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131.
A one-dimensional numerical model is developed with oscillating velocities and dispersions to simulate the migration process of a contaminant plume within tidally influenced aquifers. Model simulations demonstrate that a major effect the tidal fluctuation has on the migration process of a contaminant plume is the exit concentration discharging to the tidal estuary. Tidal fluctuation causes the exit concentration levels to be significantly diluted by the surface-water body of the estuary. Sensitivity analyses demonstrate that tidal fluctuation hastens the rate of plume migration near the bank of the estuary because of the relatively high advective and dispersive fluxes induced by tides. However, tides affect the migration process only over a short distance from the tidal-water interface (about 40 ft for the parameters used in this study). If the contaminant plume is located far beyond the interface, tidal fluctuations will not affect the rate of plume migration until an existing regional ground-water flow velocity brings the plume to the tidally active zone. With or without tides, the rate of contaminant migration increases with higher regional hydraulic gradient. Furthermore, the effects of tidal fluctuations on the transport process become insignificant with higher regional hydraulic gradients. 相似文献
132.
A receiver function study across the Dead Sea Transform 总被引:4,自引:0,他引:4
133.
A study on the dynamic response of a railway track is presented via a 3-D formulation based on the frequency domain Boundary Element Method (BEM) and the Finite Element Method (FEM). The railway track consists of a group of surface, massive, rigid footings resting on a viscoelastic half-space and connected by an overlaying rail structure. The BEM, employing the full-space fundamental solutions and quadrilateral elements, is used for the simulation of the elastic half-space while the FEM is used to model the rigid footings and the rail superstructure. The loading function consists of a set of externally applied, harmonic or transient loads. Frequency as well as transient, by way of FFT, results are presented for various modes of vibration. Various numerical studies assess the through-the-soil interaction of the adjacent footings, the influence of soil damping, the effect of the overlaying structure on the frequency content of the system, and the effective simulation of an infinitely long railway track by a truncated one. 相似文献
134.
Mohsen Jalali 《Environmental Geology》2007,53(2):365-374
Phosphorus (P) application in excess of plant requirement may result in contamination of drinking water and eutrophication
of surface water bodies. The phosphorous buffer capacity (PBC) of soil is important in plant nutrition and is an important
soil property in the determination of the P release potential of soils. Phosphorus sorption greatly affects both plant nutrition
and environmental pollution. For better and accurate P fertilizer recommendations, it is necessary to quantify P sorption.
This study was conducted to investigate available P and P sorption by calcareous soils in a semi-arid region of Hamadan, western
Iran. The soil samples were mainly from cultivated land. Olsen’s biocarbonate extractable P (Olsen P) varied among soils and
ranged from 10 to 80 mg kg−1 with a mean of 36 mg kg−1. Half of the soils had an Olsen P > 40 mg kg−1 and >70% of them had a concentration >20 mg kg−1, whereas the critical concentration for most crops is <15 mg P kg−1. Greater average Olsen P in soils occurred under garlic (56 mg kg−1) and potato (44 kg kg−1) fields than in dry-land wheat farming (24 mg kg−1), pasture (30 mg kg−1), and wheat (24 mg P kg−1) fields. A marked increase in fertilizer P rates applied to agricultural soils has caused P to be accumulated in the surface
soil. Phosphate sorption curves were well fitted to the Freundlich equation. The standard P requirement (SPR) of soils, defined
as the amount of P sorbed at an equilibrium concentration of 0.2 mg l−1 ranged from 4 to 102 mg kg−1. Phosphorus buffer capacity was relatively high and varied from 16 to 123 l kg−1 with an average of 58 l kg−1. In areas of intensive crop production, continual P applications as P fertilizer and farmyard manure have been used at levels
exceeding crop requirements. Surface soil accumulations of P are high enough that loss of P in surface runoff and a high risk
for P transfer into groundwater have become priority management concerns. 相似文献
135.
