Tesi sul tema "Bulk magnets"
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Lwin, Mark. "The dynamic compaction of the metastable hard magnet powder Sm!b2!sFe!b17!sNx to form bulk magnets". Thesis, Queensland University of Technology, 1994.
Unge, Mikael. "Molecular Electronics : A Theoretical Study of Electronic Structure of Bulk and Interfaces". Doctoral thesis, Linköpings universitet, Beräkningsfysik, 2006. http://urn.kb.se/resolve?urn=urn:nbn:se:liu:diva-6938.
Kapek, Jakub. "Modélisations 2D et 3D, conception et réalisation d’un inducteur pour aimanter un ensemble de pastilles supraconductrices". Electronic Thesis or Diss., Université de Lorraine, 2021. http://www.theses.fr/2021LORR0113.
Today, superconductors are used in many applications, for example in cables, motors, alternators or for the generation of strong magnetic fields. Superconductors are available as tapes, wires or bulk materials. The process of magnetising superconductors results in bulk superconductors with a much higher trapped magnetic field than conventional permanent magnets. Proper magnetisation is the key to a very strong trapped magnetic field. The work developed in this thesis concerns the 2D and 3D modelling, design and realisation of an inductor to magnetise a set of superconducting pellets. Generally speaking, there are three techniques for magnetising superconductors: Zero Field Cooling (ZFC), Field Cooling (FC) and Pulsed Field Magnetization (PFM). We focus on PFM because it is a more compact and less expensive solution compared to the other techniques. The mentioned magnetisation process and all the phenomena involved have been solved based on the Finite Element Method (FEM) and using different formulations. In this work, we studied and compared in 2D and 3D the A-formulation, the H-formulation and an A-H formulation by coupling the different variables on the material boundaries. The comparison showed the advantages of the A-H formulation in modelling superconducting problems. Indeed, in some cases, we have shown that the use of the A-H formulation allows to reduce the simulation time. The model developed from this formulation is therefore an interesting tool for future dimensioning work and the development of superconductor applications at GREEN laboratory. We have also dimensioned and numerically studied a complete inductor model allowing one or more superconductors to be magnetised simultaneously. We study two configurations: prototype I for magnetising a single superconductor (2D problem) and prototype II for magnetising three superconductors (3D problem). Both configurations are solved by considering the electromagnetic and thermal phenomena as well as the coupling with the circuit equations feeding the inductor. The simulations showed that the temperature rise in the superconductor of about 10 Kelvin generated during the PFM magnetisation affected the trapped magnetic field. It was observed that the presence of one or more superconducting bulks did not affect the current pulse in the inductor. The maximum trapped field obtained numerically for prototype I was 706 mT and 736 mT for prototype II. The results obtained were then compared with the simulation results. However, some of the superconductors exhibited strong inhomogeneity in their properties, which resulted in a reduction in the experimentally observed trapped magnetic field. Hypotheses were made to try to reproduce numerically these inhomogeneities and their effects. However, this numerical calculation can only be done by 3D modelling without the possibility of using symmetries, and leads to a calculation time of up to several days. Experimentation with prototypes resulted in a maximum trapped magnetic field of 686 mT when one pellet was magnetised, while it was 606 mT when several pellets were magnetised simultaneously. Lowering the temperature by using another cryogenic fluid such as liquid hydrogen or another cooling system would increase this trapped magnetic field value to much higher values for the targeted electrical engineering applications
Lewin, Richard Peter. "Superconductors and high magnetic fields". Thesis, University of Oxford, 2012. http://ora.ox.ac.uk/objects/uuid:09992030-625d-4e6c-8152-6a61bb2cdb07.
Patel, Anup. "Pulsed field magnetization of composite superconducting bulks for magnetic bearing applications". Thesis, University of Cambridge, 2013. https://www.repository.cam.ac.uk/handle/1810/256579.
Jensen, Morten R. F. "Far infrared magneto-spectroscopy of bulk and surface magnetic excitations in FeFâ†2". Thesis, University of Essex, 1996. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.361040.
De, Silvestri Federica. "Investigation of the magnetic levitation between HTS bulks and permanent magnets". Master's thesis, Alma Mater Studiorum - Università di Bologna, 2018.
Masood, Ansar. "Functional Metallic Glasses". Doctoral thesis, KTH, Teknisk materialfysik, 2012. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-101901.
