• Proceedings of the Korea Water Resources Association Conference
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• 2017.05a
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• pp.75-75
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• 2017

하천의 합류부는 서로 다른 지형학적 특성과 수리학적 특성을 가지는 두 개의 하천이 하나로 합쳐지는 구간으로 급격한 흐름의 변화 및 퇴적물의 유입과 수리학적 지형변화가 발생하는 구간이다. 이러한 합류부에서는 흐름구조와 물의 물리 화학적인 특성이 지속적으로 변화할 수 있고, 침식과 퇴적으로 인한 하상변동과 같은 하도 변화가 발생할 수 있다. 또한, 하천의 합류부는 두 지류가 만나 형성되는 지역으로 하천생태계에서 매우 중요한 역할을 하는 구간이다. 이러한 합류부 구간의 혼합 매커니즘을 이해하기 위해서는 지류의 다양한 유입조건에 따른 본류와의 수체혼합의 공간적인 패턴을 분석하는 것이 중요하다. 그러나, 대부분의 합류부 연구들은 실측에 기반한 공간적인 수체혼합의 패턴 분석의 어려움으로 인해 수리 및 수질 수치모형에 의존하여, 실측자료에 기반하여 지류의 유입에 따른 수체혼합을 공간적으로 분석하는 연구는 매우 제한적이었다. 따라서, 본 연구에서는 ADCP를 활용하여 합류부의 혼합 현상을 규명하는 인자로 유속과 수심 등 기본적인 수리학적 인자들뿐만 아니라 최근 활발하게 연구되고 있는 ADCP의 초음파반사율을 활용하여 상이한 농도의 유사가 혼합되는 양상을 측정하여 합류부의 혼합 특성을 공간적으로 분석하고자 하였다. 초음파반사율은 부유사와 관련되는 인자로 SonTek ADCP 이동식으로 측정된 SNR자료를 확산, 물에 의한 흡수를 고려하여 보정한 후 3차원 혼합거동의 공간적인 분포를 도출하였다. 그리고 초음파반사율을 활용한 방식을 검증하고 지류와 본류의 유입 전후 입도분포를 확인하기 위해 LISST 측정을 수행하였고, 드론 영상을 활용하여 유입 유사의 2차원 공간적인 분포를 확보하여 초음파반사율을 활용한 방법과 비교하였다. ADCP, LISST, 드론의 계측자료는 낙동강과 남강 합류부에서 측정되었고, ADCP로부터 제공되는 유속, 수심자료의 공간적인 분포를 분석하여 합류부의 수리특성을 분석할 수 있었고, 초음파반사율을 유사 혼합의 공간적 특성을 규명하는 인자로 활용하여 본류와 지류의 유입량에 따른 다양한 유사 혼합의 3차원 공간적인 패턴을 분석할 수 있었다.

• Journal of Biomedical Engineering Research
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• v.25 no.5
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• pp.403-414
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• 2004

In the accompanying paper, we proposed a real. time volumetric imaging method using a cross array based on receive dynamic focusing and synthetic aperture focusing along lateral and elevational directions, respetively. But synthetic aperture methods using spherical waves are subject to beam spreading with increasing depth due to the wave diffraction phenomenon. Moreover, since the proposed method uses only one element for each transmission, it has a limited transmit power. To overcome these limitations, we propose a new real. time volumetric imaging method using cross arrays based on synthetic aperture technique with linear wave fronts. In the proposed method, linear wave fronts having different angles on the horizontal plane is transmitted successively from all transmit array elements. On receive, by employing the conventional dynamic focusing and synthetic aperture methods along lateral and elevational directions, respectively, ultrasound waves can be focused effectively at all imaging points. Mathematical analysis and computer simulation results show that the proposed method can provide uniform elevational resolution over a large depth of field. Especially, since the new method can construct a volume image with a limited number of transmit receive events using a full transmit aperture, it is suitable for real-time 3D imaging with high transmit power and volume rate.

• Journal of Biomedical Engineering Research
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• v.21 no.5
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• pp.519-526
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• 2000

볼륨 렌더링은 3D 의료영상 데이터를 가시화하는 중용한 기법 중 하나이다. 그러나 볼륨 렌더링을 실시간으로 이룰 때, 많은 계산량을 필요로하는 것이 볼률 렌더링을 사용하는데 걸림돌이 되고 있다. 이 논문에서는 Superscalar와 VLIM(Very Long Instruction Word)의 구조를 가지고 있어 동시에 8개의 명령어 수행이 가능한 TI사의 TMS320C6201 DSP를 이용하여 3D 초음파 영상의 쉬어-웝 볼륨 렌더링을 구현하였다. 쉬어-웝 방법을 DSP 상에서 최적으로 구현하기 위하여 ray map 방법, one-to-four ray casting, ？디 skipping 방법을 제안하였다. 제안한 방법들을 이용한 볼륨 렌더링과 적용하지 않은 기존의 알고리즘을 DSP에 구현하여 PSNR과 렌더링 시간의 비교·평가를 통해 만족할 만한 영상 화질에 빠른 렌더링 성능을 얻을 수 있음을 보여주었다.

• Journal of the Korean Institute of Telematics and Electronics T
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• v.35T no.3
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• pp.120-127
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• 1998

In this paper, ultrasonic images of 25MHz bandwidth were acquired by applying peak value variation, time average and depth profile algorithm to acoustic microscopy and its performance was compared and analysed with each other. In the time average algorithm, total reflecting pulse wave from a spot on the coin was converted to digital data in time domain and average value of the converted 512 data was calculated in computer. Time average image was displayed by gray levels colour of acquired N x N matrix average data in the scanning area on the sample. This technique having smoothing effects in time domain make developed an ultrasonic image on a highly scattering area. In depth profile technique, time difference between the reference and the reflected signal was detected with minimum resolution performance of 2ns, thus we can acquired real 3 dimensional shape of the scanning area in accordance with relative magnitude. Through these experiments, peak value, time average and depth profile images were analysed and advantages of each algorithm were proposed.

