A Comparative Study of Autoregressive,Autoregressive Moving Average,Gene Expression Programming and Bayesian Networks for Estimating Monthly Streamflow

In the recent years, artificial intelligence techniques have attracted much attention in hydrological studies, while time series models are rarely used in this field. The present study evaluates the performance of artificial intelligence techniques including gene expression programming (GEP), Bayesian networks (BN), as well as time series models, namely autoregressive (AR) and autoregressive moving average (ARMA) for estimation of monthly streamflow. In addition, simple multiple linear regression (MLR) was also used. To fulfill this objective, the monthly streamflow data of Ponel and Toolelat stations located on Shafarood and Polrood Rivers, respectively in Northern Iran were used for the period of October 1964 to September 2014. In order to investigate the models’ accuracy, root mean square error (RMSE), mean absolute error (MAE) and coefficient of determination (R²) were employed as the error statistics. The obtained results demonstrated that the single AR and ARMA time series models had better performance in comparison with the single GEP, BN and MLR methods. Furthermore, in this study, six hybrid models known as GEP-AR, GEP-ARMA, BN-AR, BN-ARMA, MLR-AR and MLR-ARMA were developed to enhance the estimation accuracy of the monthly streamflow. It was concluded that the developed hybrid models were more accurate than the corresponding single artificial intelligence and time series models. The obtained results confirmed that the integration of time series models and artificial intelligence techniques could be of use to improve the accuracy of single models in modeling purposes related to the hydrological studies.     

An experimental investigation on the free convection heat transfer in a horizontal cavity consisting of flow diverters

The free convection heat transfer in a horizontal cavity with adiabatic vertical and isothermally horizontal walls and adiabatic diverters has been studied experimentally in this paper. The experiments have been carried out using a Mach–Zehnder interferometer. The effects of the diverter angle ranging from 0 to 90$\circ$ and Rayleigh number based on the cavity side wall length, from 6 × 10³ to 1.2 × 10⁴ on the heat transfer from the heated wall, were studied. The results indicate that, at each Rayleigh number, the maximum and the minimum heat transfer occur at a diverter angle of 30 and 90$\circ$ , respectively. © 2012 Wiley Periodicals, Inc. Heat Trans Asian Res; Published online in Wiley Online Library ( wileyonlinelibrary.com/journal/htj ). DOI 10.1002/htj.21014     

Neuro-Fuzzy Modeling of the Free Convection Heat Transfer From a Wavy Surface

In this paper an adaptive neuro-fuzzy inference system (ANFIS) is applied to model and predict the experimental results of free convection heat transfer from a vertical array of attached cylinders, which can be considered as a wavy surface, in the presence of a vertical wall. The effects of the wall–wavy surface spacing and Rayleigh number variation on average heat transfer from the wavy surface are considered via this prediction. The training data for optimizing the ANFIS structure are based on available experimental data. A hybrid learning algorithm consisting of gradient descends method and least-squares method is used for ANFIS training. The proposed ANFIS model is developed using MATLAB functions. For the best ANFIS structure obtained in this study, the mean relative errors of the train and test data were found to be 0.02% and 1.2%, respectively. The predicted results showed that ANFIS can predict the experimental results precisely.     

Biological treatment of toluene contaminated wastewater by Alcaligenese faecalis in an extractive membrane bioreactor; experiments and modeling

Conventional wastewater treatment methods are not efficient in treating wastewaters contaminated with volatile hydrocarbons such as benzene, toluene and xylenes (BTX). The aim of this study is to enhance the efficiency of an extractive membrane bioreactor (EMBR) in treating toluene contaminated wastewater by usage of pure culture of Alcaligenese faecalis. Toluene was used as a model of toxic contaminant because of its wide presence in wastewaters contaminated with petrol derivatives. The Haldane kinetic model adequately described the dynamic behavior of the toluene biodegradation by the strain of A. faecalis over a wide range of initial toluene concentrations (50-1,000 mg L(-1)) with kinetic constants micro(max) = 0.066 h(-1), k(s) = 91.7 mg/L and k(I) = 278.2. Overall mass transfer coefficient has been measured and described as resistance in the series model. No biofilm formed on the exterior surface of the membrane; however in previous works the layer of the biofilm on the exterior surface of the membrane acts as a mass transfer resistance. A mathematical model was developed to predict the pollutant concentration profile along the tube side of the membrane modules.     

International benchmarking and regulation: an application to European electricity distribution utilities

Due to a shortage of data and increased international mergers, national energy regulators are looking to international benchmarking analyses for help in setting price controls within incentive regulation. We present an international benchmarking study of 63 regional electricity distribution utilities in six European countries that aims to illustrate the methodological and data issues encountered in the use of international benchmarking for utility regulation. The study examines the effect of the choice of benchmarking methods using DEA, COLS and SFA models. We discuss what problems of international benchmarking are highlighted by the study and how they can be overcome.     