QC 20120906
Hero-m
Ahmed, Naseer. "Magneto-optics of MBE grown bulk and low dimensional III-V semiconductors". Thesis, Heriot-Watt University, 1991. http://hdl.handle.net/10399/1084.
Mitra, Chandrima. "COMPUTATIONAL STUDIES OF GADOLINIUM IN NITRIDES : BULK GDN AND GD-DOPED GAN". Case Western Reserve University School of Graduate Studies / OhioLINK, 2009. http://rave.ohiolink.edu/etdc/view?acc_num=case1238690053.
WU, DEZHEN. "Magnetic Field Effects Induced by Incorporation of Magnetic Nanoparticles on Bulk Heterojunction Polymer Solar Cells". University of Akron / OhioLINK, 2018. http://rave.ohiolink.edu/etdc/view?acc_num=akron1525107259345629.
Kato, K., T. Noda, H. Shimizu, T. Matsumura e N. Murayama. "Increase in transient resistance of Bi2223 superconducting bulk by applying external magnetic field". IEEE, 2001. http://hdl.handle.net/2237/6784.
Bhagurkar, Ashutosh. "Processing of MgB2 bulk superconductor by infiltration and growth". Thesis, Brunel University, 2017. http://bura.brunel.ac.uk/handle/2438/14777.
Xu, Zhihan. "Modelling and experimental studies of the magnetic properties of bulk high temperature superconductors". Thesis, University of Cambridge, 2013. https://www.repository.cam.ac.uk/handle/1810/265556.
Magill, Brenden A. "Microwave spectroscopy of edge and bulk modes of two dimensional electrons in magnetic field". Thesis, The Florida State University, 2013. http://pqdtopen.proquest.com/#viewpdf?dispub=3564920.
Edge magnetoplasmons (EMPs) and pinning mode resonances in two dimensional electron systems (2DESs) can both be thought of as lower hybrid modes of cyclotron and plasma resonances. This dissertation describes low temperature microwave spectroscopy of both of these modes. EMPs have oscillating charge confined at the 2DES edge by the combination of the perpendicular magnetic field and the electrostatic potential that produces the edge. Pinning mode resonances are from electron solids oscillating against confinement provided by disorder in the bulk of the 2DES.
The first part of this dissertation concerns the search for a mode similar to an EMP but confined solely by a linear magnetic inhomogeneity in the perpendicular magnetic field (Bz). While we do not observe such an excitation, we do observe a marked reduction in the velocity of an EMP in the presence of a Bz-inhomogeneity.
In the second part of this dissertation, we investigate pinning modes in “wide'' quantum well samples, for which the effective electron-electron interaction is softened at short range due to the vertical extent of the wavefunction. We observe a pinning mode resonance whose peak frequency (fpk ) vs Landau level filling (ν) shows an anomalous increase as ν moves away from ν = 1 under roughly the same conditions as anomalous quantum Hall effects observed previously in DC transport. A region of ν with enhanced fpk is interpreted as evidence for a new electron solid phase.
Matsumura, T., A. Kimura, H. Shimizu, Y. Yokomizu e M. Goto. "Fundamental performance of flux-lock type fault current limiter with two air-core coils". IEEE, 2003. http://hdl.handle.net/2237/6786.
Rich, Jason P. "Bulk and micro-scale rheology of an aging, yield stress fluid, with application to magneto-responsive systems". Thesis, Massachusetts Institute of Technology, 2012. http://hdl.handle.net/1721.1/70108.
This electronic version was submitted by the student author. The certified thesis is available in the Institute Archives and Special Collections.
Cataloged from student-submitted PDF version of thesis.
Includes bibliographical references (p. [139]-146).
