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  • Chemistry  (14)
  • 21.60.-n  (1)
  • 1
    Digitale Medien
    Digitale Medien
    Springer
    The European physical journal 339 (1991), S. 147-154 
    ISSN: 1434-601X
    Schlagwort(e): 11.10.Ef ; 21.10-k ; 21.60.-n
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Physik
    Notizen: Abstract Skyrme type potentials are known to lead — in the framework of the scaling model — to a finite-nucleus incompressibility valueK A where the volume coefficientK v equals roughly the negative surface coefficient Ks. This is found for Skyrme interactions with Kv between 200 and 360 MeV. In a semi-classical relativistic approach on the basis of theσ — ω model (linear as well as non-linear) using in addition local density approximations, we findK s to depend in particular on the surface energy coefficienta s , and not so much on the value ofK v . For a realistic value of as, both the linear and the non-linearσ — ω model (with NL1 parameter set) yield a ratio ¦K s K v ¦ of approximately 1. We discuss implications of this finding with a particular view on recent empirical results onK v andK s .
    Materialart: Digitale Medien
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  • 2
    Digitale Medien
    Digitale Medien
    Hoboken, NJ : Wiley-Blackwell
    AIChE Journal 35 (1989), S. 1385-1390 
    ISSN: 0001-1541
    Schlagwort(e): Chemistry ; Chemical Engineering
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie , Werkstoffwissenschaften, Fertigungsverfahren, Fertigung
    Zusätzliches Material: 6 Ill.
    Materialart: Digitale Medien
    Bibliothek Standort Signatur Band/Heft/Jahr Verfügbarkeit
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  • 3
    Digitale Medien
    Digitale Medien
    Hoboken, NJ : Wiley-Blackwell
    AIChE Journal 34 (1988), S. 684-687 
    ISSN: 0001-1541
    Schlagwort(e): Chemistry ; Chemical Engineering
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie , Werkstoffwissenschaften, Fertigungsverfahren, Fertigung
    Zusätzliches Material: 6 Ill.
    Materialart: Digitale Medien
    Bibliothek Standort Signatur Band/Heft/Jahr Verfügbarkeit
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  • 4
    Digitale Medien
    Digitale Medien
    Hoboken, NJ : Wiley-Blackwell
    AIChE Journal 33 (1987), S. 1644-1653 
    ISSN: 0001-1541
    Schlagwort(e): Chemistry ; Chemical Engineering
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie , Werkstoffwissenschaften, Fertigungsverfahren, Fertigung
    Notizen: Equations for the deep bed filtration problem are obtained as a special case of a general model formulated earlier. The filtration coefficient λ is expressed as an explicit function of system parameters such as fluid flow rate, pore density, and pore size distribution. For a unimodal pore size distribution it is found that λ remains constant both in space and time. In general, however, λ is shown to decrease. Explicit solutions to the problem, including particle density profiles and permeability, are obtained for the two cases of large values of the coordination number Z (capillary tube model), and for a bimodal pore size distribution with a finite coordination number.
    Zusätzliches Material: 14 Ill.
    Materialart: Digitale Medien
    Bibliothek Standort Signatur Band/Heft/Jahr Verfügbarkeit
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  • 5
    Digitale Medien
    Digitale Medien
    Hoboken, NJ : Wiley-Blackwell
    AIChE Journal 33 (1987), S. 1636-1643 
    ISSN: 0001-1541
    Schlagwort(e): Chemistry ; Chemical Engineering
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie , Werkstoffwissenschaften, Fertigungsverfahren, Fertigung
    Notizen: A mathematical model is formulated for the general class of problems that involve the transport of stable particulate suspensions in porous media. The porous medium is represented by a network of pore bodies (sites) and pore throats (bonds). Population balances for the species responsible for particle retention and permeability reduction are written in terms of the various mechanisms of particle capture and reentrainment. Rates of capture and release are evaluated using appropriate physical models. We specifically concentrate on mass transfer limited processes. The effective-medium theory is suitably formulated to determine the fluid flow distribution in the network and to calculate the permeability. The network representation of the porous medium together with the population balances and the rates of deposition and release provide a consistent model that finds application in filtration and fines migration processes.
    Zusätzliches Material: 5 Ill.
    Materialart: Digitale Medien
    Bibliothek Standort Signatur Band/Heft/Jahr Verfügbarkeit
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  • 6
    Digitale Medien
    Digitale Medien
    Hoboken, NJ : Wiley-Blackwell
    AIChE Journal 33 (1987), S. 1654-1662 
    ISSN: 0001-1541
    Schlagwort(e): Chemistry ; Chemical Engineering
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie , Werkstoffwissenschaften, Fertigungsverfahren, Fertigung
    Notizen: A model developed by Sharma and Yortsos (1987a) is applied to the processes of fines migration and fines injection in a porous medium. The first is a problem frequently encountered in oil reservoirs when release of fines is triggered by physicochemical interactions of the porous formation with the injected fluids. The second may be a problem in the filtration of relatively large particulates. Simple solutions are provided for both processes by considering size exclusion as the dominant particle retention mechanism. The solutions developed provide expressions for the particle concentration profiles, the open pore density and pore size distribution profiles, as well as the permeability reduction. These expressions are of importance in the evaluation of the extent and depth of formation damage and can be used as designing tools for remedial treatment, such as acidizing or fracturing.
