http://hdl.handle.net/2117/127 Wed, 19 Jun 2013 22:50:33 GMT 2013-06-19T22:50:33Z webmaster.bupc@upc.edu Universitat Politècnica de Catalunya. Servei de Biblioteques i Documentació no http://hdl.handle.net/2117/19561 Title: The impact of commercial quality on electricity consumer satisfaction Authors: Cruz Zambrano, Miguel; Corchero García, Cristina Abstract: Quality of supply has been one of the main aspects covered by the European Energy Policy in the last decades together with the competitiveness and the sustainability. Several regulatory actions have been taken in this regard and have been applied at European level. Most of Energy National Regulatory Agencies have implemented electricity distribution network retribution mechanisms based on the quality of supply provided by the companies responsible for that. These measures were mainly based on the technical quality: number and length of service interruptions. However, electricity consumer satisfaction has not been measured for checking how commercial quality is affecting it. In this working paper, technical and commercial quality of supply indicators for household electricity consumers in Spain are assessed together by means of an statistic model. The impact of commercial quality will allow us to identify possible policy recommendations to be implemented in the regulatory framework. Tue, 18 Jun 2013 08:27:48 GMT http://hdl.handle.net/2117/19561 2013-06-18T08:27:48Z Cruz Zambrano, Miguel; Corchero García, Cristina no Consumer satisfaction, Electricity quality of supply, Commercial quality, Electricity distribution Quality of supply has been one of the main aspects covered by the European Energy Policy in the last decades together with the competitiveness and the sustainability. Several regulatory actions have been taken in this regard and have been applied at European level. Most of Energy National Regulatory Agencies have implemented electricity distribution network retribution mechanisms based on the quality of supply provided by the companies responsible for that. These measures were mainly based on the technical quality: number and length of service interruptions. However, electricity consumer satisfaction has not been measured for checking how commercial quality is affecting it. In this working paper, technical and commercial quality of supply indicators for household electricity consumers in Spain are assessed together by means of an statistic model. The impact of commercial quality will allow us to identify possible policy recommendations to be implemented in the regulatory framework. http://hdl.handle.net/2117/19560 Title: Decay of solutions for a mixture of thermoelastic one dimensional solids Authors: Muñoz Rivera, Jaime E.; Naso, Maria-Grazia; Quintanilla de Latorre, Ramón Abstract: We study a PDE system modeling thermomechanical deformations for a mixture of thermoelastic solids. In particular we investigate the asymptotic behavior of the solutions. First, we identify conditions on the constitutive coefficients to guarantee that the imaginary axis is contained in the resolvent. Subsequently, we find the necessary and sufficient conditions to guarantee the exponential decay of solutions. When the decay is not of exponential type, we prove that the solutions decay polynomially and we find the optimal polynomial decay rate. Mon, 17 Jun 2013 16:52:48 GMT http://hdl.handle.net/2117/19560 2013-06-17T16:52:48Z Muñoz Rivera, Jaime E.; Naso, Maria-Grazia; Quintanilla de Latorre, Ramón no We study a PDE system modeling thermomechanical deformations for a mixture of thermoelastic solids. In particular we investigate the asymptotic behavior of the solutions. First, we identify conditions on the constitutive coefficients to guarantee that the imaginary axis is contained in the resolvent. Subsequently, we find the necessary and sufficient conditions to guarantee the exponential decay of solutions. When the decay is not of exponential type, we prove that the solutions decay polynomially and we find the optimal polynomial decay rate. http://hdl.handle.net/2117/19540 Title: Partitions of graphs into small and large sets Authors: Bojilov, Asen; Caro, Yair; Hansberg Pastor, Adriana; Nedyalko, Nevno Abstract: Let GG be a graph on nn vertices. We call a subset AA of the vertex set V(G)V(G)kk-small if, for every vertex v∈Av∈A, deg(v)≤n−|A|+kdeg(v)≤n−|A|+k. A subset B⊆V(G)B⊆V(G) is called kk-large if, for every vertex u∈Bu∈B, deg(u)≥|B|−k−1deg(u)≥|B|−k−1. Moreover, we denote by φk(G)φk(G) the minimum integer tt such that there is a partition of V(G)V(G) into View the MathML sourcetk-small sets, and by Ωk(G)Ωk(G) the minimum integer tt such that there is a partition of V(G)V(G) into View the MathML sourcetk-large sets. In this paper, we will show tight connections between