Faculty Publications
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Publications by NITK Faculty
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Item On the improved performance of luby transform codes over selective repeat ARQ in turbulent free space optical links(2013) Prakash, G.; Nayak, A.; Kulkarni, M.; Acharya, S.Free Space Optical (FSO) links are capable of offering high data transfer rates, secure and low interference links for connectivity as a last mile solution. However, atmospheric turbulence can degrade the performance for distances over 1 km. This degradation is in the form of packet loss and hence drop in the error performance. Error Control Coding (ECC) can be used to mitigate the effects of the atmospheric turbulence. In this paper we prove analytically and verify through simulations that Luby Transform(LT) Codes show an improved performance over Automatic Repeat Request(ARQ) schemes for FSO transmission. FSO systems are limited by the safety limits of the input power to the laser transmitter. A notable contribution in this paper is that we prove that this improvement with LT codes is within Maximum Permissible Exposure (MPE) limit for an FSO link for a BER performance of 10-5. © 2013 IEEE.Item Stabilizing switching signals for discrete-time switched linear systems: A unifying framework(Institute of Electrical and Electronics Engineers Inc., 2019) Nayak, A.; Kundu, A.This paper deals with global asymptotic stability of discrete-time switched linear systems. We present a class of stabilizing switching signals that unifies prior results based on both point-wise and asymptotic characterizations under an umbrella framework. © 2019 IEEE.Item Design of High Gain Operational Transconductance Amplifiers in 180 nm CMOS technology(Institute of Electrical and Electronics Engineers Inc., 2019) Nayak, A.; Bonthala, S.; Uppoor, Y.; Bhat, M.S.This paper presents two architectures of two-stage Operational Transconductance Amplifiers (OTAs). To achieve high gain, folded cascode topology is used. The first architecture uses an external bias which can be controlled independent of the OTA gain and bandwidth, while the second architecture uses a self-bias which reduces the power dissipation at the expense of restricted control over gain and bandwidth tuning. The two topologies are implemented using UMC 180 nm CMOS 1P9M technology. Both the architectures provide higher gain and consume less power in comparison to the previously published results. © 2019 IEEE.Item Design of High Resolution Delta Sigma Modulator in 180 nm CMOS technology(Institute of Electrical and Electronics Engineers Inc., 2019) Bonthala, S.; Uppoor, Y.; Nayak, A.; Polineni, S.; Bhat, M.S.This paper presents the design and simulation of a Delta Sigma Modulator (DSM) to be employed in a Delta Sigma Analog to Digital Converter. The designed modulator block comprises of a high gain Operational Transconductance Amplifier (OTA) of the folded cascode type providing a DC gain of 91dB and phase margin of 60° which is better than previously published results [3], [8], [5] in the similar domain. Signal to Quantization Noise ratio of 79.96 dB is obtained corresponding to an effective number of bits of 13 for a signal bandwidth of 2kHz and an oversampling ratio (OSR) of 1000, which is suitable for low frequency applications. All the necessary blocks are designed using UMC 180nm CMOS 1P9M technology with supply voltage of 1.8 V. © 2019 IEEE.Item Stability enhancement of a powered two wheeler vehicle under curve negotiation(IAEME Publication, 2016) Nayak, A.; Ashwin, H.S.; Murigendrappa, S.M.During cornering of a two wheeler under dynamic conditions when the vehicle is steered to the left or right, the axis of the wheels and other rotating parts undergoes precession along with spinning which produces a gyroscopic couple. Due to the action of these moments on the vehicles along with the centrifugal forces and gravity acting on it, the vehicle may either skid or overturn depending on the angle of tilt, velocity of the motorcycle, radius of the curve & mass of the vehicle. The main objective of this work is to ensure the safe negotiation of the turn and to prevent accidents by establishing a harmonious relationship between the effecting parameters. A device was developed to act as a feedback control system; taking the inputs from a IMU sensor, predict the equilibrium conditions and thereby control the dynamic parameters of the 2 wheeler in order to enable it negotiate the curve safely. © IAEME Publication.Item Novel strategies for glucose production from biomass using heteropoly acid catalyst(Elsevier Ltd, 2020) Nayak, A.; Pulidindi, I.N.; Sankar Rao, C.S.Bioethanol and direct glucose fuel cells pledged clean energy to the world. Cellulose depolymerization for glucose production has been a successful approach in bioethanol production. Heteropoly acids (HPAs) are strong Brønsted solid acid catalysts for biomass hydrolysis. Keggin type HPAs, namely, Silicotungstic acid (HSiW), Phosphotungstic acid (HPW), and Phosphomolybdic acid (HPMo), were used for the hydrolysis of lignocellulosic biomass to glucose. Five different biomass feedstocks, namely, miscanthus, sugarcane leaves, switchgrass, sunflower seeds, and bamboo leaves, were examined for the feasibility of total reducing sugar (TRS) yield through the composition analysis and catalytic biomass hydrolysis. Sunflower seeds contained the maximum holocellulose with 90.6%, and switchgrass contained the least i.e., 77.63%. Among the five biomass tested, switchgrass resulted in the highest TRS (5.77 wt/dry wt. %) with HPMo catalyst at a catalyst to biomass ratio of 30:100 (wt./wt. %), a reaction temperature of 120 °C for 3 h. The reaction parameters for depolymerization were optimized for all three HPAs, and the optimized conditions were 3 h and 120 °C. HPMo showed maximum TRS yield (5.77 wt/dry wt.%) among the three HPAs at 30:100 catalyst to biomass ratio. However, a catalyst to biomass ratio of 20:100 (wt./wt.%) was economical (5.25 wt/dry wt.%) for commercial application. © 2020 Elsevier LtdItem Low field-cooled induced large exchange bias effect and DFT calculations in ferromagnetic Sm2CoMnO6(Elsevier Ltd, 2024) Nayak, A.; Prashanth, C.H.; Bala, D.; Reddy, I.R.; Tarafder, K.; Adyam, V.; Jyothinagaram, K.In the present report, we study the large exchange bias effect in Sm2CoMnO6 (SCMO) polycrystalline samples synthesized with the presence of two crystallographic phases: ordered-phase (monoclinic; P21/n) and disordered-phase (orthorhombic; Pnma). X-ray photoelectron spectroscopy study revealed the presence of mixed valence states for Co (2+ & 3+) and Mn (4+ & 3+). M(T) data exhibits an inhomogeneous magnetic state with the presence of ferromagnetic ordering at TC ∼128 K due to the super-exchange interactions of Co2+-O2--Mn4+ and antiferromagnetic-like spin correlations for T < 50 K, attributed to Co3+-O2--Co3+, and Mn3+-O2--Mn3+ interactions. M(H) loop shift with a conventional exchange bias (EB) effect of 10 kOe for a field-cooled (HFC) of 10 kOe at 2 K was observed. Such a large value of the EB effect for low HFC in SCMO is comparable to that of large EB compounds, such as La1·5Sr0·5CoMnO6 and NiFe2O4/CoO nanocomposites. The zero-field cooled asymmetry in the M(H) loop is termed a spontaneous exchange bias effect (SEB) observed for T < 20 K. The systematic study of EB effects like HEB and MEB with T(K) and HFC was explained qualitatively by the presence of unidirectional anisotropy formed at the interface of inhomogeneous magnetic phases. Further, density functional theory (DFT) calculations validate the ferromagnetic ground state of SCMO with Co and Mn networks. Moreover, the semiconductor characteristics of SCMO are established with a band gap of 1.3 eV. © 2023