DOCSLIB.ORG

Cross Sea Detection Based on Synthetic Aperture Radar (Sar) Data and Numerical Wave Model (Wam)

Total Page：16

File Type：pdf, Size：1020Kb

Download full-text PDF Read full-text
Cross Sea Detection Based on Synthetic Aperture Radar (Sar) Data and Numerical Wave Model (Wam) CROSS SEA DETECTION BASED ON SYNTHETIC APERTURE RADAR (SAR) DATA AND NUMERICAL WAVE MODEL (WAM) Xiao-Ming LI(1)(2), Susanne Lehner(1) , Ming-Xia HE(2) Johannes Schulz-Stellenfleth(1) (1)German Aerospace Centre (DLR), Oberpfaffenhofen, 82234 Wessling, Germany, Email: [email protected] (2)Ocean Remote Sensing Institute, Ocean University of China, Qingdao, 266003, China ABSTRACT that is characterized by a wind sea and one or more swell systems is called a mixed sea or confused sea. If The present paper is about the detection of cross seas their directions differ, the sea state is called a cross based on ERS-2/SAR wave mode data and comparison sea. A cross sea case which occurred in the South-East to WAM model. A case of cross seas observed by Pacific was captured clearly by consecutive ERS-2 ERS-2/SAR was analyzed for its generation and SAR wave mode images acquired on August 10, 2000 development by wave mode data together with the at 17:30 UTC. One of the consecutive imagettes is WAM model two-dimensional (2-D) spectra. The sea shown in Fig. 1. The case is studied using 2-D spectra, surface elevation is estimated from these wave mode including the WAM model [2] spectra, cross spectra of data with cross sea features using a CMOD type tilt SAR complex data [3] and the non-linear retrieved algorithm. An effective method to remove the speckle PARSA spectra [4]. By a simple travel kinematic noise from SAR wave mode images is introduced, too, model, generation and development of cross seas is in order to get better results of sea surface elevation. demonstrated. 1. Introduction It is well known that Synthetic Aperture Radar (SAR) provides directional ocean wave and surface wind information on a continuous and global scale [1]. Due to the high resolution of SAR data, it is possible to analyze the structure of the ocean wave field, such as wave groups and individual wave behavior. In the framework of the project WAVEALTAS, ESA provided a two-year’s ERS-2/SAR wave mode raw data set, which was reprocessed to single-look- Figure 1. ERS-2/SAR wave mode data imaging a cross complex SAR images at DLR using the BSAR sea, acquired on August 10, 2000 at 17:30 UTC processor [1]. The processed data set contains Traditionally, SAR ocean wave measurements are typically between 1300 and 1500 images of 10km by carried out in the spectral domain to estimate the two- 5km size daily. dimensional spectrum. One approach is realized in the 1.1 SAR ocean wave spectra algorithm MPI (Max-Planck Institute) scheme [5]. Later by Two types of ocean waves usually characterize the sea making using of the SAR complex image, the cross surface, namely wind sea and swell. The first refers to spectra method was derived to retrieve ocean wave waves influenced by the local wind, the latter to waves propagation directions without ambiguity [3]. This is that have propagated out of the generating area and are the standard algorithm for ASAR wave mode data [6]. thus no longer affected by the local wind. A sea state However, all these applications do not make use of full _____________________________________________________ Proc. ‘Envisat Symposium 2007’, Montreux, Switzerland 23–27 April 2007 (ESA SP-636, July 2007) information on the two-dimensional sea surface 2. Data Set Description elevation field provided by SAR. For this study ERS-2 SAR images and ERA-40 model 1.2 Sea Surface Elevation data are used. Sea surface elevation is estimated from SAR wave 2.1 ERS-2 SAR wave mode data mode imagettes, e.g. as done by the LISE algorithm ERS SAR wave mode data is acquired over the ocean developed by DLR [7]. The objective of this paper is every 200 km along the satellite track with the to introduce a technique to estimate the sea surface coverage of 5km x 10km, when image mode data is elevation field from SAR wave mode by a CMOD not requested. type tilt algorithm ([email protected]). It is A two-year wave mode dataset from ERS-2 SAR well known that the geophysical model function acquired during 1999 and 2000, which has been CMOD describes the relationship between wind speed, reprocessed to single-look-complex data at DLR [1]. wind direction, antenna look direction and incidence 2.2 Model data angle [8]. The incidence angle chosen for SAR wave mode images is set around 23◦. This does not take After the success of ERA-15, European Centre for account into the tilt caused by the sea surface Medium-Range Weather Forecasts (ECMWF) is elevation. Although in steep wave situations, the performing