Conductivity of a two-dimensional model of a structurally anisotropic composite with a system of scratches

The conductivity of a two-dimensional model of a structurally anisotropic composite, an isotropic matrix with nonconducting inclusions in the form of parallel scratches, is considered. The centers of the scratches are randomly distributed over the (x, y) plane. An approximate method is applied to derive an expression for the effective conductivity tensor, which satisfactorily describes of the electric conductivity of the model over a wide range of concentrations.     

Electrical conductivity of a two-dimensional model for a composite material with structural anisotropy

The electrical conductivity of a structurally anisotropic two-dimensional model for a composite material is considered. The model represents an isotropic matrix with a system of nonconducting inclusions in the form of mutually perpendicular scratches of various lengths. The centers of the scratches are chaotically distributed in plane (x, y). The approximate effective medium method is used to derive an expression for effective conductivity tensor $\hat \sigma _e$ that satisfactorily describes the electrical conductivity of this model over a wide concentration range. The model conductivity in the critical region is considered in terms of the similarity hypothesis.     

Effect of scratches on the conductivity of thin films

The conductivity of a two-dimensional composite, a thin film with a system of randomly distributed nonconducting scratches, is considered. A comparison with the results of a model experiment is performed.     

Electrical conductivity of a two-dimensional model for a structurally anisotropic composite

The electrical conductivity of a two-dimensional structurally anisotropic model for a composite is considered. The model represents an isotropic matrix with a system of nonconducting inclusions in the form of infinitely thin straight line segments (scratches). The scratches make an angle θ or −θ with a preferred axis (for definiteness, axis y) at the same probability, and their centers are chaotically distributed. An approximate effective medium method is used to obtain a general expression for the effective conductivity tensor $ \hat \sigma _e $ \hat \sigma _e of this model that is valid over a wide concentration range. In this approximation, both components of tensor are $ \hat \sigma _e $ \hat \sigma _e shown to vanish at the same percolation threshold, which is expressed explicitly. The conductivity of the model in a critical region is considered in terms of the similarity hypothesis.     

表面损伤衍射双向反射分布函数模型建立及分析

建立了包括划痕和坑点在内的表面损伤的衍射双向反射分布函数(BRDF)模型,并分析了模型在各领域中的应用.通过使用非傍轴标量衍射理论,提出了采用相干窗口函数滤波的方法得到非相干光条件下的表面损伤衍射BRDF模型,得到了表面划痕和坑点的散射特性.该方法在表面损伤检测、表面损伤杂光分析以及图像渲染技术等领域都有重要的应用价值...     

基于滤波差分的双阈值弱划痕提取算法

高质量光学元件表面缺陷中存在一些深度较浅或者宽度较窄的划痕,在暗场成像检测中,该类划痕产生的散射光灰度值很低,甚至淹没在背景光中,很难被目视或常规机器视觉识别,造成划痕缺陷的漏检。针对该问题,以既有的疵病检测系统为基础,根据划痕灰度的等级特征,提出双阈值法分类处理划痕缺陷。在低阈值的弱划痕处理中,根据弱划痕和背景的频率特征以及空间对比度特征,设计了频域滤波及背景差分算法。通过空间域以及频率域的滤波处理,排除高频噪声以及高亮度噪声,根据几何特征等提取弱划痕图像中的复杂背景。经差分处理后,提取弱划痕并增强对比度,最后与正常灰度级划痕信息一同通过高阈值(正常阈值)进行后续划痕的特征提取,即得到所有的划痕信息,为划痕缺陷总长度计算以及最大长度的分级判定奠定基础。实验结果表明,该算法避免了过低二值化阈值引入的背景等不规则噪声,使得划痕与背景的对比度大大增强。目前该算法已经应用于惯性约束聚变系统中大口径光学表面划痕的定量检测,并且使长度计量的准确度已提升到约80%。     

光学元件的表面划痕及其对入射激光的调制作用

 对光学元件表面划痕进行了细致的观察,并将它们分为单划痕、双划痕和多划痕三类,采用时域有限差分方法,以加工过程中常见的直径为二分之一波长的半圆形划痕为基本研究对象,数值模拟了位于光学元件前后表面的多条划痕附近的空间光强分布,总结了在不同划痕条数下光强最大值随着划痕间距变化的曲线图。结果表明：位于光学元件后表面的划痕比位于前表面时更加容易引起光学损伤;在多条划痕情况下,空间光强最大值随着划痕间距的增大呈周期性变化,并随着划痕间距的不断增大而趋于一稳定数值。     

Small angle scattering of protons from rough A1 at grazing incidence

In this letter, some experimental results of 400 keV proton scattering at grazing angles are reported. Experiments were done on samples of pure polycristalline A1 with scratches at random directions. A good agreement is found when polished sample spectra were fitted with a multiple scattering theory.     

