细粒度金刚石砂轮形貌测量与评价

采用基于扫描白光干涉原理的三维表面轮廓仪对粒度为3 000的金刚石砂轮表面形貌进行测量,其图像拼接功能可以确保较高的横向分辨率、较高的垂直分辨率和较大的取样面积。利用频谱分析方法对砂轮表面的频率构成进行分析,通过理想的低通数字滤波消除测量仪器引起的系统噪声和砂轮表面的高频分量,然后重建砂轮表面的三维形貌,在此基础上得出砂轮的磨粒出刃高度、静态有效磨粒密度、磨粒平均间距。研究表明,采用细粒度金刚石砂轮进行超精密磨削时,磨粒出刃高度大体上服从正态分布,静态有效磨粒密度远低于理论磨粒密度,真正起切削作用的磨粒数量极少。     

Methodological basis for an autoradiographic demonstration of insulin receptor sites on the surface of whole cells: a study using light- and scanning electron microscopy

An autoradiographic technique is described which allows, on whole cells, the determination of the number of receptor sites which are occupied by ¹²⁵I-insulin according to defined binding conditions. Glutaraldehyde fixation prevents the dissociation of the bound tracer from the receptor, which is the basis for a quantitative correlation between biochemical and autoradiographical data. The homogeneous coating of whole cells with a thin emulsion layer, which was required for these experiments, was achieved by a stripping film technique. An accurate judgment of the coating was possible only with scanning electron microscopic (SEM) techniques. As observed in the SEM, the photographic layer was smooth, uniform and in good contact with the top of the cell. The signal measured in this area was analysed. The majority of the grains also originated from the top side of the cell surface, despite the evidently three-dimensional distribution of the label. As determined in test specimens, 80–85% of the grains originated from 3–4 keV electrons. Due to the short range of these electrons, the grains represent the distribution of the label on the part of the cell surface which is in close contact with the emulsion layer. 15–20% of the grains originated from β-decays with higher energies and add partially to the background. According to these data a determination of the number of receptor sites per unit area of plasma membrane (receptor density) is possible in the surface area of the cell top. Both light microscopy (LM) and SEM were used to analyse autoradiographs. LM analysis is possible in principle but the analytical facilities of SEM are yet superior for the identification of silver grains. The registration of the grains is further facilitated in SEM because of the very large depth of focus.     

BASIC programs to compute source densities from autoradiographic cross-fire matrices

Two different mathematical procedures to compute source densities from cross-fire matrices in quantitative EM autoradiography are reported. BASIC programs for a desk-top microcomputer were written to fit the hypothetical silver grain distribution to the observed real silver grain distribution using a non-iterative linear process (least-squares procedure) and an iterative method, which minimizes the chi-square component between the observed and computed silver grain distributions. The latter procedure uses a Gauss-Newton algorithm.     

Stereology 5

Light microscope autoradiographs were prepared from a ¹⁴C line source. Two factors that affect resolution were studied: emulsion thickness and section thickness. The distribution around the line source was determined using the half-distance (HD) value to quantify the resolution. An increase in HD value was observed with thicker sections or emulsion layers. The shape of the curve reflecting the grain density distributions around these line sources was very similar. After normalization in HD and relative grain density units, an average distribution was calculated and compared with the shape of normalized density distributions obtained from electron microscope autoradiographs. Other than a discrepancy near the source, an acceptable correlation was observed.     

改进掩码自编码器的滚动轴承半监督故障诊断

针对滚动轴承在不同转速条件下数据分布不同以及实际工程应用中标签样本不足导致故障诊断精度低的问题,将领域适配模块融入掩码自编码器(MAE)中,提出了改进掩码自编码器(IMAE)的滚动轴承半监督故障诊断方法。首先,对滚动轴承振动信号进行连续小波变换(CWT)得到反应信号时频特征的二维时频图,然后对时频图随机掩码,利用无标签样本进行掩码自编码器预训练,获得数据中复杂的内在特征,减少对有标签样本的依赖;其次将领域适配模块引入到预训练后的编码器中,使用少量有标签源域数据对IMAE进行微调,在希尔伯特空间中利用最小化最大均值差异减小因转速不同造成的源域与目标域间数据分布差异;最后在Softmax分类层下实现滚动轴承半监督故障诊断。通过滚动轴承数据集实验验证,所提方法检测精度均达到94%以上,证明了该方法的可行性与有效性。     

