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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.
21

Possíveis variações da obliquidade de planetas /

Oliveira, Marina Gonzaga de. January 2018 (has links)
Orientador: Tadashi Yokoyama / Banca: Othon Cabo Winter / Banca: Marcos Tadeu dos Santos / Resumo: É quase um consenso que os planetas ao serem formados, nasceram com obliquidades quase nulas. No entanto, para os planetas gigantes, exceto Júpiter, as atuais obliquidades estão longe de zero. Para Saturno, Urano e Netuno elas são, respectivamente, 25,61°, 97,86°, 28,31°. Em geral, as razões que alteraram as obliquidades estão associadas a efeitos gravitacionais como colisões ou capturas em ressonâncias. Neste trabalho pretendemos montar o sistema médio que governa a dinâmica de longo período da variação da obliquidade de um planeta considerando o Sol e um satélite com massas e distâncias diversas. Usaremos variáveis de Andoyer pois, por serem canônicas, as médias podem ser realizadas de forma rigorosa sempre que feitas em variáveis ação - ângulo. A questão do "wooble" pode ser facilmente incorporada se necessário. Pretendemos com este modelo estudar a variação da obliquidade de Netuno, mas em princípio pode ser usado também nos casos de exoplanetas (ARMSTRONG et al., 2014). O planeta Netuno, aparentemente é o único que não tem nenhum satélite regular primordial, ao contrário dos demais. Boué e Laskar (2010) fizeram uso de um satélite adicional para explicar a obliquidade de Urano. Porém, a presença de um satélite adicional de massa muito elevada, poderia desestabilizar os primordiais já existentes. No caso de Netuno, as massas dos satélites adicionais que pretendemos usar podem ser muito menores do que aquelas usadas por Boué e Laskar, o que elimina de vez, possível desestab... (Resumo completo, clicar acesso eletrônico abaixo) / Abstract: It is almost a consensus that the planets, when formed, were born with almost zero obliquities. However, for giant planets except Jupiter, the current obliquities ( ) are far from zero. For Saturn, Uranus, and Neptune they are, respectively, 25 . 6 ◦, 97 . 8 ◦, 28 . 3 ◦ . In general, the reasons that changed the obliquities are associated to gravitational effects such as collisions or captures in resonances. In this work we intend to build the average system that governs the long period dynamics of the variation of the obliquity of a planet considering the Sun and a satellite with different masses and distances. We will use Andoyer variables, because they are canonical, so averages can be performed rigorously whenever they are made in angle-action variables. The "wooble" issue can be easily incorporated if necessary. We intend with this model to study the variation of the Neptune's obliquity, but in principle it can also be used in the case of exoplanets (ARMSTRONG et al., 2014). The planet Neptune, apparently is the only one that has no regular primordial satellite, unlike the others. Boué e Laskar (2010), used an additional satellite to explain the Uranus' obliquity. However, the presence of an additional satellite with very high mass could destabilize the existing primordial ones. In the case of Neptune, the masses of the additional satellites that we intend to use may be much smaller than those used by Boué and Laskar, which eliminates possible destabilization of even... (Complete abstract click electronic access below) / Mestre
22

