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Dissertations / Theses on the topic 'Electromagnetic fields'

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Published: 4 June 2021

Last updated: 29 July 2024

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1

Alexeev, Arseny. "Quantum rings in electromagnetic fields." Thesis, University of Exeter, 2013. http://hdl.handle.net/10871/8021.

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This thesis is devoted to optical properties of Aharonov-Bohm quantum rings in external electromagnetic fields. It contains two problems. The first problem deals with a single-electron Aharonov-Bohm quantum ring pierced by a magnetic flux and subjected to an in-plane (lateral) electric field. We predict magneto-oscillations of the ring electric dipole moment. These oscillations are accompanied by periodic changes in the selection rules for inter-level optical transitions in the ring allowing control of polarization properties of the associated terahertz radiation. The second problem treats a single-mode microcavity with an embedded Aharonov-Bohm quantum ring, which is pierced by a magnetic flux and subjected to a lateral electric field. We show that external electric and magnetic fields provide additional means of control of the emission spectrum of the system. In particular, when the magnetic flux through the quantum ring is equal to a half-integer number of the magnetic flux quantum, a small change in the lateral electric field allows tuning of the energy levels of the quantum ring into resonance with the microcavity mode, providing an efficient way to control the quantum ring-microcavity coupling strength. Emission spectra of the system are calculated for several combinations of the applied magnetic and electric fields.

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2

Krug, Andreas. "Alkali Rydberg States in Electromagnetic Fields." Diss., lmu, 2001. http://nbn-resolving.de/urn:nbn:de:bvb:19-3362.

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3

Hsiang, Jen-Tsung. "Fluctuating electromagnetic fields and electron coherence /." Thesis, Connect to Dissertations & Theses @ Tufts University, 2004.

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Thesis (Ph.D.)--Tufts University, 2004.
Adviser: Lawrence H. Ford. Submitted to the Dept. of Physics. Includes bibliographical references (leaves 154-155). Access restricted to members of the Tufts University community. Also available via the World Wide Web;

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4

Burke, Mary Joset. "Visualization of electromagnetic fields using MATLAB." Honors in the Major Thesis, University of Central Florida, 1998. http://digital.library.ucf.edu/cdm/ref/collection/ETH/id/25.

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This item is only available in print in the UCF Libraries. If this is your Honors Thesis, you can help us make it available online for use by researchers around the world by following the instructions on the distribution consent form at http://library.ucf.edu/Systems/DigitalInitiatives/DigitalCollections/InternetDistributionConsentAgreementForm.pdf You may also contact the project coordinator, Kerri Bottorff, at kerri.bottorff@ucf.edu for more information.
Bachelors
Engineering
Electrical Engineering

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5

Antonoyiannakis, Emmanuel (Manolis) Ioannou. "Electromagnetic fields and forces in nanostructures." Thesis, Imperial College London, 1998. http://hdl.handle.net/10044/1/37522.

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We have developed a general methodology for computing electromagnetic (EM) fields and forces in matter, based on solving the macroscopic Maxwell's equations numerically in real space and adopting the time-averaged Maxwell Stress Tensor formalism. Our approach can be applied to both dielectric and metallic systems characterised by a local frequency-dependent dielectric function, and in principle to any size and geometry. In this study we are particularly interested in calculating forces on nanostructures, induced by a beam of monochromatic light (such as a laser) of frequency w. These forces are the direct analogue of Van der Waals interactions at a single frequency: the presence of matter scatters the light and alters the EM field, resulting in an energy-change that manifests itself as a force. The motivation behind this particular direction is the facilitation of self-assembly in colloidal systems with the aim of aiding the fabrication of photonic crystals. In order to understand the main features of light-induced EM forces, as well as to provide a testbed for our numerical methodology, we first solve (analytically and numerically) for two homogeneous systems: a half-space and a slab. We find that in passing from a low-e to a high-e medium, the light beam always attracts the interface {i.e. the surface force is negative). The implication is that light will generally induce an attraction between the surfaces of two liquids separated by a layer of lower e. For attraction between solids there is a tougher requirement: the total force must also be negative. When the EM field is that of a travelling wave the total pressure is positive. In contrast, evanescent waves may cause the total pressure to become attractive (negative). Thus by shining evanescent light in the region between two solid bodies an attraction between them may be induced. We then study numerically the influence of monochromatic light (a travelling wave) on a crystal of dielectric spheres of GaP, concentrating on total forces induced on each sphere and on the crystal as a whole. We identify three regimes in the response of the system to radiation: • At large wavelengths the crystal may be approximated by a homogeneous slab with an effective permittivity eg//. The analytical results for reflectance and forces apply. • At wavelengths comparable to the lattice constant, multiple scattering effects tune in: when lo is inside the photonic band gaps the reflectivity of a thick crystalline slab rises to unity, the beam bounces off the crystal and there is a maximum momentum exchange (and largest forces). Also, a multitude of force orientations results when the Bragg conditions for multiple outgoing waves are met. • Much more interesting is the regime where the radiation couples to the E M eigenmodes supported by isolated spheres (Mie resonances). These modes are analogous to electronic orbitals and, like their electronic counterparts, can form bonding and anti-bonding interactions between neighbouring spheres. By irradiating the system with light at the bonding frequency an attractive interaction is induced between the spheres. The photo-induced attraction is strong; for a moderate I₀ ~ 3 x 10⁸ W/m² it surpasses all other interactions present (gravitational, thermal and Van der Waals) by 1-2 orders of magnitude. These resonant forces are sensitive to absorption, but, for GaP spheres in water (a common liquid medium for colloids), their effect should still be clearly seen, even for a polydispersion of a few percent. Thus we suggest that by judicious selection of bonding states we can drive a system towards a desired structure, rather than rely on the structure dictated by gravitational and Van der Waals forces. Apart from possible applications in the fabrication of 3D photonic crystals, the resonant mechanism leading to the bonding/anti-bonding effect may contribute to our understanding of novel non-linear phenomena arising due to the application of laser light fields in nanostructures.

