• 한국가시화정보학회지
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• 제14권2호
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• pp.18-24
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• 2016

This paper presents an experimental investigation to visualize cross-sectional two-phase flow structure and identify liquid-gas interface for condensation of steam at a low mass flux in a slightly inclined tube using the axial-viewing technique, which permits to look directly into flow during condensation of steam. In this technique, two-phase flow is viewed along the axis of a pipe by locating a high-speed video camera in front of a viewer that is fitted at the outlet of the pipe. A short section of the pipe is illuminated and is recorded through the viewer, which is kept free of liquid by mildly introducing air. Experiments were conducted in a pipe of 19.05 mm in inner diameter at atmospheric pressure. Cross-sectional two-phase flow structure is obtained at a steam mass flux of $2.62kg/m^2s$ as a function of steam quality in the range from 0.5 to 0.9. The results show that stratified-wavy flow is a unique flow pattern observed in the scope of the present study. Condensate film thickness, stratification angle and void fraction were measured from the obtained flow structure images. Finally, heat transfer coefficient was calculated using the measurement data and discussed in comparison with existing correlations.

• 한국농촌건축학회논문집
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• 제22권2호
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• pp.1-8
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• 2020

This study is intended to derive the adaptive reuse techniques through the history and aspects of new construction, extension, repair, and other works, limited to the deep and narrow lots facing Seongan-gil and Nammun-gil in Nammun-ro 2 ga of Cheongju, the historic urban area. The results are as follows. 1) In the case of newly built reinforced concrete buildings, the central part of the top floor of the residence or all floors are opened to the open space(void) to facilitate lighting and ventilation. This is developed as a convection phenomenon due to the temperature difference from the slits between buildings, which affects the entire air flow of the block. 2) The buildings of extension and repair are composed of two-story masonry or steel frame, both the front store facing the road and the house on the back, but it looks like one because it is in contact with each other. If only a small gap between the front and rear buildings is restored to an external space or a space equipped with sun light, a small breath can be provided in lighting and ventilation. 3) The existing two-story wooden stores and houses have lost their external space due to repairs. With minimal intervention to restore the small courtyard, slits, and space under the eaves, it will not only improve lighting and ventilation, but also create a unique appearance as a segment of the elongated store.

• Nuclear Engineering and Technology
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• 제37권6호
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• pp.595-604
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• 2005

A new instrument, an average BDFT (Birectional Flow Tube), was proposed to measure the flow rate in single and two phase flows. Its working principle is similar to that of the Pilot tube, wherein the dynamic pressure is measured. In an average BDFT, the pressure measured at the front of the flow tube is equal to the total pressure, while that measured at the rear tube is slightly less than the static pressure of the flow field due to the suction effect downstream. The proposed instrument was tested in air/water vertical and horizontal test sections with an inner diameter of 0.08m. The tests were performed primarily in single phase water and air flow conditions to obtain the amplification factor(k) of the flow tube in the vertical and horizontal test sections. Tests were also performed in air/water vertical two phase flow conditions in which the flow regimes were bubbly, slug, and churn turbulent flows. In order to calculate the phasic mass flow rates from the measured differential pressure, the Chexal drift-flux correlation and a momentum exchange factor between the two phases were introduced. The test results show that the proposed instrument with a combination of the measured void fraction, Chexal drift-flux correlation, and Bosio & Malnes' momentum exchange model could predict the phasic mass flow rates within a $15\%$ error. A new momentum exchange model was also proposed from the present data and its implementation provides a $5\%$ improvement to the measured mass flow rate when compared to that with the Bosio & Malnes' model.

• 한국복합재료학회:학술대회논문집
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• 한국복합재료학회 2004년도 춘계학술발표대회 논문집
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• pp.292-296
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• 2004

In case of Resin Transfer Molding(RTM) process, 'race-track' effects and non-uniform fiber volume fraction may cause undesirable resin flow pattern and thus result in dry spots, which affect the mechanical properties of the finished parts. In this study, a real time RTM control strategy to prevent these unfavorable effects is proposed. The control strategy consists of two 'stages' depending on the extent the resin front has reached. Through numerical simulations and experiments, the validity of the proposed scheme is demonstrated. The results show that the proposed scheme is effective in reducing the void formation during RTM mold filling.

