• Journal of Mechanical Science and Technology
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• v.20 no.9
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• pp.1502-1513
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• 2006

This study analyzes the design and part load performance of a power generation system combining a micro gas turbine (MGT) and an organic Rankine cycle (ORC). Design performances of cycles adopting several different organic fluids are analyzed and compared with performance of the steam based cycle. All of the organic fluids recover greater MGT exhaust heat than the steam cycle (much lower stack temperature), but their bottoming cycle efficiencies are lower. R123 provides higher combined cycle efficiency than steam does. The efficiencies of the combined cycle with organic fluids are maximized when the turbine exhaust heat of the MGT is fully recovered at the MGT recuperator, whereas the efficiency of the combined cycle with steam shows an almost reverse trend. Since organic fluids have much higher density than steam, they allow more compact systems. The efficiency of the combined cycle, based on a MGT with 30 percent efficiency, can reach almost 40 percent. hlso, the part load operation of the combined system is analyzed. Two representative power control methods are considered and their performances are compared. The variable speed control of the MGT exhibits far better combined cycle part load efficiency than the fuel only control despite slightly lower bottoming cycle performance.

• Nuclear Engineering and Technology
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• v.38 no.2
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• pp.109-118
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• 2006

Various indirect power cycle options for a helium cooled gas cooled fast reactor (GFR) with particular focus on a supercritical $CO_2(SCO_2)$ indirect cycle are investigated as an alternative to a helium cooled direct cycle GFR. The balance of plant (BOP) options include helium-nitrogen Brayton cycle, supercritical water Rankine cycle, and $SCO_2$ recompression Brayton power cycle in three versions: (1) basic design with turbine inlet temperature of $550^{\circ}C$, (2) advanced design with turbine inlet temperature of $650^{\circ}C$ and (3) advanced design with the same turbine inlet temperature and reduced compressor inlet temperature. The indirect $SCO_2$ recompression cycle is found attractive since in addition to easier BOP maintenance it allows significant reduction of core outlet temperature, making design of the primary system easier while achieving very attractive efficiencies comparable to or slightly lower than, the efficiency of the reference GFR direct cycle design. In addition, the indirect cycle arrangement allows significant reduction of the GFR &proximate-containment& and the BOP for the $SCO_2$ cycle is very compact. Both these factors will lead to reduced capital cost.

• Solar Energy
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• v.19 no.3
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• pp.101-113
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• 1999

Thermodynamic performance of a simple Rankine cycle, regenerative Rankine cycle, and Kalina cycle for Ocean thermal Energy Conversion(OTEC) is evaluated under the same condition with various working fluids. The evaporator and condenser are modeled by a UA and LMTD method while the turbine and pump are modeled by considering isentropic efficiencies. As for the working fluids, R22, R134a, R32, propylene, ammonia are used for the Rankine cycles while ammonia/water and R32/R134a mixtures are used for Kalina cycle. Calculated results show that newly developed fluids such non-ozone depleting refrigerants as R134a and R32 perform as well as R22 and ammonia. The regenerative Rankine cycle showed a 1.2 to 2.8% increase in energy efficiency as compared to the simple Rankine cycle while the Kalina cycle with ammonia/water mixture showed a 1.8% increase in energy efficiency. The efficiency of the Kalina cycle with R32/R134a mixtures is the same as that of a simple Rankine cycle using R22. Therefore, the regenerative Rankine cycle turns out to be best choice for OTEC applications.

• Journal of Korean Society of Water and Wastewater
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• v.29 no.1
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• pp.11-21
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• 2015

When designing Water Distribution System (WDS), determination of life cycle for WDS needs to be preceded. And designer should conduct comprehensive design including maintenance and management strategies based on the determined life cycle. However, there are only a few studies carried out until now, and criteria to determine life cycle of WDS are insufficient. Therefore, methodology to determine life cycle of WDS is introduced in this study by using Life Cycle Energy Analysis (LCEA). LCEA adapts energy as an environmental impact criterion and calculates all required energy through the whole life cycle. The model is build up based on the LCEA methodology and model itself can simulate the aging and breakage of pipes through the target life cycle. In addition the hydraulic analysis program EPANET2.0 is linked to developed model to analyze hydraulic factors. Developed model is applied to two WDSs which are A WDS and B WDS. Model runs for 1yr to maximum 100yr target life cycle for both WDSs to check the energy tendency as well as to determine optimal life cycle. Results show that 40yr and 54yr as optimal life cycle for each WDS, and tendency shows the effective energy is keep changing according to the target life cycle. Introduced methodology is expected to use as an alternative option for determining life cycle of WDS.

