读“等效的磁荷观点”有感

文章在假想的“磁荷世界”中修改了麦克斯韦方程组和洛伦兹力公式.由磁的库仑定律出发,并根据磁荷与电荷产生的电磁场的等效性,得到真空中静磁场的高斯定理和环路定理.仿照“电荷世界”中的电流定义了磁流强度,又根据磁场的相对论变换,由毕奥—萨伐尔定律和法拉第电磁感应定律得到稳恒电场D的高斯定理和环路定理.     

Scattering response of an electrically small bianisotropic particle

Scattering response of an electrically small bianisotropic particle suspended in free space is presented. Formulation of this problem is based on the assumption that the electrical small bianisotropic particle can be modelled as both an equivalent electric and a magnetic dipole moments. It is found that cross-polarization and/or co-polarization phenomena may occur for certain constitutive relations, separatively.     

Spectral dyadic Green's function formulation for uniaxial bianisotropic superstrate-substrate structure

In this paper, spectral-domain dyadic Green's functions for the time harmonic electric current source embedded in a two-layer grounded uniaxial bianisotropic media are obtained using Fourier tranform. It is shown that in the uniaxial bianisotropic medium, total spectral electromagnetic field can also be separated into the superposition of transverse electric (TE) and transverse magnetic (TM) wave. Because of the generality of constitutive relations our results include the special cases of achiral, uniaxial, reciprocal and nonreciprocal biisotropic media.     

异向介质填充非辐射介质波导和H波导中的高次模及漏波抑制

 通过对加载异向非辐射介质波导(NRD)和H波导的全波分析,研究了此新型导波结构的传输特性。由于开口谐振环所引起的双各向异性效应,在双负参数条件下,纵剖面磁(LSM)波型和纵剖面电(LSE)波型将可能出现传播常数随频率增高而减小的异常高次模式,从而引起漏波。而在其它情况下,利用双各向异性效应却可以有效减少LSM和LSE波型的高次模漏波现象。尤其当异向介质取得单负参数时,此新型导波结构将能够完全抑制高次模漏波的出现。     

Identifying magnetic response of split-ring resonators at microwave frequencies

In this study we provide experimental methods to identify the magnetic resonance of split ring resonantors (SRR) at the microwave frequency regime. Transmission measurements were performed on both single SRR unit cell and periodic arrays of SRRs. The magnetic response of the SRR structure was demonstrated by comparing the transmission spectra of SRRs with closed ring resonators (CRR). Effects of the changes in the effective dielectric constant of the SRR medium on the band-gaps of SRR are investigated experimentally. SRRs not only exhibit a magnetic resonance band gap but also a band gap due to the electric resonance. Finally, we present the effect of electric coupling to the magnetic resonance of bianisotropic SRRs by utilizing SRRs with different orientations, and incident electromagnetic wave polarizations.     

加载异向介质非辐射介质波导中的慢波传输及应用

将开口谐振环作为加载单元,分析了含有开口谐振环结构非辐射介质波导的新型传输特性.由于异向介质的双各向异性效应,纵剖面磁波型和纵剖面电波型在此新型非辐射介质波导中的传输速度能够减慢,甚至达到零速度.对于波导中的能量关系也进行了分析,研究表明,在一定情况下,慢波传输将引起功率流动的增强.这些特性使得此新型非辐射介质波导更能满足小型化的设计要求. 关键词： 开口谐振环 异向介质 非辐射介质波导 慢波传输     

A unified optical theorem for scalar and vectorial wave fields

The generalized optical theorem is an integral relation for the angle-dependent scattering amplitude of an inhomogeneous scattering object embedded in a homogeneous background. It has been derived separately for several scalar and vectorial wave phenomena. Here a unified optical theorem is derived that encompasses the separate versions for scalar and vectorial waves. Moreover, this unified theorem also holds for scattering by anisotropic elastic and piezoelectric scatterers as well as bianisotropic (non-reciprocal) EM scatterers.     

Evolution of a Harris current sheet in an electric field

Evolution of a Harris current sheet in the presence of an electric field is studied numerically. An explicit scheme is used to recalculate the particle distribution function with respect to velocities. The mechanism of formation of electric fields is analyzed on the basis of the phase volume conservation theorem. The effects of 1D sheet compression and electron and ion acceleration near the magnetic field zero line are described.     

