Institutions of Higher Education of Sichuan Province

Chengdu, China

Institutions of Higher Education of Sichuan Province

Chengdu, China
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Huang P.,University of Sichuan | Huang P.,Sichuan Agricultural University | Lin F.,Sichuan University | Liu C.,Sichuan University | And 3 more authors.
Journal of Sensors | Year: 2015

Coverage problem is one of the major issues in wireless sensor networks (WSN). In order to optimize the network coverage, different coverage formulations have been proposed. Recently, a newly emerging coverage scheme in wireless sensor networks, sweep coverage, which uses mobile sensors to monitor certain points of interest (POIs), is proposed. However, the data delivery to sink, an important problem in WSN, is not considered in original sweep coverage and many of the existing works did not consider it yet. In this work, a novel algorithm named ACOSC (ACO-based sweep coverage) to solve the sweep coverage problem considering periodical coverage of POIs and delivery of data simultaneously is proposed. The evaluation results show that our algorithm has better performance than existing schemes. © 2015 Peng Huang et al.


Li Z.,Peking University | Zhu E.,Peking University | Shao Z.,Institutions of Higher Education of Sichuan Province | Shao Z.,Sichuan University | Xu J.,Peking University
International Journal of Computer Mathematics | Year: 2016

A graph G is uniquely k-colourable if the chromatic number of G is k and G has only one k-colouring up to permutation of the colours. Aksionov [On uniquely 3-colorable planar graphs, Discrete Math. 20 (1977), pp. 209–216] conjectured that every uniquely 3-colourable planar graph with at least four vertices has two adjacent triangles. However, in the same year, Melnikov and Steinberg [L.S. Mel'nikov and R. Steinberg, One counterexample for two conjectures on three coloring, Discrete Math. 20 (1977), pp. 203–206.] disproved the conjecture by constructing a counterexample. In this paper, we prove that if a uniquely 3-colourable planar graph G has at most 4 triangles then G has two adjacent triangles. Furthermore, for any (Formula presented.), we construct a uniquely 3-colourable planar graph with k triangles and without adjacent triangles. © 2016 Informa UK Limited, trading as Taylor & Francis Group


Shao Z.,Sichuan University | Shao Z.,Institutions of Higher Education of Sichuan Province | Xu J.,Peking University | Yeh R.K.,Feng Chia University
Journal of Combinatorial Optimization | Year: 2016

Let G = (V, E) be a graph. Denote dG(u, v) the distance between two vertices u and v in G. An L(2, 1)-labeling of G is a function f: V → {0, 1, ⋯} such that for any two vertices u and v, |f(u) - f(v)| ≥ 2 if dG(u, v)=1 and |f(u) - f(v)| ≥ 1 if dG(u, v)=2. The span of f is the difference between the largest and the smallest number in f(V). The λ-number of G, denoted λ(G), is the minimum span over all L(2, 1)-labelings of G. In this article, we confirm Conjecture 6.1 stated in X. Li et al. (J Comb Optim 25:716–736, 2013) in the case when (i) ℓ is even, or (ii) ℓ ≥ 5 is odd and 0 ≤ r≤ 8. © 2014, Springer Science+Business Media New York.


Klavzar S.,University of Ljubljana | Klavzar S.,University of Maribor | Klavzar S.,Institute of Mathematics | Shao Z.,Institutions of Higher Education of Sichuan Province | Shao Z.,Sichuan University
International Journal of Computer Mathematics | Year: 2015

A local colouring of a graph G is a function c: V(G)→ℕ such that for each S ⊆ V(G), 2≤|S|≤3, there exist u, v∈S with |c(u)−c(v)| at least the number of edges in the subgraph induced by S. The maximum colour assigned by c is the value χℓ(c) of c, and the local chromatic number of G is χℓ(G)=min {χℓ(c): c is a local colouring of G}. In this note the local chromatic number is determined for Cartesian products G □ H, where G and GH are 3-colourable graphs. This result in part corrects an error from Omoomi and Pourmiri [On the local colourings of graphs, Ars Combin. 86 (2008), pp. 147–159]. It is also proved that if G and H are graphs such that χ(G)≤⌊ χℓ(H)/2 ⌋, then χℓ(G □ H)≤χℓ(H)+1. © 2014 Taylor & Francis.


Li Z.,Peking University | Shao Z.,Institutions of Higher Education of Sichuan Province | Shao Z.,Sichuan University | Zhu E.,Peking University | Xu J.,Peking University
Information Processing Letters | Year: 2015

A local k-coloring of a graph G is a function f:V(G)→{1,2,·,k} such that for each S⊆V(G), 2≤|S|≤3, there exist u,v ∈ S with |f(u)-f(v)| at least the size of the subgraph induced by S. The local chromatic number of G is χl(G)=min{k:G has a local k-coloring}. Chartrand et al. [2] asked: does there exist a graph Gk such that χl(Gk)=χ(Gk)=k? Furthermore, they conjectured that for every positive integer k, there exists a graph Gk with χl(G)=k such that every local k-coloring of Gk uses all of the colors 1,2,·,k. In this paper we give a affirmative answer to the problem and confirm the conjecture. © 2014 Published by Elsevier B.V.


