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Mathieu Ribatet Eric Sauquet Jean-Michel Grésillon Taha B. M. J. Ouarda 《Stochastic Environmental Research and Risk Assessment (SERRA)》2007,21(4):327-339
Flood frequency analysis is usually based on the fitting of an extreme value distribution to the local streamflow series.
However, when the local data series is short, frequency analysis results become unreliable. Regional frequency analysis is
a convenient way to reduce the estimation uncertainty. In this work, we propose a regional Bayesian model for short record
length sites. This model is less restrictive than the index flood model while preserving the formalism of “homogeneous regions”.
The performance of the proposed model is assessed on a set of gauging stations in France. The accuracy of quantile estimates
as a function of the degree of homogeneity of the pooling group is also analysed. The results indicate that the regional Bayesian
model outperforms the index flood model and local estimators. Furthermore, it seems that working with relatively large and
homogeneous regions may lead to more accurate results than working with smaller and highly homogeneous regions. 相似文献
53.
Yahia E.-A. Mohamedzein Mohammed Y. Al-Aghbari Ramzi A. Taha 《Geotechnical and Geological Engineering》2006,24(6):1767-1780
This paper presents experimental results on the use of incinerator ash in stabilizing desert sands for possible use in geotechnical
engineering applications. The incinerator ash was added in percentages of 2, 4, 8, 10 and 12%, by dry weight of sand. Laboratory
tests such as compaction, unconfined compression, shear box and hydraulic conductivity were performed to measure the engineering
characteristics of the stabilized material. The results showed substantial improvements in unconfined compressive strength
and shear strength parameters (c and φ). Thus, incinerator ash can be used to improve the shear strength characteristics of desert sands. The permeability of the
sand–incinerator ash mixture was relatively low. 相似文献
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Impact of river network type on the time of concentration 总被引：1，自引：0，他引：1
Time of concentration (T c) is one of the frequently used parameters to characterize the response of a drainage basin to a rainfall event. Conceptually, it is the time runoff travels from the hydraulically most distant location in a basin to its outlet. T c was found to vary depending on river basin characteristics such as slope, soil infiltration, and flow path. In this study, we investigate if the drainage network type information can be used as an input to hydrological models, by estimating the time of concentration separately for different network types. Sixty-eight basins which have areas ranging from 24 to 965 km2 in arid and non-arid regions of the USA are compared and the effect of climate is also analyzed. It is found that the slope of the linear relationship between T c and the maximum hydraulic length of flow path shows different correlation coefficients ranging from 0.80 to 0.98 for different network types. It is observed that the slope of the regression line between T c and the maximum hydraulic length of flow path is the lowest for dendritic networks (slope of 0.26), while pinnate networks have the steepest slope of the regression line (slope of 0.59). This indicates that the drainage network type has a direct impact on the hydrological behavior of the basin and can represent a direct input in hydrological modeling. 相似文献
56.
Tectonic model of Egypt based on magnetic analysis 总被引：1，自引：0，他引：1
The main target of this work was to study the dynamics of the Earth’s crust for Egypt based on the magnetic survey. High-resolution
land magnetic data were analyzed, combined with the results of GPS and seismic stress analyses.
The constructed tectonic map shows that the N35°-N45°W trend of the structure (related to the Red Sea and Gulf of Suez tectonics)
predominates along the Gulf of Suez, Red Sea, covering wide parts of the study area. The N45°-N65°E tectonic trend (related
to the Syrian Arc tectonics), prevailing in the northern part of Egypt, is of the second rank. The Aqaba (N15°-25°E) and E-W
trends prevail in the northern part and along the transition zone of stable/unstable shelves. The depth to the basement rocks
ranges from the surface along the Red Sea and southern parts of Egypt to more than 4 km below sea level at the northern part
of the study area. 相似文献
57.
