基于软开关的SEPIC变换器设计及其效率分析

关于在光伏系统中SEPIC变换器效率优化问题,由于光伏系统承担并网发电和输出电压,要完成大功率点的跟踪,但是转换效率往往不高,尤其是在工作频率很高时,转换效率会明显下降。为解决上述问题,提出将软开关技术应用到SEPIC变换器中,并对零电压、零电流准谐振SEPIC变换器的工作原理进行了分析,采用谐振参数的选取,应用软开关技术减小开关损耗,可以提高SEPIC变换器的效率。在MATLAB平台上对有、无软开关的SEPIC变换器进行仿真,通过改变工作频率,对两种变换器效率进行比较。仿真结果证明软开关技术能够提高SEPIC变换器的效率,为变换器设计提供了依据。     

DC—DC变换器的SPICE仿真

本文讨论应用ＳＰＩＣＥ通用集成电路计算机分析程序仿真ＤＣ－ＤＣ变换器的方法。着重论述脉冲变压器的回旋器组等效模型、脉宽调制器的等效模型以及双稳态触发器和常用逻辑电路的数学模型。恰当运用上述模型，可仿真所有类型的ＤＣ－ＤＣ变换器，包括谐振变换器、ＰＷＭ变换器、软开关变换器以及开关电容变换器。文中给出了一些实例。     

软开关Boost变换器的精确数学建模与混沌仿真

该文详细分析了电压反馈型零电流开关Boost变换器的工作过程，建立了变换器工作在不连续运行模式(DCM)下的精确离散映射，对此数学模型进行了稳定性分析，确定了变换器中元件参数与其分岔稳定性的关系，在此基础上准确计算出了系统稳定运行的典型参数范围，利用Natlab6．5软件中的电力系统仿真模块(SimPowerSystems)对电路进行仿真分析，针对ZCS Boost变换器的特点建立仿真模型，并在Matlab／Simulink软件包环境下对该模型进行模拟仿真，得到了满意的结果，与理论分析取得一致。     

DC─DC变换器的SPICE仿真

本文讨论应用ＳＰＩＣＥ通用集成电路计算机分析程序仿真ＤＣ—ＤＣ变换器的方法．着重论述脉冲变压器的回旋器组等效模型、脉宽调制器的等效模型以及双稳态触发器和常用逻辑电路的数学模型．恰当运用上述模型，可仿真所有类型的ＤＣ─ＤＣ变换器，包括谐振变换器、ＰＷＭ变换器、软开关变换器以及开关电容变换器．文中给出了一些实例．     

输出连续可调节并联谐振变换器及其仿真研究

文中分析了并联谐振变换器(PRC)电路的拓扑结构及工作原理，提出了在软开关条件下实现电源输出连续可调节的方案，并通过一种实用的交流分析法分析了PRC在CCM工作模式下实现方案的可行性。最后的PSPICE以及Matlab/Simulink仿真结果表明该变换器具有输出连续可调节范围大、软开关、效率高等优点。     

基于注吸电流法的Buck-Boost变换器建模与仿真

该文详细介绍了注吸电流法的建模思想和步骤，并应用注吸电流法建立了工作在电感电流断续（DCM）模式下的Buck—Boost变换器数学模型。对Buck—Boost变换器及其PI调节器构成的闭环控制系统进行了分析研究。应用Simulink＼Sim-owerSystem模块，建立了该系统的Matlab仿真模型，并进行了相应的仿真分析。仿真结果表明，所得Buck—Boost变换器数学模型的精确性和可用性可以满足要求，能够真实反映该系统的动、静态性能。满意的仿真结果与理论分析取得了一致，验证了该模型的正确性。     

一种PWM结合PFM的ZVS准谐振变换器

准谐振变换器可以实现功率器件的零电压或零电流开关,但要得到稳定输出电压需采用脉冲频率调制(PFM),这给功率电路参数设计和系统稳定性带来困难,本文研究一种PFM结合PWM的控制模式来调节准谐振变换器输出电压,并实现其开关管的软开关,该控制方案与电压调节器协调工作,调节功率管驱动信号的脉宽和频率,保证了软开关条件和降低导通损耗,实现高频高效的功率变换。建立了100W升压准谐振变换器样机,实验结果验证了该控制方案的可行性。     

基于B-SIT的半桥谐振DC-DC变换器电路

本文介绍了串联谐振逆变器电路构成的零电流软件开关变换器,并描绘了其在稳态时的工作原理.对带有电压箝位二极管环路的半桥零电流谐振DC-DC变换器的性能进行了评价.实验结果表明,该变换器结构简单,成本低,效率高,容易实现软开关,且产生的开关损耗很小.     

SRD功率变换器的一种软开关实现策略

由于电力电子器件并非理想的开关器件,功率器件的开关损耗和电磁干扰会随开关频率的提高和容量的增大而升高,软开关技术是解决以上问题的有效手段。文章提出了一种利用准谐振直流环实现相开关零电压操作的SRD功率变换器软开关的设计方案,详细介绍了该方案的主电路结构、换相控制逻辑及谐振电路工作状态。仿真结果表明,该方案控制简单、主电路中所有功率器件均实现了软开关操作。     

ZVS—PWM DC／DC变换器电路分析与计算机仿真

本文对一个零电压开关脉宽调制降型直流／直流变换器电路，用经典控制理论进行稳态分析求得各变量的表达式，应用有关电子电路模拟软件通过计算机仿真予以对比，并说明通过计算机仿真进行模拟和数字混合电路的设计和分析在正确性和简便性。     

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.