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Direttore Vicario: Prof. Gabriele Grillo
Responsabile Gestionale: Dr.ssa Franca Di Censo

 Seminari

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Prossimi Seminari

  • Working with compositional data in coordinates
    Eva Fiserova, Palacky University Olomouc, Czech Republic
    mercoledì 21 novembre 2018 alle ore 14:30, aula Saleri VI piano
  • Illuminazione, visione e opere d’arte: il punto di vista del fisico
    Farini Alessandro, Istituto Nazionale di Ottica, CNR, Firenze
    mercoledì 21 novembre 2018 alle ore 15:00, Sala Consiglio VII piano
  • An overview of some mathematical and computational problems in Network Science
    Michele Benzi, Scuola Normale Superiore, Pisa
    giovedì 22 novembre 2018 alle ore 14:00,  Aula Consiglio VII Piano – Edificio 14, Dipartimento di Matematica POLITECNICO DI MILANO
  • BIRATIONAL EQUIVALENCE OF ALGEBRAIC VARIETIES
    Shigefumi Mori, Kyoto University Institute of Advanced Study
    lunedì 26 novembre 2018 alle ore 16:30, Aula Chisini, Diparimento di Matematica, Via C. Saldini 50
  • The Quantitative Alexandrov Theorem in Space forms
    Luigi Vezzoni, Università degli Studi di Torino
    martedì 27 novembre 2018 alle ore 15:15, Aula seminari 3° piano
  • First Principles Determination of Reaction Rates
    Carlo Cavallotti, Dipartimento di Chimica, Materiali e Ingegneria Chimica, “G. Natta”, Politecnico di Milano
    martedì 27 novembre 2018 alle ore 10:30, aula Saleri VI piano
  • Emodinamica della circolazione epatica: problemi e nuove acquisizioni
    Massimiliano Tuveri, Azienda Ospedaliera Universitaria Integrata, Verona, Italy
    giovedì 29 novembre 2018 alle ore 11:30, aula consiglio VII piano
  • Characterization of Attraction Domains for Generic Quantum Semigroups
    Damiano Poletti, Politecnico di Milano
    giovedì 29 novembre 2018 alle ore 14:30 precise, Aula Seminari III piano

Seminari Passati

  • La freccia del tempo: una direzione per lo studio della termodinamica
    Giovanni Valente, Dipartimento di Matematica, Politecnico di Milano
    mercoledì 17 ottobre 2018 alle ore 14:45 precise, Sala Consiglio VII piano
    ABSTRACT
    Ovunque nel mondo fisico che ci circonda osserviamo fenomeni irreversibili, che accadono in una direzione temporale ma non in quella opposta. Tale asimmetria è proprio ciò che ci permette di distinguere il passato dal futuro. Tuttavia, le leggi che governano la dinamica dei costituenti microscopici della materia risultano simmetriche rispetto alla direzione del tempo, e come tali appaiono in conflitto con l’irreversibilità osservata a livello macroscopico. Si pone così il problema filosofico della freccia del tempo. In questa presentazione, inseguiremo la freccia del tempo attraverso lo sviluppo di teorie fisiche come la termodinamica e la meccanica statistica.
  • On the error bound in the normal approximation for Jack measures
    Louis H. Y. Chen, National University of Singapore
    venerdì 12 ottobre 2018 alle ore 14:00 precise, Aula Seminari III piano
    ABSTRACT
    The one?parameter family of Jack_? measures on partitions of n is an important discrete analog of Dyson’s ? ensembles of random matrix theory.  Except for ? = ½, 1, 2, which have group theoretic interpretations, the Jack_ ? measure is difficult to analyze. In the case ? = 1, the Jack measure agrees with the Plancherel measure on the irreducible representations of the 
    symmetric group S_n, parametrized by the partitions of n.  The normal approximation for the 
    character ratio evaluated at the transposition (12) under the Plancherel measure has been well 
    studied, notably by Fulman (2005, 2006) and Shao and Su (2006).  A generalization of the 
    character ratio under the Jack_ ? measure has also been studied by Fulman (2004, 2006) and 
    Fulman and Goldstein (2011).  In this talk, we present results on both uniform and non?uniform 
    error bounds on the normal approximation for the Jack_ ? measure for ? > 0.   Our results 
    improve those in the literature and come very close to solving a conjecture of Fulman (2004).  
    Our proofs use Stein’s method and zero?bias coupling. This talk is based on joint work with Le 
    Van Thanh. 
  • Statistical modeling and monitoring of product and process quality in Additive Manufacturing: opportunities and challenges
    Bianca Maria Colosimo, Dipartimento di Meccanica, Politecnico di Milano
    giovedì 11 ottobre 2018 alle ore 14:00,  Aula Consiglio VII Piano – Edificio 14, Dipartimento di Matematica POLITECNICO DI MILANO
    ABSTRACT
    Additive Manufacturing (AM), commonly known as three-dimensional printing, is widely recognized as a disruptive technology, and has the potential to fundamentally change the nature of future manufacturing. Building products layer-by-layer, AM represents a paradigm shift in manufacturing with many industrial applications. It enables production of huge varieties of customized products with considerable geometric complexity, and the same time, with extended capabilities and functional performances.
    Despite tremendous enthusiasm, AM faces major research challenges for widespread adoption of this innovative technology. Specifically, addressing the unique challenges associated with quality engineering of AM processes is crucial to the eventual success of AM. This talk presents an overview of quality-related issues for AM processes and products, focusing on opportunities and challenges in quality inspection, monitoring, control.

