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  • Articles  (697)
  • Industrial Chemistry and Chemical Engineering  (612)
  • Electronic structure and strongly correlated systems
  • Humans
  • biocompatibility
  • dispersion
  • Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics  (623)
  • Technology  (74)
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  • Articles  (697)
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  • 1
    Electronic Resource
    Electronic Resource
    Polymeric microspheres by radiation copolymerization of acrolein and various monomers at low temperatures (1984)
    Springer
    Colloid & polymer science 262 (1984), S. 450-454 
    Details
    ISSN: 1435-1536
    Keywords: Polymeric microsphere ; radiation polymerization ; acrolein ; dispersion ; 2-hydroxyethyl methacrylate ; polyvinyl alcohol
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract The preparation of polymeric microspheres having aldehyde groups by radiation polymerization of acrolein solution containing various monomers at low temperatures was studied, in which the monomer solution was dispersed with polyvinyl alcohol in order to obtain monomeric microspheres and then irradiated. The particle size of the microspheres from acrolein — 2-hydroxyethyl methacrylate system varied with polymerization and dispersion condition, in which the particle size increase of the concentration of 2-hydroxy ethyl methacrylate and its particle size distribution was broadened. In acrolein — polyethyleneglycol dimethacrylate system, the effect of the molecular structure of monomers on the particle size was studied, and it was found that the particle size decreased with number of oxyethylene units in monomers.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01412039
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  • 2
    Electronic Resource
    Electronic Resource
    Steric stabilization of iron (III) hydroxide sols by various amino acids (1985)
    Springer
    Colloid & polymer science 263 (1985), S. 406-412 
    Details
    ISSN: 1435-1536
    Keywords: Iron(III) hydroxide sol ; amino acid ; dispersion ; coagulation ; electrical surface ; phenomena
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract The dispersion and coagulation phenomena of iron(III) hydroxide sols were investigated as a function of pH in the absence and presence of amino acids. The amino acids used were glycine,L-α-alanine,DL-α-amino-n-butyric acid,L-valine,L-leucine,L- isoleucine,L-glutamic acid andL-arginine. The turbidity measurements of the iron-(III) hydroxide sols, which were prepared by pouring an aqueous iron(III) chloride solution into boiling distilled water, were carried out using a spectrophotometer with an addermixer device and an automatic recording system. The zeta potentials of sol particles were obtained by ultra-microelectrophoresis. The change in turbidity of the sol, as a measure in stability of the sol, increased with increasing pH in the region of pH 2–8, and reached a maximum at the isoelectric point of the particles. The coagulation at the isoelectric point was prevented by adding amino acids, and the stabilization had an optimum point at concentrations which depended upon the kinds of amino acids. The remarkable dispersing effect of amino acids which occurred near the isoelectric point of the particles at the suitable concentration of the ammo acids may be due to the steric protection by amino acid adsorbed. The protective action was explained according to a modified DLVO theory, the modification for London-van der Waals force being applied in order to take the effect of the adsorption layer into account.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01410389
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  • 3
    Electronic Resource
    Electronic Resource
    Multifunctional Biocompatible Membrane and Its Application to Fabricate A Miniaturized Glucose Sensor with Potential for Use In Vivo (1999)
    Springer
    Biomedical microdevices 1 (1999), S. 155-166 
    Details
    ISSN: 1572-8781
    Keywords: MPC ; BMA ; AMPS ; biocompatibility ; cellulose triacetate ; diffusion-limiting effect ; glucose sensor ; needle type ; glucose oxidase ; serum ; whole blood
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine , Technology
    Notes: Abstract A multifunctional membrane with biocompatibility, diffusion-limiting effect, and the ability to curtail the responses of an H2O2 electrode to ascorbate and urate was prepared. It was composed of MB, AB, and CTA, where MB is the copolymer of 2-methacryloyloxyethyl phosphorylcholine (MPC) and n-butylmethacrylate (BMA), AB is the copolymer of acrylamide-2-methylpropane sulfonic acid (AMPS) and BMA, CTA is cellulose triacetate. Investigation of the biocompatibility of this membrane showed that, compared with CTA, relatively few platelets bound to it. The membrane was coated onto the working electrode of a needle-type glucose sensor on which immobilized glucose oxidase membrane has been coated. The sensor did not respond to ascorbate and urate at their concentration normally encountered in blood. Its response was not inhibited by metal ions in blood at usual concentration. The sensor exhibited superior thermostability in addition to a rapid response (〈90 seconds in batch operation), good reproducibility (RE〈5%), good stability (more than 36 hours continuously in heparinized whole blood), and a wide dynamic range (5–650 mg/dl glucose). The sensor was used to determine glucose in serum. The data obtained from the sensor showed good agreement with that from a clinical autoanalyzer (R=0.973).
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1009952625595
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  • 4
    Electronic Resource
    Electronic Resource
    Critical behaviour of a Timoshenko beam-half plane system under a moving load (1998)
    Springer
    Archive of applied mechanics 68 (1998), S. 158-168 
    Details
    ISSN: 1432-0681
    Keywords: Key words Critical velocities ; subcritical and supercritical state ; Mach radiation ; dispersion ; length scale
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Summary In this contribution, attention is focused on the problem of a moving load on a Timoshenko beam-half plane system. Both the subcritical and the supercritical state will be analysed via a FE-simulation. The character of the response is explained by the analytical derivation and the elaboration of the eigen-value problem that follows from the characteristic wave equations together with the boundary conditions. It will be demonstrated that also transcritical states can occur. The total number of critical states and the values of the corresponding critical velocities are determined by the beam-half plane stiffness properties as well as the contact conditions.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s004190050153
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  • 5
    Electronic Resource
    Electronic Resource
    A computerized technique for measuringin-situ concentrations during miscible displacements in porous media (1992)
    Springer
    Transport in porous media 7 (1992), S. 127-145 
    Details
    ISSN: 1573-1634
    Keywords: Miscible displacement ; dispersion ; in-situ concentration measurement ; computerized data acquisition
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Technology
    Notes: Abstract A technique for measurement of thein-situ concentration in an unconsolidated porous medium has been developed. The method involves measurement of electrical conductivityin-situ, under dynamic conditions, for flow involving brine of differing concentrations, at selected locations along the porous medium and relating it to the brine strength. Data acquisition and analysis is carried out using a Hewlett — Packard micro-computer and its interface. A user-friendly software was designed and developed for the system. The measurement technique was evaluated by studying the effect of brine concentration, brine flow rate, and by conducting miscible displacements experiment. The experimentally measured dispersion coefficients for the porous medium agreed closely with the value predicted by the correlation available in the literature.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00647393
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  • 6
    Electronic Resource
    Electronic Resource
    Analytic Solution to a Problem of Seepage in a Chequer-Board Porous Massif (1997)
    Springer
    Transport in porous media 28 (1997), S. 109-124 
    Details
    ISSN: 1573-1634
    Keywords: seepage ; conductivity ; double-periodic structure ; advection ; dispersion
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Technology
    Notes: Abstract A study is made of steady two-dimensional seepage in a porous massif composed by a double-periodic system of ‘white’ and ‘black’ chequers of arbitrary conductivity. Rigorous matching of Darcy's flows in zones of different conductivity is accomplished. Using the methods of complex analysis, explicit formulae for specific discharge are derived. Stream lines, travel times, and effective conductivity are evaluated. Deflection of marked particles from the ‘natural’ direction of imposed gradient and stretching of prescribed composition of these particles enables the elucidation of the phenomena of transversal and longitudinal dispersion. A model of pure advection is related with the classical one-dimensional vective dispersion equation by selection of dispersivity which minimizes the difference between the breakthrough curves calculated from the two models.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1006505908858
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  • 7
    Electronic Resource
    Electronic Resource
    Waves in partially saturated porous media (1992)
    Springer
    Transport in porous media 9 (1992), S. 25-37 
    Details
    ISSN: 1573-1634
    Keywords: Waves ; dispersion ; shock tube ; gas bubbles
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Technology
    Notes: Abstract The propagation of compressional waves in a porous medium is investigated in case the pore liquid contains a small volume fraction of gas. The effect of oscillating gas bubbles is taken into account by introducing a frequency-dependent fluid bulk modulus, which is incorporated in the Biot theory. Using a shock tube technique, new experimental data are obtained for a porous column subjected to a pressure step wave. An oscillatory behaviour is observed, consisting of two distinct frequency bands, which is predicted by the theoretical analysis.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01039623
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  • 8
    Electronic Resource
    Electronic Resource
    On the transient non-Fickian dispersion theory (1996)
    Springer
    Transport in porous media 23 (1996), S. 107-124 
    Details
    ISSN: 1573-1634
    Keywords: solute transport ; Fick's law ; dispersion ; dispersivity ; equation of motion ; non-Fickian dispersion equation ; scale effects
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Technology
    Notes: Abstract The Fickian dispersion equation is the basic relationship used to describe the nonconvective mass flux of a solute in a porous medium. This equation prescribes a linear relationship between the dispersive mass flux and the concentration gradient. An important characteristic of the Fickian relationship is that it is independent of the history of dispersion (e.g. the time rate of change of the dispersion flux). Also, the dispersivities are supposed to be medium constants and invariant with temporal and spatial scales of observation. It is believed that in general these restrictions do not hold. A number of authors have proposed various alternative relationships. For example, differential equations have been employed that prescribe a relationship between the dispersion flux and its time and space derivatives. Also, stochastic theories result in integro-differential equations in which dispersion tensor grow asymptotically with time or distance. In this work, three different approaches, which lead to three different non-Fickian equations with a transient character, are discussed and their primary features and differences are highlighted. It is shown that an effective dispersion tensor defined in the framework of the transient non-Fickian theory, grows asymptotically with time and distance; a result which also follows from stochastic theories. Next, principles of continuum mechanics are employed to provide a solid theoretical basis for the non-Fickian transient dispersion theory. The equation of motion of a solute in a porous medium is used to provide a rigorous derivation of various dispersion relationships valid under different conditions. Under various simplifying assumptions, the generalized theory is found to agree with the conventional Fickian theory as well as several other non-Fickian relationships found in the literature. Moreover, it is shown that for nonconservative solutes, the traditional dispersion tensor is affected by the rate of mass exchange of the solute.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00145268
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  • 9
    Electronic Resource
    Electronic Resource
    Two-dimensional adaptive Eulerian-Lagrangian method for mass transport with spatial velocity distribution (1988)
    Springer
    Transport in porous media 3 (1988), S. 473-489 
    Details
    ISSN: 1573-1634
    Keywords: Advection ; dispersion ; particles ; characteristics ; finite-element ; continuous fluid velocity
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Technology
    Notes: Abstract A Eulerian-Lagrangian scheme is used to solve the two-dimensional advection-dispersion equation. Concentration and its partial differential operator are decomposed into advection and dispersion terms. Thus, advection is formally decoupled from dispersion and solved by continuous forward particle tracking. Dispersion is handled by implicit finite elements on a fixed Eulerian grid. Translation of steep gradients of concentration in advection-dominated flow regimes, is done without numerical distortion. Continuous spatial distribution of velocities are evaluated by using Galerkin's approach in conjunction with Darcy's law based on hydraulic input data from each element. The method was implemented on coarse FE grid with linear shape functions, demonstrating no over/under shooting and practically no numerical dispersion. Simulations, covering a wide range of Peclet numbers, yield high agreement with analytic and practical results.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00138612
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  • 10
    Electronic Resource
    Electronic Resource
    The effect of dispersion model on the linear stability of miscible displacement in porous media (1989)
    Springer
    Transport in porous media 4 (1989), S. 85-96 
    Details
    ISSN: 1573-1634
    Keywords: Stability ; linear stability analysis ; miscible displacement ; aspect ratio ; mobility control ; dispersion
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Technology
    Notes: Abstract Chang and Slattery (1986, 1988b) introduced a simplified model of dispersion that contains only two empirical parameters. The traditional model of dispersion (Nikolaevskii, 1959; Bear, 1961; Scheidegger, 1961; de Josselin de Jong and Bossen, 1961; Peaceman, 1966; Bear, 1972) has three empirical parameters, two of which can be measured in one-dimensional experiments while the third, the transverse dispersivity, must be measured in experiments in which a two-dimensional concentration profile develops. It is found that nearly the same linear stability behavior results from using either model.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00134743
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  • 11
    Electronic Resource
    Electronic Resource
    The influence of free convection on soil salinization in arid regions (1996)
    Springer
    Transport in porous media 23 (1996), S. 275-301 
    Details
    ISSN: 1573-1634
    Keywords: free convection ; through flow ; vadoze zone ; salinization ; dispersion ; multigrid
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Technology
    Notes: Abstract Evaporation of groundwater in a region with a shallow water table and small natural replenishment causes accumulation of salts near the ground surface. Water in the upper soil layer becomes denser than in the depth. This is a potentially unstable situation which may result in convective currents. When free convection takes place, estimates of the salinity profile, salt precipitation rate, etc., obtained within the framework of a 1-D (vertical) model fail. Very simplified model of the process is proposed, in which the unsaturated zone is represented by a horizontal soil layer at a constant water saturation, and temperature changes are neglected. The purpose of the model is to obtain a rough estimate of the role of natural convection in the salinization process. A linear stability analysis of a uniform vertical flow is given, and the stability limit is determined numerically as a function of evaporation rate, salt concentration in groundwater, and porous medium dispersivity. The loss of stability corresponds to quite realistic Rayleigh numbers. The stability limit depends in nonmonotonic way on the evaporation rate. The developed convective regime was simulated numerically for a 2-D vertical domain, using finite volume element discretization and FAS multigrid solver. The dependence of the average salt concentration in the upper layer on the Rayleigh number was obtained.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00167100