Nonlinear mathematical modeling of seed spacing uniformity of a pneumatic planter using genetic programming and image processing

The purpose of this research was to represent the new laboratory test procedure that could be applicable in the field condition. Therefore, the performance of a pneumatic planter was investigated under laboratory conditions for maize, castor, fababean, sorghum, sugar beet, watermelon and cucumber seeds. The effect of operational speed [(1) 2.5–4 km/h and (2) 6–8.5 km/h] and vacuum pressure was evaluated by examining the quality of feed index, precision in spacing (coefficient of variation), miss index and multiple index. The most perfect operating parameter values for maize, castor, sorghum and sugar beet seeds were obtained at the first level of operating speed and 4.0 kPa pressure; for watermelon seed: second level of speed and 4.5 kPa pressure; and for cucumber seed: first level of speed and 4.5 kPa pressure. Furthermore, in order to determine the relationship between most important operating parameters affecting the performance of the pneumatic metering device and seed physical properties, regression models were developed using genetic programming (GP) algorithm. According to the results, the developed model using GP encompasses all physical properties of seeds as well as operational parameters. The model strongly describes the effect of investigated factors on seed spacing uniformity with values of the coefficient of determination R ² of 0.938, RMSE of 3.01 and MAE of 3.362087. Furthermore, the associated P value of 2.9851e−17 represents that the model is statistically significant. Model obtained from GP approach not only has a higher value of the coefficient of determination compared to regression model but is able to present the relationship between two operating parameters affecting the performance of row crop pneumatic metering device and seed physical properties, as well.

     

Cell design methodology (CDM) for balanced Carry–InverseCarry circuits in hybrid-CMOS logic style

In this paper, we propose a systematic design methodology in the category of hybrid-CMOS logic style. A huge library of circuits appropriate for low-power and high-speed applications can be obtained by employing the proposed design methodology. The methodology is before used for designing XOR/XNOR and demonstrates the excellence of the new design features. The question of whether the method can be taken advantage to design the function of Carry and its complement (Carry and InverseCarry), as the third important module of a full adder, and what to extend the answer contributes to move towards the general systematic design. All the presented designs as before have high driving capability, balanced full-swing outputs with less glitches and small number of transistors. Also these only consist of one pass-transistor in the critical path, which causes low propagation delay and high drivability. As known, hybrid-CMOS full adders can be divided into three modules, e.g., SUM, Carry and XOR. Optimising these modules has reduced power consumption, delay and the number of transistors of full adders. Therefore by embedding the balanced full-swing circuits in carry module, it can be expected that 11 new full adder circuits will possess high performance. Simulation results show that the proposed circuits exhibit better performances compared to previously suggested circuits in the proposed realistic test bench. These circuits, outperform their counterparts, are showing 24–126% improvement in the power-delay product (PDP) and 57–82% improvement in the area. All simulations have been performed with TSMC 0.13-μm technology in new full adder test bench, using HSPISE to achieve the minimum PDP.     

Effect of long-term service exposure on microstructure and mechanical properties of Alloy 617

The present work was carried out to investigate the effect of long-term service exposure on microstructure and mechanical properties of a gas turbine hot gas path component, made of Alloy 617. The results showed significant service-induced microstructural changes, such as excessive grain boundary Cr-rich M₂₃C₆ carbides formation and some oxidation features in the exposed material in compare with the solution-annealed material. Also it was found that the yield strength and hardness of the alloy have increased while the ductility of the alloy has decreased. In the similar test conditions, the stress-rupture life of the exposed alloy decreased considerably compared to the solution-annealed sample, which could be attributed to the microstructural degradation, especially formation of continuous M₂₃C₆ carbides on grain boundaries.     

Probabilistic slope stability analysis in Kahrizak landfill: effect of spatial variation of MSW’s geotechnical properties

Bulletin of Engineering Geology and the Environment - The geotechnical properties of municipal solid waste (MSW) in landfills vary considerably depending on the composition, time, and the rate of...     

Cu-TiO2 composite as fabricated by SHS method

The feasibility of Cu-TiO₂ composite production by SHS method was surveyed. Different weight percentages of CuO and Ti powders were mechanically activated, mixed, and compacted under different pressure. SHS reactions were performed in a stainless steel reactor. Combustion products were characterized by SEM, XRD, DTA, and EDS map analysis. The reaction was optimized using the HSC software results. The dispersion of reinforcing particles and the effect of compaction pressure on the hardness of produced composites were investigated. The maximum hardness value and the best dispersion of a second phase were exhibited by the specimens with an overly stoichiometric weight percentage of Ti. The principles of the process optimization were discussed.