基于消息延迟预测的自适应失效检测模型

失效检测是实现高可用性的一个关键技术,通常采用超时机制判断进程是否失效的方法实现。然而,由于网络状况的不断变化,缺乏自适应机制的失效检测器难以满足应用对QoS的需求。自适应失效检测要求失效检测器能够根据实际应用和网络负载变化而动态地改变检测的质量。在对现有自适应失效检测算法研究、分析的基础上提出一种基于消息延迟预测的失效检测模型,采用基于历史消息延迟预测下一个消息延迟的方法,实现了一种PA-AFD自适应失效检测算法。实验及分析表明该算法在保证检测准确性和完整性的同时缓解了网络延迟对失效检测的影响。     

容错云计算网络中自适应故障检测方案研究

当前大多数故障检测(FD)技术无法针对动态网络条件自动调整它们的检测服务参数,导致无法应用于实际环境中。针对容错云计算网络中的故障检测特性进行研究,提出了一种通用的容错云计算网络自适应故障检测(SFD)算法;基于上述通用算法,对当前故障检测器进行优化,提出了一种自适应累积型故障检测器,并对SFD算法的部署进行了研究。基于七种典型的广域网案例,比较评估了该故障检测算法与当前其他算法的性能。实验结果表明,该算法可以实现故障的自适应检测,满足用户需求,拥有较高的系统性能。     

Web应用服务器的适应性失效检测

失效检测是分布式系统的基本可靠性保障技术,它对运行时系统的存活状态进行及时检测.作为网络分布计算环境中的主流中间件,Web应用服务器(Web application server,简称WAS)需要提供良好的检测机制,并且要能满足适应性的需求.适应性失效检测要求失效检测器能够根据应用需求和系统环境的变化而动态地改变检测的质量.首先给出了WAS的多层失效检测模型,然后基于失效检测器的服务质量规约,提出了适应性失效检测算法,并设计了一个WAS的适应性失效检测框架.它能够满足动态调整失效检测质量和灵活集成失效检测器的要求.该工作在OnceAS应用服务器中进行了实现,并给出了OnceAS平台上的实验及数据.     

滞后估计算法在手机网络失效检测中的应用

对手机网络失效检测是一个新的研究课题。手机网络的失效往往没有明显特征,内部体现为消息的滞后性;根据这一特性,提出一种契比雪夫滞后估计算法并应用到手机网络失效检测中,给出了算法的原理,并根据手机网络传递消息滞后时间,带入算法进而估计下一次信号消息到达的滞后时间估计值,根据手机网络中消息到达的时间间隔,代入算法估计下一个数据消息可能到达的滞后间隔;设置下一个信号消息到达时刻计时器的超时值,将低于该超时值的滞后时间间隔所对应的手机网络消息节点看成失效节点,实现了对手机网络失效的准确检测;实验及分析说明该算法的估计结果同实际手机运行情况匹配度超过85%,具有较高的鲁棒性。     

匹配阈值的预测计算和自适应算法实现

基于否定选择算法,提出一种匹配阈值的预测计算方法,通过通用方程计算最优阈值,实验证明提高了检测率,同时分析了预测计算的适用范围。针对静态固定阈值的方法不能适应网络数据动态变化,利用遗传算法进化检测器同时实现阈值自适应,仿真结果表明提高了检测率,降低了误测率,能在自体集动态变化的情况下动态生成检测器。     

云网络中一种基于高服务质量的故障检测方案

当前大多数故障检测技术(FD)无法针对动态网络条件自动调整它们的检测服务参数,导致无法应用于实际环境中。对现实中的自动容错云计算网络的故障检测特性进行研究,首先提出一种通用的容错云计算网络自适应故障检测算法(SFD),然后基于上述通用算法,对当前故障检测器进行优化,提出一种自适应累积型故障检测器,并对SFD算法的部署进行研究。最后,我们基于7种典型的广域网案例,通过广泛的实验,比较评估该故障检测算法与当前其他算法的性能。实验结果表明,算法可以实现参数的自动调整,进而获得相应的服务质量,满足用户需求,拥有较高的系统性能。该SFD可以广泛应用于工业和商业领域,并为云网络带来巨大效益。     

基于二次检测的失效检测算法的改进

为了使失效检测满足分布式网络环境的要求,针对分布式网络环境中存在的网络延迟和丢包两种情形,提出了基于失效检测点和二次检测模式的失效检测改进算法。该算法根据误判次数动态计算二次检测时间,在失效检测的准确性和效率之间作了较好的权衡。理论分析和测试结果均表明该算法能够适应网络环境的变化并有效地减小网络丢包对失效检测算法的影响。     

对等网络中基于失效规律的自适应失效检测器

如何在保障准确性的前提下以较低的负载快速发现失效节点是失效检测器的设计目标,为此提出一种GA-FD的改进算法F-AFD.首先分析了P2P系统中节点的失效规律,基于对节点在线概率的预测实现对检测周期的动态调整,有效地降低了检测速度对检测周期的限制;在此基础上,为了以更低的检测负载同时满足多种应用定量描述的准确性及检测速度需求,提出了F-AFD.最后通过实验对F-AFD的正确性及检测性能进行了验证和分析,并证明了在部分同步模型下F-AFD可实现一个◇P类的失效检测器,具备解决一致性等分布式基础问题所需要的完整性和准确性.     

一种基于车载机会网络的自适应数据分发算法

车载网络通过移动车辆的无线通信装置实现数据共享,是未来智能交通系统中的重要技术。传统的车载网络数据分发大多基于泛洪的传染扩散方法,其虽能适应网络的拓扑动态性,却无法达到高效和实用的目的。提出了一种适用于车载机会网络的自适应拷贝数据分发算法ACS(Adaptive Copy and Spreading),它通过车辆移动参数(如方向、速度)动态计算所需分发数据的拷贝数并确定消息删除策略。仿真结果表明,ACS算法相比随机选择分发算法和传染扩散算法降低了对网络资源的需求,适用于多种应用场景。     

层次型IPv4网络QoS算法

网络服务质量Qo S在层次型网络中要求更高.从OSI参考模型的第二层与第三层出发,分析了传统的Qo S体系结构和三种Qo S模型的工作原理、优缺点以及网络应用环境.设计了将Int Serv与Diff Serv模型相结合的互补算法来保证层次型网络的服务质量.仿真结果表明,此模型能够从传输延迟、丢包率、延时抖动和网络吞吐量等多个方面提升网络的Qo S.     

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.     

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)

正~~     

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