• Proceedings of the Korean Institute of Navigation and Port Research Conference
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• 2015.10a
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• pp.20-23
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• 2015

In ports of Korea, the marine traffic flow is congested due to a large number of vessels coming in and going out. In order to improve the safety and efficiency of these vessels, South Korea is operating with a Vessel Traffic System, which is monitoring its waters 24-7. However despite these efforts of the VTS (Vessel Traffic System) officers, marine accidents are occurring in their assigned districts. VTS Officers are controlling subjectively based on their experience due to no VTS guideline. On this paper, we listened to Busan VHF channel for 3days and applied to collision risk model. With collision risk model, We deducted a moment which advise or recommend to vessel in encounter situation, VTSO's career, day&night.. We suggested a collision risk value as guide line of VTSO's control time.

• Bulletin of the Society of Naval Architects of Korea
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• v.23 no.4
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• pp.25-34
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• 1986

A two-dimensional linear method has been developed for the motion and the second-order steady force arising from the hydrodynamic coupling between waves and currents in the presence of a body of arbitrary shape. Interaction between the incident wave and current in the absence of the body lies in the realm beyond our interest. A Fredholm integral equation of the second kind is employed in association with the Haskind's potential for a steadily moving source of pulsating strength located in or below the free surface. The numerical calculations at the preliminary stage showed a significant fluctuation of the hydrodynamic forces on the surface-piercing body. The problem is approximately solved by using the asymptotic Green function for $U^2{\rightarrow}0$. The original Green function, however, is applied for the fully submerged body. Numerical calculations are made for a submerged and for a half-immersed circular cylinder and extensively for the mid-ship section of a Lewis-form. Some of the results are compared with other analytical results without any available experimental data. The current has strong influence on roll motion near resonance. When the current opposes the waves, the roll response are generally negligible in the low frequency region. The current has strong influence on roll motion near resonance. When the current opposes the wave, the roll response decreases. When the current and wave come from the same direction, the roll response increases significantly, as the current speed increases. The mean drift forces and moment on the submerged body are more affected by current than those on the semi-immersed circular cylinder or on the ship-like section in the encounter frequency domain.

• Proceedings of the Korean Institute of Navigation and Port Research Conference
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• 2003.05a
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• pp.192-197
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• 2003

A virtual vessel traffic control system is introduced to contribute to prevent a marine accident, e.g. ship collision or stranding. from happening. The system that comes from VTS limitaions, consists of both data acquisition by satellite remote sensing and a simulation of traffic environment stress (here, INOUE model used) based on the satellite data. Remotely sensed data cab be used to provide timely and detailed information about the marine safety, including the location, speed and direction of ships, and help us operate vessels safely and efficiently. If in the future, e.g. 5-minute after, environmental stress values that a ship may encounter on a voyage can be available, proper actions can be taken to prevent accidents. It lastly can be shown that JERS satellite data are used to track ships and extract their information.

• Journal of Navigation and Port Research
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• v.40 no.3
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• pp.105-111
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• 2016

In ports of Korea, the marine traffic flow is congested due to a large number of vessels coming in and going out. In order to improve the safety and efficiency of these vesse's movement, South Korea is operating with a Vessel Traffic System, which is monitoring its flow 24-7. However despite these efforts of the VTS (Vessel Traffic System) officers, marine accidents are occurring continuously in their control area. VTS Officers are controlling subjectively based on their experience due to no VTS control guideline of dangerous situation among vessels. On this paper, we listened to Busan VHF channel for 3days and analyzed the message. With collision risk model, We analyzed a moment of risk which officers advise or recommend to vessel in encounter situation, VTSO's career, and day&night.

• Strategy21
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• s.40
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• pp.5-36
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• 2016

Recently, the Japanese government revised the three guidelines of its security policy, the National Security Strategy(NSS), the National Defense Program Outline and Midterm Defense Buildup Plan, exceptionally at one time. This means Japan has been seeking the new strategy and strengthening military power considering changing regional security environment. Moreover, Japan revised the security laws for the right to collective self-defense, which authorized the use of force even when Japan is not under attack. Also, Japan renewed the Guidelines for Japan-U.S. Defense Cooperation in twenty years, and has expanded JSDF's scope of activity to a worldwide level. These changes imply Japan would constantly seek to build military forces focusing on naval forces. Because Japan's naval forces, the JMSDF is the means that allow Japan to use its force at anywhere overseas and expand its roles and missions in international society by the basis of the right to collective self-defense. This research will analyze Japan's new maritime strategy and trend of force development and eventually look for the implication on our maritime security These days, Japan has perceived Chinese rapid increase of naval power and pursuing of maritime hegemony as a grave threat. In response to this, Japan is designing new maritime strategy, which are "remote islands defense and recapture" and proactively develop a new type of naval forces to accomplish this new strategy. The Japan's "remote island defense and recapture strategy" is to harden its defensive posture in Nansei islands which correspond to China's 1st island chain for chinese A2/AD strategy and directly encounter with China and to protect its own dominium and maritime interest while supporting US national strategy in East Asia. Japan continues to build compact, multi-functional ship to accomplish "remote island defense and recapture strategy" and keep strengthening its maritime power projection capability to include build of new amphibious ship, and large, multi-functional ship which can provide effective C2. These changes imply that Japan is shifting its strategy from passive and defensive to proactive and aggressive way and continues to pursue naval buildup.The implication of Japan's new maritime strategy and naval buildup needs to be observed carefully and we need to keep developing naval power required to protect our maritime sovereignty and interest.

