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排序方式: 共有118条查询结果,搜索用时 31 毫秒
51.
J. Nouri B. Lorestani N. Yousefi N. Khorasani A. H. Hasani F. Seif M. Cheraghi 《Environmental Earth Sciences》2011,62(3):639-644
This study aims to assess the extent of metal accumulation by plants found in a mining area in Hamedan Province in the central
west part of Iran. It also investigates to find suitable plants for phytoextraction and phytostabilization as two phytoremediation
strategies. Plants with a high bioconcentration factor (BCF) and low translocation factor (TF) have the potential for phytostabilization
while plants with both BCFs and TFs greater than one have the potential to be used for phytoextraction. In this study, shoots
and roots of the 12 plant species and the associated soil samples were collected. The collected samples were then analyzed
by measurement of total concentrations of trace elements (Pb, Zn, Mn and Fe) using atomic absorption spectrophotometer. Simultaneously,
BCF and TF parameters were calculated for each element. Results showed that although samples suitable for phytoextraction
of Pb, Zn, Mn and Fe and phytostabilization of Fe were not detected, Scrophularia scoparia was the most suitable for phytostabilization of Pb, Centaurea virgata,
Echinophora platyloba and Scariola orientalis had the potential for phytostabilization of Zn and Centaurea virgata and Cirsium congestum were the most efficient in phytostabilization of Mn. Present study showed that native plant species growing on contaminated
sites may have the potential for phytoremediation. 相似文献
52.
Bore holes were drilled in the Senonian limestone of the Hedils-Jalta area (northern Tunisia) in order to determine their potential as an aquifer. Structural, tectonic and hydrogeologic data compilation shows the discrimination of productive and not productive zones. Differential hydraulic productivity was recognised with four distinct productive geological zones separated by a sterile corridor trending NW–SE. The structure consists of two compressional dihedrons, limited by two conjugate strike-slip faults, trending NNE–SSW and nearly E–W. The reduction of the (1) potential reservoir, (2) the low hydraulic productivity of the central band, (3) the torsion of the fold axis in eccentric arcs on both sides of the compressive relay and (4) the differential hydrogeological zonation are all related to the distribution of stress in the interference zone between conjugate strike-slip faults and to the reorientation of the stress field in their vicinity. This study constitutes a main database in establishing strategies for groundwater exploration in the similar zones. 相似文献
53.
Many methods for modeling urban expansion are available. Most of these computational models demand a variety of large‐scale environmental and socio‐economic data to investigate the relationship between urban expansion and its driving forces. These requirements are not always fulfilled, particularly in developing countries due to a lack of data availability. This necessitates methods not suffering from data limitations to ease their application. Consequently, this research presents a morphological approach for predicting urban expansion on the basis of spatiotemporal dynamics of urban margins by investigating the interior metropolitan area of Tehran, Iran as a case study. To assess the model's performance, urban expansion is monitored from 1976 to 2012. The proposed model is evaluated to ensure that the prediction performance for the year 2012 is acceptable. For the year 2024, the model predicts Tehran's urban expansion at an overall R2 of 88%. Accordingly, it is concluded that: (1) although this approach only inputs urban margins, it represents a suitable and easy‐to‐use urban expansion model; and (2) urban planners are faced with continuing urban expansion. 相似文献
54.
A reductive perturbation technique is employed to solve the fluid-Poisson equations in spherical geometry describing a weakly nonlinear electron–acoustic (EA) waves in unmagnetized plasma consisting of stationary ions, cold electrons and kappa distributed hot electrons. It is shown that a variable coefficient Kadomtsev–Petviashvili (KP) equation governs the evolution of scalar potential describing propagation of EA waves. The influence of suprathermality and geometry effects on propagation of EA solitary waves is investigated. We found that when electrons evolve toward their thermodynamic equilibrium, EA solitons are generated with large amplitudes. Also it is shown that EA solitary structures can be significantly modified by transverse perturbations. 相似文献
55.
Effect of combined translation and torsion on undrained uplift capacity of plate anchors: Plastic limit analysis (PLA) solution
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Uplift capacity of plate anchors has been the focus of numerous studies, because anchor plates are designed for pull‐out in normal operating conditions. However, the response of plate anchors under 6‐degrees‐of‐freedom loading caused during extreme loading conditions is poorly understood. The purpose of this study is to propose a simple yet sufficiently accurate analytical solution to investigate the behavior of plate anchor under combined in‐plane translation and torsion and to evaluate its effect on the plate uplift bearing capacity. To this end, a modified plastic limit analysis (PLA) approach is introduced and compared with limit equilibrium and simplified upper bound baseline solutions. The proposed method is verified with 3‐dimensional finite element. The variables considered in this study include plate aspect ratio, plate thickness, as well as load direction and eccentricity. Results of analytical solutions indicate the insensitivity of the “shape” of the shear‐torsion yield envelope to plate thickness. This finding facilitates the use of simplified yet reasonable yield envelope for infinitely thin plate obtained from simplified PLA approach for other plate thicknesses. The “size” of the failure envelope (controlled by pure torsional and translational capacity) could be predicted fairly accurately by PLA and limit equilibrium methods. Combination of these analytical methods offers a simple yet reasonably accurate solution to describe shear‐torsion response of anchor plate. The obtained shear‐torsion yield envelope is then fitted in the generalized 6‐degrees‐of‐freedom yield surface which describes the reducing effect of moment, torsion, and planar forces on the uplift capacity of plate. 相似文献
56.