Distribution of Membrane Thickness Determined By Lineal Analysis

The expected statistical distributions of intercept length are derived in terms of geometrical probability density functions pertaining to plates with known thickness penetrated by lines with random orientation. These expressions provide arithmetic and graphical solutions for obtaining distributions of membrane thickness and reciprocal membrane thickness from empirical distributions of intercept lengths. Furthermore, general relationships between probability density functions of distributions of intercept length and membrane thickness are derived as well as those between their moments. Examples of the application of the method to biological samples are given, and estimated distributions of glomerular basement membrane thickness are compared to those obtained by an independent, direct method. Various sources of bias, which in practice may occur due to departures from the sample model, are discussed and the influence of some of them is estimated. The knowledge of the probability density function of reciprocal intercepts makes it possible to perform a correction of the distributions of measured intercept length, which to some extent eliminates bias.     

基于X射线衍射线形分析的铝合金切削表层晶体特征研究

为深入研究高速高效加工条件下材料表层晶体特征形成机理,提高铝合金构件服役性能,同时解决传统观察法较难得出晶粒尺寸与位错密度统计学规律的问题,立足微观,以铝合金7050-T7451为研究对象,将材料学与物理学中基于X射线衍射线形分析的Modified Warren-Averbach和Modified Williamson-Hall方法引入切削加工表层微观组织分析中,实现了不同切削速度下切削表层微观组织结构的定量研究。研究表明,高速切削条件下已加工表面以刃位错为主,得出了位错密度值（高达1015m-2以上）与位错密度变化规律,并从塑性变形及能量角度解释了其形成机理;拟合出了晶粒尺寸分布曲线,并通过分布函数分析了已加工表面晶粒分布均匀性;当切削速度高于4500m/min时可以得到位错密度相对较低、晶体尺寸较均匀的已加工表面。     

杯形CBN砂轮端面磨削的自锐过程分析及磨削效果改善

以曲线沟槽的磨削加工为目的 ,本文对金属结合剂杯形小直径 CBN砂轮端面磨削沟槽底面时的砂轮自锐 (Self- dressing)过程进行了研究。金属结合剂杯形小直径 CBN砂轮的自锐行为表现为磨粒磨损后的破碎产生新切削刃 ,磨钝磨粒的脱落和砂轮结合剂被磨屑去除产生新磨粒 ,保持了砂轮工作面上磨粒密度的相对稳定 ,维持了砂轮的锋锐性。通过提高砂轮硬度以期减缓磨粒脱落 ,增加单个磨粒的服务期限 ,试验结果表明已加工表面粗糙度 Rz小于 3.5 μm,砂轮磨损减小了 40 % ,磨削过程稳定 ,取得了良好的磨削效果     

QD as a bifunctional cell-surface marker for both fluorescence and atomic force microscopy

Fluorescent quantum dots (QDs) are a new class of fluorescent label and have been extensively used in cell imaging. Streptavidin-conjugated QDs have a diameter of ca. 10–15 nm; therefore when used as probes to label cell-surface biomolecules, they can provide contrast enhancement under atomic force microscopy (AFM) and allow specific proteins to be distinguished from the background. In addition, the size and fluorescent properties potentially make them as probes in correlative fluorescence microscopy (FM) and AFM. In this study, we tested the feasibility of using QD-streptavidin conjugates as probes to label wheat germ agglutinin (WGA) receptors on the membrane of human red blood cells (RBCs) and simultaneously obtain fluorescence and AFM images. The results show that the distribution of QDs labeled on human RBCs was non-uniform and that the number of labeled QDs on different erythrocytes varied significantly, which perhaps indicates different ages of the erythrocytes. Thus, QDs may be employed as bifunctional cell-surface markers for both FM and AFM to quantitatively investigate the distribution and expression of membrane proteins or receptors on cell surface.     

Grinding force and power modeling based on chip thickness analysis

The ability to predict grinding force and power is important to many aspects of grinding process optimization, monitoring, and control. This paper presents the predictive modeling of grinding force and power based on the probabilistic distribution of undeformed chip thickness as a function of the kinematic conditions, material properties, wheel microstructure, and dynamic effects. The chip thickness is the main random variable and it is expected to assume a Rayleigh probability density function. The model takes into account the microstructure of the grinding wheel given by the grain geometry and the static grain density in terms of the radial depth into the wheel. The dynamic cutting edge density was calculated incorporating the effects of kinematic and dynamic phenomena such as the kinematic hidden grains and the local grain deflection. The elastic deformation of the grinding contact length was also considered. The model was used to predict the total tangential and normal forces in surface grinding and the total grinding power in cylindrical grinding. In both cases experimental measurement data in the context of chip thickness probability density, tangential force, normal force, and power have been presented and compared to model calculations.     

