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91.
Summary The algorithm of iterative geophysical tomography is presented. The medium is approximated smoothly by means of B-splines. The tww-point problem of ray computation is solved with the aid of paraxial approximation. The parameters of the medium are obtained from the iterative algorithm of minimizing the quadratic form. Two numerical 2-D examples are given.
u¶rt; au umamuuu mauu. ¶rt;a annuuaa n nu nu -na. ma na aa a nu nu naaua annuauu. aam ¶rt; n a umamu aua uuauauu a¶rt;amu . am nu¶rt; ¶rt;a 2-D u nua.相似文献
92.
a mmuu ¶rt; ¶rt;au nm u , a auauu ma mu au u. aamuam m¶rt; a, ma u mua mu ¶rt;au u ¶rt;aa u uma a; m a mu ¶rt;auu m ¶rt;muam 10% m ¶rt;au, a u nuuau m . 相似文献
93.
Cosmogenic radionuclides and mineralogical properties of the Chelyabinsk (LL5) meteorite: What do we learn about the meteoroid?
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Pavel P. Povinec Matthias Laubenstein A. J. Timothy Jull Ludovic Ferrière Franz Brandstätter Ivan Sýkora Jozef Masarik Juraj Beňo Andrej Kováčik Dan Topa Christian Koeberl 《Meteoritics & planetary science》2015,50(2):273-286
On February 15, 2013, after the observation of a brilliant fireball and a spectacular airburst over the southern Ural region (Russia), thousands of stones fell and were rapidly recovered, bringing some extremely fresh material for scientific investigations. We undertook a multidisciplinary study of a dozen stones of the Chelyabinsk meteorite, including petrographic and microprobe investigations to unravel intrinsic characteristics of this meteorite. We also study the short and long‐lived cosmogenic radionuclides to characterize the initial meteoroid size and exposure age. Petrographic observations, as well as the mineral compositions obtained by electron microprobe analyses, allow us to confirm the classification of the Chelyabinsk meteorite as an LL5 chondrite. The fragments studied, a few of which are impact melt rocks, contain abundant shock melt veins and melt pockets. It is likely that the catastrophic explosion and fragmentation of the Chelyabinsk meteoroid into thousands of stones was in part determined by the initial state of the meteoroid. The radionuclide results obtained show a wide range of concentrations of 14C, 22Na, 26Al, 54Mn, 57Co, 58Co, and 60Co, which indicate that the pre‐atmospheric object had a radius >5 m, consistent with other size estimates based on the magnitude of the airburst caused by the atmospheric entry and breakup of the Chelyabinsk meteoroid. Considering the observed 26Al activities of the investigated samples, Monte Carlo simulations, and taking into account the 26Al half‐life (0.717 Myr), the cosmic‐ray exposure age of the Chelyabinsk meteorite is estimated to be 1.2 ± 0.2 Myr. In contrast to the other radionuclides, 14C showed a very large range only consistent with most samples having been exposed to anthropogenic sources of 14C, which we associate with radioactive contamination of the Chelyabinsk region by past nuclear accidents and waste disposal, which has also been confirmed by elevated levels of anthropogenic 137Cs and primordial 40K in some of the Chelyabinsk fragments. 相似文献
94.
Vladimír Skalský 《Astrophysics and Space Science》2009,324(1):1-4
The Wilkinson Microwave Anisotropy Probe (WMAP) confirmed the model of a flat (Euclidean) expansive homogeneous and isotropic
relativistic universe with the total zero mass (energy), which describes the properties of our observed expansive homogeneous
and isotropic relativistic Universe in the first (linear, Newtonian or classical-mechanical) approximation. 相似文献
95.
¶rt;m n¶rt;u nu nm n m . m¶rt; n¶rt;am nuuu am uma au muna (6) u (10). amua aumnu m m nn unam u u, m nmu ama mm (u. 2). uu nu nm ¶rt;u am mu n¶rt; uua 15mu anau u mu u nn uua mu anau. u unauu m nn ¶rt;u am mu n¶rt; uua ¶rt; 21 anau.
Dedicated to 90th Birthday of Professor Frantiek Fiala 相似文献
Dedicated to 90th Birthday of Professor Frantiek Fiala 相似文献
96.
Summary A method of colour schlieren recording of the compressional-stress field gradients, suitable for focal zone study on models, is suggested. The study presents colour schlieren records of the compressional-stress fields in loaded square plates, containing inhomogeneities which give instant quantitative information on these fields. If the inhomogeneity is shaped like Griffith's diagonal slit, good agreement is demonstrated between the experiment and the theoretical calculation of the compressional-stress field in a model. 相似文献
97.
V. Konečný 《Bulletin of Volcanology》1971,35(1):95-116
The remains of an extensive volcanic apparatus of the Tertiary « subsequent » volcanism have been identified in the ?tiavnické pohoric Mts. in the inner belt of the Carpathians. The volcanic apparatus, of stratovolcanic type, was formed during several stages of andesitic and rhyolitic volcanism with two caldera stages. During the final stage of volcanic activity the central collapsed area was uplifted as a horst, accompanied by the formation of grabens along the periphery of the central updomed area. The fractured zones of the horst periphery, as well as zones bordering separate subsided blocks of the central area became the sites of economic ore mineralization, with the formation of lead, zinc, copper, gold, and silver bearing veins. In the uplifted central block intrusions of diorite and granodiorite in the pre-volcanic basement have been exposed by erosion. Geological, petrographical, and petrochemical criteria, as well as absolute dating indicate direct chronological and genetic relationships between the diorite-granodiorite intrusions and extrusive volcanism. 相似文献
98.
99.
Ray amplitudes in a three-dimensional inhomogeneous medium 总被引:1,自引:0,他引:1
Summary A system of five ordinary differential equations of the first order to compute the geometrical spreading of the wave front of seismic body waves in a three-dimensional medium is suggested. 相似文献
100.
Jiří Zahradník Vlastislav Červený Vladimír Barták Reviewer V. Kárník 《Studia Geophysica et Geodaetica》1981,25(4):343-355
Summary Seismic microzoning of Prague was performed using geological data and seismic response (ground shaking) computations. The Prague territory was covered by a square grid, each square 250 m×250 m being characterized by a simplified geological cross-section from the Earth's surface to the bedrock boundary. The data were obtained from detailed engineering-geological maps 1:5000. The geological cross-sections were transformed into a set of layered models, specified by the thicknesses of individual layers and corresponding compressional and shear-wave velocities, densities and parameters of the causal absorption. The seismic responses were computed by the matrix method. The main amplitude and frequency characteristics of the responses are demonstrated in the form of microzoning maps. The maps do not depend on the specific type of seismic excitation. They make it possible to predict the relative amplification of P and S waves, with respect to the bedrock outcrop, all over the city. 相似文献