TSS-BQS系统的Graceful Degradation机制

将门限签名方案分别应用于两种类型的BQS系统(Masking BQS系统和Dissemination BQS系统),可以得到两种TSS- BQS系统(文中称为TSS- mBQS系统和TSS- dBQS系统).TSS-mBQS系统的性能优于TSS- dBQS系统.由此,作者提出了TSS- BQS系统的Graceful Degradation机制:系统由n=3fd+1台服务器组成,在初始阶段以TSS-mBQS状态运行,容忍fm=[fd/2]台Byzantine失效服务器;随着系统运行,可能失效的服务器数量增大,则以降低性能为代价,切换到TSS- dBQS状态,容忍fd台Byzantine失效服务器.在不影响容错能力的前提下,Graceful Degradation机制提高了已有TSS- BQS系统的平均性能.文中完成的Graceful Degradation机制能够在不中断存储服务、不影响客户端的前提下完成状态切换,客户端也不需要知道系统的运行状态(处于TSS- mBQS或TSS- dBQS状态).     

多用户水声通信仿真平台设计

多用户水声通信仿真平台由服务器和客户端两部分组成,在PC机上实现服务器功能;在以Cyclone Ⅲ FPGA为核心的SoPC系统上实现客户端功能.信号通过客户端的数据采集处理后,传输至服务器并与模拟水声信道的冲击响应进行卷积等运算,最后将运算结果转发给其他客户端,实现多用户水声通信仿真功能.     

基于蓝牙和互联网技术的BLDC电机远程控制系统

为了满足远程控制的需求,解决现有控制方案的不足,介绍了一种基于蓝牙和互联网技术的无刷直流(BLDC)电机远程控制系统。使用控制器集成蓝牙模块,通过蓝牙通信将控制器与服务器连接。客户端与服务器通过TCP协议实现网络通信。服务器作为互联网设计的通信节点,实行客户端与控制器连接,完成无刷直流电机的远程控制系统。文章从硬件和软件两方面描述了该系统的实现。     

基于基站定位的通信协议设计与实现

为满足移动通信系统信息查找中基站定位的需要,响应手机客户端的请求,设计了一种服务器间的通信协议。该协议确定了手机客户端与前端服务器、前端服务器与中心服务器之间的通信规范。定义了协议的报文格式和通信规程,协议的功能码定义了所要完成的功能,协议内容中包含基站定位信息。测试表明,该协议可以正确地完成服务器间的数据传输,为基站定位及信息返回提供了保证。     

基于网络的产品在线检测系统*

基于TCP/IP协议,利用Socket易于客户/服务器模式(C/S)网络编程的功能,实现了客户端和服务器端之间的相互通信,并将其应用于浮法玻璃质量在线检测系统;同时提出一种自诊断方法,使得客户端可以自动检测Socket连接状态并在断开的情况下实现向服务器端的重连。     

基于XMPP扩展协议的远程控制系统研制

随着网络的发展,远程控制技术得到越来越广泛的应用。针对目前实际应用中远程控制存在的可达性不可靠、不够安全以及不易扩展等问题,对XMPP协议系统架构、消息格式、安全机制以及扩展性进行研究,通过扩展XMPP协议,设计了一种采用基于XMPP扩展协议的即时通信客户端作为控制端,通过"客户端-服务器"到"服务器-客户端"的模式架构进行通信的远程控制系统。通过系统仿真,验证了系统的有效性和可行性。     

基于TCP/IP协议和多线程的通信软件的设计与实现

为实现船舶导航监控系统可靠的数据传输,通信软件服务器端利用多线程技术实现了与通信运营商转发中心和客户端的网络通信,完成了数据采集和解析功能.通信软件客户端可以与服务器建立连接并接收实时二进制数据,解析后以数据表格形式显示.重点探讨了客户端/服务器模式下基于TCP/IP协议通信的多线程实现过程,并利用时序图和活动图进行具体描述.讨论了在软件安装调试过程中如何解决客户端死机问题和客户端数据与服务器不同步、且数据过少的问题.该软件已交付使用,运行稳定可靠.     

