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We prove that maximum three dimensional matching is a MAX SNP-hard problem. If the number of occurrences of elements in triples is bounded by a constant the problem is MAX SNP-complete. As corollaries we prove that maximum covering by 3-sets and maximum covering of a graph by triangles are MAX SNP-hard. The problems are MAX SNP-complete if the number of occurrences of the elements and the degre...

There have been significant advancements in the ability of echocardiography to provide both morphological and functional information in children with congenitally malformed hearts. This progress has come through the development of improved technology such as matrix array probes and software which allows for the off line analysis of images to a high standard. This article focuses on these develo...

‎‎a natural generalization of two dimensional cyclic code ($t{tdc}$) is two dimensional skew cyclic code‎. ‎it is well-known that there is a correspondence between two dimensional skew cyclic codes and left ideals of the quotient ring $r_n:=f[x,y;rho,theta]/_l$‎. ‎in this paper we characterize the left ideals of the ring $r_n$ with two methods and find the generator matrix for two dimensional s...