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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.
21

Alocação de dispositivos de proteção em redes de distribuição primária de energia. / Allocation of protecting devices energy primary distribution network.

Marcelo Maia 27 November 2014 (has links)
Este trabalho apresenta uma metodologia de alocação de dispositivos de proteção e manobra ao longo de alimentadores primários de um sistema de distribuição de energia elétrica, de forma a otimizar a quantidade de consumidores afetados e da energia média não distribuída, na ocorrência de desligamentos provocados por uma falha. Na alocação dos dispositivos, utiliza-se um algoritmo matemático que considera vários parâmetros envolvidos no fenômeno, que explicam o mérito de cada alternativa possível, ponderando as variações de benefício. Além de indicar os locais adequados para instalação dos dispositivos de proteção e manobra, a metodologia proposta permite a elaboração de regras para auxiliar a priorização de ações de manutenção e para otimizar os investimentos em alimentadores. Outro resultado da pesquisa é a relocação de dispositivos de proteção e manobra existentes em alimentadores, considerando o seu reposicionamento para melhorar o desempenho em face de faltas que provocam interrupções e portanto diminuindo os indicadores FEC frequência média de interrupção de fornecimento e a END pela energia média não distribuída.Com o objetivo de comprovar a eficácia da metodologia proposta, desenvolveu-se uma ferramenta para sua operacionalização e posterior aplicação com sucesso, em um Estudo de Caso real de uma Concessionária brasileira. / This paper presents a methodology for allocation of protection and switching devices along primary feeders of a system for electricity distribution in order to optimize both the number of affected consumers and the average amount of energy that is not supplied, in case of interruptions caused by a failure. For the allocation of the devices it is used a mathematical algorithm that considers various parameters involved in the phenomenon, explaining the relevance of each possible alternative and pondering benefit variations. Besides indicating the adequate places to install the protection and switching devices, the proposed methodology allows elaborating roles that help taking prior actions to maintain and optimize the investments in feeders. Other aspect of the research is the relocation of protection and switching devices that exist in the feeders, considering their replacing in order to enhance the performance in the occurrence of failures that cause interruptions and so, reducing the FEC indicators supplying interruption medium frequency and the END (Energy not supplied). Aiming to prove the effectiveness of the proposed methodology, it was developed a tool for its operation and subsequent successful application in a study case, that represents a real situation of a Brazilian electrical power retailer company.
22

Estudo da eficácia de protetores bucais para esporte quanto à espessura por meio de análise em elementos finitos / Finite element analysis of the efficacy of sports mouthguards regarding thickness

Gialain, Ivan Onone 11 September 2015 (has links)
Atletas de diversas modalidades esportivas estão sujeitos a sofrer lesões no complexo dento-maxilo-facial por diversos impactos mecânicos, como choques contra o solo, outros atletas, bolas, etc. As principais preocupações dos cirurgiões-dentistas em relação a esses choques são as lesões irreversíveis em elementos dentais e/ou bases ósseas. A melhor estratégia para controlar a ocorrência e gravidade dessas lesões é a utilização de protetores bucais invidualizados, que além da proteção, não diminuem o desempenho dos atletas. Para avaliar a eficiência dos protetores bucais a análise por elementos finitos foi empregada, e o objetivo do presente trabalho foi avaliar o comportamento mecânico do protetor em EVA de diversas espessuras diferentes. A análise por elementos finitos foi conduzida utilizando a geometria de um incisivo central obtida por meio de tomografia computadorizada. A simulação foi constituída pelo esmalte e dentina do elemento dental, protetor bucal em EVA e uma esfera de borracha que era o objeto impactante. As geometrias foram transformadas em elementos sólidos e apenas os nós do terço apical da dentina radicular foram fixados. O pré-processamento foi realizado no Hypermesh® e no LS-PrePost®,o processamento foi feito pelo software LS-DYNA®.O estudo foi observado em 3D. Foram observadas a máxima e a tensão mínima principal no esmalte e na dentina em cinco variáveis: com protetor bucal de 1mm, 2mm, 3mm e 4mm, e como grupo controle foi utilizada uma geometria simples sem EVA. A tensão mínima principal no esmalte ocorreu no centro da face vestibular e seu valor foi maior sem o protetor bucal e diminuiu com o aumento da espessura do protetor, a tensão máxima no esmalte ocorreu na união entre esmalte e dentina na face vestibular. Na dentina a tensão máxima principal ocorreu na face vestibular da raiz e a tensão mínima ocorreu na face palatina. Os resultados mostraram que o protetor bucal foi benéfico, diminuindo as tensões compressivas e de tração no esmalte, porém não mostrou significante melhoria quando as tensões na dentina foram comparadas. / In different sports, the athletes are likely to experience injuries on teeth, soft tissue and bone, usually by mechanic trauma, such as falling on the ground, shocking against other player, balls, etc. The dentist main concerns are the permanent injuries on teeth and bone complex. The best strategy to fight these impairments still is the prevention, using individualized sports mouthguards. To evaluate the efficacy of the mouthguards, the finite element analysis was used, and the purpose of the present study was to evaluate the mechanical behavior to the EVA mouthguard on different thickness. The finite element analysis was made using geometry of a superior central incisor, which was acquired by computerized tomography. The simulation was made with enamel and dentin from the tooth, an EVA mouthguard and a rubber sphere that was the impacting object. All geometries was transformed into solid elements and the knots on the apical third of the root dentin were fixed. The pre-process was made using Hypermesh® and LS-PrePost® e and processing of data was made on LS-DYNA® software. The results were the maximum and minimum main stress on the enamel and dentin solids in five different situations: no mouthguard and mouthguard with thickness of 1mm, 2mm, 3mm and 4mm. The minimum main stress on the enamel was measured at the center of the vestibular surface and the higher value was observed with no mouthguard and the values decreased as the thickness of the mouthguard increased, the maximum main stress on enamel occurred near the amelodentin junction on the vestibular surface, but no significant changes were observed among the situations. As for the dentin the maximum main stress occurred on the buccal surface of the root, and the minimum main stress on the lingual surface. The results show that the mouthguard was efficient decreasing the compressive and tensile stress on enamel, but did not make significant improvement as on both stresses on dentin.
23

