La descente et la montée étendues: the spatially <Emphasis Type="Bold">d</Emphasis>-anisotropic and the spatio-temporal case     

E. Porcu  P. Gregori  J. Mateu 《Stochastic Environmental Research and Risk Assessment (SERRA)》2007,21(6):683-693

There is a great demand for statistical modeling of phenomena that evolve in both space and time, and thus, there is a growing literature on correlation function models for spatio-temporal processes. In particular, various properties of these correlation functions have been studied only for the merely spatial or temporal case, fact that constitutes a strong motivation for our work. The goal of this paper is to inspect some properties, obtained with respect to partial differentiation and integration, of stationary spatio-temporal correlation functions for which anisotropy is obtained through isotropy between components as in Fernández-Casal et al. (Stat Comput 13(2):127–136, 2003). We show that through partial differentiation and integration it is possible to obtain permissible spatio-temporal correlation functions in the space–time domain. Other new results regard specific classes of space–time correlations introduced in recent literature. A curious result arises by differentiating scale mixtures of Euclid’s hat. Work partially funded by grant MTM2004-06231 from the Spanish Ministery of Science and Education.  相似文献   

Coastal cooling/heating events: Laboratory experiments     

Natalia Demchenko  Irina Chubarenko 《Acta Geophysica》2007,55(1):56-64

We report the results of laboratory experiments on water heating/cooling, performed in 5 m long water channel with a slope. About 63 series of photos were analyzed: for 3 locations, for 3 bottom slopes (3.7, 6.7 and 12 degrees) and for different Ra numbers. It was pointed out that there exist two types of mixing characterizing different circulations in the presence of slope: gravity current and undersurface jet; the thermal bar is the region where one type of mixing is replaced by another; the highest speed and flowrate are at the break point; the flow is three-dimensional.  相似文献   

Energy distribution of a stringy charged black hole     

Ragab?M.?GadEmail author 《Astrophysics and Space Science》2005,295(4):459-462

The energy distribution associated with a stringy charged black hole is studied using Møller’s energy-momentum complex. Our result is reasonable and it differs from that known in literature using Einstein’s energy-momentum complex.  相似文献   

Computing periodic orbits of the three-body problem: Effective convergence of Newton’s method on the surface of section     

V.?S.?Kalantonis  V.?V.?Markellos  E.?A.?PerdiosEmail author 《Astrophysics and Space Science》2005,298(3):441-451

We consider Newton’s method for computing periodic orbits of dynamical systems as fixed points on a surface of section and seek to clarify and evaluate the method’s uncertainty of convergence. Several fixed points of various multiplicities, both stable and unstable are computed in a new version of Hill’s problem. Newton’s method is applied with starting points chosen randomly inside the maximum possible—for any method—circle of convergence. The employment of random starting points is continued until one of them leads to convergence, and the process is repeated a thousand times for each fixed point. The results show that on average convergence occurs with very few starting points and non-converging iterations being wasted.  相似文献   

Finite-difference Euler Deconvolution Algorithm Applied to the Interpretation of Magnetic Data from Northern Bulgaria     

Daniela?GerovskaEmail author  Petar?Stavrev  Marcos J.?Araúzo-Bravo 《Pure and Applied Geophysics》2005,162(3):591-608

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On the applicability of Kirchoff’s law and the principle of heat balance in thermal infrared remote sensing: A non-isothermal system     

Renhua?ZhangEmail author  Zhaoliang?Li  Xiaomin?Sun  Zhilin?Zhu  Weimin?Wang 《中国科学D辑(英文版)》2005,48(1):53-64

This paper proposes a basic equation of thermal radiation interaction between surface objects on the basis of the principle of heat balance in the interface. The solution of this equation takes account of the contribution of sensible heat flux and latent heat flux more completely, compared with traditional solution for surface cooling and heating processes. By the aid of the experimental data conducted in the Xiaotangshan experimental site, Beijing, both the non-applicability of Kirchoff’s law and the measurability of surface emissivity in a non-isothermal system have been highlighted. Two methods called ventilation and time-delay compensations have been proposed to reduce the error induced by change of surface temperatures of non-isothermal objects during the measurement of emissivity. Based on the solution of the basic equation, this paper has analyzed and pointed out the misunderstanding in comprehension and application of Kirchoff’s law published in literature.  相似文献   

Detection of spheriodal free oscillation excited by Peru 8.2 <Emphasis Type="Italic">M</Emphasis><Subscript>s</Subscript> earthquake with five international superconducting gravimeter data     

Xiang’e?LeiEmail author  Houze?Xu  Heping?Sun 《中国科学D辑(英文版)》2005,48(1):123-133

In this paper, authors obtain the spectral peaks of the earth free oscillation and check all normal modes from ₀S₀ to ₀S₄₈ accurately, with the Fourier analysis and the maximum entropy spectrum method dealing jointly with six groups of the observational residual data from five international superconducting gravimeter stations. By comparing the observational results in this paper with three former groups of observations or models, authors notice an extra discrepancy between two observational ₀S₂ modes excited separately by Peru earthquake and Alaska earthquake, which probably mirrors the anisotropy of the Earth’s inner core. The analysis on the splitting ₁S₂ mode shows that the asymmetric factor of rotationwise spectral splitting is possible to be different from that of anti-rotationwise spectral splitting.  相似文献   

Contribution of stable isotopes to the understanding of the unsaturated zone of a carbonate aquifer (Nerja Cave, southern Spain)     

Francisco Carrasco  Bartolom Andreo  Cristina Lin  Jacques Mudry 《Comptes Rendus Geoscience》2006,338(16):1203-1212

We analysed the stable isotopes (¹⁸O and ²H) of rainwater and drip water within a cave (Nerja Cave) located in the unsaturated zone of a carbonate aquifer. Rainfall is more abundant and presents lower isotopic content in winter, while the volume of drip water is greater and its isotopic content is lower in summer. The flow analysis of ¹⁸O through the unsaturated zone confirms the seasonal lag between rainfall and the appearance of drip water in the cave and reveals that the unsaturated zone of the aquifer, in the sector of the cave, behaves like an inertial system with a strong capability to modulate the input signal. To cite this article: F. Carrasco et al., C. R. Geoscience 338 (2006).  相似文献   

A modified Jacobi preconditioner for solving ill‐conditioned Biot's consolidation equations using symmetric quasi‐minimal residual method     

S. H. Chan  K. K. Phoon  F. H. Lee 《国际地质力学数值与分析法杂志》2001,25(10):1001-1025

This paper identifies imbalanced columns (or rows) as a significant source of ill‐conditioning in the preconditioned coefficient matrix using the standard Jacobi preconditioner, for finite element solution of Biot's consolidation equations. A simple and heuristic preconditioner is proposed to reduce this source of ill‐conditioning. The proposed preconditioner modifies the standard Jacobi preconditioner by scaling the excess pore pressure degree‐of‐freedoms in the standard Jacobi preconditioner with appropriate factors. The performance of such preconditioner is examined using the symmetric quasi‐minimal residual method. To alleviate storage requirements, element‐by‐element iterative strategies are implemented. Numerical experiment results show that the proposed preconditioner reduces both the number of iteration and CPU execution time significantly as compared with the standard Jacobi preconditioner. Copyright © 2001 John Wiley & Sons, Ltd.  相似文献   

浅论法治与德治的结合与建设     

陈伟斌 《广东海洋大学学报》2002,22(2):58-62

市场经济的发展为法治与德治的统一提供了社会条件。全面加强社会主义法制建设和道德建设对于发展社会主义市场经济 ,建设有中国特色的社会主义具有重大的意义  相似文献