• 전력전자학회논문지
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• 제17권3호
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• pp.205-212
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• 2012

This paper proposes the fuzzy logic based variable step-size MPPT (Maximum Power Point Tracking) method for the stability at the steady state and the improvement of the transient response in the wind power system. If the change value of duty ratio is set on stability of the steady state, MPPT control traces to maximum power point slowly. And if the change value is set on improvement of the transient response, the system output oscillates at the maximum power point. By adjusting the step size with fuzzy logic, it can be improved the MPPT response speed and stability at steady state when MPPT control is performed to track the maximum power point. The effectiveness of the proposed method has been verified by simulations and experimental results.

• 아태비즈니스연구
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• 제3권1호
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• pp.29-38
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• 2012

This study aims at evaluating the impact of network formation variables and found to have positive impact on the economic performance and growth of the enterprises. The calucation of the weighted scores of networking statements brought some affirmative results to influence the performance of the enterprises. Through multiple regression and logistic regression models it is identified that network formation variables like service receiving status, consultation of the family, other business dummy and attendance in fair have some significant positive impact both on the growth and performance of the enterprises. In addition to above variables, from the set of enterprise characteristics natural logarithm of the market value of total assets and from the entrepreneurs' characteristics set of variables, schooling year and squared value of the experience have been found to have significant positive impact. Finally, it is concluded in the study that to enhance the performance and growth of the enterprises, government and policy rlated organizations need to consider important variables that have positive impact in supplying the entrepreneurial resources especially, developing the net-working relationship.

• 한국정밀공학회지
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• 제23권2호
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• pp.65-72
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• 2006

Downcoiler is one of the major facilities in hot strip mill operation. The key to good coiling is having good equipment, modem control systems, excellent maintenance and an understanding of coiling process. Therefore, this study aims to develop a program that is useful for calculating machine design parameters and simulating coiling process. In this study, the pinching and coiling mechanism of the downcoiler was thoroughly studied and some of operational factors and their effects on the coiling process were investigated. The software was developed to estimate engineering parameters for coiler component design and to determine optimal setting values for successful coiling operation. In order to check the accuracy and usefulness of the developed software, the simulation of the downcoiler in $\#2$ Hot Strip Mill in Pohang Works was performed. The simulation results suggested that the set-up value for unit tension could be lowered. Test coiling operation by using the lowered set-up value for unit tension resulted in much more successful coiling in the aspect of strip quality and power consumption.

• 대한전기학회논문지:전기물성ㆍ응용부문C
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• 제50권3호
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• pp.130-135
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• 2001

In this paper, the distribution characteristics of salt contaminants with the distance from sea in East coast, from Sokcho to Pusan of Korea peninsula were investigated to evaluate the design standard of KEPCO. To get the equivalent salt deposit density(ESDD), conventional brush wiping method was used. As the measuring period is comparatively short, and the measuring interval is long to check the maximum value, acquired ESDD data is very lower than the recommended value in the standard. The measured data didn't follow normal distribution, so it should take the statistical treatment. Through normalizing method, we could get a reliable probability data. In the past investigation, the accumulation characteristics of Japan is consulted to set the criterion, but the climatic condition of Korea is different to Japan. With the comparison of precipitation data and some measured data for long tern accumulation, we could set appropriate accumulation factor.

• 대한조선학회논문집
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• 제41권2호
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• pp.79-89
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• 2004

The viscous free surface flow around KRISO container ship (KCS) is computed using the finite volume based multi block RANS code, WAVIS developed at KRISO. The free surface is captured with the Level-Set method and the realizable k-$\varepsilon$ model is employed for turbulence closure. The computations are carried out at model scale. For accurate free surface solution and its stable convergence the computations are performed with a suitable grid refinement around the free surface by applying an implicit discretization method based on a finite volume method to the Level-Set formulation. In all computational cases the numerical results agree well with experimental measurements.

