Articles de revista
http://hdl.handle.net/2117/3918
Tue, 25 Oct 2016 19:21:38 GMT2016-10-25T19:21:38ZA hybrid approach of knowledge-based reasoning for structural assessment
http://hdl.handle.net/2117/91055
A hybrid approach of knowledge-based reasoning for structural assessment
Mujica Delgado, Luis Eduardo; Vehí Casellas, Josep; Rodellar Benedé, José; Kolakowski, P
A hybrid reasoning system is developed for damage assessment of structures. The system combines the use of a model of the structure with a knowledge-based reasoning scheme to evaluate if damage is present, its severity (severity and dimension) and its location. Using a given model (or several models), the structural dynamic responses to given excitations are simulated in the presence of different forms of damage. In a ‘learning mode’ an initial casebase is created with the principal features of these damage responses. When the system is working in its operating mode, data acquired by sensors are used to perform a diagnosis by analogy with the cases stored in the casebase, reusing and adapting old situations. Whenever a new situation is detected, it is retained in the casebase to update the available information. This paper describes the methodology and how the system is built and tuned to be ready for operation. This is illustrated by a numerical example of a cantilever truss structure and tested numerically and experimentally with a beam structure. Conclusions are presented with the emphasis on the advantages of using knowledge-based systems for structural assessment.
Tue, 25 Oct 2016 10:03:57 GMThttp://hdl.handle.net/2117/910552016-10-25T10:03:57ZMujica Delgado, Luis EduardoVehí Casellas, JosepRodellar Benedé, JoséKolakowski, PA hybrid reasoning system is developed for damage assessment of structures. The system combines the use of a model of the structure with a knowledge-based reasoning scheme to evaluate if damage is present, its severity (severity and dimension) and its location. Using a given model (or several models), the structural dynamic responses to given excitations are simulated in the presence of different forms of damage. In a ‘learning mode’ an initial casebase is created with the principal features of these damage responses. When the system is working in its operating mode, data acquired by sensors are used to perform a diagnosis by analogy with the cases stored in the casebase, reusing and adapting old situations. Whenever a new situation is detected, it is retained in the casebase to update the available information. This paper describes the methodology and how the system is built and tuned to be ready for operation. This is illustrated by a numerical example of a cantilever truss structure and tested numerically and experimentally with a beam structure. Conclusions are presented with the emphasis on the advantages of using knowledge-based systems for structural assessment.Distance mean-regular graphs
http://hdl.handle.net/2117/91052
Distance mean-regular graphs
Fiol Mora, Miquel Àngel; Diego, Victor
We introduce the concept of distance mean-regular graph, which can be seen as a generalization of both vertex-transitive and distance-regular graphs. Let G be a graph with vertex set V , diameter D, adjacency matrix A, and adjacency algebra A. Then, G is distance mean-regular when, for a given u ¿ V , the averages of the intersection numbers p h ij (u, v) = |Gi(u) n Gj (v)| (number of vertices at distance i from u and distance j from v) computed over all vertices v at a given distance h ¿ {0, 1, . . . , D} from u, do not depend on u. In this work we study some properties and characterizations of these graphs. For instance, it is shown that a distance mean-regular graph is always distance degree-regular, and we give a condition for the converse to be also true. Some algebraic and spectral properties of distance mean-regular graphs are also investigated. We show that, for distance mean regular-graphs, the role of the distance matrices of distance-regular graphs is played for the so-called distance mean-regular matrices. These matrices are computed from a sequence of orthogonal polynomials evaluated at the adjacency matrix of G and, hence, they generate a subalgebra of A. Some other algebras associated to distance mean-regular graphs are also characterized.
