Auswahl der wissenschaftlichen Literatur zum Thema „Géométrie magnétique“
Geben Sie eine Quelle nach APA, MLA, Chicago, Harvard und anderen Zitierweisen an
Inhaltsverzeichnis
Machen Sie sich mit den Listen der aktuellen Artikel, Bücher, Dissertationen, Berichten und anderer wissenschaftlichen Quellen zum Thema "Géométrie magnétique" bekannt.
Neben jedem Werk im Literaturverzeichnis ist die Option "Zur Bibliographie hinzufügen" verfügbar. Nutzen Sie sie, wird Ihre bibliographische Angabe des gewählten Werkes nach der nötigen Zitierweise (APA, MLA, Harvard, Chicago, Vancouver usw.) automatisch gestaltet.
Sie können auch den vollen Text der wissenschaftlichen Publikation im PDF-Format herunterladen und eine Online-Annotation der Arbeit lesen, wenn die relevanten Parameter in den Metadaten verfügbar sind.
Zeitschriftenartikel zum Thema "Géométrie magnétique"
Le Maire, Pauline, und Marc Munschy. „L'effet de la géométrie sur la précision dans l'estimation de la profondeur d'un réseau de type pipeline avec la méthode magnétique“. E3S Web of Conferences 342 (2022): 02006. http://dx.doi.org/10.1051/e3sconf/202234202006.
Der volle Inhalt der QuelleClowes, Ron M. „Logan Medallist 5. Geophysics and Geology: An Essential Combination Illustrated by LITHOPROBE Interpretations–Part 2, Exploration Examples“. Geoscience Canada 44, Nr. 4 (19.12.2017): 135–80. http://dx.doi.org/10.12789/geocanj.2017.44.125.
Der volle Inhalt der QuelleYoussef, Mejri. „Inverse Problem: Stability for the aligned magnetic field by the Dirichlet-to-Neumann map for the wave equation in a periodic quantum waveguide“. Revue Africaine de la Recherche en Informatique et Mathématiques Appliquées Volume 23 - 2016 - Special... (13.12.2016). http://dx.doi.org/10.46298/arima.1509.
Der volle Inhalt der QuellePelletier, Arnaud, Benjamin Ducharne, Pierre-Jean Cottinet, Eliott Brun und Fabrice Cockenpot. „Capteurs Courants de Foucault imprimés pour le monitoring de corrosion et de microstructure“. e-journal of nondestructive testing 28, Nr. 9 (September 2023). http://dx.doi.org/10.58286/28491.
Der volle Inhalt der QuelleDissertationen zum Thema "Géométrie magnétique"
Martin, Witkowski Laurent. „Écoulements engendrés par un champ magnétique tournant en géométrie cylindrique“. Grenoble INPG, 1997. http://www.theses.fr/1997INPG0218.
Der volle Inhalt der QuellePacitto, Grégory. „Instabilités hydrodynamiques à l'interface de ferrofluides en géométrie confinée“. Paris 7, 2001. http://www.theses.fr/2001PA077107.
Der volle Inhalt der QuelleBarthélemy, Quentin. „Etudes par RMN, µSR et chaleur spécifique de liquides de spins quantiques dans des matériaux à géométrie kagome“. Thesis, université Paris-Saclay, 2020. http://www.theses.fr/2020UPASP065.
Der volle Inhalt der QuelleThe kagome Heisenberg antiferromagnet decorated with quantum spins is a fascinating model where to look for exotic quantum states including the elusive spin liquids. Despite its apparent simplicity, there is still no consensus on the exact nature of the ground state and of the excitation spectrum. The current availability of quantum kagome materials, each with their own deviation to the pure Heisenberg model, allows to confront a fair amount of experimental results to theoretical predictions and study the effect of perturbations inherent to real materials. The experimental work presented in this manuscript examines two directions.First, we focus on the emblematic herbertsmithite ZnCu₃(OH)₆Cl₂, with perfect kagome planes. It is the closest materialization of the pure Heisenberg model so far (J~180 K) and exhibits attributes of a quantum spin liquid at low temperatures, with the absence of magnetic long-range order and the persistence of spin dynamics. As main perturbations, we can mention magnetic impurities between the kagome planes and a finite out-of-plane Dzyaloshinskii-Moriya component (Dz~0.06J). With a comprehensive ¹⁷O NMR study on a high-quality single crystal, we were able to measure the intrinsic (kagome) low-temperature static spin susceptibility and spin dynamics, and we show unambiguously that the excitation spectrum is gapless, at variance with valence bond crystal states and numerous spin liquid candidates that are characterized by gapped excitations. Moreover, the disclosed static spin susceptibility restores some convergence with a fermionic Dirac cone model now advocated for in most numerical works. To shed another light on the low energy density of states, we measured the specific heat on high-quality single crystals. The kagome intrinsic specific heat is obtained in high magnetic fields only: at low magnetic fields, another dominant contribution prevents any conclusive analysis. Remarkably, the kagome specific heat is found to be almost field-independent up to 34 T. This seems