Design of manufacturing systems using queueing models

Design issues in various types of manufacturing systems such as flow lines, automatic transfer lines, job shops, flexible machining systems, flexible assembly systems and multiple cell systems are addressed in this paper. Approaches to resolving these design issues of these systems using queueing models are reviewed. In particular, we show how the structural properties that are recently derived for single and multiple stage queueing systems can be used effectively in the solution of certain design optimization problems.Supported in part by the Natural Sciences and Engineering Research Council of Canada via Operating and Strategic Grants on Modeling and Analyses of Production Systems and Modeling and Implementation of Just-in-Time Cells.Supported in part by the NSF Grants ECS-8811234 and DDM-9113008 and by Sloan Foundation Grants for the Consortium for Competitiveness and Cooperation and for the study on Competitive Semiconductor Manufacturing.     

Two Variable Pfaffian Identities and Symmetric Functions

We give sign-reversing involution proofs of a pair of two variable Pfaffian identities. Applications to symmetric function theory are given, including identities relating Pfaffians and Schur functions. As a corollary we are able to compute the plethysm .     

Some Combinatorial Properties of Schubert Polynomials

Schubert polynomials were introduced by Bernstein et al. and Demazure, and were extensively developed by Lascoux, Schützenberger, Macdonald, and others. We give an explicit combinatorial interpretation of the Schubert polynomial in terms of the reduced decompositions of the permutation w. Using this result, a variation of Schensted's correspondence due to Edelman and Greene allows one to associate in a natural way a certain set of tableaux with w, each tableau contributing a single term to . This correspondence leads to many problems and conjectures, whose interrelation is investigated. In Section 2 we consider permutations with no decreasing subsequence of length three (or 321-avoiding permutations). We show for such permutations that is a flag skew Schur function. In Section 3 we use this result to obtain some interesting properties of the rational function , where denotes a skew Schur function.Sara C. Billey: Supported by the National Physical Science Consortium. William Jockusch: Supported by an NSF Graduate Fellowship. Richard P. Stanley: Partially supported by NSF grants DMS-8901834 and DMS-9206374     

The irreducibility of K(A) ∗

A finite dimensional multilinear algebraic point of view is adopted to study the theory of enumeration under a group action. The classical results of Pólya, deBruijn, and others are presented. These results are extended in various ways. These extensions include the study of patterns with prescribed symmetry or with prescribed boundary conditions. The non-discrete nature of the underlying multilinear structure is utilized to present several models for the random generation of patterns.     

关于幂平均值的一个不等式

给出关于幂平均值的一个不等式Mβ- 1( a) n+ 1 A( a) [G( a) ]n成立的充分必要条件     

Numerical approximation of anisotropic geometric evolution equations in the plane

Harald Garcke Naturwissenchaftliche Fakultät I' Mathematik, Universität Regensburg, 93040 Regensburg, Germany Robert Nürnberg Department of Mathematics, Imperial College London, London SW7 2AZ, UK Received on 13 April 2006. Revised on 20 February 2007. We present a variational formulation of fully anisotropic motionby surface diffusion and mean curvature flow, as well as relatedflows. The proposed scheme covers both the closed-curve caseand the case of curves that are connected via triple junctionpoints. On introducing a parametric finite-element approximation,we prove stability bounds and report on numerical experiments,including regularized crystalline mean curvature flow and regularizedcrystalline surface diffusion. The presented scheme has verygood properties with respect to the distribution of mesh pointsand, if applicable, area conservation.     

A fast method to block-diagonalize a Hankel matrix

In this paper, we consider an approximate block diagonalization algorithm of an n×n real Hankel matrix in which the successive transformation matrices are upper triangular Toeplitz matrices, and propose a new fast approach to compute the factorization in O(n ²) operations. This method consists on using the revised Bini method (Lin et al., Theor Comp Sci 315: 511–523, 2004). To motivate our approach, we also propose an approximate factorization variant of the customary fast method based on Schur complementation adapted to the n×n real Hankel matrix. All algorithms have been implemented in Matlab and numerical results are included to illustrate the effectiveness of our approach.     

On τ-tilting finiteness of the Schur algebra

We determined the τ-tilting finiteness of Schur algebras over an algebraically closed field of arbitrary characteristic, except for a few small cases.