光学的启示——地震资料横向分辨率问题辨析

在地震资料解释中 ,人们惯常将第一菲涅尔带半径作为地震数据横向分辨率的基准尺度。其实 ,这样定义是一种似是而非的概念性错误。依据光学衍射原理 ,阐释了这一定义所包容的几处主要错误 ,并以几何光学原理和光波干涉叠加原理为基础 ,求取任意方向分辨率的定量解析式。必须指出 ,尽管据此解析式求得的横向分辨率 ,与球面波入射时的第一菲涅尔带半径的计算式相同 ,但我们绝不能用第一菲涅尔带半径冠名 ,不然依然会产生概念上的混乱。     

An identification method of mechanical properties of materials based on the full‐field measurement method based on the fringe pattern

With the development of image processing technology, optical methods based on fringe patterns, for example, the grid method, electronic speckle pattern interferometry, moiré techniques (including moiré interferometry and digital moiré), and coherent gradient sensing, have become useful techniques for measuring the full‐field deformation of materials and structures. An important application of these techniques is to offer deformation fields for extracting constitutive parameters in the inverse methods. In this paper, we proposed a novel inversion method based on fringe patterns (IMFP), which can be used to identify constitutive model parameters by comparing simulated fringe patterns obtained using the finite element method with experimentally measured fringe patterns. The feasibility and identification accuracy of IMFP were evaluated through numerical experiments, and an additional series of numerical tests were conducted to analyse the noise immunity of IMFP and its sensitivity to the number of constitutive model parameters. Finally, IMFP was applied in the identification of the mechanical parameters of selective laser melting three‐dimensional printed stainless steel.     

A study on the analysis of O-ring under uniform squeeze rate and internal pressure by photoelastic experimental hybrid method

There are three kinds of loading conditions applied to the O-ring, The first loading condition is the case in which uniform squeeze rates are applied to the upper side and the lower side of the O-ring (the strain condition). The second loading condition is the case in which uniform squeeze rates are applied to the upper side and the lower side of the Oring and other squeeze rates are applied to the front side of the O-ring. The third loading condition is the case in which uniform squeeze rates are applied to the upper side and the lower side of the O-ring, other squeeze rates are applied to the front side of the O-ring, and internal pressures are applied to another front side of the O-ring(loading condition is the combination of stress condition and the strain condition). In this research, a new photoelastic experimental hybrid method under the third loading condition was developed and it was verified. The stresses of the O-ring under the third loading condition were analyzed by the new photoelastic experimental hybrid method developed in this research. The internal pressures applied to the O-ring were 0.98 MPa, 1.96 MPa, 2.94 MPa and 3.92 MPa. This paper was recommended for publication in revised form by Associate Editor Jooho Choi Jai-Sug Hawong received a B.S. degree in Mechanical Engineering from Yeungnam University in 1974. Then he received his M.S. degree and Ph.D. degree from Yeungnam University in Korea in 1976 and from Kanto Gakuin University in Japan in 1990, respectively. Prof. Hawong is currently a professor at the school of Mechanical Engineering at Yeungnam University, in Gyeongsan city, Korea. He is currently serving as an vise-president of Korea Society Mechanical Engineering. Prof. Hawong’s research interests are the areas of static and dynamic fracture mechanics, stress analysis, experimental mechanics for stress analysis and composite material etc.     

Measurement of interfacial fracture parameters using coherent gradient sensing (CGS)

An optical interferometry called coherent gradient sensing (CGS) has been extended for mapping interface crack tip fields and for evaluating fracture parameters. The optical technique is a double grating shearing interferometer with an on line spatial filtering arrangement. The method offers real time full field measurements and can be used both in transmission made and reflection mode. The interferometer measures small angular deflections of light rays which can be further related to in plane gradients of _x + _y in transmission through elasto-optic relations. Direct interfacial crack tip measurements in a high stiffness mismatch PMMA-aluminium bimaterial system are performed. A variety of crack tip mode mixities are studied using asymmetric four point bend specimens subjected to different far field mechanical loads. The. complex stress intensity factors and the associated phase angles are measured from CGS patterns using an asymptotic expansion field. The measurements are compared with finite element results.     

微角度的光学测量

综述了微角度的光学测量方法。就干涉法，自准直法和全内反射差动探测法等测量方法的原理及特点进行了讨论。给出了各方法的典型实验装置，讨论了各装置的特点及应用局限性，并对这些方法的进展进行了探讨。     

Design and implementation of an optimised wireless pressure sensor for biomedical application

