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     

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.     

Performance prediction of a hybrid‐excitation synchronous machine with axially arranged excitation poles and permanent‐magnet poles

This paper presents a method of predicting the steady‐state performance of a new hybrid‐excitation synchronous machine (HESM) theoretically. The field pole of this HESM is axially divided into two parts; one is an excitation part and the other a permanent‐magnet (PM) part. A nonlinear equivalent circuit, which can include the saliency of the rotor and the magnetic saturation due to the iron core, is derived. Based on this equivalent circuit, the steady‐state performance of the HESM is calculated, and the results are confirmed through experiments. © 2004 Wiley Periodicals, Inc. Electr Eng Jpn, 150(2): 43–49, 2005; Published online in Wiley InterScience ( www.interscience.wiley.com ). DOI 10.1002/eej.20033     

A survey of nitrate and nitrite content of fruit and vegetables grown in Slovenia during 1996-2002

Monitoring of nitrate (NO₃^-) and nitrite (NO₂^-) content in agricultural products in Slovenia has been carried out since 1996. The results of monitoring over the period 1996-2002 are presented. During this time 924 samples of 14 different agricultural products (potato, lettuce, apples, carrot, silage maize, cabbage, grapes, peaches, string beans, cereals, pears, cucumbers, strawberries and tomato) were analysed. The samples were taken at the time of maturity directly from growing sites and they were analysed using segmented flow analysis. The average nitrate contents were the highest in lettuce (1074 mg kg^-1), cabbage (881 mg kg^-1), string beans (298 mg kg^-1) and carrot (264 mg kg^-1), and they were moderately high in potato (158 mg kg^-1), silage maize (122 mg kg^-1), strawberries (94 mg kg^-1), cucumbers (93 mg kg^-1) and cereals (49 mg kg^-1). Low nitrate contents (below 6 mg kg^-1) were found in fruit (grapes, peaches, apples and pears) and tomato. With the exception of cereals (8.9 mg kg^-1), apples (1.5 mg kg^-1), potato (1.2 mg kg^-1) and pears (1.0 mg kg^-1) the content of nitrites did not exceed 0.5 mg kg^-1. It may be concluded that the results of the monitoring were in most cases similar to the results of investigations obtained in other countries.     

Influence of Zn ion implantation on structures and field emission properties of multi-walled carbon nanotube arrays

The structures and field emission properties of multi-walled carbon nanotube arrays implanted with Zn+ by MEVVA ion implanter have been investigated.The results revealed that Zn+implantation induced structural damage and that the top of carbon nanotubes with multi-layered graphite structure were transformed into carbon nanowires with amorphous structure.Meanwhile,C:Zn solid solution was synthesized after Zn+ implantation.The turn-on field and threshold field were 0.80 and 1.31 V/μm,respectively for original...     

基于无线通信方式的TV二次压降现场测试方法

针对传统的TV二次压降现场测试方法存在的问题,提出基于无线通信技术的检测方法。以提高工作效率,降低安全风险。     

普光气田邻井干扰压降研究

根据普光气田现场资料,分析普光气田关井压降恢复时间和稳定生产时间的关系。建立邻井干扰计算模型,评价邻井干扰压降值及邻井干扰,并对邻井干扰规律进行敏感性分析。     

“顶岗置换”模式培养高师准幼儿教师的探讨

＂顶岗置换＂模式不仅促进了一线学前教师的职后培训,更有利于高师准幼儿教师的培养;同时,＂顶岗置换＂对高师准幼儿教师的培养提出了相应的挑战：顶岗对学生的高要求——能否从学生变为教师,顶岗对学生的低回报——能否从教中学。提出相应策略,促进＂顶岗置换＂模式下准幼儿教师的培养。     

西阜高速公路石家庄段弃渣场水保措施探析

针对西阜高速公路石家庄段建设过程中弃渣量大的实际情况,在分析弃渣场选址与治理思路的基础上,提出了工程措施、植物措施和临时拦挡措施相结合的综合防治体系,并对弃渣场水保措施进行典型设计。     

变频器综合实践 第2讲： 变频器在总线控制系统中的综合实践

现场总线是将自动化最底层的现场控制器和现场智能仪表设备等互连的实时控制通讯网络,而变频总线控制系统的特点,就是通过总线可以控制和监控变频器。变频总线控制系统既可联动控制也可单独控制,能充分满足传动系统的可靠性、实时性、实用性的要求,并为实现传动系统的＂无人值班＂运行提供技术准备。