RESCON 2022

Permanent URI for this collectionhttps://ir.lib.pdn.ac.lk/handle/20.500.14444/5952

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Student and teacher perceptions on online teaching and learning science in grades 6 and 7: a case study in Kandy Education Zone
(Postgraduate Institute of Science (PGIS), University of Peradeniya, Sri Lanka, 2022-10-28) Basnayake, W.M.C.K.; Chandrasena, W.D.
Online education has been vital due to the closure of schools during the COVID-19 pandemic and, thereafter, fuel shortage in the country. However, teaching and learning science are most critical due to the practical nature of the subject. In this situation, online learning has to be empowered through necessary strategies to meet the challenges. Thus, this research aims to investigate issues related to online teaching and the learning process of science in grades 6 and 7. The data was collected through a convenience sample through teacher and student questionnaires. The sample comprised 84 teachers and 150 students from the Kandy Education Zone. Results revealed that 93% of students and 89% of teachers prefer face-to-face lessons. Moreover, 95% of teachers disagreed with conducting online lessons to deliver science due to the difficulty of teaching some scientific concepts. Further, 88% of teachers argued that assessing and evaluation could not be accomplished effectively in online mode. Around 93% of students agreed that online learning is ineffective in learning science. Though 79% of teachers have a good internet connection with powerful devices, 65% of students do not have individual devices with a good internet connection. Moreover, students in lower grades prefer face-to-face science lessons to online lessons. Lack of experience and knowledge of the technology of teachers badly affects the online teaching and learning process in Sri Lanka. Thus, it is suggested to remedy the above issues appropriately to enhance the science teaching and learning process in schools to meet national goals effectively to prepare students with 21ˢᵗCentury skills.
Conceptual understanding of genetics among grade 10 students: a case study in the Kandy Education Zone
(Postgraduate Institute of Science (PGIS), University of Peradeniya, Sri Lanka, 2022-10-28) Vidanapathirana, A.I.; Abayasekara, C.L.
Understanding Genetics at GCE (O/L) is considered difficult by the students, while most teachers believe that teaching Genetics is not easy. The objective of the current study was to investigate the conceptual understanding of Genetics among students in grade 10 (Sinhala medium) government schools in the Kandy Education Zone. The research used mixed methods, and data were gathered quantitatively through a two- tier diagnostic test and qualitatively using semi-structured and informal interviews. The sample consisted of 173 students representing both genders from six schools in the Kandy Education Zone, representing school types viz., 1 AB (Schools with Advanced Level Science stream classes), 1C (Schools with Advanced Level Arts and Commerce streams but no Science stream) and Type 2 (Schools with classes only up to grade 11). The quantitative data were analysed using Minitab statistical software. The study revealed that the extent of conceptual understanding of Genetics could be diagnosed through the two-tier diagnostic test. At the same time, the number of students who correctly answered the content choice ranged from 28.3 to 94.2% and those who answered both the content and the reason correctly ranged from 11.0 to 65.3%. This indicates that the students select content responses without a proper understanding, indicating that the tenth- grade students have several misconceptions about genetics. Thirty-two major misconceptions were identified by analysing items on the grade 10 Genetics diagnostic test. There was no statistical difference in students’ performance between gender or school type. In conclusion, the study revealed that the conceptual understanding of Genetics among grade 10 students was not satisfactory, and the students had several misconceptions about Genetics.
Enhancing students’ learning of science concepts through a blended learning approach
(Postgraduate Institute of Science (PGIS), University of Peradeniya, Sri Lanka, 2022-10-28) Ranaweera, R.K.S.P.N.; De Silva, A.D.A.
The blended learning approach is essential to enhance students’ interest in science. The primary objective of this study is to explore whether the blended learning approach can be used to enhance students’ knowledge and understanding of science concepts and their interests in learning science. Under new educational reforms to be implemented in Sri Lanka, the existing science curriculum has been revised by incorporating inquiry-based and blended learning approaches. Prior to the island-wide implementation of the reforms, newly developed curriculum materials were tested through a pilot study. The current study is based on one of the pilot studies conducted with 30 grade 10 students. The purposive sampling technique was employed. Google classroom was used as the blended learning platform. While pair work and hands- on activities were carried out in the physical classroom, introduction to the lesson, recording, reporting and self-reflection on hands-on activities were facilitated through Google classroom. Students’ views on the blended learning experience were gathered through an observation schedule and student interviews. Students’ knowledge and understanding were assessed by using rubrics. Results revealed that using the blended learning approach has enhanced students’ knowledge and understanding of some science concepts and their interest in learning science. In addition, students could develop inquiry skills and 21ˢᵗ -century skills through blended learning activities.
Impact of secondary level mathematics teachers’ pedagogical content knowledge in grade six algebra: a case study in the Galle Education Zone
(Postgraduate Institute of Science (PGIS), University of Peradeniya, Sri Lanka, 2022-10-28) Rupasinghe, D.D.; Amarasinghe, A.K.; Vitharana, P.R.K.A.
