Browsing by Author "Hansameenu, W.P.T."

Now showing 1 - 6 of 6

Analysis of the error in an iterative algorithm for solution of the regulator equations for nonlinear parabolic control system
(Faculty of Science, University of Kelaniya, Sri Lanka, 2016) Hansameenu, W.P.T.; Aulisa, E.; Gilliam, D.
This work is based on the classical geometric method, which in turn is based on the classical geometric regulation theory, which involves asymptotic tracking and disturbance rejection for nonlinear parabolic control systems. The classical geometric method is based on the solution of a coupled pair of operator equations referred to as regulator equations. In general, solving the regulator equations or even obtaining accurate numerical solutions for the simple control problem is not an easy task. In fact, most of the time the classical geometric method gives the solvability conditions of the regulator problem, rather than the actual solution. We present a methodology for tracking and disturbance rejection, which is more general than the one based on the regulator equations, and can be applied to general smooth signals. This methodology is based on an iterative method known as the 􀀈- iterative method for obtaining approximate solution for the regulator problems for a class of infinite dimensional linear control systems. This work describes the error analysis for this iterative method regarding more general references and disturbances. In this work we consider bounded input and output operators. In particular, we obtain estimates showing geometric convergence of the error, controlled by the parameter 􀀈. In addition, we demonstrate our estimates on a variety of control problems in multi-physics applications by numerically solving the 􀀈-iterative algorithm by using the finite element solver “COMSOL”.
Derivation of Equations that satisfy Dirac’s Equation and invariance of transformations similar to Guage Transformations under mixed numbers
(Research Symposium 2010 - Faculty of Graduate Studies, University of Kelaniya, 2010) Hansameenu, W.P.T.; de Silva, L.N.K.; de Silva, T.P.
Matrix representation of mixed numbers and quaternions
(Research Symposium 2009 - Faculty of Graduate Studies, University of Kelaniya, 2009) Hansameenu, W.P.T.; de Silva, T.P.; de Silva, L.N.K.
Study of double junction effect on the quantum efficiency of optical devices
(University of Kelaniya, 2008) Hansameenu, W.P.T.; Siripala, W.P.
In practical optical devices one of the most important parameter which determines the performance of the device is the quantum efficiency. Generally, an optical device is fabricated using a junction between two semiconductors or a junction between a metal and a semiconductor. However, in practice formation of unwanted junctions during the fabrication stage of the optical devices is a major problem and it will result in the reduction of the overall performance of the device. In this investigation, a theoretical study was carried out on an optical device made by using a semiconductor/ metal junction to study this eff�ct. The formation of an additional junction at the back contact was considered as the reason for the formation of a double junction. In the study, photoinduced charge separation at the two space charge layers was considered as the main contribution to the photocurrents. Both drift current and diffusion current of the majority and minority carriers are considered in the continuity equation for calculating the total current produced by the device. Absorption of photons in the semiconductor was calculated using the variation of the absorption coefficient with the wavelength of the direct band gap semiconductor Cu20. In solving the continuity equation, the absorption of light in both space charge regions and creation of electron- hole pairs and the motion of the carriers in opposite directions were considered. The computed variation of the quantum efficiency with the wavelength of the incident light agreed well with the reported experimental results. We could observe that the efficiency of the device is drastically reduced as a result of the double junction effect. Further, with our model it was possible to explain the observation of the variation of direction of photocurrent with the wavelength, as a result of the existence of a double junction. In conclusion, using the computed quantum efficiency variation with the wavelength it was possible to obtain the junction parameters of an optical device using experimental data.
Study of double junction effect on the quantum efficiency of optical devices
(Sri Lanka Association for the Advancement of Science, 2009) Hansameenu, W.P.T.; Siripala, W.P.
Vector Autoregressive (VAR) model for forecasting water level in Attanagalu Oya
(Faculty of Science, University of Kelaniya, Sri Lanka, 2020) Anuruddhika, M.L.P.; Premarathna, L.P.N.D.,; Perera, K.K.K.R.,; Hansameenu, W.P.T.; Weerasinghe, V.P.A.
Flood is one of the major natural hazards in the world. Sri Lanka also undergoes flooding incidents every year. Both natural and human-induced activities such as precipitation, unplanned infrastructures, water drainage, lack of vegetation cause floods. High precipitation is one of the main reasons for flooding. Generally, most flood incidents occur in monsoon periods and inter monsoon periods. Attanagalu Oya, one of the tributaries of Kelani river and downstream of Kelani river cause to flood in the Gampaha district, Sri Lanka. According to the literature, the water level in Attanagalu Oya has not been studied using the multivariate time series approach. Therefore, this study aims to develop a Vector Auto Regressive (VAR) model to forecast the water level in Attanagalu Oya. The fitted model might be useful to identify the flood incidents that occur due to overflowing Attanagalu Oya. The model is fitted for daily water level and rainfall data for ten years. Water level data at the Dunamale gauging station of Attanagalu Oya and rainfall data at the Henarathgoda station were obtained from the Irrigation Department and Meteorological Department respectively. The analysis was carried out using R statistical software. Missing and unusual values of rainfall data were cleaned using the average values. Cross-correlations were calculated to identify lags of the rainfall data that might be useful to predict the water level. Results indicated the significant correlations at lags 1,2 and 3 as expected in this context as it takes 1-2 days to raise the water level after rain. The best VAR model must be chosen by selecting the optimal autoregressive order which is selected based on the minimum Akaike's Information Criterion (AIC). The lowest AIC score was achieved at the order of 8. Hence, VAR (8) model was selected as the best model. Results indicated that the rainy season occurred in southwest monsoon (May-September) and second inter monsoon (October-November) periods. The water level is also increased in those periods. According to the observed values of 2019 significant increase in water level could be seen from mid-September to November and the beginning of December. Forecasted results also showed an increase in water level in those periods. Also, the model accuracy was examined using mean absolute percentage error (MAPE) and root mean squared error (RMSE). Accuracy test results showed that the MAPE and RMSE values for forecasted rainfall are 2.907063 and 16.13093 and the water levels are 0.7730767 and 0.9059733 respectively. Hence, those values indicated that the model is adequate for forecasting. Findings of this study are vital to Agricultural Department to plan their cropping calendar, and urban council to plan various development and construction activities and warn the community in Attanagalu Oya basin for staying alert in the periods in which the water level is increased. Besides, this study is continued to improve the accuracy of the existing VAR model and to advance the existing model by considering other factors such as temperature and humidity.