32 resultados para Stokes waves


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A Work Project, presented as part of the requirements for the Award of a Masters Degree in Finance from the NOVA – School of Business and Economics

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A Work Project, presented as part of the requirements for the Award of a Masters Degree in Finance from the NOVA – School of Business and Economics

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Dissertação para obtenção do Grau de Mestre em Engenharia Mecânica

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A Work Project, presented as part of the requirements for the Award of a Masters Degree in Management from the NOVA – School of Business and Economics

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Dissertação para obtenção do Grau de Doutor em Matemática

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It is important to have better evaluation and understanding of the motor neuron physiology, with the goal to early and objectively diagnose and treat patients with neurodegenerative pathologies. The Compound Muscle Action Potential (CMAP) scan is a non-invasive diagnosis technique for neurodegenerative pathologies, such as ALS, and enables a quick analysis of the muscle action potentials in response to motor nerve stimulation. This work aims to study the influence of different pulse modulated waveforms in peripheral nerve excitability by CMAP scan technique on healthy subjects. A total of 13 healthy subjects were submitted to the same test. The stimuli were applied in the medium nerve on the right wrist and electromyography signal collected on the Abductor Pollicis Brevis (APB) muscle surface on the right thumb. Stimulation was performed with an increasing intensities range from 4 to 30 mA, with varying steps, 3 stimuli per step. The procedure was repeated 4 times per subject, each repetition using a different single pulse stimulation waveform: monophasic square, monophasic triangular, monophasic quadratic and biphasic square. Results were retrieved from the averaging of the stimuli on each current intensity step. The square pulse needs less current intensity to generate the same response amplitude regarding the other waves and presents a more steep curve slope and this effect is gradually decreasing for the triangular and quadratic pulse,respectively, being the difference even more evident regarding the biphasic pulse. The control of the waveform stimulation pulse allows varying the stimulusresponse curve slope.

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The project of writing to a fictional Portuguese-speaking Queen on the crises proceeding since 2008 builds on Letters to Queen Elizabeth written by the British Academy and was first published in 2013. This expanded edition signals greater awareness of the complementarity between economic potential and cultural legacy in the Community of Portuguese-speaking Countries (CPLP) insofar as its members, observers and their areas of economic integration encompass the globe. The edition is dedicated to the memory of Manuel Jacinto Nunes, who supported the project as dean of the economics section at the Lisbon Academy of Science. The cover shows a Crown with nine CPLP flags as jewels in the shape of a 7 rising from the waves. The waves of lusophonia appear far gentler than Poe’s maelstrom, reproduced in the back flap. This material, inserted in the proceedings published on IICT’s 130th anniversary, is used at NOVASBE through its Center for Globalization and Governance (CG&G).

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The presence and importance of the sea as a factor that has helped shape the history of England since at least the Roman invasions of 55-54 BC (less successful, incidentally, than most of Caesar’s other military ventures ...) need no particular urging or demonstration. Nonetheless, a bird’s-eye view would necessarily survey the waves of invasions and settlements that, one after the other, came dashing over the centuries upon England’s shores; not to mention the requested invasion of 1688, Angles and Saxons, Scandinavians, Normans, they all crossed the whale’s path and cast anchor in England’s green and pleasant land. In the course of this retrospective voyage through the oceans of History, one would inevitably stop at the so-called ‘Discoveries’ of the 15th-16th centuries, meet their navigators, sailors and pirates extolled by Richard Hakluyt (1553?-1616), face an anonymous crowd of merchants and witness the huge expansion of trade, largely to the benefit of the ‘discovering’ countries as prescribed by the economic Gospel Adam Smith (1723-90) would later baptize as “mercantilism”.

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Double Degree in Economics from the NOVA - School of Business and Economics and Insper

