RESCON 2021

Permanent URI for this collectionhttps://ir.lib.pdn.ac.lk/handle/20.500.14444/5951

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Detection of polychlorinated biphenyls contaminated power transformers in Sri Lanka
(Postgraduate Institute of Science (PGIS), University of Peradeniya, Sri Lanka, 2021-10-29) Dissanayake, D.A.T.W.K.; Weeraman, P.I.D.; Aberathna, A.H.M.A.K.; Hettiarachchi, N.B.; Piyathissa, D.K.S.D.; Liyanaarachchi, V.V.; Mubarak, M.N.A.; Hemarathne, J.D.K.G.; Werahera, S.M.
Polychlorinated biphenyls (PCBs) classified under persistent organic pollutants are a group I carcinogen. Aroclors were one of the widely used and most reported PCB commercial mixtures globally. Aroclor 1260, Aroclor 1254, Aroclor 1242, and Aroclor 1016 have been used in transformers. Sri Lanka is a signatory of the Stockholm Convention, where PCB usage has been curtailed since 2005. PCBs have mainly been used as insulating oil in transformers and capacitors. The elimination of PCBs by 2025 is a primary goal set by the convention. Accordingly, analysing and inventorying the transformers contaminated with greater than 50 mg kg⁻¹ PCBs in Sri Lanka is in progress. This study developed a method based on the ASTM D 4059 to determine the PCB content in insulating oils. PCBs in the sample were extracted with 2,2,4-trimethylpentane followed by interference removal using activated magnesium silicate. The extracted sample was allowed to stand for 10 min to settle the magnesium silicate particles, and 1.0 mL of the supernatant and 0.1 mL of hexachlorobenzene were mixed and analysed with gas chromatography- electron capture detection (GC-ECD). A matrix-matched calibration was used to address the intensity suppression due to the mineral oil, and ratios of uniquely identified well-resolved peaks were used in quantification by adding an internal standard to both calibrators and samples. The Ceylon Electricity Board inventory has more than 30,000 transformers, of which 2,500 were screened as suspected transformers to date. The confirmatory analysis was carried out in 329 samples by GC-ECD. Some of the samples (16.4%) contained total PCBs greater than 50 mg kg¹ , out of which 16.1% had Aroclor 1260, and 1.5% contained both Aroclor 1260 and Aroclor 1254. The findings will be included in the national inventory facilitating PCB mitigation programs following the Stockholm Convention.
Guidelines to construct and validate lessons in Authentic Learning Pedagogy
(Postgraduate Institute of Science (PGIS), University of Peradeniya, Sri Lanka, 2021-10-29) Liyanage, L.S.I.; Tillekaratne, K.G.D.A.D.; Gunawardene, M.S.
Authentic Learning Pedagogy (ALP) is presented as a solution to alleviate the learning gap between theoretical knowledge and its real-world application. In ALP, learners are provided with real-world situations that include constructing, acquiring, and researching knowledge and skills needed to solve complex problems. However, designing lessons in alignment with ALP is a challenging task. The objective of this study was to set guidelines to plan lessons in ALP and a rubric to benchmark the alignment of lessons to ALP. The guideline uses ten steps with underlying principles of ALP. The design guideline helps the lesson designers to construct a complex real-world context in which the student is placed in real-world professional roles where the student performs authentic, real-world tasks that produce unique real-world products. Learning happens intrinsically while performing the tasks and constructing real-world products. The lessons are assessed by the rubric, which uses three criteria: (1) Origin, (2) Complexity, and (3) Higher order thinking skills to check for alignment of lesson elements to the ALP. The design guideline was given to teachers involved in teaching science subjects from grades 6 to 13, and the developed lessons were assessed using the rubric. The benchmarking of lessons revealed that 60% of the lessons had guided recipe-type instructions, which is against ALP principles, while lessons developed with feedback had close alignment with ALP. Feedback from teachers revealed that they found it easy to use the design guideline in the preparation of lessons. However, teachers found difficulty in constructing authentic contexts, task sequences and products, mainly due to confusion regarding definitions of authentic context, authentic tasks, authentic products, and authentic assessments. Therefore, this study shows the need for assistance by lesson designers through feedback on the alignment of elements of lessons, including context, tasks, products, and assessments to the ALP.
Critical evaluation on conducting practical sessions of G.C.E. A/L Physics: case study in Sabaragamuwa Province
(Postgraduate Institute of Science (PGIS), University of Peradeniya, Sri Lanka, 2021-10-29) Samarawickrama, W.L.; Jayalath, C.P.; Abeysundara, S.P.
