Browsing by Author "Kumar, A.S."

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Aluminum doped ZnO thin films by RF sputtering of coaxial ZnO and Al targets
(2011) Nagaraja, K.K.; Kumar, A.S.; Nagaraja, H.S.
Transparent conducting aluminum doped zinc oxide (AZO) films were deposited on glass substrates by radio (RF) frequency magnetron sputtering employing zinc oxide and aluminum targets. The targets are fixed coaxially in one cathode, by using a center hollow aluminum disc. Gas pressure was kept constant and the sputter power was varied. The nature of AZO film was found to be polycrystalline with hexagonal structure and a preferred orientation along c-axis. The Al content in the films is determined using EDXA analysis and it is found to vary with the applied power. Surface morphology of the films was found to be uniform and has fine grained structure. Electrical resistivity of the deposited films was found to be as low as 26�10-4?-cm for the film deposited at 250 W. The average transparencies up to 85% in the visible region were obtained for all the films. Optical band gap of the films show a slight blue shift as indicated by the (?h?)2 v/s h? plots. In the present investigation we have controlled Al content in the films by adjusting the power to the coaxial targets. The value of resistivity was found to decrease with the amount of Al present in the sample. � 2011 American Institute of Physics.
Combined model of fuel cell and microturbine based distributed generation system
(2011) Nayak, S.K.; Gaonkar, D.N.; Kumar, A.S.
Distributed Generation (DG) play an active role in the distribution network due to its minimum loss, maximum efficiency and environmental impact. Moreover DG can supply base load power which improves the system stability, reliability and power quality. Among the different combined DG systems like solar with wind, tidal with geothermal and others, fuel cell with microturbine is the most economical due to fuel flexibility and inner relation between each other. The hybrid system can utilize exhaust fuel and heat from fuel cell to increase the system efficiency. This paper investigates combined model solid oxide fuel cell/microturbine generator (SOFC/MTG) hybrid system, in which the anode exhaust of SOFC contains reminder of fuel. The exhaust hot gas and waste fuel are mixed with fresh fuel and compressed air is burned inside the burner. The pressurized hot gas from the combustor is expanded through turbine driving the Permanent Magnet Synchronous Machine (PMSM). The governing schemes of combined SOFC/MTG (Fuel & air flow) are controlled by the DC link voltage and current. The generated power of MTG is converted to AC/DC/AC to combine with fuel cell and frequency conversion. The hybrid model of SOFC/MTG with power converter is developed in MATLAB/Simulink library and simulation result shows transient response of hybrid SOFC/MTG DG system. � 2011 IEEE.
Combined model of fuel cell and microturbine based distributed generation system
(2011) Nayak, S.K.; Gaonkar, D.N.; Kumar, A.S.
Distributed Generation (DG) play an active role in the distribution network due to its minimum loss, maximum efficiency and environmental impact. Moreover DG can supply base load power which improves the system stability, reliability and power quality. Among the different combined DG systems like solar with wind, tidal with geothermal and others, fuel cell with microturbine is the most economical due to fuel flexibility and inner relation between each other. The hybrid system can utilize exhaust fuel and heat from fuel cell to increase the system efficiency. This paper investigates combined model solid oxide fuel cell/microturbine generator (SOFC/MTG) hybrid system, in which the anode exhaust of SOFC contains reminder of fuel. The exhaust hot gas and waste fuel are mixed with fresh fuel and compressed air is burned inside the burner. The pressurized hot gas from the combustor is expanded through turbine driving the Permanent Magnet Synchronous Machine (PMSM). The governing schemes of combined SOFC/MTG (Fuel & air flow) are controlled by the DC link voltage and current. The generated power of MTG is converted to AC/DC/AC to combine with fuel cell and frequency conversion. The hybrid model of SOFC/MTG with power converter is developed in MATLAB/Simulink library and simulation result shows transient response of hybrid SOFC/MTG DG system. Â© 2011 IEEE.
Experimental and Computational Studies of N-(4,6-Dimethylpyrimidin-2-yl)-4-[(quinazoline-4-yl)amino]-benzene-1-sulfonamide as an Effectual Corrosion Inhibitor for Mild Steel in Hydrochloric Acid
(Pleiades journals, 2021) D’Souza, P.R.; Kudva, J.; Kumar, A.S.; Nityananda Shetty, A.N.
