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Experimental and Computational Studies on the Reentry Capsule Aerodynamics with a Flap
Senthil Kumar,J K Prasad,Kim H D 한국추진공학회 2016 한국추진공학회 학술대회논문집 Vol.2016 No.5
Flow field around a typical reentry capsule has been investigated adopting experiments and computations. The reentry capsule has the flap which could be useful to obtain control force. All the studies have been made at a free stream Mach number of 2 and Reynolds number of 30 X 106. Experiments consisted of schlieren flow visualization and measurement of axial force only. Three dimensional computation has been made using FLUENT and adopting k-ω turbulence model. Effect of angle of attack and flap angle has been obtained. Based on present study, it is observed the flap increases the axial force.
UV-Blue Light Emission from ZnO Nanoparticles
Obuliraj Senthilkumar,Kazuki Yamauchi,Kasilingam Senthilkumar,Takahiro Yamamae,Yasuhisa Fujita,Naoki Nishimoto 한국물리학회 2008 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.53 No.1
Gas evaporation was employed to prepare nitrogen-doped ZnO nanoparticles, which showed in- tense UV/blue emission (380 nm) at room temperature. The thin lms were deposited by dip coating with nanoparticles dispersed in isopropanol and water. The PL spectrum showed dominant acceptor bound excitons around 371 nm at low temperatures, which was due to the substitution of nitrogen acceptors in oxygen sites. Nitrogen doping was also conrmed from Raman spectroscopy, which showed a nitrogen-related local vibrational mode (LVMN) at 583 cm-1. Gas evaporation was employed to prepare nitrogen-doped ZnO nanoparticles, which showed in- tense UV/blue emission (380 nm) at room temperature. The thin lms were deposited by dip coating with nanoparticles dispersed in isopropanol and water. The PL spectrum showed dominant acceptor bound excitons around 371 nm at low temperatures, which was due to the substitution of nitrogen acceptors in oxygen sites. Nitrogen doping was also conrmed from Raman spectroscopy, which showed a nitrogen-related local vibrational mode (LVMN) at 583 cm-1.
Senthilkumar, S.,Karthik, B.,Chandrasekar, S. The Korean Institute of Electrical Engineers 2014 Journal of Electrical Engineering & Technology Vol.9 No.5
Partial discharge (PD) detection plays a major role in the life time assessment of liquid insulation in power transformers. Many research works are being carried out to replace conventional mineral oil insulation in transformers by vegetable oils. It is necessary to understand the PD characteristics of vegetable oils before recommending them as an alternate for mineral oil. In this paper, the breakdown strength and PD characteristics of palm and corn oil were investigated in both unaged and thermally aged conditions. Laboratory experiments were performed as per IEC test procedures. PD signals were measured using wide band detection system. Phase resolved PD pattern of vegetable oils and mineral oil were compared. Effect of increase in voltage stress on the PD pattern of palm and corn oil were studied. Time and frequency domain analysis of PD pulses at needle-plane electrode configuration was carried out. Statistical analysis of PD pattern i.e. skewness and shape parameter variations with respect to applied thermal stress were also carried out. From the results, it is observed that palm and corn oils have better breakdown strength and PD characteristics even under long-term thermal stress and hence they can be used for power transformer applications.
Graphene oxide self-assembled with a cationic fullerene for high performance pseudo-capacitors
Senthilkumar, Krishnan,Prabakar, S. J. Richard,Park, Chunkuk,Jeong, Seok,Lah, Myoung Soo,Pyo, Myoungho The Royal Society of Chemistry 2016 Journal of Materials Chemistry A Vol.4 No.5
<▼1><P>Control of the microstructures of graphene oxide is realized by introducing a cationic fullerene, resulting in a high-performance pseudo-capacitor.</P></▼1><▼2><P>Control of the microstructures of graphene oxide (GO) is realized by introducing a cationic fullerene (CFU), resulting in a high-performance pseudo-capacitor. The strong electrostatic interaction between anionic GO and the CFU produces a self-assembled composite (GO/CFU), in which the CFU units intervene to form randomly stacked GO layers. The CFU acts as a spacer between GO layers, allowing a significant fraction of the oxygen-functional groups of GO to be redox-active. When tested as a pseudo-capacitor in 1.0 M H2SO4, the optimized GO/CFU composite delivers a capacitance of 357 F g<SUP>−1</SUP> at 0.4 A g<SUP>−1</SUP>, in contrast to 160 F g<SUP>−1</SUP> for GO alone, which is one of the greatest values reported for graphene composites with electro-inactive carbonaceous entities. The improvement in the capacitance by CFU incorporation is also evidenced at a high charge/discharge rate (285 and 137 F g<SUP>−1</SUP> at 5 A g<SUP>−1</SUP> for GO/CFU and GO, respectively). As a result, the GO/CFU composite delivers an energy density of 40 W h kg<SUP>−1</SUP> and a power density of 2793 W kg<SUP>−1</SUP> at 5 A g<SUP>−1</SUP>, in contrast to 19 W h kg<SUP>−1</SUP> and 2748 W kg<SUP>−1</SUP> for GO alone. During 5000 charge/discharge cycles at 5 A g<SUP>−1</SUP>, the capacitance of the GO/CFU composite increases slightly (4% increase in GO/CFU <I>vs.</I> 4% decrease in GO), which validates the effectiveness of a self-assembly strategy for high performance supercapacitor applications.</P></▼2>
Senthilkumar, Nangan,Babu, Kaliyamoorthy Justice,Gnana kumar, Georgepeter,Kim, Ae Rhan,Yoo, Dong Jin American Chemical Society 2014 INDUSTRIAL & ENGINEERING CHEMISTRY RESEARCH - Vol.53 No.25