Secondary-level mathematics teachers’ pedagogical content knowledge (PCK) in Algebra is a crucial factor of teachers’ knowledge that influences the quality of the students’ meaningful learning. This mixed methods research aimed to investigate the influences of mathematics teachers’ PCK on sixth-grade students’ comprehension of algebra. National-level statistics indicate that the students’ mathematics achievement in the GCE (O/L) examination is low, and algebra is identified as the most critical subject component contributing to this. Literature suggests that the mathematics teachers’ PCK is poor, so it is crucial to investigate to address students’ low achievement. This study was carried out in the Galle Education Zone (n=292) to investigate the mathematics teachers’ PCK in depth through the explanatory sequential research design. The mathematics teachers’ PCK in algebra was quantitatively measured with the help of a validated and reliable questionnaire. The results showed that teachers possess a medium level of PCK (43.33±6.99). The qualitative data collected from classroom observations and the post-lesson interviews were analysed from reflexive thematic analysis. In the second phase, a sample (n=8) was selected using the stratified sampling method, and each teacher taught the sixth Graders one algebraic lesson on algebraic symbols. The qualitative data reflected three themes such as building algebraic concepts in students’ minds, addressing students’ misconceptions and students’ understanding. Moreover, the mathematics teachers were unsuccessful in concept-building and addressing the students’ misconceptions. They demonstrated a lack of content knowledge in basic algebraic concepts. They use neither appropriate teaching strategies nor creative activities to develop students' thinking processes. Thus, it is suggested to offer professional development programmes for mathematics teachers to uplift the status of Science Education in Sri Lanka.
Effectiveness of using web-based materials in teaching simple harmonic motion for GCE (A/L) students: a case study in Gampaha District, Sri lanka
(Postgraduate Institute of Science (PGIS), University of Peradeniya, Sri Lanka, 2022-10-28) Weerasinghe, C.; Chandrasena, W.D.
In the Sri Lankan education system, traditional lecture methods are used to teach Combined Mathematics. Simple Harmonic Motion is one such lesson taught in Combined Mathematics for GCE (A/L) students. The primary purpose of this study is to develop a new teaching material to improve the performance level of students who are attempting simple harmonic motion questions at the GCE (A/L) examination. Past research revealed that computer-assisted teaching and learning processes encourage students’ performance in mathematics. Students (206) and teachers (15) were selected from four schools through a convenience sampling technique in the Gampaha District in the Western Province, Sri Lanka. In this study, both qualitative and quantitative data were used. A pre-test, a post-test, a questionnaire, and semi-structured interview schedules were used to collect data. Quantitative data were analysed using SPSS 22.0, and qualitative data were analysed using thematic analysis. Using pre-test results, students were assigned into two homogeneous groups, an experimental group and a control group. The experimental group was instructed with web-based assisted material with structured essay-type questions, while the control group was taught using the lecture method. The results revealed that there was no significant difference between the pre-test marks in the control (51.8±32.3) and experimental (52.6± 31.8) groups: t(204)=0.185, p= 0.854. However, the findings showed that there was a significant difference in the mean values of post-test marks for control (56.6±26.1) and experimental (69.8±23.3) groups; t(204)=3.835, p=0.0001 after the intervention. As such, the new teaching material developed using web-based resources and the structured type problems positively affect the student performance level in simple harmonic motion lessons. Thus, it is suggested to use such strategies to enhance student performance through meaningful learning.
Effect of inquiry-based learning and socratic dialogue methods on achievement of gce (a/l) chemistry compared to conventional teaching method
(Postgraduate Institute of Science (PGIS), University of Peradeniya, Sri Lanka, 2022-10-28) Mahabaduge, D.R.; Liyanage, L.; De Costa, M.D.P.
Inquiry-Based Learning (IBL.) and Socratic Dialogue (SD) are the most effective teaching approaches to problem-solving and improving critical thinking. Therefore, the present study aimed 1) to identify the effectiveness of the IBL and SD teaching on student achievement in the General Certificate of Education (GCE.) Advanced Level (A/L) chemistry and the knowledge retention of the subject matter compared to conventional teaching method (CTM), which serves knowledge as a teacher-centred method, 2) to assess the effectiveness of IBL and SD in the development of higher-order thinking skills (HOTS) and lowerorder thinking skills (LOTS), and 3) learner perceptions toward the IBL and SD methods. This study employed a quasi-experimental design using 60 selected students in the science stream from each grades 12 and 13 in St Bridget’s Convent, Colombo, Sri Lanka. Two types of teaching approaches (treatments), namely IBL and SD and CTM, were systematically designed and implemented. A chemical bonding lesson was conducted for Grade 12 students (Group I), while Grade 13 students (Group II) followed the electroplating lesson using these two treatments separately. Students' achievement was measured using test papers (pre- and post-tests) consisting of six sub-questions: three for HOTS and three for LOTS. Post-tests evaluated knowledge retention after one month for both groups. Independent sample t-tests (p < 0.05) were used for analysis. Findings confirmed that students' achievement in chemistry was significantly higher in IBL and SD treatment (76 and 53%) compared with the CTM treatment (58 and 43%) in both Group I and Group II, respectively. Also, HOTS in different groups were promoted by the IBL and SD teaching approach. LOTS of Group I students were positively affected by IBL and SD methods, while LOTS of students in Group II were comparable with those in the CTM group. Knowledge retention in the two groups was significantly higher in IBL and SD methods (72 and 51%) compared to the CTM (51 and 34%), respectively. The majority of students who learned chemical bonding and electroplating using the IBL and SD methods were positive in the rubric assignment. Therefore, this study concludes that IBL and SD strategy is more effective in understanding, memorising, and critical thinking in chemistry.
