• International Journal of Naval Architecture and Ocean Engineering
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• v.9 no.1
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• pp.55-65
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• 2017

Underwater torpedo has control fin with very low aspect ratio due to launching from limited size of cylindrical torpedo tube. If the aspect ratio of control fin of underwater vehicle is very low three-dimensional flow around control fin largely reduces control forces. In this study, the end plate was applied to reduce the three-dimensional flow effects of partially movable control fin of underwater vehicle. Through numerical simulations the flow field around control fin was examined with and without end plate for different flap angles. The pressure, vorticity, lift and torque on the control fin were analyzed and compared to experiments. The comparison have shown a reasonable agreement between numerical and experimental results and the effect of end plate on a low aspect ratio control fin. When the end plate was attached to the movable control fin, the lift increased and the actuator shaft torque did not significantly change. As this means less consumption of the actuator shaft torque compared to the control fin that has the same control force, the inner actuator capacity can be reduced and energy consumption can be saved. Considering this, it is expected to be effectively applied to the control fin design of underwater vehicles such as torpedoes.

• Journal of Advanced Marine Engineering and Technology
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• v.39 no.9
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• pp.940-946
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• 2015

In this paper, we study a method that amplifies the output gain of a high voltage pulse using 300 kHz or higher frequency. We conducted a study on a method for amplifying the output gain using the resonance between the capacitance components of the load and the parasitic components of the circuit, instead of the conservative method for amplifying the pulse-amplitude by raising the voltage of the power stage. In particular, the method simplifies the circuit configuration throughout the appliance of flyback-type topology instead of the bridge-type. There are advantages that prevent damage from overload and the heat in the output circuit through the hard switching by amplifying the gain of the output voltage applying to the load as given by the capacitance component of the output electrode to the output pulse waveform. This study proposed a method to enhance the spatial and electrical efficiency of the contact-type heating device through the dielectric heating method applied to the field of medical and industrial heating.

• Proceedings of the Korean Institute of Navigation and Port Research Conference
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• 2023.05a
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• pp.200-201
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• 2023

Digital twin technology is used in various fields as a method of creating a virtual world to minimize the cost of solving problems in the real world, and is also actively used in the maritime field, such as large-scale systems such as ships and offshore plants. In this paper, we tried to build a digital twin of coastal waters using a ship-handling simulator. The digital twin of the coastal waters developed in this way can be used to safely manage Korea's coastal waters, where maritime traffic is complicated, by providing a actual maritime traffic data. It can be usefully used to develop and advance technologies related to maritime autonomous surface ships and intelligent maritime traffic information services in coastal waters. In addition, it can be used as a 3D-based monitoring equipment for areas where physical monitoring is difficult but real-time maritime traffic monitoring is necessary, and can provide functions to safely manage maritime traffic situations such as aerial views of ports/control areas, bridge views/blind sector views of ships in operation.

• Journal of the Korean Institute of Navigation
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• v.21 no.4
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• pp.93-102
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• 1997

History will be defined as a science on human beings in both space and time(des hommes dans le temps et l'espace). Navigational History is a premise to compose Maritime History. Maritime History is a branch of General History which is classified on the basis of space and will be definded as a branch of history to examine 'inter-realtions between maritime affairs and inland affairs'. Then, what kind of 'go by sea'can be a subject of Navigational History ? A research-subject of Navigational History must be navigation rather than sail or voyage. Because while 'sail' means to 'passive and noncommercial sailing' and voyage means to journeyin a general sense that includes sail and navigation, navigation means to indicate ' to go from one place to another in a ship' adn 'to convoy goods by water'. Then, how can we define Navigation History? Navigational History in a narrow sense is to be a field of studying 'process of development of nautical science and seamanship on the side of History ofScience and Techique, whereas Navigational History in a broad sense is to be a field of analyzing 'effects of historical navigation upon history on the side of General History. On studying Navigational History in a narrow sense, there are signifiacances of disclosing what the development of nautical instruments and arts of navigation have played a role in history. Navigational History in a broad sense is a branch of General History to study effects of historical navigation upon history. In conclusion, the significance of studying Navigation History is to disclose process of developmentof arts of navigation, and on the basis of this study is to reveal how the human elements operate in historical navigation. In short, it should not cease to study Navigational History in a narrow sense, and should enlarge its perspective of research toward Navigational History in a broad sense.

• Korea Trade Review
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• v.45 no.6
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• pp.157-179
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• 2020

This study presented the results of meta-analysis through topic modeling among the papers published in the Journal of the International Trade Association for the purpose of presenting academic research trends in the field of trade insurance and future research directions. Among the total 2,010 papers included in the Journal of the Korea International Trade Association, the analyzed paper covers the subject of trade-related insurance. According to detailed topics, 33 marine insurance (42.31%), 16 export insurance (20.51%), 11 hull insurance (14.10%), and 18 others (23.08%), and 4 other products liability insurance. According to the empirical analysis results, Topic 1 was classified as marine insurance, airworthiness, notice obligation, and collateral, and Topic 2 was derived as a representative topic for loading insurance, emergency risk, and immunity as export insurance. And Topic 3 was classified as vessel, sinking and container in relation to ship insurance, and Topic 4 was analyzed as an important topic such as manufacture and British marine insurance. Through the analysis results, we selected the representative topic used for the trade insurance topic and looked at the status of major research. Trade insurance is an area that requires the development of more theoretical and practical research subjects as an optimal risk management means in international trade transactions. To this end, first, support from the Korea International Trade Association is needed to establish a continuous research subject sharing system for the development of research subjects in the field of trade insurance. Second, academic journal operation management must be continuously managed in which academic research papers can be submitted and published.

