光强极值法检测斯密特棱镜的偏振像差

线偏振光经过斯密特屋脊棱镜后形成2个不同路径的椭圆偏振光,两路径椭圆偏振光经过检偏器后,旋转检偏器在一些特殊的角度时会得到光强极大值和光强极小值,用光线追迹法获得出射光的琼斯矩阵,分析此琼斯矩阵时意外发现,两路径的椭圆偏振光的位相差是不相同的,因此可以用位相差来表征斯密特棱镜偏振像差特性.采用光强极值法来检测斯密特棱镜的偏振像差,就是通过光强极值计算相应的位相差,即获得了偏振像差.     

Understanding and measuring iridescence (spectral banding) ofanodized luminaire surfaces

Iridescence is a problem of increasing concern since the introduction of narrowband lamps and anodized luminaire surfaces. It appears as induced coloration of luminaire surfaces, much like rainbow patterns associated with thin oil or soap films on water. The causes of the effect are discussed, and an interim color measurement method based on standard CIE (1986) and ASTM (1987) practices for the measurement of color in terms of the human visual system is proposed. An analysis of the nature of the effect is provided so that the problem at hand can be better managed and understood     

对线性度和单调性的理解

文章给出了器件单调性和线性度的解释。以图示的方式给出了线性度的三种不同的定义。     

Understanding Asymmetry

When calculated fault levels lie very close to circuit breaker interrupting ratings, a thorough evaluation of the asymmetrical currents involved may become the deciding factor between breakers of varied capabilities and costs. The increasing emphasis on efficiency tends to exacerbate concerns in this area. An attempt is made to help the reader visualize the events of the first few cycles after fault inception as well as providing a rigorous quantitative analysis of the magnitude of currents involved. Equations for sizing both molded-case and power circuit breakers are developed.     

Calorimetric measuring systems

This paper discusses the calorimetric measuring system. The calorimetric principle is one of the most promising methods for accurate power measurements. A calorimetric wattmeter provides a useful tool for use in the developments of new, energy-efficient, electrical components for industrial and consumer products. Power measurements can be performed with an accuracy of 0.2% of full-scale deflection using the proposed calorimetric measuring method.     

图像测量技术及其应用

图像测量是近年来发展起来的测量技术，它利用获取的物体图像，经过计算机处理实现对物体的几何尺寸、形状的测量，广泛应用于工业监测、航空遥感等领域中。本文对该技术的现状作以简述，并介绍一个CCD(Charge Coupled Device——电荷耦合器件)图像测量系统。     

基于Internet的测控系统--网络化仪器

随着电子技术和网络通信技术的不断发展,测控网络和信息网络呈现出相互融合的趋势,由此赋予仪器仪表以新的内涵,本文介绍现代新型仪器和测量系统所具有的特点,同时指出,基于Internet的测控系统实际上就是新一代的网络化仪器。     

数字式微电容测量系统及其应用

本文针对介电常数和位移信息等应用领域对微电容测量的精度和功能要求,采用一种基于充放电原理的具有高抗寄生效应的微电容测量电路,由C8051F345实现数字化和多种软件功能.其中,利用片内可编程计数器阵列实现电子开关的死区控制,消除电路开关交叠期及电荷泄露,提高了测量精度.同时,片内10位A/D 对模拟放大电路部分的输出电压完成模拟/数字转换,进而由软件实现滤波等功能.该数字式微电容测量系统包括电容测量模块、介电常数测量模块以及位移测量模块,具备测量模式选择、量程自动调节、数据实时或定时储存等功能,测量结果由液晶显示,由串口、USB接口和网口实现与上位机及网络的通信.     

电能计量装置分类及计量方式简介

电能表是供电企业拥有量最多,装置面广量大的电测仪表。是《计量法》法定的强制检定贸易结算计量器具。电能计量装置是根据用户申请的用电容量和当地电价政策配置的,不同的用电性质和不同的供电电压安装不同类别的电能表。     

Understanding Power-System Stability

This paper discusses power-system instability and the importance of fast fault-clearing performance to aid in reliable production of power. An explanation regarding small-signal stability, high-impedance transmission lines, line loading, and high-gain fast-acting excitation systems is provided. Transient stability is discussed, including synchronizing and damping torques. The power-angle curve is used to illustrate how fault-clearing time and high initial response excitation systems can affect transient stability. The term ldquopower-system stabilityrdquo has become increasingly popular in generation and transmission. The sudden requirement for power-system stabilizers (PSSs) has created confusion about their applicability, purpose, and benefit to the system. This paper discusses the fundamentals of the PSS and its effectiveness. In today's paper industry, PSSs are being applied on larger machines in the northwest United States and Canada.     

