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        검색결과 2,503

        1901.
        2003.12 KCI 등재 구독 인증기관 무료, 개인회원 유료
        Water-soluble cutting fluids are used for processing of aluminium materials. This short article describes properties of new additives of water-soluble cutting fluids for aluminium materials. Various Diels-Alder adducts of unsaturated fatty acids with acrylic acid of maleic anhydride were prepared by thermal reactions. Triethanolamine salts of Diels-Alder adducts of dehydrated castor oil fatty acids with acrylic acid or maleic anhydride showed excellent anti-corrosion property of aluminium materals. These thermal adducts showed anti-rust property for cast-iron chips, too.
        4,000원
        1902.
        2003.12 KCI 등재 구독 인증기관 무료, 개인회원 유료
        In this paper, it was studied about the red-sensitive layer. UV-Vis data of the dye at monomeric and J-state were considered with respect to their performance(contrast, speed, density and fog) in photographic emulsion. The sensitizing effect of the dye is found to be strongly structure-dependent. Naphthctbiazolo carbocyanine dye can be used as red sensitizing dye for the spectral sensitization of photographic emulsion.
        4,000원
        1903.
        2003.12 KCI 등재 구독 인증기관 무료, 개인회원 유료
        Zirconium nitride powders were synthesized at a relatively lower temperature using methane as a reducing agent in the nitridation of zircoia. ZrO2 powder was prepared by a sol-gel technique. The resulting sol-gel was centrifuged, and the gel was washed with deionized water. Anhydrous ammonia was used as the nitrogen source and methane was used as the reducing agent. Conversion diagrams show the equilibrium solid phase as a function of reagent concentrations for a specific temperature and gas pressure for the reagent system NH3-ZrO2-CH4. The reagent concentration ranges within which pure ZrN is formed increase with increasing reaction temperature. Low pressure with an excess of hydrogen decreases the reaction temperature at which pure ZrN is formed. Low pressure together with the introduction of excess hydrogen into the reaction system increases Zr and N conversion efficiency and retards C deposition.
        4,000원
        1904.
        2003.12 KCI 등재 구독 인증기관 무료, 개인회원 유료
        Sodium azide (SA) is commonly used as propellant for inflating automatic safety bags and other chemical manufacturing purposes. The investigation of potentially thermal hazard of sodium azide and its mixture with polymers are very important because it can occur an expected traffic accident so we took a experiment s using different scanning calorimeter (DSC) in nitrogen atmosphere. The decomposition temperature were about 350~450℃. We could find not only exothermic reaction was remarkably decreased in mixture s of acrylonitrile-butadiene-styrene (ABS) and polyvinyl chloride (PVC), but also increasing mixed rate of ABS, polyvinyl alcohol (PVA) and polymethyl methacrylate (PMMA) decreased thermal decomposition heat.
        4,000원
        1905.
        2003.12 KCI 등재 구독 인증기관 무료, 개인회원 유료
        BaTiO3, powders were prepared by sol-gel process from different aging time and reaction temperature. Particle shape, size and crystal structure of prepared BaTiO3 powders were analyzed by SEM, XRD and FT-IR. Effect of aging time alternation didn't particularly show up. Spherical nano-sized BaTiO3 powders were obtained from condition more than reaction temperature 55℃, and obtained sintered BaTiO3 powders of tetragonal phase from heat-treatment at 1,100℃.
        4,000원
        1906.
        2003.12 KCI 등재 구독 인증기관 무료, 개인회원 유료
        Organic acid salt of fatty polyamide (DDDT) and acrylate of fatty carbamide (DDTCA) were synthesized as a main component for the softener. O/W type non-ionic softener (NSC) was prepared by blending DDDT and DDTCA with beef tallow, lanolin anhydride. polyoxyethylene(7) stearyl ether, and polyoxyethylene(50) oleyl ether. After treatment of NSC to all cotton fabrics, the physical properties such as tear strength, crease recovery, and flexing abrasion resistance were measured. As a result of the measurement, NSC was proved to be durable non-ionic softener with good softness.
        4,000원
        1907.
        2003.12 KCI 등재 구독 인증기관 무료, 개인회원 유료
        Crosslinked poly(methyl methacrylate) particles from 2.4 to 8.1μm in diameter were prepared by homogenized suspension polymerization. The effect of polymerization parameters such as homogenizing speed, homogenizing time and stabilizer concentration on the particle size were examined. Optical diffusion films were prepared with the crosslinked poly(methyl methacrylate) particles. The effect of film thickness, particle size, and particle size distribution on transmittance and haze of optical diffusion film was examined. Transmittance of optical diffusion film increased with increasing particle size and decreasing film thickness. Haze increased with increasing film thickness and decreasing particle size. We also found the existence of an optimum ratio for optical performance when the mixture of small particle and large particle was used.
        4,000원
        1908.
