• Korean Journal of Agricultural and Forest Meteorology
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• v.17 no.3
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• pp.254-260
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• 2015

Changes of the growth, quality and physiological response of Chinese cabbage cv 'Chunkwang' in response to five different temperature treatments based on climate change scenario were investigated during the growing season. The treatments consisted of normal year temperature $-2.0^{\circ}C$ (I), normal year temperature (II; Control group), normal year temperature $+2.0^{\circ}C$ (III), normal year temperature $+4.0^{\circ}C$ (IV), and normal year temperature $+6.0^{\circ}C$ (V). Regarding fresh weight, number of leaves, and leaf area were high in group IV, and V before the head formation stage, but it has decreased during the later growth period. Rate of frangibleness sympton was the highest in group V as 85.7%, and it was decreased in group IV (64.3%), group III (28.6%), group II (14.3%), and group I (7.1%). Regarding photosynthetic rate, group III, IV, and V showed relatively high photosynthetic rate at 20 DAP but it was reduced dramatically during the later growth period. Transpiration and stomatal conductance showed the similar trend with the photosynthetic rate. When comparing the chlorophyll fluorescence reaction of each treatment group at 50 DAP, Fv/Fm in group I was highest as 8.04 among all treatment groups and the lowest in group IV as 7.15.

• Journal of the Korean Chemical Society
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• v.47 no.6
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• pp.614-618
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• 2003

$Sr_2Ru_{1-x}Cu_xO_{4-y}(0.0{\le}x{\le}0.5)$ compounds were prepared using a conventional solid state reaction. Based on the Rietveld refinements of X-ray diffraction results, it is revealed that $Sr_2Ru_{1-x}Cu_xO_{4-y}$ compounds are the single phases with K2NiF4 type tetragonal system in the range of 0=x=0.3, while the mixed phases of$Sr_2RuO_4$ and $Sr_2CuO_3$ in the range of $0.4{\le}x{\le}0.5$. By means of X-ray photoelectron spectroscopy, the valence states of Ru and Cu in $Sr_2Ru_{1-x}Cu_xO_{4-y}$, have been confirmed to 4+ and 2+, respectively. The bond length difference between $Ru-O_1 ({\times}4)\;and\;Ru-O_2 ({\times}2)\;in\;RuO_6$ octahedron is gradually decreased with increasing Cu content in $Sr_2Ru_{1-x}Cu_xO_{4-y}$, which results in the lower c/a ratio. So, it might be assured that the variation of local symmetry of $RuO_6$ octahedron is very closely related to the transporting property of $Sr_2Ru_{1-x}Cu_xO_{4-y}$ compounds. The behavior of resistivity discloses that the metallic property in $Sr_2RuO_4$ changes into the semiconducting one in proportion to the Cu content in $Sr_2Ru_{1-x}Cu_xO_{4-y}$.

• Journal of Korean Society of Environmental Engineers
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• v.22 no.4
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• pp.765-773
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• 2000

The degradation of humic acid using $TiO_2$ coatings was studied, $TiO_2$ coatings were prepared by dip-coating method. Sol solutions for coating were prepared by mixing the gel, which can be produced by the reaction of $TiOCl_2$ and $NH_4OH$ solution, and hydrogen peroxide solution, and hydrolysis of titanium tetraisopropoxide (TTIP). It was shown from XRD that coatings from sol aged at $100^{\circ}C$ for 18h with titanium peroxo solution were crystallized to anatase in the range of temperatures of $25^{\circ}C$ to $500^{\circ}C$. In contrast, those coated from TTIP were crystallized to anatase at temperature above $400^{\circ}C$. So the sols originated from $TiCl_4$ can be applied for not only on the heat-resistance substrates but on the plastic substrates. Thickness and the quality of the films were dependent on the withdrawing speed, the concentration of sol, and the number of coating. The films showed various interference colors depending on the thickness of them. In the case that the films coated 2 times at withdrawing speed of 2.5cm per minute by 0.2M sol, the films had a transparent light blue color with thickness of around 50nm. It was known from the result of photo-degradation by $TiO_2$ coatings using humic acid that the removal efficiency of $COD_{cr}$ was over 85% after illumination of $UV/H_2O_2$ for 40min. and that of UV/VIS absorbable materials was over 95%.

