Role of Oxygen as Surface-Active Element in Linear GTA Welding Process

Although the surface-active elements such as oxygen and sulfur have an adverse effect on momentum transport in liquid metals during fusion welding, such elements can be used beneficially up to a certain limit to increase the weld penetration in the gas tungsten arc (GTA) welding process. The fluid flow pattern and consequently the weld penetration and width change due to a change in coefficient of surface tension from a negative value to a positive value. The present work is focused on the analysis of possible effects of surface-active elements to change the weld pool dimensions in linear GTA welding. A 3D finite element-based heat transfer and fluid flow model is developed to study the effect of surface-active elements on stainless steel plates. A velocity in the order of 180 mm/s due to surface tension force is estimated at an optimum concentration of surface-active elements. Further, the differential evolution-based global optimization algorithm is integrated with the numerical model to estimate uncertain model parameters such as arc efficiency, effective arc radius, and effective values of material properties at high temperatures. The effective values of thermal conductivity and viscosity are estimated to be enhanced nine and seven times, respectively, over corresponding room temperature values. An error analysis is also performed to find out the overall reliability of the computed results, and a maximum reliability of 0.94 is achieved.     

High performance of brain emotional intelligent controller for DTC-SVM based sensorless induction motor drive

This paper introduces the application of the induction motor (IM) drive brain emotional intelligent controller (BEIC). Intelligent regulation, modelled on the human brain, is capable of generating impulses and is used as a controller. A Model Reference Adaptive System is developed using stator current and stator voltages, which are further developed with BEIC to approximate the rotor rpm. This paper proposes that speed estimation using BEIC for direct torque control (DTC) of IM drive. The experimental work is conducted on a hardware-in-loop mechanism using a real-time digital simulator (Op-RTDS-OP5600). The simulation and test results are discussed. The proposed method is compared to the DTC-SVM-based IM drive speed control with the existing controllers.

     

ANN based peak power tracking for PV supplied DC motors

This paper presents an application of an Artificial Neural Network (ANN) for the identification of the optimal operating point of a PV supplied separately excited dc motor driving two different load torques. A gradient descent algorithm is used to train the ANN controller for the identification of the maximum power point of the Solar Cell Array (SCA) and gross mechanical energy operation of the combined system. The algorithm is developed based on matching of the SCA to the motor load through a buck-boost power converter so that the combined system can operate at the optimum point. The input parameter to the neural network is solar insolation and the output parameter is the converter chopping ratio corresponding to the maximum power output of the SCA or gross mechanical energy output of the combined PV system. The converter chopping ratios at different solar insolations are obtained from the ANN controller for two different load torques and are compared with computed values.     

Growth,characterization and transport properties of Pb<Subscript><Emphasis Type="Italic">x</Emphasis></Subscript>Zn<Subscript>1−<Emphasis Type="Italic">x</Emphasis></Subscript>S mixed crystals

The polycrystalline Pb _x Zn_1−x S semiconductor powder with (0 ≤ x ≤ 0·5) has been prepared by controlled co-precipitation method from an alkaline medium using thiourea as a sulphide ion source. Pellets are made with these powders applying 10 ton/sq.cm. pressure and sintered at 800°C for 2 h in nitrogen atmosphere. X-ray studies of these samples have indicated that the compounds are polycrystalline in nature with mixed hexagonal and cubic structure of ZnS and cubic structure of PbS. Lattice parameters (a and c) of all the compounds are determined from the X-ray data and are found to decrease nonlinearly with increase in Pb concentration (x). It is also observed that the grain size of the crystallites increases in samples with x = 0−0·5. Scanning electron micrographs have shown that both cubic and hexagonal crystallites are present in the mixed crystals. The electrical conductivity in Pb _x Zn_1−x S is found to decrease with increase in composition (x = 0−0·5), whereas it increases at all temperatures in all samples. Mobility of charge carrier concentration is found to increase with increasing temperature. The increase in carrier mobility in Pb _x Zn_1−x S samples may be due to reduced grain boundary potential. In Pb _x Zn_1−x S samples with x = 0−0.3, the sum of the activation energy due to charge carriers and grain boundary potential is equal to the activation energy due to conductivity.