• Journal of Ocean Engineering and Technology
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• v.26 no.4
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• pp.64-69
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• 2012

Laser welding was carried out on austenitic 304 (STS 304) and 22 APU stainless steels. In this case, the differences between the corrosion characteristics of the welding zones of the two stainless steels were investigated using electrochemical methods. The Vickers hardness values of the weld metal (WM) zones in both cases, the STS 304 and 22 APU stainless steels, showed relatively higher values than those of other welding zones. The corrosion current densities of the heat affected zone (HAZ) of the 22 APU and the base metal (BM) zone of the STS 304 exhibited the highest values compared to the other welding zones. It is generally accepted that when STS 304 stainless steel is welded using a general welding method, intergranular corrosion is often observed at the grain boundary because of its chromium depletion area. However, when laser welding was performed on both the STS 304 and 22 APU stainless steels, no intergranular corrosion was observed at any of the welding zones. Consequently, it is considered that the intergranular corrosion of stainless steel can be controlled with the application of laser welding.

• Corrosion Science and Technology
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• v.13 no.1
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• pp.15-19
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• 2014

Recently, anti-fouling paints which does not include the poison components such as tin(Sn), copper(Cu) have been increasingly developed in order to inhibit the environmental contamination of the sea water. Moreover, the wear ratios of these anti-fouling paints are very important problem to prolong their life time in economical point of view. In this study, five types of anti-fouling paints as self polishing type were investigated on the relationship between their polarization characteristics and wear ratios. It was verified that there was apparently a good relationship between the wear ratio and polarization characteristics, for example, the wear ratio increased with increasing the impedance ratio, and increased or decreased with the corrosion potential shifting in the negative or positive direction respectively. In addition, the wear ratio decreased with decreasing the corrosion current density. Consequently, it is suggested that we can qualitatively expect the wear ratio by only measuring the polarization characteristics. Therefore, before the examination of the wear ratio was actually carried out in the field, the evaluation of polarization property in the laboratory may give a available reference data for their developments.

• Journal of Advanced Research in Ocean Engineering
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• v.3 no.1
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• pp.25-31
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• 2017

Generally, underwater gliders do not have separate propellers for their forward movement. They derive a propulsive force due to the difference between their buoyancy and gravity. The attitude of an underwater glider is controlled by changing the relative position of the buoyancy center and mass center. In this study, we derived nonlinear 6-DOF dynamic and mathematical models for the motion controller and buoyancy controller. Using these equations, we performed dynamic underwater glider simulations and verified the suitability of the design and dynamic performance of the proposed underwater glider.

• Journal of the Korean Society of Marine Environment & Safety
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• v.29 no.7
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• pp.819-827
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• 2023

If respiratory arrest occurs or cardiopulmonary resuscitation (CPR) is performed for a long period on board ships, CPR with rescue breathing (not compression-only CPR) is required. Accordingly, ships must have resuscitation equipment for oxygen supply, and seafarers must have the maritime competence to use it. This study aimed to analyze the placement status of resuscitation equipment on ships and seafarers' intention to use them in order to increase the usability of resuscitation equipment on board ships and propose improvement measures. The study was conducted from February 2, 2023, to April 21, 2023, and a total of 340 seafarers were surveyed. The data were analyzed by frequency, percentage, and chi-square test using SPSS WIN 23.0. The results showed that the checking of resuscitation equipment was high among seafarers in the positions of officer, captain, deck department personnel, and ocean-going personnel. The intention of seafarers to use resuscitation equipment was low, and the main barrier was the lack of knowledge on how to use. Among the general characteristics of the study participants, those whose rank was that of officer or captain, whose working department was the deck, voyage who were ocean-going, and who managed a gross tonnage of 20,000 tons or more had a high intention to use resuscitation equipment. Participants who knew the necessity of rescue breathing and had received practice and equipment-based training were active in using resuscitation equipment. Therefore, a system should be developed so that all ships can be equipped with resuscitation equipment, and an environment must be created to increase accessibility to resuscitation equipment on board ships. In addition, an education system based on practical and resuscitation equipment training must be established to ensure that seafarers have maritime competence.

