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Item Optimization of Thermal Insulation of a Small-scale Experimental Solar Pond(Sri Lankan Journal of Physics, 2012) Jayatissa, N.W.K.; Attalage, R.; Hewageegana, P.S.; Perera, P.A.A.; Punyasena, M.A.A small-scale experimental salinity-gradient solar pond, which will be utilized for the research and development in harnessing solar energy for desalination of seawater and generation of electricity, has been constructed. The pond has effective length, width and depth of 3.0 m, 2.0 m and 2.0 m, respectively, covering a volume capacity of 12.0 m3. Thermal insulation plays a major role for the successful operation of a salinity-gradient solar pond, especially when the dimensions of the pond are relatively small. The construction details of the solar pond, with particular attention to the methodologies adapted for the thermal insulation, are reported in the present work. The expected total rate of heat loss due to conduction through the thermally insulated boundary walls, assuming a bottom temperature of 90�C, has been calculated and found to be 106.3 W. Contribution from the bottom convective zone itself to this total rate of heat loss is 69 W, which corresponds to 65% of the total value. Based on this rate, the estimated temperature drop during the period with no solar radiation present in a typical day is only 0.3�C. With such a small temperature drop, it is possible to extract the thermal energy stored in the bottom convective zone during the day time, continuously, while maintaining the stability of the solar pond.Item Multilevel nanoimprint lithography(Current Applied Physics, 2004) Alkaisi, M.M.; Jayatissa, N.W.K.; Konijn, M.Multilevel and three-dimensional (3D) patterning eliminates more complicated steps in the fabrication processes of micro and nanoscale structures. Multiple lithography processes with inter-level alignment or single lithography with multi layer resist is essential for three-dimensional patterning. Nanoimprint lithography has demonstrated the potential of 3D patterning in a single step. A number of 3D structures have found immediate applications in a range of microelectronic systems such as microoptics, microelectromechanical systems, and monolithic microwave integrated circuits [Appl. Phys. Lett. 78 (2000) 3322; Appl. Phys. Lett. 79 (2001) 2285]. In this work, electron beam lithography (EBL) with different doses followed by reactive ion etching (RIE) is employed in the fabrication of multilevel structures of SixNy molds. The multi level patterns have been transferred into the mold in single step RIE. The imprint process has been performed below the glass transition temperature of the polymer. This may alleviate the alignment errors due to different thermal expansion coefficients in various materials.Item Energy use in controlled temperature marine aquaculture(International Journal of Energy Research, 2002) Jayatissa, N.W.K.; Davis, C.; Carrington, G.; Chen, G.Temperature control offers benefits in land-based marine aquaculture: stock growth rates may be enhanced by heating in winter; mortality rates in summer may be reduced by cooling. However, if the plant is not well designed, temperature control may create very large energy demands. This paper describes the application of temperature control in abalone aquaculture in New Zealand, with a focus on energy considerations in plant design. An abalone farm using a semi-closed water conditioning system is used as a case study for which an energy model, based on a heat pump system, is developed. The model is used to determine the impact of plant design and tank conditions on the economics of the operation.Item 3D Imprint Lithography Using Sixny Molds(2002) Jayatissa, N.W.K.; Alkaisi, M.M.; Blaikie, R.J.Three-dimensional patterning reduces more complicated alignment steps in the fabrication of micro and nano-scale structures. Multiple lithography processes with interlevel alignment or single lithography with multi layer resist is essential for three dimensional patterning. A number of 3D structures have found immediate applications in a range of microelectronic systems such. as micro-optics, micro-electromechanical systems, and in monolithic microwave integrated circuits. We have previously demonstrated that imprint at low temperatures (well below the glass transition of the resist) is possible for a number of structures using silicon nitride (SixNy) molds. A low temperature process is important for pattering substrates or polymer-based materials that are intolerant of high temperatures. The advantages of using SixNy for mold making are the capability of forming reliable nanoscale structures and its surface properties that allows imprint without sticking. In this work we will present pattering results for