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- PublicationOpen AccessA 160 kJ dual plasma focus (DuPF) for fusion-relevant materials testing and nano-materials fabrication(World Scientific, 2014)
; ; Lee, SingThis paper summarizes PF-160 Dual Plasma Focus (DuPF) numerical experiments using the Lee Model code and preliminary 3D design drawings using SolidWorks software. This DuPF consists of two interchangeable electrodes enabling it to be optimized for both Slow Pinch Mode (SFM) and Fast Pinch Mode (FFM); the latter using a speed factor (SF) of 90 kA cm-1 Torr-0.5 for FFM in deuterium [S Lee et al, IEEE Trans Plasma Science 24, 1101-1105 (1996)]; and the former with SF of less than half that value for SFM. Starting with available 6 x 450 μF capacitors rated at 11kV (10% reversal), numerical experiments indicate safe operation at 9 kV, 6 Torr deuterium with FFM anode of 5 cm radius; producing intense ion beam and streaming plasma pulses which would be useful for studies of potential fusion reactor wall materials. On the other hand operating at 5 kV, 10 Torr deuterium with SFM anode of 10 cm radius leads to long- duration, uniform large-area flow which could be more suitable for synthesis of nano-materials. The dual plasma focus design is illustrated here with two figures showing FFM and SFM electrodes.548 170 - PublicationOpen AccessA 1940-2020 spatiotemporal analysis of thermal discomfort days in Southeast Asian countriesThe high temperature and humidity make Southeast Asia (SEA) one of the regions most susceptible to the occurrence of thermal discomfort days (TDDs) in the world. In the context of global warming, SEA's rapid population growth and urban expansion further exacerbated the region's exposure to TDD, posing greater risks in public health. However, there exists a significant knowledge gap in the understanding of the long-term spatiotemporal evolution of TDD, as well as its projection in the future. By utilizing the newly released ERA5 datasets of Universal Thermal Climate Index (UTCI) and Mean Radiant Temperature (MRT), this study presented the 81-year analysis of TDDs in SEA countries, spanning from 1940 to 2020, with projections extending to 2100. While the mean increase in UTCI was relatively modest, the corresponding rise in TDD likelihood was disproportionately larger, indicating a heightened risk of exposure. A distinct contrast was observed between continental and maritime regions, with maritime countries showing smaller absolute rises in both indices but larger trends in TDD frequency due to oceanic moderating effects. Seasonal analyses highlighted the dominant influence of the East Asia monsoon over SEA, and spatial analyses revealed a negative correlation between TDD occurrence and elevation, with low-lying areas being hotspots. Projections for 2050 suggest continued warming. These findings underscore the urgency of proactive measures to address climate change impacts, particularly in vulnerable maritime and low-lying areas, providing valuable insights for enhancing climate resilience and adaptation in SEA. Our findings reveal critical insights into the trends and future scenarios of thermal discomfort in the region, underscoring the urgent need for effective climate adaptation strategies.
15 352 - PublicationOpen AccessA 1D–3D interconnected δ-MnO2 nanowires network as high-performance and high energy efficiency cathode material for aqueous zinc-ion batteries(Elsevier, 2021)
; ; WOS© Citations 47Scopus© Citations 62 177 148 - PublicationOpen AccessThe 2019 Brumadinho tailings dam collapse: Possible cause and impacts of the worst human and environmental disaster in Brazil(Elsevier, 2020)
; WOS© Citations 179Scopus© Citations 250 166 329 - PublicationMetadata onlyThe 2020 Hpakant jade mine disaster, Myanmar: A multi-sensor investigation for slope failure(Elsevier, 2021)
; WOS© Citations 10Scopus© Citations 17 113 - PublicationOpen Access2023 clinical practice guidelines on autism spectrum disorder in children and adolescents in Singapore(Academy of Medicine, Singapore, 2024)
; Scopus© Citations 1 51 277 - PublicationOpen Access24 h activity guidelines in children and adolescents: A prevalence survey in Asia-Pacific Cities(MDPI, 2023)
; 38 68 - PublicationOpen AccessThe 5M route to bilingualism(Association for Supervision and Curriculum Development (Singapore), 1992)Soh, Kay Cheng
192 184 - PublicationOpen AccessAbsolute measurements of fast neutrons using yttrium(American Institute of Physics, 2010)
; ; ; Krishnan, M.Yttrium is presented as an absolute neutron detector for pulsed neutron sources. It has high sensitivity for detecting fast neutrons. Yttrium has the property of generating a monoenergetic secondary radiation in the form of a 909 keV gamma-ray caused by inelastic neutron interaction. It was calibrated numerically using MCNPX and does not need periodic recalibration. The total yttrium efficiency for detecting 2.45 MeV neutrons was determined to be ƒn∽4.1 x 10-4 with an uncertainty of about 0.27%. The yttrium detector was employed in the NX2 plasma focus experiments and showed the neutron yield of the order of 108 neutrons per discharge.
