Faculty Publications
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Item A class of two-step implicit methods involving higher-order derivatives of y for initial value problems of the form y? = f(t, y, y?)is developed. The methods involve arbitrary parameters p and q, which are determined so that the methods become absolutely stable when applied to the test equation y? + ?y? + ?y = 0. Numerical results for Bessel's and general second-order differential equations are presented to illustrate that the methods are absolutely stable and are of order O(h4), O(h6) and O(h8).(Elsevier, Obrechkoff methods having additional parameters for general second-order differential equations) Sesappa Rai, A.; Ananthakrishnaiah, U.1997Item Hydraulic performance of tandem breakwater with concrete cubes as armour units(2009) Rao, M.; Shirlal, K.G.; Rao, S.; Bharadwaj, P.Tandem breakwater system consists of a conventional breakwater protected by a seaward submerged reef. The paper discusses physical model study on the hydraulic performance of an isolated as well as tandem breakwater system subjected to varying wave climate and water depths, while keeping a constant crest width of submerged reef. The breakwater in both the cases are armoured with concrete cubes and the submerged reef is constructed with natural stones. It is found that the isolated breakwater is damaged for all waves except those of period 2.5 s. While a submerged reef of crest width (B) 0.40m placed at a seaward spacing(X) of 2.5m transmits only 52% to 81% of the incident wave height and thereby reduces the wave force on the main structure which inturn protects the inner main breakwater completely without causing any damage.Item Development of concrete armoured protected breakwater structure(CAFET INNOVA Technical Society 1-2-18/103, Mohini Mansion, Gagan Mahal Road, Domalguda, Hyderabad 500029, 2011) Rao, M.; Rao, S.; Shirlal, K.G.The present work involves the physical model study of stability of conventional single breakwater and the reef protected breakwater, constructed with concrete cube as an artificial armour unit. Regular waves of wide ranging heights and periods are used. The tests are carried out for different spacings between the two structures (X/d = 2.5-13.33) and for different relative heights (h/d = 0.625-0.833) and relative widths (B/d = 0.25-1.33) of the reef. It is observed that a reef of width (B/d) of 1.0-1.33 constructed at a seaward distance (X/d) of 6.25-8.33 exhibits a transmission coefficient (Kt) of 0.38-0.708, wave dissipates energy and protect the breakwater optimally. © 2011 CAFET-INNOVA TECHNICAL SOCIETY. All rights reserved.Item Production and characterization of biosurfactant produced by a novel Pseudomonas sp. 2B(2012) Aparna, A.; Srinikethan, G.; Smitha, H.Biosurfactant-producing bacteria were isolated from terrestrial samples collected in areas contaminated with petroleum compounds. Isolates were screened for biosurfactant production using Cetyl Tri Ammonium Bromide (CTAB)-Methylene blue agar selection medium and the qualitative drop-collapse test. An efficient bacterial strain was selected based on rapid drop collapse activity and highest biosurfactant production. The biochemical characteristics and partial sequenced 16S rRNA gene of isolate, 2B, identified the bacterium as Pseudomonas sp. Five different low cost carbon substrates were evaluated for their effect on biosurfactant production. The maximum biosurfactant synthesis (4.97g/L) occurred at 96h when the cells were grown on modified PPGAS medium containing 1% (v/v) molasses at 30°C and 150rpm. The cell free broth containing the biosurfactant could reduce the surface tension to 30.14mN/m. The surface active compound showed emulsifying activity against a variety of hydrocarbons and achieved a maximum emulsion index of 84% for sunflower oil. Compositional analysis of the biosurfactant reveals that the extracted biosurfactant was a glycolipid type, which was composed of high percentages of lipid (~65%, w/w) and carbohydrate (~32%, w/w). Fourier transform infrared (FT-IR) spectrum of extracted biosurfactant indicates the presence of carboxyl, hydroxyl and methoxyl functional groups. The mass spectra (MS) shows that dirhamnolipid (l-rhamnopyranosyl-l-rhamnopyranosyl-3-hydroxydecanoyl-3-hydroxydecanoate, Rha-Rha-C 10-C 10) was detected in abundance with the predominant congener monorhamnolipid (l-rhamnopyranosyl-?