• Journal of Korean Society of Industrial and Systems Engineering
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• v.39 no.4
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• pp.49-59
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• 2016

Naval combat system developed in-country is progressing at an alarming rate since 2000. ROK navy will be achieved all vessels that have combat system in the near future. The importance of System Engineering and Integrated Logistics Support based on reliability analysis is increasing. However, reliability analysis that everyone trusted and recognized is not enough and applied practically for development of Defense Acquisition Program. In particular, Existing Reliability Analysis is focusing on reliability index (Mean Time Between Failure (MTBF) etc.) for policy decision of defense improvement project. Most of the weapon system acquisition process applying in the exponential distribution simply persist unreality due to memoryless property. Critical failures are more important than simple faults to ship's operator. There are no confirmed cases of reliability analysis involved with critical failure that naval ship scheduler and operator concerned sensitively. Therefore, this study is focusing on Mean Time To Critical Failure (MTTCF), reliability on specific time and Operational Readiness Float (ORF) requirements related to critical failure of Patrol Killer Guided missile (PKG) combat system that is beginning of naval combat system developed in-country. Methods of analysis is applied parametric and non-parametric statistical techniques. It is compared to the estimates and proposed applications. The result of study shows that parametric and non-parametric estimators should be applied differently depending on purpose of utilization based on test of normality. For the first time, this study is offering Reliability of ROK Naval combat system to stakeholders involved with defense improvement project. Decision makers of defense improvement project have to active support and effort in this area for improvement of System Engineering.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.18 no.11
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• pp.718-724
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• 2017

Considerable efforts have been made to expand the boundaries of domestic offshore plant industries, which have focused on the construction of the structures, to the engineering field. On the other hand, time domain analysis, which is one of the most important areas in designing floating offshore plants, relies mainly on the information given by foreign companies. As an early design of the Dynamic Positioning System (DPS) is mostly conducted by several specialized companies, domestic ship builders need to spend time and money to reflect the analysis into the hull shape design. This paper presents the framework required to analyze time domain performance of floating type offshore structures, which are equipped with DPS. To easily perform time domain analysis, framework generates the required input data for the solver, and is modularized to test the control algorithm and performance of a certain DPS. The effectiveness of the developed framework was verified by a simulation with a model ship and the total time for the entire analysis work was reduced by 50% or more.

• Journal of the Korea Society for Simulation
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• v.22 no.2
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• pp.63-71
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• 2013

Developing future weapons systems has become increasingly complicated and costly. There, modeling and simulation techniques have been highly interested in developing the defense systems. Modeling and simulation techniques provide a means to simulate military training, strategies, military doctrines, and weapons acquisition. In this paper, we proposed a small scale engagement scenario generation method for engagement M&S model. Generated scenario is one of critical factors in the field of commander training, operational analysis, and tactical evaluation. The objective of this paper is to develop a scenario generation method for small scale engagement using the FSA(Finite State Automata) and DFS(Depth First Search) algorithm. The proposed method is verified using a one-on-one combat engagement scenario between assault ship and reconnaissance ship. Also, we are visualized using Delta3D$^{TM}$.

• Journal of the Society of Naval Architects of Korea
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• v.48 no.2
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• pp.147-157
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• 2011

A RANS(Reynolds averaged Navier-Stokes) based numerical method is developed for the evaluation of ship resistance and self-propulsion performances. In the usability aspect of CFD for the hull form design, the field grid around practical hull forms is generated by solving a grid Poisson equation based on the hull surface grid generated from station offsets and centerline profile. A body force technique is introduced to model the effects of the propeller in which the propeller loads are obtained from potential flow analysis using an unsteady lifting surface method. The free surface is captured by using a two-phase level-set method and the realizable $k-{\varepsilon}$ model is used for turbulence closure. The hull attitude in vertical plane, i.e., trim and sinkage, is calculated by using a quasi-steady method and then considered in the computation by translating and rotating the grid system according to the values. For the validation of the proposed method, the numerical results of resistance tests for KCS, KLNG, and KVLCC1 and of self-propulsion test for KCS are compared with experimental data.

• Journal of Ocean Engineering and Technology
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• v.27 no.3
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• pp.53-60
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• 2013

A drillship is a representative floating offshore installation. The boom in oil and gas field development has dramatically increased the demands for drillships. Drillships have a moonpool in the center area of the ship for the purpose of drilling. This moonpool has an effect on the seakeeping performance of a drillship in the vicinity of the resonance frequency. Because of the moonpool, drillships act in different resonance modes, called the sloshing mode and piston mode. The objective of this study was to find the moonpool effect on the motion of a drillship through the motion analysis of a currently operating modern compact drillship. The predicted resonance frequencies based on Molin's theoretical formula, Fukuda's empirical formula, and BEM-based numerical analysis are compared. The accuracy of the predictions using the theoretical and empirical formulas is compared with the numerical analysis and evaluated. In the case of the piston mode, the difference between the resonance frequency from theoretical formula and the resonance frequency from the numerical analysis is analyzed. The resonance frequency formula for more a complex moonpool geometry such as a moonpool with a cofferdam is necessarily emphasized.