双桨船轴频电场建模与仿真

船体由于腐蚀会产生腐蚀电流,螺旋桨-轴的转动调制腐蚀电流在海水中产生低频电场。船模电场测量实验表明,轴频电场与轴转动频率有关,其基频与轴转动频率一致的。采用一对处于相同位置的运动时谐垂直电偶极子,偶极子的频率于轴转动频率一致,建立空气-海水-海床三层模型下的双桨船轴频电场模型,进行了不同轴频频率和不同轴电流初始相位情况下的轴频电场仿真分析,结果表明,轴转动频率和初相位对轴频电场有较大影响。     

基于ANSYS的铝电解槽电场数值仿真研究

铝电解槽的电场作为形成各物理场的基础,其分布好坏直接影响电解槽的生产。采用基于ANSYS的仿真分析方法研究了铝电解槽的电场分布。采用有限元法,建立了铝电解槽电场的数学模型,并利用有限元仿真分析软件ANSYS建立电解槽三维电场有限元模型,计算了铝电解槽各导电部分的电场分布,总结了分布规律,为电解槽多物理场优化提供基础。其仿真结果与实测结果相吻合,验证了方法的正确性。     

高压输电线附近工频电场模型及仿真研究

建立了高压输电线路附近工频电场的数学模型,采用模拟电荷法在时域中计算了高压输电线路附近工频电场的分布,并利用MATLAB编程语言对此分布进行了仿真,得出了高压输电线路附近电场的分布规律及影响因素.与"国际大电网会议第36.01工作组"推荐的方法相比,使用电压瞬时值进行场强计算较易理解,且能适用于更广泛的范围.     

微电铸中电场均匀性分布与控制方法

微电铸技术用来生产金属微器件,已经成为一种重要的和有效的加工方法.为了获得理想的电铸产品结构,电铸液中电场的分布起到了重要的作用.电铸液中电场的均匀性分布可以提高微电铸的铸层质量和尺寸精度,并能提高电铸微观结构的力学性能.本文基于三电极体系提出了一种新的电场测量方法,并通过改变阳极的形状和位置来提高阴极附近电位分布的均匀性.实验结果表明,采用半圆弧形板作为阳极时,电铸液空间电场分布均匀性和阴极附近电场分布均匀性有明显的提高.因此,在实际应用中半圆弧形阳极可以改善电铸微器件的微观结构,提高铸层表面均匀性.     

高压电缆中间接头处测温装置的电场仿真

采用COMSOL Multiphysics^?多物理场仿真软件仿真了110 kV的电缆中间接头处，目的是为了研究一种基于柔性衬底的内置测温传感器在高压电缆中间接头处的电场分布情况以及它的工作性能，为此对该模型进行了电场有限元仿真计算。由仿真结果可知，高压电缆内部的接头所造成的电场分布不会因为内置的无线测温装置而造成过多的影响，与为放入测温传感器的情况相比较，测温传感器贴附于主绝缘交界处，在接头接触部分的电场分布会发生改变，其变化过小，可忽略不计。对于整体的影响几乎可以不计，因此，所提出的柔性内置式无线测温装置对于电缆线芯的测量，不会影响到电缆内部接头的电场分布。     

电磁流量计中涡旋电场分布的仿真分析

电磁流量计励磁过程中产生的涡旋电场能有效地克服浆液噪声干扰，对于电磁流量计中涡旋电场的基础理论研究变得日益重要。首先通过麦克斯韦方程与磁场元叠加的方法得出了涡旋电场的解析式及涡旋电场的三个分布特性。通过COMSOL对电磁流量计中的涡旋电场进行仿真，仿真结果表明，电磁流量计管道内的涡旋电场具有轴对称性，电场方向垂直于电极表面，且涡旋电场峰值位于电极附近。     

零值绝缘子对超高压500kV绝缘子串电场分布影响研究

作为超高压输电线路的关键部件绝缘子长期运行后其绝缘性能下降,容易产生零值绝缘子,严重时会造成经济损失。因此,利用有限元方法研究不同位置和数量的零值绝缘子对超高压500 kV绝缘子串电场分布的影响。结果表明:存在零值绝缘子以及零值绝缘子的位置和数量均会对绝缘子串的电场分布产生一定的影响,高低压端存在零值绝缘子对绝缘子串电场影响最大。且当监测路径不同时,零值绝缘子对于绝缘子电场分布的影响会存在变化。零值绝缘子数量会对电场值影响程度有所改变。最后试验与理论结果对比显示,理论值与试验值在可接受范围之内存在一定的误差。     