Hands-on experience is beneficial for better understanding the theoretical concepts in Physics. Therefore, a practical component is included in G.C.E. (A/L) Physics syllabus in Sri Lanka. This research aims to evaluate the G.C.E. (A/L) process of conducting Physics practical lessons at schools in the Sabaragamuwa Province, Sri Lanka. Sixty-five schools (Grade - 1 AB) from the Sabaragamuwa Province were selected for the study. Data were collected through two questionnaires, one for teachers who taught Physics in G.C.E. (A/L) classes and another for the Grade 12 students who follow Physics as a subject in Biological or Physical Sciences streams. All schools considered in the study have separate Physics laboratories. Although laboratories are equipped with sufficient instruments and other resources, the support from the Laboratory Assistants was not satisfactory, thus considered a barrier for the teachers to conduct practical sessions in a productive manner. However, teachers were able to complete all the practical sessions in the syllabus within the two years though student participation was poor in the last two terms of Grade 13 classes. In addition, both teachers and students have a good perception of conducting practicals in school laboratories. Despite poor attendance, all students had the experience of performing laboratory experiments during the two years. Teachers motivated students by giving them a chance to perform missed practicals and correct students' practical reports. After conducting practicals in school laboratories, students demonstrated better knowledge, skills, and attitudes towards the subject. Both teachers and students were highly satisfied with the conduct of Physics practicals in schools of Sabaragamuwa Province. There was no relationship between the student gender and the satisfaction level of conducting Physics practicals in school laboratories. The study revealed that the necessary support needs to be improved further with the help of school administration on conducting Physics practicals to meet the stipulated educational goals through meaningful learning.
Factors affecting the success of online education of physical science students in the Kandy Education Zone
(Postgraduate Institute of Science (PGIS), University of Peradeniya, Sri Lanka, 2021-10-29) Gunarathna, R.A.; De Silva, T.H.K.R.; Abeysundara, H.T.K.
The current global pandemic situation has changed the teaching and learning environment of secondary education worldwide. The traditional classroom delivery method has been transformed into an online platform. The main objective of this study was to identify the online delivery methods that are popular among teachers and students, and the key factors that affect the success of online delivery. The data was collected using a self-administered questionnaire distributed among 219 Physical Science students from seven schools in the Kandy Education Zone where online lessons were conducted. The mode of online delivery, type of equipment used, gender, family income level and ownership of the equipment were the main factors explored in this study, which were identified based on a preliminary survey. A five-point Likert scale was used to measure the overall satisfaction of the online delivery. Of the four teaching methods used by teachers, the most popular method was presentations and live videos. Among the student population tested, 47% participated in more than 50% of online sessions while 33% in all sessions. Despite most male students having their own devices, female student participation in online sessions was significantly higher than the males. The overall satisfaction of the teaching-learning process was 52% (Male: 47%, Female: 56%), and there was a significant association between the level of satisfaction and gender. Overall, findings revealed that most students participated in lessons conducted by their schools via live videos and presentations. The level of participation in online classes and the satisfaction of the teaching-learning process are gender-dependent. The outcomes of this study can be used by the relevant authorities to improve the quality of the online teaching-learning process while addressing the difficulties faced by the student community.
Analysis of G.C.E. (O/L) examination results of schools in Mawanella Education Division
(Postgraduate Institute of Science (PGIS), University of Peradeniya, Sri Lanka, 2021-10-29) Adikaram, P.L.; Abeysundara, S.P.
The General Certificate of Education (G.C.E) Ordinary Level (O/L) is conducted by the Department of Examinations of the Ministry of Education, Sri Lanka. This examination consists of six main subjects; First language, Religion, Mathematics, Science, English, and History, along with three elective subjects. This examination has become very competitive as it is a qualifying milestone for the G.C.E. Advanced Level (A/L), which determines the University entrance. The objective of the study is to analyse and identify the factors that affect the performance of students who sit the G.C.E. (O/L) examination. Of the 37 secondary schools in the Mawanella Division, Kegalle, 18 are classified as 1AB and the remaining as 1C. The examination results of all the secondary schools of the division from 2015 were used in the study. Among them, 26 schools were Sinhala medium, while 11 were Tamil medium. A student must earn at least six ordinary passes to pass the examination, including three credit passes. Preliminary analysis revealed that more than 40% of students failed the G.C.E. (O/L) examination. A chi-squared test for association indicated that the ability to pass the Language subject did not depend on the medium of delivery (χ² = 1.273, p = 0.259). However, there was a significant effect of the medium of delivery to pass other main subjects. Moreover, there was an effect on passing the English language for Sinhala- and Tamil-medium students (χ² = 216.4, p < 0.001). Further, there is an association between the type of school and the performance of the six main subjects. The odds ratios (OR) showed that the students of 1AB schools had a higher passing rate than the students in 1C schools (OR = 2.365). The students who sat the G.C.E. (O/L) examination in the Tamil medium had a higher passing rate than those in the Sinhala medium (OR = 1.999). Similar performances were noted in passing rates of individual subjects of Mathematics, Religion, Science and History. A Path Coefficient Analysis revealed a positive and significant correlation between overall results and the individual passing rates of main subjects. One of the key findings from the study includes a significant positive relationship between the passing of Mathematics and other main subjects. The result of this study is helpful for the decision-makers to identify the issues of the current education system and take remedial actions for the betterment of society.
