• Journal of the Korean Society of Safety
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• v.7 no.3
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• pp.22-29
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• 1992

Emulsion-type cometics contain many kinds of carbon and energy source i.e., vegetable oil, mineral oil and carbohydrate etc., those can be used as nutrients and caused contamination by microbials. Thereby we have to keep cosmetics from the possibility of contamination by microbials. From this viewpoint, the purpose of this study is to get the data necessary not only to prevent dermatopathia occurred by microbials but also to sustain the quality. In this experiment, we observed how many Staphylococcus aureus were grown in the prepared cosmetics with or without antiseptics so as to prevent contamination. When the contamination proceed, the stability of phase was disturbed and creaming phenomina was happened with some discoloration and bad smell. About 40 days after, the pH was changed from 7.6 to 6.5 and the refractive index of cosmetic raw materials were changed from 1.4415 to 1.4490(water : oil=70:30). By adding antiseptics Into prepared cosmetics, the number of Staphylococcus aureus with challenge test method were decreased to 7$\times$103 cell/ml. For the antibacterial effect against Staphylococcus aureus, p-hydroxy benzoic acid propyl ester in phosphoric acid buffer solution was the best.

• Journal of the Korean Ceramic Society
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• v.54 no.3
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• pp.200-204
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• 2017

Molybdenum (Mo), an electrode material of alkali metal thermal-to-electric converters (AMTEC), facilitates grain growth behavior and forms Mo-Na-O compounds at high operating temperatures, resulting in reduced performance and shortened lifetime of the cell. Mo/TiN composite materials have been developed to provide a solution for such issues. Mo is a metal that possesses excellent electrical properties, and TiN is a ceramic compound with high-temperature durability and catalytic activity. In this study, a dip-coating process with an organic solvent-based slurry was used as an optimal coating method to achieve homogeneity and stability of the electrodes. Cell performance was evaluated under various conditions such as the number of coatings, ranging from 1 to 3 times, and heat treatment temperatures of $800-1100^{\circ}C$. The results confirmed that the cell yielded a maximum power of 9.99 W for the sample coated 3 times and heat-treated at $900^{\circ}C$.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.67 no.6
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• pp.753-758
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• 2018

We investigated annealing effects of seed layers on the properties of ZnO nanorods grown on the seed layers. ZnO nanorods were grown by a hydrothermal method. ~100 nm-thick ZnO films were sputtered on oxidized Si wafers and quartz as seed layers. The ZnO films were annealed at $400^{\circ}C$, $600^{\circ}C$, and $800^{\circ}C$, respectively. ZnO nanorods were grown at $90^{\circ}C$ for 3 hours in the mixed solution of zinc nitrate hexahydrate and hexamethylenetetramine. X-ray diffraction was carried out to estimate the crystallinity and strain of ZnO films and nanorods. A field emission scanning electron microscope was employed to observe the morphology of the films and nanorods. PL(photoluminescence) measurements were conducted with 266 nm light. It was found that the annealing of seed layers increase the growth rate of nanorods, and change compressive strain of nanorods to tensile strain. The intensity of PL in the UV region reduced by using the annealed seed layers.

• Journal of Surface Science and Engineering
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• v.36 no.4
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• pp.301-306
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• 2003

Multilayered WC-Ti/suv $1-x/Al_{x}$ N coatings were deposited on AISI D2 steel using cathodic arc deposition (CAD) method. These coatings contain structural defects such as pores or droplets. Thus, the substrate is not completely isolated from the corrosive environment. The growth defects (pores, pinholes) in the coatings are detrimental to corrosion resistance of the coatings used in severe corrosion environments. The localized corrosion behavior of the coatings was studied in deaerated 3.5 wt.% NaCl solution using electrochemical techniques (potentiodynamic polarization test) and surface analyses (GDOES, SEM, AES, TEM). The porosity was calculated from the result of potentiodynamic polarization test of the uncoated and coated specimens. The calculated porosity is higher in the $WC-Ti_{0.6}$ $Al_{0.4}$ N than others, which is closely related to the packing factor. The positive effects of greater packing factor act on inhibiting the passage of the corrosive electrolyte to the substrate and lowering the localized corrosion kinetics. From the electrochemical tests and surface analyses, the major corrosion mechanisms can be classified into two basic categories: localized corrosion and galvanic corrosion.

• Journal of Radiation Industry
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• v.6 no.3
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• pp.273-279
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• 2012

Silica hybrid silver nanoparticles showing the strong antimicrobial activity, in which nano-silver is bound to silica molecules, has been synthesized using ${\gamma}-irradiation$ at room temperature. The present study relates to an antimicrobial composition for coating fiber products comprising silica hybrid silver nanoparticles. In this study, we describe antimicrobial fiber products coated with the silica hybrid silver nanoparticles and a method of antimicrobially treating fiber products by coating the fiber products with the silica hybrid silver nanoparticles. The antimicrobial fiber products exhibited excellent antimicrobial effects. In detailed practice, when the present composition comprising nanosized silica-silver was applied to a cloth (fabric) in a concentration of $6.4mg\;yard^{-1}$, the viable cell number decreased to less than 10 cells before and after laundering, resulting in a reduction of 99.9% or greater in the viable cell number. The present composition displays long-lasting potent disinfecting effects on bacteria. Also, we investigated the toxicity of silica hybrid silver nanoparticles in rats. The skin of rats was treated with a 30 ppm nanoparticles solution ($2ml\;Kg^{-1}$) for 8 days. No toxicity was detected in the treatment. These results suggest that the fiber products coated with the silica hybrid silver nanoparticles can be used to inhibit the growth of various microorganisms.

