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Dissertations / Theses on the topic 'Electrical excitation'
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1
Harrison, Nicholas Torquil. "Optical and electrical excitation of conjugated polymers." Thesis, University of Cambridge, 1998. https://www.repository.cam.ac.uk/handle/1810/251643.
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The study of luminescent conjugated polymers, and their use in light-emitting diode (LED) structures, is now a well established field of research in both the academic and industrial sectors. Since their discovery, conjugated polymers with many different properties have been developed; and light-emitting diodes (LEDs) with different emission colours, improved efficiencies, and enhanced stability manufactured. However, there is still much that is unknown or poorly controlled with respect to both polymer devices, and the polymer materials themselves. The work in this thesis investigates both materials and device physics. In particular, there is still debate about the precise nature of the electronic excited state - the exciton - which is responsible for light emission in these materials. The exciton may be envisaged as an electron-hole pair which is coupled to the geometry of the polymer chain; when the electron and hole recombine a photon is produced in the process of luminescence. There is discussion about whether the exciton is confined to one polymer chain (an intrachain excitation), or spread over two or more chains (an interchain excitation). Furthermore, it is not clear whether the absorption of light (photoexcitation) in conjugated polymers forms mainly excitons, or if a non-emissive interchain state, which has been called a polaron-pair, is the predominant generated species. The work presented in this thesis is of relevance to these two issues. Site-selective fluorescence measurements are presented for poly(p-phenylenevinylene) (PPV) which is the prototypical luminescent conjugated polymer, and four derivatives of this material. The results suggest that an intrachain exciton is responsible for luminescence in three of the five polymers (including PPV), but that interchain states form the emitting species in two of the materials. Excitation spectra, which provide information about the efficiency of exciton generation, were taken on PPV and three derivative materials. The results suggest that, for polymers prepared in Cambridge, excitons are the primary product of photoexcitation. However, similar measurements on samples of photo-oxidised PPV suggest that material quality is crucial to the process of exciton formation. This conjecture is supported by numerical modelling of the oxidation process. The research in the final third of the thesis involved driving PPV-based polymer LEDs with short high-voltage pulses, with a view to understanding a new excitation regime for these devices. The results show that extremely high peak current-densities and brightness can be achieved in these devices using these driving conditions. These results are discussed with reference to the application of polymer LEDs in multiplexed displays, and as electrically-pumped polymer lasers. The measurements also illustrate how polymeric devices may be used as a tool for elucidating basic physics, as many of the results can be explained by a strongly field-enhanced hole-mobility in the active polymer.
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Pornprompanya, Methasit. "Instability of excitation waves induced by electrical fields." [S.l. : s.n.], 2005. http://deposit.ddb.de/cgi-bin/dokserv?idn=975449834.
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Griffin, Daniel W. "Multi-band excitation vocoder." Thesis, Massachusetts Institute of Technology, 1987. http://hdl.handle.net/1721.1/14803.
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Pinner, Dickon John. "Pulsed electrical excitation of conjugated polymer light-emitting diodes." Thesis, University of Cambridge, 2001. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.620940.
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Hardwick, John C. (John Clark). "The dual excitation speech model." Thesis, Massachusetts Institute of Technology, 1992. http://hdl.handle.net/1721.1/12456.
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Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Electrical Engineering and Computer Science, 1992.Includes bibliographical references (leaves 126-133).
by John C. Hardwick.
Ph.D.
6
Wood, Vanessa Claire. "Electrical excitation of colloidally synthesized quantum dots in metal oxide structures." Thesis, Massachusetts Institute of Technology, 2010. http://hdl.handle.net/1721.1/58454.
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Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Electrical Engineering and Computer Science, 2010.Cataloged from PDF version of thesis.
Includes bibliographical references (p. 163-172).
This thesis develops methods for integrating colloidally synthesized quantum dots (QDs) and metal oxides in optoelectronic devices, presents three distinct light emitting devices (LEDs) with metal oxides surrounding a QD active layer, and uses these novel metal oxide based QD-LEDs to study mechanisms for electrical excitation of QDs. QD-LEDs have generated considerable interest for applications such as thin film displays with improved color saturation and white lighting with high color rendering index. This work demonstrates that air-stable metal oxides can be used to achieve QD-LEDs that have long shelf lives and operate at constant luminance in ambient conditions, unpackaged. Because metal oxides range from conductors to dielectrics, they can be used to develop a variety of different device architectures to explore mechanisms for electrical excitation of QDs. We report the first all-inorganic QD-LEDs with n- and p-type metal oxide charge transport layers and present design rules to enable systematic improvement of device efficiency. To shift away from direct charge injection as a means for electroluminescence (EL) in inorganic-based QD-LED structures, we develop a unipolar device architecture that presents the first evidence of field driven EL in QDs. To further explore this field driven excitation mechanism, we develop a structure that situates QDs between two insulating metal oxide layers. By eliminating the need for energy band alignment, these devices enable EL from QDs with emission peaks from 450 nm-1500 nm as well as from novel nanoparticles, such as phosphor doped-core/shell nanocrystals.
by Vanessa Claire Wood.
Ph.D.
7
Qureshi, Tabassum-Ur-Razaq. "An investigation into multi-spectral excitation power sources for Electrical Impedance Tomography." Thesis, University of Sussex, 2017. http://sro.sussex.ac.uk/id/eprint/71647/.
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Electrical Impedance Tomography is a non-invasive, non-ionizing, non-destructive and painless imaging technology that can distinguish between cancerous and non-cancerous cells by reproducing tomographic images of the electrical impedance distribution within the body. The primary scope of this thesis is the study of hardware modules required for an EIT system. The key component in any EIT system is the excitation system. Impedance measurement can be performed by applying either a current or voltage through emitting electrodes and then measuring the resulting voltages or current on receiving electrodes. In this research, both types of excitation systems are investigated and developed for the Sussex EIM system. Firstly, a current source (CS) excitation system is investigated and developed. The performance of the excitation system degrades due to the unwanted capacitance within the system. Hence two CS circuits: Enhance Howland Source (EHS) and EHS combined with a General impedance convertor (GIC: to minimise the unwanted capacitance) are evaluated. Another technique (guard-amplifier) has also been investigated and developed to minimise the effect of stray capacitance. The accuracy of both types of CS circuits are evaluated in terms of its output impedance along with other performance parameters for different loading conditions and the results are compared to show their performance. Both CS circuits were affected by the loading voltage problem. A bootstrapping technique is investigated and integrated with both CS circuits to overcome the loading voltage problem. The research shows that both CS circuits were unable to achieve a high frequency bandwidth (i.e. ≥10MHz) and were limited to 2-3MHz. Alternatively, a discrete components current source was also investigated and developed to achieve a high frequency bandwidth and other desirable performance parameters. The research also introduces a microcontroller module to control the multiplexing involved for different CS circuit configurations via serial port interface software running on a PC. For breast cancer diagnosis, the interesting characteristics of breast tissues mostly lie above 1MHz, therefore a wideband excitation source covering high frequencies (i.e. ≥1-10MHz) is required. Hence, a second type of the excitation system is investigated. A constant voltage source (VS) circuit was developed for a wide frequency bandwidth with low output impedance. The research investigated three VS architectures and based on their initial bandwidth comparison, a differential VS system was developed to provide a wide frequency bandwidth (≥10MHz). The research presents the performance of the developed VS excitation system for different loading configurations reporting acceptable performance parameters. A voltage measurement system is also developed in this research work. Two different differential amplifier circuits were investigated and developed to measure precise differential voltage at a high frequency. The research reports a performance comparison of possible types of excitation systems. Results are compared to establish their relationship to performance parameters: frequency bandwidth, output impedance, SNR and phase difference over a wide bandwidth (i.e. up to 10MHz). The objective of this study is to investigate which design is the most appropriate for constructing a wideband excitation system for the Sussex EIM system or any other EIT based biomedical application with wide a bandwidth requirement.
