• International Journal of Naval Architecture and Ocean Engineering
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• v.5 no.2
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• pp.188-198
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• 2013

In constructing a collision avoidance system, it is important to determine the time for starting collision avoidance maneuver. Many researchers have attempted to formulate various indices by applying a range of techniques. Among these indices, collision risk obtained by combining Distance to the Closest Point of Approach (DCPA) and Time to the Closest Point of Approach (TCPA) information with fuzzy theory is mostly used. However, the collision risk has a limit, in that membership functions of DCPA and TCPA are empirically determined. In addition, the collision risk is not able to consider several critical collision conditions where the target ship fails to take appropriate actions. It is therefore necessary to design a new concept based on logical approaches. In this paper, a collision ratio is proposed, which is the expected ratio of unavoidable paths to total paths under suitably characterized operation conditions. Total paths are determined by considering categories such as action space and methodology of avoidance. The International Regulations for Preventing Collisions at Sea (1972) and collision avoidance rules (2001) are considered to solve the slower ship's dilemma. Different methods which are based on a constant speed model and simulated speed model are used to calculate the relative positions between own ship and target ship. In the simulated speed model, fuzzy control is applied to determination of command rudder angle. At various encounter situations, the time histories of the collision ratio based on the simulated speed model are compared with those based on the constant speed model.

• The Journal of the Korea Contents Association
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• v.12 no.11
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• pp.110-118
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• 2012

This study was performed based on "Basic plan of landscape forming project in Jujeon village" which was performed during January ~ August 2011 as a target of "Pilot project of landscape forming in coast village" held by the Ministry of Land, Transport and Maritime Affairs. The project target, Jujeon village, Dong-gu, Ulsan metropolitan city has unique scenery and cultural and historic features. However, its distinct landscape is getting fallen due to insufficient management and development done without considering local feature. Therefore, we need to plan to increase the distinctive place value of coast village, and the landscape color plan is an essential element upon ma king entire harmony of village unit. This study, therefore, aims to suggest authentic landscape color plan and improvement plan of Jujeon village through local color research, local history, geographical feature, and resident sense research of Jujeon village. Especially, for independent landscape color plan for a small village, this study is significant to develop authentic color plan of Jujeon village based on storytelling and to provide possibility in landscape color plan through storytelling in the future.

• International Journal of Naval Architecture and Ocean Engineering
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• v.5 no.1
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• pp.132-146
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• 2013

For several decades, Asian nations such as Korea, Japan and China have been leading the shipbuilding industry since the decline in Europe and America. However, several developing countries such as India, Brazil, etc. are going to make an entrance into the shipbuilding industry. These developing countries are finding technical partners or information providers because they are in situation of little experiences and technologies. Now, the shipbuilding engineering companies of shipbuilding advanced countries are getting a chance of engineering business against those developing countries. The starting point of this business model is green field project for the construction of new shipyard. This business model is started with a design of the shipyard layout. For the conducting of the shipyard layout design, four kinds of engineering parts are required. Those are civil engineering, building engineering, utility engineering and production layout engineering. Among these parts, production layout engineering is most important because its result is the foundation of the other engineering parts and it determines the shipyard capacity during the shipyard operation lifecycle. Previous researches about the shipyard layout design are out of the range from the business requirements because most research cases are in the tower of ivory, which means that there are little consideration of real ship and shipbuilding operation. In this paper, a shipyard layout design for preliminary phase is conducted for the target of newly planned shipyard at Venezuela of South America with an integrated method that is capable of dealing with actual master data from the shipyard. The layout design method of this paper is differentiated from the previous researches in that the actual product data from the target ship and the actual shipbuilding operation data are used for the required area estimation.

• Journal of the Korean Society of Marine Environment & Safety
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• v.25 no.2
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• pp.169-177
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• 2019

It is very important to understand the intention of a target ship to prevent collisions in multiple-ship situations. However, considering the intentions of a large number of ships at the same time is a great burden for the officer who must establish a collision avoidance plan. With a distributed algorithm, a ship can exchange information with a large number of target ships and search for a safe course. In this paper, I have applied a Distributed Stochastic Search Algorithm (DSSA), a distributed algorithm, for ship collision avoidance. A ship chooses the course that offers the greatest cost reduction or keeps its current course according to probability and constraints. DSSA is divided into five types according to the probability and constraints mentioned. In this paper, the five types of DSSA are applied for ship collision avoidance, and the effects on ship collision avoidance are analyzed. In addition, I have investigated which DSSA type is most suitable for collision avoidance. The experimental results show that the DSSA-A and B schemes offered effective ship collision avoidance. This algorithm is expected to be applicable for ship collision avoidance in a distributed system.

• Journal of the Korean Society of Marine Environment & Safety
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• v.25 no.3
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• pp.259-268
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• 2019

Even if only two ships are encountered, a collision may occur due to the mistaken judgment of the positional relationship. In other words, if an officer does not know a target ship's intention, there is always a risk of collision. In this paper, the experiments are conducted to investigate how the intention affects the action of collision avoidance in cooperative and non-cooperative situations. In non-cooperative situation, each ship chooses a course that minimizes costs based on the current situation. That is, it always performs a selfish selection. In a cooperative situation, the information is exchanged with a target ship and a course is selected based on this information. Each ship uses the Distributed Stochastic Search Algorithm so that a next-intended course can be selected by a certain probability and determines the course. In the experimental method, four virtual ships are set up to analyze the action of collision avoidance. Then, using the actual AIS data of eight ships in the strait of Dover, I compared and analyzed the action of collision avoidance in cooperative and non-cooperative situations. As a result of the experiment, the ships showed smooth trajectories in the cooperative situation, but the ship in the non-cooperative situation made frequent big changes to avoid a collision. In the case of the experiment using four ships, there was no collision in the cooperative situation regardless of the size of the safety domain, but a collision occurred between the ships when the size of the safety domain increased in cases of non-cooperation. In the case of experiments using eight ships, it was found that there are optimal parameters for collision avoidance. Also, it was possible to grasp the variation of the sailing distance and the costs according to the combination of the parameters, and it was confirmed that the setting of the parameters can have a great influence on collision avoidance among ships.