Examination of the association between the frequency of helmet use and other lifestyle behaviors a report submitted in partial fulfillment ... for the degree of Master of Science, Parent-Child Nursing ... /

Yee, Michelle M. January 1996 (has links)
Thesis (M.S.)--University of Michigan, 1996.
24

Estudo da eficácia de protetores bucais para esporte quanto à espessura por meio de análise em elementos finitos / Finite element analysis of the efficacy of sports mouthguards regarding thickness

Ivan Onone Gialain 11 September 2015 (has links)
Atletas de diversas modalidades esportivas estão sujeitos a sofrer lesões no complexo dento-maxilo-facial por diversos impactos mecânicos, como choques contra o solo, outros atletas, bolas, etc. As principais preocupações dos cirurgiões-dentistas em relação a esses choques são as lesões irreversíveis em elementos dentais e/ou bases ósseas. A melhor estratégia para controlar a ocorrência e gravidade dessas lesões é a utilização de protetores bucais invidualizados, que além da proteção, não diminuem o desempenho dos atletas. Para avaliar a eficiência dos protetores bucais a análise por elementos finitos foi empregada, e o objetivo do presente trabalho foi avaliar o comportamento mecânico do protetor em EVA de diversas espessuras diferentes. A análise por elementos finitos foi conduzida utilizando a geometria de um incisivo central obtida por meio de tomografia computadorizada. A simulação foi constituída pelo esmalte e dentina do elemento dental, protetor bucal em EVA e uma esfera de borracha que era o objeto impactante. As geometrias foram transformadas em elementos sólidos e apenas os nós do terço apical da dentina radicular foram fixados. O pré-processamento foi realizado no Hypermesh® e no LS-PrePost®,o processamento foi feito pelo software LS-DYNA®.O estudo foi observado em 3D. Foram observadas a máxima e a tensão mínima principal no esmalte e na dentina em cinco variáveis: com protetor bucal de 1mm, 2mm, 3mm e 4mm, e como grupo controle foi utilizada uma geometria simples sem EVA. A tensão mínima principal no esmalte ocorreu no centro da face vestibular e seu valor foi maior sem o protetor bucal e diminuiu com o aumento da espessura do protetor, a tensão máxima no esmalte ocorreu na união entre esmalte e dentina na face vestibular. Na dentina a tensão máxima principal ocorreu na face vestibular da raiz e a tensão mínima ocorreu na face palatina. Os resultados mostraram que o protetor bucal foi benéfico, diminuindo as tensões compressivas e de tração no esmalte, porém não mostrou significante melhoria quando as tensões na dentina foram comparadas. / In different sports, the athletes are likely to experience injuries on teeth, soft tissue and bone, usually by mechanic trauma, such as falling on the ground, shocking against other player, balls, etc. The dentist main concerns are the permanent injuries on teeth and bone complex. The best strategy to fight these impairments still is the prevention, using individualized sports mouthguards. To evaluate the efficacy of the mouthguards, the finite element analysis was used, and the purpose of the present study was to evaluate the mechanical behavior to the EVA mouthguard on different thickness. The finite element analysis was made using geometry of a superior central incisor, which was acquired by computerized tomography. The simulation was made with enamel and dentin from the tooth, an EVA mouthguard and a rubber sphere that was the impacting object. All geometries was transformed into solid elements and the knots on the apical third of the root dentin were fixed. The pre-process was made using Hypermesh® and LS-PrePost® e and processing of data was made on LS-DYNA® software. The results were the maximum and minimum main stress on the enamel and dentin solids in five different situations: no mouthguard and mouthguard with thickness of 1mm, 2mm, 3mm and 4mm. The minimum main stress on the enamel was measured at the center of the vestibular surface and the higher value was observed with no mouthguard and the values decreased as the thickness of the mouthguard increased, the maximum main stress on enamel occurred near the amelodentin junction on the vestibular surface, but no significant changes were observed among the situations. As for the dentin the maximum main stress occurred on the buccal surface of the root, and the minimum main stress on the lingual surface. The results show that the mouthguard was efficient decreasing the compressive and tensile stress on enamel, but did not make significant improvement as on both stresses on dentin.
25

