• International Journal of Ocean System Engineering
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• v.3 no.4
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• pp.175-187
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• 2013

Moonpools are vertical wells in a floating body used onboard many types of vessels like Exploration and drilling vessels, Production barges, Cable-laying vessels, Rock dumping vessels, Research and offshore support vessels. Moonpool gives passage to underwater activities for different types of ships as per their mission requirements. It is observed that inside a moonpool considerable relative motions may occur, depending on shape, depth of the moonpool and on the frequency range of the waves to which the ship is exposed. The vessel responses are entirely different in zero and non-zero Froude number. Former situation is paid attention in this study as the mission requirement of the platform is to be in the particular location for long period of operation. It is well known that there are two modes of responses depending on the shape of the moonpool viz., piston mode for square shape and sloshing mode for rectangular shapes with different aspect ratios of opening like 1:1.5 and 1:2 ratios. Circular shaped moonpool is also tested for measuring the responses. The vessel moored using heavy lines are modelled and tested in the wave basin. The pretensions of the lines are varied by altering the touchdown points and the dynamic tensions on the lines are measured. The different modes of oscillations of water column are measured using wave gauge and the vessel response at a particular situation is determined. RAOs calculated for various situations provide better insight to the designer.

• Proceedings of the Korea Committee for Ocean Resources and Engineering Conference
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• 2002.10a
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• pp.142-148
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• 2002

Autonomous underwater vehicles (AUVs) are unmanned underwater vessels to investigate sea environments, oceanography and deep-sea resources autonomously. Docking systems are required to increase the capability of the AUVs to recharge the batteries and to transmit data in real time for specific underwater works, such as repeated jobs at sea bed. This paper presents a visual servo control system for an AUV to dock into an underwater station with a camera mounted at the nose center of the AUV. To make the visual servo control system, this paper derives an optical flow model of a camera, where the projected motions of the image plane are described with the rotational and translational velocities of the AUV. This paper combines the optical flow equation of the camera with the AUVs equation of motion, and derives a state equation for the visual servoing AUV. This paper proposes a discrete-time MIMO controller minimizing a cost function. The control inputs of the AUV are automatically generated with the projected target position on the CCD plane of the camera and with the AUVs motion. To demonstrate the effectiveness of the modeling and the control law of the visual servoing AUV, simulations on docking the AUV to a target station are performed with the 6-dof nonlinear equations of REMUS AUV and a CCD camera.

• Proceedings of the Korean Institute of Navigation and Port Research Conference
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• 2004.11a
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• pp.49-55
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• 2004

The manoeuvring of vessels and hydrodynamic interaction between them and bank wall in restricted waterways have been treated as important factors in channel design and safe piloting in the water areas. This paper examines the interaction forces and moments acting on two vessels running closely in the proximity if bank wall. The object if this paper is to propose a guideline of safe velocity if vessels and distance between them for navigating safely in confined sea areas.

• Journal of Navigation and Port Research
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• v.29 no.1 s.97
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• pp.17-22
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• 2005

The manoeuvring of vessels and hydrodynamic interaction between them and bank wall in restricted waterways have been treated as important factors in channel design and safe piloting in the waterway areas. This paper examines the interaction forces and moments acting on two vessels running closely in the proximity of bank wall. The object of this paper is to propose a guideline of safe velocity of vessels and distance between them for navigating safely in confined sea areas.

• Journal of the Institute of Convergence Signal Processing
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• v.5 no.2
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• pp.106-110
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• 2004

The noise characteristics of the submarines and vessels are composed of tonal signals and background noises. Tonal signals are from the revolution of the motors or engines, and background noises are from the generation and disappearing of the bubbles around the vessels. We analyze the noises from maneuvering underwater vessels with ATW algorithm. We design broadband asymptotic noise generator using Hilbert transform and design the system which can generate asymptotic noise with sum of generated background noise and synthesized tonal signals. This system can be used as a cheating system from the torpedo shacks.

• Explosives and Blasting
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• v.25 no.2
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• pp.71-78
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• 2007

In many cases of underwater blasting in South Korea, the special blasting is mainly used for deepening harbor, installing gas pipes, or well blasting to build a bridge. The procedure of well blasting is almost same with shaft blasting, but the difference is that water is filled in before blasting. In case of deepening blasting under water, the first step like drilling, arranging explosives, and wire connection is done on a barge, then the next step such as charging and tamping is accomplished under water by expert divers. Therefore, underwater blasting needs precise and exact plan before blasting. In this paper, authors would like to introduce a case of underwater blasting for deepening the Busan new port with emulsion explosives and non-electric detonators in order to get some of 8,500TEU out sized container vessels entered into the port and to make safe. Considering environment and vibration, the blasting was controlled to minimized the damage to the lighthouse nearby. It will be great help to many other blasting sites where emulsion explosives and non-electric detonators are used for underwater blasting through this case.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.7 no.6
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• pp.1123-1129
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• 2003

The noise of maneuvering submarines or vessels can be divided into the tonal signals and broadband ambient noise. Tonal signals are from the revolution of motors and engines of vessels, and broadband ambient noise is from the bubbles which are generated by the propellers and the flow of water around vessels. We can analyze the kinds and the speed of vessels if we analyze the tonal signals and ambient noise. But, it is difficult to divide the tonal signals form the ambient noise when the power of tonal signal is much weaker than the power of ambient noise. In this paper, we detect the direction of arrival(DOA) of the noises generated by vessels with the automatic tracking window(ATW) preprocessing algorithm, and make a beam to the direction of the targets. We suggest a method which can separate weak tonal signals from broadband ambient noise with the ATW algorithm.

• Journal of Navigation and Port Research
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• v.30 no.5 s.111
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• pp.315-320
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• 2006

It is well known that the ship manoeuvring motion is greatly affected by hydrodynamic forces and moments acting between two vessels passing too close to each other in confined waters, such as in a harbour or narrow channel. This interaction between two vessels could be assumed to be the functions of the longitudinal distance, transverse distance and their speeds. The aim of this study is to calculate the interaction between two vessels passing close to each other on parallel courses by simulation, and to estimate the effect of rudder action and time at collision through simulation under the condition of various longitudinal distances and different speed-ratios of the two vessels.

• Proceedings of the Korean Institute of Navigation and Port Research Conference
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• 2006.06b
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• pp.55-60
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• 2006

It is well known tint the ship manoeuvring motion is greatly affected by hydrodynamic forces and moments acting between two vessels passing too close to each other in confined waters, such as in a harbour or narrow channel. This interaction between two vessels could be assumed to be the functions of the longitudinal distance, transverse distance and their speeds. The aim of this study is to calculate the interaction between two vessels passing close to each other on parallel courses by simulation, and to estimate the effect of rudder action and time of collision through simulation under the condition of various longitudinal distances and different speed-ratios of the two vessels.

• Transactions of the Korean Society for Noise and Vibration Engineering
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• v.23 no.12
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• pp.1073-1081
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• 2013

The definition of the radiation efficiency is very important to estimated underwater radiated noise of a ship. Considering the structure of the ship, it can be found that the hull of a ship consists of a lot of plates supporting by longitudinal and transverse stiffener. Therefore, various modes of the hull vibration occur related to the combination of these plates including stiffeners. In this paper, the method to define the radiation efficiency is suggested considering the vibration mode of the hull based on Uchida's experimental equation of the radiation efficiency. The suggested method is verified by the experiments with various kinds of naval vessels.