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Natural Convection of Air in a Vertical Annulus with Partially Active Side Wall
Mani SANKAR,Soojin HONG,Younghae DO,Bongsoo JANG 한국산업응용수학회 2011 한국산업응용수학회 학술대회 논문집 Vol.6 No.1
The present numerical investigation deals with the size and location effects of a single isoflux discrete heater on the buoyancy induced convection in a cylindrical annulus. A discrete heater is placed at the inner wall, while the top and bottom walls as well as the unheated portions of the inner wall are kept adiabatic, and the outer wall is maintained at a lower temperature. The influence of the location and size of the discrete heater on the convective flow and the corresponding heat transfer are obtained for a wide range of physical parameters. The predicted numerical results reveal that the placement of heater near the middle portion of inner wall yields a maximum heat transfer and minimum hot spots rather than placing the heater near the top and bottom portions of the inner wall. We found that the location of heater affects the rates of flow circulation and heat transfer in a complex fashion. The rate of heat transfer is increasing function of radii ratio of the annulus. Further, we found that the rate of heat transfer and maximum temperature in the annular cavity are significantly modified by the heater length and location.
Numerical Study of Natural Convection in a Vertical Porous Annulus with Internal Heat Source
Mani SANKAR,Junpyo PARK,Younghae DO 한국산업응용수학회 2011 한국산업응용수학회 학술대회 논문집 Vol.6 No.1
This paper reports a numerical study of natural convection in a vertical annulus filled with a fluid-saturated porous medium and with internal heat generation subject to a discrete heating from the inner wall. The relative importance of discrete heating on natural convection in the porous annulus is examined via the Brinkman-extended Darcy equation. The inner wall of the annulus has a discrete heat source and the outer wall is isothermally cooled at a lower temperature. The top and bottom walls, and the unheated portions of the inner wall are kept adiabatic. The governing equations are numerically solved using an implicit finite difference method. A wide range of numerical simulations is conducted to understand the effects of various parameters like heat source length, heat source location, Darcy number, radii ratio and Rayleigh numbers due to external and internal heating, on the flow and heat transfer. The numerical results reveal that the placement of the heater near the middle portion of the inner wall yields the maximum heat transfer and minimum hot spots rather than placing the heater near the top and bottom portions of the inner wall. The heat transfer increases with an increase in the external Rayleigh number and Darcy number, while it decreases with an increase in the internal Rayleigh number, porosity of the porous medium and the size of the heater. Further, we found that the size and location of the heater has a profound influence on the heat transfer rate and maximum temperature in the annular cavity.
Komathi, Shanmugasundaram,Palaniappan, Subramanian,Manisankar, Paramasivam,Gopalan, Anantha Iyengar,Lee, Kwang-Pill WILEY-VCH Verlag 2010 Macromolecular chemistry and physics Vol.211 No.12
<P>We report the large scale preparation of nanostructured polyaniline-Pd nanoparticles composites (designated as PANI(NS)-PdNPs) through a “seed” induced bulk polymerization. Initially, a small quantity of PANI(NS)-PdNPs was formed inside the cavities of MCM-41 and used as the “seed” for the bulk preparation of PANI(NS)-PdNPs composite. For a comparative purpose a PANI-PdNPs composite was also prepared in the absence of the seed. FESEM image of PANI(NS)-PdNPs composite (bulk) shows nanofibrillar morphology. Further, transmission electron microscopy reveals the presence of spherical Pd nanoparticles. PANI(NS)-PdNPs composite (bulk) showed a good catalytic activity towards reduction of 4-nitrophenol.</P><P> <img src='wiley_img_2010/10221352-2010-211-12-MACP200900640-gra001.gif' alt='wiley_img_2010/10221352-2010-211-12-MACP200900640-gra001'> </P> <B>Graphic Abstract</B> <P>A “seed” induced bulk polymerization technique was proposed for the large scale preparation of nanostructured polyaniline incorporated with Pd nanoparticles composites (designated as PANI(NS)-PdNPs). PANI(NS) exhibited nanofibrils morphology and attached with spherical Pd NPs. The utility of PANI(NS)-PdNPs composite (bulk) as a catalyst for the reduction of 4-Nitrophenol has been demonstrated. <img src='wiley_img_2010/10221352-2010-211-12-MACP200900640-content.gif' alt='wiley_img_2010/10221352-2010-211-12-MACP200900640-content'> </P>
Komathi, Shanmugasundaram,Palaniappan, Subramanian,Manisankar, Paramasivam,Gopalan, Anantha Iyengar,Lee, Kwang-Pill American Scientific Publishers 2010 Journal of Nanoscience and Nanotechnology Vol.10 No.8
