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Atenuação de vibrações torcionais em uma transmissão automotiva usando um eixo periódico
Get PDFOrientador: José Roberto de França ArrudaDissertação (mestrado) - Universidade Estadual de Campinas, Faculdade de Engenharia MecânicaResumo: A geometria possui grande influência na vibração de componentes mecânicos. No caso de sistemas rotativos, os eixos usados na transmissão de torque e velocidade angular podem agir como amplificadores da vibração torcional. Entretanto, usando o conceito de estruturas periódicas, é possível obter faixas de frequência com significativa atenuação da vibração, chamadas de bandas de rejeição. Nelas a estrutura atua como filtro mecânico, impedindo a propagação de ondas elásticas e, desta forma, impossibilitando a formação de modos de vibrar. É sabido que a transmissão de potência por engrenagens gera uma vibração torcional na frequência de engrenamento, e também que motores de combustão interna são geradores de vibrações periódicas. O objeto de estudo dessa dissertação é a modelagem computacional e o teste experimental de um eixo periódico dentro de uma transmissão mecânica veicular com motor a diesel que atenue a vibração torcional tanto para a frequência de engrenamento quanto para as provenientes do motor. É mostrado que o eixo com engrenagens montadas de modo periódico produz uma ampla banda de rejeição e que o acoplamento do eixo periódico com outras inércias pode gerar modos de defeito dentro das bandas de rejeição, que podem comprometer a atenuação das vibrações. Resultados de simulação numérica e resultados experimentais são analisados tendo em vista discutir a viabilidade de aplicação deste efeito em transmissões veiculares.Abstract: The geometry has strong influence on the vibration of mechanical components. Shafts used in the transmission of torque and angular velocity can behave as torsional vibration amplifiers. However, using the concept of periodic structures, it is possible to obtain frequency bands with high attenuation, called band gaps. In these frequency bands, the structure acts as a mechanical filter, thus avoiding elastic wave propagation and, therefore, the building up of vibration modes. It is known that the gear mesh frequency causes torsional vibrations of a shaft system, and the internal combustion engine provides periodic vibration. The object of this investigation is the computational modeling and experimental test of a mechanical transmission with a periodic shaft designed to filter the both the gear mesh frequency and engine vibration. It is shown that a shaft with periodically mounted gears produces a wide band gap and that the coupling of such a shaft with other inertias can generate defect modes within the band gaps which can compromise the vibration attenuation. Numerical and experimental results are analyzed aiming at the application of this periodic design in automotive gearboxes.MestradoMecânica dos Sólidos e Projeto MecânicoMestre em Engenharia Mecânic
Navarro, Alexandre Guida. As estearias do Maranhão: a pesquisa acadêmica do laboratório de arqueologia da UFMA
No full textAutor de muitos artigos, capítulos e livros, Alexandre Navarro brinda-nos, agora, com esse volume de introdução a um tema tanto fascinante como pouco difundido: as estearias maranhenses. Esteios são estacas colocadas para sustentar algo, no caso, as habitações sobre a água. Esse tipo de ocupação ocorreu em diferentes épocas e lugares. No Maranhão, deu-se, no século IX d.C., período que coincide com o período de consolidação das três grandes religiões monoteístas no Velho Mundo (Judaísmo, Cristianismo e Islamismo), mas também com declínio Maia na Meso-América e com o colapso do governo centralizado na China; alguns relacionarão tudo isso a mudanças climáticas. Na Amazônia oriental, no atual Maranhão, povos indígenas construíram aldeias com arquitetura complexa, muito bem adaptadas ao médio aquático, em comércio com sociedades distantes, no Caribe33216516
Stochastic simulation of prices in the brazilian electricity market
