模糊自适应算法在网络主动队列管理中的研究

为了改善由于RED算法控制的主动队列管理策略(AQM)系统引起网络响应时间过长,许多文献提出了基于P/PI控制器的AQM策略。但是,由于网络具有非线性特点,论文设计了一种模糊自适应PID控制器的主动队列管理系统,根据队列长度和队列长度变化通过模糊控制规则在线调整PID控制器参数,并用Matlab进行了仿真,验证了当网络出现突发分组时,该算法能够较快的使分组稳定在队列阀值附近,同时不产生队列震荡。     

主动队列管理中的APD和APID控制器的设计*

AQM策略作为终端系统上网络拥塞控制的一种补充,能在保证较高吞吐量的基础上有效地控制队列长度,从而实现控制端到端的时延,保证QoS。理论上,很多AQM机制可以最终归结为PID控制器。因此在研究PD和PID控制器模型的基础上,设计了两种新的适应性控制机制,即APD和APID控制器,使系统在网络变化的情况下能提高其稳定性和网络性能,并仿真验证了这两种新算法的稳定性和网络性能。     

基于灰色预测可变裕度PID网络自适应算法

为了综合控制拥塞链路的队列长度,提高AQM系统对动态网络环境的自适应能力,提出了一种基于灰色预测和考虑可变裕度PID控制的自适应TCP网络主动队列管理。首先,建立相角和幅值裕度与网络参数相关的PID自适应主动队列(TCP/AQM)控制论模型,该模型可以根据网络参数的变化而动态改变控制参数,以提高AQM网络动态自适应能力,及系统的鲁棒性;其次,将灰色预测引入该模型,实现路由器队列长度的超前预测,补偿带有PID反馈模块的AQM算法给队列造成的时滞影响。与其他算法的仿真结果相比较,该设计算法能够使信息流在较短的时间内稳定在期望队列长度阈值附近。     

单神经元自适应PID控制器在AQM中的应用

主动队列管理(AQM)对于保持TCP网络高性能是一种有效的策略。AQM的基本机制是调节数据包进入路由器缓冲区的速率,从而避免网络拥塞。针对传统PID控制器在拥塞控制过程中参数固定的缺点,将神经网络理论引入AQM的研究中,设计了一种改进的单神经元自适应PID主动队列管理器。基于NS2平台的仿真结果表明,与PID控制器及传统的单神经元自适应PID控制器相比,改进的控制器对网络环境的变化有更强的适应能力和更好的稳定性。     

一种基于内模PID控制的主动队列管理算法

针对传统主动队列管理中PID控制存在的参数不易整定等缺点,通过引入内模控制思想,提出了一种基于内模控制的PID控制器（IMC－PID）,其突出特点是控制器仅有一个参数需要整定。将IMC－PID应用于网络拥塞控制中,得到了一种新的主动队列管理（AQM）算法——IMC－PID算法。仿真实验表明,IMC－PID算法有较强的鲁棒适应性及较快的队长调节速率。     

基于模型有效性评价的主动队列管理算法

TCP/AQM系统是一多时滞回路耦合时变系统,源端传输控制协议(TCP)的拥塞控制机制也各不相同,因此其机理模型复杂.设计控制器所采用动态近似模型的参数变化范围很大,这对辨识算法提出了很高要求.本文先从模型误差分配方式这一新的角度对经典辨识算法进行了分析.然后运用新分析框架,结合TCP/AQM系统特征和控制要求,设计了一种基于模型有效性评价机制的辨识算法.该辨识算法能够对控制系数进行自适应调节,满足了主动队列管理(AQM)算法的设计需求.仿真结果表明,基于模型有效性评价机制的AQM算法,能有效应对时滞和不确定性带来的负面影响.与潜在标准化AQM算法相比,新算法在保持低排队时延和高效链路利用率方面取得了更好的平衡.     

基于D稳定域和ITAE准则的主动队列管理算法

主动队列管理(active queue management,简称AQM)是网络拥塞控制的研究热点之一,其中的关键问题是如何设计反馈控制策略.提出一种新的基于D稳定域和时间乘以误差绝对值乘积积分(integral of time-weighted absolute error,简称ITAE)性能准则的比例-积分-微分(proportional-integral-differential,简称PID)优化设计方法(简称DITAE-PID),并用于AQM控制器的设计,控制闭环系统的理想动态性能.首先在复平面上设定一组理想的D稳定域,然后以ITAE为目标函数,通过数值优化算法求出控制器的参数,使得闭环系统的所有特征根都在D稳定域内,以降低排队延时,提高有效吞吐量.对比仿真实验结果表明,该算法能够预先探测和控制拥塞,有较好的鲁棒性,链路利用率更高,丢包率更小,平均队列长度更趋于期望值,同时,趋于期望队列长度的时间更短,其综合性能明显优于典型的随机早期探测(random early detection,简称RED)和比例-积分(proportional-integral,简称PI)算法.     

主动队列管理机制在突发流下的性能比较与分析

主动队列管理机制(AQM)是目前拥塞控制领域研究的热点。本文研究了几种具有代表性的AQM机制在突发流下的性能。研究结果表明，具有相位滞后特征的控制器能够减小对突发流的偏见。本文的分析和研究有助于深入理解AQM机制的性能，并且对新的AQM算法的设计具有重要的指导意义。     

Active Queue Management算法研究

主动队列管理算法对于IP网络的性能影响重大,是网络拥塞控制一个主要手段。介绍了目前主要的主动队列管理算法如RED、改进的RED以及P控制器、PI控制器、模糊控制器、鲁棒控制器、内模控制器。通过对这些算法的分析,指出其中的不足之处,并对AQM算法的设计提出了一些思路。     

一种基于可变结构的主动队列管理算法

主动队列管理算法(AQM)是近年来网络拥塞控制的研究热点之一,已经提出了许多的主动队列管理算法,例如:RED,ARED,SRED,PI,REM等.文中设计一种基于控制理论的可变结构的主动队列管理.通过分析控制机制对于非线性的TCP/AQM模式的鲁棒性和性能,展示了在不确定的RTT(round-trip time)和活跃的TCP连接个数的情况下,有很好的性能和鲁棒性,这正是主动队列管理最重要的理念.运用网络仿真软件NS对设计进行仿真验证,从不同的角度对其性能与现有队列管理算法进行比较.仿真结果显示,从稳定性和鲁棒性等角度,可变结构控制算法显著胜过现有的AQM算法     

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.     

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.     

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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