Misconceptions in mendelian genetics among G.C.E. (A/L) biological science students in the Batticaloa Education Zone, Sri Lanka: simulation as an effective teaching aid
(Postgraduate Institute of Science (PGIS), University of Peradeniya, Sri Lanka, 2021-10-29) Parthipachuthan, S.; Rajapakse, S.
Genetics is one of the difficult course modules for students in the G.C.E. (A/L) Biology curriculum. This study was designed to identify the misconceptions of G.C.E. (A/L) Biological Science students on basic concepts in Genetics and determine the effectiveness of simulations in teaching the unit Genetics. The study was carried out in Batticaloa Education Zone, Sri Lanka. A mixed-method approach was selected for this study. The data were collected from semi-structured interviews, pre-and post-tests. A two-tier multiple-choice instrument was used to diagnose misconceptions of students in Basic Genetics. The reliability of the instrument was determined with the use of Cronbach's alpha coefficient (α = 0.71). The samples consisted of 84 Grade 13 students from three selected schools and five biology teachers. Simulations of Mendel's genetics were used as a teaching aid for experimental groups, and the traditional method was used for control groups. The data were analysed using frequency counts, percentages, means and standard deviations in SPSS. Qualitative data were analysed using Grounded Theory. The results revealed that students possessed misconceptions on ten selected basic concepts in Genetics. Three concepts showed above 25% of misconceptions (gene: 46.4%, chromosomes: 31% and Punnett square: 29.8%) in the pre-test. The mean score of knowledge on Basic Genetics in students was 24.7 ± 13.1 in the pre-test. In the post-test, the mean score of the experimental group (67.0%; SD = 14.9) was significantly higher than the control group (51.4%; SD = 15.4). In addition, the number of misconceptions was significantly lessened in students in the experimental group than in the control group. Misconceptions in the two selected concepts decreased effectively in the experimental group. The study revealed that simulations could effectively eliminate students' misconceptions in the unit Genetics for G.C.E. (A/L) Biological Science students.
Relationship between talent identification methods used by level one qualified track and field coaches' and 100 m sprinting male athletes' performance in Sri Lanka
(Postgraduate Institute of Science (PGIS), University of Peradeniya, Sri Lanka, 2021-10-29) Disanayaka, W.D.M.J.; Perera, A.H.C.; Sirimuthu, M.N.S.; Wijethunga, W.M.L.R.
This study focused on the talent identification (TI) methods that are used by coaches to identify the right talent at the real stage of the athletes. The current study focused on five TI methods which include physiological, anthropometrical, psychological, sociological, and biological and their components. Other countries had investigated the gap between the TI methods which are used by coaches to identify athletes' performance and athlete's performance based on TI methods. However, literature on TI research in the Sri Lankan context is scarce. The main objective of the study was to identify the relationship between talent identification methods which are used by level one qualified track and field coaches' and their 100 m sprinting male athletes' (in the age group 18 – 25) performance in Sri Lanka. Sixty coaches who qualified of level one course for coaches were used as the study population. A questionnaire and interviews were used to gather information from the coaches. The study considered two variables in the analysis that are athletes' best running timing and five TI methods The findings revealed that, physiological, anthropometrics and psychological methods were strongly but negatively correlated with the athletes' running time while sociological and biological TI methods were correlated moderately negative with the same. The results conclude that physiological, anthropometric, and psychological TI methods are successful in identifying talents of athletes compared to other two methods tested.
Satisfaction of E-learning during the COVID-19 pandemic: case study of University College of Jaffna, Sri Lanka
(Postgraduate Institute of Science (PGIS), University of Peradeniya, Sri Lanka, 2021-10-29) M. Ramanan
Due to the COVID-19 pandemic, all educational institutes were switched from traditional classroom teaching to e-learning. Switching to e-learning ensures that the students carry out the learning process continuously without disturbances. E-learning facilitates the exchange of knowledge and information between students and teachers. The study aimed to analyse the satisfaction of e-learning in teaching and learning during the COVID-19 pandemic. The study was conducted among National Vocational Qualification (NVQ) Level 6 students and the University College of Jaffna (UCJ) teachers. The volunteer sampling method was used to gather data. Online questionnaires were sent electronically to 135 participants (110 students and 25 teachers). Of them, 91 participants (18 teachers and 73 students) responded to the survey. The online questionnaires consisted of both Likert scale and open-ended questions. The Statistical Package for Social Sciences (SPSS) version 24 was used for data analysis. The correlation analysis was used to examine the association between the independent variables (internet speed, awareness of LMS, LMS access, learning practical skills, submitting assessments, students' interest, accessing e-learning tools, teaching practical skills and conducting assessments) and dependent variables (student's satisfaction, teacher's satisfaction). According to the results, 71.2% of students claimed that teachers used only Moodle as an effective tool in e-learning and teaching, while 24.7% of students claimed that a combination of tools (Moodle, social media, Google Classroom) was used by teachers as an effective tool in e-learning. Further, the study investigated students' and teachers' satisfaction in e-learning. Based on the results, only 15.1% of students and 16.7% of teachers satisfied with the e-learning approach. Approximately 50% of students and teachers were not satisfied with e-learning. Based on the correlation analysis, internet speed at home, awareness of LMS, and LMS access at home have significant associations with student' satisfaction (r = -0.359, 0.385 and 0.455, respectively and p < 0.05). Learning practical skills and submitting assessments have no significant association with students' satisfaction (r = 0.043 and 0.221, respectively and p > 0.05). Students' interest, accessing e-learning tools at home, and teaching practical skills have significant association with the teachers' satisfaction (r = 0.503, 0.517 and -0.573, respectively and p < 0.05). Conducting assessments had no significant association with teacher satisfaction (r = 0.078 and p > 0.05). The study reveals that students' and teachers' satisfaction need to be improved in e-learning. Therefore, it is important to conduct training programs and improve other support to enhance the status of e-learning.
