1,721,255 research outputs found
High and Uniform Surface Potential and Improved Time Stability of SiO2/Si3N4 Electret charged by negative corona discharging
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Design of High-efficiency Power Amplifier System for High-directional Speaker
No full textParametric array transducers are used for highly directional speaker in an air environments. Piezoelectric micromachined ultrasonic transducers for parametric array transducers need DC-biased voltage driving signals in order to get high-directional quality-sound features. The existing power amplifier such as class A amplifiers has low efficiency and require large volume heatsinks. To overcome the above-mentioned disadvantages of the conventional amplifier, this paper proposes a new power amplifier system. The proposed power amplifier system ensures high linearity of output characteristic by utilizing the push-pull class B type amplifier. Furthermore, the proposed power amplifier system gets high efficiency because it contains the DC-DC converter-type power supply which can perform energy recovery and envelope tracking function. Also the paper suggests the detailed circuit topology. Its characteristics are verified by the detailed experimental results.11scopuskc
Technique to analyze response characteristics of the underwater acoustic transducer array considering mutual radiation effect
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Helmholtz-Kirchhoff integral formula for predicting the acoustic pressure from a radiator including irregular surface
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Fabrication Method for Thin Stepped Plate High Directional Ultrasonic Radiator with Plastic Steps
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Evaluation of Polymer Materials for MEMS Microphones
No full text`Polymers are attractive materials for the fabrication of micro-electro-mechanical system (MEMS) microphones because of their low Young's moduli, generally lower processing temperatures than silicon, and simple fabrication; such microphones are sensitive and economical. However, an earlier polymer diaphragm revealed lower sensitivity than expected. In addition, the viscoelastic properties of polymer diaphragm have been considered to degrade the sensing performance due to a high-level mechanical noise. Here, we investigated the possibility of the polymer material as a MEMS microphone in terms of stiffness and damping. Stiffness was analyzed and experimentally verified. The obtained polymer diaphragm damping coefficient was compared with the coefficient of a silicon MEMS microphone to explore whether performance was degraded by material damping. All samples were fabricated using a thin film transfer method. SU-8 was mainly used but Polymethyl methacrylate (PMMA) was also selected for comparing the material damping effect. The measured residual stress of an SU-8 diaphragm was 18 MPa; the measured flexibility was similar to the state-of-art of a silicon-based MEMS microphone, and it was proven that there is room for further improvement through process optimization. The damping effect induced by viscoelasticity was very small, compared with the effect of air damping; indeed, the intrinsic damping effect of the polymer on device performance was negligible. [2021-0213]11Nsciescopu
A method for maximization the piezoelectric coefficient of poly(γ-benzyl-α,L-glutamate) micro/nanofibers
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