• Title/Summary/Keyword: 초음파 속도

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Study on Velocity In-homogeneous Effect in fat and its Correction in Ultrasound Imaging System (초음파 의료영상에서 지방조직의 음속도 불균일 효과의 영향과 그 보상에 관한 연구)

  • Kim, Jae-Hyeon;Bae, Mu-Ho;Jeong, Mok-Geun
    • Journal of Biomedical Engineering Research
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    • v.19 no.1
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    • pp.9-18
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    • 1998
  • In this paper, we present the degradation of focusing induced by velocity inhomogeneity in human tissue. For simulation, the fatty layer which is the major factor of degradation for its lower velocity, is modeled as a uniform velocity perturbation layer. And we simulate the degradation of resolution resulting from change of beam path due to refraction and the time delay due to velocity difference. We show that focusing error can be compensated for considering the velocity inhomogeneity only. The proposed compensation method can be operated in real time in the presently used digital focusing systems.

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An Efficient Method for Estimating Average Speed of Sound in Ultrasound Medical Imaging (초음파 의료영상에서 매질의 평균음속도 측정방법에 대한 연구)

  • 정목근;권성재
    • Journal of Biomedical Engineering Research
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    • v.19 no.3
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    • pp.321-325
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    • 1998
  • This paper presents a simple, practical, and efficient method for estimating the speed of sound in reflection mode in ultrasound medical imaging. Its accurate determination is indispensable in order to obtain both good resolution and correct geometrical and volumetric information about human organs such as heart and kidney. Up to now, there have been several methods available, but they all suffer from either poor performance or high complexity. The proposed method finds out an optimum focusing delay profile in such a way that the brightness in a region of interest is maximized using continuous dynamic focusing in receive under fixed transmit focusing. Experiments carried out on a real ultrasound medical phantom reveals that the method a quite simple and effective in providing good speed of sound estimation, hence improved resolution and images, adding to dignostic utility.

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Adoption of Nonlinear Resonant Ultrasonic Spectroscopy for the Evaluation of Stress State on Concrete in Prestressed Beam (프리스트레스트 보의 콘크리트 응력 수준 평가를 위한 비선형 초음파 공진 기법의 적용)

  • Kim, Gyu-Jin;Kwak, Hyo-Gyoung
    • Journal of the Computational Structural Engineering Institute of Korea
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    • v.30 no.3
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    • pp.215-222
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    • 2017
  • In order to evaluate a stress state of concrete according to the change of tensile force of prestressed beam, improved nonlinear resonant ultrasonic spectroscopy(NRUS) method is proposed. This technique is advantageous to evaluate the stress state in initial state because the method shows much higher sensitivity than existing linear ultrasonic methods. The NRUS technique measure a nonlinearity parameter, which is calculated from the resonant frequency shift of ultrasonic wave related to the medium state, and the result is also closely related to the stress state of concrete. In this study, the nonlinearity parameter was measured with the change of tensile force to verify the close relationship between the two factors, and the effect of repetitive load cycle on the change of nonlinearity parameter was analyzed. In addition, sensitivity comparison with the linear ultrasonic pulse velocity method was performed. Through the experimental results, the possibility of NRUS technique for the evaluation of stress state in prestressed beam was confirmed.

Effects of Moisture Content and Slope of Grain on Ultrasonic Transmission Speed of Wood (함수율과 섬유경사각이 목재의 압축강도 및 초음파 전달속도에 미치는 영향)

  • Jang, Sang-Slk
    • Journal of the Korean Wood Science and Technology
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    • v.28 no.2
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    • pp.10-18
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    • 2000
  • Nondestructive testing(NDT) by using ultrasonic sound is widely applied to wood for grading, moisture and defect detecting, estimating degree of decay, etc. Before practicing such application, basic relationships between ultrasonic transmission and wood properties shall be studied first. In this study, ultrasonic NDT was applied to larch and red pine to investigate the effects of moisture content and slope of grain on ultrasonic transmission speed. Specimens for testing about moisture content were prepared to have moisture content of green state, 30%, 20%, 10% and oven-dry state. Specimens for testing about slope of grain were prepared to have grain angle of 0, 15, 30, 45, 60, 75 and 90 degree in the tangential direction. Ultrasonic transmission speed was inversely proportional to moisture content in low range of moisture content under around 30% that was considered to be close to fiber saturation point. In high moisture content range above 30%, the ultrasonic transmission speed was almost constant. The same trend was observed in the relationships between compressive strength and moisture content. Slope of grain also had inversely proportional relationship with ultrasonic transmission speed and compressive strength. The relationship between compressive strength and ultrasonic transmission speed could be expressed by a linear equation.

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Sonochemical Destruction of Aliphatic Aldehydes in an Aqueous Solution (수용액중 초음파조사에 의한 Aldehyde류의 초음파분해)

  • Yoo, Young-Eok;Howang, Kyu-Tak;Maeda, Yasuaki
    • Journal of Environmental Health Sciences
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    • v.23 no.4
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    • pp.39-44
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    • 1997
  • Propionaldehyde, n-Butyraldehyde, n-Valeraldehyde 수용액에 주파수 200 kHz, 출력 6.0 W/cm$^2$의 초음파조사후 그 분해반응에 관해 고찰했다. Aldehyde류는 초음파 조사에 의해 빠르게 분해되었고, 분해형태는 유사1차 반응을 나타내었다. 이들의 분해 속도는 Propionaldehyde

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Determination of phase velocity dispersion curve and group velocity using backward radiated leaky Lamb waves (후방복사 리키 램파를 이용한 위상속도 분산곡선과 군속도의 측정)