Tue, 25 Oct 2016 09:46:43 GMThttp://hdl.handle.net/2117/910522016-10-25T09:46:43ZFiol Mora, Miquel ÀngelDiego, VictorWe introduce the concept of distance mean-regular graph, which can be seen as a generalization of both vertex-transitive and distance-regular graphs. Let G be a graph with vertex set V , diameter D, adjacency matrix A, and adjacency algebra A. Then, G is distance mean-regular when, for a given u ¿ V , the averages of the intersection numbers p h ij (u, v) = |Gi(u) n Gj (v)| (number of vertices at distance i from u and distance j from v) computed over all vertices v at a given distance h ¿ {0, 1, . . . , D} from u, do not depend on u. In this work we study some properties and characterizations of these graphs. For instance, it is shown that a distance mean-regular graph is always distance degree-regular, and we give a condition for the converse to be also true. Some algebraic and spectral properties of distance mean-regular graphs are also investigated. We show that, for distance mean regular-graphs, the role of the distance matrices of distance-regular graphs is played for the so-called distance mean-regular matrices. These matrices are computed from a sequence of orthogonal polynomials evaluated at the adjacency matrix of G and, hence, they generate a subalgebra of A. Some other algebras associated to distance mean-regular graphs are also characterized.An algebraic framework for Diffie–Hellman assumptions
http://hdl.handle.net/2117/91050
An algebraic framework for Diffie–Hellman assumptions
Escala Ribas, Alex; Herold, Gottfried; Kiltz, Eike; Rafols Salvador, Carla; Villar Santos, Jorge Luis
We put forward a new algebraic framework to generalize and analyze Diffie-Hellman like Decisional Assumptions which allows us to argue about security and applications by considering only algebraic properties. Our D`,k-MDDH assumption states that it is hard to decide whether a vector in ¿ìs linearly dependent of the columns of some matrix in ¿`×k sampled according to distribution D`,k. It covers known assumptions such as DDH, 2-Lin (linear assumption), and k-Lin (the k-linear assumption). Using our algebraic viewpoint, we can relate the generic hardness of our assumptions in m-linear groups to the irreducibility of certain polynomials which describe the output of D`,k. We use the hardness results to find new distributions for which the D`,k-MDDH-Assumption holds generically in m-linear groups. In particular, our new assumptions 2-SCasc and 2-ILin are generically hard in bilinear groups and, compared to 2-Lin, have shorter description size, which is a relevant parameter for efficiency in many applications. These results support using our new assumptions as natural replacements for the 2-Lin Assumption which was already used in a large number of applications. To illustrate the conceptual advantages of our algebraic framework, we construct several fundamental primitives based on any MDDH-Assumption. In particular, we can give many instantiations of a primitive in a compact way, including public-key encryption, hash-proof systems, pseudo-random functions, and Groth-Sahai NIZK and NIWI proofs. As an independent contribution we give more efficient NIZK and NIWI proofs for membership in a subgroup of ¿` . The results imply very significant efficiency improvements for a large number of schemes.
Tue, 25 Oct 2016 09:11:30 GMThttp://hdl.handle.net/2117/910502016-10-25T09:11:30ZEscala Ribas, AlexHerold, GottfriedKiltz, EikeRafols Salvador, CarlaVillar Santos, Jorge LuisWe put forward a new algebraic framework to generalize and analyze Diffie-Hellman like Decisional Assumptions which allows us to argue about security and applications by considering only algebraic properties. Our D`,k-MDDH assumption states that it is hard to decide whether a vector in ¿ìs linearly dependent of the columns of some matrix in ¿`×k sampled according to distribution D`,k. It covers known assumptions such as DDH, 2-Lin (linear assumption), and k-Lin (the k-linear assumption). Using our algebraic viewpoint, we can relate the generic hardness of our assumptions in m-linear groups to the irreducibility of certain polynomials which describe the output of D`,k. We use the hardness results to find new distributions for which the D`,k-MDDH-Assumption holds generically in m-linear groups. In particular, our new assumptions 2-SCasc and 2-ILin are generically hard in bilinear groups and, compared to 2-Lin, have shorter description size, which is a relevant parameter for efficiency in many applications. These results support using our new assumptions as natural replacements for the 2-Lin Assumption which was already used in a large number of applications. To illustrate the conceptual advantages of our algebraic framework, we construct several fundamental primitives based on any MDDH-Assumption. In particular, we can give many instantiations of a primitive in a compact way, including public-key encryption, hash-proof systems, pseudo-random functions, and Groth-Sahai NIZK and NIWI proofs. As an independent contribution we give more efficient NIZK and NIWI proofs for membership in a subgroup of ¿` . The results imply very significant efficiency improvements for a large number of schemes.A review of impact damage detection in structures using strain data
http://hdl.handle.net/2117/91040
A review of impact damage detection in structures using strain data
Mujica Delgado, Luis Eduardo; Rodellar Benedé, José; Vehí Casellas, José
This paper aims to provide a state-of-the-art review on impact damage detection techniques in structures using strain data. An overview of impact detection systems is provided. These include sensors, specimens, and impact sources used for developing and testing strategies. The review is focused on approaches that use impact strain data (passive approach) to determine simultaneously the location and/or energy of an impact at the time it occurs. These approaches can be classed into two main groups, one based on analytical models and the other based on data-driven models. The former uses a first-principle model obtained from physical laws, whereas the latter describes complex relationships between input and output data obtained by experiments or simulations. Although some weaknesses and strengths are cited, we did not attempt to compare these approaches, and we do not comment the quantitative results.
