• Journal of the Korean Society of Manufacturing Process Engineers
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• v.16 no.1
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• pp.51-57
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• 2017

In the present study, the long-pitch roller-chain of a continuous ship unloader is studied. It is the vertical excavating and transporting the cargo has carried in bulk amount. The size of the pitch in the long-pitch roller chain is about 350 mm. The finite element technique is used for the structural safety of the roller chain. The objective of the study is to perform a dynamic analysis of the load at the point of contact with the sprocket of the roller chain, and analyze each point in the stress of the chain's components by using load. From the tooth sprocket optimization analysis, the results show an optimal design. Static structural analysis was safe. Contact analysis results show the greatest stress on the sprocket. By increasing the tooth size, the stress was reduced.

• Journal of Navigation and Port Research
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• v.36 no.9
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• pp.707-714
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• 2012

Recently, tug boats are widely used for towing a barge which transports building materials, a large block of a ship, offshore crane, and so on. In order to simulate the dynamics of the coupled towing system correctly, the dynamics of the towline should be well modeled. In this paper, the towline was modeled as the multiple finite elements, and each element was assumed as a rigid cylinder which moves in five degrees of freedom except roll. The external tension and its moment acting on each element of the towline were modeled depending on the position vector's direction. Tugboat's motion was simulated in six degrees of freedom where wave and current effects were included, and towed barge was assumed to move in the horizontal plane only. In order to confirm the mathematical models of the coupled towing systems, standard maneuvering trials such as course changing maneuver, turning circle test and zig-zag test were simulated. In addition, the same trials were simulated when the external disturbances like wave and current exist. As the result, it is supposed that the results might be qualitatively reasonable.

• 한국해양학회지
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• v.23 no.3
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• pp.97-109
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• 1988

The wind stress and the wind-stress curl over the East Sea of Korea are computed from the ship-observed wind data by the FRDA. In order to emphasize the role of the wind in determining the upper-layer structure, rather persistent and strong winds are selected based on the wind-rose data. The monthly averaged wind stresses are comparable in size with the average value over the Japan Sea. But the monthly averaged magnitude of the wind-stress curl is very large compared to the one over the Japan Sea. This may be due to the spatial variation of the wind speeds influenced by the local orography. The wind-driven upper-layer thickness over the East Sea suggests that the site of deep upper layer indeed exists regardless of season but the position does not appear to be fixed. The convergence of warm surface water driven by the wind could be referred as the warm core.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.29 no.7 s.238
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• pp.805-813
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• 2005

The thermal performance of a flat-strip heat pipe with inner grooves and the screen mesh cover was investigated experimentally. The heat pipes were made of 2024 aluminum alloy of which the dimensions were 30 (W) $\times$ 4 (T) $\times$ 150 (L) mm. The cross sectional dimensions of inner groove were 0.4$\times$0.9 mm and the space between grooves was 0.6 mm. To enhance the capillary force, foe screen meshes were attached to cover the grooved inner surface. In the grooved heat pipes without screen mesh cover, the maximum thermal load of 180 W (12 W/$cm^2$) was achieved for operating temperature below $130^{\circ}C$ at horizontal position. The heat pipes with screen mesh cover showed the thermal resistances less than one third of those without screen mesh cover, and showed less fluctuation in the thermal resistance values. Furthermore, the thermal performance of the former exhibited less dependence on the tilt angle and the fill charge ratio.

• Journal of the Society of Naval Architects of Korea
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• v.53 no.1
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• pp.10-17
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• 2016

When a planing hull straightly runs and turns, its floating position and pitch angle are changed depending on its speed, and large transient motion happens. In this paper, six degrees of freedom(6 DOF) equations of motion, which could simulate the motion of a planing hull, are established. Static and dynamic forces in vertical plane are modeled using pre-calculated displacements and metacentric heights depending on various draft, lift under bottom, and vertical damping coefficients which are used to tune the final motion. Hydrodynamic coefficients in horizontal plane at various equilibrium state are calculated by using Lewandowski's empirical formula and the speed-dependent equilibrium state are calculated beforehand by Savitsky's formula. The speed effects are considered by curve-fitting the coefficients at various speed to the polynomials. Accelerating, decelerating and backing, turning, and zig-zag are simulated and compared with the sea trial results, and it is confirmed that the speed reduction, roll, and pitch during such maneuvers of sea trial and simulation are well consistent.

