基于信令降频码方法的信令寻径式光纤交换机的研究

信令寻径式高速光纤交换机需要使用大量"串/并"转换器件提取信令来实现对信道的控制,这使得交换机的底板面积十分庞大,无法检测BGA封装焊接质量;针对以上问题,提出了一种使用特殊的降频码对信令进行编码,成倍地降低信令的频率,采用普通的FPGA器件即可提取信令,取代了大量占线的"串/并"转换器件,减少了PCB面积和降低了成本;并在此基础上给出了高速光纤交换机的解决方案;目前,基于信令降频码方法的信令寻径式光纤交换机已经调试成功,性能稳定,运行状态良好。     

OFDM-CDMA技术在大型公共建筑节能监控平台中的应用

采用了基于正交频分复用技术的电力线通信(PLC)调制解调器MAX2990构成的自动抄表系统(AMR),可实现大型公共建筑的水、电、气、空调等能耗数据的自动抄送;通过码分多址模组CM800A实现数据的远程传输,本系统能实时监测现场环境变量(温湿度,风速,水流量)并实现相应控制;实验数据表明,本系统具有较强的抗干扰能力、较高的带宽利用率和较快的响应速度。     

利用分级建库技术建造汉语语义词典

文章介绍了立足于机读文本资源——机读《现代汉语词典》和机读《同义词词林》,分级建造以统一管理、共享数据资源为特征的汉语语义词典的研究工作。     

VLIW体系CPU仿真器MCS的设计与实现

仿真器是进行硬件设计评估,系统软件设计开发和计算机体系结构研究的有力工具。文章以一款VLIW(超长指令字)结构的CPU仿真器———MCS为实例,讨论了指令集仿真器设计的一般原理和关键技术。在对目标CPU进行仿真的基础上,通过模拟部分操作系统功能,MCS可以导入并且运行经过目标机编译器编译的目标可执行代码,进行可配置的数据收集和数据分析,从而达到评估CPU设计,分析指令效率,支持编译系统调试的目的。     

Towards a Mobile Code Management Environment for Complex,Real-Time,Distributed Systems

We present a novel mobile code management environment,currently under design and development. Our design employs anopen architecture, suitable for ``plug-and-play' with COTS andother groups' tools. While we have studied new algorithms, costand objective functions, and other fundamental issues, the maincontribution of this experimental research work is in the environmentitself. It should be noted that networked platforms, such asthe World Wide Web, are inherently not suitable for traditional,predictable real-time applications. Thus, real-time concernsnecessarily need to be blended with others concerns, and thetarget applications, making use of our environment, will toobe a blend of partially hard real-time and partially (or mostly)soft-real- time ones. The prototype environment will thereforesupport performance-based analysis and management focusing notonly on predictability but also on compilation, efficiency, safetyand other tradeoffs. We have selected the Java language and itsbytecode format as a representation for mobile code as well asa language for our implementation.     

Empirical validation of referential integrity metrics

Databases are the core of Information Systems (IS). It is, therefore, necessary to ensure the quality of the databases in order to ensure the quality of the IS. Metrics are useful mechanisms for controlling database quality. This paper presents two metrics related to referential integrity, number of foreign keys (NFK) and depth of the referential tree (DRT) for controlling the quality of a relational database. However, to ascertain the practical utility of the metrics, experimental validation is necessary. This validation can be carried out through controlled experiments or through case studies. The controlled experiments must also be replicated in order to obtain firm conclusions. With this objective in mind, we have undertaken different empirical work with metrics for relational databases. As a part of this empirical work, we have conducted a case study with some metrics for relational databases and a controlled experiment with two metrics presented in this paper. The detailed experiment described in this paper is a replication of the later one. The experiment was replicated in order to confirm the results obtained from the first experiment.

As a result of all the experimental works, we can conclude that the NFK metric is a good indicator of relational database complexity. However, we cannot draw such firm conclusions regarding the DRT metric.     

Java移动代码的授权访问研究

Java移动代码是一种可以通过网络从一台计算机传珐另一台计算机上运行的Ｊava程序,在现代网络计算及电子商务中具有广泛应用,Ｊava的这一显著特性也蕴藏着授权管理上的不足,未授权者可以很容易地非法使用这些程序,针对Ｊava移动代码的这些不足之处,分别对Ｊava Applet及Ｊava Applet及Ｊava Servlet提出了基于数字签名算法的授权与访问控制方案,安全,有效地解决了这种新兴的授权与访问控制问题。     

基于智能Agent的实体关系模型多程序代码自动生成方法研究

基于智能Agent理论,本文提出了一种通过人机交互方式自动将实体关系模型（Entit y-Relation,ER）生成多种应用程序语言代码和数据库语言代码的智能化方法体系框架, 简要介绍了利用基于该方法的软件工具将ER模型生成程序代码的过程．     

Quantum programming languages

After giving a bird’s view of some existing quantum programming languages, this paper reports the recent results made by the quantum computation group of the State Key Laboratory for Novel Software Technology and the Department of Computer Science and Technology at Nanjing University, i.e., the quantum programming languages NDQJava, NDQFP and their processing systems.     

Freeman链码压缩算法的研究

文中提出一种新的链码编码方法。在链码中的每个码是根据它与其前一个码之间的前进方向角度差来进行编码的。统计结果表明,这样编码的每个码值的出现概率是很不同的。角度差小的码值出现概率较大,而角度差大的码值出现概率较小。这样结合霍夫曼（Huffman)编码方法就可实现链码的压缩。新链码与现有链码进行了比较。比较结果显示新链码具有最小的平均码长1．97位／码。