bluuebunny/crossref_metadata_2025_split huggingface dataset:
Measurement of the Flow Behaviour of Aerated and Fluidised Powders using a rotating viscometer
Authors: Hobbel Erik F. , Scarlett Brian 
Published: May 2005

AbstractThe rheological behaviour of a fluidised bed of alumina powder was determined using a specially designed form of rotating viscometer. Several different geometries of the inner and outer cylinder were tested. In the machine the two cylinders can be rotated independently, in either direction, which enables both their relative velocity and absolute velocity to be varied. Thus, the torque on the inner cylinder, strain‐rate and the absolute velocity have been chosen as the consistency variables. Some examples of the derived consistency surface are given. The characteristics of these surfaces could be explained by assuming different states of structure, to which a certain mobility can be ascribed. It is proposed that any state of structure which can exist in the bed is an intermediate of two extremes the first being the immobile state which is elastic and has a yield value and the second being the dynamic state which behaves like a Newtonian fluid.
Generalized Locking Profile for Angular Particles ‐ Locked Particle Theory
Authors: Meloy Thomas P. , Clark Nigel N. 
Published: May 2005

AbstractLocked particles are defined as those comminuted or particles which contain both gangue and target material. By considering the shape of the comminuted particles and assuming their random distribution in the ore body prior to comminution, it is possible to derive locking profiles which give the frequency of occurrence of particles which have a given fraction of their volume occupied by target material. For most particle shapes (spheres, angular particles, angular plates and rods) the locking profile is a deep U‐shaped curve. This suggests that few particles by number contain about 50% target material while a far greater number contain either very little or very much target material. Such a conclusion is important in planning separation processes for locked particles in the mineral industry.
Fractional Penetrations for Electrostatically Charged Fibrous Filters in the Submicron Particle Size Range
Authors: Lathrache Reda , Fissan Heinz 
Published: May 2005

AbstractParticle penetrations through commercially available, electrically charged fibrous filters have been measured. The particles were monodisperse and in charge equilibrium. Tests were conducted for several particle sizes in the range 0.02 μm ≤ x ≤ 1 μm. The face velocity was varied in the range of 2 cm/s to 30 cm/s. The penetration has a bimodal dependence on particle size. This behaviour is not found for uncharged filters. The reduction in penetration and bimodal dependence is attributed to electrical collection effects. As the face velocity is increased, the electrostatic collection effects are significantly reduced. The results agree quantitatively with a model for particle penetration through charged fibrous filters recently presented in the literature by the authors.
Real‐Time Ultrasonic Process Tomography of Flowing Mixtures
Authors: Hoyle Brian S. 
Published: May 2005

AbstractThis paper presents a generic application study of the simple but fundamental limitations in the industrial exploitation of ultrasonic process tomography to dynamic flowing mixture processes. The background to two‐dimensional ultrasonic process tomography is reviewed and the key implementation aspects which uniquely limit its performance are explored. Simple descriptors are presented, which allow the assessment of the applicability of ultrasound process tomography to particular applications.
Recent Advances of Diffraction Tomography in Geophysics, Ultrasonics, and Optics
Authors: Stamnes Jakob J. , Wedberg Torolf C. 
Published: May 2005

AbstractA tutorial review of diffraction tomography is given along with an overview of recent advances of this technique in borehole geophysics, ultrasonic imaging, and optical microscopy. First, the basic principles of diffraction tomography are presented. Then, we discuss a generalized inversion algorithm, valid for irregularly spaced data and a non‐uniform background, and present reconstructions based on ultrasonic water tank data and underground georadar data. Next, we discuss a hybrid filtered backpropagation algorithm for ultrasonic and optical imaging. Quantitative images, based on experimental data, are presented of objects embedded in water or in biological tissue and probed by ultrasound, and of fibers embedded in an index matching liquid and probed by laser light.
Applications for Tomographic Technology in Mining, Minerals and Food Engineering
Authors: Williams Richard A. , Atkinson Keith , Luke Stephen P. , Keith Barlow R. , Dyer Ben C. , Smith John , Manning Michael 
Published: May 2005

AbstractExisting and new applications for tomographic technology using optical, electrical radar and seismic sensing principles are described. It is demonstrated that important similarities link process instrumentation needs in the mineral benefication and food manufacturing sectors. The minerals industries provide a variety of challenging applications for tomography in the development and validation of models associated with acid mine drainage, the stability of mine workings, mineral exploration and other environmental needs such as monitoring landfill sites and groundwater plume dispersion.
Extinction Efficiency of Gradient‐index Microspheres
Authors: Kai Li , D'Alessio Antonio 
Published: May 2005

