• Bulletin of the Korean Chemical Society
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• 제31권5호
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• pp.1199-1203
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• 2010

Second-order rate constants ($k_N$) have been measured spectrophotometrically for Michael-type reactions of 1-(X-substituted phenyl)-2-propyn-1-ones (2a-f) with a series of alicyclic secondary amines in MeCN at $25.0{\pm}0.1^{\circ}C$. The $k_N$ value increases as the incoming amine becomes more basic and the substituent X changes form an electron-donating group (EDG) to an electron-withdrawing group (EWG). The Br${\o}$nsted-type plots are linear with ${\beta}_{nuc}$ = 0.48 - 0.51. The Hammett plots for the reactions of 2a-f exhibit poor correlations but the corresponding Yukawa-Tsuno plots result in much better linear correlations with ${\rho}$ = 1.57 and r = 0.46 for the reactions with piperidine while ${\rho}$ = 1.72 and r = 0.39 for those with morpholine. The amines employed in this study are less reactive in MeCN than in water for reactions with substrates possessing an EDG, although they are ca. 8 pKa units more basic in the aprotic solvent. This indicates that the transition state (TS) is significantly more destabilized than the ground state (GS) in the aprotic solvent. It has been concluded that the reactions proceed through a stepwise mechanism with a partially charged TS, since such TS would be destabilized in the aprotic solvent due to the electronic repulsion between the negative-dipole end of MeCN and the negative charge of the TS. The fact that primary deuterium kinetic effect is absent supports a stepwise mechanism in which proton transfer occurs after the rate-determining step.

• 자원리싸이클링
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• 제23권1호
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• pp.17-24
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• 2014

Nd와 Pr이 함유된 모나자이트 샌드의 염산 침출용액에서 PC88A와 D2EHPA를 사용하여 두 금속을 분리하기 위한 용매추출실험을 수행하였다. 이러한 목적을 위해 수상의 pH에 따른 PC88A와 D2EHPA의 비누화가 두 금속의 추출 및 분리에 미치는 영향을 조사하였다. 본 연구에서 수행한 실험조건에서 Nd의 분배계수가 Pr의 분배계수보다 크며, 수상의 pH가 높을수록 분리인자가 증가하였다. PC88A에 비해 비누화시킨 PC88A로 추출하는 경우 분배계수와 분리인자 모두 증가하였다. D2EHPA의 비누화율은 두 금속의 추출에는 영향을 미치지만, 분리인자에는 큰 변화가 없었다.

• 한국의류학회지
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• 제23권7호
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• pp.1030-1039
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• 1999

The effect of surfactant mixture 9on detergency and soil redeposition in a dry-cleaning system was investigated employing Aerosol OT as an anionic surfactant and Span 80 as a nonionic surfactant. The effect of charge system on soil deposition was also investigated in order to determine the optimum condition at which soil redeposition is minimum,. Soil deposition instead of soil redeposition on cotton, polyester and wool fabrics was measured employing petroleum solvent and perchloroethylene as organic solvents. The results were as follows. 1. Surface tension or interfacial tension was not changed by the addition of any surfactant or surfactant mixtures. In petroleum solvent however interfacial tension between solrent and water decreased when surfactants were added and increased when surfactants were mixed,. 2. The maximum amount of water solubilization increased as the mole fraction of Aerosol OT increased and more water was solubilized in petroleum solvent than in perchloroethylene. 3. The detergency of cotton was greater and the soil deposition rate was lower in Span 80 solution than in Aerosol OT solution. The soil deposition on cotton fabric decreased when water was solubilized in Aersol OT solution 4. The detergency and soil deposition rate of polyester fabric did not change by the surfactant type of the addition of surfactant mixture and soil deposition rate increased bywater solubilization. 5. Soil deposition on wool fabric was very high when Arosol OT was employed in perchloroethylene and the soil deposition did not change greatly by water solubilization.