• The Journal of the Acoustical Society of Korea
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• v.38 no.4
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• pp.467-475
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• 2019

A high-intensity ultrasound wave generates acoustic streaming and acoustic radiation forces when propagating through a medium. An acoustic radiation force generated in a three-dimensional space can produce a solid tactile sensation, delivering spatial information directly to the human skin. We placed 154 ultrasound transmit elements with a frequency of 40 kHz on a concave circular dish, and generated an acoustic radiation force at the focal point by transmitting the ultrasound wave. To feel the tactile sensation better, the transmit elements were excited by sine waves whose amplitude was modulated by a 60 Hz square wave. As an application of ultrasonic tactile sensing, a region where tactile sense is formed in the air is used as an indicator for the position of the hand. We confirmed the utility of ultrasonic tactile feedback by implementing a system that provides the number of fingers to a machine by receiving the shape of the hand at the focal point where the tactile sense is detected.

• Journal of radiological science and technology
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• v.39 no.2
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• pp.185-191
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• 2016

The objective of this study was to detect the fragments generated during IV (intravenous) catheter injection of contrast medium and drug administration in a clinical setting and removal was performed by experimentally producing a phantom, and to compare the radiography, ultrasonography, and multi-detector computed tomography (MDCT) imaging and radiation dose. A 1 cm fragment of an 18 gage Teflon$^{(R)}$ IV catheter with saline was inserted into the IV control line. Radiography, CT, and ultrasonography were performed and radiography and CT dose were calculated. CT and ultrasonography showed an IV catheter fragment clinically and radiography showed no visible difference in the ability to provide a useful image of an IV catheter fragment modality (p >.05). Radiography of effective dose ($0.2139mSv{\cdot}Gy^{-1}{\cdot}cm^{-2}$) form DAP DAP ($0.93{\mu}Gy{\cdot}m^2 $), and dose length product (DLP) ($201mGy{\cdot}cm$) to effective dose was calculated as 0.483 mSv. IV catheter fragment were detected of radiography, ultrasonography and CT. These results can be obtained by menas of an excellent IV catheter fragment of detection capability CT. However, CT is followed by radiation exposure. IV catheter fragment confirming the position and information recommend an ultrasonography.

• Journal of the Korean Institute of Intelligent Systems
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• v.13 no.1
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• pp.51-56
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• 2003

The main goal of existing mobile robot system was a complete autonomous navigation and the vision information was just used as an assistant way such as monitoring For this reason, the researches have been going towards sophistication of autonomousness gradually and the production costs also has been risen. However, it is also important to control remotely an inexpensive mobile robot system which has no intelligence at all. Such systems may be much more effective than fully autonomous systems in practice. Visual information from a simple camera and distance information from ultrasonic sensors are used for this system. Collision avoidance becomes the most important problem for this system. In this paper, we developed a force feedback joystick to control the robot system remotely with collision avoiding capability. Fuzzy logic is used for the algorithm in order to implement the expert s knowledge intelligently. Some experimental results show the force feedback joystick werks very well.

• Journal of Digital Contents Society
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• v.17 no.6
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• pp.603-611
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• 2016

Generally, the doctors manually delineated the prostate boundary seeing the image by their eyes, but the manual method not only needed quite much time but also had different boundaries depending on doctors. To reduce the effort like them the automatic delineating methods are needed, but detecting the boundary is hard to do since there are lots of uncertain textures or speckle noises. There have been studied in SVM, SIFT, Gabor texture filter, snake-like contour, and average-shape model methods. Besides, there were lots of studies about 2 and 3 dimension images and CT and MRI. But no studies have been developed superior to human experts and they need additional studies. For this, this paper proposes a method that delineates the boundary predicting its texture features and its average distribution on the prostate image. As result, we got the similar boundary as the method of human experts.

• Journal of the Korean Society of Visualization
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• v.16 no.1
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• pp.15-20
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• 2018

For the measurement of biophysical properties related with cardiovascular diseases (CVD), various microfluidic devices were proposed. However, many devices were monitored by optical equipment. Ultrasound measurement to quantify the biophysical properties can provide new insights to understand the cardiovascular diseases. This study aims to check feasibility of microfluidic device for ultrasound image analysis based on 3D printer. To facilitate acoustic transmission, agarose solution is poured around 3D mold connected with holes of the acrylic box. By applying speckle image velocimetry(SIV) technique, flow information in the bifurcated channel was estimated. Considering that ultrasound signal amplitude is determined by red blood cell (RBC) aggregation, RBC aggregation in the bifurcated channel can be estimated through the analysis of ultrasound signal. As examples of microfluidic device which mimic the CVD model, velocity fields in microfluidic devices with stenosis and aneurysm were introduced.

• Journal of the Institute of Electronics Engineers of Korea SC
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• v.43 no.3 s.309
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• pp.67-77
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• 2006

This thesis proposes an effi챠ent method for extracting a prostate volume from 3D ultrasound image by using wavelet transform and SVM classification. In the proposed method, a modulus image for each 2D slice is generated by averaging detail images of horizontal and vertical orientations at several scales, which has the sharpest local maxima and the lowest noise power compared to those of all single scales. Prostate contour vertices are determined accurately using a SVM classifier, where feature vectors are composed of intensity and texture moments investigated along radial lines. Experimental results show that the proposed method yields absolute mean distance of on average 1.89 pixels when the contours obtained manually by an expert are used as reference data.