• Journal of the Korean Society of Fisheries and Ocean Technology
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• v.39 no.4
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• pp.291-297
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• 2003

Al-brass is usually used as the tube material of vessel's heat exchanger for seawater cooling system because it has high thermal conductivity and good mechanical properties and high corrosion resistance due to cuprous oxide (Cu20) layer against seawater. However, Al-brass tubes of heat exchanger for vessel at the actual environment is reported that local corrosion such as stress corrosion cracking occurred by synergism effect between mechanical factor and corrosion environment In this paper, the effect of corrosion environment on the stress corrosion cracking of Al-brass in various NH4OH of 3.5% NaCl solution, under flow by constant displacement tester. Based on the test results, the behavior of polarization, stress corrosion crack propagation and dezincification phenomenon of Al-brass are investigated. The main results are as follows：(1) Increasing range of potential from open circuit potential to repassivation gets lower, as the contain rate of NH4OH gets higher. (2) As contain rate of NH4OH gets higher, SCC of Al-brass is become activation but the protection film(Cu20) of Al-brass is created in 3.5% NaCl solution. (3) According as content of NH4OH increases in 3.5% NaCl solution, the dezincifiction area is spread. It is concluded that dezincification occurred by localized preferential anodic dissolution at stress focusing region.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.8 no.4
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• pp.782-786
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• 2004

The Wireless-LAN was developed and Wired-LAN substitution from the field which the space where it is restricted is special it used. But, from the field which is various the use is attempted to listen to recently. The shedding of blood which the oceanic accident which occurs recently5 year for is principal is The GMDSS with the formation vessel which is managed with agreement depends here upon and it is a collision of the small-sized vessel which is not managed. Cause the Facilities for the safety-communications system is not introduced is the actual condition in poverty of the small-sized vessel. In this study, recently with the AIS where becomes the introduction it proposed similar function the system which is cheap it does.

• Nuclear Engineering and Technology
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• v.51 no.3
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• pp.723-730
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• 2019

Acquiring instrumentation signals generated from nuclear power plants (NPPs) is essential to maintain nuclear reactor integrity or to mitigate an abnormal state under normal operating conditions or severe accident circumstances. However, various safety-critical instrumentation signals from NPPs cannot be accurately measured on account of instrument degradation or failure under severe accident circumstances. Reactor vessel (RV) water level, which is an accident monitoring variable directly related to reactor cooling and prevention of core exposure, was predicted by applying a few signals to deep neural networks (DNNs) during severe accidents in NPPs. Signal data were obtained by simulating the postulated loss-of-coolant accidents at hot- and cold-legs, and steam generator tube rupture using modular accident analysis program code as actual NPP accidents rarely happen. To optimize the DNN model for RV water level prediction, a genetic algorithm was used to select the numbers of hidden layers and nodes. The proposed DNN model had a small root mean square error for RV water level prediction, and performed better than the cascaded fuzzy neural network model of the previous study. Consequently, the DNN model is considered to perform well enough to provide supporting information on the RV water level to operators.

• Journal of the Society of Naval Architects of Korea
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• v.56 no.3
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• pp.231-241
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• 2019

In this study, a simplified analysis method was developed to evaluate the fatigue damage of an ice-going ship under broken ice condition. The global ice load, which is essentially calculated at the design stage of the Arctic vessel, and the hull form information were used to estimate the local ice load acting on the outer-shell of the ship. The local ice load was applied to the finite element analysis model, and the Weibull parameters for the target fatigue point were derived. Finally, fatigue damage was evaluated by applying the S-N curve and the Palmgren-Miner rule. For the verification of the proposed method, numerical analyses using direct approach were performed for the same conditions. A numerical model that implements the interaction between ice and structure was introduced to verify the local ice load and the stress calculated from the proposed method. Finally, the fatigue analyses of the Baltic Sea for actual ice conditions were performed, and the results of the proposed method, the method using numerical analysis, and the LR method were compared.

• Transactions of the Korean Society of Mechanical Engineers
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• v.17 no.10
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• pp.2634-2645
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• 1993

Dome structures of pressure vessels subjected to internal pressure are usually analyzed by linear elastic theory assuming small deformation. Geometric and material nonlinear behaviors appear in actual dome structures because of large deformation and loads exceeding yield strength. In this paper, linear and nonlinear analyses were performed for various hemispherical and torispherical domes to check the effects of geometric and material nonliearity on the stress and displacement by the finite element method. The effect of the geometric nonlinearity decreased the stress levels a lot for very thin general torispherical domes, which enables more realistic and effective design. The material nonlinear effects are negligible for hemispherical and optimum torispherical domes, and those are large for most of the general torispherical domes.

