基于认知无线电的QoS路由算法

一般无线网络的路由协议不适合直接应用于认知无线电网络,需要提出一个新的路由算法以满足认知无线电网络端到端的服务质量(QoS)性能。认知无线电网络中的节点可以自主地进行信道选择和频谱切换,从而最大限度地满足流量需求和避免流内竞争。结合按需路由的基本流程,在充分考虑信道容量和流内竞争所带来的干扰对路由选择的影响下,提出了适用于认知无线电网络的基于容量和干扰的路由算法。仿真结果表明,基于容量和干扰的路由算法比另两种路由算法具有更好的端到端QoS性能。     

认知无线Mesh网络联合多路径路由和信道分配策略

从路径交叉的角度为认知无线Mesh网络提出一种新的联合多路径路由和信道分配策略,该策略结合按需路由的基本流程,同时根据所选路径情况设置交叉节点的中继功能,以主用户曾经占用每个信道的最少次数作为衡量标准来选择信道,并给出了一种解决信道冲突的方案。仿真结果表明,所提策略与基于链接、基于干扰的策略相比,能够显著改善平均吞吐量和时延等网络参数性能。     

基于稳定性的认知Ad Hoc网络路由协议

针对认知无线电Ad Hoc网络中各个节点可用频谱的多样性、时变性和差异性的问题,传统路由协议不能适用于认知无线电Ad Hoe网络,提出了一种基于稳定性的路由协议.该协议综合考虑认知无线电Ad Hoc网络特性,通过计算每个节点的稳定性并引入分集传输,进行传输模式选择和信道选择,利用包括路径稳定性、路径跳数、路径信道切换次数的路由尺度进行路径选择.仿真分析表明,该协议能减少路径信道切换次数,提高路径稳定性和路径建立成功概率.     

认知无线Mesh网络中基于干扰模型的信道分配策略*

从信道干扰的角度为认知无线Mesh网络提出一种新的信道分配策略。首先对网络进行分层并按层对节点设置不同的层数权值,以此来选择最佳路径,再利用信道干扰模型来选择最佳信道。新策略有效整合了路由和信道分配过程,通过路由的实现来协助节点的信道分配以获得整个网络的最优化性能。仿真结果表明,新算法相比于无线多信道网络中基于链接的信道分配算法,在时延、吞吐量上有明显的优势。     

基于认知的多信道无线mesh网络路由协议研究

在多信道无线mesh网络中,路由选择与频谱可用性之间的相互依赖性很强,这就要求设计路由协议时要充分考虑信道的选择。传统的路由协议不能很好地适用于多信道无线mesh网络,因此提出了一种基于认知无线电的无线mesh网络路由协议,其中每个节点配置两个网络接口,路由选择与信道选择同时进行,通过冲突避免的设计,充分利用了多信道的优势。仿真结果表明,相对于传统路由协议,提出的路由协议能大大提高网络的吞吐量。     

认知无线电网络信道交汇研究综述

认知无线电技术被认为是解决目前频谱资源利用率低下问题最有前景的技术,基于该技术,认知无线电网络采用动态频谱接入方式有效地提高了授权频段的利用率.然而,动态变化的信道可用性极大地增加了认知无线电网络组网的难度.信道交汇旨在为用户通信提供公共传输媒介,是实现无线网络组网的基础.介绍了认知无线电网络信道交汇的基本概念和特点,并阐述了信道交汇策略设计面临的挑战以及应考虑的性能指标.提出了信道交汇策略的分类标准和系统模型,根据该分类标准,详细剖析了当前信道交汇策略相关的研究工作.最后,讨论了认知无线电网络信道交汇研究的开放性问题,以期为未来的研究指出可能的方向和重点.     

基于信道选择的认知无线网络路由协议

为保证认知无线网络路由的稳定性,减少信道切换次数,降低端到端时延,提出基于信道选择的路由协议。以信道可用概率和信道切换时延为信道选择标准,在确保信道可用的前提下,选择端到端时延最短的路由进行数据传输,提高路由的时延性能和数据投递率。仿真结果表明,与TDRP、PUC-JRCA协议相比,该协议在数据包传输时延、数据投递率方面有明显改善。     

一种按需式双信道的Ad Hoc网络路由方法

为了提高Ad Hoc网络的信道带宽和降低通信时的相互影响，在单信道的Ad Hoc网络多路径路由方法基础上，提出了按需式的采用双信道的路由策略。在物理上，整个网络存在两个独立的信道。通过一次路由发现，获得两条节点不相交路径，按照每包分配策略，把数据交替在两个信道的不同路径上进行传输。在提高带宽的同时，降低了数据传输冲突，从而改善网络性能。     

大规模认知无线电网络的时延分析

时延作为无线网络的最基本的性能之一,对网络信息分发、路由协议设计、节点部署等都具有重要意义。与传统的无线网络不同,认知无线电网络的频谱资源具有动态变化性,该特性会对网络时延产生极大的影响。因此,如何对动态频谱环境下的大规模认知无线电网络进行时延分析,是一项很具挑战性的课题。为此,首先对动态频谱环境进行建模,将认知用户的频谱接入过程建模为一个连续时间的马尔可夫链,并建立认知用户的生存函数来量化授权用户活动以及信道数量对频谱环境的影响;其次,将上述模型与首次通过渗流理论结合起来,研究了大规模认知无线电网络时延的伸缩规律,并获取了更为精确的时延与距离比的上限值。理论分析及仿真结果表明,动态频谱环境与密度一样会对时延产生极大影响。研究结论对认知无线电网络的设计具有重要的指导意义。     

基于802.11的多信道无线网状网络的路由

无线网状网络(WirelessMeshNetworks,WMNs)已经成为下一代无线网络的研究热点,其中采用何种策略进行路由选择以使网络吞吐量最大成为目前研究的关键问题。论文分析了现有的无线网状网络路由选择策略,并在此基础上综合考虑了跳数、信道质量、链路间的多信道必然干扰以及潜在干扰,提出了一种新的路由尺度WCETTR。仿真表明,该方法能够显著地提高网络吞吐量。     

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。     

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.     

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.     

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.     

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.     

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.     

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。