• Plant Journal
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• v.15 no.2
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• pp.42-45
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• 2019

The molten carbonate fuel cell has a high temperature of waste heat and can constitute a bottoming cycle to increase the efficiency. Previous study used a bottoming cycle as steam turbine cycle. In this study, we are going to replace the bottoming cycle with a supercritical carbon dioxide power cycle. The system power was compared to consider replacing the bottoming cycle. As a result, the power of the supercritical carbon dioxide power cycle at the present development stage is lower than that of the steam turbine cycle, but theoretically, the power can be larger than the steam turbine cycle. If the supercritical carbon dioxide power cycle improves the isentropic efficiency of the turbine by 89%, the isentropic efficiency of the compressor by 83%, and the effectiveness of the recuperator by 0.9, the power can be same to the steam turbine cycle.

• IE interfaces
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• v.13 no.1
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• pp.54-59
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• 2000

Presented in this paper is a development of knowledge management system based on knowledge life cycle. Knowledge processes in an organization have a life cycle from creation to disposal. So, KMSs have to support the entire life cycle of knowledge. This paper proposes desired knowledge life cycle model, and extracted functional requirements for KMS. For the fulfillment of this requirements, we developed KMS called XM-Brenic/MSX. This system has 6 components for supporting the knowledge life cycle.

• Electronics and Telecommunications Trends
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• v.17 no.1 s.73
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• pp.54-62
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• 2002

본 연구의 목적은 IT 관련 Cycle을 체계적으로 분석하는 데 있다. 연구 범위 및 분석내용은 다음과 같이 요약된다. 첫째, 1990년 1사분기에서 2000년 4사분기까지 효율적인 Band Pass 필터링에 의하여 IT Cycle을 정의하였고, Business Cycle과의 상관관계 그리고 몇 가지 IT Cycle 특징을 Co-Spectra 분석을 통하여 동태적 관점에서 분석하였다. 둘째, 우리나라 수출 안정화 측면에서 주요 5개 산업 수출 Cycle과 IT 수출 Cycle을 중심으로 서로 간의 동태적 상관관계를 분석함으로써 산업 정책적 시사점을 제시하였다.

• Proceedings of the Korean Society of Surveying, Geodesy, Photogrammetry, and Cartography Conference
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• 2003.04a
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• pp.105-109
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• 2003

The occurrence of cycle slips is a major limiting factor to attain high precision positioning and navigation results with GPS. Cycle slips must be correctly repaired at the data processing stage. In this study, the technique to find cycle slips in the processing of data collected with Trimble 4700 GPS receivers is suggested. The use of Kalman filtering techniques is used in an attempt to reduce the effect of the noise in the different quantities involved and to improve the accuracy in cycle slip correction.

• Proceedings of the Korean Radioactive Waste Society Conference
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• 2018.05a
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• pp.94-95
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• 2018

• Proceedings of the Korean Radioactive Waste Society Conference
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• 2004.06a
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• pp.386-395
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• 2004

The Korean fuel cycle scenario has been modeled by using the dynamic analysis method. For once-through fuel cycle model, the nuclear power plant construction plan was considered, and the nuclear demand growth rate from the year 2016 was assumed to be 1%. After setup the once-thorough fuel cycle model, the DUPIC and fast reactor scenarios were modeled to investigate the environmental effect of each fuel cycle. Through the calculation of the amount of spent fuel, and the amounts of plutonium and minor actinides were estimated and compared to those of the once-through fuel cycle. The results of the once-through fuel cycle shows that the demand grows to 64 GWe and the total amount of the spent fuel would be 100 kt in the year 2100, while the total spent fuel can be reduced by 50% when the DUPIC scenario is implemented