• 한국연소학회지
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• 제11권1호
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• pp.19-26
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• 2006

Structure of edge flame established in a mixing layer, formed between two uniformly flowing pure $CH_4$ and pure $O_2$ streams, is numerically investigated by employing a detailed methane-oxidation mechanism. The numerical results exhibited the most outstanding distinction of using pure oxygen in the fuel-rich premixed-flame front, through which the carbon-containing compound is found to leak mainly in the form of CO instead of HC compounds, contrary to the rich $CH_4-air$ premixed flames in which $CH_4$ as well as $C_2H_m$ leakage can occur. Moreover, while passing through the rich premixed flame, a major route for CO production, in addition to the direct $CH_4$ decomposition, is found to be $C_2H_m$ compound formation followed by their decomposition into CO. Beyond the rich premixed flame front, CO is further oxidized into $CO_2$ in a broad diffusion-flame-like reaction zone located around moderately fuel-rich side of the stoichiometric mixture by the OH radical from the fuel-lean premixed-flame front. Since the secondary CO production through $C_2H_m$ decomposition has a relatively strong reaction intensity, an additional heat-release branch appears and the resulting heat-release profile can no longer be seen as a tribrachial structure.

• 대한화학회지
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• 제40권7호
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• pp.519-525
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• 1996

3-Carbomethoxy-1(3H)-isobenzofuraneme(9)과 .alpha., .beta.-불포화 에스테르 화합물 3a-b를 각각 반응시켜서 naphthacene-6, 7-dione 11a-b를 좋은 수율로 얻었다. 이들 중 C-9 위치에 에틸기가 없는 11a는 산화시켰을 때 naphthacene-5, 12-dione 13a가 생성되는 반면, 에틸기를 갖고 있는 11b는 naphthacene-5, 7, 12-trione 12b와 naphthacene-5, 12-dione 13b가 3:2로 생성되어졌다.

• 한국자기공명학회논문지
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• 제9권2호
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• pp.103-109
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• 2005

New PVC plasticizer, 2,2,4-trimethyl-1,3-pentanediol-1-butyrate-3-isobutyrate was synthesized via simple esterification with butyric acid and Texanol(a trademark of Eastman Chemicals), the mixture of 2,2,4-trimethyl-1,3-pentanediol-3-isobutyrate and 2,2,4-trimethyl-1,3-pentanediol-1-isobutyrate. The analysis of $^1H-1D,\;^{13}C-1D$ NMR and HMBC spectra identified internal-ester-transfer of 2,2,4-trimethyl-1,3-pentanediol-1-isobutyrate during the reaction. 2,2,4-trimethyl-1,3-pentanediol-1-butyrate-3-isobutyrate gave better properties in PVC than 2,2,4-trimethyl-1,3-pentanediol diisobutyrate(TXIB, a trademark of Eastman Chemicals) such as lower viscosity, higher tensile strength and better elongation. In particular, remarkably reduced migration compared with TXIB suggested a reduced emission of VOC(volatile organic compound) from PVC.

• 한국기계가공학회지
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• 제18권2호
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• pp.91-95
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• 2019

A new experimental approach is proposed to detect a specific polymer dissolved in a liquid. Distinctive optical properties were found using a laser scattering technique when there is a polymer compound with almost no difference in optical properties (index of refraction) in a liquid phase. The index of refraction, which determines the refraction of light, is obtained by dissolving PCL and PLA. The used samples are biodegradable materials with similar properties and dissolved in a mixture of Chloroform 7: Methanol 3. To predict the optical properties, a 632-nm diode laser was used as the light source of the device, and an integrating sphere was used as the light receiver. Although PCL and PLA had a similar index of refraction of 1.46-1.48, the dissolved PCL showed a relative transmittance of 43%, and the dissolved PLA had a relative transmittance of 34%. The difference in optical properties of the pure polymer compound in the solid state or liquid state is not significantly different, and the difference in the dissolved state in the specific solvent is remarkable because the solubility differs in a specific solution and is randomly distributed.

