• Journal of the Society of Naval Architects of Korea
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• v.41 no.3
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• pp.1-12
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• 2004

In order to prepare the fuel-economic hull form design method for fine higher-speed ships, systematic theoretical and experimental study has been performed on the relation between hull form characteristics and ship's resistance and on the effect of the optimization of main hull form characteristics. The results of this study provide not only a great insight into the relation between ship's resistance and hull form characteristics, but also a proper direction of the optimization of main hull form characteristics for the improvement of ship's resistance characteristics.

• Proceedings of the KIEE Conference
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• 2006.07a
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• pp.311-312
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• 2006

본 논문에서는 선로 전력조류제약을 고려한 경제급전(SCED : Security-Constrained economic dispatch)에 내점 선형계획법을 이용하여 최적해를 구하는 문제를 다룬다. 최적전력조류(Optimal Power Flow)식으로부터 선로의 유효전력만을 근사화하여 선로 전력조류 제약을 고려할 경제급전(SCED)의 식을 정식화한다. 선형계획법을 적용하여 최적해를 구하기 위해서 발전기출력과 유효전력, 부하, 손실과의 관계를 이용하여 경제급전의 식을 선형화 하는 알고리즘을 제시한다. 선형화 알고리즘은 목적함수로 계통 발전기의 총 연료비를 취하고 전력수급평형식으로 발전기출력증분에 대한 선로의 증분손실계수를 이용하며, 선로의 제약조건은 일반화발전 분배계수(GGDF : Generalized Generation Distribution Factor)를 이용하여 선형화한다. 최적화 기법으로서 내점법(Interior Point Method)을 적용하고자 하며 사례연구를 통하여 선형계획법 중 가장 많이 사용하는 심플렉스(Simplex)법과의 수렴특성을 비교하여 내점 법의 효용성을 확인하고자 한다.

• Journal of the Korean Institute of Intelligent Systems
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• v.4 no.1
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• pp.64-80
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• 1994

본 연구에서는 장기전원구성의 수립에 있어서 가정한 시나리오에서 최적해를 찾는 기존의 방법을 탈피하여 건설단가나 연료단가의 변동과 같은 경제성의 변동 및 최대부하의 예측의 불확실성에 대한 외부충격등에 견딜 수 있는 유연성을 정량적으로 고려할 수 있는 새로운 방법을 제안한다.그 수법으로 Fuzzy 동적계획법을 이용하여 각 대표년도별로 최적전원구성안을 결정하므로써 년도별 전원 구성의 추이를 쉽게 알 수 있고 비선형 멤버쉽함수도 용이하게 고려할 수 있도록 하였다. 여기서는 경제성, 신뢰성, 부하불확실성 및 유연성에 대한 멤버쉽 함수치를 각상태별로 계산하고 Bellman-Zadeh의 최대화 결전과정에 따라 처리하므로서 그 안을 결정하도록 하였다. 본 수법을 우리나라 KEPCO 계통에 적용하여 그 유용성을 검토하였다.

• Proceedings of the Korean Nuclear Society Conference
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• 1996.05a
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• pp.205-212
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• 1996

국내 1000 MWe급 발전소인 영광 3,4호기는 현재 표준주기 (12개월 주기)로 운전되고 있으나 향후 18개월 장주기 운전을 계획하고 있다. 본 연구에서는 영광 3,4호기의 교체노심을 대상으로 표준주기와 장주기에 대한 장기 핵연료관리계획을 수립하고 이들 평형노심에 대하여 핵연료주기비와 발전원가를 중심으로 경제성 분석을 수행하여 상호 비교하였다. 18개월 장주기로 운전할 경우 표준주기에 비하여 핵연료주기비는 약 7% 증가하나 약 4%의 발전소 이용율 향상에 따라 고정비가 약 5% 절감되어 총 발전원가를 약 4% (연간 약 99 억원) 절감할 수 있는 것으로 평가되었다. 또한 선형반응도 모델을 이용하여 핵연료 이용도(Fuel Utilization Curve)를 만들어 발전원가에 영향을 미치는 교체 신연료의 다발수, 농축도, 주기길이, 발전소 평균 부하율 및 재장전 보수기간의 변화에 따른 발전원가의 민감도 분석을 수행하였다.

• Journal of the Korean Institute of Gas
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• v.13 no.1
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• pp.28-33
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• 2009

Natural gas is the world's most plentiful combustible fuel, abundantly acailable in all continent. A fuel injector designed specifically for low energy density gaseous fuels has been developed. The injector incorporates design features that are necessary to optimize the performance for fuels such as CNG, LNG. Gaseous fuel injectors have a decisive influence upon starting performance, driveability, fuel consumption and exhaust emissions. A gaseous fuel injector has been developed to cope with the considerably larger volume flow rates and the developed gaseous fuel injector could be used at heavy duty natural gas engine. The static flow of injectors at various inlet pressure was directly proportional and the controllability showed great performance.