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Der, Ricky. "Audio coding with an excitation pattern distortion measure." Thesis, McGill University, 2005. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=82478.
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A new distortion measure for audio coding is proposed, posed as a distance measure on the space of excitation patterns. We investigate the psychoacoustic properties of the measure, as well as the implementation issues that arise under a constrained-distortion coding structure. Experimental results show that the excitation distortion metric produces higher-quality coded files than the usual Noise-to-Mask ratio measure, at the same rate.
9
Hardwick, John C. (John Clark). "A 4.8 Kbps multi-band excitation speech coder." Thesis, Massachusetts Institute of Technology, 1988. http://hdl.handle.net/1721.1/14751.
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Zelinski, Adam Charles. "Improvements in magnetic resonance imaging excitation pulse design." Thesis, Massachusetts Institute of Technology, 2008. http://hdl.handle.net/1721.1/45862.
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Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Electrical Engineering and Computer Science, 2008.Includes bibliographical references (p. 241-253).
This thesis focuses on the design of magnetic resonance imaging (MRI) radio-frequency (RF) excitation pulses, and its primary contributions are made through connections with the novel multiple-system single-output (MSSO) simultaneous sparse approximation problem. The contributions are both conceptual and algorithmic and are validated with simulations, as well as anthropogenic-object-based and in vivo trials on MRI scanners. Excitation pulses are essential to MRI: they excite nuclear spins within a subject that are detected by a resonant coil and then reconstructed into images. Pulses need to be as short as possible due to spin relaxation, tissue heating, and main field inhomogeneity limitations. When magnetic spins are tilted by only a small amount, pulse transmission may be interpreted as depositing energy in a continuous three-dimensional Fourier-like domain along a one-dimensional contour to form an excitation in the spatial domain. Pulse duration is proportional to the length of the contour and inversely proportional to the rate at which it is traversed, and the rate is limited by system gradient hardware restrictions. Joint design of the contour and a corresponding excitation pulse is a difficult and central problem, while determining near-optimal energy deposition once the contour is fixed is significantly easier. We first pose the NP-Hard MSSO problem and formulate greedy and convex relaxation-based algorithms with which to approximately solve it. We find that second-order-cone programming and iteratively-reweighted least squares approaches are practical techniques for solving the relaxed problem and prove that single-vector sparse approximation of a complex-valued vector is an MSSO problem.
(cont.) We then focus on pulse design, first comparing three algorithms for solving linear systems of multi-channel excitation design equations, presenting experimental results from a 3 Tesla scanner with eight excitation channels. Our aim then turns toward the joint design of pulses and trajectories. We take joint design in a novel direction by utilizing MSSO theory and algorithms to design short-duration sparsity-enforced pulses. These pulses are used to mitigate transmit field inhomogeneity in the human brain at 7 Tesla, a significant step towards the clinical use of high-field imaging in the study of cancer, Alzheimer's disease, and Multiple Sclerosis. Pulses generated by the sparsity-enforced method outperform those created via conventional Fourier-based techniques, e.g., when attempting to produce a uniform magnetization in the presence of severe RF inhomogeneity, a 5.7-ms 15-spoke pulse generated by the sparsity-enforced method produces an excitation with 1.28 times lower root-mean-square error than conventionally-designed 15-spoke pulses. To achieve this same level of uniformity, conventional methods must use 29-spoke pulses that are 1.4 times longer. We then confront a subset selection problem that arises when a parallel excitation system has more transmit modes available than hardware transmit channels with which to drive them. MSSO theory and algorithms are again applicable and determine surprising targetspecific mixtures of light and dark modes that yield high-quality excitations. Finally, we study the critical patient safety issue of specific absorption rate (SAR) of multi-channel excitation pulses at high field. We develop a fast SAR calculation algorithm and propose optimizing an individual pulse and time-multiplexing a set of pulses as ways to reduce SAR; the latter is capable of reducing maximum local SAR by 11% with no impact on pulse duration.
by Adam Charles Zelinski.
Ph.D.
11
Brandstein, Michael Shapiro. "A 1.5 Kbps multi-band excitation speech coder." Thesis, Massachusetts Institute of Technology, 1990. http://hdl.handle.net/1721.1/14283.
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Thesis (M.S.)--Massachusetts Institute of Technology, Dept. of Electrical Engineering and Computer Science, 1990.Includes bibliographical references (leaves 58-60).
by Michael Shapiro Brandstein.
M.S.
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Szlavik, Robert Bruce. "In vivo electrical stimulation of motor nerves." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 1999. http://www.collectionscanada.ca/obj/s4/f2/dsk1/tape8/PQDD_0032/NQ66239.pdf.
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Zendehnam, A. "Excitation processes in the positive column of electrical discharges in inert gases." Thesis, London Metropolitan University, 1987. http://repository.londonmet.ac.uk/3073/.
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The variation with the current i, of the intensity, I, of neon spectral lines emitted from low pressure positive column discharges has been studied as part of an investigation of excitation processes in these discharges. The results indicate that two-step excitation is important for many neon lines. Measurements of emission line profiles have been made using a pressure scanned Fabry-Perot interfermometer. High resolution absorption measurements have been made to give data on tha population densities of the lower excited states, and their variation with pressure and current, to assist in interpreting the intensity-current (I-i) results.
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Englebretson, Steven Carl. "Excitation and control of a high-speed induction generator." Thesis, Massachusetts Institute of Technology, 2005. http://hdl.handle.net/1721.1/34369.
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Thesis (S.M.)--Massachusetts Institute of Technology, Dept. of Electrical Engineering and Computer Science, 2005.Includes bibliographical references (leaves 97-99).
This project investigates the use of a high speed, squirrel cage induction generator and power converter for producing DC electrical power onboard ships and submarines. Potential advantages of high speed induction generators include smaller size and weight, increased durability, and decreased cost and maintenance. Unfortunately, induction generators require a "supply of reactive power" to run and suffer from variation in output voltage and frequency with any changes to the input reactive power excitation, mechanical drive speed, and load. A power converter can resolve some of these issues by circulating the changing reactive power demanded by the generator while simultaneously controlling the stator frequency to adjust the machine slip and manage the real output power. This combination of real and reactive power control will ensure a constant voltage DC bus over the full load range. Tests were performed on a three horsepower motor to help validate models and simulations at both the two kilowatt and 5 megawatt level. After determining the equivalent circuit of the demonstration motor, it was tested as a generator under grid connected and capacitor excited conditions. A stand-alone five megawatt, 12,000 RPM generator designed specifically to operate at high efficiency and power factor over the full load rang was used to design converter parameters. A variety of reactive power excitation strategies were briefly examined before the flow of reactive currents through a converter was explained using a six step inverter with two different switching schemes.
(cont.) Steady state and transient simulations matched the measured machine performance and illustrated the performance of the control strategy as the load changes. Keywords: induction generator, self-excitation, reactive power, power converter, rectifier.
by Steven Carl Englebretson.
S.M.
15
Lee, Joonsung. "Excitation and readout Designs for high field spectroscopic imaging." Thesis, Massachusetts Institute of Technology, 2011. http://hdl.handle.net/1721.1/64578.