Understanding the ways that matter deforms and flows, which is the focus of the branch of science known as rheology, is essential for the efficient processing and proper function of such practically and technologically important materials as plastics, paints, oil-drilling fluids, and consumer products. Rheology is also powerful from a scientific perspective because of the correlation between rheological properties and the structure and behavior of matter on microscopic and molecular scales. The developing sub-field of microrheology, which explicitly examines flow and deformation behavior on microscopic length scales, provides additional clarity to this connection between rheology and microstructure. Aging materials, whose rheological properties evolve over time, are one class of materials that are of significant scientific and practical interest for their rheological behavior. Also, the unique field-responsive rheological properties of magnetorheological (MR) suspensions, which can be tuned with an applied magnetic field, have been used to create active vibration damping systems in such diverse applications as seismic vibration control and prosthetics. A material that undergoes rheological aging and that has received much attention from soft matter researchers is the synthetic clay Laponite® . This material is attractive as a rheological modifier in industrial applications and consumer products because a rich array of rheological properties, including a yield stress, viscoelasticity, and a shear-thinning viscosity, can be achieved at very low concentrations in aqueous dispersions (~ 1 w%). Though this behavior has been investigated extensively using traditional 'bulk' rheology, a number of important questions remain regarding the nature of the dispersion microstructure. The techniques of microrheology, in which rheological properties are extracted from the motion of embedded microscopic probe particles, could help to elucidate the connection between microstructure and rheology in this material. Microrheological studies can be performed using passive techniques, in which probes are subject only to thermal motion, and active techniques, in which external forces are applied to probes. Because aqueous Laponite® dispersions exhibit a significant yield stress, they could be beneficial as novel matrix fluids for magnetorheological suspensions. MR fluids consist of a suspension of microscopic magnetizable particles in a non-magnetic matrix fluid. When an external magnetic field is applied, the particles attract each other and align in domain-spanning chains of particles, resulting in significant and reversible changes in rheological properties. Because of the typically large density difference between the matrix fluid and the suspended magnetic particles, however, sedimentation is often problematic in MR fluids. A yield stress matrix fluid such as an aqueous Laponite® dispersion could help address this issue. In this thesis, bulk rheology and microrheology experiments are combined in order to provide a thorough characterization of the rheological properties of aqueous Laponite® dispersions. Multiple Particle Tracking (MPT), a passive microrheology technique, is used to explore the gelation properties of dilute dispersions, while an active magnetic tweezer microrheology technique is used to examine the yield stress and shear-thinning behavior in more concentrated dispersions. MPT results show strong probe-size dependence of the gelation time and the viscoelastic moduli, implying that the microstructure is heterogeneous across different length scales. We also demonstrate the first use of magnetic tweezers to measure yield stresses at the microscopic scale, and show that yield stress values determined from bulk and micro-scale measurements are in quantitative agreement in more concentrated Laponite® dispersions. With a thorough understanding of the clay rheology, we study the magnetorheology of MR suspensions in a yield stress matrix fluid composed of an aqueous Laponite® dispersion. Sedimentation of magnetic particles is prevented essentially indefinitely, and for sufficient magnetic field strengths and particle concentrations the matrix fluid yield stress has negligible effect on the magnetorheology. Using particle-level simulations, we characterize the ability of the matrix fluid yield stress to arrest the growth of magnetized particle chains. The methods and results presented in this thesis will contribute to the fundamental understanding of the rheology and microstructure of aqueous Laponite® dispersions and provide researchers with new techniques for investigating complex fluids on microscopic length scales. Additionally, our characterization of the effects of a matrix fluid yield stress on magnetorheological properties will aid formulators of MR fluids in achieving gravitationally stable field-responsive suspensions, and provide a new method for manipulating the assembly of particle building blocks into functional structures.
by Jason P. Rich.
Ph.D.
Ashcroft, Gwynfor Rhys. "Structure and magnetic properties of bulk and thin film nickel manganite (NiMn(_2)O(_4))". Thesis, Durham University, 2003. http://etheses.dur.ac.uk/4010/.
Ziółkowski, Grzegorz. "Structural and physical properties of Fe-Nb-B-RE type of bulk magnetic nanocrystalline alloys". Doctoral thesis, Katowice : Uniwersytet Śląski, 2015. http://hdl.handle.net/20.500.12128/5907.
Duman, Nagehan. "Magnetic Monitoring Approach To Kinetics Of Phase Transformations In Multicomponent Alloy Systems". Phd thesis, METU, 2012. http://etd.lib.metu.edu.tr/upload/12614251/index.pdf.
Stoica, Mihai. "Casting and characterization of Fe-(Cr,Mo,Ga)-(P,C,B) soft magnetic bulk metallic glasses". Doctoral thesis, Saechsische Landesbibliothek- Staats- und Universitaetsbibliothek Dresden, 2005. http://nbn-resolving.de/urn:nbn:de:swb:14-1134119175311-08460.
Stöver, Harald D. H. "Sodium binding to crown ether derivatives bulk membrane transport and sodium-23 nuclear magnetic resonance studies". Thesis, University of Ottawa (Canada), 1986. http://hdl.handle.net/10393/5211.