their second reanalysis called ERA-40 [10], which covers 45 years, from 1957 until 2002. change of tilt is significant. Given the wind speed U10 and wind direction and by using CMOD, thus the tilt Starting 1991, wave height data obtained from the angle of the individual ocean wave is estimated. This altimeters on board of ERS-1 and ERS-2 are is the main idea of the approach introduced in the assimilated into ERA-40 wave data. paper. The Numerical wave model used for the research is 1.3 Speckle noise removing in SAR images the well-known WAM [2]. It is the so called the third generation model (cycle 4), in which the wave SAR images are generated by coherent processing of spectrum is computed by integration of the energy the scattered signals and they are highly susceptible to balance equation. The model resolution is chosen as 1◦ specking effects [9]. The presence of speckle in SAR by 1◦ and forced by the ERA-40 high resolution wind image reduces the ability of information extraction, field (1◦ by 1◦). especially when the ratio of signal to noise is low over the ocean. It is observed that the energy due to the 3. Observation of Cross Seas imaged ocean wave field is concentrated in narrow angular sectors of the image spectrum. Thus it is The case of cross seas imaged by SAR occurred in the possible to choose a proper threshold to remove the southeastern Pacific on Aug.10, 2000. An impressive speckle noise in the image by a Fourier Fast pattern of crossing ocean wave systems is observed on Transform (FFT) type of filter. at least 8 consecutive images, i.e. on a distance of more than 1000 km. The most distinct peaks can be The paper is structured as follows: in section 2, the observed on the image which is situated at 23.06S and data set used in this research is introduced. Section 3 is 111.6W degrees as shown in Fig. 1. Three consecutive about the generation and development of the cross seas imagettes through the cross sea area are shown in Fig. case. The technique of removing speckle noise and 2. The hindcast WAM model spectra (upper row), estimation of sea surface elevation on SAR wave observed cross spectra (middle row with wave mode data is introduced in the fourth section. traveling direction ambiguity removed by using the imaginary part of the cross spectrum) and retrieved PARSA spectra (lower row) are shown as well. It is clear from these contour plots that the cross sea As expected the PARSA inversion algorithm turns the contains two distinct swell systems travelling to peak of swell Sne towards the azimuth direction. In a northeast and northwest. These are denoted as Sne and next step the dissipation scheme of the WAM model Snw hereby respectively. The two swell systems are will be compared to the inverted SAR spectra. most dominant in the last imagette, which is shown in Fig. 2. The PARSA retrieved Sne swell system peak 4. Estimation of Sea Surface Elevation wave length is about 400m, which agrees well with the 4.1 Technique of speckle noise removing observed cross spectral peak, but the WAM model Radar signals returned from the scatterers within the hindcast result shows only about 300m. SAR resolution cell are added up coherently during the Gonzalez et al., [11] introduced a simple kinematical process, which makes images susceptible to speckle. wave model which has shown that swell generally Basically the speckle is signal-dependent and acts like obeys linear wave theory of propagation and does not multiplicative noise. Therefore, in the SAR image seem to be affected by propagating through zones of analysis, the multiplicative noise model is used [12]. steady wind. With the simple kinematical model and Iσ = I *S (1) swell group speed calculated from the WAM model In which, Iσ is SAR intensity, I is the cross section result. It is estimated that Swell S was generated by a ne information and S is speckle noise. storm about 4000km away near to the Antarctic In the SAR one-dimension directional spectrum, the Continent and after travelled 96 hours it arrived at the energy is concentrated in very small angular sectors. observation point. Swell S was generated by an anti- ne This property gives the possibility to remove the clockwise low pressure about 2200km away and speckle and extract the useful information by setting a travelled about 54 hours to the observation point. In proper threshold. Before doing the (FFT), the Fig. 4 swell travelling and cross sea generation is logarithm is calculated. Thus the multiplicative shown on a simplified map. The black dotted line speckle noise in SAR image is transformed into shows the swell great circle route from the generation additive noise i.e. area (green triangle) to the observation at the imagette log(Iσ) = log(I)+log(S) (2) location (Black Square, 23.06S and 111.6W).
