Optical strain gauge vs. traditional strain gauges for concrete elasticity modulus determination

In the field of Civil Engineering, the evaluation of concrete elasticity modulus relies heavily on traditional strain gauges like electric resistance strain gauge, demec mechanical strain and compressometer. These strain gauges work pretty well but the sample surface preparation and the strain gauge adhesion are tedious and time-consuming. On the other hand, convenient non-destructive testing methods like rebound hammer and ultrasonic pulse velocity have the disadvantage of large data scattering and low reliability. In this paper, we aim to develop a handy, reliable and cost-effective method for concrete property evaluation based on an optical technique called automatic digital image correlation (ADIC), which acts as an optical strain gauge. By incorporating an automatic searching approach, the proposed ADIC greatly expands the convergence range of normal digital image correlation (DIC) algorithms and is able to automatically determine concrete strain in real time without human interaction. After the optical strain gauge is set up, the axial concrete strain as well as the stress-strain curve is plotted in real time when the concrete sample under testing is loaded. The concrete elasticity modulus is then determined from the curve. A series of experiments have been conducted to evaluate the performance of the proposed optical strain gauge. Comparisons are also carried out between the proposed optical strain gauge and traditional strain gauges such as electronic strain gauge, compressometer and demec mechanical strain gauge, which further confirm the accuracy, convenience and reliability of the proposed technique.     

基于FPGA的FSO准同步数字复接器的实现

为了实现多路信号在同一大气信道中的传输,提出一种适用于自由空间光通信(FSO)系统的准同步数字复接方案.该方案利用数字复接扩大传输容量,通过加入滤波模块和采用择多判决的方法,提高系统的抗干扰能力.整个系统采用自顶向下模块化的方法进行设计,所有功能模块均用VHDL语言进行描述,并用现场可编程门阵列(FPGA)芯片EP1C3T100C6对整个系统进行硬件实现.以三路准同步数字信号的复接分接为例,给出了软件仿真和硬件实验结果.结果表明系统可以准确、可靠地实现三路准同步信号的复接分接.     

三线阵立体测绘相机光学镜头的设计

为了提高测绘相机的立体测绘定位准确度,设计了一种透射式像方远心光路的光学镜头,并阐述了基于可测性设计的单镜组以及整镜头的装调理念.本文设计的光学镜头传函为0.45(@77lp/mm);地面分辨率为5m;畸变为3/10000.检测及试验结果表明,各参量能够满足用户提出的指标要求.     

LED光源数字全息技术研究

研究以发光二极管(LED)作为光源的部分相干光数字全息技术.首先研究LED的时间相干性和空间相干性,尽管LED的时间相干性较差,但空间相干性可以通过减小光源发光面积来提高.利用LED的时间相干性较差、相干长度短的特点,抑制相干噪声,改善数字全息重建质量.在同一全息记录系统,通过实验,比较了用激光和LED光源的数字全息重建图像质量.结果表明:基于LED光源的数字全息,完全消除了使用激光光源的散斑噪声和由光学元件引入的寄生干涉噪声,物光场的重现质量,包括振幅和相位都得到了很大提高.但由于LED光源的较低的空间相干性,一般只适用于同轴相移数字全息,待测物体的厚度在十几微米以内,应用受到一定限制.     

点阵列标定模板图像特征点提取方法

在摄像机标定过程中,提取标定模板图像特征点的精度是影响摄像机内外参数标定精度的重要因素。本文根据条纹投影三维轮廓测量实验系统的要求制作了点阵列标定模板,在图像处理边缘理论的基础上,以圆的解析特性为依据,采用坐标转换思想,引进圆系描述点、圆对应关系,运用统计学理论,提出提取点阵列标定模板图像特征点的新方法,并通过实验验证了该方法的正确性和可行性。为下一步的摄像机内外参数求解做了铺垫。     

像移补偿技术的发展与展望

航空相机广泛采用像移补偿技术来提高成像质量和相机分辨力。本文分析了像移补偿的原理并介绍了国内外较多采用的像移补偿技术,如光学式像移补偿法、机械式像移补偿法、集成像移补偿法、数字式像移补偿法等。文中列举了像移补偿过程中获取重要参数速高比的常用方法,包括平行狭缝法、扫描相关法、外差法、光程差法、直接计算法等。最后讨论了像移补偿技术数字化的发展方向,以及速高比测量的数字化、实时化、小型化发展趋势,提出了采用面阵CCD结合高性能微处理器获取速高比的新思路。     

基于PTP协议的航空图像高速传输

为了减少传输图像数据量,提高图像传输的速度,实现对航空图像的高速传输,研究一种高速、可行的图像传输方法。基于PTP(Picture Transfer Protocol)协议,采用JPEG图像压缩算法对图像进行压缩,引进文件流的多线程传输模式,自主开发了航空数码相机图像传输系统。介绍了系统设计方案,验证了设计方案的可行性。测试结果显示,图像平均传输速率为53.641 Mb/s,误码率为0.00%,表明该系统能够很好地保证数据的原始性,防止数据丢失,有效地减少数据通道堵塞,实现了图像数据的高速、高质量传输。     

第26届全国中学生物理竞赛(决赛)实验试题的解答与考试评析(续)

3实验试题Ⅱ的解答与评析 本实验要求研究光学玻璃材料的物理特性(波长范围为400～700 nm).3.1实验装置及材料 1)玻璃样品1个(利用ZF1光学玻璃制成的三棱镜,其顶角为60°00′,误差为2.0′).     

Investigation of high resolution compact gamma camera module based on a continuous scintillation crystal using a novel charge division readout method

The objective of this study is to investigate a high performance and lower cost compact gamma camera module for a multi-head small animal SPECT system. A compact camera module was developed using a thin Lutetium Oxyorthosilicate （LSO） scintillation crystal slice coupled to a Hamamatsu H8500 position sensitive photomultiplier tube （PSPMT）. A two-stage charge division readout board based on a novel subtractive resistive readout with a truncated center-of-gravity （TCOG） positioning method was developed for the camera. The performance of the camera was evaluated using a flood 99roTe source with a four-quadrant bar-mask phantom. The preliminary experimental results show that the image shrinkage problem associated with the conventional resistive readout can be effectively overcome by the novel subtractive resistive readout with an appropriate fraction subtraction factor. The response output area （ROA） of the camera shown in the flood image was improved up to 34%, and an intrinsic spatial resolution better than 2 mm of detector was achieved. In conclusion, the utilization of a continuous scintillation crystal and a flat-panel PSPMT equipped with a novel subtractive resistive readout is a feasible approach for developing a high performance and lower cost compact gamma camera.     

InP-based InGaAs/InA1GaAs digital alloy quantum well laser structure at 2μm

The structural and optical characteristics of InP-based compressively strained InGaAs quantum wells have been significantly improved by using gas source molecular beam epitaxy grown InAs/Ino.53Ga0.47As digital alloy triangular well layers and tensile Ino.53Ga0.47As/InAiGaAs digital alloy barrier layers. The x-ray diffraction and transmission electron microscope characterisations indicate that the digital alloy structures present favourable lattice quality. Photo- luminescence （PL） and electroluminescence （EL） measurements show that the use of digital alloy barriers offers better optical characteristics than that of conventional random alloy barriers. A significantly improved PL signal of around 2.1μm at 300 K and an EL signal of around 1.95μm at 100 K have been obtained.