Faculty of Engineering

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Open Access
A Comparative Investigation of Infiltration and Channel Roughness of Ephemeral and Perennial Streams in a Mountainous Catchment
(John Wiley, 2025-06) Khaniya, B; Gomes, P.I.A; Perera,M. D.D; Wai, O, W.H
Infiltration and channel roughness, two major factors that govern stream discharge, were studied in similar-sized ephemeral and perennial streams in a mountainous tropical catchment. Seasons were defined based on two ephemeral flow conditions, i.e., with (wet season) and without (dry season) surface flow. A stream was divided transversely into low-flow areas (close to the thalweg) and high-flow areas (close to the channel margin). The highest average infiltration (~50 mm/h) was observed in the low flow areas around the thalweg of ephemeral streams in the dry season and was significantly higher than for any other spatial scale or temporal period. The infiltration in high-flow areas did not show a statistically significant difference between the two stream types, and surprisingly, perennial streams in the dry season showed higher infiltration than ephemeral streams. Since sediment moisture and organic content showed negative and positive correlations with infiltration, respectively, for both stream types and ephemeral streams showed statistically significant negative correlations between litter and infiltration during the dry season, the low infiltration in ephemeral high flow areas was attributed to stream-type dependent litter processing. The litter of ephemeral stream high-flow areas was subject to partial decomposition due to rapid drying and had residue of previously buried litter. Ephemeral channels were two to three times rougher than perennial channels. Standing crop biomass and mean particle size increased stream roughness in both stream types but were less prominent in ephemeral streams due to the presence of litter. The study demonstrated that litter has a special role in defining the infiltration pattern, channel roughness, and flood control potential of ephemeral streams.
Open Access
A Context-Aware Doorway Alignment and Depth Estimation Algorithm for Assistive Wheelchairs
(Multidisciplinary Digital Publishing Institute (MDPI), 2025-07-17) Tennekoon, S; Wedasingha, N; Welhenge, A; Abhayasinghe, N; Murray, I
Navigating through doorways remains a daily challenge for wheelchair users, often leading to frustration, collisions, or dependence on assistance. These challenges highlight a pressing need for intelligent doorway detection algorithm for assistive wheelchairs that go beyond traditional object detection. This study presents the algorithmic development of a lightweight, vision-based doorway detection and alignment module with contextual awareness. It integrates channel and spatial attention, semantic feature fusion, unsupervised depth estimation, and doorway alignment that offers real-time navigational guidance to the wheelchairs control system. The model achieved a mean average precision of 95.8% and a F1 score of 93%, while maintaining low computational demands suitable for future deployment on embedded systems. By eliminating the need for depth sensors and enabling contextual awareness, this study offers a robust solution to improve indoor mobility and deliver actionable feedback to support safe and independent doorway traversal for wheelchair users.
Open Access
Accelerated membrane durability testing of heavy duty fuel cells
(IOP Publishing, 2014-11-19) Macauley, N; Alavijeh, A. S; Watson, M; Kolodziej, J; Lauritzen, M; Knights, S; Wang, G; Kjeang, E
Regular durability testing of heavy duty fuel cell systems for transit bus application requires several thousand hours of operation, which is costly and time consuming. Alternatively, accelerated durability tests are able to generate failure modes observed in field operation in a compressed time period, by applying enhanced levels of stress. The objective of the present work is to design and validate an accelerated membrane durability test (AMDT) for heavy duty fuel cells under bus related conditions. The proposed AMDT generates bus relevant membrane failure modes in a few hundred hours, which is more than an order of magnitude faster than for regular duty cycle testing. Elevated voltage, temperature, and oxidant levels are used to accelerate membrane chemical stress, while relative humidity (RH) cycling is used to induce mechanical stress. RH cycling is found to significantly reduce membrane life-time compared to constant RH conditions. The role of a platinum band in the membrane is investigated and membranes with Pt bands demonstrate a considerable life-time extension under AMDT conditions, with minimal membrane degradation. Overall, this research serves to establish a benchmark AMDT that can rapidly and reliably evaluate membrane stability under simulated heavy duty fuel cell conditions.
