• Refine Query
  • Source
  • Publication year
  • to
  • Language
  • 91
  • 29
  • 22
  • 10
  • 6
  • 6
  • 3
  • 3
  • 2
  • 1
  • 1
  • 1
  • 1
  • 1
  • 1
  • Tagged with
  • 208
  • 23
  • 21
  • 17
  • 15
  • 13
  • 13
  • 11
  • 11
  • 10
  • 10
  • 10
  • 10
  • 10
  • 10
  • 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.
181

Roten till det onda : en studie i häxmotiv, kvinnlig sexualitet, husmoderlighet och moderlighet i Ulla Isakssons historiska roman Dit du icke vill / The Root of Evil : a study of witches, female sexuality, housewife-attitudes and disposition for maternity in Ulla Isaksson´s historical novel  Dit du icke vill

Widén, Anita January 2008 (has links)
Ulla Isaksson (1916 – 2000) wrote many novels, often with a woman or several women as protagonists. In Dit du icke vill (“Where Thou Willst Not”) from 1956 she depicts a crisis of faith in a woman, which would not have been successful had she chosen a contemporary setting. She uses an adequate historical framework, the prosecution of witches in Sweden in the 17th century, well documented in reliable sources. Her novel includes a message about oppression of women, manifest in patriarchal ambition to control ancient wisdom about healing and herbs and the denial of pre-Christian habits that include knowledge about female fertility, earlier exercised by midwives and wise women and men. In “The Root of Evil” the novel is placed in a feminist tradition, where the author, like older writers like Fredrika Bremer, Ellen Key and Elin Wägner, pleads for “social mothering”.  A major difference is that, in her own life, Ulla Isaksson has experienced pregnancy, giving birth and breastfeeding which none of the pioneering Swedish feminist writers had. Emilia Fogelklou, pioneering theologian, wrote about witches as wise women, a study that influenced Ulla Isaksson. The witches are described as mirroring Hanna “the Good Mother”. Their fantasies about life at “Blåkulla” are similar to the everyday life at a wealthy farmstead. This kind of mirroring reminds of the theories of Gilbert and Gubar, who assume that female writers in the 19th Century hid their revolt against patriarchy in mad women, like “The Madwoman in the Attic” in Jane Eyre. In the 1950s, golden age of the Swedish housewife, a female writer might well hide her anger at the circumscribed role model dedicated to women in a similar use of Anti-Women. The real witches clearly contrast the obedient protagonist, a true “Angel in the house”. The villagers´ struggle to clear the ground from the ensnaring roots that hinder the male prosecution of witches imply a symbolic reading: this evil root is ancient matriarchal knowledge of childbearing and birth control. A theory on the original causes for the witch hunts in western Europe is introduced: the population sank in the 15th century and one reason, beside plagues, starvation and warfare, was that women aware of how to prevent childbearing and giving birth to a lot of children were killed during the witch hunt. Churches and kings introduced the prosecution of witches and wise women, including midwives.
182