Immunocytochemical demonstrations of cytoplasmic and cell-surface EGF receptors in A431 cells using cryo-ultramicrotomy,surface replication,freeze-etching and label fracture

In this paper we describe the use of a number of complimentary methods to visualize cytoplasmic and cell-surface located epidermal growth factor (EGF) receptors in cultured A431 cells. Cryo-ultramicrotomy in combination with immuno-gold labelling will be shown to provide an excellent method in visualizing cytoplasmic located EGF receptors in addition to cell-surface located EGF receptors. An important aspect in this method involves the possible effects of the fixatives on antigenicity. Using radioactive labelled anti EGF receptor antibodies, it was shown that formaldehyde as a fixative had no significant effect on label-efficiency. The density and lateral distribution of EGF receptors at the cell surface has been studied by three methods, i.e. surface replication, freeze etching and label fracture, all methods in conjunction with immuno-gold labelling. These methods allow in principle a quantitation of the surface distribution of the EGF receptors. The surface-replication method involves, however, dehydration and critical-point drying steps, and using radioactive labelled anti EGF receptor antibodies it was shown that in particular OsO₄ fixation and dehydration caused a significant loss of cell-associated antibodies. This disadvantage is overcome by freeze etching and the label-fracture method, and as such these techniques provide the best methods for quantitative analysis of the planar distribution of cell-surface located EGF-receptors.     

Influence of grain orientations on the initiation of fatigue damage in an Al–Li alloy

The variation in microstructure and texture in a rectangular bar extruded from a billet of spray-cast 8090 Al–Li alloy has been examined. The fine grain size of the as sprayed billet and the moderate extrusion ratio (≈ 25 : 1) were seen to cause geometric dynamic recrystallization (GDR) in regions of higher strain towards the edge of the bar. The grain morphology varied from the expected elongated grains at the centre of the bar to equiaxed grains where GDR occurred at the bar edges. A <111> + <100> double fibre texture, significantly distorted towards rolling components and varying through the bar thickness, was found using electron backscatter diffraction. Fatigue resulted in a high density of short secondary cracks, many of which had arrested at grain boundaries. The cracks preferentially nucleated in grains from the <100> fibre texture corresponding to high Schmid factors.     

陶瓷CBN砂轮地貌建模与磨削仿真

针对砂轮表面上磨粒形状的不规则性、尺寸的不确定性以及分布的随机性特点,采用随机空间平面切分实体的方法生成了具有实际磨粒几何特征的不规则多面体磨粒;提出了虚拟格子法,实现了磨粒空间位置的随机分布,构建了陶瓷CBN砂轮地貌仿真模型;采用有限元法和光滑粒子流体动力学法的耦合方法进行了砂轮地貌模型磨削仿真,通过切削层SPH粒子的运动情况,分析了磨粒的切削机理及工件表面的创成机理。     

Interpretation of electron microscope autoradiographs: correction for cross-fire when membrane components are highly labelled

The interpretation of electron microscope autoradiographs concerns the estimate of the relative concentration of a radiolabelled molecule in subcellular compartments. Because of the radiation spread, an autoradiographic grain underlying a subcellular compartment cannot be directly assigned to the latter. Observed data must therefore be corrected for cross-fire (CF). We studied the efficiency of several methods designed for the CF correction when membrane components possess a high concentration of labelling, resulting in a high proportion of CF. Grains generated from simulated sources were subjected to the CF method, to an original method based on the simulated annealing optimization algorithm, and to the expectation-maximization algorithm. The expectation-maximization algorithm appears to be clearly superior to the two other methods. Nevertheless, the variances of the estimates were higher than expected. Since no analytical expression of the estimates is available, an objective comparison of the labelling in different compartments is not possible with a standard test. Consequently, the interpretation of autoradiographs in electron microscopy is still an open problem.     

