Almost Optimal Dispersers

A disperser is a bipartite graph with the property that every subset A of of cardinality at least K, has at least fraction of the vertices of as neighbors. Such graphs have many applications in derandomization. Saks, Srinivasan and Zhou presented an explicit construction of a disperser with an almost optimal degree , for every . We extend their result for every parameter . Received November 12, 1998/Revised June 20, 2000 RID="*" ID="*" This work was partially done while the author was at the Department of Computer Science, Weizmann Institute of Science, Rehovot, Israel. This work was supported by a Phil Zacharia postdoctoral fellowship.     

Injective hulls are not natural

In a category with injective hulls and a cogenerator, the embeddings into injective hulls can never form a natural transformation, unless all objects are injective. In particular, assigning to a field its algebraic closure, to a poset or Boolean algebra its Mac-Neille completion, and to an R-module its injective envelope is not functorial, if one wants the respective embeddings to form a natural transformation. Received January 21, 2000; accepted in final form August 10, 2001. RID="h1" RID="h2" RID="h3" ID="h1"The hospitality of York University is gratefully acknowledged by the first author. ID="h2"Third author partially supported by the Grant Agency of the Czech Republic under Grant no. 201/99/0310, and the hospitality of York University is also acknowledged. ID="h3"Partial financial assistance by the Natural Sciences and Engineering Councel of Canada is acknowledged by the fourth author.     

基于TMS320DM270的嵌入式开发平台的USB数据通道设计

为TMS320DM270嵌入式系统开发平台添加了USB数据通道。首先初始化USB控制器,使PC机能够识别USB设备。然后,将开发平台上的SRAM格式化为FAT16格式的文件系统,这样在Windows的浏览器下,该SRAM就可以视作操作系统的一个RAM盘。最后,只需要执行简单的拷贝与粘贴命令,就可以实现PC机到开发平台的数据下载。这样向开发板传送数据的速度比串口明显提高。     

基于VB．NET的智能公交管理系统软件平台的开发

VB．NET是Visual Studio．NET战略框架中的重要组成部分,它实现了完全的面向对象特征。针对以VB．NET作为开发工具,以SQL Server2000作为后台数据库的智能公交管理系统软件平台的开发。详细介绍了系统的需求分析、方案设计、功能结构和软件的实现。该系统的应用提高了管理效率,真正实现公交公司的科学化管理。     

基于USB接口的软件加密狗技术研究

详细介绍了Cypress公司EZ-USBFX2系列CY7C68013芯片的内部结构,并给出了基于此芯片的加密狗的硬件实现,并简要介绍了驱动程序和高级应用程序的制作。最后分析了本加密狗在软、硬件的技术优势。     

Windows2000中服务质量保证机制的实现

论述了Windows2000操作系统中服务质量保证机制的实现方式，探讨了如何利用Windows2000提供的服务质量套件开发具有QoS功能的应用程序。     

提升格式与JPEG2000

以D9／7双正交小波变换为例，给出了从Mallat算法出发推导提升格式的详尽步骤。与Daubechies的推导相比，高通和低通滤波同时进行，而且保证每个环节都可以采用有限长度滤波器来实现。另外，JPEG2000给出的D9／7双正交小波变换提升格式中尺度因子的数值（ρ=1.23)与推导的结果（Daubechies推导的结果：ρ=1.1496）有出入，这表明JPEG2000所实现的小波变换与真正的D9／7双正交小波变换是有出入的。就图像编码而言，这种出入并未产生明显的影响。     

基于Win2000的WDM设备驱动程序的开发

介绍了WDM设备驱动程序的原理、结构及运行等方面的内容 ,并通过一个“WDMHello”的实例讨论了WDM设备驱动程序的开发技术及过程     

校园网ISA Servre2000代理服务与防火墙技术

本文介绍了由Microsoft ISA Server2000构成的防火墙和代理服务器的功能、特点。     

Windows 2000环境下的一种SCSI冗余路径驱动程序

为提高存储系统的可用性 ,在 Windows2 0 0 0系统中实现了SCSI冗余路径驱动程序 RDP。在路径发生故障时由 RDP将 I/ O切换到其他路径。通过将 I/ O负载均衡分布在各 SCSI路径 ,能增加系统 I/ O处理能力