Tayeb Sadeghifar Maryam Nouri Motlagh Massoud Torabi Azad Mahdi Mohammad Mahdizadeh 《Marine Geodesy》2017,40(6):454-465
The prediction of wave parameters has a great significance in the coastal and offshore engineering. For this purpose, several models and approaches have been proposed to predict wave parameters, such as empirical, soft computing, and numerical based approaches. Recently, soft computing techniques such as recurrent neural networks (RNN) have been used to develop sea wave prediction models. In this study, the RNN for wave prediction based on the data gathered and the measurement of the sea waves in the Caspian Sea, in the north of Iran is used for this study. The efficiency of RNNs for 3, 6, and 12 hourly and diurnal wave prediction using correlation coefficients is calculated to be 0.96, 0.90, 0.87, and 0.73, respectively. This indicates that wave prediction by using RNNs yields better results than the previous neural network approaches. 相似文献
57.
Accumulation of heavy metals in soil and uptake by plant species with phytoremediation potential 总被引:14,自引:1,他引:13
J. Nouri N. Khorasani B. Lorestani M. Karami A. H. Hassani N. Yousefi 《Environmental Earth Sciences》2009,59(2):315-323
Contamination of heavy metals represents one of the most pressing threats to water and soil resources, as well as human health.
Phytoremediation can be potentially used to remediate metal contaminated sites. In this study, concentrations of copper, zinc,
iron, and magnesium accumulated by native plant species were determined in field conditions of Hame Kasi iron and copper mine
in the central part of Iran in Hamadan province. The results showed that metal accumulation by plants differed among species
and tissue bodies. Species grown in substrata with elevated metals contained significantly higher metals in plants. Metals
accumulated by plants were mostly distributed in root tissues, suggesting that an exclusion strategy for metal tolerance exists
widely amongst them. The mentioned species could accumulate relatively higher metal concentrations far above the toxic concentration
in the plant shoots. With high translocation factor, metal concentration ratio of plant shoots to roots indicates internal
detoxification metal tolerance mechanism; thus, they have potential for phytoextraction. The factors affecting metal accumulation
by plant species including metal concentrations, pH, electrical conductivity, and nutrient status in substrata were measured.
Mostly, concentrations of zinc and copper in both aboveground and underground tissues of the plants were significantly, positively
related to their total in substrata, while iron, zinc, and copper were negatively correlated to soil phosphorus. 相似文献
58.
The Cimmerian Orogeny in northern Iran: tectono-stratigraphic evidence from the foreland 总被引:2,自引:0,他引:2
Markus Wilmsen Franz T. Fürsich Kazem Seyed-Emami Mahmoud Reza Majidifard Jafar Taheri 《地学学报》2009,21(3):211-218
From the Permian onwards, the Gondwana-derived Iran Plate drifted northward to collide with Eurasia in the Late Triassic, thereby closing the Palaeotethys. This Eo-Cimmerian Orogeny formed the Cimmeride fold-and-thrust belt. The Upper Triassic–Middle Jurassic Shemshak Group of northern Iran is commonly regarded as the Cimmerian foreland molasse. However, our tectono-stratigraphic analysis of the Shemshak Group resulted in a revised and precisely dated model for the Triassic–Jurassic geodynamic evolution of the Iran Plate: initial Cimmerian collision started in the Carnian with subsequent Late Triassic synorogenic peripheral foreland deposition (flysch, lower Shemshak Group). Subduction shifted south in the Norian (onset of Neotethys subduction below Iran) and slab break-off around the Triassic–Jurassic boundary caused rapid uplift of the Cimmerides followed by Liassic post-orogenic molasse (middle Shemshak Group). During the Toarcian–Aalenian (upper Shemshak Group), Neotethys back-arc rifting formed a deep-marine basin, which developed into the oceanic South Caspian Basin during the Late Bajocian–Late Jurassic. 相似文献
59.
Mojtaba Naeej Mohamad Reza Naeej Jafar Salehi Reyhaneh Rahimi 《Geomechanics and Geoengineering》2017,12(2):107-114
The hydraulic conductivity, Ks, is one of the most important hydraulic properties which controls the water and solute movement into the soil. It is measured on soil specimens in the laboratory. On the other hand, sometimes it is obtained by tests carried out in the field by a number of researchers. Therefore, several experimental formulas have developed to predict it. Recently, soft computing tools have been used to evaluate the hydraulic conductivity. However, these tools are not as transparent as empirical formulas. In this study, another soft computing approach, i.e. model trees, have been used for predicting the hydraulic conductivity. The main advantage of model trees is that, unlike the other data learning tools, they are easier to use and represent understandable mathematical rules more clearly. In this paper, a new formula that includes some parameters is derived to estimate the hydraulic conductivity. To develop the new formulas, experimental data sets of hydraulic conductivity were used. A comparison is made between the estimated hydraulic conductivity by this new formula and formulas given by other’s researches. 相似文献
60.
Masoumeh Molaei Seyed Hamid Vaziri Morteza Taherpour-Khalil-Abad Jafar Taheri 《Arabian Journal of Geosciences》2017,10(14):317
Neotrocholina Reichel, 1956 is one of the most important benthic foraminifera in Early Cretaceous. Some of the species of this genus are indexes in biostratigraphy especially for this interval (e.g., Neotrocholina friburgensis: Late Barremian–Early Aptian; Neotrocholina aptiensis: Early Aptian). In order to conduct accurate paleontological investigations, sampling from the carbonate units of the Tirgan Formation in Kopet Dagh sedimentary basin is done. According to the occurrence level in the studied stratigraphic sections as well as biometric interpretations, two species of this genus (N. friburgensis and Neotrocholina valdensis) are pointed out. 相似文献