, Changchun, China 2)Department of Civil and Architectural Engineering and Mechanics, University of Arizona, Tucson, USA

Acoustic source localization (ASL) in a structure by analyzing the recorded signals at the receivers is an important process in nondestructive testing for various applications.Recent research advances on this topic goes well but some challenges still remain when the plate becomes heterogeneous. Heterogeneousstructures are commonly found in natural materials and engineering synthetic materials.The wave propagation direction deviates from a straight line when it propagates through a heterogeneous plate due to refraction at the interface. This paper considers the law of refraction based on the triangular time difference technique. No complicated nonlinear equation solution is required which avoids the problem of multiplicity and wrong solution. The process of acoustic emission source localization is fast and easy for structural healthmonitoring. Only six sensors needed for acoustic emission source localizationin a non-homogeneous plate with known velocity. When the properties is unknown only three more receiving sensors needed in each layer which means the technique works well even for multi-layers heterogeneous plate. Experimental verification of heterogeneous structure (partially water-saturated natural rock samples) was complicated with the help of single-channel acoustic emission device, oscilloscopes and ultrasonic sensors. The experiment results show the new acoustic source localization technique of heterogeneous plate can localize the acoustic source accurately. References [1] Kundu T, Das S, Jata K V. Point of impact prediction in isotropic and anisotropic plates from the acoustic emission data[J]. The Journal of the Acoustical Society of America, 2007, 122(4): 2057-2066. [2] Fluckiger M, Nelson B J. Ultrasound emitter localization in heterogeneous media[C]//2007 29th Annual International Conference of the IEEE Engineering in Medicine and Biology Society. IEEE, 2007: 2867-2870.

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Ultrasonic Nondestructive Testing The Wavenumber Method for Characterizing a Delamination in Ballastless Slab Track Guopeng Fan1, Haiyan Zhang1,Hui Zhang1, Wenfa Zhu2, Xiaodong Chai2 1)School of Communication and Information Engineering, Shanghai University, Shanghai, China 2)School of Urban Railway Transportation, Shanghai University of Engineering Science, Shanghai, China

The ballastless slab track has been widely applied in high-speed railways as it has the advantages of high structural stability, good stiffness uniformity, and long service life[1]. However, the delamination located between multi-layers is frequently observed and it may not beeasily recognized by visual investigation [2].This paper aims to adopt the wavenumber method for characterizing a delamination in ballastless slab track. Thedry-contact ultrasonic transducers located at the upper surface of the slab track are employed to actuate shear waves, which are suitable for characterizing the delamination. For the purpose of restraining the pseudomorphism, the technique of removing the surface wave has been implemented for only retaining the scattered wave caused by the delamination and the reflected wave from the bottom of bed plate. The test results indicate that the delamination and bottom of the bed plate can be accurately characterized. Compared to the total focusing method (TFM), the wavenumber method has the relatively favorable advantages in improving the computational performance and lateral resolution. The proposed method can provide valuable information for the warning of the structural failure. References [1] Z.Yu, Y.Xie,Z.Shan,et al.,Fatigue performance of CRTS III slab ballastless track structure under high-speed train load based on concrete fatigue damage constitutive law, Journal of Advanced Concrete Technology16(2018), 233–249. [2] J.Liu, X.Wen, Z.Zhang,et al., Influence of the Stabilizer on Interfacial Bonding Behavior of Cement Asphalt Mortar in Slab Ballastless Track, Journal of Materials in Civil Engineering30(2018), 04018245.

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Ultrasonic Nondestructive Testing Study of Sound Velocity under Simulated Martian Environmental Conditions Rushan Shen1,2,3, Hanyin Cui1,3, Weijun Lin1,3 1)State Key Laboratory of Acoustics, Institute of Acoustics, Chinese Academy of Science, Beijing, China 2)University of Chinese Academy of Science, Beijing, China 3)Beijing Engineering Research Center of Sea Deep Drilling and Exporation, Institute of Acoustics, Chinese Academy of Science, Beijing, China

With the gradual development of deep space exploration missions, Mars exploration has received more and more attention. Because of its environmental characteristics which are different from those on the Earth's surface, the speed of sound on Mars must be different from that on Earth. In order to use the acoustic measuring device to detect Mars more effectively, we study the sound velocity in the Martian environment. We simulated the Martian environment and performed a measurement experiment of sound velocity. The experiment involved the measurement of the speed of sound in carbon dioxide and air at a temperature of -70 to 20 ° C and a pressure of 600 to 10000 Pa. We chose to use the time-difference method to measure sound speed. For the measured experimental data, we chose to use the cross-correlation method to get the value of sound velocity. Typical experimental result is shown in the figure below. The pressure drops from 10000 to 600 Pa, and the temperature of CO2 is controlled to be around 15 ° C. When the air pressure drops to 1500 Pa, the speed of sound gradually increases, which is larger than the result calculated by the ideal gas formula. This shows that in the environment of Mars, the ideal gas formula may not provide accurate sound velocity values.

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Ultrasonic Nondestructive Testing Improved SAFT for Internal Defects of CA Mortar Layer of Ballastless Track Xiangzhen Meng1，Wenfa Zhu1，Haiyan Zhang2，Hui Zhang1，Yujie Zhang1 1)School of Urban Railway Transportation, Shanghai University of Engineering Science, Shanghai, China 2)School of Communication and Information Engineering, Shanghai University, Shanghai, China

The slab ballastless track belongs to multi-layer concrete structure and the acoustic wave velocity is different in each layer. The existing ultrasonic imaging method is only suitable for the detection of concrete structures with constant wave velocity. This paper is aimed at the internal defects of CA mortar layer of high-speed railway CRTSIII slab ballastless track. The multi-Layer Delay-And-Sum is combined with the traditional Synthetic Sperture Focusing imaging method to improve the imaging method for forming internal defects of multi-layer concrete structures with different wave velocity. By establishing a two-dimensional finite element model of CRTSIII type slab ballastless cross section, the scattering longitudinal wave signal of the internal defects of CA mortar layer is obtained, and the defect imaging effect of the improved pre-imaging method and the improved imaging method is compared. The results show that the combination is more The Synthetic Sperture Focusing method with multi-Layer Delay-And-Sum is more accurate in the detection of internal defects of CA mortar layer, which provides reference for the ultrasonic imaging detection of internal defects of multi-layer concrete structures.

