| 1. |
- 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. |
- Moiseenko, V. E., et al.
(författare)
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Stellator research at IPP KIPT : Status and prospects
- 2019
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Ingår i: PROBLEMS OF ATOMIC SCIENCE AND TECHNOLOGY. - : KHARKOV INST PHYSICS & TECHNOLOGY. - 1562-6016. ; :1, s. 3-8
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Tidskriftsartikel (refereegranskat)abstract
- Features of the recent Uragan-2M campaign are reviewed together with some theoretical advances. They include experiments with B4C limiter, studies of various 1. . . 20 kHz oscillations, development of a new in-situ diagnostics for wall conditions, i.e. the thermal desorption probe, the improved numerical model of RF plasma production in stellarators in the ion cyclotron and electron-cyclotron frequency ranges, a new positive-definite form of time-harmonic Maxwell's equations and plasma start-up studies.
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| 3. |
- Kulyk, M. M., et al.
(författare)
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Magnetic properties and anisotropic coercivity in nanogranular films of Co/Al2O3 above the percolation limit
- 2014
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Ingår i: Journal of Physics D. - : IOP Publishing. - 0022-3727 .- 1361-6463. ; 47:34, s. 345002-
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Tidskriftsartikel (refereegranskat)abstract
- Magnetic properties of nanogranular ferromagnetic Co/Al2O3 films with 74.5 at% Co, which is above the percolation limit, are investigated. It is established that the films have perpendicular magnetic anisotropy and a weaker in-plane anisotropy. The magnetization curves show that the film consists of two magnetic components: a dominating contribution from magneto-anisotropic isolated grains with the anisotropy axis perpendicular to the film plane and a weaker contribution from the percolated part of the film. This two-component magnetic composition of the films, with the dominating contribution from the nanograins, is confirmed by transmission electron microscopy as well as by ferromagnetic resonance spectroscopy. It is further established that the coercive field of the film is almost entirely determined by the percolated part of the film. In this, the angular dependence of the coercive force, H-c(theta(H)), is essentially proportional to sin(-1)theta(H), where theta(H) is the angle between the applied field and the film's normal. However, for theta(H) -> 0, H-c(theta(H)) there is a narrow minimum with H-c approaching zero. Such non-linear dependence agrees well with our modelling results for a two-component magnetic system of the film, where the non-percolated nanograins have a distinct perpendicular anisotropy. The reported results should be important for in-depth characterization and understanding the magnetism and anisotropy in inhomogeneous systems as well as for applications, specifically in perpendicular magnetic recording.
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| 4. |
- Brunnström, Kjell, et al.
(författare)
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3D Video Quality of Experience - Influence of Scale and Crosstalk Invited
- 2014
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Ingår i: Proceedings of the 8th International Workshop on Video Processing and Quality Metrics for Consumer Electronics VPQM-2014. - Scottsdale, AZ, USA.
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Konferensbidrag (refereegranskat)abstract
- This paper gives an overview of three recent studies by the authors on the topic of 3D video Quality of Experience (QoE). Two of studies [1,2] investigated different psychological dimension that may be needed for describing 3D video QoE and the third the visibility and annoyance of crosstalk[3]. The results shows that the video quality scale could be sufficient for evaluating S3D video experience for coding and spatial resolution reduction distortions. It was also confirmed that with a more complex mixture of degradations more than one scale should be used to capture the QoE in these cases. The study found a linear relationship between the perceived crosstalk and the amount of crosstalk.
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| 5. |
- Klonos, Panagiotis, et al.
