• 디지털융복합연구
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• 제10권9호
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• pp.383-390
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• 2012

본 논문에서는 지식 표상 방식을 이용한 정보 검색 시각화 도구를 제안한다. 제안하는 정보 검색 시각화 도구는 사용자 검색이력 데이터를 이용하여 검색의도를 자동 추출하고, 추출된 검색의도를 지식 표상 방식 구조로 시각화 할 수 있도록 설계하였다. 검색의도 표상 방식을 위한 스키마는 인지 심리학적 지식 표상 방법론을 활용하였으며, 행동실험을 통해 그 효용성을 증명하였다. 실험결과 정보 검색 시각화 도구는 기존 검색방법에 비해 사용자 만족도 측면에서 약 39%의 향상이 있었으며, 정보 검색 과정에서의 재검색 문제를 해결할 수 있는 방안을 제시할 수 있었다.

• 대한기계학회논문집B
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• 제22권1호
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• pp.25-33
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• 1998

An experimental study has been carried out to obtain optimal conditions for turbulent mixing of two fluid streams at various angle branches by a flow visualization method. The main purpose of this study is the utilization of flow visualization method as a fast and efficient way to find the optimal mixing conditions when several flow control parameters are superimposed. It is verified that the optimal conditions estimated by flow visualization method have good agreement with the concentration field measurements. The results demonstrate that the diameter ratio is mainly attributed to the mixing phenomena than the branch pipe angle and the Reynolds number. The most striking fact is that there exists the best diameter ratio, d/D.ident. O.17, which requires the minimum momentum ratio in the range of the present experiment. The velocity ratio for the optimal mixing condition has a value within 2 to 16 according to the different flow parameters.

• 한국가시화정보학회지
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• 제14권2호
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• pp.12-17
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• 2016

In this work, we investigate the flow velocity controllability of a diffuser-type multiple hydrofoil duct by experimental and numerical flow visualization approaches. The flow velocity controllability is analyzed by changing the angle of the hydrofoil near the outlet, which is the diffuser, while the incoming flow velocity is 0.6 m/s in the experiment. When the diffuser angle is changed from 0 to 7.5 degree, the maximum velocity inside the duct is varied from 1.35 m/s to 1.52 m/s. Also, it is shown from the numerical analysis that the maximum velocity is varied from 1.09 m/s to 1.17 m/s in the same condition. Thus, the aspect of the acceleration in the duct due to the increase of the diffuser angle is similar between the both approaches. Therefore, the multiple hydrofoil duct can be used to control the flow speed inside the duct for continuously extracting power close to a rated capacity.

• 한국가시화정보학회지
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• 제22권1호
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• pp.79-84
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• 2024

As microchips' degree of integration is getting higher, its cooling problem becomes important more than ever. One of the promising methods is using fractal microchannel heat sink by mimicking nature's Murray networks. However, most of the related works have been progressed only by numerical analysis. Perhaps such lack of direct experimental studies is due to the technical difficulty of the temperature and heat flux measurement in complex geometric channels. Here, we demonstrate the direct visualization of in situ temperature profile in a fractal microchannel heat sink. By using the temperature-sensitive fluorescent dye and a transparent Polydimethylsiloxane window, we can map temperature profiles in silicon-based fractal heat sinks with various fractal scale factors (a=1.5-3.5). Then, heat transfer rates and pressure drops under a fixed flow rate were estimated to optimize hydrodynamic and thermal characteristics. Through this experiment, we found out that the optimal factor is a=1.75, given that the differences in heat transfer among the devices are marginal when compared to the variances in pumping power. This work is expected to contribute to the development of high-performance, high-efficiency thermal management systems required in various industrial fields.

• 대한기계학회논문집B
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• 제23권3호
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• pp.408-418
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• 1999

Incompressible flow inside a circular cylinder Including periodically oscillating free surface waves was studied primarily by using a numerical method. We developed a finite difference scheme based on the MAC method applicable to three-dimensional free-surface flows, and applied it to the present flow model to study tho flow characteristics as well as the fluid stirring. To verify the validity of our scheme, we performed a simple experiment for flow visualization. We found that the numerical results show a reasonable agreement with the observed flow patterns.

• 대한기계학회논문집
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• 제18권8호
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• pp.2184-2193
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• 1994

A flow visualization experiment using water-table models was performed. The water-table models simulated the two-dimensional cold flow fields inside the combustion chambers of incinerators. The flow were visualized by small but neutrally bouyant particles photographed by an overhead camera. The experimentally simulated flow fields apparently showed distinct features of two combustion chamber shapes; counter and parallel flow types. The significance of the secondary air injection on the mixing of combustion gases were clearly observed. The effects of the recirculation zones, which were present in the secondary chamber, were discussed by considering the importance of them for optimal combustion.

