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1.
For an arbitrary subset P of the reals, a function f ： V →P is defined to be a P-dominating function of a graph G = （V, E） if the sum of its function values over any closed neighbourhood is at least 1. That is, for every v ∈ V, f（N[v]） ≥ 1. The definition of total P-dominating function is obtained by simply changing ‘closed＇ neighborhood N[v] in the definition of P-dominating function to ‘open＇ neighborhood N（v）. The （total） P-domination number of a graph G is defined to be the infimum of weight w（f） = ∑v ∈ V f（v） taken over all （total） P-dominating function f. Similarly, the P-edge and P-star dominating functions can be defined. In this paper we survey some recent progress on the topic of dominating functions in graph theory. Especially, we are interested in P-, P-edge and P-star dominating functions of graphs with integer values. 相似文献
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图的整数值控制函数 总被引：1，自引：0，他引：1
For an arbitrary subset P of the reals,a function f:V→P is defined to be a P-dominating function of a graph G=(V,E) if the sum of its function values over any closed neighbourhood is at least 1.That is,for every v∈V, f(N[v])≥1.The definition of total P-dominating function is obtained by simply changing‘closed’neighborhood N[v]in the definition of P-dominating function to‘open’neighborhood N(v).The (total) P-domination number of a graph G is defined to be the infimum of weight w(f) =∑_(v∈V)f(v) taken over all (total) P-dominating function f.Similarly,the P-edge and P-star dominating functions can be defined.In this paper we survey some recent progress oil the topic of dominating functions in graph theory.Especially,we are interested in P-,P-edge and P-star dominating functions of graphs with integer values. 相似文献
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Let G=(V, E)be a simple graph without isolated vertices. For positive integer κ, a 3-valued function f:V → {-1, 0, 1} is said to be a minus total k-subdominating function(MTκSF)if ∑u∈N(u)f(u)≥ 1 for at least κ vertices v in G, where N(v)is the open neighborhood of v. The minus total κ-subdomination number γ-κt(G)equals the minimum weight of an MTkSF on G. In this paper, the values on the minus total κ-subdomination number of some special graphs are investigated. Several lower bounds on γ-κt of general graphs and trees are obtained. 相似文献
4.
《高等教育与学术研究》2007,(3)
A Romam dominating function on a graph G = (V , E) is a function f : V → {0,1,2} satisfying the condition that every vertex v for which f(v)=0 is adjacent to at least one vertex x for which f(x)=2, denoted by f = (V0 , V1 , V2). The weight of a Roman dominating function is the value f(V)=∑v∈V=2n2 n1, where |Vi|= ni (i=0,1,2), the minimum weight of a Ronam dominating function denoted by γ R (G ). In this paper, we give an upper bound of γ R (G ), and at the same time, we answer an open problem posed in [1]. 相似文献
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Let G = （V,A） be a digraph.A set T of vertices of G is a twin dominating set of G if for every vertex v ∈ V ／ T.There exist u,w ∈ T （possibly u = w） such that （u,v）,（v,w） ∈ A.The twin domination number γ＊（G） of G is the cardinality of a minimum twin dominating set of G.In this paper we consider the twin domination number in generalized Kautz digraphs GK（n,d）.In these digraphs,we establish bounds on the twin domination number and give a sufficient condition for the twin domination number attaining the lower bound.We give the exact values of the twin domination numbers by constructing minimum twin dominating sets for some special generalized Kautz digraphs. 相似文献
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We studied the normality criterion for families of meromorphic functions related to shared sets. Let F be a family of meromorphic functions on the unit disc △, a and b be distinct non-zero values, S={a,b}, and k be a positive integer. If for every f∈ F, i） the zeros of f（z） have a multiplicity of at least k＋ 1, and ii） E^-f（k）（S） lohtain in E^-f（S）, then F is normal on .4. At the same time, the corresponding results of normal function are also proved. 相似文献
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Given a graph G,a subgraph C is called a clique of G if C is a complete subgraph of G maximal under inclusion and |C|≥2. A clique-transversal set S of G is a set of vertices of G such that S meets all cliques of G. The clique-transversal number, denoted as TC (G), is the minimum cardinality of a clique-transversal set in G. The clique-graph of G, denoted as K (G), is the graph obtained by taking the cliques of G as vertices, and two vertices are adjacent if and only if the corresponding cliques in G have nonempty intersection. Let F be a class of graphs G such that F={G|K(G) is a tree}. In this paper the graphs in F having independent clique-transversal sets are shown and thus TC (G)/|G|≤1/2 for all G ∈ F. 相似文献
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许承德 《上海大学学报(英文版)》2005,(4)
1IntroductionIn general,we followthe notation and terminologyin Refs.[1-5,7].In this paper all graphs are si mple.LetGbe a graph,V(G)the vertex set ofG,andE(G)the edge set ofG.The distance between twoverticesx,y∈V(G)is denoted bydG(x,y).Thediameter ofGis denoted byd(G).A short(x,y)-pathis an(x,y)-path with length≤d(G).An edgee∈E(G)is called cyclic if there exists a cycle inGcontaininge.To each cyclic edgee,letg(e)be thelength of the shortest cycle containinge.Ifeis abridge theng(e)… 相似文献
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The problem of monitoring an electric power system by placing as few measurement devices in the system as possible is closely related to the well-known vertex covering and dominating set problems in graph theory. In this paper, it was shown that the power domination number of an outerplanar graph with the diameter two or a 2-connected outerplanar graph with the diameter three is precisely one. Upper bounds on the power domination number for a general planar graph with the diameter two or three were determined as an immediate consequences of results proven by Dorfling, et al. Also, an infinite family of outerplanar graphs with the diameter four having arbitrarily large power domination numbers were given. 相似文献
10.
