• Journal of Korean Society for Atmospheric Environment
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• v.22 no.3
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• pp.353-360
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• 2006

This study identified a particle size distribution (PSD) of fine particulate matter and emission characteristics of V and Ni by the comparison between anthropogenic sources of oil combustion (industrial boiler, oil power plant, etc.) and lab-scale combustion using a drop-tube furnace. In oil combustion source, the mass fraction of fine particles (less than 2.5 micrometers in diameter) was higher than that of coarse particles (larger than 2.5 micrometers in diameter) in $PM_{10}$ (less than 10 micrometers in diameter) as like in lab-scale oil combustion. In addition to this, it was identified that ultra-fine particles (less than 0.1 micrometers in diameter) had a large distribution in fine particles. Toxic metals like V and Ni had large mass fractions in fine particles, and most of all was distributed in ultra-fine particles. Most of ultra-fine particles containing toxic metals have been emitted into ambient by combustion source because it is hard to control by the existing air pollution control device. Hence, we must be careful on these pollutants because it is obvious that these are associated with adverse health and environmental effect.

• Journal of the Korean Ceramic Society
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• v.36 no.12
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• pp.1356-1363
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• 1999

Self-reinforced silicon carbide was prepared by hot pressing and the control of starting phases of raw materials and its microstructural characteristics was investigated. The specimens with self-reinforced microstructure were obtained from the compacts with mixed compositions of ${\alpha}$-and ${\beta}$-SiC powders. Self-reinforced microstructure which is composed of large dispersed grains with rod-like shape and matrix with small equiaxed grains was formed by the transformation to the ${\alpha}$-SiC with 4H polytype for ${\beta}$-SiC and anisotropic grain growth during the heat treatment. Of all speimens the values of volume fraction maximum length and aspect ratio for large grains with rode-like types were the highest at the specimen with 50 vol% ${\beta}$-SiC in the starting SiC powder and therefore this specimen showed the highest fracture toughness due to the crack deflection by rod-like grains during crack propagation.

• Journal of the Society of Cosmetic Scientists of Korea
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• v.43 no.3
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• pp.231-237
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• 2017

This study was performed to cytotoxicity, tyrosinase inhibition activity, intracellular melanin contents to verify the whitening effect of fraction from Glycine soja Siebold et Zucc. (G. soja). Using western blotting, tyrosinase expression in B16F10 melanoma cells and expression levels of tyrosinase related protein-1 (TRP-1) and protein-2 (TRP-2) were examined. As a result, all of the fractions showed a high cell viability over 82% at the concentrations of 0.125, 0.25, 0.5, 2.0 mg/mL. When the whitening effects of fractions from G. soja were tested using B16F10 melanoma cells treated with the ${\alpha}$-melanocyte stimulating hormone (${\alpha}-MSH$), the EtOAc fractions inhibited tyrosinase and melanogenesis effectively. The result of protein expression measurement using western blot showed that TRP-1, TRP-2 and tyrosinase protein expression in B16F10 melanoma cells treated with extracts decreased. Therefore, it is concluded that the fractions from G. soja have whitening effect by inhibiting protein related melanogenesis.

• Korean Journal of Materials Research
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• v.26 no.12
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• pp.688-695
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• 2016

Recrystallization behavior has been investigated for commercial purity AA1050 (99.5wt%Al) and high purity 3N Al (99.9wt% Al). Samples were cold rolled with 90% of thickness reduction and were annealed isothermally at 290, 315, and 350o C for various times until complete recrystallization was achieved. Hardness measurement and Electron Backscatter Diffraction(EBSD) analyses, combined with Grain Orientation Spread(GOS), were employed to investigate the recrystallization behavior. EBSD analysis combined with GOS were distinctly revealed to be a more useful method to determine the recrystallization fraction and to characterize the recrystallization kinetics. As the annealing temperature increased, recrystallization in AA1050 accelerated more than that process did in Al 3N. Both AA1050 and Al 3N showed the same temperature dependence of the n value of the Johnson-Mehl-Avrami-Kolmogorov equation(JMAK equation), i.e., n values increased as annealing temperature increased. Activation energy of recrystallization in AA1050 is about 176 kJ/mol, which is comparable with the activation energy of grain boundary migration in cold-rolled AA1050. This value is somewhat higher than the activation energy of recrystallization in Al 3N.

