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  • 1
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    Synthesis of High-Purity Methylal via Extractive Catalytic Distillation (2012)
    Wiley
    Details
    Publication Date: 2012-04-15
    Description: An integrated continuous process, which combines catalytic distillation and extractive distillation in one column, is investigated for the synthesis of high-purity methylal from methanol and formalin in the presence of a cation-exchange resin catalyst. A feed with methanol:formaldehyde 2:1 molar ratio is chosen to evaluate the effects of operating parameters, such as extractant feeding position, ratio of extractant to feed, reflux ratio, and reboiler temperature, on the continuous synthesis of methylal. Under the optimum operating conditions and with water as extractant, the extractive catalytic distillation process operated continuously, producing a methylal purity of 98.7 % (H 2 O: 〈 1.30 %) with 98.0 % formaldehyde conversion. An integrated continuous process combining catalytic distillation and extractive distillation in one column is applied for high-purity methylal synthesis from methanol and formalin in the presence of a cation-exchange resin catalyst. Under optimum conditions, using water as extractant, the extractive catalytic distillation process provided a methylal purity of 98.7 % with 98.0 % formaldehyde conversion.
    Print ISSN: 0930-7516
    Electronic ISSN: 1521-4125
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Published by Wiley
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  • 2
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    Synthesis of High-Purity Methylal via Extractive Catalytic Distillation (2012)
    Wiley
    Details
    Publication Date: 2012-04-13
    Description: An integrated continuous process, which combines catalytic distillation and extractive distillation in one column, is investigated for the synthesis of high-purity methylal from methanol and formalin in the presence of a cation-exchange resin catalyst. A feed with methanol:formaldehyde 2:1 molar ratio is chosen to evaluate the effects of operating parameters, such as extractant feeding position, ratio of extractant to feed, reflux ratio, and reboiler temperature, on the continuous synthesis of methylal. Under the optimum operating conditions and with water as extractant, the extractive catalytic distillation process operated continuously, producing a methylal purity of 98.7 % (H 2 O: 〈 1.30 %) with 98.0 % formaldehyde conversion. An integrated continuous process combining catalytic distillation and extractive distillation in one column is applied for high-purity methylal synthesis from methanol and formalin in the presence of a cation-exchange resin catalyst. Under optimum conditions, using water as extractant, the extractive catalytic distillation process provided a methylal purity of 98.7 % with 98.0 % formaldehyde conversion.
    Print ISSN: 0930-7516
    Electronic ISSN: 1521-4125
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Published by Wiley
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  • 3
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    Improving Physical Absorption of Carbon Dioxide by Ionic Liquid Dispersion (2013)
    Wiley
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    Publication Date: 2013-07-05
    Description: An ionic liquid (IL), 1-butylimidazole hexafluoride phosphate [bmim]PF 4 , was dispersed in surfactant solution to form an IL-in-water emulsion. Physical absorption of CO 2 was carried out in this emulsion system. Absorption rates of CO 2 under different operating conditions were obtained by experimental measurements. CO 2 concentrations in the bulk of absorbent and the local volumetric mass transfer coefficients of the liquid phase were calculated by model calculation. Experimental results indicate that the dispersed IL droplets in aqueous solution can significantly enhance CO 2 mass transfer at the gas-liquid interface. This phenomenon can be ascribed to the increase of mass transfer driving force and local volumetric mass transfer coefficient. The shuttle effect and hydrodynamic effect proved to play important roles for CO 2 absorption improved by dispersed IL. The ionic liquid 1-butylimidazole hexafluoride phosphate [bmim]PF 4 is dispersed into water to create an ionic liquid-in-water emulsion which is applied to absorb CO 2 . The presence of dispersed ionic liquid droplets significantly enhances the CO 2 mass transfer rate at a gas-liquid interface due to both the shuttle effect and hydrodynamic effect.
    Print ISSN: 0930-7516
    Electronic ISSN: 1521-4125
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
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  • 4
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    Study of a coincident observation between the ROCSAT-1 density irregularity and Ascension Island scintillation (2012)
    Wiley
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    Publication Date: 2012-09-07
    Description: A coincident observation that occurred on 24 March 2000 between the irregularity structure measured by ROCSAT-1 and the scintillation experiment at the Ascension Island has been studied. The study of scintillation statistics is carried out first, and the results show that the Nakagami distribution can portray the normalized intensity of the L-band scintillation at various S4 values, up to S4 equal to 1.4. Moreover, the departure of frequency dependence on S4 predicted by the weak scintillation is noticed due to multiple forward scattering effects. The coincident feature between the characteristics of irregularity structure and the scintillation variation are then studied. The causal relationship between the fluctuation of ion density and the scintillation variation is obtained. A numerical simulation using the parabolic wave equation has been carried out with the ROCSAT-1 data in space to compare with the ground scintillation observation. The results show the reasonable scintillation level at the coincident time to indicate a direct relationship between the irregularity structure and the scintillation in both temporal and amplitudinal variations. Finally, some assumptions and limitations of the simulation model are discussed.