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Como responsáveis pela leccionação da disciplina de História da Inglaterra medieval, temos não raro sugerido aos alunos, para fins puramente lúdicos, a leitura da obra clássica de Sellar e Yeatman; no entanto, a sua condição de ‘História de Inglaterra em disparates’ faz com que de imediato aconselhemos no sentido de evitar sincronias com os períodos de avaliação escolar. Ora é precisamente de Sellar e Yeatman que citamos, em jeito de abertura, o seguinte passo: “With Edward the Confessor [1042-1066] perished the last English King [...], since he was succeeded by Waves of Norman Kings (French), Tudors (Welsh), Stuarts (Scottish), and Hanoverians (German) […]. The Norman Conquest was a Good Thing, as from this time onwards England stopped being conquered and thus was able to become top nation.” Descontada a caricatura, estas palavras e o próprio título espelham, afinal, a centralidade de 1066, parecendo reduzir todos os acontecimentos posteriores a um mero posfácio ou epílogo histórico. Esta perspectiva, manifestamente insustentável, em nada contradiz ou anula os sortilégios literário-ficcionais da data, patentes, por exemplo, num romance notável de Julian Rathbone, várias vezes reimpresso desde o seu aparecimento e amplamente merecedor de adaptação cinematográfica.

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Esta dissertação tem o intuito de validar o código numérico OpenFoam para problemas de fenómeno de vibração induzida por desprendimento de vórtices num cilindro circular com um grau de liberdade transversal ao escoamento. Na primeira parte é simulado o escoamento em torno de um cilindro circular fixo, e na segunda parte o escoamento em torno do cilindro oscilatório. O número de Reynolds é 200 para todas as simulações e o movimento do cilindro é descrito segundo um sistema massa-mola e massa-mola-amortecedor. Para o movimento do cilindro utilizou-se o solver sixDoFRigidDisplacement e para a resolução de problemas de malha móvel o solver displacementLaplacian. O código numérico utilizado para o caso do cilindro fixo foi pimpleFoam e para o caso do cilindro oscilatório o pimpleDyMFoam. As simulações foram feitas através da resolução das equações de Navier-Stokes num domínio computacional bidimensional. Na simulação do escoamento em redor do cilindro fixo, os coeficientes de arrasto e sustentação e o número de Strouhal foram calculados e comparados com resultados da literatura. Os resultados estão próximos da realidade, no entanto observa-se que a dimensão da malha é muito importante para a precisão dos mesmos. Na simulação do escoamento em torno do cilindro oscilatório foram calculados os coeficientes de arrasto e sustentação e deslocamento do cilindro, para os sistemas massa-mola e massa-mola-amortecedor. Para os dois sistemas foi apresentada e comparada a evolução destes resultados em função da velocidade reduzida e por fim foram comparados. Observa-se que o fator de amortecimento afeta as respostas do cilindro, dependo da velocidade reduzida. Os resultados obtidos em ambos os estudos foram satisfatórios e conclui-se que o código OpenFoam é uma boa ferramenta para resolver problemas com o fenómeno de vibração induzida por vórtices.

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The Electrohysterogram (EHG) is a new instrument for pregnancy monitoring. It measures the uterine muscle electrical signal, which is closely related with uterine contractions. The EHG is described as a viable alternative and a more precise instrument than the currently most widely used method for the description of uterine contractions: the external tocogram. The EHG has also been indicated as a promising tool in the assessment of preterm delivery risk. This work intends to contribute towards the EHG characterization through the inventory of its components which are: • Contractions; • Labor contractions; • Alvarez waves; • Fetal movements; • Long Duration Low Frequency Waves; The instruments used for cataloging were: Spectral Analysis, parametric and non-parametric, energy estimators, time-frequency methods and the tocogram annotated by expert physicians. The EHG and respective tocograms were obtained from the Icelandic 16-electrode Electrohysterogram Database. 288 components were classified. There is not a component database of this type available for consultation. The spectral analysis module and power estimation was added to Uterine Explorer, an EHG analysis software developed in FCT-UNL. The importance of this component database is related to the need to improve the understanding of the EHG which is a relatively complex signal, as well as contributing towards the detection of preterm birth. Preterm birth accounts for 10% of all births and is one of the most relevant obstetric conditions. Despite the technological and scientific advances in perinatal medicine, in developed countries, prematurity is the major cause of neonatal death. Although various risk factors such as previous preterm births, infection, uterine malformations, multiple gestation and short uterine cervix in second trimester, have been associated with this condition, its etiology remains unknown [1][2][3].

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Waves of globalization reflect the historical technical progress and modern economic growth. The dynamics of this process are here approached using the multidimensional scaling (MDS) methodology to analyze the evolution of GDP per capita, international trade openness, life expectancy, and education tertiary enrollment in 14 countries. MDS provides the appropriate theoretical concepts and the exact mathematical tools to describe the joint evolution of these indicators of economic growth, globalization, welfare and human development of the world economy from 1977 up to 2012. The polarization dance of countries enlightens the convergence paths, potential warfare and present-day rivalries in the global geopolitical scene.

