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- Polach, Oldrich, et al.
(författare)
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Validation of simulation models in the context of railway vehicle acceptance
- 2015
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Ingår i: Proceedings of the Institution of mechanical engineers. Part F, journal of rail and rapid transit. - : SAGE Publications. - 0954-4097 .- 2041-3017. ; 229:6, s. 729-754
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Tidskriftsartikel (refereegranskat)abstract
- The evaluation of a reliable validation method, criteria and limit values suitable for model validation in the context of vehicle acceptance was one of the objectives of the DynoTRAIN project. The presented investigations represent a unique amount of testing, simulations, comparisons with measurements, and validation evaluations. The on-track measurements performed in four European countries included several different vehicles on a test train equipped to simultaneously record track irregularities and rail profiles. The simulations were performed using vehicle models built with the use of different simulation tools by different partners. The comparisons between simulation and measurement results were conducted for over 1000 simulations using a set of the same test sections for all vehicle models. The results were assessed by three different validation approaches: comparing values according to EN 14363; by subjective engineering judgement by project partners; and using so-called validation metrics, i.e. computable measures developed with the aim of increasing objectivity while still maintaining the level of agreement with engineering judgement. The proposed validation method uses the values computed by analogy with EN 14363 and provides validation limits that can be applied to a set of deviations between simulation and measurement values.
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| 2. |
- Umrao, Sima, et al.
(författare)
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A possible mechanism for the emergence of an additional band gap due to a Ti-O-C bond in the TiO2-graphene hybrid system for enhanced photodegradation of methylene blue under visible light
- 2014
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Ingår i: RSC Advances. - : Royal Society of Chemistry (RSC). - 2046-2069. ; 4:104, s. 59890-59901
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Tidskriftsartikel (refereegranskat)abstract
- Here we report the experimental and theoretical study of two TiO2-graphene oxide (TG) and TiO2-reduced graphene oxide (TR) composites synthesized by a facile and ecological route, for enhanced visible light (similar to 470 nm) photocatalytic degradation of Methylene Blue (MB) (99% efficiency), with high rate constant values (1800% over bare TiO2). TG couples TiO2 nanopowder with Graphene Oxide (GO) while TR couples it with reduced graphene oxide (RGO). The present study, unlike previous reports, discusses never-before-reported double absorption edges obtained for both TG (3.51 eV and 2.51 eV) and TR (3.42 eV and 2.39 eV) composites, which represents the reason behind feasible visible light (2.56 eV) induced photocatalysis. TiO2 domains in the composites dominate the higher band edge, while GO/RGO domains explain the lower band edge. Formation of Ti-O-C bonds in both TG and TR drives the shifting upwards of the valence band edge and reduction in band gap. Further, these bonds provide a conductive pathway for charge carriers from TiO2 nanopowder to the degraded species via the GO/RGO matrix, resulting in decreased charge carrier recombination in TiO2 and enhanced efficiency. To attest that the developed theory is correct, density function theory (DFT) calculations were performed. DFT obtained energetics and electronic structures support experimental findings by demonstrating the role of the Ti-O-C bond, which results in double band edge phenomenon in composites. Finally, the mechanism behind MB degradation is discussed comprehensively and the effect of the weight percent of GO/RGO in the composite on the rate constant and photodegradation efficiency has been studied experimentally and explained by developing analytical equations.
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