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排序方式: 共有211条查询结果,搜索用时 296 毫秒
1.
2.
D. S. Drozdov F. M. Rivkin V. Rachold G. V. Ananjeva-Malkova N. V. Ivanova I. V. Chehina M. M. Koreisha Yu. V. Korostelev E. S. Melnikov 《Geo-Marine Letters》2005,25(2-3):81-88
A set of digital maps including geology, Quaternary sediments, landscapes, engineering-geological, vegetation, geocryological and the series of regional sources have been selected to characterize the Russian Arctic coast. Based on this data, new maps of engineering geocryological zoning and zoning of the coast with respect to the intensity of exogenous geological processes and risk of technogenic impacts have been generated at the scales of 1:4,000,000–1:8,000,000. These maps are a tool to assess the impact of industry on the Arctic coast of the country. 相似文献
3.
Stanislav D. Furta 《Celestial Mechanics and Dynamical Astronomy》1992,53(3):255-266
The author considers a problem of Lyapunov's stability of relative equilibria of a flexible nonstretchable thread attached to the satellite moving in a circular Keplerian orbit in the first approximation. When it is in the position of relative equilibrium, the thread is known to be situated either along the radius vector of the orbit (the radial equilibrium) or along the circular orbit (the tangential equilibrium) and in each case the thread can be in a folded state. The author shows that folded radial equilibria of the thread are always unstable while tangential ones are unstable if the thread is sufficiently short in comparison with the radius of the orbit. The generalized Chetaev functional has been constructed to prove the instability. 相似文献
4.
Stanislav Horník 《GeoJournal》1993,31(4):379-382
Some results of biogeographic research on meadows in the Dyje-Svratka basin in the Czech Republic. The paper shows one example of biogeographic inventory of natural ecosystems in an unflooded meadow in the Dyje-Svratka basin. It is part of the complex physio-geographic research of the Geographic Department of the Masaryk University in Brno aimed at gaining a basis for territorial interpretation of ecological regularities and territorial application of general ecological optimizing principles. A segment of biocenosis of Ulmi-fraxineta carpini has been analyzed (Zlatník 1956).The endeavour of Czech geographers to study geosystems of various dimensions completely gets in the limelight. In question is the understanding of mutual relationship of components of geosystems based on the exchange of mass and energy. There are two ways of studying them: spatial relations or approaches concentrated on processes. In contrast to the above unilateral concept, the endeavour to make the approaches compatible appears rarely. This complex view is made possible by geobiocenologically taken biogeography in papers of Zlatník and Rauer, their students and successors. This paper shows only one example of the results of biogeographic stock-taking of meadows in the Dyje-Svratka basin, indicating relations of eco- and geosystems which confirm the necessity of ecological orientation of the present biogeography and its potential contribution to ecology. 相似文献
5.
Stanislav FRANCISKOVIC-BILINSKI Halka BILINSKI Delko BARISIC Nada HORVATINCIC Institute Ruder BoSkovi POB HR- Zagre Croati E-mail: francis@rudjer.irb.hrand YUAN Daoxian Institute of Karst Geology Guilin Guangxi China 《《地质学报》英文版》2003,77(2):267-275
The paper presents an analysis of characteristic karst tufa from Guangxi, China, which has not been studied before. A comparison with tufa from Dinaric Karst of Croatia is discussed in view of the C-type climate. The major mineral is calcite. Minor minerals are quartz and dolomite, depending on location. The content of calcium carbonate varies from 65% to 92%, and that of magnesium carbonate from 0.03% to 1.77%. Among other elements, the most abundant are Fe, from 0.02% to 1.50%, and Ti, from 0.15% to 0.27%. Many other trace elements (V, Cr, Mn, Ni, Cu, Zn, As, Se, Br, Rb, Sr, Y, Zr, Hg and Pb) are also present. Specific activity of radionuclides 40K, 232Th, 137Cs, 226Ra and 238U varies from sample to sample. Concentration of U in tufa is close to that reported for sedimentary carbonate. Low concentration of 137Cs indicates that this part of the world was not exposed to nuclear explosions. The concentration of 226Ra is the highest in Mashan County. The ratio 238U/226Ra (0.21-0.71) in tufa from Mashan Co 相似文献
6.
