Recursos de colección

Archivo Digital UPM (109.118 recursos)

This is an institutional repository providing access to the research output of the institution. Primarily contains thesis.

Materia = Matemáticas

Mostrando recursos 1 - 20 de 906

  1. On the approximate parametrization problem of algebraic curves.

    Sendra Pons, Juana; Rueda Pérez, Sonia Luisa; Sendra Pons, Juan Rafael
    The problem of parameterizing approximately algebraic curves and surfaces is an active research field, with many implications in practical applications. The problem can be treated locally or globally. We formally state the problem, in its global version for the case of algebraic curves (planar or spatial), and we report on some algorithms approaching it, as well as on the associated error distance analysis.

  2. A combined algorithm for analyzing structural controllability and observability of complex networks

    Úbeda Medina, Luis; Herrera Yagüe, Carlos; Barriales Valbuena, Iker; Zufiria Zatarain, Pedro Jose; Congosto Martínez, Mariluz
    In this paper a combined algorithm for analyzing structural controllability and observability of complex networks is presented. The algorithm addresses the two fundamental properties to guarantee structural controllability of a system: the absence of dilations and the accessibility of all nodes. The first problem is reformulated as a Maximum Matching search and it is addressed via the Hopcroft- Karp algorithm; the second problem is solved via a new wiring algorithm. Both algorithms can be combined to efficiently determine the number of required controllers and observers as well as the new required connections in order to guarantee controllability and observability in real complex networks. An application to...

  3. Knowledge-based spatiotemporal linear abstraction

    Shahar, Yuval; Molina, Martin
    We present a theoretical framework and a case study for reusing the same conceptual and computational methodology for both temporal abstraction and linear (unidimensional) space abstraction, in a domain (evaluation of traffic-control actions) significantly different from the one (clinical medicine) in which the method was originally used. The method, known as knowledge-based temporal abstraction, abstracts high-level concepts and patterns from time-stamped raw data using a formal theory of domain-specific temporal-abstraction knowledge. We applied this method, originally used to interpret time-oriented clinical data, to the domain of traffic control, in which the monitoring task requires linear pattern matching along both space and...

  4. P-adaptive boundary elements for three-dimensional potential problems

    Cerrolaza Rivas, Miguel; Alarcón Álvarez, Enrique
    This paper deals with the boundary element method (BEM) p-convergence approach applied to three-dimensional problems governed by Laplace's equation. The advantages derived from the boundary discretization and hierarchical interpolation functions are collated in order to minimize human effort in preparation of input data and improve numerical results.

  5. Intelligent Therapy Assistant (ITA) for cognitive rehabilitation in patients with Acquired Brain Injury

    Solana Sánchez, Javier; Cáceres Taladriz, César; García Molina, A.; Chausa Fernández, Paloma; Opisso, Eloy; Roig Rovira, Teresa; Menasalvas Ruiz, Ernestina; Tormos Muñoz, José M.; Gómez Aguilera, Enrique J.
    This paper presents the design, development and first evaluation of an algorithm, named Intelligent Therapy Assistant (ITA), which automatically selects, configures and schedules rehabilitation tasks for patients with cognitive impairments after an episode of Acquired Brain Injury. The ITA is integrated in "Guttmann, Neuro Personal Trainer" (GNPT), a cognitive tele-rehabilitation platform that provides neuropsychological services.

  6. A new dominance intensity method to deal with ordinal information about a DM's preferences within MAVT

    Aguayo Garcia, Ernesto Aaron; Mateos Caballero, Alfonso; Jiménez Martín, Antonio
    Dominance measuring methods are a new approach to deal with complex decision-making problems with imprecise information. These methods are based on the computation of pairwise dominance values and exploit the information in the dominance matrix in dirent ways to derive measures of dominance intensity and rank the alternatives under consideration. In this paper we propose a new dominance measuring method to deal with ordinal information about decision-maker preferences in both weights and component utilities. It takes advantage of the centroid of the polytope delimited by ordinal information and builds triangular fuzzy numbers whose distances to the crisp value 0 constitute...

