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  • 1
    Electronic Resource
    Electronic Resource
    Fluids in micropores. II. Self-diffusion in a simple classical fluid in a slit pore (1988)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 88 (1988), S. 1394-1406 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: Self-diffusion coefficients D are computed for a model slit pore consisting of a rare-gas fluid confined between two parallel face-centered cubic (100) planes (walls) of rigidly fixed rare-gas atoms. By means of an optimally vectorized molecular-dynamics program for the CYBER 205, the dependence of D on the thermodynamic state (specified by the chemical potential μ, temperature T, and the pore width h) of the pore fluid has been explored. Diffusion is governed by Fick's law, even in pores as narrow as 2 or 3 atomic diameters. The diffusion coefficient oscillates as a function of h with fixed μ and T, vanishing at critical values of h, where fluid–solid phase transitions occur. A shift of the pore walls relative to one another in directions parallel with the walls can radically alter the structure of the pore fluid and consequently the magnitude of D. Since the pore fluid forms distinct layers parallel to the walls, a local diffusion coefficient D(i)(parallel) associated with a given layer i can be defined. D(i)(parallel) is least for the contact layer, even for pores as wide as 30 atomic diameters (∼100 A(ring)). Moreover, D(i)(parallel) increases with increasing distance of the fluid layer from the wall and, for pore widths between 16 and 30 atomic diameters, D(i)(parallel) is larger in the center of the pore than in the bulk fluid that is in equilibrium with the pore fluid. The opposite behavior is observed in corresponding smooth-wall pores, in which the discrete fluid–wall interactions have been averaged by smearing the wall atoms over the plane of the wall. The temperature dependence of D for fixed h is determined and the nature of melting of a pore solid is examined. It is found that the solid tends to melt first in the middle of the pore. All of the various results are related to the structural properties of the pore fluid, as manifested by the local density and pair correlation functions.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.454211
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  • 2
    Electronic Resource
    Electronic Resource
    A new computational approach to the chemical potential (1990)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 93 (1990), S. 5167-5171 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: A new approach to the computation of chemical potential and free energy is presented. The basic idea is to correct the underestimate obtained by the particle-removal method. Application of the new technique to several different thermodynamic states of the Lennard-Jones (12,6) fluid shows that it is capable of providing reliable estimates of the chemical potential, even at high density where standard methods encounter computational difficulties.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.458653
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  • 3
    Electronic Resource
    Electronic Resource
    Fluids in micropores. I. Structure of a simple classical fluid in a slit-pore (1987)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 87 (1987), S. 5464-5476 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: Equilbrium properties of a rare-gas fluid contained between two parallel fcc(100) planes of rigidly fixed rare-gas atoms were computed by means of the grand-canonical ensemble Monte Carlo method. The singlet distribution function ρ(1), and the pair-correlation function g(2) in planes parallel to the solid layers, indicate that the structure of the pore fluid depends strongly on the distance h between the solid layers. As the separation increases from less than two atomic diameters, successive layers of fluid appear. The transitions between one and two layers and three and four layers are especially abrupt and are accompanied by changes in the character of g(2) from dense fluid-like to solid-like. Long-range, in-plane order in the fluid layers diminishes with increasing h, but is still evident in the contact layer (i.e., that nearest the solid layer) at h=16.5 atomic diameters, the largest separation considered. The structure of the contact layer reflects the solid-layer structure and differs significantly from the adjacent inner fluid layers, whose g(2) resembles that of the corresponding bulk fluid. Decreasing the density of atoms in the solid layers blunts the peaks in ρ(1) and g(2), although even for the least dense layer considered the contact layers of fluid evince long-range, in-plane order. Replacing the discrete pairwise fluid–solid interactions with the mean field resulting from smearing the solid atoms over the plane of the solid layer destroys the "phase transitions'' and the associated long-range, in-plane order.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.453665
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    Paper (German National Licenses)
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  • 4
    Electronic Resource
    Electronic Resource
    Comment on: Adsorption and diffusion at rough surfaces. A comparison of statistical mechanics, molecular dynamics, and kinetic theory (1991)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 95 (1991), S. 6194-6195 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.461595
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  • 5
    Electronic Resource
    Electronic Resource
    Monte Carlo calculation of chemical potential for the Stockmayer fluid (1992)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 96 (1992), S. 7867-7868 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: The chemical potential of the Stockmayer fluid is computed by the canonical ensemble Monte Carlo methods of Widom, Bennett, and Han. Both spherical cutoff and metallic Ewald sum techniques are employed. For the states studied it is found that the Ewald sum provides little improvement over the simpler spherical cutoff, that Bennett's and Han's methods produce essentially the same results, and that for certain states Widom's method is less accurate than Bennett's or Han's. The accuracy of the chemical potential calculated via the three methods was verified with Adams' version of the grand canonical ensemble Monte Carlo method.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.462387
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  • 6
    Electronic Resource