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Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Electrical Engineering and Computer Science, 2011.Cataloged from PDF version of thesis.
Includes bibliographical references (p. 86-90).
In this thesis we state and demonstrate solutions to three engineering problems that arise in magnetic resonance imaging RF excitation with parallel transmission (pTx) and magnetic resonance spectroscopic imaging (MRSI). Recent work in parallel RF excitation in MRI has been demonstrated to offer dramatically improved flexibility for manipulation of magnetization preparation for imaging than is feasible with conventional single-channel transmission. We address two design problems that need to be solved before this emerging technology can be deployed in the clinical and research domain of human imaging at high field. First, we demonstrate a method for rapid and robust acquisition of the non-uniform fields of RF excitation due to arrays that are commonly used in pTx at high field. Our method achieves high-fidelity single-slice excitation and reception field mapping in 20 seconds, and we propose ways to extend this to multi-slice mapping in two minutes for twenty slices. A fundamental constraint to the application of pTx is the management of the deposition of power in human tissue, quantified by the specific absorption rate (SAR). The complex behavior of the spatial distribution of SAR in transmission arrays poses problems not encountered in conventional single-channel systems, and we propose a pTx design method to incorporate local SAR constraints within computation times that accommodate pTx pulse design during MRI acquisition of human subjects. Our approach builds on recent work to capture local SAR distribution with much lower computational complexity than a brute-force evaluation, and we demonstrate that this approach can reduce peak local SAR by 20~40% for commonly applied pTx design targets. This thesis focuses on the design of excitation methods for high field system (7T parallel transmit (pTx) system) and fast readout and post-processing methods to reduce the lipid contamination to the brain. The contributions include fast B1+ mapping and pTx RF pulse design with the local SAR constraints for excitation. Regarding the readout method we developed a real time filter design, variable density spiral trajectory, and iterative non-linear reconstruction technique that reduce the lipid contamination. The proposed excitation methods were demonstrated using a 7T pTx system and the readout methods were implemented in a 3T system. Our third contribution addresses a recurring problem in MRSI of the brain, namely strong contaminating artifacts in low signal-to-noise ratio brain metabolite maps due to subcutaneous, high-concentration lipid sources. We demonstrate two methods to address this problems, one during the acquisition stage where a spatial filter is designed based on spatial priors acquired from the subject being scanned, and the second is a post-processing method that applies the brain and lipid source prior for further artifact minimization. These methods are demonstrated to achieve 20~4OdB enhancement of lipid suppression in brain MRSI of human subjects.
by Joonsung Lee.
Ph.D.
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Khan, Mohammad M. A. "Coding of excitation signals in a waveform interpolation speech coder." Thesis, McGill University, 2001. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=32961.
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The goal of this thesis is to improve the quality of the Waveform Interpolation (WI) coded speech at 4.25 kbps. The quality improvement is focused on the efficient coding scheme of voiced speech segments, while keeping the basic coding format intact. In the WI paradigm voiced speech is modelled as a concatenation of the Slowly Evolving pitch-cycle Waveforms (SEW). Vector quantization is the optimal approach to encode the SEW magnitude at low bit rates, but its complexity imposes a formidable barrier.Product code vector quantizers (PC-VQ) are a family of structured VQs that circumvent the complexity obstacle. The performance of product code VQs can be traded off against their storage and encoding complexity. This thesis introduces split/shape-gain VQ---a hybrid product code VQ, as an approach to quantize the SEW magnitude. The amplitude spectrum of the SEW is split into three non-overlapping subbands. The gains of the three subbands form the gain vector which are quantized using the conventional Generalized Lloyd Algorithm (GLA). Each shape vector obtained by normalizing each subband by its corresponding coded gain is quantized using a dimension conversion VQ along with a perceptually based bit allocation strategy and a perceptually weighted distortion measure. At the receiver, the discontinuity of the gain contour at the boundary of subbands introduces buzziness in the reconstructed speech. This problem is tackled by smoothing the gain versus frequency contour using a piecewise monotonic cubic interpolant. Simulation results indicate that the new method improves speech quality significantly.
The necessity of SEW phase information in the WI coder is also investigated in this thesis. Informal subjective test results demonstrate that transmission of SEW magnitude encoded by split/shape-gain VQ and inclusion of a fixed phase spectrum drawn from a voiced segment of a high-pitched male speaker obviates the need to send phase information.
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Lim, S. P. "Electrical basis for inhibition and excitation in non-propulsive autonomically innervated smooth muscle." Thesis, University of Glasgow, 1986. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.377171.
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Zhang, Cheng. "Electrical excitation of surface plasmon polaritons by inelastic tunneling electrons with resonant nanoantennas." Thesis, Université Paris-Saclay (ComUE), 2019. http://www.theses.fr/2019SACLO007/document.
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Les plasmons polaritons de surface (SPPs) jouent un rôle central en nanophotonique, parce que ce sont des modes optiques qui peuvent être confinés dans l’espace à l’échelle de 10 nm et dans le temps à l’échelle de 10 fs. L’excitation électrique des plasmons polaritons de surface par effet tunnel inélastique peut être ultrarapide et localisée, ce qui permet de développer une nanosource pour la nanophotonique intégrée en profitant pleinement du potentiel des polaritons plasmon de surface. Pourtant, ce processus est très inefficace avec un rendement de conversion typique de 10-7~10-5 plasmon par électron.Dans ce manuscrit de thèse, nous présentons une étude théorique et expérimentale qui vise à augmenter l’émission de plasmons de surface par effet tunnel inélastique avec une nano-antenne résonante. Nous avons développé un modèle théorique pour décrire l’émission de lumière à partir d’une jonction à effet tunnel en utilisant le théorème de fluctuation-dissipation. Nous proposons deux stratégies pour augmenter le rendement de conversion électron-plasmon. Nous introduisons un mode d’antenne résonnante confiné à l’échelle du nanomètre afin de renforcer le couplage entre le courant et le champ. En outre, nous introduisons l’hybridation d’un mode plasmonique metal/isolant/metal confiné et d’un mode d’antenne. Nous prédisons théoriquement que 30% de l’énergie émise par un dipôle est sous forme de SPP pour une longueur d’onde de travail de 800nm et une épaisseur d’isolant de 1 nm.Nous avons développé les processus de fabrication pour réaliser les antennes à effet tunnel en utilisant la configuration Al/AlOx/Au. L’antenne fabriquée présente une fonctionnalité robuste concernant les propriétés électriques et optiques. Nous montrons l’antenne permet de contrôler le spectre d’émission SPP, la polarisation d’émission SPP et renforcer l’efficacité des émissions de SPP de plus de 3 ordres de grandeur. La puissance totale émise sous forme de SPP est de l’ordre de 10 pW, quatre ordres de grandeur de plus que la puissance typique émise par une pointe de microscope à effet tunnelSurface plasmon polaritons (SPPs) plays a central role in nanophotonics because they are optical modes that can be confined in space at the 10 nm scale and in time at the 10 fs scale. Electrical excitation of surface plasmon polaritons by inelastic tunneling electrons has the potential to be fast and localized so that it offers the opportunity to develop a nanosource for on-chip nanophotonics taking advantage of the full potential of surface plasmons polaritons. However, inelastic tunneling is rather inefficient with a typical electron-to-plasmon conversion efficiency of 10-7~10-5. In this thesis manuscript, we present a study for enhancing surface plasmon emission by inelastic tunneling electrons with a resonant nanoantenna. It consists of theoretical and experimental investigations. First, we have developed a theoretical model to describe the light emission from a tunnel junction based on the fluctuation-dissipation theorem. Second, we have theoretically demonstrated two strategies to improve the antenna SPP efficiency thus aiming to enhance electron-to-plasmon conversion efficiency. We introduce a resonant antenna mode with a sub-nanometer gap in order to enhance the coupling between the inelastic current and the the mode. Furthermore, we introduce the hybridization in a nanopatch antenna between a gap mode and an antenna mode to launch SPPs: we theoretically predict that 30% of the power emitted by a dipole is converted into SPP (working wavelength at 800nm) with a 1nm gap thickness. Third, we have developed the fabrication procedures to realize antenna tunnel junctions based on the Al/AlOx/Au configuration. The fabricated antenna junction shows a robust functionality both regarding electrical and optical properties. The antenna junction is demonstrated to control the SPP emission spectrum, the SPP emission polarization and enhance the SPP emission efficiency by over 3 orders of magnitude. The total SPP power emitted is in the range of 10 pW, four orders of magnitude larger than the typical fW power emitted by a scanning tunneling tip junction
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Chapman, Jeffrey W. (Jeffrey Wayne). "Feedback linearizing generator excitation control for enhanced power system stability." Thesis, Massachusetts Institute of Technology, 1992. http://hdl.handle.net/1721.1/117237.
