Correlation Functions of Random Media

Klimeš, Luděk

doi:10.1007/978-3-0348-8146-3_22

Cited by 38 publications

(48 citation statements)

References 20 publications

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“…The 2-D anatomic phantom proposed is an axial cross-section of the ductolobular structure in healthy and pathological situations. The various constitutive tissues are modeled as a random inhomogeneous continuum with density and sound speed fluctuations [26] - [29].…”

Section: Introductionmentioning

confidence: 99%

A 2-D anatomic breast ductal computer phantom for ultrasonic imaging

Franceschini

Mensah

Amy

et al. 2006

IEEE Trans. Ultrason., Ferroelect., Freq. Contr.

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Section: Introductionmentioning

confidence: 99%

A 2-D anatomic breast ductal computer phantom for ultrasonic imaging

Franceschini

Mensah

Amy

et al. 2006

IEEE Trans. Ultrason., Ferroelect., Freq. Contr.

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“…Frankel and Clayton, 1986;Frankel, 1989;Igel and Gudmundsson, 1997;Klimeš, 2002;Jahnke et al, 2008), and recently extended to nonstationary and anisotropic media by Meschede and Romanowicz (2015). For this, we generate a random, uniformly distributed phase spectrum ϕ(k) between −π and π, with k being the 3-D wavenumber.…”

Section: Appendix A: Random Model Generationmentioning

confidence: 99%

The imprint of crustal density heterogeneities on regional seismic wave propagation

2016

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Abstract. Density heterogeneities are the source of mass transport in the Earth. However, the 3-D density structure remains poorly constrained because travel times of seismic waves are only weakly sensitive to density. Inspired by recent developments in seismic waveform tomography, we investigate whether the visibility of 3-D density heterogeneities may be improved by inverting not only travel times of specific seismic phases but complete seismograms.As a first step in this direction, we perform numerical experiments to estimate the effect of 3-D crustal density heterogeneities on regional seismic wave propagation. While a finite number of numerical experiments may not capture the full range of possible scenarios, our results still indicate that realistic crustal density variations may lead to travel-time shifts of up to ∼ 1 s and amplitude variations of several tens of percent over propagation distances of ∼ 1000 km. Both amplitude and travel-time variations increase with increasing epicentral distance and increasing medium complexity, i.e. decreasing correlation length of the heterogeneities. They are practically negligible when the correlation length of the heterogeneities is much larger than the wavelength. However, when the correlation length approaches the wavelength, density-induced waveform perturbations become prominent. Recent regional-scale full-waveform inversions that resolve structure at the scale of a wavelength already reach this regime.Our numerical experiments suggest that waveform perturbations induced by realistic crustal density variations can be observed in high-quality regional seismic data. While density-induced travel-time differences will often be small, amplitude variations exceeding ±10 % are comparable to those induced by 3-D velocity structure and attenuation.While these results certainly encourage more research on the development of 3-D density tomography, they also suggest that current full-waveform inversions that use amplitude information may be biased due to the neglect of 3-D variations in density.

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“…lation length)와 가우시안 상관 함수(Gaussian correlation function)로 모델링하였다 [11] . GPR 탐사 자료에 비균일 매질이 미치는 영향을 조사하기 위하여, 대 표적인 사례로 그림 1(a)와 같이 상대유전율이 7.5인 균일 매질과 그림 1(b)처럼 상대유전율의 평균값이 참 고 문 헌…”

Section: 였다 이러한 기법에서 매질 상수는 평균값(Mean)을 기준으로 불규칙 변동폭을 분산(Variance)으로 unclassified

Eigenimage-Based Signal Processing for Subsurface Inhomogeneous Clutter Reduction in Ground-Penetrating Radar Images

Hyun¹,

Kim²

2012

The Journal of Korean Institute of Electromagnetic Engineering

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To reduce the effects of clutters with subsurface inhomogenities in ground-penetrating radar(GPR) images, an eigenimage based signal-processing technique is presented. If the conventional eigenimage filtering technique is applied to B-scan images of a GPR suvey, relatively homogeneous clutters such as antenna ringing, direct coupling between transmitting and receiving antennas, and soil-surface reflection, can be removed sufficiently. However, since random clutters of subsurface inhomogenities still remain in the images, target signals are distorted and obscured by the clutters. According to a comparison of the eigenimage filtering results, there is different coherency between subsurface clutters and target signals. To reinforce the pixels with high coherency and reduce the pixels with low coherency, the pixel-by-pixel geometric-mean process after the eigenimage filtering is proposed here. For the validity of the proposed approach, GPR survey for detection of a metal target in a randomly inhomogeneous soil is numerically simulated by using a random media generation technique and the finite-difference time-domain(FDTD) method. And the proposed signal processing is applied to the B-scan data of the GPR suvey. We show that the proposed approach provides sufficient enhance-

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Correlation Functions of Random Media

Cited by 38 publications

References 20 publications

A 2-D anatomic breast ductal computer phantom for ultrasonic imaging

A 2-D anatomic breast ductal computer phantom for ultrasonic imaging

The imprint of crustal density heterogeneities on regional seismic wave propagation

Eigenimage-Based Signal Processing for Subsurface Inhomogeneous Clutter Reduction in Ground-Penetrating Radar Images

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