• Korean Chemical Engineering Research
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• v.50 no.2
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• pp.292-299
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• 2012

We made 8 wt% silica dispersion system with fumed silica and photo curable acrylic monomer by beads mill process. These dispersions could be applied in organic/inorganic hybrid coating systems. These dispersions could be applied in organic/inorganic hybrid coating systems. The 4 species of photo curable acrylic monomer which was presence of hydroxyl group, different solubility parameter, and different molecular size were used in the silica dispersions. Stability of polar solvent, isopropyl alcohol, in silica dispersions was investigated. We investigated the stability of silica dispersions by using steady-state and dynamic rheology. As the monomer has hydroxyl group increased in mono and binary monomer silica dispersions, they showed non flocculated stable sol (loss modulus (G")> storage modulus (G')). When polar solvent IPA was added into slightly flocculated silica dispersions, they changed to non flocculated stable sol.

• Membrane Journal
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• v.8 no.2
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• pp.77-85
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• 1998

To treat effectively EDIR (electrodeposition ion removal) wastewater in terms of CO$_{Mn}$ 1,500~2,000 ppm generated from aluminum painting process, a RO (reverse osmosis) process was designed and installed to recover and reuse the concentrated solvent sent back to the electrocodeposition tank while the permeate reused as rinse water. A RO system in which three polyamide-spiral wound modules ($102\Phi \times 1,016L$ mm) connnected in series had been running to treat 20 m$^3$ in waste volume in 3 days batch operation at the condition of system recovery of 30 %, applied pressure 11.5 $kg_f/cm^2$ and room temperature. During 42 hours continuous operation leading to 5-fold decrease in waste volume, nearly constant permeation flux of 390 l/m$^2$-hr was maintained and the permeate with average CO$_{Mn}$, 300 ppm was obtained which could be used for washing the remaining paint solution in ion-exchange tower instead of demineralized water. Also COD$_{Mn}$ rejection as a function of running time was observed to be in the range of 78~87 % and the observed solvent rejections for ethyl cellusolve, buthyl cellusolve and n-butanol were 79 %, 87 % and 70 %, respectively.

• Journal of the Korean Applied Science and Technology
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• v.34 no.4
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• pp.954-961
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• 2017

We investigated the purifications of PE-gal and CPN-gal, synthesized by transgalactosylation reaction using recombinant ${\beta}$-gal. The reaction mixture containing PE and PE-gal was first mixed with EA, and thereafter PE and PE-gal were distributed in two-phase (EA/water) system. In this system, PE and PE-gal was selectively moved into EA and water phase, respectively. Then, the water phase was collected, and silica gel chromatography was carried out using the collected water phase. Finally, we compared two purified PE-gal samples using HPLC and TLC analysis, in which the one was purified only by silica gel chromatography and the other was purified by EA extraction followed by silica gel chromatography. In the latter case, the residual PE was almost completely removed, whereas, in the former case, the residual PE was remained remarkably. Additionally, the purification yield of PE-gal was about 21% on the basis of mole. In the same purification protocol, CPN-gal was able to be purified using EA extraction followed by silica gel chromatography, in which the residual CPN was almost removed when CPN-gal was purified by EA extraction followed by silica gel chromatography.

• Bulletin of the Korean Chemical Society
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• v.7 no.5
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• pp.367-371
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• 1986

Dynamic and equilibrium properties of n-alkane chains immersed in solvent molecules have been investigated by a molecular dynamics method. The n-alkane chain is assumed to be a chain of elements (CH$_2$) interconnected by bonds having a fixed bond length and bond angle, but each bond of the chain is allowed to execute hindered internal rotation. We studied the effect of the number of the chain elements (N$_c$ = 10, 15 and 20) on the equilibrium properties of the system, e.g., the pair correlation functions between a chain element and solvent molecules, g$_{cs}$(r), and between the chain elements, g$_{cc}$(r), and the configurational properties such as the mean-square end-to-end distance < R$^2$ >, the mean-square radius of gyration < S$^2$ >, and the eigenvalues of the moment-of-inertia tensor < S$_i^2$ > / < S$^2$ > (i = 1, 2 and 3). We also studied the dynamic properties of the system, e.g., the autocorrelation function C(A;t) where A = R$^2$(t), = S$^2$(t), or = ${\vec{V}}(t)({\vec{V}}$ = velocity of the center of mass), and the diffusion coefficient D. The g$_{cs}$(r)'s are almost equal irrespective of the change of Nc while g$_{cc}$(r) becomes larger as N$_c$ increases; The MD computed configurational properties < R$^2$2 > and < S$^2$ > were found to be a little different from the values calculated from the statistical equations of < R$^2$ > and < S$^2$ >, it may be due to the fact that our model for the MD simulations includes a long-range volume effect. From the < S$_i^2$ > / < S$^2$ >, it is found that the chain molecule has a nearly spherical shape irrespective of the variation of N$_c$. For the dynamic properties we found that the C(R$^2$;t) and C(S$^2$;t) of lower N$_c$ decay faster than those of higher N$_c$, while the C($\vec V$;t) of the center of mass in the chain is weakly dependent on the N$_c$. The center of mass diffusion coefficient D$_c$ decreases as N$_c$ increases while the end point diffusion coefficient D$_e$ is nearly equal irrespective of the change of N$_c$.

