• Membrane Journal
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• v.6 no.4
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• pp.250-257
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• 1996

Surface crosslinked chitosan composite membranes were prepared with glutaraldehyde and surfuric acid. Effects of neutralization for complex between chitosan and acetic acid and of water permeability for substrate membranes on pervaporation performance were investigated. For ionically crosskinked membranes, effect of active layer thickness on separation factor of water/ethanol mixture was studied. With increasing the water permeability of the substrate, the membrane showed an increased separation factor, while it maintained a constant permeate flux. Neutralized chitosan composite membranes revealed a decreased separation factor and a constant permeate flux. When the thickness of the active layer increased, an optimum crosslinking time to achieve higher separation factor shifted to a prolonged times.

• Membrane Journal
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• v.6 no.1
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• pp.37-43
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• 1996

Chitosan composite membranes were prepared by casting chitosan solution onto porous polysulfone ultrafiltration membrane. Composite membranes to separate water from aq. ethanol solution were chemically crosslinked by using various crosslinking agent, glyoxal, terephthalaldehyde and glutaraldehyde. The morphology of surface crosslinked chitosan composite membranes were examined by scanning electron microscopy. ATR-FTIR was employed to confirm the crosslinking mechanism of surface crosslinked chitosan composite membranes. In the case of glutaraldehyde, optimum separation factor and decreasing trend of flux were shown.

• Membrane Journal
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• v.10 no.3
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• pp.148-154
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• 2000

Poly(vinyl alcohol)(PVA)/sulfur-siccinic acid(SSA) membrane performances have been studied for the vapor permeation separation of methyl tort-butyl ether(MTBE)/methanol mixtures with varying operation temperatures, amount of cross-linking agents, and feed compositions. 1'here are two factors, the membrane network and the hydrogen bonding, in the swelling measurements of PVA/SSA membranes. These two factors act interdependently on the membrane swelling. The sulfuric acid group in SSA took an important role in the membrane performance. The cross-linking effect might be more dominant than the hydrogen bonding effect due to the sulfuric acid group at 7% SSA membrane. Hydrogen bonding effect was more important for 5% SSA membrane. In vapor permeation, density or concentration of methanol in vapor feed is lower than that of methanol in liquid feed, as a result, the hydrogen bonding portion between the solvent and the hydroxyl group in PVA is reduced in vapor permeation. In this case, the 7% SSA membrane shows the highest separation factor of 2187 with the flux of 4.84g/$m^2$hr for MTBE/methanol=80/20 mixtures at 3$0^{\circ}C$.

• 한국노년학
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• v.36 no.3
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• pp.541-562
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• 2016

The current study investigates the relationship and the mechanisms between bridge employment and change in marital satisfaction during midlife, using a three-wave panel dataset obtained from the Korean Baby Boomer Panel Study. A multivariate latent growth analysis reveals that the transition from career employment to bridge employment, compared to maintaining career employment, has an indirect negative effect on increase rate of marital satisfaction through the wage decrease. A steep decrease in wage following transition to bridge employment causes a lower increase in marital satisfaction. On the other hand, continuously engaging in bridge employment rather than career employment is associated with a higher increase in marital satisfaction via a higher increase in job commitment. This result implies that Baby Boomers adapt to bridge employment over time. Overall, the present study finds that the effect of bridge employment on the change in marital satisfaction during midlife varies with the duration of bridge employment. A future research needs to explore which factors can buffer the negative effect of decrease in wage during transition to the bridge employment on the change in marital satisfaction.

• Proceedings of the Korean Society for Food Science of Animal Resources Conference
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• 2005.10a
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• pp.271-275
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• 2005

본 연구결과, ${\beta}$-CD의 재활용을 위해 adipic acid로 ${\beta}$-CD를 가교시킨 후, 우유의 콜레스테롤 제거 실험에 사용한 결과, 10회 재활용하는 동안 평균 89.90%의 콜레스테롤이 제거되었으며, 이에 따른 가교화 ${\beta}$-CD의 재활용률은 97.30%로 나타났다. 재활용에 따른 가교화 ${\beta}$-CD의 수율은 8회 재활용할 때까지 감소폭이 매우 적었으며, 가교화 ${\beta}$-CD의 구조 역시, 8회 재활용할때까지는 ${\beta}$-CD간의 가교결합이 유지되다가 이후부터는 대부분 powder ${\beta}$-CD 형태로 존재하는 것으로 관찰되었다. 재활용하는 동안 콜레스테롤 제거가 가능한 ${\beta}$-CD를 정량한 결과, 8회 재활용할 때까지 일정한 수치를 유지하는 것으로 나타났다. 위 실험 결과, adipic acid로 가교시킨 ${\beta}$-CD를 이용하여 우유의 콜레스테롤 제거 시, 여러 번 사용하여도 가교화 ${\beta}$-CD의 물리적 성질에 변화가 거의 없이 자체의 특성을 유지하는 것으로 보아, 이를 유가공 산업에 적용 시, 경제적인 효과가 매우 클 것이라고 사료된다.