• International Journal of Naval Architecture and Ocean Engineering
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• v.11 no.2
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• pp.858-864
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• 2019

The increasing demands of lifting lugs can be attributed to the rapid advancement of shipbuilding and offshore-structure production technologies and an exponential increase in the size of the block units of ship structures. Therefore, to ensure safety during the transportation and turnover of large blocks, it is important to determine the structural integrity and position of lifting lugs. However, because the manufacturing cost and availability of lugs are important considerations, low cost and easily obtainable steel compositions of grades different from those of the blocks are often used as alternatives. The purpose of this study is to investigate the effect of a lifting-lug metal on the physical properties of a base metal in a dissimilar welding between the base metal and lifting lug. The effect was evaluated by observing the metal microstructures and determining the hardness and dilution values on the cross-sectional surface of the lifting lug. According to the results of the metal microstructures, impact, hardness, and emission spectrochemical analysis at the surface from where the lug was removed confirmed that the chemical composition of the lifting-lug metal did not influence the physical properties of the base metal.

• Journal of the Korean Society for Marine Environment & Energy
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• v.2 no.2
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• pp.31-37
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• 1999

In this paper, authors introduce about wide vessel traffic service(VTS) system using automatic identification system(AIS). In order to develop the prototype of wide VTS system, Koreasat is used for AIS. In this system, ship position obtained by using GPS is reported automatically to VTS center through Koreasat. By using this system, VTS center can cover more wide area than the case using radar only. And the uncertainty of information decreases. The results of test show the good possibility of VTS using satellite and AIS.

• Proceedings of the Korean Institute of Navigation and Port Research Conference
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• 2015.10a
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• pp.43-44
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• 2015

AIS-ASM is a one of the study to provide a variety of maritime safety information as well as ship's position and navigational information that is their own function since 2004. This study aims to reduce the marine officer's workload through automating marine officer's mandatory reporting items using the one of the next maritime digital communication technology (ASM2.0). For this purpose, we designed and experimented of the ASM2.0 protocol through analyzing a domestic regulation about passenger flight and AIS-ASM message.

• Bulletin of the Society of Naval Architects of Korea
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• v.19 no.4
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• pp.39-45
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• 1982

A floating rig, which has been used to develop the ocean resources has a common characteristics with the catamaran ship that it is composed of the two simple hulls. So the motion responses of the floating rig can be predicted theoretically with the aid of the strip method as those of the catamaran. And for the strip method, the two-dimensional hydrodynamic coefficients are the most important inputs to predict the results accurately. In this report, a theoretical method is proposed for calculating two-dimensional hydrodynamic forces and moments acting upon arbitrary shaped twin-hull cylinders, which are forced to make a heaving, swaying and rolling oscillation about their mean position on the free surface of a finite depth water. The theoretical results by making use of the singularity distribution method are presented. The accuracy of the coefficients was confirmed to be reasonable by the comparison with the Ohkusu's results for two circular cylinders in an infinite depth water. The depth effects on two-dimensional hydrodynamic coefficients for two circular cylinders are also checked. In some range of wave numbers, large differences in the behavior of hydrodynamic coefficients between for a finite depth and for an infinite depth are shown.

• Journal of the Society of Naval Architects of Korea
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• v.48 no.1
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• pp.15-22
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• 2011

In this paper, cavitation patterns of model tests were compared with those of full-scale measurement for a propeller of crude oil carrier which was suffered from erosions on suction side of blade tip region. Cavitation tests were performed at design and ballast draft using model and full scale nominal wakes. A model ship and wire mesh method was used for the simulation of wake patterns of model nominal wakes. For the prediction of full-scale wake patterns, a RANS solver(Fluent 6.3) was used and wire mesh method was used for the simulation of the full scale wakes. Comparison results show that cavitation patterns using predicted full-scale wake patterns are closer to cavitation patterns of full-scale measurement at ballast draft condition. Also, cloud cavitations were observed on the position of eroded area at both full-scale measurement and cavitation tests using simulated full-scale wake patterns.