  7. Motores Alternativos : Software

    Velázquez López, Ángel Gerardo; Arias Pérez, Juan Ramón
    Software del libro Motores Alternativos

  8. Medidas experimentales de la complejidad computacional de un código autoadaptativo HP para problemas abiertos acelerado mediante ACA

    Gómez Revuelto, Ignacio; Barrio Garrido, Rosa María; García Castillo, Luis Emilio; Salazar Palma, Magdalena
    The aim of the novel experimental measures presented in this paper is to show the improvement achieved in the computation time for a 2D self-adaptive hp finite element method (FEM) software accelerated through the Adaptive Cross Approximation (ACA) method. This algebraic method (ACA) was presented in an previous paper in the hp context for the analysis of open region problems, where the robust behaviour, good accuracy and high compression levels of ACA were demonstrated. The truncation of the infinite domain is settled through an iterative computation of the Integral Equation (IE) over a ficticious boundary, which, regardless its accuracy and...

  9. Plausibility of a subglacial lake under Amundsenisen Icefield (Svalbard): spatially variable water content and sensitivity to thermal effect of snow and firn layers

    Bucchignani, Edoardo; Mansutti, Daniela; Navarro Valero, Francisco Jose; Otero García, Jaime; Glowacki, Piotr
    Within our study of the plausibility of a subglacial lake under the Amundsenisen Icefield in Southern Spitzbergen, Svalbard achipelago (Glowacki et al., 2007), here we focus on the sensitivity of the system to the thermal effect of the firn and snow layers. Rough heat balance analysis shows that the firn layer plays an important role by driving the heat release to the atmosphere, so that its influence on the ice-water phase transition cannot be neglected (Bucchignani et al., 2012).

  10. Ice volume estimates from ground-penetrating radar surveys, Wedel Jarlsberg Land glaciers, Svalbard

    Navarro Valero, Francisco Jose; Martín Español, Alba; Lapazaran Izargain, Javier Jesús; Grabiec, M.; Otero García, Jaime; Vasilenko, Evgeniy; Puczko, D.
    One of the aims of the SvalGlac project is to obtain an improved estimate, with reliable error estimates, of the volume of Svalbard glaciers and their potential contribution to sea level rise. As part of this work, we present volume calculations, with detailed error estimates, for eight glaciers on Wedel Jarlsberg Land, southern Spitsbergen, Svalbard. The volume estimates are based upon a dense net of GPR-retrieved ice thickness data collected over several field campaigns spanning the period 2004-2011. The total area and volume of the ensemble are 502.9±18.6 km2 and 80.72±2.85 km3, respectively. Excluding Ariebreen (a tiny glacier, menor que...

  11. Ice volume estimates from ground-penetrating radar surveys, western Nordenskiöld Land glaciers, Svalbard

    Martín Español, Alba; Vasilenko, Evgeniy; Navarro Valero, Francisco Jose; Otero García, Jaime; Lapazaran Izargain, Javier Jesús; Lavrentiev, Ivan; Macheret, Y.Y.; Machío, F.; Glazovsky, A.
    As part of ongoing work within the SvalGlac project aimed to obtain a reliable estimate of the total ice volume of Svalbard glaciers and their potential contribution to sea level rise, in this contribution we present volume calculations, with detailed error estimates, for ten glaciers on western Nordenskiöld Land, central Spitsbergen, Svalbard. The volume estimates are based upon a dense net of GPR-retrieved ice thickness data collected over several field campaigns spanning the period 1999-2012, all of them except one within 2010-2012. The total area and volume of the ensemble are 113.38±0.09 km2 and 10.439±0.185 km3, respectively, while the individual...

  12. Local effects of depth-dependent water content of ice and snow and firn layers temperature on a conjectured subglacial lake below Amundsenisen Icefield (Svalbard)

    Bucchignani, Edoardo; Mansutti, Daniela; Navarro Valero, Francisco Jose; Otero García, Jaime; Glowacki, Piotr
    It is known that the Amundsenisen Icefield in Southern Spitzbergen (Svalbard achipelago) is temperate with an upper layer of snow and firn. It is an accumulation area and, though ice/water mass balance is clearly subject to time evolution, observation data on the long-term elevation changes over the past 40 years (Nuth et al., 2010) allow to assume constant icefield surface. Within our study of the plausibility of a subglacial lake (Glowacki et al., 2007), here, we focus on the sensitivity of the system to the thermal effect of the firn and snow layers.

