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排序方式: 共有253条查询结果,搜索用时 15 毫秒
1.
Chemical characteristics of groundwater in parts of mountainous region, Alvand, Hamadan, Iran 总被引:5,自引:0,他引:5
Mohsen Jalali 《Environmental Geology》2006,51(3):433-446
Eighty-seven groundwater samples have been collected from a mountainous region (Alvand, Iran) for hydrochemical investigations to understand the sources of dissolved ions and assess the chemical quality of the groundwater. Most water quality parameters are within World Health Organization acceptable limits set for drinking water. The least mineralized water is found closest to the main recharge zones and the salinity of water increased towards the north of the basin. The most prevalent water type is Ca–HCO3 followed by water types Ca–NO3, Ca–Cl, Ca–SO4 and Mg–HCO3. The Ca–NO3 water type is associated with high nitrate pollution. Agricultural and industrial activities were associated with elevated level of NO3−. Mineral dissolution/weathering of evaporites dominates the major element hydrochemistry of the area. Chemical properties of groundwater in Alvand region are controlled both by natural geochemical processes and anthropogenic activities. 相似文献
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The optimal seismic design of structures requires that time history analyses (THA) be carried out repeatedly. This makes the optimal design process inefficient, in particular, if an evolutionary algorithm is used. To reduce the overall time required for structural optimization, two artificial intelligence strategies are employed. In the first strategy, radial basis function (RBF) neural networks are used to predict the time history responses of structures in the optimization flow. In the second strategy, a binary particle swarm optimization (BPSO) is used to find the optimum design. Combining the RBF and BPSO, a hybrid RBF-BPSO optimization method is proposed in this paper, which achieves fast optimization with high computational performance. Two examples are presented and compared to determine the optimal weight of structures under earthquake loadings using both exact and approximate analyses. The numerical results demonstrate the computational advantages and effectiveness of the proposed hybrid RBF-BPSO optimization method for the seismic design of structures. 相似文献
3.
How to select a limited number of strong ground motion records (SGMRs) is an important challenge for the seismic collapse capacity assessment of structures. The collapse capacity is considered as the ground motion intensity measure corresponding to the drift‐related dynamic instability in the structural system. The goal of this paper is to select, from a general set of SGMRs, a small number of subsets such that each can be used for the reliable prediction of the mean collapse capacity of a particular group of structures, i.e. of single degree‐of‐freedom systems with a typical behaviour range. In order to achieve this goal, multivariate statistical analysis is first applied, to determine what degree of similarity exists between each selected small subset and the general set of SGMRs. Principal Component analysis is applied to identify the best way to group structures, resulting in a minimum number of SGMRs in a proposed subset. The structures were classified into six groups, and for each group a subset of eight SGMRs has been proposed. The methodology has been validated by analysing a first‐mode‐dominated three‐storey‐reinforced concrete structure by means of the proposed subsets, as well as the general set of SGMRs. The results of this analysis show that the mean seismic collapse capacity can be predicted by the proposed subsets with less dispersion than by the recently developed improved approach, which is based on scaling the response spectra of the records to match the conditional mean spectrum. Copyright © 2010 John Wiley & Sons, Ltd. 相似文献
4.
