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Natural Resources Research - The quality of surface waters plays a key role in the sustainability of ecological systems. Measuring water quality parameters (WQPs) is of high... 相似文献
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Mohammad Najafzadeh Jalal Shiri Mohammad Rezaie-Balf 《Marine Georesources & Geotechnology》2018,36(2):227-235
Scouring in the channel contractions occurs due to the flow concentration within them inducing excessive bed shear stress. This is a complex process, so it is difficult to describe it through a general empirical model, the present research work describes contemporary conceptual relationships to estimate the local scour depth under equilibrium and clear water conditions in rectangular channels. Incidentally, gene-expression programming (GEP), evolutionary polynomial regression (EPR), and model tree (MT)-based formulations were utilized to predict the scour depth at long contractions. The input variables comprising average flow velocity, critical threshold velocity of sediment movement, flow depth, median particle diameter, geometric standard deviation, and uncontracted and contracted channel widths were used to feed the applied models. The performances of the developed approach were compared with those calculated using existing scour prediction equations. The results showed that the developed MT approach in terms of linear relationships could predict the scour depth more precisely than GEP, EPR, and the traditional equations. What is more, dimensionless parameter of h1/b1 (ratio of upstream flow depth to uncontracted channel width) was determined as the most influential variable in predicting the scour depth in long contractions. 相似文献
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Mohammad Najafzadeh Farid Saberi-Movahed Saeed Sarkamaryan 《Marine Georesources & Geotechnology》2018,36(5):589-602
Existence of debris structures inevitably ascends the rate of scour process around bridge piers and flow area not only lead into remarkable deviation of flow but also increase the velocity around bridge piers. A myriad of experimental and field studies to understand effective parameters on the scour depth with debris effects were conducted. To reach permissible values of the scour depth for the practical uses, relationships extracted in previous investigations suffer from lack of generalization for experimental data ranges. In this way, neuro-fuzzy group method of data handling (NF-GMDH)-based self-organized models is applied to evaluate the pier scour depth. In this study, NF-GMDH network is implemented using evolutionary algorithms listed particle swarm optimization (PSO), gravitational search algorithm (GSA), and genetic algorithm (GA). In all, 243 experimental datasets including a wide range of input and output parameters to develop the proposed models were compiled from various literature. The efficiency of NF-GMDH networks for training and testing stages was perused. NF-GMDH-PSO model provided the scour depth with more precise predictions (root mean squared error (RMSE)?=?0.388 and scatter index (SI)?=?0.343) in comparison with NF-GMDH-GA (RMSE?=?0.402 and SI?=?0.361) and NF-GMDH-GSA (RMSE?=?0.456 and SI?=?0.407) networks. In addition, blockage ratio (ΔA) was taken into account as the most sumptuous parameter with utmost level of effectiveness using the sensitivity analysis. 相似文献
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ABSTRACTIn this research, group method of data handling (GMDH) as a one of the self-organized approaches is utilized to predict three-dimensional free span expansion rates around pipeline due to waves. The GMDH network is developed using gene-expression programming (GEP) algorithm. In this way, GEP was performed in each neuron of GMDH instead of polynomial quadratic neuron. Effective parameters on the three-dimensional scour rates include sediment size, pipeline geometry, and wave characteristics upstream of pipeline. Four-dimensionless parameters are considered as input variables by means of dimensional analysis technique. Furthermore, scour rates along the pipeline, vertical scour rate, and additionally scour rates in the left and right of pipeline are determined as output parameters. Results of the proposed GMDH-GEP models for the training stages and testing ones are evaluated using various statistical indices. Performances of the GMDH-GEP models are compared with artificial neural network (ANN), GEP, GMDH, and traditional equations-based regression models. Moreover, sensitivity analysis and parametric study are conducted to perceive influences of different input parameters on the three-dimensional scour rates. 相似文献
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S. Baikpour H. Motiei K. Najafzadeh 《International Journal of Environmental Science and Technology》2016,13(8):1951-1972
Solving the problem of waste is one of the central tasks of environmental protection. It is becoming increasingly difficult to find suitable sites that are acceptable to the public. Salt and salt formations have relevant properties to be utilizing as a repository for each kind of waste. The favourable properties of salt make rock salt highly suitable as a host rock, in particular for non-radioactive and radioactive wastes. Tehran and suburb as an industrial state require a waste reservoir. The Great Kavir (the largest salt desert in Iran) with more than 50 diapirs has surrounded the eastern and southern part of Tehran Province. The Qom and Garmsar basins are the nearest salt diapirs to Tehran province, and there are suitable repository for waste disposal. Great Kavir diapirs have been investigated as a case study based on surface and subsurface studies for its suitability to host a repository for various types of waste. The procedure should be based on field work for surface investigation and also include geophysical studies for subsurface investigations. This research work is presented in regard to site selection in the Central Iran Salt Basins for deposition of only certain types of waste. Results of this study will indicate if the Central Iran Salt Basins are appropriate place to deposit industrial wastes in the deep bedded salt. 相似文献
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Natural Hazards - Due to a wide range of socio-economic losses caused by drought over the past decades, having a reliable insight of drought properties plays a key role in monitoring and... 相似文献
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