115 research outputs found

    Structure, Luminescence, and Transport Properties of EuVO_4

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    Metastable scheelite EuVO_4 was stabilized by a high temperature and pressure method, which was transformed into a stable zircon phase by annealing treatment in air. Scheelite EuVO_4 gave strong emissions with a dominant peak at 617 nm associated with the ^(5)D_0-^(7)F_2 transition of Eu^(3+). ^(151)Eu Mössbauer spectra indicated that the isomer shift for the metastable scheelite phase was ca. 0.5 mm/s lower than that for the zircon phase, which was ascribed to a reduced covalency in the Eu-O bond originated via a charge transfer from oxygen to Eu3+ in scheelite lattice by producing an enhanced shielding of 4f electrons on the s orbital as well as a decrease in s electron density around Eu^(3+) nucleus. Impedance spectra for the zircon phase clearly demonstrated an ionic hopping in the bulk with a conductivity of ca. 1.0×10^(–3) S cm^(–1) at 500°C. EuVO_4 is proved to be both a potential phosphor and a potential ionic conductor

    Quality assurance plan for China collection 2.0 aerosol datasets

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    The inversion of atmospheric aerosol optical depth (AOD) using satellite data has always been a challenge topic in atmospheric research. In order to solve the aerosol retrieval problem over bright land surface, the Synergetic Retrieval of Aerosol Properties (SRAP) algorithm has been developed based on the synergetic using of the MODIS data of TERRA and AQUA satellites [1, 2]. In this paper we describe, in details, the quality assessment or quality assurance (QA) plan for AOD products derived using the SRAP algorithm. The pixel-based QA plan is to give a QA flag to every step of the process in the AOD retrieval. The quality assessment procedures include three common aspects: 1) input data resource flags, 2) retrieval processing flags, 3) product quality flags [3]. Besides, all AOD products are assigned a QA ‘confidence’ flag (QAC) that represents the aggregation of all the individual QA flags. This QAC value ranges from 3 to 0, with QA = 3 indicating the retrievals of highest confidence and QA = 2/QA = 1 progressively lower confidence [4], and 0 means ‘bad’ quality. These QA (QAC) flags indicate how the particular retrieval process should be considered. It is also used as a filter for expected quantitative value of the retrieval, or to provide weighting for aggregating/averaging computations [5]. All of the QA flags are stored as a “bit flag” scientific dataset array in which QA flags of each step are stored in particular bit positions

    Post calibration of channel 1 of NOAA-14 AVHRR: Implications on aerosol optical depth retrieval

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    In order to produce long-term aerosol optical depth (AOD) dataset over land from the Advanced Very High Resolution Radiometer (AVHRR), AVHRR data quality in terms of radiometric calibration must be maintained. A vicarious calibration method have been developed by incorporating well calibrated Sea-Viewing Wide Field-of-View Sensor (SeaWiFS) radiance data over several pseudo-invariant targets to inter-calibrate the channel 1 of AVHRR based on Bidirectional Reflectance Distribution Functions (BRDFs) and spectral band adjustment factor (SBAF) models for different targets. Comparison of our calibration coefficients with those of Pathfinder Atmospheres Extended (PATMOS-x) indicate the calibration accuracy to be within 2.5%. The operational L1B and recalibrated AVHRR radiance are applied to derive AOD maps over East America (dark surface) and West Africa (bright surface) using the land aerosol and bidirectional reflectance inversion by times series technique (LABITS) algorithm. Preliminary comparisons show that significant difference in the retrieved AOD from the two different calibration is expected, while the spatial distribution of AOD difference is complicated due to different surface brightness and deficiencies of numeric solutions

    Device modeling of superconductor transition edge sensors based on the two-fluid theory