• Korean Journal of Clinical Pharmacy
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• v.21 no.2
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• pp.145-155
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• 2011

The objective of this study was to determine whether any pretreatment parameters were associated with pharmacological effect or toxicity parameters after vincristine administration and to describe a mathematical model, which explains the interpatient pharmacodynamic variability. The relationship between patient characteristics and vincristine dose and hematological toxicity were evaluated. 68 pediatric and adolescence patients and 107 adults with acute lymphoblastic leukemia were treated with vincristine $1.5mg/m^2/day$ IV and other anticancer drugs as scheduled. Complete blood counts and other blood test results were obtained. The input variables were age, gender, weight, lean body weight (LBW), height, body surface area, vincristine dose and total vincristine dose. The outcome measures were nadir values (white blood cells, absolute neutrophil counts, hemoglobin, and platelets); the absolute decrease, relative decrease, and survival fraction of blood cells. Polynomial regression analysis was carried out to determine the other significant covariates. The variability of $WBC_{nadir}$ was modeled with good precision and accuracy with a two-covariate model. This model should be validated and improved on with further clinical data. We believe that such pharmacodynamic modeling should be explored further to determine its performance and clinical relevance compared with modeling using pharmacokinetic parameter.

• Journal of the Korean Solar Energy Society
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• v.36 no.4
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• pp.49-56
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• 2016

The objective of this work is to analyze the variation in energy performance for each flat plate collector connected in series. In this study, it was assumed that solar water heating system with annual solar fraction of 60% was installed in an office building in Seoul, South Korea. The transient energy performance corresponding to four cases, which are selected using different solar radiation and outdoor air temperature, is studied by analyzing the variation in outlet temperature, solar useful heat gain, and thermal efficiency of each collector. It is observed that the useful heat gain and the collector efficiency decrease continuously, and outlet temperature increases when increasing the number of collector connected in series. The long-term performance is assessed by evaluating the thermal efficiency of each collector for two solar radiation conditions ranging from 780 to $820W/m^2$ and from 380 to $420W/m^2$. It is found that the differences between the intercept and slope of the efficiency curves for first and eighth collectors are 3.68% and 6.74% for solar radiation of $800{\pm}20W/m^2$ and 8.57% and 12.90% for solar radiation of $400{\pm}20W/m^2$, respectively. In addition, it is interesting to note that annual useful heat gain and collector efficiency are reduced with similar rate of about 6.13% when increasing the collector area by connecting the collectors in series.

• The Korean Journal of Mycology
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• v.40 no.4
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• pp.258-265
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• 2012

Bacterial strains isolated from diseased red pepper fruits showed inhibitory effect on mycelial growth and spore germination of Colletotrichum gloeosporioides. The bacterium was identified as Paenibacillus sp. based on its physiological, biochemical characteristics and MicroLog analysis and named Paenibacillus sp. IUB225-08. The bacterium showed the highest level of antifungal activity C. gloeosporioides when cultured at $25^{\circ}C$ for 60 hrs in LB broth with initial pH of 7.0. The butanol fraction from culture extract of Paenibacillus sp. IUB225-08 effectively inhibited the mycelial growth and spore germination of C. gloeosporioides than any other agricultural chemicals tested. Pepper fruits and seeds treated with spores of C. gloeosporioides showed symptoms, while those treated with the culture extract and C. gloeosporioides together did not show any symptoms. Therefore, the culture extract of Paenibacillus sp. IUB225-08 have a potential for biocontrol agent of red pepper anthracnose.

