Faculty Publications
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Item Primary education for the specially-abled(2013) Chandra, S.; Sagar, M.; Rout, P.; Khattri, P.; Domanal, S.G.; Guddeti, G.Technology can support the children who require special needs, who if given the proper training and opportunity, can compete on a basis of equality with their peers. This should be the basic philosophy of a programmer who designs programs, standards for programs, or evaluation of programs. Proper education for these children will lead to enhancing their capability to lead a dignified life and also help them to earn a square meal. Technology is needed to teach them and hence the necessity can clearly be seen for further research and development in this field. In addition to software being used as teaching tools at schools and at-home, the learning process should be more interesting so that child should feel engaged. A daily routine, not only a syllabus/homework, using technologies such as text to speech conversion and image morphology is needed to both help them understand concepts of classroom syllabus and motivate them to learn more at home as specially-abled children need to be given enough motivation, as well as time, to succeed. The system developed proves to be useful to specially-abled children to memorize rhymes, recognize common sounds (like that of animals) as well as develop haptic abilities using a game like interface. © 2013 IEEE.Item Influence of indirect vision and virtual reality training under varying manned/unmanned interfaces in a complex search-and-shoot simulation(Springer Verlag service@springer.de, 2019) Rao, A.K.; Pramod, B.S.; Chandra, S.; Dutt, V.In the real-world, manned and unmanned vehicles may be used for a number of applications. Visual technologies like indirect visual display (IVD) and virtual reality (VR) have been used to train operators in both manned and unmanned environments. The main objective of this research was to evaluate the effectiveness of manned and unmanned interfaces in IVD and VR display designs. Using an underwater search-and-shoot scenario, we developed two variations in display designs (IVD and VR) and two variations in type of interface-based training (manned and unmanned). A total of 60 subjects participated in the experiment, where 30 subjects were randomly assigned to simulations in IVD and the rest in VR. In both the simulations, 15 randomly selected participants executed the manned interface first and the remaining 15 executed the unmanned interface first. Results revealed that the subjects performed better in VR compared to IVD, and also performed better when they executed the unmanned interface first. We highlight the implications of our results for training personnel in scenarios involving manned and unmanned operations in IVD and VR interfaces. © Springer International Publishing AG, part of Springer Nature 2019.Item Vibrational spectra of Ruthenium Carbide structures yielded by the structure search employing evolutionary algorithm(Elsevier Ltd, 2015) Harikrishnan, G.; Ajith, K.M.; Chandra, S.; Valsakumar, M.C.Out of the three dynamically stable structures of Ruthenium Carbides yielded by the exhaustive structure search employing evolutionary algorithm, Born effective charges are computed for the semiconducting RuC in Zinc blende structure using density functional perturbation theory. Using the phonon frequencies and the Born effective charge tensors of Ru and C in this structure, infrared spectrum is generated for this system. Computations of these dynamical quantities and IR spectra from first principles can be helpful in the unambiguous determination of the stoichiometry and structure by comparison of the experimental measurements with the computational predictions. The positive formation energies of the three systems show that high pressure and possibly high temperature may be necessary for their synthesis. Formation energies of these systems at different pressures are computed. One of the structurally stable systems, Ru3C with hexagonal structure (P6¯m2), has negative formation energy at 200 GPa. The system reported from the first synthesis of Ruthenium Carbide also has the same symmetry, though it has a different stoichiometry. © 2015 Elsevier Ltd. All rights reserved.Item Temperature dependent structural properties and bending rigidity of pristine and defective hexagonal boron nitride(Institute of Physics Publishing custserv@iop.org, 2015) Thomas, S.; Ajith, K.M.; Chandra, S.; Valsakumar, M.C.Structural and thermodynamical properties of monolayer pristine and defective boron nitride sheets (h-BN) have been investigated