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        검색결과 2,609

        2021.
        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
        2023.
        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
        2024.
        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
        2025.
        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
        2026.
        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
        2027.
        2003.09 KCI 등재 구독 인증기관 무료, 개인회원 유료
        A copolymer 〈HSAs : EA/EMA/2-HEMA/AAEM) which is an acrylic resin containing 70% solid content was synthesized by the reaction of monomers, including ethyl acrylate, ethyl methacrylate, and 2-hydroxyethyl methacrylate with a functional monomer, such as acetoacetoxyethyl methacrylate, which may give improvements in cross-linking density and physical properties of films. The physical properties of prepared acrylic resins, HSA containing AAEM, are as follows : viscosity, 203~550cps ; Mn, 2590~2850 ; and conversion, 82~89%, respectively. It was found from the plotting of Tg versus viscosity and Tg versus molecular weight that viscosity increased with Tg while number averaged molecular weight decreased with increasing Tg.
        4,000원
        2028.
        2003.09 KCI 등재 구독 인증기관 무료, 개인회원 유료
        Electrical properties of carbon filler/PVdF [poly(vinylidene fluoride)] composite were investigated as a funtion of carbon filler/PVdF ratio in the range of 0.2~0.5. Three kinds of comercialzied conductive carbon blacks such as Hiblack 41Y, KE300J, and KE600J, and carbon nanofibers prepared by the catalytic chemical vapor deposition of C2H4 over Ni-Cu catalysts were used as the carbon fillers. The electrical conductivity of carbon filler/PVdF composites were in the range of 0.65 to 13.5 S/cm depending the fillers' electrical conductivity ranging from 5.6 to 23.1 S/cm. Among the carbon fillers used, the KE600J carbon black showed the highest conductivity both in the composite and filler itself because of its high degree of graphitization due to the high-temperature thermal treatment and its high surface area due to the activation treatment.
        4,000원
        2029.
        2003.09 KCI 등재 구독 인증기관 무료, 개인회원 유료
        Poly(oxypropylene-oxyethylene glycol) block copolymer(PBC) oil dispersant, which has low toxicity, high biodegradability, and an excellent dispersion efficiency to crude oils and weathered W/O emulsion was prepared by blending PBC, poly(oxyethylene) oleate, and sorbitan monooleate. The dispersing efficiency was measured by swirling flask method. The PBC oil dispersant had an excellent dispersing efficiency to weathered oil products formed as stable W/O emulsion, and the low toxicity, such as 4000 ppm to Oryzias Latipes(24 hr, TLM), Brine Shrimp Artemia(24 hr, TLM).
        4,000원
        2030.
        2003.09 KCI 등재 구독 인증기관 무료, 개인회원 유료
        In this study, we synthesized p-hexyloxybenzaldehyde(HBA) by using p-hydroxybenzaldehyde and n-hexylchloride. p-dodecylaniline(DDA) prepared by nitration and reduction of dodecylbenzene. The schiff base, p-dodecylbenzylidene-p'-hexyloxyaniline (DBHA) was synthesized by reaction of HBA and DDA. The color of synthetic compound was pale-brown and the yield was 62%. All the synthetic compounds were identified by TLC, FT-IR and iH-NMR.In this study, we synthesized p-hexyloxybenzaldehyde(HBA) by using p-hydroxybenzaldehyde and n-hexylchloride. p-dodecylaniline(DDA) prepared by nitration and reduction of dodecylbenzene. The schiff base, p-dodecylbenzylidene-p'-hexyloxyaniline(DBHA) was synthesized by reaction of HBA and DDA. The color of synthetic compound was pale-brown and the yield was 62%. All the synthetic compounds were identified by TLC, FT-IR and 1H-NMR.
        4,000원
        2032.
