ISSN:0934-0866    

DOI:10.1002/ppsc.19960130402

出版商:WILEY‐VCH Verlag GmbH    

年代:1996

数据来源: WILEY

摘要:

AbstractCoherent transmission and reflection of a plane wave through a monolayer of discrete particles are considered on the basis of simple and physically transparent formulae for the single scattering approximation (SSA) corrected by introducing a multiple scattering permittivity factor. This factor allows for multiple scattering of Waves between monolayer particles, opposite to the SSA. The multiple scattering permittivity factor is considered on the basis of the quasi‐crystalline approximation (QCA) viaŤmatrix formalism. The multiple scattering permittivity factor and parameters for obtaining coherent transmission and reflection coefficients (the effective extinction coefficient and the transmission and reflection coefficients due to rescattering) are calculated within the scope of QCA and plotted for comparison with SSA results. The expressions for these values are simplified for small Rayleigh particles to simple analytical formul

ISSN:0934-0866    

DOI:10.1002/ppsc.19960130403

出版商:WILEY‐VCH Verlag GmbH    

年代:1996

数据来源: WILEY

摘要:

AbstractThis paper describes a study to determine the most appropriate particle size parameter for polydisperse powders dispersed as aerosol and detected by light scattering. It is relevant to many areas of engineering research. By means of calculations of the intensity of light scattered from particles of different sizes, it has been shown that the surface median aerodynamic diameter (SMAD) is an appropriate measure for polydisperse aerosolised powders. The microscope‐based procedure for obtaining the SMAD is described, as well as its implementation for narrowly‐graded polydisperse powders of fused alumina of type which have been widely used in studies of particle transport in wind tunnels. It was shown that for the fused alumina powders examined, SMAD = 1.25 x (PASMAD), where PASMAD is theprojected area surface median aerodynamic diame

ISSN:0934-0866    

DOI:10.1002/ppsc.19960130404

出版商:WILEY‐VCH Verlag GmbH    

年代:1996

数据来源: WILEY

摘要:

AbstractThe light scattering technique is now widely used in particle sizing, and includes the turbidimetric spectrum method. Although it has been reported that the light scattering technique, especially the turbidimetric method, is sensitive to refractive index, quantitative studies are rare. In this work, the effects of refractive index on the turbidimetric spectrum method were comprehensively investigated and detailed results are presented.

ISSN:0934-0866    

DOI:10.1002/ppsc.19960130405

出版商:WILEY‐VCH Verlag GmbH    

年代:1996

数据来源: WILEY

摘要:

AbstractComputer simulations of diffusion‐limited aggregation (DLA) for monomers to investigate the effects of size and of lognormal distribution on the fractal dimensionality of the aggregates were conducted on a two‐dimensional lattice. The results show the DLA clusters posses multifractal characteristics. For clusters consisting of monodisperse monomers, the bifurcation point on the graph of the pair correlation function (PCF) for each cluster is located right at the monomers size under investigation The textural dimension (Df1) has a stable value of about 1.65, whereas the structural dimension (Df2) decreased with increase in monomer size. For the cases with monomers in log‐normal distributions, the textural dimension is around 1.67; however, the structural dimension decreases with increasing polydispersity of monomer

ISSN:0934-0866    

DOI:10.1002/ppsc.19960130406

出版商:WILEY‐VCH Verlag GmbH    

年代:1996

数据来源: WILEY

摘要:

AbstractA concern about all reinforcing fibers is the extent to which they are respirable. The degree of respirability of a particle is frequently estimated in terms of its aerodynamic equivalent diameter being less than a certain value (typically 3.5 to 7 μ). However, the aerodynamic equivalent diameter, like the Stokes diameter, is only defined exactly for spheres, which is far from the shape of acicular fibers. Thus, it is useful to be able to calculate, based on actual fiber diameter and aspect ratio, the effective Stokes and aerodynamic equivalent diameters of various fibers. The present paper derives simple expression for relating the two effective diameters to actual fiber dimensions.Calculated results are compared with experimental data for glass fiber and three fractions of phosphate fiber [1], which is a short, reinforcing inorganic fiber. Agreement is seen to be good. Phosphate fiber was fractionated using a sedimentation technique described in the paper. The resulting fractions were characterized by semi‐manual measurements of micrographic dimensions and compared with results obtained from particle size instruments based on sedimentation principles. Based on these results, a large weight fraction of phosphate fiber is predicted not to be respirab

ISSN:0934-0866    

DOI:10.1002/ppsc.19960130407

出版商:WILEY‐VCH Verlag GmbH    

年代:1996

数据来源: WILEY

摘要:

AbstractWhen properly measured and interpreted angle of repose (AOR) can be a useful method of characterising a powder. Unfortunately, a multitude of definitions and measuring equipment is used. A review of the inherent problems is presented in the first part of this paper.The second part of the paper describes the improvements made to a measuring device developed originally for measuring the angle of repose of soda ash, so that a wider range of powders can be tested. In the improved design, the tendency of cohesive and semi‐cohesive powders to block the device's funnel has been eliminated.A total of 73 powders consisting of four different materials, and covering Groups A, A/C and C ofGeldart'sclassification, have been tested using the new equipment. The results show that AOR increases systematically with decrease in mean particle size. Combination of AOR measured in the new device with aerated bulk density provides a quick, sensitive and effective method for characterising a wide range of powder

ISSN:0934-0866    

DOI:10.1002/ppsc.19960130408

出版商:WILEY‐VCH Verlag GmbH    

年代:1996

数据来源: WILEY

摘要:

AbstractThe avalanching behaviour of two coal types was determined, one of good and the other of poor handleability characteristics. This revealed significant differences in the nature of flow of the coals. Analysis of the strange attractors of the weight series of avalanches enabled quanitification of this difference, and the establishment of practical, relative criteria for the measurement of coal handleability. These criteria will now enable a structured study of the variables that affect handleability, for example proportion of fines and moisture content, and industrial consumers of coal to specify minimum acceptable limits for its transport characteristics.

ISSN:0934-0866    

DOI:10.1002/ppsc.19960130409

出版商:WILEY‐VCH Verlag GmbH    

年代:1996

数据来源: WILEY

ISSN:0934-0866    

DOI:10.1002/ppsc.19960130410

出版商:WILEY‐VCH Verlag GmbH    

年代:1996

数据来源: WILEY

ISSN:0934-0866    

DOI:10.1002/ppsc.19960130401

出版商:WILEY‐VCH Verlag GmbH    

年代:1996

数据来源: WILEY