期刊文献+
共找到17篇文章
< 1 >
每页显示 20 50 100
Terrorist Networks, Network Energy and Node Removal: A New Measure of Centrality Based on Laplacian Energy 被引量:16
1
作者 Xingqin Qi Robert D. Duval +6 位作者 Kyle Christensen Edgar Fuller Arian Spahiu Qin Wu Yezhou Wu Wenliang Tang Cunquan Zhang 《Social Networking》 2013年第1期19-31,共13页
In this work we propose a centrality measure for networks, which we refer to as Laplacian centrality, that provides a general framework for the centrality of a vertex based on the idea that the importance (or centrali... In this work we propose a centrality measure for networks, which we refer to as Laplacian centrality, that provides a general framework for the centrality of a vertex based on the idea that the importance (or centrality) of a vertex is related to the ability of the network to respond to the deactivation or removal of that vertex from the network. In particular, the Laplacian centrality of a vertex is defined as the relative drop of Laplacian energy caused by the deactivation of this vertex. The Laplacian energy of network G with?n?vertices is defined as , where ?is the eigenvalue of the Laplacian matrix of G. Other dynamics based measures such as that of Masuda and Kori and PageRank compute the importance of a node by analyzing the way paths pass through a node while our measure captures this information as well as the way these paths are “redistributed” when the node is deleted. The validity and robustness of this new measure are illustrated on two different terrorist social network data sets and 84 networks in James Moody’s Add Health in school friendship nomination data, and is compared with other standard centrality measures. 展开更多
关键词 NETWORK CENTRALITY LAPLACIAN ENERGY 9/11 HIJACKING Bali BOMBING Terrorism
下载PDF
On a Class of Supereulerian Digraphs 被引量:10
2
作者 Khalid A. Alsatami Xindong Zhang +1 位作者 Juan Liu Hong-Jian Lai 《Applied Mathematics》 2016年第3期320-326,共7页
The 2-sum of two digraphs and , denoted , is the digraph obtained from the disjoint union of and by identifying an arc in with an arc in . A digraph D is supereulerian if D contains a spanning eulerian subdigraph. It ... The 2-sum of two digraphs and , denoted , is the digraph obtained from the disjoint union of and by identifying an arc in with an arc in . A digraph D is supereulerian if D contains a spanning eulerian subdigraph. It has been noted that the 2-sum of two supereulerian (or even hamiltonian) digraphs may not be supereulerian. We obtain several sufficient conditions on and for to be supereulerian. In particular, we show that if and are symmetrically connected or partially symmetric, then is supereulerian. 展开更多
关键词 Supereulerian Digraph 2-Sums Arc-Strong-Connectivity Hamiltonian-Connected Digraphs
下载PDF
关于超欧拉图的一个注记
3
作者 李登信 赖虹建 《应用数学》 CSCD 北大核心 2001年第S1期19-20,共2页
设G是无向无环的有限图 ,若G有一个生成子图是欧拉图 (Euler) ,则称G是超欧拉图 (Supereulerian) .本文不利用收缩方法 ,直接证明了 :当图G至多差一边有两棵边不相交的生成树时 ,G是超欧拉图或者G有割边 .
关键词 欧拉图 欧拉生成子图 超欧拉图
下载PDF
A Study of Tate Homology via the Approximation Theory with Applications to the Depth Formula 被引量:1
4
作者 Olgur CELIKBAS Li LIANG +1 位作者 Arash SADEGHI Tirdad SHARIF 《Acta Mathematica Sinica,English Series》 SCIE CSCD 2023年第3期439-458,共20页
In this paper we are concerned with absolute,relative and Tate Tor modules.In the first part of the paper we generalize a result of Avramov and Martsinkovsky by using the Auslander-Buchweitz approximation theory,and o... In this paper we are concerned with absolute,relative and Tate Tor modules.In the first part of the paper we generalize a result of Avramov and Martsinkovsky by using the Auslander-Buchweitz approximation theory,and obtain a new exact sequence connecting absolute Tor modules with relative and Tate Tor modules.In the second part of the paper we consider a depth equality,called the depth formula,which has been initially introduced by Auslander and developed further by Huneke and Wiegand.As an application of our main result,we generalize a result of Yassemi and give a new sufficient condition implying the depth formula to hold for modules of finite Gorenstein and finite injective dimension. 展开更多
