• 대한기계학회:학술대회논문집
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• 대한기계학회 2008년도 추계학술대회B
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• pp.2544-2547
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• 2008

A micro channel heat sink has been studied and optimized for mixed pressure driven and electroosmotic flows through three-dimensional numerical analysis. The effects of ionic concentration represented by zeta potential and Debye thickness are studied with the various steps of externally applied electric potential. Optimization of the micro channel heat sink has been performed considering two design variables related to the micro channel width, depth and fin width. The surrogate-based optimization is performed using a search algorithm taking overall thermal resistance as objective function. The thermal resistance is found to be more sensitive to channel width-to-depth ratio than fin width-to-depth of channel ratio.

• 한국환경과학회지
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• 제5권1호
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• pp.35-41
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• 1996

For studying of coagulation and sedimentation in estuarine clay, we obtained several flow curves with various concentrations of sea water by using Coutte type rotational rheometer. The initial shear stress on high concentration of sea water was observed big, but after this, its value is decreasing with increasing shear rate. The maximum pick of shear stress is decreasing with the decreasing of concentration of sea water The trend is same totally above for viscosity. The sedimentation times with the concentration of sea water vary in $\infty$ ~ 5 minutes. The zeta potential is changed dramatically between 114 and 118 concentration of sea water. That is consistent with the sedimentation graph. From these results, the phenomena of coagulation and sedimentation can be explained with viscoelastic terms on structual formation among particles by the changes of surface potential affected from contacting sea water to dispersed particles.

• Journal of Pharmaceutical Investigation
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• 제34권6호
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• pp.459-463
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• 2004

CR 2945, a $gastrin/CCK_B$ receptor antagonist, was conjugated to liposome and tested for the targeting of pancreatic cancer cells in vitro. Successful conjugation was confirmed by FTIR and NMR. The size of CR 2945-conjugated liposome was about 500 nm in diameter, with the zeta-potential being -16.5 mV. In vitro anti-cancer activity of this formulation with or without gemcitabine encapsulated was tested on human pancreatic cancer cells, PANC-1. The growth inhibitory effect of gemcitabine-encapsulating CR 2945-conjugated liposome was found to be 10-fold more potent than that of gemcitabine-encapsulating non-conjugated liposome, suggesting that CR 2945 could be used as a potential cancer targeting moiety by conjugating into liposome.

• 전자공학회논문지A
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• 제29A권4호
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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.

• 한국응용과학기술학회지
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• 제34권3호
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• pp.504-514
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• 2017

본 연구에서는 홍삼농축액의 유화특성을 조사하였다. 먼저, 홍삼농축액의 표면활성능을 조사하였으며, 이어서 홍삼농축액 유화액을 제조하고 이의 이화학적 성질을 조사하였다. 홍삼농축액의 물/기름 계면에서 계면장력은 홍삼농축액 농도의 증가와 더불어 감소하였다. 홍삼농축액을 이용하여 유화액을 제조한 결과, 첨가 농도의 증가와 더불어 유화 지방구 크기는 감소하였으며, 홍삼농축액 농도가 3.5 wt% 이상일 경우 일정한 지방구 크기($d_{43}$ ≒ $0.39{\mu}m$)의 안정한 유화액을 형성하였고, separation analyzer($LUMiFuge^{(R)}$)를 이용한 유화안정도 평가 결과에서도 이와 유사한 안정도 변화 경향을 확인할 수 있었다. 또한 홍삼농축액 유화액 중 지방구 크기는 pH 및 NaCl 농도변화에 의존하였는데, pH가 감소함에 따라 지방구 크기는 증가하고 음의 제타전위 값[-67.0 mV (pH 9.0) ${\rightarrow$ + 2.1 mV (pH 2.0)]은 낮아지는 경향을 보였으며, NaCl 농도(0.1 M ${\rightarrow$ 0.5 M)가 높을수록 지방구 크기는 증가하였다. 본 실험을 통해 홍삼농축액의 유화능을 확인할 수 있었다.

• Journal of Ginseng Research
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• 제45권2호
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• pp.228-235
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• 2021

Backgroud: Ginsenoside compound K (GK) is a major metabolite of protopanaxadiol-type ginsenosides and has remarkable anticancer activities in vitro and in vivo. This work used an ionic cross-linking method to entrap GK within O-carboxymethyl chitosan (OCMC) nanoparticles (Nps) to form GK-loaded OCMC Nps (GK-OCMC Nps), which enhance the aqueous solubility and stability of GK. Methods: The GK-OCMC Nps were characterized using several physicochemical techniques, including x-ray diffraction, transmission electron microscopy, zeta potential analysis, and particle size analysis via dynamic light scattering. GK was released from GK-OCMC Nps and was conducted using the dialysis bag diffusion method. The effects of GK and GK-OCMC Nps on PC3 cell viability were measured by using the 3-(4,5-dimethyl-2-thiazolyl)-2,5-diphenyl-2-H-tetrazolium bromide assay. Fluorescent technology based on Cy5.5-labeled probes was used to explore the cellular uptake of GK-OCMC Nps. Results: The GK-OCMC NPs had a suitable particle size and zeta potential; they were spherical with good dispersion. In vitro drug release from GK-OCMC NPs was pH dependent. Moreover, the in vitro cytotoxicity study and cellular uptake assays indicated that the GK-OCMC Nps significantly enhanced the cytotoxicity and cellular uptake of GK toward the PC3 cells. GK-OCMC Nps also significantly promoted the activities of both caspase-3 and caspase-9. Conclusion: GK-OCMC Nps are potential nanocarriers for delivering hydrophobic drugs, thereby enhancing water solubility and permeability and improving the antiproliferative effects of GK.