Knowledge and attitude towards polycystic ovarian syndrome among students of Kaatsu International University, Sri lanka: a cross-sectional study
(Postgraduate Institute of Science (PGIS), University of Peradeniya, Sri Lanka, 2022-10-28) Shihana, N.A.F.; Pathinathan, K.N.; Gunathilaka, A.U.; Yapa, Y.A.S.V.; Silva, W.S.R.; Wijekumar, P.J.; Ranadeva, N.D.K.; Edirisinghe, E.A.S.T.
Polycystic ovarian syndrome (PCOS) is the most prevalent metabolic and reproductive health disorder among women worldwide. This study aimed to investigate the knowledge and attitude toward polycystic ovarian syndrome among an undergraduate population and the association with specific socio-demographic factors. A descriptive cross-sectional study was conducted among 272 female undergraduates of the KAATSU International University (KIU), Sri Lanka, through a simple random sampling method. Data were collected through a pre-tested self-administered questionnaire and analysed using SPSS version 26. The study was approved by the ERC of KIU (KIU/ERC/21/93). The mean age of the sample was 24.7±3.2 years. Regarding knowledge of PCOS, 29.4% had poor, 61.4% had moderate, and only 9.2% had good knowledge, while in terms of attitude, 4.2% had a low, 32.4% had moderate, and 33.1% had a high attitude towards PCOS. Among the females who reported being diagnosed with PCOS, 65.1% (28/43) had moderate knowledge, and 55.8% (24/43) had a high attitude toward PCOS. The population’s primary source of knowledge about PCOS was the internet, followed by health education and awareness programmes. This study revealed that there was no significant association between the knowledge level about PCOS and the socio-demographic factors (age, marital status, having children) in the total population (p<0.05). At the same time, there was a significant association between marital status and attitude level (p<0.05). The results concluded that PCOS-diagnosed females had a satisfactory level of knowledge and attitude. In contrast, the overall knowledge and attitude towards PCOS are insufficient among the total population. Thus, there is a need to enhance the knowledge about PCOS and its symptoms for proper evaluation and diagnosis.
Prospective teachers’ perceptions of constructivism and its implementation in schools
(Postgraduate Institute of Science (PGIS), University of Peradeniya, Sri Lanka, 2022-10-28) Gunasekara, W.K.K.H.S.; Amarasinghe, A.K.; Madawala, H.M.S.P.
The pedagogical internship is one of the vital steps of teacher development programmes conducted by the National Colleges of Education (NCoEs) in Sri Lanka. Here, the constructivist approach is one of the most commonly used teaching-learning theories as it develops advanced skills among students. During the internship year, the prospective teachers are allowed to experience a real classroom environment. This research aimed to determine prospective teachers’ perceptions of constructivism as a learning theory and its implementation in government schools in Sri Lanka. The mixed-methods approach based on the explanatory sequential design was used in this study. The sample included 100 prospective teachers following the secondary mathematics internship from two NCoEs. Data were gathered using a questionnaire and semi-structured interviews. Semi-structured interviews were conducted only with 10 prospective secondary mathematics teachers in three schools who taught mathematics for Grades 6 to 9. Interviews were recorded, and transcripts were prepared. The responses were examined by descriptive and content analysis. The questionnaire findings revealed that 95% of prospective teachers were aware of the theory of constructivism, and 98% were optimistic about that approach in the teaching-learning process. However, despite their theoretical knowledge of constructivism, most prospective teachers (98%) faced issues while implementing it in schools due to the lack of practical experience during their training. Responses to the semi-structured interviews revealed that the prospective teachers were not given sufficient hands-on training in using the theory of constructivism during their time at NCoEs. The lack of motivation by the lecturers of NCoEs in implementing constructivism was also noted as a drawback. The research concludes that teacher development institutions should organise programmes for prospective teachers to develop and improve their hands-on skills in using the theory of constructivism during their internship to enable them to use it in schools more confidently.
