基于软件容错的动态实时调度算法

在硬实时系统中,由于任务超时完成将会导致灾难性后果,因而硬实时系统具有严格的时间及可靠性限制奈件．目前实时容错调度算法大部分针对硬件的容错,很少考虑软件运行的故障．提出了一种类似EDF基于软件容错的动态实时调度算法EBPA(expectation-based probing algorithm),该算法在任务执行过程中通过基于期望值的若干试探性检测步骤,提高了任务可执行性的预测,尽可能避免了任务早期的错误对后续任务的影响,因此提高了任务的完成率并同时有效地减少了浪费的CPU时间片．通过实验测试,同目前所知的同类算法相比,具有更佳的调度性能-调度成本比．     

基于软件容错的动态实时调度算法

在硬实时系统中，由于任务超时完成将会导致灾难性后果，因而硬实时系统具有严格的时间及可靠性限制条件．目前实时容错调度算法大多针对硬件的容错，很少考虑软件运行的故障．提出了一种类似EDF的软件容错的动态实时调度算法PKSA(Probng-step Algorithm)，本算法在任务执行过程中，通过若干试探性检测步骤，提高了任务可执行性的预测，尽可能地避免了任务早期的失败对后续任务的影响，因此提高了任务的完成率，并同时有效地减少了浪费的CPU时间片．通过实验测试．同目前所知的同类算法相比，具有更佳的调度性能-调度成本比.     

基于RTLinux的容错硬实时性的研究与实现

容错已逐渐成为实时系统的一个重要特性,针对RTLinux的实时调度机制尚未考虑容错的需求,对RTLinux进行了容错硬实时性的改造.改造了基于主/副版本容错模型对任务模型,对先前提出的基于最坏响应时间的容错实时任务可调度性分析,通过将改进的最佳容错分配因子搜索算法(improved fault-tolerant priority configuration search algorithm,IFPCS)运用到实时调度算法中,提高了RTLinux的容错实时性能,并给出了容错实时程序的设计框架.     

容错优先级可提升的抢占阈值容错调度算法

基于软件容错模型,提出了允许容错优先级提升的抢占阈值容错调度算法(extended fault-tolerantfixed-priority with preemption threshold,简称FT-FPPT*).该算法能够在抢占式容错调度算法(fault-tolerantfixed-priority preemptive,简称FT-FPP)和抢占阈值容错调度算法(fault-tolerant fixed-priority with preemptionthreshold,简称FT-FPPT)无法提高系统容错能力的情况下,进一步提高系统的容错能力.为了获得系统中任务优先级分配的最佳策略,基于任务最坏响应时间的可调度性分析,提出了一种最优的优先级配置搜索算法(priorityassignment search algorithm,简称PASA).经过深入分析和实验证明,与FT-FPPT算法相比,FT-FPPT*算法能够有效地提高硬实时系统的容错能力.     

硬实时系统中基于软件容错模型的容错调度算法

在硬实时系统中,由于任务超时完成将会导致灾难性后果,因此硬实时系统必须具有实时性和可靠性保障.软件容错模型是提高硬实时系统容错能力的一种有效方法.针对硬实时系统中容错优先级两种分配策略存在的不足,基于软件容错模型提出了一种容错优先级可提升的双重优先级分配策略.该方法通过为替代版本分配双重优先级,不仅能够提高硬实时系统的容错能力,同时还能够显著减少任务间的抢占次数.为了获得双重优先级分配的最佳策略,基于任务最坏响应时间的可调度性分析,首先提出了一种最大的双重优先级配置搜索算法(MDPCSA).然后结合MDPCSA算法,提出了一种最优的双重优先级配置搜索算法(ODPCSA).仿真实验表明,与两种分配策略相比,在提高系统容错能力和降低抢占开销方面更为有效.     

NFRL:一种分布系统的实时容错调度算法

在硬实时系统的应用中,如果硬实时任务不能在规定的时限完成,将会产生人员伤亡, 失等严重后果,为了保证在系统出错的情况下,硬实时任务仍然在能戴止时限之前完成,必须研究实时容错技术。本文从实时容错调度算法的角度出发,提出一种基于分布式系统的实时容错调度算法,并研究了该算法的时间复杂度,同时给出一个实例说明该容错调度算法的调度过程。这种容错调算法称为“无容错需求后调度算法（ＮＦＲＬ）,该实时容错调度算法     

