基于LED的高速可见光通信系统研究

LED照明与可见光通信技术相结合,构建出基于LED的可见光无线通信系统。本文介绍了白光LED的光源特性,分析了均衡技术可以克服LED较低调制带宽和提高信噪比的特性。详细介绍了不同调制体制的高速可见光无线通信系统,并比较了它们的优缺点,最后介绍了高速可见光通信系统的组网,通过对通信链路和系统信道模型进行分析讨论,指出了照明设计和接收机设计时应考虑的因素。     

改善室内可见光通信系统性能的关键技术

可见光通信是一项新兴的基于白光LED的无线光通信技术。可见光通信系统可以实现照明和通信的双重作用。通过分析影响白光LED通信性能的因素,对室内可见光通信中提高系统整体性能的若干关键技术进行了研究讨论,为改善白光LED通信系统性能提供进一步努力的依据。     

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。     

基于可见光传输的多路数字音频通信系统

针对现有点对点数字通信系统传输距离近、成本高等问题,采用白光LED设计并实现了基于可见光传输的多路数字音频通信系统。该系统结合音频编解码芯片TP3067实现多路音频信号的复用传输,采用FPGA作为主控制器控制编码信号的时隙。实验结果表明,该系统可实现最高2.048 Mbit/s的传输速率,最多可传输32路音频信号,且传输稳定。     

可见光通信的研究与发展

可见光通信是一种新型的无线通信技术。传统的无线通信技术例如蓝牙、Wi Fi等采用射频信号传输数据信息,而可见光通信在发射端采用白光发光二极管作为光源,在接收端采用光电传感器作为检测器进行数据传输。本文全面分析了可见光通信的优势,列举了可见光通信技术在国内外的应用研究与发展,并给出了目前可见光通信发展中面临的一些挑战。     

可见光通信的应用研究

随着节能环保型LED的发明及大量应用,可见光通信技术已成为一种新兴的无线光通信技术。通过阐述可见光通信技术的发展、研究过程、系统组成及原理,重点探索了可见光通信系统在无线宽带接入、特殊场所无线接入、物联网应用、室内购物导航的案例,并对可见光通信的局限性提出了设计解决方案,最后研究和分析了可见光通信的无线传输技术。     

可见光通信重点技术与应用解读

正1.概述可见光通信技术是以LED为载体的新型光无线通信技术。白光LED采用电场发光和低电压供电,具有寿命长、光效高、稳定性高、安全性好、无辐射、低功耗、抗震、可靠耐用等特点。几乎综合了各种传统光源的优点,被誉为2l世纪新固体光源时代的革命性技术。白光LED同时又具备响应时间短、高速调制的特性,因此,使得白光LED从照明领域扩展到了通信领域,能够同时实现照明和通信双重功能,催     

基于PWM调制的ACO-OFDM混合技术的研究

基于LED的可见光通信技术能够实现照明与无线通信的双重功能,因此被越来越多的人们所关注.但存在高PAPR、要求LED具有高线性特征及不适合发光亮度调节等问题,需要采用ACO-OFDM调制信号解决.但当转换一个振幅很小的信号时,需要更大的通信带宽,对于目前的LED显然是不能实现的.因此提出一种基于PWM调制的ACO-OF...     

一种基于可见光信标的室内定位系统及实现

设计了一种基于LED可见光信标的室内定位系统,具有成本低、功耗低、调制解调算法简单等优点,实验数据表明,使用光学天线可以明显减小误码率并增大可见光通信的传输距离,该室内系统定位最小所需时间为76 ms,当LED信标高度为1 m时,定位精度约为20 cm。     

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。     

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。     

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.     

Editorial: Special issue on recent advances in hybrid control theory and applications

正The demands of a rapidly advancing technology for faster and more accurate controllers have always had a strong influence on the progress of automatic control theory.In recent years control problems have been arising with increasing frequency in widely different areas,which cannot be addressed using conventional control techniques.The principal reason for this is the fact that a highly competitive economy is forcing systems to operate in regimes where     

Information for Authors

正Aim The Journals of Zhejiang University-SCIENCE(A/B/C)areedited by the international board of distinguished Chinese andforeign scientists,and are aimed to present the latest devel-opments and achievements in scientific research in China andoverseas to the world’s scientific circles,especially to stimulateand promote academic exchange between Chinese and for-eign scientists everywhere.     

基于AD9626的模拟信号采集存储卡设计

自然界的绝大部分信号都是以模拟的形式存在,因此模拟信号的采集转换存储在数字时代十分关键。文章讨论了在雷达信号处理领域基于AD9626的AD采集存储卡的设计原理、硬件结构和程序设计与芯片配置等问题,为今后相关领域的研究提供了可参考的方案。