A method for measuring the size distribution of latex particles by scanning force microscopy

A methodology has been developed to accurately determine the size distribution of latex particles using the scanning force microscope (SFM). Unlike other workers, who have generally measured the lateral dimensions of monolayers of latex particles using a global quantification method, we have measured the heights of individual latex particles located at the edges of latex monolayers that were immobilised onto mica substrates. In agreement with other work, we noted that the edges of monolayers of latex particles provided stable and reproducible scanning force imaging.

Whilst SFM imaging noise, image processing artifacts, tip/sample forces and variations in the mica substrate are sources of measurement error that should not be overlooked, our experience has been that the variation over time of the sensitivity of the Z actuator is the greatest potential uncertainty in determining the heights of latex particles. The methodology that we used requires frequent calibration of the Z actuator of the SFM, typically before and after two or three images, in order to ensure that the uncertainties in the Z sensitivity are known and minimised. This methodology was developed for an SFM instrument that was equipped with open loop piezoelectric actuators following a careful study of the behaviour of those actuators.

Using this methodology, we have measured the size distributions of populations of 300–400 latex particles from each of several different latex samples, with the maximum variation in the Z-actuator calibration experienced during the measurement of a sample being less than 2%, often about 1% and occasionally better still. In so doing, we have demonstrated that SFMs equipped with open loop actuators can be used for high confidence quantitative measurements of step heights.     

A method for measuring the size distribution and the local gas concentration in gas-liquid flows

A new optical method for measuring sizes of a dispersed phase (gas bubbles in liquid or drops of liquid in gas) illuminated by a laser “sheet” is substantiated theoretically and experimentally. The accuracy of the method is determined by the resolution of image recording systems. In a test experiment, the error for measuring the sizes of a dispersed phase was under 1%.     

Correction coefficients for the size distribution of photographically recorded spherical particles

Spheres which are part of a spatial process are photographed. The relationship is derived between the sizes of the images and the actual sphere size distribution. Non-orthogonal projection given by the linear optics of a pinhole camera is assumed. The depth of field is brought into the calculation.     

激光衍射粒径测量中的Chin-Shifrin反演算法

建立了以线阵CCD作为探测组件的激光衍射粒径测量系统用于颗粒群直径分布的测量.在数值计算的基础上,分析了传统Chin-Shifrin积分变换粒径分布反演算法存在的两个问题:小粒径反演结果的发散和多假峰现象,并结合理论分析给出了这两种现象的物理图像.提出了修正积分变换公式以解决小粒径反演结果发散的间题并针对Chin-Sh...     

A comparison of some methods for measuring the size distribution of two-dimensionally clustered latex particles in TEM images using mathematical morphology

The particle size distribution of polymer latexes of, for example, polybutadiene can be measured on transmission electron micrographs using image analysis methods. By taking suitable measures in preparing the sample it can be ensured that the image only consists of projections of two-dimensional clusters of adhering latex spheres. For the deagglomeration of these clusters a number of methods based on mathematical morphology are discussed. Speed and accuracy of the methods were tested on a personal-computer-based image analysis system and compared to manual measurements. Repeated openings or erosions applied to a binary image are relatively fast global methods with a low accuracy due to the fact that particle diameters are measured in whole numbers of pixels; only the horizontal diameters of rectangular pixels are measured. With an iterative method the individual components of the clusters are found by repeated conditional thickening of the erosion kernels. The method is accurate but very slow due to the large number of processing steps. The watershed method as applied to the original grey-scale transmission electron micrograph makes use of the sharp local maxima which arise at the interface of the projection of two adhering particles. This method is as accurate as the iterative method, but about eight times as fast.     

A study of the formative mechanism of spherical wear particles

In this paper, spherical wear particles which are produced by sliding wear processes are carefully studied by means of a scanning electron microscope and an energy-dispersive X-ray analyser etc.Much direct and indirect evidence from the examination demonstrated spherical particles to be a product of the local wear surface which is melted, i.e. droplets of the melting metal solidify into spherical particles.     

A rapid method for the visual determination of size distribution of spheres from the size distribution of their sections

The difficulty of calculating size distributions of spheres in masses from the size distributions of sectional circles is overcome by providing standard pairs of curves representing most imaginable particle-size distributions which might occur in nature. An observer needs only to match the histogram representing his own observations with one of the new curves to obtain immediately the size distribution of spheroid particles in his material.     

A model for the erosion of metals by spherical particles at normal incidence

A theoretical analysis is presented for the erosion of metals by spheres at normal incidence. The model employs a criterion of critical plastic strain to determine when material will be removed, and velocity exponents of 3 for erosion and −2 for the mass of spherical particles which must hit the surface before material is removed are predicted. The mechanical properties of the metal are described by two quantities: the dynamic hardness of the metal and the ductility of the metal under erosion conditions. Data obtained in experiments with aluminium alloys, as well as previously published data, are compared with the theory.     

Stereology of cubic particles: various estimators for the size distribution

This paper deals with stereological problems for spatial systems of homothetic particles. In contrast to the traditional technique of estimating the size distribution of the particles from the sizes of section profiles we introduce a new method exploiting size and shape of the observed profiles. The shapes of the section profiles contain additional information about the sizes of the particles. This leads to improved stereological estimation of size distribution. As an example the case is studied when the particles form cubes with random edge length. The method is applied to a two-phase WC–Co cermet structure with cubic particles.     

