一种用分谐波讯问技术实现的微波无触点辨别式异频雷达收发机

本文介绍了一种新式微波异频雷达收发机的设计和分析.该收发机在分谐波推拉式准光学混频器的基础上,由C波段讯问光束激活,转换成两个X波段频率的数字型调制辨别光信号,该响应信号与讯问信号非分谐波相关.通过运用包括考虑自偏电流影响的Volterra级数模式和在无线电连接计算中直接有效的散射米制方法对频率变换过程进行分析.该收发机能够遥控识别人员和物品.     

三维内曲面轮廓非接触式激光扫描图象测量

三维内曲面轮廓的非接触式精密测量是计测领域中的一个难题。本文基于光机电一体化的思想，针对非球型回转体内轮廓的非接触式测量，提出了激光扫描图象测量法，论述其测量原理，介绍了测量系统的特点和组成．对这一技术的研究．将有助于零件的在线非接触式测量，尤其是在恶劣的工业环境下的测量，以及计算机集成制造技术（ＣＩＭＳ）的发展     

Comparison of Different Measurement Protocols in Electrical Capacitance Tomography Using Simulations

A major problem in electrical process tomography is that there exist relatively few measurement variables, as compared with the desired resolution of the reconstructed image. This, in addition to the ill-behaved inverse problem involved, makes the image reconstruction problem difficult and severely underdetermined. Using more complex measurement protocols, in addition to an increased number of electrodes, introduces smaller rotational steps of the electric field. More information about the material distribution is obtained, and an increase in the image fidelity may be expected. In this paper, the image fidelity using protocol 3 is compared with the results using the conventional protocol 1. In addition, some performance metrics to assess the fidelity of the protocols are used in the final stage of the analysis. The results are based on simulations using COMSOL Multiphysics and MATLAB.     

Wavelet Distance Measure for Person Identification Using Electrocardiograms

In this paper, the authors present an evaluation of a new biometric based on electrocardiogram (ECG) waveforms. ECG data were collected from 50 subjects during three data-recording sessions on different days using a simple user interface, where subjects held two electrodes on the pads of their thumbs using their thumb and index fingers. Data from session 1 were used to establish an enrolled database, and data from the remaining two sessions were used as test cases. Classification was performed using three different quantitative measures: percent residual difference, correlation coefficient, and a novel distance measure based on wavelet transform. The wavelet distance measure has a classification accuracy of 89%, outperforming the other methods by nearly 10%. This ECG person-identification modality would be a useful supplement for conventional biometrics, such as fingerprint and palm recognition systems.     

Measurement Automation to Implement Evaluation Procedure of Four-Terminal-Pair Capacitance Standards Using S-Parameters

The evaluation procedure of four-terminal-pair capacitance standards using S-parameters is very complex as it involves the measurement of different parameters by multiple instruments. It also involves complex computation of effective capacitance as a function of frequency and its associated uncertainty in measurement. The reported paper presents the development of measurement automation program to implement evaluation procedure of four-terminal-pair capacitance standards of values varying between 1 and 1000 pF up to 30 MHz. The measurement automation increases the functionality with a comprehensive and flexible tool set for data acquisition, analysis, reporting and representation of results. The sequence of operations performed by the developed measurement automation program is described in detail. The program configures and measures S-parameters, converts S-parameters into corresponding impedance and admittance parameters, determines series and parallel resonance frequencies. Thereafter, it determines residual capacitive and residual inductive parameters and finally computes the effective value of each capacitance standard as a function of frequency along with the associated uncertainty in measurement. Measurement automation has provided precise and efficient way for the implementation of evaluation procedure of capacitance standards.     

Measurement of Distance and Medium Velocity Using Frequency-Modulated Sound/Ultrasound

The methods reported for the measurement of distance and medium velocity using ultrasound are based on the principles of pulse radar, pulse Doppler radar, and continuous- wave radar. In this paper, the use of frequency-modulated sonic/ultrasonic radiations for such measurements has been proposed. The required measurement setup has been described, and the mathematical model needed for extraction of distance/medium velocity from the electrical output signal has been developed. The proposed measurement setup has been implemented for distance measurement with commonly used ICs.     

