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  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
1

Experimental measurement of energy transport in tokamak plasmas

Meyerson, Dmitry 17 February 2011 (has links)
A tokamak plasma near equilibrium can be perturbed with modulated power sources, such as modulated electron cyclotron heating, or repeated cold pulse application. Temperature response to cyclical changes in profiles parameters that are induced by modulated power deposition can be used to test theoretical transport models as well as improve experimental phenomenology used to optimize tokamak performance. The goal of this document to discuss some methods of analyzing electron temperature data in the context of energy transport. Specific experiments are considered in order to demonstrate the methods discussed, as well as to examine the electron energy transport properties of these shots. Electron cyclotron emission provides a convenient way to probe electron temperature for plasmas in thermal equilibrium. We can show that in tokamak devices,barring harmonic overlap, we can associate a particular frequency with a particular location in a tokamak, by carefully selecting the detection frequency and line of sight of the responsible antenna. ECE radiometers typically measure temperature at tens of locations at a time with a spatial resolution on the order of a few centimeters. Tracking the evolution of electron energy flux depends on careful analysis of the resulting data. The most straightforward way to analyze temperature perturbations is to simply consider various harmonics of the driving source and consider the corresponding harmonics in the temperature. We can analyze the phase and amplitude of the response to find the effective phase velocity of the perturbation which can in turn be related to parameters in the selected heat flux model. The most common example is to determine , the diffusion coefficient that appears in the linearized energy transport equation. The advantages and limitation of this method will be discussed in detail in Section 3. A more involved approach involves using the perturbed temperature data to compute modulated heat flux at any given point in the perturbation cycle, rather than using the temperature data directly. As before the heat flux can then be related to measured profile parameters and theoretical predictions. The advantages and limitations of this approach will be discussed in more detail. Both of the mentioned analysis methods are used to probe electron energy transport in a quiescent H mode (QH mode) shot conducted at DIIID. The nature of the internal transport barrier that is present in the shot is considered in light of the results. / text
2

Chaos hamiltonien dans les plasmas de fusion / Hamiltonian chaos into fusion plasmas

Cambon, Benjamin 16 September 2015 (has links)
Notre travail se portera sur l’étude de la trajectoire exacte d’une particule chargée dans un champ magnétique de type tokamak. Nous considérerons des particules tests plongées dans un champ magnétique indépendant du temps. Par définition, elles n’interagissent pas entre-elles et n’ont aucun effet sur le champ magnétique. Le but de notre étude sera alors de mettre en évidence des différences de comportement majeures entre d’une part les trajectoires des particules et d’autre part les lignes de champ magnétique. Nous commencerons dans une première partie par expliciter nos motivations. Les techniques employées aujourd’hui pour simuler la dynamique d’un plasma de fusion reposent sur des modèles magnétohydrodynamiques ou gyrocinétiques dont les hypothèses sont parfois contestables. Nous exposerons ensuite l’approche hamiltonienne choisie pour simuler la trajectoire exacte d’une particule et introduirons les différents outils dont nous aurons besoin. Dans la seconde partie, nous présenterons brièvement l’outil numérique développé qu mettra en évidence des différences de comportements importantes entre ligne de champ et trajectoire de particule. Dans un premier temps, nous exhiberons du chaos de trajectoire en présence de ligne de champ intégrable en ajoutant au champ magnétique idéal une perturbation. Un même résultat sera démontré dans le cas d’un champ magnétique idéal axisymétrique. Ce résultat entrainera des questions importantes autour de l’invariance du moment magnétique μ. Enfin, la dernière partie de ce manuscrit portera sur le comportement des particules tests en présence d’un champ magnétique potentiellement chaotique. / We will work on the study of the exact trajectory of a charged particle within a magnetic field of the tokamak type. We will consider test particles immerged into a timeindependent magnetic field. They don’t interact with each other and have no effect on the magnetic field. The objective of our study will be to prove major behaviour differences between the particles’ trajectories and the magnetic field lines. We will start in part one by making our motivations explicit and especially see that the technics used nowadays to simulate the dynamic of fusion plasma are based on magnetohydrodynamic or gyrokinetic models which hypotheses are sometimes debatable. We will then present the Hamiltonian approach chosen to simulate the exact trajectory of a particle, and will introduce the various tools we will later need, including the characterizationof chaotic phenomena. we will briefly the developed digital tool which will highlight behaviour differences between field line and particle trajectory. Initially, we will exhibit trajectory chaos in the presence of integrable field lines by adding a perturbation to the ideal magnetic field. In a second phase, we will show that a similar result can be proven in the case of an asymmetrical ideal magnetic field. This result will lead to substantial questions regarding the invariance of the μ. The last part of this manuscript will finally focus on the behaviour of the test particles in the presence of a potentially chaotic magnetic field.
3

"Klimatsmartare förpackning" och "ekologiskt" : En undersökning för hur miljöetiketter påverkar konsumentens Intention To Buy och Willingness To Pay.

