高精度低功耗无线传感器网络时间同步算法

通过对无线传感器网络参考广播同步（RBS）算法的研究,针对RBS多跳算法网络开销大和不能实现全网同步的问题,在基于环形网络拓扑的参考广播环形同步（RBRS）算法基础上,提出一种改进的RBRS （IRBRS）算法.该算法引入可变周期同步法：根据贝叶斯最大后验估计原理,估算出最大相位偏差来决定同步周期,从而减少节点同步次数,并且采用最小二乘线性回归法,周期性拟合时钟偏移.运用Matlab环境进行仿真,仿真结果表明：IRBRS算法同步精度显著提高,并且能量消耗显著减少,更有利于延长无线传感器网络的寿命.     

无线传感器网络RBS的优化算法

通过对无线传感器网络时间同步以及RBS(参考广播同步)算法的研究,提出了一种RBS的优化算法.在RBS算法时间同步的过程中,针对节点时钟的不稳定性,以及节点间消息交换延迟所引起的同步误差,基于已存在的RBS时间同步算法,利用贝叶斯估计的先验知识和后验分布来减少同步误差.通过使用opnet仿真软件进行仿真,实验显示优化后的算法比原算法的同步精度有了显著的提高.     

能量有效的无线传感器网络时间同步算法

针对无线传感器网络时间同步能耗问题,提出一种能量有效的时间同步算法。该算法结合了TPSN协议和RBS协议的特点,利用无线信道的广播特性,在两个参考节点广播域里的所有节点通过监听参考节点之间的数据包交换而达到同步。并提出一种同步节点选择方法,将该同步算法扩展到多跳网络。实验结果表明,该算法在保持同步精度的同时降低了能量消耗。     

基于分量解耦融合的无线传感网时钟同步算法

无线传感器网络(WSN)时间同步精度的提高通常以增加额外同步能耗为代价,针对时间同步的高精度与低能耗的权衡问题,提出一种基于分量解耦融合的时钟同步算法。该算法结合双向广播同步机制和节点间时钟的相关性,利用分量解耦融合思想计算被同步节点与基准节点间的时钟偏差,同时根据线性无偏最小方差准则估计各个分量加权参数的取值。仿真结果表明,该算法能够在不增加额外同步能耗的条件下,相比PBS、TPSN和RBS算法,20轮同步后同步精度分别提高4.52μs、13.8μs以及25.48μs。     

无线传感器网络层次参考时间同步算法的研究

无线传感器在网络应用中要求节点间保持时间同步,但现存的经典时间同步算法,因节点的接收时间受时钟偏差和传输延迟的影响,其同步精度不高。为提高网络时间同步精度,均衡节点能耗,提出了一种改进的层次参考时间同步算法（Improved Hierarchy Referencing Time Synchronization,IHRTS）。该算法基于节点在层次结构中唯一物理位置的时间特性,采用贝叶斯估计对节点接收时间进行估算,缩小时间偏差的误差范围,获得比较精确的同步偏移量,从而改善时间同步精度;同时采用无线信道的广播特性与双向同步机制的同步思想,最小化了通信负载,均衡了节点能耗。通过仿真结果表明将贝叶斯估计方法应用到时间同步算法中,在均衡节点能量消耗同时有效地提高了网络同步精度。     

基于分量解耦融合的无线传感网时钟同步算法

无线传感器网络(WSN)时间同步精度的提高通常以增加额外同步能耗为代价,针对时间同步的高精度与低能耗的权衡问题,提出一种基于分量解耦融合的时钟同步算法。该算法结合双向广播同步机制和节点间时钟的相关性,利用分量解耦融合思想计算被同步节点与基准节点间的时钟偏差,同时根据线性无偏最小方差准则估计各个分量加权参数的取值。仿真结果表明,该算法能够在不增加额外同步能耗的条件下,相比PBS、TPSN和RBS算法,20轮同步后同步精度分别提高4.52μs、13.8μs以及25.48μs。     

矿井电网故障检测WSNs分层时间同步算法

结合经典时间同步算法TPSN、RBS的优点,提出了一种能量有效且满足一定精度要求的同步算法RBTP。该算法利用无线通信的广播特性并采用最大似然估计和最小二乘法计算时钟偏移和频偏,进而对时钟进行补偿。仿真结果表明,与TPSN和RBS算法相比,RBTP算法明显减少了节点的能量消耗,提高了同步精度,能够满足井下电网故障定位系统对时间同步的需求。     

无线传感器网络中多跳时间同步算法的研究

提出了一种基于簇型的多跳时间同步算法——CBTS。利用Leach算法将网络划分成不同的簇,在此基础上把节点间的时间同步分为水平同步和垂直同步两个阶段来完成。在水平同步阶段,通过构建基站与簇头节点的层次拓扑结构,采用双向消息交换同步机制来完成簇头节点与基站的时间同步。在垂直同步阶段,采用双向消息交换和参考广播相结合的同步机制,来完成簇头节点和簇成员之间的时间同步,并利用最小方差线性拟合的方法估计了节点的时钟偏差,提高了时钟同步的精度,最终实现了整个网络节点的时间同步。经过仿真测试,证明该算法具有较低的消息交换开销和不错的同步精度。     

基于WSNs矿山设备振动监测的时间同步算法研究

以无线传感器网络(WSNs)在矿山机械设备健康感知中的特殊应用为背景,研究了煤矿生产环境下需要的特殊感知网络结构,并构建WSNs的树形采集网络模型。在构建的模型下研究参考广播同步(RBS)算法。针对现有算法在建立时间同步时能耗较大和同步收敛时间长的问题,提出了改进的RBS(IRBS)算法。仿真分析发现改进算法能明显减少同步过程中的能量消耗和同步收敛时间。     

无线传感器网络的多跳时间同步优化算法

通过对无线传感器网络RBS时间同步算法（Reference Broadcast Synchronization,RBS）的研究,针对多跳全网的时间同步问题,提出基于环形网络拓扑的RBS环形算法（References Broadcast Bing Synchronization,RBRS）。该算法在RBS的基础上,采用广播分组和最小平方线性回归的方法实现全网时间同步。从同步误差和开销两方面对该算法和现有的RBS优化算法作理论比较。算法在众多算法中具有一定的优越性,适用于轻型、低功耗的无线传感器网络负载。使用matlab软件进行仿真,实验结果表明优化后的算法和初始算法相比误差累积小、同步开销显著减少,并且能够实现全网络的时间同步。     

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.