Poisson Line Processes and Spatial Transportation Networks
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Poisson Representations of Branching Markov and Measure-Valued
The Annals of Probability 2011, Vol. 39, No. 3, 939–984 DOI: 10.1214/10-AOP574 c Institute of Mathematical Statistics, 2011 POISSON REPRESENTATIONS OF BRANCHING MARKOV AND MEASURE-VALUED BRANCHING PROCESSES By Thomas G. Kurtz1 and Eliane R. Rodrigues2 University of Wisconsin, Madison and UNAM Representations of branching Markov processes and their measure- valued limits in terms of countable systems of particles are con- structed for models with spatially varying birth and death rates. Each particle has a location and a “level,” but unlike earlier con- structions, the levels change with time. In fact, death of a particle occurs only when the level of the particle crosses a specified level r, or for the limiting models, hits infinity. For branching Markov pro- cesses, at each time t, conditioned on the state of the process, the levels are independent and uniformly distributed on [0,r]. For the limiting measure-valued process, at each time t, the joint distribu- tion of locations and levels is conditionally Poisson distributed with mean measure K(t) × Λ, where Λ denotes Lebesgue measure, and K is the desired measure-valued process. The representation simplifies or gives alternative proofs for a vari- ety of calculations and results including conditioning on extinction or nonextinction, Harris’s convergence theorem for supercritical branch- ing processes, and diffusion approximations for processes in random environments. 1. Introduction. Measure-valued processes arise naturally as infinite sys- tem limits of empirical measures of finite particle systems. A number of ap- proaches have been developed which preserve distinct particles in the limit and which give a representation of the measure-valued process as a transfor- mation of the limiting infinite particle system. -
Poisson Processes Stochastic Processes
Poisson Processes Stochastic Processes UC3M Feb. 2012 Exponential random variables A random variable T has exponential distribution with rate λ > 0 if its probability density function can been written as −λt f (t) = λe 1(0;+1)(t) We summarize the above by T ∼ exp(λ): The cumulative distribution function of a exponential random variable is −λt F (t) = P(T ≤ t) = 1 − e 1(0;+1)(t) And the tail, expectation and variance are P(T > t) = e−λt ; E[T ] = λ−1; and Var(T ) = E[T ] = λ−2 The exponential random variable has the lack of memory property P(T > t + sjT > t) = P(T > s) Exponencial races In what follows, T1;:::; Tn are independent r.v., with Ti ∼ exp(λi ). P1: min(T1;:::; Tn) ∼ exp(λ1 + ··· + λn) . P2 λ1 P(T1 < T2) = λ1 + λ2 P3: λi P(Ti = min(T1;:::; Tn)) = λ1 + ··· + λn P4: If λi = λ and Sn = T1 + ··· + Tn ∼ Γ(n; λ). That is, Sn has probability density function (λs)n−1 f (s) = λe−λs 1 (s) Sn (n − 1)! (0;+1) The Poisson Process as a renewal process Let T1; T2;::: be a sequence of i.i.d. nonnegative r.v. (interarrival times). Define the arrival times Sn = T1 + ··· + Tn if n ≥ 1 and S0 = 0: The process N(t) = maxfn : Sn ≤ tg; is called Renewal Process. If the common distribution of the times is the exponential distribution with rate λ then process is called Poisson Process of with rate λ. Lemma. N(t) ∼ Poisson(λt) and N(t + s) − N(s); t ≥ 0; is a Poisson process independent of N(s); t ≥ 0 The Poisson Process as a L´evy Process A stochastic process fX (t); t ≥ 0g is a L´evyProcess if it verifies the following properties: 1. -
POISSON PROCESSES 1.1. the Rutherford-Chadwick-Ellis
POISSON PROCESSES 1. THE LAW OF SMALL NUMBERS 1.1. The Rutherford-Chadwick-Ellis Experiment. About 90 years ago Ernest Rutherford and his collaborators at the Cavendish Laboratory in Cambridge conducted a series of pathbreaking experiments on radioactive decay. In one of these, a radioactive substance was observed in N = 2608 time intervals of 7.5 seconds each, and the number of decay particles reaching a counter during each period was recorded. The table below shows the number Nk of these time periods in which exactly k decays were observed for k = 0,1,2,...,9. Also shown is N pk where k pk = (3.87) exp 3.87 =k! {− g The parameter value 3.87 was chosen because it is the mean