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    Effects of Particle Non‐Sphericity on Dust Optical Properties in a Forecast System: Implications for Model‐Observation Comparison (2019)
    Wiley
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    Publication Date: 2019
    Description: Abstract Mineral dust is a key player in the Earth system that affects the weather and climate through absorbing and scattering the radiation. Such effects strongly depend on the optical properties of the particles that are in turn affected by the particle shape. For simplicity, dust particles are usually assumed to be spherical. But this assumption can lead to large errors in modeling and remote sensing applications. This study investigates the impact of dust particle shape on its direct radiative effect in a next‐generation atmospheric modeling system ICON‐ART (ICOsahedral Nonhydrostatic with Aerosols and Reactive Trace gases) to verify if accounting for non‐sphericity enhances the model‐observation agreement. Two sets of numerical experiments are conducted by changing the optical shape of the particles: one assuming spherical particles and the other one assuming a mixture of 35 randomly oriented tri‐axial ellipsoids. The simulations are compared to MISR, AERONET and CALIPSO observations (with focus on North Africa). The results show that consideration of particle non‐sphericity increases the dust AOD at 550 nm by up to 28% and leads to slight enhancement of the agreement between modeled and measured AOD. However, the model performance varies significantly when focusing on specific regions in North Africa. These differences stem from the uncertainties associated with particle size distribution and emission mechanisms in the model configuration. Regarding the attenuated backscatter, the simulated profile assuming non‐sphericity differs by a factor of 2 to 5 from the experiment assuming spherical dust, and is in a better agreement with the CALIPSO observations.
    Print ISSN: 2169-897X
    Electronic ISSN: 2169-8996
    Topics: Geosciences , Physics
    Published by Wiley on behalf of American Geophysical Union (AGU).
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    Heterogeneously catalyzed hydrogenation of supercritical carbon dioxide to methanol – catalytic and thermodynamic investigations for a process concept (2017)
    Wiley
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    Publication Date: 2017-07-14
    Description: Interest in energy storage technologies is still increasing in times of the excess of electricity that is generated by wind farms or solar plants. Solar electricity can be transformed to solar-hydrogen via water electrolysis. A crucial part of the energy storage technologies plays the efficient conversion of H 2 and CO 2 from renewable resources. Here, the process conditions for continuously catalytic hydrogenation of CO 2 to CH 3 OH under supercritical conditions over lab-synthesized Cu/ZnO/Al 2 O 3  catalysts were investigated. The impact of temperature (230 – 330 °C), residence time (0.5 - 2.2 s) at moderate pressure (150 bar) but even above the supercritical parameters of CO 2 showed a selective CO 2 hydrogenation. Higher H 2 concentrations, respectively higher H 2 :CO 2 -ratios (H 2 :CO 2  = 6), lead to an increased selectivity of CH 3 OH. A possible in situ phase separation of reaction products within the reactor due to the higher densities of the reaction mixture by the highered pressure could affect the kinectics and simplfy the down-stream processing. The combination of thermodynamic studies (phase separation phenomena) as well as the catalytic performance tests for the CO2 hydrogenation under supercritical conditions are discussed. Based on these data a process concept is presented.
    Print ISSN: 0930-7516
    Electronic ISSN: 1521-4125
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Published by Wiley
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