• Composites Research
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• v.12 no.3
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• pp.8-16
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• 1999

Carbon woven fabric/C/SiC composites were fabricated by multiple impregnations of carbon woven fabric/carbon preform with the polymer precursor of SiC, i.e., polycarbosilane. In addition, two kinds of low density carbon/carbon preforms which had different fiber volume fraction and fiber orientation, i.e., a carbon woven fabric(${\thickapprox}$55 vol%)/carbon and a chopped carbon fiber${\thickapprox}$40 vol%)/carbon composites, were reaction-bonded with a silicon melt at 1$700^{\circ}C$ in a vacuum to fabricate dense carbon fiber/Si/SiC composites. The reaction-bonding process increased the density to ~2.1 g/$cm^3$ from 1.6 g/$cm^3$ and 1.15 g/$cm^3$ of a carbon woven and a chopped carbon preforms, respectively. All of the composites fractured with extensive fiber pull-out. The higher the density the higher the stiffness and proportional limit stress. The mechanical properties obtained from a three-point bend and tension tests were compared. The ratios of the peak tensile stresses to the bending strengths of a carbon woven and a chopped carbon composites were about one-third, respectively. The carbon woven fabric/Si/SiC composites with density of 2.06 g/$cm^3$ showed ~120 MPa of ultimate strength and ~80 MPa of proportional limit in bend testing.

• Journal of Pharmaceutical Investigation
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• v.32 no.3
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• pp.185-190
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• 2002

To improve the solubility of poorly water-soluble drug and to develop a sustained release tablets, the need for the technique, the formation of solid dispersion with polymeric materials that can potentially enhance the dissolution rate and extent of drug absorption was considered in this study. The 1:1, 1:4, and 1:5 solid dispersions were prepared by spray drying method using PVP K30, ethanol and methylene chloride. The dissolution test was carried out at in phosphate buffer solution at $37^{\circ}C$ in 100 rpm. Solid dispersed drugs were examined using differential scanning calorimetry and scanning electron microscopy, wherein it was found that felodipine is amorphous in the PVP K30 solid dispersion. Felodifine SR tablets were prepared by direct compressing the powder mixture composed of solid dispersed felodipine, lactose, Eudragit and magnesium stearate using a single punch press. In order to develop a sustained-release preparation containing solid dispersed felodipine, a comparative dissolution study was done using commercially existing product as control. The dissolution rate of intact felodipine, solid dispersed felodipine and its physical mixture, respectively, were compared by the dissolution rates for 30 minutes. The dissolution rates of felodipine for 30 minutes from 1:1, 1:4, 1:5 PVP K30 solid dispersion were 70%, 78% and 90%. However, dissolution rate offelodipine from the physical mixture was 5% of drug for 30 minutes. Our developed product Felodipine SR Tablet showed dissolution of 17%, 50% and 89% for 1, 4, and 7 hours. This designed oral delivery system is easy to manufacture, and drug releases behavior is highly reproducible and offers advantages over the existing commercial product. The dissolution rate of felodipine was significantly enhanced, following the formation of solid dispersion. The solid dispersion technique with water-soluble polymer could be used to develop a solid dispersed felodipine SR tablet.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.18 no.11
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• pp.802-809
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• 2017

3D printing technology is a manufacturing process for products, in which polymer and metal materials are laminated to form structures. It is advantageous for manufacturing parts requiring a high degree of design freedom and functionality. In addition, it would be a suitable technology for the production of parts for railway vehicles in the future, due to the need to produce parts in small quantities. In order to fully exploit the advantages of 3D printing technology, it is necessary to consider the process characteristics during the design of the product. In this study, the redesign and manufacturing technology of the product considering the performance and process conditions were studied for the heat exchanger in the air compressor of railway vehicles, as a trial application of the 3D printing technique. First of all, the design concept to improve the performance of the heat exchanger was defined, and the design range was specified to satisfy the performance of the present heat exchanger analyzed experimentally. Then, the detailed design was revised considering the characteristics of the metal 3D printing process, such as the manufacturing restrictions and production time. Based on the final design, the product was fabricated by the 3D printing process using aluminum material, and it was confirmed that the dimensional accuracy was satisfied. The weight of the final product was reduced by 41% compared with the existing products. The results of this study will make it possible to develop an efficient product design process for 3D printing technology.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.18 no.2
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• pp.95-101
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• 2017