Open Access
Accessbim model for environmental characteristics for vision impaired indoor navigation and way finding
(2012 International Conference on Indoor Positioning and Indoor Navigation, 2012-11) Jayakody, J. A. D. C. A; Abhayasinghe, N; Murray, I
Most blind people require assistance to navigate within buildings as there is often insufficient information about the buildings available to them. To address this problem, this paper describes the “AccessBIM” model as an approach to facility management in which a digital representation of the indoor building features is used to facilitate the exchange and interoperability of real-time information in digital format which can assist blind people to independently access unfamiliar building indoor environments. This paper discusses conceptual communication model driven architecture that can be implemented for way finding and data synchronization, generating, in real-time, an AccessBIM for a remote user.
Open Access
Accurate Pedometer for Smartphones
(2013) Jayalath, S; Abhayasinghe, N; Murray, I
Accuracy of step counting is one of the main problems that exist in current Pedometers, especially when walking slowly on flat lands and performing different activities, such as climbing up and down stairs and walking on inclined planes. Although accelerometer based pedometers provide a reasonable accuracy when walking at higher speeds, the accuracy of them are not sufficient at slow walking speeds and performing different activities. This paper proposes a novel algorithm to detect steps using single-point gyroscopic sensors embedded in mobile devices. Preliminary analysis of data collected in different environments with the involvement of male and female volunteers indicated that gyroscope alone provides sufficient information necessary for accurate step detection. Algorithm was developed based on the gyroscopic data in conjunction with zero crossing and threshold detection techniques. The results proved that gyroscope based step detection algorithm provide a high accuracy when performing different activities and at slow paced walking.
Open Access
Aeroacoustic Noise Produced from Novel Wind Turbine Rotor Design for Small-scale Applications in Sri Lanka
(SLIIT, 2022-02-11) Perera, M; Bandara, U. H
Growing concerns regarding non-renewable energy sources have driven academic and industrial scholars as well as global superpowers to seek sustainable, greener power generation alternatives. One such prominent renewable substitute is wind power which was initially utilized in harnessing electricity towards the late nineteenth century though archaeological evidence has proved that wind power had been employed for various purposes since predynastic Egypt. Extensive research and development has enabled the efficient operation of multi megawatt wind farms at present though inherent drawbacks still persist, of which aerodynamic noise, also referred to as aeroacoustic noise, is of major concern. This paper details the simulative investigation of the aeroacoustic sound levels produced by an optimized novel wind turbine design intended for the use in small scale applications with medium wind speed conditions in Sri Lanka, using ANSYS Fluent. A transient analysis using the Shear Stress Transport turbulence model was used to obtain the converged pressure fluctuations which subsequently revealed the sound pressure levels via Fast Fourier Transforms at six predetermined locations of interest. The results revealed the presence of acoustic vibrations within the Infrasonic and Low Frequency Noise range with sound pressure levels exceeding one hundred decibels, particularly up to a frequency of twenty five Hertz. Prolonged exposure to elevated levels of low frequency noise has been identified to cause severe discomfort to humans though further conclusive research is required. Finer mesh controls which incorporate minute boundary layer variations during motion and precisely encapsulate the turbine geometry could further improve the accuracy of the results, however this would require adequate computational capacity. The results of this research primarily serve as a basis for identifying possible improvements for the novel rotor design in addition to providing a comparative study for future research, both simulative and empirical, on the aerodynamic noise emissions associated with wind turbines.
