• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2000.07a
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• pp.839-842
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• 2000

The mechanical and electrical properties of the hot-pressed and annealed $\beta$-SiC-ZrB$_2$ electroconductive ceramic composites were investigated as function of the liquid forming additives of $Al_2$O$_3$+Y$_2$O$_3$. Phase analysis of composites by XRD revelled $\alpha$ -SiC(6H), ZrB$_2$, and YAG(Al$_{5}$ Y$_3$O$_{12}$ ). Owing to crack deflection, crack bridging, phase transition and YAG of fracture toughness mechanism, the fracture toughness showed the highest value of 6.3MPa.m$^{1}$2/ for composites added with 24wt% $Al_2$O$_3$+Y$_2$O$_3$additives at room temperature. The resistance temperature coefficient respectively showed the value of 2.46$\times$10$^{-3}$ , 2.47$\times$10$^{-3}$ , 2.52$\times$ 10$^{-3}$ $^{\circ}C$ for composite added with 16, 20, 24wt% A1$_2$O$_3$+Y$_2$O$_3$additives. The electircal resistivity of the composites was all positive temperature coefficient resistance(PTCR) in the temperature range of $25^{\circ}C$ to 90$0^{\circ}C$.

• Proceedings of the Korean Society of Soil and Groundwater Environment Conference
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• 2001.02a
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• pp.14-28
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• 2001

As basic study for purpose bioremedation in oil-contaminated environment, Primarily, we isolated biosurfactant producer- strains utilized of oil-agar plate, and measured surface tension and emulsifying activity. We investigated in oil-contaminated soil and sea water. In this laboratory, Pseudomonas sp. EL-012S strain isolated from oil-contaminated soil was able to product novel biosurfactant under the optimal culture condition. Its condition was n-hexadecane 2.0%, NH$_4$NO$_3$0.4%, Na$_2$HPO$_4$0.6%, KH$_2$PO$_4$0.4%, MgSO$_4$.7$H_2O$ 0.02%, CaCl$_2$.2$H_2O$ 0.001%, FeSO.7$H_2O$ 0.001%, initial pH 7.0 and aeration at 3$0^{\circ}C$, respectively. This biosurfactant was produced in both late-exponential and early-stationary phase. The biosurfactant from Pseudomonas sp. EL-012S was composed of carbohydrate, lipid and protein. The purified-biosurfactant was examined two (biosurfactant type I, II) with the silica gel G60 column chromatography and the purified biosurfactant confirmed thin layer chromatography, high performed liquid chromatography and gas chromatography. The biosurfactant type I involved in carbohydrate-lipid-protein characteristics lowered surface tension of water to 27dyne/cm and interfacial tension 4.5dyne/cm aginst to n-hexadecane and the biosurfactant type B involved in carbohydrate lipid characteristics lowered surface tension of water to 30dyne/cm and interfacial tension 8dyne/cm against to n-hexadecane. Specially type I had the properties such as strong emulsifying activity, emulsion stability, pH-stability, thermo-stability, high cleaning activity and forming ability.

• Journal of Nutrition and Health
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• v.23 no.6
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• pp.434-442
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• 1990

A new HPLC method for determining malonaldehyde content in lipid peroxidation systems was developed and antioxidant activities of $\alpha$-, $\beta$- carotene, lutein and lycopene were compared by a newly developed HPLC analysis and by TBA value. In addition, malonaldehyde forming ability of rat liver microsome was determined depending on thawing numbers. As results, malonaldehyde was eluted at a retention o f5.60 min and showed a linear relationship between peak area and concentration in standard curve. The MA content of microsome decreased with thawing numbers possible by destruction of cellular membranes. Lycopene, lutein and $\alpha$-carotene showed stronger antioxidant activities than $\beta$-carotene of DL-$\alpha$-tocopherol both in Fe+3-ADP/NADPH and in paraquat/NADPH system. The inhibitory effects of carotenoids and DL-$\alpha$-tocopherol on Fe+3-ADP/NADPH lipid peroxidation system was similar by TBA value and by the HPLC analysis for malonaldehyde.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.18 no.11
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• pp.915-922
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• 2006

