基于数据锁描述的DBMS分层排队网络模型

针对数据锁对数据库管理系统(DBMS)性能的影响,在分析数据锁工作原理的基础上提出DBMS基于数据锁描述的分层排队网络模型LQNM(Layered Queuing Network Model),运用分层算法MOL(Method of layered)实现模型的求解。通过求解后的实验结果与排队网络模型QNM(Queuing Networks Model)进行比较以此来说明该模型通过对数据锁的描述提高了模型预测精度。     

基于分层排队网络模型的分布式系统性能评价

关于并发或分布式系统的性台匕评价是一个广泛研究的课题,提供有效的数学理论工具、直观的模型描述方法和有效的模型分析方法,是系统性能评价所面临的关键问题。传统的性能模型——排队网络模型已很难分析这样复杂的系统,分层排队网络（Layered Queueing Net,LQN）模型是排队网络模型的扩展,可以用来分析相互依赖任务间的冲突。介绍了分层排队网络模型的原理及研究现状,并以DBMS为例,建立了DBMS的分层排队网络模型。     

资源同时占有平均值分析方法的C/S系统应用

利用分层排队网络模型对具有资源同时占有的客户/服务器(Client/Server,C/S)系统建模,讨论并提出了一种改进的平均值分析方法———资源同时占有平均值分析方法用于计算响应时间、吞吐率、队列长度等系统性能参数均值。着重讨论该算法用于求解排队网络模型中具有不同选道行为、对各服务结点有不同服务需求的多类顾客的情况。     

基于遗传算法和排队网的串联CONWIP系统流通卡数的确定方法

在CONWIP(constant work in process)系统中,流通卡数是系统有效运行的关键因 素.文中针对串联CONWIP系统,提出了非线性整数规划模型和排队网模型相结合的问题描述 模型,以及遗传算法与排队网络分析相结合的问题求解算法.实例仿真验证了该方法的有效性.     

铁路集装箱中心站装卸系统排队模型及分析

针对铁路集装箱中心站装卸系统的设备性能运用闭排队网络模型进行研究。根据铁路集装箱中心站装卸系统的作业特点建立其闭排队网络模型,在该模型中内部集装箱卡车作为顾客在轨道门吊和正面吊两个服务节点以及一个虚设的“运输”服务节点接受服务。由于服务节点的服务时间不能很好地用传统分布表示,导致针对乘积形式排队网络的求解方法并不适用。于是采用近似平均值分析算法求解闭排队网络模型并获得相关的设备性能参数,并分析了装卸系统的设施配置。最终通过与仿真模型所得结果的对比,验证了模型和求解算法的正确性。     

一种DBMS时态授权机制研究

通过整数限制域的方式引入时态限制域并提出一种基于DBMS的时态授权逻辑模型.该模型基于分层的限制Datalog/ ,c,并通过时态限制规则保持限制域的求反闭包性,通过授权阻塞规则解决正负授权冲突,因而具有逻辑上的一致性和可行性,能满足DBMS中各类时态授权的需要.最后对授权程序的可评价(evaluation)性、实现算法及其应用做了说明.     

计算机系统的排队网络模型及其计算方法

计算机系统性能评价是计算机科学中一门新兴的学科。本文分六节系统介绍在计算机系统性能评价中广泛应用的排队网络模型及其计算方法。第一节简述排队网络模型的由来和发展。第二节描述了几种典型的排队网络模型,定义了用于性能评价的四个基本量——利用率、平均排队长度、平均等待时间和吞吐率。第三节介绍建立排队网络模型的一般方法。第四节简介排队网络模型的理论基础之一——运行分析。第五节论述排队网络模型常用的计算方法——归一化常数法、平均值分析法和某些近似计算方法。第六节介绍分析BCMP型排队网络(目前代表性最广的一种模型)的Pascal程序包,这个程序包已在VAX——11计算机上实现并经过验证。     

基于分层多目标优化算法的无线网络规划

为满足时分-同步码分多址(TD-SCDMA)网络规划性价比最优化的需求,设计网络规划分层优化模型,该模型能很好地解决覆盖和容量的关系。为求解该模型,提出分层多目标优化算法,该算法能根据实际规划区域决定目标函数的优先层次,满足TD-SCDMA网络规划的目标和要求,并可在给定条件下实现基站布局最优。     

基于关系型DBMS构建BPM DBMS的探讨

分析了基于关系型数据库构建BPM DBMS的优越性，描述BPM DBMS的系统结构，并着重对BPM DBMS概念层的数据建模，以及利用关系型DBMS构建内层所需做的基本工作进行了简要说明。最后给出了一个算法实例。     

云环境下基于LQNM的数据库性能建模研究

在云环境下,数据库系统性能的优劣是云服务供需双方共同关注的焦点,如何形象地描述云环境下数据库系统的资源分配,合理地评价数据库系统的性能成为目前一个重要的问题。通过分析云环境下数据库系统的工作原理,提出采用分层排队网络建模技术为其建立性能模型,该模型把云环境下的数据库系统抽象为三个软件任务(客户端、查询代理进程、数据管理进程)和三个硬件任务(THINK、CPU、硬盘),并以负载特征参数作为输入,通过分层的方法求出该模型的解。通过模型预测值与实验测量值分析系统平均响应时间之间的误差,并与传统的排队网络模型进行比较,从而验证该性能模型的有效性和准确性。     

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