Articles de revista
http://hdl.handle.net/2117/3918
2017-04-29T07:33:55ZGeneral properties of c-circulant digraphs
http://hdl.handle.net/2117/103764
General properties of c-circulant digraphs
Mora Giné, Mercè; Serra Albó, Oriol; Fiol Mora, Miquel Àngel
A digraph is said to be a c-circulant if its adjacency matrix is c-circulant. This paper deals with general properties of this family of digraphs, as isomorphisms, regularity, strong connectivity, diameter and the relation between c-circulant digraphs and the line digraph technique.
2017-04-26T17:41:13ZMora Giné, MercèSerra Albó, OriolFiol Mora, Miquel ÀngelA digraph is said to be a c-circulant if its adjacency matrix is c-circulant. This paper deals with general properties of this family of digraphs, as isomorphisms, regularity, strong connectivity, diameter and the relation between c-circulant digraphs and the line digraph technique.Bifurcation diagram of Saddle/Spiral bimodal linear systems
http://hdl.handle.net/2117/103748
Bifurcation diagram of Saddle/Spiral bimodal linear systems
Ferrer Llop, Josep; Peña Carrera, Marta; Susín Sánchez, Antonio
We complete the study of the bifurcations of saddle/spiral bimodal linear systems, depending on the respective traces T and t: one 2-codimensional bifurcation; four kinds of 1-codimensional bifurcations. We stratify the bifurcation set in the (T,t)-plane and we describe the qualitative changes of the dynamical behavior at each bifurcation point.
2017-04-26T09:40:16ZFerrer Llop, JosepPeña Carrera, MartaSusín Sánchez, AntonioWe complete the study of the bifurcations of saddle/spiral bimodal linear systems, depending on the respective traces T and t: one 2-codimensional bifurcation; four kinds of 1-codimensional bifurcations. We stratify the bifurcation set in the (T,t)-plane and we describe the qualitative changes of the dynamical behavior at each bifurcation point.A unified approach to explain contrary effects of hysteresis and smoothing in nonsmooth systems
http://hdl.handle.net/2117/103747
A unified approach to explain contrary effects of hysteresis and smoothing in nonsmooth systems
Bonet Revés, Carles; Martínez-Seara Alonso, M. Teresa; Fossas Colet, Enric; Jeffrey, Mike R.
Piecewise smooth dynamical systems make use of discontinuities to model switching between regions of smooth evolution. This introduces an ambiguity in prescribing dynamics at the discontinuity: should the dynamics be given by a limiting value on one side or other of the discontinuity, or a member of some set containing those values? One way to remove the ambiguity is to regularize the discontinuity, the most common being either to smooth it out, or to introduce a hysteresis between switching in one direction or the other across it. Here we show that the two can in general lead to qualitatively different dynamical outcomes. We then define a higher dimensional model with both smoothing and hysteresis, and study the competing limits in which hysteretic or smoothing effects dominate the behaviour, only the former of which correspond to Filippov’s standard ‘sliding modes’.
2017-04-26T09:23:33ZBonet Revés, CarlesMartínez-Seara Alonso, M. TeresaFossas Colet, EnricJeffrey, Mike R.Piecewise smooth dynamical systems make use of discontinuities to model switching between regions of smooth evolution. This introduces an ambiguity in prescribing dynamics at the discontinuity: should the dynamics be given by a limiting value on one side or other of the discontinuity, or a member of some set containing those values? One way to remove the ambiguity is to regularize the discontinuity, the most common being either to smooth it out, or to introduce a hysteresis between switching in one direction or the other across it. Here we show that the two can in general lead to qualitatively different dynamical outcomes. We then define a higher dimensional model with both smoothing and hysteresis, and study the competing limits in which hysteretic or smoothing effects dominate the behaviour, only the former of which correspond to Filippov’s standard ‘sliding modes’.Rainbow eulerian multidigraphs and the product of cycles
http://hdl.handle.net/2117/103675
Rainbow eulerian multidigraphs and the product of cycles
López Masip, Susana Clara; Muntaner Batle, Francesc Antoni
An arc colored eulerian multidigraph with l colors is rainbow eulerian if there is an
eulerian circuit in which a sequence of l colors repeats. The digraph product that refers the title was introduced by Figueroa-Centeno et al. as follows: let D be a digraph and let G be a family of digraphs such that V (F) = V for every F ¿ G
2017-04-24T12:14:28ZLópez Masip, Susana ClaraMuntaner Batle, Francesc AntoniAn arc colored eulerian multidigraph with l colors is rainbow eulerian if there is an
eulerian circuit in which a sequence of l colors repeats. The digraph product that refers the title was introduced by Figueroa-Centeno et al. as follows: let D be a digraph and let G be a family of digraphs such that V (F) = V for every F ¿ GDistance labelings: a generalization of Langford sequences
http://hdl.handle.net/2117/103670
Distance labelings: a generalization of Langford sequences
López Masip, Susana Clara; Muntaner Batle, Francesc Antoni
A Langford sequence of order m and defect d can be identified with a labeling of the
vertices of a path of order 2m in which each labeled from d up to d + m - 1 appears twice and in which the vertices that have been label with k are at distance k. In this paper, we introduce two generalizations of this labeling that are related to distances.; Articles in this journal are published under Creative Commons Attribution 3.0 License
http://creativecommons.org/licenses/by/3.0/
2017-04-24T11:38:49ZLópez Masip, Susana ClaraMuntaner Batle, Francesc AntoniA Langford sequence of order m and defect d can be identified with a labeling of the
vertices of a path of order 2m in which each labeled from d up to d + m - 1 appears twice and in which the vertices that have been label with k are at distance k. In this paper, we introduce two generalizations of this labeling that are related to distances.