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6

Jones, Travis Hamilton. "On the Interactions of Electromagnetic Fields with Human Cells." The Ohio State University, 2020. http://rave.ohiolink.edu/etdc/view?acc_num=osu1587493583447491.

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7

Berry, Yoke. "The effect of pulsed electromagnetic fields on protein unfolding." Access electronically, 2005. http://www.library.uow.edu.au/adt-NWU/public/adt-NWU20060713.142625/index.html.

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8

Hamblin, Denise Lee. "The effect of mobile phone emitted electromagnetic fields on human brain activity and performance." Australasian Digital Thesis Program, 2006. http://adt.lib.swin.edu.au/public/adt-VSWT20061110.100936.

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Thesis (PhD) - Swinburne University of Technology.
Thesis for Doctor of Philosophy, Brain Sciences Institute, Faculty of Life and Social Sciences, Swinburne University of Technology - 2002. Typescript. Includes bibliographical references (p. 137-160).

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9

Piwnicki, Paul. "Electromagnetic Fields in Moving and Inhomogeneous Media." Doctoral thesis, KTH, Alfvén Laboratory, 2001. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-3270.

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The present thesis deals with electromagnetic effectscreated by the motion or inhomogeneity of a dielectricmedium.In the first paper the quantum R\"ontgen effect isdiscussed. Here a rotating Bose-Einstein condensate -- oranother kind of quantum fluid -- is placed in a chargedcapacitor. The medium's rotation creates a magnetic field.Quantum media can only rotate in form of vortices, which leadsto a magnetic field corresponding to the field of a magneticmonopole. In the remaining part of the thesis the geometricalrepresentation of electromagnetic fields in moving andinhomogeneous media is discussed. It is shown that aninhomogeneously moving dielectric, e.g., a vortex, defines aspace-time metric and light rays follow null-geodesics definedby this metric. This means that light propagation in a movingmedium is analogous to light propagation in a gravitationalfield. The possibility of creating laboratory models ofastronomical objects, e.g., black holes is discussed. Theapplicability of the newly developed media with extremely lowgroup velocity for the actual creation of such an experiment isconsidered. Furthermore, a model for the case of the slowlymoving medium is discussed. Here the light propagation isanalogous to the motion of a charged particle propagatingthrough a magnetic field. The velocity of the flow correspondsto the vector potential. Consequently, light propagation in avortex corresponds to the Aharonov-Bohm effect. Finally, acomplete geometrical description of light in an inhomogeneousdielectric at rest is presented. It is shown that lighttrajectories are geodesics of a three-dimensional metricdefined by the medium. Here even the propagation of the fieldsis discussed in the language of differential geometry and it isshown that the field vectors are parallel transported along therays. These considerations can be generalized to thefour-dimensional case where the field-strength tensor isparallel transported along the ray. This emphasizes thefar-reaching analogy between light in moving media and light ingravitational fields.

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10

Wallis, Alisdair Owen Garnett. "Ultracold molecules : the effect of electromagnetic fields." Thesis, Durham University, 2010. http://etheses.dur.ac.uk/184/.

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There is great interest within the physics and chemistry communities in the properties of ultracold molecules. Electromagnetic fields can be used to create, trap, and modify the collisional dynamics of ultracold molecules, and thus the properties of ultracold molecules in electromagnetic fields is of growing importance. This thesis examines some of the effects of externally applied electromagnetic fields on ultracold molecules. Initially, magnetic Feshbach resonances in combined electric and magnetic fields are examined in the collisions of He($^1S$)+SO($^3\Sigma^-$). Through detailed quantum scattering calculations, it is then shown that the sympathetic cooling of NH($^3\Sigma^-$) molecules with Mg atoms has a good prospect of success, a first for a neutral molecular system. Detailed quantum scattering calculations are performed for a wide range of collision energies and magnetic field strengths and it is found that the ratio of elastic to inelastic collisions is large for temperatures below 10 mK, and increases as the collision energy and magnetic field strength decrease. The near threshold collision properties of Mg+NH have been examined using a multichannel quantum defect theory approach. A new type of conical intersection, that is a function of applied electromagnetic fields only, is also demonstrated. For states of opposite parity, brought into degeneracy with a magnetic field, the degeneracy can be resolved by the addition of an electric field, forming a conical intersection. A suitable arrangement of fields could thus be used to create a conical intersection in laboratory coordinates within an ultracold trapped gas. For a Bose-Einstein condensate, in the mean-field approximation, the resultant geometric phase effect induces stable states of persistent superfluid flow that are characterized by half-integer quantized angular momentum.

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11

Khalid, M. "Exposure to electromagnetic fields from Wi-Fi." Thesis, University College London (University of London), 2011. http://discovery.ucl.ac.uk/1334466/.

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This thesis is concerned with the exposure of electromagnetic fields to school children from Wireless Local Area Networks (WLAN). The research provides insights into how wireless networks are implemented in schools, sets out to develop a systematic methodology to quantify field levels close to WLAN devices and then investigates the extent of exposure thereby assisting the Health Protection Agency (HPA) in providing advice. School children in the UK are being exposed to electromagnetic fields due to the increasing use of Wi-Fi technologies in schools. Many local government authorities and schools are facing difficulties in understanding the health issues associated with the use of WLAN networks and there is increasing pressure from parents to provide reassurance. There is lack of quantitative scientific data, and current methodologies do not provide a realistic measure of the extent of exposure. The results from the exploratory studies and the contribution from existing literature have then been synthesised to develop new methodologies. A set of measurements were made to come to an assessment of the level of radiofrequency fields adjacent to commonly used WLAN equipment. Finally, the way in which children interact with WLAN devices as part of their normal lessons was examined in determine the time averaged exposure. The outcome of this research is a robust measurement methodology and examination of extent of RF exposure to children which represents a significant contribution to the scientific knowledge. The measurement methodology has been demonstrated to be practicable and can be used with a range of wireless devices using pulsed signals and thus is capable of providing valuable information for future studies.

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12

Thurman, Hugh O. Copeland Gary E. "Neutron star electromagnetic field structure /." Connect to this resource. (Authorized users only), 2004.

