bluuebunny/crossref_metadata_2025_split huggingface dataset:
Increased Resolution of Size Distributions with the Coulter Counter
Authors: Harfield John G. , Wharton Robert A. 
Published: December 2004

AbstractThe limiting resolution of Coulter size measurements, the size within which two separate populations can be distinguished, is discussed in relation to the standard aperture.Electronic pulse editing, by comparing pulse height to width, enables small particles to be resolved from baseline instrument noise, but can give incomplete resolution of ultra‐narrow distributions from artefactually produced peaks using the standard aperture. Improvements in the minimum measurable size and in sizing resolution of narrow size ranges are also shown to be possible by improving the signal quality from the Coulter aperture.A novel mathematical approach is described for the derivation of true size spectra for narrow particle size distributions by deconvolution of the composite spectra resulting from the effect of the inhomogeneous electric field in the Coulter aperture. Simple empirical equations are used derived from the location and amplitude of the spurious peaks observed in such composites relative to the genuine peaks.The method is applied to three “industrial” materials (wide size range samples) to determine the likelihood that such size ranges are affected by the spurious or artefactual peaks. A fresh blood sample deconvoluted by this method is shown to be apparently composed of more than one population of cells.
Characterization of Powder and Pressings Based on Geometric Fundamentals
Authors: Frisch Bertram 
Published: December 2004

AbstractIn addition to chemical composition, geometric properties such as particle size, particle shape, specific surface area and microporosity are important for the production of sintered materials. They influence, e.g., the packing density of green bodies, the sinter activity and the microstructure of the final products. Different measuring methods are surveyed, with a critical view of sensitivity and evaluation of measurement data, and new devices are discussed, including laser and centrifuge methods for particle size measurement and sorption methods with krypton as adsorbate for the measurement of specific surface area and microporosity. Finally, a correlation between the particle size and the specific surface area using fractals is discussed.
Single Particle Light Scattering Size Analysis: Quantification and elimination of the effect of particle shape and structure
Authors: Bottlinger Michael , Umhauer Heinz 
Published: December 2004

AbstractWhen measuring scattered light from single particles (as realized in various methods of scattered light‐particle size counting analysis) nonspherical particles and particles with inner structure produce different signal heights (scattered light intensities) when differently oriented in the measuring volume. To study the influence of the particle shape and structure, the representative spectrum of all signal heights reflecting all of the possible orientations of the particle in the measuring volume was recorded from individual particles of a definite material in each case. Additionally from every particle an equivalent diameter was determined.The measurements lead to a very precise calibration curve and to a transformation matrix, that describes the influence of shape and structure on scattered light‐counting analyses in case of the specific material. It is then possible to simulate measurements to determine the loss in resolution caused by the influence of shape and structure and to eliminate this effect from conventional scattered light analyses.The paper presents the concept together with results of simulation and elimination calculations for the material limestone and quartz. The corrected size distributions are compared with results by other methods. On the basis of this comparison it is discussed how successful the method is to recover a higher resolution.
The Fundamentals of Particle Size Analysis by Means of Ultrasonic Spectrometry
Authors: Riebel Ulrich , Löffler Friedrich 
Published: December 2004

AbstractThe interaction of suspended particles with ultrasonic waves can lead to changes in the sonic velocity and also to extinction of the waves. An evaluation of the frequency dependence of ultrasonic extinction offers the most appropriate means of determining the concentration and size distribution of particles suspended in a fluid. With an experimental apparatus covering the frequency range from 1.7 to 81 MHz, particles ranging from about 20 to 1000 μm in diameter can be analysed. The measurements can be conducted with particle concentrations as high as 10% by volume.
Spectral Properties of the Regularized Inversion of the Laplace Transform
Authors: Ross Douglas A. , Nguyen Thoai H. 
Published: December 2004