Cybersecurity awareness among undergraduates: case study of arts undergraduates at the University of Colombo
(Postgraduate Institute of Science (PGIS), University of Peradeniya, Sri Lanka, 2021-10-29) Dissanayake, L.A.D.M.; Shakth, W.G.D.; Boparathna, A.G.B.L.R.
Over the past months, the Covid-19 pandemic has increased internet usage. Sri Lankan students are compelled to depend on the internet in schools and universities as the teaching-learning scenario is entirely or partially online. These circumstances make an understanding of cybersecurity mandatory for students and teachers to ensure their security. This quantitative study explores cybersecurity awareness and various vulnerabilities faced by new entrants to the Faculty of Arts, the University of Colombo, in 2021. The questionnaire was forwarded to all new entrants through the Learning Management System. The data were analysed using Microsoft Excel and SPSS. A majority of the sample (58%) lacked cybersecurity awareness, and there was no significant difference by gender (p = 0.364). Awareness was dependent on factors such as residence (only western province shows more than 50% of awareness), time spent on the internet per day (correlation coefficient = 0.788), experience in using the internet (correlation coefficient = 0.976), socio-economic standing (correlation coefficient = 0.887). The study shows that students become more vulnerable due to unsecure practices adopted during internet use and ignorance of and lack of attention paid to most updated cyberattacks as significant occurrences that concern activities in cyberspace. Even though the reports of international cybersecurity list Sri Lanka to be one of the most vulnerable countries in South Asia, the number of reported incidents to the Sri Lanka Computer Emergency Readiness Team is very low compared to other countries in the South Asian region (481 in 2020 without social media incidents). The present study points to privacy concerns and a lack of awareness of cyberattacks and reporting procedures (71.4%), resulting in underreporting. The findings emphasise the need to improve cybersecurity awareness among university students in Sri Lanka to ensure security in a rapidly changing virtual teaching-learning scenario.
Effectiveness of using documentaries in teaching environmental biology for G.C.E. A/L biological science students in the Batticaloa Education Zone, Sri Lanka
(Postgraduate Institute of Science (PGIS), University of Peradeniya, Sri Lanka, 2021-10-29) Prashanth, M.; Gunaratne, A.M.T.A.
As future decision-makers, the students should be provided with knowledge, skills and attitudes to involve them in environmental protection and sustainable development. This study investigated the effectiveness of using documentaries in teaching Environmental Biology for G.C.E (A/L) Biological Science students in the Batticaloa Education Zone in Sri Lanka. The objectives of the study are to determine the level of environmental knowledge, attitudes and practices and investigate the effectiveness of using documentaries in teaching Environmental Biology. Eighty students of Grade 13 from three schools were selected. Pre- and post-test papers were used to test knowledge, and a structured questionnaire was used to test their attitudes and practices. Documentaries were prepared as teaching aids for two subsections of unit eight for the experimental group. The control group was taught using the traditional lecture method. The data were analysed using descriptive statistics, Mann-Whitney, Wilcoxon signed ranks tests and Pearson correlation in SPSS. Pre-test marks revealed (39.1 ± 1.1) a low level of knowledge in Environmental Biology among the student sample. In the pre-test, the mean percentage score of students' environmental attitudes and environmentally friendly practices were 57.9 ± 1.8 and 58.3 ± 1.8, respectively. In the post-test, the students of the experimental group scored higher (77.6 ± 1.9) than the control group (55.7 ± 1.4). The knowledge gained by female students was higher than male students. The knowledge on Environmental Biology was not correlated with students' attitudes on the environment (r = 0.00) but showed a low positive correlation with environmental practices. However, environmental attitudes and practices showed a high positive correlation (r = 0.83). The study concluded that documentaries could be an effective tool in teaching Environmental Biology lessons at G.C.E (A/L) to enhance students' knowledge of the subject.
