Now showing items 165-184 of 244

    • On bipartite-mixed graphs 

      Dalfó, Cristina; Fiol, Miguel Angel; López Lorenzo, Ignacio (Wiley, 2018-04-04)
      Mixed graphs can be seen as digraphs that have both arcs and edges (or digons, that is, two opposite arcs). In this arti- cle, we consider the case where such graphs are bipartite. As main results, we show that in this ...
    • On Middle Cube Graphs 

      Dalfó, Cristina; Fiol, Miguel Angel; Mitjana, Margarida (Indonesian Combinatorial Society (InaCombS); Graph Theory and Applications (GTA) Research Centre; University of Newcastle, Australia; Institut Teknologi Bandung (ITB), Indonesia, 2015)
      We study a family of graphs related to the $n$-cube. The middle cube graph of parameter k is the subgraph of $Q_{2k-1}$ induced by the set of vertices whose binary representation has either $k-1$ or $k$ number of ones. The ...
    • On mixed almost Moore graphs of diameter two 

      López Lorenzo, Ignacio; Miret, Josep M. (Josep Maria) (Electronic Journal of Combinatorics, 2016-04-01)
      Mixed almost Moore graphs appear in the context of the Degree/Diameter problem as a class of extremal mixed graphs, in the sense that their order is one less than the Moore bound for mixed graphs. The problem of their ...
    • On super edge-magic decomposable graphs 

      López Masip, Susana-Clara; Muntaner Batle, F. A.; Rius Font, Miquel (Springer, 2012)
      Let G be any graph and let {Hi}i∈I be a family of graphs such that E(Hi) ∩ E(Hj ) = ∅ when i 6= j, ∪i∈IE(Hi) = E(G) and E(Hi) 6= ∅ for all i ∈ I. In this paper we introduce the concept of {Hi}i∈I -super edge-magic decomposable ...
    • On the ℓ-adic valuation of the cardinality of elliptic curves over finite extensions of Fq 

      Miret, Josep M. (Josep Maria); Pujolàs Boix, Jordi; Valera Martín, Javier (Springer Verlag, 2015)
      Let E be an elliptic curve defined over a finite field Fq of odd characteristic. Let l≠2 be a prime number different from the characteristic and dividing #E(Fq). We describe how the l-adic valuation of the number of points ...
    • On the beta-number of forests with isomorphic components 

      Ichishima, R.; López Masip, Susana-Clara; Muntaner Batle, F. A.; Oshima, A. (De Gruyter Open, 2018)
      The beta-number, β (G), of a graph G is defined to be either the smallest positive integer n for which there exists an injective function f : V (G) → {0, 1, . . . , n} such that each uv ∈ E (G) is labeled |f (u) − f (v)| ...
    • On the center conditions for analytic monodromic degenerate singularities 

      Giné, Jaume; Llibre, Jaume (World Scientific Publishing, 2012)
      In this paper we present two methods for detecting centers of monodromic degenerate singularities of planar analytic vector fields. These methods use auxiliary symmetric vector fields can be applied independently that the ...
    • On the extensions of the Darboux theory of integrability 

      Giné, Jaume; Grau Montaña, Maite; Llibre, Jaume (IOP Publishing, 2013)
      Recently some extensions of the classical Darboux integrability theory to autonomous and non-autonomous polynomial vector fields were completed. The classical Darboux integrability theory and its recent extensions are based ...
    • On the Formal Integrability Problem for Planar Differential Systems 

      Giné, Jaume; Algaba, Antonio; García, Cristóbal (Hindawi Publishing Corporation, 2013)
      We study the analytic integrability problem through the formal integrability problem and we show its connection, in some cases, with the existence of invariant analytic (sometimes algebraic) curves. From the results ...
    • On the Integrability of Liénard systems with a strong saddle 

      Giné, Jaume; Llibre, Jaume (Elsevier, 2017)
      We study the local analytic integrability for real Li\'{e}nard systems, $\dot x=y-F(x),$ $\dot y= x$, with $F(0)=0$ but $F'(0)\ne0,$ which implies that it has a strong saddle at the origin. First we prove that this problem ...
    • On the multiple zeros of a real analytic function with applications to the averaging theory of differential equations 

      García, I. A. (Isaac A.); Llibre, Jaume; Maza Sabido, Susana (IOP Publishing, 2018-11-21)
      In this work we consider real analytic functions $d(z,\la,\e)$, where $d : \Omega \times \mathbb{R}^p \times I \to \Omega$, $\Omega$ is a bounded open subset of $\R$, $I \subset \mathbb{R}$ is an interval containing the ...
    • On the origin of the deflection of light 

      Giné, Jaume (Elsevier, 2008)
      Action at distance in Newtonian physics is replaced by finite propagation speeds in classical post–Newtonian physics. As a result, the differential equations of motion in Newtonian physics are replaced by functional ...
    • On the origin of the inertia: the modified Newtonian dynamics theory 

      Giné, Jaume (Elsevier, 2009)
      The sameness between the inertial mass and the gravitational mass is an assumption and not a consequence of the equivalent principle is shown. In the context of the Sciama’s inertia theory, the sameness between the inertial ...
    • On the periodic orbit bifurcating from a Hopf bifurcation in systems with two slow and one fast variables 

      García, I. A. (Isaac A.); Llibre, Jaume; Maza Sabido, Susana (Elsevier, 2014)
      The Hopf bifurcation in slow-fast systems with two slow variables and one fast variable has been studied recently, mainly from a numerical point of view. Our goal is to provide an analytic proof of the existence of the ...
    • On the planar integrable differential systems 

      Giné, Jaume; Llibre, Jaume (Springer Verlag, 2011)
      Under very general assumptions we prove that the planar differential systems having a first integral are essentially the linear differential systems u˙ = u, ˙v = v. Additionally such systems always have a Lie symmetry. We ...
    • On the Randić index of graphs 

      Dalfó, Cristina (Elsevier, 2018-09-11)
      For a given graph G = (V, E), the degree mean rate of an edge uv ∈ E is a half of the quotient between the geometric and arithmetic means of its end-vertex degrees d(u) and d(v). In this note, we derive tight bounds for ...
    • On Vosperian and Superconnected Vertex-Transitive Digraphs 

      Hamidoune, Yahya Ould; Lladó, A.; López Masip, Susana-Clara (Springer, 2013)
      We investigate the structure of a digraph having a transitive automorphism group where every cutset of minimal cardinality consists of all successors or all predecessors of some vertex. We give a complete characterization ...
    • Open problems involving super edge-magic labelings and related topics 

      López Masip, Susana-Clara; Muntaner Batle, F. A.; Rius Font, Miquel (Institute of Combinatorics and its Applications, 2012)
      Graph labelings has experimented a fast development during the last four decades. Two books dedicated to this topic, a very complete survey on the subject and over 1000 papers in the literature constitute a good proof of ...
    • Optimizing the enzymatic elimination of clogging of a microfiltration membrane by Parellada grape cake 

      Conde Colom, Josep; Echavarría Vélez, Ana Paola; Ibarz Ribas, Alberto; Pagan i Gilabert, Jordi (Wiley, 2016)
      Clogging of the filtration membranes is one of the main problems in the process of obtaining grape must for white wine; therefore, clogging must be reduced to the maximum. The aim of this work was to find the optimal values ...
    • Perfect (super) Edge-Magic Crowns 

      López Masip, Susana-Clara; Muntaner Batle, F. A.; Prabu, M. (Springer, 2017)
      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 a function is ...