bluuebunny/crossref_metadata_2025_split huggingface dataset:
Fractal Characterization of Pulverised Materials
Authors: Brown Gareth J. , Miles Nick J. , Hall Steve T. 
Published: December 2004

AbstractThis paper describes preliminary work carried out on the applicability of fractal geometry in describing the products of comminution events.A nickel sulphide ore was subjected to two comminution events, impact shattering and ball milling. Fractal analysis was performed on samples of the resulting comminution products.Two differing fractal populations resulted, with the impact sample exhibiting particles having higher boundary fractal dimensions than the milled sample. The fractal dimension of the impact fragments increased with decreasing size, whereas the milled particles displayed a more complex distribution.The under‐fractal distributions, of the two populations of fragments, generate straight lines when plotted on Gaussian probability paper. This leads to the possibility of being able to predict the distribution of fragments, in fractal terms, of a particular material when subjected to comminution.
Particle Dynamics in an Electrohydrodynamic Flow Field investigated with a two‐component laser‐doppler velocimeter
Authors: Riehle Claus , Löffler Friedrich 
Published: December 2004

AbstractA laser‐Doppler instrument has been used to measure the migration velocity of NaCl particles in an electrohydrodynamic flow field of an electrical precipitator. The measured average migration velocity of 1.40‐μm particles (number distribution median with a geometric standard devitation of 1.46) is approximately five to six times higher than the calculated steady‐state velocity for a 1.40‐μm particle, provided there is a saturation charge of at least 90f%. Further, the particle velocities in the main flow direction are also influenced by the electrical operation conditions. Both observations demonstrate the important role of the state of the electrohydrodynamic flow field (superposition of moving gas ions and neutral gas molecules) on the particle transport, characterized by the dimensionless electrohydrodynamic number NEHD. A comparison between six different electrohydrodynamic states revealed that NEHD ≈︁ 1 is a critical value for the mutual interactions between the gas ions and the neutral gas phase. Whereas for NEHD values > 1 the stochastic particle motion is chiefly determined by the nonsteady‐state character of the negative corona, for NEHD values < 1 the particle velocity fluctuations are governed by the turbulence level of the neutral fluid. These finding might be helpful in adjusting the operating conditions in electrical precipitators for and optimized particle separation.
The Relevance of Particle Measurement Technology to Process Engineering
Authors: Polke Reinhard 
Published: December 2004

AbstractTo produce disperse products, the characterization of the disperse state and a knowledge of the property function are essential. Property functions are applied not only to characterize the quality of an end product, but also to determine the influence of different processing steps on its state. Hence it is necessary to know the property and process functions for quality assurance of the products and for safety of the processes.Good laboratory particle measuring technologies are available for investigating property and process functions. On the basis of these functions, process control takes place. On‐line or, better, in‐line measuring techniques are necessary to enable the accompanying process information to be obtained.
Particle Dispersion in Highly Swirling, Turbulent Flows
Authors: Blümcke Erich , Brandt Michael , Eickhoff Heinrich , Hassa Christoph 
Published: December 2004

AbstractThree‐dimensional transport processes of monosized droplets in a turbulent swirling shear layer were investigated experimentally and theoretically. A model experiment was designed that represents the spray dispersion produced by airblast atomizers. Based on the experimental results, a stochastic dispersion model was developed in the frame of a Lagrangian formulation. Comparison with these experimental data for the dispersion of monosized droplets were made and proved to be satisfactory. The analysis of the remaining differences between calculation and measurement emphasized the importance of an accurate description of gas‐phase turbulence characteristics.
Fractal Dimensions in Data Space; New descriptors for fineparticle systems
Authors: Kaye Brian H. 
Published: December 2004

AbstractFractal dimensions in data space are being used to describe fineparticle systems. The relationship between these new parametric descriptions of fineparticle systems and a more classical description of such system using the classical hyperbolic function is discussed. It is shown that fractal dimensions in data space are useful for presenting data for such diverse systems as pigment clusters in composite materials, avalanching powder systems, ballistically fractured material and pore size distribution of porous bodies as determined by mercury intrusion methods. In particular new data is presented on the usefulness of fractal dimensions for describing the flow properties of powders with and without silica flow agents.
Particle Size Distribution Analysis of Industrial Colloidal Slurries using ultrasonic spectroscopy
Authors: Pendse Hemant P. , Sharma Arvind 
Published: December 2004

