• Proceedings of the KWS Conference
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• 2002.05a
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• pp.121-122
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• 2002

• Proceedings of the KWS Conference
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• 1994.10a
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• pp.93-95
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• 1994

• Bulletin of the Korean Chemical Society
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• v.27 no.7
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• pp.1009-1014
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• 2006

Density functional theory calculations are applied to investigate the intramolecular proton transfer in the tautomers of thymine radical cation and its hydrated complexes with one water molecule. The optimized structures and energies for 6 tautomers and 6 transition states of thymine radical cation are calculated at the B3LYP/6-311++G(d,p) level. It is predicted that the order of relative stability for the keto and enol tautomers of thymine radical cation is the same with that of the neutral thymine tautomers, though the enol tautomers are more stabilized with respect to the di-keto form in the radical cation than in the neutral state. A new channel of proton transfer from >C5-$CH_{3}$ of thymine is found to open and have the lowest energy barrier of other proton transfer processes in thymine radical cation. The roles of hydration are also investigated with thymine-water 1 : 1 complex ions. The presence of water significantly lowers the barrier of the proton transfer, which clearly shows the assisting role of hydration even with one water molecule

• Journal of the Korean Society of Fisheries and Ocean Technology
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• v.26 no.3
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• pp.282-287
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• 1990

In this paper, it has been analysed that the stability and the effectivity of the solution using traditional transfer matrix method. And applying the false-position method to these, the convergence characteristics of the solution has been also analysed. As a result, the frontal transfer matrix method is superior to traditional transfer matrix method in the stability and the accuracy of the solution in high frequency region but in the economical efficiency and the effectivity of the calculation, traditional transfer matrix method is more desiable. Also, it is clear that $\omega-Det$ curve using the frontal transfer matrix method is discontinuous.

• Journal of Welding and Joining
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• v.8 no.1
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• pp.31-42
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• 1990

Arc must be stable during welding first of all other factors for obtaining sound weldment, especially in the automation of welding process. Arc stability is somewhat sophisticated phenomenon which is not clearly defined yet. In consumable electrode welding, the voltage and current variation due to metal transfer enables to assess arc stability. Recently, statistical analyses of the voltage and current waveform factors are performed to assess the degress of arc stability which is assessed and controlled by operator's own experience by now. But, considering the increasing need and the trend of automation of welding process, it is necessary to monitor arc stability in real-time. In this sutdy, the modified stability index composed of two voltage and current wvaeform factors (arc time and short circuit time) reduced from four factors (arc time, short circuit time, average arc current and average short circuit current) in Mita's index by the welding electrical circuit modeling is proposed and verified by experiments to be well estimating arc stability in the static sense. Also, the recursive calculation form estimating present arc stability in the dynamic sense is developed for real-time estimation. The results of applying the recursive index during welding show good estimation of arc stability in real-time. Therefore, the results of this study offers the mean for real-time control arc stability.

• Journal of the Korean Society of Manufacturing Process Engineers
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• v.5 no.2
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• pp.16-21
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• 2006

In this study, the analytic realization of chatter mechanism using radial basis neural network(RBNN) was introduced and compared with the conventional stability analysis. In this regard, the FFT and time series spectrum analysis was used as a criterion for the existence of chatter in end-milling force. The desired coded outputs of chatter was trained and finally converged to desired outputs. The output of the RBNN match well with the conventional desired stability lobe. Using this trained data, the stability boundary of the radial basis neural network was acquired using the contour plotting. As a result, the proposed stability lobe boundary using RBNN consists well with the conventional analytical boundary that is calculated in characteristic equation of transfer function in chatter dynamics. In this RBNN analysis, two input and three output parameters were used in this paper.

• The Transactions of the Korean Institute of Electrical Engineers A
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• v.48 no.10
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• pp.1222-1230
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• 1999

This paper presents the framework for analysis of small-signal stability. In this framework the equilibrium points of system DAE model are traced using continuation method and instability points are determined on the solution path. Especially Implicit shift QR-modified Arnoldi method is utilized to calculated the rightmost eigenvalues. Small-signal stability is becoming one of the major factors that affect the ATC in the environment of deregulation. Stability limited ATC is easily evaluated in this stability analysis process.

• KIEAE Journal
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• v.10 no.4
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• pp.75-80
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• 2010

Generally, ground-source heat pump (GSHP) systems have a higher performance than conventional air-source systems. However, the major fault of GSHP systems is their expensive boring costs. Therefore, it is important issue that to reduce initial cost and ensure stability of system through accurate prediction of the heat extraction and injection rates of the ground heat exchanger. Conventional analysis methods employed by line source theory are used to predict heat transfer rate between ground heat exchanger and soil. Shape of ground heat exchanger was simplified by equivalent diameter model, but these methods do not accurately reflect the heat transfer characteristics according to the heat exchanger geometry. In this study, a numerical model that combines a user subroutine module that calculates circulation water conditions in the ground heat exchanger and FEFLOW program which can simulate heat/moisture transfer in the soil, is developed. Heat transfer performance was evaluated for 3 different types ground heat exchanger(U-tube, Double U-tube, Coaxial).

• Journal of Institute of Control, Robotics and Systems
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• v.15 no.7
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• pp.655-660
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• 2009

In many real applications, the discrepancy problem between controller outputs and plant inputs or the abrupt variation problem of controller outputs can occur. These problems have a negative effect on control performance and stability. It is well-known that two phenomena called 'windup' and 'bump' cause these problems. So far these problems have been studied separately in each side of the anti-windup and the bumpless transfer. This paper proposes a new unified method combines the anti-windup and the bumpless transfer method using the linear quadratic minimization and a proper state space model representation for the anti-windup controller. The proposed method has a feature that it takes account of both the anti-windup and the bumpless transfer in one formula. Finally, we exemplify the performance of the proposed method via numerical examples using the controller switching between the anti-windup PID controller and the anti-windup LQ controller.

• Journal of Power Electronics
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• v.17 no.4
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• pp.884-891
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• 2017

The improved transfer functions of the modified Sheppard-Taylor (MS-T) converter, which is capable of regulating output voltage under a wide range of input voltage and load variations, negligible current ripple, and fewer components in comparison to the Sheppard-Taylor (S-T) converter, operating in continuous conduction mode (CCM) are investigated in this study. Its DC equilibrium point, small signal model, and transfer functions are derived and analyzed. Then, the voltage controller is applied for this MS-T converter. The comparisons between the derived model and the existing model are presented. The hardware circuit is designed and the circuit experiments are provided for validation. The results show that the improved transfer functions of the MS-T converter are more effective and general than the previous ones for describing its real characteristics.