AbstractThe extinction efficiency of transparent spheres with a radial gradient of refractive index irradiated by electromagnetic plane waves was obtained by using the finely stratified sphere model [L. Kai, P. Massoli, Appl. Opt. 33 (1994) 501–511]. The extinction efficiency of gradient‐index microspheres and location changes of morphology‐dependent resonances on the Mie extinction efficiency curves are discussed.
The Fragmentation Fractal – a useful descriptor of broken rock
Authors: Brown Gareth J. , Miles Nick J. 
Published: May 2005

AbstractThe fragmentation fractal has been used to accurately describe the distribution of rock progeny from single particle breakage events. This paper illustrates the underlying physical significance of the fragmentation fractal and how it may be used as a fundamental tool in understanding rock pulverisation. The experimental determination of the fragmentation fractal is based on the measurement of particle size by project area as given by image analysis. In this format the characteristic length is defined as the square root of projected area. This approach to rock particle size analysis can have advantages over other techniques especially when the mass or number of fragments is small. A brief comparison has been made with size by projected area and the corresponding sieve size of artificial objects of different shape, but equivalent characteristic length. It is suggested that projected area measurements are less sensitive to the influence of particle shape and that this may even aid the comparison of distributions of fragments of significantly different morphologies.
Arrays of Uniform Latex Spheres as Test Objects in Optical Microscopy
Authors: Davidson John A. 
Published: May 2005

AbstractIt is the purpose of this communication to illustrate the utility of regular arrays of uniform high polymer latex spheres (2‐D crystals) as resolution test objects for the optical microscope. Such test specimen slides are easily prepared, inexpensive, and can be quite accurately characterized as to size of the spheres which make up the arrays.Through their use it was possible to experimentally verify the validity of the generalized form of Abbe' s rule (see Eq. (2)) for bright field microscopy.Similarly, it was possible to demonstrate that resolution in dark field microscopy is equal to and can sometimes surpass performance in bright field.Array test objects also hold great promise in the teaching of microscopy. The importance of proper micros topic technique and the difference between resolution and non‐resolution, resolution and detection, and the effect of the wavelength of light on resolution are all easily demonstrated through the use of latex arrays.
The Effect of Flowagents on the Rheology of a Plastic Powder
Authors: Kaye Brian H. , Gratton‐Liimatainen Julie , Lloyd John 
Published: May 2005

AbstractFlow agents are widely used in industry, such as the plastics and pharmaceutical industry, to promote the flow of cohesive powders. Few studies of the quantitative effects of the flow agents on the flow of the powder have been reported. In this communication the effect of silica flow agents on the flow of a plastic powder is studied by means of avalanching behaviour. The avalanching behaviour of the powder as modified by the silica flow agents is summarized using descriptive parameters based on the calculation of fractal dimensions in data space and phase‐space strange attractors. The structure of the strange attractors are shown to be statistically self‐similar and‐effective descriptors of the change of rheology caused by the presence of the flow agents.
Streaming Current Measuring for Determining the Zeta Potential of Granular Particles
Authors: Rodier Elizabeth , Dodds John 
Published: May 2005

AbstractA simple technique is presented for determining the zeta potential of large particles ( > 20 μm) by streaming current measurements. The method has the advantage of not requiring correction for surface conductivity. The theory involves a description of pore space by either Darcy's law or the Kozeny‐Carman equation. The simplifications introduced by assimilating the pore space to a bundle of capillary tubes are discussed. Results are presented for the variation of zeta potential with pH and ionic strength for a sieve cut of spherical glass beads and two different samples of irregular particles of silicon carbide.
The Use of an Antistatic Agent to Improve Powder Flowability
Authors: Orband Jan L. R. , Geldart Derek 
Published: May 2005

AbstractSmall quantities of Larostat 519, an anti‐static agent, were added to four samples of a commercial organic powder which was giving flowability problems believed to be caused by electrostatics. The effects on standardised bulk densities, on the Hausner Ratio, and on the behaviour of the samples when exposed to various controlled relative humidities in an experimental rotating inclined pan, were significant, and are reported and interpreted.
Hydrodynamic Focusing of Particle Trajectories in light‐scattering counters and phase‐doppler analysers
Authors: Ovod Vladimir I. 
Published: May 2005

AbstractTo reduce errors when measuring sizes of particles in light‐scattering counters and phase‐Doppler analysers, the hydrodynamic focusing of particle trajectories in relation to the centre of the measurement zone is used. This focusing is effected in a special running‐type chamber. Equations describing the mechanical energy of liquid flows running through a running‐type chamber have been compiled. By solving a system of such equations, relatively simple equations for engineering calculations of the coefficient of hydrodynamic compression of particle trajectories in relation to the centre of the measurement zone have been obtained. Results of experimental research are given and the application of the proposed technique for designing improved running‐type chambers with one and two “sheaths” is demonstrated.
Studying the Avalanching Behaviour of a Powder in a Rotating Disc
Authors: Kaye Brian H. , Gratton‐Liimatainen Julie , Faddis Neil 
Published: May 2005