• Bulletin of the Korean Chemical Society
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• 제29권10호
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• pp.1911-1914
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• 2008

Second-order rate constants (kN) have been measured for Michael-type addition reactions of a series of alicyclic secondary amines to 1-phenyl-2-propyn-1-one (2) in MeCN at 25.0 ${\pm}$ 0.1 ${^{\circ}C}$. All the amines studied are less reactive in MeCN than in $H_2O$ although they are more basic in the aprotic solvent by 7-9 p$K_a$ units. The Bronsted-type plot is linear with $\beta_{nuc}$ = 0.40, which is slightly larger than that reported previously for the corresponding reactions in $H_2O$ ($\beta_{nuc}$ = 0.27). Product analysis has shown that only E-isomer is produced. Kinetic isotope effect is absent for the reactions of 2 with morpholine and deuterated morpholine (i.e., $k^H/k^D$ = 1.0). Thus, the reaction has been concluded to proceed through a stepwise mechanism, in which proton transfer occurs after the rate-determining step. The reaction has been suggested to proceed through a tighter transition state in MeCN than in H2O on the basis of the larger $\beta_{nuc}$ in the aprotic solvent. The nature of the transition state has been proposed to be responsible for the decreased reactivity in the aprotic solvent.

• 한국재료학회지
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• 제23권10호
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• pp.592-598
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• 2013

Graphene oxide powders prepared by two different drying processes, freeze drying and spray drying, were studied to compare the effect of the drying method on the physical properties of graphene oxide powder. The graphene oxide dispersion was prepared from graphite by chemical delamination with the aid of sulfuric acid and permanganic acid, and the dispersion was further washed and re-dispersed in a mixed solvent of water and isopropyl alcohol. A freeze drying method can feasibly minimize damage to the sample, but it requires a long process time. In contrast, spray drying is able to remove a solvent in a relatively short time, though this process requires exposure to a high temperature for a rapid evaporation of the solvent. The powders prepared by freeze drying and spray drying were characterized and compared by Raman spectroscopy, X-ray diffraction, field-emission scanning electron microscopy, transmission electron microscopy, and by an elemental analysis. The graphene oxide powders showed similar chemical compositions; however, the morphologies of the powders differed in that the graphene oxide prepared by spray drying had a winkled morphology and a higher apparent density compared to the powder prepared by freeze drying. The graphene oxide powders were reduced at $900^{\circ}C$ in an atmosphere of $N_2$. The effect of the drying process on the properties of the reduced graphene oxide was examined by SEM, TEM and Raman spectroscopy.

• 한국식품영양과학회지
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• 제30권4호
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• pp.717-720
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• 2001

4년근과 24년근 도라지의 화학성분 및 생리활성을 조사하였다. 24년근 장생 도라지의 화학성분 조성은 수분 82.7% 조단백 1.6% 조지방2.1%, 조회분 0.7% 총당 6.0% 총 식이섬유 2.3% 조사포닌 3.4mg% 및 비타민 C 3.0mg%였으며 4년근과의 함량차이는 크게 나타나지 않았다. 그러나 무기물의 함량은 24년근이 4년근에 비하여 모두 높게 나타났으며 그 중에서 K가 879.9mg/kg 으로 가장 높게 나타났다. 24년근과 4년근의 용매별 추출물의 생리활성 정도는 에탄올>메탄올>물의 순이었고 전자공여능은 24년근이 4년근보다 10-50% 높게 나타났으며 아질산업 소거효과도 10~40% 까지 높게 나타났다.

• 자원리싸이클링
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• 제22권5호
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• pp.35-42
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• 2013

Nd와 Pr이 함유된 염산용액에서 PC88A와 D2EHPA에 의한 두 금속의 분리에 적합한 조건을 조사하기 위해 용매추출실험을 수행하였다. 본 연구의 실험조건에서 Nd의 분배계수가 Pr의 분배계수보다 컸다. PC88A와 D2EHPA로 추출하는 경우 금속과 추출제와의 농도비의 증가가 두 금속의 추출 및 분리에 큰 영향을 미쳤다. D2EHPA의 비누화율과 초기 pH는 두 금속의 추출에는 큰 영향을 미치지만, 분리인자에는 큰 변화가 없었다.

