The Green’s function for surface acoustic waves: Comparison between theory and experiment

1996 ◽  
Vol 100 (3) ◽  
pp. 1538-1541 ◽  
Author(s):  
A. Mourad ◽  
C. Desmet ◽  
W. Lauriks ◽  
H. Coufal ◽  
J. Thoen
Keyword(s):  
Green’S Function ◽  
Green's Function ◽  
Acoustic Waves ◽  
Surface Acoustic Waves ◽  
Theory And Experiment

scholarly journals Patched Green's function method applied to acoustic wave propagation in disordered media: an interdisciplinary approach

2020 ◽  
Vol 17 (5) ◽  
pp. 914-922
Author(s):  
Francisco A Moura ◽  
Wagner A Barbosa ◽  
Edwin F Duarte ◽  
Danyelle P Silva ◽  
Mauro S Ferreira ◽  
...  
Keyword(s):  
Wave Propagation ◽  
Acoustic Wave ◽  
Green’S Function ◽  
Green's Function ◽  
Acoustic Waves ◽  
Structural Information ◽  
Computational Cost ◽  
Computational Time ◽  
Model Parameters ◽  
Large Matrix

Abstract Modern visualization can be formulated as inversion problems that aim to obtain structural information about a complex medium through wave excitations. However, without numerically efficient forward calculations, even state-of-the-art inversion procedures are too computationally intensive to implement. We adapt a method previously used to treat transport in electronic waveguides to describe acoustic wave motion in complex media with high gains in computational time. The method consists of describing the system as if it was made of disconnected parts that are patched together. By expressing the system in this manner, wave-propagation calculations that otherwise would involve a very large matrix can be done with considerably smaller matrices instead. In particular, by treating one of such patches as a target whose parameters are changeable, we are able to implement target-oriented optimization in which the model parameters can be continuously refined until the ideal result is reproduced. The so-called Patched Green's function (PGF) approach is mathematically exact and involves no approximations, thus improving the computational cost without compromising accuracy. Given the generality of our method, it can be applied to a wide variety of inversion problems. Here we apply it to the case of seismic modeling where acoustic waves are used to map the earth subsurface in order to identify and explore mineral resources. The technique is tested with realistic seismic models and compared to standard calculation methods. The reduction in computational complexity is remarkable and paves the way to treating larger systems with increasing accuracy levels.

Mean flow refraction effects on sound radiated from localized sources in a jet

1998 ◽  
Vol 370 ◽  
pp. 149-174 ◽  
Author(s):  
CHRISTOPHER K. W. TAM ◽  
LAURENT AURIAULT
Keyword(s):  
Green’S Function ◽  
Green's Function ◽  
Acoustic Waves ◽  
Flow Direction ◽  
Jet Flow ◽  
Parallel Flow ◽  
Mean Flow ◽  
Flow Approximation ◽  
Radiated Sound ◽  
Localized Sources

It is well-known that sound generated by localized sources embedded in a jet undergoes refraction as the acoustic waves propagate through the jet mean flow. For isothermal or hot jets, the effect of refraction causes the deflection of the radiated sound waves away from the jet flow direction. This gives rise to a cone of silence around the jet axis where there is a significant reduction in the radiated sound intensity. In this work, the mean flow refraction problem is investigated through the use of the reciprocity principle. Instead of the direct source Green's function, the adjoint Green's function with the source and observation points interchanged is used to quantify the effect of mean flow on sound radiation. One advantage of the adjoint Green's function is that the Green's functions for all the source locations in the jet radiating to a given direction in the far field can be obtained in a single calculation. This provides great savings in computational effort. Another advantage of the adjoint Green's function is that there is no singularity in the jet flow so that the problem can be solved numerically with axial as well as radial mean flow gradients included in a fairly straightforward manner. Extensive numerical computations have been carried out for realistic jet flow profiles with and without exercising the locally parallel flow approximation. It is concluded that the locally parallel flow approximation is valid as long as the direction of radiation is outside the cone of silence.

scholarly journals Tunable Interferometers Driven by Coherent Surface Acoustic Phonons

MRS Advances ◽  
2016 ◽  
Vol 1 (22) ◽  
pp. 1651-1656 ◽  
Author(s):  
Antonio Crespo-Poveda ◽  
Alberto Hernández-Mínguez ◽  
Klaus Biermann ◽  
Abbes Tahraoui ◽  
Bernardo Gargallo ◽  
...  
Keyword(s):  
Building Block ◽  
Acoustic Waves ◽  
Surface Acoustic Waves ◽  
Acoustic Power ◽  
Frequency Range ◽  
Acoustic Frequency ◽  
Side Channels ◽  
Multi Mode ◽  
Mode Interference ◽  
Theory And Experiment

ABSTRACTWe demonstrate a compact tunable photonic modulator driven by surface acoustic waves (SAWs) in the low GHz frequency range. The device follows a well-known Mach-Zehnder interferometer (MZI) structure with three output channels, built upon multi-mode interference (MMI) couplers. The light continuously switches paths between the central and the side channels, avoiding losses and granting a 180◦-dephasing synchronization between them. The modulator was monolithically fabricated on (Al,Ga)As, and can be used as a building block for more complex photonic functionalities. It can also be implemented in other material platforms such as Silicon or (In,Ga)P. Light modulated at multiples of the fundamental acoustic frequency can be accomplished by adjusting the applied acoustic power. An excellent agreement between theory and experiment is achieved.

scholarly journals Surface and interface acoustic waves in solid-fluid superlattices: Green’s function approach

2006 ◽  
Vol 74 (14) ◽  
Author(s):  
Y. El Hassouani ◽  
E. H. El Boudouti ◽  
B. Djafari-Rouhani ◽  
H. Aynaou ◽  
L. Dobrzynski
Keyword(s):  
Green’S Function ◽  
Green's Function ◽  
Acoustic Waves ◽  
Function Approach ◽  
Surface And Interface

Characterization of RF Sputtered ZnO Piezoelectric Films Using Transmission Electron Microscope

1975 ◽  
Vol 33 ◽  
pp. 86-87
Author(s):  
Kemining W. Yeh ◽  
Richard S. Muller ◽  
Wei-Kuo Wu ◽  
Jack Washburn
Keyword(s):  
Integrated Circuit ◽  
Acoustic Waves ◽  
New Technology ◽  
Surface Acoustic Waves ◽  
Electromechanical Properties ◽  
Leading Role ◽  
Saw Devices ◽  
Transmission Electron ◽  
High Degree

Considerable and continuing interest has been shown in the thin film transducer fabrication for surface acoustic waves (SAW) in the past few years. Due to the high degree of miniaturization, compatibility with silicon integrated circuit technology, simplicity and ease of design, this new technology has played an important role in the design of new devices for communications and signal processing. Among the commonly used piezoelectric thin films, ZnO generally yields superior electromechanical properties and is expected to play a leading role in the development of SAW devices.

Attenuation of surface acoustic waves by quantum dots

1998 ◽  
Vol 77 (5) ◽  
pp. 1195-1202
Author(s):  
Andreas Knabchen Yehoshua, B. Levinson, Ora
Keyword(s):  
Quantum Dots ◽  
Acoustic Waves ◽  
Surface Acoustic Waves
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