夏季最大负荷发生时间的预测

夏季最大负荷发生时间的预测是电力部门十分关注的问题,它关系到该地区的负荷调整方案以及购电计划制定。北京近年来夏季用电需求增长尤为突出。准确地估计夏季最大负荷发生时间,十分必要且迫切。为此,收集了北京市1990~2002年的夏季最大负荷发生时间数据,发现它是一个波动的、含有灰信息量的序列,故采用灰色系统理论进行预测建模分析。但常规的GM(1,1)模型在适应波动的数据方面,预测精度未能达到要求,故采用GM(1,1)残差周期修正预测模型来解决。经过计算发现,该模型不仅可以提高原始数据的拟合精度,而且用于预测时,与2003年夏季最大负荷发生时间的实际值进行比较,预测偏差也在允许的范围内。     

基于叠加原理大功率可编程谐波电压源的研制

针对大容量电力电子装置对测试电压谐波源的要求，本文对大功率可编程电压谐波电压源的拓扑结构和控制方法进行了研究，提出一种采用谐波与基波分离控制的实现方法，给出了系统的拓扑结构，分析了系统的控制原理。仿真和实验结果证明，该方法能有效提高系统容量，实现用小的开关器件得到大功率的电压谐波源输出的设想。该电压谐波源可以模拟各种电压质量问题，以该拓扑结构搭建的实验平台能满足大功率的电力设备对测试用电压谐波源的要求。     

嵌入式双CPU系统中Full Proxy的研究与实现

VoIP语音视频流对NAT／Firewall的穿越已经成为语音数据业务开展过程中最大的障碍。Full Proxy提供了一种NAT/Firewall穿越的有效途径。具有很强的适应性和透明性。本文深入讨论了Full Proxy的实现原理和基于Full Proxy的整个呼叫流程，最后在一个嵌入式双CPU系统的基础上实现了一个Full Proxy。     

Ge n-MOSFETs on lightly doped substrates with high-/spl kappa/ dielectric and TaN gate

In this letter, we report successful fabrication of germanium n-MOSFETs on lightly doped Ge substrates with a thin HfO/sub 2/ dielectric (equivalent oxide thickness /spl sim/10.8 /spl Aring/) and TaN gate electrode. The highest peak mobility (330 cm/sup 2//V/spl middot/s) and saturated drive current (130 /spl mu/A/sq at V/sub g/--V/sub t/=1.5 V) have been demonstrated for n-channel bulk Ge MOSFETs with an ultrathin dielectric. As compared to Si control devices, 2.5/spl times/ enhancement of peak mobility has been achieved. The poor performance of Ge n-MOSFET devices reported recently and its mechanism have been investigated. Impurity induced structural defects are believed to be responsible for the severe degradation.     

真空热处理对CoFe薄膜结构及电磁特性的影响

在本底真空度优于5×10-4Pa的室温条件下,利用电子束蒸发方法沉积CoFe薄膜,研究了不同退火温度对CoFe薄膜结构和电磁特性的影响。样品采用热氧化Si为基片,在3×10-5Pa真空度下分别进行了150、280、330、450和500℃的60min退火处理。电阻率和磁电阻测量表明,450℃退火处理能够明显降低CoFe薄膜电阻率和提高磁电阻变化率,因为这时的X射线衍射谱显示CoFe薄膜的结构已明显改善。还发现沉积在热氧化Si基片上的CoFe薄膜(111)晶面面间距明显小于靶材相应晶面面间距,而退火处理会使薄膜(111)晶面面间距接近恢复到靶材。透射电镜对沉积态样品分析表明,样品呈多晶结构但结晶不太理想。振动样品磁强计(VSM)的磁特性测量发现,500℃真空退火处理,薄膜的矫顽力和饱和磁化强度都提高近一倍,分别由室温沉积态的2337 A/m和327 emu/cm3上升到退火后的4746 A/m和649 emu/cm3。     

Tribological Properties of DLC Film Prepared by C ^＋ Ion Beam-assisted Deposition （IBAD）

C ^＋ ion beam-assisted deposition was utilized to prepare deposit diamond-like carbon （ DLC ） film. With the help of a series of experiments such as Raman spectroscopy, FT-IR spectroscopy, AFM and nanoindentation , the DLC film has been recognized as hydrogenated DLC film and its tribologicul properties have been evaluated. The bull-on-disc testing results show that the hardness and the tribologicul properties of the DLC film produced by C^ ＋ ion beam- assisted deposition are improved significantly. DLC film produced by C ^＋ ion beam- assisted deposition is positive to have a prosperous tribologicul application in the near future.     

Valence State of Active Copper in CuOx/CeO2 Catalysts for CO Oxidation

CuOx/CeO2 catalysts were prepared by adsorption-impregnation method, CO conversion was tested over the catalysts pretreated under different conditions for preferential CO oxidation in H2, and the catalysts were characterized with X-ray photoelectron spectroscopy and temperature programmed reduction. Experimental results show that there are two kinds of copper, which are Cu^＋ and Cu^2＋ in calcined CuOx/CeO2, Among them, the Cu^＋ is the key active component for CO oxidation. The main reason is as follows： CO is activated by copper for CO oxidation over CuOx/CeO2, while CO can not be activated by Cu^2＋. Only when Cu^2＋ is reduced to Cu ^＋ or Cu^0, the copper may be active for CO oxidation, moreover, the experimental results show that the reduction of Cu^2＋ does not lead to an increase of catalytic activity. So the active species is Cu^＋ in CuOx/CeO2 catalysts.     

220kV线路保护与高频收发讯机接口方式的现场应用

通过对220kV线路保护与高频收发信机两种不同接口方式的现场接线,找出了在旁代线路过程中接口方式发生变化后操作中的关键环节,提出了解决问题的方法和建议。     

深化大学生社会实践活动的思考

深化大学生社会实践活动是我国社会变革的必然要求，也是我国教育改革的重要内容。本针对大学生的特点，指出在深化大学生社会实践活动的同时，应把握好两个基本方向：服务社会和服务大学生。这不仅对于大学生的成长有不可估量的价值定义，也有利于实现素质教育的全面推进。