Dissertations / Theses on the topic 'Magnetic Islands'
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Meshcheriakov, Dmytro. "Non linear dynamics of magnetic islands in fusion plasmas." Thesis, Aix-Marseille, 2012. http://www.theses.fr/2012AIXM4785.
Full textTearing modes are known to deteriorate the confinement and limit plasma performance in fusion devices. Various studies of this mode have been performed lately including an increasing level of complexity in the physical description which is required for understanding of experimental observations. One of such extensions is the introduction of diamagnetic rotation into the system. Another physical mechanisms known to be important for tearing mode dynamics is the curvature of unperturbed magnetic field lines and neoclassical physics. In this thesis we investigate the issues of linear stability of the tearing modes in a presence of both curvature and diamagnetic rotation using the non linear full-MHD toroidal code XTOR-2F, which includes anisotropic heat transport, diamagnetic and geometrical effects. This analysis is applied to one of the fully non-inductive discharges on Tore-Supra. Such experiments are crucially important to demonstrate reactor scale steady state operation for the tokamak. In this thesis, the possibility of full linear stabilization of the tearing modes by diamagnetic rotation in the presence of toroidal curvature is shown. In the linearly stable domain, the mode is metastable: saturation level depends on the seed island size. In the non linear regime, the saturation of n=1, m=2 mode is found to be strongly reduced by diamagnetic rotation and by Lundquist number. The question of extrapolation of the obtained results towards future generation of fusion devices is also addressed. In particular, for ITER size machines, the toroidal curvature is expected to be more important due to higher performance factor β
Yu, Edmund Po-ning. "Evolution equations for magnetic islands in a reversed field pinch." Access restricted to users with UT Austin EID, 2001. http://wwwlib.umi.com/cr/utexas/fullcit?p3037030.
Full textAyten, Bircan. "Simulation Of The Stabilization Of Magnetic Islands By Ecrh And Eccd." Master's thesis, METU, 2009. http://etd.lib.metu.edu.tr/upload/12611044/index.pdf.
Full textNishimura, Seiya. "Study on multi-scale nonlinear dynamics of magnetic islands in tokamak plasmas." Aix-Marseille 1, 2009. http://www.theses.fr/2009AIX11060.
Full textThis thesis is devoted to the modelling and simulation of the nonlinear dynamics of a magnetic island in presence of a pressure gradient in a tokamak plasma. This mode called “drift tearing” is in fact a tearing mode coupled to an electronic drift wave. Tearing instabilities play an important role in the magneto-hydrodynamic stability of thermonuclear fusion plasmas. It is admitted that these instabilities will determine the pressure limit in future plasma tokamak reactors like ITER. There are still many open questions related to the conditions of appearance as well as the nonlinear dynamics of these modes. An important issue is the island rotation which develops during a tearing instability. Indeed, the rotation speed as well as its sign have an important impact on the nonlinear evolution of the magnetic island. In this thesis the physical mechanisms underlying this rotation are explored. An important result is that the rotation direction of the island depends on the viscosity and the resistivity parameters. To understand this phenomenon, a model is developed and validated by numerical simulations. A practical result is derived from this model: the rotation frequency of the magnetic island increases with the magnetic Prandtl number
Trippl, Michaela. "Islands of Innovation and Internationally Networked Labor Markets. Magnetic Centers for Star Scientists?" Institut für Regional- und Umweltwirtschaft, WU Vienna University of Economics and Business, 2009. http://epub.wu.ac.at/138/1/document.pdf.
Full textSeries: SRE - Discussion Papers
Ciuciulkaite, Agne. "Micromagnetic simulations for the investigation of magnetic vortex array dynamics." Thesis, Uppsala universitet, Materialfysik, 2016. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-280767.
Full textSpringer, Felix [Verfasser]. "Probing the energy barrier distribution in arrays of patterned magnetic nano islands / Felix Springer." Konstanz : Bibliothek der Universität Konstanz, 2011. http://d-nb.info/1017326568/34.
Full textKumar, Santhosh Tekke Athayil, and santhosh kumar@anu edu au. "Experimental Studies of Magnetic Islands, Configurations and Plasma Confinement in the H-1NF Heliac." The Australian National University. Research School of Physical Sciences and Engineering, 2008. http://thesis.anu.edu.au./public/adt-ANU20080611.171513.
Full textKumar, Santhosh Tekke Athayil. "Experimental studies of magnetic islands, configurations and plasma confinement in the H-1 NF heliac /." View thesis entry in Australian Digital Theses Program, 2007. http://thesis.anu.edu.au/public/adt-ANU20080611.171513/index.html.
Full textGallen, Sean F. "An investigation of the magnetic fabrics and the paleomagnetism of the Ghost Rocks Formation, Kodiak Islands, Alaska /." Online version, 2008. http://content.wwu.edu/cdm4/item_viewer.php?CISOROOT=/theses&CISOPTR=301&CISOBOX=1&REC=2.
