使用等效偶极子的快速时域体表面积分方程求解器

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"这篇论文是‘A Fast Time-Domain Volume Surface Integral Equation Solver Using the Equivalent Dipole Moment’,由呼延龙、李兆龙和陈如山等人撰写,发表在中国科技论文在线平台上。该研究主要关注如何利用等效偶极子方法来加速时域体面积分方程的求解,特别是针对金属与介质混合目标的瞬态电磁散射问题。文章得到了国家博士后基金的资助,作者的研究兴趣包括计算电磁学、天线、电磁散射和传播等领域。通信作者李兆龙是南京理工大学的副教授,专注于雷达前端设计、天线阵列及微波/毫米波被动和主动电路设计。" 本文的核心内容是将等效偶极子方法应用于时域推进(MOT,Marching-On-In-Time)的体面积分方程(VSIE)求解器中,以提高解决瞬态电磁散射问题的效率。等效偶极子方法是一种常用的近似技术,它通过将复杂的物体或结构简化为一系列偶极子来模拟其电磁行为,这些偶极子可以代表物体表面的电荷和电流分布。 在传统的时域体面积分方程方法中,通常需要对每个时间步长进行大量的积分计算,这可能导致计算复杂度的增加和求解速度的降低。呼延龙等人的创新之处在于,他们将等效偶极子引入到这种时间步进过程中,以减少计算量,从而实现更快的求解速度。这一改进对于处理金属和介质混合目标的瞬态电磁散射问题特别有效,因为这类问题往往涉及到复杂的电磁相互作用和动态变化。 MOT方法是一种常用的时域求解策略,它通过逐时间步长推进来解决偏微分方程,适用于模拟随时间变化的系统。结合等效偶极子,这种方法能够更有效地追踪电磁场随时间的演化,特别是在涉及大量自由电荷和电流分布的情况下。 论文还可能讨论了算法的实现细节,包括偶极子的分布和更新策略,以及如何通过数值积分技术来近似表面积分。此外,可能还进行了数值实验和对比分析,以验证新方法的准确性和效率,并与其他已知求解技术进行比较。 这项研究为解决瞬态电磁散射问题提供了一个新的高效工具,对于电磁建模和仿真领域具有重要的理论和应用价值,尤其是在雷达、通信、遥感和其他依赖于精确电磁分析的领域。通过引入等效偶极子,不仅可以优化计算过程,还能为复杂场景的电磁问题提供快速而准确的解决方案。

For macroscopically anisotropic media in which the variations in the phase stiffness tensor are small, formal solutions to the boundary-value problem have been developed in the form of perturbation series (Dederichs and Zeller, 1973; Gubernatis and Krumhansl, 1975 ; Willis, 1981). Due to the nature of the integral operator, one must contend with conditionally convergent integrals. One approach to this problem is to carry out a “renormalization” procedure which amounts to identifying physically what the conditionally convergent terms ought to contribute and replacing them by convergent terms that make this contribution (McCoy, 1979). For the special case of macroscopically isotropic media, the first few terms of this perturbation expansion have been explicitly given in terms of certain statistical correlation functions for both three-dimensional media (Beran and Molyneux, 1966 ; Milton and Phan-Thien, 1982) and two-dimensional media (Silnutzer, 1972 ; Milton, 1982). A drawback of all of these classical perturbation expansions is that they are only valid for media in which the moduli of the phases are nearly the same, albeit applicable for arbitrary volume fractions. In this paper we develop new, exact perturbation expansions for the effective stiffness tensor of macroscopically anisotropic composite media consisting of two isotropic phases by introducing an integral equation for the so-called “cavity” strain field. The expansions are not formal but rather the nth-order tensor coefficients are given explicitly in terms of integrals over products of certain tensor fields and a determinant involving n-point statistical correlation functions that render the integrals absolutely convergent in the infinite-volume limit. Thus, no renormalization analysis is required because the procedure used to solve the integral equation systematically leads to absolutely convergent integrals. Another useful feature of the expansions is that they converge rapidly for a class of dispersions for all volume fractions, even when the phase moduli differ significantly.

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