We first characterize in a simple combinatorial way all finite graphs whose edges can be directed to form an n-functional digraph, for a fixed positive integer n. Next, we prove that the possibility of directing the edges of an infinite graph to form an n-functional digraph depends on its finite subgraphs only. These results generalize Ore's result for functional digraphs.
If D = (V,A) is a digraph, its niche hypergraph NH(D) = (V, E) has the edge set ℇ = {e ⊆ V | |e| ≥ 2 ∧ ∃ v ∈ V : e = N−D(v) ∨ e = N+D(v)}. Niche hypergraphs generalize the well-known niche graphs (see [11]) and are closely related to competition hypergraphs (see [40]) as well as double competition hypergraphs (see [33]). We present several properties of niche hypergraphs of acyclic digraphs.
This paper deals with the problem of searching for the best assignments of random variables to nodes in a Bayesian network (BN) with a given topology. Likelihood functions for the studied BNs are formulated, methods for their maximization are described and, finally, the results of a study concerning the reliability of revealing BNs' roles are reported. The results of BN node assignments can be applied to problems of the analysis of gene expression profiles.
On s’intéresse ici au nombre maximum d’ordres de Slater qu’admettent les tournois vérifiant , où est un paramètre calculé à partir des scores de . On détermine ce nombre maximum d’ordres de Slater, de l’ordre de , si désigne le nombre de sommets. On donne de plus la forme des tournois vérifiant et maximisant le nombre d’ordres de Slater. En particulier, on obtient que ces tournois ne sont pas fortement connexes pour pair.
Consider the set A={1,2,3,…,2n}, n≥3 and let x∈ A be unknown element. For given natural number S we are allowed to ask whether x belongs to a subset B of A such that the sum of the elements of B equals S. We investigate for which S it is possible to find x using a nonadaptive search.
It is proved that the solution to the initial value problem , u(0,x) = 1/(1+x²), does not belong to the Gevrey class in time for 0 ≤ s < 1. The proof is based on an estimation of a double sum of products of binomial coefficients.
A loop of order possesses at least associative triples. However, no loop of order that achieves this bound seems to be known. If the loop is involutory, then it possesses at least associative triples. Involutory loops with associative triples can be obtained by prolongation of certain maximally nonassociative quasigroups whenever is a prime greater than or equal to or , an odd prime. For orders the minimum number of associative triples is reported for both general and involutory...