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  • 1
    Electronic Resource
    Electronic Resource
    New York : Wiley-Blackwell
    Die Makromolekulare Chemie 189 (1988), S. 993-1000 
    ISSN: 0025-116X
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: The thermal expansivity of semicrystalline polymers is interpreted within the framework of the composite model which has already been found useful in describing mechanical and optical properties as well as the thermal conductivity of a large number of polymers. The model assumes the polymers to be an aggregate of units composed of crystalline and amorphous phases. The thermal expansivities of the unit are calculated in terms of those of the constituents. In the undrawn state the units are distributed randomly, and the isotropic thermal expansivity of the bulk results. The development of strong anisotropy in thermal expansivity on drawing is explained in terms of preferred orientation of the units. The orientational changes on drawing have been directly calculated from the birefringence versus draw ratio data. The results of these investigations indicate that the present model is quite successful in interpreting thermal expansivity data for poly(oxymethylene) and poly(propylene) over the entire draw ratio and temperature range.
    Additional Material: 2 Ill.
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  • 2
    Electronic Resource
    Electronic Resource
    Hoboken, NJ : Wiley-Blackwell
    AIChE Journal 34 (1988), S. 2019-2029 
    ISSN: 0001-1541
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: In spite of chromate's very high selectivity at acidic pH, fixed-bed chromate-exchange processes always suffer from severe gradual breakthroughs of chromate during column runs. Earlier, Sengupta and Clifford confirmed that such a gradual breakthrough is an equilibrium phenomenon and provided the underlying ion-exchange mechanism. An algorithm, developed with the aid of the governing chromate ion-exchange mechanism, is presented here to predict the salient properties of chromate-exchange processes in a multicomponent system. The model predicts the gradual chromate breakthroughs during column runs fairly accurately and also accounts for other unusual characteristics of chromate ion exchange. Average separation factor models, often used for designing fixed-bed ion-exchange processes, are unable to predict the gradual breakthrough characteristics of a preferred component such as chromate.
    Additional Material: 11 Ill.
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  • 3
    Electronic Resource
    Electronic Resource
    Hoboken, NJ : Wiley-Blackwell
    AIChE Journal 34 (1988), S. 1698-1708 
    ISSN: 0001-1541
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: The hollow fiber contained liquid membrane (CLM) is a thin liquid film contained in the interstices of two sets of intermingled microporous hollow fine fibers. Organic CLM-s have been used here for the separation of solutes from an aqueous feed into an aqueous strip. Solutes studied are phenol and acetic acid. The separations are carried out in either hydrophilic or hydrophobic hollow fiber CLM permeator modules, using a variety of organic liquids (e.g., decanol, methyl isobutyl ketone, xylene) as membranes. First-order models have been developed to predict the overall solute transfer coefficients adequately. The transfer coefficient can be enhanced significantly when a chemical reaction is carried out on the strip side using NaOH. The advantages of the CLM structure include operational stability, independent control of membrane phase pressure, automatic replenishment of the lost membrane liquid, and absence of the need for preequilibration. These features are demonstrated here, even for systems with considerable aqueous-organic mutual solubilities.
    Additional Material: 11 Ill.
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  • 4
    Electronic Resource
    Electronic Resource
    Hoboken, NJ : Wiley-Blackwell
    AIChE Journal 34 (1988), S. 417-425 
    ISSN: 0001-1541
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Gas separation behavior of permeators containing asymmetric cellulose acetate hollow fibers with the dense skin on the outside, facing the feed gas, has been investigated experimentally and theoretically using a sweep gas technique. Two systems were studied: CO2-N2, and O2-N2 (air). If the membrane structure is assumed to be symmetric or homogeneous, the model complies with the present data much better, compared to the assumption that the membrane is asymmetric.Separation was carried out with the high-pressure feed outside the fibers as well as inside the fibers. In both cases the data were well predicted by the homogeneous model. No concentration polarization effects were found when the feed flowed inside the fibers. The inherent membrane separation capability appeared practically the same whether the feed was inside or outside the fibers. Internal pressurization did not damage the membrane performance for the low pressure range used.These findings enable the operation of asymmetric hollow-fiber permeators with the feed inside the fiber lumen, which gives better separation in high stage cut situations.
    Additional Material: 11 Ill.
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  • 5
    Electronic Resource
    Electronic Resource
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 69 (1998), S. 279-291 
    ISSN: 0020-7608
    Keywords: quantum fluid density functional theory ; quantum theory of motion ; time-dependent processes ; electronegativity ; hardness ; Chemistry ; Theoretical, Physical and Computational Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: A quantum fluid density functional theory has been developed through an amalgamation of the quantum fluid dynamics and the time-dependent density functional theory. It is used in studying typical time-dependent processes like ion-atom collisions and atom-field interaction. Temporal evolution of chemical reactivity parameters as electronegativity, hardness, entropy, and polarizability is monitored for a He atom in its ground and excited states interacting with an external electric field and an incoming proton. It is observed that these reactivity parameters either remain static or oscillate with the external field in the atom-field interaction case, whereas during the collision process, hardness and entropy maximize and polarizability minimizes for both the electronic states of the atom. The possibility of a quantum theory of motion within the purview of this quantum fluid density functional framework is also explored.   © 1998 John Wiley & Sons, Inc. Int J Quant Chem 69: 279-291, 1998
    Additional Material: 9 Ill.
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  • 6
    Electronic Resource
    Electronic Resource
    New York, NY [u.a.] : Wiley-Blackwell
    International Journal for Numerical and Analytical Methods in Geomechanics 12 (1988), S. 263-281 
    ISSN: 0363-9061
    Keywords: Engineering ; Engineering General
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Architecture, Civil Engineering, Surveying , Geosciences
    Notes: Deficiencies of different existing models on ‘Reservoir Induced Seismicity’ have been discussed and a new mathematical model, which enhances a better understanding of triggering mechanism in terms of changes in effective stresses, in situ stresses and water level variations, has been discussed in this paper. In the model fractured rock is simulated by a fluid-filled elastic material subject to Mohr-Coulomb failure criterion. The model has been found to be capable of responding effectively to site specific attributes. It can recognize and explain the phenomenon of time lag observed in several actual cases. It is also capable of simulating stabilization of rock-reservoir system after a period of activities that follow the initial stage of filling. One dimensional and two dimensional, isotropic and anisotropic cases have been analysed and the model predictions have been found to agree qualitatively with the field observations.
    Additional Material: 23 Ill.
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  • 7
    Electronic Resource
    Electronic Resource
    Chichester : Wiley-Blackwell
    International Journal for Numerical Methods in Fluids 28 (1998), S. 215-224 
    ISSN: 0271-2091
    Keywords: orthogonal grids ; hyperbolic grid generation ; Navier-Stokes equations ; higher-order methods ; Engineering ; Numerical Methods and Modeling
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Body conforming orthogonal grids were generated using a fast hyperbolic method for aerofoils, and were used to solve the Navier-Stokes equation in the generalized orthogonal system for the first time for time accurate simulation of incompressible flow. For grid generation, the Beltrami equation and the definition equation for the orthogonality are solved using a finite difference method. The grids generated around aerofoils by this method have better orthogonality than the results published by earlier investigators. The Navier-Stokes equation at Reynolds numbers of 3000 and 35 000 for NACA 0012 and NACA 0015 respectively, have been solved as an application. The obtained results match quite well with the corresponding experimental results. © 1998 John Wiley & Sons, Ltd.
    Additional Material: 6 Ill.
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