High Frequency Acoustic Waves Research Articles

Change in the characteristics of amorphous As2S3 induced by injected acoustic domains

This paper is concerned with a change in the acoustical and optical properties and X-ray diffraction patterns of a-As2S3 induced by injecting high frequency and high energy CdS acoustic domains. At first the bonding techniques for high frequency acoustic wave transmission are experimentally examined for various bonding agents. Then, high energy acoustic domains are injected into the a-As2S3 and the samples are examined by optical transmission and X-ray diffraction. The acoustic flux injection causes a structural change in the a-As2S3 which is recovered by annealing. It is shown that high energy acoustic injection is equivalent to annealing in a furnace.

A Note on the Absorption of High Frequency Acoustic Waves in Dielectric Solids

physica status solidi (b)Volume 97, Issue 1 p. K5-K8 Short Note A Note on the Absorption of High Frequency Acoustic Waves in Dielectric Solids I. F. I. Mikhail, I. F. I. Mikhail Department of Applied Mathematics, Faculty of Science, A'in Shams University, Cairo Search for more papers by this author I. F. I. Mikhail, I. F. I. Mikhail Department of Applied Mathematics, Faculty of Science, A'in Shams University, Cairo Search for more papers by this author First published: 1 January 1980 https://doi.org/10.1002/pssb.2220970144 Cairo, Egypt. AboutPDF ToolsRequest permissionExport citationAdd to favoritesTrack citation ShareShare Give accessShare full text accessShare full-text accessPlease review our Terms and Conditions of Use and check box below to share full-text version of article.I have read and accept the Wiley Online Library Terms and Conditions of UseShareable LinkUse the link below to share a full-text version of this article with your friends and colleagues. Learn more.Copy URL Volume97, Issue11 January 1980Pages K5-K8 RelatedInformation

Ultrasonic harmonic generation due to a strain dependent dielectric constant

A simple analysis of ultrasonic harmonic generation in materials with a strain dependent dielectric constant shows that non-linear acoustic effects in such materials are much stronger than in ordinary piezoelectric semiconductors. Therefore, ferroelectric semiconductors operating near their Curie temperature should provide excellent materials in which to generate high frequency acoustic waves via second harmonic generation.

A computer system for the measurement of cell and nuclear sizes.

SUMMARYA semi‐automated system has been developed for the measurement of cell (perikaryal), nuclear and nucleolar areas. The system consists essentially of a Graf/Pen data tablet (with its associated acoustical stylus and tablet electronics), an optical input system such as a camera lucida, and a small digital computer. The perikaryal, nuclear and nucleolar outlines are traced in sequence with the stylus which, on contacting the tablet surface, emits a high frequency acoustic wave that is sensed by X and Y strip microphones along the left and upper edges of the tablet. The acoustic signal is converted by a simple program into a series of X and Y coordinates which are sampled at several points around the perimeter of the profile. When the stylus tip re‐enters a 1 mm stationary window set up around the starting point, the measurement is automatically terminated and the data for this profile is printed out and stored in memory for subsequent statistical analysis. The system has an overall accuracy of about 1% and in practice it has been possible to measure objects at least ten times more rapidly than by any of the other currently available methods. The hardware and software features of the system are detailed and a number of additional uses for the system are described.

Attenuation of High-Frequency Acoustic Waves on the Low-Temperature Side of the MnF2Néel Point

We present acoustic-attenuation experiments at frequencies up to 1000 MHz in the vicinity of the N\'eel point of Mn${\mathrm{F}}_{2}$. They show that the attenuation is maximum in the low-temperature phase near the transition, and the temperature at which that maximum appears decreases as the frequency increases. A brief scanning of the theory is given which explains this new effect in terms of relaxation of staggered magnetization.

Uniform Asymptotic Theory of Diffraction by a Plane Screen by the Method of Boundary Layers

We discuss the diffraction of high frequency acoustic waves by a circular aperture in a plane screen. Our analysis shows that techniques based on boundary layers are as effective in diffraction theory as they are in fluid mechanics. By using these techniques we obtain a uniform asymptotic expansion of the diffracted field in all regions.

Liquid-Crystal Holography of High-Frequency Acoustic Waves

A cholesteric liquid-crystal area detector has been used to make acoustical holograms at 5 MHz in water. The holograms were photographed by integrated time exposure and the original images reconstructed using laser light.

Ultra high frequency acoustic waves

Abstract Two different experimental techniques are available for making ultra-high-frequency acoustic measurements. These are (i) the study of light-scattering (for solids and liquids), and (ii) the use of microwaves (so far mainly restricted to solids). The first method does not require an acoustic source or generator, but makes use of the natural Debye waves; the results show that for someliquids it is possible to observe the effects of non-elastic molecular collisions. The second method has so far been applied chiefly to quartz, but is already yielding some information on the nature of the anharmonic interactions between atoms in a crystal.

An Explanation of the Diminished Acoustic Velocity in Fluids at High Frequencies

The existence of dispersion of acoustic velocity with frequency in gases and the accompanying anomalous damping of high frequency acoustic waves have been definitely established. A satisfactory theory has also been worked out to explain these two phenomena in gases. In the case of liquids, however, the anomalous damping of ultrasonic waves of high frequency was the first to be observed. A search has been made by a number of investi-gators to find the accompanying dispersion of acoustic velocity with frequency. So far, in the ultrasonic region at any rate, the experimental results have been inconclusive for the reason that the expected changes in the ultrasonic velocity, a couple of meters per second, are of the same order of magnitude as the errors due to changes in the tempera¬ture of the liquid during the course of the experiment.

A Supersonic Interferometer for the Study of the Pressure Coefficient of Velocity

The fundamental principles of the interferometer, particularly the liquid supersonic interferometer of Hubbard and Loomis, are incorporated in an instrument in which the liquid under examination may be put under pressures up to about 10,000 lb./sq. in. The instrument and the pressure device are built into a block of special cast steel 8×5×4½ inches. The results given are preliminary and merely show the performance and precision of the instrument. A curve is given showing the change of velocity of a high frequency acoustic wave of 195 kc from 1143 meters per second at atmospheric pressure to 1233 meters per second at a pressure of 3105 lb./sq. in. in carbon disulphide at room temperature. (The room temperature varied at different readings from 22.25°C to 25.41°C.)