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Thesis (M.S.)--Massachusetts Institute of Technology, Dept. of Electrical Engineering and Computer Science, 1992.Title as it appears in the M.I.T. Graduate List, June 1992: Nonlinear control strategies for power system stability enhancement.
Includes bibliographical references (leaves 104-107).
by Jeffrey W. Chapman.
M.S.
20
Waligo, Alfred. "Condition monitoring of lithium-ion batteries using broadband multisine excitation and electrochemical impedance spectroscopy." Master's thesis, University of Cape Town, 2018. http://hdl.handle.net/11427/28109.
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Electrochemical Impedance Spectroscopy (EIS) is a well-known technique that has been employed on various electrochemical cells to obtain their impedance spectra. Lithium-ion(Li-ion) cells are some of the cells to which it has been applied. The impedance spectra obtained from EIS can be used to estimate various batteries State of Health (SOH) and State of Charge (SOC) characteristics. The lengthy acquisition time associated with standard EIS makes it unsuitable for rapid on-line impedance measurements. Alternative methods that take a shorter time have therefore been proposed. This study compares the spectra obtained by the Harmonic Compensated Synchronous Detection (HCSD) broadband signal technique with the EIS and a custom Broadband Impedance Spectroscopy (BIS) technique, at different states of charge, which mimic a real-time load. The test cells are industry standard Nickel-Cobalt and Manganese Oxide (NCM) Li-ion cells. The BIS technique is like HCSD in the selection of frequencies; however, the amplitude of the excitation broadband signal is varied to match the impedance magnitude response of the cell. Also, parameter extraction is performed on both EIS and BIS techniques for fault detection purposes.
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Andrews, Derek Joseph. "Electrical and Manufacturing Limitations for the Miniaturization of Ion Trap Devices with Digital Excitation." BYU ScholarsArchive, 2016. https://scholarsarchive.byu.edu/etd/6345.
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Developing portable mass spectrometry systems is an active area of research due to its broad range of useful applications, including environmental monitoring, threat detection, and space exploration. The mass analyzer is one of the key elements of the mass spectrometry system to develop for a portable system. Ion traps are a good candidate for the mass analyzer in a portable mass spectrometry system because the operating pressure scales with size. This allows for scaling down the other components of the system including the vacuum and electrical systems. Researchers at BYU are making an effort to develop miniature ion traps based on a planar geometry. The ion traps are made using microfabrication processes. A summary of the plates developed at BYU is presented in this work. Results from experiments to test the effects of pitch alignment on one design of planar ion trap plates are also presented. Conventional ion traps use a sinusoidal waveform to drive them. Driving the ion trap with a digital waveform has many benefits including extended mass range, lower voltage, and more control over the waveform. One of the difficulties involved in using a digital waveform is creation of a high voltage, high frequency waveform. This work details the design of a digital circuit capable of outputting a waveform with an amplitude of 100 VP-P at a frequency of 5 MHz and lower. This waveform was applied to a new ion trap design based on wire electrodes instead of planar electrodes. This trap offers many benefits over the planar ion traps developed at BYU. This work presents mass spectra obtained using a square digital waveform applied to the wire ion trap.
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Buck, John R. (John Richard). "Single mode excitation in the shallow water acoustic channel using feedback control." Thesis, Massachusetts Institute of Technology, 1996. http://hdl.handle.net/1721.1/40604.
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Kern, Johannes [Verfasser], and Bert [Gutachter] Hecht. "Optical and electrical excitation of nanoantennas with atomic-scale gaps / Johannes Kern. Gutachter: Bert Hecht." Würzburg : Universität Würzburg, 2015. http://d-nb.info/1111783861/34.
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Yu, Di. "An Application Developed for Simulation of Electrical Excitation and Conduction in a 3D Human Heart." Scholar Commons, 2013. http://scholarcommons.usf.edu/etd/4620.
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This thesis first reviews the history of General Purpose computing Graphic Processing Unit (GPGPU) and then introduces the fundamental problems that are suitable for GPGPU algorithm. The architecture of GPGPU is compared against modern CPU architecture, and the fundamental difference is outlined. The programming challenges faced by GPGPU and the techniques utilized to overcome these issues are evaluated and discussed.
The second part of the thesis presents an application developed with GPGPU technology to simulate the electrical excitation and conduction in a 3D human heart model based on cellular automata model. The algorithm and implementation are discussed in detail and the performance of GPU is compared against CPU.
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Limbo, Beulah Sepo. "Insulator aging tests with HVAC and HVDC excitation using the tracking wheel tester." Thesis, Stellenbosch : University of Stellenbosch, 2009. http://hdl.handle.net/10019.1/2529.
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Thesis (MScEng (Electrical and Electronic Engineering))--University of Stellenbosch, 2009.ENGLISH ABSTRACT: Limited research results are available on the aging impacts of surface discharges for High Voltage Direct Current (HVDC) excitation on practical insulators using the Tracking Wheel Tester (TWT) methodology. This thesis gives details of an experimental investigation to compare the aging performance of insulator samples using the TWT for High Voltage Alternating Current (HVAC) and positive and negative polarity HVDC excitation. Two series of tests were performed. The first series of tests evaluated the aging of six insulator rods, namely three Room Temperature Vulcanized Silicone Rubber (RTV SR) coated glass samples and three uncoated glass samples. Three creepage distances were used for each of the test materials, namely 277 mm, 346 mm and 433 mm. The tests were conducted with HVAC excitation and the test methodology described in the IEC 61302 standard. The second series of tests involved the testing of actual insulator samples. The test voltage and conductivity of the salt water solution were also adapted. Six insulators from different manufacturers, representing different materials and specific creepage distances, were tested with HVAC and positive and negative polarity HVDC excitation. The test samples consisted of Ethylene Propylene Diene Monomer (EPDM), High Temperature Vulcanized Silicone Rubber (HTV SR), porcelain and SR coated porcelain insulators. The aging performance of the different test samples for the three types of excitation are compared in terms of peak leakage current, visual observations of surface degradation and hydrophobicity properties. The leakage current data for HVAC excitation shows that the insulators from the different manufacturers perform differently, even for the same type of material. The results also indicate differences in the way the surfaces degrade, as well as the rate of degradation. For insulators representing the same specific creepage distance, but different materials, it has been shown that the material does influence the aging performance. Comparison of the leakage current data for the HTV SR insulators from the same manufacturer, but with different specific creepage distances, shows that the specific creepage distance affect the aging performance significantly. In general, the test insulators showed higher peak leakage currents with HVDC excitation compared to HVAC excitation. The results for positive polarity HVDC excitation show that the dry band arcing, as well as the discharges, has the same form for all six insulators. The colour of the dry band discharges ranged from a blue-ish orange to a dark yellow, depending on the intensity of the leakage currents. The hydrophobic insulators, namely the HTV SR, EPDM and RTV SR coated porcelain insulators, had lost hydrophobicity within the first week of testing. The results for negative polarity HVDC excitation show severe surface degradation compared to the results for HVAC excitation. The effect of positive polarity HVDC excitation, however, seems to be more severe in terms of leakage currents and aging compared to negative polarity HVDC excitation.
