• Journal of the Korean institute of surface engineering
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• v.46 no.1
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• pp.16-21
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• 2013

CIGS (Cu-In-Ga-Se) films were deposited on the Mo coated soda lime glass (Mo/SLG) by RF magnetron sputtering using a single sintered target with different chemical compositions. Heat treatment of the CIGS films were carried out under three different conditions, 1step ($350^{\circ}C$ for 2 hour and $550^{\circ}C$ for 2 hour) and 2step ($350^{\circ}C$ for 1 hour and $550^{\circ}C$ for 1 hour). In the case of CIGS films post-annealed on 2step method, grain size remarkably increased compared to other methods, indicating that chemical composition [Cu/(Ga+In) = 1] of CIGS films was same as CIGS target. After heat treatment by 2step method, band gap energy of the CIGS film deposited at RF 80 W showed 1.4 eV which is broadly similar to identical band gap energy (1.2 eV) of CIGS film prepared by evaporation method. Therefore, 2step heat treatment method could be expected to low temperature process.

• Tribology and Lubricants
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• v.11 no.4
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• pp.45-52
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• 1995

The wear behavior of alumina short fiber reinforced tin-bronze matrix composites was studied at the room temperature and an elevated temperature. The effect of the composition of specimens and the variation of wear conditions on the wear properties was examined by a pin-on-disc type wear testing machine. The wear mechanism according to the compositon of specimens at various wear conditions was discussed by the observation of the microstructure and the analysis of the composition on the worn surfaces. A thicker oxide layer on worn surfaces led to a lower wear loss because of the lubricating effect of oxide layers between pin and disc. As the testing temperature was raised to 350$^{\circ}$C, the fiber reinforced composites exibited markedly increased wear resistance even at a higher applied load since the reinforcement of composites with alumina fibers was not affected to a large extent by raising temperature. The results obtained by AES and EDS analysis indicated that the oxide layer of the worn surfaces formed at 350$^{\circ}$C was proved as Fe-oxide. This was explained by the faster formation of Fe-oxide than Cu-oxide at 350$^{\circ}$C.

• Journal of Korea Foundry Society
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• v.20 no.4
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• pp.230-239
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• 2000

High pressure wear characteristics of DCI(Ductile Cast Iron) were investigated through unlubricated pin-on-disc wear test. Wear test were carried out at speed of 23m/min, under pressure of 3MPa and 3.3 MPa. Cu and/or Mn were added to examine the effect of alloying elements on the high pressure wear characteristics of DCI. To investigate the relationship between wear characteristics and mechanical properties of DCI, Brinell hardness and V-notched Charpy impact energy were tested. Wear surface of each specimen was observed by SEM to determine the wear mechanism of DCI under high pressure wear condition. In the mild wear region, wear characteristics of alloyed DCI specimens were very similar to that of unalloyed DCI. But mild-severe wear transition was occurred at different wear distance and wear rate of DCI specimens were changed by alloying elements. In severe wear condition, wear rate of DCI was dramatically increased by the addition of Mn. Although the addition of Cu 0.46wt% did not decrease the wear rate of DCI in the severe wear region, but it delayed the mild-severe wear transition. Under high pressure wear condition, wear rate and mild-severe wear transition were not concerned with hardness of DCI specimens, but they were deeply associated with impact energy changed by alloying elements.

• Journal of Korean Society for Atmospheric Environment
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• v.20 no.2
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• pp.185-193
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• 2004

A catalyst with CuO ceramic filter for simultaneous treatment of dust and HAP was prepared and characterized. Catalytic ceramic filter can not only potentially achieve the substantial savings in energy but provide with effective optimization and integration of process for simultaneous removal of SO$_2$, NO$_{x}$ and particulates from flue gases. Catalytic ceramic filters remove simultaneously particulates on exterior surface of filters and reduce NO to $N_2$ and $H_2O$ by SCR (Selective Catalytic Reduction) process. Preparation of catalyst impregnated ceramic filter with disk shape (Ψ 50) follow the processing of alumino-silicate ceramic filter, support impregnation and catalyst impregnation (copper oxide). Preparation routes of alumino-silicate catalyst carrier suitable for production of catalytic filters practically were studied and developed using the sol-gel and colloidal processing, homogeneous precipitation and impregnation method. Characterization of the catalyst, catalyst carrier catalytic filter materials have been performed the using various techniques such as BET, XRD, TGA, SEM. Combination of the sol-gel and colloidal processing and impregnation method is recommended to prepare catalyst carriers economically for catalytic filter applications.s.

