• Transactions of the Korean Society of Mechanical Engineers B
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• v.30 no.7 s.250
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• pp.663-670
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• 2006

The presented study aims to investigate the colloidal droplet deposition caused by evaporation of the liquid. In the numerical analysis, the evaporation is carried out by using different evaporation function intended to obtain different shape of solute deposition. In the experiment, the colloidal droplets of different solvents are placed on a glass plate and the surface profiles are measured after drying the solvents of the droplets to investigate the effect of the solvent evaporation on the final deposition profile. Comparing the surface profiles obtained under different conditions, the optimum drying conditions of colloidal droplets are, determined to obtain uniform surface profiles. The numerical results showed that ring-shaped deposition of solute was formed at the edge of the droplet due to the coffee stain effect and the height of the ring was reduced at the lower evaporation rate. The experiments showed that the boiling point of a solvent was critical to the surface uniformity of the deposition profile and the mixture of solvents with different boiling points influenced the uniformity as well.

• Journal of the Korean Crystal Growth and Crystal Technology
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• v.7 no.4
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• pp.599-609
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• 1997

The phase behavior and dynamics of colloid suspensions and the resulting structures and properties of powder compacts were examined by a computer experimental method for cooperative packing processes. A wide range of properties and process conditions such as arbitrary particle size, medium densities, field strength, and temperature could be examined using the Peclet number (Pe). We demonstrated that an optimum range of Peclet number for the ordering of sediments was present and that the phenomena related to the ordering such as the onset of crystallization, the phase behavior, etc. strongly depend on process conditions. The present work appears to be useful to design the processing method of ceramic spherical submicron powders for the preparation of high-density green compacts.

• Journal of the Korean Applied Science and Technology
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• v.32 no.3
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• pp.386-393
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• 2015

The rheological properties of complex materials such as colloid dispersion show complicated non-Newtonian flow phenomena when they are subjected to shear flow. These flow properties are controlled by the characteristics of flow units and the interactions among the flow segments. The rheological parameters of relaxation time $({\beta}_2)_0$, structure factor $C_2$ and shear modulus $X_2/{\alpha}_2$ for various thixotropic flow curves was obtained by applying thixotropic equation to flow curves. The variations of rheological parameters are directly related to non-Newtonian flows, viscosities and activation energies of flow segments.

• Proceedings of the Korea Water Resources Association Conference
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• 2008.05a
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• pp.842-846
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• 2008

원수의 탁질 중에서 입경이 $10^{-1}$mm이상인 것은 보통침전으로 제거가 가능하지만, 입경이��$10^{-3}mm$이하가 되면 일반적으로 콜로이드입자라고 총칭하며 그대로의 상태로서는 거의 침강되지 않을 뿐만 아니라 급속여과기구에서도 포착되지 않는다. 따라서 급속여과 방식에서는 이와 같은 탁질을 효과적으로 제거하기 위한 전처리로서 응집조작으로 인한 콜로이드상의 탁질을 플록화하여 약품침전이나 급속여과에서 포착되도록 탁질의 성상을 변화시키는 조작이 반드시 필요하다. 또한 양호한 플록을 효과적으로 형성시키는 약품혼화와 플록형성 등을 강구해야 한다. 이에 본 연구에서는 현재 국내에서 운영하고 있는 정수처리시스템의 일부인 혼화지내에 혼화지점의 단면적을 축소시켜 약품혼화효과를 극대화하고 혼화기의 소요동력을 감소시켜 혼화효과를 개선하며 혼화지내 혼화기 운용의 비용 절감 효과를 증가시키기 위한 저에너지형 CF혼화장치를 개발하는데 연구 목적이 있다. 연구결과 CF혼화장치의 설치시 약품 투입 위치에 따라 $2{\sim}6%$정도의 탁도제거율의 상승과 슬러지 높이의 차이를 보이는 것으로 나타났으며 이 실험 결과 약품투입장소에서 혼화지의 Compact화로 인해 급속 혼화를 이룰 경우 더 많은 플록화로 인해 탁도 제거율이 높아지는 것을 알 수 있다.

• Journal of ILASS-Korea
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• v.8 no.1
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• pp.16-22
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• 2003

Zeta potential measurements of colloid particles suspended in a liquid are performed by a Zeta Meter developed. There are many applications of colloid stability in spray technology, paints, wastewater treatment, and pharmaceuticalse. Zeta potentials of charged particles are obtained by measuring the electrophoretic velocities of the particles using video enhanced microscopy and image analysis program. The values of zeta potential of polystyrene latex(PSL), $silica(SiO_2)$M, polyvinylidence difluoride(PVDF), silicon nitride, and alumina particles in deionized (DI) water were measured to be -40.5, -31.9, -25.2, -15.1 and -10.1mV, respectively. The particles having high zeta potential less than -20 mV are stable in DI water, because the double layers of them have strong repulsive forces mutually, and the particles having low zeta potential over -20mV are unstable due to Van Der Waals forces. Silica(>20nm), PSL, aluminum and PVDF particles were found to be stable that would remain separate and well disperse, while silicon nitride and alumina particles were found to be unstable that would gradually agglomerate in DI water.