• 한국가시화정보학회지
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• 제17권2호
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• pp.83-89
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• 2019

In this study, we show the maximum cavity radius prediction model that a droplet impacts an inclined bath. Surface tensions, viscosities, inclination angles of a bottom substrate, droplet diameters, falling heights of the droplet are varied for the experiment. We experimentally observe that the cavity grows in hemispherical shape like the cavity formed in a deep bath although the depth of the bath is non-uniform due to an inclined bottom substrate. We derive two theoretical models to predict the experimental results of the fully developed cavity. Although each model has error, we observe that qualitatively theoretical model predicts the trend of experiment results well.

• 디자인융복합연구
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• 제14권4호
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• pp.133-150
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• 2015

본 연구는 1946년부터 2012년까지 총 5211건의 UN총회 투표데이터를 활용하여 국가 간의 관계를 기간별, 이슈별 등 다양한 관점에서 분석할 수 있는 인터랙티브(Interactive) 시각화 방법을 제안하였다. 연구를 위해 국가 간 유사도 매트릭스를 고안하고, 두 가지의 시각화 방법을 개발하였다. 첫 번째는 연도별로 UN 총회의 투표에 참여한 국가 간의 관계를 사회 연결망 그래프 형태로 표현한 네트워크 그래프(Network Graph)시각화이며, 두 번째는 특정 국가를 중심으로 다른 국가 간의 관계를 분석하거나 시간에 따른 국가 간의 투표 성향 변화를 동시에 분석할 수 있도록 고안된 Proximity based Circular 시각화이다. 본 연구는 기존의 투표 데이터를 활용한 분석 사례에서 시도되지 않았던 다양한 관점에서 네트워크 분석을 하기 위해 선과 원형 그래프가 결합된 Proximity based Circular 시각화를 제안하고 이를 구현하였다는 점에서 큰 의의가 있다. 또한 두 개의 시각화에 대한 비교 실험을 실시하여 각 시각화의 상호 보완점을 도출 하였다. 연구 결과로는 Proximity based Circular 시각화가 개별 국가 노드에 대한 정보를 더 잘 나타내며, 네트워크 그래프(Network Graph)시각화는 전체 데이터의 특성과 여러 데이터 간의 성향을 더 잘 나타낸다는 결과를 도출하였다. 따라서 UN국가의 투표 성향 데이터를 분석하기 위해서는 두 개의 시각화를 병행하여 사용하는 경우가 데이터 간의 관계 파악에 가장 도움이 된다는 결론을 제시하였다.

• 한국에너지공학회:학술대회논문집
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• 한국에너지공학회 2008년도 춘계학술 발표회
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• pp.101-108
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• 2008

Polymer electrolyte membrane (PEM) fuel cells are promising power generation devices which are ideal for residential and automobile applications, thanks to their fast transient characteristics. However, liquid water produced in PEM fuel cells should be properly managed to enhance the performances and durabilities of the cells. In this study, a visualization experiment was conducted to investigate the flow behavior of water droplets in cathode channels. The visualization experiment was done with four different model flow channels which were made by varying the material (Acrylic and Teflon) and the channel width (1 mm and 2 mm). Acrylic is hydrophilic (contact angle is about $80^{\circ}$) while Teflon is hydrophobic (contact angle is about $120^{\circ}$). A computational fluid dynamics (CFD) analysis was also performed to compare the observed and the simulated two-phase water/air flow characteristics in cathode channels. The computational models were made to be consistent with the geometries and surface properties of the model flow channels. Both the experimental and numerical results showed that the Teflon cathode channel with 1 mm width has the best water management performance among four model flow channels considered. A close correlation was found between the experimental visualization results and the numerical CFD simulation results.

• 한국자동차공학회논문집
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• 제6권2호
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• pp.12-20
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• 1998

Exter ballistics of a typical high-speed projectile is studied through a flow-visualization experiment and an unstructured grid Navier-Srokes computation. Experiment produced a schlieren photograph that adequately shows the characteristic features of this complex flow, namely two kinds of oblique cone shocks and turbulent wake developing into the downstream. A hybrid scheme of finite volume-element method is used to simulate the compressible Reynolds-Averaged Navier-Stok- es solution on unstructured grids. Osher's approximate Riemann solver is used to discretize the cinvection term. Higher-order spatial accuracy is obtained by MUSCL extension and van Albada ty- pe flux limiter is used to stabilize the numerical oscillation near the solution discontinuity. Accurate Gakerkin method is used to discretize the viscous term. Explict fourth-order Runge-Kutta method is used for the time-stepping, which simplifies the application of MUSCL extension. A two-layer k-$\varepsilon$ turbulence model is used to simulate the turbulent wakes accurately. Axisymmetric folw and two-dimensional flow with an angle of attack have been computed. Grid-dependency is also checked by carrying out the computation with doubled meshes. 2-D calculation shows that effect of angle of attack on the flow field is negligible. Axi-symmetric results of the computation agrees well with the flow visualization. Primary oblique shock is represented within 2-3 meshes in numerical results, and the varicose mode of the vortex shedding is clearly captured in the turbulent wake region.