‎the global fom and gmres algorithms are among the effective‎ ‎methods to solve sylvester matrix equations‎. ‎in this paper‎, ‎we‎ ‎study these algorithms in the case that the coefficient matrices‎ ‎are real symmetric (real symmetric positive definite) and extract‎ ‎two cg-type algorithms for solving generalized sylvester matrix‎ ‎equations‎. ‎the proposed methods are iterative projection metho...

let and be a sequence with non-negative entries. if , denote by the infimum of those satisfying the following inequality: whenever . the purpose of this paper is to give an upper bound for the norm of operator t on weighted sequence spaces d(w,p) and lp(w) and also e(w,?). we considered this problem for certain matrix operators such as norlund, weighted mean, ceasaro and copson matrices. th...

the object of this paper is to establish a summability factor theorem for summabilitya, , k  1 k  where a is the lower triangular matrix with non-negative entries satisfying certain conditions.

we obtain sufficient conditions for the series σanλn to be absolutely summable of order k by atriangular matrix.

it is proved that by using bounds of eigenvalues of an interval matrix, someconditions for checking positive deniteness and stability of interval matricescan be presented. these conditions have been proved previously with variousmethods and now we provide some new proofs for them with a unity method.furthermore we introduce a new necessary and sucient condition for checkingstability of interv...

New upper bounds on codes are presented. The bounds are obtained by linear and semidefinite programming. INTRODUCTION One of the central problems in coding theory is to find upper bounds on maximum size Aq(n, d) of a code of word length n and minimum Hamming distance at least d over the alphabet Q of q ≥ 2 letters. Let us provide Q with the structure of an Abelian group, in an arbitrary way. In...

We consider a distance regular graph with diameter d and eigenvalues k d We show the intersection numbers a b satisfy k a d k a ka b a We say is tight whenever is not bipartite and equality holds above We charac terize the tight property in a number of ways For example we show is tight if and only if the intersection numbers are given by certain rational expressions involving d independent para...