Noncontact Measurement of Charge Carrier Lifetime and Mobility in GaN Nanowires

The first noncontact photoconductivity measurements of gallium nitride nanowires (NWs) are presented, revealing a high crystallographic and optoelectronic quality achieved by use of catalyst-free molecular beam epitaxy. In comparison with bulk material, the NWs exhibit a long conductivity lifetime (>2 ns) and a high mobility (820 ± 120 cm(2)/(V s)). This is due to the weak influence of surface traps with respect to other III-V semiconducting NWs and to the favorable crystalline structure of the NWs achieved via strain-relieved growth.     

扫描探针显微镜测壳聚糖材料的表面电荷分布

提出一种测量材料表面电荷是非均匀的、没有中性区的弱电荷的方法.即测试时,利用扫描探针显微镜(SPM)的静电力显微镜(EFM)测量技术,依靠轻敲模式(Tapping Mode)和抬举模式(Lift Mode),用相位成像测量有机高分子膜--壳聚糖膜(CHI)的表面电荷密度空间分布,但由于仪器设计中相位的泰勒展开是:sin△φ≈1/2△φ,所以所获的电荷图像只能确定材料的表面电荷分布和表面电荷密度的近似值.然而,嵴宽约为2.12μm表面正电荷微沟槽结构的这种特殊电荷形貌分布有利于细胞的生长,因此获得的表面电荷分布补充了生物材料表面理化性质.     

共面波导传输线电容准确测量及不确定度分析

介绍了低介质损耗共面波导(CPW)传输线电容测量方法中的反射系数测量及线电容外推测量技术,成功提取了商用校准基片101-190C上传输线的线电容。根据线电容算法模型,以校准件及矢网内部接收机动态幅相精度不理想作为误差来源,采用蒙特卡罗仿真对线电容测量结果的不确定度进行了评定。最后将线电容用于多线TRL校准,与NIST标定结果更接近,在40 GHz频率范围内,反射系数模值相差小于±0.02, 传输幅度模值相差小于±0.05 dB, 传输相位相差小于±1°。     

基于球杆仪的旋转轴几何误差测量和辨识

通过圆弧测量轨迹, 移动球杆仪测量球心在旋转工作台上3个安装位置的9项误差, 采用齐次变换理论建立几何误差辨识模型, 引入系数矩阵条件数进行安装参数的优化选取, 提出一种辨识旋转轴4项位置和6项运动误差的方法。最后, 在四轴数控加工中心上进行了测量和验证实验, 该方法可辨识出全部的几何误差项, 通过对几何误差计算出的预测值和球杆仪的测量值的比较, 预测值的绝对误差小于0. 003 mm, 具有辨识精度高、测量省时的优点。     

Measurement and Modeling Mutual Capacitance of Electrical Wiring and Humans

In a recent series of electric field sensing experiments, a theremin was used to measure the mutual capacitance between a human being and a length of electrical wiring. The instrument, based on the LM555 circuit, measures the deflections in capacitance due to the proximity of a human. The measurements are repeatable, and the difference in capacitance for a person at 0.5 m with a person at 1 m is consistent with the difference computed, assuming the human acts as a ground plane for the wiring. Much of the current literature in electric field sensing focuses on measures and models of mutual capacitance for humans interacting with plate conductors [J. R. Smith, Electric field imaging, Ph.D. dissertation, Mass. Inst. Technol., Cambridge, MA, 1999; N. Karlsson and J. O. Jarrhed, A capacitive sensor for the detection of humans in a robot cell, in Proc. IEEE IMTC Rec., May 18–20, 1993 pp. 164–166.], especially fingers near touch screens [D. Wiebe, A. Machynia, K. Mazur, and J. Epp, Human–computer interface device based on electric field sensing, Ph.D. dissertation, Univ. Manitoba, Winnipeg, MB, Canada, 2004]. The present investigation considers conducting wires to allow the development of portable rapidly deployable human proximity sensing systems that exploit existing electrical infrastructure in buildings. The experiment described here demonstrates that sensing with wires is possible at ranges on the order of a meter and provides evidence that modeling the person as a ground plane of finite extent provides a rough estimate of the change in mutual capacitance.     

