Dual behavior of the toroidal magnetic field versus the Rossby wave instability     

Mahmoud Gholipour 《Astrophysics and Space Science》2016,361(12):385

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Application of Rock Mass Characterization for Determining the Mechanical Properties of Rock Mass: a Comparative Study     

Mahmoud Hashemi  Sh. Moghaddas  R. Ajalloeian 《Rock Mechanics and Rock Engineering》2010,43(3):305-320

The results of geotechnical explorations, engineering geological investigation (including laboratory and in situ tests) and field observations have been used, along with borehole logging charts, to obtain the rock mass geotechnical data. Based on the data, the rock mass along the Sabzkuh water conveyance tunnel route was classified by rock mass rating (RMR), Q-system (Q), rock mass index (RMi) and geological strength index (GSI) (3 methods). A new series of correlations were established between the systems based on the data collected from the study area. These relationships were then compared with those reported in the literature, and two new relations were recommended. The classifications were utilized to calculate mechanical properties (rock mass strength and deformation modulus) of the rock mass along the tunnel according to available empirical relations, and to distinguish the upper-bound and lower-bound relations.  相似文献   

Structural styles and tectonic evolution of the Kolia-Boboti sedimentary Basin,Kédougou-Kéniéba inlier,eastern Senegal     

Moussa Dabo  Tahar Aïfa 《Comptes Rendus Geoscience》2010,342(10):796-805

New structural data obtained on the Birimian terranes of the Kolia-Boboti sedimentary Basin, the eastern part of the Dialé-Daléma Supergroup in the Kédougou-Kéniéba inlier show two major phases of Eburnean compressional deformation: (1) a D1 phase of thrusting tectonics affected the Lower Birimian B1 tourmalinized sediments. This first tectonic phase is characterized by isoclinals overturned to recumbent folds P1 with N040° 20°NE trending axis, associated with axial plane schistosity S₀S₁ which is mainly transposed in the bedding; (2) a D2 phase of compressional (D2a) and transpressional (D2b) tectonics is responsible for the crossfolds P2a-P2b exhibiting curved axes. These P2 folds are associated with the major schistosity S₂, north-south to SW-NE trending, mainly dipping to the south-east. The S₂ schistosity is mostly displayed in the large shear zones corridors where it steeply dips locally toward the north-west. A north-west vergence thrusting phase (D2c) of flats and ramps, associated with reverse folds, represents the last Eburnean event. This geometrical feature is characteristic of a “positive flower structure”. These different Eburnean compressional phases are separated by extensional deformation which is characterized by sedimentary deposits and volcanic flows.  相似文献   

Heavy metal and anionic contamination in the water and sediments in Al-Mujib reservoir,central Jordan     

Waleed Manasreh  Iyad Hailat  Tayel Mahmoud El-Hasan 《Environmental Earth Sciences》2010,60(3):613-621

Sixty-five sediment samples and 25 water samples were collected from Al-Mujib reservoir, central Jordan, in order to investigate the heavy metal and ionic contamination assessment. Therefore, to achieve this aim, water and sediment samples were collected during winter and summer seasons (2007) from Al-Mujib reservoir and the areas surrounding it. The study shows that there are elevated levels of SO₄ ²⁻, Cl⁻ and Na⁺ in reservoir water, which might originate from anthropogenic activities in the reservoir catchment area. In addition, the reservoir water has higher total hardness (TH) values together with high Ca and Mg contents. This might be attributed to pH of reservoir water and the nature of the rocks exposed in the catchment area. The average levels of heavy metals in reservoir sediments are Fe = 14,888.1, Cu = 17.8, Zn = 88.6, Ni = 38.7, Cd = 4.4, Mn = 337.9 and Pb = 6.1 mg/kg, which are lower than that observed in Wadi Al-Arab reservoir, northern Jordan. The values of enrichment factor are Cd = 35.5, Ni = 3.02, Zn = 2.54, Cu = 1.26, Mn = 1.2 and Pb = 0.57; these values indicate that heavy metals in sediments of Al-Mujeb reservoir have a different anthropogenic incrimination inputs. The study showed that the sediments are polluted with Cd, relatively contaminated with Ni and Zn and uncontaminated with respect to Mn, Pb and Cu.  相似文献   

Geochemical constraints on the genesis of the volcanic rocks in the southeast of Isfahan area, Iran     

Mahnaz Khodami  Moussa Noghreyan  Ali Reza Davoudian 《Arabian Journal of Geosciences》2010,3(3):257-266

