• 물과 미래
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• 제28권6호
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• pp.183-191
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• 1995

하천의 홍수유속을 측정하기 위하여, 전자파를 이용한 물 표면 유속 측정체계를 개발하였다. 현재의 개발단계는 실험용 유속측정체계 수준이다. 전자파 표면유속계는 초고주파(micro-wave) 전자파의 도플러 효과를 이용한다. 이는 전자파의 발진과 안테나를 통한 반사파 수신, 차주파수 신호의 추출로 이루어지는 RF부분과, 차주파수 신호의 A/D변환 및 고속 후리에 변환 등으로 이루어지는 신호처리부로 구성된다. 구성된 유속측정 체계로 교량 아래 유속, 대청 조정지댐 방수로 등에서 측정 실험하였고 선박해양공학 연구센터의 선박 실험용 선형수조에서 검증 실험을 수행하였다. 검증결과 A/D 변환기 제작오류에서 발생된 4% 오차 이외에 측정환경의 문제에서 비롯된 몇 %의 오차가 혼재되어 있음이 분석되었다. 그러나 0.5~3.5 m/s 유속을 측정한 결과, 기준속도와 측정속도간 선형성이 우수하고 홍수 유속 측정에 매우 유용한 장비임이 입증되었다. 향후 소형화, 경량화를 수행하고 바람, 물 표면의 불규칙 유동에 의한 영향을 분석하여 신호처리 방안을 마련하는 재제작 (re-engineering) 과정이 요구된다.

• 한국정보통신학회:학술대회논문집
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• 한국정보통신학회 2014년도 추계학술대회
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• pp.956-957
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• 2014

유속측정 레이다에서는 수신되는 도플러 신호의 스펙트럼을 추정함으로서 속도정보를 추출하게 된다. 그러나 저 유속인 경우 상대적으로 도플러 주파수 대역이 매우 저주파 영역에 나타나게 되며 이로 인하여 신호의 위상잡음이나 배경 클러터 등에 의한 영향을 심하게 받게 된다. 따라서 이러한 경우의 추정치 개선을 위한 방법을 분석하였다.

• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 2010년도 추계학술대회 논문집
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• pp.527-532
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• 2010

This paper is concerned with the measurement of static and dynamic displacement by image processing(IP) and study for prediction method of velocity and acceleration. To measure the displacement visually, the measurement system consists of a telephoto zoom camera, ccd image device and a computer. The specific target on the white board is used to calculate the displacement of the structure. The captured image is then converted into a pixel-based data and then analyzed numerically. The limitation of the system depends on the image capturing speed and the pixel-size of image. In this paper, we developed for the displacement measurement using the image processing method. The proposed method enables us to measure the vibration measurement, velocity and acceleration directly without any contact. The current resolution of the displacement measurement is limited to 1/100 millimeter scale.

• 한국콘크리트학회:학술대회논문집
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• 한국콘크리트학회 1997년도 봄 학술발표회 논문집
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• pp.544-550
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• 1997

In this study, the advanced on-sided stress wave velocity measurement method was applied to investigate the effects of composition, age and moisture content in concrete. Two concrete specimens that have different composition were used to figure out the change of the Longitudinal and Surface wave velocity due to different composition. The other concrete specimen was cast and the Longitudinal and Surface wave velocity was monitored during curing process. After 28-day old, the effect of moisture content in the concrete specimen to the stress wave velocity is presented in this paper during the time period 43-74 days after casting. For drying process. an aggregate drying oven was used. A conventional ultrasonic through transmission method was used to compare with the results determined by the one-sided method.

• 한국통신학회논문지
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• 제29권11C호
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• pp.1527-1540
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• 2004

본 논문은 트래픽 정보취득을 위하여 영상의 라인 샘플링을 이용한 고속이동물체 속도 측정 알고리즘을 제안하였다. 이동물체의 트래픽 정보 취득을 위한 속도 측정은 도로에 제 1 샘플라인과 제 2 샘플라인을 설정해 놓고, 물체가 샘플라인을 통과할 때 취득된 영상의 시변환 색조 데이터와 기준영상 색조 데이터 사이에서 차영상 기법으로 자동차를 검출하고, 자동차가 두 샘플라인 사이에 거리를 통과할 때 점유하는 프레임수로 속도를 측정하였다. 제 1 샘플라인과 제 2 샘플라인에서 각각 검출된 자동차의 색조로 동일성 판별을 하였다. 제안된 방법의 타당성을 검토하기 위하여 주행하는 자동차를 대상으로 동일성 판별 및 속도 측정을 한 결과, 동일성 판별은 두 개의 샘플링 라인을 통과하는 자동차의 색조 데이터로 판별됨을 보였고, 자동차의 속도 측정은 X-밴드 속도 측정 시스템과 비교한 결과 3% 이내임을 보였다.

