Impact of AQUA Satellite Data on Hurricane Forecast: Danielle 2010

This study focuses on the impact of AQUA satellite data from AIRS and AMSU on the forecast of hurricane Danielle by the Global Forecast System (GFS) model. The data assimilation method adopted to ingest the data is the Gridpoint Statistical method (GSI) which is based on the three dimensional variational (3DVAR) data assimilation technique. Two experiments were carried out to investigate the impact of AQUA satellite radiance observation on the forecast of hurricane Danielle. The first experiment (Control) assimilated all the available data while the second experiment (No AQUA) incorporated all the observations but the AQUA satellite data. Data assimilation cycling started one week prior to hurricane genesis, on 15 August 2010 06 UTC. The root mean square track forecast error shows slightly negative impact at the early lead time and slightly positive impact at later lead time. However, the root mean square intensity forecast errors by the Control are shown to be lower than No AQUA for all forecast hours, indicating positive impact of the AQUA data on the intensity forecast

Impact of AQUA Satellite Data on Hurricane Forecast: Danielle 2010

This study focuses on the impact of AQUA satellite data from AIRS and AMSU on the forecast of hurricane Danielle by the Global Forecast System (GFS) model. The data assimilation method adopted to ingest the data is the Gridpoint Statistical method (GSI) which is based on the three dimensional variational (3DVAR) data assimilation technique. Two experiments were carried out to investigate the impact of AQUA satellite radiance observation on the forecast of hurricane Danielle. The first experiment (Control) assimilated all the available data while the second experiment (No AQUA) incorporated all the observations but the AQUA satellite data. Data assimilation cycling started one week prior to hurricane genesis, on 15 August 2010 06 UTC. The root mean square track forecast error shows slightly negative impact at the early lead time and slightly positive impact at later lead time. However, the root mean square intensity forecast errors by the Control are shown to be lower than No AQUA for all forecast hours, indicating positive impact of the AQUA data on the intensity forecast

Iron phosphate glasses: Bulk properties and atomic scale structure

Bulk properties such as glass transition temperature, density and thermal expansion of iron phosphate glass compositions, with replacement of Cs by Ba, are investigated as a surrogate for the transmutation of 137Cs to 137Ba, relevant to the immobilisation of Cs in glass. These studies are required to establish the appropriate incorporation rate of 137Cs in iron phosphate glass. Density and glass transition temperature increases with the addition of BaO indicating the shrinkage and reticulation of the iron phosphate glass network. The average thermal expansion coefficient reduces from 19.8 × 10−6 K−1 to 13.4 × 10−6 K−1, when 25 wt. % of Cs2O was replaced by 25 wt. % of BaO in caesium loaded iron phosphate glass. In addition to the above bulk properties, the role of Ba as a network modifier in the structure of iron phosphate glass is examined using various spectroscopic techniques. The FeII content and average coordination number of iron in the glass network was estimated using Mössbauer spectroscopy. The FeII content in the un-doped iron phosphate glass and barium doped iron phosphate glasses was 20, 21 and 22 ± 1% respectively and the average Fe coordination varied from 5.3 ± 0.2 to 5.7 ± 0.2 with increasing Ba content. The atomic scale structure was further probed by Fe K-edge X-ray absorption spectroscopy. The average coordination number provided by extended X-ray absorption fine structure spectroscopy and X-ray absorption near edge structure was in good agreement with that given by the Mössbauer data

Iron phosphate glasses: Bulk properties and atomic scale structure

© 2017 The Authors Bulk properties such as glass transition temperature, density and thermal expansion of iron phosphate glass compositions, with replacement of Cs by Ba, are investigated as a surrogate for the transmutation of 137 Cs to 137 Ba, relevant to the immobilisation of Cs in glass. These studies are required to establish the appropriate incorporation rate of 137 Cs in iron phosphate glass. Density and glass transition temperature increases with the addition of BaO indicating the shrinkage and reticulation of the iron phosphate glass network. The average thermal expansion coefficient reduces from 19.8 × 10 −6 K −1 to 13.4 × 10 −6 K −1 , when 25 wt. % of Cs 2 O was replaced by 25 wt. % of BaO in caesium loaded iron phosphate glass. In addition to the above bulk properties, the role of Ba as a network modifier in the structure of iron phosphate glass is examined using various spectroscopic techniques. The Fe II content and average coordination number of iron in the glass network was estimated using Mössbauer spectroscopy. The Fe II content in the un-doped iron phosphate glass and barium doped iron phosphate glasses was 20, 21 and 22 ± 1% respectively and the average Fe coordination varied from 5.3 ± 0.2 to 5.7 ± 0.2 with increasing Ba content. The atomic scale structure was further probed by Fe K-edge X-ray absorption spectroscopy. The average coordination number provided by extended X-ray absorption fine structure spectroscopy and X-ray absorption near edge structure was in good agreement with that given by the Mössbauer data

Markets drive the specialization strategies of forest peoples

Engagement in the market changes the opportunities and strategies of forest-related peoples. Efforts to support rural development need to better understand the potential importance of markets and the way people respond to them. To this end, we compared 61 case studies of the commercial production and trade of nontimber forest products from Asia, Africa, and Latin America. The results show that product use is shaped by local markets and institutions, resource abundance, and the relative level of development. Larger regional patterns are also important. High-value products tend to be managed intensively by specialized producers and yield substantially higher incomes than those generated by the less specialized producers of less managed, low-value products. We conclude that commercial trade drives a process of intensified production and household specialization among forest peoples. Copyright © 2004 by the author(s)

A Comparison of the Impacts of Radiosonde and AMSU Radiance Observations in GSI Based 3DEnsVar and 3DVar Data Assimilation Systems for NCEP GFS

