• Bulletin of the Korean Chemical Society
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• 제32권6호
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• pp.1851-1858
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• 2011

Details of the double-bond isomerization of 1-hexene over H-ZSM-5 were clarified using density functional theory. It is found that the reaction proceeds by a mechanism which involves the Br${\o}$nsted acid part of the zeolite solely. According to this mechanism, 1-hexene is first physically adsorbed on the acidic site, and then, the acidic proton transfers to one carbon atom of the double bond, while the other carbon atom of the double bond bonds with the Br${\o}$nsted host oxygen, yielding a stable alkoxy intermediate. Thereafter, the Br${\o}$nsted host oxygen abstracts a hydrogen atom from the $C_6H_{13}$ fragment and the C-O bond is broken, restoring the acidic site and yielding trans-2-hexene. The calculated activation barrier is 12.65 kcal/mol, which is in good agreement with the experimental value. These results well explain the energetic aspects during the course of double-bond isomerization and extend the understanding of the nature of the zeolite active sites.

• Structural Engineering and Mechanics
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• 제3권4호
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• pp.299-312
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• 1995

A new reinforcing steel model which is embedded inside a concrete element and also accounts for the effect of bond-slip is developed. Unlike the classical bond-link or bond-zone element using double nodes, the proposed model is considering the bond-slip effect without taking double nodes by incorporation of the equivalent steel stiffness. After calculation of nodal displacements, the deformation of steel at each node can be found through the back-substitution technique from the first to the final steel element using a governing equation constructed based on the equilibrium at each node of steel and the compatibility condition between steel and concrete. This model results in significant savings in the number of nodes needed to account for the effect of bond-slip, in particular, when the model is used for three dimensional finite element problems. Moreover a new nonlinear solution scheme is developed in connection with this model. Finally, correlation studies between analytical and experimental results and several parameter studies are conducted with the objective to establish the validity of the proposed model.

• 한국콘크리트학회:학술대회논문집
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• 한국콘크리트학회 2005년도 봄학술 발표회 논문집(I)
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• pp.315-318
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• 2005

The objective of this study is to find out discrepancy in ability of bond behavior between Carbon fiber-reinforced polymer(CFRP Plate) and concrete by method of experiment. For the objective, single and double face shear test were tested. From the experimental results, it was analyzed bond strength of FRP to concrete, distribution of stress and strain of FRP. The bond strength and the effective bond length was evaluated by the theory of existing studies. Effective bond length of single face test was smaller than it of double face test.

• Bulletin of the Korean Chemical Society
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• 제25권11호
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• pp.1623-1624
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• 2004

• 농업과학연구
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• 제35권1호
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• pp.11-17
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• 2008

가시오가피를 실온에서 petroleum ether로 추출한 polyacetylene의 동정하기 위하여 TLC, HPLC, UV spectrum, IR, NMR로 수행하였다. TLC에 전개시킨 결과, polyacetylene 표준품과 동일한 band가 fraction 5에서 확인되었으며, HPLC에서 fraction 5를 분리시킨 결과 retention time이 4.40, 5.36, 6.40분이었다. 이를 UV spectrum에서 확인한 결과, 6.40분의 peak(compound 3)에서 polyacetylenes의 파장인 231.0nm, 239.0nm, 257.0nm을 나타내었다. IR spetrum에서 triple bond $2256cm^{-1}$과 double bond $1654cm^{-1}$의 전형적인 peak를 나타내었으며, $^{13}C$-NMR(400MHz, $CDCl_3$)에서 polyacetylenes 전형적인 64.0, 71.2, 74.2, 80.2ppm은 2개의 triple bond에 의한 peak와 121.89, 133.0ppm에서 internal double bond로 결합된 2개의 peak를 확인 할 수 있었다.

• KSBB Journal
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• 제19권6호
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• pp.489-493
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• 2004

Candida cylindracea 유래의 Lipase-OF 360,000를 사용하여 물고기 기름을 구성하고 있는 여러 종류의 지방산의 아실 체인 특성과 가수분해율 사이의 함수관계를 규명하였다. 이중결합수와 이중결합이 시작되는 위치, 즉 (n-3), (n-7) 및 (n-9)이 동일할 경우, Lipase-OF 360,000에 의한 지방산의 가수분해율은 지방산을 구성하고 있는 탄소수의 증가에 따라 가수분해율이 감소하는 아실체인 특이성을 나타내었다. 이중결합이 시작되는 탄소의 위치 또한 Lipase-OF 360,000의 가수분해 특이성에 영향을 끼쳤다. 이 외에 Lipase-OF 360,000은 지방산의 탄소수와 이중결합이 시작되는 위치가 동일할 경우, 이중결합수가 증가하면 가수분해율이 감소하는 아실 체인 특이성도 나타내었다. 또한 본 연구에서는 물고기 기름을 구성하고 있는 각 지방산의 가수분해율을 시간의 함수로 제시함으로서 원하는 지방산을 미반응 글리세라이드 혼합물 내로 농축시키는 공정개발의 기초 자료로 활용할 수 있도록 하였다.

