Now showing items 26-45 of 259

    • Algorithms and cryptographic protocols using elliptic curves 

      Miret, Josep M. (Josep Maria); Moreno Chiral, Ramiro; Pujolàs Boix, Jordi; Valls Marsal, Magda (Institut d'Estudis Catalans. Secció de Ciències i Tecnologia, 2007)
      En els darrers anys, la criptografia amb corbes el.líptiques ha adquirit una importància creixent, fins a arribar a formar part en la actualitat de diferents estàndards industrials. Tot i que s'han dissenyat variants amb ...
    • Algunas propiedades de un algoritmo de clasificación piramidal 

      Capdevila Marqués, Carles; Gil Estallo, Àngel J.; Arcas Pons, Antoni (Instituto Nacional de Estadística, 1995)
      En este trabajo se enuncia un Algoritmo de Clasificacián Ascendente Piramidal y se establecen algunas de sus propiedades, que ponen de manifiesto la mejora que éste supone respecto a otros algoritmos establecidos con ...
    • Aligning Business Processes With the Services Layer Using a Semantic Approach 

      Sosa-Sánchez, Encarna; Clemente, Pedro J.; Prieto, Álvaro E.; Ortiz-Caraballo, Carmen (Institute of Electrical and Electronics Engineers (IEEE), 2019)
      Organizations require their business processes goals and the underlying information technology (IT) to be in synchronization with each other, but the continual changes in business processes makes this difficult. To accomplish ...
    • An algebraic approach to lifts of digraphs 

      Dalfó, Cristina; Fiol, Miguel Angel; Miller, Mirka; Ryan, Joe; Sirán, Josef (Elsevier, 2018)
      We present some applications of a new matrix approach for studying the properties of the lift of a voltage digraph, which has arcs weighted by the elements of a group. As a main result, when the involved group is Abelian, ...
    • An improved Moore bound and some new optimal families of mixed Abelian Cayley graphs 

      Dalfó, Cristina; Fiol, Miguel Angel; López Lorenzo, Ignacio; Ryan, Joe (Elsevier, 2020)
      We consider the case in which mixed graphs (with both directed and undirected edges) are Cayley graphs of Abelian groups. In this case, some Moore bounds were derived for the maximum number of vertices that such graphs can ...
    • An improved upper bound for the order of mixed graphs 

      Dalfó, Cristina; Fiol, Miguel Angel; López Lorenzo, Ignacio (Elsevier B.V., 2018)
      A mixed graph G can contain both (undirected) edges and arcs (directed edges). Here we derive an improved Moore-like bound for the maximum number of vertices of a mixed graph with diameter at least three. Moreover, a ...
    • Analysing spatial correlation of weeds and harvester ants in cereal fields using point processes 

      Comas Rodríguez, Carles; Royo-Esnal, Aritz; Recasens i Guinjuan, Jordi; Torra Farré, Joel (Springer Verlag, 2016)
      The interaction between the spatial distribution of weed richness and weed cover and the spatial location of harvester ant nets was investigated in cereal fields. The understanding of such interdependencies can be relevant ...
    • Analytic integrability around a nilpotent singularity 

      Algaba, Antonio; García, Cristóbal; Giné, Jaume (Elsevier, 2019)
      In this work it is characterized the analytic integrability problem around a nilpotent singularity of a differential system in the plane under generic conditions.
    • Analytic integrability inside a family of degenerate centers 

      Algaba, Antonio; Checa, Isabel; García, Cristóbal; Giné, Jaume (Elsevier, 2016)
      In this paper we study the analytic integrability around the origin inside a family of degenerate centers or perturbations of them. For this family analytic integrability does not imply formal orbital equivalence to a ...
    • Analytic integrability of cubic-linear planar polynomial differential systems 

      Giné, Jaume; Valls, Claudia (Elsevier, 2016)
      For the cubic–linear polynomial planar differential systems with a finite singular point, we classify the ones which have a local analytic first integral around the origin and the ones that have a global analytic first integral.
    • Analytic integrability of some examples of degenerate planar vector fields 

