Orientador: André Luiz Seixlack / Banca: Marco Antonio Soares de Paiva / Banca: Sérgio Said Mansur / Resumo: Neste trabalho, apresenta-se um modelo numérico distribuído para a simulação dos escoamentos do fluido refrigerante e do ar, no regime transiente, em evaporadores de expansão seca de serpentina com tubos aletados, comuns em sistemas de refrigeração e ar condicionado. No modelo proposto, o escoamento do fluido refrigerante no interior dos tubos é dividido em duas regiões: uma de escoamento bifásico líquido-vapor e uma de escoamento de vapor superaquecido. Considera-se a queda de pressão no interior dos tubos e a condensação do vapor d'água do ar que escoa em fluxo cruzado na parte externa dos tubos. O escoamento bifásico do fluido refrigerante é simplificado como um escoamento unidimensional, considerando o deslizamento entre as fases de líquido e de vapor. Para o escoamento do refrigerante, resolvem-se as equações de conservação da massa, da quantidade de movimento e de conservação da energia. Para o escoamento de ar, são resolvidas as equações de conservação da energia e de conservação da massa (umidade). Resolve-se, também, a equação da conservação da energia para a parede do tubo, para se obter a sua temperatura. O método de volumes finitos é utilizado na discretização das equações governantes e o método de Newton-Raphson é utilizado para a solução do sistema de equações resultante. Inicialmente, condições de regime permanente são assumidas e, posteriormente, para avaliar o comportamento transiente do evaporador, uma variação em degrau da vazão em massa de refrigerante é imposta em sua entrada. O modelo permite o cálculo da vazão de refrigerante, conhecidas as condições de operação e os parâmetros geométricos, usando-se o processo de estimativa de parâmetros, com o método de minimização de Levenberg-Marquardt. Além disso, o modelo permite a análise de algumas configurações de... (Resumo completo, clicar acesso eletrônico abaixo). / Abstract: This work presents a numerical model to simulate the unsteady refrigerant fluid flow and air flow in dry-expansion finned-tube coil evaporators, the kind widely used in air conditioning and refrigeration systems. The model considers the refrigerant flow inside the tubes divided in a region of two-phase flow and a single-phase region, where the refrigerant is in the superheated state. The refrigerant pressure drop and the moisture condensation on the air flow crossing the outside of the tubes are also taking into account. The refrigerant two-phase flow is taken as one-dimensional and the slip between the liquid and vapor phases is considered. For the refrigerant flow, mass, momentum and energy conservation equations are solved in order to evaluate the specific mass, velocity, and temperature of the refrigerant fluid, respectively. For the air flow, energy and mass (humidity) conservation equations are solved, to obtain, respectively, the temperature and absolute humidity of the air crossing the evaporator. Also, the solution of energy conservation equation for the tube wall is used to determine the wall temperature distribution. Finite Volume Method is used all over to discretize the governing equations and a Newton-Raphson Scheme is utilized for the solution of the resulting system of equations. To analyze the evaporator unsteady behavior, the steady conditions are obtained initially and later a step change in the mass flow rate is imposed at the tube inlet. Obtained results such as superheating degree along the coil and air temperature at the outlet are compared to experimental data available in the open literature. From the model the refrigerant mass flow rate can be determined, from a known operating conditions and geometry parameters, using the process of parameter estimation with the method of Levenberg-Marquardt... (Complete abstract click electronic address below). / Mestre

abstract: ABSTRACT A vortex tube is a device of a simple structure with no moving parts that can be used to separate a compressed gas into a hot stream and a cold stream. Many studies have been carried out to find the mechanisms of the energy separation in the vortex tube. Recent rapid development in computational fluid dynamics is providing a powerful tool to investigate the complex flow in the vortex tube. However various issues in these numerical simulations remain, such as choosing the most suitable turbulent model, as well as the lack of systematic comparative analysis. LES model for the vortex tube simulation is hardly used in the present literatures, and the influence of parameters on the performance of the vortex tube has scarcely been studied. This study is aimed to find the influence of various parameters on the performance of the vortex tube, the best geometric value of vortex tube and the realizable method to reach the required cold out flow rate 40 kg/s . First of all, setting up an original 3-D simulation vortex tube model. By comparing experiment results reported in the literature and our simulation results, a most suitable model for the simulation of the vortex tube is obtained. Secondly, we perform simulations to optimize parameters that can deliver a set of desired output, such as cold stream pressure, temperature and flow-rate. We also discuss the use of the cold air flow for petroleum engineering applications. / Dissertation/Thesis / M.S. Mechanical Engineering 2013

