• 충청수학회지
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• 제26권1호
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• pp.53-69
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• 2013

Topology may described a pattern of existence of elements of a given set X. The family ${\tau}(X)$ of all topologies given on a set X form a complete lattice. We will give some topologies on this lattice ${\tau}(X)$ using a topology on X and regard ${\tau}(X)$ a topological space. A topology ${\tau}$ on X can be regarded a map from X to ${\tau}(X)$ naturally. Such a map will be called topology field. Similarly we can also define pe-topology field. If X is a topological flow group with acting group T, then naturally we can get a another topological flow ${\tau}(X)$ with same acting group T. If the topological flow X is minimal, we can prove ${\tau}(X)$ is also minimal. The disjoint unions of the topological spaces can describe some topological systems (topological organisms). Here we will give a definition of topological organism. Our purpose of this study is to describe some properties concerning patterns of relationship between topology fields and topological organisms.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2004년도 춘계학술대회
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• pp.1195-1200
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• 2004

A fully coupled fluid flow, heat, and solute transport model was developed to investigate turbulent flow, solidification, and macrosegregation in a continuous casting process of steel slab with EMBR. Transport equations of mass, momentum, energy, and species for a binary iron-carbon alloy system were solved using a continuum model. The electromagnetic field was described by the Maxwell equations. A finite-volume method was employed to solve the conservation equations associated with appropriate boundary conditions. The effects of intensity of magnetic field and carbon segregation were investigated. The electromagnetic field reduces the velocity of molten flow in the mold and an increase in the percentage of C in steel results in a decrease of carbon segregation ratio.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2008년도 추계학술대회B
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• pp.2088-2093
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• 2008

In this study, flow field measurement of the Pebble Bed Reactor(PBR) for the High Temperature Gas-cooled Reactor(HTGR) was performed. Large number of pebbles in the core of PBR provides complicated flow channel. Due to the complicated geometries, numerical analysis has been intensively made rather than experimental observation. However, the justification of computational simulation by the experimental study is crucial to develop solid analysis of design method. In the present study, a wind tunnel installed with pebbles stacked was constructed and equipped with the Particle Image Velocimetry(PIV). We designed the system scaled up to realize the room temperature condition according to the similarity. The PIV observation gave us stagnation points, low speed region so that the suspected high temperature region can be identified. With the further supplementary experimental works, the present system may produce valuable data to justify the Computational Fluid Dynamics(CFD) simulation method.

• 설비공학논문집
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• 제18권4호
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• pp.359-369
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• 2006

This study aims deriving analysis the flow characteristic of kitchen hood system with using 3-D numerical analysis method and improving the system to expel pollutes more efficiently. This system is applied with $k-{\varepsilon}$ turbulent model and using incompressibility viscosity flow range and boundary condition which are related to Bossinesq approximation following density variation in control volume. To understand the flow characteristics of four models, this study only focuses on velocity field, temperature field, and concentration field varying with followings whether separation plate is set or not and the shapes of separation plates. The quantity of air, speed of exhaust fan and temperature and concentration of heating source are concerned as constant values.

• 한국해양공학회지
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• 제33권3호
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• pp.229-235
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• 2019

In this study, a two-dimensional oscillating foil with forward speed in a propagating wave flow field was considered. The time-mean power to maintain the heaving and pitching motions of the foil was analyzed using the perturbation theory in an ideal fluid. The power, which was a non-linear quantity of the second-order, was expressed in terms of the quadratic transfer functions related to the mutual product of the heaving and pitching motions and incoming vertical flow. The effects of the pivot point and phase difference among the disturbances were studied. The negative power, which indicates energy extraction from the fluid, is shown as an example calculation.

• 분석과학
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• 제25권6호
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• pp.476-482
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• 2012

황사입자들은 수 나노미터에서 수 마이크론 사이의 크기를 가지는 것으로 알려져 있다. 황사가 환경 및 인체 건강에 미치는 영향은 황사 입자의 크기에 의존한다. 입자가 작을수록 멀리까지 이동하며, 인체의 호흡기관 깊숙이 침투한다. 침강장-흐름 분획법(sedimentation field-flow fractionation, SdFFF)은 채널 내 포물선형태의 흐름(parabolic flow profile)과 외부에서 가해지는 원심력의 상호작용을 이용하여 나노 및 마이크론 크기의 입자들의 분리를 제공한다. 본 연구에서는 황사입자의 크기별 분리와 특성분석을 위한 steric 모드 침강장-흐름 분획법(Sd/StFFF)의 응용 가능성을 테스트하였다. 이를 위하여 다양한 Sd/StFFF 파라미터들을(유속, stop-flow time, 원심력의 세기, 등) 최적화 하였다. Sd/StFFF 보정곡선의 $R^2$값은 0.9983으로 높은 직선성을 보였으며, 실험결과는 Sd/StFFF가 마이크론 입자의 크기별 분리에 우수함을 보여주었다. 광학현미경(optical microscopy, OM)을 이용하여 황사입자들의 크기와 모양을 조사하였다. 황사가 진할 때에는 약할 때보다 입자크기가 증가함을 보여주었다. 또한 비가 올 때에는 건조할 때보다 입자크기가 감소하였는데, 이는 입자 표면에 흡착되어 있는 성분들이 빗물에 의해 제거되었기 때문인 것으로 보여진다. 본 연구의 결과는 Sd/StFFF가 황사와 같이 환경입자의 크기특성분석에 유용함을 보여준다.