Open Access
Age-specific seasonal storage dynamics of Phragmites australis rhizomes: a preliminary study
(Kluwer Academic Publishers, 2004-10) Karunaratne, S; Asaeda, T; Yutani, K
Age-specific seasonal rhizome storage dynamics of a wetland stand of Phragmites australis (Cav.) Trin. ex Steud. in Japan, were investigated from April to October 2000. For each sampling date, above- and below-ground biomass and age-specific rhizome bulk density, ?rhiz were measured. Seven rhizome age classes were recognized, from <1 year to six years old, based on their position within the branching hierarchy as main criteria and rhizome color, condition of nodal sheaths and condition of the shoots attached to vertical rhizomes as secondary criteria. P. australis stand was moderately productive, having a net aerial and below-ground production of 1980 and 1240 g m−2, respectively, and a maximum mean shoot height of 2.33 ± 0.12 m. In spring, shoot growth started at the expense of rhizome reserves, decreasing the rhizome biomass as well as ?rhiz. Both parameters reached the seasonal minimum in May followed by a subsequent increase, indicating a translocation of reserves to rhizomes from shoots after they become self supporting. For each sampling date, ?rhiz increased with rhizome age. Given that the quantity of reserves remobilized by the rhizomes for spring shoot growth, as assessed by the drop in bulk density from April to May, were positively correlated (r = 0.97, P < 0.05) with rhizome age, it is proposed that for spring shoot formation older rhizomes remobilize stored reserves more actively than younger ones. Given that the accumulation of rhizome reserves (rise in bulk density) from May to August, May to September or May to November was negatively correlated (r = 0.97, 0.92 and 0.87, respectively, P < 0.05) with rhizome age, it seemed possible that younger rhizomes were ‘recharged’ at a higher rate than older ones. These resource allocation mechanisms pertaining seasonal rhizome storage dynamics are of paramount importance in formulating management and conservation strategies of wetlands and aquatic habitats. Our results indicate that a harvest of above-ground biomass from May to June would be more effective in reducing the growth than a harvest in July to August or later, when rhizome reserves have already been replenished. However, the latter may remove a larger shoot bound nutrient stock, still preserving a healthy stand for the subsequent years.
Open Access
An algorithm for energy driven cluster head rotation in a distributed wireless sensor network
(Colombo, 2005-12-15) Gamwarige, S; Kulasekere, E. C
Wireless sensor networks (WSNs) consists of large number of inexpensive, low-power, sensors that can be placed in an ad hoc fashion to form a communication network. Efficient techniques for inter sensor communication and information gathering is critical for prolonging the lifetime of the sensor network. Clustering provides an effective way for extending the lifetime of a sensor network. In this paper we propose a distributed and energy driven clustering algorithm where the cluster heads are selected based on relative residual energy level of sensors. Furthermore the cluster head candidacy selection phase, and the cluster head candidacy rotation among phases is triggered only when any of cluster heads energy drops below a dynamic threshold computed by the algorithm. As a result, the overheads in the inter sensor communications will be reduced and thereby the proposed algorithm will favor more powerful nodes over the weaker ones to prolong the lifetime of the entire sensor network in both homogeneous and heterogeneous sensor networks. The results have shown that the the proposed algorithm performs better when compared to existing algorithms such as LEACH, SEP, HEED and ANTCLUST based on the Percentage Node Alive (PNA) and the First Node Dies (FND) metrics.
Embargo
Alignment parameter calibration for IMU using the Taguchi method for image deblurring
(Elsevier, 2015-04-01) Chan, K.Y; Rajakaruna, N; Engelke, U; Murray, I; Abhayasinghe, N
Inertial measurement units (IMUs) utilized in smartphones can be used to detect camera motion during exposure, in order to improve image quality degraded with blur through long hand-held exposure. Based on the captured camera motion, blur in images can be removed when an appropriate deblurring filter is used. However, two research issues have not been addressed: (a) the calibration of alignment parameters for the IMU has not been addressed. When inappropriate alignment parameters are used for the IMU, the camera motion would not be captured accurately and the deblurring effectiveness can be downgraded. (b) Also selection of an appropriate deblurring filter correlated with the image quality has still not been addressed. Without the use of an appropriate deblurring filter, the image quality could not be optimal. This paper proposes a systematic method, namely the Taguchi method, which is a robust and systematic approach for designing reliable and high-precision devices, in order to perform the alignment parameter calibration for the IMU and filter selection. The Taguchi method conducts a small number of systematic experiments based on orthogonal arrays. It studies the impact of the alignment parameters and appropriate deblurring filter, which attempts to perform an effective deblurring. Several widely adopted image quality metrics are used to evaluate the deblurred images generated by the proposed Taguchi method. Experimental results show that the quality of deblurred images achieved by the proposed Taguchi method is better than those obtained by deblurring methods which are not involved with the alignment parameter calibration and filter selection. Also, much less computational effort is required by the Taguchi method when comparing with the commonly used optimization methods for determining alignment parameters and deblurring filter.
