Master of Engineering in Manufacturing Systems Engineering

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item: Thesis-Abstract
Manufacturing process and performance evaluation of thermal insulation coatings
(2022) Ranasinghe CSK; Punchihewa HKG
Manufacturing organizations are using a considerable amount of energy for their daily manufacturing operations and more than 60% of their total energy use is for thermal applications. Therefore, systems that use thermal energy as the main energy input for manufacturing operations continuously emit thermal energy to the environment, raising significant environmental, financial, human factors, and safety issues. Therefore, preventing the dissipation of thermal energy from manufacturing systems to their surroundings has become a priority in answering some of the most critical challenges. This could be done by improving energy efficiency and creating a safe workplace. However, due to the drawbacks of traditional insulation methods due to uneven hot surfaces and organizational rules and regulations on carcinogenic insulation materials, most organizations are moving toward environmentally friendly alternatives. Therefore, thermal insulation paints play an important role in substituting traditional insulations. This research aims to develop a thermal insulation paint by changing the type of pigment to minimize the thermal conductivity of the final coating mixture. A two-factor factorial design was designed that considered pigment volume concentration (PVC) and additive percentage (Sodium polyacrylate) as variable factors and the thermal conductivity as the response variable. For each variable, nine different combinations of paint samples were considered at three different levels. In this experiment, tile body powder was selected as the pigment, polyvinyl acetate (PVA) as the binder and sodium polyacrylate (NaPA) as the dispersing agent, and the thermal conductivity of the final coating layer against the selected coating substrate was measured. Then a numerical relationship was developed between the thermal conductivity (K) of the final insulation coating layer and the percentage of the weight of the two factors. The results revealed that the pigment type is the most influential factor for the insulation properties or thermal conductivity. Hence, there is an opportunity to continue the same procedure to evaluate the insulation properties while changing pigment types, especially considering ceramic base materials.
item: Thesis-Abstract
Investigation of tooltip temperature and surface roughness in turning of AISI 1045 steel with coconut oil-based hybrid nanofluid under MQL technology
(2022) Abeweera, VN; Perera GIP; Punchihewa HKG; Ranaweera RKPS
Over the past few years, positive changes have occurred in the manufacturing industry and many other fields as a direct result of current breakthroughs in nanotechnology. The integration of nano-sized solid lubricants into aerosols, suspensions, and emulsions can lead to an enhancement of the end product's tribological and thermal properties. This is because of the constituent materials' unique chemical and physical properties. Therefore, this makes it possible for lubricants or coolants to perform their functions to attain a high level of productivity in machining processes. This study aimed to investigate the effect on average surface roughness and tooltip temperature in turning AISI 1045 steel with novel coconut oil-based hybrid nanofluid under MQL technology. Al2O3 and TiO2 were chosen as the two nanoparticles to use in the experiments after conducting a survey of the relevant research in the field. In order to reach this aim, Taguchi's L16 orthogonal array, which is comprised of four factors, was utilized. Concentrations of Al2O3, TiO2, cutting speed, and air pressure are the four factors considered in this study. In this experimental design, the responses considered were average surface roughness and the temperature of the tooltip. Using the Minitab 17 software, the model fitting and optimization were carried out. The values that recorded as being optimal were, • • 0.75 wt. % of Al2O3, • • 0.00 wt. % of TiO2, • • 2.5 bar of air pressure, • • 96 m/ min of cutting speed As a direct consequence, it is clear that the developed MWFs show significantly higher performance than the other two techniques, dry cutting and coconut oil-based MQL cooling. The percentages show a 23.92 % and 37.97 % reduction in tooltip temperature compared to dry cutting conditions for MQL+ CC and Nano+ MQL+CC conditions, respectively. Also, the average surface roughness was reduced by 33.87 % and 94.85 % compared to dry cutting conditions for MQL+ CC and Nano+ MQL+CC conditions, respectively. For future work, we can use thermophysical and tribological factors rather than cost as a determining factor for better
item: Thesis-Abstract
Analysis of yarn parameters influencing the knittability of thermoplastic polyurethane yarns
(2021) Atapattu DM; Manthilake I; Punchihewa H
Knittability specially in synthetic yarns such as polyester and nylon is an essential index of the performance in ensuring the proper conversion of yarn to a knitted fabric. This can be affected by various conditions of the yarn manufacturing, yarn storage, knitting machine, knitting pattern and the environment. In footwear knitting industry, Thermoplastic Polyurethane synthetic yarn is being used due to its higher heat resistance and colour fastness properties compared to normal melt spun yarns. One of the major concerns in the process of knitting is the continuous yarn burst, which occurred significantly in thermoplastic polyurethane yarn. Occurrence of this burst appeared to be random and emerged in every yarn knitted areas. This research aimed to identify the critical factors affecting the yarn burst. After identifying the most critical factors through literature review, temporary and permanent countermeasures were developed. Initially, Prisma approach was applied to extract the relevant information from literature. Then, parameters were categorized into three based on factors related to: yarn compound, storage environment, and machine and knitting pattern. Under each category the critical parameters relevant to each factor was identified after analyzing the significance of each quantitatively and qualitatively. In terms of yarn aging, previous literature explains three types of tests namely natural exposure, field aging and artificial acceleration. According to literature, the strength of Thermoplastic Polyurethane yarn deteriorates once it is subjected to extreme conditions. In this study, the relationship between the Thermoplastic Polyurethane polymer manufactured date, the yarn lot manufactured date and the yarn burst was experimentally tested. The correlation with knittability and the yarn manufacturing dates were found to be not significant. In terms of yarn compound related factors, yarn unevenness was identified as the most critical parameter. An experimental set up was developed to measure the unevenness of black and white colourway samples. These colourways were selected as the defect rate of white colour was the highest while the black colour was the lowest. Through the statistical analysis of “t” distribution, it was identified that the statistical variance of the data set was high between the two colourways. This proves that the factor of yarn unevenness is directly correlated with defect rates. Related to machine and method related factors, the programming structures were less researched in the literature. According to the relevant footwear application, initial all needle knit structure is changed to 1*1, 1*2, and 2*2 structures. All 1*1, 1*2 and 2*2 structures prove better knittability compared to initial all needle structure. Depending on the aesthetic factors, 1*1 structure is considered as the optimum one for the relevant application. This study was limited to few parameters and the dependence of other parameters such as temperature, time and moisture absorption has to be further investigated in future works. Further, the needle knit structure is also an interesting avenue for further research.