基于遗传算法的材料特性参数的辨识

为了得到一个相对精确的材料特性参数,引入遗传算法(GA)到有限元模型更新的应用中,以一个简单的转轴模型为例,以模态实验得到的固有频率数据和模型输出数据之间的误差建立遗传算法的目标函数,以材料的特性参数为更新参数,对该转轴的有限元模型进行了修正,辨识出了材料的特性参数.然后通过比较由修正后的模型计算得到的频率响应函数(FRF)和模态实验得到的FRF,检验了基于GA辨识的有效性.最后比较了模型计算得到的固有频率、FRF和模态实验,结果表明吻合性非常好.     

Performance Maintenance of Dye-Sensitized Solar Cells Using a Latent Heat Storage Material

Recently, there has been considerable interest in various renewable energies. Among them, solar cell production has increased markedly because the photovoltaic is a clean and safe power generation method. The dye-sensitized solar cell (DSSC) has attracted much attention as an alternative to silicon solar cells due to lower manufacturing costs and plentiful resources for DSSC production. However, the performance of DSSCs has been limited by their durability and low photoelectric conversion efficiency. Temperature control of DSSCs via phase-change materials (PCMs) is expected to improve performance. In this study, DSSCs were heated or cooled with a heat exchanger copper block that was in contact with a PCM (heptadecane), while being irradiated by a solar simulator light source. The durability and photoelectric conversion efficiency of the DSSC improved under PCM temperature control.     

A Portable Noncontact Heartbeat and Respiration Monitoring System Using 5-GHz Radar

A portable noncontact heartbeat and respiration monitoring system operating in 5-GHz band is reported in this letter. Compared with the previously reported system operating at Ka-band, this system has been simplified to include only two PCB antennas, a palm-size PCB radio module, a data acquisition module, and a laptop. The system, powered by the laptop battery through USB connection, is compact, low-cost, and convenient for field test. A detection accuracy of better than 80% has been achieved at a distance of 2.8 m and at a low transmitted power of 20 muW. The system can be used for various applications in biology, medicine, and security.     

硬涂层材料特性参数辨识

采用振动梁法对硬涂层材料TiZrN的机械特性参数进行辨识测试。首先详细叙述振动梁法辨识涂层材料参数的原理性公式,并在此基础上搭建基于振动梁法的硬涂层材料机械特性参数实验系统。根据此测试系统,对硬涂层材料TiZrN的力学特性参数进行测试研究,获得对应结构涂层前后前3阶弯曲模态的固有频率和损耗因子,进而辨识出TiZrN的弹性模量和损耗因子。最后,对可能产生的参数识别误差进行分析,并结合振动梁法辨识公式,分析各输入参数对硬涂层材料力学参数识别结果的敏感性。     

长距离同轴度测量方法及实验

本文介绍了一种新型的自适应双频激光同轴度测量系统，该系统利用两个完全对称的渥拉斯顿棱镜，一个作为测量元件，另一个作为补偿元件，采用比相技术处理测量信号，因而测量元件可以暂时移出光路，能够进行同轴度的测量，系统的光学设计使激光光束的平衡和角漂不影响测量结果，对激光的漂移有自适应性，两束干涉光基本符合共光路原则，因而对大气湍流，空气扰动的影响具有更强的适应性，可用于长距离直线度，同轴度的测量。该系统与     

An Automated Noncontact Measurement System for Current Harmonics in Aerial Transmission and Distribution Systems

Using magnetic field data from under aerial power transmission lines, tomographic reconstruction techniques have been applied to determine the magnitudes and phases of currents in each power conductor. Phasor current values at fundamental (60 Hz) and harmonic frequencies are produced. This measurement technique requires no physical contact with power lines (even by clamp-around transformers) and hence should be convenient for monitoring and trouble-shooting cases of excessive harmonic currents on transmission and distribution facilities. The method has been implemented experimentally, and laboratory and initial field tests have demonstrated its basic validity.