  • Kim Young H.;Song Sung-Jin;Chun Kwon Soo;Kwon Sung-Duk
    • Proceedings of the Acoustical Society of Korea Conference
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    • spring
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    • pp.529-534
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    • 2002
  • 유도초음파는 얇은 판재와 다층재료를 평가하는데 널리 사용되는데, 이를 정량적으로 이용하기 위해서는 위상 및 군속도의 분산선도는 필수적이다. 본 연구에서는 후방복사 리키 램파를 이용하여 위상속도 분산곡선과 군속도를 측정하였다. 물에 잠긴 판재에 입사각을 변화 시키면서 판재에서 발생하는 후방복사 초음파 신호를 측정하였고, 후방복사된 초음파 신호는 유도초음파의 분산특성을 지님을 보였다. 입사각도와 수신된 파형의 주파수 분석을 통하여 램파의 위상속도 분산선도를 구하였다. 또한, 특정한 입사각에서 입사점을 변화시키면 서 론 파형의 시간대역 이동으로부터 군속도를 측정하였다.

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A Method for Noninvasive Diagnosis of Bone using Ultrasonic Doppler Method (초음파 Doppler법에 의한 생체 경조직의 비침투적인 진단을 위한 기초실험)

  • 박무훈
    • The Journal of the Acoustical Society of Korea
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    • v.17 no.7
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    • pp.3-11
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    • 1998
  • 본 논문에서는 분포정수선로의 간단한 모델을 이용해서, 외부에서 진동을 가했을 때 에 뼈 표면에서 발생하는 굴곡파의 전파속도와 종파의 전파속도를 구할 수 있는 새로운 측 정원리를 제안했다. 이 측정원리를 이용해서, 봉(brass, polymethylmethacrylate)표면에 발생 하는 정재파에 대한 속도의 공간분포를 laser Doppler법으로 측정해서, 각각의 주파수에 대 한 전파속도를 구했다. 이 새로운 측정방법은 in vivo에서 초음파 Doppler법을 이용해서 뼈 의 이상(골다공증, osteoporosis)진단의 가능성을 제시했다.

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The Contribution of OH radical and the Effect of Adding Oxidants on the Sonolytic Degradation of 1,4-Dioxane (초음파를 이용한 1,4-Dioxane의 처리에서 OH 라디칼의 기여와 산화제 첨가의 효과)

  • Son, Hyun-Seok;Choi, Seok-Bong;Khan, Eakalak;Zoh, Kyung-Duk
    • Journal of Korean Society of Environmental Engineers
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    • v.27 no.6
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    • pp.642-650
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    • 2005
  • This research investigates the effects of adding oxidants such as $Fe^0$, $Fe^{2+}$, and ${S_2O_8}^{2-}$ in the sonolysis of 1,4-D. Results indicate that the degradation could be divided into two steps (initiation and acceleration) kinetically. The initial portion agreed with zero-order expression, while the second portion could be fitted with pseudo first-order expression. In the presence of ${HCO_3}^-$, as a radical scavenger, the degradations of 1,4-D and TOC were suppressed, indicating that OH radical is an important factor in the sonolysis. The overall degradation efficiency of 79.0% in the sonolysis was achieved within 200 minutes. While $Fe^0$, $Fe^{2+}$, and ${S_2O_8}^{2-}$ were individually combined with sonication, the degradation efficiency of 1,4-D increased 18.6%, 19.1%, and 16.5% after 200 min, respectively. The addition of oxidants not only changed the kinetic model from zero to pseudo first order at initiation step, but also increased the rate constants in the acceleration step. The addition of oxidants in the sonolysis of 1,4-D also improved the mineralization of 1,4-D, however, the effect of adding oxidants on the rate increase was similar regardless of the oxidants.

Burning Rate Testing of Double Base Solid Propellants using Ultrasound (초음파를 이용한 Double Base형 고체추진제의 연소속도 측정)

  • Song, Sung-Jin;Ko, Sun-Feel;Kim, Hak-Joon;Oh, Hyun-Taek;Kim, In-Chul;Yoo, Ji-Chang;Jung, Jung-Yong
    • Proceedings of the Korean Society of Propulsion Engineers Conference
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    • 2006.11a
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    • pp.247-250
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    • 2006
  • In the previous study, we have developed an ultrasonic measurement system and analysis technique for borning rate testing of solid propellants using ultrasound. And then, using the developed system, burning rate of composite propellants were measured. So, in this study, we performed measurement of double base solid propellant, which has non-linear homing rate as pressure increasing, using the developed system in order to evaluate capability of ultrasonic method. Furthermore, accuracy of measured homing rates using ultrasound was verified by comparison to homing rate measured by the strand burner method.

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Determination of the Effective Elastic Constants of a Superlattice Film by Measuring SAW Velocities (표면탄성파 전파속도 측정에 의한 초격자 다층박막의 유효탄성계수 결정)

  • 김진오
    • The Journal of the Acoustical Society of Korea
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    • v.19 no.5
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    • pp.41-45
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    • 2000
  • The effective elastic constants of a single-crystal superlattice film have been determined by two methods based on the velocities of surface acoustic waves (SAW). One method uses formulas to calculate the effective elastic constants of a superlattice from the known elastic constants of the constituent layers. The calculated effective elastic constants are tested by comparing the corresponding SAW velocities calculated for thin-film/substrate systems with the corresponding SAW velocities measured by line-focus acoustic microscopy (LFAM). The other method determines the effective elastic constants of the superlattices by inverting the SAW velocity dispersion data measured by LFAM. The results of both methods applied to a TiN/NbN superlattice film are in good agreement.

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