• The Journal of the Acoustical Society of Korea
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• v.40 no.2
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• pp.161-168
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• 2021

In this paper, a Silent Speech Interface (SSI) technology was proposed in which Doppler frequency shifts of the reflected signal were used to synthesize the speech signals when 40kHz ultrasonic signal was incident to speaker's mouth region. In SSI, the mapping rules from the features derived from non-speech signals to those from audible speech signals was constructed, the speech signals are synthesized from non-speech signals using the constructed mapping rules. The mapping rules were built by minimizing the overall errors between the estimated and true speech parameters in the conventional SSI methods. In the present study, the mapping rules were constructed so that the distribution of the estimated parameters is similar to that of the true parameters by using Generative Adversarial Networks (GAN). The experimental result using 60 Korean words showed that, both objectively and subjectively, the performance of the proposed method was superior to that of the conventional neural networks-based methods.

• The Journal of the Acoustical Society of Korea
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• v.28 no.8
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• pp.732-739
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• 2009

Flow phantom with stenosis was manufactured using an auto-injector to obtain angiostenotic flow information and quality assurance (QA) for ultrasound diagnostic instrumentation. Effectiveness of manufactured flow phantom with stenosis was investigated with power Doppler that was known to have diagnostic efficiency for angiostenosis. The flow phantom with stenosis was manufactured to 70% stenosis with 8 mm and 2.4 mm silicon tube, and silicone tube was covered with gelatin that has acoustic characteristics similar to soft tissue. When the linear transducer was used for measurement, the estimated diameter of normal vessel was measured lower than that of normal value, and the estimated diameter of stenosed vessel was measured higher than that of normal value. The measured parameters were not affected except for the radical conditions such as gain of 60%, PRF of 3000 Hz, use of maximal filter or angle. In addition, when the convex transducer was used for measurement, measurement parameters were affected by gain, PRF, filter, and angle. Therefore it is expected that flow phantom with stenosis manufactured with an auto-injector will be utilized effectively for QA of angiostenotic diagnosis.

• Journal of Veterinary Clinics
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• v.32 no.2
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• pp.162-167
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• 2015

Tei-index has been reported as one of reliable echocardiographic factors for evaluating cardiac function in human and small animals. In this study, Tei-index were measured and evaluated with other echocardiographic parameters in normal thirteen beagle dogs and thirty-one dogs with mitral valve degeneration. Normal range of Tei index with tissue Doppler obtained at septum and left ventricular free wall was $0.58{\pm}0.07$ and $0.60{\pm}0.07$, respectively. The values between septum and left ventricular free wall did not show significant difference. Tissue Doppler derived tei index showed better reproducibility and significantly lower values than the results obtained by pulsed wave Doppler. Tei index obtained in either method increased with the progression of clinical signs. Therefore, the increase of Tei index in dogs with mitral regurgitation is thought to be an useful factor reflecting left ventricular dysfunction.

• Journal of radiological science and technology
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• v.40 no.2
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• pp.213-218
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• 2017

Recently, as the number of high-risk pregnancies increases, the use of new techniques such as Doppler, which have higher acoustic power than in the past, has been increasingly used in prenatal diagnosis and guidelines have been set up by various organizations to prevent excessive exposure. Therefore, in this study, we tried to investigate the temperature change of the body surface for each test mode according to the long time ultrasound examination and to examine the exposure time which is not influenced by the thermal effect. B mode, C mode, and PD mode according to time, and the temperature difference between exposed and unexposed sites were compared. As a result, the B mode showed a significant difference in the temperature change from 10 minutes, 50 minutes after exposed, 20 minutes from the C mode, and 30 minutes from the PD mode (p<0.01). In all three modes, the temperature difference was different (p<0.000), and PD mode was the most sensitive to temperature change. Also, it was found that the temperature rise time was shortened with the increase of the ultrasonic exposure time. Therefore, it is recommended that ultrasonography to observe the embryo or fetus should be used only for diagnostic purposes, avoiding excessive test time.