  13. Discussion of "Design Footing Area with Biaxial Bending" by Ramon Jarquio and Victor Jarquio (October, 1983)

    Hacar Benítez, Miguel Ángel; Molina Ruiz, Francisco Javier; Alarcón Álvarez, Enrique
    The authors present a very interesting criterion for choosing a rectangular foundation.The writers should like to point out that the obtention of minimum area can be reduced to the problem of finding the minimum of x*+y*, subjected to the condition x*.y*=k2 whose solution is evidently x*=y*=k

  14. Discussion of “Initial Pore Pressure from Vertical Surface Loads” by Jacobo Bielak (September, 1982)

    Alarcón Álvarez, Enrique; Martí, Pascual
    The author presents a very interesting application of the ideas developed by Scott to determine the initial pore pressure in excess of the hydrostatic pore pressure in linear, elastic, homogeneous and isotropic soil-skeleton. Scott demonstrates that under vertical surface loads the problem is governed by Laplace's equation. Nevertheless the writers' think that it could be interesting to state clearly the conditions under which this analogy can be applied.

  15. Accuracy estimates based on multifield variational principles

    Beltrán, Francisco J.; Alarcón Álvarez, Enrique
    Recent developments to fit the so called Free Formulation into a variational framework have suggested the possibility of introducing a new category of error estimates for finite element computations. Such error estimates are based on differences between certain multifield functionals, which give the same value for the true solution. In the present paper the formulation of some estimates of this kind is introduced for elasticity and plate bending problems, and several examples of their performance are discussed. The observed numerical behavior of the new accuracy measures seems to be acceptable from an engineering point of view. However, further numerical experimentation...

  16. Letters to the editor [An implementation of the Boundary Element Method for zoned media with stress discontinuities, T.J. Rudolphi, 1983]

    Alarcón Álvarez, Enrique
    En esta carta al editor, el profesor D. Enrique Alarcón Álvarez comenta el artículo de Thomas J. Rudolphi "An implementation of the Boundary Element Method for zoned media with stress discontinuities" publicado en la revista "International Journal for Numerical Methods in Engineering" Vol. 19, Nº 1, pags. 1–15, enero 1983.

  17. The Boundary Element Method in elastodynamics

    Dominguez Abascal, José; Alarcón Álvarez, Enrique
    As is well known B.E.M. is obtained as a mixture of the integral representation formula of classical elasticity and the discretization philosophy of the finite element method (F.E.M.). The paper presents the application of B.E.M. to elastodynamic problems. Both the transient and steady state solutions are presented as well as some techniques to simplify problems with a free-stress boundary.

  18. Space-time ocean wave measurement using variational stereo vision systems

    Gallego Bonet, Guillermo; Shih, Ping-Chang; Benetazzo, Alvise; Yezzi, Anthony; Fedele, Francesco
    Remote sensing imaging systems for the measurement of oceanic sea states have recently attracted renovated attention. Imaging technology is economical, non-invasive and enables a better understanding of the space-time dynamics of ocean waves over an area rather than at selected point locations of previous monitoring methods (buoys, wave gauges, etc.). We present recent progress in space-time measurement of ocean waves using stereo vision systems on offshore platforms. Both traditional disparity-based systems and modern elevation-based ones are presented in a variational optimization framework: the main idea is to pose the stereoscopic reconstruction problem of the surface of the ocean in a...

  19. Métodos numéricos en ingeniería sísmica

    Alarcón Álvarez, Enrique
    Los métodos numéricos aplicados al estudio de estructuras sometidas a esfuezos de origen sísmico han sido utilizados habitualmente en ingeniería. La limitación tradicional con que se encontraba el analista radicaba en el enorme esfuerzo de cálculo mecánico necesario para obtener respuestas significativas tan pronto como el modelo matemático a analizar presentaba una cierta complejidad. Esta situación se vió sustancialmente modificada por la aparición del ordenador que, justamente, libera al proyectista del trabajo repetitivo irracional y permite dedicar tiempo a la reflexión, a la par que aumenta espectacularmente la capacidad de modelado. No es extraño pues, que en los ultimos 30 años se...

  20. MBIS: Multivariate Bayesian Image Segmentation Tool

    Esteban Sanz-Dranguet, Oscar; Wöllny, Gert; Gorthi, Subrahmanyam; Ledesma Carbayo, María Jesús; Thiran, Jean-Philippe; Santos Lleo, Andrés; Bach-Cuadra, Meritxell
    We present MBIS (Multivariate Bayesian Image Segmentation tool), a clustering tool based on the mixture of multivariate normal distributions model. MBIS supports multi-channel bias field correction based on a B-spline model. A second methodological novelty is the inclusion of graph-cuts optimization for the stationary anisotropic hidden Markov random field model. Along with MBIS, we release an evaluation framework that contains three different experiments on multi-site data. We first validate the accuracy of segmentation and the estimated bias field for each channel. MBIS outperforms a widely used segmentation tool in a cross-comparison evaluation. The second experiment demonstrates the robustness of results...

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