• 한국산학기술학회논문지
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• 제12권9호
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• pp.4250-4256
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• 2011

활성증진 물질 Cu가 첨가된 Mn계 촉매를 제조하여 암모니아를 이용하여 질소산화물을 제거하는 SCR공정에서 질소산화물제거능을 측정하였다. 제조된 촉매를 사용하여 반응온도, 유량, 수분함량 그리고 산소농도에 대한 활성변화를 조사하였다. $H_2$-TPR 시스템에서 온도에 따른 촉매의 수소전환특성을 측정하였다. 수분공급유무를 조절함으로써 촉매반응에 대한 수분의 억제효과를 파악하였다. Mn-Cu계 촉매는 $160{\sim}260^{\circ}C$의 온도범위에서 높은 탈질효율을 보였다. 그리고 산소농도의 증가는 촉매활성 증진효과를 가져왔으나 수분함유는 촉매활성을 감소시키는 역할을 함을 알 수 있었다.

• 대한한방소아과학회지
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• 제35권4호
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• pp.156-166
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• 2021

Objectives The purpose of this study is to confirm the regulate effect of T helper (Th) 2 differentiation that Baekho-tang extract may produce to improves skin lipid barrier damages. Methods Four-weeks-old NC/Nga mice were divided into four groups: control group (Ctrl, n=10), lipid barrier eliminated group (LBE, n=10), Dexamethasone treatment after lipid barrier elimination group (DxT, n=10), and Baekho-tang extract treatment group after lipid barrier elimination group (BHTT, n=10). Baeko-tang extract was administered for 3 days after removal of the skin fat barrier in BHTT group. Then, we identified changes in external symptoms of the skin, factors affecting skin barrier such as potential of hydrogen (pH), filaggrin (FLG), transepidermal water loss (TEWL) and Th2 differentiation factors like Interleukin (IL)-4, Kallikrein Related Peptidase 7 (KLK7) and protease activated receptor 2 (PAR-2) through our immunohistochemistry. Results After lipid barrier elimination, the reduction of morphological skin inflammations was less in BHTT group than in LBE group and DxT group. Also, pH and TEWL were significantly decreased with BHTT group. However, FLG was significantly increased in BHTT group compared to LBE, DxT, and Ctrl group. All kinds of Th2 differentiation factors (IL-4, KLK7 and PAR-2) were also decreased in BHTT compared to the LBE and DxT. Conclusions As a result of this study, BHT administration decreased pH, TEWL, and increased FLG, thus participating in recovering damaged skin barrier. Since Th2 differentiation factors were decreased as well, BHT's regulatory effect in sequential immune reactions may be a possible explanation of how it enhances recovery of the damaged lipid barrier.

• 한국분말재료학회지
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• 제26권3호
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• pp.208-213
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• 2019

In this study, lanthanum oxide ($La_2O_3$) dispersed molybdenum ($Mo-La_2O_3$) alloys are fabricated using lanthanum nitrate solution and nanosized Mo particles produced by hydrogen reduction of molybdenum oxide. The effect of $La_2O_3$ dispersion in a Mo matrix on the fracture toughness at room temperature is demonstrated through the formation behavior of $La_2O_3$ from the precursor and three-point bending test using a single-edge notched bend specimen. The relative density of the $Mo-0.3La_2O_3$ specimen sintered by pressureless sintering is approximately 99%, and $La_2O_3$ with a size of hundreds of nanometers is uniformly distributed in the Mo matrix. It is also confirmed that the fracture toughness is $19.46MPa{\cdot}m^{1/2}$, an improvement of approximately 40% over the fracture toughness of $13.50MPa{\cdot}m^{1/2}$ on a pure-Mo specimen without $La_2O_3$, and this difference in the fracture toughness occurs because of the changes in fracture mode of the Mo matrix caused by the dispersion of $La_2O_3$.

• 한국분말재료학회지
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• 제28권3호
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• pp.216-220
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• 2021

The effect of tert-butyl alcohol (TBA) as a freezing solvent on the pore structure of a porous tungsten body prepared by freeze-drying is analyzed. TBA slurries with a WO3 content of 10 vol% are prepared by mixing with a small amount of dispersant and binder at 30℃. The slurries are frozen at -25℃, and pores are formed in the frozen specimens by the sublimation of TBA during drying in air. After hydrogen reduction at 800℃ and sintering at 1000℃, the green body of WO₃ is completely converted to porous W with various pore structures. Directional pores from the center of the specimen to the outside are observed in the sintered bodies because of the columnar growth of TBA. A decrease in pore directionality and porosity is observed in the specimens prepared by long-duration drying and sintering. The change in pore structure is explained by the growth of the freezing solvent and densification.