AbstractInversion of the Laplace integral equation, used in the laser scattering measurement of colloidal particle size distributions, presents sever numerical and experimental difficulties. In the presence of noise the variance of the inversion integral is infinite, indicating maximum uncertainty in the accuracy of the inversion. The regularized inversion of the Laplace intergral equation provides a convenient computational algorithm which requires no a priori knowledge of the unknown linewidth distribution. Using the eigenfunction decomposition of the Laplace kernel, the spectral properties of the regularized inversion may be seen.Regularized inversion represents a type of low pass filter which preserves the properties of the inversion spectrum at low frequencies, but provides a cutoff at a point controlled by the regularization parameter. This filtering reduces the variance of the inversion to a finite value. Regularized inversion is somewhere between optimal filtering and the abrupt truncation used in singular value decomposition and other similar methods. Two examples, a monodisperse and a bimodal linewidth distribution, are used to compare the performance of regularized inversion to that obtained through an optimal filter.
Alignment Errors in Phase Doppler Receiving Optics
Authors: Sellens Richard W. 
Published: December 2004

AbstractIt is shown that if the pinhole in a phase Doppler system' s collection optics is misaligned, even by a matter of micrometers, the effective collection aperture will be different from the aperture of the collection lens. This directly alters the phase characteristics of the resulting signal and can produce systematic and random errors in drop size measurements. The results of misalignment in a simple system are calculated, experimental evidence of the errors presented, and it is shown that replacing pinholes with vertiacl slits will reduce the sensitivity to such errors.
Application of Laser/Phase Doppler Anemometer to Dispersed Two‐Phase Jet Flow
Authors: Hishida Koichi , Maeda Masanobu 
Published: December 2004

AbstractA confined jet flow involving glass particles was examined to clarify fundamental aspects of the turbulence structure of two‐phase flow. Spherical glass particles of mean diameter 62.4 m̈m were loaded in a primary jet at a mass loading ratio of 0.3. The primary jet diameter was 13 mm and exit velocities at the centre line were set at 20 and 30 m/s. The confined pipe diameter was 60 mm and velocities were set at 10 and 15 m/s. The particle and gas flow characteristics, such as local mean velocities, their fluctuations and size distribution, are discussed for three flow conditions which were obtained by changing the velocities of primary and secondary flows.Laser Doppler anemometry was applied to measure the flows of both particles and tracer, discriminated by scattering light intensity, and the precise particle size, for examining the dependence of particle size on the flow, by phase Doppler anemometry. The signal processing of the phase Doppler anemometer was based on a fast Fourier transform method to detect not only Doppler frequency for velocity but also the phase shift of Doppler signals for particle sizing. The processing system consisted of conventional fast analogue to digital converters, multi‐digital signal processor units and a host microcomputer.
Laser Sheet Scattering by Spherical Particles
Authors: Ren Kuan Fang , Gréhan Gérard , Gouesbet Gérard 
Published: December 2004

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 out.
On‐line Surface Area Measurement of Concentrated Slurries using low field spin‐lattice relaxation NMR
Authors: Thoma Steven B. , Smith Douglas M. , Boughton John , Davies Reg 
Published: December 2004

AbstractA method for the rapid on‐line determination of surface area and solids content in flowing concentrated slurries using low field NMR spin‐lattice relaxation measurements has been developed and demonstrated. The relationship between flow and spin‐lattice relaxation time (T1) of protons in water at 20 MHz was examined using aqueous copper sulfate solutions. The ability to measure surface area and solids concentration in both stagnant (stopped flow) and flowing systems via NMR was demonstrated using several different concentrated aqueous titania and glass slurries (20 to 80 weight percent) for which the dried powder surface area was previously determined via nitrogen adsorption/BET analysis and the solids content determined gravimetrically. Surface areas were also calculated from particle size analysis and found to vary by up to an order of magnitude from the adsorption and NMR results.
Sizing Large Hollow Micro‐Balloons with the phase doppler interferometer
Authors: Sankar Subramanian V. , Kamemoto Derek Y. , Bachalo William D. 
Published: December 2004