• 한국마이크로전자및패키징학회:학술대회논문집
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• 한국마이크로전자및패키징학회 2003년도 기술심포지움 논문집
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• pp.17-20
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• 2003

The EMC's rheological effects on molding process are evaluated in this study. When considering mold processing for IC packages, the major concerning items in current studies are incomplete fill, severe wire sweeping and paddle shifts etc. To simulate EMC's fast curing rheokinetics with 3D mold flow behavior, one should select appropriate rheometry which characterize each EMC's rheological motion and finding empirical parameters for numerical analysis current studies present the new rheometry with parallel plate rheometry for reactive rheokinetic experiments, the experiment and numerical analysis is done with the commercial higher filler loaded EMC for the case of Thin Quad Plant Packages (TQFP) with package thickness below 1.0 mm. The experimental results and simulation results based on new rheometry matches well in point of the prediction of wire sweep, filling behavior of melt front advancement and void trapping position.

• Investigative Magnetic Resonance Imaging
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• 제5권1호
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• pp.38-42
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• 2001

2D TOF혈관조영술에서 presaturation RF펄스를 사용하여 정맥피에서 나오는 MR신호를 제거하고 얻은 동맥 angiogram에는 band형태로 동맥이 끊어져 나타나는 현상이 자주 보인다. 일부 동맥에서 피의 흐름은 한 심장 주기 동안에 3번의 펄스를 갖는데, 이 중 가운데 펄스는 짧은 기간 동안 역류를 한다. 이 역류하는 동맥피는 정맥피와 같은 방향이기 때문에 presaturation RF펄스에 의해 정맥피 처럼 saturation이 되어서 imaging slice로 흘러 들어가게 될 수 있다. 특히 이러한 경우가 phase encoding step의 dc 부근에서 발생하게 되면 그 때의 단면 영상에서 동맥이 강조가 될 수 없게 되어, 결과적으로 angiogram에는 그 단면을 지나는 동맥의 신호가 없어서 band 형태로 핏줄이 끊어져 나타나게 된다. Imaging slice와 saturation band와의 간격을 변화 시켜 가면서 angiogram을 얻어 봄으로서 이러한 현상을 실험적으로 확인하였다 나아가 saturation band를 rectangle형태에서 ramp 형태로 변경함으로써 이러한 artifacts를 제거 할 수 있는 방법을 제시하였다

• 한국주거학회논문집
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• 제12권4호
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• pp.195-203
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• 2001

The purpose of this study is to analyze the characteristics of Mario Botta's residential design. The characteristics of Mario Botta's residential design are following as : 1. The residential design of Mario Botta planed from 1960' to 1970's is based on the style composition method of modern design, specially by the influence of Le Corbusier and Louis I. Kahn. Botta's residential design of the 1980's is generally affected by A. Palladio, and is characterized as the representation of classic standard. The residential design of the 1980's shows the establishment level of Mario Botta's residential design, and produces particular Botta's facade. 2. The characteristics of Mario Botta's spatial composition on residential design could be implicated by the spatial distribution of each floor which is divided by three floors, simple and primitive volume which has a symmetry, opening through the massive elimination n the center of front, double skin, the contrast between void and solid, and the inflow of light through the top-light. 3. Most Botta's residential designs have Loggia in the center of facade working as a buffer space which joins outside and inside space together. They also lead the spatial continuous flow. The inside space is combined by the light coming through top-light and vertical opening. 4. They have high accomplishment in complicating details. They show the outside design of a horizontal belt according to the module of concrete block and the decorated design using compositional materials such as an unevenness piled up askew concrete block .

• Composites Research
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• 제17권3호
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• pp.1-7
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• 2004

최근 대형 복합재료 구조물 성형에 적합한 공정으로 주목받는 vacuum assisted RTM (VARTM) 공정에 있어, 보강섬유의 조직 내부에 잔류하는 공기를 제거하여 기공함유율을 낮추는 기술의 중요성이 인식되고 있다. 거대기공 혹은 불완전 함침영역은 부적절한 주입구 및 공기배출구의 위치, 혹은 금형의 형상에 의해 발생한다. 미세기공은 불균일한 수지 유동선단의 속도로 인해 유동선단 부분에서 집중적으로 형성되며, 금형충전 공정 도중 수지와 함께 이동한다. 성형이 완료된 제품내의 잔류 기공들은 완성품의 물리적 성질을 저하 및 제품의 파손을 초래할 수 있다. 본 연구에서는 VARTM 공정에서의 기공의 형성 및 이동을 해석할 수 있는 통합된 거시적/미시적 해석 방법을 개발하였다. 수치해석 프로그램을 개발하여 VARTM 공정에서의 3차원 수지 유동을 해석하였으며, 그에 따른 거대기공 및 미세기공의 분포를 예측하였다.