Articles in this journal are published under Creative Commons Attribution 3.0 License
http://creativecommons.org/licenses/by/3.0/Efficient cryptosystems from 2k-th power residue symbols
http://hdl.handle.net/2117/103661
Efficient cryptosystems from 2k-th power residue symbols
Herranz Sotoca, Javier; Libert, Benoit; Joye, Marc; Benhamouda, Fabrice
Goldwasser and Micali (J Comput Syst Sci 28(2):270–299, 1984) highlighted the importance of randomizing the plaintext for public-key encryption and introduced the notion of semantic security. They also realized a cryptosystem meeting this security notion under the standard complexity assumption of deciding quadratic residuosity modulo a composite number. The Goldwasser–Micali cryptosystem is simple and elegant but is quite wasteful in bandwidth when encrypting large messages. A number of works followed to address this issue and proposed various modifications. This paper revisits the original Goldwasser–Micali cryptosystem using 2k-th power residue symbols. The so-obtained cryptosystems appear as a very natural generalization for k=2 (the case k=1 corresponds exactly to the Goldwasser–Micali cryptosystem). Advantageously, they are efficient in both bandwidth and speed; in particular, they allow for fast decryption. Further, the cryptosystems described in this paper inherit the useful features of the original cryptosystem (like its homomorphic property) and are shown to be secure under a similar complexity assumption. As a prominent application, this paper describes an efficient lossy trapdoor function-based thereon.
2017-04-24T10:25:48ZHerranz Sotoca, JavierLibert, BenoitJoye, MarcBenhamouda, FabriceGoldwasser and Micali (J Comput Syst Sci 28(2):270–299, 1984) highlighted the importance of randomizing the plaintext for public-key encryption and introduced the notion of semantic security. They also realized a cryptosystem meeting this security notion under the standard complexity assumption of deciding quadratic residuosity modulo a composite number. The Goldwasser–Micali cryptosystem is simple and elegant but is quite wasteful in bandwidth when encrypting large messages. A number of works followed to address this issue and proposed various modifications. This paper revisits the original Goldwasser–Micali cryptosystem using 2k-th power residue symbols. The so-obtained cryptosystems appear as a very natural generalization for k=2 (the case k=1 corresponds exactly to the Goldwasser–Micali cryptosystem). Advantageously, they are efficient in both bandwidth and speed; in particular, they allow for fast decryption. Further, the cryptosystems described in this paper inherit the useful features of the original cryptosystem (like its homomorphic property) and are shown to be secure under a similar complexity assumption. As a prominent application, this paper describes an efficient lossy trapdoor function-based thereon.Evaluación de la transferencia de la formación permanente: análisis de una experiencia de talleres sobre astronomía
http://hdl.handle.net/2117/103653
Evaluación de la transferencia de la formación permanente: análisis de una experiencia de talleres sobre astronomía
Cano Garcia, Elena; Fabregat Fillet, Jaume; Ros Ferré, Rosa Maria
In the framework of a European project to bring astronomy near to children, several permanent teachers training activities were developed. These actions included workshops with teachers from various stages of the educational system.