number of decays/period for Rutherford’s data. k Nk N pk k Nk N pk 0 57 54.4 6 273 253.8 1 203 210.5 7 139 140.3 2 383 407.4 8 45 67.9 3 525 525.5 9 27 29.2 4 532 508.4 10 16 17.1 5 408 393.5 ≥ This is typical of what happens in many situations where counts of occurences of some sort are recorded: the Poisson distribution often provides an accurate – sometimes remarkably ac- curate – fit. Why? 1.2. Poisson Approximation to the Binomial Distribution. The ubiquity of the Poisson distri- bution in nature stems in large part from its connection to the Binomial and Hypergeometric distributions. The Binomial-(N ,p) distribution is the distribution of the number of successes in N independent Bernoulli trials, each with success probability p. -
On Sampling from the Multivariate T Distribution by Marius Hofert
CONTRIBUTED RESEARCH ARTICLES 129 On Sampling from the Multivariate t Distribution by Marius Hofert Abstract The multivariate normal and the multivariate t distributions belong to the most widely used multivariate distributions in statistics, quantitative risk management, and insurance. In contrast to the multivariate normal distribution, the parameterization of the multivariate t distribution does not correspond to its moments. This, paired with a non-standard implementation in the R package mvtnorm, provides traps for working with the multivariate t distribution. In this paper, common traps are clarified and corresponding recent changes to mvtnorm are presented. Introduction A supposedly simple task in statistics courses and related applications is to generate random variates from a multivariate t distribution in R. When teaching such courses, we found several fallacies one might encounter when sampling multivariate t distributions with the well-known R package mvtnorm; see Genz et al.(2013). These fallacies have recently led to improvements of the package ( ≥ 0.9-9996) which we present in this paper1. To put them in the correct context, we first address the multivariate normal distribution. The multivariate normal distribution The multivariate normal distribution can be defined in various ways, one is with its stochastic represen- tation X = m + AZ, (1) where Z = (Z1, ... , Zk) is a k-dimensional random vector with Zi, i 2 f1, ... , kg, being independent standard normal random variables, A 2 Rd×k is an (d, k)-matrix, and m 2 Rd is the mean vector. The covariance matrix of X is S = AA> and the distribution of X (that is, the d-dimensional multivariate normal distribution) is determined solely by the mean vector m and the covariance matrix S; we can thus write X ∼ Nd(m, S). -
Introduction to Lévy Processes
Introduction to L´evyprocesses Graduate lecture 22 January 2004 Matthias Winkel Departmental lecturer (Institute of Actuaries and Aon lecturer in Statistics) 1. Random walks and continuous-time limits 2. Examples 3. Classification and construction of L´evy processes 4. Examples 5. Poisson point processes and simulation 1 1. Random walks and continuous-time limits 4 Definition 1 Let Yk, k ≥ 1, be i.i.d. Then n X 0 Sn = Yk, n ∈ N, k=1 is called a random walk. -4 0 8 16 Random walks have stationary and independent increments Yk = Sk − Sk−1, k ≥ 1. Stationarity means the Yk have identical distribution. Definition 2 A right-continuous process Xt, t ∈ R+, with stationary independent increments is called L´evy process. 2 Page 1 What are Sn, n ≥ 0, and Xt, t ≥ 0? Stochastic processes; mathematical objects, well-defined, with many nice properties that can be studied. If you don’t like this, think of a model for a stock price evolving with time. There are also many other applications. If you worry about negative values, think of log’s of prices. What does Definition 2 mean? Increments , = 1 , are independent and Xtk − Xtk−1 k , . , n , = 1 for all 0 = . Xtk − Xtk−1 ∼ Xtk−tk−1 k , . , n t0 < . < tn Right-continuity refers to the sample paths (realisations). 3 Can we obtain L´evyprocesses from random walks? What happens e.g. if we let the time unit tend to zero, i.e. take a more and more remote look at our random walk? If we focus at a fixed time, 1 say, and speed up the process so as to make n steps per time unit, we know what happens, the answer is given by the Central Limit Theorem: 2 Theorem 1 (Lindeberg-L´evy) If σ = V ar(Y1) < ∞, then Sn − (Sn) √E → Z ∼ N(0, σ2) in distribution, as n → ∞. -
