bluuebunny/crossref_metadata_2025_split huggingface dataset:
Experimental Characterization of Fineparticle Profiles Exhibiting Regions of Various Ruggedness
Authors: Kaye Brian H. , Clark Garry G. 
Published: December 2004

AbstractIn previously reported studies it has been shown that a rugged two‐dimensional fineparticle profile boundary may exhibit different ruggedness at different levels of scrutiny. The different types of ruggedness can sometimes be described by a boundary fractal dimension the magnitude of which can be related to the physical processes which formed the fineparticle. New data illustrating this fact is presented. Detailed examination of some rugged fineparticle boundaries and similar structures suggests that some boundaries exhibit more than one level of ruggedness around the perimeter of the profile. Data illustrating this fact are presented. The possible physical significance of the multifractal structure around the perimeter of a fineparticle profile is discussed. The need for objective criteria to be followed when splitting profiles into regions of different ruggedness is discussed. The possibility of basing the partition algorithm on the inspection of the sequential chord length generated in an equipaced exploration of the perimeter is suggested.
Regularized Inversion of Correlation Functions in Dynamic Light Scattering
Authors: Dhadwal Harbans S. 
Published: December 2004

AbstractA linear regularized technique, requiring no a priori information, is described for the inversion of correlation data obtained from dynamic light scattering measurements of polymer/colloidal suspensions. The procedure allows the determination of the characteristic linewidth distribution function, which is normally the first step towards obtaining a particle size distribution.
A Light Scattering Instrument to Discriminate and Size Fibres Part 1: A theoretical description using the RGD approximation
Authors: Jones Alan R. , Savaloni Hadi 
Published: December 2004

AbstractAs part of the development of a light scattering instrument to detect fibres, scattered light from finite cylinders which are exposed to light at arbitrary orientation is studied using the Rayleigh – Gans – Debye approximation. Form anisotropy, which is crucial to the performance of the instrument, is allowed for by using the Shifrin modification in which the elemental volumes are considered to be prolate spheroids. For long cylinders this is compared with van de Hulst's model in which the rigorous theory for an infinite cylinder is modified by Fraunhofer diffraction on the length. For very short cylinders comparison is made with the Mie theory for spheres.
A Light Scattering Instrument to Discriminate and Size Fibres. Part II: Experimental system
Authors: Jones Alan R. , Savaloni Hadi 
Published: December 2004

AbstractA Light scattering technique is described which can discriminate, size and count airborne fibres down to 1.6 μm diameter. The results are compared with Mie theory for spheres and two models for finite cylinders based on the Rayleigh‐Gans‐Debye approximation and rigorous infinite cylinder theory modified by Fraunhofer diffraction on the length.
The Linearity and Response of Focussed Apertures
Authors: Cowan Mark P. , Harfield John G. 
Published: December 2004

AbstractPractical experience of particle size analysers using the Coulter principle shows that for measurements made over a range of 2% to 60% of the aperture diameter, the aperture responds linearly to particle volume at least for spheres. In this paper it is shown that the response of a focussed aperture is not significantly different from an unfocussed aperture. It is also shown that a simple linear equation of response successfully applied to a COULTER COUNTER® model ZM in a previous paper, can be used to predict the calibration constant of a new wide range instrument, the COULTER® MULTISIZER.
Improved Accuracy in the Measurement of Particle Size Distribution with a coulter counter equipped with a hydrodynamically focused aperture
Authors: Göransson Billy 
Published: December 2004

AbstractIt is well known that broadening of the observed particle size distribution occurs both at the finer end and at the coarser end of the distribution when using the Coulter Counter. This problem can partly be overcome with the aid of electronic pulse editing. However, it has been found that the accuracy can be further improved when the Coulter Counter is equipped with a hydrodynamically focused (HDF) aperture. The standard deviations of the main peaks of samples with diameters of 5.0, 10.2, 15.1 and 20.0 m̈m decreased by 21%‐49% with HDF. HDF also prevents artefacts at the fine side of the main peak that originate from particles re‐entering the sensing zone of a standard aperture after they have passed through it. In the experimental model used i.e. a silica sample with a diameter of 15.6 m̈m, the estimate of small particles (>10 μm) decreased from 6.5% to 0.4%.
Use of the Laser Diffraction Technique for Particle Size Measurement at high suspension densities
Authors: Ulrich Joachim , Stepanski Manfred 
Published: December 2004