L'objectif général du travail de cette thèse est de proposer des méthodes robustes pour permettre d’obtenir des critères sur l’évolution de la pathologie tumorale à partir d’études dynamiques. Actuellement, l’appréciation de l’efficacité d’un traitement antiangiogénique (destruction des vaisseaux alimentant la tumeur) repose principalement sur l’imagerie fonctionnelle dont l’objectif est de quantifier la microcirculation tumorale à partir d’acquisitions dynamiques de perfusion. Cependant, différentes limites concernant le suivi de la réponse précoce des lésions par imagerie existent (mauvaise maîtrise des mouvements respiratoires, pas de consensus sur les paramètres permettant de quantifier la microcirculation tumorale, estimation paramétrique faite à partir de données extrêmement bruitées et pour un grand nombre de zones - une estimation par voxel de la séquence dynamique d’images). Dans un contexte clinique extrêmement contraignant, nous avons mis en place un cadre rigoureux comprenant l’ensemble des étapes nécessaires pour une caractérisation plus fiable de la microcirculation tumorale à partir de séquences d’images acquises sous perfusion de produit de contraste : les contributions principales de cette thèse couvrent ainsi l’optimisation des paramètres de reconstruction, le développement d’une méthode de recalage adaptée à nos données, la sélection argumentée d’un modèle de perfusion et enfin le développement d’une méthode robuste d’estimation des paramètres. Ces travaux permettent d’envisager l’utilisation des modèles de perfusion pour la caractérisation et la prédiction de la réponse d’un patient à différents traitements antitumoraux. / The main objective is to propose robust methods to allow estimation of functional markers reflecting the tumor evolution from dynamic studies. Currently, in this domain, assessing of the efficiency evaluation of an anti-angiogenic therapy (destruction of vessels which feed the tumor) is mainly based on the functional imaging of the microcirculation, which the objective is to quantify the tumor microcirculation by dynamic acquisitions with injection of contrast product. However, several limitations are present (lack of control of the breathing movement, no consensus on the parameters permitting the quantification of tumor microcirculation, parameter estimation computed from noisy data and a large number of regions - one estimation by voxel or group of voxel of the dynamic image sequence). In a restrictive clinical context (noisy data, few number), we have developed a complete pipeline with a set of necessary steps to a reliable characterization of the tumor microcirculation from dynamic perfusion image sequence: the main contributions of this thesis cover the reconstruction parameters optimization, the development of a registration method, the argued selection of a perfusion model and the development of a robust method of parameter estimation. With these works, we can envision the utilization of these perfusion models to the characterization and the prediction of the therapy response of a patient

Os principais resultados originais relatados ao longo desse texto provêm de observações em experimentos numéricos, entretanto, na maioria dos casos, os resultados são fundamentados com instrumentos teóricos ou com modelos heurísticos. Inicialmente, introduzimos, nas equações que descrevem osciladores caóticos, uma pequena perturbação periódica a fim de observar no espaço de parâmetros a porção de parâmetros cujo comportamento caótico é extinto. Assim, constatamos que o conjunto de parâmetros correspondentes às orbitas caóticas extintas correspondem à replicas de janelas periódicas complexas previamente existentes no sistema não-perturbado. Posteriormente, utilizando as propriedades de torsão do espaço de estados dos osciladores caóticos, visualizamos transições existentes no interior das janelas periódicas complexas. Quando consideramos sequências dessas janelas sob a ótica da torsão do espaço de estados, observamos a existência de regras que relacionam janelas consecutivas ao longo dessa sequência. Adicionalmente, no espaço de parâmetros de osciladores caóticos e sistemas dinâmicos adicionais, fizemos uma estimativa da dimensão da fronteira entre o conjunto de parâmetros que leva às soluções periódicas e o conjunto que leva aos atratores caóticos. Para os sistemas investigados, os valores obtidos para essa dimensão estão no mesmo intervalo de confiança, indicando que essa dimensão é universal. / The main results reported along this text come from observations in numerical experiments, however, in most cases, results are explained by theoretical instruments or heuristic models. Initially we introduced in the equations that describe chaotic oscillators, a small periodic perturbation to observe, in the parameter space, the portion of parameters whose chaotic behavior is extinguished. Thus, we find that the set of parameters corresponding to the extinct chaotic orbits correspond to replicas of previously complex periodic windows existing in the unperturbed system. Subsequently, using the torsion properties of state spaces of chaotic oscillators, we visualize transitions within the complex periodic windows. When we consider sequences of these windows from the perspective of torsion properties of the state space, we observe the existence of rules that relate consecutive windows along these sequences. Additionally, in the parameter space of chaotic oscillators and additional dynamical systems, we estimate the dimension of the boundary between the set of parameters that leads to periodic solutions and the set that leads to chaotic attractors. For the systems considered here, the values for this dimension are in the same confidence interval, indicating that this dimension is universal.