2017-04-24T08:56:20ZCano Garcia, ElenaFabregat Fillet, JaumeRos Ferré, Rosa MariaIn the framework of a European project to bring astronomy near to children, several permanent teachers training activities were developed. These actions included workshops with teachers from various stages of the educational system.Production matrices for geometric graphs
http://hdl.handle.net/2117/103649
Production matrices for geometric graphs
Huemer, Clemens; Pilz, Alexander; Seara Ojea, Carlos; Silveira, Rodrigo Ignacio
We present production matrices for non-crossing geometric graphs on point sets in convex position, which allow us to derive formulas for the numbers of such graphs. Several known identities for Catalan numbers, Ballot numbers, and Fibonacci numbers arise in a natural way, and also new formulas are obtained, such as a formula for the number of non-crossing geometric graphs with root vertex of given degree. The characteristic polynomials of some of these production matrices are also presented. The proofs make use of generating trees and Riordan arrays.
2017-04-24T08:25:14ZHuemer, ClemensPilz, AlexanderSeara Ojea, CarlosSilveira, Rodrigo IgnacioWe present production matrices for non-crossing geometric graphs on point sets in convex position, which allow us to derive formulas for the numbers of such graphs. Several known identities for Catalan numbers, Ballot numbers, and Fibonacci numbers arise in a natural way, and also new formulas are obtained, such as a formula for the number of non-crossing geometric graphs with root vertex of given degree. The characteristic polynomials of some of these production matrices are also presented. The proofs make use of generating trees and Riordan arrays.On (non-)exponential decay in generalized thermoelasticity with two temperatures
http://hdl.handle.net/2117/103572
On (non-)exponential decay in generalized thermoelasticity with two temperatures
Leseduarte Milán, María Carme; Quintanilla de Latorre, Ramón; Racke, Reinhard
We study solutions for the one-dimensional problem of the Green-Lindsay and the Lord-Shulman theories with two temperatures. First, existence and uniqueness of weakly regular solutions are obtained. Second, we prove the exponential stability in the Green-Lindsay model, but the non-exponential stability for the Lord-Shulman model.
2017-04-20T10:27:50ZLeseduarte Milán, María CarmeQuintanilla de Latorre, RamónRacke, ReinhardWe study solutions for the one-dimensional problem of the Green-Lindsay and the Lord-Shulman theories with two temperatures. First, existence and uniqueness of weakly regular solutions are obtained. Second, we prove the exponential stability in the Green-Lindsay model, but the non-exponential stability for the Lord-Shulman model.New results on stabbing segments with a polygon
http://hdl.handle.net/2117/103547
New results on stabbing segments with a polygon
Díaz Bañez, José Miguel; Korman Cozzetti, Matías; Pérez Lantero, Pablo; Pilz, Alexander; Seara Ojea, Carlos; Silveira, Rodrigo Ignacio
We consider a natural variation of the concept of stabbing a set of segments with a simple polygon: a segment s is stabbed by a simple polygon P if at least one endpoint of s is contained in P, and a segment set S is stabbed by P if P stabs every element of S. Given a segment set S, we study the problem of finding a simple polygon P stabbing S in a way that some measure of P (such as area or perimeter) is optimized. We show that if the elements of S are pairwise disjoint, the problem can be solved in polynomial time. In particular, this solves an open problem posed by Loftier and van Kreveld [Algorithmica 56(2), 236-269 (2010)] [16] about finding a maximum perimeter convex hull for a set of imprecise points modeled as line segments. Our algorithm can also be extended to work for a more general problem, in which instead of segments, the set S consists of a collection of point sets with pairwise disjoint convex hulls. We also prove that for general segments our stabbing problem is NP-hard. (C) 2014 Elsevier B.V. All rights reserved.
2017-04-19T12:27:10ZDíaz Bañez, José MiguelKorman Cozzetti, MatíasPérez Lantero, PabloPilz, AlexanderSeara Ojea, CarlosSilveira, Rodrigo IgnacioWe consider a natural variation of the concept of stabbing a set of segments with a simple polygon: a segment s is stabbed by a simple polygon P if at least one endpoint of s is contained in P, and a segment set S is stabbed by P if P stabs every element of S. Given a segment set S, we study the problem of finding a simple polygon P stabbing S in a way that some measure of P (such as area or perimeter) is optimized. We show that if the elements of S are pairwise disjoint, the problem can be solved in polynomial time. In particular, this solves an open problem posed by Loftier and van Kreveld [Algorithmica 56(2), 236-269 (2010)] [16] about finding a maximum perimeter convex hull for a set of imprecise points modeled as line segments. Our algorithm can also be extended to work for a more general problem, in which instead of segments, the set S consists of a collection of point sets with pairwise disjoint convex hulls. We also prove that for general segments our stabbing problem is NP-hard. (C) 2014 Elsevier B.V. All rights reserved.