XU Cheng-de 《上海大学学报(英文版)》2005,9(4):306-308
The line persistence of a graph G, Pt （ G ） is the minimum number of lines which must be removed to increase the diameter of G. In Ref. [7] （J. Shanghai Univ., 2003,7（4）：352-357）, we gave a characterization of graphs of diameter five with ρ1 （ G ）≥2. In this paper we will show that each of the 8 special graphs Xi （ i = 1,2,3,4,5,6,7,8） listed in condition （2） of Theorem 1 in Ref. [7] can not be deleted. Therefore the results we obtained in Ref. [7] can not in general be improved. 相似文献
11.
设G=（V,E）是一个图,一个函数f：V∪E→{-1,＋}1,如果对每一个x∈E∪V,都有∑y∈Nt[x]f（y）≤0成立,则称f为图G的一个反符号全控制函数,其中Nt（x）表示G中与元素x相邻或相关联的元素之集,称为元素x的全邻域,Nt[x]=N（x）∪{x}为x的闭全邻域。规定图G的反符号全控制数定义为γrst（G）=max{∑x∈V∪Ef（x）f为图的反符号全控制函数}。得到了一般图的反符号全控制数的若干上界,并确定了圈Cn的反符号全控制数。 相似文献
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图G的一个k全染色是用k种颜色对图G的顶点集和边集进行染色使得相邻接的或相关联的元素染不同的颜色,图G的全色数χ＂（G）为图G的k-全染色中的最小k值.Behzad和Vizing猜想任意简单图G的全色数都不超过Δ（G）＋2,已经证明了此猜想对最大度不是6的平面图成立,而且最大度不小于9的平面图G的全色数为Δ（G）＋1.本文利用差值转移方法研究了最大度小于9的一些情况,证明了最大度为4,5,6,7,8的平面图G,如果其围长不小于8,则其全色数也为Δ（G）＋1. 相似文献
15.
设G=(V,E)是一个非空图,一个函数f:E→{-1,1},如果满足∑e’∈N[e]f(e’)≥1对于每一条边e∈E(G)均成立,则称f为图G的一个符号边控制函数。图G的符号边控制数记为r’s(G),定义为r’s(G)=min{∑e∈E(G)f(e)︱f}为G的一个符号边控制函数。全文对图的符号边控制函数进行了研究,得到了图的符号边控制数的若干新的下界。 相似文献
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几乎正则图的全符号控制 总被引：1，自引：2，他引：1
1IntroductionFor notation and graph theory terminology we ingeneral follow[1].LetG=(V,E)be a graph with thevertex setVand the edge setE,andletvbe a vertexinV.The open neighborhood ofvisN(v)={u∈V|uv∈E}and the closed neighborhood ofvisN[v]={v}∪N(v).The d… 相似文献
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设图G=G(V,E),令函数f:V→{-1,1},f的权w(f)=∑v∈Vf[v],对v∈V,定义f[v]=∑u∈N[v]f(u),这里N[v]表示V中顶点v及其邻点的集合。图G的符号控制函数为f:V→{-1,1}满足对所有的v∈V有f[v]≥1,图G的符号控制数γs(G)就是图G上符号控制数的最小权,称其f为图G的γs-函数。研究了C2n图,通过给出它的一个γs-函数得到了其符号控制数。 相似文献
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杨星星 《内江师范学院学报》2012,27(4):24-26
若图G=（V,E）,给定方向为D,A表示一个非平凡的阿贝尔群,F（G,A）表示映射f：E（G）→A的集合.若对任意f∈F（G,A）存在映射c：V（G）→A,使得G中的每一条有向边e=uv∈E（G）（方向是u→v）满足c（u）-c（v）≠f（e）,这时说图G是A-可染的.使得图G在方向D下是A-可染的,A的最小阶数为图G的群色数,记为χg（G）.主要是在分析了一些双图的特性的基础上讨论了它们的群色数.对于任意阶路的双图可得出其群色数都是3,还证明了圈的双图的群色数不超过5以及得到其它一些双图的群色数的上界. 相似文献