Faculty Publications

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Publications by NITK Faculty

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    Profiled sheets - the optimum vs the oft used
    (Techno-Press, 2010) Babu Narayan, K.S.
    Profiled sheets are used extensively in roofing, cladding, sheet piling and containments. Profile development is increasingly rapidly owing to advancement in materials and construction technology. The resistance to longitudinal bending is proportional to the depth and thickness and depends greatly on the profile itself. The strength of the profiled sheet in longitudinal bending is proportional to the depth of corrugation, thickness and on the profile itself. More often than not profiles are repetitive and most popular being of the sine wave form. Hence it may be assumed that if a quarter of the best form is determined, the most optimum profile is known. It is calculated that the strength/unit length of the most widely used sine wave form is in agreement with the best profile suggested by the calculus of variations.
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    A differential evolution based neural network approach to nonlinear system identification
    (2011) Subudhi, B.; Jena, D.
    This paper addresses the effectiveness of soft computing approaches such as evolutionary computation (EC) and neural network (NN) to system identification of nonlinear systems. In this work, two evolutionary computing approaches namely differential evolution (DE) and opposition based differential evolution (ODE) combined with Levenberg Marquardt algorithm have been considered for training the feed-forward neural network applied for nonlinear system identification. Results obtained envisage that the proposed combined opposition based differential evolution neural network (ODE-NN) approach to identification of nonlinear system exhibits better model identification accuracy compared to differential evolution neural network (DE-NN) approach. The above method is finally tested on a one degree of freedom (1DOF) highly nonlinear twin rotor multi-input-multi-output system (TRMS) to verify the identification performance. © 2010 Elsevier B.V. All rights reserved.
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    Tuning the Photocatalytic Activity of SrTiO3 by Varying the Sr/Ti Ratio: Unusual Effect of Viscosity of the Synthesis Medium
    (American Chemical Society service@acs.org, 2018) Bantawal, H.; Shenoy, U.S.; Bhat, D.K.
    SrTiO3 nanostructures were successfully synthesized in various alcohols as cosolvent as well as surfactant by a facile solvothermal method. The as-synthesized catalysts were characterized by X-ray diffraction technique, scanning electron microscopy, energy-dispersive X-ray analysis, Brunauer-Emmett-Teller analysis, diffuse reflectance spectroscopy, and photoluminescence spectroscopy. The possible formation mechanism of SrTiO3 in the presence of these alcohols is discussed, and the effect of these alcohols on the structure, Sr/Ti atomic ratio, and optical properties is related to the photocatalytic activity. First principles calculations were made use of to determine the effect of defects on the electronic structure and the band gap. The photocatalytic activity of these catalysts was evaluated by taking methylene blue as a model pollutant under visible light irradiation. It was found that the photocatalytic activity of ethanol-mediated SrTiO3 was found to be higher than the other samples because of the synergistic effect of high surface area and lesser defects. © 2018 American Chemical Society.
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    Band Engineering of SrTiO3: Effect of Synthetic Technique and Site Occupancy of Doped Rhodium
    (American Chemical Society service@acs.org, 2018) Shenoy, U.S.; Bantawal, H.; Bhat, D.K.
    It is well known that doping of Rh into the SrTiO3 lattice introduces 4d donor levels within the band gap, which causes reduction in the gap and extends the photocatalytic activity to the visible region of the solar spectrum. The mid-gap states formed also act as recombination centers and diminish the efficiency of the material. Herein, we present a combined theoretical and experimental approach to avoid the formation of the so-called acceptor mid-gap states. For the first time, we study the effect of occupancy of Rh in the Sr site. First-principles calculations reveal that mixed occupancies of Rh into Sr and Ti sites lead to the introduction of acceptor levels within the band gap, leading to decrease in photocatalytic efficiency. A facile one-pot solvothermal approach by avoiding high-temperature calcinations is reported to obtain Rh-doped SrTiO3 nanoparticles in Rh3+ states, suppressing the formation of Rh4+ states by directing Rh toward Sr sites. The photocatalytic activity of Rh-doped SrTiO3 nanoparticles is studied in the case of degradation of methylene blue, wherein the 1.0 Rh sample was found to be highly efficient. © 2018 American Chemical Society.
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    Semiconducting B13C2 system: Structure search and DFT-based analysis
    (Institute of Physics, 2019) Pillai, H.G.; Madam, A.K.; Chandra, S.; Cheruvalath, V.M.
    DFT calculation on Boron Carbide in B13C2 stoichiometry using a 15-atom unit cell necessarily results in metallic ground state regardless of the crystal structure. This is because such a unit cell consists of odd number of electrons, and hence complete filling of the top most band(s) of nonzero occupancy is impossible. This is in contrast to the observed semiconducting nature. If the crystal structure of B13C2 is made of a 30-atom unit cell which cannot be reduced to a 15 atom cell, there is a possibility of obtaining either a metallic or a semiconducting state as such a cell consists of an even number of electrons. In this work the evolutionary algorithm based structure search using 30-atom unit cells has yielded a previously unreported semiconducting system of B13C2 with unique bonding pattern. The mechanical and dynamical stability of the system have been properly established through the computation of elastic constants and phonon spectra. Its bond lengths, elastic moduli, hardness and infrared spectrum are in good agreement with experimental data. ©2019 IOP Publishing Ltd.