    Print ISSN: 0048-6604
    Electronic ISSN: 1944-799X
    Topics: Geosciences , Physics
    Published by Wiley on behalf of American Geophysical Union (AGU).
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  • 5
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    Spatiotemporal characteristics of ultraviolet radiation in recent 54 years from measurements and reconstructions over the Tibetan Plateau (2016)
    Wiley
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    Publication Date: 2016-06-21
    Description: Based on measurements of ultraviolet radiation (UV) for the period 2005-2014 that were obtained from the Chinese Ecosystem Research Network (CERN), we developed an efficient model to estimate UV radiation under various sky conditions. This model can provide an accurate reconstruction of UV radiation data with absolute mean bias error less than 9.65%. We combined this reconstruction model with a hybrid model to obtain the historical dataset of daily UV radiation from 1961 to 2014 at 37 weather stations belonging to the China Meteorological Administration (CMA) over the Tibetan Plateau (TP). Based on the historical dataset, the spatial distribution and temporal variation of UV radiation over the TP region were discussed. The decreasing and increasing periods of ultraviolet radiation over the TP were significantly different from those over the entire China. There was an increasing trend in UV radiation over the TP from 1961 to 1983, followed by a decreasing one until 2014; while UV radiation decreased from 1961 to 1989 and then increased slightly after 1989 for the entire China. The average UV radiation values in the increasing and decreasing periods over the TP were 0.598 MJ · m -2  · d -1 and 0.594 MJ · m -2  · d -1 , respectively. In addition, aerosol optical depth, column ozone and cloud prevent approximately 7.13%, 1.31%, and 15.05% of UV radiation reaching the Earth's surface respectively.
    Print ISSN: 0148-0227
    Topics: Geosciences , Physics
    Published by Wiley on behalf of American Geophysical Union (AGU).
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  • 6
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    Shear wave splitting analyses in Tian Shan: Geodynamic implications of complex seismic anisotropy (2016)
    Wiley
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    Publication Date: 2016-05-11
    Description: The Tian Shan is a tectonically complex intracontinental orogenic belt situated between the Tarim Basin and the Kazakh Shield. The vast majority of the previous SWS measurements were presented as station averages, which are only valid when the anisotropy structure can be approximated by a single layer of anisotropy with a horizontal axis of symmetry, i.e., a model of simple anisotropy. A variety of anisotropy-forming hypotheses have been proposed based on the station-averaged measurements. In this study, we measure the splitting parameters at 25 stations that recorded high-quality data from a wide back-azimuthal range for the purpose of identifying and characterizing complex anisotropy. Among the 25 stations, 15 of them show systematic azimuthal variations in the observed splitting parameters with a 90° periodicity that is consistent with a model of 2-layered anisotropy. The fast orientations of the upper layer range from 50° to 90° measured clockwise from the north, which are subparallel to the strike of the orogenic belt, and the splitting times are between 0.9-1.9 s. The corresponding values for the lower layer are -45° to -85° and 1.2-2.2 s, respectively. The remaining 10 stations demonstrate azimuthally invariant splitting parameters with strike-parallel fast orientations, and can be represented by a single layer of anisotropy with a horizontal axis of symmetry. We propose that the strike-parallel anisotropy is caused by lithospheric shortening, and anisotropy in the lower layer is associated with WNW-ward flow of asthenospheric material sandwiched between the subducting Tarim lithosphere and the thick Kazakh lithospheric root. This article is protected by copyright. All rights reserved.
    Electronic ISSN: 1525-2027
    Topics: Chemistry and Pharmacology , Geosciences , Physics
    Published by Wiley on behalf of American Geophysical Union (AGU).
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  • 7
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    Seismic Arrays to Study African Rift Initiation (2013)
    Wiley
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    Publication Date: 2013-06-12
    Description: Rifting of stable continents is a key element of plate tectonic cycles. In spite of numerous studies, the mechanism responsible for the initiation and evolution of rift valleys such as the East African Rift System (EARS) is still poorly understood, partly because most previous investigations focused on rift segments that were in the mature stage. Geodynamic modeling [ Huismans et al ., 2001] suggests that upwelling of the asthenosphere ubiquitously observed beneath mature rifts can either originate from thermal or dynamic anomalies in the deep mantle (active rifting) or be induced by thinning of the lithosphere from far-field stresses (passive rifting) [ Sengor and Burke , 1978].
