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        검색결과 146

        44.
        2013.12 KCI 등재 SCOPUS 구독 인증기관 무료, 개인회원 유료
        We present near-infrared light curves of HBC 722 after its the September 2010 outburst. We have been monitoring its near-infrared light curves since November 2010 with Korean Astronomy and Space Science Institute Infrared Camera System (KASINICS). HBC 722 exhibits large changes in optical and near-infrared brightness since its outburst. The J, H, and Ks light curves over about 2.5 years show that in all observed bands HBC 722 progressively became fainter until around April 2011, down to J ~10.7, H ~9.9, Ks ~9.3, but it is getting brighter again. Large scatter in the obtained light curve prevents us from finding whether there is any short timescale variation as reported in other optical observations. The near-infrared color of HBC 722 is becoming bluer since its outburst. The pre-outburst Spectral Energy Distribution (SED) of HBC 722 is consistent with that of a slightly reddened Class II YSO with the exception of the extraordinary IR-excess in the far-infrared region.
        4,000원
        45.
        2013.12 KCI 등재 SCOPUS 구독 인증기관 무료, 개인회원 유료
        We compare mass-loss rates of OH/IR stars obtained from radio observations with those derived from the dust radiative transfer models and IR observations. We collect radio observational data of OH maser and CO line emission sources for a sample of 1533 OH/IR stars listed in Suh & Kwon (2011). For 1259 OH maser, 76 CO(J=1-0), and 55 CO(J=2-1) emission sources, we compile data of the expansion velocity and mass-loss rate. We use a dust radiative transfer model for the dust shell to calculate the mass-loss rate as well as the IR color indices. The observed mass-loss rates are in the range predicted by the theoretical dust shell models corresponding to M = 10-8M⊙/yr - 10-4M⊙/yr. We find that the dust model using a simple mixture of amorphous silicate and amorphous Al2O3 (20% by mass) grains can explain the observations fairly well. The results indicate that the dust radiative transfer models for IR observations generally agree with the radio observations. For high mass-loss rate OH/IR stars, the mass-loss rates obtained from radio observations are underestimated compared to the mass-loss rates derived from the dust shell models. This could be because photon momentum transfer to the gas shell is not possible for the physical condition of high mass-loss rates. Alternative explanations could be the e®ects of di®erent dust-to-gas ratios and/or a superwind.
        4,000원
        50.
        2012.12 KCI 등재 구독 인증기관 무료, 개인회원 유료
        This study analyzes the structure types of salmon oil to evaluate the purity of salmon oil products based on the 38 different types of imported salmon oil products distributed in the Republic of Korea. The major types of omega-3 foods in the salmon oil are ethyl ester (EE) and triglyceride (TG). If the salmon oil contained potential contaminants and was processed in order to remove it, EE type omega-3 fatty acids are found in concentration. This provides a good guide in assessing if products were made with EE type ingredients or re-esterified contaminated materials. The results of the FT-IR analysis showed significant difference in the C=O, C-O band positions in TG and EE. There were 19 TG type products and 19 EE type products. The analysis of carbon isotope ratio was performed on the types of TG and EE. There were different properties in the 19 TG type products. In one product, the carbon isotope ratio was -25.15 and the other 18 products showed -22.15~-23.96. The carbon isotope ratio of all 19 EE type products showed -21.91~-23.74. The results of the TLC analysis showed similar results with FR-IR. The re-esterified TG form was not detected in the TG type products, confirming that the TG type products contained natural salmon oil. This study aimed to provide the basic material in classifying the types of natural salmon oil and re-esterified salmon oil, by analyzing the pattern and proportion of FT-IR spectrum, carbon isotope ratio, and TLC.
        4,000원
        51.
