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  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
31

Studies of high harmonic generation using high power lasers

Tisch, John William George January 1995 (has links)
No description available.
32

Analysis of Spherical Harmonics and Singular Value Decomposition as Compression Tools in Image Processing.

Qamar, Aamir, Din, Islamud, Khan, Muhammad Abbas January 2012 (has links)
Spherical Harmonics (SPHARM) and Singular Value Decomposition (SVD) utilize the orthogonal relations of its parameters to represent and process images. The process involve mapping of the image from its original parameter domain to a new domain where the processing is performed. This process induces distortion and smoothing is required. The image now mapped to the new parameter domain is descripted using SPHARM and SVD using one at a time. The least significant values for the SPHARM coefficients and singular values of SVD are truncated which induces compression in the reconstructed image keeping the memory allocation in view. In this thesis, we have applied SPHARM and SVD tools to represent and reconstruct an image. The image is first mapped to the unit sphere (a sphere with unit radius). The image gets distorted that is maximum at the north and south poles, for which smoothing is approached by leaving 0.15*π space blank at each pole where no mapping is done. Sampling is performed for the θ and φ parameters and the image is represented using spherical harmonics and its coefficients are calculated. The same is then repeated for the SVD and singular values are computed. Reconstruction is performed using the calculated parameters, but defined over some finite domain, which is done by truncating the SPHARM coefficients and the singular values inducing image compression. Results are formulated for the various truncation choices and analyzed and finally it is concluded that SPHARM is better as compared with SVD as compression tool as there is not much difference in the quality of the reconstructed image with both tools, though SVD seem better quality wise, but with much higher memory allocation than SPHARM.
33

Probabilistic analysis of harmonics in railway traction system

Yuen, Kwok-hoo. January 2000 (has links)
Thesis (M. Phil.)--University of Hong Kong, 2001. / Includes bibliographical references (leaves 178-186).
34

Time-resolved study of third harmonic generation from anisotropically expanding clusters

Shim, Bonggu 28 August 2008 (has links)
Not available / text
35

Adaptive tree multigrids and simplified spherical harmonics approximation in deterministic neutral and charged particle transport /

Kotiluoto, Petri. January 1900 (has links) (PDF)
Thesis (doctoral)--University of Helsinki, 2007. / Includes bibliographical references. Also available on the World Wide Web.
36

Neutral-point-clamped shunt active filter /

Van Greunen, Corneluis Erasmus. January 2005 (has links)
Thesis (MScIng)--University of Stellenbosch, 2005. / Bibliography. Also available via the Internet.
37

Time-resolved study of third harmonic generation from anisotropically expanding clusters

Shim, Bonggu, January 1900 (has links) (PDF)
Thesis (Ph. D.)--University of Texas at Austin, 2006. / Vita. Includes bibliographical references.
38

Gate bias control and harmonic load modulation for a Doherty amplifier : a thesis presented for the degree of Doctor of Philosophy in Electrical and Computer Engineering at the University of Canterbury, Christchurch, New Zealand /

Smith, Karla. January 1900 (has links)
Thesis (Ph. D.)--University of Canterbury, 2009. / Typescript (photocopy). "2 September 2009." Includes bibliographical references (p. [139]-148) and index. Also available via the World Wide Web.
39

Sistemas híbridos para mitigação de harmônicos: modelagem e estudos experimentais

