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。     

Simulation of dynamic bubble spectra in tissues

Decompression sickness (DCS) is the result of bubble formation in the body due to excessive/rapid reduction in the ambient pressure. Existing models relate the decompression stress either to the inert gas load or to the size of a single bubble in a tissue compartment. This paper presents a model that uses the gas exchange equations combined with bubble dissolution physics and population balance equations to produce a new mathematical framework for DCS modeling. This framework, the population balance model for decompression sickness (PBMDS), simulates the number of bubbles with their corresponding size distributions in a compartmental tissue array. The model has a modular structure that enables one to explore different modeling results with respect to key aspects of DCS, such as gas exchange, nucleation, and surface tension. The paper's goal is to present the derivation of PBMDS in detail, however, three simple application case studies are provided. The aim of these case studies is to suggest that PBMDS supplies additional information on bubble distribution while supporting the results from current practice.     

不同环境压强下激光空泡特性研究

构建了激光空泡测量实验平台,使用脉冲激光聚焦击穿水介质产生激光空泡,由水听器对激光空泡溃灭辐射声信号进行接收,利用充气泵对高压水箱内的气压进行精确控制。通过仿真计算和实验对不同环境压强下的激光空泡特征和其溃灭时辐射声信号的峰值变化特性进行了研究。结果表明:当环境压强处在0.1~0.7 MPa 范围内变化时,随着环境压强的增大,激光空泡首次脉动周期和空泡最大半径逐渐减小,两者的变化速率逐渐减小。空泡溃灭时辐射声信号的峰值声压在0.1~0.4 MPa内逐渐增大,在0.4~0.7MPa 内逐渐减小,且增大速率大于减小速率。     

尾流气泡激光散射的测量

采用收发分置的光学结构实现了尾流气泡对532 nm激光在散射角5°～175°内的散射测量,同时测量了水的激光散射。散射角度的改变是通过发射系统不动而转动接收系统来实现的。解决了散射信号大动态范围的压缩问题,讨论了接收视场内散射体积随散射角的变化。分析了气泡散射的信号特征,并提出了气泡散射信号的功率谱密度处理法。将实验结果与米氏理论结果进行了对比,发现尾流气泡的激光散射强度及其随散射角的变化趋势与米氏理论结果吻合得很好,与水的散射相差近一个数量级。研究结果表明利用激光可以将气泡和水的散射区别开,即利用激光探测尾流气泡的存在具有可行性。     

气液两相流三维测量中虚拟立体视觉传感器的优化设计与实验

针对高速动态的气液两相流动对象,基于双目体视原理,采用单台高速摄像机和反射镜组,对虚拟立体视觉传感器进行了优化设计;对气泡发生装置中竖直向上的气泡特征参数进行三维测量。建立虚拟立体视觉传感器三维测量模型,综合考虑实际视场、传感器结构和测量误差等因素,通过结构参数对3方面性能影响的仿真分析,最终确定传感器的结构参数。实验结果表明,传感器测量空间距离误差优于0.14 mm,相对误差优于0.49%,适于气液两相流动态测量,可以实现气泡运动的三维重建。     

Modeling the detachment and transport of bubbles from nucleation sites in small vessels

Decompression sickness is known to be due to the formation of bubbles in the body as a result of decompression. It is likely that these bubbles form from pre-existing nuclei, which, for bubbles in the bloodstream, are thought to be housed within blood vessel walls. Gas pockets emerging from these sites will be subject to forces due to blood flow, a portion of the gas eventually being swept away to form a free bubble in the bloodstream. These continue to grow and may grow to similar dimensions to the vessel, developing into elongated "gas plugs," potentially occluding the flow. In this correspondence, we derive a simple model to investigate whether this vessel occlusion is a serious concern.     

水中气泡激光后向散射衰减特性研究

采用Lambert-Beer定律对水中气泡后向散射光功率进行理论分析,并采用激光功率计对位于不同距离以及不同密度的气泡幕后向散射光功率进行测量,对测量数据进行了统计和分析.结果表明,气泡的后向光散射信号相当微弱,但由于气泡幕的存在,后向散射光功率有所增强;气泡幕后向散射光功率随气泡幕与探测器之间的距离变化,其关系服从Lambert-Beer定律;后向散射光功率与气泡密度有关,气泡密度越大,后向散射光功率越大.     

