247 research outputs found
Inter-ELM pedestal structure development in ASDEX Upgrade
Get PDFThe performance of a magnetically confined, fusion plasma is strongly impacted by the plasma edge, which is the boundary between the hot, confined plasma and the reactor walls. In a tokamak, which uses a toroidally axis-symmetric magnetic field configuration, a regime of improved plasma confinement, the high confinement mode (H-mode), has been observed. The confinement improvement originates from an edge transport barrier (ETB), which is accompanied by steep gradients of the plasma pressure, named pedestal. The maximum sustainable pedestal, i.e. the maximum pressure gradient, is usually set by an ideal magnetohydrodynamic limit, which if exceeded is leading to edge localised modes (ELMs). ELMs are instabilities that relax the pedestal and lead to a loss of the order of 10% from the plasma stored energy. The mechanisms, which set the pedestal structure before an ELM crash, keeping the pedestal stable up to this point, are not fully understood. Here, microturbulent instabilities, e.g. kinetic ballooning modes (KBMs), are expected to play an important role. The presented PhD thesis investigates the temporal development of the pedestal density and temperature profiles in between ELM crashes at the ASDEX Upgrade tokamak. The aims were comparisons of different plasma conditions, i.e. plasma collisionality (""), main isotope species and plasma shapes. Further, the impact of the conditions outside the confined plasma on the pedestal development was investigated. The extensive study of these parameters resulted in one key observation: The pedestal recovers in distinct phases in between ELM crashes with always the same sequence. Immediately after the ELM crash, the electron density (ne) pedestal is established, followed by the electron temperature (Te) pedestal. Finally, a period with constant pressure gradient appears, which can vary in duration. For a large range of ""¿ it has been found that the onset of radial magnetic fluctuations with frequencies above 200 kHz correlates with the stagnation of the electron pressure gradient in the pedestal. When these fluctuations are present, the gradients of the edge ne and Te are clamped and stable against an ELM onset. These fluctuations are signatures of microinstabilities which act in the pedestal. Their frequency, that is detected on the outboard, low field side (LFS), linearly correlates with the neoclas- sical estimate of the plasma edge background velocity, indicating that the instability propagates with the background flow. Furthermore, it has been found that the fluctuations have a global mode structure with toroidal mode numbers in the region of 11. The fluctuations are also observable on the inboard, high field side (HFS) of the tokamak with significant amplitude, which is not expected for a KBM that should have its dominant amplitude on the LFS. The comparison of hydrogen (H), deuterium (D) and helium (4He) plasmas has been performed to investigate the inter-ELM evolution of the pedestal structure in plasmas with different main ion species. The pedestal stability of all plasmas is in agreement with peeling-ballooning (PB) theory, which is independent of the main ion species mass. The inter-ELM pedestal evolution has the same sequence of recovery phases for all main ion species. Further, similar evolution of the inter-ELM magnetic signature as well as similar corresponding toroidal mode structures are found. In addition to the relaxation of the pedestal, ELMs introduce changes to the divertor and scrape-off layer (SOL) conditions. Their impact on the inter-ELM pedestal recovery was investigated with emphasis on the evolution of the ne pedestal. The particle and power fluxes expelled by the ELM crash lead to a re-attachment of the inner target plasma. After the ELM crash, the outer divertor target moves into a high recycling regime with high ne in front of the plate. On similar timescales, the inner target fully detaches and the high field side high density region (HFSHD) is formed reaching up to the HFS midplane. Neither the timescale of the appearance of the HFSHD nor the increase of the main chamber neutral fluxes fit the timescale of the ne pedestal, which is faster. It is found that the recovery phase of the ne pedestal is linked to the magnetic activity at the LFS midplane. The fluctuation amplitude is strongly reduced during the re-establishment of the ne pedestal. The plasma shape, respectively triangularity (¿), impacts on the pedestal stability. In dedicated experiments it was found that