• Title/Summary/Keyword: Ultrasonic attenuation

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In fluency on Refraction and Phase Cancellation Effect in Ultrasonic CT and its Correction (초음파 CT에서의 굴절 및 위상 상쇄 효과의 영향과 그 보정법)

  • 최종수
    • Journal of the Korean Institute of Telematics and Electronics
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    • v.19 no.6
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    • pp.33-40
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    • 1982
  • Although ultrasonic CT is one of the useful techniques for tissue characterization, the reconstructed images, such as the velocity distribution and attenuation constant distribution, are degraded by reflection and refraction of ultrasonic beam. This paper studied the degradation effects on attenuation images using agar gel phantoms which were developed to evaluate ultrasonic CT. We found that the reconstructed attenuation constants at the center of the phantoms were less than the actual values by 0.6 dB/cm when phantom velocity differs by 25 m/s from surrounding saline. We also studied a correction method for refraction and phase cancellation effects, where the correction was made using the maximum value in the received subdata, as obtained by sub-arraying microprobes located at each sampling point. Using this method, we could obtain an improvement in the reconstructed image by the correction on the attenuation effect.

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Correlations Among Speed of Sound, Broadband Ultrasonic Attenuation, Broadband Ultrasonic Reflection, and Bone Density in Bovine Cancellous Bone

  • Lee, Kang-Il;Choi, Bok-Kyoungi;Yoon, Suk-Wang
    • The Journal of the Acoustical Society of Korea
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    • v.22 no.2E
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    • pp.69-77
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    • 2003
  • Correlations between acoustic properties and bone density have been investigated in bovine cancellous bone. Speed of sound (SOS), broadband ultrasonic attenuation (BUA), and broadband ultrasonic reflection (BUR) were measured in 10 defatted bovine cancellous bone specimens in vitro. SOS showed a significant correlation with the apparent density of the bone. A comparable correlation was observed between BUA and the apparent density. BUR was rather highly correlated with the apparent density. It was shown that BUR had a weak correlation with BUA and a significant correlation with SOS. This indicates that the parameter BUR can provide important information that may not be contained in BUA and SOS and, therefore, can be useful as an alternative diagnostic parameter of osteoporosis. As expected, a linear combination of all three ultrasonic parameters in a multiple regression model resulted in a significant improvement in predicting the apparent bone density.

Improved Attenuation Estimation of Ultrasonic Signals Using Frequency Compounding Method

  • Kim, Hyungsuk;Shim, Jaeyoon;Heo, Seo Weon
    • Journal of Electrical Engineering and Technology
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    • v.13 no.1
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    • pp.430-437
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    • 2018
  • Ultrasonic attenuation is an important parameter in Quantitative Ultrasound and many algorithms have been proposed to improve estimation accuracy and repeatability for multiple independent estimates. In this work, we propose an improved algorithm for estimating ultrasonic attenuation utilizing the optimal frequency compounding technique based on stochastic noise model. We formulate mathematical compounding equations in the AWGN channel model and solve optimization problems to maximize the signal-to-noise ratio for multiple frequency components. Individual estimates are calculated by the reference phantom method which provides very stable results in uniformly attenuating regions. We also propose the guideline to select frequency ranges of reflected RF signals. Simulation results using numerical phantoms show that the proposed optimal frequency compounding method provides improved accuracy while minimizing estimation bias. The estimation variance is reduced by only 16% for the un-compounding case, whereas it is reduced by 68% for the uniformly compounding case. The frequency range corresponding to the half-power for reflected signals also provides robust and efficient estimation performance.

A poroelastic model for ultrasonic wave attenuation in partially frozen brines (부분 동결된 소금물에서의 초음파감쇠에 대한 다공성탄성 모델)

  • Matsushima, Jun;Nibe, Takao;Suzuki, Makoto;Kato, Yoshibumi;Rokugawa, Shuichi
    • Geophysics and Geophysical Exploration
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    • v.14 no.1
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    • pp.105-115
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    • 2011
  • Although there are many possible mechanisms for the intrinsic seismic attenuation in composite materials that include fluids, relative motion between solids and fluids during seismic wave propagation is one of the most important attenuation mechanisms. In our previous study, we conducted ultrasonic wave transmission measurements on an ice-brine coexisting system to examine the influence on ultrasonic waves of the unfrozen brine in the pore microstructure of ice. In order to elucidate the physical mechanism responsible for ultrasonic wave attenuation in the frequency range of 350.600 kHz, measured at different temperatures in partially frozen brines, we employed a poroelastic model based on the Biot theory to describe the propagation of ultrasonic waves through partially frozen brines. By assuming that the solid phase is ice and the liquid phase is the unfrozen brine, fluid properties measured by a pulsed nuclear magnetic resonance technique were used to calculate porosities at different temperatures. The computed intrinsic attenuation at 500 kHz cannot completely predict the measured attenuation results from the experimental study in an ice-brine coexisting system, which suggests that other attenuation mechanisms such as the squirt-flow mechanism and wave scattering effect should be taken into account.

