Browsing by Author "Jayatissa, N.W.K."

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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.
An inexpensive universal serial bus interfaced home automation system
(IET Sri Lanka Network-19th Annual conference, 2012) Wijesundera, R.P.; Abeyratne, M.D.G.M.; Kalupahana, I.U.; Buddhika, W.A.P.; Kumara, S.D.; Jayatissa, N.W.K.; Harambearachchi, J.C.; Kalingamudali, S.R.D.
Construction and performance-analysis of a 'Solar-light" for efficient use of daylight
(University of Kelaniya, 2008) Jayatissa, N.W.K.; Punyasena, M.A.
A pleasant and appealing environment, excellent color rendering, natural interior, and significant energy saving are the major advantages of using the daylight compared to the artificial lighting. Glare and heat radiation are the main drawbacks of utilizing direct sunlight for building illumination. This 'solar-light', a newly designed unit, can be used only during the day time and is operated from natural solar radiation with no additional power being required at all. It acts as a light guide which transfers the filtered visible spectrum of solar radiation from outside into the interior of the building. Solar-light that illuminates building interiors more efficiently with natural daylight, has been constructed and tested for its performance. The unit has been designed to reduce substantially the heat component of solar radiation with an IR-filter so that the building interior does not get heated up by increased cooling load due to lighting. This would considerably reduce the air-condition load of the building. The UV component of the solar spectrum is eliminated with a UV-filter installed inside the unit, thus only the filtered harmless visible spectrum is taken into the interior of the building. The Solar-light has a cylindrical shape (to minimize the internal reflection losses) with a height of 80 cm and a diameter of 26 cm. The transparent window at the top of the unit has a hemispherical shape in order to increase the effective area of the solar radiation input into the interior of the building. The small air gap between outer cylinder and reflective cylinder creates a convection path for heated air. A light-reflective coating is applied at the interior surface of the cylinder to minimize the loss of illumination. The filtered radiation finally is sent through a light diffuser also with the same diameter at the bottom of the unit before the light is finally delivered into the building. The performance of the unit has been tested in real environment and a maximum of 170 Lux was measured at the desktop height inside the building with the daylight. Diameter of the illuminated area is about 5-6 m of which the intensity variation is minimal within the . . mner regwn. A series of these solar-light units can be installed on the roofs of large buildings (ex: garments factories, ware houses etc.) to illuminate the interiors in place of fluorescent bulbs to save energy substantially reducing the electricity bill.
Energy efficient hybrid water heating system
(2016) Piyumal, P.L.A.K.; Nagahapitiya, N.W.H.G.B.; Jayatissa, N.W.K.; de Silva, D.S.M.
As the world’s energy resources are diminishing, we need to find greener solutions through renewable energy sources that can generate electricity for heating, lighting homes and for a variety of commercial and industrial uses. Among many types of renewable energy resources, such as wind and solar energy, are constantly replenished and will never run out. At present we are experiencing an electrical energy shortage in Sri Lanka. However, we are still wasting so much of electrical energy in spite of the above crisis. The University of Kelaniya has many cafeterias. The cafeteria attached to the Gymnasium is the largest food and refreshments supplier in the university. The main refreshment for the students is hot tea. Hence, every day, every hour, the canteen has to produce a large number of cups of tea by using considerable amount of electrical energy for boiling water. Hence, the purpose of this project is to minimize the electricity consumption in the boiler using freely available sunlight. Initially, the project was focused to power the boiler using a photovoltaic array. Even though this method was straight forward, investigations have shown that this method was not financially viable. Hence, the next approach was to utilize solar thermal energy to heat the make-up water to the boiler which is significantly cheaper to implement than the previous. Fresh water is circulating through the heat exchanger unit placed on the top of the roof of the cafeteria. Heated water is fed to the boiler as make-up water. Although the heating system is unable to produce boiling water. It is capable of producing nearly half of the energy requirement for boiling the water. A temperature sensor was placed to measure the boiler temperature and the output of the sensor is fed to the heating element to maintain the boiler temperature at 373 K. According to the observation it is clear that make-up water temperature in the morning is 332 K which is little lower than the temperature of make-up water in the afternoon which is 342 K due to overnight cooling of the storage tank. Therefore, morning electricity consumption of the boiler is little larger than the evening. The average daily hot water consumption for making tea is approximately 78 liters in the morning and 88 liters in the afternoon. According to the calculations, it can be shown that the hybrid system is capable of saving 50% of electrical energy of the boiler. It can be concluded that the total energy provided by the solar heating system or the saving of the system is around 2450 kWh per annum.
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.
Intelligent Window Controlling System
(Faculty of Graduate Studies, University of Kelaniya, Sri Lanka, 2016) Seneviratne, K.; Jayatissa, N.W.K.
