• 정보기술과데이타베이스저널
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• 제6권2호
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• pp.115-130
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• 1999

The price structure of housing market varies depending upon market price policy rather than low or high price policy because of IMF. The object of this study is to develop an analysis system for analyzing housing market and its demand. The analysis system consists of four major categories: macro index analysis, market decision analysis, housing market analysis, and consumer analysis. We model each category by using a variety of techniques such as generalized linear model, categorical analysis, bubble analysis, drill-down analysis, price sensitivity meter analysis, optimum price index analysis, profit index measurement analysis, correspondence analysis, conjoint analysis, and multidimensional scaling analysis. Seoul apartment data is analyzed to demonstrate the practical usefulness of the system.

• 한국음향학회지
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• 제13권3호
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• pp.71-77
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• 1994

수중에서 공기방울들의 선형 배열에 의해 방출된 음향의 주파수 특성을 이론 및 실험적으로 살펴보았다. 공기방울들의 상호 작용을 고전적 조화진동자의 결합으로 다루었으며, 이론적으로 공기방울들의 선형 배열을 인접한 공기방울들간의 효과만을 고려한 유효 결합 조화진동자 모델로서 제안하였다. 공기방울 중심 사이의 거리가 공기방울 직경의 두 배가 넘는 약한 결합의 경우에 대해, 제안된 유효 결합 조화진동자 모델은 실험 결과들과 잘 일치함을 보여주었다.

• Journal of Advanced Marine Engineering and Technology
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• 제13권4호
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• pp.40-53
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• 1989

Boiling heat transfer phenomena is widely applied to BWR and electrical heating system because of its high heat transfer coefficient. In these systems, steady state heat transfer is dependent on nucleate boiling. When the heat generating rate is sharply increased or the cooling capacity of coolant is sharply decreased, sharp wall temperature rise is occurred under the critical heat flux(CHF) condition. This paper presents the simple wall temperature fluctuation model of transition mechanism in the repeating process of overheating and quenching, when coalescent bubble passes relatively slowly on the wall and simultaneously the transition from nucleate boiling to film boiling is carried at especially onset of the CHF state. The values calculated by the present model are resulted comparatively good with the measured.

• 한국전산유체공학회:학술대회논문집
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• 한국전산유체공학회 2004년도 추계 학술대회논문집
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• pp.15-18
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• 2004

A numerical method for simulating two-phase flows including surface force is presented. The method is based on fractional step method of finite volume formulation and the interface is tracked with PLIC VOF method. In the CSF model, as color function, f, representing the location of interface varies steeply in the interface region, we need to use smoothed function f to get accurate unit normal and the curvature. Peskin kernel is used to get smoothed function f. A spherical drop in static equilibrium and three-dimensional merging of gas bubble are tested, resulting in the validation of this method

• 한국가시화정보학회지
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• 제11권2호
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• pp.27-33
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• 2013

The inlet flow of centrifugal blower were quantitatively visualized using particle image velocimetry. Because the centrifugal blower system is one of the key parts of EV battery cooling system, the quantitative information of flow field of centrifugal blower is important to design and optimize the cooling system. Two types of inlet parts were used in this study. One is the straight inlet and the other is a bended one. The results showed the flow asymmetry exists in the straight model due to the pressure difference in the blower. In case of the bended one, the separation bubble and the increase of head loss appeared compared with the straight model.

• 한국안전학회지
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• 제19권1호
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• pp.1-5
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• 2004

In the present study, the gas injection system based on air-water model was designed to investigate the flow characteristics of liquid phase. A PIV system was applied to analyze the flow pattern in a ladle which gas stated to rise upward from the bottom. Gas flow is one of most important factors which could feature a flow pattern in a gas injection system. As the gas injected into the liquid, the kinetic energy of bubble transfer to liquid phase and a strong circulation flow develops in the liquid phase. Such a flow in the liquid develops vortex and improve the mixing process. Due to the centrifugal force, circulation flow was well developed near both wall sides and upper region respectively. Increasing gas flow was helpful to remove dead zone but, weak flow zone still exists in spite of the increasement of gas flow rate.

