LMDS宽带无线接入技术及其应用

LMDS是近年来兴起的一种宽带无线接入技术，充分利用LMDS过去未被很好开发利用的频率资源，并融合在通信领域成功应用的先进技术可以实现更大的频谱利用率，更丰富的业务接入能力及更灵活的带宽分配。论述了LMDS的概念、技术原理及特点、系统结构、系统的优缺点及系统的应用。     

网上教学软件的开发与实现

叙述了网上教学软件在开发过程中的需求分析、总体设计及详细设计等环节·重点介绍了网上课堂的详细设计理念及其使用方法,数据库结构设计,数据流图及如何利用ActiveServerPages实现网上课堂的应用程序·     

试论加入WTO后企业图书工作的管理办法

我国企业应加强对图书管理工作的重视程度，提高图书工作在企业发展中的影响力，尽快建立适应WTO的图书室软、硬件系统，建立高素质图书管理人才队伍，加大现有图书资料的开发利用，以适应加入WTO后的新形势。     

计算机局域网络概论

局域网络日益发展,该文论述了局域网络的标准、术语和技术方面的问题。     

Increased competence as a process of surviving in shared information spaces

Connections between people and groups are growing more frequent and more intense. Cultural events, changes in laws, activities of organizations, and new ideas elsewhere affect one's own decisions and activities more and more. This development has strong implications for the way people can increase their competence and how they can affect what happens to their own community or geographical area. In this paper consequences are considered for a special type of tool, the so-called problem language, that appears to be intimately entwined with many other tools in operations research, cybernetics, and systems research. The language appears most adequate in situations where boundaries can be found such that external events have minimal impact on what happens inside those boundaries. The change in connectivity makes finding such boundaries less and less probable. This suggests looking for another language, to structure the processes necessary when one intends to overcome difficulties that cannot be represented and solved as problems. A language of access is proposed, derived partly from studies in areas where it has never been possible to find boundaries as indicated. Within the framework of this language one can derive methods of externalization that imply speeding up flows of information in a shared workspace or shared information space. Their implementation is greatly facilitated—or even made possible at all—by recent developments in information technology.     

Chromatofocusing coupled with automated assay forβ-hexosaminidase isoenzymes in GM2 gangliosidosis

Summary Good separations of the two major -hexosaminidase forms from human leukocytes were achieved by chromatofocusing, a technique which separates proteins on the basis of their isoelectric points. The use of an automated and reliable method is described for the identification of homozygotes and carriers of the GM₂ gangliosidosis.Work supported by MPI and CNR, Rome     

基于时间的RBAC转授权模型

目的扩充基于角色的访问控制模型(RBAC),使RBAC具有感知时间的能力。方法提出了一种基于时间的角色访问控制模型(TRBAC)。结果在该模型中,对原有的授权约束进行了时间域上的扩充,同时对该模型的授权和授权撤销规则进行系统的论述。该模型能够使系统更加安全有效,降低大规模网络应用的复杂性和安全管理的费用。结论TRBAC模型极大地减少的管理员权限管理的难度,为网络安全防护产生更大的经济和技术效益。     

一种应用于低轨卫星的APRMA MAC协议

针对低轨卫星通信信道碰撞检测能力弱,时延较长和大业务量的特点,提出一种具有接入控制机制的自适应APRMA MAC协议。通过对信道负载和业务优先级判断来确定不同业务的接入概率函数,并且接入概率在每个时隙中通过更新来动态适应系统资源的变化。该MAC协议确保多个终端合理共享有限的无线资源同时,系统能达到高容量。通过仿真对语音业务丢包概率、数据包平均时延和数据业务吞吐量三个衡量协议性能指标与传统协议进行分析对比,证明了APRMA协议的性能。