• Journal of Environmental Science International
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• v.19 no.5
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• pp.577-584
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• 2010

The generation of $TiO_2$ nanoparticles by a thermal decomposition of titanium tetraisopropoxide (TTIP) was carried out experimentally using a tubular electric furnace at various synthesis temperatures (700, 900, 1100 and $1300^{\circ}C$) and precursor heating temperatures (80, 95 and $110^{\circ}C$). Effects of degree of crystallinity, surface area and anatase mass fraction of those $TiO_2$ nanoparticles on photocatalytic properties such as decomposition of methylene blue was investigated. Results show that the primary particle diameter obtained from thermal decomposition of TTIP was considerably smaller than the commercial photocatalyst (Degussa, P25). Also, those specific surface areas were more than 134.4 $m^2$/g. Resultant $TiO_2$ nanoparticles showed improved photocatalytic activity compared with Deggusa P25. This is contributed to the higher degree of crystallinity, surface area and anatase mass fraction of $TiO_2$ nanoparticles compared with P25.

• Composites Research
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• v.28 no.6
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• pp.340-347
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• 2015

As resin impregnates through the fiber preform in vacuum assisted resin transfer molding process, the volume of fibers is changed by expansion of fiber mat according to filling time. It causes not only the change in dimension but also the decrease of mechanical properties of the composite product. Moreover, it results in the economic loss by increase of the used amount of resin especially in the large product such as wind turbine blade. In this study, the ways to control fiber volume fraction were investigated by both the experimental and theoretical analyses on the expansion of fiber preform as the preform was impregnated by resin in the VARTM process. Two kinds of swelling stage were observed as flow front progressed, which was analyzed by comparing the experimental and simulation results. The process parameters are expected to be optimized by investigating the swelling behavior of fiber preform in the manufacturing process of the composite product.

• Composites Research
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• v.30 no.5
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• pp.310-315
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• 2017

In this study, we have investigated microstructure, mechanical properties and wear characteristic of aluminum metal matrix composites with a high volume fraction and uniformly dispersed SiC particles which produced by a liquid pressing process. The volume fraction of bimodal SiC/Al7075 composite was 12% higher than that of the monomodal SiC/Al7075 composite and a compressive strength is increased about 200 MPa. As a result of the abrasion test, the wear width and depth of the bimodal SiC/Al7075 composite were $285.1{\mu}m$ and $0.45{\mu}m$, respectively. The coefficient of friction of bimodal SiC/Al7075 was 0.16.

• Journal of Soil and Groundwater Environment
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• v.17 no.5
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• pp.20-30
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• 2012

In case of analyzing PAHs (EPA 16 compounds) in oil-contaminated soils, the lump of peaks may occur because of the aliphatic and polar compounds in oil. This phenomenon is due to the lower accuracy of the analysis. To solve this problem, evaluation of application of silicagel-alumina multi-layer fraction was performed using standard substances and oil-contaminated soils. As a result of application of silicagel-alumina multi-layer fraction cleanup method using standard substances, recovery rates of surrogate standards (5 compounds including Naphthalene-d8) were 83~100% and those of target standards were 75~129%. These were to meet the target values (60~130%) in this study. When used 4% water-silicagel column analyze PAHs in oil-contaminated soils, Some problems were generated for quantitative analysis of PAHs; concentration of PAHs was underestimated due to an upward baseline of internal standard (recovery rate: less than 60%) and overestimated by the lump of peaks which were not purified (the biggest recovery rate: more than 400%). On the other hand, in case of silicagel-alumina multi-layer fraction cleanup method, recovery rate of surrogate standards were 61~101.6%. Therefore this cleanup method was considered a valid method to improve accuracy of analysis of PAHs in oil-contaminated soils.

• Journal of the Korean Magnetics Society
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• v.22 no.6
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• pp.216-220
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• 2012

Magnetic properties of composite materials consisting of polymer filled with ferromagnetic powders (MnZn ferrite, Fe-Si alloy) were investigated in this study. The volume fraction of magnetic powders as fillers was varied from 70 % to 95 %. This paper presents the fabrication method of polymer magnetic composites in an effort to produce the 0-3 types of MnZn ferrite and FeSi as fillers with a proper complex permeability through the optimization of some experimental parameters. The polymer matrix composites were prepared by mixing the crushed ferrites and flaky FeSi powders homogenously with low-density resins (EPDM, epoxy). The relationships among the manufacturing technology of these materials, their filler volume fraction, as well as their complex permeability were measured and analyzed.

• Journal of Soil and Groundwater Environment
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• v.10 no.2
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• pp.44-51
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• 2005

Fractional composition and mobility of some heavy metals in sediments from Okdong stream are investigated. The fractional scheme for heavy metals in the sediment was established for five chemically defined heavy metal forms as adsorbed fraction, carbonate fraction, reducible fraction, organic fraction, and residual fraction. The most abundant fraction heavy metals in the sediments is reducible and secondly abundant is organic fraction. Adsorbed fraction is minor part of the total heavy metals. Mobilization of heavy metals in the sediments from Okdong stream occur $19.8{\sim}56.7%$ of total cadmium concentrate. The most abundant fraction of the sediment metal is organic fraction in Cu, Pb metals investigated. Labile fraction of sediment metals are $0.5{\sim}48.5%$ of total Zn, $2.6{\sim}48.1%$ of total Pb, and $0.2{\sim}36.9%$ of total Cu, respectively. Most of labile fraction consists of reducible fraction for Cd, Zn, adsorbed fraction for Pb, reducible fraction for Cu, adsorbed fraction for Ni. The Mobilization of Zn and Cu is most likely to occur when oxygen depletes and that of Pb and Ni occurs when physical impact, oxygen depletion and pH reduction.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2008.11a
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• pp.207-207
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• 2008

