Spectroscopic investigation and JuddeOfelt analysis of silver nanoparticles embedded Er3+-doped tellurite glass

Raja J. Amjad,M.R. Dousti,M. R. Sahar 한국물리학회 2015 Current Applied Physics Vol.15 No.1

A series of silver nanoparticles (NPs) embedded zinc-tellurite glass is prepared by melt-quenching technique. The transmission electron microscopic images reveal spherical as well as anisotropic silver NPs having average diameter in the range of 14-48 nm. The Er3+-free glass sample containing AgCl exhibits surface plasmon resonance (SPR) band of Ag NPs centered at ~ 501 nm. From Judd-Ofelt analysis, it is found that by increasing the concentration of NPs, the value of Ω2 is enhanced suggesting increased covalency and decreased symmetry around the Er3+ ions. Integrated emission cross-section (IEC) is enhanced as the concentration of silver NPs is increased up to 0.5 mol% AgCl. Fourier infrared spectra show that the intensity of the vibrational band of the water molecule and fundamental stretching band of OH group are suppressed. Furthermore, under an excitation wavelength of 786 nm, three prominent upconversion emissions are observed at 520 nm, 550 nm and 650 nm which are attributed to 2H11/2→4I15/2, 4S3/2→4I15/2, and 4F9/2→4I15/2 transitions, respectively. The upconversion emissions are enhanced significantly by introduction of silver NPs. The enhancement is mainly attributed to the local field effect of silver NPs. Studied nanocomposites are potential candidates for the development of solid state lasers.

Investigations on Eco Friendly Insulating Fluids from Rapeseed and Pongamia Pinnata Oils for Power Transformer Applications

R. Thanigaiselvan,T. Sree Renga Raja,R.Karthik 대한전기학회 2015 Journal of Electrical Engineering & Technology Vol.10 No.6

Transformer mineral oil which is normally hydrocarbon based is non- biodegradable and pollutes the environment in all aspects. Though vegetable oils are eco-friendly in nature and potentially could be used in transformers as a replacement for the mineral oil, there usage is restricted because of their oxidative instability. The present work focuses on using rapeseed oil and pongamia (pongamia pinnata) oil as effective alternatives for the traditional mineral oil in power transformer. The oxidative stability of the rapeseed oil and pongamia oil is increased by using combinations of the natural and synthetic anti-oxidants as additives. The parameters like breakdown voltage, viscosity, flash point, fire point are measured for the rapeseed oil and pongamia oil with and without the additives as per IEC and ASTM standards. The results shown encouraging changes in the parameter values and ensures the use of the oils as a potential alternative insulation in power transformers.

A novel fabrication of superhydrophobic surfaces on aluminium substrate by picosecond pulsed laser

R. Samuel Sanjay Raja,P. Selvakumar,P. Dinesh Babu 대한기계학회 2020 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.34 No.4

Superhydrophobic surfaces have emerged because of their unique properties like corrosion resistance, self-cleaning, anti-icing and being anti-bacterial. A simplistic and highly effective ultra-fast laser technology was used to fabricate superhydrophobic surface on aluminum substrate. Compared to other laser systems, picosecond laser systems have smaller thermal affected area on the aluminum substrate. They also offer high efficiency, not as much of waste materials and cover enormous areas for mass production. Tilted groove patterns of various angles with respect to horizontal were textured on the substrate by using picosecond laser pulses. The laser parameters, such as hatching distance (HD) and scanning speed (SS), can be varied by keeping the laser power as constant for the various tilted angle of the groove pattern. The textured surfaces were initially super hydrophilic when kept in polyethylene zip lock cover and which also exhibits super hydrophobicity of maximum 155.5° when observed after 15 days. The morphology of surface was characterized by scanning electron microscope, EDX and X-ray diffraction.

Exponential Stability for Delayed Stochastic Bidirectional Associative Memory Neural Networks with Markovian Jumping and Impulses

Sakthivel, R.,Raja, R.,Anthoni, S. M. Springer-Verlag 2013 Journal of optimization theory and applications Vol.158 No.1

Investigations on Eco Friendly Insulating Fluids from Rapeseed and Pongamia Pinnata Oils for Power Transformer Applications

Thanigaiselvan, R.,Raja, T. Sree Renga,Karthik, R. The Korean Institute of Electrical Engineers 2015 Journal of Electrical Engineering & Technology Vol.10 No.6

Transformer mineral oil which is normally hydrocarbon based is non- biodegradable and pollutes the environment in all aspects. Though vegetable oils are eco-friendly in nature and potentially could be used in transformers as a replacement for the mineral oil, there usage is restricted because of their oxidative instability. The present work focuses on using rapeseed oil and pongamia (pongamia pinnata) oil as effective alternatives for the traditional mineral oil in power transformer. The oxidative stability of the rapeseed oil and pongamia oil is increased by using combinations of the natural and synthetic anti-oxidants as additives. The parameters like breakdown voltage, viscosity, flash point, fire point are measured for the rapeseed oil and pongamia oil with and without the additives as per IEC and ASTM standards. The results shown encouraging changes in the parameter values and ensures the use of the oils as a potential alternative insulation in power transformers.