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    In order to support the design and study of sophisticated large scale transition edge sensor (TES) circuits, we use basic SPICE elements to develop device models for TESs based on the superfluid-normal fluid theory. In contrast to previous studies, our device model is not limited to small signal simulation, and it relies only on device parameters that have clear physical meaning and can be easily measured. We integrate the device models in design kits based on powerful EDA tools such as CADENCE and OrCAD, and use them for versatile simulations of TES circuits. Comparing our simulation results with published experimental data, we find good agreement which suggests that device models based on the two-fluid theory can be used to predict the behavior of TES circuits reliably and hence they are valuable for assisting the design of sophisticated TES circuits.Comment: 10pages,11figures. Accepted to IEEE Trans. Appl. Supercon

    Re-appearance of precipitated aragonite crystal fans as evidence for expansion of oceanic dissolved inorganic carbon reservoir in the aftermath of the Lomagundi-Jatuli Event

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    The initial accumulation of atmospheric oxygen is marked by the unprecedented positive δ13Ccarb excursions of the Lomagundi-Jatuli Event (LJE) and records an interval of abnormal O2 production through elevated rates of organic carbon burial. Emerging evidence suggests that the post-LJE atmosphere-ocean system might have suffered a significant deoxygenation. These dynamic perturbations in the oceanic redox state and biogeochemical cycles would have led to fundamental changes in carbonate precipitation dynamics. Here, we report the discovery of centimeter-sized crystal fans in the post-LJE Huaiyincun Formation, Hutuo Supergroup in the North China Craton. The hexagonal cross-sections and square terminations suggest that these fan-like dolomitic structures were originally aragonite crystal fans (ACF). Variations of stromatolite morphology and frequent occurrences of storm-related deposits in the Huaiyincun Formation point to repeated cycles of sea level changes. The bedding-parallel distribution of the ACF and the homogeneous δ13C values of the ACF-bearing dolostones are consistent with a primary depositional origin for the ACF. An updated compilation of published records of ACF throughout geological history highlights a clear absence of ACF from the initiation of the Paleoproterozoic Great Oxidation Event until the end of the LJE, and a global reappearance of ACF in the post-LJE late Paleoproterozoic. We propose that the reappearance of ACF is in agreement with the expansion of the oceanic dissolved inorganic carbon reservoir. At the same time, consumption of dissolved oxygen during the oxidation of organic matter might have been stimulated by ferruginous deep seawater, facilitating the formation of Huiayincun ACF

    Towards a comprehensive view of dust events from multiple satellite and ground measurements: exemplified by the May 2017 East Asian dust storm

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    One or several aspects of the source, distribution, transport, and optical properties of airborne dust have been characterized using different types of satellite and ground measurements, each with unique advantages. In this study, a dust event that occurred over the East Asia area in May 2017 was exemplified to demonstrate how all the above-mentioned aspects of a dust event can be pictured by combining the advantages of different satellite and ground measurements. The data used included the Himawari-8 satellite Advanced Himawari Imager (AHI) true-colour images, the Cloud-Aerosol Lidar and Infrared Pathfinder Satellite Observation (CALIPSO) Cloud-Aerosol Lidar with Orthogonal Polarization (CALIOP) aerosol vertical profiles, the Aura satellite Ozone Monitoring Instrument (OMI) aerosol index images, and the ground-based Aerosol Robotic Network (AERONET) aerosol properties and the ground station particulate matter (PM) measurements. From the multi-satellite/sensor (AHI, CALIOP, and OMI) time series observations, the dust storm was found to originate from the Gobi Desert on the morning of 3 May 2017 and transport north-eastward to the Bering Sea, eastward to the Korean Peninsula and Japan, and southward to south-central China. The air quality in China deteriorated drastically: the PM10 (PM&thinsp;&lt;&thinsp;10&thinsp;µm in aerodynamic diameter) concentrations measured at some air quality stations located in northern China reached 4333&thinsp;µg&thinsp;m−3. At the AOE_Baotou, Beijing, Xuzhou-CUMT, and Ussuriysk AERONET sites, the maximum aerosol optical depth values reached 2.96, 2.13, 2.87, and 0.65 and the extinction Ångström exponent dropped to 0.023, 0.068, 0.03, and 0.097, respectively. The dust storm also induced unusual aerosol spectral single-scattering albedo and volume size distribution.</p

