基于节点代理的数据库集群服务器

将集群服务器能够实现的任务划分为parallelism型及anycast型，指出Web集群服务器的应用关键在于通过数据库集群服务器透明处理variability型动态页面，有3种原子方式搭建数据库集群服务器，讨论了基于节点代理方式的用户案例模型及IDL对象描述，说明实现这种数据库集群服务器的通用途径及核心问题。     

基于马尔可夫过程模型的服务器集群数据可用性分析

可用性是衡量服务器集群的重要指标,在基于马尔可夫过程的服务器状态转移模型基础上，推出根据单台服务器的可用性计算服务器集群可用性的形式化方法，建立了单服务器可用性、服务单元可用性和整个服务器集群可用性之间的量化关系，进而得到多副本分布集群的数据可用性公式,本文的成果有效支持给定服务结点可用性参数的约束下准确估计服务器集群的可用性，对于从可用性角度辅助用户进行集群设计具有理论价值和实际意义．     

多媒体集群服务器的一种混合访问控制策略

分析多媒体集群服务器结构和特点，结合基于角色和内容的访问控制方法，提出了一种适合多媒体集群服务器的混合访问控制策略，给出多媒体集群服务器的访问控制系统设计方案，并讨论了其实现。     

一种集群服务器并行网页预取模型

提出了集群服务器并行网页预取模型，模型采用了马尔科夫链分析访问路径并在Web集群服务器的各节点上并行预取页面，把集群技术的高性能和高可靠性与预取技术的快速响应能力结合起来。实验表明，将此模型应用于集群服务器的分发器上，服务器系统具有更高的请求命中率和更大的吞吐量。     

LCFS中元数据服务器的可靠性分析模型

可靠性问题是研究大规模集群存储系统的一个重要方面，元数据服务器是大规模集群存储的中心。本文针对基于镜像复制和共享存储的服务器实现方案，采用马尔可夫补偿模型研究元数据服务器的状态迁移概率，分析了元数据服务器集群的可靠性以及数据一致性对可靠性的影响，对实现大规模集群文件系统中的元数据服务器有重要的指导意义。     

一种新的服务器集群系统的设计与实现

互联网的飞速发展给我们带来极大便利的同时，也对网络服务器的性能提出了新的挑战。集群技术已成为解决服务器瓶颂问题的有效手段。本文在对服务器集群系统存在的瓶颈问题进行分析的基础上，提出了一种新的服务器集群系统解决方案。该方案通过对传统socket通讯模型进行扩展，并结合直接路由技术，有效地减轻虚拟服务器的负载；同时，通过采用主动自调度策略以解决真实服务器的瓶颈问题，对原型的测试表明该模型是可行的，且提高了服务器集群系统的性能。     

服务器集群技术及设置（二）

在上一期文章中，我们着重介绍了服务器集群技术的分类和双机热备份集群的设置，今天我们将介绍Linux下另外两种服务器集群的设置——不间断服务集群和负载均衡集群。     

分布式数据流处理系统的动态负载平衡技术

设计了一种新的大规模分布式数据流处理系统的体系结构。系统由一组异构的服务器集群组成，负载在每个服务器集群内部多台同构的服务器之间获得平衡，从而达到整个系统的负载平衡。集群设计的主要目标之一是以资源换性能，服务器集群中服务器的最大数目足够保证系统不再发生过载现象，不再需要会降低性能的卸载技术。而且投入运行的服务器的数目根据实际的系统负载来决定，负载较轻时，一部分服务器可以进入休眠状态来减少能源的消耗。根据系统动态增减服务器的特点，设计了全新的初始化算法、动态负载平衡算法。与以前的分布式数据流处理系统相比，由于单个集群的服务器的数目大大减少，算法复杂性降低、速度加快、优化的空间增大。     

一种基于集群的VOD媒体服务器方案设计

根据电信级视频服务器和集群系统的特点，在Linux虚拟服务器构建网络服务器的基础上，提出了一种基于集群的VOD媒体服务器的解决方案，使其具有负载均衡、高可用性和动态扩展的特点，最后给出了VOD服务器集群系统的系统实现方案和测试结果。该方案的实现对其他大规模VOD系统的设计有一定的参考意义。     

基于遗传算法的Web服务器集群负载均衡研究

近年来，Web服务器集群技术以其扩展性好、处理能力强等优点受到了国内外研究机构的广泛关注和应用，其中的负载均衡算法更是研究的热点；对Web服务器集群负载均衡进行了研究，为有效地实现任务的均衡分配，提出一种了根据Web服务器系统中各个服务器的负载情况进行动态任务分配的遗传算法，实验表明该方法能有效地实现Web服务器集群的负载均衡服务。     

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.     

Only connect: teaching, technology and telesis

Abstract This paper describes an approach to the design of interactive multimedia materials being developed in a European Community project. The developmental process is seen as a dialogue between technologists and teachers. This dialogue is often problematic because of the differences in training, experience and culture between them. Conditions needed for fruitful dialogue are described and the generic model for learning design used in the project is explained.     

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.     

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.     

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