数字可调检测电源的设计

针对目前电子市场缺少专门对电磁阀供电的检测电源以及现有电源抗冲击电流弱的问题,设计了一种用于电磁阀检测的专用数字可调电源,以检测电磁阀长时间运行的稳定性.电源系统硬件主要由电压和频率控制电路、相关电压处理电路、频率处理电路以及综合输出电路组成;软件设计采用C51编程控制,实现了在0~36 V内连续电压可调和0~25 kHz内连续频率可调.实践表明该检测电源完全满足电磁阀感性负载可能产生大冲击电流的需求.     

基于555定时器的开关电源的设计

提出了一种中小功率开关电源设计,该电源是用555定时器等组成的脉宽调整电路构成稳压源。主要介绍了开关电源的主要组成部分的原理图及设计、555定时器及有其组成的脉宽调整电路和功率MOSFET管。此电源电路结构简单,功耗小,控制线性好,稳压范围宽,能实现较好的控制,输出电压在(3～20)V连续可调,电流0～5A。     

高精度数控可调直流稳压电源设计

针对常规直流稳压电源的输出电压精度不高和调节较为繁琐的缺点,设计了一款高精度数控可调直流稳压线性电源。该电源输出电压0～30V可调,输出电流最大值可达4A。通过输出电压/电流取样电路、差动放大电路及电压/电流调整电路等所构成的闭环负反馈环节和软件上的双线性插值误差补偿方法,提高了输出电压的精度。该电源输出电压和电流的最大值既可通过旋转编码器和实体按键进行调节,也可以通过在所用触控液晶模块中创建的虚拟键盘直接进行设置,操作简便。实际测试结果表明,该电源的输出电压精度高,12V输出时的负载调整率仅为0.15%,且参数设置操作简便,可满足一般教学、科研的应用需求。     

基于能量自循环模式的矿用直流斩波器测试平台

针对现有直流斩波器测试平台存在电源输出纹波大、大功率负载选择难、测试效率低和测试能耗大等问题,提出了一种基于能量自循环模式的矿用直流斩波器测试平台。该平台采用三相变压器+三相不控整流电路+Buck电路和恒压限流控制策略实现可调电压源输出电压0～750V,采用Boost电路和恒流控制策略实现能量自循环负载输出电流0～240A,从而实现电压和电流大范围调节,提高测试效率;同时将能量自循环负载输出能量反馈至可调电压源输出端,实现能量自循环,降低测试能耗。仿真和试验结果验证了该平台的有效性。     

用固定稳压块组装的可调电源

本文介绍一种用7815、7915组装的稳压电源,但它可以在一定范围内作可调电源使用,输出电流最大可达1.5A。图1为电路图。使用可调正电源时,先将电位器W1旋到最下端,即电源接地端0点。这时B点对0点为-15V,所以电位器W2动片对0点的电压为-15V～0V。由于7815的3端与2脚间总稳定为15V,所以A点相对0点在调节W2时可在0～15V之间变化,使用时以0点作为输出可调正电源的地。负可调电源的使用方法与正电源相似。若把A对B或B对A作为输出端,在上述调节过程中就能得到±15～30V范围的可调电源。如     

基于MSP430单片机的数控直流稳压电源的设计

随着现代电力电子技术的不断发展,大量高精度电子设备出现,这些设备的稳定运行都离不开高品质直流稳压电源的支持。基于MSP430单片机设计并实现了一款数控直流稳压电源,该电源由单片机控制电路、稳压输出电路、液晶显示电路、辅助电源电路等组成。可通过按键实现输出电压的预置,并通过液晶显示,输出电压在0V～20V之间可调,通过“+”“-”两键操作,电压最小步进值为0.1V,可根据实际需求设置输出电压值。该电源带负载能力强,具有过流过压保护功能,并且具有精度高、稳定性好,线路简单等特点     

基于单片机的输出可调锯齿波发生器

介绍一种以8031单片机为核心组成的锯齿波发生器及其电路的设计思想和软件设计的方法。测试表明,电路可实现输出幅度在0～30V内连续可调,输出信号频率在10kHz以内连续可调。     

一种输出可调CMOS带隙基准源

从调整电路结构着手,介绍了一种可变输出电压的基准源.这种基准电压能够在保持相对较小的电源电压和温度敏感度的情况下实现可调输出电压.     

一种简单的高精度电源

<正> 我们设计了一种串联型稳压电源,线路十分简单,但精度较高,现介绍如下: 此电源性能:输出电压:3～10V可调输出电流:0～3A 电网电压波动±10％,输出电压变化小于0.02％电源内阻r_n=0.01Ω此电路性能较好的原因,是采用了二个恒流管(2DH05,2DH10),2DH05是差分放大器中的放大管     

一种输出可调智能开关稳压电源设计

设计了一种输出可调智能开关稳压电源.该系统由场效应管组成DC-DC推挽拓扑电路,采用AT89S52单片机控制DA芯片调整开关电源控制芯片SG3525输出脉宽,实现PWM控制输出电压.系统测试和运行结果表明,该稳压电源具有在一定范围内可调,结构简单,工作可靠的特点,是一种较为理想的实用化电源.     

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。     

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.