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.     

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.     

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.     

利用系统辨识的星敏感器模型修正与测角精度检测

2.中国科学院大学,北京100049)摘要:为了提高星敏感器的测角精度,提出了一种采用系统辨识法对星敏感器模型进行修正以及测角精度检测的方法。首先分析了星敏感器的理论测量模型以及像面坐标与星点目标的空间位置关系,然后给出了用模型修正来提高星敏感器测角精度的原理和数学模型。修正模型由系统辨识方法得到,同时为了提高辨识精度,文中采用将星敏感器像面划分为多个区域,每个区域单独建模辨识的方式。最后利用某星敏感器进行了实验,利用该方法进行模型修正后,星敏感器的测角精度为σx=1.68″、σy=1.91″,而修正前的测角精度为σx=17.43″、σy=23.46″。结果表明,采用该方法可以使星敏感器测角精度得到大幅提高,同时也完成了测角精度的检测。     

A Bayesian Nonparametric Mixture Measurement Error Model With Application to Spatial Density Estimation Using Mobile Positioning Data With Multi-Accuracy and Multi-Coverage

Abstract

The development of mobile network technologies has made it possible to collect location data of mobile devices through various positioning technologies. The location data can be used to estimate the spatial density of mobile devices, which in turn can be used by mobile service providers to plan for network capacity improvements. The two most prevalent positioning technologies are the assisted global positioning system (AGPS) and cell tower triangulation (CTT) methods. AGPS data provide more accurate location information than CTT data but can cover only a fraction of mobile devices, while CTT data can cover all mobile devices. Motivated by this problem, we propose a Bayesian nonparametric mixture measurement error model to estimate the spatial density function by integrating both noise-free data (i.e., AGPS data) and data contaminated with measurement errors (i.e., CTT data). The proposed model estimates the true latent locations from contaminated data, and the estimated latent locations, combined with noise-free data, are used to infer the model parameters. We model the true density function using a Dirichlet process (DP) mixture model with a bivariate beta distribution for the mixture kernel and a DP prior for the mixing distribution. The use of bivariate beta distributions for the mixture kernel allows the density function to have various shapes with a bounded support. Moreover, the use of a DP prior for the mixing distribution allows the number of mixture components to be determined automatically without being specified in advance. Therefore, the proposed model is very flexible. We demonstrate the effective performance of the proposed model via simulated and real-data examples.     

Measurement of the Fluorescence Quantum Yield Using a Spectrometer With an Integrating Sphere Detector

A method is proposed for measuring the fluorescence quantum yield (QY) using a commercial spectrophotometer with a 150 mm integrating sphere (IS) detector. The IS detector is equipped with an internal cuvette holder so that absorbance measurements can be performed with the cuvette inside the IS. In addition, the spectrophotometer has a cuvette holder outside the IS for performing conventional absorbance measurements. It is shown that the fluorescence quantum yield can be obtained from a combination of absorbance measurements of the buffer and the analyte solution inside and outside the IS detector. Due to the simultaneous detection of incident and fluorescent photons, the absorbance measurements inside the IS need to be adjusted for the wavelength dependence of the photomultiplier detector and the wavelength dependence of the IS magnification factor. An estimate of the fluorescence emission spectrum is needed for proper application of the wavelength-dependent adjustments. Results are presented for fluorescein, quinine sulfate, myoglobin, rhodamine B and erythrosin B. The QY of fluorescein in 0.1 mol/L NaOH was determined as 0.90±0.02 where the uncertainty is equal to the standard deviation of three independent measurements. The method provides a convenient and rapid estimate of the fluorescence quantum yield. Refinements of the measurement model and the characteristics of the IS detector can in principle yield an accurate value of the absolute fluorescence quantum yield.     

An Amperometric Glucose Biosensor With Enhanced Measurement Stability and Sensitivity Using an Artificially Porous Conducting Polymer

A conducting polymer [polypyrrole (PPy)]-based amperometric biosensor fabricated on a platinum-coated nanoporous alumina electrode has been described. This fabricating process introduced artificial porosity into the PPy film, and the template pore sizes were carefully chosen to match the size of the glucose oxidase (GOx) molecule. The $hbox{PF}_{6}^{-}$-doped PPy film was synthesized with 0.05 M pyrrole and 0.1 M $hbox{NaPF}_{6}$ at a current density of 0.3 $hbox{mA/cm}^{2}$ for 90 s. Immobilization was done by physically adsorbing 5 $muhbox{L}$ of GOx on the nanoporous PPy film. Glutaraldehyde (0.1 wt.%, 5 $muhbox{L}$) was used for cross-linking. The synthesized films were characterized by using an electrochemical technique and scanning electron microscopy (SEM). Amperometric responses were measured as a function of different concentrations of glucose at 0.4 V. Nanoporous electrodes lead to high enzyme loading, whereas the use of a cross-linking agent increased stability, sensitivity, reproducibility, repeatability, and shelf life.      

测量力的确定及测力机构

在使用接触式量仪进行测量时,必须有适当的测量力来保证量仪测头与工件被测面的可靠接触,进而保证测量精度.本文介绍了精密仪器中几种常用的测力机构,探讨了影响测量力的主要因素以及减小测量力影响的措施.