Estudo da estabilidade local e das bifurcações num sistema polinomial quadrático em ℝ³ oriundo de uma equação escalar de terceira ordem.

Esta Dissertação de Mestrado trata do estudo da estabilidade local e das bifurcações de Hopf genéricas de uma família de equações diferenciais quadráticas em ℝ³ dependentes de três parâmetros reais negativos. Essa família é oriunda de outra família a três parâmetros de equações diferenciais escalares quadráticas de terceira ordem. O estudo da estabilidade dos equilíbrios é feito utilizando-se o critério de estabilidade de Routh-Hurwitz. Utilizamos ainda este critério para a determinação da superfície de Hopf no espaço de parâmetros. Calculamos analiticamente as condições de não degenerescência e transversalidade das bifurcações de Hopf genéricas. Aplicamos os resultados obtidos no estudo de um caso particular conhecido em Teoria de Controle como sistema de Lur'e

Experiments and Simulations of Laminar Forced Convection With Water–Alumina Nanofluids in Circular Tubes

This work reports fundamental experimental-theoretical research related to heat transfer enhancement in laminar channel flow with nanofluids, which are essentially modifications of the base fluid with the dispersion of metal oxide nanoparticles. The nanofluids were synthesized by a two-step approach, using a dispersant and an ultrasound probe or a ball mill for alumina nanoparticles dispersion within the aqueous media. The theoretical work involves the proposition of an extension of the thermally developing flow model that accounts for the temperature variation of all the thermophysical properties, including viscosity and the consequent variation of the velocity profiles along the thermal entry region. The simulation was performed by making use of mixed symbolic-numerical computation on the Mathematica 7.0 platform and a hybrid numerical-analytical methodology (generalized integral transform technique, GITT) in accurately handling the governing partial differential equations for the heat and fluid flow problem formulation with temperature dependency in the thermophysical properties. Experimental work was also undertaken based on a thermohydraulic circuit built for this purpose, and sample results are presented to verify the proposed model. The aim is to confirm that both the constant properties and temperature-dependent properties models, besides available correlations previously established for ordinary fluids, provide adequate prediction of the heat transfer enhancement observed in laminar forced convection with such nanofluids and within the experimented Reynolds number range.Indisponível

Toward Human-AI Co-creation to Accelerate Material Discovery

There is an increasing need in our society to achieve faster advances in Science to tackle urgent problems, such as climate changes, environmental hazards, sustainable energy systems, pandemics, among others. In certain domains like chemistry, scientific discovery carries the extra burden of assessing risks of the proposed novel solutions before moving to the experimental stage. Despite several recent advances in Machine Learning and AI to address some of these challenges, there is still a gap in technologies to support end-to-end discovery applications, integrating the myriad of available technologies into a coherent, orchestrated, yet flexible discovery process. Such applications need to handle complex knowledge management at scale, enabling knowledge consumption and production in a timely and efficient way for subject matter experts (SMEs). Furthermore, the discovery of novel functional materials strongly relies on the development of exploration strategies in the chemical space. For instance, generative models have gained attention within the scientific community due to their ability to generate enormous volumes of novel molecules across material domains. These models exhibit extreme creativity that often translates in low viability of the generated candidates. In this work, we propose a workbench framework that aims at enabling the human-AI co-creation to reduce the time until the first discovery and the opportunity costs involved. This framework relies on a knowledge base with domain and process knowledge, and user-interaction components to acquire knowledge and advise the SMEs. Currently,the framework supports four main activities: generative modeling, dataset triage, molecule adjudication, and risk assessment.Comment: 9 pages, 5 figures, NeurIPS 2022 WS: AI4Scienc

Epidemiological profile of patients hospitalized by COVID-19 in an Intensive Care Unit in the interior of Brazil

Objective: To describe the epidemiological profile of patients admitted by COVID-19 to the intensive care unit of a hospital in the interior of the northeastern countryside. Methods: Observational and retrospective study based on data from the electronic protocol of the service of patients admitted between April 24, 2020 and December 31, 2020. Data regarding gender, age, health insurance, need for orotracheal intubation and outcome were evaluated. Results: 118 patients were included in the study. Men were more affected than women. The mean age of patients was 65.35 years, with the mean age of women (70.53 years) being higher than the mean age of men (62.37 years). Regarding age group, the elderly accounted for 66.11% of patients. 48.31% of the patients required orotracheal intubation, of which 61.40% were male, with an outcome of death in 75.44% of the intubated patients. Of the total number of patients in the study, 40.68% died. Conclusion: Greater involvement and lethality were observed in men and in the elderly. The number of adult men admitted was triple the number of adult women admitted.Objetivo: Descrever o perfil epidemiológico de pacientes admitidos por COVID-19 em unidade de terapia intensiva em hospital de uma cidade do interior nordestino. Métodos: Estudo observacional e retrospectivo a partir de dados do protocolo eletrônico do serviço dos pacientes com admissão entre 24 de abril de 2020 e 31 de dezembro de 2020. Foram avaliados dados referentes a sexo, faixa etária, convênio, necessidade de intubação orotraqueal e desfecho. Resultados: Um total de 118 pacientes foram incluídos no estudo. Homens foram mais acometidos do que mulheres. A média de idade dos pacientes foi de 65,35 anos, sendo a média de idade das mulheres (70,53 anos) maior que a média de idade dos homens (62,37 anos). Em relação à faixa etária, os idosos corresponderam a 66,11% dos pacientes. 48,31% dos pacientes necessitaram de intubação orotraqueal, destes 61,40% eram do sexo masculino, com desfecho para óbito em 75,44% dos pacientes intubados. Do total de pacientes do estudo, 40,68% evoluíram para óbito. Conclusão: Observou-se maior acometimento e letalidade em homens e em idosos. A quantidade de homens adultos admitidos foi o triplo da quantidade de mulheres adultas admitidas

