Magíster en Ciencias de la Ingeniería, Mención Ingeniería Sísmica / Ingeniero Civil / Este estudio presenta una evaluación del Método de Análisis Modal Espectral para estructuras con sistemas pasivos de disipación de energía del estándar estadounidense ASCE 7 del año 2010. La evaluación se realizó comparando las predicciones del método de análisis simplificado, con la respuesta inelástica exacta de un edificio de hormigón armado de 35 pisos, equipado con disipadores viscosos no lineales, viscoelásticos e histeréticos, previa adaptación del método simplificado a las condiciones sísmicas chilenas. El Método de Análisis Modal Espectral del ASCE 7, se desarrolla teóricamente en base a un tipo de método estático no lineal, denominado Método del Espectro de Capacidad, que fue propuesto originalmente para su uso en la rehabilitación de edificios mediante disipadores de energía por el FEMA 273/274, en el contexto de la ingeniería basada en desempeño. Es por ello que, en primera instancia, fue necesario estudiar el origen, el desarrollo y la evolución de los métodos estáticos no lineales durante estas últimas dos décadas. Luego, se estudió la modificación de un espectro elástico de desplazamientos para niveles de amortiguamiento diferentes a un 5% del crítico, cuya aplicación es muy relevante en las predicciones del método. Se propusieron ecuaciones ajustadas por mínimos cuadrados a la media de los factores de amplificación o reducción que permiten llevar a cabo esta tarea, considerando una base de datos de 130 registros de aceleración chilenos. Considerando la modificación de las ordenadas espectrales propuesta, se revaluó el Método del Espectro de Capacidad aplicado en sistemas inelásticos de un grado de libertad con disipadores de energía, en 14310 sistemas que permitieron abarcar casi la totalidad de los casos de mayor interés práctico. Para ello, se utilizaron set de registros debidamente seleccionados y escalados a un espectro elástico de diseño en particular para diferentes tipos de suelo. Los resultados mostraron que el método simplificado proporciona erráticas predicciones del desplazamiento inelástico, y que el límite de desplazamiento mínimo otorgado por la solución del sistema considerando que la estructura permanece elástica mejora significativamente las estimaciones. Por el contrario, la velocidad relativa se predice de forma muy errática a través de la seudo velocidad, por lo cual se proponen factores de corrección basados en la misma base de datos de 130 acelerogramas, obteniendo mejoras que son muy importantes para el diseño de disipadores que poseen una componente viscosa. Finalmente, se lleva a cabo una completa adaptación del Método de Análisis Modal Espectral a las condiciones sísmicas chilenas, para luego ser aplicado a sistemas de múltiples grados de libertad. En base a los resultados obtenidos, se descarta el uso del Método del Espectro de Capacidad, y se propone un método simplificado que asume un comportamiento elástico de la estructura, el cual proporciona predicciones bastante aceptables en sistemas regulares con importantes incursiones en el rango inelástico, con errores relativos acotados entre -20 y 30% para las principales variables de diseño de la estructura y los sistemas disipadores analizados, donde errores positivos indican predicciones conservadoras y errores negativos lo contrario.

