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        검색결과 24

        1.
        2020.12 KCI 등재 SCOPUS 구독 인증기관 무료, 개인회원 유료
        We report the discovery of a giant exoplanet in the microlensing event OGLE-2017-BLG-1049, with a planet―host star mass ratio of q = 9.53 ± 0.39 × 10-3 and a caustic crossing feature in Korea Microlensing Telescope Network (KMTNet) observations. The caustic crossing feature yields an angular Einstein radius of θE = 0.52 ± 0.11 mas. However, the microlens parallax is not measured because the time scale of the event, tE ≃ 29 days, is too short. Thus, we perform a Bayesian analysis to estimate physical quantities of the lens system. We fi nd that the lens system has a star with mass Mh = 0.55+0.36 -0.29 M⊙ hosting a giant planet with Mp = 5.53+3.62 -2.87 MJup, at a distance of DL = 5.67+1.11 -1.52 kpc. The projected star{planet separation is aㅗ = 3.92+1.10 -1.32 au. This means that the planet is located beyond the snow line of the host. The relative lens{source proper motion is μrel ~ 7 mas yr-1, thus the lens and source will be separated from each other within 10 years. After this, it will be possible to measure the flux of the host star with 30 meter class telescopes and to determine its mass.
        4,000원
        2.
        2020.03 KCI 등재 구독 인증기관 무료, 개인회원 유료
        스리랑카는 채소의 주년 생산에 적합한 기후를 갖고 있는 열대국가이다. 열대, 아열대 채소의 재배면적은 전체 농지(105,062 ha)의 약 3%이다. 지난 50년 동안 스리랑카에서 채소 육종에 관한 체계적인 연구가 이루어졌고 채소 부문은 지속적으로 증가하였다. 하지만 채소 육종, 재배 및 가공과 관련된 기술이 선진국에 비해 많이 뒤떨어져 있는 형편이다. 전통 육종법을 통해 개발된 다양한 농업적 형질을 가진 품종이 현재까지 스리랑카의 채소 생산에 이용되고 있지만 생명공학적 방법을 접목한 채소 품종 육종법의 중요성이 점차로 부각되고 있다. 본 논문은 스리랑카에서 중요한 채소 작물인 토마토, 고추류, 콩류, 가지 및 여주의 육종과 품종 현황을 소개하고 향후 스리랑카 육종 전망에 대해 논의하였다.
        4,000원
        3.
        2019.06 KCI 등재 구독 인증기관 무료, 개인회원 유료
        This study focused on the development of Fe–Co/kaolin catalyst by a wet impregnation method. Response surface methodology was used to study the influence of operating variables such as drying temperature, drying time, mass of support and stirring speed on the yield of the catalyst. The catalyst composite at best synthesis conditions was then calcined in an oven at varied temperature and time using 22 factorial design of experiment. The catalyst with optimum surface area was then utilized to grow carbon nanofiber (CNF) in a chemical vapour deposition (CVD) reactor. Both the catalyst and CNF were characterized using high-resolution scanning electron microscopy, high-resolution transmission electron microscopy, thermogravimetric analysis (TGA), X-ray diffraction (XRD) and X-ray photoelectron spectroscopy. On the influence of operating variables on the yield of catalyst, the results showed that an optimum yield of 96.51% catalyst was obtained at the following operating conditions: drying time (10 h), drying temperature (110 °C), stirring speed (100 rpm) and mass of support (9 g). Statistical analysis revealed the existence of significant interactive effects of the variables on the yield of the catalyst. The HRSEM/XRD/BET/TGA analysis revealed that the particles are well dispersed on the support, with high surface area (376.5 m2/g) and thermally stable (330.88 °C). The influence of operating parameters on the yield of CNF was also investigated and the results revealed an optimum yield of 348% CNF at the following operating conditions: reaction temperature (600 °C), reaction time (40 min), argon flow rate (1416 mL/min) and acetylene/hydrogen flow rate (1416 mL/ min). It was found from statistical analysis that the reaction temperature and acetylene/hydrogen flow rates exerted significant effect on the CNF yield than the other factors. The contour and surface plots bi-factor interaction indicated functional relationship between the response and the experimental factors. The characterization results showed that the synthesized CNF is thermally stable, twisted and highly crystalline and contain surface functional groups. It can be inferred from the results of various analyses that the developed catalyst is suitable for CNF growth in a CVD reactor.
        5,700원
        5.
