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  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
91

Mecanismos de transferência de carga em estacas escavadas em solos arenosos através de provas de carga instrumentadas

Sestrem, Liamara Paglia January 2018 (has links)
A experiência acumulada quanto à análise do comportamento de fundações, em relação aos diversos perfis de solos, vem confirmando a necessidade de realizar ensaios em verdadeira grandeza para avaliação de desempenho desses elementos. Aplicação de metodologias empíricas e semi-empíricas, limitadas à prática construtiva regional e às condições específicas que contemplaram o seu estabelecimento, resultam em incertezas nos métodos de previsão e dispersão entre valores de capacidade de carga medidos e previstos. Com base nessas evidências, os ensaios de prova de carga representam a técnica mais comumente empregada para previsão e avaliação da capacidade de suporte em estacas. Como resultado, obtém-se uma curva carga versus deslocamento a partir de um carregamento estático no topo do elemento. Quando executadas em estacas instrumentadas ao longo do fuste, permitem avaliar a mobilização (transferência) de resistências (cargas) ao longo da profundidade e dos carregamentos. Alternativamente, o uso de células expansivas bidirecionais, comumente denominadas de “O-cell”, vem crescendo em nível internacional e confirmando seu potencial de aplicação, embasado por vantagens que incluem a ausência de um sistema de reação e a obtenção de forma direta da resistência de ponta e atrito lateral durante os carregamentos. No intuito de contribuir para uma melhor compreensão dos mecanismos de transferência de carga envolvidos em ensaios estáticos, o presente estudo comparou resultados dessas duas metodologias através de três de ensaios estáticos convencionais e um bidirecional realizados em duas estacas escavadas de grande diâmetro em areia. A distribuição dos carregamentos medidos em função do deslocamento em termos de carga total e de atrito lateral ao longo desses quatro ensaios caracterizou-se por resultados similares. Pequenas diferenças foram observadas entre o ensaio de topo e bidirecional executados em um mesmo elemento de fundação e estão possivelmente associadas aos diferentes níveis de deformação obtidos com as duas técnicas. As condições de limpeza e integridade da ponta em estacas moldadas in loco estão associadas a incertezas ainda que os procedimentos usuais de controle e limpeza tenham sido executados. Divergências entre a parcela de contribuição de ponta ao longo dos ensaios avaliados podem estar associadas a esses fatores e a pequenas variações da geometria descritas em detalhes no trabalho. Deformações medidas pelos strain gages instalados ao longo do fuste da estaca permitiram avançar no entendimento dos mecanismos de transferência de carga existentes durante os carregamentos impostos. Os resultados indicam que o atrito começa a ser mobilizado desde os primeiros incrementos de carga e permanece se desenvolvendo com o aumento das deformações que não são constantes ao longo da profundidade. O comportamento medido ao longo do fuste varia em função do nível de confinamento e ainda da densidade relativa do solo subjacente. Os resultados permitem concluir também que ainda que existam esforços residuais atuantes, sua ordem de grandeza não reflete mudanças importantes no comportamento de elementos de fundação moldados in loco. / The gained experience in foundations behavior analysis on different soil profiles confirms the need to perform tests on full-scale elements to evaluate pile performance. Application of empirical and semi-empirical methodologies, limited to the regional constructive practice and the specific conditions that led to its establishment, result in uncertainties in the prediction and dispersion methods between measured and predicted load capacity values. Based on these evidences, the load tests represent the most commonly used technique for predicting and evaluating pile capacity. As a result, a load versus displacement curve is obtained from a static load at the top of the element. When carried out in piles instrumented along the shaft, it is possible to evaluate the mobilization (transfer) of resistances (loads) along the depth and the loads. Alternatively, the use of bidirectional expansive cells, commonly referred to as "O-cell", has been growing internationally, which confirms its potential, based on advantages that include the absence of a reaction system and obtaining the toe resistance and lateral friction directly during loading. In order to contribute to a better understanding of the load transfer mechanisms involved in static loading tests, the present study compared the results of these two methodologies through three conventional and one bidirectional load tests carried out on two large diameter bored piles. The distribution of loadings measured as a function of the displacement in terms of total load and lateral friction over these four tests was characterized by similar results. Small differences were observed between conventional top-down and bidirectional tests performed on the same foundation member and are possibly associated with the different deformation levels obtained with the two techniques. Cleaning conditions and pile toe integrity in bored piles are associated with uncertainties even though the usual control and cleaning procedures have been performed. Divergences between the contributions of the pile toe resistance along the evaluated tests may be associated with these factors and small variations of the geometry. Deformations measured by the strain gages installed along the pile shaft allowed improving the understanding of the load transfer mechanisms during the loading procedures. The results indicate that shaft friction begins to be mobilized since the first load increments and continues to increase with the strains, which are not linear along the pile shaft. The behavior measured along the shaft is a function of vertical effective stress and relative density. The results also show that although there are active residual stresses, their magnitude does not reflect important changes in the behavior of bored piles.
92

