出舱稳定装置检测台的新型霍尔测速方法研究

阐述了一种非接触式出舱稳定装置检测台速度测试系统.该系统由非接触式双冗度磁开关霍尔传感器、电源监控电路、实时数据采集系统、PC计算机等组成,霍尔元件响应速度大于100kHz,并采用了机器周期小于150ns、单时钟周期指令的高速嵌入式微控制器,可以很好地模拟弹射椅发射时的飞机的飞行速度,提高了可靠性.采用的霍尔传感器为非漏磁的单片集成电路芯片,可以连续工作在温度高至1500C的环境中.在温度与电压同时变化的情况下仍然能够保持其稳定性.     

精品推介

TP1系列磁致伸缩位移/长度传感器诺我传感器贸易上海有限公司Novotechnik公司最新推出采用非接触式,磁致伸缩测量原理,采用NOVOSTRICTIVE测量技术,可在采集和显示应用中对位移和长度进行直接精准的测量。它可以采用导轨式磁块,也可以使用悬浮式磁块,从而实现真正的非接触式测量,因此传感器不会有任何磨损。     

霍尔数字式汽车速度表

采用新型的霍尔集成传感器研究成功了霍尔数字式汽车速度表。阐述了非接触式霍尔开关传感器的工作原理、电路组成、结构特点、检测过程以及性能指标。该速度表具有新颍性、多功能和广阔的发展前途。     

数字式皮革收缩温度测试仪的设计

采用单片机AT89S52为硬件核心,设计了数字式皮革收缩温度测试仪,软件采用基于单片机C51语言的单片机测量系统软件和采用Visual C＋＋6.0开发平台编译而成的可视化人机交互计算机测量系统软件。本设计采用霍尔传感器的非接触式检测,从而实现了同时测量四个样品的高效率。     

三维磁敏传感器的设计及误差分析

采用三维磁敏传感器有助于降低磁场测量系统的复杂性和提高磁场测量速度.介绍了基于霍尔元件的三维磁敏传感器的设计方法,分析了霍尔元件的粘贴角度偏差、传感器的体积对测量精度的影响,并对传感器的总体误差进行了估算,其分析结果对三维集成磁敏传感器的设计具有指导意义.     

基于大电流检测的霍尔传感器应用

介绍了传统开环和闭环霍尔传感器的基本原理,并就传统霍尔传感器配合磁环的方法和新型磁集极霍尔传感器在大电流检测中的应用方案进行了对比,分析了它们的优缺点.以MLX91205磁集极霍尔传感器为例,重点研究了磁集极霍尔传感器在电动汽车中的电机控制器的大电流情况下的测量应用,实验结果表明:其具有测量范围宽、高线性度、低磁滞、高...     

非接触式磁感应角度传感器在超市入口的应用

Novotechnik公司是一家有60年行业制造经验的生产高品质电位计传感器和非接触式直线角度位移传感器的德国公司,产品获得行业高度认同。采用霍尔原理的非接触角度传感器,自带转动轴或无轴结构,能够广泛地应用在工程机械、自动化制造设备和电控执行机构以及汽车制造等行业。本文主要介绍RFC4800系列产品在超市中的应用。     

机车热抱弛缓在线监测系统的设计

利用霍尔传感器技术和红外测温技术,设计了机车轮箍弛缓在线监测系统。介绍了系统的构成方案、霍尔传感器和温度测弛缓的原理。利用单片机技术设计了电路系统,利用汇编语言进行了软件设计。在实验室进行了霍尔传感器测弛缓位移的模拟实验,并对实验情况进行了分析,实验结果表明:测量精度可以达到0.5mm,能满足系统对精度提出的要求。     

绝对式磁编码器设计及其在伺服系统的应用

磁编码器作为一种非接触式位置传感器,已经在伺服控制领域得到越来越多的关注和应用。相比接触式位置传感器,或光电编码器,磁编码器更加可靠,且更容易制作为绝对式位置传感器。本文介绍了绝对式磁编码器工作原理以及反正切法角度解算方法,提出了一种基于角度跟踪的角度解算算法,并基于Macrochip的dsPIC33EV芯片实现了采用两种角度解算算法的绝对式磁编码器,然后对两种磁编码器自身特性及其在伺服系统中的表现进行了对比,通过对两种算法进行充分的对比和试验验证,总结了两种算法的优缺点及适用场景。     

无触点磁敏电位器自动测试仪研制 ‘

无触点InSb磁敏电位器是利用半导体磁阻效应制成的非接触式传感器,它具有无接触摩擦、分辨率高、寿命长等优点,可广泛地用作角度传感器、直线位移传感器、压力传感器、倾斜角传感器等.天津大学王文生教授等在国内率先研制成功无触点InSb磁敏     

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。     

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.     