Chikara, Shalinee. "A SYSTEMATIC STUDY OF THERMODYNAMIC AND TRANSPORT PROPERTIES OF LAYERED 4D AND 5D CORRELATED ELECTRON SYSTEMS". UKnowledge, 2011. http://uknowledge.uky.edu/gradschool_diss/843.
Haider, Muhammad Baseer. "Surface and Bulk Properties of Magnetically Doped GaN and Their Dependence on the Growth Conditions". Ohio University / OhioLINK, 2005. http://rave.ohiolink.edu/etdc/view?acc_num=ohiou1132011994.
Dalpian, Gustavo Martini. "A natureza de defeitos de Bulk e na superfície de semicondutores". Universidade de São Paulo, 2003. http://www.teses.usp.br/teses/disponiveis/43/43134/tde-09082012-202357/.
Using ab initio methods, based on Density Functional Theory, we have systematically investigated problems of interest for semiconductor physics: (i)The SixGe1-x alloy: we observe a small bowing in the lattice parameter, as a function of concentration, and that a larger variation in interatomic distances occurs for Ge-Ge bonds. The behavior of vacancies in this alloy is intermediate between Si and Ge, with formation energies (EF) varying from 2,06 eV to 2,90 eV, depending on the neighborhood of the vacancy. We propose a model for the diffusion of Ge in this alloy. As the vacancy with four Ge atoms as first neighbors hás smaller formation energy, the diffusion of the vacancies Will take place along paths that resemble purê Ge, for Ge-rich alloys; (ii)Surfaces: we study the adsorption of Ge monomers and dimers on Si(100). For monomers, there are several local mínima of the potential energy surface, for the same (x, y) position in the surface, depending on the buckling of the surface dimers near the adatom. We show that this can be identified in theoretical STM (Scanning Tunelling Microscopy) images. This kind of effect also occurs for dimers, and hás already been observed experimentally, but with a wrong interpretation. Through our study, we propose a new structure for the experimental images. The behavior of Si and Ge atoms and dimers near steps is also analyzed. Due to the differencein the lattice parameter of Si and Ge, we show that the adsorption becomes different when only two atoms are in the surface. Through these results, we propose a model to explain the reversion of step roughness due to Ge deposition on Si(100); (iii)Mn impurities in Si: we analise the behavior of Mn impurities in bulk Si ando n the surface. For the bulk, we observe that EF is lower for intersititial than for substitutional sites. On the surface, there is a substitutional site that hás the same EF AS A INTESTITIAL ONE. This fact may be important to the development of Si based ferromagnetic semiconductors. A method is proposed to verify this fact experimentally, through STM images.
Pandey, Sudip. "EXPLORING THE STRUCTURAL, ELECTRONIC, AND MAGNETORESPONSIVE PROPERTIES OF NOVEL MAGNETIC MATERIALS IN BULK, RIBBONS, AND THIN FILMS". OpenSIUC, 2019. https://opensiuc.lib.siu.edu/dissertations/1682.
Hirsch, Sebastian. "Compression-sensitive Magnetic Resonance Elastography". Doctoral thesis, Humboldt-Universität zu Berlin, Mathematisch-Naturwissenschaftliche Fakultät, 2015. http://dx.doi.org/10.18452/17205.
This thesis introduces the concept of compression-sensitive Magnetic Resonance Elastography. Compression-sensitive MRE detects the propagation of pressure waves, providing insight into the compressibility of a material based on a poroelastic tissue model. Poroelastic models incorporate compressibility through interaction of compartments, even as each individual compartment remains incompressible. Hydrostatic tissue pressure abnormalities are associated with a number of diseases, such as normal pressure hydrocephalus or hepatic portal hypertension. Since pore pressure plays a central role in the poroelastic wave equations, compression-sensitive MRE could potentially serve as a diagnostic tool, providing information complimentary to shear-wave MRE data. This thesis describes the development of a fast single-shot EPI MR sequence capable of quantifying volumetric strain induced by external vibrations. Compression-sensitive MRE was validated in porous gel phantoms, in the human lung at two different respiratory states, in an ex vivo sheep liver at varying levels of hydrostatic pressure, and finally in human liver and brain. Results illustrate that compression-sensitive MRE is capable of quantifying volumetric strain in phantoms and in human organs. It was found that volumetric strain was sensitive toward pressure changes associated with different physiological states, whereas shear strain remained constant. In an additional study, pulsation of the human brain, driven by the heart cycle, was used as the actuation source instead of the external vibration generator. Results indicate local expansion of brain parenchyma upon the arrival of the arterial pulse wave, followed by a slow return to the initial state during the diastolic phase. Numerical values for the pressure wave modulus M were calculated from measured volumetric strain through inversion of the pressure wave equation. Measurement noise was identified as the primary effect causing a severe underestimation of M.