Dinâmica e origem de asteroides de alta inclinação

Machuca, James Freddy Luis [UNESP] 27 October 2011 (has links) (PDF)
Made available in DSpace on 2014-06-11T19:25:29Z (GMT). No. of bitstreams: 0 Previous issue date: 2011-10-27Bitstream added on 2014-06-13T19:47:34Z : No. of bitstreams: 1 machuca_jfl_me_guara.pdf: 8805916 bytes, checksum: a079609323009e7947c11ada2408948e (MD5) / Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES) / Asteroides de alta inclinação são objetos com sin(i) > 0.3. Entre estes asteroides podemos distinguir objetos com inclinação menor que o centro da ressonância secular ν6 = g−g6 e objetos com inclinação superior. Os atuais mecanismos de mobilidade dinâmica não podem aumentar facilmente inclinações menores do que do centro da ressonância ν6. A presença de objetos de alta inclinação pode, portanto, estar relacionada com fases iniciais do Sistema Solar. Neste trabalho obtemos elementos próprios sintéticos para a região da família de Pallas, encontramos grupos dinâmicos e determinamos a significância estatística destes grupos. Estudamos a evolução dinâmica devida a perturbações planetárias e efeitos não gravitacionais das famílias e clumps identificados na região das famílias de Pallas e Hansa (Carruba 2010b). Estudamos regiões dinamicamente estáveis, que são surpreendentemente caracterizadas por um número muito baixo de asteroides, contrariamente a objetos de baixa inclinação que ocupam tudo a região dinamicamente viável. Identificamos duas areas caracterizadas por tempos de permanência de 100 milhões de anos o mais, quando a força Yarkovsky é considerada, com baixa densidade de asteroides. Obtemos elementos próprios sintéticos para 10865 objetos na região da família de Euphrosyne e identificamos famílias e clumps no domínio dos elementos próprios e frequências. Com relação a outros trabalhos sobre identificação de famílias na área, aqui nos investigamos o efeito que a rede local de ressonâncias seculares tem sobre a evolução dinâmica das famílias e clumps. Identificamos por primeira vez, novas populações de objetos em estados ressoantes de libração anti-alinhada de ν6 e anti-alinhada e alinhada de ν5. / Highly inclined asteroids are objects with sin(i) > 0.3. Among these asteroids we can distinguish between objects with inclinations lower than the center of the secular resonance ν6 = g−g6 and objects with higher inclinations. The current mechanisms of dynamical mobility cannot easily increase inclinations to value higher than that of the center of the ν6 resonance. The presence of high inclination objects may therefore be related to early stages of the Solar System. In this work we obtained synthetic proper elements for the region of the Pallas family, we found dynamical groups and determined the statistical significance of these groups. We studied the dynamic the dynamical evolution caused by planetary perturbations and non-gravitational effects of the families and clumps identified in the region of the Pallas and Hansa families (Carruba 2010b). We studied regions dynamically stable that on surprisingly characterized by a low number of asteroids, contrary to objects of lower inclinations that tend to occupy all the viable stable regions. We identified two areas characterized by permanence time of 100 Myr or more when the Yarkovsky force is considered, but with a small number density of bodies. We obtained synthetic proper elements for 10865 objects in the region of the Euphrosyne families and identify families and clumps in the domain of proper elements and frequencies. With respect to other work on family identification in the area, here we investigated the role that the local web of secular resonances has had on the dynamical evolution of families and clumps. We identify for the first time, new populations of objects inν6 anti-aligned libration and ν5 anti-aligned and aligned resonant states.
23

Mobilidade asteroidal induzida por encontros próximos com vários asteroides massivos