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13

Foo, Seng-Lee. "Analysis of electromagnetic fields in loaded TEM cells." Thesis, University of Ottawa (Canada), 1988. http://hdl.handle.net/10393/5170.

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14

Read, Smith Sarah Jane. "The effects of radiofrequency electromagnetic fields on cognition." Thesis, University of Surrey, 2007. http://epubs.surrey.ac.uk/843071/.

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The acute effects of radiofrequency electromagnetic fields (RF EMF) on human cognitive performance were investigated. Cognitive tasks were identified from RF EMF cognitive research; tests used most extensively were psychomotor performance, attention, working and episodic memory tasks. Review of published imaging research enabled selection of a battery of cognitive tasks for use in the experimental studies. Effects of practice and the test-retest reliabilities on the tests were evaluated and the relationship between the tests within the battery and measures of ability and personality investigated. Three studies were conducted to identify whether RF EMF produced by occupational communication systems had reliable effects on cognitive performance and self-reports of mood, anxiety and workload. Double-blind repeated measures design was used to investigate the following fields in comparison to sham; a high frequency (HF) 29MHz continuous wave (CW) signal, a very high frequency (VHF) 75MHz CW field, an Ultra High Frequency (UHF) modulated 448MHz field, a UHF 1206MHz CW signal and a TETRA 388MHz field pulse modulated at 17.6Hz. The first study demonstrated no significant effects of the VHF signal on performance when compared to sham. The HF signal appeared to reduce response time to two of the cognitive tasks and affect error rate on one of them. Investigation of the two UHF signals showed no reliable differences between conditions on the cognitive measures. The third study showed reliable differences between TETRA exposure and sham conditions on two of the tasks. Overall the results indicate that RF EMF signals at the frequencies and power levels used in these studies are well tolerated in healthy subjects. In general, the signals do not appear to have reliable and robust effects on human cognitive performance. However, there may be subtle transitory effects of RF EMF that are not well understood at the present time.

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15

Håkansson, Niclas. "Occupational exposure to electromagnetic fields and chronic diseases /." Stockholm, 2003. http://diss.kib.ki.se/2003/91-7349-719-3/.

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16

Pinchuk, Amy Ruth. "Spectrally correct finite element analysis of electromagnetic fields." Thesis, McGill University, 1988. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=75780.

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Direct solution for three dimensional electric or magnetic field vectors throughout the frequency spectrum is accomplished by a finite element formulation which includes displacement and conduction currents, and requires no special treatment for material interfaces. Analysis of bus bar and Bath cube eddy current problems demonstrate the capabilities of the method.
Spurious components in solutions to vector field problems are shown to corrupt deterministic solutions. These corruptions are identifiable with spurious modes familiar to high frequency modal analysis. Spectrally correct mixed order finite elements are demonstrated to retrieve accuracy in deterministic analyses.
The formulation may be limited by computer round-off at matrix assembly which affects the solenoidality of vector fields. Furthermore, extreme values encountered in low frequency eddy current analysis lead to ill conditioning and unreliable solutions. These numerical instabilities are overcome by parametric adjustment of permittivities. Error estimates are established to monitor inaccuracies introduced by permittivity adjustment.

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17

Shepherd, Nolan Miller. "Manipulating Electromagnetic Fields in Colloidal Metal Nanoparticle Systems." Thesis, The University of Chicago, 2019. http://pqdtopen.proquest.com/#viewpdf?dispub=10977604.

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Colloidal metal nanoparticles are renowned for their ability to strongly scatter and absorb light due to size- and environment-dependent plasmon modes. Active areas of research focus on using both single and collections of nanoparticles to control the shape of electromagnetic fields on the nanoscale. The excitation of plasmon modes in the nanoparticles confines the energy from incident fields to sub-wavelength scales with distributions controlled by the morphology of the particles, and multiple particles arranged in the near-field can extend the excitation into a collective mode. The excitation of plasmon modes can create enhancements of the field intensity, which have been leveraged for enhancing radiative rates of light-emitting particles and molecules and increasing molecular sensing signals. However, many of these applications rely on electric field enhancements in the near field and using static nanoparticle arrangements. We present extensions to this paradigm, first by exploring the excitation of collective plasmon modes in optically-patterned linear nanoparticle arrays with separations on the order of the wavelength of light, demonstrating new mechanisms for coupling beyond the well-known near-field interactions. The collective excitation over the intermediate-scale arrays is also shown to redirect the scattered light perpendicular to the expected forward scattering. Next, we demonstrate that self-arranged optically bound linear arrays act as optical cavities for co-trapped single-photon emitters, modifying the local density of electromagnetic states in the vicinty of the nanoparticle system. Finally, we probe optically 'dark' modes in a core-satellite nanostructure by exciting magnetic responses separately from electric modes with structured excitation light.

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18

Manuwong, Theerapatt. "Solidification of metal alloys in pulse electromagnetic fields." Thesis, University of Hull, 2015. http://hydra.hull.ac.uk/resources/hull:11671.

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This research studies the evolution of solidification microstructures in applied external physical fields including in a pulse electric current plus a static magnetic field, and a pulse electromagnetic field. A novel electromagnetic pulse device and a solidification apparatus were designed, built and commissioned in this research. It can generate programmable electromagnetic pulses with tuneable amplitudes, durations and frequencies to suit different alloys and sample dimensions for research at university laboratory and at synchrotron X-ray beamlines. Systematic studies were made using the novel pulse electromagnetic field device, together with finite element modelling of the multiphysics of the pulse electromagnetic field and microstructural characterisation of the samples made using scanning electron microscopy, X-ray imaging and tomography. The research demonstrated that the Lorentz force and magnetic flux are the dominant parameters for achieving the grain refinement and enhancing the solute diffusion. At a discharging voltage from 120 V, a complete equaxied dendritic structure can be achieved for Al-15Cu alloy samples, the strong Lorentz force not only disrupts the growing direction of primary dendrites, it is also enough to disrupts the growing directions of primary intermetallic Al2Cu phases in Al-35Cu alloy, resulting a refined solidification microstructures. The applied electromagnetic field also has significant effect on refining the eutectic structures and promoting the solute diffusion in the eutectic laminar structure. The research has demonstrated that the pulse electromagnetic field is a promising green technology for metal manufacture industry.