Goodwin, Conrad. "Synthesis and properties of early metal bulky silylamide complexes". Thesis, University of Manchester, 2017. https://www.research.manchester.ac.uk/portal/en/theses/synthesis-and-properties-of-early-metal-bulky-silylamide-complexes(72b303fb-67c2-4749-a1fc-ada1f677a844).html.
Stoica, Mihai [Verfasser]. "Casting and characterization of Fe-(Cr,Mo,Ga)-(P,C,B) soft magnetic bulk metallic glasses / Mihai Stoica". Aachen : Shaker, 2005. http://d-nb.info/1186588829/34.
Kinjo, Ryota. "Generation and Modeling of Alternating Magnetic Field in Undulator Using Bulk High-Temperature Superconductor with Staggered Array Configuration". Kyoto University, 2014. http://hdl.handle.net/2433/188827.
Tkach, Igor. "Optically detected magnetic resonance of arsenic antisite related defects in semi-insulating bulk and low temperature MBE-grown GaAs". [S.l. : s.n.], 2002. http://deposit.ddb.de/cgi-bin/dokserv?idn=965647722.
Lim, Hui Fern Michele. "Low Temperature Co-fired Ceramics Technology for Power Magnetics Integration". Diss., Virginia Tech, 2008. http://hdl.handle.net/10919/30156.
Ph. D.
GALIZIA, PIETRO. "Production and morphological and microstructural characterization of bulk composites or thick films for the study of multiphysics interactions". Doctoral thesis, Politecnico di Torino, 2017. http://hdl.handle.net/11583/2674672.
Michael, Thomas [Verfasser], Steffen [Akademischer Betreuer] Trimper, Jamal [Akademischer Betreuer] Berakdar e Wolfgang [Akademischer Betreuer] Nolting. "Analytical description of ferroelectric nanostructures and bulk systems with non-collinear magnetic order / Thomas Michael. Betreuer: Steffen Trimper ; Jamal Berakdar ; Wolfgang Nolting". Halle, Saale : Universitäts- und Landesbibliothek Sachsen-Anhalt, 2010. http://d-nb.info/1025133609/34.
Ordikhani-Seyedlar, Amin Verfasser], Siegfried [Akademischer Betreuer] [Stapf, Andreas [Gutachter] Bund e Monika [Gutachter] Schönhoff. "Nuclear magnetic resonance relaxometry and diffusometry study of bulk and confined complex liquids / Amin Ordikhani-Seyedlar ; Gutachter: Andreas Bund, Monika Schönhoff ; Betreuer: Siegfried Stapf". Ilmenau : TU Ilmenau, 2016. http://d-nb.info/1178174786/34.
Paolella, Maurizio. "Correlations between structural and magnetic properties in powder and bulk Mg(B1-xCx)2 prepared using carbon chemical vapour doped boron and silica coated boron". Thesis, University of Southampton, 2015. https://eprints.soton.ac.uk/397082/.
Belo, Fernandes Ivan. "Geometallurgical approach to understand how the variability in mineralogy at Zinkgruvan orebodies affects the need for copper activation in the bulk rougher-scavenger flotation". Thesis, Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, 2017. http://urn.kb.se/resolve?urn=urn:nbn:se:ltu:diva-65392.
Salvo, Christopher. "Design and Implementation of a Multiphase Buck Converter for Front End 48V-12V Intermediate Bus Converters". Thesis, Virginia Tech, 2019. http://hdl.handle.net/10919/101938.
Master of Science
Najafi, Syed Ahmed Ali. "Energy Harvesting From Overhead Transmission Line Magnetic Fields". University of Akron / OhioLINK, 2019. http://rave.ohiolink.edu/etdc/view?acc_num=akron1548448189459464.
Lobato, Salatiel de Castro. "Fonte de corrente para aplicação em magnetos de aceleradores de partículas". Universidade Federal de Juiz de Fora (UFJF), 2016. https://repositorio.ufjf.br/jspui/handle/ufjf/3646.
