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Vijaykumar, S.,Prasannkumar, S.,Sherigara, B.S.,Shelke, N.B.,Aminabhavi, Tejraj M.,Reddy, B.S.R. The Polymer Society of Korea 2009 Macromolecular Research Vol.17 No.12
Copolymers of N-vinylpyrrolidone (NVP) comonomer with styrene (St), hydroxypropyl methacrylate (HPMA) and carboxyphenyl maleimide (CPMI) were synthesized by free radical polymerization using 2,2'-azobisisobutyronitrile (AIBN) initiator in 1,4-dioxane solvent. The copolymers formed were characterized by FTIR, $^1H$ NMR and $^{13}C$ NMR techniques and their thermal properties were studied by DSC and TGA. Copolymer composition was determined by $^1H$ NMR and/or by elemental analysis and monomer reactivity ratios (MRR) were estimated by the linear methods of Kelen-Tudos (K-T) and extended Kelen-Tudos (EK-T) and the non-linear approach. Copolymers of St and HPMA with NVP formed blocks of one of the monomer units, whereas alternating copolymers were obtained in CPMI-NVP, depending upon the side chain substitution. The MRR values are discussed in terms of monomer structural properties such as electronegativity and electron delocalization. The sequence distribution of monomers in the copolymers was studied by statistical method based on the average reactivity ratios obtained by EK-T method.
Copper oxide nano-particles as friction-reduction and anti-wear additives in lubricating oil
Vijaykumar S. Jatti,T. P. Singh 대한기계학회 2015 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.29 No.2
Lubricants based on hydrocarbon-type mixtures do not satisfy all requirements of OEMs (Original equipment manufacturers) for modernapplications. The usual solution is the addition of small amounts of certain additive compounds that render significant improvementsin base oil properties such as oxidative degradation, tribological performance and other characteristics. This study examined the tribologicalbehavior of copper oxide nanoparticles as additives in mineral based multi-grade engine oil. All tests were performed undervarying loads and concentrations of nanoparticles in lubricating oil. The friction and wear experiments were performed using pin on disctribotester. The results demonstrated that nanoparticle additives can effectively improve the engine oil lubricating properties. This is becausenanoparticles enter the friction zone along with the flow of lubricant. They convert sliding friction into rolling friction, thus reducingthe effective friction coefficient. This work also included an analysis of worn surface morphology by scanning electron microscopy. This surface examination revealed that nanoparticle additives resulted in smoother worn surfaces. From the viscosity test it can be inferredthat viscosity of engine oil contains CuO nanoparticles is a function of nanoparticles concentration. Stribeck curves are used toreveal the lubrication regimes where the CuO nano-particles are most effective. It was found that the addition of CuO nanoparticles to thebase oil results in up to 50% reduction in coefficient of friction in the mixed lubricant regime.
Deepak Kumar,Sridhar Chirumarry,B. V. D. Vijaykumar,S. J. Harshavardhan,장기완,이동하,신동수 대한화학회 2015 Bulletin of the Korean Chemical Society Vol.36 No.4
An efficient synthesis of (3Z,6Z)-cis-9,10-epoxy-3,6-henicosadiene (1), the major component of sex pheromone of saltmarsh caterpillar moth Estigmene acrea (Drury), was accomplished from commercially available pentadec-3-yn-1-ol and bromoundecane. Chirality was introduced by employing Sharpless asymmetric dihydroxylation on cis-olefin intermediate in the synthesis of 1, for the first time. The other key reactions include metal-dissolving coupling, Lindlar's catalyst-assisted partial hydrogenation, one-pot, three-step epoxidation from vicinal diol, and Wittig olefination. The overall yield of 1 was 24.7% in eight steps. The efficiency and simplicity of this synthesis allow the potential use of pheromone 1 in pest management programs.
