• Journal of the Korean Society for Railway
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• v.9 no.3 s.32
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• pp.10-16
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• 2006

• Information Systems Review
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• v.4 no.2
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• pp.237-255
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• 2002

In this study, we develop a four phase model of ERP implementation, which includes Chartering phase, Project phase, Shakedown phase, and Onward and upward phase. We then examine how the completeness of each phase influences the implementation success as well as the completeness of next phase. The results of this study show that project phase and onward and upward phase both have significant impacts on the implementation success. We also find that all relationships between the completeness of previous phase and next phase are significantly positive.

• 전기의세계
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• v.21 no.3
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• pp.7-18
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• 1972

An analysis is made for the performance of twin stator single-phase induction machine having any movable asymmetrical angle of stator windings, with any symmetrical or asymmetrical magnetizing reactance and winding turn-ratio between two stators, provided that asymmetrical common squirrel cage rotor is utilized. This mechanism is a new type, which has the advantage of mading only not the performance prediction in applications as a single-phase electromagnetic driving mechanism but also the analysis prediction of single-phase induction motor with not in quadrature axis. The basis of the analyses are lead by Kron's primitive machine matrix and Morrill's double-revolving field concept. All the performances can be calculated from the test values and design details of the asymmetrical magnetizing reactance twin stator single-phase induction machine and verified by test. And its validity is still demonstrated to the pure twin stator single-phase induction machine.

• Journal of Korea Society of Industrial Information Systems
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• v.20 no.1
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• pp.49-55
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• 2015

This paper proposes a 2.4 GHz RF oscillator with a very low close-in phase noise performance. This is composed of a low frequency crystal oscillator and three frequency multipliers such as two doubler (X2) and one tripler (X3). The proposed oscillator is implemented as a hybrid type circuit design using a discrete silicon bipolar transistor. The measurement results of the proposed oscillator structure show -115 dBc/Hz close-in phase noise at 10 kHz offset frequency, while only dissipating 5 mW from a 1-V supply. Its close-in phase noise level is very close to that of a low frequency crystal oscillator with little degradation of noise performance. The proposed structure which is consisted of a low frequency crystal oscillator and a frequency multiplier provides new method to implement a low power low close-in phase noise RF local oscillator.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.58 no.3
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• pp.523-530
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• 2009

This paper presents a study on a small scale single-phase UPFC preliminary researches on power quality compensating schemes of electrical railway. As the UPFC is very complicated power-electronic system consisting of grid-connected transformers, four single phase inverters interconnected with dc-link capacitors and various electrical apparatuses, multiple controllers and control algorithms are needed, and entire UPFC has been modelled in the form of block diagrams and simulated by using Simulink. The main purpose of the compensating system is to manage reactive and active powers with the four single phase inverters, so, the control effort has been focused on the power flow control and has been realized through the hysteresis current control of the single phase inverters. And transport-delayed PLL with additional delay-time compensating term has been used to synchronize a grid voltage and the simulation results have shown that the compensating term could improve PLL performance under some frequency variation of the voltage.

• Proceedings of the KIEE Conference
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• 2005.11a
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• pp.79-80
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• 2005

The solid precursor produced by the dehydration of the gel at $120^{\circ}C$ for 12h is not in the amorphous state as expected but in a crystalline state. X-ray diffraction peaks of nearly the same angular position as the peaks of high Tc phase were observed in the precursor. Experimental results suggest that the intermediate phase formed before the formation of the superconducting phase may be the most important fact in determining whether it is easy to form the superconducting phase or not, because the nucleation barriers of the two superconducting phase may be altered by the variation of the crystal structures of those intermediate phase.

• Proceedings of the KIEE Conference
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• 2002.07c
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• pp.1919-1921
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• 2002

In this paper, we were designed the ferroelectric phase shifter using 3-dB, $90^{\circ}$ branch-line hybrid coupler with two ports terminated in symmetric phase-controllable reflective networks. The design of phase shifter is based on reflection theory of terminating circuits. In order to find the optimum conditions of reflect phase, the effect of a change of capacitance and transmission line connected with two coupled ports of a coupler have been investigated. To obtain more accurate design parameters, finite element method is applied. We were showed large phase variation with small capacitance variation in the parallel connection of capacitor and transmission line by using EM-simulation and circuit-simulation.

• ETRI Journal
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• v.27 no.6
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• pp.677-684
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• 2005

A phased array antenna was fabricated using four-element ferroelectric phase shifters with a coplanar waveguide (CPW) transmission line structure based on a $Ba_{0.6}Sr_{0.4}TiO_3(BST)/MgO$ structure. Epitaxial BST films were deposited on MgO (001) substrates by pulsed laser deposition. To attain the large differential phase shift and small losses for a ferroelectric CPW phase shifter, an impedance-matching-part adding technique between the effective transmission line and connecting cable was used. The return loss and insertion loss for this techniqueadapted BST CPW device were improved with respect to those for a normal BST CPW device. For an X-band phased array antenna system consisting of ferroelectric BST CPW phase shifters, power divider, dc block, patch antenna, and programmed dc power, the steering beam could be tilted by $15^{\circ}$ in either direction.

• Journal of Power Electronics
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• v.9 no.4
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• pp.535-543
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• 2009

In this paper, pulse-width modulation (PWM) control strategy of various topologies of matrix converters is presented, which is based on direct duty ratio PWM (DDPWM). Because the DDPWM method has the characteristics of the inherent per-phase modular structure, it can be effectively applied to single-phase, two-phase and three-phase four-leg matrix converters as well as the common three-phase to three-phase matrix converter. Also, this paper treats command generation method in each matrix converter. The feasibility and validity of the proposed method are verified by experimental results.

• Proceedings of the KIEE Conference
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• 2005.07c
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• pp.1966-1967
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• 2005

The solid precursor produced by the dehydration of the gel at $120^{\circ}C$ for 12h is not in the amorphous state as expected but in a crystalline state. X-ray diffraction peaks of nearly the same angular position as the peaks of high Tc phase were observed in the precursor. Experimental results suggest that the intermediate phase formed before the formation of the superconducting phase may be the most important fact in determining whether it is easy to form the superconducting phase or not, because the nucleation barriers of the two superconducting phase may be altered by the variation of the crystal structures of those intermediate phase.