Na sociedade atual as estruturas de linhas de transmissão são consideradas componentes essenciais do sistema de infraestrutura urbana. Sua função é a de transmitir a eletricidade gerada nas fontes de produção até o consumidor através de uma rede de distribuição. Este tipo de estruturas por sua extensão, exposição e variações topográficas, se mostram vulneráveis ao carregamento dinâmico de ventos originados a partir tormentas elétricas, tais como downbursts e tornados. No Brasil tem-se observado nos últimos tempos um aumento de acidentes neste tipo de estrutura, principalmente devido à incidência de fortes ventos. No presente trabalho estuda-se o comportamento dinâmico de um trecho de linha de transmissão da empresa Eletrobrás FURNAS quando submetido à ação de ventos provenientes de downburst. Na pesquisa foram identificados os principais modelos analíticos disponíveis na literatura que oferecem o campo de velocidades horizontais e verticais médias e a componente flutuante. Com base e alguns dos modelos identificados na revisão bibliográfica, implementou-se um programa computacional capaz de simular todas as componentes do campo de velocidades de um downburst em movimento. A partir do programa implementado foi realizado um estudo paramétrico onde identificou-se a combinação de variáveis do evento que provoca a maior energia cinética armazenada. Finalmente é apresentada uma revisão estrutural dos montantes da torre central da linha modelada, através da análise da relação demanda/capacidade na altura da coluna. Dos resultados obtidos, pode-se concluir que a combinação de variáveis que provoca os resultados de forças internas mais críticos varia em relação a cada componente da linha considerado. O estudo de sensibilidade das variáveis envolvidas nos modelos implementados revelou que existe um incremento monotônico crescente da energia cinética armazenada com o aumento dos parâmetros e para a maioria dos casos, exceto quando =500 . Da flutuação e sua influência no comportamento dinâmico na linha analisada, conclui-se que a consideração das flutuações na resposta dinâmica dos cabos condutores e para-raios pode ser desprezada, fato que foi comprovado através dos valores obtidos na inclinação das linhas de tendência realizadas. / Transmission Lines (TL) are considered one of the essential components of the urban infrastructure. Their role is to transmit electricity from sources of production to the distribution system and then to consumers. This type of structure for its length, exposure and topographical variations, show themselves vulnerable to dynamic loading winds originated from electrical storms such as tornadoes and downbursts. In Brazil, it has been observed recently, an increase in the accidents of this type of structure, primarily due to incidence of strong winds. In the present research, is analyzed the dynamic behavior of a transmission line system of Eletrobras Furnas Company when subjected to downburst. In the investigation, the main analytical models available in the literature that offer the wind field of horizontal and vertical speeds and the fluctuating component were identified. Based on some of the models identified in the literature review, was implemented a computer program capable of simulating all components of the velocity of a moving downburst. Based on the implemented program was conducted a parametric study in order to identify the combination of variables that causes the greatest kinetic stored energy. Finally is presented a structural review of the columns of the central tower of the system, by examining the demand/capacity relationship. Regarding to the parametric study, it was found that the combination of variables which causes the most critical internal forces varies for each component of the line considered. The sensibility study of the variables involved the models used in this study revealed that there is a growing monotonic increase in the stored energy with the accretion of and 1.parameters for most of the cases, except when 0=500 . Analyses conducted using the fluctuations in the mean wind field reveal that the resonant response of the conductor and ground wire cables can be neglected, a fact that was confirmed by the values obtained from the slope of the trend lines held.