Embargo
Analysis and interpretation of dissolved gases in transformer oil: A case study
(IEEE, 2012-09-23) Hettiwatte, S. N; Fonseka, H. A
Condition monitoring plays a vital role in any asset management plan. Dissolved gas analysis is a routine test carried out on power transformers to monitor their condition. Four power transformers selected from a repository of power transformers due to their dissolved gas levels exceeding the normal levels are analyzed using the Key Gas Method, the Roger's Ratio Method and the Duval Triangle Method to diagnose any faults. The results show that for some transformers all three diagnosis methods agree on the type of fault, whilst for others it is not so straightforward in diagnoses. In this study, the condition of each power transformer is predicted using the above methods.
Embargo
Analysis of household cooking energy demand and its environmental impact in Sri Lanka
(Pergamon, 2002-11-01) Attalage, R. A; Wijayatunga, Priyantha DC
This paper presents the results and analysis of a study conducted with the objective of investigating the cooking energy requirements in the Sri Lanka domestic sector and the environmental emissions associated with it. The study was conducted out through a sample and showed that the main household energy supply sources were biomass, liquefied petroleum gas (LPG), electricity and kerosene with electricity being used largely for water boiling in all subsectors. It was observed that the urban sector cooking is largely dominated by LPG (95% of urban households) while the rural sector cooking is confined mainly to biomass (95% of rural households). The suburban sector consists of a mixture of all the sources (LPG-70% and biomass-85% of suburban households). Similarly, LPG dominates in electrified households (76.4% of electrified households), while biomass dominates in all non-electrified households. It was found in the analysis that the highest level of gaseous emissions due to cooking activity occurs in the rural areas, mainly due to the relatively large use of biomass, while the lowest level of emissions is recorded in a typical suburban household. Also, the analysis shows that fuel switching in domestic cooking activities from biomass to LPG and kerosene can be used as a measure to reduce emissions due to higher stove efficiencies and lower emission factors associated with these fuels. Substitution of 50% of biomass usage by kerosene in the rural households will result in 39–50% reduction in emissions within the rural sector. Further, substitution of 50% of biomass usage in urban and suburban sectors by LPG results in 4–49% reduction in emissions within these sectors.
Open Access
Analysis of Meandering River Morphodynamics Using Satellite Remote Sensing Data—An Application in the Lower Deduru Oya (River), Sri Lanka
(MDPI, 2022-07-16) Basnayaka, V; Samarasinghe, J. T; Gunathilake, M. B; Muttil, N; Hettiarachchi, D. C; Abeynayaka, A; Rathnayake, U
River meandering and anabranching have become major problems in many large rivers that carry significant amounts of sediment worldwide. The morphodynamics of these rivers are complex due to the temporal variation of flows. However, the availability of remote sensing data and geographic information systems (GISs) provides the opportunity to analyze the morphological changes in river systems both quantitatively and qualitatively. The present study investigated the temporal changes in the river morphology of the Deduru Oya (river) in Sri Lanka, which is a meandering river. The study covered a period of 32 years (1989 to 2021), using Landsat satellite data and the QGIS platform. Cloud-free Landsat 5 and Landsat 8 satellite images were extracted and processed to extract the river mask. The centerline of the river was generated using the extracted river mask, with the support of semi-automated digitizing software (WebPlotDigitizer). Freely available QGIS was used to investigate the temporal variation of river migration. The results of the study demonstrated that, over the past three decades, both the bend curvatures and the river migration rates of the meandering bends have generally increased with time. In addition, it was found that a higher number of meandering bends could be observed in the lower (most downstream) and the middle parts of the selected river segment. The current analysis indicates that the Deduru Oya has undergone considerable changes in its curvature and migration rates.