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  • 12
    Electronic Resource
    Electronic Resource
    Influence of capillary pressure, adsorption and dispersion on chemical flood transport phenomena (1996)
    Springer
    Transport in porous media 24 (1996), S. 275-296 
    Details
    ISSN: 1573-1634
    Keywords: chemical flooding ; ternary ; immiscible ; surfactant ; numerical simulation ; interfacial tension ; phase behavior ; miscibility ; capillarity ; numerical grid ; adsorption ; dispersion
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Technology
    Notes: Abstract This is the second of two joint papers which study the influence of several physical properties on the transport phenomena in chemical flooding. To that aim, we use a previously reported ternary two-phase model into which representative physical properties have been incorporated as concentration-dependent functions. Physical properties such as phase behavior, interfacial tensions, residual saturations, relative permeabilities, phase viscosities and wettability have been analyzed in the first paper. In this paper, we discuss the influence of capillary pressure, adsorption of the chemical component onto the rock and dispersion. Although arising from different phenomenological sources, these transport mechanisms show some similar effects on concentration profiles and on oil recovery. They are studied for systems with different phase behavior. A numerical analysis is also presented in order to determine the relevance of the number of grid blocks taken in the discretization of the differential equations. This numerical analysis provides useful guidelines for the selection of the appropriate numerical grid in each type of displacement.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00154094
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  • 13
    Electronic Resource
    Electronic Resource
    Saltwater transport in a heterogeneous formation: A case study (1988)
    Springer
    Transport in porous media 3 (1988), S. 217-256 
    Details
    ISSN: 1573-1634
    Keywords: Salinity ; advection ; dispersion ; aquifers ; flow model ; transport model ; simulation ; sea water ; connate water ; leakage
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Technology
    Notes: Abstract Historical information of the hydraulic and salinity aspect, detailed geological information, and information on the physical characteristics of the different layers comprising the formation, are needed for simulating the saltwater transport process in aquifers. In most simulation studies of field situations, there is an inadequacy of data and the modeller has to make justifiable assumptions to analyze a particular situation in order to provide an insight into the problem. A quasi-three-dimensional solute transport model is used to analyze the saltwater encroachment phenomena in aquifers underlying the City of Bangkok; first by calibrating the model's performance with available historical data and then by assessing the extent of future saltwater encroachment with the implementation of the regulatory pumpage to be followed in order to restrict the alarming rate of land subsidence. Model simulation indicates a substantial reduction in the rate of encroachment of the saltwater front with a reduction of pumpage after 1987.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00235330
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  • 14
    Electronic Resource
    Electronic Resource
    An adaptive domain decomposition method for simulation of transport in porous media (1988)
    Springer
    Transport in porous media 3 (1988), S. 549-562 
    Details
    ISSN: 1573-1634
    Keywords: Adaptive mesh ; finite element method ; dispersion
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Technology
    Notes: Abstract A Galerkin finite element method is used along with a self-adaptive strategy of domain discretisation to model dispersion in an axisymmetric cylindrical porous medium. A solution strategy is proposed based on the use of a Gear scheme for the time stepping and partial vectorisation of the code. The domain is highly discretised in the area of the sharp transient front, while the remainder is coarsely discretised. The area covered by the fine mesh is determined by the value of the local concentration gradients. Numerical results are presented for the one and two dimensional cases.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00959102
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  • 15
    Electronic Resource
    Electronic Resource
    On the Influence of Pore-Scale Dispersion in Nonergodic Transport in Heterogeneous Formations (1998)
    Springer
    Transport in porous media 30 (1998), S. 57-73 
    Details
    ISSN: 1573-1634
    Keywords: groundwater ; nonergodic transport ; dispersion ; heterogeneous formations ; hydrogeology
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Technology
    Notes: Abstract Flow of an inert solute in an heterogeneous aquifer is usually considered as dominated by large-scale advection. As a consequence, the pore-scale dispersion, i.e. the pore scale mechanism acting at scales lower than that characteristic of the heterogeneous field, is usually neglected in the computation of global quantities like the solute plume spatial moments. Here the effect of pore-scale dispersion is taken into account in order to find its influence on the longitudinal asymptotic dispersivity D11we examine both the two-dimensional and the three-dimensional flow cases. In the calculations, we consider the finite size of the solute initial plume, i.e. we analyze both the ergodic and the nonergodic cases. With Pe the Péclat number, defined as Pe=Uλ/D, where U, λ, D are the mean fluid velocity, the heterogeneity characteristic length and the pore-scale dispersion coefficient respectively, we show that the infinite Péclat approximation is in most cases quite adequate, at least in the range of Péclat number usually encountered in practice (Pe 〉 102). A noteworthy exception is when the formation log-conductivity field is highly anisotropic. In this case, pore-scale may have a significant impact on D11, especially when the solute plume initial dimensions are not much larger than the heterogeneities' lengthscale. In all cases, D11 appears to be more sensitive to the pore-scale dispersive mechanisms under nonergodic conditions, i.e. for plume initial size less than about 10 log-conductivity integral scales.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1006548529015
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  • 16
    Electronic Resource
    Electronic Resource
    A Solute Transport in Stratified Media (1998)
    Springer
    Transport in porous media 31 (1998), S. 133-143 
    Details
    ISSN: 1573-1634
    Keywords: transport ; solute ; flux-averaged concentration ; stratification ; conductivity ; distribution ; arrival time ; dispersion
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Technology
    Notes: Abstract Two-dimensional and steady solute transport in a stratified porous formation is analysed under assumption that the effect of pore-scale dispersion is negligible. The longitudinal dispersion produced as a result of the vertical variation of hydraulic conductivity is analysed by averaging the variability of a solute flux concentration and conductivity. The evolution of the solute flux concentration is expressed with respect to the correlated variable, that is the travel (arrival) time τ at a fixed location and the averaging procedure is constructed to satisfy the boundary condition where the inlet concentration is a known function of time. In such a statement, a velocity-averaged solute flux concentration is described by a conventional dispersion model (CDM) with a dispersion coefficient which is a function of the arrival time. It is demonstrated that such CDM satisfies the assumption that hydraulic conductivity of the layers is gamma distributed with the parameter of distribution which is chosen to represent a reasonable value of the field scale solute dispersion. The overall behaviour of the model is illustrated by several examples of two-dimensional mass transport.
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    URL: http://dx.doi.org/10.1023/A:1006557032656
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  • 17
    Electronic Resource
    Electronic Resource
    Comment on ‘fractal and superdiffusive transport and hydrodynamic dispersion in heterogeneous porous media’, by Muhammad Sahimi (1995)
    Springer
    Transport in porous media 21 (1995), S. 175-188 
    Details
    ISSN: 1573-1634
    Keywords: diffusion ; dispersion ; percolation ; fractals ; scaling
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Technology
    Notes: Abstract Two fundamental questions regarding the application of percolation theory to transport in porous media are addressed. First, when ‘critical path’ arguments (based on a sufficiently wide spread of microscopic transition rates) are invoked (in analogy to the case of transport in disordered semiconductors) to justify the application of percolation theory to the determination of relevant transport properties, then for long time scales (compared to the inverse of the ‘critical’ percolation rate), the fractal structure of the ‘critical’ path is relevant to transport, but not at short time scales. These results have been demonstrated concretely in the case of disordered semiconductors, and are in direct contradiction to the claims of the review. Second, the relevance of deterministic or stochastic methods to transport has been treated heretofore by most authors as a question of practicality. But, at least under some conditions, concrete criteria distinguish between the two types of transport. Percolative (deterministic) transport is temporally reproducible and spatially inhomogeneous while diffusive (stochastic) transport is temporally irreproducible, but homogeneous, and a cross-over from stochastic to percolative transport occurs when the spread of microscopic transition rates exceeds 4–5 orders of magnitude. It is likely that such conditions are frequently encountered in soil transport. Moreover, clear evidence for deterministic transport (although not necessarily percolative) exists in such phenomena as preferential flow. On the other hand, the physical limitation of transport to (fractally connected) pore spaces within soils (analogously to transport in metal-insulator composites) can make transport diffusive on a fractal structure, rather than percolative.
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    URL: http://dx.doi.org/10.1007/BF00613755
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  • 18
    Electronic Resource
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    A Fickian diffusion model for the spreading of liquid plumes infiltrating in heterogeneous media (1996)
    Springer
    Transport in porous media 24 (1996), S. 1-33 
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    ISSN: 1573-1634
    Keywords: unsaturated flow ; large-scale averaging ; dispersion ; high-resolution numerical simulations ; NAPL spills
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Technology
    Notes: Abstract Infiltration of water and non-aqueous phase liquids (NAPLs) in the vadose zone gives rise to complex two- and three-phase immiscible displacement processes. Physical and numerical experiments have shown that ever-present small-scale heterogeneities will cause a lateral broadening of the descending liquid plumes. This behavior of liquid plumes infiltrating in the vadose zone may be similar to the familiar transversal dispersion of solute plumes in single-phase flow. Noting this analogy we introduce a mathematical model for ‘phase dispersion’ in multiphase flow as a Fickian diffusion process. It is shown that the driving force for phase dispersion is the gradient of relative permeability, and that addition of a phase-dispersive term to the governing equations for multiphase flow is equivalent to an effective capillary pressure which is proportional to the logarithm of the relative permeability of the infiltrating liquid phase. The relationship between heterogeneity-induced phase dispersion and capillary and numerical dispersion effects is established. High-resolution numerical simulation experiments in heterogeneous media show that plume spreading tends to be diffusive, supporting the proposed convection-dispersion model. Finite difference discretization of the phase-dispersive flux is discussed, and an illustrative application to NAPL infiltration from a localized source is presented. It is found that a small amount of phase dispersion can completely alter the behavior of an infiltrating NAPL plume, and that neglect of phase-dispersive processes may lead to unrealistic predictions of NAPL behavior in the vadose zone.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00175602
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  • 19
    Electronic Resource
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    The dispersion of hydrophilic and hydrophobic flame-hydrolysed silicas in short-chained alkanols (1987)
    Springer
    Colloid & polymer science 265 (1987), S. 535-541 
    Details
    ISSN: 1435-1536
    Keywords: Aerosil ; dispersion ; hydrophobicity ; viscosity ; QELS
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract The ultrasonic dispersion of Aerosil 200 and some n-alkyl surface-modified derivatives thereof in alkanols have been examined. The sizes of the aggregates formed during this process were investigated from measurements of sol viscosity and quasi-elastic light scattering (QELS). In the former technique, the aggregate volume ratios (AVR) were calculated at very low volume fractions of silica. The AVR values so obtained indicated that the silica monomers were highly aggregated in all systems, as expected. Differences between the various alkanols were found, however. Decreasing continuum polarity from water to hexan-1-ol produced decreasing AVRs. From hexan-1-ol to octan-1-ol, however, the AVRs increased. The n-alkyl surface-modified silicas gave AVRs substantially different to A 200, related most likely to wetting and solvation of the solid surface during dispersion. QELS measurements were subsequently found to be of limited use for these systems, since the aggregate size distributions in these sols were evidently very broad. The results indicated that these size distribution were non-Gaussian. The use of QELS to investigate systems of such high aggregation appears to be limited.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01412508
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  • 20
    Electronic Resource
    Electronic Resource
    A Probability Density Function Method for Modelling Liquid Fuel Sprays (2000)
    Springer
    Flow, turbulence and combustion 63 (2000), S. 379-394 
    Details
    ISSN: 1573-1987
    Keywords: droplets ; fuel sprays ; combustion ; turbulence ; dispersion
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract A stochastic model is proposed for modelling the turbulent dispersion of liquid fuel sprays. The approach adopted is based on the evolution equation for the joint probability density function (PDF) of the droplet properties. Turbulent dispersion is described by Langevin's equation in which a Weiner process is used to represent the stochastic force term. The method leads to plausible results when applied to a kerosene spray flame and provides a rational framework for the incorporation of liquid film break up and droplet formation processes.
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    URL: http://dx.doi.org/10.1023/A:1009984220148
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    Modeling Turbulent Droplet Motion in Vaporizing Sprays (2000)
    Springer
    Flow, turbulence and combustion 65 (2000), S. 1-29 
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    ISSN: 1573-1987
    Keywords: turbulence ; spray ; model ; vaporization ; dispersion
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract The present article is concerned with the influence of turbulent gas-velocity fluctuations on both droplet dispersion and droplet-gas slip velocity in the context of spray simulation. The role of turbulence in generating slip and thus enhancing interphase heat and mass transfer has so far received little attention and is investigated in this work. A model for turbulent gas-velocity fluctuations along droplet trajectories is presented and is first tuned to reproduce elementary dispersion phenomena. It is then shown to give good results for more general dispersion problems as well as for slip velocities. As a fundamental source of information and for the purpose of model validation and comparison, direct numerical simulation (DNS) of droplet motion in homogeneous isotropic steady turbulence (HIST) is used. Dispersion of “injected” droplets (i.e. droplets under the influence of drift due to high injection velocity) as well as slip velocities for linear and nonlinear droplet drag are studied, and reasonable agreement is found with the model. The distributions of the slip velocity are found to be very similar for linear and highly nonlinear drag law. The present model is also used to investigate the influence of turbulence on droplet penetration. Comparison is made with an eddy-interaction model (the KIVA-2 model), which reveals various weaknesses of this model, in particular the underprediction of average slip velocity. The influence of slip due to turbulence on vaporization is shown for a fuel spray injected into a premix gas-turbine combustor. The classical eddy-interaction model is seen to underestimate the rate of vaporization due to the underprediction of slip.
