Departament de Matemàtiques
http://hdl.handle.net/2117/3917
2016-02-11T11:23:20ZScience and technology in world exhibitions
http://hdl.handle.net/2117/82816
Science and technology in world exhibitions
Roca Rosell, Antoni Maria Claret
2016-02-11T09:21:30ZRoca Rosell, Antoni Maria ClaretGreen operators of networks with a new vertex
http://hdl.handle.net/2117/82783
Green operators of networks with a new vertex
Carmona Mejías, Ángeles; Encinas Bachiller, Andrés Marcos; Gago Álvarez, Silvia; Mitjana Riera, Margarida
Any elliptic operator defines an automorphism on the orthogonal subspace to the eigenfunctions associated with the lowest eigenvalue, whose inverse is the orthogonal Green operator. In this study, we show that elliptic Schrödinger operators on networks that have been obtained by adding a new vertex to a given network, can be seen as perturbations of the Schrödinger operators on the initial network. Therefore, the Green function of the new network can be computed in terms of the Green function of the original network.
2016-02-10T13:59:21ZCarmona Mejías, ÁngelesEncinas Bachiller, Andrés MarcosGago Álvarez, SilviaMitjana Riera, MargaridaAny elliptic operator defines an automorphism on the orthogonal subspace to the eigenfunctions associated with the lowest eigenvalue, whose inverse is the orthogonal Green operator. In this study, we show that elliptic Schrödinger operators on networks that have been obtained by adding a new vertex to a given network, can be seen as perturbations of the Schrödinger operators on the initial network. Therefore, the Green function of the new network can be computed in terms of the Green function of the original network.Recovering the conductances on grids
http://hdl.handle.net/2117/82775
Recovering the conductances on grids
Arauz Lombardia, Cristina; Carmona Mejías, Ángeles; Encinas Bachiller, Andrés Marcos; Mitjana Riera, Margarida
2016-02-10T13:11:22ZArauz Lombardia, CristinaCarmona Mejías, ÁngelesEncinas Bachiller, Andrés MarcosMitjana Riera, MargaridaA shared-parameter joint model for prostate cancer risk and psa longitudinal profiles
http://hdl.handle.net/2117/82670
A shared-parameter joint model for prostate cancer risk and psa longitudinal profiles
Serrat Piè, Carles; Rué, Montserrat; Perpiñán Fabuel, Hèctor; Forte, Anabel; Armero, Carmen; Piulachs, Xavier; Páez, Álvaro; Gómez Melis, Guadalupe
The paper describes the use of frequentist and Bayesian shared-parameter joint models of longitudinal measurements of prostate specific antigen (PSA) and the risk of prostate cancer (PCa). The motivating dataset corresponds to the screening arm of the Spanish branch of the European Randomized Screening for Prostate Cancer (ERSPC) study. The results show that PSA is highly associated with the risk of being diagnosed with PCa and that there is an age-varying effect of PSA on PCa risk. Both the frequentist and Bayesian paradigms produced very close parameter estimates and subsequent 95% confidence and credibility intervals. Dynamic estimations of disease-free probabilities obtained using Bayesian inference highlight the potential of joint models to guide personalized risk-based screening strategies.
2016-02-08T12:54:41ZSerrat Piè, CarlesRué, MontserratPerpiñán Fabuel, HèctorForte, AnabelArmero, CarmenPiulachs, XavierPáez, ÁlvaroGómez Melis, GuadalupeThe paper describes the use of frequentist and Bayesian shared-parameter joint models of longitudinal measurements of prostate specific antigen (PSA) and the risk of prostate cancer (PCa). The motivating dataset corresponds to the screening arm of the Spanish branch of the European Randomized Screening for Prostate Cancer (ERSPC) study. The results show that PSA is highly associated with the risk of being diagnosed with PCa and that there is an age-varying effect of PSA on PCa risk. Both the frequentist and Bayesian paradigms produced very close parameter estimates and subsequent 95% confidence and credibility intervals. Dynamic estimations of disease-free probabilities obtained using Bayesian inference highlight the potential of joint models to guide personalized risk-based screening strategies.Region-based approximation algorithms for visibility between imprecise locations
http://hdl.handle.net/2117/82487
Region-based approximation algorithms for visibility between imprecise locations
Buchin, Kevin; Kostitsyna, Irina; Löffler, Maarten; Silveira, Rodrigo Ignacio
In this paper we present new geometric algorithms for approximating the visibility between two imprecise locations amidst a set of obstacles, where the imprecise locations are modeled by continuous probability distributions. Our techniques are based on approximating distributions by a set of regions rather than on approximating by a discrete point sample. In this way we obtain guaranteed error bounds, and the results are more robust than similar results based on discrete point sets. We implemented our techniques and present an experimental evaluation. The experiments show that the actual error of our region-based approximation scheme converges quickly when increasing the complexity of the regions.
2016-02-03T11:58:09ZBuchin, KevinKostitsyna, IrinaLöffler, MaartenSilveira, Rodrigo IgnacioIn this paper we present new geometric algorithms for approximating the visibility between two imprecise locations amidst a set of obstacles, where the imprecise locations are modeled by continuous probability distributions. Our techniques are based on approximating distributions by a set of regions rather than on approximating by a discrete point sample. In this way we obtain guaranteed error bounds, and the results are more robust than similar results based on discrete point sets. We implemented our techniques and present an experimental evaluation. The experiments show that the actual error of our region-based approximation scheme converges quickly when increasing the complexity of the regions.Stabbing segments with rectilinear objects
http://hdl.handle.net/2117/82298
Stabbing segments with rectilinear objects
Claverol Aguas, Mercè; Garijo, Delia; Korman, Matias; Seara Ojea, Carlos; Silveira, Rodrigo Ignacio
We consider stabbing regions for a set S of n line segments in the plane, that is, regions in the plane that contain exactly one endpoint of each segment of S. Concretely, we provide efficient algorithms for reporting all combinatorially different stabbing regions for S for regions that can be described as the intersection of axis-parallel halfplanes; these are halfplanes, strips, quadrants, 3-sided rectangles, and rectangles. The running times are O(n) (for the halfplane case), O(n log n) (for strips, quadrants, and 3-sided rectangles), and O(n2 log n) (for rectangles).