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Ultrasonic Nondestructive Testing Quantitative Characterization of Axial Defects in Pipes Based on Circumferential SH Guided Waves Jiuhong Jia , Tianyang Liu, Xuecheng Liu, Yun Tu, Shandong Tu Key Laboratory of Pressure Systems and Safety, Ministry of Education, East China University of Science and Technology, Shanghai, China

Damages of pipes gradually accumulate, which may lead to pipe leakage or even explosion with the increase of service time. On-line monitoring of pipes is an important method to ensure their safety. In the present research, the propagating theory of the circumferential fundamental shear horizontal wave (shorten for SH0 wave) in pipe walls are analyzed by finite element simulation, and a method about SH0 wave to quantitatively describe pipe axial defects are studied by both finite element simulation and experiment. Results show that the higher bending coefficient of the pipe is, the closer the propagation characteristics of circumferential SH0 wave in pipes are to the propagation characteristics of SH0 wave in plates. Moreover, reflection and transmission coefficient change monotonously with increase of the length and depth of the axial defect. The corresponding quantitative formula can be used to evaluate growth of defects. References [1] X. Zhang, Z. W. An, G. S. Lian, et al, Circumferential guided wave detection of defects in the inner wall of thin-wall pipeline. Journal of Acoustics 6 (2016): 857-862. [2] S. Wang, S. Huang, W. Zhao, et al, 3D modeling of circumferential SH guided waves in pipeline for axial cracking detection in ILI tools. Ultrasonics 56 (2015):325-331

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Ultrasonic Nondestructive Testing Wavenumber Imaging Using Diffuse Field Full Matrix for Near- surface Defects in Rails Hui Zhang1, Haiyan Zhang1, Jianquan Liu1, Guopeng Fan1, Wenfa Zhu2 1)School of Communication and Information Engineering, Shanghai University, Shanghai, China 2)School of Urban Railway Transportation, Shanghai University of Engineering Science, Shanghai, China

Wavenumber imaging of diffuse field full matrix is used to realize fast imaging for near-surface defects in rails. Compared to traditional total focusing method in time domain, wavenumber algorithm in Fourier-domain has higher lateral resolution and significant computational efficiency as well[1]. The cross-correlation of the diffuse field signals is performed to reconstruct the Green's function between the array elements. Thus, the early time defect information submerged by the limit can be retrieved[2]. Experiments are conducted on rails with different near-surface defects. The results confirm the effectiveness of the cross-correlation method to reconstruct the Green's function for the detection of near-surface defects. Different kinds of ultrasonic phased array probes are applied to collect experimental data on the surface of the rail, indicating that the Green's function recovery is related to the number of phased array elements and the excitation frequency. In addition, choosing appropriate parameters related to diffuse field signal also is vital for acquiring a high- quality image. References [1] E. Moghimirad, C.Villagomez-Hoyos, A. Mahloojifar, et al., Synthetic Aperture Ultrasound Fourier Beamformation Using Virtual Sources, IEEE transactions on ultrasonics, ferroelectrics, and frequency control63 (2016), no. 12, 2018-2030. [2] J. Potter, P. Wilcox, and A. Croxford, Diffuse field full matrix capture for near surface ultrasonic imaging. Ultrasonics 82(2018), 44-48.

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Ultrasonic Nondestructive Testing Ultrasonic Transducer Acoustic Pressure Measurement Method Based on Laser Reflection Tomography Weiyin Wang, Yi Chen, Shiquan Wang, Liuqing Yang Hangzhou Applied Acoustics Research Institute, Fuyang, China

The ultrasonic transducer is the core component of ultrasonic medical equipment, and its acoustic performance largely determines the overall performance of ultrasonic medical equipment. By measuring the absolute acoustic pressure in the acoustic field of the ultrasonic transducer, the acoustic performance of the transducer can be diagnosed and evaluated. Based on the analysis of the theoretical acoustic field calculation method of ultrasonic transducer, the acoustic field reconstruction algorithm and the mechanism of acousto-optic effect, the application of laser reflection tomography in the acoustic pressure measurement of ultrasonic transducer was systematic studied and simulated. At 180 kHz, using the built laser reflection tomography test system, the measurement of the radiation field distribution and the acoustic pressure measurement of the ultrasonic planar transducer was carried out. In order to verify the accuracy of the measurement results, a comparative experiment was conducted using a hydrophone scanning method. The measurement results of the two methods have good consistency, which verifies the feasibility of laser reflection tomography to measure the acoustic field and acoustic pressure of ultrasonic transducers, and provides a reliable and accurate measurement method for acoustic field reconstruction and acoustic pressure measurement of medical ultrasound transducers. References [1] F. P. Higgins, S. J. Norton, M. Linzer, Optical interferometric visualization and computerized reconstruction of ultrasonic fields, Journal of the Acoustical Society of America 68 (1980), no. 4, 1169-1176. [2] S. P. Robinson, P. D. Theobald, G. Hayman , et al, The use of optical techniques to map the acoustic field produced by high frequency sonar transducers, Proceedings of The Institute of Acoustics 1 (2006), no. 28, 726-734.

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Ultrasonic Nondestructive Testing Interface Defects Detection of Steel-Concrete Structure Based on Ultrasonic Guided Waves Yujie Zhang1, Wenfa Zhu1, Haiyan Zhang2, Hui Zhang1, Xiangzhen Meng1 1)School of Urban Railway Transportation, Shanghai University of Engineering Science, Shanghai, China 2)School of Communication and Information Engineering, Shanghai University, Shanghai, China

The steel-concrete bonded structure has the advantages of strong structure, reliability and stability, so it is widely used in infrastructure. Deterioration can result from a series of damage mechanisms and environmental loads during the construction process and service life. There is a large mismatch in the difference of acoustic impedance between the layers of the bonded structure, as well as the high sound attenuation and dispersion characteristics of the material, which makes the nondestructive testing of the bonding quality between the multi-layer interfaces of the composite structure still a problem. Aiming at this, a method for detecting the interface bonding case by using the attenuation of ultrasonic guided waves is proposed. Firstly, the theoretical attenuation dispersion curve under different bonding cases is calculated by using the ultrasonic propagation theory in the layered bonding structure. The result shows When the A0 mode changes with frequency, the attenuation change is not obvious in each bonding case; when the S0 mode changes with frequency, the attenuation changes obviously in each bonding case. Then the finite element model is established by Lamb wave propagation in the layered bonding structure with different bonding cases by air-coupled ultrasonic. The results show that a large amount of S0 mode energy leaks into the concrete layer in the early stage of propagation under the condition of well bonded. In the case of weak bonded, less S0 mode energy leaks into the concrete layer; in the case of disbonded, the S0 mode propagates in the steel-cladding without energy leaking into the concrete. Finally, the finite element results are subjected to two-dimensional Fourier Transform. The results show that the interface layer is completely bonded, weakly bonded, and disbonded. The attenuation of the S0 mode is obvious, while the A0 mode is basically unaffected.

