| 1. |
- Bécoulet, A., et al.
(författare)
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Science and technology research and development in support to ITER and the Broader Approach at CEA
- 2013
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Ingår i: Nuclear Fusion. - : IOP Publishing. - 1741-4326 .- 0029-5515. ; 53:10
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Tidskriftsartikel (refereegranskat)abstract
- In parallel to the direct contribution to the procurement phase of ITER and Broader Approach, CEA has initiated research & development programmes, accompanied by experiments together with a significant modelling effort, aimed at ensuring robust operation, plasma performance, as well as mitigating the risks of the procurement phase. This overview reports the latest progress in both fusion science and technology including many areas, namely the mitigation of superconducting magnet quenches, disruption-generated runaway electrons, edge-localized modes (ELMs), the development of imaging surveillance, and heating and current drive systems for steady-state operation. The WEST (W Environment for Steady-state Tokamaks) project, turning Tore Supra into an actively cooled W-divertor platform open to the ITER partners and industries, is presented.
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| 2. |
- Decker, J., et al.
(författare)
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Modelling of LHCD at various densities in tore supra tokamak
- 2012
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Ingår i: 39th EPS Conference on Plasma Physics 2012, EPS 2012 and the 16th International Congress on Plasma Physics; Stockholm; Sweden; 2 July 2012 through 6 July 2012; Code 96757. - 9781622769810 ; 2, s. 934-937
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Konferensbidrag (refereegranskat)
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| 3. |
- Denti, Leif, 1983, et al.
(författare)
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Sweden's largest Facebook study
- 2012
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Rapport (övrigt vetenskapligt/konstnärligt)abstract
- The emergence of the Internet has made it easier for people to socially interact than ever before. Today, the most popular channel is Facebook with over 845 million users world wide. In Sweden, the number of users amount to approximately half of the population. We had two aims with this study. First, we investigate which areas of Facebook usage that Swedish Facebook users consider more important vis-a-vis less important. We were also interested in how users convey their persona through their status updates, including what they status update about, and the underlying reasons for updating one’s status. Second, we investigate what psychological effects Facebook may induce. More specifically, we look at the psychological constructs self-esteem and well-being in relation to Facebook usage. We surveyed 1011 Swedish Facebook users with our questionnaires, measuring respondents’ Facebook usage patterns, well-being and self-esteem. Our analyses revealed that on average Swedish women spend 81 minutes per day on Facebook, whereas Swedish men are logged on to the site about 64 minutes per day. Generally, Facebook is used for social network maintenance, such as maintaining contact with people one doesn’t meet so often. However, Facebook is seldom used for meeting new people. Another finding is that Facebook users generally tend to update their status about positive events, major events and when they are feeling well, rather than negative events and when they are feeling bad. Women seem to be more engaged and active on Facebook than men, agreeing that a vast number of uses is significantly more important. Furthermore, women tend to write more about their thoughts and feelings, whereas twice as many men state that they provoke others on Facebook. Pertaining to Facebook’s psychological effects, the amount of time spent on Facebook had no relationship with self-esteem when controlling for gender, age, education and income. $is result runs counter to previous findings. However, women who spend more time on Facebook report feeling less happy and feel less content with their lives. For men, this relationship was not evident. The study teaches that Facebook is used as a tool for affiliating with friends and family, as well as a personal showcase, where users show their positive sides. Herein lies also a danger. When Facebook users compare their own lives with others’ seemingly more successful careers and happy relationships, they may feel that their own lives are less successful in comparison.
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| 4. |
- Dumont, R.J., et al.
(författare)
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Advances in multi-megawatt, long pulse operation in Tore Supra
- 2012
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Ingår i: 39th EPS Conference on Plasma Physics 2012, EPS 2012 and the 16th International Congress on Plasma Physics; Stockholm; Sweden; 2 July 2012 through 6 July 2012; Code 96757. - 9781622769810 ; 2, s. 1118-1121
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Konferensbidrag (refereegranskat)
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| 5. |
- Dumont, R. J., et al.
