Now showing items 1-20 of 248

    • Cyclicity of Nilpotent Centers with Minimum Andreev Number 

      García, I. A. (Isaac A.) (Springer, 2019-10-07)
      We consider polynomial families of real planar vector fields for which the origin is a monodromic nilpotent singularity having minimum Andree's number. There the centers are characterized by the existence of a formal inverse ...
    • Idoneidad didáctica en educación infantil: matemáticas con robots Blue-Bot. 

      Ricart Aranda, María; Estrada Roca, M. Asunción; Margalef Martíl, María (Universidad de Córdoba, 2019)
      El objetivo de este trabajo es valorar la idoneidad didáctica de un proceso de enseñanza y aprendizaje de orientación espacial con el robot Blue-Bot. Primero, se contextualiza la experiencia innovadora implementada con ...
    • Flow resistance equations without explicit estimation of the resistance coefficient for coarse-grained rivers 

      López Alonso, Raúl; Barragán Fernández, Javier; Colomer, M. Àngels (Maria Àngels) (Elsevier, 2007)
      The uncertainty and subjectivity inherent in estimating the resistance coeffi-cient is one of the main sources of error in the application of flow resistance equations tonatural channels. Various studies have shown that ...
    • Reply to the comment by D.E. Rupp and G.M. Smart on "Flow resistance equations without explicit estimation of the resistance coefficient for coarse-grained rivers" 

      López Alonso, Raúl; Barragán Fernández, Javier; Colomer, M. Àngels (Maria Àngels) (Elsevier, 2007)
    • 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 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 ...
    • Spectra and eigenspaces of arbitrary lifts of graphs 

      Dalfó, Cristina; Fiol, Miguel Angel; Pavlíková, Sona; Sirán, Josef (Faculty of Mathematics, Physics and Informatics, Comenius University, 2019)
      We describe, in a very explicit way, a method for determining the spec-tra and bases of all the corresponding eigenspaces of arbitrary lifts of graphs (regularor not).
    • El mètode de les línies per a la resolució aproximada d'equacions en derivades parcials 

      Dalfó, Cristina; Fiol, Miguel Angel (Societat Catalana de Matemàtiques, Institut d’Estudis Catalans, 2019)
      En aquest treball es descriu un mètode numèric semidiscret per a la resolució d'un tipus d'equacions en derivades parcials. És conegut com el mètode de les línies (MOL, per les sigles en anglès), i es basa en la discretització ...
    • The diameter of cyclic Kautz digraphs 

      Böhmová, Katerina; Dalfó, Cristina; Huemer, Clemens (Faculty of Sciences and Mathematics, University of Nis, Serbia, 2017)
      We present a new kind of digraphs, called cyclic Kautz digraphs CK(d, ɭ), which are subdigraphs of the well-known Kautz digraphs K(d,ɭ). The latter have the smallest diameter among all digraphs with their number of ...
    • 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 ...
    • A note on a new general family of deterministic hierarchical networks 

      Dalfó, Cristina; Fiol, Miguel Angel (World Scientific Publishing, 2019)
      It is known that many networks modeling real-life complex systems are small-word (large local clustering and small diameter) and scale-free (power law of the degree distribution), and very often they are also hierarchical. ...
    • Magic coverings and the Kronecker product 

      López Masip, Susana-Clara; Muntaner Batle, F. A.; Rius Font, Miquel (2014)
      In this paper we study a relationship existing among (super) magic coverings and the well known Kronecker product of matrices. We also introduce the concept of Zn-property for digraphs in order to study this relation ...
    • 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 ...
    • The power of digraph products applied to labelings 

      Ichishima, R.; López Masip, Susana-Clara; Muntaner Batle, F. A.; Rius Font, Miquel (Elsevier, 2012)
      The ⊗h-product was introduced in 2008 by Figueroa-Centeno et al. as a way to construct new families of (super) edge-magic graphs and to prove that some of those families admit an exponential number of (super) edge-magic ...
    • Bi-magic and other generalizations of super edge-magic labelings 

      López Masip, Susana-Clara; Muntaner Batle, F. A.; Rius Font, Miquel (Cambridge University Press, 2011)
      In this paper, we use the product ⊗h in order to study super edge-magic labelings, bi-magic labelings and optimal k-equitable labelings. We establish, with the help of the product ⊗h, new relations between super edge-magic ...
    • Every tree is a large subtree of a tree that decomposes Kn or Kn,n 

      Lladó, A.; López Masip, Susana-Clara; Moragas, J. (Elsevier, 2010)
      Let T be a tree with m edges. A well-known conjecture of Ringel states that every tree T with m edges decomposes the complete graph K2m+1. Graham and H¨aggkvist conjectured that T also decomposes the complete bipartite ...
    • Vertex‐transitive graphs that remain connected after failure of a vertex and its neighbors 

      Hamidoune, Yahya Ould; Lladó, A.; López Masip, Susana-Clara (Wiley, 2011)
      A d-regular graph is said to be superconnected if any disconnecting subset with cardinality at most d is formed by the neighbors of some vertex. A superconnected graph that remains connected after the failure of a vertex ...
    • Center cyclicity of Lorenz, Chen and Lü systems 

      García, I. A. (Isaac A.); Maza Sabido, Susanna; Shafer, Douglas S. (Elsevier, 2018-11-09)
      This work provides upper bounds on the cyclicity of the centers on center manifolds in the well-known Lorenz family, and also in the Chen and Lü families. We prove that at most one limit cycle can be made to bifurcate from ...
    • A new approach to gross error detection for GPS networks 

      Dalfó, Cristina; Fiol, Miguel Angel (Elsevier, 2019)
      We present a new matrix-based approach to detect and correct gross errors in GPS geodetic control networks. The study is carried out by introducing a new matrix, whose entries are powers of a (real or complex) variable, ...
    • New problems related to the valences of (super) edge-magic labelings 

      López Masip, Susana-Clara; Muntaner Batle, F. A.; Rius Font, Miquel (2013)
      A graph G of order p and size q is edge-magic if there is a bijective function f : V (G) ∪ E(G) −→ {i} p+q i=1 such that f(x) + f(xy) + f(y) = k , for all xy ∈ E(G) . The function f is an edge-magic labeling of G and the ...