• 대한화장품학회지
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• 제36권1호
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• pp.1-16
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• 2010

본 총설에서는 나노미터 크기의 고체 입자가 오일-물 계면에 흡착됨으로써 안정화된 에멀젼의 제조와 성질에 대하여 기술하였다. 이렇게 제조된 에멀젼을 Pickering 에멀젼이라 하며 이 에멀젼을 계면활성제로 안정화된 일반적인 에멀젼과 비교하였다. Pickering 에멀젼의 독특한 성질은 입자의 계면 흡착 에너지가 큰 점에 기인하며 일반 에멀젼과 주요한 차이점은 고체 입자가 비가역적으로 계면에 흡착한다는 사실이다. Pickering 에멀젼의 전상은 w/o (water-in-oil) 타입에서 o/w (oil-in-water)로 수상의 분율이 증가함에 따라 발생한다. 친수성의 입자는 o/w 에멀젼을 형성하는 경향을 보이고 친유성 입자는 w/o 에멀젼을 형성하는 경향을 보이며 이는 고체 입자의 오일-물 계면에서의 접촉각에 따른다. Pickering 에멀젼의 안정성은 많은 부분에서 일반적인 에멀젼과는 다른 거동을 보였다. 저자는 또한 Pickering 에멀젼의 화장품 응용 가능성에 대해서도 논의하였다.

• Journal of the Korean Wood Science and Technology
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• 제51권6호
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• pp.481-492
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• 2023

The ecofriendly lifestyle has attracted considerable support for sustainable development. Natural dyes, as sustainable products, have become a research focus and development area for many scientists. Ecofriendly processing also supports circular sustainable development. This study effectively obtained tannins as a natural dye from merbau (Intsia bijuga) sawdust using water as an ecofriendly solvent. Merbau sawdust is an underutilized industrial waste. Temperature and solid-solvent ratio variations were performed to extract tannins from merbau sawdust. Temperature and solid-solvent ratio positively affected solution yield and tannin concentration. The optimal condition was identified using response surface methodology and experimental observations. A yield of 0.2217 g tannins/g merbau was obtained under the conditions of 333.15 K and 0.125 solid-solvent ratio. Extraction was controlled by convective mass transfer at the interface of solid particles.

• The Journal of the Acoustical Society of Korea
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• 제15권1E호
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• pp.70-76
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• 1996

We proposed to use shear waves instead of longitudinal waves in a STAM (scanning tomographic acoustic microscope system) in which the specimens are solid. For any specimen with a shear modulus, mode conversion will take place at the water-solid interface. Some of the energy of the insonifying longitudinal waves in the water will convert to shear wave energy within the specimen. The shear wave energy is detectable and can be used for tomographic reconstruction. The resolution limitation of STAM depends on the available angular view and the acoustic wavelength. While wave transmission in most solid specimens is limited to about 20°for longitudinal waves, we show that it is about twice that high for shear waves. Since the wavelength of the shear wave is shorter than that of the longitudinal wave, we are able to achieve the high resolution. In order to compare the operation of a shear-wave STAM with that of the conventional longitudinal-wave STAM we have simulated tomographic reconstruction for each. Our simulation results with aluminum specimen and back-and-forth propagation algorithm showed resolution of a shear-wave STAM is better than that of a longitudinal-wave STAM.

• Tribology and Lubricants
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• 제39권6호
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• pp.273-277
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• 2023

This paper presents a molecular dynamics simulation-based numerical investigation of the influence of surface energy on water lubrication. Models composed of a crystalline substrate, half cylindrical tip, and cluster of water molecules are prepared for a tribological-characteristic evaluation. To determine the effect of surface energy on lubrication, the surface energy between the substrate and water molecules as well as that between the tip and water molecules are controlled by changing the interatomic potential parameters. Simulations are conducted to investigate the indentation and sliding processes. Three different normal forces are applied to the system by controlling the indentation depth to examine the influence of normal force on the lubrication of the system. The simulation results reveal that the solid surface's surface energy and normal force significantly affect the behavior of the water molecules and lubrication characteristics. The lubrication characteristics of the water molecules deteriorate with the increasing magnitude of the normal force. At a low surface energy, the water molecules are readily squeezed out of the interface under a load, thus increasing the frictional force. Contrarily, a moderate surface energy prevents expulsion of the water molecules due to squeezing, resulting in a low frictional force. At a high surface energy, although squeezing of the water molecules is restricted, similar to the case of moderate surface energy, dragging occurs at the soil surface-water molecule interface, and the frictional force increases.

• 대한조선학회논문집
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• 제49권6호
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• pp.461-468
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• 2012

In this study, a Cartesian-grid method based on finite volume approach is applied to simulate the ship motions in large amplitude waves. Fractional step method is applied for pressure-velocity coupling and TVD limiter is used to interpolate the cell face value for the discretization of convective term. Water, air, and solid phases are identified by using the concept of volume-fraction function for each phase. In order to capture the interface between air and water, the tangent of hyperbola for interface capturing (THINC) scheme is used with weighed line interface calculation (WLIC) method which considers multidimensional information. The volume fraction of solid body embedded in the Cartesian grid system is calculated using a level-set based algorithm, and the body boundary condition is imposed by a volume weighted formula. Numerical simulations for the two-dimensional barge type model and Wigley hull in linear waves have been carried out to validate the newly developed code. To demonstrate the applicability for highly nonlinear wave-body interactions such as green water on the deck, numerical analysis on the large-amplitude motion of S175 containership is conducted and all computational results are compared with experimental data.