AbstractA combined theoretical and experimental study has been conducted to evaluate the effectiveness of using large, hollow micro‐balloons as LDV seed particles. The study has focused on the ability of phase Doppler systems to size hollow microballoons, the ability of large micro‐balloons to respond to high frequency spatial and temporal flow field variations, and the overall advantages and disadvantages of using large microballoons instead of conventional LDV seed particles, such as very small water droplets or polystyrene latex (PSL) particles. This paper discusses the development of a theoretical phase Doppler response model for stratified spheres, the experimental facility, and the theoretical and experimental results.
A Study of the Fracture of Pellets Fired Against a Target
Authors: Austin Leonard G. , Trubelja Paula M. , Scarlett Brian 
Published: December 2004

AbstractPellets of sintered Al2O3 of approximately 3 mm diameter and length were broken in the Brazilian mode and the distribution of strength obtained. It was found that there was also a distribution of Young's modulus E. Hertzian theory implies that the maximum impact force of a pellet fired against a rigid target would depend on E. However, since the pellets can strike in different geometries there is a distribution of impact force for a fixed E. Comparison of theory with data obtained with a force‐time transducer as the target showed that the major variation of maximum recorded force could be assigned to the variation of E. The median of the maximum recorded force varied with velocity as v6/5, implying that the pellets behaved approximately as impacting spheres. An attempt was made to predict the probability of breakage in one impact from convoluting the distribution of impact force with the strength distribution from the Brazilian test converted to the equivalent strength distribution expected for impacting spheres. This gave the correct order of magnitude but did not accurately predict the experimental values.
Precision of the Grain Size Coefficient (K‐Coefficient) of concrete aggregates — a problem of sampling, sample division and sieve analysis
Authors: Rasemann Winfried , Schmatz Petra 
Published: December 2004

AbstractConcrete quality is influenced to a high degree by the granulometry of the aggregates used. In the construction industry, the grain size coefficient of K‐coefficient is used as a quantity for the characterization of granulometry. In practice, this quantity is determined experimentally, and it is therefore a random variable influenced by material heterogeneity and errors in sampling, sample preparation and size analysis. Depending on the final use, in concrete production often an aggregate is required, the grain size coefficient of which can be adjusted to a given value Krequ with a prescribed precision. For this reason, continuous supervision of the aggregate quality is necessary using, e. g., automatic sampling and opto‐electronic measuring equipment. In order to determine the optimum conditions for the installation of such equipment, the variances of the possible errors must be established. Further, methods for their restriction are necessary. In this paper, investigations involving hand sampling and hand sieving and on the example of a reference gravel plant are reported. The investigations reveal that, for the materials involved, primary samples of at least 1600 g were necessary, which then could be reduced to 200 g by sample splitting, in order to obtain the accuracy desired.
Innovative Phase Doppler Systems and their Applications
Authors: Naqwi Amir A. 
Published: December 2004

AbstractTheoretical and practical limits on the applicability of PDA are established, using generalized theoretical formulations of various physical processes governing the operation of a phase Doppler system. Furthermore, several innovative solutions are introduced to prevent the commonly occuring problems of PDA, such as Gaussian profile effect, non‐monotonic response and 2π‐ambiguity. Generalized formulations have also enabled new applications, such as sizing of submicron particles, particle material recognition, measurements with non‐standard geometries. Selected results of measurements in particulate flows, using innovative PDA systems, are also presented.
Reconstruction of Real Size Distributions Hidden in Phase‐Doppler Anemometry results obtained form droplets of inhomogeneous liquids
Authors: Manasse Uwe , Wriedt Thomas , Bauckhage Klaus 
Published: December 2004