• The Journal of the Acoustical Society of Korea
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• v.38 no.2
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• pp.168-176
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• 2019

When an array receives a signal with a frequency higher than the design frequency, there is an ambiguity in beamforming due to spatial aliasing. In order to overcome this problem, Abadi proposed frequency-difference beamforming. However, there is a constraint that the minimum frequency bandwidth is required according to the value of the difference frequency. In this paper, we propose a method to find the direction of the target signal with spatial aliasing based on the frequency-wavenumber spectrum combined with Radon transform. The proposed method can estimate the direction of the target without ambiguities when the signal has nonnegligible bandwidth. We tested the algorithm by simulating a broadband signal and verified the results with the frequency-difference beamforming method using SAVEX15 (Shallow Water Acoustic Variability EXperiment 2015)'s shrimp noise data.

• Proceedings of the Korean Institute of Navigation and Port Research Conference
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• 2004.11a
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• pp.169-174
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• 2004

To design ship channel is one of important factors for planning and developing a port. In most case, the core factors for designing ship channel are the layout and width of dvnnel provided the net underkeel clearance is assessed as safety. In this study, Variable Bumper Area(VBA) model is applied to design and assess ship channel. This model reflects ship's principle dimension, ship domain theory, ship speed, conning officer's ship handling skill and experience and all external forces which cause leeway, set and drift and the change of ship maneuvering characteristics. Full Mission Ship Handling Simulator is used to analyze ship dynamic data according to conning officer's ship control, external forces, etc. This model uses Domain-index for assessing the efficiency and safety of the channel. The proposed model is applied to Ulsan new port plan which has a channel width of 1.5 times the length if the largest vessel, a radius if 5 times the length of the largest vessel in a curve of 57 degree centerline angle and SBM facility adjacent to the lateral edge if channel. The result of this study shows tint the width and radius of channel curve are suitable for the target ship but the difficulty of ship handling is caused by the large course change and SBM located in the vicinity if channel.

• Journal of the Korean Society of Marine Environment & Safety
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• v.24 no.5
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• pp.497-503
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• 2018

Passenger ships and training ships have a common feature in that they serve many passengers. Thus, safe navigation is very important. During normal sailing, a ship may turn using various types of steering, including maneuvers to avoid collisions with dangerous target. When a ship turns, a heeling angle occurs. If trouble arises during sailing, a dangerous heeling angle may result or a capsizing accident. In this study, the heeling angle during turning was measured through experimentation with two training ships similar to passenger ships. These findings were compared with theoretical formulas for heeling angle when turning. We confirmed that the limit of the maximum heeling angle estimation using heeling angle formula when turning presented in IMO stability criteria. In addition, it was confirmed that the maximum estimated heeling angle can be reached by applying the result calculated in the theoretical formula 1.4 times when turning right and 1.1 times when turning left to reflect sailing speed when of rudder hard over. It is expected that this study will provide basis data for establishing safe operation standards for the prevention of dangerous heeling angles when turning.

• Journal of Korean Society of Coastal and Ocean Engineers
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• v.30 no.2
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• pp.39-50
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• 2018

In this study, the nonlinear interaction of irregular waves with wave breaking and currents around permeable submerged breakwater was investigated with the aid of olaFlow model which is open source CFD software published under the GPL license. The irregular wave performance of olaFlow applied in this study was verified by comparing and evaluating the target frequency spectrum and the generated frequency spectrum for applicability to irregular waves. Based on the applicability of this numerical model to irregular wave fields, in the coexistence fields of irregular waves and currents, the characteristics of wave height, frequency spectrum, breaking waves, averaged velocity and turbulent kinetic energy around porous submerged breakwater with the respect to the beach type and current direction versus wave propagation were carefully investigated. The numerical results revealed that the shape of wave breaking on the crown of the submerged breakwater and the formation of the mean flow velocity around the structure depend greatly on the current directions and the type of the beach. In addition, it was found that the wave height fluctuation due to the current direction with respect to the wave propagation is closely related to the turbulent kinetic energy.

• Journal of Navigation and Port Research
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• v.29 no.1 s.97
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• pp.9-15
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• 2005

To design ship channel is one of important factors for planning and developing a port. In most case, the core factors for designing ship channel are the layout and width of channel provided the net underkeel clearance is secured to be safe enough to pass. In this study, Variable Bumper Area(VBA) model is applied to design and assess ship channel. This model reflects ship's particular, ship domain theory, ship speed and mariner's ship handling skill and experience, especially external forces which cause leeway, set and drift and the change of ship maneuvering characteristics. A real time, full mission shiphandling simulator is used to analyze ship dynamic data according to mariner's ship control, external forces, ete. This model defines Domain degree and Domain-index for assessing the efficiency and safety of the channel. The proposed model is applied to Ulsan new port plan which has a channel width of 1.5 times the length of the largest vessel, a radius of 5 times the length of the largest vessel in a curve of 57 degree centerline angle and SBM facility adjacent to the lateral edge of channel. The result of this study shows that the width of the channel and radius of channel curve are suitable for the target ship but the difficulty of ship handling is caused by the large course change and SBM located in the vicinity of channel.