A single-sided access simultaneous solution of acoustic wave speed and sample thickness for isotropic materials of plate-type geometry

2006 ◽  
Author(s):  
Brett A. Rinker
Keyword(s):  
Acoustic Wave ◽  
Wave Speed ◽  
Sample Thickness ◽  
Simultaneous Solution ◽  
Isotropic Materials ◽  
Plate Type

Molecular Beam Epitaxy of AlN Layers on Si (111)

2008 ◽  
Vol 1068 ◽  
Author(s):  
Jean-Christophe Moreno ◽  
Eric Frayssinet ◽  
Fabrice Semond ◽  
Jean Massies
Keyword(s):  
Molecular Beam Epitaxy ◽  
Acoustic Wave ◽  
Wave Speed ◽  
Molecular Beam ◽  
Bulk Acoustic Wave ◽  
X Ray Diffraction ◽  
High Crystalline Quality ◽  
Force Microscopy ◽  
Atomic Force ◽  
Film Bulk

ABSTRACTIn this work, we present a study of epitaxial Aluminium Nitride (AlN) for thin film bulk acoustic wave (BAW) applications. Molecular beam epitaxy (MBE) was used to perform high crystalline quality AlN thin films growth on different silicon substrate preparations. A morphological study was performed by atomic force microscopy (AFM) and scanning electron microscopy (SEM), while structural properties and acoustic wave speed were respectively assessed by X-ray diffraction and acoustic picoseconds.

Acoustic wave speed and attenuation in suspensions

1992 ◽  
Vol 18 (4) ◽  
pp. 577-592 ◽  
Author(s):  
C.M. Atkinson ◽  
H.K. Kytömaa
Keyword(s):  
Acoustic Wave ◽  
Wave Speed

scholarly journals Suppress Numerical Oscillations in Transient Mixed Flow Simulations with a Modified HLL Solver

Water ◽  
2020 ◽  
Vol 12 (5) ◽  
pp. 1245 ◽  
Author(s):  
Zhonghao Mao ◽  
Guanghua Guan ◽  
Zhonghua Yang
Keyword(s):  
Acoustic Wave ◽  
Wave Speed ◽  
Hydraulic Systems ◽  
Simple Method ◽  
Flow Simulations ◽  
Flow Regime Transition ◽  
Pressurized Flows ◽  
Numerical Oscillations ◽  
Two Parameters ◽  
Good Agreement

Transition between free-surface and pressurized flows is a crucial phenomenon in many hydraulic systems. During simulation of such phenomenon, severe numerical oscillations may appear behind filling-bores, causing unphysical pressure variations and computation failure. This paper reviews existing oscillation-suppressing methods, while only one of them can obtain a stable result under a realistic acoustic wave speed. We derive a new oscillation-suppressing method with first-order accuracy. This simple method contains two parameters, Pa and Pb, and their values can be determined easily. It can sufficiently suppress numerical oscillations under an acoustic wave speed of 1000 ms−1. Good agreement is found between simulation results and analytical results or experimental data. This paper can help readers to choose an appropriate oscillation-suppressing method for numerical simulations of flow regime transition under a realistic acoustic wave speed.

Compressible and Leaky Trains in Tunnels

1987 ◽  
Vol 201 (3) ◽  
pp. 209-215 ◽  
Author(s):  
A E Vardy ◽  
J A Fox
Keyword(s):  
Acoustic Wave ◽  
Wave Speed ◽  
Alternative Explanation ◽  
Blockage Ratio ◽  
Potential Influence ◽  
Wave Speeds ◽  
Effective Wave ◽  
Measured Pressure ◽  
Phase Differences

It is hypothesized that phase differences commonly observed between computed and measured pressure histories in railway tunnels may be caused in part by reduced acoustic wave speeds in the annular regions of flow alongside trains. Such reductions in wave speed are shown to be a possible consequence of the compressibility of trains and/or the leakage of air into and out of trains. These effects are shown to be capable in principle of reducing the effective wave speed by a factor of (1-β)1/2 where β denotes the train-tunnel area blockage ratio. The potential influence of reduced wave speeds due to these causes is shown to be much greater in short tunnels than in long tunnels. An alternative explanation for the discrepancies observed in long tunnels has yet to be found.