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19

Ani, Chinenye Jane. "Chaotic behaviour of charged particles in electromagnetic fields." Master's thesis, Faculty of Science, 2018. http://hdl.handle.net/11427/30058.

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In order to understand the motion of charged particles we numerically investigate the chaoticity of magnetic field lines of tokamak fields, as charged particles move along field lines. In particular, the symmetric tokamap was studied to determine the physical quantities that influence the system’s chaotic behaviour. We implement several chaos detection techniques: the construction of Poincaré maps, the computation of the maximum Lyapunouv characteristic exponent (mLCE), as well as the Smaller Alignment Index (SALI). The analyses performed showed that the mLCE and SALI methods accurately quantified magnetic field lines’ chaotic behaviour and that the relative perturbation strength influences the system’s chaoticity. In addition, we illustrate the diffusive properties of magnetic field lines, using statistical measures like the mean square displacement (MSD) and calculating diffusion coefficients. Lastly, we present the construction of explicit near-symplectic mappings of the symmetric tokamap with Lie-generating functions.

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20

Yaguchi, Hiroko. "Biological Effects and Psychosocial Implications of Electromagnetic Fields." Kyoto University, 2001. http://hdl.handle.net/2433/150736.

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Kyoto University (京都大学)
0048
新制・課程博士
博士(人間・環境学)
甲第9021号
人博第114号
12||116(吉田南総合図書館)
新制||人||28(附属図書館)
UT51-2001-F351
京都大学大学院人間・環境学研究科人間・環境学専攻
(主査)教授新宮一成, 教授池永満生, 教授杉万俊夫, 助教授宮越順二
学位規則第4条第1項該当

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21

Kodali, Venkateswararao. "Characterization and analysis of close lightning electromagnetic fields." [Gainesville, Fla.] : University of Florida, 2003. http://purl.fcla.edu/fcla/etd/UFE0000724.

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22

Park, Young C. (Young Chul) 1960. "A Study of Some Biological Effects of Non-Ionizing Electromagnetic Radiation." Thesis, University of North Texas, 1996. https://digital.library.unt.edu/ark:/67531/metadc278105/.

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The experimental studies of this work were done using a microwave cavity spectrometer, Escherichia coli (E-coli) bacteria, and other peripheral equipment. The experiment consists of two steps. First, a general survey of frequencies from 8 GHz to 12 GHz was made. Second, a detailed experiment for specific frequencies selected from the first survey were further studied. Interesting frequency dependent results, such as unusually higher growing or killing rates of E-coli at some frequencies, were found. It is also concluded that some results are genetic, that is, the 2nd, and 3rd subcultures showed the same growing status as the 1st cultures.

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23

Son, Hungsun. "Effects of magnetic field models on control of electromagnetic actuators." Diss., Atlanta, Ga. : Georgia Institute of Technology, 2007. http://hdl.handle.net/1853/26616.

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Thesis (Ph.D)--Mechanical Engineering, Georgia Institute of Technology, 2008.
Committee Chair: Lee, Kok-Meng; Committee Member: Bill Singhose; Committee Member: David G. Taylor; Committee Member: Eric Johnson; Committee Member: Nader Sadegh. Part of the SMARTech Electronic Thesis and Dissertation Collection.

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24

Moss, Alison Jeanne. "The effects of applied fields on environmental systems." Thesis, Brunel University, 1996. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.272364.

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25

Tentor, Lawrence B. "Characterization of an Electromagnetic Tuned Vibration Actuator." Diss., Virginia Tech, 2000. http://hdl.handle.net/10919/27906.

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Tuned vibration absorbers (TVA) have been discussed in literature since the early twentieth century. These devices are implemented to suppress the systemâ s vibration by transferring energy to the absorber mass. This research examines an electromagnetic tuned vibration absorber that can have its tuned frequency altered by gap and current variation. The advantage of an adjustable TVA is that the system can be tuned to various excitation frequencies to cancel vibration. This research examines a unique embodiment using permanent magnets and an electromagnetic absorber to alter the system dynamics. The focus is to allow changes in tuned frequency to cancel system vibrations. This research develops the electromagnetic theory, presents absorber system simulations, and tests the dynamic absorberâ s response. The electromagnetic field is investigated to determine the field between a stationary magnet and the absorber electromagnet. This field can be numerically calculated as the superposition of four constituent fields. With the electromagnetic field determined, the force to displacement relation between the stationary magnet and the absorber electromagnet is calculated. The best fit is determined to be an inverse square relationship. Once the spring force relation is determined, the damping mechanisms are discussed and experiments proposed to isolate the different damping mechanisms. In the simulations, it is found that by having an adjustable electromagnetic TVA the natural frequency can be adjusted 2-3% with a +10 amp input and over 50% for a variable gap. The advantage of the variable gap is that it may be adjusted once and then no additional energy is needed, while the advantage of the variable current is that the system may be rapidly altered. The experiments are undertaken to test the constructed absorber for the spring and damping force. The tests confirm the spring force relation and quantify the high damping present in the tested configuration. Then the absorber system transfer functions are recorded. The absorber is then applied to a single degree of freedom system to verify its cancellation results by a gap variation.
Ph. D.

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26

Dai, Qi, and 代祺. "Efficient eigenvalue based analysis of bounded and unbounded electromagnetic fields." Thesis, The University of Hong Kong (Pokfulam, Hong Kong), 2013. http://hdl.handle.net/10722/196029.

