摘要:

AbstractFractal Geometry developed in 1977 byB. Mandelbrotdescribes the structure of rugged systems by extending the concepts of classical dimensional analysis to include a fractional addendum to the topological dimension of a system in order to describe the space filling properties of the rugged system. In the 15 years since the publication ofMandelbrot's book describing his seminal ideas fractal geometry has found many applications in fineparticle science and technology. This body of applied knowledge is now known as Applied Fractal Geometry. The purpose of this review is to focus on the various branches of applied fractal geometry of interest to the fineparticle specialist in a systematic manner. The first part is concerned with ruggedness of fineparticle boundaries, the structure of simple porous bodies, fragmentation and powder production, the assessment of the properties of such materials as paper, and the characterization of rough surfaces. The second part will explore the use of fractal dimensions to describe mixing operations, composite bodies, such as synthetic bones, and paint films.

ISSN:0934-0866    

DOI:10.1002/ppsc.19930100302

出版商:WILEY‐VCH Verlag GmbH    

年代:1993

数据来源: WILEY

摘要:

AbstractThe Extended Boundary Condition Method (EBCM), also known as the T‐matrix method, is used to compute exactly the scattered intensities from homogeneous isotropic circular cylinders characterized by relative refractive index N, diameter D and length L. The domain of convergence of the method regarding the parameters N, D, L is established. The effect of the geometry of the fiber ends on the scattered intensities is considered. The incident field is assumed to be a linearly polarized plane harmonic wav

ISSN:0934-0866    

DOI:10.1002/ppsc.19930100303

出版商:WILEY‐VCH Verlag GmbH    

年代:1993

数据来源: WILEY

摘要:

AbstractThe practical performances of single and multi‐angle photon correlation spectroscopy (PCS) for resolving bimodal distributions of industrial poly (methyl methacrylate) samples was investigated in a comparative study by several users affiliated to academic and industrial groups and by two suppliers of commercial equipment. The results for the harmonic intensity averaged diameters obtained by cumulants analysis reported by the different laboratories are in agreement, in addition to the results for the normalized second cumulants. The uncertainty on the latter quantities is large, however. For the bimodal samples with two populations with average diameters in a ratio of about 2.5 : 1, not all users were able to resolve the distribution in its components by single‐angle PCS. Some slight improvement was obtained by multi‐angle PCS. Other indirect techniques (polarization intensity differential scattering, static light scattering data and disc photosedimentometer) appeared to be superior for resolving the bimodal distribu

ISSN:0934-0866    

DOI:10.1002/ppsc.19930100304

出版商:WILEY‐VCH Verlag GmbH    

年代:1993

数据来源: WILEY

摘要:

AbstractLaser Doppler anemometry (LDA) is one of the most advanced optical measuring techniques for flow velocities and is widely used in industrial and academic laboratories. Based on numerous applications in the past, there is no doubt that LDA is one of the most accurate flow measuring techniques. However, recent investigations have shown that the period lengths of LDA signal bursts are not as constant as one might expect within the individual burst. This can induce an additional scatter in the signal frequency and in the determination of flow velocity from individual bursts. This paper describes experimental investigations which show qualitatively and quantitatively that the particle passage through the laser beams shortly before the point of intersection, i. e. the LDA measuring volume, yields a distorted LDA fringe pattern. The latter results in a scatter of the measured velocity data for those particles passing the center of the measuring volume at the same time.

ISSN:0934-0866    

DOI:10.1002/ppsc.19930100305

出版商:WILEY‐VCH Verlag GmbH    

年代:1993

数据来源: WILEY

摘要:

AbstractEssentially the laser two‐focus (L2F) and laser Doppler anemometer (LDA) are time‐of‐flight anemometers. The velocity of particles in the micrometre range is determined within the limits of an optically fixed measurement distance. For this only one optoelectronic receiver for the detection of the scattered light is required [1, 2]. With an arrangement of two receiving optics, positioned under an off‐axis angle φ and an elevation angle ± ψ to the optical axis of the measurement system, a resolution of three‐dimensional structures can be achieved and with regard to spherical particles it is possible to determine the dimensions by means of the temporal or phase shift of the signals in the receiving optics. A particle size‐dependent distance inside the measurement volume can be fixed, which has to be passed in order to change the signal from one receiving optics to the other. An LDA with an arrangement of two receiving optics for particle sizing is known as a phase Doppler anemometer (PDA); an L2F designed with two receiving optics can be termed a pulse‐displacement two‐focus anemometer (P2F). The physical analysis of the two methods with respect to a temporal signal displacement in the receivers y

ISSN:0934-0866    

DOI:10.1002/ppsc.19930100306

出版商:WILEY‐VCH Verlag GmbH    

年代:1993

数据来源: WILEY

摘要:

AbstractThis paper is devoted to the description of the interaction between a spherical particle and a laser sheet beam (Gaussian beam focused by a cylindrical lens) by using the generalized Lorenz‐Mie theory (GLMT). Comparisons between the scattering properties of laser sheet, Gaussian beam and plane wave are carried ou

ISSN:0934-0866    

DOI:10.1002/ppsc.19930100307

出版商:WILEY‐VCH Verlag GmbH    

年代:1993

数据来源: WILEY

摘要:

AbstractVarious methods are available for reducing or ceasing growth of aggregating suspensions including the addition of highly charged adsorbents (such as gelatin), reduction of ionic strength by dilution, increase in surface charge by alteration in pH and reduction in suspension temperature. The effectiveness of each of these methods in stopping the aggregation of colloidalhematite without altering the aggregate size distribution is examined in this study. Reduction in aggregate temperature is found to be a particularly effective way of stopping the aggregation of hematite while preserving size distribution information.

ISSN:0934-0866    

DOI:10.1002/ppsc.19930100308

出版商:WILEY‐VCH Verlag GmbH    

年代:1993

数据来源: WILEY

ISSN:0934-0866    

DOI:10.1002/ppsc.19930100309

出版商:WILEY‐VCH Verlag GmbH    

年代:1993

数据来源: WILEY

ISSN:0934-0866    

DOI:10.1002/ppsc.19930100301

出版商:WILEY‐VCH Verlag GmbH    

年代:1993

数据来源: WILEY