Load more

Recommended publications
  • Sea State in Marine Safety Information Present State, Future Prospects
    Sea State in Marine Safety Information Present State, future prospects Henri SAVINA – Jean-Michel LEFEVRE Météo-France Rogue Waves 2004, Brest 20-22 October 2004 JCOMM Joint WMO/IOC Commission for Oceanography and Marine Meteorology The future of Operational Oceanography Intergovernmental body of technical experts in the field of oceanography and marine meteorology, with a mandate to prepare both regulatory (what Member States shall do) and guidance (what Member States should do) material. TheThe visionvision ofof JCOMMJCOMM Integrated ocean observing system Integrated data management State-of-the-art technologies and capabilities New products and services User responsiveness and interaction Involvement of all maritime countries JCOMM structure Terms of Reference Expert Team on Maritime Safety Services • Monitor / review operations of marine broadcast systems, including GMDSS and others for vessels not covered by the SOLAS convention •Monitor / review technical and service quality standards for meteo and oceano MSI, particularly for the GMDSS, and provide assistance and support to Member States • Ensure feedback from users is obtained through appropriate channels and applied to improve the relevance, effectiveness and quality of services • Ensure effective coordination and cooperation with organizations, bodies and Member States on maritime safety issues • Propose actions as appropriate to meet requirements for international coordination of meteorological and related communication services • Provide advice to the SCG and other Groups of JCOMM on issues related to MSS Chair selected by Commission. OPEN membership, including representatives of the Issuing Services for GMDSS, of IMO, IHO, ICS, IMSO, and other user groups GMDSS Global Maritime Distress & Safety System Defined by IMO for the provision of MSI and the coordination of SAR alerts on a global basis.
    [Show full text]
  • Headland Sediment Bypassing Processes
    UNIVERSIDADE DE LISBOA FACULDADE DE CIÊNCIAS HEADLAND SEDIMENT BYPASSING PROCESSES Doutoramento em Geologia Especialidade em Geodinâmica Externa Mónica Sofia Afonso Ribeiro Tese orientada por: Professor Doutor Rui Pires de Matos Taborda Doutora Aurora da Conceição Coutinho Rodrigues Bizarro Documento especialmente elaborado para a obtenção do grau de doutor 2017 UNIVERSIDADE DE LISBOA FACULDADE DE CIÊNCIAS HEADLAND SEDIMENT BYPASSING PROCESSES Doutoramento em Geologia Especialidade em Geodinâmica Externa Mónica Sofia Afonso Ribeiro Tese orientada por: Professor Doutor Rui Pires de Matos Taborda Doutora Aurora da Conceição Coutinho Rodrigues Bizarro Júri: Presidente: ● Doutora Maria da Conceição Pombo de Freitas Vogais: ● Doutor António Henrique da Fontoura Klein ● Doutor Óscar Manuel Fernandes Cerveira Ferreira ● Doutora Anabela Tavares Campos Oliveira ● Doutor César Augusto Canelhas Freire de Andrade ● Doutor Rui Pires de Matos Taborda Documento especialmente elaborado para a obtenção do grau de doutor Fundação para a Ciência e Tecnologia, no âmbito da Bolsa de Doutoramento com a referência SFRH/BD/79126/2011 2017 Em memória do meu irmão Luís Acknowledgments | Agradecimentos O doutoramento é um processo exigente, por vezes solitário, mas que só é possível com o apoio e a colaboração de outras pessoas e instituições. Portanto, resta-me agradecer a todos os que contribuíram para a conclusão deste trabalho. Em primeiro lugar agradeço aos meus orientadores, Rui Taborda e Aurora Bizarro, que têm acompanhado o meu trabalho desde os meus primeiros passos na Geologia Marinha, já lá vão 10 anos! A eles agradeço o incentivo para iniciar este projeto, o apoio demonstrado em todas as fases do trabalho, a confiança e a amizade. Ao Rui agradeço, em particular, a partilha e discussão de ideias e os desafios constantes que me permitiram evoluir.
