• 한국연소학회:학술대회논문집
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• 2003.12a
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• pp.11-18
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• 2003

The soot formation and oxidation characteristics with different radiation boundary conditions have been studied experimentally in a co-flow ethylene/air laminar diffusion flame. The boundary conditions are two cases, one is a fully refractive radiation boundary condition by a polished aluminum cylinder(AL) and the other is a fully absorbing radiation boundary condition by a black body cylinder(BB). The AL case compared with BB condition show the lower inception point, denser soot volume fraction, wider and longer annular soot area owing to the reabsorption of radiating energy.

• Transactions of the Korean Society of Automotive Engineers
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• v.7 no.5
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• pp.40-54
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• 1999

The flame structure and soot formation in the counterflow Ethylene-Air nonpremixed flame are numerically analyzed. The present soot reaction mechanism involves nucleation, surface growth, particle coagulation, and oxidation steps. The gas phase chemistry and the soot nucleation, surface growth reactions are coupled by assuming that the nucleation and soot mass growth has the certain relationship with the concentration of benzene and acetylene. In terms of the centerline velocity and the soot volume fraction, the predicted results are compared with the experimental data. The detailed discussion has been made for the sensitivity of model constants and the deficiencies of the present model. Numerical results indicated that the acetylene addition to the soot surface plays the dominant role in the soot mass growth for the counterflow nonpremixed flame.

• Bulletin of the Korean Chemical Society
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• v.19 no.10
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• pp.1054-1059
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• 1998

Fluorescence and dynamic light scattering measurements were applied to the study of formation and structure of aggregated colloidal particles in modified poly(ethylene-co-methylacrylate) ionomers in aqueous solution. Both 8-anillino-l-naphthalene-sulfonic acid (ANS) and pyrene were used as fluorescence probe to obtain the information on the structure of particle surface and inside, respectively. Three different ionomers used in this study started to aggregate at very dilute concentration, 3-8 x 10-6 g/mL. In this study, we demonstrate that the polyethylene ionomers can form stable nanoparticles. The hydrophobic core made of the polyethylene backbone chains is stabilized by the ionic groups on the particle surface. Such a formed stable nanoparticles have a relatively narrow size distribution with an average radius in the range of 27-48 nm, depending on the kind of ionic groups. Once the stable particles are formed, the particle size distributions were nearly constant. This study shows another way to prepare surfactant-free polyethylene nanoparticles.

• Bulletin of the Korean Chemical Society
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• v.21 no.4
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• pp.383-388
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• 2000

Multiblock copolymers consisting of poly( g-benzyl L-glutamate) (PBLG) as the hydrophobic part and poly(ethylene oxide) (PEO) as the hydrophilic part (GEG) were synthesized and characterized. GEG polymeric micelles were prepared by the dialysis technique. Particle size distributions based on intensity,volume, and number-average were 22.6 $\pm$ 11.9 nm, 23.5 $\pm$ 4.6 nm, and 23.7 $\pm$ 37 nm, respectively. It was observed that par-ticle size and size distribution of GEG polymeric micelles changed significantly with the choice of initial sol-vent. Transmission electron micrographs (TEM) showed the polymeric micelles to be spherically shaped, with sizes ranging from 20 nm to 40 nm in diameter. Fluorescence spectroscopy measurements suggested that GEG block copolymers wereassociated in water to form polymeric micelles, and the critical micelle concentrations (CMC) value of the block copolymers was 0.0094 g/L. Further evidenceof micelle formation of GEG block copolymers and limited mobility of the PBLG chain in the core ohe micelle was obtained with 1 H NMR in D2O.

• Proceedings of the Korean Fiber Society Conference
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• 1993.06b
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• pp.202-207
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• 1993

• Membrane Journal
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• v.28 no.4
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• pp.260-264
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• 2018

Poly (ethylene oxide) (PEO)/Ag nanoparticles (AgNPs)(precursor : $AgBF_4$)/p-benzoquinone (p-BQ) composite membrane was prepared for olefin/paraffin separation. As a result, the performance of composite membrane was observed to be maintained at selectivity of 10 and permeance of 15 GPU up to 100 hours. The performance of the membrane was maintained for 100 hours was attributable to that Ag ions could be converted into stable Ag NPs by addition of p-BQ. Furthermore, the surface was partially polarized by the electron acceptor p-BQ, resulting in the formation of olefin carrier. In this study, since the cost of $AgBF_4$ used as a precursor of Ag NPs was relatively higher, $AgNO_3$ was utilized. As a result, it was confirmed that $AgNO_3$ couldn't show the stable formation of nanoparticle, resulting in the poor separation performance.

