• Journal of Navigation and Port Research
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• v.43 no.6
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• pp.369-376
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• 2019

Ship hydrodynamics in the confined waterways is challenging. When a ship is maneuvering in confined waterways, the hydrodynamic behavior may vary significantly because of the hydrodynamic interaction between the bottom of the ship hull and the seabed, or so-called shallow water effects. Thus, an accurate prediction of shallow water and bank effects is essential to minimizing the risk of the collision and the grounding of the ships. The hydrodynamic derivatives measured by the virtual captive model test provide a path to predicting the change in ship maneuverability. This paper presents a numerical simulation of captive model tests to predict the maneuverability of a ship in confined waterways. Also, straight and zig-zag simulation were conducted to predict the trajectory of a ship maneuvering in confined waterways. The results showed that the asymmetric flow around a ship induced by vicinity of banks causes pressure differences between the port and starboard sides and the trajectory of a ship maneuvering in confined waterways.

• Journal of Navigation and Port Research
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• v.29 no.1 s.97
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• pp.43-58
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• 2005

Piracy is the enemy of the human race. Pirates commit acts of murder, robbery, plunder or other villainous deeds at sea, cruelly against humanity. The Republic of Korea(ROK), as a big maritime country, is obliged to suppress piracy under international treaties it ratified, including the UN Convention on the Law of the Sea and the two 1988 Conventions against maritime terrorism The Korean government is recently taking a positive attitude towards the regional cooperation which is necessary for the suppression of piracy in the waters of Southeast Asia In spite of the effects of international cooperation to prevent piracy, it is recently on an increasing trend every year. Such circumstances may have a bad effect on the sound development of world economy by means of trade at sea as well as treat to the safety of crews and safe operation of ships. This paper aims to suggest the countermeasures against piracy in terms of criminal law, civil law and international law in order to secure safe operation of vessels at sea.

• Journal of Navigation and Port Research
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• v.39 no.1
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• pp.1-6
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• 2015

In this study, with the awareness of the limitations set in the currently operated calculations of holding power and the holding power coefficient of anchors of naval ships due to its simple application of a specific value, various factors that impact the holding power and its coefficient were verified based on existing data analysis of literature research and numerous experiment results from anchor manufacturers, research institutes and academic community in order to overcome the aforementioned limitations. In addition, holding power and holding power coefficient were compared and analyzed by the shape of anchors. As a result, we came to know that the holding power of AC-14 type anchor is stronger than that of ASS type anchor or U.S. Navy Standard type anchor which makes it possible to reduce the weight of the anchor and therefore ease the process of naval shipbuilding. Furthermore, we confirmed the fact that U.S. Navy Standard type anchor does not react sensitively to the weight change of the anchor. Lastly, we found out that Danforth type anchor's holding power coefficient is in inverse proportion to the weight. Moreover, instructions for managing anchor are arranged easily for your information. The results of this study is expected to provide anchor - operating naval crew with a reliable theoretical basis pertaining to an anchor's holding power and its coefficient and contribute much for the safety of their act of anchoring.

• Journal of Korean Society of Transportation
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• v.21 no.1
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• pp.41-49
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• 2003

Marine traffic management could be defined as the implementation of managerial technical measures to improve vessel traffic safety. The managerial elements of vessel traffic management for ports and harbours or narrow channels include the total amount of traffic control, the vessel traffic separation scheme, speed restriction, traffic control by signals, the navigation information service and so forth. This research aims to quantify how much the traffic separation schemes(TSS) contribute to the alleviation effect of ship handling difficulty and to propose a design standard when the individual management measure is applied in an actual waterway. Traffic separation schemes have now been established in most of the major routes and congested waters of the world, and the number of collisions and groundings have often been dramatically reduced. In this part, the relationship between the alleviation of ship handling difficulty and the reduction of encounter figures among ships is quantitatively clarified by applying the ES model. As results of simulation analysis, it is recognized that a traffic separation system is most effective in the case of narrow width and heavy traffic volume. The centre buoy installation reduces about 1/4 of the alleviation of ship handling difficulty, TSS establishment 1/3, and design change to one-way traffic from two-way traffic reduces 1/2.

• Journal of the Society of Naval Architects of Korea
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• v.50 no.5
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• pp.324-333
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• 2013

Recently, rudder erosion due to cavitation has been frequently reported on a semi-spade rudder of a high-speed large ship. This problem raises economic and safety issues when operating ships. The semi-spade rudders have a gap between the horn/pintle and the movable wing part. Due to this gap, a discontinuous surface, cavitation phenomenon arises and results in unresolved problems such as rudder erosion. In this study, we made a rudder model for 2-D experiments using the NACA0020 and also manufactured gap flow blocking devices to insert to the gap of the model. In order to study the gap flow characteristics at various rudder deflection angles($5^{\circ}$, $10^{\circ}$, $35^{\circ}$) and the effect of the gap flow blocking devices, we carried out the velocity measurements using PIV(Particle Image Velocimetry) techniques and cavitation observation using high speed camera in Seoul National University cavitation tunnel. To observe the gap cavitation on a semi-spade rudder, we slowly lowered the inside pressure of the cavitation tunnel until cavitation occurred near the gap and then captured it using high-speed camera with the frame rate of 4300 fps(frame per second). During this procedure, cavitation numbers and the generated location were recorded, and these experimental data were compared with CFD results calculated by commercial code, Fluent. When we use gap flow blocking device to block the gap, it showed a different flow character compared with previous observation without the device. With the device blocking the gap, the flow velocity increases on the suction side, while it decreases on the pressure side. Therefore, we can conclude that the gap flow blocking device results in a high lift-force effect. And we can also observe that the cavitation inception is delayed.