Scanning acoustic microscopy of biological cryosections: the effect of local thickness on apparent acoustic wave speed

2014 ◽  
Vol 1621 ◽  
pp. 143-148
Author(s):  
Craig J. Williams ◽  
Helen. K. Graham ◽  
Xuegen Zhao ◽  
Riaz Akhtar ◽  
Christopher E.M. Griffiths ◽  
...  
Keyword(s):  
Acoustic Wave ◽  
Wave Speed ◽  
Acoustic Microscopy ◽  
Specimen Thickness ◽  
Sampling Point ◽  
Scanning Acoustic Microscopy ◽  
Glass Slides ◽  
Nominal Thickness ◽  
Longitudinal Acoustic Wave ◽  
Multiple Regions

ABSTRACTScanning acoustic microscopy (SAM), when applied to biological samples has the potential to resolve the longitudinal acoustic wave speed and hence stiffness of discrete tissue components. The heterogeneity of biological materials combined with the action of cryosectioning and rehydrating can, however, create variations in section topography. Here, we set out to determine how variations in specimen thickness influence apparent acoustic wave speed measurementsCryosections (5μm nominal thickness) of human skin biopsies were adhered to glass slides before washing and rehydrating in water. Multiple regions (200x200 μm; n = 3) were imaged by SAM to generate acoustic wave speed maps. Subsequently co-localised 30x30 μm sub-regions were imaged by atomic force microscopy (AFM) in fluid. The images were then registered using Image J. Each pixel was allocated both a height and wave speed value before their relationship was then plotted on a scattergram. The mean section thickness measured by AFM was 3.48 ± 1.12 (SD) μm. Regional height variations influenced apparent wave speed measurements. A 3.5 μm height difference was associated with a 400 ms-1 increase in wave speed. In the present study we show that local variations in specimen thickness influence apparent wave speed. We also show that a true measure of wave speed can be calculated if the thickness of the specimen is known at each sampling point.

scholarly journals Acoustic wave propagation through solar granulation: Validity of effective-medium theories, coda waves

2020 ◽  
Vol 643 ◽  
pp. A168
Author(s):  
P.-L. Poulier ◽  
D. Fournier ◽  
L. Gizon ◽  
T. L. Duvall
Keyword(s):  
Wave Propagation ◽  
Acoustic Wave ◽  
Wave Field ◽  
Multiple Scattering ◽  
Acoustic Waves ◽  
Wave Speed ◽  
Coda Waves ◽  
Acoustic Wave Propagation ◽  
Solar Granulation ◽  
Effective Wave

Context. The frequencies, lifetimes, and eigenfunctions of solar acoustic waves are affected by turbulent convection, which is random in space and in time. Since the correlation time of solar granulation and the periods of acoustic waves (∼5 min) are similar, the medium in which the waves propagate cannot a priori be assumed to be time independent. Aims. We compare various effective-medium solutions with numerical solutions in order to identify the approximations that can be used in helioseismology. For the sake of simplicity, the medium is one dimensional. Methods. We consider the Keller approximation, the second-order Born approximation, and spatial homogenization to obtain theoretical values for the effective wave speed and attenuation (averaged over the realizations of the medium). Numerically, we computed the first and second statistical moments of the wave field over many thousands of realizations of the medium (finite-amplitude sound-speed perturbations are limited to a 30 Mm band and have a zero mean). Results. The effective wave speed is reduced for both the theories and the simulations. The attenuation of the coherent wave field and the wave speed are best described by the Keller theory. The numerical simulations reveal the presence of coda waves, trailing the ballistic wave packet. These late arrival waves are due to multiple scattering and are easily seen in the second moment of the wave field. Conclusions. We find that the effective wave speed can be calculated, numerically and theoretically, using a single snapshot of the random medium (frozen medium); however, the attenuation is underestimated in the frozen medium compared to the time-dependent medium. Multiple scattering cannot be ignored when modeling acoustic wave propagation through solar granulation.

Time-of-Flight Measurements of Acoustic Wave Speed in a Sandy Sediment at 0.6–20 kHz

2010 ◽  
Vol 35 (3) ◽  
pp. 502-515 ◽  
Author(s):  
P C Hines ◽  
J C Osler ◽  
J G E Scrutton ◽  
L J S Halloran
Keyword(s):  
Acoustic Wave ◽  
Wave Speed ◽  
Time Of Flight ◽  
Sandy Sediment ◽  
Flight Measurements
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