Thesis (Ph. D.)--University of Missouri-Columbia, 1997. / Typescript. Vita. Includes bibliographical references (leaves 223-229). Also available on the Internet.

Thesis (Ph. D.)--University of Missouri-Columbia, 1997. / Typescript. Vita. Includes bibliographical references (leaves 223-229). Also available on the Internet.

Orientador: Paulo Roberto Gardel Kurka / Dissertação (mestrado) - Universidade Estadual de Campinas, Faculdade de Engenharia Mecanica / Made available in DSpace on 2018-08-14T09:04:50Z (GMT). No. of bitstreams: 1 Izuka_JaimeHideo_M.pdf: 3067570 bytes, checksum: 82a84bf138484b1bf94c984320ee5486 (MD5) Previous issue date: 2009 / Resumo: O objetivo do presente trabalho é a modelagem dinâmica e a simulação das cargas e dos deslocamentos correntes nos mancais de um compressor alternativo. O modelo de mancal, integrado à cinética do conjunto, permite avaliar de forma precisa a influência dos pequenos movimentos dos suportes hidrodinâmicos no comportamento global do compressor. Soluções numéricas do problema de lubrificação hidrodinâmica são pesquisadas com o uso dos métodos de diferenças finitas, volumes finitos e elementos finitos. Resultados das soluções analíticas de mancal curto e longo são comparados com as soluções dos modelos numéricos de mancal. Escolhe-se assim a implementação e uso do modelo de elementos finitos para a simulação dos mancais hidrodinâmicos utilizados no compressor. O método de Newton-Euler é utilizado para a obtenção das equações diferenciais que representam o modelo de movimento do sistema dinâmico do conjunto eixo/biela/pistão. A implementação da solução numérica de mancal hidrodinâmico integrada à cinética do sistema exige um grande esforço computacional, demandando a utilização de técnicas de processamento paralelo. Assim, apresenta-se e compara-se com a literatura, os resultados de simulação de cargas e órbitas de mancais, na operação de um compressor alternativo de refrigeração. / Abstract: The present works simulates the loads and displacements of the bearings of a reciprocating compressor. The bearing model, which is integrated to the kinetics of the system, allows a precise evaluation of the influence of small movements of the hydrodynamic supports into the global behavior of the compressor Numerical solutions of the problem of hydrodynamic lubrication are studied using the methods of finite differences, finite volumes and finite elements. Results of analytical solutions for short and long bearing are compared with the numerical models of bearings. The finite element model of hydrodynamic bearings is used in the simulation of the compressor. The Newton-Euler method is used to obtain the differential equations representing the model of motion of the crankshaft/conrod/piston dynamic system. Implementation of the integrated numerical solution for the hydrodynamic bearing and the kinetics of the system requires a large computational effort, demanding the use of parallel processing techniques. The results of simulation of orbits and bearing loads in the operation of an alternative refrigeration compressor is thus presented and compared with the literature. / Mestrado / Mecanica dos Sólidos e Projeto Mecanico / Mestre em Engenharia Mecânica