Orientador: Marcio Jose Menon / Dissertação (mestrado) - Universidade Estadual de Campinas, Instituto de Fisica Gleb Wataghin / Made available in DSpace on 2018-08-14T22:56:28Z (GMT). No. of bitstreams: 1 Silva_GeovannaLuizPereirada_M.pdf: 9792515 bytes, checksum: 1b4a308cdedc594904027c57497be003 (MD5) Previous issue date: 2009 / Resumo: Apresenta-se um estudo das Representações de Parâmetro de Impacto e Eiconal através de uma análise empírica dos dados experimentais de espalhamento elástico próton-próton, na região de mais alta energia com informações experimentais disponíveis (seis conjuntos de dados no intervalo de energia no centro de massa 19.4 - 62.5 GeV). Fazendo-se uso de uma nova parametrização independente de modelo para a amplitude de espalhamento e através de reduções (ajustes) dos dados experimentais de seção de choque diferencial, determina-se as funções de perfil (partes real e imaginária), recobrimento inelástica e eiconal (partes real e imaginária) no espaço de parâmetro de impacto. Utilizando-se um método semi-analítico, determina-se a função opacidade (parte imaginária da eiconal) no espaço de momento transferido. Todos os resultados empíricos para essas grandezas são determinados com as incertezas correspondentes, calculadas através da propagação de erros dos parâmetros livres de ajuste (variâncias e covariâncias). Em particular, mostra-se que a função de recobrimento inelástica apresenta um efeito periférico em torno de 2,0 fm e que os resultados empíricos para a função opacidade podem ser analiticamente parametrizados por três contribuições gaussianas, dominantes nas regiões de pequeno, médio e grande momento transferido. Discute-se interpretações físicas dos resultados (aspectos ópticos/geométricos e baseados na QCD), bem como a aplicabilidade dos resultados empíricos na seleção, construção e desenvolvimento de modelos fenomenológicos, em particular, aqueles baseados ou inspirados na QCD / Abstract: The Impact Parameter and Eikonal Representations are investigated by means of an empirical analysis of the experimental data on proton-proton elastic scattering, at the highest energy region with experimental information available (six data sets at center of mass energies 19.4 - 62.5 GeV). Making use of a novel model-independent parametrization for the scattering amplitude and data reductions (fits) to differential cross section data, we extract the profile function (real and imaginary parts), the inelastic overlap function and the eikonal function (real and imaginary parts) in the impact parameter space. By means of a semi-analytical method, the opacity function (imaginary part of the eikonal) is also extracted in the momentum transfer space. All the empirical results for these quantities are determined with the corresponding uncertainties, evaluated through error propagation from the free fit parameters (variances and covariances). In particular, it is shown that the inelastic overlap functions present a peripheral effect around 2.0 fm and that the empirical results for the opacity function can be analytically parametrized by three Gaussian components each one with leading contribution at small, intermediate and large values of the momentum transfer. Physical interpretations of the results are discussed (optical/geometrical and QCD-based aspects), as well as the applicability of the empirical results in the selection, construction and development of phenomenological models, mainly those based or inspired in QCD / Mestrado / Física das Particulas Elementares e Campos / Mestra em Física