On the sampling of three-dimensional polycrystalline microstructures for distribution determination

How to sample three-dimensional microstructure and effectively reduce experimental error is a challenging problem. Taking seven single-phase polycrystalline structures generated by 400×400×400 Potts Monte Carlo simulation as the study object, effects of sampling strategy on the determination of various characteristic parameters of the grain size distribution and grain topology distribution are studied. The mean voxel value (or volume) of individual grains in the three-dimensional simulated microstructure varies from 4.56×10(4) to 1.0×10(3) , and the number of grains contained in the structure varies from 63 901 to 1403. The results show that, a minimum of 200 sampled grains can ensure the relative error to be less than 5% for determination of the mean grain volume, the mean grain face number and the coefficient of variance of the distribution of grain size and the grain face number. Whereas for the coefficient of the skewness and the kurtosis of grain size distribution or grain face number distribution, a minimum of 800 sampled grains are required for the same error level. However, if some exceptional big grains appear, e.g. a grain larger than with eight multiples of mean grain volume and/or three multiples of mean grain face number, abnormal values of the two parameters would be resulted, even the number of examined grains is over 1000.     

基于谐波分析的磁弹拉力测量改进方法研究

基于磁弹检测机理,提出一种磁弹拉力测量改进方法,即将谐波分析法应用于磁弹信号处理,通过统计信号频域各阶次谐波幅值,引入电气工程中表征波形相对正弦波畸变程度性能参数——总谐波畸变率来表征结构拉力。采用双套筒线圈式磁弹传感器在7芯钢绞线中获取磁弹检测试验信号,对比时域与谐波分析两种处理方法的特点,结果表明,谐波分析法处理过程更为简洁,所确立的标定方程的特性参数(线性拟合方程确定系数、斜率)随统计阶次增加而趋于稳定,且均优于时域处理结果,线性拟合方程确定系数可达0.996以上。同时,应用于高压输电导线的拉力测试,结果再次验证了总谐波畸变率与拉力间的良好线性关系。针对两种试验对象,当总谐波畸变率为1时,不同谐波统计阶次对应的标定方程对拉力的估算值间的相对误差均小于3%(其中7芯钢绞线最大为2.4%,高压输电线最大为2.9%)。该方法为磁弹拉力测量提供了一种新的表征及数据处理手段。     

Sub-structure characterization of experimentally and naturally deformed ice using cryo-EBSD

In this work, we present first results of high‐resolution EBSD for ice with a spatial resolution down to 0.25 μm. The study highlights the potential of EBSD to significantly increase our understanding of deformation and annealing processes associated with the build‐up of internal stresses due to strain incompatibility between grains. Two polycrystalline samples were analyzed: a natural sample of polar ice from the Vostok ice core (Antarctica) and an experimentally deformed sample of laboratory grown columnar ice. In summary, we observe the following: (1) inhomogeneous deformation through the grains is translated into lattice distortions that are concentrated mainly at grain boundaries and triple junctions (natural and experimental sample), (2) these distortions may be continuous (natural and experimental sample) or may form distinct tilt boundaries and sub‐grains of 10–50 μm size (experimental sample). These form mainly by rearrangement of basal edge dislocations into low‐energy configurations (i.e. tilt boundaries) in various prism planes. Continuous lattice distortions originate from screw or mixed edge and screw dislocations lying in the basal plane.     

A study of improving overlay accuracy for a stepper in IC manufacture

In integrated circuit manufacture, owing to the limited optical system capability and the possibility of inaccurate mask installation in a stepper, image distortion of the mask pattern projected onto the wafer surface may occur during exposure. In this paper, the overlay distribution geometry was analysed to explore the physical properties of parameters in an overlay accuracy model for a stepper. The multiple linear regression method was also used to analyse overlay models to compare the error parameters obtained by different overlay models and the extent of possible improvements in overlay accuracy. If an appropriate overlay accuracy model can be established to reduce the systematic errors, overlay accuracy can be effectively improved. A multiple linear regression analysis of a simulation study was carried out. The elimination of the systematic error parameters was achieved by finding out the causes of these systematic errors in the overlay and eliminating them. This can reduce the standard deviation of the residual overlay to 19% of the original overlay and thus significantly improve the overlay.     

A compact STED microscope providing 3D nanoscale resolution

The advent of supercontinuum laser sources has enabled the implementation of compact and tunable stimulated emission depletion fluorescence microscopes for imaging far below the diffraction barrier. Here we report on an enhanced version of this approach displaying an all-physics based resolution down to (19 ± 3) nm in the focal plane. Alternatively, this single objective lens system can be configured for 3D imaging with resolution down to 45 × 45 × 108 nm in a cell. The obtained results can be further improved by mathematical restoration algorithms. The far-field optical nanoscale resolution is attained in a variety of biological samples featuring strong variations in the local density of features.