Synthèse de fréquence par couplage d'oscillateurs spintroniques

Zarudniev, Mykhailo 28 January 2013 (has links) (PDF)
La tendance actuelle dans le domaine des télécommunications mène à des systèmes capables de fonctionner selon plusieurs standards, et donc plusieurs fréquences porteuses. La synthèse de la fréquence porteuse est un élément clef, dont les propriétés reposent essentiellement sur les performances de l'oscillateur employé. Pour assurer le fonctionnement de systèmes compatibles avec plusieurs standards de télécommunication, la solution conventionnelle consiste à intégrer plusieurs oscillateurs locaux. Cette solution est coûteuse, d'autant plus que, malgré le fait que les technologies actuelles atteignent des niveaux d'intégration très importants, la surface occupée par des oscillateurs traditionnels de type LC ne peut pas être diminuée, alors que le coût de fabrication au millimètre carré devient de plus en plus élevé. Il serait donc très intéressant de remplacer les oscillateurs LC, ce qui nous amène à rechercher des solutions alternatives parmi de nouvelles technologies. L'oscillateur spintronique (STO) est un nouveau dispositif issu des études sur les couches minces magnétiques. Il apparait comme un candidat potentiel de remplacement des oscillateurs LC du fait de sa grande accordabilité en fréquence et de son faible encombrement. Toutefois des mesures effectuées sur les STOs ont montré que la performance en puissance et en bruit de phase d'un oscillateur seul ne permet pas de remplir les spécifications pour des applications de télécommunication. Nous proposons de remplir ces spécifications en couplant un nombre d'oscillateurs spintroniques important. Dans ce cadre se posent plusieurs questions qui concernent les procédures de modélisation, d'analyse et de synthèse des systèmes interconnectés. Les procédures de modélisation incluent la démarche de recherche de modèles à complexité croissante qui décrivent les propriétés entrée-sortie d'un oscillateur spintronique, ainsi que la démarche de généralisation des modèles des oscillateurs dans le cadre du réseau. Les procédures d'analyse cherchent à vérifier la stabilité et évaluer la performance des systèmes interconnectés. Les procédures de synthèse permettent de concevoir des interconnexions sophistiquées pour les oscillateurs afin d'assurer toutes les spécifications du cahier des charges. Dans ce document, nous établissons tout d'abord le problème de la synthèse de fréquence par couplage avec un cahier des charges formalisé en termes de gabarits fréquentiels sur des densités spectrales de puissance. Le cahier des charges posé amène la nécessité de modéliser l'oscillateur spintronique pour pouvoir simuler et analyser son comportement. Ici, nous proposons une modélisation originale selon des degrés de complexité croissante. Ensuite, nous discutons de la structure de la commande de l'ensemble des oscillateurs afin de remplir les spécifications du cahier des charges. La structure de commande proposée nécessite de développer une méthode de conception des interconnexions du réseau d'après les critères de performance. Dans les deux derniers chapitres, nous proposons deux méthodes fréquentielles de synthèse originales pour résoudre le problème de synthèse de fréquence par couplage. La première méthode de synthèse permet de prendre en compte un critère mathématique du cahier des charges, qui correspond à un gabarit fréquentiel à respecter, et permet d'obtenir une matrice d'interconnexion des sous-systèmes, telle que le module de la réponse fréquentielle du réseau approxime le gabarit imposé par le cahier des charges. La deuxième méthode de synthèse permet de prendre en compte plusieurs gabarits fréquentiels à la fois. La solution obtenue est une matrice d'interconnexion des sous-systèmes, qui résout le problème de la synthèse de fréquence par couplage d'oscillateurs spintroniques.
183

The terraces of the Conway Coast, North Canterbury: Geomorphology, sedimentary facies and sequence stratigraphy

McConnico, Tim January 2012 (has links)
A basin analysis was conducted at the Conway Flat coast (Marlborough Fault Zone, South Island, New Zealand) to investigate the interaction of regional and local structure in a transpressional plate boundary and its control on basin formation. A multi-tiered approach has been employed involving: (i) detailed analysis of sedimentary deposits; (ii) geomorphic mapping of terraces, fault traces and lineaments; (iii) dating of deposits by 14C and OSL and (iv) the integration of data to form a basin-synthesis in a sequence stratigraphy framework. A complex thrust fault zone (the Hawkswood Thrust Fault Zone), originating at the hinge of the thrust-cored Hawkswood anticline, is interpreted to be a result of west-dipping thrust faults joining at depth with the Hundalee Fault and propagating eastwards. The faults uplift and dissect alluvial fans to form terraces along the Conway Flat coast that provide the necessary relief to form the fan deltas. These terrace/fan surfaces are ~9 km long and ~3 km wide, composite features, with their upper parts representing sub-aerial alluvial fans. These grade into delta plains of Quaternary Gilbert-style fan deltas. Uplift and incision have created excellent 3D views of the underlying Gilbert-style fan delta complexes from topsets to prodelta deposits. Erosive contacts between the Medina, Rafa, Ngaroma and modern Conway fan delta deposits, coupled with changes in terrace elevations allow an understanding of the development of multiple inset terraces along the Conway Flat coast. These terraces are divided into five stages of evolution based on variations in sedimentary facies and geomorphic mapping: Stage I involves the uplift of the Hawkswood Range and subsequent increased sedimentation rate such that alluvial fans prograded to the sea to form the Medina fan delta Terrace. Stage II began with a period of incision, from lowering sea level or changes in the uplift and sedimentation rate and continued with the deposition of the Dawn and Upham fan deltas. Stage III starts with the incision of the Rafa Terrace and deposition of aggradational terraces in the upper reaches. Stage IV initiated by a period of incision followed by deposition of estuarine facies at ~8ka and Stage V began with a period of incision and continues today with the infilling of the incised valley by the modern fan delta of the Conway River and its continued progradation. New dates from within the Gilbert-type fan deltas along the Conway Flat coast are presented, using OSL and 14C dating techniques. Faulting at the Conway Flat coast began ~ 94 ka, based on the development of the Medina Terrace fan delta with uplift rates ~1.38~1.42 m/ka. The interplay of tectonics and sea level fluctuations continued as the ~79 ka Rafa Terrace fan deltas were created, with uplift rates calculated at ~1.39 m/ka. Detailed 14C ages from paleoforest (~8.4-~6.4 ka) in the Ngaroma Terrace and from the mouths of smaller streams have established uplift rates during the Holocene ~1-3 m/ka, depending on sea level.
184