During the 21st century the global surface temperature has increased dramatically as a result of that, Air conditioners are often used to improve thermal comfort and indoor air quality. In both developed and developing countries, air conditioners increase the occupancy ratio of building areas. But air conditioners are expensive option for this issue. Because of that we need to optimize usage of air conditioners only in comfort zone. This research is conducted due to the growing energy management interest in the airconditioning industry. Most of the places outside air temperature and humidity drop down to human comfort levels during the night time. It may take considerable time to transfer these environmental conditions into the room. Insulated thermal envelope may be slowing this process furthermore. The objective of this research was to transfer the fresh outside air into the air conditioned room when the outside environment is in the comfort zone. Comfort zone is an area marked in the psychrometric chart which is comfortable for human being. The American Society of Heating, Refrigeration and Air-conditioning Engineers (ASHRAE’s) publication on thermal environmental conditions for human occupancy has defined the comfort zone with suitable temperature and relative humidity (RH) ranges. The specified temperature and humidity ranges for the designed system are 22 Celsius & 40 RH to 27 Celsius & 60 RH respectively. The designed controller detects the outside temperature and relative humidity every 15 minutes and opens the windows of the room if the outside fall into comfort zone. When the windows are opened the air conditioner is switched off by the controller at the same time. The designed system consists of three separate items such as outdoor unit, indoor unit and actuator driver. Relative humidity and temperature of the outside air are measured and transmitted to the room via radio frequency (RF) communication system by the outdoor unit. The indoor unit receives the transmitted signal from the outdoor unit, process it and produce appropriate signals to both actuator driver and air conditioner. Therefore, actuator driver is controlled the window according to the outside environmental conditions. The designed system is commissioned in Thailand and it is proven that the device is significantly saving the energy in the residential sector.
Investigating the thermal efficiency of commercially available thermo-foils in Sri Lanka
(Journal of Science of the University of Kelaniya Sri Lanka, 2011) Maduranga, A.D.; Sumathipala, H.H.; Jayatissa, N.W.K.
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. It?s becoming popular in Sri Lankan building construction sector. In this research, an investigation of the efficiency of the thermo-foils is done for commonly used brands. The important thermal properties are analyzed for thermo-foils with a thickness of 3mm, 5mm and 8mm and it is tested using a miniature building model for the further evaluation of the efficiency. It was observed that the aluminium layer of the thermo-foil could reflect most of the radiation back and the polyethylene foam layer could keep a temperature gradient of a few degrees. A temperature drop of 1.6 to 2.8 degrees was noted. The results obtained were discussed with an analysis of the thermal insulation properties. A heat transfer model for a residential building was also proposed.
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.
Lesson 14: Introduction to Microcontroller
(Research Services Centre, Faculty of Science, University of Kelaniya, 2015) Jayatissa, N.W.K.
Lesson 15: Programmable Logic Controllers
(Research Services Centre, Faculty of Science, University of Kelaniya, 2015) Jayatissa, N.W.K.
Lesson 19: Introduction to Pumps
(Research Services Centre, Faculty of Science, University of Kelaniya, 2015) Jayatissa, N.W.K.
Low Cost Method for Prototyping Printed Circuit Boards.
(In: Proceedings of the International Postgraduate Research Conference 2017 (IPRC – 2017), Faculty of Graduate Studies, University of Kelaniya, Sri Lanka., 2017) Wanigasekara, R.M.G.; Agalawaththa, J.C.; Chrandrasena, B.G.D.R.; Jayatissa, N.W.K.
Printed Circuit Boards (PCBs) are very commonly used in almost all of the electronic applications, due to ease of use. There are several modern methods of transferring circuit wiring diagrams to circuit board. Many of these methods are good for only producing large number of PCBs because making one or two PCB is very expensive. However, in an electronic research laboratory needed for producing various type of prototype boards is much needed. There are several difficulties in fulfilling this need; time to produce, cost of production, difficulty to produce large and complicated PCBs. The PCB drawing machine is designed to overcome these difficulties in prototyping PCBs for electronic laboratory use. The three dimensional axis of the designed machine is controlled by three independent stepper motors. A drawing pen holder is attached to the z-axis control and any permanent marker pen can be attached to the holder. The accuracy of the z-axis is 0.1 mm. Initially, the user designed circuit diagram (drawing) should be loaded to the computer which is connected to the drawing machine. The computer reads the drawing and replicate it on the copper board using the permanent marker pen. The total area of the x-y plane is 300mm x 200 mm. The required software for this operation is a development of an open source, which can send Gcode (RS-274) protocol commands to the device. Generally, RS-274 or G-code is known as numerical control (NC) programming language. This machine uses both computer numerical control (CNC) technique and CAD software to complete the task. The machine could also be used to remove the unwanted copper areas of a circuit board by connecting special carving bits to the machine instead of the pen. This method is much faster than the previous drawing method to replicate circuit to the copper board but more costly due to rapid wear of the milling bits. Finally, the designed drawing machine is able to draw 300 x 200 mm2 size circuit layouts with 0.1 mm line separations.
