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        검색결과 2,636

        1781.
        2008.12 KCI 등재 구독 인증기관 무료, 개인회원 유료
        This research is related to the process of refining the raw material, industrial 2-propanone to the 2-propanone of the electronic grade. With this view, the high purity of 2-propanone was obtained through the complex preprocessing(physical adsorption method), distillation process and membrane-filtration of distillate. Impurities were identified by GC and UV, and then we assayed the water content in 2-propanone passing adsorption step made of activated carbon and Zeolite 4A. Furthermore, the distillation was performed with the packed column distillation apparatus to eliminate impurities such as acetaldehyde. Particulates were removed by reduced-pressure filtration through 0.5μm membrane filter and the number of the particulates was measured by particulate counter to confirm the removal of impure particles.
        4,000원
        1782.
        2008.12 KCI 등재 구독 인증기관 무료, 개인회원 유료
        To investigate the synergy effect on the pyrolysis of mixture of polyethylene(PE) and polystyrene(PS), the pyrolysis of PE, PS and the mixture of PE-PS was carried out in a batch reactor at the atmospheric pressure and 450℃. The pyrolysis time was from 20 to 80 mins. The liquid products formed during pyrolysis were classified into gas, gasoline, kerosene, gas oil and heavy oil according to the distillation temperatures based on the petroleum product quality standard of Korea Institute of Petroleum Quality. The analysis of the product oils by GC/MS showed that the new components produced by mixing were not detected. The synergy effect according to mixing of PE and PS did not also appear. The conversion and yield of mixtures were in proportion to the mixing ratio of sample.
        4,000원
        1783.
        2008.12 KCI 등재 구독 인증기관 무료, 개인회원 유료
        The acrylic coating emulsions were prepared by the emulsion polymerization to protect the surface of steel plate from the corrosion chemicals like acid, base and salt water. MMA(methyl methacrylate), styrene, BA(butyl acrylate), and 2-HEMA(2-hydroxyethyl methacrylate) were used as monomer. KPS(potassium persulfate) and SBS(sodium bisulfite) as redox initiator and SDBS(sodium dodecylbenzene sulfonate) as emulsifier were used on the emulsion polymerization reaction. The most stable in-situ coating was obtained when 10% of MMA was added. Both particle size and quantity in emulsion were decreased as increasing the mount of SDBS. the most stable prepared coating emulsion with polyisocyanate crosslinker showed very high anticorrosion properties on the coated steel layer to salt water, whereas no significant improvement of anticorrosion property to acdic and basic condition it showed.
        4,000원
        1784.
        2008.12 KCI 등재 구독 인증기관 무료, 개인회원 유료
        It is inevitable to use chemical germicidal agents like paraben, imidazolidinyl urea and phenoxyethanol to preserve the emulsions which is usually used in cosmetics. Although these chemical preservatives are good enough to reduce the microbiological contamination, they are irritative, allergenic to the skin. Several kinds of polyols are used in cosmetics as moisturizer and solvent. In this study, we evaluate the effects of polyols on anti-microbial activities, safety and resistant index. MIC(minimal inhibitory concentration) of polyols determined against 6 germs including Staphylococcus aureus. The order of MIC was PG ≅ DPG ≅ 1,3BG 〉 HG 〉 1,2-PD 〉 1,2-HD ≅ 1,2-OD. The 2~3 wt% of 1,2-HD(hexanediol) shows good anti-microbial effects in emulsions without allergenic response. Resistant index of 1,2-HD was less than 2 and this value was smaller than that of chemical preservatives. The mechanism of antimicrobilogical effect might be disturb the membrane of germs by investigating using electron microscope. Added to that, using this paradigm, low preservative contents, paraben-free system, and even preservative-free systems can be expected from these results.
        4,000원
        1785.