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    URL: http://dx.doi.org/10.1023/A:1009903802812
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    A linear stability analysis for miscible displacements (1986)
    Springer
    Transport in porous media 1 (1986), S. 179-199 
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    ISSN: 1573-1634
    Keywords: Stability ; linear stability analysis ; miscible displacement ; dispersion ; mobility control
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Technology
    Notes: Abstract A linear stability analysis has been performed for a miscible displacement in a semi-infinite system of finite thickness and unbounded width. A more general description of dispersion has been adopted than those used by previous workers. It is shown that, when there is a step change in concentration and the mobility ratio is unfavorable, the displacement can be unstable at the injection boundary. But, if the concentration is changed sufficiently slowly with time at the entrance to the system, the displacement is stable to infinitesimal perturbations, no matter how unfavorable the mobility ratio. When the mobility ratio is favorable, the displacement is unconditionally stable.
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    URL: http://dx.doi.org/10.1007/BF00714691
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    Issues in flow and transport in heterogeneous porous media (1986)
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    Transport in porous media 1 (1986), S. 319-338 
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    ISSN: 1573-1634
    Keywords: heterogeneity ; dispersion ; saturated flow ; unsaturated flow
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Technology
    Notes: Abstract This invited lecture enumerates various categories of flow and transport in heterogeneous media with particular reference to this Symposium. Specific attention is given to five topics within these categories. (1) We explore the compounding of spatially variable local permeability K to produce an apparent permeability K * on a scale large compared with that of variation of K. An inverse method generates and analyzes flow systems with K spatially periodic in two and three dimensions. (2) Physical arguments indicate that apparent hydraulic properties of an unsaturated composite medium may not represent any conceivable mean of the properties of the component media. (3) Conventionally, buried holes are thought to stay empty during generally unsaturated soil-water flow. The hole, however, acts as an obstacle to flow so that water may seep through it. The larger the hole the more likely this will happen. (4) Dispersion in heterogeneous porous systems with no maximum scale of variation is explored using a Lagrangian mode of analysis. (5) Comments are offered on ‘geostatistics’ and its application to heterogeneous soils and aquifers.
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    Advective and dispersive mixing in stratified formations (1995)
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    Transport in porous media 18 (1995), S. 231-243 
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    ISSN: 1573-1634
    Keywords: Stratified formations ; kinematic mixing ; dispersion ; random fields
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Technology
    Notes: Abstract The mixing process in fluid flow is presented as the bending and stretching of material lines or filaments. A mixing exponent, which quantifies their specific rate of stretching, is defined and analyzed for the case of groundwater flow though stratified formations characterized by a Gaussian autocovariance function. The analysis is performed for purely advective mixing as well as for advective-dispersive mixing. The mixing exponent was found to be proportional to the variance of hydraulic conductivity and inversely proportional to the correlation scale of hydraulic conductivity and to the pore-level dispersion coefficient.
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    Scaling mixing during miscible displacement in heterogeneous porous media (1991)
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    Transport in porous media 6 (1991), S. 607-626 
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    ISSN: 1573-1634
    Keywords: dispersion ; dispersivity ; heterogenity ; miscible ; porous media ; scaling
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Technology
    Notes: Abstract This paper discusses scaling of mixing during miscible flow in heterogeneous porous media. In large field systems dispersivity appears to depend on system length due to heterogeneities. Three types of scaling are discussed to investigate the heterogeneous effects. Dimensional analysis of mixing during flow through geometerically scaled heterogeneous models is illustrated using measured dispersion. Fractal analysis of mixing in statistically scaled heterogeneous porous media is discussed. Analog scaling of pressure transients in heterogeneous porous media is suggested as an in-situ method of estimating dispersion.
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    Modelling fluid flow in cross-bedded sections (1993)
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    Transport in porous media 12 (1993), S. 143-159 
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    ISSN: 1573-1634
    Keywords: Heterogeneity ; layers ; displacement ; numerical simulation ; flow in porous media ; dispersion
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Technology
    Notes: Abstract Beadpack experiments and numerical simulations have been carried out to study flow displacements, effluent profiles and streamline patterns for layered systems with flow not parallel to the layers. The effects of layer thickness, permeability contrast, angle of layer to flow direction, mobility ratio and flood rate have been examined. Each of these parameters influence the displacement profiles, and disperse the flood front. Such real effects must be considered when subsuming reservoir heterogeneities in average reservoir parameters in simulation studies, or interpreting core tests.
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    Fractal and superdiffusive transport and hydrodynamic dispersion in heterogeneous porous media (1993)
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    Transport in porous media 13 (1993), S. 3-40 
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    ISSN: 1573-1634
    Keywords: Diffusion ; dispersion ; percolation ; fractals ; scaling
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Technology
    Notes: Abstract We review and discuss diffusion and hydrodynamic dispersion in a heterogeneous porous medium. Two types of heterogeneities are considered. One is percolation disorder in which a fraction of the pores do not allow transport to take place at all. In the other type, the permeabilities of various regions of the pore space are fractally distributed with long-range correlations. Both systems give rise to unusual transport in which the mean square displacement 〈r 2(t)〉 of a particle grows nonlinearly with time. Depending on the heterogeneities and the mechanism of diffusion and disperison, we may havefractal transport in which 〈r 2〉 growsslower than linearly with time, orsuperdiffusive transport in which 〈r 2〉 growsfaster than linearly with time. We show that percolation models can give rise to both types of transport with scale-dependent transport coefficients such as diffusivity and dispersion coefficients, which are consistent with many experimental observations.
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    A theory of macrodispersion for the scale-up problem (1993)
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    Transport in porous media 13 (1993), S. 97-122 
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    ISSN: 1573-1634
    Keywords: Scale up ; dispersion ; porous media ; random field
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Technology
    Notes: Abstract Dispersion is the result, observable on large length scales, of events which are random on small length scales. When the length scale on which the randomness operates is not small, relative to the observations, then classical dispersion theory fails. The scale up problem refers to situations in which randomness occurs on all length scales, and for which classical dispersion theory necessarily fails. The purpose of this article is to present non-Fickian, theories of dispersion, which do not assume a scale separation between the randomness and the observed consequences, and which do not assume a single length scale. Porous media flow properties are heterogeneous on all length scales. The geological variation on length scales below the observational length scale can be regarded as unknown and unknowable, and thus as a random variable. We develop a systematic theory relating scaling behavior of the geological heterogeneity to the scaling behavior of the fluid dispersivity. Three qualitatively distinct regimes (Fickian, non-Fickian and nonrenormalizable) are found. The theory gives consistent answers within several distinct analytic approximations, and with numerical simulation of the equations of porous media flow. Comparison to field data is made. The use of Kriging to generate constrained ensembles for conditional simulation is discussed.
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    An experimental investigation of dispersion in layered porous media (1994)
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    Transport in porous media 15 (1994), S. 15-30 
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    ISSN: 1573-1634
    Keywords: Experiment ; dispersion ; layered heterogeneity ; permeability ; averaging ; permutation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Technology
    Notes: Abstract Experiments were run in three linear, homogeneous, nonuniform porous media constructed in lucite columns using spherical glass beads. The columns were also joined end to end to create an in series layered heterogeneous porous media. Each column, all combinations of columns and several permutations were studied with a factorial experimental design to determine the effects of porosity, permeability, velocity, length, and column order upon dispersion. Attempts to predict the heterogeneous results from the homogeneous results were made, and a statistical regression based on the factorial design was calculated. Results showed that no simple averaging procedure accurately predicted the heterogeneous results. The statistical regression showed permeability, velocity, viscosity, length and column order to be significant.
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    A LGA model for dispersion in heterogeneous porous media (1994)
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    Transport in porous media 17 (1994), S. 19-32 
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    ISSN: 1573-1634
    Keywords: LGA model ; heterogeneous porous media ; miscible displacement ; dispersion ; tracer
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Technology
    Notes: Abstract The lattice gas automaton (LGA) model proposed in the previous paper is applied to the problem of simulating dispersion and mixing in heterogeneous porous media. We demonstrate here that tracer breakthrough profiles and longitudinal dispersion coefficients can be computed for heterogeneous porous media.
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    A stream tube model for miscible flow (1995)
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    Transport in porous media 18 (1995), S. 245-261 
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    ISSN: 1573-1634
    Keywords: Porous media ; miscible flow ; tracer ; dispersion ; convective flow ; stochastic ; stream tube ; continuous time random walk
    Source: Springer Online Journal Archives 1860-2000
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    Notes: Abstract A simple theoretical model is described for deriving a 1-dimensional equation for the spreading of a tracer in a steady flow at the field scale. The originality of the model is to use a stochastic appoach not in the 3-dimensional space but in the 1-D space of the stream tubes. The simplicity of calculation comes from the local relationship between permeability and velocity in a 1-D flow. The spreading of a tracer front is due to local variations in the cross-sectional area of the stream tubes, which induces randomness in travel time. The derived transport equation is averaged in the main flow direction. It differs from the standard dispersion equation. The roles of time and space variables are exchanged. This result can be explained by using the statistical theory of Continuous Time Random Walk instead of a standard Random Walk. However, the two equations are very close, since their solutions have the same first and second moments. Dispersivity is found to be equal to the product of the correlation length by the variance of the logarithm of permeability, a result similar to Gelhar's macrodispersion.
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    A stream tube model for miscible flow (1995)
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    Transport in porous media 18 (1995), S. 263-282 
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    ISSN: 1573-1634
    Keywords: Porous media ; dispersion ; miscible flow ; heterogeneities ; stochastic ; stream tube ; layered ; fractal
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Technology
    Notes: Abstract Large-scale dispersion in heterogeneous porous media is studied by using a simple model based on stochastic calculation of convective flow in a bundle of stream tubes. The advantage of this approach is that there is a local relationship between velocity and permeability in the 1-dimensional space of the stream tubes. Dispersion is due to the variation in stream tube cross-section, related to the permeability field. First, the arrival times of the tracer in the stream tubes are related to the stochastic properties of the permeability field (variance and covariance). Then, transport equations are derived from the moments of the arrival times. The results agree with more complicated studies. For a permeability field with long-range correlation, the transport equation is not unique. It depends on the assumptions involving moments higher than two. Assuming a Gaussian shape for the tracer flux leads to equations similar to the ones obtained in previous studies of time-dependent dispersivity. Without this approximation, the equation is non-local (integrodifferential) and leads to a memory effect. In the last part of this paper, the general results are illustrated with several correlation functions for the permeability field: purely random, exponential and power law covariance, and perfectly layered media.
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    Experimental investigation of solute transport in large, homogeneous and heterogeneous, saturated soil columns (1995)
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    Transport in porous media 18 (1995), S. 283-302 
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    ISSN: 1573-1634
    Keywords: Solute transport experiments ; heterogeneous media ; dispersion ; scale-dependency
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Technology
    Notes: Abstract Laboratory tracer experiments were conducted to investigate solute transport in 12.5-m long, horizontally placed soil columns during steady saturated water flow. Two columns having cross-sectional areas of 10×10cm2 were used: a uniformly packed homogeneous sandy column and a heterogeneous column containing layered, mixed, and lenticular formations of various shapes and sizes. The heterogeneous soil column gradually changed, on average, from coarse-textured at one end to fine-textured at the other end. NaCl breakthrough curves (BTC's) in the columns were measured with electrical conductivity probes inserted at 50- or 100-cm intervals. Observed BTC's in the homogeneous sandy column were relatively smooth and sigmoidal (S-shaped), while those in the heterogeneous column were very irregular, nonsigmoidal, and exhibited extensive tailing. Effective average pore-water velocities (v eff) and dispersion coefficients (D eff) were estimated simultaneously by fitting an analytical solution of the convection-dispersion equation to the observed BTC's. Velocity variations in the heterogeneous medium were found to be much larger than those in the homogeneous sand. Values of the dispersivity,α=D eff/v eff, for the homogeneous sandy column ranged from 0.1 to 5.0 cm, while those for the heterogeneous column were as high as 200cm. The dispersivity for transport in both columns increased with travel distance or travel time, thus exhibiting scale-dependency. The heterogeneous soil column also showed the effects of preferential flow, i.e., some locations in the column showed earlier solute breakthrough than several locations closer to the inlet boundary. Spatial fluctuations in the dispersivity could be explained qualitatively by the particular makeup of the heterogeneities in the column.
