• 한국지반공학회논문집
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• 제36권1호
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• pp.29-38
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• 2020

최근 환기구, 비상탈출용 수직구, 취수탑 가시설 등 지중 가물막이 또는 차수벽체로 원형 가물막이가 많이 적용되고 있다. 원형단면의 경우 벽체에 작용하는 토압이 원형가물막이 형상에 따라 아칭효과(arching effect)로 인하여 작용토압에 대한 구조체의 부재력이 감소하는 것으로 알려져 있다. 본 연구에서는 원형 가물막이에 대한 2D 유한요소해석(FEM)을 활용하여 원형띠장(ring beam) 강성을 산출 후 탄소성해석에 적용하여 부재의 단면력을 검토하였다. 더불어 3D 유한요소해석(FEM)을 통하여 원형단면의 가물막이가 다각형 형태의 가물막이보다 전단력, 휨모멘트, 그리고 발생변위가 최소값을 갖는 것으로 나타났으며, 이로써 원형단면 가물막이가 구조적으로 보다 효율적인 단면 형태임을 확인하였다

• 접착 및 계면
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• 제16권4호
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• pp.146-151
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• 2015

황칠원액을 에탄올로 추출한 황칠의 essential oil을 올레핀 메타테시스(olefin metathesis) 반응의 하나인 ROMP(ring opening metathesis polymerization)법을 이용하여 경화 반응을 수행하였으며, 자연 경화 및 UV 광경화법의 경화 특성 및 경화된 필름의 물성에 대해서 비교 연구하였다. 경화 전후의 황칠의 조성 변화에 대해서 가스 크로마토그래피 질량분석법(GC-MS, gas chromatography mass spectrometry)을 통해 연구하였으며, ROMP법에 의해 경화된 필름의 겔 함량(gel contents, 40%)은 자연 경화(8%)나 UV 광경화법(25%)에 비해 높은 값을 보여주었다. $100^{\circ}C$의 온도 및 2 wt%의 Grubbs' catalyst 조건에서 ROMP 경화반응은 2 h 이내의 경화 반응이 완료되어 자연 경화에 비해 비교적 빠른 경화 속도를 보여주었으며, UV 광경화법에 비해 주름이 없으며 외관상 균일한 도막이 형성됨을 확인하였다. 또한 기존에 경화반응에 참여하는 것으로 알려져 있는 폴리아세틸렌계 성분 이외에 sesquiterpene류인 ${\alpha}$-selinene, ${\beta}$-selinene, ${\delta}$-cadinene 등도 ROMP 경화 반응에 참여함을 확인하였다.

• 한국염색가공학회지
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• 제28권2호
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• pp.70-76
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• 2016

Silver nanoparticles(AgNPs) were attached to wool fibers using glycidyltrimethylammonium chloride(GTAC), which is a type of quaternary ammonium salt. GTAC, which contains an epoxy functional group that, under high temperatures, generates a ring-opening reaction with wool fibers, which contain the amine group. Then, the AgNPs are attached to the surface of the GTAC-treated wool fibers by treatment with a silver colloidal solution. The process involves the following procedures: (1) The wool fibers are immersed in the GTAC solution, followed by pre-drying at $80^{\circ}C$ and curing at $180^{\circ}C$ to induce an alteration in the chemical structure; and (2) The wool fibers treated with GTAC are immersed in the silver colloid at $40^{\circ}C$ for 120 min to chemically induce a strong attachment of the AgNPs to the wool fibers. Scanning electron microscopy was used to analyze the influence of the concentrations of GTAC and the silver colloid, as well as the influence of the applied temperature of the silver colloid on the wool fibers, and the influence of the morphological changes in the wool fiber surfaces. As a result, the enhanced concentrations of GTAC and the silver colloid together with an elevated applied temperature of silver colloid have a tendency to increase in Ag atomic%.