AbstractSeveral solid‐liquid suspensions containing submicron particles at moderate to high concentrations (5 to 50 volume percent) are encountered in industrial slurry processing. Measurements of ultrasonic attenuation spectra are used in a newly developed AcoustoPhor particle analysis system to get particle size distributions of such colloidal suspensions. This paper deals with the performance evaluation of the AcoustoPhor system. The automated ultrasonic spectrometer component of the AcoustoPhor system was tested using a reference silicone liquid for its accuracy and precision. The particle size distribution (PSD) estimation capabilities were evaluated using a set of well‐dispersed slurries covering a wide range of particle concentrations. Sensitivity to process variations was evaluated in field tests at a pigment manufacturing plant. The AcoustoPhor system appears to be capable of providing reliable PSD data for inorganic pigment slurries with particle diameters ranging from 0.01 to 100 micrometers at particle concentrations as high as 50 volume percent.
Tomographic Techniques for Characterising Particulate Processes
Authors: Williams Richard A. , Xie Cheng‐Gang 
Published: December 2004

AbstractA review of existing and developing process tomographic instrumentation suitable for characterising dry and wet particulate systems is presented. Factors governing the selection of sensing techniques appropriate for static and dynamic imaging of a wide range of single and multiphase particulate processes are discussed. The paper presents a systematic comparison of different image reconstruction methods. Examples of existing, developing and proven applications are cited. Future needs and ways in which these needs can be met are suggested, including the use of multi‐modality methods in which different types of sensing methods are embodied in a single tomographic instrument.
In‐Process Particle Size Distribution Measurements and Control
Authors: Harvill Thomas L. , Holve Donald J. 
Published: December 2004

AbstractIn‐process measurement of particle size and concentration distributions provides continuous analysis and quality control of a product stream. Elimination of sample handling and operator manipulation is now possible for most pneumatic flows using optical methods which are properly interfaced with the process stream.The EPCS (Ensemble Particle Concentration & Size) described in the following has been used to obtain detailed size distribution measurements in powder production facilities at two second intervals, and has been successfully used for automatic feedback control.
New Generation of Phase‐Doppler Instruments for particle velocity, size and concentration measurements
Authors: Aizu Yoshihisa , Domnick Joachim , Durst Franz , Gréhan Gérard , Onofri Fabrice , Qiu Hui‐He , Sommerfeld Martin , Xu Tien‐Hua , Ziema Maris 
Published: December 2004

AbstractPhase‐Doppler anemometry (PDA) is applied for particle size, velocity and concentration measurements in two‐phase or multi‐phase flows of ever increasing complexity. For accurate measurements the experimenter must be provided with software and hardware which permit an optimal layout of the PDA optics for a given application, reliable detection of signals over a wide particle diameter range, accurate determination of particle concentration and precise discrimination between particles of different composition. Recent work at LSTM, Erlangen, has been directed to developing a complete PDA package for the above purposes. Progress in this direction is summarized in this paper.
The Phase‐Doppler Method Applied to Very Small Particles
Authors: von Benzon Hans‐Henrik , Buchhave Preben 
Published: December 2004

AbstractUsing a computer model based on Lorenz‐Mie and generalized Lorenz‐Mie theory, various optical confiugurations of a phase‐Doppler system were analysed with regard to their suitability for diameter measurements in the sub‐micron range. The major concern in this size range is multi‐valuedness of the phase‐diameter characteristic, the relatively small signal‐to‐noise ratio obtained with the very low scattered intensity and the small value of the phase difference to be measured. It is shown numerically and by experiment that for particles in a free stream the multi‐valuedness and the shot noise need not prohibit measurements in the sub‐micron size range. The major source of phase error results from light scattered form objects or material other than the particle inside the measuring volume. Using an optical set‐up with nearly counter‐propagating incident beams and a large angle between the detectors, measurements were obtained for particle diameters down to 200 nm, and it is estimated that with some improvements in receiver optics measurement down to 100 nm will be possible.
The Phase Doppler Method: Analysis, performance evaluations, and applications
Authors: Bachalo William D. 
Published: December 2004

