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Sparse PDE for SAR image speckle suppression

IET IMAGE PROCESSING 2017年第6期11卷 425-432页

作者： Wang, Zelong Tan, Xintong Yu, Qi Zhu, Jubo Natl Univ Def Technol Coll Sci Changsha Hunan Peoples R China

Speckle suppression is extremely important for understanding and utilising synthetic aperture radar (SAR) images, while the emphasis of the traditional methods for speckle suppression is usually focused on removing the noise instead of keeping the scattering character of imaging objects, which has caused serious interference to the subsequent applications of SAR images. The authors aim to develop sparse partial differential equation (PDE) for speckle suppression of SAR image, where the PDE model is associated with the sparse prior of objects and the statistical property of speckle. The PDE model has been proved to have the ability of denoising and edge-preserving by proper design, and the sparse prior of the point- and line-like objects on SAR images has been also illustrated, both of which help for keeping the scattering characters. To solve the proposed sparse PDE model, a numerical algorithm is designed and the sparse constraint is realised in each step of the diffusion process. In experiments, several real SAR images are utilised to validate the performance of the proposed method.

关键词： synthetic aperture radar radar imaging partial differential equations image denoising statistical analysis SAR image speckle suppression synthetic aperture radar noise removal imaging objects partial differential equation statistical property image denoising edge-preserving line-like objects point-like objects scattering characters sparse PDE model numerical algorithm sparse constraint diffusion process

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Wavelet transform for quasi-birth-death process with a continuous phase set

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APPLIED MATHEMATICS AND COMPUTATION 2015年 252卷 354-376页

作者： Jiang, Shuxia Latouche, Guy Liu, Yuanyuan Cent South Univ Forestry & Technol Sch Traff & Logist Changsha 410004 Hunan Peoples R China Univ Libre Bruxelles Dept Informat B-1050 Brussels Belgium Cent South Univ Sch Math & Stat Changsha 410083 Hunan Peoples R China Cent South Univ Sch Traff & Transportat Engn Changsha 410075 Hunan Peoples R China

We consider the computational questions which arise when analyzing quasi-birth-death processes with a continuous phase set. We develop a framework based on the wavelet transform and we propose a numerical algorithm for computing the steady-state probabilities based on the fast orthogonal wavelet transform. We conclude with a few examples to illustrate the effectiveness of our numerical algorithm. (c) 2014 Elsevier Inc. All rights reserved.

关键词： Quasi-birth-and-death process Continuous phase Stationary probability Wavelet series numerical algorithm

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Stochastic subspace identification based data-driven approach for monitoring electromechanical dynamics from phasor measurement units

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IET GENERATION TRANSMISSION & DISTRIBUTION 2020年第19期14卷 3983-3991页

作者： Jiang, Tao Yuan, Haoyu Zhao, Junbo Wu, Tianying Li, Fangxing Jia, Hongjie Northeast Elect Power Univ Dept Elect Engn Jilin 132012 JL Peoples R China Univ Tennessee Dept Elect Engn & Comp Sci Knoxville TN 37996 USA Mississippi State Univ Dept Elect & Comp Engn Starkville MS 39762 USA Washington State Univ Sch Elect Engn & Comp Sci Pullman WA 99163 USA Tianjin Univ Minist Educ Key Lab Smart Grid Tianjin 300072 Peoples R China

This study proposes to extend the numerical algorithm for subspace state space system identification (N4SID) for power grid electromechanical dynamics monitoring using the multi-channel noisy synchrophasor measurements. The oscillation modes, mode shapes, participation factors and coherent groups are estimated in a comprehensive manner. It consists of five key steps: (i) estimation of power system state subspace model via N4SID;(ii) electromechanical modes discrimination from the trivial modes by developing the generalised inverse and mode assurance criterion;(iii) calculations of the mode shapes using the estimated states and output subspace matrices;(iv) estimation of participation factors estimated by the calculated mode shapes and (v) the generator coherency identification by developing the direction cosine denoted coherency inductor. Test results on the IEEE 16-machine 68-bus test system and the practical China Southern power Grid using field synchrophasor measurements are performed. Comparison results with other existing methods show that the proposed method achieves better accuracy and efficiency for power system electromechanical dynamics monitoring in the presence of measurement noise.

