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        검색결과 98

        63.
        2001.06 KCI 등재 구독 인증기관 무료, 개인회원 유료
        The conventional debinding process in metal injection molding is very long time-consuming and unfriendly environmental method. Especially, in such a case of injection molded parts from hard and fine metal powder, such as WC-Co, an extremely long period of time is necessary in the conventional slow binder removal process. On the other hand, supercritical debinding is thought to be the effective method which is appropriate to eliminate the aforementioned inconvenience in the prior art. The supercritical fluid has high diffusivity and density, it can penetrate quickly into the inside of the green metal bodies, and extract the binder. In this paper, super-critical debinding is compared with wicking debinding process. Wax-based binder system is used in this study. The binder removal rate in supercritical have been measured at , 75 in the pressure range from 20 MPa to 28 MPa. Pores and cracks in silver bodies after sintering were observed using SEM When the super-critical debinding was carried out at 75, almost all the wax (about 70 wt% of binder) was removed in 2 hours under 28 MPa and 2.5 hours under 25 MPa.
        4,000원
        64.
        2001.05 KCI 등재 구독 인증기관 무료, 개인회원 유료
        3,000원
        71.
        1997.08 KCI 등재 구독 인증기관 무료, 개인회원 유료
        It was tested the possibility that EPA and DHA could be separated from fish oil fatty acid ethyl ester(FAEE) in the supercritical carbon dioxide rectification method. Experiments were carried out in the 1800mm tall and temperature gradient packed rectification column at the pressure of 100bar and carbon dioxide flow rate of 52.43NL/min. Experimental results showed that this method was useful to separate the FAEE by the relative volatility of the components. The maximum attainable concentration of EPA, DHA and both of them in product were 41%, 43% and 57% respectively in this rectification column using raw fish oil feed.
        4,000원
        72.
        1997.08 KCI 등재 구독 인증기관 무료, 개인회원 유료
        Separation of EPA and DHA from fish oil fatty acid ethyl ester (FAFE) by urea adductive crystallization method was carried out in the supercritical carbon dioxide (SC CO2) as a solvent. Our results showed that SC CO2 is a good candidate as a solvent in the urea adductive crystallization to separate FAFE by the number of unsaturated bonds. Compared to the separation process using methanol. SC CO2 yielded better performance in the overall selectivity of EPA and DHA. The effect of process variables on separation of EPA and DHA was discussed in detailed. A hybrid technology of SC CO2 fractionation and urea adductive crystallization with SC CO2 was conformed as a viable process to separate and concentrate EPA and DHA from fish oil.
        4,000원
        73.
        1996.11 KCI 등재 SCOPUS 구독 인증기관 무료, 개인회원 유료
        본 연구에서는 resorcinol과 formaldehyde를 이요하여 수상에서 축중합시켜 겔을 만든 후 저온 초임계 건조 공정을 이용하여 겔 구조의 변형없이 용매를 제거하여 내무 표면적과 같은 에어로겔의 최종 물성에 미치는 영향을 알아보기 위하여 고형분의 농도(2-5%)를 변화시켜 실험한 결과 초기 반응조건이 반응시간 및 최종물성에 변수가 됨을 알 수 있었다. 또한 제조된 에어로겔에 100-300˚C까지 온도를 가하며 표면 특성을 분석한 결과 열을 가함에 따라 기공의 크기가 커지고 표면적이 감소됨을 관찰할 수 있었다.
        4,000원
        74.
