Applying acoustic ray tracing from the full wave equation solution to determine the nonair conduction pathways into the human head.

2008 ◽  
Vol 124 (4) ◽  
pp. 2456-2456
Author(s):  
Jared McNew ◽  
Alessandro Bellina ◽  
William D. O'Brien
Keyword(s):  
Wave Equation ◽  
Ray Tracing ◽  
Human Head ◽  
Equation Solution ◽  
Full Wave

Wave‐equation traveltime inversion

Geophysics ◽  
1991 ◽  
Vol 56 (5) ◽  
pp. 645-653 ◽  
Author(s):  
Y. Luo ◽  
G. T. Schuster
Keyword(s):  
Wave Equation ◽  
Ray Tracing ◽  
High Frequency ◽  
Velocity Model ◽  
Head Wave ◽  
Inversion Method ◽  
Diffraction Reflection ◽  
Traveltime Inversion ◽  
Wave Inversion ◽  
Full Wave

This paper presents a new traveltime inversion method based on the wave equation. In this new method, designated as wave‐equation traveltime inversion (WT), seismograms are computed by any full‐wave forward modeling method (we use a finite‐difference method). The velocity model is perturbed until the traveltimes from the synthetic seismograms are best fitted to the observed traveltimes in a least squares sense. A gradient optimization method is used and the formula for the Frechét derivative (perturbation of traveltimes with respect to velocity) is derived directly from the wave equation. No traveltime picking or ray tracing is necessary, and there are no high frequency assumptions about the data. Body wave, diffraction, reflection and head wave traveltimes can be incorporated into the inversion. In the high‐frequency limit, WT inversion reduces to ray‐based traveltime tomography. It can also be shown that WT inversion is approximately equivalent to full‐wave inversion when the starting velocity model is “close” to the actual model. Numerical simulations show that WT inversion succeeds for models with up to 80 percent velocity contrasts compared to the failure of full‐wave inversion for some models with no more than 10 percent velocity contrast. We also show that the WT method succeeds in inverting a layered velocity model where a shooting ray‐tracing method fails to compute the correct first arrival times. The disadvantage of the WT method is that it appears to provide less model resolution compared to full‐wave inversion, but this problem can be remedied by a hybrid traveltime + full‐wave inversion method (Luo and Schuster, 1989).

scholarly journals Depth-Extrapolation-Based True-Amplitude Full-Wave-Equation Migration from Topography

2021 ◽  
Vol 11 (7) ◽  
pp. 3010
Author(s):  
Hao Liu ◽  
Xuewei Liu
Keyword(s):  
Wave Equation ◽  
Partial Derivative ◽  
Model Experiment ◽  
Surface Velocity ◽  
Seismic Exploration ◽  
Initial Condition ◽  
Reverse Time ◽  
Reverse Time Migration ◽  
Full Wave ◽  
Time Migration

The lack of an initial condition is one of the major challenges in full-wave-equation depth extrapolation. This initial condition is the vertical partial derivative of the surface wavefield and cannot be provided by the conventional seismic acquisition system. The traditional solution is to use the wavefield value of the surface to calculate the vertical partial derivative by assuming that the surface velocity is constant. However, for seismic exploration on land, the surface velocity is often not uniform. To solve this problem, we propose a new method for calculating the vertical partial derivative from the surface wavefield without making any assumptions about the surface conditions. Based on the calculated derivative, we implemented a depth-extrapolation-based full-wave-equation migration from topography using the direct downward continuation. We tested the imaging performance of our proposed method with several experiments. The results of the Marmousi model experiment show that our proposed method is superior to the conventional reverse time migration (RTM) algorithm in terms of imaging accuracy and amplitude-preserving performance at medium and deep depths. In the Canadian Foothills model experiment, we proved that our method can still accurately image complex structures and maintain amplitude under topographic scenario.

Randomized HSS acceleration for full-wave-equation depth stepping migration

2014 ◽  
Author(s):  
Lina Miao* ◽  
Polina Zheglova ◽  
Felix J. Herrmann
Keyword(s):  
Wave Equation ◽  
Full Wave

scholarly journals Numerical treatment of the spatio-temporal electromagnetic beam-wave packet

2017 ◽  
Vol 68 (2) ◽  
pp. 109-116
Author(s):  
L’ubomír Šumichrast ◽  
Jaroslav Franek
Keyword(s):  
Numerical Simulation ◽  
Wave Equation ◽  
Wave Packet ◽  
Paraxial Approximation ◽  
Two Dimensional ◽  
Numerical Treatment ◽  
Beam Wave ◽  
Electromagnetic Beam ◽  
Full Wave ◽  
Spatio Temporal

Abstract Propagation of a two-dimensional spatio-temporal electromagnetic beam wave is analysed. In parabolic (paraxial) approximation the exact analytical results for a spatio-temporal Gaussian impulse can be obtained. For solution of the full wave equation the numerical simulation has to be used. The various facets of this simulation are discussed here.

scholarly journals Small Triple-Band Meandered PIFA for Brain-Implantable Biotelemetric Systems: Development and Testing in a Liquid Phantom

2021 ◽  
Vol 2021 ◽  
pp. 1-13
Author(s):  
Nikta Pournoori ◽  
Lauri Sydänheimo ◽  
Yahya Rahmat-Samii ◽  
Leena Ukkonen ◽  
Toni Björninen
Keyword(s):  
State Of The Art ◽  
Data Communication ◽  
Human Head ◽  
The Body ◽  
Head Model ◽  
Wireless Power ◽  
Wireless Data ◽  
Full Wave ◽  
Implantable Antennas ◽  
Triple Band

We present a meandered triple-band planar-inverted-F antenna (PIFA) for integration into brain-implantable biotelemetric systems. The target applications are wireless data communication, far-field wireless power transfer, and switching control between sleep/wake-up mode at the Medical Device Radiocommunication Service (MedRadio) band (401–406 MHz) and Industrial, Scientific and Medical (ISM) bands (902–928 MHz and 2400–2483.5 MHz), respectively. By embedding meandered slots into the radiator and shorting it to the ground, we downsized the antenna to the volume of 11 × 20.5 × 1.8 mm3. We optimized the antenna using a 7-layer numerical human head model using full-wave electromagnetic field simulation. In the simulation, we placed the implant in the cerebrospinal fluid (CSF) at a depth of 13.25 mm from the body surface, which is deeper than in most works on implantable antennas. We manufactured and tested the antenna in a liquid phantom which we replicated in the simulator for further comparison. The measured gain of the antenna reached the state-of-the-art values of −43.6 dBi, −25.8 dBi, and −20.1 dBi at 402 MHz, 902 MHz, and 2400 MHz, respectively.

scholarly journals Approximate Cloaking for the Full Wave Equation via Change of Variables

2012 ◽  
Vol 44 (3) ◽  
pp. 1894-1924 ◽  
Author(s):  
Hoai-Minh Nguyen ◽  
Michael S. Vogelius
Keyword(s):  
Wave Equation ◽  
Change Of Variables ◽  
Full Wave

Gulf of Suez acquisition design using 2D and 3D full wave equation simulation

2003 ◽  
Author(s):  
Dana Jurick ◽  
Jeff Codd ◽  
Fatmir Hoxha ◽  
Julia Naumenko ◽  
David Kessler
Keyword(s):  
Wave Equation ◽  
Gulf Of Suez ◽  
Full Wave ◽  
2D And 3D
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