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    Dispersion in consolidated sandstone with radial flow (1995)
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    Transport in porous media 19 (1995), S. 37-66 
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    ISSN: 1573-1634
    Keywords: dispersion ; sandstone ; radial flow
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Technology
    Notes: Abstract This paper presents some experimental and theoretical results for dispersion processes occurring in consolidated Berea sandstone with radial flow geometry. A comprehensive review of the derivation and application of several analytical solutions is also presented. The Galerkin finite element method is applied to solve the advection-dispersion equation for unidimensional radial flow. Individual and combined effects of mechanical dispersion and molecular diffusion are examined using velocity-dependent dispersion models. Comparison of simulated results with experimental data is made. The effect of flow rates is examined. The results suggest that a linear dispersion model,D=αu, whereD is the dispersion coefficient,u the velocity andα a constant, is not a good approximation despite its wide acceptance in the literature. The most suitable mathematical formulation is given by an empirical form of $$D = D_0 + \mathop \alpha \limits^` u^m$$ , whereD ois the molecular diffusion coefficient. For the range of Péclet number (Pe=vd/D m,wherev is the characteristic velocity,d the characteristic length andD mthe molecular diffusion coefficient in porous media) examined (Pe=0.5 to 285), a power constant ofm=1.2 is obtained which agrees with the value reported by some other workers for the same regime. From the results of experiments and numerical modelling, the effect of mobility ratios (defined as the ration of viscosities of displaced and displacing fluids) on dispersion is found to be negligible, provided that the ratio is favourable.
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    Dispersion and Attenuation of Surface Waves in a Fluid-Saturated Porous Medium (1997)
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    Transport in porous media 29 (1997), S. 207-223 
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    ISSN: 1573-1634
    Keywords: dispersion ; attenuation ; surface waves ; Rayleigh wave ; Love wave
    Source: Springer Online Journal Archives 1860-2000
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    Notes: Abstract An investigation is conducted of propagation of surface waves in a porous medium consisting of a microscopically incompressible solid skeleton in which a microscopically incompressible liquid flows within the interconnected pores, and particularly the case where the solid skeleton deforms linear elastically. The frequency equations of Rayleigh- and Love-type waves are derived relating the dependence of wave numbers, being complex quantities, on frequency, as a result those waves are dispersive as well as inhomogeneous. Nevertheless, the amplitudes of both surface waves attenuate along the surface of the porous medium, whereas they decay exponentially receding from the surface of the medium.
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    Experiments on Solute Transport in Aggregated Porous Media: Are Diffusions Within Aggregates and Hydrodynamic Dispersion Independent? (1997)
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    Transport in porous media 29 (1997), S. 281-307 
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    ISSN: 1573-1634
    Keywords: solute transport ; nonequilibrium ; heterogeneous porous media ; dispersion ; diffusion ; experiments ; modelling
    Source: Springer Online Journal Archives 1860-2000
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    Notes: Abstract Two region models for solute transport in porous media assume that hydrodynamic dispersion in mobile water and solute diffusion within immobile water regions are independent. Experimental and theoretical results for transport through a macropore indicate that hydrodynamic dispersion and solute exchange are interdependent. Experiments were carried out to investigate this problem for a column packed with spherical porous aggregates. The effective diffusion coefficient of a tracer within the agreggates was determined from specific experiments. The dispersivity of the bed was determined from experiments carried out with a column filled with nonporous beads. We took advantage of the dependence of hydrodynamic dispersion on density ratios between the invading and displaced solutions to obtain a set of breakthrough curves corresponding to situations where the diffusion coefficient remains constant, whereas the dispersivity varies. Simulations reproduce correctly the experiments. Small discrepancies are noted that can be corrected either by increasing the dispersion coefficient or by fitting the external mass transfer coefficient. Increased dispersion coefficients probably reveal a modification of Taylor dispersion due to solute exchange. The fitted external mass transfer coefficients are close to the values obtained with classical correlations of the chemical engineering literature.
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    Stability of vertical miscible displacements with developing density and viscosity gradients (1988)
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    Transport in porous media 3 (1988), S. 277-297 
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    ISSN: 1573-1634
    Keywords: Stability ; linear stability analysis ; miscible displacement ; aspect ratio ; mobility control ; dispersion
    Source: Springer Online Journal Archives 1860-2000
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    Notes: Abstract Viscous fingering and gravity tonguing are the consequences of an unstable miscible displacement. Chang and Slattery (1986) performed a linear stability analysis for a miscible displacement considering only the effect of viscosity. Here the effect of gravity is included as well for either a step change or a graduated change in concentration at the injection face during a downward, vertical displacement. If both the mobility ratio and the density ratio are favorable (the viscosity of the displacing fluid is greater than the viscosity of the displaced fluid and, for a downward vertical displacement, the density of the displacing fluid is less than the density of the displaced fluid), the displacement will be stable. If either the mobility ratio or the density ratio is unfavorable, instabilities can form at the injection boundary as the result of infinitesimal perturbations. But if the concentration is changed sufficiently slowly with time at the entrance to the system, the displacement can be stabilized, even if both the mobility ratio and the density ratio are unfavorable. A displacement is more likely to be stable as the aspect ratio (ratio of thickness to width, which is assumed to be less than one) is increased. Commonly the laboratory tests supporting a field trial use nearly the same fluids, porous media, and displacement rates as the field trial they are intended to support. For the laboratory test, the aspect ratio may be the order of one; for the field trial, it may be two orders of magnitude smaller. This means that a laboratory test could indicate that a displacement was stable, while an unstable displacement may be observed in the field.
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    An analysis of the viability of polymer flooding as an enhanced oil recovery technology (1988)
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    Transport in porous media 3 (1988), S. 591-618 
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    ISSN: 1573-1634
    Keywords: Polymer flooding ; viscous fingering ; multiphase flow ; dispersion
    Source: Springer Online Journal Archives 1860-2000
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    Notes: Abstract The concept of improving oil recovery through polymer flooding is analysed. It is shown that while the injection of a polymer solution improves reservoir conformance, this beneficial effect ceases as soon as one attempts to push the polymer solution with water. Once water injection begins, the water quickly passes through the polymer creating a path along which all future injected water flows. Thus, the volume of the polymer slug is important to the process and an efficient recovery would require that the vast majority of the reservoir be flooded by polymer. It is also shown that the concept of grading a polymer slug to match the mobilities of the fluids at the leading and trailing edges of a polymer slug does not work in a petroleum reservoir. While this process can supply some additional stability to the slug, it is shown that for the purposes of enhanced oil recovery this additional stability is not great enough to be of any practical use. It is found that in this case the instability has simply been hidden in the interior of the slug and causes the same sort of instability to occur as was the case for the uniform slug.
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    Tracer Dispersion in Rough Open Cracks (1998)
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    Transport in porous media 32 (1998), S. 97-116 
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    ISSN: 1573-1634
    Keywords: dispersion ; anomalous diffusion ; Taylor dispersion ; roughness ; self-affine
    Source: Springer Online Journal Archives 1860-2000
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    Notes: Abstract Tracer dispersion is studied in an open crack where the two rough crack faces have been translated with respect to each other. The different dispersion regimes encountered in rough-wall Hele-Shaw cell are first introduced, and the geometric dispersion regime in the case of self-affine crack surfaces is treated in detail through perturbation analysis. It is shown that a line of tracer is progressively wrinkled into a self-affine curve with an exponent equal to that of the crack surface. This leads to a global dispersion coefficient which depends on the distance from the tracer inlet, but which is still proportional to the mean advection velocity. Besides, the tracer front is subjected to a local dispersion (as could be revealed by point measurements or echo experiments) very different from the global one. The expression of this anomalous local dispersion coefficient is also obtained.
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    Automaton Simulations of Dispersion in Porous Media (1998)
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    Transport in porous media 32 (1998), S. 187-198 
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    ISSN: 1573-1634
    Keywords: diffusion ; dispersion ; miscible ; automaton
    Source: Springer Online Journal Archives 1860-2000
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    Notes: Abstract A thermodynamic lattice gas (automaton) model is used to simulate dispersion in porous media. Simulations are constructed at two distinctly different scales, the pore scale at which capillary models are constructed and large scale or Darcy scale at which probabilistic collision rules are introduced. Both models allow for macroscopic (pore scale) phase separation. The pore scale models clearly show the effect of pore structure on dispersion. The large scale (mega scale) simulations indicate that when the pressure difference between the displacing phase and displaced phase is properly chosen (representing the average pressure gradient between the phases). The simulation results are consistent with both theoretical predictions and experimental observations.
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    Stochastic-Perturbation Analysis of a One-Dimensional Dispersion-Reaction Equation: Effects of Spatially-Varying Reaction Rates (1998)
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    Transport in porous media 32 (1998), S. 139-161 
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    ISSN: 1573-1634
    Keywords: dispersion ; reaction ; perturbation theory ; stochastic modeling
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Technology
    Notes: Abstract We carry out a stochastic-perturbation analysis of a one-dimensional convection–dispersion-reaction equation for reversible first-order reactions. The Damköhler number, Da, is distributed randomly from a distribution that has an exponentially decaying correlation function, controlled by a correlation length, ξ. Zeroth- and first-order approximations of the dispersion coefficient, D are computed from moments of the residence-time distribution obtained by solving a one-dimensional network model, in which each unit of the network represents a Darcy-level transport unit, and the solution of the transfer function in zeroth- and first-order approximations of the transport equation. In the zeroth-order approximation, the dispersion coefficient is calculated using the convection–dispersion-reaction equation with constant parameters, that is, perturbation corrections to the local equation are ignored. This zeroth-order dispersion coefficient is a linear function of the variance of the Damköhler number, 〈(ΔDa)2〉. A similar result was reported in a two-dimensional network simulation. The zeroth-order approximation does not give accurate predictions of mixing or spreading of a plume when Damköhler numbers, Da ≪ 1 and its variance, 〈(ΔDa)2〉 〉 0.25 〈Da2〉. On the other hand, the first-order theory leads to a dispersion coefficient that is independent of the reaction parameters and to equations that do accurately predict mixing and spreading for Damköhler numbers and variances in the range √〈(ΔDa)2〉/〈Da〉≤0.3
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1006575527731
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    On the Modelling of Generalized Taylor–Aris Dispersion in Chromatographs via Multiple Scales Expansions (1999)
    Springer
    Transport in porous media 36 (1999), S. 307-339 
    Details
    ISSN: 1573-1634
    Keywords: dispersion ; chromatography ; porous media ; adsorption ; homogenization ; multiple scales expansions.
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Technology
    Notes: Abstract This paper is devoted to the computation of effective equations for the transport of a solute in a chromatograph. We focus our attention on models that retain dispersion effects. A chromatograph is a biporous periodic heterogeneous medium, made up of macropores, and of small porous adsorbing crystals that have a retention effect on the solute. We use the method of multiple scales expansions. Various macroscopic behaviours appear, according to the respective orders of magnitude of the dimensionless characteristic parameters: Peclet number in the macropores, ratio of the characteristic time of diffusion in the macropores to the characteristic time of diffusion in the crystals, adsorption coefficient. Dispersion occurs for a Peclet number of order ε−1. We then discuss the effective behaviour of the solute, with respect to the orders of magnitude of the other characteristic parameters. To our knowledge, most of the models are new. Our modelling is not restricted to chromatographs. It applies to various situations of physic and chemical engineering: fixed bed reactors, catalytic cracking, ground water for instance.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1006654621514
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    Experimental Investigation of Mixing in Aperiodic Heterogeneous Porous Media: Comparison with Stochastic Transport Theory (1999)
    Springer
    Transport in porous media 37 (1999), S. 169-182 
    Details
    ISSN: 1573-1634
    Keywords: experiment ; aperiodic heterogeneity ; dispersion ; stochastic modeling.
