bluuebunny/crossref_metadata_2025 huggingface dataset:
Resin flow through fiber beds during composite manufacturing processes. Part I: Review of newtonian flow through fiber beds
Authors: Skartsis L. , Kardos J. L. , Khomami B.
Published: December 2004

A critical part of any master model used to simulate or control a composite material manufacturing process is the description of resin flow through the fiber bed. We present here a review of both theoretical and experimental studies of fluid flow through porous media, including fiber beds. For the practical porosity range of interest in continuous fiber composites processing (0.3< ϵ < 0.6), the permeability cannot be accurately described using the Blake‐Kozeny‐Carman equation, even though the flow is Newtonian at very low Reynold's number. For aligned fiber situations, the Kozeny constant,k, deviates radically from theory, depends on bed nonuniformities, and is only constant over very narrow porosity ranges. Thus, one cannot experimentally determinekat high porosities and use this value to describe low porosity situations. Theoretical attempts, based on perfectly spaced and aligned arrays of cylinders, adequately describe the transverse permeability of ideal fiber beds in the high porosity range, but do not succeed at porosities below 0.6. For axial flow through aligned fiber beds, the theory yields permeabilities much lower than are experimentally observed throughout the entire porosity range. For randomly arranged fibers, random cylinder theory also predicts permeabilities that are significantly lower than are measured.
Resin flow through fiber beds during composite manufacturing processes. Part II: Numerical and experimental studies of newtonian flow through ideal and actual fiber beds
Authors: Skartsis L. , Khomami B. , Kardos J. L.
Published: December 2004

Proper description of the resin flow through fibrous media is an important input to the modeling of composite manufacturing processes. Based on our conclusions in a recent review of pertinent literature (see Part I, this issue), Newtonian flow through ideal cylinder arrangements has been analyzed and measured. The analytical and numerical solutions agreed well with both our own experimental observation and those of others. Experiments with actual carbon fiber beds revealed significant deviations from ideal bed behavior. These deviations include dependence of the permeability on the nature of the permeant and the applied pressure difference, both of which make questionable the use of the Blake‐Kozeny‐Carman (BKC) equation to describe flow in real carbon fiber beds. Experiments that simulate the autoclave process by featuring combined permeation and consolidation of fiber beds have yielded additional dependencies of the permeability on process characteristics, such as the consolidation load and the original resin‐rich areas within the fiber beds.
The effects of transcrystalline interphase in advanced polymer composites
Authors: Chen Eric J. H. , Hsiao Benjamin S.
Published: December 2004

Surface‐induced transcrystallization in fibers has been reported in some advanced polymer composites. It is believed that transcrystalline interphase may affect stress transfer efficiency between the reinforcing fiber and the matrix. In this study, attempts were made to examine the effects of transcrystallinity on composite performance, particularly on fiber‐matrix interfacial bond strength, and to investigate possible attributes of transcrystallization. Three polymer resins, poly(etherketoneketone) (PEKK), poly(etheretherketone) (PEEK), and poly(phenylenesulfide) (PPS), and four types of fiber, polyacrylonitrile (PAN)‐based AU‐4 (untreated AS‐4) carbon, pitch‐based carbon, poly (p‐phenylene terephthalamide) (PPDT) aramid, and E‐glass were used. It was found that PPDT aramid and pitch‐based carbon fibers induce a transcrystalline interphase in all three polymers because of an epitaxial effect. Under certain conditions, transcrystallization was also observed in PAN‐based carbon and E‐glass fibers, which may be partially attributed to the thermal conductivity mismatch between the fiber and the matrix. Plasma treatment on fiber surface showed a negligible effect on inducing transcrystallization, whereas solution‐coating of PPDT on the fiber surface showed a positive effect. The Microdebonding test, which measures the interfacial bond strength between the fiber and the matrix, consistently showed more than 40% increments for various single filament systems with transcrystalline interphase versus without. However, the effects of transcrystallinity on the interfacial bond strength appeared to decrease as the fiber content increased in composites.
Interpretation of fiber fragmentation in carbon/epoxy single fiber composites: Possible fiber pre‐tension effects
Authors: Scherf J. , Wagner H. D.
Published: December 2004

The fiber straightening pre‐tension applied during the sample preparation of single fiber composites is suggested here to significantly affect the number of fragments as well as the value of the Kelly‐Tyson interface shear strength obtained from single filament composite tests. This implies that fragmentation tests performed under seemingly identical conditions, but in which the fiber pre‐tension is not accurately controlled during sample preparation, might yield widely differing experimental results. We present and discuss a new set of experimental results dealing with fiber pre‐tension effects in carbon/epoxy single fiber composites.
Environmental stress cracking resistance of blow moded poly(ethylene terephthalate) containers
Authors: Tekkanat Bora , McKinney Bryan L. , Behm Dale
Published: December 2004