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O objetivo geral desta dissertação é o aperfeiçoamento do projeto de uma nova fonte de corrente em desenvolvimento para o acelerador de partículas Sirius. A corrente da fonte é aplicada em magnetos de elevada indutância e são programadas para apresentar forma de onda com significativa componente senoidal em corrente contínua e em baixa frequência, de acordo com as características operacionais necessárias do Sirius. Para efeitos de estudo, a metodologia empregada consiste essencialmente em desacoplar a análise e o projeto do controle em um estágio regulador de tensão seguido de um estágio de síntese da corrente. Foram realizados ensaios em uma fonte em construção no Laboratório Nacional de Luz Síncroton e em um protótipo desenvolvido na UFJF. As principais contribuições descritas nesta dissertação são: i) atenuação da propagação de distúrbios de baixa frequência para a rede elétrica; ii) emprego de retificador de tensão controlado para regulação da tensão do barramento CC, melhoria do fator de potência e redução de componentes harmônicas. Os resultados experimentais evidenciam que as alterações de projeto propostas nesta dissertação apresentam grande potencial para melhorar o desempenho da fonte de corrente em termos da qualidade de energia elétrica e da sintetização de corrente senoidal no magneto do acelerador de partículas.
This work consists in the evaluation and improvement of a current source for a particle accelerator. The output current presents a DC sinusoidal waveform in low frequecy which flows through the windings of high inductance electromagnets. The methodology consists in separating the analysis and project of the control into two parts: a voltage regulator stage,followedbyacurrentsynthesisstage. Testswereperformedonacurrentsourceunder construction at the Brazilian Synchrotron Light Laboratory (LNLS) and on a prototype developed at UFJF. The work main contributions are: i) Attenuation of the low frequency disturbances on the electrical grid; ii) Use of a controlled rectifier to regulate the voltage of the DC bus, improvement in power factor and reduction of harmonic components. The experimental results show that the proposed changes have potential in improving the performace of the current source in terms of its electric power quality and synthesis of sinusoidal current in the particule accelerator.
Prüser, Henning [Verfasser], Rainer G. [Akademischer Betreuer] Ulbrich, Thomas [Akademischer Betreuer] Pruschke e Richard [Akademischer Betreuer] Berndt. "Scanning tunneling spectroscopy of magnetic bulk impurities: From a single Kondo atom towards a coupled system / Henning Prüser. Gutachter: Rainer G. Ulbrich ; Thomas Pruschke ; Richard Berndt. Betreuer: Rainer G. Ulbrich". Göttingen : Niedersächsische Staats- und Universitätsbibliothek Göttingen, 2013. http://d-nb.info/1044767782/34.
Prüser, Henning Verfasser], Rainer G. [Akademischer Betreuer] Ulbrich, Thomas [Akademischer Betreuer] Pruschke e Richard [Akademischer Betreuer] [Berndt. "Scanning tunneling spectroscopy of magnetic bulk impurities: From a single Kondo atom towards a coupled system / Henning Prüser. Gutachter: Rainer G. Ulbrich ; Thomas Pruschke ; Richard Berndt. Betreuer: Rainer G. Ulbrich". Göttingen : Niedersächsische Staats- und Universitätsbibliothek Göttingen, 2013. http://nbn-resolving.de/urn:nbn:de:gbv:7-11858/00-1735-0000-000E-0B5C-8-1.
Meyer, Tricia Lynn. "Structure, magnetism and transport properties of CaxSr1-xMn0.5Ru0.5O3 bulk and thin film materials". The Ohio State University, 2013. http://rave.ohiolink.edu/etdc/view?acc_num=osu1386001173.
Combe, Quentin. "Éjection électromagnétique : modèle et réalisation". Electronic Thesis or Diss., Université de Lorraine, 2022. http://www.theses.fr/2022LORR0107.