• The Korean Journal of Rheology
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• v.11 no.1
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• pp.28-33
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• 1999

Introducing boric acid to the polyviny alcohol(PVA) solutions has a profound effect on the rheological properties through crosslinking between hydroxyl groups of PVA. This study investigates the effect of boric acid on the rheological properties of polyvinyl alcohol(PVA)/dimethyl sulfoxide(DMSO)/water systems in the absence of cations. The viscosity of PVA/ DMSO/water systems containing 1 wt.% boric acid was decreased with increasing water content. PVA/DMSO systems containing 1 wt.% boric acid exhibited rheological properties similar to elastic gels by forming crosslinked structures. On the other hand, PVA/water systems containing 1 wt.% boric acid exhibited rheological properties typical of viscous materials. In-corporation of boric acid into PVA/DMSO system caused a notable change in the viscosity of the system, whereas boric acid had little effect on the viscosity of PVA/water system. PVA/DMSO/boric acid system gave the greatest storage modulus among the PVA solution systems. Increasing water level in the mixed solvent of DMSO and water diminished the storage modulus of the systems.

• Journal of Sericultural and Entomological Science
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• v.51 no.1
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• pp.15-19
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• 2013

Antheraea pernyi silkworm is one of typical wild silkworms, which spins a tawny color cocoon. The cocoon has been used as a resource for textile material due to strong chemical stability and good mechanical properties. In this study, to increase the solubility efficiency of A. pernyi silk fibroin, the composition of dissolution solvent were examined. Calcium chloride tertiary system, normally used for dissolution of Bombyx mori silk fibroin, does not act on A. pernyi silk fibroin. Calcium nitrate system dissolves A. pernyi silk fibroin, and calcium nitrate ethanol system do more easily than calcium nitrate system. Amino acid composition of A. pernyi silk fibroin obtained after dissolution is mainly composed of alanine, glycine, and serine. A. pernyi silk fibroin would be used for non-textile applications near future.

• Molecular & Cellular Toxicology
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• v.1 no.2
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• pp.99-105
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• 2005

Perchloroethylene (tetrachloroethylene, PCE), a dry cleaning and degreasing solvent, can enter ground-water through accidental leak or spills. PCE can be degraded to trichloroethylene (TCE), 1, 1-dichloroethylene (DCE) and vinyl chloride (VC) as potential bio-product. These compounds have been reported that they can cause clinical diseases and cytotoxicity. However, only a little genotoxic information of these compounds has been known. In this study, we investigated DNA single strand breaks of PCE, TCE, DCE and VC by single cell gel electrophoresis assay, (comet assay) which is a sensitive, reliable and rapid method for DNA single strand breaks with mouse lymphoma L5178Y cells. From these results, $37.5\;{\mu}g/ml$ of PCE, $189\;{\mu}g/ml$ of TCE and $56.4\;{\mu}g/ml$ of DCE were revealed significant DNA damages in the absence of S-9 metabolic activation system meaning direct-acting mutagen. And in the presence of S-9 metabolic activation system, $41.5\;{\mu}g/ml$ of PCE, $328.7\;{\mu}g/ml$ of TCE and $949\;{\mu}g/ml$ of DCE were induced significant DNA damage. In the case of VC, it was revealed a significant DNA damage in the presence of S-9 metabolic activation system. Therefore, we suggest that chloroethylene compounds (PCE, TCE, DCE and VC) may be induced the DNA damage in a mammalian cell.