• 한국결정성장학회지
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• 제23권3호
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• pp.135-141
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• 2013

본 연구에서는 $CrSi_2$ 열전화합물을 제조하기 위하여 순금속 $Cr_{33}Si_{67}$ 혼합분말을 기계적 합금화 처리하였다. 초미세 $CrSi_2$계 열전화합물을 얻기 위하여 최적 볼밀조건 및 열처리 조건을 X선 회절분석과 시차주사 열량분석을 이용하여 조사하였다. 순금속 $Cr_{33}Si_{67}$ 혼합분말을 70시간까지 볼밀 처리 후 $650^{\circ}C$까지 열처리함으로써 평균 결정립 크기가 70 nm 인 초미세 $CrSi_2$ 열전화합물을 얻을 수 있었다. MA 분말시료의 벌크화를 위하여 소결온도 $600{\sim}1000^{\circ}C$, 압력 60 MPa에서 SPS 소결을 실시하였다. SPS 과정에서 MA 분말의 수축은 소결 개시 후 $600^{\circ}C$ 전후에서 크나 전반적으로 급격하게 발생하지 않으며 $1000^{\circ}C$까지 비교적 단조롭게 수축함을 알 수 있었다. 여기서 수축이 $600^{\circ}C$ 부근에서 큰 이유는 열분석 결과에서도 보여주듯이 $CrSi_2$ 화합물의 생성과 관련이 있는 것으로 판단된다. SPS 성형체의 전기전도도 및 제벡계수는 $900^{\circ}C$까지 측정을 실시하였으며, 그 결과로부터 제벡계수는 $400^{\circ}C$에서 $125{\mu}V/K$ 및 파워팩터는 $350^{\circ}C$에서 $4.3{\times}10^{-4}W/mK^2$의 최대값을 각각 나타내었다.

• 한국산림과학회지
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• 제95권4호
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• pp.429-434
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• 2006

독일가문비(Picea ahies Karsten) 잎을 채취하여 건조시킨 후 분쇄하여 1.5 kg을 acetone-$H_2O$(7:3, v/v)로 추출하고 핵산, 메틸렌클로라이드, 에틸아세테이트 및 물 가용부로 분획하여 동결건조 시켰다. 에틸아세테이트 및 물 가용부를 Sephadex LH-20으로 충진한 칼럼에서 MeOH와 EtOH-n-hexane 혼합액을 용출용매로 사용하여 칼럼크로마토그래피를 실시하였다. 단리된 화합물들은 셀룰로오스 박층크로마토그래피(TLC)로 확인한 후 $^1H$-, $^{13}C$-NMR 등의 스펙트럼을 사용하여 정확한 구조를 규명하였고 FAB 및 El-MS로써 분자량을 측정하였다. 독일가문비 잎의 에틸아세테이트 가용부에는 (+)-catechin(화합물 I), (-)-epicatechin(화합물 II), kaempferol-3-O-${\beta}$-D-glucopyranoside(화합물 III), 4-hydroxyacetophenone(화합물 IV)가 분리되었으며 물 가용부에서는 (+)-catechin(화합물 I)과 protocatechuic acid(화합물 V)가 분리되었다. 각 분획물 및 단리된 화합물들은 DPPH 라디칼 소거법을 이용하여 항산화 시험을 실시하였으며, 분획물중에는 에틸아세테이트 가용부, 그리고 화합물중에는 (T)-catechin과 (-)-epicatechin에서 기준물질과 유사한 우수한 항산화 효능이 있는 것으로 나타났다.

• 한국식품영양과학회지
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• 제36권2호
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• pp.155-162
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• 2007

본 연구에서는 녹차(Camellia sinensis)잎 추출물, 구아바(Psidium guajava)잎 추출물 그리고 장미(Rosa hybrida)꽃잎 추출물로 이루어진 식물추출 복합물(PEM381)에 대하여 제I형 알레르기 반응 억제 효능 및 생화학적 기전을 밝히기 위하여 COX 억제 활성, LO 억제 활성, compound 48/80에 의한 랫드 복강 비만세포의 탈과립과 히스타민 유리에 미치는 영향 그리고 수동피부아나필락시스 반응 억제효능을 측정하였다. 그 결과 PEM381은 5-LO $IC_{50}$ 값이 $14.11{\pm}0.51ppm$으로 나타났고, COX-1에 비해 COX-2를 선택적으로 억제하는 것으로 나타났다. 또한 PEM381은 compound 48/80에 의한 비만세포의 탈과립과 히스타민 유리를 농도 의존적으로 억제할 뿐만 아니라 수동피부아나필락시스 반응도 억제하였다. 이상의 결과로 PEM381은 알레르기성 비염, 아토피 피부염 및 기관지천식 같은 제I형 알레르기 질환에 대하여 예방 및 치료에 유용하게 사용될 수 있을 것으로 생각된다.

