• The Transactions of The Korean Institute of Electrical Engineers
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• v.65 no.3
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• pp.382-387
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• 2016

This paper deals with the assessment of voltage sags regarding the variation of system operating conditions. In general, voltage sag assessment is performed by assuming the constant operating condition throughout the year. However, the assumption can lead to assessment errors in case of considerable changes of system operation condition. This paper presents a method to estimate ESF(expected sag frequency) considering the operating conditions according to the changes of power demand throughout the year.

• The Transactions of the Korean Institute of Electrical Engineers A
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• v.48 no.4
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• pp.351-357
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• 1999

This paper proposes the coordinated control of SVC and UTLC at the distribution substation to get larger operating margin of SVC for the voltage stability control by reactive power compensation. In the conventional method, ULTC doesn't respond to the variation of source voltage, so SVC has the entire responsibility for it. It could cause the lack of operating margin of SVC in some condition. It, however, is important to secure an operating margin for the dynamic stability control in emergancy. This paper proposes the coordinated control method that SVC controls the supply voltage and ULTC respond to the SVC compensation valve based on the relation between SVC compensation and ULTC tap position. The numerical simulation verifies that the proposed system could increase the operating margin of SVC compared with the conventional system.

• Journal of the Korean Society for Aviation and Aeronautics
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• v.26 no.4
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• pp.149-154
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• 2018

Risk Based Oversight is a way of performing oversight, where planning is driven by the combination of risk profile and safety performance. Risk Based Oversight enables prioritization and allocation of State's safety management resources commensurate with the safety risk profile of each service provider. This paper presents the concept of Risk Based Oversight and applies it to the current Korean aviation safety oversight process. In particular, this study presents a method for generating operating profiles, one of the key concepts of Risk Based Oversight. Operations Specifications of Part 121 Airlines can generate operating profiles. In this study, a practical study was conducted to generate the operating profile and scoped DCTs using Part 121 Airlines's Operations Specifications.

• Journal of Korean Academy of Fundamentals of Nursing
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• v.15 no.4
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• pp.566-577
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• 2008

Purpose: Developing a curriculum(DACUM) is a method of analyzing job focused competency, which is obtained from the data of an expert belonging to a certain career. In this study the DACUM method was used to analyze the jobs of operating room nurses. Method: Through the DACUM workshop which was arranged by two DACUM facillitators, a definition of the role of operating room nurses was developed and then duties and tasks of operating room nurses' were identified. For the workshop, a DACUM committee with 10 operating room nurses was organized. Finally, the duties and tasks which were identified were validated by 422 nurses for importance, difficulty and frequency. Results: Thirteen duties and 105 tasks were identified on the DACUM chart, where importance, difficulty, and frequency of tasks were represented by alphabet letters A, B, and C as higher degree of importance. The determinant coefficient(DC) showed that the most important duty was assisting with operations(DC=6.61), and the least, managing operating materials(DC=4.22). For tasks, the most important ones were assisting in orthostatic surgery(DC=7.60), and assisting in thoracic surgery(DC=7.38), and the least important making gauze ball(DC=2.39), and saving of operation site((DC=3.27). Conclusion: The results suggest a need to develop an education program using the DACUM chart as a basis for the development and as a clinical career ladder and for curriculum of operating room nursing.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.67 no.3
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• pp.358-364
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• 2018

In this study, the theoretical methodology is presented for estimating cost function based on operating modes for Combined Cycle Power Plant. The proposed method has estimated cost functions using the relationship between the gas turbine heat input and the output ratio of the steam turbine. In order to verify the proposed method, a regression analysis was performed using the single cost function estimated by the existing performance test method and the cost function for each operating mode estimated by the proposed method. The results of case studies using the 2016 generator input and output data are presented to show the effectiveness of the proposed method.

• Transactions of the Korean hydrogen and new energy society
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• v.27 no.2
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• pp.144-154
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• 2016

HT-PEMFC (high temperature polymer electrolyte membrane fuel cell) using PA (phosphoric acid) doped PBI (polybenzimidazole) membrane has been researched for extending the lifetime. However, the existing work on durability of HT-PEMFC focuses on identifying degradation causes of lab scale. The short life time of HT-PEMFC is still the problem for its commercialization. In this paper, an operating method to maximize life time of 5kW HT-PEMFC stack are proposed. The proposed method includes major steps such as minimization of OCV (Open Circuit Voltage) exposure, control of the proper stack temperature, and N2 purging for the stack. This long life operating method was based on the fragmentary results of degradation from previous research works. Experimentally, the 5 kW homemade HT-PEMFC stack was operated for a long time based on the proposed method and the stack successfully can operate within the desired degradation rate for the target life time.

• Journal of Power Electronics
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• v.19 no.3
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• pp.761-770
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• 2019

This paper proposes a hybrid phase windings excitation method for improving the efficiency of a 7-phase brushless DC (BLDC) motor in the electric propulsion system of a ship. The electrical losses of a BLDC motor system depend on the operating region and the number of excited phase windings (2-phase, 4-phase or general 6-phase windings). In this paper the operating region and torque/speed characteristics according to the motor rotation speed and propeller load are analyzed for a number of excitation methods. In addition, it analyzes the electrical losses of the system under each of the excitation methods in the entire operating region of the motor. In every sampling time, the proposed control method calculates the electrical loss of the system for each of the excitation methods and operates a 7-phase BLDC motor by selecting the excitation method that results a decreased electrical loss at the operating speed. The usefulness of the proposed control algorithm is verified through experimental results.

• Journal of Electrical Engineering and Technology
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• v.10 no.4
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• pp.1441-1452
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• 2015

This paper proposes a new Hybrid Particle Swarm Optimization (HPSO) method that integrates the Evolutionary Programming (EP) and Particle Swarm Optimization (PSO) techniques. The proposed method is applied to solve Economic Dispatch(ED) problems considering prohibited operating zones, ramp rate limits, capacity limits and power balance constraints. In the proposed HPSO method, the best features of both EP and PSO are exploited, and it is capable of finding the most optimal solution for the non-linear optimization problems. For validating the proposed method, it has been tested on the standard three, six, fifteen and twenty unit test systems. The numerical results show that the proposed HPSO method is well suitable for solving non-linear economic dispatch problems, and it outperforms the EP, PSO and other modern metaheuristic optimization methods reported in the recent literatures.

• Journal of Energy Engineering
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• v.11 no.4
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• pp.317-323
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• 2002

This paper proposed the calculation method of the generation operating avoided cost to cost-effectiveness evaluation of energy conservation programs that compounded the Proxy Plant Method and Load Decrement Method. This method introduced an operating index of the Energy Efficiency Demand-Side Management (EEDSM) resources based on the end-user's behaviors on the electricity power usage. The operation index is applied to calculate the hourly operating capacity of diffused high-efficiency appliances. And the operating capacity on the peak load hours for reference load is computed through the reduction of the peak load that contributes to that hour. Also, the proposed method evaluated the effect of EEDSM resources. The IEEE-RTS is adopted as a sample system to analyze impacts of an EEDSM. This paper, we have analyzed the effect of EEDSM upon the changes in the generation of generator, generation cost and the system marginal price (SMP). This method can be used to evaluate the impact of the diffused DSM resource and to estimate the impact in short-term EEDSM program. Further, result of the calculation can be utilized to pabulum for effect analysis of EEDSM resources.

• Proceedings of the Korea Society for Simulation Conference
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• 1999.04a
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• pp.212-216
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• 1999

We propose a method for simulation optimization using stochastic genetic algorithm(GA) to get the best design and operating policies in a Direct-Input-Output Automated Manufacturing System (DIOMS).