Fractal dimension of long electrical discharges

Journal Articles
D. Amarasinghe, D.U.J. Sonnadara, M. Berg and V. Cooray
Journal of Electrostatics, 73, 33-37
Publication year: 2015

Fractal dimension of long electrical discharges, D. Amarasinghe, D.U.J. Sonnadara, M. Berg and V. Cooray, Electrostatics (2014)

A Markov chain probability model to describe wet and dry patterns of weather at Colombo

ClimateJournal Articles
D.U.J. Sonnadara and D.R. Jayewardene
Theoretical and Applied Climatology, 119 (1-2), 333-340 (2015)
Publication year: 2015

The hypothesis that the wet and dry patterns of daily precipitation observed in Colombo can be modeled by a first order Markov chain model was tested using daily rainfall data for a 60-year period (1941–2000). The probability of a day being wet or dry was defined with respect to the status of the previous day. Probabilities were assumed to be stationary within a given month. Except for isolated single events, the model is shown to describe the observed sequence of wet and dry spells satisfactorily depending on the season. The accuracy of modeling wet spells is high compared to dry spells. When the model-predicted mean length of wet spells for each month was compared with the estimated values from the data set, a reasonable agreement between the model prediction and estimation is seen (within ±0.1). In general, the data show a higher disagreement for the months having longer dry spells. The mean annual duration of wet spells is 2.6 days while the mean annual duration of dry spells is 3.8 days. It is shown that the model can be used to explore the return periods of long wet and dry spells. We conclude from the study that the Markov chain of order 1 is adequate to describe wet and dry patterns of weather in Colombo.

Performance of lightning locating systems in extracting lightning flash characteristics

Journal Articles
U. Sonnadara, V. Kathriarachchi, V. Cooray, R. Montano and T. Gotschl
Atmospheric and Solar-Terrestrial Physics, 112, 31-37
Publication year: 2014

Performance of lightning locating systems in extracting lightning flash characteristics, U. Sonnadara, V. Kathriarachchi, V. Cooray, R. Montano and T. Gotschl, J. Atmospheric and Solar-Terrestrial Physics (2014)

Assessment of the Impacts of Sri Lanka’s Programme for School Improvement on Students’ Academic Progress

Journal Articles
H. Aturupane, P. Glewwe, R. Ravina, U. Sonnadara, S. Wisniewski
J. of Development Studies
Publication year: 2014

Assessment of the Impacts of Sri Lanka’s Programme for School Improvement on Students’ Academic Progress, H. Aturupane, P. Glewwe, R. Ravina, U. Sonnadara, S. Wisniewski, J. of Development Studies (2014)

Reconstruction of missing monthly temperature observations in Jaffna, Sri Lanka

Journal Articles
A. Thevakaran and D.U.J. Sonnadara
J. National Science Foundation, 41 1 , 23-30
Publication year: 2013

Reconstruction of missing monthly temperature observations in Jaffna, Sri Lanka, A. Thevakaran and D.U.J. Sonnadara, J. National Science Foundation, 41 1 (2013) 23-30

Computer simulation of tree development with random variations and probabilistic growth of branches

Journal Articles
K.D.S. Jinasena and D.U.J. Sonnadara
J. National Science Foundation, 41 3 , 229-235
Publication year: 2013

Computer simulation of tree development with random variations and probabilistic growth of branches, K.D.S. Jinasena and D.U.J. Sonnadara, J. National Science Foundation, 41 3 (2013) 229-235

Study of Diurnal and Seasonal Wind Characteristics for Wind Resource Assessment

Journal Articles
R.M. Weerasinghe, A.S. Pannila, M.K. Jayananda and D.U.J. Sonnadara
International Energy Journal, 13 4 , 177-188
Publication year: 2012

Study of Diurnal and Seasonal Wind Characteristics for Wind Resource Assessment, R.M. Weerasinghe, A.S. Pannila, M.K. Jayananda and D.U.J. Sonnadara, International Energy Journal, 13 4 (2012) 177-188

Fractal Nature of Simulated Lightning Channels

Journal Articles
M.D.N. Perera and D.U.J. Sonnadara
Sri Lankan J. Physics, 13 2 , 9-25
Publication year: 2012

Fractal Nature of Simulated Lightning Channels, M.D.N. Perera and D.U.J. Sonnadara, Sri Lankan J. Physics, 13 2 (2012) 9-25

Transforming School Education in Sri Lanka: from cut stones to polished jewels

Academic Publications/Books
World Bank, SASED
ISBN: 978-955-8908-41-9
Publication year: 2011

