• Proceedings of the KSME Conference
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• 2000.04b
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• pp.502-507
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• 2000

Fundamental studies on the drag reduction of the circular cylinder having dimple were conducted by the measurement of the fluid force acting on the cylinder and by the flow visualization around the cylinder. The drag coefficients were changed by the shape and the space for the arrangement of the dimple. The drag of the cylinder was reduced about 50% by the proper arrangement of the dimple. The flowfield around the cylinder having dimple, which was the minimum drag, was visualized by the hydrogen bubble technique. In this case, the separation points were moved rearward and the wake region was small in comparison with the cylinder having no dimple.

• Proceedings of the Korean Society of Marine Engineers Conference
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• 2001.05a
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• pp.129-134
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• 2001

The drag reduction of the cylinder having square dimpled surface was studied by the measuring the drag force acting on the cylinder. The level of the drag reduction was changed by the arrangement shape of the square grooves and Reynolds number. The drag of the cylinder was reduced about 28% with proper arrangement of square grooves. The flow field around the cylinder having grooves at the minimum drag was visualized by using post color ink in order to see the influence of the grooves. In this case, the separation points were sifted rearward and the wake region was smaller than that of the smooth cylinder.

• Journal of Advanced Marine Engineering and Technology
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• v.26 no.2
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• pp.233-239
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• 2002

The drag reduction of the cylinder having square dimpled surface was studied by the measuring the drag force acting on the cylinder. The level of the drag reduction was changed by the arrangement shape of the square grooves and Reynolds number. The drag of the cylinder was reduced about 28% with proper arrangement of square grooves. The flow field around the cylinder having grooves at the minimum drag was visualized by using post color ink in order to see the influence of the grooves. In this case, the separation points were silted rearward and the wake region was smaller than that of the smooth cylinder.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.7 no.3
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• pp.471-475
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• 2006

Filling the microchannels is very important in designing micro-injection molding, microdevices, etc. In this paper, flow dynamics was studied in injection molding with microchannels. A transparent PMMA mold was designed and the flow dynamics was observed. The experiment was performed using poly (ethylene oxide) (PEO) and polyacrylamide (PA) aqueous solutions. The transignt dynamic flow and flow competition between the base plate and the microchannels were observed. The flow observation was used to explain previous filling length results in microchannels during micro-injection molding.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.30 no.3
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• pp.96-104
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• 2002

탄체가속기용 초기 발사장치로 사용 가능한 건국대 초고속 발사장치가 개발되었다. 이는 2단계 기포 (gas gun) 형태의 발사장치로 공기를 작동 기체로 사용하여 무게 22g의 탄체를 750m/sec로 가속할 수 있 는 성능을 보인다. 초고속 발사장치의 성능 특성을 알아보기 위하여, 구동부의 압축 특성과 작동 특성에 대한 성능 실험을 수행하였으며 실험으로부터 피스톤에 의한 압축 이득과 1,2차 구동부간에 발사장치의 성능을 최상으로 유지할 수 있는 값들이 존재함을 확인하였다. 초고속 비행체의 공력 특성 및 주위의 유동 해석에 응용 가능한 고속 탄환체에 대한 흐름의 가시화를 수행하여 수치적 계산 결과와 비교하였으며, 향후 고속유동의 물리적 현상 해석에 이용될 수 있음을 확인하였다.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.42 no.7
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• pp.561-566
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• 2014

Our Korean traditional cultural inheritance Bangpae Kite has the stable rectangular shield shape decorated with artistic paint or poem and a good flight performance due to the central wind hole. In this paper, to analyse the wind hole effect to kite performance we performed the wind tunnel testing of the various design factor of kite model and air flow visualization passing through the wind hole. As the result of aerodynamic analysis, we knew that the wind hole of kite displays similar function of slot system for the wing high lift device. This fact demonstrates that our ancestor understood the function of slot system and applied effectively to the development of kite flight performance.

• Journal of the Korean Society of Visualization
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• v.7 no.2
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• pp.64-71
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• 2010

The flow and noise characteristics of wake behind wind-turbine blades have been investigated experimentally using a two-frame particle image velocimetry (PIV) technique. Experiments were carried out in a POSTECH subsonic large wind-tunnel ($1.8^W{\times}1.5^H{\times}4.3^L\;m^3$) with KBP-750D (3-blade type) wind-turbine model at a freestream velocity of $U_o\;=\;15\;m/s$ and a tip speed ratio $\lambda\;=\;6.14$ (2933 rpm). The wind-turbine blades are connected to an AC servo motor, brake, encoder and torque meter to control the rotational speed and to extract a synchronization signal for PIV measurements. The wake flow was measured at four azimuth angles ($\phi\;=\;0^{\circ}$, $30^{\circ}$, $60^{\circ}$ and $90^{\circ}$) of the wind-turbine blade. The dominant flow structure of the wake is large-scale tip vortices. The turbulent statistics such as turbulent intensity are weakened as the flow goes downstream due to turbulent dissipation. The dominant peak frequency of the noise signal is identical to the rotation frequency of blades. The noise seems to be mainly induced by the tip vortices.

• Proceedings of the KSME Conference
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• 2008.11b
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• pp.2530-2535
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• 2008

The Visualizations of the flowfield through tube banks with in-line and staggered arrangements were investigated by PIV. Strouhal numbers, velocity vectors and velocity profiles around the cylinders with in-line and staggered arrangements were observed at the pitch ratio $P_t/D=2.0$ and Reynolds number of $Re=4.0{\times}10^3$. As the results The flow patterns through tube banks were almost a straight line in case of the in-line arrangement while it was almost 八 type in case of the staggered arrangement in the direction of the wake. The average velocity in the rear region of the tube banks with the staggered arrangement was far smaller than that with the in-line arrangement. The Strouhal number in the last rank was far smaller than that in the front ranks in both of the in-line and staggered arrangements. The wake of each cylinder changed with time and with the position of the cylinder.

• The Journal of the Institute of Internet, Broadcasting and Communication
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• v.18 no.6
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• pp.11-19
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• 2018

Recently, many companies offer various web-based map that is based on GIS(Geographic Information System) information. Google Map, Open street, Bing Map, Naver Map, Daum Map, Vwolrd Map, etc are the few examples of such system. In this paper, we propose a method to visualize ocean forecasting model data considering the flow diagram of tidal current, streamline expression algorithm, and user convenience by using vector field data information that is currently being served. It is confirmed that the proposed method of the flow diagram of tidal current, and stream line expression algorithm is faster than that of conventional ocean prediction model data by more than 2 times.

• Journal of the Korean Institute of Landscape Architecture
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• v.48 no.6
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• pp.39-47
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• 2020

This paper interprets the social and cultural significance of the "landscape" in North Korea by exploring the object and context of the text referring to the "landscape" in North Korean literature. To this end, the paper first classified the objects describing "landscapes" in serial publications and newspaper articles by types and grouped them according to trend. As a result, the social and cultural significance of the "landscape" in North Korea can be divided among "Projection Object of Orthodoxy", "Visuality extended to the City" and "Visible Socialist-Fairyland". First, in an article about Baekdusan (Mt. Baekdu), "landscape" was used as a medium to prove the legitimacy of the successor. Next, in the Kim Jong-Un regime, "landscape" was used as a word to describe the visual interactions by human economic activities. Finally, as a way to visualize the achievements in the landscape sector, a term for ranking landscapes such as "Socialist-Fairyland" was adopted during Kim Jong-Un's reign. This can be interpreted as one of the devices visualizing the "landscape" and is clearly distinguished from the past.