Institutional-Repository, University of Moratuwa
Welcome to the University of Moratuwa Digital Repository, which houses postgraduate theses and dissertations, research articles presented at conferences by faculties and departments, university-published journal articles and research publications authored by academic staff. This online repository stores, preserves and distributes the University's scholarly work. This service allows University members to share their research with a larger audience.
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Recent Submissions
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Aerodynamic performance analysis of a twin tower building for alternative designs
(IEEE, 2024) Rathnayake, CM; Lewangamage, CS
The design and construction of tall buildings present unique challenges, particularly when it comes to the effects of wind loading. A series of computational fluid dynamics (CFD) simulations were conducted to analyse the aerodynamic behaviour of a twin tower building featuring alternative designs. The mean wind overturning moment coefficients derived from the CFD simulations were meticulously analysed to determine the most aerodynamically advantageous building design. The analysed results facilitated a comprehensive comparison and discussion of their aerodynamic characteristics. The results revealed the alternative model, which demonstrates superior aerodynamic behaviours compared to others for the main wind angles, in both along-wind and across-wind directions. The findings emphasise the critical role of building geometry, architectural features, and surface area in influencing windinduced loads on tall buildings, providing valuable information for the design and evaluation of future structures.
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Dynamic modeling and simulation of the impact of micro-aeration on anaerobic treatment of sulfate-rich wastewater
(IEEE, 2024) Madhubhani, MLP; Rathnasiri, PG
This study investigates the application of microaeration to remove dissolved sulfide produced during the anaerobic treatment of wastewater containing sulfate. A completely mixed batch reactor was used to develop a dynamic model of batch anaerobic digestion with micro-aeration of the liquid phase using BioWin (version 6.2) software to simulate the performance of sulfate reduction and sulfide oxidation in a single reactor unit. When calibrating the micro-aerated model, maximum specific growth rate for sulfur-reducing acetotrophic bacteria was altered to 0.38 d-1, switching function (which determines the minimum DO concentration at which oxidation of hydrogen sulfide to elemental sulfur takes place) was altered to 0.0001 mgO2/L and air was introduced to the system for 12 hours (after half an hour of feeding) at a rate of 0.018 m3/hr and another 12 hours at a rate of 0.015 m3/hr. Although methane production improved over the first half of the micro-aerated time period, a negative impact of the presence of oxygen on methanogens could be evident when the oxygen presents in the system beyond 13 hours. The micro-aerated system shows a significant decrease in dissolved sulfides when compared to the anaerobic system. Moreover, an average of 80% H2S removal could be achieved with micro-aeration.
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Dynamic modeling and simulation of the impact of lipid inhibition on anaerobic digestion of desiccated coconut wastewater
(IEEE, 2024) Welarathna, WGDS; Rathnasiri, PG
Desiccated Coconut Wastewater is categorized as a lipid-rich wastewater that can be treated using anaerobic digestion. Within the anaerobic digester, lipids are hydrolyzed into long chain fatty acids (LCFAs) and glycerol. LCFAs cause potential inhibitory effects significantly on acetoclastic methanogens and deteriorate digester performance. To study the impact of LCFA inhibition, the BioWin 6.2 integrated Anaerobic Sludge Digestion Model (ASDM) was extended with the lipid inhibition function. Out of the 7 kinetic constants used in the rate equations, maximum specific growth rates of acetate and lipids degraders, half saturation rate of acetate degraders and LCFA inhibition constant are the most sensitive parameters toward methane production. The calibrated model with lipid inhibition (Model 2) showed a higher negative impact on COD reduction, acetoclastic methanogen concentration, and methane production compared to model without lipid inhibition (Model 1), indicating a significant impact of lipid inhibition on anaerobic digestion. If Model 1 is used to simulate anaerobic digestion of lipid rich wastewater, deviations between the actual results and the model predicted results will be high. Thus, Model 2 can be used as a tool to predict the COD reduction, effect on the acetoclastic methanogens, and methane production in anaerobic digestion, which utilizes lipid-rich wastewater.
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Comparative analysis of resampling techniques on class imbalance in body shaming phrase detection
(IEEE, 2024) Puvanendran, R; Wijikumar, P; Rathnayaka, T; Thilakarathna, K; Jayasiri, P; Roopasinghe, H; Kavishan, M; Jeyamohan, M; Thurshikan, K
In this present era, body shaming has pervasive and detrimental effects on individuals’ psychological and physical well-being. Hence, a profound significance in its potential to elucidate and address the textual based body shaming phrases is needed. Natural Language Processing (NLP) and Machine learning are employed to detect body shaming phrases. This research paper presents the machine learning methodology for the detection and classification of body shaming phrases. The standard TF-IDF has been employed for feature extraction. The SVM classifier exhibited an exceptional accuracy of 98.5%. In order to improve performance and address the issue of overfitting, the dataset is subjected to resampling procedures, which are carefully applied to ensure the appropriate selection of the model. The methodology encompasses four resampling strategies for achieving data balance, namely SMOTE, ADASYN,
SMOTE-Tomek and SMOTE-ENN. The efficacy of the suggested methodology is evaluated by comparing it against five machine learning classifiers, The findings suggest that SVM exhibit superior performance compared to other models in both the SMOTE and SMOTE-Tomek balanced datasets. Specifically, SVM achieves accuracy, recall, precision, and F1-score scores of
99.1%, 99.59%, 99.18%, and 99 .38% respectively. The study concludes that the utilization of resampling approaches, specifically SMOTE and SMOTE-Tomek enhances the model’s performance.
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The Impact of construction industry supply chain risk management for imported items due to the economic crisis; contractors’ perspective in Sri Lanka
(IEEE, 2024) Thejani, DN; Vithana, NDI
Supply chain management integrates suppliers, manufacturers, retailers, and warehouses to efficiently produce, distribute, and maintain products at the right times and quantities. The Sri Lankan construction industry faces unexpected risks due to the economic crisis, particularly in the supply chain for imported items. This study investigates these risks, and their impact on contractors, and aims to identify effective risk management strategies to prevent such disruptions. While achieving the objectives, both quantitative and qualitative approaches were followed. The data for the study was collected through closed-ended questions using a survey and semi-structured interviews were carried out to find further information. The quantitative analysis has been done using the Relative Importance Index (RII) and qualitative analysis has been done using content analysis. Based on this study, identified that the economic crisis of Sri Lanka has impacted the supply chain for imported items in the construction industry such as mainly the impact of local taxes and charges, price increasing rapidly for import items, and due to that it has affected the constructors such as cost overrun, loss of profit. The study suggests that Sri Lanka should focus on manufacturing quality and standard items to mitigate the impact of the current economic crisis and prevent future similar situations.