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Ultrasonic Nondestructive Testing Focused Sound Field in Austenitic Stainless Steel Weld by Ultrasonic Phased Array Shouguo Yan1, Zhongcun Guo1,2, Bixing Zhang1,2 1)State Key Laboratory of Acoustics, Institute of Acoustics, CAS, Beijing, China 2)University of Chinese Academy of Sciences, Beijing, China

The detection of austenitic steel welds is one of the most difficult problem in ultrasonic nondestructive testing. Austenitic steel is a coarse-grained material that is generally inhomogeneous and anisotropic. Especially in the welding process, the crystalline grains will grow along the maximum thermal gradient when cooling [1], which causes the coarser columnar grain in the weld and the grain orientation varies with position. Since the grain size has reached or exceeded the ultrasonic wavelength, skewed and distorted will occur when the sound beam propagates therein, which brings difficulty in ultrasonic non-destructive testing. The detection scheme should be designed more reasonable if the ultrasonic propagation characteristics are studied well in the austenitic steel weld, and also the accuracy of ultrasonic testing can be improved. However, due to the lack of suitable theoretical models and calculation methods, previous studies on the characteristics of sound beams in austenitic steel welds have been less. In order to solve this problem, based on the Ogilvy [2] weld model, the sound field of ultrasonic phased array in such welds is calculated by combining the Gaussian beam equivalent point source model [3] and the Dijkstra path finding algorithm [4] in this paper. The deflection and focused sound field distribution of the ultrasonic phased array in the austenitic butt weld structure are calculated by this method. The phased array sound field characteristics under the Ogilvy weld model are discussed. The effects of grain orientation and weld groove on the focused acoustic field of phased array are analyzed. These work provide theoretical support for the actual use of ultrasonic phased arrays for defect detection of austenitic steel welds. References [1] Liu Q, Wirdelius H 2007 Biochemical & Biophysical Research Communications 40 229 [2] J A. Ogilvy, Computerized ultrasonic ray tracing in austenitic steel. Ndt International, 1985, 18(2): 67-77 [3] Schmerr, Huang, Sedov. The simulation of ultrasonic beams with a Gaussian beam equivalent point source model. Chinese Journal of Acoustics, 2010(2):97- 106. [4] Dijkstra E. A note on two problems in connexion with graphs. Numerische Mathematik 1959, 1:269–271.

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Ultrasonic Nondestructive Testing Ultrasound Beam Engineering via a Programmable Transducer Array Yaxi Shen1, Xuefeng Zhu1, Feiyan Cai2, Teng Ma2, Jie Zhu3, and Hairong Zheng2 1)School of Physics and Innovation Institute, Huazhong University of Science and Technology, Wuhan, China 2)Paul C. Lauterbur Research Center for Biomedical Imaging, Institute of Biomedical and Health Engineering, Shenzhen Institute of Advanced Technology, Chinese Academy of Science, Shenzhen, China 3)Department of Mechanical Engineering, the Hong Kong Polytechnic University, Hong Kong, China

Ultrasound beam engineering is an important field for versatile applications. For example, focused ultrasound is widely used in ultrasound imaging, which also has been adopted in clinics to destroy tumor cells or treat neurological diseases. Nondiffraction bending ultrasound is employed to manipulate microparticles in the application of drug delivery. In this paper, we will investigate two distinct types of ultrasound beam engineering via a programmable transducer array. First, we explore how to eliminate grating lobes of a focused ultrasound beam, which is unavoidable in the projected ultrasound field from a transducer array. In the medical ultrasound therapy, those unavoidable grating lobes may cause harmful physical heating in non- targeted regions. Our results demonstrate that the grating lobes due to the structure diffraction and the inhomogeneous phase delays on the transducer array can be completely eliminated by tailoring the element width and imposing the Gaussian- shaped amplitude modulation. Second, we show a generalized numerical method for designing a bending ultrasound beam with an arbitrarily prescribed trajectory. The theory is based on the principle of geometric sound ray propagation. The designed bending beams can preserve their shapes during the propagation and have amazing self-healing properties when there exist large scattering objects on the curved trajectory. We observed nondiffraction bending ultrasound beams in experiments. References [1] J. W. Goodman, Introduction to Fourier Optics, 2. ed., McGraw Hill Higher Education, New York, 1996, ISBN: 978-0-070-24254-8. [2] Y. Shen, X. Zhu, F. Cai, T. Ma, F. Li, X. Xia, Y. Li, C. Wang, and H. Zheng, Active acoustic metasurface: complete elimination of grating lobes for high- quality ultrasound focusing and controllable steering, Phys. Rev. Appl. 11 (2019), no. 3, 034009. [3] E. Greenfield, M. Segev, W. Walasik, and O. Raz, Accelerating light beams along arbitrary convex trajectories, Phys. Rev. Lett. 106 (2011), no. 21, 213902. [4] P. Zhang, T. Li, J. Zhu, X. Zhu, S. Yang, Y. Wang, X. Yin, and X. Zhang, Generation of acoustic self-bending and bottle beams by phase engineering, Nat. Commun. 5 (2014), 4316.

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Ultrasonic Nondestructive Testing Defect Localization in Fiber Reinforced Polymer Composites with Diffuse Ultrasonic Waves Qi Zhu1, Yuxuan Ding1, Dawei Tu1, Haiyan Zhang2 1)School of Mechatronic & Automation Engineering, Shanghai University, Shanghai 200444, China; 2)School of Communication and Information Engineering, Shanghai University, Shanghai 200444, China

The structures of fiber reinforced composites are designable in multi-scales thanks to the modern manufacturing technologies. Diffuse ultrasonic waves benefit from the multiple scattering and is suitable for the nondestructive testing of such complex structures with high sensitivity [1]. This paper aims to realize and optimize the defect localization in a cross-ply carbon fiber reinforced polymer composite with the diffuse wave field. Experimentally, the wave diffusivity and dissipation parameters are determined from the diffuse waveforms. Great dissipation is found due to the strong viscoelasticity of such plate. The decorrelation coefficients decrease initially due to the wave field-defect interaction and subsequently increase due to the low signal-to-noise ratio. Together with the defect sensitivity kernel calculated under constant diffusion property assumption, the defect can be localized with an error of 7% by four receivers. The sensor placement is restricted due to the low signal-to- noise ratio at off-axis directions. It can be further optimized through numerical simulations [2]. The localization resolution converges after an initial improvement when the number of receivers increases. Localization results fluctuate when the source-receiver pairs are distant from the defect. This method is promising for the early damage detection in various fiber reinforced polymer composite structures. References [1] V. Rossetto, L. Margerin, T. Plaǹs, and É. Larose, Locating a weak change using diffuse waves: Theoretical approach and inversion procedure, J. Appl. Phys. 109 (2011), 034903 [2] F. Xie, E. Larose, L. Moreau, Y. Zhang, and T. Planes, Characterizing extended changes in multiple scattering media using coda wave decorrelation : numerical simulations scattering media, Waves in Random and Complex Media 28 (2018), 1–14.

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Sound-structure Interaction Acoustic Energy Harvesting Based on Phononic Crystals Tianyu Zhang1, Han Zhang23, Xiaoxing Su1 1)Schcool of Civil Engineering, Beijing Jiaotong University, Beijing, China 2)Key Laboratory of Noise and Vibration, Institute of Acoustics, CAS, Beijing, China 3)State Key Laboratory of Acoustics, Institute of Acoustics, CAS, Beijing, China

To obtain renewable and clean forms of energy is to be one of the focus topics of current researches because of the environmental issues caused by industrial productions increasing rapidly nowadays. For example, energy harvesting of sunlight, wind, heat or mechanical vibration is an important aspect for later use. Traditionally, piezoelectric material is always employed due to its capacity of converting acoustic energy to electric energy. However, it is not practical due to the inherent drawback of low power density. We proposed an acoustic energy harvester composed of a piezoelectric structure with square phononic crystals which achieved power harvesting efficiently 625 times larger than that without phononic crystals. Because acoustic energy can be localized before it can be effectively harvested and converted. In addition, acoustic band gaps can be designed to realize acoustic energy harvesting based on the mechanisms of the Bragg scattering and local resonance. The defect structure of PCs is proposed to overcome the mass density law of ordinary PCs which shows the properties of low sound transmission loss and strong strain energy confinement at a low frequency range. Considering the effects of different PCs on energy harvesting, such as the geometry, material and distribution density on the scattering matrix, we compare the simulating results by using COMSOL and the theoretical calculations. The cylindrical scatters show more efficient energy harvesting than that cuboid. The density of material determines energy harvesting efficiency as well, higher density materials should be selected. The output voltage of with the 8×8 phononic crystal at 4kHz is 1.47 times than that with 5×5 phononic crystal at 4 kHz. Finally, the optimal structure is obtained from the series of comparisons above. The defect embedded in phononic crystals can act as a resonant cavity. The stub- plate structure with a defect in center cannot support the propagation of the mechanical wave from side to the plate, thus confining the energy in the defect area. Based on this phenomenon, the piezoelectric material mounted on the defect is able to convert the acoustic energy to electric energy at the resonant frequency of the defect with much more higher efficiency of energy transformation.

