一种基于复杂网络理论的移动自组网路由算法研究*

针对移动自组网中节点之间数据包发送成功率不高、路由开销大和包平均延时长等问题,提出了一种基于复杂网络理论的移动自组网路由算法。在该算法中,路由发现基于路由消息在邻域范围的相互借阅,若持续时间在网络平均路由发现时间范围内,则采取动态随机路由,考核跳级数是否满足复杂网络理论的条件来选择以最少跳级数或者最短路径为指标的最优路径建立路由,否则采取位置路由,采取方向最有益的最优路径建立路由。实验分析表明,即使节点稀疏时该路由算法仍具有很好的包发送成功率和包平均延时,其综合性能优于OLSR协议和AODV协议。     

基于K-最近邻基站的移动手机自组网路由协议

通过分析AODV算法及其存在的问题,结合节点的移动速度和方向等信息, 提出了一种基于K-最近邻基站的移动手机自组网混合路由协议。在新协议中, 当网络的本地基础设施发生故障时,每个本地节点首先生成并维护一个K-最近邻基站信息表,然后基于该K-最近邻基站信息表,利用改进的AODV协议来进行按需路由。理论分析与仿真结果表明, 新算法的性能要优于传统的按需路由协议AODV,因此,更适合移动手机自组网中的路由。     

移动节点在ZigBee网络中路由无缝切换的改进

ZigBee是一种新兴的无线通信技术,广泛用于自动化、远程监控等领域.由于ZigBee网络中静态路由节点与移动终端节点通信延迟严重,限制了ZigBee的应用,针对此问题提出一种改进的方案.首先简介ZigBee协议栈以及ZigBee网络层,分析现有的Z-AODV协议,并在此基础上提出移动节点快速路由的机制,从而减少通信延迟,实现移动终端节点在静态路由间的平滑无缝切换.     

家庭自动化无线传感器／执行器网络路由协议的设计

家庭自动化无线传感器／执行器网络有着自己的特点,如节点间供电能力、计算能力、移动性具有显著 差异,本文在分析这些差异的基础上提出一种基于地理位置的按需路由协议．该路由协议利用静态节点位置限定路 由请求包,并且利用静态邻居节点作为辅助节点完成动态节点的路由发现,避免了对移动节点定位技术的依赖性． 利用NS2 比较了该路由协议和AODV 路由协议的性能．仿真结果显示本文的路由协议能降低路由开销从而提高稳 定性．     

基于MAC层信息的OLSR改进方案

针对移动Ad Hoc网络通信节点共享通信介质且易受网络负荷影响的特点,提出了一种基于MAC层信息的OLSR协议改进方案。该方案通过对HELLO消息、TC消息的修改来获取并传输MAC层的拥塞信息,对路径选择算法进行改进以评估节点的网络负荷,选择出一条网络负荷和冲突较轻的路由,从而减少数据在MAC层和物理层的丢包。方案改进了TC消息源头节点的发送方式,采用源节点二次发送机制以降低对路由性能有重要影响的信令信息丢失的概率,稳定路由协议的性能,减少数据在网络层的丢包。仿真实验表明改进后的方案在网络负荷较重时,在不同的移动速率下均能提高数据传输的成功率,增强网络承受负荷的能力,提高其路由传输的性能。     

基于负载均衡的战场自组织网络多径路由研究

移动Ad hoc网络中的多路径路由协议能够减小路由发现延迟,提高网络生存时间,受到了人们的广泛关注.详细分析了AOMDV多路径路由协议的机制和特点,针对多径路由协议在负载均衡时采用的随机转发策略,提出了一种改进的基于AOMDV协议的负载均衡传输方案,该方案能够避免TCP在多径传输时的乱序.仿真结果表明,在不影响UDP性能的情况下,该方法能显著改善TCP的传输性能.     