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Eigenvalue problems find important applications in engineering electromagnetics. The most studied examples are cavity resonance problems and wave guidance problems, in which the electromagnetic fields are bounded or semi-bounded. Efficient eigenvalue based analysis is developed to investigate both bounded and unbounded fields in a unified manner. Incorporating a locally-conformal finite difference technique, a modal expansion based model order reduction is proposed to elucidate complicated physics of wave-matter interaction, and the fast field approximation provides quick guidance to design and optimization problems of a variety of devices. As the key to modal expansion, modal analysis for interior spectrum needs to be carried out efficiently in large scale applications. A null-space shift algorithm and a fast cosine- and sine- transform based preconditioning scheme are proposed to greatly enhance the performance of a conventional eigensolver. To model multi-junction parallel plate waveguides, both explicit and implicit mode matching schemes are introduced, where eigenanalysis are incorporated. Both schemes intelligently conform to the geometrical characteristics, which are suitable for demonstrating interesting phenomena of zero index materials. Finally, a differential forms inspired discretization scheme is proposed for the edge element based finite element analysis of waveguide problems where the variational expressions involve transverse fields only. Differential forms provide useful insight on the discretization of complicated variational expressions.
published_or_final_version
Electrical and Electronic Engineering
Doctoral
Doctor of Philosophy

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27

Sehatzadeh, Shayan. "Occupational exposure to electromagnetic fields and female breast cancer." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 1997. http://www.collectionscanada.ca/obj/s4/f2/dsk2/ftp04/mq29212.pdf.

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Tigga, Celine. "Modelling of Measurement Equipment for High Frequency Electromagnetic Fields." Thesis, Högskolan i Gävle, Avdelningen för elektronik, matematik och naturvetenskap, 2015. http://urn.kb.se/resolve?urn=urn:nbn:se:hig:diva-18894.

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The aim of this thesis was to develop a model of a receiver which could be quickly used to analyze radiated interference levels from data captured at the output of the antenna equipment used to measure radiated energy. Active circuits were mainly used in developing this model for the ease with which the design and simulations could be carried out in OrCAD. The guiding document for the thesis work has been CISPR 16-1-1 (International Special Committee on Radio Interference part 16-1-1) which specifies the characteristics and performance of equipment for the measurement of radiated interference. The testing of this receiver model was carried out as far as possible based on the test setups recommended in CISPR, and all results have been compared with the standards laid down for the model. Using the results, it will be shown that a CISPR EMI receiver can be modeled as a simple EMI receiver consisting of filtering, mixing and detecting circuits built according to specifications.

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29

Culligan, Allan James. "The electromagnetic fields from a two-wire transmission line." Thesis, University of East Anglia, 1997. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.267710.

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30

Deans, Jacqueline Kim. "Effect of radio-frequency electromagnetic fields on nervous tissue." Thesis, University of Southampton, 2004. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.400539.

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31

Manuel, Mario John-Errol. "Rayleigh-Taylor-Induced electromagnetic fields in laser-produced plasmas." Thesis, Massachusetts Institute of Technology, 2013. http://hdl.handle.net/1721.1/80660.

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Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Nuclear Science and Engineering, 2013.
Cataloged from PDF version of thesis.
Includes bibliographical references.
Spontaneous electromagnetic fields can be important to the dynamic evolution of a plasma by directing heat flow as well as providing additional pressures on the conducting fluids through the Lorentz force. Electromagnetic fields are predicted to affect fluid behavior during the core-collapse of supernovae through generation of fields due to hydrodynamic instabilities. In the coronae of stars, self-generated magnetic fields lead to filamentary structure in the hot plasma. Recent experiments by Gregori et al. investigated sources of protogalactic magnetic fields generated by laser-produced shock waves. In inertial confinement fusion experiments, self-generated electromagnetic fields can also play a role and have recently become of great interest to the community. Present day laser facilities provide a unique opportunity to study spontaneous field-generation in these extreme environments under controlled conditions. Instability-induced electromagnetic fields were investigated using a novel monoenergetic-proton radiography system. Fusion protons generated by an 'exploding-pusher' implosion were used to probe laser-irradiated plastic foils with various preimposed surface perturbations. Imaging protons are sensitive to electromagnetic fields and density modulations in the plasma through the Lorentz force and Coulomb collisions, respectively. Corresponding x-ray radiographs of these targets provided mass density distributions and Coulomb effects on protons were assessed using a Monte Carlo code written using the Geant4 framework. Proton fluence distributions were recorded on CR-39 detectors and Fourier analyzed to infer path-integrated field strengths. Rayleigh-Taylor (RT) growth of preimposed surface perturbations generated magnetic fields by the RT-induced Biermann battery and were measured for the first time. Good data were obtained during linear growth and when compared to ideal calculations, demonstrated that field diffusion near the source played an important role. At later times in the plasma evolution, 3-D cellular structures were observed for all foil types. These features were found to be analogous to previously observed filamentary field structures by Séguin et al. in laser-driven spherical targets. Face-on images of these field structures provided good data to quantitatively analyze the size of these features, not previously attainable due to the complexity of the 3-D spherical data. Work presented here demonstrates that these field structures are likely caused by the magnetothermal instability in the underdense corona.
by Mario J.-E. Manuel.
Ph.D.

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Martino, Carlos F. "On the effects of electromagnetic fields on biological systems." Connect to online resource, 2008. http://gateway.proquest.com/openurl?url_ver=Z39.88-2004&rft_val_fmt=info:ofi/fmt:kev:mtx:dissertation&res_dat=xri:pqdiss&rft_dat=xri:pqdiss:3337129.

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Leong, Harrison Mon Fook Fox Geoffrey C. "Frequency dependent electromagnetic fields : models appropriate for the brain /." Diss., Pasadena, Calif. : California Institute of Technology, 1986. http://resolver.caltech.edu/CaltechETD:etd-03192008-111015.

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34

Lech, James Chrystopher. "Constructing an EMF radiation Hygeia framework and model to demonstrate a public interest override." Thesis, Rhodes University, 2018. http://hdl.handle.net/10962/58695.