In this paper, the sizing removal condition for the pretreatment of composite materials is obtained numerically by applying an image processing algorithm and nickel-plated carbon fiber is fabricated by a dry process method to enhance its electromagnetic shielding performance. Sizings that are wrapped in a polymer type material during the manufacturing of carbon fiber should be removed for dry coating. A numerical value, that is the correlation, can be obtained by determining the regular pattern of the carbon fiber in the image taken by a scanning electron microscope (SEM) after the sizing is removed. The application of the proposed numerical method to the SEM image of the fiber after the sizing is removed with solution, compressed air, solution and compressed air (hybrid), showed that this method of eliminating the sizing is superior to the hybrid method. Then, by spreading the carbon fiber roll with the sizing removed, we were able to produce nickel plated carbon fiber by the roll-to-roll sputtering method. The electromagnetic shielding performance of the fabricated 30, 40 and 100 nickel coated carbon fibers was measured. The Korea Advanced Institute of Science and Technology evaluated the electromagnetic shielding performance of the 100 nickel-coated carbon fiber to have a maximum value of 73.2 (dB) and a minimum value of 66.7 (dB). This is similar to the electromagnetic shielding rate of copper and shows that this material can be used as a cable for EV / HEV automobiles.

• Journal of the Korean Applied Science and Technology
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• v.30 no.4
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• pp.701-714
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• 2013

Recently, due to the activation policy of biodiesel, the blending biodiesel to petroleum product is increasing. Low-temperature fluidity and oxidation stability are the most significant issues to the marketers and end users of biodiesel. Thus, the way to control the quality of biodiesel blended fuels was investigated by duplicating the real storage situation of biodiesel blended fuels and evaluating the effect of oxidation trend and quality degradation. From the results of oxidation degradation test of biodiesel blended fuels, no special quality degradation has been observed through the evaporation for 18 weeks in a summer season under a storage circumstance without exposure to the sun light. However, the severe quality degradation was observed in PE vessel in only 2 weeks of storage. This oxidation degradation was also verified with FT-IR spectrum change. However, the special symptom cannot be distinguished by the quality test because the quality specifications were satisfied despite of the drastic oxidation degradation. Namely, the problem in a vehicle could be occurred by oxidation materials(polymer, organic acid. etc.) under oxidation even though it satisfied the quality specification.

• Korean Chemical Engineering Research
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• v.48 no.1
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• pp.45-52
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• 2010

Two different imide oligomers(6FDA-ODA/APA and 6FDA-MDA/MA) having crosslinkable end groups were prepared by using a solution imidization method and their properties were investigated. Also, semi-interpenetrating polymer networks(semi-IPN) were prepared using the blends of imide oligomers with polyetherimide $Ultem^{(R)}$, which is used in dual-ovenable packaging materials. The characteristic properties of semi-IPN films were interpreted by using TGA, Thin Film Diffusion Analyzer, and WAXD. Molecular weights of imide oligomers were successfully controlled utilizing 2-aminophenylacetylene(APA) and maleic anhydride(MA) as an endcapping agent. Exotherm reactions by crosslinking appeared and the amount of exthotherm heat was linearly increased as the content of imide oligomers was increased. For semi-IPNs of $Ultem^{(R)}$ and imide oligomers, 5% and 10% weight loss temperatures increased as the contents of imide oligomers were increased. Diffusion coefficient and water uptake of semi-IPNs decreased as the content of imide oligomers was increased, which might be resulted from hydrophobic fluorine group and high packing density. It was concluded that relatively low thermal stability and hydrolytic stability of polyetherimide $Ultem^{(R)}$ were improved by incorporating new developed imide oligomers.