(författare)
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Multi-megawatt, gigajoule plasma operation in Tore Supra
- 2014
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Ingår i: Plasma Physics and Controlled Fusion. - : IOP Publishing. - 1361-6587 .- 0741-3335. ; 56:7
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Tidskriftsartikel (refereegranskat)abstract
- Integrating several important technological elements required for long pulse operation in magnetic fusion devices, the Tore Supra tokamak routinely addresses the physics and technology issues related to this endeavor and, as a result, contributes essential information on critical issues for ITER. During the last experimental campaign, components of the radiofrequency system including an ITER relevant launcher (passive active multijunction (PAM)) and continuous wave/3.7 GHz klystrons, have been extensively qualified, and then used to develop steady state scenarios in which the lower hybrid (LH), ion cyclotron (IC) and electron cyclotron (EC) systems have been combined in fully stationary shots (duration similar to 150 s, injected power up to similar to 8MW, injected/extracted energy up to similar to 1 GJ). Injection of LH power in the 5.0-6.0MW range has extended the domain of accessible plasma parameters to higher densities and non-inductive currents. These discharges exhibit steady electron internal transport barriers (ITBs). We report here on various issues relevant to the steady state operation of future devices, ranging from operational aspects and limitations related to the achievement of long pulses in a fully actively cooled fusion device (e. g. overheating due to fast particle losses), to more fundamental plasma physics topics. The latter include a beneficial influence of IC resonance heating on the magnetohydrodynamic (MHD) stability in these discharges, which has been studied in detail. Another interesting observation is the appearance of oscillations of the central temperature with typical periods of the order of one to several seconds, caused by a nonlinear interplay between LH deposition, MHD activity and bootstrap current in the presence of an ITB.
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| 6. |
- Eriksson, Alexander, et al.
(författare)
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Vindkraft – en möjlighet förbiologisk mångfald på slätten?
- 2011
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Rapport (övrigt vetenskapligt/konstnärligt)abstract
- Kan man dra nytta av utbyggnaden av vindkraft för att skapa variation och nyalivsmiljöer för den vilda mångfalden i områden som domineras av intensivtslättjordbruk? Frågan analyseras i den här studien som är ett tvärvetenskapligtpilotprojekt som omfattar fältinventering, litteraturgenomgång, attitydundersökning,anläggning och demonstration av visningsbiotoper samt framtagande av en praktiskhandbok med åtgärdsförslag.Studien visar att småbiotoper (stenrösen, småvatten etc.) försvinner i samband medvindkraftetableringar. Samtidigt tillkommer restytor (tillfartsvägar, uppställningsplatseretc.). Dessa kan utnyttjas för anläggning av naturmiljöer. Arealen tillkomna ytor ärstörre än arealen försvunna småbiotoper. Givet planeringsramen för utbyggnad avvindkraft t.o.m. 2020 och givet att insatser vidtas för att förhindra att småbiotoperförstörs i samband med vindkraftetableringar är potentialen för småbiotoper i anslutningtill vindkraftverk i Sveriges slättbygder drygt 600 hektar. Jordbruksverkets bedömningär att det behövs minst 500 hektar nya och specifikt anpassade småbiotoper i direktanslutning till åkermark samt mer än 50 000 hektar i form av extensiva åtgärder (t.ex.fleråriga trädor och våtmarker) för att uppnå miljömålet ett rikt odlingslandskap.Vindkraftföretag är generellt sett positiva till att anlägga naturmiljöer. Markägare ärtveksamma mot vissa typer av anläggningar eftersom dessa riskerar att fångas av detgenerella biotopskyddet som fortsätter att gälla även efter det att tillståndet förvindkraftverket har gått ut. Störst skepsis mot att kombinera vindkraft med naturvårdfinns bland tillståndsmyndigheter.I rapporten lanseras begreppetkreotop. En kreotop är en anlagd naturmiljö. Genomatt utgå från färdiga kreotopkoncept slipper man att uppfinna hjulet på nytt vid varjenyanläggning. Kommunikationen mellan närboende, markägare, myndigheter ochvindkraftföretag blir smidigare om man från början har en gemensam bild av vad somkan åstadkommas.Studien, med dess exempel på konkreta åtgärder, avser restytor i anslutning tillvindkraftverk på åkermark. Exemplen är dock giltiga även i andra restmiljöer iåkerlandskapet. För att till fullo bedöma och för att följa upp den ekologiska potentialenav kreotoper är det angeläget att göra återkommande inventeringar.
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| 7. |
- Hillairet, J., et al.
