• 자원환경지질
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• 제37권2호
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• pp.225-234
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• 2004

춘궁동 오층석탑(보물 제12호)의 암석학적 풍화와 훼손도를 진단하였다. 이 석탑의 정면은 N30$^{\circ}$W를 향하고 있으며, 구성암석은 안구상 편마암과 흑운모 화강암이다. 석탑을 이루는 암석은 박리와 변색이 심하고, 조암광물은 화학적 및 광물학적 풍화에 의하여 점토광물로 변질되어 있다. 석탑의 표면과 부재사이에는 지의류와 이끼류의 모근 및 포자류가 기생하고 있으며, 하단부는 이미 고등식물이 천이하고 있다. 따라서 석탑의 표면에 피복된 지의류와 불연속면에 서식하고 있는 잡초를 제거하기 위한 생화학적 처리가 요구된다. 이 석탑의 구조적 안정을 위해서는 부재사이에 틈이 없도록 재조립을 해야 하며, 삽입한 철편도 제거한 후에 석조문화재 보강용 충전제를 이용한 보존처리가 필요하다. 또한 석탑에 미치는 지면의 습도를 저감하기 위한 차수층의 설치도 고려되어야 할 것이다.

• Bulletin of the Korean Chemical Society
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• 제31권6호
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• pp.1496-1500
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• 2010

Sibutramine enantiomers were separated successfully by capillary zone electrophoresis using substituted cyclodextrins as chiral selectors. The effects of cyclodextrin concentration, pH, voltage, buffer type, and electrolyte concentration on the migration time and resolution of enantiomers were examined. Separation of sibutramine enantiomers on an unmodified fused silica capillary (total length, 54 cm; effective length, 45 cm) was achieved using a mixed buffer of 20 mM phosphate/10 mM citrate containing either 5 mM methyl-${\beta}$-cyclodextrin (pH 4.3) or 5 mM carboxymethyl-${\beta}$-cyclodextrin (pH 6.5). Samples were injected with a pressure of 50 mbar for 5 s and were detected at a wavelength of 223 nm. The established method showed good precision and accuracy, with intra- and inter-day variations of less than 2.9 and 4.7%, respectively, and recoveries of 95.7 - 103.8%. The stability constants of (R)- and (S)-sibutramine demonstrated that the resolution of sibutramine enantiomers was attributable primarily to the difference in stability constants. When this optimized method was applied to the determination of sibutramine enantiomers in commercial drug formulations, it proved to be economical and convenient, affording sufficient accuracy, precision, and reproducibility as well as sensitivity and selectivity.

• 한국해안·해양공학회논문집
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• 제30권5호
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• pp.207-216
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• 2018

본 연구에서는 한계평형해석에 근거하는 Talren97과 SoilWorks 그리고 유한요소해석에 근거하는 Midas GTS를 이용하여 비탈면의 최소안전율을 비교 분석하였다. 해석 변수로는 비탈면 높이, 소단조건, 지반정수, 지하수위, 비탈면 경사이며 지하수위를 제외한 모든 변수들에 대한 해석은 건기와 우기로 나누어 수행하였다. 그 결과 동일한 이론을 기반으로 하는 Talren97과 SoilWorks에 의한 비탈면 최소안전율은 동일한 값을 나타내어 프로그램간의 차이는 없는 것으로 확인되었다. 한계평형해석에 비하여 유한요소해석 결과가 다소 높은 안전율을 나타내었으며 평균적으로 약 2.4% 높게 나타나는 것으로 확인되었다. 그러나 한계평형해석과 유한요소해석의 결과 값 차이는 실무에서는 무시할 수 있는 범위이므로 프로그램 및 해석방법에 따른 비탈면 안전율의 차이는 없는 것으로 판단되었다.

