Now showing items 1-20 of 445

  • 3-colorability of pseudo-triangulations 

    Aichholzer, Oswin; Aurenhammer, Franz; Hackl, Thomas; Huemer, Clemens; Pilz, Alexander; Vogtenhuber, Birgit (2015)
    Article
    Open Access
    Deciding 3-colorability for general plane graphs is known to be an NP-complete problem. However, for certain families of graphs, like triangulations, polynomial time algorithms exist. We consider the family of pseudo-tri ...
  • 4-labelings and grid embeddings of plane quadrangulations 

    Barrière Figueroa, Eulalia; Huemer, Clemens (2009-06-03)
    External research report
    Open Access
    We show that each quadrangulation on $n$ vertices has a closed rectangle of influence drawing on the $(n-2) \times (n-2)$ grid. Further, we present a simple algorithm to obtain a straight-line drawing of a quadrangulation ...
  • Abelian Cayley digraphs with asymptotically large order for any given degree 

    Aguiló Gost, Francisco de Asis L.; Fiol Mora, Miquel Àngel; Pérez Mansilla, Sonia (2016-04-29)
    Article
    Open Access
    Abelian Cayley digraphs can be constructed by using a generalization to Z(n) of the concept of congruence in Z. Here we use this approach to present a family of such digraphs, which, for every fixed value of the degree, ...
  • A block algorithm for the algebraic path problem and its execution on a systolic array 

    Núñez, Fernando J.; Valero Cortés, Mateo (Institute of Electrical and Electronics Engineers (IEEE), 1989)
    Conference report
    Open Access
    The solution of the algebraic path problem (APP) for arbitrarily sized graphs by a fixed-size systolic array processor (SAP) is addressed. The APP is decomposed into two subproblems, and SAP is designed for each one. Both ...
  • A Boolean algebra approach to the construction of snarks 

    Fiol Mora, Miquel Àngel (John Wiley & Sons, 1991)
    Part of book or chapter of book
    Open Access
    This work deals with the construction of snarks, that is, cubic graphs that cannot be 3-edge-colored. A natural generalization of the concept of "color", that describes in a simple way the coloring ("0" or "1") of any set ...
  • A Constraint-Based Hypergraph Partitioning Approach to Coreference Resolution 

    Sapena Masip, Emilio; Padró, Lluís; Turmo Borras, Jorge (2013-12)
    Article
    Open Access
    This work is focused on research in machine learning for coreference resolution. Coreference resolution is a natural language processing task that consists of determining the expressions in a discourse that refer to the ...
  • A construction of Small (q-1)-Regular Graphs of Girth 8 

    Abreu, Marien; Araujo Pardo, Gabriela; Balbuena Martínez, Maria Camino Teófila; Labbate, D. (2015-04-21)
    Article
    Open Access
    In this note we construct a new infinite family of (q - 1)-regular graphs of girth 8 and order 2q(q - 1)(2) for all prime powers q >= 16, which are the smallest known so far whenever q - 1 is not a prime power or a prime ...
  • A construction of small regular bipartite graphs of girth 8 

    Balbuena Martínez, Maria Camino Teófila (2009-01)
    Article
    Open Access
    Let q be a prime a power and k an integer such that 3 ≤ k ≤ q. In this paper we present a method using Latin squares to construct adjacency matrices of k-regular bipartite graphs of girth 8 on $2(kq^{2}-q)$ vertices. Some ...
  • Active learning in Crowdsourcing classification problems using Sampling Theory for graph signals 

    Maroto Morales, Javier Alejandro (Universitat Politècnica de Catalunya, 2017-05-15)
    Bachelor thesis
    Open Access
    Covenantee:  University of Southern California
  • A differential approach for bounding the index of graphs under perturbations 

    Dalfó Simó, Cristina; Fiol Mora, Miquel Àngel; Garriga Valle, Ernest (2011-03)
    External research report
    Open Access
  • A differential approach for bounding the index of graphs under perturbations 