Leila Abdi Hossain Rahimpour-Bonab Mohsen Mirmohammad-Makki Johann Probst Saeed Rezaeian Langeroudi 《Arabian Journal of Geosciences》2018,11(19):589
Playas are shallow ephemeral lakes that form in arid and semi-arid regions. Iran has a large number of playas such as Meyghan Playa, which is located in the northeast of Arak city that borders the central Iran and Sanandaj-Sirjan zones. This study aims to investigate the mineralogical, sedimentological, and geochemical characteristics of the playa sediments. In order to determine the palaeoenvironment, we carried out X-ray diffraction (XRD), X-ray fluorescence (XRF), and scanning electron microscopy (SEM) studies. Meyghan Playa sediments consist of very fine-grained sediments and contain both evaporite and clastic minerals. The evaporite minerals include calcite, gypsum, halite, glauberite, and thenardite, whereas clastic minerals are quartz and clay. The calcite abundance decreases from the margin to the central portion of the playa but gypsum and halite abundances show an increasing trend from the margin to the center. This observation is consistent with the general zonation of other playas. Variations of calcite and gypsum concentration profiles present increasing and decreasing trends with depth, which could be ascribed to the changes in climatic factors. These factors include brine chemical modifications owing to changes in evaporation and precipitation rates and variations in relative abundance of anions-cations or in the rate of clastic and evaporite minerals due to variations in the freshwater influx (climatic changes) with time. A decrease in calcite and increase in sulfate minerals (especially gypsum) with depth is probably due to the higher water level and rainfall, a more humid climate, and salinity variations. 相似文献
136.
137.
Karim Zadeh Zarin Ghafory-Ashtiany Mohsen Kalantari Afshin Shokuhirad Sahar 《Bulletin of Earthquake Engineering》2022,20(11):5905-5942
Bulletin of Earthquake Engineering - One of the main components for developing regional seismic risk models is the fragility functions of common building types. Due to the differences between the... 相似文献
138.
Hasan Ghasemzadeh Mohsen Tarzaban Mohammad Mahdi Hajitaheriha 《Geotechnical and Geological Engineering》2018,36(4):2189-2215
Battered piles are usually used to counteract lateral forces in a pile group. As there is little spacing between piles, they are affected by one another, and there is interaction between them. In this study, pile–soil–pile interaction in a group of battered piles was numerically simulated using finite element analysis. Double and frictional pile groups under static lateral and axial loadings were analyzed separately. The effects of batter angle, slenderness ratio, spacing between piles, pile–soil stiffness ratio, and soil plasticity on interaction factors were computed and presented in curves. 相似文献
139.
A series of scalar and vector intensity measures is examined to determine their suitability within the seismic risk assessment of liquid storage tanks. Using a surrogate modelling approach on a squat tank that is examined under both anchored and unanchored support conditions, incremental dynamic analysis is adopted to generate the distributions of response parameters conditioned on each of the candidate intensity measures. Efficiency and sufficiency metrics are used in order to perform the intensity measure evaluation for individual failure modes, while a comparison in terms of mean annual frequency of exceedance is performed with respect to a damage state that is mutually governed by the impulsive and convective modes of the tank. The results reveal combinations of spectral acceleration ordinates as adequate predictors, among which the average spectral acceleration is singled out as the optimal solution. The sole exception is found for the sloshing‐controlled modes of failure, where mainly the convective period spectral acceleration is deemed adequate to represent the associated response due to their underlying linear relationship. A computationally efficient method in terms of site hazard analysis is finally proposed to serve in place of the vector‐valued intensity measures, providing a good match for the unanchored tank considered and a more conservative one for the corresponding anchored system. 相似文献
140.
Nima Aein Najarchi Mohsen Hezaveh Seyyed Mohammad Mirhosseini Mehdi NajafiZadeh Mohammad Zeighami Ehsanollah 《Water Resources》2020,47(4):537-549
Water Resources - Combined weir-gate structure is one of the important structures which are control the water level, measure discharge and avoid sediment deposition behind the weir. In this study,... 相似文献