• 대한화장품학회지
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• 제38권1호
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• pp.1-13
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• 2012

본 총설에서는 기포의 화장품 이용에 대해서 논의하고자 하였다. 기포의 생성은 기포형성제와 기포 생성 장치 등을 이용하며 생성된 기포는 다양한 특성을 나타낸다. 기포는 기체의 용매에 대한 분산 형태로 발생된다. 기포의 안정성과 유변학적인 성질 등을 평가하는 것은 기포를 제형으로 이용하기 위한 출발점이다. 기포의 의약품과 화장품에 대한 이용은 점차 증가 추세에 있다. 의약품의 경우 기포 제형은 직장(rectal), 질(vaginal) 및 피부(dermal)용으로 대별될 수 있으며 화장품 영역의 경우 기포 제형은 모발 및 메이크업 영역에서는 헤어 무스, 파운데이션 등에서 이용되고 있으며 기초화장품에서는 자외선 차단 화장품에 이용되고 있다. 최근 유효성분의 안정화 및 유효성분의 피부 전달 측면에서 많은 연구와 특허가 출원되고 있어 향후 기능성화장품의 새로운 제형으로 활용이 기대된다.

• 한국원자력학회:학술대회논문집
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• 한국원자력학회 1996년도 춘계학술발표회논문집(2)
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• pp.331-336
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• 1996

The effects of a mixing vane on air-water mixed flow have been experimentally studied in this work, to investigate the basic mechanisms that the mixing vane affects critical heat flux (CHF). Experiment was performed for various flow rates focusing on bubbly flow and annular flow patterns. Acrylic tube (1.7m long, 11 mm I.D.) and the split vane type mixing vane were used, and ring-type conductance probes were used to measure the liquid film thickness in annular flow. Experimental results show that, (a) bubbly-to slug flow transition and churn-to-annular flow transition occur respectively near the mixing vane compared to the tests without mixing vane, (b) in bubbly flow region, the mixing vane breaks the bubbles into smaller ones and forwards bubbles to the center region of the tube by the centrifugal force, (c) the liquid film thickness in annular flow is decreased near the mixing vane for mass fluxes.

• 한국멀티미디어학회논문지
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• 제21권7호
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• pp.787-794
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• 2018

We propose a new framework which expresses the mist and scratches of cracked ice by an impact. We combine the grid projection technique, boundary particles method, and level-set method commonly used in fluid simulations to determine the region on the surface of an ice object which is affected by a collision. Mist is then generated in proportion to the impact, and immediately diffused, using a geodesic distance field to limit dissipation. The gradient of the mist is subsequently used to create realistic patterns of scratches and elongated air bubbles. Cracks of the ice object can also be considered, and the density of the mist made to vary realistically between fragments. As a result, our method not only represents high-quality ice effects, but also allows easy integration into existing rigid body simulation solvers.

• 설비공학논문집
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• 제15권9호
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• pp.727-732
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• 2003

In the present study, a PIV measurement and image processing technique were applied in order to investigate the flow characteristics in the gas injected liquid bath. The circulation of liquid was induced by upward bubble flow. Due to the centrifugal force, the flow was well developed near both wall sides than in the center of a bath. The vortex flow irregularly repeated generation and disappearance which helped to accelerate the mixing process. The bubble rise velocity in the bottom region was relatively lower than in the upper region because the energy generated by bubbles' behavior in the region near the nozzle was almost converted into kinetic energy But bubble rise velocity increases with the increase of the axial distance since kinetic energy of rising bubbles is added to buoyancy force. In conclusion, the flow increased bubble rise velocity and the flow of the bottom region became more active.

• Korean Journal of Chemical Engineering
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• 제35권11호
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• pp.2164-2171
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• 2018

Heavy duty diesel vehicles deteriorate urban air quality by discharging a large volume of air pollutants such as soot and nitrogen oxides. In this study, a newly introduced auxiliary device a fuel activation device (FAD) to improve the combustion efficiency of internal engines by utilizing the cavitation effect was closely investigated by the fluid flow mechanism via a numerical analysis method. As a result, the FAD contributed to fuel atomization from the injection nozzle at lower inlet pressure by reducing the pressure energy. The improved cavitation effect facilitated fuel atomization, and ultimately reduced pollutant emission due to the decrease in fuel consumption. The axial velocity along the flow channel was increased 8.7 times with the aid of FAD, which improved the primary break-up of bubbles. The FAD cavitation effect produced 1.09-times larger turbulent bubbles under the same pressure and fuel injection amount than without FAD.