• Korea-Australia Rheology Journal
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• 제16권1호
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• pp.27-33
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• 2004

Application of gas assisted injection molding has been expanded during last two decades because of many advantages such as design flexibility, dimensional stability, reduction of machine tonnages, and so on. However, the surface defects including hesitation mark and gloss difference are observed for thick parts. Difficulties in lay-out of the gas channel and processing condition are another disadvantages. Liquid gas assisted injection molding(LGAIM), in which a liquid with a boiling point lower than the temperature of the polymer melt is injected into the melt stream, and travels with the melt into the mold where it vaporizes and pushes the melt downstream and against the cavity walls to create hollow channels within the part, is a good alternative of the conventional gas assisted injection molding especially in manufacturing simple and very thick parts. Though this is a new frontier of the innovation in the injection molding industry, there is no guideline for the design and processing conditions. In this paper, theoretical analysis has been made to describe the hollow formation dynamics in LGAIM. This model provides an insight into LGAIM process: explains why LGAIM has advantages over conventional gas assisted injection molding, and gives a guideline for the design and processing conditions.

• Bulletin of the Korean Chemical Society
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• 제34권12호
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• pp.3671-3676
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• 2013

A series of carbon nanotube, $C_{60}$, and graphene modified $TiO_2$ nanocomposites were prepared by hydrothermal method. X-ray diffraction, $N_2$ adsorption, UV-Vis spectroscopy, photoluminescence, and Electrochemical impedance spectra were used to characterize the prepared composite materials The results reveal that incorporating $TiO_2$ with carbon materials can extend the adsorption edge of all the $TiO_2$-carbon nanocomposites to the visible light region. The photocatalytic activities were tested in the degradation of 2,4,6-trichlorophenol (TCP) under visible light. No obvious difference in essence was observed in structural and optical properties among three series of carbon modified $TiO_2$ nanocomposites. Three series of carbon materials modified $TiO_2$ composites follow the analogous tentative reaction mechanism for TCP degradation. GR modified $TiO_2$ nanocomposite exhibits the strongest interaction and the most effective interfacial charge transfer among three carbon materials, thus shows the highest electron-hole separation rate, leading to the highest photocatalytic activity and stability.

• Elastomers and Composites
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• 제53권1호
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• pp.6-12
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• 2018

Styrene-butadiene Rubber (SBR) Latex composites, incorporated with cellulose/starch-silica hybrids synthesized by gel-adsorption method, were filled into rubber by the latex compounding method. The structure morphology, mechanical properties, and thermodynamic properties of gel-silica hybrids were characterized. The states of hybrids which used as fillers were also characterized by SEM. As the fillers ratio increased, the difference for storage modulus of samples had been morphology by rubber process analyzer (RPA). Then, as more fillers ratio was filled into the matrix, the best tensile strength result, and the largest modulus value were also proved by UTM and RPA. As for thermal stability, increase in the ratio of fillers led to higher initial decomposition temperature, which was also proved by TGA. The swelling ratio of samples has also been characterized. From the results of all the tests, cellulose-silica hybrid showed the best results as a filler, and the best filling ratio of this hybrid is about 10 phr, which has the best storage modulus and great tensile strength.

• Bulletin of the Korean Chemical Society
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• 제29권3호
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• pp.590-594
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• 2008

The inclusion complexes of cyclodextrins (CDs) with flavones in aqueous solution were investigated by phase solubility measurements. The effect of b -cyclodextrin (b -CD), heptakis (2,6-di-O-methyl) b -cyclodextrin (DM-b -CD) and 2-hydroxypropyl-b -cyclodextrin (HP-b -CD) on the aqueous solubility of three flavones, namely, chrysin, apigenin and luteolin was investigated, respectively. Solubility enhancements of all flavones obtained with three CDs followed the rank order: HP-b -CD > DM-b -CD > b -CD, and besides, CDs show higher stability constant on luteolin than that on others flavones. 1H-nuclear magnetic resonance (NMR) spectroscopy and molecular modeling was used to help establish the model of interaction of the CDs with luteolin. NMR spectroscopic analysis suggested that A-C ring, and part of the B ring of luteolin display favorable interaction with the CDs, which was also confirmed by docking studies based on the molecular simulation. The observed augmentation of solubility of luteolin by three CDs was explained by the difference of electrostatic interaction of each complex, especially hydrogen bonding.

