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991.
In the present paper we describe the use of group actions, double cosets and homomorphisms in the constructive theory of discrete structures, as we found it useful from both a theoretical and a practical point of view. By means of examples we should like to demonstrate that these methods are useful both as unifying principles and as efficient methods for applications. 相似文献
992.
Tomáš Kaiser Zdeněk Ryjáček Daniel Král Moshe Rosenfeld Heinz‐Jürgen Voss 《Journal of Graph Theory》2007,56(4):249-269
The prism over a graph G is the Cartesian product G □ K2 of G with the complete graph K2. If G is hamiltonian, then G□K2 is also hamiltonian but the converse does not hold in general. Having a hamiltonian prism is shown to be an interesting relaxation of being hamiltonian. In this article, we examine classical problems on hamiltonicity of graphs in the context of having a hamiltonian prism. © 2007 Wiley Periodicals, Inc. J Graph Theory 56: 249–269, 2007 相似文献
993.
994.
Oriented graphs in which every pair of vertices can be connected by a unique path of given length (not depending on the choice
of the pair of vertices) are studied. These graphs are a natural extension of the well-known de Bruijn graphs and retain their
most important properties. Some results on the structure of and methods for constructing such graphs are obtained.
Translated fromMatematicheskie Zametki, Vol. 62, No. 4, pp. 540–548, October, 1997.
Translated by O. V. Sipacheva 相似文献
995.
This paper gives a pathwise construction of Jackson-type queueing networks allowing the derivation of stability and convergence theorems under general probabilistic assumptions on the driving sequences; namely, it is only assumed that the input process, the service sequences and the routing mechanism are jointly stationary and ergodic in a sense that is made precise in the paper. The main tools for these results are the subadditive ergodic theorem, which is used to derive a strong law of large numbers, and basic theorems on monotone stochastic recursive sequences. The techniques which are proposed here apply to other and more general classes of discrete event systems, like Petri nets or GSMPs. The paper also provides new results on the Jackson-type networks with i.i.d. driving sequences which were studied in the past.The work of this author was supported in part by a grant from the European Commission DG XIII, under the BRA Qmips contract.The work of this author was supported by a sabbatical grant from INRIA Sophia Antipolis. 相似文献
996.
997.
扩展时间事件图的分析 总被引:2,自引:0,他引:2
本文研究了一类扩展时间事件图的分析问题,证明了系统的输出时间序列有三类.有限序列,准周期序列,近似于Dlogp q的序列. 相似文献
998.
We introduce a new oriented evolving graph model inspired by biological networks. A node is added at each time step and is connected to the rest of the graph by random oriented edges emerging from older nodes. This leads to a statistical asymmetry between incoming and outgoing edges. We show that the model exhibits a percolation transition and discuss its universality. Below the threshold, the distribution of component sizes decreases algebraically with a continuously varying exponent depending on the average connectivity. We prove that the transition is of infinite order by deriving the exact asymptotic formula for the size of the giant component close to the threshold. We also present a thorough analysis of aging properties. We compute local-in-time profiles for the components of finite size and for the giant component, showing in particular that the giant component is always dense among the oldest nodes but invades only an exponentially small fraction of the young nodes close to the threshold. 相似文献
999.
A cyclic face 2‐colourable triangulation of the complete graph Kn in an orientable surface exists for n ≡ 7 (mod 12). Such a triangulation corresponds to a cyclic bi‐embedding of a pair of Steiner triple systems of order n, the triples being defined by the faces in each of the two colour classes. We investigate in the general case the production of such bi‐embeddings from solutions to Heffter's first difference problem and appropriately labelled current graphs. For n = 19 and n = 31 we give a complete explanation for those pairs of Steiner triple systems which do not admit a cyclic bi‐embedding and we show how all non‐isomorphic solutions may be identified. For n = 43 we describe the structures of all possible current graphs and give a more detailed analysis in the case of the Heawood graph. © 2002 Wiley Periodicals, Inc. J Combin Designs 10: 92–110, 2002; DOI 10.1002/jcd.10001 相似文献
1000.
We consider uniform random walks on finite graphs withn nodes. When the hitting times are symmetric, the expected covering time is at least 1/2n logn-O(n log logn) uniformly over all such graphs. We also obtain bounds for the covering times in terms of the eigenvalues of the transition matrix of the Markov chain. For distance-regular graphs, a general lower bound of (n-1) logn is obtained. For hypercubes and binomial coefficient graphs, the limit law of the covering time is obtained as well. 相似文献