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排序方式： 共有81条查询结果，搜索用时 31 毫秒
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Ojala Antti E. K. Virtasalo Joonas J. Lindsberg Elina Markovaara-Koivisto Mira 《Geotechnical and Geological Engineering》2021,39(7):4855-4876
Geotechnical and Geological Engineering - Understanding the local stratigraphy and geometry of sediment units is necessary for successful 3D modelling and the prediction of ground behaviour and... 相似文献
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Abstract It is suggested that reverse currents seen in recent numerical reconnection experiments (Biskamp, 1986; Forbes and Priest, 1983) are caused by the choice of outflow boundary conditions. The specification of the normal velocity at the outflow boundary may result in a mismatch in velocity at the diffusion region which is manifested as a spike of reverse current. 相似文献
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Atmospheric numerical models depend critically on realistic treatment of the lower boundary conditions. In strongly thermally-stratified
conditions, turbulence may be very weak and the models may find it difficult to produce a good forecast near the surface.
Under clear skies and for weak synoptic winds the determining factors are the turbulent kinetic energy and surface-layer parameterizations,
which can be very different between models. Here, two state-of-the-art mesoscale models (MM5 and Meso-NH) are operated under
exactly the same conditions for two different nights over the Duero basin in the Iberian Peninsula: one night with a well-defined
synoptic wind and a second with practically no horizontal pressure gradient. The models are inter-compared and checked against
available information, and their performances are evaluated. 相似文献
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One interesting method of constraining the dense matter Equations of State is to measure the advancement of the periastron of the orbit of a binary radio pulsar (when it belongs to a double neutron star system). There is a great deal of interest on applicability of this procedure to the double pulsar system PSR J0737-3039 (A/B). Although the above method can be applied to PSR A in future within some limitations, for PSR B this method cannot be applied. On the other hand, the study of genesis of PSR B might be useful in this connection and its low mass might be an indication that it could be a strange star. 相似文献
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Manjari Bagchi Rachid Ouyed Jan Staff Subharthi Ray Mira Dey † Jishnu Dey ‡ 《Monthly notices of the Royal Astronomical Society》2008,387(1):115-120
We study the effects of temperature on strange stars. It is found that the maximum mass of the star decreases with the increase of temperature, as at high temperatures the equations of state become softer. Moreover, if the temperature of a strange star increases, keeping its baryon number fixed, its gravitational mass increases and its radius decreases. This leads to a limiting temperature, where it turns into a black hole. These features are the result of a combined effect of the change of gluon mass and the quark distribution with temperature. We report on a new type of radial oscillation of strange stars, driven by what we call 'chromothermal' instability. We also discuss the relevance of our findings in the astrophysics of core collapse supernovae and gamma-ray bursts. 相似文献
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Tomi P. Luoto Liisa Nevalainen Tommi Kauppila Mira Tammelin Kaarina Sarmaja-Korjonen 《Quaternary Research》2012,78(2):248-255
A sediment core from Lake Arapisto, Finland, was examined for fossil diatom assemblages to reconstruct changes in Holocene nutrient availability. Our aim was to investigate the long-term relationship between lake trophic status and climate by comparing the diatom-based phosphorus reconstruction with paleoclimatic proxies. Our results showed that the cold early Holocene was characterized by elevated nutrient conditions concurrent with newly exposed fertile ground. As the climate rapidly warmed and ice sheet further retreated, the catchment vegetation developed, which resulted in decreased nutrient flux into the lake. The Holocene Thermal Maximum (HTM), between ~ 8000 and 4000 cal yr BP, was characterized by oligotrophic conditions, which may have been caused by low effective precipitation and stable watershed vegetation. After the HTM, the lake became more productive. There was no particular increase in the trophic state that could be connected to more recent human influence. Although lake productivity has been shown to be affected by temperature, our record indicated that the nutrient dynamics were driven by complex interactions between changes in temperature, precipitation, catchment, and in-lake processes. Understanding of long-term nutrient dynamics and the associated processes can help in resolving relationships between lake productivity and climate during past and present climate changes. 相似文献
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Understanding the interactions of climate, physical erosion, chemical weathering and pedogenic processes is essential when considering the evolution of critical zone systems. Interactions among these components are particularly important to predicting how semiarid landscapes will respond to forecasted changes in precipitation and temperature under future climate change. The primary goal of this study was to understand how climate and landscape structure interact to control chemical denudation and mineral transformation across a range of semiarid ecosystems in southern Arizona. The research was conducted along the steep environmental gradient encompassed by the Santa Catalina Mountains Critical Zone Observatory (SCM-CZO). The gradient is dominated by granitic parent materials and spans significant range in both mean annual temperature (>10 °C) and precipitation (>50 cm a?1), with concomitant shift in vegetation communities from desert scrub to mixed conifer forest. Regolith profiles were sampled from divergent and convergent landscape positions in five different ecosystems to quantify how climate-landscape position interactions control regolith development. Regolith development was quantified as depth to paralithic contact and degree of chemical weathering and mineral transformation using a combination of quantitative and semi-quantitative X-ray diffraction (XRD) analyses of bulk soils and specific particle size classes. Depth to paralithic contact was found to increase systematically with elevation for divergent positions at approximately 28 cm per 1000 m elevation, but varied inconsistently for convergent positions. The relative differences in depth between convergent and divergent landscape positions was greatest at the low and high elevation sites and is hypothesized to be a product of changes in physical erosion rates across the gradient. Quartz/Plagioclase (Q/P) ratios were used as a general proxy for bulk regolith chemical denudation. Q/P was generally higher in divergent landscape positions compared to the adjacent convergent hollows. Convergent landscape positions appear to be collecting solute-rich soil–waters from divergent positions thereby inhibiting chemical denudation. Clay mineral assemblage of the low elevation sites was dominated by smectite and partially dehydrated halloysite whereas vermiculite and kaolinite were predominant in the high elevation sites. The increased depth to paralithic contact, chemical denudation and mineral transformation are likely functions of greater water availability and increased primary productivity. Landscape position within a given ecosystem exerts strong control on chemical denudation as a result of the redistribution of water and solutes across the landscape surface. The combined data from this research demonstrates a strong interactive control of climate, landscape position and erosion on the development of soil and regolith. 相似文献