• Nuclear Engineering and Technology
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• 제37권6호
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• pp.525-536
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• 2005

The interfacial area transport equation dynamically models the changes in interfacial structures along the flow field by mechanistically modeling the creation and destruction of dispersed phase. Hence, when employed in the numerical thermal-hydraulic system analysis codes, it eliminates artificial bifurcations stemming from the use of the static flow regime transition criteria. Accounting for the substantial differences in the transport mechanism for various sizes of bubbles, the transport equation is formulated for two characteristic groups of bubbles. The group 1 equation describes the transport of small-dispersed bubbles, whereas the group 2 equation describes the transport of large cap, slug or chum-turbulent bubbles. To evaluate the feasibility and reliability of interfacial area transport equation available at present, it is benchmarked by an extensive database established in various two-phase flow configurations spanning from bubbly to chum-turbulent flow regimes. The geometrical effect in interfacial area transport is examined by the data acquired in vertical fir-water two-phase flow through round pipes of various sizes and a confined flow duct, and by those acquired In vertical co-current downward air-water two-phase flow through round pipes of two different sizes.

• Journal of Korean Neurosurgical Society
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• 제56권5호
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• pp.410-418
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• 2014

Objective : The epidural fluid collection (EFC) as a complication of cranioplasty is not well-described in the literature. This study aimed to identify the predictive factors for the development of EFC as a complication of cranioplasty, and its outcomes. Methods : From January 2004 to December 2012, 117 cranioplasty were performed in our institution. One-hundred-and-six of these patients were classified as either having EFC, or not having EFC. The two groups were compared to identify risk factors for EFC. Statistical significance was tested using the t-test and chi-square test, and a logistic regression analysis. Results : Of the 117 patients undergoing cranioplasty, 59 (50.4%) suffered complications, and EFC occurred in 48 of the patients (41.0%). In the t-test and chi-test, risk factors for EFC were size of the skull defect (p=0.003) and postoperative air bubbles in the epidural space (p<0.001). In a logistic regression, the only statistically significant factor associated with development of EFC was the presence of postoperative air bubbles. The EFC disappeared or regressed over time in 30 of the 48 patients (62.5%), as shown by follow-up brain computed tomographic scan, but 17 patients (35.4%) required reoperation. Conclusion : EFC after cranioplasty is predicted by postoperative air bubbles in the epidural space. Most EFC can be treated conservatively. However, reoperation is necessary to resolve about a third of the cases. During cranioplasty, special attention is required when the skull defect is large, since EFC is then more likely.

• 한국지반환경공학회 논문집
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• 제9권2호
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• pp.31-37
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• 2008

Diffused Aeration System (DAS) 기법은 휘발성 유기 화합물들을 포함하고 있는 지하수를 양수하여 반응조 내에서 폭기시킨 후, 액체 내에 존재하는 오염물질을 기체로 전이시켜 오염물질을 대기 중으로 배출시키는 정화법이다. 본 연구에서는 지하수 내 TCE 농도가 높은 2개 지역을 선정하여 3회에 걸쳐 DAS 기법의 적용성 평가 시험을 실시하였다. 반응조에는 각각 17.1, 44.8, 76.5 1/min의 속도로 공기를 주입하였으며, 시험 중 지하수 수질의 변화와 반응조에서 배출되는 TCE의 농도를 측정하였다. 처리 후 배출되는 기체의 농도를 측정한 결과, TCE 농도는 6~8 min 만에 최고 농도로 배출되었고, 시간이 지날수록 천천히 감소하는 모습이 관찰되었다. TCE의 농도 변화는 공기 유입 속도에 따라 매우 큰 변화를 보였다. 또한, 액체에서 기체로의 총괄물질전달계수 ($K_La$)를 산정한 결과, test 1, 2, 3에서 각각 0.444, 1.158, 1.836 1/hr였으며, 이로부터 공기 주입률이 빨라지면 DAS의 효율성이 높아짐을 정량적으로 확인할 수 있었다.

• Journal of Advanced Marine Engineering and Technology
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• 제39권8호
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• pp.801-806
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• 2015

The experimental analysis of a crevice-type vapor chamber heat pipe (CVCHP) is investigated. The heat source of the CVCHP is a high-power light-emitting diode (LED). The CVCHP, which exhibits a bubble pumping effect, is used for heat dissipation in a high-heat-flux system. The working fluid is R-141b, and its charging ratio was set at 60 vol.% of the vapor chamber in a heat pipe. The total thermal conductivity of the falling-liquid-film-type model, which was a modified model, was 24% larger than that of the conventional model in the LED package. Flow visualization results indicated that bubbles grew larger as they combined. These combined bubbles pushed the working fluid to the top, partially wetting the heat-transfer area. The thermal resistance between the vapor chamber and tube in the modified design decreased by approximately 32%. The overall results demonstrated the better heat dissipation upon cooling of the high-power LED package.

• 한국환경보건학회지
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• 제2권1호
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• pp.25-28
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• 1975

The main purpose of the aeration units in activated sludge process is to enable micro-organisms to metabolize the constituents of the waste effectively by supplying sufficient oxygen for their respiration. Normally, aeration is achieved by bringing the mixture of waste and sludge into intimate contact with air. The main type of aeration unit is diffused air unit in which air is injected into the liquid in the form of bubbles. The object of these laboratory studies is to compare the performance of three laboratory scale aeration systems at various depths of submergence, aerating water with and without the addition of a surface active agent.