WOS© Citations 4Scopus© Citations 5 432 277 - PublicationOpen AccessAbsolute stereochemistry of the β-hydroxy acid unit in hantupeptins and trungapeptinsTheβ-hydroxyl amino acid unit is a common structural feature of many bioactive marine cyanobacterial depsipeptides. In this study, the absolute stereochemistry of the β-hydroxyl acid moieties in hantupeptins and trungapeptins were determined through their synthesis and HPLC analysis of the Mosher ester derivatives. Synthesis of two3-hydroxy-2-methyloctanoic acid (Hmoa) stereoisomers, (2S,3R)-Hmoa and (2S,3S)-Hmoa, were achieved using diastereoselective asymmetric method and the retention times of all four Hmoa isomers were established indirectly by RPLC-MS analysis of their Mosher ester derivative standards. Based on the retention times of the standards, the absolute configuration of the Hmoa unit in hantupeptin C (3) and trungapeptin C (6) was assigned as (2R,3S)- and (2S,3R)-Hmoa, respectively. The use of the Mosher's reagents, coupled with HPLC analysis, provided a viable alternative to the absolute stereochemical determination of -hydroxy acid units in depsipeptides.
242 312 - PublicationMetadata onlyThe absolute values of the perfect matching derangement graph’s eigenvalues almost follow the lexicographic order of partitions
In 2013, Ku and Wong showed that for any partitions μ and μ' of a positive integer n with the same first part u and the lexicographic order μ ⊲ μ', the eigenvalues ξμ and ξμ' of the derangement graph Γη have the property | ξμ| ≤ |ξμ'|, where the equality holds if and only if u = 3 and all other parts are less than 3. In this article, we obtain an analogous conclusion on the eigenvalues of the perfect matching derangement graph of M2n of K2n by finding a new recurrence formula for the eigenvalues of M2n.
Scopus© Citations 1 11 - PublicationOpen AccessThe abyss observatory designing for remote collaboration, self-directed discovery and intuition development in multi-user interactive 3D virtual environments(Virtual Worlds Research Consortium, 2012)
; Koyamada, KojiThe Abyss Observatory is a museum of Earth Systems Science, Marine Life and Undersea Technology created in Second Life, currently supported by JAMSTEC as a test bed for remote collaboration and 3D visualization to create new scientific value. First, Second Life is a remarkable platform for remote, interdisciplinary and international collaboration. Second, Second Life has also been useful not only for visualization of such content but also for visualization of the relations between the different content. Such exhibits need to arrange related content in a narrative - not only through linguistic communication (such as text and speech) - but also through visual. For this purpose, we attempt to learn curating methods from Art museums. Third, the Abyss attempts to create new scientific value by assimilation or synthesis of 3D models and data from the real world. 3D models are incomplete but so is data from the real world. For example, deep-sea-life samples quickly changed their shape and color at surface atmospheric pressure. On the other hand, photo and video of such specimens in their natural habitat are also limited in terms of viewing angle and resolution. We are working on 3D modelling of Bolinopsis infundibulum which can apply to taxonomic descriptions based on tracking observation of researcher’s eyes, and are presently evaluating the scientific value of such endeavors.362 167 - PublicationOpen Access
WOS© Citations 7Scopus© Citations 15 132 1675 - PublicationOpen AccessAcademic resilience and test anxiety: The moderating role of achievement goalsThe present study examined the associations of academic resilience and achievement goals with test anxiety, and the moderating role of achievement goals in the relation between academic resilience and test anxiety among 1632 secondary one students from eight secondary schools in Singapore. Results showed that students who reported lower levels of academic resilience also reported higher levels of cognitive test anxiety, and those who reported higher levels of avoidance-goal endorsement reported higher levels of cognitive test anxiety. Importantly, the relationship between academic resilience and test anxiety was moderated by avoidance-based goals endorsement level. Specifically, this relationship was stronger for those who endorsed higher levels of avoidance-based goals. Approach-based achievement goals did not significantly interact with academic resilience to influence test anxiety. Implications of the findings are discussed.
