• Proceedings of the Korea Committee for Ocean Resources and Engineering Conference
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• 2006.11a
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• pp.60-66
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• 2006

This paper presents a new way achieving better welding results of gas mental arc welding (GMAW) system by using a decentralized control method. In this paper, the GMAW system is considered as two separated subsystems such as a power source of GMAW (PS-GMAW) and a wire feed unit (WFU). The mathematical modeling of PS-GMAW and WFU are presented. Based on the modeling of two subsystems, a sliding mode controller and a proportional controller is designed for controlling the PS-GMAW and the WFU, respectively. Two decentralized controllers have to be designed to control the out welding arc of the GMAW to be stable and tracking the setting value accurately during the welding process. Furthermore, the simulation and experimental results are shown to prove the effectiveness of the proposed controllers.

• Journal of Ocean Engineering and Technology
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• v.25 no.6
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• pp.1-8
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• 2011

This paper describes a new method for a digital gas metal arc welding (GMAW) system. The GMAW system is an arc welding process that incorporates the GMAW power source (PS-GMAW) with a wire feed unit (WFU). The PS-GMAW requires an electric power of constant voltage. A constant magnitude is maintained for the arc current by controlling the wire-feed speed of the WFU. A mathematical model is derived, and a self-tuning fuzzy proportional-integral-derivative (PID) controller is designed and applied to control the welding current. The electrode wire feeding mechanism with this controller is driven by a DC motor, which can compensate for both the molten part of the electrode and undesirable fluctuations in the arc length during the welding process. By accurately maintaining the output welding current and welding voltage at constant values during the welding process, excellent welding results can be obtained. Simulation and experimental results are shown to prove the effectiveness of the proposed controller.

• The Journal of Fisheries Business Administration
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• v.46 no.3
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• pp.83-101
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• 2015

The main purpose of this study is to explore a way of South-North Korea fisheries cooperation through international organizations under the principles of the Korean peninsula trust process. Considering the government policy toward the North, although some humanitarian aids or cooperations may be plausible with permission of the Ministry of Reunification. direct cooperations between the South and the North Korea must be much limited at leat under the present government. The 5.24 measures taken in 2010 banned in fact all economic/humanitarian cooperations by private sectors and government. Noting the present and the visible future, an important question is whether the North accepts all cooperations including fisheries, bartering giving up nuclear weapon development for the 5.24 measures. It would be a difficult question to be answered, because win-set to both parties is too narrow, so far as there is no change in the South-North conflicting priority policies. If so, one way of implementing South-North fisheries cooperations is to drive forward cooperative programs through UN organizations. Since for instance FAO and WFP secure justification and roles and has a global network, they have sufficient capacity of being abe to organize fisheries experts. If the South can finance the budget necessary for the programs, FAO or WFP would lead the programs through a negotiation with the North. In other words, it is a type of cooperative model that FAO or WFP leads the programs and the South finances. In addition, if World Fisheries University(WFU) is invited to the Republic of Korea, it might make a great contribution to expert exchange of the North.