• 대한의용생체공학회:의공학회지
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• 제5권1호
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• pp.55-62
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• 1984

A digital spectrum analysis technique was used to estimate the tissue characteristic parameters (transmission velocity and attenuation coefficient) in the phantom study and the human liver's ultrasound scanning. The soft tissue equivalent phantom was made with the combination materials of agar, water, powdered graphite, and n-propyl alcohol. In the human study, twenty five normal subjects and three patients with liver diseases were studied using the ultrasonic reflection signals and the spectrum analysis method The following results were obtained; 1. The soft tissue-equivalent materical could be produced with various acoustic parameters by changing the composition amount of the powdered graphite and n-propyl alcohol. 2. Attenuation coefficients of normal human liver tissue were estimated to be 0. 36 dB/cm MHz$\pm$0.11. In patients with liver disese, tile attenuation coefficients were shown to be different from the above normal values.

• International Journal of Fuzzy Logic and Intelligent Systems
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• 제14권1호
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• pp.41-48
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• 2014

This paper analyzes the Monte Carlo localization (MCL) method, which estimates the pose of an indoor mobile robot. A mobile robot must know where it is to navigate in an indoor environment. The MCL technique is one of the most influential and popular techniques for estimation of robot position and orientation using a particle filter. For the analysis, we perform experiments in an indoor environment with a differential drive robot and ultrasonic range sensor system. The analysis uses MATLAB for implementation of the MCL and investigates the effects of the control parameters on the MCL performance. The control parameters are the uncertainty of the motion model of the mobile robot and the noise level of the measurement model of the range sensor.

• The Journal of the Acoustical Society of Korea
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• 제29권2E호
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• pp.64-72
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• 2010

Osteoporosis is a skeletal disease characterized by two factors: reduced bone mass and microstructure disruption of bone tissue. These symptoms increase bone fragility and can contribute to eventual fracture. In recent years, quantitative ultrasound (QUS) technologies have played a growing role in the diagnosis of osteoporosis. Most of the commercial bone sonometers measure speed of sound and/or broadband ultrasound attenuation at peripheral skeletal sites. However, QUS parameters are purely empirical measures that have not yet been firmly linked to physical parameters, such as bone strength or porosity, and the underlying physics for their variations in cancellous bone is not well understood yet. This paper reviews the QUS technologies for the diagnosis of osteoporosis and also addresses several theoretical models, such as the Biot model, the scattering model, the stratified model, and the modified Biot-Attenborough model, for ultrasonic wave propagation in bone.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2004년도 춘계학술대회
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• pp.290-295
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• 2004

In this study, the pressure vessel piping with corrosion used during long term were investigated from the time-frequency analysis method. The damage of piping could be evaluated the attenuation factor by ultrasonic parameters such as center frequency and echo waveform. Based on NDE analysis by time-frequency analysis method, it should also be possible to evaluate from various damages and defects in piping members.

• 한국항해항만학회지
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• 제29권4호
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• pp.341-347
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• 2005

A unique technique to extract the phase in time domain is proposed in order to measure the time parameters such as speed and depth by transmitting sound and electric waves. In the signal analysis processing, the phase of pulse signal can be transformed and digitalized with local data in real time without the effect of direct current bias and Nyquist limits. This method is sensitive to base frequency of pulse signal with high spacial resolution and is effective to compare two signals which have different forms. It is expected that the phase analysis technique will be applied to the measurement of the speed and depth accurately by ultrasonic pulse signal in water.

• 동력기계공학회지
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• 제10권1호
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• pp.77-82
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• 2006

In this study, dissimilar friction welding were produced using 15mm diameter solid bar in chrome molybedenum steel(SCM440) to carbon steel(S45C) to investigate their mechanical properties and the relationship between the weld parameters and the nondestructive coefficients, such as AE counts and ultrasonic attenuation coefficient. The main friction welding parameters were selected to endure good quality welds on the basis of visual examination, tensile tests, Vickers hardness surveys of the bond of area and heat affected zone. The specimens were tested as-welded and post weld heat treated(PWHT). The tensile strength of the friction welded steel bars was increased up to 100％ of the S45C base metal under the condition of all heating time. The ductility of PWHT specimens is higher than as-welded.