Full textAlam, Khan. "Growth, Structural, Electronic, and Magnetic Characterization of GaN, CrN, Fe Islands on CrN, and Fe/CrN Bilayer Thin Films." Ohio University / OhioLINK, 2016. http://rave.ohiolink.edu/etdc/view?acc_num=ohiou1478024656083129.
Full textMonteiro, Luiz Henrique Alves. "Superfícies magnéticas de campos helicoidais toroidais em tokamaks." Universidade de São Paulo, 1990. http://www.teses.usp.br/teses/disponiveis/43/43131/tde-22052014-142315/.
Full textIt is proposed to analyse theoretically the disruptive instability that occurs in confined plasmas in Tokamaks, through investigation of the influence of resonant helical fields on their equilibrium. With this aim, a superposition of the magnetic field of the plasma in static MHD equilibrium with the field associated with the resonances is considered, taking into account the toroidal geometry of the tokamak. Due to the lack of symmetry, the lines of the total magnetic field resulting from this superposition must form magnetic surfaces only around some regions of the plasma. Using the averaging method, functions of approximate magnetic surfaces are obtained (analitically) around the regions of resonances of the plasma (they contain the lines of this total magnetic field). It was verified that these approximate surfaces have structures of magnetic islands.
Taborda, David Ciro. "Magnetic field modeling for non-axisymmetric tokamak discharges." Universidade de São Paulo, 2016. http://www.teses.usp.br/teses/disponiveis/43/43134/tde-04012017-142757/.
Full textNeste trabalho estuda-se a modelagem do campo magnético em configurações realistas de plasmas em equilíbrio não-axissimétrico e o fluxo de calor nos componentes em contato com o plasma em descargas de tokamaks com desviadores poloidais. Começa-se estabelecendo a relação entre configurações magnéticas arbitrárias e sistemas dinâmicos Hamiltonianos. Então aplicamos o conceito de helicidade magnética, que é usado para estabelecer limitações topológicas sobre as linhas de campo magnético em plasmas ideais, assim como para compreender a auto-consistência das superfícies magnéticas reconectadas em configurações não-axissimétricas. Após esta discussão teórica, apresentam-se alguns resultados sobre o equilíbrio magnetohidrodinâmico e o uso de soluções analíticas à equação de Grad-Shafranov para descrever descargas reais em tokamaks, com base em diagnósticos experimentais e condições de contorno realistas. Também realiza-se uma comparação entre a reconstrução do equilíbrio de uma descarga do DIII-D, obtida mediante uma rotina numérica desenvolvida para esta pesquisa, com a obtida mediante o código EFIT, usado amplamente em diversos tokamaks. Após isso, apresenta-se uma descrição simplificada do campo magnético não-axissimétrico, criado por fontes determinadas, e a sua implementação para descrever o campo magnético devido às correntes externas em tokamaks. Então, usam-se estas rotinas para desenvolver um procedimento numérico que ajusta um conjunto adequado de parâmetros não-lineares de correntes filamentares internas, com as quais pretende-se modelar a resposta do plasma com base nas medidas de campo magnético fora do plasma. Finalmente, estes métodos são utilizados para modelar o campo magnético criado por uma instabilidade com rotação lenta numa descarga do DIII-D. Com base nas medidas das sondas magnéticas é possível modelar os campos criados em regiões arbitrárias próximas da borda do plasma. Usando esta informação é possível determinar a borda não-axissimétrica do plasma mediante as invariantes magnéticas calculadas com a utilização de uma rotina desenvolvida durante este trabalho. A intersecção da superfície invariante com a câmara do tokamak coincide satisfatoriamente com as medidas de fluxo de calor nas placas do divertor para a mesma descarga, indicando o desenvolvimento de uma variedade giratória criada pelas correntes de plasma não-axissimétricas, e sustentando quantitativamente a nossa descrição simplificada do campo magnético, assim como a definição da borda do plasma mediante as invariantes magnéticas.
Silva, Elton Cesar da. "Efeitos da geometria toroidal na atuação de campos helicoidais ressonantes em Tokamaks." Universidade de São Paulo, 2001. http://www.teses.usp.br/teses/disponiveis/43/43131/tde-09102012-151302/.
Full textIn this work, we have considered the effects of an external resonant magnetic field on the plasma confined in a tokamak. This resonant field can be produced by helical windings or by a chaotic magnetic limiter. The main purpose of this resonant magnetic field is to create a region of chaotic field lines at the edge of the plasma that can improve the confinement of the plasma. The equilibrium tokamak field was obtained by solving the GRAD-SHAFRANOV equation in an intrinsically toroidal coordinate system (the toroidal polar coordinates). We have obtained the magnetic field which has been generated by helical windings through an explicit solution of the LAPCACE equation in the same coordinate system. From this magnetic field, taken in its lowest order, we have analytically obtained a sympletic stroboscopic map for a set of chaotic magnetic limiters. We have calculated this sympletic stroboscopic map by using a Hamiltonian formulation and by supposing the action of the chaotic magnetic limiters as a sequence of delta-function pulses. With this sympletic stroboscopic map we have characterized some resonant magnetic islands and the onset of global chaos through their overlap. We have used this sympletic stroboscopic map in order to study the transport of the field lines at the edge of the plasma. The loss of chaotic field lines that reach the inner wall of the tokamak follows a POISSON distribution. We have also calculated the average number of toroidal turns for a chaotic field line to reach the inner wall of the tokamak.
