Browsing by Author "Rajapakse, A"

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1st International Conference on Electrical Engineering 2016 (Pre Text)
(Institute of Electrical and Electronics Engineers, Inc., 2016-12) Rajapakse, A; Prasad, WD
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Ascertaining the kinetic patterns of informal spaces in the commercial streets of Pettah, Sri Lanka
(Department of Architecture, University of Moratuwa, 2013-10-15) Makevita, U; Rajapakse, A; Dayarathne, R; Wijesundara, J
The study is an investigation of “kinetic” patterns in the urban informal commercial sector of Pettah, Colombo. Kinetic spaces refer to the transforming temporary physical developments and structures that complement the “static”/ permanent built fabric of cities. They introduce a humanized scale to the city in terms of “form” and “function”. Kinetic patterns represent development of the informal sector as connecting patterns between the static city and the activity patterns. Pettah is the main commercial and transportation centre in the country, which is currently undergoing transformations by removal of all informal, kinetic spaces and functions in a city beautification process. Yet, these patterns establish distinct characteristics within the city and need to be accommodated as part of the identity of the urban context. Based on Christopher Alexander’s “Pattern Language” and patterns related to the commercial context of cities, a theoretical framework was developed to explore examples of similar patterns in the kinetic developments in Pettah. They were traced and presented in a hierarchical order. The method of analysis was mainly through careful on site observations, activity maps and 2D and 3D maps documenting spatial and functional connections, photographs of the selected areas etc. The identified framework is place specific and primarily presented through graphical representations of the re-interpretation of Alexander’s generic images of the universal pattern, to establish the kinetic patterns of Pettah. The research ascertains that there is logic in the development of kinetic spaces and that the kinetic patterns follow the logic of the general pattern language of the city in terms of the practical connectivity of functions and physical spaces. The essential components of theses pattern relationships are extracted to establish what is specific to the context.
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Ascertaining the sense of safety in urban neighborhood streets : the case of Kotahena, Sri Lanka
Karunananda, S; Rajapakse, A; Rathnayaka, R
Streets are primary elements through which the character of urban neighborhoods are experienced and expressed. The “sense of safety” in neighborhood streets is paramount to social and psychological wellbeing of its residents and visitors. The intention of this study was to explore environmental and social cues of a neighborhood, which evoke fear of crime, which will help designers to prevent the generation of such negative feelings and promote more safe and comfortable spaces in our cities. This study used interviews, group discussions and observations to identify fear-generating factors with a sample of participants in the multi ethnic neighborhood of Kotahena in Colombo, Sri Lanka. Field data was analyzed through visual documentation and photographic surveys. Moreover, group discussions, interviews and personal observations were used to synergize the study objectives. The findings inform that fear of crime on streets is influenced by both environmental and social cues to varying degrees. Feelings of fear were associated with gender, ethnicity and less familiarity with the place as participants were from an ethnic minority within the community. Literature has emphasized that fear of crime has a connection to actual crime locations. The research findings, however, indicate that fear of crime spots identified by the residents do not have a direct relationship to the actual crime locations.
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Comparison of techniques based on current signature analysis to fault detection and diagnosis in induction electrical motors
(Institute of Electrical and Electronics Engineers, Inc., 2016-12) Fontes, AS; Cardoso, CAV; Oliveira, LPB; Rajapakse, A; Prasad, WD
The wide use of electrical induction motors in industries throughout the world requires, increasingly, more precision in fault diagnosis. Techniques of predictive maintenance such as Motor Current Signature Analysis (MCSA) and Motor Current Square Signature Analysis (MSCSA) are used to detect and diagnose faults patterns, characterized by the stator current spectrum, in induction motors. In this article, these techniques are applied and compared for different faults in real motors, such as inter-turn short circuit in the stator winding and eccentricity in the air gap. To assist in the comparison of these patterns of the stator current spectrum with and without faults, a theoretical model of a healthy electrical induction motor was used, with the same values of the real supply voltages, which generated the frequency spectrum patterns. The results presented in this article, which should be emphasized, demonstrated that the techniques mentioned above were suitable for the cited faults, whose comparison between the techniques showed the suitability of each one.
