scholarly journals Reverberation-Ray Matrix Analysis of Acoustic Waves in Multilayered Anisotropic Structures

10.5772/9788 ◽  
2010 ◽  
Author(s):  
Yongqiang Guo ◽  
Weiqiu Che
Keyword(s):  
Acoustic Waves ◽  
Matrix Analysis ◽  
Anisotropic Structures

Influence of Pump-Circuit Coupling on Acoustic Waves in Pipelines and Pump Velocity Fields

2013 ◽  
Author(s):  
Jens Keller ◽  
Jorge Parrondo ◽  
Eduardo Blanco ◽  
Raúl Barrio ◽  
Carlos Suárez
Keyword(s):  
Acoustic Impedance ◽  
Acoustic Waves ◽  
Rotation Axis ◽  
Pressure Fluctuations ◽  
Acoustic Emissions ◽  
Fast Response ◽  
Velocity Fields ◽  
Matrix Analysis ◽  
Centrifugal Pumps ◽  
Pressure Transducers

Hydraulic piping systems are sensitive to excessive acoustic emissions which can give rise to vibrations or to failure of mechanical elements due to fatigue. Common excitation sources are centrifugal pumps due to the periodic interaction of the impeller with the volute tongue. They radiate pressure fluctuations into the connected circuit at the blade-passing frequency which are reflected in the circuit. The aim of the present investigation was the experimental characterization of the perturbations induced in a piping network as a function of the acoustic impedance of the circuit using fast-response pressure transducers. Three transducers were placed along the discharge pipe to decompose the pressure signal into the radiated and reflected acoustic wave, with amplitude and phase. The speed of sound in the water pipelines was determined experimentally. Results of impedance at the pump tongue were compared with a theoretical approach, using a Transfer Matrix Analysis, where each pipe element is represented by a 2×2-matrix, relating the acoustic pressure and velocity fluctuations at the two ports. Attenuation was considered by using complex wavenumbers. The acoustic impedance was changed by using different rotation speeds and by using a cavity which works as a harmonic oscillator whose resonance frequency can be changed. The results presented for different operating points show the influence of changing impedance on the pressure perturbations due to pump-circuit acoustic coupling. The pump was built with a transparent impeller and volute to conduct Particle Image Velocimetry (PIV) measurements in a plane perpendicular to the pump rotation axis. Phase-averaged velocity fields were obtained at different blade positions in the zone around the tongue. Vorticity fields were derived from it and turbulence is shown by representing in-plane turbulent kinetic energy (TKE). Strong vorticity and turbulence occurred in the volute channel behind the blade and near the tongue tip.

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.

New polarized-light microscope for fast and orientation independent measurement of birefringent fine structure

1993 ◽  
Vol 51 ◽  
pp. 82-83
Author(s):  
Rudolf Oldenbourg
Keyword(s):  
Light Microscope ◽  
Polarized Light ◽  
Video Camera ◽  
Limited Range ◽  
Image Point ◽  
Computer Assisted ◽  
Optical Modulators ◽  
Anisotropic Structures ◽  
Long Time ◽  
Computer Assisted Image

The polarized light microscope has the unique potential to measure submicroscopic molecular arrangements dynamically and non-destructively in living cells and other specimens. With the traditional pol-scope, however, single images display only those anisotropic structures that have a limited range of orientations with respect to the polarization axes of the microscope. Furthermore, rapid measurements are restricted to a single image point or single area that exhibits uniform birefringence or other form of optical anisotropy, while measurements comparing several image points take an inordinately long time.We are developing a new kind of polarized light microscope which combines speed and high resolution in its measurement of the specimen anisotropy, irrespective of its orientation. The design of the new pol-scope is based on the traditional polarized light microscope with two essential modifications: circular polarizers replace linear polarizers and two electro-optical modulators replace the traditional compensator. A video camera and computer assisted image analysis provide measurements of specimen anisotropy in rapid succession for all points of the image comprising the field of view.

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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