Kalezhi, Josephat. "Modelling data storage in nano-island magnetic materials." Thesis, University of Manchester, 2011. https://www.research.manchester.ac.uk/portal/en/theses/modelling-data-storage-in-nanoisland-magnetic-materials(9b449925-1a39-4711-8d55-82e6d8ac215c).html.
Full textYee, Chin-ming. "Magnetic and gradiometer survey of a site in northeastern Lantau Island Hong Kong." Click to view the E-thesis via HKUTO, 2002. http://sunzi.lib.hku.hk/hkuto/record/B43895025.
Full textLamarche, Amy J. "Magnetic structure of Loihi Seamount, an active hotspot volcano in the Hawaiian Island chain." Thesis, Texas A&M University, 2003. http://hdl.handle.net/1969.1/296.
Full textYee, Chin-ming, and 庾前明. "Magnetic and gradiometer survey of a site in northeastern Lantau Island Hong Kong." Thesis, The University of Hong Kong (Pokfulam, Hong Kong), 2002. http://hub.hku.hk/bib/B43895025.
Full textBoltaev, A. P., I. A. Sherstnev, and F. A. Pudonin. "Multilayered Structures from Periodically Alternating Magnetic Island Layers: Magnetization Processes and Magnetoresistance." Thesis, Sumy State University, 2012. http://essuir.sumdu.edu.ua/handle/123456789/35303.
Full textKikuchi, Y., H. Takahashi, Y. Uesugi, and S. Takamura. "Suppression of Externally Induced Magnetic Island by Plasma Current Oscillation in HYBTOK-II." IEEE, 2003. http://hdl.handle.net/2237/7109.
Full textRobinson, David. "Evaluation of the performance of the Magnetic Island Solar Suburb - Townsville Solar City." Thesis, Robinson, David (2010) Evaluation of the performance of the Magnetic Island Solar Suburb - Townsville Solar City. Masters by Coursework thesis, Murdoch University, 2010. https://researchrepository.murdoch.edu.au/id/eprint/41508/.
Full textRoberts, Clive Lynton. "Tertiary and Carboniferous magmatism around Lundy Island and the outer Bristol Channel : a geophysical and geochemical perspective." Thesis, Open University, 1997. http://oro.open.ac.uk/54615/.
Full textZlotnicki, Jacques. "Sur les effets volcanomagnetiques et tectonomagnetiques." Paris 7, 1987. http://www.theses.fr/1987PA077296.
Full textShi, Yuanjing. "Investigation of island geometry variations in bit patterned media storage systems." Thesis, University of Manchester, 2011. https://www.research.manchester.ac.uk/portal/en/theses/investigation-of-island-geometry-variations-in-bit-patterned-media-storage-systems(b16092b6-7260-4dc5-aa30-7dabb2c7a46f).html.
Full textSasco, Romain. "Développement d'un outil chronostratigraphique pour les archives climatiques : datations absolues (K/Ar,⁴⁰Ar/³⁹Ar) et paléomagnétisme appliqués aux laves." Thesis, Paris 11, 2015. http://www.theses.fr/2015PA112009/document.
