A hybrid SVM-FFA method for prediction of monthly mean global solar radiation     

Shahaboddin Shamshirband  Kasra Mohammadi  Chong Wen Tong  Mazdak Zamani  Shervin Motamedi  Sudheer Ch 《Theoretical and Applied Climatology》2016,125(1-2):53-65

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Effect of Fines Type and Content of Sand on Correlation Between Shear Wave Velocity and Liquefaction Resistance     

Nima Akbari Paydar  Mohammad Mehdi Ahmadi 《Geotechnical and Geological Engineering》2016,34(6):1857-1876

The use of shear wave velocity (V _s) measurements as an in situ test for evaluation of liquefaction potential has increased substantially due to its advantages. Relatively large numbers of studies have been performed to establish the correlation between V _s and liquefaction resistance (CRR) of clean sands. Usually, natural sands contain silt and/or clay, and previous studies have shown that both the amount of fines and their nature influence the values of CRR as well as V _s. Therefore, the CRR–V _s correlations may also be affected by fines content and type of sandy soils. However, effect of fines content and especially fines type of sandy soils on the correlation between V _s and CRR is inadequately addressed in the literature. In this study, cyclic triaxial and bender element tests were conducted on samples of sand containing various amounts of different types of fines, and the effects of fines on the values of CRR and V _s are investigated. The results show that G ₀ and CRR reduce even when small amounts of fines are added to sand. Therefore, use of plasticity index (PI) of the fines fraction is better than the PI of the overall soil when trying to assess the effects of fines. Using obtained experimental data as well as the established semiempirical CRR–V _s relationship, the CRR–V _s correlation was developed for all the tested soils, and the effect of fines type on the correlation is also examined. Based on the results obtained in this study, CRR–V _s correlation is affected by both the amount and the plasticity of the fines present in the sand, and this correlation is soil specific.  相似文献   

Spatiotemporal analysis of precipitation and temperature concentration using PCI and TCI: a case study of Khuzestan Province,Iran     

Ahmadi  Farshad  Nazeri Tahroudi  Mohammad  Mirabbasi  Rasoul  Kumar  Rohitashw 《Theoretical and Applied Climatology》2022,149(1-2):743-760

Theoretical and Applied Climatology - Temperature and precipitation are the basic elements of climate, and their variation can change the water demands of different uses. In this study, the trend...  相似文献   

Effects of extrinsic curvature as modified Chaplygin gas and Lorentz violation     

F. Ahmadi 《Astrophysics and Space Science》2016,361(5):156

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Stability of elastic frames subjected to earthquake excitations     

Goodarz Ahmadi  Samir Abdel-Rahman 《地震工程与结构动力学》1986,14(3):455-474

Dynamic stability of elastic multistorey frame structures subjected to vertical earthquake ground accelerations is studied. Different stationary, non-stationary, white and non-white random models for earthquake strong motion are considered. The concepts of mean-square and almost-sure stability are reviewed and the corresponding stability theorems are presented. Several general criteria regarding the dynamic stability of the equilibrium state of multistorey frames subjected to random excitations are developed. A few examples concerning the stability of single and multi-degree-of-freedom structures under earthquake excitations are presented. The stability of motion of frames under combined horizontal–vertical acceleration is also briefly discussed.  相似文献   

Bounds on earthquake response of elastic columns     

Goodarz Ahmadi  Naser Mostaghel 《地震工程与结构动力学》1982,10(6):769-777

The dynamics of an elastic column subjected to vertical as well as horizontal ground acceleration during an earthquake strong motion is considered. The Liapunov method of stability analysis is employed and several bounds on the maximum lateral displacement and bending stress are obtained and discussed.  相似文献   

Predicting Formation Pore-Pressure from Well-Log Data with Hybrid Machine-Learning Optimization Algorithms     

Farsi  Mohammad  Mohamadian  Nima  Ghorbani  Hamzeh  Wood  David A.  Davoodi  Shadfar  Moghadasi  Jamshid  Ahmadi Alvar  Mehdi 《Natural Resources Research》2021,30(5):3455-3481

Natural Resources Research - Accurate prediction of pore-pressures in the subsurface is paramount for successful planning and drilling of oil and gas wellbores. It saves cost and time and helps to...  相似文献   

Temporal variability of suspended sediment sources in an alpine catchment combining river/rainfall monitoring and sediment fingerprinting     

