An Exploratory Study of Pre-service Primary Teachers’ Understanding of Uncertainty in Measurements in Singapore

This study was set in the context of a reform agenda for Singapore’s science curriculum to adopt inquiry in teaching and learning science (MOE, 2008). Teachers, including pre-service primary teachers (PSTs) who were subjects of this study, are expected to engage their students with scientific evidence including measurements taken during science investigations. The inherent nature of measurements is that they are always affected by errors that caused uncertainty. Understanding this, as well as other procedural ideas underpinning uncertainty would be important for understanding evidence before looking at data that are subjected to uncertainties in measurements. Such understandings would be important for the PSTs when they teach their future students how to obtain valid and reliable data, and to evaluate the methods of investigation or scientific conclusions based on evidence. This study, therefore, was aimed at exploring such understandings using the Concepts of Evidence (Gott, Duggan, and Roberts, 2008) as a theoretical framework. The lack of a research instrument customised to such a need motivated this study to develop one. The study was carried out in two phases. The first involved fifty-five PSTs and directed towards getting an accurate interpretation of procedural ideas underlying uncertainty by triangulating the evidence from questionnaire and interviews and iteratively refining the “probes” as the study progressed. The second phase focused on developing a questionnaire based on findings from the first and testing it on twenty PSTs. The results revealed that most PSTs could recognise uncertainties in measurements and suggest the right actions to deal with them, but they generally had difficulties explaining their actions implying shallow understanding of concepts underpinning uncertainty, and reliance on routine knowledge. This has strong implications for teacher preparatory programmes as well as the teaching of procedural understanding

Aerosol spectral optical depths over the Bay of Bengal: role of transport

Recent experiments have shown the potential role of air masses in transporting aerosols to locations far away from source regions. Despite the importance of the Bay of Bengal to Indian climate and monsoon, no serious aerosol observations are available for this region. Extensive aerosol optical depth estimates, made for the first time from an island location, Port Blair (11.63°N; 92.71°E) in the Bay of Bengal, during the Indian winter of 2002, are used to examine the impact of air trajectories in modifying the optical depths and their spectral dependences. The results are examined for their distinctiveness with respect to the origin as well as transport. It is seen that the trajectories arriving from the regions east of the station (South China, Thailand, Laos, Cambodia, Vietnam, Burma) are richer in aerosol abundance, more in the sub micron size range, than those arriving from the west, across the Indian landmass

Aircraft measurements of aerosol black carbon from a coastal location in the North-East part of peninsular India during ICARB

During the Integrated Campaign for Aerosols, gases and Radiation Budget (ICARB) over India, high-resolution airborne measurements of the altitude profiles of the mass concentrations (MB) of aerosol black carbon (BC) were made off Bhubaneswar (BBR, 85.82°E, 20.25°N), over northwest Bay of Bengal, in the altitude region upto 3 km. Such high-resolution measurements of altitude profiles of aerosols are done for the first time over India. The profiles showed a near-steady vertical distribution of MB modulated with two small peaks, one at 800m and the other at ~2000m. High resolution GPS (Global Positioning System) sonde (Vaisala) measurements around the same region onboard the research vessel Sagar Kanya (around the same time of the aircraft sortie) revealed two convectively well mixed layers, one from ground to ~700m with an inversion at the top and the other extends from 1200m to ~2000m with a second inversion at ~2200m and a convectively stable region in the altitude range 700-1200m. The observed peaks in the MB profile are found to be associated with these temperature inversions. In addition, long-range transport from the Indo- Gangetic Plain (IGP) and deserts lying further to the west also influence the vertical profile of BC. Latitudinal variation of MB showed a remarkable land ocean contrast at the 500m altitude (within the well mixed region) with remarkably lower values over oceans, suggesting the impact of strong sources over the mainland. However, above the ABL (at 1500m), the latitudinal variations were quite weak, and this appears to be resulting from the impact of long-range transport. Comparison of the altitude profiles of MB over BoB off BBR with those obtained during the earlier occasion over the inland stations of Hyderabad and Kanpur showed similarities above ~500m, with MB remaining around a steady value of ~1 μg m-3. However, large differences are seen within the ABL. Even though the observed MB values are not unusually high, their near constancy in the vertical column will have important implications to radiative forcing

Aerosol spectral optical depths over the Bay of Bengal, Arabian sea and Indian ocean