Este trabalho apresenta e compara alguns meios para o estudo do comportamento dinâmico de uma lavadora de roupas de eixo vertical durante o processo de extração de água das roupas, também conhecido como centrifugação. Os três métodos utilizados para estudar o comportamento dinâmico de uma lavadora de roupas de eixo vertical foram: analítico, experimental e simulação através de multicorpos. O interesse nesta etapa é devido ao fato dos problemas de vibração de uma lavadora ocorrerem principalmente durante a centrifugação. A modelagem de uma lavadora de roupas durante a etapa de centrifugação permite a obtenção de seu comportamento dinâmico bem como de suas principais características. Um outro tópico estudado neste trabalho foi o fenômeno de deslocamento da lavadora, um dos principais motivos de reclamação dos usuários de lavadoras de roupa automáticas. / This work presents and compares some ways to study the dynamic behavior of a vertical axis washing machine during the water extraction process, also called spinning stage. The three methodologies used to study the dynamic behavior of a vertical axis washing machine area: analytical, experimental and simulation using Multi Body System. The interest in this stage is due to the fact that the main vibration problems of an automatic washing machine occur in the spinning cycle. Since the unbalance force that causes the vibration problems is centrifugal in nature, this makes intuitive sense as the rotational speed of the basket is the largest during the spin extraction cycle. Thus, modeling the washing machine during the spinning cycle allow us to get its dynamic behavior as well as the main characteristics of this behavior. Another topic studied in this work was the walking phenomenon, the main complaint of the users.

Les palettes sont très largement utilisées pour le transport, le stockage et la manutention de marchandises. Une palette chargée de bouteilles d'eau (emballage tertiaire) est constituée : d'une palette en bois, des packs (emballages secondaires) contenant un ensemble de 6 bouteilles d'eau (emballages primaires) enveloppés par un film plastique, des intercalaires en carton ondulé, et d'une housse plastique rétractable ou étirable pour le maintien et la protection de la marchandise palettisée. L'objectif général de cette thèse est de modéliser et de simuler le comportement statique et dynamique d'une palette durant le transport routier à l'aide du logiciel Abaqus. La simulation détaillée des bouteilles, des packs et des intercalaires constituants la palette est très fastidieuse et complexe à mettre en œuvre. Nous proposons de réaliser l'homogénéisation sur les packs et les intercalaires pour diminuer largement le temps de préparation des géométries et des maillages, ainsi que le temps CPU. Un modèle d'homogénéisation de l'intercalaire en carton ondulé est proposé. Il consiste à calculer les rigidités globales pour une plaque homogène équivalente. Ce modèle d'homogénéisation analytique permet de calculer rapidement et correctement ces rigidités globales et leurs couplages. Le comportement suivant l'épaisseur de l'intercalaire a beaucoup d'influence sur le glissement des packs. Nous avons donc développé un modèle solide en trois couches pour prendre compte le comportement élasto-plastique suivant l'épaisseur. Le pack de 6 bouteilles d'eau a été homogénéisé en caractérisant son comportement global par des essais expérimentaux et des simulations par la méthode des éléments finis. Le remplacement des packs par des solides homogènes de forme simplifiée permet de diminuer largement le nombre d'éléments et d'éviter le traitement du contact bouteille-bouteille et bouteille-film. De nombreux essais expérimentaux et simulations numériques avec nos modèles d'homogénéisation ont été réalisés pour étudier le comportement statique et dynamique de palettes chargées de bouteilles d'eau. Les résultats obtenus par les essais expérimentaux et les simulations numériques sont comparés pour valider nos modèles d'homogénéisation. / Pallet systems are widely used for the transport, storage, stacking and handling of goods. A pallet charged with bottles of water (tertiary packaging) is composed of: a wooden pallet, packs (secondary packaging) containing a set of 6 bottles of water (primary packaging) wrapped with a plastic film, the cardboard sheet insert, and a plastic film for the maintenance and protection of the palletized goods. The aim of this thesis is to model and to simulate the static and dynamic behaviors of a charged pallet during the transport using the Abaqus software. The detailed simulation of the bottles, the packs and the cardboard sheet inserts constituting the pallet is very tedious and complex. We propose to homogenize the packs and cardboard inserts to largely reduce the time for the preparation of geometries and meshes, as well as the CPU time. A homogenization model for the cardboard inserts is proposed. It consists in calculating the global stiffness of the equivalent homogeneous plate. This analytical homogenization model allows calculating these global rigidities and their couplings quickly and correctly. The behavior in the thickness direction of the cardboard has a great influence on the sliding of the packs. We have developed a three layers solid model to take into account the elasto-plastic behavior through the thickness. The pack of 6 bottles of water is homogenized by characterizing its global behavior by experimental measurements and simulations with the finite element method. Replacing the packs by a simplified homogeneous solid permit to greatly reduce the number of elements and avoid the contact treatment between bottle-bottle and bottle-film. Many experimental tests and numerical simulations using our homogenization models have been achieved to study the static and dynamic behaviors of pallets. The results obtained by experimental tests and numerical simulations are compared to validate our homogenization models.

