• Laser Solutions
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• v.4 no.2
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• pp.13-19
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• 2001

When a high-power laser beam is irradiated on the surface of material, it is well known that a cavity, called a keyhole induced by the pressure action of the vapor plume, is generated in the molten material. This paper describes the interaction between a pulsed CO$_2$ laser beam and water. The laser-beam is used to generate and maintain a conical depression in the water surface similar to the keyhole created during laser penetration welding. Experimental results show that the depth of laser-beam penetration is limited by hydrodynamic instability. The instability of the surface cavity can be understood by the capillary instability of a hollow jet. Theoretical computation of the steady keyhole shape has been performed. modifying the model suggested by Andrews et al. (1976). The model predicts the qualitative behavior of the keyhole but significantly underestimates the average diameter.

• The Bulletin of The Korean Astronomical Society
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• v.44 no.1
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• pp.41.3-41.3
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• 2019

Ices in interstellar environments are well traced mostly by their absorption features in the near- to mid-infrared spectrum. The infrared camera (IRC) aboard AKARI provides us the near-infrared spectroscopic data which cover $2.5-5.0{\mu}m$ with a spectral resolution of R ~ 120. Our AKARI spectroscopic survey of young stellar objects (YSOs), including low-luminosity protostars and background stars, revealed the absorption features of $H_2O$, $CO_2$, CO, and XCN ice components. We present near-infrared spectra of the observed targets and compare their ice abundances with those previously derived from various YSOs and the background stars behind dense molecular clouds and cores. In addition, we suggest possible science cases for SPHEREx, NASA's new near-infrared space observatory, based on the results from our AKARI IRC spectroscopic study.

• The Korea Journal of Herbology
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• v.37 no.6
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• pp.19-28
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• 2022

Objectives : To develop natural ingredients that help prevent or treat anti-inflammatory-related diseases and use themas basic data, we investigated anti-inflammatory activity of Cynanchi Atrati Radix Et Rhizoma water extracts(CWE) in lipopolysaccharide(LPS)-induced murine macrophage cell line, RAW 264.7 cells. Methods : The cell viabilities were evaluated with RAW 264.7 cells. The production of nitric oxide(NO), prostaglandin E2(PGE2), pro-inflammatory cytokines such tumor necrotic factor(TNF)-α and interleukin(IL)-6 were assessed in LPS-induced RAW 264.7 cell treated with CWE. Furthermore, the protein expression of inducible nitric oxide synthase (iNOS), cyclooxygenase-2(COX-2), and mitogen-activated protein kinase(MAPK) were assessed by western blotting. Results : In RAW 264.7 cell, the cell viability by CWE treatment was more than 98.4% at a concentration of 100-400 ㎍/mL. At a concentration of 800 ug/ml of CWE, the cell viability was as low as 86%. At doses of 100, 200 and 400 ㎍/mL, CWE inhibited the production of NO, PGE2, TNF-𝛼 and IL-6 in a dose-dependent manner and also decreased the expression of iNOS and COX-2 from LPS-induced RAW 264.7 cells. In addition, CWE significantly inhibited the MAPK pathway including decreased the phosphorylation of the p38, c-Jun N-terminal kinase(JNK) and extracellular signal-regulated kinase(ERK1/2). Conclusions : Our study provides evidence that CWE inhibits the production of main pro-inflammatory molecules in LPS-induced RAW 264.7 cells via expression of p38, JNK, and ERK1/2 MAPK signaling pathways. Therefore, CWE is expected to be widely used as a natural ingredient for anti-inflammatory functional foods or pharmaceuticals in the future.

• Bulletin of the Korean Chemical Society
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• v.33 no.12
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• pp.4028-4034
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• 2012