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Technology
    Notes: Abstract An electrochemical technique was used to measure concentration distributions in an aperiodic heterogeneous model for comparison with a stochastic transport theory. Four identical columns, each filled with a homogeneous distribution of glass beads, were threaded together to create a single model with aperiodic heterogeneity. The layers in the model were arranged in different ways providing 24 realizations of the permeability distribution. Comparisons between experimental moment data and moments of simulated mean concentration distributions showed that the model was not able to accurately predict experimentally observed mixing behavior.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1006602620606
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    Spontaneous formation of zwitterionic vesicles: chemical structure-vesicle formation relationships (1997)
    Springer
    Colloid & polymer science 105 (1997), S. 224-227 
    Details
    ISSN: 1435-1536
    Keywords: Zwitterionic surfactants ; vesicles ; lamellar phase ; X-ray diffraction ; dispersion
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract New double-chain zwitterionic surfactants were shown to undergo spontaneous dispersion as vesicles in water by means of simple dilution of the lamellar phase. The molecular parameters of relevance were investigated in a systematic study of the structure of the lamellar phase and of the ability of spontaneous formation of vesicles in a series of homologous zwitterionic surfactants. Thus, the double-chain zwitterionic surfactants which occupies a small interfacial area per molecule in spite of the large size of their hydrophilic headgroup can form spontaneous vesicles. In this case, the bending modulus ¯k of the surfactant film is strongly negative and the short-range repulsive interactions between hydrophilic groups protruding from the surfactant films into water allow a large swelling of the lamellar phase, and are the origin of the colloidal stability of the vesicles dispersion.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01188955
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    Order-disorder transition in aqueous dispersions of ionic colloidal silica particles (1997)
    Springer
    Colloid & polymer science 106 (1997), S. 270-273 
    Details
    ISSN: 1435-1536
    Keywords: Order-disorder transition ; crystallization ; ionic colloid ; silica ; dispersion ; ultra-small-angle X-ray scattering
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract Order (crystal structure)-disorder (liquid structure) transition of aqueous dispersion of colloidal silica particles (average particle diameter=0.12×10−6 and 0.11×10−6 m) was examined at a silica volume fraction of 3×10−2, and various (analytical) surface charge densities of the particle, σa, and salt concentrations, Cs. The value of σa was changed by varying concentration of the coexisting sodium hydroxide. Phase diagram for the order-disorder transition was determined at σa〈1.4 × 10−6 C cm−2. It was found that there existed lower and upper limits of σa for the ordering, at givenC s's. The grain size was large near the order-disorder transition points in the σa-C s diagram. The structure of the ordered state was studied using an ultra-small-angle X-ray scattering method. Several orders of Bragg reflection having a 6-fold symmetry was observed for large grains. For small grains, the scattering profile was powder-like. In both cases, the ordered structure had a bodycentered-cubic lattice symmetry. The observed closest interparticle distances were smaller than the average interparticle distance, suggesting the non-space-filling nature of the ordered structure and existence of grain-boundary regions.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01189536
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    Influence of the viscoelastic properties of the respiratory system on the energetically optimum breathing frequency (1993)
    Springer
    Annals of biomedical engineering 21 (1993), S. 489-499 
    Details
    ISSN: 1573-9686
    Keywords: Work of breathing ; Inspiratory pressure-time integral ; Respiratory modeling ; Dogs ; Humans
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine , Technology
    Notes: Abstract We hypothesized that the viscoelastic properties of the respiratory system should have significant implications for the energetically optimal frequency of breathing, in view of the fact that these properties cause marked dependencies of overall system resistance and elastance on frequency. To test our hypothesis we simulated two models of canine and human respiratory system mechanics during sinusoidal breathing and calculated the inspiratory work ( $$\dot W$$ ) and pressure-time integral (PTI) per minute under both resting and exercise conditions. The two models were a two-compartment viscoelastic model and a single-compartment model. Requiring minute alveolar ventilation to be fixed, we found that both models predicted almost identical optimum breathing frequencies. The calculated PTI was very insensitive to increases in breathing frequency above the optimal frequencies, while $$\dot W$$ was found to increase slowly with frequency above its optimum. In contrast, both $$\dot W$$ and PTI increased sharply as frequency decreased below their respective optima. A sensitivity analysis showed that the model predictions were very insensitive to the elastance and resistance values chosen to characterize tissue viscoelasticity. We conclude that the $$\dot W$$ criterion for choosing the frequency of breathing is compatible with observations in nature, whereas the optimal frequency predictions of the PTI are rather too high. Both criteria allow for a fairly wide margin of choice in frequency above the optimum values without incurring excessive additional energy expenditure. Furthermore, contrary to our expectations, the viscoelastic properties of the respiratory system tissues do not pose a noticeable problem to the respiratory controller in terms of energy expenditure.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00000004
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    The multiple-scale averaging and dynamics of dispersion-managed optical solitons (1999)
    Springer
    Journal of engineering mathematics 36 (1999), S. 163-184 
    Details
    ISSN: 1573-2703
    Keywords: fiber optics ; nonlinear Schrödinger equation ; multiple scales ; dispersion ; solitons.
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mathematics , Technology
    Notes: Abstract Multiple-scale averaging is applied to the nonlinear Schrödinger equation with rapidly varying coefficients, and use the results to analyze pulse propagation in an optical fiber when a periodic dispersion map is employed. The effects of fiber loss and repeated amplification are taken into account by use of a coordinate transformation to relate the pulse dynamics in lossy fibers to that in equivalent lossless fibers. Second-order averaging leads to a general evolution equation that is applicable to both return-to-zero (soliton) and non-return-to-zero encoding schemes. The resulting equation is then applied to the specific case of solitons, and an asymptotic theory for the pulse dynamics is developed. Based upon the theory, a simple and effective design of two-step dispersion maps that are advantageous for wavelength-division-multiplexed soliton transmission is proposed. Theuse of these specifically designed dispersion maps allows simultaneous minimization of dispersive radiation in several different channels.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1004554209222
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    Creep Behavior of Dispersion-Hardened Aluminum Materials (1999)
    Springer
    Mechanics of time-dependent materials 3 (1999), S. 1-13 
    Details
    ISSN: 1573-2738
    Keywords: back stress ; creep ; dislocation ; dispersion ; grain boundary ; Norton plot ; particle hardening ; reaction-milling ; threshold stress ; work hardening
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract Dispersion-hardened aluminum materials of pure aluminum with extremely fine oxide and carbide dispersions and very fine grain sizes were creep-deformed under compressive loadings between 573 and 773 K. The creep behavior of the investigated materials is influenced by time, temperature, stress level and microstructure. An increasing content of dispersions causes increasing threshold stresses σthand resistances against creep. The Norton plots of the minimum creep rate $$\dot \varepsilon _{\min } $$ versus stress σ are characterized by extremely high stress exponents n. On the basis of the threshold concept it is demonstrated that the same diffusion process dominates in the dispersion-hardened aluminum materials as in pure aluminum. Their true stress exponents n*as the slopes of the best fit lines of the $$\log \dot \varepsilon _{\min } {\text{ }}versus{\text{ }}\log (\sigma - \sigma _{{\text{th}}} )$$ are close to 5. The threshold stress decreases considerably with increasing temperature due to the thermally activated recovery of long-range internal back stresses of quasi-planar dislocation structures on the grain boundaries.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1009875316242
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    Study on the Influence of Waves on Coastal Diffusion Using Image Analysis (1997)
    Springer
    Flow, turbulence and combustion 59 (1997), S. 191-204 
    Details
    ISSN: 1573-1987
    Keywords: wave flows ; surf zone turbulence ; dispersion
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract A series of novel image analysis techniques have been used to study surf-zone hydrodynamics taking advantage of recent advances in digital processing of images taken from video recordings of the sea surface near the coast. The use of image analysis allows the estimation of both spatial and temporal characteristics of wave fields, surface circulation and mixing in the surf zone. The dispersion of blobs of dye released at different distances from the coastline under very different sea conditions is used to measure surface eddy diffusivities. A preliminary set of field measurements were done in the Ebro Delta where the methodology was tested. Further experiments have been performed at Vilanova, Spain and Recife, Brazil. There is an increase of diffusivity with wave height but only if the wave Reynolds number, Rw, is greater than 103. No such trend is observed for Rw greater than 106. The other important factors are wind speed and tidal and longshore currents.
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    URL: http://dx.doi.org/10.1023/A:1001131304881
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  • 50
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    Calculation of the Electrical Field within an Electrical Sensing Zone Counter (1984)
    Weinheim : Wiley-Blackwell
    Particle and Particle Systems Characterization 1 (1984), S. 37-43 
    Details
    ISSN: 0934-0866
    Keywords: Chemistry ; Industrial Chemistry and Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Iterative numerical analysis methods, similar to those used for ray tracing in electron and ion guns, have been employed to calculate the electrical potential distribution in the vicinity of the orifice of an electrical sensing zone (esz) instrument. In particular, the electrical potential across the mouth of the orifice is considered and the effects of numerically bevelling the sharp peripheral edge are demonstrated.The results support the empirical equation: \documentclass{article}\pagestyle{empty}\begin{document}$$ {\rm d}\phi {\rm /d}x \sim 1 + \alpha '\{(r/R)/(1 - r/R)\} ^{\beta '} $$\end{document} for the axial component of the potential gradient, dφ/dx, at the mouth of the orifice expressed as a function of the radial distance, r, from the centre of the orifice of radius R; α′ and β′ are empirical constants. This equation was derived from previously reported experimental data on relative shifts and heights of artefact peaks apparent on the coarse side of size distributions measured via the esz method on a series of latex copolymers.
    Additional Material: 9 Ill.
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    URL: http://dx.doi.org/10.1002/ppsc.19840010107
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    The Development of a True Biaxial Shear TesterPaper presented at the International Symposium on Reliable Flow of Particulate Solids, August 20-22, 1985, Bergen, Norway. (1985)
    Weinheim : Wiley-Blackwell
    Particle and Particle Systems Characterization 2 (1985), S. 149-153 
    Details
    ISSN: 0934-0866
    Keywords: Chemistry ; Industrial Chemistry and Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Process Engineering, Biotechnology, Nutrition Technology
    Notes: To investigate the influence of the stress history on the yield limit a shear tester was developed, in which stresses or strains in x- and y-direction can be applied independently of each other. Since there are no shear stresses on the boundary surfaces of the sample these stresses are principal stresses and the Mohr stress circles are known for each state of stress. First results from shear tests with limestone show a significant influence of the different ways of consolidation on the yield limit, i. e. the flow properties of a bulk solid will depend on the stress history. The flow function, however, which is essential for silo design, proves to be invariable of the stress history.
    Additional Material: 10 Ill.
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    URL: http://dx.doi.org/10.1002/ppsc.19850020127
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    Masthead (1986)
    Weinheim : Wiley-Blackwell
    Particle and Particle Systems Characterization 3 (1986) 
    Details
    ISSN: 0934-0866
    Keywords: Chemistry ; Industrial Chemistry and Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Process Engineering, Biotechnology, Nutrition Technology
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/ppsc.19860030101
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    Pore Structure Analysis of Porous Particles by Equivalent Model (1986)
    Weinheim : Wiley-Blackwell
    Particle and Particle Systems Characterization 3 (1986), S. 20-25 
    Details
    ISSN: 0934-0866
    Keywords: Chemistry ; Industrial Chemistry and Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Starting from Wheeler's composite theory, which takes both the multilayer adsorption and the capillary condensation into consideration, and assuming the equivalent cylindrical model, we have deduced a strict and relatively simpler formula for the calculation of pore size distribution by solving the integral equation directly. The formula is more convenient for application because of its recursion form. Following the same line of reasoning and using the mean value theorem of definite integrals under different conditions, we have unified the equations of Barrett-Joyner-Halenda, Dubinin, Cranston-Inkley, Dollimore-Heal and Roberts. A table of parameters which is required in the calculation is given. Besides the adsorption of nitrogen, the adsorption with water vapor as the adsorbate is investigated and the corresponding empirical equation of adsorption thickness is given.
    Additional Material: 2 Ill.
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    URL: http://dx.doi.org/10.1002/ppsc.19860030105
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    The Relevance of Powder/Liquid Wettability to the Cohesiveness of Carbon Black Agglomerates (1986)
    Weinheim : Wiley-Blackwell
    Particle and Particle Systems Characterization 3 (1986), S. 26-31 
    Details
    ISSN: 0934-0866
    Keywords: Chemistry ; Industrial Chemistry and Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Particle size enlargement operations often involve the use of a liquid to improve powder cohesiveness. Capillary suction and surface tension forces acting through liquid menisci between particles are the primary source of the cohesive bonding. The strength of these forces, and consequently the strength of the wet agglomerate, is dependent upon the total liquid content, its distribution within the agglomerate, and the powder wettability (characterized by the liquid surface tension and powder/liquid contact angle).The tensile strength of powder compacts containing submicron carbon black particles has been measured as a function of saturation level for several liquids. It is found that the compact strength increases with increasing surface tension for liquids that exhibit a zero contact angle. Above the critical surface tension for wetting a more complicated situation exists where both the surface tension and contact angle are important.
    Additional Material: 7 Ill.
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    URL: http://dx.doi.org/10.1002/ppsc.19860030106
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    The Influence of Particle Shape and Particle Size Distribution on fluidisation behaviour of granular activated carbon in the aqueous phase (1984)
    Weinheim : Wiley-Blackwell
    Particle and Particle Systems Characterization 1 (1984), S. 143-152 
    Details
    ISSN: 0934-0866
    Keywords: Chemistry ; Industrial Chemistry and Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Process Engineering, Biotechnology, Nutrition Technology
    Notes: This paper deals with the influence of particle shape and particle size distribution on the fluidisation behaviour of granular activated carbon in the aqueous phase. Methods for relating the degree of expansion, as a function of liquid velocity, to particle shape and particle size distribution are discussed and tested. Two different types of activated carbon, both containing irregularly shaped particles but with differences in shape, are used to test the models discussed. A tentative method which takes into account the influence of water temperature on fluidisation behaviour is proposed.
    Additional Material: 8 Ill.
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    URL: http://dx.doi.org/10.1002/ppsc.19840010125
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    Minimum Sintering Temperatures of Fluidizable Particles (1984)
    Weinheim : Wiley-Blackwell
    Particle and Particle Systems Characterization 1 (1984), S. 171-177 
    Details
    ISSN: 0934-0866
    Keywords: Chemistry ; Industrial Chemistry and Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Experimental methods to determine minimum sintering temperatures of a variety of granules such as polymers, glass, coal, inorganic salts, etc. are presented. These methods include the use of a dilatometer in which the contraction-dilation characteristics of a small sample is measured, a differential scanning calorimeter test and an Instron machine by which yield strengths are measured. It is clearly shown that for the majority of materials studied, the different methods give similar values for the minimum sintering temperature but that the dilatometer experiment is the simplest as well as the most reliable method. Since the minimum sintering temperature is always less than the solid's melting point, an efficient method of measuring this temperature is very important for all fluidizable granules subjected to high temperatures. The danger of agglomeration during fluidization increases tremendously at temperatures higher than minimum sintering and therefore special precautions must be taken to avoid defluidization under these conditions.
