磁弹耦合扭转波位移传感器输出电压理论研究

磁弹耦合位移传感器感应线圈电压是由应力波引起的磁化强度变化决定的,而应力与偏置磁铁处的材料磁导率密切相关,因此磁导率与磁化强度变化率的确定是建立输出电压模型的关键.根据铁磁材料的弹性力学理论和磁机耦合模型,确定了扭转波运动方程;建立材料等效场分布模型,并结合麦克斯韦方程和磁化强度进动方程,确定波导丝磁导率;根据磁机效应的Jiles-Atherton理论,建立了波导丝弹性形变感应磁化强度模型.根据磁导率及磁化强度模型,并借助电磁感应定律构建了感应线圈的输出电压模型.利用实验平台验证了接收线圈匝数和激励脉冲的脉宽、频率对输出电压的影响,为磁弹耦合位移传感器的研究提供了理论依据.     

发明与专利

一种采用多层绕线线圈的高性能磁致伸缩传感器 【摘要】本实用新型是一种采用多层绕线线圈的高性能磁致伸缩传感器,属于声学传感器技术领域。本实用新型使用永磁铁在传感器附近产生偏置磁场,当漆包线两端加上交变电压时,会在钢绞线上产生交变磁场,由于铁磁材料存在磁致伸缩效应,在钢绞线中会产生局部的机械振动,这种振动会从激励源向两个方向同时传播,根据磁致伸缩逆效应而被接收传感器捕获到。     

用于板结构损伤检测的磁致伸缩传感器

基于铁磁性材料的磁致伸缩特性,提出一种用于非铁磁性板结构损伤检测的磁致伸缩传感器。该传感器分为激励和接收两部分,由8字型线圈、镍带以及偏置永磁铁组成。根据磁致伸缩效应,激励部分在板中激励导波,波在板中传播,遇缺陷及边缘反射,通过磁致伸缩逆效应,由接收部分接收其反射信号。根据反射信号的到达时间和波在板中传播的速度,可判断出板中缺陷所在位置。改变恒定偏置磁场与时变磁场的方向可以在板中激励不同波型的导波。实验结果证明:该传感器设计是可行的,且具有价格便宜、灵敏度高、可与被测结构分离等优点。     

基于阻抗原理的磁弹性传感器测试仪设计

设计了一种基于阻抗原理的磁弹性传感器共振频率测试仪。系统集成了微控制器、交流激励信号发生单元、直流偏置信号发生单元和有效值检测电路单元,并通过RS-232串口总线实现与上位机之间的通信。交流激励信号电路采用压控电流源方式,避免了线圈阻抗变化对交流激励电流的影响。实验结果表明：测试仪可以快速检测磁弹性传感器的共振频率,稳定性好,精度高,系统操作简单,集成度高,能够满足磁弹性传感器研究中的检测要求。     

新型脉冲漏磁检测法的表面缺陷检测特征分析

针对脉冲漏磁检测技术对不同方向的漏磁分量进行分析时存在一定局限性的问题,基于脉冲漏磁(PMFL)检测中的U型磁轭和脉冲涡流(PEC)检测中的矩形空心激励线圈,提出了脉冲聚磁(PMC)检测方法.通过仿真和实验分析了铁磁性试件在脉冲漏磁和脉冲聚磁两种检测模式下,缺陷部位的响应信号X,Y和Z3个分量的检测效果.结果表明:脉冲聚磁检测方法在进行铁磁性材料构件的缺陷检测时,激励探头对被测试件的3个方向的分量激励效果更明显,同时对于不同深度的表面缺陷,脉冲漏磁响应信号的三维分量具有更高的检测灵敏度.     

大位移磁致伸缩传感器的弹性波建模与分析

磁致伸缩位移传感器是一种测量精度高,测量位移大的新型位移传感器.传感器设计涉及多学科交叉,难以建立统一数学模型.以FeGa材料作为磁致伸缩位移传感器的核心波导丝,建立了波导丝材料磁致伸缩弹性波振动模型,波导丝磁机耦合模型和信号检测模型;同时分析了弹性波信号的受限因素,信号衰减特性.在数学模型基础上,搭建磁致伸缩位移传感器系统,设计了扭转波信号检测电路.实验结果表明信号的输出随着传感距离的增加而减小,该模型对大位移磁致伸缩传感器研究有积极意义.     

长线磁致伸缩位移传感器的磁极化强度模型

长线磁致伸缩位移传感器是一种利用磁致伸缩材料的磁致伸缩效应及其逆效应实现位移测量的传感器.运用电磁学和铁磁学相关理论,构建了磁极化强度模型,讨论了该种传感器中扭转式弹性波的产生机理.通过建立有限元模型,使用ANSYS仿真平台进行了激励磁场的仿真模拟.理论模型对仿真结果数据的进一步计算获得了磁致伸缩线体内应力的分布特性.计算结果与实验数据的比较,证明了磁极化强度模型相关理论的合理性.为构建有效的弹性波信号,提高该种传感器检测精度提供了理论依据和实验数据.     

磁致位移传感器检测线圈和驱动脉冲优化设计

在磁致伸缩式位移传感器中,检测线圈和驱动脉冲的设计直接影响整个系统的精度.基于弹性波理论和法拉第电磁感应定律,分析了加载在波导丝上的驱动脉冲和检测线圈的各项特性参数对感应波形的影响,通过试验选择了同时满足理论推导和实际应用的最佳值并进行了相关参数优化设计.经试验验证,优化后的传感器系统能够输出高信噪比的前端感应信号.     

基于MSP430的磁弹性传感器检测系统设计

磁弹性传感器无线无源的优点使其在无损检测、在体分析等领域具有非常广阔的应用前景.通过对磁弹性传感器检测原理的分析,设计了一种基于MSP430平台的小型化磁弹性传感器检测系统.该系统以MSP430单片机为控制核心,利用永磁铁作为偏置磁场激励,集成了交流激励信号产生单元、有效值检测单元和AD采样单元,并通过RS-232实现与上位机之间的通信.实验结果表明:该检测系统可以方便快捷地实现对磁弹性传感器共振特性的检测,具有稳定性好、集成度高、功耗低的特点,能够满足磁弹性传感器在不同状态和环境下共振特性的精确检测需求.     

激励电流对超磁致伸缩换能器动态特性的影响

本文研究了不同激励电流脉冲宽度对超磁致伸缩换能器输出位移动态特性的影响。利用有限元分析软件ANSYS建立了超磁致伸缩换能器的二维轴对称有限元模型。通过压磁-压电比拟法,对不同激励电流脉冲宽度下不同发射头质量的超磁致伸缩换能器输出位移动态特性进行了模拟研究。结果表明:激励电流脉冲宽度大小不仅直接决定超磁致伸缩换能器瞬态输出位移的大小,而且决定超磁致伸缩换能器的最佳工作状态。此研究结果为超磁致伸缩换能器的优化与应用奠定了基础。     

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.