Knowledge, prevention practices, and barriers in response to COVID-19 infection in a tertiary educational institute
(Postgraduate Institute of Science (PGIS), University of Peradeniya, Sri Lanka, 2022-10-28) Upeshadi, I.M.; Bandara, K.R.I.; Sahardeen, A.; Kalpana, T.S.H.; Lakruwan, N.D.D.S.; Dunukara, J.D.K.; Gunasekara, T.D.C.P.
Variants of COVID–19 are highly contagious, resulting in a major threat to human life and the global economy. Infection control involves recommended preventive measures, but barriers could hinder following the guidelines. Therefore, the study was conducted to assess the knowledge and preventive measures for COVID-19 and to identify the barriers among undergraduate students at Kaatsu International University (KIU). A descriptive cross-sectional online survey was carried out from August 2021 to May 2022 among 350 undergraduates using a convenience sampling method. Data were collected through a self-administered, pre-tested questionnaire disseminated through social media after obtaining ethical approval (KIU/ERC/21/86). Data were analysed using SPSS version 25, and all hypotheses were tested at the 95% confidence interval (with 0.05 marginal error). Values for the total score of knowledge and preventive practice were defined and modified as poor (<33%), average (34 - 66%) and good (>67%), respectively. Most respondents were female (78.2%), while 52.4% of the sample represented the Western Province. Biomedical science students (40.8%) and 4ᵗʰ -year students (47.8%) had good knowledge of the disease. A significant correlation (p<0.05) was observed between the total knowledge score, degree program, and academic year. 46.7% demonstrated an average level of preventive practices. Only academic year, degree programme, gender and employment status were significantly associated with total preventive practice score (p<0.05). The usage of hand sanitisers was identified as a burden to employed undergraduates (p<0.033). Public transportation (74.5%) was identified as the highest obstacle to following preventive practices, and 50.1% of respondents had difficulty maintaining social distancing. In conclusion, most respondents had poor knowledge of COVID-19, while the practice of preventive measures was satisfactory among the study population.
Impact of teaching and learning process on students’ science learning: a case study in Badulla Education Zone
(Postgraduate Institute of Science (PGIS), University of Peradeniya, Sri Lanka, 2022-10-28) Bandara, K.M.N.T.K.; Manike, A.A.
The teaching-learning process is vital in education. Thus, the results of a successful teaching-learning process are invaluable. However, it is not easy to separate the learning process from the teaching-learning process, as they interact closely. Therefore, it is essential to recognise the impact of the teaching and learning process on students’ science education. Three hundred students and 25 teachers from GCE Ordinary Level classes from 21 schools in the Badulla Education Zone were used to achieving this goal. Mixed methods were used in the study. From that, simple random and stratified sampling techniques were used in the quantitative method. The purposive sampling technique was used in the qualitative method. Data were collected from questionnaires, interviews, and observations. Data were analysed using statistical packages and thematic analysis techniques. The information on the teaching-learning process was collected under the following factors: teaching strategies, teaching methodology, feedback and evaluation, and positive and negative reinforcement. According to the results, there was a linear correlation between Science scores, teaching methods and materials, teaching strategies, feedback and evaluation, and positive and negative reinforcement (p<0.05). Similarly, the Pearson correlation coefficient values (r) of the above variables were 0.747, 0.723, 0.742, and 0.695, respectively. Furthermore, there was a very strong linear positive correlation among factors such as teaching strategies vsteaching methods and materials (p<0.0001, r=0.935) and teaching strategies against feedback and evaluation (p<0.0001, r=0.954). Furthermore, qualitative analyses showed similar results with notable influences of the following themes on the teaching- learning process of science: teaching strategies, teaching methodology, feedback and evaluation, and positive and negative reinforcement for student performance. Therefore, by enhancing the quality and effectiveness of the teaching-learning process, students’ academic and non-academic achievements can be improved.
Extraction and characterization of cellulose nanocrystals from filter paper using sulfuric acid hydrolysis
(Postgraduate Institute of Science (PGIS), University of Peradeniya, Sri Lanka, 2022-10-28) Samarawickrama, K.G.R.; Wijayapala, U.G.S.; Fernando, C.A.N.
Cellulose nanocrystals are celluloses at the nanoscale that are taken from natural fibres and arranged in a tightly structured crystalline particle structure. The aim of this study was to look into the utilization of Whatman filter papers as a source of raw materials for the extraction of cellulose nanocrystals. Whatman filter paper is a cellulose paper created by utilizing a significant amount of alpha-cellulose. Its contents are a sign of its consistency and excellent quality, as alpha cellulose is thought to be the most stable form of cellulose. Cellulose nanocrystals extraction from Whatman filter papers using sulfuric acid hydrolysis was studied, and extracted cellulose nanocrystals were characterized. The sulfuric acid hydrolysis was performed with 64% (w/w) sulfuric acid and combined using a liquor ratio of 1:20 with Whatman filter paper while being subjected to strong magnetic stirring at 50 °C for 90 min. The extracted cellulose nanocrystals have been characterized by Transmission Electron Microscopy (TEM) analysis, Fourier Transform Infrared (FTIR) spectroscopy analysis and X-ray Diffraction (XRD) analysis. The TEM analysis clearly showed the formation of needle-shaped CNC particles having a size range between 10-30 nm in diameter and 100-200 nm in length. The FTIR spectrum showed the functional groups of the isolated cellulose nanocrystals from Whatman filter paper using sulfuric acid hydrolysis. XRD pattern confirmed that the CNCs from the Whatman filter paper could be extracted through sulfuric acid hydrolysis.
