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Computer Modeling in Engineering & Sciences 2024年第8期140卷 2079-2102页

作者： Yujing Ma Zhongwang Wang Jieyuan Zhang Ruijin Huo Xiaohui Yuan College of Architecture and Civil Engineering Xinyang Normal UniversityXinyang464000China Henan International Joint Laboratory of Structural Mechanics and Computational Simulation College of Architecture and Civil EngineeringHuanghuai UniversityZhumadian463000China Academy of Military Sciences Beijing100091China Henan New Environmentally-Friendly Civil Engineering Materials Engineering Research Center Xinyang Normal UniversityXinyang464000China

In this paper,an adaptive polynomial chaos expansion method(PCE)based on the method of moments(MoM)is proposed to construct surrogate models for electromagnetic scattering and further sensitivity analysis.The MoM is applied to accurately solve the electric field integral equation(EFIE)of electromagnetic scattering from homogeneous dielectric targets.Within the bistatic radar cross section(RCS)as the research object,the adaptive PCE algorithm is devoted to selecting the appropriate order to construct the multivariate surrogate model.The corresponding sensitivity results are given by the further derivative operation,which is compared with those of the finite difference method(FDM).Several examples are provided to demonstrate the effectiveness of the proposed algorithm for sensitivity analysis of electromagnetic scattering from homogeneous dielectric targets.

关键词： Adaptive polynomial chaos expansion method method of moments radar cross section electromagnetic scattering

Extended velocity slip boundary condition for non-equilibrium gas flows from the method of moments

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Extended velocity slip boundary condition for non-equilibriu...

Application of a multiregion model to the EM scattering from a rough surface with or without a target above it

第十一届全国流体力学学术会议

作者： Qin Yang Haijun Zhang College of Mechanical & Electrical Engineering Jiaxing University College of Mathematics and Physics Engineering Jiaxing University

One of the drawbacks of the existing slip boundary conditions for the Navier-Stokes equation is that the slip coefficients are fixed, which limits the use of the high order slip models in the near transition regime(0.1 < Kn ≤ 1). In this paper, according to the linearized regularized 13 moment equations and their boundary conditions, an extended velocity slip boundary condition for non-equilibrium gas flows has been proposed and its slip coefficients would change with the Knudsen number and the accommodation coefficient. In comparison with the existing slip models, the mass flow rate predicted by the extended slip model shows a better agreement with that computed by the linearized Boltzmann equation.

关键词： slip boundary non-equilibrium gas flows method of moments

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Chinese Physics B 2011年第5期20卷 12-22页

作者：王安琪郭立新柴草 School of Science Xidian University

An efficient multiregion model is introduced to calculate the electromagnetic scattering from a perfectly electrical conducting （PEC） rough surface with or without a PEC target above it. In the multiregion model, the rough surface is split into multiple regions depending on their position along the rough surface. Two intermediate regions are chosen as the dominant region. If a target is located above the rough surface, the target will also be included in the dominant region. The method of moments （MOM） is only adopted on the dominant region to ensure validity. Hence, the new model can greatly reduce the number of unknowns associated with full MOM analysis. The induced electric currents on the other regions are obtained by approximately considering the mutual coupling between different regions along the rough surface. Compared with the published hybrid method, this new model is not only suitable for EM scattering from a target above a rough surface but also applicable for just rough surfaces. Several numerical simulations are presented to show the validity and efficiency of the multiregion model.

关键词： multiregion model electromagnetic scattering rough surface method of moments

Efficient approaches of determining the motion of a spherical particle in a swirling fluid flow using weighted residual methods

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Particuology 2015年第6期13卷 68-74页

作者： Seiyed E. Ghasemi M. Vatani D.D. Ganji Young Researchers and Elite Club Qaemshahr Branch Islamic Azad University Qaemshahr lran Department of Mechanical Engineering Babol University of Technology Babol lran

The motion of a spherical particle released in a swirling fluid flow is studied employing the least-squares method and method of moments. The governing equations are obtained and solved employing the two methods. The accuracy of the results is examined against the results of a fourth-order Runge-Kutta numer- ical method. The effects of various parameters, namely the initial radius, initial radial velocity, initial angular velocity, and drag-to-inertia ratio, on the non-dimensional velocity profiles and particle position distribution are considered. The results show that the radial velocity increases over time while the angular velocity decreases, and that an increase in the initial radial velocity increases the particle radial distance and angular velocity but decreases the radial velocity profile.

关键词： Spherical particle Swirling flow Radial velocity Angular velocity Least-squares method method of moments

MoM-based topology optimization method for planar metallic antenna design

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Acta Mechanica Sinica 2016年第6期32卷 1058-1064页

作者： Shutian Liu Qi Wang Renjing Gao State Key Laboratory of Structural Analysis for Industrial Equipment Dalian University of Technology

The metallic antenna design problem can be treated as a problem to find the optimal distribution of conductive material in a certain domain. Although this problem is well suited for topology optimization method, the volumetric distribution of conductive material based on 3D finite element method (FEM) has been known to cause numerical bottlenecks such as the skin depth issue, meshed 'air regions' and other numerical problems. In this paper a topology optimization method based on the method of moments (MoM) for configuration design of planar metallic antenna was proposed. The candidate structure of the planar metallic antenna was approximately considered as a resistance sheet with position-dependent impedance. In this way, the electromagnetic property of the antenna can be analyzed easily by using the MoM to solve the radiation problem of the resistance sheet in a finite domain. The topology of the antenna was depicted with the distribution of the impedance related to the design parameters or relative densities. The conductive material (metal) was assumed to have zero impedance, whereas the non-conductive material was simulated as a material with a finite but large enough impedance. The interpolation function of the impedance between conductive material and non-conductive material was taken as a tangential function. The design of planar metallic antenna was optimized for maximizing the efficiency at the target frequency. The results illustrated the effectiveness of the method.