Acknowledgements: This work is supported by National Natural Science Foundation of China (Grant NO.11772349).

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Sound-structure Interaction Multilayer Structure Optimization of Pentamode Acoustic Cloaking Based on PSO Algorithm Chao Sun1, Han Zhang2,3, Yang Jun2,3,4 1)Hebei University of Water Resources and Electric Engineering, Cangzhou, China 2)Key Laboratory of Noise and Vibration, Institute of Acoustics, CAS, Beijing, China 3)State Key Laboratory of Acoustics, Institute of Acoustics, CAS, Beijing, China 4)University of Chinese Academy of Sciences, Beijing 100190, China A theory of pentamode acoustic cloaking was developed using the transformation or change-of-variables method for mapping the cloaked region to a point with vanishing scattering strength by Prof. Norris of Rutgers University in 2008. However, it is hard to achieve a pentamode acoustic cloaking with high performance through the complicated design of microstructure. Aimed to solve this problem, multi-layered cloaking is used as piecewise approximation of the continuous attribute distribution of pentamode acoustic materials. In this paper, we mainly analyze acoustic properties of the cloak under the condition of single direction and single frequency incident waves. The density and modulus of each layer of the cloak are calculated by linear mapping in the theory of transformation acoustics. The stealth performance can be quantitatively characterized by scattering cross-sectional area. We propose to employ PSO algorithm to find out the optimal distribution of geometric attributes with the combination of finite element modeling of acoustic field in this paper.PSO algorithm has the advantages of fast search speed, high efficiency and good integration with the problem. The results show that when the target frequency is 5kHz, the scattering cross-sectional area of the optimized structure decreases by36%compared with that of the structure with uniform thickness. Besides the target frequency point, the scattering cross-sectional area of other frequency points is generally lower than that without optimization.By optimizing the material parameter distribution of each layer, even if only a few layers of pentamode materials can achieve better stealth effect. This shows the obvious advantage of anisotropic pentamode materials in acoustic control. This study can guide the design of cell configurations of pentamode materials at different locations and greatly simplify the complexity of the preparation process of pentamode materials. Acknowledgements: This work is supported by National Natural Science Foundation of China (Grant No. 11772349).

Fig1. Flow chart of POS algorithm Fig.2 Comparison of scattering cross sections before and after optimization

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Sound-structure Interaction Vortex Beams Formed with An Annular Acoustic Sources Hongzhen Bi1, Han Zhang2,3, Jun Yang2,3,4, Muguang Wang1 1)Collage of Electronic Information, Beijing Jiaotong University, Beijing, China ; 2)Key Laboratory of Noise and Vibration, Institute of Acoustics, CAS, Beijing, China; 3)State Key Laboratory of Acoustics, Institute of Acoustics, CAS, Beijing, China; 4)University of Chinese Academy of Sciences, Beijing, China

Vortex beam is characterized by its screw wavefront - that is, surface of the constant phase - dislocation. Wave front dislocation is the intrinsic property of the vortex field, which was first studied in acoustics. Recently, acoustic vortex beam propagation starts to be involved in many prospective researches. However, the performance of acoustic vortex beam plays an important role in these jobs. Therefore, it is necessary to make sure how to produce and modulate standard acoustic vortex beams at first. We proposed to set up a model of vortex beams formed with an annular array of acoustic sources in three-dimensional cylindrical coordinates. In the wavefront dislocation of a screw monochromatic, continuous traveling acoustic wave beam, there is a phase dependence on the azimuthal angle  , which can be formed of exp(i) , where the integer  is called topological charge or the order of the screw beam whose sign and value determines the orientation of the spiral and the magnitude of the OAM, respectively. Hence, acoustic vortex beam is emitted by active phase arrays, and pre-multiplex by means of digital signal processing in digital domain to obtain a series of excitation signals driving the corresponding array elements. Acoustic vortex fields with topological charge from -3 to +3 driven by a 20-elements circular array are formed as the following pictures. We gave out the production, propagation and modulation of acoustic vortex beams with an annular array of acoustic sources in three-dimensional cylindrical coordinates. It will support the future researches of acoustic vortex beams.

Fig 1. Acoustic vortex fields with topological charge from -3 to +3 driven by a 20-elements circular array

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Sound-structure Interaction Acoustic Vortex Beam Generation by a Piezoelectric Transducer Using Spiral Electrodes Han Zhang1,2, Hongzhen Bi3, Tianyu Zhang4 1)Key Laboratory of Noise and Vibration, Institute of Acoustics, CAS, Beijing, China 2)State Key Laboratory of Acoustics, Institute of Acoustics, CAS, Beijing, China 3)Collage of Electronic Information, Beijing Jiaotong University, Beijing, China 4)Schcool of Civil Engineering, Beijing Jiaotong University, Beijing, China

Acoustic vortex beams with spiral phase dislocations have attracted great attention in recent years due to the energy and phase distributions make them show great potential for applications. Non-contact transfer of the angular momentum enables acoustic vortex beams to be used as acoustic wrenches. Acoustic power presents a circular distribution enables them to be used as acoustic tweezers. And the multi-order in the topological dimension indicates a great potential of channel multiplexing in acoustic communication. However, the generation of acoustic vortex beams is involved with the complexity of the overall circuit of the system substantially causing difficulty in integration and bringing high costs. In this paper, we employed an interdigital transducer array coated with paired spiral electrodes to obtain the acoustic vortex beans with high power. A focused acoustic vortex beam can be generated by applying its beam synthesis principle. With the design of the electrode, the phases of the beams are controlled. Commercial simulating software COMSOL Multiphysics is utilized to calculate and analyze he acoustic field excitation characteristics of the active acoustical vortex beam generation transducer. The results show that this method has the advantages of higher acoustic power, simpler operation and lower cost compared with the traditional approaches based on passive and active method. Therefore, this kind of structure makes the compactness, integration and flexibility of the active vortex beam generation transducer greatly improved. And it provides a theoretical basis for promoting the practical application of acoustic vortex beams in acoustic communication and manipulation of particles, microorganisms, and cells in the future.

Acknowledgements: This work is supported by National Natural Science Foundation of China (Grant NO.11772349).