激光探测尾流微气泡的偏振特性研究

为了研究尾流中激光照明气泡幕的散射光强度和偏振的特性,利用基于偏振光传输的蒙特卡洛模型,对偏振激光入射含气泡群水体的三维空间分布模式进行仿真计算。研究了气泡和气泡群在不同气泡尺度,不同散射角条件下的散射光强和偏振状态;分析了气泡幕的气泡数密度,厚度对于散射光强度和偏振状态的影响。研究表明,散射光的强度和偏振度对气泡尺度和散射角较为敏感,气泡尺度参数越大,散射光强和偏振特征越趋向于集中在传输方向的小角度散射;气泡幕的数密度和厚度越大,散射光的强度随散射角度变化的敏感度下降,退偏振效果增强。     

Light Fueled Manipulation of Bubble Motion Against Buoyancy via Photosensitive Substrate

Flexibly and precisely controlling bubbles is of paramount significance for biological and chemical analysis, reaction engineering, etc. However, the buoyancy force acting on bubbles is significant, making it difficult to precisely manipulate bubbles. Particularly, controlling the anti-buoyancy motion of bubbles remains a fundamental challenge. Herein, a versatile light strategy for manipulating the anti-buoyancy motion of bubbles via a photosensitive substrate is developed. Upon focused laser beam irradiation, an intense Marangoni effect associated with non-uniform temperature distribution is induced underneath the bubble. The created excess Laplace pressure drives the bubble to move against the buoyancy force downward to the focused-laser-acted region, manifesting an excellent phototaxis motion. Theoretical analysis demonstrates that the Marangoni effect is responsible for actuating the anti-buoyancy motion of a bubble. With this light strategy, the bubble collection, transportation, and on-demand release can be flexibly implemented. Moreover, the phototaxis motion of bubbles inspires a manipulation protocol via the integration of 3D-structured design of photosensitive substrate. This light strategy for manipulating bubbles not only possesses sufficiently high accuracy and quick response, but also circumvents the limitation of the liquid volatility and multi-dimensional motion, which provides new ideas for rational control of bubble behaviors.     

熔石英表面损伤修复点上气泡特征及控制方法的研究

损伤修复点上的气泡是诱导修复点在激光辐照下再次损伤的主要因素,研究了蒸发式和非蒸发式两种损伤修复方式在修复过程中产生的气泡的类型和特征。结果表明,无论哪种修复方式在修复过程中得到的气泡都可以分为球形和非规则椭形气泡两种类型,且气泡的类型与损伤点周围裂纹的形状和尺寸有极大关系。损伤考核结果表明,修复点的损伤阈值会随着气泡数量的增加而呈指数递减趋势变化。讨论了在修复过程中控制和消除气泡的方法和措施,给出优化的处理参数。     

Three-dimensional measurement of bubble volume based on dual perspective imaging

This paper presents a new three-dimensional (3D) volume measurement approach of bubble in gas-liquid two-phase flow. According to the dual perspective imaging principle, bubble feature images can be captured from two different view angles. The least square ellipse fitting algorithm is used to figure out the feature parameters from the captured images. Then the 3D volume of bubble can be quantitatively measured. Compaerd with the traditional volume estimation methods based on single perspective imaging, it can effectively reduce the loss of bubble feature information. In the experiment, the 3D volume reconstruction of bubbles from dual perspective images is conducted, and the variation of bubble volume in the bubble rising process is studied. The results show that the measurement accuracy based on the proposed 3D method is higher than those based on traditional methods. The volume of rising bubble is periodically changed, which indicates that bubble achieves periodic rotation and deformation in the rising process.     