论复杂磁路和非线性直流电路的普遍解法

一、前言 复杂磁路和非线性电路的求解自来是个难题。1952年克鲁格等著的“电工原理”一书曾经明确指出,复杂的非线性电路的一般解法直到现在还未被研究出来(见该书第五章第六节)。过了一个时期,非线性电路的解法,在以戴维南定理为根据的“取出电动势法”的基础上,已有进一步的发展(见1954年聶孟著“电工学底理论基础”第六章§§36—39)。但适用于含有任意多个非线性元件的直流电路的一般解法似还未被提出来。至于磁路,由于并无类似的戴维南定理可资利用,目前所能解决的似只限于含有三个支路的情形(能     

Black hole solutions in heterotic string theory on a torus

We construct the general electrically charged, rotating black hole solution in the heterotic string theory compactified on a six-dimensional torus and study its classical properties. This black hole is characterized by its mass, angular momentum, and a 28-dimensional electric charge vector. We recover the axion-dilaton black holes and Kaluza-Klein black holes for special values of the charge vector. For a generic black hole of this kind, the 28-dimensional magnetic dipole moment vector is not proportional to the electric charge vector, and we need two different gyromagnetic ratios for specifying the relation between these two vectors. We also give an algorithm for constructing a 58 parameter rotating dyonic black hole solution in this theory, characterized by its mass, angular momentum, a 28-dimensional electric charge vector and a 28-dimensional magnetic charge vector. This is the most general asymptotically flat black hole solution in this theory consistent with the no-hair theorem.     

Depolarization regions of nonzero volume in bianisotropic homogenized composites

In conventional approaches to the homogenization of random particulate composites, the component phase particles are often treated mathematically as vanishingly small, point-like entities. The electromagnetic responses of these component phase particles are provided by depolarization dyadics which derive from the singularity of the corresponding dyadic Green functions. Through neglecting the spatial extent of the depolarization region, important information may be lost, particularly relating to coherent scattering losses. We present an extension to the strong-property-fluctuation theory in which depolarization regions of nonzero volume and ellipsoidal geometry are accommodated. Therein, the size, shape and spatial distribution of the component phase particles are taken into account. The analysis is developed within the most general linear setting of bianisotropic homogenized composite mediums (HCMs). Numerical results are presented for a representative example of a bianisotropic HCM, namely a Faraday chiral medium. These studies reveal that estimates of the HCM constitutive parameters in relation to volume fraction, particle eccentricity, particle orientation and correlation length are all significantly influenced by the size of the component phase particles.     

平行柱体对平面波/高斯波束电磁散射

基于等效原理和互易性定理，研究了N个相互平行二维柱体对平面波/高斯波束的电磁散射特性，给出了求解N阶散射场公式.一阶散射可通过求解单个柱体的散射场得到，但对于高阶散射场而言，由于耦合散射的复杂性，很难给出精确的解析解.为了解决这一问题，借助等效原理和互易性定理给出了求解N阶散射场的面积分公式.只要给出柱体的i-1阶散射场及相关目标表面上的等效电流和(或)等效磁流，就可应用此公式求解i阶散射场.应用该近似方法计算了相互平行非均匀等离子体涂层导体圆柱的单/双站散射宽度，讨论了束腰半径、等离子体涂层厚度、电子密度、碰撞频率及雷达频率等对散射结果的影响.     

Landau problem with a general time-dependent electric field

The time evolution is studied for the Landau level problem with a general time dependent electric field E(t) in a plane perpendicular to the magnetic field. A general and explicit factorization of the time evolution operator is obtained with each factor having a clear physical interpretation. The factorization consists of a geometric factor (path-ordered magnetic translation), a dynamical factor generated by the usual time-independent Landau Hamiltonian, and a nonadiabatic factor that determines the transition probabilities among the Landau levels. Since the path-ordered magnetic translation and the nonadiabatic factor are, up to completely determined numerical phase factors, just ordinary exponentials whose exponents are explicitly expressible in terms of the canonical variables, all of the factors in the factorization are explicitly constructed. New quantum interference effects are implied by this result. The factorization is unique from the point of view of the quantum adiabatic theorem and provides a seemingly first rigorous demonstration of how the quantum adiabatic theorem (incorporating the Berry phase phenomenon) is realized when infinitely degenerate energy levels are involved. Since the factorization separates the effect caused by the electric field into a geometric factor and a nonadiabatic factor, it makes possible to calculate the nonadiabatic transition probabilities near the adiabatic limit. A formula for matrix elements that determines the mixing of the Landau levels for a general, nonadiabatic evolution is also provided by the factorization.     

