摘要:

AbstractA complete theory of Gaussian beam scattering by a sphere is exposed. It is a generalization of the Lorenz‐Mie Theory to the case of Gaussian beam illumination. The spherical, isotropic and homogeneous scatterer may be located anywhere with respect to the beam. The Bromwich Scalar Potentials are used to solve the scattering problem and expressions are obtained for the scattered field (both in the near field and far field regions), the scattered intensities and the phase angle. In the limit of special cases the expressions agree with previous works restricted to more particular problem

ISSN:0934-0866    

DOI:10.1002/ppsc.19880050102

出版商:WILEY‐VCH Verlag GmbH    

年代:1988

数据来源: WILEY

ISSN:0934-0866    

DOI:10.1002/ppsc.19880050101

出版商:WILEY‐VCH Verlag GmbH    

年代:1988

数据来源: WILEY

摘要:

AbstractWhen a particle crosses a laser beam out of the focal plane, the light attenuation signal occuring on the beam axis contains some information regarding the particle size and trajectory.These attenuation signatures are analysed and predicted with a simplified model based on Fraunhofer diffraction. Numerical and experimental results are found to be in good agreement.A modified laser Doppler velocimeter using this sizing method is able to perform simulataneous measurement of size and velocity of spherical particle in the range 10 μm–500

ISSN:0934-0866    

DOI:10.1002/ppsc.19880050103

出版商:WILEY‐VCH Verlag GmbH    

年代:1988

数据来源: WILEY

摘要:

AbstractThe size distributions of carefully screened √2 size fractions of ground materials were determined using a Microtrac laser diffractometer. The size distributions were fitted to the empirical functionP(x) = 1/[1 + (x50/x)λ] whereP(x) is cumulative mass fraction less than Microtrac size,x. The standard deviation of λ for a 50 second test time was approximately 0.5, so that seventeen test times give a mean with an estimated error within ± 0.25 (95% confidence level). Values of λ were 5.44, 4.82, 4.40 for a coal ground under different conditions, indicating statistically different shape distributions; the average value for mica was 2.91 owing to the high aspect ratio of the particles. The ratio ofx50to the geometric mean sieve size was 1.2 for the coal and 0.70 for

ISSN:0934-0866    

DOI:10.1002/ppsc.19880050104

出版商:WILEY‐VCH Verlag GmbH    

年代:1988

数据来源: WILEY

摘要:

AbstractIn the wide field of fluid mechanics and multiphase flows, particle characterization plays an important role for massmomentum‐ and energy‐balances. Using the phase‐Doppler‐difference method for absolute measurements of the particle sizes and velocities from these data also predictions of the local particle fluxes and the particles' kinetic energy fluxes are possible. A description of the method will be given and the required optical and electronical equipment for these measurements and for the appropriate data presentation, will be di

ISSN:0934-0866    

DOI:10.1002/ppsc.19880050105

出版商:WILEY‐VCH Verlag GmbH    

年代:1988

数据来源: WILEY

摘要:

AbstractExperiments with common powder laboratory apparatus are used to illustrate the problems of sampling a poorly mixed quantity of glass ballotini. The use of known and easily sieved mixtures permits the quantitative analysis of the results to show how bias in samples may be detected.

ISSN:0934-0866    

DOI:10.1002/ppsc.19880050106

出版商:WILEY‐VCH Verlag GmbH    

年代:1988

数据来源: WILEY

摘要:

AbstractThe limiting resolution of Coulter size measurements, the size within which two separate populations can be distinguished, is discussed in relation to the standard aperture.Electronic pulse editing, by comparing pulse height to width, enables small particles to be resolved from baseline instrument noise, but can give incomplete resolution of ultra‐narrow distributions from artefactually produced peaks using the standard aperture. Improvements in the minimum measurable size and in sizing resolution of narrow size ranges are also shown to be possible by improving the signal quality from the Coulter aperture.A novel mathematical approach is described for the derivation of true size spectra for narrow particle size distributions by deconvolution of the composite spectra resulting from the effect of the inhomogeneous electric field in the Coulter aperture. Simple empirical equations are used derived from the location and amplitude of the spurious peaks observed in such composites relative to the genuine peaks.The method is applied to three “industrial” materials (wide size range samples) to determine the likelihood that such size ranges are affected by the spurious or artefactual peaks. A fresh blood sample deconvoluted by this method is shown to be apparently composed of more than one population of

ISSN:0934-0866    

DOI:10.1002/ppsc.19880050107

出版商:WILEY‐VCH Verlag GmbH    

年代:1988

数据来源: WILEY

摘要:

AbstractWe try to evaluate the level of confidence that can be placed in the optical methods available for sizing cometary dust (and, at the same time, deriving all its other characteristics). We use for this purpose the new informations provided by the in‐situ sampling of Comet Halley dust. We try to determine whether data from this origin are compatible with visible and I. R. spectra of this comet acquired from the Earth, and with earlier interpretations of such spectra. We find that, as happens frequently when remote sensing and local sampling techniques data can be compared, none of these techniques can claim to be fully satisfactory. In the case of cometary dust, current estimates based on optical sizing only may be much less accurate than precedingly assumed. Improvements in the observational approaches appear needed, as well as new laboratory investigations and theoretical developments to improve the capabilities of the optical studies of cometary dus

ISSN:0934-0866    

DOI:10.1002/ppsc.19880050108

出版商:WILEY‐VCH Verlag GmbH    

年代:1988

数据来源: WILEY

ISSN:0934-0866    

DOI:10.1002/ppsc.19880050109

出版商:WILEY‐VCH Verlag GmbH    

年代:1988

数据来源: WILEY

ISSN:0934-0866    

DOI:10.1002/ppsc.19880050110

出版商:WILEY‐VCH Verlag GmbH    

年代:1988

数据来源: WILEY