to be at odds with a fermionic nature for the excitations, which in such a case would form field-induced Fermi pockets. Yet, as expected for Dirac particles, the density of states appears to vanish in the zero-temperature limit. Although the exact nature of the excitations remains unclear, our results severely constrain future theoretical developments. Further, thanks to NMR and specific heat, we were also able to identify field-induced transitions or crossovers at very low temperatures, and we present a tentative phase diagram. We also used µSR to investigate the robustness of the spin liquid state, which extends at least up to 28 kbar. Second, we introduce two new closely related materials, that implement interesting variants of herbertsmithite: the insulating yttrium kapellasites YCu₃(OH)₆OxCl₃-x, with compositions x=0 and x=1/3. These two compounds are fortuitous outcomes of the ongoing – and still unsuccessful – effort for doping herbertsmithite, by replacing the divalent zinc cations by monovalent or trivalent cations. In yttrium kapellasites, copper ions also build a kagome lattice with antiferromagnetic in-plane couplings, and the structure forbids interlayer impurities. The ground state properties are determined using bulk thermodynamics and µSR on powdered samples. The x=0 compound has a perfect kagome geometry but displays an ordered ground state, which is attributed to a large Dzyaloshinskii-Moriya anisotropy. The x=1/3 compound has a slightly distorted kagome geometry displaying anisotropic interactions, but exhibits features of spin liquid physics. Yet, we show with a comparative ³⁵Cl NMR study, that single crystal samples of the latter material actually develop static magnetism at variance with the polycrystalline samples. We conclude that Dzyaloshinskii-Moriya anisotropy and/or the modified kagome magnetic lattice in the x=1/3 compound are likely at the origin of the low-temperature magnetic transition
Serret, Emmanuelle. „Etude de réseaux de nanojonctions Josephson : compétition entre le champ magnétique et la géométrie“. Université Joseph Fourier (Grenoble), 2002. http://www.theses.fr/2002GRE10164.
Der volle Inhalt der QuelleOrain, Jean-Christophe. „Frustration géométrique et nouveaux états quantiques de spins dans les composés vanadates fluorés à géométrie kagomé“. Thesis, Université Paris-Saclay (ComUE), 2015. http://www.theses.fr/2015SACLS113/document.
Der volle Inhalt der QuelleThe search for quantum liquid state is a very active field in condensed matter research. In two dimensions, the antiferromagnetic spin 1/2 kagome lattice seems to be the most able to stabilize such a ground state. Indeed, from recent theoretical investigations, we are now quite sure that this model has a quantum spin liquid ground state. However, we still do not know its nature, in particular the nature of its correlations. They could be short ranged with a gap in the excitation spectrum, or long ranged with a gapless excitation spectrum. On the experimental side, only few materials exist and only one possesses a geometrically perfect lattice, the Herbertsmithite. All the experiments that have been done on this compound reveal a gapless spin liquid state along with deviations to the spin 1/2 Heisenberg hamiltonian which could be responsible of the gap closure.This thesis deals with the experimental study, mainly by NMR and µSR, of new vanadium based kagomé compounds which are part of a newly synthesized family, the kagome fluoride vanadates. The material that we studied the most is a spin 1/2 kagomé compound based on V4+, (NH4)2[C7H14N][V7O6F18] (DQVOF). The magnetic model of this compound can be decomposed in two rather independent parts, trimerized kagome planes and quasi paramagnetic V3+ ions. The µSR studies, showing the absence of frozen moment down to 20 mK, reveal a spin liquid ground state in DQVOF. The heat capacity and the NMR experiments point out a gapless behavior despite trimerization and likely weak Dzyaloshinskii Moriya interactions. Our results demonstrate that the gapless ground state, whether intrinsic or due to deviation to the ideal hamiltonian, is a rather robust characteristic of kagome materials.Furthermore, we studied another compound of this family, (NH4)2[C2H8N][V3F12] (DDVF), which magnetic lattice is made of uncoupled kagomé planes based on V3+ (S = 1). The lattice shows large deviations to the ideal kagomé and the thermodynamic experiments and the µSR studies reveal a magnetic transition to a frozen state at 10 K with a long distance order which is effective only below 6 K
Renaud, Denis. „Caractérisation du propulseur PEGASES : diagnostics du filtre magnétique et du faisceau : optimisation de la géométrie“. Thesis, Orléans, 2016. http://www.theses.fr/2016ORLE2018/document.