the higher pedestal top ne, which is observed at high ¿, is already established in the ne pedestal recovery phase. The lowering of the ELM repetition frequency (fELM) with increasing ¿ is related to longer pedestal recovery phases. In all investigated discharge intervals, the pre-ELM pedestal profiles are in agreement with PB theory. The detailed investigation of the pedestal recovery phases after an ELM crash showed for the first time that the sequence of recovery phases evolves independently of main ion species, plasma collisionality and plasma shape till the stability limit, which is well described by PB theory, is reached. Furthermore, it was evidenced that the fast increase of the ne pedestal is not dominated by the neutral dynamics in the divertor or main chamber because it occurs on faster timescales. The magnetic fluctuations, occurring in the pre-ELM phase with constant pressure gradient, were characterised in detail for the first time. It has been shown that the underlying instability is located close to the minimum of the radial electric field, exhibits a toroidal mode number of 11 and is also detectable on the HFS, indicating a significant peeling contribution.Die Leistungsfähigkeit eines magnetisch eingeschlossenen Fusionsplasmas hängt stark vom Plasmarand ab, der die Grenze zwischen dem heißen, eingeschlossenen Plasma und der Reaktorwand darstellt. In einem Tokamak, der eine toroidale, axialsymmetrische Magnetfeldkonfiguration besitzt, wurde ein Regime mit verbessertem Plasmaeinschluss, die High Confinement Mode (H-Mode), beobachtet. Der verbesserte Einschluss wird durch eine Randtransportbarriere (ETB) bedingt, welche mit der Formierung von steilen Gradienten des Plasmadrucks einhergeht, die als Pedestal bezeichnet werden. Das maximal erreichbare Pedestal, d.h. der maximale Druckgradient, ist normalerweise durch ein magnetohydrodynamisches Limit begrenzt, dessen überschreitung zu sogenannten Edge Localised Modes (ELMs) führt. ELMs sind Instabilitäten, die das Pedestal abflachen und zu einem Verlust von rund 10 % der im Plasma gespeicherten Energie führen. Die Mechanismen, die die Pedestalstruktur vor einem ELM Ausbruch bestimmen, sind nicht vollständig verstanden. Es wird erwartet, dass mikroturbulente Instabilitäten, z.B. Kinetische Ballooning Moden (KBMs), hierbei eine wichtige Rolle spielen. Die vorgelegte Dissertation untersucht die zeitliche Entwicklung der Dichteund Temperaturprofile des Pedestals zwischen ELM Ausbrüchen am ASDEX Upgrade Tokamak. Die Ziele waren Vergleiche von unterschiedlichen Plasmabedingungen, wie der Kollisionalität ("") des Plasmas, verschiedenen Hauptionenspezies und unterschiedlichen Plasmaformen. Weiters wurde der Einfluss der Bedingungen außerhalb des eingeschlossenen Plasmas auf die Pedestalentwicklung untersucht. Die umfassende Studie dieser Parameter resultierte in einer Schlüsselbeobachtung: Das Pedestal baut sich in unterschiedlichen Phasen zwischen ELM Ausbrüchen auf, deren Abfolge immer gleich ist. Unmittelbar nach dem ELM Ausbruch wird das Elektronendichtepedestal hergestellt, anschließend das Elektronentemperaturpedestal. Abschließend tritt eine Phase mit konstanten Druckgradienten auf, die unterschiedlich lange andauern kann. über einen weiten Bereich von "" wurde beobachtet, dass das Einsetzen von Magnetfeldfluktuationen mit Frequenzen über 200 kHz mit einer Stagnation des Elektronendruckgradienten im Pedestal korreliert. Wenn diese Fluktuationen vorhanden sind, steigen die Gradienten von Elektronendichte und -temperatur nicht weiter an und sind stabil gegen einen ELM Ausbruch. Die Fluktuationen sind Signatur von Mikroinstabilitäten, die sich im Pedestal befinden. Ihre Frequenz, die an der Außenseite, der i " ""Niederfeldseite (LFS), detektiert wird, korreliert linear mit der neoklassischen Approximation der Hintergrundgeschwindigkeit am Plasmarand, was indiziert, dass sich die Instabilität mit der Hintergrundgeschwindigkeit des Plasmas bewegt. Darüber hinaus konnte den Fluktuationen eine globale Modenstruktur mit toroidalen Modenzahlen im Bereich von 11 zugeordnet werden. Die Fluktuationen sind auch auf der Innenseite, der Hochfeldseite (HFS), des Tokamaks mit signifikanter Amplitude messbar, was für eine KBM nicht erwartet wird, deren dominante Amplitude auf der LFS liegen sollte. Ein Vergleich von Wasserstoff (H), Deuterium (D) und Helium (4He) Plasmen wurde durchgeführt, um die inter-ELM Entwicklung der Pedestalstruktur in Plasmen mit verschiedenen Hauptionenspezies zu untersuchen. Die Pedestalstabilität aller Plasmen stimmt mit der "Peeling-Ballooning" (PB) Theorie