Wild taro (Colocasia esculenta) starch-based bioplastics for various applications
(Postgraduate Institute of Science (PGIS), University of Peradeniya, Sri Lanka, 2022-10-28) Karunarathna, R.G.T.P.; Sivakumar, V.
The plastic industry relies strongly on the use of petroleum-derived materials. However, the low degradability of these materials is a major environmental concern. Starch is a natural polymer, and starchbased bioplastic materials are more environmentally friendly as they degrade faster than conventional plastic materials. Therefore, starch-based bioplastics as substitutes for petroleum-derived materials have attracted the attention of many researchers. Literature shows that most researchers have used corn, potato, cassava etc., as starch sources for bioplastics. However, less work is reported on the utilization of wild taro (Colocasia esculenta) as a source of starch. Wild taro contains a high amount of starch (70-80%) by mass and is abundantly available in Sri Lanka. This study aimed to produce, characterize, and investigate the possible applications of wild taro starch-based bioplastics. The major applications tested during this study were food packaging, the production of grow bags for young plants and ornamentation using thin sheets. Glycerol and gelatin were used as plasticizers during the production of bioplastics. The bioplastic samples were prepared with various amounts of plasticizers and thicknesses. Properties such as density, solubility, biodegradability, sealing properties, morphology, chemical resistance, wettability, and tensile strength were tested for the prepared samples. The density and water solubility of the sample was calculated to be 10.9 g cm⁻³ and 27.9%, respectively. The wettability of the surface was tested by measuring the contact angle between the surface and the water. The surface is less hydrophilic with contact angles in the range of 70° - 80° . The measured tensile strength and Young’s modulus were 0.04 MPa and 3.70×10⁴ N m⁻² , respectively. The overall results showed that wild taro starch-based bioplastics are suitable for packaging, ornamentation, and producing grow bags.
Optical and structural properties of polyvinyl alcohol based polarized films modified with Ag-nanoparticles and iodine
(Postgraduate Institute of Science (PGIS), University of Peradeniya, Sri Lanka, 2022-10-28) Dharmasiri, K.S.; Hapuarachchi, H.A.M.M.; Pemasiri, B.M.K.; Seneviratne, V.A.
At present, polymer materials are being used for many applications due to their unique physical, mechanical, and optical properties. Many studies have been done on polyvinyl alcohol (PVA) polymer for various applications because PVA has some useful properties compared to many other polymers, such as, solubility in water, film-forming ability, and flexibility. Plasticizers can also be used in order to change some physical properties of PVA polymers. In this study, several modifications are done for the PVA films, which can be used as light polarizers. For this purpose, Ethylene glycol (EG) added PVA, Ag nanoparticles (NPs) added PVA, and Iodine added PVA films were tested for optical and structural characteristics using UV-Visible data and Powder X-ray diffraction (PXRD) data. The UV-Visible data for EG/PVA films show that adding EG to the PVA films decreases the transmittance of the film. The XRDs of EG/PVA films show that EG is decreasing the crystallinity of the PVA film. UV-Visible data of PVA/Ag-NPs films show that the addition of Ag nanoparticles reduces the films' transmittance in the visible region. Particularly the transmittance value is much lower at around 400 nm than that of pure PVA film, indicating more absorption of blue light. Therefore PVA/AgNPs films can be used as blue light filters. The addition of Ag nanoparticles can be used to increase the crystallinity of the PVA polymer matrix, which is vital for the strength of the film. UV-Visible data for stretched PVA/Iodine films show low transmittance compared to the pure PVA film in the visible region, which is almost equal above 700 nm.
Construction and application of a portable muon detector
(Postgraduate Institute of Science (PGIS), University of Peradeniya, Sri Lanka, 2022-10-28) Senadheera, S. A. K. D.; Ranawaka, T.P.; Jayalath, J.A.C.P.; Mendis, D.R.A.