Tris(2-phenylphenoxo)aluminum ($(2-PhC_6H_4O)_3Al$) exists as a dimeric form in toluene. When toluene-insoluble anhydrous cobalt acetate is treated with tris(2-phenylphenoxo)aluminum in toluene, the toluene-soluble adduct $(2-PhC_6H_4O)_3Al{\cdot}Co(OAc)_2$ is formed. The 2-phenylphenoxo ligand in the adduct can be replaced with another aryloxo ligand to give (aryloxo)$(2-PhC_6H_4O)_2Al{\cdot}Co(OAc)_2$ (aryloxo = 2-methylphenoxo, 2-isopropylphenoxo, 4-methylphenoxo, 4-isopropylphenoxo, or 4-tert-butylphenoxo). These complexes are active for butadiene polymerization without gel formation when activated with an equivalent amount of $(2-PhC_6H_4O)AlEt_2$ for 2 h. The highest activity, 175 kg/mol-Co (turnover number, 3200) was achieved with $(2-PhC_6H_4O)_3Al{\cdot}Co(OAc)_2$ at $65^{\circ}C$ for 2 h. The microstructure of the polymer chains is mostly trans-1,4-configuration (70-75%) with the remaining being 1,2-vinyl. The cis-1,4-configuration observed by IR is minimal (1-5%). By replacing the 2-phenylpheoxo with a 4-alkylphenoxo ligand, the amount of 1,4-configuration slightly increases, resulting in increase in the endothermic melting signal at $-30{\sim}50^{\circ}C$ in the DSC curve. The molecular weights of the polymers are high ($M_n$: 300000~800000) with a fairly narrow molecular weight distribution ($M_w/M_n$, 2.0-2.7).

• Carbon letters
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• v.4 no.2
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• pp.57-63
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• 2003

In polymer precursor based activated carbon, the structure of starting material is likely to have profound effect on the surface properties of end product. To investigate this aspect phenolic resins of different types were prepared using phenol, mcresol and formaldehyde as reactants and $Et_3N$ and $NH_4OH$ as catalyst. Out of these resins two resol resins PFR1 and CFR1 (prepared in excess of formaldehyde using $Et_3N$ as catalyst in the basic pH range) were used as raw materials for the preparation of activated carbons by both chemical and physical activation methods. In chemical activation process both the resins gave activated carbons with high surface areas i.e. 2384 and 2895 $m^2/g$, but pore size distribution in PFR1 resin calculated from Horvath-Kawazoe method, contributes mainly in micropore range i.e. 84.1~88.7 volume percent of pores was covered by micropores. Whereas CFR1 resin when activated with KOH for 2h time, a considerable amount (32.8%) of mesopores was introduced in activated carbon prepared. Physical activation with $CO_2$ leads to the formation of activated carbon with a wide range of surface area (503~1119 $m^2/g$) with both of these resins. The maximum pore volume percentage was obtained in 3-20 ${\AA}$ region by physical activation method.

• Bulletin of the Korean Chemical Society
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• v.10 no.6
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• pp.535-543
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• 1989

We have investigated the infrared absorption spectra for carbon monoxide chemisorbed on reduced and oxidized Rh/$SiO_2$ with and without potassium coating within the frequency range of 1800-2200 $cm^{-1}$ at various Rh concentrations, CO pressures, and temperatures. In case of no potassium coating, only two bands at 2070 and 1900 $cm^{-1}$ appeared for CO adsorbed on reduced Rh/$SiO_2$ while for oxidized Rh/$SiO_2$ four bands were found at 2100, 2070, 2040, and 1900 $cm^{-1}$. We have successfully tried to explain the differences between our observations and those by other investigators who used the Rh/$Al_2O_3$ system instead of Rh/$SiO_2$ on the basis of the suggestions by Yates et al. Accordingly, we propose that the surface OH groups are deeply involved in producing the $Rh^{+1}$ sites which are responsible for the gem-dicarbonyl species. On coating with potassium all the IR bands for three carbonyl species were found to suffer red shift, the magnitude of which increased with increasing Rh/CO ratio.

• Journal of Microbiology and Biotechnology
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• v.29 no.6
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• pp.944-951
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• 2019

Lipases are industrial enzymes that catalyze both triglyceride hydrolysis and ester synthesis. The overexpression of lipase genes is considered one of the best approaches to increase the enzymatic production for industrial applications. Subfamily I.2. lipases require a chaperone or foldase in order to become a fully-activated enzyme. The goal of this research was to isolate, clone, and co-express genes that encode lipase and foldase from Burkholderia territorii GP3, a lipolytic bacterial isolate obtained from Mount Papandayan soil via growth on Soil Extract Rhodamine Agar. Genes that encode for lipase (lipBT) and foldase (lifBT) were successfully cloned from this isolate and co-expressed in the E. coli BL21 background. The highest expression was shown in E. coli BL21 (DE3) pLysS, using pET15b expression vector. LipBT was particulary unique as it showed highest activity with optimum temperature of $80^{\circ}C$ at pH 11.0. The optimum substrate for enzyme activity was $C_{10}$, which is highly stable in methanol solvent. The enzyme was strongly activated by $Ca^{2+}$, $Mg^{2+}$, and strongly inhibited by $Fe^{2+}$ and $Zn^{2+}$. In addition, the enzyme was stable and compatible in non-ionic surfactant, and was strongly incompatible in ionic surfactant.

