Closed-form solutions for one-dimensional inhomogeneous anisotropicmedium in a special case. II. Inverse scattering problem

For pt. I see ibid., vol.45, no.5, p.936, 1997. An analytical method is presented for the inverse scattering problem of a one-dimensional (1-D) inhomogeneous anisotropic medium in a special case. Using the closed-form formulations for the reflection coefficients derived in the first part of this paper, reconstruction formulas are obtained for the wave impedance profiles, permittivity profiles or permeability profiles of the anisotropic medium, all of which are given in closed form. In the meantime, a partial inverse scattering method for the electric parameters at the interface of the medium with free space is also investigated by using a Wedtzel-Kramers-Brillouin (WKB) approximation. Numerical examples show the validity of the methods     

Accurate model of arbitrary wire antennas in free space, above orinside ground

An accurate model of wire antennas in free space, above or inside lossy ground is presented in which the current is assumed to flow on the surface of the wire and the testing is also performed on the surface. To replace the traditional delta-gap source, a more accurate source model is developed by using the Huygens' principle. From this principle and reciprocity theorem, a variational formulation of the input admittance is derived. When the triangle function is chosen as both basis and weighting functions, all the elements of impedance matrix and source vector are formulated in closed forms, which can be rapidly computed. Several numerical results are given. Comparing with measured data, both the current distribution and input impedance by this model are more accurate than those of delta-gap model     

Phase equilibria of Sn-In based micro-soldering alloys

The phase equilibria of Sn-In-X (X=Ag, Bi, Sb, Zn), the most basic information necessary for the development of Pb-free micro-soldering alloys, were studied using the CALPHAD method. Thermodynamic analyses for describing the Gibbs energies of the constituent phases were made by optimizing the obtained data on the experimental phase diagrams, and such data in the literature, including data on thermochemical properties. The present results combined with the thermodynamic database which was recently developed by our group [I. Ohnuma et al., J. Electron. Mater. 28, 1164 (1999)] provide various information on phase equilibria such as liquidus and solidus surfaces, isothermal and vertical section diagrams, mole fractions of the phase constitutions, etc., and thermodynamic properties such as activity, heat of mixing, surface energy, viscosity, etc., in multi-component soldering alloy systems including the elements of Pb, Bi, Sn, Sb, Cu, Ag, Zn, and In. Typical examples for the phase diagrams and thermodynamic properties of Sn-In-X ternary systems are shown. The application of the database to the alloy design for Pb-free solders is also presented.     

高级加密标准AES候选之一--MARS算法

本文对MABS算法进行了详细介绍．描述了MABS算法的加解密过程及子密钥生成过程．     

均匀会聚菲涅尔透镜设计及性能研究

提出了一种均匀会聚菲涅尔透镜设计方案,透镜基于离轴聚焦设计,采用方形非旋转对称结构,利用光强叠加实现均匀会聚.文章基于该方法建立了几何聚光比分别为56、100、400和900倍,焦距分别为300 mm、400 mm、500和600 mm的透镜模型,并利用光学仿真软件对其聚光性能进行分析.研究结果表明:基于该方法设计的透镜能够较好地实现均匀会聚,且聚光效率和聚光分布均匀度均超过80％,可以满足聚光光伏需要.     

基于WEB3.0的高校学生工作网络平台构建研究

Web3.0建立在Web2.0的基础之上,是一个无限渗透的智能化和个性化网络。其具有的跨平台、跨语种等特点,为信息化的学生工作提供了保障。本文通过分析Web3.0相关技术为高校学生工作网络平台构建的影响,探讨基于Web3.0的高校学生工作网络平台的构建及其所实现的功能。     

SISTM系统与声像定位技术

1 声音定位技术的历史及现状 声音定位技术的研究,已有六七十年的历史.从两声道,人工头开始,其间出现多种程式,如两声道立体声,四声道立体声,波前制立体声等,但试验均不理想,在剧场中,实际上还是单声道扩声.     

A MULTI-RESOLUTION SPECTRUM SENSING （MRSS） SCHEME UNDER MEASUREMENT-BASED CHANNEL MODELS IN COGNITIVE RADIO

Spectrum sensing is one of the key technologies in Cognitive Radios (CRs). Previous works are accomplished under simple channel models, which may lead to unreliable results when it applied to the over-the-air systems. In this paper, we investigate the performance of a Multi-Resolution Spectrum Sensing (MRSS) algorithm under measurement-based channel models in China. MRSS is a wavelet based algorithm which is suitable for non-stationary, wideband signal analysis. Using statistical modeling, measurement-based channel models are presented under typical urban and suburban scenarios in Shanghai, China. Then, the performance of the MRSS algorithm is evaluated under the measurement-based channel models. Simulation results show that, using MRSS, the performance is always better in the scenarios where Line-Of-Sight (LOS) path exist; also, in LOS scenarios, rich scattering effect helps to increase the performance.     

变压器励磁电流空载电流和磁化电流辨析

阐述了变压器励磁电流、空载电流和磁化电流这三个密切相关的电流瓣物理意义,分析了它们之间的关系和概念上的区别。     

Inverse scattering method for one-dimensional inhomogeneous lossymedium by using a microwave networking technique

The formulation of reflection coefficients from an inhomogeneous lossy medium illuminated by TE and TM waves is approximately derived, in closed form, by using a microwave network method. From the formulation, a novel inverse scattering scheme to reconstruct simultaneously the permittivity and conductivity profiles, is proposed. This scheme is suitable for both continuous and discontinuous profiles, under both the weak scattering and strong scattering conditions. It has also been shown that when the conductivity of the medium equals zero, the reconstructed result of this scheme will reduce to the one formulated by Ladouceur and Jordan (1985). Numerical and closed-form reconstruction examples show the validity of the scheme