Particle physics studies the fundamental aspects of nature, the very building blocks of the universe, and has revolutionized the way we observe our known universe. Even though working with powerful accelerators and sophisticated detectors is ideal, not all institutions have such facilities. Therefore, a low-cost muon detector was built according to the design of the desktop muon detector by the Massachusetts Institute of Technology. A plastic scintillator is used as the scintillation material in the detector due to its low cost and ability to be shaped into the required shape and size. A silicon photomultiplier is used as the electronic light sensor as it is much cheaper, smaller, and better at detecting the excitation energies of charged particles compared to the photomultiplier tubes. Other components include basic electronic components such as an Arduino nano, operational amplifiers, resistors, capacitors, and inductors. The detector was used to obtain count rates in Colombo, Sri Lanka. Under several approximations, the muon flux obtained in Colombo at sea level is 9.6 × 10 m⁻² s ⁻¹ sr⁻¹ . During calibration, the triggering threshold was set so that the detector would trigger for particles with higher energies compared to typical surface background radiation energies. Therefore, to calculate the approximate total muon flux, a correction was made to account for the muons with lower energies than the trigger threshold. The correction was done by comparing two count rate vs silicon photomultiplier voltage graphs. One graph was plotted using a detector that was not calibrated, and the other graph was obtained from the literature. The graph obtained from the literature contains a plot obtained using detectors of the same design operated in coincidence mode. This is the major approximation used to calculate the muon flux. The flux value obtained was 4% lower relative to the muon flux recorded at higher latitudes, according to the literature. This observation is justifiable because Colombo is close to the geomagnetic equator and muon flux varies with the geomagnetic latitudes. Moreover, the data obtained from the detector follows a Poisson distribution where the theoretical and experimental distributions closely correlate, thereby confirming the detection of truly random events. This detector provides a new avenue of research as there are numerous applications in various fields.
Enhancement of thermoelectric properties of copper (I) thiocyanate using graphite
(Postgraduate Institute of Science (PGIS), University of Peradeniya, Sri Lanka, 2022-10-28) Heshan, J.A.J.; Bandara, T.M.W.J.; Narangammana, L.K.
The effects of global warming and the depletion of fossil fuels led the world to pursue reliable renewable energy sources and to improve the efficiencies in current energy conversions. Thermoelectricity is the direct conversion of heat energy into electricity. Recently, this phenomenon has been applied as an efficient waste heat recovery mechanism. Thermoelectric generators (TEGs) are incorporated in generating thermoelectricity under applied temperature differences. A TEG contains an array of p-n junctions created using two dissimilar thermoelectric materials (TEMs). Using expensive and toxic rare earth materials such as Tellurium in room temperature TEGs has limited the commercialisation of this technology. Copper (I) thiocyanate (CuSCN) has recently earned significant attention as a p-type semiconductor due to its excellent hole-transporting characteristics. Thus, it is used in many optoelectronic applications, including perovskite solar cells. This project investigates and optimises the thermoelectric properties of CuSCN pellets by doping with a carbonaceous material. Pellets pressed with a diameter of 13 mm and a thickness of 1.5 mm using commercial CuSCN powder were used to investigate thermoelectric properties. Graphite was used as a dopant to modify the thermoelectric performance of CuSCN pellets. Electrical conductivity, thermal conductivity, and Seebeck coefficient were measured for CuSCN pellets as well as for graphitedoped CuSCN (G-CuSCN) pellets. The figures of merit values were also calculated at the respective temperatures. The obtained electrical conductivities of CuSCN and G-CuSCN pellets at 373 K were 722.2 and 77.4 S m⁻¹ , respectively. The thermal conductivities of CuSCN and G-CuSCN pellets at 373 K were 1.28 and 0.81 W m K ⁻¹ , respectively. G-CuSCN showed a positive Seebeck coefficient of 0.67 mV K⁻¹ at 373 K, confirming the p-type semiconductor nature of this material. In order to generate a steady state voltage, CuSCN should be heated up to 423 K. G-CuSCN resulted in a figure of merit value of 1.69×10⁻⁸ at 373 K. CuSCN and G-CuSCN generated maximum output power of 29.9 and 139.9 nW at average temperature gradients of 393 K and 343 K, respectively. After the incorporation of graphite into CuSCN, the thermal conductivity of the material decreased, indicating the improvement of favourable properties needed for an efficient TEM. In addition, G-CuSCN generated more power than CuSCN, revealing that graphite can improve the thermoelectric properties of CuSCN.
Dielectric behaviour of cyanoethylated cellulose-hydroxyapatite nanocomposites
(Postgraduate Institute of Science (PGIS), University of Peradeniya, Sri Lanka, 2022-10-28) Arachchige, S.G.G.; Sandaruwan, C.; Manatunga, C.H.; Perera, V.P.S.; Rajapakse, R.M.G.; Adassooriya, N.M.
