• Korean Journal of Computational Design and Engineering
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• v.16 no.3
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• pp.207-215
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• 2011

Due to its large size, a ship is first divided into scores of blocks and then each block is constructed through various shops, such as the assembly shop, the painting shop, and the outfitting shop. However, each block may not be directly moved to the next shop and may be temporarily laid on a block stockyard because the working time in each shop is different. If blocks are laid on the block stockyard without any planning, the rearrangement of the blocks by a transporter are required because the blocks have the different in and out time. In this study, an optimal layout method based on the genetic algorithm was proposed in order to minimize the rearrangement of the blocks in the block stockyard. To evaluate the applicability of the proposed method, it was applied to a simple layout problem of the block stockyard.

• Journal of the Korean Society of Manufacturing Process Engineers
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• v.16 no.1
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• pp.51-57
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• 2017

In the present study, the long-pitch roller-chain of a continuous ship unloader is studied. It is the vertical excavating and transporting the cargo has carried in bulk amount. The size of the pitch in the long-pitch roller chain is about 350 mm. The finite element technique is used for the structural safety of the roller chain. The objective of the study is to perform a dynamic analysis of the load at the point of contact with the sprocket of the roller chain, and analyze each point in the stress of the chain's components by using load. From the tooth sprocket optimization analysis, the results show an optimal design. Static structural analysis was safe. Contact analysis results show the greatest stress on the sprocket. By increasing the tooth size, the stress was reduced.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.16 no.3
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• pp.1853-1862
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• 2015

Naval maintenance system carries out repairs of battle ships. Korean Navy has four maintenance stations to maximize the readiness of the battle ships. Since each station can provide different services according to characteristics(specific size of ships, type of maintenances) and the maintenance ability of stations is predetermined, it has been one of complex problems for the Korean Navy to find the optimal resource allocation. We investigate the operation of the stations from the perspective of the human resource allocation which plays crucial role in the performance of the maintenance stations. Using a queueing model and optimization technique, we present a way to derive the optimal personnel allocation which minimize the waiting number of battle ships at each station, leading to the improvement of the military readiness in the Korean Navy.

• Transactions of the Korean Society for Noise and Vibration Engineering
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• v.23 no.3
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• pp.209-217
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• 2013

This paper presents an optimal design of a magnetorheological(MR) fluid-based mount(MR mount) that can be used for to vibration control in diesel engines of ships. In this work, a mount that uses mixed-modes(squeeze mode, flow mode, and shear mode) is proposed and designed. To determine the actuating damping force of the MR mount required for efficient vibration control, the excitation force from a diesel engine is analyzed. In this analysis, a model of a V-type engine is considered. The relationship between the velocity and pressure of gas in terms of the torque acting on the piston is derived. Subsequently, by integrating the field-dependent rheological properties of commercially available MR fluid with the excitation force, the appropriate size of the MR mount is designed. In addition, to achieve the maximum actuating force under geometric constraints, design optimization is undertaken using the ANSYS parametric design language software. Through magnetic density analysis, optimal design parameters such as the bottom gap and radius of coil are determined.

• Journal of the Korean Society of Marine Environment & Safety
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• v.25 no.5
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• pp.617-626
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• 2019

This study analyzes the optimal location of gas detectors through the gas dispersion in a cargo compressor room of a 174K LNG carrier equipped with high-pressure cargo handling equipment; in addition, we propose a reasonable method for determining the safety regulations specified in the new International Code of the Construction and Equipment of Ships Carrying Liquefied Gases in Bulk (IGC). To conduct an LNG gas dispersion simulation in the cargo compressor room-equipped with an ME-GI engine-of a 174 K LNG carrier, the geometry of the room as well as the equipment and piping, are designed using the same 3D size at a 1-to-1 scale. Scenarios for a gas leak were examined under high pressure of 305 bar and low pressure of 1 bar. The pinhole sizes for high pressure are 4.5, 5.0, and 5.6mm, and for low pressure are 100 and 140 mm. The results demonstrate that the cargo compressor room will not pose a serious risk with respect to the flammable gas concentration as verified by a ventilation assessment for a 5.6 mm pinhole for a high-pressure leak under gas rupture conditions, and a low-pressure leak of 100 and 140 mm with different pinhole sizes. However, it was confirmed that the actual location of the gas detection sensors in a cargo compressor room, according to the new IGC code, should be moved to other points, and an analysis of the virtual monitor points through a computational fluid dynamics (CFD) simulation.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.18 no.6
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• pp.389-394
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• 2017