La saturation annoncée du débit maximal d'information véhiculable par des fibres optiques monomodes rend nécessaire l'étude de nouvelles technologies susceptibles de répondre aux besoins toujours croissants des utilisateurs. La technologie de multiplexage spatial semble très prometteuse et nécessite d'adapter/développer l'ensemble des briques élémentaires qui constitueraient la nouvelle ligne de transmission. Le but de cette thèse est d'approfondir les travaux initiés sur cette thématique en associant théorie et expérience de façon à réaliser des répéteurs optiques adaptés au cas du multiplexage modal dans des fibres légèrement multimodes. La principale contrainte qui s'applique à ce type d'amplificateurs est de réaliser l'égalisation simultanée des gains sur les différents canaux de transmission. Des outils numériques de modélisation et d'optimisation de ces amplificateurs ont été développés pour explorer de nombreuses configurations et identifier celles qui sont optimales. Un modèle numérique tenant compte du battement de modes et du couplage entre modes induit par le milieu amplificateur a été développé. Une nouvelle configuration de fibre à cœur micro-structuré permettant de dépasser les limitations liées aux méthodes conventionnelles de fabrication de fibres a été étudiée. Ce type de fibre permet d'obtenir un gain élevé et égalisé sur l'ensemble des canaux et favorise l'efficacité énergétique du composant. Un autre volet de ce travail de thèse a consisté à étudier la possibilité d'intégrer les amplificateurs légèrement multimodes au sein du réseau monomode actuel de façon à partager la fonction d'amplification à un coût avantageux en terme d'énergie et de composants. / The capacity crunch announced for single mode long-haul telecommunication networks necessitates the study of new technologies able to meet the ever-growing needs of users. The technology of space division multiplexing seems promising and necessits to adapt/to develop all the fiber components that make up an optical fiber network to a high level of performance for future implementation of an optical cable based on SDM technology. The purpose of this thesis consists in pursuing the works introduced on this topic by associating theory and experiments so as to realize optical repeaters adapted to mode division multiplexing in few-mode fibers. The main constraint for this kind of amplifiers is to realize the simultaneous gain equalization of the different telecommunications channels: spatial modes and wavelengths. Numerical tools have been developed to model and optimize these amplifiers so as to explore numerous configurations and identify the most appropriates. Particularly, a numerical model taking into account mode beating and mode coupling induced by the amplifying medium has been developped. Within the framework of this study, a new fibre configuration with micro-structured core allowing to overcome the limitations of the conventional fabrication methods has been studied. This fiber configuration is very predictive and can provide high and equalized gain over the different channels while optimizing the energy efficiency of the component. Another dimension of this thesis has been to study the possibility to integrate few-mode fiber amplifiers in the current single mode network, in order to share the amplification function and so realize cost savings.

No description available.

Orientador: Jose Roberto de França Arruda / Tese (doutorado) - Universidade Estadual de Campinas, Faculdade de Engenharia Mecanica / Made available in DSpace on 2018-07-20T07:00:12Z (GMT). No. of bitstreams: 1 Vercosa_CarlsonAntonioMendes_D.pdf: 30086773 bytes, checksum: ebc3ffb0fcde8fb3351e8d3cf09a7661 (MD5) Previous issue date: 1995 / Resumo: A vida útil de um elemento estrutural é, em geral, abreviada devido a uma redução da capacidade de carga para a qual o elemento é inicialmente projetado. Em dinâmica estrutural esta redução chama-se falha estrutural. Falhas estruturais promovem a degradação da estrutura e informações sobre sua existência e localização podem ser usadas para garantir a integridade da estrutura. Neste trabalho investiga-se a possibilidade de detectar e localizar fa14as em estruturas. A hipótese básica é que falhas estruturais causam mudanças nas propriedades físicas da estrutura que, por sua vez, afetam freqüências naturais e modos de vibração. A localização de falhas se desenvolve através de métodos de ajuste de modelos por matriz ótima, que conjugam as matrizes de massa e rigidez teóricas da estrutura na condição intacta com freqüências naturais e modos de vibração medidos da estrutura na condição deteriorada. Os dados teóricos são obtidos pelo método de elementos finitos e os dados experimentais por técnicas de análise modal experimental. Introduz-se um novo método de ajuste de modelos e propõe-se uma reformulação no método de Kabe através da incorporação do conceito de pseudo-esparsidade que decorre do cancelamento de forças devido à simetria do modelo estrutural. Exemplos experimentais e de simulação numérica são utilizados para validar a metodologia proposta e investigar a influência do truncamento modal, no que tange à localização de falhas estruturais. Variações nos parâmetros modais são indicadores sensíveis de alterações estruturais. Na ausência de ruído, os métodos que ajustam a matriz de rigidez elemento-a-elemento reproduzem exatamente os coeficientes de rigidez e preservam o modelo de esparsidade da estrutura, o que não ocorre com os métodos denominados de globais. Contudo, ambos os tipos de métodos proporcionam a exata localização de falhas estruturais. Na presença de modos contaminados com ruído, os métodos de caráter global têm melhor desempenho no processo de localização de falhas estruturais / Abstract: The service life of a structural element is, in general, shortened when there is a reduction of the load capacity to which it was originally designed. In structural dynamics this reduction is referred to as a structural fault. Structural faults cause the deterioration of the structure and, therefore, information about their existence and location may be used to ensure its integrity. The basic hypothesis implied here is that structural faults cause changes in the p~ysical properties of the structure which, in turn, affect its natural frequencies and mode shapes. In this work, fault localization is done using optmal-matrix update methods which involve the analytical mass and stiffness matrices of the original structure and the natural frequencies and mode shapes of the flawed structure. The analytical model is obtained using the finite element method and the experimental data is obtained using experimental modal analysis. A new model update method is presented as well as a modification of Alvar Kabe's method, which incorporates the concept of pseudo-sparsity caused by force cancellation when assembling the stiffness matrix. Numerical simulation and experimental results are used to validate the proposed method and to investigate the influence of the modal base truncation in the fault localization processo It is shown that, in the absence of noise, the methods that adjust the stiffness matrix element-by-element reproduce exact1y the stiffness coefficients and preserve the matrix sparsity. This is not the case when using the methods called global. Nevertheless, both types of methods allow the exact localization of the structural faults. In the presence of noise in the experimental modes, the global methods have a better performance in the process of localizing structural faults / Doutorado / Doutor em Engenharia Elétrica

