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    ABSTRACT: This paper presents the characterization and modeling of a permanent-magnet (PM) microgenerator operating at high temperatures. Due to the thermal dependence of the relevant properties of the conductor and magnetic materials, degradation of the output electrical power with increased temperature is expected. Each material of the PM microgenerator is magnetically or electrically characterized up to 375 °C. For a rotor designed for high temperature operation using SmCo magnets, 2.7 W of DC power has been obtained at 100 °C and 210,000 rpm, which is a 35% drop as compared to the output power at room temperature. This result is in good agreement with theory. Calculations showed that this PM generator is capable of 2.4 W of DC output power at an operating temperature of 300 °C if the rotational speed is increased up to the 300,000 rpm, as achieved with previous room temperature devices. This work demonstrates that MEMS-based permanent-magnet microgenerators are good candidates as a component of a heat-engine-driven electrical power generation system.
    Sensors and Actuators A Physical 11/2008; · 1.84 Impact Factor
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    ABSTRACT: First Page of the Article
    1978 Ultrasonics Symposium; 02/1978
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    ABSTRACT: A noncontact optical system for generation and detection of ultrasound is described. A confocal Fabry-Perot interferometer combined with a multimode optical fiber is used to reconstruct ultrasound images on a sample with a rough surface. The optical fiber is automatically adjusted to optimal positions for effective collection of scattered light from the sample. The confocal Fabry-Perot interferometer provides sensitive detection independent of surface roughness. The system is applied to a fatigue test sample, with which a conventional interferometer has poor sensitivity because of irregularities on the sample surface. The 2D profiles of the fatigue crack are successfully obtained at temperatures up to 1000°C. The crack length estimated from the profile agrees well with that measured using an optical method.
    Japanese Journal of Applied Physics 01/1993; 32:2540-2542. · 1.07 Impact Factor

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