Considering heat pipe design principles in fabrication and operational performances, water is one of the most recommended working fluids to make mid to low tempera lure heat pipes. But the conventional water heat pipes might encounter the failure in a cold start-up operation when socked at a chilling temperature lower than the freezing point. If they are subjected to a heat supply for start-up at a temperature around $-20^{\circ}C$, the rate of the vapor flow and the corresponding heat transfer from the evaporator to the condenser is so small that the vapor keeps to stick on the surface of the chilling condenser wall, forming an ice layer, resulting in a liquid deficiency in the evaporator. This kind of problems was resolved by Kang et al. in 2004 by adopting a gas loading heat pipe technology to the conventional water heat pipes. This study was conducted to examine a chilling start-up procedure of gas loading heat pipes by investigating the behaviors of heat pipe wall temperatures. And the thermal resistance of the gas loaded heat pipe that depends on the operating temperatures and heat loads was measured and examined. Two water heat pipes were designed and fabricated for the comparison of performances, one conventional and the other loaded with $N_2$ gas. They were put on start-up test at a heat supply of 30 W after having been socked at an initial temperature around $-20^{\circ}C$. It was observed that the gas loaded one had succeeded in chilling start-up operation.

• Journal of the Korean Society of Manufacturing Process Engineers
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• v.18 no.7
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• pp.83-89
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• 2019

In the conventional casting and forging method, there is a disadvantage that a mold is an essential addition, and a production cost is increased when a small quantity is produced. In order to overcome this disadvantage, a metal 3D printing production method capable of directly forming a shape without a mold frame is mainly used. In particular, overseas research has been conducted on various materials, one of which is a metal printer. Similarly, domestic companies are also concentrating on the metal printer market. However, In this case of the conventional metal 3D printing method, it is difficult to meet the needs of the industry because of the high cost of materials, equipment and maintenance for product strength and production. To compensate for these weaknesses, printers have been developed that can be manufactured using sand mold, but they are not accessible to the printer company and are expensive to machine. Therefore, it is necessary to supply three-dimensional casting printers capable of metal molding by producing molds instead of conventional metal 3D printing methods. In this study, we intend to reduce the unit price by replacing the printing method used in the sand casting printer with the FDM method. In addition, Ag paste is used to design the output conditions and enable ceramic printing.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.23 no.4
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• pp.416-422
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• 2019

This paper proposes a GPU-based modeling and rendering of 3D clouds using procedural functions. The formation of clouds is based on modified noise function made with fbm(Fractional Brownian Motion). Those noise values turn into densities of droplets of liquid water, which is a critical parameter for forming the three different types of clouds. At the rendering stage, the algorithm applies the ray marching technique to decide the colors of cloud using density values obtained from the noise function. In this process, all lighting attenuation and scattering are calculated by physically based manner. Once we have the clouds, they are blended on the sky, which is also rendered physically. We also make the clouds moving in the sky by the wind force. All algorithms are implemented and tested on GPU using GLSL.

• Journal of Powder Materials
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• v.28 no.6
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• pp.483-490
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• 2021

A new Fe-Cr-Mo-B-C amorphous alloy is designed, which offers high mechanical strength, corrosion resistance as well as high glass-forming ability and its gas-atomized amorphous powder is deposited on an ASTM A213-T91 steel substrate using the high-velocity oxygen fuel (HVOF) process. The hybrid coating layer, consisting of nanocrystalline and amorphous phases, exhibits strong bonding features with the substrate, without revealing significant pore formation. By the coating process, it is possible to obtain a dense structure in which pores are hardly observed not only inside the coating layer but also at the interface between the coating layer and the substrate. The coating layer exhibits good adhesive strength as well as good wear resistance, making it suitable for coating layers for biomass applications.

