外平面图的对策色数

本讨论了图的色对策Ⅱ，给出了外平面图的几个性质，并且利用性质证明了外平面图的对策色数至多是6。     

最大度为6的极大外平面图的完备色数

证明了最大度为６的极大外平面图的完备色数为７。     

一类非平面图的色性（英文）

本文研究了一类非平面图K_(3,3)剖分图的色性.利用分析图的色多项式及图的结构特点,获得了与K_(3,3)剖分图色等价的图的结构特点,推广了非平面图的色性问题.     

极大外平面图（r,k）——扇的4染色

定义了一类极大外平面图：(r,k）--扇。证明了当G是以r个顶点的圈Qr为标定界环的(r,k）一扇，G'是以Qr为标定界环的任意极大外平面图时，G和G'有公共四染色；同时对△(G)=r-3的极大外平在图也得到相同的结论。从而证明了四色定理的等价命题在给定条件下成立。     

极大外平面图的关联色数

简要介绍了图的关联着色问题的起源、发展情况及目前已有的结论，对一类特殊的图——极大外平面图(△≠6)，给出了其关联色数．     

极大外平面图的星边染色

如果图G的一个正常边染色使得G中没有长为4的路或4-圈是2-边染色的,则称此染色是G的一个星边染色.对G进行星边染色所需的最少颜色数称为G的星边色数,记作x′s(G).该文证明了最大度为4的极大外平面图的星边色数等于6,对任一n(≥8)阶极大外平面图Gn,有6≤x′s(Gn)≤n-1成立,并且上界和下界都是可达的.     

简单完整正则平面图

对简单完整正则平面图的特性和结构进行了分析和讨论 ,找出了简单完整正则平面图的可能的种类 .此外 ,对各种简单完整正则平面图的色数进行了求解 ,并用不同的方法给出了各个简单完整正则平面图的作色方案 .     

Δ(G)=5的2-连通外平面图的邻点可区别全染色

Smarandachely邻点可区别全染色是指相邻点的色集合互不包含的邻点可区别全染色，是对邻点可区别全染色条件的进一步加强。本文研究了平面图的Smarandachely邻点可区别全染色，即根据2-连通外平面图的结构特点，利用分析法、数学归纳法，刻画了最大度为5的2-连通外平面图的Smarandachely邻点可区别全色数。证明了：如果$G$是一个$\Delta （G）=5$的2-连通外平面图，则$\chi_{\rm sat}（G）\leqslant 9$。     

平面图的循环色数与临界性

循环着色是普通着色的推广。本文中,我们研究了一类平面图的循环着色问题,并证明了这类平面图是循环色临界的,但不是普通色临界的,同时,我们还研究了循环着色与图G_k~d中的链之间的关系．     

开集与色树理论

Ｗｈｉｔｎｅｙ和Ｔｕｔｔｅ为了探讨四色问题的理论证明曾把平面四色问题与圈上的４染色集的性质联系起来进行研究，提出了开集的概念和色树理论。本文研究圈上４染色集的性质，证明开集在某种组合运算后仍为开集，从而发展了色树理论，为研究平面图的染色问题提供了新的方法。文末提出了一些进一步研究的问题。     

Game chromatic number of outerplanar graphs

This note proves that the game chromatic number of an outerplanar graph is at most 7. This improves the previous known upper bound of the game chromatic number of outerplanar graphs. © 1999 John Wiley & Sons, Inc. J Graph Theory 30: 67–70, 1999     

CHROMATIC NUMBER OF SQUARE OF MAXIMAL OUTERPLANAR GRAPHS

Let x（G^2） denote the chromatic number of the square of a maximal outerplanar graph G and Q denote a maximal outerplanar graph obtained by adding three chords y1 y3, y3y5, y5y1 to a 6-cycle y1y2…y6y1. In this paper, it is proved that △ ＋ 1 ≤ x（G^2） ≤△ ＋ 2, and x（G^2） = A ＋ 2 if and only if G is Q, where A represents the maximum degree of G.     

Chromatic number of sparse colored mixed planar graphs

A colored mixed graph has vertices linked by both colored arcs and colored edges. The chromatic number of such a graph G is defined as the smallest order of a colored mixed graph H such that there exists a (arc-color preserving) homomorphism from G to H. We study in this paper the colored mixed chromatic number of planar graphs, partial 2-trees and outerplanar graphs with given girth.     