kk-small sets, respectively kk-large sets, and the kk-independence number, the clique number and the chromatic number of a graph. We shall develop greedy algorithms to compute in linear time both φk(G)φk(G) and Ωk(G)Ωk(G) and prove various sharp inequalities concerning these parameters, which we will use to obtain refinements of the Caro–Wei Theorem, Turán’s Theorem and the Hansen–Zheng Theorem among other things. Wed, 12 Jun 2013 13:07:19 GMT http://hdl.handle.net/2117/19540 2013-06-12T13:07:19Z Bojilov, Asen; Caro, Yair; Hansberg Pastor, Adriana; Nedyalko, Nevno no kk-small set, kk-large set, kk-independence, Clique number, Chromatic number Let GG be a graph on nn vertices. We call a subset AA of the vertex set V(G)V(G)kk-small if, for every vertex v∈Av∈A, deg(v)≤n−|A|+kdeg(v)≤n−|A|+k. A subset B⊆V(G)B⊆V(G) is called kk-large if, for every vertex u∈Bu∈B, deg(u)≥|B|−k−1deg(u)≥|B|−k−1. Moreover, we denote by φk(G)φk(G) the minimum integer tt such that there is a partition of V(G)V(G) into View the MathML sourcetk-small sets, and by Ωk(G)Ωk(G) the minimum integer tt such that there is a partition of V(G)V(G) into View the MathML sourcetk-large sets. In this paper, we will show tight connections between kk-small sets, respectively kk-large sets, and the kk-independence number, the clique number and the chromatic number of a graph. We shall develop greedy algorithms to compute in linear time both φk(G)φk(G) and Ωk(G)Ωk(G) and prove various sharp inequalities concerning these parameters, which we will use to obtain refinements of the Caro–Wei Theorem, Turán’s Theorem and the Hansen–Zheng Theorem among other things. http://hdl.handle.net/2117/19517 Title: The efficiency of tissue P systems with cell separation relies on the environment Authors: Macias Ramos, Luis F.; Pérez Jiménez, Mario J.; Riscos Nuñez, Agustín; Rius Font, Miquel; Valencia Cabrera, Luis Abstract: The classical definition of tissue P systems includes a distinguished alphabet with the special assumption that its elements are available in an arbitrarily large amount of copies. These objects are shared in a distinguished place of the system, called the environment. This ability of having infinitely many copies of some objects has been widely exploited in the design of efficient solutions to computationally hard problems by means of tissue P systems. This paper deals with computational aspects of tissue P systems with cell separation where there is no such environment as described above. The main result is that only tractable problems can be efficiently solved by using this kind of P systems. Bearing in mind that NP–complete problems can be efficiently solved by using tissue P systems without environment and with cell division, we deduce that in the framework of tissue P systems without environment, the kind of rules (separation versus division) provides a new frontier of the tractability of decision problems. Wed, 05 Jun 2013 12:21:28 GMT http://hdl.handle.net/2117/19517 2013-06-05T12:21:28Z Macias Ramos, Luis F.; Pérez Jiménez, Mario J.; Riscos Nuñez, Agustín; Rius Font, Miquel; Valencia Cabrera, Luis no biological tissues biology cellular biophysics computational complexity The classical definition of tissue P systems includes a distinguished alphabet with the special assumption that its elements are available in an arbitrarily large amount of copies. These objects are shared in a distinguished place of the system, called the environment. This ability of having infinitely many copies of some objects has been widely exploited in the design of efficient solutions to computationally hard problems by means of tissue P systems. This paper deals with computational aspects of tissue P systems with cell separation where there is no such environment as described above. The main result is that only tractable problems can be efficiently solved by using this kind of P systems. Bearing in mind that NP–complete problems can be efficiently solved by using tissue P systems without environment and with cell division, we deduce that in the framework of tissue P systems without environment, the kind of rules (separation versus division) provides a new frontier of the tractability of decision problems. http://hdl.handle.net/2117/19437 Title: Thomason cohomology of categories Authors: Gálvez Carrillo, Maria Immaculada; Neumann, Frank; Tonks, Andrew Abstract: We investigate cohomology and homology theories of categories with general coefficients given by functors on simplex categories first studied by Thomason. These generalize Baues–Wirsching cohomology and homology of a small category, and coincide with Gabriel–Zisman cohomology and homology of the simplicial nerve of the category. Thus Baues–Wirsching cohomology of categories is seen to be a special case of simplicial cohomology. We