AbstractThis review of the recent developments in the phase Doppler method provides information on the advances made to the method and delineates some potential error sources. Methods used to eliminate these potential error sources are also discussed. It is shown through comparison to the Lorenz‐Mie theory and the GLMT that the geometrical optics theory offers a reliable and efficient computational tool for the analysis of the light scattering with the phase Doppler method. The geometrical optics theory was then used to optimize the measurement parameters in the system designs and a significant reduction in the measurement uncertainty was realized. Limitations on the particle concentrations in which the instrument will operate reliably are also addressed. A brief discussion of the instrumentation and, in particular, the signal processing is presented. The advantages in using the Fourier transform approach are discussed. As a demonstration of the capabilities of the instrument, several performance tests were reviewed and examples of the application to spray combustion and turbulent dispersion of particles are given.
Response of Laser Diffraction Particle Sizer to Anisometric Particles
Authors: Gabas Nadine , Hiquily Noël , Laguérie Claude 
Published: December 2004

AbstractThis study deals with the size measurement of non‐spherical particles by the laser diffraction technique. Size analyses of three sets of identical metallic bodies (cubes, tablets and cylinders) were performed by means of a Malvern 2600 instrument. The results prove that under the operating conditions chosen and in the case of anisometric objects, the mean total surface area is not measurable either because the Malvern software, strictly valid for spheres, is not applicable to such particles or because the particles adopt preferential orientations in the measurement cell. Further, a way of processing diffraction data is proposed in order to determine two characteristic dimensions of identical anisometric particles. It is based on the measurement of the minimum and maximum projected surface areas of the particles. The experimental results obtained with our particles show the procedure to be reliable.
Trajectory Ambiguities in Phase Doppler Systems: Study of a near forward and a near‐backward geometry
Authors: Gréhan Gérard , Gousebet Gérard , Naqwi Amir , Durst Franz 
Published: December 2004

AbstractGeneralized Lorenz‐Mie theory for the scattering of arbitrarily shaped beams by spherical particles has been applied to two standard phase Doppler layouts, employing receiving units at 30° and 150° off‐axis locations. It is shown that the particle trajectory effects may lead to inaccurate size measurements for the near‐forward receiver and may make the near‐backward measurements totally misleading when a large particle size range (1:40) needs to be covered. Only limited improvements can be achieved by using two phase‐shift signals from a single receiving unit for discrimination. The errors associated with the trajectories are also detrimental to the concentration measurements based on the existing criteria. However, an extended optical system employing two identical receiving units, located symmetrically about the plane of the laser beams, provides a robust solution to the trajectory ambiguity. It can be used to measure correctly the particle size and the particle location in the measuring volume. The difficulties associated with estimating the effective size of the measuring volume as a function of the particle diameter (in order to determine the true size distribution and the particle number density) may also be resolved by employing an extended system. Hence, despite a higher cost, this arrangement is attractive, at least for obtaining some benchmark simultaneous measurements of sizes and velocities in two‐phase particulate flows.
Particle Breakup in Shock Waves Studies by single Particle Light Scattering
Authors: Strecker Jörgt J. F. , Roth Paul 
Published: December 2004

AbstractThe breakup of suspended, agglomerated submicron particles was studied by exposing the aerosol to weak shock waves of varying strength under conditions 400 ms−1⩽v⩽880 ms−1. A newly developed laser light‐scattering diagnostic employing a top hat laser profile was used to size the particles passing through a very small scattering volume. By Comparing the optically measured particle size in front of and behind shock waves, the breakup of agglomerated particles could be clearly identified. The experiments indicate that the aerodynamic forces behind an incident shock overcome the particle binding force resulting in disintegration of the submicron agglomerates. The results are presented in form of a modified Weber number.
Influence of the Measurement Volume on the Phase Error in Phase Doppler Anemometry. Part 1: Reflective mode operation
Authors: Albrecht Heinz‐E. , Borys Michael , Wenzel Marcus , Wriedt Thomas 
Published: December 2004