• International Journal of Precision Engineering and Manufacturing
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• v.5 no.1
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• pp.55-59
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• 2004

This study developed a fully automated test system for pressure vessels, containing such as oxygen, nitrogen, which is widely used in many industries. The pressure vessel test has three major parts including weight measurement test, water-hydraulic test and leakage test followed by cleaning and drying. The control system for these tests consists of three parts: a PLC, a monitoring system and a database management system. The PLC oversees overall control of test machines, while the monitoring system measures and displays weight, pressure, flow etc. for every situations, and the database management system stores test data. These three modules are designed to communicate with one another at 1 Hz frequency alerting problematic situations to the operator. The system has gone through actual field tests for verification of performances.

• Journal of the Korean Institute of Navigation
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• v.10 no.2
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• pp.11-29
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• 1986

As per the expanding needs of marine exploitation, many floating structures have been built. Among these, box-type vessel is considered as the most basic shape, to which plant barges and crane barges belong. Stability problem is very important for vessel. In order to increase transverse stability, this paper employs bulwarks along the upper deck sides of box-type vessels and the emphasis is laid upon the effect of bulwarks on transverse stability. In the present paper, the calculation method of heeling moment acting to the ship due to hydrostatic pressure is suggested, and actual procedures of the calculation for box-type vessels with bulwarks are shown. Furthermore corresponding model tests are carried out in small water tank. Through the comparison between calculated and measured values, it is confirmed that the preset calculation method is useful. And employing bulwarks on box-type vessels is very effective for increase of transverse stability at the heeling angles from about 15 degrees to about degrees.

• Proceedings of the Korean Society for Technology of Plasticity Conference
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• 2008.05a
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• pp.349-352
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• 2008

In this study, a design method of developed shape for double-curved pressure vessel segment heads was proposed in consideration of in-plane strain induced by forming works. In order to obtain the developed shape of double-curved plate, at first, the segments are subdivided into elements and then they are stacked into a series of strips producing the outline of the approximately developed shape. The developed shape was determined by imposing the in-plane displacement obtained from forming analysis and regression analysis on the outline of the approximately developed shape. The validation of the proposed design method was verified by applying it to the actual products.

• Transactions of the Korean Society of Pressure Vessels and Piping
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• v.14 no.2
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• pp.16-23
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• 2018

In order to investigate the ways to enhance the seismic performance of APR1400 seismic fragile equipment by direct design changes, four equipment such as Reactor Vessel Support, Integrated Head Assembly, Remote Shutdown Console, and Pressurizer are reviewed using information of the main dimensions, seismic stress evaluation results, design FRS, etc. in this paper. In addition to the direct reinforcement of equipments, the feasibility of seismic isolation for the safety related cabinet is also investigated and the actual adaption plan of a commercial spring-damper system is briefly reviewed.

• Journal of the Korean Society of Fisheries and Ocean Technology
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• v.53 no.4
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• pp.423-429
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• 2017

As invigoration plan of the marine tourism, Busan City has the plan to operate the cruise ship inside of the harbor, but the area has narrow water way with heavy traffic. As a result it is requested to evaluate the safety for the preparation of actual navigation. In this study, the Ship Handling Simulation (SHS) Assessment was conducted, which is regulated by the Maritime Traffic Safety Audit Scheme (MTSAS) in compliance with the Marine Safety Law and the Maritime Traffic Risk Assessment System based on the Electronic Chart Display and Information System (ECDIS). The proximity assessment, control assessment and subjective assessment were implemented, which is enacted by the Marine Safety Law by using the SHS. In the case of proximity assessment, the probability of trespass was not analyzed. As the control assessment, the swept path was measured at 11.7 m and 11.5 m for port entry and port departure respectively, which exceeded the width of the model vessel, 10.4 m over; it was considered as a marginal factor. As a result of the subjective evaluation of the navigator, there would be no difficulty on ship maneuvering by paying particular attention to the mooring vessel nearby the Busan Bridge and Yeongdo Bridge as well as the coming vessel from the invisible sea area when the vessel is entering and departing the port. The Marine Traffic Risk Assessment System analyzed as [Cautious] level until the vessel passed the Busan bridge and the curved area at 5 kts and it became to [Dangerous] level from where it left 75 m to the Busan Bridge. When the vessel passed the Busan Bridge and the curved area at 10 kts and entered the narrow area, it indicated the [Dangerous] level and became to [Very dangerous] level from where it left 410 m to the Busan bridge. In conclusion, the vessel should maintain at the speed of 5 kts to reduce the risk when it passes this area.