移动自组网中一种洞椭圆化的避洞路由协议

基于地理位置信息的路由协议具有很好的可扩展性。然而,当源节点和目的节点之间存在洞时,该类路由协议可能遇到局部最优的问题。针对此问题,提出了一种基于洞椭圆化的避洞路由协议。该协议通过把洞规则化为一个椭圆,并把洞的信息向外局部广播,从而有效地解决了该问题。模拟结果表明该路由协议具有路由延迟小、路径短等特点。     

一种基于改进RTS/CTS的MANET高效报文转发策略

MANET网络由可自主移动的无线节点组成。节点的自主移动导致了链路路由的改变,因此需要有一个机制维护和发现路由信息。目前人们已经针对MANET网络提出了几种路由协议,但这些路由协议都是基于IP的且路由维护的代价高,这严重影响了MANET网络的稳定性、可扩展性和用户有效带宽。本文提出了一种基于改进RTS/CTS的MANET高效报文转发策略。该策略对标准IEEE 802.11协议进行了修改,利用改进的RTS/CTS报文信息,进行报文转发,从而避免了使用MANET网络路由协议给网络性能带来的影响。使用改进的NS-2模拟了基于改进RTS/CTS的MANET高效报文转发策略。模拟结果表明:该策略可以有效地降低路由维护的开销并降低报文传输的延迟。     

MANET中基于位置的无信标路由算法与DSR的性能比较

由于节点的移动性、无线链路的带宽有限、可获得的能量有限等原因,对移动Ad hoc网络进行路由提出了具有挑战性的要求。基于位置的路由协议由于不必维护明确的路由,在这种高度动态的网络中具有很好的扩展性。该文通过仿真将一种基于位置的贪婪转发路由:基于改进进程无信标路由(IPPBBLR),与一种基于拓扑的路由:动态源路由(DSR)进行了性能比较。仿真结果表明基于位置的路由比基于拓扑的路由在移动的情况下可以达到更高的发送成功率和更小的端到端延迟,且端到端延迟几乎不受移动速率的影响。     

基于冲突避免的DSR协议研究

基于自适应移动多跳Ad Hoc网络,针对其DSR协议的路由缓存机制,分析不足之处,探索对现有的路由缓存机制的优化方法.提出了缓存路由有效期的概念,为网络中节点的路由表添加一个用于反馈的“缓存路由跳数”参数,节点选择此参数值最小者的路由信息.仿真实验表明,经过改进的缓存机制有效地避免了响应冲突问题,实现了路由的最短优化,在平均传输延迟、分组投递率、吞吐量性能方面都有提高.     

Only connect: teaching, technology and telesis

Abstract This paper describes an approach to the design of interactive multimedia materials being developed in a European Community project. The developmental process is seen as a dialogue between technologists and teachers. This dialogue is often problematic because of the differences in training, experience and culture between them. Conditions needed for fruitful dialogue are described and the generic model for learning design used in the project is explained.     

European Community policy and the market

Abstract This paper starts with some reflections on the policy considerations and priorities which are shaping European Commission (EC) research programmes. Then it attempts to position the current projects which seek to capitalise on information and communications technologies for learning in relation to these priorities and the apparent realities of the marketplace. It concludes that while there are grounds to be optimistic about the contribution EC programmes can make to the efficiency and standard of education and training, they are still too technology driven.     

一种自适应子融合集成多分类器方法

融合集成方法已经广泛应用在模式识别领域,然而一些基分类器实时性能稳定性较差,导致多分类器融合性能差,针对上述问题本文提出了一种新的基于多分类器的子融合集成分类器系统。该方法考虑在度量层融合层次之上通过对各类基多分类器进行动态选择,票数最多的类别作为融合系统中对特征向量识别的类别,构成一种新的自适应子融合集成分类器方法。实验表明,该方法比传统的分类器以及分类融合方法识别准确率明显更高,具有更好的鲁棒性。     

Avoiding semantic and temporal gaps in developing software intensive systems

Development of software intensive systems (systems) in practice involves a series of self-contained phases for the lifecycle of a system. Semantic and temporal gaps, which occur among phases and among developer disciplines within and across phases, hinder the ongoing development of a system because of the interdependencies among phases and among disciplines. Such gaps are magnified among systems that are developed at different times by different development teams, which may limit reuse of artifacts of systems development and interoperability among the systems. This article discusses such gaps and a systems development process for avoiding them.     

