数据仓库环境中多级负荷的全局缓冲管理

数据仓库查询要求为数据库和导出数据提供有效的全局缓冲管理。本文描述一个兼顾数据库页和导出数据的全局缓冲管理器，提出收益量度用以比较缓存导出数据，为查询操作提供工作空间的效果，并在此基础上设计算法，为多查询生成有效的缓冲分配方案。分配算法与不同的替换策略结合形成一族全局缓冲管理方法，将其与简单ＬＲＵ和ＬＲＵ－Ｋ策略进行实验比较，结果表明本文提出的方法更适于数据仓库中的多级负荷。     

高效可控本地环路系统

ＲＡＤ公司已研制成由ＬＲＳ－２４ＳＮＭＰ控制的２４端口调制解调器接入架。这一设备适合任意２４ｘＤＳＬ、基带或光纤调制解调器,并且支持从１．２ｋｂｐｓ到４５Ｍｂｐｓ的各种数据传输速率。 通过ＵＮＩＸ操作系统,ＰＣ平台或ＡＳＣⅡ终端可以对ＬＲＳ－２４进行控制．通过以太网,ＬＲＳ－２４可以从中心管理站控制很多接入架．通过ＲＡＤ　ｖｉｅｗ－ＨＰＯＶ或ＲＡＤｖｉｅｗ－ＰＣ　ＳＮＭＰ管理系统可以对ＬＲＳ－２４卡进行控制．高效可控本地环路系统     

路径存储法在生成树形结构中的应用研究

动态树形结构应用十分广泛,现有的"遍历节点法"、"层点展开法"、"多表存储法"等技术在生成树形结构时有利有弊。本文将节点在树分支中的线性结构关系作为路径,把路径信息存储在节点数据表的一个字段中,并将路径信息作为检索排序依据,实现对树节点排序,从而按照此序列生成树形结构的路径存储法。该方法提高了"遍历节点法"访问节点算法的效率,解决了"层点展开法"的访问子树节点问题,优化了"多表存储法"的存储结构。     

一种在连续MFR中快速挖掘频繁访问路径的新算法

频繁访问路径挖掘是Web数据挖掘的重要研究内容。论文主要研究在最大前向引用中发现连续频繁访问路径的问题,提出了一种快速有效的CAP算法,该算法借助于访问路径树进行挖掘,只需一次扫描数据库,且简化了对访问路径树的挖掘过程,试验表明在执行效率上明显优于WAP算法。     

无线传感器网络的组密钥更新算法*

提出了一种适用于无线传感器网络的基于改进密钥链接树的组密钥更新算法。通过在基于密钥链接树的组密钥管理方案中引入问题密钥路径,并延迟这些问题密钥路径上的密钥更新操作,从而减少密钥链接树中辅助节点上的重复密钥更新。实验结果表明,与现有的组密钥管理方案相比,基于改进密钥链接树的组密钥更新算法在节点添加和删除操作时产生更少的密钥更新消息和消耗更少的能量。     

基于访问路径树的Web频繁访问路径挖掘算法研究

频繁访问路径发现是Web数据挖掘的重要研究内容。提出了一种挖掘连续频繁访问路径的高效算法：PS2算法,该算法利用访问路径树挖掘频繁扩展子路径,只需一次数据库扫描,试验表明该算法在效率上优于类Apriori的算法。     

基于最小生成树的非均匀分簇路由算法

发现现有的针对非均匀分簇路由算法没有充分考虑簇首与基站之间最优路径选择,而导致传输路径上的能量消耗不均衡的问题。为了更好地均衡传输路径上节点能量的消耗,提出了基于最小生成树的非均匀分簇的路由算法。该算法利用节点剩余能量和节点到基站的距离选举簇首,然后通过建立最小生成树搜寻最优传输路径,这样可以减少传输路径上的能量消耗,有效地解决能耗不均衡问题。理论分析和实验结果均表明,该算法无论在存活节点个数还是在能量消耗上都明显优于EEUC算法和EBCA。     

无线Mesh网络中节点分级协作缓冲机制研究

在无线Mesh中,由于每个节点缓冲的数据量不同,可能会造成某些节点的缓冲区利用率低,某些节点因为缓冲任务繁重而进行频繁的数据置换操作,从而造成节点存储空间使用不均衡,降低数据缓冲的效率。提出了一种基于节点分级管理的协作缓冲算法,该算法为网络中的每个节点在网络中构造一个分布式缓冲区域,利用该缓冲区域来替代节点本身的缓冲区,通过合理地利用每个节点的存储空间,增加单个节点的数据缓冲能力。理论分析和实验结果表明,该算法可以有效提高数据访问命中率,减少缓冲区数据的置换操作,降低节点的能量消耗。     

基于Hash树热点窗口的存储器完整性校验方法

该文描述了一种存储器完整性校验的硬件方案．首先．介绍了存储器完整性校验的情况；然后．提出了基于Hash树热点窗口的存储器完整性校验方法．该方法将存储器访问的局部性特征与Hash树完整性校验原理相结合．通过缩短多数情况下校验所需路径的长度以及对节点实施恰当的缓冲，来有效减小完整性检验的代价．该文描述了该方法的原理、算法与系统实现．并进行了模拟．理论分析和模拟结果表明该方法在应用上是高性能的，同时也是低代价的．     

改进的基于R树的空间连接代价模型

针对Yannis Theodoridis等人提出的空间连接代价模型存在比较理想化的限制条件——假设数据均匀分布,缓冲策略使用简单的缺点,利用划分子空间并抽样获取非均匀数据实际密度的策略,提出了优先保存查询集合树的最新访问路径的有效中间节点的缓冲区算法,给出了改进后的评估公式。实验结果表明,改进后的模型比原模型提高了评估的精确度。     

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