    Contact: piercesare.secchi@polimi.it
  • Caputo Evolution Equations with time-nonlocal initial condition
    Lorenzo Toniazzi, University of Warwick
    martedì 9 ottobre 2018 alle ore 15:15, Aula Seminari 3° piano
    ABSTRACT
    Consider the Caputo evolution equation (EE) $\partial_t^\beta u =\Delta u$ with initial condition $\phi$ on $\{0\}\times\mathbb R^d$, $\beta\in(0,1)$. As it is well known, the solution reads $u(t,x)=\mathbf E_x[\phi(B_{E_t})]$. Here $B_t$ is a Brownian motion and the independent time-change $E_t$ is an inverse $\beta$-stable subordinator. The fractional kinetic $B_{E_t}$ is a popular model for subdiffusion \cite{Meerschaert2012}, with remarkable universality properties \cite{BC11,Hai18}.\
    We substitute the Caputo fractional derivative $\partial_t^\beta$ with the Marchaud derivative. This results in a natural extension of the Caputo EE featuring a \emph{time-nonlocal initial condition} $\phi$ on $(-\infty,0]\times\mathbb R^d$. We derive the new stochastic representation for the solution, namely $u(t,x)=\mathbf E_x[\phi(-W_t,B_{E_t})]$. This stochastic representation has a pleasing interpretation due to the non-obvious presence of $W_t$, elucidating the notion of time-nonlocal initial conditions. Here $W_t$ denotes the waiting/trapping time of the fractional kinetic $B_{E_t}$. We discuss classical-wellposedness \cite{T18}, and time permitting weak-wellposedness \cite{DYZ17,DTZ18} for the respective extensions of Caputo-type EEs (such as in \cite{chen,HKT17}).

    Bibliography:


    Barlow, \u Cern\’y (2011). Probability theory and related fields, 149.3-4: 639-673.


    Chen, Kim, Kumagai, Wang (2017). arXiv:1708.05863.


    Du, Toniazzi, Zhou (2018). Preprint. Submitted in Sept. 2018.


    Du, Yang, Zhou (2017). Discrete and continuous dynamical systems series B, Vol 22, n. 2.


    Hairer, Iyer, Koralov, Novikov, Pajor-Gyulai (2018). The Annals of Probability, 46(2), 897-955.


    Hern\’andez-Hern\’andez, Kolokoltsov, Toniazzi (2017). Chaos, Solitons \& Fractals, 102, 184-196.


    Meerschaert, Sikorskii (2012). De Gruyter Studies in Mathematics, Book 43.


    Toniazzi (2018). To appear in: Journal of Mathematical Analysis and Applications. arXiv:1805.02464.
  • Computational Prediction of Blood Damage
    Marek Behr, Chair for Computational Analysis of Technical Systems Faculty of Mechanical Engineering, RWTH Aachen
    lunedì 1 ottobre 2018 alle ore 14:00, Aula Consiglio VII Piano – Edificio 14, Dipartimento di Matematica POLITECNICO DI MILANO
    ABSTRACT
    Modeling and computational analysis play an increasingly important role in bioengineering, particularly in the design of implantable ventricular assist devices (VAD) and other blood-handling devices. Numerical simulation of blood flow and associated physiological phenomena has the potential to shorten the design cycle and give the designers important insights into causes of blood damage and suboptimal performance. A set of modeling techniques is presented which are based on stabilized space-time finite element formulation of the Navier-Stokes equations. Alternate methods that represent the rotating components in an averaged sense using a rotating frame of reference will be discussed. In order to obtain quantitative hemolysis prediction, cumulative tensor-based measures of strain experienced by individual blood cells must be developed; red blood cells under shear can be modeled as deforming droplets, and their deformation tracked throughout the flow volume. The methods are applied to a simplified rotary blood pump, which is currently a subject of an inter-laboratory round-robin study.

