• 한국전기전자재료학회논문지
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• 제33권3호
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• pp.177-180
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• 2020

This paper focuses on the 1,200-V level reverse conducting-insulated gate bipolar transistor (RC-IGBT). The structure of the RC-IGBT has an n+ collector at the collector terminal. The breakdown voltage, V_th, V_ce-sat, and turn-off time, and the electrical characteristics of a field-stop IGBT (FS-IGBT) and RC-IGBT are compared and analyzed using simulations. Based on the results, the RC-IGBT obtained a turn-off time of 320.6 ㎲ and a breakdown voltage of 1,720 V, while the FS-IGBT obtained a turn-off time of 742.2 ㎲ and a breakdown voltage of 1,440 V. Therefore, RC-IGBTs have faster on/off transitions and a higher breakdown voltage, which can reduce the size of the element.

• 한국시스템다이내믹스연구
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• 제11권4호
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• pp.25-59
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• 2010

The Korean government has operated various mega-development projects in order to help nation progress into the future. However, many problems and concerns have been raised on the mega-projects' delay and failure in South Korea. Moreover, there are many technical and executive problems; such as trial and error of development work, failure of validity test, complicated decision-making processes, and so on. With these concerns and problems to mega-development projects, finding a sustainable development from mega-projects is becoming a new issue in the field of mega-development projects. Therefore, the main purpose of this study is to investigate whether or not most mega-development projects conducted by the government exactly corresponds with sustainable development (such as environmental soundness, economic efficiency and social equity) focusing on Saemangeum project. Using causal loop analysis, this study gives some significant results to us. First, for environmental soundness, both central and local government should ensure water-purity control system for farming, industry, leisure, and others. Second, for economic efficiency, both governments not only have to secure a budget for completion of infrastructure of the Saemangeum project but also support financial assistance to Saemangeum project. Third, for social equity, three local governments (i.e., Gunsan, Gimje, and Buan) should stop debate and conflict with regard to an administrative district of Saemangeum region. Finally, most politicians should not use Saemangeum project for political means. Rather, they should recognize the project as a motive power for economic development of Jeollabukdo.

• 한국전기전자재료학회논문지
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• 제24권10호
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• pp.807-811
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• 2011

When the high voltage motor fails in power plants, there will be an occurrence where the generator's output would be reduced or the generators would trip. Despite of these effects, the causes of deterioration of the high voltage motor is very seldom investigated. In this paper, the collected data which tested in the field over 10 years have been treated statistically, and analyzed to correlate the insulation deterioration of high voltage motor and installation environment, number of start/stop, and service life. Moreover, the proper period of insulation test is developed to map out maintenance strategy and reduce maintenance costs.

• 플랜트 저널
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• 제4권4호
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• pp.56-61
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• 2008

The phenomena of oil whip in steam turbines take place for the unbalance force between a rotor shaft and bearing oil film. The several parameters that affect onset of oil whip have been well known. However, the major parameter of oil whip is shaft mis-alinement. A oil whip causes the high vibration and the shutdown of rotor system. We mostly stop the steam turbine to adjust a shaft re-alinement concerning oil whip. In this case, it needs many costs for maintenance and long shutdown times. In this study, we study and observe the oil whip of the 300MW steam turbine in many years and we conduct the field test for another steam turbine for reducing vibration from oil whip. The results of this study are that a oil whip takes place with a particular rotating speed or a particular turbine output and the oil temperature change is a very effective method for on-line oil whip treatment.

• 수산해양교육연구
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• 제23권4호
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• pp.684-694
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• 2011

The purpose of this study is to provide the basics of effective Fisheries and Merchant Marine High School education by analyzing Fisheries and Merchant Marine High School students' perceptions about their educational environment and school education. To achieve the purpose of this research, the study carried out a survey targeting 350 Fisheries and Merchant Marine High School students. The findings are as follows: First, the perceptions about instructions of department is generally positive. And they demand expansion of practice instruction. Second, the perceptions about curriculum is generally positive. And they demand field-experience learning. Third, the perceptions about school management and administration is generally positive. But they dissatisfied with considering their opinion about school management and administration. Fourth, the perceptions about counselling and personality guidance is generally positive. And the efforts to stop school violence are valued most positive. But the satisfaction in club activities is relatively low, so we need to come up with measure to increase club activities.

• Nuclear Engineering and Technology
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• 제51권3호
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• pp.908-914
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• 2019

Fusion power shutdown system (FPSS) is a safety system to stop plasma in case of accidents or incidents. The gas injection system for the FPSS presented in this work is designed to research the flow development in a closed system. As the efficiency of the system is a crucial property, plenty of experiments are executed to get optimum parameters. In this system, the flow is driven by the pressure difference between a gas storage tank and a vacuum vessel with a source pressure. The idea is based on a constant volume system without extra source gases to guarantee rapid response and high throughput. Among them, valves and gas species are studied because their properties could influence the velocity of the fluid field. Then source pressures and volumes are emphasized to investigate the volume flow rate of the injection. The source pressure has a considerable effect on the injected volume. From the data, proper parameters are extracted to achieve the best performance of the FPSS. Finally, experimental results are used as a quantitative benchmark for simulations which can add our understanding of the inner gas flow in the pipeline. In generally, there is a good consistency and the obtained correlations will be applied in further study and design for the FPSS.

