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1.
Because of the different ways in which contact materials work, the basic requirements for silver metal oxide contact materials are different. They are anti-welded and anti-erosion when closed, anti-erosion when broken, and arc easily moved and have smaller contact resistance. In this paper, La2O3 is used as a stable oxide in contact material to replace CdO. A new type of Ag/SnO2-La2O3-Bi2O3 contact material is first obtained through using powder metallurgical method. Then electrical contact material parameter tester is used to test the electrical contact performance of the contact material. Through experiments, the arcing voltage and current curves, arcing energy curves, fusion power curves while broken and contact resistance while closed were obtained. Analysis of the results showed that the addition of La2O3 makes the contact material have the following advantages: smaller electrical wear, smaller arc energy, smaller contact resistance and arc is more easily extinguished. 相似文献
2.
WANG Jing-qin WANG Hai-tao WEN Ming ZHU Yan-cai 《浙江大学学报(A卷英文版)》2007,8(3):459-463
Because of the different ways in which contact materials work, the basic requirements for silver metal oxide contact materials are different. They are anti-welded and anti-erosion when closed, anti-erosion when broken, and arc easily moved and have smaller contact resistance. In this paper, La2O3 is used as a stable oxide in contact material to replace CdO. A new type of Ag/SnO2-La2O3-Bi2O3 contact material is first obtained through using powder metallurgical method. Then electrical contact material parameter tester is used to test the electrical contact performance of the contact material. Through experiments, the arcing voltage and current curves, arcing energy curves, fusion power curves while broken and contact resistance while closed were obtained. Analysis of the results showed that the addition of La2O3 makes the contact material have the following advantages： smaller electrical wear, smaller arc energy, smaller contact resistance and arc is more easily extinguished. 相似文献
3.
In this paper,an equation system of electrohydrodynamics(EHD)based onthe fluid motion equations is discussed.Emphasis is put on the effects of electrical forceand surface tension upon the fluid motion.The Marker and Cell method is used to set up acomputational simulation program of electrically driven motion of fluid.With the help ofthe program,a cylindrical fluid under the influences of electrical field and surface tensionhas been calculated.The result is in good agreement with the experimental observation. 相似文献
4.
The aim of this paper is to propose a useful method for exploring regional ventilation and perfusion in the chest and also separation of pulmonary and cardiac changes.The approach is based on estimating both electrical impedance tomography(EIT) measurements and reconstructed images by means of principal component analysis(PCA).In the experiments in vivo,43 cycles of heart-beat rhythm could be detected by PCA when the volunteer held breath;9 breathing cycles and 50 heart-beat cycles could be detected by PCA ... 相似文献
5.
Vacuum interrupter, high reliability component of distribution switches, circuit breakers and contactors 总被引：1，自引：0，他引：1
SLADE Paul G LI Wang-pei MAYO Stephen SMITH R. Kirkland TAYLOR Erik D 《浙江大学学报(A卷英文版)》2007,8(3):335-342
The use of vacuum interrupters(VIs)as the current interruption component for switches,circuit breakers,reclosers and contactors operating at distribution voltages has escalated since their introduction in the mid-1950’s.This electrical product has developed a dominating position for switching and protecting distribution circuits.VIs are even being introduced into switching products operating at transmission voltages.Among the reasons for the VI’s popularity are its compactness,its range of application,its low cost,its superb electrical and mechanical life and its ease of application.Its major advantage is its well-established reliability.In this paper we show how this reliability has been achieved by design,by mechanical life testing and by electrical performance testing.We introduce the“sealed for life”concept for the VI’s integrity.We discuss this in terms of what is meant by a practical leak rate for VIs with a life of over 30 years.We show that a simple high voltage withstand test is an easy and effective method for monitoring the long-term vacuum integrity.Finally we evaluate the need for routine inspection of this electrical product when it is used in adverse ambient environments. 相似文献
6.
LV Bin ZHOU Sheng-jun ZHAO Lan-yan 《浙江大学学报(A卷英文版)》2007,8(3):506-510
Pin and socket contacts are the key parts of electrical connector as aerospace electronic components. The contacts are also the direct carriers for signal transmitting of electronic equipments, passing the signal from the input end to the output end of electrical connector. The reliability of pin and socket contacts directly influences signal transmission. The goal of this study is to enhance the contact reliability of aerospace electrical connector. Computer simulation analysis was made on contacts performance data by utilizing the simulation system developed by PCL Language of MSC software. Furthermore, the results were experi- mentally validated so as to realize the objective of optimizing contacts design. 相似文献
7.
