Quaderni di Dipartimento
Collezione dei preprint del Dipartimento di Matematica.
La presenza del full-text è lacunosa per i prodotti antecedenti maggio 2006.
Trovati 868 prodotti
-
QDD13 - 15/02/2007
El-Shanawany R. A. ; Higazy M. Sh. ; Scapellato R.
Orthogonal Double Covers of Complete Bipartite Graphs by Symmetric Starters | Abstract | | Let H be a graph on n vertices and C a collection of n subgraphs of H, one for each vertex. Then C is an orthogonal double cover (ODC) of H if every edge of H occurs in exactly two members of C and any two members of C share exactly an edge whenever the corresponding vertices are adjacent in H. If all subgraphs in C are isomorphic to a given graph G, then C is said to be an ODC of H by G.
We construct the ODCs of the complete bipartite graph with two classes of n vertices by a
graph G which is the union of a m-path and
a (n-m)-star, where the center of the star is a one of the path ends, for all m=5,6,7,8,9,10. In all cases, G is a symmetric starter of the cyclic group of order n. |
-
QDD12 - 03/01/2007
Pierotti, D.
On the plane problem of the flow around a submerged beam | Abstract | | We consider the problem of the steady flow of an ideal heavy fluid around a submerged beam. The problem is obtained from the free-boundary problem of the flow past a submerged obstacle in the limit of bodies of vanishing thickness. We introduce a special Sobolev space formulation of the problem in term of a perturbed stream function and prove its unique solvability for every value of the unperturbed flow velocity, with the possible exception of a discrete set depending on the geometry of the domain. The asymptotic properties of the solutions are discussed. |
-
QDD11 - 19/12/2006
Guatteri, G.; Tessitore, G.
Backward Stochastic Riccati Equations and Infinite Horizon L-Q Optimal Control with Infinite Dimensional State Space and Random Coefficients | Abstract | | We study the Riccati equation (BSRE) arising in a class of quadratic optimal control problems with
infinite dimensional stochastic differential state equation and infinite horizon cost functional. We allow the coefficients, both in the state equation and in the cost, to be random.
In such a context BSREs are backward stochastic differential equations in the whole positive real axis that involve quadratic non-linearities and take values in a non-Hilbertian space. We prove existence of a minimal non-negative solution and, under additional assumptions, its uniqueness. We show that such a solution allows to perform the synthesis of the optimal control and investigate its
attractivity properties. Finally the case where the coefficients are stationary is addressed and an example concerning a controlled wave equation in random media is proposed. |
-
QDD10 - 18/12/2006
Carriero, M.; Leaci, A.; Tomarelli, F.
Candidate local minimizer of Blake & Zisserman functional (Appendix to QDD 9 (Euler equations for Blake & Zisserman functional)) | Abstract | | Almansi decomposition and explicit coefficients of asymptotic expansion around the origin for bi-harmonic functions in a disk with a crack are evaluated by simbolic computations with Mathematica 5.0 .
We deduce S.I.F. and modes coefficients of the leading term in the expansion for candidate local minimizer of Blake & Zisserman functional. |
-
QDD9 - 13/12/2006
Carriero, M. ; Leaci, A. ; Tomarelli, F.
Euler equations for Blake & Zisserman functional | Abstract | | We derive many necessary conditions for
minimizers of a functional depending on free discontinuities, free gradient discontinuities and second derivatives, which is related
to image segmentation.
A candidate for minimality of main part
of the functional is explicitly exhibited. |
-
QDD8 - 30/11/2006
Barchielli, A.; Lupieri, G.
Information gain in quantum continual measurements | Abstract | | Inspired by works on information transmission through quantum channels, we propose the use of a couple of mutual entropies to quantify the efficiency of continual measurement schemes in extracting information on the measured quantum system. Properties of these measures of information are studied and bounds on them are derived. |
-
QDD6 - 07/11/2006
Causin, P.; Sacco, R.
Static condensation procedures for hybridized mixed finite element methods | Abstract | | Stemming from the characterization of the static condensation procedure for mixed hybridized methods introduced in [9],[10], in this paper
we use Helmholtz decompositions to obtain a substructuring of the local mapping problems, in order to end up with simpler systems of reduced size. This procedure is effective especially when dealing with high degree or variable degree
approximations. Moreover, we extend the variational characterization of static condensation
to more general saddle-point formulations.
Two relevant examples of hybridized mixed methods are considered, namely, the classical Galerkin Dual-Mixed Hybridized scheme and the Discontinuous Petrov-Galerkin (DPG) scheme of [7]. |
-
QDD7 - 07/11/2006
Longaretti, M.; Marino, G.; Chini, B.; Jerome, J.W.; Sacco, R.
Computational models in nano-bio-electronics: simulation of ionic transport in voltage operated channels | Abstract | | In this article, a novel mathematical and computational model is proposed for the
numerical simulation of Voltage Operated ionic Channels (VOC) in Nano-Bio-Electronics applications.
This is a first step towards a multi-physics description of hybrid bio-electronical devices such as bio-chips.
The model consists of a coupled system of nonlinear partial differential equations, comprising a Poisson-Nernst-Planck system to account for electro-chemical phenomena, and a Navier-Stokes system to account for fluid-mechanical phenomena.
Suitable functional iteration techniques for problem decoupling and finite element methods for discretization are proposed and discussed. Numerical results on realistic VOCs illustrate the validity of the model and its accuracy by comparison with relevant computed channel equivalent electrical parameters with measured data. |
|