        2003.06 KCI 등재 구독 인증기관 무료, 개인회원 유료
        Ultra-thin films of amphiphillic squarylium dye were prepared on the hydrophillic substrate by Langmuir-Blodgett(LB) technique. In this study, the photoelectric properties of a amphiphillic squarylium dye LB film was investigated. The visible light(λ = 684nm ) of xenon lamp was illuminated on the amphiphillic squarylium dye LB films and light absorptivity and photoconductivity were observed. The photoconductivity was nearly constant regardless of nominal layer number. The photoelectric properties of the amphiphillic squarylium dye LB films with bottom electrode showed better than that top electrode.
        4,000원
        2033.
        2003.06 KCI 등재 구독 인증기관 무료, 개인회원 유료
        We have seen the effects of buffer layer in organic light-emitting diodes using poly(N-vinylcarbazole)(PVK). Polymer PVK buffer layer was made using static spin-casting method. Two device structures were made; one is ITO/TPD/Alq3/Al as a reference and the other is ITO/PVK/TPD/Alq3/Al to see the effects of buffer layer in organic light-emitting diodes. Current-voltage characteristics, luminance-voltage characteristics and luminous efficiency were measured with a variation of spin-casting speeds. We have obtained an improvement of luminous efficiency by a factor of two and half when the PVK buffer layer is used.
        3,000원
        2034.
        2003.06 KCI 등재 구독 인증기관 무료, 개인회원 유료
        Fireproofing polyolefin nanocomposite for the application of power distributing panel was prepared by compounding linear low density polyethylene(LLDPE), decabromodiphenyl oxide (DBDPO), Sb2O3 as flame retardant agents, and modified nano clay as filler. The optimized formulation ratio of compounds to prepare the fireproofing polyolefin nanocomposite was obtained. The flame retardant properties for nanocomposite prepared by compounding 22.5 phr of nano clay and 18 phr of DBDPO based on 100 phr of LLDPE were shown that the combustion time. 10~18 s, combustion distance, 12~15 mm and non-melt dropping characteristics. In particular. the content of DBDPO in nanocomposite could be decreased to 18 phr from 40 phr DBDPO for fireproofing composite containing 30 phr of clay. The electrical properties measured from tracking test, had an excellent antitracking properties by not showing the phenomenon of leakage current and sparking.
        4,000원
        2035.
        2003.06 KCI 등재 구독 인증기관 무료, 개인회원 유료
        This paper has applied a simple model to the mass transfer mechanism of Cr(VI) with crownether in a batch-type, supported liquid membrane module. Concentration at pH 3 are as follows : 0.012 kmol/m3≤18-crown-6≤0.036 kmol/m3 and 20 g/m3≤ Cr(VI)≤500 g/m3. The measured values of forward- and backward-reaction rate constants between Cr(VI) and 18-crown-6 were used to simulate the model with the mass conservation equation and associated boundary conditions. Comparison between the experimental and simulated facilitated factor of Cr(VI) transport led to classification of reaction regions.
        4,200원
        2036.
        2003.06 KCI 등재 구독 인증기관 무료, 개인회원 유료
        Electron transfer through an Langmuir-Blodgett(LB) monolayer film sandwiched between metal electrodes. We used an eicosanoic acid material and the material was very famous as a thin film insulating material. Eicosanoic acid monolayer was deposited by Langmuir-Blodgett(LB) technique and a subphase was a CdCl2 solution as a 2×10-4 mol/L. Also we used a bottom electrode as an Al/Al2O3 and a top electrode as a Al and Ti/Al. Here, the Al2O3 on the bottom electrode was deposited by thermal evaporation method. The Al2O3 layer was acted on a tunneling barrier and insulating layer in tunnel diode. It was found that the proper transfer surface pressure for film deposition was 25 mN/m and the limiting area per molecule was about 24 a2/molecule. When the positive and negative bias applied to the molecular device, the behavior shows that a tunnel switching characteristics. This result were analyzed regarding various mechanisms.
        4,000원
        2037.