• Journal of Microbiology and Biotechnology
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• 제11권4호
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• pp.712-715
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• 2001

A new combined method including the enzymatic hydrolysis of $\beta$-cyclodextrin ($\beta$-CD) and solvent extraction fo cholesterol from the hydrolyzed mixture was developed to recover cholesterol from a $\beta$-CD-cholesterol complex prepared from dairy products, such as cream, milk, and cheese. Cyclomaltodextrinase (cyclomatodextrin dextrin hydrolase, EC 3.2.1.54, DCase_ prepared form alkalophilic Bacillus sp. KJ 133 hydrolyzed the $\beta$-DC of the $\beta$-CD-cholesterol complex, and then, free cholesterol was efficiently extracted from the hydrolyzed mixture by a nonpolar solvent such as ethyl acetate. To increase the stability of free CDase, immobilized CDase was developed using sodium alginate as a carrier. The immobilized CDase showed a high recovery yield of cholesterol in a time-dependent manner compared to the free CDase. A gas chromatography analysis showed that more than 70% of cholesterol was recovered from the $\beta$-DC-cholesterol complex of cream by the immobilized CDase, whereas only 3% and 29% of cholesterol were recovered when the solvent extraction and free CDase treatment were used, respectively. The cholesterol recovered can be used as a raw material for steroid synthesis. Furthermore, this method can be an efficient way to recover cholesterol or other organic compounds that are bound in a $\beta$ -DC-cholesterol or -organic compound complex.

• Biotechnology and Bioprocess Engineering:BBE
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• 제9권4호
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• pp.285-291
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• 2004

A simulated moving bed (SMB) chromatography system is a powerful tool for preparative scale separation, which can be applied to the separation of chiral compound. We have de-signed our own lab-scale SMB chromatography using 5 HPLC pumps, 6 stainless steel columns and 4 multi-position valves, to separate a racemic mixture of ketoprofen in to its enantiomers. Our design has the characteristics of the low cost for assembly for the SMB chromatography and easy repair of the unit, which differs from the designs suggested by other investigators. It is possible for the flow path through each column to be independently changed by computer control, using 4 multi-position rotary valves and 5 HPLC solvent delivery pumps. In order to prove the operability of our SMB system, attempts were made to separate the (S)-ketoprofen enantiomer from a ketoprofen racemic mixture. The operating parameters of the SMB chromatography were calculated for ketoprofen separation from a batch chromatography experiment as well as by the triangle theory. With a feed concentration of 1 mg/mL, (S)-ketoprofen was obtained with a purity of 96% under the calculated operating conditions.

• 한국도로학회논문집
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• 제20권2호
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• pp.27-34
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• 2018

PURPOSES : It is necessary to prevent premature failure of concrete pavements caused by durability problems. The purpose of this study was to find factors affecting the durability of concrete pavements, and suggest improvement methods for existing concrete mix design. METHODS : Factors influencing durability were derived from laboratory test data for common field failure conditions and main properties of concrete cores taken from the field. The improvement of concrete properties was investigated by evaluating the performance of existing and proposed mix proportion designs and curing methods. RESULTS : The compressive strength and the absorbing performance of the low Blaine cement and the high-strength mixture were better than those of the Type I cement. Wet curing showed better compressive strength, elastic modulus, coefficient of thermal expansion, and absorption performance than air curing or compound curing. As a result of comparing concrete cores collected in the field, the sections with good durability showed good performance in terms of resistance to chloride ion penetration, absorption, and initial absorption rate. CONCLUSIONS : The absorption performance was considered as a possible foactor affecting durability of cement concrete pavements as a result of field core tests. In order to improve the durability of the pavement concrete, it is necessary to improve the existing mixtures and curing methods.