• Journal of the Korea Academia-Industrial cooperation Society
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• v.9 no.5
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• pp.1150-1153
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• 2008

The coupled oscillation of multi-walled carbon-nanotube (MWCNT) oscillators consisting of (5n, 5n) CNTs was investigated by molecular dynamics simulations. The results show that the inter-wall coupling leads to frequency splits. And there are consistently three primary frequency peaks for the quadric-walled, penta-walled and hexa-walled CNT oscillators. It is independent of the wall parameters, suggesting applications as triple-frequency generators. Furthermore, at least one of the primary frequencies of a MWCNT oscillator is lower than that of its double-walled counterpart.

• Archives of Pharmacal Research
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• v.27 no.3
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• pp.278-282
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• 2004

A number of 8-arylflavones have been synthesized as congeners of wogonin and evaluated for their inhibitory activities of $PGE_2$ production. 8-Arylflavones were obtained from commercially available chrysin via two different synthetic pathways. Most 8-arylflavones exhibited much reduced inhibitory activities against COX-2 catalyzed $PGE_2$ production compared to that of wogonin. Functional group replacement at the 8-position of wogonin from methoxy to aryl group caused loss of inhibitory activity. Our present results imply that the functional group at the 8-position of flavones seems to play very important roles for bioactivity.

• Journal of the Korean Applied Science and Technology
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• v.28 no.2
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• pp.185-195
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• 2011

Carbon nanotube(CNT) plays an essential role in various fields of nano based science and technology. Recently, silica coated CNT composites are interested because they are useful for the optical, magnetical, and catalytic applications. In this report, carboxyl groups were introduced on the MWCNT using nitric acid. In order to maximize the silica encapsulation efficiency, carboxyl groups of MWCNT reacted with a silane coupling agent were used to prepare silica coated MWCNT. Due to their strong interaction between modified MWCNT and TEOS. Silica layer with a controllable thickness was achieved. Silica coated MWCNT were further utilized as the template for the synthesis of hollow silica nanotubes after $800^{\circ}C$ calcination.

• Current Optics and Photonics
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• v.5 no.2
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• pp.180-185
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• 2021

A femtosecond-laser inscribed Yb:YAG surface channel waveguide (WG) laser with single-walled carbon nanotubes deposited on the top surface of the WG was passively Q-switched by evanescent field interaction. Q-switched operation of the 14-mm-long compact Yb:YAG WG laser was achieved near 1031 nm with two different pumping schemes (single- and double-pass pumping) with an output coupling transmission of 91%. The Q-switched pulse characteristics depending on the absorbed pump power were investigated for both pumping geometries and analyzed in detail based on theoretical modeling. The best performances (energy/pulse duration) for each configuration were 204.4 nJ/75 ns at a repetition rate of 1.87 MHz, and 201.1 nJ/81 ns at 1.75 MHz for single- and double-pass pumping, respectively.

• Bulletin of the Korean Chemical Society
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• v.27 no.8
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• pp.1171-1174
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• 2006

Various off-the-shelf Lewis acids in conjunction with various onium salts are screened for coupling reaction of $CO_2$ with epoxides. Among the tested ones, $VCl_3/n-Bu_4NOAc$, $VCl_3/(n-Bu_4NCl$ or PPNCl), $FeCl_3/ n-Bu_4NOAc$, and $FeCl_3/ n-Bu_4NOAc$are proved to be highly active. Propylene oxide, epichlorohydrin, styrene oxide, and cyclohexene oxide can be converted over 90% yields to the corresponding cyclic carbonates without the use of organic solvents under mild conditions by 0.1-1.0 mol% catalyst charge.

• KSBB Journal
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• v.8 no.2
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• pp.110-114
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• 1993

Vinblastine, an anticancer agent was produced by chemical coupling of two different monomeric indole alkaloids, vinblastine and catharanthine in the presence of ferric ion. Vindoline was efficiently extracted from the leaves of vinca (Cafharanthus roseus) by using supercritical carbon dioxide, whereas catharanthine was chemically extracted from the in vitro cultured hairy roots. The extracted crude monomeric precursors were purified by a two-step preparative TLC. The coupling reaction was carried out in the 0.1M glycine buffer(pH 2.0, 5ml) containing 40mM FeC13 with purified vindoline(0.3mg) and catharanthine(0.3mg) at 4$^{\circ}C$. The production yields (weight %) of vinblastine and 3', 4'-anhy-drovinblastine in the products were 23.2 and 26.0, respectively. The produced vinblastine was confirmed by FAB-MS.