Abstract: The inhibition efficacy of N-(4,6-dimethylpyrimidin-2-yl)-4-[(quinazoline-4-yl)amino]benzene-1-sulfonamide (DMQS) as a new corrosion inhibitor on mild steel (MS) in 0.1 M HCl medium at varied temperature has been analysed and it has ensued 97.6% high efficiency at 4 × 10–5 M of DMQS. The electrochemical techniques employed were impedance spectroscopy and potentiodynamic polarization. Surface analysis of MS was carried out through scanning electron microscopy (SEM) and energy dispersion spectroscopy (EDS). Inhibitory effect of DMQS escalated with elevated concentration and declined with elevation in solution temperature. The adsorption of DMQS on MS has consent with the Langmuir adsorption isotherm. The computational study using density functional theory (DFT) with the B3LYP/3-21G basis set level for DMQS was investigated through the association between their molecular and electronic structure. The parameters involved in quantum chemical calculations were energy gap, EHOMO, ELUMO, absolute electronegativity, electrophilicity, softness, global hardness, energy gap, ionisation energy, electron affinity and dipole moment. DMQS shows EHOMO value of –6.256 eV, fortifying MS from corrosive attack and implicating it to be an effectual inhibitor. The results of the implemented studies show the corrosion inhibition efficiency of the DMQS is in good accord. © 2021, Pleiades Publishing, Ltd.
Experimental and Theoretical Approach for the Corrosion Deceleration of Mild Steel in Hydrochloric Acid Medium by Two Sulfonamide Derivatives
(John Wiley and Sons Inc, 2024) D’Souza, P.R.; Kudva, J.; Kumar, A.S.; Shekara, P.; Naral, D.; Nityananda Shetty, A.N.
In the pursuit to find corrosion inhibitors of superior efficacy, N-(pyrimidin-2-yl)-4-[(quinazoline-4-yl)amino]benzene-1-sulfonamide (PQS) and N-(4-methylpyrimidin-2-yl)-4-[(quinazoline-4-yl)amino]benzene-1-sulfonamide (MQS) are the two new sulfonamides employed, which have decelerating effect on mild steel (MS) corrosion in a medium 0.5 M HCl and were found to have an efficiency of 98.7 % and 96.8 % respectively (303 K for 40 ppm concentration) deliberated through the electrochemical techniques (PDP and EIS). The inhibitory efficacy relies on the temperature of the solution and inhibitor concentration. PQS had greater stability than MQS at higher temperatures which is indicative in the obtained experimental data. The relative adsorption process was in consonance with the Langmuir adsorption isotherm. The SEM, EDS, FT-IR, and AFM analysis validated PQS and MQS to form a barrier on MS, opposing corrosion. The potential energy surfaces (PES) scan and a theoretical study for PQS and MQS were probed employing density functional theory (DFT) at B3LYP/6-311+G(d, p) basis set level that explicated the formation of a complex between the sulfonamides and MS. The corrosion inhibition efficiency of PQS and MQS inferred from experimental and theoretical data comply, making them credible corrosion inhibitors. © 2024 Wiley-VCH GmbH.
Fabrication and characterization of ZnO/AI/ZnO multilayers by simultaneous DC and RF magnetron sputtering
(2015) Nagaraja, K.K.; Kumar, A.S.; Nagaraja, H.S.
The present investigation reports the fabrication and characterization of multilayered transparent electrodes by simultaneous DC and RF magnetron sputtering on glass substrates. The multilayer structure consists of three layers (ZnO/Al/ZnO). The influence of Al layer thickness on the electrical and optical properties was investigated. Optimum thickness of Al was determined for high transmittance and good electrical conductivity. High quality films having resistance as low as 25 ?/sq with optical transmittance upto 65% were obtained at room temperature. � Published under licence by IOP Publishing Ltd.
Growth and temperature dependent electrical properties of ZnO nanostructures
(2013) Kumar, A.S.; Nagaraja, K.K.; Nagaraja, H.S.
