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    Stochastic processes with jumps and non-vanishing higher-order kramers–moyal coefficients

    , Article Understanding Complex Systems ; 2019 , Pages 99-110 ; 18600832 (ISSN) Rahimi Tabar, M. R ; Sharif University of Technology
    Springer Verlag  2019
    Abstract
    In this chapter we study stochastic processes in the presence of jump discontinuity, and discuss the meaning of non-vanishing higher-order Kramers–Moyal coefficients. We describe in details the stochastic properties of Poisson jump processes. We derive the statistical moments of the Poisson process and the Kramers–Moyal coefficients for pure Poisson jump events. Growing evidence shows that continuous stochastic modeling (white noise-driven Langevin equation) of time series of complex systems should account for the presence of discontinuous jump components [1–6]. Such time series have some distinct important characteristics, such as heavy tails and occasionally sudden large jumps.... 

    Equivalence of langevin and fokker–planck equations

    , Article Understanding Complex Systems ; 2019 , Pages 61-68 ; 18600832 (ISSN) Rahimi Tabar, M. R ; Sharif University of Technology
    Springer Verlag  2019
    Abstract
    In this chapter we show the equivalence between the Langevin approach and the Fokker–Planck equation, and derive the equation for the statistical moments of the process whose dynamics is described by the Langevin equation. © 2019, Springer Nature Switzerland AG  

    Stochastic processes with jumps and non-vanishing higher-order kramers–moyal coefficients

    , Article Understanding Complex Systems ; 2019 , Pages 99-110 ; 18600832 (ISSN) Rahimi Tabar, M. R ; Sharif University of Technology
    Springer Verlag  2019
    Abstract
    In this chapter we study stochastic processes in the presence of jump discontinuity, and discuss the meaning of non-vanishing higher-order Kramers–Moyal coefficients. We describe in details the stochastic properties of Poisson jump processes. We derive the statistical moments of the Poisson process and the Kramers–Moyal coefficients for pure Poisson jump events. Growing evidence shows that continuous stochastic modeling (white noise-driven Langevin equation) of time series of complex systems should account for the presence of discontinuous jump components [1–6]. Such time series have some distinct important characteristics, such as heavy tails and occasionally sudden large jumps.... 

    Equivalence of langevin and fokker–planck equations

    , Article Understanding Complex Systems ; 2019 , Pages 61-68 ; 18600832 (ISSN) Rahimi Tabar, M. R ; Sharif University of Technology
    Springer Verlag  2019
    Abstract
    In this chapter we show the equivalence between the Langevin approach and the Fokker–Planck equation, and derive the equation for the statistical moments of the process whose dynamics is described by the Langevin equation. © 2019, Springer Nature Switzerland AG  

    Uncertainty Quantification of Two Phase Immiscible Water Oil Flow

    , M.Sc. Thesis Sharif University of Technology Mahmoudi, Mehrdad (Author) ; Taghizadeh Manzari, Mehrdad (Supervisor)
    Abstract
    In this project، the immiscible two phase flow of oil-water in the absence of gravity in the two dimensional domain is investigated. The uncertainty quantification of pressure and saturation of fluid in the reservoir are calculated by the methods of statistical moment equation (presented by Tchelepi) and probabilistic collocation method combined with Karhunen Loeve expansion (presented by Heng Lee). Then the results are compared with Monte Carlo simulation. Matlab Reservoir Simulation Toolbox is used for flow simulation. The main problem based on Tchelepi’s work[56[ ، is a horizontal two dimensional problem that there is two injection and production wells at the two end point grids (a... 

    Sensitivity analysis of ray tracing to the geometrical description of the environment

    , Article IET Microwaves, Antennas and Propagation ; Volume 10, Issue 11 , 2016 , Pages 1225-1234 ; 17518725 (ISSN) Mohtashami, V ; Shishegar, A. A ; Sharif University of Technology
    Institution of Engineering and Technology 
    Abstract
    In ray-tracing-based propagation modelling, the electromagnetic field at the receiver is obtained by coherent summation of the fields of multipath components. It is therefore crucial to accurately calculate the phase of the electromagnetic field of each ray. In practice, when preparing the plan of the environment for ray tracing simulation, the lateral positions of the walls may not be included accurately in the database. This alters the phases of the fields as well as the delays of arrival of multipath components which may consequently lead to less accurate results. In this study, the sensitivity of ray tracing results to this type of geometrical inaccuracy is investigated through the... 

    Effects of geometrical uncertainties on ray tracing results for site-specific indoor propagation modeling

    , Article Proceedings of the 2013 IEEE-APS Topical Conference on Antennas and Propagation in Wireless Communications, IEEE APWC 2013 ; 2013 , Pages 836-839 ; 9781467356893 (ISBN) Mohtashami, V ; Shishegar, A. A ; Sharif University of Technology
    Abstract
    The plan of the environment used in a ray tracing simulation is not usually in exact accordance with the actual environment plan. Errors on the order of several centimeters may be present in describing the lateral wall positions. Such errors are comparable to the wavelength in indoor wireless applications and hence, can severely alter the phases of multipath components and lead to inaccurate electromagnetic field at the receiver. In this paper, the impact of this type of geometrical errors on the ray tracing results is investigated. Lateral wall positions are considered as random variables to account for possible geometrical errors. The statistical moments of some channel parameters are... 