基于计算机视觉的管壳表面划痕检测技术研究

针对火工品管壳表面划痕人工检测工作量大、较为繁琐且人为误差较大的状况，将计算机视觉技术用于微小管壳表面划痕的检测分析中，在数字图像处理技术的基础上，应用二值图像轮廓提取的方法得到划痕的特征参数，根据形态学知识对零件表面划痕的形态特征进行比较分析。实验结果表明，通过将划痕显微图像中面积、短长径比等参数提取出来作为检测的依据，不但可以有效地克服现有的人工视觉检测方法的缺陷，而且稳定性和准确度也得到了提高。     

CO_2激光光栅式扫描修复熔石英表面缺陷的实验研究与数值模拟

基于熔石英材料对波长为10.6μm的CO2激光具有强吸收作用这一特点,提出采用CO2激光光栅式多次扫描修复熔石英光学元件表面密集分布的划痕和抛光点等缺陷的方法.实验结果表明,在合理的扫描参数下,元件表面的划痕和抛光点等缺陷可被充分地消除.损伤阈值测试结果表明,表面划痕和抛光点等缺陷被完全消除的元件的损伤阈值可回复到或超过基底的损伤阈值.同时结合有限元软件Ansys的模拟结果分析了CO2激光扫描修复及消除元件表面划痕和抛光点等缺陷的过程.本文为消除元件表面划痕和抛光点等缺陷提供了非常有意义的参考.     

基于表面增强拉曼光谱技术的金表面耐腐蚀性分析

金属表面耐腐蚀性能与其微观结构密切相关。以金为分析对象,采用不同粒径氧化铝抛光粉抛光处理金片表面,经扫描电镜和原子力显微镜观察,表明金片表面具备与实际工件类似的微观结构,在此基础上,研究金片表面微观划痕结构对表面增强拉曼散射(SERS)以及耐腐蚀性能的影响。以罗丹明B为探针分子,对不同特征尺寸的微观划痕进行SERS分析,获得了罗丹明B的SERS信号强度随划痕平均特征尺寸的变化规律。通过改变拉曼激发光偏振方向与划痕方向的夹角大小,发现SERS信号主要归因于激发光与划痕相互作用产生的横向表面等离激元。划痕平均特征尺寸在50 nm附近时,横向表面等离激元最强,之后随着划痕平均特征尺寸增加,横向表面等离激元逐渐变弱。另一方面,对具有不同特征尺寸微观划痕的金片进行电化学极化测试,获得了各样品的自腐蚀电位,发现金片的自腐蚀电位随着划痕平均特征尺寸增大而降低。结果表明,当划痕平均特征尺寸大于50 nm,金表面的SERS信号与自腐蚀电位间存在良好的线性对应关系,这为SERS技术用于工件耐蚀性分析提供了依据。通过在工件表面滴涂探针分子并使用便携式拉曼光谱仪测量有望可以对工件耐蚀性进行现场快速预判。     

一种基于小波分析的唐卡图像划痕检测

唐卡图像在其保存和搬运过程中较易出现细微的划痕,针对所出现的垂直(水平)划痕进行了自动检测算法研究。垂直(水平)划痕实质上属于特殊的边缘,首先利用该特性采用小波模极大值描述图像中目标的多尺度边界;然后再通过投影变换放大划痕中心的亮度极值特性,并基于多尺度突变点检测找到划痕的位置;最终采用标注联通分量、设置高度和宽度约束得到划痕的掩膜。实验结果表明,利用该方法取得了较好的检测效果。     

Tribochemical reduction of Pb in Pb containing glazes: An ESCA investigation

Most white glazes, used in the ceramics industry for the coating of tiles, show deep, black scratches after tribological treatment with other glazes. Contrary to similar scratches produced during scraping with metals, these failures cannot be removed by polishing. ESCA investigations on Pb containing transparent and white glazes have shown unambiguously that during the tribological treatment the Pb in the surface of the glaze is partially reduced to metallic Pb which could at least partially explain the deep, black scratches seen on the tiles after the treatment.     

The excess thermal conductivity and viscosity of hard-sphere mixtures

The excess thermal conductivity and viscosity of fluid mixtures are examined on the basis of Thorne's extension of Enskog's dense hard-sphere gas transport theory. The results show good correspondence between theory and experiment for thermal conductivity for which the majority of systems exhibit a negative excess conductivity. Agreement of experiment with theory in the case of viscosity is not as complete.     