item: Thesis-Full-text
Investigation on thermal behavior of NITINOL based actuating elements for biomedical applications
(2020) Perera HSL; Amarasinghe YWR
In modern material world, important consideration is given to the group of fascinating materials called shape memory materials (SMMs) which respond quickly to a definite change of heat, light and chemical. The shape memory materials that have been established to date are shape memory alloys (SMA), shape memory polymers (SMPs) and shape memory hybrids (SMH). SMA play a significant role in various applications such as sensors, actuators, clamping devices, etc. Nickel – titanium (NiTiNOL) alloys are heavily used in SMA due to their strain recovery, excellent thermal characteristics, reliability and commercial availability, in addition to being used in macro and micro electro mechanical systems based biomedical applications (BMA) due to high biocompatibility, resistance to corrosion and high fatigue limit. Previous researches have focused on developing integration between thermal stability and SMA microstructure. But they don't have enough thermal behavior data with different heat treatment temperatures. Although phase transformation temperatures and microstructure patterns with different heat treatment temperatures are unique characteristics of NiTiNOL. The aim of this study is to investigate NiTiNOL characteristics and thermal behavior of SMA based actuating elements for biomedical applications. The overall objective of this research study is to investigate the phase transformation temperatures for NiTiNOL alloy during different heat treatment temperatures and to propose the appropriate geometric shape of the actuating element in BMAs. Therefore, a number of experiments were done at the laboratory level to characterize the thermal related behavior of the NiTiNOL alloy. Differential scanning calorimetry test measurements are used in this study to analyze the dissimilarities in phase transformation temperatures and properties of NiTiNOL (Ni-54 and Ti-46, weight percentages) alloy due to the variation of heat treatment temperature ranging from 400 °C to 600 °C. Further, microstructure and Energy – dispersive X-ray are determined using Scanning Electron Microscopy. It is found that most critical phase transformations are taken place between heat treatment temperatures of 550 °C and 600 °C and extraordinary unique behavior of phase transformations are exhibited by the respective specimens subjected to these temperatures. Further it is found that thermal behavior of actuator elements is dominated by the changes incurred in the microstructure of the NiTiNOL alloy during heat treatment.
item: Thesis-Full-text
Location planning tool for biomass boilers
(2020) Jeewakaratna SYR; Punchihewa HKG
Steam boilers constitute an important part of a production facility. Though traditionally, fossil fuel has been used predominantly in steam boilers, the environmental impacts of using fossil fuel and the higher economics have fuelled exploration on alternative fuels such as biomass and in 2016 demand for biomass energy in Sri Lanka has been 194.3 PJ out of which 75.8 PJ has been industry demand which is an increase of 300 TJ compared to previous year. In light of above, this study has been carried out with the aim of mitigating the environmental impacts of using biomass as a fuel for boilers in Sri Lanka and to improve related economics by developing a location planning tool for biomass boilers & with the objectives of assessing factors that would govern the environmental and financial costs associated with the operation of a steam boiler with respect to heavy oil and biomass variants leading to proposing of a framework to rank the fuel variants based on environmental performance and finances. Methodology followed in this study was carrying out a life cycle assessment (LCA) to assess the environmental loads of each biomass variant in context via data collected in surveys and analysing reports of 60 steam boilers followed by comprehensive financial analysis and sensitivity analysis enabling comparison of relative contribution of each step in the process. It was identified due to extremely adverse impact of using fossil fuel, using biomass where sustainable has become the best alternative regardless the location of the boiler and subsequent distance from biomass source to the application, in Sri Lankan Context, consequently the threshold points for switching to biomass lie in the economic factors as cost of transportation dominates whether the process is feasible. Sawdust was identified as the most environmentally friendly fuel followed by wood chips, wood logs and husk respectively. Distances from wood log, husk, wood chip, and sawdust biomass sources to the point of application to equal the financial cost of heavy oil-based boiler operation were identified as 530 km, 554 km, 595.5 km and 604 km respectively. It was identified, ranking order of financial performance of fuels, toggle along with distance from respective biomass source to point of application, such that a fuel more feasible compared to another at similar relatively lower distance from fuel source to point of application would not necessarily be so at higher similar distances. Though husk usage is costlier than sawdust at relatively smaller distances, at similar distances over 140 km from respective fuel source to point of application, sawdust becomes the more viable fuel. Similarly, chips usage though expensive at relatively lower similar distances equivalent to other biomass variants, becomes more viable compared to husk and wood logs at similar distances over 460 km and 355 km respectively. Precise data on biomass sources in Sri Lanka are lacking and taking measures to develop a biomass resources map would contribute to location planning process of biomass boilers favourably and streamline supply chain process.