Late Miocene–Pliocene to Quaternary calc-alkaline lava flows and domes are exposed in southeast of Isfahan in the Urumieh Dokhtar magmatic belt in the Central Iran structural zone. These volcanic rocks have compositions ranging from basaltic andesites, andesites to dacites. Geochemical studies show these rocks are a medium to high K calc-alkaline suite and meta-aluminous. Major element variations are typical for calc-alkaline rocks. The volcanic rocks have SiO₂ contents ranging between 53.8% and 65.3%. Harker diagrams clearly show that the dacitic rocks did not form from the basaltic andesites by normal differentiation processes. They show large ion lithophile elements- and light rare earth elements (LREE)-enriched normalized multielement patterns and negative Nb, Ti, Ta, and P. Condrite-normalized REE patterns display a steep decrease from LREE to light rare earth elements without any Eu anomaly. These characteristics are consistent with ratios obtained from subduction-related volcanic rocks and in collision setting. The melting of a heterogeneous source is possible mechanism for their magma genesis, which was enriched in incompatible elements situated at the upper continental lithospheric mantle or lower crust. The geochemical characteristics of these volcanic rocks suggested that these volcanic rocks evolved by contamination of a parental magma derived from metasomatized upper lithospheric mantle and crustal melts.  相似文献   

Assessing the impact of the hydraulic properties of a crusted soil on overland flow modelling at the field scale     

Nane Chahinian  Marc Voltz  Roger Moussa  Gwenn Trotoux 《水文研究》2006,20(8):1701-1722

Soil surface crusts are widely reported to favour Hortonian runoff, but are not explicitly represented in most rainfall‐runoff models. The aim of this paper is to assess the impact of soil surface crusts on infiltration and runoff modelling at two spatial scales, i.e. the local scale and the plot scale. At the local scale, two separate single ring infiltration experiments are undertaken. The first is performed on the undisturbed soil, whereas the second is done after removal of the soil surface crust. The HYDRUS 2D two‐dimensional vertical infiltration model is then used in an inverse modelling approach, first to estimate the soil hydraulic properties of the crust and the subsoil, and then the effective hydraulic properties of the soil represented as a single uniform layer. The results show that the crust hydraulic conductivity is 10 times lower than that of the subsoil, thus illustrating the limiting role the crust has on infiltration. Moving up to the plot scale, a rainfall‐runoff model coupling the Richards equation to a transfer function is used to simulate Hortonian overland flow hydrographs. The previously calculated hydraulic properties are used, and a comparison is undertaken between a single‐layer and a double‐layer representation of the crusted soil. The results of the rainfall‐runoff model show that the soil hydraulic properties calculated at the local scale give acceptable results when used to model runoff at the plot scale directly, without any numerical calibration. Also, at the plot scale, no clear improvement of the results can be seen when using a double‐layer representation of the soil in comparison with a single homogeneous layer. This is due to the hydrological characteristics of Hortonian runoff, which is triggered by a rainfall intensity exceeding the saturated hydraulic conductivity of the soil surface. Consequently, the rainfall‐runoff model is more sensitive to rainfall than to the subsoil's hydrodynamic properties. Therefore, the use of a double‐layer soil model to represent runoff on a crusted soil does not seem necessary, as the increase of precision in the soil discretization is not justified by a better performance of the model. Copyright © 2005 John Wiley & Sons, Ltd.  相似文献   

Petrogenesis of the Az Zabirah south zone bauxite ore deposits,central northern Saudi Arabia     

Al-Mutairi  Abdulaziz N.  Galmed  Mahmoud A.  Aldamegh  Khaled S. 《Arabian Journal of Geosciences》2015,8(4):2327-2339

Arabian Journal of Geosciences - The bauxite ore deposits are mainly found around the Az Zabirah area in the central northern part of Saudi Arabia. The age of the Az Zabirah bauxites was suggested...  相似文献   

Geoelectrical and Hydrogeochemical Studies for Delineating Ground-Water Contamination Due to Salt-Water Intrusion in the Northern Part of the Nile Delta, Egypt   总被引：3，自引：0，他引：3  

Abdel-Azim M. Ebraheem  Mahmoud M. Senosy  Kamal A. Dahab 《Ground water》1997,35(2):216-222

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Temperature variations of one well-known UV ceti type flare star     

Farouk M. Mahmoud 《Astrophysics and Space Science》1995,234(1):107-123

Temperature variations of the flare star, EV Lac, at its quiet-state luminosity were computed from its colour indices,B - V, which were measured in Johnson's system, these daily temperature changes are the essential reason of the short-term behaviour appearance in the flare star which is due to the presence of active region(s) causing a temperature difference of a few hundred degrees from the photosphere. A correlation between the annual mean of temperature variations of the flare star at its quiet-state and the annual rate of some physical parameters of the flare star at its active-state was detected. This correlation can interpret the occurrence of the long-term behaviour of the flare star at its quiescent-state as found by Mavridiset al. (1982).  相似文献   

Structure of magnetogasdynamic weak shock waves     

M. A. Khidr  S. S. Elghabaty  M. A. A. Mahmoud 《Astrophysics and Space Science》1987,136(2):379-391

The problem of the detailed structure of magnetogasdynamic shock waves is investigated. It is assumed that the flow takes place under normal magnetic fieldH ₀ and the conductivity of the medium is considered infinite. An approximate analytical solution of the nonlinear differential equations describing the phenomena is obtained. The suggested analytical results in this paper are in good agreement with the previous numerical computations for the thickness and the velocity distribution inside the transition region. In addition, the enthalpy distribution inside the shock front is predicted.  相似文献