• Journal of the Society of Cosmetic Scientists of Korea
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• v.32 no.3 s.58
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• pp.141-148
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• 2006

This study is intended to analyze the impact of PMMA on color changes comparatively by making 2 types of cheek color items with red-color pigments: one containing PMMA, which is one of the recently developed circular polymers and used when producing color make-up items that have aero powder as the chief ingredient, and the other without it. To accomplish the purpose, we have reviewed literature on raw materials that have aero powder as the chief ingredient. Also, after making compounds of PMMA and pigments lot aero powder, such as Talc, Mica, OMC Talc As, Mica As, we examined them compared to those without PMMA using spectrophotometer, a questionnaire survey, and Digital camera. Besides, the particles were analyzed using SEM. As a result of the analysis, cosmetics containing PMMA represent more vivid and rich colors, putting on one's face softly. Since the entire specific surface area of PMMA is large enough to absorb oil evenly, it yields vivid and rich colors. But, Mica, one of natural pigments, shows a result as opposed to that of Mica As, one of silicon-compounded pigments, suggesting that pearl effect may possibly causes defused reflection. Based on these findings, it is expected that cosmetics will have more vivid colors, or improved color presentation, as well as the softer sense of touch when a circular polymer of PMMa is added to the manufacturing process of color make-up items.

• Journal of the Society of Cosmetic Scientists of Korea
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• v.42 no.1
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• pp.1-7
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• 2016

Highly porous polymethyl methacrylate (PMMA) microspheres impregnated by $TiO_2$ powder were prepared by spray drying method. The particle size and the porosity were controlled by optimizing the co-solvent ratio and the polymer concentration. $TiO_2$ powder was impregnated into the microspheres upto 74.6 wt% content based on the weight of the resultant $PMMA/TiO_2$ microspheres. SEM images showed that $TiO_2$ powder was well distributed throughout the inside of the microsphere. EDX mapping showed that the Ti signal was well detected from every part of the microspheres, which was the evidence of the formation of the $PMMA/TiO_2$ composite. Hg porosimetry result showed that the porosity was found to be over 50% regardless of the $TiO_2$ contents. The final product was found to have high oil-absorbing capacity and great hiding power, both of which are key properties in designing the microsphere materials for make-up cosmetics application.

• Journal of the Society of Cosmetic Scientists of Korea
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• v.38 no.1
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• pp.83-89
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• 2012

Medicinal herbs have been shown to have protective functions for skin and hair. We investigated the effects of complex of soluble ${\beta}$-cyclodextrin and phytochemicals on the functions of skin and hair. In previous report, we evaluated the safety of supramolecules and found their anti-microbial effects and anti-fungal effect against Gram (+) and Malassezia furfur which is known to cause dandruff. Here we present that functional supramolecules-containing cream promotes the biological skin activity by inducing the collagen formation. And treatment of supramolecules-containing hair tonic increased the rate of hair growth of mouse. Taken together, supramolecular cosmetic compounds containing water insoluble phytochemicals and water soluble ${\beta}$-cyclodextrin exhibit the potential ability for hair growth promotion and delaying the aging of skin.

• Journal of Hydrogen and New Energy
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• v.19 no.1
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• pp.18-25
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• 2008

The membrane electrode assembly(MEA) was prepared by a nonequilibrium impregnation- reduction (I-R) method. Nafion 117 and covalently cross-linked sulfonated polyetherether with tungsto- phosphoric acid (CL-SPEEK/TPA30) prepared by our laboratory, were chosen as polymer electrolyte membrane(PEM). $Pt(NH_3)_4Cl_2$, $RuCl_3$ and reducing agent $(NaBH_4)$ were used as electrocatalytic materials. Electrochemical activity surface area(ESA) and specific surface area(SSA) of Pt cathodic electrode with Nafion 117 were $22.48m^2/g$ and $23.50m^2/g$ respectively under the condition of 0.8 M $NaBH_4$. But Pt electrode prepared by CL-SPEEK/TPA30 membrane exhibited higher ESA $23.46m^2/g$ than that of Nafion 117. In case of Pt-Ru anodic electrode, the higher concentration of Ru was, the lower potential of oxygen reduction and region of hydrogen desorption was, and Pt-Ru electrode using 10 mM $RuCl_3$ showed best properties of SSA $34.09m^2/g$ with Nafion 117. In water electrolysis performance, the cell voltage of Pt/PEM/Pt-Ru MEA with Nafion 117 showed cell property of 1.75 V at $1A/cm^2$ and $80{\circ}C$. On the same condition, the cell voltage with CL-SPEEK/TPA30 was the best of 1.73 V at $1A/cm^2$.