• 보존과학연구
• /
• s.14
• /
• pp.1-34
• /
• 1993

1. Metallurgical Properties of Iron artifacts excavated from Yangju-Mountain fortress were studied for the scientific conservation and metallurgical history of ancient Iron artifacts.2. Iron artifacts form Yangju-Mountain fortress were found to be the products of having well-established Carburizing and remelting technique in that period.3. These artifacts seem to be manufactured from very pure ores, because very pure ferrite structure and low impurity.4. Especially evidence of very suitable carburizing technic well-established and usealloying method of Fe-C system on purpose were found.5. Cast iron artifacts were found to be eutectic composition (4.31%) having lowestmelting point in Fe-C system.

• Archives of Pharmacal Research
• /
• v.29 no.1
• /
• pp.108-111
• /
• 2006

The economic and effective method for preparation of R-(-)-ibuprofen by diastereomer crystallization was developed. R-(-)-ibuprofen was resolved from racemic ibuprofen by forming R-(-)ibuprofen-R-(+)-$\alpha$-methylbenzylamine diastereomeric salt with R-(+)-$\alpha$-methylbenzylamine and crystallization. The purity of R-(-)-ibuprofen-R-(+)-$\alpha$-methylbenzylamine diastereomeric salt was tested and confirmed using HPLC and $^1H-NMR$ method. The pure diastereomeric salt collected from repeated recrystallization was further fractionated by liquid-liquid extraction to the pure enantiomer without racemization. R-(-)-ibuprofen was recovered producing overall yield of 2.4% with the purity more than 99.97%.

• Proceedings of the Korean Society For Composite Materials Conference
• /
• 2000.11a
• /
• pp.84-87
• /
• 2000

Square tubes used for vehicle structure components have an important role on keeping its stiffness and preserving occupant safety in vehicle collision and rollover in which it experience axial collapse, bending collapse or both. Bending collapse, which absorbs kinetic energy of the impact and retains a survival space for the occupant, is a dominant failure mode in oblique collision and rollover. Thus, in this paper, the bending collapse characteristics such as the maximum bending moment and energy absorption capacity of the square tube replaced by light-weight material were evaluated and presented. The bending test of cantilever tubes which were fabricated with aluminum, GFRP and aluminum/ GFRP hybrid by co-curing process was performed. Then the maximum bending moment and the energy absorption capacity from the moment-angle curve were evaluated. Based on the test results, it was found that aluminum/ GFRP hybrid tube can show better specific energy absorption capacity compared to the pure aluminum or GFRP tube and can convert unstable collapse mode which may occur in pure GFRP tube to stable collapse mode like a aluminum tube in which plastic hinge is developed.

• Korean Journal of Materials Research
• /
• v.8 no.4
• /
• pp.312-316
• /
• 1998

ZnO- TiO$_2$, and Sn0$_2$ - Ti0$_2$ ceramic composites doped with TiO$_2$ were prepared and their electrical and 1000ppm CO gas sensing properties were investigated. The phases of samples were analyzed by XRD, and the microsturctures of the fractured surface of samples were observed by SEM. A carbon monoxide gas sensitivity was de¬fined as the ratio of the resistance in dry air atmosphere(R$drt air$) to the resistance in 1000ppm CO gas atmosphere(R$_co$) The CO gas sensitivity of Smol% Ti0$_2$-added ZnO decreased about 1.7 times compared to that of pure ZnO. On the other hand, the maximum CO gas sensitivity of Ti0$_2$-added SnO$_2$ increased about 2.5 times compared to that of pure SnO$_2$. Therefore, the CO gas sensitivies of SnO$_2$-TiO$_2$ composite were better than those of ZnO- Ti0$_2$ and the temper¬ature range showing the maximum sensitivity for Sn0$_2$-TiO$_2$ composite was lower than that for ZnO- Ti0$_2$.

• Journal of Environmental Science International
• /
• v.16 no.12
• /
• pp.1431-1437
• /
• 2007

Cobalt titanates($CoTiO_x$), such as $CoTiO_3$ and $Co_2TiO_4$, have been synthesized via a solid-state reaction and characterized using X-ray diffraction(XRD) and X-ray photoelectron spectroscopic(XPS) measurement techniques, prior to being used for continuous wet trichloroethylene(TCE) oxidation at $36^{\circ}C$, to support our earlier chemical structure model for Co species in 5 wt% $CoO_x/TiO_2$(fresh) and(spent) catalysts. Each XRD pattern for the synthesized $CoTiO_3$ and $Co_2TiO_4$ was very close to those obtained from the respective standard XRD data files. The two $CoTiO_x$ samples gave Co 2p XPS spectra consisting of very strong main peaks for Co $2p_{3/2}$ and $2p_{1/2}$ with corresponding satellite structures at higher binding energies. The Co $2p_{3/2}$ main structure appeared at 781.3 eV for the $CoTiO_3$, and it was indicated at 781.1 eV with the $Co_2TiO_4$. Not only could these binding energy values be very similar to that exhibited for the 5 wt% $CoO_x/TiO_2$(fresh), but the spin-orbit splitting(${\Delta}E$) had also no noticeable difference between the cobalt titanates and a sample of the fresh catalyst. Neither of all the $CoTiO_x$ samples were active for the wet TCE oxidation, as expected, but a sample of pure $Co_3O_4$ had a good activity for this reaction. The earlier proposed model for the surface $CoO_x$ species existing with the fresh and spent catalysts is very consistent with the XPS characterization and activity measurements for the cobalt titanates.