        2003.12 KCI 등재 구독 인증기관 무료, 개인회원 유료
        Particulate leaching method for the preparation of porous PLLA scaffolds was carried out and especially, the effect of PLLA/CHCl3 solution concentration on the salt leaching rate and the pore structure of PLLA scaffolds were considered. It was found that maintaining lower PLLA/CHCl3 concentration and higher CHCl3 evaporation temperature in the preparation of PLLA/NaCl mixtures resulted in the enhancement of salt leaching rat e and higher porosity. This is understood that those conditions could minimize the formation of dense PLLA layer on the surface of PLLA/NaCl mixture as well as introducing better porosity on the surface. Higher salt leaching temperature accelerated the salt leaching rate but it seems that there is no influence on the porosity of PLLA scaffolds.
        4,000원
        1909.
        2003.12 KCI 등재 구독 인증기관 무료, 개인회원 유료
        Zinc complexes with bis[2-(o-hydroxyphenyl) naphtol [1,2] oxazolato ligands (ZnPBO-4) and its derivatives (ZnPBO-S) were synthesized, and luminescent properties of these materials were investigated. Both the fluorescent emission band and electroluminescent emission band were discussed based on their ligand structure differences. The emission band found that it strongly depends on the molecular structure of introduced ligand. It was tuned from 446 nm to 491 nm by changing the ligand structures. Spreading of the π-conjugation in 2-(o-hydroxyphenyl) group gives rise to a blue shift. The EL properties also showed good consistency with their differences of ligand structure. Bright-blue EL emission with a maximum luminance of 3,100 cd/m2 at 12V, current density, 575 mA/m2 was obtained from the organic light-emitting diodes (OLEDs) using ZnPBO-4 as emitting layer. It was also found that the newly synthesized materials were suitable to be used as emitting materials in organic EL device.
        4,000원
        1910.
        2003.12 KCI 등재 구독 인증기관 무료, 개인회원 유료
        Extraction of Natural Artemisia by using super critical carbon dioxide is operated under 40-50℃ and 200-250 atm, thus, conversion rate is very low as 7wt% while high energy is being wasted. When Natural Artemisia Extract is applied in the control of microbe, concentration and reaction time greatly affected to the growth of microbe. Especially, when refined oil concentration from Natural Artemisia added more than 1,000ppm, staphylococcus aureus and fungi are terminated completely. Thus, it is proven that Natural Artemisia Extract has antimicrobial effect.
        4,000원
        1911.
        2003.12 KCI 등재 구독 인증기관 무료, 개인회원 유료
        The capacity and long life of gel electrolyte batteries is connected with gas recombination producting PbO2 and Pb electrode. We were prepared with phosphoric acid gel electrolyte to know gel characteristics per density to assemble VRLA batteries. We studied by measuring electrolyte dispersion using Brewster-angle microscope(BAM), charge-discharge cycle and electrode structure using scanning election microscope(SEM) per electrolyte density. As a results, phosphoric acid density 1.210 was excellent gel dispersion in sol condition, electrode condition after fifty cycles in this study.
        4,500원
        1912.
        2003.12 KCI 등재 구독 인증기관 무료, 개인회원 유료
        Synthesis gas is produced commercially by a steam reforming process. However, the process is highly endothermic and energy intensive. Thus, this study was conducted to produce synthesis gas by the partial oxidation of methane to cut down the energy cost. Supported Ni catalysts were prepared by the impregnation method. To examine the activity of the catalysts, a differential fixed bed reactor was used, and the reaction was carried out at 750~850℃ and 1 atm. The fresh and used catalysts were characterized by XRD, XPS, TGA and AAS. The highest catalytic activity was obtained with the 13wt% Ni/MgO catalyst, with which methane conversion was 81%, and H2 and CO selectivities were 94% and 93%, respectively. 13wt% Ni/MgO catalyst showed the best MgNiO2 solid solution state, which can explain the highest catalytic activity of the 13wt% Ni/MgO catalyst.
        4,000원
        1913.
        2003.12 KCI 등재 구독 인증기관 무료, 개인회원 유료
        Alkaline powder cleaning agents (APCAs) were prepared by blending of Na2CO3 tetrasodium pyrophosphate (TSPP). sodium orthosilicate (Na-OSi), Na-dioctyl sulfosuccinate (303C), Demol C, and MJU-100A (100A). The physical properties of APCAs tested with steel specimen showed the following results. The cleaning powers of APCA-6 (Na2CO3 250g/TSPP 70g/Na-OSi 40g/303C 60g/Demol C 50g/100A 30g mixture) for press-rust preventing oil was 97% and 98% degreasing at 2wt%, 70℃ and 90℃, respectively; for Quenching oil, the cleaning power of APCA-6 was 95% degreasing at 2wt% and 70℃. From the results, it was ascertained that APCA-6 exhibited a good cleaning power. Also low foaming power tests proved that the APCA-6 maintained good defoaming effect.
        4,000원
        1914.