This thesis focuses on the subject of electromagnetic ejection applied in the context of the metal recycling industry. The aim of this thesis is the modeling and the development of an architecture of energy conversion allowing the realization of this ejection. The generated variable magnetic field is used to separate non-ferromagnetic metallic materials such as aluminum or copper from a waste stream by means of a Laplace force generated by the conjunction between the magnetic field created and the magnetic field induced by the eddy currents in the conductive materials.The developed architecture is composed of several elements: a rectifier, an inverter and an inductor. The rectifier part with a wide operating range connected to the three-phase grid network allows to obtain an adjustable DC voltage and ensures a sinusoidal current in phase with the voltage. The inverter part allows to control the transferred power, by adjusting the amplitude and frequency of the current flowing through the last part of the system represented by the inductor, responsible for the generation of the variable magnetic field.The rectifier is based on the classical Buck rectifier structure because of the low impedance of the inductor used. Although this structure allows to lower the three-phase grid voltage, its operating range can be easily increased without the addition of passive components. The classical control of this rectifier is based only on its output variables which can lead to uncontrolled oscillations caused by the resonance of the lightly damped input LC filter excited by the harmonics generated by the switching of transistors. In this thesis, we proposed a new control method that deals with both its input and output variables and that allows both to control the oscillations of the input LC filter while obtaining a better dynamic response when the system is subjected to a load step. This control method is based on the flatness properties of differential systems, so it does not depend on the operating point and guarantees the large signal stability of the system.The single-phase inverter is based on a full bridge structure allowing the application of three voltage levels and a wide choice of control of the amplitude, shape and frequency of the current flowing through the inductor. Different controls of this converter have been studied and compared. These allow to vary the power injected in the inductor, have an impact on the harmonic content of the current flowing through it and on the constraints of the different components of the system.A modeling of the inductor as well as an estimation of the value of the magnetic field necessary for the ejection is carried out. The different methods proposed are verified by numerical simulations but also by experimental tests performed on the whole system
Mousavioun, Payam. "Properties of lignin and poly(hydroxybutyrate) blends". Thesis, Queensland University of Technology, 2011. https://eprints.qut.edu.au/46668/1/Payam_Mousavioun_Thesis.pdf.
Zabihi, Sasan. "Flexible high voltage pulsed power supply for plasma applications". Thesis, Queensland University of Technology, 2011. https://eprints.qut.edu.au/48137/1/Sasan_Zabihi_Sheykhrajeh_Thesis.pdf.
Lai, Yi-Hsiang, e 賴奕翔. "Effects of applied magnetic field on the magnetic properties of directly casted NdFeTiB and NdFeTiZrCrBC bulk magnets". Thesis, 2010. http://ndltd.ncl.edu.tw/handle/56326054552414387206.
國立中正大學
物理所
98
In order to simplify the manufacturing process for making isotropic magnet, in this study, we adopted the copper mold casting method to fabricate permanent magnetic alloy sheets with a size of 0.9×4×15 mm3 and 1.1×4×15 mm3. During casting process, magnetic fields with different field strength were applied. At first, for the Nd9.5Febal.Ti3B15 alloys, the remanence Br, the intrinsic coercivity iHc and the maximum magnetic energy product (BH)max are significantly improved after applying magnetic fields. The stronger the magnetic field is applied, the better magnetic properties can be obtained. The microstructure studies reveal the samples casted with magnetic field have finer grains and more homogeneous microstructure than the samples casted without magnetic field, leading to the improvement of the exchange coupling effect and also the reduction of nucleation sites of reverse domain,and consequently, the magnetic properties are enhanced. The thermodynamic analyses show that the existence of magnetic Gibbs free energy can lead to the decrease of the nucleation potential energy and the critical nucleation radius, thus refining the grain size. Second, compared with different size of alloy sheets, the magnetic properties of alloys increase with the decrease of the thickness of sheets. The smaller thickness the alloy is, the higher the cooling rate can be obtained. The high cooling rate is helpful to refine the grain size, thus improving the magnetic properties. Moreover, according to the grain refinement by multi-element effect, the Nd9.5Febal.Ti2.5Zr0.5Cr1B14.5C0.5 alloy contains more elements than the Nd9.5Febal.Ti3B15 alloy, which is helpful to refine the microstructure and improve the magnetic properties. Among above series sheets, the optimal magnetic properties of Br=6.1 kG, iHc=10.3 kOe and (BH)max=7.3 MGOe could be achieved in Nd9.5Febal.Ti2.5Zr0.5Cr1B14.5C0.5 alloy sheet cast in a magnetic field strength of 3.7 kOe. Finally, the magnetic properties of Nd9.5Febal.Ti3B15 and Nd9.5Febal.Ti2.5Zr0.5Cr1B14.5C0.5 alloys with rod shape and sheet shape were compared. Due to the higher cooling rate, the rod shape magnets have better magnetic properties than the sheet shape magnets, even using the same alloy composition. Applying a magnetic field during the casting process can enhance the magnetic properties of bulk magnets effectively. Through applying a 3.7 kOe magnetic field during the casting process, we can maintain the attractive magnetic properties of Nd9.5Febal.Ti2.5Zr0.5Cr1B14.5C0.5 alloy with a sheet shape of 0.9×4×15 mm3.
