半导体激光器驱动电路的计算机仿真分析

直接调制的大电流窄脉宽驱动电源是半导体激光器获得高峰值功率输出的重要保证.为了研究半导体激光器驱动电路,提高系统的精度和抗干扰能力,采用计算机仿真的方法分析了半导体激光器脉冲电源基本电路和雪崩晶体管脉冲电源电路.通过仿真结果表明,脉冲电源中元件的寄生电感及串联电阻对激光器工作电流脉冲的波形影响很大.当奇生电感小时,放电电流波形的上升时间就短.可为设计半导体激光器驱动电路时,提供选取R、C、L的依据,并保证工作在欠阻尼的情况下,要获得最大的放电电流,储能电容器上的充电电压要高,使电路的串联电阻尽量要小.     

光纤耦合输出半导体激光器的可靠性检测系统

介绍了一种光纤耦合输出半导体激光器的可靠性测试系统.该系统基于电导数原理,能够对光纤耦台输出半导体激光器的主要光电参数、电导数曲线以及电导数参数进行快速无损检测,具有体积小、成本低等优点.     

基于支持向量机回归的Lyapunov 指数计算方法研究

Lyapunov指数是描述动力学系统混沌性质的重要指标,在小样本条件下准确、快速地计算Lyapunov指数是一个难题.对此,提出一种基于支持向量机回归的Lyapunov指数计算方法,通过量子遗传算法对支持向量机模型的参数进行优化,推导了支持向量机回归应用于计算Lyapunov指数的公式.通过对混沌序列进行仿真实验,仿真结果表明,在小样本数据情况下,此方法可行有效.     

一种实验用近场光盘记录激光器驱动电路

为了满足近场光盘记录实验研究的需要,使半导体激光器在加入高频调制的情况下,仍能稳定可靠地工作,并能满足较宽输出功率和调制频率的要求,设计了一个带调制的可控半导体激光器驱动电路。该电路也可用于其它一些仪器装置中。     

半导体激光器驱动器输出电路的设计

本文提出了半导体激光器驱动器输出电路的设计方案,应用负反馈的原理来实现对输出电流的控制.本文阐述了半导体激光器驱动器输出电路的设计方法以及针对输出电路的仿真结果分析.结果表明驱动器输出电路即恒电流驱动电路的电路设计准确,可确保输出稳定的250mA电流.     

一个新超混沌系统及其线性反馈控制

为提高混沌吸引子的拓扑结构的复杂性,构造了一个新的四维超混沌系统.用数值模拟的方法研究了该系统的超混沌吸引子的相图、系统的分岔图、Lyapunov指数谱图和Lyapunov维数等.分析结果表明,新的四维系统当参数满足一定条件时,具有两个正的Lyapunov指数,是一个超混沌系统,系统的分岔图与Lyapunov指数谱是完全吻合的,随着参数变化呈现周期、混沌及超混沌动力学行为.利用线性反馈控制法镇定了超混沌系统的不稳定平衡点,数值模拟结果表明该方法的可行性和有效性.     

RCLSJ约瑟夫森结混沌系统动力学特性分析与追踪控制

采用Lyapunov指数谱、分岔图、相图、FuzzyEn和C0算法等方法分析了系统偏置电流值连续变化时的动力学变化规律.从分析结果来看,随着偏置电流的变化RCSLJ约瑟夫森结混沌系统表现出丰富的动力学特性,可分别处于定态、周期态、混沌态、拟周期态.复杂度能够很好反映出系统的动力学特性,RCLSJ约瑟夫森结混沌系统随电流变化时具有复杂度相对较大的较长区间.为使系统能够应用到实际应用领域,设计了追踪控制器,从理论方面证明了控制器能够使系统每一维分别逼近不同信号,从仿真方面证明了受控后,系统能够逼近定点、周期信号和混沌信号.     

一种基于ICL8038芯片的LD外围电路

本文研究了半导体激光器(LD)的调制电路、自动功率控制电路(APC)以及自动温度控制电路(ATC),并基于单片函数发生器ICL8038制作了频率连续可调、占空比可调的半导体激光器调制电路,有效地抑制了尖峰脉冲。     

基于遗传算法的半导体激光器温度智能控制系统

半导体激光器输出波长随温度变化会发生漂移,影响其精度及使用寿命,为了使半导体激光器稳定工作,要保持它的温度稳定.设计了基于遗传算法的半导体激光器智能温度控制系统,采用MATLAB进行仿真,验证了温控系统的应用效果.     

基于DSP芯片的半导体激光器稳频控制方法研究

本文提出一种新的稳频方法,此方法的设计思想是：检测出半导体激光器频率的变化量,通过温度粗调电流细调的方法对半导体激光器进行稳频,根据此想法设计了基于DSP控制的半导体激光器稳频系统的硬件和软件,对数控电流源进行了仿真,并且对仿真结果进行了分忻;对半导体激光器稳频系统进行了理论分析,频率稳定度达到了6．73×10^-7.     

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.