Zinc oxide (ZnO) nanostructured films are grown using Polyvinyal alcohol (PVA)-citric acid modified sol gel process and the effect of (0, 1, and 2Wt%) PVA content on growth, crystallanity, microstructure and electrical properties are investigated. The XRD patterns confirm that the films are polycrystalline nature. 1 Wt% assisted grown samples are found to be good crystallanity with (002) preferred orientation. The SEM micrographs confirm that the 1 Wt% PVA assisted grown films are composed of vertically oriented ?1.2 ?m length nanorods. The temperature dependent electrical resistivity of the films has been measured using the four-probe method. The electrical resistivity found to be 7.08 ?-cm at room temperature for vertically oriented nanorods composed films, which are grown using 1Wt% PVA. � 2013 AIP Publishing LLC.
Implementation of Enhanced Parallel port interface for Frequency analysis in a configurable Ring Oscillator PUF circuits on Xilinx Spartan 3E architecture
(Institute of Electrical and Electronics Engineers Inc., 2019) Jeeru, D.R.; Vittal, K.P.; Anikethan, H.V.U.; Kumar, A.S.
Hardware security has evolved from physical one-way functions to Physically Unclonable Functions (PUFs). A PUF produces a response for a given challenge by performing a functional operation. This paper demonstrates the Configurable Ring Oscillator (CRO) based PUF circuit with frequency meter. Frequencies are read through Enhanced Parallel Port (EPP) interface to enable efficient communication between the host and the Field Programmable Gate Array (FPGA) device. As a part of the work, 128 CROs are implemented on 128 Configurable Logic Blocks (CLBs) of the Spartan 3E FPGA device and frequencies are measured for every configuration of the CRO to generate the Challenge Response Pair (CRP) for each device. This experimental setup is carried out on 4 different FPGA devices and specific methodologies are used to generate responses which are consistent with time for every reading analyzed and different for different FPGA devices. The process involves selecting the optimum unit time pulse window to measure the frequencies of CROs and optimum number of CROs grouped as hard macro to enhance inter and intra Hamming Distance (HD) consequently improving uniqueness, reliability and uniformity metrics. Â© 2019 IEEE.
Performance analysis of variable speed wind energy conversion system in grid connected mode
(2012) Kumar, A.S.; Gaonkar, D.N.
This paper represents the modeling and simulation of wind energy based grid connected distributed generation system. A control scheme is presented to control the power flow of the inverter. The controller is able to restore the pre fault condition very quickly. The grid side controller is able to manage the constant dc-link voltage while maintaining the power injection according to the wind speed variations. The performance of the system for wide range of wind speed is presented. The battery is considered for energy storage and is directly connected to the dc-link. The results for variation in load and fault conditions are shown. � 2012 IEEE.
Performance analysis of variable speed wind energy conversion system in grid connected mode
(2012) Kumar, A.S.; Gaonkar, D.N.
This paper represents the modeling and simulation of wind energy based grid connected distributed generation system. A control scheme is presented to control the power flow of the inverter. The controller is able to restore the pre fault condition very quickly. The grid side controller is able to manage the constant dc-link voltage while maintaining the power injection according to the wind speed variations. The performance of the system for wide range of wind speed is presented. The battery is considered for energy storage and is directly connected to the dc-link. The results for variation in load and fault conditions are shown. Â© 2012 IEEE.
Performance of wind system with battery-UC in grid connected mode
(2017) Kumar, A.S.; Gaonkar, D.N.
In this paper the performance analysis of wind system connected to grid along with battery and Ultracapacitor (UC) is presented. The variation in battery discharge rate for varying wind speed has been shown. The battery-UC combination is used to smooth wind power output and to control battery discharge rate. The control schemes are employed for controlling and operating the wind based power generation system with storage in grid connected mode. The system performance for different wind speeds, load change is given. The charging of battery and ultracapacitor using wind power is presented. The dispatchable ability of wind system with storage is shown in this work. The power sharing between grid and inverter is also shown with simulation results. � 2016 IEEE.
Performance of wind system with battery-UC in grid connected mode
(Institute of Electrical and Electronics Engineers Inc., 2017) Kumar, A.S.; Gaonkar, D.N.
In this paper the performance analysis of wind system connected to grid along with battery and Ultracapacitor (UC) is presented. The variation in battery discharge rate for varying wind speed has been shown. The battery-UC combination is used to smooth wind power output and to control battery discharge rate. The control schemes are employed for controlling and operating the wind based power generation system with storage in grid connected mode. The system performance for different wind speeds, load change is given. The charging of battery and ultracapacitor using wind power is presented. The dispatchable ability of wind system with storage is shown in this work. The power sharing between grid and inverter is also shown with simulation results. Â© 2016 IEEE.