Full textThe understanding of climatic mechanisms and rapid climate changes requires a high-resolution, robust, and precise timescale which allows long-distance and multi-archives correlations.An appropriate tool to construct such a timescale is provided by the Earth magnetic field (EMF). The EMF is independent from climatic variations and its past evolution, global at the surface of the Earth, is recorded by most of the geological/climatic archives. Sedimentary sequences provide continuous records of relative intensities of the EMF on timescales usually based on ice core age models or orbital tuning. Lavas, though discontinuously emitted through time, record the absolute intensity of the EMF during their cooling at the surface of the Earth. Lavas are dated using 2 complementary methods: ⁴⁰Ar/³⁹Ar and K-Ar, both independent from climatic parameters. Lavas have therefore the potential to deliver tie-points (age-paleointensity couples) enabling the time calibration of sedimentary sequences and their transfer onto absolute intensity scale and chronological time scale. This timescale can then be transferred to other climatic archives. The present study focusses on the last 200 ka with lavas sampled from young volcanoes of Ardèche (South Massif Central, France) and recent phases of volcanism in the Canary Islands.Lava flows from Ardèche provided unexploitable paleointensity results and ages with large uncertainties. Therefore, they failed to provide suitable tie-points. However, our geochronological results evidence how crucial the combination of both the K-Ar and 40Ar/39Ar methods is to test the accuracy and geological meaning of the ages. Ardèche lavas have abundant mantellic and crustal xenoliths, potential carriers of excess ⁴⁰Ar*. Our study suggests that the argon excess is located in sites that decrepitate at low temperature (<600°C). Because ⁴⁰Ar/³⁹Ar ages are not affected by excess ⁴⁰Ar*, they provide reliable results. The new age dataset indicates that the volcanic activity of Ardèche can be divided in 3 phases: the oldest one (180±30 ka) took place in the northern part of the studied area and 2 younger phases are expressed in the South (31±4 ka and 24±8 ka).The study of the Canarian lavas produced 14 tie-points (9 out of 14 dated combining K-Ar and ⁴⁰Ar/³⁹Ar results). These data have been added to the available ones for the same time period. The published data have been selected on the basis of robust analytical protocols and accuracy. The 51 data finally selected are compared to available sedimentary stacks. Over the last 80 ka, the volcanic data corroborate the calibration of GLOPIS-75, initially based on volcanic and archeomagnetic data between 10-20 ka and the low intensity observed in the Laschamp excursion. Three newly produced data, dated between 45 and 60 ka, extend the database initially used to older periods and they are also consistent with the initial calibration of GLOPIS-75. Between 80 and 140 ka, though volcanic data have significant uncertainties (in age and/or paleointensity), they are consistent with available sedimentary records and validate their calibration level on the long-term. At a shorter time scale, volcanic data corroborate the intensity low reached during the older phase of the Blake excursion (120 ka) by PISO-1500, whereas this low does not appear in SINT-2000. For ages older than 140 ka, not only the volcanic data are scattered, but also the sedimentary records are different from one another and no conclusions could be drawn. Finally, 2 of our data suggest a brief geomagnetic event around 155 ka. Such an event cannot be seen on available global sedimentary stacks or models, even though some individual studies report a local geomagnetic event around 150 ka (Austria, Russia, and China Sea)
Beal, Irina. "Event Sedimentology and Hydrodynamic Hindcasting of Storm Surge Deposits: Hurricane Sandy, New Jersey." Master's thesis, Temple University Libraries, 2014. http://cdm16002.contentdm.oclc.org/cdm/ref/collection/p245801coll10/id/281770.
Full textM.S.
The impact of Hurricane Sandy (October 2012) on the Atlantic Coast of the United States resulted in massive overtopping (aggradation) of coastal barriers, along with localized overwash and breaching. A combination of high-frequency ground-penetrating radar (800 MHz GPR), low-field magnetic susceptibility (MS), and textural and mineralogical analyses was used to reconstruct the sedimentological and hydrodynamic parameters of the storm surge at two New Jersey sites immediately north of hurricane landfall: 1) Mantoloking and 2) Island Beach State Park (IBSP). Mantoloking represents a developed, scour-channelized backdune area with a 30-60 cm thick deposit consisting of 20-23 event horizons. Geophysical images reveal gently landward-dipping reflections. In contrast, IBSP site is a broad (width: 40 m) vegetated dune swale. GPR transects show landward-dipping tangential-oblique reflections as well as a conformable channel cut-and-fill structure (width: 7 m; depth: 1.5 m), producing a 0.7-1.5-m-thick deposit with 24-30 horizons. Within each sand-dominated event horizon, an upward 5-15% increase in mean grain size and 80-100% decrease in MS highlight the importance of hydrodynamic equivalency in lithological segregation within mixed-density fractions. Basal sub-layers enriched in heavy minerals (magnetite, ilmenite, garnet) yield MS of 100-350 μSI, in contrast to <40 μSI in quartz-rich upper sub-layers and pre-storm deposits. Several peaks in MS values correspond to an up to 65% increase in threshold shear stresses associated with individual unidirectional surge flows, with several most-enriched event horizons likely corresponding to waning-stage storm surge peaks recorded by offshore buoys. The sharp contact with the pre-storm surface produces distinct GPR reflections that allow accurate mapping of the thickness and extent of hurricane deposits. Together with potential correlation between lithological anomalies and high amplitude georadar signal return, the approach used in this study has applications to reconstructing event deposits in Quaternary sedimentary records. The new research findings have potential implications for reconstructing surge dynamics of recent hurricane events as well as quantitative hindcasting of hydrodynamic conditions responsible for lithologically diverse intervals in ancient tempestites.
Temple University--Theses
Beal, Irina. "Beal_Calculations.xls." Master's thesis, Temple University Libraries, 2014. http://cdm16002.contentdm.oclc.org/cdm/ref/collection/p245801coll10/id/281771.
Full textM.S.
