scholarly journals Propagation of waves in micropolar solid-solid semispaces in the presence of a compressional wave source in the upper solid substratum

2001 ◽  
Vol 34 (5-6) ◽  
pp. 557-563 ◽  
Author(s):  
N.C. Ghosh ◽  
S. Nath ◽  
L. Debnath
Keyword(s):  
Compressional Wave ◽  
Wave Source ◽  
Solid Substratum ◽  
Propagation Of Waves

VpVs from mode‐converted P-SV reflections

Geophysics ◽  
1989 ◽  
Vol 54 (7) ◽  
pp. 843-852 ◽  
Author(s):  
William P. Iverson ◽  
Bill A. Fahmy ◽  
Scott B. Smithson
Keyword(s):  
Shear Velocity ◽  
Compressional Wave ◽  
Seismic Profile ◽  
Seismic Section ◽  
P Waves ◽  
Wave Source ◽  
Reflection Time ◽  
Interval Velocities ◽  
Synthetic Models ◽  
Comparison Technique

P-SV reflections are generated by a compressional‐wave source and result from P waves that are converted to shear (SV) waves upon reflection. Recording both the P and SV components yields compressional and shear data simultaneously. Verifying that the easily detected events really are P-SV reflections is accomplished by noting the good correlation of surface CDP data with vertical seismic profile (VSP) reflections. Stacking velocities from P-SV CDP gathers determine the [Formula: see text] product when source‐to‐receiver offset is less than the depth of the reflector but data from synthetic models show that P-SV reflections are nonhyperbolic for shallow reflections or when source‐to‐receiver offset is too large. Shear velocity [Formula: see text] can be calculated from P-SV reflections by one of two techniques: comparison of stacked section P-P and P-SV reflection times or by using the P-P and P-SV stacking velocities. Unfortunately, most P-SV reflections on a P-SV seismic section do not necessarily originate from exactly the same depth as P-P reflections. When this depth discrepancy occurs, the reflection‐time comparison technique fails. In addition, [Formula: see text] cannot be calculated from P-SV reflections, and we must settle for the [Formula: see text] product from P-SV reflection stacking velocities. When P-SV stacking velocities are input to the familiar Dix equation, the resulting interval velocities yield the [Formula: see text] product.

Transient Propagation of Waves in a Flume

1993 ◽  
Author(s):  
Kwok Fai Cheung ◽  
Michael Isaacson ◽  
Etienne Mansard
Keyword(s):  
Propagation Of Waves

A Methodology for Studying the Bioinert System "Solid Substratum - Organisms - Water flowing around them"

2001 ◽  
Vol 37 (3) ◽  
pp. 13
Author(s):  
K. M. Khaylov ◽  
Yu. Yu. Yurchenko ◽  
D. M. Smolev
Keyword(s):  
Solid Substratum

Incompleteness of General Relativity, Einstein's Errors, and Related Experiments-- American Physical Society March meeting, Z23 5, 2015 --

2015 ◽  
Vol 8 (2) ◽  
pp. 2135-2147 ◽  
Author(s):  
C. Y. Lo
Keyword(s):  
General Relativity ◽  
Einstein Equation ◽  
Reaction Force ◽  
Radiation Reaction ◽  
Gravitational Energy ◽  
Energy Conditions ◽  
Experimental Investigations ◽  
Positive Mass Theorem ◽  
Wave Source ◽  
Photonic Energy

General relativity is incomplete since it does not include the gravitational radiation reaction force and the interaction of gravitation with charged particles. General relativity is confusing because Einstein's covariance principle is invalid in physics. Moreover, there is no bounded dynamic solution for the Einstein equation. Thus, Gullstrand is right and the 1993 Nobel Prize for Physics press release is incorrect. Moreover, awards to Christodoulou reflect the blind faith toward Einstein and accumulated errors in mathematics. Note that the Einstein equation with an electromagnetic wave source has no valid solution unless a photonic energy-stress tensor with an anti-gravitational coupling is added. Thus, the photonic energy includes gravitational energy. The existence of anti-gravity coupling implies that the energy conditions in space-time singularity theorems of Hawking and Penrose cannot be satisfied, and thus are irrelevant. Also, the positive mass theorem of Yau and Schoen is misleading, though considered as an achievement by the Fields Medal. E = mc2 is invalid for the electromagnetic energy alone. The discovery of the charge-mass interaction establishes the need for unification of electromagnetism and gravitation and would explain many puzzles. Experimental investigations for further results are important.