• Smart Structures and Systems
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• 제6권9호
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• pp.1025-1039
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• 2010

Measuring displacement response for civil structures is very important for assessing their performance, safety and integrity. Recently, video-based techniques that utilize low-cost high-resolution digital cameras have been developed for such an application. These techniques however have relatively low sampling frequency and the results are usually contaminated with noises. In this study, an integrated visual-inertial measurement method that combines a monocular videogrammetric displacement measurement technique and a collocated accelerometer is proposed for displacement and velocity measurement of civil engineering structures. The monocular videogrammetric technique extracts three-dimensional translation and rotation of a planar target from an image sequence recorded by one camera. The obtained displacement is then fused with acceleration measured from a collocated accelerometer using a multi-rate Kalman filter with smoothing technique. This data fusion not only can improve the accuracy and the frequency bandwidth of displacement measurement but also provide estimate for velocity. The proposed measurement technique is illustrated by a shake table test and a pedestrian bridge test. Results show that the fusion of displacement and acceleration can mitigate their respective limitations and produce more accurate displacement and velocity responses with a broader frequency bandwidth.

• 한국수자원학회:학술대회논문집
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• 한국수자원학회 2001년도 학술발표회 논문집(I)
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• pp.52-59
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• 2001

Methods to measure and estimate transpiration of a forest composed of evergreen broad-leaved trees (Pasania edulis Makino) are studied. Heat pulse velocity has been measured along with soil moisture and micrometeorological factors at the Fukuoka Experimental Forest, the Research Institute of Kyushu University Forests in Fukuoka, Japan (33$^{\circ}$38'N, 130$^{\circ}$31'E, alt. 75m). Tree cutting measurement was conducted to convert the heat pulse velocity into sap flow and transpiration. A big leaf model to calculate transpiration and Interception loss is examined and the estimated values are compared with the measured values obtained from the heat pulse measurement. The results show that 1) Pasania edulis Makino posessing radial pore structure had relatively high water content and high heat pulse velocity even within the central part of the stem near the pith, 2) the heat pulse velocity was well correspond to the water uptake in the tree cutting measurement, 3) the estimation of sap flow based on the heat pulse velocity is accurate, and 4) the big leaf model using the parameters obtained from measurement of a portable photosynthesis system in one day in summer gives reasonable estimation of transpiration independent of seasons and weather.

• 한국해양공학회지
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• 제35권2호
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• pp.150-160
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• 2021

To ensure the international competitiveness of the domestic offshore plant industry, a consensus has been formed regarding the requirement for large offshore basins for performing offshore plant performance verification. Accordingly, the Korea Research Institute of Ships & Ocean Engineering has built the world's largest deep ocean engineering basin (DOEB). The purpose of this study is to evaluate the characteristics of velocity distribution under various conditions of the DOEB. An independent measuring jig is designed and manufactured to measure the current velocities of many locations within a short time. The measurement jig is a 15-m-high triangular-truss structure, and the measurement sensors can move 15 m vertically through an electric motor-wire device. The current speed is measured under various impeller revolutions per minute and locations of the DOEB using the jig. The spatial distribution characteristics of the current velocity in the DOEB and the performance of the current generator are analyzed. The maximum speed is 0.56 m/s in the center of the DOEB water surface, thereby confirming sufficient current velocity distribution uniformity for model testing.

• 한국가시화정보학회:학술대회논문집
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• 한국가시화정보학회 2001년도 Proceedings of 2001 Korea-Japan Joint Seminar on Particle Image Velocimetry
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• pp.23-35
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• 2001

Due to advances in digital image processing, computer and optical hardware, it is possible to extract full flow information from visualized flow images. Recently, the PIV/PTV methods have been accepted as a reliable velocity field measurement technique. In my laboratory, several velocity field measurement techniques have been developed and they were applied to various thermo-fluid flow problems. In this paper, some of the industrial applications will be discussed. As a result, the PIV/PTV technique was proved to be a powerful tool for industrial fluid flow diagnosis.

• 대한기계학회논문집B
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• 제28권12호
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• pp.1567-1572
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• 2004

Although accurate measurement of velocity profiles, multiple velocity vectors, and shear stress in arteries is important, there is still no easy method to obtain such information in vivo. This study shows the utility of combining ultrasound contrast imaging with particle image velocimetry (PIV) for non-invasive measurement of velocity vectors. The steady flow analytical solution and optical PIV measurements (for pulsatile flow) were used for comparison. When compared to the analytical solution, both echo PIV and optical PIV resolved the steady velocity profile well. Error in shear rate as measured by echo PIV (8%) was comparable to the error of optical PIV (6.5%). In pulsatile flow, echo PIV velocity profiles agreed well with optical PIV profiles. Echo PIV followed the general profile of pulsatile shear stress across the artery but underestimated wall shear at certain time points. These studies indicate that echo PIV is a promising technique for the non-invasive measurement of velocity profiles and shear stress.