基于UC3844反激开关电源的反馈回路参数设计

介绍了基于UC5844芯片实现的反激开关电源的工作原理，结合用于电机控制的电源模块实际所需要的功率大小，进行了反馈回路参数和误差补偿回路参数设计，最后通过实验验证了参数设计的合理性，实验结果表明该电路具有良好的电压调整率和负载调整率，并且具有电压纹波小和工作稳定可靠等优点。     

某微型车前纵梁与前轮罩连接结构改进

整车可靠性路试和小批量造车是检验车身设计是否成功的重要手段。文章针对某微型车前轮罩总成的结构件在整车耐久性路试(路试里程为39 000 km)中的开裂问题、生产车间关于此部分零件的造车问题反馈以及冲压工艺问题进行分析,并成功地解决和优化。     

Improved rangeland management with an Earth Resource Survey system

Recent advances in communications and satellite technology now make it possible to provide large, synoptic imagery of the earth's surface at relatively low cost. This paper reports on acase study that was designed to estimate the benefits that might be realized by rangeland managers from an Earth Resources Survey system. Information needs and current practices are first discussed and then related to available remote sensing and data distribution techniques. The analysis showed that cost savings from an applications system would be broadly evident in the areas of resource re-allocation, range productivity, and livestock management. Depending upon the assumptions concerning the discount rate and factors affecting technological diffusion, total benefits were estimated to range from $38.7 million to $115.4 million over 10-year operational period.     

基于UC1842的高可靠低纹波多路输出开关电源的设计

依据UC1842的优势,研制了一款高可靠低纹波多路输出开关电源。它将开关电源与三端稳压器件结合,输出具有低纹波的特点,而且可通过极少的元件实现多路隔离输出,因此在军用、医用及通信领域广泛适用。通过实际生产验证,此电源具有可靠性高、纹波低及适用性强的特点。     

Communications

The University of California, Berkeley sends more undergraduate students to economics PhD programs than any other public university. While this fact is surely a function of its size, there may be lessons from the Berkeley experience that others could adopt. To investigate why Berkeley generates so many economics PhD students, the author convened and interviewed two groups: economics student services staff and a self-selected focus group of twelve economics undergraduates who plan to apply to PhD programs. Four factors came up repeatedly in these conversations: math preparation, advanced track for theory courses, research opportunities, and availability of information. A fifth factor was implicit in the conversations: peer effects.     

基于UC3875的新型DC／DC变换器研究

围绕带钳位二极管的移相全桥ZVS变换器的工作原理、软开关实现条件、整流桥选用及其寄生振荡的抑制、电压型单环控制等问题进行了理论分析,设计了一套基于UC3875移相芯片的电压型单环控制系统,并搭建了实验平台,在实验平台上进行了实验,给出了实验结果。实验结果说明了控制方案的可行性,验证了电路设计的正确性。     

开关电源电路分析与技术改进

本文介绍了以电流控制型脉宽调制芯片UC3842构成的开关电源的原理,分析了其保护电路的缺陷,并提出了一种改进的思路。