    [Show full text]
  • North Pacific Ocean
    468 ¢ U.S. Coast Pilot 7, Chapter 11 31 MAY 2020 Chart Coverage in Coast Pilot 7—Chapter 11 124° NOAA’s Online Interactive Chart Catalog has complete chart coverage 18480 http://www.charts.noaa.gov/InteractiveCatalog/nrnc.shtml 126° 125° Cape Beale V ANCOUVER ISLAND (CANADA) 18485 Cape Flattery S T R A I T O F Neah Bay J U A N D E F U C A Cape Alava 18460 48° Cape Johnson QUILLAYUTE RIVER W ASHINGTON HOH RIVER Hoh Head 18480 QUEETS RIVER RAFT RIVER Cape Elizabeth QUINAULT RIVER COPALIS RIVER Aberdeen 47° GRAYS HARBOR CHEHALIS RIVER 18502 18504 Willapa NORTH PA CIFIC OCEAN WILLAPA BAY South Bend 18521 Cape Disappointment COLUMBIA RIVER 18500 Astoria 31 MAY 2020 U.S. Coast Pilot 7, Chapter 11 ¢ 469 Columbia River to Strait of Juan De Fuca, Washington (1) This chapter describes the Pacific coast of the State (15) of Washington from the Washington-Oregon border at the ENCs - US3WA03M, US3WA03M mouth of the Columbia River to the northwesternmost Chart - 18500 point at Cape Flattery. The deep-draft ports of South Bend and Raymond, in Willapa Bay, and the deep-draft ports of (16) From Cape Disappointment, the coast extends Hoquiam and Aberdeen, in Grays Harbor, are described. north for 22 miles to Willapa Bay as a low sandy beach, In addition, the fishing port of La Push is described. The with sandy ridges about 20 feet high parallel with the most outlying dangers are Destruction Island and Umatilla shore. Back of the beach, the country is heavily wooded.
    [Show full text]
  • Waves and Tides the Preceding Sections Have Dealt with the Types Of
    CHAPTER XIV Waves and Tides .......................................................................................................... Introduction The preceding sections have dealt with the types of motion in the ocean that bring about transport of water massesin a definite direction during a considerable length of time. They have also dealt with the random motion, the turbulence, which is superimposed upon the general flow. Besidesthese types, one has also to consider the oscillating motion characteristic of waves. In general, this motion manifests itself to the observer more by the riseand fall of the sea surface than by the motion of the individual water particles. Waves have attracted attention since before the beginning of recorded history, and in recent years they have been the subject of extensive theoretical studies. Surveys of our knowledge as to the character of ocean waves have been presented by Cornish (1912, 1934), Krtimmel (1911), Patton and Mariner (1932) and by Defant (1929). Lamb (1932) has discussed the hydrodynamic theories of waves, and Thorade (1931) has given a comprehensive review of the theoretical studies of ocean waves and has compiled a long list of literature covering the period from 1687 to 1930. Our understanding of the waves of the ocean, how they are formed and how they travel, is as yet by no means complete. The reason is, in the first place, that actual observations at sea are so difficult that the characteristicsof the waves cannot easily be determined. In the second place, the theories that serve to bring the observed sequence of events in nature into intimate connection with experience gained by other methods of study are still incomplete, particularly because most theories are based on classicalhydrodynamics, which deal with wave motion in an idealized fluid.