• Journal of the Korean Society of Marine Environment & Safety
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• v.18 no.2
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• pp.153-159
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• 2012

This study gives the vertical motion analysis in multi-directional irregular waves using a commercial code(MAXSURF v.16) based on linear strip theory for a training ship. To verify the commercial code prior to the analysis, we guarantees the reliability of this paper's results using the commercial code by comparing with the results(Flokstra, 1974) of same hull and experimental conditions on a Panamax container. The analysis conditions are Beaufort wind scale No. 5($\bar{T}=5.46$, $H_{1/3}=2m$) based on ITTC wave spectrum, encounter angle Head & bow seas($150^{\circ}$) and Froude number Fn=0.257. Finally, we calculates heave RAO, pitch RAO and obtains the result of ship's response spectra for heave and pitch motions. In the motion response spectrum under the multi-directional irregular waves, heave motion reacts slightly high in short-crested waves and pitch motion reacts high in long-crested waves.

• Journal of the Korean Society of Marine Environment & Safety
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• v.17 no.3
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• pp.227-233
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• 2011

Korea coastal area is highly potential dangerous zone of marine accident due to frequent ship's encounters. VTS center can't identify ship's information because of beyond VHF range. It is also difficult of us to efficiently manage vessel traffic beyond VTS control area, so that it can't prevent marine accident. Presently, korean government is conducting maritime traffic safety assessment according to enlargement of harbor & development of new port but do not have the system which provide danger of information depending on maritime traffic environment with real time. So it is necessary to develop evaluation index which can assess sea risk through the evaluation of maritime traffic environment. In this paper, on the basis of vessel navigator's risk consciousness, we carried out survey & statistical analysis vessel navigator's subjective risk depending on the LOA, crossing situation($045^{\circ}$, $090^{\circ}$, $135^{\circ}$), overtaking, head-on situation, encountering vessel's side, within or outside harbor, speed with other vessel(ex. same, fast or slow), speed difference with other vessel and distance with other vessel & propose basic expression to develop maritime traffic safety evaluation model. And by using this model, we can confirm that this proposing expression is suitable for domestic maritime traffic environment.

• Journal of Advanced Research in Ocean Engineering
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• v.1 no.4
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• pp.252-267
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• 2015

Offshore structures might encounter several environmental and operating conditions during their lifetime of several decades. In order to predict the dynamic behavior of offshore structures, several simulation cases should be considered to deal with all the combinations of ocean environments and operating conditions. Because a sophisticated time-domain coupled dynamic analysis requires an extremely large amount of computational time to handle all the possible cases, an efficient preliminary process to prescreen the probability of severe environmental conditions can be helpful in downsizing the number of simulation cases and computational effort. In this study, a prescreening procedure to reduce the number of environmental conditions for dynamic analyses of offshore structures is proposed. For the efficiency of the procedure, frequency-domain theories were adopted to estimate the platform offset, using quasi-static analyses in line tension prediction. The results were validated by comparing with those of dynamic analysis coupled between platform and mooring lines, and reasonable agreement was observed. In addition, the characteristics of environmental conditions classified to be severe to the system were investigated through the application of the developed prescreening scheme to several actual environmental conditions.

• Journal of the Korean Society of Marine Environment & Safety
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• v.14 no.1
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• pp.65-69
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• 2008

Now it is said that the insufficency of the designated anchorage for ships in approaching waters of Wan-do port is the one of reasons for marine safety accidents, when vessels encounter rough weather near the port. This research examined geographical feature in approaching areas of Wan-do port and suggested appropriate weather anchorage. The situations of fishing nets areas were investigated Marine vessel traffic flow was also examined. Through these research the optimal anchorage was suggested in the approaching waters of Wan-do port.

• Bulletin of the Society of Naval Architects of Korea
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• v.26 no.1
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• pp.1-10
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• 1989

When a ship is travelling in following seas, the encounter frequency is reduced to be very low. n that case surf-riding, broaching-to and capsizing phenomena are most likely to occur. In the present paper, the emphasis is laid upon the transverse stability of ships in following seas, which is related to capsizing phenomenon. The authors intend to clarify the mechanism of the stability variation in following seas. In order to predict that variation, the theoretical calculation method and computer programming are developed. The theoretical calculation is based on Froude-Krylov Hypothesis and static equilibrium condition in waves. Through the application of present calculation method to cargo vessel and fishing boat, it is verified that the transverse stability in following seas with crest amidships can be reduced to a half extent in comparison with calm water stability. On the other hand, the present calculation results are compared with existing experimental data.