Shao Z.,Sichuan University | Shao Z.,Institutions of Higher Education of Sichuan Province | Vesel A.,University of Maribor
The Scientific World Journal | Year: 2014

An L (2,1) -labeling of a graph G = (V, E) is a function f from the vertex set V (G) to the set of nonnegative integers such that the labels on adjacent vertices differ by at least two and the labels on vertices at distance two differ by at least one. The span of f is the difference between the largest and the smallest numbers in f (V). The λ -number of G, denoted by (G), is the minimum span over all L (2,1) -labelings of G. We consider the λ -number of P n C m and for n ≤ 11 the λ -number of C n C m. We determine λ -numbers of graphs of interest with the exception of a finite number of graphs and we improve the bounds on the λ -number of C n C m, m ≥ 24 and n ≥ 26. © 2014 Zehui Shao and Aleksander Vesel.


Shao Z.,Institutions of Higher Education of Sichuan Province | Shao Z.,Sichuan University | Vesel A.,University of Maribor
IET Communications | Year: 2013

Let u and v be vertices of a graph G = (V, E) and d(u, v) be the distance between u and v in G. For positive integers k1, k2,.., kn with k1>k2 > .. > kn an L(k1, k2,.., kn)-labelling of G is a function f : V(G)→{0, 1,..} such that for every u, v∈ V (G) and for all 1≤i≤n, f(u) - f(v)≤ki if d(u, v) = i. The span of f is the difference between the largest and the smallest numbers in f (V(G)). Theλk1,k2,..,kn -number of G is the minimum span over all L(k1, k2, .., kn)-labellings of G. In this study, an integer linear programming model and a satisfiability test reduction for an L(k1, k2, .., kn)-labelling are proposed. Both approaches are used for studying the Λ3,2,1-numbers of strong, Cartesian and direct products of paths and cycles. © The Institution of Engineering and Technology 2013.


Hu D.-K.,Sichuan University | Hu D.-K.,Institutions of Higher Education of Sichuan Province | Lin J.,University of Electronic Science and Technology of China
Applied Mechanics and Materials | Year: 2013

A multi-feature bio-inspired model for scene image classification (MFBIM) is presented in this work; it extends the hierarchical feedforward model of the visual cortex. Firstly, each of three paths of classification uses each image property (i.e. shape, edge or color based features) independently. Then, BPNN assigns the category of an image based on the previous outputs. Experiments show that the model boosts the classification accuracy over the shape based model. Meanwhile, the proposed approach achieves a high accuracy comparable to other reported methods on publicly available color image dataset. © (2013) Trans Tech Publications, Switzerland.


Zhang X.,Sichuan University | Zhang X.,Institutions of Higher Education of Sichuan Province
Journal of Computational and Theoretical Nanoscience | Year: 2014

An L(d,1)-labeling for a graph G is a function f : V (G)→{0,1, } such that f (u)?f (v) ≥ d whenever uv ε E(G) and f (u)?f (v) ≥ 1 whenever u and v are at distance two apart. The span of f is the difference between the largest and the smallest numbers in f V (G). The λd-number for G, denoted by λ(G), is the minimum span over all L(d,1)-labelings of G. In this paper, a constructive labeling algorithm for the L(d,1)-labeling of Cartesian product of two complete graphs is presented. Based on this algorithm, the λd-numbers of some Cartesian product of two complete graphs are determined for 1 ≤ d ≤ 9.Copyright © 2014 American Scientific Publishers Copyright © 2014 American Scientific Publishers.


Zhang Z.,Institutions of Higher Education of Sichuan Province | Zhang Z.,Chengdu University of Technology | Shao Z.,Institutions of Higher Education of Sichuan Province | Shao Z.,Chengdu University of Technology
Journal of Computational and Theoretical Nanoscience | Year: 2015

A vertex separator in an undirected graph is a subset of the vertices, whose removal disconnects the graph in at least two nonempty connected components. Given a connected undirected graph G = (V ,E) with |V| = n, an integer 1 ≤ b ≤ n, the vertex separator problem (VSP) asks to find a partition of V into disjoint sets A, B, C, with A and B nonempty, such that (1) E contains no edge (i, j) with i ϵ A, j ? B, (2) max{|A|} |B|} = b, (3) |C| is minimized. The vertex separator problem is a classic NP complete problem. It is widely applied to circuit design, computer network communication, protein combination in bioinformatics, etc. At present there has already been exact algorithm to search vertex separator of undirected graph, while there are only few heuristic algorithms. Aiming at the VSP and a solution design for heuristic algorithm, this paper designs an improved K-OPT local search algorithm. In order to compare the searching efficiency of a variety of heuristic algorithms for VSP, this paper also designs simulated annealing algorithm and variable neighborhood search algorithm, and performs comparative experiments on these algorithms using DIMACS graph, MATRIXMARKET graph, MIPLIB graph. The experimental results show that the improved K-OPT local search algorithm goes the best. In the experiment, using improved K-OPT local search algorithm, existing Relax-and-Cut algorithm is further compared, whose experimental results show that in some graph tests, the improved K-OPT local search algorithm goes better than Relax-and-Cut algorithm. © 2015 American Scientific Publishers.

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