Editorial: Special issue on recent advances in hybrid control theory and applications

正The demands of a rapidly advancing technology for faster and more accurate controllers have always had a strong influence on the progress of automatic control theory.In recent years control problems have been arising with increasing frequency in widely different areas,which cannot be addressed using conventional control techniques.The principal reason for this is the fact that a highly competitive economy is forcing systems to operate in regimes where     

Information for Authors

正Aim The Journals of Zhejiang University-SCIENCE(A/B/C)areedited by the international board of distinguished Chinese andforeign scientists,and are aimed to present the latest devel-opments and achievements in scientific research in China andoverseas to the world’s scientific circles,especially to stimulateand promote academic exchange between Chinese and for-eign scientists everywhere.     

Enhancing a leaf radiative transfer model to estimate concentrations and in vivo specific absorption coefficients of total carotenoids and chlorophylls a and b from single-needle reflectance and transmittance

The relative concentrations of different pigments within a leaf have significant physiological and spectral consequences. Photosynthesis, light use efficiency, mass and energy exchange, and stress response are dependent on relationships among an ensemble of pigments. This ensemble also determines the visible characteristics of a leaf, which can be measured remotely and used to quantify leaf biochemistry and structure. But current remote sensing approaches are limited in their ability to resolve individual pigments. This paper focuses on the incorporation of three pigments—chlorophyll a, chlorophyll b, and total carotenoids—into the LIBERTY leaf radiative transfer model to better understand relationships between leaf biochemical, biophysical, and spectral properties.Pinus ponderosa and Pinus jeffreyi needles were collected from three sites in the California Sierra Nevada. Hemispheric single-leaf visible reflectance and transmittance and concentrations of chlorophylls a and b and total carotenoids of fresh needles were measured. These data were input to the enhanced LIBERTY model to estimate optical and biochemical properties of pine needles. The enhanced model successfully estimated reflectance (RMSE = 0.0255, BIAS = 0.00477, RMS%E = 16.7%), had variable success estimating transmittance (RMSE = 0.0442, BIAS = 0.0294, RMS%E = 181%), and generated very good estimates of carotenoid concentrations (RMSE = 2.48 µg/cm², BIAS = 0.143 µg/cm², RMS%E = 20.4%), good estimates of chlorophyll a concentrations (RMSE = 10.7 µg/cm², BIAS = − 0.992 µg/cm², RMS%E = 21.1%), and fair estimates of chlorophyll b concentrations (RMSE = 7.49 µg/cm², BIAS = − 2.12 µg/cm², RMS%E = 43.7%). Overall root mean squared errors of reflectance, transmittance, and pigment concentration estimates were lower for the three-pigment model than for the single-pigment model. The algorithm to estimate three in vivo specific absorption coefficients is robust, although estimated values are distorted by inconsistencies in model biophysics. The capacity to invert the model from single-leaf reflectance and transmittance was added to the model so it could be coupled with vegetation canopy models to estimate canopy biochemistry from remotely sensed data.     

Mr. Twinn’s bombes

This article discusses the history and design of the special versions of the bombe key-finding machines used by Britain’s Government Code & Cypher School (GC&CS) during World War II to attack the Enigma traffic of the Abwehr (the German military intelligence service). These special bombes were based on the design of their more numerous counterparts used against the traffic of the German armed services, but differed from them in important ways that highlight the adaptability of the British bombe design, and the power and flexibility of the diagonal board. Also discussed are the changes in the Abwehr indicating system that drove the development of these machines, the ingenious ways in which they were used, and some related developments involving the bombes used by the U.S. Navy’s cryptanalytic unit (OP-20-G).