• 대한한방소아과학회지
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• 제36권1호
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• pp.57-64
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• 2022

Objectives The purpose of this study is to confirm the regulate effect of T helper (Th) 2 differentiation that Sabaek-san extract may produce to improves skin lipid barrier damage. Methods Four-weeks-old NC/Nga mice were divided into four groups: control group (Ctrl, n=10), lipid barrier eliminated group (LBE, n=10), Dexamethasone treatment after lipid barrier elimination group (DXT, n=10), and Sabaek-san extract treatment group after lipid barrier elimination (SBT, n=10). Sabaek-san extract was administered for 3 d after removal of the skin fat barrier in SBT group. Then, we identified changes in external symptoms of the skin, factors affecting skin barrier such as potential of hydrogen (pH), filaggrin, transepidermal water loss (TEWL) and Th2 differentiation factors like Interleukin (IL)-4, Kallikrein Related Peptidase 7 (KLK7), and protease activated receptor 2 (PAR-2) through our immunohistochemistry. Results After lipid barrier elimination, the reduction of morphological skin inflammations was less in SBT group than in LBE and DXT group. Also, pH and TEWL were significantly decreased with SBT group. However, filaggrin was significantly increased in SBT group compared to LBE, DXT, and Ctrl group. All kinds of Th2 differentiation factors (IL-4, KLK7 and PAR-2) were also decreased in SBT compared to the LBE and DXT. Conclusions As a result of this study, SBT administration decreased pH, TEWL, and increased filaggrin, thus participating in recovering damaged skin barrier. Since Th2 differentiation factors were decreased as well, SBT's regulatory effect in sequential immune reactions may be a possible explanation of how it enhances recovery of the damaged lipid barrier.

• 한국주조공학회지
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• 제41권6호
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• pp.543-549
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• 2021

알루미늄 주철은 내산화성, 내황화성 및 부식성이 우수하다. Ti, Ni 합금에 비해 비전략적 원소인 Fe를 사용하는 비용이 상대적으로 저렴하여 구조재 및 스테인리스강의 대체재로 기대되고 있다. 이는 스테인리스 스틸을 사용하는 경우에 비해 약 30%의 중량 감소 효과를 가져온다. 알루미늄 합금의 경우 최근 몇 년간 주철의 합금원소로 널리 사용되고 있는 원소이다. 실온에서 연성이 부족하고 600℃를 초과하면 강도가 급격히 감소하여 실용화가 지연되었다. 실온 연성이 약한 원인은 수소에 의한 환경 취화로 알려져 있으며, 이러한 특성의 약점을 개선하기 위해 다양한 합금원소의 첨가가 시도되고 있다. 회주철의 경도와 내마모성을 높이기 위해 주로 바나듐, 크롬, 망간 등의 합금원소를 사용하고 있지만, 이러한 원소를 포함하는 완제품의 가격과 합금화의 문제는 많은 한계가 있다.

• 한국분말재료학회지
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• 제29권3호
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• pp.247-251
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• 2022

This study demonstrates the effect of the compaction pressure on the microstructure and properties of pressureless-sintered W bodies. W powders are synthesized by ultrasonic spray pyrolysis and hydrogen reduction using ammonium metatungstate hydrate as a precursor. Microstructural investigation reveals that a spherical powder in the form of agglomerated nanosized W particles is successfully synthesized. The W powder synthesized by ultrasonic spray pyrolysis exhibits a relative density of approximately 94% regardless of the compaction pressure, whereas the commercial powder exhibits a relative density of 64% under the same sintering conditions. This change in the relative density of the sintered compact can be explained by the difference in the sizes of the raw powder and the densities of the compacted green body. The grain size increases as the compaction pressure increases, and the sintered compact uniaxially pressed to 50 MPa and then isostatically pressed to 300 MPa exhibits a size of 0.71 m. The Vickers hardness of the sintered W exhibits a high value of 4.7 GPa, mainly due to grain refinement.