Modern Adaptive Protection and Control Techniques for Enhancing Distribution Grid Resiliency

Barik, Tapas Kumar 04 June 2021 (has links)
Power distribution systems have underwent a lot of significant changes in the last two decades. Wide-scale integration of Distributed Energy Resources (DERs) have made the distribution grid more resilient to abnormal conditions and severe weather induced outages. These DERs enhance the reliability of the system to bounce back from an abnormal situation rather quickly. However, the conventional notion of a radial system with unidirectional power flow does not hold true due to the addition of these DERs. Bidirectional power flow has challenged the conventional protection schemes in place. The most notable effects on the protection schemes can be seen in the field of islanding or Loss of Mains(LOM) detection and general fault identification and isolation. Adaptive protection schemes are needed to properly resolve these issues. Although, previous works in this field have dealt with this situation, a more comprehensive approach needs to be taken considering multiple topologies for developing adaptive protection schemes. The most common protective devices widely deployed in the distribution system such as overcurrent relays, reverse power relays at Point of Common Coupling(PCC), fuses, reclosers and feeder breakers need to studied in implementing these schemes. The work presented in this dissertation deals with simulation based and analytical approaches to tackle the issues of islanding and adaptive protection schemes. First we propose a multiprinciple passive islanding detection technique which relies on local PCC measurements, thus reducing the need of additional infrastructure and still ensuring limited Non Detection Zone (NDZ). The next step to islanding detection would be to sustain a islanded distribution system in order to reduce the restoration time and still supply power to critical loads. Such an approach to maintain generator load balance upon islanding detection is studied next by appropriate shedding of non-critical and low priority critical loads based upon voltage sensitivity analysis. Thereafter, adaptive protection schemes considering limited communication dependency is studied with properly assigning relay settings in directional overcurrent relays (DOCRs), which are one of the most widely deployed protective devices in distribution systems by catering to multiple topologies and contingencies. A simulation based technique is discussed first and then an analytical approach to solve the conventional optimal relay coordination problem using Mixed Integer Linear Programming (MILP) with the usage of multiple setting groups is studied. All these approaches make the distribution more robust and resilient to system faults and ensure proper fault identification and isolation, ensuring overall safety of system. / Doctor of Philosophy / With widespread integration of inverter-based distributed energy resources (DERs) in the distribution grid, the conventional protection and control schemes no longer hold valid. The necessity of an adaptive protection scheme increases as the DER penetration in the system increases. Apart from this, changes in system topology and variability in DER generation, also change the fault current availability in the system in real-time. Hence, the protection schemes should be able to adapt to these variations and modify their settings for proper selectivity and sensitivity towards faults in the system, especially in systems with high penetration of DERs. These protection schemes need to be modified in order to properly identify and isolate faults in the network as well as correctly identify Loss of Mains (LOM) or islanding phenomenon. Special attention is needed to plan the next course of action after the islanding occurrence. Additionally, the protective devices in distribution system should be utilized to their maximum capability to create an adaptive and smart protection system. This document elaborately explains the research work pertaining to these areas.
26

Filtration des nanoparticules : application aux appareils de protection respiratoire / Filtration of nanoparticles : Application to Respiratory Protecting Devices

