Faculty Publications
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Item A new approach has been proposed for improving the performance of the Wigner-Ville distribution. This approach is based on signal decomposition and modified magnitude group delay function. Signal decomposition achieved by perfect reconstruction filter bank reduces significantly the existence of crossterms. The Gibbs ripple effect is due to truncation of the Wigner-Ville distribution kernel. The modified magnitude group delay function overcomes this effect without applying any window. Compared to those of Pseudo Wigner-Ville distribution and its versions, the proposed method has significantly improved performance in both time and frequency resolution as there is no time and frequency smoothing. Further, this method obeys better the desirable properties of time-frequency representation and has a better noise immunity. © 2003 Elsevier B.V. All rights reserved.(Improved Wigner-Ville distribution performance by signal decomposition and modified group delay) Narasimhan, S.V.; Nayak, M.B.2003Item A novel procedure for determination of hydrodynamic pressure along upstream face of dams due to earthquakes(2010) Gogoi, I.; Maity, D.The estimation of hydrodynamic pressures along the upstream face of the dam is a critical parameter for the accurate analysis and design of a dam. The accurate estimation of the hydrodynamic pressures necessitates the consideration of interaction between the dam, the reservoir and the foundation. The interaction effects of the unbounded domain of the reservoir and the absorptive materials deposited at the reservoir bottom are frequency dependent which can be incorporated in a frequency domain procedure easily. But in a time domain procedure the frequency dependent interaction effects are lost. In a frequency domain solution, the excitation frequencies are extracted from the earthquake signal using a Fourier transformation, but do not give any information about how it varies with time. To overcome this, a short-time Fourier transform based formulation is presented in this paper to evaluate the hydrodynamic pressures in time domain to account for the frequency dependent interaction effects of the dam-reservoir system. Thus, the adequate accuracy in the determination of hydrodynamic pressure under earthquake excitation is ensured with the proposed truncation boundary condition. © 2010 Elsevier Ltd. All rights reserved.Item Microwave-assisted synthesis and magnetic studies of cobalt oxide nanoparticles(2011) Bhatt, A.S.; Bhat, D.K.; Tai, C.-W.; Santosh, M.S.An efficient microwave-assisted route has been used to synthesize nanoparticles of cobalt oxide. The particles were well characterized by transmission electron microscopy (TEM) which showed that the average diameter of the particles is around 6 nm. X-ray diffraction (XRD) studies further confirmed the formation of the spinel Co3O4. Purity of the products was detected by Fourier transform infrared spectroscopy (FTIR) combined with thermal gravimetric analysis (TG/DTG). The magnetic measurements revealed a small hysteresis loop at room temperature indicating a weak ferromagnetic nature of the synthesized Co3O4 nanoparticles. The magnetic moment of the particles was measured to be 4.27 ?eff. © 2010 Elsevier B.V. All rights reserved.Item Thermo-physical analysis of natural shellac wax as novel bio-phase change material for thermal energy storage applications(Elsevier Ltd, 2020) B.V., B.V.; Gumtapure, V.The high energy density of latent heat storage makes it more competent than other types of thermal energy storage (TES) systems. Studying thermophysical and rheological properties of phase change material (PCM) is required for effective storage design, simulation, and applications. Bio-based PCM (BPCM) is a renewable and eco-friendly option for commercial paraffin-based PCMs. This study intends to characterize the shellac wax using the conventional and non-conventional approach as novel BPCM. Analysis of Fourier transforms infrared spectrophotometer (FTIR) indicates that shellac wax has aliphatic hydrocarbons, carboxylic acid, alcohol, and esters functional group. Thermogravimetric analysis (TGA) shows shellac wax has no mass change for operating temperature range (50–85 °C). Differential scanning calorimetry (DSC) analysis reported enthalpy of melting and crystallization as 148 kJ/kg and 161 kJ/kg, respectively. The crystallization enthalpy measured in the T-history method (THM) is 210.5 kJ/kg. However, DSC analysis of sample undergone 0,100,200 and 300 thermal cycle shows no significant change in thermal properties. Other properties like thermal conductivity, density, specific heat and viscosity are comparable to the present PCM used in storage applications. The overall study outcome that shellac wax is thermally stable and is potential BPCM for the TES application like solar desalination, district heating, waste heat recovery and solar cooking. © 2020 Elsevier LtdItem Decavanadate-graphene oxide nanocomposite as an electrode material for electrochemical capacitor(Taylor and Francis Ltd., 2022) Maity, S.; Das, P.P.; Mal, S.We have synthesized new electrode material for the supercapacitor application. Polyoxovanadates (POVs) have been used for energy storage electrode materials due to their fast multi-electron redox properties. The formation of SDV/GO composites was confirmed using various analytical methods, e.g., Fourier transforms infrared spectroscopy (FTIR) and powder X-ray diffraction (XRD), followed by scanning electron microscopy (SEM) and transmission electron microscopy (TEM). The composite electrode’s electrochemical behavior was studied using a neutral 1 M sodium sulphate (Na2SO4) solution in three-electrode cyclic voltammetry (CV) system. The SDV/GO composite electrode showed a specific capacitance of 306 F/g for a scan rate of 5 mV/s and a corresponding energy density of 42.4 Wh/Kg. Galvanostatic charge/discharge exhibits a specific capacitance of 310 F/g with energy densities of 43.08 Wh/kg. Electrochemical impedance spectroscopy (EIS), which was used to investigate interface property, yielded a considerably higher power density of 172.41 KW/kg with an equivalent series resistance of 5 ?. © 2021 Informa UK Limited, trading as Taylor & Francis Group.Item Dewatering performance of sludge using coconut shell biochar modified with ferric chloride (Sludge dewatering using bio-waste)(Springer Science and Business Media Deutschland GmbH, 2022) Rashmi, H.R.; Devatha, C.P.Coconut shell is a bio-waste, and its availability is high to waste in the coastal region of Karnataka, India. The present study focused on using coconut shell biochar modified with ferric chloride to enhance the sludge dewaterability, and it is evaluated experimentally (Capillary suction time, moisture content, settleability, zeta potential, heavy metals, and phosphate). Further, scanning electron microscopy, Fourier transformation infrared spectroscopy, and X-ray diffraction characterization were carried out to identify the structure's change. A significant reduction in capillary suction time (56 s) and the moisture content (96.5%) of the dewatered sludge cake was obtained. Sludge dewatering using coconut shell biochar modified with ferric chloride was optimized by a Box Behnken method with three main factors including dosage, rapid mixing time, and slow mixing time. Optimum capillary suction time (55.6 s) was achieved at coconut shell biochar modified with ferric chloride dosage (41% dry solids), rapid mixing time (10 min), and slow mixing time (19 min). The significant structural change in sludge particles was confirmed through characterization studies. During the dewatering process, the removal of heavy metal (cadmium, chromium, lead, and nickel) and phosphate (50.6%) was evident. Hence attempt of coconut shell biochar modified with ferric chloride as a skeleton material is an economical and promising option for sludge dewatering. © 2021, Islamic Azad University (IAU).