Modern industry has focused on processing that produce low- loss dielectric substrates used complex micron-sized devices using tick film technologies such as tape casting and slip casting. However, these processes have inherent disadvantages fabricating high density interconnect with embedded passives for high speed communication electronic devices. Here, we have successfully fabricated porous alumina dielectric layer infiltrated with polymer solution by using inkjet printing process. Alumina suspensions were formulated as dielectric ink that were optimized to use in inkjet process. The layer was confirmed by field emission scanning electron microscope (FE-SEM) for measuring microstructure and volume fraction. In addition, the reaction kinetics and electrical properties were characterized by FT-IR and the impedance analyzer. The volume fraction of alumina in porous dielectric alumina layer is around 70% much higher than that in the conventional process. Furthermore, after infiltration on the dielectric layer using polymer resins such as cyanate ester. Excellent Q factors of the dielectric is about 200 when confirmed by impedance analyzer without any high temperature process.

• Journal of Physiology & Pathology in Korean Medicine
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• v.17 no.5
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• pp.1288-1292
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• 2003

This study was carried out to evaluate cytotoxic effects of Houttuynia cordata T/sub HUNB/ extracts on A549 (lung cancer), MDA-MB231 (breast cancer), SNU-C4 (colon cancer) and B16 (mouse melanoma) cell lines. We have determined by 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyl-2H-tetrazoliumbromide (MTT) assay. The 150 ㎍/㎖ concentration of methanol extract (63.81 %) of Houttuynia cordata T/sub HUNB/ was shown significantly antitoxic activity on A549 cell lines. The order of cytotoxicity fractions of methanol from Houttuynia cordata T/sub HUNB/ extracts against cancer cell lines in vitro is as follows : hexane fraction layer > chloroform fraction layer > ethyl acetate fraction layer > buthanol fraction layer > water fraction layer. These results suggest that the hexane fraction of methanol extract from Houttuynia cordata T/sub HUNB/ extract may be a valuable choice for the development of antitumor agents.

• Journal of Animal Science and Technology
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• v.58 no.9
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• pp.33.1-33.7
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• 2016

Background: The continuing growth of the ethanol industry has generated large amounts of various distillers grains co-products. These are characterized by a wide variation in chemical composition and ruminal degradability. Therefore, their precise formulation in the ruminant diet requires the systematic evaluation of their degradation profiles in the rumen. Methods: Three distillers grains plus soluble co-products (DDGS) namely, corn DDGS, high-protein corn DDGS (HP-DDGS), and wheat DDGS, were subjected to an in situ trial to determine the degradation kinetics of the dry matter (DM) and crude protein (CP). Soybean meal (SBM), a feed with highly degradable protein in the rumen, was included as the fourth feed. The four feeds were incubated in duplicate at each time point in the rumen of three ruminally cannulated Hanwoo cattle for 1, 2, 4, 6, 8, 12, 24, and 48 h. Results: Wheat DDGS had the highest filterable and soluble A fraction of its DM (37.2 %), but the lowest degradable B (49.5 %; P < 0.001) and an undegradable C fraction (13.3 %; P < 0.001). The filterable and soluble A fraction of CP was greatest with wheat DDGS, intermediate with corn DDGS, and lowest with HP-DDGS and SBM; however, the undegradable C fraction of CP was the greatest with HP-DDGS (41.2 %), intermediate with corn DDGS (2.7 %), and lowest with wheat DDGS and SMB (average 4.3 %). The degradation rate of degradable B fraction ($%\;h^{-1}$) was ranked from highest to lowest as follows for 1) DM: SBM (13.3), wheat DDGS (9.1), and corn DDGS and HP-DDGS (average 5.2); 2) CP: SBM (17.6), wheat DDGS (11.6), and corn DDGS and HP-DDGS (average 4.4). The in situ effective degradability of CP, assuming a passage rate of $0.06h^{-1}$, was the highest (P < 0.001) for SBM (73.9 %) and wheat DDGS (71.2 %), intermediate for corn DDGS (42.5 %), and the lowest for HP-DDGS (28.6 %), which suggests that corn DDGS and HP-DDGS are a good source of undegraded intake protein for ruminants. Conclusions: This study provided a comparative estimate of ruminal DM and CP degradation characteristics for three DDGS co-products and SBM, which might be useful for their inclusion in the diet according to the ruminally undegraded to degraded intake protein ratio.

• Composites Research
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• v.34 no.2
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• pp.88-95
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• 2021

VARTM (Vacuum-assisted resin transfer molding) process is a low-cost process technology and affiliated with OoA (Out of Autoclave). Besides, it has been widely used in various fields. However, because of its lower quality than the autoclave process, it isn't easy to apply the VARTM process to the aerospace industry, which requires high reliability. The main problem of the VARTM process is the loss of mechanical properties due to the low fiber volume fraction and high void content in comparison to the autoclave. Therefore, many researchers have studied to reduce void and increase fiber volume fraction. This study examines whether the method of controlling atmospheric pressure could increase the fiber volume fraction and reduce void during the resin impregnation process. Reliability evaluation was confirmed by compressive strength test, fiber volume fraction analysis, and optical microscopy. As a result, it was confirmed that increasing the atmospheric pressure step by step in the VARTM process of impregnating the preform with resin effectively increases the fiber volume fraction and reduces void.