• 한국해양학회지
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• v.6 no.2
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• pp.63-77
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• 1971

An year-long survey of chemical water quality for Lake Eui-am in Kang-won Province, Korea, was conducted from June 1970 to May 1971 to study the water quality and seasonal variations of productivities in relation to selected physical and chemical environmental factors. A monthly series of water samples were taken at the deepest basin of 18m depth of the lake. Water quality parameters determined were water temperature, Secchi disc reading(transparency), pH, O$\_$2/, CO$\_$2/, alkalinity, acidity, Cl, hardness, Ca, Mg, total residue, total ignitious residue, COD, BOD$\_$5/, nutrients, total-Fe, soluble Fe, Mn and Cu. On the whole, the results indicate that the chemical water quality of Lake Eui-am is high, and vary with season. The lake water is characterized that higher levels of dissolved oxygen(8.6 ml/L in mean of whole water) or percent saturation of dissolved oxygen(114%), and of nitrate nitrogen (523 $\mu\textrm{g}$/L). On the other hand, CO$\_$2/(9.6ppm), chlorides(3.5ppm), Ca(7.7ppm) Mg(2.2ppm), hardness(28.5ppm), silica(2.4ppm) and BOD$\_$5/(1.08ppm) are quite low. In terms of nutrient levels, the lake water exhibit slight signs of eutrophication. The high values for nitrate nitrogen, soluble iron and Cu of the lake water suggest that there are some imputs such as domestic and industrial discharges to the lake.

• Tribology and Lubricants
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• v.10 no.3
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• pp.39-46
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• 1994

In order to investigate the effect of the ceramic reinforcements on the wear properties of aluminum bronze composites, Cu-8wt%Al aluminum bronze alloys reinforced with the Saffil alumina short fiber were produced by the powder metallurgical method and tested by a pin-ondisc wear testing machine. The wear surfaces of the pin specimens and discs, wear debris, and the cross sections of the wear specimens were observed by SEM. The wear mechanism according to various wear conditions and the change of microstructure in the composites were also discussed. In the results, the reinforcement of the composites with alumina short fiber was very effective at the higher applied load over 10N. The material transportation to the counter disc was observed in the alloy specimens without reinforcements. However, the composites reinforced with ceramic particles and fibers showed the resistance against the material transportation.

• Bulletin of the Korean Chemical Society
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• v.29 no.2
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• pp.389-392
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• 2008

High purity carbon nano fibers/tubes (CNF/Ts) which contain 97% pure graphitic carbon are prepared by a new catalytic method. These carbon nano fibers/tubes are ready to use without any further purification. The striking feature of this method is the production of carbon nano fibers/tubes of narrow distribution range. The developed catalytic method also produces pure hydrogen. An additional advantage of this catalytic method is that catalyst can be reused without reactivation. Ni:Cu catalyst system is embodied into SCHOTT-DURAN filter disc of large pore size (40-100 mm). Due to the production of hydrogen in the reaction catalyst stability is enhanced and deactivation process is considerably slowed down.

• Journal of the Korean Society of Food Science and Nutrition
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• v.41 no.8
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• pp.1049-1056
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• 2012