This dissertation investigates how German young adults use modal particles (MPs) when communicating in online chat forums. Simply stated, MPs help to clarify a speaker’s intent and mood, without having any syntactical function or adding specific semantic content. For many years, MPs were ignored, described as useless fill-words, or even regarded as "Lice in the fur of our language." (Reiners, 1967). During the last three decades though, their usefulness and importance has been recognized. It has long been established that the correct use of MPs in German causes spoken discourse to sound more fluent and warm, while spoken German without the use of MPs appears wooden and cold. Although various areas of MP research have been explored, the use of MPs by young adults has not yet received much attention. In order to provide a first account of how MPs are used by young adults in informal settings, online conversations (chats) were analyzed to determine the frequency of their MP use. Additionally, this research investigates whether gender differences for MP use in young adults exist, and relates the results within the framework of current research in the areas of pragmatics and gender specific language. The analyzed online conversations were collected from the German chat forum ‘meet-teens.de.’ Approx. 2,000 words of chat data, each from 15 male and 15 female young adult users aged between 16 and 21 were collected. The data consists of conversations between five male-male pairs, five female-female pairs, and five male-female pairs. The analyses of the data found that the female participants in this research used significantly more MPs than their male counterparts. Furthermore, the MPs ‘bloß’, ‘halt’, and ‘mal’ were used significantly more frequently by male participants, while the MPs ‘denn’, ‘eben’, and ‘wohl’ were significantly more frequently used by female participants. The analyses also found that female young adults speaking to other females used the MPs ‘denn’, ‘halt’, and ‘mal’ significantly more often than when speaking to their male counterparts, while male young adults, with the exception of the MP ‘bloß’, did not change their use of MPs depending on the gender of their conversational partner.

To provide the average golfer with more consistent results, manufacturers have continued to improve the available equipment. This has led to larger club-heads, with larger ?sweet spots?, different shaft thickness for different swing styles, and the use of advanced materials, such as graphite and titanium, for the construction. The development of improved equipment, which utilizes advanced materials, has spurred the need for advanced scientific analysis using a variety of techniques. Among the most prevalent of these methods are finite element analysis and experimental modal analysis, and use of these techniques in examining a golf club is the focus of this research. The primary goals of this work are the development and correlation of an appropriate finite element model, the characterization of the hands-free boundary condition and the examination of the club golf dynamic response. To accomplish these objectives, the physical parameters of the golf club are determined to develop the finite element model. The analysis of natural frequencies and mode shapes correlate well with the results extracted from experimental modal analysis for the free-free and clamped-free boundary conditions. With the correlation established, a third boundary condition, hands-free, is tested experimentally to ascertain the effects of the golfer?s grip on the boundary conditions. With the FEA model confirmed, a nonlinear dynamic response of the club during the down-swing is investigated using the nonlinear solver in Algor, and the club-head position relative to the shaft is predicted. / Master of Science