• 한국패류학회지
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• 제25권2호
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• pp.97-103
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• 2009

본 연구에서 바지락 부유 유생은 저질입경이 클수록 착저율(${\Omega}_b$)이 높았으며, 생물적으로도 저질을 선택하고 있다는 것을 확인할 수 있었다. 또 침투류의 발생에 의한 유동장에 있어서는 유속이 10 cm/s, 저질 중앙입경 1.211 mm, 침투 유속 0.3 cm/s일 경우, 3.1-5.1 배의 부유 유생 착저 효과 $\alpha$ (=${\Omega}_b/{\Omega}_{b0}$)가 증가되는 것을 확인하였다. 부유 유생에 있어서 저질입경의 선택성은 생물적인 요인에 의존하고, 유동장에 있어서 착저 촉진 효과는 물리적인 안정 조건에 지배되어 있었다. 그리고 이번 새롭게 도입한 안정 지표(${\lambda}p$)에 의해 통일적으로 평가할 수 있는 것을 확인하였다. 유생의 안정 지표(${\lambda}p$)에 의하면, 유속이 작용했을 경우의 부유 유생은 저질입경에 영향을 받지 않고 거의 일정 값을 가지며, 초기 이동한계유속 및 전면 이동 한계유속에 대응하는 ${\lambda}p$값은 각각 0.14, 1.06 이였고, 새롭게 제안한 안정 지표(${\lambda}p$)의 타당성이 검증되었다. 따라서 본 연구 결과에 의해 어떤 해역의 바지락 부유 유생의 부유 밀도, 저질 입경, 유동 조건이 명확할 때, 바지락 부유 유생의 착저율을 추측할 수 있는 결과를 얻을 수 있었다.

• Bulletin of the Korean Chemical Society
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• 제32권4호
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• pp.1315-1320
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• 2011

Whey protein (WP) is a mixture of proteins, and is of high nutritional values. WP has become an important source of functional ingredients in various health-promoting foods. In this study, size-exclusion chromatography (SEC) and asymmetrical flow field-flow fractionation (AsFlFFF) were used for separation and analysis of whey proteins. It was found that a lab-prepared WP from raw milk is mostly of ${\beta}$-lactoglobulin with small amount of higher molecular weight components, while a commercial whey protein isolate (WPI) powder contains relatively larger amount of components other than ${\beta}$-lactoglobulin, including IgG and protein aggregates. Results suggest that AsFlFFF provides higher resolution for the major whey proteins than SEC in their normal operation conditions. AsFlFFF could differentiate the BSA and Albumin, despite a small difference in their molecular weights, and also was able to separate much smaller amount of aggregates from monomers. It is noted that SEC was able to show the presence of low molecular weight components other than the major whey proteins in the WP samples, which AsFlFFF could not show, probably due to the partial loss of those low molecular weight species through the membrane.

• 한국수산과학회지
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• 제40권1호
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• pp.31-38
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• 2007

This study investigated the fluid force acting on an artificial reef and the scour pattern at the bottom of the artificial reef in a steady-flow field using the finite difference method (Flow-3D). The structure was tetragonal in shape, like similar objects found in nature. The numerical analysis showed that the hydrodynamic characteristics and incipient scouring pattern matched natural phenomena. The velocity distribution around the tetragon was symmetric and wake occurred inside the tetragon and behind the bottom of the tetragon. The length of the recirculation flow behind the tetragon for each velocity was about 4-5 cm and the magnitude of the recirculation flow inside the tetragon generally increased with the Reynolds' number, although it decreased slightly for Reynolds' numbers from 11,000 to 12,000. In addition, the total fluid force acting on the tetragon increased with the inflow velocity, although the increment was smaller when the velocity exceed 18 cm/sec. The incipient pattern for the scouring of sediment matched the natural phenomenon.

• 한국연소학회:학술대회논문집
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• 한국연소학회 2005년도 제31회 KOSCO SYMPOSIUM 논문집
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• pp.181-188
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• 2005

Large eddy simulation(LES) methodology used to model the isothermal swirling flows in a dump combustor and the turbulent premixed flame in a model gas turbine combustor. The LES solver was implemented on parallel computer consisting 16 processors. In isothermal flow simulation, the results was compared with that of ${\kappa}-{\varepsilon}$ model as well as experimental data, in order to verify the capability of LES code. To model the turbulent premixed flame in a gas turbine, the G-equation flamelet model was used. The results showd that LES and RANS well predicted the mean velocity field of a non-swirling flow. However, in swirling flow, LES showed a better performance in predicting the mean axial and azimuthal velocities, and the central recirculation zone than those of RANS. In a model gas turbine combustor, the operation condition of high pressure and temperature induced the different phenomena, such as flame length and flow-field information, comparing with the condition of ambient pressure and temperature. Finally, it was identified that the flame and heat release oscillations are related to the vortex shedding generated by swirl flow and pressure wave propagation.