item: Thesis-Full-text
Performance evaluation of white coconut oil based metal working fluid
(2020) Wickramasinghe KC; Perera GIP; Punchihewa HKG; Senevirathne SWMAI
Metal Working Fluids (MWFs) play a significant role in metal machining operations and vastly used in aerospace, automotive and marine industries to produce high tech components. The main purpose of using MWF during cutting operation is to facilitate a layer of lubricant between work tool interfaces to abate friction and heat. In the present context, industries practice to use mineral-based MWFs as of its good functional performance. However, health and environmental legislations have bounded the usage due to its carcinogenic behavior and adverse effects to the environment. Therefore, the requirement of ecological and user-friendly cutting fluid has raised substantially in manufacturing industries. Researchers have taken much effort to find an alternative for mineral oils and concluded the importance of vegetable oils as a substitute to use for the MWF. However, neat vegetable oil express poor cooling capability during machining due to its low oxidation stability. The authors have formulated a white coconut oil-based water soluble MWF to overcome the poor cooling ability by using water and permitted food grade surfactants. The main intention of the research is to assess the industrial applicability of the formulated fluid in term of functional performance while ensuring health and safety of the operators and environmental impact. The surface quality, chip curl radius, chip formation of 0.2% C and AISI 304 steels while using formulated novel white coconut oil based MWF, mineral oil based MWF in flood cooling and dry machining configurations have investigated for the conventional turning operation. The machining parameters were selected according to the recommended specifications of the work materials and tool manufacturers. Coated carbide indexable inserts have been used for the turning operation and surface quality of each set of cutting parameters were measured. Further, tool wear was investigated using scanning electron microscope (SEM). Work tool interface temperature was simulated using the DEFORM platform. The invented novel white coconut oil based MWF expressed better values for almost all the set of machining parameters when compared to the other cooling configurations and proven its industrial applicability for the sustainable machining. The performance of the formulated white coconut oil based MWF can be enhanced by adding nanoparticles and it is worthwhile to conduct the machining operations for hard to cut materials for further confirmation of the industrial applicability.
item: Thesis-Full-text
Detection of defects on warp knitted fabric surfaces
Wijesingha, HRDR; Jayasekara, AGBP
This thesis is concerned with the development of a novel learning algorithm based method for detection of defects on patterned, textured surfaces of warp knitted fabric surfaces using neural networks. The acquired images were subjected to several filtering processes and morphological operations to improve the state of the image and enhance texture details. The proposed method was developed by considering textural abnormality as a defect. Since the warp knitted fabric surface is a repetitive patterned texture the image was splitted into windows prior to analysis in order to enhance detectability of defects. Also, gray level co-occurrence matrix and local binary pattern were used as the texture models of an image window. Selected set of statistical measurements were used to extract the texture from gray level co-occurrence matrix. Since detection of defects on an image is a binary classification problem an anomaly detection scheme was proposed. This enabled the development of the detection model by learning the feature space of one particular class of problem. A self-organizing map was used to learn the texture patterns on images of the non defective fabric samples. The resultant Euclidian distance of a window from the self-organizing map was used as the measure of similarity to non-defective windows while thresholding the similarity measure by using the maximum value similarity of non-defective windows as the threshold. The proposed anomaly detection scheme enabled detection of defects on particular type of texture. There were different surface types associated with warp knitted fabrics. Self-organizing map based clustering approach was used to discretize the detection problem according to surface texture type and the intention was to simplify the detection problem and solve it with respect to specific texture. Furthermore, the histogram of the local binary pattern was used for development of compressed self-organizing map to represent the local texture of a window of different surface types. All the calculations, analysis tasks and development of mathematical models were performed in a matlab environment. The appropriate graphical user interfaces were also developed with the proposed method been applied on images with seven different types of defects on seven surface types. The quality percentage was calculated based on the number of false positives/false negatives of the detection results for the image windows in order to evaluate the validity of the proposed method. The method results quality percentage was in the 80% range during the detection of defects.