Ravagnani, Lídia Luciana [UNESP] 31 October 2008 (has links) (PDF)
Made available in DSpace on 2014-06-11T19:30:50Z (GMT). No. of bitstreams: 0 Previous issue date: 2008-10-31Bitstream added on 2014-06-13T19:00:48Z : No. of bitstreams: 1 ravagnani_ll_dr_ilha.pdf: 3403805 bytes, checksum: ec5d7df903a0df16a3323c714e843e81 (MD5) / Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES) / Diante do aumento expressivo de cargas não-lineares nos sistemas de energia elétrica cresce também, em proporções alarmantes, os problemas relacionados com as distorções harmônicas nas tensões e correntes. Com vistas à mitigação das distorções harmônicas, o uso de filtros e dispositivos de compensação harmônica são as técnicas comumente utilizadas para atenuar o fluxo das principais componentes harmônicas que compõem a citada distorção. Este trabalho está particularmente direcionado para investigações relacionadas ao uso de dispositivos de filtragem de natureza passiva, compreendendo arranjos híbridos, compostos por filtros ressonantes e filtros eletromagnéticos. Neste contexto, esta tese apresenta contribuições inéditas relacionadas com o desenvolvimento de modelos matemáticos no domínio da freqüência para filtros eletromagnéticos e a generalização de metodologias para análise de desempenho baseado no comportamento das componentes harmônicas seqüenciais. O desempenho e a aderência dos modelos propostos são avaliados numa base comparativa de natureza experimental, utilizando-se um protótipo de um filtro eletromagnético de potência reduzida, construído a partir das diretrizes metodológicas oriundas das análises teóricas. Os modelos desenvolvidos são utilizados na composição de um aplicativo computacional para análise de desempenho e otimização de projetos de sistemas de filtragem harmônica. A descrição analítica proporcionada por esta ferramenta de cálculo possibilita a investigação individualizada e sistemática do comportamento do sistema elétrico para as diferentes componentes harmônicas seqüenciais. Pela investigação detalhada das contribuições individuais de cada fonte harmônica, é possível identificar ações para a escolha adequada das topologias e de outros ajustes, visando à maximização do desempenho... / Due to the expressive increase of non linear loads in the electric power systems it also grows, in alarming proportions, the problems related with harmonic distortions present in voltages and currents. Aiming the mitigation of harmonic distortions, the use of filters and devices of harmonic compensation are the techniques commonly used to reduce the flow of the main harmonic components that composes the mentioned distortion. This work is particularly addressed to investigations related to the use of filtering devices of passive nature, composed by hybrid arrangements of tuned filters and electromagnetic filters. In this context, this thesis presents unpublished contributions related with the development of mathematical models in the frequency domain for electromagnetic filters and the generalization of methodologies for performance analysis based on the behavior of the sequential harmonic components. The performance and adherence of the proposed models are evaluated in a comparative base of experimental nature, using a prototype of an electromagnetic filter of reduced power built considering the methodological guidelines originating from the theoretical analyses. The obtained models are used in the development of a computational application for performance analysis and optimization of projects of harmonic filtering systems. The analytical description proportioned for this calculation tool makes possible the individualized and systematic investigation of the electric system behavior for different sequential harmonic components. The detailed investigation of the individual contributions of each harmonic source, makes it is possible to identify actions for the appropriate choice of the topologies and other adjustments seeking the maximization performance of the filtering system, such as the definition of the number of resonant branches and respective syntonization frequencies... (Complete abstract click electronic access below)
40

An investigation of the effects of voltage and current harmonics on an electrical distribution island network

Modipane, Kabelo Clifford 26 February 2009 (has links)
M.Ing. / With the advances in technology and the increase in industrial facilities, the harmonic content of an electrical network has always been a major concern among power system engineers. This is especially in an industrial environment, where the usage of power is very high as there are many large-scale types of equipment being used. Thus, it would be useful to know the sources, distortion level, impact on the power system and the equipment of harmonic currents on the harmonically rich electrical network. The presence of harmonics on electrical networks poses many problems to power system engineers and inconvenience or loss to the industries. Their effects on power system apparatus include resonance, reduced operating life of rotating machines and error in power calculations. For this study, the author would like to find out the implications of this issues, following these harmonic problems by analyzing, with some amount of simulations, practical measurements and assessments. In this way, a better understanding could be gained about these harmonic problems and harmonic contents. Steps could be taken to protect the power system equipment that could be affected by high harmonic currents and raise the quality of power supply.

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