Oldrich Navratil  Olivier Evrard  Michel Esteves  Cédric Legout  Sophie Ayrault  Julien Némery  Ainhoa Mate‐Marin  Mehdi Ahmadi  Irène Lefèvre  Alain Poirel  Philippe Bonté 《地球表面变化过程与地形》2012,37(8):828-846

Influence of the rainfall regime on erosion and transfer of suspended sediment in a 905‐km² mountainous catchment of the southern French Alps was investigated by combining sediment monitoring, rainfall data, and sediment fingerprinting (based on geochemistry and radionuclide concentrations). Suspended sediment yields were monitored between October 2007 and December 2009 in four subcatchments (22–713 km²). Automatic sediment sampling was triggered during floods to trace the sediment origin in the catchment. Sediment exports at the river catchment outlet (330 ± 100 t km^‐2 yr^‐1) were mainly driven (80%) by widespread rainfall events (long duration, low intensities). In contrast, heavy, local and short duration storms, generated high peak discharges and suspended sediment concentrations in small upstream torrents. However, these upstream floods had generally not the capacity to transfer the sediment down to the catchment outlet and the bulk of this fine sediment deposited along downstream sections of the river. This study also confirmed the important contribution of black marls (up to 70%) to sediment transported in rivers, although this substrate only occupies c. 10% of the total catchment surface. Sediment exports generated by local convective storms varied significantly at both intra‐ and inter‐flood scales, because of spatial heterogeneity of rainfall. However, black marls/marly limestones contribution remained systematically high. In contrast, widespread flood events that generate the bulk of annual sediment supply at the outlet were characterized by a more stable lithologic composition and by a larger contribution of limestones/marls, Quaternary deposits and conglomerates, which corroborates the results of a previous sediment fingerprinting study conducted on riverbed sediment. Copyright © 2012 John Wiley & Sons, Ltd.  相似文献   

Probabilistic reservoir operation using Bayesian stochastic model and support vector machine   总被引：3，自引：0，他引：3  

Mohammad Karamouz  Azadeh Ahmadi  Ali Moridi   《Advances in water resources》2009,32(11):1588-1600

Available water resources are often not sufficient or too polluted to satisfy the needs of all water users. Therefore, allocating water to meet water demands with better quality is a major challenge in reservoir operation. In this paper, a methodology to develop operating strategies for water release from a reservoir with acceptable quality and quantity is presented. The proposed model includes a genetic algorithm (GA)-based optimization model linked with a reservoir water quality simulation model. The objective function of the optimization model is based on the Nash bargaining theory to maximize the reliability of supplying the downstream demands with acceptable quality, maintaining a high reservoir storage level, and preventing quality degradation of the reservoir. In order to reduce the run time of the GA-based optimization model, the main optimization model is divided into a stochastic and a deterministic optimization model for reservoir operation considering water quality issues.The operating policies resulted from the reservoir operation model with the water quantity objective are used to determine the released water ranges (permissible lower and upper bounds of release policies) during the planning horizon. Then, certain values of release and the optimal releases from each reservoir outlet are determined utilizing the optimization model with water quality objectives. The support vector machine (SVM) model is used to generate the operating rules for the selective withdrawal from the reservoir for real-time operation. The results show that the SVM model can be effectively used in determining water release from the reservoir. Finally, the copula function was used to estimate the joint probability of supplying the water demand with desirable quality as an evaluation index of the system reliability. The proposed method was applied to the Satarkhan reservoir in the north-western part of Iran. The results of the proposed models are compared with the alternative models. The results show that the proposed models could be used as effective tools in reservoir operation.  相似文献   

Predicting blast-induced ground vibration using various types of neural networks     

M. Monjezi  M. Ahmadi  M. Sheikhan  A. Bahrami  A.R. Salimi 《Soil Dynamics and Earthquake Engineering》2010

Prediction of vibration is very important in mining operations as well as civil engineering projects. In this paper, multi layer perceptron neural network (MLPNN), radial basis function neural network (RBFNN) and general regression neural network (GRNN) were utilized to predict ground vibration level in a Sarcheshmeh copper mine, Iran. It was observed that the MLPNN gives the best results. For this technique root mean square error and coefficient of correlation were found 0.03 and 0.954, respectively. Sensitivity analysis showed that distance from the blast, number of holes per delay and maximum charge per delay are the most effective parameters in making ground vibration in the blasting operation.  相似文献