关键词 Depth formula homological dimensions ABSOLUTE relative and Tate Tor modules semidualizing modules
原文传递
More Compactification for Differential Systems
5
作者 Harry Gingold Daniel Solomon 《Advances in Pure Mathematics》 2013年第1期190-203,共14页
This article is a review and promotion of the study of solutions of differential equations in the “neighborhood of infinity” via a non traditional compactification. We define and compute critical points at infinity ... This article is a review and promotion of the study of solutions of differential equations in the “neighborhood of infinity” via a non traditional compactification. We define and compute critical points at infinity of polynomial autonomuos differential systems and develop an explicit formula for the leading asymptotic term of diverging solutions to critical points at infinity. Applications to problems of completeness and incompleteness (the existence and nonexistence respectively of global solutions) of dynamical systems are provided. In particular a quadratic competing species model and the Lorentz equations are being used as arenas where our technique is applied. The study is also relevant to the Painlevé property and to questions of integrability of dynamical systems. 展开更多
关键词 Nonlinear Polynomial COMPACTIFICATION Ultra Extended Euclidean Space CRITICAL POINT Equilibrium POINT CRITICAL POINT at INFINITY CRITICAL Direction at INFINITY BASIN of Divergence BASIN of Convergence Ideal Solutions Asymptotic Stability Global Globally Asymptotically Stable Jacobian Painleve Analysis Competing Species Model Lorenz Equations Periodic Surface Differential Geometry Attractor REPELLER
下载PDF
<i>Supereulerian Digraph</i>Strong Products
6
作者 Hongjian Lai Omaema Lasfar Juan Liu 《Applied Mathematics》 2021年第4期370-382,共13页
A vertex cycle cover of a digraph <i>H</i> is a collection C = {<em>C</em><sub>1</sub>, <em>C</em><sub>2</sub>, …, <em>C</em><sub><em&g... A vertex cycle cover of a digraph <i>H</i> is a collection C = {<em>C</em><sub>1</sub>, <em>C</em><sub>2</sub>, …, <em>C</em><sub><em>k</em></sub>} of directed cycles in <i>H</i> such that these directed cycles together cover all vertices in <i>H</i> and such that the arc sets of these directed cycles induce a connected subdigraph of <i>H</i>. A subdigraph <i>F</i> of a digraph <i>D</i> is a circulation if for every vertex in <i>F</i>, the indegree of <em>v</em> equals its out degree, and a spanning circulation if <i>F</i> is a cycle factor. Define <i>f</i> (<i>D</i>) to be the smallest cardinality of a vertex cycle cover of the digraph obtained from <i>D</i> by contracting all arcs in <i>F</i>, among all circulations <i>F</i> of <i>D</i>. Adigraph <i>D</i> is supereulerian if <i>D</i> has a spanning connected circulation. In [International Journal of Engineering Science Invention, 8 (2019) 12-19], it is proved that if <em>D</em><sub>1</sub> and <em>D</em><sub>2</sub> are nontrivial strong digraphs such that <em>D</em><sub>1</sub> is supereulerian and <em>D</em><sub>2</sub> has a cycle vertex cover C’ with |C’| ≤ |<em>V</em> (<em>D</em><sub>1</sub>)|, then the Cartesian product <em>D</em><sub>1</sub> and <em>D</em><sub>2</sub> is also supereulerian. In this paper, we prove that for strong digraphs<em> D</em><sub>1</sub> and <em>D</em><sub>2</sub>, if for some cycle factor <em>F</em><sub>1</sub> of <em>D</em><sub>1</sub>, the digraph formed from <em>D</em><sub>1</sub> by contracting arcs in F1 is hamiltonian with <i>f</i> (<i>D</i><sub>2</sub>) not bigger than |<em>V</em> (<em>D</em><sub>1</sub>)|, then the strong product <em>D</em><sub>1</sub> and <em>D</em><sub>2</sub> is supereulerian. 展开更多
关键词 Supereulerian Digraph Direct Product Strong Product Cycle Factors Eulerian Digraph
下载PDF
Group Connectivity and Group Colorings of Graphs -- A Survey 被引量:4
7
作者 Hong-Jian LAI Xiangwen LI +1 位作者 Yehong SHAO Mingquan ZHAN 《Acta Mathematica Sinica,English Series》 SCIE CSCD 2011年第3期405-434,共30页