Este trabalho apresenta um estudo sobre taxas de aniquilação de pósitrons em gases moleculares por meio do cálculo do parâmetro de aniquilação Zeff. O modelo Gribakin-Lee (GL) formula de maneira fenomenológica um mecanismo de captura do pósitron mediado por uma interação dipolar, descrevendo uma contribuição ressonante para Zeff dos modos vibracionais ativos-IR da molécula. Este modelo concorda muito bem quando testado aos halometanos no experimento com feixes de pósitrons, porém, falha quando aplicado ao experimento com pósitrons térmicos. Neste contexto, foram testadas algumas hipóteses para explicar a discordância entre o modelo GL aplicado ao experimento com feixes de pósitrons e ao experimento com pósitrons térmicos. Foi mostrado como o modelo GL pode ser obtido como um caso particular do formalismo dos operadores de projeção de Feshbach. As hipóteses testadas para explicar a discrepância entre os modelos foram: (i) desconsiderar a aproximação de largura zero, para uma convolução mais realista do parâmetro de aniquilação Zeff com a distribuição energética dos pósitrons; (ii) incluir combinações de modos vibracionais e overtones IR-ativos, além de modos com atividade Raman no cálculo de Zeff térmico; (iii) incluir ressonâncias rotacionais no modelo GL; e (iv) propor um modelo simplificado para a densidade eletrônica considerando a sua dependência em relação às coordenadas nucleares da molécula. Verificou-se que considerar larguras finitas na convolução de Zeff térmico e Zeff para o feixe não leva a uma diferença significativa em comparação com o modelo GL, sendo legítimo a utilização da aproximação de largura zero para as ressonâncias vibracionais de Feshbach. Quanto à inclusão de overtones e combinações ativos-IR, verificou-se que apesar deste método ser de extrema importância para ajustar Zeff no caso do experimento com feixes de pósitrons para as moléculas de metanol e etileno, a influência desta contribuição para Zeff térmico é modesta. Moléculas com baixíssimas energias de ligação, como o CH3F, podem apresentar uma possível contribuição rotacional para Zeff, representando quase que a totalidade da contribuição ressonante ao parâmetro de aniquilação. / This work presents a study of the rates of annihilation of positrons in molecular gases by calculating the annihilation parameter Zeff. The Gribakin-Lee (GL) model formulates a dipole-interaction-mediated positron capture mechanism, describing a resonant contribution to Zeff of the active-IR vibrational modes of the molecule. This model agrees very well when tested to the halomethanes in the experiment with positron beams, but fails when applied to the experiment with thermal positrons. In this context, some hypotheses were tested to explain the discrepancy between the GL model applied to the experiment with positron beams and the experiment with thermal positrons. It was shown how the GL model can be obtained as a particular case of the Feshbach projection operators formalism. The hypotheses tested to explain the discrepancy between the models were: (i) to disregard the zero-width approximation for a more realistic convolution of the annihilation parameter Zeff with the energy distribution of the positrons; (ii) to include combinations of IR-active vibrational modes and overtones, in addition to modes with Raman activity in the calculation of thermal Zeff; (iii) to include rotational resonances in the GL model and; (iv) to propose a simplified model for the electron density considering its dependence on the nuclear coordinates of the molecule. It has been found that considering finite widths in the convolution of thermal Zeff and Zeff for the beams does not lead to a significant difference from the GL model, being legitimate the use of the zero width approximation for the vibrational Feshbach resonances. Regarding the inclusion of overtones and combinations IR-active, it was found that although this method is of extreme importance to fit Zeff in the case of the experiment with positron beams for methanol and ethylene, the influence of this contribution to thermal Zeff is modest. Molecules with very low binding energies, such as CH3F, may present a possible rotational contribution to Zeff, representing almost the entire resonant contribution to the annihilation parameter.

