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- Labit, B., et al.
(författare)
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Dependence on plasma shape and plasma fueling for small edge-localized mode regimes in TCV and ASDEX Upgrade
- 2019
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Ingår i: Nuclear Fusion. - : IOP Publishing. - 1741-4326 .- 0029-5515. ; 59:8
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Tidskriftsartikel (refereegranskat)abstract
- © 2019 Institute of Physics Publishing. All rights reserved. Within the EUROfusion MST1 work package, a series of experiments has been conducted on AUG and TCV devices to disentangle the role of plasma fueling and plasma shape for the onset of small ELM regimes. On both devices, small ELM regimes with high confinement are achieved if and only if two conditions are fulfilled at the same time. Firstly, the plasma density at the separatrix must be large enough (ne,sep/nG ∼ 0.3), leading to a pressure profile flattening at the separatrix, which stabilizes type-I ELMs. Secondly, the magnetic configuration has to be close to a double null (DN), leading to a reduction of the magnetic shear in the extreme vicinity of the separatrix. As a consequence, its stabilizing effect on ballooning modes is weakened.
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| 2. |
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| 3. |
- de Carolis, Stefano, et al.
(författare)
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Structure and electronic properties of Ca-doped CeO2 and implications on catalytic activity : An experimental and theoretical study
- 1999
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Ingår i: J PHYS CHEM B. - : American Chemical Society (ACS). - 1089-5647. ; 103:36, s. 7627-7636
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Tidskriftsartikel (refereegranskat)abstract
- Doping CeO2 with for example, Ca gives an enhanced reactivity toward reduction of SO2 by CO, and total combustion of methane. Theoretical modeling using static minimizations and molecular dynamics (MD) simulations of the doped (110) face in combination with ab initio quantum chemical cluster models shows large effects on the Ce(IV)/Ce(III) balance due to the doping. Computed oxygen-to-cerium charge-transfer energies are strongly reduced as a result of the introduction of defects and oxygen vacancies, but not sufficiently to explain the observed reactivities. The structures resulting from the MD simulations for both the doped and undoped material are in good agreement with recent experimental pulsed neutron scattering results.
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| 4. |
- Triguero, Luciano, et al.
(författare)
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Metal oxides : O2- chemistry and dynamical effects on oxide reactivity
- 1999
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Ingår i: FARADAY DISCUSS. - : Royal Society of Chemistry (RSC). - 0301-7249. ; 114, s. 351-362
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Tidskriftsartikel (refereegranskat)abstract
- Doping of CeO2 with calcium introduces defects and oxygen vacancies and leads to a strong increase of the catalytic activity. Desulfurization of SO2 with CO involves oxygen abstraction from the lattice and charge-transfer (CT) excitation; this reaction runs at a 70 degrees C lower temperature on the doped substrate. The doping reduces the CT energy cost and the oxygen binding energy, but oxygen abstraction by CO is still not favorable for the lattice at 0 K. The charge state of the ion depends on the Madelung potential, which depends on the lattice structure. Introducing changes in temperature is found to generate vibrations of sufficiently large amplitudes that oxygen anions and cerium cations sometimes can be found at positions where they are sufficiently destabilized so as to be reactive. As the CT energies and oxygen binding energies depend on the instantaneous positions of the ions, active sites appear and disappear at the surface dynamically. The activity of the catalyst substrate is a dynamical quantity that depends on the amplitudes of thermal motion of the surface ions.
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