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Sound-structure Interaction Numerical Simulation and Analysis of Flow Field and Sound Field of Hydraulic Vortex Whistle Xiaopin Wang, Yu Liu, Mingduo Zhang, Anqian Tan Shaanxi Key Laboratory of Ultrasonics, College of Physics and Information Technology, Shaanxi Normal University, Xi’an , China

The vortex whistle is a fluid-powered generator, and both gas and liquid can be used as power source[1-2]. In this paper, using the water as the power source, to simulate and analyze the flow field and the sound field of the vortex whistle based on the Fluent software. Firstly, a realizable model is selected to obtain a steady flow field. Secondly, the sound field is obtained by combining the large eddy simulation with the sound analogy model `on the basis of the steady state results when the driving water pressure increases. In order to analyze the contribution of different sound sources to the total sound radiation of the vortex whistle, three intergral source surfaces will be taken: the wall of vortex whistle (dipole sound source), a truncated cone-shaped in an outflow field (quadrupole source) and the combination surface of the above two intergral source surfaces. The acoustic radiation characteristics of a vortex whistle are analyzed by power spectral density. The results show that under the same water pressure, the power spectral density of sound signal is obtained based on three different sound source models. The value of sound power density corresponding to the peak of the integrated source surface is the largest, the dipole source is second and close to it, the quadrupole source is the smallest. This result is consistent with the steady-state analysis. In other words, the sound of the vortex whistle is mainly concentrated in the whistle. At the same time, when the water pressure increased from 0.3 MPa to 0.7 MPa at an interval of 0.1 MPa, the turbulent kinetic energy, velocity, sound pressure level and sound power on the axis of voetex whistle increase accordingly. The values of physical quantity are lower than when the power source is air, because the density and viscosity coefficient of water are larger than that of air, which is in line with the actual situation. References [1] Robert C. Chanaud, Experiments concerning the vortex whistle[J]. The Journal of the Acoustical Society of America, 1963, 35(7): 953-960. [2] Irving Michelson, Theory of Vortex Whistle[J]. The journal of the acoustical society of America, 1995, 27(5): 930-931.

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Sound-structure Interaction A Benchmark Study on Fluid-loaded Structural Modes Martin Eser1, Stefan Schneider2, Suhaib Koji Baydoun1, Felix Kronowetter1, Steffen Marburg1 1)Department of Mechanical Engineering, Technical University of Munich, Garching, Germany 2)Knorr-Bremse AG, Munich, Germany The consideration of fluid-structure-interaction (FSI) is of significant importance for the vibration behavior of thin-walled elastic structures submerged in heavy fluids. In some engineering applications, these structures are modeled to radiate sound into an exterior acoustic domain of infinite extent which is modeled by a compressible, inviscid fluid. The structure as well as the fluid are assumed to follow linear and time-harmonic behavior and hence can be described by the Helmholtz equation. Such exterior acoustic problems can be numerically treated with different discretization methods. The discretization with the finite element method (FEM) requires an artificial truncation of the acoustic domain along with a special treatment of the truncated infinite domain using e.g. so-called infinite elements (IFEM) in order to model the sound pressure decay in the far-field. The boundary element method (BEM) is a popular alternative to FEM for the numerical modeling of exterior acoustics since the discretization is restricted to the sound radiating surface of the structure. The far-field radiation condition is implicitly satisfied in the BEM formulation [1]. In the past years, research on numerical analysis of exterior acoustic FSI problems has been carried out considering either BEM, IFEM or alternative approaches independently. In this work, the authors therefore present a comparison between the two former numerical methods with respect to their applicability to the modal analysis of exterior acoustic FSI problems. The scope of this work is the comparison of the modal analysis of a spherical steel shell submerged in water using a coupled FEM-BEM approach on the one hand and a coupled FEM-IFEM approach on the other hand. The structural domain is modeled identically with shell finite elements in both approaches. The collocation discretization is applied in the FEM-BEM approach, while conjugated Astley-Leis elements are used in the complementary, infinite domain of the FEM-IFEM approach. The fluid-loaded structural modes and their corresponding eigenfrequencies from both approaches are verified with respect to the analytical solution [2]. The FEM- BEM and the FEM- IFEM approaches are compared to each other with respect to accuracy, convergence behavior and computational time. References [1] S. Marburg, B. Nolte, Computational acoustics of noise propagation in fluids- finite and boundary element methods, 1. ed., Springer, Berlin, 2008, ISBN: 978- 3-540-77447-1. [2] M. C. Junger, D. Feit, Sound, structures, and their interaction, 2. ed., MIT Press, Cambridge, Massachusetts, London, England, 1986, ISBN: 0-262-10034-7. 247

Sound-structure Interaction Energy Transmission Analysis of A Water-Filled Pipe Baffled with A Finite Elastic Plate Yajun Li1,2,Hongling Sun1,Luyang Sun1,Jun Yang1,2 1)Key Laboratory of Noise and Vibration Research, Institute of Acoustics, Chinese Academy of Sciences, Beijing, China 2)University of Chinese Academy of Sciences, Beijing, China

Research on the vibroacoustic characteristics of a water filled pipe baffled with a finite elastic plate is considered to be important in various applications, especially in the field of aerospace and ship engineering. Previous study focused on the vibration and sound radiation characteristics of the relatively complex system (a water filled pipe baffled with a finite elastic plate), while the energy transmission of this system is hardly analyzed. In this work, we concentrate on analyzing how the energy flow transmits between the structure and the fluid. Firstly, the sound energy flow through a pipe and a plate simultaneously is carried out using the finite element method; then the dynamic characteristics of this coupled system is analyzed under different initial conditions; finally, other results are also derived by using different system parameters, which includes aspect ratio, density ratio, thickness of the pipe and the plate, etc., to illustrate the coupling phenomena between the pipe and the plate in the structural and the acoustic filed. This work helps to give some physical insights into the coupled system and offers an idea for the active control by using the energy transmission method. References [1] C.R.FULLER, The effects of wall discontinuities on the propagation of flexural waves in cylindrical shells. Journal of Sound and Vibration 75(1981), 207-228. [2] L.CHENG and J.NICOLAS. Free vibration analysis of a cylindrical shell- circular system with general coupling and various boundary conditions. Journal of Sound and Vibration, 155 (1992), 231-247. [3] Bilong Liu, Jie Pan, Xiaodong Li and Jing Tian, Sound radiation from a water- filled pipe radiation into light fluid, Journal of Sound and Vibration 112 (2002), 2814-2824. [4] H.S.Kim, H.J.Kang and J.S.Kim, A vibration analysis of plates at high frequencies by the power flow method. Journal of Sound and Vibration 174 (1994), 493-504.

