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        검색결과 10

        1.
        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
        2.
        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
        3.
        2006.09 구독 인증기관·개인회원 무료
        In order to investigate 95% retained critical current of Bi-2223/Ag tapes under various stress-strain conditions, load cell attached tension and bending apparatus was used. The critical current of stress-strained tape was degraded below 95% retained critical current when tension and bending was simultaneously applied together. But only one of this tension or bending did not degrade the tape below 95% retained critical current. Deformation temperature was important to maintain the 95% retained Ic of Bi-2223/Ag tapes after bending or tension deformation because mechanical strength of tapes can be changed drastically between room temperature and 77 K.
        4.
        2006.09 구독 인증기관·개인회원 무료
        Five kinds of double stacked 385 (55 x7) filamentary Bi2212/Ag round wires and 55 filamentary tapes with different Ag ratios (silver area/superconductor area) have been fabricated via PIT method, and the effects of Ag ratio and processing factors on critical current density were studied. The effects of the maximum temperature and average filament diameter on critical current density were also studied. The wire of 0.74 mm diameter having Ag ratio 3.7 showed critical current density of at 4.2 K, 0 T.
        5.
        2006.09 KCI 등재 구독 인증기관 무료, 개인회원 유료
        Direct decomposition of methane over three types of carbon black (N330-p, N330-f, and HI-900L) was carried out in a fluidized bed quartz reactor. Properties of carbon black before and after reaction were measured and found to be related with surface structure and weight gain. For N330-p and N330-f, some carbon deposit on the surface was considered to be the reason for the increase of BET surface area and pore volume with weight gain. Carbon deposits on the surface and the conglutination of some aggregates may explain the slight increase of particle size. Properties of HI-900L changed much more significantly with weight gain. It is supposed that the increase of aggregate size of HI-900L were due to some unknown oily components. The corresponding agglomeration might be the reason for the decrease of BET surface area with weight gain, as compared with the increase of that for the case of N330 black.
        4,000원
        6.
        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
        7.
        2004.03 KCI 등재 구독 인증기관 무료, 개인회원 유료
        New electroluminescent materials based on anthracene chromophore with naphthylethenyl substituent, 9,10-bis(α-naphthylethenyl)anthracene (a-BNA), as well as four kinds of its derivatives were synthesized, and luminescent properties of these materials were investigated. Electrolumineecent(EL) emission band was discussed based on their substituent structure differences. It was found that the emission band strongly depends on the molecular structure of introduced substituent. It can be tuned from 557 nm to 591 nm by changing the substituent structures. On the other hand, the anthracene chromophore with bulky substituent possessed high melting point and they gave stable films through vacuum-sublimation. The double layer EL device of ITO/TPD/emission layer/Mg:Ag was employed, and exhibited efficient orange light originating from emitting materials. EL emission with a maximum luminance was observed in the b-BNA emitting material, : maximum luminance was about 8,060 cd m-2 at an applied voltage of 10 V and current density of 680 mA/cm2. In conclusion, the electroluminescent properties also showed good difference with their substituent structure.
        4,000원
        8.
        2007.12 KCI 등재 서비스 종료(열람 제한)
        The high-performance liquid chromatography(HPLC) method for the determination of trans-resveratrol in 34 germplasms and processing methods of peanut seeds has been modified. Peanut germplasms contained trans-resveratrol contents of 0.14~4.96μg/g, but findings for the testa color were not significant. However, two germplasms, 'KIGAN' and 'CS1', contained more trans-resveratrol contents than the other germplasms. The contents of their were 2.26μg/g and 4.96μg/g. The tested processing methods caused no significant changes in trans-resveratrol contents. The contents of fresh, boiled, and roasted peanuts were 0.36, 0.32, and 0.40μg/g, respectively in cv. Palkwang, and 0.22, 0.22, and 0.26μg/g, respectively, in cv. Jakwang. Differences were not significant among fresh, boiled, and roasted peanuts. The grains of 'Palkwang' and 'Jakwang' contained trans-resveratrol contents of 0.34μg/g and 0.24μg/g, and testa contained 1.12μg/g and 1.00μg/g, respectively. However, when comparing absolute quantity, the trans-resveratrol contents appears to be approximately 3~4 times higher in the testa than in the grain of the peanut, although the total contents were not different because the ratio of testa was low in peanut seeds.
        9.
        2007.12 KCI 등재 서비스 종료(열람 제한)
        The purpose of this study is to establish an extraction and analysis method for α-tocopherol, and to then distinguish among varieties. The α-tocopherol contents of 22 varieties of peanut seeds were analyzed by HPLC. Peanut seeds of cv. Palkwang were processed in two ways, by boiling and roasting. The α-tocopherol contents of the two types of peanuts were compared with fresh seeds without any processing. α-Tocopherol was detected at a retention time of 2.95 minutes. Five standards of α-tocopherol covering a range of 20~100μg/ml were made up in 2% isopropyl alcohol/n-hexane and analyzed in duplicate. The α-tocopherol contents differed according to extraction temperature. The contents were 85μg/g or less at 10℃ and 20℃ and 94μg/g at 30℃, but they were decreased at 40℃ or higher. The α-tocopherol contents in 22 peanut varieties were 61.36~96.80μg/g according to variety. Fresh peanuts contained 106.7μg/g of α-tocopherol, while boiled peanuts contained 108.8μg/g of α-tocopherol, and roasted peanuts contained 109.2μg/g of α-tocopherol.
        10.
        2001.12 KCI 등재 서비스 종료(열람 제한)
        This study was conducted to determine the optimal planting distance in cultivation of yacon (Polymnia sonchifolia Poeppig & Endlicher). Plug seedlings were planted with 6 different plant densities of 80 ~times 60, 80 ~times 50, 70 ~times 50, 70 ~times 45, 70 ~times 40 and 60 ~times 45 cm. The plant height and the petiole length were increased with increasing the planting distance. The tallest plant height of yacon was 165.4cm with the plant density of 80 ~times 60 cm. However, branch number per plant, leaf number on main stem and stem diameter were not significantly difference among planting densities. Tuberous root was harvested 31.42 tons/ha in 70 ~times 50 cm spacing. The ratio of heavier tuberous roots than 200 g to total tuberous roots decreased significantly according to increase of planting density. Fresh weights of shoot and root, contain the crown bud, were decreased, as planting distance was shorter. Tuberous root number was fewer but its weight was heavier in wide planting than in dense planting. We think that optimal planting density is about 30,000 plants/ha, if it were to be 70 cm row spacing, intrarow spacing should calculate about 47cm.