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951.
Lili Zhang 《Discrete Mathematics》2008,308(24):6588-6595
Let G be an infinite graph embedded in a surface such that each open face of the embedding is homeomorphic to an open disk and is bounded by finite number of edges. For each vertex x of G, we define the combinatorial curvature
952.
Mohamed Barraa 《Journal of Mathematical Analysis and Applications》2008,347(1):315-322
In this paper we investigate perturbations of the regular spectrum of an upper triangular operator matrix such as acting on a Hilbert space H⊕K. 相似文献
953.
Seok-Zun Song Kyung-Tae Kang LeRoy B. Beasley Nung-Sing Sze 《Linear algebra and its applications》2008,429(1):209-223
An m×n matrix A over a semiring is called regular if there is an n×m matrix G over such that AGA=A. We study the problem of characterizing those linear operators T on the matrices over a semiring such that T(X) is regular if and only if X is. Complete characterizations are obtained for many semirings including the Boolean algebra, the nonnegative reals, the nonnegative integers and the fuzzy scalars. 相似文献
954.
Abel's lemma on summation by parts is reformulated to investigate systematically terminating theta hypergeometric series. Most of the known identities are reviewed and several new transformation and summation formulae are established. The authors are convinced by the exhibited examples that the iterating machinery based on the modified Abel lemma is powerful and a natural choice for dealing with terminating theta hypergeometric series. 相似文献
955.
基于灰色关联分析和主成分分析组合权重的确定方法研究 总被引:3,自引:0,他引:3
为了提高综合评价模型中权重的准确性和客观性,以主成分分析法和灰色关联分析法为基础,建立了组合权重模型,从而修正了灰色关联分析法和主成分分析法在确定权重过程中的缺陷,为综合评价体系中权重的确定提出一种新的思路. 相似文献
956.
Miroslav S. Pranić Lothar Reichel Giuseppe Rodriguez Zhengsheng Wang Xuebo Yu 《Numerical Linear Algebra with Applications》2016,23(6):1007-1022
The rational Arnoldi process is a popular method for the computation of a few eigenvalues of a large non‐Hermitian matrix and for the approximation of matrix functions. The method is particularly attractive when the rational functions that determine the process have only few distinct poles , because then few factorizations of matrices of the form A ? zjI have to be computed. We discuss recursion relations for orthogonal bases of rational Krylov subspaces determined by rational functions with few distinct poles. These recursion formulas yield a new implementation of the rational Arnoldi process. Applications of the rational Arnoldi process to the approximation of matrix functions as well as to the computation of eigenvalues and pseudospectra of A are described. The new implementation is compared to several available implementations. 相似文献
957.
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959.
Bi53+ Polycations in Ordered and Plastic Crystals of Bi5[AlI4]3 and Bi5[AlBr4]3 Dark‐red air‐sensitive crystals of pentabismuth‐tris(tetrabromoaluminate) Bi5[AlBr4]3 and black crystals of Bi5[AlI4]3 have been crystallized from melts of Bi, BiX3 and AlX3 (X = Br, I). X‐ray diffraction on a single crystal of Bi5[AlI4]3 (T = 293(2) K; space group Pnma; a = 2143.6(3) pm, b = 1889.1(1) pm, c = 811.74(5) pm) revealed an ordered packing of Bi53+ trigonal bipyramids and [AlI4]? tetrahedra that corresponds to the PuBr3 structure type. Contrary to the so far known Bi53+ polycations with accurate D3h symmetry, the bismuth cluster found in Bi5[AlI4]3 holds only Cs symmetry. The room temperature structure of the tetrabromoaluminate Bi5[AlBr4]3, which is related to the AuCu3 type, shows a dynamic disorder of the Bi53+ polycations (T = 293(2) K; space group ; a = 1766.2(3) pm). Slight cooling induces the transition into an ordered rhombohedral phase isostructural to Bi5[AlCl4]3 (T = 260(2) K; space group a = 1241.5(8) pm, c = 3041(2) pm). 相似文献
960.