PostgreSQL闪存缓冲区置换算法扩展与性能验证

针对闪存缓冲区置换算法的性能验证基本采用仿真模拟的现状,提出了一种基于PostgreSQL的有说服力的性能验证方法,重点讨论了在PostgreSQL上扩展闪存缓冲区置换算法的方法和实现技术,并以CFLRU(clean first least recently used)和CCFLRU(cold clean first least recently used)算法为例,给出了具体的扩展过程。然后以一块固态硬盘作为数据存储设备进行性能测试,测试结果证明了基于PostgreSQL的扩展方法在缓冲区置换算法性能验证上的有效性。     

基于.NET的数据访问基类的构建

为提高数据库应用程序的设计效率,基于VS.NET开发平台,利用ADO.NET的强大数据访问功能,设计了抽象的数据访问基类.主要通过代码的方式阐述了整个基类的创建过程,并重点介绍了创建存储过程参数的操作方法,在调用存储过程中,通过方法重载实现不同的数据库操作.利用该类并结合存储过程的优势构造数据服务层,统一整个系统的数据操作入口,提高开发效率,便于系统的升级、维护和移植.     

基于.NET的数据访问基类的构建

为提高数据库应用程序的设计效率,基于VS.NET开发平台,利用ADO.NET的强大数据访问功能,设计了抽象的数据访问基类。主要通过代码的方式阐述了整个基类的创建过程,并重点介绍了创建存储过程参数的操作方法,在调用存储过程中,通过方法重载实现不同的数据库操作。利用该类并结合存储过程的优势构造数据服务层,统一整个系统的数据操作入口,提高开发效率,便于系统的升级、维护和移植。     

模拟配方功能的算法研究与应用

针对西门子S7-200系列PLC的配方功能不能同时修改不同配方参数的现象,提出了新的具有同时操作不同配方中参数数据功能的扩展配方算法.通过研究原始配方功能的算法,对参数的数据存储区地址分配进行分析,使用指针间接寻址的方法对参数数据的读取、设置、调用等操作方法作出说明,并进一步探索该算法的扩展.以某汽车变速器自动化装配生产线中的输入轴压机为例,介绍了该算法的应用.现场运行结果表明,新算法优化了生产过程,提高了生产效率和产品质量,具有良好的实用性和可操作性.     

面向企业级数据库管理——介绍Sybase的Adaptive Server Enterprise(三)

扩展存储过程 ASE支持系统定义和用户定义的“扩展存储过程”,它提供了一种方法,能够在Adaptive Server中调用过程语言编写的函数。这样Adaptive Server不仅能识别T-SQL,而且能识别其他的过程语言。扩展存储过程能够象ASE中其它存储过程一样被使用,可包括输入/输出参数,还可返回结果集和状态值。每一个扩展存储过程与一个外部函数对应,这些外部函数可在Adaptive Server中被激活。     

基于PostGIS的空间数据库设计与实现

PostGIS是开源对象关系型数据库系统PostgreSQL的扩展。本文基于PostGIS空间数据库,实现对矢量地图数据存储、管理和操作。搭建PostGIS空间数据库,以中国矢量地图数据为例,实现PostGIS数据库对矢量地图数据管理。     

基于扩展存储过程的数据库加密技术研究

提出了一种基于扩展存储过程的数据库加密系统方案,并阐述了主要的功能模块.该方案应用扩展存储过程和UDF(用户自定义函数)对动态链接库进行封装,实现了加密功能,并对两级密钥采用智能卡进行存储,从而在不影响系统原有功能的基础上,提高了数据库系统的安全性.     

PostgreSQL数据库性能优化

PostgreSQL是优秀的开源对象关系型数据库管理系统fORDBMS）,应用范围十分广泛。通过对PostgreSQL数据库配置文件中相关参数及OpenBSD系统中影响数据库性能的参数的分析,给出OpenBSD下PostgreSQL性能优化的思路,提出了相关优化方法。     

行列混合存储数据库系统的研究

通过研究列存储技术的特点,提出了一种行列混合存储数据库系统的设计方案.该方案在存储层设立独立的行存储引擎和列存储引擎,采用早物化技术在数据读出之后将列表转换成行表,然后以行的形式完成后续处理.因此,该方法既获得了列存储的读优势又复用了行数据库系统的成熟部件,降低了开发的风险和复杂度.基于PostgreSQL的原型开发与测试证明了该方案的可行性和有效性.     

PostgreSQL中基于ACL的数据访问控制技术

数据库系统允许用户共享数据,但必须通过访问控制保证数据安全,防止数据的篡改、泄漏或丢失.PostgreSQL借助ACL(Access Control List)技术达到控制访问请求和信息保护的目的.该系统中的数据库对象都有一个ACL,只有出现在ACL中并且具有所需权限的用户才能够访问该对象.PostgreSQL将对象的ACL按抽象数据类型加以维护并用于访问控制,实现方法简洁,易于增强和扩展.它还通过用户组、ACL压缩等技术进一步优化数据访问控制的性能.同时对扩展列级授权给出建议.     

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.     

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.     

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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