主桙副版本模型中预分配容错实时调度算法

实时系统中任务的超时完成可能导致灾难性后果,因此要求系统具备容错处理能力,以保证系统出错后的实时性及可靠性。主/副版本模型是提高实时系统容错能力的有效技术。传统的容错实时调度算法通过为副版本预留处理器时间来实现软件容错,为副版本预留的处理器时间在系统运行过程中需动态调整,增加了系统的容错调度开销。提出一种基于res‐backw ards‐RM 预分配子算法的容错实时调度算法BCE*,通过限制预分配过程中高优先级任务的抢占条件,在不影响系统可调度性的同时可以有效避免副版本预留时间的动态调整,降低系统的容错调度开销。仿真实验验证了BC E*算法的可行性及有效性,且在系统出错概率及主版本负载较低的环境下,BC E*算法对系统容错调度开销的优化效果更显著。     

软件容错模型中的容错实时调度算法

在软件容错模型的容错实时调度算法中,主部分可执行性的预测精度是影响调度算法性能的关键.针对此问题提出了DPA(deep-prediction based algorithm)和EDPA(EDF-based DPA)算法.算法考虑当前时间至替代部分通知时间之间的任务执行情况,通过构建预测表对待执行主部分的可执行性进行精确预测.当主部分不发生错误时算法根据预测表调度任务. DPA依照预测表中通知时间的先后顺序调度主部分,而EDPA则按照EDF算法调度预测表中的主部分.模拟结果表明,DPA和EDPA较目前同类算法可获得更多的主部分执行时间,降低CPU的消耗.当软件错误率较低、任务周期较短时,算法能够以较小的调度开销获得较高的调度性能.     

多处理机系统的一种实时容错调度算法

实时容错调度算法是实时系统容错研究中的重要问题.提出了一种多处理机系统的实时任务容错调度算法.该算法结合了基版本/副版本(Primary/Backup)方法和三模冗余(TMR)方法,以保证在一个节点机失效时,任务可以在其截止时限内完成.     

一种基于多处理机的容错实时任务调度算法

容错是实时系统的重要要求,在实时系统中,若一个实时任务没在规定的时间期限内完成,则认为系统出现错误,针对多处理机实时系统提出了一种容错调度算法．算法采用了任务的主从备份技术和Ｆｉｒｓｔ－ｆｉｔ启发式方法,通过为可能因处理机故障而执行失败的实时任务预留重新运行的时间来实现容错功能;并通过对预留时间段的重叠利用和无错时预留时间的回收分配,来提高处理机的利用率和系统对任务的接收率．模拟结果表明算法是有效     

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.     

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.     

法律信息库系统

本文分析了法律数据库的结构和特点，介绍了采用面向对象设计方法和超文本数据库技术开发和实现法律信息库系统将作为重要网络资源之一为不同用户进行法律咨询服务。     

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.     

International Journal of Automation and Computing Table of Contents

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Information for authors

正SCIENCE CHINA Information Sciences(Sci China Inf Sci),cosponsored by the Chinese Academy of Sciences and the National Natural Science Foundation of China,and published by Science China Press,is committed to publishing highquality,original results of both basic and applied research in all areas of information sciences,including computer science and technology;systems science,control science and engineering(published in Issues with odd numbers);information and communication engineering;electronic science and technology(published in Issues with even numbers).Sci China Inf Sci is published monthly in both print and electronic forms.It is indexed by Academic OneFile,Astrophysics Data System(ADS),CSA,Cabells,Current Contents/Engineering,Computing and Technology,DBLP,Digital Mathematics Registry,Earthquake Engineering Abstracts,Engineering Index,Engineered Materials Abstracts,Gale,Google,INSPEC,Journal Citation Reports/Science Edition,Mathematical Reviews,OCLC,ProQuest,SCOPUS,Science Citation Index Expanded,Summon by Serial Solutions,VINITI,Zentralblatt MATH.     

Erratum to: Fast global kernel fuzzy c-means clustering algorithm for consonant/vowel segmentation of speech signal

正Erratum to:J Zhejiang Univ-Sci C(ComputElectron)2014 15(7):551-563doi:10.1631/jzus.C1300320The original version of this article unfortunately contained mistakes.Algorithm 6 should be as follows:Algorithm 6 FGKFCM-F clustering Input:(1)X={x_1,x_2,…,x_N},,x_iR~d,i=1,2,…,N,the dataset;(2)C,1C≤N,the number of clusters;(3)ε0,the stopping criterion;     

Journal of Zhejiang University-SCIENCE C (Computers & Electronics) Total contents

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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.