• The Transactions of The Korean Institute of Electrical Engineers
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• v.62 no.2
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• pp.213-218
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• 2013

In this study, epoxy/mica composite was prepared by mixing with mechanical stirrer together with homogenizer, and the effect of amino-type silane coupling agent was also studied. To reduce the viscosity without any decrement of other properties, 1,4-Butanediol diglycidyl ether (1,4-BDGE) as an aliphatic epoxy reactive diluent was introduced to the epoxy/mica composite in order to use as vanish for high voltage motor and generator stator winding. It was confirmed by scanning electron microscopy (SEM) observation that interfacial characteristics between organic epoxy and inorganic mica was modified by coupling agent treatment so that glass transition temperature increased, and tensile strength and electrical breakdown strength increased. The properties were estimated by Weibull statistical analysis and the ac electrical breakdown strength was 20.2% modified by treating silane coupling agent.

• Journal of the Korean Society of Safety
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• v.23 no.6
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• pp.91-99
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• 2008

The identification of thermal hazards associated with a process such as heats of reaction and understanding of thermodynamics before any large scale operations are undertaken. The evaluation of thermal behavior with operating conditions such as a reaction temperature, stirrer speed and reactants concentration in neutralization process of pigment plant are described. The experiments were performed by a sort of calorimetry with multimax reactor system The aim of the study was to evaluate the results of heat of reaction in terms of safety reliability to be practical applications. It suggested that we be proposed safe operating conditions and securities for accident prevention on reactor explosion through this study.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2007.06a
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• pp.219-219
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• 2007

Ni stamper위에 100nm의 Si 코팅후 자기조립 단문자막(SAM)을 액상 코팅방식으로 형성 하였고, 내구성 및 열적 안정성을 검증하기 위해 반복적인 이형 및 압력인가test가 실시하였다. 20 회 이상의 이형실험을 통해 열적, 기계적 안정성을 확인하고, 접촉각 측정을 통해 이형특성의 안정성도 고찰하였다. 이를 Imprint공법을 적용 fine pattern의 구조물을 얻을수 있었다. SAM코팅은 TRICHLOROSILANE을 사용하였으며 Hexane과 1000:1의 비율로 섞어서 stirrer에서 mixing하는 방식을 사용했으며, UV-ozone처리를 통한 이형성 제거 효과도 관찰하였다.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2007.11a
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• pp.209-209
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• 2007

Ni stamper위에 100nm의 Si 코팅후 자기조립 단분자막(SAM)을 액상 코팅방식으로 형성 하였고, 내구성 및 열적 안정성을 검증하기 위해 반복적인 이형 및 압력인가 test가 실시하였다. 20회 이상의 이형실험을 통해 열적, 기계적 안정성을 확인하고, 접촉각 측정을 통해 이형특성의 안정성도 고찰하였다. 이를 Imprint공법을 적용 fine pattern의 구조물을 얻을 수 있었다. SAM코팅은 TRICHLOROSILANE을 사용하였으며 Hexane과 1000:1의 비율로 섞어서 stirrer에서 mixing하는 방식을 사용했으며, UV-ozone처리를 통한 이형성 제거 효과도 관찰하였다.

• Journal of the Korean Society of Marine Environment & Safety
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• v.22 no.2
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• pp.240-245
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• 2016

This paper describes the rheological behavior study such as viscosity and change of shear stress regarding marine lubricating oil according to the amount of Marine Gas Oil (MGO) dilution. The viscosity reduction due to fuel dilution is crucially important characteristic to decreasing engine durability because of the abrasion of piston ring or liner. The lubricating oil used in this paper was blended with magnetic stirrer diluted High Sulfur Diesel (HSD, 0.05 wt%) ratio of 3 %, 6 %, 10 %, 15 % and 20 %. The viscosity and shear stress of diluted lubricating oil were measured with the temperature range from $-10^{\circ}C$ to $80^{\circ}C$ using a rotary viscometer (Brookfield Viscometer). As the amount of MGO dilution increasing in lubricating oil, the viscosity and stress of those decreased, because the lubricating oil diluted MGO with low viscosity show the trends to decreased viscosity and shear stress. Especially, the viscosity and shear stress of lubricating oil radically decreased at low temperature ($0{\sim}-10^{\circ}C$) and doesn't effect in MGO dilution at over $40^{\circ}C$. As temperature risen, the reduction of the viscosity and shear stress in lubricating oil shows the Newtonian behavior. The lubricating oil was required to check up periodically to improve engine durability since the viscosity reduction by MGO dilution accelerating the engine abrasion.

• Food Science and Preservation
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• v.23 no.2
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• pp.233-238
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• 2016

A effect of extraction methods, including stirrer extraction method (SE), ultrasonification extraction method (USE), reflux extraction method (RE), autoclave extraction (AE) and low temperature high pressure extraction (LE) method on the antioxidative and antimicrobial activities of ethanol extracts of Oenothera biennis was investigated. The extraction yield (46.33%), total polyphenol (463.05 mg GAE/g) and flavonoid (71.71 mg RHE/g) content of Oenothera biennis extract obtained by RE were higher than those from other extraction methods. The antimicrobial activity of Oenothera biennis extract was only observed against Bacillus cereus among other tested organisms (Bacillus cereus, Staphylococcus aureus, Escherichia coli and Salmonella Typhimurium). Oenothera biennis obtained by RE showed the best DPPH radical scavenging ability (74.40%), ABTS radical scavenging ability (65.29%), reducing power (1.370 ($OD_{700}$)) and ferrous ion chelating ability (90.14%) compared with other tested extraction methods tested. The RE method was the most efficient method for extracting crude antioxidant and antimicrobial substances from Oenothera biennis. These results suggested that Oenothera biennis obtained by RE could be used as a bioactive and functional material in the food industry.