• 접착 및 계면
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• 제10권4호
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• pp.174-181
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• 2009

고 고형분 점착제의 점도 개선을 위해 seed 중합을 이용하여 수용성 저점도 점착제를 중합하였다. Seed 바인더 중합 중 최적 중합 조건을 산출하고, 점착제 중합 시 seed 바인더와 acrylic acid의 함량을 변화시켜 점도변화와 피착면에 대한 점착박리강도를 측정하여 다음과 같은 결과를 얻었다. 점착제 중합에서 seed 바인더의 함량이 7 wt%/monomer일 때 60%의 고형분에서 2,100 cps의 낮은 점도를 나타내고 평활한 점착제 필름을 제조할 수 있었다. Acrylic acid함량 변화에 따른 기계적 물성 측정에서는 4 wt%/monomer의 acrylic acid를 사용 했을 때 우수한 점착박리강도와 유지력을 나타내었다.

• 한국고분자학회:학술대회논문집
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• 한국고분자학회 2006년도 IUPAC International Symposium on Advanced Polymers for Emerging Technologies
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• pp.279-279
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• 2006

We report a fabrication of carbon nanotube (CNT) monolayer thin film using liquid-liquid interface. The multiwalled carbon nanotube (MWCNT), which were synthesized by the alumina template method formed a monolayer at the liquid-liquid interface after sonicating the MWCNT water-oil dispersion. Moreover, with the addition of ethanol, the MWCNT monlayer was also formed at the liquid-liquid interface. The monolayer is transferable onto solid substrates and the transferred film was observed using atomic force microscopy (AFM)

• 대한환경공학회지
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• 제35권2호
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• pp.75-83
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• 2013

본 연구는 기존의 고상추출(SPE) 과정을 분석장비인 LC/MSD에 on-line으로 연결함으로써 cartridge의 건조를 막아 target 물질의 손실을 최대한 억제하였으며 11종의 PFCs에 대해 실제 matrix가 있는 낙동강 원수를 이용한 실험에서 $80.4{\pm}5.2%{\sim}109.5{\pm}1.4%$ 범위의 높은 회수율을 구할 수 있었다. 낙동강에서의 PFCs 분포를 조사한 결과 하수처리장 방류수의 영향을 받는 지역(진천천과 금호강 하류)은 고농도의 PFCs가 검출되었으며, 낙동강 하류의 매리원수에서는 검출농도가 급격히 감소하여 PFOA만 8.0 ng/L의 농도로 검출되었다. 외국의 PFCs 검출현황을 보고한 연구결과들과 비교해 볼 때 낙동강 지류에서는 비교적 높은 농도로 PFCs가 검출되어 안심할 수 있는 수준은 아니었으며, 낙동강 본류의 경우도 여러 지역의 상수원으로 이용되기 때문에 주기적인 모니터링이 필요한 것으로 나타났다.

• Korean Chemical Engineering Research
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• 제51권4호
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• pp.527-530
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• 2013

이 논문은 콜로이드 입자가 기름-물 사이의 계면으로 흡착될 때 필수적으로 존재하는 정전기적 반발력에 대한 실험적, 이론적 연구이다. 광집게(optical laser tweezers)와 피에조(piezo controller)를 사용하여, 개별 입자를 트랩(trap)한 후, 계면으로 강제 전이시킨다. 이때 수용액이 전해질을 포함한 경우에만, 입자가 계면으로 전이되며, 포함하지 않을 경우에는 흡착이 일어나지 않는다. 이러한 현상을 근본적으로 이해하기 위해, 광학 트랩핑 힘(optical trapping force)과 입자와 계면 사이에 존재하는 정전기적 분리압력(electrostatic disjoining pressure)를 정량적으로 계산하였다. 이를 바탕으로, 입자가 계면으로 흡착될 때, 그들 사이에는 필연적으로 문턱 에너지(threshold energy)가 존재함을 밝혀냈다. 콜로이드 입자가 에멀젼(emulsions)이나 거품(foams)등 두 개 이상의 섞이지 않는 유체계면을 안정화 시키는 "콜로이드 계면 활성제(colloid surfactants)" 역할을 한다는 사실을 고려했을 때, 본 연구는 이러한 입자의 흡착 현상을 근본적으로 이해하는데 있어서 중요한 지식을 제공한다.

• 대한조선학회논문집
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• 제50권2호
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• pp.79-87
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• 2013

In this paper, an Euler equation solver based on a Cartesian-grid method and non-uniform staggered grid system is applied to predict the ship motion response and added resistance in waves. Water, air, and solid domains are identified by a volume-fraction function for each phase and in each cell. For capturing the interface between air and water, the tangent of hyperbola for interface capturing (THINC) scheme is used with a weighed line interface calculation (WLIC) method. The volume fraction of solid body embedded in a Cartesian-grid system is calculated by a level-set based algorithm, and the body boundary condition is imposed by volume weighted formula. Added resistance is calculated by direct pressure integration on the ship surface. Numerical simulations for a Wigley III hull and an S175 containership in regular waves have been carried out to validate the newly developed code, and the ship motion responses and added resistances are compared with experimental data. For S175 containership, grid convergence test has been conducted to investigate the sensitivity of grid spacing on the motion responses and added resistances.