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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Artificial intelligence techniques in hydrology and water resources management and their applicability to Sri Lankan river basins
(IEEE, 2024) Karunarathna, SD; Rajapakse, RLHL
Artificial Intelligence techniques are increasingly being used in hydrology for tasks such as groundwater modelling, streamflow prediction, and rainfall time series generation. In Sri Lanka, traditional water resource management methods have limitations and are less accurate in predicting rainfall-runoff, flood events, and drought conditions due to complex parameters and seasonal rainfall patterns. AI methodologies were integrated into hydrological modelling to enhance water resource management practices in Sri Lankan River basins. The study evaluated the applicability of AI techniques in hydrology and water resources management by using data-driven models like RNN-LSTM and RNN-GRU, and physical-based models like HEC-HMS. The study focused on the Kalu River basin and Kirindi Oya basin from October 01, 2000, to September 30, 2011. The evaluation criteria included NASH, MRAE, and R2, as determined based on existing literature. LSTM and GRU models performed well simulating Kalu River basin streamflow. However, all three models failed to simulate streamflow accurately in the Kirindi Oya basin due to inconsistency of input features. While AI models offer efficient simulation of flash flood scenarios, limited and unreliable rainfall data can impact accuracy. Dry zone simulations require further model development to improve reliability as current models perform well only in wet zones.
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Full-Field deformation measurement system for early age concrete cracking
(IEEE, 2024) Silva, NSS; Gamage, ES; Mallikarachchi, C
Identifying early age shrinkage cracks in fresh concrete is imperative due to their potential to compromise structural serviceability. Understanding the tensile strain capacity of fresh concrete is a key factor in this regard. Nevertheless, measuring deformations in fresh concrete presents challenges, given its semi-solid state, casting doubt on the reliability of contact-based deformation measurement tools. This study is focused on developing a full-field deformation measurement tool for early age concrete. An in-house 3D digital image correlation-based system was utilized in tandem with a direct tensile apparatus, with modifications made to enhance accuracy. The proposed system demonstrates an accuracy of over 94% in measuring displacement and strain variations, underscoring its reliability for full-field displacement and strain measurements.
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Transferability of basin hydrological parameters for assessing hydrological processes in Sri Lankan wet zone river basins
(IEEE, 2024) Gayashan, K; Rajapakse, L
In the context of urbanization and population growth, sustainable water management is crucial. This study examines hydrological parameter transferability within Sri Lankan wet zone river basins, using the Hydrologic Engineering Center's Hydrologic Modelling System (HEC-HMS) modeling to overcome data limitations for accurate streamflow estimation. The HEC-HMS model was applied to three subbasins: Ellagawa, Ratnapura, and Baddegama in the Kalu River and Gin River basins. Spatial and temporal transferability approaches were assessed using Nash-Sutcliffe Efficiency (NSE) and Mean Ratio Absolute Error (MRAE) as objective functions. Model performance for the calibrated sub-basins yielded satisfactory NSE values (0.62-0.78) and MRAE (0.35-0.74). Within-basin transferability showed moderate success (NSE 0.60-0.63, MRAE 0.51-0.84), while across-basin transferability initially resulted in low accuracy. However, adjusting sensitive parameters improved performance to an overall accuracy of 85-87% in both sub-basins. The temporal transferability approach achieved better results, suggesting its potential for transferring parameters from main to sub-basins. These findings demonstrate the applicability of the HEC-HMS model with transferable parameters for sustainable water resource management in Sri Lanka.
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Influence of number of plies on flexural behavior of ultra-thin woven composites
(IEEE, 2024) Wanasinghe, C; Mallikarachchi, C
Deep space missions require weight-sensitive structures capable of supporting numerous operational configurations. The high strength-to-weight ratio and flexible material properties of woven fiber composites make them ideal for aerospace structures. The high curvature experienced by space structures during folding and deployment points out the critical importance of understanding their bending behavior for optimizing future structures. This paper introduces micromechanical models to capture the impact of ply count on the mechanical characteristics of thin woven fiber composites. In addition, the study aims to investigate the behavior of results derived from Classical Lamination Theory under varying numbers of plies. The reduction in bending stiffness between classical lamination theory predictions and finite element simulations across all ply configurations varies from approximately 500% for single-ply laminates to 90% for threeply laminates, highlighting the efficacy of the classical lamination theory approach in accurately predicting bending properties with increasing number of plies.
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Assessment of water availability and demand in Huruluwewa Catchment, Sri Lanka: case study focusing on trans-basin water management
(IEEE, 2024) Peiris, NK; Rajapakse, RLHL
Many river basins are increasingly vulnerable to extremely high or low flows due to climate change. Transbasin water transfers offer a sustainable solution, mitigating uneven water distribution by redirecting surplus water to deficit areas. This study focused on the impact of climate change on water resources and the applicability of trans-basin water transfer in Sri Lanka's dry zone. Future precipitation and temperature data were generated using the CNRM-CM6-1-HR model, downscaled with LARS-WG software. Projected inflow to the Huruluwewa reservoir was simulated using HEC-HMS software. The study shows that trans-basin water transfer reduced the water deficit from 20.7 MCM to 4.2 MCM during the 2018-2019 water year. Findings indicate an expected increase in annual rainfall by 6.4% and 5.5% during the 2030-2049 period under SSP1-2.6 and SSP5-8.5 scenarios, respectively. Both monsoonal rainfall patterns show an upward trend under these scenarios. However, projections indicate a decreasing trend in monthly average rainfall during the dry season, suggesting even drier future conditions. Rising temperatures will lead to higher evapotranspiration rates, resulting in a projected 27% decrease in annual inflow to the reservoir. Consequently, the required annual trans-basin water transfer is projected to increase to 24.7 MCM and 29.4 MCM under SSP1-2.6 and SSP5-8.5, respectively.