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An inverse method based on Simulated Annealing was proposed in previous work, to help determining the first and second order temperature coefficients of the components of the LGS material tensors. The motivation and objective of this work were to improve the method, by drastically reducing the optimization time that lasted from several hours to several days. The main idea was to use the Design of...
Acoustic properties for Ca3Nb(Ga1−xAlx)3Si2O14 [CNGAS(x)] single crystals were experimentally investigated as a function of Al substitution content. Several plate specimens of the X-, Y-, Z-, 40°Y-, and 145°Y-cut were prepared from CNGAS(x) single crystal ingots (x=0, 0.25, and 0.50) grown by Czochralski technique. Velocities of longitudinal wave, shear wave, and leaky surface acoustic wave (LSAW)...
Effects which arise as a result of Hertzian contact between adjacent spheres of a granular chain can potentially change the nature of a signal as it propagates down the chain. The possibility thus exists of generating signals with a different harmonic content to the signal input into one end of the chain. This transduction mechanism has the potential to be of use in both diagnostic and therapeutic...
Phononic crystals (PnC) consist of two or more materials arranged in a spatially periodic manner. Introduction of a defect into the crystal lattice is a technique to create resonant modes. The idea behind the application of a PnC as sensor element is the dependence of the characteristic features of those modes on speed of sound. Currently the sensor designs are based on common 2D phononic crystal...
This work is focused on the application of Phononic Crystals to reduce anchor losses of MEMS contour mode resonators. Anchor losses dominates the losses in these type of released resonators at low frequency and at low temperature. The use of phononic crystals, intended as finite-periodic distribution of holes in the anchor, is fully compatible with fabrication processes and moreover it is easy to...
we examined acousto-optic interaction in the KH2PO4 crystal used in devices providing control of optical radiation parameters. The crystal was applied in a wide-angle tunable acousto-optic filter capable of image processing in the ultraviolet region of spectrum. The filter operated at different temperature conditions because of changes of environmental temperature and also due to heating of the crystal...
Acoustic waves in a phononic crystal (PnC) showed properties of band gaps and anisotropic propagation and promised many applications. By arranging the filling fraction of PnCs gradually in space, a gradient-index (GRIN) PnC was proposed to bend the wave propagation. GRIN PnCs were reported and applied as an acoustic lens to focus acoustic waves. Theoretically, this kind of lens has a hyperbolic secant...
In the paper, an algorithm has been proposed to detect anomaly/damage in anisotropic piezoelectric crystals. Lithium Niobate piezoelectric single crystal is our test model to demonstrate the damage quantification algorithm. Surface acoustic waves (SAW) sensors are highly sensitive to surface perturbation and abrasions which reduce the performance of piezoelectric sensors. A macro-scale surface flaw...
In this experiment, [100]. [110] and [111] single crystal silicon wafers were interrogated by line focused ultrasonic transducer with large aperture. Lamb waves generated in the wafers were detected by same transducer, and the rf signals, V (t, z) were acquired as varying defocusing distance. Since Lamb wave is dispersive, a numerous modes were mixed in the detected rf signal. A series of signal processing...
High frequency (≥20 MHz) phased-array ultrasound transducers exhibit many benefits in biomedical applications. However, high performance array transducers, with high resolution and high sensitivity, are hard to fabricate due to the limitation of their rigorous dimensions. In this study, to achieve a high −6 dB bandwidth, a 20-MHz 64-elements phased-array transducer based on a PMN-0.3PT single crystal...
In this study, phononic crystals are employed to elastic waveguide transducers for controlling its beam patterns. When signals from the transducer array are inputted to a homogeneous waveguide, they are distorted as propagating due to generation of multiple wave modes and wave dispersion. For this reason, it is difficult to apply transducer array to manipulate the beam pattern of waveguide transducers...
The aim of this work is to study the mechanisms of enlargement of band gaps in phononic strips and to present the characterization of such a structure. Indeed, to our knowledge, the gap-to-midgap ratio of the PC strips used for applications in literature does not exceed 45%. Yet, large band gaps generally imply better performances for phononic devices and a stronger robustness to fabrication tolerances...
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