• Journal of the Korean Chemical Society
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• v.51 no.5
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• pp.407-411
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• 2007

Mie theory has been used to calculate the extinction of a gold nanoparticle in water by varying its diameter from 1 to 1000 nm. Utilizing this size-dependent theoretical spectrum, we have calculated the extinction spectrum of a colloidal gold by taking into account the size distribution of particle. Such calculation is in better agreement with experiment than the calculation without considering the size distribution. A least-squares fitting is used to deduce the size distribution from an experimental extinction spectrum. For particles with their diameters ranging from 10 to 28 nanometers, the fitting gives reasonable agreement with the size distribution obtained from tunneling electron microscope images.

• Journal of Korean Academy of Fundamentals of Nursing
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• v.5 no.2
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• pp.181-195
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• 1998

This study is to evaluate the decubitus ulcer healing effect of occlusive dressing with hydrocolloid and traditional dry dressing for home care nursing clients. Study design was quasi-experimental pre-post test design. Control group(15 person) was treated decubitus wound with traditional dry gauze dressing, and experimental group(17 persons) was treated decubitus ulcer with occlusive dressing with hydrocolloid and calcium alginate(17 persons). Study period was from 8/1/97 to 12/31/97. Subject subjects was 17 males and 15 females with 2nd phase over decubitus ulcer aged 30 to 70 who have been registered as home care nursing clients in Nurse's Association in Seoul city. Outcome variables were stages, size of decubitus ulcer, pain at dressing time and exudate amount. Study result as follows. Occlusive dressing with hydrocolloid was superior to traditional gauze dressing decreasing ulcer size and phase, and shortening treatment period. Dressing change of occlusive dressing was easier than that of traditional gauze dressing. In conclusion, occlusive dressing was recommended to treat decubitus ulcer in home care patients even if hydrocolloid is expensive to gauze dressing because of treatment effect and easeness of dressing.

• Proceedings of the Korean Vacuum Society Conference
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• 2014.02a
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• pp.131-131
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• 2014

양자점은 전통적인 유기 염료에 비해 흡광영역이 넓고 발광 피크의 폭이 좁으며, 흡광과 발광 사이의 에너지 차가 커서 검출이 용이하고, 광안정성이 우수할 뿐만 아니라, 단순히 크기를 조절함으로써 발광 피크의 에너지를 제어할 수 있는 특장 때문에 많은 연구가 진행되었다. 그러나 많은 나노입자들과 마찬가지로 실질적인 응용을 위해서는 양자점 나노입자들도 대부분 표면개질을 거쳐야 하는데, 이 과정이 까다롭고 또 표면개질 중에 나노입자들의 응집이 일어나거나 광특성이 나빠지는 등의 문제가 흔히 발생한다. 한편, 서브미크론 크기의 입자들은 나노입자에 비해 응집현상이 미미해서 상대적으로 취급이 용이하다. 그 중에서도 실리카 입자들은 합성방법도 쉽게 확립되어 있고 생체친화성이 우수하며 그 표면화학 반응이 이미 잘 알려져 있어서 활용하기가 매우 용이하다. 따라서 양자점 층을 실리카 표면 가까이에 자기조립을 통해 배열한 하이브리드 구조는 양자점의 장점을 편리하게 이용할 뿐만 아니라 실리카의 표면개질 특성도 그대로 이용할 수 있다는 이중의 장점이 있다. 본 논문에서는 코어/쉘 구조로 안정화된 II-VI 반도체 양자점 층을 아래 그림 1과 같이 실리카 콜로이드 내에 배열한 하이브리드 구조를 소개하고, 이 하이브리드 구조를 표면개질 하여 LED 칩 위에 패키징 함으로써 백색광을 제조한 연구 및 더 나아가 중심에 초상자성 클러스터 핵을 배치하고 이를 둘러싼 실리카 콜로이드 표면 가까이에 양자점 층을 배열한 초상자성 하이브리드 구조를 합성하여 이를 on-site sensor에 적용한 연구 결과를 소개한다.

• Korean Journal of Food Science and Technology
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• v.25 no.3
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• pp.277-281
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• 1993

To elucidate the conformational stability of proteins in colloidal food system, molecular properties of various proteins such as chemically modified ${\beta}-lactoglobulin$, bovine serum albumin (BSA) structural intermediates, and ${\beta}-casein$ under chaotropic conditions, were examined using circular dichroism, SS bond content, and hydrodynamic radius determination. As refolding time increases, BSA intermediates approach the conformation of native BSA. And succinylation made ${\beta}-lactoglobulin$ have more aperiodic structure by increasing net negative charge. Also, under chaotropic conditions, the conformation of P-casein was affected by hydrophobic interactions. This study clearly indicates that hydrophobic interactions and electrostatic interactions are major contributing factors in conformational stability of proteins.

• Journal of Korean Society of Environmental Engineers
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• v.32 no.2
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• pp.149-154
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• 2010

The feasibility of lead removal by electrolytic coprecipitation was investigated. Electrolysis bath was divided into anode and cathode chamber with anion exchange resin filled membrane. Sea water was electrolyzed and pH of the electrolyte in cathode chamber was increased. Consequently it induced the formation of $Mg(OH)_2$ and $CaCO_3$. The colloidal type precipitates, hich have high surface area, adsorbed lead ions in sea water and coprecipitated. Sea water electrolyses were conducted at different current density. Concentrations of Mg, Ca and Pb in the solution were measured with titration and ASV method. Morphology and crystallography were analyzed with SEM, EDS and XRD. As pH and current density increased, most of lead ions in the sea water were successfully removed.