A method is developed for determining the environmental stress cracking resistance (ESCR) of blow molded poly(ethylene terephthalate) (PET) containers. By this method, the internal chamber of a container is presurized in 68.9 kPa (10 psi) increments while the outside of the base is being exposed to an environmental stress cracking (ESC) agent. The base of the container is examined after each 68.9 kPa of pressurization if crazing has occurred. The process is continued until a threshold value of craze initiation pressure (CIP) can be determined. Low CIP for the type of containers tested generally corresponds to a high rate of field failures. The method does not only gage the susceptibility of different types of one‐piece PET containers to ESC but also provides helpful information to improve the container designs.
A pulse rheometer for reacting foams
Authors: Carriere Craig J. , Bank David H. , Christenson Christopher P.
Published: December 2004

A foam rheometer has been developed based on the impulse theory of linear viscoelasticity. The rheometer is a large‐volume parallel‐plate device which operates under gap‐loaded conditions, and is designed as an add‐on fixture for the Materials Testing System Model 312. The rheometer provides characterization data of the pre‐gel (via the zero‐shear viscosity) or the post‐gel (via the equilibrium modulus) properties of a foaming cellular polymer with a precision of better than ± 15%.
DSC and FTIR characterization of biodegradation of polyethylene
Authors: Raghavan D. , Torma A. E.
Published: December 2004

Aspergillus niger, a fungus, was used in the degradation of commercially available thermoplastic polyethylene films. Quantitative calorimetric measurements performed on as‐received, abiotic, and biotic treated polyethylene samples, revealed that the amorphocity of the sample decreases during biodegradation. In addition, it was found that the external substrates (sucrose) in the growth medium influenced the biodegradation process of polyethylene. Furthermore, the crystallinity data on different biotreated samples indicated that the adapted microorganisms were able to metabolize a small portion of polyethylene. The significance of the Fourier transform infrared (FTIR) results of polyethylene samples have been discussed.
Influence of a core/shell rubber phase on the morphology and the impact resistance of a PC/SAN blend (75/25)
Authors: Debier D. , Devaux J. , Legras R. , Leblanc D.
Published: December 2004

At 75/25 concentration ratio, bisphenol a polycarbonate (PC)/styreneacry‐lonitrile copolymer (SAN) blend has poor impact resistance compared to PC/ABS. A rubber phase methacrylate‐butadiene‐styrene (MBS) of core/shell type was dispersed in PC/SAN blend. The morphology of the unmodified and modified blend was investigated. The influence of the acrylonitrile ratio in the SAN on the microstructure was studied. It clearly shows that core/shell resides at the interface between PC and SAN. It seems that core/shell particles enhance the adhesion between the different phases. Their presence influences the interface mobility; i.e., the coalescence of the dispersed phase observed in pure PC/SAN is considerably reduced when the MBS particles are added. The impact resistance of the samples was correlated with the morphology.
Rubber modified epoxy resin. I: Cure kinetics and chemorheology
Authors: Kim Dae Su , Kim Sung Chul
Published: December 2004

The curing and vitrification effect during the reaction of ATBN modified epoxy resin was studied through the dynamic differential scanning calorimetry method and a new reaction kinetic equation containing generalized WLF equation was developed to describe the reaction rate at both glassy and rubbery state. An autocatalytic mechanism was found to describe adequately the cure kinetics of the rubber modified epoxy resin and the overall order of reaction was assumed to be 2. The kinetic parameters were determined from the DSC data through the Marquardt's multivariable nonlinear regression method and Runge–Kutta integration technique. The presence of rubber indicated minor effect on the cure kinetics of epoxy resin. The Arrhenius type viscosity function was employed to establish a relationship between viscosity data measured by RMS and chemical conversion calculated from the reaction kinetic equation.
The use of flexural tests in the study of environmental stress cracking of polymers
Authors: Arnold J. C.
Published: December 2004

The use of bend testers for the determination of critical strains in the study of environmental stress cracking has been assessed. Using the combination of polystyrene in ethanol, various factors affecting the measurement of critical strains were investigated, including the strain applied during the bend testing, the time of immersion in the liquid prior to straining, the surface finish, and the extent of physical aging. It was concluded that the best determination of critical strain is the strain at which a sample just shows signs of crazing, rather than the strain at the outer edge of a band of crazes. The measured value of critical strain increases with increased prior immersion time, decreased surface roughness, and decreased physical aging time. Reasons for these variations are discussed. It is concluded that although the use of bend testers is valuable for qualitative testing, careful testing methodologies need to be adopted for it to be a useful quantitative test.
History of commercial polymer alloys and blends (from a perspective of the patent literature)
Authors: Utracki L. A.
Published: December 2004

Polymer blends are defined as mixtures of at least two polymeric species. Thus, the first patent polymer blend was a mixture of natural rubber, NR, with gutta percha patented by Alexander Parkes, an artist of Birmingham, in 1846. The first man‐made polymer, nitrocellulose, NC was prepared by Braconnot in 1833. The resin was commercialized in 1868, but its first blends (with NR) were patented three years earlier. The first patent on blends of two synthetic polymers was granted in 1928 for poly(vinylchloride)/poly(vinylacetate), PVC/PVAc (latex blending). During the intervening 65 years, the polymer blend patent literature grew at an exponential rate; since 1983 the annual output has doubled, to exceed 3000 patents/year in 1993.
Blockiness of olefin copolymers and possible microphase separation in the melt
Authors: Wardhaugh Leigh T. , Williams Michael C.
Published: December 2004

