基于移动状态的车载自组织网络路由算法

传统的AODV协议应用于车载自组织网络,尽管分组投递率比较高,但在数据分组需要发送时才建立路由,网络延迟较大。而DSDV中通过周期性的路由更新机制,网络延迟小,但需维护大量不必要的路由,并且拓扑结构变化使许多路由无效,导致分组投递率非常低。为了综合满足VANET分组投递率和网络延迟的要求,将AODV和DSDV两种路由建立机制相互融合,形成混合式路由协议。首先,根据车辆节点的位置、速度和方向等移动状态周期性地选择稳定且距离适中的链路,形成网络主干并更新路由;其次,当数据分组目的节点路由不存在时,发起路由发现过程建立路由,在路由请求报文前进和路由应答报文回溯过程中求出路由过期时间。仿真实验表明,尽管路由开销有所增大,分组投递率略低于AODV,但是网络延迟显著降低。     

基于双转发机制的车载自组织网络路由算法

在车载自组织网络(VANET)中,节点高速移动性与动态拓扑快速变化会引起控制开销大、链路不稳定等问题.利用节点的位置、运动速度等信息,提出一种基于双转发机制的VANET路由算法.在路由寻路阶段,运用方向转发、动态概率转发限制路由请求(RREQ)包的洪泛广播.在路由回溯阶段,运用链路预测机制,选择路径失效时间最大的路径作为传输路径.在路由维护阶段,设置定时器,在路径断裂前触发新的路由寻路,寻找新路径替换即将断裂的旧路径.实验结果表明,与链路时间预测-按需路由算法以及无线自组织网络按需距离向量路由算法相比,该算法在转发的RREQ包数量、平均端到端延迟、传输吞吐率及报文投递率方面的性能较好.     

多速率环境下AODV协议的改进

分析AODV协议在多速率环境下的不足,提出一种改进的协议AODV-HC.AODV-HC采用传输容量作为判断路径优劣的标准,通过链路单向稳定性和链路传输能力的度量,构建路径传输容量度量体系.在路径选择上将每条链路的稳定性和链路可承载的容量纳入考虑因素,能有效解决多速率环境下多跳低速链路带来的吞吐量限制.通过对AODV协议的路由请求信息和路由表的扩充以及对路由发现和路由回复过程的改进来实现AODV-HC协议.仿真实验表明基于传输容量度量的AODV-HC协议在节点高密度分布时能够提高网络的饱和吞吐量和分组交付率,降低平均分组传输时延.     

城市环境下跨层VANET路由协议研究

车载自组织网络(VANET)单一分层结构路由协议考虑因素较少,导致分组投递率低、端到端时延较高。为此,考虑车辆位置、速度、路口密度、无线链路质量、MAC层误帧率等影响因素,提出一种应用于城市环境的基于位置信息的VANET跨层路由协议(MCLPR)。设计路口车辆节点选择算法提取无线链路质量和MAC层误帧率的跨层信息,采用层次分析法计算各影响因素的权重值,确定最佳转发路径。仿真结果表明,与AODV,DSDV等路由协议相比,MCLPR路由协议具有较高的分组投递率及较低的端到端时延,保证了数据传输的可靠性与高效性,适用于网络密度与负载较大、车辆移动速度较快的城市环境。     

基于速度向量的VANET位置预测路由协议

针对车辆自组网（VANET）中车辆快速移动引起的网络拓扑快速变化及路由路径频繁切换引起的网络性能下降问题,提出一种适用于城市环境的基于速度向量的位置预测路由协议（VPRP）。该协议根据行驶方向将车辆分组,根据速度和当前位置预测下一步位置,选择路径中所有节点总的方向差异最小且总的距离变化最小的路径作为路由路径。仿真实验结果表明,VPRP比AODV和VHRP在吞吐量、分组投递率、平均传输延迟、控制开销等方面均有改进。     

基于局部邻居节点和链路权值的改进AODV路由协议

在节点高速移动的Ad Hoc网络环境中,广播风暴对网络性能的影响尤为重要,且网络拓扑结构的频繁变化极易导致路由中断.传统的AODV路由协议在路由发现阶段直接使用广播转发RREQ（路由请求分组）机制,容易导致广播风暴降低网络性能;同时,协议选择跳数最少的路径作为路由,没有考虑到节点的快速移动导致路由频繁失效,因此无法适应节点高速移动的网络环境.针对上面存在的问题,提出一种对AODV进行改进的协议.该协议在路由发起过程中,基于局部邻居节点数量计算动态转发概率;选择路由时,利用跨层思想,结合网络节点移动速度提出链路权值,依据链路权值选择路由路径.NS2仿真结果表明：该改进协议提高了数据包的投递率,缩短了端到端的传输时延,能够更好地适应节点高速移动的网络环境.     