Sri Lanka stands upon the threshold of two great transformations. The first transformation is the advancement and progress of the nation from a low-income country to a middle-income country. The second transformation is the transition of the nation from a country in conflict to a country in lasting peace. The general education sector is at the heart of these two great transformations. The school system makes a unique and foundational contribution to the economic development of a country. The school system also makes a unique and foundational contribution to the social development of a nation. As such, the general education sector, which covers primary and secondary education, can and should play a prominent role in the economic and social transformation of the country. According to the information Sri Lanka is one of the better performers among developing countries, with an adult literacy rate above the expected value for its level of per capita income. However, there are a number of countries in other regions of the world, at similar or lower levels of per capita income, that enjoy literacy rates above the predicted values for their levels of per capita income, and which display a performance on literacy superior to that of Sri Lanka. These include countries such as Bolivia, Indonesia, Mongolia and the Philippines. There are also countries that have higher per capita incomes than Sri Lanka and perform better on adult literacy, such as Argentina, Brazil, Costa Rica, Colombia, China, Thailand and Uruguay. Overall, Sri Lanka performs well, but not exceptionally so.

Traffic noise enhancement due to speed bumps

Journal Articles
S.N. Wewelwala and D.U.J. Sonnadara
Sri Lankan J. Physics, 12 , 1-6
Publication year: 2011

Traffic noise enhancement due to speed bumps, S.N. Wewelwala and D.U.J. Sonnadara, Sri Lankan J. Physics, 12 (2011) 17-23

Strengthening Science Education in Sri Lanka

Academic Publications/Books
H. Aturupane, V. Dissanayake, R. Jayewardene, M. Sojo, U. Sonnadara
World Bank, Discussion Paper Series, 45
Publication year: 2011

Scientific literacy is essential to stimulate an environment conducive to new knowledge generation, discovery and innovation. A quality school science education is central to building a scientifically literate population. Science education in Sri Lanka has progressed both quantitatively and qualitatively since the 1950s. Access to science education has grown steadily. This paper addresses the challenges to providing a good science education and considers pathways to the future. Policy initiatives supporting science education at present are considered. The science programme in schools is reviewed taking into account parameters such as curriculum, teaching and learning methods, learning assessments, teaching material and deployment and training of science teachers. First, learning achievements in science are assessed in the context of test scores in national assessments administered at grade eight. It is assumed that the national examinations are a suitable instrument to test learning outcomes and that at least in part reflect the quality of education.

Strengthening Mathematics Education in Sri Lanka

Academic Publications/Books
H. Aturupane, V. Dissanayake, R. Jayewardene, M. Sojo, U. Sonnadara
World Bank, Discussion Paper Series, 43
Publication year: 2011

A well-informed and knowledgeable community is of vital importance for the economic and social development of a modem society. The knowledge and skills required for present day activities are much more complex than those required in the past. Today, many jobs require expert thinking and non-routine analytical skills, to identify and solve problems. Mathematics education focuses on developing a person’s analytical and problem solving abilities. Thus a high quality mathematics education win ensure that students develop the skills that are essential not only in science and technology, but also in everyday life and the workplace. The government of Sri Lanka, recognizing the need for a high quality mathematics education has implemented several reforms in the recent past. Although the progress achieved is commendable, there is still room for improvement in certain important aspects of the learning teaching process. The main aim of the mathematics curriculum under these reforms is to create individuals who are able to think mathematically and apply mathematical knowledge effectively and responsibly in problem solving and decision making.

Performance of neural networks in forecasting short range occurrence of rainfall

Journal Articles
V.S. Rathnayake, H.L. Premaratne and D.U.J. Sonnadara
J. National Science Foundation, 39 3 , 251-260
Publication year: 2011

Performance of neural networks in forecasting short range occurrence of rainfall, V.S. Rathnayake, H.L. Premaratne and D.U.J. Sonnadara, J. National Science Foundation, 39 3 (2011) 251-260

An Impact Evaluation of Sri Lanka’s Policies to Improve the Performance of Schools and Primary School Students through its School Improvement and School Report Card Programs

Academic Publications/Books
World Bank, South Asia human development sector
Discussion paper Series, 35
Publication year: 2011

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A Simple Reconfigurable Microprocessor in a 36 Macrocell CPLD

Journal Articles
W.A.S. Wijesinghe, M.K. Jayananda and D.U.J. Sonnadara
J. National Science Foundation, 39 3 , 261-266
Publication year: 2011

