Articles authored by UoM staff

Permanent URI for this collectionhttp://192.248.9.226/handle/123/2106

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item: Article-Abstract
1/8 Factorial study of metal effects on acid neutralization by cement
Stegemann, J; Perera, ASR; Cheeseman, C; Buenfeld, N;
The acid neutralization capacity of a cement/waste product is important because the integrity of the monolithic matrix and contaminant precipitation are dependent on the maintenance of alkaline conditions. A 1/8 fractional factorial experiment was used to selectively examine the main effects of seven pure metal compounds on strength development and acid neutralization capacity of portland cement paste and to obtain information regarding interactions between the compounds. The hydration products in a portland cement paste appear as plateaus in its titration curve. Metal contaminants were found to affect the pH and acid neutralization capacities of these plateaus, suggesting that they change the hydration products. Cr(NO3)3 and ZnCl2, which exhibited individual effects and also interacted, caused the predominant effects. Comparison between predictions by a simple empirical linear model based on these contaminants and acid neutralization capacity of a real solidified metal plating waste showed that additional factors play an important role in real wastes.
item: Article-Abstract
6-REXOS: Upper limb exoskeleton robot with Improved pHRI
Gunasekara, M; Gopura, R; Jayawardana, TSS
Close interaction can be observed between an exoskeleton robot and its wearer. Therefore, appropriate physical human-robot interaction (pHRI) should be considered when designing an exoskeleton robot to provide safe and comfortable motion assistance. Different features have been used in recent studies to enhance the pHRI in upperlimb exoskeleton robots. However, less attention has been given to integrating kinematic redundancy into upper-limb exoskeleton robots to improve the pHRI. In this context, this paper proposes a six-degrees-of-freedom (DoF) upperlimb exoskeleton robot (6-REXOS) for the motion assistance of physically weak individuals. The 6-REXOS uses a kinematically different structure to that of the human lower arm, where the exoskeleton robot is worn. The 6-REXOS has four active DoFs to generate the motion of the human lower arm. Furthermore, two flexible bellow couplings are attached to the wrist and elbow joints to generate two passive DoFs. These couplings not only allow translational motion in wrist and elbow joints but also a redundancy in the robot. Furthermore, the compliance of the flexible coupling contributes to avoiding misalignments between human and robot joint axes. The redundancy in the 6- REXOS is verified based on manipulability index, minimum singular value, condition number and manipulability ellipsoids. The 6-REXOS and a four-DoF exoskeleton robot are compared to verify the manipulation advantage due to the redundancy. The four-DoF exoskeleton robot is designed by excluding the two passive DoFs of the 6- REXOS. In addition, a kinematic model is proposed for the human lower arm to validate the performance of the 6- REXOS. Kinematic analysis and simulations are carried out to validate the 6-REXOS and human-lower-arm model.
item: Article-Full-text
A comparison of storage enhancement practices : Case study of two reservoirs in Kurunegala district of Sri Lanka
Wijesekera, NTS; Karunaratna, KNC; Nishantha, KGKR
Sri Lanka's dry zone is studded with nearly 12,500 small tanks built by ancient kings to store rain water for irrigation purposes. Most of them are called minor tanks which cater to land extents less than 80 ha.. Farmers--^nder these reservoirs request assistance to rehabilitate .Aese reservoirs to increase storage for increased water security. Though the common method of increasing the capacity is to increase the spill level, it is often not possible to carryout such raising because of the threat of upstream inundation. Most of the farmers are of. the belief that the bed excavation or desilting is the best solution for the need to increase water storage. Though there are some who favour the desilting/bed excavation, some are for the spill level raising. A literature survey identified the need of a comparative study of these options to determine which could facilitate the safe cultivation of more land under the reservoir. The present work carried out a comparative monthly water balance on two already desiited/excavated tanks from the dry zone of Sri Lanka. The study revealed that the advantages of spill raising or bed excavation depends on the rainfall received by each catchment, the topography, location and extent of earth removal from the tank bed ,etc. In the studied reservoirs it was felt that the increase If capacity contributed to the irrigation water release was negligible. The water balance provided comparative results that could be used as an eye opener for any attempts of reservoir storage enhancements.