AbstractThe use of a rotating disc to study the avalanching behaviour of a powder is discussed. It is shown that the strange attractor plotted in discreet time maps summarizes useful information on the rheological behaviour of powders and powder mixtures. In particular it is shown that the avalanching behaviour is related to the particle size distribution of the powder and that one can study the changes in rheological behaviour as another powder is mixed with it. The strange attractor patterns generated are dependent upon the environmental conditions under which the experiments are carried out. For this reason the measurements are referred to as an assessment of the holistic powder rheology. The potential use of the disc to study the holistic rheology of powder systems is outlined.
Symmetrical and Asymmetrical Flow Field‐Flow Fractionation for Particle Size Determination
Authors: Schauer Thadeus 
Published: May 2005

AbstractMeasurements on paint components have been conducted with symmetrical flow field‐flow fractionation (sym flow FFF) and asymmetrical flow FFF (asym flow FFF). Both methods are based on the same principle of separation, but they differ in the construction of the fractionation channel and the configuration of the channel flow and crossflow. On the basis of the good selectivity and resolution of these techniques, it was possible to determine the particle size of each individual constituent of a three‐component mixture of a paint binder, pigment and filler, characterized by relatively broad and overlapping distributions, and to follow the changes on mixing them. In the case of sym flow FFF, it was possible to use thinner fractionation channels, with no system peaks and good selectivity in both the normal and steric‐hyperlayer mode. The main features of asym flow FFF are the simpler construction of the fractionation channel and the possibility of focusing the sample in the channel better and of following visually the separation. This variant should be preferably used in the normal mode of operation.
Investigations on the Behaviour of an Aerodynamic Particle Sizer and its applicability to calibrate an optical particle counter
Authors: Heidenreich Steffen , Büttner Helmut , Ebert Fritz 
Published: May 2005

AbstractThe calibration of an optical particle counter (OPC) by means of the Aerodynamic Particle Sizer APS (TSI, Model 3310) was investigated. The pulse‐height distribution and the aerodynamic size distribution were measured by parallel use of an OPC and the APS. A calibration curve was obtained by comparison of the two different cumulative distribution curves. First calibration results are presented for spherical particles (water droplets and glycerine droplets): A comparison of these results with Mie calculations and aerodynamic calibrations by means of sampling cyclones shows good agreement. Furthermore, measurements were carried out with non‐spherical particles. Quartz dust was used for these measurements. In order to calibrate the OPC by means of the APS, the behaviour of both devices was investigated.
Detection of Deposited Particles from the Backside of a Glass Plate
Authors: Semleit Dirk , Fissan Heinz , Yu Guangjian 
Published: May 2005

AbstractMicrocontamination of product surfaces by deposited particles is an important problem in clean technologies. A most sensitive product to contamination by particles is a wafer during chip production. Therefore, methods for monitoring particle deposition on wafer surfaces have been developed in the last decade. A wafer with an unstructured and reflecting surface is inserted into the process equipment. After some time, depending on the process, this wafer is removed from the process equipment and is analysed with respect to the number of deposited particles using a wafer scanner. However, in situ particle detection in a process chamber is not possible with this technique. This would be possible if, instead of a monitor wafer, a transparent glass plate is mounted, e.g. in the housing of the process equipment. Then the illuminating and scattered light detection equipment can be mounted outside the process equipment. Since both the illuminating laser beam and the scattered light have to be transmitted through the glass plate, losses will occur, which will reduce the lower limit of detection with respect to particle size. In this article we estimate the detection possibilities theoretically and experimentally.A simple model based on Mie and vector scattering theory has been developed to describe the light‐scattering behavior of a single spherical particle on a glass plate with random surface irregularities. The scattered light of individual particles of four particle sizes (1.03, 1.6, 2.92 and 4.23 μm) on the same glass surface and from the uncontaminated area of the glass plate was measured for unpolarized and normally incident light. The values of the scattered light from this model were compared with the experimental results. The comparison shows a reasonable agreement of the angular distribution of the scattered light. The developed model is used to predict the lower limit of detection for particles on a transparent surface. The theoretical estimations show that it should be possible to detect particles of a diameter down to 0.2 μm with the described measurement technique.
Lorenz‐Mie Theory for Spheres Immersed in an absorbing host medium
Authors: Quinten Michael , Rostalski Jörn 
Published: May 2005

