Superluminal,advanced and retarded propagation of electromagnetic potentials in quantum mechanics

In some gauges part of the classical electromagnetic potentials can propagate faster than the speed of light. In other gauges part of the electromagnetic potentials can be advanced, even though the electromagnetic field is retarded. If the conventional interaction between electromagnetic radiation and quantum mechanical charged particles, which involves the vector and scalar potentials, is used, an atom has a nonzero probability of being excited before the electromagnetic field arrives. If part of the potentials are advanced, the atom could even be excited before the sources are turned on. These spurious effects, which are gauge dependent and violate energy conservation, relativity, and causality, are due to use the conventional (gauge-dependent) interaction. When the interaction of the electromagnetic radiation and matter is treated in a manifestly gauge-invariant way, the atom is not excited before the electromagnetic field arrives, regardless of which gauge is used.     

On the axioms of topological electromagnetism

The axioms of topological electromagnetism that were given by Hehl, Obukhov, and Rubilar are refined by the use of geometrical and topological notions that are found on orientable manifolds. The central problem of defining the spacetime electromagnetic constitutive law in terms of the geometrical and topological structure of the spacetime manifold is elaborated upon in the linear and nonlinear cases. The manner by which the spacetime metric might follow from the electromagnetic constitutive law is examined in the linear case. The possibility that the intersection form of the spacetime manifold might play a role in defining a topological basis for a nonlinear electromagnetic constitutive law is explored. The manner by which electromagnetic wave motion relates to the geometric structure is also discussed.     

Turbulence-induced changes in degree of polarization, degree of coherence and spectrum of partially coherent electromagnetic beams

Based on a recently formulated unified theory of coherence and polarization, a method is described to study turbulence-induced changes in the polarization, the coherence and the spectrum of partially coherent electromagnetic beams on propagation. The electromagnetic Gaussian Schell-model beam is taken as a typical example of partially coherent electromagnetic beams, and the closed-form expressions for the degree of polarization, the degree of coherence and the spectrum of electromagnetic Gaussian Schell-model beams propagating through atmospheric turbulence are derived in the quadratic approximation of Rytov's phase structure function. Some interesting results are obtained, which are illustrated by numerical examples and are explained in physics.     

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将等离子体作为磁流体,考虑其流体属性和电磁属性,介绍了利用FLUENT软件包并将其进行二次开发,解算电磁场方程、质量连续性方程、动量守恒方程、以及能量守恒方程的数值模拟方法,得到了以磁矢势为表达形式的电磁场分布、温度分布和速度分布.数值模拟了粉末球化所用的感应耦合等离子体炬电磁场分布、温度分布、速度分布.分析了温度分布、速度分布产生的物理原因,为感应耦合等离子体炬球化粉末颗粒提供理论性指导.     

Ku/K波段双频涡旋电磁阵列天线设计

涡旋电磁波具有携带轨道角动量的特性,利用这一特性,采用涡旋电磁波作为信号的载体,可以实现同一时间、同一频段的多路信号传输,极大地提高系统容量和频带利用率。以同轴馈电的半圆型开槽微带天线为单元,设计出了一种能工作在Ku波段和K波段的涡旋电磁阵列天线。使用三维电磁场仿真软件建模并且优化参数,最终得到在中心频率分别为17.1 GHz和19.7 GHz时,阵列天线产生的电磁波携带有轨道角动量。结论表明:该阵列天线能够产生双频涡旋电磁波。     

Scattering of electromagnetic wave by perfect electromagnetic conductor (PEMC) sphere placed in chiral media

A theoretical investigation has been carried out for electromagnetic waves scattering from a perfect electromagnetic conductor (PEMC) sphere which is placed in chiral media. The formulation of the problem is realized by expanding the incident as well as the scattered electromagnetic fields in terms of left circularly polarized (LCP) and right circularly polarized (RCP) waves. By applying the boundary conditions at the chiral-PEMC interface, eight simultaneous equations are generated, which yield the scattering coefficients associated with the Left and Right electromagnetic waves. The relative contribution of Co-polarized and Cross-polarized components of fields to the calculations of scattering cross-section is presented. The effect of admittance parameter and the effect of chirality parameter in cases of lossless, lossy permittivity and lossy permeability on Co and Cross components of scattering cross sections are observed. The results are also compared with available published literatures which are in good agreement.     