        2016.06 KCI 등재 SCOPUS 구독 인증기관 무료, 개인회원 유료
        We report the characterization of a massive (mp = 3:91:4Mjup) microlensing planet (OGLE- 2015-BLG-0954Lb) orbiting an M dwarf host (M = 0:33  0:12M ) at a distance toward the Galactic bulge of 0:6+0:4 􀀀0:2 kpc, which is extremely nearby by microlensing standards. The planet-host projected separation is a?  1:2AU. The characterization was made possible by the wide- eld (4 deg2) high cadence (􀀀 = 6 hr􀀀1) monitoring of the Korea Microlensing Telescope Network (KMTNet), which had two of its three telescopes in commissioning operations at the time of the planetary anomaly. The source crossing time t = 16 min is among the shortest ever published. The high-cadence, wide- eld observations that are the hallmark of KMTNet are the only way to routinely capture such short crossings. High-cadence resolution of short caustic crossings will preferentially lead to mass and distance measurements for the lens. This is because the short crossing time typically implies a nearby lens, which enables the measurement of additional e ects (bright lens and/or microlens parallax). When combined with the measured crossing time, these e ects can yield planet/host masses and distance.
        4,000원
        14.
        2006.09 구독 인증기관·개인회원 무료
        We studied formation of nanostructured -Cu composites under shock wave conditions. We investigated the influence of preliminary mechanical activation (MA) of Ti-B-Cu powder mixtures on the peculiarities of the reaction between Ti and B under shock wave. In the MA-ed mixture the reaction proceeded completely while in the non-activated mixture the reagents remained along with the product . titanium diboride. The size of titanium diboride particles in the central part of the compact was 100-300 nm.
        16.
        2006.04 구독 인증기관·개인회원 무료
        High velocity compaction (HVC) is a production technique with capacity to significantly improve the mechanical properties of powder metallurgy (PM) parts. Investigated here are green body data such as density, tensile strength, radial springback, ejection force and surface flatness. Comparisons are performed with conventional compaction using the same pressing conditions. Cylindrical samples of a pre-alloyed water atomized iron powder are used in this experimental investigation. The HVC process in this study resulted in a better compressibility curve and lower ejection force compared to conventional quasi static pressing. Vertical scanning interferometry measurements show that the HVC process gives flatter sample surfaces.
        18.
        2004.12 KCI 등재 SCOPUS 구독 인증기관 무료, 개인회원 유료
        We present photometric results for four new variable stars discovered in the vicinity of the ZZ Ceti-type pulsating white dwarf BR Cam. Observations were performed on 5 nights in November 2003 using the 1.8m telescope at Bohyunsan Optical Astronomy Observatory with no filter, on 3 nights in December 2003 using the 0.61m telescope at Sobaeksan Optical Astronomy Observatory with V, I filters, and on 3 nights in October 2004 using the 1.0m telescope at Mt. Lemmon Optical Astronomy Observatory with V, I filters. We estimated their periods from the phase-match technique for one eclipsing binary and the multiple frequency analysis for three pulsating stars. By considering the light curve shape, period and amplitude difference between two passbands, we classified the objects by their variability types as follows: V1 (USNO-A2.0 1425-05691757) is a W UMa-type eclipsing binary with an orbital period of 0d.4641; V2 (USNO-A2.0 1425-05703335) is a multi-periodic δ Sct-type pulsating star with a dominant period of 0d.0649; V3 (USNO-A2.0 1425-05699659) is also a δ Sct-type pulsating star with a period of 0d.1408; and V4 (USNO-A2.0 1425-05707705) is a RR Lyr-type pulsating star with a period of 0d.2643.
        4,000원
        19.
        2004.09 KCI 등재 구독 인증기관 무료, 개인회원 유료
        Laccase는 여러개의 Cu를 포함하는 효소로서 분자상 산소를 환원시키면서 패놀성 및 비페놀성화합물의 산화를 촉매하는 작용을 한다. 이들 효소들은 미생물 고유의 혹은 유도상의 동위효소의 형태로 목질화된 세포벽을 침투하게 된다. 백색부후균은 많은 종류의 고유의 혹은 유도상의 동위효소를 생산한다. 이들 균체 laccase효소들은 통상 Cu2+, Cd2+ Ca2+, Li+, Mn2+, Ag+, Hg2+, Mn 및 Fe3+이온과 같은 금속이온들, 페놀성 화합물, ethanol, isopropanol, cAMP, caffeine, p-anisidine, viscosinamide 및 paraquat 등과 같은 유기화합물, 질소 및 열충격 등에 의하여 유도될 수 있다. Cu 및 pHB (p-hydroxybenzoic acid)의 조합으로 laccase 활성을 30배이상 유도시킬 수 있었다. 여러 가지 inducer 가운데, 2,5-xylidine이 담자균 및 기타 다른 고등균류로부터 160배이상의 가장 효과적인 laccase의 유도효과를 나타냈다. 한편 laccase효소는 Pycnoporus cinnabarinus의 gene family로부터 자주 code로 표시되었는데, lcc3-1 혹은 lac1 및 lac3-2의 페어 gene으로 클론 및 시퀀싱되었다. 유도형 laccase의 경우 mRNA의 합성에 의존하여 laccase가 생성되며, 이러한 유도효과는 결국 새로운 단백질의 합성으로부터 기인된다.
        4,500원
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