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1992년과 1999년의 농가 비료이용 실태 변화 비교
김석철,박양호,이연,이주영,김충수,김필주,Kim, Seok-Cheol,Park, Yang-Ho,Lee, Youn,Lee, Ju-Young,Kim, Chung-Su,Kim, Pil-Joo Korean Society of Soil Science and Fertilizer 2003 한국토양비료학회지 Vol.36 No.5
Korea is one of those countries that have very high usage rates of chemical fertilizers per unit area of cropland. To reduce the fertilizer application rate, a variety of agricultural polices has been introduced since the 1990s. In this study, fertilizer usage was surveyed on the farm base throughout the country in 1999, and the data were compared with those of 1992. Organic fertilizer application rates were decreased in most cereal crops with time pass, but maintained similar levels in vegetables grown in plastic-film houses and in upland soils. Chemical fertilizer application rates were decreased in most of the cereal crops and vegetables surveyed; however, this reduction was concentrated in phosphate and potassium usage, but not in nitrogen. In spite of this decrease, the fertilizer application levels to most crops were maintained at levels much higher than recommended. In the nutrient balance, which was calculated from the difference between input (chemical and organic fertilizers) and output (agricultural products), the nitrogen nutrient surplus did not decrease; however, phosphate and potassium decreased by 21% and 13%, respectively, in 1999 compared with 1992. To reduce fertilizer utilization and to conserve environment, further reduction of fertilizer application is essential. 우리나라는 농경지 단위면적 당 화학비료 시용량이 높은 국가로 분류되고 있다. 화학비료 시용량 저감을 위해 정부에서는 1990년 들어 다양한 정책적 지원을 지속해오고 있다. 본 연구에서는 1999년 전국의 시군을 대상으로 농가비료이용실태를 작물별, 농지이용유형별로 조사하여 1992년 농가비료이용실태와 비교하였다. 주요 작물에 대한 유기질비료의 평균 시용율은 최근 크게 감소하였으나, 시설재배지와 밭토양에서의 유기물 시용율은 1992년과 큰 변화가 없었다. 농가포장의 화학비료 시용율은 대부분의 곡류와 채소작물에서 다소 감소하는 경향을 보였다. 화학비료 중 질소질 비료 시용율 감소는 거의 없었으며, 인산과 칼리질 비료의 시용량 감소가 전체 화학비료 시용량에 감소에 영향을 주었다. 이러한 화학비료 시용량 감소에도 불구하고 대부분의 작물에 대한 비료사용량은 추천 시비량을 크게 초과하고 있었다. 양분 투입량과 회수량간 차이를 이용하여 계산된 양분수지를 계산한 결과, 질소의 과잉시용은 거의 감소되지 않고 있으나, 인산과 칼리의 시용량은 1992년에 비해 1999년 각각 21%와 13% 감소되었다. 결과적으로 정부와 관련기관의 적극적인 홍보에도 불구하고 1999년 현재까지 농가포장에서는 비료가 과잉시용되고 있었으며, 이를 개선하기 위해 토양검정치를 기준으로 산정한 추천시비량 수준으로 양분 시용량의 저감을 위한 효과적인 기술지원과 지도관리가 필요할 것으로 판단되었다.
Fuzzy-FMEA를 활용한 시공사의 리스크 요인 분석
김석철,Kim, Seok Cheol 대한안전경영과학회 2017 대한안전경영과학회지 Vol.19 No.4
The purposes of this study are to analyze risks of construction step BIM(Building Information Modeling) applied project and improve it. Recently, construction industry has emphasized an importance of BIM for efficient utilization of various information. In the whole life cycle of huge construction project, there are cases introducing BIM and projects applying BIM are gradually increased to the work of construction step. However, the process of communication is not established, so the contents of BIM process of construction step are just showing rough fields and concepts of working utilization, so it's restrictive to utilize BIM actively on constructions step. Through results of case study in this research, constructor risks of BIM business should be efficiently treated with Fuzzy-FMEA that is more precise than existing danger evaluation.
김석철,배동규,한지웅,금성민,이창언,Kim, Seok-Cheol,Bae, Dong-Kyu,Han, Ji-Woong,Kum, Sung-Min,Lee, Chang-Eon 대한기계학회 2000 大韓機械學會論文集B Vol.24 No.9
The purpose of this study is to develop the non-gravity fluidized dryer. In this non-gravity fluidized dryer the fluidized zone is produced by two paddles in mixer, which maximizes the surface area of materials and then heated air through the guiding panels dehumidify them. This can conduct the drying process quickly and control moisture contents to lower limits. The ventilation system is closed loop system, which can be changeable to open system, and can be used as a multi-purposed dryer in which mixing, drying, granulating and cooling process is conducted. In order to develop the non-gravity fluidized dryer, in the first fundamental experiments were performed to mixing accuracy and then the other parts of dryer and control system were examined to check whether they were designed properly and operated harmoniously with mixer. Also the preparatory experiments were fulfilled to examine the efficiency and reliability of the dryer. Lastly, on the basis of preparatory experiments, performance test for the non-gravity fluidized dryer carried out for the variation of the initial moisture contents, desired moisture contents, heated air velocity and heating temperature.
응축형 가스보일러 열교환기의 열전달특성에 관한 수치적 연구
김석철,금성민,이창언,Kim, Seok-Cheol,Geum, Seong-Min,Lee, Chang-Eon 대한기계학회 2001 大韓機械學會論文集B Vol.25 No.12
Characteristics of fluid flow and heat transfer in a tube with disk and annular baffle for heat exchanger of condensing boiler was numerically studied. The STAR-CD code was used to solve the governing equations and the temperature and flow fields were investigated. The interval between tube and annular baffle, height and diameter of baffle were selected as important design parameters, and the effects of these parameters on heat transfer and fluid flow were studied. As a result, in the case of with interval, the pressure was decreased, but heat transfer was increased. Heat transfer was slowly increased as the size of disk and annular baffle were increased and the distance between baffles were decreased. The pressure drop was rapidly changed fur diameter and size of disk and annular baffle. In addition, it was desirable that optimal conditions to design heat exchanger were about B$\_$a/R=0.5, L/R=1.