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Reeves, Kevin. "Dynamic-systems analysis of self-excitation associated with a capacitor-coupled substation (CCS) - induction machine system." Master's thesis, University of Cape Town, 2006. http://hdl.handle.net/11427/5116.
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Includes bibliographical references.The purpose of this thesis is therefore to establish the cause of SSR at the Meru-Petronet system, and other similar systems, and investigate various compensation techniques.
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Chen, Yi. "Propagation and Excitation of Electromagnetic Modes for Travelling-wave MRI Applications." The Ohio State University, 2016. http://rave.ohiolink.edu/etdc/view?acc_num=osu1449158025.
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Zempoaltecatl, Lynnell Uilani Wai Yee. "Liquid Core Waveguide Sensors with Single and Multi-Spot Excitation." BYU ScholarsArchive, 2013. https://scholarsarchive.byu.edu/etd/3956.
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Using silicon based microfabrication and materials, a photonic platform, capable of single bioparticle analysis, has been developed. This platform combines liquid and hollow core waveguides on the micron-scale (5 µm x 12 µm) to isolate femtoliter sized sample volumes. Fluorescence excitation and signals in the visible range are directed into and out of the sample volume at an orthogonal angle to maximize signal-to-noise. In order to guide light in a low-index material antiresonant reflecting optical waveguides (ARROWs) were incorporated into the platform. This thesis reveals the development path of these structures over several device generations including innovations in material, geometries, and fabrication techniques to increase detection sensitivity. As a result of these developments, this photonic platform has shown to successfully detect virus samples and other particles. This thesis also presents a new idea for increasing the signal to noise ratio (SNR) by incorporating Y-splitter devices into the design. Specifically, the 1 x 2 and 1 x 4 splitter structures can be used as orthogonal excitation points to the liquid core waveguide. When fluorescently tagged particles are introduced into the hollow core, these points create an optical signal that is correlated in time and space. The data collected by a photodetector can then be processed by an algorithm to increase SNR. Such advancements have shown to increase the SNR by 175 times.
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Hua, Yahan. "Sensorless control of surface mounted permanent magnet machine using fundamental PWM excitation." Thesis, University of Nottingham, 2009. http://eprints.nottingham.ac.uk/11999/.
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This thesis describes the development of a sensorless control method for a surface mounted permanent magnet synchronous machine drive system. The saturation saliency in the machine is tracked from the stator current transient response to the fundamental space vector PWM (pulse width modulation) excitation. The rotor position and speed signals are obtained from measurements of the stator current derivative during the voltage vectors contained in the normal fundamental PWM sequence. In principle, this scheme can work over a wide speed range. However, the accuracy of the current derivative-measurements made during narrow voltage vectors reduces. This is because high frequency current oscillations exist after each vector switching instant, and these take a finite time to die down. Therefore, in this thesis, vector extension and compensation schemes are proposed which ensure correct current derivative measurements are made, even during narrow voltage vectors, so that any induced additional current distortion is kept to a minimum. The causes of the high frequency switching oscillations in the AC drive system are investigated and several approaches are developed to reduce the impact of these oscillations. These include the development of a novel modification to the IGBT gate drive circuit to reduce the requirement for PWM vector extension. Further improvements are made by modifications to the current derivative sensor design together with their associated signal processing circuits. In order to eliminate other harmonic disturbances and the high frequency noise appearing in the estimated position signals, an adaptive disturbance identifier and a tracking observer are incorporated to improve the position and speed signals. Experimental results show that the final sensorless control system can achieve excellent speed and position control performance.
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Cheng, Tak Keung. "The excitation andn dynamics of coherent lattice vibrations in semimetals and narrow-gap semiconductors." Thesis, Massachusetts Institute of Technology, 1994. http://hdl.handle.net/1721.1/12008.
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Laurence, Brent. "Modelling and control of the piezoelectric excitation of an automotive windshield for active noise cancellation." Thesis, McGill University, 2013. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=119658.
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In this thesis, a technique for implementing active noise control within an automotive vehicle is presented utilizing the actuation of a piezoelectrically driven windshield to create the anti-noise signal. The acoustic linearity of the power efficient speaker is also improved to match that of a traditional, high-performance cone speaker. With direct measurement of the corrupting noise signal impractical, a closed-loop feedback control system is designed to achieve both objectives simultaneously. Modelling of the plant dynamics is carried out by deterministic subspace identification on filtered empirical data of a laboratory apparatus which is scaled to match vehicular installations. A noise estimator, based on internal models of the system dynamics, generates a stream of synthetic noise measurements on which stochastic subspace identification is performed to produce periodically updated models of the plant disturbance. The spectral density estimate of the output disturbance is incorporated directly into H-infinity synthesis to identify an optimal feedback controller. Ambient highway noise and the window buffeting phenomenon, experienced by the driver-side passenger within the vehicle, are formulated and solved by independent optimization problems to maximize improvement of the passenger's acoustic experience.Dans cette thèse, une technique pour réaliser le contrôle actif du bruit dans un véhicule automobile est présentée en utilisant des actionneurs piézoélectriques qui font osciller un pare-brise pour créer le signal d'anti-bruit. L'efficacité énergétique du haut-parleur piézoélectrique est également améliorée avec la linéarité acoustique pour correspondre à celle d'un haut-parleur conique traditionnel. La mesure directe du signal de bruit étant impossible, un système de régulation par rétroaction est conçu pour atteindre les deux objectifs simultanément. La modélisation de la dynamique du système est effectuée par identification déterministe en sous-espaces sur des mesures empiriques filtrées d'un ap-pareil de laboratoire calibré en fonction de linstallation dans un véhicule. Un estimateur de bruit, basé sur des modèles internes de la dynamique du système, génère un flux demesures de bruit de synthèse sur lequel une identification stochastique en sous-espaces est effectuée pour produire des modèles mis à jour de manière périodique de la perturbation. L'estimation de la densité spectrale de la perturbation à la sortie est incorporée directement dans la synthèse H-infinity pour identifier un contrôleur rétroactif optimal. Le bruit ambiant de l'autoroute et le phénomène de turbulence causé par une fenêtre ouverte (window buffeting), subis par le passager du côté conducteur dans le véhicule, sont formulés et résolus par des problèmes d'optimisation indépendants afin de maximiser l'amélioration de l'expérience acoustique du passager.
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Zarafshani, Ali. "A high-performance, multi-frequency micro-controlled Electrical Impedance Mammography (EIM) excitation and phantom validation system." Thesis, University of Sussex, 2016. http://sro.sussex.ac.uk/id/eprint/61524/.