Solid‐catalyzed copolymerization reactions of ethylene and α‐olefins can produce complex mixtures generally regarded as “polyethylenes” (including linear low‐density polyethylene). The selective nature of those catalysts can lead to block‐like character in segments of polymer molecules, and these segments are sufficiently dissimilar (from a thermodynamic viewpoint) to allow for the possibility of microphase separation in the melt. Such a molecular‐level phase separation would substantially alter the melt rheology, the crystallization process, and hence the mechanical and optical properties of the resulting product. It would, in principle, be identical to those occurring in conventional well‐defined block copolymers, allowing the thermodynamic models developed for those systems to be extended to block‐like polyolefins.
The development of laminar morphology during extrusion of polymer blends
Authors: Kamal M. R. , Garmabi H. , Hozhabr S. , Arghyris L.
Published: December 2004

Studies of the microstructure and permeability of extruded ribbons of polypropylene (PP)/ethylene vinyl alcohol copolymer (EVOH) and polyethylene (PE)/polyamide‐6 (PA‐6) blends have shown that it is possible to control the flow‐induced morphology to generate discontinuous overlapping platelets of EVOH or PA‐6 dispersed phase in a PP or HDPE matrix phase. The effects of the following factors on morphology development and blend properties were considered: blending sequence, melt temperature, composition, compatibilizer level, die design, screw type, and cooling conditions. The impact properties and interfacial adhesion of laminar blends of PP and EVOH were improved without diminishing the barrier properties. The oxygen and toluene permeability of extruded samples with EVOH content of 25 vol% resembled values obtained with multilayer systems. Processing conditions had a major influence on the morphology of blends of high density polyethylene and polyamide‐6 (HDPE/PA‐6), and, under special processing conditions, laminar morphology was obtained in this system. The toluene permeability of extruded ribbons of HDPE/PA‐6 blends was in the range obtained with multilayer systems.
Ultrasonic behavior of polymer blends
Authors: Gendron R. , Tatibouët J. , Guèvremont J. , Dumoulin M. M. , Piché L.
Published: December 2004

During the last few years, improvements in control strategies became a necessity, with controls being targeted on material properties. The ever‐increasing demand for polymer blends spells the need for in‐line instrumentation capable of monitoring blend properties such as morphology. Since ultrasonics have proved to be sensitive to properties of multiphase materials, their performance for discriminating blend morphology was explored here. In‐line and off‐line (static, with no flow) ultrasonic measurements were made on different blends of polystyrene (PS), polyethylene (PE), and polypropylene (PP) for various viscosity ratios, and over the entire range of composition. Blends were compounded on a ZSK‐30 Werner & Pfleiderer intermeshing co‐rotating twin‐screw extruder. In‐line ultrasonic measurements were performed on both single‐screw and twin‐screw extruders. Ultrasonic properties (velocity and attenuation) were found to vary approximately linearly with composition. Mixing rules were evaluated for the description of ultrasonic behavior. For the attenuation measurements, the positive deviations from these rules were found significant. The additional attenuation was attributed to scattering generated by the presence of the minor phase inclusions.
Development of polymer blend morphology during compounding in a twin‐screw extruder. Part IV: A new computational model with coalescence
Authors: Huneault M. A. , Shi Z. H. , Utracki L. A.
Published: December 2004

In Part II of this series of publications, the first generation model of morphology evolution during polymer blending in a twin‐screw extruder was presented. The model was based on a simplified flow analysis, and an assumption that dispersion occurs via drop fibrillation followed by disintegration. In the present Part IV, several modifications of the model are discussed. (i) The flow analysis was refined by computing the pressure profiles. (ii) The flow paths and strain history of the dispersed droplets within the screw elements are computed directly, which makes it possible to determine the drop susceptibility to deformation and break. (iii) Besides the fibrillation mechanism, a drop‐splitting mechanism for low supercritical capillary numbers is incorporated. (iv) The choice of breakup mechanism is based on micro‐rheological criteria. (v) The coalescence effects are taken into account. (vi) The theoretical model is self‐consistent, without adjustable parameters. The validity of theoretical assumptions was evaluated by comparing the model predictions with the experimental droplet diameters at different positions in the twin‐screw extruder.
The conducting behavior and stability of conducting polymer composites
Authors: Chen X. B. , Issi J‐P. , Devaux J. , Billaud D.
Published: December 2004