Brochot, Clothilde 11 May 2012 (has links)
Cette étude a pour objectif de déterminer dans quelle mesure les APR, dont les performances sont qualifiées pour des particules supérieures à 100 nm, sont efficaces pour des nanoparticules. En effet, dans le cas où l'utilisation d'une filtration collective est insuffisante, le port d'un Appareil de Protection Respiratoire (APR) est le dernier rempart préconisé. Une synthèse bibliographique a montré qu'aucune recherche n'a porté sur l'efficacité de demi-masques avec filtres pour des nanoparticules. Le banc d'ETude des NAnoparticules a été dimensionné et réalisé afin de pallier ces manques. Deux demi-masques ont été testés selon différentes configurations d'essais : débit constant et débit cyclique (débit moyen de 84 L/min) ; taille des particules (de 5 à 100 nm) ; pose du masque (scellée, libre, ou avec des fuites calibrées). Les résultats montrent que, dès lors que les APR utilisés contiennent des media (non électrets) efficaces pour des particules de la zone MPPS (100 nm - 300 nm), les APR sont plus efficaces pour les particules nanométriques. De plus, les résultats obtenus, en présence de fuites réelles et calibrées, ont mis en évidence l'importance des fuites au visage dans la détermination des performances des APR. Un modèle de calcul du facteur de protection a été établi, basé sur la différenciation des débits d'air traversant la fuite et le filtre. Cette modélisation a été validée à l'aide des mesures obtenues en présence des fuites calibrées, et appliquée pour l'analyse de nos résultats en pose libre / This study aims to determine how the respiratory protective devices (RPD), whose performances are qualified for particles above 100 nm, are effective for nanoparticles. Indeed, if the use of a collective filtration is inadequate, wearing a RPD is the last protection recommended. A literature review showed that no research concerned the effectiveness of half-masks for nanoparticles. The test bench ETNA has been sized and built to overcome these lacks. Two half masks were tested according to different configurations: constant flow rate and cyclic flow rate (average flow of 84 L /min) ; particle size (from 5 to 100 nm) ; positions of the mask (sealed, usual, or with calibrated leaks). The results show that, since the RPD contain high efficiency filter media (without charged fibers) for the most penetrating particle size (100 nm - 300 nm), the RPD is more efficient for nanoparticles. Furthermore, the results obtained in the presence of actual and calibrated leaks, highlighted the importance of faceseal leakages in determining the performance of RPD. A model for calculating the protection factor was established based on the balance between the airflow through the filter and the leak. This model was validated using measurements obtained in the presence of calibrated leaks, and applied for the analysis of our results in usual position
27

Músicos de pop-rock: efeitos da música amplificada e avaliação da satisfação no uso de protetores auditivos / Pop-rock musicians: effects of amplified music and assessment of satisfaction provided by the use hearing protectors

Santoni, Cristiane Bolzachini 28 February 2008 (has links)
Made available in DSpace on 2016-04-27T18:12:29Z (GMT). No. of bitstreams: 1 Cristiane Bolzachini Santoni.pdf: 934977 bytes, checksum: bee3fb27cb9f3fae28c2855452c296e7 (MD5) Previous issue date: 2008-02-28 / Coordenação de Aperfeiçoamento de Pessoal de Nível Superior / Purpose: The aim of the present study was to evaluate hearing and assess the satisfaction provided by the use hearing protectors in pop-rock musicians. Background: Studies have shown evidences of the risk of pop-rock musicians to develop hearing loss and other symptoms related to amplified music, as well as to adopt preventive measurements to protect their hearing. Method: It was evaluated 24 pop-rock musicians, male gender and ages between 25 to 45 years old, with professional experience between 3 to 21 years. It was accomplished: anamnesis, audiometric evaluation, transient otoacoustic emission (TEOAE), distortion product otoacoustic emission (DPOAE) and also was applied an ear protective devices satisfaction assessment questionnaire. Results: The prevalence of noise-induced hearing loss was 20.8%. In normal audiograms, there was a notch in high-frequencies in 58.4%, in at least one ear. The responses of TEOAEs were absent in 45.8% of the musicians and DPOAEs were absent in 58.4%. Concerning to satisfaction with the ear protective devices usage, 75.0% of the musicians evaluated them above grade 7.0. Conclusions: There was a high prevalence of hearing losses as well as alterations in TEOAEs and DPOAEs responses. Therefore, it is fundamental to develop and implement hearing loss preventive programs for musicians. There was a positive tendency towards the use of the ear protective devices / Objetivo: Avaliar a audição e o uso de protetores auditivos em músicos de bandas de pop-rock. Justificativa: Estudos demonstram evidências dos músicos de pop-rock apresentarem risco para o desenvolvimento de perda auditiva e outros efeitos associados à exposição à música amplificada, bem como a necessidade de adotar medidas de proteção à audição desses profissionais. Método: Foram avaliados 24 músicos de pop-rock, do sexo masculino, com idades entre 25 e 45 anos e com tempo de profissão entre três e 21 anos. Os sujeitos responderam a uma anamnese, realizaram avaliação audiométrica, realizaram os testes de emissões otoacústicas evocadas por estímulo transiente (EOAET) e emissões otoacústicas produto de distorção (EOAPD) e preencheram um questionário sobre a satisfação após o uso do protetor auditivo. Resultados: A prevalência de perdas auditivas sugestivas de PAIR foi de 20,8%. Dentre os audiogramas classificados como normais 58,4% apresentaram entalhe audiométrico em pelo menos uma orelha. No teste de emissões otoacústicas, 45,8% dos músicos tiveram respostas ausentes nas EOAET e 58,4% nas EOAPD. 75,0% dos músicos forneceram nota maior do que 7,0 para refletir sua satisfação no uso do protetor auditivo. Conclusões: Tanto a prevalência de perdas auditivas, quanto o número de ausências nos testes de EOAET e EOAPD foram elevados. Assim sendo, é necessária a implementação de um programa de prevenção de perdas auditivas com músicos. Houve uma tendência favorável à aceitação do protetor auditivo
28

