Volume 23 - 2016 - Special issue for LEM2I 2016

Editors : Mourad Bellassoued, Nabil Gmati , Mohamed Jaoua, and Gilles Lebeau

1. Solvability of Mixed Problems With Integral Condition for Singular Parabolic Equations

Almomani, Raid.
In this paper we proved the existance and uniqness of strong generalized solution of mixed problems wih integral condition for singular parabolic equaions depending on a theorem proved in [1] in which a priori estimaion of the solution for such problems was derived.

2. Inverse heat source problem for a coupled hyperbolic-parabolic system

Bellassoued, Mourad ; Riahi, Bochra.
Dans ce papier, on a prouvé une estimation de stabilité de type Höldérienne pour un problème inverse de détermination du terme source de l'équation de la chaleur à l'aide d'une inégalité de Carleman pour un système d'équations hyperbolique-parabolique couplé. ABSTRACT. In this paper we consider a coupled system of mixed hyperbolic-parabolic type which describes the Biot consolidation model in poro-elasticity. Using a local Carleman estimate for a coupled hyperbolic-parabolic system, we prove the uniqueness and a Hölder stability in determining the heat source by a single measurement of solution over ω × (0, T), where T > 0 is a sufficiently large time and a suitable subbdomain ω ⊂ Ω such that ∂ω ⊃ ∂Ω. MOTS-CLÉS : Problème inverse, estimation de Carleman, système couplet

3. Inverse Problem: Stability for the aligned magnetic field by the Dirichlet-to-Neumann map for the wave equation in a periodic quantum waveguide

Youssef, Mejri.
Dans ce papier, on a prouvé une estimation de stabilité pour le problème inverse de dé-termination du champ magnétique dans l'équation des ondes donné sur un domaine non borné à partir de l'opérateur de Dirichlet-to-Neumann. On a montré un résultat de stabilité pour ce problème inverse, dont la démonstration est basée sur la construction de solutions optique géométrique pour l'équation des ondes avec un potentiel magnétique 1-périodique. ABSTRACT. We consider the boundary inverse problem of determining the aligned magnetic field appearing in the magnetic wave equation in a periodic quantum cylindrical waveguide from boundary observations. The observation is given by the Dirichlet to Neumann map associated to the wave equation. We prove by means of the geometrical optics solutions of the magnetic wave equation that the knowledge of the Dirichlet-to-Neumann map determines uniquely the aligned magnetic field induced by a time independent and 1-periodic magnetic potential. We establish a Hölder-type stability estimate in the inverse problem.

4. An alternative algorithm for regularization of noisy volatility calibration in Finance

Ibtissam, Medarhri ; Rajae, Aboulaich ;  Naima, Debit.
This contribution is an extension of the work initiated in [1], presenting a strategy for the calibration of the local volatility. Due to Morozov's discrepancy principle [6], the Tikhonov regularization problem introduced in [7] is understood as an inequality-constrained minimization problem. An Uzawa procedure is proposed to replace this latter by a sequence of unconstrained problems dealt with in the modified Thikonov regularization procedure in [1]. Numerical tests confirm the consistency of the approach and the significant speed-up of the process of local volatility determination.

5. Coupling Parareal with Non-Overlapping Domain Decomposition Method

In this paper, we present a new parallel algorithm for time dependent problems based on coupling parareal with non-overlapping domain decomposition method in order to increase parallelism in time and in space. For this we focus on the iterative methods of parallization in space to solve the interface problem like Neumann-Neumann method. In the new algorithm, the coarse temporel propagator is defined on the global domain and the Neumann-Neumann method is chosen as a fine propagator with a few iterations. We present the rigorous convergence analysis of the new coupled algorithm on bounded time interval. Numerical experiments illustrate the performance of this new algorithm and confirm our analysis. RÉSUMÉ. Dans ce papier, nous présentons un nouvel algorithme parallèle pour les problèmes dé-pendant du temps basé sur le couplage du pararéel avec les méthodes de décomposition de domaine sans recouvrement afin d'augmenter le parallélisme dans le temps et l'espace. Nous nous concen-trons sur les méthodes itératives de parallélisation en espace pour résoudre le problème d'interface par la méthode de Neumann-Neumann. Dans ce nouvel algorithme, le propagateur grossier est dé-finie sur le domaine global et la méthode de Neumann-Neumann est choisi pour le propagateur fin avec quelques itérations. Nous présentons l'analyse rigoureuse de convergence du nouvel algorithme couplé sur un intervalle de temps borné. Des expèriences numériques illustrent les performances de ce nouvel algorithme […]


Bellassoued, Mourad ; Ben Aicha, Ibtissem.
This paper deals with an hyperbolic inverse problem of determining a time-dependent coefficient a appearing in a dissipative wave equation, from boundary observations. We prove in dimension n greater than two, that a can be uniquely determined in a precise subset of the domain, from the knowledge of the Dirichlet-to-Neumann map.

7. Reconstruction of missing boundary conditions from partially overspecified data : the Stokes system

Ben Abda, Amel ; Khayat, Faten.
We are interested in this paper with the ill-posed Cauchy-Stokes problem. We consider a data completion problem in which we aim recovering lacking data on some part of a domain boundary , from the knowledge of partially overspecified data on the other part. The inverse problem is formulated as an optimization one using an energy-like misfit functional. We give the first order opti-mality condition in terms of an interfacial operator. Displayed numerical results highlight its accuracy.

8. Regular Bohr-Sommerfeld quantization rules for a h-pseudo-differential operator. The method of positive commutators

Ifa, Abdelwaheb ; Rouleux, Michel.
We revisit in this Note the well known Bohr-Sommerfeld quantization rule (BS) for a 1-D Pseudo-differential self-adjoint Hamiltonian within the algebraic and microlocal framework of Helffer and Sjöstrand; BS holds precisely when the Gram matrix consisting of scalar products of some WKB solutions with respect to the " flux norm " is not invertible.

9. Chemotherapy models

Charif, Fayssal ; Helal, Mohamed ; Lakmeche, Abdelkader.
A chemotherapeutic treatment model for cell population with resistant tumor is considered. We consider the case of two drugs one with pulsed effect and the other one with continuous effect. We investigate stability of the trivial periodic solutions and the onset of nontrivial periodic solutions by the mean of Lyapunov-Schmidt bifurcation.