### Seminari

### Prossimi Seminari

**Dealing with unreliable computing platforms at extreme scale**

Luc Giraud, INRIA (Inria Bordeaux – Sud-Ouest)

mercoledì 23 gennaio 2019 alle ore 14:00, Aula Consiglio VII Piano – Edificio 14, Dipartimento di Matematica POLITECNICO DI MILANO**Poroelasticity: Discretizations and fast solvers based on geometric multigrid methods**

Francisco José Gaspar Lorenz, Department of Applied Mathematics -Zaragoza University – Spain

giovedì 31 gennaio 2019 alle ore 14:00, Sala Consiglio VII Piano – Edificio 14, Dipartimento di Matematica POLITECNICO DI MILANO**Application of Polyconvexity and multivariable convexity of energy potentials in nonlinear solid mechanics**

Javier Bonet, University of Greenwich

giovedì 14 febbraio 2019 alle ore 14:00, Aula Consiglio VII Piano – Edificio 14, Dipartimento di Matematica POLITECNICO DI MILANO

### Seminari Passati

**Difetti in cristalli liquidi e proteine in membrane lipidiche: analisi variazionale dei sistemi complessi**

Paolo Biscari, Dip. di Matematica del Politecnico di Milano

mercoledì 1 ottobre 2003**Implicit-Explicit Runge-Kutta schemes and applications to hyperbolic systems with relaxation**

Giovanni Russo, Dipartimento di Matem. – Univ. di Catania

martedì 30 settembre 2003 alle ore 11:00, Aula Seminari MOX – 6° piano dip. di MatematicaABSTRACTWe consider implicit-explicit (IMEX) Runge Kutta methods for

hyperbolic systems of conservation laws with stiff relaxation

terms. Here we restrict our analysis to diagonally implicit Runge

Kutta (DIRK) schemes and consider schemes that are asymptotic

preserving (AP) and strong-stability-preserving (SSP) in the zero

relaxation limit. Accuracy and stability properties of these

schemes are studied both analytically and numerically. The IMEX

schemes are then combined with a weighted essentially non

oscillatory (WENO) finite difference strategy in space to obtain

fully discrete high order schemes. Several applications to

hyperbolic relaxation systems in stiff and non stiff regimes show

the efficiency and the robustness of the present approach.

**Emumerative problems inspired by Mayer’s theory of cluster integrals in thermodynamics.**

Pierre Leroux, Université du Québec a Montréal

venerdì 26 settembre 2003 alle ore 11:30, Dipartimento di Matematica – Politecnico di Milano**Ferromagnetic and Anti-Ferromagnetic Systems**

Jalal Shatah, Courant Institute of Mathematical Sciences, NY (U.S.A.)

martedì 23 settembre 2003 alle ore 17:00, Dipartimento di Matematica – Università degli Studi di Milano – Via Saldini 50 – Milano – Sala di RappresentanzaABSTRACTDispersive geometric evolution equations have received much attention in the past few decades. Some of these equations describe the dynamics of micromagnetics, vortex motion in liquid crystals, or vibrations of certain crystalline lattices. In this talk we will present some recent results on the equations describing ferromagnetic and anti-ferromagnetic materials concerning existence of solutions and the relation between anti-ferromagnetic equations (Schrodinger maps) and wave maps.**Equazioni di Volterra stocastiche**

Stefano Bonaccorsi, Universita di Trento

lunedì 22 settembre 2003 alle ore 15:00, Dipartimento di Matematica**Differential Geometry and the Control of Nonlinear Systems**

Kurt Schlacher, Johannes Kepler Universität, Linz (Austria)

lunedì 22 settembre 2003 alle ore 17:00, Dipartimento di Matematica – Università degli Studi di Milano – Via Saldini 50 – Milano – Sala di RappresentanzaABSTRACTControl theory makes significant progress, since nonlinear systems and differential geometry have been brought together about 30 years ago. The main advantage is that a description of the control system is avalaible, which does not require the choice of special coordinates. Now, many important properties of dynamic systems can be characterized in a geometric way. Within this framework nonlinear systems are considered as geometric objects, defined on smooth manifolds. E.g., a nonlinear control system can be identified with a submanifold of a certain geometric structure. Non observable or non accesible systems generate a foliation, and so on. This talk gives an introduction to the geometric description of nonlinear control systems, described by a set of ordinary differential equations. It starts with a short overview, where time invariant and time variant systems with or without control input are characterized by its geometric properties. At the same time a short introduction to the required mathematical tools will be presented. Having this preliminaries at our disposal we develop the concept of accessibility and observability by geometric ideas. It will turn our that this approach is not confined to explicit systems, on the contrary it can be generalized to more complex ones. Fortunately these methods are not only useful for the analysis of systems, where equivalence means that solutions of one system can be transformed to solutions of the other and vice versa. Using the idea that a dynamic system is also a certain sybmanifold, we show that equivalent systems describe the same submanifold in different coordinates only. From a systems designer’s point of view, it is important to construct equivalent systems such that the control loop design can be reduced to an already solved problem Finally, this talk finishes with an industrial application of the present methods. The hydraulic gap control of stands in steel rolling mills is a challenging task because of the intrinsic nonlinear behaviour of these systems. We present new design ideas and controllers and prove the performance by simulations and measurements taken in mills located in the US and Europe.**Finite element approximation to infinite Prandtl number Boussinesq equations with temperature dependent viscosity and its application to Earth s mantle convection problem**

Masahisa TABATA, Department of Mathematical Sciences- Kyushu Univer

giovedì 18 settembre 2003 alle ore 15:00, aula seminari MOX-6° piano dip. mat.ABSTRACTA stabilized finite element scheme for infinite Prandtl number Boussinesq

equations with temperature dependent viscosity is analyzed.

The domain is a spherical shell and the P1-element is employed for every

unknown function.

The finite element solution is proved to converge to the exact one in the

first order of the time increment and the mesh size.

The scheme is applied to Earth s mantle convection problems with

viscosities strongly dependent on the temperature and some numerical

results are shown.**Faà di Bruno formula and determinantal identities**

Chu Wenchang, Univ. degli Studi di Lecce

giovedì 18 settembre 2003 alle ore 00:00, CNR, via Bassini 15, Milano