• 한국물환경학회지
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• 제23권3호
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• pp.303-308
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• 2007

Three types dyeing wastewater (dark, medium, light color) discharged from cotton textile dyeing with reactive dye was collected at each step of process. Each process dying wastewater was analyzed and treated by ionized gas. The analysis focused on $COD_{Cr}$, SS and color. Bleaching & scouring process wastewater has the highest $COD_{Cr}$ value in the three type dyeing wastewater. SS shows the highest value at dyeing process wastewater in dark and medium color but light color has at finishing process wastewater. The result of process wastewater treatment by ionized gas was that the ionized gas was effective in $COD_{Cr}$ removing of bleaching & scouring process and finishing process wastewater but was not good at dyeing process wastewater. From that result it is estimated that the ionized gas could not work in opening the aromatic ring and react only in aliphatic component of the molecule. Because the surfactants contained in bleaching & scouring process and finishing process wastewater have only one aromatic ring in its molecular structure, in contrast with the reactive dye compounds consist of aromatic rings great part of its molecular structure. The color almost removed in 1.5 hrs reaction time but $COD_{Cr}$ removal effiency was only 30.7% through 3hrs in 1500 mL of total dyeing wastewater treated by 10 L/min ionized gas.

• Journal of Microbiology and Biotechnology
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• 제23권8호
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• pp.1060-1069
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• 2013

Genome organization near cyclomaltodextrinases (CDases) was analyzed and compared for four different hyperthermophilic archaea: Thermococcus, Pyrococcus, Staphylothermus, and Thermofilum. A gene (CL1_0884) encoding a putative CDase from Thermococcus sp. CL1 (tccd) was cloned and expressed in Escherichia coli. TcCD was confirmed to be highly thermostable, with optimal activity at $85^{\circ}C$. The melting temperature of TcCD was determined to be $93^{\circ}C$ by both differential scanning calorimetry and differential scanning fluorimetry. A size-exclusion chromatography experiment showed that TcCD exists as a monomer. TcCD preferentially hydrolyzed ${\alpha}$-cyclodextrin (${\alpha}$-CD), and at the initial stage catalyzed a ring-opening reaction by cleaving one ${\alpha}$-1,4-glycosidic linkage of the CD ring to produce the corresponding single maltooligosaccharide. Furthermore, TcCD could hydrolyze branched CDs (G1-${\alpha}$-CD, G1-${\beta}$-CD, and G2-${\beta}$-CD) to yield significant amounts (45%, 40%, and 46%) of isomaltooligosaccharides (panose and $6^2$-${\alpha}$-maltosylmaltose) in addition to glucose and maltose. This enzyme is one of the most thermostable maltogenic amylases reported, and might be of potential value in the production of isomaltooligosaccharides in the food industry.

• 대한화학회지
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• 제40권5호
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• pp.357-364
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• 1996

아세톡시 1,3-옥사티올란 1의 이성체들의 입체화학을 두 가지 방법에 의해 결정하였다. 첫째, 산촉매하에서 디히드로옥사티인 2로의 전환되는 반응속도 차이에 의해 알파이성체 7과 베타이성체 9의 구조를 결정하였다. 이탈기인 아세톡시기가 황원자와 트랜스 위치에 있을 때 1,3-옥사티올란 고리에 대한 입체장애가 적은 이성체가 알파이성체 7이며 반응속도가 느린 이성체가 베타이성체 9이었다. 둘째, 술폭시드의 각각의 diastereomer들의 중수소 치환반응에서, methine 수소가 중수소로 치환된 화합물은 시스이성체 15, 17, 그리고 메틸기의 수소가 중수소로 치환된 화합물은 트랜스이성체 16, 18이었다. Methine 또는 메틸기의 수소의 중수소로의 치환은 [2,3] 시그마트로픽 전위에 의한 입체특이적 개환 및 폐환의 결과였다.