überein, die unabhängig von der Hauptionenspeziesmasse ist. Die inter-ELM Pedestalentwicklung zeigt dieselbe Phasensequenz im Pedestalaufbau für alle Hauptionenspezies. Weiters wurde eine ähnliche inter-ELM Signatur der magnetischen Fluktuationen sowie gleiche zugehörige toroidale Modenstrukturen gemessen. Zusätzlich zum Abflachen des Pedestals beeinflussen ELMs das Plasma im Divertor und in der Abschälschicht (SOL). Der Einfluss der geänderten Bedingungen außerhalb des eingeschlossenen Plasmas auf die inter-ELM Pedestalentwicklung wurde untersucht, wobei der Fokus auf der Entwicklung der Elektronendichte lag. Die Teilchenund Leistungsflüsse, die durch den ELM ausgestoßen werden, führen zu einem "Re-Attachment" des Plasmas im inneren Divertor. Nach dem ELM Ausstoß geht der äußere Divertor in ein Regime mit hohem Neutralenrecycling über, welches eine hohe Elektronendichte vor den Divertorkacheln bedingt. Auf ähnlichen Zeitskalen hebt sich das Plasma vollständig vom inneren Divertor ab ("Detachment") und eine Hochfeldseitenhochdichteregion (HFSHD) formiert sich, die bis zur Mittelebene auf der HFS ausgedehnt ist. Weder die Zeitskala der Formation der HFSHD noch der Anstieg der Neutralenflüsse in der Hauptkammer weisen dieselbe Zeitskala wie das Elektronendichtepedestal auf, das sich schneller aufbaut. Es wurde beobachtet, dass der Aufbau des Elektronendichtepedestals mit der magnetischen Aktivität an der LFS Mittelebene verknüpft ist, deren Amplitude während des schnellen Aufbaus des Elektronendichtepedestals stark reduziert ist. Die Form des Plasmas, beziehungsweise die Triangularität, beeinflusst die Stabilität des Pedestals. In dedizierten Experimenten wurde beobachtet, dass die erhöhte Elektronendichte, die in hochtriangulären Plasmen auftritt, bereits während der Phase des Elektronendichteaufbaus erreicht wird. Die Erniedrigung der ELM Frequenz bei größerer Triangularität ist mit längeren Aufbauphasen des Pedestals verbunden. In sämtlichen untersuchten Entladungsintervallen befanden sich die pre-ELM Pedestalprofile in übereinstimmung mit der PB Theorie. Die detaillierte Untersuchung der einzelnen Phasen des Wiederaufbaus der Randgradienten nach einem ELM zeigte erstmals, dass die Phasensequenz unabhängig von Hauptionenspezies, Kollisionalität und Form des Plasmas immer gleich abläuft, bis die Stabilitätsgrenze, die gut mit der PB Theorie beschrieben werden kann, erreicht ist. Außerdem konnte gezeigt werden, dass der schnelle Anstieg des Elektronendichtepedestals nicht von der Dynamik der Neutralen im Divertor oder Hauptraum dominiert wird, da er auf schnelleren Zeitskalen erfolgt. Die magnetischen Fluktuationen, die in der Phase vor dem ELM auftreten, in der sich der Druckgradient nicht mehr ändert, konnten erstmals genauer charakterisiert werden. Es wurde gezeigt, dass die zugrundeliegende Instabilität im Minimum des radialen elektrischen Feldes lokalisiert ist, eine toroidale Modenzahl von 11 aufweist und auch auf der HFS messbar ist, was für einen signifikanten "Peeling"-Anteil spricht
Traducir el Quijote
No full textSe examinan y comparan en este artículo las traducciones francesas del Quijote, desde la de César Oudin y François de Rosset (1614-1618), las de Filleau de Saint-Martin (1677-1678), Florian (1799), Louis Viardot (1836), y las de Xavier de Cardaillac y Jean Labarthe (1923-1926), Jean Cassou (1928) y Francis de Miomandre (1935), hasta las más recientes de Aline Schulman (1997) y Jean Canavaggio (2001).L’auteur examine et compare ici les traductions françaises du Quichotte, depuis celle de César Oudin et de François de Rosset (1614-1618), celles de Filleau de Saint-Martin (1677-1678), de Florian (1799), de Louis Viardot (1836), et celles de Xavier de Cardaillac et de Jean Labarthe (1923-1926), de Jean Cassou (1928) et Francis de Miomandre (1935), jusqu’aux traductions plus récentes d’Aline Schulman (1997) et de Jean Canavaggio (2001).The author examines and compares French translations of Don Quixote, from that of César Oudin and François de Rosset (1614-1618), those of Filleau de Saint-Martin (1677-1678), Florian (1799), Louis Viardot (1836), and those of Xavier de Cardaillac and Jean Labarthe (1923-1926), Jean Cassou (1928) and Francis de Miomandre (1935), to the most recent ones by Aline Schulman (1997) and Jean Canavaggio (2001)
CHOREOGRAPHIC DEVICES 1
Get PDFChoreography is no longer simply the art of making dances: complex models of the choreographic are increasingly tasked to investigate and animate the intersecting spatial, corporeal, affective and informational dimensions of being entangled with the world.
