基于日盲紫外光通信的自组织网络技术研究*

日盲紫外光通信技术是一种新兴的基于大气散射和吸收的无线光通信技术,非常适用于近距离高速通信和中距离低速传感器信息传输的场合。介绍了视距和非视距紫外光通信的特点以及影响紫外光散射通信的主要大气因素;分析了日盲紫外光散射信道的链路模型和发射功率衰减规律;研究了日盲紫外自组织网络的关键技术和大气信道模型、网络接入技术和网络路由技术,这些技术将会在民用和军事领域得到广泛的应用。     

无线光通信调制方式性能分析

无线光通信有多种调制方式,但缺少综合的分析.误码率(BER)是衡量无线光通信系统不同调制方式优劣的重要性能指标,如何正确统计误码性能显得尤为重要.介绍了无线光通信系统以及不同调制方式的基本原理,利用计算机仿真软件,研究在理想信道下实现无线光通信系统误码性能分析的方法,在对四种典型的无线光通信调制方式一OOK、PPM、DPPM和DPIM调制方式的符号结构分析的基础上,分析比较了上述四种调制方式的功率利用率、带宽利用率、传输容量以及抗码间干扰等性能.理论分析及仿真结果表明:DPPM和DPIM调制方式更加适合于未来无线光通信系统.为无线光通信调制方式的选取提供一定的参考依据,并指出其发展趋势.     

紫外非视距通信的MLSE均衡器

针对无线非视距紫外通信中的大气信道模拟问题,提出将最大似然序列估计均衡器应用于无线非视距紫外通信中.推导紫外通信中接收信号的概率密度函数,以此近似研究均衡器的输出误码率.理论分析与仿真结果表明,在短距离通信时,大气衰减系数与信道带宽的变化不影响均衡器性能.在接收信噪比不变的较长距离通信时,两者的变化对均衡器性能影响明显.信道记忆长度等因素对均衡器性能影响显著,而对调制方式不敏感.     

基于DSP的紫外光通信语音压缩系统设计

紫外光通信系统由于其特殊的波段范围和特殊的运用方向而受到了广泛的重视.文章主要介绍了紫外光通信的原理,以及G.729编解码标准算法在DM6437 DSP开发板上实现的软硬件设计方法,并将该方法加入紫外光语音通信系统中,提高语音传输质量.     

基于VLC的室内无线视频语音通信系统的设计和实现

根据半导体照明与可见光通信(VLC)相融合的无线接入方式,提出了一种新型室内无线视频语音通信系统;可见光通信提供了从室内接入点到室内终端之间的无线互联,该接入点由照明光源组成,室内终端由用户终端组成;在需要安装VLC系统的地方对LED照明系统进行合适的改造,在照明光源和用户终端之间搭建了一个采用Manchester编解码OOK调制方式的最简VLC系统;介绍了全双工的实现技术及TCP/IP的组网方案等,讨论了室内可见光通信中提高系统整体性能的若干关键技术,并通过试验验证了该系统的可行性。     

基于ATmega8的紫外语音通信系统接收解调技术研究

紫外通信相对于常规无线通信具有灵活、难以截获、抗干扰性强等诸多特点,并具备一定的非视距通信能力。应用调频技术实现对电光信号调制转换,再通过接收频率变换的紫外光信号,并进行光电转换,解调后正确还原出原始信号。提出了一种基于AVR单片机解调的接收系统设计,很好地处理了2FSK信号的过渡带问题,使传输的信息经调制后能正确解调,传输速率可以达到4．8Kbit／s,成功实现了实时语音通信。     

一种新型的无线光通信脉冲波形研究

针对无线光通信系统中高斯脉冲、升余弦脉冲、三角波脉冲等几种常用的脉冲信号通信可靠性相对较低、误码率相对较高的问题,为消除噪声干扰,提高通信可靠性,提出结合无线光通信系统中常用的调制后脉冲波形设计了一种新的合成脉冲波形,合成脉冲用一个持续时间与单个相应脉冲相等的脉冲代替相应的连续脉冲,且与原始脉冲属性相同,能量和原始的连续脉冲相等.理论分析和仿真结果表明,当合成脉冲波形用于几种特定的调制信号,使调制信号的峰值会出现在几个固定的位置,可以映射出原始信源信号.经过仿真证明,误码率性能较原始常用脉冲波形有较大提高.     

无线光通信中LDPC码在DPIM调制下的优化设计

介绍了DPIM调制阶数和LDPC码码率的关系,分析了选取调制阶数及码率使通信系统达到最佳效果的途径。同时介绍了DPIM调制方式的误码率的计算方法,为1T一旋转LDPC码在无线光通信DPIM下的仿真研究奠定了理论基础,在DPIM调制方式下对1T一旋转LDPC码进行了仿真性能分析。     

白光LED煤矿工作面可见光通信调制技术研究

介绍了煤矿工作面可见光通信系统总体结构;研究了煤矿工作面可见光通信关键技术,包括载波调制技术、调制驱动电路设计以及调制带宽,得出兼顾带宽和发光效率的白光LED是理想的可见光通信系统光源。     

白光LED煤矿工作面可见光通信调制技术研究

介绍了煤矿工作面可见光通信系统总体结构;研究了煤矿工作面可见光通信关键技术,包括载波调制技术、调制驱动电路设计以及调制带宽,得出兼顾带宽和发光效率的白光LED是理想的可见光通信系统光源。     

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。     

基于QTE的蒙古文显示机制研究与实现

蒙古语言是中国蒙古族使用的通用语言,由于蒙古文区别于其他文字的书写方式和其自身变形机制等特点,在很多通用的文字处理引擎中都不被支持。在嵌入式产品开发与应用领域中Linux加QTE已经成为流行方式。该文给出了一种在QTE环境上实现基于标准Unicode的蒙古文点阵显示和变形算法, 并自定义了支持蒙古文的QTE组件,扩展了QTE功能,为在Linux加QTE方式的嵌入式体系结构中处理蒙古文提供了一种解决方法。