        2008.12 KCI 등재 구독 인증기관 무료, 개인회원 유료
        The synthesis of cyclic carbonate from butyl glycidyl ether (BGE) and carbon dioxide was performed in the presence of three different types of ionic liquid : quarternary ammonium salt, alkyl pyridinium salt, and alkylimidazolium salt. Ionic liquids of different alkyl groups (C3, C4, C6 and C8) and anions (Cl-, Br- and I-) were used for the reaction which was carried out in a batch autoclave reactor at 60~120℃. The catalytic activity was increased with increasing alkyl chain length in the order of C3 〈 C4 〈 C6. But the ionic liquid with longer alkyl chain length (C8) decreased the conversion of BGE because it is too bulky to form an intermediate with BGE. For the counter anion of the ionic liquid catalysts, the BGE conversion decreased in the order Cl- 〉 Br- 〉 I-.
        4,000원
        1786.
        2008.12 KCI 등재 구독 인증기관 무료, 개인회원 유료
        Methyl methacrylate(MMA) was grafted onto microcrystalline cellulose(MCC) with ceric ammonium nitrate(CAN) as a redox initiator at the various conditions. The cellulose triacetate(CTA) composite films added MCC and MMA-grafted MCC powders were prepared on a glass plate. The graft yield(GY) and graft efficiency(GE) of the grafted MCC were calculated with the simple equations by the weight balance method. The double bond of C=O on the grafted MCC surfaces was confirmed by the fourier transform infrared spectroscopy with attenuated total reflection(FT-IT ATR) spectrophotometer. After grafting, the degree of crystallinity of cellulose powders was decresed by judging from x-ray diffraction(XRD) data. Scanning electron microscope(SEM) photos showed the only solvent and CAN solution could change the roughness of MCC powders and the effect of powder dispersions in composite matrix. The tensile strength of MCC/CTA composite films was decreased with increase of MCC powder contents. When 5% grafted MCC was added, the tensile strength of grafted MCC/CTA composite films was increased from 82.3 MPa to 97.2 MPa. The thermal property of powders was also analyzed by the thermogravimetric analysis(TGA).
        4,000원
        1787.
        2008.12 KCI 등재 구독 인증기관 무료, 개인회원 유료
        Essential fatty acids (EFA) are fatty acids that must be obtained from the diet because they can not be biosynthesized by human or animals. Gamma fatty acids contain gamma-linolenic acid (GLA, 18:3n-6) and dihomo-gamma-linolenic acid (DHGLA, 20:3n-6) as intermediate metabolites of linoleic acid (LA, 18:2n-6), which is an EFA found in vegetable oils. GLA is an important essential fatty acid that is required by human and animals to function normally. Recently, studies have indicated that GLA may be an essential component of the cell membrane, as well as an active component of dietary supplements and medicine. GLA must beadministered through the diet because it is converted into DHGLA in the body quickly and completely. DHGLA is a key material involved in the metabolism of LA. GLA is biosysthesized by the rate limiting step of δc6-desaturase, which is an enzyme that desaturates LA, there by allowing it to be converted into DHGLA via chain elongation. In addition, DHGLA exerts bioactive effects via action as a precursor of eicosanoid series 1. Breast milk contains an abundant amount of GLA; however, GLA is also available directly in evening primrose oil, black currant seed oil, borage oil and hemp seed oil. In addition, GLA enriched animal and plant can be produced using biotechnology, and highly pure GLA can be extracted using supercritical fluids, such as supercritical carbon dioxide, which will allow economically feasible production of GLA for use in medicines.
        4,500원
        1788.
        2008.12 KCI 등재 구독 인증기관 무료, 개인회원 유료
        For recipe prediction of colorant proportion showing nonlinear behavior, we modeled the effects of colorant proportion of basic colors on the target colors and predicted colorant proportion necessary for making target colors. First, colorant proportion of basic colors and color information indicated by the instrument was applied by a linear model and a multi-layer perceptrons model with back-propagation learning method. However, satisfactory results were not obtained because of nonlinear property of colors. Thus, in this study the neuro-fuzzy model with merit of artificial neural networks and fuzzy systems was presented. The proposed model was trained with test data and colorant proportion was predicted. The effectiveness of the proposed model was verified by evaluation of color difference(δE).
