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이태구,김기성,홍지우,안병권,이경준 한국가시화정보학회 2022 한국가시화정보학회지 Vol.20 No.3
Cavitation occurs inevitably in marine propellers rotating at high speed in the water, which is a major cause of underwater radiated noise. Cavitation-induced noise from propellers rotating at a specific frequency not only reduces the sonar detection capability, but also exposes the ship's location, and it causes very fatal consequences for the survivability of the navy vessels. Therefore cavity inception speed (CIS) is one of the important factors determining the special performance of the ship. In this study, we present a method using computer vision that can detect and quantitatively estimate tip vortex cavitation on a propeller rotating at high speed. Based on the model test results performed in a large cavitation tunnel, the effectiveness of this method was verified.
이태구,공명석,이은진,정하일,김이현,정구복,양재의,김성철,김기인,김권래,채미진 한국토양비료학회 2019 한국토양비료학회지 Vol.52 No.4
Heavy metal (HM) pollution in agricultural lands and waters, which is rapidly increasing due to social andindustrial activities, such as mining and smelting. Moreover, HM contamination causes serious environmental problems and adversely influences on the safety of agricultural production. This study established the concentrations of HM on the arable lands near industrial complexes in Gangwon (GW), Chungnam (CN), Jeonnam (JN), and Gyeongnam (GN) in South Korea. Soil samples were collected and established from 600 sites of agricultural lands nearby 60 industrial complexes in the selected provinces. Eight HMs (Cd, Cu, Pb, Zn, Ni, Cr, As and Zn) were analyzed to compare degrees of the HM pollution using standard analytical methods. The average total concentration of all HMs from samples of the analyzed soils did not exceed the warning criteria as suggested by the Soil Environmental Conservation Law of Korea. The concentration of Cd, Cu, Pb, Zn, Ni, As and Hg were mostly distributed below one half concentration of warning criteria, except for the Cr and Hg. Particularly, 99.2% of Hg concentrations among the assessed samples distributed below one-twentieth values of the warning criteria. Contamination degree () of GW and GN provinces were moderate degree, CN and JN province were low degree contamination. Four provinces were classified as “uncontaminated” by (Pollution index).
이태구,옥정훈,김명숙,전상호,정하일 한국토양비료학회 2022 한국토양비료학회지 Vol.55 No.1
The early maturing rice is a species that can be cultivated at various times, such as early, normal season, andlate cultivation, depending on the purpose. There are many studies on the characteristics of rice according tothe transplanting time for these early maturing rice, but studies on the runoff of nutrients are insignificant. Thesurface runoff of NH4+-N was the highest among the treatment at 1.337 g m-2 (2020 year) in the Clay Loam(CL) & late cultivation, and the smallest treatment was the Sandy Loam (SL) & normal season cultivation(0.005 g m-2, 2019 year). The highest NO3--N surface runoff was 0.137 g m-2 (2020 year) in the CL & latecultivation. In the case of phosphate, there were more nutrients runoff from late cultivation with large outflowsthan normal season cultivation. The underground runoff of NH4+-N was the highest among the treatment at0.147 g m-2 (2020 year) in the SL & late cultivation, and the smallest treatment was the CL & normal seasoncultivation (0.007 g m-2, 2019 year). The highest NO3--N underground runoff was 2.113 g m-2 (2019 year) inthe SL & normal season cultivation. In order to compare rice growth, the dry weight of leaves, shoots, and earsafter rice harvest was compared. ear was a little larger in the normal season cultivation than in the latecultivation in 2019 (p < 0.05), but there was no difference in ear according to soil texture and the transplantingtime in 2020. There may be differences in nutrient outflow and rice growth depending on the soil texture andtransplanting time when cultivating early maturing rice, and the results of this study can be used as basic dataon nutrient outflow in paddy when cultivating early maturing rice.
부분 침수 프로펠러의 bollard pull 추력 및 토오크 특성 연구
이태구,백광준,박형길,최순호 대한조선학회 2011 대한조선학회 학술대회자료집 Vol.2011 No.11
도크 내 공정을 마치고 진수된 선박은 안벽에 계류된 상태로 주기관 등의 시험 검사를 수행하게 된다. 주기관 시험을 수행할 경우 선박은 안벽에 고정된 상태에서 수면 위로 날개가 노출된 프로펠러를 회전시켜야 하므로, 이 때 발생하는 추력과 토오크를 예상하여 안전상 문제가 없도록 시험 조건 선정 및 설치를 수행하여야 한다. 프로펠러가 수면으로 노출된 프로펠러는 회전수 및 축 잠김 깊이에 따라 수면 노출 및 공기 유입 등의 영향으로 추력 및 토오크 감소율이 변화하게 된다. 본 논문에서는 당사 실적 선박 프로펠러에 대해 모형 시험과 수치 해석을 통하여 회전수 및 축 잠김 깊이에 따른 추력 및 토오크 변화 특성을 파악하고 이를 바탕으로 부분 침수 프로펠러의 bollard pull 조건에 대한 추정식을 도출하였다. 도출된 추정식을 실선 계측 결과와 비교하여 정도 높은 추정 결과를 제공하고 있는 것을 확인하였다.