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Abstract An isochemical uni-phase model of whole mantle convection has been developed in terms of which factors influencing the onset of time dependent chaotic behavior may be assessed. The model is spherical but restricted in generality to the analysis of axisymmetric solutions. In this paper we have employed it to examine the impact of compressibility and sphericity on the nature and onset of time dependence. Particular attention has been given to an examination of the impact that the onset of time dependence has upon the power law relation that connects the heat transfer (represented by the Nusselt number) to the strength of the thermal forcing (represented by the Rayleigh number). In order to obtain these results very extensive numerical simulations were required and the results themselves should be rather useful in the context of models of the thermal history of the planet. 相似文献
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Based on classification tests, oedometer tests, fall-cone tests and triaxial tests, physical and mechanical properties of sediments in the Storegga Slide region were analysed to assess parameter interrelationships. The data show good relationships between a number of physical and mechanical parameters. Goodness of fit between compression index and various physical parameters can be improved by multiple regression analysis. The interclay void ratio and liquidity index correlate well with the undrained shear strength of clay. Sediments with higher water content, liquid limit, activity, interclay void ratio, plasticity index and liquidity index showed higher compression index and/or lower undrained shear strength. Some relationships between parameters were tested by using data from two other sites south of the Storegga Slide. A better understanding of properties of sediments in regions such as that of the Storegga Slide can be obtained through this approach. 相似文献
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A cluster of craterlike depressions in the central Barents Sea are several hundred meters across, have steep walls, and are cut into underlying Triassic rocks. Their formation is explained in relation to the glacial history of the region, and a possible model suggests that gas from a deeper, thermogenic source allowed a hydrate layer of considerable thickness to form during the Late Weichselian, when grounded ice covered the area and increased the hydrostatic pressure. After a rapid retreat of the marinebased ice sheet, the hydrates decomposed and the layer thinned rapidly until pressurized free gas, trapped below the hydrates, erupted and formed the sea-floor depressions. 相似文献
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This project is part of a world wide cooperation aimed at investigating properties of white dwarf stars to determine their constitution and evolution. The project is based on two recent developments:-The first is the discovery, of pulsational instabilities in some white dwarf stars, giving rise to non-radial pulsations which can be observed as flux modulations with low amplitude.-The second is to study the mass transfer between interacting binary white dwarf stars, which transports processed material from the interior of the donating star to the accretor. We present a study of four interacting binary white dwarf systems based on IUE spectra.Paper presented at the 11th European Regional Astronomical Meetings of the IAU on New Windows to the Universe, held 3–8 July, 1989, Tenerife Canary Islands, Spain. 相似文献
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O'Donoghue Koen Solheim Barstow Dobbie O'Brien Clemens Sullivan & Kawaler 《Monthly notices of the Royal Astronomical Society》1998,296(2):296-305
PB 8783 is a member of the newly discovered class of pulsating sdB stars, the EC 14026 stars. The potential of the pulsations of these stars as diagnostic probes of their interiors can only be realized fully by intensive campaigns of multisite time series photometry. To this end we have undertaken a campaign spanning 2 weeks and involving data from five different sites. 183 h of data were obtained. Frequency analysis yielded at least 11 pulsation periods in seven discrete groups between 94 and 136 s. Three of the periods in one specific group are equally spaced in frequency, with a spacing of 0.94 μHz. The frequency spacings amongst the members of other groups are similar to this. A rotation period of ∼12 d is implied. A general scheme for identifying the observed modes is suggested. The periods from a detailed model are in good overall agreement with the observed periods, but some difficulties remain. Three additional periods in the range 61–63 s, and with very low amplitude, were also found. No convincing interpretation of these could be devised. 相似文献
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