AbstractA laser diffraction technique for the on‐line measurement of crystal growth rates was developed. The crystal growth experiments were executed in a fluidized bed apparatus with a specially designed measuring chamber. It is typical in crystallization from solutions to deal with non‐spherically shaped particles at high suspension densities (3‐25 Vol.‐%). The results achieved in a first approach with commercially available instruments were not understandable. It was shown that the particle size distributions from experiments at high suspension densities depend on the volume concentration. This effect was examined by experiments with constant particle sizes and different volume concentrations.If the volume concentration is detected and used to correct the results achieved for the particle size distribution, understandable and reproducible results can be obtained.The necessary correlation function for the measurements at high suspension densities is introduced.
Technologically Relevant Particle Shape Analysis
Authors: Drescher Sigrun , Heidenreich Eberhard , Müller Gerhard 
Published: December 2004

AbstractThe current state in shape analysis is distinguished by a number of characterization methods, but the great variety of specific shapes complicates the selection of parameters that are relevant for a particular problem. Therefore, the preferred approach is to characterize single particles "free of presupposition" and to select technologically relevant parameters using cluster and discriminance algorithms.Parameter vectors including elongation, bulkiness, fractal dimension and area‐equivalent diameter are calculated on the basis of image analysis. First applications to bacteria and agricultural freestuffs exemplify the concept and illustrate that technologically relevant particle shape analysis permits the classification of single particles and the quantification of property functions.
Standard Media for Particle Size and Number‐Density Calibrations in single, multiple and dependent scattering
Authors: Guidt Jean‐Bernard , Toulouzan Jean Noël Le , Thioye Massamba , Gouesbet Gérard 
Published: December 2004

AbstractTwo kinds of standard media for particle size and number‐density measurements and calibration are described. Although the main concern is multiple scattering situations, they might also be useful for single and dependent scattering. One medium is made of particles embedded in a solid polymer matrix and the other of particles embedded in a gel. Transmittance measurements at two wavelengths (visible and far‐infrared) are used to exemplify the use of these media.
Dual‐Cylindrical Wave Method for Particle Sizing
Authors: Naqwi Amir A. , Liu Xiao‐Z. , Durst Franz 
Published: December 2004

AbstractA new laser Doppler method for particle sizing has been developed. In contrast to the standard phase Doppler technique, which uses scattering from plane waves for a measurement, the proposed method employs cylindrical waves of incident light. The main advantage is that signal frequency, instead of the signal phase, becomes a function of particle diameter and a standard frequency measuring device may be used as a signal processor. The advantages of spectrum analysis as the signal processing method are highlighted.The laws of geometrical optics applied to the present scattering problem provide a relationship for the frequency of the collected signal which is expressed as the sum of two terms, the conventional Doppler frequency and the "anisotropic frequency", which is directly dependent on the particle size. These theoretical assertions were examined experimentally. Measurements on glass and metal particles of known diameters showed good agreement with the theory.
Calculated Characteristics of Droplet Size and Velocity Distributions in liquid sprays
Authors: Li Xianguo , Tankin Richard S. , Renksizbulut Metin 
Published: December 2004

AbstractPredictions of the droplet size and velocity distributions in sprays under isothermal conditions are reported. The calculations are based on the maximum entropy formalism, complying with the conservation laws of liquid mass, momentum and energy. This theoretical approach considers only the macroscopic quantities about the atomization processes, without resorting to the details of the liquid breakup processes such as the onset and growth of instabilities. The derived joint droplet size and velocity distribution function depends on the Weber number as well as the liquid mass, momentum and energy source terms.These parameters represent the conditions under which the atomization occurs. The droplet velocity distributions are truncated Gaussian distributions for any specific sizes. The nondimensional Sauter mean diameter decreases slightly with the Weber number and then approaches an asymptotic constant. The calculated values of D21/D30 are very close to unity which agrees with the experimental observations. The computations also show that the atomization efficiency is very low; less than 2.6 percent.
Use of One‐Parameter Models for the Assessment of Particle Interactions by photon correlation spectroscopy
Authors: Finsy Robert 
Published: December 2004

AbstractThe use of very simple one‐parameter models of particle interactions for the analysis of the concentration dependence of the collective diffusion coefficient as determined by photon correlation spectroscopy is illustrated by measurements on two different systems. In one, a micro‐emulsion, attractive interactions are dominant whereas in the other, a silica dispersion, repulsive interactions play the major role.
The Use of Simulated Fractals in Particle Characterization
Authors: Gentry James W. 
Published: December 2004

AbstractThe principal focus in this paper is the development of a general method to simulate irregulary shaped particles whose perimeters are fractal. It is shown that this method can produce a particle of almost arbitrary fractal dimension. The Fourier components of these fractals are then computed. It is shown that these components were either independent of the fractal dimension or that any dependence is less important than other properties of the cluster such as symmetry and aspect ratio.
Sizing Nanoparticles by Means of Elliptically Polarized Scattered Light: A suggested method
Authors: Bohren Craig F. 
Published: December 2004

