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.     

广义传播矩阵法分析分层各向异性材料对电磁波的反射与透射

在实验室坐标系下由Maxwell旋度方程出发构造了横向场的状态矢量和耦合矩阵,讨论了各 向异性介质中的特征波.通过引入横向场的传播矩阵,进而得到分层各向异性介质的反射系数和透射系数的解析表达式.该式可以适用于一般情况,包括分层单轴各向异性材料和回旋介质,以及半空间各向异性介质的反射和透射问题. 关键词： 广义传播矩阵 各向异性介质 反射与透射     

双相各向异性随机介质伪谱法地震波场特征分析

各向异性、双相孔隙以及非均匀性是描述油气储层时应综合考虑的. 结合随机介质理论和双相介质模型建立了双相各向异性随机介质模型,采用伪谱法模拟了双相各向异性随机介质地震波场,结果表明：双相各向异性随机介质地震波场存在散射波、旅行时扰动等复杂的波场特征,这些特征强烈依赖于随机介质模型参数. 在大非均匀空间尺度下,非均匀幅度主要影响波的旅行时扰动;在小非均匀空间尺度下,非均匀幅度主要影响波的散射. 该研究使人们有可能在统计意义下反演油气储层的非均匀特征,有益于加深对地震波在油气储层中传播规律的认识. 关键词： 双相各向异性 随机介质 伪谱法 地震波     

电偶极子在磁各向异性介质中的辐射功率

在经典电动力学框架下对磁各向异性介质中的电磁辐射问题进行研究, 得到了电偶极子在磁各向异性介质中的辐射功率表达式. 当介质为磁各向同性时其结果与文献报道的结果相符合, 验证了推导结果的正确性. 利用本文结果可对电偶极子在磁各向异性介质中的辐射效果做出判断, 而且对于进一步研究磁各向异性介质的电磁特性、更有效地开发利用磁各向异性介质具有实际意义.     

各向异性介质多分量感应测井三维Born几何因子理论研究

几何因子理论被广泛运用于感应测井仪器设计、响应特征分析及高分辨率曲线处理, 现有的感应测井几何因子主要适用于二维各向同性介质, 难以满足各向异性介质多分量感应测井的研究需要. 本文基于Born近似方法将Born几何因子扩展至各向异性介质, 推导了各向异性介质多分量感应测井三维Born几何因子表达式, 随后进一步考察了多分量感应测井对地层各向异性的敏感性和探测能力. 数值模拟结果表明, 各向异性系数越大, 多分量感应测井几何因子空间分布越复杂, 其对各向异性的敏感性越高. 多分量感应测井仪器在不同倾斜角度对各向异性均具有较高的敏感性. 直井条件下, xx共面分量受各向异性影响严重, 井斜角在40°–60°时, xz/zx交叉分量对各向异性的敏感性高, 水平井中zz同轴分量则对各向异性的探测能力最强. 各向异性介质三维Born几何因子弥补了现有几何因子理论的不足, 可为国内新型多分量感应测井仪器研发及储层各向异性评价方法的发展提供有利条件.     

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。     

各向异性金刚石结构的光子晶体

基于平面波展开法,理论分析了填充率、介质各向异性的程度对单轴金刚石结构三维光子晶体禁带的影响.结果表明,当填充率和介质各向异性取合适的值,单轴各向异性金刚石结构光子晶体存在着完全带隙.介质各向异性的引入使该晶体的带隙变窄甚至完全关闭.在各个布里渊区域里,带隙率和带隙宽度随介质各向异性程度的变化而变化.各向异性的引入为调整光子禁带提供了一种方法.     

各向异性磁化等离子体JEC-FDTD算法

将色散介质的电流密度卷积-时域有限差分(JEC-FDTD)算法推广到各向异性磁化等离子体色散介质.该算法同时解决了电磁波在各向异性和频率色散介质中传播的难题，给出了各向异性磁化等离子体JEC-FDTD算法的公式.计算磁化等离子体平板对平行于磁场传播的电磁波的反射和透射系数，通过与解析结果的比较，验证了该算法的高效性和高精度. 关键词： 色散介质 FDTD算法 各向异性 磁化等离子体     

磁偶极和电四极在磁各向异性介质中的辐射功率

在经典电动力学的框架下,研究了磁各向异性介质中的电磁辐射问题,得到了磁偶极和电四极在磁各向异性介质中的辐射功率表达式.进一步地,通过把各向同性介质中的μrii代入所得辐射功率表达式,得到了与文献相符合的结果,验证了所得结果的正确性.研究结果表明磁偶极和电四极在磁各向异性介质中的辐射功率大小与磁各向异性介质的μrii大小有关,对判断磁偶极和电四极在磁各向异性介质中的辐射效果有较大的帮助.     

以各向异性介质为衬底的共面紧凑型光子带隙结构

共面紧凑型光子带隙（UC_PBG）结构是一种以微带基片为载体的周期性平面结构.将介质衬 底取为各向异性媒质并运用直线法进行分析，详细介绍了方法的实现过程.对不同介质参数 的UC_PBG进行了计算，结果表明，在这些UC_PBG能带结构中带隙存在甚至有所展宽. 关键词： 共面紧凑型光子带隙 各向异性介质 直线法     

Reflection and transmission of Laguerre Gaussian beam from uniaxial anisotropic multilayered media

Based on angular spectrum expansion and 4 × 4 matrix theory, the reflection and transmission characteristics of a Laguerre Gaussian(LG) beam from uniaxial anisotropic multilayered media are studied. The reflected and transmitted beam fields of an LG beam are derived. In the case where the principal coordinates of the uniaxial anisotropic media coincide with the global coordinates, the reflected and transmitted beam intensities from a uniaxial anisotropic slab and three-layered media are numerically simulated. It is shown that the reflected intensity components of the incident beam, especially the TM polarized incident beam, are smaller than the transmitted intensity components. The distortion of the reflected intensity component is more evident than that of the transmitted intensity component. The distortion of intensity distribution is greatly affected by the dielectric tensor and the thickness of anisotropic media. We finally extend the application of the method to general anisotropic multilayered media.     