Comprehensive investigations during the last decade have clearly established that aerosols have a significant impact on the climate. No serious attempts were made to characterize the aerosols over the Bay of Bengal, despite its role in the regional climate system. This paper reports the results of the measurements of aerosol spectral optical depths made over the Bay of Bengal and compares them with those made over the equatorial Indian Ocean and the Arabian Sea, on-board the oceanographic research vessel, Sagar Kanya during its cruise #161-B in March 2001. The aerosol optical depth was found to decrease with distance from the coast with an exponential scale distance of ~1000 km for visible wavelengths and ~1600 km for near infra-red wavelengths. A significant dominance of small particle concentration near the coast is observed both over the Arabian Sea and the Bay of Bengal. The mean aerosol optical depth was higher over the Bay of Bengal compared to the Arabian Sea, at the shorter wavelengths. Over the equatorial Indian Ocean regions, aerosol optical depths were much lower compared to the Arabian Sea and the Bay of Bengal and showed lesser wavelength dependence. The relative dominance of small particles is more over the Bay of Bengal compared to the Arabian Sea. Back-trajectory analysis shows that during the cruise period, the Arabian Sea was mainly influenced by air masses from the countries lying northwest of India, the Bay of Bengal by air masses from the east coast of India and the equatorial Indian Ocean mostly by the west coast and central India. The observed features are compared with long-term climatology of aerosol optical depth observations from the east and west coast of India and an island station in the Arabian Sea

Aerosol characteristics at a remote island: minicoy in southern Arabian sea

Extensive measurements of aerosol optical and microphysical properties made at a remote island, Minicoy in southern Arabian Sea for the period (February 2006-March 2007) are used to characterize their temporal variability and Black Carbon (BC) mass mixing ratio. Large decrease in aerosol BC (from ~800 ng m-3 to ~100 ng m-3) was observed associated with change in airmass characteristics and monsoon rains. The total aerosol mass varied between ~80 and 20 μg m-3. Though the total mass fell drastically, a slight increase in super micron mass was observed during the June-August period associated with high winds. The mass fraction of Black Carbon aerosols during the prevalence of continental airmass is found to be ~1.2% of the composite aerosols, which is much lower than the values reported earlier for this region

The role of low-frequency intraseasonal oscillations in the anomalous Indian summer monsoon rainfall of 2002

We analyze the dynamical features and responsible factors of the low-frequency intraseasonal time scales which influenced the nature of onset, intensity and duration of active/break phases and withdrawal of the monsoon during the anomalous Indian summer monsoon of 2002 - the most severe drought recorded in recent times. During that season, persistent warm sea surface temperature anomalies over the equatorial Indian Ocean played a significant role in modulating the strength of the monsoon Hadley circulation. This in turn affected the onset and intense break spells especially the long break during the peak monsoon month of July. Strong low-frequency intraseasonal modulations with significant impact on the onset and active/break phases occurred in 2002 which were manifested as a good association between low-frequency intraseasonal oscillations and the onset and active/break spells. Further, SST anomalies over the equatorial Indo-Pacific region on low-frequency intraseasonal time scales were found to affect the equatorial eastward and thereby off-equatorial northward propagations of enhanced convection over the Indian region. These propagations in turn modulated the active/break cycle deciding the consequent severity of the 2002 drought

Aerosol properties and BC mass mixing ratios over the Arabian Sea during ARMEX 2004

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Large latitudinal gradients and temporal heterogeneity in aerosol black carbon and its mass mixing ratio over southern and northern oceans observed during a trans-continental cruise experiment

Extensive, and collocated measurements of the mass concentrations (MB) of aerosol black carbon (BC) and (MT) of composite aerosols were made over the Arabian Sea, tropical Indian Ocean and the Southern Ocean during a trans-continental cruise experiment. Our investigations show that MB remains extremely low (<50 ng m-3) and remarkably steady (in space and time) in the Southern Ocean (20°S to 56°S). In contrast, large latitudinal gradients exist north of ~20°S; MB increasing exponentially to reach as high as 2000 ng m-3 in the Arabian Sea (~8°N). Interestingly, the share of BC showed a distinctly different latitudinal variation, with a peak close to the equator and decreasing on either side. Large fluctuations were seen in MT over Southern Ocean associated with enhanced production of sea-salt aerosols in response to sea-surface wind speed. These spatio-temporal changes in MB and its mixing ratio have important implications to regional and global climate

Research Article Research on Sliding Wear Behavior of TiO 2 Filled Glass Fiber Reinforced Polymer Composite

Abstract: In this study, Titanium Oxide (TiO 2 ) particulate filled e-glass fiber reinforced composites in the unsaturated polyester resin matrix were prepared and its dry sliding wear behavior was optimized. Composites of varying fiber lengths of 1, 2 and 3 cm, respectively with different fiber content of 30, 40 and 50 wt. %, respectively were made. The particulate was varied with 2, 5 and 9 wt. %, respectively. The hybrid reinforced composites were prepared by hand layup method and the wear was measured adopting pin-on-disk system. Taguchi's experimental design approach was used to make a parametric analysis of the variable fiber length, fiber content and filler material content. The influencing parameter on the wear rate was determined using the Signal-to-Noise (S/N) ratio and Analysis of Variance (ANOVA). The fiber content emerged as the most significant factor affecting the wear rate of the composites. The regression analysis was carried out to determine the nonlinear analysis for the prediction of the optimized model