Results of measurements of the electrical conductivity of low density polyethylene/polypyrrole and polystyrene/polypyrrole composites are reported. It is observed that the electrical conductivity of the composite vs. concentration follows the power law predicted by the percolation theory. The manufacturing process influences the homogeneity of the composite at microscopic scale and thus the percolation threshold. Annealing studies show that the stability of the electrical conductivity of the composite is related to the thermal expansion of the polymers and the relaxation of the polymer chains. The decrease of the electrical conductivity of the composite is attributed to the interruption of the percolation path.
Diffusion of low molecular weight substances into a laminar film. I: Rigorous solution of the diffusion equation in a composite film of multiple layers
Authors: Fukuda Mitsuhiro , Kawai Hiromichi
Published: December 2004

A rigorous solution of the diffusion of penetrant into a laminar film comprised of multilayers of m components is presented by an orthogonal‐expansion method. As the simplest practical cases of m − 2 and m − 3, with stepwise distribution of both diffusion coefficients and solubility coefficients at the boundary between respective layers, the diffusion properties in the transient state are analyzed in detail. That is, changes in the penetrant concentration distribution within the laminar film and the total amount of penetrant sorbed within the film both with time after exposing the film to an atmosphere of fixed penetrant concentration are calculated for A–B as well as A–B–A type layer arrangements. The calculation is performed while keeping (L2/L1) at a constant value of 2.0 but varying the diffusion coefficient ratio of (D1/D2) from 102 to 10−2, and/or varying the solubility coefficient ratio of (S1/S2) from 1 to 10, where L1 and (L2 − L1) are the thickness D1 and D2 are the diffusion coefficients of penetrant, and S1 and S2 are the solubility coefficients in the A‐component and B‐component, respectively. The sorption curves deviate considerably from those of Fickian curves of homogeneous film with (D1/D2) − 1 in their respective ways. The results obtained here can be applied to the diffusion in a single component polymer film having a surface layer with different diffusion properties from that of the inner side of the film caused by differing distributions in molecular orientation or degrees of crystallinity.
An experimental and computational evaluation of ethylene/styrene copolymerization with a homogeneous single‐site titanium(IV)‐constrained geometry catalyst
Authors: Martínez S. , Exposito M. T. , Ramos J. , Cruz V. , Martínez M. C. , López M. , Muñoz‐Escalona A. , Martínez‐Salazar J.
Published: December 2004

Styrene was copolymerized with ethylene using the geometry constrained Me2Si(Me4Cp)(N‐tert‐butyl)TiCl2 Dow catalyst activated with methylaluminoxane. Increasing the styrene/ethylene ratio in the reactor feed had the effects of reducing both the activity of the catalyst and the molecular weight of the copolymers produced. However, the higher the styrene/ethylene ratio used, the greater the amount of styrene that became incorporated in the copolymer. We discuss these experimental findings within the framework of a computational analysis of ethylene/styrene copolymerization performed through hybrid density functional theory (B3LYP). In general, there was good agreement between the experimental and theoretical results. Our findings point to the suitability of combining experimental and theoretical data for clarifying the copolymerization mechanisms that take place in α‐olefin‐organometallic systems. © 2004 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 43: 711–725, 2005
A new method for Characterization of the Surface Energy of Hydrophobic Particles
Authors: Fuerstenau Douglas W. , Williams Mark C.
Published: December 2004

A film flotation technique has been developed for assessing the hydrophobicity/hydrophilicity of an assembly of particles which have a distribution of surface energies. With this method, particles are partitioned by placing them on the surface of a series of aqueous solutions of different surface tensions and determining the fraction imbibed into the liquid. From the results, a cumulative distribution of particles versus their critical wetting surface tension (surface energy) can be made. The mean critical wetting surface tension can be used as an index for making correlations with surface‐based processes.
Laser Diffraction Spectrometry: Fraunhofer Diffraction Versus Mie Scattering
Authors: de Boer Gerben B. J. , de Weerd Cornelis , Thoenes Dirk , Goossens Hendrik W. J.
Published: December 2004

Laser diffraction spectrometry (LDS) is often claimed to operate on the principle of Fraunhofer diffraction. This is only true, however, if particles are large compared to the wavelength of light or if the ratio of the refractive indices of the disperse and continuous phases, m, is clearly different from unity. In this study it has been established that LDS, as applied to particle and droplet sizing in suspensions and emulsions, is based on Miescattering. Scattering patterns of single particles may be calculated if the refractive indices of both phases are known. Thus, a theoretical basis has been provided for the application of LDS to size‐measurement in suspensions and emulsions, and for extension of this method to the lower size ranges and those cases in which the refractive indices of the disperse and continuous phases are similar. Extension of the work presented in this paper will enable the calculation of scattering matrices so that calibration of the apparatus with standard materials may be avoided.
The Probable Number of Particles in Contact when Spread on a Microscope Slide
Authors: Hawkins Arthur E.
Published: December 2004

It is shown that the number of particles which may be placed upon a slide is surprisingly limited if each particle is to be isolated. This is particularly relevant if automatic image analysis of size or shape is to be achieved without tedious editing. Using a simple mathematical treatment it is possible to calculate, for any particular size of particle, the number of particles on a slide which should not be exceeded.
Laser Doppler Anemometry – a non‐intrusive optical measuring technique for fluid velocity
Authors: Ruck Bodo
Published: December 2004

