4,654 research outputs found

    Synthesis optimization and charge carrier transfer mechanism in LiLuSiO<sub>4</sub>:Ce, Tm storage phosphor

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    LiLuSiO4:Ce and LiLuSiO4:Ce, Tm show very efficient charge carrier storage properties upon beta irradiation after samples have received treatment in vacuum. They outperform the commercial storage phosphor BaFBr(I):Eu2+ in many aspects. The influence of the synthesis conditions, Ce and Tm concentration, nonstoichiometry and codoping with Ca, Hf, Al and Ge are reported. Based on the results of the synthesis optimization, thermoluminescence (TL) emission and TL excitation spectra a mechanism of charge carrier transfer, storage, and recombination during irradiation and thermal or optical readout is proposed.Accepted Author ManuscriptRST/Fundamental Aspects of Materials and EnergyRST/Luminescence Material

    Performance of ERA5 data in retrieving Precipitable Water Vapour over East African tropical region

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    The accuracy of surface meteorological measurements is vital to derive accurate Global Positioning System (GPS) Precipitable Water Vapour (PWV) data. However, in absence of surface meteorological data, data from Numerical Weather Prediction Models (NWP) are used. The accuracy of these models varies depending on the model, region, season and other climatic conditions. In this study, GPS data for derivation of PWV is collected from 13 geodetic permanent stations for the years 2013 to 2016. Five out of 13 GPS stations are equipped with meteorological sensors. The interpolated European Centre for Medium-Range Weather Forecasts (ECMWF) 5th Re-Analysis (ERA5) dataset at these locations is first validated using the meteorological data from these sensors. The assessment shows that the average root mean square errors (RMSE) of surface pressure and temperature values are about 0.72 hPa and 1.04 K respectively. PWV determined also requires information on the weighted mean temperature (Tm); the Tm at the 13 GPS stations was also evaluated using three methods: the temperature and humidity profiles from ERA5 (ERA5 Tm), as well as the Tm derived from Bevis and Yao Tm - Ts relationships. The Tm derived from ERA5 was used as a reference to assess the errors of the Bevis and Yao Tm. The comparisons show that the average RMSE values of Tm derived from the two methods are 2.05 K and 2.02 K respectively. The GPS PWVs calculated using the ERA5 interpolated data (GPS ERA5 PWV) were compared to GPS PWV calculated using the sensor meteorological data (GPS MET PWV) at the 5 stations. The GPS ERA5 PWV values were used as the reference. The RMSE values of the two PWV datasets are in the range of 0.19 mm to 0.90 mm with overall average value of 0.44 mm. Also the computed ERA5 PWV data are compared to GPS ERA5 PWV at the 13 stations. ERA5 PWV values were used as the reference and the RMS errors of the two PWV values are in the range 1.35 mm to 2.25 mm with the overall average value of 1.66 mm. Regarding the seasonal variations, the stations between latitudes 4 °S and 4 °N and latitudes 12 °S to 4 °S have the highest PWV values in spring and summer while the lowest values occur in summer and winter respectively.Water Resource

    Robust Subjective Visual Property Prediction from Crowdsourced Pairwise Labels

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    This research of Jiechao Xiong was supported in part by National Natural Science Foundation of China: 61402019, and China Postdoctoral Science Foundation: 2014M550015. The research of Yuan Yao was supported in part by National Basic Research Program of China under grant 2012CB825501 and 2015CB856000, as well as NSFC grant 61071157 and 11421110001. The research of Yanwei Fu and Tao Xiang was in part supported by a joint NSFC-Royal Society grant 1130360, IE110976 with Yuan Ya

