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  • 1
    Electronic Resource
    Electronic Resource
    Springer
    Il nuovo cimento della Società Italiana di Fisica 16 (1994), S. 1627-1633 
    ISSN: 0392-6737
    Keywords: Brillouin and Rayleigh scattering ; Liquids ; Emulsions and suspensions ; Order-disorder and statistical mechanics of model systems ; Conference proceedings
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Summary We have performed extensive small-angle light scattering (SALS) measurements on a three-component microemulsion (AOT/decane/water) as a function of the dispersed phase concentration and the temperature. All samples have a water/AOT molar fractionw=40.8. Such a system presents a very complex phase diagram with many structural configurations. With the SALS technique, we have been able to observe all the phase separation lines. In particular we give details on the system structure on the percolation phenomenon and on the bicontinuous phase recently observed. In particular we show that the percolation is driven by a long-scale aggregation between microemulsion droplets.
    Type of Medium: Electronic Resource
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  • 2
    Electronic Resource
    Electronic Resource
    Springer
    Il nuovo cimento della Società Italiana di Fisica 18 (1996), S. 1317-1332 
    ISSN: 0392-6737
    Keywords: Brillouin and Rayleigh scattering ; other light scattering ; Emulsions and suspensions ; Specific phase transitions
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Summary We have performed extensive studies of a three-component microemulsion system composed of AOT-water-decane (AOT=sodium-bis-ethylhexyl-sulfosuccinate is an ionic surfactant) using small-angle light scattering (SALS). The small-angle scattering intensities are measured in the angular interval 0.001–0.1 radians, corresponding to a Bragg wave number range of 0.14 μm−1〈Q〈〈1.4 μm−1. The measurements were made by changing temperature and volume fraction ϕ of the dispersed phase (water + AOT) in the range 0.05〈ϕ〈0.75. All samples have a fixed water-to-AOT molar ratio,w=[water]/[AOT]=40.8, in order to keep the same average droplet size in the stable one-phase region. With the SALS technique, we have been able to observe all the phase boundaries of a very complex phase diagram with a percolation line and many structural organizations within it. We observe at the percolation transition threshold, a scaling behavior of the intensity data. This behavior is a consequence of a clustering among microemulsion droplets near the percolation threshold. In addition, we describe in detail a structural transition from a droplet microemulsion to a bicontinuous one as suggested by a recent small-angle neutron scattering experiment. The loci of this transition are located several degrees above the percolation temperatures and are coincident with the maxima previously observed in shear viscosity. From the data analysis, we show that both the percolation phenomenon and this novel structural transition are derived from a large-scale aggregation between microemulsion droplets.
    Type of Medium: Electronic Resource
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  • 3
    Electronic Resource
    Electronic Resource
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 32 (1992), S. 724-731 
    ISSN: 0032-3888
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: A methodology is set forth for the numerical solution of the transient freezing problem of a viscous power-law fluid flowing in a cold empty tube with a frozen layer forming on the inside tube surface. The fluid considered is the melt of a semicrystalline polymer with temperature dependent viscosity. The solution domain encompasses both the liquid and solid phases. Coordinate transformations are employed to immobilize and to straighten the moving, curved interface. An implicit finite difference method is employed to solve the governing equations. Numerical results are analyzed by examining the effects of the Peclet number, Nahme number, Stefen number, and the power law index on the profiles of the frozen layer. Variations of the thickness of the frozen layer as a function of time and axial coordinate are also presented.
    Additional Material: 9 Ill.
    Type of Medium: Electronic Resource
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  • 4
    Electronic Resource
    Electronic Resource
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 20 (1980), S. 40-50 
    ISSN: 0032-3888
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Diffusivities D ranging over six orders of magnitude with values as low as 2 × 10-13 cm2/s have been obtained by a recently developed permeation apparatus, employing a gas-flow method and a flame ionization detector; Log D for hydrocarbons in bisphenol-A polycarbonate (PC) at 120°C is proportional to the square of the molecular diameter (d2) as given by the Lennard-Jones 6-12 potential. This correlation holds even for the nonspherical n-hexane molecule. The activation energy for diffusion is also linearly related to d2, with values of 9.5 and 23 kcal/mol for methane and neopentane in PC, respectively. Comparison of PC with two similar polymers of higher glass-transition temperatures (Tg) indicates that our diffusion data do not correlate with the Tg of these polymers. The presence of subsidiary transitions, however, appears to enhance segmental mobilities, increasing the rate of diffusion of the hydrocarbons. The thermodynamic solubility of alkanes in glassy PC can be directly related to their boiling points, and in addition, their enthalpy of solution is linearly related to the heat of condensation of these permeants.
