Physics

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Author: search.filters.author.Jayakody, J.R.P.Has files: No

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    Observation of n-type Photoconductivty in Electrodeposited Copper Oxide Film Electrodes in a Photoelectrochemical cell
    (Solar Energy Materials, 1986) Siripala, W.; Jayakody, J.R.P.
    Copper oxide films were cathodically deposited on various metal substrates (Cu, Ti and Pt) using a basic solution of CuSO4, and it is found that they produce n-type photoconductivity in a photoelectrochemical cell. The photoresponse of these films is more pronounced than the previously known thermally grown p-Cu2O films, and the n-type behaviour could be converted to p-type by heating the samples in air. It is tentatively proposed that oxygen ion vacancies in the electrodeposited copper oxide films would result in n-Cu2O.
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    Study of Daytime Variation of Convective and Non-Convective Zones in Salt Pan Solar Ponds
    (Annual Research Symposium, Faculty of Graduate Studies, University of Kelaniya, 2002) Perera, P.A.A.; Amarasekara, C.D.; Jayakody, J.R.P.; Punyasena, M.A.
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    Construction and Filling of a Large-area Deep-tank Solar Pond for Harnessing Solar Energy
    (Annual Research Symposium, Faculty of Graduate Studies, University of Kelaniya, 2002) Jayakody, J.R.P.; Punyasena, M.A.; Perera, P.A.A.; Amarasekara, C.D.; Kumarasinghe, M.A.S.
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    Daytime Variation of Temperature and Salinity Profiles in Large-Area Saltpan Solar Ponds at Palavi, Sri Lanka
    (Proceedings of the 18th Technical Session of the Institute of Physics - Sri Lanka, 2002) Perera, P.A.A.; Amarasekara, C.D.; Jayakody, J.R.P.; Punyasena, M.A.
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    Investigation of Temperature and Density Profiles of Brines in Evaporating Salt Pans at Palaviya in the North-Western Region of Sri Lanka
    (Proceedings of the 16th Technical Session of the Institute of Physics - Sri Lanka, 2001) Hewageegana, P.S.; Amarasekara, C.D.; Jayakody, J.R.P.; Punyasena, M.A.
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    A Study of Wind Effects on Thermal Stability of Salt Pan Solar Ponds
    (Annual Research Symposium, Faculty of Graduate Studies, University of Kelaniya, 2001) Punyasena, M.A.; Amarasekara, C.D.; Jayakody, J.R.P.; Perera, P.A.A.
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    A Study of Temperature and Salinity Variations with Depth in Salt Pans at Palavi in North-West Region of Sri Lanka
    (Annual Research Symposium, Faculty of Graduate Studies, University of Kelaniya, 2000) Hewageegana, P.S.; Amarasekara, C.D.; Jayakody, J.R.P.; Punyasena, M.A.
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    Investigation of temperature and density profile of brine in evaporating salt pans at Palavi in north-western Sri Lanka
    (2001) Hewageegana, P.; Amarasekara, C.D.; Jayakody, J.R.P.; Punyasena, M.A.
    Measurements of temperature and density variations with depth in salt pans having a stable salinity gradient are presented. The density variation of brine has been correlated to the temperature variation with depth. The convective and nonconvective zones were identified. Gradients in salinity and temperature in the nonconvective zone were observed. Temperature and salinity were observed to remain the same throughout the convective bottom layer of brine in the ponds. The investigation has been extended to different ponds filled to different depths and storage periods of brine. A maximum temperature of around 55 0C was observed in the bottom layers while the surface remained as low as 29 0C. This is a consequence of positive salt-density gradient, which suppresses convection and allows a temperature gradient to develop downwards. The temperature measurements of different ponds filled to different heights indicate that the convective bottom layer temperature of a pond will increase if the pond is filled with brine to a higher level. These results indicate that the large area deep salt pans with long term storage periods can be used as solar ponds to collect and store solar energy in addition to the usual salt production. Based on our results we speculate that the bottom temperatures of these ponds could be increased to about 80 0C by filling the ponds to a height of about 1.5 meters. Thermal energy stored in the convective bottom layer of these ponds could be extracted for many applications. The moderate temperature desalination of seawater especially in the areas where fresh water is in short supply is identified as one of the promising applications of thermal energy stored in solar pond-salt pans.
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    NMR Studies of Mass Transport in High-Acid-Content Fuel Cell Membranes Based on Phosphoric Acid and Polybenzimidazole
    (Journal of Electrochemical Society, 2007) Jayakody, J.R.P.; Chung, S.H.; Durantino, L.; Zhang, H.; Xiao, L.; Benicewicz, B.; Greenbaum, S.G.
    Mass-transport studies of phosphoric acid (PA)-doped meta-polybenzimidazole (PBI) fuel cell membranes are described. In this study, the fundamental differences in transport properties between m-PBI/PA membranes prepared by conventional imbibing procedures and the polyphosphoric acid (PPA) process are explored. The membranes were characterized by proton conductivity and multinuclear (1H and 31P) magnetic resonance measurements. Both short-range and long-range dynamical processes were investigated by spin?lattice and spin?spin relaxation time measurements and by pulsed ?eld gradient diffusion, respectively. Comparative data for pure PA and PPA are included. The high proton conductivity(0.13 S/cm at 160�C) of the PPA-processed membranes is correlated with rapid proton self-diffusion (3 x 10?6 cm2/s at 180�C). The 31P results reveal the presence of both PA and the dimeric pyrophosphoric acid and indicate strong interaction between the phosphate groups and the m-PBI matrix, with negligible anionic transport for both kinds of membranes. The higher concentration of PA in the PPA-processed membranes and differences in membrane morphology may provide an additional proton-transport mechanism involving rapid exchange between the PA and pyrophosphoric acid species.
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    Studies of Water in Nafion Membranes: Using Deuteron and Oxygen?17 Nuclear Magnetic Resonance, and Dielectric Relaxation Techniques
    (Journal of Electrochemical Society, 1993) Chen, R.S.; Jayakody, J.R.P.; Greenbaum, S.G.; Pak, Y.S.; Xu, G.; McLin, M.G.; Fontanella, J.J.
    Deuteron and oxygen-17 nuclear magnetic resonance measurements and dielectric relaxation studies of Nafion-117 membranes with variable water content (approximately 5-18% by weight) have been carried out. Glassy behavior of the water domains at low temperature, below ca. 200 K, is evidenced by the specific nature of the 2H NMR line shapes. Activation energies extracted from H spin-lattice relaxation data on the high temperature side of the T1 minimum exhibit a steady increase with increasing water content. In spite of a high degree of molecular mobility, angular-dependent spectra in both as-received and stretched samples reflect considerable anisotropy of the host polymer. A dielectric loss peak is observed which previously has been attributed to the glass transition of the aqueous domains.