Co-creation experience of a postgraduate programme: case of masters programme on building resilience in tropical agroecosystems
(Postgraduate Institute of Science (PGIS), University of Peradeniya, Sri Lanka, 2021-10-29) Basnayake, B.M.R.L.; Esham, M.; Liyanage, C.L.; Khajenoori, L.; Carmichael, A.; Elapata, M.S.; De Silva, D.A.M.
The co-creation approach increasingly becomes the preferred model for designing and delivering solutions with the participation of a knowledgeable community. This study describes a co-creation experience with academia, industry stakeholders and policymakers from agroecosystem setting in designing a Master programme on tropical agroecosystems with the objectives of identifying stakeholder landscape, a co-design a platform and co-create the framework for the planned Master degree programme in tropical agroecosystems. The co-creation process was initiated with a comprehensive literature review followed by several consultations with both European and Sri Lankan partners to develop the framework. Subsequently, an online co-design workshop with the participation of 38 key industry-academia stakeholders was held. Purposive and snowball sampling techniques were used to ensure the inclusion of key participants in the co-creation platform. Co-creation of the Master programme began with the comprehensive literature review of the consortium's academic experts, which facilitated recognising the key thematic areas directly and indirectly in line with tropical agroecosystems. Secondly, two focus group discussions among the consortium members facilitated the laying of the programme structure and identifying program objectives (POs), intended learning outcomes (ILO) and modules, both compulsory and optional. A concept note on programme framework including objectives, intended learning outcomes and modules were developed and shared among the identified stakeholders and was allocated two weeks for review before the co-creation online workshop. Thirdly, an online co-creation workshop on curriculum design was implemented through the Zoom online platform. The stakeholder landscape of the co-creation of the Master programme was developed based on the information derived from the participants. The co-design workshop formed the basis for refining the framework of the Master programme, which comprised objectives, PLOs, ILOs and course modules.
Demographic factors affecting the use of ICT in teaching learning process among university teachers
(Postgraduate Institute of Science (PGIS), University of Peradeniya, Sri Lanka, 2021-10-29) Sarawana, P.H.; Deegalla, D.S.
The appropriate use of Information and Communications Technology (ICT) in teaching and learning has been challenging for many higher educational institutes during the COVID-19 pandemic. The study examined the demographic factors that influence the adoption and integration of ICT to enhance the university teaching and learning process. The study adopted a cross-sectional survey design. Data was obtained from academics at the Eastern University of Sri Lanka (EUSL) via a paper-based quantitative survey. Respondents were selected based on a convenience sampling method. Structured questionnaires were distributed among academics in different faculties. Out of 180 questionnaires, 155 were valid for data analysis, representing a response rate of 86%. ICT adoption in teaching and learning, the dependent variable, was not normally distributed. Therefore, non-parametric tests were used to conduct the analysis. The results revealed that gender (z = -1.046, p = 0.296) and age (χ² (3) = 5.927, p = 0.296) did not influence university teachers' adoption and integration of ICT. However, educational qualification (χ² (3) = 8.293, p = 0.040) and teaching stream (χ² (5) = 14.351, p = 0.014) significantly influenced the university teachers' adoption and integration of ICT. The pairwise comparison revealed a significant difference in ICT use in teaching and learning among those holding a bachelor's degree and a doctorate as their highest educational qualification. Teachers with doctoral degrees adopted ICT better than the other degree holders. There is a significant difference in the adoption of ICT between the Academics who teach Science and Fine Arts. Academics who teach Information Technology (IT) claimed that they use ICT more extensively in teaching and learning than other academics. The survey results show that upgrading educational qualifications would increase the quality of teaching practice of academics, thus incorporating ICT into the teaching and learning process to meet the current needs. Therefore, it is of great importance to improve academics' attitudes towards ICT across all faculties.
Pyricularia oryzae isolates regardless of their origin from different symptomatic organs caused neck blast in inoculated rice plants
(Postgraduate Institute of Science (PGIS), University of Peradeniya, Sri Lanka, 2021-10-29) Dissanayaka, D.M.H.R.; Daundasekera, W.A.M.; Ariyarathna, H.A.C.K.
