Partitioning series-parallel multigraphs into υ*-excluding edge covers

We prove that, for any given vertex υ* in a series-parallel graph G, its edge set can be partitioned into k = min{κ'(G) + 1,δ(G)} subsets such that each subset covers all the vertices of G possibly except for υ*, where δ(G) is the minimum degree of G and κ'(G) is the edge-connectivity of G. In addition, we show that the results in this paper are best possible and a polynomial time algorithm can be obtained for actually finding such a partition by our proof.     

Kautz图的限制边连通度

限制边连通度是对传统边连通度的推广 ,而且是计算机互连网络容错性的一个重要度量 .本文考虑两类重要的网络模型———Kautz有向图K(d ,n)和Kautz无向图UK(d ,n)的限制边连通度λ′,并得到如下结果 :除了λ′(K( 2 ,1) )不存在外 ,均有λ′(K(d ,n) ) =2d-2 ;当d≥ 3 ,n≥ 3时 ,4d-5≤λ′(UK(d ,n) ) ≤ 4d -4 .     

Complexity of 3-edge-coloring in the class of cubic graphs with a polyhedral embedding in an orientable surface

A polyhedral embedding in a surface is one in which any two faces have boundaries that are either disjoint or simply connected. In a cubic (3-regular) graph this is equivalent to the dual being a simple graph. In 1968, Grünbaum conjectured that every cubic graph with a polyhedral embedding in an orientable surface is 3-edge-colorable. For the sphere, this is equivalent to the Four-Color Theorem, but we have disproved the conjecture in the general form. In this paper we extend this result and show that if we restrict our attention to a class of cubic graphs with a polyhedral embedding in an orientable surface, then the computational complexity of the 3-edge-coloring problem and its approximation does not improve.     

Super Connectivity of Line Graphs and Digraphs

The h-super connectivity κh and the h-super edge-connectivity λh are more refined network reliability indices than the conneetivity and the edge-connectivity. This paper shows that for a connected balanced digraph D and its line digraph L, if D is optimally super edge-connected, then κ1（L） = 2λ1 （D）, and that for a connected graph G and its line graph L, if one of κ1 （L） and λ（G） exists, then κ1（L） = λ2（G）. This paper determines that κ1（B（d, n） is equal to 4d- 8 for n = 2 and d ≥ 4, and to 4d-4 for n ≥ 3 and d ≥ 3, and that κ1（K（d, n）） is equal to 4d- 4 for d 〉 2 and n ≥ 2 except K（2, 2）. It then follows that B（d,n） and K（d, n） are both super connected for any d ≥ 2 and n ≥ 1.     

Cyclic edge-cuts in fullerene graphs

In this paper, we study cyclic edge-cuts in fullerene graphs. First, we show that the cyclic edge-cuts of a fullerene graph can be constructed from its trivial cyclic 5- and 6-edge-cuts using three basic operations. This result immediatelly implies the fact that fullerene graphs are cyclically 5-edge-connected. Next, we characterize a class of nanotubes as the only fullerene graphs with non-trivial cyclic 5-edge-cuts. A similar result is also given for cyclic 6-edge-cuts of fullerene graphs.     

中国存贷款派生过程的实证研究

以存款总额、贷款总额、储蓄存款、企业存款、银行贷款、收入、利率、CPI为变量,依据变量之间的经济关系,构建6组VAR模型,考察存贷款派生关系以及与其他影响因素之间的关系,并且进一步利用协整分析、误差修正模型、景气分析方法考察上述不同组经济变量之间的影响方向、时滞和力度.实证分析结果显示存贷款之间具有派生关系,但是不同存贷款科目的派生过程各有不同.特别地,存款是贷款的先行指标,存贷款之间的增长拐点大概有9--12个月的时滞.存款是指标组中影响贷款最重要的指标,但是贷款不是影响存款最重要的指标.贷款转化成存款的速度很快,但是存款转化成贷款需要一个过程.除了存贷款之间的相互影响外,CPI、收入对存款有影响,CPI对贷款有影响,但是名义利率对存款和贷款没有显著影响.     

常系数线性差分方程组的一种解法

本文给出常系数线性差分方程组求通解的一种方法：循环特征向量列法。     

The Structure of Hypergroup on the Cyclical Group

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A variational principle and best proximity points

We generalize Ekeland's Variational Principle for cyclic maps. We present applications of this version of the variational principle for proving of existence and uniqueness of best proximity points for different classes of cyclic maps.