Mycielski图的循环色数

通过引入一类点集划分的概念,研究了Mylielski图循环染色的性质,证明了当完全图的点数足够大时,它的Mycielski图的循环色数与其点色数相等.     

关于Mycielski图循环色数的猜想

通过引进Mycielski图点集的一类特殊划分,利用该划分在Mycielski图循环着色中的特点改进了如下猜想:完全图的Mycielski图的循环色数等于它的点色数.     

Halin图的Alon-Tarsi数

图G的Alon-Tarsi数,是指最小的k使得G存在一个最大出度不大于k-1的定向D满足G的奇支撑欧拉子图的个数不同于偶支撑欧拉子图的个数.通过分析Halin图的结构,利用Alon-Tarsi定向的方法确定了Halin图的Alon-Tarsi数.     

关于图的子着色

本文主要讨论了子色唯一图的结构，并给出了唯一k-子色图、最大子色图的边临界子色图的特征．     

关于K_(2n)-E(C_m)的点可区别边色数

图G的一个k-正常边染色f被称为点可区别边染色是指任何两点的点及其关联边的色集合不同,所用最小的正整数k被称为G的点可区别边色数,记为X'_(vd)(G).用k_(2n)-E(C_m)表示2n阶完全图删去其中一条m阶路的边后得到的图,得到了K_(14)-E(C_4),K_(16)-E(C_4),K_(18)-E(C_5),K_(20)-E(C_5)的点可区别边色数分别为14,16,18,20.     

互补图的星色数

本文给出互补图的星色数所满足的一些必要条件，并确定一些图类的星色数．     

色临界图的最大度与色数的一个关系式

研究了一类简单图G的色数x(G)与最大度△(G)的关系,对满足x(G)>(S~2+S)/2的X(G)+S阶色临界图G,证明了x(G)=△(G)+1-S,或等价地,△(G)+1-[((8△(G)+17~(1/2)-3/2]≤X(G)≤△(G)+1,这一结果部分改进了Brooks经典不等式X(G)≤△(G)+1,并完全刻画n+3(n≥4)个顶点的n-临界图的结构。     

临界图的边数

本文研究了△－临界图的边数下界，其中△＝１０，１１，１２，１３。     

边色数的分类及其有关性质

设图G为简单连通图,由Vizing定理知:Δ(G)≤x′(G)≤Δ(G) 1,其中Δ(G)表示图G的最大顶点次,x′(G)为图G的边色数。若x′(G)=Δ(G),则称G为第一类图,记为G∈C~1;若x′(G)=Δ(G) 1,则称G为第二类图,记为G∈C~2。其他图论术语见一般参考书。一边e(或者顶点v)称为临界的,如果成立x′(G)>x′(G\e)(或者x′(G)>x′(G\v))。图G称为是临界的,如果G∈C~2,且G的每一边是临界的。对于v∈V(G),令d~*(v)=|{u|(v,u)∈E(G)且d(u)=Δ(G)}|。设F={u|d(u)=Δ(G),u∈V(G)},记G_Δ=G[F]。令图G_Δ的圈秩数为b(G_Δ)。     

关于完全图的Mycielski图的循环色数的若干结果

给出了任意图G的多重Myeielski图M^m(G)的简单定义方式，用不同的方法证明了当完全图Kn的阶数n足够大时，M^m(Kn)的循环色数等于其点色数．特别证明了，n=7，8，9时，M^3(Kn)的循环色数等于其点色数，从而使得“当n≥m 2，有xc(M^m))=x(M^m(Kn))=m n成立”的猜想有了更新的进展．     

关于乘法分拆数的一个猜想和上界

本文证明了乘法分拆数的一个上界,由此证明了Hughes-Shallit的第二猜想,同时证明了对任意的正数a,存在一个自然数N,当n≥N时,n的乘法分拆数f(n)0,使这个集合中的自然数的乘法分拆数≤n~a。     

模糊数的运算性质及模糊数的距离与极限

通过对零模糊数以及模糊数的序关系的重新定义,使得模糊数与实数有了更相似的运算性质。定义了模糊数的距离,讨论了模数列的极限及性质。     

积分中值定理的较一般情况的几何意义及其推广形式

描述了积分中值定理的较一般情况的几何意义,给出了积分中值定理的推广形式.     

On the sizes of graphs and their powers: The undirected case

Let G be an undirected graph and G^r be its r-th power. We study different issues dealing with the number of edges in G and G^r. In particular, we answer the following question: given an integer r≥2 and all connected graphs G of order n such that G^r≠K_n, what is the minimum number of edges that are added when going from G to G^r, and which are the graphs achieving this bound?     

任意除环上一矩阵方程组的一般解与中心和反中心对称解

Necessary and sufficient conditions are given for the existence of the general solution, the centrosymmetric solution, and the centroskewsymmetric solution to a system of linear matrix equations over an arbitrary skew field. The representations of such the solutions of the system are also derived.     

The order of a zero of a Wronskian and the theory of linear dependence

Every root of the top Wronskian of a Wronskian matrix whose rank at the root is equal to the number of columns, is of integer order even if the highest derivatives exist only at the root. If the rank of a Wronskian matrix is constant and smaller than the number of rows, then the number of independent linear relations between the functions in the first row is equal to the number of functions minus the rank. These results were proved under additional assumptions by Bôcher, Curtiss, and Moszner. Their proofs are simplified.     

An upper bound for the restrained domination number of a graph with minimum degree at least two in terms of order and minimum degree

Let G=(V,E) be a graph. A set S⊆V is a restrained dominating set if every vertex in V−S is adjacent to a vertex in S and to a vertex in V−S. The restrained domination number of G, denoted γ_r(G), is the smallest cardinality of a restrained dominating set of G. We will show that if G is a connected graph of order n and minimum degree δ and not isomorphic to one of nine exceptional graphs, then .     

The Cambridge Mathematical Journal and its descendants: the linchpin of a research community in the early and mid-Victorian Age

The Cambridge Mathematical Journal and its successors, the Cambridge and Dublin Mathematical Journal, and the Quarterly Journal of Pure and Applied Mathematics, were a vital link in the establishment of a research ethos in British mathematics in the period 1837–1870. From the beginning, the tension between academic objectives and economic viability shaped the often precarious existence of this line of communication between practitioners. Utilizing archival material, this paper presents episodes in the setting up and maintenance of these journals during their formative years.     

矩阵的初等标准形与线性方程组

指出矩阵的初等标准形理论是线性方程组问题的理论基础