Tecnologias relacionadas aos veículos elétricos e análise de um modelo de carregador para uso em redes de distribuição

Echeverri, Wberney Sanchez January 2014 (has links)
Orientador: Prof. Dr. Thales Sousa / The world has been searching different sorts of technology to mitigate any energetic crises in function in a growing demand of energy, resulting by generation of pollutants from the actual energy source uses. Developments of new technology application as electric transport with rechargeable cell are actually trends to mitigate these problems, cooperating to reduce energetic and environmental issues. In order, the present work proposes a two electric vehicles study, emphasizing the different classification of each other, depending on how electric and combustion energies are integrated. Different promising technological trend are presented to enhance the driving autonomy from the vehicles as the different ways to storage of energy and fuel feeding methods. Otherwise, the impacts on distribution network, environmental impacts and economic impacts are defined. Ultimately, it¿s made analysis bidirectional battery charger to an electric vehicle, considering every charger module in coupled manner, as the practice must be provided. The charger is made-up by a CA/CC Full-bridge bidirectional converter with power factor controller PFC, and CA/CC Full-bridge bidirectional converter isolation properties. These converters work altogether, providing from the energy distribution network to charge a battery cell and providing energy from the battery cell to the energy distribution network. / Dissertação (mestrado) - Universidade Federal do ABC, Programa de Pós-Graduação em Engenharia Elétrica, 2014. / O mundo vem buscando diferentes tecnologias que mitiguem a possibilidade de uma crise energética, em função de uma demanda crescente de energia e uma crise ambiental, resultante das emissões de poluentes advinda das fontes de energia atualmente utilizadas. O desenvolvimento de novas tecnologias, como por exemplo, os meios de transporte elétricos recarregáveis, contribuem para que esses problemas sejam mitigados, colaborando para a minimização dos problemas energéticos e ambientais. Nesse sentido, o presente trabalho propõe o estudo dos veículos elétricos, enfatizando as diferentes classificações dos mesmos, dependendo de como a energia elétrica e a energia de combustão são integradas. São apresentadas também, as tecnologias de geração de energia mais promissoras para o aumento de autonomia de condução, bem como as formas de armazenamento da energia e como os veículos elétricos são alimentados. Adicionalmente, são indicados os impactos dos veículos elétricos na rede de distribuição, os impactos ao ambiente e os impactos econômicos. Por último, é feita uma análise de um carregador de baterias bidirecional para um veículo elétrico, considerando todos os módulos do carregador de maneira acoplada, conforme deve ser previsto na pratica. O carregador esta composto por um conversor bidirecional CA/CC Full-Bridge com propriedades de correção de fator de potência e, um conversor bidirecional CC/CC Full-Bridge isolado. Estes conversores trabalham em conjunto fornecendo da rede de distribuição energia para carregar um banco de baterias e entregando energia das baterias à rede de distribuição.
93

