• 산업공학
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• 제24권1호
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• pp.78-86
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• 2011

To mitigate space restriction and to raise productivity, some shipbuilding companies use floating-docks on the sea instead of dry-docks on the land. In that case, a floating-crane that can lift very heavy objects (up to 3,600 tons) is used to handle the blocks which are the basic units in shipbuilding processes, and so, very large blocks (these are called the mega-blocks) can be used to build a ship. But, because these mega-blocks can be made only in the area near the floating-dock and beside the sea, the space is very important resource for the process. Therefore, our problem is to make an efficient spatial schedule for the mega-block assembly yard. First of all, we formulate this situation into a mathematical model and find optimal solution for a small problem using a commercial optimization software. But, the software could not give optimal solutions for practical sized problems in a reasonable time, and so we propose a GA-based heuristic algorithm. Through a numerical experiment, finally, we show that the spatial scheduling algorithm can provide a very good performance.

• Applied Microscopy
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• 제38권2호
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• pp.117-124
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• 2008

생이가래는 수생 양치식물로 한 쌍의 부유엽은 식물체 부유 및 광합성의 기능을 하며, 수중의 침수엽은 가늘고 길게 세분되어 뿌리의 형태 및 기능을 수행한다. 많은 수생식물에서는 표피 조직에 엽침이나 모용 등의 이형세포를 형성하는데, 생이가래는 모용이 엽육 표피조직에 밀생한다. 이에 본 연구에서는 생이가래속 Salvinia natans 및 S. molesta 2종의 부유엽 상피조직에 발달하는 모용의 분화발달 양상을 주사 및 투과전자현미경으로 연구 하고자 한다. 연구된 2종의 생이가래 부유엽 상피조직에 발달하는 모용은 매우 다른 양상을 나타낸다. S. natans의 모용은 중맥을 중심으로 엽신 양면에 일정하게 20${\sim}$25열로 발달한다. 각각의 열에는 8${\sim}$10개 세포로 구성된 $200{\sim}290{\mu}m$ 크기의 타원형 세포들이 나선 형상으로 배열된다. 이들 모용 4개가 모여 하나의 단위체를 이루 지만 정단부위가 융합되지 않는 'knuckle-crane' 형태로 발달한다. 반면, S. molesta에서는 독특한 유형의 모용으로 분화한다. 분화초기 부유엽 상피조직에서 모용들이 돌기형태로 돌출되고 8${\sim}$10개의 원통형 세포들이 $400{\sim}600{\mu}m$으로 신장한 후 이들 모용4개가 하나의 단위를 이룬다. 이들 단위체내 각 모용들의 정단부위가 융합되어 'egg-beater' 형태로 발달하기 시작한다. 이후 $300{\sim}600{\mu}m$의 다세포성 병세포들이 모용 기저부위에서 상피표면 위로 신장하여 돌출한다. 성숙한 'egg-beater' 형태의 모용은 0.6${\sim}$1.2mm로 발달하고 'knuckle-crane' 형태에 비해 3${\sim}$4배 길게 신장한다. 연구된 생이가래 2종 모용세포 내 액포는 분화초기에는 세포용적의 극히 일부를 차지하나 분화후기에는 세포용적의 대부분을 차지하여 세포질의 밀도를 매우 낮게 하는 특징을 나타낸다. 이와 같이 생이가래속 식물체내 모용의 구조적 특성은 생이가래가 수중에서 부유기능을 수행하는 데 있어 엽육조직 내통기조직과 함께 매우 중요한 역할을 수행하는 것으로 추정되고 있다.

• 대한기계학회논문집A
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• 제36권6호
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• pp.681-689
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• 2012

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.

• 한국안전학회지
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• 제14권1호
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• pp.33-40
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• 1999

In this paper, a damaged example of hanging guide frame used in the lifting of shore protection caisson was investigated. An examination of the stress and stability of members was carried out by structural analysis and the causes of damages was investigated. The stability analysis considering local and global stress buckling was performed. As a result of stability analysis. the first structure was unstable structure. Therefore improved structure was examined and the best effective methodology was the reassignment of wire.

• International Journal of Ocean System Engineering
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• 제1권4호
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• pp.198-204
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• 2011

Recently, several problems have occurred in the space, infra-structure, and facility of the contiguity of existing harbors due to the trend of enlarged container vessels. In this regard, the Mobile Harbor has been proposed conceptually in this study as an effective solution for these problems. The concept is that of a transfer loader that transfers containers from a large container ship to the harbor on land, and is a catamaran type floating barge. The catamaran-type vessel is well known for its advantage in maneuverability, resistance, and effectiveness for working on board. For the safe and effective operation of the two floating bodies (a container ship and the mobile harbor in the near sea detached from the quay), robot arms, novel crane systems, and pneumatic fenders are specially devised with an additional mooring facility or DP (dynamic positioning) system. In this study, this concept is to be verified through comparison and simulation studies under various environmental conditions. It is shown that the proposed concept is in general feasible but there are several areas for further investigation and improvement.

