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        검색결과 8

        1.
        2023.07 KCI 등재 SCOPUS 구독 인증기관 무료, 개인회원 유료
        This paper is written as a follow-up observations to reinterpret the radial velocity (RV) of HD 36384, where the existence of planetary systems is known to be ambiguous. In giants, it is, in general, difficult to distinguish the signals of planetary companions from those of stellar activities. Thus, known exoplanetary giant hosts are relatively rare. We, for many years, have obtained RV data in evolved stars using the high-resolution, fiber-fed Bohyunsan Observatory Echelle Spectrograph (BOES) at the Bohyunsan Optical Astronomy Observatory (BOAO). Here, we report the results of RV variations in the M giant HD 36384. We have found two significant periods of 586 d and 490 d. Considering the orbital stability, it is impossible to have two planets at so close orbits. To determine the nature of the RV variability variations, we analyze the HIPPARCOS photometric data, some indicators of stellar activities, and line profiles. A significant period of 580 d was revealed in the HIPPARCOS photometry. H𝛼 EW variations also show a meaningful period of 582 d. Thus, the period of 586 d may be closely related to the rotational modulations and/or stellar pulsations. On the other hand, the other significant period of 490 d is interpreted as the result of the orbiting companion. Our orbital fit suggests that the companion was a planetary mass of 6.6 𝑀J and is located at 1.3 AU from the host.
        4,000원
        2.
        2022.02 KCI 등재 구독 인증기관 무료, 개인회원 유료
        The poor durability issue of polymer electrolyte membrane fuel cells is a major concern in terms of their commercialization. To understand the degradation mechanism of the catalysts, an accelerated durability test (ADT) was conducted according to the protocol established by internationally accredited organizations. However, reversible and irreversible factors contributing to the loss of activity have not yet been practically segregated because of the limitations of a batch-type three-electrode system, leading to the misunderstanding of the deactivation mechanism. In this study, we investigated the effect of a fresh electrolyte on the ADT and recovery process. When the fresh electrolyte was used at every range of the cycle, the chances of incorrect detection of dissolved CO and Pt ions in the electrolyte were very low. When the same electrolyte was used throughout the test, the accumulated Pt ions were deposited on the surface of the Pt nanoparticles or carbon support, affording an increased electrochemical surface area (ECSA) of Pt. Therefore, we believe that periodic replacement by a fresh electrolyte or a continuous-flow electrolyte is essential for the precise determination of the structural and electrochemical changes in Pt/C catalysts.
        4,000원
        3.
        2016.04 구독 인증기관·개인회원 무료
        Oxalic acid has a nematicidal activity against the root-knot nematode Meloidogyne incognita. High producer of oxalic acid was isolated, and then named as Aspergillus niger F22. Oxalic acid production was investigated under various temperatures from 20 – 33oC and rotational speeds in 5 L jar fermenters. Yield of oxalic acid increased with decreasing temperature. The highest yield was obtained at 23oC, showing the yield of oxalic acid of 8.7 g/L, whereas oxalic acid production was least at 33oC. At 20oC, the yield was lower than that of 23oC. At a rotational speed of 300 rpm, serious oxygen depletion was present from 48 - 72 h, resulting in low productivity of 26.2 mg /L·h. When a rotational speed was set at 600 rpm, dissolved oxygen tension was over 40% and oxalic acid production increased up to approximately 55%. Viscosity during the culture differed with temperatures. Viscosity increased with the increment of temperatures. When A. niger F22 was cultured at 23oC, viscosity was 810 cP, which was favorable for oxalic acid production.
        4.
        2016.04 구독 인증기관·개인회원 무료
        Biological control has been tried for integrated pest management. It is often comparable, safe, and environment-friendly, making itself an alternative for chemical agents. Filamentous microorganisms, i.e., fungi and streptomystes, produce many kinds of useful metabolites, and some of them have been developed as a biocontrol agent. However, they still have a long way because of the concern of manufacturing cost. Therefore, process development was intensively studied to meet cost-effectiveness. Operating conditions of bioreactor, e.g., agitation and aeration, had an effect on biological and physiological responses such as mycelial morphology, oxygen and nutrient transfer. Understanding relationship between operating parameters and microbial responses in terms of growth, substrate and oxygen consumption, and production yield was critical for process development. This study dedicated to build strategies for mass production of biological control agent using aerobic filamentous microorganisms.
        8.
        2014.12 KCI 등재 서비스 종료(열람 제한)
        The egg development and early life history of Korean spotted sleeper, Odontobutis interrupta which is Korean endemic species from Sora-choen was investigated. The Korean spotted sleeper were caught at Sora-myeon, Yeosu-si, Jeollanamdo, from Korea at May in 2014. The fertilized eggs were 4.23 ± 0.05 mm in long diameter and had oil globules. Hatching time of the embryo began about 442 hr 14 min after fertilization under water temperature of 19.5oC. The newly hatched larvae were 4.27 ± 0.35 mm in total length and their anus were not yet opened. 3 days after hatching postlarvae was measured 6.20 ± 0.11 mm in total length. 10 days after hatching postlarvae was measured 6.69 ± 0.14 mm in total length.