Der volle Inhalt der QuelleThe PEGASES ion thruster differs from standard electric propulsion technologies through its use of electronegative gases, such as SF₆, as a propellant. Its operation relies on the trapping of electrons using a magnetic field and the creation of a plasma dominated by positive and negative ions. These ions are alternately accelerated to produce thrust, and later undergo a recombination to ensure beam neutrality. This thruster eliminates the need for an electron-producing neutralizer, which is a standard feature in other sources such as the Hall thruster. This thesis is divided into three parts. The first describes the development and implementation of a new EXB probe for the study of the ion beam properties, the identification of the beam chemical composition and the verification of the presence of negative and positive ion species. The second part concerns the design and application of a new laser photodetachment diagnostic for the measurement of the negative ion fraction. Lastly, a new ion-ion thruster with a circular geometry, known as AIPE, has been designed, constructed and successfully tested. This prototype eliminates the plasma asymmetry present in PEGASES and reveals the importance of the magnetic filter to source operation
Laribi, Elias. „Modélisation numérique de l'impact de la géométrie magnétique sur le plasma de bord des tokamaks“. Electronic Thesis or Diss., Aix-Marseille, 2021. http://www.theses.fr/2021AIXM0298.
Der volle Inhalt der QuelleThis phD work has shown that, in a limiter configuration, the elongation of magnetic surfaces has a stabilizing effect with respect to the edge plasma turbulence. This leads to a reduction of the edge plasma width when the elongation increases. Regarding triangularity, this phD work revealed that its effects on the edge plasma were weaker than those of elongation. A better understanding of these trends has been possible thanks to a theoretical work on a simplified interchange model. This work has also revealed the importance of the magnetic field spatial variability on the poloidal size of turbulent structures and therefore on the radial turbulent fluxes. In a second step, the study of a divertor configuration with one X point has shown that the the magnetic field spatial variability was so important that it could be one of the reasons that explain the enhancement of the low field side ballooned nature of edge plasma turbulence in a divertor geometry. Still concerning the divertor geometry, this phD also revealed that the internal material receives more heat compared to the external material when the toroidal magnetic field is oriented in the direct direction (= magnetic drift of the ions pointing towards the X point). A possible explanation of this observation is the existence of a significant plasma circulation from the low field side to the high field side at the X point that we observed in this configuration. Finally, we were able to confirm that one way to improve this heat flux distribution on the walls was to merge two X points perfectly (= ideal snowflake proposed in 2007 by Ryutov and Sukhanovsky)
Olariu, Areta. „Antiferromagnétisme frustré à deux dimensions : de la géométrie triangulaire dans NaCrO2 à la géométrie kagomé dans Cu3Zn(OH)6Cl2“. Phd thesis, Université Paris Sud - Paris XI, 2007. http://tel.archives-ouvertes.fr/tel-00268177.
Der volle Inhalt der QuelleNous présentons l'étude par RMN et µSR du composé triangulaire à côtés partagés NaCrO2, un système Heisenberg modèle de spin 3/2. Nous mettons ainsi en évidence un régime de fluctuations très étendu en dessous d'un maximum de chaleur spécifique, signature d'excitations originales spécifiques à cette classe de systèmes.
Nous présentons ensuite l'étude de l'Herbertsmithite ZnCu3(OH)6Cl2, première réalisation expérimentale d'une structure kagomé parfaite de spin 1/2. Nous montrons par µSR que dans la famille plus large des Paratacamites ZnxCu4-x(OH)6Cl2, lorsque x passe de 0 à 1, le système évolue à basse température d'un état ordonné à longue distance vers un état fluctuant, type liquide de spin, pour x>0.66. Les mesures de RMN de l'oxygène 17 dans l'Herbertsmithite nous ont permis d'isoler la contribution intrinsèque de celle des défauts issus des substitutions Cu/Zn. L'évolution de la susceptibilité, ainsi que les mesures de relaxation démontrent l'absence de gap dans le spectre des excitations magnétiques. Nos mesures suggèrent que ces excitations ont un poids constant sur toute la zone de Brillouin, comme prédit théoriquement. L'évolution de la raie des défauts est en accord qualitatif avec l'image théorique de la localisation de singulets non magnétiques autour de l'impureté.
Gardiennet-Doucet, Carole. „Exploitation de l'anisotropie de déplacement chimique pour l'étude de la géométrie moléculaire et des contacts intermoléculaires par résonance magnétique nucléaire à l'état solide“. Nancy 1, 2005. http://www.theses.fr/2005NAN10010.
Der volle Inhalt der QuelleThis work presents various methodologies to probe the molecular geometry and the nature of intermolecular contacts in organic and inorganic solids. The first part gives a brief description of basic principles of solid-state NMR that are used through these studies. In the second part, the variation of chemical shielding tensor principal values of carboxy carbon-13 and phosphate phosphorus-31 upon deprotonation is correlated with ionisation state, conformation and nature of the intermolecular interactions. The third part deals with the characterisation of the strong hydrogen bond involving the silanols of sodium hydrous polysilicates, using complementary methods such as 1H-29Si cross-polarisation dynamics and dipolar modulation of the 29Si chemical shift anisotropy at slow spinning frequency
Heitz, Millet Annie. „Étude conformationnelle par résonance magnétique nucléaire et le programme de calcul distance géométrie (DISGEO) d'un nouvel inhibiteur de trypsine extrait d'Ecballium elaterium“. Montpellier 2, 1988. http://www.theses.fr/1988MON20197.
Der volle Inhalt der Quelle