Changing Characteristics of Droughts over Kerala, India: Inter-Annual Variability and Trend
Abhilash S.,E. K. Krishnakumar,P. Vijaykumar,A. K. Sahai,B. Chakrapani,Girish Gopinath 한국기상학회 2019 Asia-Pacific Journal of Atmospheric Sciences Vol.55 No.1
Realized changes in the climate over Kerala received more attention during recent times under the back to back drought conditions prevailing over the state. The year 2016 registered as one of the worst and extreme drought year over Kerala in recent past. This extreme drought condition may be attributed to the combined effect of realized changes in the mean climate state as well as the climate variability.Both the recent and historic drought events over Kerala is examined and its possible impacts on different sectors like agriculture and water resource are studied using the standardized precipitation index (SPI). Historical occurrence of both the short term and long term water stress associated with deficit rainfall during monsoon and postmonsoon season is presented in the paper. It is found that south west monsoon rainfall over Kerala is decreasing over south Kerala during recent decades, whereas the post-monsoon rainfall is found to be increasing especially over south Kerala. There exists a weak relationship between Pacific SSTand Kerala rainfall. Trend analysis of SPI on different time scale showed negative trend and that negative trend increases with increasing time scale.
Synthesis of POSS Derived Organic-Inorganic Hybrid Esters for Insulating Oil Applications
Kyeong-min Choi,S. J. Harshavardhan,Ch. Sridhar,B. V. D. Vijaykumar,Deepak Kumar,장기완,이만식,신동수 대한화학회 2014 Bulletin of the Korean Chemical Society Vol.35 No.9
In this work, a new family of polyhedral oligomeric silsesquioxanes (POSS) based esters have been synthesized that consists eight ester functional groups. These are classified into Type-I and Type-II esters based on the starting materials, octakis(3-chloropropyl)silsesquioxane (Cl-POSS) and octakis(3-hydroxypropyldimethylsiloxy) octasilsesquioxane (OHPS) respectively. These new POSS type ester moieties can be used as insulating oils and oil additives in the transformers and also considered to be alternatives to mineral and vegetable oils that are presently used in the insulation system.
Electrochemical supercapacitors of anodized-brass-templated NiO nanostrutured electrodes
AL-Osta, Ahmed,Jadhav, Vijaykumar V.,Zate, Manohar K.,Mane, Rajaram S.,Hui, K.N.,Han, Sung-Hwan Elsevier 2015 Scripta materialia Vol.99 No.-
<P>This paper reports the electrochemical synthesis of nickel oxide (NiO) onto a substrate template of anodized-brass (Cu–Zn). Structurally and morphologically all the electrodes, i.e. pristine, anodized and NiO-covered Cu–Zn electrodes, are different from one another. NiO-covered Cu–Zn electrodes were annealed at different temperatures (300–600°C at 100°C intervals) and appear suitable for electrochemical supercapacitors; a wide potential range (0.1–0.6V) and optimum specific capacitance (91.43Fg<SUP>−1</SUP>) are obtained for 400°C in 0.5M NaOH electrolyte at 2mVs<SUP>−1</SUP> scan rate.</P> <P><B>Graphical abstract</B></P> <P>[DISPLAY OMISSION]</P>
Synthesis of POSS Derived Organic-Inorganic Hybrid Esters for Insulating Oil Applications
Choi, Kyeong-Min,Harshavardhan, S.J.,Sridhar, Ch.,Vijaykumar, B.V.D.,Kumar, Deepak,Jang, Kiwan,Lee, Man-Sig,Shin, Dong-Soo Korean Chemical Society 2014 Bulletin of the Korean Chemical Society Vol.35 No.9
In this work, a new family of polyhedral oligomeric silsesquioxanes (POSS) based esters have been synthesized that consists eight ester functional groups. These are classified into Type-I and Type-II esters based on the starting materials, octakis(3-chloropropyl)silsesquioxane (Cl-POSS) and octakis(3-hydroxypropyldimethylsiloxy) octasilsesquioxane (OHPS) respectively. These new POSS type ester moieties can be used as insulating oils and oil additives in the transformers and also considered to be alternatives to mineral and vegetable oils that are presently used in the insulation system.