• Journal of the Korean institute of surface engineering
• /
• v.37 no.6
• /
• pp.319-325
• /
• 2004

Fe thin films containing Si particles were prepared on metallic substrates by electrodeposition method in sulfate solutions and the content of codeposited Si particles in the films was investigated as a function of applied current density, the content of Si particels in the solution, solution pH, solution temperature and concentration of $FeSO_4$$7H_2$O in the solution. The amount of Si codeposited in the film was not dependent on the applied current density, solution pH and solution temperature, while it was dependent on the content of Si particles in the solution and the concentration of $FeSO_4$$7H_2$O in the solution. The amount of Si codeposited in the film increased with increasing content of Si particles in the solution but reached a maximum value of about 6 wt% when the content of Si particles in the solution exceeds 100 g/l. On the other hand, the content of Si codeposited in the film increased up to about 17 wt% with decreasing concentration of $FeSO_4$$7H_2$O in the solution. These results would be applied to the fabrication of very thin Fe-6.5 wt% Si sheets for electrical applications.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
• /
• v.17 no.11
• /
• pp.1192-1198
• /
• 2004

Hole transporting polymer(poly［N-(p-diphenylamine)phenylmethacrylamide］, PDPMA) was doped with nile red dye at various concentrations to study the influence of doping on the energy transfer during light emitting processes. Organic LEDs composed of ITO/blend(PDPMA -nile red)/ Alq$_3$/Al as well as thin films of blend(PDPMA -nile red)/ Alq$_3$ were manufactured for investigating photoluminescence, electroluminescence, and current-voltage characteristics. Atomic Force Microscopy was also used to observe surface morphology of the blend films. It was found that such doping. significantly influences the efficiency of the energy transfer from the Alq$_3$ layer to blended layer and the optical/electrical properties could be optimized by choosing the right concentration of the dye molecule. The results also showed a interesting correlation with the morphological aspect, i.e. the optimum luminescence at the concentration with the least surface roughness. When the concentration of nile red was 0.8 wt%, the maximum energy transfer could be achieved.

• Journal of Korean Society of Water and Wastewater
• /
• v.20 no.6
• /
• pp.813-822
• /
• 2006

Soluble manganese removal was analyzed as a function of filter media, filter depth, presence or absence of chlorination, and surface manganese oxide concentration in water treatment processes. Sand, manganese oxide coated sand (MOCS), sand+MOCS, and granular activated carbon(GAC) were used as filter media. Manganese removal, surface manganese oxide concentration, turbidity removal, and regeneration of MOCS in various filter media were investigated. Results indicated that soluble manganese removal in MOCS was rapid and efficient, and most of the removal happened at the top of the filter. When filter influent (residual chlorine 1.0mg/L) with an average manganese concentration of 0.204mg/L was fed through a filter column, the sand+MOCS and MOCS columns can remove 98.9% and 99.2% of manganese respectively on an annual basis. On the other hand, manganese removal in sand and the GAC column was minimal during the initial stage of filtration, but after 8 months of filter run they removed 99% and 35% of manganese, respectively. Sand turned into MOCS after a certain period of filtration, while GAC did not. In MOCS, the manganese adsorption rate on the filter media was inversely proportional to the filter depth, while the density of media was proportional to the filter depth.

• Korean Journal of Materials Research
• /
• v.15 no.9
• /
• pp.604-607
• /
• 2005

Dependence of the crystallinity, surface roughness, carrier concentration, carrier mobility, electrical resistivity and transmittance of Al-doped ZnO films deposited on glass substrates by RF-magnetron sputtering on effects of the ratio of the RF power for AlZnO to that for ZnO (R) have been investigated. X-ray diffraction spectra show strong preferred orientation along the c-axis. The full width at half maximum (FWHM) of the ZnO (002) peak decreases slightly as R increases in the range of R<1.0, whereas it increases substantially in the range of R>1.0. Scanning electron micrographs (SEM) show that the ZnO film surface becomes coarse as R increases. The carrier concentration and the carrier mobility in the ZnO thin film are maximal for R=1.5 and 1.0, respectively. The electrical resistivity is minimal for R=1.0 The transmittance of the ZnO:Al film tends to increase, but to decrease slightly in the range of R>0.5. It may be concluded that the optimum R value is 1.0, considering all these analysis results. The cause of the changes in the structure and physical properties of ZnO thin films with R are also discussed.

• Journal of the Korean Society of Food Science and Nutrition
• /
• v.19 no.3
• /
• pp.234-238
• /
• 1990

The effects of salt concentration immersion time in a salt solution prior to air dehydration and heating of air temperature during dehydration upon the browning reaction and pyruvic acid content of air dried garlics to a 6.5% moisture content(wet basis) were analyzed by a response surface methodology(RSM), Those values were also predicted by using a second degree polynomial regression model. Heating of air temperature was the most significant factor affecting the both browning reaction and pyruvic acid content. Salt concentration had more influence to browning reaction than immersion time whereas immersion time was more impor-tant factor than salt concentration on a retention of pyruvic acid sugested different processing conditions. While the processing conditions to minimize the browning reaction(O.D=0.009) were 0.3% of salt solution 9 min of immersion time and 5$0^{\circ}C$ of air temperature compared to control(O.D=0.022) of air dehydration at 5$0^{\circ}C$ Pyruvic acid contents were maximized(174 $\mu$mole/g garlic solid) at the 0.1% of salt solution 3 min of immersion time and 5$0^{\circ}C$ of air temperature compared to control(147 $\mu$mole/g garlic solid) of air dehydration at 5$0^{\circ}C$