analyze naturality and functoriality properties of these theories and construct associated spectral sequences for functors between small categories. Wed, 29 May 2013 07:58:01 GMT http://hdl.handle.net/2117/19437 2013-05-29T07:58:01Z Gálvez Carrillo, Maria Immaculada; Neumann, Frank; Tonks, Andrew no We investigate cohomology and homology theories of categories with general coefficients given by functors on simplex categories first studied by Thomason. These generalize Baues–Wirsching cohomology and homology of a small category, and coincide with Gabriel–Zisman cohomology and homology of the simplicial nerve of the category. Thus Baues–Wirsching cohomology of categories is seen to be a special case of simplicial cohomology. We analyze naturality and functoriality properties of these theories and construct associated spectral sequences for functors between small categories. http://hdl.handle.net/2117/19434 Title: On k-domination and j-independence in graphs Authors: Hansberg Pastor, Adriana; Pepper, Ryan Abstract: Let GG be a graph and let kk and jj be positive integers. A subset DD of the vertex set of GG is a kk-dominating set if every vertex not in DD has at least kk neighbors in DD. The kk-domination numberγk(G)γk(G) is the cardinality of a smallest kk-dominating set of GG. A subset I⊆V(G)I⊆V(G) is a jj-independent set of GG if every vertex in II has at most j−1j−1 neighbors in II. The jj-independence numberαj(G)αj(G) is the cardinality of a largest jj-independent set of GG. In this work, we study the interaction between γk(G)γk(G) and αj(G)αj(G) in a graph GG. Hereby, we generalize some known inequalities concerning these parameters and put into relation different known and new bounds on kk-domination and jj-independence. Finally, we will discuss several consequences that follow from the given relations, while always highlighting the symmetry that exists between these two graph invariants. Wed, 29 May 2013 07:33:27 GMT http://hdl.handle.net/2117/19434 2013-05-29T07:33:27Z Hansberg Pastor, Adriana; Pepper, Ryan no kk-domination, jj-independence, Domination, Independence Let GG be a graph and let kk and jj be positive integers. A subset DD of the vertex set of GG is a kk-dominating set if every vertex not in DD has at least kk neighbors in DD. The kk-domination numberγk(G)γk(G) is the cardinality of a smallest kk-dominating set of GG. A subset I⊆V(G)I⊆V(G) is a jj-independent set of GG if every vertex in II has at most j−1j−1 neighbors in II. The jj-independence numberαj(G)αj(G) is the cardinality of a largest jj-independent set of GG. In this work, we study the interaction between γk(G)γk(G) and αj(G)αj(G) in a graph GG. Hereby, we generalize some known inequalities concerning these parameters and put into relation different known and new bounds on kk-domination and jj-independence. Finally, we will discuss several consequences that follow from the given relations, while always highlighting the symmetry that exists between these two graph invariants. http://hdl.handle.net/2117/19427 Title: Safety indicators for microsimulation-based assessments Authors: Barceló Bugeda, Jaime; Dumont, André-Gilles; Montero Mercadé, Lídia; Perarnau, Josep; Torday, Alexandre Abstract: In the field of ITS applications evaluation, micro-simulation is becoming more and more a useful and powerful tool. In the evaluation process, one of the most important steps is the safety analysis. For that purpose, classical micro-simulation outputs give some helpful information, but which aren’t sufficient for an accurate analysis in many cases. Nevertheless, the microscopic level of traffic description offers the possibility of tracking the simulated vehicles getting at each time step their relative position, speed and deceleration. This paper explains how a safety indicator can be calculated with these different parameters. This safety indicator is used in a ramp metering case study to illustrate the utility of such output for a safety analysis. However, this indicator is limited to the linear collision probability and gives therefore no information on crossing trajectories conflicts like in junctions. On the other hand the likelihood of an incident to happen depends not only on traffic conditions but on the influence of many other factors as for example the geometry of the road, the visibility or the pavement conditions (wet, dry, etc.). When significant statistical information is available an estimation of the probability of an incident to happen can be computed, and used in microsimulation analysis. The paper is completed with the development and testing of hierarchical logit based model to estimate this probability. Tue, 28 May 2013 11:40:20 GMT http://hdl.handle.net/2117/19427 2013-05-28T11:40:20Z Barceló Bugeda, Jaime; Dumont, André-Gilles; Montero