Search for dissertations about: "magnetic fields"

Showing result 1 - 5 of 340 swedish dissertations containing the words magnetic fields.

  1. 1. Radiofrequency fields : exposure, dose and health

    Author : Jonna Wilén; Umeå universitet; []
    Keywords : ENGINEERING AND TECHNOLOGY; TEKNIK OCH TEKNOLOGIER; electromagnetic fields; SAR; Specific Absorption; subjective symptoms;

    Abstract : The overall aim of this thesis is to increase our knowledge of relevant exposure parameters when discussing possible health implication from exposure to radiofrequency electromagnetic fields (RF), especially effects that might occur at non-thermal levels.In this thesis an effort is made to broaden the exposure assessment and to take the exposure time into account and combine it with the Specific Absorption Rate (SAR) and the field parameters (electric and magnetic field strength) to approach a dose concept. READ MORE

  2. 2. Analysis and control of magnetic forces in synchronous machines

    Author : J. J. Pérez-Loya; Urban Lundin; Anouar Belahcen; Uppsala universitet; []
    Keywords : eccentricity; electromagnetics; electromagnetic forces; excitation; magnetic fields; magnetic forces; magnetic thrust bearing; rotor drive; split rotor; starting; synchronous generators; synchronous machines; synchronous motors; unbalanced magnetic pull; Engineering Science with specialization in Science of Electricity; Teknisk fysik med inriktning mot elektricitetslära;

    Abstract : In a synchronous machine, radial, tangential, and axial forces are generated. In this thesis, three different technologies to control them are proposed. The first one, involves the utilization of the radial forces that arise between the rotor and the stator. READ MORE

  3. 3. Generation of magnetic fields on galactic scale

    Author : Fabio Del Sordo; Axel Brandenburg; Oliver Gressel; Stockholms universitet; []
    Keywords : NATURAL SCIENCES; NATURVETENSKAP; NATURVETENSKAP; NATURAL SCIENCES; Magnetic fields; galaxies; astronomi; Astronomy;

    Abstract : In these pages we will go through the topic of astrophysical magnetic fields, focusing on galactic fields, their observation and the theories that have been developed for a proper understanding of the these physical phenomena.We review the main work in the study of galactic magnetic fields, often seeing how it is important to deal with problems of general validity in order to be able to point out the right elements needed for a correct interpretation of specific situations. READ MORE

  4. 4. Characterization of the MRI patient exposure environment and exposure assessment methods for magnetic fields in MRI scanners

    Author : Jennifer Frankel; Jonna Wilén; Anders Garpebring; Johan Olsrud; Peter Lundberg; Umeå universitet; []
    Keywords : MEDICAL AND HEALTH SCIENCES; MEDICIN OCH HÄLSOVETENSKAP; MEDICIN OCH HÄLSOVETENSKAP; MEDICAL AND HEALTH SCIENCES; electromagnetic fields; exposure assessment; magnetic resonance imaging; switched gradient fields; radiofrequency fields; exposure metrics; radiofysik; radiation physics;

    Abstract : Magnetic resonance imaging (MRI) has become one of the most common imaging modalities available in modern medicine, and it is an indispensable diagnostic tool thanks to the unparalleled soft-tissue contrast and high image resolution. It is also a unique exposure environment consisting of a complex mix of magnetic fields. READ MORE

  5. 5. Resonant magnetic perturbation effect on the tearing mode dynamics : Novel measurements and modeling of magnetic fluctuation induced momentum transport in the reversed-field pinch

    Author : Richard Fridström; Per Brunsell; Lorenzo Frassinetti; Tommaso Bolzonella; KTH; []
    Keywords : NATURAL SCIENCES; NATURVETENSKAP; NATURVETENSKAP; NATURAL SCIENCES; RFP; reversed-field pinch; tokamak; tearing mode; RMP; fusion; plasma; resonant magnetic perturbation; stochastic; magnetic; field; viscosity; mode; locking; Electrical Engineering; Elektro- och systemteknik;

    Abstract : The tearing mode (TM) is a resistive instability that can arise in magnetically confined plasmas. The TM can be driven unstable by the gradient of the plasma current. When the mode grows it destroys the magnetic field symmetry and reconnects the magnetic field in the form of a so-called magnetic island. READ MORE