超疏水表面的减阻研究

为探索超疏水表面的减阻机制,利用位错刻蚀法在铝板上制备出接触角为156°、滚动角小于5°的超疏水表面,并分别以具有超疏水表面和亲水表面的铝板为基板,构建了两种流动状态可视化测试的微粒子图像测速(Particle Image Velocimetry ,PIV)微通道,通过PIV粒子图像测试技术对水在超疏水微通道和亲水微通道中的速度流动情况进行实验测定与对比,得出超疏水表面确实有减阻效果,最大减阻效果可达8.72%,并从多角度进行了解释分析.     

微通道板式WSZ位敏阳极探测器的图像拖尾处理

分析了极紫外成像仪图像拖尾的原因,提出了消除该现象的方法.分析了坐标计算公式中各个分量变化对图像的影响,结果显示:信号叠加和微通道板(MCP)反馈是系统对坐标分量影响最大的两种因素.通过对图像数据的分析,排除了信号叠加的两种情况即峰堆积和尾堆积产生拖尾的可能性.对拖尾最严重处电荷变化量的计算表明,MCP反馈是产生拖尾的主要原因,而MCP所加高压的幅度是产生反馈的重要因素之一.最后,用在2 950 V和2 800 V高压下采集的图像验证了拖尾是由MCP反馈引发的,并通过实验给出了解决方案:通过烘烤减少MCP通道内的气体残留并定期对MCP进行电子束清刷来降低反馈发生的几率,减小拖尾的影响.     

基于视觉原理的三维光阱刚度测量系统

光阱刚度是表征光镊捕获微小颗粒能力的重要参数。文中搭建了一套基于视觉原理的三维光阱刚度测量系统。测量系统中采用波长1 064 nm的近红外激光光镊捕获直径2μm的聚苯乙烯微球,采用基于视觉原理的光路对微球成像,由高速摄像机记录微球的布朗运动。对高速摄像机采集的相邻图像进行亚像素的位移提取,获取微球的三维位移,采用功率谱法得到相应的光阱刚度。     

基于CoaXPress的图像采集系统设计

针对目前高帧频相机输出图像数据量大的特点,为实现高速图像数据的稳定采集与传输,设计了一种高吞吐率、高稳定性、高抗干扰能力的CoaXPress协议图像采集系统。该系统以FPGA作为核心处理及控制单元,采用GTH收发器实现高速图像数据接收,设计了单链路逻辑、流复用与解码以及相机控制等模块,实现了符合CoaXPress协议的数据传输、相机控制以及高速图像流解码,系统开放了透明的数据接口以进行二次开发。板级测试表明,采集系统实现了吞吐率高达2.09GB/S的稳定高速图像采集且误码率小于10-10,通过串口指令对相机实时控制,可满足高精度视觉测量应用需求,具有广泛的应用价值。     

磁力搅拌湍流场的PIV测量及流场演变的POD分析

为了解磁力搅拌过程湍流特性,对其开展了激光粒子图像测速(PIV)试验,并进行了本征正交分解(POD)分析.分析表明,在测量平面转子外部区域,除平均流动,含能量较高的流动结构为循环剪切流和转子旋转的尾涡结构.在搅拌槽底部具有较高的旋涡强度,有利于固体颗粒悬浮.流体与转子之间的流-固耦合作用使转子产生振荡,随转速升高,系统...     

微球动态涂敷状态实时监测系统的实现

设计一套新型的微球动态涂敷状态实时监测系统。利用QM-1显微望远系统和GDS-50摄影镜头相结合获得位于1.2m处25mm视场内直径为0.2mm~0.5mm的多个微球涂敷时的清晰像,视频处理系统采集微球的像,并用数字图像处理的方法对采集到的图像进行处理,有效区分背景、运动目标和静止目标。一旦发现有微球停止运动给出警告,实现涂敷作业的自动监视。     

工件表面质量检测中高速图像采集技术研究

针对工件表面质量在线检测过程中的高速图像采集环节,提出了一种工件图像高速采集方法。分析了图像采集中定位精度、运动模糊、曝光时间和工件运行速度之间的定量关系,研究了传送机构与工件表面的振动对图像采集的影响,设计了图像采集时序。利用光电传感器实现工件的快速触发,使用高精度延时模块实现工件的准确定位,通过减小曝光时间控制运动模糊。基于高速采集方法设计了高速图像采集系统,定位精度小于0.1mm,运动模糊小于1pixel,保证了工件的准确定位和图像的清晰度,有效保证了工件表面质量检测。     

基于高速摄像的引线键合高尔夫球现象形成规律实验研究

利用高速摄像系统记录不同打火参数下打火杆放电、尾丝熔化成球的序列图像。通过MATLAB对图像进行图像处理,得到最终成球的直径及其球心与尾丝中心线的偏距。实验发现,在较大的打火电流(I=60mA)或较小的预设球直径(D=40.64μm(1.6mil))等条件下,球心与尾丝中心线的偏距不稳定且相差较大,易出现高尔夫球现象,严重影响引线键合的质量。     