What kind of choreographic arrangements can we compose to put diverse thinkers and practitioners in relation to one another? What kinds of time spaces can be plotted, imagined and enacted, when the symposium itself is choreographed and takes shape as a sequence of sessions, each brought to life by different hosts? Through contributions and interventions by over 30 international protagonists from across an expanded ecology of practices, this multi-format symposium speculates on the affordances of choreographic (re-)arrangements and their complex forms of co-production, and tests how organisational formats, material assemblages, and modes of being alongside each other, might be choreographed otherwise.
Choreographic Devices assembles contributors operating across multiple disciplinary boundaries, including Murat Adash (artist), Edwina Ashton (artist), D. Graham Burnett (teacher, writer, interdisciplinary maker), Ofri Cnaani (artist), Augusto Corrieri (artist), Critical Interruptions (Diana Damian Martin + Bojana Janković) (artists), Lou Forster (art historian, curator), keyon gaskin (artist), Martin Hargreaves (dramaturg, writer, performer), Vlatka Horvat (artist), Lenio Kaklea (choreographer, dancer, writer), Sarah Keenan (writer, theorist), André Lepecki (performance studies theorist, curator), Jason Edward Lewis (digital media theorist, poet, software designer), Raimundas Malasauskas (silk painter), Tavi Meraud (artist), Samaneh Moafi (architect, investigator), Rebecca Moss (artist), Harun Morrison (artist, writer), Sandra Noeth (body theorist, curator), Lara Pawson (writer), Daniela Perazzo (dance and performance theorist), Stamatia Portanova (theorist), Filipa Ramos (writer, curator), Irit Rogoff (educator, theorist), Florian Roithmayr (artist), Georgia Sagri (artist), Edgar Schmitz (artist), SERAFINE1369 (artist), Noémie Solomon (theorist, curator), Matthias Sperling (artist, choreographer, performer), Starhawk (author, permaculture designer, teacher, activist), Soap Bubble (complex mathematical problem), and Arkadi Zaides (choreographer)
Cytosim codebase extensions for a 2D T cell model
No full textCode is used in "Kinesin-4 KIF21B limits microtubule growth to allow rapid centrosome polarization in T cells", by Peter Jan Hooikaas, Hugo G.J. Damstra, Oane J. Gros, Wilhelmina E. van Riel, Maud Martin, Yesper T.H. Smits, Jorg van Loosdregt, Lukas C. Kapitein, Florian Berger, Anna Akhmanova. The code is an extended form of Cytosim, made by François Nedelec (https://gitlab.com/f.nedelec/cytosim). Only the minor extensions outside of the base code, listed in the README.txt file, can be attributed to author O.J.Gros, other authors are taken from the registered contributors on the cytosim gitlab, as having worked on the code base that was extended
Frustration and isoperimetric inequalities for signed graphs
No full textAbstractLet Gσ=(V,E,σ) be a connected signed graph. Using the equivalence between signed graphs and 2-lifts of graphs, we show that the frustration index of Gσ is bounded from below and above by expressions involving another graph invariant, the smallest eigenvalue of the (signed) Laplacian of Gσ. From the proof, stricter bounds are derived. Additionally, we show that the frustration index is the solution to a l1-norm optimization problem over the 2-lift of the signed graph. This leads to a practical implementation to compute the frustration index. Also, leveraging the 2-lifts representation of signed graphs, a straightforward proof of Harary’s theorem on balanced graphs is derived. Finally, real world examples are considered
Correction to: System characterization of a human-sized 3D real-time magnetic particle imaging scanner for cerebral applications (Communications Engineering, (2024), 3, 1, (47), 10.1038/s44172-024-00192-6)
No full textCorrection to: Communications Engineeringhttps://doi.org/10.1038/s44172-024-00192-6, published online 14 March 2024 Author correction: In the original version of this Article, financial support from the Open Access Publication Fund of UKE - Universitätsklinikum Hamburg-Eppendorf was not acknowledged. This has now been corrected in both the PDF and HTML versions of the Article. The Acknowledgements section needs to be revised to: We thank Florian Sevecke for technical support during the realization of numerous scanner components. We further thankfully acknowledge the financial support by the German Research Foundation (DFG, grant numbers KN 1108/7-1 and GR 5287/2-1). We also thank the developers of Makie.jl supporting us by answering technical questions when creating Figs. 3 and 4. Finally, we are grateful to Christian Findeklee for their discussions and insights into resonant circuit decoupling. We acknowledge financial support from the Open Access Publication Fund of UKE - Universitätsklinikum Hamburg-Eppendorf
