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호남지역의 시설원예재배시 지하수중 화학성분 변동요인 조사
이경보,이덕배,이경수 한국환경농학회 1996 한국환경농학회지 Vol.15 No.3
This study was carried out to investigate factors influencing on the groundwater quality at controlled horticulture in Honam area in 1995. The deeper groundwater sampling, the lower concentrations of NH₄-N and NO₃-N were observed. There was no difference in concentrations of SO₄^(2-) and Na^+ in the groundwater below 15m. Contents of NH₄-N, NO₃-N and PO₄^(3-) in groundwater were the highest at rice transplanting season(the late May) and that of SO₄^(2-), Na^+ and Cl^- were the highest at dry season(the mid-February). Continuous cultivation of horticultural crops showed higher concentration of NH₄-N, NO₃-N, PO₄^(3-), Na^+ and Cl^- in groundwater than rotational culture with rice. The longer cultivation years with horticultural crops, the higher concentrations of NO₃-N, PO₄^(3-), SO₄^(2-) and Cl^- were shown, and constitutional ratio of NO₃-N among the anions increased gradually. Nitrate-N level, exceeded 20㎎/ℓ, the critical level for agricultural usage, frequently at Yongjinmyeon Wanju and Janglockdong Kwangju, and PO₄^(3-) levels were higher at Seogtandong Iksan than the other places.
지구관측용 위성군 개발에 적합한 위성 구조체 설계 및 해석
이경보 한국기계기술학회 2017 한국기계기술학회지 Vol.19 No.4
In general, the design concepts of earth-observation satellites are established depending on the purposes of utilization such as commercial imagery business, public services, scientific research. Nowadays, The lightweight satellite structure is considered as an effective method for developing the earth-observation satellite. This paper introduces a design concept of the lightweight satellite structure for the constellation of earth-observation satellites. The modular design of the satellite structure is applied to save manpower and shorten the AIT process, in addition, a propulsion module is adopted to allow a hydrazine propulsion system to be installed on the satellite. The finite element method is used for the structural analysis of the satellite. The axial and lateral frequency requirements of satellite structure were verified by mode analysis. also, the margin of safety of satellite structure parts were satisfied with design requirements. As a result, the structural integrity of the suggested satellite structure is verified by mode analysis and static analysis.