• Macromolecular Research
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• 제17권10호
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• pp.770-775
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• 2009

$\omega$-Anhydride-functionalized poly(ethylene oxide) (PEO) obtained from chain-end functionalization and anionic ring-opening polymerization of ethylene oxide using n-butyllithium with potassium t-butoxide in the presence of dimethylsulfoxide (DMSO) was found to be an efficient material for the preparation of water-soluble, polymeric pro-drugs. The reaction of $\omega$-anhydride-functionalized PEO with sulfonamide or with vancomycin provided an efficient method to produce corresponding, water-soluble, PEO-conjugated sulfonamide or PEO-conjugated, vancomycin pro-drugs. These were used successfully to prepare water-dispersible, silver nanoparticles. In this study, the particle sizes were in the range of $5{\sim}40$ nm. The resulting products were characterized by $^1H$ NMR spectroscopy, transmission electron microscopy, electron and X-ray diffraction, size exclusion chromatography, and UV/Visible spectroscopy.

• Bulletin of the Korean Chemical Society
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• 제27권7호
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• pp.981-985
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• 2006

Novel copolymers consisting of poly(2-hydroxyethyl aspartamide-co-N,N'-dimethyl-1,3-propane aspartamide) (PHEA-DPA) were prepared from polysuccinimide (PSI), which is the thermal polycondensation product of aspartic acid, via a ring-opening reaction with N,N'-dimethyl-1,3-propane diamine (DPA) and ethanolamine. The prepared water-soluble copolymer was then crosslinked by reacting it with hexamethylene diisocyanate to provide the corresponding gel. The swelling behavior and morphology of the crosslinked hydrogels were investigated. The degree of swelling decreased with increasing crosslinking reagent due to the higher crosslinking density. It was also confirmed that the swelling property is affected by pH. At low pH (< pH 4), swelling is increased due to the ionization of DPA with a tertiary amine moiety. In addition, a reversible swelling and de-swelling behavior was demonstrated by adjusting the pH of the solution. The prepared hydrogels showed a well-interconnected microporous structure with regular 5-20 $\mu$m sized pores.

• 한국재료학회지
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• 제28권4호
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• pp.227-234
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• 2018

We investigate the effect of the modification of cellulose acetate propionate as an organic vehicle for silver paste on solar cell efficiency. For the modification of cellulose acetate propionate, poly(ethylene glycol) is introduced to the hydroxyl groups of a cellulose acetate propionate backbone via esterification reaction. The chemical structure and composition of poly(ethylene glycol) functionalized cellulose acetate propionate is characterized by Attenuated total reflectance Fourier transform infrared, $^1H$ nuclear magnetic resonance, differential scanning calorimetry and thermogravimetric analysis. Due to the effect of structural change for poly(ethylene glycol) functionalized cellulose acetate propionate on the viscosity of silver paste, the solar cell efficiency increases from 18.524 % to 18.652 %. In addition, when ethylene carbonate, which has a structure similar to poly(ethylene glycol), is introduced to cellulose acetate propionate via ring opening polymerization, we find that the efficiency of the solar cell increases from 18.524 % to 18.622 %.

• Macromolecular Research
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• 제10권2호
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• pp.85-90
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• 2002

Poly (ethylene oxide)/polylatide/poly(ethylene oxide) (PEO/PL/PEO) tri-block copolymers, which each block is connected by ester bond, were synthesized by coupling reaction of PL with PEO in the presence of pyridine. PL/PEO/PL tri-block copolymer was synthesized by ring opening polymerization of L-lactide initiated by PEO in the presence of stannous octoate. Degradation behavior of the copolymers was investigated in a pH 7.4 phosphate buffer saline (PBS) at 37$\pm$1 $^{\circ}C$. Gel permeation chromatography (GPC) and $^1$H-nuclear magnetic resonance (NMR) were used to monitor the change of mass loss, molecular weight and composition of copolymers. In hydrolytic degradation, the PEO/PL/PEO tri-block copolymer with high PEO contents affected the increase of its mass loss, and resulted in the decrease of its molecular weight as well as PEO composition. However, when PL/PEO/PL and PEO/PL/PEO tri-block copolymers had similar PEO contents, PEO/PL/PEO decreased faster in molecular weight and PEO composition than PL/PEO/PL.