248

Sound-structure Interaction Vibro-acoustic Analysis of a Rectangular Enclosure Bounded by a Ribbed Flexible Wall Yuan Wang, Nai-Fei Ren, Zheng-Wei Qiu School of Mechanical Engineering, Jiangsu University, Zhenjiang, China

The coupled model between rectangular cavity and its ribbed clamped flexible wall is developed using modal coupling theory and vibro-acoustic coupling methods. Meanwhile, the coupling coefficient and coupling strength between ribbed panel and rectangular enclosure modes are proposed. Based on the coupled model, the effect of location and stiffness of rib on the response of coupled system is analyzed and compared with the case of unribbed one. It is found that the influence of rib location and bending stiffness on the response of coupled system is large. However, the effect of twisting stiffness of rib on the response of coupled system can be neglected. References [1] XIN F X, LU T J, Sound radiation of parallelly stiffened plates under convected harmonic pressure excitation, SCIENCE CHINA Technological Sciences, 2012, 55(2), no. 496-500. [2] KESSISSOGLOU N J, An analytical and experimental investigation on active control of the flexural wave transmission in a simply supported ribbed plate, Journal of Sound and Vibration, 2001, 240(1) , no. 73-85. [3] DOZIO L, RICCIARDI M, Free vibration analysis of ribbed plates by a combined analytical-numerical method, Journal of Sound and Vibration, 2009, 319, no. 681-697. [4] LIN T R, PAN J, A closed form solution for the dynamic response of finite ribbed plates, The Journal of the Acoustical Society of America, 2006,119(2) , no. 917-925. [5] LIN T R, An analytical and experimental study of the vibration response of a clamped ribbed plate, Journal of Sound and Vibration, 2012, 331, no. 902-913. [6] LIN T R, A study of modal characteristics and the control mechanism of finite periodic and irregular ribbed plates, The Journal of the Acoustical Society of America, 2008,123(2) , no. 729-737.

249

Authors Index

Aage, Niels ...... 168 Chiu, Linus ...... 145, 211 Agerkvist, Finn Thomas ...... 200 Chu, Wei-Yen ...... 106 Akamatsu, Tomonari ...... 39 Chu, Zhigang ...... 126 An, Bu-chao ...... 202, 203 Croaker, Paul ...... 176 Andersen, Peter Risby ...... 168 Cui, Hanyin ...... 233 Ba, Jing ...... 155, 159, 161, 162, 165, 214 Cui, Zhiwen ...... 231 Bai, Jin ...... 94 Dai, Tengfei ...... 64 Baydoun, Suhaib Koji ...... 247 Dai, Yu-xiang ...... 69 Ben, Jianlin ...... 154 Dai, Zhiqiang ...... 199 Benezeth, Yannick ...... 55 Deng, Fangqing ...... 51, 67, 153 Bi, Hongzhen ...... 244, 245 Deng, Mingxi ...... 110, 111 Bilal, Muhammad ...... 60 Ding, Yuxuan ...... 241 Cai, Feiyan ...... 240 Djellouli, Rabia ...... 68 Cai, Wei ...... 71 Dong, Lijun ...... 104 Cao, Cheng-Hao ...... 214 Dong, Xingmeng ...... 51, 67, 153 Cao, Huaigang ...... 98 Du, Bingyi ...... 152 Cao, Huan ...... 196 Du, Shuyuan ...... 215, 216 Cao, Jingpu ...... 216 Duan, Hang ...... 50 Chai, Xiaodong ...... 232 Duan, Yunda ...... 76 Chang, Andrea ...... 145, 211 Eser, Martin ...... 247 Chao, Yun-Feng ...... 77, 78, 79 Fan, Guopeng ...... 232, 236 Che, Xiaohua ...... 154, 160, 166 Fan, Shi...... 128 Chen, Bingyao ...... 110 Fan, Shuyao ...... 116,117 Chen, Chi-Fang ...... 89, 103, 105, 106, 145 Fan, Zhenxiang ...... 181 Chen, Daoyu ...... 43, 190 Fang, Xinding ...... 158 Chen, Haibo ..... 167, 169, 170, 172, 173, 175 Fang, Yin-Ying ...... 103 Chen, Hao ...... 75, 80, 81, 82, 83 Fang, Zheng ...... 205 Chen, Hongling ...... 43, 186 Fehler, Michael ...... 151 Chen, Jianyou ...... 48 Feng, Feng ...... 62 Chen, Jiayi ...... 112 Feng, Yixuan...... 57 Chen, Leilei ...... 167, 169, 172, 173 Figueroa, Antonio ...... 127 Chen, Lianrong ...... 96 Fournier, Aimé ...... 151 Chen, Lingguang ...... 127 Fu, Jia ...... 231 Chen, Tian ...... 91 Fu, Li-Yun ...... 158, 214 Chen, Tiansheng ...... 155 Fu, Rui ...... 153 Chen, Wenchao ...... 48 Fu, Zhuo-jia ...... 180 Chen, Xi ...... 56 Gabard, Gwénaël ...... 45 Chen, Xingjie ...... 108 Gao, Dazhi ...... 138 Chen, Yan ...... 57 Gao, Jiahui ...... 221, 224 Chen, Yang ...... 59 Gao, Jianzheng ...... 124 Chen, Yanli ...... 96 Gao, Jinghuai ...... 43, 183, Chen, Yi ...... 229, 237 184, 185, 186, 187, 188, 189, 190, 193, 194 Chen, Yuchen ...... 137 Gao, Wei ...... 138 Cheng, Arthur ...... 157 Gao, Yongxin ...... 73 Cheng, Chen ...... 135 Gao, Zhaoqi ...... 43, 184, 188 Cheng, Guangli ...... 218 Ge, He...... 143 Cheng, Li ...... 114 Geng, Xuan ...... 58 Chiu, Ching-Sang ...... 145, 211 Gerstoft, Peter ...... 140

