MEI系数的快速计算及其在电大尺寸电磁散射问题中的应用

本文针对电大尺寸导体柱电磁散射问题,利用跳点平均的方法来加速MEI系数的求取,并结合快速MEI算法,使总的求解时间在快速MEI的基础上缩短近十倍。数值计算结果证明了该方法的正确性和有效性,并进一步讨论了合适的跳点距离。     

MEI系数循环卷积的快速解法

提出了一种用于减少不变量测试方程(MEI)法计算时间的快速算法,循环卷积和快速多极子(FMM)技术(CC-FMM)分别用于不同区域对应的MEI系数,可以加速建立不变量测试方程所需系数的计算.由于循环卷积和FMM的计算效率明显高于直接求和,故整个算法的计算时间明显减少.二维验算实例验证了这种算法的有效性和准确度.     

基于MEI方法的贴体网格FDTD方法

利用Thompson变换在任意形状的散射体外部产生共形的外部计算网格,并使FDTD计算区域的截断边界与散射体边界形状完全一致,时域不变性测试方程(MEI)方法被作为该截断边界上的局域吸收边界条件,从而大大压缩了FDTD的计算空间.数值试验结果证实,该方法可在不降低计算精度的前提下减少计算机内存需求.     

基于MEI吸收边界条件的导体柱散射问题模拟

首次在圆柱坐标系时域有限差分 (FDTD)法中采用基于时域不变性测试方程 (MEI)方法的吸收边界条件 ,对导体圆柱的电磁散射问题进行了数值模拟研究。在相同计算条件下 ,与应用Bayliss Turkel二阶辐射边界条件的FDTD结果相比较 ,直观地表明MEI方法结果与解析解吻合更好     

时域MEI方法在矩形导体柱散射问题中的应用

本文用时域有限差分法（FDTD）模拟二维矩形导体柱的电磁散射场，采用时域不变性测试方程（MEI）作为吸收边界条件对该散射场进行求解。将所得计算结果与截断边界网格点采用Mur二阶吸收边界条件所得的数值结果相比较，两者吻合很好。结果表明使用时域MEI方法作为吸收边界条件能有效缩短截断边界与物体边界的距离，且能得到足够精确的解。     

传输线与延迟线

0102204时域 MEI 方法初探[刊]/廖成//电波科学学报.—2000,15(3).—323～327(K)对时域 MEI 方法进行了初步探索,根据 MEI 方法的基本原理.建立起时域 MEI 方法的一阶吸收边界条件.应用该条件对线源辐射问题的数值实验和研究表明.它可使截断边界离源更近。同时也证实了时域MEI方法的可行性和精确性。参13Y2000-62483-45 0102205嵌入式自定时系统的芯片级动态再校准延迟线=Anon-chip dynamically recalibrated delay line for embeddedself-timed systems[会,英]//2000 IEEE 6th Internation-al Symposium on Advanced Research in AsynehronousCircuits and Systems.—45～51(EC)     

基于MEI方法的贴体网格FDTD方法

利用Thompson变换在任意形状的散射体外部产生共形的外部计算网络,并使FDTD计算区域的截断边界与散射体边界形状完全一致,时域不变性测试方程（MEI）方法被作为该截断边界上的局域吸收边界条件,从而大大压缩了FDTD的计算空间。数值试验结果证实,该方法可在不降低计算精度的前提下减少计算机内存需求。     

非均匀介质多柱体散射的计算

本文运用迭代MEI过程对非均匀介质柱的多柱体散射进行了计算。该迭代过程充分运用了不变性特点，使MEI方程在各次迭代中反复使用，不仅减少了计算量也大大减少了所需的内存空间．对于不规则网格剖分下有限差分方程的建立，则采用了一种广义的测试系数的方法。文中将均匀介质多柱体散射作为非均匀情况之特例，与已有结果作了对比，获得良好的一致性。对非均匀介质柱的计算，也提供了算例。     

合作目标与背景温度对比度的确定

在对武器装备中的红外系统进行靶场测试时,需要确定合作目标与背景的温度对比度.以作为测量基准.以测温热像仪摄取的图像为基本信息,基于目标与背景温度对比度的定义,参考常规检测和选取方法,结合合作目标的特点编制了确定温度对比度的软件,得出温度对比度的具体数值.通过实验测试,分析了不同选取方法对温度对比度的影响,对靶场测试等实际应用有参考价值,也为进一步建立各参数与温度对比度之间的关系模型提供了基础.     