• 한국전기전자재료학회논문지
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• 제32권3호
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• pp.256-261
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• 2019

The use of military lithium batteries in this field accelerates the generation of internal pressure because the active materials, lithium and the electrolyte, react to form sulfur dioxide gas. This also reduces the amount of electrolyte. In this condition, batteries can 'vent' or 'explode' especially when completely discharged. Such venting and explosion can be regarded as a safety accident, as toxic gases and shrapnel are ejected from the batteries which can harm the user. A DTaQ was carried out in 2017 as a quality problem solution project to solve this safety issue. A protection circuit was thereby developed, which included a micro controller unit (MCU) which can stop battery usage when in an over-discharging state by sensing its low-voltage condition. In 2018, this concept was expanded to lithium batteries for the remote controlled ammunition system. This paper reports results of the improved performance.

• Steel and Composite Structures
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• 제47권2호
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• pp.239-251
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• 2023

The stiffness evaluation of cracked base metal is of great guidance to fatigue crack reinforcement. By carrying out fatigue tests and numerical simulation of typical cracking details in steel box girder, the strain-degradation law of cracked base metal was analyzed and the relationship between base metal stress and its displacement (stiffness) was explored. The feasibility of evaluating the stress of cracked base metal based on the stress field at the crack tip was verified. The results demonstrate that the stiffness of cracked base metal shows the fast-to-slow degradation trend with fatigue cracking and the base metal at 50mm or more behind the crack tip basically lose its bearing capacity. Drilling will further accelerate stiffness degradation with the increase of hole diameters. The base metal stress has a negative linear relation with its displacement (stiffness), The stress of cracked base metal is also related to stress intensity factor and its relative position (distance, included angle) to the crack tip, through which the local stiffness can be effectively evaluated. Since the stiffness is not uniformly distributed along the cracked base metal, the reinforcement patch is suggested to be designed according to the stiffness to avoid excessive reinforcement for the areas incompletely unloaded.

• 수산경영론집
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• 제54권2호
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• pp.15-29
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• 2023

This study aims to establish a development strategy for higher education in Indonesia's marine and fisheries sector and to present a direction for international development cooperation through evaluating policies and current problems related to higher education in marine and fisheries sector. To achieve the goals of human resources development in marine and fisheries sector, Indonesian government needs to secure non-salary expenditures to strengthen support for areas directly related to the effects of education, such as improving educational facilities, expanding scholarships, and so on. Education institution needs to develop effective teaching methods and systematic practice-based curriculum that reflects the needs of the local fishermen community and fisheries industry. In addition, it is necessary to support the supply of manpower throughout the fisheries industry. Fisheries industry needs to stop relying on the government or education institutions to secure excellent human resources and actively participate and cooperate in the education field so that excellent human resources can flow into the industry. Based on this strategy, international development cooperation for human resources development in Indonesia's marine and fisheries sector should focus on qualitative rather than quantitative expansion of higher education institutions.

• Journal of Plant Biotechnology
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• 제6권4호
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• pp.221-227
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• 2004

Protocol was established for production of virus free healthy seeds using meristem ($0.3-0.5\;\cal{mm}$ in size) culture and field management under net house condition in tomato. The isolated meristem was found well established in MS liquid medium containing $0.1\;\cal{mg}\;1^{-1}\;of\;GA_3$. For shoot and root development either from primary meristem or from nodal segment of meristem derived plants, semisolid MS medium having $0.5\;\cal{mg}\;1^{-1}$ of IBA was found most effective. The elimination of the studied viruses (ToMV, CMV, ToLCV) in meristem-derived plants was confirmed by DAS-ELISA test. For field management of the virus eradicated meristem-derived plants, use of net house was found very effective measures to check viral vector visit and eventually infection. The meristem-derived plants were vigor and high yielder than the native seed derived plants and produced healthy seeds. Due to stop vector visit, no viral symptoms were observed in both $R_1\;and\;R_2$ plants cultivated in net house condition. Starting of viral infestation was observed in $R_2$ generation when they were planted in open house condition without control of vector visit. Therefore, for management of viral diseases, use of virus free meristem derived plantlets and their subsequent cultivation in soil under net house condition without using any vector killing insecticide can be recommended for producing healthy seeds in tomato. The developed protocol for environmentally healthy tomato seed production in Bangladesh may be used in the countries having similar tropical like environment conducive for viral vector visit.