    [Show full text]
  • Ocean Wave Forecasting at ECMWF
    Ocean Wave Forecasting at ECMWF Jean-Raymond Bidlot Marine Aspects Section Predictability Division of the Research Department European Centre for Medium-range Weather Forecasts (E.C.M.W.F.) Reading, UK Slide 1 Ocean waves: We are dealing with wind generated waves at the surface of the oceans, from gentle to rough … Ocean wave Forecasting at ECMWF Slide 2 Ocean Waves Forcing: earthquake wind moon/sun Restoring: gravity surface tension Coriolis force 10.0 1.0 0.03 3x10-3 2x10-5 1x10-5 Frequency (Hz) Ocean wave Forecasting at ECMWF Slide 3 What we are dealing with? Water surface elevation, η Wave Period, T Wave Length, λ Wave Height, H Ocean wave Forecasting at ECMWF Slide 4 Wave Spectrum l The irregular water surface can be decomposed into (infinite) number of simple sinusoidal components with different frequencies (f) and propagation directions (θ ). l The distribution of wave energy among those components is called: “wave spectrum”, F(f,θ). Ocean wave Forecasting at ECMWF Slide 5 l Modern ocean wave prediction systems are based on statistical description of oceans waves (i.e. ensemble average of individual waves). l The sea state is described by the two-dimensional wave spectrum F(f,θ). Ocean Wave Modelling Ocean Wave Modelling Ocean wave Forecasting at ECMWF Slide 6 Ocean Wave Modelling l For example, the mean variance of the sea surface elevation η due to waves is given by: 〈η2〉 = F( f ,θ)dfdθ ∫∫ l The mean energy associated with those waves is: 2 energy= ρηw g l The statistical measure for wave height, called the significant wave height (Hs): 2 H s = 4 η The term significant wave height is historical as this value appeared to be well correlated with visual estimates of wave height from experienced observers.
    [Show full text]
  • Remote Sensing
    remote sensing Article Contribution of Remote Sensing Technologies to a Holistic Coastal and Marine Environmental Management Framework: A Review Badr El Mahrad 1,2,3,* , Alice Newton 3, John D. Icely 3,4 , Ilias Kacimi 2, Samuel Abalansa 3 and Maria Snoussi 5 1 Murray Foundation, Brabners LLP, Horton House, Exchange Street, Liverpool L2 3YL, UK 2 Laboratory of Geoscience, Water and Environment, (LG2E-CERNE2D), Department of Earth Sciences, Faculty of Sciences, Mohammed V University of Rabat, Rabat 10000, Morocco; [email protected]. 3 CIMA, FCT-Gambelas Campus, University of Algarve, 8005-139 Faro, Portugal; [email protected] (A.N.); [email protected] (J.D.I.); [email protected] (S.A.) 4 Sagremarisco, Apartado 21, 8650-999 Vila do Bispo, Portugal 5 Department of Earth Sciences, Faculty of Sciences, Mohammed V University of Rabat, Rabat 10000, Morocco; [email protected] * Correspondence: [email protected] Received: 1 May 2020; Accepted: 13 July 2020; Published: 18 July 2020 Abstract: Coastal and marine management require the evaluation of multiple environmental threats and issues. However, there are gaps in the necessary data and poor access or dissemination of existing data in many countries around the world. This research identifies how remote sensing can contribute to filling these gaps so that environmental agencies, such as the United Nations Environmental Programme, European Environmental Agency, and International Union for Conservation of Nature, can better implement environmental directives in a cost-effective manner. Remote sensing (RS) techniques generally allow for uniform data collection, with common acquisition and reporting methods, across large areas. Furthermore, these datasets are sometimes open-source, mainly when governments finance satellite missions.
    [Show full text]
  • The Wind and the Waves
    The wind and the waves The windway Wave wars Graveyards Conflicting seas 17 The windway Sept-Îles Swell and wind waves Waves that have been formed elsewhere or before the wind - “We have to cross to Anticosti today, or we'll have trouble changed direction are called swell. The swell can be an indication tomorrow. They're calling for 30 knot winds tomorrow and the of approaching winds. sea will be too high for my liking. Sailing is a lot of fun, but you If the waves are flowing in the same direction as the wind, how- need strong nerves.” ever, you are looking at wind waves. If the wind should shift, you will encounter cross seas Fetch If there were never any wind, the St Lawrence would be a gigantic mirror, rising and falling with the tides. But that is not the case at all. Fetch: 50 nautical miles The St Lawrence is a vast surface that can be whipped up into Duration: 6 hours violent seas depending on the direction, duration and speed of the wind. Fetch is the distance over which the wind has been blowing from the same direction. The longer the fetch, the higher and longer WIND 15 KNOTS = WAVES 1.5 METRES = LENGTH 25 METRES the waves. After 12 hours at the same speed, though, the wind has almost no effect on the waves, except that it may cause them to lengthen, distance permitting. WIND 25 KNOTS = WAVES 3 METRES = LENGTH 32 METRES Since the fetch is limited on the St Lawrence, the waves cannot lengthen as much as they do out in the open ocean, so they often become very steep.