No full textOrientador: Paulo Sergio Franco BarbosaDissertação (mestrado) - Universidade Estadual de Campinas, Faculdade de Engenharia Civil, Arquitetura e UrbanismoResumo: A comercialização de energia oferece grandes oportunidades de ganho, mas também a exposição ao risco devido à volatilidade dos preços. Um modelo de preço aderente ao mercado é um elemento-chave da análise de risco por empresas atuantes no mercado de eletricidade e representa uma forte ferramenta para fornecer um melhor entendimento da dinâmica do mercado. Este trabalho aplica Simulação de Monte-Carlo aliada ao Movimento Browniano Geométrico e a decomposição de Cholesky, procedimentos estocásticos amplamente utilizados nos mercados financeiro e de ações, para simular curvas estocásticas de preços futuros para o mercado brasileiro de energia, com foco no submercado Sudeste/Centro-Oeste, que corresponde à maior parte da comercialização de energia no país. Os resultados deste trabalho representam convenientemente a incerteza nos preços do mercado brasileiro de energia, demonstrando resultados robustos mesmo quando aplicados para os recentes períodos de alta volatilidade que o mercado brasileiro vem passando devido às crises hídricas e econômicas desde o ano 2012 até a recente crise com a pandemia de 2020. Ao fim, um caso prático de otimização de portfólio consolida a utilização das ferramentas estocásticas propostas neste trabalho como dados de entrada para a solução do problema de uma comercializadora de energiaAbstract: Energy trading offers great gain opportunities but also exposure to risk due to price volatility. A proper price model is a key element of risk analysis by electricity market traders and represents a strong tool for providing a better understanding of market dynamics. This work applies Monte-Carlo simulation combined with the Brownian Geometric Movement and the Cholesky decomposition, stochastic procedures widely used in the financial and stock markets, to simulate stochastic curves of future prices for the Brazilian energy market, with focus on the Southeast/Midwest submarket, which accounts for the majority of the energy commercialization in the country. The results of this work conveniently represent the uncertainty in the prices of the Brazilian energy market, demonstrating robust results even when applied to the recent periods of high volatility that the Brazilian market has been going through due to hydric and economic crises from the year 2012 until the recent crisis with the 2020 pandemic. Finally, a practical case of portfolio optimization consolidates the use of the stochastic tools proposed in this work as input data for solving the problem of an energy trading companyMestradoRecursos Hídricos, Energéticos e AmbientaisMestre em Engenharia Civi
Development of composite outcomes for individual patient data (IPD) meta-analysis on the effects of diet and lifestyle in pregnancy: a Delphi survey
No full textObjectiveTo develop maternal, fetal, and neonatal composite outcomes relevant to the evaluation of diet and lifestyle interventions in pregnancy by individual patient data (IPD) meta-analysis.
DesignDelphi survey.
SettingThe International Weight Management in Pregnancy (i-WIP) collaborative network. Sample Twenty-six researchers from the i-WIP collaborative network from 11 countries.
MethodsA two-generational Delphi survey involving members of the i-WIP collaborative network (26 members in 11 countries) was undertaken to prioritise the individual outcomes for their importance in clinical care. The final components of the composite outcomes were identified using pre-specified criteria.
Main outcome measuresComposite outcomes considered to be important for the evaluation of the effect of diet and lifestyle in pregnancy.
ResultsOf the 36 maternal outcomes, nine were prioritised and the following were included in the final composite: pre-eclampsia or pregnancy-induced hypertension, gestational diabetes mellitus (GDM), elective or emergency caesarean section, and preterm delivery. Of the 27 fetal and neonatal outcomes, nine were further evaluated, with the final composite consisting of intrauterine death, small for gestational age, large for gestational age, and admission to a neonatal intensive care unit (NICU).
ConclusionsOur work has identified the components of maternal, fetal, and neonatal composite outcomes required for the assessment of diet and lifestyle interventions in pregnancy by IPD meta-analysis.
