Tools for schools [mathematical software packages]

The latest math packages for engineering education offer: programming through icons; collaboration over the Internet; electronic textbooks; and free courseware on the Web. Mathematical software tools can be divided into two groups: programs that chiefly perform symbolic manipulations (also called computer algebra programs for their ability to find exact solutions to analytical expressions) and programs used primarily for large numerical calculations. But the line between these tools is blurring, for some leading vendors now produce packages that include both numerical and symbolic capabilities. The author discusses both types of program and describes some of the features and functions of the programs     

工频电磁场监测报警系统设计

针对一般高压,大电流供电的平台系统易产生较强危害性和电磁环境的电磁干扰问题,设计了工频电磁场监测报警系统,通过实时监测平台高压供电网络产生的工频电磁场状态,设置超限值报警和停留时间提醒,对高危区域进行实时监测提醒,以便有充足的反应时间,采取应对措施。从而可以降低工频电磁场对人员和设备的不良影响,保证人员和设备长期工作的健康和安全。     

Comments on “High frequency performance of multilayercapacitors” [and reply]

For the original paper see ibid., vol.43, no.9, p.2007-15 (1995). The commenters state that are pleased to see this addition to the analysis of high-frequency (HF) capacitors as given in the aforementioned paper. They go on to discuss various points which have arisen in the analysis owing to the use of the transmission-line model. In reply the author clarifies several of the aspects considered     

各向异性脑组织内的电磁场分布

推导出用时域有限差分（ＦＤＴＤ Ｍｅｔｈｏｄ）计算电导率为各向异性脑组织内部电磁场的一般迭代公式,在此基础上计算了典型各向异性脑组织在几种入射情况下内部电磁场的分布,得出有益的结论。此导出的公式可应用于电磁兼容和生物效应的研究之中。     

Broadband modeling and measurement of the signal behavior in S/390MCM packages

In this work, we investigate the electrical performance of critical signal paths in IBM's S/390 MCM packages. We present lumped RLC-models suitable for standard circuit simulators like e.g. SPICE. The models are developed from finite element simulations of typical signal path segments. By comparing S-parameters from simulations of the models to two-port network analyzer measurements we validate the models in a frequency range up to 3 GHz     

三面角反射器的高频电磁散射分析

角反射器是一种宽角域的常见无源干扰设备,常被用于保护关键目标. 但传统金属角反射器特性固定,需借助新型电磁材料实现角反射器的特性优化. 有源频率选择表面（adaptive frequency selective surface,AFSS）是在单元间加载一系列可变有源器件而构成的具有可调电磁特性的新型结构. 为拓展角反射器的适用范围、分析电磁材料角反射器的散射特性以更好地保护关键目标,本文设计了一种基于单面AFSS的电控角反射器,并仿真计算分析了该电控角反射器的散射特性. 仿真结果表明设计的电控角反射器的散射特性可灵活调控,即不同偏置电流下AFSS单元可对入射电磁波能量产生不同反射效果;同时验证了该电磁调控角反射器的宽角域特性,其调控角域在方位向、俯仰向均大于60°,实现了基于无源散射体的宽角域实时调控效果. 相较于传统角反射器和平面电磁材料,所设计电控角反射器兼具实时调控性和宽角域特性,拓展了角反射器的应用场景和适用范围.

     

基于LMBP神经网络的MCM布局电磁场预测模型

通信微波多芯片组件(MCM)内不合理的芯片布局将会导致电磁干扰加剧。对具有不同布局的MCM多层布线基板的电磁场进行了仿真分析,并以仿真分析结果作为样本数据,建立了基于LMBP神经网络的MCM布局电磁场预测模型,然后用该模型对两种单面芯片布局下的MCM的坡印廷矢量数值进行了预测。结果显示,MCM电磁场的仿真与模型预测差值分别为0.332e–7W/m2和0.263e–7W/m2,证明了该预测模型的可用性。     

Finite element computation of electromagnetic fields [hyperthermiatreatment]

A three dimensional finite element solution scheme is developed for numerically computing electromagnetically induced power depositions. The solution method is applicable to those problems for which it can be reasonably assumed that the magnetic permeability is homogeneous. The method employs an incident field/scattered field approach where the incident field is precalculated and used as the forcing function for the computation of the scattered field. A physically logical condition is used for the numerical boundary conditions to overcome the fact that electromagnetic problems are generally unbounded (i.e., the boundary condition is applied at infinity) but numerical models must have a boundary condition applied to some finite location. At that numerical boundary, an outgoing spherical wave is simulated. Finally, an alternate to a direct solution scheme is described. This alternate method, a preconditioned conjugate gradient solver, provides both a storage and CPU time advantage over direct solution methods. For example, a one-thousand fold decrease in CPU time was achieved for simple test cases. Unlike most iterative methods, the preconditioned conjugate gradient technique used has the important property of guaranteed convergence. Solutions obtained from this finite element method are compared to analytic solutions demonstrating that the solution method is second-order accurate     

Switched-capacitor frequency control loop [digital transducer]

A novel approach to digital transduction of physical quantities using a switched-capacitor frequency control loop is presented. The operation of the loop as well as its properties are explained. A few applications are outlined with supporting experimental results.     

