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        검색결과 9

        3.
        2008.12 구독 인증기관 무료, 개인회원 유료
        The present study reports the protective properties of a total methanol extract of B. platyphylla var. japonica against ultraviolet (UV)-C irradiation. Pretreatment of Chinese hamster fibroblast (V79-4) cells with a total methanol extract significantly increased cell survival following 300J/m² of UV-C irradiation. The total methanol extract was further fractionated into 5 fractions: n-hexane, dichloromethane, ethylacetate, n-butanol and water fractions. Among these fractions, B. platyphylla var. japonica ethylacetate, butanol and water fractions showed significant protective effects against the cellular damage induced by UV-C irradiation. In order to elucidate the mechanism underlying this protective effect, DPPH (Editor note: abbreviations should be spelled out at first use.) radical scavenging and lipid peroxidation inhibitory activity were measured. Significant radical scavenging and lipid peroxidation inhibitory activities were observed for the ethylacetate fraction. In summary, the present data demonstrate that an extract of B. platyphylla var. japonica has a significant protective effect against UV-C irradiation. The underlying mechanism of this protective effect may involve radical scavenging and inhibition of lipid peroxidation by the B. platyphylla var. japonica extract.
        4,000원
        5.
        2007.03 KCI 등재 SCOPUS 구독 인증기관 무료, 개인회원 유료
        About 10 percent of quasars are known to exhibit deep broad absorption troughs blueward of prominent permitted emission lines, which are usually attributed to the existence of outflows slightly above he accretion disk around the supermassive black hole. Typical widths up to 0.2c of these absorption roughs indicate the velocity scales in which special relativistic effects may not be negligible. Under he assumption of the ubiquity of the broad absorption line region in quasars, the broad emission line flux will exhibit Thomson scattered components from these fast outflows. In this paper, we provide our Monte Carlo calculation of linear polarization of singly Thomson scattered line radiation with the careful considerations of special relativistic effects. The scattering region is approximated by a collection of rings that are moving outward with speeds υ =cβ < 0.2c near the equatorial plane, and the scattered line photons are collected according to its direction and wavelength in the observer's rest frame. We find that the significantly extended red tail appears in the scattered radiation. We also find that the linear degree of polarization of singly Thomson scattered line radiation is wavelength-dependent and hat there are significant differences in the linear degree of polarization from that computed from classical physics in the far red tail. We propose that the semi-forbidden broad emission line C III]1909 may be significantly contributed from Thomson scattering because this line has small resonance scattering optical depth in the broad absorption line region, which leads to distinct and significant polarized flux in this broad emission line.
        4,000원
        6.
        2003.06 KCI 등재 SCOPUS 구독 인증기관 무료, 개인회원 유료
        We report the results of the ionospheric measurement obtained from the instruments on board the Korea Multi-Purpose Satellite - 1 (KOMPSAT-l). We observed a deep electron density trough in the nighttime equatorial ionosphere during the great magnetic storm on 15 July 2000. We attribute the phenomena to the up-lifted F-layer caused by the enhanced eastward electric field, while the spacecraft passed underneath the layer. We also present the results of our statistical study on the equatorial plasma bubble formation. We confirm the previous results regarding its seasonal and longitudinal dependence. In addition, we obtain new statistical results of the bubble temperature variations. The whole data set of measurement for more than a year is compared with the International Reference Ionosphere (IRI). It is seen that the features of the electron density and temperature along the magnetic equator are more prominent in the KOMPSAT-l observations than in the IRI model.
        4,000원
        7.
        2015.05 서비스 종료(열람 제한)
        Reuse, recycling and recovery (3R) of industrial wastes are common and encouraging in Korea. Industrial symbiosis is one of typical methods for implementing 3R and has been defined as engaging “traditionally separate industries in a collective approach to competitive advantage involving physical exchange of materials, energy, water, and by-products”. The keys to industrial symbiosis are collaboration and the synergistic possibilities offered by geographic proximity. Recently, several countries in East Asia such as Taiwan, South Korea, Japan and China are promoting ‘designed’ symbiosis networks in various industrial complexes based on their national Eco-industrial Park (EIP) demonstration programs. Despite the recently promoted EIP initiatives worldwide, only very few studies furnish the operational and functional details of ‘designed’ industrial symbiosis networks, starting from the planning to implementation stage. The production of terephthalic acid (TPA) in Korea is 6.5 million ton based on 2011. The production of waste generated in the process of TPA is about 15,000 ton/yr and included useful materials like residue TPA as well as isophthalic acid (iPA), benzoic acid (BA) and p-toluic acid (p-TL). Until now, TPA waste was incinerated due to high caloric value. This study was conducted for recovery of valuable materials from industrial waste and utilization of recovered material as an example of Korean EIP. In this study, the experiment was performed to separate above four materials from the waste by solvent (methanol and water) extraction. The solubility of TPA (0.1g/100g) for methanol is relatively low compared to other materials. Also the solubility of BA (68g/L at 95℃) and p-TL (11.6g/L at 98℃) for water is relatively high in comparison with other materials. Finally, BA was separated from p-TL by molecular distillation system. The purity of recovered materials was analyzed by ultra-high performance liquid chromatography (Waters Xevo TQ system). The recovery rate and purity of BA is 90% and 93%. The recovered BA could be recycled the companies which are produced plastic plasticizer and paints.