MATLAB Based Software Tool for Grain Classification and Their Quality Identification
(In: Proceedings of the International Postgraduate Research Conference 2017 (IPRC – 2017), Faculty of Graduate Studies, University of Kelaniya, Sri Lanka., 2017) Atapattu, H.R.S.; Jayatissa, N.W.K.
At present, the field of agriculture is the most prevalent and enduring industry in the world. Among the existing food crops, grain varieties have attracted more attention of farmers since they play a major role in providing daily nutritional rations of human beings. Hence, it is important to develop accurate, efficient and cost effective methodology for classification and identification of grain varieties in order to yield high quality products while boosting the profit of farmers. In this study, an attempt was made to develop a software tool based on MATLAB by using the techniques of image processing to classify grain varieties namely; green gram and rice grains into their sub varieties and identify foreign particlespresent and the percentage of broken grains in a given sample. The decisions in classification and identification of grains were taken based on their different morphological features extracted based on the still images acquired using a digital camera. Theimages acquired were initially conceded through several image pre-processing steps namely; RGB to gray conversion, gray to binary conversion, noise filtering and image erosion. The resulting binary images were then labeled and segmented based on the similarities that exist and the labels given. Subsequently, the features (area, perimeter, centroid, major axis length and minor axis length) of the segmented imageswere extracted and system decisions in classification of grain varieties and identification of the foreign particles & the percentage of broken grains were performed based on the features extracted with 95 % and 97 % accuracies respectively utilizing 35 training sets and 15 testing sets for each category. The subsequentprocessing steps were employed to convertnumerical values into string values and the final results were displayed and readout loud to enhance the user friendliness of the software tool developed. The graphical user interface of the software tool was also based on the MATLAB. Furthermore, the whole process tooka maximum of 5s execution time for one trail of grain classification or quality identification.
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.
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.
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.
UV absorption properties of natural solutions
(University of Kelaniya, 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.
Voltage and wire standards for domestic DC distribution systems
(Faculty of Science, University of Kelaniya, Sri Lanka, 2020) Ariyarathne, Y.S.S.,; Jayatissa, N.W.K.; De Silva, D.S.M.
Home micro-grid concepts have gained interest in the modern world due to the increased distributed generations with renewable energy sources. The present "DC-AC-DC" route from distributed generations to DC loads via inverters may not be rational from the viewpoint of system simplicity and energy efficiency. Considering the increasing prevalence of DC home appliances, establishing reasonable DC distribution standards for domestic buildings is significant. In this study, the Wattage of household electric appliances and the time duration they are being used were collected. The monthly power consumption of each appliance category was calculated. According to the results, the average monthly electricity demand of a Sri Lankan family is 111 kWh. Only eight equipment categories consume nearly 90% of domestic power. Those are refrigerators (22%), lights (16%), fans (16%), rice cookers (14%), TV (8%), irons (7%), washing machines (4%) and water pumps (3%). When considering the average maximum power demand, the most commonly available appliances have less than 1 kW maximum power demand. By considering the power requirements, to minimize the loss, and keep the system's safety at the maximum level, the midpoint grounding system with main wires at +60 VDC and -60 VDC is proposed. Using this topology, 120 V line to line potential difference can be archived with keeping the ground to line voltage within safety extra-low voltage limit as proposed by the European telecom standards. Following the IEE wiring standards, three commonly available wire sizes (2.5 𝑚𝑚2 , 4 𝑚𝑚2 , 6 𝑚𝑚2 ) were selected to analyze the suitability for the system's sub circuits. Voltage drop, power loss, short circuit current, and insulation resistance were considered to select the maximum allowable current for each wire size in a sub-circuit. Since the wire length for a sub-circuit of a domestic distribution system is usually less than 10 m, the voltage drops and the power losses are too small and negligible. The insulation resistance of each wire was tested against high voltages. All the wires show infinite resistance (more than 1 𝑇Ω) up to 2500 V. The most critical factor in wire selection is the short circuit current. According to the results, for a high power sub-circuit that require power up to 2400 W, wire size of 6 𝑚𝑚2 can be used with 20 A circuit breaker. For sub circuits with power requirement less than 1800 W, 4 𝑚𝑚2 wires can be used with a 15 A circuit breaker. And for low power sub-circuits, 2.5 𝑚𝑚2 wire can be used with 10 A circuit breaker to supply power up to 1200 W. Further studies must be carried out to determine the power/voltage losses and increase the whole distribution system's efficiency under these conditions.