AbstractReal process fluids such as emulsions and suspensions are optically absordent as well as inhomogeneous. Using phase‐Doppler anemometry (PDA)for investigating the spray cone, the inhomogeneites have led to incomprehensible size distributions. In this paper, solutions of instant coffee and condensed milk, representing typical process fluids, were chosen for PDA measurements in comparison with PDA applied to water droplets with the same atomization process in order to clarify the reasons for the measured broad size distributions. By applying PDA to monodisperse droplets and to “monodisperse” and real polydisperse sprays consisting of such fluids, it is shown how the measured size distributions arise, Based on this knowledge, the real size distributions are reconstructed and compared with that of water atomization. Therefore, PDA can in future also be applied to real process fluids, and process control, based on the information provided by PDA, is coming nearer.
The Use of Azimuthal Intensity Variations in Diffraction Patterns for Particle Shape Characterization
Authors: Heffels Cameil M. G. , Heitzmann Daniel , Dan Hirleman E. , Scarlett Brian 
Published: December 2004

AbstractForward light scattering is a well established technique for measuring particle size distributions. The light intensity fluctuations which can be observed in the diffraction plane of the instrument can be used to stabilize the inversion process [1]. Particle shape information is also present in these fluctuations. It is shown that an azimuthal‐type of detector can be used to extract this information from the statistical correlations of the detector signals.
Development of a Mathematical Model for Light Scattering by statistically irregular particles
Authors: Al‐Chalabi Souad A. M. , Jones Alan R. 
Published: December 2004

AbstractA mathematical model is described to predict Fraunhofer diffraction by statistically irregular particles. It is demonstrated that the particles are characterised by a probability distribution of radius and a correlation function in the surface. The results of calculation show that at angles not too far from the forward scattering direction and for irregularity heights within a limited range, the irregular particles may be represented approximately by spheres with a size distribution equal to the probability distribution of radius. However, the calculations are highly sensitive to the exact nature of the probability functions. Comparisons of the results with those of a simpler model are not satisfactory beyond the first forward scattering lobe.
Imaging of Drop and Vapour Clouds in an Evaporating Fuel Spray by ultraviolet and visible lasers
Authors: Suzuki Mamoru , Nishida Keiya , Hiroyasu Hiroyuki 
Published: December 2004

AbstractA laser‐based method was developed for the simultaneous and quantitative imaging of drop and vapour clouds in an evaporating fuel spray. The method was based on extinction of two wavelengths, that is, ultraviolet and visible laser light through the fuel spray due to absorption by the vapour and scattering by the drops. α‐Methylnaphthalene was selected as an injection fuel, since it absorbs the ultraviolet laser light but does not absorb the visible laser light. Subtraction of the transmissivity of the visible laser light from that of the ultraviolet laser light made it possible to image the distribution of the vapour cloud in the evaporating fuel spray. The distribution of the drop cloud is imaged by the transmissivity of the visible laser light. The method was applied to the fuel spray injected from a nozzle of a direct injection diesel engine into high‐pressure and high‐temperature nitrogen gas in a bomb.
Size of the Detection Area of a Phase‐Doppler Anemometer for reflecting and refracting particles
Authors: Schöne Frank , Bauckhage Klaus , Wriedt Thomas 
Published: December 2004

AbstractMeasurements of particle size distributions in multi‐phase flows with a phase‐Doppler anemometer yield incorrect results if polydisperse particles are investigated. For weighting biased size distributions, different in situ methods, requiring the size of the detection area, are known, but all of these weighting procedures are restricted to very small measuring volumes if off‐axis instrument configurations are considered. Moreover, the weighting functions have some disadvantages in the case of poor statistics in single size classes or the results are not suitable for determining the size of the detection area for particles which are larger than the beam waist.Therefore, the intention in this work was to measure the size of the detection area for different kinds of monodisperse particles, different instrument configurations and varied instrument sensitivities experimentally and to develop an improved weighting procedure that copes with the above difficulties. The application of the results obtained from the investigations with monodisperse particles to measured particle size distributions and volume flux densities of polydisperse water droplets in a spray cone of an atomizer confirms the applicability of this weighting procedure. It is still restricted to directed flows, perpendicular to the fringes.
A More General Treatment of Abrasion‐Chipping Processes applicable to FAG/SAG Milling
Authors: Austin Leonard G. , Tangsripongkul Sukanya 
Published: December 2004