(författare)
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Effects of Molecular Weight below the Entanglement Threshold on Interfacial Nanoparticles/Polymer Dynamics
- 2016
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Ingår i: Macromolecules. - : American Chemical Society (ACS). - 0024-9297 .- 1520-5835. ; 49:24, s. 9457-9473
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Tidskriftsartikel (refereegranskat)abstract
- This work deals with effects of polymer molecular W-m, below the entanglement threshold W-m,W-e, on molecular dynamics of polydimethylsiloxane (PDMS) adsorbed onto silica particles, employing differential scanning calorimetry (DSC) and two dielectric techniques: broadband depolarization currents (TSDC). The rigid amorphous dielectric spectroscopy (BDS) and thermally stimulated polymer fraction at interfaces, RAF(int), was found suppressed for larger W-m by all techniques in qualitative agreement with each other. Results on RAF(int) were supported by evaluating, for the first time, the coverage of hydroxyls at the surfaces of nanoparticles by polymer chains (S relaxation). The mobility of interfacial polymer (alpha(int) relaxation) was followed by BDS and TSDC, showing suppression of dynamics and cooperativity with decreasing W-m. We suggest that interfacial polymer fraction and dynamics are dominated by the concentration of polymer-particle contact points, the latter increasing for smaller W-m due to more free chain ends, as expected below W-m,W-e. Furthermore, adopting models that describe multiple conformations for polymers adsorbed on solid surfaces, we explain our results in terms of promotion of tail/loop-like conformations in the particle-polymer interfacial layer for shorter/longer polymer chains, respectively. The model was further checked by employing surface modification of initial silica, which resulted in smoothening of nanoparticle surface and led to further suppression of RAF(int) and interfacial polymer dynamics.
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| 6. |
- Kulyk, Mykola, et al.
(författare)
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Magnetotransport properties of nanogranular composites with low-field positive magnetoresistance
- 2020
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Ingår i: Low temperature physics (Woodbury, N.Y., Print). - : American Institute of Physics (AIP). - 1063-777X .- 1090-6517. ; 46:8, s. 792-797
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Tidskriftsartikel (refereegranskat)abstract
- A low-temperature feature is detected in nanogranular magnetic films with perpendicular anisotropy that have a low-field positive magnetoresistance: positive magnetoresistance is observed during the initial magnetization of the demagnetized sample, but is absent when the magnetic field is removed and/or during subsequent magnetizations. This effect is studied using a Co-x(Al2On)(1-x)film withx = 0.60, consisting of Co metal nanogranules in an Al(2)O(n)insulating matrix withnclose to 3. It is found that together with perpendicular anisotropy, the film has local in-plane anisotropy with randomly oriented easy axes, which prevents the reorientation of the granules' magnetic moment projections in the film plane below a certain blocking temperature. The restoration of the local short-range order in the orientation of the magnetic moments of the demagnetized film's neighboring granules, which is optimal for conductivity and is destroyed by the introduction of a magnetic field, is prevented at temperatures below the blocking temperature and is not restored during subsequent cycles of introducing/removing the magnetic field without heating to temperatures above the blocking temperature.
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| 7. |
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| 8. |
- Moiseyenko, Volodymyr, et al.
(författare)
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FUSION RESEARCH IN STELLARATOR DEPARTMENT OF IPP NSC KIPT
- 2022
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Ingår i: PROBLEMS OF ATOMIC SCIENCE AND TECHNOLOGY. - : Problems of Atomic Science and Technology. - 1562-6016. ; :6, s. 3-8, s. 3-8
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Tidskriftsartikel (refereegranskat)abstract
- This paper briefly describes intrinsic and collaborative scientific activities in the Stellarator Department of the Institute of Plasma Physics of the National Science Center "Kharkov Institute of Physics and Technology" in last two years. These activities include experiments on JET tokamak, stellarators Wendelstein 7-X and Uragan-2M, TOMAS toroidal device and theoretical studies related to modeling of radio-frequency fields in plasma and conceptual development of the stellarator-mirror fission-fusion hybrid.
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| 9. |
- Sobolev, Egor, et al.
(författare)
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Megahertz single-particle imaging at the European XFEL
- 2020
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Ingår i: Communications Physics. - : Springer Science and Business Media LLC. - 2399-3650. ; 3:1
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Tidskriftsartikel (refereegranskat)abstract
- The emergence of high repetition-rate X-ray free-electron lasers (XFELs) powered by superconducting accelerator technology enables the measurement of significantly more experimental data per day than was previously possible. The European XFEL is expected to provide 27,000 pulses per second, over two orders of magnitude more than any other XFEL. The increased pulse rate is a key enabling factor for single-particle X-ray diffractive imaging, which relies on averaging the weak diffraction signal from single biological particles. Taking full advantage of this new capability requires that all experimental steps, from sample preparation and delivery to the acquisition of diffraction patterns, are compatible with the increased pulse repetition rate. Here, we show that single-particle imaging can be performed using X-ray pulses at megahertz repetition rates. The results obtained pave the way towards exploiting high repetition-rate X-ray free-electron lasers for single-particle imaging at their full repetition rate.
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