基于介电泳的电极阵列电场仿真研究

介电泳方法被广泛地应用于微纳颗粒的分离和操纵中,实现介电泳操作的关键是设计满足所需电场分布的电极阵列.针对目前在微电极阵列设计中尚缺乏简单有效的电场解析方法的现状,提出一种基于格林公式的电极阵列电场的解析方法.首先介绍了传统介电泳和行波介电泳的概念和计算模型,分析了介电泳过程与电极上所施加的交变电压的频率和幅度的关系,然后在确立电极电势的边界条件的基础上,采用基于格林公式的电场解析方法,建立了非均匀电场的解析模型,得出不同条件下的电极阵列电场分布的仿真结果,最后利用FEMLAB有限元仿真软件对解析模型进行了对比仿真, 验证了该解析模型的可行性.基于格林公式的电场解析求解方法能够有效地提高电极阵列设计中的针对性以及缩短电极设计的时间.     

超级结电场分布仿真分析

为详细研究超级结体内独特的二维电场分布,通过Silvaco软件建立半导体超级结器件基本结构(超级结PiN),展开直观的定量仿真分析。在仿真中对漏极施加正向电压,得到电场分布图和包括电场峰值、谷值在内的多个特征点。通过连接特征点得到四类特征电场线,沿着各个特征电场线观察其电场变化,验证纵向电荷场对横向电荷场的调制作用。对传统超级结模型进行优化,添加N-缓冲层仿真出半超结P(或N)漂移区中心电场分布,并与传统结构进行对比。     

110kV高压电力电缆中间接头电场-温度场的仿真分析

为研究运行中的电缆接头内部电场分布情况,改善绝缘性能,对电缆接头电场与温度场进行了仿真研究.在综合分析电缆接头内部热源的基础上,从介质损耗基本公式出发,建立基于等效电容的电场-温度场耦合分析的数值计算公式.采用有限元分析软件——ANSYS对110 kV电缆中间接头进行了电场和温度场的仿真,分析了110 kV电缆中间接头...     

Time-optimal control of a particle in a dielectrophoretic system

We study the time-optimal control of a particle in a dielectrophoretic system. This system consists of a time-varying nonuniform electric field which acts upon the particle by creating a dipole within it. The interaction between the induced dipole and the electric field generates the motion of the particle. The control is the voltage on the electrodes which induces the electric field. Since we are considering the motion of a particle on an invariant line in a chamber filled with fluid flowing at low Reynolds number, the dynamics have a two dimensional state; one for the particle position and the other for the induced dipole moment. In regard to time-optimal control, we address the issue of existence and uniqueness of optimal trajectories, and explicitly compute the optimal control and the corresponding minimum time. Finally, we cast our analysis in the framework of symplectic reduction theory in order to provide geometric insight into the problem.     

Electromagnetic scattering by arbitrarily shaped stratified anisotropic media using the equivalent dipole moment method

The equivalent dipole moment method, which was used to model the isotropic media, is extended and applied to the analysis of the electromagnetic scattering characteristics of arbitrarily shaped multilayer electric anisotropic media in this work. The initial motivation to put forward this method is based on the intrinsic physical properties of the electric anisotropic media whose constitutive parameter permittivity is a tensor matrix that can be modeled as equivalent electric dipole moment. This method employs the method of moments to solve the electric field volume integral equation (VIE) formulated by discretizing the scattering body into tetrahedral volume elements, in which the electrical parameters are assumed constant in each element. Then the VIE is solved directly to obtain the scattered field. Numerical results are given to validate the accuracy and efficiency of this method. © 2010 Wiley Periodicals, Inc. Int J RF and Microwave CAE, 2010.     

Localization of current dipole within a sphere by magnetic measurements

The principal objective of this study is the development of computer programs to determine the location and strength of neural electric activity within the brain from noninvasive magnetic field measurements at the surface of the head. This report presents theoretical calculations and computer programs derived from the method described by Williamson and Kaufman to determine the depth and strength of a current dipole in a sphere. From the location of the magnetic field radial component extremes, Br maximum and Br minimum, the orientation and location of the current dipole can be determined. The accuracy of the solution is dependent on precise location of of the magnetic field extremes as measured from the surface of a sphere, e.g. the head. To validate the program for locating the dipole, theoretical calculations and computer programs related to the total magnetic field vector resulting from a hypothetical current source within a homogeneous sphere were generated. The errors in calculations of the current dipole depth and strength are presented.     