item: Thesis-Full-text
Development of a prosthetic hand for power grasping applications
Herath, HMCM; Gopura, R; Lalitharathne, T
The human hand is an is an exceptionally significant part of the human body with a very complex biological system having bones, joints, and muscles, to provide many degrees of freedom. Among all the grasp patterns of hand, power grasping plays a crucial role in daily activities of a human. During the past few years, there was a rapid development in prosthetic limb technology to be used for the upper limb amputees. In this research, a prosthetic terminal device has been developed to assist the power grasping activities of daily living ofupper limb amputees. The designed terminal device includes four fingers, which generates eight degrees of freedom. In order to generate finger movements, a novel linkage mechanism has been proposed. Notably, the proposed mechanism can be characterized as a combination ofparallel and series links. The mobility of the system has been analyzed according to ChebychevGriibler-Kutzbach criterion for a planar mechanism. By considering the easy fabrication, the linkage finger mechanism was redesigned based on the design for manufacturing guidelines. With the intention of verifying the effectiveness of the mechanism, kinematics analysis has been carried out by means ofthe geometric representation and Denavit-Hartenberg parameter approaches. Subsequently, a Matlab program has been developed, in order to proceed with the numerical study. Furthermore, the motion simulation and static structural analysis proved that the mechanism is capable of generating the required finger movements for power grasping. Furthermore, trajectories and the configuration space of the proposed finger mechanism has been determined by using the motion simulations inbuilt with Solidworks software package. The movements of the finger mechanism, which is fabricated by 3D printing was experimentally tested. Experimental results proved the effectiveness of the proposed mechanism to accomplish the expected motion generation. In addition, the finite e
item: Thesis-Full-text
Effect of air and chilled emulsion minimum quality lubrication (ACEMQL) in machining hard to cut metals
Senevirathne, SWMAI; Punchihewa, HKG
Effect of Air and Chilled Emulsion Minimum Quantity Lubrication in Machining Hard to Cut Metals A novel approach of cutting fluid application was developed and its performance in machining hard to cut metalswas investigated. The study focused on turning AISI P20 and D2 tool steels using coated carbide cutting tools. For this study, an improved minimum quantity lubrication (MQL) method named, air and chilled emulsion minimum quantity lubrication (ACEMQL) method was developed to evaluate its effect on tool life and surface finish of material being machined. Trials were carried outfor ACEMQL with cutting fluid temperatures from 5°C to 20 °C in steps of 5 °C.In order to obtain a benchmark for comparison ofresults, set oftrials were carried out for dry cutting and flood cooling at 25 °C while all other parameters kept same as in ACEMQL method. Trials for ACEMQL method resulted in better tool life and surface finish for both AISI P20 and AISI D2 tool steels when compared with dry cutting and regular flood cooling methods. Minimum tool wear in machining AISI P20, was observed at 15 °C with ACEMQL, and it has shown a trend of increasing tool wear when temperature was lowered to 10 °C and 5 °C. A tool wear reduction of 97% from dry cutting, and 93% of flood cooling, is observed with ACEMQL at 15 °C. At 10 °C also ACEMQL has shown a reduction in tool wear by 94% compared with dry cutting and 86% compared with flood cooling. However, at 20 °C, it is observed that there is an increase in tool wear compared to flood cooling by 29%. Similarly, in machining AISI D2, minimum tool wear was observed at 15 °C with ACEMQL, and it has shown a trend of increasing tool wear when temperature was further lowered to 10 °C and 5 °C. A tool wear reduction of 96% from dry cutting, and 93% offlood cooling, is observed with ACEMQL at 15 °C. At 10 °C also ACEMQL has shown a reduction in tool wear by 71% compared with diy cutting and 57% compared with flood cooling. Although use of ACEMQL shows an improvement in surface finish in machining both AISI P20 and D2, it has not shown significant difference with reduction oftemperature in the investigated steps oftemperatures. For AISI P20, the least surface roughness obtained is 0.97 pm Ra and it is at 5 °C. It is a 35% reduction with respect to dry cutting condition and 31% reduction in comparison with flood cooling condition. For AISI D2, the minimum surface roughness obtained is 0.82 pm Ra and it is at 5 °C. It is a 49% reduction with respect to dry cutting condition and 40% reduction in comparison with flood cooling condition.Research on the effect of cutting velocity, feed rate and depth of cut, on tool life and surface finish with ACEMQL is suggested as future work. Further, economic feasibility analysis is suggested to find out the suitability of ACEMQL in local die and mould manufacturing industry, and also research on relationship between chip colour and cutting condition, and reasons for the colourisation is suggested as future work.