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The research concentrates on the design, development and calibration of a high performance Electrical Impedance Mammography (EIM) system for early detection of breast cancer at the macro and micro scale (at an early stage applicable for different breast sizes and shapes). The enhancement of the Electrical Impedance Tomography (EIT) system focuses on developing electrical and electronic instrumentations and improving the current source topologies to make them operate at multiple frequencies for the purpose of measuring permittivity and conductivity of different breast tissues. The calibration, assessment systems have employed current calibration in the EIT to evaluate the impedance distribution. This facilitates the acquisition of accurate impedance images to enable images of the internal structure of the breast to be constructed. A constraint on EIT systems is that the current injection system suffers from the effects of stray capacitance having a major impact on the hardware subsystem as the EIT is an ill-posed inverse problem which depends on the noise level in EIT measured data and regularization parameter in the reconstruction algorithm. This research aims are to prevent this problem by using a capacitance cancellation method based on a General Impedance Converter (GIC) implemented by operation of a second generation of current conveyor called OCCII-GIC and calibration methods to facilitate operation in the high frequency range. An EIT system based on a planar 85-electrode channel and using a Microcontroller unit (MCU) for addressing control between 85 electrodes and implementing calibration methods has been constructed. In EIT systems, assessment, validation of the performance and calibration of systematic errors in the electrical field generated inside of the interrogated volume is important. Evaluation of the EIT system will be assessed using a realistic electronic phantom (E-phantom). This enables the evaluation of the different conductivity values of the tissue, which has been created and evaluated based on the RSC circuit model for the different electrical conductivities and electrical impedivities in breast tissue.
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Lineaweaver, Sean Kenneth Ridgway. "Dynamic spiral lumped element model of electrical field distribution and neural excitation in the implanted cochlea /." Thesis, Connect to this title online; UW restricted, 2003. http://hdl.handle.net/1773/6092.
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Qunais, Thaer. "Parametric Average-Value Model of Rectifiers in Brushless Excitation Systems." UKnowledge, 2013. http://uknowledge.uky.edu/ece_etds/37.
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An average-value model of a rotating rectifier circuit in a brushless excitation system is set forth, where a detailed simulation is required to extract the essential averaged-model parameters using numerical averaging. In the proposed approach, a synchronous machine model with saturation and cross saturation and an arbitrary rotor network representation that uses a voltage-behind-reactance representation for the field winding of the main machine is proposed. This allows the field winding to be represented as branches in a circuit solver, permitting straightforward simulation with connected circuitry. Also a brushless exciter model is introduced to be compatible with the averaged-model, where the exciter armature windings are represented using a voltage-behind-reactance formulation. The resulting average-value model is verified in time domain against detailed simulation, and its validity is demonstrated in all rectifier modes of operation.
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Strojny, Brandan Thomas. "EXCITATION AND ANALYSIS OF CHARACTERISTIC MODES ON COMPLEX ANTENNA STRUCTURES." The Ohio State University, 2011. http://rave.ohiolink.edu/etdc/view?acc_num=osu1301006813.
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Izad, Olivier. "Computationally Efficient Method in Predicting Axonal Excitation." Cleveland, Ohio : Case Western Reserve University, 2009. http://rave.ohiolink.edu/etdc/view?acc_num=case1232751033.
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Patil, Anjali Narendra. "Delamination Detection in Concrete Using Disposable Impactors for Excitation." BYU ScholarsArchive, 2013. https://scholarsarchive.byu.edu/etd/3885.
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Delaminations in concrete bridge decks result primarily from corrosion of the reinforcing bars (or rebar). This corrosion leads to volumetric expansion of the rebar. When the rebar expands, concrete cracks, and there is a localized separation of the concrete cover from the underlying concrete. Impact-echo testing is an effective technique to map delaminations on concrete bridge decks. However, mapping speed is limited by necessary retrieval of the impactor for traditional tests. To achieve higher scanning speeds, it is advantageous to use both a non-contact measurement (air-coupled impact-echo) and disposable-impactor excitation. Disposable impactors have the potential advantage of achieving greater deck scanning speeds because they do not need to be retrieved, and they can also be used with air-coupled measurement systems. This thesis reports impact excitation of concrete using disposable impactors such as water droplets and ice balls. The impact characteristics of these impactors are compared with those of steel balls and chain links. Comparing the acoustic recordings on intact and delaminated concrete surface shows that water droplets and ice balls are able to excite flexural resonant modes associated with delamination defects. The use of water droplets and ice balls for shallow delamination detection in concrete is thus demonstrated.
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Rasel, Rafiul Karim. "Toward Imaging of Multiphase Flows using Electrical Capacitance Tomography." The Ohio State University, 2019. http://rave.ohiolink.edu/etdc/view?acc_num=osu155715027714914.
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Fairbanks, Jerrie Vincent. "LED Excitation and Photomultiplier Tube Biasing and Gating Circuitry for Fluorescence Instrumentation." Diss., The University of Arizona, 2015. http://hdl.handle.net/10150/556849.
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Fluorescence technologies have only begun exploiting the transient recording of lifetime-based signals and images for low nanosecond lifetimes, but the method has tremendous potential for scientific and medical applications. Low nanosecond lifetime recording in real-time can enable the tracking of metabolite concentrations in cells and tissues (e.g. cancerous tissues) without introducing foreign substances. It will also enable the tracking of reactive species (e.g. ozone) and intermediate/short-lived states in chemical reactions in the atmosphere. Current techniques all employ laser excitation, but LEDs can also be used which cause considerably less damage to live tissue. We have developed a high speed fluorescence prototype using high intensity LED pulses and novel PMT gating technology. Precision timing circuitry generates tunable width pulse signals which are driven through the LED using a comparator-based push-pull architecture. The timing circuitry also generates PMT gating pulses which are applied to the dynode chain via high voltage operational amplifiers. LED pulses with fall times (99%) as short as 2ns and PMT gating times (10% to 90%) of 3.6ns have been achieved. The prototype has been used to successfully measure the fluorescent lifetimes of Alexa Fluor 610X dye (1.7ns and 4.7ns) and riboflavin (4.5ns). Lifetimes of acridine orange were measured as follows: alone (2ns), in solution with ssDNA (3.7ns), in solution with dsDNA (5.8ns), and in solution with dsRNA (5.9ns). Finally, dsRNA was heated and allowed to cool revealing lifetimes that started at 3.7ns when hot and increased to nearly 5ns when cool.
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Xiong, Han. "Detection and Pattern Recognition of Partial Discharge in Electric Machine Coils with Pulsed Voltage Excitation." The Ohio State University, 2019. http://rave.ohiolink.edu/etdc/view?acc_num=osu1555592971342072.
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Frisk, Johan. "Technical Feasibility Study of an IGBT-based Excitation System." Thesis, Uppsala universitet, Elektricitetslära, 2017. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-324193.
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This thesis aims to design a cabinet to house some of the required hardware to realize a 1000 A IGBT inverter controlled static excitation system. In the thesis practical design considerations are identified and solved. The suggested excitation system requires a cabinet to house the inverters. Together with inverter requirements stated by the inverter manufacturer and possible electromagnetic interference from switching of the IGBT:s, practical design considerations arise when realizing the system. Identified design considerations are heat dissipation, EMI, IP-code requirements and mechanical stresses at inverter connections. In this study, the design considerations are addressed and a cabinet design with required components inside is suggested. The suggested cabinet together with its components could fulfil the suggested system's- and the inverter's requirements. However, the IP-code allowed by the suggested EMC-seals might be lower than the IP54 required by the inverter. The cabinets EMC-properties will probably be lowered if regular rubber gaskets are used. The study suggests one possible configuration which is possible to realize. It is suggested that further consideration is dedicated to the EMI reducing properties of the cabinet if it is to be installed in an environment sensitive to EMI.