In 1950s, Tutte introduced the theory of nowhere-zero flows as a tool to investigate the coloring problem of maps, together with his most fascinating conjectures on nowhere-zero flows. These have been extended by Jaeg... In 1950s, Tutte introduced the theory of nowhere-zero flows as a tool to investigate the coloring problem of maps, together with his most fascinating conjectures on nowhere-zero flows. These have been extended by Jaeger et al. in 1992 to group connectivity, the nonhomogeneous form of nowhere-zero flows. Let G be a 2-edge-connected undirected graph, A be an (additive) abelian group and A* = A - {0}. The graph G is A-connected if G has an orientation D(G) such that for every map b : V(G) → A satisfying ∑v∈V(G)b(v) : 0, there is a function f : E(G) → A* such that for each vertex v ∈ V(G), the total amount of f-values on the edges directed out from v minus the total amount of f-values on the edges directed into v is equal to b(v). The group coloring of a graph arises from the dual concept of group connectivity. There have been lots of investigations on these subjects. This survey provides a summary of researches on group connectivity and group colorings of graphs. It contains the following sections. 1. Nowhere-zero Flows and Group Connectivity of Graphs 2. Complete Families and A-reductions 3. Reductions with Edge-deletions, Vertex-deletions and Vertex-splitting 4. Group Colorings as a Dual Concept of Group Connectivity 5. Brooks Theorem, Its Variations and Dual Forms 6. Planar Graphs 7. Group Connectivity of Graphs 7.1 Highly Connected Graphs and Collapsible Graphs 7.2 Degrees Conditions 7.3 Complementary Graphs 7.4 Products of Graphs 7.5 Graphs with Diameter at Most 2 7.6 Line Graphs and Claw-Free Graphs 7.7 Triangular Graphs 7.8 Claw-decompositions and All Tutte-orientations 展开更多
关键词 Group connectivity group connectivity number group coloring group chromatic number
原文传递
Upper Bounds on List Star Chromatic Index of Sparse Graphs 被引量:3
8
作者 Jia Ao LI Katie HORACEK +1 位作者 Rong LUO Zheng Ke MIAO 《Acta Mathematica Sinica,English Series》 SCIE CSCD 2020年第1期1-12,共12页
A star k-edge-coloring is a proper k-edge-coloring such that every connected bicolored subgraph is a path of length at most 3.The star chromatic indexχ'_(st)(G)of a graph G is the smallest integer k such that G h... A star k-edge-coloring is a proper k-edge-coloring such that every connected bicolored subgraph is a path of length at most 3.The star chromatic indexχ'_(st)(G)of a graph G is the smallest integer k such that G has a star k-edge-coloring.The list star chromatic index ch'st(G)is defined analogously.The star edge coloring problem is known to be NP-complete,and it is even hard to obtain tight upper bound as it is unknown whether the star chromatic index for complete graph is linear or super linear.In this paper,we study,in contrast,the best linear upper bound for sparse graph classes.We show that for everyε>0 there exists a constant c(ε)such that if mad(G)<8/3-ε,then■and the coefficient 3/2 ofΔis the best possible.The proof applies a newly developed coloring extension method by assigning color sets with different sizes. 展开更多
关键词 Star edge coloring list edge coloring maximum average degree
原文传递
Generalized Riemann problem for Euler system Dedicated to Professor LI TaTsien on the Occasion of His 80th Birthday
9
作者 CHEN ShuXing LI DeNing 《Science China Mathematics》 SCIE CSCD 2017年第4期581-592,共12页
This article is a survey on the progress in the study of the generalized Riemann problems for MD Euler system. A new result on generalized Riemann problems for Euler systems containing all three main nonlinear waves(s... This article is a survey on the progress in the study of the generalized Riemann problems for MD Euler system. A new result on generalized Riemann problems for Euler systems containing all three main nonlinear waves(shock, rarefaction wave and contact discontinuity) is also introduced. 展开更多
关键词 Euler system Riemann problem shock rarefaction wave contact discontinuity or vortex sheet
原文传递
On the Sizes of k-edge-maximal r-uniform Hypergraphs