气泡尾流光束衰减测量中的复散射校正

为了分析复散射对气泡尾流衰减测量的影响,采用小角度辐射传输方程,引入了表征复散射效应强弱的校正因子,通过数值求解分析了典型的尾流气泡尺度分布和数密度条件下复散射校正因子与接收视场角、光学厚度、光束大小和接收截面大小等参量之间的关系。结果表明,接收视场角在前向小角度范围内的变化对复散射校正因子的影响很大,而视场角较大时对复散射校正因子的影响基本相同;光学厚度的变化对复散射校正因子的影响显著,且在光学厚度小于1时,影响更明显;接收截面大小的变化在光学厚度小于1时对复散射校正因子的影响很小,但在光学厚度较大时,对复散射校正因子的影响比较明显;光束大小的变化对复散射因子的影响相对较小,且在光束束腰较大时对复散射因子的影响基本不变。该研究为尾流光束衰减测量条件的选择和优化提供了理论依据。     

Study of the Formation of Bubbles in Rigid Substrate-Flexible Substrate Bonding Using Anisotropic Conductive Films and the Bubble Effects on Anisotropic Conductive Film Joint Reliability

The formation of process-related bubbles that become entrapped inside the anisotropic conductive film (ACF) layer during bonding processes remains an issue. The formation of these bubbles is strongly influenced by the process variables, such as bonding pressure and bonding temperature. Therefore, bonding process variables of bonding temperature, bonding pressure, and type of flexible substrate (FS) were changed in order to investigate the effects of the changes as they concern the formation of bubbles. According to the results, the tendency toward bubble formation was closely related to these three factors. The bubble area increased as the bonding temperature increased. Moreover, the shape and tendency of bubbles coincided with temperature distribution in␣the ACF layer. Two different types of FS, each with different surface roughnesses and energies, were used. The bubbles formed only on the FS with the larger roughness and lower surface energy. According to the results from a surface energy measurement of FS types using goniometry, a FS with a higher surface energy is favorable for a bubble-free assembly, as the higher surface energy provides better wettability. In addition, in order to investigate the effect of bubbles on the reliability of ACF joints, the pressure cooker test (PCT) was performed, and all samples with bubbles electrically failed after 72 h of a PCT, as the process-related bubbles provided a moisture penetration path and entrapment site for moisture. However, all type 1 test vehicles (TVs) survived even after 120 h of a PCT. Therefore, Ar and O₂ plasma treatments were performed on the FS with the lower surface energy in order to improve the surface energies and wettability. Following this, the bubbles were successfully removed at rigid substrate (RS)–FS bonding joints using ACFs.     

不同环境压强下激光空泡溃灭射流的实验研究

为了研究环境压强对固壁面附近激光空泡溃灭射流的影响,采用光偏转方法对固体壁面附近空泡溃灭行为进行了实验研究,得到了不同环境压强下空泡的溃灭时间、溃灭射流冲击压强。结果表明,相同激光能量下,环境压强对空泡溃灭时间、射流冲击压强都有非线性的影响关系,环境压强越大,溃灭时间越小,射流冲击压强越大;在空泡溃灭的前期,泡壁加速率较小且受环境压强的影响较小;在溃灭的后期,射流形成,空泡上表面泡壁中心点速率迅速增大,且相应阶段的加速率随着环境压强的增大而增大。这一结果对激光水下加工及空泡动力学的研究有积极的意义。     

Annealing behavior of electrodeposited gold containing entrapments

An experimental study of electrodeposited gold shows that the presence of entrapments, mostly in the form of gas bubbles containing hydrogen, can drastically affect its physical and mechanical properties. These property changes are expected to manifest themselves as unique problems in many electronic packaging applications. It has been shown that bubbles, ranging from less than 50 to 2000 angstroms in diameter, can be present in densities as high as 10¹⁷/cm³. Annealing studies in conjunction with changes in bubble size and density, electrical resistivity, outgassing, and hardness are specifically discussed.     

An Innovative Design by Single‐Layer Superaerophobic Mesh: Continuous Underwater Bubble Antibuoyancy Collection and Transportation

Underwater bubbles are unavoidable in the natural world and industrial production. Understanding the behavior of underwater bubbles and manipulating gas bubbles are vital important to both fundamental scientific research and industrial application. Although there has been some progress in controlling underwater bubbles, continuous underwater bubble collection and transportation remain challenging targets. Herein, inspired by the mechanism of water spider's gas storage, a strategy to collect and transport underwater gas bubble is demonstrated by design of a single‐layer underwater superaerophobic mesh (USM) assembled with a quartz tube. Gas bubbles supplied by a syringe pump penetrate the mesh pore and then gather to form a gas column in the quartz tube. Collapse occurs when the gas column reach the maximum storage height/pressure. Under a continuous supply of gas bubbles, the change of pressure becomes a cyclic process, which acts in a pump‐like manner to transport bubbles continuously from the water to the gas phase in the USM device assembled with an asymmetric U‐tube. This novel gas collection and transport system provides a new inspiration for developing new technologies for applications in pipes, sensors, gas collection, and environment protection.     

