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401.
Pavel Mayer Magdy A. Hanna Marek Wolf Drahos Chochol 《Astrophysics and Space Science》1998,262(2):163-169
Many early-type main sequence stars are known spectroscopic binaries, while early type spectroscopic binaries with evolved components are rather rare and well-determined masses are available only in some cases. For this reason a program to study stars with suspected variable velocity among early-type evolved stars has been initiated some time ago. In the present paper 54 coudé spectra for a sub-group formed of six early-type stars, namely HD 7902, HD 28446, HD 42087, HD 187983, HD 195592 and HD 208501 have been measured and the results of these plates have been presented. 相似文献
402.
Pavel Ditmar 《Geophysical Prospecting》2002,50(2):209-223
Various aspects of structural inversion are considered. The aim of the inversion is limited to finding the shape of an isolated 2D homogeneous body, although the technique may be generalized to the case of interfaces with steep fragments, faults or overhangs. The unknown parameters are shifts of border points. The shift directions can be normal to the initial heterogeneity configuration or to another contour. Medium properties (seismic velocities, densities, etc.) within the heterogeneity are assumed to be known. The optimal shape is determined iteratively, a quadratic objective function being minimized at each iteration with the conjugate‐gradient method. Special attention is paid to preventing self‐intersections, for which purpose each unknown parameter is forced to lie within a certain predetermined interval. In order to achieve this, the classical conjugate‐gradient method has been modified accordingly. Three numerical examples are considered. These illustrate how the developed technique can be applied to different practical problems. The first example is devoted to monitoring an oil/steam interface by gravity gradiometry measurements. In the second example, a cross‐hole seismic experiment is simulated. It is shown that a structural inversion can restore the configuration of a local body much more accurately than traditional seismic tomography. In the third example, the shape of a salt dome is reconstructed by joint inversion of refracted traveltimes and gravity measurements. This example demonstrates how different kinds of data, used simultaneously in a structural inversion, can complement each other. 相似文献
403.
Pavel Vyskocil 《Tectonophysics》1979,52(1-4)
Preliminary analysis of the new results of repeated levellings within the territory of the Bohemian Massif and its border with the Carpathians is made, and the correlation between horizontal gradients of vertical movements and main fault zones discussed. The results indicated the continuance of the main movement's tendencies, determined by the foregoing measurements. Also discussed are the vertical and horizontal crustal movements between the Bohemian Massif and the Carpathians. The active zones are connected with the main fault systems, and the horizontal movements indicated the spreading tendencies between both geological structures. These results are in accord with the tendencies of horizontal movements in the Soviet Carpathians. 相似文献
404.
Pavel JeŽek Dipl.-Geol. Dr. Arne P. Willner Prof. Dr. Florencio G. AceÑolaza Prof. Dr. Hubert Miller 《International Journal of Earth Sciences》1985,74(3):573-584
During the Late Precambrian to Early Cambrian a large basin with a homogeneous psammitic-pelitic sediment fill existed in the area of the NW-Argentine Andes. It is now exposed in different tectonic levels. This basin of meridional elongation was situated on a stable continental margin at the western edge of the Brazilian shield. It was underlain by segmented older continental crust. According to the modal and chemical composition of the greywackes and subgreywackes a predominant metasedimentary source may be supposed. Four clastic facies types indicate a transport by gravity currents within a submarine fan system, while massive red pelites represent cut-off periods, and rare carbonates deposition on rises. The gravity currents derived from easterly directions. The sedimentation age is proved by a rich ichnofauna and some medusoid impressions.
Zusammenfassung Im Jungpräkambrium bis Unterkambrium existierte im Bereich der NW-argentinischen Anden ein ausgedehnter Trog mit homogener psammitisch-pelitischer Füllung, die heute in verschiedenen Gebirgsstockwerken aufgeschlossen ist. Dieses Becken lag an einem stabilen Kontinentalrand im Westen des Brasilianischen Schildes und war von segmentierter älterer, kontinentaler Kruste unterlagert. Nach der modalen und chemischen Zusammensetzung der Grauwacken und Subgrauwacken sind überwiegend metasedimentäre Herkunftsgesteine anzunehmen. Vier klastische Faziestypen lassen auf Transport durch Trübeströme in submarine Fächer schließen, während mächtige Rotpelite Ruhezeiten und die seltenen Karbonate Ablagerungen auf Schwellen anzeigen. Die Schüttungen stammen aus östlichen Richtungen. Das Sedimentationsalter ist durch eine reichhaltige Ichnofauna und einige Medusenabdrücke dokumentiert.
