支持频繁更新的移动对象混合索引方法

TPR-tree是目前广泛使用的移动对象当前及未来位置索引技术,但是其频繁更新性能低下.通过在TPR-tree上增加一个指向索引树中间节点的直接访问表（direct-access table）内存结构和建于叶节点之上的Hash辅助索引结构,提出了一种支持频繁更新的移动对象混合索引HTPR-tree,并提出了基于HTPR-tree的扩展自底向上（EBUU）更新算法.性能分析和实验表明,采用EBUU算法的HTPRtree动态更新性能大大高于TPR^＊-tree等索引,而查询性能仅仅稍逊.     

面向移动对象的高效预测范围聚集查询方法

预测范围聚集查询是移动对象数据库中重要的查询类型之一.提出了一种PRA树高效预测范围聚集查询索引,对速度域进行规则划分,根据速度矢量大小将移动对象映射到不同的速度桶中,针对每个速度桶,提出了一种聚集TPR树索引,通过在TPR树中间节点中加入聚集信息以减少预测范围聚集查询所需要的节点访问代价.PRA树索引增加了一个建于叶节点之上的Hash辅助索引结构,并采用自底向上的删除搜索算法,具有很好的动态性能和并发性.提出了一种增强预测范围聚集查询EPRA算法,采用更精确的剪枝搜索准则,减少了查询所需要访问的节点代价.实验结果与分析表明,基于PRA树索引的EPRA查询算法具有良好的查询性能,优于通用的TPR*树索引.     

移动点对象HR索引及反向最近邻查询

在此提出了一种基于速度分布的HR树索引结构,首先在速度域中对移动对象集进行规则划分,根据速度标量大小将移动对象划分到不同的速度树中,每棵速度树中移动对象具有相近的速度;对每棵速度树中的移动对象,则利用时间间隔进行划分。HR树索引增加了两个分别建于叶节点和根节点之上的Hash辅助索引结构,并基于HR树提出了反向最近邻查询算法,具有很好的动态更新性能和并发性。实验结果与分析表明,基于HR树索引的反向最近邻查询算法具有良好的更新及查询性能,优于通用的TPR树索引。     

移动点对象HR索引及反向最近邻查询

在此提出了一种基于速度分布的HR树索引结构,首先在速度域中对移动对象集进行规则划分,根据速度标量大小将移动对象划分到不同的速度树中,每棵速度树中移动对象具有相近的速度;对每棵速度树中的移动对象,则利用时间间隔进行划分。HR树索引增加了两个分别建于叶节点和根节点之上的Hash辅助索引结构,并基于HR树提出了反向最近邻查询算法,具有很好的动态更新性能和并发性。实验结果与分析表明,基于HR树索引的反向最近邻查询算法具有良好的更新及查询性能,优于通用的TPR树索引。     

支持预测查询和部分历史查询的移动对象索引方法

针对TPR*-tree隐含移动对象部分最近历史信息但不能提供历史信息查询的问题,将移动对象创建或更新时间引入到索引树中,提出一种既支持预测查询又支持部分历史信息查询的索引树Basic HTPR*-tree,为全时态查询奠定了坚实的基础.同时,为了支持移动对象的频繁更新,在Basic HTPR*-tree索引树基础上引入内存概要结构和Hash辅助索引结构,提出支持自底向上更新策略的HTPR*-tree索引结构.实验结果表明,HTPR*-tree更新性能优于TPR*-tree和Basic HTPR*-tree(TD_HTPR*-tree),预测查询性能仅仅稍逊于TPR*-tree.     

一种基于BX树的移动对象混合索引方法

为实现移动对象当前及未来位置索引,提出了一种自适应SABX树（Self-Adapt BX-tree）,考虑到移动对象在现实世界中分布密度不同的特点,利用时间划分和空间填充曲线技术计算移动对象位置信息,并引进了一个以秩的范围为标识的Hash辅助索引表,文中给出了SABX树的插入、删除、更新方法以及范围查询算法。实验表明,该索引结构的动态更新性能和查询效率优于BX树和传统的TPR树。     

支持频繁位置更新的不确定移动对象索引策略

移动数据采集和处理技术的迅速发展给研究人员提出了新的应用需求,如何在频繁位置更新应用中索引不确定移动对象的当前及未来位置信息成为当前的研究热点之一.TPU树是针对不确定移动对象的当前及未来位置信息索引的策略,其具有较高的概率域查询效率,但是其采用的传统自顶向下更新算法,存在频繁位置更新效率低下的问题.通过在TPU树上增加一个记录不确定移动对象状态特征的更新备忘录(UM)内存结构,文中提出了一种支持频繁位置更新的不确定移动对象索引策略TPU2M树,并在此基础之上提出了一种改进的基于备忘录(MMBU/I)的更新/插入算法.代价分析和实验仿真表明,采用MMBU/I算法的TPU2M树频繁更新性能大大优于TPU树和ABx树索引,且概率查询性能与传统索引大致相当,因此具有很好的实用价值和广泛的应用前景.     

基于受限移动对象当前及将来时刻检索的时空索引结构研究

在给定的空间及时间范围内,如何构建高效的时空索引结构,以实现对移动对象快速有效的检索,是实现定位服务、智能交通、数字化战争等诸多应用中所迫切需要解决的问题.本文依据移动对象的运动特点,提出了一种面向当前及将来时刻快速更新及有效检索的索引结构—PQR树.PQR树是综合PMRQuad树和R*树的结构,首先依据道路分布用PMRQuad树将移动对象的索引空间实行粗略的层分割,将所有快速移动对象与道路相关联.然后用R*树索引分布在各个子空间块内的类静止对象.实验结果表明PQR树具有良好的更新和查询性能.     

基于TPR树的索引技术研究

分析了移动对象位置的索引技术，介绍了可以有效的索引移动对象的当前和未来位置的索引结构——TPR树（time—parameterized R tree），并对其进行改进，改善了其查询性能。     

移动对象数据库预测范围聚集查询技术研究

针对预测范围聚集查询处理技术，提出了一种面向移动对象的聚集TPR树索引。聚集TPR树索引在TPR树中间节点中加入移动对象聚集信息以减少预测范围聚集查询所需要的节点访问代价。并增加了一个建于移动对象标识上的哈希辅助索引结构以支持自底向上的删除搜索算法，具有很好的动态更新性能和并发性。提出了一种EPRA查询算法，采用更精确的剪枝搜索准则，大大减少了查询所需要访问的磁盘节点，具有良好的查询性能。     

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