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1.
Maurizio M. D’Eliseo 《Celestial Mechanics and Dynamical Astronomy》2007,98(2):145-154
It is shown how the generalized Laplace coefficients can be employed to deduce explicit formulas for ordinary and Newcomb
derivatives of the Laplace coefficients.
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The quality and integrity of spatial data is very important to support interoperability among different systems. To reach this aim integrity rules defined by the application play an important role (for example, constraints between object classes). In this article, we propose a methodology to define integrity constraints using user level spatial relations between classes of individuals. We will also provide mapping rules from user level relations to geometric level operators to allow the computation of relations. As a case study, we will define the constraints for the class of rivers and some of its specializations. 相似文献
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E. Carretta R. G. Gratton G. Clementini 《Monthly notices of the Royal Astronomical Society》2000,316(4):721-728
The discrepancy between a long distance-scale derived from Hipparcos -based distances to globular clusters via main-sequence fitting to local subdwarfs, and a short distance-scale derived from the absolute magnitude of field RR Lyraes via statistical parallaxes and the Baade–Wesselink method could be accounted for whether an intrinsic difference of about ∼0.1–0.2 mag was found to exist between horizontal branch (HB) stars populating the sparse general field and the dense globular clusters. In this paper we discuss the possible existence of such a systematic difference comparing the period-shifts observed for field and cluster RR Lyraes. Various approaches based on different parameters and data sets for both cluster and field variables were used in order to establish the size of such a hypothetical difference, if any. We find that on the whole very small not significant differences exist between the period–metallicity distributions of field and cluster RR Lyraes, thus confirming with a more quantitative approach, the qualitative conclusions by Catelan . This observational evidence translates into a very small difference between the horizontal branch luminosity of field and cluster stars, unless RR Lyraes in globular clusters are about 0.06 M⊙ more massive than field RR Lyraes at same metallicity, which is to be proven. 相似文献
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Maurizio M. D’Eliseo 《Astrophysics and Space Science》2011,332(1):121-128
We study the general relativistic orbital equation and using a straightforward perturbation method and a mathematical device
first introduced by d’Alembert, we work out approximate expressions of a bound planetary orbit in the form of trigonometrical
polynomials and the first three terms of the power series development of the perihelion advance. The results are applied to
a more precise determination of the total mass of the double pulsar J0737-3039. 相似文献
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Vyacheslav M. Zobin Juan José Ramírez Hydyn Santiago Eliseo Alatorre Carlos Navarro 《Bulletin of Volcanology》2011,73(1):91-99
Continuous tilt changes during the 2004–2005 effusive-explosive episodes at Volcán de Colima (México) were recorded simultaneously
by two tiltmeters installed on opposite sides of the volcano at elevations of 2200 m and 3060 m above sea level. Data indicate
that the 2004 lava extrusion was preceded by an inflation accompanied by a deflation. The 2005 explosion sequences were associated
with a deflationary–inflationary tilt. The period between the 2004 extrusion and the 2005 explosions was characterized by
an inflationary tilt during a 3 month period. Two deformation sources were located. The first was situated at a depth between
300 m and 1800 m beneath the crater at the northern flank of the volcano and was responsible for volcano deformation during
the preliminary September 2004 stage, the October 2004 extrusion, and the initial stage of the transition period and the March
2005 explosion sequence. The second source was located at a depth between 1800 m and 2800 m beneath the crater at the southern
flank of the volcano and was responsible for volcano deformation during the final stage of the transition period and the May–June
2005 explosion sequence. 相似文献
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Eliseo Hernandez-Martinez Teresa Perez-Muñoz Jorge X. Velasco-Hernandez Armando Altamira-Areyan Luis Velasquillo-Martinez 《Mathematical Geosciences》2013,45(4):471-486
Well-log (radioactivity, density and resistivity) analysis constitutes a standard approach for inferring lithology from wells. However, due to inherent complexity of the signals (such as highly heterogeneous deep-water sedimentary sequences) lithology recognition is not straightforward. We used a rescaled range analysis, calibrated with cores, to recognize lithological patterns from signal recorded along wireline logs. The detected intervals coincide with zones of visual electro-facies associations proposed by geologist well-log interpreters. In addition, we propose a rescaled range multifractal analysis to identify ranges of well-log signal complexities, which could be related to sedimentary process variations at specific stratigraphic order cycles. 相似文献
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Michael A. Dopita Marcella Marconi Gisella Clementini Enzo Brocato 《Astrophysics and Space Science》2012,338(1):1-2
In recent papers we had developed a unified picture of black hole entropy and curvature which was shown to lead to Hawking
radiation. It was shown that for any black hole mass, holography implies a phase space of just one quantum associated with
the interior of the black hole. Here we study extremal rotating and charged black holes and obtain unique values for ratios
of angular momentum to entropy, charge to entropy, etc. It turns out that these ratios can be expressed in terms of fundamental
constants in nature, having analogies with other physical systems, like in condensed matter physics. 相似文献
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G. Fiorentino G. Clementini M. Marconi I. Musella A. Saha M. Tosi R. Contreras?Ramos F. Annibali A. Aloisi R. van?der Marel 《Astrophysics and Space Science》2012,341(1):143-150
The cosmological distance ladder crucially depends on classical Cepheids (with P=3–80 days), which are primary distance indicators up to 33 Mpc. Within this volume, very few SNe Ia have been calibrated through classical Cepheids, with uncertainty related to the non-linearity and the metallicity dependence of their period–luminosity (PL) relation. Although a general consensus on these effects is still not achieved, classical Cepheids remain the most used primary distance indicators. A possible extension of these standard candles to further distances would be important. In this context, a very promising new tool is represented by the ultra-long period (ULP) Cepheids (P≳80 days), recently identified in star-forming galaxies. Only a small number of ULP Cepheids have been discovered so far. Here we present and analyse the properties of an updated sample of 37 ULP Cepheids observed in galaxies within a very large metallicity range of 12+log(O/H) from ∼7.2 to 9.2 dex. We find that their location in the colour-magnitude (V−I,V) diagram as well as their Wesenheit (V−I) index-period (WP) relation suggests that they are the counterparts at high luminosity of the shorter-period (P≲80 days) classical Cepheids. However, a complete pulsation and evolutionary theoretical scenario is needed to properly interpret the true nature of these objects. We do not confirm the flattening in the studied WP relation suggested by Bird et al. (Astrophys. J. 695:874, 2009). Using the whole sample, we find that ULP Cepheids lie around a WP relation similar to that of the LMC, although with a large spread (∼ 0.4 mag). 相似文献