item: Article-Abstract
A framework for subcontractor integration in alliance contracts
Vilasini, N; Neitzert, TR; Rotimi, JOB; Windapo, AO
Project alliancing involves the active collaboration of construction project owners and non owner participants (designer, contractors, and suppliers) to deliver projects in an atmosphere of shared responsibilities and liabilities. Alliancingcon notes integration but in real practice, it fails to create a true alliance environment since only part of the value chain (owner, designer, main contractor) is considered for integration. Consequently subcontractors are very often left out of the key alliance. Therefore this study identifies improvement areas to current alliance practice and suggests changes that will permit critical sub-contracting processes to be integrated into a project’s main alliance. To achieve this objective the research follows a comparative study approach. Information obtained from relevant literature is used to identify current subcontractor management practices and best practices for subcontractor integration in alliances. A case study of an alliance project is used to identify improvement areas in subcontractor management practices in an alliance environment. From these findings, the study proposes a revised alliance framework that integrates subcontractors from the early stages in alliance contracts, thus enabling the realisation of benefits accruable to projects through early contractor involvement.
item: Article-Abstract
A framework to identify droughts using temporal satellite data - a study of upper brantas watershed in east java of Indonesia
Shofivati, R; Wijesekera, NTS; Honda, K
dentifying drought-affected regions is usually done using ground based data collection such as rainfall or field V\veys. However in data scarce regions or of large spatial extent, such assessment is difficult and time consuming. Remote using data provides opportunities to assess the status of vegetation and these can be effectively used to assess drought conditions. NDVI values computed with NOAA AVHRR data are shown to reflect the drought condition. Vegetation response to rainfall indicated an approximately one-month time lag. In this study a comparison of a drought year and an adjacent year which did not experience a drought enabled the identification of a framework for drought monitoring using remote sensing data. In this study a NDVI value of less than 0.3 was recognized as an appropriate threshold for the identification of drought affected areas. Landsat TM data was used for land cover classification.
item: Article-Abstract
A GIS approach to identify road network improvement needs- Case Study of Kaduwela, Sri Lanka
Chandimal, WPAIM; Wijesekera, NTS
Moving from one place to another has become a major concern in today's context. On one hand there is an increasing financial requirement due to cost of vehicles and escalating fuel price, and on the other hand there is traffic congestion thereby increasing the time spent on the road which is considered as unproductive. One of the most important problems that should be looked at by today's leaders, managers, planners, etc., is the improvements that need to be made to the road network in order to reduce wastage of time, fuel and other valuable resources. In this context it is of great importance for the decision-makers to identify the problem causing area to provide attention by means of prioritizing suitable actions, such as road surface improvements, expanding the carriageway or by providing alternative paths. GIS is a tool which provides opportunities for the rational identification of planning and management alternative utilizing Geographic data and managerial experiences. In this work spatial accessibility of Kaduwela area in the outskirts of Colombo is identified using a simple GIS model which incorporates spatial variation of roads, road condition and population in the context of road network accessibility and road service accessibility. Model results indicates the options for improvements to particular pathways in a priority sequence so that, a manager could identify a temporal sequence to provide attention to relevant spatial extents and identify the improvements to the entire geographic area. An Affected Road Index (ARI) is computed for each of the GN divisions. The present work used ArcGIS software with spatial data of 1:50,000 scale to carryout a multilayer GIS analysis to demonstrate the strength of GIS applications in carrying out spatial resource management for the reduction of road congestion.
item: Article-Abstract
A Novel Reclaiming Agent for Ground Rubber Tyre (GRT). Part 1: Property Evaluation of Virgin Natural Rubber (NR)/Novel Reclaimed GRT Blend Compounds
Premachandra, BAJK; Edirisinghe, DG; De Silva, MIA
Use of reclaimed rubber as a component of a blend with virgin rubber or as a replacement for the virgin material in most rubber applications, especially in tyre components, has increased in the recent past. This is due to the increase in prices of natural and synthetic rubbers and growing concern about environmental issues. This research is aimed at evaluating the properties of rubber compounds produced by blending virgin natural rubber (NR) with ground rubber tyre (GRT), which was modified using a readily available, environmentally friendly, low-cost amino compound. Initially, reclaiming of 40 mesh GRT in the presence of rubber processing oil was studied at four different concentrations of the amino compound and two milling time periods. Mechanochemical reclaiming/devulcanisation was performed at a temperature of 30–70°C, using a laboratory two-roll mill. Properties such as initial plasticity, swelling ratio, crosslink density, and molecular weight between two crosslinks (Mc) of the reclaimed rubber samples were evaluated. Rubber compounds were prepared in the second stage by blending the reclaimed GRT samples with virgin NR in a ratio of 15:85. Mooney viscosity, initial plasticity, cure characteristics, and dynamic properties of the above blend compounds were evaluated and compared with those of the control compounds. This study shows that the amino compound acts as a devulcanising/reclaiming agent for GRT. Rubber compounds prepared by blending virgin NR with novel reclaimed rubber exhibit higher stock viscosity, lower scorch resistance, and lower hysteresis in comparison with the control compounds.