Tweetable abstractComposite outcomes in IPD meta-analysis on diet and lifestyle in pregnancy1232190198sem informaçã
Values and DSM-5: looking at the debate on attenuated psychosis syndrome
No full textBackground: Although values have increasingly received attention in psychiatric literature over the last three decades, their role has been only partially acknowledged in psychiatric classification endeavors. The review process of the fifth edition of the Diagnostic and Statistical Manual of Mental Disorders (DSM-5) received harsh criticism, and was even considered secretive by some authors. Also, it lacked an official discussion of values at play. In this perspective paper we briefly discuss the interplay of some values in the scientific and non-scientific debate around one of the most debated DSM-5 category proposals, the Attenuated Psychosis Syndrome (APS). Then, we point out some ethical consequences of a facts-plus-values perspective in psychiatric classification17sem informaçã
Hannah Arendt sobre Thomas Hobbes e o racismo imperialista
No full textEsse artigo se propõe a rastrear em Origens do totalitarismoalgumas das razões –históricas e filosóficas -que teriam levado Arendt, em A crise da cultura, a identificar no juízo de gosto kantiano as características definidoras do juízo político. Na primeira seção, veremos brevemente que o totalitarismo destrói justamente as condições para aquilo que Arendt chamará mais tarde de “mentalidade alargada”. Na segunda seção, eu procuro sugerir que a mentalidade alargada, tal como caracterizada em A crise na cultura, pode ser interpretada como antítese da mentalidade racista da burguesia europeia do século XIX que, de acordo com Arendt em Origens, pavimentou de algum modo o caminho do totalitarismo. Por fim, veremos que a mentalidade alargada é o avesso da mentalidade do homem hobbesiano, que, segundo Arendt, é o precursor filosófico do europeu imperialista1426685This article proposes to trace in Theorigins of totalitarianism some of the reasons -historical and philosophical -that would have led Arendt, in The crisis in culture, to identify in the Kantian judgment of taste the defining characteristics of political judgment. In the first section, wewill see briefly that totalitarianism just destroys the conditions for what Arendt will later call "enlarged mentality". In the second section, I try to suggest that the enlarged mentality, as characterized in The crisis in Culture, can be interpreted as an antithesis of the imperialist mentality of the 19th century, which, according to Arendt in The origins, somehow paved the way for totalitarianism. Finally, we will see that the enlarged mentality is the opposite of the mentality of the Hobbesian man, who, according to Arendt, is the philosophical precursor of the imperialist European bourgeoi
Influence of heat treatments on microstructure and mechanical behaviour of compressible al matrix, low density composites
No full textThis work investigates the influence of solution/ageing treatments on mechanical properties under compression of a compressible, low-density composite based on AA7075 alloy as matrix, reinforced with porous ceramic particulates (foamed SiO2/Al2O3/Fe2O3). Composites were produced by thixoforming and products were characterized related to mechanical behaviour under semi-static compression, in different conditions: as thixoformed and after solution/ageing treatments. Structure of thixoformed material requires particular heat treatment conditions due to coarser secondary phases, when compared to as-cast situation. Products presented relative density around 0.5 and compression behaviour characteristic of cellular metals, showing plastic deformation plateau due to collapse of porosity, which gives the composites potential applications as energy absorbers. Effect of heat treatments upon the properties showed increase in the order of 2x of the maximum strength required to start plastic deformation and 5x in the average plateau strength, with only 15% reduction of plastic deformation7141148Annual Conference and Exposition of the Society-for-Experimental-Mechanics on Experimental and Applied Mechanics2015-06-08Costa Mesa, CA, Estados Unidossem informaçã
Is zonal distribution of index tumor different in radical prostatectomies comparing whites vs African-Brazilians?