Recent seismic events have raised concerns over the safety and vulnerability of reinforced concrete moment resisting frame “RC-MRF” buildings. The seismic response of such buildings is greatly dependent on the computational tools used and the inherent assumptions in the modelling process. Thus, it is essential to investigate the sensitivity of the response demands to the corresponding modelling assumption. Many parameters and assumptions are justified to generate effective structural finite element (FE) models of buildings to simulate lateral behaviour and evaluate seismic design demands. As such, the present study focuses on the development of reliable FE models with various levels of refinement. The effects of the FE modelling assumptions on the seismic response demands on the design of buildings are investigated. the predictive ability of a FE model is tied to the accuracy of numerical analysis; a numerical analysis is performed for a series of symmetric buildings in active seismic zones. The results of the seismic response demands are presented in a comparative format to confirm drift and strength limits requirements. A proposed model is formulated based on a simplified modeling approach, where the most refined model is used to calibrate the simplified model. 相似文献
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Nahla S. El-Shenawy Tarak I. S. Moawad Mahmoud E. Mohallal Ismail M. Abdel-Nabi Inas A. Taha 《Ocean Science Journal》2009,44(1):27-34
Clam Ruditapes decussates was used as a biomonitoring organism to measure the potential impact of pollution. The present study investigated histological alterations of R. decussates following a long-term exposure to a sublethal-level of pesticides Reldan and Roundup. The clams were taken to the laboratory and kept for days to adjust to a continuous closed flow system with quality water control. After the adjustment period, clams were exposed either to sublethal concentrations of Reldan (0.6 μl L?1) or Roundup (1.1 μl L?1) for 90 days. Clams were taken to determine the histological damage at 30, 60 and 90 days. Most histological alterations were highly localized in the glandular cells of the gills, mantle tissues and digestive gland; secretions of glandular cells were found to be increased by increasing the time of exposure. Histopathological results showed the activation of resistance mechanisms that allowed the clams to survive under sublethal stresses. Thus, histological changes on localized tissues were sensitive and they have positive correlation to the time of exposure to the pesticides, suggesting that they may serve as biomarkers for Reldan and Roundup exposures. 相似文献
59.
Haider Taha 《Boundary-Layer Meteorology》2008,127(2):219-239
Two of several surface modification (heat-island reduction) strategies, increased surface albedo and urban reforestation,
are evaluated via mesoscale meteorological and photochemical modelling of regulatory episodes in central and southern California.
The simulations suggest that these strategies can have beneficial impacts on air quality, with increased albedo being relatively
more effective than urban reforestation. The simulations also show that air quality indices, such as regional 1-h peaks, area
peaks, 8-h relative reduction factors, 24-h averages, etc., improve for both central and southern California and that for
the range of strategies evaluated here, the improvements in air quality can be significant. The simulations of southern California
suggest that there may be a threshold beyond which further surface modifications tend to produce smaller net improvements in ozone air quality. 相似文献
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The current study examines the recently proposed “bias correction and stochastic analogues” (BCSA) statistical spatial downscaling technique and attempts to improve it by conditioning coarse resolution data when generating replicates. While the BCSA method reproduces the statistical features of the observed fine data, this existing model does not replicate the observed coarse spatial pattern, and subsequently, the cross-correlation between the observed coarse data and downscaled fine data with the model cannot be preserved. To address the dissimilarity between the BCSA downscaled data and observed fine data, a new statistical spatial downscaling method, “conditional stochastic simulation with bias correction” (BCCS), which employs the conditional multivariate distribution and principal component analysis, is proposed. Gridded observed climate data of mean daily precipitation (mm/day) covering a month at 1/8° for a fine resolution and at 1° for a coarse resolution over Florida for the current and future periods were used to verify and cross-validate the proposed technique. The observed coarse and fine data cover the 50-year period from 1950 to1999, and the future RCP4.5 and RCP8.5 climate scenarios cover the 100-year period from 2000 to 2099. The verification and cross-validation results show that the proposed BCCS downscaling method serves as an effective alternative means of downscaling monthly precipitation levels to assess climate change effects on hydrological variables. The RCP4.5 and RCP8.5 GCM scenarios are successfully downscaled. 相似文献