-hydroxydecanoyl-?-hydroxydecanoate, Rha-C 10-C 10). The crude oil recovery studies using the biosurfactant produced by Pseudomonas sp. 2B suggested its potential application in microbial enhanced oil recovery and bioremediation. © 2012 Elsevier B.V..Item Local convergence for multi-point-parametric Chebyshev-Halley-type methods of high convergence order(Elsevier, 2015) Argyros, I.K.; George, S.; Magreñán Ruiz, Á.A.We present a local convergence analysis for general multi-point-Chebyshev-Halley-type methods (MMCHTM) of high convergence order in order to approximate a solution of an equation in a Banach space setting. MMCHTM includes earlier methods given by others as special cases. The convergence ball for a class of MMCHTM methods is obtained under weaker hypotheses than before. Numerical examples are also presented in this study. © 2014 Elsevier B.V. All rights reserved.Item A quadratic convergence yielding iterative method for the implementation of Lavrentiev regularization method for ill-posed equations(Elsevier Inc. usjcs@elsevier.com, 2015) Padikkal, P.; Shubha, V.S.; George, S.George and Elmahdy (2012), considered an iterative method which converges quadratically to the unique solution x?? of the method of Lavrentiev regularization, i.e., F(x) + ?(x - x0) = y?, approximating the solution x of the ill-posed problem F(x) = y where F:D(F)?X?X is a nonlinear monotone operator defined on a real Hilbert space X. The convergence analysis of the method was based on a majorizing sequence. In this paper we are concerned with the problem of expanding the applicability of the method considered by George and Elmahdy (2012) by weakening the restrictive conditions imposed on the radius of the convergence ball and also by weakening the popular Lipschitz-type hypotheses considered in earlier studies such as George and Elmahdy (2012), Mahale and Nair (2009), Mathe and Perverzev (2003), Nair and Ravishankar (2008), Semenova (2010) and Tautanhahn (2002). We show that the adaptive scheme considered by Perverzev and Schock (2005) for choosing the regularization parameter can be effectively used here for obtaining order optimal error estimate. In the concluding section the method is applied to numerical solution of the inverse gravimetry problem. © 2014 Elsevier Inc. All rights reserved.Item Derivative Free Iterative Scheme for Monotone Nonlinear Ill-posed Hammerstein-Type Equations(International Association of Engineers, 2021) Erappa, S.M.; George, S.An iterative scheme which is free of derivative is employed to approximately solve nonlinear ill-posed Hammer-stein type operator equations )TG(x) = Y, where G is a non-linear monotone operator and ) is a bounded linear operator defined on Hilbert spaces X,Y,Z. The convergence analysis adapted in the paper includes weaker Lipschitz condition and adaptive choice of Perverzev and Schock(2005) is employed to choose the regularization parameter U. Furthermore, order optimal error bounds are obtained and the method is validated by a numerical example. © 2021, IAENG International Journal of Applied Mathematics. All Rights Reserved.Item Enhancement in structural, elemental and optical properties of boron–phosphorus Co-doped ZnO thin films by high-temperature annealing(Elsevier B.V., 2021) Sushama, S.; Murkute, P.; Ghadi, H.; Pandey, S.K.; Chakrabarti, S.The inherent n-type nature of zinc oxide (ZnO) and its unstable p-type behavior with single dopant species have encouraged researchers to explore the effect of multiple dopants as a viable solution for long-term stability and repeatability. Herein, we report boron (B) and phosphorus (P) co-doped ZnO thin films engineered through an optimized ion implantation technique followed by annealing at 1000 °C in oxygen ambiance. We investigated their structural, chemical, and optical properties to capture the effect of both boron implantation duration and annealing temperature. Co-doping with boron was observed to boost phosphorus incorporation