50 years after independence : preservation of places, spaces and memory / Fifty years after independence

Weiler, Emily A. 05 May 2012 (has links)
This thesis will study three specific subjects in order to document changing viewpoints in American culture in relation to nationalism, patriotism, and memories from older generations. It will be studying a space- Bunker Hill, a place- Independence Hall and a person- Marquis Lafayette at approximately fifty years after the signing of the Declaration of Independence. Each subject will explore the ways the memory of the soldiers involved in the American Revolution have been preserved and remembered. It is the intent of this thesis to establish the importance of the passage of time especially when it comes to preserving historic artifacts and buildings and the way the changing associations have on how we preserve these artifacts. / The triumphal tour of Marquis Lafayette -- Independence Hall -- Bunker Hill Monument. / Department of Architecture
185

Le mythe de la fin du monde dans Les chaises de Ionesco et Fin de partie de Beckett

Manascurta, Calin 04 1900 (has links)
À partir d’un dispositif théorique et méthodologique emprunté au structuralisme figuratif de Gilbert Durand, ce mémoire propose une exploration du Mythe de la Fin du Monde dans quelques unes de ses manifestations romanesques et théâtrales. Les postulats de base qui fondent notre démarche sont au nombre de trois : a) l’œuvre littéraire possède toujours un substrat mythique ; b) un mythe représente un noyau de mythèmes, dont le trait définitoire est la redondance ; c) il n’y a pas de version privilégiée ou primitive du mythe, qui doit être vu comme une constante de l’esprit humain. Au niveau des applications pratiques, notre travail s’articule en deux démarches complémentaires, reprises d’une section à l’autre. Dans un premier temps, en nous appuyant sur le corpus romanesque – où le mythe nous semble abondant et complet – nous identifions les redondances internes et génériques que nous qualifions de «mythèmes». Dans un second temps, nous vérifions la présence et le fonctionnement de ces mythèmes dans le corpus dramatique. / Within the theoretical and methodological framework of the figurative structuralism devised by Gilbert Durand, this work sets out to explore the Myth of the End of the World based on two corpora: five novels and two plays. Three main postulates underlie our research: a) the literary work is always based on a mythical substratum; b) myth is an aggregation of mythemes, whose defining characteristic consists in their redundancy; c) myth is a constant of the human spirit and therefore none of its versions takes precedence over another. As far as the applications of the theory are concerned, our work is articulated in two distinct phases, repeated form one section to another. Based on the body of novels, where the myth manifests itself in its most complete and abundant form, phase 1 is devoted to the identification of redundancies, both internal to each work and generic, that are categorized as mythemes. Phase 2 verifies their presence in the body of plays.
186

Agö, orixá! gestão de uma jornada afro-estética-trágica : o relato de um aprendizado e de uma formação pedagógica vivida no candomblé

