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| 2. |
- Schick, Bastian, et al.
(författare)
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Modelling of pantograph-catenary interaction around critical speed
- 2022
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Ingår i: Proceedings of the Fifth International Conference on Railway Technology: Research, Development and Maintenance.
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Konferensbidrag (refereegranskat)abstract
- The dynamic interaction of pantograph and catenary in electrified railway systems has considerable research attention, both in terms of simulation and of measurements. The simulation benchmark of 2015 proved a good base of agreement between established models, but also showed that deviations between the different models increase when the simulated system approaches critical speeds. From these deviations it can be concluded that some of the models in the benchmark better depict the system behaviour around critical speed than others. Therefore, this paper analyses and compares measurement data from the Green Train project in Sweden, which includes speed at and over critical level, to simulations performed with one of the participating models, the finite element (FE) based CaPaSIM model. Based on this comparison,modelling alternatives are implemented and tested in CaPaSIM, to examine if they improve the accuracy of the model in the speed range around critical speeds. These alternative modelling approaches are to a large extent based on previous studies in thefield, such as other models that participated in the benchmark. The varied aspects include choice of element type for single components of the catenary and element mesh resolution. On the pantograph side, the effect of separately modelling independent flexible collector strips is studied. The modelling choices that prove to be most promising during the initial variation tests are presented and recommendations are given for further investigations of possible improvements.
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| 4. |
- Schmising, Clemens von Korff, et al.
(författare)
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Element-Specific Magnetization Dynamics of Complex Magnetic Systems Probed by Ultrafast Magneto-Optical Spectroscopy
- 2020
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Ingår i: Applied Sciences. - : MDPI AG. - 2076-3417. ; 10:21
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Tidskriftsartikel (refereegranskat)abstract
- The vision to manipulate and control magnetism with light is driven on the one hand by fundamental questions of direct and indirect photon-spin interactions, and on the other hand by the necessity to cope with ever growing data volumes, requiring radically new approaches on how to write, read and process information. Here, we present two complementary experimental geometries to access the element-specific magnetization dynamics of complex magnetic systems via ultrafast magneto-optical spectroscopy in the extreme ultraviolet spectral range. First, we employ linearly polarized radiation of a free electron laser facility to demonstrate decoupled dynamics of the two sublattices of an FeGd alloy, a prerequisite for all-optical magnetization switching. Second, we use circularly polarized radiation generated in a laboratory-based high harmonic generation setup to show optical inter-site spin transfer in a CoPt alloy, a mechanism which only very recently has been predicted to mediate ultrafast metamagnetic phase transitions.
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| 5. |
- Tardivo, Alessio, et al.
(författare)
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Effectiveness of EU-funded R&I programmes from the perspective of the European railway sector stakeholders
- 2023
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Ingår i: 2022 Conference Proceedings Transport Research Arena, TRA Lisbon 2022. - : Elsevier B.V.. ; , s. 1256-1263
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Konferensbidrag (refereegranskat)abstract
- The paper provides a methodology for measuring the adherence of Research & Innovation (R&I) actions in railways to the stakeholders' requirements and expected benefits. After collecting the stakeholders' requirements, the R&I objectives are extracted from high-level documents such as Europe's Rail Joint Undertaking Master Plan and Multi Annual Work Programme. Lastly, after standardization of the requirements and the technology concepts, a top-down analysis is performed. The results show that network management and vehicle technologies have the highest benefit for the stakeholders, and ERRAC and Regulatory Bodies' requirements are well addrebed. However, the end-users requirements are only partially fulfilled. The necessity of increasing multimodal transport and cooperation with other transport modes is shown, while stronger focus can be placed on the employees and education/training.
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| 6. |
- Wu, Q., et al.
(författare)
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Freight train air brake models
- 2021
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Ingår i: International Journal of Rail transportation. - : Informa UK Limited. - 2324-8378 .- 2324-8386.
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Tidskriftsartikel (refereegranskat)abstract
- This paper is an outcome of an international collaborative research initiative. Researchers from 24 institutions across 12 countries were invited to discuss the state-of-the-art in railway train air brake modelling with an emphasis on freight rains. Discussed models are classified as empirical, fluid dynamics and fluid-empirical dynamics models. Empirical models are widely used, and advanced versions have been used for train dynamics simulations. Fluid dynamics models are better models to study brake system behaviour but are more complex and slower in computation. Fluid-empirical dynamics models combine fluid dynamics brake pipe models and empirical brake valve models. They are a balance of model fidelity and computational speeds. Depending on research objectives, detailed models of brake rigging, friction blocks and wheel-rail adhesion are also available. To spark new ideas and more research in this field, the challenges and research gaps in air brake modelling are discussed.
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