• Journal of Information Display
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• v.7 no.3
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• pp.13-18
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• 2006

Currently, the flexible organic light emitting devices (OLEDs) are investigated. They are very vulnerable to moisture, and thus have been found to show some problems. Thus, an effective barrier layer is needed to protect from moisture in air. We deposited thin films with magnesium oxide (MgO) and silicon oxide $(SiO_{2})$ compounds mixed at various mixture ratios on flexible polyether sulfone (PES) substrates by an electron-beam evaporator to investigate their applizability for transparent barrier applications. In this study, we found that as the MgO fraction increased, thin films comprised of MgO and $(SiO_{2})$ compounds became more amorphous and their surface morphologies become smoother and denser. In addition, zirconium oxide $(ZrO_{2})$ was added to the above-mentioned compound mixtures. $ZrO_{2}$ made thin mixture films more amorphous and made the surface morphology denser and more uniform. The water vapor transmission rates (WVTRs) of the whole films decreased rapidly. The best WVTR was obtained by depositing thin films of Mg-Si-Zr-O compound among the whole thin films. As the thin mixture films became more amorphous, and the surface morphology become denser and more uniform, the WVTRs decreased. Therefore, the thin mixture films became more suitable for flexible OLED applications as transparent passivation layers against moisture in air.

• Journal of Powder Materials
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• v.19 no.1
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• pp.25-31
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• 2012

In this study, a high energy ball milling process was employed in order to improve the densification of direct nitrided AlN powder. The densification behavior and the sintered microstructure of the milled AlN powder were investigated. Mixture of AlN powder doped with 5 wt.% $Y_2O_3$ as a sintering additive was pulverized and dispersed up to 50 min in a bead mill with very small $ZrO_2$ beads. Ultrafine AlN powder with a particle size of 600 nm and a specific surface area of 9.54 $m^2/g$ was prepared after milling for 50 min. The milled powders were pressureless-sintered at $1700^{\circ}C-1800^{\circ}C$ for 4 h under $N_2$ atmosphere. This powder showed excellent sinterability leading to full densification after sintering at $1700^{\circ}C$ for 4 h. However, the sintered microstructure revealed that the fraction of yitttium aluminate increased with milling time and sintering temperature and the newly-secondary phase of ZrN was observed due to the reaction of AlN with the $ZrO_2$ impurity.

• Advances in nano research
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• v.13 no.4
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• pp.313-323
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• 2022

The microstructure and mechanical properties of Cr-Ni steel and Cr-Ni steel-matrix nanocomposites reinforced with nano-ZrO₂ particles were investigated in this study. Cr-Ni steel and Cr-Ni/ZrO₂ nanocomposites were produced using a combination of high-energy ball milling, pressing, and sintering processes. The microstructures of the specimens were analyzed using EDX and XRD. Compression and hardness tests were performed to determine the mechanical properties of the specimens. Nano-ZrO₂ particles were effective in preventing chrome carbide precipitate at the grain boundaries. While t-ZrO₂ was detected in Cr-Ni/ZrO₂ nanocomposites, m-ZrO₂ could not be found. Few α'-martensite and deformation bands were formed in the microstructures of Cr-Ni/ZrO₂ nanocomposites. Although nano-ZrO₂ particles had a negligible impact on the strength improvement provided by deformation-induced plasticity mechanisms in Cr-Ni/ZrO₂ nanocomposites, the mechanical properties of Cr-Ni steel were significantly improved by using nano-ZrO₂ particles. The hardness and compressive strength of Cr-Ni/ZrO₂ nanocomposite were higher than those of Cr-Ni steel and enhanced as the weight fraction of nano-ZrO₂ particles increased. Cr-Ni/ZrO₂ nanocomposite with 5wt.% nano-ZrO₂ particles had almost twofold the hardness and compressive strength of Cr-Ni steel. The nano-ZrO₂ particles were considerably more effective on particle-strengthening mechanisms than deformation-induced strengthening mechanisms in Cr-Ni/ZrO₂ nanocomposites.