    Additional Material: 15 Ill.
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    URL: http://dx.doi.org/10.1002/ppsc.19840010129
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    Measurement of Particle Size Distributions in Gas Flows with an Optical particle counter (1985)
    Weinheim : Wiley-Blackwell
    Particle and Particle Systems Characterization 2 (1985), S. 20-24 
    Details
    ISSN: 0934-0866
    Keywords: Chemistry ; Industrial Chemistry and Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Process Engineering, Biotechnology, Nutrition Technology
    Notes: In order to characterize flow separation and classification processes, particle size distributions must be measured in the airborne state without affecting the state of dispersion or disturbing the flow. Light scattering devices with an optically defined measuring volume are specially designed for this purpose. However the light scattering device must be calibrated using non-ideal particles which are present within the multiphase flow, preferably on an equivalent diameter based on settling rate. Such a calibration can be achieved by measuring with an optical particle counter before and after an impactor in droplet systems and a sampling cyclone in systems of solid particles. By measuring the calibration curves the size distribution of the investigated particles are also determined. This measuring technique allows the best use of the optical particle counter in industrially relevant cases which may have high particle concentrations, wide distributions, non-ideal particles and an undefined state of dispersion.
    Additional Material: 8 Ill.
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    URL: http://dx.doi.org/10.1002/ppsc.19850020104
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    Approximate Mathematical Description of Particle-Size Distributions - Possibilities and limitations as to the assessment of comminution and classification processesPaper presented at the 3rd European Symposium on Particle Characterization (PARTEC), May 9-11, 1984, Nuremberg, FRG. (1985)
    Weinheim : Wiley-Blackwell
    Particle and Particle Systems Characterization 2 (1985), S. 49-55 
    Details
    ISSN: 0934-0866
    Keywords: Chemistry ; Industrial Chemistry and Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Disperse materials are often characterized by their particle-size distributions which can be determined by different measuring methods. Frequently the quantitative portions of the particle size classes obtained by way of experiment are considered insufficient and one strives for approximating the measured values by an analytic function. This can be reached, more or less satisfactorily, by power, exponential, or normal distribution functions which may include two, three, or four parameters.Publications as well as common practice have proved again and again that due to very rough or incorrect approximations wrong conclusions are derived from test and operating results, so that it appears expedient to investigate - when such an approximation would actually be advisable and - which function would be expedient in the specific case.Application of distriction functions will always be justified then when there is an actual need for utilizing the advantages connected with an approximation. Evaluation of a great number of measuring results revealed that the two-parameter functions in most cases only permit an utmost rough approximation which might give rise to wrong conclusions. Carefully classified products, however, mostly require three- or four-parameter functions for making an appropriate approximation.The functions, which appear appropriate for certain types of products, are set out in Table 1.In order to make the tabulated individual results accessible to a practical utilization a systematization was attempted. The outcome is a graph which is meant as an assistance for the practician and which presents the possibility of a quick selection of function type.
    Additional Material: 4 Ill.
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    URL: http://dx.doi.org/10.1002/ppsc.19850020108
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    The Influence of Particle Attrition on the Wall Friction Coefficient of a free flowing particulate solid (1985)
    Weinheim : Wiley-Blackwell
    Particle and Particle Systems Characterization 2 (1985), S. 71-76 
    Details
    ISSN: 0934-0866
    Keywords: Chemistry ; Industrial Chemistry and Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Process Engineering, Biotechnology, Nutrition Technology
    Notes: In this paper a reciprocating shear cell, which has been developed to measure dynamic wall friction, is described. The cell has also been used to study the attrition behaviour of sand samples at the bounding wall. This attrition causes a considerable change in the angle of wall friction.
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    URL: http://dx.doi.org/10.1002/ppsc.19850020112
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    Photometric On-line Measurement of Surface Area of Powders (1985)
    Weinheim : Wiley-Blackwell
    Particle and Particle Systems Characterization 2 (1985), S. 81-90 
    Details
    ISSN: 0934-0866
    Keywords: Chemistry ; Industrial Chemistry and Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Amongst the well known methods to measure surface area of particulate matter, preferably dry powders, only photometric methods can be used on-line.The basic equation for the photometric measurement of surface area is Lambert-Beer's law, which describes the attenuation of light (extinction) due to the presence of particles in a light beam. The attenuation being dependent not only on the size distribution of the particles in the light beam but also on their volume concentration. Since both effects alter the attenuation simultaneously the solids volume concentration has to be measured independently of the attenuation in a true on-line system. The instrument developed combines the extinction of white light with the absorption of γ-rays.Since the absorption of γ-rays demands more particles in the measuring zone than the attenuation of light, an aerosol stream of rectangular cross section has been used which allows the simultaneous measurement of extinction and γ-ray absorption.Apart from a brief description of the theoretical background of the instrument experimental evidence will be given of its suitability for on-line application [1, 2].
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    URL: http://dx.doi.org/10.1002/ppsc.19850020116
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    Errata (1985)
    Weinheim : Wiley-Blackwell
    Particle and Particle Systems Characterization 2 (1985), S. 123-123 
    Details
    ISSN: 0934-0866
    Keywords: Chemistry ; Industrial Chemistry and Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Process Engineering, Biotechnology, Nutrition Technology
    Notes: No. Abstract.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/ppsc.19850020122
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    Particle Deposition in High Capacity Preseparators (1985)
    Weinheim : Wiley-Blackwell
    Particle and Particle Systems Characterization 2 (1985), S. 133-136 
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    ISSN: 0934-0866
    Keywords: Chemistry ; Industrial Chemistry and Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Process Engineering, Biotechnology, Nutrition Technology
    Notes: High capacity preseparators are used to reduce bounce and blow-off of large particles in cascade impactors. In this paper, results are presented of a detailed analysis of the deposition of particles in two slightly different preseparators of the impactor-type which are used in connection with the Andersen Stack Sampler. The advantage of using any preseparator for aerosols mixed with large particles (x 10 μm) is clearly shown.A preseparator which is integrated into the impactor has the advantages of smaller overall size, accessible surfaces and, therefore, easier handling. The results of the study show that the reduction of unwanted particle losses is rather small when compared with a separate preseparator.
    Additional Material: 8 Ill.
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    URL: http://dx.doi.org/10.1002/ppsc.19850020124
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    Laser Doppler Anemometry - a non-intrusive optical measuring technique for fluid velocityGerman version was published in “Laser und Optoelektronik” 17 (1985) 362-375. (1987)
    Weinheim : Wiley-Blackwell
    Particle and Particle Systems Characterization 4 (1987), S. 26-37 
    Details
    ISSN: 0934-0866
    Keywords: Chemistry ; Industrial Chemistry and Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Process Engineering, Biotechnology, Nutrition Technology
    Notes: 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.
    Additional Material: 18 Ill.
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    URL: http://dx.doi.org/10.1002/ppsc.19870040107
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    Measurement of velocities and diameters of small particles by using fast digital circuits for the on-line evaluation of laser-doppler-signalsPaper presented at the meeting of the “GVC-Fachausschuß Partikelmeßtechnik” on 22. 02. 1985 at Duisburg (FRG). (1985)
    Weinheim : Wiley-Blackwell
    Particle and Particle Systems Characterization 2 (1985), S. 113-118 
    Details
    ISSN: 0934-0866
    Keywords: Chemistry ; Industrial Chemistry and Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Inspection of the scattered light by two photodetectors makes it possible to investigate the velocities of droplets as well as their size in disperse systems and has some advantages against related methods. When this method is used, the size of the droplets can be derived from the phase difference of the signals from the first and the second photodetector.Special problems of this method are discussed in the paper. A system with fast signal processing facilities, working mostly digitally, was developed in order to solve these problems. This system derives several digital signals from the signals of high frequencies that are gained from the photodetectors. These digital signals are combined by digital circuits of the ECL-type. The resulting pulse series are fed into several digital counters. The data from the counters and from some other inputs are further processed by a real time computer that was developed for this special task, using an 8088 micro processor. This real time computer is connected to an ordinary personal computer by a parallel interface.
    Additional Material: 8 Ill.
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    URL: http://dx.doi.org/10.1002/ppsc.19850020120
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    The Measurement of Spatial Aerosol Distributions in Enclosures by Means of computed tomography (1985)
    Weinheim : Wiley-Blackwell
    Particle and Particle Systems Characterization 2 (1985), S. 137-142 
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    ISSN: 0934-0866
    Keywords: Chemistry ; Industrial Chemistry and Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Process Engineering, Biotechnology, Nutrition Technology
    Notes: A measurement method that approximates the spatial distribution of inhomogeneously distributed aerosols in a limited measurement plane is described. It is based on the evaluation of a comparably small number of infrared extinction measurements taken from the measurement plane boundary. The measured data are processed by means of computed tomography. The results are displayed on a monitor in a colour-coded picture of the aerosol-“density”-pattern. The basic design and the principal characteristics of the method are mathematically described and verified by simulation tests and practical results which are obtained from an experimental set up using smoldering wood as an aerosol source.
    Additional Material: 6 Ill.
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    URL: http://dx.doi.org/10.1002/ppsc.19850020125
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    Estimation of Particle Size Distributions Using Pipet-Withdrawal Centrifuges (1986)
    Weinheim : Wiley-Blackwell
    Particle and Particle Systems Characterization 3 (1986), S. 122-128 
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    ISSN: 0934-0866
    Keywords: Chemistry ; Industrial Chemistry and Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Process Engineering, Biotechnology, Nutrition Technology
    Notes: The mathematical treatments used in the evaluation of particle size distribution from pipet-withdrawal centrifuge data are reviewed. An error in the published procedure for multiple-sample withdrawal systems is pointed out and a corrected formulation is presented. An alternative treatment, based on a piece-wise linearization of the size distribution is described. Computer simulations of the analytical and data evaluation procedures indicate that the errors in the original formulation are not generally serious and that the corrected and alternative procedures lead to very similar estimates. Except for some cases involving very narrow size distributions, the alternative approach appears to give slightly closer estimates of the size distribution. Comparisons based on actual experimental data are also described.
    Additional Material: 1 Ill.
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    URL: http://dx.doi.org/10.1002/ppsc.19860030306
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    Applications of Condition Numbers A-priori Analysis of Moment Method for Describing Size Distributions (1986)
    Weinheim : Wiley-Blackwell
    Particle and Particle Systems Characterization 3 (1986), S. 104-110 
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    ISSN: 0934-0866
    Keywords: Chemistry ; Industrial Chemistry and Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Process Engineering, Biotechnology, Nutrition Technology
    Notes: A procedure for estimating the effectiveness of algorithms which retrieve size distribution parameters from cumulative fractions or moments is described. The principle of the algorithm is to select moments, or cumulative fractions, which minimize the condition number. Extensive tests of the algorithm for a distribution consisting of the sum of two log normal distributions were carried out. This procedure can be easily extended to use different numbers and types of constituent functions. The simulations indicated that moment methods which include positive and negative moments give the best result. When the means of the constituent distribution are close, the large condition numbers indicate that no algorithm will give unambiguous values for the parameters.
    Additional Material: 10 Ill.
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    URL: http://dx.doi.org/10.1002/ppsc.19860030303
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    Particle Size Analysis of Some Difficult Measurable SystemsPaper presented at the 4th meeting “Granulometrie” 1985 at Dresden. (1986)
    Weinheim : Wiley-Blackwell
    Particle and Particle Systems Characterization 3 (1986), S. 163-167 
    Details
    ISSN: 0934-0866
    Keywords: Chemistry ; Industrial Chemistry and Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Knowledge of the granulometric behaviour of dispersed systems is vital for a full and complete characterisation. Despite the variety of methods and devices which have been developed for this purpose, difficulties frequently arise in the practical determination of particle size distribution. In this paper it is shown, by means of examples, how measurements for surface modified and porous particles can be influenced by the behaviour of the material, and which approaches exist to obtain accurate values by taking this into account.
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    URL: http://dx.doi.org/10.1002/ppsc.19860030405
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    A Rapid Method for Determination of Changes in Shape of Comminuted Particles Using a Laser Diffractometer (1988)
    Weinheim : Wiley-Blackwell
    Particle and Particle Systems Characterization 5 (1988), S. 13-15 
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    ISSN: 0934-0866
    Keywords: Chemistry ; Industrial Chemistry and Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Process Engineering, Biotechnology, Nutrition Technology
    Notes: The size distributions of carefully screened √2 size fractions of ground materials were determined using a Microtrac laser diffractometer. The size distributions were fitted to the empirical function P(x) = 1/[1 + (x50/x)λ] where P(x) is cumulative mass fraction less than Microtrac size, x. The standard deviation of λ for a 50 second test time was approximately 0.5, so that seventeen test times give a mean with an estimated error within ± 0.25 (95% confidence level). Values of λ were 5.44, 4.82, 4.40 for a coal ground under different conditions, indicating statistically different shape distributions; the average value for mica was 2.91 owing to the high aspect ratio of the particles. The ratio of x50 to the geometric mean sieve size was 1.2 for the coal and 0.70 for mica.
