基于AD633模拟鉴相的Q表设计

为解决万用表无法测量Q、D等参数的问题,设计了基于A1D633模拟鉴相的Q表.该测量仪采用DDS芯片AD9851产生正弦激励信号和基准信号,利用高集成度模拟乘法器AD633对信号进行模拟鉴相,并采用差分转换器AD8138对鉴相输出信号进行单端转差分变换,由C8051F060内部自带的ADC对差分信号进行模数转换和数据处理.Q表具有多量程自动切换和LCD实时显示等功能,且体积小、成本低,能满足工程、教学科研测量的需要.     

一种新型铂热电阻数字测温电路

本文介绍了一种采用连续式非线性A/D转换法进行线性化的新型铂热电阻数字测温仪,在—200℃至 650℃<的温度范围内,线性化误差仅为0.058%,采用了有源电桥和四线制等技术,使引线电阻对测量精确度的影响可忽略不计,并消除了基准电压对测量误差的影响。     

基于Cu50的精确温度测量系统

在基于热电阻的温度测量过程中,由于元器件差异和漂移的影响,会大大降低温度测量准确度;针对这一问题,提出了一种自校正技术的4电阻测量法,通过比较4组测量信号的相对大小来求得被测热电阻的电阻值,进而计算出温度值;该方法的优点是可以抵消测量电路中漂移和元器件差异的影响,从而实现在不同的温度环境下的高精度的温度测量;通过计量炉的实测的数据比较,测量误差小于0.063℃,表明了该方法的有效性和正确性。     

基于V-F变换的硅压阻压力传感器的处理电路

针对硅压阻压力传感器提出了一种基于电桥本身参数的温度自补偿方法,并设计了一种差分输入、双参数输出的高精度处理电路用以获得电桥参数。该电路用简单元件搭建差分输入的电荷平衡式V/F转换器,根据不同组态的频率输出解算电桥参数。该电路巧妙地利用差分输入方式消除了共模电压引起的误差,巧妙借用参考电阻消除了基准频率的影响,最终的输出频率只与被测量和参考电阻有关。经实验验证,电桥电阻的测量精度能达到0.0068%,经补偿后的压力传感器精度可达0.039%,相比补偿之前提高了一个数量级。     

具有自动标定功能的发酵罐多点温度采集系统

为系统地研究发酵罐内的温度分布,开发啤酒、制药等行业所需的端面测温传感器,本文利用自制的测量多点温度的传感器,采用热电阻自动标定、曲线分段拟合非线性校正和热电阻矩阵网络等多种处理方法及微功耗的单片机技术,设计了一种新型的计算机多点温度采集系统。温度测量精度达0.1℃,完全满足系统精度要求。     

一种新型热电阻温度传感器测量电路

一、引言 目前,热电阻和热电偶是工业生产过程自动化最常用的两种温度传感器。热电阻由于在测量灵敏度、线性度等诸多方面均优于热电偶,因此,在600℃以下的低温区得到了更广泛的应用。鉴此,进一步探讨与这种传感器配用的测量电路具有重要意义。 二、测量电路必须考虑的基本问题 热电阻传感器的工作原理是将被测温度的变化转换成电阻的变化,要想获取被测温度信号,必须通过测量电路才能实现。因此,测量电路性能的好坏直接关系到测量结果的精确程度。根据测量电路本身的作用,不论采用何种方式,都要考虑以下一些基本问题。     

三线制铂电阻高精度测温方法

基于可补偿引线电阻影响的三线制铂电阻测量电路提出了一种高精度测温方法.该方法利用双积分ADC,采用比例法测量铂电阻的阻值,并可补偿测量电路的误差.误差分析表明,在环境温度变化±10℃的条件下,对0～500℃测温范围其测温误差不大于10-3.     

基于铂热电阻的高温检测系统设计与优化

为了实现基于金属铂材料制作的热电阻温度传感器在高温测量环境下实现对温度数据的高精度测量,提出一种基于优化电路参数及阻温方程参数的温度检测系统设计方案。设计利用恒压源电路,获得稳定的理想电压,通过不平衡电桥差分放大电路和二阶有源滤波电路得到理想采集信号;设计优化了电路参数,校正了铂热电阻因高温产生的非线性。通过熔融沉积成型(FDM) 3D打印喷头实验平台,验证了设计方案的有效性,实现了在高温测量环境下对温度数据高精度测量的目的。     

工业热电阻测温输入电路

一、热电阻测温输入电路对于一个测温精度较高的温控系统,信号提取部分的设计是关键.热电阻测温输入电路,总的来讲是R/V转换电路,就是如何把温度t下的电阻相对0℃时电阻的变化值△R_t转换成对应的电压V,即V=f(△R_t).电阻/电压转换电路有两种基本的转换形式,即不平衡电桥电阻/电压转换电路和恒流源电阻/电压转换电路.本节主要讨论恒流源电阻/电压转换电路.     