No full textsem informação292218A218A105th Annual Meeting of the United-States-and-Canadian-Academy-of-Pathology2016-03-12Seattle, WA, Estados Unidossem informaçã
Mapping tree species in tropical seasonal semi-deciduous forests with hyperspectral and multispectral data
No full textAccurately mapping the spatial distribution of tree species in tropical environments provides valuable insights for ecologists and forest managers. This process may play an important role in reducing fieldwork costs, monitoring changes in canopy biodiversity, and locating parent trees to collect seeds for forest restoration efforts. However, mapping tree species in tropical forests with remote sensing data is a challenge because of high floristic and spectral diversity. In this research, we discriminated and mapped tree species in tropical seasonal semi-deciduous forests (Brazilian Atlantic Forest Biome) by using airborne hyperspectral and simulated multispectral data in the 450 to 2400 nm wavelength range. After quantifying the spectral variability within and among individual tree crowns of eight species, three supervised machine learning classifiers were applied to discriminate the species at the pixel level. Linear Discriminant Analysis outperformed Support Vector Machines with Linear and Radial Basis Function (RBF-SVMs) kernels and Random Forests in almost all the tested cases. An average classification accuracy of 70% was obtained when using the visible/near-infrared (VNIR, 450-919 nm) bands. The inclusion of shortwave infrared bands (SWIR, 1045-2400 nm) increased the accuracy to 84%. Narrow-band vegetation indices (VIs) were also tested and increased the classification accuracy by up to 5% when combined with VNIR features. Furthermore, the spectral bands of the WorldView-3 (WV-3) satellite sensor were simulated for classification purposes. WV-3 VNIR bands provided an accuracy of 57.4%, which increased to 74.8% when using WV-3 SWIR bands. We also tested the production of species maps by using an object-oriented approach that integrated a novel segmentation algorithm that was tailored to delineate tree crowns and label high class membership pixels inside each object. In this scenario, RBF-SVMs produced the best species maps, correctly identifying 84.9% of crowns with hyperspectral data and 78.5% with simulated WV-3 data. The use of a reduced set of hyperspectral bands, which were selected with stepwise regression, did not significantly affect the classification accuracies but allowed us to depict the most important wavelengths to discriminate the species. These wavelengths were located around the green reflectance peak (550 nm), at the red absorption feature (650 nm) and in the SWIR range at 1200,1700, 2100 and 2300 nm. These encouraging results suggest the feasibility of the proposed approach for mapping pioneering and climax tree species in the Brazilian Atlantic Forest Biome, highlighting its potential use in forest recovery and inventory initiatives1796678CONSELHO NACIONAL DE DESENVOLVIMENTO CIENTÍFICO E TECNOLÓGICO - CNPQCOORDENAÇÃO DE APERFEIÇOAMENTO DE PESSOAL DE NÍVEL SUPERIOR - CAPESFUNDAÇÃO DE AMPARO À PESQUISA DO ESTADO DE SÃO PAULO - FAPESP314625/2014-3; 303563/2008-73424/2015-042013/11.589-
HOTMAP: Global hot target detection at moderate spatial resolution
No full textImagery from polar orbiting satellites can be used to mitigate global hazards from wildfires and volcanoes. An incipient constellation of moderate spatial resolution sensors (i.e. Landsat 8 and Sentinel 2) will provide an unprecedented combined spatial and temporal resolution of imagery with 20 to 30 m pixels and a revisit period of 2 to 4 days. This data stream could provide an invaluable contribution to existing hot target monitoring systems. We developed hot target detection algorithms for both daytime and nighttime imagery using Landsat 8 data. Performance was compared to existing state-of-the-art methods for daytime detection using a global database of active wildfires. The new approach was able to detect 80% of hot pixels (i.e. compared to 50 to 80% detected by the previous approaches) with a low false alarm rate (i.e. <10%) and fast processing speed (i.e. orders of magnitude faster than one of the previous approaches). The new detection algorithms put forward here could form the basis of the first, moderate spatial resolution, global hot target detection system. This vision is currently being realized through development of the Hotmap software within the Grid Processing on Demand (G-POD) environment of the European Space Agency (ESA)1777888FUNDAÇÃO DE AMPARO À PESQUISA DO ESTADO DE SÃO PAULO - FAPESP2013/03711-