    Validation of Aerosol Products from AATSR and MERIS/AATSR Synergy Algorithms—Part 1: Global Evaluation

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    The European Space Agency’s (ESA’s) Aerosol Climate Change Initiative (CCI) project intends to exploit the robust, long-term, global aerosol optical thickness (AOT) dataset from Europe’s satellite observations. Newly released Swansea University (SU) aerosol products include AATSR retrieval and synergy between AATSR and MERIS with a spatial resolution of 10 km. In this study, both AATSR retrieval (SU/AATSR) and AATSR/MERIS synergy retrieval (SU/synergy) products are validated globally using Aerosol Robotic Network (AERONET) observations for March, June, September, and December 2008, as suggested by the Aerosol-CCI project. The analysis includes the impacts of cloud screening, surface parameterization, and aerosol type selections for two products under different surface and atmospheric conditions. The comparison between SU/AATSR and SU/synergy shows very accurate and consistent global patterns. The global evaluation using AERONET shows that the SU/AATSR product exhibits slightly better agreement with AERONET than the SU/synergy product. SU/synergy retrieval overestimates AOT for all surface and aerosol conditions. SU/AATSR data is much more stable and has better quality; it slightly underestimates fine-mode dominated and absorbing AOTs yet slightly overestimates coarse-mode dominated and non-absorbing AOTs.N/

    Dust detection and intensity estimation using Himawari-8/AHI observation.

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    In this study, simple dust detection and intensity estimation methods using Himawari-8 Advanced Himawari Imager (AHI) data are developed. Based on the differences of thermal radiation characteristics between dust and other typical objects, brightness temperature difference (BTD) among four channels (BT11–BT12, BT8–BT11, and BT3–BT11) are used together for dust detection. When considering the thermal radiation variation of dust particles over different land cover types, a dynamic threshold scheme for dust detection is adopted. An enhanced dust intensity index (EDII) is developed based on the reflectance of visible/near-infrared bands, BT of thermal-infrared bands, and aerosol optical depth (AOD), and is applied to the detected dust area. The AOD is retrieved using multiple temporal AHI observations by assuming little surface change in a short time period (i.e., 1–2 days) and proved with high accuracy using the Aerosol Robotic Network (AERONET) and cross-compared with MODIS AOD products. The dust detection results agree qualitatively with the dust locations that were revealed by AHI true color images. The results were also compared quantitatively with dust identification results from the AERONET AOD and Ångström exponent, achieving a total dust detection accuracy of 84%. A good agreement is obtained between EDII and the visibility data from National Climatic Data Center ground measurements, with a correlation coefficient of 0.81, indicating the effectiveness of EDII in dust monitoring.N/

    Growth and Comprehensive Quality Index of Tomato under Rain Shelters in Response to Different Irrigation and Drainage Treatments

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    The effects of two levels of irrigation water (100%, 60%) and buried underground pipe depths (0.8 m, 0.6 m) under rain shelters’ conditions on yield and some quality parameters of tomato were investigated. A fully randomized factorial experiment was conducted between April and August in 2011 and 2012 at Hohai University. It was found that drainage treatments enhanced biomass production, whereas soil desiccation led to biomass reduction. At 60 cm buried underground pipe depths, the drought treatments increased the mean root weight and root-shoot ratio by 14% and 39%, respectively. The main effects of drainage treatments on the fruit quality were increases in total soluble solids (TSS), soluble sugar (SS), and vitamin C (VC) compared to the control. In addition, drainage treatments increased the average yield by 13% and 9%, respectively, in both years. The drought treatments did not significantly alter fruit yield, although mean single fruit weight was slightly reduced. Instead, these treatments tend to have great potential to improve fruit quality (TSS, SS, and VC) to variable extents. In both years, the drought treatment at 60 cm buried underground pipe depths proved to possess the highest comprehensive quality index based on Principal Component Analysis
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