Now showing items 329-348 of 358

    • The problem of distinguishing between a center and a focus for nilpotent and degenerate analytic systems 

      Giacomini, Héctor; Giné, Jaume; Llibre, Jaume (Elsevier, 2006)
      In this work we study the centers of planar analytic vector fields which are limit of linear type centers. It is proved that all the nilpotent centers are limit of linear type centers and consequently the Poincaré–Liapunov ...
    • The Risk of Hospitalization in COVID-19 Patients Can Be Predicted by Lung Ultrasound in Primary Care 

      Martínez Redondo, Javier; Comas Rodríguez, Carles; Pujol Salud, Jesús; Crespo Pons, Montserrat; García-Serrano, Cristina; Ortega Bravo, Marta; Palacín Peruga, Jose María (MDPI, 2021)
    • The role of algebraic solutions in planar polynomial differential systems 

      Giacomini, Héctor; Giné, Jaume; Grau Montaña, Maite (Cambridge University Press, 2007)
      We study a planar polynomial differential system, given by . We consider a function , where gi(x) are algebraic functions of with ak(x) and algebraic functions, A0(x,y) and A1(x,y) do not share any common factor, h2(x) is ...
    • The solution of the Poincaré problem on the rational first integral for the Liénard polynomial differential equations 

      Giné, Jaume; Llibre, Jaume (Elsevier, 2023)
      In this work we classify the polynomial Liénard differential equations ̈𝑥 + 𝑓(𝑥) ̇𝑥 + 𝑥 = 0, having a rational first integral. Such classification was asked by Poincaré in 1891 for any general polynomial differential ...
    • The spectra of lifted digraphs 

      Dalfó, Cristina; Fiol, Miguel Angel; Sirán, Jozef (Springer, 2019-01-02)
      We present a method to derive the complete spectrum of the lift Γα of a base digraph Γ , with voltage assignment α on a (finite) group G. The method is based on assigning to Γ a quotient-like matrix whose entries are ...
    • The spectra of subKautz and cyclic Kautz digraphs 

      Dalfó, Cristina (Elsevier, 2017)
      Kautz digraphs K(d, `) are a well-known family of dense digraphs, widely studied as a good model for interconnection networks. Closely related with these, the cyclic Kautz CK(d, `) and the subKautz sK(d, 2) digraphs were ...
    • The spectral excess theorem for graphs with few eigenvalues whose distance- 2 or distance-1-or-2 graph is strongly regular 

      Dalfó, Cristina; Fiol, Miguel Angel; Koolen, Jack (Taylor & Francis, 2018-07-13)
      We study regular graphs whose distance-2 graph or distance-1-or-2 graph is strongly regular. We provide a characterization of such graphs Γ (among regular graphs with few distinct eigenvalues) in terms of the spectrum and ...
    • The three-dimensional center problem for the zero-Hopf singularity 

      García, I. A. (Isaac A.); Valls, Claudia (American Institute of Mathematical Sciences, 2016-03-01)
      In this work we extend well-known techniques for solving the Poincar\'e-Lyapunov nondegenerate analytic center problem in the plane to the 3-dimensional center problem at the zero-Hopf singularity. Thus we characterize the ...
    • The unique mixed almost moore graph with parameters k = 2, r = 2 and z = 1 

      Buset, Dominique; López Lorenzo, Ignacio; Miret, Josep M. (Josep Maria) (World Scientific Publishing, 2017-11-02)
      A natural upper bound for the maximum number of vertices in a mixed graph with maximum undirected degree r, maximum directed out-degree z and diameter k is given by the mixed Moore bound. Graphs with order attaining the ...
    • Towards a quantum universe 

      Giné, Jaume (Springer Verlag, 2012)
      In this short review we study the state of the art of the great problems in cosmology and their interrelationships. The reconciliation of these problems passes undoubtedly through the idea of a quantum universe.
    • Transversal conics and the existence of limit cycles 

      Giacomini, Héctor; Grau Montaña, Maite (Elsevier, 2015)
      This paper deals with the problem of location and existence of limit cycles for real planar polynomial differential systems. We provide a method to construct Poincaré-Bendixson regions by using transversal conics. We present ...
    • Triangle randomization for social network data anonymization 