<p>Predmet ove doktorske disertacije je analiza dinamičkog ponašanja<br />kotrljajnih ležaja primenom veštačkih neuronskih mreža. Na bazi<br />rezultata eksperimentalnog ispitivanja obučene su veštačke<br />neuronske mreže koje su sposobne da predvide amplitude brzine<br />vibracija ležaja. Vibracije koje ležaj generiše zavise od niza<br />uticajnih parametara koji se mogu podeliti na konstrukcione,<br />tehnološke i eksploatacione. Modeli dobijeni primenom veštačkih<br />neuronskih mreža određuju zavisnosti između uticajnih parametara i<br />amplituda brzine vibracija koje ležaj generiše. Validacija<br />neuronskih modela izvršena je na osnovu eksperimentalnih rezultata.<br />Analiziran je uticaj svakog parametra ležaja na amplitude brzine<br />vibracija u karakterističnim područjima frekvencija. U radu su<br />prikazani i rezultati međusobnog uticaja više parametara. Modelima<br />su dobijene preporučene vrednosti uticajnih parametara ležaja. Pri<br />analizi tehnoloških parametara uvedeni su: parametar ekvivalentne<br />površinske hrapavosti, parametar ekvivalentne valovitosti i<br />parametar ekvivalentnog odstupanja od kružnosti staza kotrljanja.<br />Novouvedeni parametri omogućavaju bolje razumevanje uticaja na<br />dinamičko ponašanje. U radu je pokazano da su neuronski modeli<br />sposobni da na osnovu parametara ležaja predvide klasu kvaliteta<br />ležaja.</p> / <p>The subject of this doctoral dissertation is the analysis of the dynamic<br />behavior of ball bearings using artificial neural networks. Based on the<br />results of the experimental test, artificial neural networks were trained to be<br />able to predict the amplitudes of the bearing vibration velocity. The vibrations<br />generated by the bearing depend on a number of influential parameters that<br />can be divided into construction, technological and exploitation. Models<br />obtained by applying artificial neural networks determined the dependences<br />between the influencing parameters and the amplitudes of the vibration<br />velocity generated by the bearing. Validation of neural models was<br />performed based on experimental results. The influence of each parameter<br />on the vibration velocity amplitudes in the characteristic frequency ranges<br />was analyzed. The paper also presents the results of the mutual influence of<br />several parameters. The models obtained the recommended values of the<br />influential bearing parameters. In the analysis of technological parameters,<br />the following parameters were introduced: the parameter of equivalent<br />surface roughness, the parameter of equivalent waviness and the parameter<br />of equivalent roundness error of raceways. The newly introduced parameters<br />provide a better understanding of the impact on dynamic behavior. The paper<br />shows that neural models are able to predict the bearing quality class based<br />on bearing parameters.</p>