基于STM32的建筑物接地电阻检测仪的研制

针对目前建筑物接地电阻检测装置存在的缺陷,提出一种基于STM32的建筑物接地电阻检测的系统方案。该方案根据三极补偿原理,采用嵌入式系统控制的主从机软硬件实现接地电阻的精确测量。检测系统包括交流合成、信号采集和数据处理三部分。检测系统由STM32控制产生频率精度高、波形稳定的交流电流注入接地网,对地网中的电压电流信号经带通滤波、差分放大、同步AD转换、FFT处理得到精确地接地电阻值。本检测系统能够提高检测精度以及检测效率,实现检测工作的智能化。     

Call for Papers The 6^th International Conference on Grid and Cooperative Computing

Recent years have seen rapid advances in various grid-related technologies, middleware, and applications. The GCC conference has become one of the largest scientific events worldwide in grid and cooperative computing. The 6th international conference on grid and cooperative computing (GCC2007) Sponsored by China Computer Federation (CCF),Institute of Computing Technology, Chinese Academy of Sciences (ICT) and Xinjiang University ,and in Cooperation with IEEE Computer Soceity ,is to be held from August 16 to 18, 2007 in Urumchi, Xinjiang, China.     

煤矿井下安全监控分站的设计及其仿真实现

为了设计一种具有低成本、低功耗、易操作、功能强且可靠性高的煤矿井下安全分站,针对煤矿安全生产实际,文章提出了采用MCS-51系列单片机为核心、具有CAN总线通信接口的煤矿井下安全监控分站的设计方案;首先给出煤矿井下安全监控分站的整体构架设计,然后着重阐述模拟量输入信号处理系统的设计过程,最后说明单片机最小系统及其键盘、显示、报警、通信等各个组成部分的设计;为验证设计方案的可行性与有效性,使用Proteus软件对设计内容进行仿真验证,设计的煤矿井下安全监控分站具有瓦斯、温度等模拟量参数超标报警功能和电机开停、风门开闭等开关量指示功能;仿真结果表明:设计的煤矿井下安全监控分站具有一定的实际应用价值.     

法律信息库系统

本文分析了法律数据库的结构和特点，介绍了采用面向对象设计方法和超文本数据库技术开发和实现法律信息库系统将作为重要网络资源之一为不同用户进行法律咨询服务。     

View-based model-driven architecture for enhancing maintainability of data access services

In modern service-oriented architectures, database access is done by a special type of services, the so-called data access services (DAS). Though, particularly in data-intensive applications, using and developing DAS are very common today, the link between the DAS and their implementation, e.g. a layer of data access objects (DAOs) encapsulating the database queries, still is not sufficiently elaborated, yet. As a result, as the number of DAS grows, finding the desired DAS for reuse and/or associated documentation can become an impossible task. In this paper we focus on bridging this gap between the DAS and their implementation by presenting a view-based, model-driven data access architecture (VMDA) managing models of the DAS, DAOs and database queries in a queryable manner. Our models support tailored views of different stakeholders and are scalable with all types of DAS implementations. In this paper we show that our view-based and model driven architecture approach can enhance software development productivity and maintainability by improving DAS documentation. Moreover, our VMDA opens a wide range of applications such as evaluating DAS usage for DAS performance optimization. Furthermore, we provide tool support and illustrate the applicability of our VMDA in a large-scale case study. Finally, we quantitatively prove that our approach performs with acceptable response times.     

International Journal of Automation and Computing Table of Contents

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Information for authors

正SCIENCE CHINA Information Sciences(Sci China Inf Sci),cosponsored by the Chinese Academy of Sciences and the National Natural Science Foundation of China,and published by Science China Press,is committed to publishing highquality,original results of both basic and applied research in all areas of information sciences,including computer science and technology;systems science,control science and engineering(published in Issues with odd numbers);information and communication engineering;electronic science and technology(published in Issues with even numbers).Sci China Inf Sci is published monthly in both print and electronic forms.It is indexed by Academic OneFile,Astrophysics Data System(ADS),CSA,Cabells,Current Contents/Engineering,Computing and Technology,DBLP,Digital Mathematics Registry,Earthquake Engineering Abstracts,Engineering Index,Engineered Materials Abstracts,Gale,Google,INSPEC,Journal Citation Reports/Science Edition,Mathematical Reviews,OCLC,ProQuest,SCOPUS,Science Citation Index Expanded,Summon by Serial Solutions,VINITI,Zentralblatt MATH.     

Erratum to: Fast global kernel fuzzy c-means clustering algorithm for consonant/vowel segmentation of speech signal

正Erratum to:J Zhejiang Univ-Sci C(ComputElectron)2014 15(7):551-563doi:10.1631/jzus.C1300320The original version of this article unfortunately contained mistakes.Algorithm 6 should be as follows:Algorithm 6 FGKFCM-F clustering Input:(1)X={x_1,x_2,…,x_N},,x_iR~d,i=1,2,…,N,the dataset;(2)C,1C≤N,the number of clusters;(3)ε0,the stopping criterion;     

Journal of Zhejiang University-SCIENCE C (Computers & Electronics) Total contents

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A pragmatic multi-method investigation of discrepant technological events: Coping,attributions, and ‘accidental’ learning

Discrepant technological events or situations that entail a problem, a misunderstanding or a difficulty with the Information Technology (IT) being employed, are common in the workplace, and can lead to frustration and avoidance behaviors. Little is known, however, about how individuals cope with these events. This paper examines these events by using a multi-method pragmatic approach informed by coping theory. The results of two studies – a critical incident study and an experiment – serve to build and test, respectively, a theoretical model that posits that individuals use a variety of strategies when dealing with these events: they experience negative emotions, make external attributions, and adopt engagement coping strategies directed at solving the event, eventually switching to a disengagement coping strategy when they feel they have no control over the situation. Furthermore, users’ efforts may result in ‘accidental’ learning as they try to overcome the discrepant IT events through engagement coping. The paper ends with a discussion of the results in light of existing literature, future opportunities for research, and implications for practice.