        2012.09 KCI 등재 구독 인증기관 무료, 개인회원 유료
        We present new constraints on the cosmic optical background (COB) obtained from an analysis of the Pioneer 10/11 Imaging Photopolarimeter (IPP) data. After careful examination of the data quality, the usable measurements free from the zodiacal light are integrated into sky maps at the blue ( ∼0.44μm) and red (∼0.64μm ) bands. Accurate starlight subtraction was achieved by referring to all-sky star catalogs and a Galactic stellar population synthesis model down to 32.0 mag. We find that the residual light is separated into two components: one component shows a clear correlation with the thermal 100μm brightness, whilst the other shows a constant level in the lowest 100μm brightness region. The presence of the second component is significant after all the uncertainties and possible residual light in the Galaxy are taken into account, thus it most likely has an extragalactic origin (i.e., the COB). The derived COB brightness is ((1.8±0.9)×10−9 and (1.2±0.9)×10−9ergs−1cm−2sr−1 \AA−1 in the blue and red spectral regions, respectively, or 7.9±4.0 and 7.7±5.8nWm−2sr−1 . Based on a comparison with the integrated brightness of galaxies, we conclude that the bulk of the COB is comprised of normal galaxies which have already been resolved by the current deepest observations. There seems to be little room for contributions from other populations including "first stars" at these wavelengths. On the other hand, the first component of the IPP residual light represents the diffuse Galactic light (DGL)-scattered starlight by the interstellar dust. We derive the mean DGL-to- 100μm brightness ratios of 2.1×10−3 and 4.6×10−3 at the two bands, which are roughly consistent with previous observations toward denser dust regions. Extended red emission in the diffuse interstellar medium is also confirmed.
        3,000원
        56.
        2011.08 KCI 등재 SCOPUS 구독 인증기관 무료, 개인회원 유료
        A 20' X 20' region around 30 Doradus in the Large Magellanic Cloud (LMC) is observed and analyzed in the near-infrared. We obtain polarimetry data in the J, H, and Ks bands using the SIRIUS polarimeter SIRPOL at the Infrared Survey Facility 1.4 m telescope. We measure the Stokes parameters of 2562 point-like sources to derive the degree of polarization and the polarization position angles. We discuss the statistics of the groups classified by color-magnitude diagram and proper motions of the sources, in order to separate the Galactic foreground sources from those present in the LMC. We notice that groups classified by the proper motion data show a tendency towards different polarimetric properties.
        4,000원
        57.
        2011.04 KCI 등재 SCOPUS 구독 인증기관 무료, 개인회원 유료
        New organic light-emitting diodes with structure of indium-tin-oxide[ITO]/N,N'-diphenyl-N, N'-bis-[4-(phenyl-m-tolvlamino)-phenyl]-biphenyl-4,4'-diamine[DNTPD]/1,1-bis-(di-4-poly-aminophenyl) cyclohexane[TAPC]/bis(10-hydroxy-benzo(h)quinolinato)beryllium[Bebq2]/Bebq2:iridium(III)bis(2-phenylquinoline-N,C2')acetylacetonate[(pq)2Ir(acac)]/ET-137[electron transport material from SFC Co]/LiF/Al using the selective doping of 5%-(pq)2Ir(acac) in a single Bebq2 host in the two wavelength (green, orange) emitter formation were proposed and characterized. In the experiments, with a 300Å-thick undoped emitter of Bebq2, two kinds of devices with the doped emitter thicknesses of 20Å and 40Å in the Bebq2:(pq)2Ir(acac) were fabricated. The device with a 20Å-thick doped emitter is referred to as "D-1" and the device with a 4Å-thick doped emitter is referred to as "D-2". Under an applied voltage of 9V, the luminance of D-1 and D-2 were 7780 cd/m2 and 6620 cd/m2, respectively. The electroluminescent spectrum of each fabricated device showed peak emissions at the same two wavelengths: 508 nm and 596 nm. However, the relative intensity of 596 nm to 508 nm at those wavelengths was higher in the D-2 than in the D-1. The D-1 and D-2 devices showed maximum current efficiencies of 5.2 cd/A and 6.0 cd/A, and color coordinates of (0.31, 0.50) and (0.37, 0.48) on the Commission Internationale de I'Eclairage[CIE] chart, respectively.
        3,000원
        60.
        2011.02 KCI 등재 SCOPUS 구독 인증기관 무료, 개인회원 유료
        We study near-infrared properties of the old open cluster King 11, based on the 2MASS photometric data. We determine the location of the red giant clump(RGC) in the (K, J - K) colo-magnitude diagram and derive the distance modulus of King 11 to be (m-M)0 = $12.50 ± 0.10 using the mean K magnitude of RGC. From the red giant branch slope - [Fe/H] relation we obtain the metallicity of this cluster, [Fe/H]=-0.17±0.07. The age and interstellar reddening of this cluster are estimated to be log t = 9.48±0.05, E(B-V)=0.90±0.03, by applying Padova isochrone fits to the data.
        4,000원
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