SENSOR-BASED HUMAN ACTIVITY RECOGNITION USING BIDIRECTIONAL LSTM FOR CLOSELY RELATED ACTIVITIES

Pavai, Arumugam Thendramil 01 December 2018 (has links)
Recognizing human activities using deep learning methods has significance in many fields such as sports, motion tracking, surveillance, healthcare and robotics. Inertial sensors comprising of accelerometers and gyroscopes are commonly used for sensor based HAR. In this study, a Bidirectional Long Short-Term Memory (BLSTM) approach is explored for human activity recognition and classification for closely related activities on a body worn inertial sensor data that is provided by the UTD-MHAD dataset. The BLSTM model of this study could achieve an overall accuracy of 98.05% for 15 different activities and 90.87% for 27 different activities performed by 8 persons with 4 trials per activity per person. A comparison of this BLSTM model is made with the Unidirectional LSTM model. It is observed that there is a significant improvement in the accuracy for recognition of all 27 activities in the case of BLSTM than LSTM.
94

Particle Trajectories in Wall-Normal and Tangential Rocket Chambers

Katta, Ajay 01 August 2011 (has links)
The focus of this study is the prediction of trajectories of solid particles injected into either a cylindrically- shaped solid rocket motor (SRM) or a bidirectional vortex chamber (BV). The Lagrangian particle trajectory is assumed to be governed by drag, virtual mass, Magnus, Saffman lift, and gravity forces in a Stokes flow regime. For the conditions in a solid rocket motor, it is determined that either the drag or gravity forces will dominate depending on whether the sidewall injection velocity is high (drag) or low (gravity). Using a one-way coupling paradigm in a solid rocket motor, the effects of particle size, sidewall injection velocity, and particle-to-gas density ratio are examined. The particle size and sidewall injection velocity are found to have a greater impact on particle trajectories than the density ratio. Similarly, for conditions associated with a bidirectional vortex engine, it is determined that the drag force dominates. Using a one-way particle tracking Lagrangian model, the effects of particle size, geometric inlet parameter, particle-to-gas density ratio, and initial particle velocity are examined. All but the initial particle velocity are found to have a significant impact on particle trajectories. The proposed models can assist in reducing slag retention and identifying fuel injection configurations that will ensure proper confinement of combusting droplets to the inner vortex in solid rocket motors and bidirectional vortex engines, respectively.
95

Vuxna influeras av barn och barn influeras av vuxna : - en litteraturstudie om kommunikationsprocesser vid konflikter och konflikthantering