Interest in rock slope stability in mountainous regions has increased greatly in recent years.This issue has become a topic of major interest for geoscientists and engineering professionals,as well as for private citizens and local administrators,in many parts of the world.This paper evaluates the stability of seven rock slopes along the KamyaranMarivan tourist road,Kurdistan province,Iran,using various methods.The two main reasons for performing this research were to determine whether different methods of stability analysis provide the same results,and to determine how different factors such as the presence of water,tension cracks,and seismic forces affect the stability of these rock slopes.Firstly,field investigations were performed to obtain the engineering characteristics of the rock masses,discontinuities,and intact rocks of the slopes.Secondly,laboratory tests were carried out on rock samples obtained from the slopes,to determine the engineering properties of the intact rocks.Then for each rock slope,the contour diagram of discontinuities and slope face was drawn in the Dips v.5.1 software environment,and the failure mechanism was determined based on the kinematic or stereographic method.Next,the factors of safety of the rock slopes were calculated using the limit equilibrium method,based on the failure mechanisms resulting from the kinematic method.The accuracy of the results obtained by these two methods was investigated using SWedge v.4.0 software.The results indicated that four rock slopes have a potential for plane,wedge,and toppling failure,and three others are stable.Also,it was found that the stability of the studied rock slopes decreases greatly in the presence of water,tension cracks,and seismic forces. 相似文献
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Integrating cellular automata,artificial neural network,and fuzzy set theory to simulate threatened orchards: application to Maragheh,Iran 总被引:1,自引:0,他引:1
Urbanization processes challenge the growth of orchards in many cities in Iran. In Maragheh, orchards are crucial ecological, economical, and tourist sources. To explore orchards threatened by urban expansion, this study first aims to develop a new model by coupling cellular automata (CA) and artificial neural network with fuzzy set theory (CA–ANN–Fuzzy). While fuzzy set theory captures the uncertainty associated with transition rules, the ANN considers spatial and temporal nonlinearities of the driving forces underlying the urban growth processes. Second, the CA–ANN–Fuzzy model is compared with two existing approaches, namely a basic CA and a CA coupled with an ANN (CA–ANN). Third, we quantify the amount of orchard loss during the last three decades as well as for the upcoming years up to 2025. Results show that CA–ANN–Fuzzy with 83% kappa coefficient performs significantly better than conventional CA (with 51% kappa coefficient) and CA–ANN (with 79% kappa coefficient) models in simulating orchard loss. The historical data shows a considerable loss of 26% during the last three decades, while the CA–ANN–Fuzzy simulation reveals a considerable future loss of 7% of Maragheh’s orchards in 2025 due to urbanization. These areas require special attention and must be protected by the local government and decision-makers. 相似文献
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An accurate estimate of the groundwater inflow to a tunnel is one of the most challenging but essential tasks in tunnel design and construction. Most of the numerical or analytical solutions that have been developed ignore tunnel seepage conditions, material properties and hydraulic-head changes along the tunnel route during the excavation process, leading to inaccurate prediction of inflow rates. A method is introduced that uses MODFLOW code of GMS software to predict inflow rate as the tunnel boring machine (TBM) gradually advances. In this method, the tunnel boundary condition is conceptualized and defined using Drain package, which is simulated by dividing the drilling process into a series of successive intervals based on the tunnel excavation rates. In addition, the drain elevations are specified as the respective tunnel elevations, and the conductance parameters are assigned to intervals, depending on the TBM type and the tunnel seepage condition. The Qomroud water conveyance tunnel, located in Lorestan province of Iran, is 36 km in length. Since the Qomroud tunnel involved groundwater inrush during excavating, it is considered as a good case study to evaluate the presented method. The groundwater inflow to this tunnel during the TBM advance is simulated using the proposed method and the predicted rates are compared with observed rates. The results show that the presented method can satisfactorily predict the inflow rates as the TBM advances. 相似文献
10.
Asiyeh SHEIKHZADEH Hossein BASHARI Mostafa TARKESH ESFAHANI SayedHamid MATINKHAH Mohsen SOLEIMANI 《山地科学学报》2019,(6)
This study aimed to identify indicator species and explore the most important environmental and management variables contributing to vegetation distribution in a hilly upper dam landscape in Zagros Mountain chain, Iran. A stratified random sampling method was used to collect topographic, edaphic, management and vegetation data. The density and cover percentage of perennial species were measured quantitatively. Indicator species were identified using the two-way indicator species analysis. Besides calculating physiognomic factors in sample sites, 24 soil samples were collected from 0 to 30 cm of soil depth and analyzed in terms of gravel percentage, texture, saturation moisture, organic matter, pH and electrical conductivity in saturation extract, lime percentage, soluble calcium and magnesium, available phosphorus, Cation Exchange Capacity(CEC) and soluble sodium and potassium. Multivariate techniques including Canonical Correspondence Analysis and Multi-Dimensional Scaling were used to explore the relationships of species with environmental and management variables. Seven plants were identified as indicator species due to being significantly correlated with management(grazing or non-grazing) and edaphic variables such as CEC, soil texture, pH, CaCO_3 percentage and physiographic variable including slope, elevation, and convex and concave formations(p 0.05). Overall, overgrazing and its subsequent effects on soil characteristics, loss of vegetation cover and trampling were found as the major causes of deterioration. Sustainable and integrated management practices such as the implementation of appropriate grazing systems were suggested to enhance soil quality and reduce the accelerated erosion in upper dam zones. 相似文献