Voltage Division Position Sensitive Detectors Based on Photoconductive Materials— Part I: Principle of Operation

A simple contact structure is proposed for the realization of position sensitive detectors based on a voltage division principle in which the sensors operate in a photoconductive regime. The transfer function of the system is calculated by a detailed analysis of the operative principle of the device. Moreover, the expected performances of the photodetectors are discussed as a function of the main system parameters, underlying the benefits due to the adopted design.     

Effects of moisture absorption on the electrical parameters of embedded capacitors with epoxy-BaTiO3 nanocomposite dielectric

In this work the effects of moisture absorption on the electrical parameters of embedded capacitors is investigated. Capacitors of two different areas embedded inside a four-layered printed wiring board were selected for this work. The dielectric was a nanocomposite of epoxy and BaTiO₃ which is common dielectric material used in embedded capacitors. These capacitors were exposed to elevated temperature and humidity conditions (85?°C and 85% RH) and two parameters, capacitance and dissipation factor, were measured in situ. The diffusion of moisture in the dielectric was also modeled using the finite element method (FEM), and the changes in electrical parameters were calculated theoretically. The FEM methodology was then verified by applying it on capacitors of different dimensions.     

Small punch test for determining a flow stress by using a hybrid inverse procedure

A flow stress of the structural materials used in nuclear and fossil power plants is determined by using the small punch test. An inverse method is proposed to deal with a non-uniform deformation in a specimen used for the small punch test. The objective function of the inverse analysis is the difference between the measured load–displacement response and the calculated one during a deformation. The convergence of the objective function to a global minimum is assured by adopting a simulated annealing. During the optimization process, the load–displacement response under given material parameters is calculated by means of an artificial neural network. Material parameters are accurately identified for the numerical test data. The present method is verified by applying it to the experimental data for the as-received and ex-service materials. The results show that the flow stress of the materials used in this study is predicted with a reasonable accuracy.     

Distortion tolerant image recognition receiver by use of a multiple-hypothesis method

A multiple-hypothesis method is used to detect a target or a reference signal in the presence of additive noise with unknown statistics. The receiver is designed to detect the target and to be tolerant of the variations in rotation and illumination of the target. A multiple-hypothesis test with unknown-noise parameters is used to locate the target position. The proposed method does not use any specific distortion-invariant-filtering technique, but it relies on a multiple-hypothesis approach. Maximum-likelihood estimates of the illumination constant and the unknown noise parameters are obtained. Computer simulations are presented to evaluate the performance of the receiver for various distorted noisy true-class targets with varying illumination and false-class objects.     

Voltage-Mode Multifunction Filters Employing a Single DVCC and Grounded Capacitors

In this paper, two novel voltage-mode (VM) single-input–three-output (SITO) second-order multifunction analog filters for simultaneously realizing low-pass, bandpass, and high-pass responses from the same topology are proposed. They employ a single dual-output differential voltage current conveyor (DVCC), two grounded capacitors, and three resistors. Both of the proposed filters offer the following two important features: the simultaneous realization of low-pass, bandpass, and high-pass responses and the use of a minimum number of grounded capacitors and a single DVCC. The nonideal gain effects of the developed structures are examined. To show the performance of the proposed VM filters, computer simulation results using the SPICE program, together with ideal ones, are drawn.      

安装差动胶泥缓冲器的舰炮检验弹入膛仿真分析

舰炮检验弹由于结构不同于实弹,入膛时反弹速度过大,造成相关零部件断裂和关闩故障。故设计采用差动胶泥缓冲器吸收过大的动能以保证检验弹的入膛可靠性。为评估差动胶泥缓冲器在检验弹上的缓冲效能,以及分析检验弹的入膛运动规律,提出一种结合缓冲器流体数值分析(computational fluid dynamics,CFD)和入膛多体动力学分析(multi-body dynamic,MBD)的仿真分析方法。计算结果表明:此方法能够准确计算和预测缓冲器的缓冲效能,检验弹的缓冲器满足设计技术要求;静压过程在活塞后方形成多个涡旋,而冲击过程流线平稳无涡旋;黏性阻抗分力随压缩速率降低先增大后减小。研究不仅为胶泥缓冲器在舰炮检验弹上的应用提供理论支撑,还为胶泥缓冲器本身的研究提供新的分析方法。     

Monitoring changes in the error distribution of autoregressive models based on Fourier methods

We develop a procedure for monitoring changes in the error distribution of autoregressive time series while controlling the overall size of the sequential test. The proposed procedure, unlike standard procedures which are also referred to, utilizes the empirical characteristic function of properly estimated residuals. The limit behavior of the test statistic is investigated under the null hypothesis as well as under alternatives. Since the asymptotic null distribution contains unknown parameters, a?bootstrap procedure is proposed in order to actually perform the test and corresponding results on the finite?Csample performance of the new method are presented. As it turns out the procedure is not only able to detect distributional changes but also changes in the regression coefficient.     