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Scientific views on EMF radiation dosimetry and models increasingly suggest that even a tiny increase in the incidence of diseases resulting from exposure to EMF radiation could have broad¹ implications for public health, social accounting and the economy. In South Africa (SA) there is no national EMF radiation exposure protection standard, statutory monitoring or regulations. Multinational High Court deliberations indicate the need for public interest EMF radiation exposure protection standards in South Africa. Domestic citizens, academics, as well as regulatory and legislative practitioners, are unable to effectively monitor and investigate EMF radiation exposure emissions from infrastructure sources, because industries refuse to provide the required data. Industries have, since 2003, continually obstructed access to the data and the establishment of a national EMF radiation standard, citing that it would be in conflict with their strategic economic interests. The demonstration of a public interest override (PIO) function is legislatively required to gain access to the required data. This study constructed (1) a framework and (2) a model to perform test simulations against the (3) PIO criteria to demonstrate a PIO function and tested one PIO simulation scenario. Testing the PIO scenario firstly required the construction of a public interest framework, drawing input from multiple disciplines. The framework literature review used systematic case law and scientific-technical analysis whilst the framework science sought to understand the connections, feedbacks, and trajectories that occur as a result of natural and human system processes and exchanges. The EMF radiation exposure system functions to support human wellbeing needs and to explore the benefits and losses associated with alternative futures with the goal to uncover the current and future limits thereof. In the second instance a HYGEIA² model was selected as a base investigation and forecast simulation tool. The study had to uncover the key attributes and parameters necessary to construct and to run successful EMF radiation exposure simulations. Thereafter the HYGEIA model was modified to specifically identify and evaluate EMF radiation exposure hazard conditions. Through subsequent simulation runs, the constructed framework was then tested. Requested anthroposphere information was synthesized within a systems model to forecast ecosystem services and human-use dynamics under alternative scenarios. The simulation used the model, the model references and the framework for guidelines, thus allowing multiple simulation / demonstration runs for different contexts or scenarios. The third step was the construction of a PIO checklist which guides criteria testing and provides a means of gaining pertinent information for further studies, based on this dissertation. Framework EMF radiation policy inputs into the model were intersected with identified vulnerable area facilities which were selected based on international criteria. The research output revealed potential EMF radiation violations which served as system feedback inputs in support of a demonstrated PIO function. The research recommends that the identified EMF radiation exposure violations of public health undergo a Promotion of Access to Information Act (PAIA) judicial review process to confirm the research findings. The judicial qualification of a PAIA PIO function of ‘substances released into the environment’ and ‘public safety or environmental risk’ would enable access to EMF radiation emissions data essential to future studies.

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35

Xu, Xiaoming. "New approximations in finite element calculation in high frequency." Thesis, London South Bank University, 1997. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.245127.

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Bradley, G. "Risk perception and communication within a personal construct theory framework." Thesis, Queen's University Belfast, 2003. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.273180.

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Carey, John Joseph. "Near field effects of terahertz pulses." Thesis, University of Strathclyde, 2003. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.273433.

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38

Jhavar, Ashwin B. "Triggered-lightning properties inferred from measured currents and very close magnetic fields." [Gainesville, Fla.] : University of Florida, 2005. http://purl.fcla.edu/fcla/etd/UFE0013160.

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39

TAKAHASHI, JIRO. "Projeto e construcao de uma estrutura aceleradora de eletrons de onda continua." reponame:Repositório Institucional do IPEN, 1997. http://repositorio.ipen.br:8080/xmlui/handle/123456789/10641.

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Made available in DSpace on 2014-10-09T12:42:40Z (GMT). No. of bitstreams: 0
Made available in DSpace on 2014-10-09T14:01:48Z (GMT). No. of bitstreams: 1 05030.pdf: 6618082 bytes, checksum: b37bbbe1087da50e0aecf20762c5f711 (MD5)
Tese (Doutoramento)
IPEN/T
Instituto de Pesquisas Energeticas e Nucleares - IPEN/CNEN-SP

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40

Fu, Ying. "Analysis of exposure to electromagnetic fields within the near-field of HF broadcast antennas." Thesis, University of Sheffield, 2013. http://etheses.whiterose.ac.uk/4699/.

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This thesis presents a study of the relationship between field strength and the actual levels of SAR in the human body encountered in close proximity to high gain high power HF broadcast antennas. In order to assess the human exposure against ICNIRP guidelines, it has led to the development of a series of assessments of modelling techniques, mechanical configuration and environment of a transmission site. Due to the complex nature of this EM problem, each chapter of this thesis covers the key developments of particular sub-projects in different areas. The findings of each area correspond to the ICNIRP occupational and public exposure guidelines; they formed the reference parameters in the primary assessments which could apply to a range of similar EM scenarios. The chapters of this thesis do not necessarily follow a chronological order. Various potential influential aspects of assessing the human exposure levels were addressed during continuous problem solving processes, including several issues have not been covered in other research before. There are three areas that have been covered in this thesis, firstly relating whole body SAR to incident plane-wave fields in correlation with ICNIRP basic restriction and reference levels. Second, near-zone incident fields characteristic were assessed by simulations and analyses the results, where some exposure assessment protocols for ICNIRP compliance was derived. Thirdly real-time field measurements were carried out to consolidate the findings from the theoretical modelling analysis. Experimental results are shown to be in agreement with these predicted by theory and in general, the electromagnetic E-field strengths within the near-field of the antenna are found to be significantly below these recommended by ICNIRP.

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Kimn, Edward Sun. "A parametric finite element analysis study of a lab-scale electromagnetic launcher." Thesis, Georgia Institute of Technology, 2011. http://hdl.handle.net/1853/39498.

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The purpose of the study is to better understand the factors that affect melt-wear in the armature-to-rail contact interface of an electromagnetic launcher (EML). In order to investigate the factors, the study uses finite element analysis (FEA) to vary parameters of a lab-scale EML at the Georgia Institute of Technology. FEA is used due to the complex nature of the system, which includes the geometry and various engineering aspects that the EML incorporates. The study focuses on an uncoupled analysis of the structural, electromagnetic (EMAG), thermal, and modal aspects. The reason for the uncoupled analysis was because the system was complex and there were computational limits. Also, by uncoupling the analysis fields, the way the parameters affected melt-wear could be viewed separately. The study varied the geometry of the armature, the stiffness of the rail system (compliance layer), and the material of the armature. The structural analysis was for the initial contact of the rail to the armature and found the von Mises stresses, contact area, and contact pressure. The EMAG analysis found the Lorentz forces in the system based on a current curve used in the lab-scale EML. The thermal analysis consisted of friction heating and Joule heating. The modal analysis was for the unstressed and pre-stressed armature. Based on the study conducted, it was found that aluminum would provide the best speeds due to its lighter mass, but lacked in the thermal resistance area. Tungsten provided the better thermal resistance, but lacked in the potential speed due to its heavier mass.

