• Journal of Electrical Engineering and Technology
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• v.5 no.3
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• pp.400-406
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• 2010

This paper deals with parameter tuning of the Power System Stabilizer (PSS) for 612 MVA thermal power plants in the KEPCO system and its validation in a field test. In this paper, the selection of parameters, such as lead-lag time constants for phase compensation and system gain, is optimized using linear and eigenvalue analyses. This is then verified through the time-domain transient stability analysis. In the next step, the performance of PSS is finally verified by the generator's on-line field test. After the field test, measured and simulated data are also compared to prove the effectiveness of the models used in the simulations.

• Journal of Astronomy and Space Sciences
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• v.17 no.2
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• pp.257-266
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• 2000

A satellite RF communication link is analyzed based on a simple fundamental equations by systematic approach in this paper. The number of variables related to a design and analysis of satellite RF link is often a dozen or more, thus it is a tedious and time-consuming task. With the given input data, the important parameters are calculated step by step and three communication characteristics such as communication channel capacity, carrier-to-noise ratio(CNR) at the satellite and ground station are analyzed. It gives very useful information to the system engineers for designing and analyzing the overall satellite communication system in the conceptual design phase.

• International Journal of Railway
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• v.5 no.2
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• pp.84-88
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• 2012

Derailment due to wheel failure would cause a tremendous social and economical cost in service operation. It is necessary to evaluate quantitatively the safety with respect to high-speed train. Although the safety of railway wheel has been ensured by an regular inspection, all critical defects cannot be detected in inspection cycles and the wheel has been replaced because a defect quickly become critical for safety. Therefore, it is important to calculate quantitatively the fracture limit and remnant life of damaged railway wheel in wheel-rail system. In present paper, the critical crack size of wheel for high-speed train is simulated based on fracture scenario and the safety of wheel is evaluated.

• Structural Engineering and Mechanics
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• v.3 no.2
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• pp.135-144
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• 1995

Since structural systems may fail in any one of several failure modes, computation of system reliability is always difficult. A method using numerical quadrature for computing structural system reliability with either one or more than one failure mode is presented in this paper. Statistically correlated safety margin equations are transformed into a group of uncorrelated variables and the joint density function of these uncorrelated variables can be generated by using the Maximum Entropy Method. Structural system reliability is then obtained by integrating the joint density function with the transformed safety domain enclosed within a set of linear equations. The Gaussian numerical integration method is introduced in order to improve computational accuracy. This method can be used to evaluate structural system reliability for Gaussian or non-Gaussian variables with either linear or nonlinear safety boundaries. It is also valid for implicit safety margins such as computer programs. Both the theory and the examples show that this method is simple in concept and easy to implement.

• Proceedings of the KIEE Conference
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• 1996.11a
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• pp.80-83
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• 1996

This paper develops a method for reliably estimating an UEP(Unstable Equilibrium Point) which is located in the direction of SEP(Stable Equilibrium Point)'s moving as system load is getting heavy. As power systems are getting loaded heavily, the SEP which is an operable solution, and the UEP which is occurring voltage collapse, are moving toward each other linearly. The estimated UEP is used as a good initial guess for the real UEP. The proposed method is tested by 3 bus system and Stagg 5 bus system. It is demonstrated that the proposed method is very useful for assessing system voltage stability in the case of heavy loaded power system. The result solutions are often used in conjunction with energy methods and the stability margin.

• Proceedings of the Korean Information Science Society Conference
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• 1999.10b
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• pp.598-600
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• 1999

본 논문은 수공으로 이루어지는 치과 치료 및 보철물 제작을 3차원 컴퓨터 모델링을 하여 좀 더 정확하고 빠른 시간에 처리할 수 있는 시스템을 소개한다. 이 시스템은 기존 2차원 기반이 아닌 3차원 기반으로 설계되었으며, 구강의 석고 모형을 3차원으로 컴퓨터에 모델링한 후, 모델링 정보로부터 능선(ridge), 교두(crusp), 피트(pit), 열구(fissure), 변연(margin) 등과 같은 치아 특성 정보추출과 교합면 생성을 통하여 보철물, 예를 들어 Conus 내관과 외관을 제작한다. 해부학적으로 무수히 많은 변수를 갖고 있는 구강 구조에 대해 본 논문에서는 이들 일련의 과정에서 요구되는 컴퓨터 모델링의 주요 기술들을 제시한다.

• 제어로봇시스템학회:학술대회논문집
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• 1997.10a
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• pp.468-471
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• 1997

In this paper, we investigate the time-sampling effects on the digital implementation of singular perturbation based STT autopilot with excellent performance and propose a compensation method for the time-sampling effects. In digitization of analog STT autopilot, it is found that the stability margin of the fast dynamics is mostly affected to lead to rapid decrease. Under the this analysis, a composite digital controller with additional compensator for fast dynamics is proposed to improve the time-sampling effect and a simulation verifies the result.

• 제어로봇시스템학회:학술대회논문집
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• 2005.06a
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• pp.2183-2187
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• 2005

In this paper we propose a new fault detection and isolation (FDI) method for those faults of parameter change type. First, we design a residual generator based on the ${\delta}$-operator model of the plant by using the stable pseudo inverse system. Second, the parameter change is estimated by using the property of the block Hankel operator. Third, reliability with respect to stability is quantified. Fourth, the limitations for the meaningful diagnosis in our method are given. The numerical examples demonstrate the effectiveness of the proposed method.

• Proceedings of the KIEE Conference
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• 1992.07a
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• pp.279-281
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• 1992

In this paper, an LQG/LTR procedure for stable nonminimum phase systems is suggested using predictor scheme. In the method, the performance of the target feedback loop can be easily adjusted and the recovery error is less dependent on the location of NMP zeros than previous methods. The gain and phase margin and the robust ness for modeluncertainty of the suggested control system are obtained.

• 제어로봇시스템학회:학술대회논문집
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• 1990.10a
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• pp.529-533
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• 1990

This paper treats the computational time delay issue in designing digital control systems. The computational time delay margin, within which the closed-loop stability is guaranteed, is analyzed using Rouche theorem. A PID control algorithm is proposed for compensating the computational time delay. Finally, the analyzed and the exact computational time delay margins are compared, and the performance of the proposed PID controller is shown through an illustrative example.