AbstractLight scattering by particles is often used to determine velocities or concentrations of particles in gaseous or liquid streams. Within the Lorenz‐Mie theory, light scattering is well understood both for a single compact spherical particle and a single multilayered particle in a non‐absorbing surrounding medium. However, in some cases of practical importance the Lorenz‐Mie theory in its present form may fail to describe the scattering because the host medium is absorbing (e.g. water droplets in oil). In this case, a new treatment of the scattering theory is required. In previous work, solutions were obtained in the far‐field of the scattering sphere. In this paper, a rigorous solution is derived from the calculation of the total absorption rate of the particle in the host medium, which is valid for all distances from the surface of the encapsulated particle. It is shown that it is necessary to consider finite sizes R of the integrating sphere when dealing with absorbing host media. Cross‐sections are defined which are characteristic quantities not only for the particle, depending on the size of a conceptual sphere around the scatterer and the imaginary part of the refractive index of the host medium. The results obtained are discussed for the case of non‐absorbing host media and in the far‐field approximation. Some numerical examples are given which are also related to experimental results.
Optical Cross‐Sections of Soot Agglomerates: The model of the virtual refractive index and first‐order multiple scattering
Authors: Dittmann Rolf 
Published: May 2005

AbstractA new technique for the calculation of the optical properties of agglomerated spherical primary particles is presented. By means of the so‐called virtual refractive index, the multiple scattering within the agglomerate is decribed by a modified Mie solution, thus avoiding restrictions with respect to the primary particle size. An additional benefit of the method is the small numerical expense required, permitting practical use for complex agglomerate structures such as real combustion aerosols. Utilizing this method, attention is focused on the calculation of the extinction cross‐section of real combustion aerosols in order to discuss the results of multiple‐wavelength extinction measurements within combustion systems. It is found that approximately the primary particle diameter is determined. Furthermore, the error that occurs can be avoided by means of the method presented without a detailed knowledge of the agglomerate size. Thus, the present work eliminates some current uncertainties inherent in optical combustion aerosol characterization.
Influence of Refractive Index Gradients within droplets on rainbow position and implications for rainbow refractometry
Authors: Anders Klaus , Roth Norbert , Frohn Arnold 
Published: May 2005

AbstractRainbow refractometry allows the determination of the refractive indices of droplets if a homogeneous refractive index can be assumed throughout the whole droplet. The influence of gradients on the angular position of the rainbow was examined for refractive index distributions with constant gradients and for distributions as they occur during cooling, heating and burning of droplets. Geometrical optics were used to determine rainbow positions. For a given value of refractive index at the surface, the rainbow position is in many cases a measure for the gradient itself. It was found that information obtained for constant gradients can often be used in cases with more complex distributions, which are found, for instance, for droplets undergoing heat‐transfer processes. Significant errors may be obtained only for a very short initial phase of the process. Experimental results obtained with monosized droplet streams, which confirm theoretical predictions of the influence of gradients on the rainbow position, are presented.
Light Reflection and Transmission by layers with oriented spheroidal particles
Authors: Berdnik Vladimir V. , Loiko Valery A. 
Published: May 2005

AbstractOn the basis of the numerical solution of the radiative transfer equation (RTE), the influence of non‐sphericity of oriented spheroidal particles on radiation intensity formation in a layer with a multiple scattering regime is considered. For solving the RTE with characteristics depending on the propagation direction of the radiation beam, an algorithm is developed based on the method of layer doubling. Calculations are presented of angle correlations for intensities of radiation in a layer with Fresnel reflection on the boundaries, and reflection and transmission coefficients.
Monodisperse Sprays for Various Purposes — Their production and characteristics
Authors: Brenn Günter , Durst Franz , Tropea Cameron 
Published: May 2005

AbstractThe production of liquid sprays represents a key technology for a wide range of industrial proceses. Most applications currently use pressure or air‐assisted atomization, resulting in the production of polydisperese sprays. Recent advances in experimental and numerical techniques for investigating liquid spraying processes, however, have enabled a closer examination of parameter optimization, leading to the conclusion that in may cases, a much narrower size distribution, or even a monodisperse spray, may exhibit many advantages. Currently monodisperse droplet generators, or drop‐on‐demand generators, do not meet this challenge of producing monodisperse sprays, primarily owing to the very low volume flow rate of liquid which is atomized. In the present work, a monodisperse sprya generator is introduced, which overcomes this difficulty for many applications.
Some Recent Developments in Twin‐Fluid Atomization
Authors: Lefebvre Arthur H. 
Published: May 2005

AbstractThe results of recent researches on twin‐fluid atomization are briefly reviewed, with particular emphasis on the effects of air and liquid properties on mean drop size. It is stressed that no single equation for the mean drop sizes produced in twin‐fluid atomization can satisfactorily correlate all the experimental data from any given atomizer. This is because for all types of atomizers the mechanism of liquid breakup changes from one basic mode to another with changes in atomizer operating conditions and/or liquid properties. These different modes of atomization exhibit different dependencies on atomizer dimensions and various physical properties such as liquid viscosity and air density. Equations for estimating the mean drop sizes produced in the various modes of twin‐fluid atomization are presented and discussed.