• Proceedings of the Korean Vacuum Society Conference
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• 2014.02a
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• pp.162-162
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• 2014

최근 들어 wearable computing에 대한 수요가 증가하면서 flexible device에 대한 연구가 활발히 진행되고 있다. 하지만, flexible device를 구현하기 위해서는 기판의 damage를 줄이기 위한 저온공정, device life-time 향상을 위한 passivation, 와이어 본딩 등 다양한 문제들이 해결 되어야 한다. 이러한 문제들 중, polymer 기판과 금속간의 접착력을 향상시키기 위해서 많은 연구자들은 기판의 표면에 adhesive layer를 도포하거나 금속잉크의 solvent를 변화시키는 등의 연구를 진행해왔다. 종래의 연구는 기존 device를 대체 할 수 있을 정도의 생산성과 polymer 기판에 대한 열 적인 손상 이 문제가 되었다. 종래의 문제를 해결하기 위하여 저온공정, in-line system이 가능한 준 준 대기압 플라즈마를 사용하였다. 본 연구에서는 금속잉크를 Ink-jet으로 jetting하여 와이어 본딩 하는 과정에서 전도성 ink의 선폭을 유지시키고 접착력을 향상하기 위하여 준 대기압 플라즈마 공정을 이용하여 이러한 문제점을 해결하고자 하였다. Polymer 기판 표면에 roughness를 만들기 위해 대략 수백 nm 크기를 갖는 graphene flake를 spray coating하여 마스크로 사용하고 준 대기압 플라즈마를 이용하여 표면을 식각 함으로써 roughness를 형성시켰다. 준 대기압 플라즈마를 발생시키기 위해 double discharge system에서 6 slm/1.5 slm (He/O2) gas composition을 하부 전극에 흘려보내고 60 kHz, 5 kV 파워를 인가하였다. 동시에 상부 전극에는 30 kHz, 5 kV 파워를 인가하여 110초 동안 표면 식각 공정을 진행하였다. Graphene flake mask가 coating되어 있는 유연기판을 산소 플라즈마 처리 한 후 물에 3초 동안 세척하여 표면에 남아있는 graphene flake를 제거하고 6 slm/0.3 slm (He/SF6)의 유량으로 주파수와 파워 모두 동일 조건으로 110초 동안 표면 처리를 하였다. Figure 1은 표면 개질 과정과 graphene flake를 mask로 사용하여 얻은 roughness 결과를 SEM을 이용하여 관찰한 결과이다. 이와 같이 실험한 결과 ink와 기판간의 접촉면적을 늘려주고 접촉 각을 조절하여 Wenzel model 을 형성 할 수 있는 표면 roughness를 생성하였고 표면의 화학적 결합을 C-F group으로 치환하여 표면의 물과 접촉각 이 $47^{\circ}$에서 $130^{\circ}$로 증가하는 것을 확인하였다.

• Food Science of Animal Resources
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• v.24 no.4
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• pp.411-415
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• 2004

The transparisation technology for milk and milk products could be applied widely and very importantly to various determination because transparisation can economize the cost and increase with precision in the milk payment system. Component of butanone or Triton in transparisation solvent would inhibit the growth of bacteria and method. Enzymatic determination of leucocytes were proposed to evaluate milk quality as mastitis in the milk payment system, this can be easily applied to simplify automation of the determation with the lowest investment cost in milk pay system. The significance of this technique, it can be used in the quality control of raw milk and milk products, milk payment system, and programming of national dairy project. Transparisation technology is used in somatic cell counting by enzymic methods. The range of deviation for this method is 16％ in 74 samples. But the deviation is increased to 20％ when the Infoss method is used. It is affected by the percentage of epithelial cells and white blood cells in somatic cells from different animals and the stages of aging. NAgase activity has an obvious correlation with white-blood cells in milk. In the case of mastitis the white-blood cells is 90-95％ in somatic cells in milk, it is showing greater precision in measuring the state of mastitis. In conclusion the enzymic method of somatic cell counting is a relatively simple and easy method of measurement and can be easily practiced. And the importance of this method is also worth utilizing for indirect counting of Somatic cells by use of synthetic substrates to NAgase. In the future, with the further development of the research in this field, it will b possible to automatize the measurement.

• Polymer(Korea)
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• v.35 no.5
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• pp.458-466
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• 2011

In the mixed system of supercritical carbon dioxide/organic solvents, poly(vinyl alcohol)(PVA) film of high degree of hydrolysis could be dyed with a dichroic dye of C. I. direct black 22(DB22) and as a result, high durability was obtained. Especially, as a dye dispersant in a supercritical fluid phase, a mixed solvent system of ethylene glycol: dimethyl sulfoxide=4 : 6 weight ratio was investigated. Then the optimum pressure for dyeing could be reduced down to 200 bar. Using this supercritical fluid system, the maximum dyeing appeared as the transmittance of less than 1% and the waste amount was reduced to the level of 1/10. After 500% drawing of this PVA film, both the polarizing efficiency of 94% and the single piece transmittance of 30% were obtained. The limitation of DB22 and further improvements were also discussed.