摘要:

AbstractThe investigations of single and combined properties of particles or of particulate matter still belongs to the most important areas of present research and practical applications of Particle Characterization. Methods to measure single particle properties, as for instance particle size, shape, composition and velocity, are of much higher sophistication than before and they still aim at improved accuracy and higher resolution. There still is a considerable lack of understanding, and lack of theoretical interpretation and of experimental evidence of the differences seen in the correlation of different equivalent diameters, obtained when analysing the same irregularly shaped particle, or a distribution of particles, using different physical principles. Furthermore, there still is a lack of understanding of the influence of shape on the results obtained with optical methods using diffraction, light scattering etc., thus asking for more information with respect to the transferability of results from one physical principle to another. The measurement of combined particle properties comprises the simultaneous measurement of, for instance, size, velocity and concentration, which is of particular importance in the comprehensive description of multiphase flow systems. Those instruments which are in working order are highly complicated, not easy to use and to handle and they are in most cases special adaptations for a limited range of the variables to be analysed. There is also growing interest in the evaluation of socalled property functions. Particle Characterization will remain for quite a number of years just as exciting as it has been in the past. If industrial demand enforces the use of on‐line instrumentation it might even become more interestin

ISSN:0934-0866    

DOI:10.1002/ppsc.19860030302

出版商:WILEY‐VCH Verlag GmbH    

年代:1986

数据来源: WILEY

摘要:

AbstractA procedure for estimating the effectiveness of algorithms which retrieve size distribution parameters from cumulative fractions or moments is described. The principle of the algorithm is to select moments, or cumulative fractions, which minimize the condition number. Extensive tests of the algorithm for a distribution consisting of the sum of two log normal distributions were carried out. This procedure can be easily extended to use different numbers and types of constituent functions. The simulations indicated that moment methods which include positive and negative moments give the best result. When the means of the constituent distribution are close, the large condition numbers indicate that no algorithm will give unambiguous values for the parameters.

ISSN:0934-0866    

DOI:10.1002/ppsc.19860030303

出版商:WILEY‐VCH Verlag GmbH    

年代:1986

数据来源: WILEY

摘要:

AbstractThe performance of a Po‐210 radioactive ionizer for aerosol charge neutralization and bipolar charging has been evaluated. Monodisperse neutral and singly charged aerosols have been passed through the ionizer and their approach to the steady‐state Boltzmann charge measured by measuring the fraction of particles that are electrically charged. The result shows that anNtof approximately 2.5 × 105cm−3s is needed for the development of a steady‐state charge fraction equal to that given by the Boltzmann' s law whereNis the ion concentration andtis the residence time of the aerosol in the neutralizer. In addition, the performance of the ionizer for particle charge neutralization in a vibrating‐orifice aerosol generator has been evaluated and the result shows that the source is less effective for this application and the residual charge on the particles is considerably higher than that given by the Boltz

ISSN:0934-0866    

DOI:10.1002/ppsc.19860030304

出版商:WILEY‐VCH Verlag GmbH    

年代:1986

数据来源: WILEY

摘要:

AbstractThis paper describes an experimental investigation of the charge acquired by a single polymer particle when striking a plate. The particle was projected from a pneumatic gun with variable velocity and angle of impact. The deflected particle was then captured in a Faraday cup and the net acquired charge so measured. The measurements of charge are related, particularly, to the initial potential of the surfaces and to their work functions.

ISSN:0934-0866    

DOI:10.1002/ppsc.19860030305

出版商:WILEY‐VCH Verlag GmbH    

年代:1986

数据来源: WILEY

摘要:

AbstractThe mathematical treatments used in the evaluation of particle size distribution from pipet‐withdrawal centrifuge data are reviewed. An error in the published procedure for multiple‐sample withdrawal systems is pointed out and a corrected formulation is presented. An alternative treatment, based on a piece‐wise linearization of the size distribution is described. Computer simulations of the analytical and data evaluation procedures indicate that the errors in the original formulation are not generally serious and that the corrected and alternative procedures lead to very similar estimates. Except for some cases involving very narrow size distributions, the alternative approach appears to give slightly closer estimates of the size distribution. Comparisons based on actual experimental data are also desc

ISSN:0934-0866    

DOI:10.1002/ppsc.19860030306

出版商:WILEY‐VCH Verlag GmbH    

年代:1986

数据来源: WILEY

摘要:

AbstractIn the field of material science, especially for polydisperse materials, many questions arise which cannot be answered sufficiently and precisely without information which represents the random character of the structure in space. Computer simulation is here an effective tool used to create random arrangements of particles which may be regarded as a realistic representation of the underlying material. Of course, the presumption that the shape of each particle is a sphere is an idealization which is a certain handicap in modeling all the possible system properties. Nevertheless, it can be demonstrated that, by having an adequate subroutine, many phenomena which are influenced by the local topology of the particles and their interaction forces can be studied in more detail.

ISSN:0934-0866    

DOI:10.1002/ppsc.19860030307

出版商:WILEY‐VCH Verlag GmbH    

年代:1986

数据来源: WILEY

摘要:

AbstractWith the three‐plate‐capacitor method, as described previously by the author, reactions and heating processes in freely suspended particles (diameter 5‐50 μm) were investigated by using the diffraction pattern of a laser beam. Change of weight can be registered, during operation, by the a. c. and d. c. voltage connected to a capacitor. This device enables information to be obtained, from inside the droplets, on the gradient of density or the precipitation of small particles and on the formation and solution process of a crystal nucleus in anorganic and low molecular organic substances. The behaviour of high polymer materials was studied during heating in the central region ca. 4 μm of the droplet.The diffraction patterns are similar to those of crystals (micells), but they do not show any crystal nucleus in the center. The application of heat, up to the softening point, gradually diffuses this cell arrangement. Such phenomena have not previously been studied within a

ISSN:0934-0866    

DOI:10.1002/ppsc.19860030308

出版商:WILEY‐VCH Verlag GmbH    

年代:1986

数据来源: WILEY

ISSN:0934-0866    

DOI:10.1002/ppsc.19860030309

出版商:WILEY‐VCH Verlag GmbH    

年代:1986

数据来源: WILEY

ISSN:0934-0866    

DOI:10.1002/ppsc.19860030310

出版商:WILEY‐VCH Verlag GmbH    

年代:1986

数据来源: WILEY

ISSN:0934-0866    

DOI:10.1002/ppsc.19860030301

出版商:WILEY‐VCH Verlag GmbH    

年代:1986

数据来源: WILEY