Sri Lankan Journal of Physics, Volume 8, March 2007.
Comparison of RegCM3 simulated meteorological parameters
in Bangladesh: Part I-preliminary result for rainfall
Md. Mizanur Rahman1, Md. Nazrul Islam2, Ahsan Uddin
Ahmed3 and Romee Afroz1
1SAARC Meteorological Research Centre, Dhaka, Bangladesh,
2Department of Physics, Bangladesh University of Engineering and
Technology, Dhaka, Bangladesh, 3Bangladesh Unnayan Parishad, Niketan,
Gulsan 1, Dhaka, Bangladesh
A Regional Climate Model of version 3 (RegCM3) is employed for the study of meteorological parameters in Bangladesh. To adopt the RegCM3 for this region comparison of model outputs with surface observational data is essential. In this connection, this paper represents the comparison of model rainfall with surface observational data of 29 stations throughout the country collected by the Bangladesh Meteorological Department (BMD). RegCM3 is run at 0.54° × 0.54° horizontal grid resolution in two parameterizations: Grell scheme with Arakawa-Schubert (GAS) and Fritch-Chappell (GFC) assumptions. GAS run used Lateral Boundary Conditions (LBCs) data for 1995-2000 whereas GFC run used LBC data for 1991, 1994, 1996 and 1999. For the entire rainy season (March-November), model estimates about 101% of the surface rain for GFC option whereas model overestimates in pre-monsoon and underestimates in monsoon periods. The GFC option is found better than the GAS option in estimating rainfall by the model.
Sri Lankan Journal of Physics, Volume 8, March 2007.
Comparison of RegCM3 simulated meteorological parameters
in Bangladesh: Part II-preliminary result for temperature
Md. Mizanur Rahman1, Md. Nazrul Islam2, Ahsan Uddin
Ahmed3 and Romee Afroz1
1SAARC Meteorological Research Centre, Dhaka,
Bangladesh, 2Department of Physics, Bangladesh University of Engineering
and Technology, Dhaka, Bangladesh, 3Bangladesh Unnayan Parishad,
Niketan, Gulsan 1, Dhaka, Bangladesh
Simulation of meteorological parameters and comparison of rainfall for Bangladesh is described in part I. This part II describes the comparison of model simulated temperature for Bangladesh. The parameters are simulated by Regional Climate Model version 3 (RegCM3). Temperature simulated by RegCM3 is compared with surface air temperature collected by the Bangladesh Meteorological Department (BMD) at 29 locations throughout the country. RegCM3 is run at 60 km × 60 km horizontal grid resolution in a large domain that covers 65-117°E and 5-38°N. Grell scheme with Arakawa-Schubert (GAS) and Fritch-Chappell (GFC) assumptions are used in model simulation. GAS run used Lateral Boundary Conditions (LBCs) data for the years of 1995-2000 whereas GFC run used LBC data for 1991, 1994, 1996 and 1999. It is found that a systematic cold bias is existed in simulating temperature for Bangladesh. The model underestimates about 2°C in calculating temperature. In GAS assumption, the model can simulate temperature with about 94% accuracy to the surface air temperature in annual scale. It is found that the GAS option is better than the GFC in simulating temperature in Bangladesh.
Sri Lankan Journal of Physics, Volume 8, March 2007.
Effect of sputtering conditions on the gas sensitivity of
copper oxide thin films
P. Samarasekara and N. U. S. Yapa
Department of Physics, University of Ruhuna, Matara, Sri Lanka
Copper Oxide (CuO) thin films were deposited on conductive glass substrates using DC reactive sputtering in a mixture of Argon and Oxygen gases. The sputtering pressure and the substrate temperature were increased from 6 to 8.5 mbar and from 70 to 192 0C, respectively. All the synthesized films contain single phase of CuO in this range of pressure and substrate temperature. According to Scherrer formula, the crystallite sizes vary from 9.03 to 22.47 nm as sputtering pressure is varied from 8.5 to 6 mbar. The crystallites favoring perpendicular orientations dominate at higher deposition pressures due to higher deposition rates. Due to smaller crystallite sizes, the film deposited at 192 0C under 8.5 mbar pressure provides a gas sensitivity as high as 19.26 after keeping10 minutes in CO2 gas at room temperature. The sample fabricated at 192 0C and 9 mbar indicates a sharp drop of CO2 gas sensitivity from 3.67 to 0.84 at operating temperature 75 0C. All theses samples are not sensitive to N2 gas according to cross-sensitivity measured in N2 gas.