Correia, Paulo Petronilio January 2009 (has links)
A Tese problematiza o aspecto estético, ético e pedagógico do Ilê axé Oya Gbembale em Goiânia. Propõe-se compreender o Terreiro de Candomblé como espaço de aprendizagem, onde o trágico ganha um contorno pela sua plasticidade, movimento e complexidade que povoa o Cotidiano e a vida do Povo do Santo. Assim, a Educação no Axé ganha uma dimensão política e epistemológica na medida em que as vozes do Terreiro se revelam formando uma ética e uma estética do estar – junto, edificando uma Pedagogia que se constrói na experiência vivida e partilhada com a tribo do Candomblé. Intensifica-se assim, os laços existentes entre os vários aspectos da iniciação pedagógica e do mimetismo, dando um contorno a essa tragédia que faz do Candomblé um espaço vital, alegre e festivo, instaurando aí uma viscosidade nas relações humanas fruto das relações pedagógicas, ontológicas e existenciais entre os Pais e Filhos de Santo. No entanto, a Tese versa-se em torno de um relato que testemunha a gestão de uma vida e das relações dionisíacas que estabeleci com o Povo do Santo, a partir das jornadas que percorri desde o meu processo- de- iniciaçãopedag ógica, entregando-me a essa sensibilidade diante dos signos do Candomblé. Assim, tento decifrar o espaço sagrado e mitológico dos Orixás. Proponho, em outras palavras, mostrar a voz do Terreiro, dentro de uma magia fruto da conjunção humana que é tecida no interior do Terreiro e que faz dessa religião uma verdadeira obra de arte. Estabeleço um entrelaçamento entre a Antropologia Filosófica e a Educação, penetrando nas encruzilhadas teóricas de Michel Maffesoli, Martin Heidegger, Edgar Morin, Georges Balandier, Nietzsche, Deleuze, Gilbert Durand e René Girard. / The Thesis discusses about the esthetical, ethical and pedagogical aspect of Ilê axé Oyá Gbembale in Goiânia. It purposes to comprehend the "Yard of Ritual" of Candomblé as a space for learning, where the tragic gets an outline by its plasticity, movement and complexity which fills up the Holy People everyday and life. Thus, education according to Axé gets a political and epistemological dimension while the voices of the "Yard of ritual" reveal themselves forming ethics and esthetics of being - together, building the pedagogy that is constituted through the living and sharing experience with the tribe of Candomblé. It intensifies like this, the links among the several aspects of the pedagogical initiation, of mimetiza, giving appearance to this tragedy that turns Candomblé a vital space, happy and festive, establishing then a viscosity in the human relationship as a product of the pedagogical, ontological and existential relationship between "Parents and Children from Saints". However, the Thesis studies about a description which testifies a gestion of a life and of the dionysical relationship that I established with the Holy People, it starts from the journey that I went through since my pedagogical-process-of-initiation, handing me over this sensibility before the signs of Candomblé. Thus, I try to decipher the mythological and sacred space of the Orixás. I purpose, in other words, to show the voice of the "Yard of ritual", into a magic as a result of the human conjunction that is formed inside the "Yard of ritual" and that turns this religion a true art work. I establish a mixing up among the Philosophical Anthropology and the Education, going into the theorical cross-roads of Michel Maffesoli, Martin Heidegger, Edgar Morin, Georges Balandier, Nietzsche, Deleuze, Gilbert Durand e René Girard.
187

Agö, orixá! gestão de uma jornada afro-estética-trágica : o relato de um aprendizado e de uma formação pedagógica vivida no candomblé

Correia, Paulo Petronilio January 2009 (has links)
A Tese problematiza o aspecto estético, ético e pedagógico do Ilê axé Oya Gbembale em Goiânia. Propõe-se compreender o Terreiro de Candomblé como espaço de aprendizagem, onde o trágico ganha um contorno pela sua plasticidade, movimento e complexidade que povoa o Cotidiano e a vida do Povo do Santo. Assim, a Educação no Axé ganha uma dimensão política e epistemológica na medida em que as vozes do Terreiro se revelam formando uma ética e uma estética do estar – junto, edificando uma Pedagogia que se constrói na experiência vivida e partilhada com a tribo do Candomblé. Intensifica-se assim, os laços existentes entre os vários aspectos da iniciação pedagógica e do mimetismo, dando um contorno a essa tragédia que faz do Candomblé um espaço vital, alegre e festivo, instaurando aí uma viscosidade nas relações humanas fruto das relações pedagógicas, ontológicas e existenciais entre os Pais e Filhos de Santo. No entanto, a Tese versa-se em torno de um relato que testemunha a gestão de uma vida e das relações dionisíacas que estabeleci com o Povo do Santo, a partir das jornadas que percorri desde o meu processo- de- iniciaçãopedag ógica, entregando-me a essa sensibilidade diante dos signos do Candomblé. Assim, tento decifrar o espaço sagrado e mitológico dos Orixás. Proponho, em outras palavras, mostrar a voz do Terreiro, dentro de uma magia fruto da conjunção humana que é tecida no interior do Terreiro e que faz dessa religião uma verdadeira obra de arte. Estabeleço um entrelaçamento entre a Antropologia Filosófica e a Educação, penetrando nas encruzilhadas teóricas de Michel Maffesoli, Martin Heidegger, Edgar Morin, Georges Balandier, Nietzsche, Deleuze, Gilbert Durand e René Girard. / The Thesis discusses about the esthetical, ethical and pedagogical aspect of Ilê axé Oyá Gbembale in Goiânia. It purposes to comprehend the "Yard of Ritual" of Candomblé as a space for learning, where the tragic gets an outline by its plasticity, movement and complexity which fills up the Holy People everyday and life. Thus, education according to Axé gets a political and epistemological dimension while the voices of the "Yard of ritual" reveal themselves forming ethics and esthetics of being - together, building the pedagogy that is constituted through the living and sharing experience with the tribe of Candomblé. It intensifies like this, the links among the several aspects of the pedagogical initiation, of mimetiza, giving appearance to this tragedy that turns Candomblé a vital space, happy and festive, establishing then a viscosity in the human relationship as a product of the pedagogical, ontological and existential relationship between "Parents and Children from Saints". However, the Thesis studies about a description which testifies a gestion of a life and of the dionysical relationship that I established with the Holy People, it starts from the journey that I went through since my pedagogical-process-of-initiation, handing me over this sensibility before the signs of Candomblé. Thus, I try to decipher the mythological and sacred space of the Orixás. I purpose, in other words, to show the voice of the "Yard of ritual", into a magic as a result of the human conjunction that is formed inside the "Yard of ritual" and that turns this religion a true art work. I establish a mixing up among the Philosophical Anthropology and the Education, going into the theorical cross-roads of Michel Maffesoli, Martin Heidegger, Edgar Morin, Georges Balandier, Nietzsche, Deleuze, Gilbert Durand e René Girard.
188

