Orientador: Kyoko Furuya / Dissertação (mestrado) - Universidade Estadual de Campinas, Instituto de Fisica Gleb Wataghin / Made available in DSpace on 2018-08-12T21:50:29Z (GMT). No. of bitstreams: 1 Netto_DomeniqueVelloso_M.pdf: 11311141 bytes, checksum: 3ff0f796112fbf62feb5f0de7b56c879 (MD5) Previous issue date: 2009 / Resumo: Neste trabalho realizamos para o modelo de Jahn-Teller E Ä b, que descreve a interação de um qubit com um modo de um oscilador, um estudo do emaranhamento e o relacionamos com a bifurcação do ponto fixo do análogo clássico do modelo. Estudamos também a incidência de caos e sua variação em função dos parâmetros do sistema. Confirmamos os indícios de que no limite massivo do oscilador (m ® ¥ ) o emaranhamento do estado fundamental do sistema como função do seu parâmetro crítico apresenta uma mudançã não suave no seu comportamento quando esse parâmetro atinge o valor crítico. Confirmamos também que para esse mesmo valor crítico o análogo clássico apresenta uma bifurcação de alguns de seus pontos fixos. Sobre a possível influência do caos no emaranhamento, pudemos observar que o aparecimento de região caótica substancial no modelo clássico ocorre quando o parâmetro crítico está nas vizinhanças do valor crítico. A análise da função de Husimi no estado fundamental nos permitiu estabelecer dois aspectos: (i) uma conexão entre a localização do máximo desta função e a localização dos pontos fixos no espaço de fase, comprovando a ocorrência da bifurcaçãco no estado quãntico nesta representação; (ii) verificar que de fato há uma aproximação do limite clássico do oscilador quando aumentamos o parâmetro do modelo associado à quebra de degenerescência das energias do sistema. / Abstract: In this work we realize a study of entanglement for the Jahn-Teller E Ä b model, wich describes the interaction of a qubit with an oscillator mode, and relate it with the bifurcation of the fixed point of the classical analogue of the model. We also study qualitatively the ocurrence of chaos and its variation as a function of the parameters of the system. We have confirmed the signs that in the massive limit of the oscillator ( m ® ¥ ) the entanglement of the fundamental state of the system presents a non-smooth change (as a function of its critical parameter) in its behavior as this parameter attains the critical value. We also confirm that at this same critical value the classical analogue presents a bifurcation of some of its fixed points. Concerning the possible influence of chaos on the entanglement, we have been able to see the appearance of a substantial chaotic region in the classical phase space when the critical parameter is in the vici-nity of its critical value. The analysis of the Husimi function in the fundamental state allowed us to establish two things: (i) a connection between the localization of the maximum of this function and the localization of the fixed points in the phase space, confirming the occurrence of the bifurcation in the quantum state in this representation; (ii) verification that in fact the classical limit of the oscillator is approached when we increase the energy degeneracy breaking parameter of the system. / Mestrado / Física / Mestre em Física

The anatomy of bifurcations in trees requires further scientific investigation as the current anatomical model for them is logically flawed. The provision of a better model will assist in scientific studies of woody plants, the risk assessment of junctions in mature trees and provide bio-inspiration for Y-shaped joints in composite materials. In this study, the xylem formed in the central axis of a hazel (Corylus avellana L.) bifurcation is shown to provide a disproportionately greater amount of its tensile strength. CT scanning identified that this centrally-placed xylem was 28.1% denser, with 63% less vessels formed in this tissue, such vessels being 50.5% of the diameter and 32.5% of the length of those formed in adjacent stem tissues. The wood grain pattern at the bifurcation apices were 22 times more tortuous, forming interlocking patterns that acted to resist tensile forces by requiring the extraction or breaking of wood fibres along their length (the axial tensile strength of wood). Subsequent tests confirmed that this conferred more than 100% additional tensile strength to these specialised xylem tissues. These findings provided the basis of a novel anatomical model for bifurcations in woody plants. Further to this, the effects of several factors upon junction strength and biomechanical behaviour were assessed in bifurcations of hazel, identifying the weakening effect of bark inclusions and three types of artificial modification as well as differences in wind-induced movement between bifurcation types. This study concludes that further investigations of bifurcations in a wider range of woody plants and observations of the developmental stages of the interlocking wood grain patterns found at bifurcations would usefully add to existing knowledge.

The bony fin rays of the zebrafish caudal fin are a convenient system for studying bone morphogenesis and patterning. Joints and bifurcations in fin rays follow predictable spatial patterns, though the mechanisms underlying these patterns are not well understood. We developed simulation models to explore ray pattern formation mechanisms in growing fins. In all models, the fin ray growth rates are based on quantitative experimental data. The different models simulate ray joint formation and bifurcation formation using different hypothetical mechanisms. In the most plausible model, ray joint and bifurcation formation result from the accumulation of two substances, arbitrarily named J and B. Model parameters were optimized to find the best fit between model output and quantitative experimental data on fin ray patterns. The model will be tested in the future by evaluating how well it can predict fin ray patterns in different fin shapes, mutant zebrafish fins, and other fish species.

Dissipative spots are found in physical experiments of many branches of natural science. In this thesis we use three-component reaction-diffusion systems on two-dimensional domains in order to generate these patterns. Using a dynamical system approach we proceed with a Fourier analysis on a linearized reaction-diffusion system in order to provide the bifurcation conditions for a given homogeneous state. We validate our results and establish it's limitations through numerical experiments. We report very interesting behavior during these simulations, notably hysteresis and multi-stability. We will then turn our attention to the relatively unexplored phenomenon of rotating spots. Based on previous work done for spiral waves, we investigate the effect of translational symmetry-breaking on a rotating spot mainly through careful numerical analysis.