AbstractGiven the paucity of optical methods for sizing nanoparticles (those between 1 and 100 nm), more methods are needed if, as has been predicted, such particles have a bright future. Linearly polarized light is transformed into elliptically polarized light upon scattering by small spheres at 90°. The resulting circular polarization increases as the fifth power of particle diameter and the shift of the azimuth of the vibration ellipse from the vertical increases as the square if the particles are negligibly absorbing. Titanium dioxide spheres (in air) with diameters between 20 and 120 nm give circular polarizations between about 10−5 and 10−1 for incident light of wavelength 450 nm. The corresponding azimuth shifts (in radians) lie between about 10−2 and 1. These values are within reach of experimental techniques based on polarization modulation. Metallic spheres yield much larger circular polarizations and azimuth shifts (with signs opposite those for negligibly absorbing spheres), both of which increase approximately as the square of particle diameter.
Particle Dispersion in Turbulent Flow: The effect of particle size distribution
Authors: Sommerfeld Martin 
Published: December 2004

AbstractThe measured velocity fluctuation of particles in dispersed twophase flow systems is discussed and an interpretation of particle velocity statistics is given. Besides the turbulent velocity fluctuations resulting from the particle's response to the fluid turbulence, two additional apparent fluctuation components may be distinguished, caused by inertial effects of the particles and by a polydisperse particle phase.Especially for larger particles inertial effects may become important and therefore the particle motion in the flow field is strongly governed by the inlet conditions, namely the instantaneous particle velocity. Therefore, the measured axial particle velocity fluctuation at a given location may be considerably increased as particles from different starting locations with different initial velocities may cross the same measuring point. This dynamic particle behaviour is demonstrated by the numerical simulation of particle trajectories in a given flow field. The results show the importance of including appropriate inlet conditions for the numerical prediction of particulate two‐phase flows.Further, in experimental realizations of particulate two‐phase flows, the particles usually exhibit a certain size distribution. Owing to the different responses of the different sized particles to both the mean flow field and the turbulence characteristics of the flow, the measured particle velocity fluctuations are higher than in the comparable monodisperse case. Therefore, the particle size distribution was taken into account in the present numerical calculations in order to obtain results which are comparable to the corresponding experiments. In this numerical simulation the particle mean velocity and the rms value of the velocity fluctuation were obtained by averaging over the whole particle size distribution and then compared with the measured values. Calculations are presented for two different shaped particle size distributions with a different mean size and compared with calculations with a monosized particle material and experimental results.Further, the behaviour of the different sized particles in the particle size distribution is discussed by considering the changes in the particle size distribution and the particle velocity distribution throughout the flow field.
The Kinetics and Shape Factors of Ultrafine Dry Grinding in a laboratory tumbling ball mill
Authors: Austin Leonard G. , Yekeler M. , Dumm Timothy F. , Hogg Richard 
Published: December 2004

AbstractThe kinetics of batch grinding quartz from a feed of 600 by 425 m̈m to a product of 80% less than 10 m̈m have been determined using screening and laser diffractometer sizing for size analysis. The specific rates of breakage decreased by a factor of about three when the material became less than about 100 m̈m in size, but the primary breakage distribution function also changed to give proportionately more fine material, so that the grinding efficiency expressed as the development of surface area (B.E.T.) per unit of energy input did not decrease. Analysis of the shape of the particles in the 25 × 38 m̈m size range showed that particles of this size produced by roll crushing or by 8 minutes of grinding of a 425 × 600 m̈m feed were not different but at long grinding times the particles were rounded. This suggests that the breakage mechanism changes to give more chipping and abrasion and less disintegrative fracture. As the material approached the ultrafine size range it adhered to the mill case and there was no further size reduction. However, a technique for striking the mill case to dislodge the particles was successful in allowing further grinding to 40% by weight less than 2 μm.
Bipolar Ion and Electron Diffusion Charging of Aerosol Particles in high purity argon and nitrogen
Authors: Wiedensohler Alfred , Fissan Heinz J. 
Published: December 2004