• Journal of information and communication convergence engineering
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• 제20권1호
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• pp.58-64
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• 2022

Breast ultrasonic reading is critical as a primary screening test for the early diagnosis of breast cancer. However, breast ultrasound examinations show significant differences in diagnosis based on the difference in image quality according to the ultrasonic equipment, experience, and proficiency of the examiner. Accordingly, studies are being actively conducted to analyze the texture characteristics of normal breast tissue, positive tumors, and malignant tumors using breast ultrasonography and to use them for computer-assisted diagnosis. In this study, breast ultrasonography was conducted to select 247 ultrasound images of 71 normal breast tissues, 87 fibroadenomas among benign tumors, and 89 malignant tumors. The selected images were calculated using a statistical method with 21 feature parameters extracted using the gray level co-occurrence matrix algorithm, and classified as normal breast tissue, benign tumor, and malignancy. In addition, we proposed five feature parameters that are available for computer-aided diagnosis of breast cancer classification. The average classification rate for normal breast tissue, benign tumors, and malignant tumors, using this feature parameter, was 82.8%.

• Environmental Engineering Research
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• 제8권2호
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• pp.72-81
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• 2003

• Journal of the Korean Wood Science and Technology
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• 제44권1호
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• pp.1-8
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• 2016

목재 데크재에 인위적인 결함인 구멍을 부여하고 이들의 성능평가를 위해 초음파 비파괴 시험법을 적용하였다. 구멍의 크기와 개수를 달리하여 각각에 대한 초음파 전달속도를 측정하고 탄성계수를 산정하여 그 영향을 비교분석하였다. 시험결과 구멍의 크기가 커짐에 따라 초음파 전달속도와 탄성계수는 감소하였으며 이들 상호간에는 직선상관관계를 보였다. 구멍의 크기가 증가하면 초음파의 전달 길이는 증가하며 이에 따라 초음파속도는 감소하였지만 구멍의 크기가 15 mm 이하로 작은 경우에는 구멍이 없는 부재에 비해 그 차이가 작게 나타났다. 구멍의 개수가 많아짐에 따라 초음파 전달속도와 탄성계수는 감소하였으며 이들 상호간에는 높은 직선상관관계를 보였다. 구멍의 개수가 3개인 경우 초음파속도는 약 3.5% 정도 감소한데 비하여 탄성계수는 27% 정도로 현저히 감소하여 더 큰 감소경향을 나타내었다. 이들의 결과로부터 구멍의 크기와 개수는 초음파 전달속도와 탄성계수에 영향을 미치며 구멍의 크기가 크고 개수가 많아질수록 그 영향은 더욱 커질 것으로 여겨진다. 또한 작은 결함의 탐지를 위해서는 초음파 전달속도에만 의지할 것이 아니라 여러 초음파 변수를 고려하여 적용하는 방법을 고려하여야 할 것으로 생각된다.

• 융합신호처리학회논문지
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• 제12권4호
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• pp.341-347
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• 2011

본 논문에서는 유효 빔 폭 개념을 새로이 도입하여 중첩 초음파 센서 링의 성능 평가, 최적 설계, 그리고 복합 장애물 탐지에 대해 기술하도록 한다. 일군의 동종 저지향성 초음파 센서들이 반경이 영이 아닌 원주 상에 일정 간격으로 상호 빔 폭이 중첩되도록 배치된다고 가정한다. 첫째, 중첩 초음파 센서 링의 전역 위치 불확실성을 전체 장애물 탐지 범위 내에서의 국부적 위치 불확실성의 평균값으로 나타낸다. 중첩 초음파 센서 링의 유효 빔 폭을 동일한 전역 위치 불확실성을 갖는 단일 초음파 센서의 빔 폭으로 산정하고 이를 바탕으로 정규화된 장애물 탐지 성능 평가 지수를 정의한다. 둘째, 정의된 성능 평가 지수를 이용하여 장애물 탐지 시 위치 불확실성이 최소화되도록 중첩 초음파 센서 링의 설계 사양을 최적화한다. 주어진 초음파 센서의 사용 개수에 대한 중첩 초음파 센서 링의 최적 반경 그리고 주어진 중첩 초음파 센서 링의 반경에 대한 초음파 센서의 최적 사용 개수를 결정한다. 셋째, 3개의 인접 초음파 센서로부터의 장애물 거리 간의 대소 관계에 의거한 복수 장애물의 위치 불확실성 영역 판정 기준을 제시한다. 제시된 위치 불확실성 영역판정 기준을 이용하여 다양한 형태의 장애물로 구성된 복합 장애물 환경에서의 장애물 윤곽 추출 결과를 보인다.