Open Access
Analysis of physical and chemical properties of alternative substrate material for sustainable green roofs
(Research Square, 2022-07-14) Kader, S. A
Green roof is the roof of a building that is partially or completely enfolded with vegetation and its associated components. It promotes the sustainability of buildings and provides comfort for urban ecosystem. We have investigated the viability of using organic waste as a growing medium. This study determines the most suitable growing substrate by investigating organic wastes of Sawdust, Wood bark, Bio char, Coir, Compost and Base medium under the parameters of density, moisture content, drought resistance and thermal resistance, contribution for vegetation growth, pH, electric conductivity and nutrient constituents. Investigation of chemical parameters is a unique aspect of this study. New methodologies using mathematical concepts were used to find thermal conductivity and EC of specimens in our research. Preliminary study results shows that the most substrate composition will comprise 60% growing medium and 40% base medium (fertilizer + potting mix). During the experimental studies, we have compared the test results of each organic waste specimens under the mentioned physical and chemical parameters. Base medium (90:10) has highest bearing capacity to withstand 2 external loads including vegetation and other imposed loads. Sawdust (60:40) exhibited optimum attributes for lightweight substrate by having least saturated unit weight, dry unit weight and the highest moisture content. In terms of drought resistance and vegetation growth, Bio char (60:40) was exceptional. Wood bark (60:40) exhibited the most convincing thermal resistance. The best characteristics in terms of pH, EC and nutrient content were exhibited by Sawdust (60:40), Coir (60:40) and Compost (60:40) correspondingly. Based on final ratings by considering all the experimental results, Coir (60:40) have emerged as the optimum growing medium in terms of physical and chemical properties. The authors emphasize to utilize this experimental study results into large-scale construction industries to promote the urban ecosystems through sustainable green roof constructions.
Open Access
Analysis of recent trends and variability of temperature and relative humidity over Sri Lanka
(India Meteorological Department, 2022-07-01) Rathnayake, U; Gunathilake, M. B; Senatilleke, U; Alyousifi, Y
The world is experiencing adverse consequences of climate change and shifts in climate regimes. Hence, studying the trends and patterns of meteorological variables is of major importance for many parties, including meteorologists, climatologists, agriculturists and hydrologists. Although several researchers have examined the trends and patterns in historical rainfall, only a few have examined the trends in atmospheric temperature. Noteworthy none of the previous studies have attempted to investigate trends in relative humidity over Sri Lanka. Therefore, identifying this existing research gap, this present paper presents a trends and variability analysis of atmospheric temperature and relative humidity of Sri Lanka. The long-term variations of minimum and maximum temperature and relative humidity records at 18 stations distributed in the three climatic zones namely, the dry zone, the intermediate zone and the wet zone in Sri Lanka were investigated for 30 years from 1990 to 2019. Annual and monthly trends were assessed using non-parametric statistical tests, including the Mann Kendall test (MK), Sen’s slope and Spearman’s rho test, while the changing points of temperature and humidity were determined using the Pettit test. In addition, the variability of climate parameters was estimated using the Coefficient of Variation (CoV). Interesting and encouraging results were obtained from the present analysis. Badulla in the intermediate climatic zone was identified with unexpected decreasing temperature trends, while several other areas were identified with expected increasing temperature and relative humidity trends. The adaptation practices based on these results would be interesting to incorporate in achieving sustainable development goals for the country
Embargo
Analysis of rural household energy supplies in Sri Lanka: energy efficiency, fuel switching and barriers to expansion
(Pergamon, 2003-05-01) Attalage, R. A; Wijayatunga, Priyantha DC
A majority of the households in Sri Lanka, as in the case of many developing countries, is concentrated in the rural areas of the country. Unfortunately, very little attention has been paid until recently to analyse and address various issues associated with rural energy supplies, particularly those issues regarding barriers to penetration of clean and convenient sources of energy. This paper presents the results and analysis of a study conducted through a sample study on domestic energy supplies in rural Sri Lanka with emphasis on cooking and lighting energy requirements. The paper has attempted to highlight policy issues associated with rural energy supplies and possible solutions to them in the context of the country’s overall picture of the energy sector.
Embargo
An analysis of signalized intersections: Case of traffic light failure
(IEEE, 2017-01-27) Mohamed Mafas, A. M; Amarasingha, N
Traffic congestion due to failure of traffic lights is one of the problems in Colombo. To study traffic congestions due to failure of traffic lights, the traffic characteristics at intersections should be investigated. Capacity of the intersection is the main factor influenced for congestions. Data were collected at three intersections Malabe, Battaramulla and Rajagiriya and capacity of each identified. The capacity of each intersection was studied according to the Peak Hour Malabe and Rajagiriya had PHF of 0.95 and Battaramulla had the value of 0.91. Accordingly, the effective simple suggestions to manage these intersections may be introduction of telephone booth and police cabin to use the case of emergency.
