• Proceedings of the Korean Institute of Navigation and Port Research Conference
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• 2007.12a
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• pp.376-382
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• 2007

A Collapse of bridge by ship's collision to the bridge post may lead a great calamity. This paper investigates on avoiding collision between a ship and bridge by improvement of environmental factors, submitting a counter plan of reducing collision effect by triangular type of collision protecting bar and ship maneuvering skills. Putting up collision protecting bar fences of triangular type around the bridge posts would decrease the collision impact force by 75 percent.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2003.11a
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• pp.672-676
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• 2003

Recently, the importance of ship vibration is emerging due to the large scaling, high speed and lightning of ship. For pleasantness in a cabin, shipbuilders ask for strict vibration criteria and the degree of vibration level at a deckhouse became an important condition for taking order from customers. This study conducted optimum design to attenuate vibration level of a deckhouse to solve above problems. New method was implemented, that is NASTRAN external call type independence optimization method. The merit of this method is global searching after setting various object functions and design variables. The global optimization algorithm used here is R-Tabu search method, which has fast converging time and searching various size domains. By modeling similar type to ship structure, validity of the suggested method was investigated.

• Proceedings of the Korean Institute of Navigation and Port Research Conference
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• 2022.06a
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• pp.106-107
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• 2022

The ship type identification of the surrounding ship is important information for navigators and VTS officers since they can estimate the maneuverability and near-future route of the ships. However, it is more than frequent that the information is not provided due to transmission trouble and seafarers' unfamiliarity with AIS. Thus, this study suggests predicting ship types through the Random Forest classifier after preparing a training and test dataset that contains ship features and types. The AIS data for Ulsan coast in 2018 was used for this study. The method may provide the effect that many navigators and VTS officers discuss and share the experience of predicting ship types.

• Journal of Navigation and Port Research
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• v.44 no.4
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• pp.275-282
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• 2020

Recently, the occurrence of a ship capsizing was analyzed as the main cause of the lack of stability or loss because of the improper management of the center of gravity, the movement of cargo or heavy weight when excessive steering occurs or when navigating during bad weather. Thus, to prevent a ship from capsizing, it is necessary to secure stability to enable the ship's return to its upright position, even if a dangerous heel occurs. The GM is a crucial evaluation factor regarding stability, which the navigation officer uses to preserve stability. In this study, based on the stability data collected from the operating of ships for five years, The GM by ship's type according to the operating status was analyzed specifically such as a ship's length, breadth, and gross tonnage. The feature of the GM distribution according to a ship's length was confirmed, and after performing the correlation analysis between the breadth and the GM, the ratio of the GM to breadth was calculated, and the result was compared with the previous ratio. Additionally, a simple approximation formula and minimum GM for the estimation of the GM by ship type were proposed by the regression analysis of the GM using the gross tonnage (GT)/breadth (B) to reflect the trend of larger ships being built. The results of this study are expected to be used as data for the review of securing a stable GM on ships.

• Proceedings of the Korea Committee for Ocean Resources and Engineering Conference
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• 2001.05a
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• pp.266-269
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• 2001

This paper describes the effect of hull form on motion characteristics of FPSO. The purpose of the present study is to investigate seakeeping performance of ship type FPSO in comparison with those of barge type FPSO. Model test result shows that the barge type FPSO is better in heave and pitch motion, while the ship type FPSO is superior in roll motion.

• Proceedings of the KWS Conference
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• 2009.11a
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• pp.102-102
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• 2009

The purpose of this study is to establish the predictive equation of transversal residual stress at the thick weldment of large container ship. In order to do it, the variables used for this study were restraint degree, yield strength of base material, thickness of weldment and welding heat input. Here, the level of restraint degree at the thick weldment of container ship having the various welding sequence was calculated using FEA. From the result, the h-type specimen was designed to simulate the level of restraint degree at the actual weldment of containership. With H-type test specimen designed, the effect of the variables on the distribution of transversal residual stress at the weldment in a container ship was evaluated using the comprehensive FEA. Based on the results, the predictive equations of mean value and the distribution of transverse residual stress in each location of residual stress were established using dimensional analysis and multiple-regression method. The validation of predictive equations was verified by comparing with measured results by XRD in the actual weldment of the ship.