钢纤维钢筋混凝土梁柱节点抗震设计方法

基于压杆模型和软化桁架模型,提出钢纤维钢筋混凝土梁柱节点的一种新的抗震设计方法。掺入节点核心区的钢纤维可被等效为部分水平和竖向剪力筋。在节点核心区与梁或柱相交端截面处建立平衡方程、协调方程和本构方程,可以求出传给节点压杆模型和软化桁架模型的地震作用。提出的设计方法能够对节点的水平和竖向抗剪承载力进行设计,其可靠性得到七个钢纤维钢筋混凝土梁柱外节点试验数据的验证。     

The potential transformer bridge with current comparator formeasuring the voltage dependence of compressed-gas capacitors

In this paper, an alternative method for measuring the voltage dependent capacitance variation (VDCV) of compressed-gas capacitors is described. In the proposed method, the VDCV of the capacitor under test is measured by comparing it with a capacitor standard supplied with the secondary (low) voltage of a potential transformer. This transformer has its primary parallel connected with the capacitor under test. The paper presents and criticizes the test results obtained in which an uncertainty of at least 0.5 ppm is achieved     

Failure analysis of miniaturized multilayer ceramic capacitors in surface mount printed circuit board assemblies

New failure analysis results of miniaturized multilayer ceramic capacitors (sizes 0402, 0603, 0805 and 1206) which have been subjected to various degrees of thermal shock up to 450°C by ice-water or dry ice quenching are reported. The thermal shock resistance of 0402 multilayer ceramic capacitors was found to be about 400°C and considerably better than those of the larger ones. Microstructural and layer-by-layer insulation resistance analyses have clearly identified the physical locations responsible for the electrical leakage of defective capacitors. Further, no evidence of silver migration as a dominant failure mechanism has been observed for any of the defective capacitors under usual operating stresses. Comparisons ofI–V characteristics for multilayer ceramic capacitors quenched by ice-water and dry ice confirm that water plays a significant role in causing electrical failure at nominal bias. Comparisons with results obtained from practical surface mount printed circuit board assembly of mobile telephones is discussed. From these, failure mechanisms are proposed to explain the failure of miniaturized multilayer ceramic capacitors under normal service conditions.     

高压脉冲电容器性能参数优选实验方法研究

文章针对高压脉冲电容器的参数、特性以及性能等问题,利用国内目前所用到的不同种类材料的高压脉冲电容器,提出高压脉冲电容器性能参数的优选实验方法。优选实验结果表明：作为冲击片雷管发火的储能元件高压脉冲电容器,陶瓷电容器的性能参数最优,耐压和使用寿命很难满足使用要求;云母电容器性能参数次之,体积却相对较大,能够满足目前的爆炸箔起爆器的储能元件使用要求。     

浅海倾斜海底声场空间相关性研究

针对浅海倾斜海底海洋环境,对声场的空间相关性进行了研究。利用抛物方程法,对浅海声场的空间相关系数进行数值模拟,并结合2001年东中国海中美联合实验数据,分析了声场空间相关系数与海底倾斜角度、接收阵元与参考阵元的间隔、参考阵元深度及声源深度之间的关系。对于上坡海底,浅海声场空间相关性随着海底倾斜角度、接收阵元与参考阵元间隔的变大而变弱,且垂直相关系数随着接收阵元与参考阵元间隔的增大,先衰减再出现起伏。     

Selection of capacitors to regulate voltage of a short-shunt induction generator

A self-excited induction generator (SEIG) has poor voltage regulation and that restricts wide applicability of the generator. A simple method of selecting the values of fixed and switched capacitors in a short-shunt SEIG driven by a regulated prime mover to maintain the load voltage within the upper and lower acceptable limits is proposed. The values of the capacitors are selected very carefully to minimise the number of switched capacitors needed to satisfy the above voltage criterion, and that would minimise the cost and complexity of the voltage regulator. This requires evaluating the generator characteristics under constant voltage operation. The equations needed to obtain such characteristics are also derived and solved using a numerical based routine 'fsolve' given in MATLAB. The proposed method of selecting the capacitor values is then tested on a three-phase, 1.5 kW induction generator operating in a short-shunt configuration. The simulation results obtained by the proposed method are also compared with the corresponding actual values found through an experimental setup and are observed to be in very good agreement.     

