1,056 research outputs found

    Highly confined Love waves modes by defect states in a holey SiO2 /quartz phononic crystal

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    Highly confined Love modes are demonstrated in a phononic crystal based on a square array of etched holes in SiO 2 deposited on the ST-cut quartz. An optimal choice of the geometrical parameters contributes to a wide stop-band for shear waves' modes. The introduction of a defect by removing lines of holes leads to the nearly flat modes within the band gap and consequently paves the way to implement advanced designs of electroacoustic filters and high-performance cavity resonators. The calculations are based on the finite element method in considering the elastic and piezoelectric properties of the materials. Interdigital transducers are employed to measure the transmission spectra. The geometrical parameters enabling the appearance of confined cavity modes within the band gap and the efficiency of the electric excitation were investigated

    Micro-systèmes et contrôle d'écoulements

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    Les micro-systèmes magnéto-mécaniques présentent des possibilités intéressantes en matière de contrôle d'écoulements. Ils permettent de remplir les cahiers des charges des constructeurs aéronautiques ou automobiles. Ils sont également plus facilement intégrables sur les prototypes que les MEMS issus de microtechnologies entièrement intégrées. On présentera quelques tests en soufflerie. Les effets sur les écoulements seront discutés et les perspectives tracées

    A millimeter-wave inflatable frequency-agile elastomeric antenna

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    This letter reports a millimeter-wave frequency agile microstrip antenna printed on an ultrasoft elastomeric PDMS substrate. The microstrip patch antenna is supported by a PDMS membrane suspended over an air cavity. The distance H between the patch and the ground plane, and thus the resonant frequency of the antenna, are tuned using pneumatic actuation, taking advantage of the extreme softness of the PDMS membrane. A continuous frequency shift varying from 55.35 to 51 GHz ( ≈8%) has been obtained for a tuning range of H between 200µm and 575µm. In all configurations, the antenna remains matched and its radiation characteristics are very satisfactory
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