    Electronic Resource
    Solutions to the stochastic transport problem of O(σ V N ) for conservative solutes (1997)
    Springer
    Stochastic environmental research and risk assessment 11 (1997), S. 297-302 
    Details
    ISSN: 1436-3259
    Keywords: Perturbation ; conservative chemical ; velocity variance ; eulerian
    Source: Springer Online Journal Archives 1860-2000
    Topics: Architecture, Civil Engineering, Surveying , Energy, Environment Protection, Nuclear Power Engineering , Geography , Geosciences
    Notes: Abstract A recursive perturbation solution to the eulerian transport problem for a conservative solute in a random conductivity field is reported. The stochastic concentration is given to arbitrary order inσ ν, the variance of fluctuating velocity. The result gives the stochastic concentration as a perturbation to the deterministic concentration for constant mean flow. The closed form solution is easy to implement numerically via FFT.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02427920
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  • 7
    Electronic Resource
    Electronic Resource
    Multiscale adaptive estimation of the conductivity field using pump test data (1993)
    Springer
    Stochastic environmental research and risk assessment 7 (1993), S. 241-253 
    Details
    ISSN: 1436-3259
    Keywords: Parameter identification ; multiscale ; adaptive ; inverse
    Source: Springer Online Journal Archives 1860-2000
    Topics: Architecture, Civil Engineering, Surveying , Energy, Environment Protection, Nuclear Power Engineering , Geography , Geosciences
    Notes: Abstract An inverse problem is posed in terms of log-conductivities which are decomposed into macroscale deterministic and microscale stochastic components. The macroscale and microscale conductivities conceptualize hierarchical, scale-dependent aquifer parameters. A deterministic parameter estimation scheme divides a flow domain into a limited number of macroscale constant conductivity zones. A stochastic microscale parameter estimation scheme is used to obtain fluctuations about the macroscale averages in terms of geostatistical models. Both the macroscale and the microscale conductivities are estimated via maximum likelihood, adjoint-state methodologies. Monte Carlo-type approaches are used to examine the distribution of macroscale and microscale conductivity estimates.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01581613
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  • 8
    Electronic Resource
    Electronic Resource
    Nonequilibrium statistical mechanical derivation of a nonlocal Darcy's Law for unsaturated/saturated flow (1994)
    Springer
    Stochastic environmental research and risk assessment 8 (1994), S. 109-116 
    Details
    ISSN: 1436-3259
    Keywords: Unsaturated ; nonlocal ; memory ; statistical physics
    Source: Springer Online Journal Archives 1860-2000
    Topics: Architecture, Civil Engineering, Surveying , Energy, Environment Protection, Nuclear Power Engineering , Geography , Geosciences
    Notes: Abstract As illustrated variously by wetting and drying scanning curves, flow in unsaturated porous media is inherently nonlocal. This nonlocality is also manifest in hysteresis in the classical Darcy conductivity. It is the authors' belief that most current theories of unsaturated/saturated flow are often inadequate, as they do not account for spatial nonlocality and memory. Here we provide a fundamental theory in which nonlocality of the flow constitutive theory is a natural consequence of force balances. The results are derived from general principles in statistical physics and under appropriate limiting conditions, the classical Darcy's Law is recovered for saturated flow. A notable departure in this theory from other nonlocal flow theories is that a classical Darcy type equation on a small scale need not exist.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01589892
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  • 9
    Electronic Resource
    Electronic Resource
    Multiscale adaptive estimation of the conductivity field from head and tracer data (1993)
    Springer
    Stochastic environmental research and risk assessment 7 (1993), S. 66-82 
    Details
    ISSN: 1436-3259
    Keywords: Parameter identification ; multiscale ; transport ; adaptive
    Source: Springer Online Journal Archives 1860-2000
    Topics: Architecture, Civil Engineering, Surveying , Energy, Environment Protection, Nuclear Power Engineering , Geography , Geosciences
    Notes: Abstract Large scale fluctuations in the conductivity field are regionalized and estimated via a maximum likelihood, adjoint-state methodology. Small-scale fluctuations within each region are estimated adaptively via a Kalman-like stochastic filter. The variance and integral scale within each region are assumed to control the small-scale fluctuations. A Monte Carlo technique is used to examine the distribution of large-scale conductivity estimates.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01581567
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  • 10
    Electronic Resource
    Electronic Resource
    Development of stochastic partial differential equations for subsurface hydrology (1987)
    Springer
    Stochastic environmental research and risk assessment 1 (1987), S. 241-262 
    Details
    ISSN: 1436-3259
    Keywords: Martingale ; stochastic-convective ; stochastic-relativist ; spectral-integral ; perturbative ; statistical-mechanical
    Source: Springer Online Journal Archives 1860-2000
    Topics: Architecture, Civil Engineering, Surveying , Energy, Environment Protection, Nuclear Power Engineering , Geography , Geosciences
    Notes: Abstract The use of stochastic models in subsurface hydrology is growing at a logistic pace. To tie together a number of different stochastic methodologies for deriving subsurface transport equations, we have put together a brief review of some of the more common techniques. Our attention is confined to a few select methodologies so that we might delve in detail into assumptions required by the various approaches and their strengths and weaknesses. The methods reviewed include: Martingale, stochastic-convective, stochastic-relativist, spectral-integral, perturbative, statistical-mechanical, and generalized hydrodynamics. Within this list, we also have included a few stochastic methodologies which have been used solely to develop expressions for the dispersion tensor.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01543097
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