• KIEAE Journal
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• 제7권6호
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• pp.9-15
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• 2007

Ventilation of buildings provide occupants with comfort and plays a very informant role in supplying indoor ventilation requirement. Also, natural ventilation is more comfortable than forced ventilation taking account of mental comfort. Especially factors, airflow velocity and direction etc., should be reflected in establishment of comfortable indoor environment because indoor airflow can directly affect comfort of occupants. However, a device which enables indoor air movement to be analyzed has not existed until now. Hence, it has mostly depended on simulation results of fluid analysis but the results often differ far from reality. PST(Particle-Streak-Tracking) System, an alternative to improve this problem, is currently applied to natural ventilation in building, air conditioning, and airflow analysis in the inside of a plane etc. This study closely examine the property and strength and weakness of PST that is first introduced into KICT and then evaluate applicable possibility.

• 한국유변학회:학술대회논문집
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• 한국유변학회 2006년도 춘계 학술발표회 논문집
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• pp.61-64
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• 2006

Soft materials, such as polymer solutions, gels and filamentous protein materials in cells, show complicated behavior due to their complex structures and dynamics with multiple characteristic time and length scales. Several complementary techniques have been developed to measure viscoelastic of soft materials. Especially, particle tracking microrheology, using the Brownian motion of particles in a medium to get rheological properties, has recently been improved both theoretically and experimentally. Compared to other conventional methods, video particle tracking microrheology has some advantages such as small sample volume, detecting spatial variation of local rheological properties, and less damage to sample materials. With these advantages, microrheology is more suitable to measure the properties of complex materials than other mechanical rheometries.

• Journal of Mechanical Science and Technology
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• 제18권7호
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• pp.1236-1245
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• 2004

In this study, an optical imaging method was developed for the measurements of the sizes and velocities of droplets in sprays. Double-exposure single-frame spray images were captured by the imaging system. An image processing program was developed for the measurements of the sizes and positions of individual particles including separation of the overlapped particles and particle tracking and pairing at two time instants. To recognize and separate overlapping particles, the morphological method based on watershed segmentation as well as separation using the perimeter and convex hull of image was used consecutively. Better results in separation were obtained by utilization of both methods especially for the multiple or heavily-overlapped particles. The match probability method was adopted for particle tracking and pairing after identifying the positions of individual particles and it produced good matching results even for large particles like droplets in sprays. Therefore, the developed optical imaging method could provide a reliable way of analyzing the motion and size distribution of droplets produced by various sprays and atomization devices.

• 대한기계학회논문집B
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• 제27권7호
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• pp.859-866
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• 2003

The Lagrangian dispserion of fluid particles in inhomogeneous turbulence is investigated by a direct numerical simulation of turbulent channel flow. Fluid particle velocity and acceleration along a particle trajectory are computed by employing several interpolation schemes such as linear interpolation, high-order Lagrange polynomial interpolation and the Hermite interpolation schemes. The performances of the schemes are evaluated through comparison of errors in computed particle positions, velocities and accelerations against spectral interpolation. Adopting the four-point Hermite interpolation in the homogeneous directions and Chebyshev polynomials in the wall-normal direction appears to produce most reliable Lagrangian statistics including acceleration correlations with a reasonable amount of computational overhead.

• 로봇학회논문지
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• 제8권2호
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• pp.104-115
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• 2013

For natural human-robot interaction, we need to know location and shape of facial feature in real environment. In order to track facial feature robustly, we can use the method combining particle filter and active appearance model. However, processing speed of this method is too slow. In this paper, we propose two ideas to improve efficiency of this method. The first idea is changing the number of particles situationally. And the second idea is switching the prediction model situationally. Experimental results is presented to show that the proposed method is about three times faster than the method combining particle filter and active appearance model, whereas the performance of the proposed method is maintained.

• 대한기계학회논문집B
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• 제30권3호
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• pp.215-221
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• 2006

A stereoscopic particle tracking velocimetry (SPTV) technique based on the 2-frame hybrid particle tracking velocimetry (PTV) method was developed. The expansion of 2D PTV to SPTV is facilitated by the fact that the PTV method tracks individual particle centroids. To evaluate the performance and measurement accuracy of the present SPTV technique, it was applied to flow images of rigid body translation and synthetic standard images of jet shear flow and impinging jet flow. The data processing routine and measurement uncertainty of the SPTV technique are compared with those of conventional stereoscopic particle image velecimet.y (SPBV). In addition, the centroid translation effect of 2D particle image velocimetry (PIV) is defined and its effect on SPIV measurements is discussed. Compared to the SPIV method, the SPTV technique has inherited merits of concise and precise velocity evaluation procedures and provides better spatial resolution and measurement accuracy.