激光聚焦线扫描法测量KDP晶体坯片的体缺陷

为了快速准确测量磷酸二氢钾(KDP)晶体坯片的体缺陷,提出了高速激光聚焦线扫描散射成像方法,并建立了相应的测量系统。研究了该系统的测量原理和图像采集、图像处理和体缺陷信息提取方法。基于激光散射技术,结合高速运动装置对晶体坯片内部进行三维扫描,用线阵CCD探测器接收气泡、包裹物等体缺陷产生的散射光。然后利用折射率匹配液消除粗糙表面带来的不利影响。最后结合数字图像处理技术,对采集的图像进行实时处理。通过去除背景后与设定阈值比较得到具有体缺陷特征的图像,再对其进行二值化处理,提取得到体缺陷的位置和尺寸信息。利用该检测装置对KDP晶体坯片体缺陷进行了测量,结果显示其检测分辨率优于40μm,能够为晶体坯片的精确切割和最大程度的利用提供依据,从而节省了大量成本。     

PLC电机转速测量系统设计与实现

针对工业控制领域电机转速测量问题,设计了一种通用测量系统。该系统采用光电编码器作为电机转速的脉冲产生装置,利用西门子S7-200 PLC的高速计数器采集光电编码器产生的脉冲信号,根据M法测速方式,由PLC实时计算电机转速。测试表明,该通用测速系统快速可靠准确,可用于工业控制领域电机转速测量。     

Phase discrimination and a high accuracy algorithm for PIV image processing of particle–fluid two-phase flow inside high-speed rotating centrifugal slurry pump

PIV technology is an efficient and powerful measurement method to investigate the characteristics of fluid flow field. But for PIV particle image post-processing, some problems still exit in two-phase particles discrimination and velocity field algorithm, especially for high-speed rotating centrifugal slurry pump. In this study, through summarization and comparison of the various phase discrimination methods, we proposed a two-phase identification method based on statistics of gray-scale level and particle size. The assessment of performance through experimental PIV images shows that a satisfying effect for particle identification. For high speed rotation of the impeller, a combination of adaptive cross-correlation window deformation algorithm and multistage grid subdivision is presented. The algorithm is applied to experimental PIV images of solid–liquid two-phase flow in a centrifugal slurry pump, the results show that the algorithm in the present study has less pseudo vector number and more matching particle pairs than those of fixed window and window translation methods, having the ability to remove pseudo vector efficiently. It confirmed that the algorithm proposed in the present study has good performance and reliability for PIV image processing of particle–fluid two-phase flow inside high-speed rotating centrifugal slurry pump.     

A real-time vision system for defect inspection in cast extrusion manufacturing process

The cast extrusion manufacturing process is the initial step which enables the creation of the raw materials, such as clear polypropylene film, needed for the flexible packaging printing process. The current methodology of controlling extrusion-related defect occurrences is attempted by a combination of statistical sampling and human inspection. However, due to the fact that the defects are small in size and hard to visualise in a clear thin film 2 m in width moving at a speed of 50 m/min. This results in poor product quality and high return ratio from customers. To the best of our knowledge, there is no system available that can accurately detect such defects. This research investigates possible defect detection methodologies and has subsequently proposed a system that is capable of real-time monitoring of defects on the cast extrusion manufacturing process. The proposed system utilises the refraction of a collimated light source, which is referred to as Mie light scattering. A vision analysis system is subsequently used to perform a blob analysis to detect the contrasting dark regions of the defects. Two test rigs were constructed to test the feasibility of the system. The first test rig was created to test the theoretical Mie scattering principles and the performance of the image analysis software in practice. The second test rig was created to test the practicability of integrating the Mie scattering theory on the physical cast extrusion line. The results obtained from the tests indicated a success rate of 90% in identifying gels and a 100% success rate in correctly identifying all the die lines presented in the tested samples. It is also deduced that the software has a capability to detect gel granules with a diameter greater than 480 μm and die lines with a thickness greater than 320 μm amid complete repeatability, ensuring that the proposed system fully conforms to the standard industrial requirements.     

尘埃粒子的激光散射测量

激光散射法是快速、准确测定尘埃粒子大小的新方法。从Mie散射理论出发,提出了尘埃粒子的激光散射测量系统中各部分的设计要求,以及达到这些要求的一般方法。给出了一个测量系统的实例。     

Detection of river flow slow-down through sensing system and quasi-real time imaging

Flow slow-down in rivers and artificial canals is a basic aspect to be monitored and kept strictly under control. Flow slow-downs can become a major concern in the event of extreme phenomena. The paper illustrates an advanced image processing method that uses particle tracking velocimetry in conjunction with a monadic approach to better characterize water flow in the presence of waste or debris that block normal water flow within a river. An high-speed camera installed beneath a bridge takes periodic images of the water flow. The measured water level and the images taken by the camera are sent to a central system in real-time. Results demonstrate the capability of the proposed method to accurately detect the presence of debris from the measured water flow.     