Rickblad, Maria, Ågren, Sarah January 2011 (has links)
Syftet med den här litteraturstudien är att skapa perspektiv kring kommunikationen vid konflikter och konflikthantering. Fokus ligger främst på vuxnas och barns samspel, med stark betoning på lärare/pedagog - elev/barn relationer. De tre frågeställningarna som ligger till grund för denna studie är; Var, hur, när och varför sker kommunikation enligt åtta engelskspråkiga artiklar? Vad anser åtta engelskspråkiga artiklar om hur kommunikation i form av samtal kan främja konflikthantering? och Vilken betydelse får relationer för konflikter och konflikthantering enligt åtta engelskspråkiga artiklar? Svaren till frågeställningarna har hittats genom att belysa åtta studier och dess resultat. Forskningsöversikten är tänkt att ge läsaren en tydlig bild över kommunikationens betydelse vid konflikter och konflikthantering. Resultatet av studien visar att kommunikation i form av exempelvis samtal är av stor vikt vid konflikter och hanteringen av dessa. Andra huvudfaktorer som är av vikt är bland annat relationers betydelse, dubbelriktad påverkan, samt reflektion, utvärdering, och kontinuitet. Det har visat sig att vuxna influerar barn och att barn påverkar vuxna. Den dubbelriktade påverkan blir därmed en högst relevant faktor för kommunikationen i relationer. Att barn och vuxna har en god relation kan vara avgörande för konflikters uppkomst. I resultatet framkommer även att många konflikthanteringsprogram saknar kontinuitet, vilket denna studie konstaterat behövs för att konflikthanteringsprogrammen ska utnyttjas till fullo. / The purpose of this literature study is to provide perspectives on communication in conflict and conflict management. The focus is primarily on adults' and children's interactions, with a strong emphasis on teacher - child relationships. The three questions that form the basis of this study is: Where, how, when and why does communication take place according to eight english-language articles? What do eight english-language articles consider about how communication in the form of conversations can promote conflict resolution? and What impact have relationships of conflict and conflict management according to eight english-language articles? The answers to these questions have been found by highlighting eight studies and their results. The research review is intended to give the reader a clearer picture over the importance of communication in conflict and conflict management. The results of this study show that communication in the form of conversations is of great importance to the conflicts and how they are being managed. Other key factors that are of importance, include the significance of relationships, bidirectional influences, reflection, evaluation, and continuity. It has been shown that adults influence children and children affect adults. The bidirectional influence is a highly relevant factor for communication in relationships. Good relationships between children and adults are of importance in how conflicts emergence. The result also reveals that many conflict management programs lacks continuity, which this study found necessary, for conflict management programs so that they could be fully utilized.
96

Bidirectional LAO* Algorithm (A Faster Approach to Solve Goal-directed MDPs)

Bhuma, Venkata Deepti Kiran 01 January 2004 (has links)
Uncertainty is a feature of many AI applications. While there are polynomial-time algorithms for planning in stochastic systems, planning is still slow, in part because most algorithms plan for all eventualities. Algorithms such as LAO* are able to find good or optimal policies more quickly when the starting state of the system is known. In this thesis we present an extension to LAO*, called BLAO*. BLAO* is an extension of the LAO* algorithm to a bidirectional search. We show that BLAO* finds optimal or E-optimal solutions for goal-directed MDPs without necessarily evaluating the entire state space. BLAO* converges much faster than LAO* or RTDP on our benchmarks.
97

Behavioural Studies and Computational Models Exploring Visual Properties that Lead to the First Floral Contact by Bumblebees

Orbán, Levente L. 16 April 2014 (has links)
This dissertation explored the way in which bumblebees' visual system helps them discover their first flower. Previous studies found bees have unlearned preferences for parts of a flower, such as its colour and shape. The first study pitted two variables against each other: pattern type: sunburst or bull's eye, versus the location of the pattern: shapes appeared peripherally or centrally. We observed free-flying bees in a flight cage using Radio-Frequency Identification (RFID) tracking. The results show two distinct behavioural preferences: Pattern type predicts landing: bees prefer radial over concentric patterns, regardless of whether the radial pattern is on the perimeter or near the centre of the flower. Pattern location predicts exploration: bees were more likely to explore the inside of artificial flowers if the shapes were displayed near the centre of the flower, regardless of whether the pattern was radial or concentric. As part of the second component, we implemented a mathematical model aimed at explaining how bees come to prefer radial patterns, leafy backgrounds and symmetry. The model was based on unsupervised neural networks used to describe cognitive mechanisms. The results captured with the results of multiple behavioural experiments. The model suggests that bees choose computationally "cheaper" stimuli, those that contain less information. The third study tested the computational load hypothesis generated by the artificial neural networks. Visual properties of symmetry, and spatial frequency were tested. Studying free-flying bees in a flight cage using motion-sensitive video recordings, we found that bees preferred 4-axis symmetrical patterns in both low and high frequency displays.
98