Magnetovision [magnetic field scanning system]

The experimental analysis of magnetic fields by scanning methods can effectively support and verify modern numerical methods. The scanning methods are especially suitable for testing the material structure and as a method for material evaluation. By applying the appropriate imaging techniques it is possible to reconstruct the magnetic field strength in an arbitrary plane. In the Magnetovision system, the specific area of a material is magnetized using a C-yoke. A line of miniature thin-film magnetoresistive sensors measures the magnetic field strength above the magnetized sample. Graphical results of the magnetic field strength scanned around steel samples are presented, showing that Magnetovision could be an effective system for nondestructive materials testing.     

Computer-aided design tool for electromagnetic sensors - [instrumentationnotes]

Numerical simulation is an invaluable tool for the designer of any device. By providing a model of the sensor within the design parameters, simulation can substantially speed up and simplify the design process and give a reliable estimation. The use of optimization algorithms can lead to much better sensor characteristics and reduce sensor costs and operation.     

On the sharpness of a needle [electromagnetic propagation]

In a recent paper [Oct. 2003], Van Bladel discussed in detail the behavior of fields and surface charges near singularities of metallic structures, such as a hollow circular cylinder, a circular cone, a thin prolate spheroid, and a uniformly charged segment. At times, the reasoning in [Van Bladel, Oct. 2003] leads to conclusions not as definitive as one might wish because of the various approximations introduced, such as the electrostatic limit for the field or idealized singularities for the conductors (e.g., the tip of a cone). In this work, an example is provided that may assist in shedding some light on the questions raised in [Van Bladel, Oct. 2003], because it consists of an exact, closed-form, simple solution to a boundary-value problem that is valid at all frequencies. The problem consists of a plane wave propagating in free space and axially incident on the convex side of a paraboloid of revolution. This problem was solved by Schensted [1955] for a perfectly conducting (PEC) paraboloid, and by Roy and Uslenghi [Oct. 1997] for an isorefractive paraboloid, which comprises the PEC paraboloid as a particular case. A remarkable fact is that these exact solutions are also the geometrical optics solutions.     

战术无线电通信系统所面临的复杂电磁环境建模与仿真

复杂电磁环境是信息化战争的重要特征,运用计算机仿真技术模拟和分析战场复杂电磁环境,是建立未来高技术条件下作战仿真系统的重要基础.对无线电跳频电台的工作效能产生负面影响的电磁现象复杂多样,作者进行全面的总结和分析,做了概括和抽象,并运用matlab软件进行仿真.在此基础上,根据电磁环境分级标准,建立了复杂电磁环境仿真模型;在建立的模型中考虑到电磁现象的发生概率,以及干扰准则等因素.     

矩形波导中电磁场分布特征研究

波导内电磁场结构复杂,为了解矩形波导中电磁场分布特征,由矩形波导中的TM波和TE波场方程确定波导空间任意时刻、任意位置各分量量值,进而确定空间任意位置电场和磁场矢量的指向,模拟出波导截面和纵剖面的TM11波和TE11波的电磁场分布图。模拟结果得出的结论符合实际,正确地反映了矩形波导中电磁波传播特征,对了解波导中电磁场特性具有重要意义。     

高速电路与MCM互连线的分析

介绍了高速电路与 MCM互连线分析方面的研究与开发工作 ,包括两种新的传输线瞬态分析方法 ,及基于 SPICE的互连线分析系统。     

High and dry [Dryformer power transformer]

In this paper the authors describe Dryformer, an innovative high-voltage transformer design that, by eliminating the need for oil, promises a host of performance and environmental benefits     

Comments on “The electromagnetic field of a vertical electricdipole over the Earth or sea” [and reply]

Yokoyama makes some comments on the “numerical distance” contained in the surface wave term in the paper by King and Sandler (see ibid., vol.42, p.383, 1994) comparing it with the one obtained by former authors. He comments on the parameter P in the Fresnel-integral term in the paper. Yokoyama concludes that for the calculation of such a problem in a semi-sphere, the spherical polar coordinate system is preferable to the cylindrical coordinate system including the case of lateral waves. King and Sandler reply to the Comment     

Comments on "A SPICE model for multiconductor transmission lines excited by an incident electromagnetic field" [and reply]

In a recent paper, C.R. Paul (see ibid., vol.36, p.342, 1994) discusses the concept of using the SPICE circuit analysis code for simulating field-to-wire coupling. He may not be aware that similar work has already been undertaken. A paper by Broyde et al. (1991) appears to be the first published implementation of this idea. The present comments on Paul's mostly theoretical paper emphasize some practical aspects of the simulation of EMC problems using a SPICE simulation program when multiconductor transmission lines (MTL) models are implemented. C.R. Paul responds to the comments.