    [Show full text]
  • Satellites HY-1C and Landsat 8 Combined to Observe the Influence of Bridge on Sea Surface Temperature and Suspended Sediment Concentration in Hangzhou Bay, China
    water Article Satellites HY-1C and Landsat 8 Combined to Observe the Influence of Bridge on Sea Surface Temperature and Suspended Sediment Concentration in Hangzhou Bay, China Shuyi Huang 1, Jianqiang Liu 2 , Lina Cai 1,*, Minrui Zhou 1, Juan Bu 1 and Jieni Xu 1 1 Marine Science and Technology College, Zhejiang Ocean University, Zhoushan 316004, China; [email protected] (S.H.); [email protected] (M.Z.); [email protected] (J.B.); [email protected] (J.X.) 2 National Satellite Ocean Application Service (NSOAS), Beijing 100081, China; [email protected] * Correspondence: [email protected] Received: 8 August 2020; Accepted: 13 September 2020; Published: 17 September 2020 Abstract: We analyzed the influence of a cross-sea bridge on the sea surface temperature (SST) and suspended sediment concentration (SSC) of Hangzhou Bay based on landsat8_TIRS data and HY-1C data using an improved single window algorithm to retrieve the SST and an empirical formula to retrieve the SSC. In total, 375 paired sampling points and 70 transects were taken to compare the SST upstream and downstream of the bridge, and nine transects were taken to compare the SSC. The results show the following. (i) In summer, when the current flows through the bridge pier, the downstream SST of the bridge decreases significantly, with a range of 3.5%; in winter, generally, the downstream SST decreases but does not change as obviously as in summer. The downstream SSC increases obviously. (ii) The range of influence of the bridge pier on the downstream SST is about 0.3–4.0 km in width from the bridge and that on the downstream SSC is approximately 0.3–6.0 km.
    [Show full text]
  • Coastal Water Mangement Towards a New Spatial Agenda for the North Sea Region Region the North Sea for Spatial Agenda a New Towards
    Coastal Water Mangement Towards a New Spatial Agenda for the North Sea Region Region the North Sea for Spatial Agenda a New Towards European Union The European Regional Development Fund Coastal Water Management Towards a New Spatial Agenda for the North Sea Region Prepared for Interreg IIIB North Sea Region Programme by Resource Analysis, IMDC, PLANCO, ATKINS, INREGIA Authors: Elke Claus, Holger Platz, Michael Viehhauser, Jon McCue, Koen Trouw and Barbara De Kezel 37, Wilrijkstraat 2140 Antwerpen, Belgium Tel: +32 3 270 00 30 E-mail: [email protected] TOWARDS A NEW SPATIAL AGENDA FOR THE NORTH SEA REGION Between 1998 and 2001, a spatial vision for the North Sea Region was developed, based on the principles of the European Spatial Development Perspective (ESDP). NorVision, as it was called, is a key advisory document, which has strongly influenced territorial cooperation in the North Sea Region. It describes the existing state of spatial development and suggests directions for the future. Projects that have been developed under INTERREG IIIB NSR put many of them into practice In mid 2004 the Programme Monitoring Committee for the Interreg IIIB North Sea Programme decided that there should be a selective update to NorVision to have valuable strategic input for the future cooperation in North Sea Region. They agreed that the original NorVision document continues to be relevant and should not be evaluated or reworked. The new spatial agenda, as is has become known, should focus on issues, which have become more urgent or important in recent years or which have not been thoroughly addressed in the original document.