Huaman Espinoza, Mariela [UNESP] 04 March 2013 (has links) (PDF)
Made available in DSpace on 2014-06-11T19:22:30Z (GMT). No. of bitstreams: 0 Previous issue date: 2013-03-04Bitstream added on 2014-06-13T20:28:59Z : No. of bitstreams: 1 huamanespinoza_m_me_guara.pdf: 968832 bytes, checksum: d9143c9ac2bced7e7e596dfec1f9845b (MD5) / Encontros próximos com asteroides massivos são conhecidos por ser um mecanismo de mobilidade dinâmica que pode alterar significativamente elementos próprios de corpos menores, e eles são a principal fonte de mobilidade dinâmica para asteroides médios e grandes dimensões (D>20 km, aproximadamente). A mobilidade orbital causada pelos encontros próximos com asteroides massivos foi estudado no passado e pode ser um mecanismo viável para produzir a localização atual orbital de alguns dos asteroides tipo V atualmente fora da família Vesta. É bem conhecido, no entanto, que as frequências próprias da precessão do pericentro g e longitude do nodo s de planetas terrestres mudam quando um ou mais dos outros planetas não é considerado no esquema de simulação. Por exemplo as frequências g4 e s4 são diferentes quando o sistema solar completo é considerado ou quando somente Marte e os planetas jovianos foram contabilizadas. Neste trabalho consideramos os efeitos de que a inclusão de um ou mais asteroides massivos no esquema de simulação tiver na órbita dos asteroides massivos e, indirectamente, sobre as estatísticas de mudanças no semieixo maior causada pelos encontros próximos com este asteroide massivo. Nós descobrimos que os asteroides massivos, as frequências próprias são dependentes do número de outros asteroides massivos considerados no esquema de simulação e que, como resultado, as estatísticas inteiras do encontros com asteroides massivos também é afetada. As variações da mudança no semieixo maior próprio a causada pelos quatro asteroides mais massivos variou de até 36,3% nos cinco esquemas de simulações que utilizamos, e o número de encontros que causou a fortes mudanças na semieixo maior variou até um fator de 2. O efeito indireto causado pela presença de outros asteroides massivos, portanto... / Close encounters with massive asteroids are known to be a mechanism of dynamical mobility that can significantly alter proper elements of minor bodies, and they are the main source of dynamical mobility for medium-sized and large asteroids (D>20 km, approximately). Orbital mobility caused by close encounters with massive asteroids has been studied in the past and could be a viable mechanism to produce the current orbital location of some of the V-type asteroids currently outside the Vesta family. It is well known, however, that the proper frequencies of precession of pericenter g and longitude of the node s of terrestrial planets change when one or more of the other planets is not considered in the integration scheme. For instance, the g4 and s4 frequencies are different when the full solar system is considered or when only Mars and the Jovian planets are accounted for. In this work we consider the effect that including one or more massive asteroids in the integration scheme has on the massive asteroids orbit, and, indirectly on the statistics of changes in semi-major axis caused by close encounters with this com mais de ummassive asteroid. We find that massive asteroid proper frequencies are dependent on the number of other massive asteroids considered in the integration scheme and that, as a result, the whole statistics of encounters with asteroid is also affected. Variances of the change in proper a caused by the four most massive asteroids varied up to 36.3% in the five integration schemes that we used, and the number of encounters that caused the strongest changes in semi-major axis varied up to a fator 2. The indirect effect caused by the presence of other massive asteroids therefore introduces an additional source of uncertainty in estimating the long-term effect of close encounters with massive asteroids that was not accounted for in... (Complete abstract click electronic access below)
24

Three-dimensional evolution of Mercury's spin-orbit resonance

Brenner, Norman Mitchell. January 1975 (has links)
Thesis: Ph. D., Massachusetts Institute of Technology, Department of Earth and Planetary Sciences, 1975 / Vita. / Bibliography: leaves 53-55. / by Norman Brenner. / Ph. D. / Ph. D. Massachusetts Institute of Technology, Department of Earth and Planetary Sciences
25

Alight, the dead of night: Ascertaining the collection and use of nighttime site inventory in landscape architecture professional practice

Felkins, Jacob Zachary 13 August 2024 (has links) (PDF)
In landscape architecture, site inventory is a common precursor and perpetual informant of site design, toolkit development, and best management practices. Within inventory-specific texts, inventory is primarily geared, collected, and applied toward the daytime, and thusly, one might consider the bulk of inventory to be “daytime inventory” which pays greater heed to a diurnal humanity and lesser heed to the nocturnal world. With a greater attention to nighttime site conditions, we explored “nighttime inventory” through a series of primary considerations - nighttime lighting, light pollution, site ecology, and the night sky – along with several secondary considerations. We then surveyed 811 landscape practitioners from 12 states - receiving 51 responses - and via Likert, open-response, and yes/no inquiries; we assessed whether practitioners acknowledge and/or design per those nighttime considerations in their professional practice. Summarily, we found landscape practitioners paid less heed to nighttime inventory considerations – with some notable exceptions.
26

