摘要:

AbstractA new computer‐aided image analysis procedure for characterizing the number and sharpness of potential cutting facets on the profiles of the image of an abrasive fineparticle is described. In the method, the digitized profile is explored by a running chord generating procedure which generates what is described as the facet signature of the profile. This signature can be processed at different threshold levels to recognize facets of the profile having different levels of sharpness as defined by the acute angle of the facet. Several different ways in which data from the procedure could be used to describe a population of polishing powder fineparticles are outlined. The potential use of the new descriptive characterization procedures for following the physical changes in the powder corresponding to the degeneration in performance of a polishing powder during use is outlined. The possible use of the new methodology to describe the health hazards of angular shaped dust fineparticles and flake type fillers (such as mica) in composite material technology is outline

ISSN:0934-0866    

DOI:10.1002/ppsc.19920090102

出版商:WILEY‐VCH Verlag GmbH    

年代:1992

数据来源: WILEY

摘要:

AbstractTwo dimensional images are often used as a basic for calculating shape descriptors of particles. An edge roughness descriptor, the fractal dimension, can be found from a Richardson plot of measured perimeter versus the measuring step length. Data Scatter on these plots is shown to be related to the incipient formation of polygonal harmonics, which are regular polygons formed during a structured walk around the image edge. This relationship was verified using both computer generated fractal images and real particle outlines.

ISSN:0934-0866    

DOI:10.1002/ppsc.19920090103

出版商:WILEY‐VCH Verlag GmbH    

年代:1992

数据来源: WILEY

摘要:

AbstractAgglomerates of uniformly sized primary spheres are found in many aerosol and colloidal systems. Such particles have been described as fractal although they possess selfsimilarity over only a narrow range of length scales. Previous work suggests that, for such objects, ideal fractal scaling laws may require substantial corrections. The problem is particularly acute for measurements of particle structure from 2d images. The relation between the structure of an agglomerate and the characteristics of its projection is investigated using simple analytical models and clusters generated by a modified cluster cluster aggregation simulation. The morphology of the simulated clusters is varied by changing the ratio of masses of the colliding clusters. The fractal dimensionsDf3of the simulated clusters were typically 10–20% higher than those measured for the projections,Df2, even thoughDf3>2. This difference decreases as the cluster size increases. It was found that the fraction of primary particles visible in the 2d image is more sensitive to cluster size than to fractal dimension for clusters with less than several thousand primary particle

ISSN:0934-0866    

DOI:10.1002/ppsc.19920090104

出版商:WILEY‐VCH Verlag GmbH    

年代:1992

数据来源: WILEY

摘要:

AbstractA single parameter, denoted as the "aggregation probability", is introduced to represent the average potential of clustering in a suspension in which the aggregates are undergoing random and simultaneous coagulation and breakup by means of mechanical stirring. The parameter may be useful for obtaining quick estimates of the equilibrium cluster size distributions in such systems.

ISSN:0934-0866    

DOI:10.1002/ppsc.19920090105

出版商:WILEY‐VCH Verlag GmbH    

年代:1992

数据来源: WILEY

摘要:

AbstractTo understand the roles that wear particles play in disk crashes, analytical and numerical approaches have been used to study three dimensional fluid flow and wear particle transport and deposition in computer disk drives. The study shows that wear particles are flying very close to the disk surface. They can deposit on the disk surface and cause damage to disk drives. Cooling air flow through the disk hub of corotating disks has been found to play important roles in removing wear particles from disk drives. Parametric study has shown that the optimum cooling air flow rate is 12 slpm for 8″ disk with the Reynolds number of 150,00

ISSN:0934-0866    

DOI:10.1002/ppsc.19920090106

出版商:WILEY‐VCH Verlag GmbH    

年代:1992

数据来源: WILEY

摘要:

AbstractThe use of monosized droplet streams for the calibration and testing of optical particle sizing methods and their application to the study of basic phenomena in two‐phase systems are discussed. Owing to their coherent structure–all the droplets have the same size and spacing–such droplet streams are very useful tools for these applications. The droplets streams have been produced with a vibrating‐orifice generator. Limitations and problems that occur during the operation of these generators are described. Special emphasis is laid on the problem of the loss of coherence with increasing distance from the exit of the generator, which sometimes restricts the application of the generator for certain p

ISSN:0934-0866    

DOI:10.1002/ppsc.19920090107

出版商:WILEY‐VCH Verlag GmbH    

年代:1992

数据来源: WILEY

摘要:

AbstractThe newly developed dual‐cylindrical wave laser system is an alternative to the phase Doppler technique. It requires only frequency measurements for particle sizing and velocimetry, and hence prevents the difficulties associated with the phase measurements. This technique was evaluated experimentally using monosize liquid droplets of water and diethyl phthalate. The experimental results are compared with the theoretical predictions of the system response, based on geometrical optics and the electromagnetic theory of light, under certain simplifying assumptions. Although the measurements generally agree with the theory, some minor oscillations in the measured response are only roughly represented by the theory. Also, the experimental data indicate a large deviation from the theory if the particle is within a distance of three diameters from the origin of the cylindrical waves, hence defining the boundary of the region in which the theory is applicable. This work indicates that a properly laid out dual‐cylindrical wave laser system can be employed for sizing of small droplets in liquid spr

ISSN:0934-0866    

DOI:10.1002/ppsc.19920090108

出版商:WILEY‐VCH Verlag GmbH    

年代:1992

数据来源: WILEY

摘要:

AbstractMUSCAT is a Monte Carlo code for numerical simulation of Multiple Scattering. Only the general restrictive assumptions of the steady‐state, scalar radiative transfer equation are required, hence the MUSCAT code can deal with a broad field of applications. The algorithm follows the physical phenomena as closely as possible and realistic 3‐D problems can be handled without geometric simplifications. Special care has been devoted to the analysis and validation of the pseudo‐random generator subroutine. Global validations of the code in 1‐D and 2‐D geometries have been successfully carried out. An example of application is reported concerning 3‐D studies of visibility in fo

ISSN:0934-0866    

DOI:10.1002/ppsc.19920090109

出版商:WILEY‐VCH Verlag GmbH    

年代:1992

数据来源: WILEY

摘要:

AbstractA semi‐analytical model of multi‐component droplet vaporization in a convective environment is formulated. The model includes many important physical effects such as variable properties, non‐unity Lewis number, transient liquid phase heat and mass transport, and the blowing effect of evaporation on heat, mass and momentum transfer. The liquid phase heating is calculated from a Nusselt number model which incorporate heat transfer enhancement due to internal circulation. The model predictions are in good agreement with detailed numerical results for droplets vaporizing in various ambient conditions. The behavior of droplets in simultaneously changing concentration, temperature and velocity fields, is also exa

ISSN:0934-0866    

DOI:10.1002/ppsc.19920090110

出版商:WILEY‐VCH Verlag GmbH    

年代:1992

数据来源: WILEY

摘要:

AbstractA general procedure for the design of a phase Doppler system is presented, which includes computations based on the computer codes described previously. The utility of Mie computations is demonstrated through six examples pertaining to sizing of large particles; in particular, new considerations in bubble sizing are pointed out. Through additional examples, it is shown that the phase Doppler technique may be used for sizing of submicron particles as well as large particles. Recognition of particle material, in addition to the measurement of diameter, is also made possible.

ISSN:0934-0866    

DOI:10.1002/ppsc.19920090111

出版商:WILEY‐VCH Verlag GmbH    

年代:1992

数据来源: WILEY