Made available in DSpace on 2014-06-11T19:31:24Z (GMT). No. of bitstreams: 0 Previous issue date: 2010-12-20Bitstream added on 2014-06-13T20:41:38Z : No. of bitstreams: 1 sanoja_a_dr_ift.pdf: 582908 bytes, checksum: 608a543719b2da86f0b937d5c00bfbba (MD5) / Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES) / Fazemos uma revisão do modelo cosmológico padrão, apresentando suas bases observacionais e mostrando os aspectos conceituais mais relevantes. Depois realizamos uma revisão da teoria de in ação, indicando as motivações conceituais que levaram à formulação da teoria, o mecanismo que faz possível a in ação cósmica e como esse processo resolve os problemas clássicos da cosmologia padrão. Após mostrar que a in ação é um mecanismo bem-sucedido para explicar a origem das perturbações de densidade primordiais, concentramo-nos em descrever a evolução das perturbações de densidade cosmológica, tanto na sua fase linear como não-linear. Além disso, mostramos como o campo de perturbações de densidade linear permite predizer estatisticamente a abundância e a distribuição das estruturas cósmicas. Posteriormente, consideramos a expansão acelerada do universo e discutimos os candidatos que têm sido propostos para tentar explicar a origem dessa aceleração, especialmente o candidato da energia escura, no qual nos detemos para revisar os modelos básicos propostos com respeito à sua natureza. Adicionalmente, mostramos como sua presença afeta a evolução das perturbações de densidade. Finalmente, baseandonos no modelo de Lemaître-Tolman-Bondi, fazemos uma generalização do modelo do colapso esférico para estudar a evolução não-linear de perturbações de densidade inhomogêneas, tanto em um universo Einstein-de Sitter como em um universo CDM / We present a review of the standard cosmological model, showing both its observational basis as well as the most revelant conceptual aspects. Subsequently, we give an overview of the in ation theory , pointing out the conceptual motivations that led to its formulation, the mechanism that allow the cosmic in ation and how that process resolves the classical problems of the standard cosmology. After showing that the in ation theory provides a successful mechanism to explain the origin of the primordial density perturbations, we focus on describing the evolution of the cosmological density perturbations, both in linear and nonlinear phase. On the other hand, we show how the linear density perturbation eld allows to predict statistically the abundance and distribution of the cosmic structures. Next, we consider the accelerated expansion of the universe and mention the candidates that have seen proposed to try to explain the origin of the acceleration; especially the dark energy candidate, in which we pause to examine the basic models proposed about its nature. Further, we expose how its presence a ects the evolution of the density perturbations. Finally, based on the Lemaître-Tolman-Bondi, we make a generalization of the spherical collapse model to study the evolution of inhomogeneous nonlinear density perturbations, both in an Einstein-de Sitter as CDM universe

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published_or_final_version / abstract / Mechanical Engineering / Master / Master of Philosophy

Errata pasted onto front end-paper. Bibliography: leaves 101-104. This thesis employs integral equation methods, or boundary element methods (BEMs), for the solution of three kinds of engineering problems associated with inhomogeneous materials or media: a class of elliptical boundary value problems (BVPs), the boundary value problem of static linear elasticity, and the calculation of the solution of the initial-boundary value problem of non-linear heat conduction for anisotropic media.

