均匀各向异性介质球散射的解析研究

将均匀各向异性介质重构为电学上的无耗各向同性介质,得到了重构目标的散射截面;进而得到了主坐标系中无耗各向异性介质球的散射截面,将介质退化到各向同性介质时,各向异性介质球的散射截面与Mie理论完全一致,验证了所得结果的正确性;仿真结果表明:散射截面正比于目标介电常数张量的元素且随入射方向的变化而变化;所得结果为复杂形体各向异性介质目标的散射评判提供了理论基础。     

磁化冷等离子体球的太赫兹散射特性

基于位函数的引入与介质参量无关,将各向异性目标内外的电场展为级数形式,得到了任意各向异性目标n阶散射场、目标内场的递推表达式,给出了介电常量张量的变换关系,在平面波任意入射的条件下,并给出了传播单位矢量与极化单位矢量的一般关系.以磁化冷等离子体为例,给出了一阶散射场的具体表达式,并对二阶散射场引起的误差进行了评估.在THz波段和光波段,对所得结果进行了部分仿真.结果表明:微分散射对电波频率和极化状态等因素的影响较为敏感,介电常量张量的非对角元素对散射的影响不大,当波长与目标尺寸一定时,仿真结果不仅适用于THz波段,对其它波段也成立.     

双向隐形传态方案及安全性分析

基于位函数的引入与介质参量无关,将各向异性目标内外的电场展为级数形式,得到了任意各向异性目标n阶散射场、目标内场的递推表达式,给出了介电常量张量的变换关系,在平面波任意入射的条件下,并给出了传播单位矢量与极化单位矢量的一般关系.以磁化冷等离子体为例,给出了一阶散射场的具体表达式,并对二阶散射场引起的误差进行了评估.在THz波段和光波段,对所得结果进行了部分仿真.结果表明:微分散射对电波频率和极化状态等因素的影响较为敏感,介电常量张量的非对角元素对散射的影响不大,当波长与目标尺寸一定时,仿真结果不仅适用于THz波段,对其它波段也成立.     

磁化冷等离子体球的瑞利散射

给出了不同坐标系中介质参数张量的变换,得到了磁化冷等离子体球电场的表达式,得出了任意各向异性目标散射场的表达式,研究了磁化冷等离子体球的微分散射截面、散射截面等的函数关系,仿真结果与有关文献一致,表明了本算法的有效性,从而为各向异性目标识别等提供理论支持。     

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给出了不同坐标系中介质参数张量的变换,得到了磁化冷等离子体球电场的表达式,得出了任意各向异性目标散射场的表达式,研究了磁化冷等离子体球的微分散射截面、散射截面等的函数关系,仿真结果与有关文献一致,表明了本算法的有效性,从而为各向异性目标识别等提供理论支持。     

基于多尺度理论的电各向异性介质椭球内电场

 基于电磁场的多尺度变换理论,将一个各向异性介质椭球重构为一个各向同性介质椭球,进一步得到了新椭球的形体参数。利用各向同性椭球电磁场与各向异性椭球电磁场的多尺度关系,得出了各向异性介质椭球内电场的解析表达式,对所得结果进行了验证。计算了椭球内电场方向与外电场方向的夹角,仿真结果表明：外电场的方向对椭球内电场的影响不大,介电常数张量对椭球内电场的方向和大小有较大的影响。     

介质球的各向异性瑞利散射

基于电磁场的多尺度理论,研究了各向异性介质球内、外电场的规律,导出了各向异性目标散射场的表达式,得到了各向异性介质目标散射振幅、散射截面等的解析表达式,并对其正确性进行了检验.仿真结果表明:各向异性介质球的散射具有偶极辐射的特点,介电常量越大,产生的偶极矩也愈大,散射也越强.其结果可为各向异性目标监测、各向异性光散射研究等提供理论支持.     

双光束任意入射各向异性涂层球的散射特性

基于广义洛伦兹-米理论,研究两个聚焦的高斯光束沿着任意方向入射单轴各向异性涂层球的散射特性。基于球矢量波函数的正交特性,推导得到双高斯光束的球矢量波函数展开表达式。通过引入傅里叶变换,求解得到各向异性涂层区域内的电磁场展开式,将涂层球各区域的电磁场用球矢量波函数展开,再结合边界条件,得到沿任意方向传播的双高斯光束入射到涂层球的散射系数和雷达散射截面。数值模拟了雷达散射截面随散射角变化的分布,将单轴各向异性涂层球退化为单轴各向异性球时的散射结果与文献进行对比,结果十分吻合。分析双光束的入射角、粒子内半径、涂层厚度与内半径的比值、电和磁各向异性对散射强度及其散射角分布的影响。该理论和数值分析能够为激光对涂层颗粒的探测、散射以及光学操作提供有益帮助。     

结构各向异性对传输平均自由程的影响研究

本文研究了由定向排布的椭球形粒子组成的无序介质中微纳结构的各向异性对辐射传输平均自由程的影响机理。采用离散偶极子算法(DDA)计算单个椭球形粒子的各向异性辐射特性,为了得到多重散射下的各向异性介质的辐射特性,采用随机行走方法研究了传输平均自由程随粒子浓度、长径比、分布角度的变化关系,并与各向同性理论的计算结果进行了对比,证明了现有理论的不足。最后,利用辐射传递方程的扩散理论得到了椭球形粒子各向异性介质的表面反射能量分布图。结果表明,微纳结构的各向异性对辐射传输平均自由程和表面辐射能量分布有较大影响,对于各向异性较强的介质,在理论计算中必须加以考虑。     