The antioxidant activities and antibacterial activities of grape pomace fermented using a variety of useful microorganisms were analyzed. There were several experimental groups: the control, with non-fermented grape pomace; the BS group, fermented by Bacillus subtilis; the LP group, fermented by Lactobacillus plantarum; the LC group, fermented by L. casei; the CU group, fermented by Candida utilis; the Y1 group, fermented by Saccharomyces cerevisiae strain CHY1011; the Y2 group, fermented by S. cerevisiae strain ZP 541; and the M group, fermented by a mixed strain culture of LP, LC, and CU. The yield of freeze-dried powder of fermented grape pomace by BS, LP, LC, CU, Y1, Y2, and M was 10.74%, 9.36%, 8.68%, 9.55%, 7.49%, 9.60%, and 9.71% w/w, respectively. The total polyphenol content of grape pomace showed the highest value in the control, but the fermented LP had higher total polyphenol content than those of other fermented grape pomace. The control and fermented LP had 0.16 mg/mL and 0.28 mg/mL as $IC_{50}$ values on DPPH radical scavenging, and 0.22 mg/mL and 0.53 mg/mL of ABTS radical scavenging activity, respectively. The FRAP value (5 mg/mL) showed the highest value on fermented LP (2.44 mM) but did not show a significant difference in the control group (12.27 mM). The fermented LC showed the antimicrobial activities against B. cereus (11 mm), B. subtilis (11 mm), Staphylococcus aureus (12 mm), Escherichia coli (12 mm), Enterobacter cloacae (10.5 mm), Salmonella enterica (11.5 mm), and Pseudomonas aerugionsa (11 mm) at 5 mg/disc, but the control and other fermented grape pomace did not show antimicrobial activities. Thus, fermented grape pomace by LC is shown to be producing a material that has antibacterial activity. In conclusion, grape pomace fermentation using various lactic acid bacteria strains showed excellent effects in promoting the production of functional materials. Especially, using L. casei exhibited an increase in antibacterial activity, and using L. plantarum exhibited antioxidant activity.

• Microbiology and Biotechnology Letters
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• v.25 no.2
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• pp.166-172
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• 1997

Aspergillus niger was selected as a strain producing the potent raw starch hydorlyzing enzyme. These experiments were conducted to investigate the conditions of the glucoa- mylase production, the purification of the enzyme, some characteristics of the purified enzyme and hydrolysis rate on various raw starches such as com, rice, potato, glutinous rice, sweet potato, wheat and barley. The optimum cultural temperature and time for the enzyme production on wheat bran medium were $30^{\circ}C$ and 96hrs, respectively. The respective addition of yeast extract and nutrient broth on wheat bran medium increased slightly the enzyme production. The enzyme was purified by ammonium sulfate fractionation and DEAE-cellulose column chromatography. The specific activity of the purified enzyme was 30.7u/mg-protein and the yield of enzyme activity was 25.8%. The purified enzyme showed a single band on polyacrylamide disc gel electrophoresis and its molecular weight was estimated to be 56,000 by SDS-polyacrylamide disc gel electrophoresis. The isoelectric point for the purified enzyme was pH3.7. The optimum temperature and pH were $65^{\circ}C$ and pH 4.0, respectively. The purified enzyme was stable in the pH range of pH 3.0-9.5 and below $45^{\circ}C$, and its thermal stability was slightly increased by the addition of $Ca^{2+}$. The purified enzyme was activated by $Co^{2+},\;Sr^{2+},\;Mn^{2+},\;Fe^{2+},\;Cu^{2+}$. Raw rice starch, raw corn starch, raw glutinous rice starch, raw sweet potato starch, raw wheat starch and raw barley starch showed more than 90% hydrolysis rate in 48hrs incubation. Even raw potato starch, most difficult to be hydrolyzed, showed 80% hydrolysis rate. The purified enzyme was identified as glucoamylase.

• Tribology and Lubricants
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• v.30 no.6
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• pp.330-336
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• 2014

Sintered metallic brake pads and low alloy heat resistance steel disks are applied to mechanical brake systems in high energy moving machines that are associated with recently developed 200km/h trains. This has led to the speed-up of conventional urban rapid transit. In this study, we use a lab-scale dynamometer to investigate the effects of the composition of friction materials on the tribological characteristics of sintered metallic brake pads and low alloy heat resistance steel under dry sliding conditions. We conduct test under a continuous pressure of 5.5 MPa at various speeds. To determine the optimal composition of friction materials for 200 km/h train, we test and the evaluate frictional characteristics such as friction coefficients, friction stability, wear rate, and the temperature of friction material, which depend on the relative composition of the Cu-Sn and Fe components. The results clearly demonstrate that the average friction coefficient is lower for all speed conditions, when a large quantity of iron power is added. The specimen of 25 wt% iron powder that was added decreased the wear of the friction materials and the roughness of the disc surface. However when 35 wt% iron powder was added, the disc roughness and the wear rate of friction materials increased By increasing the amount of iron powder, the surface roughness, and temperature of the friction materials increased, so the average friction coefficients decreased. An oxidation layer of $Fe_2O_3$ was formed on both friction surfaces.