    Additional Material: 10 Ill.
    Type of Medium: Electronic Resource
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  • 5
    Electronic Resource
    Electronic Resource
    Hoboken, NJ : Wiley-Blackwell
    AIChE Journal 41 (1995), S. 2661-2663 
    ISSN: 0001-1541
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Additional Material: 4 Ill.
    Type of Medium: Electronic Resource
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  • 6
    Electronic Resource
    Electronic Resource
    Hoboken, NJ : Wiley-Blackwell
    AIChE Journal 42 (1996), S. 1706-1714 
    ISSN: 0001-1541
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Experimental studies of polymer melt flow in the filling and post-filling stages of the injection molding process were performed using the sequential injection of transparent and colored polystyrene resin. Effects of fountain flow in the filling stage, geometrical factors caused by edges and corners, as well as flow through contractions and expansions, were identified. Significant polymer melt flow which increases with increased packing pressure was observed in the post-filling process. The melt flow is more concentrated around the gate area than away from the gate. It was also found that the polymer melt flows across the gap center, resulting in partial annihilation of the weld line. Simulations based on the control-volume/finite-element method employed within each gapwise layer combined with the dual-filling-parameter technique were developed to trace the advancements in melt fronts for both skin and core materials. Numerical simulations show reasonable consistency with experimental results in both skin and core material distribution. If the edge effect is taken into account using a shape factor as a geometrical correction, the simulation accuracy is further improved.
    Additional Material: 15 Ill.
    Type of Medium: Electronic Resource
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  • 7
    Electronic Resource
    Electronic Resource
    Hoboken, NJ : Wiley-Blackwell
    AIChE Journal 32 (1986), S. 1367-1371 
    ISSN: 0001-1541
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Tracer diffusion coefficients were measured for benzene, toluene, mesitylene, naphthalene, and phenanthrene in dense ethanol at 0.56 ≤ TR ≤ 1.07 and ρR ≥ 1.44. The results were used to examine the temperature dependence of the degree of association between ethanol molecules across the entire range of temperature. The hard-sphere tracer diffusion equation and the Stokes-Einstein equation were used to develop two engineering correlations. The former approach was found to be adequate for solvents of relatively compact molecules, and the latter to be more general in its applications. The absolute deviation of prediction from observed values of tracer diffusivities is 4%, with a maximum error of 13%.
    Additional Material: 5 Ill.
    Type of Medium: Electronic Resource
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  • 8
    Electronic Resource
    Electronic Resource
    Hoboken, NJ : Wiley-Blackwell
    AIChE Journal 32 (1986), S. 1043-1048 
    ISSN: 0001-1541
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Additional Material: 5 Ill.
    Type of Medium: Electronic Resource
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  • 9
    Electronic Resource
    Electronic Resource
    Hoboken, NJ : Wiley-Blackwell
    AIChE Journal 18 (1972), S. 984-989 
    ISSN: 0001-1541
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: A Markov chain model was used to model the axial mixing of solid particles in a motionless mixer having no moving parts. One step transition probabilities were determined experimentally for the model. Based on these transition probabilities, the model was able to predict spatial distribution of tracer particles up to seven steps of the Markov chain, which was equivalent to seven consecutive passes of the mixture through the mixer. Experimental results were in good agreement with those predicted from the Markov chain model.
    Additional Material: 9 Ill.
    Type of Medium: Electronic Resource
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  • 10
    Electronic Resource
    Electronic Resource
    Hoboken, NJ : Wiley-Blackwell
    AIChE Journal 31 (1985), S. 1904-1910 
    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 conditions under which the Taylor-Aris dispersion phenomenon can be employed to generate accurate tracer diffusion data in supercritical dense fluids are established. The technique is used to determine the diffusivities of benzene, toluene, naphthalene, and phenanthrene in supercritical dense 2,3-dimethylbutane as a function of temperature and pressure. A molecular theory incorporating the Sung-Stell formulation of molecular dynamic correlations in smooth-hardsphere fluids and the Baleiko-Davis molecular roughness for polyatomics with the Enskog-Thorne dense gas diffusivity relationship is found to represent our experimental data to within ±4%. The values of the effective hard-sphere diameters involved in the present theory can be predicted fairly accurately from the critical volumes of the solutes and solvent considered here.
    Additional Material: 5 Ill.
    Type of Medium: Electronic Resource
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