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1.
We obtain some cosmological models that are exact solutions of Einstein's field equations. The metric utilized is Marder's metric which is Bianchi Type I and the curvature source is a cloud of strings which are one dimensional objects. Bianchi type cosmological models play an important role in the study of the universe on a scale which anisotropy is not ignored. In this paper we have investigated the effect of cosmic strings on the cosmic microwave background anisotropy. Various physical and geometrical properties of the model are also discussed. The solutions have reported that the cosmic microwave background anisotropy may due to the cosmic strings. 相似文献
2.
Improper design, faulty planning, mismanagement and incorrect operation of irrigation schemes are the principle reasons for
the deterioration of groundwater quality in a large number of countries, in particular in semi-arid and arid regions. The
aim of this study is to determine the dimensions of groundwater quality after surface irrigation was begun in the semi-arid
Harran Plain. Physical and chemical parameters of the groundwater including pH, temperature, electrical conductivity (EC),
sodium, potassium, calcium, magnesium, chloride, bicarbonate, sulphate, nitrate, nitrite, ammonium, total phosphorus, total
organic carbon and turbidity were determined monthly during the 2006 water year. The quality of the groundwater in the study
area was assessed hydrochemically in order to determine its suitability for human consumption and agricultural purposes. In
the general plain, the EC values measured were considerably above the guide level of 650 μS/cm, while nitrate in particular
was found in almost all groundwater samples to be significantly above the maximum admissible concentration of 50 mg/l for
the quality of water intended for human consumption as per the international and national standards. Total hardness reveals
that a majority of the groundwater samples fall in the very hard water category. Interpretation of analytical data shows that
Ca–HCO3 and Ca–SO4 are the dominant hydrochemical facies in the study area. 相似文献
3.
AquantitativeanalysisontheEgyptianMediterraneanwaters¥M.A.SaidandF.M.Eid(ReceivedSeptember21,19931accfeptedJanuary15,1994)Abs... 相似文献
4.
A mathematical model of primary oil migration as a separate phase out of compacting shales is presented. During burial and oil generation, source rock porosity decreases and oil saturation increases until residual oil saturation is reached. At this stage oil is expelled out by capillary and excess fluid pressure gradients. The model is a system of differential equations which relate changes in oil and water saturation in time to water and oil flow out of the source rock during burial. An additional set of equations for periods of erosion of overburden are also provided. The equations can be numerically solved by finite difference method. If oil and water flow is to be simulated during oil generation, then at each time step, changes by oil generation in oil and water saturations and porosity must be calculated. The solution procedure is briefly outlined. 相似文献
5.
The accurate prediction of extreme excursion and mooring force of floating offshore structures due to multi-variete environmental conditions which requires the joint probability analysis of environmental conditions for the worst case situation is still impractical as the processing of large amount of met-ocean data is required. On the other hand, the simplified multiple design criteria (e.g. the N-year wave with associated winds and currents) recommended by API known as traditional method does lead neither to the N-year platform response nor to the N-year mooring force. Therefore, in order to reduce the level of conservatism as well as uncertainties involved in the traditional method the response-based method can be used as a reliable alternative approach. In this paper this method is described. In order to perform the calculations faster using large databases of sea states, Artificial Neural Networks (ANN) is designed and employed. In the paper the response-based method is applied to a 200,000 tdw FPSO and the results are discussed. 相似文献
6.
On the use of gravity and magnetic anomalies for locating probable areas of metallic mineralization in South Sinai, Egypt 总被引:1,自引:0,他引:1
The present study deals with processing and interpreting the potential gravity and magnetic data in order to locate promising
sites for metallic mineral occurrences in the basement rocks of South Sinai. Two promising sites were anticipated by combining
the geophysical results and the available geological information. Each site was profiled and interpreted to the nearly approximated
subsurface feature model, and the geometrical parameters of the expected subsurface structures may form mineralized bodies
such as depth, thickness, width, dipping, density contrast, and magnetic susceptibility contrast could be delineated. Detailed
ground Very Low Frequency (VLF) and Vertical Magnetic Gradient (VMG) methods were carried out in the site A2, eight VLF and
VMG anomalies were determined, and their depths were calculated. 相似文献
7.
