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Acoustic interferometer
About: Acoustic interferometer is a research topic. Over the lifetime, 1493 publications have been published within this topic receiving 19355 citations.
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TL;DR: In this article, the authors measured the attenuation of liquid argon, nitrogen, and oxygen at their boiling points with a variable path-length two-crystal acoustic interferometer.
Abstract: The ultrasonic attenuation at 1 GHz was measured in liquid argon, nitrogen, and oxygen at their boiling points with a variable‐path‐length two‐crystal acoustic interferometer. The attenuation in argon shows an absorption in excess of the value calculated from the classical Stokes‐Kirchhoff equation for shear viscosity and thermal conductivity. The excess absorption can be attributed to a volume viscosity predicted by Gray and Rice, and is in good agreement with the lower‐frequency measurements of others such as Naugle and Squire. The attenuation measurement in nitrogen shows a similar excess absorption and is in good agreement with the lower frequency values of Singer and Lunsford. The ultrasonic attenuation measurements in oxygen indicate that it may also have a volume viscosity. In the process of aligning the apparatus, some data were obtained in methanol that give a lower volume viscosity than that observed at lower frequencies.
1 citations
18 May 1997
TL;DR: In this paper, the effect of photo-induced index change in the surrounding material on the transmitted light was investigated and photodarking occurred in the wings of the 270-pm-diameter write beam.
Abstract: CTuX3 Fig. 1 White-light transmission image of an array of microlenses in Ge,,Se,,. Spaced 400 pm apart, their diameters are 150 2 20 pm. The rings surrounding the lenses are not depressions, but rather the effect of a photoinduced index change in the surrounding material on the transmitted light. This photoinduced change is due to photodarkening occurring in the wings of the 270-pm-diameter write beam. The beam was cw at 800 nm with an incident intensity of 120 W/cmZ.
1 citations
TL;DR: In this article, the hydrodynamic action functional is constructed for a magnetized electron-ion plasma by the method of successive integration, first with respect to fast and slow fields, respectively, and the absorption of the longitudinal electromagnetic waves is computed with the aid of this functional.
Abstract: The path integration method is used to study the absorption of waves in plasma. The absorption is considered of longitudinal electromagnetic waves as a consequence of scattering on the transverse waves, which requires the introduction of an integration with respect to a supplementary field of the vector potential. The scattering on the transverse waves becomes the determining one for a one-component plasma in the long wavelength limit. The hydrodynamic action functional is constructed for a magnetized electron-ion plasma by the method of successive integration, first with respect to “fast” fields and, next, with respect to “slow” fields. The absorption of the longitudinal waves is computed with the aid of this functional. The domains of frequencies of the order of the plasma frequency and of the order of the cyclotron frequency are considered. In comparison with the case of a free plasma, here the Coulomb logarithm is varied.
1 citations
Patent•
12 Dec 2012TL;DR: In this article, the prostate gland or other region of interest is stimulated with either a light source or an ultrasound source, resulting in photoacoustic or ultrasound acoustic waves which are focused by an acoustic lens and captured by a specific 1- or 2D sensor array and subsequently displayed as a C-scan on a computer screen.
Abstract: The prostate gland or other region of interest is stimulated with either a light source or an ultrasound source, resulting in photoacoustic or ultrasound acoustic waves which are focused by an acoustic lens and captured by a specific 1- or 2D sensor array and subsequently displayed as a C-scan on a computer screen. The amplitude of the waves generated by the stimulation is proportional to the optical absorption of the tissue element at that spatial location. Variability in tissue absorption results in C-scan image contrast.
1 citations
17 Oct 1999
TL;DR: In this article, the authors investigated the influence of a thin conducting layer on the velocity and attenuation of plate waves and found that changes in these parameters as high as 50% and 30 dB per wavelength can be achieved for change in layer sheet conductance from 10-7 to 10-5 S.
Abstract: The characteristics of acoustic waves propagating in thin plates of single crystal potassium niobate are theoretically investigated. It is found that acoustic plate waves can provide extremely high values of electromechanical coupling. For example, values of Δv/v, the fractional velocity change produced by electrical shorting of the surface, as high as 0.5 can be obtained with the shear horizontal (SH0) wave. The influence of a thin conducting layer on the velocity and attenuation of plate waves is investigated. It is shown that variations in these parameters as high as 50% and 30 dB per wavelength can be achieved for change in layer sheet conductance from 10-7 to 10-5 S.
1 citations