• 한국해양공학회:학술대회논문집
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• 한국해양공학회 2003년도 추계학술대회 논문집
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• pp.87-92
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• 2003

Generally, in jack up rig design for harsh environment, its leg height is a major factor for achieving a sufficient serviceability & operability in terms of the worst environment and the workable depth. Due to difficulties in constructing such a high-slender leg, inaccessibility of yard fabrication equipment, etc. the construction of Jack up rig fur harsh deep sea has not been common. Method using heavy crawler crane, fabrication tower or extension by the floating crane vessel is still conventional construction but, considering high cost fur mobilizing heavy lift vessel (HLV) or additional marine work for implementing preload / full height test at sea, the ground-base construction is much advantageous. Air skidding method (ASM hereafter) is ground-based construction methodology, newly developed due to such requests. ASM could also be extended to similar engineering fields. This paper presents the operating sequence, design parameters and procedure which were verified through successful operation at the end of May 2002.

• International Journal of Naval Architecture and Ocean Engineering
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• 제11권2호
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• pp.699-722
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• 2019

It is difficult to observe the potential risks of lifting or turn-over operations in the early stages before a real operation. Therefore, many dynamic simulations have been designed to predict the risks and to reduce the possibility of accidents. These simulations, however, have usually been performed for predetermined and fixed scenarios, so they do not reflect the real-time control of an operator that is one of the most important influential factors in an operation; additionally, lifting or turn-over operations should be a collaboration involving more than two operators. Therefore, this study presents an integrated method for a collaborative simulation that allows multiple workers to operate together in the virtual world. The proposed method is composed of four components. The first component is a dynamic analysis that is based on multibody-system dynamics. The second component is VR (virtual reality) for the generation of realistic views for the operators. The third component comprises the control devices and the scenario generator to handle the crane in the virtual environment. Lastly, the fourth component is the HLA (high-level architecture)-based integrated simulation interface for the convenient and efficient exchange of the data through the middleware. To show the applicability of the proposed method, it has been applied to a block turn-over simulation for which one floating crane and two crawler cranes were used, and an offshore module installation for which a DCR (dual-crane rig) was used. In conclusion, the execution of the proposed method of this study is successful regarding the above two applications for which multiple workers were involved.

• 한국항해학회지
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• 제10권2호
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• pp.11-29
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• 1986

As per the expanding needs of marine exploitation, many floating structures have been built. Among these, box-type vessel is considered as the most basic shape, to which plant barges and crane barges belong. Stability problem is very important for vessel. In order to increase transverse stability, this paper employs bulwarks along the upper deck sides of box-type vessels and the emphasis is laid upon the effect of bulwarks on transverse stability. In the present paper, the calculation method of heeling moment acting to the ship due to hydrostatic pressure is suggested, and actual procedures of the calculation for box-type vessels with bulwarks are shown. Furthermore corresponding model tests are carried out in small water tank. Through the comparison between calculated and measured values, it is confirmed that the preset calculation method is useful. And employing bulwarks on box-type vessels is very effective for increase of transverse stability at the heeling angles from about 15 degrees to about degrees.

• International Journal of Naval Architecture and Ocean Engineering
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• 제9권1호
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• pp.45-54
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• 2017

The purpose of this study is to evaluate various means of wind power turbines installation in the Korean west-south wind farm (Test bed 100 MW, Demonstrate site 400 MW). We presented the marine environment of the southwest offshore wind farm in order to decide the appropriate installation vessel to be used in this site. The various vessels would be WTIV (Wind turbine installation vessel), jack-up barge, or floating crane ${\cdots}$ etc. We analyzed the installation cost of offshore wind turbine and the transportation duration for each vessel. The analysis results showed the most suitable installation means for offshore wind turbine in the Korean west-south wind farm.

• 한국전산구조공학회:학술대회논문집
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• 한국전산구조공학회 2010년도 정기 학술대회
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• pp.192-195
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• 2010

본 논문에서는 해상 크레인과 중량물의 동적 거동을 시뮬레이션하기 위해, 유한 요소 정식화(finite element formulation)를 이용하여 해상 크레인의 붐(boom)을 탄성체로 모델링 하였다. 붐은 3차원 탄성 빔(beam) 요소로 가정하고, 각 요소의 변형에 의한 변위는 형상 함수(shape function)과 절점 좌표(nodal coordinate)를 이용하여 정의하였다. 변형 변위를 이용하여 탄성 붐의 강성 행렬(stiffnes matrix)을 유도하고, 탄성 변위를 포함하는 위치 벡터를 이용하여 질량 행렬을 유도한다. 해상 크레인과 중량물로 이루어진 운동 방정식에 탄성 붐을 포함하여 유연 다물체계(flexible multibody system) 운동 방정식을 구성한다. 외력으로는 선박 유체정역학적 힘, 유체동역학적 힘, wire rope의 장력, 중력 그리고 계류력(mooring force)이 고려되었다. 먼저 요소의 개수를 변경하며 탄성 붐의 동적 거동을 시뮬레이션 하여, 유한 요소 정식화를 이용한 모델링의 타당성을 검증하였다. 그리고 해상 크레인과 중량물의 동적 거동 시뮬레이션에 탄성 붐 모델을 적용하였다.