Gabriela Marinoschi

An age-structured model of epidermis growth

We propose a model with age and space structure for the evolution of the supra-basal epidermis. The model includes different types of cells: proliferating cells, differentiated cells, corneous cells, and apoptotic cells. We assume that all cells move with the same velocity and that the local volume fraction, occupied by the cells is constant in space and time. This hypothesis, based on experimental evidence, allows us to determine a constitutive equation for the cell velocity. We focus on the stationary case of the problem, that takes the form of a quasi-linear evolution problem of first order, and we investigate conditions under which there is a solution.

Degenerate Nonlinear Diffusion Equations

1 Parameter identification in a parabolic-elliptic degenerate problem.- 2 Existence for diffusion degenerate problems.- 3 Existence for nonautonomous parabolic-elliptic degenerate diffusion Equations.- 4 Parameter identification in a parabolic-elliptic degenerate problem.

Convergence of the Finite Difference Scheme for a Fast Diffusion Equation in Porous Media

We are concerned with an implicit scheme for the finite difference solution to a nonlinear parabolic equation with a multivalued coefficient that describes the fast diffusion in a porous medium. The boundary conditions contain the multivalued function as well. We prove the stability and the convergence of the scheme, emphasizing the precise nature of convergence in this specific case, and compute the error level of the approximating solution. The method is aimed to simplify the numerical computations for the solutions to equations of this type, without performing an approximation of the multivalued function. The theory is illustrated by numerical results.

Existence for a time-dependent rainfall infiltration model with a blowing up diffusivity

A difficulty in the modelling of water infiltration into an unsaturated soil is due to the presence of a diffusion coefficient that blows up at the moisture saturation value. This is put in evidence in some well-known hydraulic models like those of Broadbridge and White and van Genuchten. In this paper, we obtain results concerning the existence, uniqueness and regularity properties of the solution of unsaturated water flow determined by a time-dependent rainfall, with a nonlinear flux boundary condition on the outflow boundary and a singular diffusion coefficient. Some considerations related to the possibility of saturation occurrence and the extension of the results to the model describing the infiltration into an nonhomogeneous stratified soil are finally made.

Sliding Mode Control for a Nonlinear Phase-Field System

In the present contribution the sliding mode control (SMC) problem for a phase-field model of Caginalp type is considered. First we prove the well-posedness and some regularity results for the phase-field type state systems modified by the state-feedback control laws. Then, we show that the chosen SMC laws force the system to reach within finite time the sliding manifold (that we chose in order that one of the physical variables or a combination of them remains constant in time). We study three different types of feedback control laws: the first one appears in the internal energy balance and forces a linear combination of the temperature and the phase to reach a given (space dependent) value, while the second and third ones are added in the phase relation and lead the phase onto a prescribed target. While the control law is non-local in space for the first two problems, it is local in the third one, i.e., its value at any point and any time just depends on the value of the state.

Identification of a diffusion coefficient in strongly degenerate parabolic equations with interior degeneracy

We are concerned with the identification of the diffusion coefficient u(x) in a strongly degenerate parabolic diffusion equation. The strong degeneracy means that

An Asymptotic Solution to a Nonlinear Reaction-Diffusion System with Chemotaxis

{u \in W^{1,\infty}}

Identification for degenerate problems of hyperbolic type

u∈W1,∞, u vanishes at an interior point of the space domain and