无线传感器网络中异常节点快速定位算法研究

研究无线传感器网络的准确定位问题,为了确定医疗、森林火险等事件的发生地,要搜索定位,及时预报.针对传统的集中式无线传感器网络定位方法,全网络中需要定位的异常节点都需传递信息到参照节点才能得到定位信息,过于依赖参照节点,造成参照节点负载过大,导致定位效率下降,不能快速完成异常节点定位的问题.现提出一种禁忌搜索( TabooSearch,TS)分布式定位算法,通过启发式逐步寻优算法,把定位过程分布到网络中相关通信节点上,通过异常节点与周边节点通信获取局部信息,利用局部网络信息对异常节点位置进行估计,避免了传统集中式方法对参照节点的过度依赖.实验证明,对TS分布式定位算法进行实验,证明能够有效利用网络信息,对异常节点实现快速定位,取得了满意的结果.     

一种基于离群点检测的定位算法

DV-Hop算法在无线传感器网络节点分布不均匀时定位误差较大。针对上述问题,利用离群点检测算法提高计算未知节点坐标的精度。在采用多边测量算法估计未知节点的坐标位置时用离群点检测算法LOF对未知节点的估计坐标进行分析和筛选,最终确定未知节点位置。仿真实验表明,该方法能提高节点的定位精度,减小定位误差。     

不定攻击中网络最弱节点定位技术仿真

快速查找攻击中的最弱节点能够更好的保证网络安全.传统的最弱节点定位方法在应用到随机攻击的状况下时,由于受攻击节点随机性增大,节点间的空间关联性迅速下降,攻击节点位置不定,因此很难对特定节点建立准确的约束模型,导致节点定位存在盲点,定位准确性较差.提出了一种改进粒子群节点特征寻优算法的不定网络攻击中最弱节点定位方法.计算网络节点之间的特征差值,在不定攻击中网络节点特征提取残差参数,进行极小化处理,通过设置粒子群中的每个粒子代表一个差异化节点定位的解,最大程度减小随机性带来的关联特征弱化问题.实验结果表明,利用改进后的算法进行不定攻击中网络最弱节点定位,能够有效提高节点定位的准确性,从而保证了网络的安全性.     

井下救援人员定位中的信号抗干扰技术研究

研究井下救援人员准确定位问题.针对井下通信情况较为复杂,存在大量的非线性乘性噪声,使得无线定位通信信号大幅减弱,人体运动中产生的干扰也很难抑制.传统的CAB算法在弱信号强干扰的条件下不能抑制干扰,且对运动干扰的稳健性较差,造成人员定位不准.为了避免上述缺陷,提出了一种采用特征分离算法的井下救援人员准确定位方法.对采集的信号进行连续小波变换处理,去除信号中的干扰信息,提高信号的准确性.利用特征分离方法,分离出救援人员定位信号,从而实现井下救援人员定位.实验结果表明,利用特征分离算法能够去除外界因素的干扰,提高井下救援人员定位的准确性.     

基于信道质量分析传感器弱节点定位模型仿真

对传感器弱节点进行有效定位能够保证传感器网络的稳定运行。传统方法进行传感器弱节点定位时,没有考虑传感器信道由于节点分布不均产生的稀疏性,致使定位过程中出现大量无意义的零值抽头估计计算,从而降低了定位效率。提出一种基于信道质量分析的传感器弱节点定位方法,对传感器信道进行导频插入,在支持向量机的基础上引入递归机制,并对代价函数进行改进,实现对传感器信道子载波处的信道频率强度的准确预测,完成传感器信道质量的分析。然后,将分析结果转换为距离信息,并以接收数据的参考传感器节点为圆心、以距离为半径画圆,对每一个传感器节点的坐标赋予权值,最终得到传感器弱节点的定位结果。仿真结果表明,改进后的算法能够极大提高传感器弱节点的定位精度,效果令人满意。     