        4,000원
        1789.
        2008.12 KCI 등재 구독 인증기관 무료, 개인회원 유료
        The p-dioxanone can be used to make a variety of commercially useful products particularly where biodegradability is desired, such as fibers, sutures, molded articles, containers, medical devices and surgical clips, film and compostable trash bags. The mole fraction solubility of p-dioxanone in various solvents such as acetone, ethylacetate, tetrahydrofuran, methanol, ethanol, 1-propanol, 1-butanol and 1-pentanol were measured over the temperature range from 263.05 K to 288.45 K. The solubility of p-dioxanone increases with increasing polarity of the solvents.
        4,000원
        1790.
        2008.12 KCI 등재 구독 인증기관 무료, 개인회원 유료
        Transesterification of fat of Tra catfish with methanol in the presence of the KOH catalyst yields fatty acid methyl esters (FAME) and glycerol (GL). The effects of the reaction temperature and reaction time on rate constants and kinetic order were investigated. Three regions were observed. In the initial stage, the immiscibility of the Tra fat and methanol limited the reaction rate, hence this region was controlled by the mass transfer. Subsequent to this region, produced FAME like a co-solvent made the reaction mixture homogeneous, therefore the conversion rate increased rapidly so it was controlled by the kinetic parameters of the reaction until the equilibrium was approached in the final slow region. A second-order kinetic mechanism was proposed involving second regions for the forward reaction. The rate determining step for the overall KOH catalyzed-methanolysis of Tra fat was the conversion of triglycerides (TG) to diglycerides (DG). This rate constant was increased from 0.003 to 0.019min-1 when the reaction temperature was increased from 35 to 60℃. Its calculated activation energy was 14.379 (kcal.mol-1).
        4,200원
        1791.
        2008.12 KCI 등재 구독 인증기관 무료, 개인회원 유료
        A group of new N,N-bis(5-acetylpyridin-2-yl)phenylamine derivatives was synthesized in good yield applying an optimized Buchwald-Hartwig amination protocol. The synthesized compounds showed UV absorption maxima in the range of 320-360 nm, and showed good luminescence at dilute concentrations in the blue region of the spectra (in the range of 480-497 nm). They showed also a bathochromic shift associating the increase in solvent polarity. The synthesized compounds could be investigated for use in OLEDs or as potential monomers for PLEDs.
        4,000원
        1792.
        2008.09 KCI 등재 구독 인증기관 무료, 개인회원 유료
        The core-shell composite particles of inorganic/organic were polymerized by using styrene(St) as a shell monomer and potassium persulfate (KPS) as an initiator. We studied the effect of core-shell structure of silicone dioxide/styrene in the presence of an anionic surfactant sodium lauryl sulfate (SLS) and polyoxyethylene alky lether sulfate (EU-S133D). We found that when SiO2 core/PSt shell polymerization was prepared on the surface SiO2 particle, to minimize the coagulation during the shell polymerization, the optimum conditions were at concentration of 2.56×10-2mole/L SLS. The structure of core-shell polymer was confirmed by measuring the thermal decomposition of polymer composite using thermogravimetric analyzer and morphology of core-shell polymer particles by transmission electron microscope (TEM).
        4,000원
        1793.
        2008.09 KCI 등재 구독 인증기관 무료, 개인회원 유료
        In this study, the characteristics of emulsified fuel were studied. The emulsified fuel which was composed of water and diesel was manufactured by using homogenizer and ultrasonic generator. The more the percentage of water contents increases, the more the density increases to the emulsified fuel. However, the viscosity increased in the 60% of water contents and decreased in the 70% of water contents because the O/W type was formed. The 3 minutes's ultrasonic waves during the irradiation time was appropriate of 16,000 rpm. And the energy density of ultrasonic waves was 87.5J/g. The emulsion stability has improved in the lower temperature, the lower percentage of water contents, and the most stable emulsion state was obtained from 20%(w/w) of water contents. Also, the emulsion stability was related to the HLB values of emulsifiers. Especially, the HLB values of emulsifier were appropriate from 4 to 7 values.