This article is intended for exploration and critique of some issues of the syllabus for Certificate in English for Business. The issues examined are what ideologies are behind the design, what types of the syllabus are and whether it is likely to develop the communicative competence. In addition, the comparison between the learning outcomes and objectives of the education program is also included. Next, the process-oriented syllabus which is different from the category of the teaching plan is taken into consideration as well. Finally, minor problems on whether the design is likely to meet the learners’needs and motivate the learners, whether it is likely for the teacher to the implement the plan are covered, being discussed briefly. 相似文献
8.
Xiayue Fan Bin Liu Jie Liu Jia Ding Xiaopeng Han Yida Deng Xiaojun Lv Ying Xie Bing Chen Wenbin Hu Cheng Zhong 《天津大学学报(英文版)》2020,26(2):92-103
Grid-level large-scale electrical energy storage(GLEES) is an essential approach for balancing the supply–demand of electricity generation, distribution, and usage. Compared with conventional energy storage methods, battery technologies are desirable energy storage devices for GLEES due to their easy modularization, rapid response, flexible installation, and short construction cycles. In general, battery energy storage technologies are expected to meet the requirements of GLEES such as peak shaving and load leveling, voltage and frequency regulation, and emergency response, which are highlighted in this perspective. Furthermore, several types of battery technologies, including lead–acid, nickel–cadmium, nickel–metal hydride, sodium–sulfur, lithium-ion, and flow batteries, are discussed in detail for the application of GLEES. Moreover, some possible developing directions to facilitate efforts in this area are presented to establish a perspective on battery technology, provide a road map for guiding future studies, and promote the commercial application of batteries for GLEES. 相似文献
9.
"Chen Ou Style"is one of the most popular discourses and widely used by many people in communication. In this paper, it is analyzed from a memetics perspective that regards"Chen Ou Style"as a strong meme. The purpose is to find out the internal generating mechanism for a meme to become successful, to reveal the evolution process of language, and to provide some useful guidelines and references for better language use. It is concluded that the replication and transmission of"Chen Ou Style"indicates the existence of language memes, and memetics provides a new perspective for the analysis of language imitation, transmission, change and development. 相似文献
10.
Helen Corkill 《美中教育评论》2008,5(1):1-8
Higher education in the United Kingdom is currently undergoing major changes. In the foreseeable future, it will also undergo farther change. The nature of these changes can be attributed to several key areas-government demand for change, industry demand for change and student demand for change. The UK, like many other major economies and not for the first time in recent history, is having to face the implications of severe skills shortages in its workforce, coupled with the increasing competitiveness of more globalised workforees and workplaces. A recent major government report has set out the country＇s skills agenda until 2020 and UK higher education is starting to wrestle with the implications of these changes, some of which challenge the traditional preserves of university education. This paper will focus on the implications of these skills shortages and the impact that is having on UK higher education. In particular, reference will be made to the impact of the new 2 years vocational Foundation Degrees, to the shift from supply-led to demand-led higher education, the increasing integration and tensions of work-based learning and to the accreditation of Continuous Professional Development （CPD） within an academic framework. This paper presents one story of the growing and changing relationship between higher education and industry. 相似文献
11.
The undergraduate electrical engineering program at The Johns Hopkins University has undergone extensive revision. The most striking revision has been in the laboratory program. Laboratory courses which are distinct from the lecture courses have been developed. These laboratory courses embrace the fields of basic and advanced electrical measurements, transducers, passive circuits, active networks, communications, microwaves, materials, computers, servomechanisms, and energy conversion. The experiments in each one of these fields are designed to give the student insight into both the basic and advanced concepts involved. The sequence of presentation of the experiments is chosen to allow the most complete coverage of a subject as possible, based on the order in which the electrical engineering lecture courses are taken. The use of laboratory manuals, notebooks, reports, and examinations has been given careful thought and some significant ideas have been evolved with regard to their use in establishing a successful laboratory course. 相似文献
12.