Correction to: System characterization of a human-sized 3D real-time magnetic particle imaging scanner for cerebral applications (Communications Engineering, (2024), 3, 1, (47), 10.1038/s44172-024-00192-6)
No full textCorrection to: Communications Engineeringhttps://doi.org/10.1038/s44172-024-00192-6, published online 14 March 2024 Author correction: In the original version of this Article, financial support from the Open Access Publication Fund of UKE - Universitätsklinikum Hamburg-Eppendorf was not acknowledged. This has now been corrected in both the PDF and HTML versions of the Article. The Acknowledgements section needs to be revised to: We thank Florian Sevecke for technical support during the realization of numerous scanner components. We further thankfully acknowledge the financial support by the German Research Foundation (DFG, grant numbers KN 1108/7-1 and GR 5287/2-1). We also thank the developers of Makie.jl supporting us by answering technical questions when creating Figs. 3 and 4. Finally, we are grateful to Christian Findeklee for their discussions and insights into resonant circuit decoupling. We acknowledge financial support from the Open Access Publication Fund of UKE - Universitätsklinikum Hamburg-Eppendorf.3
Three necessary conditions for establishing effective Sustainable Development Goals in the Anthropocene
Get PDFabstract: The purpose of the United Nations-guided process to establish Sustainable Development Goals is to galvanize governments and civil society to rise to the interlinked environmental, societal, and economic challenges we face in the Anthropocene. We argue that the process of setting Sustainable Development Goals should take three key aspects into consideration. First, it should embrace an integrated social-ecological system perspective and acknowledge the key dynamics that such systems entail, including the role of ecosystems in sustaining human wellbeing, multiple cross-scale interactions, and uncertain thresholds. Second, the process needs to address trade-offs between the ambition of goals and the feasibility in reaching them, recognizing biophysical, social, and political constraints. Third, the goal-setting exercise and the management of goal implementation need to be guided by existing knowledge about the principles, dynamics, and constraints of social change processes at all scales, from the individual to the global. Combining these three aspects will increase the chances of establishing and achieving effective Sustainable Development Goals.Resilience Alliance requires that use of any work in whole or part be cited correctly; Author(s). Year. Title. Journal Volume (Issue) : Article Number
Ice-structure interaction in the Baltic Sea: defining a feasibility map for monopiles
No full textThe increasing popularity of offshore wind as a result of the demand for renewable energy, forces the industry to consider the development of wind farms in sub-arctic areas. One of these areas is the Baltic Sea, where the potential for wind energy is very large, but which is also prone to the occurrence of ice. For the design of offshore foundations it is paramount that ice-structure interaction is appropriately considered as ice-induced vibrations are known to significantly increase the loads. As a result, ice-mitigating measures may need to be included in the design. However, such measures will substantially increase the cost estimates requiredfor competitive tenders. Hence it is valuable for developers to have early screening tools to assess this. The aim of the research was to provide a ‘feasibility map’, which predicts the necessity for ice-mitigating measures in the entire Baltic region. Feasibility of monopiles was considered both technically and economically. The former by imposing design, installation & fabrication constraints and the latter was measured in terms of weight increase of monopiles. Offshore and Dredging Engineerin
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