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31.
32.
Hussein Abd-Elmotaal 《Journal of Geodesy》1995,69(4):304-307
The attraction of a topographic mass element on a spherical earth is derived. The case of a distant mass element is treated. The procedure of calculating the attraction of the topographic masses from a combination of digital models of different grid sizes is studied. The limitation of using the point mass formula of the distant mass elements is illustrated. The results show that using an artificial very fine DHM (made by dividing each cell of the fine DHM into a very fine sub-cells having the same height as the original cell) in the neighbourhood of the computational point (about 2.5 km) reduces the errors on calculating the attraction of the topographic masses. 相似文献
33.
The Late Proterozoic ophiolite of Sol Hamed,NE Sudan 总被引:1,自引:0,他引:1
W.R. Fitches R.H. Graham I.M. Hussein A.C. Ries R.M. Shackleton R.C. Price 《Precambrian Research》1983,19(4):385-411
The Sol Hamed complex, a sequence from ultramafics, through gabbros, thin sheeted dykes, to pillow lavas, is an ophiolite. It was obducted, tilted nearly to vertical, eroded and covered unconformably by the Nafirdeib Series. This is a volcaniclastic series, dated at 712 ± 58 Ma, the lower part of which includes conglomerates with ophiolitic clasts, olistostromes, one with large oolitic limestone slabs, felsitic and dacitic tuffs, turbidites and black shales, with andesites above. Some of the structures in the ophiolite are attributed to sub-oceanic deformation. Deformation after the deposition of the Nafirdeib Series produced folds and cleavage trending about NE-SW and, more locally, a cleavage trending NW in a shear zone where the ophiolite was thrust northeastwards over the Nafirdeib Series. The ophiolite and the Nafirdeib Series were intruded by the batholithic granite dated elsewhere at ca. 669 Ma. The ophiolite is thought to occur on a suture with the Nafirdeib Series representing part of an island arc sequence. 相似文献
34.
A comparison of two numerical models for the prediction of vibrations from underground railway traffic 总被引:2,自引:0,他引:2
S. Gupta M.F.M. Hussein G. Degrande H.E.M. Hunt D. Clouteau 《Soil Dynamics and Earthquake Engineering》2007,27(7):608-624
Two prediction models for calculating vibration from underground railways are developed: the pipe-in-pipe model and the coupled periodic finite element–boundary element (FE–BE) model.The pipe-in-pipe model is a semi-analytical three-dimensional model that accounts for the dynamic interaction between the track, the tunnel and the soil. The continuum theory of elasticity in cylindrical coordinates is used to model two concentric pipes: an inner pipe to represent the tunnel wall and an outer pipe to represent the surrounding soil. The tunnel and soil are coupled accounting for equilibrium of stresses and compatibility of displacements at the tunnel–soil interface. This method assumes that the tunnel is invariant in the longitudinal direction and the problem is formulated in the frequency–wavenumber domain using a Fourier transformation. A track, formulated as an Euler–Bernoulli beam, is then coupled to this model. Results are transformed to the space domain using the inverse Fourier transform.The coupled periodic FE–BE model is based on a subdomain formulation, where a boundary element method is used for the soil and a finite element method for the tunnel. The Craig–Bampton substructuring technique is used to efficiently incorporate the track in the tunnel. The periodicity of the tunnel is exploited using the Floquet transformation to formulate the track–tunnel–soil interaction problem in the frequency–wavenumber domain and to compute the wave field radiated into the soil.An invariant concrete tunnel, embedded in a homogeneous full space is analyzed using both approaches. The pipe-in-pipe model offers an exact solution to this problem, which is used to validate the coupled periodic FE–BE model. The free field response due to a harmonic load in the tunnel is predicted and results obtained with both models are compared. The advantages and limitations of both models are highlighted. The coupled periodic FE–BE model has a greater potential as it can account for the complex periodic geometry of the tunnel and the layering in a soil medium. The effect of coupling a floating slab to the tunnel–soil system is also studied with both models by calculating the insertion gain. 相似文献
35.
Hussein O. Okail P. Benson Shing William M. McGinley Richard E. Klingner Seongwoo Jo David I. McLean 《地震工程与结构动力学》2011,40(5):509-530
This paper presents the findings of shaking‐table experiments conducted to examine the seismic performance of a full‐scale, one‐story, wood‐framed structure with masonry veneer. The structure was designed and constructed in accordance with current U.S. code provisions. The veneer was attached to the wood backing with two kinds of metal anchors, corrugated ties fastened with 8d nails and rigid ties fastened with #8 screws. The tests have shown that the use of nails to fasten veneer anchors to the wood studs is highly unreliable due to the high variation of the nail extraction capacity, which can be influenced by the moisture content of the wood. Other than this, both the wood frame and the masonry veneer performed well under severe ground motions far exceeding a design level earthquake for Seismic Design Category D. Good performance was observed for the rigid veneer ties, which were attached to the wood studs with screws. The results have shown that the veneer walls parallel to the direction of shaking helped to restrain the motion of the wood structure and therefore should not be simply treated as added mass. The detailing of wood roof diaphragms requires special attention in consideration of the out‐of‐plane inertia force of the veneer that can be transmitted through the top plate of the wood‐stud wall to the rim joist. Copyright © 2010 John Wiley & Sons, Ltd. 相似文献
36.
