大功率开关电源的设计与实现

介绍了开关电源设计中需要考虑的几个基本问题,包括频率的确定、最大占孔比Dm的确定、逆变变压器的设计和开关功率管的选择,并以一种1 kW的PWM大功率半桥式开关电源为例,详细介绍实际的开关电源设计方案,并给出了实验结果.     

Investigation on vapor-cooled current leads operating in a pulse mode

This paper describes transient numerical modeling for thermal characteristic of vapor-cooled current leads under pulse operation. The transient thermal analysis considers the temperature difference between a helium gas flow and a copper lead with temperature dependent properties of helium gas, copper and stainless steel. The numerical analysis was validated by an experiment with commercially available 100 A vapor-cooled current leads. A proper overloading factor calculation and the effect of intermediate cooling are presented for the current leads under pulse operation, which can significantly reduce heat input to a cryostat.     

Threshold and growth mechanism of fatigue cracks under mode II and III loadings

ABSTRACT The fatigue crack growth behaviour of 0.47% carbon steel was studied under mode II and III loadings. Mode II fatigue crack growth tests were carried out using specially designed double cantilever (DC) type specimens in order to measure the mode II threshold stress intensity factor range, ΔK_IIth. The relationship ΔK_IIth > ΔK_Ith caused crack branching from mode II to I after a crack reached the mode II threshold. Torsion fatigue tests on circumferentially cracked specimens were carried out to study the mechanisms of both mode III crack growth and of the formation of the factory‐roof crack surface morphology. A change in microstructure occurred at a crack tip during crack growth in both mode II and mode III shear cracks. It is presumed that the crack growth mechanisms in mode II and in mode III are essentially the same. Detailed fractographic investigation showed that factory‐roofs were formed by crack branching into mode I. Crack branching started from small semi‐elliptical cracks nucleated by shear at the tip of the original circumferential crack.     

一种基于PWM的半桥型开关电源

主要介绍了由SG3525组成的半桥型开关稳压电路的结构和工作原理，阐述了PWN集成电路SG3525的特性和主要功能。实践表明：该系统工作稳定，运行效果良好。     

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。     

The TDCPR Management Mode of Engineering Equipment

The Three Gorges Project is a very large project,and its structure is very complex.Interna-tional advanced engineering equipment is broadly used.The state of equipment running directly influ-ences project building qualities and limited time.According to the factud conditions of the Three Gor-ges Project,the characteristics of engineering equipment are analyzed.At the same time ,some theories about equipment management are induced ,and the TDCPR management mode of engineering equip-ment of the Three Gorges Project is put forwared in order to gain the aim of managing and using equip-ment well and speeding up the project construction.     

ATM协议的测试研究及其应用

协议一致性测试和互操作性测试是保证不同厂商的ＡＴＭ产品和服务实现完全的互通的重要技术手段，本文分析了ＡＴＭ协议的测试需求，提出了适合的测试结构和测试描述技术，并结合适配层协议ＣＰＡＡＬ５讨论了协议集成测试系统ＰＴＴＳ在ＡＴＭ协议测试中的应用。     

多棒高功率固体激光器动态模匹配研究

采用光学矩阵分析了多元热透镜谐振腔内模式的动态匹配特征,给出了平平腔参数调整的关系式,实验结果与理论分析相符,并在两棒连续Nd:YAG系统上得到0W～530W功率范围的稳定输出.     

分子振动态及其跃迁的激光相干控制

讨论了激光合成相干叠加态的原理及其性质 ,针对 XY2 型分子 ,证明了合成局域模振动的可行性 ,然后给出相干叠加态的跃迁几率特征 ,发现它仍表现出相干的特性 ,对之进行分析研究表明 ,分子的振动态具有可控性 ,态跃迁几率具有可控性。