The impact of Hurricane Sandy (October 2012) on the Atlantic Coast of the United States resulted in massive overtopping (aggradation) of coastal barriers, along with localized overwash and breaching. A combination of high-frequency ground-penetrating radar (800 MHz GPR), low-field magnetic susceptibility (MS), and textural and mineralogical analyses was used to reconstruct the sedimentological and hydrodynamic parameters of the storm surge at two New Jersey sites immediately north of hurricane landfall: 1) Mantoloking and 2) Island Beach State Park (IBSP). Mantoloking represents a developed, scour-channelized backdune area with a 30-60 cm thick deposit consisting of 20-23 event horizons. Geophysical images reveal gently landward-dipping reflections. In contrast, IBSP site is a broad (width: 40 m) vegetated dune swale. GPR transects show landward-dipping tangential-oblique reflections as well as a conformable channel cut-and-fill structure (width: 7 m; depth: 1.5 m), producing a 0.7-1.5-m-thick deposit with 24-30 horizons. Within each sand-dominated event horizon, an upward 5-15% increase in mean grain size and 80-100% decrease in MS highlight the importance of hydrodynamic equivalency in lithological segregation within mixed-density fractions. Basal sub-layers enriched in heavy minerals (magnetite, ilmenite, garnet) yield MS of 100-350 μSI, in contrast to <40 μSI in quartz-rich upper sub-layers and pre-storm deposits. Several peaks in MS values correspond to an up to 65% increase in threshold shear stresses associated with individual unidirectional surge flows, with several most-enriched event horizons likely corresponding to waning-stage storm surge peaks recorded by offshore buoys. The sharp contact with the pre-storm surface produces distinct GPR reflections that allow accurate mapping of the thickness and extent of hurricane deposits. Together with potential correlation between lithological anomalies and high amplitude georadar signal return, the approach used in this study has applications to reconstructing event deposits in Quaternary sedimentary records. The new research findings have potential implications for reconstructing surge dynamics of recent hurricane events as well as quantitative hindcasting of hydrodynamic conditions responsible for lithologically diverse intervals in ancient tempestites.
Temple University--Theses
Beal, Irina. "Beal_CAMSIZERdata.xlsx." Master's thesis, Temple University Libraries, 2014. http://cdm16002.contentdm.oclc.org/cdm/ref/collection/p245801coll10/id/281772.
Full textM.S.
The impact of Hurricane Sandy (October 2012) on the Atlantic Coast of the United States resulted in massive overtopping (aggradation) of coastal barriers, along with localized overwash and breaching. A combination of high-frequency ground-penetrating radar (800 MHz GPR), low-field magnetic susceptibility (MS), and textural and mineralogical analyses was used to reconstruct the sedimentological and hydrodynamic parameters of the storm surge at two New Jersey sites immediately north of hurricane landfall: 1) Mantoloking and 2) Island Beach State Park (IBSP). Mantoloking represents a developed, scour-channelized backdune area with a 30-60 cm thick deposit consisting of 20-23 event horizons. Geophysical images reveal gently landward-dipping reflections. In contrast, IBSP site is a broad (width: 40 m) vegetated dune swale. GPR transects show landward-dipping tangential-oblique reflections as well as a conformable channel cut-and-fill structure (width: 7 m; depth: 1.5 m), producing a 0.7-1.5-m-thick deposit with 24-30 horizons. Within each sand-dominated event horizon, an upward 5-15% increase in mean grain size and 80-100% decrease in MS highlight the importance of hydrodynamic equivalency in lithological segregation within mixed-density fractions. Basal sub-layers enriched in heavy minerals (magnetite, ilmenite, garnet) yield MS of 100-350 μSI, in contrast to <40 μSI in quartz-rich upper sub-layers and pre-storm deposits. Several peaks in MS values correspond to an up to 65% increase in threshold shear stresses associated with individual unidirectional surge flows, with several most-enriched event horizons likely corresponding to waning-stage storm surge peaks recorded by offshore buoys. The sharp contact with the pre-storm surface produces distinct GPR reflections that allow accurate mapping of the thickness and extent of hurricane deposits. Together with potential correlation between lithological anomalies and high amplitude georadar signal return, the approach used in this study has applications to reconstructing event deposits in Quaternary sedimentary records. The new research findings have potential implications for reconstructing surge dynamics of recent hurricane events as well as quantitative hindcasting of hydrodynamic conditions responsible for lithologically diverse intervals in ancient tempestites.
Temple University--Theses
Hilscher, Paul Peter. "Study of multi-scale interaction and dissipation based on gyro-kinetic model in fusion plasmas." Kyoto University, 2013. http://hdl.handle.net/2433/180447.
Full textFévrier, Olivier. "Modélisation globale du contrôle des îlots magnétiques dans les tokamaks." Thesis, Aix-Marseille, 2016. http://www.theses.fr/2016AIXM4070/document.