The scale-transformation of electromagnetic theory and its applications

The scale-transformation of electromagnetic theory is investigated in detail based on the form of Maxwell equations in scale-transformation being unchanged in different coordinate systems. The relations of electromagnetic parameters in a rectangular coordinate system and in a spherical coordinate system are presented respectively. The scale-transformation invariants for electromagnetic field are derived and their physical meaning is also presented. It is indicated by simulation that the electromagnetic waves located in medium can be considered to be isotropic due to the fact that the size of propagating vector affected by the scale factors and observing azimuth is on a size of 10^-9, which provides a new approach for investigating the electromagnetic characteristics of ellipsoidal targets.     

Generation of tunable electromagnetic radiation by a dust ripple in dusty plasmas

It is shown that a pre-existing dust ripple in a dusty plasma may excite tunable electromagnetic radiation. For our purposes, we use the Maxwell equation and the electron equation of motion to derive a Mathieu equation in the presence of a spatially oscillating dust ripple. The Mathieu equation admits instability of an electromagnetic wave. Criteria under which instability occurs are presented. Explicit expression for the electromagnetic radiation frequency and the growth rate are obtained. The possible relevance of our investigation to nonthermal electromagnetic radiation sources from laboratory and cosmic dusty plasmas is considered.     

超短波跳频电台复杂电磁环境适应能力评估方法

以某型超短波通信电台为例,分析了该电台工作于跳频组网状态时所面临的复杂电磁信号环境,在电台使用区域内,根据构成威胁电磁环境、目标电磁环境和背景电磁环境的各电子设备的频谱占用度、时间占有度、空间覆盖率的不同,提出了复杂电磁环境量化分级标准。采取实装构设与模拟仿真技术相结合的手段,分别构建了针对该电台的简单、轻度、中度和重度等不同级别的复杂电磁环境,并给出了电台对不同等级复杂电磁环境适应能力的初步评估结论。项目成果可为今后电子信息装备复杂电磁环境适应性的理论研究工作提供有益借鉴。     

建筑物墙壁电磁耦合截面建模及应用

电磁波照射下的建筑物室内电磁环境具有混响效果,因此可采用功率平衡法（PWB）快速评估室内电磁环境水平。然而目前PWB方法中电大腔壁耦合截面（CCS）的计算模型建立在腔内电磁波不穿透腔壁的条件下,无法直接用于电磁波可穿透室内建筑物墙壁的耦合截面计算。为此,提出了一种适用于电磁波穿透有限厚度建筑物墙壁的CCS计算新模型。该模型考虑实际建筑物墙体的厚度和材料电磁特性,能够充分反映电磁波因有限厚度墙壁多次反射对室内电磁环境水平的影响。将该模型应用于室内电场水平的快速评估,预测结果与实际测量结果吻合较好,证明了所提有限厚度建筑物墙壁CCS模型的合理性。     

时域全波电磁计算程序JEMS-FDTD在复杂电磁环境研究中的应用

将自主研发的大规模并行三维全波电磁场时域求解程序JEMS-FDTD应用于复杂电磁环境问题,计算并分析了楼宇内电波传播特性和飞行器瞬态电磁特性。对楼宇内电波传播特性的计算获得了建筑物内任意位置的电磁场分布和电磁脉冲在建筑物内的时域传播过程,其结果可用于无线通信和电磁环境安全研究;对飞行器瞬态电磁特性的计算获得了飞行器舱内外瞬态电磁近场分布,其结果可用于飞行器强辐射场防护等研究。     

国家关键基础设施电磁恢复力

随着国家关键基础设施建设规模和信息化水平的提升,其在高空电磁脉冲、有意电磁干扰和地磁暴等强电磁环境下的电磁安全逐渐受到了国内外的关注。强电磁环境属于小概率、高风险事件,其影响机理和评估方法与雷电、系统内过电压等常规电磁事件有较大不同,采用期望风险指标的常规可靠性分析方法难以有效评估管理强电磁环境相关风险。从电磁恢复力视角出发,提出了关键基础设施电磁安全的三棱锥模型,并重点以电网为例,探讨关键基础设施电磁恢复力的内涵和外延,并对开展电磁恢复力研究提出建议。     