<P>Highly selective and efficient nonenzymatic electrochemical glucose sensors were fabricated by using electrospun polyvinylidenefluoride-<I>co</I>-hexafluoropropylene (PVdF-HFP) composite nanofiber membranes. The homogeneous, smooth and strongly interconnected nanofibers were identified for the bare PVdF-HFP membrane and beads in the PVdF-HFP nanofibers were observed for the PVdF-HFP/Ni and PVdF-HFP/Ni/Co nanofiber membranes. The face-centered cubic structure of Ni nanoparticles doped in the PVdF-HFP nanofibers has not been altered, even after the alloy formation with Co. The electrochemical oxidation of glucose in an alkaline medium was chosen as a probe for the detection of glucose and was achieved through the fabricated nanofiber membranes. Among the fabricated nanofiber membranes, the PVdF-HFP/Ni/Co membrane exhibited an excellent sensing behavior toward glucose with the low limit of detection and linear range of 0.26 μM and 1 μM to 7 mM, respectively. Furthermore, the fabricated nanofiber membrane exhibited good selectivity, high stability and reproducibility, which promises its applications in nonenzymatic glucose sensors.</P><P><B>Graphic Abstract</B> <IMG SRC='http://pubs.acs.org/appl/literatum/publisher/achs/journals/content/iecred/2014/iecred.2014.53.issue-25/ie500755m/production/images/medium/ie-2014-00755m_0016.gif'></P>
Senthilkumar, Baskar,Khan, Ziyauddin,Park, Seungyoung,Kim, Kyoungho,Ko, Hyunhyub,Kim, Youngsik The Royal Society of Chemistry 2015 Journal of Materials Chemistry A Vol.3 No.43
<▼1><P>A high energy hybrid capacitor fabricated from highly porous graphitic carbon and novel electrode material Ni2P2O7 delivers a maximum energy density of 65 W h kg<SUP>−1</SUP> at a power density of 800 W kg<SUP>−1</SUP>, good rate capability and cycling stability in an aqueous Na-ion based electrolyte.</P></▼1><▼2><P>An aqueous Na-ion based hybrid capacitor has been successfully developed by using highly porous graphitic carbon (HPGC) derived from waste writing paper and a new electrode material as a negative and positive electrode, respectively. HPGC was prepared <I>via</I> hydrothermal carbonization and subsequent KOH activation of waste writing paper which showed a highly porous stacked sheet-like morphology with an exceptionally high BET specific surface area (1254 m<SUP>2</SUP> g<SUP>−1</SUP>). HPGC exhibited typical electrical double layer capacitor (EDLC) behavior with a high specific capacitance of 384 F g<SUP>−1</SUP> and good negative working potential (−1.0 V) in an aqueous electrolyte. On the other hand, Ni2P2O7 was synthesized by a simple co-precipitation technique and tested as a cathode material which delivered a maximum specific capacitance of 1893 F g<SUP>−1</SUP> at 2 A g<SUP>−1</SUP> current density. The fabricated HPGC‖Ni2P2O7 hybrid device displayed excellent cyclic stability up to 2000 cycles and delivered a maximum energy density of 65 W h kg<SUP>−1</SUP> at 800 W kg<SUP>−1</SUP> power density in a Na-ion based aqueous electrolyte.</P></▼2>
Methyl Isocyanate and Carcinogenesis: Bridgeable Gaps in Scientific Knowledge
Senthilkumar, Chinnu Sugavanam,Sah, Nand Kishore,Ganesh, Narayanan Asian Pacific Journal of Cancer Prevention 2012 Asian Pacific journal of cancer prevention Vol.13 No.6
Methyl isocyanate may have a role in cancer etiology, although the link is unclear. There is evidence in the literature that it can induce cancer in animals but the carcinogenic potency is weak. Pheochromocytoma of adrenal medulla and acinar cell tumors of pancreas have been observed in methyl isocyanate exposed animals. Conversely, emerging data from population-based epidemiological studies are contradictory since there is no evidence of such cancers in methyl isocyanate exposed humans. Recently, we reported a high prevalence of breast and lung cancers in such a population in Bhopal. In vitro findings appearing in the latest scientific literature suggest that genomic instability is caused by methyl isocyanate analogs in lung, colon, kidney, ovary epithelial cells, and that hepatocytes may undergo oncogenic transformation, have obvious implications. The conflicting information prompted us to present this update over the last three decades on methyl isocyanate-induced cancers after an extensive literature search using PubMed. While the pertinent literature remains limited, with a scarcity of strong laboratory analyses and field-epidemiological investigations, our succinct review of animal and human epidemiological data including in vitro evidences, should hopefully provide more insight to researchers, toxicologists, and public health professionals concerned with validation of the carcinogenicity of methyl isocyanate in humans.
Senthilkumar K.M,Kathiravan N,Girisha L,Sivaperumal M 한양대학교 세라믹연구소 2022 Journal of Ceramic Processing Research Vol.23 No.4
In the recent years, mankind has established that the protection of the environment becomes a vital part in the discovery ofany engineering applications. Several engineering applications in the areas of agriculture, forestry, energy industries, havedeveloped several composite materials in place of other materials for its effectiveness. This work focuses on synthesis of acomposite material and the matrix material used in the research work was epoxy resin. Glass fibres were used as thereinforcement material for the preparation of the hybrid epoxy based composite. The epoxy used in this work is LB011 epoxyresin lapox B_11. The hardener used is Triethylenetetraamine (TETA). The composite laminates are prepared by varying theweight proportion of the glass fibres and tested for its mechanical properties. The composite laminate with high tensile strengthis selected for the investigation of machining properties of the composite laminate. Optimization of machining parameter arecarried out by a novel analysis called Desirability Function Analysis (DFA), which is an optimal tool considered for theproblems with multi objective optimization function.