Method of relaxation applied to optimization of discrete systems.
Méthode d'éléments finis pour le modèle des plaques en flexion de Naghdi-Reissner
Méthodes d'éléments finis quasilinéaires en déplacement pour l'étude de milieux incompressibles
Metodo della differenza ali'indietro e determinazione dei moduli tangenti per analisi evolutive elastoplastiche a passi finiti
Si discute l'applicazione di un procedimento per "differenza all'indietro" ("backward difference") all'integrazione numerica nel tempo di leggi costitutive elastoplastiche e se ne esaminano alcuni aspetti peculiari. Con riferimento a modelli costitutivi isotropi per i quali le funzioni di snervamento dipendono dall'invariante primo delle tensioni, dall'invariante secondo del deviatore delle tensioni e da opportune variabili interne, si ricavano le relazioni non lineari implicite in termini di incrementi...
Microlocal analysis and seismic imaging
We study certain Fourier integral operators arising in the inversion of data from reflection seismology.
Microscopic Modelling of Active Bacterial Suspensions
We present two-dimensional simulations of chemotactic self-propelled bacteria swimming in a viscous fluid. Self-propulsion is modelled by a couple of forces of same intensity and opposite direction applied on the rigid bacterial body and on an associated region in the fluid representing the flagellar bundle. The method for solving the fluid flow and the motion of the bacteria is based on a variational formulation written on the whole domain, strongly...
Minimization of a convex quadratic function subject to separable conical constraints in granular dynamics
The numerical solution of granular dynamics problems with Coulomb friction leads to the problem of minimizing a convex quadratic function with semidefinite Hessian subject to a separable conical constraints. In this paper, we are interested in the numerical solution of this problem. We suggest a modification of an active-set optimal quadratic programming algorithm. The number of projection steps is decreased by using a projected Barzilai-Borwein method. In the numerical experiment, we compare our...
Minimizers with topological singularities in two dimensional elasticity
For a class of 2-D elastic energies we show that a radial equilibrium solution is the unique global minimizer in a subclass of all admissible maps. The boundary constraint is a double cover of ; the minimizer is and is such that vanishes at one point.
Minimizers with topological singularities in two dimensional elasticity
For a class of 2-D elastic energies we show that a radial equilibrium solution is the unique global minimizer in a subclass of all admissible maps. The boundary constraint is a double cover of S1; the minimizer u is C1 and is such that vanishes at one point.
Mixed finite element analysis of semi-coercive unilateral contact problems with given friction
A unilateral contact 2D-problem is considered provided one of two elastic bodies can shift in a given direction as a rigid body. Using Lagrange multipliers for both normal and tangential constraints on the contact interface, we introduce a saddle point problem and prove its unique solvability. We discretize the problem by a standard finite element method and prove a convergence of approximations. We propose a numerical realization on the basis of an auxiliary “bolted” problem and the algorithm of...
Mixed finite element approximation of 3D contact problems with given friction : error analysis and numerical realization
This contribution deals with a mixed variational formulation of 3D contact problems with the simplest model involving friction. This formulation is based on a dualization of the set of admissible displacements and the regularization of the non-differentiable term. Displacements are approximated by piecewise linear elements while the respective dual variables by piecewise constant functions on a dual partition of the contact zone. The rate of convergence is established provided that the solution...
Mixed finite element approximation of 3D contact problems with given friction: Error analysis and numerical realization
This contribution deals with a mixed variational formulation of 3D contact problems with the simplest model involving friction. This formulation is based on a dualization of the set of admissible displacements and the regularization of the non-differentiable term. Displacements are approximated by piecewise linear elements while the respective dual variables by piecewise constant functions on a dual partition of the contact zone. The rate of convergence is established provided that the solution...
Mixed finite element discretization of some variational inequalities arising in elasticity problems in domains with cracks.
Mixed finite element methods for elastic rods of arbitrary geometry.
Mixed Finite Elements in IR3 .
Mixed formulation for elastic problems - existence, approximation, and applications to Poisson structures
A mixed formulation is given for elastic problems. Existence and uniqueness of the discretized problem are given for conformal continuous interpolations for the stress tensor components and for the components of the displacement vector. A counterpart of the problem is discussed in the case of an even-dimensional Euclidean space with an associated Hamiltonian vector field and the Poisson structure. For conformal interpolations of the same order the question remains open.
Mixed formulations for a class of variational inequalities
A general setting is proposed for the mixed finite element approximations of elliptic differential problems involving a unilateral boundary condition. The treatment covers the Signorini problem as well as the unilateral contact problem with or without friction. Existence, uniqueness for both the continuous and the discrete problem as well as error estimates are established in a general framework. As an application, the approximation of the Signorini problem by the lowest order mixed finite element...
Mixed formulations for a class of variational inequalities
A general setting is proposed for the mixed finite element approximations of elliptic differential problems involving a unilateral boundary condition. The treatment covers the Signorini problem as well as the unilateral contact problem with or without friction. Existence, uniqueness for both the continuous and the discrete problem as well as error estimates are established in a general framework. As an application, the approximation of the Signorini problem by the lowest order mixed finite element...
Mixed control of flexible structures.
Mixed interface problems for anisotropic elastic bodies.