• Environmental and Resource Economics Review
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• v.13 no.4
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• pp.593-619
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• 2004

This study analyzes the interfuel substitution of energy demand in Korean manufacturing sector using static and dynamic linear logit models. For the period of 1981~2002, this study uses petroleum, electricity, natural gas and coal as energy sources. According to the empirical results, firstly, the own-price elasticity of coal has been increased steadily even though its elasticity is smallest compared with those of other energy sources. On the other hand, price elasticity of natural gas is largest, but its value has been decreased after 1997. Price elasticities of petroleum and electricity are very stable over the sample period. One of the main features in trends of interfuel substitution is as follows. Substitution effect of a change in price of natural gas on both petroleum and coal has been increased especially after 1997. The implication of the empirical results is summarized as follows: First, the fact of inelastic own-price elasticity of petroleum implies that the dependency of Korean manufacturing sector on petroleum and coal will be persistent even in a sharp fluctuation of petroleum price. Second, the effects of price increase in natural gas on demand for petroleum and coal are very significant. Thus, price decline of natural gas rather than price declines of coal and petroleum could be more effective as an energy price policy for the reduction of $CO_2$ emission. The assessment on this implication will remain for future researches.

• Nuclear Engineering and Technology
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• v.20 no.1
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• pp.19-26
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• 1988

The low leakage leading pattern has features as the placement of some fresh fuel assemblies in the core interior to reduce the neutron fluence on the pressure vessel and to enhance the neutron economics. But as fresh fuel assemblies are loaded in the core interior, the local power tends to exceed safety limit due to the high reactivity of the fresh assemblies. Therefore, a large number of burnable poisons must be utilized in a low leakage scheme to suppress the high assembly power as well as the excess reactivity. In this study the effects of burnable poisons are treated as a perturbation on the power distribution, and the 'Power Sensitivity Coefficient' concept is adopted. An application study is performed for cycle 1 of the Korea Nuclear Unit-7 (KNU-7) to justify the usefulness of the reverse depletion method coupled with the above concept. To obtain the optimal burnable poision distribution at the given burnup step, the linear programming technique is adopted. The result shows maximum 4.5% error in the amount of burnable poisons between the calculated and the reference values. It is concluded that the design methodology which consists of the reverse depletion, the power sensitivity coefficient concept, and the linear programming technique can be used to find the optimal turnable poison distribution.

• The Proceedings of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.8 no.1
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• pp.37-45
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• 1994

A method of optimal active and reactive power control for economic operation in electrical power system is presented in this paper. The major features and techniques of this paper are as follows: 1) The method presented for obtaining the equivalent active power balance equation applying the sparse Jacobian matrix of power flow equation instead of using B constant as active power Balance equation considering transmission loss, and for determining directly optimal active power allocation without repeating calculations. 2) More reasonable and economic profit by minimizing total fuel cost of thermal power plants instead of using transmission loss as objective function of reactive Power control can be achieved. 3) Particularly in reactive power control, computing time can be considerably reduced by using Fuzzy Linear Programming instead of using conventional Linear Programming.

• The Korean Journal of Petroleum Geology
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• v.14 no.1
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• pp.45-52
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• 2008

The GTL(Gas to Liquids) technology, manufacturing synthesized oil from natural gas, had been developed about 1920 for the military purpose by Fischer and Tropsch, German scientists. And 1960, Sasol company had started commercializing the FT(Fischer-Tropsch) synthesis technology, for the transport fuel in South Africa. Until a recent date, the commercialization of GTL technology had been delayed by low oil price. But concern about depletion of petroleum resources, and development in synthesizing technology lead to spotlight on the GTL businesses. Especially, Qatar, which has rich natural gas fields, aims at utilizing natural gas like conventional oil resources. Therefore, around this nation, GTL plants construction has been promoted. There are mainly 3 processes to make GTL products(Diesel, Naphtha, lube oil, etc) from natural gas. The first is synthesis gas generation unit reforming hydrogen and carbomonoxide from natural gas. The second is FT synthesis unit converting synthesized gas to polymeric chain-hydrocarbon. The third is product upgrading unit making oil products from the FT synthesized oil. There are quite a little sulfur, nitrogen, and aromatic compounds in GTL products. GTL product has environmental premium in discharging less harmful particles than refinery oil products from crude to the human body. In short, the GTL is a clean technology, easier transportation mean, and has higher stability comparing to LNG works.

• Journal of the Korean Society of Marine Environment & Safety
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• v.21 no.5
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• pp.558-570
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• 2015

A study on the green ship design for Ultra Large Container Ship (ULCS, 18,000 TEU Class Container Ship) was performed based on the four step procedures of the initial design and hull form optimization to maximize economic and propulsive performance. The first, the design procedure for ULCS was surveyed with economic evaluation considering environmental rules and regulations. The second, the characteristics of single and twin skeg container ships were investigated in view of initial design and performances. The third, the hull form optimization for single and twin skeg ships with the same dimensions was conducted to improve the resistance and propulsive performances at design draught and speed by several variations and the results of the optimization were verified by numerical calculations of CFD and model test. The last, for the estimated operating profile of draught and speed, the hull forms of single and twin sked ships were optimized by CFD. From this study, the methodologies to optimize the hull form of ULCS were proposed with considerations during the green ship design and the improvement of the energy efficiency for the optimized hull forms was confirmed by the proposed formula of the total energy considering design conditions, operating profile and fuel oil consumption.