Influência da razão água/cimento na capacidade de suporte de carga de pastas cimentícias projetadas para impressão 3D

O princípio da impressão 3D é a construção de estruturas camada por camada a partir de um modelo digital. Os fatores de influência relacionados a viabilidade desta são, basicamente: as propriedades reológicas da mistura no estado fresco e a resistência mecânica no estado endurecido. Este estudo foca na reologia e capacidade de sobreposição de camadas de pastas cimentícias com diferentes teores de água. Pastas com razões de água/cimento (a/c) entre 0,28 e 0,32 foram testadas sobrepondo filamentos em camadas com um molde, e por ensaio de espalhamento (flow table). Os resultados mostram que as misturas com razão a/c de 0,28 apresentaram as propriedades reológicas aprimoradas para impressão. A capacidade de suporte de carga pode ser associada a um espalhamento na flow table inferior a 115 mm

Os mártires e a cristianização do território na América portuguesa, séculos XVI e XVII

O artigo investiga um grupo de atores sociais bastante relevante para viabilizar a cristianização na América portuguesa: os mártires cristãos, indivíduos muito especiais, dispostos a regar a terra com seu próprio sangue, de forma a tornar definitiva e irreversível a ocupação cristã do território. Os mártires - e principalmente a narrativa em torno deles - parecem ter sido bastante acionados para integrar a América portuguesa e seus habitantes nativos à temporalidade e territorialidade cristã. Os mártires dos séculos XVI e XVII, principalmente missionários, reeditavam os martírios do início da cristandade, que espalharam o cristianismo rumo a diversas partes do mundo na antiguidade. Dessa forma, viabilizaram a cristianização das novas fronteiras, consagrando o solo com seu sangue divino e viabilizando posteriores processos de urbanização. Além da função estratégica dos mártires para os cristãos, o texto mostra que eles também tiveram significado peculiar na interlocução com as culturas ameríndias, que tinha como um de seus principais personagens o grande guerreiro, disposto a perder seu sangue em prol de seu grupo.This paper looks into a group of social agents who played a significant role in the Christianization of Portuguese America, namely, the Christian martyrs - very special individuals who were ready to wet the land with their own blood in order to make possible a definitive and irreversible occupation of the territory by Christian settlers. The martyrs, and above all the stories told about them, seem to have been called upon to integrate Portuguese America and its native inhabitants into the temporalities and territory of Christendom. Mostly made up of missionaries, this group of 16th and 17th-century martyrs reedited the martyrdom of early Christians, who spread their creed across numerous parts of the Ancient World. They enabled the Christianization of new frontiers by consecrating the soil with their divine blood and paving the way for subsequent processes of urban development. In addition to their strategic significance for Christianity, the text also shows that their martyrdom played a specific role in the Christian settlers' interaction with Amerindian culture, whose main cults included the figure of the great warrior, ever ready to shed his own blood for his group

Pervasive gaps in Amazonian ecological research

Biodiversity loss is one of the main challenges of our time,1,2 and attempts to address it require a clear un derstanding of how ecological communities respond to environmental change across time and space.3,4 While the increasing availability of global databases on ecological communities has advanced our knowledge of biodiversity sensitivity to environmental changes,5–7 vast areas of the tropics remain understudied.8–11 In the American tropics, Amazonia stands out as the world’s most diverse rainforest and the primary source of Neotropical biodiversity,12 but it remains among the least known forests in America and is often underrepre sented in biodiversity databases.13–15 To worsen this situation, human-induced modifications16,17 may elim inate pieces of the Amazon’s biodiversity puzzle before we can use them to understand how ecological com munities are responding. To increase generalization and applicability of biodiversity knowledge,18,19 it is thus crucial to reduce biases in ecological research, particularly in regions projected to face the most pronounced environmental changes. We integrate ecological community metadata of 7,694 sampling sites for multiple or ganism groups in a machine learning model framework to map the research probability across the Brazilian Amazonia, while identifying the region’s vulnerability to environmental change. 15%–18% of the most ne glected areas in ecological research are expected to experience severe climate or land use changes by 2050. This means that unless we take immediate action, we will not be able to establish their current status, much less monitor how it is changing and what is being lostinfo:eu-repo/semantics/publishedVersio