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2003.05a
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• pp.91-93
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• 2003

A comprehensive numerical study is carried out to investigate for the understanding of the flow evolution and flame development in a supersonic combustor with normal injection of ncumally injecting hydrogen in airsupersonic flows. The formulation treats the complete conservation equations of mass, momentum, energy, and species concentration for a multi-component chemically reacting system. For the numerical simulation of supersonic combustion, multi-species Navier-Stokes equations and detailed chemistry of H2-Air is considered. It also accommodates a finite-rate chemical kinetics mechanism of hydrogen-air combustion GRI-Mech. 2.11[1], which consists of nine species and twenty-five reaction steps. Turbulence closure is achieved by means of a k-two-equation model (2). The governing equations are spatially discretized using a finite-volume approach, and temporally integrated by means of a second-order accurate implicit scheme (3-5).The supersonic combustor consists of a flat channel of 10 cm height and a fuel-injection slit of 0.1 cm width located at 10 cm downstream of the inlet. A cavity of 5 cm height and 20 cm width is installed at 15 cm downstream of the injection slit. A total of 936160 grids are used for the main-combustor flow passage, and 159161 grids for the cavity. The grids are clustered in the flow direction near the fuel injector and cavity, as well as in the vertical direction near the bottom wall. The no-slip and adiabatic conditions are assumed throughout the entire wall boundary. As a specific example, the inflow Mach number is assumed to be 3, and the temperature and pressure are 600 K and 0.1 MPa, respectively. Gaseous hydrogen at a temperature of 151.5 K is injected normal to the wall from a choked injector.A series of calculations were carried out by varying the fuel injection pressure from 0.5 to 1.5MPa. This amounts to changing the fuel mass flow rate or the overall equivalence ratio for different operating regimes. Figure 1 shows the instantaneous temperature fields in the supersonic combustor at four different conditions. The dark blue region represents the hot burned gases. At the fuel injection pressure of 0.5 MPa, the flame is stably anchored, but the flow field exhibits a high-amplitude oscillation. At the fuel injection pressure of 1.0 MPa, the Mach reflection occurs ahead of the injector. The interaction between the incoming air and the injection flow becomes much more complex, and the fuel/air mixing is strongly enhanced. The Mach reflection oscillates and results in a strong fluctuation in the combustor wall pressure. At the fuel injection pressure of 1.5MPa, the flow inside the combustor becomes nearly choked and the Mach reflection is displaced forward. The leading shock wave moves slowly toward the inlet, and eventually causes the combustor-upstart due to the thermal choking. The cavity appears to play a secondary role in driving the flow unsteadiness, in spite of its influence on the fuel/air mixing and flame evolution. Further investigation is necessary on this issue. The present study features detailed resolution of the flow and flame dynamics in the combustor, which was not typically available in most of the previous works. In particular, the oscillatory flow characteristics are captured at a scale sufficient to identify the underlying physical mechanisms. Much of the flow unsteadiness is not related to the cavity, but rather to the intrinsic unsteadiness in the flowfield, as also shown experimentally by Ben-Yakar et al. [6], The interactions between the unsteady flow and flame evolution may cause a large excursion of flow oscillation. The work appears to be the first of its kind in the numerical study of combustion oscillations in a supersonic combustor, although a similar phenomenon was previously reported experimentally. A more comprehensive discussion will be given in the final paper presented at the colloquium.

• Journal of the Korea Concrete Institute
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• v.27 no.2
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• pp.95-102
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• 2015

In this paper, the effects of sodium hydroxide (NaOH) and aluminum potassium sulfate ($AlK(SO_4)_2{\cdot}12H_2O$) dosage on strength properties were investigated. For evaluating the property related to the dosage of alkali activator, sodium hydroxide (NaOH) of 4% (N1 series) and 8% (N2 series) was added to 1~5% (K1~K5) dosage of aluminum potassium sulfate ($AlK(SO_4)_2{\cdot}12H_2O$) and 1% (C1) and 2% (C2) dosage of calcium oxide (CaO). W/B ratio was 0.5 and binder/ fine aggregate ratio was 0.5, respectively. Test result clearly showed that the compressive strength development of alkali-activated slag cement (AASC) mortars were significantly dependent on the dosage of NaOH and $AlK(SO_4)_2{\cdot}12H_2O$. The result of XRD analysis indicated that the main hydration product of $NaOH+AlK (SO_4)_2{\cdot}12H_2O$ activated slag was ettringite and CSH. But at early ages, ettringite and sulfate coated the surface of unhydrated slag grains and inhibited the hydration reaction of slag in high dosage of $NaOH+AlK(SO_4)_2{\cdot}12H_2O$. The $SO_4{^{-2}}$ ions from $AlK(SO_4)_2{\cdot}12H_2O$ reacts with CaO in blast furnace slag or added CaO to form gypsum ($CaSO_4{\cdot}2H_2O$), which reacts with CaO and $Al_2O_3$ to from ettringite in $NaOH+AlK(SO_4)_2{\cdot}12H_2O$ activated slag cement system. Therefore, blast furnace slag can be activated by $NaOH+AlK(SO_4)_2{\cdot}12H_2O$.