AbstractIn phase Doppler anemometry (PDA), phase difference errors are caused by the Gaussian intensity distribution of the laser beam and the curvature of the phase fronts outside of the beam waist. This results in erroneous particle sizes. Based on a physical analysis by geometrical optics [1], this phase difference error is evaluated for reflected mode operation (Part I) and for refracted mode operation (Part II). By varying the particle trajectories statistically, the error in determining the particle size and the mass flow can be simulated. By the method described the error in the measured phase difference can easily be estimated.
Quasi‐Self‐Preserving Log‐Normal Size Distributions in the Transition Regime
Authors: Otto Eckhard , Stratmann Frank , Fissan Heinz , Vemury Srinivas , Pratsinis Sotiris E. 
Published: December 2004

AbstractA log‐normal model, based on the extended SIMPLER‐algorithm utilizing the Modal Aerosol Dynamics Modelling Technique, and a sectional model are compared for Brownian coagulation in the transition regime. The models are in good agreement with respect to the calculated particle size distribution moments. Applying the log‐normal model a simple coagulation model consisting of a closed set of five equations is developed that does not require the solution of ordinary diferential equations.
Interaction of Annular Air Jet with a Non‐Evaporating Liquid Spray
Authors: Friedman Jacob A. , Renksizbulut Metin 
Published: December 2004

AbstractThe effects of a concentric annular air jet on the structure of a liquid spray have been examined under isothermal conditions using Phase Doppler interferometry, and flow visualization techniques. Local measurements of drop size, velocity, volume flux, and number density have been made simultaneously and non‐intrusively. The results show that the initial spray cone widens substantially with increasing air flow while the overall spray envelope remains essentially the same. The air jet creates a narrow high mass flux region of small droplets in the core of the spray, surrounded by a nearly uniform flux region extending almost to the boundary of the spray. Line averaged mean diameters are found to be slightly smaller, indicating that the annular air jet plays a role improving the atomization process as well.
Characterizing the Rheology of Powders by studying dynamic avalanching of the powder
Authors: Rastogi Saurabh , Klingzing George E. 
Published: December 2004

AbstractAvalanching of solids is an important multivariable dependent phenomenon that can be a valuable tool for characterization of solids flowability. Although avalanching by itself is primarily chaotic it appears that the fractal analysis of its avalanching mass data can yield very interesting and significant information that is of importance in determining suitability of a material in solids handling and pneumatic transport.
Application of Regression Analysis in spectroturbidity size‐characterization methods
Authors: Vavra Jozef , Antalik Jozef , Liška Marek 
Published: December 2004

AbstractThe possibilities of applying specific turbidity and turbidity theoretical computations of light‐scattering characteristics, the ratio methods in the distributional analysis of PVC and SiO2 exact Lorenz‐Mie theory was applied. A good correlation with dispersions with spherical particles are discussed. The calculation of the best estimates of distribution function parameters was found were performed numerically using the simplex method. For theoretical computations of light‐scattering characteristics, th exact Lorenz‐Mie theory was applied. A good correlation with the results of angular light scattering and electron microscopy was found.
An appraisal of the present position and future potential of inelastic electron tunnelling spectroscopy (IETS)
Authors: Shott P. N. , Field B. O. 
Published: December 2004

AbstractThe present position regarding the preparation of junctions suitable for IETS investigation and the various doping procedures is outlined, and a comparison is drawn between IETS and other surface spectroscopies. A survey of the systems already studied of interest in the fields of surface chemistry, heterogeneous catalysis, analytical chemistry and environmental pollution monitoring, adhesion science, radiation damage, biological chemistry and electronic energy level studies is presented. The parameters thought to affect the development of this technique and some potential applications to corrosion inhibitors and metal protection, lubrication studies, solid‐state devices and photochemical energy converters are considered.
Reference levels in electron‐excited and X‐ray‐excited Auger spectra
Authors: Wagner C. D. , Taylor J. Ashley 
Published: December 2004