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    Porous Graphene Wrapped SrTiO3 Nanocomposite: Sr-C Bond as an Effective Coadjutant for High Performance Photocatalytic Degradation of Methylene Blue
    (American Chemical Society service@acs.org, 2019) Bantawal, H.; Sethi, M.; Shenoy, U.S.; Bhat, D.K.
    Porous graphene-SrTiO3 (PGST) composite prepared by a facile solvothermal method was tested for its photocatalytic activity in degradation of methylene blue (MB) dye. First-principles density functional theory calculations were also carried out to study the effect of nanocomposite formation on the electronic structure and density of states. The combined experimental and theoretical study gave insights regarding the formation of the Sr-C bond which enhanced the charge transport, effectively separating the charge carriers and reduced their recombination rate. The formation of PGST nanocomposite favorably tuned the electronic structure with decreased band gap due to introduction of the hybridized states extending the absorption to the visible region of electromagnetic spectrum. The microscopy studies revealed loofah like PG wrapped SrTiO3 nano structures with contusions providing high surface area facilitating adsorption of MB dye. Degradation of ?92% was obtained by 7.5 PGST in 120 min with high cyclic stability indicating its suitability as an efficient photocatalyst for the treatment of pollutants. © 2019 American Chemical Society.
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    Enhancement of quantum capacitance by chemical modification of graphene supercapacitor electrodes: a study by first principles
    (Indian Academy of Sciences, 2019) Sruthi, T.; Tarafder, K.
    In this paper, we specify a powerful way to boost quantum capacitance of graphene-based electrode materials by density functional theory calculations. We performed functionalization of graphene to manifest high-quantum capacitance. A marked quantum capacitance of above 420?Fcm-2 has been observed. Our calculations show that quantum capacitance of graphene enhances with nitrogen concentration. We have also scrutinized effect on the increase of graphene quantum capacitance due to the variation of doping concentration, configuration change as well as co-doping with nitrogen and oxygen ad-atoms in pristine graphene sheets. A significant increase in quantum capacitance was theoretically detected in functionalized graphene, mainly because of the generation of new electronic states near the Dirac point and the shift of Fermi level caused by ad-atom adsorption. © 2019, Indian Academy of Sciences.
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    Zn: a versatile resonant dopant for SnTe thermoelectrics
    (Elsevier Ltd, 2019) Bhat, D.K.; Shenoy, U.S.
    SnTe-based materials have been receiving increasing heed in the field of thermoelectrics (TEs) because of their tunable electronic structure. Until now, only In and Bi are reported to introduce resonance level in SnTe. In this work, for the very first time, we report Zn as a resonant dopant in SnTe using first-principles density functional theory calculations. We show that the resonant states introduced by Zn raises the heavy hole valence sub-band above light hole valence sub-band leading to both record high room temperature Seebeck coefficient (~127 ?VK?1 at 300 K) and figure of merit, ZT (~0.28 at 300 K) for SnTe-based materials. The transport properties calculated using Boltzmann transport equations predicts Zn-doped SnTe to be a promising TE material, further confirmed by experimental ZTmaximum of ~1.49 at 840 K and ZTaverage of ~0.78 with 300 K and 840 K as cold and hot ends, respectively. © 2019 Elsevier Ltd
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    Bi and Zn co-doped SnTe thermoelectrics: Interplay of resonance levels and heavy hole band dominance leading to enhanced performance and a record high room temperature: ZT
    (Royal Society of Chemistry, 2020) Shenoy, U.S.; Bhat, D.K.
    Lead free SnTe with a tunable electronic structure has become the front runner in eco-friendly thermoelectrics. Herein, we show through first-principles density functional theory calculations that Bi and Zn doping introduces a resonance level in SnTe. The dominance of the heavy hole valence band at room temperature in Bi-Zn co-doped SnTe leads to a record high room temperature ZT of ?0.3 (at 300 K) for SnTe based materials. The increase in the Seebeck coefficient value due to the interaction between the resonance states and formation of the nanoprecipitates leading to an appreciably low lattice thermal conductivity of 0.68 W m-1 K-1 results in a peak ZT of ?1.6 at 840 K. A record high ZTaverage of ?0.86 with 300 K and 840 K as cold and hot ends, respectively, makes Bi-Zn co-doped SnTe a potential material for thermoelectric applications. This strategy of using two resonant dopants, to not only improve the room temperature ZT but also high temperature values, can very well be extended to other systems. This journal is © The Royal Society of Chemistry.