(författare)
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Recent progress on lower hybrid current drive and implications for ITER
- 2013
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Ingår i: Nuclear Fusion. - : IOP Publishing. - 1741-4326 .- 0029-5515. ; 53:7
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Tidskriftsartikel (refereegranskat)abstract
- The sustainment of steady-state plasmas in tokamaks requires efficient current drive systems. Lower hybrid current drive is currently the most efficient method to generate a continuous additional off-axis toroidal plasma current and to reduce the poloidal flux consumption during the plasma current ramp-up phase. The operation of the Tore Supra ITER-like lower hybrid (LH) launcher has demonstrated the capability to couple LH power at ITER-like power densities with very low reflected power during long pulses. In addition, the installation of eight 700 kW/CW klystrons at the LH transmitter has allowed increasing the total LH power in long-pulse scenarios. However, in order to achieve pure stationary LH-sustained plasmas, some R&D is needed to increase the reliability of all the systems and codes, from radio-frequency (RF) sources to plasma scenario prediction. The CEA/IRFM is addressing some of these issues by leading a R&D programme towards an ITER LH system and by the validation of an integrated LH modelling suite of codes. In 2011, the RF design of a mode converter was validated at a low power. A 500 kW/5 s RF window is currently under manufacture and will be tested at a high power in 2012 in collaboration with the National Fusion Research Institute. All of this work aims to reduce the operational risks associated with the ITER steady-state operations.
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| 8. |
- Karlgren, Jussi, et al.
(författare)
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Semantic Topology
- 2014
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Ingår i: Proceedings of the 23d ACM international conference on Conference on information & knowledge management (CIKM '14). - New York : Association for Computing Machinery (ACM). - 9781450325981 ; , s. 1939-1942
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Konferensbidrag (refereegranskat)abstract
- A reasonable requirement (among many others) for a lexical or semantic component in an information system is that it should be able to learn incrementally from the linguistic data it is exposed to, that it can distinguish between the topical impact of various terms, and that it knows if it knows stuff or not.We work with a specific representation framework – semantic spaces – which well accommodates the first requirement; in this short paper, we investigate the global qualities of semantic spaces by a topological procedure – mapper – which gives an indication of topical density of the space; we examine the local context of terms of interest in the semantic space using another topologically inspired approach which gives an indication of the neighbourhood of the terms of interest. Our aim is to be able to establish the qualities of the semantic space under consideration without resorting to inspection of the data used to build it.
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| 9. |
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| 10. |
- Nilsson, Emelie, 1985, et al.
(författare)
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Comparative modelling of lower hybrid current drive with two launcher designs in the Tore Supra tokamak
- 2013
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Ingår i: Nuclear Fusion. - : IOP Publishing. - 1741-4326 .- 0029-5515. ; 53:8
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Tidskriftsartikel (refereegranskat)abstract
- Fully non-inductive operation with lower hybrid current drive (LHCD) in the Tore Supra tokamak is achieved using either a fully active multijunction (FAM) launcher or a more recent ITER-relevant passive active multijunction (PAM) launcher, or both launchers simultaneously. While both antennas show comparable experimental efficiencies, the analysis of stability properties in long discharges suggest different current profiles. We present comparative modelling of LHCD with the two different launchers to characterize the effect of the respective antenna spectra on the driven current profile. The interpretative modelling of LHCD is carried out using a chain of codes calculating, respectively, the global discharge evolution (tokamak simulator METIS), the spectrum at the antenna mouth (LH coupling code ALOHA), the LH wave propagation (ray-tracing code C3PO), and the distribution function (3D Fokker-Planck code LUKE). Essential aspects of the fast electron dynamics in time, space and energy are obtained from hard x-ray measurements of fast electron bremsstrahlung emission using a dedicated tomographic system. LHCD simulations are validated by systematic comparisons between these experimental measurements and the reconstructed signal calculated by the code R5X2 from the LUKE electron distribution. An excellent agreement is obtained in the presence of strong Landau damping (found under low density and high-power conditions in Tore Supra) for which the ray-tracing model is valid for modelling the LH wave propagation. Two aspects of the antenna spectra are found to have a significant effect on LHCD. First, the driven current is found to be proportional to the directivity, which depends upon the respective weight of the main positive and main negative lobes and is particularly sensitive to the density in front of the antenna. Second, the position of the main negative lobe in the spectrum is different for the two launchers. As this lobe drives a counter-current, the resulting driven current profile is also different for the FAM and PAM launchers.
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