基于激光视觉原理测量玻璃中气泡的尺寸

为了实现玻璃中气泡尺寸的在线测量,基于激光视觉原理,采用线结构激光器、线阵CCD相机和运动控制系统在实验室搭建玻璃气泡的动态测量系统。投射到玻璃表面的线结构激光光斑经变焦镜头成像在相机的光敏阵列上,相机的横向扫描与运动平台的纵向扫描配合,利用Sapera CamExpert图像采集软件获得玻璃气泡的灰度图像;理论上讨论了图像的纵向和横向精度,给出了气泡图像失真的判断依据及工作像素时钟频率与玻璃板纵向运动速率之间的匹配关系;采集了不同纵向运动速率下气泡的灰度图像,利用Sapera Architect软件测量气泡图像的横向和纵向像素数,通过理论计算得出气泡的横向和纵向尺寸,并与直尺测量结果比较,发现纵向尺寸相对误差为0.18,横向尺寸相对误差为0.05。结果表明,在相机工作距离、焦距和像元尺寸确定的情况下在误差允许的范围内该系统可以用来测量气泡的横向尺寸。     

Measurement accuracy in X-ray computed tomography metrology: Toward a systematic analysis of interference effects in tomographic imaging

In this paper an investigation of interference effects leading to limitations of metrological performance of X-ray computed tomography (CT) used as a coordinate measuring technique is presented. Using reconstruction data, image quality metrics, and calculations of artifact formation, a deeper understanding and explanation of the physical and technical limitations of CT used in dimensional metrology is given. This is demonstrated in a case study using a simple hollow cylinder made of steel as a test object and calibration measurements from a tactile coordinate measuring machine (CMM). Two different threshold determination strategies for surface computation are applied. Within the study it is also shown that CT image properties, threshold determination strategies, and systematic and random measurement errors must have a definite correlation. As a conclusion it is recommended to focus more strongly on the correlation of local CT image quality and data evaluation operations in order to reduce systematic errors in surface computation and to increase repeatability of dimensional CT measurements.     

基于改进遗传算法的DBN结构自适应学习算法

针对动态贝叶斯网络(dynamic bayesian network,DBN)是NP困难问题,提出基于改进遗传算法的DBN结构自适应学习算法.该算法计算最大互信息和时序互信息完成DBN结构搜索空间的初始化.在此基础上设计改进遗传算法,引入评分标准差构建交叉概率和变异概率的自适应调节函数,以降低结构学习过程陷入局部最优解...     

Permeability differences based on three-dimensional geometrical information of void spaces

In this study,the permeabilities of Berea and Otway sandstones were measured under different confining pressures,and porosity was investigated through mercury intrusion porosimetry(MIP).The total porosities of the Berea and Otway sandstones were approximately 17.4%and 25%,respectively.Pore size distributions of each sandstone were almost the same,but the pores in the Otway sandstone were slightly narrower.However,the permeability of the Otway sandstone was smaller than that of the Berea sandstone by one order of magnitude.Three-dimensional(3D)void geometry and geometrical properties of the void spaces relevant to flow were compared to obtain the relation between the permeability differences and porosities of the two sandstones.The 3D geometrical analysis using microfocus X-ray computed tomography(CT)was performed,and the pore geometries of both sandstones were compared using the 3D medial axis(3DMA)method.Pore and throat radii,pore coordination number,tortuosity,number of connecting paths,connecting path volume,and other factors were determined using 3DMA.The Otway sandstone was characterized by a small effective throat/pore radius ratio.Based on the fluid flow mechanism,the lower effective throat/pore radius ratio results in a lower permeability induced by the fluid energy loss,which means that the 3D geometrical shape of void spaces affects the permeability value.     

双小波非凸稀疏正则化去噪算法研究

针对航空发动机ECT滑油监测数据在采集传输过程中易受噪声干扰而影响数据有效特征提取的问题,提出了一种双小波去噪算法.在2个小波域下对数据进行分解,通过阈值函数进行滤波,利用小波系数的分布差异,迫使2个小波域下的去噪信号相同,反正切函数作为罚函数,得到更加稀疏的系数表达.实验结果表明:与传统的小波去噪方法相比,连续信号和...     

用脉冲星的脉冲序号复现坐标时方法

为实现包括地球和地球以外的时间统一, 需要运用相对时间观的两种时间来替代目前时间计量体系中的标准时间, 这两种时间分别是:原时和坐标时, 其中坐标时可溯源到脉冲星时间基准上。 为构建简单的本地轨道参数历表, 阐明分层嵌 套的空间包含关系, 形成时间相对统一的观点。 从计量角度, 提出了一种脉冲星复现坐标时的理论, 运用相对时间观中的时 间和空间不可分割观点, 归纳了统一时间的广域坐标系所必须具备的基本特征, 强调了原点观者的特殊性, 提出了基于原点 观者的脉冲星脉冲序号和初始历元的定义方法。 首先, 把一组脉冲星的脉冲序号约定为坐标时基准, 用来复现坐标时, 约定 一组脉冲星的脉冲周期为固定的常数数组, 约定后不再测定,常数的单位仍是国际单位制[秒], 常数可理解为脉冲序号的坐 标时间隔与[秒]之间换算的系数。 然后,基于平面电磁波模型, 把脉冲星的脉冲电磁波经过原点的时刻与脉冲序号一一对应, 于是原点观者的坐标时与连续的脉冲序号成为线性函数关系, 最后, 分析了脉冲星稳定特点, 给出了以一组序号为变量的脉 冲星集合稳定性判据。     

基于频偏应答的ADCP流速现场校准方法研究

针对声学多普勒流速剖面仪(ADCP)现场校准困难的问题,介绍了一种基于频偏应答的ADCP流速现场校准方法.通过声信号应答器,设置回发信号相对于发射信号的频偏实现速度矢量的模拟,并以频率为溯源量,对ADCP发射的信号及应答器回发频偏信号进行频率校准,进而实现ADCP流速参数的现场校准.研制了一套基于频偏应答的ADCP流速...     

非自动衡器测量不确定度评估及其在符合性判定中的应用

以OIMLR76国际建议中非自动衡器的称量试验为例,列举了2种容易对非自动衡器称量性能做出误判的情形.结合电子天平称量试验的3个案例,分析了修正误差与最大允许误差限较为接近时,直接采用"简单判定原则"作出符合性判定的误判风险,通过对线性载荷误差测量不确定度评估,分别对3个案例给出了95.45％、80.6％和18.1％的...     

基于YOLOv3检测和特征点匹配的多目标跟踪算法

针对传统多目标跟踪算法中行人检测速度慢、易受光照变化、行人快速移动及部分遮挡因素的影响造成行人目标跟踪性能差等问题,提出一种根据经典的Tracking-by-Detection模式,采用深度学习YOLOv3算法检测行人目标,然后利用FAST角点检测算法与BRISK特征点描述算法对相邻帧间的行人目标进行特征点匹配,实现多...     

激光剪切干涉用于在线表面测量的特性分析

为探讨和证明双折射晶体激光剪切干涉仪用于在线表面精密测量的可能性,推导了该干涉仪中光传输和实现表面测量的模型,分析了其抗振特性,模拟了相当的振动条件对其抗振特性进行实验测试.分析和实验证明了该干涉仪具有良好的抗振能力,适合应用于在线表面精密测量.