• Proceedings of the KSME Conference
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• 2000.04a
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• pp.714-719
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• 2000

In this paper, an application program is made to simulate the behavior of a ship block under various crane works and to generate data of lu9 reactions and wire tensions. The program is based on a CAD program, Pro/ENGINEER. A ship is composed of more than 100 ship blocks. In order to lift, move, turn, or put a ship block at a convenient location fur assembling, workers in a shipyard use cranes, wires, and lugs temporarily attached to the block. In the procedure of lifting and turning a ship block with a crane, it is important to find suitable lug points and wires to do the handling efficiently and prevent accidents. Evaluation of forces in lugs and wires is necessary, but the problem is rather complex due to nonlinearity and nonuniqueness. In the present development, the nonlinear system of equations for quasi-static equilibriums is derived and a Newton type solution method is adopted to solve the system. The importance of initial estimates to the solution is illustrated and two approaches are utilized and compared. With the program developed, users can assign lug points on the CAD model by mouse and choose various linking devices at each crane point. Users can try to simulate the motion for any prescribed conditions, compare the motion of the block and the reactions and choose appropriate lug points and the type of wires and lugs.

• Journal of the Korean Institute of Navigation
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• v.9 no.2
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• pp.13-26
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• 1985

The purpsoe of automatic steering system is to keep the ship's course stable with the minimum course error and rudder angle, and there have been a number of studies as to the optimal design and adjustment of the autopilot. Recently, modern control theories are being used widely in analyzing and designing the system. When a ship is at sea, autopilot installed on the ship plays an important role, particularly in the respect of economic aspects, that is, when the design and the adjustment of adjustable parameters are not conducted perfectly, the amount of loss in energy and the extension of sailing distance become large. Therefore the optimal design and adjustment of a autopilot are very important. Though P.I.D type autopilots are widely spread and generally used in modern ships, the suitability and the adjusting method are not clarified. In this paper the authors considered the stabilaity and the economical efficiency of the P.I.D. type autopilot and investigated various facts which should be considered at the time of designing and using the P.I.D. type autopilot through the digital computer simulation.

• Journal of the Society of Naval Architects of Korea
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• v.52 no.2
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• pp.135-142
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• 2015

The Anti-Rolling Tank(ART) has an advantage over the other roll stabilizing devices, when ship is staying and working at one site of sea. An important design point of ART is the tank tuning, that is, matching the tank natural period to the ship's roll natural period. Since the load condition and consequently the roll natural period of ship is to be changed widely, the natural period of ART also has to be changed widely. In case of the existing U-tube type ART with a single layer duct, the tank natural period can be changed in a relatively narrow range. This paper suggests a new U-tube type ART system using a double layer duct to enable wide change of ART natural period. Through the roll experiments performed in regular beam waves for a box-type model ship, it is shown that the double layer duct ART has about two times wider period range and a better reducing effect of roll magnitude than the single layer duct ART.

• Proceedings of the KIPE Conference
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• 2008.06a
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• pp.136-138
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• 2008

The output voltage of synchronous generator is regulated constantly by field current control in excitation system. Most of ship generator exciter system uses the thyristor phase controlled rectifier. However this rectifier is difficult to realize that the speed control system because its control period is slower than MOSFET and IGBT type converter. Therefore, this paper deals with PMG(Permanent Magnet Generator) type digital excitation system using MOSFET for ship synchronous generator. The organization of this excitation system is very simple. When the generator is under the short circuit accident, the output voltage becomes zero state and AVR can not operate. Thus generator requires the function for flowing output current through CBS. The performance of the proposed system is evaluated on a 10kVA experimental prototype circuit in place of real ship generator.