item: Article-Abstract
A statistical analysis of examination performances: A case study of candidate performance at the IESL professional review examination
Wijesekera, NTS
The analysis of the examination performance of candidates provides knowledge of insight in the areas which require improvement both in the candidate capability in the areas tested and the examination itself. The candidates appearing for the professional review of the Institution of Engineers Sri Lanka had often shown concern with respect to the poor performance at one particular section of the review. In order to investigate the performance of candidates, in this study, a statistical analysis of the professional review examination pertaining to four consecutive examinations held over two years was carried out. The study results clearly indicate the rather poor performance in this particular section of the professional review thus suggesting a through evaluation of both the candidates and the examination to achieve improvements. Among the other findings the study shows that on the average, the candidates from the civil engineering discipline had not fared in this particular section as well as the candidates from the other engineering disciplines.
item: Article-Abstract
A system for land development approval management using geographic information systems : A case study of Thimbirigasyaya Ward, Colombo
Leelananda, HH; Wijesekera, NTS; Peiris, TA
In a developing Country like Sri Lanka, it is very important to plan and manage its land development programmes to attract investments to develop land resources. In this context special emphasis should be given to urban areas. The prevailing systems of issuing preliminary land development clearance by the Urban Development Authority (UDA) which is based on a manual filing system consumes significant time and is unable to provide alternative solutions to prospective developers. Most of the countries use Geographic Information Systems (GIS) for similar land management work. A study was carried out, selecting Thimbirigasyaya ward of Colombo Municipal Council (CMC) to develop a GIS based land data management system in order to carry out the management of the land clearances in an efficient manner. Land parcel information obtained from CMC and UDA were scanned, spatial data were georeferenced and a mosaic was constructed. Input data were subjected to accuracy checks and were verified. Accuracies of data duplication, length, extent etc., were found satisfactory and adequate for UDA land clearance work. The database also incorporates the UDA conditions stipulated for location, zone and regulations enabling the checking of applications. The developed land information system was designed to include all functional aspects in the previous systems and additional capability to provide alternative solutions. The system developed using GIS was verified for computational accuracy using manual calculations. Adequacy checks were done with respect to the approved regulations. The developed Land Management Information system reduces the application processing time from 40 days to 5 days enabling quick decision-making. Present day IT tools such as Geographic Information Systems enable easy management of land parcels and possesses capability to overlay and analyze special data with minimum time. The present study highlights the data and accuracy requirements of the methodology to develop spatial databases for land development management. It also provides alternative solutions and can be used for land management policy analysis
item: Article-Abstract
Accommodating the Informal Sector: A Strategy for Urban Environmental Management
Perera, LASR; Amin, ATMN
Livelihoods of the urban poor, particularly the informal economic activities operating on streets and other public places, are usually seen as undesirable for environmental management by urban authorities which are preoccupied with keeping their cities clean. Hence, informal sector activities are often seen as "eye-sores" and are evicted from city centers in the name of "public cleanliness and orderliness". However, it is seen that environmental problems associated with the informal sector are mostly manifestations of unresponsive physical planning systems rather than attributes inherent to the sector's respective activities. An environmental impact analysis shows that provision of proper business premises to informal enterprises is an effective measure to curb the environmental problems associated with the sector. From this viewpoint, accommodating the informal sector in the urban built-environment is seen as an effective strategy for urban environmental management.
item: Article-Abstract
Accurate decision-making for timely washing of substation insulators, based on a pollution model
Goto, S; Nakamura, M; Nannyakkara, N; Taniguchi, T
Substation insulators near coastal areas rapidly become polluted due to the salty wind blowing in from the sea. Hazardous levels of pollution deposit cause higher leakage currents under damp conditions, resulting in system blackouts and damage to substations due to flash-overs. This research is aimed at developing a method of reliable decision-making to determine the time at which to wash polluted insulators to avert detrimental conditions. The proposed method consists of modelling the pollution deposits, and deciding on the best time to wash the insulators by using the actual data related to pollution deposits and weather information. The effectiveness of the proposed method is demonstrated by applying it to actual data taken at the Karatsu substation in Japan.