This paper presents design and implementation of a wireless pressure sensor system for biomedical application. The system consists of a front-end Micro-Electro- Mechanical System (MEMS) sensing capacitor along with an optimised MEMS-based oscillator for signal conditioning circuit. In this design, vertical fringed comb capacitor is employed due to the advantages of smaller area, higher linearity and larger full scale change in capacitance compared to parallel plate counterparts. The MEMS components are designed in Coventorware design suite and their Verilog-A models are extracted and then imported to Cadence for co-simulation with the CMOS section of the system using AMI 0.6-micron CMOS process. In this paper, an optimisation method to significantly reduce the system power consumption while maintaining the system performance sufficient is also proposed. A phase noise optimisation approach is based on the algorithm to limit the oscillator tail current. Results show that for the pressure range of 0–300 mmHg the device capacitance range of 1.31 pF – 1.98 pF is achieved which results in a frequency sweep of 2.54 GHz – 1.95 GHz. Results also indicate that a 42% reduction of power consumption is achieved when the optimisation algorithm is applied. This characteristic makes the sensor system a better candidate for wireless biomedical applications where power consumption is the major factor. Hai Phuong Le received his B.E. (Hons) degree in Electronic and Computer System Engineering from University of Tasmania, Hobart, Australia in 2000. He received his Ph.D. degree in Microelectronics from Victoria University, Melbourne, Australia in 2005. At present, he is a post-doctoral research fellow and lecturer in the Centre for Telecommunications and Microelectronics, Victoria University. His research and teaching interests include data acquisition system, mixed-signal integrated circuit design and wireless smart sensor systems. Kriyang Shah received his B.E. Degree in Electronics and Communication Engineering from Sardar Patel University, Vallabh Vidyanagar, Gujarat, India and his Master Degree in Microelectronics in 2004. He is currently a Ph.D. research student in the Centre for Telecommunications and Microelectronics, Victoria University, Melbourne, Australia. His research interests include MEMS Sensors, RF MEMS, process integration for MEMS and CMOS and MEMS-CMOS co-simulation. Jugdutt (Jack) Singh received his B.Sc. in Electronics Engineering from University of Brighton, UK and M.Sc. in Electronics Engineering from University of Alberta, Canada in 1978 and 1986 respectively. He completed his Ph.D. at Victoria University, Australia in 1997. Since 1989 he has been at Victoria University, Melbourne, Australia. Currently he is a Professor of Microelectronics in the Centre for Telecommunications and Microelectronics at Victoria University. His major area of research interests are in the RF, analog and mixed signal design, reconfigurable architectures, low power VLSI circuits and systems design. He has published number of articles in education and research in microelectronics and small technologies area. Aladin Zayegh received his B.E. degree in Electrical Engineering from Aleppo University in 1970 and Ph.D. degree from Claude Bernard University, France in 1979. In 1980, he joined the Faculty of Engineering, Tripoli, Libya. Since 1984 he has held lecturing position at Victoria University, Melbourne, Australia. He is currently an Associate Professor and the Head of School in the School of Electrical Engineering, Faculty of Health, Engineering and Engineering and Science at Victoria University. His research interest includes microprocessor-based system, instrumentation, data acquisition and interfacing, and microelectronics.     

一种检测平晶和透镜面形的方法

介绍了数字式激光平面干涉仪的测量优势,阐述了利用其进行平面和球面面形的测量方法,弥补了传统平面等厚干涉仪只能测量平面平晶的不足。同时分析了影响测量结果的几个因素,并利用ZEMAX软件模拟平晶位置,观察干涉条纹。     

同时线成像和分幅面成像任意反射面速度干涉仪测速技术

研制了一套线面同时成像任意反射面速度干涉仪(VISAR)用于激光驱动飞片速度场时空分辨测量。将传统VISAR改为成像干涉结构,用变像管扫描相机和高速光电分幅相机分别记录作为信号载体的梳状干涉条纹,实现靶面一条线上各点速度历史和多个时刻二维靶面上所有点速度的测量。所研制的线面同时成像VISAR具有小于10μm的空间分辨和约15m/s的速度分辨能力,线成像VISAR时间分辨小于50ps,面成像VISAR曝光时间小于5ns。用其测量了激光驱动带约束刀口铝膜飞片的速度场,给出了高时空分辨全场速度分布,从中可以清晰看出飞片的演化发展过程。实验结果表明,线面同时成像VISAR将是各种飞片产生技术及相应加载手段中全场速度诊断的有力工具。     

基于Curvelet变换的ESPI图像散斑噪声抑制算法研究

重点研究了Curvelet变换的去噪原理及方法,并结合ESPI条纹图中散斑乘性噪声的特性,提出了改进的Curvelet变换去噪方法,即在去噪之前,先将图像进行对数变换,使得乘性噪声变成加性噪声,然后再进行Curvelet变换去噪,这样会更有利于噪声与边缘信息的分离。并把该方法应用在对轮胎的激光无损检测图像处理系统中,实验结果表明该方法在有效去除散斑噪声的同时,较好地保持了条纹图的边缘细节信息。     

一种高效的平面点集凸包递归算法

凸包是计算几何的基本结构, 在许多图形图像相关领域得到了广泛应用. 本文提出了一种简单快速的平面点集凸包算法, 使用了主成分分析法(Principle component analysis, PCA)对点集进行预处理, 并研究了适用的排序规则和凸包边缘点判定原则. 该算法已成功应用于一光栅投影三维形貌快速测量系统,对相位干涉图中密集残留点所形成的最小凸包进行提取. 系统将提取的凸包区域进行掩码标记, 从而避免密集残留点造成相位展开错误, 保证了三维形貌重构的准确性. 实验结果表明, 该算法准确可靠, 并且运行效率较高.