item: Thesis-Full-text
Devolopment of a mechanical dryer for drying coco peat to use growing media
Adikari, AJL; Punchihewa, HKG; Manthilaka, MMID
Coir peat which is a by-product of extracting fibre from coconut husk is considered an excellent growing media in horticulture industry. The basic features of coco peat is having good water holding capacity, ability to control PH and EC (electric conductivity) and good air porosity. Demand for the coco peat is increased continuously due to the above reasons. In addition, use of sphagnum peat moss and rock wool is replaced by coco peat very easily due to scarcity and environment issues ofthose growing media. In the present Sri Lankan context, sun drying is widely using to dry the wet coco peat up to the required moisture level before it is compressed. Since coco peat is having a low density (0.1 kg/L), it is needed to be compress before transportation. However sun drying is totally depending on the weather pattern and it is not advisable to depend on sun shine due to the present demand and reliability' on the industry. Therefore possibility to look at thermal drying is important while retaining the relevant properties of coco peat. Studies were carried out to evaluate the performance of combining both rotary drum dryer and flash dryer which are used in similar industries. Four key factors were taken into the study are moisture level, temperature, feed rate and residence time. A set of combinations of the above factors were tested and studied. More than two hundred samples were taken under different settings and corresponding output moisture percentages were measured. Compressed coco pellets were made out of dried samples and then expansion height of each sample was also measured for verification ofthe expansion quality of dry material. The low moisture levels of feeding material affected the temperature of the system and feed rate. The frequency didn’t play a major role. However feed material with high moisture, temperature and rotating frequency positively affected the output moisture while feeding rate was negatively affected. According to the research and considered input variable, this system shows coco peat can be dried when input material moisture is around 60% and temperature 90 -100° C and feed rate around 15 1/min and output material will be comply the requirement to use as growing media. Coco peat with low moisture contents should be exposed to heat at low temperature with higher feed rates, but, material with high moisture content should be exposed to high temperatures and low feed rates as seen with this research. However, it is advisable to take more measurements with very close steps to fine tune the model parameters before implemented on the field.
item: Thesis-Full-text
Design and development of a fixture for Kelly bar mounting
Perera, PFS; Jayaweera, ND; Punchihewa, HKG
The Kelly bar is a bulky, long and heavy device that is used in piling. The Kelly bar surface is not smooth and contains ribs and grooves. The Drilling process makes many damages to the Kelly bar. These damages are required to be repaired in a workshop. Therefore,the gap of this research was the difficulty and the high cost associated with Kelly bar maintenance.The aim was to design a suitable fixture.The Objectives were to study the process and then create a new fixture and implement it in the workshop. In the methodology, the development process of the fixture and testing was explained. The research focused on the design and the development of the Kelly bar mount The. Kelly bar mount was required to do sliding and rotation both. This mount was required to be designed so as to prevent injuries to workers and damage to the environment, with low energy consumption.A Literature review was done.Thus,the main areas of the report were to identify a suitable fixture, to design and produce the mount and then test the mount. Next, a Project plan was developed and a project path was identified. Then a free hand sketch was identified. Then the optimal solution by design tree was shown and the conceptual design was obtaitend. Next, calculations for engineering strength were carried out. The material requirement plans and machine requirement plans were prepared. Afterwards,the model was designed,and carried out. So, the actual model was made. Based on this,the cost of production was analyzed . The investment and the cost saving points were discussed. After which the production was carried out. Next , testing was done.Then it was implemented in the workshop. Finally it was painted. For this research, the cost of production and opportunity cost were calculated. Based on this, a simple payback period as 29 days was calculated. Based on these results, finally,it was concluded that, implementing this fixture reduced the cost of operation massively in the workshop.
item: Thesis-Abstract
A Study on the applicability of centrifuge filtration for production of ayurvedic arishta and asava
(2019) Chandrasekara KDMA; Punchihewa HKG
Arishta and Asava are kind of herbal wines which are manufactured by natural alcoholic fermentation process, and used in the countries where traditional Ayurveda or indigenous medical systems are established. Fermentation and sedimentation are two major processes in herbal wine manufacturing. Natural fermentation process in ayurvedic Arishta and Asava preparation takes nearly 30days whereas this period of some wines spans to one year or more. In natural fermentation, alcohol is self- generated and this process is not induced by adding artificial accelerators to enhance the process. Sedimentation process of ayurvedic Arishta and Asava takes nearly 7-8days period and this process also is allowed to complete naturally. With the completion of fermentation process, bigger suspended particles precipitate slowly due to gravitational force and specific gravity will become stable at the end of the sedimentation process. In Sri Lanka and India, it is very difficult to find a manufacturer who adopts any process improvement technique to enhance fermentation process or sedimentation process in production of ayurvedic Arishta and Asava. Productivity improvement of these medications without violating the traditional medicinal quality has become vital important due to increase global trend towards usage of ayurvedic Aristas and Asavas and compliance of regulatory requirements in addition to achievement of desired organizational objectives. The aim of this research is to study and verify the applicability of the centrifuge filtration method for production of Arishta and Asava. Proposed centrifuge filtration method has been focused to ayurvedic Arishta and Asava medications. Research methodology is mainly based on experimental techniques, data analysis and conclusions derived from findings of the literature survey. The research has focused on determination of physiochemical parameters of ayurvedic Arishtas and Asavas, study on different filtration and centrifugation methods, analysis of TLC profiles of selected Arishtas, determination of optimum fermentation and sedimentation times of selected ayurvedic Arishtas. Experimental results of TLC profiles of Aswagandha Arishtaya and Nimba Arishtaya revealed that qualities of end products with natural sedimentation are similar to those with centrifuge filtration. Also, case study-1 and case study-2 carried out under the research verified that the adoption of centrifuge filtration for clarification of ayurvedic Arishtas and Asavas is viable method instead of relying on time consuming natural sedimentation process. Based on the research findings, it is recommended to adopt centrifuge filtration method for production of ayurvedic Arishtas and Asavas.