AbstractAuger spectroscopy and X‐ray photoelectron spectroscopy have evolved using different reference levels for electron energy measurement. Electron‐excited Auger spectra are referenced to the vacuum level, and X‐ray‐excited Auger spectra are referenced to the Fermi level. This can cause confusion, especially when both are recorded in the N(E) mode in the same instrument.
Secondary ion mass spectrometry/X‐ray photoelectron spectroscopy study of CO adsorption on Ni and of Fischer–Tropsch synthesis on FeRu alloys
Authors: Fleisch T. , Delgass W. N. , Winograd N. 
Published: December 2004

AbstractThe adsorption of CO on a Ni(100) single crystal surface has been investigated by X‐ray photoelectron spectroscopy and static secondary ion mass spectrometry. At room temperature CO chemisorbs molecularly on Ni. A saturation coverage of about 0.5 monolayer is reached after 2 L CO exposure. The NiCO+/Ni2CO+ratio increases from very low values at low coverage to a saturation value of about 4.5. Dynamic studies of Ni+and NiCO+yields during exposure to 1.3 × 10−6to 1.3 × 10−5Pa of CO show reversible pressure and temperature dependent changes in addition to chemisorption. We ascribe these effects to CO weakly adsorbed on both the clean and CO‐covered Ni surface. The interaction of CO and H2with FeRu alloy surfaces has been studied by XPS and SIMS as well as by kinetic measurements. Fe surface enrichment is observed which explains the catalytic behavior of the alloys in Fischer–Tropsch synthesis (FTS). Ru rich surfaces remain unchanged during FTS but an extensive and rapid carbon build‐up is found on the alloy surfaces. Silica supported alloys coke more slowly. The carbon build up on pure Fe is preceded by a carbide formation that coincides with a maximum in hydrocarbon synthesis activity. Potassium promoted Fe exhibits a faster carbon deposition than pure Fe, but the potassium appears to stay on the uppermost surface by diffusing through the carbon layers.
Semiconductor crystal growth by sputter deposition
Authors: Greene J. E. , Eltoukhy A. H. 
Published: December 2004

AbstractRecently, understanding of the physics of ion–surface interactions has progressed sufficiently to allow sputter deposition to be used as a crystal growth technique for depositing a wide variety of single crystal elemental, compound, alloy, and superlattice semiconductors. In many cases, films with essentially bulk values of carrier concentrations and mobilities have been obtained. The controlled use of low energy particle bombardment of the growing film during sputter deposition has been shown to affect all stages of crystal growth ranging from adatom mobilities and nucleation kinetics to elemental incorporation probabilities. Such effects provide inherent advantages for sputter deposition over other vapor phase techniques for the low temperature growth of compound and alloy semiconductors and are essential in allowing the growth of new and unique single crystal metastable semiconductors. This review includes sections on the physics of sputtering, experimental techniques, and ion bombardment effects on film growth as well as a discussion of recent results in the growth of elemental, III–V, II–VI, IV–VI, metastable, and other compound semiconductors.
Experimental study of matrix effects in quantitative auger analysis of binary metal alloys
Authors: Mathieu H. J. , Landolt D. 
Published: December 2004

AbstractThe importance of matrix effects in quantitative AES is investigated by comparing experimental results with theory. Experimental AES amplitude ratios are presented as a function of composition of five different binary alloy systems Ni–Mg, Ni–Pd, Ag–Pd, Mo–Fe and Cr–Fe. Contamination free surfaces were produced by fracturing in situ under UHV conditions. Matrix correction factors were evaluated applying literature data and considering the influence of atomic density variation, of the escape depth of Auger electrons and of backscattered electrons. The influence of the matrix is large only for alloy components differing widely in density and atomic number. Comparison of calculated with experimental data reveals that agreement can be achieved within 2–15% depending on the alloy system considered.