Tue, 25 Oct 2016 08:06:20 GMThttp://hdl.handle.net/2117/910402016-10-25T08:06:20ZMujica Delgado, Luis EduardoRodellar Benedé, JoséVehí Casellas, JoséThis paper aims to provide a state-of-the-art review on impact damage detection techniques in structures using strain data. An overview of impact detection systems is provided. These include sensors, specimens, and impact sources used for developing and testing strategies. The review is focused on approaches that use impact strain data (passive approach) to determine simultaneously the location and/or energy of an impact at the time it occurs. These approaches can be classed into two main groups, one based on analytical models and the other based on data-driven models. The former uses a first-principle model obtained from physical laws, whereas the latter describes complex relationships between input and output data obtained by experiments or simulations. Although some weaknesses and strengths are cited, we did not attempt to compare these approaches, and we do not comment the quantitative results.Extended PCA visualisation of system damage features under environmental and operational variations
http://hdl.handle.net/2117/91039
Extended PCA visualisation of system damage features under environmental and operational variations
Mujica Delgado, Luis Eduardo; Rodellar Benedé, José; Vehí Casellas, Josep; Worden, K; Staszewski, W
This paper explores the use of Principal Component Analysis (PCA), an extended form of PCA and, the T2- statistic and Q-statistic; distances that detect and distinguish damages in structures under varying operational and environmental conditions. The work involves an experiment in which two piezoelectric transducers are bonded on an aluminium plate. The plate is subjected to several damages and exposed to different levels of temperature. A series of tests have been performed for each condition. The approach is able to determine whether the structure has damage or not, and besides, gives qualitative information about its size, isolating effects of the temperature.
Copyright 2009 Proceedings of SPIE, the International Society for Optical Engineering. One print or electronic copy may be made for personal use only. Systematic electronic or print reproduction and distribution, duplication of any material in this paper for a fee or for commercial purposes, or modification of the content of the paper are prohibited.
Tue, 25 Oct 2016 07:35:36 GMThttp://hdl.handle.net/2117/910392016-10-25T07:35:36ZMujica Delgado, Luis EduardoRodellar Benedé, JoséVehí Casellas, JosepWorden, KStaszewski, WThis paper explores the use of Principal Component Analysis (PCA), an extended form of PCA and, the T2- statistic and Q-statistic; distances that detect and distinguish damages in structures under varying operational and environmental conditions. The work involves an experiment in which two piezoelectric transducers are bonded on an aluminium plate. The plate is subjected to several damages and exposed to different levels of temperature. A series of tests have been performed for each condition. The approach is able to determine whether the structure has damage or not, and besides, gives qualitative information about its size, isolating effects of the temperature.Combinatorial recurrences and linear difference equations
http://hdl.handle.net/2117/90923
Combinatorial recurrences and linear difference equations
Jiménez Jiménez, M. Jose; Encinas Bachiller, Andrés Marcos
In this work we introduce the triangular arrays of depth greater than 1 given by linear recurrences, that generalize some well known recurrences that appear in enumerative combinatorics. In particular, we focussed on triangular arrays of depth 2, since they are closely related with the solution of linear three–terms recurrences. We show through some simple examples how this triangular arrays appear as essential components in the expression of some classical orthogonal polynomials and combinatorial numbers
Thu, 20 Oct 2016 11:43:50 GMThttp://hdl.handle.net/2117/909232016-10-20T11:43:50ZJiménez Jiménez, M. JoseEncinas Bachiller, Andrés MarcosIn this work we introduce the triangular arrays of depth greater than 1 given by linear recurrences, that generalize some well known recurrences that appear in enumerative combinatorics. In particular, we focussed on triangular arrays of depth 2, since they are closely related with the solution of linear three–terms recurrences. We show through some simple examples how this triangular arrays appear as essential components in the expression of some classical orthogonal polynomials and combinatorial numbersStability of Markov jump systems with quadratic terms and its application to RLC circuits
http://hdl.handle.net/2117/90847
Stability of Markov jump systems with quadratic terms and its application to RLC circuits
Vargas, Alessandro; Pujol Vázquez, Gisela; Acho Zuppa, Leonardo
The paper presents results for the second moment stability of continuous-time Markov jump systems with quadratic terms, aiming for engineering applications. Quadratic terms stem from physical constraints in applications, as in electronic circuits based on resistor (R), inductor (L), and capacitor (C). In the paper, an RLC circuit supplied a load driven by jumps produced by a Markov chain—the RLC circuit used sensors that measured the quadratic of electrical currents and voltages. Our result was then used to design a stabilizing controller for the RLC circuit with measurements based on that quadratic terms. The experimental data confirm the usefulness of our approach.
