P2P分域网络动态负载均衡调度的抗脆弱性策略

P2P网络中集散节点的存在加重了网络的脆弱性。提出一种动态负载均衡调度的抗脆弱性策略,该策略依据节点物理位置的邻近性对网络进行了分域,并设计出更为公平的函数对节点的负载进行动态的量化,当消费节点发出下载请求后,选择负载动态变化因子最小的节点作为服务节点,避免了单个节点负载猛增的情况,均衡了节点的负载。仿真证明该策略能有效抑制网络中集散节点的形成,增强网络的健壮性,从而达到保障P2P网络可持续健康发展的目的。     

P2P中应用平衡机制抑制搭便车行为的研究

针对近年来P2P网络中存在大量“搭便车”节点的问题,在判断一个节点是否是搭便车节点时提出一种基于平衡机制的算法,其不仅考虑节点自身的理性行为方面,还考虑节点所处的物理环境特征,并采用降低搭便车节点下载资源速度的方法来抑制其搭便车行为。仿真实验表明,该平衡机制算法可以有效降低网络中搭便车节点的数量,并提高网络的下载成功率,同时增强网络的公平性、稳定性,达到抑制搭便车行为的目的。     

P2P网络应用动态规划算法控制搭便车行为的研究

针对P2P网络中节点共享存储资源时存在的“搭便车”问题,在节点存储资源分配时引入控制机制,节点根据请求者的贡献值分配其存储资源,以使贡献值小的节点获取资源少,从而抑制搭便车行为。仿真实验表明,该控制机制的动态规划算法能有效地实现P2P网络中存储资源分配的公平性,达到控制节点搭便车行为的目的。     

缓存与迁移策略下对等网络节点负载控制算法

在非结构化对等(P2P)网络中,节点“搭便车”行为以及用户查询不均匀会造成网络节点负载分布严重失衡。为此,提出一种节点负载控制算法,采用缓存和链路迁移策略,将重载节点中的剩余负载向其他轻载节点转移,同时在链路节点中缓存网络中的热门文件资源。实验结果表明,在用户查询服从Zipf分布的环境下,该算法能使网络中节点负载达到较好的均衡,降低系统整体负载。     

一种基于公钥体系的P2P激励机制

针对P2P网络的搭便车行为及网络资源的同质化现象，提出了一个基于PKI体系和结构化P2P网络的激励机制。该激励机制不但鼓励节点提供资源下载，还让资源发布者从中受益，从而有效地抑制搭便车行为，减轻了资源的同质化现象。     

P2P网络中搭便车行为分析与抑制机制建模

在现实网络中,节点日益严重的搭便车行为对P2P可信流媒体网络的健壮性、可用性、服务响应速度和生命周期等产生了重要的影响.设计合理且有效的搭便车行为抑制和鼓励自私节点为系统作贡献的策略已成为P2P可信流媒体系统应用研究的一个重要方向.在全面分析节点的搭便车行为机理和搭便车行为对网络性能影响的基础上,对节点在P2P可信流媒...     

P2P视频直播系统中的分布式负载均衡算法

在分析了P2P网络应用模式优势的基础上,针对现有的基于P2P的视频直播系统中的负载均衡算法存在的问题,提出了一种分布式负载均衡算法。该算法不仅可以协同考虑节点的处理能力和网络延时,还可以在开销较小的前提下有效的降低组播树高度和平均源到端延时。     

一种结构化P2P网络动态负载均衡算法的研究

负载均衡是P2P网络的研究热点之一,当前负载均衡技术存在负载均衡程度低、假设条件过多等问题.提出一了种增强型负载均衡算法ELB_P2P,它根据节点的承栽能力为其分配相应大小的可动态调整的ID地址空间以及合理的载荷,在负载转移时自动选择延迟小带宽高的轻栽节点,并引入负载转移流量控制机制.实验表明,相对于Chord等传统P2P协议,ELB_P2P算法有更快的负载均衡速度、更小的负载均衡开销,系统稳定性好,在网络重栽情况下也能取得较低的负载不平衡度,并且对节点属性没有苛刻的限制和假定.     

一种层次结构化P2P网络中的负载均衡方法

相对于扁平结构化P2P网络,层次结构化P2P网络可利用稳定、高性能的超级节点提高P2P网络在动态环境下的性能.然而,超级节点的负载不均是层次结构化P2P网络面临的基本问题之一.对此,作者提出一种超级节点的负载均衡方法,通过分离超级节点负责的关键字空间和负责的叶子节点空间来为均衡负载提供条件,通过采用"力矩平衡原理"来实现兼顾均衡超级节点负责的叶子节点空间和查询请求负载.实验结果表明:在节点承载容量服从Zipf分布和查找请求服从正态分布或Pareto分布的环境下,负载均衡方法可使超级节点的负载达到较好的均衡,实现了用较少的超级节点承担较大的负载总量.     

P2P文件共享系统中面向协商的激励机制

借鉴经济活动中的协商机制提出一种面向协商的P2 P激励机制。文件供求节点通过订立协议对双方的行为进行制约,新节点和信誉度较低的节点也可以通过订立协议参与文件交易,达到提高节点的文件交易成功率的目的。仿真结果表明,该机制有效抑制了搭便车行为,明显提高了网络文件资源的利用率。     

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