• Bulletin of the Korean Chemical Society
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• 제33권11호
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• pp.3719-3726
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• 2012

Formation of Z-DNA, a left-handed double helix, from B-DNA, the canonical right-handed double helix, occurs during important biological processes such as gene expression and DNA transcription. Such B-Z transitions can also be induced by high salt concentration in vitro, but the changes in the relative stability of B-DNA and Z-DNA with salt concentration have not been fully explained despite numerous attempts. For example, electrostatic effects alone could not account for salt-induced B-Z transitions in previous studies. In this paper, we propose that the B-Z transition can be explained if counterion entropy is considered along with the electrostatic interactions. This can be achieved by conducting all-atom, explicit-solvent MD simulations followed by MM-PBSA and molecular DFT calculations. Our MD simulations show that counterions tend to bind at specific sites in B-DNA and Z-DNA, and that more ions cluster near Z-DNA than near B-DNA. Moreover, the difference in counterion ordering near B-DNA and Z-DNA is larger at a low salt concentration than at a high concentration. The results imply that the exclusion of counterions by Z-DNA-binding proteins may facilitate Z-DNA formation under physiological conditions.

• 멤브레인
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• 제32권6호
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• pp.383-389
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• 2022

막 분리 공정은 다양한 응용 분야에서 사용되는 중요한 기술이다. 이러한 분리 공정은 농도 구배, 압력 또는 전위구배 등의 구동력에 의해 수행된다. 투과증발은 용액 메커니즘에 기초한 분리 과정 중 하나이다. 분리막을 투과한 쪽에서 압력은 진공에 의해 감소되고 분리는 압력차에 의해 구동된다. 다공성 제올라이트 분리막을 통한 탈수 공정에 의해 에탄올 또는 이소프로필 알코올과 같은 연료 및 화학 물질의 순도를 향상시킨다. 이러한 분리막들은 높은 열적, 화학적, 기계적 안정성을 가지고 있다. 이 총설에서는 제올라이트 분리막에 의한 에탄올 회수 및 바이오 오일 탈수라는 두 개의 섹션으로 나누어 소개한다.

• 한국식품영양과학회지
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• 제34권2호
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• pp.255-260
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• 2005

방사선 조사 황기(Astragall Radix)에 대한 기능성 및 화학적 성분에 대한 안정성을 평가하였다. 기능성 평가시험으로서 방사선 조사 황기의 ethanol추출물 및 ethyl acetate분획물에 대한 DPPH 라디칼 소거 활성은 4∼28%및 13∼50%를 각각 보였으며 비조사 황기는 4∼29% 및 17∼57%로서 거의 동등한 라디칼 소거활성을 보였다(p>0.07).지질과 산화 억제시험에서 방사선 조사 황기의 ethanol추출물 및 ethyl acetate 분회 물은 각각 17∼54% 및 50∼84%의 억제활성을 보였고 비조사 황기는 각각 16∼58% 및 52∼86%를 나타냄으로써 지질과산화 억제활성도 방사선 조사에 거의 영향을 받지 않는 것을 알 수 있었다(p>0.05). Comet assay를 이용한 DNA 방어효과 시험에서 방사선 조사 황기의 ethanol 추출물 및 ethyl acetate 분획물은 24∼55% 및 49∼58%였고 비조사 황기는 각각 20∼46% 및 38∼54%로써 거의 동등한 DNA의 산화적 경감효과를 보였다(p>0.05).화학적 성분에 대한 안정성 평가시험인 HPLC분석시험에서 방사선 조사 황기의 ethyl acetate 분획물은 비조사 황기의 ethyl acetate 분획물과 거의 대등한 peak 양상을 나타냄으로써 화학적 성분의 안정성이 유지되는 것을 확인할 수 있었다. 따라서 방사선 조사 황기에 대한 본 연구의 결과와 이전의 유전독성학적 안전성 결과를 종합하여 볼 때 부가적인 실험이 동반된다면 실제적으로 위생화를 위한 방사선 조사 품목의 하나로서 그 적용 가능성이 시사되었다.