The heterogeneous dynamics exhibited by supercooled liquids near the glass transition temperature (𝑇_𝑔) has been a topic of much research over the past several decades. In particular, the advent of single molecule (𝖲𝖬) methods has permitted great insight into the extent of both spatial and temporal heterogeneities in these systems, information which is either difficult or impossible to access via ensemble approaches. Despite this, the related phenomenon of rotational-translation decoupling, whereby the translational motion observed in supercooled systems is enhanced relative to Debye-Stokes-Einstein predictions, is difficult to study with 𝖲𝖬 approaches. This is due to the very low localization uncertainty required to accurately report the extremely slow translational motion in supercooled systems near 𝑇_𝑔. In this thesis, a new approach for quantifying rotational dynamics in supercooled liquids is introduced which leverages fluorescence intensity fluctuations due to out-of-plane fluorophore rotations. Unlike linear dichroism (LD) measurements, the most common experiment used to access rotational dynamics, this technique does not require a polarizing optical element, thus improving localization precision in the acquired images. This intensity fluctuation-based approach is shown to report comparable rotational correlation timescales (𝝉_𝘤) and information on dynamic heterogeneity to that typically extracted via LD measurements. On a probe-by-probe basis, rotational correlation times obtained from simultaneous measurement of LD (𝝉_𝘤,𝘓𝘋) and intensity fluctuations (𝝉_𝘤,𝘐 ) are found to be only moderately well-correlated. We postulate that this is a consequence of dynamic heterogeneity due to temporal dynamic exchange, the process in which a probe (and its surroundings) undergoes sudden changes in dynamics. This hypothesis is explored through simulations, which reveal that the Pearson R correlation coefficients associated comparing log 𝝉_𝘤,𝘐 and log 𝝉_𝘤,𝘓𝘋 increases as the time between dynamic exchange increases. The information obtained from such simulations is then used to estimate the exchange timescales from experimental data. When examined in concert with experimentally measured degrees of relaxation non-exponentiality - generally considered a metric of heterogeneity in an interrogated supercooled liquid – this permits access to previously inaccessible information regarding the breadth of the distribution of underlying timescales experienced by these supercooled systems. In addition to this work focused on rotational dynamics, we also aim to further clarify information contained in 𝖲𝖬 experiments characterizing translational dynamics, towards the goal of full understanding of rotational-translational decoupling. Here, two widefield fluorescence imaging setups are optimized to minimize localization uncertainty, and differences in how localization uncertainties manifest in perceived translational motion near 𝑇_𝑔 are examined. The setup with greater localization uncertainty reports faster translational dynamics compared to the other optical setup, suggesting significant influence of the localization noise floor on perceived dynamics and highlighting the importance of maximizing the signal to noise ratio of 𝖲𝖬 experiments aiming to study the underlying cause of rotational-translational decoupling.

Thesis (Ph.D.)--McMaster University (Canada), 1995. / Source: Dissertation Abstracts International, Volume: 57-03, Section: B, page: 2118. Adviser: G. F. Round.

Orientadores: Jose Manoel Balthazar, Paulo R. G. Kurka / Tese (doutorado) - Universidade Estadual de Campinas, Faculdade de Engenharia Mecanica / Made available in DSpace on 2018-08-09T22:56:56Z (GMT). No. of bitstreams: 1 Pereira_DaniloCarlos_D.pdf: 3711639 bytes, checksum: 2413d33f619760c04be8cc5320c0a84b (MD5) Previous issue date: 2007 / Resumo: Neste trabalho analisou-se a dinâmica não linear de uma aeronave em vôo longitudinal. Efetuou-se a análise do comportamento bifurcacional da aeronave F-8 ¿Cruzader¿. Na análise bifurcacional foi estudado o comportamento topológico desta aeronave tomando-se dois parâmetros de controle: a deflexão do profundor e a alteração da massa da referida aeronave. Ante a pesquisa desenvolvida, foi proposto um projeto de controle linear ótimo com o objetivo de estabilizar as oscilações do ângulo de ataque, considerando-se regiões criticas do comportamento não linear da aeronave. Adicionalmente, incluiu-se no modelo matemático a variação da velocidade longitudinal da aeronave, visto tratar-se de simulações numéricas em um túnel de vento virtual / Abstract: In this work it was analyzed the non linear dynamic of an aircraft taken onto longitudinal flight. It was done analysis of the bifurcacional behavior of the aircraft F-8 ¿Cruzader¿. In the bifurcational analysis was studied the topological behavior of this aircraft taken into account two parameters of control: the deflection of the elevator and the alteration of the mass of the related aircraft. In the face of the developed research, an optimum linear control project was proposed with the objective of stabilizing the oscillations of the angle-of-attack. Additionally, the variation of the longitudinal speed of the aircraft was included in the mathematic model in order to simulate the oscillatory movement of the aircraft considered, in a tunnel of virtual wind / Doutorado / Materiais e Processos de Fabricação / Mestre em Engenharia Mecânica