AbstractThe bipolar diffusion charging process is studied theoretically for aerosol particles in high purity argon and nitrogen. The Fuchs theory is extended by the incorporation of the free electron charging of the aerosol particles. The ion parameters for positive and negative ions are assumed to be identical. The influence of the free electrons explains the differences between the mean mobility and mean mass of negative and positive ions. The ratio of the electron number concentration to the number concentration of negative ions is used to fit the curves, calculated by the extended model, to the experimentally determined bipolar charge distribution in argon and nitrogen. The extended Fuchs model was found to be rather insensitive to variations in the mobility and mass compared with the model with four different ion parameters. Further experimental studies of the bipolar charge distribution in a gas mixture of pure nitrogen and sulfur hexafluoride, SF6, indicate the importance of the free electrons in the bipolar diffusion charging process.
Measurement of Size, Number Concentration and Velocity of Aerosol Particles using an optical particle counter
Authors: Sachweh Bernd 
Published: December 2004

AbstractAn aerosol measurement instrument is presented which allows for the simultaneous measurement of the size distribution, number concentration and velocities of particles. A commercial optical particle counter (OPC) was modified in terms of optics and signal evaluation to provide the required measurement information. The design of this instrument allows the definition of a cubic measuring volume by purely optical means. This is achieved by an aperture/lens system which projects a sharply defined light beam into a stream of aerosol flow. Light scattered from single particles at average angles of 90° is collected by two opposite receiver units, each projecting light on to a separate photomultiplier. The intensity of the scattered light with this instrument is found to be an unambiguous function of the particle size. The total number of particles detected per unit time results in the particle flux. The particle velocity can be calculated, in principle, through the correlation of the signal length and the optical length of the measuring volume, provided that the particles have a straight trajectory through the measuring volume and the measuring volume length in the mean flow direction is well defined. The absence of sharpness in real optical projections effects a border zone of definite length, in which the illumination declines to zero. This leads, together with the low‐pass filtering of the particle signals, to an increase in the length of the signal slopes, causing some difficulties in the determination of the signal length. A digital signal evaluation technique was developed that renders possible the clear differentiation between the slope and the kernel region of the signal. The latter represents the motion of particles through the completely illuminated region, which can be a more accurate parameter to define the signal length. In addition to the signal length determination, a cross‐correlation technique was tested for its potential to obtain particle velocity. the instrument has two interlaced measuring volumes of nearly the same size, which are shifted for this special application in the main flow direction by 20 μm. The phase difference between the signals from the two photomultipliers, together with the optical distance, yields the particle velocity.
Particle Sizing by Dynamic Light Scattering: Noise and distortion in correlation data
Authors: Ross Douglas A. , Dimas Nicholas 
Published: December 2004

AbstractTwo undesirable effects occur in particle sizing by dynamic light scattering; statistical noise, and distortion of correlation data. Statistical noise in the correlation data, caused by estimating the autocorrelation of scattered laser light by a time average, leads to non‐physical artifacts in the resulting linewidth distribution. These may be removed by regularization, computer modeling, or other techniques. The regularized kernel function for inverting the Laplace transform is calculated, and used to illustrate the problem of noise. Correct choice of the regularization parameter gives the minimum overall error. It is found that excessive error occurs unless the linewidth distribution is modeled over a finite range. Analytical models for the linewidth with finite range, based on the beta distribution of probability theory, are given.Distortion of correlation data may occur in three ways, through a focused or otherwise nonuniform laser beam in the optical system, by insufficient bit resolution in the quantized detection of scattered laser light, or by calculating a first order field autocorrelation from a second order intensity autocorrelation. Unlike noise, distortion cannot be removed by any known methods, since the exact nature of the distortion is unknown. Several examples illustrate how distortion can lead to artifacts in the linewidth distribution which could easily be misinterpreted as segments of a size distribution, not present in the physical sample.
In‐Line Particle Size Determination for Jet Agglomeration Processes
Authors: Schuchmann Harald , Schubert Helmar 
Published: December 2004

AbstractIn jet agglomeration plants, powders are agglomerated to obtain good instant properties. The free‐falling initial material is wetted in a spray cone by droplets or in a steam jet by condensation at the particle surface. In a subsequent region of high particle concentration, collision between particles occurs and agglomerates form, if the forces of adhesion are strong enough. A commercial measurement device, working according to the principle of Fraunhofer diffraction, was modified for in‐line application. It was used to measure particle size distributions and concentrations of solid particles and droplets in jets. A model is presented to calculate local particle sizes by means of mass balances from integral measurements over large volumes. The results of in‐line particle size and agglomerate size analyses show the practical importance of dry agglomeration during transport and lead to a better understanding of the subsequent wet agglomeration process.
Light Scattering by Anthophyllite‐Crocidolite Asbestos Fibers. Part I: The domain of convergence of the EBCM theory
Authors: Lapalme René , Patits Tom A. J. 
Published: December 2004

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 wave.
Cessation of Aggregate Growth
Authors: Amal Rose , Raper Judy A. , Waite T. David 
Published: December 2004

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.