In a conventional ship structure, stiffeners with an asymmetric section, such as inverted angles, are used widely despite the disadvantage of strength compared to the stiffeners with a symmetric section, such as a built-up T. On the other hand, T-type built-up members are attracting more attention than L-type inverted angles due to the increased size of ships. The purpose of this study was to develop an optimal design program for a built-up T, and apply an evolution strategy as an optimization technique. In the optimization process, the gross thickness concept was adopted for the design variables and objective function, and the constraints are set up based on HCSR (Harmonized Common Structural Rules). Using the developed program in this study, the optimal stiffener design was carried out for 300K VLCC and 158K COT of which the orders were obtained lately. The optimal results revealed the weight reduction effect of 144 tons and 60 tons, respectively.

• Journal of the Korean Society of Propulsion Engineers
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• v.17 no.4
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• pp.1-9
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• 2013

An active anti-ship missile decoy system was designed conceptually to analyze propulsion system requirements and feasibility to use a liquid bi-propellant rocket engine. Overall mass, size, and shape were assumed referring to specifications of Nulka which was developed by US and Australia in 1990s. The propulsion system was assumed to be a 1,000 N-class $H_2O_2$/kerosene rocket engine with a pressurized feed system. A three-degree-of-freedom optimal trajectory was calculated based on the assumptions, and mass budget was designed from the calculation results. It was found that the requirements for the propulsion system is that it shall be operated more than 100 sec; it shall be re-ignitable; it shall have a throttle capability of a range from 35% to 100% when the maximum thrust at sea level is 1,000 N.

• Journal of Ship and Ocean Technology
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• v.5 no.2
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• pp.14-26
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• 2001

This paper presents a novel design approach that could generate structural design alternatives having different topologies and then, select the optimum structure from them with simulataneously determining its optimum design variables related to geometry and the member size subjected to the multiple objective design environments. For this purpose, a specialized genetic algorithm, called StrGA_DeAl + MOGA, which can handle the design alternatives and multi-criteria problems very effectively, is developed for the optimal structural design. To validate the developed method, method, plain truss design problems are considered as illustrative example. To begin with, some possible topological of the truss structure are suggested based on the stability criterion that should be satisfied under the given loading condition. Then, with the consideration of the given multi-criteria, several different topology forms are selected as design alternatives for the second step of the conceptual design process. Based on the chosen topolgy of truss structures, the sizing or shaping optimization process starts to determine the optimum design parameters. Ten-bar truss problems are given in the paper to confirm the above concept and methodology.

• International Journal of Naval Architecture and Ocean Engineering
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• v.5 no.3
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• pp.376-391
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• 2013

Brackets in ships and offshore structures are added structures that can endure stress concentrations. In this study, a concurrent engineering solution was proposed, and a high strength low carbon cast steel alloy applicable to offshore structures was designed and developed. The yield strength and ultimate tensile strength of the designed steel were 480 and 600 MPa, respectively. The carbon equivalent of the steel was 0.446 with a weld crack susceptibility index of 0.219. The optimal structural design of the brackets for offshore structures was evaluated using ANSYS commercial software. The possibility of replacing an assembly of conventional built-up brackets with a single casting bulb bracket was verified. The casting process was simulated using MAGMAsoft commercial software, and a casting fabrication process was designed. For the proposed bulb bracket, it was possible to reduce the size and weight by approximately 30% and 50%, respectively, compared to the conventional type of bracket.

• Journal of Korea Port Economic Association
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• v.29 no.4
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• pp.73-95
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• 2013

This paper analyzes a competitive shipping market in East Asia in order to explore how container carriers make decisions on ship size, number of ships, service frequency, and service route. A sequential-move game based on non-cooperative game theory is applied to establish the models for the decision-makings involving the transportation volumes, freight rates, costs, and market shares of the service routes from Shanghai or Hong Kong to the ports in Busan, Gwangyang, and Incheon. According to the sub-game perfect Nash equilibrium solutions proposed by these models, carriers' decisions in such a competitive environment vary depending on sailing distance, transport demand, and freight rates. Therefore, carriers are recommended to reflect the optimal equilibrium solutions and a variety of decision factors when formulating strategies for transportation networks and operating fleets. Furthermore, ports should establish management strategies for these factors to provide optimal equilibrium solutions for carriers' transportation networks.