item: Thesis-Full-text
A Genetic algorithm approach for solving a dynamic job shop scheduling problem
(2019) Kurera PBC; Dassanayake VPC
Job Shop Scheduling Problem (JSSP) is a non-deterministic, polynomial-time (NP) hard combinatorial optimization problem. It is one of the most common problems in manufacturing due to its widespread application and the usability across the manufacturing industry. Due to the vast solution space the JSSP problem deals with, it is impossible to apply brute force search techniques to obtain an optimal solution. Indeed, it is not possible to obtain an optimal solution when the number of jobs and the machines increase. Numerous researches have been carried out studying many approaches to solve this problem. In this research, Genetic Algorithm (GA) which is another widely used nonlinear optimization technique has been used to propose an algorithm. A novel chromosome representation (indirect) with an encoding based on time is introduced in this research. The proposed solution is capable of handling multiple disruptions which are new job arrivals, sudden machine breakdown and unplanned machine maintenance. The proposed algorithm is tested against benchmark problems in Static JSSP and some developed scenarios to simulate Dynamic JSSP conditions. The results show that the proposed algorithm generates near optimal schedules for Static JSSP. This algorithm can be used as a planning tool by the planners. It is possible to simulate almost all the real-life scenarios using this algorithm and schedules can be generated satisfying the required conditions. The algorithm can be developed further by employing a local search algorithm which produced more precious, optimal schedules.
item: Thesis-Full-text
Experiment and simulation based selection of oscillating buoys for rack & pinion power take-off wave energy converters
(2019) Hikkaduwa HGS; Fernando MARV
Wave Energy Converters (WECs) are explored on finding solutions to the energy sector as a renewable energy source for electricity and trying to convert the immense power available with ocean waves in the most efficient way. Many researches have been undertaken to improve varieties of WECs. However researchers have paid less attention towards the improvements of Rack & Pinion Power Take-off (PTO) WECs. Oscillating buoys are the most important part in most of the mechanical WECs which are used to absorb initial power from ocean waves. The aim of this thesis is to select the best performing oscillating buoys for Rack and Pinion PTO WECs by fulfilling the three objectives: (1) To identify Oscillating buoys suitable for Rack and Pinion PTO WECs, (2) To carry out simulation analysis to select the best performing oscillating buoys for Rack and Pinion PTO WECs, and (3) To conduct experimental analysis to select the best performing oscillating buoys for Rack and Pinion PTO WECs. The DMAIC (Define, Measure, Analyse, Improve & Control) cycle was used as the basis for the methodology. Six buoy types were selected based on the commonly available other types of WECs and this thesis focussed on simulation & experimental analysis to select the best performing oscillating buoys for Rack and Pinion PTO WECs. Simulations of all buoys were carried out with the help of Computational Fluid Dynamics (CFD) software X-Flow and three parameters, namely: Static Pressure, Vorticity & Liquid Phase, which were compared with each other. Proto type Rack and Pinion PTO WEC with regular wave making facility in a testing tank and six types of buoys in equal weight with the height to width ratio as 1 were fabricated and experimental testing were undertaken by creating four different wave heights for each buoy. Simulation and experimental results were analysed carefully and the best performing buoys for the proto type model of oscillating buoy operated, Rack & pinion PTO WEC were selected.
item: Thesis-Full-text
Improving the performance of the formal milk supply chain using a life cycle approach
(2019) Bandara BMNWK.; Punchihewa HKG.
In Sri Lanka, approximately 54.2 percent of the entire milk available for 2015 came from the formal milk supply chain and the rest was directed informally and consumed at home. The performance of supply chains in sustainability, is always on focus of continued trade growth. Therefore, new strategies and methods are required for risk-oriented and opportunity-oriented supply chain management. The methodology for the Life Cycle Assessment (LCA) can be described as a scientific technique to systematically evaluate the resource use of the product or service during the life cycle. Because of the high degree of intensity of energy affecting the overall performance of the dairy industry, the life cycle impacts linked with energy consumption in the formal milk supply chain is a particular concern. The aim of this study was thus to increase the performance of the formal milk supply chain by employing a life - cycle approach to examine the effects of energy use in the dairy sector in Sri Lanka and to suggest a framework for evaluating the resulting impact of energy use on the environment. Accordingly, the definite objectives are to examine the use of energy in Sri Lanka's formal milk supply chain, to measure the environmental impacts during the recognized stages of the supply chain, to identify the most critical processes and to explore the resulting impacts of various alternative energy supply situations on the performance of the formal milk supply chain. The study on the key stages of Sri Lanka's formal milk supply chain directed to the development of a methodology for assessing the impact of energy consumption on the environment during the life cycle. A case study was then carried out at a large-scale dairy manufacturer in Sri Lanka in which a life cycle assessment which was based on the supply chain and energy consumption was carried out. Finally, an impact assessment was done on potential performance variations in various energy supply scenarios. The impact evaluation of the life cycle was carried out by means of the Midpoint (H) method of ReCiPe (Ver 1.11, Dec 2014) in openLCA (version 1.7.0) with the ELCD database (version 3.2, Oct 2015). The results of the research were taken into account to determine the intensity of effects on the environment at the main stages of the supply chain process and to determine the possibility to mitigate negative impacts on the environment. Finally, it was found that the dairy factory operation phase generally has the highest impact on the environment (64.0 %). Raw milk transportation phase also plays an important role being the second highest (26.3%). By comparing the different alternative energy supply scenarios, solar photovoltaic electricity generation can provide the highest environmental benefits. It was verified with the case study that the dairy sector can reduce the overall impacts approximately by 30% by replacing furnace oil with biomass for thermal energy supply. The use of solar power in milk-producing facilities and milk chilling centers to replace conventional power sources can, however, further reduce the total impact by up to 60 percent. In the long run, substituting conventional energy sources based on fossil fuel with local renewable (green) energy sources will also bring financial advantages to the country, whilst ensuring energy security and independence.