Las nuevas aplicaciones y servicios web, cada vez má¡s populares en nuestro día a día, han cambiado completamente la forma en la que los usuarios interactúan con la Web. En menos de media década, el papel que juegan los usuarios ha evolucionado de meros consumidores pasivos de información a activos colaboradores en la creación de contenidos dinámicos, típicos de la Web actual. Y, además, esta tendencia se espera que aumente y se consolide con el paso del tiempo. Este comportamiento dinámico de los usuarios es una de las principales claves en la definición de cargas de trabajo adecuadas para estimar con precisión el rendimiento de los sistemas web. No obstante, la dificultad intrínseca a la caracterización del dinamismo del usuario y su aplicación en un modelo de carga, propicia que muchos trabajos de investigación sigan todavía empleando cargas no representativas de las navegaciones web actuales. Esta tesis doctoral se centra en la caracterización y reproducción, para estudios de evaluación de prestaciones, de un tipo de carga web más realista, capaz de imitar el comportamiento de los usuarios de la Web actual. El estado del arte en el modelado y generación de cargas para los estudios de prestaciones de la Web presenta varias carencias en relación a modelos y aplicaciones software que representen los diferentes niveles de dinamismo del usuario. Este hecho nos motiva a proponer un modelo más preciso y a desarrollar un nuevo generador de carga basado en este nuevo modelo. Ambas propuestas han sido validadas en relación a una aproximación tradicional de generación de carga web. Con este fin, se ha desarrollado un nuevo entorno de experimentación con la capacidad de reproducir cargas web tradicionales y dinámicas, mediante la integración del generador propuesto con un benchmark de uso común. En esta tesis doctoral también se analiza y evalúa por primera vez, según nuestro saber y entender, el impacto que tiene el empleo de cargas de trabajo dinámicas en las métrica / Peña Ortiz, R. (2013). Accurate workload design for web performance evaluation [Tesis doctoral]. Editorial Universitat Politècnica de València. https://doi.org/10.4995/Thesis/10251/21054 / Palancia

In this study the author reports the effects of surface roughness on dynamic behavior of water droplets on different types of rough structures. First, the influence of roughness geometry on the Wenzel/ Cassie-Baxter transition of water droplets on one-tier (solid substrates with Si micropillars) surfaces is studied (Chapter 3). In order to address distinct wetting behaviors of the advancing and receding motions, the author investigates the Wenzel/ Cassie-Baxter transition of water droplets on one-tier surfaces over a wide range of contact line velocities and droplet volumes in both advancing and receding movements. The discussions are strengthened by experimental results. According to the author’s analysis, the advancing contact zone tends to follow the Cassie-Baxter behavior for a wider range of geometric ratios than the receding contact zone. Physical phenomena such as advancing contact line rolling mechanism and the pinning of the receding contact line are introduced to justify distinct transition points of the advancing and receding movements respectively. Based on the analysis provided in Chapter 3, the author experimentally investigates the contact line fluctuations and contact line friction coefficients of water droplets on smooth, one-tier, and two-tier (with carbon nanotubes (CNTs) grown on Si micropillars) surfaces in Chapters 4 and 5. Both the advancing and receding contact line fluctuations/friction coefficients have been measured, analyzed and compared on smooth, one-tier, and two-tier surfaces over a wide range of contact line velocities and droplet volumes. A comprehensive analysis is provided to explain the experimental observations.

No description available.

No description available.

No description available.

System dynamics has been used to better understand the dynamics within complex natural and social systems. This understanding enables us to make decisions and define strategies that help to resolve the problematic behaviors associated within these systems. For example within an operating environment such as the US Navy, decisions taken today can have long lasting impact on system performance. The Navy has experienced large cost overruns during the new technology implementation process on ship systems that can also have an impact on total life cycle performance. The integration phase of the implementation process represents most of the cost overruns experienced in the overall new technology life cycle (development, integration, and operation/support/disposal). We have observed a general concern that there is a lack of understanding for the dynamic behavior of those processes which comprise the integration phase, among ship-builders and planners. One of the goals of our research effort has been to better understand the dynamic behavior of the new technology integration processes, using a dynamic modeling technique known as System Dynamics. Our approach has also been to provide a comprehensive knowledge elicitation process in which members from the shipbuilding industry, the US Navy, and the Virginia Tech System Performance Laboratory take part in group model building exercises. The system dynamics model that is developed in this manner is based on data obtained from the experts. An investigation of these dynamics yields a dominant cost behavior that characterizes the technology integration processes. This behavior is S-shaped growth. The following two dynamic hypotheses relative to lifecycle cost and performance of the inserted new technology were confirmed: (1) For the current structure of the model we observe the more the complexity of the new technology, the less affordable a technology becomes; (2) Integration of immature (less developed) technologies is associated with higher costs. Another interesting insight is that cost is very sensitive to the material procurement. Future research can be addressed to a more detailed level of abstraction for various activities included in the technology integration phase, such as testing and evaluation, cost of rework and risks associated with inadequate testing etc. This will add to our evolving understanding of the behavior of individual activities in the technology integration process. / Master of Science