2016-01-29T18:03:01ZClaverol Aguas, MercèGarijo, DeliaKorman, MatiasSeara Ojea, CarlosSilveira, Rodrigo IgnacioWe consider stabbing regions for a set S of n line segments in the plane, that is, regions in the plane that contain exactly one endpoint of each segment of S. Concretely, we provide efficient algorithms for reporting all combinatorially different stabbing regions for S for regions that can be described as the intersection of axis-parallel halfplanes; these are halfplanes, strips, quadrants, 3-sided rectangles, and rectangles. The running times are O(n) (for the halfplane case), O(n log n) (for strips, quadrants, and 3-sided rectangles), and O(n2 log n) (for rectangles).Disturbance decoupling problem for switched linear systems. A geometric approach
http://hdl.handle.net/2117/82288
Disturbance decoupling problem for switched linear systems. A geometric approach
García Planas, María Isabel
In this paper disturbance decoupling problem for switched linear systems is formulated under a geometrical
point of view. Necessary and sufficient conditions for the problem with standardizable condition to be
solvable are given
2016-01-29T12:57:45ZGarcía Planas, María IsabelIn this paper disturbance decoupling problem for switched linear systems is formulated under a geometrical
point of view. Necessary and sufficient conditions for the problem with standardizable condition to be
solvable are givenOverdetermined partial resolvent kernels for finite networks
http://hdl.handle.net/2117/82285
Overdetermined partial resolvent kernels for finite networks
Arauz Lombardia, Cristina; Carmona Mejías, Ángeles; Encinas Bachiller, Andrés Marcos
In [2], a study of the existence and uniqueness of solution of partial overdetermined boundary value problems for finite networks was performed. These problems involve Schrodinger operators and the novel feature is that no data are prescribed on part of the boundary, whereas both the values of the function and of its normal derivative are given on another part of the boundary. In the present work, we study the resolvent kernels associated with overdetermined partial boundary value problems on finite network and we express them in terms of the well-known Green operator and the Dirichlet-to-Robin map. Moreover, we analyze their main properties and we compute them in the case of a generalized cylinder. The obtained expression involve polynomials that can be seen as a generalization of Chebyshev polynomials, and indeed when the conductances along axes are constant the expressions for the overdetermined partial resolvent kernels are given in terms of second kind Chebyshev polynomials. (C) 2015 Elsevier Inc. All rights reserved.
2016-01-29T12:49:33ZArauz Lombardia, CristinaCarmona Mejías, ÁngelesEncinas Bachiller, Andrés MarcosIn [2], a study of the existence and uniqueness of solution of partial overdetermined boundary value problems for finite networks was performed. These problems involve Schrodinger operators and the novel feature is that no data are prescribed on part of the boundary, whereas both the values of the function and of its normal derivative are given on another part of the boundary. In the present work, we study the resolvent kernels associated with overdetermined partial boundary value problems on finite network and we express them in terms of the well-known Green operator and the Dirichlet-to-Robin map. Moreover, we analyze their main properties and we compute them in the case of a generalized cylinder. The obtained expression involve polynomials that can be seen as a generalization of Chebyshev polynomials, and indeed when the conductances along axes are constant the expressions for the overdetermined partial resolvent kernels are given in terms of second kind Chebyshev polynomials. (C) 2015 Elsevier Inc. All rights reserved.Problem A-20: A rational sum
http://hdl.handle.net/2117/82241
Problem A-20: A rational sum
Díaz Barrero, José Luis; Gibergans Baguena, José
2016-01-28T16:21:22ZDíaz Barrero, José LuisGibergans Baguena, JoséWeierstrass per ell mateix: alguns trets del seu pensament matemàtic
http://hdl.handle.net/2117/82230
Weierstrass per ell mateix: alguns trets del seu pensament matemàtic
Massa Esteve, Maria Rosa
El coneixement de Karl Weierstrass (1815-1897) a través dels teoremes que s’estudien a les classes de matemàtiques ens aporta una visió parcial del personatge.
En aquesta ponència es pretén enriquir aquesta visió apropant-nos tant a l’home com al matemàtic, des d’un altre vessant, a través de les seves paraules i dels seus deixebles.
Es reflexionarà sobre alguns trets característics de les contribucions de Weierstrass a la matemàtica, com ara la unitat del seu pensament matemàtic, la seva fonamentació aritmètica de l’Anàlisi i la seva cerca del rigor.
Presentació feta a la Jornada Weierstrass a l'FME: curs 2014-2015
2016-01-28T15:45:06ZMassa Esteve, Maria RosaEl coneixement de Karl Weierstrass (1815-1897) a través dels teoremes que s’estudien a les classes de matemàtiques ens aporta una visió parcial del personatge.
En aquesta ponència es pretén enriquir aquesta visió apropant-nos tant a l’home com al matemàtic, des d’un altre vessant, a través de les seves paraules i dels seus deixebles.
Es reflexionarà sobre alguns trets característics de les contribucions de Weierstrass a la matemàtica, com ara la unitat del seu pensament matemàtic, la seva fonamentació aritmètica de l’Anàlisi i la seva cerca del rigor.