• Archives of Pharmacal Research
• /
• v.27 no.4
• /
• pp.436-441
• /
• 2004

SJ compounds (SJ8002 and related compounds) are a group of novel anticancer agents (Cho, Chung, Lee, Kwon, Kang, Joo, and Oh. PCT/KR02/00392). To explore the anticancer mechanism of these compounds, we examined the effect of SJ8002 on microtubules of six human cell lines. At a high concentration ($2\;{\mu}g/mL$), SJ8002 effectively disrupted microtubules of the six cell lines within 1 h. At lower concentrations ($0.05\~1.0\;{\mu}g/mL$), the antimicrotubule activity of SJ8002 varied defending on cell lines. The inhibition of in vitro polymerization of pure tubulin by SJ8002 suggested that SJ8002 acts on free tubulin, inhibits the polymerization of tubulin dimer into microtubules, and hence induces the depolymerization of microtubules.

• Journal of Sensor Science and Technology
• /
• v.29 no.2
• /
• pp.112-117
• /
• 2020

Xylene is a hazardous volatile organic compound that should be precisely measured to monitor indoor air quality. However, the selective and sensitive detection of ppm-level xylene using oxide-semiconductor gas sensors remains a challenge. In this study, pure and Cr-doped Co₃O₄ nanoparticles (NPs) were prepared using flame spray pyrolysis, and their gas-sensing characteristics to 5-ppm xylene at 250 ℃ were investigated. The 4 at% Cr-doped Co₃O₄ NPs exhibited a high gas response to 5-ppm xylene (resistance ratio to gas and air = 39.1) and negligible cross-responses to other representative and ubiquitous indoor pollutants such as ethanol, benzene, formaldehyde, carbon monoxide, and ammonia. In this paper, the enhancement of the gas response and selectivity of Co₃O₄ NPs to xylene by Cr doping was discussed in relation to the catalytic promotion of the gas-sensing reaction. This sensor can be used to monitor indoor xylene.

• Journal of the Korean Society of Clothing and Textiles
• /
• v.37 no.2
• /
• pp.224-234
• /
• 2013

This study investigates the fabrication of core-sheath nanocomposite fibers by locating germanium (Ge) and silicon dioxide ($SiO_2$) nanoparticles selectively in the sheath layer by co-axial electrospinning. Co-axially spun fibers were prepared by electrospinning a pure PVA solution and Ge/$SiO_2$/PVA solution as the core and sheath layer, respectively. Core-sheath nanocomposite fibers were electrospun under a variety of conditions that include various feed rates for the core and sheath solutions, voltages, and concentric needle diameters, in order to find an optimum spinning condition. Ge/$SiO_2$ nanocomposite fibers were also prepared by uniaxial electrospinning to compare fiber morphology and nanoparticle distribution with core-sheath nanofibers. Using scanning electron microscopy, transmission electron microscopy, and energy dispersive X-ray analysis, it was demonstrated that the co-axial approach resulted in the presence of nanoparticles near the surface region of the fibers compared to the overall distribution obtained for uni-axial fibers. The co-axially electrospun Ge/$SiO_2$/PVA nanofiber webs have possible uses in high efficiency functional textiles in which the nanoparticles located in the sheath region provide enhanced functionality.

• Journal of environmental and Sanitary engineering
• /
• v.15 no.1
• /
• pp.39-45
• /
• 2000

The purpose of this study was conducted to indentified the fixing quality of $CO_2$, the most important greenhouse effect gas, by microalgae Chlorella ellipsoidea in batch test apparatus. The glass flask of $1.4{\ell}$ culture media which was saturated with 99.99% pure $CO_2$ gas was setted water bath of $25^{\circ}C$, 5000Lux, and seeded 100$m\ell$ algae liquid. We checked the change of inorganic carbon concentration and algae population with time in culture media. The result were next: the growth of algae population relied on aquatic IC(inorganic carbon) concentration. And the pH was increased with decrease of IC concentration. The growth of algae population had positive correalation with $CO_2$ concentration, and the coefficient of correlation was 0.982. The specific growth rate($\mu$) of Chlorella ellipsoidea was 1.104/d, the maximum specific growth $rate({\mu}_{max}$) of 9.21/d, and helf velocity constant($K_s$) of $259mg/{\ell}$ by Monod equation.

• Journal of Energy Engineering
• /
• v.13 no.1
• /
• pp.1-11
• /
• 2004

Gasification is the essential technology that can meet the interim hydrogen demand of large quantity before entering the hydrogen economy. Although the hydrogen production that is based upon the pure renewable energy like wind and solar power will eventually prevail, the interim mass production of hydrogen for the next ten to twenty years will come from the technologies that can demonstrate the economic feasibility in production cost with a high potential in minimizing CO$_2$ generation and in improving plant efficiency. Particularly, feedstock such as natural gas, coal, petroleum residual oil, wastes, and biomass appears to be utilized in Korea as hydrogen source, at least during the short and medium period of time, owing to the advantage in production cost. Because one of the main reasons behind the recent hydrogen issue is the reduction requirement of CO$_2$ that would be controlled according to the climate change protocol, hydrogen production technologies must be developed to yield the minimal CO$_2$ generation.