Acoustic Field
Mostrando 13-24 de 79 artigos, teses e dissertações.
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13. The fundamental elements in certain inverse acoustic problems: their roles and interactions
Acoustic holography and holophony, wave field synthesis and active noise control are based on common elements which are causality, model, objective, and regularization. In the frequency domain (putting causality aside), a simple formulation states the influence - not the interaction - of errors of the model and objective and of regularization of the results.
J. Braz. Soc. Mech. Sci. & Eng.. Publicado em: 2012
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14. Inversão sísmica para impedância acústica na caracterização de reservatórios : impacto da extração da wavelet e do aumento da banda de frequências / Seismic inversion to acoustic impedance in reservoir caracterization : the impact of wavelet extraction and increase the frequency band
The substrates that constitute a reservoir are identified using seismic data. The process consists of determining reservoir petrophysical properties. However, sub-seismic layers structures are masked due to the limitation of conventional seismic data. The failure provided by these data produces an erroneous model of reservoir. The lack of vertical resolution
IBICT - Instituto Brasileiro de Informação em Ciência e Tecnologia. Publicado em: 25/11/2011
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15. Coeficiente de espalhamento sonoro de painéis perfurados / Scattering sound coefficient of perforated panels
Project studios, concert halls, theaters or places that require quality acoustics for musical activities, require studies on its volume, shape and composition of their surfaces, in order to achieve a place that fulfills its function acoustics. In cases where the volume and shape of these rooms are already defined, it is the acoustic designer to define materi
IBICT - Instituto Brasileiro de Informação em Ciência e Tecnologia. Publicado em: 10/08/2011
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16. Resolução temporal auditiva de crianças usuárias de implante coclear / Auditory temporal resolution in children using cochlear implantation
Auditory temporal resolution is considered one of the most important skills for acoustic signal processing along the time. It allows the identification of fine differences of speech segmental aspects, such as phonemes and the beginning and end of words in linked phrases. Children using a cochlear implant (CI) present specific characteristics of speech sign d
IBICT - Instituto Brasileiro de Informação em Ciência e Tecnologia. Publicado em: 15/07/2011
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17. Employment of acoustic field for pollutant emission reduction under lean combustion
Pulsating combustion is a technique that directly intervenes in combustion processes modifying pollutant emissions and increasing thermal efficiency by varying pressure and temperature in the flame region. The pulsations accelerate mixture rate between oxidant and fuel, resulting in a more intense combustion process, with low fuel waste and potential for low
IBICT - Instituto Brasileiro de Informação em Ciência e Tecnologia. Publicado em: 13/07/2011
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18. Métodos geoestatísticos de co-estimativas: aplicação aos dados do Campo Escola de Namorado / Co-estimation geostatistical methods: applications to the Namorado Oil Field data
Data used for studying petroleum reservoirs are obtained through drill core, well logs, seismic records and, as a consequence, they present different sampling scales. Multivariate geostatistics is a manner of integrating these data in order to co-estimate a poorly sampled variable based not only on its own information but also on a densely sampled variable.
IBICT - Instituto Brasileiro de Informação em Ciência e Tecnologia. Publicado em: 03/06/2011
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19. Modelagem de ondas ultrassônicas refletidas por superfícies de geometrias diversas. / Modeling for ultrasonics waves of reflected surfaces of various geometries.
Neste trabalho são analisados os campos acústicos gerados por transdutores ultrassônicos planos e circulares, do tipo pistão plano, no modo pulso-eco, trabalhando como emissor e receptor de ondas, com freqüências de 1,6 MHz, 2,25 MHz e 5 MHz. As ondas emitidas por esses transdutores interagem com interfaces denominadas alvos, com diversas geometrias de
IBICT - Instituto Brasileiro de Informação em Ciência e Tecnologia. Publicado em: 20/05/2011
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20. Acoustic beam modeling of ultrasonic transducers and arrays using the impulse response and the discrete representation methods
The impulse response of the velocity potential and the discrete representation methods were used in order to model the acoustic field radiated by ultrasonic transducers and arrays. The first method deals with the calculation of the exact impulse response, in which solutions are possible only for simple geometries, such as the circular piston. The second meth
Journal of the Brazilian Society of Mechanical Sciences and Engineering. Publicado em: 2011-12
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21. Observational consequences of a dark interaction model
We study a model with decay of dark energy and creation of the dark matter particles. We integrate the field equations and find the transition redshift where the evolution process of the universe change the accelerated expansion, and discuss the luminosity distance, acoustic oscillations and the statefinder parameters.
Brazilian Journal of Physics. Publicado em: 2010-12
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22. Estudo de materiais magnéticos através de técnicas fototérmicas : efeito magnetocalórico e filmes finos / Study of magnetic materials using photothermal techniques : magnetocaloric effect and thin films
The magnetocaloric effect (MCE) has been widely studied because of its possible application in magnetic refrigeration. The search for suitable materials has intensified over the last decade, with a demand not only for the preparation of new materials but also for their complete characterization. The aim of this work is to apply the photothermal techniques to
Publicado em: 2010
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23. Tin and zinc oxides semiconductor devices / Dispositivos semicondutores a partir de óxidos de estanho e zinco
This work presents the study and development of semiconductor devices base on tin and zinc oxides. The first device is related to the development of pH sensors based on field effect, while the second device uses surface acoustic waves for the transport of carriers related to a single photon detector device. Initially, the semiconductors were used as hydrogen
Publicado em: 2009
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24. Espalhamento e absorção de campos bosônicos por buracos negros estáticos e análogos / Scattering and absorption of bosonic fields by static blach holes and analogues
Nesta tese apresentamos a análise da absorção e do espalhamento de partículas não massivas de spins 0 e 1 por buracos negros de Schwarzschild, assim como a absorção e espalhamento por análogos acústicos destes buracos negros. Apresentamos também a análise da absorção e do espalhamento do campo escalar não massivo por buracos negros de Reissner-
Publicado em: 2009