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71.
运用一种新的动力学突变检测方法——排列熵(permutation entropy,PE)算法,计算并分析了中国华北地区52个站点1960年—2000年逐日平均气温资料的排列熵演化情况,发现中国华北地区气温在20世纪70年代中期、80年代初均发生了较大突变;进一步用经验模态分解(empirical mode decomposition,EMD)方法对排列熵序列进行逐级平稳化处理,结果发现这一地区的气温突变与准10年这一年代际时间尺度的周期变率密切相关,其原因与太阳黑子活动有着密切联系.
关键词:
华北
突变
排列熵算法
经验模态分解 相似文献
72.
We discuss whether an appropriately defined dimensionless scalar function might be an acceptable candidate for the gravitational entropy, by explicitly considering Szekeres and Bianchi type VI
h
models that admit an isotropic singularity. We also briefly discuss other possible gravitational entropy functions, including an appropriate measure of the velocity dependent Bel-Robinson tensor.
PACS: 04.20.-q 95.30.Sf 98.80.Jk 相似文献
73.
David Loffreda 《Surface science》2006,600(10):2103-2112
Adsorption thermodynamics based on density functional theory (DFT) calculations are exposed for the interaction of several multifunctional molecules with Pt and Au(1 1 0)-(1 × 2) surfaces. The Gibbs free adsorption energy explicitly depends on the adsorption internal energy, which is derived from DFT adsorption energy, and the vibrational entropy change during the chemisorption process. Zero-point energy (ZPE) corrections have been systematically applied to the adsorption energy. Moreover the vibrational entropy change has been computed on the basis of DFT harmonic frequencies (gas and adsorbed phases, clean surfaces), which have been extended to all the adsorbate vibrations and the metallic surface phonons. The phase diagrams plotted in realistic conditions of temperature (from 100 to 400 K) and pressure (0.15 atm) show that the ZPE corrected adsorption energy is the main contribution. When strong chemisorption is considered on the Pt surface, the multifunctional molecules are adsorbed on the surface in the considered temperature range. In contrast for weak chemisorption on the Au surface, the thermodynamic results should be held cautiously. The systematic errors of the model (choice of the functional, configurational entropy and vibrational entropy) make difficult the prediction of the adsorption-desorption phase boundaries. 相似文献
74.
We find the existence of a quantum thermal effect, “Hawking absorption.” near the inner horizon of the Kerr–Newman black hole. Redefining the entropy, temperature, angular velocity, and electric potential of the black hole, we give a new formulation of the Bekenstein–Smarr formula. The redefined entropy vanishes for absolute zero temperature of the black hole and hence it is interpreted as the Planck absolute entropy of the KN black hole. 相似文献
75.
76.
77.
78.
E. Alper Yildirim Xiaofei Fan-Orzechowski 《Computational Optimization and Applications》2006,33(2-3):229-247
We study the maximum stable set problem. For a given graph, we establish several transformations among feasible solutions
of different formulations of Lovász's theta function. We propose reductions from feasible solutions corresponding to a graph
to those corresponding to its induced subgraphs. We develop an efficient, polynomial-time algorithm to extract a maximum stable
set in a perfect graph using the theta function. Our algorithm iteratively transforms an approximate solution of the semidefinite
formulation of the theta function into an approximate solution of another formulation, which is then used to identify a vertex
that belongs to a maximum stable set. The subgraph induced by that vertex and its neighbors is removed and the same procedure
is repeated on successively smaller graphs. We establish that solving the theta problem up to an adaptively chosen, fairly
rough accuracy suffices in order for the algorithm to work properly. Furthermore, our algorithm successfully employs a warm-start
strategy to recompute the theta function on smaller subgraphs. Computational results demonstrate that our algorithm can efficiently
extract maximum stable sets in comparable time it takes to solve the theta problem on the original graph to optimality.
This work was supported in part by NSF through CAREER Grant DMI-0237415. Part of this work was performed while the first author
was at the Department of Applied Mathematics and Statisticsat Stony Brook University, Stony Brook, NY, USA. 相似文献
79.
Hui-Ling Li De-Jiang Qi Qing-Quan Jiang Shu-Zheng Yang 《International Journal of Theoretical Physics》2006,45(12):2428-2436
An extension of the Parikh-Wilczek's semi-classical quantum tunneling method, the tunneling radiation of the charged particle from a torus-like black hole is investigated. Difference from the uncharged mass-less particle, the geodesics of the charged massive particle tunneling from the black hole is not light-like, but determined by the phase velocity. The derived result shows that the tunneling rate depends on the emitted particle's energy and electric charge, and takes the same functional form as uncharged particle. It proves also that the exact emission spectrum is not strictly pure thermal, but is consistent with the underlying unitary theory.
PACS Numbers: 04.70.Dy, 97.60.Lf, 05.30.Ch. 相似文献
80.
Thomas Andreae 《Journal of Graph Theory》2002,39(4):222-229
For a graph A and a positive integer n, let nA denote the union of n disjoint copies of A; similarly, the union of ?0 disjoint copies of A is referred to as ?0A. It is shown that there exist (connected) graphs A and G such that nA is a minor of G for all n??, but ?0A is not a minor of G. This supplements previous examples showing that analogous statements are true if, instead of minors, isomorphic embeddings or topological minors are considered. The construction of A and G is based on the fact that there exist (infinite) graphs G1, G2,… such that Gi is not a minor of Gj for all i ≠ j. In contrast to previous examples concerning isomorphic embeddings and topological minors, the graphs A and G presented here are not locally finite. The following conjecture is suggested: for each locally finite connected graph A and each graph G, if nA is a minor of G for all n ? ?, then ?0A is a minor of G, too. If true, this would be a far‐reaching generalization of a classical result of R. Halin on families of disjoint one‐way infinite paths in graphs. © 2002 Wiley Periodicals, Inc. J Graph Theory 39: 222–229, 2002; DOI 10.1002/jgt.10016 相似文献