• Polymer(Korea)
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• v.28 no.4
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• pp.344-351
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• 2004

Poly(ethylene glycol)-based diblock and triblock polyester copolymers stimulating to temperature were studied as injectable biomaterials in drug delivery system because of their nontoxicity, biocompatibility and biodegradability. We synthesized the diblock copolymers consisting of methoxy poly(ethylene glycol) (MPEG) (M$_{n}$=750 g/mole) and poly($\varepsilon$-caprolactone) (PCL) by ring opening polymerization of $\varepsilon$-CL with MPEG as an initiator in the presence of HCl . Et$_2$O. The aqueous solution of synthesized diblock copolymers represented sol phase at room temperature and a sol to gel phase transition as the temperature increased from room temperature to body temperature. To confirm the in vivo gel formation, we observed the formation of gel in the mice body after injection of 20 wt% aqueous solution of each block copolymer. After 2 months, we observed the maintenance of gel without dispersion in mice. In this study, we synthesized diblock copolymers exhibiting sol-gel phase transition and confirmed the feasibility as biomaterials of injectable implantation.n.

• Korean Journal of Plant Tissue Culture
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• v.21 no.4
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• pp.193-200
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• 1994

The effects of sucrose concentration and nitrogen source on shoot growth and in vitro formation of garlic (Allium sativum L. cv Seosan) bulblet were investigated in order to systematize propagation of high quality garlic through a shoot apical meristem culture. Shoot differentiation was not affected by sucrose concentration and nitrogen source, but plantlets which contain medium of NH$_4$- N or NH$_4$ + NO$_3$ were vigorous and healthy in .appearance. Shoot growth was vigorous in changeing of nitrogen source. The best quality of in vitro bulblets was obtained in culture on the medium containing 8% sucrose and NH$_4$ - N, and the formation of bulblet was more effective when plantlets were subjected to cold treatment before use. NH$_4$-N was a major factor for shoot growth and bulblet development, but NO$_3$-N was not and suppressed $K^{+}$absorption. The level of ethylene production was not affected by different nitrogen sources, however this production was enhanced in medium containing a higher concentration of sucrose.e.

• Journal of the Korean Society of Marine Environment & Safety
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• v.16 no.3
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• pp.301-306
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• 2010

DME(Di-Methyl Ehter, $CH_3OCH$) is currently attracting worldwide attention due to its environmentally friendly characteristics. Until now it was researched as a major alternative fuel of diesel automobile because it is a clean fuel producing low soot. Therefore, in this study, in order to investigate the effect of DME mixing on number density and size of soot particle, DME has been mixed in opposed-flow ethylene diffusion flame with the mixture ratios 5%, 14% and 30%. A laser extinction/scattering technique has been adopted to measure the volume fraction, number density, and size of soot particles. The experimental results showed that the soot concentration of mixture flames with the mixture ratios 5% and 14% produces soot more, even though that of 30% was decreased. This means that even though DME has been known to be a clean fuel for soot formation, the mixing of DME in diffusion flame of ethylene, where acetylene maintains high concentration in soot formation regions, could produce enhanced production of soot.

• Journal of Radiation Industry
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• v.5 no.2
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• pp.119-124
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• 2011

Silver nano-particles (AgNPs) have attracted much attention for centuries due to their unique optical properties, electrical conductivities, oxidative catalysis, and antibacterial effect. In this study, AgNPs have been prepared by using aqueous $AgNO_3$ solution in the poly(vinyl alcohol) (PVA)/poly(ethylene glycol) (PEG) hydrogels. PVA and PEG powders were dissolved in deionized water, and then irradiated by a gamma-ray with a radiation dose of 50 kGy to make hydrogels. PVA/PEG hydrogels were dipped into $1.0{\times}10^{-2}M$ $AgNO_3$ solution for 1 hour. After that, the swollen hydrogels were irradiated by gamma-ray for the formation of AgNPs. FE-SEM is used to observe the formation of AgNPs as a function of the content of PEG and the irradiation dose. Also, AgNPs in the PVA/PEG hydrogels were monitored by UV-Vis. It is observed that the content of PEG and gamma-ray irradiation in the hydrogel is crucial to the formation of AgNPs. Finally, antibacterial tests indiacted that the hydrogel containing silver nanoparticle has antibacterial activity.