D. Lang C. Mengelkamp R. S. Jäger D. Geoffroy M. Billaud T. Zimmer 《European Journal of Engineering Education》2007,32(1):57-72
This study investigates opportunities for conducting electrical engineering experiments via the Internet rather than in an actual laboratory. Eighty-four French students of electrical engineering (semester 1, 2004) at Bordeaux University 1 participated in practical courses. Half of the students performed experiments in a laboratory while the other half performed them via the Internet. Questionnaires were used to obtain students' views as to acceptance, usability, learning effect and usefulness in studying and vocational terms. The learning effect was also measured by a knowledge test. The results show that conducting experiments via the Internet is just as successful as conducting experiments in an actual laboratory. The experiments performed score well for usability and moderately for acceptance and usefulness in studying and vocational terms. Greater use of webcams is suggested as a way of improving acceptance, as this allows more direct contact to the experiments. 相似文献
13.
A recent study of programmed learning, including experimental use in an electrical engineering department, indicated that the most fruitful application of teaching machine methods is in the presently nonprogrammed or loosely programmed hours spent by students outside classroom or laboratory periods. Programs already developed for use in this study have been concerned with analytical skills; further programs under development are concerned with concepts. Larger scale experiments are planned in which additional questions can be answered, particularly as to whether exposure to programmed instruction adversely affects the capacity of the student to learn independently. 相似文献
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15.
为了克服传统电器实验室系统的不足,构建了基于真实实验设备的网络化电器实验系统.该实验系统分为客户端、服务器端和现场设备层3个部分,采用UDP自定义协议及MODBUS/RTU协议实现客户端与服务器、服务器与现场设备之间的通信.文章最后还介绍了温升实验在网络化实验平台中的应用. 相似文献
16.
理论与实践教学互动,提高学生工程实践能力 总被引：1，自引：2，他引：1
该文结合湖南工学院电工电子省级示范实验室建设及省级优秀实习基地建设的实践,从设计课程体系,合理安排实验、实习等工程实践环节,以开放实验室为依托,将理论教学与实践教学形成互动,校内实习与校外实习相结合等方面探讨了提高高职高专电气信息类专业学生的工程实践能力,实现就业中错位竞争的方法。 相似文献
17.
Changes are being made in the content of presentday electrical engineering curriculums which require a fresh, modern outlook with regard to techniques pertaining to problem assignments and laboratory projects. Course content is being upgraded and broadened in the direction of a fundamental analytical approach. The recent revision of the electrical engineering curriculum at The Pennsylvania State University, University Park, includes liberal use of an ac network calculator in all electrical engineering options, which are outlined in this paper. The uniqueness of the ac network calculator at the University is that it is used exclusively for educational purposes, especially in the Department of Electrical Engineering. This paper discusses the "when, where, and how" of the utilization of this facility in the electrical engineering curriculum. 相似文献
18.
在系统分析了电气学科实验室组成结构的基础上,对实验室的管理机制、人员及设备管理方法等内容进行探索。对建立的集中和分散相结合的实验室管理模式改革做了分析和总结。 相似文献
19.
Traditionally, the education in electrical engineering is roughly divided into two areas, viz. electronics and telecommunication on the one hand and electrical energy on the other. Though the borders between these two areas have become vague, this division is still clearly observable, in particular when it comes down to the student's perception of these areas as potential fields of study. Electrical energy has an old-fashioned image. Furthermore, over the last decades there has been a shift from laboratory experiments to computer simulations. In this paper a new approach is introduced, which is aimed at raising first-year students' awareness of the potential attractiveness of electrical energy as an area of study. The approach is project-oriented and based on teamwork. Projects are carried out that are aimed at the design, implementation and verification of small total energy systems. The problems involved are related to energy production, system design, energy storage and consumption. 相似文献
20.
As more and more material becomes relevant for laboratory work in the undergraduate curriculum in electrical engineering, it becomes increasingly important to find more efficient systems for setting up the equipment for laboratory experiments. Any such system should result in a neat, easily followed arrangement when assembled, should be flexible with respect to the experiments which can be performed, and should not result in stereotyped experiments. This paper describes a system which has been evolved utilizing chassis upon which are mounted an array of banana jacks on three-quarter inch centers. Many different circuits can be assembled easily and quickly by plugging in components which are mounted on double banana plugs. Different chassis are arranged for different circuits such as a dual triode, single pentode, and push-pull power amplifier. 相似文献