Borehole sonic array processing and the group versus phase velocity debate

Said Assous; Laurie Linnett; Peter Elkington

doi:10.1121/1.5101483

Group versus Phase Velocity of Shear Waves in Soft Tissues

Ultrasonic Imaging ◽

10.1177/0161734618796217 ◽

2018 ◽

Vol 40 (6) ◽

pp. 343-356 ◽

Cited By ~ 9

Author(s):

Kevin J. Parker ◽

Juvenal Ormachea ◽

Zaegyoo Hah

Keyword(s):

Phase Velocity ◽

Wave Speed ◽

Soft Tissues ◽

Group Versus ◽

Rheological Models ◽

Shear Wave Speed ◽

Versus Phase ◽

Phase Velocities ◽

Group And Phase Velocities ◽

Group Velocities

Across the varieties of waves that have been studied in physics, it is well established that group velocities can be significantly greater than or less than phase velocities measured within comparable frequency bands, depending on the particular mechanisms involved. The distinction between group and phase velocities is important in elastography, because diagnoses are made based on shear wave speed estimations from a variety of techniques. We review the general definitions of group and phase velocity and examine their specific relations within an important general class of rheological models. For the class of tissues and materials exhibiting power law dispersion, group velocity is significantly greater than phase velocity, and simple expressions are shown to interrelate the commonly measured parameters. Examples are given from phantoms and tissues.

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Radiation in Materials

Electromagnetic Radiation ◽

10.1093/oso/9780198726500.003.0009 ◽

2019 ◽

pp. 303-365

Author(s):

Richard Freeman ◽

James King ◽

Gregory Lafyatis

Keyword(s):

Magnetic Fields ◽

Time Domain ◽

Measurement Techniques ◽

Group Versus ◽

Index Of Refraction ◽

The Real ◽

Versus Phase ◽

Fundamental Relationship ◽

Electric And Magnetic Fields ◽

The Time Domain

The interaction of electromagnetic radiation and matter is examined, specifically electric and magnetic fields in materials with real and imaginary responses: under certain conditions the fields move through the material as a wave and under others they diffuse. The movement of a pulse of radiation in dispersive materials is described in which there are two wave velocities: group versus phase. The reflection of light from a sharp interface is analyzed and the Fresnel reflection/transmission equations derived. The response of materials to applied electric and magnetic fields in the time domain are correlated to their frequency response of the material’s polarization. The generalized Kramers–Kronig equations are derived and their applicability as a fundamental relationship between the real and imaginary parts of any material’s polarizability is discussed in detail. Finally, practical measurement techniques for extracting the real and imaginary components of a material’s index of refraction are introduced.

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Analyzing sound speed fluctuations in shallow water from group-velocity versus phase-velocity data representation

The Journal of the Acoustical Society of America ◽

10.1121/1.4792354 ◽

2013 ◽

Vol 133 (4) ◽

pp. 1945-1952 ◽

Cited By ~ 7

Author(s):

Philippe Roux ◽

W. A. Kuperman ◽

Bruce D. Cornuelle ◽

Florian Aulanier ◽

W. S. Hodgkiss ◽

...

Keyword(s):

Phase Velocity ◽

Shallow Water ◽

Group Velocity ◽

Sound Speed ◽

Data Representation ◽

Velocity Versus ◽

Velocity Data ◽

Versus Phase ◽

Speed Fluctuations

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Phase velocity tomography of surface waves using ambient noise cross correlation and array processing

Journal of Geophysical Research Solid Earth ◽

10.1002/2013jb010446 ◽

2014 ◽

Vol 119 (1) ◽

pp. 519-529 ◽

Cited By ~ 24

Author(s):

Pierre Boué ◽

Philippe Roux ◽

Michel Campillo ◽

Xavier Briand

Keyword(s):

Phase Velocity ◽

Surface Waves ◽

Ambient Noise ◽

Cross Correlation ◽

Array Processing ◽

Noise Cross Correlation ◽

Velocity Tomography

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Estimating phase velocity and attenuation of guided waves in acoustic logging data

Geophysics ◽

10.1190/1.1442733 ◽

1989 ◽

Vol 54 (8) ◽

pp. 1054-1059 ◽

Cited By ~ 12

Author(s):

K. J. Ellefsen ◽

C. H. Cheng ◽

K. M. Tubman

Keyword(s):

Phase Velocity ◽

Wave Velocity ◽

Guided Waves ◽

Array Processing ◽

Transverse Isotropy ◽

S Wave ◽

Acoustic Logging ◽

Processing Methods ◽

Phase Velocity And Attenuation

In acoustic logging, the guided waves which propagate along the borehole are affected by the properties of the formation. For acoustic logging tools with many receivers, array processing methods can be used to calculate the phase velocity and attenuation of these waves. This information is crucial in estimating formation properties like permeability, transverse isotropy, and S-wave velocity.

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Vestibular Function and Motion Sickness Susceptibility: Videonystagmographic Evidence From Oculomotor and Caloric Tests

American Journal of Audiology ◽

10.1044/2020_aja-19-00050 ◽

2020 ◽

Vol 29 (2) ◽

pp. 188-198

Author(s):

Cynthia G. Fowler ◽

Margaret Dallapiazza ◽

Kathleen Talbot Hadsell

Keyword(s):

Phase Velocity ◽

Motion Sickness ◽

Repeated Measures ◽

Short Form ◽

Vestibular Function ◽

Slow Phase ◽

Test Results ◽

Normal Range ◽

Slow Phase Velocity ◽

Caloric Tests

Purpose Motion sickness (MS) is a common condition that affects millions of individuals. Although the condition is common and can be debilitating, little research has focused on the vestibular function associated with susceptibility to MS. One causal theory of MS is an asymmetry of vestibular function within or between ears. The purposes of this study, therefore, were (a) to determine if the vestibular system (oculomotor and caloric tests) in videonystagmography (VNG) is associated with susceptibility to MS and (b) to determine if these tests support the theory of an asymmetry between ears associated with MS susceptibility. Method VNG was used to measure oculomotor and caloric responses. Fifty young adults were recruited; 50 completed the oculomotor tests, and 31 completed the four caloric irrigations. MS susceptibility was evaluated with the Motion Sickness Susceptibility Questionnaire–Short Form; in this study, percent susceptibility ranged from 0% to 100% in the participants. Participants were divided into three susceptibility groups (Low, Mid, and High). Repeated-measures analyses of variance and pairwise comparisons determined significance among the groups on the VNG test results. Results Oculomotor test results revealed no significant differences among the MS susceptibility groups. Caloric stimuli elicited responses that were correlated positively with susceptibility to MS. Slow-phase velocity was slowest in the Low MS group compared to the Mid and High groups. There was no significant asymmetry between ears in any of the groups. Conclusions MS susceptibility was significantly and positively correlated with caloric slow-phase velocity. Although asymmetries between ears are purported to be associated with MS, asymmetries were not evident. Susceptibility to MS may contribute to interindividual variability of caloric responses within the normal range.

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