基于链路预测的VANET路由算法

在车载自组织网络(VANET)中,AODV路由算法存在控制开销大、路由发现和修复时间长等不足。为此,对AODV算法进行局部优化,提出一种改进的路由算法,利用节点位置、运动速度等信息预测链路失效时间。在路由发现阶段,将链路失效时间最大的路径作为传输路径;在路由维护阶段,设置定时器并提前触发路由寻路,减少路径搜寻时间。仿真结果表明,与AODV算法相比,该算法在数据包端到端延迟、传输吞吐率及报文投递率等方面性能较好。     

WSN中基于链路质量和节点能量的AODV路由算法研究

为了满足无线传感网络能量的高效使用以及数据传输的稳定性的要求,需要对无线传感网络路由层协议进行改进。本文提出一种基于节点之间链路质量和节点能量状态的LE-AODV路由协议,LE-AODV路由协议采用跨层设计,路由发现过程中通过MAC层和物理层获取链路质量信息和节点能量信息来选取最优路径,并通过节点能量状态更新机制避免网络中热点的产生。本文使用Castalia仿真器对LE-AODV路由协议进行仿真,仿真结果表明,LE-AODV路由协议可以有效的提高分组投递率和网络生存时间。     

一种MANET网络的位置辅助路由协议

Ad-Hoc网络（即MANET）由于节点的移动，导致路由频繁变化．基于位置辅助路由协议（LAR1），本文提出了一种带路径优化的增强LAR1协议（ELAR1）．节点通过在接收到的路由请求包中获取其携带的其它转发节点位置信息，提高发起路由请求时预知目的节点位置的几率，降低网络内路由广播包的数量．针对路由路径中可能存在非最短路由，利用位置信息对获得的路由进行路径优化．仿真结果表明，ELAR1比LAR1有较低的路由请求开销、较高的包投递率和较低的端到端延迟．     

一种基于混合运动参数的移动自组织网AODV协议

在移动自组织网中由于节点的移动性引起网络拓扑变化，成为影响网络性能优劣的关键因素。在反应式路由算法的基础上，提出了一种基于节点位置、速度与方向混合参数的路由协议AODV-PVD(AODV Routing Protocol based on Node Position, Velocity and Direction)以衡量链路稳定性并预测链路持续时间。在路由发现阶段，根据节点的混合运动信息，使用节点筛选机制排除相对不稳定的链路，并通过节点相对移动速度预测链路持续时间，为数据传输选取稳定且路径较短的路由。NS2仿真结果显示，相较于按需距离矢量路由AODV(Ad Hoc On-demand Distance Vector)及现有改进协议，AODV-PVD路由协议可以获得更好的分组投递率、端到端传输时延和吞吐量性能。     

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.     

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.     

法律信息库系统

本文分析了法律数据库的结构和特点，介绍了采用面向对象设计方法和超文本数据库技术开发和实现法律信息库系统将作为重要网络资源之一为不同用户进行法律咨询服务。     

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.     

International Journal of Automation and Computing Table of Contents

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Information for authors

正SCIENCE CHINA Information Sciences(Sci China Inf Sci),cosponsored by the Chinese Academy of Sciences and the National Natural Science Foundation of China,and published by Science China Press,is committed to publishing highquality,original results of both basic and applied research in all areas of information sciences,including computer science and technology;systems science,control science and engineering(published in Issues with odd numbers);information and communication engineering;electronic science and technology(published in Issues with even numbers).Sci China Inf Sci is published monthly in both print and electronic forms.It is indexed by Academic OneFile,Astrophysics Data System(ADS),CSA,Cabells,Current Contents/Engineering,Computing and Technology,DBLP,Digital Mathematics Registry,Earthquake Engineering Abstracts,Engineering Index,Engineered Materials Abstracts,Gale,Google,INSPEC,Journal Citation Reports/Science Edition,Mathematical Reviews,OCLC,ProQuest,SCOPUS,Science Citation Index Expanded,Summon by Serial Solutions,VINITI,Zentralblatt MATH.     

Erratum to: Fast global kernel fuzzy c-means clustering algorithm for consonant/vowel segmentation of speech signal

正Erratum to:J Zhejiang Univ-Sci C(ComputElectron)2014 15(7):551-563doi:10.1631/jzus.C1300320The original version of this article unfortunately contained mistakes.Algorithm 6 should be as follows:Algorithm 6 FGKFCM-F clustering Input:(1)X={x_1,x_2,…,x_N},,x_iR~d,i=1,2,…,N,the dataset;(2)C,1C≤N,the number of clusters;(3)ε0,the stopping criterion;     

Journal of Zhejiang University-SCIENCE C (Computers & Electronics) Total contents

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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.