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Synthesis, Optical and Electrical Studies of Nonlinear Optical Crystal: L-Arginine Semi-oxalate
Vasudevan, P.,Sankar, S.,Jayaraman, D. Korean Chemical Society 2013 Bulletin of the Korean Chemical Society Vol.34 No.1
L-Arginine semi-oxalate (LASO) single crystal has been grown by solution growth technique at room temperature. The crystal structure and lattice parameters were determined for the grown crystal by single crystal X-ray diffraction studies. Photoluminescence studies confirm the violet fluorescence emission peak at 395 nm. Optical constants like band gap, refractive index, reflectance, extinction coefficient and electric susceptibility were determined from UV-VIS-NIR spectrum. The dielectric constant, dielectric loss and ac conductivity of the compound were calculated at different temperatures and frequencies to analyze the electrical properties. The solid state parameters such as plasma energy, Penn gap, Fermi energy and polarizability were calculated to analyze second harmonic generation (SHG). Nonlinear optical property was discussed to confirm the SHG efficiency of the grown crystal.
Synthesis, Optical and Electrical Studies of Nonlinear Optical Crystal: L-Arginine Semi-oxalate
P. Vasudevan,S. Sankar,D. Jayaraman 대한화학회 2013 Bulletin of the Korean Chemical Society Vol.34 No.1
L-Arginine semi-oxalate (LASO) single crystal has been grown by solution growth technique at room temperature. The crystal structure and lattice parameters were determined for the grown crystal by single crystal X-ray diffraction studies. Photoluminescence studies confirm the violet fluorescence emission peak at 395 nm. Optical constants like band gap, refractive index, reflectance, extinction coefficient and electric susceptibility were determined from UV-VIS-NIR spectrum. The dielectric constant, dielectric loss and ac conductivity of the compound were calculated at different temperatures and frequencies to analyze the electrical properties. The solid state parameters such as plasma energy, Penn gap, Fermi energy and polarizability were calculated to analyze second harmonic generation (SHG). Nonlinear optical property was discussed to confirm the SHG efficiency of the grown crystal.
R. Srinivasan,D. Vasudevan,P. Padmanabhan 대한기계학회 2013 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.27 No.7
This paper presents the development of predictive models for bend force and final bend angle (after springback) in air bending of electrogalvanized steel sheet employing response surface methodology. The models are developed based on five-level half factorial central composite design of experiments with strain hardening exponent, coating thickness, die opening, die radius, punch radius, punch travel,punch velocity as input parameters and bend force and final bend angle as responses. The results obtained from the models are in good accord with the experimental results. The effects of individual parameters and their interactions on the responses have also been analyzed in this study.
Surface grain boundary engineering of Alloy 600 for improved resistance to stress corrosion cracking
Telang, A.,Gill, A.S.,Tammana, D.,Wen, X.,Kumar, M.,Teysseyre, S.,Mannava, S.R.,Qian, D.,Vasudevan, V.K. Elsevier Sequoia 2015 Materials science & engineering. properties, micro Vol.648 No.-
In this paper, we demonstrate a novel method for grain boundary engineering in Alloy 600 using iterative cycles of ultrasonic nanocrystal surface modification (UNSM) and strain annealing to modify the near surface microstructure (~250@?m) for improved stress corrosion cracking (SCC) resistance. These iterative cycles resulted in increased fraction of special grain boundaries whilst decreasing the connectivity of random grain boundaries in the altered near surface region. A disrupted random grain boundary network and a large fraction of low CSL boundaries (Σ3-Σ27) reduced the propensity to sensitization. Slow strain rate tests in tetrathionate solutions at room temperature show that surface GBE lowered susceptibility to intergranular SCC. Detailed analysis of cracks using Electron Back-scattered Diffraction showed cracks arrested at J1(1-CSL) and J2 (2-CSL) type of triple junctions. The probability for crack arrest, calculated using percolative models, was increased after surface GBE and explains the increase in resistance to SCC.
Buckling optimization of laminated composite plate with elliptical cutout using ANN and GA
Nicholas, P. Emmanuel,Padmanaban, K.P.,Vasudevan, D. Techno-Press 2014 Structural Engineering and Mechanics, An Int'l Jou Vol.52 No.4
Buckling optimization of laminated composite plates is significant as they fail because of buckling under in-plane compressive loading. The plate is usually modeled without cutout so that the buckling strength is found analytically using classical laminate plate theory (CLPT). However in real world applications, the composite plates are modeled with cutouts for getting them assembled and to offer the provisions like windows, doors and control system. Finite element analysis (FEA) is used to analyze the buckling strength of the plate with cutouts and it leads to high computational cost when the plate is optimized. In this article, a genetic algorithm based optimization technique is used to optimize the composite plate with cutout. The computational time is highly reduced by replacing FEA with artificial neural network (ANN). The effectiveness of the proposed method is explored with two numerical examples.
Buckling optimization of laminated composite plate with elliptical cutout using ANN and GA
P. Emmanuel Nicholas,K.P. Padmanaban,D. Vasudevan 국제구조공학회 2014 Structural Engineering and Mechanics, An Int'l Jou Vol.52 No.4
Buckling optimization of laminated composite plates is significant as they fail because ofbuckling under in-plane compressive loading. The plate is usually modeled without cutout so that thebuckling strength is found analytically using classical laminate plate theory (CLPT). However in real worldapplications, the composite plates are modeled with cutouts for getting them assembled and to offer theprovisions like windows, doors and control system. Finite element analysis (FEA) is used to analyze thebuckling strength of the plate with cutouts and it leads to high computational cost when the plate isoptimized. In this article, a genetic algorithm based optimization technique is used to optimize the compositeplate with cutout. The computational time is highly reduced by replacing FEA with artificial neural network(ANN). The effectiveness of the proposed method is explored with two numerical examples.
Comparison of mechanisms of advanced mechanical surface treatments in nickel-based superalloy
Gill, A.,Telang, A.,Mannava, S.R.,Qian, D.,Pyoun, Y.S.,Soyama, H.,Vasudevan, V.K. Elsevier Sequoia 2013 Materials science & engineering. properties, micro Vol.576 No.-
Mechanical surface enhancement techniques are used to introduce compressive residual stresses to enhance the fatigue life and corrosion resistance of metallic components. In this study, we compare the effects of three advanced mechanical surface enhancements treatments: laser shock peening, cavitation shotless peening and ultrasonic nano structure modification on residual stress, hardness, plastic deformation and changes in near surface microstructure introduced in a Ni-Base superalloy, IN718 SPF(Super plastic forming). Coupons of the alloy were peened using two different conditions of each treatment and results compared to achieve a better understanding of underlying mechanisms of these techniques. Results indicate that there are significant differences in mechanisms of these surface treatments leading to differences in material response.