• Design & Manufacturing
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• v.16 no.3
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• pp.9-15
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• 2022

In order to reduce the manufacturing costs of the glass lens, it is necessary to manufacture a lens using a UV curable resin or a thermosetting resin, which is a curable material, in order to replace a glass lens. In the case of forming a lens using a thermosetting material, it is necessary to form several lenses at once using the wafer-level lens manufacturing technologies due to the long curing time of the material. When a lens is manufactured using a curable material, an error in the shape of the lens due to the shrinkage of the material during the curing process is an important cause of defects. The major factors for these shape errors and deformations are the shrinkage and the change of mechanical properties in the process of changing from a liquid material during curing to a solid state after complete curing. Therefore, it is necessary to understand the curing process of the material and to examine the shrinkage rate and change of physical properties according to the degree cure. In addition, it is necessary to proceed with CAE for lens molding using these and to review problems in lens manufacturing in advance. In this study, the viscoelastic properties of the material were measured during the curing process using a rheometer. Using the results, Rheological investigation of cure kinetics was performed. At the same time, The shrinkage of the material was measured and simple mathematical models were created. And using the results, the molding process of a single lens was analyzed using Comsol, a commercial S/W. In addition, the experiment was conducted to compare and verify the CAE results. As a result, it was confirmed that the shrinkage rate of the material had a great influence on the shape precision of the final product.

• Food Science and Preservation
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• v.22 no.2
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• pp.225-231
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• 2015

This study was conducted to examine the physicochemical properties and micro-encapsulation process of rice fermented with Bacillus subtilis CBD2. The viable bacterial cell, pH, and amylase activity of the rice liquid culture were 7.61 log CFU/mL, pH 5.08 and 159.43 units/mL, respectively. The micro-encapsulated rice liquid culture was manufactured via spray drying with different forming agents: i.e., alginic acid 1.0% and chitosan 0.3%, 0.5%, and 1.0%. The moisture contents of the spray-dried powders were approximately 2.90~3.68%. The color of the L and a value decreased whereas that of the b and ${\Delta}E$ value increased. The particle size and outer topology of the spray-dried rice liquid culture were $48.13{\sim}68.48{\mu}m$ and globular, respectively. The water absorption index of the spray-dried powder (2.40~2.65) was lower than that of the freeze-dried powder (2.66). The water solubility index of the spray-dried powder (9.17~10.89%) was higher than that of the freeze-dried powder (7.12%). The in vitro dissolution was measured for five hours in pH 1.2 simulated gastric fluid, and pH 6.8 and pH 7.4 simulated intestinal fluids, using a dissolution tester at $37^{\circ}C$ with 50 rpm agitation. The amylase survival in the fermented rice was 85.93% through the spray-drying and it was very effectively controlled.

• Journal of the Korean Ceramic Society
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• v.40 no.5
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• pp.494-500
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• 2003

The effects of $Al_2$O$_3$ addition upon the sintering range of clay-EAF dust (the specified wastes produced from steel making process) system body which would be used as a constructing bricks were investigated. The slope of apparent density to sintering temperature decreased for Clay-dust body containing 5~15 wt% A1203 sintered at 1200-125$0^{\circ}C$, and the absorption(%) of specimen sintered above 125$0^{\circ}C$ decreased due to the formation of open pores produced by pore bloating. For the specimen without any $Al_2$O$_3$ addition sintered at 1275$^{\circ}C$, the major phase was cristobalite, the small amount of mullite (3Al$_2$O$_3$ 2SiO$_2$) formed and the hematite (Fe$_2$O$_3$) remained. In the Clay-dust system body containing $Al_2$O$_3$ 15 wt%, however, the cristobalite disappeared and the major phase was mullite. Also the part of $Al_2$O$_3$ reacted with hematite to form hercynite (FeAl$_2$O$_4$). From the these results, addition of $Al_2$O$_3$ to Clay-dust system body enlarges a sintering range; decreasing an apparent density and absorption slop to sintering temperature owing to consumption of liquid phase SiO$_2$ at higher temperature and gas-forming component Fe$_2$O$_3$ at reduced atmosphere which would decrease an amount of liquid formed and increase the viscosity of the liquid produced during the sintering process.