光散射法测试粒径的一种优化反演组合算法

在目前常用的激光粒度仪反演算方法的优点和缺点基础上,为了实现各种方法的稳定性与准确性的统一,提出一种基于退火演化算法和遗传算法组合的随机反演方法,该方法具有更强的全局收敛性,也具有对粒径分布形状不敏感、抗噪声能力强等优点。该算法能对具有单峰及双峰分布形式的颗粒尺寸进行精确求解,并获得合理的颗粒粒径分布结果。     

A critical study of the erosion of an aluminium alloy by solid spherical particles at normal impingement

Detailed observations of the mechanism of material removal in aluminium alloys eroded at normal incidence by spherical particles are reported in this paper.Eroded specimens were examined by scanning electron microscopy and were sectioned for metallographic examination. Important features observed included surface ripples of uniform wavelength and the formation of platelets on the surface. Beneath each surface examined was a layer, clearly delineated from the bulk material, with approximately four times the hardness of the bulk. This layer had a laminar structure and contained numerous embedded fragments of erodent particles. The layer was of relatively uniform thickness and was perforated in places by bulk material penetrating to the surface. Markers were placed beneath the surface of the specimens; after the specimens had been sectioned at different stages of erosion, the movement and distortion of the markers enabled the following mechanism of erosion to be identified.In the early stages of erosion, before a linear erosion rate is established, the subsurface microstructure is developed. Then, by a process akin to backward extrusion, bulk material is forced to the surface through fissures in the hard layer. The breaks in the layer coincide with peaks in the surface topography. The softer material is beaten into platelets by subsequent particle impacts, and wear results from the detachment of these platelets.     

A multiresonance method for measuring the reflection coefficient in a waveguide

A new method for measuring the complex reflection coefficient in rectangular waveguides using a scalar network analyzer is proposed. This method is based on measurements of the resonance characteristics of a quasi-resonator, i.e., a portion of the waveguide between a reflecting object on one side and an object with a known scattering matrix on the other side. One advantage of the multiresonance technique is that simultaneous analysis is performed for the entire set of resonance frequencies, which substantially increases the accuracy in finding the reflection coefficient. The errors in measuring the magnitude and phase of the reflection coefficient in actual experiments were close to 0.015 and 1.5°, respectively.Translated from Pribory i Tekhnika Eksperimenta, No. 1, 2005, pp. 94–100.Original Russian Text Copyright © 2004 by Ponomarenko, Popov.     

采用科里奥利质量流量计的流体黏度测量方法及装置设计

通过对弯曲振动运动进行分析,并结合流体运动及内摩擦力耗能情况,提出了一种新的黏度检测方法,导出了流体动力黏度与科里奥利质量流量计振动参数的关系,通过实验验证了方法的正确性.采用FPGA为主要器件,构成了黏度测量装置.该方法简单、实用,拓展了科氏流量计的应用领域,为其增加了一种新的功能.     

A new method for measuring subgrade settlement in high-speed railway by using a linear CCD

With the rapid development of high-speed railway in China, measurements and controls of subgrade settlement have attracted much attention in recent years. A novel method to measure the subgrade settlement is proposed and a device has been developed. The device mainly contains a point light source and a point-position measurement device that uses a linear CCD to detect the position change of the point light’s image. Any position change of the point light source can be measured and the settlement for one point can be obtained remotely. The multi-point settlements can be obtained by using a series of such devices. Some methods such as self-calibration of the magnification, automatic background subtractions have been adopted to enhance the stability, adaptability and accuracy of the measurement system. The device has been used in some China high-speed railway sites and it has the advantages of high accuracy, low-cost and easy installation.     

On the nature of spherical wear particles in a Babbitt-steel sliding system

The mechanism of spherical particle formation was investigated in sliding systems formed of a steel ring on which either a pure Babbitt pin or a graphite fiber-Babbitt matrix composite pin was slid. Spherical Babbitt particles (indicative of tribological distress) were detected only in the pure Babbitt-steel system under conditions of dry sliding. These particles were probably formed from non-spherical wear debris by severe plastic deformation at the interface. With the composite pins, only spherical steel particles (generated in the pretest grinding operation) were found. These steel particles were, in general, clustered, smooth and hollow, indicating that they formed by a process of melting and solidification of fine grinding chips.     

一种新的锁相测速方法

文中介绍了一种全新的精密数字锁相测量电机转速的方法和电路，此种方法不同于目前普遍采用的M／T测速方法。使用该方法，可以直接获得始终跟随电机速度变化的测速值，测速精度高、应用简单，目前已经成功地应用于笔者研制的交流伺服系统的反馈通道中。     

A novel 3D optical method for measuring and evaluating springback in sheet metal forming process

A novel 3D optical method for measuring and evaluating the springback in sheet metal forming is presented and its principle, program and steps are studied. The optical method includes a measuring method and evaluation indexes. The point cloud, obtained using photogrammetry and surface scanning systems, is used as the workpiece shape after springback. The original mould is regarded as the CAD model before springback. The point cloud and CAD model are aligned in Geomagic Qualify. A cutting line for the point cloud or CAD model can be obtained at any point in any direction of their cross sections. The springback is calculated as the difference between any two corresponding key points on the two cutting lines. The evaluation index S consists of a 3D springback value w and its vectors along x, y and z directions. Feasibility of the optical method is verified by using a refrigerator door shell.     

A mechanism for the accelerated wear of high speed sliding surfaces in the presence of spherical particles

A mechanism for the accelerated wear of bearing surfaces due to the cutting action of the spherical particles between bearing surfaces in sliding contact is proposed and verified experimentally.