关键词： Metallic antenna design Topology optimization method of moments Resistance sheet Impedance boundary condition

Efficient Analysis of Surface-Wire Configurations Using AIM and Best Uniform Rational Approximation

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Chinese Journal of Electronics 2015年第4期24卷 877-883页

作者： DONG Hailin GONG Shuxi WANG Xing ZHANG Penfei ZHAO Bo Science and Technology on Antenna and Microwave Laboratory Xidian University

The Adaptive integral method(AIM) in conjunction with the best uniform approximation technique is applied to analyze the electromagnetic problems of surface-wire junction geometries over a wide frequency band. To improve the computation efficiency, the best uniform approximation method is utilized. The AIM can reduce memory requirements and accelerate the matrixvector multiplications in iterative process. Some numerical examples are shown to demonstrate the efficiency and accuracy of the proposed method. Compared with the direct solution method and Asymptotic waveform evaluation(AWE) technique, the proposed technique is found to be efficient in a broadband with the lower Central processing unit(CPU) time required and without loss of accuracy.

关键词： Surface-wire junctions Adaptive integral method Best uniform approximation Asymptotic waveform evaluation method of moments

Electromagnetic scattering from two-layered rough interfaces with a PEC object:vertical polarization

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Chinese Physics B 2011年第5期20卷 23-32页

作者：王安琪郭立新柴草 School of Science Xidian University

Electromagnetic （EM） scattering from a stack of two rough interfaces separating a homogeneous medium with a perfectly electric conducting （PEC） object has been calculated through the method of moments for vertical polarization. Theoretical formulations of EM scattering from multi-layered rough interfaces with a PEC object have been derived in detail and the total fields and their normal derivatives on the rough interfaces are solved. The two-layered model is a special case. In this work, a Gaussian rough surface was applied to simulate the rough interface. A cylinder was located above, between or below the two-layered rough interfaces. Through numerical simulations, the validity of this work is demonstrated by comparing it with existing scattering models, which are special cases that include a PEC object located above/below a single-layered rough interface and two-layered rough interfaces without an object. Subsequently, the influences of characteristic parameters, such as the relative permittivity of the medium, as well as the average height between the two rough surfaces, on the bistatic scattering coefficient are discussed.

关键词： composite scattering two-layered rough interfaces electromagnetic wave scattering method of moments

Texture invariant estimation of equivalent number of looks based on log-cumulants in polarimetric radar imagery

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Journal of Systems Engineering and Electronics 2017年第1期28卷 58-66页

作者： Xianghui Yuan Tao Liu School of Electronic Engineering Naval University of EngineeringWuhan 430033China

A novel estimation of the equivalent number of looks (ENL) is proposed in statistical modeling of multilook polarimetric synthetic aperture radar (PolSAR) images for the product model, which is based on the log-determinant moments (LDM). The LDM estimators discovered by looking at certain log-cumulants of the intensities of different polarization channels and the multilook polarimetric covariance matrix, which can be used for both the Gaussian model and all product models. This estimator has analytic expressions, and uses the full covariance matrix and intensities as input, which makes more statistical information available. Experiments based on simulated data and real data are performed. The comparisons among the widely used methods of equivalent number of looks (ENL) estimation for the product model such as K and G0 distributions show that the performance of the LDM estimator is outstanding. The performance of estimators for the real data of San Francisco and Flevoland is analyzed and the results are according to those of simulated data. Finally, it can be concluded that the LDM estimator is well robust to each product model with low computational complexity and high accuracy. ? 1990-2011 Beijing Institute of Aerospace Information.

关键词： Covariance matrix Matrix algebra method of moments Parameter estimation Polarimeters Radar Radar imaging Tracking radar

Moment method with Wavelet Expansions for Fractal Rough Surface Scattering

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Chinese Physics Letters 2002年第11期19卷 1617-1620页

作者： Guo Li-Xin Wu Zhen-Sen School of Science Xidian University Xi'an 710071

We study the moment method (MM) to deal with Harr wavelet basis due to the problem of electromagnetic scattering from the fractal rough surface. The vanishing moment properties and the capability of the wavelets to adjust themselves to the fractal surface lead to a sparse impedance matrix and faster computation. Compared to the measured data and the conventional MM, the result shows that the wavelet basis functions provide substantial reductions in both memory requirements and computation time.

关键词： method of moments

Nanotaper mode converter based on silicon pillar waveguide

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Chinese Optics Letters 2009年第4期7卷 312-314页

作者：易华祥祝阳周治平 Wuhan National Laboratory for Optoelectronics College of Science and EngineeringHuazhong University of Science and Technology State Key Laboratory on Advanced Optical Communication Systems and Networks Peking University School of Electrical and Computer Engineering Georgia Institute of Technology

A two-dimensional （2D） optimized nanotaper mode converter is presented and analyzed using the finite- difference time-domain （FDTD） method. It can convert the mode size in a silicon pillar waveguide （PWG） from 4 μm to 1 μm over a length of 7 μm and achieve a transmission efficiency of 83.6% at a wavelength of 1.55 μm. The dual directional mode conversion of the nanotaper and its ability to perform mode compression and expansion are also demonstrated. The broadband with high transmittance is satisfied in this structure. Using this silicon-based nanotaper, mode conversion between integrated photonic devices can be more compact and efficient.

关键词： Finite difference time domain method method of moments Plants (botany) Waveguides