in a wide temperature range by carrying out atomistic simulations using a tuned Tersoff-type inter-atomic empirical potential. The temperature dependence of lattice parameter, radial distribution function, specific heat at constant volume, linear thermal expansion coefficient and the height correlation function of the thermally excited ripples on pristine as well as defective h-BN sheet have been investigated. Specific heat shows considerable increase beyond the Dulong-Petit limit at high temperatures, which is interpreted as a signature of strong anharmonicity present in h-BN. Analysis of the height fluctuations, ?h2?, shows that the bending rigidity and variance of height fluctuations are strongly temperature dependent and this is explained using the continuum theory of membranes. A detailed study of the height-height correlation function shows deviation from the prediction of harmonic theory of membranes as a consequence of the strong anharmonicity in h-BN. It is also seen that the variance of the height fluctuations increases with defect concentration. © 2015 IOP Publishing Ltd.Item Evolutionary algorithm based structure search for hard ruthenium carbides(Institute of Physics, 2015) Harikrishnan, G.; Ajith, K.M.; Chandra, S.; Valsakumar, M.C.An exhaustive structure search employing evolutionary algorithm and density functional theory has been carried out for ruthenium carbides, for the three stoichiometries Ru1C1, Ru2C1 and Ru3C1, yielding five lowest energy structures. These include the structures from the two reported syntheses of ruthenium carbides. Their emergence in the present structure search in stoichiometries, unlike the previously reported ones, is plausible in the light of the high temperature required for their synthesis. The mechanical stability and ductile character of all these systems are established by their elastic constants, and the dynamical stability of three of them by the phonon data. Rhombohedral structure is found to be energetically the most stable one in Ru1C1 stoichiometry and hexagonal structure , the most stable in Ru3C1 stoichiometry. RuC-Zinc blende system is a semiconductor with a band gap of 0.618 eV while the other two stable systems are metallic. Employing a semi-empirical model based on the bond strength, the hardness of RuC-Zinc blende is found to be a significantly large value of ?37 GPa while a fairly large value of ?21GPa is obtained for the RuC-Rhombohedral system. The positive formation energies of these systems show that high temperature and possibly high pressure are necessary for their synthesis. © 2015 IOP Publishing Ltd.Item Pressure-induced variation of structural, elastic, vibrational, electronic, thermodynamic properties and hardness of Ruthenium Carbides(Elsevier Ltd, 2016) Harikrishnan, H.; Ajith, K.M.; Natarajan, S.; Chandra, S.; Mundachali Cheruvalath, V.Three of the five structures obtained from the evolutionary algorithm based structure search of Ruthenium Carbide systems in the stoichiometries RuC, Ru2C and Ru3C are relaxed at different pressures in the range 0-200 GPa and the pressure-induced variation of their structural, elastic, dynamical, electronic and thermodynamic properties as well as hardness is investigated in detail. No structural transition is present for these systems in this pressure range. RuC-Zinc blende is mechanically and dynamically unstable close to 100 GPa. RuC-Rhombohedral and Ru3C-Hexagonal retain mechanical and dynamical stability up to 200 GPa. For all three systems the electronic bands and density of states spread out with pressure and the band gap increases with pressure for the semiconducting RuC-Zinc blende. From the computed IR spectrum of RuC-Zinc blende at 50 GPa it is noted that the IR frequency increases with pressure. Using a semi-empirical model for hardness it is estimated that hardness of all three systems consistently increases with pressure. The hardness of RuC-Zinc blende increases towards the superhard regime up to the limiting pressure of its mechanical stability while that of RuC-Rhombohedral becomes 30 GPa at the pressure of 150 GPa. © 2016 Elsevier Ltd. All rights reserved.Item Evolutionary algorithm based structure search and first-principles study of B12C3polytypes(Elsevier Ltd, 2017) Harikrishnan, H.; Ajith, K.M.; Chandra, S.; Mundachali Cheruvalath, V.The structure search based on evolutionary algorithm has yielded six unique Boron Carbide structures in B12C3stoichiometry, three of them with negative formation energies. Their formation energies lie within a band of 166 meV/atom, so they can be formed together in any optimal high temperature synthesis of B12C3and they are