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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-Full-text
A 3-D coupled Smoothed Particle Hydrodynamics and Coarse-Grained model to simulate drying mechanisms of small cell aggregates
(Elsevier, 2019) Rathnayaka, CM; Karunasena, HCP; Senadeera, W; Polwaththe-Gallage, HN; Gu, YT
Recently, meshfree-based computational modelling approaches have become popular in modelling biological phenomena due to their superior ability to simulate large deforma- tions, multiphase phenomena and complex physics compared to the conventional grid- based methods. In this article, small plant cell aggregates were simulated using a three di- mensional (3-D) Smoothed Particle Hydrodynamics (SPH) and Coarse-Grained (CG) coupled computational approach to predict the morphological behaviour during drying. The model predictions of these cell aggregate models have been compared qualitatively and quantita- tively through comparisons with experimental findings. The results show that the shrink- age and wrinkling behaviour of cell cluster models are in fairly good agreement with real cellular structures. The agreement between the cell aggregate model predictions and the experimental findings are closer in the high and medium moisture content values ( X / X 0 ≥0.3), than highly dried stages ( X / X 0 < 0.3). Further, optimisation and sensitivity studies have been conducted on model parameters such as particle resolution, smoothing length, mass transfer characteristics and wall forces. Overall, the 3-D nature of this model allows it to predict real 3-D morphological changes more realistically compared to the previous meshfree based 2-D cellular drying models. The proposed 3-D modelling approach has a higher potential to be used to model larger plant tissues with complicated physical and mechanical interactions as well as their multiscale interactions.
item: Article-Full-text
A 3-D sparse FIR frustum filter for enhancing broadband plane waves
(IEEE, 2019) Wijesekara, RT; Edussooriya, CUS; Bruton, LT; Agathoklis, P
A 3-D FIR frustum filter having sparse coefficients is proposed for enhancing broadband plane waves received by uniform aperture arrays. Motivated by the design technique of 1-D interpolated FIR filters, the proposed filter is realized by cascading a spatially-upsampled 3-D FIR prototype filter having a frustum-shaped passband and a 3-D FIR masking filter having a parallelepiped passband. Sparsity of the filter coefficients is achieved through the spatial upsampling of the coefficients of the prototype filter and by hard-thresholding the coefficients of both prototype and masking filters. The proposed 3-D FIR frustum filter saves 39:5% multiplications and 66:6% additions compared to the state-of-the-art 3-D FIR frustum filters without degrading the performance in enhancing broadband plane waves.
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-Full-text
A personalized measure of thermal comfort for building controls
Daum, D; Haldi, F; Morel, N
A personalized measure for thermal comfort has been applied for use in combination with smart controls for building automation. Using data from a field study, we first show the superiority of personalized measures for thermal comfort compared to standard non-adaptive methods. Based on this knowledge we describe a methodology, using logistic regression techniques, to convert user votes to a probability of comfort. We also describe the interface used to collect the votes. We show that, for a given subject, our thermal profile converges against the probabilities found in the field study. As a case study we implemented the measure in a control algorithm to control the shading devices. The results clarify the mode of action and also show the effectiveness of the method.
item: Article-Full-text
A point-set-based approximation for areal objects: A case study of representing localities
Liua, Y; Yuan, Y; Xiao, D; Zhang, Y; Hu, J
Since partonomy knowledge is an important component of human cognition, we propose a point-set-based region (PSBR) model to approximate areal objects, especially vague areal objects. Two major properties of this model are that it is cognition-accordant and that it can represent vague regions easily. Given a point-set-based model, we can estimate the corresponding region using various methods, including convex hull, minimum bounding box, one-class support vector machine, and point density. We can examine the spatial relationships between two PSBRs using the derived areal objects. Additionally, we present a number of methods to compute relationships directly, based on two PSBRs. In the case study, we use a number of localities in China to demonstrate applications of the PSBR model. The proposed model can be implemented easily in an object-relational database management system. Hence, it provides a reasonable representation for vague objects that takes both manageability and approximation into account, especially now that Web 2.0 is making point data more convenient to collect.
item: Article-Full-text
A Satisfying leadership behaviour model for design consultants
Cheung, SO; Thomas, NGS; Lama, KC; Yue, WM
Design of construction project is a collective effort involving a team of specialists from different organisations. A lack of direct contractual relationships makes the line of authority subtle. The leadership of the design team leader could affect the productivity of the design team and therefore the project success. This paper aims to establish the relationship between leadership behaviours of design team leader and the satisfaction of the design team members. An empirical survey was carried out in Hong Kong and the results indicate that "charismatic" and "participative" leadership behaviours of the design team leader primarily determine the satisfaction of the team members. A satisfying leadership behaviours (SLB) model has been developed by multiple regression analysis based on the identified leadership behaviours. The SLB model was validated and the result reveals that the prediction error of the model is satisfactory. The practical usage of the SLB model has also been examined in this paper.
item: Article-Full-text
A simplified mathematical model for urban microclimate simulation
Yao, R; Luo, Q; Li, B
Techniques for modelling urban microclimates and urban block surfaces temperatures are desired by urban planners and architects for strategic urban designs at the early design stages. This paper introduces a simplified mathematical model for urban simulations (UMsim) including urban surfaces temperatures and microclimates. The nodal network model has been developed by integrating coupled thermal and airflow model. Direct solar radiation, diffuse radiation, reflected radiation, long-wave radiation, heat convection in air and heat transfer in the exterior walls and ground within the complex have been taken into account. The relevant equations have been solved using the finite difference method under the Matlab platform. Comparisons have been conducted between the data produced from the simulation and that from an urban experimental study carried out in a real architectural complex on the campus of Chongqing University, China in July 2005 and January 2006. The results show a satisfactory agreement between the two sets of data. The UMsim can be used to simulate the microclimates, in particular the surface temperatures of urban blocks, therefore it can be used to assess the impact of urban surfaces properties on urban microclimates. The UMsim will be able to produce robust data and images of urban environments for sustainable urban design.