Invalid proofs on incidence coloring

Incidence coloring of a graph G is a mapping from the set of incidences to a color-set C such that adjacent incidences of G are assigned distinct colors. Since 1993, numerous fruitful results as regards incidence coloring have been proved. However, some of them are incorrect. We remedy the error of the proof in [R.A. Brualdi, J.J.Q. Massey, Incidence and strong edge colorings of graphs, Discrete Math. 122 (1993) 51-58] concerning complete bipartite graphs. Also, we give an example to show that an outerplanar graph with Δ=4 is not 5-incidence colorable, which contradicts [S.D. Wang, D.L. Chen, S.C. Pang, The incidence coloring number of Halin graphs and outerplanar graphs, Discrete Math. 256 (2002) 397-405], and prove that the incidence chromatic number of the outerplanar graph with Δ≥7 is Δ+1. Moreover, we prove that the incidence chromatic number of the cubic Halin graph is 5. Finally, to improve the lower bound of the incidence chromatic number, we give some sufficient conditions for graphs that cannot be (Δ+1)-incidence colorable.     

Game chromatic number of strong product graphs

The graph coloring game is a two-player game in which the two players properly color an uncolored vertex of G alternately. The first player wins the game if all vertices of G are colored, and the second wins otherwise. The game chromatic number of a graph G is the minimum integer k such that the first player has a winning strategy for the graph coloring game on G with k colors. There is a lot of literature on the game chromatic number of graph products, e.g., the Cartesian product and the lexicographic product. In this paper, we investigate the game chromatic number of the strong product of graphs, which is one of major graph products. In particular, we completely determine the game chromatic number of the strong product of a double star and a complete graph. Moreover, we estimate the game chromatic number of some King's graphs, which are the strong products of two paths.     

外平面图的有界染色

图G的k-有界染色是图G的一个最多有k个顶点染同一种颜色的顶点染色．图 G的k-有界染色数Xk(G)是指对G进行k-有界染色用的最少颜色数．本文给出了n个顶点的外平面图能用[n/k]种颜色k-有界染色的一些充分条件．     

Oriented coloring of triangle-free planar graphs and 2-outerplanar graphs

A graph is 2-outerplanar if it has a planar embedding such that the subgraph obtained by removing the vertices of the external face is outerplanar (i.e. with all its vertices on the external face). An oriented k-coloring of an oriented graph G is a homomorphism from G to an oriented graph H of order k. We prove that (1) every oriented triangle-free planar graph has an oriented chromatic number at most 40, and (2) every oriented 2-outerplanar graph has an oriented chromatic number at most 40, that improves the previous known bounds of 47 and 67, respectively.     

The chromatic number of oriented graphs

We introduce in this paper the notion of the chromatic number of an oriented graph G (that is of an antisymmetric directed graph) defined as the minimum order of an oriented graph H such that G admits a homomorphism to H. We study the chromatic number of oriented k-trees and of oriented graphs with bounded degree. We show that there exist oriented k-trees with chromatic number at least 2^k+1 - 1 and that every oriented k-tree has chromatic number at most (k + 1) × 2^k. For 2-trees and 3-trees we decrease these upper bounds respectively to 7 and 16 and show that these new bounds are tight. As a particular case, we obtain that oriented outerplanar graphs have chromatic number at most 7 and that this bound is tight too. We then show that every oriented graph with maximum degree k has chromatic number at most (2k - 1) × 2^2k-2. For oriented graphs with maximum degree 2 we decrease this bound to 5 and show that this new bound is tight. For oriented graphs with maximum degree 3 we decrease this bound to 16 and conjecture that there exists no such connected graph with chromatic number greater than 7. © 1997 John Wiley & Sons, Inc. J Graph Theory 25: 191–205, 1997     

The list chromatic numbers of some planar graphs

In this paper, the choosability of outerplanar graphs, 1-tree and strong 1-outerplanargraphs have been described completely. A precise upper bound of the list chromatic number of 1-outerplanar graphs is given, and that every 1-outerplanar graph with girth at least 4 is 3-choosable is proved.