The present paper gives an introduction to laser Doppler anemometry. The fundamental principles of this measuring technique, as well as the basic features of its instrumental realizations, are explained. The application of laser Doppler anemometry to fluid investigations often requires an adaptation of the LDA‐system to the measuring problem. Basic formulas for the lay‐out and adaptation are given.
Polygonal Harmonics of Silhouettes: Shape analysis
Authors: Clark Nigel N. , Diamond Harvey , Gelles Gregory , Bocoum Brigitte , Meloy Thomas P.
Published: December 2004

One well documented method for finding the fractal dimension of a silhouette involves approximating the silhouette with polygons which have all but one side equal and the vertices of which fall upon the silhouette edge. These are constructed using a divider stepping method or a computer algorithm which mimics this process. If one does not complete the polygon with an unequal side, as is usually done, but continues the analysis by stepping around the silhouette several times, the dividers start to „walk in their own footsteps”︁ and describe an equilateral polygon in the silhouette. These phenomena, termed polygonal harmonics, are examined and discussed in detail. A rule is developed for harmonic stability and specific cases of the circle, triangle and smooth curves are examined to gain insight into the convergence process.
In‐situ Determination of the Molecular Composition of Aerosol Particles in a Monodisperse Model Aerosol
Authors: Schweiger Gustav
Published: December 2004

The in‐situ determination of the molecular composition of aerosol particles, composed of DES and DBP and suspended in an air flow, is described. The laser‐Raman scattering technique was applied to determine the composition of a monodisperse, model aerosol, 10 m̈m in diameter, which flows through the scattering volume.
How to Reduce Errors in Test Sieving
Authors: Müller Helmut , Kubier Bernd , Rudolph Lutz
Published: December 2004

Studies of and experiences with the reduction of errors in test sieving are presented. The preparation of the test material and, above all, the errors in sample splitting are included in the considerations. Errors due to the manufacture of test sieves are discussed, for example the influence of the aperture width distribution. The method applied at the Forschungsinstitut für Aufbereitung (FIA) for the inspection and calibration of test sieves is described in detail. The use of test materials for the calibration of sieves is recommended.
Persistence of Polygonal Harmonics as Shape Descriptors
Authors: Hurter Patricia , Clark Nigel N.
Published: December 2004

Characterization of the overall (lage scale) shape of rugged particles poses a problem which is not readily solved by existing shape analysis techniques. Recent research on the divider stepping method used in factal analysis has led to the examination of polygonal harmonics which can be constructed in both smooth and rugged particle silhouettes. The persistence of these harmonics is defined as the ratio of the longest step length to shortest step length which can be used to create that harmonic. It is proposed that the persistences of the first three harmonics provide useful descriptors for particle shape. Variation of these persistences within several geometric figures is explored, protocols for the analysis are adopted and some preliminary work on rugged silhouettes is discussed. Characterization by this technique holds great promise in the development of a general approach to particle shape description.
Particle Size Analysis of Carbon Black
Authors: Blackford David B. , Simons Gary R.
Published: December 2004

A new technique is described for measuring the size distribution of submicrometer sized powders, such as carbon black. Powder is first dispersed as an aerosol and the particle size is subsequently measured with a differential mobility classifier and an aerosol concentration detector.

The technique has been used to provide a size distribution for seven American Society for Testing and Materials (ASTM)/D1765 designated grades of carbon black (N110, N234, N299, N330, N650, N683, N762). In addition, four grades (N234, N330, N683, N762) are designated by ASTM D24 committee on carbon black as Standard Reference Blacks in the SRB‐3 series (C3, B3, D3, A3, respectively).

The effectiveness of the dispersion technique is discussed and size distribution data is presented on the seven ASTM grades of carbon black. For the sake of comparison, the same carbon blacks have been sized with a completely different measurement technique. This technique measures the diffusion coefficient of a dilute particle suspension from which a mean hydrodynamic particle diameter is determined. Size distribution data using this technique is also presented.
Optimal Scaling of the Inverse Fraunhofer Diffraction Particle Sizing Problem: The linear system produced by quadrature
Authors: Dan Hirleman E.
Published: December 2004

Solution of the linear system of equations obtained by discretization and numerical quadrature of the Fredholm integral equation describing Fraunhofer diffraction by a distribution of particles is considered. The condition of the resulting system of equations depends on the discretization strategy. However, the specific set of equations is shown to depend on the discretization scheme used for the scattering angle domain (the number, positions and apertures of the detectors) and for the size domain (the number and extent of the discrete size classes). The term scaling is used here to describe particular formulations or configurations of the scattering angles and size classes, and a method for optimally scaling the systems is presented. Optimality is determined using several measures of the condition (stability) of the resulting system of linear equations. The results provide design rules for specifying an optimal photodetector configuration of a Fraunhofer diffraction particle sizing instrument.
Modeling of Multiple Scattering Effects in Fraunhofer Diffraction Particle Size Analysis
Authors: Dan Hirleman E.
Published: December 2004