The mechanism for the formation of slug flow in vertical gas–liquid two-phase flow

This paper studies the mechanism for the formation of a slug flow in vertical gas–liquid two-phase flow. By analyzing void fraction waves and their instability, it is proved that the formation of a slug flow regime is due to the increase of void fraction waves, which causes the conglomeration of gas bubbles and the coalescence of bubble clusters in unstable bubbly flow. Experiments and analysis show that intense turbulence can restrain the formation of Taylor bubbles. Therefore, in a large diameter vertical pipe, a Taylor bubble can form under a condition of low continuous volume flux due to the action of void fraction waves. However, the coalescence effect of void fraction waves as it affects bubbles is suppressed in high continuous volume flux, and therefore, a slug flow regime cannot be observed in the evolution of flow patterns. Under a condition of high continuous volume flux (V_L=0.15 m/s) described in the paper, the flow pattern evolution is from cap bubbly flow to cap churn flow, and then gradually to churn flow with the increase of void fraction.     

Manipulating Bubbles in Aqueous Environment via a Lubricant‐Infused Slippery Surface

Designing functional interfaces to control solid/fluid interactions has emerged as an indispensable strategy for developing advanced materials and optimizing current technologies. Surfaces exhibiting special wettability offer many paradigms for regulating fluid behavior in practical applications including oil–water separation and fog harvesting. Nevertheless, the flexible manipulation of air bubbles under water still has room for further exploration. Here, it is reported that the lubricant‐infused slippery (LIS) surface with water repellency is applicable to manipulate bubbles in an aqueous environment. On the basis of the sufficient bubble adhesion, the shaped LIS tracks can be used in guiding the bubble delivery and facilitating continuous bubble distribution. Through the incorporation of an asymmetrical structure into the LIS surface, a triangle‐shaped bubble holder is capable of controlling a single bubble with ease. Moreover, the LIS surface is integrated with a H₂ microbubble evolving apparatus, demonstrating a potential method for in situ capture and delivery of microbubbles. The current finding reveals the meaningful interaction between underwater bubbles and the LIS surface, providing several examples for the applications of this bubble carrier, which should shed new light on the development of bubble‐controlling interfaces.     

基于聚类预分割和高低精度距离重构的彩色浮选泡沫图像分割

该文针对矿物浮选过程泡沫图像质量不理想、气泡大小形状灰度不均的问题,提出一种基于聚类预分割和高低精度距离重构的泡沫图像分割方法。首先,利用k-均值聚类进行前景泡沫与背景矿浆彩色图像分割,依据灰度分布和形状分布特征对提取到的泡沫图像进行滤波;然后,基于形态重构提出结合高低精度距离变换对距离图像进行重构,同时利用面积重构h顶改进变换为分水岭变换提取准确的特征标识;最后利用分水岭算法得到分水线,从而完成浮选泡沫的分割。由分割后的泡沫图像可统计分析出气泡个数与尺寸等物理特征参数从而为浮选控制提供依据。仿真结果表明了方法的有效性。     

基于涡流锁相热成像的刹车片内部气泡检测

刹车片是汽车必不可少的制动部件,其内部气泡严重影响行车安全。传统敲击听声检测方法主观性强,检测效率低,难以满足准确高效的检测需求。基于涡流锁相热成像具有非接触、大面积检测的特点,将其应用于少金属摩擦材料汽车刹车片的内部气泡检测。采用有限元仿真探索了刹车片结构和内部气泡对相位的影响,并以背钢处相位为参考,分离出气泡存在。对刹车片试样进行检测,并采用水切割观察剖面的方法验证结果。实验表明涡流锁相热成像检测方法能有效检测少金属摩擦材料汽车刹车片的内部气泡。