AC/DC电路故障检测仪设计

本文介绍了一种可在被检测设备电路不带电状态下工作的AC/DC电路故障检测仪,并对其电路工作原理、测试方法进行了较详细的分析.     

Ethical dilemmas in evaluating programs with family court related clients

Two ethical dilemmas are discussed; breaching client confidentiality in order to intervene in the client's illegal behavior, and defining the role of evaluator as expert witness. The evaluation context concerns a combined program development and evaluation project with clients involved in family court proceedings for child abuse or neglect. Different perspectives, approaches, and experiences in resolving each dilemma are reviewed. The conclusion argues that approaches to ethical dilemmas in evaluation projects must go beyond techniques to disguise data, to include an assessment of the values and value commitments connected to the different roles an evaluator must perform.     

单片DC/DC变换器的分析与设计

在0.35μm硅衬底CMOS工艺条件下,分析了集成平面电感器的单片DC/DC变换器的功率损耗,折中考虑了设计中的难点以及各种影响因素。优化了变换器的转换效率,确定其开关频率为100MHz;考虑片上集成平面电感器的单位面积电感值与品质因数的大小也是决定DC/DC变换器性能的关键因素,该文给出了双层平面螺旋电感器的物理设计与几何参数优化,获得了双层平面螺旋电感。模拟结果表明该变换器工作稳定,转换效率可以达到62%。     

高频开关电源技术在电信电源系统中的应用

介绍了高频开关电源技术在电信电源系统中的具体应用,结合具体框图对高频开关整流器模块及通信用二次电源模块的组成及功能作了叙述,并从功率器件、开关技术、工作频率、功率因数校正、同步整流、负载均流等诸多方面阐明了开关电源技术在电信电源系统中的应用。     

Resolving conflicting demands on evaluation: A test demonstration of videotex for farmers

Evaluating an innovation for federal, state, and local policymakers and program managers alike entails conflicting demands on the evaluation study. Policymakers at federal, state, and local levels are best assisted by impact evaluations, whereas state and local program managers are best assisted by process evaluations. In-house evaluators often have an advantage in conducting process evaluations; external evaluators generally have an advantage in conducting impact evaluations. A cost-effective approach may be to combine in-house process evaluation and external impact evaluation. This dual approach was found to reduce conflicting demands on the evaluation of an experimental videotex system for agricultural producers.     

DC元数据在中国数字图书馆建设中的应用之我见

最新版本的DCMI元数据术语规定了元数据元素、元素限定词和编码体系修饰词定义的必备属性和有则必备属性。本文区分了DC元数据标准中关于修饰词的几个概念,介绍了DCMI元数据术语定义规范和DC元数据在数字图书馆建设中的优势,探讨了本地应用纲要制定中应注意的问题。     

溅射功率和氧氩比对TiO2薄膜亲水性的影响

摘要：用直流磁控溅射制备TiO2薄膜,分析了氧氩比和溅射功率两项制备参数对退火后形成的锐钛矿二氧化钛薄膜亲水性的影响。实验结果表明,适中的氧氩比2：3和功率126W下制备的薄膜具有很好的亲水性。     

具有浮动限幅特性直流伺服系统的稳定性分析及仿真研究

建立了具有浮动限幅特性直流伺服系统的数学模型.基于描述函数的概念和方法进行了稳定性分析,结果表明浮动限幅特性可能引起系统不稳定.基于Matlab/Simulink仿真环境进行了仿真研究,确定了在阶跃和斜坡输入信号作用下系统稳定运行的范围及获得的性能指标.     

脉宽调制型DC—DC变换器的线性描述函数分析法

介绍了一种分析开关变换器的新方法－线性描述函数法的理论证明及实验结果,这种方法具有精确度高的优点。     

Should evaluators judge whether services are appropriate?

If an Aid for Dependent Children (AFDC) mother receives a cash reward for helping police apprehend a criminal, she automatically loses part of her children's benefits. Is this appropriate? More central to this article, does an evaluator of the AFDC program have the right to judge whether this is appropriate? Although decision makers' abilities to rectify such situations are increasingly constrained, they clearly need to know about such seemingly inappropriate aspects of services. But should evaluators be a source for this information? Yes — even though there are undeniable risks involved. This article discusses these issues and offers 18 suggestions for gathering and presenting information on appropriateness.