item: Thesis-Full-text
Development of a queuing simulation model for train passengers
Wimalarathne, KKS; Punchihewa, HKG
Sri Lanka Railway (SLR) is currently having a schedule with uneven time intervals between trains. It reduces the popularity of the railway system and as a result new passengers hesitate to join the system. Hence, this current system is generally used by regular travellers only. In order to seek ways to improve the train schedules simulation based approaches have not been used in Sri Lanka. Therefore, the aim of the research was to develop a simulation model to minimise queuing time of passengers while maintaining an even interval between trains. A passenger survey and a railway survey were carried out to find current issues related to the timetable and the service. Considering the feedback of passengers, a simulation model was created using the Anylogic simulation software for the current train scheduling and the proposed train scheduling systems. The simulation model shows that passenger queuing time is able to be changed using the parameters of the model. Results also indicate that queuing can be potentially reduced using even time intervals between trains. However there could be a necessity to change the number of compartments to cater for the number of commuters in the proposed system. In addition the proposed system needs to be piloted in order to understand and overcome the practical limitations. This could potentially help to improve the popularity of the railway system in Sri Lanka. The operation model was developed between two stations due to limitation of the software. Thus, it is proposed to develop the model to cover the entire train fleet and the network to obtain more accurate and repetitive results.
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A Study of semen parameters in welders and non-welders in the Sri Lanka navy
Nanayakkara, NSMDK; Punchihewa, HKG; Fernando, DMS
Introduction: Welding is a metal joining process widely used in fabrication industry worldwide. Welding emissions are known to cause adverse effects on male reproductive system. The degree of hazard depends on the composition, concentration, and the length of exposure to emissions. Sri Lanka Navy has more than 300 welders at key establishments but their fertility status has not been assessed. Objectives: The objective of this study was to describe the socio-demographic and lifestyle factors of welders and non-welders, and to describe the occupational exposures of welders of Sri Lanka Navy working in Colombo. The lifestyle factors, occupational factors and sperm parameters of welders and non-welders were compared. Methodology: A descriptive study was done with welders (n=44) and non-welders (n=44) of Sri Lanka Navy base in Colombo. Socio-demographic and lifestyle factors of both groups and occupational factors of welders were studied. Semen samples were obtained from welders and non-welders after informed consent. Semen fluid analysis (SFA) was performed according to guidelines of WHO (2010), at Naval General Hospital Colombo and sperm parameters were compared in welders and non-welders. Correlation between lifestyle and occupational factors, and sperm parameters of welders were assessed. Ethical clearance was obtained from the Faculty of Medicine, Kothelawela defense University. Results: The socio-demographic characters and lifestyle factors of both welders and non-welders were similar. Welders working in shipyard /on board ships were more exposed to welding emissions than those welders in fabrication workshop. The sperm parameters were normal in 70% of welders when compared to 86% for non-welders. Among welders sperm concentration was abnormal in 16% and sperm motility was abnormal in 11%. In contrast only 7% of non-welders had abnormal sperm concentration and motility was normal in all of them. Although the dose of exposure (hours/day) to welding emissions did not have a significant effect on sperm parameters of welders, the total duration of exposure (number of years of exposure) had a significant effect on sperm concentration of welders (r = -0.4 p = 0.007). Squatting position and wearing synthetic underpants had a significant association with sperm concentration of welders. Conclusion: In this study the socio demographic and life style factors among welders and non-welders of the SLN base in Colombo were similar. Long term exposure to welding emission had a significant effect on sperm concentration but there were no effects with short duration of exposure. Welding in squatting position and wearing of dark coloured synthetic underpants was associated with a lower sperm concentration in welders.
