排序方式: 共有37条查询结果,搜索用时 62 毫秒
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MR Eskildsen AB Abrahamsen PL Gammel DJ Bishop NH Andersen K Mortensen PC Canfield 《Pramana》2002,58(5-6):903-905
We compare the results of small angle neutron scattering on the flux line lattice (FLL) obtained in the borocarbide superconductor
LuNi2B2C with the applied field along the c- and a-axes. For H‖c the temperature dependence of the FLL structural phase transition from square to hexagonal symmetry was investigated. Above
10 K the transition onset field. H
2(T), rises sharply, bending away from H
c2(T) in contradiction to theoretical predictions of the two merging. For H‖a a first order FLL reorientation transition is observed at H
tr=3–3.5 kOe. Below H
tr the FLL nearest neighbor direction is parallel to the b-axis, and above H
tr to the c-axis. This transition cannot be explained using nonlocal corrections to the London model. 相似文献
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Francesco Barioli Wayne Barrett Shaun M. Fallat H. Tracy Hall Leslie Hogben Bryan Shader P. van den Driessche Hein van der Holst 《Journal of Graph Theory》2013,72(2):146-177
Tree‐width, and variants that restrict the allowable tree decompositions, play an important role in the study of graph algorithms and have application to computer science. The zero forcing number is used to study the maximum nullity/minimum rank of the family of symmetric matrices described by a graph. We establish relationships between these parameters, including several Colin de Verdière type parameters, and introduce numerous variations, including the minor monotone floors and ceilings of some of these parameters. This leads to new graph parameters and to new characterizations of existing graph parameters. In particular, tree‐width, largeur d'arborescence, path‐width, and proper path‐width are each characterized in terms of a minor monotone floor of a certain zero forcing parameter defined by a color change rule. 相似文献
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The semileptonic decay width of heavy baryons such as (Λ
b
→ Λcev) has been estimated in the framework of a nonrelativistic field theoretic quark model where four component quark field
operators along with a harmonic oscillator wave function are used to describe translationally invariant hadronic states. The
present estimation does not make an explicit use of heavy quark symmetry and has a reasonable agreement with the experimentally
measured decay width, polarisation ratio and form factors with the harmonic oscillator radii and quark momentum distribution
inside the hadron as free parameters. 相似文献
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Perron components and algebraic connectivity for weighted graphs 总被引:8,自引:0,他引:8
The algebraic connectivity of a connected graph is the second-smallest eigenvalue of its Laplacian matrix, and a remarkable result of Fiedler gives information on the structure of the eigenvectors associated with that eigenvalue. In this paper, we introduce the notion of a perron component at a vertex in a weighted graph, and show how the structure of the eigenvectors associated with the algebraic connectivity can be understood in terms of perron components. This leads to some strengthening of Fiedler's original result, gives some insights into weighted graphs under perturbation, and allows for a discussion of weighted graphs exhibiting tree-like structure. 相似文献
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Raman and resonance-Raman spectra of the I?3 ion isolated within CsI crystals have been studied using 647 nm and 488 nm exciting radiation. Sample temperatures between 300 and 20 K have been used. Eleven overtones of the symmetric stretching mode (nν1) have been observed in the resonance-Raman spectrum excited by the 488 nm Ar+ laser line. Bands centred at 153, 170, 264 and 304 cm?1 have been assigned as ν3, 2ν2, ν1+ν3 and 2ν3(Σ+) respectively. The remaining structure between the nν1 lines has been assigned as due to combinations of these lines with the lattice vibrations of the CsI crystal. 相似文献