Submitted by Marcele Costal de Castro (costalcastro@gmail.com) on 2017-09-19T15:52:09Z No. of bitstreams: 1 ANTÔNIO CARLOS DE ABREU MOL M.pdf: 3169272 bytes, checksum: 207fddec998bd369cc10bf8f8a6db03c (MD5) / Made available in DSpace on 2017-09-19T15:52:09Z (GMT). No. of bitstreams: 1 ANTÔNIO CARLOS DE ABREU MOL M.pdf: 3169272 bytes, checksum: 207fddec998bd369cc10bf8f8a6db03c (MD5) Previous issue date: 1996-01 / A implementação de sistemas computadorizados de auxílio à operação de usinas nucleares teve início após o acidente nuclear da usina americana de Three Mile Island . Naquela oportunidade foi introduzido o conceito de “Safety Parameter Display Sistem” (SPDS), mais especificamente o do seu módulo de Funções Críticas de Segurança. A definição original destes sistemas não era clara e objetiva o suficiente para uma implementação adequada de tais sistemas nas salas de controle das usinas nucleares. Como consequência surgiram surgiram diferentes versões de SDPS que, em sua grande maioria, apresentam sérias deficiências, tornando-os incompatíveis com o objetivo precípuo de aumento de segurança na operação de usinas nucleares. O presente trabalho teve como meta inicial a revisão crítica do conceito de “SAfety Parameter Display Sistem” (SDPS) com base na regulamentação e experiência operacional existentes. E teve como desdobramentos dessa meta inicial a proposta de solução para as flutuações das taxas de partidas usadas na monitoração das funções críticas de segurança, e o estudo de viabilidade da automatização dos procedimentos de recuperação das referidas funções críticas. Em particular, a solução para as flutuações das taxas de partida tornou-se relevante em face a constatação de que todos os SDPS que monitoravam as árvores de estado das funções críticas de segurança apresentavam este problema, devido a composição intrínseca dos canais de detecção dos fluxos de nêutrons em reatores nucleares. Neste trabalho, também é apresentado um resumo das principais inspeções realizadas em SDPS , em operação em várias usinas nucleares americanas.

Technology has a major role in today’s world. The development and massive access to information technology has enabled the use of computers to provide assistance on a wide range of tasks, from the most trivial daily ones to the most complex challenges we face as human kind. In particular, optimisation algorithms assist us in taking decisions, improving processes, designing solutions and they are successfully applied in several contexts such as industry, health, entertainment, and so on. The design and development of effective and efficient computational algorithms is, thus, a need in modern society.Developing effective and efficient optimisation algorithms is an arduous task that includes designing and testing of several algorithmic components and schemes, and requires considerable expertise. During the design of an algorithm, the developer defines parameters, that can be used to further adjust the algorithm behaviour depending on the particular application. Setting appropriate values for the parameters of an algorithm can greatly improve its performance. This way, most high-performing algorithms define parameter settings that are “finely tuned”, typically by experts, for a particular problem or execution condition.The process of finding high-performing parameter settings, called algorithm configuration, is commonly a challenging, tedious, time consuming and computationally expensive task that hinders the application and design of algorithms. Nevertheless, the algorithm configuration process can be modelled as an optimisation problem itself and optimisation techniques can be applied to provide high-performing configurations. The use of automated algorithm configuration procedures, called configurators, allows obtaining high-performing algorithms without requiring expert knowledge and it enables the design of more flexible algorithms by easing the definition of design choices as parameters to be set. Ultimately, automated algorithm configuration could be used to fully automatise the algorithm development process, providing algorithms tailored to the problem to be solved.The aim of the work presented in this thesis is to study the automated configuration of algorithms. To do so, we formally define the algorithm configuration problem and analyse its characteristics. We study the most prominent algorithm configuration procedures and identify relevant configuration techniques and their applicability. We contribute to the field by proposing and analysing several configuration procedures, being the most prominent of these the irace configurator. This work presents and studies several modifications of the configuration process implemented by irace, which considerably improve the performance of irace and broaden its applicability. In a general context, we provide insights about the characteristics of the algorithm configuration process and techniques by performing several analyses configuring different types of algorithms under varied situations. And, finally, we provide practical examples of the usage of automated configuration techniques showing its benefits and further uses for the application and design of efficient and effective algorithms. / Doctorat en Sciences de l'ingénieur et technologie / info:eu-repo/semantics/nonPublished