• Journal of the Korean Society of Food Science and Nutrition
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• v.13 no.3
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• pp.291-306
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• 1984

The possibility of formation of carcinogenic N-nitrosamines such as nitrosodimethylamine(NDMA), nitrosodiethylamine (NDEA) and nitrosopyrolidine (NPYR) during the fermentation of Kimchi was investigated. Three different types of Kimchi, formulated with chinese cabbage, red pepper powder and garlic, with or without one of both fermented shrimp and anchovy juice, were cured for 75 days at $5^{\circ}C$. The changes in contents of nitrates, nitrites, pH, ascorbic acid, secondary amines, trimethyl-aminoxide (TMAO), trimethylamine (TMA) and NDMA were analyzed periodically during the fermentation. TMAO, TMA. DMA, nitrate, nitrite and ascorbic acid were analyzed by colorimetric methods, and NDMA, NPYR and NDEA were determined by the method of GLC-TEA. Although the total secondary amines markedly increased, no significant changes in the levels of TMAO and TMA were observed during the fermentation Kimchi added with fermented shrimp or anchovy juice. The predominating component of secondary amines was confirmed to be dimethylamine by means of nitrosating technique coupled with gas chromatography. No appreciable increase in the level of nitrites was appeared although nitrate level in the Kimchi apparently decreased. Non detectable or trace level of nitrosamine formation was detected whereas the nitrates fairly decreased during the fermentation of Kimchi. This could be explained by the fact that the lack of nitrites was resulted in the system due to rapid consumption of nitrites formed from nitrates by the reactions with ascorbic acid and amino acids which have been known as inhibitors of nitrosation reaction.

• Resources Recycling
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• v.5 no.4
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• pp.32-41
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• 1996

The objective of this study was to investigate the facton affecting the property of CaCO, farmed from CaClz-Na,CO,-HiOsystem. The effcct of the concentmtlon of reaclants, impurity, the pH of reaction, the addition of sccd crystal, and injectingvelocity af reaclant solution an thc yield oI CaCO; polymorphs. parlide size and whiteness of CaCO, were investigated. Thcmqor resulls are ;o fallows; I The optimum concentratinn of reildilnts for forming vaterlte and aragonite is the range of 0.1-1.0 mol/l, when the yicld of vittcrite and araga~nles howed 7542% and XU-90%. respedively. 2. Among thc composition of impunticscontained h limestone, Fe' decrease the wh~tcness nf CaCO;. md Mg" increase the yield of aragonite. 3. The pHrange of vaterite and aragonite are formed with high yield is 8-11, and Calcite is famed in pH 6-8 with big particle size of 1over and in pH 11-13 with small particle size of I under. 4. The yicld of calcite and aragonite was increased by addingthc seed cryst.al nf itself.d cryst.al nf itself.

• Korean Chemical Engineering Research
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• v.45 no.6
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• pp.656-662
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• 2007

Fuel reformer using plasma and shift reactor for CO oxidation were designed and manufactured as $H_2$ supply device to operate a polymer electrolyte membrane fuel cell (PEMFC). $H_2$ selectivity was increased by non-thermal plasma reformer using GlidArc discharge with Ni catalyst simultaneously. Shift reactor was consisted of steam generator, low temperature shifter, high temperature shifter and preferential oxidation reactor. Parametric screening studies of fuel reformer were conducted, in which there were the variations of the catalyst temperature, gas component ratio, total gas ratio and input power. and parametric screening studies of shift reactor were conducted, in which there were the variations of the air flow rate, stema flow rate and temperature. When the $O_2/C$ ratio was 0.64, total gas flow rate was 14.2 l/min, catalytic reactor temperature was $672^{\circ}C$ and input power 1.1 kJ/L, the production of $H_2$ was maximized 41.1%. And $CH_4$ conversion rate, $H_2$ yield and reformer energy density were 88.7%, 54% and 35.2% respectively. When the $O_2/C$ ratio was 0.3 in the PrOx reactor, steam flow ratio was 2.8 in the HTS, and temperature were 475, 314, 260, $235^{\circ}C$ in the HTS, LTS, PrOx, the conversion of CO was optimized conditions of shift reactor using simulated reformate gas. Preheat time of the reactor using plasma was 30 min, component of reformed gas from shift reactor were $H_2$ 38%, CO<10 ppm, $N_2$ 36%, $CO_2$ 21% and $CH_4$ 4%.

