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51.
Some properties of the dumbbell satellite attitude dynamics 总被引:1,自引:0,他引:1
Alessandra Celletti Vladislav Sidorenko 《Celestial Mechanics and Dynamical Astronomy》2008,101(1-2):105-126
The dumbbell satellite is a simple structure consisting of two point masses connected by a massless rod. We assume that it moves around the planet whose gravity field is approximated by the field of the attracting center. The distance between the point masses is assumed to be much smaller than the distance between the satellite’s center of mass and the attracting center, so that we can neglect the influence of the attitude dynamics on the motion of the center of mass and treat it as an unperturbed Keplerian one. Our aim is to study the satellite’s attitude dynamics. When the center of mass moves on a circular orbit, one can find a stable relative equilibrium in which the satellite is permanently elongated along the line joining the center of mass with the attracting center (the so called local vertical). In case of elliptic orbits, there are no stable equilibrium positions even for small values of the eccentricity. However, planar periodic motions are determined, where the satellite oscillates around the local vertical in such a way that the point masses do not leave the orbital plane. We prove analytically that these planar periodic motions are unstable with respect to out-of-plane perturbations (a result known from numerical investigations cf. Beletsky and Levin Adv Astronaut Sci 83, 1993). We provide also both analytical and numerical evidences of the existence of stable spatial periodic motions. 相似文献
52.
In geophysical studies investigating the lithosphere structure, topographic, bathymetric, and density contrasts stripping corrections are applied to gravity data. The ocean density contrast is typically calculated as the difference between the mean densities of crust and seawater. The approximation of the actual seawater density by its mean value yields relative errors up to 2%. To reduce these errors, we adopt a depth-dependent seawater density model to account for increasing density with pressure/depth. This approximation reduces errors to less than 0.1%. This density model is utilized in newly derived expressions for the bathymetric stripping corrections. 相似文献
53.
Ladislav Strnad Vojtech Ettler Martin Mihaljevic Jindrich Hladil Vladislav Chrastny 《Geostandards and Geoanalytical Research》2009,33(3):347-355
We report new data on the trace element concentrations of Mg, Cr, Mn, Co, Ni, Cu, Zn, Sr, Cd, Ba, La, Ce, Nd, Pb and U in USGS carbonate reference materials (MACS-1 and MACS-2) and compare solution ICP-MS and LA-ICP-MS trace element determinations on landfill calcites using calibration to different reference materials (MACS-1 and MACS-2 carbonate and NIST SRM 612 glass). Very good agreement (differences below 10% relative) was found between laser ablation and solution ICP-MS data for MACS-1 with higher concentrations of trace elements (values between 100 and 150 μg g−1 ), with the exception of Cu and Zn. Similarly good agreement was found for MACS-2 with lower trace element concentrations (units to tens of μg g−1 ), with the exception of Cr, Co and Zn. The MACS-1 reference material for calibration of LA-ICP-MS was found to be extremely useful for in situ determination of trace elements in real-world carbonate samples (landfill calcites), especially those present in calcite in higher concentrations (Mn, Sr, Ba; < 5% RSD). Less accurate determinations were generally obtained for trace elements present at low concentrations (∼ units of μg g−1 ). In addition, good agreement was observed between the instrument calibration to MACS and NIST SRM 612 glass for in situ measurements of trace elements in landfill calcites K-2, K-3 and K-4 (differences below 15% relative for most elements). Thus, the application of MACS carbonate reference materials is promising and points to the need for the development of new carbonate reference materials for laser ablation ICP-MS. 相似文献
54.