On neck load among helicopter pilots : effects of head-worn equipment, whole-body vibration and neck position /

Thuresson, Marcus, January 2005 (has links) (PDF)
Diss. (sammanfattning) Stockholm : Karolinska institutet, 2005. / Härtill 5 uppsatser.
29

Examination of the association between the frequency of helmet use and other lifestyle behaviors a report submitted in partial fulfillment ... for the degree of Master of Science, Parent-Child Nursing ... /

Yee, Michelle M. January 1996 (has links)
Thesis (M.S.)--University of Michigan, 1996.
30

Uma nova metodologia para o desenvolvimento de projetos de proteção de redes ativas de distribuição de energia elétrica /

Conceição, Katiani Pereira January 2018 (has links)
Orientador: Javier Sanz Contreras / Resumo: Neste trabalho, apresenta-se uma nova proposta de metodologia para alocar, determinar e es-pecificar os tipos de dispositivos de controle e proteção em redes de distribuição com geração distribuída (GD). Esta metodologia é baseada em técnicas de otimização multiobjetivo para efetuar a alocação otimizada, coordenada e seletiva destes dispositivos. O modelo é composto por duas funções objetivo que consideram aspectos econômicos e da confiabilidade da rede, e um conjunto de restrições composto por restrições físicas, operacionais e um subconjunto de restrições baseadas em regras práticas das empresas do setor de distribuição e previstas em normas técnicas nacionais e internacionais que estabelecem a especificação, coordenação e seletividade dos dispositivos de controle e proteção instalados na rede. No modelo considera-se a possibilidade de transferência de carga entre alimentadores vizinhos e a operação ilhada da GD. Dessa forma, obtém-se um modelo genérico de programação não linear inteira mista (PNLIM) cujo diferencial com relação a outros modelos matemáticos da literatura é propor que no mesmo processo de otimização seja realizada a alocação otimizada dos dispositivos de controle e proteção na rede juntamente com a coordenação do sistema de proteção. A eficiên-cia do modelo matemático é comprovada comparando-se os resultados obtidos entre dois tes-tes com o auxílio do algoritmo genético (AG) mono-objetivo que considera a ponderação dos objetivos, enquanto que para a solução ... (Resumo completo, clicar acesso eletrônico abaixo) / Abstract: This paper, presents a new methodology for placing, selecting and specifying the control and the protective devices system of distribution networks with distributed generation (DG). This methodology is based on multiobjective optimization techniques to perform the optimized, coordinated and selective allocation of the control and protective devices. The proposed mathematical model consists of two objective functions that consider economic factors and network continuity indexes. Physical and operational constraints are taken into account, with an emphasis on the set of constraints based on practical rules of distribution utilities defined in international technical standards, which require the specification, coordination, and selectivity of protective devices installed in the network. The possibility of load transfer from neighboring feeders and the islanded DG operation are also considered in the model. In this way, we obtain a generic model of mixed-integer nonlinear programming (MINLP) whose differential in relation to other mathematical models of the literature is to propose, in the same optimization process, the optimized allocation of the control and protective devices in the network along with the coordination of the protection system. The efficiency of the mathematical model is proven by comparing the results obtained in two tests with the aid of the genetic algorithm (GA) while for the solution of the multiobjective MINLP model the NSGA-II multiobjective genetic algor... (Complete abstract click electronic access below) / Doutor

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