A model for the direct problem of calculating the forward scattering signature of a multiple scattering medium is presented. The new formulation is optimized for integration into schemes for reconstructing the particle size distribution from laser diffraction (forward scattering) signatures obtained from optically thick media. The analysis is valid for media where the particle sizes and interparticle spacings are large (relative to the wavelength and the particle size, respectively) such that Fraunhofer diffraction theory adequately describes the properties of the forward scattered light from individual scattering events. The simulated performance of laser diffraction particle sizing instruments was then studied using predictions of the scattered light signatures which would be measured by laser diffraction instrument under multiple scattering conditions. The results were compared with experimental data and theoretical calculations based on other models.
Interaction between a Sphere and a Gaussian Beam: Computations on a micro‐computer
Authors: Corbin Frédéric , Gréhan Gérard , Gouesbet Gérard , Maheu Bruno
Published: December 2004

This paper presents some characteristics of the light scattered by one spherical particle illuminated by a Gaussian beam. The basic theory is a generalization of the Lorenz‐Mie Theory. The fact that the computations can be easily carried out on a micro‐computer is pointed out.
Phase‐Doppler‐Anemometry and the Log‐Hyperbolic Distribution applied to Liquid Sprays
Authors: Bhatia Jagdish C. , Domnick Joachim , Durst Franz , Tropea Cameron
Published: December 2004

The paper provides a description of the local drop‐size distributions in a liquid spray issuing from a 60° oil‐burner nozzle obtained experimentally using a phase‐doppler anemometer. The details of the optical system and the signal processing electronics of the phase‐Doppler anemometer are included.

Details have also been given concerning the use of the log‐hyperbolic distribution and in particular of a procedure for determining the four defining parameters from a given experimental distribution, in this case that of drop size. Analytical formulae to compute moments of the distribution and the mean diameters are also given.

All size distributions are shown to be well described by the log‐hyperbolic distribution involving four parameters. The variation of these parameters along the axis of the jet clearly reveals a developing region of the spray followed by a fully developed state, for which physical reasons are given. The parameters can also be used to predict the local drop‐size distribution at any intermediate location on the spray axis.
Measurement of Particle Rotational Velocity Using a Laser Anemometer
Authors: Kale Sunil R. , Ramezan Massood , Anderson Rodney J.
Published: December 2004

An electrodynamic balance and a frequency shifted Laser Doppler Anemometer (LDA) were used to obtain rotational velocity data from nonspherical particles undergoing pure rotation. A charged oil shale particle (150μm × 150 μm × 60 to 80 μm thick) was suspended in an electric field and rotated at a constant velocity by subjecting it to a vertical air jet. The measuring volume of the LDA was located on the particle, and Doppler bursts were observed from both stationary and rotating particles. This observation suggests that micron‐sized surface irregularities can act as individual scattering sources for LDA measurements. Signal analysis was performed with a counter type processor and a PDP‐11 computer. The particle motion was recorded on video tapes from which the true rotational velocity and maximum radius of rotation were obtained. Within the experimental uncertainties, the maximum rotation‐induced surface velocity measured with the LDA agreed well with that obtained from video tapes.
Particle Dispersion in a Swirling Confined Jet Flow
Authors: Sommerfeld Martin , Krebs Werner
Published: December 2004

The characteristics of swirling single‐ and two‐phase flows discharging into a sudden pipe expansion were studied in detail by the use of laser‐Doppler anemometry. The results are compared with those for the comparable non‐swirling case. The central recirculation zone established for a swirl number of 0.56 was found to have an annular shape, which was a result of the subcritical nature of the flow and the area contraction at the end of the test section.

The behaviour of the particles in both swirling and non‐swirling flow was studied by flow visualization, particle concentration and velocity measurements. Initially, the spreading of the particle jet is about the same for both cases owing to the particle inertia. In the middle of the recirculation bubble the particles start to spread more rapidly under the acting of centrifugal forces established in a swirling flow. This finally results in a high concentration of particles near the wall of the test section and a particle‐free region in the core of the vortex. The numerical simulations of the non‐swirling flow showed good agreement for both the gas and particle phases in comparison with the experimental results.
Aerosol Generation from the Sanding, Cutting, and Breaking of Floor Tiles
Authors: Lundgren Dale A. , Vanderpool R. W. , Liu Benjamin Y. H.
Published: December 2004

Various types of floor tile were tested in a controlled and isolated environment to determine quantitatively the wear rate and size characteristics of material generated from floor tile during operations of sanding, cutting, and breaking. Size characteristics were determined for the aerosolized fractions as well as the settled material worn from the tile surface. In addition to the vinyl composition tile, tests were also conducted with floor tile containing various amounts of glass fiber and sodium phosphate fibers. The tests were conducted in a specially designed glove box which allowed complete sampling and fractionization of the generated aerosol. Due to good measurement repeatability, aerosol generation differences from the various flooring types were determinable.