P-wave velocity anisotropy in crystalline rocks 总被引:1,自引:0,他引:1
Vladislav Babuka 《Geophysical Journal International》1984,76(1):113-119
Summary. Compressional wave velocities and anisotropy coefficients determined at high hydrostatic pressures are compiled from the data published for the main types of crystalline rocks. The crack-free elastic anisotropy of igneous crustal rocks is generally very low, between 1 and 3 per cent on average. The anisotropy of metamorphic rocks is higher (up to 22 per cent), but very variable. The average anisotropy coefficients in schists and amphibolites are about 10 per cent, in gneisses between 3 and 7 per cent, and in granulites less than 3 per cent. The average anisotropy of olivine ultramafites is between 7 and 12 per cent, whereas in pyroxenites and eclogites it is usually less than 4 per cent. A comparison of ranges of average velocities and average anisotropies for the individual rock groups suggests that, whereas in the crust the lateral velocity variations are mainly due to compositional changes, in the olivine of the uppermost mantle the velocity variations due to anisotropic structures could be of the same magnitude as the variations due to inhomogeneities. 相似文献
55.
56.
Vladislav Babuška 《Studia Geophysica et Geodaetica》1970,14(3):296-309
Zusammenfassung Der Artikel macht auf die Wahrscheinlichkeit von Ver?nderungen elastischer Anisotropie der Erdkruste und des obersten Erdmantels
mit der Tiefe aufmerksam und weist auf eine M?glichkeit der Entstehung von seismischen Grenzfl?chen zwischen den Medien mit
verschiedener elastischer Anisotropie hin. Diskutiert wird die M?glichkeit einer Interpretation der Moho-Diskontinuit?t als
einer Grenzfl?che zwischen der isotropen oder heterogen anisotropen Erdkruste und dem transversal isotropen obersten Erdmantel.
In unhydrostatischem Kraftfeld mit überwiegender vertikaler Druckkomponente stellt die Moho-Diskontinuit?t eine „Isofl?che”
mit gleichen physikalischen Bedingungen dar, die zur Entstehung der Vorzugsorientation von Olivin geeignet sind. Die Vorzugsorientation
von Olivinfl?chen (010) in einer horizontalen Ebene (d. i. senkrecht auf die Richtung der Hauptkomponente des Drucks) würde
als ein Impuls zur Entstehung laminarer Strukturen gelten, die die Anisotropie des obersten Erdmantels und seinen Kontrast
gegenüber der Erdkruste erh?hen. Durch die Entstehung der überwiegend aus den vorzugsweise orientierten Olivinkristallen zusammengesetzten
transversal isotropen Schicht kommt es im Vergleich mit einem isotropen oder sonst anisotropen Aggregat zu einer pl?tzlichen
Erh?hung der Geschwindigkeit der Longitudinalwellen in horizontaler Ebene und umgekehrt zu ihrer Herabsetzung in der vertikalen
Richtung. Dabei ist der Unterschied in der Dichte oberhalb und unterhalb der Moho-Diskontinuit?t nur durch allm?hliche Ver?nderungen
der chemischen Zusammensetzung mit der Tiefe gegeben. Vom seismologischen Gesichtspunkt aus handelt es sich also um ein Gradientmedium,
das im obersten Erdmantel transversal isotrop ist.
Address: Boční II, Praha 4-Spořilov. 相似文献
Address: Boční II, Praha 4-Spořilov. 相似文献
57.
Věra Vaňková Vladislav Babuška Reviewer J. Fiala 《Studia Geophysica et Geodaetica》1972,16(4):383-392
Summary The coefficient of the gamma-ray absorption
Cs
137
investigated in eclogites of the Bohemian Massif varies with fresh samples from0.2477 cm
–1
to 0.2804 cm
–1
. Symplectite is the main factor decreasing the value of down to0.242 cm
–1
. On the contrary, the coefficient increases with the increasing content of clinopyroxene and especially of garnet. The linear dependence of the coefficient on the density may be expressed by the equation =0.0682+0.028. 相似文献
58.
59.
60.
Jaroslava Plomerová Vladislav Babuška Libuše Ruprechtová Reviewer A. Zátopek 《Studia Geophysica et Geodaetica》1984,28(1):56-66
mam mm ua a na Pn, Pg, Sn u Sg nu¶rt;u u au -ma. aa, m ¶rt; amu 5° m numa ua¶rt;a ¶rt;am mu a na n au ma¶rt;amu u mu anmau , uu m n u ma¶rt;am¶rt;a. am nmau a uu m anmau mmu aua. 相似文献