• Journal of the Korean Professional Engineers Association
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• v.31 no.5
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• pp.44-48
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• 1998

• Proceedings of the Korean Society of Dyers and Finishers Conference
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• 2001.11a
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• pp.89-94
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• 2001

• Proceedings of the Korean Society for Food Science of Animal Resources Conference
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• 2006.05a
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• pp.133-137
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• 2006

본 연구의 목적은 $\beta$-CD를 가교화 시켜 육가공 제품의 주원료인 lard에 내재하는 cholesterol을 효과적으로 제거하기 위한 최적조건 확립이다. 따라서 adipic acid로 가교화한 $\beta$-CD를 이용하여 lard에서 cholesterol을 제거하고 더 높은 효율을 찾기 위하여 실시되었다. 가교화 $\beta$-CD를 이용해 lard에서 cholesterol 제거 실험결과의 최적 조건은 lard:distilled water=1:1, 가교화 $\beta$-CD 5%, 교반온도 $40^{\circ}C$, 교반시간 10분, 교반속도 150rpm으로 실험한 결과 cholesterol 제거율이 평균 92.32%이었다. 또한 10회 재활용 결과 평균 98.04%의 재활용률을 보였으며, 8회 이후에는 유의적으로 감소하여 가교화 $\beta$-CD의 효율적인 재활용이 가능함을 시사하였다. 이 실험의 결과 가교화 $\beta$-CD로 lard의 cholesterol 제거 최적조건을 규명함으로써 콜레스테롤을 저하시킨 육가공 제품의 생산 가능성을 보였다.

• Proceedings of the Korean Society for Food Science of Animal Resources Conference
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• 2004.05a
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• pp.341-344
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• 2004

본 연구의 목적은 cholesterol를 가교화 시켜 우유 및 유제품의 cholesterol을 효과적으로 제거하고, 이들의 재활용이 용이하게 되어지는 것을 규명하는데 있으며, 이를 이용해 cholesterol을 제거하고 재활용 하는데 문제가 되었던 점을 고려해 가교화 ${\beta}$-CD를 이용해 우유 및 유제품에서 cholesterol을 제거하고 재활용의 더 높은 효율을 위하여 실시되었다. 가교화 ${\beta}$-CD를 이용해 우유에서 cholesterol 제거 실험결과의 최적 조건은 가교화 ${\beta}$-CD 1%를 첨가해 교반온도 $10^{\circ}C$, 교반시간 10분, 교반속도 400rpm으로 실험한 결과 cholesterol 제거율이 평균 81.6%이었다. 또한 가교화 ${\beta}$-CD의 재활용율은 92%로 나타났다. 이 실험의 결과 ${\beta}$-CD의 가교화가 우유의 cholesterol제거와 재활용 면에서 긍정적인 것으로 사료되며 산업화의 가능성을 시사하였다.

• Journal of Labour Economics
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• v.27 no.2
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• pp.1-27
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• 2004

The share of self-employment shows a downward trend until 1990 and then an upward trend since then. The upward trend is mainly due to more employers and more male self-employed, which implies that self-employment plays a significant role as an alternative form of employment. This paper examines whether self-employment can be a bridge between no work and wage work in the processes entering into or exiting labor market, and if so, what determines the choice of self-employment as a bridge, using the data from the Korea Labor and Income Panel Survey(Wave 1 to Wave 5). Empirical analysis employing the probit model shows that the older, female, the less educated, and persons with bad health are more likely to choose self-employment as a bridge in the exit process and that they are less likely to choose it as a bridge in the entry process. Business cycle has a statistically significant negative effect on its role of bridge employment in the exit process but not in the entry process. The result implies that, in the ageing society, labor market policy should consider self-employment as a better alternative than wage work for the aged.