Concentration measurements of bubbles in a water column using an optical tomography system

Optical tomography provides a means for the determination of the spatial distribution of materials with different optical density in a volume by non-intrusive means. This paper presents results of concentration measurements of gas bubbles in a water column using an optical tomography system. A hydraulic flow rig is used to generate vertical air-water two-phase flows with controllable bubble flow rate. Two approaches are investigated. The first aims to obtain an average gas concentration at the measurement section, the second aims to obtain a gas distribution profile by using tomographic imaging. A hybrid back-projection algorithm is used to calculate concentration profiles from measured sensor values to provide a tomographic image of the measurement cross-section. The algorithm combines the characteristic of an optical sensor as a hard field sensor and the linear back projection algorithm.     

一种泡沫柱中气泡特性的测试装置

介绍了采用光－电原理测试泡沫柱中气泡特性的装置。采用两对红外发射对管作传感器，数据采集采用单片机，一次可采集１００００个气泡。通过计算机进行数据处理，可获得气泡的平均直径、气泡分布、含气率及气泡密度。用该装置测试具有迅速、准确、适应范围广的特点。     

PET block detector calibration using subtractive clustering algorithm and comparison with hough transform algorithm

Detector calibration plays an important role in improving of image quality and increasing performance of positron emission tomography (PET) systems. To achieve this aim, raw data coordinate event-byevent are mapped to the index of the crystal in which the particle is absorbed. We proposed and tested subtractive clustering and Hough transform algorithms to determine crystal peak position and generate an appropriate look-up table. The results show superiority of Hough transform to the subtractive clustering and other methods because this algorithm determines position of all peaks, even in irregular and unclear data. The acquired results can be beneficial for all of the medical imaging instruments such as PET and single-photon emission computed tomography detectors based on pixilated scintillators.     

A semiautomated approach for artefact removal in serial tissue cryosections

Thinly sliced serial tissue sections of an organ can be imaged using optical microscopy at a resolution detailing individual cells. When the tissue sections are first subjected to in situ hybridization or immunohistochemistry, these data sets can be analysed for changes in gene expression and gene products. Such spatial information is important for understanding the functional effects of experimental or environmental challenges to the organism. However, a critical step in analysing these data sets is mitigating artefacts that result from the preparation of the tissue sections. In this paper, we describe an automated method with manual validation tools that together enable detecting and addressing artefacts including dust particles and air bubbles.     

Data fusion in dual-mode tomography for imaging oil–gas two-phase flow

Process tomography (PT) techniques have been developed rapidly for visualizing the internal behavior of industrial processes, e.g. multi-phase flow measurement. Most of tomography systems employ a single measurement technique, such as computerized tomography (CT), optical tomography (OT), electrical resistance tomography (ERT) or electrical capacitance tomography (ECT). It is now possible to fit two or more tomographic systems to an industrial process. Detailed information from different modalities can be gained by inspection of separate tomographs, and the advantage of the strongest features provided by each unit can be taken. A combined tomogram can be produced of superior quality to any of the separate tomograms. To maximize the information available from the combined tomographic system, data fusion is the better option. In this paper, a dual-mode tomography system based on capacitance sensor and gamma sensor was developed to capture oil–gas two-phase flow. The two modalities can work at the same time. Two fusion methods, namely image fusion method and data fusion method, are proposed. Both simulation and static experiments for oil–gas two-phase flow were conducted. The reconstruction results of different fusion methods and modalities were compared and discussed.     

在轨光学相机探测图像数字仿真系统设计与实现

根据在轨光学相机测量原理与工作环境,建立了空间目标相对运动学与反射光学特征模型、相机成像模型以及背景恒星成像模型;分析了相机测量噪声及相机探测灵敏度并在仿真中考虑了对干扰因素成像质量的影响,完成了现有星表中背景恒星的视星等根据相机的探测波段范围进行了仪器星等的等效计算,以提高仿真图像的逼真度;根据相机工作原理设计了仿真流程,应用Visual C++与Open GL技术完成了仿真软件的实现。     

Comparison between wire-mesh sensor and ultra-fast X-ray tomograph for an air–water flow in a vertical pipe