    Contact: luca.dede@polimi.it
  • Space-Time Adaptive THMC Simulation with Hybrid FEM-FVM Methods Applied to CO2 Geo-Sequestration
    Stephan Matthai, Peter Cook Centre for CCS, The University of Melbourne at Parkville, VIC 3010, Australia
    giovedì 27 settembre 2018 alle ore 14:00, Aula Seminari ‘Saleri’ VI Piano MOX-Dipartimento di Matematica, Politecnico di Milano – Edificio 14
    ABSTRACT
    Modelling the highly localised plume spreading during CO2 geo-sequestration using conventional synchronous time-driven simulation (TDS) has been impeded by the stringent Courant-Fredrich-Levy (CFL) condition, which leads to an excessive number of time steps and consequently long computing times. To overcome this problem, we present an asynchronous discrete event simulation (DES) scheme based on local time stepping criteria, specifically developed for the CSMP++ CO2 geo-sequestration simulator. The proposed DES method is applied to a complex and heterogeneous heuristic CO2 storage model, where it proves that DES is able to concentrate the computational effort on the active regions where fast CO2 flow occurs. As a result, the execution time for the modelling of a 5-year injection is significantly reduced from over 91 days (estimated for TDS) to only 0.5 days. This dramatic speedup facilitates the modelling of CO2 injection and long-term plume spreading behaviours at the scales of field storage sites. The benefits of the new method scale with the level of refinement of geologic detail and include a distinct increase in the level of physical realism of the simulations because fast and slow events are equally well resolved in contrast with TDS implicit schemes which are robust, but fail to resolve the events captured by the new asynchronous scheme.

    Contact: paolo.zunino@polimi.it
  • Coupled problems in Environmental and medical applications
    Hiroshi Suito, Mathematical Science Group, Advanced Institute for Materials Research, Tohoku University, Japan
    martedì 18 settembre 2018 alle ore 14:00, Aula Consiglio VII Piano – Edificio 14, Dipartimento di Matematica POLITECNICO DI MILANO
    ABSTRACT
    Fluid–structure interaction (FSI) problems arise under various circumstances including environmental and medical applications. This talk firstly presents numerical simulations for motions of aquatic plants interacting with surrounding fluids using immersed boundary method (IBM) with finite-difference approximation on fixed meshes. We also present simulations for blood flows in aorta solved on finite-element meshes moving with the vessel wall. Aortic aneurysms and aortic coarctations are considered here. Geometrical characteristics such as curvature and torsion help us to understand the essential difference for morphologies among patients. The latter problem is followed by a machine learning approach by which wall shear stress and oscillatory shear index distributions are estimated using geometrical characteristics of the vessels.

    Contact: alfio.quarteroni@polimi.it
  • An inverse boundary value problem arising from cardiac electrophisiology
    Luca Ratti, Politecnico di Milano
    martedì 18 settembre 2018 alle ore 15:15, Politecnico di Milano, Dipartimento di Matematica, Aula Seminari 3° Piano
    ABSTRACT
    The cardiac electrical activity can be comprehensively described throughout the monodomain model, consisting of a semilinear parabolic equation coupled with a nonlinear ordinary differential equation.

    In my talk, I will introduce the inverse problem of identifying conductivity inhomogeneities in the monodomain system, taking advantage of data acquired on the boundary of the domain. Due to the complexity of the task, I will first tackle the stationary counterpart of the problem, regarding which it is possible to formulate well-posedness results both for the forward and for the inverse problem, and to rigorously introduce reconstruction procedures. Similar results are then generalized to the full complexity of the original model.


    Throughout the presentation, I will focus on the problem of localizing small size inhomogeneities, as well as arbitrarily large ones, by means of the constraint optimization of a suitable misfit functional. The first task is achieved by relying on an asymptotic expansion of the boundary voltage with respect to the size of the inclusion, and employing tools from the topological optimization theory. The second issue is analyzed by means of the regularization theory of inverse problems and introducing a convenient relaxation of the optimization problem. The theoretical results are supported by numerical experiments, which are exhaustively reported.


    This is a joint work with Elena Beretta, Cristina Cerutti, Cecilia Cavaterra, Andrea Manzoni and Marco Verani.