无线网络信号衰退测量方法研究与仿真

研究无线网络信号衰退测量问题。在无线网络中,随着传输距离的增加,信号的频率和振幅等属性将存在较大程度的差异,造成差异性较大的信号特征在融合处理的过程中出现信号冲突的问题,导致无线网络信号衰退。传统的信号衰退测量方法是根据衰退特征进行测量的,由于信号融合过程中存在冲突,导致信号特征准确率降低,无法实现无线网络信号衰退程度的准确测量。为此,提出了一种基于多特征差值算法的无线网络信号衰退测量方法。利用多特征信息融合方法进行无线网络信号相关信息整合处理,为无线网络信号衰退测量提供数据基础。利用多特征差值算法,计算准确的无线网络信号衰退特征。实验结果表明,利用本文算法能够有效提高无线网络信号衰退测量的准确性,取得了令人满意的结果。     

水利安全中混凝土松软程度报警网络模型仿真

针对混凝土松软程度进行及时报警,关系到水利建设的安全.由于在大型水利设施中,混凝土松软的程度很容易受到地下水流干扰,使无线传感节点监测到的混凝土松软程度出现无规则的波动,造成报警节点出现误判的问题,提出采用信号译码重构算法的大型水利设施混凝土松软程度传感网络报警模型.利用信号译码重构的方法对无线传感节点监测到的疑似信号进行译码与重构,消除水声干扰信号造成的影响,获取准确的混凝土松软程度信号,设置中继节点为参考节点,根据信号在水中传输情况,随着距离衰落的特性计算报警节点的空间位置,实现混凝土松软程度报警节点的准确定位.实验结果表明,利用改进算法能够实现大型水利设置中混凝土松软程度的准确监测.     

基于分数间隔均衡技术的GPS定位修正算法

移动终端节点阵列分布具有波特间隔不均衡特性,节点分布的波特数随信道码间干扰所覆盖信息码元数量的增加成指数增长,导致在小区域内GPS定位精度不准确,需要对定位信息进行修正.为了提高GPS定位精度,首先提出一种改进的基于分数间隔均衡技术的GPS定位修正算法,设计波特间隔均衡器对GPS定位信号波特率并进行采样;然后提出采用分数间隔均衡技术进行变步长修正移动终端节点接收信号的频谱混迭响应特性,最后采用静态电位估计算法,补偿GPS定位接收信号中的信道畸变,修正目标位置信息.仿真结果表明,算法特别适用于300m内小区域短距离终端用户GPS定位,能有效对抗相干干扰,定位方位角均方根误差较传统方法缩小,定位准确度大幅提高.     

基于Doppler效应的无线传感器网络射频干涉定位方法

文中提出一种基于Doppler效应的无线传感器网络射频干涉定位方法,两个锚节点同时发射具有一定频差的单音信号形成射频干涉,使得各接收节点获得一个低频变化的接收场强指示(RSSI)信号.基于其中一个锚节点移动产生的Doppler效应,在锚节点移动的时间段内,各节点通过测量RSSI信号的振动周期数,便可以获得自身到移动锚节点起点和终点的距离差.从而,通过锚节点的多次移动,各节点根据多组距离差信息,依据双曲线定位算法得到自身的地理位置估计.该定位方法仅需利用节点的无线通信设备,不需要额外的辅助测量装备,同时各节点独立进行自身的位置估计,不需要进行集中处理,是一种分布式的定位方法.理论分析和实验仿真均验证了该方法的可行性.     

基于WSN定位算法的井下单相接地故障研究

由于井下配电网的布线很复杂,故障检测传感器节点的分布却很分散,在故障信号传输过程中如果受到井下环境的干扰,容易造成消弧线圈的故障特征电流很小。传统的故障检测模型针对小电流故障特征很难进行高效准确采集,无法提供准确的故障检测,提出了一种Zigbee改进Music故障定位算法,采用Zigbee网络技术对故障区域进行定位,建立了多通道数据传输机制。改进Music算法通过对阵列输出扩展虚拟矩阵,解决了传统算法只能估计出少于阵元数信号方向的问题,将共轭信息引入到了Music算法中,利用二阶共轭增强法大幅度降低了算法的运算量。仿真结果表明,在相同锚节点密度的情况下,定位精度和定位覆盖率都得到了显著提高。通过单相接地故障电路实验对线路的零序电流进行了实际测量分析,验证了上述方案的可行性,可以有效地解决由于单相接地引起的井下故障问题。     

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.