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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.
1

Rock-Around Orbits

Bourgeois, Scott K. 2009 December 1900 (has links)
The ability to observe resident space objects (RSOs) is a necessary requirement for space situational awareness. While objects in a Low-Earth Orbit are easily ob- servable by ground-based sensors, diffculties arise when trying to monitor objects with larger orbits far above the Earth's surface, e.g. a Geostationary Orbit. Camera systems mounted on satellites can provide an eff ective way to observe these objects. Using a satellite with a speci c orbit relative to the RSO's orbit, one can passively observe all the objects that share the RSO's orbit over a given time without active maneuvering. An orbit can be defi ned by ve parameters: semi-major axis, eccentricity, right ascension of ascending node, inclination, and argument of perigee (a; e; ; i; !). Using these parameters, one can create an orbit that will surround the target orbit allowing the satellite in the Rock-Around Orbit (RAO) orbit to have a 360 degree view of RSOs in the target orbit. The RAO orbit can be applied to any circular or elliptical target orbit; and for any target orbit, there are many possible RAO orbits. Therefore, diff erent methods are required to narrow down the selection of RAO orbits. These methods use distance limitations, time requirements, orbit perturbations, and other factors to limit the orbit selections. The first step is to determine the range of RAO semi-major axes for any given target orbit by ensuring the RAO orbit does not exceed a prescribed maximum al- lowable distance, dmax from the target orbit. It is then necessary to determine the eccentricity range for each possible RAO semi-major axis. This is done by ensuring the RAO still does not exceed dmax but also ensuring that the RAO orbit travels inside and outside of the target orbit. This comprises one half of the rock-around motion. The final step is to determine the inclination of the RAO orbit. Only a small inclination different from that of the target orbit is required to complete the rock-around motion while the maximum inclination is found by making sure the RAO orbit does not exceed dmax. It is then important to consider orbit perturbations, since they can destroy the synchronization between the RAO and target orbit. By examining the e ffects of the linear J2 perturbations on the right ascension of ascending node and argument of perigee, the correct semi-major axis, eccentricity, and inclination can be chosen to minimize the amount of fuel required for station keeping. The optimal values can be found by finding the Delta v needed for di fferent combinations of the variables and then choosing the values that provide the minimum Delta v. For any target orbit, there are multiple RAO orbit possibilities that can provide 360 degree coverage of a target orbit. Even after eliminating some of them based on the methods already described, there are still many possibilities. The rest of the elimination process would then be based on the mission requirements which could be the range of an on-board sensor, the thruster or reaction wheel controls, or any other number of possibilities.
2

O prazer de ouvir rock and roll: uma análise sob a perspectiva do receptor / The pleasure of hearing rock and roll: an analysis under the recipient's perspective

Invernizzi, Rodrigo Candido 30 March 2017 (has links)
Submitted by Cássia Santos (cassia.bcufg@gmail.com) on 2017-05-30T11:39:10Z No. of bitstreams: 2 Dissertação - Rodrigo Candido Invernizzi - 2017.pdf: 3587342 bytes, checksum: e5155b3e6300c865d7d57f2eed54cdc5 (MD5) license_rdf: 0 bytes, checksum: d41d8cd98f00b204e9800998ecf8427e (MD5) / Approved for entry into archive by Luciana Ferreira (lucgeral@gmail.com) on 2017-05-30T15:57:09Z (GMT) No. of bitstreams: 2 Dissertação - Rodrigo Candido Invernizzi - 2017.pdf: 3587342 bytes, checksum: e5155b3e6300c865d7d57f2eed54cdc5 (MD5) license_rdf: 0 bytes, checksum: d41d8cd98f00b204e9800998ecf8427e (MD5) / Made available in DSpace on 2017-05-30T15:57:10Z (GMT). No. of bitstreams: 2 Dissertação - Rodrigo Candido Invernizzi - 2017.pdf: 3587342 bytes, checksum: e5155b3e6300c865d7d57f2eed54cdc5 (MD5) license_rdf: 0 bytes, checksum: d41d8cd98f00b204e9800998ecf8427e (MD5) Previous issue date: 2017-03-30 / Fundação de Amparo à Pesquisa do Estado de Goiás - FAPEG / The dissertation in question aims at a look at rock and roll with a focus on the listener and on the possible auditory sensations and brain connections occasioned at the moment when the music reaches the receiver. Based on the theoretical discussion about the possibilities of analyzing a work, based on Imbert (1987), we seek to understand where such a fascination for rock and roll comes from, especially the work Rock around the clock (understood here as the music that inaugurates the rock and roll genre). The work methodology consisted of a bibliographical review aiming to contribute with analyzes about the musical genre studied. In order to do so, we initially used the analytical approaches systematized by Imbert (1987), and then, in a second moment, to focus on the analysis of the reception, by the jakobsonian model, of the cultural industry and the imaginary. Finally, we observed the act of fruition, which involved diving into the field of acoustics and psychoacoustics, based on Schafer (1977). It was verified that: the function, the meanings and the feelings attributed to the music also arise from the biological conditions and not only from the socio-cultural references of the artist. In addition, both the acoustic context and the soundscape play important roles in the construction of musical reception theory. Finally, it is suggested the comprehensiveness of the analyzes about rock and roll and the receiver of this musical genre. / A dissertação em questão visa um olhar sobre o rock and roll com foco no ouvinte e nas possíveis sensações auditivas e conexões cerebrais ocasionados no momento em que a música atinge o receptor. A partir da discussão teórica a respeito das possibilidades de análise de uma obra, baseando em Imbert (1987), buscamos entender de onde vem tamanha fascinação pelo rock and roll, em especial pela obra Rock around the clock (entendida aqui como a música que inaugura o gênero rock and roll). A metodologia do trabalho consistiu em revisão bibliográfica com vistas a contribuir com análises a cerca do gênero musical estudado. Para tanto, inicialmente, foram utilizados as abordagens analíticas sistematizadas por Imbert (1987), para posteriormente, em um segundo momento, concentrar na análise da recepção, pelo modelo jakobsoniano, da indústria cultural e do imaginário. Por fim observou-se o ato de fruição, que implicou em mergulhar no campo da acústica e da psicoacústica tendo como base Schafer (1977). Constatou-se que: a função, os significados e os sentidos atribuídos à música brotam também das condições biológicas e não apenas das referências sócio-culturais do fruidor. Além disso, tanto o contexto acústico quanto a paisagem sonora exercem papeis relevantes na construção da teoria da recepção musical. Por fim, sugere-se a abrangência das análises a cerca do rock and roll e do receptor desse gênero musical.

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