Time optimal control of a dielectrophoretic system

This paper examines a time optimal control problem for a dielectrophoretic system. The system consists of a neutrally buoyant and neutrally charged particle in a chamber filled with a fluid flowing with a low Reynolds number. At the bottom of this chamber is a series of parallel electrodes with a controlled time‐varying voltage. The voltage on the electrodes creates a time‐varying nonuniform electric field inducing a dipole moment in the particle. This induced dipole moment interacts with the electric field to generate a force on the particle. There are two state variables x and y, where x is the position of the particle and y is the induced dipole moment in the particle. The system has two parameters α and c which depend on the electric characteristics of the particle and the ambient fluid. The parameter c is always positive by the laws of physics, but α can have either sign. We solve the time optimal control problem for this system when α≥0 and y(0) is arbitrarily prescribed. Copyright © 2010 John Wiley and Sons Asia Pte Ltd and Chinese Automatic Control Society     

新型偶极电场探测器及对空间电场的测量

介绍一种带有偶极天线的空间电场探测器的研制及对有界波EMP模拟器空间场的测量方法。该探测器结构简单、体积小、灵敏度高、动态范围大 ,尤其是具有高输入阻抗和频带宽的特点 ,能够实现对模拟器中瞬态电场的原波形测量。     

Recursive algorithm and accurate computation of dyadic Green’s functions for stratified uniaxial anisotropic media

A recursive algorithm is adopted for the computation of dyadic Green＇s functions in three-dimensional stratified uniaxial anisotropic media with arbitrary number of layers. Three linear equation groups for computing the coefficients of the Sommerfeld integrals are obtained according to the continuity condition of electric and magnetic fields across the interface between different layers, which are in correspondence with the TM wave produced by a vertical unit electric dipole and the TE or TM wave produced by a horizontal unit electric dipole, respectively. All the linear equation groups can be solved via the recursive algorithm. The dyadic Green＇s functions with source point and field point being in any layer can be conveniently obtained by merely changing the position of the elements within the source term of the linear equation groups. The problem of singularities occurring in the Sommerfeld integrals is efficiently solved by deforming the integration path in the complex plane. The expression of the dyadic Green＇s functions provided by this paper is terse in form and is easy to be programmed, and it does not overflow. Theoretical analysis and numerical examples show the accuracy and effectivity of the algorithm.     

Electric dipole transition moments and permanent dipole moments for spin–orbit configuration interaction wave functions

A procedure for calculating electric dipole transition moments and permanent dipole moments from spin–orbit configuration interaction (SOCI) wave functions has been developed in the context of the COLUMBUS ab initio electronic structure programs. The SOCI procedure requires relativistic effective core potentials and their corresponding spin–orbit coupling operators to define the molecular Hamiltonian, electric dipole transition moment and permanent dipole moment matrices. The procedure can be used for any molecular system for which the COLUMBUS SOCI circuits are applicable. Example applications are reported for transition moments and dipole moments for a series of electronic states of LiBe and LiSr defined in diatomic relativistic ωω-coupling.     

Implementing a noise protected logical qubit in methyl groups via microwave irradiation

We propose a proof-of-principle experiment to encode one logical qubit in noise protected subspace of three identical spins in a methyl group. The symmetry analysis of the wavefunction shows that this fermionic system exhibits a symmetry correlation between the spatial degree of freedom and the spin degree of freedom. We show that one can use this correlation to populate the noiseless subsystem by relying on the interaction between the electric dipole moment of the methyl group with a circularly polarized microwave field. Logical gates are implemented by controlling both the intensity and phase of the applied field.     

Reachability and controllability of a particle in a dielectrophoretic system

A dielectrophoretic (DEP) force is a result of the interaction between a nonuniform electric field and a polarizable particle. As the electric field is dominant at the micro/nano scale, this force can be effectively used to manipulate and control particles on this scale. We consider the motion of a particle on an invariant line with the suspending medium being a fluid with a low Reynolds number. This DEP system has two states and two parameters: the two states are indicative of the particle’s position and the induced dipole moment and the two parameters are α and c which depend upon the electric properties of the particle and the medium. The system is described by a set of ordinary differential equations with a quadratic term in the control variable (control being the applied voltage on the electrodes which induces the electric field) making the system non-affine in control. In the existing literature, the controllability studies of the DEP system have been restricted to reachability issues in the context of the time-optimal control problem. Here we present a comprehensive study of reachability, accessibility and controllability.