Faculty Publications
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Publications by NITK Faculty
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Item Network lifetime analytical model for node-disjoint multipath routing in wireless sensor networks(Inderscience Publishers, 2013) Murthy, S.G.; D'Souza, R.J.; Varaprasad, G.The objective of every sensor node in a sensor network is to send the sensed data in the phenomena to a sink node. The network lifetime is maximal, when the energy consumption of each node is uniform. Many routing protocols select an optimal path to increase the network lifetime in sensor networks. The energy of the nodes along this optimal path is consumed more, causing their early death. In the multipath routing, data traffic is distributed among the multiple paths, instead of a single optimal path. This work proposes a theoretical frame work to study the node-disjoint multipath wireless sensor network reliability. With higher reliability, higher network lifetime can be achieved. Simulation results show that when the data is transmitted through multiple paths with different data rates, the network lifetime increases. The node criticality factor enhances the network lifetime analysis effectively. © 2013 Inderscience Enterprises Ltd.Item Prediction of modulus at various strain rates from dynamic mechanical analysis data for polymer matrix composites(Elsevier Ltd, 2017) Zeltmann, S.E.; Prakash, K.A.; Doddamani, M.; Gupta, N.Understanding and modeling the behavior of polymers and composites at a wide range of quasi-static and high strain rates is of great interest to applications that are subjected to dynamic loading conditions. The Standard Linear Solid model or Prony series frameworks for modeling of strain rate dependent behavior are limited due to simplicity of the models to accurately represent a viscoelastic material with multiple relaxations. This work is aimed at developing a technique for manipulating the data derived from dynamic mechanical analysis to obtain an accurate estimate of the relaxation modulus of a material over a large range of strain rate. The technique relies on using the time-temperature superposition principle to obtain a frequency-domain master curve, and integral transform of this material response to the time domain using the theory of viscoelasticity. The relaxation function obtained from this technique is validated for two polymer matrix composites by comparing its predictions of the response to uniaxial strain at a prescribed strain rate to measurements taken from a separate set of tension experiments and excellent matching is observed. © 2017 Elsevier LtdItem Preprocessing of Multi-Time Instant PV Generation Data(Institute of Electrical and Electronics Engineers Inc., 2018) Prusty, B.; Jena, D.For the evaluation of system overlimit risk indices in a PV-integrated power system, PV generation data at specific instants of time (in each day for several years) are required to be collected. Such data have inherent annual periodic variations, which are different at various places. These variations are skewed and/or multimodal, which contributes significantly toward the overall variance of data and is primarily attributable to the Sun's position. This letter proposes a regression model that assumes the observed data as a function of few influencing factors related to the Sun's position and trend in data. Finally, the estimated variations using the developed model are removed from the data to characterize the unpredictable components. © 1969-2012 IEEE.Item Structural damage identification of bridge using high dimensional model representation(Bellwether Publishing, Ltd., 2021) Naveen, B.O.; Balu, A.S.Any engineering structure under the action of various internal and external factors like changes in the material properties, inadequate design, faulty construction, deterioration due to malfunctioning are susceptible to damages. In the past, many methods have attempted to identify damage by solving an inverse problem, which inevitably needs an analytical model. However, often the construction of these analytical model requires considerable effort in building a mathematical framework with acceptable level of accuracy and reliability which makes these approaches less attractive. To circumvent this complexity, this work presents a computationally efficient approach in structural damage identification using high dimensional model representation. © 2020 Taylor & Francis Group, LLC.Item A semi-analytical nonlocal elasticity model for static stability and vibration behaviour of agglomerated CNTs reinforced nano cylindrical panel under non-uniform edge loads(Elsevier Inc., 2022) Twinkle, C.M.; Jeyaraj, J.A semi analytical nonlocal elasticity model to analyze the effect of non-uniform edge loads on static stability and free vibration characteristics of agglomerated carbon nanotubes (CNTs) reinforced nano cylindrical panels are presented. Effective material properties of the agglomerated CNT reinforced composite are obtained using a two-parameter micro-mechanics model while Eringen's non-local theory is used to account the size effect. Sinusoidal shear deformation theory is adopted to analyze the buckling and vibration parameters using Galerkin's approach. The accuracy of the proposed model is presented first by comparing the results in the literature. Then a comprehensive study is carried out to analyze the influence of various degrees of agglomeration (complete, partial), nature of edge load, and non-local effects on the buckling and free vibration response of CNT reinforced nano cylindrical panel. The results revealed that non-local size effect leads to a reduction in stiffness and thus reduces buckling and dynamic characteristics. Moreover, it is observed that critical buckling load varies with type of in plane load and reduction in natural frequency is different for different in plane loading conditions. © 2021 Elsevier Inc.Item ANN Model to Predict Joint Stiffness of White-topped Pavements Using Falling Weight Deflectometer (FWD) Data(Springer, 2023) Bellary, A.; Suresha, S.N.The performance of white-topping pavements depends mainly on the functionality of joints. The functionality of joints is measured in terms of its load transfer efficiency (LTE). Falling weight deflectometer (FWD) device is most commonly used to evaluate the performance of joints in the field. Joint stiffness is used as an input parameter in the finite element (FE) based software to compute the LTE. In the present study, an improvement to the existing analytical model is presented that can be used to compute the joint stiffness of white-topping pavements directly from the FWD deflection