three-dimensional structures using nanoimprint lithography with SixNy molds. The mold material consists of a 1?m thick low stress SixNy layer deposited by low-pressure chemical vapour deposition (LPCVD) on to a silicon substrate. Patterning of the SixNy was performed using electron beam lithography at 50keV into ma-N 24033 negative tone resist.Item UV absorption properties of natural solutions(2008) Wijesiri, W.D.S.; Jayatissa, N.W.K.; Jayakody, J.R.P.Electromagnetic radiation is classified into types according to the frequency of the waves such as radio waves, microwaves, terahertz radiation, infrared radiation, visible light, ultraviolet radiation, X-rays and gamma rays. UV radiation is a part of the electromagnetic spectrum emitted by the sun, and is divided according to wavelength into three regions known as UVA, UVB and UVC. The UVC is completely absorbed by the atmospheric ozone, water vapor, oxygen and carbon dioxide. However, both UVA and UVB are of major importance to human health. These radiations may penetrate into the skin and eyes, causing the adverse health effects, such as skin cancers, cataracts and immune suppression. The objective of this work is to support the mankind to prevent from the kind of threats and conflicts that they will face due to the harmful solar radiation using natural and available materials. Initially the study is focused to identify the UV absorption properties of natural materials. In order to achieve this goal several fruit juices, vegetable juices and plant leaf extractions are analyzed by using UV /VIS spectrum. The sample path length (1 Omm) and concentration (0.75mol/l & pH = 2.3) are kept constant during the experiment. The Citrus family exhibited interesting UV absorption behavior compared with the other tested materials. The experiments are carried out using both distilled water and isopropyl alcohol as solvents. Especially chlorophyll of the plant extract is removed by dissolving it in isopropyl alcohol and filtering it through activated carbon. When electromagnetic radiation passes through the compound, energy from the radiation is used to promote an electron from a bonding or non-bonding orbital into one of the empty anti-bonding orbital. The electron jump can be occurred or absorption takes place only when the energy associated with the particular wavelength is provided. In terms of Chemistry, Flavonoides are water soluble Polyphenolic molecules containing fifteen Carbon atoms. The Flavonoides, belongs to the polyphenol family, are found in most plant material and dietary sources. It is presumed that absorptions occurred in the citrus family due to the double bonds of the Flavonoides. Energy of the incident radiation is promoted electron jumps ( n:-+n:*, n-+n*, n-+a*) which caused to the absorption spectrum as discussed earlier. It is clearly illustrated that lime juice absorbed the wavelength from 290nm to 400nm where UV-B and UV-A radiations exist. Zero transmittance of incident radiation in between 290 and 400nm's for lime juice is observed in the experiment. It is interesting to find the optimal path length for zero transmittance and it determines the minimum thickness of the filter. One of the interesting applications of this finding is it can be converted any moisturizing cream into a moisturizing plus sunscreen by adding natural Flavonoides, just before the application.Item Investigating the Thermal Efficiency of Thermo-foils as a Roof Insulation Material and Developing a New Roof Insulation Material Using Coir Fiber(2011) Maduranga, A.D.; Jayatissa, N.W.K.; Sumathipala, H.H.The thermo-foil is an insulation material which can be used to insulate roofs of residential buildings which causes less energy to accomplish a comfortable temperature inside the building. In this study, an investigation of the efficiency of the thermo-foils in building insulation is performed. The thermal insulation properties and structure of the thermo-foil were analyzed as well as how these properties affect the decrease of temperature inside the residential building. The thermo-foils were tested using miniature building models for a more general conclusion. A heat transfer mechanism for a residential building is also proposed. A new roof insulation material is designed using an efficient and low cost natural fiber, coconut fiber or coir. The insulation properties unique to the coir fiber are enhanced as an insulation material. The new foil which is called Coir-Foil is tested together with thermo-foil. The Coir-Foil could achieve considerable higher performance than the currently available thermo-foil. The performance analysis for new coir foil and existing thermo-foils was used to conclude how they affect the energy conservation of residential buildings, through reducing the cooling load.