Método para análise da interação fluido-estrutura em travessas do pré-distribuidor de turbinas hidráulicas.

Um dos grandes desafios enfrentados pelos fabricantes de turbinas hidráulicas é prevenir o aparecimento de vibrações induzidas pelo escoamento nas travessas do pré-distribuidor e pás do rotor. Considerando apenas as travessas, e atribuídos a tais vibrações, foram relatados 28 casos de trincas ou ruídos anormais nas últimas décadas, que acarretaram enormes prejuízos associados a reparos, atrasos e perda de geração. O estado da arte na prevenção destes problemas baseia-se na utilização de sofisticados, e caros, programas comerciais de dinâmica dos fluidos computacional para o cálculo transiente do fenômeno. Este trabalho faz uma ampla revisão bibliográfica e levantamento de eventos de trincas ou ruídos ocorridos em travessas nos últimos 50 anos. Propõe, então, um enfoque alternativo, baseado exclusivamente em ferramentas de código aberto. A partir de hipóteses simplificadoras devidamente justificadas, o problema é formulado matematicamente de forma bidimensional, no plano da seção transversal da travessa, levando em conta a interação fluido-estrutura. Nesta estratégia, as equações de Navier-Stokes são resolvidas pelo método dos elementos finitos por meio da biblioteca gratuita oomph-lib. Um código especial em C++ é desenvolvido para o problema de interação fluido-estrutura, no qual o fenômeno de turbulência é levado em consideração por meio de um algoritmo baseado no modelo de Baldwin-Lomax. O método proposto é validado por meio da comparação dos resultados obtidos com referências e medições disponíveis na literatura, que tratam de problemas de barras retangulares suportadas elasticamente. O trabalho finaliza com a aplicação do método a um estudo de caso envolvendo uma travessa particular.

Lettres de Héléodore adressés à Napoléon Bonaparte, depuis le 13 ventôse an 8 (ou 4 mars 1800) jusqu'au 17 mars 1814. Lettre d'un français adressée à M. le comte d'Artois en messidor an 12 (ou juillet 1804) ...

Mode of access: Internet.

Sistema de conversão de energia eólica baseado no gerador de indução duplamente alimentado: análise e contribuição ao controle da máquina

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.

Dialogização de vozes: o fio construtor do estilo de José Bezerra Gomes no romance A porta e o vento

This research aims to investigate the process of stylistic construction in novelistic prose of Northeastern Brazilian writter José Bezerra Gomes, taking as a corpus his novel called A porta e o vento. The theoretical foundations supporting this study are related to the ideas disseminated by a group of linguistic researchers known as Bakhtin Circle, especially the notions of dialogic language, literary word, concrete utterance, social voices, and sociological style/stylistic. Concerning to methodological guidance, this work is characterized by adopting the interpretive paradigm of socio-historical background, still situated in the great field of Applied Linguistics, an undisciplinary area of research and frontier whose primary focus is concrete and situated language. The analysis allowed me to hear several social voices embodied therein, realizing a variety of dialogs, numerous worldviews in constant struggle, that due to the management and the finish given by the author, eventually create a tone, a unique composition compared to other discourses and current styles in his midst. Ideological clashes are evident: the voice of tradition versus particular character Santos’ voice regarding the institution of marriage; confrontation between antagonistic hinterland pictures - a living hinterland (rich and diverse) as opposed to the stereotypical notion of hinterland (poor and sterile); and the door and the wind as a metaphor of a fighting arena and a hint of poeticization of the language of prose. The main feature of Bezerra’s style in A porta e o vento is related to the aforesaid modes dialogization voices present in the novel. Therefore, one can found veiled polemic, dialogical replicas and veiled dialogues, which are categories already discussed in Bakhtin's theory, but also other new modes dialogization, grounded in the dynamics of living and concrete language

Abordagens de estudo e performance da obra Responsório ao vento para violoncelo solo de Sílvio Ferraz

Recognized for his relevant writing for the cello, Silvio Ferraz wrote , in 2012, Segundo Responsório for cello solo and chamber group which followed Responsório ao Vento , a version of the same piece for solo cello . The work is characterized by the idea of continuity of sound moving through different textures , timbres , dynamics and musical gestures. The composer uses extended techniques, such as large sections in sul tasto playing three strings simultaneously, trills of natural harmonics , muffled trills with natural harmonics , col legno batuto , different types of glissando and simultaneous sounds of harmonic and non harmonic notes corroborate to a wealth of sounds and layers that create different textures. This article investigates the relationship of the composer with the cello, and relates Responsório ao Vento to his other works and studies the influences of the composer addressing technical and interpretive aspects of the piece drawn from performance experiences.