    GA Landsat 5 TM Analysis Ready Data Collection 3

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    Maintenance and Update Frequency: asNeededStatement: This product is derived from the USGS Landsat Collection 1 archive. The Moderate Resolution Imaging Spectroradiometer (MODIS) MCD43A1 Version 6 Bidirectional Reflectance Distribution Function and Albedo (BRDF/Albedo) Model Parameters dataset was provided by the National Aeronautics and Space Administration (NASA). It was produced daily using 16 days of Terra and Aqua MODIS data at 500 m resolution. The ozone data was provided by Environment Canada. The Aerosol Optical Thickness data was provided by the Commonwealth Scientific and Industrial Research Organisation (CSIRO). The Precipitable Water for Entire Atmosphere data was provided by the National Oceanic and Atmospheric Administration (NOAA) / Earth System Research Laboratory (ESRL) / Physical Sciences Division (PSD). The baseline Digital Surface Model (DSM) data produced from the Shuttle Radar Topography Mission (SRTM) was provided by the National Geospatial-Intelligence Agency (NGA). Level 1 Collection 1 data was provided by the United States Geological Survey (USGS)'s Earth Resources Observation and Science (EROS) Center.&lt;b&gt;BACKGROUND&lt;/b&gt;&lt;br/&gt;&lt;p&gt;&lt;br/&gt;&lt;p&gt;The United States Geological Survey's (USGS) Landsat satellite program has been capturing images of the Australian continent for more than 30 years. This data is highly useful for land and coastal mapping studies. &lt;br/&gt;&lt;p&gt;In particular, the light reflected from the Earth’s surface (surface reflectance) is important for monitoring environmental resources – such as agricultural production and mining activities – over time. &lt;br/&gt;&lt;p&gt;We need to make accurate comparisons of imagery acquired at different times, seasons and geographic locations. However, inconsistencies can arise due to variations in atmospheric conditions, sun position, sensor view angle, surface slope and surface aspect. These need to be reduced or removed to ensure the data is consistent and can be compared over time. &lt;br/&gt;&lt;p&gt;&nbsp&lt;/p&gt;&lt;br/&gt;&lt;b&gt;WHAT THIS PRODUCT OFFERS&lt;/b&gt;&lt;br/&gt;&lt;p&gt;&lt;br/&gt;&lt;p&gt;GA Landsat 5 TM Analysis Ready Data Collection 3 takes Landsat 5 Thematic Mapper (TM) imagery captured over the Australian continent and corrects for inconsistencies across land and coastal fringes. The result is accurate and standardised surface reflectance data, which is instrumental in identifying and quantifying environmental change. &lt;br/&gt;&lt;p&gt;&lt;br/&gt;&lt;p&gt;The TM instrument is an advanced, multispectral scanning, Earth resources sensor which is designed to categorise the Earth's surface. It is particularly useful for agricultural applications and identification of land use. &lt;br/&gt;&lt;p&gt;&lt;br/&gt;&lt;p&gt;This product is a single, cohesive Analysis Ready Data (ARD) package, which allows you to analyse surface reflectance data as is, without the need to apply additional corrections. &lt;br/&gt;&lt;p&gt;&lt;br/&gt;&lt;p&gt;It contains three sub-products that provide corrections or attribution information:&lt;br/&gt;&lt;p&gt;&lt;br/&gt;&lt;p&gt;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;1) GA Landsat 5 TM NBAR Collection 3 &lt;br/&gt;&lt;p&gt;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;2) GA Landsat 5 TM NBART Collection 3&lt;br/&gt;&lt;p&gt;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;3) GA Landsat 5 TM OA Collection 3&lt;br/&gt;&lt;p&gt;&lt;br/&gt;&lt;p&gt;The resolution is a 30 m grid based on the USGS Landsat Collection 1 archive

    The dependence of light extraction improvement on optimized surface microstructure for AlGaN-based UVC-LEDs considering TM-polarized emission

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    In order to improve the light extraction of AlGaN-based short wavelength ultraviolet light emitting diodes (DUC-LEDs), a type of microstructure with high aspect ratio is introduced and optimized on the AlN substrate surface. And, particle swarm optimization (PSO) algorithm is used to inverse design of the surface microstructure to maximize the light extraction efficiency (LEE). Considering that the propagation characteristics of TM-polarized light are different from that of TE-polarized light, the optical field distribution and LEE is analyzed for the UVC-LEDs with different TE-polarized component when the optimized surface microstructure is applied. Furthermore, the preparation process tolerance of the high aspect ratio structure is discussed by calculating the LED's LEE when the structural deviation occurs or morphology changes. Simulation results show that, by using the optimized surface microstructure based on parabola cone array, the LEDs' LEE is increased from 4.4% to 8.7% and from 0.4% to 3.7% for TE-polarized and TM-polarized emission, respectively. In addition, it is demonstrated that the light extraction improvement by the surface microstructure has a good tolerance to the structural deviation and morphology. The results are significant for improving light extraction and realizing high efficient short wavelength AlGaN-based UVC-LEDs by designing surface microstructures.Green Open Access added to TU Delft Institutional Repository 'You share, we take care!' - Taverne project https://www.openaccess.nl/en/you-share-we-take-care Otherwise as indicated in the copyright section: the publisher is the copyright holder of this work and the author uses the Dutch legislation to make this work public.ImPhys/Esmaeil Zadeh grou

    Rigor and relevance in empirical TM research: Key issues and challenges Author links open overlay panel

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    This paper aims to offer a critical reflection on the way Talent Management (TM) is investigated in practice, by addressing the key issues regarding the quality (in terms of rigor and relevance) of academic empirical TM research and therefore the critical scrutiny of TM scholars’ work. We will argue that despite the growth in the quantity, the quality of many empirical TM papers is lagging behind and hindering the progress of the academic field of TM. Based on a content analysis of 174 peer-reviewed articles published between 2006 and 2017, the paper outlines nine critical issues regarding the quality of the existent empirical TM research. In order to improve the positioning of the field as well as the impact of TM research on practice itis absolutely necessary for TM scholars to secure the quality of academic empirical TM research. Also, the collaboration between practitioners and scholars should increase.Peer ReviewedPostprint (author's final draft
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