Full textMagneto-Hydro-Dynamic (MHD) instabilities are susceptible to develop within a tokamak plasma. These instabilities manifest themselves as magnetic islands which reduce the plasma confinement. The islands can however be controlled by driving current inside them. In this thesis, we consider the modeling of the magnetic islands and their control using first principle approaches, which rely on a global MHD description of the plasma. We have detailed the inclusion a RF-driven current like source term in an MHD code, which requires special care to be given to the modeling of the current density evolution. The implementation has been benchmarked against the asymptotic models, allowing us to retrieve the influence of parameters such as deposition width or misalignment with respect to the island width and position. Beyond these aspects, we have evidenced new effects, linked to the 3D nature of the current deposition. We have observed a flip instability in which an island, reduced by the ECCD, brutally inverse its phase so that its X-Point faces the current deposition, allowing the mode the grow further. We then moved on to the topic of the best suitable control strategies for the control of the island. We have implemented in XTOR a control system that mimics the experimental ones and adapt the current deposition in function of a preset strategy. Nonlinear MHD simulations have been carried out using different control schemes, allowing us to quantify the gain to expect from each of these methods depending on the characteristics of the current deposition
Mills, Carol. "“The Pilot’s Wife” and Hosting Tourism on Magnetic Island: A Memoir and Autoethnographic Enquiry of Place, Self and Narrative within Structures of Authority and Power." Thesis, Curtin University, 2018. http://hdl.handle.net/20.500.11937/76666.
Full textPoye, Alexandre. "Dynamique des ilots magnétiques en présence de feuille de courant et en milieu turbulent." Thesis, Aix-Marseille, 2012. http://www.theses.fr/2012AIXM4793/document.
Full textThe fusion plasma stability is a critical point for the developpement of newenergy source. The interaction between the plasma and the magnetic field can drive to the confinement descrution : it is a disruption. The topic of this thesis is the magnetic island, one of disruption causes. Those magnetic islands are observed theoretically and numerically. The theory can predict the growth and the final size of magnetic islands, but restrictions of its validity range are strong and they decorrelate the experimental and theoritical validity domain. In the first part, we show that the dynamic method of magnetic island control, based on the link between the island size and the perturbed magnetic flux at the resonance, should take in account the modification of the magnetic flux averaged along the field line. We show aswell the limitation of our assertion (magnetic island coalescence, X point collapse ...). The second part of the thesis address a new effet du to the current on sides of the magnetic island. This effect changes the magnetic island dynamics and the perception we got on it. Until now, the magnetic island dynamics have been studied through active mechanisms at the resonance. We show that the presence of current on sides can play an important role on the growth and saturation of the magnetic island. The last part of thesis details how the turbulence on the outskirts of a magnetic island can affect the island growth. We show that a turbulence generate by an interchange instability can penetrate into a stable zone concerning tearing mode and induce by a 3D mechanisme the growth of an magnetic island
Mannoubi, Soumaya. "Caractérisation de MamK et Mamk-like les "actins-like" responsables de l'alignement des magnétosomes chez Magnetsirillum magneticum AMB-1." Thesis, Aix-Marseille, 2014. http://www.theses.fr/2014AIXM4004.
Full textMagnetotactic bacteria (MTB) have the ability to orient in a magnetic field through a prokaryotic organelle composed of a magnetic nanocrystal surrounded by a biological membrane: the magnetosome. The synthesis of this organelle is a genetically complex process controlled by a series of specific genes (mam genes) grouped together on the bacterial chromosome. In the strain model Magnetospirillum magneticum AMB-1 this set of genes form a genomic island (MAI) and a second distinct group of seven genes homologous to mam genes (mam-like genes) recently identified. The physiological role of this islet magnetosome (MIS) is very little characterized to date.Among the products of mam genes, MamK is involved in the alignment of the magnetosomes. This « actin-like » which forms prokaryote filaments according an ATP - dependent process has been characterized in recent years. In the MIS of AMB-1, a homologous gene mamK-like was identified. And various multidisciplinary approaches have been developed to understand the role of MamK and MamK-like. The MIS gene expression was quantified. The strains lacking genes of mamK, mamK-like and the obtained of double mutant were then phenotyped by different imaging techniques. The interactions between the two proteins were also tested. Finally, the two proteins were overexpressed and their biochemical properties characterized. All of these data allows us to propose a model whereby MamK and MamK-like participate in both the alignment of bacterial magnetosomes, presumably by the formation of hybrid filaments
Perinotto, Hélène. "Dynamique de mise en place des avalanches de débris sur les flancs aériens des volcans insulaires : le cas de La Réunion." Thesis, Bordeaux, 2014. http://www.theses.fr/2014BORD0414/document.
Full textDebris avalanches, resulting from flank collapses that shape volcanic and mountainous edifices are rapidand dangerous gravity-driven granular flows that travel long run out distances. The dynamic and the transport mechanisms behind this high mobility remain poorly understood. The numerous models proposed to explain this high mobility include processes based on lubrication or fluidisation of the granular mass of the flow body, but also the dynamic disintegration of the transported particles. To date,all these proposed mechanisms lack observational support and quantification of the state of the particles of the granular mass during the transport. To identify the main transport mechanisms, we propose here detailed field studies of volcanic debris avalanches deposits resulting of flank-collapse events on an oceanic shield volcano, the Piton des Neiges (La Réunion Island, Indian Ocean). This study has been combined with morphometric (fractal dimension and circularity), exoscopic and grain-size analyses. Moreover, the fabric of the deposits has been investigated by with the characteristics of the anisotropy of the magnetic susceptibility (ASM). From these data we highlight a proximal to distal evolution of the debris avalanches transport and emplacement dynamics. We demonstrate that syn-transport dynamic disintegration continuously operates with the distance from the source down to a grinding limit of 500μm. Below this limit, the particle size reduction exclusively results from the attrition of the particles by frictional interactions. Thus, the exceptional mobility of debris avalanches may be explained by thecombined effect of elastic energy release during the dynamic disintegration of the larger clasts (> 500μm) and frictional reduction within the matrix due to the dispersive interactions between the finer particles (< 500 μm). All these data also allow to specify the transport direction and the approximate size of the debris avalanches related to the Piton des Neiges destabilisations
Siccinio, Mattia [Verfasser]. "Kinetic investigation of magnetic islands in tokamaks / Mattia Siccinio." 2010. http://d-nb.info/1004277571/34.