Mohamed W. Ali-Bik Hussein I. M. Metwally Mohamed G. Kamel Ashraf M. A. Wali 《Environmental Earth Sciences》2011,62(1):151-159
Biogenic gypsum in the form of microbialite and potential domal stromatolite as well as endoevaporitic dolomite are deposited
in a perennial saline basin characterized by microbial bloom. Deposition environment, mode of occurrence, and microscopic
investigation including SEM of these precipitates are discussed in conjunction with XRD, XRF, and FTIR data. Combined effects
of salinity gradient and the wind action on the maturity of gypsum outcrop are evident. A characteristic multi-color vertical
gypsum profile reflects steep gradient of oxi-anoxic microenvironments and encodes diverse seasonal microbial communities.
Direct impact of microbial signature in gypsum crystal habit is conspicuous. Endoevaporitic authigenic dolomite is recorded
in specific horizons in interstices of selenite layers. 相似文献
37.
Source parameters and ground motion of the Suez-Cairo shear zone earthquakes,Eastern Desert,Egypt 总被引:1,自引:0,他引:1
Three felt earthquakes with local magnitudes 4.0 (June 29th, 2000), 4.2 (July 07th, 2005) and 3.7 (October 30th, 2007) occurred
to the southeast of Cairo along the Suez-Cairo shear zone. Being the most well recorded events by the Egyptian National Seismic
Network (ENSN) in this area, they provide us an excellent opportunity to study the tectonics, the stress field, the source
parameters, and the expected ground motion at Cairo. The focal mechanisms of the three events based on the first motion P-wave
polarities indicate mainly normal faulting with a slight strike-slip component along nodal planes trending nearly EW and NW–SE.
The three focal solutions imply a rejuvenation of the pre-existing EW and NW–SE faults due to a partly transfer of rifting
deformation from the Red Sea-Gulf of Suez along these trends. Dynamic source parameters of these events are estimated from
the P-wave spectra of the closest ENSN stations. The average values of the seismic moment, stress drop, rupture radius, and
fault dislocation are estimated from six stations and interpreted in the context of the tectonic setting. These parameters
in addition to the effects of site and path are used to synthesize the ground motion seismograms using stochastic modeling
technique at the recorded stations and at some strategic sites. 相似文献
38.
Analysis of cumulative human impacts in the marine environment is still in its infancy but developing rapidly. In this study, existing approaches were expanded upon, aiming for a realistic consideration of cumulative impacts at a regional scale. Thirty-eight human activities were considered, with each broken down according to stressor types and a range of spatial influences. To add to the policy relevance, existing stressors within and outside of conservation areas were compared. Results indicate the entire continental shelf of Canada's Pacific marine waters is affected by multiple human activities at some level. Commercial fishing, land-based activities and marine transportation accounted for 57.0%, 19.1%, and 17.7% of total cumulative impacts, respectively. Surprisingly, most areas with conservation designations contained higher impact scores than the mean values of their corresponding ecoregions. Despite recent advances in mapping cumulative impacts, many limitations remain. Nonetheless, preliminary analyses such as these can provide information relevant to precautionary management and conservation efforts. 相似文献
39.
Hussein Mustapha Snehamoy Chatterjee Roussos Dimitrakopoulos 《Mathematical Geosciences》2014,46(1):95-123
Simulation of categorical and continuous variables is performed using a new pattern-based simulation method founded upon coding spatial patterns in one dimension. The method consists of, first, using a spatial template to extract information in the form of patterns from a training image. Patterns are grouped into a pattern database and, then, mapped to one dimension. Cumulative distribution functions of the one-dimensional patterns are built. Patterns are then classified by decomposing the cumulative distribution functions, and calculating class or cluster prototypes. During the simulation process, a conditioning data event is compared to the class prototype, and a pattern is randomly drawn from the best matched class. Several examples are presented so as to assess the performance of the proposed method, including conditional and unconditional simulations of categorical and continuous data sets. Results show that the proposed method is efficient and very well performing in both two and three dimensions. Comparison of the proposed method to the filtersim algorithm suggests that it is better at reproducing the multi-point configurations and main characteristics of the reference images, while less sensitive to the number of classes and spatial templates used in the simulations. 相似文献
40.
Guleid Artan Hussein Gadain Jodie L. Smith Kwabena Asante Christina J. Bandaragoda James P. Verdin 《Natural Hazards》2007,43(2):167-185
Floods are the most common and widespread climate-related hazard on Earth. Flood forecasting can reduce the death toll associated
with floods. Satellites offer effective and economical means for calculating areal rainfall estimates in sparsely gauged regions.
However, satellite-based rainfall estimates have had limited use in flood forecasting and hydrologic stream flow modeling
because the rainfall estimates were considered to be unreliable. In this study we present the calibration and validation results
from a spatially distributed hydrologic model driven by daily satellite-based estimates of rainfall for sub-basins of the
Nile and Mekong Rivers. The results demonstrate the usefulness of remotely sensed precipitation data for hydrologic modeling
when the hydrologic model is calibrated with such data. However, the remotely sensed rainfall estimates cannot be used confidently
with hydrologic models that are calibrated with rain gauge measured rainfall, unless the model is recalibrated.
G. Artan, J. L. Smith and K. Asante – work performed under USGS contract 03CRCN0001. 相似文献