Ekebergh, Charlotta, To, Thai January 2021 (has links)
Sammanfattning Titel: "Klimatsmartare förpackning" och "ekologiskt" En undersökning för hur miljöetiketter påverkar konsumentens Intention To Buy och Willingness To Pay. Nivå: Examensarbete på Grundnivå (kandidatexamen) i ämnet företagsekonomi Författare: Charlotta Ekebergh och Thai To Handledare: Patrik Sörqvist Datum: juni, 2021 Syfte: Syftet med föreliggande studie var att undersöka konsumentens intention to buy (ITB) och willingness to pay (WTP) för olika typer av vinförpackningar samt att se om dessaskattningar kan påverkas genom Systembolagets märkningar "klimatsmartare förpackning" och "ekologiskt". Studien undersökte även om det finns några skillnader mellanrespondenternas ITB och WTP för självskattad miljövänlighet, enligt studiens miljöindex. Metod: Studien utfördes med ett faktoriell kvasiexperiment (4x4) med totalt 102 deltagare, där respondenterna fick ge svar utefter en 7-gradig Likertskala i en enkätundersökning innehållandes manipulerade bilder för att besvara studiens hypoteser. Resultat & Analys: Denna studie visar att respondenternas skattade intention att köpa (ITB) och betalningsvilja (WTP), skiljer sig mycket åt beroende på förpackningstyp för vin. Dessa skattningar har i vissa fall visat sig kunna påverkas av Systembolaget etiketter "klimatsmartare förpackning" och "ekologiskt". Resultaten visade att det i stora drag stämmer överens med tidigare empiriska resultat men att även motsättningar har kunnat bekräftas genom statistiskt signifikanta resultat. Examensarbetets bidrag: Denna studie visar signifikanta skillnader för respondenternas skattade intention att köpa (ITB) och betalningsvilja (WTP) för de olika förpackningsalternativen för vin i kombination med de olika etiketterna "klimatsmartare förpackning" och "ekologiskt". Resultatet från studien kan tänkas indikera konsumenters intention att köpa (ITB) och betalningsvilja (WTP) för vin i alternativa förpackningar i kombination med de olika etiketterna. Förslag till fortsatt forskning: Denna studie föreslår vidare forskning där man undersöker konsumenters faktiska köp på Systembolaget i förhållande till konsumentens skattade ITB förekologiska produkter och produkter i klimatsmartare förpackningar. Ytterligare förslag ges för vidare forskning att undersöka om liknande förhållanden råder för andra produktgrupper på Systembolaget. Samt att undersöka konsumenters intention att köpa (ITB) och betalningsvilja (WTP) för alternativa, klimatsmartare förpackningar för andra typer av livsmedel. Nyckelord: Wine, Intention To Buy (ITB), Willingness To Pay (WTP), Organic, Label,Packaging / Abstract Title: "Klimatsmartare förpackning" and "ekologiskt"A study researching how climate friendly labels affect the consumers’ Intention To Buy and Willingness To Pay. Level: Student theses, final assignment for Bachelor Degree in Business Administration Author: Charlotta Ekebergh and Thai To Supervisor: Patrik Sörqvist Date: June – 2021 Aim: The aim for this study was to research whether the consumers intention to buy (ITB)and willingness to pay (WTP) for different types of wine packaging could be altered through the use of Systembolaget’s labels, "klimatsmartare förpackning" and "ekologiskt". (In english the labels would read "climate friendlier packaging" and "organic"). Further, this study aimed to research whether any differences between the respondents ITB and WTP occurs according to the respondent’s self-evaluated environmental friendliness, and this studies’ environmental index. Method: This study was performed with a factorial Quasi-experiment (4x4) with a total of 102 participants, responding through a 7-grade Likert scale in a questionnaire containing manipulated images to answer the hypotheses of this study. Result & Conclusions: This study shows that the respondents estimated intention to buy (ITB) and willingness to pay (WTP) differs greatly depending on the type of wine packaging. These estimates have in some cases been influenced by the Systembolaget’s labels "klimatsmartare förpackning" and "ekologiskt". The results from this study largely showed that they are in line with previous empirical results. However, this study has proven some contradictions to be statistically significant. Contribution of the thesis: This study shows statistically significant differences between therespondents estimated intention to buy (ITB) and willingness to pay (WTP) for the different types of wine packaging in combination with the two labels "klimatsmartare förpackning" and "ekologiskt". The results show an actual indication of consumers intention to buy (ITB) and willingness to pay (WTP) for wine in different types of packaging in combination with the two labels. Suggestions for future research: This study suggests future research to investigate consumers actual purchases at Systembolaget in relation to their estimated intention to buy (ITB) of organic products and products in a more climate friendly packaging. Further suggestions are to investigate whether similar relationships occur for other types of products at Systembolaget. Lastly, investigate whether the consumers intention to buy (ITB) and willingnessto pay (WTP) for alternative, more climate friendly packaging for other types of food. Key words: Wine, Intention To Buy (ITB), Willingness To Pay (WTP), Organic, Label, Packaging
4