VxWorks系统下的UDP通信在实时系统中的应用

首先简要介绍了某一实时武器系统的网络组成,以及网络通信的基本结构。实时系统采用嵌入式操作系统VxWorks和TCP/IP网络通信协议。讨论了TCP协议与UDP协议各自适用的场合和优缺点。通过比较,系统采用了VxWorks系统下的UDP通信。接着介绍了Socket网络编程,并针对客户端/服务器通信模式的优缺点,给出了此实时系统的客户端与服务器的设计思路与步骤。最后给出了部分代码作为示例说明。     

一种面向用电信息采集系统的WSNs多信道MAC协议

由于无线传感器网络（WSNs）单信道介质访问控制（MAC）协议无法满足用电信息采集系统的数据量大和并发性强的特点,提出了一种面向分簇网络的多信道MAC协议.网络簇间通信采用多信道并行传输方式,簇内通信采用基于信道质量实时评估的自适应信道切换机制.基于OMNeT＋＋的仿真结果表明：与单信道MAC协议相比,该MAC协议可以有效提高网络吞吐量和抗干扰能力.     

基于Android平台的移动智慧校园系统设计与实现

基于Android系统平台、J2EE技术设计实现校园信息管理。客户端通过移动网络访问服务器,服务器使用Servlet及Apache HTTP协议与客户端通信,移动智慧校园系统为教师和学生即时交流提供了一个高效平台。     

煤矿井下安全监控分站的设计及其仿真实现

为了设计一种具有低成本、低功耗、易操作、功能强且可靠性高的煤矿井下安全分站,针对煤矿安全生产实际,文章提出了采用MCS-51系列单片机为核心、具有CAN总线通信接口的煤矿井下安全监控分站的设计方案;首先给出煤矿井下安全监控分站的整体构架设计,然后着重阐述模拟量输入信号处理系统的设计过程,最后说明单片机最小系统及其键盘、显示、报警、通信等各个组成部分的设计;为验证设计方案的可行性与有效性,使用Proteus软件对设计内容进行仿真验证,设计的煤矿井下安全监控分站具有瓦斯、温度等模拟量参数超标报警功能和电机开停、风门开闭等开关量指示功能;仿真结果表明:设计的煤矿井下安全监控分站具有一定的实际应用价值.     

Call for Papers The 6^th International Conference on Grid and Cooperative Computing

Recent years have seen rapid advances in various grid-related technologies, middleware, and applications. The GCC conference has become one of the largest scientific events worldwide in grid and cooperative computing. The 6th international conference on grid and cooperative computing (GCC2007) Sponsored by China Computer Federation (CCF),Institute of Computing Technology, Chinese Academy of Sciences (ICT) and Xinjiang University ,and in Cooperation with IEEE Computer Soceity ,is to be held from August 16 to 18, 2007 in Urumchi, Xinjiang, China.     

View-based model-driven architecture for enhancing maintainability of data access services

In modern service-oriented architectures, database access is done by a special type of services, the so-called data access services (DAS). Though, particularly in data-intensive applications, using and developing DAS are very common today, the link between the DAS and their implementation, e.g. a layer of data access objects (DAOs) encapsulating the database queries, still is not sufficiently elaborated, yet. As a result, as the number of DAS grows, finding the desired DAS for reuse and/or associated documentation can become an impossible task. In this paper we focus on bridging this gap between the DAS and their implementation by presenting a view-based, model-driven data access architecture (VMDA) managing models of the DAS, DAOs and database queries in a queryable manner. Our models support tailored views of different stakeholders and are scalable with all types of DAS implementations. In this paper we show that our view-based and model driven architecture approach can enhance software development productivity and maintainability by improving DAS documentation. Moreover, our VMDA opens a wide range of applications such as evaluating DAS usage for DAS performance optimization. Furthermore, we provide tool support and illustrate the applicability of our VMDA in a large-scale case study. Finally, we quantitatively prove that our approach performs with acceptable response times.     