Agö, orixá! gestão de uma jornada afro-estética-trágica : o relato de um aprendizado e de uma formação pedagógica vivida no candomblé

Correia, Paulo Petronilio January 2009 (has links)
A Tese problematiza o aspecto estético, ético e pedagógico do Ilê axé Oya Gbembale em Goiânia. Propõe-se compreender o Terreiro de Candomblé como espaço de aprendizagem, onde o trágico ganha um contorno pela sua plasticidade, movimento e complexidade que povoa o Cotidiano e a vida do Povo do Santo. Assim, a Educação no Axé ganha uma dimensão política e epistemológica na medida em que as vozes do Terreiro se revelam formando uma ética e uma estética do estar – junto, edificando uma Pedagogia que se constrói na experiência vivida e partilhada com a tribo do Candomblé. Intensifica-se assim, os laços existentes entre os vários aspectos da iniciação pedagógica e do mimetismo, dando um contorno a essa tragédia que faz do Candomblé um espaço vital, alegre e festivo, instaurando aí uma viscosidade nas relações humanas fruto das relações pedagógicas, ontológicas e existenciais entre os Pais e Filhos de Santo. No entanto, a Tese versa-se em torno de um relato que testemunha a gestão de uma vida e das relações dionisíacas que estabeleci com o Povo do Santo, a partir das jornadas que percorri desde o meu processo- de- iniciaçãopedag ógica, entregando-me a essa sensibilidade diante dos signos do Candomblé. Assim, tento decifrar o espaço sagrado e mitológico dos Orixás. Proponho, em outras palavras, mostrar a voz do Terreiro, dentro de uma magia fruto da conjunção humana que é tecida no interior do Terreiro e que faz dessa religião uma verdadeira obra de arte. Estabeleço um entrelaçamento entre a Antropologia Filosófica e a Educação, penetrando nas encruzilhadas teóricas de Michel Maffesoli, Martin Heidegger, Edgar Morin, Georges Balandier, Nietzsche, Deleuze, Gilbert Durand e René Girard. / The Thesis discusses about the esthetical, ethical and pedagogical aspect of Ilê axé Oyá Gbembale in Goiânia. It purposes to comprehend the "Yard of Ritual" of Candomblé as a space for learning, where the tragic gets an outline by its plasticity, movement and complexity which fills up the Holy People everyday and life. Thus, education according to Axé gets a political and epistemological dimension while the voices of the "Yard of ritual" reveal themselves forming ethics and esthetics of being - together, building the pedagogy that is constituted through the living and sharing experience with the tribe of Candomblé. It intensifies like this, the links among the several aspects of the pedagogical initiation, of mimetiza, giving appearance to this tragedy that turns Candomblé a vital space, happy and festive, establishing then a viscosity in the human relationship as a product of the pedagogical, ontological and existential relationship between "Parents and Children from Saints". However, the Thesis studies about a description which testifies a gestion of a life and of the dionysical relationship that I established with the Holy People, it starts from the journey that I went through since my pedagogical-process-of-initiation, handing me over this sensibility before the signs of Candomblé. Thus, I try to decipher the mythological and sacred space of the Orixás. I purpose, in other words, to show the voice of the "Yard of ritual", into a magic as a result of the human conjunction that is formed inside the "Yard of ritual" and that turns this religion a true art work. I establish a mixing up among the Philosophical Anthropology and the Education, going into the theorical cross-roads of Michel Maffesoli, Martin Heidegger, Edgar Morin, Georges Balandier, Nietzsche, Deleuze, Gilbert Durand e René Girard.
189