In this thesis, we use nonequilibrium molecular dynamics (NEMD) methods to investigate the structural and dynamic properties of highly confined atomic and polymeric fluids undergoing planar Poiseuille flow. We derive 'method of planes' expressions for pressure tensor and heat flux vector for confined inhomogeneous atomic fluids under the influence of three-body forces. Our derivation is validated against NEMD simulations of a confined atomic fluid acted upon by a two-body Barker-Fisher-Watts force coupled with the Axilrod-Teller three-body force. Our method of planes calculations are in excellent agreement with the equivalent mesoscopic route of integrating the momentum and energy continuity equations directly from the simulation data. Our calculations reveal that three-body forces have an important consequence for the isotropic pressure, but have negligible in�uence on the shear stress and heat flux vector for a confined simple fluid. We use the non-local linear hydrodynamic constitutive model, proposed by Evans and Morriss [1] for computing a viscosity kernel, a function of compact support, for inhomogeneous nonequilibrium fluids. Our results show that the viscosity kernel, �(y), has a peak at y = 0, and gets smaller and decays to zero as y increases. Physically, it means that the strain rate at the location where we want to know the stress contributes most to the stress, and the contribution of the strain rate becomes less significant as the relative distance y increases. We demonstrate that there is a limitation in the model when it is applied to our confined fluids due to the effect of domain restriction on inverse convolution. We study the nanorheology of simple polymeric fluids. Our NEMD simulation results show that sufficiently far from the walls, the radius of gyration for molecules under shear in the middle of the channel follows the power law, Rg / N�, where N is the number of bonds and the exponent has a value � = 0:60�0:04, which is larger than the melt value of 0:5 for a homogeneous equilibrium �uid. Under the conditions simulated, we find that viscous forces dominate the flow, resulting in the onset of plug-like flow velocity pro�les with some wall slippage. An examination of the streaming angular velocity displays a strong correlation with the radius of gyration, being maximum in those regions where Rg is minimum and vice-versa. The angular velocity is shown to be proportional to half the strain rate su�ciently far from the walls, consistent with the behaviour for homogeneous fluids in the linear regime. Finally, we make some concluding remarks and suggestions for future work in the final chapter.

Errata pasted onto front end-paper. / Bibliography: leaves 101-104. / xi, 174 leaves : ill. ; 30 cm. / Title page, contents and abstract only. The complete thesis in print form is available from the University Library. / This thesis employs integral equation methods, or boundary element methods (BEMs), for the solution of three kinds of engineering problems associated with inhomogeneous materials or media: a class of elliptical boundary value problems (BVPs), the boundary value problem of static linear elasticity, and the calculation of the solution of the initial-boundary value problem of non-linear heat conduction for anisotropic media. / Thesis (Ph.D.)--University of Adelaide, Dept. of Applied Mathematics, 2002

Thesis (Ph.D) -- McMaster University, 1997. / Includes bibliographical references (p. 157-172). Also available via World Wide Web.

Thesis (M. Phil.)--University of Hong Kong, 2008. / Also available in print.

Thesis (Ph.D.)-- University of Adelaide, Dept. of Applied Mathematics, 2002. / Errata pasted onto front end-paper. Bibliography: leaves 101-104.

Ultrasonic wave field is modeled inside non-planar and inhomogeneous structures using a newly developed mesh-free semi-analytical technique called Distributed Point Source Method (DPSM). Wave field inside a corrugated plate which is a non-planar structure is modeled using DPSM when the structure is excited by a bounded acoustic beam generated by a finite-size transducer. The ultrasonic field is computed both inside the plate and in the surrounding fluid medium. It is observed that the reflected beam strength is weaker for the corrugated plate in comparison to that of the flat plate, as expected. Whereas the backward scattering is found to be stronger for the corrugated plate. DPSM generated results in the surrounding fluid medium are compared with the experimental results.Ultrasonic wave field is also modeled inside inhomogeneous structures. Two types of inhomogeneity are considered - a circular hole and a damaged layered half-space. Elastic wave scattering inside a half-space containing a circular hole is first modeled using DPSM when the structure is excited with a bounded acoustic beam. Then the ultrasonic wave field is computed in presence and absence of a defect in a layered half-space. For the layered problem geometry it is shown how the layer material influences the amount of energy that propagates through the layer and that penetrates into the solid half-space when the solid structure is struck by a bounded acoustic beam. It is also shown how the presence of a crack and the material properties of the layer material affect the ultrasonic fields inside the solid and fluid media.After solving the above problems in the frequency domain the DPSM technique is extended to produce the time domain results by the Fast Fourier Transform technique. Time histories are obtained for a bounded beam striking an elastic half-space. Numerical results are generated for normal and inclined incidences, for defect-free and cracked half-spaces. A number of useful information that is hidden in the steady state response can be obtained from the transient results.