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901.
We present a streamlined approach to relative oscillation criteria based on effective Prüfer angles adapted to the use at the edges of the essential spectrum.Based on this we provided a new scale of oscillation criteria for general Sturm-Liouville operators which answer the question whether a perturbation inserts a finite or an infinite number of eigenvalues into an essential spectral gap. As a special case we recover and generalize the Gesztesy-Ünal criterion (which works below the spectrum and contains classical criteria by Kneser, Hartman, Hille, and Weber) and the well-known results by Rofe-Beketov including the extensions by Schmidt. 相似文献
902.
J. Vermeer 《Linear algebra and its applications》2008,428(1):382-392
Any square matrix over a field is similar to its transpose and any square complex matrix is similar to a symmetric complex matrix. We investigate the situation for real orthogonal (respectively complex unitary) similarity. 相似文献
903.
Grzegorz Bobiński 《Journal of Pure and Applied Algebra》2008,212(6):1457-1471
We investigate sets of the common zeros of non-constant semi-invariants for regular modules over canonical algebras. In particular, we show that if the considered algebra is tame then for big enough vectors these sets are complete intersections. 相似文献
904.
Alegra Daji? 《Linear algebra and its applications》2008,429(7):1779-1809
This paper reviews the equations ax = c and xb = d from a new perspective by studying them in the setting of associative rings with or without involution. Results for rectangular matrices and operators between different Banach and Hilbert spaces are obtained by embedding the ‘rectangles’ into rings of square matrices or rings of operators acting on the same space. Necessary and sufficient conditions using generalized inverses are given for the existence of the hermitian, skew-hermitian, reflexive, antireflexive, positive and real-positive solutions, and the general solutions are described in terms of the original elements or operators. New results are obtained, and many results existing in the literature are recovered and corrected. 相似文献
905.
Let Z be a field of characteristic ≠2, D be a quaternion division algebra over Z and have a nonstandard involution of the first kind. The fundamental theorem of geometry of 2× 2 Hermitian matrices over D are proved. Thus, if D is a quaternion division algebra over Z with an involution of the first kind, then the fundamental theorem of geometry of 2× 2 Hermitian matrices over D are obtained. 相似文献
906.
对 0<α <∞, Nα 是开单位圆盘 D 上满足 sup z∈ D(1-|z|2)α f# (z)<∞ 的亚纯函数类, 其中 f# (z)=|f'(z)|/(1+|f(z)|2) 是 f 的球面导数. 该文给出了 D 上的 α -正规函数类的一些积分准则, 并用 Bergman-Carleson 测度的形式予以表示. 相似文献
907.
Two α-aminoxy diamides with fluorinated side chains were synthesized. Their secondary structures characterization was carried out by 1H NMR, and IR spectrometries as well as X-ray crystallography studies. α N-O turn secondary structures are adopted insusceptibly by side-chain-fluorinated α-aminoxy residues. Thus the fluorinated α-aminoxy diamide can be a potential residue as a biological tracer to be incorporated into aminoxy peptides. 相似文献
908.
909.
In this paper, compact bulk nanocomposite Nd2Fe14B/α-Fe magnetic materials were prepared by hot extrusion of amorphous and nanocrystalline powders, which were prepared by high-energy ball-milling (HEBM) of the Nd2Fe14 B-type hard magnetic phase with 20 vol% of α-Fe as soft magnetic phase. The extrusion temperature has important influence on magnetic properties and microstructure of magnetic materials. The results show that the grain size of Nd2Fe14B and α-Fe phase increases steadily with increasing extrusion temperature. Furthermore, optimal extrusion temperature of 1223 K occurs, at which the highest magnetic properties and relative density can be obtained. 相似文献
910.