高功率电磁脉冲对砷化镓金属半导体场效应管的影响

 采用时域有限差分方法,通过求解麦克斯韦方程、热传导方程和载流子方程,模拟了在电磁脉冲辐射下,场效应管器件温度和端口散射参数的变化过程。研究了不同幅度脉冲序列和上升沿不同的脉冲对砷化镓金属半导体场效应管的影响,对比了各种不同脉冲作用下场效应管性能的变化规律。该方法克服了传统电路模型无法模拟电磁波与器件内部活动粒子作用过程的缺点,可以直接模拟器件温度和散射参数在高功率电磁脉冲辐射下的时域变化过程。     

导电介质中电磁波相移常数与振幅衰减常数的方向关系的讨论

对文献上给出的非均匀电磁波在同一均匀导电介质中传播时,电磁波的相移常数和振幅衰减常数方向之间满足定量关系的结论,重新进行了分析和推导,利用电磁波在导电介质界面的边界条件,给出了两种情况下的相移常数和振幅衰减常数的表达式,以及它们与界面法线的夹角正弦的表达式.结果表明,在同一均匀导电介质中,非均匀电磁波的相移常数的方向和振幅衰减常数的方向之间一般不满足定量关系.     

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     

Covariant derivation of the electromagnetic boundary conditions in General Relativity

The covariant derivation of the electromagnetic boundary conditions seems not to have been given. It is presented here, for general electromagnetic sources and distributions of matter which are independent of time. Thus the boundary conditions are suitable for use in stationary solutions in General Relativity.     

电磁脉冲模拟器电磁场计算

 利用电磁场张量法计算了平行板电磁脉冲模拟器内的电磁场并推导了其时域解析表达式。按照模拟器的平行板段和前后三角板的结构将平板近似为线网格。场的幅值由各线段元的不同滞后时间叠加来确定,其方向由线段元和场点的单位矢量经简单矢量运算来确定。计算结果表明：平行板段内的场具有横电磁分布特性,而靠近三角板处由于各线段元的非对称性贡献将使场出现其它分量。通过对模拟器的电场测量值与理论计算值相比较可知,两者大致相同。     

线电流源激励下无耗异向介质层覆盖导体圆柱电磁特性的研究

研究了线电流源平行放置在无耗异向介质层覆盖的无限长导体圆柱附近模型的电磁特性.首先，给出了电磁模型描述，求出此电磁模型的精确解.其次，利用精确解进行数值计算，得到几何参数和电磁参数不同情况下电磁模型的近场图形，并通过方向性系数和归一化辐射阻抗研究其远场特性.利用异向介质的负折射特性，在异向介质层的近场图形内得到明显的“焦点”，这个焦点在普通介质层中是不存在的.该电磁模型同前人方法进行了比较，验证了本电磁模型的有效性. 关键词： 线电流源 异向介质 方向性系数 辐射阻抗     

孔缝对金属腔体强电磁脉冲耦合特性影响研究

核电磁脉冲和高功率微波等强电磁脉冲易造成电子设备功能失效甚至损毁,在实际工程实施中用金属腔体对电子设备进行屏蔽是常用的强电磁脉冲抑制手段。基于电磁仿真计算,对含矩形孔缝金属腔体的强电磁脉冲耦合特性进行了系统研究,阐述了孔缝宽长比、腔体尺寸等因素对多种不同类型强电磁脉冲（核电磁脉冲、宽带高功率微波、窄带高功率微波）作用下腔体内耦合场的影响;并以此为基础,重点分析了强电磁脉冲与含孔缝金属腔体之间的作用机制。研究结果表明:不同类型强电磁脉冲耦合信号差异明显,金属腔体对强电磁脉冲的响应是腔体谐振模式、孔缝谐振频率与强电磁脉冲共同作用的结果;当腔体谐振模式、孔缝谐振频率在强电磁脉冲的带内时,腔体内部的耦合场会出现增强效应;特别地,腔体与孔缝间的相互作用还可造成腔体与缝隙的谐振频率发生偏移。因此,在为电子设备设计金属屏蔽外壳时,应基于不同强电磁脉冲的频带范围,对腔体与孔缝的尺寸进行综合设计,抑制腔体、孔缝谐振及谐振频率偏移,提升其强电磁脉冲防护性能。