        4,000원
        1794.
        2008.09 KCI 등재 구독 인증기관 무료, 개인회원 유료
        본 논문에서는 용액 공정을 이용한 고분자 절연층을 갖는 top-gate 구조의 펜타센 박막 트랜지스터(Thin Film Transistor, TFT)의 특성을 연구하였다. Top-gate 구조의 펜타센 TFT 제작에 앞서 유기 반도체인 펜타센의 결정성 성장을 돕기 위해서 가교된 PVP (cross-linked poly(4-vinylphenol))를 유리 기판 상에 스핀 코팅을 이용하여 형성한 후, 노광 공정을 통해 니켈/은 구조를 갖는 채널 길이 10μm의 소오스, 드레인 전극을 형성하였다. 그리고 열 증착을 이용하여 60 nm 두께의 펜타센 층을 성막하였고, 고분자 절연체로서 PVA(polyvinyl alchol) 또는 가교된 PVA를 용액공정인 스핀 코팅을 이용하여 형성한 후 열 증착으로 알루미늄 게이트 전극을 성막하였다. 이로써 제작된 소자들의 전기적 특성을 확인한 결과 가교된 PVA를 사용한 펜타센 TFT 보다 PVA를 게이트 절연체로 사용한 소자가 전기적 특성이 우수한 것으로 관찰되었다. 이는 PVA의 가교 공정에 의한 펜타센 박막의 성능 퇴화에 기인한 것으로 사료된다. 실험 결과 0.9μm 두께의 PVA 게이트 절연막을 사용한 top-gate 구조의 펜타센 TFT의 전계 효과 이동도와 문턱전압, 그리고 전류 점멸비는 각각, 약 3.9×10-3 cm2/Vs, -11.5 V, 3×105으로써 본 연구에서 제안된 소자가 용액 공정형 top-gate 유기 TFT 소자로서 우수한 성능을 나타냄을 알 수 있었다.
        4,000원
        1795.
        2008.09 KCI 등재 구독 인증기관 무료, 개인회원 유료
        The effects of the applied stretch and MgADP binding on the structure of the actin and myosin cross-bridges in rabbit fibers in the rigor state have been investigatedwith improved resolution by x-ray diffraction using synchrotron radiation. To clarify the structure of the ATP hydrolysis intermediates formed by actin and myosin cross-bridges,the effects of various phosphate analogs in the of MgADP on the structure of the thin and thick filaments in glycerinated rabbit muscle fibers in the rigor state investigated by x-ray diffraction with a short exposure time using synchrotron radiation. These results strongly suggest that when MgADP and phosphate analogs such as metallofluorides(BeF3 and AlF4)and vanadate(VO4(Vi)) were added the rigor fibers in the presence of the ATP-depletion backup system, the intensities of the actin-based layer lines were markedly weakened. We found that the intensity of the 14.5 nm-based meridional reflections increase by 20-50% when phosphate analogs such as metallofluorides(BeF3 and AlF4) and vanadate(VO4(Vi)) was added to the rigor muscle.
        4,000원
        1796.
        2008.09 KCI 등재 구독 인증기관 무료, 개인회원 유료
        Akt, a serine/threonine protein kinase as a viral oncogene, is a critical regulator of PI3K-mediated cell proliferation and survival. On translocation, Akt is phosphorylated and activated, ultimately resulting in stimulation of cell growth and survival. As a part of our program toward the novel Akt1 inhibitors with potent activity over PI3K signaling pathway, we found primary hit compound 2 with an IC50 value of 620μM from protein kinase focused library. Based on the structural features of 2, new 1,3,4-thiadiazole derivatives were designed by the introduction of aromatic and heteroaromatic moieties onto thiadiazole nucleus. In this work, a series of 1,3,4-thiadiazole derivatives 1a-1 were synthesized and evaluated for Akt1 inhibitory activity.