thermodynamically stable at temperatures up to 660 K. This work is the first independent confirmation using structure search that B11Cp(CBC) is the ground state structure of B12C3stoichiometry. New structures like the 14-atom-cage and the supercell (B11Cp)(B10Cpe 2)(CBC)(CBB) have also emerged in the structure search. Five structures have base-centered monoclinic symmetry and the supercell has triclinic symmetry, implying that the determination of monoclinic symmetry in B12C3by experimental measurements is an option for further inquiry. The mechanical stability of these systems are established through the analysis of their elastic constants and their dynamical stability from the phonon data. The high value of Bulk modulus (?250 GPa) indicates their high hardness and the B/G value confirms their brittle nature. The electronic structure shows that they are semiconductors with a significant reduction in the band gap when the structure does not contain the CBC chain. The curve fitting of the cumulative IR spectrum against the experimental spectrum implies that the presence of B11Cp(CBC) in the ground state composition could mostly be through structures of larger unit cells. The hardness values of these systems estimated by using the semi-empirical model based on bond strength are in excellent agreement with the experimental values. For the four structures with chain the hardness values are close to the superhard regime (>40 GPa). © 2016 Elsevier B.V.Item 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.Item Chaotic Scenario in Three-Component Fermi Plasma(Abdus Salam International Centre for Theoretical Physics, 2020) Ghosh, T.; Pramanick, S.; Sarkar, S.; Dey, A.; Chandra, S.Electron Acoustic Solitary structures in Fermi Plasma with two temperature electrons have various applications in space and laboratory-made plasmas. Formulation of an adequate theory is important to understand various physical systems with various physical parameters. The motion of two temperature electrons in a quantum Fermi plasma system highly affects the solitary profile of the system. We study the quantum Fermi plasma system with two temperature electrons where the streaming velocities of two-electron population are opposite. We consider quantum hydrodynamic model (QHD) and derive a linear dispersion relation for the system. For non-linear study of the system, we use standard perturbative technique to derive Kortewegde Vries Burger's equation and show the evolution of solitary profile with different plasma parameters. We analyse the stable Rouge wave structure using NLSE and show simulation results. We study the dynamical properties and phase plot for two-stream quantum Fermi plasma system with two temperature electrons. © 2020. All Rights Reserved.Item Investigating the influence of conflicting flow's composition on critical gap under heterogeneous traffic conditions(Elsevier B.V., 2021) Mohan, M.; Chandra, S.The choice to accept or reject an available gap at unsignalized intersections depends on several factors that include driver and vehicle characteristics, intersection geometry, weather conditions, etc. Although drivers in heterogeneous traffic conditions accept shorter gaps than their counterparts in developed countries, they are reluctant to accept the same gap offered by a large-sized vehicle instead of a smaller vehicle. This influence of traffic stream's composition on the critical gap is not well-established. The present research attempts to quantify this influence by realizing its importance, especially under heterogeneous traffic conditions. Data were collected from six unsignalized intersections located in different parts of India through videography. Details about gaps and lags which were accepted and rejected, types of vehicles involved in the gap acceptance process, and the amount of conflicting traffic faced by each of the turning vehicles were extracted from the recorded videos. Critical gaps for different vehicle types making right-turns at each of the intersections were estimated based on Occupancy Time Method. Further, a non-linear regression revealed that the estimated critical gaps vary logarithmically with the percentage of large-sized vehicles in the conflicting flows. Based on these relationships, the base values of the critical gap and the adjustment for the proportion of large-sized vehicles in conflicting flows are estimated for turning movements at unsignalized intersections in heterogeneous traffic conditions. These relationships will be useful in assessing the capacity of unsignalized intersections of developing countries. © 2021 Tongji University and Tongji University Press