The following problem arises in the design of some interconnection networks for distributed systems. Namely, to construct digraphs with given maximum out-degree, reduced diameter, easy routing, good connectivity, and good expand-ability. To this end, a new method based on the concept of partial line digraph is presented. This proposal, which turns out to be a generalization of the so-called lin...

A digraph D is said to satisfy the k-Meyniel’s condition if each odd directed cycle of D has at least k diagonals. The study of the k-Meyniel’s condition has been a source of many interesting problems, questions and results in the development of Kernel Theory. In this paper we present a method to construct a large variety of kernel-perfect (resp. critical kernel-imperfect) digraphs which satisf...

Containment and overlap representations of digraphs are studied, with the following results. The interval containment digraphs are the digraphs of Ferrers dimension 2, and the circular-arc containment digraphs are the complements of circular-arc intersection digraphs. A poset is an interval containment poset if and only if its comparability digraph is an interval containment digraph, and a grap...

An embedding of an Eulerian digraph in orientable surfaces was introduced by Bonnington et al. They gave some problems which need to be further studied. One of them is whether the embedding distribution of an embeddable digraph is always unimodal. In this paper, we first introduce the method of how to determine the faces and antifaces from a given rotation scheme of a digraph. The genus distrib...

In this note we present a general approach to construct large digraphs from small ones. These are called expanded digraphs, and, as particular cases, we show the close relationship between lifted digraphs of voltage digraphs and line digraphs, which are two known ways to obtain dense digraphs. In the same context, we show the equivalence between the vertex-splitting and partial line digraph tec...

OF DOCTORAL DISSERTATION HELSINKI UNIVERSITY OF TECHNLOGY P.O. BOX 1000, FI-02015 TKK http://www.tkk.fi Author Hui Cheng Name of the dissertation Causal digraph reasoning for fault diagnosis in paper making applications Manuscript submitted 02.02.2009 Manuscript revised Date of the defence 05.06.2009 Monograph Article dissertation (summary + original articles) Faculty Faculty of Chemistry and M...

P2p -factorization of a complete bipartite graph for p, an integer was studied by Wang [1]. Further, Beiling [2] extended the work of Wang[1], and studied the P2k -factorization of complete bipartite multigraphs. For even value of k in Pk -factorization the spectrum problem is completely solved [1, 2, 3]. However for odd value of k i.e. P3 , P5 and P7 , the path factorization have been studied ...

— A new class of generating Systems (the bdg Systems), is introduced and they are shown to be equivalent to the class of programmed grammars. They have independent interest since their définition gives doser ties between language theory and graph theory. This in turn gives rise to a number of interesting hybrid graph — grammar open problems.

— A new class of generating Systems (the bdg Systems), is introduced and they are shown to be equivalent to the class of programmed grammars. They have independent interest since their définition gives doser ties between language theory and graph theory. This in turn gives rise to a number of interesting hybrid graph — grammar open problems.

We consider finite and simple digraphs. Usually, we use G to denote a graph and D to a digraph. Undefined terms and notations will follow [6] for graphs and [3] for digraphs. In particular, κ(G), κ′(G), α(G) ans α′(G) denote the connectivity, the edge connectivity, the independence number, and the matching number of a graph G; and λ(D) denotes the arc-strong connectivity of a digraph D as well ...