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Development of an anthropometric database to determine school furniture dimensions for grade six students
Meedeniya, KL; Punchihewa, HKG
Anthropometry of school children is essential for decide the dimensions of furniture. However, no students‟ anthropometric studies have been carried out in Sri Lanka after 1979. Thus Sri Lanka depends on anthropometric measurements of other populations when designing furniture and other components. The deviations from the expected data and the available data of anthropometry may lead to errors in making decisions for selecting suitable furniture, equipment, and other components and importing them as well. Use of such incorrect items may result in long term health effects. Therefore Sri Lanka needs to establish anthropometric data for school children. The aim of this dissertation was thus to study anthropometric measurements required to determine the dimensions of school furniture for grade six based on a study in the Sabaragamuwa province of Sri Lanka. The research was carried out using 508 students. The results obtained from the data analysis were used to compare existing furniture dimensions available in the selected schools and standard furniture sizes specified in Indian standard IS 4837:1990 for school furniture dimensioning. A set of recommended desk and chair sizes of grade six students based on the anthropometric data taken from the students in Sabaragamuwa province have been proposed at the end of the report. However, a comprehensive island wide anthropometric survey is recommended covering all districts, including student categories from grade 1 to grade 12 and revisit the existing furniture dimensions because no detailed study has been performed after 1979 in Sri Lanka and also students‟ anthropometry may have changed with the change of standard of living, food habits, intra-individual, inter-individual, and secular variation of measurements during the past 40 years.
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Development of a decision support tool to determine the state of train wagons in Sri Lanka railways
Keerthirathne, CU; Punchihewa, HKG
Different countries use different models to condemn railway wagons once they reach the end of their service life. However, in Sri Lanka, such transparent method is not being used. The method currently practiced mainly depends on the experience of the assessors. The Sri Lanka Railway (SLR) has 53 types wagons in its rolling stock and wrong decisions to condemn wagons can lead to considerable loss to the SLR and country’s economy in general. Therefore, this study focused on developing a decision supporting mechanism to condemn the train wagons in SLR by assessing their status using a well-defined and transparent mechanism. The objectives were to study the existing procedures for valuation and condemning process of BCGS in SLR, to develop a decision support mechanism to condemn BCGS and analyse the scrap value in a transparent manner, and to evaluate the mechanism. Data were collected using documents, and surveys, interviews and focus group discussions with relevant 18 employees in the SLR. Then, the decision support mechanism was developed based on Microsoft excel. Finally, it was evaluated by letting 3 evaluators to assess the status of two wagons of different conditions using the existing and the proposed mechanisms. The proposed decision support mechanism showed consistency compared to the current method. Extension of the developed method to encompass other types of units in the rolling stock is proposed as future work.
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Development a cinnamon bark peeling equipment
Ranaweera, KS; Punchihewa, H
The Cinnamon Industry has been in Sri Lanka for hundreds of years and the product is commonly known as Ceylon Cinnamon. Sri Lanka is the dominant supplier in the world cinnamon market from the past due to its special taste and quality. Therefore, this has been a solid export earner over the years for Sri Lanka. At present it accounts for 80 % of the global cinnamon market and brings in an annual income of LKR 3,000 million. Although the cinnamon industry is bringing in foreign exchange to the country, development activities in the cinnamon industry have been rare compared to the other industries. There is potential to develop the industry in various facets. The cinnamon peeling is one such process that needs development in this industry. It is a time consuming process. This is also a labour intensive process, and requires highly skilled labour to perform the task. Therefore, the new generation is reluctant to work in this sector. This has badly affected the entire cinnamon industry. In addition, only primitive tools are being used in the cinnamon peeling process. Thus, mechanization of process is one of the options available to overcome the existing issues in the industry. In the current study, a new cinnamon peeling equipment was developed by introducing a new peeling technology. Existing cinnamon peeling method and other peeling technologies have been scrutinised to propose an appropriate peeling method. Cinnamon peelers‟ (n = 12) and exporters (n = 2) feedback was gathered to improve the design. It was identified that the introduced equipment in general can be used with minimal training and knowledge. The study also showed that the safety and efficiency of the cinnamon peeling process is increased significantly when the equipment was used. Apart from that, there is a possibility to automate the process and it is suggested as future work. The Cinnamon Industry has been in Sri Lanka for hundreds of years and the product is commonly known as Ceylon Cinnamon. Sri Lanka is the dominant supplier in the world cinnamon market from the past due to its special taste and quality. Therefore, this has been a solid export earner over the years for Sri Lanka. At present it accounts for 80 % of the global cinnamon market and brings in an annual income of LKR 3,000 million. Although the cinnamon industry is bringing in foreign exchange to the country, development activities in the cinnamon industry have been rare compared to the other industries. There is potential to develop the industry in various facets. The cinnamon peeling is one such process that needs development in this industry. It is a time consuming process. This is also a labour intensive process, and requires highly skilled labour to perform the task. Therefore, the new generation is reluctant to work in this sector. This has badly affected the entire cinnamon industry. In addition, only primitive tools are being used in the cinnamon peeling process. Thus, mechanization of process is one of the options available to overcome the existing issues in the industry. In the current study, a new cinnamon peeling equipment was developed by introducing a new peeling technology. Existing cinnamon peeling method and other peeling technologies have been scrutinised to propose an appropriate peeling method. Cinnamon peelers‟ (n = 12) and exporters (n = 2) feedback was gathered to improve the design. It was identified that the introduced equipment in general can be used with minimal training and knowledge. The study also showed that the safety and efficiency of the cinnamon peeling process is increased significantly when the equipment was used. Apart from that, there is a possibility to automate the process and it is suggested as future work.