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이학봉,권오성 한국항공운항학회 2023 한국항공운항학회지 Vol.31 No.3
The overall Air Force's serious accident rate is decreasing, but the trainer's accident rate is on the rise from 0.24% in ‘00~’09 to 0.77% in ‘01~’19. Base on the SHELL model recommended by the ICAO, the risk factors of the introductory flight training course were analyzed, implications were examined, and safety promotion measures were proposed. A survey of 25 questions was organized based on regulations, guidelines, and related data for each component of the SHELL model in accordance with the introductory course of Air Force flight training. The survey was divided into a student group and instructor group and compared and analyzed into L-L, L-S, L-H, and L-E based on the results after conducting it, and implications for this were derived. Compared to other analysis factors, L-L showed that the average of the instructor group was relatively higher that of the student group in all questions.
Polyvinyl Chloride의 산과 염기에 대한 내화학성 연구
이학봉,이경섭,한태희 한국섬유공학회 2023 한국섬유공학회지 Vol.60 No.2
Plastic manufacturing is increasing due to its advantages (low cost, durability,water-proof property) to various application fields such as agriculture, electronics, medicalequipment, and others. At the same time, despite recyclability of plastics, byproducts ofplastics are ever increasing resulting in the generation of secondary microplastics (MPs; lessthan 5 μm in size) caused by various environmental and physicochemical factors. Althoughpretreatment of MPs was studied due to the hazardous effect of MPs to the ecosystems,chemical effects of agents on the MPS used in the pretreatment were not deeply studied. In this study, the chemical effect of acid, alkali, and oxidizing agent on the PVC based MPswas studied. The PVC MPs were reacted with acids, alkalis, and oxidizing agent at 70 °C for7 days, and changes of morphologies and chemical properties were observed when PVCMPs were reacted with sulfuric acid. The results pertaining to the chemical variations ofPVC MPs could be a foundation stone for future research related to the pretreatment ofMPs with various chemical agents.
이학봉,강혜순 한국생태학회 2018 Journal of Ecology and Environment Vol.42 No.4
Background: Temperature-driven variation in pollinator assemblage and activity are important information, especially at high altitudes, where rising temperature trends exceed global levels. Temporal patterns of pollinators in a flowering season can be used as a proxy to predict the changes of high-altitude plants’ mutualistic relationships. We observed a spring temperature change in one population of a high-altitude endemic species, Megaleranthis saniculifolia on Mt. Sobaeksan, and related it to pollinator assemblage and activity changes. Methods: This study was conducted at two sites, each facing different slopes (NE and NW), for two times in the spring of 2013 (early-flowering, April 27–28, vs. mid-flowering, May 7–8, 2013). We confirmed that the two sites were comparable in snowmelt regime, composition of flowering plants, and flower density, which could affect pollinator assemblage and activity. Pollinator assemblage and activity were investigated at three quadrats (1m2 with 5-m distance) for each site, covering a total of 840min observation for each site. We analyzed correlations between the temperature and visitation frequency. Results: Twelve pollinator species belonging to four orders were observed for M. saniculifolia at both sites during earlyand mid-flowering times. Diptera (five species) and hymenopteran species (four species) were the most abundant pollinators. Pollinator richness increased at both sites toward the mid-flowering time [early vs. mid = 7 (NE) and 3 (NW) vs. 9 (NE) and 5 (NW)]. Compared to the early-flowering time, visitation frequency showed a fourfold increase in the mid-flowering time. With the progression of spring, major pollinators changed from flies to bees. Upon using data pooled over both sites and flowering times, hourly visitation frequency was strongly positively correlated with hourly mean air temperature. Conclusions: The spring temperature change over a relatively brief flowering period of M. saniculifolia at high altitudes can alter pollinator assemblages through pollinator dominance and visitation frequency changes. Thus, this study emphasizes information on intra- and inter-annual variations in the mutualistic relationship between pollinators and M. saniculifolia to further assess the warming impacts on M. saniculifolia’s reproductive fitness.