      Algaba, Antonio; García, Cristóbal; Giné, Jaume (Springer, 2016)
      This paper is devoted to the classification of analytic integrable cases of two families of degenerate planar vector fields with a monodromic singular point at the origin. This study falls in the still open degenerate ...
    • Analytic nilpotent centers as limits of nondegenerate centers revisited 

      García, I. A. (Isaac A.); Giacomini, Héctor; Giné, Jaume; Llibre, Jaume (Elsevier, 2016-04-25)
      We prove that all the nilpotent centers of planar analytic differential systems are limit of centers with purely imaginary eigenvalues, and consequently the Poincaré--Liapunov method to detect centers with purely imaginary ...
    • Analytic reducibility of nondegenerate centers: Cherkas systems 

      Giné, Jaume; Llibre, Jaume (Bolyai Institute, University of SzegedHungarian Academy of Sciences, 2016)
      In this paper we study the center problem for polynomial differential systems and we prove that any center of an analytic differential system is analytically reducible. x˙=y,y˙=P0(x)+P1(x)y+P2(x)y2, We also study the ...
    • Analytical solution for the steady-state diffusion towards an inlaid disc microelectrode in a multi-layered medium 

      Galceran i Nogués, Josep; Salvador, José; Puy Llorens, Jaume; Cecilia Averós, Joan; Gavaghan, David J. (Elsevier Science, 1997)
      The rigorous analytical expression for the steady-state diffusion-limited current produced by an electroactive species diffusing towards an inlaid disc electrode through a multi-layered medium (such as the membrane covered ...
    • Análisis de las actitudes y conocimientos estadísticos elementales en la formación del profesorado 

      Estrada Roca, M. Asunción; Batanero, Carmen; Fortuny, Josep Maria (Universidad Autónoma de Madrid, 2006)
      Resumimos la tesis doctoral de Dña Assumpta Estrada Roca, dirigida por Carmen Batanero y Josep María Fortuny, y presentada en la Universidad Autónoma de Barcelona en septiembre de 2002, reflexionando sobre las implicaciones ...
    • Análisis de las actitudes y conocimientos estadísticos elementales en la formación del profesorado 

      Estrada Roca, M. Asunción (Sociedad Andaluza de Educación Matemática "Thales", 2002)
    • Assessing Prospective Teachers’ Affective Component Related to Working with Statistical Projects 

      Gea, María M.; Estrada Roca, M. Asunción; Batanero, Carmen (Universidade Luterana do Brasil, 2019)
      The aim of this paper was to evaluate the cognitive component of Spanish prospective high school teachers about correlation and regression. The evaluation is based on the analysis of the cognitive suitability of a statistical ...
    • Assessing the impact of removal scenarios on population viability of a threatened, long-lived avian scavenger 

      Margalida, Antoni; Colomer, M. Àngels (Maria Àngels); Oro, Daniel; Arlettaz, Raphaël; Donázar, José A. (Nature Publishing Group, 2015)
      The removal of eggs or chicks from wild populations to create captive populations, reinforce free-ranging populations or reintroduce species into the wild is a restoration tool that requires an assessment of potential ...
    • Averaging methods of arbitrary order, periodic solutions and integrability 

      Giné, Jaume; Llibre, Jaume; Wu, Kesheng; Zhang, Xiang (Elsevier, 2016)
      In this paper we provide an arbitrary order averaging theory for higher dimensional periodic analytic differential systems. This result extends and improves results on averaging theory of periodic analytic differential ...
    • Averaging theory at any order for computing periodic orbits 

      Giné, Jaume; Grau Montaña, Maite; Llibre, Jaume (Elsevier, 2013-05)
      We provide a recurrence formula for the coefficients of the powers of ε in the series expansion of the solutions around ε=0 of the perturbed first-order differential equations. Using it, we give an averaging theory at any ...