Mercadé, Lídia; Perarnau, Josep; Torday, Alexandre no In the field of ITS applications evaluation, micro-simulation is becoming more and more a useful and powerful tool. In the evaluation process, one of the most important steps is the safety analysis. For that purpose, classical micro-simulation outputs give some helpful information, but which aren’t sufficient for an accurate analysis in many cases. Nevertheless, the microscopic level of traffic description offers the possibility of tracking the simulated vehicles getting at each time step their relative position, speed and deceleration. This paper explains how a safety indicator can be calculated with these different parameters. This safety indicator is used in a ramp metering case study to illustrate the utility of such output for a safety analysis. However, this indicator is limited to the linear collision probability and gives therefore no information on crossing trajectories conflicts like in junctions. On the other hand the likelihood of an incident to happen depends not only on traffic conditions but on the influence of many other factors as for example the geometry of the road, the visibility or the pavement conditions (wet, dry, etc.). When significant statistical information is available an estimation of the probability of an incident to happen can be computed, and used in microsimulation analysis. The paper is completed with the development and testing of hierarchical logit based model to estimate this probability. http://hdl.handle.net/2117/19418 Title: Solving electric market quadratic problems by branch and fix coordination methods Authors: Heredia, F.-Javier (Francisco Javier); Corchero García, Cristina; Mijangos Fernández, Eugenio Abstract: The electric market regulation in Spain (MIBEL) establishes the rules for bilateral and futures contracts in the day-ahead optimal bid problem. Our model allows a price-taker generation company to decide the unit commitment of the thermal units, the economic dispatch of the bilateral and futures contracts between the thermal units and the optimal sale bids for the thermal units observing the MIBEL regulation. The uncertainty of the spot prices is represented through scenario sets. We solve this model on the framework of the Branch and Fix Coordination metodology as a quadratic two-stage stochastic problem. In order to gain computational efficiency, we use scenario clusters and propose to use perspective cuts. Numerical results are reported Mon, 27 May 2013 17:23:43 GMT http://hdl.handle.net/2117/19418 2013-05-27T17:23:43Z Heredia, F.-Javier (Francisco Javier); Corchero García, Cristina; Mijangos Fernández, Eugenio no The electric market regulation in Spain (MIBEL) establishes the rules for bilateral and futures contracts in the day-ahead optimal bid problem. Our model allows a price-taker generation company to decide the unit commitment of the thermal units, the economic dispatch of the bilateral and futures contracts between the thermal units and the optimal sale bids for the thermal units observing the MIBEL regulation. The uncertainty of the spot prices is represented through scenario sets. We solve this model on the framework of the Branch and Fix Coordination metodology as a quadratic two-stage stochastic problem. In order to gain computational efficiency, we use scenario clusters and propose to use perspective cuts. Numerical results are reported http://hdl.handle.net/2117/19408 Title: Characterization, modeling and assessment of Roll-N-Cage isolator using the cable-stayed bridge benchmark Authors: Abdel Kareem Moustafa, Mohamed Ismail; Rodellar Benedé, José; Carusone, Gennaro; Domaneschi, Marco; Martinelli, Luca Abstract: This paper presents the results of an extensive series of simulation tests to identify the mechanical characteristics of an innovative isolation device known as the Roll-N-Cage (RNC) isolator. The seismic performance of an RNC passive control scheme is subsequently investigated on a model of the cable-stayed bridge benchmark. Starting from different configurations studied in the laboratory for a 1/10 reduced-scale prototype, the RNC isolator stiffness and damping properties are investigated in terms of cyclic tests with different parameters. Tests at the ultimate level state consisting of monotonic shear and axial loading have been also carried out as a part of the qualification process. The goal of this study is twofold: first, to examine the main integrated mechanisms of the RNC isolator through sophisticated 3D finite element simulation models using a multi-purpose finite element code. The main result of this step is to attempt modeling the force–displacement relationship using the standard Bouc–Wen model of smooth hysteresis. The second aim of this study is the numerical