    Additional Material: 2 Ill.
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    URL: http://dx.doi.org/10.1002/ppsc.19880050104
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    Forward Scattering Signature of a Spherical Particle Crossing a Laser Beam out of the Beam WaistPresented at the International Symposium on Optical Particle Sizing: Theory and Practice, Rouen (France), 12-15 May 1987. (1988)
    Weinheim : Wiley-Blackwell
    Particle and Particle Systems Characterization 5 (1988), S. 9-12 
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    ISSN: 0934-0866
    Keywords: Chemistry ; Industrial Chemistry and Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Process Engineering, Biotechnology, Nutrition Technology
    Notes: When a particle crosses a laser beam out of the focal plane, the light attenuation signal occuring on the beam axis contains some information regarding the particle size and trajectory.These attenuation signatures are analysed and predicted with a simplified model based on Fraunhofer diffraction. Numerical and experimental results are found to be in good agreement.A modified laser Doppler velocimeter using this sizing method is able to perform simulataneous measurement of size and velocity of spherical particle in the range 10 μm-500 μm.
    Additional Material: 4 Ill.
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    URL: http://dx.doi.org/10.1002/ppsc.19880050103
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    Increased Resolution of Size Distributions with the Coulter Counter (1988)
    Weinheim : Wiley-Blackwell
    Particle and Particle Systems Characterization 5 (1988), S. 29-37 
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    ISSN: 0934-0866
    Keywords: Chemistry ; Industrial Chemistry and Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Process Engineering, Biotechnology, Nutrition Technology
    Notes: The 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.
    Additional Material: 12 Ill.
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    URL: http://dx.doi.org/10.1002/ppsc.19880050107
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    Modeling of Multiple Scattering Effects in Fraunhofer Diffraction Particle Size AnalysisPresented at the International Symposium on Optical Particle Sizing: Theory and Practice, Rouen (France), 12-15 May 1987. (1988)
    Weinheim : Wiley-Blackwell
    Particle and Particle Systems Characterization 5 (1988), S. 57-65 
    Details
    ISSN: 0934-0866
    Keywords: Chemistry ; Industrial Chemistry and Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Process Engineering, Biotechnology, Nutrition Technology
    Notes: 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.
    Additional Material: 9 Ill.
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    URL: http://dx.doi.org/10.1002/ppsc.19880050202
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    A Theoretical Interpretation of Meloy's Law of Morphological Coefficients (1988)
    Weinheim : Wiley-Blackwell
    Particle and Particle Systems Characterization 5 (1988), S. 85-86 
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    ISSN: 0934-0866
    Keywords: Chemistry ; Industrial Chemistry and Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Process Engineering, Biotechnology, Nutrition Technology
    Notes: This note deals with the Fourier representation of particle shape. A frequency distribution pn, n = 1,2, …, expressing the contribution of the different harmonics to the dispersion of the position vector is defined. The Meloy law of morphological coefficients may be derived by optimizing the value of the informational entropy which is attached to pn.
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    URL: http://dx.doi.org/10.1002/ppsc.19880050206
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    Small Angle Light Scattering Patterns from Micrometer-Sized SpheroidsPresented at the International Symposium on Optical Particle Sizing: Theory and Practice, Rouen (France), 12-15 May 1987. (1987)
    Weinheim : Wiley-Blackwell
    Particle and Particle Systems Characterization 4 (1987), S. 134-140 
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    ISSN: 0934-0866
    Keywords: Chemistry ; Industrial Chemistry and Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
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    Notes: By using a physical optics approximation, the scattering functions, i1 (θ), may be calculated for spheroidal particles of parameter sizes larger than 10. Emphasis is put on the angular location of their first extrema, as function of the refractive index, shape, size and orientation of the spheroid, which may greatly influence the outlook of their small angle 2 D patterns.
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    URL: http://dx.doi.org/10.1002/ppsc.19870040128
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    Particle Sizing by Laser Light Diffraction: Improvements in Optics and AlgorithmsPresented at the International Symposium on Optical Particle Sizing: Theory and Practice, Rouen (France), 12-15 May 1987. (1987)
    Weinheim : Wiley-Blackwell
    Particle and Particle Systems Characterization 4 (1987), S. 151-156 
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    ISSN: 0934-0866
    Keywords: Chemistry ; Industrial Chemistry and Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Process Engineering, Biotechnology, Nutrition Technology
    Notes: A major problem encountered in particle sizing by laser light diffraction concerns the inversion of the diffraction pattern measured in a given experiment.Conventional methods for solving the linear system obtained can not be used in this problem, because the matrix is ill-conditioned and also because the diffraction pattern is usually determined with a low resolution annular diode detector. These problems may be solved with up to date optical detectors (linear CCD-arrays comprising 1024 photodiodes) and refined inversion techniques (conjugate gradient method and the analytical formulation due to Shifrin).These two aspects are described in this paper. Two inversion methods are compared and experimental results are discussed.
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    URL: http://dx.doi.org/10.1002/ppsc.19870040131
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    Announcements (1988)
    Weinheim : Wiley-Blackwell
    Particle and Particle Systems Characterization 5 (1988), S. 47-49 
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    ISSN: 0934-0866
    Keywords: Chemistry ; Industrial Chemistry and Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Process Engineering, Biotechnology, Nutrition Technology
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/ppsc.19880050109
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    Visible Infra-red Double Extinction Measurements in Densely Laden Media, New ProgressPresented at the International Symposium on Optical Particle Sizing: Theory and Practice, Rouen (France), 12-15 May 1987. (1988)
    Weinheim : Wiley-Blackwell
    Particle and Particle Systems Characterization 5 (1988), S. 51-56 
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    ISSN: 0934-0866
    Keywords: Chemistry ; Industrial Chemistry and Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
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    Notes: This paper describes new progress obtained with an optical technique called V.I.D.E. (Visible Infra-red Double Extinction) which simultaneously measures mean particle size in the range of 10-120 μm and mean number density in densely laden media (up to 0.1% volume fraction). The underlying theory, taking account of multiple light scattering, is recalled. Simultaneous size and concentration measurements are obtained by simultaneously recording transmittances of the medium at two well chosen wavelengths. Experimental results for suspensions of glass particles in air, are described and discussed. The size of particles given by the technique agrees with that given by optical microscopy and Malvern diffractometry. The V.I.D.E. technique is shown to be very suitable to investigate dense media whose optical thickness is up to nine and for which other techniques fail.
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    Analysis of the Inorganic Constituents of Particles on a Particle-by-Particle Basis using a Computerized SEM-EDS System (1988)
    Weinheim : Wiley-Blackwell
    Particle and Particle Systems Characterization 5 (1988), S. 77-84 
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    ISSN: 0934-0866
    Keywords: Chemistry ; Industrial Chemistry and Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Process Engineering, Biotechnology, Nutrition Technology
    Notes: This paper is based on the development of the Moza-Austin technique for characterizing thousands of coal particles by approximate analysis of the major inorganic constituents Ca, Al, Si, K, Na, Fe and S in each particle. The technique has sufficient sensitivity to work on small volumes, is fast enough to handle large number of particles within a reasonable period of time, and consists of scanning electron microscopy combined with energy dispersive x-ray spectrometry (SEM-EDS). A computerized SEM-EDS system that allows the automated analysis of hundreds of particles per hour is described. The analysis is based on the location and tracing of exposed areas of particles embedded in a polished specimen, the selection of sampling points on the traced sections, the collection of an x-ray spectrum from each sampled point for a defined period of time, and the processing of the x-ray intensity to calculate point composition using ZAF corrections. Procedures for correcting for dead time, spectrum background, x-ray detector efficiency and spectrum overlap are described. Problems and future work are discussed.
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    Announcements (1988)
    Weinheim : Wiley-Blackwell
    Particle and Particle Systems Characterization 5 (1988), S. 100-102 
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    ISSN: 0934-0866
    Keywords: Chemistry ; Industrial Chemistry and Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Process Engineering, Biotechnology, Nutrition Technology
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/ppsc.19880050209
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    Optimal Filtering Applied to the Inversion of the Laplace TransformPresented at the International Symposium on Optical Particle Sizing: Theory and Practice, Rouen (France), 12-15 May 1987. (1988)
    Weinheim : Wiley-Blackwell
    Particle and Particle Systems Characterization 5 (1988), S. 109-115 
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    ISSN: 0934-0866
    Keywords: Chemistry ; Industrial Chemistry and Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Inversion of the Laplace transform, used in the laser scattering measurement of colloidal particle size distributions, presents severe numerical difficulties. In the presence of noise the variance of the inversion integral is infinite, indicating maximum uncertainty in the inversion. This paper applies the method of minimum variance, or “optimal”, filtering to the eigenfunction spectrum of the Laplace transform, giving an inversion which has finite variance.Spectral decomposition using the eigenfunctions of the Laplace transform gives a representation of the noise and desired signals analogous to the Fourier spectrum used in linear system theory. It is possible to obtain a filtered estimate of the unknown linewidth distribution. The requirement that the variance of this filtered estimate is minimum leads to a Wiener-Hopf integral equation defining the optimal filter.The results of this paper provide a basis of comparison of all methods of inversion of the Laplace transform, including the extensive literature of colloidal particle sizing by laser scattering or photon correlation.
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    Determination of the Adhesivity on Acrylics of Fresh Coal Fly Ash Particles (1988)
    Weinheim : Wiley-Blackwell
    Particle and Particle Systems Characterization 5 (1988), S. 130-138 
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    ISSN: 0934-0866
    Keywords: Chemistry ; Industrial Chemistry and Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
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    Notes: The adhesivity of fresh coal fly ashes from two Australian power stations on Dralon-T monofilaments has been experimentally analysed. It was found that one of the dusts was more adhesive to the fiber and its particles were also more strongly electrostatically charged. These obervations explain the reported large differences in the pressure loss across the fabric filters at the two stations. By precharging the particles, the technique can also be utilized in determining the adhesivity of fly ashes which carry relatively small natural electrostatic charging.
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    URL: http://dx.doi.org/10.1002/ppsc.19880050305
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    Phase-Doppler-Anemometry and the Log-Hyperbolic Distribution applied to Liquid Sprays (1988)
    Weinheim : Wiley-Blackwell
    Particle and Particle Systems Characterization 5 (1988), S. 153-164 
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    ISSN: 0934-0866
    Keywords: Chemistry ; Industrial Chemistry and Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
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    Notes: 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.
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    URL: http://dx.doi.org/10.1002/ppsc.19880050401
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    Regeneration of Form by Fourier Technique and its Application in Powder Characterization (1988)
    Weinheim : Wiley-Blackwell
    Particle and Particle Systems Characterization 5 (1988), S. 179-185 
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    ISSN: 0934-0866
    Keywords: Chemistry ; Industrial Chemistry and Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Conventional shape parameters have serious limitations because of their inability to capture finer surface morphology as well as to regenerate the particle form. This problem has been successfully circumvented by applying Fourier analysis technique to the projected image of the particle profile to obtain Fourier coefficients which have been shown to be size inveriant and insensitive to starting point for digitization. Synthesis technique to regenerate the particle profile from Fourier coefficients has revealed that gradual addition of higher order harmonics brings the regenerated form very close to its original counterpart. The regeneration of the form of particles of different shapes as well as application of few strategy to harmonic amplitudes have amply demonstrated the capability of the technique as a potential tool for characterization of powders.
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    URL: http://dx.doi.org/10.1002/ppsc.19880050405
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    Computation of the Frequency Distributions of Distances Between Particles Randomly Dispersed in a Fluid Flow (1989)
    Weinheim : Wiley-Blackwell
    Particle and Particle Systems Characterization 6 (1989), S. 13-16 
    Details
    ISSN: 0934-0866
    Keywords: Chemistry ; Industrial Chemistry and Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Pulse holography can be used as a method for the experimental investigation of transport processes that occur in flows of dispersed phases. Since a complete evaluation of a hologram involves the measurement and recording of the position of every individual particle, it delivers all the information about the spatial distribution of particles at the instant of exposure.An exact knowledge of the spatial distribution of the dispersed phase is particularly important for those chemical engineering processes which require the spatial distribution of particles to be as homogeneous as possible. Maximum homogeneity is achieved when the particles are distributed purely randomly. For this case, the distributions of distances between neighbouring particles are calculated. They represent a standard which can be adopted as the basis for the assessment of real particle distributions, such as exist momentarily in flows of dispersed phases and are determined by the evaluation of pulse holograms.
    Additional Material: 4 Ill.
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    URL: http://dx.doi.org/10.1002/ppsc.19890060102
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    Announcements (1989)
    Weinheim : Wiley-Blackwell
    Particle and Particle Systems Characterization 6 (1989), S. 48-50 
    Details
    ISSN: 0934-0866
    Keywords: Chemistry ; Industrial Chemistry and Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Process Engineering, Biotechnology, Nutrition Technology
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/ppsc.19890060107
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    Measurement of Particle Rotational Velocity Using a Laser AnemometerPresented at the 4th International Symposium on Applications of Laser Anemometry to Fluid Mechanics, Lisbon (Portugal), July 11-14, 1988. (1989)
    Weinheim : Wiley-Blackwell
    Particle and Particle Systems Characterization 6 (1989), S. 59-63 
    Details
    ISSN: 0934-0866
    Keywords: Chemistry ; Industrial Chemistry and Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Process Engineering, Biotechnology, Nutrition Technology
    Notes: 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.