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Pålsson, Emma. "Vibration analysis of a fast response brushless excitation system." Thesis, Uppsala universitet, Elektricitetslära, 2019. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-394098.
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The aim of this study is to measure and analyze vibrations on a fast response brushless exciter (FRBE) at a real hydropower plant and identify vibration origins through frequency analysis. Moreover, the observed vibrations are evaluated in relation to generator vibration standards and estimated tangential eigenfrequencies of the studied FRBE. It is concluded that the pulsations in the air gap torque, originating from the rotating thyristor bridge rectifier, is the source of the strongest vibrations. Some additional vibration sources are also identified. The requirements of the generator vibration standards are mostly fulfilled and no tangential eigenfrequencies are triggered in the vibration recordings. For further studies it is recommended that alternative control strategies and optimization of the FRBE mechanical design, with respect to its ability to withstand vibrations, should be investigated.
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Mouton, Gerton Nicolaas Jacobus. "An evaluation of different material line insulators under high voltage AC and bipolar DC excitation in a marine polluted environment." Thesis, Stellenbosch : Stellenbosch University, 2012. http://hdl.handle.net/10019.1/71940.
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Thesis (MScEng)--Stellenbosch University, 2012.ENGLISH ABSTRACT: The worldwide increase in the popularity of high voltage direct current (HVDC) power transmission application has led to questions regarding the performance of high voltage alternating current (HVAC) insulators when energized under HVDC excitation. These questions have led researchers conduct numerous research projects worldwide. A particular question NamPower (the power utility in Namibia) has faced is: how do these insulators perform and age when energized under HVDC excitation in heavily polluted environments? This question was only partly answered by some insulator ageing tests conducted under laboratory conditions for HVDC excitation. However, the natural ageing tests on insulators, which are preferred, have to date been confined predominantly to HVAC excitation voltages. Thus, this research was initiated to investigate the natural ageing performance of insulators under both HVAC and HVDC excitations, when subjected to harsh marine pollution environments. This research project involved performance and ageing tests on three identical sets of line insulators made from different insulator materials, energised under HVAC and both polarities HVDC excitations respectively. The tests were conducted at Koeberg insulator pollution test station (KIPTS), which is a natural marine pollution insulator test station located near Cape Town, along the west coast of South Africa, approximately 50 m from the sea. The set of insulators consisted of EPDM silicone alloy rubber, HTV silicone rubber, RTV silicone rubber coated porcelain, Porcelain and Glass insulators. The HVAC excitation voltage was chosen as 12.7 kV r.m.s. phase-to-ground and it was decided to use a HVDC excitation voltage equal to this value. The research results showed that the insulators made from HTV silicone rubber performed better than the insulators made from EPDM silicone alloy rubber under all excitation voltages. It is also showed that RTV silicone rubber coated porcelain insulators performed better than Glass and Porcelain insulators under all excitation voltages.
AFRIKAANSE OPSOMMING: Die wêreld wye toename in gewildheid van hoë spanning gelyk stroom (HSGS) krag transmisie aplikasie het gelei na vrae oor die effektieweteit van hoë spanning wissel stroom (HSWS) insolators in HSGS aplikasies. Hierdie vrae het gelei na baie navorsings projekte. Een vraag waarmee NamPower (die krag voorsienings maatskapy in Namibia) gekonfronteer was, was hoe gaan die insolators wat onderworpe is aan ’n HSGS toevoer reageer in ’n baie besoedelde omgewing. Hierdie vraag was slegs gedeeltelik beantwoord deur verouderings toetse op insolators wat gedoen is in ’n labaratorium met ’n HSGS toevoer. Inteendeel, die meeste natuurlike verouderings toetse op insolators, soos verkies, is meestal gedoen met ’n HSWS toevoer. Om hierdie rede was hierdie navorsing begin om natuurlike verouderings toetse te doen op insolators onderworpe beide aan HSWS en HSGS toevoere binne ’n marien besoedelde omgewing. Hierdie navorsings projek gaan oor prestering en verouderings toetse op drie, identiese, transmissie lyn insolator stelle, wat onderskeidelik onderworpe was aan HSWS en beide polariteite HSGS toevoere. Die toetse was gedoen by Koeberg insolator besoedeling toets stasie (KIBTS) wat naby Kaapstad geleë is langs die weskus van Suid Africa omtrent 50 m van die see. ’n Stel toets insolators bestaan uit EPDM silikon allooi rubber, HTV silikon rubber, RTV silikon rubber bedekte porselein, Porselein en Glas insolators. Die HSWS waarde waarmee die insolators getoets was, was 12.7 kV w.g.k., fase-na-grond, en dit was besluit om ’n HSGS waarde gelyk aan hierdie spannings waarde te gebruik. Die navorsings resultate wys dat insolators wat gemaak is met HTV silikon rubber presteer beter as insolators wat met EPDM silikon allooi rubber gemaak is onder al die verskillende toevoere. Dit wys ook dat RTV silikon rubber bedekte porselein presteer beter as Porselein en Glas insolators onder al die verskillende toevoere.
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Jamaly, Nima. "Comparative Study of Different Excitation Techniques for Microstrip-like Structures over an Infinite Perfect Electric Conductor Plane." Thesis, University of Gävle, Department of Technology and Built Environment, 2006. http://urn.kb.se/resolve?urn=urn:nbn:se:hig:diva-326.
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The overall goal of the thesis is to establish detailed comparisons among different well-known models of excitations in their application on Microstrip-like Monopoles. Comparisons are made over the input impedances predicted by these excitations. In this way, the Galerkin’s version of the Method of Moment is applied and rooftops functions are chosen as our basis/weighting functions. Different excitation models have their influence over the excitation vector and a unique MoM matrix is used to give input impedances. We shall elicit the effects of several parameters over relative input self/mutual impedances derived from these excitation models and finally make conclusions about their differences in anticipating the input Resistance, input Reactance and also resonance frequencies.
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Tzanidis, Ioannis. "Ultrawideband Low-Profile Arrays of Tightly Coupled Antenna Elements: Excitation, Termination and Feeding Methods." The Ohio State University, 2011. http://rave.ohiolink.edu/etdc/view?acc_num=osu1316439948.
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Katkar, Rajesh A. "The Effect Of Stationary UV Excitation On The Optical Behavior Of Electrochemically Self-Assembled Semiconductor Nanowires." VCU Scholars Compass, 2006. http://hdl.handle.net/10156/1983.
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Yuan, Weiqiang. "Simulation of Hexagonal Boron Nitride Deep Ultra-Violet ac-Driven Electroluminescence Devices." Ohio University / OhioLINK, 2020. http://rave.ohiolink.edu/etdc/view?acc_num=ohiou1586958083835764.
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Riemer, Owen D. "The Theory and Design of Class E Power Amplifiers for Impulse Excitation in Nuclear Magnetic Resonance." Wright State University / OhioLINK, 2021. http://rave.ohiolink.edu/etdc/view?acc_num=wright1625743337280261.
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Cao, Shuiyan. "Using plasmonic nanostructures to control electrically excited light emission." Thesis, Université Paris-Saclay (ComUE), 2018. http://www.theses.fr/2018SACLS042/document.