• Proceedings of the Korea Water Resources Association Conference
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• 2009.05a
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• pp.405-409
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• 2009

현재 하천의 유량측정을 위해 국내외에서 설치, 운영되고 있는 자동유량측정시설은 대부분 초음파유속계를 이용한 실시간 하천유량측정시스템이다. 이러한 초음파유속계는 도플러 방식 초음파유속계(ADVM)와 이동 시간차 방식 초음파유속계(UVM)로 구분되는데, 한강대교 등에 적용된 ADVM 방식에 비해 UVM 방식은 초음파 도달거리의 특성으로 인해 대부분 중소규모의 하천에 적용되어왔다. 이러한 UVM 방식을 하폭이 넓고 홍수시 수위변화가 심한 대규모하천에 적용하기 위해서는 여러 회선을 다층으로 구성하여 설치할 필요가 있는데, 한강의 여주지점은 16개의 회선을 5개의 층으로 구성하여 측정의 정확도를 높이고 홍수시 수위상승시에도 다양한 회선으로 유속을 측정할 수 있도록 하였다. 본 연구에서는 여주지점에 설치되어 운영 중에 있는 이동 시간차 방식 자동유량측정시설의 운영결과를 검토하고 측정치에 대한 검증을 위해 2008년 1월부터 12월까지의 유량측정결과를 검토하였다. 평 저수시는 유속계와 ADCP 이동보트를 이용한 연속측정결과와 비교하였으며 홍수시에는 봉부자 측정결과와 비교하였다. 기존 실측은 2008년 2월부터 12월까지 저수위 및 중 고수위에 걸쳐 실시하였으며, 프라이스유속계 22회, 이동식 ADCP 6회 그리고 부자를 이용한 방법 6회등, 총 34회가 이루어졌으며, 비교 결과 수위 1.5m 이하의 저 평수기에 평균 5.5%의 오차를 보였으며, 홍수시 검증측정유량과의 비교결과 7.6%의 오차를 보였다.

• Journal of the Korean Society of Radiology
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• v.85 no.2
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• pp.415-420
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• 2024

Lymphoma is an uncommon type of breast malignancy, with low prevalence. The ultrasonographic findings of breast lymphoma have been described as nonspecific. Breast lymphoma most commonly appears as a solitary hypoechoic mass on US, and usually shows hypervascularity on color Doppler US. Herein, we report an unusual case of breast lymphoma that presented as multiple bilateral hyperechoic nodules on US.

• Journal of Veterinary Clinics
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• v.28 no.6
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• pp.613-616
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• 2011

A 5-year-old male German shepherd dog was presented with a 4 day-history of anorexia and depression. Abdominal radiographs showed a large soft tissue mass and loss of serosal detail. Ultrasonographs revealed splenomegaly with the lacy pattern parenchyma, perivenous hyperechoic region at the splenic hilum, and loss of splenic venous flow. Computed tomographic findings included the enlarged non-enhanced spleen except perivenous region at the splenic hilum and a whirled soft tissue mass at the splenic hilum. Exploratory laparotomy confirmed the diagnosis of splenic torsion. Ultrasonographic findings including lacy appearance, hyperechoic perivenous echogenicity and absence of splenic blood flow and CT findings including no or minimal enhancement of the spleen and a whirled appearance of splenic pedicle could be useful for diagnosing isolated splenic torsion in the dog.