      Brankovic, Ljiljana; López Lorenzo, Ignacio; Miller, Mirka; Sebé Feixas, Francesc (Society of Mathematicians, Physicists and Astronomers of Slovenia; Institute of Mathematics, Physics, and Mechanics; University of Primorska (Slovenia), 2014-06-27)
      In order to protect privacy of social network participants, network graph data should be anonymised prior to its release. Most proposals in the literature aim to achieve $k$-anonymity under specific assumptions about the ...
    • Trisection for supersingular genur 2 curves in characteristic 2 

      Miret, Josep M. (Josep Maria); Pujolàs Boix, Jordi; Thériault, Nicolas (American Institute of Mathematical Sciences (AIMS), 2014)
      By reversing reduction in divisor class arithmetic we provide efficient trisection algorithms for Jacobians of supersingular genus 2 curves over finite fields of characteristic 2. With our technique we obtain new results ...
    • Trisections and cubes in elliptic curves 

      Pujolàs Boix, Jordi; Thériault, Nicolas (Elsevier, 2023)
      We show how to compute the pre-images of multiplication by 3 in the group of points of an elliptic curve E over a field k of characteristic different from 2 and 3 such that E[3](k) = E[3]. We show Q = (xQ, yQ) ∈ [3]E(k) ...
    • Two different epidemiological scenarios of border disease in the populations of Pyrenean chamois (Rupicapra p. pyrenaica) after the first disease outbreaks 

      Fernández Sirera, Laura; Cabezón Ponsoda, Óscar; Allepuz Palau, Alberto; Rosell Bellsola, Rosa; Riquelme Guerrero, Cristina; Serrano Ferrón, Emmanuel; Lavín González, Santiago; Marco, Ignasi (Public Library of Science, 2012)
      Since 2001 several outbreaks of a new disease associated with Border disease virus (BDV) infection have caused important declines in Pyrenean chamois (Rupicapra pyrenaica) populations in the Pyrenees. The goal of this ...
    • Uma fala no ambiente escolar: legitimando significados algébricos 

      Lopes, Antonio José; Giménez, Joaquín; Vanegas, Yuly Marsela (Edur, 2018)
      In this article, the purpose is to re-aim (= look again) the speech of 13-year-old students while solving relational situations that lead to algebraic thinking. For this we use the Semantic Field Model (MCS) to identify ...
    • Universal centers and composition conditions 

      Giné, Jaume; Grau Montaña, Maite; Llibre, Jaume (London Mathematical Society, 2013)
      In this paper, we characterize the universal centres of the ordinary differential equations , where ai(θ) are trigonometric polynomials, in terms of the composition conditions. These centres are closely related with the ...
    • Universal centers in the cubic trigonometric Abel equation 

      Giné, Jaume; Grau Montaña, Maite; Santallusia Esvert, Xavier (Bolyai Institute. University of Szeged; Hungarian Academy of Sciences, 2014)
      We study the center problem for the trigonometric Abel equation dρ/dθ=a1(θ)ρ2+a2(θ)ρ3,dρ/dθ=a1(θ)ρ2+a2(θ)ρ3, where a1(θ)a1(θ) and a2(θ)a2(θ) are cubic trigonometric polynomials in θθ. This problem is closely connected with ...
    • Using PRRSV-resilient sows improve performance in endemic infected farms with recurrent outbreaks 

      Abella Falcó, Glòria; Pagès Bernaus, Adela; Estany Illa, Joan; Pena i Subirà, Ramona Natacha; Fraile Sauce, Lorenzo José; Pla Aragonés, Lluís Miquel (MDPI, 2021)
      The selection of porcine reproductive and respiratory syndrome (PRRS) resilient sows has been proposed as a strategy to control this disease. A discrete event-based simulation model was developed to mimic the outcome of ...
    • Uso de criterios de calidad en la reflexión sobre la práctica de los futuros profesores de secundaria de matemáticas 

      Ferreres Valls, Susana; Vanegas, Yuly Marsela (Elsevier, 2015)
      En este artículo se muestra como los futuros profesores de Secundaria de Matemáticas usan criterios de calidad, para reflexionar y mejorar su propia práctica. Se describen dichos usos, a partir del análisis de sus producciones. ...