Band 4, Heft 3

Abstract. In this paper we give some approximated solutions for an operator equation where is a bounded bijection and a self-adjoint operator on a separable Hilbert space  H . We use canonical dual frames in order to precondition the linear equation so that convergence of iterative methods is improved and by Richardson iterative method we approximate the solution of the equation. We design an adaptive algorithm based on frames and the Richardson iterative method.

Abstract. In the present work the closedness of an operator and the existence of a resolvent for a class of mixed type operators with increasing coefficients in an unbounded domain are proved.

Abstract. In this article, a posteriori error analysis of a finite volume method based on the nonconforming rotated Q 1 element for the two-dimensional Stokes equations is investigated. An explicit residual-based computable error indicators are presented and analyzed in H 1 - and L 2 -norm respectively.

Abstract. Applying the weak s -semipermutability of some primary subgroup, we investigate the structure of finite groups. Some recent known results are generalized and unified.

Abstract. Let V be a set of cardinality v (possibly infinite). Two graphs G and with vertex set V are isomorphic up to complementation if is isomorphic to G or to the complement of G . Let k be a non-negative integer. The graphs G and are k -hypomorphic up to complementation if for every k -element subset K of V , the induced subgraphs and are isomorphic up to complementation. A graph G is k -reconstructible up to complementation if every graph which is k -hypomorphic to G up to complementation is in fact isomorphic to G up to complementation. We prove that a graph G has this property provided that . Moreover, under these conditions, if or , then G and are the only graphs k -hypomorphic to G up to complementation. A description of pairs of graphs with the same 3-homogeneous subsets is a key ingredient in our proof.