Nanofillers exhibit high dielectric constant, but they have poor flexibility and breakdown strength. Polymers have excellent flexibility, low dielectric loss and high breakdown strength but have much lower dielectric constants. Thus, the incorporation of nanoparticles into a polymer has a greater potential to enhance the dielectric behaviour of the overall composite. During this study, hydroxyapatite nanoparticles (HA Nps) were synthesized using wet chemical precipitation, and different weight fractions of nanoparticles, 5%, 10% and 15% in cyanoethylated polymer (CRS), were prepared. Powder X-ray diffraction patterns confirmed the presence of HA Nps and CRS polymer. Scanning electron microscopy was used to analyze the morphology of the synthesized HA Nps and to measure the thicknesses of nanocomposite films. Fourier transform infrared spectroscopy was used to study bonding interactions of synthesized compounds. Capacitance values were measured in the frequency range from 1 kHz to 1 MHz, and all nanocomposite films showed higher dielectric constants at lower frequencies than CRS bare polymer (21). The dielectric constants of composites at 1 kHz were 32, 44, 67 for 5%, 10% and 15% weights, respectively. All nanocomposites showed a lower leakage current when increasing the voltage. The dielectric constant of nanocomposites has increased with increasing the loading of HA Nps, which may be due to the formation of large volumes of interfacial regions. It can be thought that nanoparticles in 15% HA composite have agglomerated at higher loading, thus showing the most significant decrease in dielectric constant when increasing the frequency. At lower frequencies, all types of polarization mechanisms are involved, which leads to an increased dielectric constant. When the frequency increases, relaxation processes occur. Therefore, the dielectric constant decreases with increasing frequency as all polarization mechanisms do not contribute. Significant attention is not given to investigating the dielectric properties of CRS-based nanocomposites in the literature. These results suggest that CRS-HA polymer nanocomposite is a potential candidate for applications in the dielectric material of capacitors.
Optimization of electrospinning parameters to produce poly (Ethylene oxide) nanofibers
(Postgraduate Institute of Science (PGIS), University of Peradeniya, Sri Lanka, 2022-10-28) Bandara, M.H.M.A.K.; Gunathilake, W.S.S.; Uduwela, D.R.; Jayasinghe, J.M.S.; Wickramasinghe, A.
Electrospinning, one of the most cost-effective nanofiber production techniques, involves converting polymeric solution into solid nanofibers by applying an electric force. The technique needs optimization of several parameters, such as solution parameters (viscosity, concentration, surface tension, conductivity, temperature, and type of the solvent), instrumental parameters (shape of collector, geometry of spinneret, solution flow rate, drum speed, tip to collector distance and applied voltage), and ambient parameters (air velocity, temperature, and humidity of the environment) to refine nanofiber morphology, diameter, and porosity. However, certain promising materials, such as chitosan and protein-based biopolymers, cannot be electrospun in their pure form. It has been found that blending these materials with poly (ethylene oxide) (PEO) increases their spinnability. Therefore, this study aimed to optimize the solution and instrumental parameters for PEO to produce uniform fine nanofibers without beads, using the electrospinning technique and to identify the most determinant factor in this process. The effect of the polymer concentration, solvent, voltage, flow rate, drum speed, temperature, and tip-to-collector distance was tested and optimized in this study. The prepared nanofibers were characterized using Scanning Electron Microscopic (SEM) images. The polymer concentration and type of solvent were the most determinant solution factors that affected the electrospinning process of PEO. Six per cent (w/w) PEO concentration and 90% (w/w) acetic acid are the best solution conditions to obtain uniform fibres without beads. The voltage and the tip-to-collector distance are the most determinant instrumental parameters. Flow rate and drum speed could easily be optimized after the optimization of polymer concentration, solvent, voltage, and tip-to-collector distance. Based on SEM data, it could be concluded that the best instrumental parameters for the formation of uniform fine fibres without beads, with an average diameter of 268.6 nm are 20 kV voltage, 20 cm tip-to- collector distance, 700 rpm drum speed, and 0.5 ml/h flow rate at room temperature.
Nickel concentration in imitation jewellery sold by small-scale retailers in Kandy area
(Postgraduate Institute of Science (PGIS), University of Peradeniya, Sri Lanka, 2022-10-28) Udugama, U.A.L.; Wijethunga, L.H.G.B.S.; Ariyasena, J.A.T.C.
Nickel (Ni) is usually incorporated in the imitation jewellery industry. When exposed to higher levels, Ni can be the main source of Allergic Contact Dermatitis (ACD). The present study investigates the Ni concentration in imitation jewellery sold by small-scale retailers in the Kandy area. According to the nickel directive of the European Union (EU), the nickel released from the jewellery to pierced parts of the body should be <0.2 µg cm⁻² week⁻¹ . Nickel released from the jewellery coming into direct and prolonged contact with the skin should be <0.5 µg cm⁻² week⁻¹ . If the nickel concentration is > 0.05% w/w (500 µg g-1 ), it is not advisable to come into direct contact with healing wounds after piercing. In order to investigate whether the small-scale retailers in the Kandy area adhere to standard regulations, the imitation earring samples were collected from five small-scale retailer shops in the Kandy area once a month for 12 months. The samples were collected in monthly intervals as the retailers renewed their stocks monthly. Surface analysis of the earring samples was performed using XRF to have an initial estimation of the metal composition, and the accurate concentrations were determined using atomic absorption spectrophotometry (AAS). The artificial sweat immersion method was used to determine the nickel concentrations released into the sweat solutions by preparing artificial sweat solutions with ultra-pure water, 0.5% sodium chloride, 0.1% urea, and 0.1% lactic acid. pH value was adjusted to 6.5 using 1% ammonia. Each earring sample was placed in the artificial sweat and stored in an incubator at 34 ℃ for 7 days. The nickel concentrations ranged from 0.04 µg cm⁻² week⁻¹ to 317.70 µg cm⁻² week⁻¹ . Percentage Ni concentrations in earring samples were determined using AAS after dissolving in aqua regia in order to extract all Ni into solution. The results showed that Ni concentration ranged from 0.01 µg g⁻¹ to 4.70 µg g⁻¹ . Out of 180 earring samples tested, 110 samples exceeded the threshold limit of 0.2 µg cm⁻² week⁻¹ from the sweat solution method, and 130 samples exceeded the accepted threshold level of 0.05% w/w. All tested small-scale retailers have exceeded the permissible level of Ni during the investigated period.