• Elastomers and Composites
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• v.50 no.3
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• pp.159-166
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• 2015

Silica which is used for reinforcing filler in tire industry is widely known as eco-friendly material exerting $CO_2$ reduction effect through decrease of rolling resistance and improvement of wet grip. Generally silica is classified as a highly polar filler because it contains a large number of silanol (Si-OH) group on its surface. And also silica gives a lower reinforcing effect than carbon black due to its poorer rubber-filler interaction. Therefore silica is treated with silane coupling agent or activator, then following the conventional rubber blend method, vulcanized sheets were prepared using a hot press, and cure characteristics, mechanical properties and abrasion resistance of the test specimens were investigated. It was found that with an increase in the silane coupling agent content the tensile strength, 300% modulus and abrasion resistance increased while Mooney viscosity decreased and crosslink density slightly increased with an increase of activator.

• Elastomers and Composites
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• v.55 no.4
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• pp.339-346
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• 2020

We functionalized a wear-resistant carbon-based MoS2 filler to solve its limited wear condition problem. The filler exhibits excellent lubricative properties. The surface modification of MoS2 was carried out using a (3-glycidyloxypropyl)trimethoxysilane (GPTMS) silane coupling agent to improve the low compatibility and dispersibility of the filler that generally degrade the performance of composites. A silane coupling agent was employed for the functionalization of MoS2, and its effect on the wear resistance of MoS2/Polyamide-6,6 was investigated. The silanization of MoS2 was identified by contact angle analysis and Fourier-transform infrared, energy dispersive X-ray, and X-ray photoelectron spectroscopies. The wear resistance of the composite was found to be improved significantly by the surface functionalization of MoS2.

• New & Renewable Energy
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• v.18 no.2
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• pp.50-59
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• 2022

The Korean government announced the "1st Basic Plan for the Transition to Hydrogen Economy" in 2021 and declared the establishment of a hydrogen industry ecosystem by 2040. To build a low-carbon power system, resources that can efficiently accommodate renewable energy are required, and green hydrogen is considered a potential solution. This study analyzed the economic feasibility of green hydrogen-based sector coupling to reduce curtailment of renewable generation in the Jeju power system by 2025 under the scenario of with or without HVDC#3. The result showed that HVDC#3 significantly reduced the frequency of curtailment from 16.1% to 3.0%. In addition, green hydrogen-based sector coupling was an economically feasible option as result showed an IRR of 4.86% when HVDC#3 was connected and 11.45% when it was not under the condition of achieving 50% curtailment reduction. This study shows that the higher the level of renewable energy deployment, the more delayed the HVDC connection between Jeju and the main land, and the lower the SMP, the more economically feasible the green hydrogen-based sector coupling is. Furthermore, this study suggests that the policy goal of completely reducing curtailment is not economically efficient.

• Applied Chemistry for Engineering
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• v.27 no.6
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• pp.627-632
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• 2016

Ethyl methacrylate (EMA) monomer coupling onto the polyvinylidene fluoride (PVDF) film surface was attempted to enhance the interfacial adhesive force between PVDF-polyvinyl chloride (PVC) bilayer films via dielectric barrier corona discharge. The interfacial forces were quite enhanced when PVDF films were treated by corona discharge in an EMA 1% atmosphere. The contact angle of PVDF films decreased due to corona treatment. X-ray photoelectron spectroscopy (XPS) analysis showed that the carbon and oxygen content of the PVDF film surface increased with corona discharge while the fluoride content decreased. The curve fitting of XPS $C_{1s}$ peaks revealed that the non-polar C-C bonded carbon and oxygen-bonded carbon increased gradually with corona treatment, while the fluorine-bonded carbon decreased.