EFFICIENT ESTIMATION and SIMULATION of the TRUNCATED MULTIVARIATE STUDENT-T DISTRIBUTION
Efficient estimation and simulation of the truncated multivariate student-t distribution Zdravko I. Botev, Pierre l’Ecuyer To cite this version: Zdravko I. Botev, Pierre l’Ecuyer. Efficient estimation and simulation of the truncated multivariate student-t distribution. 2015 Winter Simulation Conference, Dec 2015, Huntington Beach, United States. hal-01240154 HAL Id: hal-01240154 https://hal.inria.fr/hal-01240154 Submitted on 8 Dec 2015 HAL is a multi-disciplinary open access L’archive ouverte pluridisciplinaire HAL, est archive for the deposit and dissemination of sci- destinée au dépôt et à la diffusion de documents entific research documents, whether they are pub- scientifiques de niveau recherche, publiés ou non, lished or not. The documents may come from émanant des établissements d’enseignement et de teaching and research institutions in France or recherche français ou étrangers, des laboratoires abroad, or from public or private research centers. publics ou privés. Proceedings of the 2015 Winter Simulation Conference L. Yilmaz, W. K V. Chan, I. Moon, T. M. K. Roeder, C. Macal, and M. Rosetti, eds. EFFICIENT ESTIMATION AND SIMULATION OF THE TRUNCATED MULTIVARIATE STUDENT-t DISTRIBUTION Zdravko I. Botev Pierre L’Ecuyer School of Mathematics and Statistics DIRO, Universite´ de Montreal The University of New South Wales C.P. 6128, Succ. Centre-Ville Sydney, NSW 2052, AUSTRALIA Montreal´ (Quebec),´ H3C 3J7, CANADA ABSTRACT We propose an exponential tilting method for exact simulation from the truncated multivariate student-t distribution in high dimensions as an alternative to approximate Markov Chain Monte Carlo sampling. The method also allows us to accurately estimate the probability that a random vector with multivariate student-t distribution falls in a convex polytope. -
Applied Mathematics 1
Applied Mathematics 1 MATH 0180 Intermediate Calculus 1 Applied Mathematics MATH 0520 Linear Algebra 2 1 APMA 0350 Applied Ordinary Differential Equations 2 & APMA 0360 and Applied Partial Differential Equations Chair I 3 4 Bjorn Sandstede Select one course on programming from the following: 1 APMA 0090 Introduction to Mathematical Modeling Associate Chair APMA 0160 Introduction to Computing Sciences Kavita Ramanan CSCI 0040 Introduction to Scientific Computing and The Division of Applied Mathematics at Brown University is one of Problem Solving the most prominent departments at Brown, and is also one of the CSCI 0111 Computing Foundations: Data oldest and strongest of its type in the country. The Division of Applied CSCI 0150 Introduction to Object-Oriented Mathematics is a world renowned center of research activity in a Programming and Computer Science wide spectrum of traditional and modern mathematics. It explores the connections between mathematics and its applications at both CSCI 0170 Computer Science: An Integrated the research and educational levels. The principal areas of research Introduction activities are ordinary, functional, and partial differential equations: Five additional courses, of which four should be chosen from 5 stochastic control theory; applied probability, statistics and stochastic the 1000-level courses taught by the Division of Applied systems theory; neuroscience and computational molecular biology; Mathematics. APMA 1910 cannot be used as an elective. numerical analysis and scientific computation; and the mechanics of Total Credits 10 solids, materials science and fluids. The effort in virtually all research 1 ranges from applied and algorithmic problems to the study of fundamental Substitution of alternate courses for the specific requirements is mathematical questions. -
Spatio-Temporal Cluster Detection and Local Moran Statistics of Point Processes