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DC microgrid as a solution for utilisation of solar photovoltaic sources
(Institute of Electrical and Electronics Engineers, Inc., 2016-12) Bandara, AIMH; Binduhewa, P; Ekanayake, J; Rajapakse, A; Prasad, WD
MicroGrid (MG) is a convenient solution to integrate renewable energy sources to the existing power network. Though ac MicroGrids are widely studied, researches are focused towards the implementation of dc MicroGrids in order to improve the utilization of renewable sources with dc power output. In this study a MicroGrid architecture for commercial buildings and domestic houses with solar photovoltaic (PV) as the renewable energy source is proposed. The dc MicroGrid was implemented in PSCAD/EMTDC software package and simulations studies were conducted to validate the operation.
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Design and testing of an arduino-based network jammer device
(Information Technology Research Unit, Faculty of Information Technology, University of Moratuwa., 2022-12) Najath, MNM; Herath, HMDS; Rajapakse, A; Sumathipala, KASN; Ganegoda, GU; Piyathilake, ITS; Manawadu, IN
A computer network is described as two or more devices connecting and communicating, each known as a computer network. These types of networks work on wired and wireless mediums. A sort of transmission medium is wired communications, also referred to as directed media. This form of communication is more reliable than wireless since it is the most stable. In wired communication, twisted pair cable, coaxial cable, and fiber optic cable are used to send data from the source to the destination. Wireless communication is also called "unguided" or "unrestricted" transmission media. In this mode, no physical medium is required to transmit electromagnetic signals. On the other hand, in wireless communication, a message can transfer through the air, water, or vacuum, i.e., infrared, radio, and microwave waves. Therefore, this research mainly focuses on wireless communication using radio frequency technology. This technology is also used on TVs, radios, laptops, modems, mobile phones, and pagers. People constantly interact with this technology in the modern world, and all these people have secure data and confidential information. However, in this case, someone uses this technology and tries to get the data illegally. It is a big problem for all civilians and the government. In this situation, a network jammer device can be used to protect those data from snooping attempts, location tracking, limiting cell phone activity, and cheating. This paper describes a low-cost network jammer that uses an Arduino and an RF 433 MHz module to create a frequency between 315 MHz and 433 MHz. It uses the denial-of-service technique to prevent illegal activities within a 100-meter range.
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Development of a test platform for synchrophasor applications with real-time digital simulator
(Institute of Electrical and Electronics Engineers, Inc., 2016-12) Gurusinghe, DR; Rajapakse, AD; Rajapakse, A; Prasad, WD
The rapid advance of synchrophasor technology and the growth of phasor measurement unit (PMU) installations in the recent years have substantially increased the feasibility of deploying practical synchrophasor applications. These novel applications need to be thoroughly evaluated before their actual implementations on real power systems. The most feasible solution is to use real-time power system simulators. Therefore, this paper presents a real-time digital simulator (RTDS) based test platform to implement and to validate various synchrophasor applications range from simple monitoring algorithms to advanced response based wide area monitoring, protection and control systems. The proposed test platform can also be used to validate PMU performances as well as to assess cyber-security issues of synchrophasor networks. The effectiveness of the test platform is demonstrated with a real-time monitoring application.
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Development of an automated microscopic imaging system for TB screening
(Institute of Electrical and Electronics Engineers, Inc., 2016-12) Samarasinghe, HDTG; Sampath, LLR; Thilakarathna, HRMMVB; Gopura, RARC; Lalitharatne, TD; Amarasinghe, YWR; Rajapakse, A; Prasad, WD
This paper proposes an automated microscopic imaging system (MIS) for TB screening. Mainly, the system consists of integrated hardware and software components for sputum smear slides feeding, controlling and carrying out microscopic and image processing functions of the system. The MIS is used to distinguish TB positive and negative cases. The hardware system and controlling mechanism of MIS are discussed. Algorithms for focusing of the microscope and image processing are presented. Experiments are carried out to evaluate the proposed automated microscopic imaging system
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Evaluation of the impact of integrating pumped-storage systems in a small power system with high wind penetration
(Institute of Electrical and Electronics Engineers, Inc., 2016-12) Peiris, KRD; Kalpage, KMT; Perera, KAIRP; Wickramarathna, MTAP; Siriwardana, MGCI; Lidula, NWA; Rajapakse, A; Prasad, WD
High wind penetration in a small power system can create overwhelming stability issues at contingencies. Hybrid wind and pumped-storage systems are widely adopted to harness the maximum wind energy potential locally. Similarly, integration of pumped-storage power plants can be considered for islands or small power systems to integrate more wind farms while improving stability of the system. A small power system was derived based on the IEEE-12 bus system to evaluate the system behavior with increased wind penetration and pumped-storage integration. The integrated system was simulated in PSCAD/EMTDC to analyze the system transient stability under different scenarios. The studies revealed that the integration of pumped-storage systems into small power systems with high wind penetration not only supports more wind penetration into the system but also improves the transient stability.