A Frick‐Taber accelerated wear machine was employed to establish comparative wear rates of the different flooring materials. Test results were repeatable and measured relative wear rates correlate well with published measurements. Results indicate that the presence of up to 13% glass fibers or phosphate fibers in the tile does not improve the tile's wear characteristics or significantly alter the size distribution of the generated material. Although asbestos‐containing floor tile was not tested in this study, results from the simulant fiber tile tests may enable prediction of the behavior of vinyl‐asbestos tile under the influence of similar wear mechanisms.
Drop Sizing by Laser Light Scattring Exploiting Intensity Angular Oscillation in the mie regime
Authors: Ragucci Raffaele , Cavaliere Antonio , Massoli Patrizio
Published: December 2004

The intensity angular pattern of the light scattered by a drop at a scattering angle of ca. 90° is related to the size of the scattering drop. A simple relationship between the number of fringes per degree and the size is presented. The possibility of measuring the drop size through visualization of the fringe pattern is demonstrated.
Pulse Holography and Phase‐Doppler Technique. A comparison when applied to swirl pressure‐jet atomizers
Authors: Umhauer Heinz , Löffler‐Mang Martin , Neumann Peter , Leuckel Wolfgang
Published: December 2004

Pulse holography and the phase‐Doppler technique are two of the very few methods with which the size and velocity of individual particles within a two‐phase flow may be simultaneously measured. This enables the two‐dimensional frequency distributions of particle size and velocity to be compiled and allows the existence of mutual correlations to be verified.

The application of both methods to investigations into water droplet collections within the hollow spray cone of a swirl pressure‐jet atomizer is described. When comparing the results of measurements obtained by the two methods under identical conditions, one fundamental difference must be taken into account: whereas pulse holography delivers space‐averaged concentration‐dependent frequency distributions, those derived from the phase‐Doppler technique are time‐averaged fluxdependent. The methods hence deliver different, but equivalent, results. Since the possibility of conversion exists, both representations are always available. As far as the particle size distributions are concerned, the results obtained from the two methods confirm the expected differences, whilst verifying the compliance of the interconverted size distribution data. Regarding the velocity distributions, however, some unexplained discrepancies still remain.
Estimation of the Effective Measuring Volume of Single‐Fibre Reflection Probes for solid volume concentration measurements
Authors: Rensner Detlef , Werther Joachim
Published: December 2004

The working principle of the single‐fibre reflection (SFR) probe is that light emitted by a laser diode is guided into the measuring volume by the same fibre which receives the proportion of light reflected by the particles in the vicinity of the probe tip and transmits it back to a photosensitive element. In contrast to other configurations of fibre optical probes, the SFR probe is characterized by an unambiguous calibration graph over the entire range of solid volume concentration values. SFR probes have been successfully applied to different kinds of multiphase flow systems, e.g. fluidized beds, pneumatic conveying lines, elutriators and thickeners.

A particular question for the interpretation of measurements has always been the effective size of the measuring volume, which is mainly determined by the solid volume concentration. In this paper a simplified mathematical model of the signal generation by backscattering of the emitted light at the particle surfaces is given. The theory takes into account the average optical properties of the solids and their particle size distributions.

The particle properties are determined on the basis of this model, which finally delivers the shape, size and depth of the effective measuring volume. For particle sizes between 30 and 120 μm the depth of the measuring volume of a 600‐μm fibre probe is between 0.2 mm for solid concentrations near the fixed‐bed state and approximately 4 mm for solid volume concentrations as low as 0.1 vol.‐%.
Particle Sizing by Photon Correlation Spectroscopy. Part IV: Resolution of bimodals and comparison with other particle sizing methods
Authors: Finsy Robert , Deriemaeker Lue , De Jaeger Nicolas , Sneyers Rik , Vanderdeelen Jan , Van der Meeren Paul , Demeyere Hugo , Stone‐Masui Jeanine , Haestier Anne , Clauwaert Julius , De Wispelaere Walter , Gillioen Pascal , Steyfkens Sabine , Geladé Erik
Published: December 2004

The practical performances of single and multi‐angle photon correlation spectroscopy (PCS) for resolving bimodal distributions of industrial poly (methyl methacrylate) samples was investigated in a comparative study by several users affiliated to academic and industrial groups and by two suppliers of commercial equipment. The results for the harmonic intensity averaged diameters obtained by cumulants analysis reported by the different laboratories are in agreement, in addition to the results for the normalized second cumulants. The uncertainty on the latter quantities is large, however. For the bimodal samples with two populations with average diameters in a ratio of about 2.5 : 1, not all users were able to resolve the distribution in its components by single‐angle PCS. Some slight improvement was obtained by multi‐angle PCS. Other indirect techniques (polarization intensity differential scattering, static light scattering data and disc photosedimentometer) appeared to be superior for resolving the bimodal distributions.
Measurement of Aggregate Fractal Dimensions Using Static Light Scattering
Authors: Raper Judy A. , Amal Rose
Published: December 2004

Aggregates formed from colloidal particles will vary in shape according to the aggregation regime prevalent. Compact structures are formed when the aggregation is slow, whilst loose tenuous structures are formed when rapid (or diffusion limited) aggregation prevails. These structures can be fractal in nature, that is, there is a relationship between porosity and the number of primary particles making up the aggregate, and is described by the fractal dimension, dF. Fractal dimensions of hematite aggregates have been measured experimentally using the static light scattering technique. Fractal dimensions varied with aggregation regimes; for the rapid aggregation regime, dF was found to be 2.8, whilst for conditions in which aggregation was slow (retardation forces prevail), dF's of 2.3 were measured. For conditions which lead to aggregation in which both diffusion and retardation forces play a part, structures with fractal dimensions such that 2.3 < dF < 2.8 were found.