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-Full-text
A study on the potential of natural ventilation and cooling for large spaces in subtropical climatic regions
Lin, JT; Chuah, YK
The potential of natural ventilation and cooling due to stack effects was investigated for large spaces with high ceilings. Different opening area ratios with respect to floor area were studied. Parameters of stack effects that consider floor heights were analyzed. Performance of natural ventilation was evaluated with cooling effects and indoor air quality for different months of the year. Three cities in northern, middle and southern Taiwan were used to represent typical subtropical weather types. It was found that opening ratio above 0.9％ is sufficient to provide fresh air to meet IAQ requirement. Two different temperature control strategies, fixed indoor temperature (FIT) and operative indoor temperature (OIT) were proposed and studied. A sensible cooling potential, fpc, was proposed. Different levels of fpc, namely, strong, medium, weak and not available were used to evaluate the number of days for which natural cooling, hybrid ventilation, mechanical air conditioning are to be applied to satisfy the cooling requirement. The research results presented can be used in the design of openings for large spaces, and also the airconditioning control strategies for different seasons of the year.
item: Article-Abstract
A sub-structure condensation technique in finite element analysis for the optimal use of computer memory
Fonseka, MCM
Application of the finite element method in structural analysis frequently involves manipulation of a large amount of data which is obviously a heavy burden on the computer. ‘Condensation’ is a popular technique adopted in such situations to avoid large systems of equations having to be solved, but condensed data may have to be stored for subsequent use at some stage in the analysis. In this regard, it is important to use an efficient condensation technique in the analysis for the proper use of available computer power and avoid any detrimental effects on the computer system. The condensation technique presented here has been developed to accomplish this in incorporating sub-structures in shells of revolution. This technique has the ability of using fixed-size arrays in the computer program irrespective of the size of the sub-structure, thus allowing the optimum use of computer memory.
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-Full-text
Academic research in emerging knowledge-based economies: The case of Sri Lankan construction industry
(Emerald Publishing Limited, 2018) Hadiwattege, C.; Senaratne, S; Sandanayake, Y; Fernando, NG
Purpose – Knowledge-based economies are popular in the present world. Simultaneously, universities are becoming more responsible for leading economic development through research. As a key contributor to the national economy, it is vital for the construction industry to move beyond outdated practices, and hence, reviewing the role of academic research in empowering the construction industry with knowledge is essential. The purpose of this paper is to focus on how relevant theories conceptualise the expected role of academic research in the innovative development of an industry and the specific location in the Sri Lankan construction industry. Design/methodology/approach – Following a comprehensive literature review, empirical data were collected from the Sri Lankan context with a mixed approach informed by a pragmatist philosophical stance. The perspective of academia and industry practitioners were deductively obtained through surveys and inductively explored through qualitative interviews. Findings – This study provides evidence that academic research in Sri Lanka does not contribute effectively to innovative construction management. Due to the absence of industry-focussed knowledge dissemination strategies, the academic–industry relationships are mostly non-research based. The industry lacks in research-informed-decision making, leading to lesser innovations. Research limitations/implications – The research conclusions are more applicable to the developing country construction industry contexts. Practical implications – The research urges the need for improved academic–industry research collaborations and strategic knowledge dissemination movements. Originality/value – The research confirms that academic research is a major integral part of the developing construction industry in a knowledge-based economy. In establishing the expected role of academic research, the research revealed the current practice to be under-located. Hence, the research prescribes the necessary actions; research collaborations in major and subsequent requirements.
item: Article-Full-text
Acceptance of health information systems in Sri Lanka using fuzzy set qualitative comparative analysis
(Faculty of Graduate Studies, 2024) Senthilrajah, T; Ahangama, S
The global doctor-patient ratio is 17 per 1000 population, however, it is 1.23 per 1000 population in Sri Lanka [1]. As it is far behind the expected numbers, the Sri Lankan public health sector is facing challenges in providing efficient services to citizens free of charge, including surgeries and cancer treatments. Looking at Nordic countries adoption of HIS has reached 95%-100% and the health sector has been digitalized using powerful Health Information Systems (HIS) in the form of Electronic Health Records (EHR), Personal Health Records (PHR), and Electronic Medical Records (EMR). The Government of Sri Lanka (GoSL) has launched various initiatives to digi-talize the public health sector and trailed Hospital Health Management Information Systems (HHMIS). However, it is noted that the acceptance of HIS is low among healthcare stakeholders. The empirical findings suggest the main reasons for low acceptance could be issues relating to usability. Therefore, this study is focused on identifying the factors impacting the acceptance of HIS by doctors and nurses in the public health sector.
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.