The impact of observations can be dependent on many factors in a data assimilation (DA) system including data quality control, preprocessing, skill of the model, and the DA algorithm. The present study focuses on comparing the impacts of observations assimilated by two different DA algorithms. A three-dimensional ensemble-variational (3DEnsVar) hybrid data assimilation system was recently developed based on the Gridpoint Statistical Interpolation (GSI) data assimilation system and was implemented operationally for the National Center for Environmental Prediction (NCEP) Global Forecast System (GFS). One question to address is, how the impacts of observations on GFS forecasts differ when assimilated by the traditional GSI-three dimensional variational (3DVar) and the new 3DEnsVar. Experiments were conducted over a 6-week period during Northern Hemisphere winter season at a reduced resolution. For both the control and data denial experiments, the forecasts produced by 3DEnsVar were more accurate than GSI3DVar experiments. The results suggested that the observations were better and more effectively exploited to increment the background forecast in 3DEnsVar. On the other hand, in GSI3DVar, where the observation will be making mostly local, isotropic increments without proper flow dependent extrapolation is more sensitive to the number and types observations assimilated

Synthesis and characterization of iron-based two-dimensional ferromagnets

Research and development of 2D magnetic materials are quintessential for realizing the next generation of Spintronic memory devices. Due to the advancements in big data and the Internet of things, there is a massive demand for low-power consuming data storage and processing devices. Low power-consuming data storage devices can bypass the Von Neumann bottleneck problem by realizing high-density nonvolatile memory devices. 2D ferromagnetic magnetic materials are potential candidates for fabricating spintronic memory devices such as Spin logic memory devices, magnetic tunnel junctions (MTJ) for magneto-resistive random-access memory (MRAM), etc. This project mainly focuses on establishing the direct growth of 2D ferromagnets on Si/SiO2 substrates. The growth-based research of 2D magnets is currently limited to chemical vapor transport (CVT). In the CVT process, a single crystal 2D magnet is grown in a sealed furnace over time, and then subsequent mechanical exfoliation methods are required to obtain an ultra-thin 2D magnet layer. This process is non-consistent, laborious, and requires an additional step to transfer the exfoliated material to a compatible substrate capable of device fabrication. Chemical vapor deposition (CVD) can overcome this issue by facilitating the growth of 2D magnets directly on Si/SiO2 substrates. The materials studied in this thesis are two-dimensional iron di sulfide and iron germanium telluride magnets.Doctor of Philosoph

Studies on the structural and ionic transport properties at elevated temperatures of La1-xMnO3 +/-delta synthesized by a wet chemical method

Structural transformation and ionic transport properties are investigated on wet-chemically synthesized La1-xMnO3 (X=0.0-0.18) compositions. Powders annealed in oxygen/air at 1000-1080 K exhibit cubic symmetry and transform to rhombohedral on annealing at 1173-1573 K in air/oxygen. Annealing above 1773 K in air or in argon/helium at 1473 K stabilized distorted rhombohedral or orthorhombic symmetry. Structural transformations are confirmed from XRD and TEM studies. The total conductivity of sintered disks, measured by four-probe technique, ranges from 5 S cm(-1) at 298 K to 105 S cm(-1) at 1273 K. The ionic conductivity measured by blocking electrode technique ranges from 1.0X10(-6) S cm(-1) at 700 K to 2.0X10(-3) S cm(-1) at 1273 K. The ionic transference number of these compositions ranges from 3.0X10(-5) to 5.0X10(-5) at 1273 K. The activation energy deduced from experimental data for ionic conduction and ionic migration is 1.03-1.10 and 0.80-1.00 eV, respectively. The activation energy of formation, association and migration of vacancies ranges from 1.07 to 1.44 eV. (C) 2002 Elsevier Science B.V. All rights reserved

Sensitivity analysis of WOFOST for yield simulation of cassava over the major growing areas of India

A study was conducted to assess the meteorological sensitivity of the WOFOST crop model in simulating the yield of cassava. The sensitivity was designed by changing the present meteorological data by ±1 to ±5 %. The results has shown the minimum temperature influencing the yield of cassava (variation: 4.94 to -7.65 %) followed by the maximum temperature (yield variation: 6.39 to -6.03 %) and solar radiation (yield variation: -2.41 to 2.07 %). The trends of these meteorological variables have been further analyzed over the major cassava growing regions in India to link its variations with cassava production. A significant trend has been detected during the monsoon season in northeast India, with a decadal change of 0.63ºC. At the same time, a significant trend was detected in the peninsular region during the winter season, with a value of 0.74ºC/decade. The rate of solar dimming in northeast India during the monsoon season was -0.53 hour/decade and during the autumn season, it was -0.25 hour/decade, respectively. The meteorological sensitivity of crop model on its yield and trends may assist the decision-makers in developing appropriate plans mitigations strategies to enhance crop production to ensure food security

Controlled synthesis of atomically layered hexagonal boron nitride via chemical vapor deposition

Hexagonal boron nitrite (h-BN) is an attractive material for many applications including electronics as a complement to graphene, anti-oxidation coatings, light emitters, etc. However, the synthesis of high-quality h-BN is still a great challenge. In this work, via controlled chemical vapor deposition, we demonstrate the synthesis of h-BN films with a controlled thickness down to atomic layers. The quality of as-grown h-BN is confirmed by complementary characterizations including high-resolution transition electron microscopy, atomic force microscopy, Raman spectroscopy and X-ray photo-electron spectroscopy. This work will pave the way for production of large-scale and high-quality h-BN and its applications as well.NRF (Natl Research Foundation, S’pore)MOE (Min. of Education, S’pore)Published versio