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211.
Majid Mirzaei Yuk Feng Huang Teang Shui Lee Ahmed El-Shafie Abdul Halim Ghazali 《Natural Hazards》2014,71(2):1227-1239
Uncertainty in depth–duration–frequency (DDF) curves is usually disregarded in the view of difficulties associated in assigning a value to it. In central Iran, precipitation duration is often long and characterized with low intensity leading to a considerable uncertainty in the parameters of the probabilistic distributions describing rainfall depth. In this paper, the daily rainfall depths from 4 stations in the Zayanderood basin, Iran, were analysed, and a generalized extreme value distribution was fitted to the maximum yearly rainfall for durations of 1, 2, 3, 4 and 5 days. DDF curves were described as a function of rainfall duration (D) and return period (T). Uncertainties of the rainfall depth in the DDF curves were estimated with the bootstrap sampling method and were described by a normal probability density function. Standard deviations were modeled as a function of rainfall duration and rainfall depth using 104 bootstrap samples for all the durations and return periods considered for each rainfall station. 相似文献
212.
This article presents the first study of the head-on collision between two magnetoacoustic solitary waves (MASWs) in magnetized quantum plasma consisting of electrons, positrons, and ions, using the extended Poincaré-Lighthill-Kou (PLK) method. The effects of the magnetic field intensity, the positron to ion number density ratio, the quantum parameter, the Fermi temperature ratio, and plasma number density on the solitary wave collisions are investigated. It is shown that these factors significantly modify the phase shift. 相似文献
213.
This paper examines the gravitational collapse in plane symmetry with a perfect fluid using a linear equation of state p=kρ. We find a class of collapse models satisfying the Einstein field equations and also the regularity as well as energy conditions. For a given initial data, the outcome of the collapse turns out to be a black membrane or a naked singularity depending upon the equation of state parameter. We conclude that this parameter plays a crucial role in determining the final fate of the collapse. 相似文献
214.
The Kachchh Basin is a pericratonic rift basin situated at the western margin of the Indian plate. The Habo Dome embodies
an important exposure of Bathonian to Kimmergian sediments among the Kachchh Mainland exposures. Based on vertical facies
transitions, facies associations were documented: mixed shallow marine (Facies association 1), shoreface and lagoon deposits
(Facies association II) and subtidal innershelf below fair weather wave base (Facies association III). The documented facies
associations reflect that Habo Dome sediments deposited in a variety of environments from shallow marine to fluvio-deltaic
and were strongly influenced by fluctuation of relative sea level. The dominance of floating grains and point contacts in
the sandstone indicate that detrital grains do not show much pressure effects as a result of either shallow burial or early
cementation. The sandstones were cemented by iron oxide, carbonate and silica in order of abundance. Three types of cements,
blocky, rim and fibrous cement occur in the studied limestone representing phreatic, fresh water phreatic and deep burial
diagenetic stages. Neomorphism and micritization are common. Both primary and secondary porosity exists in these sediments.
Different graphs of porosity versus depth suggest a depth of burial in the range of 615–769 m. 相似文献
215.
An Analytical Study of the Diurnal Variations of Wind in a Semi-geostrophic Ekman Boundary Layer Model 总被引:1,自引:0,他引:1
A time-dependent semi-geostrophic Ekman boundary-layer model based on the geostrophic momentum approximation is used to study the diurnal wind variation in the planetary boundary layer (PBL) and the evolution of the low-level nocturnal jet (LLJ). The coefficient of eddy viscosity varies periodically with time, varies linearly with height in the surface layer and is constant above the surface layer. The influence of horizontal advection of momentum on the diurnal wind variation in the PBL, the development of inertial oscillations (IOs) and the formation of the LLJ are examined.In comparison with the Ekman solutions, the diurnal wind variation in semi-geostrophic Ekman boundary-layer dynamics has the following features: (1) the phase angle of the diurnal wind wave shifts with height, the rate of shifting is increased in anticyclonic regions and decreased in cyclonic regions, (2) the time of occurrence of the low-level maximum wind speed is later in anticyclonic regions and earlier in cyclonic regions, (3) the height of occurrence of the maximum wind speed is higher in the anticyclonic and lower in cyclonic regions, (4) the wind speed maximum and the amplitude of the diurnal wind variation are larger in anticyclonic and smaller in cyclonic regions, (5) the period of IOs is larger in anticyclonic regions and smaller in cyclonic regions, (6) anticyclonic vorticity is conducive to the generation of LLJ in the PBL. These features are interpreted by means of the physical properties of semi-geostrophic Ekman boundary-layer dynamics and inertial oscillation dynamics. 相似文献
216.
217.
This paper presents the results of a study on the variation of Re in the Sar Cheshmeh porphyry copper‐molybdenum deposit in Iran. The Re content was determined in monomineralic molybdenite separates from veinlets and from molybdenum milled floatation concentrates. Mineralogical data and chemical analyses indicate two generations of veinlet molybdenites in the Sar Cheshmeh deposit. The first generation (molybdenite I), which contains low Re, is found as intergrowth with quartz in silicified rocks with low total sulfide content, and the second generation (molybdenite II), which contains high Re, is found in veinlets with low quartz content. There is a positive correlation between the elevation of molybdenite deposition and Re content. Decrease in the temperature and pH of the hydrothermal fluids are effective for the accumulation Re in molybdenite. X‐ray diffraction study of 14 molybdenite samples indicate that the molybdenites are of the 2H polytype. 相似文献