首页 | 本学科首页   官方微博 | 高级检索  
相似文献
 共查询到10条相似文献,搜索用时 125 毫秒
1.
Let L be the set of all additive and hereditary properties of graphs. For P1, P2 L we define the reducible property R = P1 P2 as follows: G P1P2 if there is a bipartition (V1, V2) of V(G) such that V1 P1 and V2 P2. For a property P L, a reducible property R is called a minimal reducible bound for P if P R and for each reducible property R′, RRP R′. It is proved that the class of all outerplanar graphs has exactly two minimal reducible bounds in L. Some related problems for planar graphs are discussed.  相似文献   

2.
Let X1, X2,…be identically distributed random variables from an unknown continuous distribution. Further let Ir(1), Ir(2),…be a sequence of indicator functions defined on X1, X2,…by Ir(k) = 0 if k < r, Ir(k) = 1 if Xk is a r-record AND = 0 otherwise. Suppose that we observe X1, X2,… at times T1 < T2 <… where the Tk's are realisations of some regular counting process (N(τ)) defined on the positive half-line. Having observed [0, τ], say, the problem is to predict the future behaviour of the counting processes (Rr(τ, s)) = # r-records in [τ, s]. More specifically the objective of this paper is to show that these processes can be (inhomogeneous) Poisson processes even if (N(τ))τ0 has dependent increments.

The strong link between optimal selection and optimal stopping of record sequences or record processes, perhaps not fully recognized so far, is pointed out in this paper. It is shown to lead to a unification of the treatment of problems which, at first sight, are rather different. Moreover the stopping of record processes in continuous time can lead to rigorous and elegant solutions in cases where dynamic programming is bound to fail. Several examples will be given to facilitate a comparison with other methods.  相似文献   


3.
We study the asymptotic behaviour of the occupation time process ∫t0 IA(W1(L2(s)))ds, t 0, where W1 is a standard Wiener process and L2 is a Wiener local time process at zero that is independent from W1. We prove limit laws, as well as almost sure upper and lower class theorems. Possible extensions of the obtained results are also discussed.  相似文献   

4.
Neighborhood unions and cyclability of graphs   总被引:1,自引:0,他引:1  
A graph G is said to be cyclable if for each orientation of G, there exists a set S of vertices such that reversing all the arcs of with one end in S results in a hamiltonian digraph. Let G be a 3-connected graph of order n36. In this paper, we show that if for any three independent vertices x1, x2 and x3, |N(x1)N(x2)|+|N(x2)N(x3)|+|N(x3)N(x1)|2n+1, then G is cyclable.  相似文献   

5.
一种新型的N部件串联可修系统及其可靠性分析   总被引:4,自引:0,他引:4  
本文研究一种Ⅳ部件串联可修系统的一个新模型,该模型在经典。部件串联可修系统中引入了修理工可多重延误休假的概念,并且考虑了修理工使用修理设备在修理失效部件过程中可能因修理设备失效而立即更换修理设备对整个系统可靠性造成的影响,假定修理工的延误休假时间、部件的寿命和修理设备的寿命均服从指数分布,部件的修理时间、修理设备的更换时间和修理工的休假时间均服从一般连续型分布,通过使用补充变量法和广义马尔可夫过程方法得到了系统和修理设备的一些重要可靠性指标.  相似文献   

6.
本文考虑两类具有N-策略和服务员单重休假的M/G/1排队系统,其中一类是休假不可中断,另一类是休假可中断。利用系统稳态队长的随机分解特性导出稳态队长的概率母函数,并讨论了系统空闲率与附加平均队长对系统一些参数的敏感性。进一步,在建立费用结构的基础上,应用更新报酬过程理论导出了系统长期运行单位时间内所产生的成本期望费用的显示表达式,同时通过数值计算实例确定了使得系统在长期运行单位时间内所产生的成本期望费用最小的控制策略N*,以及当休假时间为定长T时的二维最优控制策略(N*T*)。  相似文献   

7.
In this note, we characterize those pairs of nonzero r-by-d complex matrices that satisfy N2(AB) = N2(A)N2(B), in which N2(·) is the spectral norm and · is the Hadamard product.  相似文献   

8.
Let $A \subset {{\Bbb Z}_N}$, and ${f_A}(s) = \left\{ {\begin{array}{*{20}{l}}{1 - \frac{{|A|}}{N},}&{{\rm{for}}\;s \in A,}\\{ - \frac{{|A|}}{N},}&{{\rm{for}}\;s \notin A.}\end{array}} \right.$ We define the pseudorandom measure of order k of the subset A as follows, Pk(A, N) = $\begin{array}{*{20}{c}}{\max }\\D\end{array}$|$\mathop \Sigma \limits_{n \in {\mathbb{Z}_N}}$fA(n + c1)fA(n + c2) … fA(n + ck)|, where the maximum is taken over all D = (c1, c2, . . . , ck) ∈ ${\mathbb{Z}^k}$ with 0 ≤ c1 < c2 < … < ckN - 1. The subset A ⊂ ${{\mathbb{Z}_N}}$ is considered as a pseudorandom subset of degree k if Pk(A, N) is “small” in terms of N. We establish a link between the Gowers norm and our pseudorandom measure, and show that “good” pseudorandom subsets must have “small” Gowers norm. We give an example to suggest that subsets with “small” Gowers norm may have large pseudorandom measure. Finally, we prove that the pseudorandom subset of degree L(k) contains an arithmetic progression of length k, where L(k) = 2·lcm(2, 4, . . . , 2|$\frac{k}{2}$|), for k ≥ 4, and lcm(a1, a2, . . . , al) denotes the least common multiple of a1, a2, . . . , al.  相似文献   

9.
Lingsheng Shi   《Discrete Mathematics》2003,270(1-3):251-265
The Ramsey number R(G1,G2,…,Gk) is the least integer p so that for any k-edge coloring of the complete graph Kp, there is a monochromatic copy of Gi of color i. In this paper, we derive upper bounds of R(G1,G2,…,Gk) for certain graphs Gi. In particular, these bounds show that R(9,9)6588 and R(10,10)23556 improving the previous best bounds of 6625 and 23854.  相似文献   

10.
Pairs (A1B1) and (A2B2) of matrices over a principal ideal domain R are called the generalized equivalent pairs if A2=UA1V1B2=UB1V2 for some invertible matrices UV1V2 over R. A special form is established to which a pair of matrices can be reduced by means of generalized equivalent transformations. Besides necessary and sufficient conditions are found, under which a pair of matrices is generalized equivalent to a pair of diagonal matrices. Applications are made to study the divisibility of matrices and multiplicative property of the Smith normal form.  相似文献   

设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司  京ICP备09084417号