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The thesis presents a method of evaluation for blade damage in Combustion Turbine Compressor Section. This method involves use of multiple domains within a single Finite Element Model to predict the effect of damage on the blade properties. This approach offers significant time and effort savings when compared to traditional evaluation methods of similar problems. It is demonstrated via examples that the multi-domain modeling approach yields acceptable accuracy results. The economical implications of described method are readily applicable to both the industrial and the aerospace Combustion Turbine fields. It is economically impractical to replace the blade at each damage occurrence. However, the evaluation time involved in making associated decisions can be extensive if traditional methods of evaluation are used. The specific contributions of this study are twofold: 1. Time savings during evaluation 2. Compressor Blades may be returned to service which are otherwise replaced

The nonlinear nonplanar steady-state responses of cantilever beams to direct and parametric harmonic excitations are investigated using perturbation techniques. Modal interactions between the bending-bending and bending-bending-twisting motions are studied. Using a variational formulation, we obtained the governing equations of motion and associated boundary conditions for monoclinic composite and isotropic metallic inextensional beams. The method of multiple scales is applied either to the governing system of equations and associated boundary conditions or to the Lagrangian and virtual-work term to determine the modulation equations that govern the slow dynamics of the responses. These equations are shown to exhibit symmetry properties, reflecting the conservative nature of the beams in the absence of damping. It is popular to first discretize the partial-differential equations of motion and then apply a perturbation technique to the resulting ordinary-differential equations to determine the modulation equations. Due to the presence of quadratic as well as cubic nonlinearities in the governing system for the bending-bending-twisting oscillations of beams, it is shown that this approach leads to erroneous results. Furthermore, the symmetries are lost in the resulting equations. Nontrivial fixed points of the modulation equations correspond, generally, to periodic responses of the beams, whereas limit-cycle solutions of the modulation equations correspond to aperiodic responses of the beams. A pseudo-arclength scheme is used to determine the fixed points and their stability. In some cases, they are found to undergo Hopf bifurcations, which result in limit cycles. A combination of a long-time integration, a two-point boundary-value continuation scheme, and Floquet theory is used to determine in detail branches of periodic and chaotic solutions and assess their stability. The limit cycles undergo symmetry-breaking, cyclic-fold, and period-doubling bifurcations. The chaotic attractors undergo attractor-merging and boundary crises as well as explosive bifurcations. For certain cases, it is determined that the response of a beam to a high-frequency excitation is not necessarily a high-frequency low-amplitude oscillation. In fact, low-frequency high-amplitude components that dominate the responses may be activated by resonant and nonresonant mechanisms. In such cases, the overall oscillations of the beam may be significantly large and cannot be neglected. / Ph. D.

<p> A coarse grained amphibolite from the metamorphosed rim of the Whitestone Anorthosite was prepared in several ways for the purpose of determining the modal abundance of the constituent minerals by calibrated X-ray diffraction. A simple two component amphibolite consisting of plagioclase and amphibole was chosen and five major methods of mounting the specimens for X-ray diffraction were employed.</p> <p> It was hoped that a method could be found which would produce randomly oriented, homogeneous samples. A series of such samples each of a different component ratio would then provide a calibration curve from which the mode of a whole rock specimen could be estimated.</p> <p> The calibrated X-ray charts were produced on Philips scanning X-ray diffractometers.</p> <p> The inconsistencies in the results indicate that better technical procedures are required.</p> / Thesis / Bachelor of Science (BSc)