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  • 1
    Publication Date: 1999-01-01
    Print ISSN: 0938-8974
    Electronic ISSN: 1432-1467
    Topics: Mathematics , Physics
    Published by Springer
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  • 2
    Electronic Resource
    Electronic Resource
    Springer
    Journal of mathematical biology 4 (1977), S. 353-362 
    ISSN: 1432-1416
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Mathematics
    Notes: Summary The formation of spatially patterned structures in biological organisms has been modelled in recent years by various mechanisms, including pairs of reaction-diffusion equations $$u_t = D_{\text{1}} \nabla ^{\text{2}} u + f(u,v)$$ , $$v_t = D_{\text{2}} \nabla ^{\text{2}} v + g(u,v)$$ . Their analysis has been by computer simulation. In some cases, u can be interpreted as an activator and v an inhibitor. The following problem is treated: given a “pattern” u = ϕ(x), v = Ψ(x), find a system which has it as a stable stationary solution (stability is used in various senses in the paper). This inverse problem is shown to have solutions for reasonable ϕ and Ψ. The solutions constructed are of activator-inhibitor type with D 2〉D 1.
    Type of Medium: Electronic Resource
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  • 3
    Electronic Resource
    Electronic Resource
    Springer
    Journal of nonlinear science 9 (1999), S. 641-669 
    ISSN: 1432-1467
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mathematics , Physics
    Notes: Summary. A general class of nonlinear evolution equations is described, which support stable spatially oscillatory steady solutions. These equations are composed of an indefinite self-adjoint linear operator acting on the solution plus a nonlinear function, a typical example of the latter being a double-well potential. Thus a Lyapunov functional exists. The linear operator contains a parameter ρ which could be interpreted as a measure of the pattern-forming tendency for the equation. Examples in this class of equations are an integrodifferential equation studied by Goldstein, Muraki, and Petrich and others in an activator-inhibitor context, and a class of fourth-order parabolic PDE's appearing in the literature in various physical connections and investigated rigorously by Coleman, Leizarowitz, Marcus, Mizel, Peletier, Troy, Zaslavskii, and others. The former example reduces to the real Ginzburg-Landau equation when ρ = 0 . The most complete results, including threshold results for the appearance of globally minimizing patterns and many other properties of the patterns themselves, are given for complex-valued solutions in one space variable. A complete linear stability analysis for all such sinusoidal solutions is also given; it extends the set of stable solutions considerably beyond the global minimizers. Other results, including threshold results and the existence of large amplitude patterns as well as of bifurcating solutions, are provided for real-valued solutions; these results are relatively independent of the number of space variables. Finally, a slightly different class of evolution equations is given for which no patterned global minimizer exists, but a sequence of patterned solutions exist whose instabilities (if they are unstable) become ever weaker and the fineness of the oscillation becomes ever more pronounced.
    Type of Medium: Electronic Resource
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  • 4
    Electronic Resource
    Electronic Resource
    Springer
    Archive for rational mechanics and analysis 33 (1969), S. 116-138 
    ISSN: 1432-0673
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mathematics , Physics
    Type of Medium: Electronic Resource
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  • 5
    Electronic Resource
    Electronic Resource
    Springer
    Archive for rational mechanics and analysis 64 (1977), S. 93-109 
    ISSN: 1432-0673
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mathematics , Physics
    Type of Medium: Electronic Resource
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  • 6
    Electronic Resource
    Electronic Resource
    Springer
    Open systems & information dynamics 5 (1998), S. 99-123 
    ISSN: 1573-1324
    Source: Springer Online Journal Archives 1860-2000
    Topics: Computer Science , Natural Sciences in General
    Notes: Abstract This paper addresses the issue of thermodynamically consistent derivations of field equations governing nonisothermal processes with diffuse interfaces and their implications for interface conditions in the associated sharp interface theories. We operate within the framework of extended irreversible thermodynamics, allowing gradient terms to be present not only in the free energy and entropy densities but also in the internal energy, for both nonconserved and conserved order parameter theories. These various gradient terms are shown to relate to the splitting of the surface tension into an energetic and an entropic part. It is shown that the principle of nondecreasing local entropy production does not single out uniquely the form of the governing field equations. Instead it leads naturally to a one-parameter family of alternative theories which do not contradict the Curie principle of irreversible thermodynamics. The principal applications are to the solidification of a pure material and of a binary alloy. In the case of a pure substance an asymptotic analysis is developed in the vicinity of the solidification front. The main effect of the alternative theories, as well as of the splitting of the surface tension, on the corresponding free boundary problem is manifested in the first order terms in the nonequilibrium contributions to the interface undercooling. We also consider the possibility of assigning from empirical data some specific values to the phenomenological parameters involved in these models.
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  • 7
    Electronic Resource
    Electronic Resource
    Springer
    Journal of statistical physics 95 (1999), S. 1141-1164 
    ISSN: 1572-9613
    Keywords: solidification of alloys ; phase field models ; interfaces ; nonlocal effects ; solidus curves ; solute trappings ; partition coefficient ; asymptotics
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract A discussion is given of recent advances in phase-field modeling of materials which change phase. On one hand, general models incorporating elasticity properties of the material, nonconserved and conserved order parameters, and nonlocal effects are now available. On the other hand, gradient theories for binary alloys have been developed which reflect such effects as the dependence of capillarity on the concentration of impurities, solute trapping in its dependence on velocity of solidification fronts, and other nonequilibrium phenomena.
    Type of Medium: Electronic Resource
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