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Factor analysis, hessian local linear embedding and isomap for epilepsy classification from EEG
(Institute of Electrical and Electronics Engineers, Inc., 2016-12) Prabhakar, SK; Rajaguru, H; Rajapakse, A; Prasad, WD
In this present generation, more than 1% of the whole world’s population is affected by this seizure disorder. Due to genetic predispositions like tumours, strokes and drug misuse, epilepsy is caused. Epilepsy is a common brain disorder in which cluster of neuronal signals function abnormally. For preventing seizures, medications are available but only some patients can respond well to the medication. Other remedial measures such as neurostimulation, surgery, maintaining a healthy diet are not always successful in treating the patient. Because of epilepsy, the patients have to live with persistent anxiety throughout their lives and also leading a normal life and performing day to day and social tasks becomes more difficult for them. For the analysis and diagnosis of epilepsy, the detection and classification of seizures forms the most important step. The vital information regarding the dynamics of the brain can be easily measured by Electroencephalogram (EEG). Since the recordings of the EEG data are pretty long, the obtained data is too huge to process and so, in this study, the dimension of the EEG data is reduced by Dimensionality Reduction (DR) techniques such as Factor Analysis (FA), Hessian Local Linear Embedding (HLLE) and Isomap (IM). The dimensionally reduced values are then classified with the help of Genetic Algorithm (GA) and Generalized Regression Neural Network (GRNN). The performance metrics are analyzed with parameters such as performance index, sensitivity, specificity, time delay, quality value and accuracy. The results show that when FA, HLLE and Isomap are classified with GRNN, then a perfect classification of 100% and an accuracy of 100% are obtained. If the dimensionality reduction techniques classified with GA are compared, then a high accuracy of 95.24% is obtained when it is classified with HLLE-GA combination.
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The impact of distributed generation on transmission and distribution losses in Sri Lankan power system
(Institute of Electrical and Electronics Engineers, Inc., 2016-12) Priyangika, AAC; Wijayapala, WDAS; Banda, HMW; Rajapakse, A; Prasad, WD
Share of Non-Conventional Renewable Energy (NCRE), small hydro, wind, solar, bio-mass etc based electricity generation in Sri Lanka at present is 10% of the total annual generation. The Government of Sri Lanka has declared a national target of 20% from NCRE by 2020[1]. Most of NCRE power plants have been connected to the distribution network and are termed as Distributed Generators (DGs). With the increase of share of DGs, it affects system reliability, power quality and economic operation of the distribution network. This paper focuses on the impact of economic operation of transmission and distribution network due to distributed generation in Sri Lankan power system. Network simulation studies have been carried out for transmission network and for four grid substations to which many DGs have been connected. The analysis revealed that transmission network losses have reduced with increase penetration of DGs to the system while distribution network losses are dependent on the amount of DG capacities connected to the distribution network. However, there is a reduction of network losses when overall network is considered thereby giving financial benefit from DGs added to the system.
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Local detection of distribution level faults in a distributed sensor monitoring network using HMM
(Institute of Electrical and Electronics Engineers, Inc., 2016-12) Balachandran, T; Aravinthan, V; Thiruvaran, T; Rajapakse, A; Prasad, WD
The Smart distribution system initiative requires an increased usage of the distribution feeder-level communication infrastructure to improve automation. Using a distributed sensor network for monitoring the distribution system is proposed by various researchers. Such distributed sensor communication architecture requires information to be received within an allowable delay and a minimum processing time at the control center. Increasing the number of sensors in the network also increases the data flow in the communication medium. Therefore, to reduce the burden in the communication medium, an event driven communication protocol could be utilized. This communication architecture assumed that the sensors used a local fault detection system to detect the abnormal event before communicating with the control center. This work focusses on local detection of faults in a distributed sensor network using a Hidden Markov Model considering a minimum processing time.
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Mainstreaming renewable energy developments into traditional planning: a Sri Lanka case study
(Institute of Electrical and Electronics Engineers, Inc., 2016-12) Chathuranga, JHKK; Wijayapala, WDAS; Wijayatunga, PDC; Rajapakse, A; Prasad, WD
This study examines the Sri Lankan generation planning practices and recommends several methodological changes and models to successfully integrate and evaluate Non-Conventional Renewable Energy (NCRE) resources in the present planning approaches. The paper proposes the peak period capacity factor method to calculate the capacity credit of NCRE generation. A methodology is presented to model a wind power plant in Wien Automatic System Planning Package IV (WASP IV) and also to evaluate the benefits of modeled NCRE plants. The Mean Variance Portfolio Theory (MVPT) is proposed as a complementary planning tool to assess the risks of generation portfolios and finally, these concepts are applied on the Sri Lankan system to demonstrate the applicability.
