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911.
912.
A direct time-domain numerical procedure is proposed to analyse the transient dynamic response of two-dimensional reservoir–dam–soil systems. The reservoir extends to infinity and the dam is supported by an unbounded soil. The structure with either linear or non-linear material properties is modelled by the Finite Element Method (FEM). The soil is assumed to be an elastic, isotropic and homogeneous half-space represented by a boundary condition in the form of generalized impedance determined by the transient Lamb's solution due to a uniformly distributed traction imposed on the free surface, Guan and Novak.1 Moreover, a technique is developed to include the influence of the reservoir on the dam in terms of nodal accelerations along their interface at different time steps. The advantages of the proposed procedure are obvious. For example, it avoids any additional discretization of the boundaries except the soil–dam interface, and the influence matrix of the fluid is obtained explicitly using shape functions defined at the upstream face of the dam without the finite analysis of the reservoir so that it works very efficiently. Numerical results for a system consisting of reservoir, elastic dam and foundation subjected to the San Fernando, 1971 earthquake ground motion are presented. 相似文献
913.
Michael N. Moore 《Marine pollution bulletin》1985,16(4):134-139
914.
Everett K. Gibson Carleton B. Moore Thomas M. Primus Charles F. Lewis 《Meteoritics & planetary science》1985,20(3):503-511
Total sulfur abundances have been measured for 48 achondrites. For twenty eucrites they ranged from 370 to 3700 μgS/g with a median sulfur content of 1180 μgS/g. Sulfur abundances for howardites ranged from 1490 to 3240 μgS/g and had a median sulfur concentration of 2340 μgS/g. Diogenites' sulfur abundances ranged from 130 to 3170 μgS/g, with a median value of 1280 μgS/g. Four shergottites had a median sulfur content of 1940 μgS/g and ranged from 740 to 2540 μgS/g. Enstatite achondrites contained the greatest sulfur abundances of any achondrite group. They ranged from 2450 to 8580 μgS/g and had a median sulfur content of 6020 μgS/g. A single Chassignite had a sulfur concentration of 360 μgS/g. The wide variations in sulfur concentrations for the achondrites reflect the small scale heterogeneous nature of these unique extraterrestrial materials due in large part to discrete sulfide mineral grains. 相似文献
915.
916.
Platynereis dumerilii is found in large numbers in parchment-like tubes attached to sublittoral accumulations of detached maroalgae (principally Laminaria saccharina) in Kames Bay, Isle of Cumbrae and Lochranza, Isle of Arran. Its rôle in weed decomposition has been examined by comparing its responses (behavioural choice, growth rates, absorption efficiencies of both carbon and protein, gut retention times and rate of faecal output) to fresh and rotting weed. Worms grew significantly on either diet, with older individuals gaining more weight than small individuals. Animals of a standard size (derived from measurements of maximum bite size) feeding on fresh weed, however, grew significantly faster than those feeding on rotting weed. The former had a significantly higher protein absorption efficiency which was linearly related to protein content of ingested weed. This was not so on rotting weed. Organic carbon absorption efficiencies did not differ significantly between the two groups, neither did gut retention times nor rates of faecal output. Given a choice, Platynereis chooses to build its tube, and to feed, on fresh kelp—a strategem which ensures both maximum scope for occupancy before fronds decay and a superabundance of preferred food. Platynereis feeds around its tube entrance, recropping small areas for 2–3 days, prior to switching to another area nearby. Ciliate population densities on Platynereis faeces are much lower than on either homogenized or intact weed, associated with their lower, nutritional value (at first). Platynereis bubes act to bind kelp fronds together stabilizing the faecal input to infaunal detritivores. Platynereis is an example of a detritivore which exploits the detrital substratum directly. 相似文献
917.
Comparison of hot plasma data from ATS-6 and GEOS-1 when the satellites were near dawn L.T. conjunction reveals the presence of strong gradients separating plasmas differing by more than two orders of magnitude in keV particle fluxes. These gradients are observed at off-equatorial geomagnetic latitudes of 25–30° on field lines outside the synchronous orbit. They are associated with magnetic storms and are distinct from magnetopause crossings. Interpretation of these events in terms of a boundary between magnetospheric and polar-cap plasma leads to the following conclusions: (1) the polar cap/lobe region is essentially devoid of keV plasma at these times; (2) the field lines defining this boundary are significantly distorted from a dipolar to a more stretched form consistent with the presence of a storm-ring current, (3) smaller substorm-scale motions are superposed on the gross motion of the boundary with some evidence present for structure in the plasma spatial profile, and (4) magnetosheath-like plasma finds access to the inner magnetosphere at dawn L.T., much as it does near noon, along polar-cap boundary-layer field lines which close through the low latitude magnetospheric boundary layer. 相似文献
918.
A summary of total sulfur abundances representative of the Apollo Missions is presented. Lunar crystalline rocks range from
0 to 3100μg S g−1. Lunar soils range from 310 to 1300μg S g−1. Rock mixing models evaluate the distribution of sulfur and define indigenous rock components and extralunar contributions
of sulfur in lunar soils. Extralunar sulfur shows a positive correlation with a CC-1 like meteoritic component and solar wind
derived total carbon content in the Apollo 16 and 17 lunar soils.
Presented at the 25th International Geological Congress, Sydney, Australia, Section 15, Planetology.
Contribution No. 105 from the Center for Meteorite Studies. 相似文献
919.
Frictional heating on a fault zone with finite thickness 总被引:5,自引:0,他引:5
R. K. Cardwell D. S. Chinn G. F. Moore D. L. Turcotte 《Geophysical Journal International》1978,52(3):525-530
Summary. The problem of frictional heating on a fault of finite thickness is considered. Temperature distributions during and after faulting are obtained for faults of various thicknesses. A thick fault approximation is shown to be valid if a fault has a thickness greater than about 1 cm. The thickness of the melted zone is predicted for various frictional stress levels and displacements. The predicted thicknesses are shown to be in reasonable agreement with field observations. 相似文献
920.
Beverley J. Moore 《Geophysical Journal International》1980,63(3):671-689
b
In this paper, the method of small perturbations is applied to the ray and energy transport equations in an investigation of the effect of weak inhomogeneities on the propagation of seismic rays through a layer of fixed thickness. Just as Aki et al . have used travel-time residuals to infer first-order velocity perturbations in their block-modelling procedure, it is proposed that surface slowness and amplitude data may be used to give additional information about the structure of the velocity perturbations beneath the observer. 相似文献
In this paper, the method of small perturbations is applied to the ray and energy transport equations in an investigation of the effect of weak inhomogeneities on the propagation of seismic rays through a layer of fixed thickness. Just as Aki et al . have used travel-time residuals to infer first-order velocity perturbations in their block-modelling procedure, it is proposed that surface slowness and amplitude data may be used to give additional information about the structure of the velocity perturbations beneath the observer. 相似文献