A Simple Reconfigurable Microprocessor in a 36 Macrocell CPLD, W.A.S. Wijesinghe, M.K. Jayananda and D.U.J. Sonnadara, J. National Science Foundation, 39 3 (2011) 261-266

Simulation of Diffusion Limited Aggregation in Field Programmable Gate Arrays

Journal Articles
W.A.S. Wijesinghe, M.K. Jayananda and D.U.J. Sonnadara
J. National Science Foundation, 38 4 , 213-218
Publication year: 2010

Simulation of Diffusion Limited Aggregation in Field Programmable Gate Arrays, W.A.S. Wijesinghe, M.K. Jayananda and D.U.J. Sonnadara, J. National Science Foundation, 38 4 (2010) 213-218

Performance of neural network in forecasting daily precipitation using multiple sources

Journal Articles
H.D.P. Weerasinghe, H.L. Premaratne and D.U.J. Sonnadara
J. National Science Foundation, 38 3 , 163-170
Publication year: 2010

Performance of neural network in forecasting daily precipitation using multiple sources, H.D.P. Weerasinghe, H.L. Premaratne and D.U.J. Sonnadara, J. National Science Foundation, 38 3 (2010) 163-170

The towers of learning: Performance, peril and promise of higher education in Sri Lanka

Academic Publications/Books
World Bank, GEDDR
ISBN: 978-955-8908-35-8
Publication year: 2009

Sri Lanka is poised on the crest of two great waves of opportunity. The first wave can transform the nation from a low-income country to a middle-income country. The second wave can transform the nation from a country in conflict to a country at peace. The higher education sector can and must lead Sri Lanka successfully over the crests of these two waves of golden opportunity. Higher education institutions should drive and accelerate the country’s ascent to middle-income (MIC) status. Also, the higher education system should inspire the country’s values, ethics and social institutions so that Sri Lanka becomes celebrated as an enlightened and peaceful multi-ethnic, multi-religious and multi-cultural society. Sri Lanka’s future in the global knowledge economy of the twenty-first century depends critically on the country’s intellectual and human capital. The ability of people to think and act creatively, work industriously and productively, and innovate and adapt available technologies to strengthen economic activities is cardinally important in the modern world. In this context, Sri Lanka needs a higher education system that can produce skilled, hard-working and enterprising graduates. Also, the country needs research and innovation capacity capable of promoting dynamic economic development.

Predicting three-dimensional fractal dimensions of electrical discharges using two-dimensional projections

Journal Articles
D. Amarasinghe and U. Sonnadara
J. Science, Eastern University of Sri Lanka, 6 ,57-67
Publication year: 2009

Predicting three-dimensional fractal dimensions of electrical discharges using two-dimensional projections, D. Amarasinghe and U. Sonnadara, J. Science, Eastern University of Sri Lanka, 6 (2009) 57-67

Measurement of noise within passenger trains on a coastal railway line

Journal Articles
N.S. Pahalavithana and D.U.J. Sonnadara
Sri Lankan J. Physics, 10 ,44-56
Publication year: 2009

Measurement of noise within passenger trains on a coastal railway line, N.S. Pahalavithana and D.U.J. Sonnadara, Sri Lankan J. Physics, 10 (2009) 44-56

Performance of artificial neural networks for forecasting daily occurrence and annual depth of rainfall at a tropical site

ClimateJournal Articles
A.D. Kumarasiri and D.U.J. Sonnadara
Hydrological Processes, 22(17), 3535-3542 (2008)
Publication year: 2008

Performance of a feed-forward back-propagation artificial neural network on forecasting the daily occurrence and annual depth of rainfall at a single meteorological station is presented. Both short-term and long-term forecasting was attempted, with ground level data collected by the meteorological station in Colombo, Sri Lanka (79° 52′E, 6° 54′N) during two time periods, 1994–2003 and 1869–2003. Two neural network models were developed; a one-day-ahead model for predicting the rainfall occurrence of the next day, which was able to make predictions with a 74·3% accuracy, and one-year-ahead model for yearly rainfall depth predictions with an 80·0% accuracy within a ± 5% error bound. Each of these models was extended to make predictions several time steps into the future, where accuracies were found to decrease rapidly with the number of time steps. The success rates and rainfall variability within the north-east and south-west monsoon seasons are also discussed.