    Print ISSN: 0096-3941
    Electronic ISSN: 2324-9250
    Topics: Geosciences
    Published by Wiley on behalf of American Geophysical Union (AGU).
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  • 8
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    The Heavy Ion Diffusion Region In Magnetic Reconnection in the Earth's Magnetotail (2015)
    Wiley
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    Publication Date: 2015-04-10
    Description: While the plasma in the Earth's magnetotail predominantly consists of protons and electrons, there are times when a significant amount of oxygen is present. When magnetic reconnection occurs, the behavior of these heavy ions can be significantly different from that of the protons, due to their larger gyroradius. In this study, we investigate the heavy ion distribution functions in the reconnection ion diffusion region from a 2.5D three-species particle-in-cell numerical simulation and compare those with Cluster observations from the near-earth magnetotail. From the simulation results, we find that the heavy ions are demagnetized and accelerated in a larger diffusion region, the heavy ion diffusion region. The ion velocity distribution functions show that, inside the heavy ion diffusion region, heavy ions appear as counter-streaming beams along z in the GSM xz plane, while drifting in y, carrying cross-tail current. We compare this result with Cluster observations in the vicinity of reconnection regions in the near-earth magnetotail and find that the simulation predictions are consistent with the observed ion distribution functions in the ion diffusion region, as well as the inflow, exhaust and sepatratrix regions. Based on the simulation and observation results, the presence of a multi-scale diffusion region model, for O + abundant reconnection events in the Earth's magnetotail, is demonstrated. A test particle simulation shows that in the diffusion region, the H + gains energy mainly through E x , while the O+ energy gain comes equally from E x and E y .
    Print ISSN: 0148-0227
    Topics: Geosciences , Physics
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  • 9
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    The Geometry of an Electron Scale Magnetic Cavity in the Plasma Sheet (2019)
    Wiley
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    Publication Date: 2019
    Description: Abstract Electron scale magnetic cavities are electron vortex structures formed in turbulent plasma, while the evolution and electron dynamics of these structures have not been fully understood. Recently, high‐energy, angular, and temporal electron measurements from Magnetospheric Multiscale have enabled the application of an energetic particle sounding technique to these structures. This study analyzes an electron scale magnetic cavity observed by Magnetospheric Multiscale on 7 May 2015 in the plasma sheet. A comprehensive sounding technique is applied to obtain the geometry and propagation velocities of the boundaries. The result shows that the scale size of the structure is ∼90 km, and the leading and trailing boundaries are moving in the same direction but with different speeds (∼11.5 ± 2.2 and ∼18.1 ± 3.4 km/s, respectively). The speed difference suggests a shrinking of the structure that may play a significant role in magnetic energy dissipation and electron energization of electron scale magnetic cavities.
    Print ISSN: 0094-8276
    Electronic ISSN: 1944-8007
    Topics: Geosciences , Physics
    Published by Wiley on behalf of American Geophysical Union (AGU).
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  • 10
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    Azimuthal anisotropy beneath north central Africa from shear wave splitting analyses (2015)
    Wiley
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    Publication Date: 2015-03-28
    Description: This study represents the first multi-station investigation of azimuthal anisotropy beneath the interior of north central Africa, including Libya and adjacent regions, using shear wave splitting (SWS) analysis. Data used in the study include recently available broadband seismic data obtained from 15 stations managed by the Libyan Center for Remote Sensing and Space Science, and those from 5 other stations at which data are publicly accessible. A total of 583 pairs of high-quality SWS measurements utilizing the PKS, SKKS, and SKS phases demonstrate primarily N-S fast orientations with an average splitting delay time of approximately 1.2 s. An absence of periodic azimuthal variation of the observed splitting parameters indicates the presence of simple anisotropy, and lack of correlation between surficial features and the splitting parameters suggests that the origin of the observed anisotropy is primarily asthenospheric. This conclusion is enhanced by non-periodic azimuthal variation of the splitting parameters observed at one of the stations located near the boundary of areas with different anisotropic properties. We interpret the observed anisotropy to be the consequence of northward movement of the African plate relative to the asthenosphere toward the Hellenic and Calabrian subduction zones. Local variance in fast orientations may be attributable to flow deflection by the northern edge of the African continental root. The observations provide critical and previously lacking constraints on mantle dynamic models in the vicinity of the convergent boundary between the African and Eurasian plates. This article is protected by copyright. All rights reserved.
    Electronic ISSN: 1525-2027
    Topics: Chemistry and Pharmacology , Geosciences , Physics
    Published by Wiley on behalf of American Geophysical Union (AGU).
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