Magnetoelectric-Field Electrodynamics: Search for Magnetoelectric Point Scatterers

Resonant scattering of electromagnetic (EM) waves by small particles is considered as one of the basic problems in metamaterial science. At present, special subwavelength resonators are considered as structural elements in chiral and bianisotropic metamaterials. There is a general consensus that these small scatterers behave like “artificial atoms” with strong electrical and magnetic responses and an interconnection between these responses. However, the observed effect of magnetoelectric (ME) coupling in these meta-atoms is not associated with the near-field manipulation properties caused by intrinsic magnetoelectricity. This arises the question whether ME point scatterers of EM radiation really exist. In this paper, we show that there are mesoscopic structures with electric and magnetic dipole-carrying excitations that behave like point scatterers with their inherent magnetoelectricity. In such subwavelength resonators, coherent oscillations of the electric polarization and magnetization can be considered as quasistatic oscillations described by electrostatic (ES) and magnetostatic (MS) scalar wave functions. The ME resonance effect arises from the coupling of two, ES and MS, oscillations. The near fields of these resonators, called the ME near fields, are characterized by simultaneous violation of time reversal and inversion symmetry. In study of ME fields and EM problems associated with these fields, we put forward the concept of ME-field electrodynamics.     

Depolarization regions of nonzero volume in bianisotropic homogenized composites

In conventional approaches to the homogenization of random particulate composites, the component phase particles are often treated mathematically as vanishingly small, point-like entities. The electromagnetic responses of these component phase particles are provided by depolarization dyadics which derive from the singularity of the corresponding dyadic Green functions. Through neglecting the spatial extent of the depolarization region, important information may be lost, particularly relating to coherent scattering losses. We present an extension to the strong-property-fluctuation theory in which depolarization regions of nonzero volume and ellipsoidal geometry are accommodated. Therein, the size, shape and spatial distribution of the component phase particles are taken into account. The analysis is developed within the most general linear setting of bianisotropic homogenized composite mediums (HCMs). Numerical results are presented for a representative example of a bianisotropic HCM, namely a Faraday chiral medium. These studies reveal that estimates of the HCM constitutive parameters in relation to volume fraction, particle eccentricity, particle orientation and correlation length are all significantly influenced by the size of the component phase particles.     

两个相邻目标对平面波、高斯波束的光散射

基于等效原理和互易性定理研究了两个靠近目标对平面波、高斯波束的光散射问题,给出了这一复合光散射模型的二阶散射结果。通常一阶散射结果容易求解,但由于耦合效应的复杂性,很难给出二阶散射结果的解析形式。为了解决这一问题,应用互易性定理给出了求解任意相邻介质目标二阶散射场的公式,同时借助等效原理将求解散射场公式中的体积分简化为面积分的形式,从而降低了求解难度。求解了两相邻球形粒子的复合散射场,并将求解结果与应用时域积分方程法求得的结果进行了比较。同时,还讨论了束腰半径、目标位置对散射截面及偏振度的影响。     

Electroweak interactions and high-energy limit

An introduction to the equivalence theorem for longitudinally polarized vector bosons and unphysical Goldstone scalars in electroweak theories is presented and the problem of high-energy behaviour of scattering amplitudes in the Standard Model is briefly reviewed. The equivalence theorem is first illustrated on simple examples, and the idea of a general proof based on the concept of BRS symmetry is then explained. To make the treatment self-contained, basics of the Standard Model are summarized in the appendix.     

等效原理和互易性定理在两个相邻球形目标电磁散射中的应用

基于等效原理和互易性定理研究了两个相邻目标的电磁散射问题，给出了这一复合电磁散射模型的二阶散射结果. 通常平面入射波的一阶散射结果容易求解，但由于耦合效应的复杂性，很难给出二阶散射结果的解析形式. 应用互易性定理给出了求解任意相邻导体/介质目标二阶电磁散射场的公式，并利用等效原理将求解散射场公式中的体积分简化为面积分的形式，从而降低了求解难度. 同时还推导了两个目标的二次散射场之间的关系. 最后应用给出的公式，求解了两相邻球形目标的复合散射场，对双站散射结果进行了讨论，同时与应用时域积分方程法求得的结果进行了比较. 关键词： 等效原理 互易性定理 电磁散射 相邻圆球     

Generalized Pearson distributions for charged particles interacting with an electric and/or a magnetic field

The linear Boltzmann equation for elastic and/or inelastic scattering is applied to derive the distribution function of a spatially homogeneous system of charged particles spreading in a host medium of two-level atoms and subjected to external electric and/or magnetic fields. We construct a Fokker-Planck approximation to the kinetic equations and derive the most general class of distributions for the given problem by discussing in detail some physically meaningful cases. The equivalence with the transport theory of electrons in a phonon background is also discussed.     

超声波电发生器的最大输出功率和效率

本文从电路理论中的最大功率传输定理出发，分析了超声波电发生器与普通电源的异同，提出了最大功率传输定理的扩展条件，从而将一般电源的匹配和超声波发生器的匹配这两种概念统一起来。文章应用扩展后的最大功率传输定理，从一个新的角度对超声波电发生器的最大输出功率和效率进行了分析，得到与图解法等其他方法相同的结果。