AbstractEquations are derived for the rate of loss of mass from a screen interval when the size reduction process is an abrasion‐chipping process which follows a wear law of the Bond form or the Davis form, giving cores and fragments. The treatment is extended to steady‐state continuous grinding in a fully‐mixed reactor, and to the case where first‐order disintegrative fracture processes also occur.
Multiple Wavelength Extinction Technique for Particle Characterization in Dense Particle Clouds
Authors: Dittmann Rolf , Feld Heinz‐Jürgen , Samenfink Wolfgang , Wittig Sigmar 
Published: December 2004

AbstractIn utilizing the advantages of extinction measurements in micron and especially submicron particle characterization, the properties of a multiple wavelength extinction technique have been the subject of extended theoretical studies. Furthermore, an experimental set‐up was designed which provides high flexibility owing to its modular design. The performance of the technique described is demonstrated by a large variety of applications in aerosol and combustion research and in large‐scale industrial systems. It was found to be a reliable tool in characterizing dense particulate systems.
A method for investigating the orientational behaviour of fibrous particles in gaseous flow
Authors: Hirst Edwin , Kaye Paul H. , Buckley Keith M. , Saunders Spencer J. 
Published: December 2004

AbstractA method is described by which the angular orientation distribution of fibrous particles carried in a gaseous stream may be investigated. The method is based upon the interpretation of the spatial intensity distribution or scattering profile of laser light scattered by individual fibres. The scattering instrument used to capture the profiles is described, and the mathematical computation required to ascertain the orientation of each particle at the measurement point is detailed. Illustrative results are given for a study of airborne micromachined silicon particles of 12 μm length and 1.0 μm by 1.5 μm cross‐section. The method is currently being employed by the authors to investigate ways of improving the orientation control over nonspherical particles in systems such as aerodynamic particle sizers and particle shape classifiers, since lack of particle orientation control is known to adversely affect the measurement accuracy of both these types of instrument.
Particle Shape Investigations with a light‐scattering optical instrument
Authors: Neeße Thomas , Dück Johann , Thaufelder Thomas 
Published: December 2004

AbstractA light‐scattering instrument that is normally used for particle size analysis was applied to obtain information about particle shape. Micro‐cuboids of dimensions a × b × c in the range between 10 and 1000 μm, which can be accurately manufactured employing special technology, were used as labelled samples for the determination of 3‐D features. Particle projections at different orientations due to turbulent motion were measured sequentially. The laser diffraction of cuboids rotating in a turbulent flow is described theoretically using a simplified model, i.e. rotation of a rectangle. The change in the projection areas of rotating cuboids is connected with their rotational velocity. The power spectrum density of rotational velocity of cuboids and spheres was determined and the influence of particle shape on the power spectrum density established. The frequency distribution of projection sizes was found to be suitable for particle shape estimation.
On‐line Determination of Particle Size Distribution during the manufacture of compound feed
Authors: Heidenreich Eberhard , Sundermeier Thomas 
Published: December 2004

AbstractExperimental investigations were carried out with mainly a Mogensen‐Sizer, compared with test screening and additionally laser diffraction and light extinction, in order to check the qualification for on‐line determination of particle size distribution under the specific conditions of feed milling. The different components of compound feed, the degree of milling, the difference in measured particle characteristics and the possibility of sample dispersion affect the comparability of the results. The results show that laser diffraction is a manysided method with accurate recording of the distribution. The modified Mogensen‐Sizer can be a robust low‐price alternative if the control of selected distribution parameters is sufficient.