基于DSP的雪崩光电二极管数控偏压源设计

为保证雪崩光电二极管(APD)增益恒定,不受温度变化的影响而处于最佳工作状态,通过分析APD的增益和温漂特性,设计了一种APD偏压随温度按一定规律变化的数控偏压电路.采用DSP芯片TMS320F2812为主控制器,启动A/D转换对温度传感模块输出的电压信号进行采集,经计算处理得到APD的温度,然后由DSP输出相应的PWM信号来调节APD的偏压,从而保持APD增益恒定.该电路通用性好、可靠性高、操作性强,适合于高频连续信号检测的光电系统.     

基于背向拉曼散射的分布式光纤温度 传感器APD最佳雪崩增益的分析

本文分析了基于背向拉曼散射的分布式光纤温度传感器中光电接收用雪崩光电二极管雪崩增益对接收电路信噪比的影响,给出了使传感系统接收电路输出信号信噪比最大这一最佳意义下APD雪崩增益的表达式并进行了分析,实验结果和理论分析基本一致。     

激光陀螺中雪崩光电管增益温度补偿

为保证激光陀螺中雪崩光电二极管(APD)在温度变化的情况下始终处于最佳工作状态,从APD的倍增机理出发,分析了温度对雪崩增益的影响,建立了虚警率与APD倍增因子的数学模型,并采用监测雪崩噪声平均过阈率的方法,得到器件的实际击穿电压温度系数γ=6.088×10-3/℃,按实测γ进行温度补偿,有利于提高APD增益的稳定性。     

基于负反馈技术的嵌套式直流失调消除电路

基于UMC 40 nm CMOS工艺,设计了一种带有直流失调消除电路(DCOC)的可编程增益放大器(PGA),该PGA采用闭环电阻反馈结构,由两级增益单元级联构成.DCOC电路基于传统的直流负反馈结构,针对多级级联的方式,提出了一种嵌套式反馈方法,可降低电路功耗和面积.仿真结果表明,DCOC在0-52 dB的增益变化范...     

基于TL494的单闭环温度控制系统的设计

针对传统温度控制系统设计复杂的缺点,提出了一种新的温度控制设计思路。以TL494为控制单元,采用AD590为温度传感器,组成温度闭环控制系统.该系统具有结构新颖、电路简单和控制方便等优点。实际运行结果表明,该系统控制精度高、运行稳定,控制效果良好。     

全光纤电流互感器中的TEC温控模块电路设计

在全光纤电子式互感器采集系统中,针对半导体激光器(LD)对温度稳定性的特殊要求,设计了基于ADI公司热电制冷控制芯片ADN8834的自适应温度控制电路。详细介绍了半导体激光器温度控制模块的系统及工作原理,并用仿真软件对电路的稳定性进行了仿真分析。该控制电路采用闭环负反馈结构,利用温度测量输出与给定量之间出现的偏差,通过PID补偿网络形成负反馈,使LD最终稳定在设定温度。通过工程实践,给出了优化PID外围阻容参数的方法,以实现最优的温度控制响应时间和最大振荡幅度的最佳值。经试验验证,该温控电路能够使LD温度在1 s内稳定在设定温度。在-25～+55℃温度范围内,温度控制精度为0.01℃,稳定度可达0.04℃。该温控电路为模块化设计,易于集成,工作范围宽且成本低廉,完全能够满足现场应用需要。     

基于盖革APD阵列的单通道激光雷达信号读出电路设计

随着测量技术的发展,激光雷达技术成为研究的热点,选取工作在盖革模式下的集成APD阵列雪崩二极管作为激光雷达的光电探测器,在探测距离为100-200m范围内,选择上升沿为5ns的激光脉冲,则接收带宽在70MHz~88MHz范围内,在此范围内APD探测器将接收到的回波信号转化为电信号,用TIA跨阻放大器反向放大模式将电流信号转化为电压信号,并将信号有效放大,输入至时刻鉴别电路,时刻鉴别电路用电压比较器来实现,最终可输出COMS逻辑电平信号;用TINA仿真软件进行仿真,仿真结果表明在接收带宽范围内TIA放大器的增益动态范围达到了54dB,总体电路延迟约为10ns。     

I-FOG光电转换电路稳定性分析与设计

本文出于提高闭环干涉式光纤陀螺(I-FOG)检测精度的目的,根据I-FOG的信号特征,说明了光电转换电路的稳定性问题。详细分析了转换电路的系统模型。基于S域分析的方法,阐述了使光电转换电路稳定工作的电路结构。应用这种结构设计了一款光电转换电路。经实验得到了优良的零漂、零偏、低噪声指标,可满足闭环I-FOG的实用要求。     

基于ADN8831的高性能温度控制系统设计

在光电领域中,有许多无源光器件对温度稳定性的要求很高,基于这一点设计了一个高性能、高精度的温度控制系统。介绍了温度控制原理,讨论了基于ADN8831的温度控制电路的设计,通过试验对所设计的温度控系统进行了测试,测试结果表明:设计的温度控制系统完全符合光电领域对温度稳定性的要求。     

基于980nm泵浦激光器的恒温驱动设计

利用高性能的TEC控制器ADN8831芯片为核心设计并制作了980nm泵浦激光二极管的温度控制电路,利用该芯片驱动980nm半导体的制冷器(TEC)来实现对激光二极管进行温度调节的目的。微处理器配合ADN8831芯片对激光器内外部温度进行检测,利用差分放大,PID补偿以及PWM驱动等调节网络构成一个闭环温度控制系统。测试结果表明:该驱动电路可将半导体激光器的工作温度控制在0.1℃的范围内,将该温度控制器成功应用于980nm泵浦激光器的驱动中。     

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.