250

Authors Index Gong, Changchao ...... 63 Jih, Richard ...... 89 Gong, Zaixiao ...... 140 Jin, Xia ...... 64 Gu, Bingluo ...... 49 Jing, Yan ...... 222 Gu, Yuantong ...... 64 Joly, Patrick ...... 65 Guan, Wei ...... 76 Ju, Xiaodong ...... 154, 166 Guerbuez, Caglar ...... 177 Katsnelson, Boris...... 131 Guo, Junxin ...... 158 Kessissoglou, Nicole ...... 176 Guo, Lianghao ...... 99 Kong, Qian ...... 121 Guo, Qiang...... 155, 162 Kronowetter, Felix ...... 61, 247 Guo, Shengming ...... Kundu, Tribikram ...... 231 ...... 95, 98, 132, 134, 142, 146, 213 Lan, Xuekai ...... 201 Guo, Xinyi ...... 101, 102 Lan, Zifeng ...... 111 Guo, Zhongcun ...... 239 Lange, Sebastian ...... 74 Guo, Zhongyuan ...... 54 Lei, Bo ...... 135 Han, Tongcheng ...... 158, 214, 163 Lei, Shuang ...... 201 He, Pei ...... 152 Li, Yunyue Elita ...... 157 He, Runfa ...... 161 Li, Chao ...... 55 He, Shitang ...... 115 Li, Chao ...... 83 He, WeiWei ...... 152 Li, Chuang ...... 194 He, Xiao ...... 81, 82, 83 Li, Fan ...... 134 Henriquez, Vicente Cutanda .... 168, 174, 200 Li, Fan ...... 159 Hong, Li ...... 115 Li, Fenghua ...... 148 Hou, Qiannan ...... 227, 228 Li, Guihua ...... 181, 198 Hu, Ding-Yu...... 119, 120 Li, Gui-juan ...... 94 Hu, Hengshan ...... 76 Li, Guonan ...... 207, 208 Hu, Ping, ...... 130 Li, He ...... 102 Hu, Tao ...... 97, 132, 134 Li, Hui ...... 187 Hu, Wei-Chun ...... 103 Li, Jiapu ...... 201 Hu, Yangming ...... 84, 85, 86 Li, Na ...... 150 Hu, Zhi ...... 185 Li, Peng ...... 225 Huang, Jianchun ...... 54 Li, Qianqian ...... 223 Huang, Jiaqiang ...... 152 Li, S. M...... 195 Huang, Juan ...... 69 Li, Songhai ...... 104 Huang, Yongjun ...... 229 Li, Weibin ...... 110, 111 Huthewaite, Peter ...... 128 Li, Wen ...... 148 Imperia, Sébastien ...... 65 Li, Xiaolei ...... 138 Iqbal, Kashif ...... 143 Li, Xiukun ...... 221 Jelich, Christopher ...... 171 Li, Xueling ...... 116, 117 Jensen, Jakob Søndergaard ...... 200 Li, Yajun ...... 248 Ji, Fang ...... 207, 208 Li, Yan ...... 54 Ji, Yunjia ...... 81 Li, Zhenchun ...... 49 Jia, Jiuhong ...... 235 Li, Zhenglin ...... 133, 140, 147 Jia, Lian-hui ...... 94 Li, Zhi ...... 84, 86, 87 Jia, Lu ...... 109 Li, Zhongxiao ...... 49 Jia, Ning ...... 54 Liang, Minshuai ...... 219 Jia, Ya-na ...... 118 Lin, Gaoxiang ...... 108 Jia, Yuqing ...... 95 Lin, Jianheng ...... 150 Jiang, Fuhan ...... 172 Lin, Mingli ...... 104 Jiang, Genshan ...... 121 Lin, Tianran ...... 64 Jiang, Lijun ...... 93 Lin, Weijun ...... 233 Jiang, Pengfei...... 150 Ling, Wenchang ...... 162 Jiang, Ren ...... 152 Liu, Biao ...... 54 Jiang, Tao ...... 77, 78, 79 Liu, Chenglin ...... 152 Jiang, Weikang ...... 122, 124 Liu, Daipei ...... 176 251

Authors Index Liu, Guangda ...... 79 Ni, Haiyan ...... 212 Liu, Jia ...... 90, 93 Nielsen, Daniel Gert ...... 200 Liu, Jiangtao ...... 207, 208 Ning, Fangli ...... 125 Liu, Jianquan ...... 236 Niu, Chen ...... 209 Liu, Jianshe ...... 222 Niu, Haiqiang ...... 140 Liu, Jin ...... 148 Oliveira, S. P...... 70 Liu, Jiuling ...... 115 Ouyang, Fang ...... 84, 85, 86, 87 Liu, Lin ...... 164 Ozanich, Emma ...... 140 Liu, Mingming ...... 104 Pan, Feng ...... 125 Liu, Naihao ...... 193 Pan, Yue ...... 82 Liu, Qing Huo ...... 72 Pan, Zhibin ...... 188 Liu, Songzuo ...... 60 Pei, Ming ...... 59 Liu, Tianyang ...... 235 Peng, Dayong ...... 92 Liu, Tuo ...... 114 Peng, Linhui ...... 219 Liu, Wen-Yang ...... 89 Peng, Zhaohui ...... 130 Liu, Xiaozhou ...... 47 Peplow, Andrew...... 123 Liu, Xiujuan ...... 179 Piao, Shengchun ...... 91, 143 Liu, Xuecheng ...... 235 Pine, Matthew K...... 100 Liu, Yanyan ...... 230 Qi, Hui ...... 165 Liu, Yi-hao ...... 202, 203 Qi, Li-Bo ...... 204 Liu, Yong-wei ...... 209 Qi, Qiaomu ...... 157 Liu, Yu ...... 246 Qi, Yubo ...... 215, 216 Liu, Yuechao ...... 121 Qiao, Gang ...... 60 Liu, Yujian ...... 178 Qiao, Wenxiao ...... 154. 160, 166 Liu, Zhe ...... 206 Qin, Ji-xing ...... 147 Lou, Jiann-Yuh...... 211 Qin, Qi ...... 205 Lu, C...... 169, 173 Qiu, Weirong ...... 182 Lu, Junqiang ...... 154 Qiu, Zheng-Wei ...... 249 Lu, Licheng ...... 142, 146, 213 Qu, Ke ...... 136 Lu, Yanyang ...... 144 Quan, Hongjuan...... 197 Luo, Cong ...... 161, 165 Ren, Junyu ...... 156 Luo, Xiayun ...... 218 Ren, Nai-Fei ...... 249 Lyu, Wenhan ...... 112 Ren, Qunyan ...... 97, 146, 212 Ma, Dingyi ...... 221, 224 Ren, Suiling ...... 96 Ma, Jianwei ...... 52, 53 Ren, Yun ...... 131, 133 Ma, Jun ...... 137 Rodríguez, Jerónimo ...... 65 Ma, Li ...... 57, 92, Rouseff, Daniel ...... 38 95, 97, 98, 101, 102, 132, 142, 146, 210, 212 Schneider, Stefan ...... 247 Ma, Ming yang ...... 90 Sepahvand, Kheirollah ...... 61, 206 Ma, Rupeng ...... 161, 165 Seriani, Géza ...... 41 Ma, Shiwei ...... 230 Shan, Yuanchun ...... 150 Ma, Teng ...... 240 Shang, Dajing ...... 229 Ma, Yuanliang ...... 135 Shang, De-jiang ...... 202, 209 Maeder, Marcus ...... 123 Shang, Er-Chang ...... 210, 225, 227 Marburg, Steffen ...... Shang,De-jiang ...... 203 ... 61, 123, 169, 170, 171, 176, 177, 206, 247 Shen, Rushan ...... 233 Martínez, Jorge Albella ...... 65 Shen, Yaxi ...... 240 Men, Baiyong ...... 154 Sheng, Meiping ...... 205, 207, 208 Meng, Delin ...... 182 Sheng, Xueli ...... 220 Meng, Luwen ...... 218 Shi, Juan ...... 223 Meng, Xiangzhen ...... 234, 238 Shih, Chiu-Kuan ...... 103 Ming, Pingshou ...... 223 Shui, Guo-Shuang ...... 66 Mo, Yaxiao ...... 213 Siddagangaiah, Shashidhara ...... 105 Moheit, Lennart ...... 61 Song, Guoli ...... 102 252