Os mukashi banashi da literatura japonesa: uma análise do feminino e do casamento entre seres diferentes no contexto dos contos do japão antigo / The mukashi banashi of the Japanese literature: an analysis about the female and the marriages between different beings in the context of ancient Japan

Namekata, Marcia Hitomi 14 March 2011 (has links)
O presente trabalho propõe-se a uma análise dos mukashi banashi (contos antigos) da literatura japonesa sobre os casamentos entre seres diferentes, com enfoque nas imagens da esposa animal e da esposa celestial que surgem nestas narrativas. Apresentando uma estrutura que difere bastante daquela segundo a qual que se constroem os contos de magia ocidentais, pode-se dizer que parte dos mukashi banashi que integra esta subcategoria de contos reflete o modo de pensar característico do japonês da antiguidade. Através da análise das narrativas que integram o corpus desta pesquisa, será feita uma tentativa de se aplicar as teorias ocidentais aos contos em questão, em especial as de E. M. Meletínski que, num âmbito maior que o de seu predecessor, V. I. Propp, estendeu seus estudos sobre o conto de magia ao mito; a partir disso, deverá ser proposta uma classificação para os contos selecionados. Considerando-se a origem antiga destes mukashi banashi, pretende-se também realizar a análise da esfera de ação das protagonistas femininas, no intuito de se verificar as projeções míticas nos contos, que revelam a vida dos povos antigos, bem como a descoberta da matriz imagética desses contos japoneses e discussão da mensagem subjacente às narrativas. / This work intends to analyse the mukashi banashi (ancient tales) of the Japanese literature about the marriages between different beings, focusing the images of the animal wife and the celestial wife that appear in these narratives. Having a structure which differs from the structure of the western fairy tales, we can say that part of the mukashi banashi from this subcategory of tales reflects the way of thinking of the ancient Japanese people. Through the analysis of the narratives of this research corpus, we will try to apply some western theories about the fairy tale in these Japanese tales, specially the theories of E. M. Meletinsky who, in a wider point of view than his predecessor, V. I. Propp, expanded his studies about the fairy tale to the myth; we also intend to present a classification for the selected tales. Considering the ancient origin of these mukashi banashi, we intend to do an analysis of the action of the female protagonists, in order to verify the mythical projections in the tales, which reveals the life of ancient people, as well as to discover the main images of these mukashi banashi and discuss about the message which lies under these narratives.
27

Os mukashi banashi da literatura japonesa: uma análise do feminino e do casamento entre seres diferentes no contexto dos contos do japão antigo / The mukashi banashi of the Japanese literature: an analysis about the female and the marriages between different beings in the context of ancient Japan

Marcia Hitomi Namekata 14 March 2011 (has links)
O presente trabalho propõe-se a uma análise dos mukashi banashi (contos antigos) da literatura japonesa sobre os casamentos entre seres diferentes, com enfoque nas imagens da esposa animal e da esposa celestial que surgem nestas narrativas. Apresentando uma estrutura que difere bastante daquela segundo a qual que se constroem os contos de magia ocidentais, pode-se dizer que parte dos mukashi banashi que integra esta subcategoria de contos reflete o modo de pensar característico do japonês da antiguidade. Através da análise das narrativas que integram o corpus desta pesquisa, será feita uma tentativa de se aplicar as teorias ocidentais aos contos em questão, em especial as de E. M. Meletínski que, num âmbito maior que o de seu predecessor, V. I. Propp, estendeu seus estudos sobre o conto de magia ao mito; a partir disso, deverá ser proposta uma classificação para os contos selecionados. Considerando-se a origem antiga destes mukashi banashi, pretende-se também realizar a análise da esfera de ação das protagonistas femininas, no intuito de se verificar as projeções míticas nos contos, que revelam a vida dos povos antigos, bem como a descoberta da matriz imagética desses contos japoneses e discussão da mensagem subjacente às narrativas. / This work intends to analyse the mukashi banashi (ancient tales) of the Japanese literature about the marriages between different beings, focusing the images of the animal wife and the celestial wife that appear in these narratives. Having a structure which differs from the structure of the western fairy tales, we can say that part of the mukashi banashi from this subcategory of tales reflects the way of thinking of the ancient Japanese people. Through the analysis of the narratives of this research corpus, we will try to apply some western theories about the fairy tale in these Japanese tales, specially the theories of E. M. Meletinsky who, in a wider point of view than his predecessor, V. I. Propp, expanded his studies about the fairy tale to the myth; we also intend to present a classification for the selected tales. Considering the ancient origin of these mukashi banashi, we intend to do an analysis of the action of the female protagonists, in order to verify the mythical projections in the tales, which reveals the life of ancient people, as well as to discover the main images of these mukashi banashi and discuss about the message which lies under these narratives.
28