Full textYu, Edmund Po-ning 1972. "Evolution equations for magnetic islands in a reversed field pinch." 2001. http://hdl.handle.net/2152/10894.
Full textChen, Shou-Yuan, and 陳士元. "The magnetic properties of Fe/Ag submicrometer pyramidal islands on Si(100)." Thesis, 2003. http://ndltd.ncl.edu.tw/handle/97448163949383341774.
Full text國立臺灣科技大學
機械工程系
91
In this study, we deposited Ag buffer layer with various thickness on an RCA-cleaned Si(100) substrate in a molecular-beam epitaxial system. Small pyramidal Ag islands with a (100) truncated top and four (111) sidewalls were successfully formed on Si(100) substrates. We systematically studied the magnetic properties of Fe films grown on the buffer of Ag layers at 100℃. The magnetic behavior of Fe films is strongly dependent on the thickness, morphology, and surface roughness of the Ag buffer layers. The Ag film, in order to reduce the total surface free energy, forms isolated three-dimensional square islands with a (100) truncated top and four (111) sidewalls on the Si(100) substrate. The average height, grain size and surface roughness of these Ag islands were tuned by varying the deposition thickness of the Ag film. From RHEED observation, we found that Ag(100) plane matched with Si(100) plane. The orientation relationship between Ag and Si is Ag(100)[011] // Si(100)[011]. The coercivity of the Fe films increased as the roughness of the Ag buffer layer increased. The in-plane easy axis of the Fe film was rotated 45° while the thickness of the Ag buffer layer reaches 100 Å and the Ag rough surface provides a source of domain wall pinning. The Fe film that deposited on the sidewalls of the pyramidal islands played an important role on the magnetic properties of the parallel and perpendicular of the directions and initial magnetization reversal.
Hölzl, Matthias [Verfasser]. "Diffusive heat transport across magnetic islands and stochastic layers in tokamaks / Matthias Hölzl." 2010. http://d-nb.info/1000443388/34.
Full textVan, Vuuren Gary Wayne. "The influence of rotating and locked magnetic islands on edge transport in Tokoloshe tokamak." Thesis, 1993. http://hdl.handle.net/10413/6469.
Full textThesis (Ph.D.)-University of Natal, 1993.
Kumar, Santhosh Tekke Athayil. "Experimental Studies of Magnetic Islands, Configurations and Plasma Confinement in the H-1NF Heliac." Phd thesis, 2007. http://hdl.handle.net/1885/49287.
Full textLloyd, Sally Stevens. "Simulating magnetic islands of the H-1NF heliac using the MHD equilibrium code HINT." Phd thesis, 2003. http://hdl.handle.net/1885/146369.
Full textChin, An-Li, and 秦安立. "Investigation of magnetic islands on Si(111)-5×2/Au Surface with Scanning Tunneling Microscopy." Thesis, 2003. http://ndltd.ncl.edu.tw/handle/40323786130594547151.
Full text國立中正大學
物理系
91
We make the Si (111)-5×2/Au by depositing Au 0.5 ML as the substrate. Then the substrate is deposited Co at room temperature and annealed for 5 min. We investigate the self-assembly of magnetic islands are on Si (111)-5×2/Au, and the feature of the clusters are as follow.The density of the islands is as a liner function with cobalt coverage, and the islands size increase with temperature. Now we observe that the shape of the cluster is hexagon when we anneal at 600°C and 700°C. Espe. When temperature of the substrate is 500°C, the surface is mixed by domed and hexagonal islands which is formed phase transition.
"Effects of Resonant Magnetic Perturbations on the STOR-M Tokamak Discharges." Thesis, 2014. http://hdl.handle.net/10388/ETD-2014-04-1539.
Full textCahyna, Pavel. "Difuze částic z tokamaku vlivem stochastizace magnetických siločar." Doctoral thesis, 2010. http://www.nusl.cz/ntk/nusl-296117.
Full textTuen, Li Huey. "Stability of a two-volume MRxMHD model in slab geometry." Master's thesis, 2017. http://hdl.handle.net/1885/131789.
Full textLin, Ger-Pin, and 林哲平. "Study of magnetic properties and microstructures of FePt island films." Thesis, 2010. http://ndltd.ncl.edu.tw/handle/01227935614145379058.