• Journal of the Korean earth science society
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• v.33 no.6
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• pp.544-553
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• 2012

A simple experimental method was developed to help students understand the effect of the Coriolis force on typhoon genesis and movement. It consists of rotating tanks with and without a sloping bottom, and a small stirrer to produce cyclonic typhoon-like vortices by locally stirring the water. Vortices were able to last for more than 3 minutes without dissipation in the rotating tank. However, vortices were hardly maintained without rotation, and would rather disappear as soon as the stirrer stopped mixing. Since the dynamical properties of the rotating water are similar to those of the atmosphere influenced by the Coriolis force, the experiments show that the Coriolis force is indispensable to the typhoon genesis. When the tank had both the sloping bottom and rotation, vortices would move in a particular direction. Considering the topographical beta effect, this result indicates that typhoons are drifted not only by the steering wind but also by the meridional gradient of the Coriolis force. The methodology developed in this study, would be useful for both students and teachers to better the relationship between the Coriolis force and the typhoon genesis.

• Resources Recycling
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• v.3 no.3
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• pp.32-49
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• 1994

Hydration process is one of the basic carbonation system. Limestone sludge produced in Pohang Iron & Steel Co., Ltd. We tested for identify of hydration characteristics. The result obtained in this study can be summarized as follows; 1. The classify of limestone sludge is type of ground calcium carbonate(-3mm+325mesh)and the major mineral of calcite, and further more high grade(CaO 51%), fine powder(15~22$\mu\textrm{m}$). 2. Limestone sludge mixed two process sludge, first one is washing process sludge and the other one is wet collect kiln dust. The composition rate is about 8:2. Wet collect kiln dust is major mineral of calcite, too. But the sludge is assumed to one by quick lime, slaked lime and unreacted natural limestone. So, the ideal process is dividing of the washing process sludge and wet collect kiln dust. 3. We manufactured of slaked lime from limestone sludge. To investigate the effect of hydration reactor, the experiments was done with various reactor type as magnetic stirrer, shaking incubator and ultrasonic vibration reactor, respectively. Generally, ultrasonic vibration reactor is excellent hydration for limestone sludge and produced very fine slaked lime powder with ideal distribution. 4. The optimum condition is 10% pulp density, when the manufacture of fine slaked lime powder by ultrasonic vibration reactor. And hydration times to compare the results of the study with ultrasonic vibration reactor of generalized most short time(5~10 min). 5. Finally, the dispersive characteristics of slaked lime powder measured 1~5 $\mu\textrm{m}$ from limestone sludge were compared with those of natural limestone ones(10~20$\mu\textrm{m}$), in order to check applicability of slaked lime with hydration process from limestone sludge.

• Resources Recycling
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• v.30 no.6
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• pp.61-67
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• 2021

This work investigated the cementation of iridium from iridium-containing hydrochloric acid leachate. Zinc powder was used as the reducing agent, and the effects of the stoichiometric ratio of Zn/Ir, initial Ir concentration, initial pH, reaction time, and ultrasound irradiation on iridium recovery were investigated. When only the stirrer was used for cementation, the iridium recovery increased with the addition amount of zinc, and the recovery of about 70% at 40 times the stoichiometric ratio of Zn/Ir. In contrast, when employing ultrasonic irradiation with stirring, the recovery of iridium decreased at 20 times or less the stoichiometric amount of zinc. The recovery of iridium increased at 40 times the stoichiometric ratio of Zn/Ir. This result may be due to the ionization of zinc and re-dissolution of iridium during the ultrasound irradiation treatment. When a combination of ultrasonic irradiation and stirring was used for cementation, the iridium recovery increased by more than 27% compared to that when using only the stirrer. It was possible to recover 99% of iridium under the following conditions: reaction time, 60 min; initial pH, 0.01; volume of leachate, 100 mL; 1770 ppm Ir, 40 times the stoichiometric ratio of Zn/Ir.

• Composites Research
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• v.30 no.5
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• pp.303-309
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• 2017

Organo-montmorillonite (OMMT) has attracted much attention for fiber-reinforced polymer composites as a filler material due to high aspect ratio and low charge density. The present study focused on the fabrication of nanocomposites using Vinyl ester and Jute fabric as matrix and reinforcement respectively. The OMMT was uniformly dispersed in vinyl ester resin at 1, 2 and 3 wt%, loading through high speed mechanical stirrer at room temperature and further nanocomposites were manufactured through vacuum assisted resin infusion (VARI) technique. Effects of OMMT on the mechanical properties of vinyl ester/Jute composites were carefully investigated through tensile, bending and Izod impact tests, which revealed significant improvement in mechanical properties. The morphology of the nanocomposites after tensile test was investigated by SEM which affirmed that OMMT filled nanocomposites has improved interactions with the host matrix than the pure composites. Based on the nature and flame retardancy mechanism, the OMMT slightly improved the flammability property which was clearly explained by horizontal burning test.