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  • 1
    Electronic Resource
    Electronic Resource
    Fluids with internal degrees of freedom. I. Extended thermodynamics approach (1987)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 86 (1987), S. 4208-4215 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: Extended irreversible thermodynamics (EIT) is used to derive a complete set of time evolution equations for the state variables describing a general polyatomic fluid. The internal degrees of freedom of the fluid are represented by suitable nonconserved variables. In particular, these time evolution equations are shown to resemble relaxation-type equations. The sign of the unknown coefficients included in such equations is undetermined. However, when a comparison is made with the results obtained from the moment solution method of a kinetic equation for a dilute polyatomic fluid, several of the general features of the phenomenological results are clarified. Indeed, the predictions of kinetic theory fully agree with the basic equations of EIT. This provides a mesoscopic foundation for the theory. The sign of the unknown coefficients appearing in the relaxation-type equations for the nonconserved variables is such that the corresponding relaxation times are positive definite. Therefore, such equations are indeed relaxation equations. Other features of the phenomenological theory are also discussed on the light of the kinetic theoretical results. Further, the usefulness of the theory will be addressed in connection with a subsequent paper where the results here obtained will be used to compute the Rayleigh–Brillouin spectrum for a polyatomic fluid.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.451880
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  • 2
    Electronic Resource
    Electronic Resource
    Fluids with internal degrees of freedom. II. Rayleigh–Brillouin scattering (1987)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 86 (1987), S. 4216-4220 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: The extended thermodynamic treatment developed in part I for a fluid with internal degrees of freedom, is used to calculate its Rayleigh–Brillouin spectrum. A hydrodynamic model is first constructed which involves unspecified phenomenological coefficients. When these coefficients are identified in terms of experimental parameters, reasonably good agreement is obtained between the calculated and measured dynamic structure factor of CS2 at 20 °C with a density 1.262 g/cm3 and for k=8.608×10 cm−1. It is also shown that when the relaxation times of the trace and the nondeviatoric part of the stress tensor of the fluid tend to zero, the results previously derived by Mountain are recovered. The possible connections between this extended thermodynamic approach and Rytov's hydrodynamic theory are also hinted at.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.451881
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  • 3
    Electronic Resource
    Electronic Resource
    Extended thermodynamic description of diffusion in an inert binary mixture (1985)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 83 (1985), S. 4099-4102 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: The equilibrium concentration autocorrelation function for an inert binary mixture is calculated by means of extended irreversible thermodynamics. The ensuing generalized transport coefficient is explicitly evaluated and the corresponding k-dependent relaxation time is also obtained. The connection with neutron scattering experiments is suggested and expressions for the dynamic structure factor and the half-width dispersion relation are given.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.449075
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  • 4
    Electronic Resource
    Electronic Resource
    Model for the electrorheological effect in flowing polymeric nematics (1999)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 110 (1999), S. 8197-8204 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: An analytical model to study the response of a polymeric nematic confined in a rectangular cell, to a dc electric field is presented. The effect of a pressure-driven plane Poiseuille flow and its competition with the electric field is explicitly considered. For the final stationary state where the induced reorientation of the director has already occurred, an aligned structure with a greatly enhanced viscosity (electrorheological effect) is produced. For this same state the first normal stress difference is calculated as a function of position and of the applied field. For this quantity, regions of negative and positive values develop along the direction of the velocity gradient and an increase in the electric field or the flow causes an augmented effect in its profiles. The net force between the plates is also calculated. As the Reynolds number increases, it is found that it also changes sign from positive to negative, and the effect is more pronounced as the strength of the electric field increases. Finally, the paper is closed by discussing the scope and limitations of the model and methods employed. © 1999 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.478721
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  • 5
    Electronic Resource
    Electronic Resource
    Temperature effects in the Rayleigh problem for a convected Jeffreys fluid (1989)
    Springer
    Rheologica acta 28 (1989), S. 233-237 
    Details
    ISSN: 1435-1528
