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An additional investigation has been carried out of the rational model (Aslanov, 2000) of the separation of drops from the tops of the unstable wave formation on the molten surface of a meteoroid. The ratio of the wavelength of unstable hydrodynamic disturbances to the diameter of drops has been calculated in a mathematically closed form. Particular theoretical estimates of the size of the region of spraying of molten drops agree with prevailing sizes given in the known classification of the forms of meteoroid fragmentation. 相似文献
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The question of what lies ahead is of particular concern for Latin Americanists. The last decade has witnessed a serious erosion of both the popularity of their specialty, and an equally troublesome reduction in employment opportunities. This paper uses Association of American Geographers (AAG) data bases to document the age-gender structure of contemporary Latin Americanist geographers, and projects likely compositional changes through the end of the century. 相似文献
347.
A. V. Mityukov A. M. Nikishin O. A. Almendinger S. N. Bolotov V. A. Lavrishchev N. K. Myasoedov E. V. Rubtsova 《Moscow University Geology Bulletin》2012,67(2):81-92
This work is based on the results of 2-D and 3-D surveys in the Tuapse Basin and field works in the Crimea-Caucasus region. Seven zones were outlined in the model of sedimentation starting from the eroded mountain structure of the Greater Caucasus down to deep water sediments of the Tuapse Basin. The slope and deep-water sediments of channels and fan complexes are characterized. Volume models of the sedimentation system in the Black Sea are shown for the first time. 相似文献
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Marina Hruška William Corea Donald Seeburger William Schweller William H. Crane 《Mathematical Geosciences》2009,41(6):703-716
We describe a wavelet-transform-based method for automated segmentation of resistivity image logs that takes into account
the apparent dip in the data and addresses the problem of discriminating lithofacies boundaries from noise and intrafacies
variations. Our method can be applied to borehole measurements in general, but might have an advantage when applied to resistivity
image logs as it addresses explicitly the large variability in facies segments recorded with a high-resolution multiple-sensor
tool. We have developed an algorithm based on this method that might outperform other existing segmentation methods in the
cases of low to moderate dip. We made a detailed comparison of the segmentation from our method with the one done by a geologist
to delineate different lithofacies blocks in a well drilled in a deepwater depositional environment. Our results show considerable
success rates in reproducing the geologically defined lithofacies boundaries, and the generality of our procedure suggests
it could also be applied to other depositional environments. 相似文献
350.
The isotopic composition of lutetium has been measured in a range of terrestrial and meteoritic materials using solid-source mass spectrometric techniques. The meteoritic and terrestrial isotopic abundances are identical within experimental errors. The absolute 175Lu/176Lu ratio as determined in this work is 37.36 ± 0.07 at the 95% confidence level. On the basis of this measurement the atomic weight of lutetium has been calculated to be 174.967 ± 0.002, which is in good agreement with the currently accepted figure of 174.97 ± 0.01.Using the stable isotope dilution technique the abundance of lutetium has been determined in 25 stone, 1 stony-iron and 8 iron meteorites, and in 12 standard rocks, with an accuracy of ±5% at the 95% confidence level. In general, there is good agreement between this work and other published data.The 176Lu-176Hf pair has been proposed as an s process nucleocosmochronometer, because of the long half-life of 176Lu and the unique fact that both are s process isobars. The isotopic and elemental abundances of lutetium as measured in this work have been used with published nuclear data to estimate the mean age of s process nucleosynthesis for this isobaric pair, using the Schramm-Wasserburg formalism. The mean age cannot be accurately determined at the present time because of the lack of 30 keV neutron capture cross-section data for s only process nuclides and an accurate measurement of the branching ratio of 175Lu + n. However, it is possible to place constraints on the nuclear parameters in this mass region using a reasonable s process chronology based on the decay of 176Lu. 相似文献