• Journal of the Society of Cosmetic Scientists of Korea
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• v.34 no.2
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• pp.117-127
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• 2008

In this study, the antioxidative effects, inhibitory effects on elastase, and components of Cayratia japonica extracts were investigated. The free radical(1,1-diphenyl-2-picrylhydrazyl, DPPH) scavenging activities($FSC_{50}$) of extract/fractions of Cayratia japonica were in the order: 50% ethanol extract(114.3 ${\mu}g/mL$)${\mu}g/mL$)${\mu}g/mL$). Reactive oxygen species(ROS) scavenging activities($OSC_{50}$) of some Cayratia japonica extracts in $Fe^{3+}-EDTA/H_2O_2$ system were investigated using the luminol-dependent chemiluminescence assay. The order of ROS scavenging activities were deglycosylated flavonoid aglycone fraction($OSC_{50},\;3.30{\mu}g/mL$)<50% ethanol extract(1.21 ${\mu}g/mL$)${\mu}g/mL$). Ethyl acetate fraction showed the most prominent scavenging activity. The protective effects of extract/fractions of Cayratia japonica on the rose-bengal sensitized photohemolysis of human erythrocytes were investigated. The Cayratia japonica extracts suppressed photohemolysis in a concentration dependent manner($1{\sim}25{\mu}g/mL$), particularly deglycosylated flavonoid aglycone fraction exhibited the most prominent celluar protective effect(${\tau}_{50}$, 175.05min at 25 ${\mu}g/mL$). Aglycone fractions obtained from the deglycosylation reaction of ethyl acetate fraction among the Cayratia japonica extracts, showed 2 bands in TLC and 2 peaks in HPLC experiments(360 nm). Two components were identified as luteolin(composition ratio, 47.50%), apigenin(52.50). TLC chromatogram of ethyl acetate fraction of Cayratia japonica extract revealed 3 bands and HPLC chromatogram showed 4 peaks, which were identified as luteolin-7-O-${\beta}$-D-glucopyranoside(composition ratio, 11.14%), apigenin-7-O-${\beta}$-D-glucuronopyranoside(15.38%), luteolin(23.55%) and apigenin(49.92%) in the order of elution time. The inhibitory effect of aglycone fraction on elastase($IC_{50},\;70.5{\mu}g/mL$) was very high. These results indicate that extract/fractions of Cayratia japonica can function as antioxidants in biological systems, particularly skin exposed to UV radiation by scavenging $^1O_2$ and other ROS, and protect cellular membranes against ROS. And component analysis of Cayratia japonica extract and antioxidative effects could be applicable to new cosmetics.

• Journal of the Society of Cosmetic Scientists of Korea
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• v.34 no.1
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• pp.25-35
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• 2008

In this study, the antioxidative effects and inhibitory effects on elastase and tyrosinase of Geranium nepalense extracts were investigated. The free radical(1,1-diphenyl-2-picrylhydrazyl, DPPH) scavenging activities ($FSC_{50}$) of extract/fractions of Geranium nepalense were in the order: 50% ethanol extract(15.0 ${\mu}g/mL$)${\mu}g/mL$). ${\mu}g/mL$). Reactive oxygen species (ROS) scavenging activities($OSC_{50}$) of some Geranium nepalense extracts on ROS generated in $Fe^{3+}-EDTA/H_2O_2$ system were investigated using the luminol-dependent chemiluminescense assay. The order of ROS scavenging activities were 50% ethanol extract($OSC_{50},\;0.23{\mu}g/mL$)${\mu}g/mL$)${\mu}g/mL$). Deglycosylated flavonoid fraction showed the most prominent scavenging activity. The protective effects of extract/fractions of Geranium nepalense on the rose-bengal sensitized photohemolysis of human erythrocytes were investigated. The Geranium nepalense extracts suppressed photohemolysis in a concentration dependent manner, particularly deglycosylated flavonoid fraction exhibited the most prominent celluar protective effect (${\tau}_{50}$, 676.7 min at 50 ${\mu}g/mL$). The inhibitory effect of aglycone fraction on tyrosinase($IC_{50}$, 70.0 ${\mu}g/mL$) and elastase ($IC_{50}$, 19.9 ${\mu}g/mL$) was very high. Aglycone fractions obtained from the deglycosylation reaction of ethyl-acetate fraction among the Geranium nepalense extracts, showed 2 bands in TLC and 2 peaks in HPLC experiments (370 nm). Two components were identified as quercetin(composition ratio, 15.3%), kaempferol(82.8%). These results indicate that extract/fractions of Geranium nepalense can function as antioxidants in biological systems, particularly skin exposed to UV radiation by scavenging $^1O_2$ and other ROS, and protect cellular membranes against ROS. And component analysis of Geranium nepalense extract and inhibitory activity on elastase of the aglycone fraction could be applicable to new functional cosmetics for smoothing wrinkles.