排序方式： 共有85条查询结果，搜索用时 31 毫秒
51.
Ebrahim Ahmadisharaf Alfred J. Kalyanapu Jason R. Lillywhite Gina L. Tonn 《水文科学杂志》2013,58(12):1776-1790
ABSTRACTThis study presents a probabilistic framework to evaluate the impact of uncertainty of design rainfall depth and temporal pattern as well as antecedent moisture condition (AMC) on design hydrograph attributes – peak, time to peak, duration and volume, as well as falling and rising limb slopes – using an event-based hydrological model in the Swannanoa River watershed in North Carolina, USA. Of the six hydrograph attributes, falling limb slope is the most sensitive to the aforementioned uncertainties, while duration is the least sensitive. In general, the uncertainty of hydrograph attributes decreases in higher recurrence intervals. Our multivariate analysis revealed that in most of the return periods, AMC is the most important driver for peak, duration and volume, while time to peak and falling limb slope are most influenced by rainfall pattern. In higher return periods, the importance of rainfall depth and pattern increases, while the importance of AMC decreases. 相似文献
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Fardin Mousivand Ebrahim Rastad Sebastien Meffre Jan M. Peter Mohammad Mohajjel Khin Zaw Mohammad Hashem Emami 《Mineralium Deposita》2012,47(8):911-931
The Bavanat Cu–Zn–Ag Besshi-type volcanogenic massive sulfide (VMS) deposit occurs within the Surian volcano-sedimentary complex in the Sanandaj–Sirjan zone (SSZ) of southern Iran. The Surian complex is comprised of pelite, sandstone, calcareous shale, basalt, gabbro sills, and thin-bedded limestone. Mineralization occurs as stratiform sheet-like and tabular orebodies hosted mainly by greenschist metamorphosed feldspathic and quartz feldspathic sandstone, basalt, and pelites. The basalts of the Surian complex show predominantly tholeiitic to transitional affinities, with a few samples that are alkalic in composition. Primitive mantle-normalized trace and rare earth element (REE) patterns of the Surian basalts display depletions in light REE, negative anomalies of Nb, Ta, and Ti, and positive anomalies of P. Positive P anomalies are indicative of minor crustal contamination. Furthermore, Th enrichments in the mid-ocean ridge basalt-normalized patterns of the Surian basalts are characteristic of rifted arc basalts emplaced in continental margin subduction zones. The high MgO content (>6?wt.%) of most Surian basalts and low TiO2 content of two samples (0.53 and 0.62?wt.%) are characteristic of boninites. The aforementioned features of the basalts indicate arc tholeiites emplaced in intra-arc rift environments and continental margin subduction zones. U–Pb dating by laser ablation- inductively coupled plasma mass spectrometry of detrital zircons extracted from the host feldspathic and quartz feldspathic sandstone yields various ages that are predominantly Permian and Triassic; however, the youngest zircons give a mean Early Jurassic concordant U–Pb age of 191?±?12?Ma. This age, together with geological and petrochemical data, indicate that VMS mineralization formed in the Early Jurassic in pull-apart basins within the SSZ. These basins and the VMS mineralization may be temporally related to an intra-arc volcano–plutonic event associated with Neo-Tethyan oblique subduction. 相似文献
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Reza Rashidi 《Astrophysics and Space Science》2013,343(1):383-390
The possibility of avoiding the big bang singularity by means of a generalized uncertainty principle is investigated. In relation with this matter, the statistical mechanics of a free-particle system obeying the generalized uncertainty principle is studied and it is shown that the entropy of the system has a finite value in the infinite temperature limit. It is then argued that negative temperatures and negative pressures are possible in this system. Finally, it is shown that this model can remove the big bang singularity. 相似文献
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We consider the cosmological dynamics of a tachyon field localized on the extended DGP braneworld scenario. We present a detailed analysis of the critical points in the phase space of the model, their stability and late-time cosmological viability of the solutions. We study the luminosity distance behavior of this ?EDGP model and compare it with ΛCDM model. Also we show that the EDGP solutions in the presence of tachyon field can explain late time acceleration of the universe. 相似文献
55.