• 폴리머
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• 제35권6호
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• pp.610-614
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• 2011

본 연구에서는 방사선 전조사법으로 ETFE(polyethylene-co-tetrafluoroethylene) 불소고분자 필름에 VBC(vinylbenzyl chloride) 단량체를 그래프트할 경우 사용되는 용매의 영향을 평가하였다. ETFE 필름을 전자선을 조사하여 필름에 라디칼을 형성시킨 후 톨루엔, 햅탄, 이소프로판올 등 다양한 용매로 희석된 VBC 단량체 혼합물에 넣어 그래프트 반응을 진행시켜 그래프트율을 측정하였다. VBC-g-ETFE 필름은 FTIR 기기를 사용하여 성공적으로 그래프트 되었음을 확인하였다. 여러 용매에서 제조된 필름의 기계적 강도와 필름 단면에 그래프트된 VBC 고분자의 분포도를 측정하여 용매의 영향을 평가하였다.

• 보존과학회지
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• 제35권1호
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• pp.19-31
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• 2019

To study the cleaning effects and post-treatment stability assessment of various methods of cleaning textiles with metal thread, six naturally-soiled historical textiles with metal thread were investigated at the Metropolitan Museum of Art, New York. Prior to the cleaning of fabricated gold, silver, and copper thread that had been glued onto a paper substrate, the artificial deterioration was carried out in a controlled environment with light(UV and daylight), and temperature and humidity factors which would weaken and damage the samples. A synthetic soil mixture was applied to the samples to imitate soil found on the historic and archaeological textiles with metal thread; the cleaning effect and post-treatment assessment were investigated by use of three textile cleaning methods: mechanical cleaning, wet cleaning, and solvent cleaning. While investigating the naturally-soiled textiles with metal thread, it was determined that the soil colors and sizes of contaminating particles of each textile were different due to the diversity of original environmental factors and conditions. After cleaning with kneaded rubber, Stoddard solvent, n-decane or n-hexane, a bright, clean effect was apparent. Kneaded rubber was successful in picking up both large and small particles, but its stickiness caused some of the metal leaf to peel off. Stoddard solvent produced a good cleaning effect, but after use of n-hexane and n-decane in the cleaning process, a white layer of residue remained on the textile's surface. Wet cleaning was not effective and the rapid humidity changes between wet and dry conditions caused the edges of the paper substrate to lose their original shape.

• Bulletin of the Korean Chemical Society
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• 제34권1호
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• pp.201-206
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• 2013

The second-order rate constants have been measured spectrophotometrically for the reactions of paraoxon 1 and parathion 2 with a series of alicyclic secondary amines, $OH^-$ and $HOO^-$ ions in $H_2O$ at $25.0{\pm}0.1^{\circ}C$. A linear Br${\o}$nsted-type plot with ${\beta}_{nuc}$ = 0.40 was obtained for the reactions of 1 with amines and $OH^-$. The reaction has been concluded to proceed through a concerted mechanism. $HOO^-$ deviates positively from the linear Br${\o}$nsted-type plot, implying that the ${\alpha}$-effect is operative. The magnitude of the ${\alpha}$-effect ($k_{HOO^-}/k_{OH^-}$) was found to be ca. 55 for the reaction of 1 and 290 for that of parathion 2, indicating that $HOO^-$ is highly effective in decomposition of the toxic phosphorus compounds although it is over 4 $pK_a$ units less basic than $OH^-$. Among the theories suggested as origins of the ${\alpha}$-effect (e.g., TS stabilization through an intramolecular Hbonding interaction, solvent effect, and polarizability effect), polarizability effect appears to be the most important factor for the ${\alpha}$-effect in this study, since the polarizable $HOO^-$ exhibits a larger ${\alpha}$-effect for the reaction of the more polarizable substrate 2.