陀螺稳定系统参数测试仪设计

设计了一种陀螺稳定系统参数测试仪,主要用于对舰载陀螺稳定系统各环节进行参数测试,直观显示参数信息,并可通过网口串口发往其他设备;仪器不仅能多路采集信号,也可采集一些特殊信号如多路接收检测同步机转角信号、旋转变压器转角信号、电平信号、脉冲信号等;仪器检测精度可达2个角分,检测时间由以前的3小时缩短为20～30分钟;经上舰验证,该仪器对于检测设备是否正常,判断精度是否满足技术指标,提高维修检测有很大的帮助作用.     

基于SE故障特征提取的虚拟仿真系统研究

虚拟仪器是一种新的仪器技术,是对传统仪器的重大变革,它集成软硬件结合的技术进行实时、在线测量,并将电子测试技术与故障诊断结合起来,这是故障诊断、检测、识别技术与测试技术相结合发展的重要趋势.介绍了虚拟仪器仿真技术的特点和构成,将现代信号处理新理论谱熵(spectral Entropy,简称SE)引入到虚拟仿真的信号分析之中,对传动系统的故障进行了特征提取,对不同类型的故障进行了聚类分析,并对系统的运行状态进行了预测,以VC++软件开发平台为基础,并结合MATLAB语言研制和开发出了机械故障诊断虚拟仿真系统,设计了各种功能模块,包括振动信号的采集、分析、处理和系统故障的特征提取、聚类和诊断等.从而实现了故障诊断虚拟仿真系统应有的功能.     

基于FPGA的光纤陀螺信号采集处理卡设计

光纤陀螺姿态测量系统中的信号采集和处理是系统的一个重要环节;文章介绍了基于FPGA的光纤陀螺信号采集处理卡的设计过程,采用Verilog HDL实现FPGA内部逻辑电路设计,选用AD7846完成信号的数模转换,通过FPGA编程实现光纤陀螺的标定和误差补偿,设计了RS232/422通用异步串口通信硬件电路并在FPGA上实现了串口通信;实验结果表明:该卡能够准确实时地采集并按预定的设计处理光纤陀螺信号。     

基于神经网络自学习的模拟电路故障诊断方法

由于传统方法在模拟电路故障诊断中应用效果不佳,不仅错误诊断数量较多,而且故障诊断用时较长,无法达到预期的故障诊断效果,提出基于神经网络自学习的模拟电路故障诊断方法。将模拟电路等效为一个双端口网络,利用便携式模拟仪器采集双端口网络运行数据,通过小波变换信号提取模拟电路信号时域特征和频域特征,利用神经网络自学习模型卷积运算信号特征,诊断并识别电路故障。经实验证明,设计方法错误诊断数量占总样本数量的比例较小,诊断用时较短,在模拟电路故障诊断方面具有良好的应用前景。     

基于FPGA的心音信号采集

设计了基于FPGA的心音采集系统,该系统包括高性能的心音传感器、预处理电路、A/D转换电路和串口通信电路。传感器将心音信号转换成电信号,通过预处理电路的放大和滤波,再经过A/D转换电路送到FPGA,FPGA把现场采集到的数据及时可靠地传递给PC。实验结果表明,该系统能无创、快速、廉价地采集心音信号。     

基于小波变换和TMS320F2812的水泵故障诊断系统研究

对于水泵等旋转机械来说,通过采集水泵振动信号并进行分析,能够较全面地判断出水泵设备运行状态;因此,振动信号的采集就成为设备状态监测与故障诊断的关键部分;设计了一套基于小波变换和DSP的水泵故障诊断系统,该系统可以实现对水泵振动信号的实时采集;为了提高振动信号的信噪比,得到较为纯净的振动信号,采用小波消噪的技术对采集的振动信号进行消噪处理;并且以水泵机组正常运行和发生绕组过热、轻度不平衡、严重不平衡、支座松动等故障为例进行诊断实验,并且故障集参数amax,smax,Tamax,Tsmax和amin,smin,Tamin,Tsmin分别为1.1500,0.1600,46.9787,446.5000和0.9000,0.0700,40.9825,410.6000;实验结果表明,该系统可以有效发现故障,区分故障类型及识别故障程度,为水泵机组故障诊断提供了又一种有效的方法,对其它类似机械故障诊断具有一定的指导意义。     

基于状态监测的全数字预测倍频技术研究

随着信息技术的迅速发展,在电力、石化等众多行业里得到广泛的重视和应用的旋转机械状态监测技术面临着巨大的发展和挑战。对振动信号的采集与分析是设备状态监测和故障诊断的基础,本文在对传统数字倍频器的分析基础上,结合现场实际情况设计出一种带预测功能的全数字倍频器,该项技术在状态监测系统中得到了很好的应用。     

新型角加速度测量系统及其在旋转机械中的应用

设计了一种新型角加速度测量系统,包括机械测量平台及信号处理模块.其中机械测量平台包括底座、磁粉制动器与控制器、被测旋转机械、可升降支架、角加速度传感器和三维滑台;信号处理模块包括无线发射电路、无线接收电路、信号采集电路和上位机可视化联机软件.通过调节机械测量平台中的升降支架和三维滑台,可以实现被测旋转机械与传感器的高度同心,通过信号处理模块够将角加速度信息通过无线的方式发送至上位机软件,处理后可以实时的显示角加速度值.最后将研制的角加速度测量系统用于实际旋转机械的运行状态测试,验证了系统的可靠性.     

表面肌电采集信号的系统设计与算法分析

针对表面肌电信号的微弱性、低频性和强噪声性,设计了高共模抑制比、抗干扰能力强的表面肌电信号采集系统,并对采集到的信号进行处理分析.系统中包含放大电路、滤波电路、电平抬升电路、主控电路,采集受试者手臂放松、握拳、展臂、模拟震颤四种姿势的表面肌电信号,经串口通信将传感器所采集到的数据上传至上位机,之后将采集到的表面肌电信号...     

3kW调频广播发射机微机控制器的硬件设计

应陕西广播数字设备厂要求,结合调频广播发射机微机控制器项目技术要求,将分布式控制系统设计思想应用到广播发射机微机控制器硬件电路的设计中,采用多颗51单片机分别控制电源信号采集板和功率信号采集板,分担了系统风险,提高了系统的可靠性;对于数据存储、故障记录和菜单显示等管理任务则集中在主控板单片机中,实现了管理的集中和良好的人机界面;最后给出了对待干扰问题在硬件电路模拟量通道和串口通道设计中的解决方法。     

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).