基于PEPA的组合服务性能建模与分析

当前对于组合服务的分析主要侧重在功能方面,缺乏有效地进行性能分析的手段和工具.针对此问题,提出一种基于PEPA(performance evaluation process algebra)的组合服务性能建模与评价方法.基于服务组合图对组合服务中原子服务的交互行为进行分析,证明了组合服务和PEPA模型是同构的.给出组合服务和PEPA的映射规则,并建立服务组合的性能模型.提出组合服务性能建模和分析方法.实践结果表明该方法更加简单、有效,易于工程实现.     

UbiCloud:一种面向普适终端的云计算系统

针对低性能终端的复杂计算需求,设计了面向普适终端的云计算系统UbiCloud.通过对云中计算资源的描述、发现、访问、评价等问题进行研究,在前端普适终端与后端云之间构建虚拟计算环境,实现了一个异构终端的云计算服务发布及访问平台.在对服务质量的评价上结合AHP算法给出了一个有效的服务评价模型,在建立判断矩阵的过程中提出了两种一致性矩阵构建方法.最后对系统进行了性能测试,结果表明系统在应用响应时间等指标方面可以达到设计目的.     

基于膜计算的蝙蝠算法在云计算资源调度的研究

如何进一步实现云计算环境下的资源利用最大化是目前研究的热点.建立云计算环境下的资源分配模型,云计算资源调度使用蝙蝠算法,同时引入膜计算概念,提出一种基于膜计算的蝙蝠算法,将膜系统内部分解为主膜和辅助膜,在辅助膜内进行蝙蝠的个体局部寻优,将优化后的个体传送到主膜间进行全局优化,从而达到了云计算资源优化分配要求.通过CloudSim平台与其他算法进行仿真对比表明算法提高了云计算环境下的系统处理时间和效率,使得云计算环境下的资源分配更加合理.     

基于高斯变异的人工萤火虫算法在云计算资源调度中的研究

如何合理地分配云计算资源一直都是研究的热点.建立云计算环境下的资源调度模型,通过人工萤火虫算法个体最优与云计算节点资源分配对应起来,在算法中引入高斯变异算法,通过与经典函数比较,优化后的算法在搜索精度上以及收敛速度上有了很大的提高.通过在CloudSim平台上与经典智能算法的比较,该算法能够有效地提高云计算中的资源调度性能,缩短任务完成的时间,提高系统整体处理能力.     

基于TOPSIS模型的网格资源分配决策算法

针对如何在网格环境中提高整个网格平台的性能和效率问题,提出了逼近理想解的排序法,即TOPSIS(technique for order preference by similarity to ideal solution)多指标综合评价模型,对网格节点的网络性能进行评价,将评价结果用于网格资源分配决策,得到了最短任务完成时间的资源分配方案.用网格模拟器GridSim搭建了包括路由器的网格环境,测试及与随机算法对比结果表明了TOPSIS多指标网格资源分配决策算法的可用性和高效性.     

云计算中一种改进的猴群算法在资源分配中研究

针对云计算中的任务完成时间和费用如何进行更好的分配问题,文章将猴群算法引入到云计算资源分配中,针对猴群算法自身存在收敛速度快,易陷入局部最优的情况;在猴群算法的初始化中引入混沌算法来优化位置,对算法中的爬过程采用定位步长和对望过程的视野距离引入参数进行改进;改进后的算法在性能和收敛速度有了明显了改进,通过CloudSim仿真平台表明文章算法与其他智能算法相比在资源分配时间,能量消耗以及资源节点吞吐量,传输率方面方面具有一定的改进,提高了云计算资源分配效率。     

基于改进的蝙蝠算法在云计算中的资源分配

云计算中的资源分配一直都是研究的重点, 提出了一种基于改进的蝙蝠算法的云计算资源分配方法. 在蝙蝠算法中引入差分遗传算法, 通过变异, 交叉和选择等操作避免个体陷入局部最优, 以及过早产生最优解的可能,改进后的蝙蝠算法能够有效的提高收敛速度和精度. 仿真实验表明, 本文算法不但有效提高了算法性能, 还优化了云计算系统中的资源调度能力, 提高了云计算资源的利用率.     

改进的猴群算法在云计算资源分配中的研究

如何能够更好的解决云计算资源分配问题一直都是研究的热点, 引入猴群算法, 针对猴群算法中出现的局部收敛速度快, 容易造成局部最优值的缺点, 首先在猴群算法中引入混沌算法和反向学习来初始化猴群的初始位置, 其次, 通过猴群算法中的爬, 望, 跳三个过程的改进使得改算法收敛精度提高. 通过经典函数测试后, 本文算法相比其他智能算法的性能有了明显的改进. Cloudsim平台证明将本文算法运用到云计算资源分配中, 在任务完成时间, 资源消耗方面都有了很大的提高.     

基于用户体验的计算系统多元性能评价模型

传统的性能监控系统通过监控系统资源的使用情况来间接地反映和评价系统的运行状态,但是该方法与用户感知的系统性能有较大出入。对于终端用户,其最直接的体验就是请求的响应时间,它受系统运行过程中多种因素的综合影响。基于基因表达式编程理论,提出了一种对计算系统性能进行多元评价的基因表达式编程算法,其通过对多种系统资源数据的分析,建立响应时间对多种系统资源的数学模型,以此预测系统性能的变化。最后,针对具体的仿真环境和采样数据,采用该算法获得了响应时间的多元非线性模型。结果表明,该模型能较好地预测系统的性能变化情况。     

异构云平台性能监控与分析研究

云计算是近年来兴起的一种新型的计算和服务模式,它采用多租户策略和按需付费计算模型,弹性地向用户提供看似无限的计算和存储资源。当前,云计算已经成为互联网环境下新型计算模式研究的焦点和热点。但是,云计算刚刚处于起步阶段,还没有形成统一的、公认的云计算标准。如何比较和评价多个不同公司、不同类型云平台的性能,为用户选择云平台提供依据,成为现在云计算性能评估的一个迫切需要解决的问题。针对以上问题,设计并构建了跨云平台的性能监控系统,该系统根据用户性能需求定义为多种云平台提供实时性能数据监控,进行跨云平台的性能比较分析,并且图形化地展示给用户。     

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)

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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