        2018.04 KCI 등재 SCOPUS 서비스 종료(열람 제한)
        The roots of Rosa multiflora Thunberg have been used in traditional oriental medicine as remedies for rheumatic arthralgia and scabies. In this study, the anti-fungal, anti-oxidant, and anti-inflammatory activities of a supercritical extract of Rosa multiflora root were investigated in vitro. To investigate the anti-oxidant and anti-inflammatory effects of the supercritical extract, 2,2'-azino-bis(3-ethylbenzothiazoline-6-sulphonic acid (ABTS) radical scavenging activity, and the inhibition of nitric oxide production in lipopolysaccharide (LPS)-stimulated RAW 264.7 cells were examined, respectively. In addition, the anti-fungal activities of the extract were assessed. The results showed a concentration-dependent, increase in ABTS radical scavenging activity. The supercritical fluid extracts of Rosa multiflora root exhibited low toxicity to RAW 264.7 cells at 100 μg/mL the highest concentration tested. Cells stimulated with LPS produced more nitric oxide than normal control cells; however, cells treated with the supercritical fluid extract decreased this production in a concentration-dependent manner. Finally, the supercritical fluid extracts showed significant anti-fungal activity. These results suggest that extracts of the roots of Rosa multiflora might be used to develop potent anti-fungal, anti-oxidant, and anti-inflammatory agents, and may be useful as ingredients for related new functional cosmetic materials.
        75.
        2018.04 KCI 등재 서비스 종료(열람 제한)
        Background: To obtain useful cosmetic resources, this study aimed to determine the non-saponin fatty acid and inhibitory activities of collagenase and elastase by treatment of Saccharomyces cerevisiae in supercritical fluid extracted oil of the adventitious root culture of wild mountain ginseng. Methods and Results: We performed supercritical fluid extraction at various conditions such as pressure, temperature, time, and use of co-solvents, unlike the n-hexane extraction for the adventitious roots culture of wild mountain ginseng. The non-saponin-fatty acid obtained from the oil of the adventitious roots culture was incresed by treatment with S. cerevisiae. The supercritical fluid extraction was conducted using gas chromatography. Non-saponin-fatty acid content, in the oil of adventitious roots culture of wild mountain ginseng treated with S. cerevisiae for 2 days were three times higher than that in the control. In addition, the oil of the adventitious roots culture treated with S. cerevisiae was investigated for the anti-wrinkle effect by using collagenase and elastase. The oil of adventitious roots culture treated with S. cerevisiae exhibited higher collagenase and elastase inhibitory activities than those in the control. Conclusions: Supercritical fluid extracted oil of the adventitious roots culture of wild mountain ginseng treated with S. cerevisiae was found to have decreased ratio of saturated fatty acids and incresed ratio and content of unsaturated fatty acids increased. Furthermore, it showed anti-wrinkle effects in vitro.
        76.
        2016.10 서비스 종료(열람 제한)
        Background : The effective components of Omija(Schisandra chinensis Bailllon) are lignans (schizandrins and gomisins), and this components were contented mostly in seed part on Omija, which have various physiological functionalities such as anti-cancer, anti-inflammatory, and antioxidant activities. Methods and Results : This study was carried out to determine effective condition(CO2, CO2+ethanol) on extraction using supercritical carbon dioxide extraction (SFE) system and to find interrelation on effective components and antioxidant activity of extracts and residues obtained after extraction. Effective components were analysed lignans and phenolic compounds and antioxidant activirty was determined for DPPH radical scavenging ability on methanol extracts of SFE-extract and SFE-residue. On SFE with ethanol, SFE extract was separated two phase, upper(water phase) and lower(oil phase). SFE-extract showed the highest total lignans content(61.36 mg/g, 72.14 mg/g on lower, 50.58 mg/g on upper) and the lowest total phenolic compounds(6.52 mg/100g) and SFE-residue showed the lowest total lignans content(1.45 mg/g) and the highest total phenolic compounds(16.23 mg/100g) by extracted on CO2+ethanol treatment. SFE-residue methanol extract showed the highest DPPH radical scavenging abilities and SFE-extract upper showed the lowest. Conclusion : Thus, this results showed SFE-extract showed the highest total lignans content, but SFE-residue showed the highest DPPH radical scavenging ability although the lowest total lignans content.
        77.