• International Journal of Air-Conditioning and Refrigeration
• /
• v.17 no.3
• /
• pp.88-93
• /
• 2009

Lubricant oil is needed in air conditioning and refrigeration system because the compressor requires oil to prevent surface to surface contact between its moving parts, to remove heat, to provide sealing, to keep out contaminants, to prevent corrosion, and to dispose of debris created by wear. Thus, the oil separation in an oil separator is one of the most important characteristics for proper compressor operation. In this study, a gravity type of oil separator is used. Oil separation characteristics have been investigated for $CO_2$/PAG mixture in the range of oil concentration 0 to 5 weight-percent and the mixture temperature range of $0^{\circ}C$ to $15^{\circ}C$ at 50 bar and $70^{\circ}C$ to $90^{\circ}C$ at 80 bar. The results obtained indicate that the oil separation is increased with an increase in the oil concentration. It is also found that the oil separation in liquid state is increased with an increase in the mixture temperature while the oil separation in gas state is decreased.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
• /
• v.26 no.8
• /
• pp.351-356
• /
• 2014

Typical trouble patterns in solar thermal systems include working fluid leakage and freezing other than breakdown of pump. A fluid sensor for measuring electric resistance of fluid was developed and installed at the top of the collector piping in order to check the fault of solar system. Working fluid level in the pipe was determined by measuring electric resistance from a fluid sensor. On the base of this, it was confirmed that the fluid sensor diagnoses leakage of fluid. Electric resistance of propylene glycol aqueous solution was measured in the range of $0{\sim}70^{\circ}C$ and 0~40% of concentration. The response surface analysis was performed by using a central composite design, and the regression equation was derived from the relationship between electric resistance, temperature, and concentration. Through the experiment in a real solar system, we can estimate a concentration of working fluid when a pump is not operating and predict a possibility of freezing. Finally, an effective algorithm for trouble shooting was proposed to operate and maintain the solar system.

• Environmental Engineering Research
• /
• v.23 no.4
• /
• pp.374-382
• /
• 2018

Petroleum hydrocarbons pollutants, such as diesel fuel, have caused ecosystem damage in terrestrial and aquatic habitats. They have been recognized as one of the most hazardous wastes. This study was designed to optimize the effect of Tween 80 concentration, nitrogen (N)/phosphorus (P) ratio and salinity level on diesel biodegradation by Vibrio alginolyticus (V. alginolyticus). Response surface methodology with Box-Behnken design was selected with three factors of Tween 80 concentration (0, 5, 10 mg/L), N/P ratio (5, 10, 15) and salinity level (15‰, 17.5‰, 20‰) as independent variables. The percentage of diesel degradation was a dependent variable for 14 d of the remediation period. The results showed that the percentages of diesel degradation generally increased with an increase in the amount of Tween 80 concentration, N/P ratio and salinity level, respectively. The optimization condition for diesel degradation by V. alginolyticus occurred at 9.33 mg/L of Tween 80, 9.04 of N/P ratio and 19.47‰ of salinity level, respectively, with percentages of diesel degradation at 98.20%. The statistical analyses of the experimental results and model predictions ($R^2=0.9936$) showed the reliability of the regression model and indicated that the addition of biostimulant can enhance the percentage of diesel biodegradation.

• Food Engineering Progress
• /
• v.21 no.3
• /
• pp.256-266
• /
• 2017

This study was designed to optimize ethanol extraction process of unfertilized corn silk (UCS) to maximize phytochemical contents and bioactivities. The response surface methodology (RSM) with central composite design (CCD) was employed to obtain the optimal extraction conditions. The influence of ethanol concentration, extraction temperature and extraction time on total polyphenol contents, total flavonoid contents, maysin contents, 2,2-diphenyl-1-picrylhydrazyl(DPPH) radical scavenging activities and tyrosinase inhibition were analyzed. For all dependable variables, the most significant factor was ethanol concentration followed by extraction temperature and extraction time. The following optimum conditions were determined by simultaneous optimization of several responses with the Derringer's desirability function using the numerical optimization function of the Design-Expert program: ethanol concentration 80.45%, extraction temperature $53.49^{\circ}C$, and extraction time 4.95 h. Under these conditions, the predicted values of total polyphenol contents, total flavonoid contents, maysin contents, DPPH radical scavenging activity and tyrosinase inhibition were $2758.74{\mu}g\;GAE/g$ dried sample, $1520.81{\mu}g\;QUE/g$ dried sample, 810.26 mg/100g dried sample, 56.86% and 43.49%, respectively, and the overall desirability (D) was 0.74.

• Journal of the Korean institute of surface engineering
• /
• v.55 no.6
• /
• pp.433-440
• /
• 2022

Environmental pollution caused by power plant exhaust gas is highlighted and eco-friendly regulations are being strengthened. However, due to the abundant reserves and low prices of coal, still the most used for power generation in the world. Therefore, flexible operation of coal-fired power plants to reduce emissions has become an inevitable option. However, lowering the output increases the possibility of acid dew point corrosion as the exhaust gas temperature decreases. The dew point corrosion occurs when condensable gases such as SO₃, HCl, NO₂ and H₂O cools below the saturation temperature. SO₃ is already well known to cause severe low- temperature corrosion in coal-fired power plants. Therefore, this study aims to prevent damage that may occur during operation by analyzing the dew point and corrosion resistance with exhaust gas temperature and sulfuric acid concentration of the power plant economizer tube.