Coding for Relay Networks with Parallel Gaussian Channels

Huang, Yu-Chih 03 October 2013 (has links)
A wireless relay network consists of multiple source nodes, multiple destination nodes, and possibly many relay nodes in between to facilitate its transmission. It is clear that the performance of such networks highly depends on information for- warding strategies adopted at the relay nodes. This dissertation studies a particular information forwarding strategy called compute-and-forward. Compute-and-forward is a novel paradigm that tries to incorporate the idea of network coding within the physical layer and hence is often referred to as physical layer network coding. The main idea is to exploit the superposition nature of the wireless medium to directly compute or decode functions of transmitted signals at intermediate relays in a net- work. Thus, the coding performed at the physical layer serves the purpose of error correction as well as permits recovery of functions of transmitted signals. For the bidirectional relaying problem with Gaussian channels, it has been shown by Wilson et al. and Nam et al. that the compute-and-forward paradigm is asymptotically optimal and achieves the capacity region to within 1 bit; however, similar results beyond the memoryless case are still lacking. This is mainly because channels with memory would destroy the lattice structure that is most crucial for the compute-and-forward paradigm. Hence, how to extend compute-and-forward to such channels has been a challenging issue. This motivates this study of the extension of compute-and-forward to channels with memory, such as inter-symbol interference. The bidirectional relaying problem with parallel Gaussian channels is also studied, which is a relevant model for the Gaussian bidirectional channel with inter-symbol interference and that with multiple-input multiple-output channels. Motivated by the recent success of linear finite-field deterministic model, we first investigate the corresponding deterministic parallel bidirectional relay channel and fully characterize its capacity region. Two compute-and-forward schemes are then proposed for the Gaussian model and the capacity region is approximately characterized to within a constant gap. The design of coding schemes for the compute-and-forward paradigm with low decoding complexity is then considered. Based on the separation-based framework proposed previously by Tunali et al., this study proposes a family of constellations that are suitable for the compute-and-forward paradigm. Moreover, by using Chinese remainder theorem, it is shown that the proposed constellations are isomorphic to product fields and therefore can be put into a multilevel coding framework. This study then proposes multilevel coding for the proposed constellations and uses multistage decoding to further reduce decoding complexity.
99

Mecanismos de transferência de carga em estacas escavadas em solos arenosos através de provas de carga instrumentadas