Scopus© Citations 2 105 639 - PublicationOpen AccessAcademic self-efficacy, task importance and interest: Relations with English language learning in an Asian contextThe present study examined the relations between three motivational variables, i.e. academic self-efficacy, task importance, and interest with three types of learning behaviours, i.e. class engagement, metacognitive self-regulation, and avoidance coping with 1954 secondary students in Singapore. Positive correlations were found between the three motivational variables, class engagement and metacognitive self-regulation, whereas negative correlations were found between the three motivational variables and avoidance coping. Multiple regression analysis results showed that academic self-efficacy, interest and task importance all significantly predicted class engagement. However, only academic self-efficacy and interest significantly predicted metacognitive self-regulation and avoidance coping, but not task importance. The results were similar for both boys and girls. These findings suggest that academic self-efficacy and interest have a more desirable motivational function in comparison with task importance, especially when students face challenging tasks in learning English. Important implications for teaching are discussed.
WOS© Citations 24Scopus© Citations 46 159 958 - PublicationOpen AccessAcademic success, engagement and self-efficacy of first-year university students: Personal variables and first-semester performanceHigher education can be hugely transformative for students and has an important role in empowering human capital, innovation, and society’s social, cultural, and environmental development. The expansion of higher education has promoted access for a more heterogeneous mix of students, but ensuring access does not guarantee academic success. This paper aims to analyse predictors of academic achievement in 447 first-year students in their 1st and 2nd semesters, considering variables including sex, age, parents’ educational level and grades on entering higher education, along with levels of students’ academic engagement and self-efficacy after some weeks at university. Results show statistically significant paths for sex, age, and GPA to 1st-semester achievement, for parent’s educational levels to perceived self-efficacy, for students’ academic engagement to 1st-semester achievement, and 1st-semester achievement to 2nd-semester achievement. Students’ academic engagement also had an indirect effect on the 2nd-semester achievement. The correlation between academic engagement and self-efficacy was positive, strong, and statistically significant. The model explained 35.2% of the variance in 2nd-semester achievement and 15.0% of the variance in 1st-semester achievement. Knowledge about predictors of academic achievement and the importance of engagement and self-efficacy will support timely interventions, promoting success and preventing failure and dropout.
Scopus© Citations 2 79 545 - PublicationOpen AccessAccelerometer-based physical activity in need satisfaction profiles of schoolchildren: A 3-year follow-upThis study examined moderate-to-vigorous physical activity (MVPA) trends in physical education (PE) classes and beyond school hours in children's need satisfaction profiles over 3 years. Participants were 445 (girls 256, boys 189) Finnish schoolchildren (Mage = 11.26 ± 0.32 years). Need satisfaction self-reports and accelerometer-based MVPA data were collected in 17 comprehensive schools over four assessment phases. Four latent profiles based on the need satisfaction trends over time were found: Profiles with Large Decrease, Small Decrease, Small Increase, and Large Increase. The children with the most prominent need satisfaction decreases showed a significant decline in out-of-school MVPA. All the children, irrespective of their need satisfaction profile, exhibited similar patterns of MVPA in PE over the 3-year follow-up. Developing need satisfactions and out-of-school MVPA of the children with the greatest need satisfaction decreases may require enhancements in need-supportive PE activities.