Migrating Myofibroblastic Iliotibial Band-Derived Fibroblasts Represent a Promising Cell Source for Ligament Reconstruction

Schwarz, Silke, Gögele, Clemens, Ondruschka, Benjamin, Hammer, Niels, Kohl, Benjamin, Schulze-Tanzil, Gundula 10 January 2024 (has links)
The iliotibial band (ITB) is a suitable scaffold for anterior cruciate ligament (ACL) reconstruction, providing a sufficient mechanical resistance to loading. Hence, ITB-derived fibroblasts attract interest for ligament tissue engineering but have so far not been characterized. This present study aimed at characterizing ITB fibroblasts before, during, and after emigration from cadaveric ITB explants to decipher the emigration behavior and to utilize their migratory capacity for seeding biomaterials. ITB and, for comparison, ACL tissues were assessed for the content of alpha smooth muscle actin (αSMA) expressing fibroblasts and degeneration. The cell survival and αSMA expression were monitored in explants used for cell isolation, monolayer, self-assembled ITB spheroids, and spheroids seeded in polyglycolic acid (PGA) scaffolds. The protein expression profile of targets typically expressed by ligamentocytes (collagen types I–III, elastin, lubricin, decorin, aggrecan, fibronectin, tenascin C, CD44, β1-integrins, vimentin, F-actin, αSMA, and vascular endothelial growth factor A [VEGFA]) was compared between ITB and ACL fibroblasts. A donor- and age-dependent differing percentage of αSMA positive cells could be detected, which was similar in ITB and ACL tissues despite the grade of degeneration being significantly higher in the ACL due to harvesting them from OA knees. ITB fibroblasts survived for several months in an explant culture, continuously forming monolayers with VEGFA and an increased αSMA expression. They shared their expression profile with ACL fibroblasts. αSMA decreased during the monolayer to spheroid/scaffold transition. Using self-assembled spheroids, the migratory capacity of reversible myofibroblastic ITB cells can be utilized for colonizing biomaterials for ACL tissue engineering and to support ligament healing.
5

Caractérisation, Modélisation et Contrôle des Scénarios Avancés dans le Tokamak Européen JET

Tresset, Guillaume 26 September 2002 (has links) (PDF)
Les scénarios avancés, développés depuis moins d'une dizaine d'année avec la découverte des barrières internes de transport et la maîtrise du profil de courant, insufflent un nouvel élan au tokamak en direction d'un futur réacteur à fusion thermonucléaire contrôlée. Le Joint European Torus (JET) installé au Royaume-Uni, est actuellement le dispositif expérimental le plus performant au monde en terme de puissance fusion. Il a permis d'acquérir une riche expertise sur ces régimes à confinement amélioré. La réduction du transport turbulent, désormais indissociable de l'optimisation de la forme du profil de courant - obtenue par exemple avec l'onde hybride ou le courant autogénéré de bootstrap, peut être caractérisée simplement à l'aide d'un critère qui donne accès à la plupart des informations utiles concernant les barrières . Ses deux principaux domaines d'utilisation sont l'analyse des bases de données et les applications temps réel. Les modèles de transport dits de courbe en « S » exhibent des propriétés intéressantes que conforte l'expérience, tandis que les dépendances non-linéaires et multivariables de la diffusivité thermique du plasma peuvent être approchées grâce à un réseau de neurones, suggérant un nouveau moyen d'investigation et de modélisation du transport. Enfin, les toutes premières démonstrations expérimentales de contrôle en temps réel des barrières internes de transport et du profil de courant ont été réalisées sur JET, ouvrant la voie à des systèmes d'asservissement sophistiqués.

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