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        검색결과 7

        1.
        2017.04 KCI 등재 SCOPUS 구독 인증기관 무료, 개인회원 유료
        Carbon nanofiber (CNF) is used as an electrode material for electrical double layer capacitors (EDLCs), and is being consistently researched to improve its electrochemical performance. However, CNF still faces important challenges due to the low mesopore volume, leading to a poor high-rate performance. In the present study, we prepared the unique architecture of the activated mesoporous CNF with a high specific surface area and high mesopore volume, which were successfully synthesized using PMMA as a pore-forming agent and the KOH activation. The activated mesoporous CNF was found to exhibit the high specific surface area of 703 m2 g−1, total pore volume of 0.51 cm3 g−1, average pore diameter of 2.9 nm, and high mesopore volume of 35.2 %. The activated mesoporous CNF also indicated the high specific capacitance of 143 F g−1, high-rate performance, high energy density of 17.9-13.0Wh kg−1, and excellent cycling stability. Therefore, this unique architecture with a high specific surface area and high mesopore volume provides profitable synergistic effects in terms of the increased electrical double-layer area and favorable ion diffusion at a high current density. Consequently, the activated mesoporous CNF is a promising candidate as an electrode material for high-performance EDLCs.
        4,000원
        2.
        2014.06 KCI 등재 구독 인증기관 무료, 개인회원 유료
        A study was conducted to investigate the levels of representation in memory constructed as an outcome of L2 reading comprehension, and the effects of L2 proficiency, prior knowledge, and L1 reading skills on the construction of the representation. A total number of 128 Korean EFL learners participated in the study. Their L2 reading comprehension was tested through verification measure and comprehension questions designed to assess different levels of understanding including the sentence-level, textbase understanding and the situation model, or the deeper level of understanding of what the text is about. Results showed that the representation the L2 readers constructed was characterized as consisting of rather loose textbase understanding and relatively weak, but varying degrees of, situational understanding. Only L2 proficiency, among the three factors, appeared to have a significant effect on the levels of understanding in the representation the L2 readers constructed.
        6,300원
        3.
        2008.09 KCI 등재 구독 인증기관 무료, 개인회원 유료
        Two component polyurethane (PU) flame retardant coatings were prepared by blending trichloro modified polyesters (TCMPs) and isophorone diisocyanate isocyanurate. TCMPs were synthesized by polycondensation of trichlorobenzoic acid (TCBA), a flame retardant component, with adipic acid, 1,4 butanediol, and trimethylolpropane. The content of TCBA was varied in 10, 20, and 30 wt% for the reaction. Theses new flame retardant coatings showed various properties comparable to other non flame retardant coatings. Moreover, we carried out the combustion test and the flammability test for our flame retardant coatings. The results of vertical burning test for the coatings containing more than 20 wt% of TCBA were determined as no burn. The results of flammability test for the coatings with 20 wt% and 30 wt% of TCBA contents indicated the limiting oxygen index (LOI) values of 26% and 29% respectively, which implied relatively good flame retardancy.
        4,000원
        4.
        2008.03 KCI 등재 구독 인증기관 무료, 개인회원 유료
        To prepare weather-resistant modified silane acrylic resin coatings for an architectural purpose, tetrapolymers were synthesized by radical polymerization. 3-Methacryloxypropyltrimethoxysilane (MPTS) as a silicone monomer and n-butyl acrylate, methyl methacrylate, and n-butyl methacrylate as acrylic monomers were used. The composition of monomers was adjusted to fix the glass transition temperature of acrylic polymer for 20℃. The composition of MPTS in the synthesized polymer were varied from 10 wt% to 30 wt%. On the basis of synthesized resin amber paints were prepared and their physical properties and effects on weatherability were examined. The presence of MPTS in modified silane acrylic resins generally resulted in low molecular weight and broad molecular weight distribution, and also lowered the viscosity of the copolymers. The coated films prepared from these resins showed good and balanced properties in general. Adhesion to the substrate was outstanding in particular. Weatherability tests were carried out in three different types such as outdoor exposure, QUV, and SWO. The test results showed that the modified silane acrylic resins containing 30 wt% of MPTS had superior weathering properties.
        4,600원
        6.
        2006.04 구독 인증기관·개인회원 무료
        Undoped powders were synthesized by mechanical alloying (MA) of elemental powders using a nominal stoichiometric composition. Nano-structured, single-phase skutterudite was successfully produced by vacuum hot pressing (VHP) using MA powders without subsequent annealing. Phase transformations during synthesis were investigated using XRD, and microstructure was observed using SEM and TEM. Thermoelectric properties in terms of Seebeck coefficient, electrical conductivity, thermal conductivity and figure of merit(ZT) were systematically measured and compared with the results of analogous studies. Lattice thermal conductivity was reduced owing to increasing phone scattering in nano-structured MA , leading to enhancement in the thermoelectric figure of merit. MA associated with VHP technique offers an alternative potential processing route for the process of skutterudite.
        7.
        2005.03 KCI 등재 구독 인증기관 무료, 개인회원 유료
        Chlorine-containing modified polyester polyols were synthesized by two-step condensation reactions. Intermediate was synthesized by the esterification of monochloroacetic acid with trimethylolpropane in the first step. Polycondensation of the intermediate (MCAOs), 1,4-butanediol, and trimethylolpropane with adipic acid was carried out. Two-component polyurethane (PU) coatings were prepared by blending MCAOs and IPDI-isocyanurate. There new flame-retardant coatings showed various properties comparable to other non-flame-retardant coatings. They were superior to flammable coatings from the experimental results showing rapid and 10 to 13 hours of pot-life. Coatings with 30wt% monochloroacetic acid was not flammable by the vertical flame retardancy test.
        4,000원