Rice blast disease caused by Pyricularia oryzae is attributed to 30% annual yield loss. Although the pathogen infects the whole plant, neck blast is the most destructive. During a recent island- wide blast outbreak, the fields were completely infected with neck blast, and there were only a few or no leaf blast symptoms. Therefore, this study aimed to determine the nature of symptom development by P. oryzae on the leaf, leaf collar, panicle, neck and rachis. Disease samples were collected from infected fields at Waththegama (Kandy District). Pyricularia oryzae was isolated from typical blast symptoms on a leaf, leaf collar, panicle, neck and rachis. Characteristic conidial morphology was used to confirm the identity of the pathogen following sporulation induction treatments. Suspensions of the mycelium of each isolate were evenly sprayed on aerial parts of rice plants cultivar BG 1/94 in triplicate. Two and half months-old rice plants raised in pots were used for inoculation. The plants were kept inside humidity chambers at ambient conditions until the development of the disease. The rice plants inoculated with different isolates showed neck blast symptoms, but none of the other organs was infected. The outcome of the study indicated possible infection by P. oryzae isolated from different organs. Furthermore, the results showed possible associations between disease development, plant developmental stage, environmental conditions or others. The observation affirms the importance of robust screening programs at different host development stages for effective varietal screening. Since sporulation of blast fungus is limited to artificial media, spraying with mycelia can be recommended as a simple and efficient method for pathogenicity testing for breeding programs.
Simultaneous kinetics and ring-down (SKaR) in a pulsed uniform supersonic laval flow- kinetics of the reaction CN(v=1) + O₂
(Postgraduate Institute of Science (PGIS), University of Peradeniya, Sri Lanka, 2021-10-29) Thawoos, S.; Hall, G.; Suits, A.
We report the development of a new apparatus that combines cw-cavity ringdown spectroscopy with a pulsed Laval flow (UF-CRDS). This is related to the CRESU (a French acronym for Reaction Kinetics in Uniform Supersonic Flows) technique, developed in France to study reaction kinetics at low temperatures. Cavity ringdown spectroscopy (CRDS) is a highly sensitive absorption technique relying on the decay of light between two high reflectivity mirrors of a cavity. For time-independent absorbing samples, the enhanced rate of power loss compared to the empty cavity leads to faster exponential decays. When the concentration of the absorbing species changes on the empty cavity ringdown time scale, non-exponential decays result, for which the instantaneous decay rate in excess of the empty cavity reference case provides a time-resolved measure of the sample absorbance. The long hydrodynamic time of the flow provides uniform temperature and pressure conditions well-matched to kinetic ringdown measurements in the time regime from 10 – 300 μs. This simultaneous kinetics and ringdown (SKaR) technique are coupled with a uniform flow for the first time. We will be reporting the design and operation of the newly developed UF-CRDS instrument and the rate constants measured for the reaction of CN(v = 1) with O₂ at 70 K and 24 K obtained with this approach.
Effect of seed layer on morphology enhancement of chemical bath deposited ZnO nanowires for gas sensing applications
(Postgraduate Institute of Science (PGIS), University of Peradeniya, Sri Lanka, 2021-10-29) Abeykoon, Y.K.; Munasinghe, M.A.H.M.; Dassanayake, B.S.; Gunawardhana, N.
Metal oxide (MOx) semiconductor has stirred great attention in the gas sensors in the past decades due to the high sensitivity, fast recovery, low working temperature, and low cost. Nanowire-based MO gas sensors which possess a higher surface-to-volume ratio result in higher sensitivity and higher response to the chemical gases. However, it is crucial to synthesise long, thin MOx nanowires with uniform morphology to have superior sensing performance throughout the substrate. The chemical bath deposition (CBD) technique is a widely used technique to synthesise metal oxide nanostructures due to its relatively low-temperature growth conditions (< 100 °C), low cost, and scalability in the deposition. When considering the CBD technique, the seed layer is a significant concern for the well-growth of nanowires. Here, ZnO nanowires were grown on ZnO seeded silicon substrates, using the mixture of Zn(CH3COO)2 and monoethanolamine as the initial solution. The study aims to obtain a uniformly distributed seed layer and understand the effect of seed layer thickness on nanowire formation. ZnO nanowires were synthesised on a seeded glass substrate via CBD. Two different samples were deposited using (a) spin-coated and (b) spray-coated seed layers before carrying out low temperature CBD. An absorption edge at 378 nm, which corresponds to the ZnO nanoparticles, was observed in the UV-visible spectra of both the spin-coated and the spray-coated seed layers. Synthesised NWs showed an absorption edge at 376 nm, confirming the presence of ZnO NWs. The SEM images show that the spray-coated seed layer was uniformly distributed throughout the surface compared to the spin-coated. After the CBD process, the nanowires grown on the spray-coated substrates were well-aligned compared to those grown on the spin-coated seed layer. Nanowires with the spin-coated seed layer were not uniformly distributed, and random clusters were found to have formed on the top of the nanowires. Therefore, the spray-coated seed layer was selected as the better method. Seed layer thickness is a major factor for the formation of vertically aligned nanowires. Thus, the number of layer stacks of the spray-coated seed layer was optimised. The obtained SEM images reveal that nanowires grown on top of 10 layers of spray-coated seed were vertically well oriented throughout the surface compared to the nanowires grown on the surface with five and eight layers of spray-coated seed.
Chemical reduction of Graphene Oxide using L-Ascorbic Acid
(Postgraduate Institute of Science (PGIS), University of Peradeniya, Sri Lanka, 2021-10-29) Maddumage, D.C.; Panamaldeniya, S.A.; Kimbulapitiya, K.M.M.D.K.; Munasinghe, M.A.H.M.; Pemasiri, B.M.K.; Gunawardhana, N.; Dassanayake, B.S.