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Barbieri, Nicholas. "MEASUREMENT AND CHARACTERIZATION OF MICROWAVE TRANSIENT ELECTROMAGNETIC FIELDS GENERATED FROM LASER/MATTER INTERACTION." Master's thesis, University of Central Florida, 2005. http://digital.library.ucf.edu/cdm/ref/collection/ETD/id/3417.

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From past experiments conducted with high intensity lasers, it has been known for some time that laser matter interactions result in the emission of short, transient electromagnetic pulses. Previous investigations into laser generated electromagnetic pulses provide basic information regarding frequencies where such pulses may be present, along with the time duration of the pulses. Such investigations have also demonstrated a number of measurement techniques in which basic information on the pulses may be obtained. The purpose of this current investigation is to obtain a more thorough description and understands of electromagnetic pulses generated for laser matter interaction. To this end, spatial radiation patterns emanating from various laser excited matter sources was predicted using antenna theory for far field radiators. Experimentally, it is the intention of this investigation to gather comprehensive time and frequency domain data on laser matter generated electromagnetic pulses using a number of specific laser targets. Radiation detection techniques using broadband, calibrated EMC horn antennas were devised. A unique measurement system known as an inverse superhetereodyne receiver was designed, tested and demonstrated. An experimental setup using such instrumentation was established. Using the above instrumentation and experimental setup should yield comprehensive time and frequency domain data over a spectra range of 1-40 GHz and with a time resolution of 50 ps. Because the experimental system employed is calibrated, measurements can be corresponded to incident electromagnetic fields. Several tests were conducted to ensure the proper operation of experimental apparatus. A modulation test was conducted on the inverse superhetereodyne receiver to ensure that the experimentally observed signals appeared when and where predicted within the receiver's bandwidth. The experimental setup was used to measure radiation emitted from an electrostatic discharge source of known distance and discharge voltage. Frequency domain data from the discharges were collected and compiled using a Matlab application ultimately intended to measure laser matter interaction generated electromagnetic pulses, resulting in a compiled frequency domain description comprising 1-17 GHz. The inverse Fourier transform was used to retrieve the time domain response from the compiled data. The discharge gaps characteristics where systematically altered as to allow a parametric study of the compiled data. The discharge measurements demonstrate the measurement system's ability to analyze unknown, short duration; broadband microwave signals.
M.S.
Department of Physics
Arts and Sciences
Physics

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43

McKay, Allan John. "Geoelectric fields and geomagnetically induced currents in the United Kingdom." Thesis, University of Edinburgh, 2004. http://hdl.handle.net/1842/639.

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This thesis investigates geo-electric fields in the United Kingdom with particular regard to Geomagnetically Induced Currents (GIC) in the Scottish Power electricity transmission network (SPTN). The joint spectral characteristics of Scottish Power GIC and Eskdalemuir magnetic observatory data are analysed, and GIC are shown to be coherent with magnetic field variations over the period range 2-1100s. A bi-variate transfer function model of the physical link between magnetic field variations and GIC demonstrates that long-period (>200s) induction makes a first order contribution to the observed GIC at one SPTN site, and dominates the response at another. Thin-sheet modelling at a period of 750s is used to explore the relative influence of three factors on the size and spatial distribution of the calculated electric field: (i) the contrast in conductance between the sea and the land; (ii) variations in conductance due to sea depth; (iii) lateral variations in conductance representative of those in the geographic area occupied by the SPTN. The modelling suggests that a `coast-only' model (i) will over-predict electric field magnitudes in the SPTN region by a factor of 2-5 in comparison with model (iii). Distortion analysis of Magnetotelluric (MT) data at a period of 750s acquired over numerous field campaigns reveal pervasive galvanic distortion of the electric field in the SPTN region. GIC transfer functions of one site are consistently interpreted as proxy MT responses, and it is shown that galvanic distortion of the electric field modifies significantly the GIC amplitude response. A prototype model of the SPTN developed by the British Geological Survey and the Finnish Meteorological Institute is used to calculate GIC. It is shown that neglect of lateral variations of conductivity may lead to false conclusions about the direction of the external electric field that maximises GIC. Time derivatives of the Eskdalemuir horizontal magnetic field are used as an index of GIC activity, and to select events which may have led to large GIC in the time period (1983-2000) prior to the monitoring of GIC by Scottish Power. Backwards-prediction using the GIC transfer functions and observatory magnetic data suggests that GIC at the Scottish Power monitoring sites have amplitudes less than approximately 30A.

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Callaham, John Minton. "Joint-inversion of wenner resistivity and frequency domain electromagnetic data." Thesis, Georgia Institute of Technology, 1994. http://hdl.handle.net/1853/26007.

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45

Veilleux, Douglas L. "Melting in a low gravity environment with applied electromagnetic fields /." View online ; access limited to URI, 2005. http://0-wwwlib.umi.com.helin.uri.edu/dissertations/dlnow/3186925.

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46

Gardner, Christopher L. "The penetration of electromagnetic fields through open and loaded apertures." Thesis, University of Ottawa (Canada), 1993. http://hdl.handle.net/10393/6576.

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To ensure that an electronic system will work properly under all conditions, its designer must control the flow of electromagnetic (EM) fields to and from the system. The principal method of control is the use of a metallic enclosure or shield. In many cases, the effectiveness of the shield is determined, not by the bulk material properties, but by apertures that exist in the shield. These apertures may be introduced intentionally, as in the case of windows in the skin of an aircraft, or unintentionally, as in the case of an improperly welded seam of poorly gasketed door. To minimize the penetration of EM fields through a large aperture, the aperture is sometimes loaded with a conductive material. Previous workers have shown that the penetration of EM fields through open or loaded apertures can be calculated by determining the equivalent magnetic surface currents, $\vec M\sb{s}$, that exist over the surface of the aperture. For small apertures, the equivalent magnetic and electric dipole moments (and polarizabilities) are related to the irrotational and solenoidal components of $\vec M\sb{\rm s}$ respectively. In this thesis, the relevant integro-differential equations are solved using the Method of Moments to determine $\vec M\sb{s}$ and to calculate the equivalent polarizabilities and shielding effectiveness of a small, square aperture loaded with an impedance sheet. Results of measurements of the penetration of EM fields through an aperture loaded with conductive material made using a dual transverse electromagnetic (TEM) cell over a frequency range of 2 to 200 MHz are presented and compared with the numerical results. The conductive materials examined include carbon, hybrid and non-carbon composite materials, and metallic grids and meshes. The composite samples were fabricated to study the effects of fibre orientation, conductivity, sample lay-up, and degree of hybridization on the electromagnetic shielding properties. Wire grids and meshes were fabricated to study the effect of wire spacing on shielding properties.