assessment of the device efficiency through its implementation into a bridge model considering several ground motions as external excitations. Based on these extensive studies, it was found that the RNC isolator is promising as a reliable isotropic horizontal isolation device for bridge structures. Mon, 27 May 2013 12:47:49 GMT http://hdl.handle.net/2117/19408 2013-05-27T12:47:49Z Abdel Kareem Moustafa, Mohamed Ismail; Rodellar Benedé, José; Carusone, Gennaro; Domaneschi, Marco; Martinelli, Luca no Bouc–Wen model, Isolation bearing, Rubber bearing, Seismic response This paper presents the results of an extensive series of simulation tests to identify the mechanical characteristics of an innovative isolation device known as the Roll-N-Cage (RNC) isolator. The seismic performance of an RNC passive control scheme is subsequently investigated on a model of the cable-stayed bridge benchmark. Starting from different configurations studied in the laboratory for a 1/10 reduced-scale prototype, the RNC isolator stiffness and damping properties are investigated in terms of cyclic tests with different parameters. Tests at the ultimate level state consisting of monotonic shear and axial loading have been also carried out as a part of the qualification process. The goal of this study is twofold: first, to examine the main integrated mechanisms of the RNC isolator through sophisticated 3D finite element simulation models using a multi-purpose finite element code. The main result of this step is to attempt modeling the force–displacement relationship using the standard Bouc–Wen model of smooth hysteresis. The second aim of this study is the numerical assessment of the device efficiency through its implementation into a bridge model considering several ground motions as external excitations. Based on these extensive studies, it was found that the RNC isolator is promising as a reliable isotropic horizontal isolation device for bridge structures. http://hdl.handle.net/2117/19390 Title: On periodic solutions of 2-periodic Lyness' equations Authors: Bastien, Guy; Mañosa Fernández, Víctor; Rogalski, Marc Abstract: We study the existence of periodic solutions of the nonautonomous periodic Lyness' recurrenceun+2 = (an + un+1)/un, where {an}n is a cycle with positive values a, b and with positive initial conditions. It is known that for a = b = 1 all the sequences generated by this recurrence are 5-periodic. We prove that for each pair (a, b) ≠ (1, 1) there are infinitely many initial conditions giving rise to periodic sequences, and that the family of recurrences have almost all the even periods. If a ≠ b, then any odd period, except 1, appears. Fri, 24 May 2013 08:04:20 GMT http://hdl.handle.net/2117/19390 2013-05-24T08:04:20Z Bastien, Guy; Mañosa Fernández, Víctor; Rogalski, Marc no Difference equations with periodic coefficients, elliptic curves, Lyness' type equations, QRT maps, rotation number, periodic orbits. We study the existence of periodic solutions of the nonautonomous periodic Lyness' recurrenceun+2 = (an + un+1)/un, where {an}n is a cycle with positive values a, b and with positive initial conditions. It is known that for a = b = 1 all the sequences generated by this recurrence are 5-periodic. We prove that for each pair (a, b) ≠ (1, 1) there are infinitely many initial conditions giving rise to periodic sequences, and that the family of recurrences have almost all the even periods. If a ≠ b, then any odd period, except 1, appears. http://hdl.handle.net/2117/19386 Title: Review on "Pairing computation on twisted Edwards form elliptic curves" Authors: Alsina Aubach, Montserrat Thu, 23 May 2013 15:32:56 GMT http://hdl.handle.net/2117/19386 2013-05-23T15:32:56Z Alsina Aubach, Montserrat no http://hdl.handle.net/2117/19366 Title: IT or not to be: the impact of Moodle in the education of developing countries Authors: García Almiñana, Jordi; Somé, Michel; Ayguadé Parra, Eduard; Cabré Garcia, José M.; Casany Guerrero, María José; Frigola Bourlon, Manel; Galanis, Nikolaos; García-Cervigon Gutiérrez, Manuel; Guerrero Zapata, Manel; Muñoz Gracia, María del Pilar Abstract: E-learning environments, such as Moodle, provide a technology that fosters the improvement of the educational system in developed countries, where education is traditionally performed with relatively high standards of quality. A large number of case studies and research have been conducted to demonstrate how e-learning technologies can be applied to improve both training and learning processes. However, these technologies have not been proved efficient when applied to developing countries. The challenges that must be addressed in developing countries, both technological and societal, are much more complex and the possible solution margins are more constrained than