Chemical oxidation-reduction is one of the most promising and cost-effective methods for bulk production of reduced graphene oxide (RGO). The oxidation step causes the exfoliation of graphite to obtain graphene oxide (GO). The reduction process with several washing steps eliminates residual oxygen functional groups and metallic precipitates. The reduction procedure of GO significantly affects the structure as well as the morphology of RGO. In the reporting case, Sri Lankan natural graphite in powder form was used as starting material. The Hummers method with some modifications was used for the oxidation of graphite. During the oxidation process, ultrasonic treatment was carried out to peel off the oxidised outer graphite layers, allowing inner layers to undergo oxidation. The reduction process of GO was carried out at 95 °C for different time durations from 0.5 to 2.0 h using L-Ascorbic acid as the reduction agent. The surface morphology of products was studied using scanning electron microscopy (SEM), and structural analysis was done using powder X-ray diffraction (PXRD), Raman spectroscopy, and X-ray photoelectron spectroscopy (XPS). XPS analysis reveals that carbon to oxygen atomic ratio (C/O) decreases after oxidising graphite into GO from 23.4% to 2.3%. PXRD and Raman analysis exhibit the emergence of turbostratic disorder of layers and an increase in the level of disorder in GO compared to graphite. The minimum level of disorder and maximum crystallinity was exhibited by the GO sample reduced for 1.5 h. Compared to the GO sample, the RGO sample reduced for 1.5 h showed an increased C/O ratio (8.5%) and decreased d-spacing (3.62 Å), implying the elimination of some residual oxygen functionalities after the reduction step.
Nano-structured TiO2-B for lithium-ion battery applications
(Postgraduate Institute of Science (PGIS), University of Peradeniya, Sri Lanka, 2021-10-29) Panamaldeniya, S.A.; Maddumage, D.C.; Sandaruwan, R.D.L.; Munasinghe Arachchige, H.M.M.; Kumarage, W.G.C.; Dassanayake, B.S.; Gunawardhana, N.
Many researchers have investigated electrode materials for the lithium-ion battery (LIB) industry in the past decade. Among them, titanium dioxide (TiO₂) has attracted a great deal of attention due to its excellent properties, such as high operating potential, chemical and mechanical stability. However, the poor electrical conductivity and low ionic diffusivity are the main obstacles that hinder the production of high-performance LIBs with Titanium anodes. These drawbacks can be minimised by adding (a) conductive additives, (b) controlling the morphology, respectively. This work presents an extensive study of the TiO₂-B nanobelts-based electrode with the reduced graphene oxide (rGO). As a conductive additive, rGO (~5 layers) was synthesised using Modified Hummer’s method. The optimum hydrothermal temperature for growing TiO₂ nanobelt was noted as 176 °C. The length of the synthesised TiO₂-B nanobelt was between 410 nm & 15 µm with an average width of 45 nm. The electrochemical performance of the TiO₂-B/rGO composite anode was tested using constant current charge/discharge studies in the potential range of 1.0 – 3.0 V vs Li/Li⁺ . The first discharging and charging capacities were 177.2 and 138.9 mA h g⁻¹ , respectively. The second discharge and charge capacities were 142.7 and 137 mA h g⁻¹ , respectively. The composite anode material of LIB’s shows low cyclic performance and retained a low discharge capacity of 112 mA h g⁻¹ over 80 cycles, which is a significant capacity loss. A possible capacity fading mechanism will be discussed.
Thermoelectric properties of commercial Zinc Oxide and Aluminium doped Zinc Oxide
(Postgraduate Institute of Science (PGIS), University of Peradeniya, Sri Lanka, 2021-10-29) Bandara, Y.M.D.C.Y.; Narangammana, L.K.; Bandara, T.M.W.J.