WOS© Citations 1Scopus© Citations 2 40 121 - PublicationOpen AccessAccounting for the concreteness and neighborhood effects in a high frequency word list for poor readers
Some poor readers show little or no progress in literacy interventions as their susceptibility to the concreteness and neighborhood effect is not accounted for during intervention. This study aims to develop a resource for poor readers by revising the Dolch list to account for the concreteness and neighborhood (orthographic, phonological and semantic) effect. Psycholinguistic techniques were employed to recategorize 220 Dolch list words according to concreteness via function and content word categories, and include the associated orthographic, phonological and semantic neighbors of each word into a new High Frequency List with Neighbors (HFLN). One-way analysis of variance (ANOVA), Bonferroni post hoc test and Levene’s test of variance homogeneity were carried out as measures of statistical significance and variability. The HFLN contains a total of 220 words with 1057 neighbors across five function and content word categories. Both measures of statistical significance and variability show that grade categories in the Dolch list contain greater mean concreteness values with overlapping similarities and higher variability. Conversely, the HFLN effectively delineates concreteness value clusters between categories with lower variability. The HFLN aids in targeted intervention of poor readers by presenting the available orthographic, phonological and semantic neighbors according to the descending order of concreteness.
73 378 - PublicationOpen AccessAccounting for the SES-math achievement gap at school entry: Unique mediation paths via executive functioning and behavioral self-regulationChildhood socioeconomic status (SES) is strongly predictive of math achievement in early childhood and beyond. In this study, we aimed to further our understanding of the mechanisms underpinning the SES-achievement gap by examining whether two aspects of self-regulation—executive functions (EF) and behavioral self-regulation (BSR)—mediate between SES and math achievement. Using data from a longitudinal study in Singapore (n = 1,257, 49% males), we examined the predictive link from SES to math achievement at entry to formal education (age 7), and the role of EF (child-assessed) and BSR (child-assessed and teacher-rated) as mediators of the SES-math achievement relationship. After accounting for children’s non-verbal reasoning and prior math achievement, EF and BSR (both child-assessed) emerged as significant partial mediators between SES and math. A key contribution of our study is in demonstrating that both components of self-regulation play a small role in explaining SES disparities in math achievement. Our findings further suggest that a balanced focus on enhancing EF and BSR skills of children from low-SES families may help to attenuate the SES-math achievement gap. More generally, our research contributes new insights to the ongoing debate about the theoretical distinctions between EF and BSR.
Scopus© Citations 2 145 164 - PublicationOpen AccessAchievement goal profiles and their associations with math achievement, self‐efficacy, anxiety and instructional quality: A single and multilevel mixture studyBackground There is growing interest in studying the co-occurrence of multiple achievement goals and how different goal profiles relate to educational outcomes. Further, contextual aspects of the classroom have been known to influence the goals students pursue but existing studies remain confined within certain traditions and confounded by methods not well suited for studying classroom climate effects. Aims This study sought to investigate achievement goal profiles in mathematics and their associations with background covariates (i.e., gender, prior achievement) and correlates at the student-level (i.e., achievement, self-efficacy, anxiety) and class-level (instructional quality dimensions of classroom management, supportive climate, instructional clarity and cognitive activation). Sample Participants were 3836 Secondary-3 (Grade-9) students from 118 mathematics classes in Singapore. Methods Achievement goal profiles and their relationships with covariates and student-level correlates were examined with updated procedures of latent profile analysis. Subsequently, multilevel mixture analysis assessed the associations of student-level goal profiles and different class-level dimensions of instructional quality. Results Four profiles were identified: Average-All, Low-All, High-All and High-Approach. These profiles differed across covariates and correlates, with High-Approach students associated with positive outcomes and High-All students with math anxiety. Cognitive activation and instructional clarity predicted stronger membership in High-Approach profile than Average-All and Low-All, but not High-All. Conclusion Certain goal profile patterns were consistent with past studies and supported the fundamental separation of approach and avoidance goals. Less differentiating profiles were associated with undesirable educational outcomes. Instructional quality can be considered as an alternative framework for examining classroom climate effects of achievement goals.
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