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47

Liu, Xiaoming. "Exploration of the interaction of electromagnetic fields with nanoscale materials." Thesis, Queen Mary, University of London, 2012. http://qmro.qmul.ac.uk/xmlui/handle/123456789/8559.

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Nanoscale materials usually present strikingly different properties in comparison with their bulk counterparts, such as quantum size effects, surface plasmon resonance (SPR). To explore new properties as well as for novel applications, nanomaterials are being extensively investigated. This project investigates the interactions of electromagnetic fields with nanoscale materials, particularly gold nanoparticles (GNPs), over a wide range of frequency bands, including static field, 261 kHz, 13.56 MHz, 2.45 GHz, millimetre wave, THz, and the visible light. Especially, the efforts have been devoted to the study of heating effect of GNPs in association with potential biomedical applications. To explain the electromagnetic heating of GNPs, dielectric properties of GNP dispersions has been studied from 100 MHz to 20 GHz, as well as in the millimetre wave and THz ranges. The static field induced effects on the size distribution of GNPs has also been examined using ultra-violet spectroscopy and correlated to SPR. It has been revealed that purified GNPs cannot increase the specific absorption rate substantially at whichever frequency points of 261 kHz, 13.56 MHz, or 2.45 GHz. However, a greater temperature rise has been observed in the impurified GNP dispersions compared to deionisedwater, after 10 min RF treatment at 13.56 MHz. The measurements on dielectric properties show that impurified samples have much higher effective conductivity than that of deionised-water, while the conductivity change of purified ones is very small and not detectable within the measurement accuracy. This observation supports that the heating effect of GNP dispersions is mostly contributed by the impurities and disproves that GNPs can increase the specific absorption rate significantly. The magnetic field heating at 261 kHz suggests that GNPs have very weak magnetic properties. It has been found that a static field can change the size distribution of GNPs. Up to 2 THz, it is measured that the dielectric properties of GNP dispersions have no convincing change compared to deionised-water, implying that the electromagnetic heating of GNP below 2 THz may be insignificant. In addition, it is confirmed that GNPs have strong absorption in the visible light range due to SPR.

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Shepherd, Sebastian James. "The effects of extremely low frequency electromagnetic fields on insects." Thesis, University of Southampton, 2018. https://eprints.soton.ac.uk/422277/.

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Flying insect species are currently in decline, including many species that provide important pollination ecosystem services. Combined exposure to various environmental stressors are associated with insect declines, including land-use change, pesticide use and climate change, but the potential biological and environmental effects of extremely low frequency electromagnetic fields (ELF EMFs) are poorly understood. ELF EMFs are pervasive in the environment, and anthropogenic ELF EMF pollution has increased greatly in recent years. Despite this, little has been done to consider the potential environmental impacts of ELF EMFs. Given that there is evidence that ELF EMFs can have biological effects, it is important to explore these biological stimuli and their potential to affect insects in the environment. Here the biological effects of ELF EMFs on important insect species were investigated, with two-fold aims of both increasing understanding of the biological effects of ELF EMFs, and determining whether field-realisitc levels of ELF EMFs have the potential to cause envrionemental stress to insects. ELF EMF impacts were investigated with the desert locust, as an economically important agricultural pest and a species that provides utility in understanding insect neurophysiology, and the honey bee, as a globally important pollinator and a well known study species for insect cognitive behaviour. Short-term exposure to high levels of ELF EMFs was found to affect neurophysiology, and reduce locomotory function in locusts, as well as increase stress protein levels in bees and locusts, and affect honey bee cognitive behaviour. Acute exposure to ELF EMFs at levels that can be encountered regularly in the environment around man-man sources for ELF EMFs reduced honey bee performance in olfactory learning assays, affected flight behaviour, and affected feeding and flight performance in a semi-field scenario. Further to this, some of these impacts of ELF EMFs on cognitive behaviour and flight were reduced when ELF EMFs were applied in combination with other well-known environmental stressors, neonicotinoid insecticides. These findings give a more detailed indication of some of the physiological effects that may underpin changes in insect locomotory behaviour that occur after short-term exposure. This is the first time that powerline simulating ELF EMFs have been directly measured and applied to insects in the context of considering the ecological effects (and thus using field-realistic exposure levels) of the ELF EMFs, rather than just the biological effects. This is the first indication that short-term and acute ELF EMF exposure can affect insect cognitive behaviour, and these effects have been shown to occur at levels which can be encountered in the field by a globally important pollinator species, the honey bee. This is also the first indication that acute field-realistic ELF EMF exposure can affect insect locomotory behaviour in the environement. This research describes new effects of ELF EMFs on insect biology and establishes that ELF EMFs have a potential to affect insect ecology, such that future ELF EMF understanding must be focused in further exploring mechanisms by with ELF EMFs cause biological effects, as well as the larger scale ecological risk assessment of ELF EMF impacts from powerlines.

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Dadhich, Anang. "Electromagnetic Propulsion System for Spacecraft using Geomagnetic Fields and Superconductors." University of Cincinnati / OhioLINK, 2016. http://rave.ohiolink.edu/etdc/view?acc_num=ucin1461592799.

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Garg, Ayush A. "Electromagnetic Fields Alter the Motility of Metastatic Breast Cancer Cells." The Ohio State University, 2019. http://rave.ohiolink.edu/etdc/view?acc_num=osu1563816767104018.

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