Inverse problems for finite Jacobi matrices and Krein–Stieltjes strings

2021 ◽  
Vol 0 (0) ◽  
Author(s):  
Alexander Mikhaylov ◽  
Victor Mikhaylov
Keyword(s):  
Dynamical System ◽  
Inverse Problems ◽  
Jacobi Matrix ◽  
Jacobi Matrices ◽  
Unknown Parameters ◽  
Stieltjes String ◽  
Propagation Of Waves ◽  
Dynamic Inverse

Abstract We consider dynamic inverse problems for a dynamical system associated with a finite Jacobi matrix and for a system describing propagation of waves in a finite Krein–Stieltjes string. We offer three methods of recovering unknown parameters: entries of a Jacobi matrix in the first problem and point masses and distances between them in the second, from dynamic Dirichlet-to-Neumann operators. We also answer a question on a characterization of dynamic inverse data for these two problems.

scholarly journals Wave Propagation Characteristics in Gas Hydrate-Bearing Sediments and Estimation of Hydrate Saturation

Energies ◽  
2021 ◽  
Vol 14 (4) ◽  
pp. 804
Author(s):  
Lin Liu ◽  
Xiumei Zhang ◽  
Xiuming Wang
Keyword(s):  
Gas Hydrate ◽  
Clay Content ◽  
Clean Energy ◽  
Compressional Wave ◽  
Physical Parameters ◽  
Well Log ◽  
Log Data ◽  
Phase Velocities ◽  
Hydrate Saturation ◽  
Hydrate Bearing Sediments

Natural gas hydrate is a new clean energy source in the 21st century, which has become a research point of the exploration and development technology. Acoustic well logs are one of the most important assets in gas hydrate studies. In this paper, an improved Carcione–Leclaire model is proposed by introducing the expressions of frame bulk modulus, shear modulus and friction coefficient between solid phases. On this basis, the sensitivities of the velocities and attenuations of the first kind of compressional (P1) and shear (S1) waves to relevant physical parameters are explored. In particular, we perform numerical modeling to investigate the effects of frequency, gas hydrate saturation and clay on the phase velocities and attenuations of the above five waves. The analyses demonstrate that, the velocities and attenuations of P1 and S1 are more sensitive to gas hydrate saturation than other parameters. The larger the gas hydrate saturation, the more reliable P1 velocity. Besides, the attenuations of P1 and S1 are more sensitive than velocity to gas hydrate saturation. Further, P1 and S1 are almost nondispersive while their phase velocities increase with the increase of gas hydrate saturation. The second compressional (P2) and shear (S2) waves and the third kind of compressional wave (P3) are dispersive in the seismic band, and the attenuations of them are significant. Moreover, in the case of clay in the solid grain frame, gas hydrate-bearing sediments exhibit lower P1 and S1 velocities. Clay decreases the attenuation of P1, and the attenuations of S1, P2, S2 and P3 exhibit little effect on clay content. We compared the velocity of P1 predicted by the model with the well log data from the Ocean Drilling Program (ODP) Leg 164 Site 995B to verify the applicability of the model. The results of the model agree well with the well log data. Finally, we estimate the hydrate layer at ODP Leg 204 Site 1247B is about 100–130 m below the seafloor, the saturation is between 0–27%, and the average saturation is 7.2%.

scholarly journals Lorentz force induced shear waves for magnetic resonance elastography applications

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Guillaume Flé ◽  
Guillaume Gilbert ◽  
Pol Grasland-Mongrain ◽  
Guy Cloutier
Keyword(s):  
Magnetic Resonance ◽  
Shear Wave ◽  
Lorentz Force ◽  
Wave Attenuation ◽  
Shear Waves ◽  
Estimation Method ◽  
Biological Tissues ◽  
Magnetic Resonance Elastography ◽  
Motion Generation ◽  
Wave Source

AbstractQuantitative mechanical properties of biological tissues can be mapped using the shear wave elastography technique. This technology has demonstrated a great potential in various organs but shows a limit due to wave attenuation in biological tissues. An option to overcome the inherent loss in shear wave magnitude along the propagation pathway may be to stimulate tissues closer to regions of interest using alternative motion generation techniques. The present study investigated the feasibility of generating shear waves by applying a Lorentz force directly to tissue mimicking samples for magnetic resonance elastography applications. This was done by combining an electrical current with the strong magnetic field of a clinical MRI scanner. The Local Frequency Estimation method was used to assess the real value of the shear modulus of tested phantoms from Lorentz force induced motion. Finite elements modeling of reported experiments showed a consistent behavior but featured wavelengths larger than measured ones. Results suggest the feasibility of a magnetic resonance elastography technique based on the Lorentz force to produce an shear wave source.

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