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61.
Daniel E. Vogler Ana Lorencak Julien M. Rey Markus W. Sigrist 《Optics and Lasers in Engineering》2005,43(3-5):527
A novel sensitive technique for the determination of losses in fiber cavities is presented. The method is based on the cavity ringdown scheme implemented in silica-based single-mode fibers. Bending losses of fiber cavities of different lengths have been measured showing all an oscillating behavior with respect to the curvature radius of the fiber as predicted by a theoretical model. The best minimum detectable absorbance per cavity pass achieved by this new method is 1.72×10−3 dB within a 10 m-long cavity. This limit suffices well for an accurate determination of optical bending losses even in bend-insensitive fibers. Furthermore, the comparison of the measured bending losses with a theoretical model allows the extraction of different fiber parameters. Good agreement has been found between the experimentally derived parameters and literature data. 相似文献
62.
We demonstrate how optimization problems arise in the field of pattern classification, in particular in using piecewise-linear classification and classification based on an optimal linear separator. We motivate the need in this area for a general purpose optimization approach. We discuss ALOPEX, a biased random search approach, from the point of view of this need. While ALOPEX itself failed to fulfil our need, a newly-introduced generalization of it (iterated ALOPEX) was found to be appropriate for the optimization problems of our particular concern. We conclude the paper with a brief critical evaluation of this approach as compared to our original aims. 相似文献
63.
We prove a Beurling–Lax theorem for a family of reproducing kernel Hilbert spaces of functions analytic in an open subset of the unit ball containing the origin. The spaces under consideration are characterized by functions called Schur multipliers. Using the theory of linear relations in Pontryagin spaces we also give coisometric realizations of Schur multipliers. To cite this article: D. Alpay et al., C. R. Acad. Sci. Paris, Ser. I 334 (2002) 349–354. 相似文献
64.
N. Barrier P. Gall P. Gougeon 《Acta Crystallographica. Section C, Structural Chemistry》2007,63(11):i102-i104
Trisamarium molybdenum heptaoxide, Sm3MoO7, is isomorphous with Ln3MoO7 (Ln = La and Pr). The crystal structure consists of chains of corner‐linked MoO6 octahedra running parallel to the b axis and separated from each other by seven‐ or eight‐coordinate Sm–O polyhedra. In contrast to La3MoO7 and Pr3MoO7, a splitting of one Sm site into two positions is observed. 相似文献
65.
A test statistic is developed that checks the validity of the extreme value conditions without specifiying the shape parameter of the limiting extreme value distribution. 相似文献
66.
The transmission line method is used for the analysis of microstrip antennas fed by several nonlinear slots with 'H' shapes or new geometries. This analysis allows the input impedance of nonlinear slot coupled microstrip antennas to be calculated for the four different structures.<> 相似文献
67.
Daniel Král’ Jan Kratochvíl Andrzej Proskurowski Heinz-Jürgen Voss 《Discrete Applied Mathematics》2006,154(4):660-672
A mixed hypergraph is a triple (V,C,D) where V is its vertex set and C and D are families of subsets of V, called C-edges and D-edges, respectively. For a proper coloring, we require that each C-edge contains two vertices with the same color and each D-edge contains two vertices with different colors. The feasible set of a mixed hypergraph is the set of all k's for which there exists a proper coloring using exactly k colors. A hypergraph is a hypertree if there exists a tree such that the edges of the hypergraph induce connected subgraphs of the tree.We prove that feasible sets of mixed hypertrees are gap-free, i.e., intervals of integers, and we show that this is not true for precolored mixed hypertrees. The problem to decide whether a mixed hypertree can be colored by k colors is NP-complete in general; we investigate complexity of various restrictions of this problem and we characterize their complexity in most of the cases. 相似文献
68.
69.
Summary Comparison theorems for weak splittings of bounded operators are presented. These theorems extend the classical comparison theorem for regular splittings of matrices by Varga, the less known result by Wonicki, and the recent results for regular and weak regular splittings of matrices by Neumann and Plemmons, Elsner, and Lanzkron, Rose and Szyld. The hypotheses of the theorems presented here are weaker and the theorems hold for general Banach spaces and rather general cones. Hypotheses are given which provide strict inequalities for the comparisons. It is also shown that the comparison theorem by Alefeld and Volkmann applies exclusively to monotone sequences of iterates and is not equivalent to the comparison of the spectral radius of the iteration operators.This work was supported by the National Science Foundation grants DMS-8807338 and INT-8918502 相似文献
70.
Daniel Berend 《Journal d'Analyse Mathématique》1988,50(1):123-142
Given measure preserving transformationsT 1,T 2,...,T s of a probability space (X,B, μ) we are interested in the asymptotic behaviour of ergodic averages of the form $$\frac{1}{N}\sum\limits_{n = 0}^{N - 1} {T_1^n f_1 \cdot T_2^n f_2 } \cdot \cdots \cdot T_s^n f_s $$ wheref 1,f 2,...,f s ?L ∞(X,B,μ). In the general case we study, mainly for commuting transformations, conditions under which the limit of (1) inL 2-norm is ∫ x f 1 dμ·∫ x f 2 dμ...∫ x f s dμ for anyf 1,f 2...,f s ?L ∞(X,B,μ). If the transformations are commuting epimorphisms of a compact abelian group, then this limit exists almost everywhere. A few results are also obtained for some classes of non-commuting epimorphisms of compact abelian groups, and for commuting epimorphisms of arbitrary compact groups. 相似文献