those existing in the context where these technologies have been created. In this paper we show how Moodle can be used to improve the quality of education in developing countries and, even more important, how can be used to turn the educational system more sustainable and effective in the long-term. We describe our experience in implementing a programming course in Moodle for the Higher School of Informatics at the Université Polytechnique de Bobo-Dioulasso, in Burkina Faso (West Africa), joining efforts with local professors in designing and implementing the learning system. The case example has been designed having in mind a number of contextual problems: lack of lecturers, excessive teaching hours per lecturer, massive classes, and curricula organization and stability, among others. We finally discuss how the teaching effort is reduced, the students’ knowledge and capacity improves, and the institutional academic model can be guaranteed with the proposal. For this reason, we claim that information technologies in developing countries are a cost-effective way to guarantee the objectives originally defined in the academic curricula and, therefore, deal with the problem of the education. Wed, 22 May 2013 07:16:25 GMT http://hdl.handle.net/2117/19366 2013-05-22T07:16:25Z García Almiñana, Jordi; Somé, Michel; Ayguadé Parra, Eduard; Cabré Garcia, José M.; Casany Guerrero, María José; Frigola Bourlon, Manel; Galanis, Nikolaos; García-Cervigon Gutiérrez, Manuel; Guerrero Zapata, Manel; Muñoz Gracia, María del Pilar no Moodle, e-Learning, Education in developing countries, Programming course E-learning environments, such as Moodle, provide a technology that fosters the improvement of the educational system in developed countries, where education is traditionally performed with relatively high standards of quality. A large number of case studies and research have been conducted to demonstrate how e-learning technologies can be applied to improve both training and learning processes. However, these technologies have not been proved efficient when applied to developing countries. The challenges that must be addressed in developing countries, both technological and societal, are much more complex and the possible solution margins are more constrained than those existing in the context where these technologies have been created. In this paper we show how Moodle can be used to improve the quality of education in developing countries and, even more important, how can be used to turn the educational system more sustainable and effective in the long-term. We describe our experience in implementing a programming course in Moodle for the Higher School of Informatics at the Université Polytechnique de Bobo-Dioulasso, in Burkina Faso (West Africa), joining efforts with local professors in designing and implementing the learning system. The case example has been designed having in mind a number of contextual problems: lack of lecturers, excessive teaching hours per lecturer, massive classes, and curricula organization and stability, among others. We finally discuss how the teaching effort is reduced, the students’ knowledge and capacity improves, and the institutional academic model can be guaranteed with the proposal. For this reason, we claim that information technologies in developing countries are a cost-effective way to guarantee the objectives originally defined in the academic curricula and, therefore, deal with the problem of the education. http://hdl.handle.net/2117/19298 Title: A phase-field fracture model of ferroelectric materials under electro-mechanical loading Authors: Abdollahi Hosnijeh, Amir; Arias Vicente, Irene Abstract: A phase-field model is proposed for the coupled simulation of microstructure and fracture evolution in ferroelectric materials. The model is based on energetic phase-field approaches for brittle fracture and ferroelectric domain formation and evolution. The variational nature of these approaches makes their coupling very natural. However the main challenge is to encode the electro-mechanical conditions of the sharp crack faces into the phase-field framework since the crack in this model is smeared and represented by an internal layer. We develope the model for different crack face boundary conditions. Simulations show the microstructure induced by the presence of the crack. Interactions between the microstructure and the crack are investigated under different electro-mechanical loadings. Thu, 16 May 2013 12:58:07 GMT http://hdl.handle.net/2117/19298 2013-05-16T12:58:07Z Abdollahi Hosnijeh, Amir; Arias Vicente, Irene no Coupled simulation, Crack faces, Electro-mechanical, Ferroelectric domains, Fracture model, Internal layers, Phase fields, Phase-field approaches, Phase-field models, Sharp crack A phase-field