University of Tabriz

About: University of Tabriz is a education organization based out in Tabriz, Iran. It is known for research contribution in the topics: Population & Nanocomposite. The organization has 12141 authors who have published 20976 publications receiving 313982 citations.

New hybrid structure for multilevel inverter with fewer number of components for high-voltage levels

Abstract: Application of multilevel inverters for higher voltage goals in industries has become more popular. In this study, new structures for symmetric, asymmetric and hybrid multilevel inverter are recommended. The proposed hybrid structure is used in high-voltage levels. The proposed structures can generate a great number of output voltage levels with minimum number of power electronic components such as insulated gate bipolar transistors (IGBTs) and gate drivers. For proposed asymmetric and hybrid inverter, new methods for determination of dc voltage sources values are presented. Comparison of the results of various multilevel inverters is presented to reflect the merits of the recommended structures. The operations of the proposed multilevel inverter structures are verified with the experimental and simulation results of an asymmetric 15-level prototype and a 19-level hybrid inverter. Fundamental frequency-switching method is applied to the new topologies to trigger the power switches for controlling the voltage levels generated on the output. Verification of the analytical results is performed using MATLAB/SIMULINK software.

A comparative study of artificial neural network (MLP, RBF) and support vector machine models for river flow prediction

Abstract: This study investigates the applicability of multilayer perceptron (MLP), radial basis function (RBF) and support vector machine (SVM) models for prediction of river flow time series. Monthly river flow time series for period of 1989–2011 of Safakhaneh, Santeh and Polanian hydrometric stations from Zarrinehrud River located in north-western Iran were used. To obtain the best input–output mapping, different input combinations of antecedent monthly river flow and a time index were evaluated. The models results were compared using root mean square errors and the correlation coefficient. A comparison of models indicates that MLP and RBF models predicted better than SVM model for monthly river flow time series. Also the results showed that including a time index within the inputs of the models increases their performance significantly. In addition, the reliability of the models prediction was calculated by an uncertainty estimation. The results indicate that the uncertainty in the SVM model was less than those in the RBF and MLP models for predicting monthly river flow.

Phase Diagrams for the Aqueous Two-Phase Ternary System Containing the Ionic Liquid 1-Butyl-3-methylimidazolium Bromide and Tri-potassium Citrate at T ) (278.15, 298.15, and 318.15) K

Abstract: Liquid−liquid equilibria (LLE) for the aqueous 1-butyl-3-methylimidazolium bromide ([C4mim]Br) + tri-potassium citrate system have been experimentally determined at T = (278.15, 298.15, and 318.15) K. An empirical nonlinear expression developed by Merchuk was used for reproducing the experimental binodal data. In this work, the three fitting parameters of the Merchuk equation were obtained with the temperature dependence expressed in the linear form with (T − T0) K as a variable. The effect of temperature on the phase-forming ability in the investigated system has also been studied on the basis of a salting-out coefficient obtained from fitting the tie-line data to a Setschenow-type equation for each temperature. The values of the salting-out coefficients may reflect the extent of the preferential hydration of the ionic liquid. Furthermore, the kosmotropicity of tri-potassium citrate for the exclusion of [C4mim][Br] in an aqueous solution has been examined in comparison with the previously studied kosmotr...