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Full-Text Articles in Physics
Temperature And Pressure Effects On Elastic Properties Of Relaxor Ferroelectrics And Thermoelectrics: A Resonant Ultrasound Spectroscopy Study, Sumudu Tennakoon
Temperature And Pressure Effects On Elastic Properties Of Relaxor Ferroelectrics And Thermoelectrics: A Resonant Ultrasound Spectroscopy Study, Sumudu Tennakoon
Electronic Theses and Dissertations
Relaxor ferroelectric lead magnesium niobate-lead titanate (PMN-PT) material exhibits exceptional electromechanical properties. The material undergoes a series of structural phase transitions with changes in temperature and the chemical composition. The work covered in this dissertation seek to gain insight into the phase diagram of PMN-PT using temperature and pressure dependence of the elastic properties. Single crystal PMN-PT with a composition near morphotropic phase boundary (MPB) was investigated using a resonant ultrasound spectroscopy (RUS) methodologies in the temperature range of 293 K - 800 K and the pressure range from near vacuum to 3.4 MPa. At atmospheric pressure, significantly high acoustic …
Computation Of Acoustic Ressure Fields Produced In Feline Brain By High-Intensity Focused Ultrasound, Nazanin Omidi
Computation Of Acoustic Ressure Fields Produced In Feline Brain By High-Intensity Focused Ultrasound, Nazanin Omidi
Electronic Theses and Dissertations
In 1975, Dunn et al. (Jasa 58:512-514) shothat a simple relation describes the ultrasonic threshold for cavitation induced changes in the mammalian brain. The thresholds for tissue damage were estimated for a variety of acoustic parameters in exposed feline brain. The goal of this study was to improve the estimates for acoustic pressures and intensities present in vivo during those experimental exposures by estimating them using nonlinear rather than linear theory. In our current project, the acoustic pressure waveforms produced in the brains of anesthetized felines were numerically simulated for a spherically focused, nominally f1-transducer (focal length = 13 cm) …