Ultrasonic Evaluation of Pearlite Interlamellar Spacing in Eutectoid Steel (초음파를 이용한 공석강의 펄라이트 층상간격 평가)

  • Kim, J.S.;Byeon, J.W.;Kwun, S.I.;Lee, Seung Seok;Ahn, Bongyoung
    • Journal of the Korean Society for Heat Treatment
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    • v.14 no.1
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    • pp.22-26
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    • 2001
  • The microstructural changes with pearlite formation heat treatment in eutectoid steel(railway steel) consisting of only pearlite structure were evaluated by the ultrasonic attenuation and velocity measurements. The result of this investigation showed a strong linear dependence of ultrasonic attenuation on pearlite interlamellar spacing, and accordingly on fracture strength of the pearlite.

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Numerical Evaluation of Phase Velocity and Attenuation of Ultrasonic Waves in Fiber-Reinforced Composites Using the Mass-Spring-Dashpot Lattice Model

  • Baek, Eun-Sol;Yim, Hyun-June
    • Journal of the Korean Society for Nondestructive Testing
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    • v.28 no.6
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    • pp.483-495
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    • 2008
  • The paper presents a numerical study to evaluate the phase velocities and attenuations of the average longitudinal and shear ultrasonic waves resulting from multiple scattering in fiber-reinforced composites. A computational procedure developed in this work is first used to produce a random, yet largely even distribution of fibers. Both the viscoelastic epoxy matrix and lossless randomly distributed graphite fibers are modeled using the mass-spring-dashpot lattice model, with no damping for the latter. By numerically simulating ultrasonic through-transmission tests using this direct model of composites, phase velocities and attenuations of the longitudinal and shear waves through the composite are found as functions of frequency or fiber concentration. The numerical results are observed to generally agree with the corresponding results in the literature. Discrepancies found in some detail aspects, particularly in the attenuation results, are also addressed.

Nondestructive Evaluation for Material Degradation of 2.25Cr-1Mo steel by Ultrasonic Wave (초음파를 이용한 재질열화의 비파괴적 평가)

  • 김정석;박은수;박인근;김현묵
    • Proceedings of the Korean Society of Machine Tool Engineers Conference
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    • 2000.10a
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    • pp.369-374
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    • 2000
  • This study has been achieved on the characteristics of ultrasonic wave in 2.25Cr-1Mo steel to evaluate the feasibility of ultrasonic nondestructive technique on the assessment of aging degradation. The measured values were used find a relationship between the ultrasonic propagation properties and degradation such as coarsening of carbides and precipitates. The ultrasonic attenuation coefficient was mainly affected by the grain size of prior austenitic phase as well as degradation. In this results, degradation and grain size in 2.25Cr-1Mo steel was able to cope with the changes in ultrasonic wave properties by applying the nondestructive evaluation method

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Ultrasonic Signal Characteristics of Corona Discharges in Air (공기중 코로나방전의 초음파신호 특성)

  • Lee, Sang-Woo;Kim, In-Sik;Lee, Kwang-Sik;Lee, Dong-In;Lee, Dong-Heoon;Bae, Sang-Jun
    • Proceedings of the KIEE Conference
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    • 1998.07e
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    • pp.1702-1704
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    • 1998
  • In order to establish the usefulness of ultrasonic techniques for detecting corona discharges in high-voltage power apparatus, it is first necessary to determine the relationship between electrical and ultrasonic signals of corona discharges in air. In this paper, various characteristics of ultrasonic signal detection for point-to-plane corona discharges using a 200[kHz] ultrasonic sensor are examined. In regard to the attenuation and directivity of ultrasonic signals, the signals were inversely proportional to the distance between corona sources and ultrasonic receiving sensors, and half attenuation angles were approximately 7.0 degree. Ultrasonic signals of positive polarities were first obserbed at corona inception voltages. and the signals were increased with increasing the applied voltages.

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Estimation of Ultrasound Attenuation Coefficient by Homomorphic Deconvolution Method (Homomorphic Deconvolution 법에 의한 초음파 감쇄정수 추정)

  • Hong, Seung-Hong;Huh, Woong
    • Journal of Biomedical Engineering Research
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    • v.5 no.1
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    • pp.39-46
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    • 1984
  • In order to improve the performance of ultrasonic diagnostic equipment, it is important to development the signal processing considering the ultrasonic properties of biological medium and propagation mechanism in tissue. Attenuation coefficient is not only important factor to analyze propagation properties, but also it is significant to estimate it in view of tissue characterization, so we show one of the method to estimate attenuation coefficient of biological tissue and the results of estimation.

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Degradation Assessment of Aluminum Alloy 6061-T6 Using Ultrasonic Attenuation Measurements (초음파 감쇠 측정을 이용한 Al6061-T6 열화 평가)

  • Kim, Hun-Hee;Kang, To;Seo, Mu-Kyung;Song, Sung-Jin;Kim, Hak-Joon;Kim, Kyung-Cho;Kim, Young-Bum
    • Journal of the Korean Society for Nondestructive Testing
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    • v.33 no.1
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    • pp.20-25
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    • 2013
  • Ultrasonic methods are widely used to degradation assessment. Remaining-life cycle of metal can be estimated by ultrasonic parameters because ultrasonic velocity and attenuation are affected by change of material properties with accumulated fatigue in the metal. Therefore, in this study, we will estimate overall change of material properties by 2D C-scan image. Fatigued aluminum alloy 6061-T6 samples from 0 to 85% were prepared for evaluating fatigue life cycle. Also, degraded image of materials using attenuation is proposed to estimate degree of material degradation for determining degraded area of fatigued samples. Finally, we will predicts process pf degradation with measured attenuation of fatigued aluminum alloy 6061-T6 samples.