10
作者 Ying-zhi TIAN Hong-Jian LAI +1 位作者 Ji-xiang MENG Li-qiong XU 《Acta Mathematicae Applicatae Sinica》 SCIE CSCD 2022年第3期532-539,共8页
Let H=(V,E)be a hypergraph,where V is a set of vertices and E is a set of non-empty subsets of V called edges.If all edges of H have the same cardinality r,then H is an r-uniform hypergraph;if E consists of all r-subs... Let H=(V,E)be a hypergraph,where V is a set of vertices and E is a set of non-empty subsets of V called edges.If all edges of H have the same cardinality r,then H is an r-uniform hypergraph;if E consists of all r-subsets of V,then H is a complete r-uniform hypergraph,denoted by K_(n)^(r),where n=|V|.A hypergraph H′=(V′,E′)is called a subhypergraph of H=(V,E)if V′⊆V and E′⊆E.The edge-connectivity of a hypergraph H is the cardinality of a minimum edge set F⊆E such that H−F is not connected,where H−F=(V,E\F).An r-uniform hypergraph H=(V,E)is k-edge-maximal if every subhypergraph of H has edge-connectivity at most k,but for any edge e∈E(K_(n)^(r))\E(H),H+e contains at least one subhypergraph with edge-connectivity at least k+1.Let k and r be integers with k≥2 and r≥2,and let t=t(k,r)be the largest integer such that(t−1 r−1)≤k.That is,t is the integer satisfying(t−1 r−1)≤k<(t r−1).We prove that if H is an r-uniform k-edge-maximal hypergraph such that n=|V(H)|≥t,then(i)|E(H)|≤(t r)+(n−t)k,and this bound is best possible;(ii)|E(H)|≥(n−1)k−((t−1)k−(t r))[n/t],and this bound is best possible. 展开更多
关键词 EDGE-CONNECTIVITY k-edge-maximal hypergraphs r-uniform hypergraphs
原文传递
Weight Choosability of Graphs with Maximum Degree 4
11
作者 You LU Chong LI Zheng Ke MIAO 《Acta Mathematica Sinica,English Series》 SCIE CSCD 2020年第6期723-732,共10页
Let k be a positive integer.A graph G is k-weight choosable if,for any assignment L(e)of k real numbers to each e∈E(G),there is a mapping f:E(G)→R such that f(uv)∈L(uv)and∑e∈∂(u)^f(e)≠∑e∈∂(u)^f(e)for each uv∈... Let k be a positive integer.A graph G is k-weight choosable if,for any assignment L(e)of k real numbers to each e∈E(G),there is a mapping f:E(G)→R such that f(uv)∈L(uv)and∑e∈∂(u)^f(e)≠∑e∈∂(u)^f(e)for each uv∈E(G),where?(v)is the set of edges incident with v.As a strengthening of the famous 1-2-3-conjecture,Bartnicki,Grytczuk and Niwcyk[Weight choosability of graphs.J.Graph Theory,60,242–256(2009)]conjecture that every graph without isolated edge is 3-weight choosable.This conjecture is wildly open and it is even unknown whether there is a constant k such that every graph without isolated edge is k-weight choosable.In this paper,we show that every connected graph of maximum degree 4 is 4-weight choosable. 展开更多
关键词 1-2-3 conjecture weighting weight choosability Combinatorial Nullstellensatz
原文传递
类Vandermonde恒等式的新组合恒等式:第一部分 被引量:5
12
作者 GOULD Henry Wadsworth 《中国科学:数学》 CSCD 北大核心 2015年第9期1505-1512,共8页
Vandermonde卷积恒等式为n∑k=0(xk)(yn-k)=(x+yn),其中x和y为复数,n为非负整数.本文研究如下形式n∑k=0(x k)(y k)=(x+yn)+R(x,y,n)与其他相关扩充的关系.
关键词 组合恒等式 Vandermonde卷积 代数恒等式
原文传递
Supereulerian Graphs and the Petersen Graph 被引量:1
13
作者 Xiao Min LI Lan LEI +1 位作者 Hong-Jian LAI Meng ZHANG 《Acta Mathematica Sinica,English Series》 SCIE CSCD 2014年第2期291-304,共14页
A graphG is supereulerian if G has a spanning eulerian subgraph.Boesch et al.[J.Graph Theory,1,79–84(1977)]proposed the problem of characterizing supereulerian graphs.In this paper,we prove that any 3-edge-connecte... A graphG is supereulerian if G has a spanning eulerian subgraph.Boesch et al.[J.Graph Theory,1,79–84(1977)]proposed the problem of characterizing supereulerian graphs.In this paper,we prove that any 3-edge-connected graph with at most 11 edge-cuts of size 3 is supereulerian if and only if it cannot be contractible to the Petersen graph.This extends a former result of Catlin and Lai[J.Combin.Theory,Ser.B,66,123–139(1996)]. 展开更多
关键词 Supereulerian graphs petersen graph edge-cut REDUCTION CONTRACTION
原文传递
Multigraphic Degree Sequences and Hamiltonian-connected Line Graphs
14
作者 Ren-sen MA Ai-mei YU +1 位作者 Ke-ke WANG Hong-Jian LAI 《Acta Mathematicae Applicatae Sinica》 SCIE CSCD 2021年第4期800-806,共7页
