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범게, Orithyia sinica 유생의 생존과 성장에 미치는 암모니아와 아질산의 영향
구자근,김종만,장차환,지정훈,강주찬 한국어병학회 2004 한국어병학회지 Vol.17 No.1
범게, Orithyia sinica 유생을 대상으로 암모니아와 아질산에 대한 생존 및 성장에 관한 실험을 실시하였다. 암모니아 노출 실험구에서 zoea기 유생은 노출 20일후, 대조구가 80%의 생존율을 나타내었지만 10㎎/L 이상의 실험구에서는 37-45%의 생존율을 나타내었고, megalopa기 유생에서도 유사한 경향을 나타내었다. 암모니아가 범게 유생의 성장에 미치는 영향을 조사한 결과, zoea기 유생은 20㎎/L 이상의 농도에서 megaloparl 유생은 50㎎/L 이상의 농도에서 유의한 차이를 나타내었다. (P<0.05). 아질산 노출 실험에서는 zoea기 유생과 meglaopa기 유생에서 농도와 노출기간에 비례하여 생존율이 감소하였으며, 특히 150㎎/L 이상의 아질산 농도에 노출된 zoea기 유생가 megalopa기 유생은 대조구와 비교하여 유의한 성장 지연을 나타내었다(P<0.05). This study investigates the influence of waterborne ammonia and nitrite on the zoea and megalopa stage larvae of tiger crab, Orithyiu sinicu under laboratory condition, focusing on the effects on survival and growth as deleterious responses of toxicant. Survival rate of zoea stage larvae exposed to control levels, and to 5, 10,20 and 50 ㎎/L total ammonia-N, using a continuous flow system for 20 days was 80, 77, 45, 40 and 37%, respectively. Growth rate of zoea stage larvae exposed to 20 and 50 ㎎/L total ammonia was significantly lower than in controls after 20 days (P< 0.05). Survival rate and growth rate of megalopa stage larvae exposed to ammonia also decreased at greater than 10 and 50 ㎎/L, respectively. In the nitrite exposure experiment with zoea and megalopa stage larvae of tiger crab, survival rate was decreased in a concentration and exposure period-dependent way. The growth rate of zoea and megalopa stage larvae of tiger crab exposed to nitrite decreased at greater than 150 ㎎/L nitrite concentration.
Cha, Ju-Hwan,Nam, Bo-Woo,Ha, Sol Korean Society of Ocean Engineers 2018 Journal of advanced research in ocean engineering Vol.4 No.1
In this paper, safety analysis of the process of installing offshore structures such as manifolds and jacket-type substructures using floating cranes and barges in waves is performed. The safety analysis consists of three components. First, the dynamic responses of the offshore structure, cranes, and barge, all of which are moored and connected using wire ropes, are analyzed. Second, tensions in the wire ropes connecting the cranes and the offshore structures are calculated. Finally, any collision between the offshore structure and the cranes or the barge that transports the offshore structure is detected. Equations of motion of the offshore structure, cranes, and barge are formulated based on multibody dynamics, as well as considering the hydrostatic, hydrodynamic, and mooring forces. Additionally, proportional-derivative control of the tagline between the cranes and the offshore structure is performed to verify the safety of the installation process, as well as for reducing the dynamic response and collisions among them.
병렬 연결된 해상 크레인을 이용한 대형 중량물 인양 작업의 동적 거동 계산 시뮬레이션
차주환(Ju-Hwan Cha),구남국(Nam-Kug Ku),노명일(Myung-Il Roh),이규열(Kyu-Yeul Lee) 대한기계학회 2012 大韓機械學會論文集A Vol.36 No.6
본 연구에서는 병렬 연결된 해상 크레인을 이용하여 5,000ton 이상의 기가 블록급 대형 중량물을 인양할 때 해상 크레인과 대형 중량물 사이에 연결된 와이어 로프에 작용하는 장력을 계산하기 위해 다물체계 동역학 시뮬레이션을 수행하였다. 이를 위해, 해상 크레인, 바지선, 대형 중량물은 각각 6 자유도 운동을 하고, 이들 사이에는 서로간의 구속에 의한 연성을 가지도록 모델링 하였다. 또한 해상 크레인 및 바지선에 작용하는 외력으로 유체 정역학 힘과 유체 동역학 힘을 고려하였고, 각각의 물체에 독립적으로 작용한다고 가정하였다. 본 시뮬레이션 결과, 향후 해상크레인을 병렬 연결하여 대형 중량물을 인양하는 공법의 안정성을 확인하고 공학적인 지침을 마련할 수 있는 근간이 될 수 있으리라 예상한다. In this study, we performed a simulation of the dynamic response of a multibody system to calculate the tension acting on wire ropes connecting floating cranes and a heavy cargo such as a Giga Block weighing over 5000 tons when the cargo is salvaged using parallel connected floating cranes. In this simulation, we supposed that the motion of the floating cranes, barge ship, and heavy cargo has 6 degrees of freedom and that the interaction is determined by constraints among them. In addition, we considered independent hydrostatic and hydrodynamic forces as external forces acting on the floating cranes and barge ship. The simulation result can be a basis for verifying the safety of construction methods in which heavy cargo is salvaged by parallel connected floating cranes, and it can also be used to guide the development of such construction methods.
연성된 과대 경사 각도를 고려한 부유식 구조물의 비선형 유체정역학 힘과 자세
차주환(Ju-Hwan Cha),구남국(Namkug Ku),박광필(Kwang-Phil Park) (사)한국CDE학회 2016 한국CDE학회 논문집 Vol.21 No.1
When ships and offshore plants are flooded or the floating crane is equipped with a heavy object, these floating structures are excessively inclined. In this case, immersion, heel, and trim affecting the hydrostatic restoration performance are very large and are coupled each other. In this paper, in order to calculate a static equilibrium position of floating structures with excessive inclination, the nonlinear governing equations were constructed by sequential linearization. In the governing equation, the immersion, heel, and trim are fully coupled, and the equations are represented using a plane area, a primary moment, and a moment of inertia of the water plane area. Therefore, it is possible to calculate the additional factor related the water plane area for estimating stability. Position and orientation of the floating structure are obtained by iterative calculation. The calculated results are compared with the previous studies in the aspect to the performance and the accuracy.
차환주(Hwan-Ju Cha),김자희(Ja-Hee Kim) 한국경영과학회 2016 韓國經營科學會誌 Vol.41 No.1
Although the demand for IT outsourcing (ITO) has increased recently because of the recent recession, concerns about business discontinuity in the transition phase cause companies to hesitate to adopt ITO. Therefore, a guideline to improve the prospects is needed. However, studies on the success factors of the transition phase in ITO are lacking. In this study, we develop an expert hierarchical value map (HVM) of the success of the transition phase in ITO by using cognition scientific methodologies. We empirically verify how success factors affect the success of the transition phase. Specifically, we derive an HVM of main stakeholders by using in-depth interviews and approaches, such as repertory grid technique (RGT) and laddering, based on means–end chain theory. We validate the success factors empirically through a bipolar analysis of RGT. Finally, we determine the most important cluster of success factors through cluster analysis.