    [Show full text]
  • Dry Active Matter Exhibits a Self-Organized'cross Sea'phase
    Dry Active Matter exhibits a self-organized “Cross Sea” Phase Rüdiger Kürsten and Thomas Ihle Institut für Physik, Universität Greifswald, Felix-Hausdorff-Str. 6, 17489 Greifswald, Germany (Dated: February 8, 2020) The Vicsek model of self-propelled particles is known in three different phases: (i) a polar ordered homogeneous phase also called Toner-Tu phase, (iii) a phase of polar ordered regularly arranged high density bands (waves) with surrounding low density regions without polar order and (iv) a homogeneous phase without polar order. It has been questioned whether the band phase (iii) should be divided into two parts [1]: one with periodically arranged and one with strongly interacting but not ordered bands. We answer this question by showing that the standard Vicsek model has a fourth phase for large system sizes: (ii) a polar ordered cross sea phase. Close to the transition towards (i) this phase becomes unstable and looks like strongly interacting bands. We demonstrate that the cross sea phase is not just a superposition of two waves, but it is an independent complex pattern. Furthermore we show that there is a non-zero mass flow through the structure of the cross sea pattern within its co-moving frame. PACS numbers: 05.65+b, 45.70.Qj, 64.60.De, 64.60.Ej Active matter is characterized by the transformation of interact at discrete instances of time n∆t and remain free energy into directed motion. The energy is supplied constant between those collisions. The interactions are e.g. by chemicals (or food), external fields or radiation. given by the following rule On the other hand, active particles dissipate energy into " # their environment such that there is an interplay between X cos θj(t) energy supply and dissipation.
    [Show full text]
  • Middle Pleistocene Sea-Crossings in the Eastern Mediterranean?
    Journal of Anthropological Archaeology 42 (2016) 140–153 Contents lists available at ScienceDirect Journal of Anthropological Archaeology journal homepage: www.elsevier.com/locate/jaa Middle Pleistocene sea-crossings in the eastern Mediterranean? ⇑ Duncan Howitt-Marshall a, , Curtis Runnels b a British School at Athens, 52 Souedias, 106 76 Athens, Greece b Department of Archaeology, Boston University, 675 Commonwealth Avenue, Boston, MA 02215, USA article info abstract Article history: Lower and Middle Palaeolithic artifacts on Greek islands separated from the mainland in the Middle and Received 11 February 2016 Upper Pleistocene may be proxy evidence for maritime activity in the eastern Mediterranean. Four Revision received 9 April 2016 hypotheses are connected with this topic. The first is the presence of archaic hominins on the islands in the Palaeolithic, and the second is that some of the islands were separated from the mainland when hominins reached them. A third hypothesis is that archaic hominin technological and cognitive capabil- Keywords: ities were sufficient for the fabrication of watercraft. Finally, the required wayfinding skills for open sea- Palaeolithic maritime activity crossings were within the purview of early humans. Our review of the archaeological, experimental, Wayfinding ethno-historical, and theoretical evidence leads us to conclude that there is no a priori reason to reject Greek islands Middle Pleistocene the first two hypotheses in the absence of more targeted archaeological surveys on the islands, and thus Human
    [Show full text]
  • REDESIGN of CORE GROYNE USING NATURAL MATERIALS Maulida Amalia Rizki Civil Engineering Faculty Narotama University Surabaya Jl
    CORE Metadata, citation and similar papers at core.ac.uk Provided by Universitas Narotama Surabaya (UNNAR): Journals Volume 03 Number 01 September 2019 REDESIGN OF CORE GROYNE USING NATURAL MATERIALS Maulida Amalia Rizki Civil Engineering Faculty Narotama University Surabaya Jl. Arif Rahman Hakim 51 Surabaya [email protected] ABSTRACT Coastal abrasion is one of the serious problems with shoreline change. In addition to natural processes, such as wind, currents and waves. One method for overcoming coastal abrasion is the use of coastal protective structures, where the structure functions as a wave energy damper at a particular location. Coastal buildings are used to protect the beach against damage due to wave and current attacks. Groyne is a coastal safety structure that is built protrudes relatively perpendicular to the direction of the coast, the importance of built coastal security with a groyne structure on the Jetis beach is as a flood control infrastructure that is as a final disposal of floods in the Ijo Watershed system, addressing coastal abrasion in detail. So we get the design drawings of sediment control buildings to reduce sedimentation / siltation from the direction of the sea into the river mouth, material structure costs and time schedule. Keywords: Abrasion, Groin, Material, Cost, Time Schedule. INTRODUCTION Research Background The problem at the Jetis beach is a estuary sedimentation, so that the flood discharge and economic activities of the people who use the river estuary channel as their fishing boat route are disrupted. Jetty or Groin which was built for the purpose of protecting the channel protrudes towards the sea to a distance of 300 m, with such conditions the river mouth is expected to get optimal protection.
    [Show full text]