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The work presented in this thesis aims at developing a new separation process based on the application of supported magnetic ionic liquid membranes, SMILMs, using magnetic ionic liquids, MILs. MILs have attracted growing interest due to their ability to change their physicochemical characteristics when exposed to variable magnetic field conditions. The magnetic responsive behavior of MILs is thus expected to contribute for the development of more efficient separation processes, such as supported liquid membranes, where MILs may be used as a selective carrier. Driven by the MILs behavior, these membranes are expected to switch reversibly their permeability and selectivity by in situ and non-invasive adjustment of the conditions (e.g. intensity, direction vector and uniformity) of an external applied magnetic field. The development of these magnetic responsive membrane processes were anticipated by studies, performed along the first stage of this PhD work, aiming at getting a deep knowledge on the influence of magnetic field on MILs properties. The influence of the magnetic field on the molecular dynamics and structural rearrangement of MILs ionic network was assessed through a 1H-NMR technique. Through the 1H-NMR relaxometry analysis it was possible to estimate the self-diffusion profiles of two different model MILs, [Aliquat][FeCl4] and [P66614][FeCl4]. A comparative analysis was established between the behavior of magnetic and non-magnetic ionic liquids, MILs and ILs, to facilitate the perception of the magnetic field impact on MILs properties. In contrast to ILs, MILs show a specific relaxation mechanism, characterized by the magnetic dependence of their self-diffusion coefficients. MILs self-diffusion coefficients increased in the presence of magnetic field whereas ILs self-diffusion was not affected. In order to understand the reasons underlying the magnetic dependence of MILs self-diffusion, studies were performed to investigate the influence of the magnetic field on MILs’ viscosity. It was observed that the MIL´s viscosity decreases with the increase of the magnetic field, explaining the increase of MILs self-diffusion according to the modified Stokes- Einstein equation. Different gas and liquid transport studies were therefore performed aiming to determine the influence of the magnetic behavior of MILs on solute transport through SMILMs. Gas permeation studies were performed using pure CO2 andN2 gas streams and air, using a series of phosphonium cation based MILs, containing different paramagnetic anions. Transport studies were conducted in the presence and absence of magnetic field at a maximum intensity of 1.5T. The results revealed that gas permeability increased in the presence of the magnetic field, however, without affecting the membrane selectivity. The increase of gas permeability through SMILMs was related to the decrease of the MILs viscosity under magnetic field conditions.(...)

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Durante séculos o papel do Estado na vida económica e social das nações foi crescendo, atingindo um desenvolvimento assinalável a partir da segunga guerra mundial, em execução do novo paradigma que dela resultou. Desenvolvimento que conheceu fortes críticas com paragem e posterior inversão de sentido durante a década de 80 em que se gerou alguma diluição da intervenção do Estado, criando-se um movimento de relativo cepticismo relativamente à bondade, à eficiência e aos custos daquela intervenção. Foi nesse contexto e paralelamente com o aumento da vontade de intervir do sector privado que surgiram as chamadas três «vagas» de intervenção privada, sucessivamente dirigidas às actividades públicas (i) em sectores industriais, comerciais ou de serviços não estratégicos, (ii) no domínio das infra-estruturas e, finalmente, (iii) na área social, recorrendo com diferentes níveis de sucesso, a diversos processos, da privatização às parcerias público-privadas (PPP), passando pela empresarialização. O movimento de reforma nascido de reservas quanto à eficiência do sector público não passou ao lado da saúde, particularmente do hospital público, em que assumiu objectivos e modos específicos, das «reformas de gestão» às «reformas de financiamento» e às «reformas organizacionais », para, na sequência do movimento anteriormente ocorrido noutros domínios, também recorrer às parcerias público-privadas. Depois de situar estas iniciativas no contexto do movimento que rodeou o aumento da intervenção privada na produção e na prestação pública, o artigo procura identificar os requisitos de compatibilidade das parcerias público-privadas com sistemas de saúde organizados e que perseguem a universalidade da cobertura, a acessibilidade e compreensividade dos cuidados e a equidade do acesso, com especial atenção ao facto de (designadamente em Portugal) a partilha de riscos e tarefas poder atribuir ao sector privado a gestão das dimensões clínicas da prestação.