<P>This is the first report on the preparation of nanobelts/nanodiscs of poly(1,5-diamino naphthalene) (PDAN-P) in bulk quantities through a 'hard-soft combined templates' approach. PDAN was nanostructured within the channels of MCM-41 (hard template) in the presence of beta-napthalene sulfonic acid (beta-NSA) (soft template) and further used as the seed for the bulk preparation of pure PDAN nanobelts/nanodiscs of PDAN (PDAN-P). Field emision scanning electron microscope image reveals that a typical nanobelt has a length of approximately 3 microm, with a uniform breadth of approximately 150 nm and a thickness of approximately 50 nm. UV-Visible spectrum reveals that the electronic features of PDAN-P are different from PDAN prepared by conventional method (PDAN-C). The electrochemical and interfacial characteristics of PDAN-P were evaluated by cyclic voltammetry and impedance spectroscopy and compared with PDAN-C. The current density characteristics of ITO/PDAN-P and ITO/PDAN-C were also compared. The potential for the onset of current and the current densities beyond the onset potentials were higher at ITO/PDAN-P than for ITO/PDAN-C. Results from electrochemical imedance spectroscopy informed that the ac conductivity of PDAN-P is higher than PDAN-C. Thus, PDAN-P exhibits distinctly different electronic and electrochemical characteristics as compared to PDAN-C.</P>
Electrochemical Properties of Nickel Oxide Nanoparticles Loaded Poly(o-toluidine) Composites
Shanmugasundaram Komathi,Pothum Selvi,Paramasivam Manisankar,Anantha Iyengar Gopalan,이광필 한국전기화학회 2011 한국전기화학회지 Vol.14 No.1
New nanocomposites, composed of poly(o-toludine) (POT) and nickel oxide nanoparticles (NiO-NPs), were prepared through oxidative polymerization of o-toludine (OT) in the presence of NiO-NPs. Films of NiO/POT were prepared with different amount of NiO-NPs (x) and different concentrations of OT (y) and designated as NiO(x)/POT(y) nanocomposites (x = amount of NiO-NPs (mg), y = concentration of OT (mM)). Field emission scanning electron microscopy images revealed that NiO-NP_s have nanorod like morphology. The two peaks, 0.39 V and 0.77V,are attributed to the redox conversion of leucoemeraldine to emeraldine and emeraldine to fully oxidized forms of POT, respectively. Electroactivity of the NiO(x)/POT(y) films showed dependence on x and y. Efficient electrocatalysts could be obtained by tuning x and y.
Jayamani, A.,Thamilarasan, V.,Sengottuvelan, N.,Manisankar, P.,Kang, S.K.,Kim, Y.I.,Ganesan, V. Pergamon 2014 Spectrochimica acta. Part A, Molecular and biomole Vol.122 No.-
The mononuclear copper(II) complexes (1&2) of ligands L<SUP>1</SUP> [N,N'-bis(2-hydroxy-5-methylbenzyl)-1,4-bis(3-iminopropyl)piperazine] or L<SUP>2</SUP> [N,N'-bis(2-hydroxy-5-bromobenzyl)-1,4-bis(3-iminopropyl) piperazine] have been synthesized and characterised. The single crystal X-ray study had shown that ligands L<SUP>1</SUP> and L<SUP>2</SUP> crystallize in a monoclinic crystal system with P2<SUB>1</SUB>/c space group. The mononuclear copper(II) complexes show one quasireversible cyclic voltammetric response near cathodic region (-0.77 to -0.85V) in DMF assignable to the Cu(II)/Cu(I) couple. Binding interaction of the complexes with calf thymus DNA (CT DNA) investigated by absorption studies and fluorescence spectral studies show good binding affinity to CT DNA, which imply both the copper(II) complexes can strongly interact with DNA efficiently. The copper(II) complexes showed efficient oxidative cleavage of plasmid pBR322 DNA in the presence of 3-mercaptopropionic acid as reducing agent through a mechanistic pathway involving formation of singlet oxygen as the reactive species. The Schiff bases and their Cu(II) complexes have been screened for antibacterial activities which indicates that the complexes exhibited higher antimicrobial activity than the free ligands.
Yu, Hak Ki,Balasubramanian, Kannan,Kim, Kisoo,Lee, Jong-Lam,Maiti, Manisankar,Ropers, Claus,Krieg, Janina,Kern, Klaus,Wodtke, Alec M. American Chemical Society 2014 ACS NANO Vol.8 No.8
<P>We present a simple approach to improving the quality of CVD grown graphene, exploiting a Cu(111) foil catalyst. The catalyst is epitaxially grown by evaporation on a single crystal sapphire substrate, thickened by electroplating, and peeled off. The exposed surface is atomically flat, easily reduced, and exclusively of (111) orientation. Graphene grown on this catalyst under atmospheric CVD conditions and without wet chemical prereduction produces single crystal domain sizes of several hundred micrometers in samples that are many centimeters in size. The graphene produced in this way can easily be transferred to other substrates using well-established techniques. We report mobilities extracted using field-effect (as high as 29 000 cm<SUP>2</SUP> V<SUP>–1</SUP> s<SUP>–1</SUP>) and Hall bar measurement (up to 10 100 cm<SUP>2</SUP> V<SUP>–1</SUP> s<SUP>–1</SUP>).</P><P><B>Graphic Abstract</B> <IMG SRC='http://pubs.acs.org/appl/literatum/publisher/achs/journals/content/ancac3/2014/ancac3.2014.8.issue-8/nn503476j/production/images/medium/nn-2014-03476j_0007.gif'></P><P><A href='http://pubs.acs.org/doi/suppl/10.1021/nn503476j'>ACS Electronic Supporting Info</A></P>