N. Chubachi

Bio: N. Chubachi is an academic researcher. The author has an hindex of 1, co-authored 1 publications receiving 530 citations.

Material Characterization by Line-Focus-Beam Acoustic Microscope

Abstract: On propose une nouvelle methode de caracterisation tres precise des materiaux. On mesure les caracteristiques de propagation des ondes de fuite a la limite entre l'eau et l'echantillon; la vitesse de phase et l'attenuation sont determinees a travers des mesures de la courbe V(z). On presente une methode d'analyse spectrale pour obtenir les proprietes acoustiques a partir des courbes V(z). Description des mesures effectuees en utilisant des materiaux isotropes ou anisotropes pour lesquels les vitesses s'etendent de 2000 a 11000 m/s. On examine tous les modes d'ondes de fuite impliques dans les phenomenes d'interferences dans les courbes V(z). Resultats experimentaux confirmant les resultats theoriques. Application a l'analyse de la structure des materiaux polycristallins

Elastic constants of single‐crystal transition‐metal nitride films measured by line‐focus acoustic microscopy

Abstract: The elastic constants of single‐crystal NbN, VN, and TiN films were determined from surface acoustic wave (SAW) dispersion curves obtained by the use of an acoustic microscope with a line‐focus beam. Measurements were carried out for single‐crystal nitride films grown on the (001) plane of single‐crystal cubic‐symmetric MgO substrates. The phase velocities measured as functions of the angle of propagation display the expected anisotropy. Dispersion curves of SAWs propagating along the symmetry axes were obtained by measuring the wave velocities for various film thicknesses and frequencies. Using a modified simplex method, an inversion of the SAW dispersion data yielded the elastic constants of cubic symmetry, namely c11, c12, and c44. The Rayleigh surface wave velocities calculated from the determined elastic constants and known mass densities agree well with a result measured by Brillouin scattering spectroscopy reported elsewhere.

Generation and control of sound bullets with a nonlinear acoustic lens

Abstract: Acoustic lenses are employed in a variety of applications, from biomedical imaging and surgery to defense systems and damage detection in materials. Focused acoustic signals, for example, enable ultrasonic transducers to image the interior of the human body. Currently however the performance of acoustic devices is limited by their linear operational envelope, which implies relatively inaccurate focusing and low focal power. Here we show a dramatic focusing effect and the generation of compact acoustic pulses (sound bullets) in solid and fluid media, with energies orders of magnitude greater than previously achievable. This focusing is made possible by a tunable, nonlinear acoustic lens, which consists of ordered arrays of granular chains. The amplitude, size, and location of the sound bullets can be controlled by varying the static precompression of the chains. Theory and numerical simulations demonstrate the focusing effect, and photoelasticity experiments corroborate it. Our nonlinear lens permits a qualitatively new way of generating high-energy acoustic pulses, which may improve imaging capabilities through increased accuracy and signal-to-noise ratios and may lead to more effective nonintrusive scalpels, for example, for cancer treatment.

Advances in acoustic microscopy

Abstract: Characterization of Electronic Components by Acoustic Microscopy G. Pfannschmidt. Interaction of Acoustic Waves with Solid Surfaces Y. Tsukahara, et al. Scanning Acoustic Microscopy with Phase Contrast W. Grill, et al. Ultrasonic Focusing with Time Reversal Mirrors M. Fink, C. Prada.

Material Characterization by the Inversion of V(z)

Abstract: Absfmet-It is demonstrated that the reflectance function R(@) of a liquid-solid interface can be obtained by inverting the complex V(z) data collected with an acoustic microscope. The inversion algorithm is based on a nonparaxial formulation of the V(z) integral, which establishes the Fourier transform relation between R(@) and V(z). Examples are given to show that with this measurement technique, the acoustic phase velocities of the propagating modes in the solid medium can easily be determined and material losses can be estimated. The same technique is also used for characterizing imaging performance of focused systems. Applications In thin-6lm measurement are also discussed.

Fundamentals And Applications Of Ultrasonic Waves

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