Let G be a multigraph.Suppose that e=u1v1 and e′=u2v2 are two edges of G.If e≠e′,then G(e,e′)is the graph obtained from G by replacing e=u1v1 with a path u1vev1 and by replacing e′=u2v2 with a path u2ve′v2,where... Let G be a multigraph.Suppose that e=u1v1 and e′=u2v2 are two edges of G.If e≠e′,then G(e,e′)is the graph obtained from G by replacing e=u1v1 with a path u1vev1 and by replacing e′=u2v2 with a path u2ve′v2,where ve,ve′are two new vertices not in V(G).If e=e′,then G(e,e′),also denoted by G(e),is obtained from G by replacing e=u1v1 with a path u1vev1.A graph G is strongly spanning trailable if for any e,e′∈E(G),G(e,e′)has a spanning(ve,ve′)-trail.The design of n processor network with given number of connections from each processor and with a desirable strength of the network can be modelled as a degree sequence realization problem with certain desirable graphical properties.A sequence d=(d1,d2,⋯,dn)is multigraphic if there is a multigraph G with degree sequence d,and such a graph G is called a realization of d.A multigraphic degree sequence d is strongly spanning trailable if d has a realization G which is a strongly spanning trailable graph,and d is line-hamiltonian-connected if d has a realization G such that the line graph of G is hamiltonian-connected.In this paper,we prove that a nonincreasing multigraphic sequence d=(d1,d2)⋯,dn)is strongly spanning trailable if and only if either n=1 and d1=0 or n≥2 and dn≥3.Applying this result,we prove that for a nonincreasing multigraphic sequence d=(d1,d2,⋯,dn),if n≥2 and dn≥3,then d is line-hamiltonian-connected. 展开更多
关键词 strongly spanning trailable graphs multigraphic degree sequence hamiltonian-connected graphs line graph
原文传递
Nowhere-zero 15-Flow in 3-Edge-connected Bidirected Graphs
15
作者 Er Ling WEI Wen Liang TANG Dong YE 《Acta Mathematica Sinica,English Series》 SCIE CSCD 2014年第4期649-660,共12页
It was conjectured by Bouchet that every bidirected graph which admits a nowhere-zero κ flow will admit a nowhere-zero 6-flow. He proved that the conjecture is true when 6 is replaced by 216. Zyka improved the result... It was conjectured by Bouchet that every bidirected graph which admits a nowhere-zero κ flow will admit a nowhere-zero 6-flow. He proved that the conjecture is true when 6 is replaced by 216. Zyka improved the result with 6 replaced by 30. Xu and Zhang showed that the conjecture is true for 6-edge-connected graphs. And for 4-edge-connected graphs, Raspaud and Zhu proved it is true with 6 replaced by 4. In this paper, we show that Bouchet's conjecture is true with 6 replaced by 15 for 3-edge-connected graphs. 展开更多
关键词 Bidirected graph integer flow signed graph
原文传递
Kai Lai Chung (1917-2009) in Memoriam
16
作者 Henry W.Gould 《Journal of Mathematical Research and Exposition》 CSCD 2009年第6期952-953,共2页
The passing of Kai Lai Chung (钟开来) on 1 June 2009 at the venerable age of 91 reminds me forcibly of the importance of Chung's work in my own life.
关键词 钟开莱 职业 数学家 个人
下载PDF
Annihilation Coefficients, Binomial Expansions and q-Analogs
17
作者 H.W.GOULD J.QUAINTANCE 《Journal of Mathematical Research and Exposition》 CSCD 2010年第2期191-204,共14页
Let {An}∞n=0 be an arbitary sequence of natural numbers. We say A(n,k;A) are the Convolution Annihilation Coefficients for {An}n∞=0 if and only if n∑κ=0A(n,k;A)(x-Aκ)n-k=xn. (0.1) Similary, we define B(n... Let {An}∞n=0 be an arbitary sequence of natural numbers. We say A(n,k;A) are the Convolution Annihilation Coefficients for {An}n∞=0 if and only if n∑κ=0A(n,k;A)(x-Aκ)n-k=xn. (0.1) Similary, we define B(n,k;A) to be the Dot Product Annihilation Coefficients for {An}n∞=0 if and only if n∑κ=0A(n,k;A)(x-Aκ)n-k=xn. (0.2) The main result of this paper is an explicit formula for B(n,k;A), which depends on both k and {An}∞n=0. This paper also discusses binomial and q-analogs of Equations (0.1) and (0.2). 展开更多
关键词 Annihilation coefficient Binomial expansion stirling number of the first kind stirling number of the second kind vadermonde convolution.
下载PDF
上一页 1 下一页 到第
使用帮助 返回顶部