An optimal control problem with feedback for a mathematical model of the motion of weakly concentrated water polymer solutions with objective derivative

We study a problem with feedback for a mathematical model of the motion of weakly concentrated water polymer solutions with smoothed Jaumann objective derivative. We prove the existence of an optimal solution yielding the minimum of a specified bounded lower semicontinuous quality functional. To establish the existence of an optimal solution, we use the topological approximation method for studying problems of hydrodynamics.     

Pullback attractors for a two-dimensional Navier-Stokes model in an infinite delay case

We prove the existence of solutions for a Navier-Stokes model in two dimensions with an external force containing infinite delay effects in the weighted space C_γ(H). Then, under additional suitable assumptions, we prove the existence and uniqueness of a stationary solution and the exponential decay of the solutions of the evolutionary problem to this stationary solution. Finally, we study the existence of pullback attractors for the dynamical system associated to the problem under more general assumptions.     

Optimal control problem for a stationary model of low concentrated aqueous polymer solutions

We study the existence of an optimal control for lower bounded upper semicontinuous functionals and weak solutions of a system of equations describing the stationary motions of low concentrated aqueous polymer solutions in a bounded domain with locally Lipschitz boundary.     

Pullback attractors for a class of non-autonomous nonclassical diffusion equations

We consider the first initial boundary value problem for the non-autonomous nonclassical diffusion equation u_t−εΔu_t−Δu+f(u)=g(t), ε∈[0,1], in a bounded domain in R^N. Under a Sobolev growth rate of the nonlinearity f and a suitable exponential growth of the external force g, using the asymptotic a priori estimate method, we prove the existence of pullback D-attractors in the space and the upper semicontinuity of at ε=0.     

Solvability of a stationary model of motion of weak aqueous polymer solutions

In this paper we study the solvability in a weak sense of the boundary-value problem for a system of equations that describes the stationary motion of weak aqueous polymer solutions in a bounded domain with a locally Lipschitz boundary.     

Pullback attractors for a nonautonomous damped wave equation with infinite delays in weighted space

In this paper, we investigate the existence of solutions for a damped wave equation with infinite delays in the weighted space and , respectively. In addition, we study the existence of pullback attractor for the process associated to the problem by a direct and simple compactness method.     

Pullback attractors for a class of extremal solutions of the 3D Navier-Stokes system

In this paper we construct a dynamical process (in general, multivalued) generated by the set of solutions of an optimal control problem for the three-dimensional Navier-Stokes system. We prove the existence of a pullback attractor for such multivalued process. Also, we establish the existence of a uniform global attractor containing the pullback attractor. Moreover, under the unproved assumption that strong globally defined solutions of the three-dimensional Navier-Stokes system exist, which guaranties the existence of a global attractor for the corresponding multivalued semiflow, we show that the pullback attractor of the process coincides with the global attractor of the semiflow.     

Optimal feedback control in the stationary mathematical model of low concentrated aqueous polymer solutions

In this article we will consider the feedback control problem in the stationary model of motion of low concentrated aqueous polymer solutions. We demonstrate the solvability of an approximating problem, using some a priori estimates and the topological degree theory. Then the convergence (in some generalized sense) of solutions of approximating problems to a solution of the given problem is proved. Moreover, we show the existence of a solution minimizing a given convex, lower semicontinuous functional.     

Pullback exponential attractors for evolution processes with the difference of 2 solutions lacking smoothing property

In this paper, we construct the pullback exponential attractors for evolution processes in which the difference of 2 solutions lacks the smoothing property. To do this, by the uniform squeezing property of the corresponding discrete process, we add the points to the pullback attractor such that every new set of it has the finite fractal dimension and pullback exponentially attracts every bounded subset of the phase space. As the applications, we establish the existence of pullback exponential attractors for non‐autonomous reaction‐diffusion equation without any restriction on the growing order of nonlinear term and non‐autonomous strongly damped wave equation in with critical nonlinearity.     

Weak solutions and attractors for motion equations for an objective model of viscoelastic medium

We study the boundary value problem for the equations of motion of incompressible viscoelastic medium with an objective constitutive law of Jeffreys kind. We show existence of global weak solutions for any initial data and construct their minimal uniform trajectory attractor and uniform global attractor. (© 2008 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)     

Global attractors for a discrete selection model with periodic immigration

A one-island selection-migration model is used to study the periodic immigration of a population of fixed allele frequency into a natural population. Density-dependent selection and immigration are the primary factors affecting the demographic and genetic change in the island population. With the assumptions of complete dominance (CD) or no dominance (ND) and homozygote superiority in fitness, the existence and location of global attractors are established. Analysis of this model provides rudimentary information about the migration of transgenes into a natural population.     

On the motion of a vortex ring with a sharply concentrated vorticity

We study an incompressible non‐viscous fluid with axial symmetry without swirl, in the case when the vorticity is supported in an annulus. It is well known that there exist particular initial data for which the Euler evolution reduces to a translation with a constant speed. In this paper we prove a similar property for any initial condition in the limit situation in which the initial vorticity is sharply concentrated. Copyright © 2000 John Wiley & Sons, Ltd.