Dinâmica e origem de asteroides de alta inclinação /

Machuca, James Freddy Luis. January 2011 (has links)
Orientador: Valerio Carruba / Banca: Ernesto Vieira Neto / Banca: Fernando Virgilio Roig / Resumo: Asteroides de alta inclinação são objetos com sin(i) > 0.3. Entre estes asteroides podemos distinguir objetos com inclinação menor que o centro da ressonância secular ν6 = g−g6 e objetos com inclinação superior. Os atuais mecanismos de mobilidade dinâmica não podem aumentar facilmente inclinações menores do que do centro da ressonância ν6. A presença de objetos de alta inclinação pode, portanto, estar relacionada com fases iniciais do Sistema Solar. Neste trabalho obtemos elementos próprios sintéticos para a região da família de Pallas, encontramos grupos dinâmicos e determinamos a significância estatística destes grupos. Estudamos a evolução dinâmica devida a perturbações planetárias e efeitos não gravitacionais das famílias e clumps identificados na região das famílias de Pallas e Hansa (Carruba 2010b). Estudamos regiões dinamicamente estáveis, que são surpreendentemente caracterizadas por um número muito baixo de asteroides, contrariamente a objetos de baixa inclinação que ocupam tudo a região dinamicamente viável. Identificamos duas areas caracterizadas por tempos de permanência de 100 milhões de anos o mais, quando a força Yarkovsky é considerada, com baixa densidade de asteroides. Obtemos elementos próprios sintéticos para 10865 objetos na região da família de Euphrosyne e identificamos famílias e clumps no domínio dos elementos próprios e frequências. Com relação a outros trabalhos sobre identificação de famílias na área, aqui nos investigamos o efeito que a rede local de ressonâncias seculares tem sobre a evolução dinâmica das famílias e clumps. Identificamos por primeira vez, novas populações de objetos em estados ressoantes de libração anti-alinhada de ν6 e anti-alinhada e alinhada de ν5. / Abstract: Highly inclined asteroids are objects with sin(i) > 0.3. Among these asteroids we can distinguish between objects with inclinations lower than the center of the secular resonance ν6 = g−g6 and objects with higher inclinations. The current mechanisms of dynamical mobility cannot easily increase inclinations to value higher than that of the center of the ν6 resonance. The presence of high inclination objects may therefore be related to early stages of the Solar System. In this work we obtained synthetic proper elements for the region of the Pallas family, we found dynamical groups and determined the statistical significance of these groups. We studied the dynamic the dynamical evolution caused by planetary perturbations and non-gravitational effects of the families and clumps identified in the region of the Pallas and Hansa families (Carruba 2010b). We studied regions dynamically stable that on surprisingly characterized by a low number of asteroids, contrary to objects of lower inclinations that tend to occupy all the viable stable regions. We identified two areas characterized by permanence time of 100 Myr or more when the Yarkovsky force is considered, but with a small number density of bodies. We obtained synthetic proper elements for 10865 objects in the region of the Euphrosyne families and identify families and clumps in the domain of proper elements and frequencies. With respect to other work on family identification in the area, here we investigated the role that the local web of secular resonances has had on the dynamical evolution of families and clumps. We identify for the first time, new populations of objects inν6 anti-aligned libration and ν5 anti-aligned and aligned resonant states. / Mestre
29