关键词： oscillations phasor measurement eigenvalues and eigenfunctions state-space methods stochastic processes power system transient stability matrix algebra power system stability power system control power system measurement power grids power system electromechanical dynamics measurement noise stochastic subspace identification data-driven approach monitoring electromechanical dynamics phasor measurement units numerical algorithm subspace state space system identification N4SID power grid electromechanical dynamics multichannel noisy synchrophasor measurements oscillation modes participation factors coherent groups comprehensive manner power system state subspace model electromechanical modes discrimination trivial modes generalised inverse mode assurance criterion output subspace matrices calculated mode shapes generator coherency identification direction cosine denoted coherency inductor IEEE 16-machine 68-bus test system practical China Southern power Grid using field synchrophasor measurements

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An analytic approach for optimal coordination of overcurrent relays

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IET GENERATION TRANSMISSION & DISTRIBUTION 2013年第7期7卷 674-680页

作者： Mahari, Arash Seyedi, Heresh Univ Tabriz Fac Elect & Comp Engn Tabriz Iran

This study presents a new analytic approach to optimal coordination of directional overcurrent relays. This approach is based on the selection of optimum pickup current and time dial setting, in order to obtain minimum operating time for the relays, while satisfying various coordination and boundary constraints. Based on the new optimal relay setting procedure, an iterative numerical solution is proposed. The proposed numerical algorithm converges to the global optimum values, which are independent of initial values and the order of relay setting. The proposed method is applied to three different test systems. The new method is compared with some previously proposed analytic and evolutionary approaches. The results demonstrate the advantages of the proposed method over the previous works.

关键词： evolutionary computation iterative methods overcurrent protection relay protection directional overcurrent relay optimal coordination optimum pickup current selection boundary constraints iterative numerical algorithm numerical algorithm evolutionary approaches analytic approach overcurrent relay protection time dial setting selection

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Non-fourier heat conduction modeling in a finite medium

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INTERNATIONAL JOURNAL OF THERMOPHYSICS 2004年第4期25卷 1261-1268页

作者： Gembarovic, J Gembarovic, J TPRL Inc W Lafayette IN 47906 USA

A novel, simple iterative algorithm is used to calculate the temperature distribution in a finite medium for the case of non-Fourier (hyperbolic) heat conduction. In this algorithm the temperature is calculated explicitly in one simple calculation that is repeated for each time step as the heat wave propagates through the medium with constant speed. When the wave reaches a boundary of the medium, it bounces back and moves in the opposite direction. All simple initial and boundary conditions can be modelled. An example of using the algorithm for the case of a finite, thermally insulated medium is given, and the results are compared with an exact analytical solution.

关键词： non-Fourier heat conduction numerical algorithm temperature distribution

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Research on eddy current losses algorithm in solid rotor of high speed squirrel cage induction motor

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IET ELECTRIC POWER APPLICATIONS 2020年第6期14卷 1023-1029页

作者： Chou, Weixiang Liang, Yanping Gao, Lianlian Wang, Dongmei Harbin Univ Sci & Technol Coll Elect & Elect Engn Harbin Peoples R China

Aiming at the shortcomings of the analytical algorithm and numerical algorithm for calculating the eddy current losses in the solid rotor of high speed squirrel cage induction motor, this study proposes a semi-analytical algorithm. Based on the magnetic field of the rotor surface and Maxwell's equations, the analytical formula of this algorithm is derived. According to the law of energy conservation, the losses in rotor and rotor bars are calculated, respectively, so that the eddy current losses in the solid rotor are calculated indirectly. Taking a high speed squirrel cage induction motor as an example, the eddy current losses in the solid rotor are calculated by the semi-analytical method. The calculation result is verified by the two-dimensional transient finite-element method, and the calculation result meets the basic requirements of engineering practice.

关键词： rotors squirrel cage motors finite element analysis eddy current losses energy conservation magnetic fields Maxwell equations eddy current losses algorithm solid rotor analytical algorithm numerical algorithm semianalytical algorithm rotor surface rotor bars semianalytical method high speed squirrel cage induction motor magnetic field Maxwell equations energy conservation two-dimensional transient finite-element method

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Variational assimilation with covariance matrices of observation data errors for the model of the Baltic Sea dynamics

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RUSSIAN JOURNAL OF numerical ANALYSIS AND MATHEMATICAL MODELLING 2018年第3期33卷 149-160页

作者： Agoshkov, Valery I. Parmuzin, Eugene I. Zakharova, Natalia B. Shutyaev, Victor P. RAS Inst Numer Math Moscow 119333 Russia Moscow Inst Phys & Technol Dolgoprudnyi 141701 Moscow Region Russia

The mathematical model of the Baltic Sea dynamics developed at the Institute of numerical Mathematics of RAS is considered. The problem of variational assimilation of average daily data for the sea surface temperature (SST) is formulated and studied with the use of covariance matrices of observation data errors. Based on variational assimilation of satellite observation data, we propose an algorithm for solving the inverse problem of the heat flux reconstruction on the sea surface. The results of numerical experiments on reconstruction of the heat flux function are presented for the problem of variational assimilation of observation SST data.