Performance evaluation of multipliers in reconfigurable hardware

Journal Articles
W.A.S. Wijesinghe, M.K. Jayananda and D.U.J. Sonnadara
J. National Science Foundation, 36 3 , 249-251
Publication year: 2008

Performance evaluation of multipliers in reconfigurable hardware, W.A.S. Wijesinghe, M.K. Jayananda and D.U.J. Sonnadara, J. National Science Foundation, 36 3 (2008) 249-251

Modelling free flowing vehicular traffic noise

Journal Articles
R.T. Sooriaarachchi and D.U.J. Sonnadara
Engineer, 40 2 (2008) 43-37
Publication year: 2008

Modelling free flowing vehicular traffic noise, R.T. Sooriaarachchi and D.U.J. Sonnadara, Engineer, 40 2 (2008) 43-37

Fractal characteristics of simulated electrical discharges

Journal Articles
D.I. Amarasinghe and D.U.J. Sonnadara
J. of National Science Foundation, 36 2 , 137-143
Publication year: 2008

Fractal characteristics of simulated electrical discharges, D.I. Amarasinghe and D.U.J. Sonnadara, J. of National Science Foundation, 36 2 (2008) 137-143

Detecting and preventing plagiarism in online assessment

Journal Articles
C.T. Wannige, D.U.J. Sonnadara, H.A. Usoof, K.P. Hewagamage
J. Science University of Kelaniya, 4 , 95-104
Publication year: 2008

Detecting and preventing plagiarism in online assessment, C.T. Wannige, D.U.J. Sonnadara, H.A. Usoof, K.P. Hewagamage, J. Science University of Kelaniya, 4 (2008) 95-104

Correlation between brightness and channel currents of electrical discharges

Journal Articles
D. Amarasinghe, U. Sonnadara, M. Berg, and V. Cooray
IEEE Transactions on Dielectrics and Electrical Insulation, 14(5), 115-1160
Publication year: 2007

Correlation between brightness and channel currents of electrical discharges, D. Amarasinghe, U. Sonnadara, M. Berg, and V. Cooray, IEEE Transactions on Dielectrics and Electrical Insulations, 14 5 (2007) 115-1160

Channel tortuosity of long laboratory sparks

Journal Articles
D. Amarasinghe, U. Sonnadara, M. Berg, and V. Cooray, J. Electrostatics
Journal of electrostatics, 65(8), 521-526
Publication year: 2007

Channel tortuosity of long laboratory sparks, D. Amarasinghe, U. Sonnadara, M. Berg, and V. Cooray, J. Electrostatics, 65 8 (2007) 521-526

The lightning radiation field spectra of cloud flashes in the interval 20kHz to 20MHz

Journal Articles
U. Sonnadara, V. Cooray, and M. Fernando
IEEE Transactions on Electromagnetic compatibility, 48(1), 234-239
Publication year: 2006

The lightning radiation field spectra of cloud flashes in the interval 20kHz to 20MHz, U. Sonnadara, V. Cooray, and M. Fernando, IEEE Transactions on Electromagnetic Compatibility, 48 1 (2006) 234-239

Characteristics of cloud to ground lightning flashes over Sweden

Journal Articles
U. Sonnadara, V. Cooray and T. Gotschl
Physica scripta, 74, 1-8
Publication year: 2006

Characteristics of cloud to ground lightning flashes over Sweden, U. Sonnadara, V. Cooray and T. Gotschl, Physica Scripta, 74 (2006) 1-8

Trends of rainfall in Sri Lanka over the last century

ClimateJournal Articles
H.K.W.I. Jayawardene, D.U.J. Sonnadara and D.R. Jayewardene
Sri Lankan Journal of Physics, 6, 7-17 (2005)
Publication year: 2005

Utilizing over 100 years of rainfall records in 15 meteorology stations, an analysis was carried out to extract the trends of annual rainfall depth in Sri Lanka over the last century. A statistically significant increasing trend of rate 3.15 mm/year was observed at Colombo and decreasing trends were observed at Nuwara Eliya and Kandy with rates of 4.87 mm/year and 2.88 mm/year respectively. Since no coherent increase or decrease of rainfall in any group of stations in the wet or dry zones was observed, the possibility of large scale change over the past century was ruled out. However, more recent data records (1949 onwards), revealed a decreasing trends in 13 of the 15 stations. Thus, traces of a temporal change seem to be apparent in the rainfall records over the last half century. In general, the downward trends in recent decades are steeper than the long term variations. For the recent data records, the largest downward trend of 11.16 mm/year was observed at Batticaloa.