        2003.12 KCI 등재 구독 인증기관 무료, 개인회원 유료
        Aqueous polyurethane dispersion was synthesized using phosphorus compound which received significant attention for the replacement of halogenated flame retardants. In this study, polyols which have phosphorus moity in their structural unit were synthesized by two-step polycondensation reaction using dimethyl phenylphosphonate, ethylene glycols. adipic acid, and 1,4-butanediol. In the next step, polyurethane dispersion was prepared using these polyols, isophorone diisocyanate with dimethyl propionic acid. The particle size of polyurethane latex was reduced from 347 nm to 240 nm with increasing DMPA content. It was observed that the LOI values of prepared coatings increased from 27% to 35% with increasing phosphorus content.
        4,000원
        1915.
        2003.09 KCI 등재 구독 인증기관 무료, 개인회원 유료
        IASL(iodo acetamide spin label) and MSL(maleimide spin label) disordered the orderly helix arrangement of myosin in the rest state of spin level. Especially the effect of IASL was great. The muscle was isometrically tetanized with three trains of 3ms pulses every 50ms between 5℃ with 25℃. Equatorial reflection change inferred that myosin head was moved to the vicinity of actin filament by spin level. The intensity change of 143a and 72a could offer information of the mass projection of population of myosin head along the filament axis. The slope of intensity profile of the mass projection of 143a and reflection of IASL is appeared and that of MSL is appeared sharply. The decrease of 215a reflection intensity the periodical character of 143a reflection by spin label. The raise of MSL actin reflection at 51a and 59a in the actin reflection change refers that the shifted myosin head binds a certain actin or changes an actin structure by spin label effect. Because iodo acetamide has a tendency to decease the actin reflection, actin dose not bind myosin head. From this result, we can conclude that IASL and MSL are spin labeled on SH of myosin head and disordered the helix arrangement of actin.
        4,000원
        1917.
        2003.09 KCI 등재 구독 인증기관 무료, 개인회원 유료
        Biodiesel as methyl esters derived from vegetable oils has considerable advantages in terms of environmental protetion. In the present work, methyl esters were produced from soybean oil by lipase-catalyzed transesterification. To reduce inactivation of commercial immobilized lipases emulsified two-step process was developed using the stepwise addition of methanol with 4:1 molar ratio at 4h intervals. Also with immobilized lipase from Candida antarctica(Novozym 435) high conversion of 98.5 percent was possible at 45℃ of reaction temperature with 4:1 of methanol-to-oil molar ratio and 1%(v/v) methyl glucoside oleic polyester as an emulsifier in the presence of cosolvent.
        4,000원
        1918.
        2003.09 KCI 등재 구독 인증기관 무료, 개인회원 유료
        Poly(methyl methacrylate)/clay nanocomposite particles with particle size of 275~292 nm range were successfully prepared using emulsion polymerization. The content of montmorillonite based on the methyl methacrylate monomer was chosen as 30 wt.%. 2,2-azobis(isobuthylamidine hydrochloride) and n-dodecyltrimethylammonium chloride were used as an initiator and a surfactant in cationic emulsion system. Potassium persulfate and sodium lauryl sulfate were used as an initiator and a surfactant in anionic emulsion system. The evidence of intercalated /exfoliated structure of montmorillonite in the nanocomposite prepared in our experiment was confirmed by wide angle x-ray diffraction patterns of d001 plane. Thermal behavior of nanocomposite was traced using DSC and TGA. It was found that the nanocomposite particle prepared by cationic emulsion system showed intercalated structured. We also found that the nanocomposite particle obtained from anionic emulsion system resulted in the fully exfoliated structure.
        4,000원
        1919.
        2003.09 KCI 등재 구독 인증기관 무료, 개인회원 유료
        The high-solid coatings were prepared by blending the synthesized acrylic resin in the previous paper and hexamethylene diisocyanate-trimer and curing it at room temperature. The characterization of the films of the prepared coatings was performed. The impact resistance, 60℃ specular gloss, cross-hatch adhension, and heat resistance of the films proved to be good, and the pencil hardness and drying time proved to be slightly poor. Especially, there was a remarkable improvement in the heat resistance. This improvement may stem from the regular arrangement of ethyl groups introduced into the acrylic resin. From a viscoelastic measurement using a rigid-body pendulum, curing was accelerated with the Tg value. With the increase in Tg, log damp value was lowered and dynamic viscoelasic Tg of a cured film was increased.
        4,000원
        1920.
        2003.09 KCI 등재 구독 인증기관 무료, 개인회원 유료
        Synthesis gas is commercially produced by a steam reforming process. However, the process is highly endothermic and energy-consuming. Thus, this study was conducted to produce synthesis gas by the partial oxidation of methane to decrease the energy cost. Supported Ni catalysts were prepared by the impregnation method. To examine the activity of the catalysts, a differential fixed bed reactor was used, and the reaction was carried out at 750~850℃ and 1 atm. The fresh and used catalysts were characterized by XRD, XPS, TGA and AAS. The highest catalytic activity was obtained with the 13wt% Ni/MgO catalyst, with which methane conversion was 81%, and H2 and CO selectivities were 94% and 93%, respectively. 13wt% Ni/MgO catalyst showed the best MgNiO2 solid solution state, which can explain the highest catalytic activity of the 13wt% Ni/MgO catalyst.
        4,000원