• International Journal of Naval Architecture and Ocean Engineering
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• v.10 no.4
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• pp.499-507
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• 2018

Autonomous Underwater Vehicle (AUV), which are becoming more and more important in ocean exploitation tasks, needs energy conservation urgently when sailing the complex mission path in long time cruise. As hull lines optimization design becomes the key factor, which closely related with resistance, in AUV preliminary design stage, uncertainty parameters need to be considered seriously. In this research, Myring axial symmetry revolution body with parameterized expression is assumed as AUV hull lines, and its travelling resistance is obtained via modified DATCOM formula. The problems of AUV hull lines design for the minimum travelling resistance with uncertain parameters are studied. Based on reliability-based optimization design technology, Design For Six Sigma (DFSS) for high quality level is conducted, and is proved more reliability for the actual environment disturbance.

• Proceedings of KOSOMES biannual meeting
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• 2017.11a
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• pp.266-266
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• 2017

• Proceedings of the Korean Institute of Navigation and Port Research Conference
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• 2022.06a
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• pp.207-208
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• 2022

Recently, with the development of digital technology, new research cases which applied new technology were increased. Also, the related equipment and services are being developed in the industry. Before new equipment is developed and released, it must go through a verification process. In the maritime industry, equipment is verified through simulation tests or environmental tests on land. However, if only the test on land is conducted, verification data in the actual operating environment might be insufficient. In this paper, considerations are described in the development of an onboard demonstration scenario for verification in the operating environment.

• Proceedings of the Korean Institute of Navigation and Port Research Conference
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• 2021.11a
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• pp.119-120
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• 2021

Radio equipment for maritime service and navigation aids installed on fishing vessels are required to comply with the performance standards KN60945_60533 that apply IEC 60945. The LTE-M transceiver was excluded from the target because it did not belong to the radio equipment of the ship station, and it acted as a cause of audible noise in the radio equipment for maritime service installed in the fishing vessel due to interference by radiated emission or conducted emission. In this paper, we analyze the impact of interference based on related cases and present institutional solutions for the diversification of LTE-M.

• International Journal of Ocean System Engineering
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• v.2 no.4
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• pp.239-243
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• 2012

The cylinder liner of a low speed engine is one of the most important parts of the marine diesel engines used in merchant ships. However, a sufficient degree of precision in the manufacturing method for these cylinder liners has never existed. Conventional honing stones have always been used for machining large marine cylinder liners. Therefore, it is necessary to develop a honing process that optimizes the honing characteristics. In this study, a CBN honing stone was manufactured to improve the honing performance for a cylinder liner and shorten the processing time, and machining experiments on a practical cylinder liner were carried out. Then, a comparison was made between the CBN honing and honing with a conventional GC stone using parameters such as the honing time, machining quantity, and honing cost. As a result, for a #60 CBN stone, the machining amount was significantly improved compared to the conventional one by about $1.1{\mu}m$/min, and in respect to the machining cost, a reduction of about 57% was achieved. However, an improvement in the process with a #800 CBN stone could not be expected because it did not show a significant difference compared to the case of the existing stone. From the above results, if the liner were honed using a CBN honing stone, the rough machining and intermediate processing during an early stage of the honing process were excellent compared to the conventional one. However, we could not find a significant difference in the case of finish honing.

• International Journal of Ocean System Engineering
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• v.2 no.4
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• pp.209-213
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• 2012

Recently, the fuel using in the diesel engines of marine ships has been changed to a low quality of heavy oil because of the steady increase in the price of oil. Therefore, the wear and corrosion in all parts of the engine such as the cylinder liner, piston crown, and spindle and seat ring of exhaust valves has correspondingly increased. The repair welding of a piston crown is a unique method for prolonging its lifetime from an economic point of view. In this case, filler metals with a high corrosion and wear resistance are mainly being used for repair welding. However, often at a job site on a ship, a piston crown is actually welded with mild filler metals. Therefore, in this study, mild filler metals such as CSF350H, E8000B2, and 435 were welded to SS401 steel as the base metal, and the corrosion properties of the weld metals with and without post weld heat treatment were investigated using some electrochemical methods in a 0.1% $H_2SO_4$ solution. The weld metal welded with CSF350H filler metal exhibited the best corrosion resistance among these filler metals, irrespective of the heat treatment. However, the weld metal zones of the E8000B2 and 435 filler metals exhibited better and worse corrosion resistance with the heat treatment, respectively. As a result, it is suggested that in the case of repair welding with CSF350H and 435 filler metals, no heat treatment is advisable, while heat treatment is desirable if E8000B2filler metal is used with repair welding.