Eddy-current losses in thin circular and rectangular plates

Contents A method of analysis of the eddy currents induced in thin plates by the time-harmonic magnetic field is presented. The question is reduced to the Dirichlet boundary-value problem for the Helmholtz equation. An integral formula for the eddy-current losses is derived. The formulae for the eddy-current losses in circular and rectangular plates are presented.

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Wirbelstromverluste in dünnen, kreisförmigen und rechteckigen Platten

Übersicht Es wird eine Methode der Analyse von den durch das harmonische magnetische Feld in dünnen Platten induzierten Wirbelströmen dargestellt. Die betrachtete Aufgabe wird in der Form des Dirichletschen Problems für die Helmholtzsche Gleichung formuliert. Eine integrale Formel für die Wirbelstromverluste wird abgeleitet. Die Formeln für die Wirbelstromverluste in kreisförmigen und rechteckigen Platten werden angegeben.

     

A generalized dielectric polarization evolution equation

In this paper a non-equilibrium statistical-mechanical theory of dielectric relaxation is developed. This approach differs from previous work in that a generalized nonlocal evolution equation for the polarization is constructed. General equations of motion are presented for the polarization, internal energy, and entropy which include effects of memory. These equations can be expressed in terms of reduced-correlation functions, and are valid for non-equilibrium and arbitrary field strengths. Expressions for an effective local field also are developed. The Fourier transform of the evolution equation yields a general compact expression for the Fourier transform of the memory function and a specific form for the susceptibility. The kernel, Fourier transform of the memory function are developed, and relaxation-time functions for special cases. In the limit of a single relaxation time, a Debye response is obtained. In the subsequent special cases exponential and Gaussian forms for the memory functions are assumed. The final special case relates a power-law circuit transfer function to the theory of Dissado and Hill. In this case the memory kernel and relaxation times are derived from the Dissado-Hill response function     

Systems for measuring and tracking electrophysiologic distributions

Electrocardiographic mapping has played an important role in the study and analysis of cardiac electrophysiologic phenomena. The first systems used for experimental or clinical studies were expensive, cumbersome, and limited in their ability to sample the complex electrophysiologic events associated with cardiac function and disease. New insights into the mechanisms of arrhythmias and the need for timely detection and characterization of changing cardiac states have made it essential that new tools be available to measure the spatial characteristics and dynamics of electrophysiologic events. For example, observation of the distribution and dynamics of ventricular repolarization is critical to predicting arrhythmia prone states, detecting reperfusion or reocclusion in patients undergoing post myocardial infarction therapy or angioplasty, or to accurately detect acute infarction in patients presenting with chest pain. Technology now permits affordable, flexible systems for making the critical observations. The authors present an example of such a system and its applications in this article     

非接触式距离测量系统

接近传感器可以在不与目标实物接触的情况下检测到靠近传感器的金属物体位移。该系统以C8051F310为主控制器,通过连接接近传感器,实现非接触式距离测量。接近传感器的模拟输出信号经过信号调理、ADC转换,变换为数字信号,传输给单片机。单片机根据传感器的输出信号和检出物体的距离关系,通过计算处理接近传感器的输出信号,获得检出物体的位移距离,并在显示屏实时显示检出物体的位移距离。本系统经过测试和实验,实现了非接触式距离测量,并设计了高精度显示和全量程显示2种界面。     

疲劳监测调节系统的设计

采用温度传感器AD7416、光电开关和时钟芯片DS1302作为测量元件,采集环境温度以及工作者工作起止时间。核心元件AT89S52根据情况启动语音提醒、音乐理疗及冷暖调节装置,以实现对工作者疲劳状态的监测和调节。     

微小电容测量电路

针对目前微小电容测量电路的测量方法进行分析和比较.介绍了代表性电容测量电路的基本原理,评述了各种电路的优缺点以及主要技术指标.并指出微小电容测量电路的发展趋势.