Parinaz Rashidi Andrew Skidmore Tiejun Wang Roshanak Darvishzadeh Shadrack Ngene Anton Vrieling 《International journal of geographical information science》2018,32(3):622-636
Knowledge about changes in wildlife poaching risk at fine spatial scale can provide essential background intelligence for law enforcement and crime prevention. We assessed interannual trends and seasonal changes in elephant poaching risk for Kenya’s Greater Tsavo ecosystem for 2002 to 2012 using spatio-temporal Bayesian modeling. Poaching data were obtained from the Kenya Wildlife Service’s database on elephant mortality. The novelty of our paper is (1) combining space and time when defining poaching risk for elephant; (2) the inclusion of environmental risk factors to improve the accuracy of the spatio-temporal Bayesian model; and (3) the separate analysis of dry and wet seasons to understand season-dependent poaching patterns. Although Tsavo’s overall poaching level increased over time, the risk of poaching differed significantly across space. Three of the 34 spatial units had a consistently high poaching risk regardless of whether models included environmental risk factors. Adding risk factors enhanced the model’s predictive power. We found that highest poaching risk areas differed between the wet and dry season. The findings improve our understanding of elephant poaching and highlight high risk areas within Tsavo where action to reduce elephant poaching is required. 相似文献
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Farrokhzad Farzad Golpour Ebrahim Taghavinezhad Maryam Choobbasti Asskar Janalizadeh 《Geotechnical and Geological Engineering》2021,39(8):5665-5674
Geotechnical and Geological Engineering - Due to the economic and tourist importance of Bandar-e Anzali coastal zone and also the high seismic risk in this area, this article provides an... 相似文献
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A modified version of the 3D finite-element hydrostatic model QUODDY-4 is used to quantify the changes in the dynamics and energetics of the M 2 surface tide in the North European Basin, induced by the spatial variability in bottom roughness. This version differs from the original one, as it introduces a module providing evaluation of the drag coefficient in the bottom boundary layer (BBL) and by accounting for the equilibrium tide. The drag coefficient is found from the resistance laws for an oscillatory rotating turbulent BBL over hydrodynamically rough and incompletely rough underlying surfaces, describing how the wave friction factor as well as other resistance characteristics depend on the dimensionless similarity parameters for the BBL. It is shown that the influence of the spatial variability in bottom roughness is responsible for some specific changes in the tidal amplitudes, phases, and the maximum tidal velocities. These changes are within the model noise, while the changes in the averaged (over a tidal cycle) horizontal wave transport and the averaged dissipation of barotropic tidal energy may be of the same orders of magnitude as are the above energetic characteristics as such. Thus, contrary to present views, ignoring the spatial variability in bottom roughness at least in the North European Basin is only partially correct: it is valid for the tidal dynamics, but is liable to break down for the tidal energetics. 相似文献
59.
B. A. Kagan A. A. Timofeev E. H. A. Rashidi 《Izvestiya Atmospheric and Oceanic Physics》2012,48(4):432-443
To find variations in the dynamics of the surface M 2 tide in the White Sea induced by the spatially inhomogeneity of the resistance coefficient, we use a modified version of the QUODDY-4 three-dimensional finite-element hydrostatic model. This version differs from the original version in that it has a module introduced to calculate the resistance coefficient in the bottom boundary layer (BBL). The resistance coefficient is found from resistance laws for an oscillating rotating turbulent BBL over hydrodynamically rough and partially rough (smoothly rough) underlying surfaces describing the dependence of the resistance coefficient and other integral characteristics of resistance on dimensionless similarity parameters: the sea-bottom Rossby number Ro, the streaming Reynolds number Re, and the relative (normalized to tidal frequency) inertial frequency f/σ. The use of spatial inhomogeneity of the resistance coefficient was shown not to lead to considerable changes in tidal characteristics. The values of these characteristics are several times larger than the instrumental measurement errors for the level and velocity but less than the errors in their calculation. 相似文献
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