Stanislav V. Sinogeikin Jay D. Bass Bridget O'Neill Tibor Gasparik 《Physics and Chemistry of Minerals》1997,24(2):115-121
The adiabatic elastic moduli of polycrystalline En50Py50 and En80Py20 majorite-garnet solid solutions (where En=4MgSiO3, Py=Mg3Al2Si3O12) and the end-member En100 tetragonal majorite were determined at ambient conditions using Brillouin spectroscopy. The adiabatic bulk modulus, K, and
shear modulus, μ, of En50Py50 were found to be K=173.1 (20) and μ=92.3 (10) GPa, and are indistinguishable from those of the end-member pyrope, Py100. The moduli of the more majorite-rich samples are significantly lower and are virtually identical to each other (K=162.6(11)
and μ=85.7(7) for En80Py20; K=166(5) and μ=88(2) for En100). In combination with previously reported moduli for this system, we conclude that both K and μ are constant over the compositional
range from Py100 to a majorite content of about 70–80%, whereupon the moduli decrease substantially. For compositions ranging from En80Py20 to the end-member majorite, the moduli are also approximately independent of composition, but at a lower value. An alternative
model with a continuous decrease in moduli with increasing majorite content cannot be excluded, within the uncertainties of
existing measurements. The contrast in moduli between aluminous pyrope garnet and Al-free majorite are small compared with
the modulus changes accompanying the pyroxene – majorite phase transformation.
Received August 16, 1995 /Revised, accepted January 12, 1996 相似文献
7.
A.B. Kuznetsov V.A. Melezhik I.M. Gorokhov N.N. Melnikov G.V. Konstantinova E.P. Kutyavin T.L. Turchenko 《Precambrian Research》2010
Rb–Sr systematics has been studied in 13C-rich carbonate rocks of the Paleoproterozoic (2.09 ± 0.07 Ga) Tulomozero Formation in the northern Onega Lake area, the SE Fennoscandian Shield. The formation is divided into eight members (A–F) consisting of greenschist-facies-grade, variegated sandstones, siltstones, mudstones, stromatolitic dolostones and subordinate crystalline limestones. Samples of carbonate rocks were obtained from two overlapping drillholes intersecting the entire thickness of the Tulomozero Formation. Prior to isotope analysis, the rocks powders were treated with 1N ammonium acetate for partial removal of the late epigenetic carbonate phases. Major resetting of the Rb–Sr systems in the Tulomozero carbonate rocks appears to take place during the Svecofennian regional metamorphic event, and it was screened by using Mn/Sr, Fe/Sr, Mg/Ca, and 18O/16O ratios. High Sr content (up to 2080 μg/g in limestones, and 530 μg/g in dolostones) coupled with low Fe/Mn (<0.40) ratios in the Tulomozero carbonate rocks of Members A, B (the lower part), D, F, and E are consistent with accumulation of original carbonate sediments in evaporitic lacustrine, playa, and sabkha environments. A decrease in the Sr content with concurrent increase in the Fe/Mn ratio (>0.40) in dolostones of the upper part of Member B, and of Members G and H is indicative of seawater influxes (sea transgression) into the Tulomozero basin. The 87Sr/86Sr values in the least altered (Mn/Sr < 2.0) marine dolostones are 0.70418–0.70442 and 0.70343–0.70409 for the earlier and late phases of the marine transgression, respectively. The decrease in the 87Sr/86Sr ratio in ca. 2.1 Ga seawater is attributable to an increase in hydrothermal flux Sr into the Palaeoproterozoic ocean. 相似文献
8.
A. N. Kurchatova V. P. Melnikov V. V. Rogov E. A. Slagoda 《Doklady Earth Sciences》2016,468(2):571-573
Basic chemical and mineralogical anomalies in permafrost caused by hydrocarbon migration are considered. Direct evidence for bacterial oxidation of light hydrocarbons, primarily methane, were first obtained in fluid permeability zones in the permafrost as a stepwise formation of authigenic minerals such as iron sulfides and oxides, carbonates, silicates, and gypsum. 相似文献
9.
Koroleva E. S. Slagoda E. A. Melnikov V. P. Babkina E. A. Khomutov A. V. Opokina O. L. Danko M. M. Tikhonravova Ya. V. 《Doklady Earth Sciences》2021,498(2):465-470
Doklady Earth Sciences - The upper part of the subsurface component of the Earth’s cryosphere—polygonal peatlands—are considered in this paper. The polygonal peatlands are... 相似文献
10.
Khamitov I. M. Bikmaev I. F. Burenin R. A. Glushkov M. V. Melnikov S. S. Lyapin A. R. 《Astronomy Letters》2020,46(1):1-11
Astronomy Letters - An example of simultaneous spectroscopic redshift measurements for a large number of galaxies in a cluster by multiobject spectroscopy with the medium- and low-resolution TFOSC... 相似文献