Old Dominion University ODU Digital Commons Mathematics & Statistics Theses & Dissertations Mathematics & Statistics Spring 2019 Spatio-Temporal Cluster Detection and Local Moran Statistics of Point Processes Jennifer L. Matthews Old Dominion University Follow this and additional works at: https://digitalcommons.odu.edu/mathstat_etds Part of the Applied Statistics Commons, and the Biostatistics Commons Recommended Citation Matthews, Jennifer L.. "Spatio-Temporal Cluster Detection and Local Moran Statistics of Point Processes" (2019). Doctor of Philosophy (PhD), Dissertation, Mathematics & Statistics, Old Dominion University, DOI: 10.25777/3mps-rk62 https://digitalcommons.odu.edu/mathstat_etds/46 This Dissertation is brought to you for free and open access by the Mathematics & Statistics at ODU Digital Commons. It has been accepted for inclusion in Mathematics & Statistics Theses & Dissertations by an authorized administrator of ODU Digital Commons. For more information, please contact [email protected]. ABSTRACT Approved for public release; distribution is unlimited SPATIO-TEMPORAL CLUSTER DETECTION AND LOCAL MORAN STATISTICS OF POINT PROCESSES Jennifer L. Matthews Commander, United States Navy Old Dominion University, 2019 Director: Dr. Norou Diawara Moran's index is a statistic that measures spatial dependence, quantifying the degree of dispersion or clustering of point processes and events in some location/area. Recognizing that a single Moran's index may not give a sufficient summary of the spatial autocorrelation measure, a local -
Stochastic Simulation APPM 7400
Stochastic Simulation APPM 7400 Lesson 1: Random Number Generators August 27, 2018 Lesson 1: Random Number Generators Stochastic Simulation August27,2018 1/29 Random Numbers What is a random number? Lesson 1: Random Number Generators Stochastic Simulation August27,2018 2/29 Random Numbers What is a random number? “You mean like... 5?” Lesson 1: Random Number Generators Stochastic Simulation August27,2018 2/29 Random Numbers What is a random number? “You mean like... 5?” Formal definition from probability: A random number is a number uniformly distributed between 0 and 1. Lesson 1: Random Number Generators Stochastic Simulation August27,2018 2/29 Random Numbers What is a random number? “You mean like... 5?” Formal definition from probability: A random number is a number uniformly distributed between 0 and 1. (It is a realization of a uniform(0,1) random variable.) Lesson 1: Random Number Generators Stochastic Simulation August27,2018 2/29 Random Numbers Here are some realizations: 0.8763857 0.2607807 0.7060687 0.0826960 Density 0.7569021 . 0 2 4 6 8 10 0.0 0.2 0.4 0.6 0.8 1.0 sample Lesson 1: Random Number Generators Stochastic Simulation August27,2018 3/29 Random Numbers Here are some realizations: 0.8763857 0.2607807 0.7060687 0.0826960 Density 0.7569021 . 0 2 4 6 8 10 0.0 0.2 0.4 0.6 0.8 1.0 sample Lesson 1: Random Number Generators Stochastic Simulation August27,2018 3/29 Random Numbers Here are some realizations: 0.8763857 0.2607807 0.7060687 0.0826960 Density 0.7569021 . -
Alireza Sheikh-Zadeh, Ph.D
Alireza Sheikh-Zadeh, Ph.D. Assistant Professor of Practice in Data Science Rawls College of Business, Texas Tech University Area of Information Systems and Quantitative Sciences (ISQS) 703 Flint Ave, Lubbock, TX 79409 (806) 834-8569, [email protected] EDUCATION Ph.D. in Industrial Engineering, 2017 Industrial Engineering Department at the University of Arkansas, Fayetteville, AR Dissertation: “Developing New Inventory Segmentation Methods for Large-Scale Multi-Echelon In- ventory Systems” (Advisor: Manuel D. Rossetti) M.Sc. in Industrial Engineering (with concentration in Systems Management), 2008 Industrial Engineering & Systems Management Department at Tehran Polytechnic, Tehran, Iran Thesis: “System Dynamics Modeling for Study and Design of Science and Technology Parks for The Development of Deprived Regions” (Advisor: Reza Ramazani) AREA of INTEREST Data Science & Machine Learning Supply Chain Analytics Applied Operations Research System Dynamics Simulation and Stochastic Modeling Logistic Contracting PUBLICATIONS Journal Papers (including under review papers) • Sheikhzadeh, A., & Farhangi, H., & Rossetti, M. D. (under review), ”Inventory Grouping and Sensitivity Analysis in Large-Scale Spare Part Systems”, submitted work. • Sheikhzadeh, A., Rossetti, M. D., & Scott, M. (2nd review), ”Clustering, Aggregation, and Size-Reduction for Large-Scale Multi-Echelon Spare-Part Replenishment Systems,” Omega: The International Journal of Management Science. • Sheikhzadeh, A., & Rossetti, M. D. (4th review), ”Classification Methods for Problem Size Reduction in Spare Part Provisioning,” International Journal of Production Economics. • Al-Rifai, M. H., Rossetti, M. D., & Sheikhzadeh, A. (2016), ”A Heuristic Optimization Algorithm for Two- Echelon (r; Q) Inventory Systems with Non-Identical Retailers,” International Journal of Inventory Re- search. • Karimi-Nasab, M., Bahalke, U., Feili, H. R., Sheikhzadeh, A., & Dolatkhahi, K. -