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Dans cette thèse, nous utilisons différentes nanostructures plasmoniques pour contrôler l'émission de lumière excitée électriquement. Notre émission électrique provient d'une "nanosource STM" qui utilise le courant tunnel inélastique entre la pointe d'un microscope à effet tunnel (STM) et un échantillon métallique, pour exciter localement les plasmons polaritons de surface localisés et propagatifs. L’interaction de notre nanosource STM et d'une lentille plasmonique circulaire (une série de fentes concentriques gravées dans un film d'or épais) produit une microsource radialement polarisée de faible dispersion angulaire (≈ ± 4 °). L'influence des paramètres structuraux sur la propagation angulaire de la microsource résultante est également étudiée. En outre, une faible dispersion angulaire (<± 7 °) pour une grande plage de longueurs d'onde (650-850 nm) est obtenue. Ainsi, cette microsource électrique de lumière presque collimatée a une réponse spectrale large et est optimale sur une large plage d'énergie, en particulier en comparaison avec d'autres structures plasmoniques résonantes telles que les nanoantennes Yagi-Uda. L'interaction de notre nanosource STM et d'une lentille plasmonique elliptique (une seule fente elliptique gravée dans un film d'or épais) est également étudiée. Lorsque l'excitation STM est située au point focal de la lentille plasmonique elliptique, un faisceau lumineux directionnel à faible divergence est acquis. De plus, expérimentalement, nous trouvons qu'en changeant l'excentricité de la lentille plasmique elliptique, l'angle d'émission varie. On constate que plus l'excentricité de la lentille elliptique est grande, plus l'angle d'émission est élevé. Cette étude permet de mieux comprendre comment les nanostructures plasmoniques façonnent l'émission de lumière. L'interaction de SPP excités par STM et d'une structure de pile multicouche planaire plasmonique est également étudiée. Il est démontré qu'en utilisant l'excitation STM, nous pouvons sonder la structure de bande optique de la pile Au-SiO₂-Au. Nous trouvons que l'épaisseur du diélectrique joue un rôle important dans la modification du couplage entre les modes. Nous comparons également les résultats obtenus par excitation laser et STM de la même structure de pile. Les résultats indiquent que la technique STM est supérieure en sensibilité. Ces résultats mettent en évidence le potentiel de la STM en tant que technique de nanoscopie optique sensible pour sonder les bandes optiques des nanostructures plasmoniques. Enfin, l'interaction d'une nanosource STM et d'une plaque triangulaire individuelle est également étudiée. Nous trouvons que lorsque l'excitation STM est centrée sur la plaque triangulaire, il n'y a pas d'émission de lumière directionnelle. Cependant, lorsque la nanosource STM est située sur le bord du triangle, on obtient une émission de lumière directionnelle. Cette étude nous fournit une nouvelle voie pour atteindre l'émission de lumière directionnelle. Nous étudions également l'exploration du LDOS optique du triangle avec la nanosource STM. Ainsi, nos résultats montrent que la manipulation de la lumière est réalisée par des interactions SPP-matière. En utilisant des nanostructures plasmoniques, nous contrôlons la collimation, la polarisation et la direction de la lumière provenant de la nanosource STMIn this thesis, we use different plasmonic nanostructures to control the emission of electrically-excited light. Our electrical emission is from an “STM-nanosource” which uses the inelastic tunnel current between the tip of a scanning tunneling microscope (STM) and a metallic sample, to locally excite both localized and propagating surface plasmon polaritons. The interaction of our STM-nanosource and a circular plasmonic lens (a series of concentric slits etched in a thick gold film) produces a radially polarized microsource of low angular spread (≈±4°). The influence of the structural parameters on the angular spread of the resulting microsource is also investigated. In addition, a low angular spread (<±7°) for a large wavelength range (650-850 nm) is achieved. Thus this electrically-driven microsource of nearly collimated light has a broad spectral response and is optimal over a wide energy range, especially in comparison with other resonant plasmonic structures such as Yagi-Uda nanoantennas. The interaction of our STM-nanosource and an elliptical plasmonic lens (a single elliptical slit etched in a thick gold film) is also studied. When the STM excitation is located at the focal point position of the elliptical plasmonic lens, a directional light beam of low angular spread is acquired. Moreover, in the experiment we find that by changing the eccentricity of the elliptical plasmonic lens, the emission angle is varied. It is found that the larger the eccentricity of the elliptical lens, the higher the emission angle. This study provides a better understanding of how plasmonic nanostructures shape the emission of light. The interaction of STM-excited SPPs and a planar plasmonic multi-layer stack structure is also investigated. It is demonstrated that using STM excitation we can probe the optical band structure of the Au-SiO₂-Au stack. We find that the thickness of the dielectric plays an important role in changing the coupling between the modes. We also compare the results obtained by both laser and STM excitation of the same stack structure. The results indicate that the STM technique is superior in sensitivity. These findings highlight the potential of the STM as a sensitive optical nanoscopic technique to probe the optical bands of plasmonic nanostructures. Finally, the interaction of an STM-nanosource and an individual triangular plate is also studied. We find that when the STM excitation is centered on the triangular plate, there is no directional light emission. However, when the STM-nanosource is located on the edge of the triangle, directional light emission is obtained. This study provides us a novel avenue to achieve directional light emission. We also study probing the optical LDOS of the triangle with the STM-nanosource. Thus, our results show that the manipulation of light is achieved through SPP-matter interactions. Using plasmonic nanostructures, we control the collimation, polarization, and direction of the light originating from the STM-nanosource
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Daanoune, Abdeljalil. "Contribution à l'étude et à l'optimisation d'une machine synchrone à double excitation pour véhicules hybrides." Thesis, Grenoble, 2012. http://www.theses.fr/2012GRENT126.
Full textAbstract:
Dans un contexte ou la question de la préservation de l'environnement est devenue un sujet sociétal majeur, la recherche de nouvelles technologies pour remplacer la voiture à essence constitue un véritable enjeu industriel. Les véhicules hybrides et électriques sont une alternative prometteuse aux véhicules conventionnels. Ce travail de thèse porte sur la conception et l'optimisation des machines électriques pour la motorisation de ces voitures.Au cours de ces travaux, nous avons développé une nouvelle méthodologie de dimensionnement et d'optimisation des machines synchrones à double excitation. L'intérêt de cette méthode est son bon compromis entre la précision et le temps de calcul et sa capacité d'adaptation à plusieurs types de machines. Le second volet de la thèse est consacré à la proposition d'une nouvelle structure de machine synchrone à rotor bobiné. Une technique originale de compensation de la réaction magnétique d'induit est mise en place, elle consiste en l'insertion d'aimants secondaires permettant de créer un flux dans l'axe q de la machine. Ce dernier a pour rôle d'affaiblir le flux de la réaction magnétique d'induitIn a context where the question of the environmental protection has become a major social problem, research new technologies to replace the gasoline car is a real industrial challenge. The hybrid and electric vehicles are a promising alternative to conventional vehicles. This thesis focuses on the design and optimization of electrical machines for electric and hybrid cars.In this work, we developed a new methodology for design and optimization of hybrid excitation synchronous machines. The advantage of this method is its good compromise between accuracy and computation time and its ability to be adapted to a wide range of machines. The second part of this thesis is devoted to the development of a new structure of a wound rotor synchronous machine. A novel technique for compensating the armature reaction of this machine is introduced, it involves the insertion of secondary magnets to produce a quadratic axis flux (q-axis), this latter has the function of weakening the armature reaction flux