• 한국전산유체공학회:학술대회논문집
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• 2003.10a
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• pp.19-20
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• 2003

Brownian-dynamics simulation on highly charged colloidal suspensions is performed by employing Tokuyama effective force recently proposed. The radial distribution function suggests that there exist three novel phases, a gas phase, a liquid droplet phase, and a face-centered cubic (FCC) crystal droplet phase, depending on the minimum values of that potential. The dynamics of droplet growth is also investigated both in liquid droplet phase and in crystal droplet phase. Thus, different types of characteristic growth stages are found.

• Journal of the Korean Institute of Telematics and Electronics A
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• v.29A no.4
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• pp.22-27
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• 1992

The cyclic voltammogram characteristics at the magnetized SrO${\cdot}6Fe_{2}O_{3}$ ceramics/(($10^{-3}$M KCI + p-Si powders) and /(($10^{-4}$M CsNO$_3$ + n-GaAs powders) suspension interfaces have been studied using the microelectrophoresis and the cyclic voltammetric method. The negatively charged ions are specifically absorbed on the virgin and the magnetized SrO${\cdot}6Fe_{2}O_{3}$ ceramics surfaces. The zeta potentials of the p-Si and n-GaAs colloidal semiconductors are + 41mV and -44.8mV, respectively. The magnetization effects act as potential barriers at the magnetized SrO${\cdot}6Fe_{2}O_{3}$ interfaces. The positivelely charged p-Si and the negatively charged n-GaAs colloidal semiconductors act as potential barriers at the virgin SrO${\cdot}6Fe_{2}O_{3}$ interfaces. On the other hand, the charged p-Si and n-GaAs colloidal semiconductors act as potential barrier scavengers at the magnetized SrO${\cdot}6Fe_{2}O_{3}$ interfaces. The magnetization effects and the charged colloidal semiconductor effects are irreversible and interdependent.

• Journal of Ceramic Processing Research
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• v.20 no.2
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• pp.158-163
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• 2019

Er3+/Yb3+-codoped NaLa(MoO4)2 colloidal nanocrystals were synthesized by pulsed laser ablations in de-ionized water and sodium dodecyl sulfate (NaC12H25SO4, SDS) aqueous solution for up-conversion (UC) luminescence bio-labeling applications. The influences of the SDS molecules on the crystallinities, crystal morphologies, crystallite sizes, and UC luminescence properties of the prepared Er3+/Yb3+-codoped NaLa(MoO4)2 colloidal nanocrystals were investigated in detail. Under a 980-nm excitation, the Er3+/Yb3+-codoped nanocolloidal NaLa(MoO4)2 suspension exhibited a weak red emission near 670 nm and strong green UC emissions at 530 and 550 nm, corresponding to the intra 4f transitions of Er3+ (4F9/2, 2H11/2, 4S3/2) → Er3+ (4I15/2). When the SDS solution was used, a smaller average crystallite size, narrower size distribution, and enhanced UC luminescence were observed. These characteristics were attributed to the amphoteric SDS molecules attached to the positively charged Er3+/Yb3+-codoped NaLa(MoO4)2 colloidal nanocrystals, effectively occupying the oxygen defect on their surfaces. The Er3+/Yb3+-codoped nanocrystalline NaLa(MoO4)2 suspension prepared in the SDS solution exhibited a remarkably strong green emission visible to the naked eyes.

• Proceedings of the Korea Association of Crystal Growth Conference
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• 2000.06a
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• pp.215-232
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• 2000

The Valence(Z) of positively and negatively charged alumina particles in the dilute suspensions was analyzed with the electrical conductivity of the suspensions. The mobility of negative particles was lower than that of positive particles at a similar Z value because of the stronger effect of chemical bonding over the hydrated particle surfaces. The apparent viscosity of acidic suspensions of 1-40 vol % solid was lower than that of basic suspensions. This result was discussed based on the three important effects of the valence, concentration and nature of hydrated surface of alumina particles. The density of alumina compacts consolidated by filtration through gypsum molds became lower for the basic suspensions than for the acidic suspensions. This result was correlated to the properties of the colloidal alumina suspensions.

• Journal of Soil and Groundwater Environment
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• v.12 no.3
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• pp.44-52
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• 2007

Contaminated sediments more than 30 million/$m^3$ is generated from dredging work for harbours and coastal maintenance in Korea. Approximately 300 million/$m^3$ of sediments is dredged to deepen harbours and shipping lanes in US and of which $3{\sim}12million/m^3$ is highly contaminated. Although much is known about technologies for the remediation of heavy metal contaminated soil, much less is known about the treatment of contaminated sediment. In general, negatively charged fine particles will migrate towards positively charged system of electrodes under the influence of electrophoresis. However, the electrically induced migration of colloidal particles contaminated with heavy metals may be hindered by the positively charged heavy metal contaminants adsorbed onto the soil surfaces depending on the contamination level. This paper demonstrates settling behaviour of clayey soil by comparison with electrophoretic particle movement under the effects of heavy metal contamination, applied electric field strength, and its polarity changed by the electrode configuration.

• Journal of The Korean Society of Agricultural Engineers
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• v.47 no.5
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• pp.27-39
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• 2005

In the recent design of high ductile fiber-reinforced ECC (engineered cementitious composite), optimizing both processing and mechanical properties for specific applications is critical. This study presents an innovative method to develop new class ECCs, which possess the different fluid properties to facilitate diverse types of processing (i.e., self-consolidating or shotcrete processing) while maintaining ductile hardened properties. In the material design concept, we employ a parallel control of fresh and hardened properties by using micromechanics and cement rheology. Control of colloidal interaction between the particles is regarded as a key factor to allow the performance of the specific processing. To determine how to control the particle interactions and the viscosity of cement suspension, we first introduce two chemical admixtures including a highly charged polyelectrolyte and a non-ionic polymer. Optimized mixing steps and dosages we, then, obtained within the solid concentration predetermined based on micromechanical principle. Test results indicate that the rheological properties altered by this approach were revealed to be highly effective in obtaining the desired function of the fresh ECC, allowing us to readily achieve hardened properties, represented by pseudo strain-hardening behavior in uniaxial tension.