Multivariate Stochastic Simulation with Subjective Multivariate Normal
MULTIVARIATE STOCHASTIC SIMULATION WITH SUBJECTIVE MULTIVARIATE NORMAL DISTRIBUTIONS1 Peter J. Ince2 and Joseph Buongiorno3 Abstract.-In many applications of Monte Carlo simulation in forestry or forest products, it may be known that some variables are correlated. However, for simplicity, in most simulations it has been assumed that random variables are independently distributed. This report describes an alternative Monte Carlo simulation technique for subjectivelyassessed multivariate normal distributions. The method requires subjective estimates of the 99-percent confidence interval for the expected value of each random variable and of the partial correlations among the variables. The technique can be used to generate pseudorandom data corresponding to the specified distribution. If the subjective parameters do not yield a positive definite covariance matrix, the technique determines minimal adjustments in variance assumptions needed to restore positive definiteness. The method is validated and then applied to a capital investment simulation for a new papermaking technology.In that example, with ten correlated random variables, no significant difference was detected between multivariate stochastic simulation results and results that ignored the correlation. In general, however, data correlation could affect results of stochastic simulation, as shown by the validation results. INTRODUCTION MONTE CARLO TECHNIQUE Generally, a mathematical model is used in stochastic The Monte Carlo simulation technique utilizes three simulation studies. In addition to randomness, correlation may essential elements: (1) a mathematical model to calculate a exist among the variables or parameters of such models.In the discrete numerical result or outcome as a function of one or case of forest ecosystems, for example, growth can be more discrete variables, (2) a sequence of random (or influenced by correlated variables, such as temperatures and pseudorandom) numbers to represent random probabilities, and precipitations. -
Stochastic Simulation
Agribusiness Analysis and Forecasting Stochastic Simulation Henry Bryant Texas A&M University Henry Bryant (Texas A&M University) Agribusiness Analysis and Forecasting 1 / 19 Stochastic Simulation In economics we use simulation because we can not experiment on live subjects, a business, or the economy without injury. In other fields they can create an experiment Health sciences they feed (or treat) lots of lab rats on different chemicals to see the results. Animal science researchers feed multiple pens of steers, chickens, cows, etc. on different rations. Engineers run a motor under different controlled situations (temp, RPMs, lubricants, fuel mixes). Vets treat different pens of animals with different meds. Agronomists set up randomized block treatments for a particular seed variety with different fertilizer levels. Henry Bryant (Texas A&M University) Agribusiness Analysis and Forecasting 2 / 19 Probability Distributions Parametric and Non-Parametric Distributions Parametric Dist. have known and well defined parameters that force their shapes to known patterns. Normal Distribution - Mean and Standard Deviation. Uniform - Minimum and Maximum Bernoulli - Probability of true Beta - Alpha, Beta, Minimum, Maximum Non-Parametric Distributions do not have pre-set shapes based on known parameters. The parameters are estimated each time to make the shape of the distribution fit the data. Empirical { Actual Observations and their Probabilities. Henry Bryant (Texas A&M University) Agribusiness Analysis and Forecasting 3 / 19 Typical Problem for Risk Analysis We have a stochastic variable that needs to be included in a business model. For example: Price forecast has residuals we could not explain and they are the stochastic component we need to simulate.