        4,000원
        1797.
        2008.09 KCI 등재 구독 인증기관 무료, 개인회원 유료
        In the present work, the choice of the nano carbon black and optimum mixed ratio and effectiveness of the mixed carbon black to get a raw data for a manufacturing method of conductive complex board. Optimum mixed ratio of paper sludge & water was 1 : 2.5 for reformations. HB-41-Y was cheaper than Super-P with the single carbon black. Also electric conductivity of HB-41-Y(6.406×10-2 Ωcm-1) was about 6.5 times higher than Super-P(9.741×10-3 Ωcm-1) at 20 wt% carbon black. This time optimum mixture ratio of the paper sludge and the carbon black to be about 15 wt%, optimum mixed ratio HB-41Y and Graphite about 3:1 and its electric conductivity was 5.824×10-2 Ωcm-1.
        4,000원
        1798.
        2008.09 KCI 등재 구독 인증기관 무료, 개인회원 유료
        One of the popular domestic sewage treatment process (called step feed oxic-anoxic-oxic process) for nitrogen removal was analyzed in this study by theoretical analysis based on the nitrification and denitrification reaction. Total nitrogen removal efficiency was suggested by considering influent qualities(i.e., ammonia, nitrite, nitrate, alkalinity, and COD). Total nitrogen removal efficiency depends on r (influent allocation ratio). In the case that all influent components are enough, the total nitrogen removal follows equation 100-b/(1+b), when r is 1/(1+b). Finally, it can be concluded that step feed oxic-anoxic-oxic process could be effective for nitrogen removal.
        4,000원
        1799.
        2008.09 KCI 등재 구독 인증기관 무료, 개인회원 유료
        This study was done to investigate the antidiabetic effect of polygoni radix in Streptozotocin(STZ)-induced diabetic rats. Diabetes was induced by intravenous injection of STZ at a dose of 45mg/kg dissolved in citrate buffer. The ethanol extract of polygoni radix was orally administrated once a day for 7 days. The content of serum glucose, triglyceride(TG), total cholesterol were significantly decreased in polygoni radix treated STZ-sample group compared to the those of STZ-control group. The content of hepatic glycogen and activities of glucose-6-phosphate dehydrogenase(Glucose-6-PDH), glucokinase were significantly increased, but activity of glucose-6-phoshatase was decreased in polygoni radix treated STZ-sample group compared to the those of STZ-control group. These results indicated that ethanol extract of polygoni radix would have antidiabetic effect in STZ-induced diabetic rats.
        4,000원
        1800.
        2008.09 KCI 등재 구독 인증기관 무료, 개인회원 유료
        Cellulose nanofibers from microfibril cellulose (MFC) was prepared by hydrobromic acid (HBr) treatment at different concentrations. Polyvinyl alcohol (PVA) composite films at various loading level of nanofibers were manufactured by a film casting method. The analysis of degree of polymerization (DP), crystallinity (Xc) and molecular weight (Mw) of cellulose after acid treatment was conducted. The mechanical and thermal properties of the cellulose nanofibers reinforced PVA films were characterized using tensile tests and thermogravimetric analysis (TGA). The DP and Mw of MFC by HBr hydrolysis considerably decreased, but Xc showed no significant change. After acid hydrolysis, the diameter of cellulose nanofibers was in the range of 100 to 200 nm. The thermal stability of the films was steadily improved with the increase of nanofiber loading. There was a significant increase in the tensile strength of PVA composite films with the increase in MFC loading. Finally, 5 wt.% nanofiber loading exhibited the highest tensile strength and thermal stability of PVA composite films.
        4,000원