in the film. Compared with P-doping, P–B co-doping increased the dominance of acceptor-bound exciton peak and also, suppressed non-radiative/visible emission which is due to reduced Madelung energy. After high-temperature annealing at 1000 °C, further narrowing of optical emission peaks generated due to acceptor incorporation was observed. Also, the co-doped samples showed stability in the acceptor behavior for more than one year. © 2021 Elsevier B.V.Item Torque generation in lightweight four rotor magnetorheological brake(Springer, 2024) Kadam, S.; Kariganaur, A.K.; Kumar, H.Non-Newtonian behaviour of the Magnetorheological (MR) fluid under the influence of external magnetic field can be commissioned to design various applications such as MR brake, damper, and clutches, etc. Better design strategies, material selection and characterization led to realize the potential of MR brakes to replace conventional brakes. The present study emphasises on developing lightweight (1.8 kg) multi-rotor MR brake (MMRB). Finite element method magnetics (FEMM) software is utilized to determine the material required for a single-rotor MRB. FEMM material selection analysis is incorporated into the modeled MMRB, and the nature of magnetic flux density throughout the MR gap was obtained. Magnetic circuit analysis of the proposed brake is carried out to find torque estimation using analytical equations and Bingham plastic model. The proposed brake is fabricated and characterized using commercial MRF (132 DG, Lord Corporation). The study compares the torque outputs obtained experimentally with finite element analysis (FEA) and analytical approach. The average maximum magnetic flux density through FE analysis is found to be 0.45 T @ 3 A current. The average error between FE obtained and experimentally obtained torque output of the brake is around 5%. Further, an alternate design is proposed by utilizing same rotor diameter and number of electromagnetic coils. The new design is lighter in weight (0.8 kg) and exhibits enhancement in the torque output and torque to weight ratio by around 31% and 55%, respectively than the present design. © Indian Academy of Sciences 2024.Item Machine learning enhanced multi-scale dynamic viscoelastic analysis of 3-D printable PETG nanocomposite filaments: Leveraging FFT-based mesh-free computational homogenization for complex microstructures(Elsevier B.V., 2025) Aher, Y.; Mahesh, V.; Joseph, A.; Mahesh, V.; Kattimani, S.; Harursampath, D.The article investigates the influence of organically modified montmorillonite nanoclay (OMMT-NC) and short carbon fibers (SCF) on temperature-dependent mechanical properties of additively manufactured glycol-modified polyethylene terephthalate (PETG) nanocomposites. This work utilizes Dynamic Mechanical Analysis (DMA) to explore the influence of microstructure on the multiscale viscoelastic properties and the resulting stiffness-damping trade-off in porous nanocomposites. Machine learning (ML) and X-ray Micro-Computed Tomography (micro-CT) are employed to bridge the gap between experimental measurements from DMA and computational modelling. A novel mesh-free computational approach, combining fast Fourier transform (FFT)-based homogenization and the Lippmann-Schwinger (LS) method, was applied to analyze the porous heterogeneous microstructures. The analysis of pore geometry and fiber distribution, along with the associated stress-strain behavior, provides valuable information regarding stress concentration at critical material interfaces. The proposed method revealed a higher Von Mises stress and strain in the matrix surrounding the fiber ends, a principal locus of load transmission. Further, the experimental DMA results highlight the importance of considering interfacial adhesion, friction, segmental mobility, and intercalation effects on modulus, Tg, and tan ?. PETG +15 wt % SCF demonstrated high damping (tan ?: 0.19) and a 35 % and 122 % rise in modulus in glassy and rubbery states, respectively. Meanwhile the relative modulus of PETG +1 wt % OMMT-NC + 5 wt % SCF and PETG +3 wt % OMMT-NC + 5 wt % SCF nanocomposites improved by over 41 % in the glassy state. © 2025 Elsevier B.V.