Fluorescence imaging with a laser trapping scanning near-field optical microscope

We investigated fluorescence imaging using a near-field scanning optical microscope which uses a laser-stabilized gold nanoparticle as a near-field probe. This microscope is suitable for observations of biological specimens in aqueous solutions because the probe particle is held by a noncontact force exerted by a laser beam. Theoretical calculations based on Mie scattering theory are presented to evaluate the near-field enhancement by a gold particle of 40 nm diameter. We also present fluorescence images of a single fluorescent bead and discuss the near-field contribution to the fluorescence image in this type of microscope.     

Fluorescence imaging with a laser trapping scanning near-field optical microscope

We investigated fluorescence imaging using a near-field scanning optical microscope which uses a laser-stabilized gold nanoparticle as a near-field probe. This microscope is suitable for observations of biological specimens in aqueous solutions because the probe particle is held by a noncontact force exerted by a laser beam. Theoretical calculations based on Mie scattering theory are presented to evaluate the near-field enhancement by a gold particle of 40 nm diameter. We also present fluorescence images of a single fluorescent bead and discuss the near-field contribution to the fluorescence image in this type of microscope.     

Three-dimensional laser interferometric CT (LICT) measurement of shock wave interaction around a circular cylinder

Three-dimensional (3-D) laser interferometric computed tomography (LICT) measurement has been applied to high-speed and unsteady flow including shock waves. The purpose of our investigation is to clarify 3-D flow phenomena quantitatively by using LICT. We used a diaphragm-less shock tube to clarify the unsteady shock wave behavior with the shot by shot method. The diaphragm-less shock tube enables us to obtain shock wave propagation reproduction in quick succession. By LICT the 3-D internal density structure of the shock–vortex flow field can be clarified. In this LICT method the observation system consists of a CCD camera, Mach–Zehnder interferometer, and nitrogen pulse laser as a light source with a suitable delay signal controller. The 3-D density CT data can be reconstructed typically from the 19 2-D density images which have a 5° interval among every shot of the diaphragm-less shock tube. As for the method to get many projection images, the optical system is fixed, while the model with a cylindrical duct and a cylinder is rotated by a fixed degree of intervals in the designated observation angle for every shot. In this paper the shock wave interaction with a finite length circular cylinder is observed by LICT measurement. For reconstruction of density distribution the Algebraic Reconstruction Technique (ART) is applied to reduce the artifact, together with precise observation.     

用于机械系统瞬时目标的双视角高速视觉检测系统

基于高速相机研发了双视角高速视觉检测系统。该系统可从不同角度对周期机械运动进行长时间、无接触的同步实时检测,并可自动判断和存储异常动作的瞬时高帧率视频图像。基于机械系统运动特性提取理论,提出了多视角高帧率视频图像的离线处理算法,利用两个高速相机准确建立了样本图像数据库及它们的对应关系。提出了多视角同步实时检测算法,完成了对目标的实时视觉检测,并实现了瞬时保存关键图像的功能。为验证算法的有效性和系统的稳定性,搭建了双视角高速视觉检测系统,对真实的机械系统进行了实验。结果显示,提出的系统实现了500fps的双目高速相机同步检测,以及0.1s内运动目标的自动判断,同时完成了对关键图像的瞬时保存。文中的研究为机械系统的非接触检测提供了一种高速可视化的检测方法。     

污染扩散流场数字图像量测系统

为在环境风洞实验中模拟污染物的扩散流场及变化情况,基于光学粒子散射理论和数字图像处理技术,并利用粒子图像测速(particle image velocimetry,PIV)技术,研制了一套具有全流场量测、非接触及低成本等特征的瞬态流场定量光学测量系统。将系统用于环境风洞模拟中,可对城市小区、街道峡谷及交通高架污染物等的扩散状况进行定性观察,还可对污染物的流场进行定量量测。可为污染物流场的理论研究、数值计算及环境规划提供参考。     

微脉冲激光雷达反演气溶胶的水平分布

城市近地面气溶胶的分布随时空快速变化,常用的地基定点监测只能获取区域内有限位置的气溶胶质量浓度,大致反映区域内气溶胶的分布情况。为确定气溶胶和污染物在城市近地面水平路径上的分布情况,利用微脉冲激光雷达(MPL)、粒子计数器、能见度仪和颗粒物质量浓度监测仪获得的气溶胶数据,根据Mie散射理论建立了气溶胶消光系数、粒子谱分布和质量浓度等参数的数学模型,反演得到了水平路径上的气溶胶质量浓度分布。该方法可以以测量点为中心进行0~6km的360°的水平扫描,具有监测范围大、分辨率高的优点。最后开展了气溶胶水平分布的实际测量,获得了距离6km长的水平路径上近地面气溶胶质量浓度的实时分布。这为研究城市气溶胶的污染来源和动态变化提供了有效的数据支持。