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1.
M. Madkour 《Astrophysics and Space Science》1990,174(1):1-11
Radiation transfer problem in the slowing-down region for cylindrical geometry with diffuse reflectivity and internal source is connected with source-free problem with isotropic boundary condition. Modelled kernels are used to represent the slowing-down kernel. Calculations are performed for the radiation flux at the boundary of the cylinder. Numerical results are obtained using the bi-variation technique. 相似文献
2.
The transport of thermal radiation has been considered within a finite slab which absorb and scatter anisotropically. The problem involves the space-dependent single-scattering albedow(x). Two approximations are taken forw(x). In the first it is represented in exponential form asw(x)=w
0 exp(–x/s), wherew
0 ands are given constants andx is the optical variable. The second approximation assumes the formw(x) =
r=0
R
d
r
*
p
r
(x/a), whered
r
*
are known expansion coefficients anda is the half optical thickness of the slab. Analytic expressions for the forward, backward radiation intensities and fluxes are given in each approximation. The solution of the linear transport equation is performed on the basis of integral Fourier transforms. 相似文献
3.
Natural Hazards - The sliding incidences along the mountainous roads in the northern part of Algeria are considered a major hazard, often with huge impacts on infrastructures, causing terrible... 相似文献
4.
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
5.
Waleed K. Zubari 《Hydrogeology Journal》1999,7(2):197-208
Over-abstraction of the Dammam aquifer, the principal aquifer in Bahrain, by the agricultural and domestic sectors, has led
to its salinization by adjacent brackish and saline water bodies. A hydrochemical study identified the locations of the sources
of aquifer salinization and delineated their areas of influence. The investigation indicates that the aquifer water quality
is significantly modified as groundwater flows from the northwestern parts of Bahrain, where the aquifer receives its water
by lateral underflow from eastern Saudi Arabia, to the southern and southeastern parts. Four types of salinization of the
aquifer are identified: brackish-water up-flow from the underlying brackish-water zones in north-central, western, and eastern
regions; seawater intrusion in the eastern region; intrusion of sabkha water in the southwestern region; and irrigation return
flow in a local area in the western region. Four alternatives for the management of groundwater quality that are available
to the water authorities in Bahrain are discussed and their priority areas are proposed, based on the type and extent of each
salinization source, in addition to groundwater use in that area. The effectiveness of the proposed management options in
controlling the degradation of water quality in the Dammam aquifer should be evaluated using simulation modeling.
Received: June 1998 Revised: November 1998 Accepted: December 1998 相似文献
6.
7.
We present a theoretical weakly nonlinear analysis of the dynamics of an inviscid flow submitted to both rotation and precession of an unbounded cylindrical container, by considering the coupling of two Kelvin (inertial) waves. The parametric centrifugal instability known for this system is shown to saturate when one expands the Navier–Stokes equation to higher order in the assumed small precession parameter (ratio of precession to rotation frequencies) with the derivation of two coupled Landau equations suitable to describe the dynamics of the modes. It is shown that an azimuthal mean flow with differential rotation is generated by this modes coupling. The time evolution of the associated dynamical system is studied. These theoretical results can be compared with water experiments and also to some numerical simulations where viscosity and finite length effects cannot be neglected. 相似文献
8.
Waleed M. M. Mahmoud Nareman D. H. Khaleel Ghada M. Hadad Randa A. Abdel‐Salam Annette Haiß Klaus Kümmerer 《洁净——土壤、空气、水》2013,41(9):907-916
Sulfonamides (SAs) are one of the most frequently used antibiotics. SAs have been found in various environmental compartments. If SAs are not degraded in the environment, they can affect bacteria by their antibiotic properties and contribute to bacterial antibiotic resistance. Therefore, the biodegradability of 11 SAs (sulfanilamide, sulfaguanidine monohydrate, sulfadiazine, sulfathiazole, sulfapyridine, sulfamerazine, sulfamethoxypyridazine, sulfachloropyridazine, sulfamethazine, sulfamethoxazole, and sulfadimethoxine) was studied. For this purpose, the Closed Bottle Test (CBT, OECD 301D) was performed, which includes a toxicity control. In order to monitor the environmental fate of the parent compound and to check for transformation products, a simple, efficient, and reliable HPLC–UV method for the simultaneous determination of these SAs has been developed. Acetonitrile and water (with 0.1% formic acid) were used as mobile phase solvents for gradient elution. The method was validated in terms of precision, detection and quantitation limits, selectivity, and analytical solution stability. In the CBT, none of these SAs was readily biodegradable. The HPLC–UV analysis confirmed that no degradation of any SA took place. In the toxicity control, these SAs showed no toxic effect in the used concentration of environmental bacteria applied in the test. 相似文献
9.
The maximum-entropy approach is used to calculate the Chandrasekhar'sX- andY-function and their moments. Numerical results are obtained and compared. 相似文献
10.
Waleed S. IBRAHIM 《《地质学报》英文版》2021,95(6):2045-2062
The Wadi Ibib area is situated in the northern part of the Neoproterozoic Hamisana Shear Zone (HSZ), which is a high strain zone evolved during the late stages of the Pan-African orogeny, likely as a tectonic escape structure. Amphibolite facies pelitic metasedimentary windows crop out in the axial parts of the HSZ and are noticeably associated with numerous N-trending pegmatite dikes. Whole-rock geochemistry of the pegmatites reveals a peraluminous (S-type) affinity, with low K/Rb ratios and elevated concentrations of U, Th, REE, Rb, Li, Cs, Y, Nb and Ta. Structurally, the pegmatite sets intrude along the shear plane of the HSZ, corresponding to the regional N-trending tectonic fabrics, such as axial planar foliation and dextral-shearing in the metasedimentary host rock. Field relationships, including structural context, coupled with geochemical characteristics of the Wadi Ibib pegmatites, do not support their formation as a complementary part of evolved granitic magmas. Space-localized decompression-induced partial melting of peraluminous garnet-bearing metapelites was alternatively the underlying process for formation of these pegmatites. Such decompression was associated with regional escape tectonics and stress axes permutations during the late deformation stage (D3) in the evolution of the south Eastern Desert terrane, due to end-orogeny system pressure-release. 相似文献