An analysis of shielding against DC magnetic fields generated by electric railways. Evaluation of effective permeability of fine structure

This paper describes an effective analysis of magnetic shielding based on homogenization. The analyses become time‐consuming if the problems include the magnetic substances having fine structure. The homogenization of the structure makes it possible to analyze effectively the magnetic fields. The authors introduce a method to estimate the effective permeability of the homogenized substance. This method can be applied to any periodic structure made of magnetic substance. The magnetic shielding effects by the structures against direct‐current (DC) fields generated by electric railways are analyzed by using the present method. As a result, it is found that the overhead way and the protective fence near the railway work as a magnetic shield, whose effects can be improved by appropriate arrangement of those constructions. © 2007 Wiley Periodicals, Inc. Electr Eng Jpn, 160(4): 7–15, 2007; Published online in Wiley InterScience ( www.interscience.wiley.com ). DOI 10.1002/eej.20310     

反拍卖采购:一种新的采购模式

反拍卖采购技术以其新的理念和对信息技术的融合，能够使企业采购成本大幅度降低。通过对我国传统采购模式与反拍卖采购模式的对比分析，可以了解到反拍卖采购技术的应用前景。     

连轧机用人字轮齿轴断裂失效分析

用宏观断口分析、化学检验、力学性能测定、低倍检查、金相组织及夹杂物评定鉴别、受力分析及强度寿命定量估算的方法，对人字轮被动齿轴端断裂失效原因进行分析，并提出改进措施。     

舰载火箭武器系统随机响应分析

利用随机振动复模态分析，提出了一种求解时变线性系统，在确定性激励与随机激励共同作用下非平稳随机响应的计算方法，并以舰载火箭武器系统为研究对象，用该法探讨了海浪对舰面火箭发射初始扰动和系统振动特性的影响。     

本钢炼焦煤最佳配比分析

结合本钢的生产实际，对炼焦煤的最佳配比作了比较具体的分析，同时对资源，质量、成本也作了比较详细的调查，并提出了本钢焦化厂最佳配煤比方案，由此可看出，最大限度地降低采购成本，继续开发合理的配煤比例，具有广阔的前景。     

Nonlinear electrical transport in K-TCNQ at low temperatures

A remarkable nonlinearity has been observed for electric transport in K-TCNQ (potassium tetracyanoquinodimethane) quasi-one-dimensional conductor. The negative differential resistance region appears afterV _m (turn over voltage), beyond which voltage goes down with increase of current. A possible mechanism is discussed in terms of dynamics of charged solitons and domain walls in one-dimensional molecular stacks of these types of crystals.     

小型水电站联网改造应注意的几个问题

针对铜鼓县小水电站联网时存在的问题及其不利影响进行了分析，井提出了改进途径，指出小水电站的联网改造应立足安全，争取效益。     

实验应变／应力模态分析若干问题的进展评述

本文评述了实验应变／应力模态分析进展的若干基本问题。主要是：应变响应与位移响应的关系；应变频响函数矩阵的特点及其测量方法；应变模态的加权正交性及其识别方法；以及其他问题。     

Analysis of brushless three-phase synchronous generator without exciter

Recently, a demand for small-capacity generators has been increasing as electric sources in small ships and automobiles or as portable electric sources driven by engines. It is desired that the structure of small-capacity generators be simple and robust, and that the generators be highly reliable, easily maintained and controlled. This paper describes an analysis of the original brushless synchronous generator without exciter. The output voltage can be adjusted in the wide range by controlling the stator dc current. To analyze the characteristics of this generator, the finite element method is applied. It is found that the results of theoretical analysis agree well with the experimental results.