C波段球体目标系的瑞利复合散射特性

在C波段研究了一对介质球体目标的瑞利复合电磁散射特性, 得到了目标复合散射截面解析式, 验证了所得结果的正确性; 研究了入射波极化状态、目标距离、目标大小、介电常数等因素对复合散射截面的影响, 结果表明, 邻近目标对本目标散射的影响具有偶极辐射的特点, 主目标的复合散射截面是邻近目标的大小、介电常数及其位置等因素的函数; 结果为目标散射截面的准确测量、电磁相互作用等奠定了理论基础。     

Born expansion of the Casimir–Polder interaction of a ground-state atom with dielectric bodies

Within leading-order perturbation theory, the Casimir–Polder potential of a ground-state atom placed within an arbitrary arrangement of dispersing and absorbing linear bodies can be expressed in terms of the polarizability of the atom and the scattering Green tensor of the body-assisted electromagnetic field. Based on a Born series of the Green tensor, a systematic expansion of the Casimir–Polder potential in powers of the electric susceptibilities of the bodies is presented. The Born expansion is used to show how and under which conditions the Casimir–Polder force can be related to microscopic many-atom van der Waals forces, for which general expressions are presented. As an application, the Casimir–Polder potentials of an atom near a dielectric ring and an inhomogeneous dielectric half space are studied and explicit expressions are presented that are valid up to second order in the susceptibility. PACS 12.20.-m; 34.50.Dy; 34.20.-b; 42.50.Nn     

Fast iterative approach to the difference scattering from a dielectric target above a rough surface

The difference field RCS (d-RCS) has been defined to analyze the scattering from the target above a rough surface. The electric field integral equations (EFIEs) of the difference induced currentJ _sd on the rough surface, the induced electric currentJ _o and magnetic currentK _o on the dielectric target under a TE wave incidence are derived. A small portion of the rough surface towards the target along the specular direction is taken to compute the scattering contributionE _s0 from the rough surface towards the target, which improves the computation speed. A numerical iterative approach is developed to solve the EFIEs and bistatic d-RCS. The surface length for iterations is dependent on the scattering angle and discussed for comparison with Johnson’s method. Using the Monte-Carlo method to generate the Pierson-Morkowitz (P-M) ocean-like rough surface, bistatic d-RCS of the dielectric target, e.g. a cylinder or a square column, above the rough surface is numerically simulated. The induced electric and magnetic currents on the dielectric target and the difference induced current on the rough surface are numerically discussed.     

Fast iterative approach to the difference scattering from a dielectric target above a rough surface

1 Introduction Electromagnetic scattering from the target above or beneath a rough surface has at- tracted much interest during recent years, because of extensive applications to radar surveillance, target detection, ground radar probing, and so on[1―3]. In order to numeri- cally simulate scattering from composite model of the target and underlying rough sur- face, some fast numerical methods, such as general forward backward method and spec- trum acceleration algorithm (GFBM/SAA)[4,5], fin…     

Anisotropic ellipsoidal inclusion with an anisotropic shell in an isotropic medium subjected to a uniform electric field

An electrostatic problem has been solved for a dielectric inclusion that consists of an anisotropic core and an anisotropic shell. The inclusion is immersed in a uniform isotropic medium (matrix) subjected to a uniform electric field. It is assumed that the outer boundaries of the core and shell are ellipsoidal and become confocal after a linear nonorthogonal transformation that removes the anisotropy of the dielectric properties of the shell. Analytical expressions have been derived for the potential and strength of the electric field in the matrix and also in the shell and core of the inclusion, and an expression for the polarizability tensor of the inclusion has been deduced. It has been shown that the results agree with the well-known solutions in partial (limiting) cases.     

Dielectric tensor elements for the description of waves in rotating inhomogeneous magnetized plasma spheroids

The dielectric permittivity tensor elements of a rotating cold collisionless plasma spheroid in an external magnetic field with toroidal and axial components are obtained. The effects of inhomogeneity in the densities of charged particles and the initial toroidal velocity on the dielectric permittivity tensor and field equations are investigated. The field components in terms of their toroidal components are calculated and it is shown that the toroidal components of the electric and magnetic fields are coupled by two differential equations. The influence of thermal and collisional effects on the dielectric tensor and field equations in the rotating plasma spheroid are also investigated. In the limiting spherical case, the dielectric tensor of a stationary magnetized collisionless cold plasma sphere is presented.     

Tensor polarized γ-deuteron Compton scattering in effective field theory

The differential cross section for γ-deuteron Compton scattering from a tensor polarized deuteron is computed in an effective field theory. The first non-vanishing contributions to this differential cross section are the interference terms between the leading electric coupling diagrams and the subleading single potential pion exchange diagrams or the subleading magnetic moment coupling diagrams. At 90° photon scattering angle, only the pion term contributes at this order to the tensor polarized differential cross section. This provides a clean way to study the photon pion dynamics in the two nucleon sector. The effect is measurable for photon energies between 40 and 80 MeV provided the uncertainty in the measured cross sections are ≲ 7%.