Gan, Jian-You, e 甘健佑. "Magnetic properties and phase evolution of directly quenched RFeTiZrCrBC (R = Nd、Pr and Mischmetal) bulk magnets". Thesis, 2009. http://ndltd.ncl.edu.tw/handle/60516715834863166374.
國立中正大學
物理所
97
Abstract In order to simplify the manufacturing process for making isotropic magnet, in this study, we adopt the copper mold casting method to fabricate permanent magnetic alloy rods with a diameter of 1.1 mm and a length of 16 mm. At first, for Nd9.5Febal.Ti2.5Zr0.5B15-xCx (x=0-1) and Nd9.5Febal.Ti2.5Zr0.5CrxB14.5C0.5(x=0-3) alloys, C and Cr substitution for B and Fe, respectively, is helpful to refine the microstructure, leading to the improvement of the exchange coupling effect, and consequently, the magnetic properties are enhanced. Among above two series rods, the optimal magnetic properties of Br=5.9 kG, iHc=8.2 kOe and (BH)max=7.2 MGOe could be achieved in Nd9.5Febal.Ti2.5Zr0.5Cr1B14.5C0.5 alloy rod. On the other hand, for Nd9.5Febal.Ti2.5Zr0.5Cr1BxC0.5 (x=12.5-19.5) alloys, with increasing B content, the iHc is increased and Br is decreased, due to the grain refinement, but magnetic properties is deteriorated due to the appearance of amorphous phase for higher B content, i.e. x= 17.5-19.5. Besides, for RyFebal.Ti2.5Zr0.5Cr1B14.5C0.5 (R=Nd, Pr, and various Mischmetals; y=8-10.5) alloys, the iHc is increased and σ12kOe is decreased with the increase of the content of rare earth element, arisen from the increase of the volume fraction of magnetically hard 2:14:1 phase. Furthermore, low cost rare-earth, Mischmetals (Mm), were adopted as the main rare-earth elements, and the attractive magnetic properties of Br=5.7 kG, iHc=10.3 kOe and (BH)max=6.9 MGOe could be obtained for Mm(B)9.5Febal.Ti2.5Zr0.5Cr1B14.5C0.5 alloy rod, where Mm(B) mainly comprises 73.13 wt% Nd and 26.87 wt% Pr element. They can not only exhibit excellent magnetic performance but also reduce cost of the material effectively. Finally, comparing the magnetic properties and microstructure of Nd9.5Febal.Ti3B15 and Nd9.5Febal.Ti2.5Zr0.5Cr1B14.5C0.5 alloys with various diameters (0.7-1.5 mm), the magnetic properties of both series alloys are decreased with the increase of the diameter of rod, and the latter alloy, consisting of more elements, can keep attractive magnetic properties up to larger diameter of 1.3 mm, due to the grain refinement by multi-element effect.
Yang, Te-Yan, e 楊德彥. "Study of Micro/Nano Scale Displacement by Electro-Maglev System Using Bulk Superconductors and Permanent Magnets". Thesis, 2005. http://ndltd.ncl.edu.tw/handle/44470852381253479928.
國立成功大學
材料科學及工程學系碩博士班
93
For developments of scientific and technically application, the size of devices has been reduced from centimeters to micrometers. In order to control the displacement within micro/nano-scale, in this study, an active-maglev system composed of an YBCO bulk and a permanent magnet in a DC magnetic field was constructed. The magnetic field, its magnitude and distribution can be estimated, is generated by the coil. There are two important issues of this system: (1) Flux trapping occurs between a superconductor and magnet is a stable state, (2) A magnetic field can be controlled by the input current density of a coil. Stable levitation can be achieved without any control system when the permanent magnet is levitated above the YBCO bulk superconductor, which is cooled by liquid nitrogen and cryo-cooler respectively. The levitation height of permanent magnet is adjusted by changing small operating current in the coil with the sensibility of �嫀, and the result shows that small-scale displacement can be achieved in these two systems. Through the optic-fiber displacement sensor, the displacement under 5 micro-meters can be measured. The relationship between applied current and displacement is determined by the liner fitting.
Yu-ChengShih e 施昱丞. "Study of Magnetic Drug Delivery System Using High Temperature Bulk Superconducting Magnet". Thesis, 2015. http://ndltd.ncl.edu.tw/handle/bjwn4m.