Recent Submissions

  • New cyclic Kautz digraphs with optimal diameter 

    Böhmová, Katerina; Dalfó, Cristina; Huemer, Clemens (University of Calgary, 2021-12-31)
    We obtain a new family of digraphs with minimal diameter, that is, given the number of vertices and out-degree, there is no other digraph with a smaller diameter. This new family of digraphs are called `modified cyclic ...
  • On the spectra and eigenspaces of the universal adjacency matrices of arbitrary lifts of graphs 

    Dalfó, Cristina; Fiol, Miguel Angel; Pavlíková, Sona; Sirán, Jozef (Taylor & Francis, 2022-02-19)
    The universal adjacency matrix U of a graph Γ, with adjacency matrix A, is a linear combination of A, the diagonal matrix D of vertex degrees, the identity matrix I, and the all-1 matrix J with real coefficients, that is, ...
  • Center problem with characteristic directions and inverse integrating factors 

    García, I. A. (Isaac A.); Giné, Jaume (Elsevier, 2022)
    We consider the center-focus problem for analytic families of planar vector fields having a monodromic singularity with characteristic directions. We give a method to compute the center conditions of the family provided ...
  • Invariant Algebraic Curves of Generalized Liénard Polynomial Differential Systems 

    Giné, Jaume; Llibre, Jaume (MDPI, 2022)
    In this study, we focus on invariant algebraic curves of generalized Liénard polynomial differential systems x 0 = y, y 0 = −fm(x)y − gn(x), where the degrees of the polynomials f and g are m and n, respectively, and ...
  • Full wave analysis of stripping chronopotentiometry at scanned deposition potential (SSCP): obtaining binding curves in labile heterogeneous macromolecular systems for any metal-toligand ratio. 

    Pinheiro, José-Paulo; Galceran i Nogués, Josep; Rotureau, Elise; Companys Ferran, Encarnació; Puy Llorens, Jaume (Elsevier, 2020)
    The different deposition potentials applied in Scanned Stripping ChronoPotentiometry (SSCP) probe different values of the free metal and complex concentrations at the electrode surface. The knowledge of these concentrations ...
  • Analytic integrability around the origin of certain differential system 

    Giné, Jaume; Valls, Claudia (Wilmington Scientific Publisher, 2022)
    In this work we consider the polynomial differential system x˙=−y+xyn−1, y˙=x+ayxn−1, where a∈R and n≥2 with n∈N. This system is a certain generalization of the classical Liénard system. We study the center problem and ...
  • Analytic integrability around a nilpotent singularity: The non-generic case 

    Algaba, Antonio; Díaz, María; García, Cristóbal; Giné, Jaume (American Institute of Mathematical Sciences, 2020)
    Recently, in [9] is characterized the analytic integrability problem around a nilpotent singularity for differential systems in the plane under generic conditions. In this work we solve the remaining case completing the ...
  • Liouvillian integrability of a general Rayleigh-Duffing oscillator 

    Giné, Jaume; Valls, Claudia (AtlantisTaylor & Francis, 2019)
    We give a complete description of the Darboux and Liouville integrability of a general Rayleigh-Duffing oscillator through the characterization of its polynomial first integrals, Darboux polynomials and exponential factors.
  • Integrability Conditions for Complex Homogeneous Kukles Systems 

    Giné, Jaume; Valls, Claudia (Atlantis and Taylor & Francis, 2018)
    In this paper we study the existence of local analytic first integrals for complex polynomial differential systems of the form ẋ = x + Pn(x, y), ẏ = −y, where Pn(x,y) is a homogeneous polynomial of degree n, called the ...
  • The center problem for Z_2-symmetric nilpotent vector fields 

    Algaba, Antonio; García, Cristóbal; Giné, Jaume; Llibre, Jaume (Elsevier, 2018)
    We say that a polynomial differential system ˙x = P(x, y), ˙y = Q(x, y) having the origin as a singular point is Z2-symmetric if P(−x, −y) = −P(x, y) and Q(−x, −y) = −Q(x, y). It is known that there are nilpotent centers ...
  • New constructions for the n-queens problem 