        2003.06 KCI 등재 구독 인증기관 무료, 개인회원 유료
        Oxidized polyethylene wax is obtained by oxidation of polyethylene wax and it is composed of various chemicals, e.g., fatty acid, alcohol, ketone and ester. The application of oxidized polyethylene wax is determined by the composition of these chemical substances. In this basic study we observed the basic reaction parameters of time, temperature, oxygen concentration and catalysts on the oxidation reaction of low molecular weight polyethylene(PE wax) by analyzing the acid value, physical and chemical properties of oxidized PE wax to develop a new oxidation process. Acid values are increased with temperature increase in the rage of 150℃~180℃ but decreased beyond 190℃. Acid values are also increased with oxygen concentration. As the oxidation reaction proceeds the molecular weight and softening points of oxidation products are decreased by cracking reaction, but the viscosities are increased. To observe the crystallinity of oxidation products SEM experiment was performed. To obtain a high acid-value product in a mild condition, we adopted free radical catalysts and the acid value of the product using catalyst was higher than the product obtained without catalyst in the same reaction condition. The effective initiators were dicumyl peroxide(DCPO), t-butylperoxy-2-ethyl hexanoate(HOPO) and benzoyl peroxide(BPO) having long half-life.
        4,000원
        2038.
        2003.06 KCI 등재 구독 인증기관 무료, 개인회원 유료
        In order to improve the lithium ion battery's performance, the carbon nanofibers were introduced to the anode electrode fabricated with natural graphite particles. The influence of structural adjustment of the particles by the introduction method of carbon nanofibers and the content of carbon nanofibers on the electrical property and charge/discharge characteristics of the electrode were investigated. The electrode fabricated with the mixture of 10 wt% of carbon nanofibers grown separately and 90 wt% of graphite particles showed an excellent discharge capacity of 400 mAh/g and the improved cycle performance. The improved performance could be explained by that the carbon nanofibers shortened and uniformly distributed on the surface of graphite particles by ball milling increased the stability for the intercalation/deintercalation of lithium ion and increased the electrical conductivity due to the closed packing between graphite particles.
        4,200원
        2039.
        2003.06 KCI 등재 구독 인증기관 무료, 개인회원 유료
        The effects of molecular structure on the redox properties of the organic electroluminescent materials (Ir(ppy)3 Ir(m-ppy)3 Ir(p-toly)3) were studied using cyclic voltammetry and spectroscopy. These iridium complexes show reversible oxidation and reduction on the electrode, which produce the symmetric cyclic voltammogram. It indicates that these materials are very stable under repetitive oxidation/reduction cycles. The electrochemically determined ionization potentia/electron affinity values are 5.4OeV/3.02eV for Ir(ppy)3, 5.36eV/2.96eV for Ir(m-ppy)3, and 5.35eV/2.97eV for Ir(p-toly)3 from the SCE(Standard Calomel Electrode). The electrically determined band gaps are 2.38eV (521nm), Ir(ppy)3, 2.4OeV (517nm), Ir(m-ppy)3, and 2.38eV (521nm). Ir(p-toly)3, which are similar with the optical band gaps. The position of methyl group on 2-phenylpyridine (ppy) effects do not influence much on the ionization potential, electron affinity, and band gap of Ir(ppy)3 derivatives.
        4,000원
        2040.
        2003.06 KCI 등재 구독 인증기관 무료, 개인회원 유료
        Silver nanoparticles was synthesized by the method of W/O microemulsions with AOT (bis(2-ethylhexyl) sodium sulfosuccinate). The nucleation particle growth and aggregation was controlled by the droplet exchange process. The intermicellar exchange reaction is varied by changing the AOT and the H2O concentration. The synthesized W/O microemulsions was found to give the nanoparticles, which was confirmed by SEM, TEM, particle-size-analyzer, and UV-spectrometer. The most stable particles was obtained at 0.056 mole AOT solution, and the particle size distribution was found in the range from 27 to 31 nm. The mean particle size was reduced by adding Tween 20 significantly, and distribution was found from 14 to 16 nm. And, It's size was reduced by cosurfactants as toluene and benzyl alcohol. In case of toluene and benzyl alcohol, the range of particle size was found 7~11 nm and 8~12 nm.
        4,000원