Design and Analysis of a Tri-Axis Gyroscope Micromachined by Surface Fabrication

This paper presents an innovative microgyroscope design. Solely by planar fabrication and wet etching, the proposed microgyroscope is capable to detect three-axis angular rates. The induced motion of individual seismic mass modules are designed to respond in the directions orthogonal to each other in order to decouple the obtained measures. In our work, three pairs of high-resolution differential capacitors with signal processing circuits are employed to measure the angular velocity components in three axes. On the other hand, the drive electrode comb is used to constantly vibrate the outer-ring in tangential direction by sinusoidal voltage. The signal bandwidth about the principle axis is increased by distributed translational proof masses, placed 90$^circ$ apart orderly around a circle. Each individual translational proof mass is designed to move in radial direction so that superior mode matching (i.e., resonance mode) can be easily, to some extent, achieved. The planar suspension flexures are particularly designed in geometry to resist acceleration in drive mode but increase the stroke of tilting angular displacement of the outer-ring such that the resolution of detected angular rate for the corresponding sense mode is upgraded. By considering the complicated geometry of the suspension flexures, finite-element method (FEM) is employed to examine the potential maximum induced mechanical stress. The dynamic equations of the proposed gyroscope are established are well so that the embedded gyroscopic effects are unveiled. More importantly, the efficacy of the drive and sense circuits modules is verified by commercial softwares Hspice and Multisim. By intensive computer simulations and preliminary experimental studies, the resolution, bandwidth and sensitivity of the tri-axis gyroscope are expected to be fairly enhanced if a certain degree of tradeoff is preset.      

噪声为厚尾过程的非参数函数变点的小波估计

本文给出了随机设计下非参数回归模型中噪声为无穷方差过程的小波检测和估计方法。利用基于经验小波系数的检验统计量,在原假设成立的条件下,推导出任意尺度上检验的临界值,证明了检验的一致性;在备择假设成立的条件下,得到变点个数、变点位置的相合估计与收敛速度。数值模拟以及IBM股票数据实例分析的结果均表明方法是有效的。     

海上风机单立柱三桩基础灌浆连接段轴向承载力试验研究

结合某海上风机单立柱三桩基础,对海上风机灌浆连接段进行轴向承载力试验。共设计四个试验模型,包括两个带剪力键的模型和两个无剪力键的模型。试验结果表明:带剪力键的模型承载力和延性比无剪力键的模型显著提高;受过疲劳荷载的带剪力键模型虽然延性有一定降低,但其承载力仍与未受过疲劳荷载的模型相当。该文还讨论了UK规范、API规范和新旧DNV规范建议的四个灌浆连接段轴向承载力经验公式。各公式之间的对比表明,它们都存在一定的缺点:API规范公式和旧版DNV规范公式形式还不太成熟,而UK规范公式和新版DNV规范公式试验数据参数范围不全。因此,该文最后建议提出一个灌浆连接段界面抗剪强度的新公式,以适应更广泛的工程应用条件。     

Performance analysis of single-phase induction motor based on voltage source complex finite-element analysis

In this paper, to make a compromise between accuracy and efficiency in the design of single-phase induction motors, voltage source complex finite-element model, which is combined with the equivalent circuit method to carry out the performance analysis, is presented. The voltage source complex finite-element method is used to determine equivalent circuit parameters by simulating the no-load tests and locked-rotor tests, while the conventional method is adopted to calculate the performances. Good agreement is achieved between the calculated results and test results, which verifies the effectiveness of the presented method.     

A novel method of measurement of L and C

A novel method of measurement of component values of inductors and capacitors is described. The technique is independent of the voltage across or current through the unknown inductor or capacitor, as it involves only a set of phase measurements. The unknown capacitor/inductor is connected in series with a known standard resistance and this series circuit is excited by a source of required voltage and frequency. The resistive and reactive parts of the unknown component are measured by measuring the phase displacement between the three voltages, namely, voltage applied, voltage across the inductor/capacitor and the voltage across standard resistance. The proposed scheme is verified both by simulation as well as by building a prototype. The relationship between the range of the measurement and obtainable accuracy level is established. For the prototype built, with a one decade span in the measurement range, a commercially acceptable accuracy of ±2.0% was achieved. However, this accuracy can be further improved by suitable circuit modifications     

Lightweight biometric detection system for human classification using pyroelectric infrared detectors

We use pyroelectric detectors that are differential in nature to detect motion in humans by their heat emissions. Coded Fresnel lens arrays create boundaries that help to localize humans in space as well as to classify the nature of their motion. We design and implement a low-cost biometric tracking system by using off-the-shelf components. We demonstrate two classification methods by using data gathered from sensor clusters of dual-element pyroelectric detectors with coded Fresnel lens arrays. We propose two algorithms for person identification, a more generalized spectral clustering method and a more rigorous example that uses principal component regression to perform a blind classification.     

Radar detection based on Bayesian estimation of target amplitude

A new approach to detect a target with an unknown amplitude in clutter is proposed. The received signal models under two hypotheses, H/sub 0/and H/sub 1/, are assumed to be the same, except that the target amplitude is zero under H/sub 0/. Using the Bayesian approach, it is shown that the likelihood ratio can be calculated as the ratio of the prior to posterior probabilities of the target amplitude. Based on this relation, a new method for target detection in Gaussian clutter is presented. This method is applied to cases with both known and unknown clutter statistics and in each case, white and coloured clutters are considered. Simulation results show that the proposed detector has a much better performance compared with conventional generalised likelihood ratio test detectors.