• Journal of Ocean Engineering and Technology
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• v.19 no.3
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• pp.31-38
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• 2005

Ocean developments gradually move to deep-sea in the 21 century. A deep-sea unmanned underwater vehicle is one of important tools for ocean resource survey. A marine cable plays an important role for the safe operation and signal transmission of a deep-sea unmanned underwater vehicle. The umbilical cable of a deep-sea unmanned underwater vehicle is excited by surface vessel motion and shows non-linear dynamic behaviors. A numerical method is necessary for analysing the dynamic behavior of a marine cable. In this study, a numerical program is established based on a finite difference method. The program is appled to 6000m long cable for a deep-sea unmanned underwater vehicle and shows good reasonable results.

• Proceedings of the Korea Committee for Ocean Resources and Engineering Conference
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• 2004.05a
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• pp.123-130
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• 2004

Ocean developments gradually move to deep-sea in the 21 century. A deep-sea unmanned underwater vehicle is one of important tools for ocean resource survey. A marine cable plays an important role for the safe operation of a deep-sea unmanned underwater vehicle. The first cable of a deep-sea unmanned underwater vehicle is excited by surface vessel motion and shows non-linear dynamic behaviors. A numerical method is necessary for analysing the dynamic behaviour of the first marine cable. In this study, a numerical program is estabilished based on a finite difference method. The program is appled to a 6000m long cable for a deep-sea unmanned underwater vehicle and shows good reasonable results.

• Proceedings of the Korea Committee for Ocean Resources and Engineering Conference
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• 2004.11a
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• pp.198-203
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• 2004

Ocean developments gradually move to deep-sea in the 21 century. A deep-sea unmanned underwater vehicle is one of important tools for ocean resource survey. A marine cable plays an important role for the safe operation and signal transmission of a deep-sea unmanned underwater vehicle. The first cable of a deep-sea unmanned underwater vehicle is excited by surface vessel motion and shows non-linear dynamic behaviors. A ROV launcher is also excited by the 1st cable motion. A numerical method is necessary for analysing the dynamic behaviour of the first marine cable and the ROV launcher. In this study, a numerival program is appled to a 6,000m long cable for a deep-sea unmanned underwater vehicle to shaw shows the dynamic behaviour of the cable and the ROV launcher under combined excitations.

• The Journal of the Korea institute of electronic communication sciences
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• v.10 no.9
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• pp.979-986
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• 2015

Security solutions using fiber-optic cable have not yet secured a solid technical stability, through which the Acoustic detection security system also did not have a complete defense techniques such as false alarm and detecting fail due to a number of variables. In this paper, we investigate 4 characteristics for the channel of underwater acoustic communication. We also construct detection system as a construction method for security system using optical cable through the analysis of acoustic signal in underwater. We perform analysis of signal characteristics and noise of underwater optical cable, and then we confirms the possibility of real application.

• Journal of Ocean Engineering and Technology
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• v.20 no.6 s.73
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• pp.75-81
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• 2006

In this study, the dynamic response of the umbilical cable in a deep-water unmanned underwater vehicle system was analyzed. In order to analyze the forces acting on the cable, the launcher and umbilical cable were modeled by the simple 1-D mass-spring system. Damping and dynamic analysis was carried out by a direct time integration scheme using the $Newmark-{\beta}$ method with inverse iteration procedure, considering the nonlinear drag forces acting on the launcher. The obtained results of the present study can be used for the design of connecting the structure of the launcher and cable of the UUV system.

• Journal of the Society of Naval Architects of Korea
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• v.53 no.5
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• pp.388-399
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• 2016

A motion analysis of an underwater towed cable is a complex task due to its nonlinear nature of the problem. The major source of the nonlinearity of the underwater cable analysis is that the motion of the cable involves large rigid-body motion. This large rigid-body motion makes difficult to use standard displacement-based finite element method. In this paper, the authors apply recently developed nodal position-based finite element method which can deal with the geometric nonlinearity due to the large rigid-body motion. In order to enhance the stability of the large-scale nonlinear cable motion simulation, an efficient time-integration scheme is proposed, namely predictor/multi-corrector Newmark scheme. Three different predictors are introduced, and the best predictor in terms of stability and robustness for impulsive cable motion analysis is proposed. As a result, the nonlinear motion of underwater cable is predicted in a very efficient manner compared to the classical finite element of finite difference methods. The efficacy of the method is demonstrated with several test cases, involving static and dynamic motion of a single cable element, and also under water towed cable composed of multiple cable elements.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2005.07a
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• pp.229-231
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• 2005