Designing economic np control charts: A programmed simulation approach

This paper presents control charts models and the necessary simulation software for the location of economic values of the control parameters. The simulation program is written in FORTRAN, requires only 10K of main storage, and can run on most mini and micro computers. Two models are presented - one describes the process when it is operating at full capacity and the other when the process is operating under capacity. The models allow the product quality to deteriorate to a further level before an existing out-of-control state is detected, and they can also be used in situations where no prior knowledge exists of the out-of-control causes and the resulting proportion defectives.     

The development of robot art

Going through a few examples of robot artists who are recognized worldwide, we try to analyze the deepest meaning of what is called “robot art” and the related art field definition. We also try to highlight its well-marked borders, such as kinetic sculptures, kinetic art, cyber art, and cyberpunk. A brief excursion into the importance of the context, the message, and its semiotics is also provided, case by case, together with a few hints on the history of this discipline in the light of an artistic perspective. Therefore, the aim of this article is to try to summarize the main characteristics that might classify robot art as a unique and innovative discipline, and to track down some of the principles by which a robotic artifact can or cannot be considered an art piece in terms of social, cultural, and strictly artistic interest. This work was presented in part at the 13th International Symposium on Artificial Life and Robotics, Oita, Japan, January 31–February 2, 2008     

Explanation and prediction: an architecture for default and abductive reasoning

Although there are many arguments that logic is an appropriate tool for artificial intelligence, there has been a perceived problem with the monotonicity of classical logic. This paper elaborates on the idea that reasoning should be viewed as theory formation where logic tells us the consequences of our assumptions. The two activities of predicting what is expected to be true and explaining observations are considered in a simple theory formation framework. Properties of each activity are discussed, along with a number of proposals as to what should be predicted or accepted as reasonable explanations. An architecture is proposed to combine explanation and prediction into one coherent framework. Algorithms used to implement the system as well as examples from a running implementation are given.     

Three Process Perspectives: Organizations, Teams, and People

This paper provides the author's personal views and perspectives on software process improvement. Starting with his first work on technology assessment in IBM over 20 years ago, Watts Humphrey describes the process improvement work he has been directly involved in. This includes the development of the early process assessment methods, the original design of the CMM, and the introduction of the Personal Software Process (PSP)^SM and Team Software Process (TSP){^SM}. In addition to describing the original motivation for this work, the author also reviews many of the problems he and his associates encountered and why they solved them the way they did. He also comments on the outstanding issues and likely directions for future work. Finally, this work has built on the experiences and contributions of many people. Mr. Humphrey only describes work that he was personally involved in and he names many of the key contributors. However, so many people have been involved in this work that a full list of the important participants would be impractical.     

基于复小波噪声方差显著修正的SAR图像去噪

提出了一种基于复小波域统计建模与噪声方差估计显著性修正相结合的合成孔径雷达(Synthetic Aperture Radar,SAR)图像斑点噪声滤波方法。该方法首先通过对数变换将乘性噪声模型转化为加性噪声模型,然后对变换后的图像进行双树复小波变换(Dualtree Complex Wavelet Transform,DCWT),并对复数小波系数的统计分布进行建模。在此先验分布的基础上,通过运用贝叶斯估计方法从含噪系数中恢复原始系数,达到滤除噪声的目的。实验结果表明该方法在去除噪声的同时保留了图像的细节信息,取得了很好的降噪效果。     

How do children do mathematics with LOGO?

Abstract  This paper considers some results of a study designed to investigate the kinds of mathematical activity undertaken by children (aged between 8 and 11) as they learned to program in LOGO. A model of learning modes is proposed, which attempts to describe the ways in which children used and acquired understanding of the programming/mathematical concepts involved. The remainder of the paper is concerned with discussing the validity and limitations of the model, and its implications for further research and curriculum development.