Stellar Streams, Dwarf Galaxy Pairs, and the Halos in which they Reside

Pearson, Sarah January 2018 (has links)
In this Dissertation we explore how the nature of tidal interactions tear gravitationally bound systems apart into distinct morphological and kinematic structures. We use the properties of these structures, persisting for billions of years, to investigate the potential of the Milky Way Galaxy and to disentangle the baryonic evolution of gas in dwarf galaxy interactions. We approach these problems through a combination of observations, and simulations, as well as comparisons between the two. In particular, we use the properties of the thin, curved stellar stream emerging from the old, Milky Way globular cluster, Palomar 5 (Pal 5) to show that its mere existence can rule out a moderately triaxial potential model of our Galaxy. Pal 5-like streams on appropriate orbits diffuse much further in space from the orbital path (dubbed “stream-fanning”) in this triaxial potential than in the oblate case. We further show that torques from the Milky Way’s Galactic bar, can create ever-widening gaps in stellar streams. The fact that the bar can create such under densities, demonstrates that we should be careful when interpreting gaps in stellar streams as indirect evidence of the existence of dark matter subhalos in our Galaxy. We carry out a systematic study of resolved neutral hydrogen (HI) synthesis maps of 10 interacting dwarf galaxy pairs. The pairs are located in a range of environments and captured at various interaction stages. We find that the neutral gas is extended in the interacting pairs when compared to non-paired analogs, indicating that gas is tidally pre- processed. Additionally, we find that dwarf-dwarf interactions enable the “parking” of gas at large distances to serve as a continual gas supply channel to the dwarfs until accretion by a more massive host. We model a specific dwarf pair in our sample, NGC 4490/85, which is an isolated analog of the Magellanic Clouds and is surrounded by a ∼50 kpc extended HI envelope. We use hybrid N-body and test-particle simulations along with a visualization interface to simultaneously reproduce the observed present-day morphology and kinematics. Our numerical results con- firm that encounters between two dwarf galaxies can “park” baryons at very large distances, without the aid of environmental effects. The extended tidal features will continue to evolve over several billion years which will affect the efficiency of gas stripping if such dwarf pairs are accreted by a massive host. In contrast, in isolated environments dwarf-dwarf interactions can create a long-lived supply mode of gas to the merger remnant potentially explaining the population of dwarfs in the field with large gas envelopes, but limited star formation. All of these topics share the common theme of utilizing morphological and kinematic structures left behind from ongoing gravitational interactions on various scales.
30

The role of environment in infrared surveys : from supernovae to clusters

Thomson, Matthew G. January 2011 (has links)
In this thesis we investigate several aspects of galaxy evolution. We begin by giving a brief introduction to the subject of galaxy evolution in the context of the Universe as we know it today. We discuss infrared surveys of galaxies as a tool for studying galaxy evolution. Initially, we are interested in the large scale environment of galaxies and identify clusters of galaxies at high redshift. We compare the mass and star-formation properties of galaxies in the cluster and field environments. To take this further we look to the AKARI all- sky survey and assess the potential of this survey for future studies. We calculate the completeness and reliability of the survey. Such wide surveys also allow for the possibility of studying rare and extreme phenomena. Such phenomena can push theories of galaxy evolution to their extremes and constrain these theories. We present the discovery of four such objects in the SWIRE survey. Finally, since environment plays a large role in the evolution of galaxies we extend this investigation to smaller scales. We investigate the progenitors of Type Ia Supernovae from a study of their host galaxies, which have implications for their use as standardisable candles.

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