Surface behavior during abrasive grain action in the glass lapping process

In this study the surface behavior during its contact with the abrasive grain in the glass lapping process was studied using practical simulation which is the scratch test and the real contact between glass surfaces and α-alumina abrasive grains during lapping process. Formations and dimensions of the produced scratches were investigated to explain the grain action on the surface and the glass material removal rate. It has been found that humid environment created by the use of the slurry of loose abrasives causes more significant damages than the dry one. The use of slurry produces higher glass material removal rate in this environment and proves its utility in the lapping process. The shape of abrasive grains influences the nature of their action. Indeed, the worn grains produce scratches and chippings less than the sharp grains. During lapping, the number of scratches and theirs dimensions depend on the contact time and the abrasive grain size. It was concluded that the glass material removal rate during lapping depends on the cumulative actions of individual grains which produce scratches and chippings.     

熔石英元件抛光表面的亚表面损伤研究

通过结合HF酸洗和微分干涉差显微成像对两组抛光元件的亚表面损伤进行直接观测和分析。结果显示微分干涉差显微成像相比于传统的明场成像具有更好的分辨率,可以更有效检测HF酸洗后暴露的各种浅塑性亚表面损伤。对两组抛光元件的亚表面损伤的对比分析发现熔石英元件在抛光中会产生大量的亚表面损伤,这些亚表面损伤绝大多数是浅塑性的划痕和坑,仅有少量的脆性断裂损伤,较大的抛光颗粒会产生更多更严重的亚表面损伤,并且这些亚表面损伤被表面沉积层所掩盖,表面粗糙度不能反映亚表面损伤的严重程度。     

Application of a He3Ne infrared laser source for detection of geometrical dimensions of cracks and scratches on finished surfaces of metals

In this study, the authors addressed a new method of measurement for microscratches and cracks on finished metallic surfaces. The technology proposed here can be used in aviation, automobile, machine-tools, bearings, electrical and thermal devices (detection of electrical and thermal contact resistance), and many other industrial fields where finished surfaces have to be inspected for quality before use. The technology is based on the application of He3Ne laser optics. This measurement method allows for the inspection of geometrical parameters such as depth and width of scratches and cracks and consists of a low-energy He3Ne red laser beam (wavelength 633 nm) with a cross-section of 0.48 mm, beam expander with special designed slit, multi-axis stage with sample holder and CCD (charge-coupled device) visual detection system. Using experimental data, a mathematical algorithm was created in order to calculate the depths and widths of the scratches and cracks where the method of center of gravity (centroid) of the imaged area was used. The results showed a good correlation between the experimental and calculated values of the dimensions of the scratches. Future work will deal with the determination of the geometrical dimensions of microcracks.     

The thermal conductivity of mixtures of methane with argon and neon

The paper reports new measurements of the thermal conductivity of mixtures of neon and argon with methane at a temperature of 27.5°C. The measurements have been performed with a transient hot-wire instrument within the pressure range 1 to 22 MPa and the results have an estimated uncertainty of ±0.3%.The thermal conductivity data for the mixtures in the limit of zero density can be represented with the aid of the best available kinetic theory formulae, but not within their experimental uncertainty. The density dependence of the thermal conductivity of the mixtures is adequately described by a semi-empirical correlation scheme based on the modified Enskog theory.     

Dark-field detection method of shallow scratches on the super-smooth optical surface based on the technology of adaptive smoothing and morphological differencing

There exist some shallow scratch defects on the super-smooth optical surface. Their detection has a low efficiency with the existing technologies. So a new detection method, dark-field detection of adaptive smoothing and morphological differencing(DFD-ASMD), is proposed. On one hand, the information of shallow scratches can be kept in dark-field images. On the other hand, their weak characteristics can be separated and protected from being overly reduced during the elimination of noise and background in the image. Experiments show the detection rate of shallow scratches is around 82%, and DFD-ASMD can lay a foundation for quality control of defects on the high-quality optical surface.     

Soft ESD phenomena in GMR heads in the HDD manufacturing process

GMR (giant magnetoresistive) heads used for HDD (hard disk drives) are very sensitive to ESD (electrostatic discharge). Some kinds of ESD damages will cause soft magnetic degradations of head performance with a progressive nature. We report examples of head degradations by ESD damages as well as other damages due to head scratches, electro-migration effects and corrosion of GMR stack. It is usually very difficult to distinguish these phenomena explicitly by QST (quasistatic tester) and spinstand measurement test. We show that head scratches can cause damages similar to damages caused by ESD and that re-magnetization has certain potential to correct the damaged magnetic structure caused by such scratches.