The objective of this dissertation is to investigate several dynamical approaches aiming to improve the sensitivity and performance of microelectromechanical systems (MEMS) resonant sensors. Resonant sensors rely on tracking shifts in the dynamic features of microstructures during sensing, such as their resonance frequency. We aim here to demonstrate analytically and experimentally several new concepts aiming to sharpen their response, enhance the signal to noise ratio, and demonstrate smart functionalities combined into a single resonator. The dissertation starts with enhancing the excitations of the higher order modes of vibrations of clamped-clamped microbeam resonators. The concept is based on using partial electrodes with shapes that induce strong excitation of the mode of interest. Using a half electrode, the second mode is excited with a high amplitude of vibration. Also, using a two-third electrode configuration is shown to amplify the third mode resonance amplitude compared with the full electrode under the same electrical loading conditions. Then, we demonstrate the effectiveness of higher order mode excitation and metal organic frameworks (MOFs) functionalization for improving the sensitivity and selectivity of resonant gas sensors. Also, using a single mode only, we show the possibility of realizing a smart switch triggered upon exceeding a threshold mass when operating the resonator near the dynamic pull-in instability. The second part of the dissertation deals with the dynamics of the microbeam under a two-source harmonic excitation. We experimentally demonstrate resonances of an additive and subtractive type. It is shown that by properly tuning the frequency and amplitude of the excitation force, the frequency bandwidth of the resonator is controlled. Finally, we employ the multimode excitation of a single resonator to demonstrate smart functionalities. By monitoring the frequency shifts of two modes, we experimentally demonstrate the effectiveness of this technique to measure the environmental temperature and gas concentration. Also, we present a hybrid sensor and switch device, which is capable of accurately measuring gas concentration and perform switching when the concentration exceeds a specific (safe) threshold. In contrast to the single mode operation, we show that monitoring the third mode enhances sensitivity, improves accuracy, and lowers the sensor sensitivity to noise.

After the pilot phase of a simulation study, if the model contains many factors, then direct experimentation may need too much computer processing time, therefore the purpose of screening simulation experiments is to eliminate negligible or unimportant factors of a simulation model in order to concentrate the efforts upon a short list of important factors. For this matter the Sequential bifurcation procedure developed by Bettonvil and Kleijnen [3] is an efficient and effective screening method which can be used. In this study, the Sequential bifurcation screening method is used to determine the important factors of a simulation based decision support model designed by The Swedish Defense Research Agency (FOI) meant for testing operational plans. By using this simulation model, a decision maker is able to test a number of feasible plans against possible courses of events. The sequential bifurcation procedure was applied and sorted the most important factors involved in this simulation model based on their relative importance.

Smooth muscle contraction regulates the size of the blood vessel lumen which directly affects the mechanical response of the vessel. Folding in arteries has been observed in arteries during excessive contraction, known as a coronary artery spasm. The interplay of muscle contraction, geometry, and material responses and their effects on stability can be understood through mathematical models. Here, we consider a three-layer cross-sectional model of a coronary artery with anisotropic properties and intimal thickening, and perform a linear stability analysis to investigate the circumferential folding patterns that emerge due to muscle contraction. Our model shows that a critical level of contractile activity yields a uniform strain distribution across the arterial wall. When the muscle is contracted above this critical level, the tissue behaves isotropically and it is more prone to circumferential instability. This theoretical framework could serve as a valuable tool to understand the relationship between arterial lumen morphology and wall contraction in health and disease.

Many existing dams in the United States were built without hydroelectric generating accessories and are now being considered for hydroelectric installations. A bifurcation is regularly used as the method for diverting the water to the new generators. With a bifurcation installed as part of the new piping system, cavitation could become a problem. Although widely used, there are no published data on cavitation characteristics or head loss coefficients for these bifurcations. Dimensional analysis has not been adequate for experimentally quantifying the cavitation potential and full scale testing is prohibitive for many large geometries. Therefore this study utilized Computational Fluid Dynamics (CFD) in conjunction with a physical model to predict conditions that would cause the onset of cavitation. Head loss coefficients were also calculated from the CFD simulations and physical model. Based on these results, the authors have produced recommended operating conditions that will allow bifurcations to operate within safe limits of cavitation. This study was not exhaustive but presents data that has previously been unavailable and will assist designers and operators to better understand the performance of such bifurcations.

京都大学 / 0048 / 新制・課程博士 / 博士(理学) / 甲第18040号 / 理博第3918号 / 新制||理||1566(附属図書館) / 30898 / 京都大学大学院理学研究科数学・数理解析専攻 / (主査)教授 國府 寛司, 教授 加藤 毅, 准教授 浅岡 正幸 / 学位規則第4条第1項該当 / Doctor of Science / Kyoto University / DFAM

京都大学 / 0048 / 新制・課程博士 / 博士(理学) / 甲第18053号 / 理博第3931号 / 新制||理||1567(附属図書館) / 30911 / 京都大学大学院理学研究科物理学・宇宙物理学専攻 / (主査)講師 市川 正敏, 教授 山本 潤, 教授 佐々 真一 / 学位規則第4条第1項該当 / Doctor of Science / Kyoto University / DFAM