• Journal of Digital Convergence
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• v.16 no.10
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• pp.169-178
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• 2018

Gyeongin Port has low awareness, insufficient hinterland infrastructures, and lower competitiveness. So, in this study, we conducted Fuzzy-IPA analysis reflecting the recognition of the consignor companies that are using Gyeongin port to suggest present practical improvement measures for the activation of the operation of Gyeongin port hereafter. As a result of the analysis, three factors, that is, cargo loading/unloading/storage costs, port facility fees, and incentive and support were derived as priority investment areas. Three factors, that is, cargo safety, infrastructure equipment, and inland transportation costs were derived as the areas for maintenance strengthening and factors related to cargo handling and service factors were derived as areas for maintenance of the status quo and areas for gradual improvement, respectively. This study is significant in that it analyzed the recognition of the consignor companies that are using Gyeongin port using a quantifying method and suggested realizable measures for activation based on the results of the analysis. In future studies, the frequency of ships' calling at the port and measures to diversify the sea routes should be additionally reflected on the analysis.

• Journal of Advanced Marine Engineering and Technology
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• v.39 no.4
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• pp.463-467
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• 2015

When unforeseen accidents occur in a ship, it is important to save passengers safely and remove them from the accident area quickly. To solve such a situation, site information of passengers on board always must be identified. This paper implemented a site monitoring of crews and passengers based on the BLE and PLM combination, to prepare for unexpected accidents of the ships. This system was composed of BLE tag for crews, passengers and each room, PLM networks, data server, and monitoring PC. In this system, site information derived from the tag attached to the bodies and cabins of crews and passengers are transmitted through a power line network, and monitored on the screen of a monitoring PC. The proposed system guides them into the only authorized area considering the ship security and passengers' safety, and even has a special alarm call to warn them after entering an unauthorized area. This system enables the BLE-embedded tag battery to use for a long time because the BLE consumes low electric power, and can gain an economic advantage.

• Journal of Navigation and Port Research
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• v.41 no.6
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• pp.373-380
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• 2017

Operational errors caused by human factors, which is the major cause of marine accidents, include lack of knowledge, misunderstanding knowledge, and inadequate procedures. Recently, the type of propulsion mounted on KCG cutters has been diversified. In particular, the water jet propulsion unit, which was mainly installed in small boats, have been gradually expanded to medium and large size Coast Guard cutters, reaching 50% of the total. Axes types are divided into 2 to 4, and the bucket types are divided into Double Reverse Bucket(DRB) and Single Reverse Bucket(SRB); in these, the backward and steering control methods are completely different. Diversification of these operating systems can increase factors causing human error by the ships' operators. However, there is a lack of research on the maneuvering methods, considering the inherent active characteristics of each type of water jet. In this paper, we analyze the sideway method suitable for the condition of Coast Guard Exclusive wharf without assistance, based on the astern performance of each type. Then, a ship handling simulator was used for the experiment; they compared and verified through interviews of captains.

• Proceedings of the Korean Institute of Navigation and Port Research Conference
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• 2005.10a
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• pp.111-116
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• 2005

The approaching waters of Po-hang port will be increased the traffic volume and passage of larger vessel according to the opening of Young-il new port in 2006. But the adjacent area of Po-hang port still exist the danger elements of safe navigation, the disordered navigation and traffic congestion. Therefore the safety of traffic must be improved in Po-hang vicinity area. This paper describes the status of marine traffic flow and navigational characteristics based on the marine traffic survey using the exclusive software, and the results of marine traffic survey classify into the ship's types and tonnage and track history of passing ships through the statistical method. Finally the examinations of main traffic route, traffic flow and navigational characteristics are discussed, and these results can be utilized the best design of ship's routing at the Po-hang approaching water.

• Journal of the Korean Society for Nondestructive Testing
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• v.34 no.2
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• pp.155-164
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• 2014

Carbon-fiber-reinforced plastic (CFRP) composites are increasingly being used in a variety of industry applications, such as aircraft, automobiles, and ships because of their high specific stiffness and high specific strength. Aircraft are exposed to high temperatures and high humidity for a long duration during flights. CFRP materials of the aircraft can absorb water, which could decrease the adhesion strength of these materials and cause their volumes to change with variation in internal stress. Therefore, it is necessary to estimate the characteristics of CFRP composites under actual conditions from the viewpoint of aircraft safety. In this study air-coupled ultrasonic testing (ACUT) was applied to the evaluation of water absorption properties of CFRP composites. CFRP specimens were fabricated and immersed in distilled water at $75^{\circ}C$ for 30, 60, and 120 days, after which their ultrasonic images were obtained by ACUT. The water absorption properties were determined by quantitatively analyzing the changes in ultrasonic signals. Further, shear strength was applied to the specimens to verify the changes in their mechanical properties for water absorption.