    Zusätzliches Material: 15 Ill.
    Materialart: Digitale Medien
    Bibliothek Standort Signatur Band/Heft/Jahr Verfügbarkeit
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  • 7
    Digitale Medien
    Digitale Medien
    Hoboken, NJ : Wiley-Blackwell
    AIChE Journal 24 (1978), S. 369-400 
    ISSN: 0001-1541
    Schlagwort(e): Chemistry ; Chemical Engineering
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie , Werkstoffwissenschaften, Fertigungsverfahren, Fertigung
    Notizen: This review evaluates the present state of the art on backmixing in gas-liquid and gas-liquid-solid reactors. A brief outline of numerous techniques for measuring residence time distribution (RTD) of various phases in a multiphase reactor is presented. This is followed by a brief description of differential and stagewise models for characterizing backmixing from RTD measurements. Both simple (that is, single-parameter axial dispersion model) and more complex (that is, two-, three-, or four-parameter models) models are evaluated. Backmixing characteristics of various gas-liquid columns such as trickle beds, spray columns, mechanically agitated columns, plate columns, fluidized bed columns, etc., are subsequently evaluated. The performance of a bubble column under various reaction conditions is analyzed. Criteria for the elimination of backmixing in packed-bed reactors are presented, and the effect of backmixing on the multiple steady states in a gas-liquid reactor is briefly reviewed. Finally, the scale-up problems associated with gas-liquid reactors with various degrees of backmixing and the recommendations for the future work in RTD and macromixing models are outlined.
    Zusätzliches Material: 11 Ill.
    Materialart: Digitale Medien
    Bibliothek Standort Signatur Band/Heft/Jahr Verfügbarkeit
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  • 8
    ISSN: 0001-1541
    Schlagwort(e): Chemistry ; Chemical Engineering
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie , Werkstoffwissenschaften, Fertigungsverfahren, Fertigung
    Notizen: The surface properties, microscopic structure of foam, and flow through porous media behavior of mixed surfactant solutions (sodium lauryl sulfate plus lauryl alcohol) have been studied at various temperatures in relation to enhanced heavy oil recovery processes. The studies reported here suggest that temperature has a remarkable influence on the microscopic structure of foam and the flow through porous media behavior of the surfactant solutions. The surface tension and bubble size decreased as the temperature increased. The foam volume increased, whereas foam half-life (or foam stability) decreased with increasing temperature. A linear increase in bubble size with time was observed at different temperatures. The rate of change in bubble size increased with temperature. A significant reduction in effective air mobility and an improvement in fluid displacement efficiency were observed with increasing temperature. All measured parameters changed strikingly in the temperature range of 20-40°C, whereas they exhibited small changes between 40 and 80°C for the surfactant system investigated. The effect of temperature on half-life of foam and on the effective air mobility was most pronounced as compared to that on other parameters. An attempt is made to correlate quantitatively the foam volume of surfactant solution with fluid displacement efficiency in porous media.
    Zusätzliches Material: 9 Ill.
    Materialart: Digitale Medien
    Bibliothek Standort Signatur Band/Heft/Jahr Verfügbarkeit
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  • 9
    Digitale Medien
    Digitale Medien
    Hoboken, NJ : Wiley-Blackwell
    AIChE Journal 32 (1986), S. 46-55 
    ISSN: 0001-1541
    Schlagwort(e): Chemistry ; Chemical Engineering
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie , Werkstoffwissenschaften, Fertigungsverfahren, Fertigung
    Notizen: Previous models of noncatalytic gas-solid reactions are based primarily on parallelpore representations, thus excluding important topological effects of the porous medium. This paper utilizes network representations and percolation theory to develop expressions for pore closure time and the evolution of accessible volume, effective diffusivity, and conversion rates.
    Zusätzliches Material: 12 Ill.
    Materialart: Digitale Medien
    Bibliothek Standort Signatur Band/Heft/Jahr Verfügbarkeit
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  • 10
    Digitale Medien
    Digitale Medien
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 6 (1966), S. 30-35 
    ISSN: 0032-3888
    Schlagwort(e): Chemistry ; Chemical Engineering
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie , Maschinenbau , Physik
    Notizen: The paper reviews the various classical failure theories essentially developed for metals and then seeks to show that the same theories with slight modifications could be used to describe failure of polymeric materials. These modifications consist in the consideration of the effect of rate loading on failure behavior. In addition, the paper reports experimental results on failure of two polymeric materials under uniaxial tension loading and several biaxial stress fields corresponding to pure internal pressure, internal pressure combined with tension and torque loadings and several biaxial stress fields corresponding to pure internal pressure, internal pressure cobined with tension and torque loadings. The failure behavior under various stress fields has been studied for maximum principal rates ranging from 0.05 to 60 psi. sec. The predictions based on various criteria of faliure, which considers the effect of rate of loading, are compared with the experimental results. Finally, it is shown that failure behavior under triaxial stress fields can be reasonably predicted from biaxial stress failure data.
    Zusätzliches Material: 9 Ill.
    Materialart: Digitale Medien
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