• 대한한방내과학회지
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• 제42권6호
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• pp.1269-1284
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• 2021

Objectives: Phragmitis Rhizoma is the fresh or dried rhizome of Phragmites communis Trin., which has been prescribed in traditional Korean medicine to relieve fever and vomiting and to nourish the body fluids. Recently, the protective effect of Phragmitis Rhizoma extract or its components on myelotoxicity and inflammatory responses have been reported, but no study has yet been conducted on oxidative stress. Methods: The present study investigated whether an ethanol extract of Phragmitis Rhizoma (PR) could protect against cellular damage induced by oxidative stress in Chang liver cells. Results: Pretreatment with PR significantly suppressed the hydrogen peroxide (H₂O₂)-induced reduction of Chang cell viability and generation of reactive oxygen species (ROS), thereby deferring apoptosis. PR also markedly inhibited H₂O₂-induced comet tail formation and phospho-γH2AX expression, suggesting that PR protected against oxidative stress-mediated DNA damage. PR also effectively prevented the inhibition of ATP synthesis in H₂O₂-treated Chang cells by inhibiting the loss of mitochondrial membrane potential, indicating that PR maintains energy metabolism through preservation of mitochondrial function while eliminating ROS generated by H₂O₂. Immunoblotting results indicated that PR attenuated the H₂O₂-induced downregulation of Bcl-2 and upregulation of Bax expression. Conclusions: PR protects against oxidative injury in Chang liver cells by regulating energy homeostasis via ROS generation blockade, which is at least partly mediated through inactivation of the mitochondria-mediated apoptosis pathway.

• 대한본초학회지
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• 제28권6호
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• pp.79-86
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• 2013

Objectives : The purpose of this study is to investigate neuroprotective effects and molecular mechanisms of luteolin against ${\beta}$-amyloid ($A{\beta}_{25-35}$)-induced oxidative cell death in BV-2 cells. Methods : The protective effects of luteolin against $A{\beta}_{25-35}$-induced cytotoxicity and apoptotic cell death were determined by MTT dye reduction assay and TUNEL staining, respectively. The apoptotic cell death was further analyzed by measuring mitochondrial transmembrane potential and expression of pro- and/or anti-apoptotic proteins. To elucidate the molecular mechanisms underlying the protective effects of luteolin, intracellular accumulation of reactive oxygen species, oxidative damages, and expression of antioxidant enzymes were examined. Results : Luteolin pretreatment effectively attenuated $A{\beta}_{25-35}$-induced apoptotic cell death indices such as DNA fragmentation, dissipation of mitochondrial transmembrane potential, increased Bax/Bcl-2 ratio, and activation of c-Jun N-terminal kinase and caspase-3 in BV-2 cells. Furthermore, $A{\beta}_{25-35}$-induced intracellular formation of reactive oxygen species and subsequent oxidative damages such as lipid peroxidation and depletion of endogenous antioxidant glutathione were suppressed by luteolin treatment. The neuroprotective effects of luteolin might be mediated by up-regulation of cellular antioxidant defense system via up-regulation of ${\gamma}$-glutamylcysteine ligase, a rate-limiting enzyme in the glutathione biosynthesis and superoxide dismutase, an enzyme involved in dismutation of superoxide anion into oxygen and hydrogen peroxide. Conclusions : These findings suggest that luteolin has a potential to protect against $A{\beta}_{25-35}$-induced neuronal cell death and damages thereby exhibiting therapeutic utilization for the prevention and/or treatment of Alzheimer's disease.

• Journal of the Korean Wood Science and Technology
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• 제50권4호
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• pp.283-298
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• 2022

Wood has always been used for various day-to-day applications such as interior or exterior construction materials, and household products. However, it can undergo photodegradation and discoloration by environmental factors including ultraviolet (UV) light, and thus has shortened its service life. Bleaching or delignification of wood surfaces is a suitable solution to stabilize wood against weathering by UV because these techniques can alter or remove the chromophores in lignin, which is a main factor of wood discoloration. To improve the color stability of wood surface according to the lifespan, surface delignification was conducted using peracetic acid (PAA) and hydrogen peroxide (HP) on the woods of Larix kaempferi and Quercus mongolica. After the PAA treatment, L^* increased considerably from 60-70 to 90-95. Furthermore, wood surface color did not change significantly after UV exposure. The color differences (𝜟E^*) between before and after PPA treatment of wood showed the 4.8-12.2 of L. kaempferi, and 1.7-3.7 of Q. mongolica, respectively. The lignin-related peaks in Fourier transform infrared spectroscopy (FT-IR) spectra disappeared with increased duration of PAA treatment. These results confirmed that the lignin component was partially or completely removed after the PAA treatment; the color differences (𝜟E^*) clearly showed that there was a reduction in redness (a^*) and yellowness (b^*), and an increase in lightness (L^*) owing to the removal of lignin. Based on these results, this study demonstrated that the partial removal of lignin from wood surfaces is a fundamental method for resolving photo-degradation.