    Keywords: Non-linearviscoelasticity ; Jeffreys model ; non-isothermal effects ; Rayleigh problem ; irreversiblethermodynamics
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: Abstract We use a thermodynamic approach to non-linear viscoelasticity which predicts a coupling between the stress tensor and the heat flux, to generalize the Rayleigh problem for an Oldroyd B model of a fluid. For a special choice of the external temperature gradient, we show that thermal effects do alter the hydrodynamic velocity field as well as the first and second normal stress differences. These quantities depend on renormalized parameters wich explicitly depend on temperature and on the strength of the coupling. In particular we find that in contrast to the isothermal situation, the second normal stress difference does not vanish. The possibility of an experimental verification of our theoretical predictions is also mentioned.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01332855
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  • 6
    Electronic Resource
    Electronic Resource
    Competition between evaporation and fission: Stochastic aspects (1989)
    Springer
    The European physical journal 334 (1989), S. 109-110 
    Details
    ISSN: 1434-601X
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract The coupled dynamics of particle evaporation and fission is addressed in a stochastic framework. The effect of nucleus shape fluctuation on the statistical properties of emitted particles is studied in the time regime prior to fission events. Methodological consequences of this study and the convenience of a simulation approach to the coupled stochastic process are discussed.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01294393
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  • 7
    Electronic Resource
    Electronic Resource
    Linear viscoelasticity and irreversible thermodynamics (1986)
    Springer
    Rheologica acta 25 (1986), S. 207-213 
    Details
    ISSN: 1435-1528
    Keywords: Irreversible thermodynamics ; constitutive equation ; Maxwell model ; viscoelasticity ; auto-correlation function
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: Abstract The underlying thermodynamic aspects of linear viscoelasticity are discussed. In particular, from the Extended Irreversible Thermodynamics theory we systematically derive the Maxwell model exhibiting its compatibility with thermo-dynamics and assessing its conditions of validity. We also calculate the equilibrium transverse velocity auto-correlation function and the frequency dependent shear viscosity. Nonlinear generalizations of our model are suggested and the possible role of extended thermodynamics in selecting constitutive equations is also discussed.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01357948
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  • 8
    Electronic Resource
    Electronic Resource
    A thermodynamic approach to non-linear viscoelasticity (1988)
    Springer
    Rheologica acta 27 (1988), S. 217-223 
    Details
    ISSN: 1435-1528
    Keywords: Irreversiblethermodynamics ; non-linearviscoelasticity ; Oldroyd model ; constitutive equation ; structural theory ; rheological equation of state
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: Abstract We show that Extended Irreversible Thermodynamics (EIT) may be regarded as a unifying thermodynamic scheme which generates a variety of non-linear viscoelastic equations of state. In particular, we show how the so-called eight-constants Oldroyd model, with all its invariant properties, may be derived from the postulates of EIT. It is also shown that the structure of the thermodynamic based rheological equations of state is in complete agreement with that of the representation theorems formulation of constitutive relationships originally proposed by Rivlin and Ericksen. We discuss how more complex rheological models can be derived from higher order approximations of the theory. Finally, the connections between our approach and other related works are briefly discussed.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01329737
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  • 9
    Electronic Resource
    Electronic Resource
    On the foundations of extended irreversible thermodynamics (1984)
    Springer
    Journal of statistical physics 37 (1984), S. 465-484 
    Details
    ISSN: 1572-9613
    Keywords: Extended irreversible thermodynamics ; kinetic theory ; fluctuations ; memory functions ; projection operators ; flux relaxation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract A theory of macroscopic systems which takes as independent variables the slow (conserved) ones plus the fast dissipative fluxes is carefully analyzed at three levels of description: macroscopic (thermodynamic), microscopic (projection operators) and mesoscopic (fluctuation theory). Such a description is compared with the memory function approach based only on the conserved variables. We find that the first theory is richer and wider than the second one, and some misunderstandings in this connection are clarified and discussed.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01011845
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  • 10
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    Absorption effects in liquid crystal waveguides (2003)
    American Physical Society
    Details
    Publication Date: 2003-10-27
    Print ISSN: 1063-651X
    Electronic ISSN: 1095-3787
    Topics: Physics
    Published by American Physical Society
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