• Korean Journal of Optics and Photonics
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• v.11 no.5
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• pp.306-311
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• 2000

This paper deals with the development of Laser Doppler Vibrometer (LDV) that can mea~ure the tlequency and amphlude of the ultrasonic vibralion. Hc-Ne laser (632.8 om) is used as a light source, and Michelson interferometer in winch frequency of the objective beam is shIfted by Bragg cell IS adopted The frequency modulated signal centered at 40 MHz flom the PIN diode IS amplified. down-col1vel1ed to 2.5 MHz, filtered and digiLized. The voltage output that is proportional to the velocity of the vibratwg surface is obtawed using digItal PLL. A microprocessor is used to extract the frequcncy aud amplitude of the vibratIOn from the voltage output. It is found that the developed LDV can measure up to 300 kHz vibratIOn and the mlillmUITI measurable amplitude is I nm at 300 kHz. We believe thatlhis LDV can be used to measure the vibratIOn of the heavy electric maclllnery and micro-size structures. tures.

• Proceedings of the Korea Water Resources Association Conference
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• 2021.06a
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• pp.18-18
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• 2021

초음파 도플러 유속계(ADCP)는 초음파를 이용하여 하천의 유속 및 수심을 측정하는 장비로 기존의 지점식 유속계와는 다르게 수심방향 유속분포와 수심을 한번에 측정하게 되며, 보트를 이용하여 하천을 횡단하게 되면 기존의 유속-면적법을 이용하는 방식보다 간편하고 빠르게 한 단면의 유량을 측정할 수 있다. 이와 같은 이점으로 인해 국내뿐만 아니라 해외에서도 대하천에서부터 중·소규모의 하천까지 다양한 범위에서 유량을 측정하는 장비로서 사용되어지고 있다. ADCP의 측정 유량은 유량관측소에서 수위-유량관계식을 구축할 때 사용하고 있으며, 이렇게 제공되는 유량은 하천의 중·장기 계획 수립, 수공구조물의 설계 및 수문·수리분야의 연구에 활용되고 있다. 하지만 ADCP의 유량측정은 ADCP의 미측정 영역의 유량 추정, ADCP 잠김깊이의 정확도, 하안에서의 고정 측정시간 등 ADCP의 측정 과정이나, 유량 추정 방법에 따라 영향을 받게 되며. 이외에도 하천의 수심, 하상의 상태와 같은 측정 조건에 따라서도 정확도의 변화가 발생할 수 있다. 측정결과의 정확성을 향상시키고, 신뢰도가 높은 자료를 제공하기 위해서는 ADCP의 유량 측정결과에 대한 불확도를 발생시키는 요인들에 대한 분석과 이를 감소시킬 수 있는 방법을 찾는 것이 중요하다. 1993년 ISO, BIPM, IFCC 등 6개 기구에서는 측정불확도를 산정하기 위한 측정불확도 산정 지침서(GUM, Guide to the expression of Uncertainty of Measurement)를 제시하였다. GUM 표준안은 측정과정에서 발생하는 다양한 불확도 요인들을 불확도 전파법칙을 통해 전체 불확도를 산정하는 방식으로 WMO와 ISO의 유량 측정분야에서도 GUM 표준안을 측정불확도 산정 기준으로 공인하여 사용하고 있다(JCGM 100, 2008; ISO 25377, 2020). 이에 본 연구에서는 GUM 표준안을 이용하여 ADCP로 측정된 유량의 측정불확도를 산정하는 방법을 개발하고 각 요인들에 대한 실험 및 분석을 진행하였다. ADCP의 측정 정확도를 분석하기 위한 실험은 자연에 가까운 형상을 모의하고 있고, 소하천 규모를 갖고 있는 하천연구센터에서 수행하였으며, 요인들에 대한 분석 방법 및 총 불확도를 계산하는 방법에 대하여 제시하였다.

• Proceedings of the KOSOMBE Conference
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• v.1992 no.11
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• pp.43-46
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• 1992

$\underline{In\;vitro}$ velocity measurements were made using both the pulsed Doppler ultrasound (PDU) machine and laser Doppler anemometer (LDA) system in order to investigate the flow characteristics near the aortic bifurcation. Velocities measured from the PDU machine was in good agreement with those from the LDA. The flow in the daughter branches was three-dimensional with a secondary flow. The oscillating wall shear stress with this secondary fluid motion is well correlated with the localization of the atherosclerosis.