model is proposed for the coupled simulation of microstructure and fracture evolution in ferroelectric materials. The model is based on energetic phase-field approaches for brittle fracture and ferroelectric domain formation and evolution. The variational nature of these approaches makes their coupling very natural. However the main challenge is to encode the electro-mechanical conditions of the sharp crack faces into the phase-field framework since the crack in this model is smeared and represented by an internal layer. We develope the model for different crack face boundary conditions. Simulations show the microstructure induced by the presence of the crack. Interactions between the microstructure and the crack are investigated under different electro-mechanical loadings. http://hdl.handle.net/2117/19287 Title: The Manhattan product of digraphs Authors: Comellas Padró, Francesc de Paula; Dalfó Simó, Cristina; Fiol Mora, Miquel Àngel Abstract: We study the main properties of a new product of bipartite digraphs which we call Manhattan product. This product allows us to understand the subjacent product in the Manhattan street networks and can be used to built other networks with similar good properties. It is shown that if all the factors of such a product are (directed) cycles, then the digraph obtained is a Manhattan street network, a widely studied topology for modeling some interconnection networks. To this respect, it is proved that many properties of these networks, such as high symmetries, reduced diameter and the presence of Hamiltonian cycles, are shared by the Manhattan product of some digraphs. Moreover, we show that the Manhattan product of two Manhattan streets networks is also a Manhattan street network. Finally, some sufficient conditions for the Manhattan product of two Cayley digraphs to be also a Cayley digraph are given. Throughout our study we use some interesting recent concepts, such as the unilateral distance and related graph invariants. Thu, 16 May 2013 11:26:48 GMT http://hdl.handle.net/2117/19287 2013-05-16T11:26:48Z Comellas Padró, Francesc de Paula; Dalfó Simó, Cristina; Fiol Mora, Miquel Àngel no We study the main properties of a new product of bipartite digraphs which we call Manhattan product. This product allows us to understand the subjacent product in the Manhattan street networks and can be used to built other networks with similar good properties. It is shown that if all the factors of such a product are (directed) cycles, then the digraph obtained is a Manhattan street network, a widely studied topology for modeling some interconnection networks. To this respect, it is proved that many properties of these networks, such as high symmetries, reduced diameter and the presence of Hamiltonian cycles, are shared by the Manhattan product of some digraphs. Moreover, we show that the Manhattan product of two Manhattan streets networks is also a Manhattan street network. Finally, some sufficient conditions for the Manhattan product of two Cayley digraphs to be also a Cayley digraph are given. Throughout our study we use some interesting recent concepts, such as the unilateral distance and related graph invariants. http://hdl.handle.net/2117/19246 Title: Modelling a linguistic variable as a hierarchical family of partitions induced by an indistinguishability operator Authors: Soto, De A R; Recasens Ferrés, Jorge Abstract: This work shows a method to obtain a hierarchy of partitions on the universe [0,1] in such a way that each of them is compatible with a refinement of Lukasiewicz indistinguishability operator. The classes of the partition at a given level present a relation of antonymy between them. Moreover, the partition at a certain level can be seen as the refinement of a previous level by means of a class of linguistic modifiers. Due to this fact, they seem appropriate for modeling linguistic labels of a linguistic variable. The associated indistinguishability operators show the increasing granularity when the number of classes rises up. Wed, 15 May 2013 11:39:15 GMT http://hdl.handle.net/2117/19246 2013-05-15T11:39:15Z Soto, De A R; Recasens Ferrés, Jorge no This work shows a method to obtain a hierarchy of partitions on the universe [0,1] in such a way that each of them is compatible with a refinement of Lukasiewicz indistinguishability operator. The classes of the partition at a given level present a relation of antonymy between them. Moreover, the partition at a certain level can be seen as the refinement of a previous level by means of a class of linguistic modifiers. Due to this fact, they seem appropriate for modeling linguistic labels of a linguistic variable. The associated indistinguishability operators show the increasing granularity when the number of classes rises up.