HVDC(High Voltage Direct Current) is an underwater cable between Jeju Island and Haenam in main land and supplies approximately 50% of electrical usage in Jeju Island. If there is any power failure due to HVDC, it will cost approximately 50,000 US dollars per day including Thermal Electrical Generation. Therefore it is absolutely necessary to recover the problem in rapid timely basis. In conclusion, evaluation methode of HVDC cable is needed urgently to upgrade current HVDC underwater cable repair technique in Korea to minimize the cost and time factors.

• Journal of Ocean Engineering and Technology
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• v.32 no.5
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• pp.324-332
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• 2018

It is known that damages to the subsea cables used for electric power transmission between islands and countries, including renewable energy from offshore wind power, current, tides, etc., cost much to restore, which causes social and economic losses. Various types of fishing rigs and anchors have been reported to be the greatest hazards to subsea cables. It is possible to design and construct a suitable protection facility for a subsea cable by precisely estimating the underwater behavior of such hazardous apparatuses. In this study, numerical simulations of the underwater behaviors of various hazardous apparatuses were carried out using fluid-structure interaction (FSI) analysis as a basic study to simulate the actual behavior phenomena of hazardous apparatuses in relation to a subsea cable. In addition, the underwater drop characteristics according to the types of hazardous apparatuses were compared. In order to verify the accuracy of the FSI analysis method used in this study, we compared the test results for underwater drops of a steel ball bearing. Stock anchors, stockless anchors, and rocket piles, which were actually reported to be the cases of damage to subsea cables along the southwest coast of Korea, were considered as the hazardous apparatuses for the numerical simulations. Each hazardous apparatus was generated by a Lagrangian model and coupled with the fluid domain idealized by the Eulerian equation to construct the three-dimensional FSI analysis model. The accuracy of the numerical simulation results was verified by comparing them with the analytical solutions, and the underwater drop characteristics according to the types of hazard apparatuses were compared.

• Journal of Sensor Science and Technology
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• v.32 no.3
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• pp.199-206
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• 2023

This study presents a novel monitoring technique for underwater high-voltage direct current (HVDC) cables based on the Distributed Acoustic Sensor (DAS). The proposed technique utilizes vibration and acoustic signals generated on HVDC cables to monitor their condition and detect events such as earthquakes, shipments, tidal currents, and construction activities. To implement the monitoring system, a DAS based on phase-sensitive optical time-domain reflectometry (Φ-OTDR) system was designed, fabricated, and validated for performance. For the HVDC cable monitoring experiments, a testbed was constructed on land, mimicking the cable burial method and protective equipment used underwater. Defined various scenarios that could cause cable damage and conducted experiments accordingly. The developed DAS system achieved a maximum measurement distance of 50 km, a distance measurement interval of 2 m, and a measurement repetition rate of 1 kHz. Extensive experiments conducted on HVDC cables and protective facilities demonstrated the practical potential of the DAS system for monitoring underwater and underground areas.

• International Journal of Naval Architecture and Ocean Engineering
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• v.7 no.2
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• pp.409-425
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• 2015

In this paper, we employ a dynamics modeling method for investigating a multi-body dynamics system of semi-submersible autonomous underwater vehicles consisting of a towing vehicle operated near the water surface, a tow cable, and a towfish. The towfish, which is towed by a marine cable for the purposes of exploration or mine hunting, is modeled with a Six-Degree-of-Freedom (6-DOF) equation of motion that reflects its hydrodynamics characteristics. The towing cable, which can experience large displacements and deformations, is modeled using an absolute nodal coordinate formulation. To reflect the hydrodynamic characteristics of the cable during motion, the hydrodynamic force due to added mass and the drag force are imposed. To verify the completeness of the modeling, a few simple numerical simulations were conducted, and the results confirm the physical plausibility of the model.