    Dalfó Simó, Cristina; Fiol Mora, Miquel Àngel; Garriga Valle, Ernest (2011-09-02)
    Article
    Open Access
    This paper presents bounds for the variation of the spectral radius (G) of a graph G after some perturbations or local vertex/edge modifications of G. The perturbations considered here are the connection of a new vertex ...
  • A discussion on the design of graph database benchmarks 

    Domínguez Sal, David; Martínez Bazán, Norbert; Muntés Mulero, Víctor; Baleta Ferrer, Pedro; Larriba Pey, Josep (2011)
    Article
    Open Access
    Graph Database Management systems (GDBs) are gaining popularity. They are used to analyze huge graph datasets that are naturally appearing in many application areas to model interrelated data. The objective of this paper ...
  • Adjacency matrices of polarity graphs and of other C4-free graphs of large size 

    Abreu, M.; Balbuena Martínez, Maria Camino Teófila; Labbate, D. (2010)
    Article
    Restricted access - publisher's policy
    In this paper we give a method for obtaining the adjacency matrix of a simple polarity graph $G_q$ from a projective plane PG(2,q), where q is a prime power. Denote by ex(n;C₄) the maximum number of edges of a graph on n ...
  • A family of mixed graphs with large order and diameter 2 

    Araujo Pardo, Gabriela; Balbuena Martínez, Maria Camino Teófila; Miller, Mirka; Zdimalova, Maria (2017-02)
    Article
    Open Access
    A mixed regular graph is a connected simple graph in which each vertex has both a fixed outdegree (the same indegree) and a fixed undirected degree. A mixed regular graphs is said to be optimal if there is not a mixed ...
  • A framework for building OLAP cubes on graphs 

    Ghrab, Amine; Romero Moral, Óscar; Skhiri, Sabri; Vaisman, Alejandro; Zimányi, Esteban (Springer, 2015)
    Conference report
    Open Access
    Graphs are widespread structures providing a powerful abstraction for modeling networked data. Large and complex graphs have emerged in various domains such as social networks, bioinformatics, and chemical data. However, ...
  • AGAMOS: A graph-based approach to modulo scheduling for clustered microarchitectures 

    Aleta Ortega, Alexandre; Codina Viñas, Josep M.; Sánchez Navarro, F. Jesús; González Colás, Antonio María; Kaeli, D (2009-06)
    Article
    Open Access
    This paper presents AGAMOS, a technique to modulo schedule loops on clustered microarchitectures. The proposed scheme uses a multilevel graph partitioning strategy to distribute the workload among clusters and reduces the ...
  • A graph semantics for a variant of the ambient calculus more adequate for modeling SOC 

    Mylonakis Pascual, Nicolás (2017-02-07)
    External research report
    Open Access
    In this paper we present a graph semantics of a variant of the well known ambient calculus. The main change of our variant is to extract the mobility commands of the original calculus from the ambient topology. Similar ...
  • Algebraic characteritzacions of bipartite distance-regular graphs 

    Fiol, Miquel Àngel (2010-06-10)
    Audiovisual
    Open Access
  • Algebraic characterizations of bipartite distance-regular graphs 

    Fiol Mora, Miquel Àngel (Iniciativa Digital Politècnica, 2011)
    Conference report
    Open Access
    Bipartite graphs are combinatorial objects bearing some interesting symmetries. Thus, their spectra—eigenvalues of its adjacency matrix—are symmetric about zero, as the corresponding eigenvectors come into pairs. Moreover, ...
  • Algebraic characterizations of distance-regular graphs 

    Fiol Mora, Miquel Àngel (Elsevier, 2002)
    Article
    Open Access
    We survey some old and some new characterizations of distance-regular graphs, which depend on information retrieved from their adjacency matrix. In particular, it is shown that a regular graph with d+1 distinct eigenvalues ...