Sestrem, Liamara Paglia January 2018 (has links)
A experiência acumulada quanto à análise do comportamento de fundações, em relação aos diversos perfis de solos, vem confirmando a necessidade de realizar ensaios em verdadeira grandeza para avaliação de desempenho desses elementos. Aplicação de metodologias empíricas e semi-empíricas, limitadas à prática construtiva regional e às condições específicas que contemplaram o seu estabelecimento, resultam em incertezas nos métodos de previsão e dispersão entre valores de capacidade de carga medidos e previstos. Com base nessas evidências, os ensaios de prova de carga representam a técnica mais comumente empregada para previsão e avaliação da capacidade de suporte em estacas. Como resultado, obtém-se uma curva carga versus deslocamento a partir de um carregamento estático no topo do elemento. Quando executadas em estacas instrumentadas ao longo do fuste, permitem avaliar a mobilização (transferência) de resistências (cargas) ao longo da profundidade e dos carregamentos. Alternativamente, o uso de células expansivas bidirecionais, comumente denominadas de “O-cell”, vem crescendo em nível internacional e confirmando seu potencial de aplicação, embasado por vantagens que incluem a ausência de um sistema de reação e a obtenção de forma direta da resistência de ponta e atrito lateral durante os carregamentos. No intuito de contribuir para uma melhor compreensão dos mecanismos de transferência de carga envolvidos em ensaios estáticos, o presente estudo comparou resultados dessas duas metodologias através de três de ensaios estáticos convencionais e um bidirecional realizados em duas estacas escavadas de grande diâmetro em areia. A distribuição dos carregamentos medidos em função do deslocamento em termos de carga total e de atrito lateral ao longo desses quatro ensaios caracterizou-se por resultados similares. Pequenas diferenças foram observadas entre o ensaio de topo e bidirecional executados em um mesmo elemento de fundação e estão possivelmente associadas aos diferentes níveis de deformação obtidos com as duas técnicas. As condições de limpeza e integridade da ponta em estacas moldadas in loco estão associadas a incertezas ainda que os procedimentos usuais de controle e limpeza tenham sido executados. Divergências entre a parcela de contribuição de ponta ao longo dos ensaios avaliados podem estar associadas a esses fatores e a pequenas variações da geometria descritas em detalhes no trabalho. Deformações medidas pelos strain gages instalados ao longo do fuste da estaca permitiram avançar no entendimento dos mecanismos de transferência de carga existentes durante os carregamentos impostos. Os resultados indicam que o atrito começa a ser mobilizado desde os primeiros incrementos de carga e permanece se desenvolvendo com o aumento das deformações que não são constantes ao longo da profundidade. O comportamento medido ao longo do fuste varia em função do nível de confinamento e ainda da densidade relativa do solo subjacente. Os resultados permitem concluir também que ainda que existam esforços residuais atuantes, sua ordem de grandeza não reflete mudanças importantes no comportamento de elementos de fundação moldados in loco. / The gained experience in foundations behavior analysis on different soil profiles confirms the need to perform tests on full-scale elements to evaluate pile performance. Application of empirical and semi-empirical methodologies, limited to the regional constructive practice and the specific conditions that led to its establishment, result in uncertainties in the prediction and dispersion methods between measured and predicted load capacity values. Based on these evidences, the load tests represent the most commonly used technique for predicting and evaluating pile capacity. As a result, a load versus displacement curve is obtained from a static load at the top of the element. When carried out in piles instrumented along the shaft, it is possible to evaluate the mobilization (transfer) of resistances (loads) along the depth and the loads. Alternatively, the use of bidirectional expansive cells, commonly referred to as "O-cell", has been growing internationally, which confirms its potential, based on advantages that include the absence of a reaction system and obtaining the toe resistance and lateral friction directly during loading. In order to contribute to a better understanding of the load transfer mechanisms involved in static loading tests, the present study compared the results of these two methodologies through three conventional and one bidirectional load tests carried out on two large diameter bored piles. The distribution of loadings measured as a function of the displacement in terms of total load and lateral friction over these four tests was characterized by similar results. Small differences were observed between conventional top-down and bidirectional tests performed on the same foundation member and are possibly associated with the different deformation levels obtained with the two techniques. Cleaning conditions and pile toe integrity in bored piles are associated with uncertainties even though the usual control and cleaning procedures have been performed. Divergences between the contributions of the pile toe resistance along the evaluated tests may be associated with these factors and small variations of the geometry. Deformations measured by the strain gages installed along the pile shaft allowed improving the understanding of the load transfer mechanisms during the loading procedures. The results indicate that shaft friction begins to be mobilized since the first load increments and continues to increase with the strains, which are not linear along the pile shaft. The behavior measured along the shaft is a function of vertical effective stress and relative density. The results also show that although there are active residual stresses, their magnitude does not reflect important changes in the behavior of bored piles.
100

Design of Bidirectional DC/DC Battery Management System for Electrical Yacht

Celius Zacharek, Daniel, Sundqvist, Filip January 2018 (has links)
Electrical vehicles are getting more popular as the technology around batteries and electrical motors are catching up to the more common combustion engines. Electrical boats are no exception but there are still a lot of boats using old combustion engines that have a big impact on the environment. This study aims to deepen the understanding of the integration of electrical motors into boats by proposing a design of a system using a bidirectional synchronous buckboost converter. This converter is designed to handle the power transfer in a dual battery application, namely consisting of a 12 V battery and a 48 V battery. The converter includes proposed components, a PCB design, as well as the software that is required for the control of the power transfer. The results show that the converter design meets specification and, when using a test-bench, the software is capable of controlling the converter to achieve constant current and constant voltage in both directions.

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