| 1. |
- Golub, Mikhail, 1982, et al.
(författare)
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Modelling of elastic wave propagation through damaged interface via effective spring boundary conditions
- 2018
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Ingår i: Springer Proceedings in Physics. - Cham : Springer International Publishing. - 0930-8989 .- 1867-4941. ; 207, s. 375-387
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Konferensbidrag (refereegranskat)abstract
- The present work deals with the application of spring boundary conditions in order to describe elastic wave propagation in composites with damaged interfaces. Dynamic behaviour of the damaged zone is described by means of a distribution of micro-cracks and introduction of spring boundary conditions, where stresses are proportional to the jump in displacement along the damaged interface and the proportionality factor is the distributed spring stiffness. The stiffness in the spring boundary conditions is determined from the equivalence of the transmission coefficients for these two models. As a result, the normal and tangential components of the spring stiffness tensor depend on the concentration of the defects, their typical size and elastic properties of the contacting materials. The three-dimensional problem with elastic wave scattering by a random or periodic distribution of rectangular microcracks is considered, the latter with a boundary integral equation method. The transmission through the damaged interface with random and periodic distribution of rectangular cracks is compared with a good correspondence giving confidence that the models are appropriate.
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| 2. |
- Minelli, Guglielmo, 1988, et al.
(författare)
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Numerical Investigation of the Actuated Flow on a Bluff Body
- 2016
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Ingår i: Springer Proceedings in Physics. - Cham : Springer International Publishing. - 0930-8989 .- 1867-4941. ; 185, s. 295-302
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Konferensbidrag (refereegranskat)abstract
- Large Eddy Simulations (LES) are conducted to study the Active Flow Control (AFC) of the separation of the boundary layer on a rounded leading edge frontstep. This bluff body imitates the flow around a section of a simplified truck cabin and focuses on the separation arising at the front rounded corner, the so called A-pillar. The LES data show the connection between the actuation and drag reduction. The actuated and unactuated flows are analysed using modal decomposition and frequency analysis. Different configurations are tested and a strong influence of the actuation on both drag reduction and separation mechanism was observed. Relevant results, in terms of drag coefficient and recirculation bubble reduction, are achieved when the flow is actuated. LES shows an increased unsteadiness in the flow, introduced by the actuation. An analysis that investigates the connection between actuation and induced unsteadiness is presented.
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| 3. |
- Mirzaei, Maryam, 1982, et al.
(författare)
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Large Eddy Simulations of Flow Around Two Generic Vehicles in a Platoon
- 2016
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Ingår i: Springer Proceedings in Physics. - Cham : Springer International Publishing. - 0930-8989 .- 1867-4941. - 9783319306025 ; 185, s. 283-288
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Konferensbidrag (refereegranskat)abstract
- A detailed analysis of the effect of inter-vehicle distance on the flow structure of a two-model platoon is presented. Simulations are made for two Ahmed bodies with a slant angle of 25 degrees and for three inter-vehicle distances, d/L = 0.3, 0.5 and 1. The Reynolds number based on the body height was 30000. A drag increase was observed for the follower with d/L = 0.5, compared to the drag value of a single body in isolation. To explain the underlying reasons for the increase in drag, various instantaneous and time-averaged plots are presented and compared for different distances, and a significant change in flow structure was found in flows between the set-ups with d/L = 0.5 and d/L = 1.
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| 4. |
- Mirzaei, Maryam, 1982, et al.
(författare)
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Numerical Study of Aerodynamic Interactions in a Homogeneous Multi-vehicle Formation
- 2016
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Ingår i: Springer Proceedings in Physics. - Cham : Springer International Publishing. - 0930-8989 .- 1867-4941. - 9783319306025 ; 185, s. 289-294
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Konferensbidrag (refereegranskat)abstract
- An accurate and affordable method to study the flow features associated with vehicles in a homogeneous platooning is presented in this paper. It was found that only one pitch of a long-line periodic platoon would provide a sufficiently accurate observation of the flow interaction in the inter-vehicle region of the vehicles offering a significant reduction of the computational effort. The simulations of flow at Reynolds number of 30000 are made for a periodic platoon including slanted-back Ahmed bodies with a slant angle of 25 degrees and for four inter-vehicle distances, d/L = 0.1, 0.3, 0.5 and 1.
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| 5. |
- Seres, J., et al.
(författare)
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Attosecond dynamics of parametric amplification at 11 nm
- 2016
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Ingår i: X-Ray Lasers 2014 - Proceedings of the 14th International Conference on X-Ray Lasers. - Cham : Springer International Publishing. - 1867-4941 .- 0930-8989. - 9783319195209 ; 169, s. 173-178
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Konferensbidrag (refereegranskat)abstract
- X-ray parametric amplification is a high order parametric process with the capability to amplify ultrashort laser pulses with broad spectrum ranging from the extreme ultraviolet to the soft x-ray. In this contribution, the dynamics of this broadband amplification schema is studied with sub-20-as temporal resolution by seeding the amplifier with a train of 200-as-long pulses at 11 nm central wavelength.
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| 6. |
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| 7. |
- Rohringer, N., et al.
(författare)
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Stimulated X-Ray Raman Scattering with Free-Electron Laser Sources
- 2016
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Ingår i: X-Ray Lasers 2014. - Cham : Springer. - 0930-8989. - 9783319195216 - 9783319195209 ; , s. 201-207
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Bokkapitel (refereegranskat)abstract
- Stimulated electronic x-ray Raman scattering is the building block for several proposed x-ray pump probe techniques, that would allow the study of electron dynamics at unprecedented timescales.We present high spectral resolution data on stimulated electronic x-ray Raman scattering in a gas sample of neon using a self-amplified spontaneous emission x-ray free-electron laser. Despite the limited spectral coherence and broad bandwidth of these sources, high-resolution spectra can be obtained by statistical methods, opening the path to coherent stimulated x-ray Raman spectroscopy. An extension of these ideas to molecules and the results of a recent experiment in CO are discussed.
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| 8. |
- Schuette, B., et al.
(författare)
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Recombination-Induced Autoionization Process in Rare-Gas Clusters
- 2015
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Ingår i: Ultrafast Phenomena XIX. - Cham : Springer International Publishing. - 0930-8989. ; 162, s. 56-59
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Konferensbidrag (refereegranskat)abstract
- We investigate electron-ion recombination to excited states in atomic clusters exposed to intense NIR and XUV pulses, which leads to a yet undiscovered autoionization mechanism as a consequence of multiple recombination processes.
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| 9. |
- Wikberg, J. M., et al.
(författare)
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Evolving Magnetization Dynamics in Mn3-xGa
- 2015
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Ingår i: Springer Proceedings in Physics. - Cham : Springer International Publishing. - 0930-8989. ; 159, s. 23-25, s. 23-25
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Konferensbidrag (refereegranskat)abstract
- Magnetic materials with high magnetic coercivity (Hc), magnetic anisotropy (Ku) and low Gilbert damping (α) are of great importance for future spintronics devices. For instance, for spin-transfer-torque (STT) memory devices low α and high Ku are desired. Such a combination of material properties includes a built in contradiction since both Ku and α are dependent on the spin-orbit interaction (SO); a high Ku material is expected to have a high α. However, recent experimental investigations of Mn3-xGa, a material exhibiting high Curie temperature (Tc) > 700 K and (out-of-plane) perpendicular anisotropy, have shown that such a contradictorily low α and high Ku material exists.
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