In this paper we outline a Matrix Ansatz approach to some problems of combinatorial enumeration. The idea is that many interesting quantities can be expressed in terms of products of matrices, where the matrices obey certain relations. We illustrate this approach with applications to moments of orthogonal polynomials, permutations, signed permutations, and tableaux. To Dennis Stanton with admir...

A keyH is a semi-standard tableau of partition shape whose evaluation is a permutation of the shape. We give a necessary and sufficient condition that the Knuth class of a key equals the set of shuffles of its columns. In particular, on a three-letter alphabet the Knuth class of a key equals the set of shuffles of its columns, and on a four-letter alphabet, the Knuth class of a key is either th...

A bulk M/G/1 system is considered that responds to large increases (decreases) of the queue during the service act by alternating between two service modes. The switching rule is based on two "up" and "down" thresholds for total arrivals over the service act. A necessary and sufficient condition for the ergodicity of a Markov chain embedded into the main queueing process is found. Both complex-...

This paper treats direct methods of matrix factorisation as being approximated by analytic recursions. From this viewpoint, a new class of preconditioners is motivated, which is denoted by approximate analytic factorisation (AAF). Due to analyticity and exploitation of invariances, their computational and storage cost is usually rather cheap. AAF are derived for a variety of practically relevan...

This paper proposes a new method for finding fuzzy weights in the fuzzy analytic hierarchy process (FAHP), which fuzzifies the derived formulation of an eigenvector directly. The presented formulation only needs information about the upper triangular matrix and the assumption about the reciprocal matrix is not necessary. This characteristic makes the FAHP feasible because the property of recipr...

This work is a study of the inter-translatability of two closely related proof methods, i.e. tableau (or sequent) and connection based, in the case of the propositional modal logics K, K4, T, S4, paying particular attention to the relation between matrix multiplicity and multiple use of 0-formulae (contractions) in tableaux/sequent proofs. The motivation of the work is the following. Since the ...