• Journal of the Korea Society of Computer and Information
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• v.17 no.2
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• pp.87-94
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• 2012

Mechanical break system used in train, that mixed air break & electronic break system. this system suggest lots of ways for modify efficiency and solution of environmental problems due to recently intend to green growth. The mechanical break system has environmental & economical problem. Environmental sides(problem) are dust and noise etc and economical sides(problem) are replaced the spare parts that are breaking shoe and lining ect. For compensate those kind of weak points, we needs a wide territories of electronic break which is from high speed range to stop. This research is estimated the load torque due to an incline and stop the train method also check the characteristic of stop the train to estimate a torque follow the sharp drop.

• Journal of the Korean Crystal Growth and Crystal Technology
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• v.22 no.1
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• pp.5-10
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• 2012

In general, the fabrications of the LEDs with mesa structure are performed grown by MOCVD method. In order to etch and separate each chips, the LEDs are passed the RIE and scribing processes. The RIE process using plasma dry etching occur some problems such as defects, dislocations and the formation of dangling bond in surface result in decline of device characteristic. The SAG method has attracted considerable interest for the growth of high quality GaN epi layer on the sapphire substrate. In this paper, the SAG method was introduced for simplification and fabrication of the high quality epi layer. And we report that the size of selective area do not affect the characteristics of original LED. The diameter of SAG circle patterns were choose as 2500, 1000, 350, and 200 ${\mu}m$. The SAG-LEDs were measured to obtain the device characteristics using by SEM, EL and I-V. The main emission peaks of 2500, 1000, 350, and 200 ${\mu}m$ were 485, 480, 450, and 445 nm respectively. The chips of 350, 200 ${\mu}m$ diameter were observed non-uniform surface and resistance was higher than original LED, however, the chips of 2500, 1000 ${\mu}m$ diameter had uniform surface and current-voltage characteristics were better than small sizes. Therefore, we suggest that the suitable diameter which do not affect the characteristic of original LED is more than 1000 ${\mu}m$.

• Journal of Surface Science and Engineering
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• v.41 no.5
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• pp.181-188
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• 2008

A.C. impedance properties of HA/Ti compound layer coated Ti-30Ta-($3{\sim}15$)Nb alloys have been studied by electrochemical method. Ti-30Ta binary alloys contained 3, 7, 10 and 15 wt% Nb were manufactured by the vacuum furnace system. And then specimen was homogenized at $1000^{\circ}C$ for 24 hrs. The sample was cut and polished for corrosion test and coating. It was coated with HA/Ti compound layer by magnetron sputter. The non-coated and coated morphology of Ti alloy were analyzed by X-ray diffractometer (XRD), energy X-ray dispersive spectroscopy (EDX) and filed emission scanning electron microscope (FE-SEM). The corrosion behaviors were investigated using A.C. impedance test (PARSTAT 2273, USA) in 0.9% NaCl solution at $36.5{\pm}1^{\circ}C$. Ti-30Ta-($3{\sim}15\;wt%$)Nb alloys showed the ${\alpha}+{\beta}$ phase, and $\beta$ phase peak was predominantly appeared in the case of increasingly Nb contents. The microstructures of Ti alloy were transformed from needle-like structure to equiaxed structure as Nb content increased. From the analysis of coating surface, HA/Ti composite surface uniformed coating layer with 750 nm thickness. The growth directions of film were (211), (112), (300) and (202) for HA/Ti composite coating on the surface after heat treatment at $550^{\circ}C$, whereas, the growth direction of film was (110) for Ti coating. The polarization resistance ($R_p$) of HA/Ti composite coated Ti-alloys were higher than those of the Ti and HA coated samples in 0.9% NaCl solution at $36.5{\pm}1^{\circ}C$. Especially, corrosion resistance of Ti-Ta-Nb system increased as Nb content increased.

• Journal of the Korean Crystal Growth and Crystal Technology
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• v.21 no.4
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• pp.175-180
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• 2011

The doping effect of Cu in the Sr-doped lanthan manganites (LSM) has been investigated in terms of structural analysis and thermal expansion coefficient (TEC). The $La_{0.8}Sr_{0.2}Mn_{1-x}Cu_xO_3$ ($0{\leq}x{\leq}0.3$) were prepared by solid state reaction method and their crystal structure and TEC were measured. A decrease in the lattice parameters and the TEC were observed with increase eu content, whereas they were decreased for x = 0.3. For $0{\leq}x{\leq}0.2$, the decrease of the lattice parameter and the TEC with increase Cu content were attributed to the reduction of ionic radius of Cu ions due to the presence of $Cu^{3+}$ ions. For x = 0.3, however, the increase was originated from the formation of oxygen vacancies due 10 the presence of $Cu^{2+}$ and $Mn^{4+}$.

• Journal of the Korean Crystal Growth and Crystal Technology
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• v.26 no.4
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• pp.131-134
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• 2016

The conditions for chemical polishing and etching technique were investigated to reveal surface defects in RE : YAG ($RE=Nd^{3+},\;Er^{3+},\;Yb^{3+}$) single crystals grown by Czochralski method. The optimal condition for chemical polishing was in 85 % $H_3PO_4$ solution at $330^{\circ}C$ for 30 minutes with a specimen fixed in the vertical direction. In addition, the optimal condition for chemical etching was in 85 % $H_3PO_4$ solution at $260^{\circ}C$ for 1 hour, and $70{\sim}80{\mu}m$ sized triangular etch pits were observed on (111) face. As a result of defect density analysis, $1.9{\times}10^3/cm^2$ for Nd(1 %) : YAG, $4.3{\times}10^2/cm^2$ for Er(7.3 %) : YAG, and $5.1{\times}10^2/cm^2$ for Yb(15 %) : YAG were measured.