    Universal image steganalysis using singular values of DCT coefficients

    , Article 2013 10th International ISC Conference on Information Security and Cryptology ; 2013 Heidari, M ; Gaemmaghami, S ; Sharif University of Technology
    IEEE Computer Society  2013
    Abstract
    We propose a blind image steganalysis method based on the Singular Value Decomposition (SVD) of the Discrete Cosine Transform (DCT) coefficients that are revisited in this work. We compute geometric mean, mean of log values, and statistical moments (mean, variance and skewness) of the SVDs of the DCT sub-blocks that are averaged over the whole image to construct a 480-element feature vector for steganalysis. These features are fed to a Support Vector Machine (SVM) classifier to discriminate between stego and cover images. Experimental results show that the proposed method outperforms most powerful steganalyzers when applied to some well-known steganography algorithms  

    Iterative histogram matching algorithm for chromosome image enhancement based on statistical moments

    , Article Proceedings - International Symposium on Biomedical Imaging ; 2012 , Pages 214-217 ; 19457928 (ISSN) ; 9781457718588 (ISBN) Ehsani, S. P ; Mousavi, H. S ; Khalaj, B. H ; Sharif University of Technology
    IEEE  2012
    Abstract
    Vivid banding pattern of the chromosome image is a crucial part for diagnosis in karyotype medical test. Furthermore, thriving computer aided segmentation and classification depend on the initial image quality. In this paper, we propose an adaptive and iterative histogram matching algorithm for chromosome contrast enhancement especially in banding patterns which is one of the most important information laid in chromosome image. Objective histogram, with which the initial image needs to be matched, is created based on processes on the initial image histogram. Calculation of statistical moments of image histogram and determination of parameters in each step of iteration based on these moments... 

    CBS: Contourlet-based steganalysis method

    , Article Journal of Signal Processing Systems ; Volume 61, Issue 3 , 2010 , Pages 367-373 ; 19398018 (ISSN) Sajedi, H ; Jamzad, M ; Sharif University of Technology
    2010
    Abstract
    An ideal steganographic technique embeds secret information into a carrier cover object with virtually imperceptible modification of the cover object. Steganalysis is a technique to discover the presence of hidden embedded information in a given object. Each steganalysis method is composed of feature extraction and feature classification components. Using features that are more sensitive to information hiding yields higher success in steganalysis. So far, several steganalysis methods have been presented which extract some features from DCT or wavelet coefficients of images. Multi-scale and time-frequency localization of an image is offered by wavelets. However, wavelets are not effective in... 

    A steganalysis method based on contourlet transform coefficients

    , Article 2008 4th International Conference on Intelligent Information Hiding and Multiedia Signal Processing, IIH-MSP 2008, Harbin, 15 August 2008 through 17 August 2008 ; 2008 , Pages 245-248 ; 9780769532783 (ISBN) Sajedi, H ; Jamzad, M ; Sharif University of Technology
    2008
    Abstract
    Steganalysis is a technique to detect the presence of hidden embedded information in a given data. Each steganalyzer is composed of feature extraction and feature classification components. Using features that are more sensitive to data hiding yields higher success in steganalysis. The present paper offers a new universal approach to steganalysis that uses statistical moments of contourlet coefficients as features for analysis. A non-linear SVM classifier is used to classify cover and stego images. The effectiveness of the proposed method is demonstrated by extensive experimental investigations. The proposed steganalysis method is compared with two well known steganalyzers against typical... 

    Development of Alzheimer's disease recognition using semiautomatic analysis of statistical parameters based on frequency characteristics of medical images

    , Article 2007 IEEE International Conference on Signal Processing and Communications, ICSPC 2007, Dubai, 14 November 2007 through 27 November 2007 ; 2007 , Pages 868-871 ; 9781424412365 (ISBN) Torabi, M ; Moradzadeh, H ; Vaziri, R ; Razavian, S. M. J ; Dehestani Ardekani, R ; Rahmandoust, M ; Taalimi, A ; Fatemizadeh, E ; Sharif University of Technology
    2007
    Abstract
    The paper presents an effective algorithm to analyze MR-images in order to recognize Alzheimer's Disease (AD) which appeared in patient's brain. The features of interest are categorized in Features of the Spatial Domain (FSD's) and Features of the Frequency Domain (FFD's) which are based on the first four statistic moments of the wavelet transform. Extracted features have been classified by a multi-layer perceptron Artificial Neural Network (ANN). Before ANN, the number of features is reduced from 44 to 12 to optimize and eliminate any correlation between them. The contribution of this paper is to demonstrate that by using the wavelet transform number of features needed for AD diagnosis has...