Ammonia gas detection using doped Zinc oxide thin films
(Postgraduate Institute of Science (PGIS), University of Peradeniya, Sri Lanka, 2022-10-28) Ranasinghe, R.A.U.D.; Bandaranayake, P.W.S.K.
Ammonia is a toxic gas which is harmful to human health and the environment. It is mainly emitted from agricultural fertilizer and in manufacturing plastics, dyes and fabrics. The exposure limit of ammonia to the human being is 25 mg l⁻¹ for 8 h or 35 mg l⁻¹ for 10 minutes. Therefore, accurate monitoring of ammonia gas in the environment is critical. The present study investigates doped zinc oxide thin films for constructing low-cost, quick-response and high-sensitivity ammonia gas sensors. Pure zinc oxide (ZnO), Al-doped and Fe-doped ZnO thin films were synthesized on glass or alumina slides via a simple and costeffective sol-gel method using zinc acetate, 2-methoxyethanol and monoethanolamine. The elemental composition, structure and surface morphology of crystals were characterized by X-ray fluorescence (XRF), X-ray diffraction (XRD) and scanning electron microscopy (SEM), respectively. In addition, the effects of various doping materials on optical properties were investigated by UV-Visible spectroscopy. The bandgap energy (Eg) for pure ZnO thin films was 3.40 eV, and the lowest bandgap energy of 3.38 eV was observed for Al-doped thin films. The sensor responses for Al-doped ZnO thin film are 83% and 49% for 500 mg l⁻¹ NH3 at operating temperatures of 200 ⁰C and at room temperature, respectively. The response time and recovery time at 200 ⁰C were 11 and 7 min, respectively. The gas sensing analysis showed that increased NH₃ concentration and doping material improved the gas sensing response.
Fabrication of reduced graphene Oxide-based paper using L-ascorbic acid
(Postgraduate Institute of Science (PGIS), University of Peradeniya, Sri Lanka, 2022-10-28) Samarakkody, H.H.; Dahanayake, D.W.P.; Liyange, J.P.; Bandara, L.R.A.K.
Reduced graphene oxide (rGO) is a material with potentially interesting properties which leads to many applications. Paper-based rGO is effective in applications like bioelectrical electrodes, water purification and sensors. Fabrication of paper-based rGO begins with oxidizing graphite to graphene oxide (GO) and reducing paper-based GO using chemical or thermal reduction. In chemical reduction, hydrazine hydrate (H₆N₂O), sodium borohydride (NaBH₄), and hydroiodic acid (HI) are used, as they are strong reducing agents. However, their toxic nature has doubted the possibility of using paper-based rGO for bioelectric signal acquisition and water purification. Therefore, there is a necessity to fabricate paper-based rGO using green and non-toxic methods. This study presents a novel method of fabricating cellulose membrane (CM) filter paper-based rGO using L-ascorbic acid, a non-toxic reducing agent. The precursor, GO, was synthesized by the modified Hummer's method using Sri Lankan graphite. The vacuum filtration technique was used to deposit GO on the CM filter paper, and the CM filter paper-based GO reduced at 70 ºC using L-ascorbic acid. Fourier-transform infrared spectroscopy (FTIR) and Raman spectroscopy confirmed the deposition of GO and the reduction state of paper-based GO. Oxygen functional groups seen in the FTIR spectrum of CM filter paper-based GO confirmed the hydrophilic nature, which helps the proper bonding between GO and CM filter paper. Raman analysis revealed a significant increase in ID/IG ratio from 0.886 to 1.186 and I2D/IG ratio from 0.030 to 0.076 after reducing CM filter paper-based GO with the concentration of 500 mg l⁻¹ at 70 ºC. This increase showed the reduction ability of L-ascorbic acid and the restoration of carbon-carbon bonds under sp² hybridization. Also, the I2D/ IG ratio increased as the GO concentration increased from 62.5 mg l⁻¹ to 500 mg l⁻¹, indicating that the optimized CM filter paper-based rGO may have high electrical properties.

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