The effects of adsorbed fulvic acid, a naturally occuring organic acid, on the kinetics of hematite aggregation and on the resulting structure of hematite aggregates were also investigated. The study of aggregate structure shows that the fractal dimensions of hematite aggregates which are partially coated with fulvic acid molecules are higher than those obtained with no adsorbed fulvic acid. The scattering exponents obtained from static light scattering experiments of these aggregates range from 2.83 ± 0.08 to 3.42 ± 0.1. The scattering exponents of greater than 3 indicate that the scattering is the result of objects that contains pores which are bounded by surfaces with a fractal structure, and can be related only to surface fractal dimension. The high fractal dimensions are due to restructuring within the aggregates, which only occured at low coverage by the organic acid.
Particle Shape Analysis as an example of knowledge extraction by neural nets
Authors: Kohlus Reinhard , Bottlinger Michael
Published: December 2004

An investigation is presented concerning the ability of neural nets to classify particles using contour data. Different nets were trained to classify limestone, quartz and coffee particles by their outer boundaries. The contour lines of the analysed particles were similar and differed only in a complex way. A new method of interpreting the Fourier coefficients is shown, which might lead to a possibility of defining particle shape classes by examples. Information is given concerning the selection and design of the appropriate neural net, e.g. back‐propagation, and self‐organizing maps. In addition, a possibility of interpreting the trained neural nets is demonstrated.
Evaluation of a Particle Sizing Technique Based on Laser Sheets
Authors: Gréhan Gérard , Ren Kuan Fang , Gouesbet Geŕrd , Naqwi Amir , Durst Franz
Published: December 2004

The use of a laser sheet (or elliptical Gaussian beam) in meas‐urement techniques is of growing interset. Some of these techniques take advantage of the wavefront curvature of such beams as in a dual‐crylindrical wave system (DCW). Nevertheless, up to now, the analysis of the properties of the light scattered by spherical particles form the beam has been carried out largely by using geometrical optics or classical Lorenz‐Mie theory. In this paper, the generalized Lorenz‐Mie theory (GLMT) is applied to the analysis of an existing DCW measurement system. Differences between the results predicted by classical approaches and by GLMT are emphasized.
The Pulse Displacement Technique — a single particle counter with a size range larger than 1000: 1
Authors: Hess Cecil F. , Wood Craig P.
Published: December 2004

This paper describes the pulse displacement technique(PDT) to simultaneously measure particle size and velocity in applications characterized by a large size range and high particle concentration. PDT is based on the detection of scattered refraction and reflection pulses which sweep past a detector at different times as a particle traverses a narrow probe volume. Basic analytical relationships are presented which allow the calculation of the spatial and temporal widths and separations of the reflection and refraction pulse as a function of particle diameter and velocity. Two implementations of PDT are discussed using one or two receivers with two laser sheets having the same or different wavelengths. This paper also discusses several methods to measure particle velocity with PDT, discusses the limitations associated with signal broadening in practical systems, and briefly presents experimental results which show that the temporal separation between the refraction and reflection and reflection pulse maxima is independent of collecting lens f‐number from f/3 to f/20 for particle sizes ranging from 250 to 2000 μm.
Morphological shape characterization: Application to oxalate crystals
Authors: Vivier Hervé , Marcant Bruno , Pons Marie‐Noëlle
Published: December 2004

The characterization of the concave crystal shapes obtained during precipitation in a well mixed reactor of alkaline earth and transition metal oxalates by means of a morphological spectral analysis method is proposed. The method is based on series of openings performed on the crystal outline and on its complement with respect to its convex hull. Four parameters are used to describe and classify the shapes. The method can be applied to any concave shape.
Simultaneous Measurement of Velocity and Equivalent Diameter on Non‐Spherical Particles
Authors: Morikita Hiroshi , Hishida Koichi , Maeda Masanobu
Published: December 2004

The performance of a laser‐based optical technique to measure simultaneously the velocity and equivalent diameter of nonsphercial particles was evaluated. The size information was provided by the absolute intensity of diffractively scattered light by a particle crossing a single laser beam, which is concentric with a laser Doppler probe volume. The response curve (size‐intensity relationship) of the technique was estimated by calculations using the Fraunhofer approximation. Experiments with spherical glass and polyethylene and non‐spherical metal and ceramic particles ranging from 20 to 200 μm confirmed the operation of the technique and in all the measurements the maximum error of the average diameter was 10 μm as compared with size information provided by a microscope.