关键词： Variational assimilation covariance matrices numerical algorithm determination of heat fluxes sea surface temperature

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Determination of the relaxation modulus of a linearly viscoelastic material

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MECHANICS OF TIME-DEPENDENT MATERIALS 2006年第2期10卷 125-133页

作者： Sorvari, Joonas Malinen, Matti Univ Kuopio Dept Phys FIN-70211 Kuopio Finland

In this paper, a numerical method for computing the relaxation modulus of a linearly viscoelastic material is presented. The method is valid for relaxation tests where a constant strain rate is followed by a constant strain. The method is similar to the procedure suggested by Zapas and Phillips. Unlike Zapas-Phillips approach, this new method can be also applied for times shorter than t (1)/2, where t (1) denotes time when the maximum strain is achieved. Therefore this method is very suitable for materials that experiences fast relaxation. The method is verified with numerical simulations. Results from the simulations are compared with analytical solution and Zapas-Phillips method. Results indicate that the presented approach is suitable for estimating the relaxation modulus.

关键词： numerical algorithm relaxation test finite ramp time relaxation modulus linear viscoelasticity

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Tensor projection mechanism and algorithm implementation

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APPLIED INTELLIGENCE 2021年第11期51卷 8176-8191页

作者： Wang, Fei Wang, Zhanchang Li, Xiang Chen, Yu Univ Technol Sydney Sydney NSW Australia China Geol Survey Xian Geol Survey Ctr Xian 710054 Peoples R China China Software & Technol Serv Co Ltd Beijing 102200 Peoples R China

This paper analyses the mechanism of tensor projection transformation in depth and introduces a high-efficiency original algorithm developed in a quantum computing language for forward and backward projection between multidimensional tensors and one-dimensional vectors. Additionally, the author compares this algorithm with similar methods from both the Python scientific computing package and other relative development kits in method calls and source code to demonstrate the innovation of the tensor projection algorithm. On this basis, the classical convolution operation program commonly used in machine learning has been parallelized and improved, the analysis algorithm of the Beidou communication satellite view area has been parallelized and improved, and the actual operating efficiency has been greatly improved. After verification, the tensor projection transformation successfully solves the problem of location index mapping of the entity units among different dimensions, can provide a means for optimizing the traditional model of traversal algorithm, and can have significant reference value in eigenspace transformation against a tensor field.

关键词： Tensor projection numerical algorithm Parallelization Quantum computation language

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From Gauss-Newton method solving nonlinear least squares problem of static overdetermined system to multi-instant neurodynamic algorithms handling future time-variant situation

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NONLINEAR DYNAMICS 2024年第20期112卷 18163-18193页

作者： Wu, Dongqing Zhang, Yunong Zhongkai Univ Agr & Engn Sch Math & Data Sci Guangzhou 510225 Peoples R China Sun Yat Sen Univ Sch Comp Sci & Engn Guangzhou 510006 Peoples R China Sun Yat Sen Univ Shenzhen Res Inst Shenzhen 518057 Peoples R China

Gauss-Newton method is mainly designed and exploited to solve the nonlinear least squares problems of static overdetermined systems with order-2 precision. When the system comes to the future time-variant situation, the disadvantages of the Gauss-Newton method in effectiveness and precision need to be overcome. On the basis of Zhang neurodynamics, the first Zhang neurodynamics model and the second Zhang neurodynamics model are constructed and discussed to obtain the nonlinear least squares solution of the time-variant overdetermined system in the future time-variant situation. Then, we propose a novel eleven-instant Zhang time discretization formula whose convergenceness and truncation errors of order-6 are proved through rigorous mathematical derivation. The proposed eleven-instant Zhang time discretization formula is thus utilized to discretize the constructed first Zhang neurodynamics model and second Zhang neurodynamics model, respectively. Consequently, a novel discrete-time eleven-instant first Zhang neurodynamics-based algorithm and a novel discrete-time eleven-instant second Zhang neurodynamics-based algorithm are proposed and generalized to obtain the predictive nonlinear least squares solution of the time-variant overdetermined system in the future time-variant situation. Furthermore, the precisions of the proposed discrete-time eleven-instant first Zhang neurodynamics-based and second Zhang neurodynamics-based algorithms are proved to be of order-6 through mathematical derivation. Moreover, this work reveals the facts that the Gauss-Newton method is actually the simplified version of the discrete-time two-instant first Zhang neurodynamics-based algorithm and the discrete-time two-instant second Zhang neurodynamics-based algorithm, respectively. Finally, five challenging numerical experiments, including the problem-solving of the critical force of a crane in a complicated environment, are carried out. The experimental results further substantiate the appli

关键词： Nonlinear least squares problem Zhang neurodynamics algorithm Time-variant overdetermined system Gauss-Newton method numerical algorithm

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