Tue, 18 Oct 2016 11:55:38 GMThttp://hdl.handle.net/2117/908472016-10-18T11:55:38ZVargas, AlessandroPujol Vázquez, GiselaAcho Zuppa, LeonardoThe paper presents results for the second moment stability of continuous-time Markov jump systems with quadratic terms, aiming for engineering applications. Quadratic terms stem from physical constraints in applications, as in electronic circuits based on resistor (R), inductor (L), and capacitor (C). In the paper, an RLC circuit supplied a load driven by jumps produced by a Markov chain—the RLC circuit used sensors that measured the quadratic of electrical currents and voltages. Our result was then used to design a stabilizing controller for the RLC circuit with measurements based on that quadratic terms. The experimental data confirm the usefulness of our approach.On the Caginalp phase-field systems with two temperatures and the Maxwell–Cattaneo law
http://hdl.handle.net/2117/90781
On the Caginalp phase-field systems with two temperatures and the Maxwell–Cattaneo law
Miranville, Alain; Quintanilla de Latorre, Ramón
Our aim in this paper is to study generalizations of the nonconserved and conserved Caginalp phase-¿eld systems based on the Maxwell–Cattaneo law with two temperatures for heat conduction. In particular, we obtain well-posedness results and study the dissipativity of the associated solution operators.
This is the peer reviewed version of the following article: Miranville, A., and Quintanilla, R. (2016) On the Caginalp phase-field systems with two temperatures and the Maxwell–Cattaneo law. Math. Meth. Appl. Sci., 39: 4385–4397, which has been published in final form at http://dx.doi.org/10.1002/mma.3867. This article may be used for non-commercial purposes in accordance with Wiley Terms and Conditions for Self-Archiving
Fri, 14 Oct 2016 10:40:07 GMThttp://hdl.handle.net/2117/907812016-10-14T10:40:07ZMiranville, AlainQuintanilla de Latorre, RamónOur aim in this paper is to study generalizations of the nonconserved and conserved Caginalp phase-¿eld systems based on the Maxwell–Cattaneo law with two temperatures for heat conduction. In particular, we obtain well-posedness results and study the dissipativity of the associated solution operators.Continua of periodic points for planar integrable rational maps
http://hdl.handle.net/2117/90779
Continua of periodic points for planar integrable rational maps
Gasull Embid, Armengol; Llorens, Mireia; Mañosa Fernández, Víctor
We present three alternative methodologies to find continua of periodic points with a prescribed period for rational maps having rational first integrals. The first two have been already used by other authors and apply when the maps are birational and the generic level sets of the corresponding first integrals have either genus 0 or 1. As far as we know, the third one is new and it works for rational maps without imposing topological properties to the invariant level sets. It is based on a computational point of view, and relies on the use of resultants in a suitable setting. We apply them to several examples, including the 2-periodic Lyness composition maps and some of the celebrated McMillan–Gumovski–Mira maps
Fri, 14 Oct 2016 08:39:04 GMThttp://hdl.handle.net/2117/907792016-10-14T08:39:04ZGasull Embid, ArmengolLlorens, MireiaMañosa Fernández, VíctorWe present three alternative methodologies to find continua of periodic points with a prescribed period for rational maps having rational first integrals. The first two have been already used by other authors and apply when the maps are birational and the generic level sets of the corresponding first integrals have either genus 0 or 1. As far as we know, the third one is new and it works for rational maps without imposing topological properties to the invariant level sets. It is based on a computational point of view, and relies on the use of resultants in a suitable setting. We apply them to several examples, including the 2-periodic Lyness composition maps and some of the celebrated McMillan–Gumovski–Mira mapsAveraged dynamics of a coupled-inductor boost converter under sliding mode control using a piecewise linear complementarity model
http://hdl.handle.net/2117/90749
Averaged dynamics of a coupled-inductor boost converter under sliding mode control using a piecewise linear complementarity model
Carrero Candelas, Niliana Andreina; Batlle Arnau, Carles; Fossas Colet, Enric
An averaged model of a coupled-inductor boost converter using the piecewise complementarity model of the converter under sliding motions is obtained. The model takes into account the idealized voltage–current characteristic of passive switches (diodes) present in the converter. Because of its lower complexity, the averaged model is more suitable for control design purposes when compared with the linear complementarity systems (LCS) model of the converter. The dynamic performance of the LCS model and the averaged models of the converter are validated through computer simulations using Matlab.
Thu, 13 Oct 2016 13:52:49 GMThttp://hdl.handle.net/2117/907492016-10-13T13:52:49ZCarrero Candelas, Niliana AndreinaBatlle Arnau, CarlesFossas Colet, EnricAn averaged model of a coupled-inductor boost converter using the piecewise complementarity model of the converter under sliding motions is obtained. The model takes into account the idealized voltage–current characteristic of passive switches (diodes) present in the converter. Because of its lower complexity, the averaged model is more suitable for control design purposes when compared with the linear complementarity systems (LCS) model of the converter. The dynamic performance of the LCS model and the averaged models of the converter are validated through computer simulations using Matlab.