Résumén Durante el Precámbrico superior hasta el Cámbrico inferior en los Andes del NW Argentino se extendía una larga cuenca rellena de sedimentos psamo-pelíticos homogéneos, que hoy afloran en distintos pisos tectónicos. Esta cuenca de elongación meridional estaba situada en un margen continental estable al lado occidental del escudo brasileño, sobre corteza continental segmentada más antigua. Según su composición modal y química, las grauvacas y subgrauvacas derivaron predominantemente de rocas metasedimentarias. Cuatro tipos de facies clásticas indican su transporte en corrientes de gravedad, provenientes del este, y sedimentación en conos submarinos. Pelitas rojas macizas representan períodos de sedimentación pelágica, mientras que los escasos carbonatos se depositaron en dorsales. Una icnofauna amplia y algunas impresiones de medusoides documentan la edad de sedimentación.
- , - , . . - . , , , , . , , . .相似文献
405.
Summary The results of the winter anomaly observations at the Panská Ves Observatory on 2775 kHz and 2614 kHz (A3 method, feq1 and 0.8 MHz) are studied for the winters of 1971/72 and 1972/73. Ionospheric responses to minor (1972) and major stratospheric warmings are found to be different and relatively small. A regular winter-anomaly background absorption increase with a maximum in January was observed during both winters studied. Magnetic storms are found to play an insignificant, if any, role in the winter-anomaly phenomenon. The relation between magnetic activity and ionospheric absorption seems to be better in non-anomalous periods. 相似文献
406.
407.
Documenting and detecting long-term precipitation trends: Where we are and what should be done 总被引:1,自引:0,他引:1
A brief review of problems and achievements in documenting precipitation changes during the period of instrumental measurements is presented. Concern is expressed that without appropriate studies in the coming period of a new generation of precipitation measurements, technological progress in instrumentation may adversely and inadvertently affect our capability for monitoring and detecting future changes in terrestrial precipitation. At the same time, only a new generation of instrumentation will be capable of resolving the problems of monitoring precipitation over oceans.Special attention is paid to validation of the increasing trend in terrestrial precipitation observed during the past hundred years at high latitudes of the northern hemisphere - a feature of global warming predicted by most climate models. 相似文献
408.
Jaroslava Bošková František Jiříček Pavel Tříska B. V. Lundin D. R. Shklyar Reviewer M. Hvoždara 《Studia Geophysica et Geodaetica》1988,32(2):199-212
Summary In a number of VLF experiments with low-orbiting Intercosmos satellites, high-intensity, discrete VLF emissions at frequencies above the local LHR were observed predominantly between L=2.3 and 4.0. The frequency of their intensity maximum varies continuously with geomagnetic latitude, and approximately parallels the value of a quarter of the equatorial electron gyrofrequency. An attempt is made to interprete these emissions in terms of quasi-electrostatic whistler-mode waves, generated in the near-equatorial region and propagating downward in the quasi-resonance mode. The generating mechanism is supposed to be the kinetic instability connected with the loss-cone and temperature anisotropy of the distribution function of energetic electrons. Some features of the discrete plasmaspheric emissions are discussed on the basis of theoretical considerations.
¶rt; num a umu nmua m a¶rt;au umu ¶rt;um -uu a amma, a amm , num ¶rt; L=2,3 u L=4. amma aua umumu mu uu um uuaum um u nuuum aa mmu amuauamm m. ¶rt;numa nnma umnmuam mu uu mua aummamuu um , ¶rt;a nuamua amu u anmau u au-a u. ¶rt;naam, m mu uu ¶rt;am mam umu mumu an¶rt;u u m, aumnu mnam u nm u uu an¶rt;u. n mmu aau ¶rt;am m mu ¶rt;umm na uu.相似文献
409.
410.
We report the results from a 250 km long transect, from the Danish coast to the North Sea at 55°30′ N, which was sampled every
32 km in order to study the composition and distribution of phytoplankton, and their dependence on the distance from the coast,
depth and other environmental factors. Altogether 144 species of algae were identified by light, epifluorescence and electron
microscopy. Some ecological preferences were found on the basis of measured environmental parameters and compared with the
literature. Possible controlling mechanisms for the distribution patterns of the plankton algae were analyzed by multivariate
statistics. Only distance from the coast was found to be a significant factor for algal distribution along the transect. Three
main areas of the transect were found: the coastal, middle and oceanic areas. Diatoms, mainly the centric ones, were the most
abundant group of algae. The other less abundant groups were Dinophyceae, Dictyochophyceae, Prasinophyceae and Chlorophyceae.
The pattern of distribution of diatoms and dinophytes along the transect was more or less similar, with larger numbers of
cells found close to both the eastern and western parts of the transect, although the species composition was different. Some
species were found to prefer coastal waters, other species were characterized as oceanic, and several species were found at
all stations. Porosira glacialis showed an atypical distribution along the transect, with highest abundances at both coastal and oceanic stations. 相似文献