| 1. |
- Joffrin, E., et al.
(författare)
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Overview of the JET preparation for deuterium-tritium operation with the ITER like-wall
- 2019
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Ingår i: Nuclear Fusion. - : IOP Publishing. - 1741-4326 .- 0029-5515. ; 59:11
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Forskningsöversikt (refereegranskat)abstract
- For the past several years, the JET scientific programme (Pamela et al 2007 Fusion Eng. Des. 82 590) has been engaged in a multi-campaign effort, including experiments in D, H and T, leading up to 2020 and the first experiments with 50%/50% D-T mixtures since 1997 and the first ever D-T plasmas with the ITER mix of plasma-facing component materials. For this purpose, a concerted physics and technology programme was launched with a view to prepare the D-T campaign (DTE2). This paper addresses the key elements developed by the JET programme directly contributing to the D-T preparation. This intense preparation includes the review of the physics basis for the D-T operational scenarios, including the fusion power predictions through first principle and integrated modelling, and the impact of isotopes in the operation and physics of D-T plasmas (thermal and particle transport, high confinement mode (H-mode) access, Be and W erosion, fuel recovery, etc). This effort also requires improving several aspects of plasma operation for DTE2, such as real time control schemes, heat load control, disruption avoidance and a mitigation system (including the installation of a new shattered pellet injector), novel ion cyclotron resonance heating schemes (such as the three-ions scheme), new diagnostics (neutron camera and spectrometer, active Alfven eigenmode antennas, neutral gauges, radiation hard imaging systems...) and the calibration of the JET neutron diagnostics at 14 MeV for accurate fusion power measurement. The active preparation of JET for the 2020 D-T campaign provides an incomparable source of information and a basis for the future D-T operation of ITER, and it is also foreseen that a large number of key physics issues will be addressed in support of burning plasmas.
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| 2. |
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| 3. |
- Carvajal, Gisela, 1983, et al.
(författare)
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Comparison between current fields detected with infrared radiometry and modeled currents around Sweden
- 2013
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Ingår i: 33rd IEEE International Geoscience and Remote Sensing Symposium (IGARSS); 2013, Melbourne. - 9781479911141 ; , s. 1270-1273
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Konferensbidrag (refereegranskat)abstract
- The understanding of the relationship between surface currents derived from weather models and remote sensing data is essential in order to produce an improved and integrated surface current information of high quality and resolution. The large availability of satellite derived infrared radiometer data at the high latitudes of the coastal waters surrounding Sweden makes the Maximum Cross Correlation (MCC) method a feasible alternative to produce real time measurements of surface currents. This work compares current retrievals from the MCC method and model data around Sweden. Our results indicate a similar magnitude for both sources of current fields in most of the locations. However, there exist small discrepancies in the localization of the larger current values. Also, the MCC retrievals generally present more features than the modeled ones. Possible reasons for these discrepancies might be the MCC detection of circulation patterns not predicted by the model, or the depreciation in the MCC performance due to the influence of diurnal variability of the sea surface temperature, wind driven mixing due to upwelling or tides.
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| 4. |
- Enjin, Anders, et al.
(författare)
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Developmental disruption of recurrent inhibitory feedback results in compensatory adaptation in the Renshaw cell-motor neuron circuit
- 2017
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Ingår i: Journal of Neuroscience. - 0270-6474 .- 1529-2401. ; 37:23, s. 5634-5647
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Tidskriftsartikel (refereegranskat)abstract
- When activating muscles, motor neurons in the spinal cord also activate Renshaw cells, which provide recurrent inhibitory feedback to the motor neurons. The tight coupling with motor neurons suggests that Renshaw cells have an integral role in movement, a role that is yet to be elucidated. Here we used the selective expression of the nicotinic cholinergic receptor α2 (Chrna2) in mice to genetically target the vesicular inhibitory amino acid transporter (VIAAT) in Renshaw cells. Loss of VIAAT from Chrna2Cre-expressing Renshaw cells did not impact any aspect of drug-induced fictive locomotion in the neonatal mouse or change gait, motor coordination, or grip strength in adult mice of both sexes. However, motor neurons from neonatal mice lacking VIAAT in Renshaw cells received spontaneous inhibitory synaptic input with a reduced frequency, showed lower input resistance, and had an increased number of proprioceptive glutamatergic and calbindin-labeled putative Renshaw cell synapses on their soma and proximal dendrites. Concomitantly, Renshaw cells developed with increased excitability and a normal number of cholinergic motor neuron synapses, indicating a compensatory mechanism within the recurrent inhibitory feedback circuit. Our data suggest an integral role for Renshaw cell signaling in shaping the excitability and synaptic input to motor neurons.
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| 5. |
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| 6. |
- Johansson, Malin, 1980, et al.