• 상하수도학회지
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• 제12권1호
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• pp.81-87
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• 1998

The possibility of collision of two particles slowly settling one after another in water can be described using the collision efficiency factor in differential sedimentation (${\alpha}_{DS}$). ${\alpha}_{DS}$ was found to be a function of several parameters particle size, particle size ratio, Hamaker constant, density of liquid and particle, gravity acceleration. Previous researches were limited to the case when there is no electric repulsion assuming that the suspension is destabilized. In this paper, ${\alpha}_{DS}$ is calculated for the stabilized condition. The relative trajectory of two particles are calculated including hydrodynamics, attraction and repulsion forces. Ionic strength and surface potential significantly affect the collision possibility of two settling particles. Depending on the surface potential and ionic strength, ${\alpha}_{DS}$ value is divided into three regions; stable, unstable and transition zone. ${\alpha}_{DS}$ increases as the ionic strength increases, and as the surface charge decreases. This result can be used to model both destabilized and stabilized suspension incorporating the collision efficiency factors of the other coagulant mechanisms such as fluid shear and Browian motion.

• 한국세라믹학회지
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• 제36권7호
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• pp.691-697
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• 1999

TiO2 powder was adsorbed on the surface of mica using the heterocoagulation method in water TiO2 powder was prepared from hydrolysis of titanium-iso propoxide in a mixed solvent of anhydrous ethanol and water. When the molar ratio of water to titanium iso-propoxide was 0.25 monodispersed spherical TiO2 particles were obtained. The prepared TiO2 powder showed anatase phase after heat treatment at 50$0^{\circ}C$ for 2 h and then transformed to rutile phase after heat treatment at 100$0^{\circ}C$ for 2h. The iso-electric points of TiO2 and Mica were pH 3.9 and pH 3.25 respectively which were measured by the Z-potential analysis in water base. The maximum Z-potential difference between two powders was observed in the range of pH 3.6~3.7 TiO2 powder was adsorbed on the surface of mica by heterocoagulation method in pH 3.6~3,7 The properties of prepared TiO2 powder was haracterized by TG-DTA, XRD and SEM The morphology and thermal properties of TiO2-adsorbed mica were examined.

• Corrosion Science and Technology
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• 제23권1호
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• pp.54-63
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• 2024

This work investigated the influence of concentration and applied potential on the characteristics of zinc powder (purity, apparent density, morphology, particle size distribution, and particle zeta potential) produced by the electrochemical process from waste brass. High-purity zinc powder is obtained using selective leaching of industrial brass waste in acidic, neutral, and alkaline solutions. The free immersion method with and without voltage using linear polarization technique is used. In the electrochemical process, hydrochloric acid HCl in three different concentrations (0.1, 0.2, and 0.3) M is used. The time and the distance between the electrodes are set to be 30 min and 3 cm, respectively. It has been found that the percentage purity is 98%, 96%, and 94% for the acidic, neutral, and alkaline solutions, respectively. In addition, the morphology of zinc powder analyzed by SEM was dendritic and mossy. It has been recorded that the purity of zinc increases with the increase of the concentration and applied potential. The highest value of purity for zinc powder was %98.58 in 1000 mV and 0.3M concentration for graphite cathode.

• 한국결정성장학회지
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• 제29권6호
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• pp.372-378
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• 2019

산화구리를 함유하는 전통 세라믹 유약은 황색포도상구균과 대장균에 대해 항균활성을 나타낸다. 환원 분위기에 소결한 모든 시편들은 황색포도상구균과 대장균에 대해 항균활성을 나타내나 산화분위기에서 소결한 일부 시편들만 황색포도상구균과 대장균에 대해 항균활성을 나타내었다. 산화구리를 함유하는 전통 세라믹 유약의 항균기작을 설명하기 위해 유약의 결정상, 미세구조, 이온용출, 표면 제타전위 분석을 실시하였다. 환원 분위기에서 소결한 시편들은 유약층에 Cu 입자들이 형성되는 것을 확인할 수 있다. Cu 용출량은 전체적으로 0.05 ppm 이하이며 가장 많이 용출되는 이온은 Ca 이었다. 산화구리를 3 wt.% 이상 첨가한 모든 시편들은 높은 음극의 표면 제타전위를 나타내었다. 세라믹 유약의 항균활성은 일반적으로 용출되는 양이온들과 연관되어 보이나 산화분위기에서 소결한 시편들의 대장균에 대한 항균활성은 직접적인 연관성이 나타나지 않는다. 세라믹 유약 시편의 표면 제타전위가 이온용출과 더불어 대장균에 대한 항균활성에 보조적 기여를 하는 것으로 보인다.