996 resultados para Estresse Mecânico


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Já é bem estabelecido que, após a realização de exercícios aos quais não se está acostumado, principalmente se esses envolverem contrações excêntricas, ocorre um processo conhecido como dano muscular (DM). Esse processo consiste na desorganização e/ou rompimento de células musculares graças a elevados níveis de estresse mecânico e/ou metabólico. Esse processo pode ser identificado pela manifestação de sintomas clássicos como dor muscular, diminuição da amplitude de movimento, perda de força e extravasamento de proteínas intracelulares para a corrente sanguínea, entre outros. Sabe-se que, após a ocorrência do DM, o músculo acometido se recupera e passa a ser mais resistente a esse fenômeno, apresentando respostas atenuadas desses sintomas. Recentemente, diferentes estratégias de proteção contra o DM que não envolvem a realização de contrações excêntricas máximas vêm sendo apresentadas, como a realização de contrações excêntricas submáximas, contrações isométricas, treinamento de flexibilidade e aumento da temperatura muscular previamente ao exercício. O objetivo do presente estudo foi revisar essas estratégias de proteção contra o DM para melhor entender esse fenômeno. Foram realizadas pesquisas em importantes bases de dados e, os artigos encontrados que forem relevantes ao tema serão revisados e didaticamente explanados ao longo do trabalho

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Pós-graduação em Ciências Biológicas (Genética) - IBB

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Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)

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Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

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Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

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A resiliência física de solos é proveniente de processos regenerativos que incluem ciclos de umedecimento e secamento, congelamento e descongelamento, assim como as atividades biológicas. Este estudo testou a hipótese de que as propriedades físicas do solo, como a permeabilidade do solo ao ar, densidade do solo, porosidade de aeração e porosidade total, são indicadores físicos eficientes para quantificar a resiliência de solos de diferentes texturas submetidos ao estresse mecânico (compactação) e após subsequentes ciclos de umedecimento e secamento. O objetivo foi avaliar o comportamento e a resiliência do solo por meio de propriedades físicas de dois Latossolos Vermelhos. Foram retiradas 25 amostras indeformadas (0,00-0,05 m) de dois solos: solo I, com textura argilosa, e solo II, com textura franco-argilo-arenosa, realizando as determinações das propriedades físicas nos tratamentos: antes da compactação (A), depois da compactação (C0) e após ciclos de umedecimento e secamento (C1, C2, C3 e C4). As propriedades densidade do solo e porosidade total não apresentaram recuperação da condição inicial após a compactação nos solos I e II; as propriedades conteúdo volumétrico de água e porosidade de aeração mostraram recuperação parcial apenas no solo I; e a permeabilidade do solo ao ar foi a propriedade que apresentou a melhor recuperação e a maior resiliência. Em relação ao distinto comportamento dos dois solos, observou-se que o solo I foi mais resiliente que o solo II nas propriedades que apresentaram recuperação.

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The humanity reached a time of unprecedented technological development. Science has achieved and continues to achieve technologies that allowed increasingly to understand the universe and the laws which govern it, and also try to coexist without destroying the planet we live on. One of the main challenges of the XXI century is to seek and increase new sources of clean energy, renewable and able to sustain our growth and lifestyle. It is the duty of every researcher engage and contribute in this race of energy. In this context, wind power presents itself as one of the great promises for the future of electricity generation . Despite being a bit older than other sources of renewable energy, wind power still presents a wide field for improvement. The development of new techniques for control of the generator along with the development of research laboratories specializing in wind generation are one of the key points to improve the performance, efficiency and reliability of the system. Appropriate control of back-to-back converter scheme allows wind turbines based on the doubly-fed induction generator to operate in the variable-speed mode, whose benefits include maximum power extraction, reactive power injection and mechanical stress reduction. The generator-side converter provides control of active and reactive power injected into the grid, whereas the grid-side converter provides control of the DC link voltage and bi-directional power flow. The conventional control structure uses PI controllers with feed-forward compensation of cross-coupling dq terms. This control technique is sensitive to model uncertainties and the compensation of dynamic dq terms results on a competing control strategy. Therefore, to overcome these problems, it is proposed in this thesis a robust internal model based state-feedback control structure in order to eliminate the cross-coupling terms and thereby improve the generator drive as well as its dynamic behavior during sudden changes in wind speed. It is compared the conventional control approach with the proposed control technique for DFIG wind turbine control under both steady and gust wind conditions. Moreover, it is also proposed in this thesis an wind turbine emulator, which was developed to recreate in laboratory a realistic condition and to submit the generator to several wind speed conditions.

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The aim of this research was to study the effect of chemical additives (lime and Portland cement) associated with sodium silicate on soil in order to obtain compressed soil bricks. Mini panels were constructed with such bricks being their physical and mechanical characteristics determined in laboratory conditions and their behavior evaluated through the association of destructive and non-destructive methods. For this purpose a sandy soil and a finely divided one were added to Portland cement and lime in the dosage of 6% and 10% taken in dry weight basis in relation to the dry soil. The sodium silicate dosage of 4% was also taken in dry weight basis in relation to the dry soil-cement or to the dry soil-lime. The compressed soil bricks were cured in a humidity chamber for 7; 28; 56 and 91 days. The bricks were laid on the fourteenth day to form prismatic mini panels each one with four layers of bricks. After 28; 56 and 91 days the mini panels were submitted to both; ultrasonic and compressive tests to determine its elastic properties (dynamic modulus) and the compressive resistance. The best results in terms of compressive strength, water absorption capacity or dynamic elastic modulus, were reached by the sandy soil added to 10% of Portland cement or lime associated with sodium silicate.

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Civil society and sugarcane farmer demands indicate that harvesting technology has enough limitations to jeopardize production in large sugar cane producing areas. This work analyses the current mechanical harvesting compared to a semi-mechanical harvesting proposal, on the bases of eleven characteristics considered determinant for a quick spreading of green cane harvesting on hilly areas, with lower impact on agricultural labor and farmers investment capacity.

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Fresh tomato harvest is traditionally made without harvesting aids. The main goal of this research was to evaluate performance parameters of fresh tomato harvesting aid equipment and compare it to traditional harvest, in the state of São Paulo. Therefore, an equipment was developed and the harvest process was evaluated in four different ways: traditional system (harvest system used in Santa Luzia farm, Brotas, SP, Brazil), picker walking with a harvesting aid equipment, picker seated in a harvesting aid equipment and a composition of both systems: two pickers seated and one picker walking in two different velocities ranges. The different systems using harvesting aid showed an average yield by picker more efficient than reference. Harvest system using three pickers showed an increase of 290% on yield average by picker, on the range of 0.5-1.0 fruit per plant, followed by the systems with a walking picker, that increased productivity in 41%, and picker seated harvester, that showed an increase of 35%. These results demonstrate the importance of using a harvesting aid equipment.

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The aim of this paper was to identify, according to gender, the indexes of Mental Health and the Psychosocial Risk Factors in workers at a state University. A sample of 400 was randomly selected, 253 female and 147 male. They were assessed by means of The Questionnaire SWS Survey (Self, Work and Social) (Ostermann & Gutiérrez, 1992), validated in Brazil by Guimarães and Macfadden (1999). Univariate, bivariate, multivariate statistics were assessed. Significant associations emerged from Mental Health and Gender, and Psychosocial Risk Factors and Gender. Women showed greater Psychosocial Risk Factors, Work and Social Stress, worst mental health than men (p < 0.05), which place them at greater risk for developing physical and/or mental illness.

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Universidade Estadual de Campinas. Faculdade de Educação Física