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Mapping and path planning for long distance autonomous navigation using multisensory data
(Institute of Electrical and Electronics Engineers, Inc., 2016-12) Weerasinghe, KKDKU; Silva, LCJ; Basnayake, BMSS; Sandanayaka, SDM; Kumarawadu, SP; Chandima, DP; Jayasekara, AGBP; Rajapakse, A; Prasad, WD
This paper presents a methodology and a concept behind the autonomous navigation which can be used in field robots. Long distance navigation in an outdoor environment is a challenging task owing to floor profile variations and slipping problem. The concept is based on SLAM (Simultaneous Localization and Mapping) GMapping algorithm with particle filter approach in mapping process and AMCL (Adaptive Monte Carlo Localization) in navigation process. Experimental results are presented in this paper with the implementation of mobile robot platform using ROS (Robot Operating System). Further, reasons for the errors and methodology to overcome the problems are proposed.
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A novel mathematical model to improve the power output of a solar panel using reflectors
(Institute of Electrical and Electronics Engineers, Inc., 2016-12) Wijesuriya, DTP; Wijesinghe, LS; Wickramathilaka, KDSH; Vithana, DM; Perera, HYR; Rajapakse, A; Prasad, WD
Sri Lanka is located in an ideal position in the world map to harness more solar power compared to the countries situated away from the equator. Yet, Sri Lanka has been unable to gain the maximum advantage out of it due to the lower usage of solar harnessing systems partially due to the higher pay back periods of imported solar panels. The main purpose of this study is to optimize the electrical power output of a Solar Panel in a more cost effective method than solar tracking. In this research a novel mathematical model is presented for optimizing the positioning of fixed flat reflectors to enhance the solar insolation on a silicon based solar module throughout the day. The effect on the electrical energy output due to the increment of the solar insolation and the operating temperature is mainly considered in this research.
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Optimization of the usage of Samanalawewa water resource for power generation
(Institute of Electrical and Electronics Engineers, Inc., 2016-12) Pathiraja, MPW; Wijayapala, WDAS; Rajapakse, A; Prasad, WD
Samanalawewa hydropower project includes a reservoir, a water way system and a 120MW power plant as the stage I development. Some provisions have been kept for stage II development to add another 120MW power plant to operate as a peak serving power plant. Since the impounding of the reservoir, there is a water leak which causes more than one fifth of energy loss of the current energy generation by Samanalawewa power plant. The construction of stage II is suspended with lower energy generation due to the leak. This research discusses about a Leak Pump Back System which will curtail the net water outflow from the leak. The leaked water pumping head is much lower than the design head of Samanalawewa power plant, resulting in high net energy gain. Since the pumped back water is regulated by the reservoir, the extra energy generation is dispatchable. This will further improve the feasibility of Samanalawewa stage II development. Currently Samanalawewa mini-hydropower plant is operating using the leaked water. The mini hydro plant can recover less than one third of energy which could be recovered by leak pump back system. Therefore the combined operation of mini hydro and leak pump back system will give more benefits, though the leak pump back system is going to limit the water supply to the mini hydro plant.
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People places: attributes that enable a convivial walk trail in Diyatha uyana, Kotte, Sri Lanka
(Department of Architecture University of Moratuwa, 2014) Jagodaarachchi, A; Rajapakse, A; Dayaratne, R; Wijesundara, J
Introducing ‘green walk-trails’ to urban environments in Sri Lanka has become a popular intervention in the recent practice of urban development. People have embraced these trails as they fulfil the need for breathing-places/lungs associated with open green areas. In addition to beautification of the urban fabric, walk-trails serve a larger purpose of offering urban residents the opportunity to relax, rejuvenate and achieve mental and physical wellbeing. In order to fulfil such objectives walk-trails need to be ‘convivial’ places. Conviviality is an all-encompassing concept that emphasises the importance of fine grain, local nuances and adaptability that is the root of a more humane approach to urban development that encourages positive social interaction. Conviviality is ‘place-specific’ and based on an amalgamation of Geographical, Physical and Sensorial attributes. The objective of the study was to explore key attributes that contribute towards enabling a convivial walk-trail in the specific context of “Diyatha Uyana”, Sri Lanka. Based on the theoretical framework established to analyse conviviality, the analysis was ‘User-centred’ and ‘Place-centred’ to explore the qualitative aspects in depth. The main data gathering technique of the study was through narrative-mapping which incorporated cognitive maps supported by a narration. Data gathered were analysed via content-analysis in order to come-up with necessary interpretations. It was found that the sensorial experiences were generated by the specific geographical and physical attributes, the vitality and dynamism in the way they combined and enabled unique micro contexts within the overall place. This enables strong visual and non-visual perceptions of the place. Such perceptions are key motivating entities that attract people to a public place, which is a decisive factor in the successful usage of public places.