Performance study of grid connected fuel cell based distributed generation system with ultracapacitor
(2011) Kumar, A.S.; Gaonkar, D.N.; Nayak, S.K.
Fuel cell based power generation is becoming one of the promising distributed generation system Fuel cell system can generate power as long as fuel is supplied However fuel cells cannot respond quickly to sudden load change due to slow dynamic response. Hence energy storage system is required during transient period In this paper a grid connected fuel cell system performance is studied considering the ultracapacitor as energy storage device. To interface ultracapacitor with fuel cell bidirectional converter is used Simulation results presented here show that the bidirectional converter effectively controls power flow from ultracapacitor. The dynamic responses of the fuel cell system under different load conditions are presented The results presented in this paper demonstrate the load transient mitigation capability of ultracapcitor. � 2011 IEEE.
Performance study of grid connected fuel cell based distributed generation system with ultracapacitor
(2011) Kumar, A.S.; Gaonkar, D.N.; Nayak, S.K.
Fuel cell based power generation is becoming one of the promising distributed generation system Fuel cell system can generate power as long as fuel is supplied However fuel cells cannot respond quickly to sudden load change due to slow dynamic response. Hence energy storage system is required during transient period In this paper a grid connected fuel cell system performance is studied considering the ultracapacitor as energy storage device. To interface ultracapacitor with fuel cell bidirectional converter is used Simulation results presented here show that the bidirectional converter effectively controls power flow from ultracapacitor. The dynamic responses of the fuel cell system under different load conditions are presented The results presented in this paper demonstrate the load transient mitigation capability of ultracapcitor. Â© 2011 IEEE.
Polymer assisted preparation and characterization of ZnO and Sn doped ZnO nanostructures
(2015) Kumar, A.S.; Nagaraja, K.K.; Nagaraja, H.S.
Zinc oxide (ZnO) and tin doped ZnO are wide band gap semiconducting materials with excellent optoelectronic properties. In the present study ZnO and Sn: ZnO films are prepared using polymer assisted sol gel process. The thermal behaviour of the dried gel sample studied using DTA and TG analysis. TG-DTA result shown that most of the organic of PVA and CH3COO group of zinc acetate and other volatiles are removed below 500�C. The effect of Sn on the crystallinity, microstructral properties of the deposited films was investigated. XRD patterns of undoped and Sn doped ZnO films indicate enhanced intensities for the peak corresponding to (002) plane, resulting preferential orientation along the c-axis. The SEM images confirm that the grown films are composed of nanorods. � Published under licence by IOP Publishing Ltd.
Soil classification using airborne hyperspectral data employing various approaches
(2017) George, J.K.; Kumar, V.; Tarun, B.; Kumar, S.; Kumar, A.S.
Hyperspectral remote sensing technology is one of the advance technology for detailed land cover feature extraction. Hyperspectral datasets contain large number of contiguous spectral bands with a narrow spectral bandwidth which enables identification of peculiar absorption features for distinguishing different type of soils. The potential of Airborne Visible Infrared Imaging Spectrometer-Next Generation (AVIRIS-NG) data was tested for distinguishing black and red soils in the ICRISAT area near Hyderabad, Telangana. The AVIRIS-NG data captured in 432 narrow contiguous bands (346�2505 nm) with spectral sampling of 5 nm bandwidth and a 4m ground pixel size was used in this study. The dataset was first spectrally subsetted by identification and removal of bad bands and was atmospherically corrected by converting it to surface reflectance using FLAASH. The data was finally georeferenced using the Internal Geometry Module (IGM) parameters. Optimal spectral bands from the reflectance data were selected on the basis of different characteristics of various soils. Data dimensionality reduction technique Minimum Noise Fraction (MNF) was also performed to extract noise free components. Total five classes including red and black soils were considered for land cover classification. Pixel based classification techniques such as Spectral Angle Mapper(SAM) and Support Vector Machine (SVM) were performed on the reflectance as well as MNF transformed data. SVM was also performed on data containing noise free MNF components and the selected optimal spectral bands. In the resultant classified output of reflectance data, SVM classifier provided higher accuracy and was able to classify black and red soil in a better way than SAM technique. The results also suggested that use of MNF components and specific spectral bands altogether improvised the classification of black and red soil. � 2017 ACRS. All rights reserved.