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        검색결과 24

        3.
        2023.08 KCI 등재 구독 인증기관 무료, 개인회원 유료
        Since interstellar objects like 1I/`Oumuamua and 2I/Borisov originate from exoplanetary systems, evenif we do not visit the exoplanetary systems,yby, rendezvous, and sample return missions of interstellarobjects can provide clues to solve the mysteries of cosmic life phenomena such as the origin of exoplanetarysystems, galactic evolution, biosignatures (or even technosignatures), and panspermia. In this paper, wereview space missions for interstellar object exploration in the stage of mission design or concept studysuch as Project Lyra, Bridge, Comet Interceptors, and LightcraftTM. We also review space missions,OSIRIS-REx and NEA Scout, designed for Near Earth Asteroids(NEA) explorations, to investigate thecurrent state of basic technologies that can be extended to explore interstellar objects in a velocity of~ 6AU/year. One of the technologies that needs to be developed for interstellar object exploration is aspacecraft propulsion method such as solar sail, which can catch up with the fast speed of interstellarobjects. If this kind of propulsion becomes practical for space explorations, interstellar object explorationswill mark a new era and serve as a driving force to provide evidences of cosmic life.
        4,300원
        7.
        2018.08 KCI 등재 SCOPUS 구독 인증기관 무료, 개인회원 유료
        Active Galactic Nucleus (AGN) variability can be used to study the physics of the region in the vicinity of the central black hole. In this paper, we investigated intra-night optical variability of AGN in the COSMOS field in order to understand the AGN instability at the smallest scale. Observations were performed using the KMTNet on three separate nights for 2.5 to 5 hours at a cadence of 20 to 30 min. We find that the observation enables the detection of short-term variability as small as ∼ 0.02 and 0.1 mag for R ∼ 18 and 20 mag sources, respectively. Using four selection methods (X-rays, mid-infrared, radio, and matching with SDSS quasars), 394 AGN are detected in the 4 deg2 field of view. After differential photometry and X2−test, we classify intra-night variable AGN. The fraction of variable AGN (0–8%) is statistically consistent with a null result. Eight out of 394 AGN are found to be intra-night variable in two filters or two nights with a variability level of 0.1 mag, suggesting that they are strong candidates for intra-night variable AGN. Still they represent a small population (2%). There is no sub-category of AGN that shows a statistically significant intra-night variability.
        5,800원
        13.
        2010.12 KCI 등재 구독 인증기관 무료, 개인회원 유료
        In this study, the antioxidative effect, cellular protective effect and inhibitory effect on tyrosinase of Cosmos bipinnatus extracts were investigated. The ethyl acetate fraction of Cosmos bipinnatus flower extract (11.48 μg/mL) showed more excellent free radical (1,1-diphenyl-2-picrylhydrazyl radical, DPPH) scavenging activity (FSC50) than those of leaf and stem extracts (17.45 μg/mL). Reactive oxygen species (ROS) scavenging activity (OSC50) of Cosmos bipinnatus extracts on ROS generated in Fe3+-EDTA/H2O2 system were investigated using the luminol-dependent chemiluminescence assay. The ethyl acetate fraction of Cosmos bipinnatus flower extract (0.56 μg/mL) showed 3 times more excellent ROS scavenging activity than L-ascorbic acid (1.50 μg/mL). The protective effects of the ethyl acetate fractions of extracts from different parts of Cosmos bipinnatus on the rose-bengal sensitized photohemolysis of human erythrocytes were investigated. The ethyl acetate fractions of leaf and stem extract and flower extracts suppressed photohemolysis in a concentration dependent manner (10~50 μg/mL). The inhibitory effect of ethyl acetate fraction of Cosmos bipinnatus flower extract (62.75 μg/mL) on tyrosinase was investigated to assess the whitening efficacy. The ethyl acetate fraction of Cosmos bipinnatus flower extract showed 3.5 times higher tyrosinase inhibitory effect than arbutin (226.88 μg/mL) known as an effective whitening agent. These results indicate that fractions of Cosmos bipinnatus extracts can function as antioxidants in biological systems, particularly skin exposed to UV radiation by scavenging 1O2 and other ROS, and protect cellular membranes against ROS. Fractions of Cosmos bipinnatus extracts can be applicable to new functional cosmetics for antioxidant and whitening.
        4,000원
        15.
        2005.06 KCI 등재 SCOPUS 구독 인증기관 무료, 개인회원 유료
        The Cosmic Evolution Survey (COSMOS) is a Hubble Space Telescope (HST) treasury project. The COSMOS aims to perform a 2 square degree imaging survey of an equatorial field in I(F814W) band, using the Advanced Camera for Surveys (ACS). Such a wide field survey, combined with ground-based photometric and spectroscopic data, is essential to understand the interplay between large scale structure, evolution and formation of galaxies and dark matter. In 2004, we have obtained high-quality, broad band images of the COSMOS field (B, V, r', i', and z') using Suprime-Cam on the Subaru Telescope, and we have started our new optical multi-band program, COSMOS-21 in 2005. Here, we present a brief summary of the current status of the COSMOS project together with contributions from the Subaru Telescope. Our future Subaru program, COSMOS-21, is also discussed briefly.
        3,000원
        16.
        2004.12 KCI 등재 SCOPUS 구독 인증기관 무료, 개인회원 유료
        It is argued that the key task in understanding magnetic fields in the cosmos is to comprehend the origin of their order or coherence over large length scales in galaxies. Obtaining magnetic fields can be done in stars, whose lifetime is usually 1010 rotations, while galactic disks have approximately 20 to 50 rotations in their lifetime since the last major merger, which established the present day gaseous disk. Disorder in the galactic magnetic fields is injected on the disk time scale of about 30 million years, about a tenth of the rotation period, so after one half rotation already it should become completely disordered. Therefore whatever mechanism Nature is using, it must compete with such a short time scale, to keep order in its house. This is the focal quest.
        4,000원
        18.
        2002.10 구독 인증기관·개인회원 무료
        20.
        2015.03 KCI 등재 서비스 종료(열람 제한)
        The purpose of this study is to examine the tendency of certified organic cosmetics market and the certification standards and regulations they are under, compare one of the most commonly used COSMOS-standard AISBL with the Korea Ministry of Food and Drug Safety (MFDS) organic cosmetic standard regulation. And then examining their differences and any potential issues is to present suggestions to be made as data for certification standard for natural & organic cosmetics in Korea regulation. This contents of study will be used as good research and development to promote the sustainable growth of the natural & organic cosmetic ingredients which have been grown by organic farmers certified. Also certified organic ingredients may help to growth the organic industry. I believe these are actual comparative for application to develop of natural and organic cosmetics in Korea as well the strengthening of the competitiveness of organic cosmetics certified in the world.
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