大功率LED针翅式散热器散热性能数值模拟

发光二极管(LED)作为新一代光源,得到广泛应用.然而在工作过程中,大部分的电能会转变为热能,使LED的结温升高,可靠性降低.为了使LED芯片产生的热量能够及时有效地散发出去,通常采用翅片散热方法对其进行散热.采用数值模拟的方法对大功率LED针翅式散热器的散热性能进行了研究.为了验证模型的准确性,利用K型热电偶和安捷伦数据采集仪对散热器进行了实验测试.实验结果表明,该数值模型方程能够很好地模拟散热器的散热性能.此外,研究了大功率LED针翅式散热器的几何参数(翅片高度、半径、排数、列数)对LED散热性能(结温、对流换热系数和热阻)的影响,并且对翅片结构进行了优化分析.     

Domain-decomposed MEI method for field computation in single andmultiple regions

The domain-decomposed measured equation of invariance (DDMEI) method is proposed for field computation in single and multiple regions. The whole computing domain is partitioned into a cluster of subdomains. For single region problems, this partition splits the computing domain into many subdomains artificially. For multiple regions problems, these subdomains can be taken as those regions separated geometrically. The contribution of sources residing in a subdomain is approximated by a set of sources selected out of these original sources with greatly reduced amounts. The approximation is implemented numerically by the MEI method. The resultant MEI matrices are blocked matrices and each submatrix is highly sparse. Approaches and numerical results are given respectively for the applications of the DDMEI to the scattering of single conducting cylinders, radiation of wire arrays, and capacitance matrix computation for multiconductor transmission lines. The DDMEI proposed in this paper is an improved version of the surface current MEI method (SCMEI). Compared with the SCMEI, the DDMEI improves the sparsity of the MEI matrices and the feasibility of measuring out the MEI coefficients. Furthermore, the DDMEI makes it possible to apply the kind of on-surface MEI methods (OSMEI) to multiple region problems for the first time     

An iterative algorithm based on the measured equation of invariancefor the scattering analysis of arbitrary multicylinders

It is known that the measured equation of invariance (MEI) is generally valid for outgoing waves just as other absorbing boundary conditions (ABCs). However, for the scattering problem of multicylinders, the scattered field from one cylinder is just the in-going incident wave to other cylinders. So the MEI cannot be directly applied to the scattering problem of multicylinders. In this paper, an iterative algorithm based on the MEI is first proposed for the scattering problems of multicylinders with arbitrary geometry and physical parameters. Each cylinder is coated with several layers of meshes and the MEIs are applied to the truncated mesh boundaries. It has been demonstrated that the MEI can truncate the meshes very close to the surfaces of the cylinders and then results in dramatically savings in memory requirements and computational time. The MEI coefficients of each cylinder can be stored and reused to form the sparse matrices during each iteration procedure as they are independent of excitations. So more central processing unit (CPU) time is saved as the MEI coefficients are calculated only once in the algorithm. The method can be applied to problems of various kinds of multiple cylinders with arbitrary configurations and cross sections. Numerical results for the scattered fields are in good agreement with the data available. Finally, examples are given to show the iterative algorithm applicable to electrically large multicylinders coated with lossy media     

Measured equation of invariance with linear tensor relation for three-dimensional scattering problems

The postulate of a linear tensor relation in the measured equation of invariance (MEI) is proposed for three-dimensional (3D) problems. As a result, all three components of the field vector to be solved are coupled in the MEI. Combined with the finite difference method, the present method is applied to the analysis of scattering by 3D conducting objects and results in a significant improvement in the accuracy of numerical results as compared to those obtained with an uncoupled linear relation.     