Phase and group velocity considerations for dynamic modulus measurement in anisotropic media

In anisotropic media, the direction of energy propagation does not necessarily coincide with the wave normal, i.e. the energy flux vector does not coincide with the wave normal. Since, experimentally, one measures group velocity not phase velocity, one must therefore be careful in interpreting ultrasonic wave speed measurements in anisotropic media. This is of particular importance in elastic property reconstruction where acoustic velocity measurements are used as the basis for determining anisotropic material properties. In this work, the consequences of energy flux deviation from the wave normal are considered for typical experimental geometries. Particular attention is devoted to developing appropriate relationships between the phase velocity and ultrasonic transit time measurements, as these relations are most useful for elastic property reconstruction. In all the cases considered, it is shown that the phase velocity can be directly calculated from appropriate time delay measurements.     

Pseudo-Hermiticity and electromagnetic wave propagation: The case of anisotropic and lossy media

Pseudo-Hermitian operators can be used in modeling electromagnetic wave propagation in stationary lossless media. We extend this method to a class of non-dispersive anisotropic media that may display loss or gain. We explore three concrete models to demonstrate the utility of our general results and reveal the physical meaning of pseudo-Hermiticity and quasi-Hermiticity of the relevant wave operator. In particular, we consider a uniaxial model where this operator is not diagonalizable. This implies left-handedness of the medium in the sense that only clockwise circularly polarized plane-wave solutions are bounded functions of time.     

各向异性磁化等离子体涂敷三维导体目标FDTD分析

把电流密度卷积-时域有限差分法(JEC-FDTD)推广应用于三维各向异性色散介质——磁化等离子体中，该算法同时解决了电磁波在各向异性和频率色散介质中传播的难题，给出了各向异性磁化等离子体中JEC-FDTD迭代公式.计算了各向异性磁化等离子体涂敷二面角反射器和球锥体后其RCS的变化情况，分析了电子回旋频率对其RCS的影响.计算结果表明磁化等离子体吸收性能更好. 关键词： 时域有限差分方法 各向异性磁化等离子体     

Characteristics of surface waves in anisotropic left-handed materials

We report the coexistence of TE and TM surface modes in certain same frequency domain at the interface between one isotropic regular medium and another biaxially anistotropic left-handed medium. The conditions for the existence of TE and TM polarized surface waves in biaxially anisotropic left-handed materials are identified, respectively. The Poynting vector and the energy density associated with surface modes are calculated. Depending on the system parameters, either TE or TM surface modes can have the time averaged Poynting vector directed to or opposite to the mode phase velocity. It is seen that the characteristics of surface waves in biaxially anisotropic left-handed media are significantly different from that in isotropic left-handed media.     

Extension of the generalized multipole technique to anisotropic medias

This paper presents an extension of the generalized multipole technique (GMT) for 2D anisotropic scatterers. New expansions similar to the Bessel multipole expansion are derived for arbitrary anisotropic media. Numerical simulations prove the accuracy and the rapid convergence of these expansions. As the results obtained are extremely accurate, this technique is most helpful for the evaluation of reference solutions and for the understanding of the physical interaction of light with arbitrary anisotropic media.     

Propagation of partially polarized Gaussian Schell-model beams in anomalously dispersive media

By use of a tensor method, analytical transform formulae for isotropic partially polarized GSM beams propagating in anomalously dispersive media are derived. Based on the derived formula, the propagation properties of isotropic partially polarized GSM beams in anomalously dispersive media are studied in detail. The results show that the polarization and the irradiance distribution and the coherence degree properties are influenced by the anomalously dispersive media and beam's initial coherence. In addition, the evolution of the spectrum shows that spectrum splitting and spectral shift occur during propagation in anomalously dispersive media.     

Analytical methods for modeling of ultrasonic nondestructive testing of anisotropic media

Many modern structural materials exhibit anisotropic elastic behavior leading to complicated wave propagation phenomena. To ensure the reliability of ultrasonic nondestructive testing techniques, these material properties as well as the influence of microstructural inhomogeneities and the effects of interfaces on ultrasonic wave propagation have to be taken into account. In this respect, mathematical modeling provides an efficient method of assisting analysis. Two computationally efficient analytical approaches--a Gaussian beam and a point source superposition technique--are presented, which are well-suited for performing ultrasonic wave propagation and scattering simulations for anisotropic media. Results for homogeneous as well as inhomogeneous anisotropic media like composites and weld material are presented.     

Coherence properties of the scattered electromagnetic field generated by anisotropic quasi-homogeneous media

The coherence properties of the scattered field generated by linearly polarized and uniformly unpolarized electromagnetic plane waves incident on anisotropic quasi-homogeneous media are studied. The analytical expressions for the spectral density and the spectral degree of coherence of the three dimensional scattered field are derived. The results of the numerical simulations indicate that not only the properties of the anisotropic media have a great effect on the coherence properties of the scattered field, but also the polarization of the incident wave. And most important, the effect of the polarization of the incident wave on the coherence properties of the scattered field nearly concerns the properties of the anisotropic media. There are also close and interesting relations between the coherence properties of the scattered field that generated by the anisotropic media and by the corresponding isotropic media.