The characteristics and origin of the Gould's Belt     

F. Comerón  J. Torra  A. E. Gómez 《Astrophysics and Space Science》1992,187(2):187-195

Some statistical studies on the nearby early-type stars proposed for observations by HIPPARCOS are presented. Results on spatial orientation and kinematics are in agreement with those found in the literature. An age estimate based on non-kinematical hypothesis is found to be somewhat smaller than expansion ages derives by some authors.Finally, it is suggested that Gould's Belt may have formed as a result of high-velocity cloud impact on the galactic disk, and some estimations are presented.  相似文献   

Inversion of temperature measurements in lake sediment     

P. Y. Shen  A. E. Beck 《Geophysical Journal International》1988,94(3):545-558

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On the effect of the mantle elasticity on the earth's rotation     

Juan Getino  José M. Ferrándiz 《Celestial Mechanics and Dynamical Astronomy》1995,61(2):117-180

Starting from the Hamiltonian model for a solid Earth with an elastic mantle previously developped by the authors, analytical expressions are derived which give the nutation series corresponding to the plane perpendicular to the angular momentum vector, to the plane perpendicular to the rotational axis and to the equator of figure, as well as the series that give the polar motion. The effects of the different perturbations — solid Earth, centrifugal and tidal potentials — are calculated separately. The corrections due to the elasticity of the mantle, which mostly correspond to the Oppolzer terms, are calculated with an accuracy of 10^–6 arc sec., given that the intrinsic observational accuracy has reached 0.01 mas.  相似文献   

The identification of conceptual hydrological models for surface water acidification     

H. S. Wheater  K. H. Bishop  M. B. Beck 《水文研究》1986,1(1):89-109

Ambiguity in parameter identification represents a potentially serious limitation to the application of models of surface water acidification. Previous work has concentrated on manipulation of two of the three factors affecting model identifiability, namely model structure and estimator properties. A new technique is proposed which uses different modes of response within the data to improve parameter identification. Preliminary results, obtained using the Birkenes model of surface water acidification, appear to show promise. The technique is robust in recovering model parameters from synthetic data, with and without error, and in assimilating problems of structural error.  相似文献   

Convection theory before relaxation     

L. Herrera  N. Falcón 《Astrophysics and Space Science》1995,234(1):139-152

The well known mixing length theory of convection is revised for times shorter than the effective time of relaxation into diffusion.Using the Cattaneo equation for the heat flux, we show that the revised theory predicts, before relaxation, a convective flux which is quite different from the flux obtained with the Maxwell-Fourier law.Implications of this result in the outcome of some astrophysical processes are commented upon.  相似文献   

Figures of equilibrium in close binary systems     

J. A. López Ortí  A. López García  R. López Machí 《Celestial Mechanics and Dynamical Astronomy》1992,53(4):311-322

The equilibrium configurations of close binary systems are analyzed. The autogravitational, centrifugal and tidal potentials are expanded in Clairaut's coordinates. From the set of the total potential angular terms an integral equations system is derived. The reduction of them to ordinary differential equations and the determination of the boundary conditions allow a formulation of the problem in terms of a single variable.  相似文献   

Simplify or perish     

André Deprit  Bruce Miller 《Celestial Mechanics and Dynamical Astronomy》1988,45(1-3):189-200

Three suggestions are made for breaking the gridlock which paralyses progress in automating massive symbolic calculations in celestial mechanics: (i) simplifications by canonical transformations, (ii) object oriented programming to endow the algebra of Poisson series with various structures, (iii) massively parallel processing.  相似文献   

Seasonal variation of gaseous HNO3 and NH3 at a Tropical Savannah site     

Alberto Rondón  Eugenio Sanhueza 《Journal of Atmospheric Chemistry》1990,11(3):245-254

Gaseous nitric acid and ammonia were sampled with annular denuders at a forest savannah site from April to December 1987. The analysis of the extract was made spectrophotometrically and by a selective electrode for NO₃ ^– and NH₄ ⁺, respectively. Higher concentrations were observed during the vegetation burning period at the end of the dry season. In the studied savannah area, large soil emissions of NO occur during the rainy season, although very low concentrations of HNO₃ (0.035 ppb) and also of particulate NO₃ ^– (0.43 g m^-3) were observed; it is likely that NO_x are lost by fast vertical transport to the upper troposphere. During the nonburning period, the average concentration of NH₃ was 2.7 ppb, which is much lower than values given in the literature for the tropical America atmosphere. The concentrations of HNO₃ and NH₃ were always below the values needed to produce ammonium nitrate aerosols.  相似文献   

Improving reservoir description by using geostatistical and multivariate data analysis techniques     

Henrique Garcia Pereira  António Costa e Silva  Amilcar Soares  Luis Ribeiro  Justino de Carvalho 《Mathematical Geosciences》1990,22(8):879-913

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The type-II plateau supernova 1988A in M58: What mechanism powers its late-time luminosity?     

P. Ruiz-Lapuente  M. Kidger  R. López  R. Canal 《Astrophysics and Space Science》1990,169(1-2):281-285

The detection of high late-time luminosity in the type-II plateau supernova 1988A about 500 days after maximum indicates that some mechanism is still providing large amounts of energy to the supernova at this very late phase.We present a review of the observations of this supernova at different phases, and examine the possible mechanisms that can power the late light curve in the classical type-II plateau scenario.Paper presented at the 11th European Regional Astronomical Meetings of the IAU on New Windows to the Universe, held 3–8, July, 1989, Tenerife, Canary Islands, Spain.  相似文献