A comparison between ultra-fast X-ray CT and a wire-mesh sensor is presented. The measurements were carried out in a vertical pipe of 42 mm inner diameter, which was supplied with an air–water mixture. Both gas and liquid superficial velocities were varied. The X-ray CT delivered 263 frames per second, while the wire-mesh sensor was operated at a frequency four times higher. Two different gas injectors were used: four orifices of 5 mm diameter for creating large bubbles and gas plugs and a sintered plate with a pore size of 100 μm for generating a bubbly flow. It was found that the wire-mesh sensor has a significantly higher resolution than the X-ray CT. Small bubbles, which are clearly shown by the wire-mesh sensor, cannot be found in the CT images, because they cross the measuring plane before a complete scan can be performed. This causes artifacts in the reconstructed images, instead. Furthermore, there are large deviations between the quantitative information contained in the reconstructed tomographic 2D distributions and the gas fractions measured by the sensor, while the agreement is very good when the gas fraction is obtained by a direct evaluation of the X-ray attenuation along the available through-transmission chords of the tomography set-up. This shows that there is still potential for an improvement of the image reconstruction method. Concerning the wire-mesh sensor it was found that the gas fraction inside large bubbles is slightly underestimated. Furthermore, a significant distortion of large Taylor bubbles by the sensor was found for small liquid velocities up to 0.24 m/s. This effect vanished with growing superficial water velocity.     

Application of ECT and relative change ratio of capacitances in probing anomalous objects in water

Nowadays electrical capacitance tomography (ECT) is mainly adopted for detecting dielectrics of low permittivity in chemical and petroleum industries. In these fields, to meet the demand of measuring capacitances within the range of low values, ECT still needs relatively high requirements of designing its system. In this work, an ECT system is simplified to probe anomalous objects in water with high permittivity. Additionally, the relative change ratio (RCR) of capacitances is presented for image reconstruction in terms of the high permittivity background. RCR is the change value of a capacitance divided by its background value. To verify the effectiveness of the simplification of an ECT system and the method of RCR for image reconstruction, simulations and experiments associated with media of high permittivity (i.e. water) were conducted. The obtained results demonstrate that the simplified ECT system based on RCRs of simulated and measured capacitances is capable of effectively probing anomalous objects in tap-water and sodium chloride solutions with different concentrations. Therefore the RCR is recommended when the sensing domain of ECT is of the high permittivity background. Besides the simplification of ECT systems can be appealing and beneficial to introduced ECT into other fields associated with water flows, such as hydrology, hydrogeology, hydroponics, environment science, etc.     

Experimental PIV and LIF characterization of a bubble column flow

Experimental 2D Particle Image Velocimetry (PIV) measurements, with uniform background lighting and Laser Induced Fluorescence (LIF) of the tracking particles, were performed in order to characterize the air-water biphasic flow and the 2D bubble column rising velocity in static water. Some applications require knowledge of the simultaneity of two-phase flow characteristics. The two phase flow air/water are common application in industry as chemical, hydraulic and nuclear industry, water treatment by aeration, and measurements are implemented to characterize the behaviour of the air bubbles column flow. The bubble flow studied in this paper is related to the optimization of the aeration in hydraulic turbines with micro-bubbles. The first step of this study, presented in the paper, is a complete characterization of a bubble column issued from a metallic sparger with holes of 0.5 mm diameter. For its complete characterization is determined simultaneously, via image processing technics, the flow velocity field induced by the column of bubbles in water, and the bubbles features: the bubble ascension velocity, diameter variation, interfacial area and shape factor. The results are compared with bibliographical data.     

Information characteristics of a crystallization zone image in the Czochralski method

Data on computer modeling a meniscus image of a crystal grown by the Czochralski method from a high-temperature melt are presented. A fine structure of the crystallization zone image formed by an optical projection system is investigated as well as the image components conditioned by intrinsic emission of the heater, melt, and crystal, and by emission reflections from melt and crystal surfaces. Causes of meniscus image parallax are analyzed; its influence on metrological characteristics of the optical crystal geometry control system is assessed.     

血液流动性的计算机可视化测定及其技术应用

简要描述了日本MCFAN研究所生产的血液流动性可视化检测仪的测定原理、实验方法和临床应用。血液流动性的可视化测定仪（以HR300型为例）将进样系统、计算机处理系统、显微摄像等一体化（Micro Channel Array Flow Analyzer,MCFAN）,使操作繁琐的血液流变性观察检测变得简便易行,并通过液晶显示器可观察到血流的状态,具有直观形象的特点。广泛用于预防医学、药物研究、疾病诊断和健康教育等领域,并为大众健康咨询提供了直接支持,本文比较全面的介绍了血液流动性的检测方法及其临床应用。     

液体中气泡生成影响因素的试验研究

为了提高浆态床反应器内的气含率,提高反应速率,利用高速摄影技术,研究了气泡在液体中形成的特性,在不同气孔内径、不同气体流量下分别考察了平面孔、内伸孔2种进气方式对气泡在水中生成的影响,测算了气泡脱离时的大小及生成所用时间;并考察了内伸孔高度、水温对气泡生成的影响。结果表明:相同试验条件下,生成气泡大小分别随着气孔内径、气体流量的增大而增大,内伸孔进气生成的气泡体积小,用时短,且与内伸孔的内伸高度有关;高温水中气泡生成用时较短,体积较小。     

