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- Ade, Peter, et al.
(författare)
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The Simons Observatory : science goals and forecasts
- 2019
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Ingår i: Journal of Cosmology and Astroparticle Physics. - : IOP Publishing. - 1475-7516. ; :2
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Tidskriftsartikel (refereegranskat)abstract
- The Simons Observatory (SO) is a new cosmic microwave background experiment being built on Cerro Toco in Chile, due to begin observations in the early 2020s. We describe the scientific goals of the experiment, motivate the design, and forecast its performance. SO will measure the temperature and polarization anisotropy of the cosmic microwave background in six frequency bands centered at: 27, 39, 93, 145, 225 and 280 GHz. The initial con figuration of SO will have three small-aperture 0.5-m telescopes and one large-aperture 6-m telescope, with a total of 60,000 cryogenic bolometers. Our key science goals are to characterize the primordial perturbations, measure the number of relativistic species and the mass of neutrinos, test for deviations from a cosmological constant, improve our understanding of galaxy evolution, and constrain the duration of reionization. The small aperture telescopes will target the largest angular scales observable from Chile, mapping approximate to 10% of the sky to a white noise level of 2 mu K-arcmin in combined 93 and 145 GHz bands, to measure the primordial tensor-to-scalar ratio, r, at a target level of sigma(r) = 0.003. The large aperture telescope will map approximate to 40% of the sky at arcminute angular resolution to an expected white noise level of 6 mu K-arcmin in combined 93 and 145 GHz bands, overlapping with the majority of the Large Synoptic Survey Telescope sky region and partially with the Dark Energy Spectroscopic Instrument. With up to an order of magnitude lower polarization noise than maps from the Planck satellite, the high-resolution sky maps will constrain cosmological parameters derived from the damping tail, gravitational lensing of the microwave background, the primordial bispectrum, and the thermal and kinematic Sunyaev-Zel'dovich effects, and will aid in delensing the large-angle polarization signal to measure the tensor-to-scalar ratio. The survey will also provide a legacy catalog of 16,000 galaxy clusters and more than 20,000 extragalactic sources.
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| 3. |
- Johansson, Ted, et al.
(författare)
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Characterization of LaRhO3 perovskites for dry (CO2) reforming of methane (DRM)
- 2014
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Ingår i: Chemické zvesti. - : Springer Science and Business Media LLC. - 0366-6352 .- 1336-9075. ; 68:9, s. 1240-1247
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Tidskriftsartikel (refereegranskat)abstract
- This work reports on the characterization of LaRhO3 perovskite as a catalyst for dry reforming of methane. The catalyst was studied using CH4-temperature programmed reduction (TPR), H-2-TPR, and temperature programmed surface reaction (TPSR), and the changes in the crystal structure of the catalyst due to these treatments were studied by X-ray diffraction (XRD). XRD pattern of the freshly calcined perovskites showed the formation of highly crystalline LaRhO3 and La2O3 phases. H-2-TPR of the fresh calcined catalyst showed a shoulder at 342A degrees C and a broad peak at 448A degrees C, suggesting that the reduction of Rh in perovskite occurs in multiple steps. XRD pattern of the reduced catalyst suggests complete reduction of the LaRhO3 phase and the formation of metallic Rh and minor amounts of La(OH)(3). The CH4-TPR data show qualitatively similar results as H-2-TPR, with a shoulder and a broad peak in the same temperature range. Following the H-2-TPR up to 950A degrees C, the same batch of catalyst was oxidized by flowing 5 vol. % O-2/He up to 500A degrees C and a second H-2-TPR (also up to 950A degrees C) was conducted. This second H-2-TPR differed significantly from that of the fresh calcined catalyst. The single sharp peak at 163A degrees C in the second H-2-TPR suggests a significant change in the catalyst, probably causedby the transformation of about 90 % of the perovskite into Rh/La2O3. This was confirmed by the XRD studies of the catalyst reduced after the oxidation at 500A degrees C. TPSR of the dry reforming reaction on the fresh calcined catalyst showed CO and H-2 formation starting at 400A degrees C, with complete consumption of the reactants at 650A degrees C. The uneven consumption of reactants between 400A degrees C and 650A degrees C suggests that reactions other than DRM occur, including reverse water gas shift (RWGS) and the Boudouard reaction (BR), probably as a result of in-situ changes in the catalyst, consistent with the H-2-TPR results. TPSR, after a H-2-TPR up to 950A degrees C, showed that the dry reforming reaction did not light off until 570A degrees C, which is much higher temperature than the one observed using fresh calcined catalyst. This shows that the uniform sites produced during the 950A degrees C H-2-TPR are catalytically less active than those of the fresh calcined catalyst, and that no significant side reactions such as RWGS or the Boudouard reaction occur. This suggests that reduction leads to the formation of a single type of sites which do not catalyze simultaneous side reactions.
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