Quaderni di Dipartimento
Collezione dei preprint del Dipartimento di Matematica.
La presenza del full-text è lacunosa per i prodotti antecedenti maggio 2006.
Trovati 866 prodotti
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QDD103 - 24/06/2011
Ieva, F.;Paganoni,A.M.;Pigoli,D.;Vitelli,V.
Multivariate Functional Clustering for the Morphological Analysis of ECG Curves | Abstract | | Cardiovascular ischemic diseases are one of the main causes of death all over the world. In this kind of pathologies, it is fundamental to be well-timed in order to obtain good prognosis in reperfusive treatment. In particular, an automatic classification procedure based on statistical analyses of tele-transmitted ECG traces would be very helpful for an early diagnosis. This work presents an analysis on
electrocardiographic (ECG) traces (both physiological and pathological ones) of patients whose 12-leads pre-hospital ECG has been sent by life supports to 118 Dispatch Center of Milan. The statistical analysis starts with a preprocessing step, in which functional data are reconstructed from noisy observations and biological variability is removed by a non linear registration procedure. Then, a multivariate
functional k-means clustering is carried out on reconstructed and registered ECG curves and their first derivatives. Hence, a new semi-automatic diagnostic procedure, based on the sole ECG’s morphology, is proposed to classify ECG traces
and the performance of this classification method is evaluated. |
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QDD102 - 23/06/2011
Maddalena, F.; Percivale, D.; Tomarelli, F.
Elastic structures in adhesion interaction | Abstract | | We study a variational model describing the interaction of two 1-dimensional elastic bodies through an adhesive layer, with the
aim of modeling a simplified CFRP structure: e.g. a concrete beam or a medical rehabilitation device glued to a reinforcing polymeric fiber. Different constitutive assumptions for the adhesive layer are investigated: quadratic law and two kinds of softening law. In all cases properties of the equilibrium states of the structural system are analytically deduced.
In the case of adhesion with softening, the minimum length of the elastic fiber avoiding debonding failure is estimated in terms of glue carrying capacity and the constitutive parameter of the fiber. |
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QDD101 - 09/06/2011
Gazzola, F.; Pavani, R.
Blow up oscillating solutions to some nonlinear fourth order differential equations | Abstract | | We give strong theoretical and numerical evidence that solutions to some nonlinear fourth order ordinary differential equations blow up in finite time with infinitely many wild oscillations. We exhibit an explicit example where this phenomenon occurs.
We discuss possible applications to biharmonic partial differential equations and to the suspension bridges model. In particular, we give a possible new explanation of the collapse of bridges. |
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QDD100 - 30/05/2011
Barutello, V.; Terracini, S.; Verzini, G.
Entire Parabolic Trajectories as Minimal Phase Transitions | Abstract | | For the class of anisotropic Kepler problems in any spatial dimension, with homogeneous potentials, we seek parabolic trajectories having prescribed asymptotic directions at infinity and which, in addition, are Morse minimizing geodesics for the Jacobi metric. Such trajectories correspond to saddle heteroclinics on the collision manifold, are structurally unstable and appear only for a codimension-one submanifold of such potentials. We give them a variational characterization in terms of the behavior of the parameter-free minimizers of an associated obstacle problem. We then give a full characterization of such a codimension-one manifold of potentials and we show how to parameterize it with respect to the degree of homogeneity. |
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QDD99 - 26/05/2011
Raimondi, M.; Causin, P.; Mara, A.; Nava, M.; Lagana , M.; Sacco, R.
Breakthroughs in Computational Modeling of Cartilage Regeneration in Perfused Bioreactors | Abstract | | We report about two specific breakthroughs, relevant to the mathematical modelling and numerical simulation of tissue growth in the context of cartilage tissue engineering in vitro. The proposed models are intended to form the building blocks of a bottom-up multiscale analysis of tissue growth, the idea being that a full Microscale analysis of the construct, a 3D PDE problem with internal moving boundaries, is computationally unaffordable. We propose to couple a PDE Microscale model of a single functional tissue sub-unit with the information computed at the Macroscale by 2D-0D models of reduced computational cost. Preliminary results demonstrate the effectiveness of the proposed models in describing the interplay among interstitial perfusion flow, nutrient delivery and consumption and tissue growth in realistic scaffold geometries. |
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QDD98 - 19/05/2011
Fragalà, I.; Gazzola, F.; Kawohl, B.
Overdetermined problems for the $ infty$-Laplacian and web functions | Abstract | | We give necessary and sufficient conditions for functions to be solutions to overdetermined problems for the equation $- Delta_ infty u=1$ in a bounded domain of $R^n$. To this end, we introduce a P-function for the study of the Dirichlet problem and we make use of its properties. |
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QDD94 - 06/05/2011
Bertacchi, D.; Zucca, F.
Recent results on branching random walks | Abstract | | This paper is a collection of recent results on discrete-time and continuous-time branching random walks.
Some results are new and others are known. Many aspects of this theory are considered: local, global and strong local survival,
the existence of a pure global survival phase and the approximation of branching random walks by means of multitype contact processes or spatially confined branching random walks.
Most results are obtained using a generating function approach: the probabilities of extinction are seen as fixed points of an infinite dimensional power series. Throughout this paper we provide many nontrivial examples and
counterexamples. |
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QDD95 - 06/05/2011
Bonforte, M.; Gazzola, F.; Grillo G.; Vazquez J.L.
Classification of radial solutions to the Emden-Fowler equation on the hyperbolic space | Abstract | | We study the Emden-Fowler equation on the hyperbolic n-dimensional space. We are interested in radial solutions, namely solutions depending only on the geodesic distance from a given point. The critical exponent for such equation is p=(n+2)/(n-2) as in the Euclidean setting, but the properties of the solutions show striking differences with the Euclidean case. |
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