8.
The main objective of the research work isthe homogenisation of the two recentAlgerian earthquake catalogues for thecommon covered period of time, from 1900 to1990, for the region under considerationlimited by [33°N–38°N,4°E-9.5°E] and the updatingof the catalogue for the twentieth century(1900–2000). To mitigate the deficiencyof the incompleteness of catalogue, aneffort was made to establish a correlationbetween surface-wave magnitude Ms andbody-wave magnitude mb in the form ofMs = a + b (mb). A complete, exact andhomogeneous earthquake catalogue as much aspossible, comprising 870 seismic events,has been compiled. Seismicity analysis ofthe region shows a strong concentration ofseismicity along a band of no more than400 km width oriented mainly in theeast-west direction parallel to the coast.Moreover, earthquakes in this zone arerather associated to strike-slip mechanism.The focal mechanism show a regional stressregime that corresponds to horizontalcompression in NW-SE to N-S direction. As aresult of the review of the seismicity ofnorth-eastern Algeria from the compilationof checked and corrected data and itscorrelation with other geologic andgeophysical investigations based ondocumentary sources, it was possible toconstruct a most complete seismotectonicmap. It leads also to delineate fourseismogenic zones in the Tellian Atlas, aless important zone in the Saharan Atlas, asixth zone at the boundary of both Atlasand finally, a seventh one along thecoastal zone. The seismicity-active faultscorrelation of some of these defined zonesis examined in details with a specialattention to the Saharan Atlas zone, theHodna and Biban zone as well as Soummam andBabor zone where further research workallowed to find some neotectonic featuresconsidered as a significant sign of recenttectonic activity. 相似文献
9.
A Markov method of analysis is presented for obtaining the seismic response of cable‐stayed bridges to non‐stationary random ground motion. A uniformly modulated non‐stationary model of the random ground motion is assumed which is specified by the evolutionary r.m.s. ground acceleration. Both vertical and horizontal components of the motion are considered to act simultaneously at the bridge supports. The analysis duly takes into account the angle of incidence of the earthquake, the spatial correlation of ground motion and the quasi‐static excitation. A cable‐stayed bridge is analysed under a set of parametric variations in order to study the non‐stationary response of the bridge. The results of the numerical study indicate that (i) frequency domain spectral analysis with peak r.m.s. acceleration as input could provide more r.m.s. response than the peak r.m.s. response obtained by the non‐stationary analysis; (ii) the longitudinal component of the ground motion significantly influences the vertical vibration of the bridge; and (iii) the angle of incidence of the earthquake has considerable influence on the deck response. Copyright © 2003 John Wiley & Sons, Ltd. 相似文献
10.
Azma Hanim Ismail Mashhor Mansor Wan Maznah W O 《湿地科学》2005,3(4):258-268
A study has been conducted on the status of water quality in two disused man made lakes, which have potential for cage aquaculture project. This study highlights the quality of water analyzed with reference to various physical - chemical parameters in two selected lakes and their suitability for fish farming. A number of parameters were measured including the amount of NH3 - N, NO3 - N, NO2 - N and total phosphorus while in - situ measurement including DO, pH, temperature, conductivity, TDS and Secchi disk visibility. Beside the physical -chemical of water, the location, morphometry and climate conditions were also investigated. The chemical data analyzed for six months indicated that Lake A and Lake B are characterized by relatively high DO, slightly neutral pH and low TSS. The concentration of NH3 -N and NO2 -N was very low (0. 058 mg/L and 0. 04 mg/L, respectively) and total phosphorus was usually in low concentration and sometimes would seem negligible. Besides, NO3 - N occurred in slightly higher concentration (1.75 mg/L). Results obtained indicated that the study site has high potentiality for development of inland fisheries practices. 相似文献