Embargo
An analysis of signalized intersections: Case of traffic light failure
(Faculty of Graduate Studies and Research, 2017-01-26) Mohamed Mafas, A.M.; Amarasingha, N.
Traffic congestion due to failure of traffic lights is one of the problems in Colombo. To study traffic congestions due to failure of traffic lights, the traffic characteristics at intersections should be investigated. Capacity of the intersection is the main factor influenced for congestions. Data were collected at three intersections Malabe, Battaramulla and Rajagiriya and capacity of each identified. The capacity of each intersection was studied according to the Peak Hour Malabe and Rajagiriya had PHF of 0.95 and Battaramulla had the value of 0.91. Accordingly, the effective simple suggestions to manage these intersections may be introduction of telephone booth and police cabin to use the case of emergency.
Embargo
An analysis of the time of use electricity price in the residential sector of Bangladesh
(Elsevier, 2017-12-01)
Time of Use (TOU) pricing is a cost-reflective electricity pricing scheme; it has proven to be an effective approach for reducing peak electricity demand in the residential sector around the world, especially in developed countries. The implementation of TOU pricing in low and lower-middle income economies is less appealing than in other settings. This is mainly because a traditional TOU pricing scheme may increase the cost of electricity for low income consumers. The lack of a suitable TOU pricing strategy for these countries results in high peak demand, poor utilization of network infrastructure and, consequently, higher electricity prices than necessary. The purpose of this study is to analyse and propose a TOU pricing scheme for the residential sector that will be suitable for countries with a high percentage of low income household consumers. In this study, Bangladesh will be used as an exemplar of a lower-to-middle income developing country. In Bangladesh, the residential sector is responsible for half the country's total electricity consumption, and constitutes an even greater proportion of the peak demand. Residential consumers currently pay inclining block usage rates that provide no financial incentive for them to shift their electricity usage from peak to non-peak periods. The proposed TOU pricing scheme is a combination of the traditional TOU and inclining block usage pricing schemes, based on a realistic load shifting capacity that is applicable to Bangladesh, and to other similar developing countries. Analysis of this pricing system for different income levels of residential consumers shows that the proposed scheme effectively reduces the peak demand, while ensuring minimum impact on consumer monthly energy bills and comfort levels.
Embargo
Analytic hierarchy process for selection of ERP software for manufacturing companies
(SAGE Publications, 2008-10) Perera, H. S. C; Costa, W. K. R
Enterprise Resource Planning (ERP) systems are popular as an IT enabled tool, which integrates different functional areas of business. ERP systems are implemented as a total business solution that supports major functionalities of business. However, many of the implementations are not success stories. Most post implementation problems are due to the inappropriate selection of systems. This paper describes multi-criteria decision model using Analytic Hierarchy Process for the selection of ERP systems for manufacturing companies. First, ERP evaluation criteria are developed by using past literature and through a questionnaire distributed among Sri Lankan manufacturing companies. Seven major criteria are identified and under each criterion several sub-criteria are identified. Selection of the best suited ERP system leads to a multi-criteria decision making problem as ERP systems should be evaluated based upon many criteria. Using the identified main and sub criteria, an Analytic Hierarchy Process (AHP) model is developed for ranking the ERP software. An example of a case is presented to show the actual implementation of AHP model. Expert Choice software is used to solve this AHP model.
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An analytical framework for cluster distribution of EDCR class of algorithms in Wireless Sensor Networks
(IEEE, 2009-12-28) Gamwarige, S; Kulasekere, E. C
Energy Driven Cluster-Head Rotation (EDCR) class of algorithms are energy aware distributed clustering techniques for effective ad hoc deployed Wireless Sensor Network (WSN) organization. The application of this class of algorithms requires the setting of salient parameters at the design stage of the WSN to achieve desired results. Two such parameters which should be known in advance are the cluster density and the distance between neighbouring cluster heads (CHs). In this research we analyze the effect of algorithm design based on these two parameters. Simulation techniques are given to support and verify the analytical results.