item: Article-Full-text
Adaptations and negotiations of local people towards 'development': case of Hambantota, Sri Lanka
(2014-04-09) Mariyathas, S; Sooriyagoda, K
"Planners, designers and architects are not paying attention in knowing how things work in cities. On the contrary, they havegone togreat pains to learn how cities have to Ivork and what have to begoodfor people " (Jacobs, 1961). This has made them create cities in a way which they found 'ideal' to achieve lvhat they (mis)understood as 'development'. Furthermore, the trend of the recent ciry development in ma1!Yparts of the world incfuding Sri Lanka has been 'changing the existing according to what power wants'. All of which do not seem appropriate to the socio-cultural spaces that are produced by the localpeople in their dailY life. The localpeople, therefore, adapt various strategies to transform tuba: is given into hOJVit can be lived. This research examines such adaptation process and the responsive negotiations of local people towards 'development' in the case of Hambantota, Sri Lanka.
item: Article-Abstract
Adjudication practice and Its enforceability in the Sri Lankan construction industry
Jayasinghe, HM; Ramachandra, T
Construction activities involve many temporarily assembled multiple stakeholders with multiple interests, which make the process complex. This results in numerous disputes on construction projects. Although various forms of dispute-resolution methods are available, an increased preference toward adjudication over the other methods is seen in many jurisdictions. However, in Sri Lanka it has yet to receive its recognition, and there is no legislative framework to enforce an adjudicator’s decision. This research therefore investigates the effectiveness of the current adjudication practice with the special emphasis on need for its enforceability in the current context. Practitioners’ views were sought using semi structured interviews conducted among 20 experts who constituted two major groups: construction professionals and legal professionals practicing in Sri Lanka. Content-analysis technique was used to analyze the collected views. According to analysis, 71 % (out of 92) of disputes referred to adjudication were unsuccessful where neither party was satisfied with the final outcome. However, 94% of 71% of those disputes were subsequently resolved amicably on the basis of adjudicators’ determination while the remaining 6% were referred to arbitration. This suggests that although adjudication is being practiced as a resolution method, it is not effective in its own right Certain limitations of the adjudication practice in Sri Lanka affected its effectiveness. Key limitations include lack of awareness among industry practitioners, absence of legal ascent, and lack of competent adjudicators to resolve complex disputes. Findings further indicate that the meager enthusiasm among the practitioners toward enactment is due to the inability to ascertain the extent of enforcing and failure to understand the benefits of statutory adjudication. The research therefore suggests that the relevant government bodies need to work toward enactment of statutory adjudication while establishing an appropriate climate for its implementation in Sri Lanka. DOI: 10.1061/(ASCE)LA .1943-4170.0000178. © 2015 American Society of Civil Engineers.
item: Article-Abstract
Adsorption of residual oil from oily wastewater using natural adsorbents
Anurangi, WAJ; Amarasinghe, BMWPK; De Alwis, AAP
Pollution of water due to oil contamination is a major environmental problem. This study focuses on the removal of emulsified oil from oily wastewater. Generally emulsified oil is treated using chemicals and therefore it causes series of problems. In this study, oil adsorption capacity of thermally treated rice husk prepared by carbonizing rice husk at 600 °C for 3 hours was tested. Batch experiments were conducted to determine the optimum value of process parameters. Adsorbent dosage, initial oil concentration, solution pH and adsorbent size affect the oil removal capacity. Oil removal was measured by the percentage of COD reduction. The experiments revealed that the optimum particle size range of carbonized rice husk for oil treating was 605~m.The adsorbent to solution ratio affects the degree of oil removal and percentage COD reduction of 40 and 100 were observed with 0.5g and 109 of adsorbent dose per litre of wastewater respectively. Kinetic data tend to fit well in second order kinetics and the Langmuir isotherm best represent the adsorption of oil onto carbonised rice husk. Monolayer oil adsorption capacity of 2.24mg of oil / g of carbonised rice husk was observed.
item: Article-Abstract
Affective E learning model for recognising learner emotions
Sandanayake, TC; Madurapperuma, AP; Dias, D
Online learning is commonly accepted as a support tool for educators as well as a medium of delivery of any-time, any-where content of a wide range of study programs to a widely dispersed learner community. Web-based learning environments are a relatively new medium of learning to Sri Lankan universities. Characteristics of learners of such environments vary widely, from technology geniuses to technological novices, from high bandwidth access to slow Internet connections etc. There are predictions of a near future boom of digital learning in Asian educational context, challenging the conventional face to face learning environments. Like any learning process, digital learning depends on effective communication of human knowledge, whether this occurs in a face-to-face classroom or across the Internet. The effectiveness of digital learning also depends on establishing two-way communication between facilitators and learners, and among learners themselves. Within the state university settings, learners experience varied emotions and interest towards learning. Although both emotions and interest can increase learners’ likelihood to engage in traditional learning, little is known about the influence of emotions and interest in learning activities in a digital environment. Previous research have identified that emotions occur while individuals assess events in their environment that are related to the needs, goals and well-being. Moreover, recent research on the emotional response to online learning has focused on the importance of learners’ feelings in relation to the community of learning. Major objective of this research study is to introduce a new model of online learning with relevance to the emotional response of the learning community. The study is based on Barry Kort’s Learning Spiral Model which is a four quadrant learning model in which emotions change while the learner moves through quadrants and up the spiral.