• The Bulletin of The Korean Astronomical Society
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• v.37 no.1
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• pp.78.2-78.2
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• 2012

Orion A 분자운은 별탄생이 활발하게 일어나는 영역이면서 태양계에 비교적 가깝다. 그렇기 때문에 낮은 분해능으로도 자세한 관측이 가능하다. Orion A 분자운까지의 거리가 450 pc 이므로 대덕전파안테나 1' beam으로 0.13 pc 가 된다. 이곳에는 필라멘트 구조가 있는데 FCRAO를 통한 다파장관측을 통해서 필라멘트 구조가 확인되었다.(Melnick et al. 2011). 필라멘트는 길이 4.8 pc, 너비 1.5 pc 로 대덕전파망원경의 1' beam으로 자세한 관측이 가능하였다. 2010년 11월-2011년 5월까지 Orion A 분자운을 대덕전파망원경을 이용하여 $^{12}CO$, $^{13}CO$(J=1-0) 분자선 관측을 하였으며, 관측영역은 적경: 5h 32m - 5h 37m, 적위: $-5^{\circ}$ 14' - $-5^{\circ}$ 37'으로 ($1^{\circ}{\times}1^{\circ}$) 영역을 관측하였다. 그 결과 필라멘트구조를 확인할 수 있었으며 일자 형태로 분포되어 있다는 구조적 결과 얻었다. 관측된 필라멘트 덩어리의 전형적인 크기는 약 0.7 pc, 밀도는 약 $10^4cm^{-3}$, 질량은 약 500 $M_{\odot}$이다. 매우 밀한 곳은 1000 M${\bigodot}$이상의 질량분포도 나타내고 있다. 이것은 이 지역이 일반적인 분자운과 비교했을 때 고밀도 영역임을 나타내고 있다. 더욱 자세한 밀도구조와 질량분포를 밝혀보고 별탄생과의 관련성을 연구하고자 한다.

• Journal of Wetlands Research
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• v.14 no.4
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• pp.597-605
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• 2012

This study was conducted in order to determine changes in the growth responses of Quercus serrata and Q. aliena which are potential natural vegetation of riverine in Korea under four light gradients within ambient and elevated $CO_2$ concentration and temperature levels. As a result, growth responses of two species were affected by light factor. Aboveground, belowground, plant biomass and root:shoot ratio of two species grown under the control and treatment were increased in the highest light level. Plant biomass and root:shoot ratio of two oak species were not significantly affected by elevated $CO_2$ and temperature, while aboveground biomass of them was lower in the treatment than control. Belowground biomass of Q. serrata was lower in the treatment than control under the gradients that are more than 70% of light level. As light intensity increases, elevated $CO_2$ and temperature promoted root growth of two oak species but had a negative effect on aboveground growth. According to the principal component analysis(PCA), two oak species were discriminatively arranged based on factor 1 and 2. Also, the reactions towards the ambient and elevated $CO_2$ and temperature were slightly different. It is clearly visible that all features relied on axis 1 and axis II are highly correlated with most variables except for stem and shoot length.

• Journal of Korean Tunnelling and Underground Space Association
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• v.20 no.1
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• pp.145-160
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• 2018

Long subsea tunnel is subject to many restrictions in terms of spatial limitation when vertical or inclined shafts are built for tunnel ventilation. So, the construction of some artificial island is required to provide ventilation. But, because of construction difficulty and cost increase, it is necessary to minimize the artificial island construction. As a result, ventilation distance become longer and supply airflow becomes excessive due to air leakage, So, duct mounting for temporary ventilation is impossible or fan pressure and power increase exponentially. Therefore, in order to build a long subsea tunnel, it is necessary to overcome these practical problems and to develop technical solution that can keep the comfortable condition of tunnel environment during construction. In previous study, we have found that air leakage is the key factor in solving these problems and experimental results show that the new connection method has a leakage rate of about $1.46mm^2/m^2$ (Jo et al., 2017). In this study, we present the experimental results of the measurement of the leakage rate of the prototype with the new connection method, and analyze experimentally the improvement of the leakage rate when applying the flexible cover inside the duct to improve the leakage performance of the existing connection method.