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People Places: Attributes that enable a Convivial Walk Trail in Diyatha Uyana, Kotte, Sri Lanka
(2015-10-02) Jagodaarachchi, A; Rajapakse, A
Introducing ‘green walk-trails’ to urban environments in Sri Lanka has become a popular intervention in the recent practice of urban development. People have embraced these trails as they fulfil the need for breathing-places/lungs associated with open green areas. In addition to beautification of the urban fabric, walk-trails serve a larger purpose of offering urban residents the opportunity to relax, rejuvenate and achieve mental and physical wellbeing. In order to fulfil such objectives walk-trails need to be ‘convivial’ places. Conviviality is an all-encompassing concept that emphasises the importance of fine grain, local nuances and adaptability that is the root of a more humane approach to urban development that encourages positive social interaction. Conviviality is ‘place-specific’ and based on an amalgamation of Geographical, Physical and Sensorial attributes. The objective of the study was to explore key attributes that contribute towards enabling a convivial walk-trail in the specific context of “Diyatha Uyana”, Sri Lanka. Based on the theoretical framework established to analyse conviviality, the analysis was ‘User-centred’ and ‘Place-centred’ to explore the qualitative aspects in depth. The main data gathering technique of the study was through narrative-mapping which incorporated cognitive maps supported by a narration. Data gathered were analysed via content-analysis in order to come-up with necessary interpretations. It was found that the sensorial experiences were generated by the specific geographical and physical attributes, the vitality and dynamism in the way they combined and enabled unique micro contexts within the overall place. This enables strong visual and non-visual perceptions of the place. Such perceptions are key motivating entities that attract people to a public place, which is a decisive factor in the successful usage of public places.
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Potential for promotion of demand side management in Sri Lanka through a market based approach
(Institute of Electrical and Electronics Engineers, Inc., 2016-12) Karunadasa, JP; Siyambalapitiya, T; Hemachandra, EAEH; Rajapakse, A; Prasad, WD
Today with the developments in technology, expansion and developments in industries, and increase in the standard of living of the society, the demand for electricity keeps rising every day. It is the responsibility of the utility to increase its supply to meet this demand in order maintain the demand supply balance. It is not always economical to meet this increasing demand by building new power plants. Hence today, more interest is shown towards controlling the demand, through Demand Side Management (DSM). Several customer categories in Sri Lanka were studied in order to identify the potential DSM options that can be implemented. The selected option was Chilled Water Storage (CWS) in buildings, by constructing storage tanks to store chilled water during the off-peak period, and using the stored chilled water to meet the peak-time cooling demand. The technical potential for savings that can be obtained through this technology in Sri Lankan context is analyzed, and the potential saving that can be achieved in the General Purpose and Hotel category customer group is calculated.
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Smart irrigation controlling system for green roofs based on predicted evapotranspiration
(Institute of Electrical and Electronics Engineers, Inc., 2016-12) Bandara, AGN; Balasooriya, BMAN; Bandara, HGIW; Buddhasiri, KS; Muthugala, MAVJ; Jayasekara, AGBP; Chandima, DP; Rajapakse, A; Prasad, WD
A green roof is a roof of a building that is covered from a vegetation. Green roofs are beneficial in number of ways for buildings. Crops in green roofs are exposed to direct solar radiation and strong winds. Furthermore, the substrate is shallow and it can hold limited amount of water. Therefore, artificial irrigation methods are required especially for green roofs in tropical countries. This paper proposes a novel irrigation controlling method for green roof based on predicted evapotranspiration. The system is capable of predicting the evapotranspiration and deciding the amount of water to be irrigated based on that. The rationale behind the proposed method is also explained. Particulars on designing and developing a prototype irrigation controller and a laboratory test bed for experimenting with green roofs are presented. Experiments have been carried out and the experimental results are discussed in order to analyze the performance of the proposed system. The experimental results validate the applicability of the proposed system.