        2013.12 KCI 등재 서비스 종료(열람 제한)
        This study investigates the effect of supercritical fluid extract (CMPB803-C) of Lithospermum erythrorhizon,shikonin and acetylshikonin isolated from Lithospermum erythrorhizon on IL-1β-induced chondrocytes and monosodiumiodoacetate (MIA)-induced osteoarthritis in rat. Shikonin (50μM) and acetylshikonin (3μM) treatment reduced signifi-cantly the mRNA expression and enzyme activity of matrix metalloproteinase (MMP)-1, −3 and −13 in IL-1β-inducedSW1353 chondrosarcoma cells. The chondro-protective effects of CMPB803-C and acetylshikonin were than analyzed in arat OA model using a single intra-articular injection of MIA (1㎎) in the right knee joint. CMPB803-C (200㎎/㎏) or ace-tylshikonin (5㎎/㎏) was orally administered daily for two weeks starting after 1 week of MIA injection. In the histologicalobservation, CMPB803-C and acetylshikonin clearly improved OA lesions being comparable to or better that control group.Our results demonstrated that CMPB803-C and acetylshikonin as active compound of Lithospermum erythrorhizon have astrong chondro-protective effect in OA rats, which likely attributes to its anti-inflammatory activity and inhibition ofMMPs production.
        78.
        2013.11 서비스 종료(열람 제한)
        Hydrolysis of triacylglycerol(TAG) from fats and oils to glycerol and free fatty acid (FFA), also referred to as fat splitting, is an important reaction for the olechemical industry. Typically, hydrolysis is carried out at 100-260℃ and 100-7000 kPa using 0.4-0.15(w/w) initial water to oil ratio with or without catalysts. It is an endothermic reaction occurs in a stepwise manner where TAG is initially hydrolyzed to diacyglycerol (DAG) then to monoacylglycerol(MAG) and finally to glycerol. Water, in its subcritical state, can be used as both a solvent and reactant for the hydrolysis of triglycerides. subcritical water (150℃<T<370℃,0.4<p<22Mpa) can act as an acid or base catalyst. To investigate milder reaction conditions, in this study, waste cooking oil and fresh soybean oils will be hydrolyzed to free fatty acids with deionized water under SC CO2 medium in a batch reactor. Effects of the reaction temperature, time and solvent to feed ratio on FFA in the hydroysis at equilibrium will also observed for optimum conversion of oil. The reaction products will be analyzed by acid-base titration, GC FID and HPLC.
        79.
        2013.11 서비스 종료(열람 제한)
        Recently biodiesel has drawn much attraction as renewable enegy due to its environmental benefits and the fact that it is made from renewable resources. However, the production cost of biodiesel is one of the main hurdle to commercialize it. One of the way to reduce the biodiesel production cost is to use the waste cooking oil as feedstock. In the conventional transesterification process of waste cooking oils for biodiesel production, the presence of free fatty acids and water causes severe problems such as formation of soap and decreasing of catalyst yield. Much effort has been devoted to solve the above problems and one of the promising way is the supercritical methanol treatment which is performed at the methanol supercritical environment (>239.45℃, >8.10 Mpa)one of the serious problems of the application of SCM process for the biodiesel production is the tough operation condition(high pressure, high temperature. In this study, we have studied about the supercritical methanol treatment for the biodiesel production with the soybean waste cooking oil as a feedstock in the present of various heterogeneous solid catalysts such as mesoporous silica and acid-doped mesorpous silica. Biodiesel conversion was increased at more mild opreation condition to the previous studies by using the catalysts. The conversion was more enhanced by modifying the catalysts.
        80.
        2013.10 KCI 등재 SCOPUS 서비스 종료(열람 제한)
        In this study, we searched for bioactive compounds from natural resources with a supercritical extract. We selected the extracts of Chrysanthemum zawadskii, Lufa cylindrica, Paeonia lactiflora, Gardenia jasminoides and Scutellaria baicalensis, as natural materials, and evaluated the effects of their skin barrier function. We found that these extracts increased the transactivation activity of the PPAR-responsive element (PPRE) and the anti-oxidation with different priorities, respectively. In addition, these extracts promoted the expression of proteins related to cornified envelope (CE) formation, such as involucrin. From these results, we suggest that natural materials from supercritical extracts will be pertinent candidates for the improvement of the epidermal permeability barrier function.
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