data. Further, ANN models have been developed and compared for the proposed and previously available analytical models in the literature. The joint stiffness calculated from the ANN model developed from the proposed analytical model is used as an input parameter in FE model and LTE is compared with the field studies. It is concluded that the proposed ANN model can predict the joint stiffness of white-topping pavement accurately and in addition to that, it will also reduce the computation time and cost. © 2021, The Author(s), under exclusive licence to Chinese Society of Pavement Engineering.Item Downscaled XCO2 Estimation Using Data Fusion and AI-Based Spatio-Temporal Models(Institute of Electrical and Electronics Engineers Inc., 2024) Pais, S.M.; Bhattacharjee, S.; Anand Kumar, M.; Chen, J.One of the well-known greenhouse gases (GHGs) produced by anthropogenic human activity is carbon dioxide (CO2). Understanding the carbon cycle and how negatively it affects the ecosystem requires analysis of the rise in CO2 concentration. This work aims to map CO2 concentration for the entire surface, making it useful for regional carbon cycle analysis. Here, column-averaged CO2 dry mole fraction, called XCO2, measured by the orbiting carbon observatory-2 (OCO-2) satellite, is used. Because of spectral interference by the clouds and aerosols, there are many missing footprints in the Level-2 swath of OCO-2, making it disruptive to understand any assessment related to the carbon cycle. The objective of this work is to predict 1 km2 XCO2 using data resampling and machine learning models. This work achieves a minimum mean absolute error (MAE) and root mean square error (RMSE) of 0.3990 and 0.8090 ppm, using the monthly models. © 2004-2012 IEEE.Item Analytical modelling of ultra-small group delay variation of ultra-broadband RF power amplifier using NSGA-II algorithm(John Wiley and Sons Ltd, 2024) Kumar, K.; Kumar, S.; Kumar Kanaujia, B.K.This paper proposes a ± 9.4 ps ultra-small group delay (GD) variation of fully integrated 65 nm complementary metal oxide semiconductor (CMOS) power amplifier (PA) over 6.5–17 GHz broadband for wireless application. The proposed CMOS PA is realised by using broadband stage, RLC inter-stage and power stage topologies. The non-dominated sorting genetic algorithm (NSGA-II) is employed for PA parameter optimisation to ensure a small GD variation of ±9.4 ps over broadband with an excellent small signal gain flatness of 23.65 ± 1.85 for 6.5–17 GHz. The small GD variation of ±9.4 ps and ± 11.05 ps are attained under two cases of DC supply voltages of 2.4/1.2 V and 1.2/1.2 V, respectively. To the best of author's knowledge, the achieved GD variations are lowest among all CMOS PAs as reported so far. In addition, an analytical modelling of GD is derived to validating the minimum GD variation using zero-pole compensation. With supply voltages of 2.4/1.2 V at 6.5 GHz, the large signal power gain, Psat and OP1dB are 26 dB, 19.3 dBm and 17.94 dBm, respectively, while peak power added efficiency (PAE) is 38.196%. At reduced supply voltages of 1.2/1.2 V, the PA achieves maximum power gain of 17.7 dB and peak PAE of 35% at 6.5 GHz. The CMOS PA occupies an area of 0.206 mm2. © 2023 John Wiley & Sons Ltd.Item An improved Fourier series-based analytical model for threshold voltage and sub-threshold swing in SOI junctionless FinFET(Elsevier Ltd, 2024) Mathew, S.; Chennamadhavuni, S.; Rao, R.In this work, Fourier series-based analytical models for threshold voltage (Vth) and Sub-threshold Swing (SS) are developed for Junctionless Fin Field Effect Transistor (JLFinFET) on Silicon On Insulator (SOI) substrate, taking into account the location of the onset of current conduction in the channel. Rigorous simulations were conducted to analyse the current conduction path when JLFinFET surpasses the threshold voltage. Based on the findings from these simulations, threshold voltage condition used for deriving the threshold voltage model is modified. This modified model gives a better prediction of Vth for JLFinFET than the already existing model which doesn't include approximations based on the location of onset of current conduction. The analytical model developed for SS is also capable of closely predicting the SS of JLFinFET obtained from the TCAD simulator down to a gate length of 20 nm. © 2024 Elsevier LtdItem Experimental and numerical investigation on the elastic properties of luffa–cenosphere-reinforced epoxy hybrid composite(John Wiley and Sons Inc, 2024) Gurjar, A.K.; Kulkarni, S.M.; Joladarashi, S.; Doddamani, S.Estimating the elastic characteristics of natural fiber-reinforced polymer composites such as luffa fiber reinforced with epoxy is challenging. The structure of luffa cylindrica is complex, like a three-dimensional natural fibrous mat, netting-like structure. The multiscale modeling of such structures is the challenge to be addressed. The prime objective of this work is to determine the specific elastic properties of luffa–cenosphere-reinforced epoxy (LCE) composite, considering the effect of filler volume fractions. Furthermore, multiscale modeling techniques, such as representative volume elements (RVEs) of finite element techniques with chopped, unidirectional, plain, and twill weaving fiber arrangements, were employed. The longitudinal modulus, transverse modulus, shear modulus, and Poisson's ratio were predicted through these modeling approaches. However, experimental and analytical methodologies, including the rule of mixture and Halpin–Tsai, were considered to validate the finite element analysis results. The elastic characteristics of LCE composite were therefore shown to be enhanced by increasing filler volume fraction. However, the cenosphere's 20% volume fraction has the highest elastic properties as determined by analytical, experimental, and computational models. Analytical and finite element simulation results were compared with the experimental results, and based on the findings, the most suitable (unidirectional, chopped, plain, and twill weaving) RVE was identified for finite element modeling of LCE composite for the evaluation of elastic properties. Results from practical approaches and the RVE twill weaving model showed good agreement, with less than 1% error, compared to the other analytical and finite element methods. Highlights: NFCs are gaining ground in polymer composites. Overcoming challenges in modeling of luffa fiber inside epoxy matrix. The study uses multiscale modeling with diverse fiber arrangements. Experimental and analytical methods used to confirm FEA results. Increased cenosphere volume fraction boosts LCE composite properties. © 2024 Society of Plastics Engineers.