Asymptotic stability of delayed stochastic genetic regulatory networks with impulses

Sakthivel, R,Raja, R,Marshal Anthoni, S Royal Swedish Academy of Sciences 2010 Physica scripta Vol.82 No.5

<P>In this paper, the asymptotic stability analysis problem is considered for a class of delayed stochastic genetic regulatory networks with impulses. Based on the Lyapunov stability technique and stochastic analysis theory, stability criteria are proposed in terms of linear matrix inequalities (LMI). It is shown that the addressed stochastic genetic regulatory networks are globally asymptotically stable if four LMIs are feasible, where the feasibility of LMIs can be readily checked by Matlab LMI toolbox. Finally, a numerical example is given to demonstrate the usefulness of the proposed result.</P>

Analysis of the vibration behavior of FGM cylindrical shells including internal pressure and ring support effects based on Love-Kirchhoff theory with various

M. R. Isvandzibaei,H. Jamaluddin,R. I. Raja Hamzah 대한기계학회 2014 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.28 No.7

This paper presents the study on vibration behavior of functionally graded material (FGM) cylindrical shell with the effects of internalpressure and ring support. The FGM properties are graded along the thickness direction of the shell. The FGM shell equations with internalpressure and ring support are established based on strain-displacement relationship using Love-Kirchhoff shell theory. The governingequations of motion were solved by using energy functional and by applying Ritz method. The boundary conditions represented by endconditions of the FGM cylindrical shell are simply supported-simply supported (SS-SS), clamped-clamped (C-C), free-free (F-F),clamped-free (C-F), clamped-simply supported (C-SS), free-simply supported (F-SS), free-sliding (F-SL) and clamped-sliding (C-SL). To check the validity and accuracy of the present method, the results obtained are compared with those available in the literature. Theinfluence of internal pressure, ring support position and the effect of the different boundary conditions on natural frequencies characteristicsare studied. These results presented can be used as important benchmark for researchers to validate their numerical methods whenstudying natural frequencies of shells with internal pressure and ring support.

Implementation of Robust Prediction Observer Controller for DC-DC Converter

R. Shenbagalakshmi,T. Sree Renga Raja 대한전기학회 2013 Journal of Electrical Engineering & Technology Vol.8 No.6

A discrete controller is designed for low power dc-dc switched mode power supplies. The approach is based on time domain and the control loop continuously and concurrently tunes the compensator parameters to meet the converter specifications. A digital state feedback control combined with the load estimator provides a complete compensation, which further improves the dynamic performance of the closed loop system. Simulation of digitally controlled Buck converter is performed with MATLAB/Simulink. Experimental results are given to demonstrate the effectiveness of the controller using LabVIEW with a data acquisition card (model DAQ Pad . 6009).

Blockchain Technology and Advancements in the Agri-food Industry

R Thirukumaran,Priya Vijay Kumar Anu,Raja Vijayakumar,Nimbkar Shubham,Moses J. A.,Anandharamakrishnan C. 한국농업기계학회 2024 바이오시스템공학 Vol.49 No.2

Purpose The purpose of this article is to present the fundamental concepts, features, advantages, limitations, and possible applications in the agri-food supply chain. Blockchain technology helps in minimizing transaction costs and time, boosting process efficiency, and safety, including transparency, and increasing stakeholder confidence. Methods Several scientific databases were searched with specific keywords and relevant research and review articles were collected and reported. Results Maintaining data immutably and facilitating speedy monitoring through all phases of the food supply chain, blockchain increases transparency across all levels of the agri-food sector. Though the potential of the technology is proven, the implementation faces some challenges that require to be explored further with various conceptual frameworks developed for that purpose. Conclusion This review explores the potential, features, and applications of blockchain technology to enable the flexible agri-food supply chain, various conceptual frameworks developed to achieve a traceable food supply chain, and barriers associated with the implementation of the technology.

Stress Corrosion Cracking Susceptibility of 316LN Grade Stainless Steel Weld Joint in Boiling Magnesium Chloride Hexahydrate Environment

R. Rajasekaran,A. K. Lakshminarayanan,M. Vasudevan,P. Vasantha Raja 대한금속·재료학회 2022 METALS AND MATERIALS International Vol.28 No.11

The 316LN Stainless Steel (SS) weld joints were fabricated using Tungsten Inert Gas (TIG) Welding and Activated FluxTungsten Inert Gas (A-TIG) Welding techniques with suitable process parameters. Initially, basic mechanical properties wereevaluated across weld joints. Further microstructural study of the base metal, TIG, and A-TIG joints were accomplishedusing Optical Microscopy (OM), Transmission Electron Microscopy (TEM), and Scanning Electron Microscopy (SEM)techniques. The microstructural characterization revealed higher grain size variations at the fusion zone of the A-TIG jointdue to the slow cooling rate and reversed Marangoni convection effect. The Stress Corrosion Cracking (SCC) susceptibilityof the TIG and A-TIG welded joints was assessed using five different loading/Stress conditions. The constant load boiling45 wt% Magnesium Chloride Hexahydrate (MgCl2.6H2O) solution as per ASTM G36-94 standard was used to evaluate theSCC susceptibility of the welded joints. The SCC (crack initiation and propagation) of the base metal and welded jointsoccurred by the anodic dissolution and Hydrogen Induced Cracking mechanisms. For the welded joints additionally, thedissolution of the δ-ferrite increased the crack growth rate. The A-TIG joint exhibited lesser SCC resistance than the TIGjoint for the following major reasons: (i) Formation of the large dendrites (ii) Presence of the higher grain size variations atthe fusion zone. Moreover, both welded joints showed lesser SCC resistance than the base metal due to the dissolution ofthe δ-ferrite and the residual stress formation. The fractographic studies for the base metal, TIG, and A-TIG joints revealedthe brittle nature of transgranular SCC failure.