5 research outputs found

    Characterizing AGB stars in Wide-field Infrared Survey Explorer (WISE) bands

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    Since asymptotic giant branch (AGB) stars are bright and extended infrared objects, most Galactic AGB stars saturate the Wide-field Infrared Survey Explorer (WISE) detectors and therefore the WISE magnitudes that are restored by applying point-spread-function fitting need to be verified. Statistical properties of circumstellar envelopes around AGB stars are discussed on the basis of a WISE AGB catalog verified in this way. We cross-matched an AGB star sample with the WISE All-Sky Source Catalog and the Two Mircon All Sky Survey catalog. Infrared Space Observatory (ISO) spectra of a subsample of WISE AGB stars were also exploited. The dust radiation transfer code DUSTY was used to help predict the magnitudes in the W1 and W2 bands, the two WISE bands most affected by saturation, for calibration purpose, and to provide physical parameters of the AGB sample stars for analysis. DUSTY is verified against the ISO spectra to be a good tool to reproduce the spectral energy distributions of these AGB stars. Systematic magnitude-dependent offsets have been identified in WISE W1 and W2 magnitudes of the saturated AGB stars, and empirical calibration formulas are obtained for them on the basis of 1877 (W1) and 1558 (W2) AGB stars that are successfully fit with DUSTY. According to the calibration formulae, the corrections for W1 at 5 mag and W2 at 4 mag are 0.383-0.383 and 0.217 mag, respectively. In total, we calibrated the W1/W2 magnitudes of 2390/2021 AGB stars. The model parameters from the DUSTY and the calibrated WISE W1 and W2 magnitudes are used to discuss the behavior of the WISE color-color diagrams of AGB stars. The model parameters also reveal that O-rich AGB stars with opaque circumstellar envelopes are much rarer than opaque C-rich AGB stars toward the anti-Galactic center direction, which we attribute to the metallicity gradient of our Galaxy.Comment: 9 pages in two column format, 7 figures, accepted for publication in A&

    Coastal water environment regulation and simulation based on tidal power control

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    As the carrier of water resources, water environment and water ecology, river course is very important to human and ecological environment in coastal areas. The rapid economic development of coastal areas needs to take into account the improvement of regional water environment in order to achieve a higher level of development. The characteristics of coastal water environment are closely related to tidal fluctuation. It is an important direction for coastal water control to improve the water environment and restore the self-purification capacity of the river by guiding and draining the tidal power. In this paper, the YACHONG River Basin, which borders Macau and Zhuhai, is selected as the study area. The semi-exchange period and water exchange rate are taken as the main evaluation indexes. The water quantity and quality model is used to simulate the scenario model and analyze the effect of water diversion and drainage regulation in different tidal periods. The results show that, compared with the drainage dispatch during spring tide, the drainage dispatch during neap tide prolongs the water exchange time, and the effect of water exchange is obviously better than that during spring tide. The research results of this paper provide reference for water environmental regulation in coastal area

    Coastal water environment regulation and simulation based on tidal power control

    No full text
    As the carrier of water resources, water environment and water ecology, river course is very important to human and ecological environment in coastal areas. The rapid economic development of coastal areas needs to take into account the improvement of regional water environment in order to achieve a higher level of development. The characteristics of coastal water environment are closely related to tidal fluctuation. It is an important direction for coastal water control to improve the water environment and restore the self-purification capacity of the river by guiding and draining the tidal power. In this paper, the YACHONG River Basin, which borders Macau and Zhuhai, is selected as the study area. The semi-exchange period and water exchange rate are taken as the main evaluation indexes. The water quantity and quality model is used to simulate the scenario model and analyze the effect of water diversion and drainage regulation in different tidal periods. The results show that, compared with the drainage dispatch during spring tide, the drainage dispatch during neap tide prolongs the water exchange time, and the effect of water exchange is obviously better than that during spring tide. The research results of this paper provide reference for water environmental regulation in coastal area

    Complete Hydrodesulfurization of Dibenzothiophene via Direct Desulfurization Pathway over Mesoporous TiO<sub>2</sub>-Supported NiMo Catalyst Incorporated with Potassium

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    Mesoporous TiO2 containing different potassium content was prepared from potassium titanate by mediating the pH value of the ion exchange, which was used as catalytic support to load NiMo for hydrodesulfurization of dibenzothiophene. The as-prepared samples were characterized by X-ray diffraction, N2 physical adsorption/desorption, temperature-programmed reduction, scanning electron microscope/energy dispersive X-ray mapping analysis, high resolution transmission electron microscopy, and pyridine-adsorbed Fourier transform infrared spectroscopy. The characterization results showed that NiO and MoO3 were well dispersed on mesoporous TiO2 with varying potassium content. A crystal NiMoO4 phase was formed on the TiO2 with relatively high potassium content, which could decrease the reduction temperature of oxidized active species. The evaluation results from the hydrodesulfurization displayed that as the potassium content of the catalyst increased, the dibenzothiophene conversion firstly increased and then slightly decreased when potassium content exceeded 6.41 wt %. By contrast, the direct desulfurization selectivity could continuously increase along with the potassium content of catalyst. Furthermore, the change in direct desulfurization selectivity of a TiO2-supported NiMo catalyst was independent of the reaction condition. The mesoporous TiO2-supported NiMo catalyst incorporated with potassium could have near both 100% of dibenzothiophene and 100% of direct desulfurization selectivity. According to the structure&#8211;performance relationship discussion, the incorporation of potassium species could benefit the formation of more sulfided active species on mesoporous TiO2. Moreover, excessive free potassium species may poison the active sites of the hydrogenation pathway. Both factors determined the characteristics of complete hydrodesulfurization of dibenzothiophene via a direct desulfurization pathway for potassium-incorporated mesoporous TiO2 supported NiMo catalysts
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