Sri Lankan Journal of Physics, Volume 8, March 2007.
Optical properties of Poly-[2-methoxy-5-(2-ethyl-hexyloxy)-phenylene
vinylene and its application in photovoltaic cells
P. M. Sirimanne and E. V. A. Premalal
Nano-Science Laboratory, Institute of Fundamental Studies, Hantana Road,
Kandy, Sri Lanka
A conjugated polymer poly[2-methoxy-5-(2-ethyl-hexyloxy)-phenylene vinylene] (MEH-PPV) exhibits unique absorption band in the visible region due to electron transitions between nonlocalized bands and emits light in three different wavelength regions. Doping of iodine increases absorption in the visible region of polymer. MEH-PPV is used as a hole-conductor and a sensitizer in titana based solid-state photovoltaic cells. Maximum photocurrent of 1.3 mAcm-2 and voltage of about 543 mV are observed for a photovoltaic cell with the polymer sensitizing layer. However, slightly higher photocurrent (2.4 mAcm-2) with a decrement of voltage (465 mV) is observed for a solid-state cell with a configuration of TiO2|dye|MEHPPV| I2, under AM 1.5 conditions. Incident light to power conversion efficiency of these cells is about 0.6 %.
Sri Lankan Journal of Physics, Volume 8, March 2007.
Artificial muscles based on polyacrylonitrile based polymer
electrolyte
Kumudu Perera1, K.P. Vidanapathirana1, M.A.K.L. Dissanayake2
1Department of Electronics, Wayamba University of Sri Lanka,
Kuliyapitiya, 2Department of Physics, University of Peradeniya, Peradeniya.
A system capable of converting chemical energy into mechanical energy can be treated as an artificial muscle or an actuator. Direct drive actuators incorporating materials like ferroelectric ceramics and piezoelectric polymers suffer from various limiting factors. It has been realized that polymers can be used to fabricate such muscles with appreciable performances. Movement of the muscles takes place as a result of incorporation and ejection of ions. In this study, the fabrication of a dry muscle using a Polyacrylonitrile (PAN) based electrolyte and two polypyrrole (PPy) electrodes and investigation of its performance is discussed.
The composition of the polymer electrolyte was 21mol%PAN : 39mol%EC : 33mol%PC
: 7mol%LiCF3SO3) and it has a good mechanical stability. Two identical polypyrrole
electrodes have been polymerized in the presence of dodecylbenzenesulfonate
(DBS). An assembly of PPy : polymer electrolyte : PPy was formed in the normal
atmosphere. Movements were observed using cyclic voltametry technique. Simultaneously,
horizontal displacement of the muscle was observed. A rough estimation was done
about the velocity of the muscles during oxidation and reduction. During reduction,
a faster movement was obtained.
Sri Lankan Journal of Physics, Volume 8, March 2007.
Electrochemical propertis of LiCo0.4Ni0.6º2 and its
performance in rechargable lithim batteries
N.W.B. Balasooriya1 and P.W.S.K. Bandaranayake2
1Faculty of Applied Sciences, South Eastern University of Sri
Lanka, 2Department of Physics, University of Peradeniya, Peradeniya
Intercalation cathode materials belonging to the 4-volt class electrodes, lithiated cobalt oxide LiCoO2 and lithiated nickel cobalt oxide LiCo0.4Ni0.6O2, were synthesized by sol-gel technique. The structural characteristics of the compounds were studied using XRD, FTIR and DSC. The compounds were used as cathode materials for assembling rechargeable lithium-batteries and their electrochemical performances were studied. The potentiostat and galvanostat techniques were used to determine the electrochemical characteristics. The irreversible capacity loss of LiCoO2 during the first charge-discharge is about 20% and for LiCo0.4Ni0.6O2 is about 90% for two different current rates of 5 and 10 A kg-1. The overall electrochemical capacity of LiCo0.4Ni0.6O2 has been drastically reduced due to the s-block or p-block metal substitution. Also the un-reacted materials remained as impurities gave a very poor cycleability. However more stable charge-discharge performances have been observed for LiCoO2 at different current rates. Differences and similarities between these two cathode materials in batteries are also discussed. The Li-ion batteries were assembled using the sol-gel synthesized cathode materials, natural untreated vein graphite of Sri Lanka as the anode material and 1 M LiPF6 in EC/DMC as liquid electrolyte, and their performances were tested.