• 한국정보통신학회논문지
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• 제20권8호
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• pp.1537-1545
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• 2016

실시간영상에서 객체의 분할 및 추적은 침입자 감시와 로봇의 물체 추적, 증강현실의 객체 추적등 다양한 분야에서 사용되고 있다. 본 논문에서는 초기 입력 영상의 일부를 학습하여 배경모델로 제작한 후, 배경제거 방법을 이용하여 움직이는 객체의 분할을 통해 객체를 검출하였다. 검출된 객체의 영역을 기반으로 HSV 색상히스토그램과 파티클 필터를 이용하여 객체의 움직임을 추적하는 방법을 제안한다. 제안한 분할 방법은 평균 배경모델을 이용한 방법보다 주변환경 변화의 영향을 적게 받으며, 움직이는 객체의 검출 성능이 더욱 우수하였다. 또한 단일 객체 및 다수의 객체가 존재하는 환경에서 추적 객체가 유사한 색상 객체와 겹치는 경우, 추적 객체의 영역 절반 이상이 가려지는 경우에도 지속적으로 추적하는 결과를 얻을 수 있었다. 2개의 비디오 영상을 사용한 실험결과는 평균 중첩율 85.9%, 추적률 96.3%의 성능을 보여준다.

• 한국정보통신학회논문지
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• 제10권11호
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• pp.2032-2038
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• 2006

연속되는 이미지 중에서 인간의 동작을 인식하는 것은 인간과 컴퓨터 의 상호 작용에서 매우 중요하고 도전할 분야이다. 본 논문에서는 CONDENSATION 알고리즘을 이용하여 입자 필터(particle filter)에 기반한 동작 인식 알고리즘을 제안한다. 입자 필터는 조건 확률 전파 모델(Conditional Density Propagation)인 베이시안(Bayesian) 추정 규칙을 적용하는 추적구조를 갖고 있기 때문에 다른 어떤 종류의 추적 알고리즘보다 뛰어난 성능을 보인다. 본 논문에서는 알고리즘의 성능평가를 위해서 두 개의 동작 모델을 가정하였고, 영상에 대한 전처리를 위해서는 MATLAB를 이용하였으며 입자필터는 고속 처리를 위하여 C++로 구현하였다. 두 개의 동작 실험 결과를 통해, 동작 인식 입자 필터가 복잡한 환경 속에서 강인한 추적 성능을 나타냄을 확인하였다.

• ALGAE
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• 제34권4호
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• pp.315-326
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• 2019

Northeastward drifts of massive Sargassum patches were observed in the East China Sea (ECS) and Yellow Sea (YS) by the Geostationary Ocean Color Imager (GOCI) in May 2017. Coverage of the brown macroalgae patches was the largest ever recorded in the ECS and YS. Three-dimensional circulation modeling and Lagrangian particle tracking simulations were conducted to reproduce drifting trajectories of the macroalgae patches. The trajectories of the macroalgae patches were controlled by winds as well as surface currents. A windage (leeway) factor of 1% was chosen based on sensitivity simulations. Southerly winds in May 2017 contributed to farther northward intrusion of the brown macroalgae into the YS. Although satellite observation and numerical modeling have their own limitations and associated uncertainties, the two methods can be combined to find the best estimate of Sargassum patch trajectories. When satellites were unable to capture all patches because of clouds and sea fog in the ECS and YS, the Lagrangian particle tracking model helped to track and restore the missing patches in satellite images. This study suggests that satellite monitoring and numerical modeling are complementary to ensure accurate tracking of macroalgae patches in the ECS and YS.

• Journal of Power Electronics
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• 제18권5호
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• pp.1470-1478
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• 2018

Recently, wireless power transfer (WPT) via coupled magnetic resonances has attracted a lot of attention owing to its long operation distance and high efficiency. However, the WPT systems is over-coupling and a frequency splitting phenomenon occurs when resonators are placed closely, which leads to a decrease in the transfer power. To solve this problem, an adaptive frequency tracking control (AFTC) was used based on a closed-loop control scheme. An improved particle swarm optimization (PSO) algorithm was proposed with the AFTC to track the maximum power point in real time. In addition, simulations were carried out. Finally, a WPT system with the AFTC was demonstrated to experimentally validate the improved PSO algorithm and its tracking performance in terms of optimal frequency.