位置敏感探测器（PSD）的研究进展

回顾了位置敏感传感器(PSD)的发展历史,介绍了各种光敏面结构的PSD。并结合研究成果,阐述了单晶硅、氢化非晶硅、有机材料、大面积挠性薄膜、CMOS型,一维及二维阵列PSD等采用各种组成材料和工艺制作的PSD的发展现状,并对今后的发展和研究方向进行了展望。     

便携数字式超声探伤仪

介绍了超声检测在起重运输机械中的应用,在分析超声波探伤原理的基础上,提出超声波探伤系统的硬件和软件设计方法.该系统用于起重运输以及其相关的行业,是安全作业和运行的有力保障.经过长时间的运行,证实系统工作稳定、性能良好.     

一种红宝石荧光光纤温度传感器的研究

介绍一种基于具有稳定的物理和化学性能、价格便宜的红宝石晶体荧光光谱温度特性的光纤温度传感器的原理及系统设计方法。研究结果表明,该光纤传感器具有性能稳定、成本低的特点,特别适合于对大型机电设备内部温度以及各种加热炉、感应炉的温度测量。     

基于多层Hopfield神经网络的X射线焊缝气泡检测

提出利用Hopfield神经网络来分割X射线焊缝图像以判断焊缝是否存在气泡,将焊缝图像的分割问题转化为一个优化问题进行处理.针对焊缝图像噪声大、气泡出现位置随机的特点,构造Hopfield神经网络的能量函数.通过试验计算,确定能量函数系数的选取原则.在此基础上,提出基于神经网络的X射线焊缝图像分割算法,算法结合中值滤波和神经网络以便有效地去除噪声和检测气泡.对某实际生产线的焊缝图像进行处理的结果表明,中值滤波结合多层Hopfield神经网络可以准确地检测到焊缝中的气泡.     

基于时域结构的光学相干层析系统的调试

基于时域结构的光学相干层析系统由于光线多次通过,按照光路可逆原理调整会很困难.在理论分析和多次实验基础上,现总结出一套快速调试方法,大大缩短光路调试时间.详细分步骤描述了纵向傅里叶快速扫描光学延迟线和横向扫描部分的调试方法,给出快速寻找干涉系统光程匹配点的调试方法.利用构建好的光学相干层析系统进行层析成像实验调试,纵向...     

Linear computed tomography of two-phase distribution in a rectangular channel

Two-phase flow is closely linked with the efficiency and safety of industrial processes in many fields, and there are various instruments for measuring the two-phase distribution. Among them, γ-ray and ultrafast X-ray tomography systems are most promising to break the technical barrier of gas-liquid measurement in the flow channel of high-temperature and high-pressure (up to 15 MPa/342 °C) nuclear reactors. Hence, A CT measurement method has been developed for imaging a two-phase distribution of a central plane oriented in axial direction in a rectangular duct, which was tested theoretically using a numerical phantom and experimentally on a preliminary tomographic hardware with a mechanically traversed gamma source and a detector unit, as well as a static phantom simulating gas bubbles in the pipe. After completing experimental and numerical imaging of a multi-bubbles phantom, the two-phase contrast and locations of bubbles in the experimental and simulated reconstruction images showed a good agreement and supported the feasibility of applying the linear scanning technique to realize two-phase detection in rectangular channels. The sensitivity analyses of scanning range, photon-registering time and scanning step length conveyed the optimal experimental strategy for this system. Morphological operation has also been imposed on image processing achieving elimination of severe ringing artefacts.     

红外探测器件在低温背景下的探测率测试

建立了红外探测器件低温背景探测率测试系统,实验研究了红外探测器件在低温背景下的探测特性,用于支持红外探测低温光学系统的合理设计.首先,介绍并分析了红外探测系统的噪声和响应特性,建立了低温光学系统设计与红外探测器件在低温背景下探测性能之间的关系;在热真空环境下搭建了基于变温面源黑体的低温背景探测率测试系统.然后,针对某红外器件在低温背景下的探测率进行了实验测量.最后,通过计算得到了低温背景下极限积分时间及探测特性相对于常温背景下的一般变化规律.实验结果表明:低温背景下极限积分时间及探测率均比常温背景下提高近20倍,提出的测试技术可为低温光学系统的指标设计提供依据与参考.     

Development of a mathematical model of the hydroerosive wear of the piston couple in hydraulic machines: Part 1

The paper presents a definition of hydroerosive wear, which occurs in hydraulic machines due to water/air presence in fluid, obtained from a mathematical model. The model includes fatigue processes related to the influence of hydraulic water droplets inside of air bubbles in the surface layer of metal, as well as a sharp increase in temperature caused by adiabatic compression in the piston chamber of a hydraulic machine.