International Research Symposium on Pure and Applied Sciences (IRSPAS)

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Author: search.filters.author.Wijayawardhana, H. N. A. M.

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    Periodic time series modeling for temperature data in Nuwara Eliya
    (4th International Research Symposium on Pure and Applied Sciences, Faculty of Science, University of Kelaniya, Sri Lanka, 2019) Wijayawardhana, H. N. A. M.; Hewaarachchi, A. P.
    Many climatological time series display interesting properties such as trend, seasonality and autocorrelation. In addition to the autocorrelation, some time series display periodic autocorrelation, which is not readily visible. Time series, which depict periodic correlation are called as periodic time series and they can be modeled using autoregressive moving average models with periodically varying parameters. The key objective of this study was to model monthly temperature data using a periodic autoregressive model and to predict under the periodic correlation. In this research monthly mean minimum temperature series and monthly mean maximum temperature series in Nuwara Eliya district were considered. Since considered data were monthly data, the period of the data sets was twelve. In this research Fisher’s g-test was used to detect periodic correlation. Fisher’s g-test showed that only monthly mean minimum temperature series has a significant periodic correlation structure. Seasonally adjusted mean minimum temperature series was modeled using periodic autoregression (PAR) model. Using the Akaike information criterion, PAR model of order 1 with zero mean was chosen as the best fitted model for representing the seasonally adjusted data. The parameters of the model were estimated using periodic Yule-Walker estimation. Further, to check whether the periodic model was the best time series model for modeling and forecasting monthly mean minimum temperature data in Nuwara Eliya, different seasonal autoregressive integrated moving average models (SARIMA) were fitted. Finally, using forecast accuracy measurements such as Mean Error (ME), Root Mean Squared Error (RMSE) and Mean Absolute Percentage Error (MAPE), all models were compared and the best model was identified as the PAR(1) model that showed a ME value of -0.0861, RMSE value of 0.613 and MAPE value of 4.664%. According to comparison, periodic auto regression model of order 1 has the best forecasting accuracy among all fitted time series models
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    Study on the selection of mobile service providers: Special reference to the students at Faculty of Science, University of Kelaniya.
    (International Research Symposium on Pure and Applied Sciences, 2017 Faculty of Science, University of Kelaniya, Sri Lanka., 2017) Dassanayake, D. A. R. C.; Wijayawardhana, H. N. A. M.; Premathilaka, L. M.; Senarath, S. A. K. B.; Weerasekara, W. M. D. D.; Thilakarathne, K. H. K. D. S.; Goonetilleke, H. R.; Sandaruwan, B. H. S.; Winisinghe, W. T. D.; Kumara, J. L. S. M.; Attanayake, A. M. C. H.
    Mobile service providers are important in the rapid development of telecommunication and information technology. Major mobile service providers in Sri Lanka are Dialog, Mobitel, Airtel, Etisalat and Hutch. The aim of this study is to understand the selection of mobile service providers in Sri Lanka by students of the Faculty of Science. The objectives are to identify the most popular mobile service provider among the students of the Faculty of Science and reason for it, categorize the most popular mobile service provider by gender, year of study and relationship type of students and measure the satisfaction on available facilities of service providers. A survey was conducted during the period of September – December 2016. Among the 1670 students registered in the Faculty of Science, 181 respondents were randomly selected using simple random sampling method (without replacement). An appropriate questionnaire was developed in order to gather data and achieve the objectives. After the initial pilot survey was conducted, a questionnaire was administered in person and online (for unavailable students) while personal interviews were also conducted to improve the response rate from students who had not responsed due to their heavy workload. The analysis reveals that the majority of students (67%) of the Faculty of Science preferred to use Mobitel, whereas 21% of the students preferred Dialog and only 5% of the students, used Airtel. Most of the female students (55%) preferred to use Mobitel as their mobile phone provider whereas 74% of male students preferred to use the same network. The main reason for their selection was cited as the providers’ wider coverage. The results remained the same for majority of students studying in the first, second, and third year. The results remained the same irrespective of the stuts, i.e. single, in a relationship or married category. When considering individual service providers, only Hutch users were 100% satisfied with their service. In conclusion, this survey discloses important findings about the selection of mobile service providers by students of the Faculty of Science.