    Bača, Martin; López Masip, Susana-Clara; Muntaner Batle, Francesc Antoni; Semaničová-Feňovčíková, Andrea (Springer, 2020-02)
    Let D be a digraph, possibly with loops. A queen labeling of D is a bijective function l:V(G)⟶{1,2,…,|V(G)|} such that, for every pair of arcs in E(D), namely (u, v) and (u′,v′) we have (i) l(u)+l(v)≠l(u′)+l(v′) and (ii) ...
  • (Di)graph decompositions and magic type labelings: a dual relation 

    López Masip, Susana-Clara; Muntaner Batle, Francesc Antoni; Prabu, M. (Springer, 2020-10)
    A graph G is called edge-magic if there is a bijective function f from the set of vertices and edges to the set {1, 2, . . . , |V (G)| + |E(G)|} such that the sum f(x) + f(xy) + f(y) for any xy in E(G) is constant. Such ...
  • Contrariando o “velho do Restelo”: análise global e componentes das atitudes em relação à estatística em professores Portugueses 

    Martins, José Alenxadre; Estrada Roca, M. Asunción; Nascimento, Maria Manuel (Universidade de Aveiro, 2018)
    Es necesario conocer las actitudes de los profesores hacia la estadística, en el sentido de entender mejor su predisposición y compromiso hacia el proceso de enseñanza-aprendizaje y su formación. Así, este ...
  • Cospectral digraphs from locally line digraphs 

    Dalfó, Cristina; Fiol, Miguel Angel (Elsevier, 2016-07)
    A digraph Γ =(V, E) is a line digraph when every pair of vertices u, v∈V have either equal or disjoint in-neighborhoods. When this condition only applies for vertices in a given subset (with at least two elements), we say ...
  • Deterministic hierarchical networks 

    Barrière, Lali; Comellas, Francesc; Dalfó, Cristina; Fiol, Miguel Angel (IOP Publishing, 2016-05)
    It has been shown that many networks associated with complex systems are small-world (they have both a large local clustering coefficient and a small diameter) and they are also scale-free (the degrees are distributed ...
  • The degree/diameter problem in maximal planar bipartite graphs 

    Dalfó, Cristina; Huemer, Clemens; Salas Piñón, Julián (Electronic Journal of Combinatorics, 2016)
    The (∆, D) (degree/diameter) problem consists of finding the largest possiblenumber of verticesnamong all the graphs with maximum degree ∆ and diameter D. We consider the (∆, D) problem for maximal planar bipartite ...
  • A note on the order of iterated line digraphs 

    Dalfó, Cristina; Fiol, Miguel Angel (Wiley Periodicals Inc., 2016-06)
    Given a digraph G, we propose a new method to find therecurrence equation for the number of vertices nk of the k-iterated linedigraph Lk(G), for k≥0, where L0(G)=G. We obtain this result by usingthe minimal polynomial of ...
  • On quotient digraphs and voltage digraphs 

    Dalfó, Cristina; Fiol, Miguel Angel; Miller, Mirka; Ryan, Joe (Combinatorial Mathematics Society of Australasia (CMSA), 2017)
    We study the relationship between two key concepts in the theory of digraphs, those of quotient digraphs and voltage digraphs. These techniques contract or expand a given digraph in order to study its characteristics, or ...
  • From expanded digraphs to lifts of voltage digraphs and line digraphs 

    Dalfó, Cristina; Fiol, Miguel Angel; Miller, Mirka; Ryan, Joe (Combinatorial Mathematics Society of Australasia (CMSA), 2017)
    In this note we present a general approach to construct large digraphs from small ones. These are called expanded digraphs, and, as particular cases, we show the close relationship between lifted digraphs of voltage digraphs ...
  • Edge distance-regular graphs 

    Cámara Vallejo, Marc; Dalfó, Cristina; Fàbrega Canudas, José; Fiol, Miguel Angel; Garriga Valle, Ernest (Elsevier, 2011-12)
    Edge-distance-regularity is a concept recently introduced by the authors which is similar to that of distance-regularity, but now the graph is seen from each of its edges instead of from its vertices. More precisely, a ...

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