Authors Index Song, Wenhua ...... 138, 139, 141 Wang, Yang ...... 135 Song, Zelin...... 222 Wang, Yi-Ze ...... 66 Su, Lin ...... 95, 97 Wang, Yuan ...... 249 Su, Xiaoxing ...... 242 Wang, Yue-Sheng ...... 66 Sui, Yuhan ...... 53 Wang, Zhen ...... 132 Sun, Bingwen...... 213 Wang, Zhiguo ...... 183 Sun, Chao ...... 243 Wei, Liping ...... 57 Sun, Hongling ...... 248 Wei, Yintao ...... 206 Sun, Jianhao ...... 121 Wen, Chih-yung ...... 114 Sun, Junping ...... 150 Weng, Jing ...... 126 Sun, Langqiu ...... 84, 85, 86 Wimmer, Georg ...... 74 Sun, Luyang ...... 248 Wu, Bangyu ...... 182 Sun, Yuefeng ...... 88, 197 Wu, Haijun ...... 122, 124 Sun, Zhifeng ...... 81 Wu, Hao ...... 193 Tai, YuPeng ...... 56 Wu, J. T...... 192, 195 Tan, Anqian ...... 246 Wu, Jinrong ...... 212, 225, 226, 227, 228 Tao, Guo ...... 151 Wu, Sean F...... 127 Telenko, Michael Jr...... 127 Wu, Shuang-lin ...... 147 Teng, Yu-Chiung ...... 181 Wu, X. H...... 195 Tian, Yajun ...... 189 Wu, Xianmei...... 112 Tian, Zhangfu ...... 63 Wu, Yinting ...... 191 Tu, Dawei ...... 241 Wu, Zhenyun ...... 172 Tu, Shandong ...... 235 Xi, Qiang ...... 180 Tu, Yun...... 235 Xia, Hui ...... 153 Wang, Debao...... 48 Xiao, Dong ...... 57 Wang, Ding ...... 100 Xiao, Shuang ...... 155 Wang, Dong ...... 96 Xiao, Zengjia ...... 84, 86, 87 Wang, Dongdong ...... 73 Xie, Zhinan ...... 221, 224 Wang, Haibin ...... 55, 56 Xu, Denghui ...... 158, 163 Wang, Haozhong ...... 138 Xu, Feng ...... 90, 91, 93, 107 Wang, Hua ...... 151 Xu, Hongbin ...... 108 Wang, Jian ...... 75 Xu, Liang ...... 217 Wang, Jie ...... 167 Xu, Peng ...... 48 Wang, Jingqi ...... 198 Xu, Peng ...... 99 Wang, Jingye...... 77, 78, 79 Xu, Weijiang ...... 112 Wang, Jun ...... 56 Xu, Wen ...... 129, 149 Wang, Kexiong ...... 100 Xu, Yun ...... 198 Wang, Lingling ...... 182 Xu, Zongben ...... 188 Wang, Meng-yuan ...... 147 Xu, Zongben ...... 43 Wang, Muguang ...... 244 Yan, Chao ...... 99 Wang, Pengyu ...... 139, 141 Yan, Lu ...... 91 Wang, Qiang ...... 62 Yan, Shouguo ...... 69, 109, 239 Wang, Shiquan ...... 237 Yang, Da-Peng ...... 77 Wang, Tao ...... 119 Yang, Fan ...... 55 Wang, Tongchen ...... 129 Yang, Fanlin ...... 223 Wang, Weiyin ...... 237 Yang, Huaze ...... 64 Wang, Wen ...... 116, 117, 118 Yang, Jun ...... 243, 244, 248 Wang, Wenbo ...... 97, 212 Yang, Jun Ou ...... 201 Wang, Xianhui ...... 178 Yang, Kunde ...... 144 Wang, Xiaojing ...... 52 Yang, Liuqing ...... 229, 237 Wang, Xiaopin ...... 246 Yang, Shubo ...... 166 Wang, Xin ...... 78, 79 Yang, T.C...... 129, 149 Wang, Xiu-Ming ...... 83, 164 Yang, Tao ...... 184 Wang, Xue ...... 156 Yang, Xiaofei ...... 201 253

Authors Index Yang, Yan ...... 186 Zhang, Minghui ...... 136, 143 Yang, Yang ...... 126 Zhang, Mingmin ...... 218 Yang, Zhiqiang...... 51, 67 Zhang, QiaoHua ...... 107 Yao, Meijuan ...... 142 Zhang, Qing-qing ...... 133 Yi, Xiaofeng...... 92 Zhang, Tianyu ...... 242, 245 Yi, Xuejuan ...... 150 Zhang, Weiyu ...... 99 Yin, Jingwei ...... 221, 222, 224 Zhang, Xiaoming ...... 178 Yin, Lijun ...... 227, 228 Zhang, Xiu-mei ...... 164 Yin, Shenxin ...... 231 Zhang, Yang ...... 94 Yin, Yi-ning ...... 118 Zhang, YongLin ...... 56 Ying, Liu ...... 135 Zhang, Yujie ...... 234, 238 Yu, Cun ...... 159 Zhang, Yuxiang...... 221, 224 Yu, Gaokun ...... 219 Zhao, Fan ...... 205 Yu, Liang ...... 122 Zhao, Jianguo ...... 84, 85, 86, 87 Yu, Xuan ...... 58 Zhao, Min ...... 57 Yuan, Jun ...... 218 Zhao, Rui ...... 114 Zeng, Fu-Qiang ...... 83 Zhao, Shuhong ...... 196 Zeng, Juan ...... 92, 210 Zhao, Wenchang ...... 167, 169, 170, 172, 173 Zeng, Xinwu ...... 63 Zhao, Yue ...... 93 Zhai, Yuwen ...... 51, 67, 153 Zhao, Yun ...... 63 Zhan, Qiwei ...... 72 Zhao, Zhendong...... 98, 210, 225 Zhan, Tingting ...... 80 Zheng, Changjun ...... 167, 175 Zhang, Bing ...... 183, 184 Zheng, Fan ...... 78 Zhang, Bixing ...... 69, 109, 239 Zheng, Hairong ...... 240 Zhang, Bo ...... 148 Zheng, Jing-Han ...... 77 Zhang, Bo ...... 193 Zheng, Wei ...... 156 Zhang, Chao...... 202, 203 Zhou, Jian ...... 159 Zhang, Chaojin ...... 213, 227 Zhou, Menglin ...... 59 Zhang, Chengwei ...... 160 Zhou, Qi ...... 77, 78 Zhang, Chun ...... 107 Zhou, Shihong ...... 215, 216 Zhang, Guangbin ...... 199 Zhou, Xiang ...... 66 Zhang, Haigang ...... 137, 217 Zhu, Benpeng ...... 201 Zhang, Haiyan . 230, 232, 234, 236, 238, 241 Zhu, Fengqin ...... 136 Zhang, Han ...... 242, 243, 244, 245 Zhu, Guangming ...... 191, 197 Zhang, Hanfei ...... 230 Zhu, Guangping ...... 222 Zhang, Huadong ...... 207, 208 Zhu, Jie ...... 114, 240 Zhang, Hui ...... 113, 232,234, 236, 238 Zhu, Ming ...... 156 Zhang, Jianlan ...... 226 Zhu, Peimin ...... 50, 71 Zhang, Jing ...... 152 Zhu, Qi ...... 241 Zhang, Kai ...... 149 Zhu, Wenfa ...... 108, 120, 232, 234, 236, 238 Zhang, Kai ...... 223 Zhu, Xuefeng ...... 240 Zhang, Lei ...... 75 Zhu, Yanping ...... 59 Zhang, Man-Ying ...... 119, 120 Zhuang, Mingwei ...... 72 Zhang, Mingduo ...... 246 Zou, Ming-Song ...... 204

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