    Additional Material: 10 Ill.
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    URL: http://dx.doi.org/10.1002/ppsc.19890060109
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    Announcements (1989)
    Weinheim : Wiley-Blackwell
    Particle and Particle Systems Characterization 6 (1989), S. 89-91 
    Details
    ISSN: 0934-0866
    Keywords: Chemistry ; Industrial Chemistry and Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Process Engineering, Biotechnology, Nutrition Technology
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/ppsc.19890060115
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  • 88
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    Size Characterization of Liquid-Borne Particles by light scattering counters (1989)
    Weinheim : Wiley-Blackwell
    Particle and Particle Systems Characterization 6 (1989), S. 93-99 
    Details
    ISSN: 0934-0866
    Keywords: Chemistry ; Industrial Chemistry and Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Process Engineering, Biotechnology, Nutrition Technology
    Notes: The sizing accuracy of a commercially available laser optical liquid-borne particle counter is investigated. A calibration study, using aqueous suspensions of non-absorbing, monodisperse, spherical polymer particles, and a study using suspensions of non-spherical polydisperse, alumina particles are conducted. The experimental results from the spherical polymer study show an excellent agreement with the theoretical Mie light scattering calculations. The accuracy of the spherical polymer sizing is shown to be within 20% of the actual size. The alumina particle readings are compared to the readings of four different particle sizing instruments and to scanning electron microscope pictures. Although quantitative comparisons are difficult to make between the instruments, the results show a good agreement for the batch of particles with a narrower size distribution.
    Additional Material: 9 Ill.
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    URL: http://dx.doi.org/10.1002/ppsc.19890060117
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    A Light Scattering Instrument to Discriminate and Size Fibres Part 1: A theoretical description using the RGD approximation (1989)
    Weinheim : Wiley-Blackwell
    Particle and Particle Systems Characterization 6 (1989), S. 110-118 
    Details
    ISSN: 0934-0866
    Keywords: Chemistry ; Industrial Chemistry and Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Process Engineering, Biotechnology, Nutrition Technology
    Notes: As part of the development of a light scattering instrument to detect fibres, scattered light from finite cylinders which are exposed to light at arbitrary orientation is studied using the Rayleigh - Gans - Debye approximation. Form anisotropy, which is crucial to the performance of the instrument, is allowed for by using the Shifrin modification in which the elemental volumes are considered to be prolate spheroids. For long cylinders this is compared with van de Hulst's model in which the rigorous theory for an infinite cylinder is modified by Fraunhofer diffraction on the length. For very short cylinders comparison is made with the Mie theory for spheres.
    Additional Material: 8 Ill.
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    URL: http://dx.doi.org/10.1002/ppsc.19890060119
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  • 90
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    Single Particle Light Scattering Size Analysis: Quantification and elimination of the effect of particle shape and structure (1989)
    Weinheim : Wiley-Blackwell
    Particle and Particle Systems Characterization 6 (1989), S. 100-109 
    Details
    ISSN: 0934-0866
    Keywords: Chemistry ; Industrial Chemistry and Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Process Engineering, Biotechnology, Nutrition Technology
    Notes: When 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.
    Additional Material: 14 Ill.
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    URL: http://dx.doi.org/10.1002/ppsc.19890060118
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    The Characterization of Water-Droplet Aerosols by polytec optical particle analysersPresented at the 4th European Symposium Particle Characterization, Nürnberg, 19-21. April 1989. (1989)
    Weinheim : Wiley-Blackwell
    Particle and Particle Systems Characterization 6 (1989), S. 119-123 
    Details
    ISSN: 0934-0866
    Keywords: Chemistry ; Industrial Chemistry and Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Process Engineering, Biotechnology, Nutrition Technology
    Notes: A single-stage impactor has been used to calibrate a Polytec HC-15/1 optical aerosol analyser so that this instrument can be used to study water droplets from approximately 1 to 20 μm aerodynamic diameter. The resulting calibration data were in good agreement with calculations based on Mie light scattering theory, and gave a conversion factor of 2.0 ± 0.2 between polystyrene latex microspheres and water droplets of the same aerodynamic diameter.Monodisperse water droplets were sampled by a Polytec HC-70/2 analyser, calibrated using the conversion factor of 2.0. The measured count median diameter agreed closely with that predicted from the well-defined operating conditions of the vibrating orifice aerosol generator. Size measurements of a polydisperse water-droplet spray were also undertaken with both a Malvern laser diffractometer and a Polytec HC-15 analyser; good agreement was achieved between the two techniques.
    Additional Material: 8 Ill.
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    URL: http://dx.doi.org/10.1002/ppsc.19890060120
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  • 92
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    Announcements (1989)
    Weinheim : Wiley-Blackwell
    Particle and Particle Systems Characterization 6 (1989), S. 133-133 
    Details
    ISSN: 0934-0866
    Keywords: Chemistry ; Industrial Chemistry and Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Process Engineering, Biotechnology, Nutrition Technology
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/ppsc.19890060123
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  • 93
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    The Fundamentals of Particle Size Analysis by Means of Ultrasonic Spectrometry (1989)
    Weinheim : Wiley-Blackwell
    Particle and Particle Systems Characterization 6 (1989), S. 135-143 
    Details
    ISSN: 0934-0866
    Keywords: Chemistry ; Industrial Chemistry and Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Process Engineering, Biotechnology, Nutrition Technology
    Notes: The 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.
    Additional Material: 13 Ill.
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    URL: http://dx.doi.org/10.1002/ppsc.19890060124
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    Lower Detection Limit of an Optical Particle Counter in the measurement of particle size distributionsPresented at the 4th European Symposium Particle Characterization, Nürnberg, 19.-21. April 1989. (1989)
    Weinheim : Wiley-Blackwell
    Particle and Particle Systems Characterization 6 (1989), S. 124-128 
    Details
    ISSN: 0934-0866
    Keywords: Chemistry ; Industrial Chemistry and Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Process Engineering, Biotechnology, Nutrition Technology
    Notes: An Optical Particle Counter with optically defined measuring volume was investigated with regard to an application in the range of fine particles (f.i. water droplets less then 1.5 μm in diameter). Because of a problematic detection behaviour in the examined size range caused by the analogue signal processor, it was necessary to explore signals generated by the measurement system. In view of the results obtained an alternative signal evaluation method was developed on basis of a digital system. The high flexibility of software systems in signal processing rendered possible on the one hand a clear definition of the lower detection limit of the instrument. On the other hand it was possible to lower the detection limit and herewith the size of particles to be resolved. A practical application for the new evaluation technique is given by the measurement of fractional efficiency curves of technical separators and classifiers, which clearly shows the advantages of the system presented. Most recent investigations are concerned with the maximum number concentration detectable with the Optical Particle Counter, which could be increased up to five times.
    Additional Material: 7 Ill.
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    URL: http://dx.doi.org/10.1002/ppsc.19890060121
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    A Light Scattering Instrument to Discriminate and Size Fibres. Part II: Experimental system (1989)
    Weinheim : Wiley-Blackwell
    Particle and Particle Systems Characterization 6 (1989), S. 144-150 
    Details
    ISSN: 0934-0866
    Keywords: Chemistry ; Industrial Chemistry and Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Process Engineering, Biotechnology, Nutrition Technology
    Notes: A Light scattering technique is described which can discriminate, size and count airborne fibres down to 1.6 μm diameter. The results are compared with Mie theory for spheres and two models for finite cylinders based on the Rayleigh-Gans-Debye approximation and rigorous infinite cylinder theory modified by Fraunhofer diffraction on the length.
    Additional Material: 10 Ill.
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    URL: http://dx.doi.org/10.1002/ppsc.19890060125
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  • 96
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    The Use of Particle Image Velocimetry to Study Roping in Pneumatic ConveyancePresented at the 4th European Symposium Particle Characterization, Nürnberg 19.-21 April 1989. (1989)
    Weinheim : Wiley-Blackwell
    Particle and Particle Systems Characterization 6 (1989), S. 129-132 
    Details
    ISSN: 0934-0866
    Keywords: Chemistry ; Industrial Chemistry and Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Particle Image Velocimetry (PIV) is a new technique which provides an instantaneous velocity profile of a flow field. A PIV system at Edinburgh University has been adapted to study the phenomenon of roping in a pneumatic particle conveyance rig. The principle features of this PIV system are as follows. Double images of the particles transported by the fluid are recorded on photographic film using a conventional camera. The displacement of the particle pairs, which determines the velocity at a particular point, is determined to an automatic analysis system. PIV is proving to be a powerful method in the investigation of roping. A rope is a high density ribbon of particles which is created when a uniform air-coal flow segregates at a pipe bend into two regimes: one has a low coal to air ratio whereas the second regime, termed the rope, has a high coal to air ratio. This particular problem is connected with the pulverised fuel (pf) pipes of coal-fired electricity generating stations. The flow, as seen on Figure 1, is reproduced in a 26 mm scale model encompassing the main aerodynamic features of pf pipes. The rope forms in the vertical to horizontal 90° bend, falls from the top to the bottom of the horizontal pipe and creats a deposit.
    Additional Material: 9 Ill.
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    URL: http://dx.doi.org/10.1002/ppsc.19890060122
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    Comparative Study of some Probability Distributions Applied to Liquid Sprays (1989)
    Weinheim : Wiley-Blackwell
    Particle and Particle Systems Characterization 6 (1989), S. 151-162 
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    ISSN: 0934-0866
    Keywords: Chemistry ; Industrial Chemistry and Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Process Engineering, Biotechnology, Nutrition Technology
    Notes: A comparative study of a few probability distributions generally used in describing various spray properties based on droplet size and velocity is described. Four different size distributions and three different coupled distributions, representing jointly size and velocity, are considered. A comparison of the results calculated for eight sets of data, taken from three different sources for the size distribution, and one data set for the joint size and velocity distribution, shows that the log-hyperbolic function presents the best choice among both one- and two-dimensional distributions.Considerations on one- and two-dimensional probability distributions are followed by a description of the conservation laws and their use in the prediction of the loss of momentum and energy of doplets. Finally, a proposal is made for how the sprays should be studied experimentally and analysed theoretically in order to obtain the maximum possible information. A few suggestions are then provided for further research in this direction.
    Additional Material: 11 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/ppsc.19890060126
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    Determination of Effective Surface Area for the Chemical Reaction of Fine Particulate Materials (1989)
    Weinheim : Wiley-Blackwell
    Particle and Particle Systems Characterization 6 (1989), S. 163-167 
    Details
    ISSN: 0934-0866
    Keywords: Chemistry ; Industrial Chemistry and Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Process Engineering, Biotechnology, Nutrition Technology
    Notes: A concept of effective surface area was defined as a geometrical controlling factor for a chemical reaction involving powdery materials. It is not uniquely determined for the specific material but depends on the sort of chemical reaction as well as the state of agglomeration. Case studies were given for dissolution or decomposition reaction for MgO, Mg(OH)2 and Pb(CO)3 with and without preliminary mechanical activation and granulation. The effective surface area for dissolution is mostly the external surface of the agglomerates, although the internal surface plays a role to some extent, depending on the compactness of the agglomerates.
    Additional Material: 8 Ill.
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    URL: http://dx.doi.org/10.1002/ppsc.19890060127
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  • 99
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    Fractal Mathematics Applied to Flow in Porous Systems (1989)
    Weinheim : Wiley-Blackwell
    Particle and Particle Systems Characterization 6 (1989), S. 168-175 
    Details
    ISSN: 0934-0866
    Keywords: Chemistry ; Industrial Chemistry and Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Process Engineering, Biotechnology, Nutrition Technology
    Notes: The Leitz TAS-Plus image analysis system was programmed to automatically measure both the ‘shape’ fractal and ‘fragmentation’ fractal for various types of fine particle filter cakes. The automated nature of the analysis facilitated the collection of statistically significant volumes of ‘fractal’ data. This data was then revised, where possible, to conventional theories of flow behavior. Several new insights evolved from the study as explained in the following analysis.
    Additional Material: 10 Ill.
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    URL: http://dx.doi.org/10.1002/ppsc.19890060128
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    Properties of SpraysPaper prepared for presentation at the International Conference on Mechanics of Two-Phase Flows, Taipei, Taiwan, June 12-15, 1989. (1989)
    Weinheim : Wiley-Blackwell
    Particle and Particle Systems Characterization 6 (1989), S. 176-186 
    Details
    ISSN: 0934-0866
    Keywords: Chemistry ; Industrial Chemistry and Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Process Engineering, Biotechnology, Nutrition Technology
    Notes: The spray properties of most practical importance, namely mean drop size, drop size distribution, radial and circumferential liquid distribution, cone angle and penetration, are discussed in the context of plain orifice, pressure-swirl, plain-jet airblast and prefilming airblast atomization. Equations are presented for estimating mean drop size and spray cone angle in terms of the relevant liquid properties, gas properties, atomizer dimensions, and atomizer operating conditions. The relative merits of these equations are discussed and compared. Some aspects of atomization in need of further research are indicated.
    Additional Material: 10 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/ppsc.19890060129
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