“电工电子学”课程内容的思考与教学实践

本文对"电工电子学"(电工学)课程教学内容的选取、相关内容如电工技术与电子技术、分立电路与集成电路、基本理论与工程应用、单元电路与综合系统等的关系和处理都提出了几点思考,并在教学过程中进行了探索和实践,其结果是使学生的知识综合运用能力得到很大的提高。     

超结硅锗功率二极管电学特性的研究

超结SiGe功率开关二极管可以克服常规Si功率二极管存在的一些缺陷,如阻断电压增大的同时,正向导通压降也将增大,反向恢复时间也变长。该新型功率二极管有两个重要特点:一是由轻掺杂的p型柱和n型柱相互交替形成超结结构,代替传统功率二极管的n-基区;二是p+区采用很薄的应变SiGe材料。该器件可以同时实现高阻断电压、低正向压降和快速恢复的电学特性。与相同器件厚度的常规Si功率二极管相比较,反向阻断电压提高了42%,反向恢复时间缩短了40%,正向压降减小了约0.1V(正向电流密度为100A/cm2时)。应变SiGe层中Ge含量和器件的基区厚度是影响超结SiGe二极管电学特性的重要参数,详细分析了该材料参数和结构参数对正向导通特性、反向阻断特性和反向恢复特性的影响,为器件结构设计提供了实用的参考价值。     

Location‐based distributed caching for device‐to‐device communications underlaying cellular networks

Device‐to‐device (D2D) communications have been viewed as a promising data offloading solution in cellular networks because of the explosive growth of multimedia applications. Because of the nature of distributed device location, distributed caching becomes an important function of D2D communications. By taking advantage of the caching capacity of the device, in this work, we explore the device storage and file frequent reuse to realize distributed content dissemination, that is, storing contents in mobile devices (named helpers). Specifically, we first investigate the average and lower bound of helper amount by dividing the network into small areas where the nodes are within each other's communication radius. Then, optimal helper amount is derived based on average helper amount and network topology. Subsequently, a location‐based distributed helper selection scheme for distributed caching is proposed based on the given optimal helper amount. In particular, nodes are selected as helpers according to their locations and degrees, and contents are placed in the manner for maximizing total user utility. Extensive simulation results demonstrate the factors that affect the optimal helper amount and the total user utility. Copyright © 2015 John Wiley & Sons, Ltd.     

Analog Circuit Design Methodology in a Low Power RISC Microprocessor

There are various kinds of analog CMOS circuits in microprocessors. IOs, clock distribution circuits including PLL, memories are the main analog circuits. The circuit techniques to achieve low power dissipation combined with high performance in newest prototype chip in the Super H RISC engines are described. A TLB delay can be decreased by using a CAM with a differential amplifier to generate the match signal. The accelerator circuit also helps to speed up the TLB circuit, enabling single-cycle operation. A fabricated 96-mm² test chip with the super H architecture using 0.35-m four metal CMOS technology is capable of 167-MHz operation at 300 Dhrystone MIPS with 2.0-W power dissipation.     

P2P文件共享系统防止重复下载的方法研究

在P2P文件共享系统中,文件名的差异经常会导致文件被同一节点重复下载,为了降低P2P文件共享系统中摘要算法对文件进行整体和分块处理,下载前先比较文件MD5散列值的方资源重复下载率高的问题,文章提出采用MD5报文法来确定是否需要下载文件,从而有效地防止共享文件被同一节点重复下载.通过分析和利用MATLAB软件进行模拟试验,证明该方法能提高文件的下载效率.     

水在渠道防渗工程冻害中的作用及防治冻害对策

我国东北、华北、西北等寒冷地区的渠道防渗工程，因多为薄板式结构，裸露面很大，同时经常与水接触，甚至在冬季负温下仍要输水运用，故其冻胀破坏更为严重，影响了工程效益的充分发挥。本文在简述水在渠道防渗工程冻害中的作用后，从渠道防渗工程的设计、施工和管理运用方面，提出了保证防渗层工程质量、降低基上水分、防止外水渗（流）入渠基、降低地下水位和管理运用等防治冻害较为具体的对策。     

Effect of 0.1 at.% zirconium on the cyclic oxidation resistance ofβ-NiAl

The effect of 0.1 at.% Zr (0.2 wt.% Zr) on the cyclic oxidation of hipped -NiAl was studied. Oxidation testing was performed in static air at 1100–1200 °C, using 1-hr exposure cycles for test times up to 3000 hr. The weight change versus time data were modeled with the COSP computer program to analyze and predict cyclic-oxidation behavior. Zr additions significantly change the nature of the scale-spalling process during cooling so that the oxide spalls near the oxide-air interface at a relatively low depth within the scale. Without Zr, the predominantly -Al₂O₃ scale tends to spall randomly to bare metal at relatively high effective-scale-loss rates, particularly at 1150°C and 1200°C. This leads to higher rates of Al consumption for the Zr-free aluminide and much earlier depletion of Al, leading to eventual breakaway (i.e., failure).     

宽带内容平台技术基础

本文首先分析了当今支撑宽带应用和内容的两大技术：流媒体技术和内容分发网络（CDN）技术，结合上海电信的宽带信息源建设项目，介绍邓电信的IP城域网架构上建设1 4的CDN和流媒体融合的平台。通过CDN和流媒体的技术方案，希望为宽带的发展提供一定的技术参考。     

ZnO压敏陶瓷最佳掺杂含量的理论计算

从对电子薄膜材料研究中得到的最佳掺杂含量定量理论推广到ZnO陶瓷材料。该理论建立了电子薄膜材料的某一物理性能与晶体结构、制备方法和掺杂剂含量之间的联系，给出了一个能够拟合实验曲线的具有确定物理意义的抛物线方程。该方程的极值点确定了最佳掺杂含量与晶体结构和制备方法之间的定量关系，进而得到了一个掺杂最佳含量的表达式。系统地分析了ZnO压敏陶瓷的掺杂改性的实验结果，应用此表达式定量计算了ZnO压敏陶瓷的最佳掺杂含量，定量计算的结果与实验数据相符合。该理论也适用于其他薄膜材料最佳掺杂含量的理论计算。     

面向多级安全的跨域交换技术研究

跨域交换技术为不同安全域之间的数据通信提供了便利,但由于跨域信息系统开放了域内多个端口,面临着各种来自系统内外部的安全威胁,导致了信任危机。针对现有跨域信息系统在数据交换方面的安全需求,首先分析了当前跨域信息交换存在的问题,接着设计了面向多级安全的跨域交换系统架构,该架构能够有效地实现多域信息系统的安全互联与资源共享,然后研究了安全标签绑定、内容过滤等关键技术,最后对下一步的研究工作进行了展望。