• 한국가시화정보학회:학술대회논문집
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• 한국가시화정보학회 2006년도 추계학술대회 논문집
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• pp.86-91
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• 2006

In this parer, we present the bubble forming and motion in the micro channel by using the two-dimensional numerical computation and experiment. In the numerical computation, The Lattice Boltzmann method(LBM) and free-energy model is used to treat the interfacial force and deformation of binary fluid system, drawn in to a micro channel and a numerical simulation is carried out by using the parallel computation method. The urn in this investigation is to examine the applicability of LBM to numerical analysis and experimental method of binary fluid separation and motion in the micro channel.

• Structural Engineering and Mechanics
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• 제77권3호
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• pp.395-406
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• 2021

Near-field underwater explosion (UNDEX) phenomena were investigated by experiments and numerical simulations. The UNDEX experiments were performed in a water tank using a ship-like model. One kilogram of TNT, one of the most widely used military high explosives, was used for the experiments. Numerical simulations were performed under the same conditions as in the experiments using the commercial software LS-DYNA. Underwater pressures, accelerations, velocities, and strains by shock waves were measured at multiple locations. Further, the bubble pulsation period and the whipping deformations of the ship-like model were explored. The experimental results are presented and examined through comparison with the results obtained from widely used empirical equations and numerical simulations.

• 한국원자력학회:학술대회논문집
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• 한국원자력학회 1996년도 춘계학술발표회논문집(2)
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• pp.108-113
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• 1996

Several analytical models for the departure from nucleate boiling (DNB) phenomenon have been developed during the last decade. Among these, Chang & Lee's model based on a bubble crowding mechanism is remarkable in the fundamental features characterized as the formulation of mass, energy, and momentum balance equation at thermal-hydraulic conditions leading to the DNB. However, Bricard and Souyri remarked that the assumption of stagnant bubbly layer at the DNB condition is questionable and the signs on the axial projections of the momentum fluxes at the core/bubbly layer interface in the momentum balance equations are erroneous. From this remark, Chang & Lee's model has been re-examined and modified by correcting the erroneous treatments in the momentum balance equations and removing the spurious assumptions. The revised model predicts well the extensive DNB data of water in uniformly heated tubes at low qualities and shows more accurate prediction compared with the original model.

• 한국수자원학회논문집
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• 제48권4호
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• pp.281-290
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• 2015

표준 k-${\varepsilon}$, RNG k-${\omega}$ 그리고 k-${\omega}$ SST 난류 모형과 VOF (volume of fluid)기법을 이용하여 사각형 광정위어를 통과하는 난류 흐름의 수면 변화와 유속분포를 수치모의 하였다. 지배방정식은 2차 정확도의 유한체적기법을 이용하여 해석하였으며, 두 개의 서로 다른 격자해상도에서 계산을 수행하여 수치해석 결과의 격자 민감도를 분석하였다. 계산 결과를 Kirkgoz et al. (2008)의 실험 결과 그리고 Moss (1972) 및 Zachoval et al. (2012) 무차원화된 실험값과 비교 분석하여 적용한 수치모형의 정확도를 평가하였다. 수치모의 결과는 사각형 개수로에 설치된 광정위어 흐름의 실험결과들을 합리적으로 예측하고 있으면 적용한 난류모형에 따라서 두 개의 주요 흐름분리 영역에서 계산 결과에 차이가 있는 것으로 나타났다. 표준 k-${\varepsilon}$ 모형은 이들 두 개의 흐름분리영역의 크기를 과소산정하고 있으며, k-${\omega}$ SST 모형은 위어 전면부에서 발생하는 흐름분리 영역을 다소 과대 산정하는 것으로 나타났다. RNG k-${\varepsilon}$ 모형은 전반적으로 양호하게 두 흐름분리 영역을 예측하는 한편, k-${\omega}$ SST 모형은 위어 상류부 모서리에서 발생하는 박리거품의 발생 형태를 가장 잘 예측하는 것으로 나타났다.