item: Article-Abstract
Ageing of pipes and sustainability of water supply
Ratnasooriya, AHR; Wijesekera, NTS
With ageing, the sustainability of the level of service of water supply in a pipe network may be adversely affected due to the reduction of flow rates caused by corrosion or scale deposition in pipes. In this study, attention is focussed on the effect of scaling on frictional losses in pipes and increased roughness values for pipes, based on experimental investigations, are presented. The influence of scaling on the performance of a small pipe network is analysed and relevant design issues are discussed.
item: Article-Abstract
Algorithms for incorporating reactive power into market dispatch
Ranatunga, RASK; Annakkage, UD; Kumble, CS
This paper proposes some methods for incorporating reactive power dispatch into nodal pricing and dispatch algorithms in poolbased electricity markets. The current approach of dispatching real power using a simplified power flow model and subsequently allocating reactive power as an ancillary service has the problem of getting suboptimal and some times infeasible solutions. However the complete a.c. power flow formulation can lead to problems, due to non-convexity and resource limitations. This paper proposes an improvement to the standard decoupled linear formulation approach. In the proposed method real power is dispatched first and then reactive power is dispatched allowing small changes to real power dispatch. The results of case studies show that this method gives similar results to the full non-linear solution for real and reactive power dispatch and prices.
item: Article-Abstract
An assessment of communication development needs based on target group requirements
Wijesekera, NTS
The need for the improvement of communication capabilities of engineers had been recognised by the engineers themselves and this effort had been built into the activities of most leading engineering institutions. The Institution of Engineers Sri Lanka (IESL) also had realised this need for quite a long period and had been implementing several activities to ensure the primary goal of enhancing communication capabilities of engineers. It had been noted that there had been no study carried out to get an input from the target group to identify their own with the communication training needs. A questionnaire survey was carried out to identify the communication needs of the target group through self assessments. This paper presents the methodology adopted and the findings of a study which investigated the English communication needs of the IESL membership. The results of this survey indicate the most preferred training areas in communication skill development and the preferences in the mode and place of conducting such training programmes, from the point of view of the target group. Therefore the findings of this work could be utilised as a guideline to organise effective training in communication skill development.
item: Article-Abstract
An experimental study of rip channel flow
Drønen, N; Karunarathna, H; Fredsøe, J; Sumer, BM; Deigaard, R
A laboratory study of the flow over a bar with a single rip channel has been performed. First, the well-known pattern of a bar circulation cell with a strong offshore-directed current out through the rip channel and a weaker onshore-directed return flow over the bar is documented. Then measurements of the three-dimensional structure of the flow in the area where the rip channel, the bar and the trough meet and well inside the rip channel are presented. These measurements reveal that 3D effects play an important role, and that a depth-integrated viewpoint may not always be sufficient for predicting the flow in the near bed region. Particle-tracking experiments illustrate the near bed flow pattern over the entire area. These demonstrate how the overall trajectory pattern changes as a function of the distance of wave breaking from the bar crest: For some conditions, the rip current is fed from the trough and for other conditions it is fed directly from the bar. Both the 3D measurements and the trajectory tests show the existence of a weaker onshore-directed near-bed drift in the area where the rip current ceases. Finally, in a series of sensitivity tests, measurements of the rip current intensity for different wave climate and water level conditions reveal a strong correlation between the rip current intensity and the wave height (both normalized).
item: Article-Abstract
An Intelligent Supervisory Control System For A Fish Processing Workcell
De Silva, CW; Wickramarachchi, N
A laboratory workcell has been developed for fish cutting. The workcell, which uses a variety of sensors, actuators, and hardware for component interface and control, operates with the help of a dedicated supervisory control system. A layered architecture has been used for the system. It has several knowledge-based modules for carrying out tasks such as workcell monitoring, controller tuning, workcell conditioning, and product quality assessment. The paper describes the workcell and the intelligent supervisory control system. Performance of the supervisory system is studied through fish cutting experiments