Piezoelectric Transducers
Mostrando 13-21 de 21 artigos, teses e dissertações.
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13. Determinação experimental do fluxo térmico em um corpo rombudo em regime hipersônico com adição de energia à montante / Experimental heat flux to a blunt body in hypersonic flow with upstream laser energy deposition
Due to the high heat transfer rates which takes place in hypersonic flight and the consequent necessity of prohibitively massive thermal protection equipment, new methods of flow control are required to enable flight in such regimes. Here arises the Direct Energy Air Spike concept, where electromagnetic energy (laser/microwaves) is focalized upstream of the
Publicado em: 2005
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14. DEVELOPMENT OF METHODOLOGY FOR CALIBRATING PIEZOELECTRIC TRANSDUCERS USED IN INTERNAL BALLISTICS FOR TRANSIENT PRESSURE MEASUREMENTS / DESENVOLVIMENTO DE METODOLOGIA DE CALIBRAÇÃO DE TRANSDUTOR PIEZELÉTRICO DE PRESSÃO UTILIZADO EM BALÍSTICA INTERNA
The current research, of armaments industry`s interest, more specifically in the quality control of ammunition lots, is related to the development of methodology for calibrating piezoelectric transducers for transient pressure measurements associated with events whose duration is of the order of milliseconds. As its main contribution, this work presents prop
Publicado em: 2004
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15. Study of apodization of piezoeletric ceramics / Estudo da apodização de ceramicas piezoeletricas
The objective of this work was to optimize the process of apodization of piezoelectric ceramics disks, looking for the better relation between the insulating oil bath temperature and the smaIlest period of time through which the poling field must be applied. The apodization of the piezoelectric ceramic is performed to reduce the diffraction in the acoustic f
Publicado em: 2003
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16. Development of characterization techniques of piezoelectric transducers. / Desenvolvimento de técnicas de caracterização de transdutores piezelétricos.
O projeto de transdutores piezelétricos envolve modelagens matemáticas e verificações experimentais, que são necessárias para validá-los. Através das análises dos transdutores verificam-se as influências das condições de contorno experimentais e as dificuldades para modelá-las. No entanto, na literatura atual este ponto não é discutido de form
Publicado em: 2002
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17. MODELS FOR PIEZOELECTRIC INTERDIGITAL TRANSDUCERS FOR THE EXCITATION OF GUIDED WAVES IN COMPOSITE BEAMS / MODELAGEM DE ATUADORES PIEZOELÉTRICOS INTERDIGITAIS PARA GERAÇÃO DE ONDAS GUIADAS EM VIGAS COMPÓSITAS
O presente trabalho apresenta uma modelagem da geração de ondas guiadas em estruturas laminadas compósitas através de atuadores piezoelétricos interdigitais.O estudo foi desenvolvido a partir de uma técnica que se baseia na teoria discreta de Reddy e modela os campos de deslocamento e esforços e velocidades generalizadas nas interfaces de uma estrutur
Publicado em: 2002
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18. Efeitos da polarização não-uniforme de ceramicas piezoeletricas no campo de Transdutores de ultra-Som
The objective of apodization (non uniform polarization) was to obtain piezoelectric ceramic discs that would vibrate more intensively in the central region than in the edge, to produce ultrasound transducers with acoustic fields where the contributions of the edge waves were minimal, reducing diffraction effects. A program to implement the Finite Element Met
Publicado em: 1998
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19. Direct measurement of local pressures in the cadaveric human hip joint during simulated level walking.
Eleven piezoelectric pressure transducers, each supporting an area of articular cartilage about 3 mm in diameter, were inserted through the bone of the acetabulum. Nine cadaveric hip joints, thus instrumented, were subjected to forces representing six instants in a typical level walking cycle, including the highest and lowest force. Under the highest force,
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20. Thermodynamic response of soft biological tissues to pulsed infrared-laser irradiation.
The physical mechanisms that achieve tissue removal through the delivery of short pulses of high-intensity infrared laser radiation, in a process known as laser ablation, remain obscure. The thermodynamic response of biological tissue to pulsed infrared laser irradiation was investigated by measuring and analyzing the stress transients generated by Q-sw Er:Y
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21. The thermodynamic response of soft biological tissues to pulsed ultraviolet laser irradiation.
The physical mechanisms that enable short pulses of high-intensity ultraviolet laser radiation to remove tissue, in a process known as laser ablation, remain obscure. The thermodynamic response of biological tissue to pulsed laser irradiation was investigated by measuring and subsequently analyzing the stress transients generated by pulsed argon fluorine (Ar