Most of the available machinery at operation generates excess heat, and hence a significant amount (around 66%) of the input fuel energy is wasted as heat. Therefore, waste heat recovery technologies such as thermoelectric generators are important to increase their overall energy efficiency. Thermoelectric generators are considered reliable technology that directly converts thermal energy into electrical energy. These devices are generally fabricated using alternative arrangements of suitable p-type and n-type semiconductors electrically in series and thermally in parallel. Zinc oxide (ZnO) is an inorganic n-type semiconductor that has received a great deal of attention to realise a high-temperature thermoelectric generator. In the present study, thermoelectric properties of pellets prepared using commercial ZnO and aluminium doped ZnO were observed at relatively lower temperatures. For this purpose, Al-doped ZnO was synthesised using a new chemical method. The successful synthesis of ZnO hexagonal wurtzite phase and doping were confirmed using powder X-ray diffraction pattern (JCPDF-01-079-0205). Pellets of synthesised Al-doped ZnO and commercially available ZnO powder were prepared at an applied uniaxial (non-isostatic) pressure of 295 MPa, which was lower than the pressures used in the literature, and their individual thermoelectric properties were observed at lower temperatures. The findings of this study are the synthesis method, lowpressure palletisation using wet ZnO and the generation of relatively high potential difference at low temperatures. The electrical conductivities of commercial ZnO and Al-doped ZnO were 31.3 S m⁻¹ and 35.6 S m⁻¹ (at 373 K). The thermal conductivities of these materials were 2.38 W m⁻¹ K ⁻¹ and 1.40 W m⁻¹ K ⁻¹ (at 373 K), respectively. Both materials showed negative Seebeck coefficient values of -165 µV K⁻¹ and -225 µV K⁻¹ , respectively, indicating the n-type semi-conductive behaviour. The dimensionless parameter figure of merit (ZT) characterises a material’s ability to convert thermal energy into electricity. The ZT for ZnO and Al-doped ZnO were 1.34 × 10⁻⁴ and 4.80 × 10⁻⁴ (at 373 K), respectively. Commercial ZnO and Al-doped ZnO generated a potential difference of 14.9 mV and 19.9 mV, respectively, at a 90 K temperature difference across the hot and cold ends.
Future onset of deceleration of the expanding Universe
(Postgraduate Institute of Science (PGIS), University of Peradeniya, Sri Lanka, 2021-10-29) Karunathilaka, E.L.N.L.; Katugampala, K.D.W.J.
The expansion of the Universe is one of the most important topics of discussion in cosmology. When the Universe is expanding, the expansion rate will change with cosmic time either through acceleration or deceleration. Hence, those changes can be discovered by using experimental data. Otherwise, it can be used as a suitable mathematical model related to the expansion of the Universe. The main purpose of this study is to explain the expansion of the future onset of deceleration with cosmic time. Robertson Walker metric and Einstein’s field equations were used as major equations to obtain the relevant expressions. Non-vanishing Christoffel symbols and Ricci tensor components were obtained by using the Robertson Walker metric. Then, two independent equations with four unknown variables were obtained using modified Einstein’s field equations. Here, the pressure of the Universe is considered to be zero (zero models) as the matter is distributed to space with the big bang. Moreover, the Universe is assumed to continue as a spherical shape throughout the expansion. All the calculations depended on four-dimensional space-time coordinates. Three boundary conditions were used to support calculations. The appropriate model solution of R (radius of the Universe) was used to explain the main objective of this study. The variation of expanding rate of the Universe graph was plotted using the second derivative of the model. Then, cosmic time of future onset of deceleration was obtained when 𝑅̈= 0. According to the calculations, the future deceleration of the expanding Universe will start from 1.85 × 10¹⁶ s (0.58 billion years) after the present epoch. Thus, the deceleration in the present, past and future can be explained using this model. The Supernovae observations are the evidence to verify this graphical explanation.
Impact of temperature on accuracy of dry rubber content measurement affecting the manufacturing process and quality of crepe rubber
(Postgraduate Institute of Science (PGIS), University of Peradeniya, Sri Lanka, 2021-10-29) Athukorala, V.H.; Jayasekara, A.G.B.P.; Rathnayake, M.
Sri Lanka is the largest manufacturer and exporter of natural crepe rubber in the world. Dry rubber content (DRC) measurement of natural rubber latex is critical in the crepe rubber manufacturing process. It is used as the guide for standardising the latex and determining the quantity of sodium bisulphite added for the fractionation process. Currently, the DRC is measured through a density calculation using a hydrometer on a sample of diluted field latex. The hydrometer reading is compared with a standard chart published by the Sri Lanka Standards Institute and Rubber Research Institute of Sri Lanka (RRISL). This chart is based on a standard temperature of 29 °C. However, since the temperature has an inverse relationship with density, it affects the DRC value calculated. Incorrect DRC measurement leads to incorrect chemical dosages, improper standardisation, enhancing rubber wastages, and long process times. These result in inferior quality in the final crepe rubber sheets leading to rejections and price drops in the export markets and lower output yield impeding the returns for the manufacturer. This study focuses on the significance of accompanying the temperature with the current measurement method when calculating DRC. The error in measured DRC was calculated for a series of diluted field latex samples of different temperatures based on a temperature-corrected DRC chart by Kudaligama et al. The calculations indicated a significant error component involved in the DRC measurement using the standard chart when temperature variation in the field latex was considered. Due to this error component, DRC is underestimated for temperatures below 29 °C and overestimated for temperatures above 29 °C; with maximum error percentages of approximately 14% at 24 °C and 11% at 32 °C. Hence, this study strongly recommends accompanying a temperature measurement with the hydrometer reading and referring to the temperature-adjusted DRC chart instead of the standard chart. The adverse consequences of erroneous DRC measurements are further discussed, including a quantitative analysis of rubber wastages at different temperatures.

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