A pragmatic multi-method investigation of discrepant technological events: Coping,attributions, and ‘accidental’ learning

Discrepant technological events or situations that entail a problem, a misunderstanding or a difficulty with the Information Technology (IT) being employed, are common in the workplace, and can lead to frustration and avoidance behaviors. Little is known, however, about how individuals cope with these events. This paper examines these events by using a multi-method pragmatic approach informed by coping theory. The results of two studies – a critical incident study and an experiment – serve to build and test, respectively, a theoretical model that posits that individuals use a variety of strategies when dealing with these events: they experience negative emotions, make external attributions, and adopt engagement coping strategies directed at solving the event, eventually switching to a disengagement coping strategy when they feel they have no control over the situation. Furthermore, users’ efforts may result in ‘accidental’ learning as they try to overcome the discrepant IT events through engagement coping. The paper ends with a discussion of the results in light of existing literature, future opportunities for research, and implications for practice.     

The Distributed Time-Triggered Simulation Scheme: Core Principles and Supporting Execution Engine

Distributed real-time simulation is a young technology field but its practice is under increasing demands. In recent years the author and his collaborators have been establishing a new approach called the distributed time-triggered simulation (DTS) scheme which is conceptually simple and easy to use but widely applicable. The concept was initiated in the course of developing a new-generation object-oriented real-time programming scheme called the time-triggered message-triggered object (TMO) programming scheme. Some fundamental issues inherent in distributed real-time simulation that were learned during recent experimental studies are discussed along with some approaches for resolving the issues. An execution engine developed to support both the TMOs engaged in control computation and the TMOs engaged in DTS is also discussed along with its possible extensions that will enable significantly larger-scale DTSs.     

Software-Konfigurationsmanagement in großen Softwareprojekten

Zusammenfassung Mit zunehmender Größe der Softwaresysteme verschärfen sich die für die Software-Herstellung typischen Probleme: Beherrschen großer Objektmengen, Erhalten der Systemkonsistenz, Kontrolle der ständigen Änderungseinflüsse und Gewährleisten einer langen Lebensdauer. Die Disziplin Konfigurationsmanagement bildet den methodischen Ansatz, diese Probleme besser zu beherrschen. Software-Konfigurationsmanagement faßt die Herstellung von Softwaresystemen als eine Abfolge von kontrollierten Änderungen an gesicherten Zwischen- und Endergebnissen auf. Dargestellt werden die Objekte und Funktionen des Software-Konfigurationsmanagements sowie die hierfür in großen Software-Projekten benötigten Methoden, Instanzen und Hilfsmittel.     

Information for Authors

正http://www.zju.edu.cn/jzus http://www.springerlink.com Aim The Journals of Zhejiang University-SCIENCE(A/B/C)are edited by the international board of distinguished Chinese and foreign scientists,and are aimed to present the latest developments and achievements in scientific research in China and     

Editorial:Brain-machine interface(BMI) and cyborg intelligence

正Brain-machine interfaces(BMIs)aim at building a direct communication pathway between the brain and an external device,and represent an area of research where significant progress has been made during the past decade.Based on BMIs,mind information can be read out by neural signals to control     

Information for Authors

正http://www.zju.edu.cn/jzus http://www.springerlink.com Aim The Journals of Zhejiang University-SCIENCE(A/B/C)are edited by the international board of distinguished Chinese and foreign scientists,and are aimed to present the latest developments and achievements in scientific research in China and overseas to the world’s scientific circles,especially to stimulate     

SCIENCE CHINA Information Sciences SUBJECT INDEX TO VOLUME 57(2014)

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