MEI系数的快速算法

不变性测试方程法已被证明是解决电磁问题的一种有效方法。目前电大尺寸问题中ＭＥＩ系数的计算已成为一个瓶颈。提出了一个快速算法用于加速ＭＥＩ系数的计算,它使用快速多极子方法计算测试子的散射场,使得ＭＥＩ系数的计算速度从Ｏ（Ｎ＾２）变为Ｏ（Ｎ＾１．５Ｌｏｇ２Ｎ）。     

An efficient mixed algorithm of L-MEI and DDM for the wavescattering by a concave cylinder

In this paper, a localized MEI method (L-MEI) is developed and combined with the domain decomposition method (DDM) for the simulation of scattering by a concave cylinder. In the L-MEI, the whole domain is decomposed into many subdomains. Different from the conventional MEI method, the MEI coefficients of the L-MEI method in each subdomain are only dependent on the localized metrons that are defined in the subdomain. The localization of metrons has the following advantages: (1) speeding up the calculation of MEI coefficients and saving memory, (2) making the MEI method available for concave structures, and (3) obtaining a band sparse matrix directly without any modification     

Electrostatic solution for three-dimensional arbitrarily shapedconducting bodies using finite element and measured equation ofinvariance

Differential equation techniques such as the finite element (FE) and finite difference (FD) have the advantage of sparse system matrices that have relatively small memory requirements for storage and relatively short central processing unit (CPU) time requirements for solving electrostatic problems. However, these techniques do not lend themselves as readily for use in open-region problems as the method of moments (MoM) because they require the discretization of the space surrounding the object where the MoM only requires discretization of the surface of the object. A relatively new mesh truncation method known as the measured equation of invariance (MEI) is investigated augmenting the FE method for the solution of electrostatic problems involving three-dimensional (3-D) arbitrarily shaped conducting objects. This technique allows truncation of the mesh as close as two node layers from the object. The MEI views sparse-matrix numerical techniques as methods of determining the weighting coefficients between neighboring nodes and finds those weights for nodes on the boundary of the mesh by assuming viable charge distributions on the surface of the object and using Green's function to measure the potentials at the nodes. Problems in the implementation of the FE/MEI are discussed and the method is compared against the MoM for a cube and a sphere     

Validity of the measured equation of invariance

The measured equation of invariance (MEI) is derived without any postulates. It is shown that the coefficients of the MEI are invariant to the field of excitation. However, the accuracy of the MEI solution is closely related to the number of nodes in the MEI. Coupling more nodes improves progressively the accuracy of the MEI solution. With increasing nodes, the matrix problem for the determination of the MEI coefficients becomes seriously ill conditioned and generally must be solved using multiple precision arithmetic. The consequences of the ill-conditioning phenomenon are discussed     

Application of discrete periodic wavelets to measured equation ofinvariance

Recently, the wavelet expansions have been applied in field computations. In the frequency domain, the application is focused on the thinning of matrices arising from the method of moment (MoM). The thinning of matrices can best be done by the measured equation of invariance (MEI), which provides sparsity almost without sacrificing accuracy in that the boundary equation it entails is convertible to that of the MoM. The real power of the wavelet expansions is to give high resolution in convolution integrals. High resolution is also needed in the process of finding the MEI coefficients, which are obtained via an integration process almost identical to that of the MoM. In this paper, it is shown that when the fast discrete periodic wavelets (FDPW) are used as metron currents in the MEI method, the resolutions of the MEI coefficients are improved at high-frequency computations or at geometric extremities. The level of sparsity of the MEI is much more favorable than that achievable by the thinning of MoM matrix using the wavelet expansions. The role of FDPW in the MEI happens to be more fitting than its place in the MoM