Full text臺灣大學
材料科學與工程學研究所
98
The development of recording media of continuous films is restricted by super-paramagnetic limit. Patterned media has been suggested as a potential solution for this physical limit. In this study, we describe a simple and cheap method to fabricate large-area patterned media. The grain size of the magnetic films must be reduced to improve the signal-to-noise ratio. The exchange coupling effect between magnetic grains should be minimized in order to decrease transition noise. This discontinuous nano-size island magnetic film was suggested to reduce the exchange coupling effect between magnetic islands and increased the recording density. In order to increase the recording density, the size of magnetic islands must be reduced by modifying the experiment condition. FePt films (15 nm) were fabricated with (Fe/Pt)n multilayer on amorphous glass substrates then post-annealed at 700 ℃ for 30 mins to obtain better perpendicular magnetic anisotropy and ordering degree. The chemical composition of FePt films is Fe59Pt41. The magnetic easy axis [001] of L10 FePt phase in the FePt films was perpendicular to the film plane. This nano-size island-shape FePt film with perpendicular magnetic anisotropy may be a good candidate for ultra-high density recording media. The X-ray diffraction patterns of the annealed FePt films with heat treatment on amorphous glass substrates shown that the fct-FePt(001) peak and fct-FePt(002) peak appeared in 5-nm FePt film. However, the intensity of the fct-FePt(001) peak and fct-FePt(002) peak were weaker as the thickness of FePt film increasing to 30 nm, but the intensity of the fct-FePt (111) peak enhanced. As the thickness of FePt films was increased, the easy axis orientation of FePt films would turn from perpendicular to parallel to the film plane. However, the ordering degree of the FePt film would increase with FePt film thickness. The particle size of 1-nm thick FePt film on glass that annealed at 700 ℃ for 10 minutes distributed between 2.5 to 5 nm, and the density of islands is 1.37×1013 islands/inch2. A discontinuous and well-separated nano-size island magnetic film can reduce the exchange coupling of the media and increase the recording density. The driving force of FePt island formation was the surface energy difference between the substrate and FePt alloy. The nucleation site number of FePt islands increased with the surface energy difference between the substrate and FePt alloy. Therefore, the density of islands of 1-nm thick FePt film annealed at 700 ℃ for 10 minutes on carbon film (1.44×1013 islands/inch2) was slightly larger than that of 1-nm thick FePt film annealed at 700 ℃ for 10 minutes on glass. But, the fcc-FePt phase still existed in the 1-nm thick FePt film which annealed at 700 ℃ for 10 minutes on carbon film. Due to the thick Ag under-layer, the grain growth and island cluster occurred easily in the FePt (1 nm~7.5 nm)/Ag (100 nm) bi-layer films, and the size distribution of metallic islands would be very broad. However, the Ag under layer could improve the ordering of FePt film. The lattice mismatch between Ag under layer and FePt film would provide additional strain energy and promote the occurrence of the fct-FePt (111) preferred orientation. The orientation of magnetic easy axis of FePt (1 nm~7.5 nm) films with Ag (100 nm) under-layer would turn from perpendicular to parallel to the film plane. Due to the Ag atom has larger diffusion coefficient during annealing process, the metallic islands had better roundness in FePt (1 nm)/Ag (1 nm ~3 nm) bi-layer films. Investigation of the microstructures and magnetic properties of the ordered FePt films revealed that the 1 nm-FePt film annealed at 700 ℃ for 10 minutes had perpendicular magnetic anisotropy and formed well-separated FePt nano-size islands. It is suitable for ultra-high density magnetic recording media. But, the out-of-plane coercivity of the well-separated FePt nano-size islands was about 20 kOe, and it was too large for recording head to reverse its moments. In order to reduce the writing field of FePt nano-island film, we introduced Fe capping layer (0.5~5 nm) on the FePt nano-island films. The exchange coupling effect between Fe capping layer and FePt nano-island would decrease the writing field of the island films.
Martin-Smith, Keith Michael. "The role of epifaunal crustaceans on Sargassum spp. at Magnetic Island, Great Barrier Reef, Australia." Thesis, 1994. https://researchonline.jcu.edu.au/24116/1/01front.pdf.
Full textHu, Wenbao. "A model study of the electromagnetic response of a channel, an island and a seamount in the South China Sea." Thesis, 1986. http://hdl.handle.net/1828/5723.
Full textHarrington, Jane Therese. "'Being here': heritage, belonging and place making: a study of community and identity formation at Avebury (England), Magnetic Island (Australia) and Ayutthaya (Thailand)." Thesis, 2004. https://researchonline.jcu.edu.au/71/1/01front.pdf.
Full textHarrington, Jane Therese. "Being here : : heritage, belonging and place making : a study of community and identity formation at Avebury (England), Magnetic Island (Australia) and Ayutthaya (Thailand) /." 2004. http://eprints.jcu.edu.au/71/1/01front.pdf.
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