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981.
982.
A. K. Varma R. M. Gairola A. K. Mathur B. S. Gohil Vijay K. Agarwal 《Journal of Earth System Science》2002,111(3):247-256
In this paper, MSMR geophysical products like Integrated Water Vapour (IWV), Ocean Surface Wind Speed (OWS) and Cloud Liquid
Water (CLW) in different grids of 50, 75 and 150 kms are compared with similar products available from other satellites like
DMSP-SSM/I and TRMMTMI. MSMR derived IWV, OWS and CLW compare well with SSM/I and TMI finished products. Comparison of MSMR
derived CLW with that derived from TMI and SSM/I is relatively in less agreement. This is possibly due to the use of 37 GHz
in SSM/I and TMI that is highly sensitive to CLW, while 37 GHz channels are not available on MSMR. Monthly comparison of MSMR
geophysical products with those from TMI is all carried out for climatological purpose. The monthly comparisons were much
better compared to instantaneous comparisons. In this paper, details of the data analysis and comparison results are presented.
The usefulness of the MSMR vis-à-vis other sensors is also discussed. 相似文献
983.
Hydraulic Characteristics of Rough Fractures in Linear Flow under Normal and Shear Load 总被引:19,自引:3,他引:19
Summary
A hydro-mechanical testing system, which is capable of measuring both the flow rates and the normal and shear displacement
of a rock fracture, was built to investigate the hydraulic behaviour of rough tension fractures. Laboratory hydraulic tests
in linear flow were conducted on rough rock fractures, artificially created using a splitter under various normal and shear
loading. Prior to the tests, aperture distributions were determined by measuring the topography of upper and lower fracture
surfaces using a laser profilometer. Experimental variograms of the initial aperture distributions were classified into four
groups of geostatistical model, though the overall experimental variograms could be well fitted to the exponential model.
The permeability of the rough rock fractures decayed exponentially with respect to the normal stress increase up to 5 MPa.
Hydraulic behaviours during monotonic shear loading were significantly affected by the dilation occurring until the shear
stress reached the peak strength. With the further dilation, the permeability of the rough fracture specimens increased more.
However, beyond shear displacement of about 7 to 8 mm, permeability gradually reached a maximum threshold value. The combined
effects of both asperity degradation and gouge production, which prohibited the subsequent enlargement of mean fracture aperture,
mainly caused this phenomenon. Permeability changes during cyclic shear loading showed somewhat irregular variations, especially
after the first shear loading cycle, due to the complex interaction from asperity degradations and production of gouge materials.
The relation between hydraulic and mechanical apertures was analyzed to investigate the valid range of mechanical apertures
to be applied to the cubic law.
Received June 12, 2001; accepted February 26, 2002 Published online September 2, 2002 相似文献
984.
985.
Poroelastic analysis of cover-collapse sinkhole formation by piezometric surface drawdown 总被引:1,自引:0,他引:1
T. Tharp 《Environmental Geology》2002,42(5):447-456
Where the water table is above the soil-rock contact in karst regions, cover-collapse sinkholes in the soil and soft sediment above the rock commonly occur as a result of drawdown of the piezometric surface in the karst aquifer. Transient stresses and pore pressures around soil voids at the soil-rock contact can cause hydraulic fracturing of the soil near the wall of the void. After the first such fracture, successive sloughing of soil propagates the soil void rapidly to the surface, resulting in a cover-collapse sinkhole. Sinkhole formation by this mechanism should be strongly a function of rate and magnitude of piezometric surface drawdown, permeability and tensile strength of the soil, and the size, depth, and geometry of the initial soil void. Large soil voids and those with walls that are partly planar or of low curvature are most susceptible to hydraulic fracture and the resulting progression to sinkhole formation. 相似文献
986.
Heavy metal concentrations in surficial sediments from accreting and eroding areas along the coast of Guyana 总被引:1,自引:0,他引:1
987.
The fine structure of the FeI λ 532.4185-nm line of neutral iron is studied with high spatial (0.5″) and temporal (9.3 s) resolution using observations of a quiet region at the center of the solar disk. The character of the line asymmetry depends strongly on the nature of the velocity field, i.e., on whether it is due to convective or wave motions. The magnitude of the asymmetry due to acoustic waves is comparable to that due to convective motions. The propagation of acoustic waves in moving granules and intergranular lanes is studied by solving a system of hydrodynamical equations in a three-dimensional model for the solar atmosphere. The temporal variations in the bisector of the line synthesized in a non-LTE approximation agree well with the observational data. 相似文献
988.
V. P. Grinin 《Astronomy Reports》2002,46(5):380-389
We consider the effect of binarity of young stars on the spectral energy distribution of the IR radiation from circumstellar dust. The formation of a common dust envelope in a binary system with a low-mass secondary component is strongly affected by the disk wind from the secondary. The small velocities in peripheral areas of the wind are such that it can be partially or entirely captured by the primary, even when the distance between the components is up to several astronomical units. As a result, an envelope with a rather complex spatial and kinematic structure is formed. Its mass is many orders of magnitude smaller than that of the accretion disk around the binary. However, the thermal radiation emitted by dust particles of the envelope can be comparable to the total radiation of the accretion disk. This result is discussed in the context of the deficit at near-IR wavelengths (2–10µm) in current models for accretion disks around young stars. 相似文献
989.
Mass exchange in white-dwarf binary systems with mass ratios 0.35–0.55 and total masses exceeding the Chandrasekhar limit could lead to the disruption of the less massive component of the system and the formation of a torus around the more massive component. 相似文献
990.
Refined analytical expressions for the frequencies corresponding to the Chandler motion of the pole and the diurnal rotation of the deformable Earth are derived. Numerical estimates of the period and amplitude of the polar oscillations are presented. The trajectory of the Chandler polar motion derived via numerical modeling is in qualitative and quantitative agreement with experimental data from the International Earth Rotation Service (IERS). An evolutionary model describing slow variations in the Earth’s rotation parameters under the action of the dissipative moments of the tidal gravitational forces on time scales considerably longer than the precession period of the Earth’s axis is constructed. The axis of the Earth’s figure tends to approach the angular momentum vector of the proper rotation. 相似文献