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排序方式: 共有54条查询结果,搜索用时 15 毫秒
1.
A three dimensional rectangular grid model is applied to resolve the temperature–salinity dynamics of Ruwais, a segment of the UAE coast which is well known as dense water formation zone. The model employs a heat flux module and a turbulence closure scheme that facilitate realistic calculation of temperature–salinity dynamics. A field survey campaign is carried out to support the modeling study, involving measurements of tide, currents, temperature, and salinity. Investigation is done for two meteorologically extreme conditions, i.e. summer and winter. The model study showed that the western flux develops an anticlockwise circulation in the study area. The water industrial discharges elevated the temperature and salinity of the water near the southeastern shoreline. This water mass propagated towards north under the influence of gravity. 相似文献
2.
Ben Ameur W Ben Hassine S Eljarrat E El Megdiche Y Trabelsi S Hammami B Barceló D Driss MR 《Marine environmental research》2011,72(5):258-264
Concentrations of ten polybrominated diphenyl ethers (PBDEs) and eight methoxylated polybrominated diphenyl ethers (MeO-PBDEs) in mullet (Mugil cephalus) and sea bass (Dicentrarchus labrax) collected from the Bizerte Lagoon and the Mediterranean Sea were investigated. To the best of our knowledge, this is the first report of these compounds in marine fishes from Tunisia. The PBDE mean concentrations in fish from Bizerte Lagoon were 45.3 and 96.2 ng g(-1) lw respectively in mullet and sea bass, while the concentrations of these compounds in mullet and sea bass from Mediterranean Sea were 7.80 and 27.9 ng g(-1) lw respectively. MeO-PBDE concentrations in mullet and sea bass from Bizerte Lagoon ranged from 6.46 to 286 ng g(-1) lw and from 49.4 to 798 ng g(-1) lw respectively, while the concentrations of these compounds in mullet and sea bass from Mediterranean Sea ranged from 190 to 401 ng g(-1) lw and from 353 to 578 ng g(-1) lw respectively. The total PBDEs and total MeO-PBDEs concentration in fish from Bizerte Lagoon were similar or slightly lower than those reported for other species from other locations around the world. 相似文献
3.
Four colour contrasts have been studied for 104 lunar regions between wavelengths 4000 Å and 8000 Å. Distinct colour differences are found. The greatest contrast between topographs occurs at longer wavelengths. The regional colour differences between the two short wavelengths 4035 Å and 5538 Å show a general trend of increasing reddening with age. For the other three colour differences \(\Delta (\tfrac{{{\text{4 7 6 5}}}}{{{\text{7 9 2 2}}}}), \Delta (\tfrac{{{\text{4 7 6 5}}}}{{{\text{6 6 9 2}}}}) and \Delta (\tfrac{{{\text{6 6 9 2}}}}{{{\text{7 9 2 2}}}})\) , a trend of variation with albedo is detected, and the less scatter on points for the colour differences above the wavelength 6000 Å. 相似文献
4.
An Experimenting Field Approach for the Numerical Solution of Multiphase Flow in Porous Media 下载免费PDF全文
In this work, we apply the experimenting pressure field technique to the problem of the flow of two or more immiscible phases in porous media. In this technique, a set of predefined pressure fields are introduced to the governing partial differential equations. This implies that the velocity vector field and the divergence at each cell of the solution mesh can be determined. However, since none of these fields is the true pressure field entailed by the boundary conditions and/or the source terms, the divergence at each cell will not be the correct one. Rather the residue which is the difference between the true divergence and the calculated one is obtained. These fields are designed such that these residuals are used to construct the matrix of coefficients of the pressure equation and the right‐hand side. The experimenting pressure fields are generated in the solver routine and are fed to the different routines, which may be called physics routines, which return to the solver the elements of the matrix of coefficients. Therefore, this methodology separates the solver routines from the physics routines and therefore results in simpler, easy to construct, maintain, and update algorithms. 相似文献
5.
R. B. Salama 《Australian Journal of Earth Sciences》2013,60(6):751-765
The Salt River System forms the connection between the saline lakes of the Yilgarn River catchment in the east and the rejuvenated Avon River System in the west. Judging from the age of the deposits in the palaeochannels of the Salt River after the Darling uplift and from the deltaic deposits of the river before the uplift, it appears that the river has been occupying this same course since the Early Tertiary. The uplift dammed the course of the river and caused the formation of large inland lakes. The inland lake at Yenyening persisted for a long time until the opening of the northern outlet of the Avon. This explains the absence of sedimentary deposits from the Avon in the Perth Basin during the closure time. The relatively thick sediments that fill up the palaeochannels comprise three formations of the Salt River Group: South Caroline Clay, Yenyening Formation and Quairading Sandstone. The reconstruction of the palaeoriver showed that the river was occupying a steep gorge about 70 m deep with a slope of about 0.35 m km‐1. 相似文献
6.