• 한국정보통신학회논문지
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• 제9권3호
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• pp.498-503
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• 2005

Turbine Load Set Motor장치는 노후화 된 화력 발전소에서 출력 부하를 결정하는 중요한 장치로서, Motor를 가변하면서 발전 출력 부하를 조정하게 된다. 이러한 종래 발전시스템에서는 Set Up Range를 운영자가 수동으로 조작한 Set Up값에 따라 Motor를 회전시키게 되며, Motor를 포함한 내부적 동작에 의해서 발전 출력 부하 결정이 이루어지게 된다. 따라서 본 논문에서는 수동적으로 출력부하를 작동되는 Turbine Motor Drive Unit를 대처할 수 있는 Digital Drive Unit 장치를 개발하여 기존 Turbine Load Set Motor 성능을 지닐 수 있는 장비를 구현한다. 또한 구현한 Digital Drive Unit을 바탕으로 발전 출력 부하를 결정하는 기본 기능을 기존 Motor Drive Unit과 연결하여 작동될 수 있도록 제어 알고리즘 구현과 구현된 제어 시스템을 통해 기존 Turbine Load Set Motor Drive와 연결 가능성을 확인한다.

• 한국기술혁신학회:학술대회논문집
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• 한국기술혁신학회 2001년도 추계학술대회
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• pp.307-337
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• 2001

In this paper, we propose the valuation frame of the IT(Information Technology) ventures using ROV(Real Options Valuation) model. Generally, ROV can comprises the traditional valuation method such as DCF(Discounted Cash Flow), which can measure only the tangible value of a firm from the expected future earnings, in that ROV can additionally measure the intangible value such as the strategic value of a firm in the uncertain environment. We set up the hypothetic IT venture future investment plan and assume that there are a growth option and a switching option consequently along the investment time horizon, which are caused by each characteristics of ventures and IT technologies, especially modularity. In the case that there are several embedded real options in the firm's investment plan in a row, we should apply the compound option pricing model as a real option valuation model in order to consider the value interaction between real options. In an addition, we present the results of optimal investment timing analysis using real options approach and compare them. with those of the original assumed investment timing.

• 한국지능시스템학회논문지
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• 제14권2호
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• pp.125-129
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• 2004

There are several kinds of fuzzy set extensions in the fuzzy set theory. Among them, this paper is concerned with interval-valued fuzzy sets, intuitionistic fuzzy sets, and bipolar-valued fuzzy sets. In interval-valued fuzzy sets, membership degrees are represented by an interval value that reflects the uncertainty in assigning membership degrees. In intuitionistic fuzzy sets, membership degrees are described with a pair of a membership degree and a nonmembership degree. In bipolar-valued fuzzy sets, membership degrees are specified by the satisfaction degrees to a constraint and its counter-constraint. This paper investigates the similarities and differences among these fuzzy set representations.

• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 2001년도 추계학술대회논문집 I
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• pp.444-449
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• 2001

The purpose of the work is to improve comfort of a car seat, especially dynamic comfort which affects driver's discomfort during the long time driving. Definition of dynamic comfort was made before the investigation of which parameter affects seat comfort. In order to optimize design parameters so as to maximize seat comfort as well as to know the cause of discomfort, benchmarking on a target vehicle and competitive vehicles was performed, which showed both the vibration transmission characteristics and the compression set due to dynamic loading should be reduced. As a solution ball rebounds was increased by about 10％ of the original foam, which showed reduction of S.E.A.T. value by 10％ and of compression set by 60％.

• 한국지능시스템학회:학술대회논문집
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• 한국퍼지및지능시스템학회 2001년도 춘계학술대회 학술발표 논문집
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• pp.12-15
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• 2001

There are several kinds of fuzzy set extensions in the fuzzy set theory. Among them, this paper is concerned with interval-valued fuzzy sets, intuitionistic fuzzy sets, and bipolar-valued fuzzy sets. In interval-valued fuzzy sets, membership degrees are represented by an interval value that reflects the uncertainty in assigning membership degrees. In intuitionistic sets, membership degrees are described with a pair of a membership degree and a nonmembership degree. In bipolar-valued fuzzy sets, membership degrees are specified by the satisfaction degrees to a constraint and its counter-constraint. This paper investigates the similarities and differences among these fuzzy set representations.