• 한국응용과학기술학회지
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• 제19권3호
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• pp.222-244
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• 2002

A mixture of methyl ester derivatives of fatty acids from the oils of pine nuts was well resolved to five fractions differing by degree of unsaturation by silver ion solid-phase extraction column chromatography ($Ag^{+}$-SEC). Polyunsaturated fatty acid with non-methylene interrupted conjugated double bond (NMiDB) radical held more strongly to silver ions in the column than methylene interrupted conjugated double bond (MiDB) one when they had the same number of double bonds. Although both the picolinyl ester and DMOX derivative provided clear mass ion species powerful enough to elucidate the structure of the polyunsaturated fatty acid (PUFA) with NMiDB and/or methylene interrupted conjugated double bond (MiDB) radical in the oils, the picolinyl ester of PUFA with NMiDB radical did not provide a cluster of mass ions neighboring diagnostic mass ions induced by the double bond in the proximal to the carboxyl group. However, the DMOX derivative of PUFA with NMiDB group as well as MiDB showed abundant mass ion species differing by gaps of 12 amu, which made it possible with greater ease to locate the double bonds in the molecule. The oil contained $C_{18:2{\omega}6}$ (46.2 %) and $C_{18:1{\omega}9}$ (25.4 %) as main components, and considerable amounts of PUFAs with NMiDB radical such as ${\Delta}^{5.\;9.\;12}-C_{18:3}$ (16.0 %), ${\Delta}^{5.\;9}-C_{18:2}$ (2.3 %) and ${\Delta}^{5.\;11.\;14}-C_{20:3}$ (0.8 %).

• Advances in concrete construction
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• 제13권3호
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• pp.265-279
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• 2022

The roughness of substrate concrete interfaces before new concrete placement has a major effect on the interface bond behaviour. However, there are challenges associated with the consistency of the final roughness interface prepared using conventional roughness preparation methods which influences the interface bond performance. In this study, five quantitative interface roughness textures with different roughness tooth angles, depths, and tooth distribution were created to ensure consistency of interface roughness and to evaluate the bond behaviour at a precast and new concrete interface using the splitting tensile test, slant shear test, and double-shear test. In addition, smooth interface specimens and two separate the pitting interface roughness were also utilized. Obtained results indicate that the quantitative roughness has a very limited effect on the interface tensile bond strength if no extra micro-roughness or bonding agent is added at the interface. The roughness method however causes enhanced shear bond strength at the interface. Increased tooth depth improved both the tensile and shear bond strength of the interfaces, while the tooth distribution mainly influenced the shear bond strength. Major failure modes of the test specimens include interface failure, splitting cracks, and sliding failure, and are influenced by the tooth depth and tooth distribution. Furthermore, the interface properties were obtained and presented while a comparison between the different testing methods, in terms of bond strength, was performed.

• Journal of Biosystems Engineering
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• 제43권1호
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• pp.37-44
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• 2018

Purpose: The objective of this study was to investigate the high-efficiency anaerobic digestion of organic wastes with high fat content. Specifically, the analysis focused on biogas production performance with a focus on carbon number and the double bond count of the long-chain fatty acids (LCFAs), which are hydrolysis products of triglycerides. Methods: Experiments were performed under mesophilic anaerobic conditions with a feed-to-microorganism ratio (F/M) of 1.0. Biogas production performance was analyzed through biogas production patterns, lag-phase, and the time required for 90% biogas production (T90). Results: Biogas production increased when the content of unsaturated LCFAs (containing relatively large numbers of carbon atoms) increased. In substrate containing LCFAs with four or more double bonds, although the initial lag-phase in biogas production was shortened, development of a three-step lag-phase resulted in decreased biogas production. These results suggest that high rates of anaerobic digestion are possible when the LCFAs have high unsaturated fatty acid content with three or fewer double bonds. Conclusions: When various types of LCFAs are digested anaerobically, biogas production performance can be improved if the unsaturated fatty acid content and number of double bonds are optimized for maximum production.

• 한국해양바이오학회지
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• 제10권2호
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• pp.44-52
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• 2018

A synthetic pathway, which consisted of fatty acid double bond hydratase, alcohol dehydrogenase, and Baeyer-Villiger monooxygenase, was applied to Chlorella oil to produce ester fatty acids, which can be hydrolyzed into medium chain fatty acids. Since linoleic acid is a major fatty acid constituent of Chlorella oil, a fatty acid double bond hydratase from Lactobacillus acidophilus NBRC13951, which is able to convert linoleic acid into 13-hydroxyoctadec-9-enoic acid, was used. Recombinant Escherichia coli expressing the fatty acid double bond hydratase from L. acidophilus NBRC13951 successfully transformed linoleic acid in Chlorella oil hydrolysates into 13-hydroxyoctadec-9-enoic acid with approximately 60% conversion yield. 13-Hydroxyoctadec-9-enoic acid was further converted into ester fatty acids by the recombinant E. coli expressing a long chain secondary alcohol dehydrogenase and a Baeyer-Villiger monooxygenase. The resulting ester fatty acids were then hydrolyzed into medium chain fatty acids by a lipase. Overall, industrially relevant medium chain fatty acids were produced from Chlorella oil hydrolysates. Thereby, this study may contribute to biosynthesis of medium chain fatty acids from microalgae oils as well as long chain fatty acids.