Abstract The multiple–input multiple–output (MIMO) technique, applying several transmit and receive antennas in wireless communications, has emerged as one of the most prominent technical breakthroughs of the last decade. Wideband MIMO parameter estimation and its applications to the MIMO orthogonal frequency division multiplexing (MIMO–OFDM) channel estimation and mobile positioning are studied in this thesis. Two practical MIMO channel models, i.e., correlated-receive independent-transmit channel and correlated-transmit-receive channel, and associated space-time parameter estimation algorithms are considered. Thanks to the specified structure of the proposed training signals for multiple transmit antennas, the iterative quadrature maximum likelihood (IQML) algorithm is applied to estimate the time delay and spatial signature for the correlated-receive independent-transmit MIMO channels. For the correlated-transmit-receive MIMO channels, the spatial signature matrix corresponding to a time delay can be further decomposed in such a way that the angle of arrival (AOA) and the angle of departure (AOD) can be estimated simultaneously by the 2-D unitary ESPRIT algorithm. Therefore, the combination of the IQML algorithm and the 2-D unitary ESPRIT algorithm provides a novel solution to jointly estimate the time delay, the AOA and the AOD for the correlated-transmit-receive MIMO channels. It is demonstrated from the numerical examples that the proposed algorithms can obtain good performance at a reasonable cost. Considering the correlated-receive independent-transmit MIMO channels, channel coefficient estimation for the MIMO–OFDM system is studied. Based on the parameters of the correlated-receive independent-transmit MIMO channels, the channel statistics in terms of the correlation matrix are developed. By virtue of the derived channel statistics, a joint spatial-temporal (JST) filtering based MMSE channel estimator is proposed which takes full advantage of the channel correlation properties. The mean square error (MSE) of the proposed channel estimator is analyzed, and its performance is also demonstrated by Monte Carlo computer simulations. It is shown that the proposed JST minimum mean square error (MMSE) channel estimator outperforms the more conventional temporal MMSE channel estimator in terms of the MSE when the signals in the receive antenna array elements are significantly correlated. The closed form bit error probability of the space-time block coded OFDM system with correlation at the receiver is also developed by taking the channel estimation errors and channel statistics, i.e., correlation at the receiver, into account. Mobile positioning in the non-line of sight (NLOS) scenarios is studied. With the knowledge of the time delay, the AOA and the AOD associated with each NLOS propagation path, a novel geometric approach is proposed to calculate the MS's position by only exploiting two NLOS paths. On top of this, the least squares and the maximum likelihood (ML) algorithms are developed to utilize multiple NLOS paths to improve the positioning accuracy. Moreover, the ML algorithm is able to estimate the scatterers' positions as well as those of the MSs. The Cramer-Rao lower bound related to the position estimation in the NLOS scenarios is derived. It is shown both analytically and through computer simulations that the proposed algorithms are able to estimate the mobile position only by employing the NLOS paths.

Recent advances in technology for brain imaging and high-throughput genotyping have motivated studies examining the influence of genetic variation on brain structure. In this setting, high-dimensional regression for multi-SNP association analysis is challenging as the brain imaging phenotypes are multivariate and there is a desire to incorporate a biological group structure among SNPs based on their belonging genes. Wang et al. (Bioinformatics, 2012) have recently developed an approach for simultaneous estimation and SNP selection based on penalized regression with regularization based on a novel group l_{2,1}-norm penalty, which encourages sparsity at the gene level. A problem with the proposed approach is that it only provides a point estimate. We solve this problem by developing a corresponding Bayesian formulation based on a three-level hierarchical model that allows for full posterior inference using Gibbs sampling. For the selection of tuning parameters, we consider techniques based on: (i) a fully Bayes approach with hyperpriors, (ii) empirical Bayes with implementation based on a Monte Carlo EM algorithm, and (iii) cross-validation (CV). When the number of SNPs is greater than the number of observations we find that both the fully Bayes and empirical Bayes approaches overestimate the tuning parameters, leading to overshrinkage of regression coefficients. To understand this problem we derive an approximation to the marginal likelihood and investigate its shape under different settings. Our investigation sheds some light on the problem and suggests the use of cross-validation or its approximation with WAIC (Watanabe, 2010) when the number of SNPs is relatively large. Properties of our Gibbs-WAIC approach are investigated using a simulation study and we apply the methodology to a large dataset collected as part of the Alzheimer's Disease Neuroimaging Initiative. / Graduate