(författare)
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Remote sensing for risk analysis of oil spills in the Arctic Ocean
- 2013
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Ingår i: Proceedings of the ESA Living Planet Symposium 2013, 9 - 13 September 2013, Edinburgh, UK.
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Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
- Predicted decreases in sea-ice extent and shift from multiyear ice to seasonal ice open up for commercial shipping routes within the Arctic. With expected further growth of maritime activities the potential threat of accidents is increasing. Moreover, there is a lack of information on how an oil spill would affect the Arctic Ocean environment. A robust tool following international risk assessment standards is therefore vital to 1) try to prevent oil spills through use of scenario runs and 2) increase the possibilities to delimit the damage should a spill occur. We use remote sensing images to extract information about oil spill redistribution mechanisms. This combined with information about estimated volume, type ofoil and ecotoxicological data enables identification of areas in the Arctic Ocean especially vulnerable to maritimeactivities. We also include estimates on the probability ofan oil spill occurrence.
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| 7. |
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| 8. |
- Svensson, Nina, 1988-, et al.
(författare)
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Ride the future – strategisk satsning : fem studier med fokus på autonoma bussar i städer
- 2022
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Rapport (övrigt vetenskapligt/konstnärligt)abstract
- Fem noga utvalda förstudier har initierats av VTI som en del i den strategiska satsningen ”Ride the future” kopplad till framtidens mobilitetslösningar. Förstudiernas titel är följande: ▪ Databearbetning och visualisering av mobila luftkvalitetsmätningar. ▪ SUMO och Unreal Engine för co-simulering. ▪ Exploring spatio-temporal accessibility in Lambohov: a pre-study. ▪ Vägytans betydelse för vibrationer och komfort i långsamma fordon. ▪ Infrastrukturbehov vid busshållplatser. Föreliggande pm innehåller en kort beskrivning av studierna och den mer utförliga redovisningen återfinns i bilagan.
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| 9. |
- Wilkie, George, 1983, et al.
(författare)
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First principles of modelling the stabilization of microturbulence by fast ions
- 2018
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Ingår i: Nuclear Fusion. - : IOP PUBLISHING LTD. - 0029-5515 .- 1741-4326. ; 58:8
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Tidskriftsartikel (refereegranskat)abstract
- The observation that fast ions stabilize ion-temperature-gradient-driven microturbulence has profound implications for future fusion reactors. It is also important in optimizing the performance of present-day devices. In this work, we examine in detail the phenomenology of fast ion stabilization and present a reduced model which describes this effect. This model is derived from the high-energy limit of the gyrokinetic equation and extends the existing 'dilution' model to account for nontrivial fast ion kinetics. Our model provides a physically-transparent explanation for the observed stabilization and makes several key qualitative predictions. Firstly, that different classes of fast ions, depending on their radial density or temperature variation, have different stabilizing properties. Secondly, that zonal flows are an important ingredient in this effect precisely because the fast ion zonal response is negligible. Finally, that in the limit of highly-energetic fast ions, their response approaches that of the 'dilution' model; in particular, alpha particles are expected to have little, if any, stabilizing effect on plasma turbulence. We support these conclusions through detailed linear and nonlinear gyrokinetic simulations.
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| 10. |
- Ahlström, Christer, et al.
(författare)
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Validating speed and road surface realism in VTI driving simulator III
- 2012
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Rapport (övrigt vetenskapligt/konstnärligt)abstract
- Nya simulatormodeller för vibrationer, ljud och grafik har utvecklats och implementerats i VTI:S fordonssimulator III. Syftet med denna studie är att validera simulatorn med avseende på hastighet och återgivandet av olika vägyteparametrar. Tjugofyra försökspersoner deltog i studien. De fick köra en och samma rutt i såväl simulator III som på verklig väg. Tre vägavsnitt med olika kvalitet på vägytan, från mycket slät till ganska ojämn, ingick i försöket. Såväl den objektiva förarparametern hastighet som olika subjektiva parametrar avseende förarens uppfattning om vägytans egenskaper (jämnhet, tysthet, komfort) jämfördes. Ett vägavsnitt med skiftande hastighetsgränser var av speciellt intresse. Ingen signifikant skillnad kunde noteras mellan körning i simulator och på verklig väg vare sig avseende hastighet (på avsitt med konstant hastighetsgräns) eller gradering av jämnhet och tysthet. För sträckan med skiftande hastighetsgränser fanns dock en signifikant skillnad mellan hastigheten i bil jämfört med hastigheten i simulator, trots liknande hastighetsprofiler. Såväl accelerationerna som retardationerna var snabbare i simulatorn. Vägkomforten graderades högre i bil än i simulator, men i båda fallen var tendensen den att slätare vägar gav högre värdering av komforten. Dessa resultat indikerar absolut validitet för graderingen av jämnhet och tysthet och för det objektiva måttet hastighet, medan relativ validitet indikerades för såväl hastighet vid skylt för hastighetsändring som för gradering av komfort.
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