Wide-azimuth seismic data can be used to derive anisotropic parameters on the subsurface by observing variation in subsurface seismic response along different azimuths. Layer-based high-resolution estimates of components of the subsurface anisotropic elastic tensor can be reconstructed by using wide-azimuth P-wave data by combining the kinematic information derived from anisotropic velocity analysis with dynamic information obtained from amplitude versus angle and azimuth analysis of wide-azimuth seismic data. Interval P-impedance, S-impedance and anisotropic parameters associated with anisotropic fracture media are being reconstructed using linearized analysis assuming horizontal transverse anisotropy symmetry. In this paper it is shown how additional assumptions, such as the rock model, can be used to reduce the degrees of freedom in the estimation problem and recover all five anisotropic parameters. Because the use of a rock model is needed, the derived elastic parameters are consistent with the rock model and are used to infer fractured rock properties using stochastic rock physics inversion. The inversion is based on stochastic rock physics modelling and maximum a posteriori estimate of both porosity and crack density parameters associated with the observed elastic parameters derived from both velocity and amplitude versus angle and azimuth analysis. While the focus of this study is on the use of P-wave reflection data, we also show how additional information such as shear wave splitting and/or anisotropic well log data can reduce the assumptions needed to derive elastic parameter and rock properties. 相似文献
7.
A. M. Heras E. Wieprecht H. Feuchtgruber F. Lahuis K. Leech R. Lorente P. Morris A. Salama B. Vandenbussche 《Experimental Astronomy》2000,10(2-3):177-197
We present a trend analysis of the ISO-SWS detector performance and a study of the space radiation effects on the SWS detectors. In particular, dark currents, dark current noise and detector responses have been checked as a function of time through the mission and as a function of time in arevolution. The results show that these parameters were stable during the mission in all bandsbut for band 3 (Si:As). Dark currents and responses were found to be higherin the first hours following the start of the science window,especially in band 2 (Si:Ga). We have studied the impacts of cosmic rays and radiation belt particles on the SWS detectors, as well as of the only large solar proton event on November 6, 1997,that occurred during the ISO mission (operated during solar minimum).The observed glitch rates in all SWS bands are found to be between 2 and4 times higher than the value predicted by the CREME96 model for the cosmic ray flux in the period considered. The bands that registered the highest glitch rates showed also a correlation with the electron fluxes measured on theGOES 9 spacecraft. From the distribution of glitchheights (voltage jumps in the detector signal), we have derived the deposited energy distributions of the particles hits. Our results lead to the conclusion that secondaryparticles produced in the shield and the detectors contributed at least as much as cosmic rays to the observed glitch rate. The effects on the detectors of the November 6, 1997 event, which caused that all observationsin a revolution were declared failed, are described in detail. 相似文献
8.
S.P.S. Eyres A. Evans A. Salama P. Barr J. Clavel N. Jenkins K. Leech M. Kessler T. Lim L. Metcalfe B. Schulz 《Astrophysics and Space Science》1997,255(1-2):361-366
A number of symbiotic stars have been observed with ISO. In addition to a number of emission lines, SWS observations of the
symbiotic novae RR Tel and V1016 Cyg reveal prominent, broad 10 & 18 μm silicate dust features. The 10 μm features are similar
to the crystalline silicate profiles seen in classical novae. There is some evidence that the silicate brightness in V1016
Cyg varies with Mira-component phase. However, the silicate feature in RR Tel also showed some variation even though observations
were made at very similar Mira-component phases. PHT observations of S-type symbiotic stars show the IR emission to be dominated
by the red-giant component. However, an excess in the PHT-P filters from 10 to 15 μm is evident in all the stars, and there
may be a broad 3.2 μm absorption feature or a broad 3.8 μm emission feature. At this time we have no adequate physical explanations
for any of these features.
This revised version was published online in August 2006 with corrections to the Cover Date. 相似文献
9.
10.
Contributions of groundwater conditions to soil and water salinization 总被引:21,自引:2,他引:21
Salinization is the process whereby the concentration of dissolved salts in water and soil is increased due to natural or
human-induced processes. Water is lost through one or any combination of four main mechanisms: evaporation, evapotranspiration,
hydrolysis, and leakage between aquifers. Salinity increases from catchment divides to the valley floors and in the direction
of groundwater flow. Salinization is explained by two main chemical models developed by the authors: weathering and deposition.
These models are in agreement with the weathering and depositional geological processes that have formed soils and overburden
in the catchments. Five soil-change processes in arid and semi-arid climates are associated with waterlogging and water. In
all represented cases, groundwater is the main geological agent for transmitting, accumulating, and discharging salt. At a
small catchment scale in South and Western Australia, water is lost through evapotranspiration and hydrolysis. Saline groundwater
flows along the beds of the streams and is accumulated in paleochannels, which act as a salt repository, and finally discharges
in lakes, where most of the saline groundwater is concentrated. In the hummocky terrains of the Northern Great Plains Region,
Canada and USA, the localized recharge and discharge scenarios cause salinization to occur mainly in depressions, in conjunction
with the formation of saline soils and seepages. On a regional scale within closed basins, this process can create playas
or saline lakes. In the continental aquifers of the rift basins of Sudan, salinity increases along the groundwater flow path
and forms a saline zone at the distal end. The saline zone in each rift forms a closed ridge, which coincides with the closed
trough of the groundwater-level map. The saline body or bodies were formed by evaporation coupled with alkaline-earth carbonate
precipitation and dissolution of capillary salts.
Received, May 1998 · Revised, July 1998 · Accepted, September 1998 相似文献