Relativistic theory of laser-induced magnetization dynamics

Mondal, Ritwik January 2017 (has links)
Ultrafast dynamical processes in magnetic systems have become the subject of intense research during the last two decades, initiated by the pioneering discovery of femtosecond laser-induced demagnetization in nickel. In this thesis, we develop theory for fast and ultrafast magnetization dynamics. In particular, we build relativistic theory to explain the magnetization dynamics observed at short timescales in pump-probe magneto-optical experiments and compute from first-principles the coherent laser-induced magnetization. In the developed relativistic theory, we start from the fundamental Dirac-Kohn-Sham equation that includes all relativistic effects related to spin and orbital magnetism as well as the magnetic exchange interaction and any external electromagnetic field. As it describes both particle and antiparticle, a separation between them is sought because we focus on low-energy excitations within the particle system. Doing so, we derive the extended Pauli Hamiltonian that captures all relativistic contributions in first order; the most significant one is the full spin-orbit interaction (gauge invariant and Hermitian). Noteworthy, we find that this relativistic framework explains a wide range of dynamical magnetic phenomena. To mention, (i) we show that the phenomenological Landau-Lifshitz-Gilbert equation of spin dynamics can be rigorously obtained from the Dirac-Kohn-Sham equation and we derive an exact expression for the tensorial Gilbert damping. (ii) We derive, from the gauge-invariant part of the spin-orbit interaction, the existence of a relativistic interaction that linearly couples the angular momentum of the electromagnetic field and the electron spin. We show this spin-photon interaction to provide the previously unknown origin of the angular magneto-electric coupling, to explain coherent ultrafast magnetism, and to lead to a new torque, the optical spin-orbit torque. (iii) We derive a definite description of magnetic inertia (spin nutation) in ultrafast magnetization dynamics and show that it is a higher-order spin-orbit effect. (iv) We develop a unified theory of magnetization dynamics that includes spin currents and show that the nonrelativistic spin currents naturally lead to the current-induced spin-transfer torques, whereas the relativistic spin currents lead to spin-orbit torques. (v) Using the relativistic framework together with ab initio magneto-optical calculations we show that relativistic laser-induced spin-flip transitions do not explain the measured large laser-induced demagnetization. Employing the ab initio relativistic framework, we calculate the amount of magnetization that can be imparted in a material by means of circularly polarized light – the so-called inverse Faraday effect. We show the existence of both spin and orbital induced magnetizations, which surprisingly reveal a different behavior. We establish that the laser-induced magnetization is antisymmetric in the light’s helicity for nonmagnets, antiferromagnets and paramagnets; however, it is only asymmetric for ferromagnets.
190

Numerical methods for dynamic micromagnetics

Shepherd, David January 2015 (has links)
Micromagnetics is a continuum mechanics theory of magnetic materials widely used in industry and academia. In this thesis we describe a complete numerical method, with a number of novel components, for the computational solution of dynamic micromagnetic problems by solving the Landau-Lifshitz-Gilbert (LLG) equation. In particular we focus on the use of the implicit midpoint rule (IMR), a time integration scheme which conserves several important properties of the LLG equation. We use the finite element method for spatial discretisation, and use nodal quadrature schemes to retain the conservation properties of IMR despite the weak-form approach. We introduce a novel, generally-applicable adaptive time step selection algorithm for the IMR. The resulting scheme selects error-appropriate time steps for a variety of problems, including the semi-discretised LLG equation. We also show that it retains the conservation properties of the fixed step IMR for the LLG equation. We demonstrate how hybrid FEM/BEM magnetostatic calculations can be coupled to the LLG equation in a monolithic manner. This allows the coupled solver to maintain all properties of the standard time integration scheme, in particular stability properties and the energy conservation property of IMR. We also develop a preconditioned Krylov solver for the coupled system which can efficiently solve the monolithic system provided that an effective preconditioner for the LLG sub-problem is available. Finally we investigate the effect of the spatial discretisation on the comparative effectiveness of implicit and explicit time integration schemes (i.e. the stiffness). We find that explicit methods are more efficient for simple problems, but for the fine spatial discretisations required in a number of more complex cases implicit schemes become orders of magnitude more efficient.

Page generated in 0.1201 seconds