Piezoelectric Ultrasonic Micromotors

This report describes development of micro-fabricated piezoelectric ultrasonic motors and bulk-ceramic piezoelectric ultrasonic motors. Ultrasonic motors offer the advantage of low speed, high torque operation without the need for gears. They can be made compact and lightweight and provide a holding torque in the absence of applied power, due to the traveling wave frictional coupling mechanism between the rotor and the stator. This report covers modeling, simulation, fabrication and testing of ultrasonic motors. Design of experiments methods were also utilized to find optimal motor parameters. A suite of 8 mm diameter x 3 mm tall motors were machined for these studies and maximum stall torques as large as 10^(- 3) Nm, maximum no-load speeds of 1710 rpm and peak power outputs of 27 mW were realized. Aditionally, this report describes the implementation of a microfabricated ultrasonic motor using thin-film lead zirconate titanate. In a joint project with the Pennsylvania State University Materials Research Laboratory and MIT Lincoln Laboratory, 2 mm and 5 mm diameter stator structures were fabricated on 1 micron thick silicon nitride membranes. Small glass lenses placed down on top spun at 100-300 rpm with 4 V excitation at 90 kHz. The large power densities and stall torques of these piezoelectric ultrasonic motors offer tremendous promis for integrated machines: complete intelligent, electro-mechanical autonomous systems mass-produced in a single fabrication process.

D'on v??nen els aliments?. '??De d??nde vienen los alimentos?'

Disponible el video en beta

Tú y yo. = Nde ha Che. Primer Ciclo EBB.

En este libro del participante de la educación básica bilingüe para jóvenes y adultos se incluyen dos partes claramente difeenciadas. La primera parte va dirigida a los docentes de este Ciclo de la EBJA y se recogen los objetivos generales, orientaciones para el logro de competencias, distribución de tiempos y orientaciones para la evaluación. En la segunda parte, dirigida a docentes y estudiantes se organiza el contenido de aprendizaje en torno a cinco ejes organizadores: Mi lindo país, Soy sano y feliz, Nos alimentamos mejor. Lo mejor de mi tierra y Nos ayudamos. Con una metodologia basada en la reflexión-acción pretende el desarrollo de capacidades de lecto-escritura y cálculo en participantes que no poseen las competencias instrumentales básicas. .

Hacia d??nde va la formaci??n permanente en Am??rica Latina

El art??culo forma parte del monogr??fico de la revista dedicado a: la formaci??n permanente del profesorado

??D??nde situamos las emociones?

Se trata de un reportaje relacionado con la implantaci??n de una asignatura de Educaci??n Emocional en Bachillerato. La experiencia se lleva a cabo en el IES Asta Regia de Jerez de la Frontera (C??diz). Se describen los objetivos del proyecto, su organizaci??n y la programaci??n de las actividades, entre otras el taller de padres y madres, as?? como una valoraci??n de los resultados.

??A d??nde va la pedagog??a social? : Exaptation como modelo pedag??gico de desarrollo en la era de la crisis global

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El escenario de la calidad en la Universidad espa??ola : de d??nde venimos y hacia d??nde vamos

Monogr??fico con el t??tulo: "Calidad en la Educaci??n Superior: una visi??n en perspectiva"

??Por d??nde empiezo? : Reflexiones desde la pr??ctica

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??De d??nde son los hijos de los inmigrantes? : la construcci??n de la identidad y la escuela

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Are there hazardous auditory effects of high-frequency turbines and ultrasonic dental scalers on dental professionals?

The purpose of this pilot study was to survey dentists in the St. Louis area to assess their subjective opinion of commonly used dental handpieces as well as history of noise exposure and use of hearing protection. Selected handpieces were then chosen to measure their output levels and determine if emissions are hazardous to the auditory system.

Sonic to ultrasonic Q of sandstones and limestones: Laboratory measurements at in situ pressures

Laboratory measurements of the attenuation and velocity dispersion of compressional and shear waves at appropriate frequencies, pressures, and temperatures can aid interpretation of seismic and well-log surveys as well as indicate absorption mechanisms in rocks. Construction and calibration of resonant-bar equipment was used to measure velocities and attenuations of standing shear and extensional waves in copper-jacketed right cylinders of rocks (30 cm in length, 2.54 cm in diameter) in the sonic frequency range and at differential pressures up to 65 MPa. We also measured ultrasonic velocities and attenuations of compressional and shear waves in 50-mm-diameter samples of the rocks at identical pressures. Extensional-mode velocities determined from the resonant bar are systematically too low, yielding unreliable Poisson's ratios. Poisson's ratios determined from the ultrasonic data are frequency corrected and used to calculate the sonic-frequency compressional-wave velocities and attenuations from the shear- and extensional-mode data. We calculate the bulk-modulus loss. The accuracies of attenuation data (expressed as 1000/Q, where Q is the quality factor) are +/- 1 for compressional and shear waves at ultrasonic frequency, +/- 1 for shear waves, and +/- 3 for compressional waves at sonic frequency. Example sonic-frequency data show that the energy absorption in a limestone is small (Q(P) greater than 200 and stress independent) and is primarily due to poroelasticity, whereas that in the two sandstones is variable in magnitude (Q(P) ranges from less than 50 to greater than 300, at reservoir pressures) and arises from a combination of poroelasticity and viscoelasticity. A graph of compressional-wave attenuation versus compressional-wave velocity at reservoir pressures differentiates high-permeability (> 100 mD, 9.87 X 10(-14) m(2)) brine-saturated sandstones from low-permeability (< 100 mD, 9.87 X 10 (14) m(2)) sandstones and shales.