• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.16 no.1
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• pp.76-84
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• 2002

Voltage sags caused by line faults in transmission and distribution lines have become one of the most important power quality problems facing industrial customers and utilities. Voltage sags are normally described by characteristics of both magnitude and duration, but phase angle shifts should be taken account in identifying sag phenomena and finding their solutions. In this paper, voltage sags due to line faults such as three phase-to-ground, single line-to-ground, and line-to-line faults are characterized by using symmetrical component analysis, for fault impedance variations. Voltage sags and their effect on the magnitude and phase angle are examined. Balanced sags of three phase-to-ground faults show that voltages and currents are changed with equivalent levels to all phases and the zero sequence components become zero. However, for unbalanced faults such as single line-to-ground and line-to-line faults, voltage sags give different magnitude variations and phase angle shifts for each phase. In order to verify the analyzed results, some simulations based on power circuit models are also discussed.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.19 no.4
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• pp.691-700
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• 1994

A power line in not so good in characteristics for communication, because it is a media to transfer the commercial electrical power, and its load noise and high frequency noise are so much. Thus, a simple method to transfer a remote control signal on the power line is studied. The already-existing method is that two signals with upper part eliminated is transmitted every N step. But the method is investigated which the transmitter sends a period signal eliminated in arbitrary phase. Thus the transmission power loss due to elimination of signal can be reduced to the minimum. To implement it, a timer calculating the time from zero-crossing point to the phase is required. The micro-controller, 87C51, precisely calculates the phase using one of two built-in timers. As a result, a remote control signal tramsmitter and receiver using a partially eliminated signal, which is better than the conventional technique using half-eliminated signal in a efficiency of power transmission, is realized, and its characteristics are analyzed.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.29 no.8
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• pp.576-582
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• 2018

In this paper, a planar equi-phase power divider is proposed using fixed phase shifters. As the integrability of a phased array antenna increases for accurate beam steering, a conventional method to excite equi-phase signals to all element antennas, extending the feedline, has spatial limitations. Therefore, the planar equi-phase power divider is designed using a defected ground structure with a planar phase shift function without intentional feedline extension. The defected ground structure has been considered for a low insertion loss and a controllable phase shift, whereas the power divider has been designed and implemented with a port-to-port isolation and a planar configuration.

• Journal of the Korean Geographical Society
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• v.41 no.2 s.113
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• pp.188-194
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• 2006

Three-dimensional topological data is essential for 3D modeling and application such as emergency management and 3D network analysis. This paper reviewed current 3D topological data model and developed a method to construct 3D topological node-relation data structure from 2D computer aided design (CAD) data. The method needed two steps with medial axis-transformation and topological node-relation algorithms. Using a medial-axis transformation algorithm, the first step is to extract skeleton from wall data that was drawn polygon or double line in a CAD data. The second step is to build a topological node-relation structure by converting rooms to nodes and the relations between rooms to links. So, links represent adjacency and connectivity between nodes (rooms). As a result, with the conversion method 3D topological data for micro-level sub-unit of each building can be easily constructed from CAD data that are commonly used to design a building as a blueprint.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.8 no.5
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• pp.452-461
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• 1997

In this paper, we present a computer-aided design(CAD) technique for minimizing the phase shift in microstrip PIN diode attenuators due to the junction capacitance in the equivalent circuit model of PIN diode. Microstrip PIN diode attenuators use the characteristics which the reactance of microstrip line changes from inductive to capacitive as the frequency sweeps across the band. Microstrip PIN diode attenuator designed utilizes the quarter-wavelength transmission line terminating with the half-moon radial stub, which is designed for negligible phase shifting effect over the intersted bandwidth. The attenuator has similar phase shift at 0 dB and 10 dB of attenuation within average $1.27^{\circ}$ between 1.2GHz and 1.9GHz. The input and output return losses between 1.4 GHz and 1.9 GHz are less than 10 dB over the attenuation range of 0 dB and 10 dB.

• Korean Journal of Optics and Photonics
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• v.14 no.2
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• pp.184-188
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• 2003

We fabricated a P-I-i-I-N $GaAs/Al_{0.35}Ga_{0.65}As$waveguide phase modulator with significant phase shift for the TE mode but negligible for the TM mode. We selected the P-I-i-I-N structure to cause a phase shift about the TM mode. The wavelength of $\lambda=1.55$\mu\textrm{m}$ was measured for both the TE and TM modes, respectively. As a result, the measured phase shift efficiency ($\Delta\phi$) by using the Fabry-Perot resonance method was $7.9^{\circ}/V.mm$ for TE-polarized light. Also, no modulation was observed for TM-polarized light.

• Journal of the Institute of Electronics Engineers of Korea TE
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• v.42 no.2
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• pp.7-14
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• 2005

This paper presents a method to reduce torque ripple of brushless DC motor by compensating phase delay due to winding inductance. For considering torque ripple comes from the phase winding inductance, torque equation of one phase is derived as Fourier series that is function of the delay. From the equation, also the resultant equation that the current delay is compensated is derived. It is validated that the compensated torque has a form of Fourier series for rectangular wave that is ideal torque, and torque ripple is reduced, consequently. Experimental method for the compensation is realized by replacing switching pattern of inverter by pattern of compensated rotor position. The effectiveness of the proposed method to reduce torque ripple has been demonstrated by the simulation and experimental results using 3 phase 4 pole brushless DC moor.

• Journal of the Korean earth science society
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• v.38 no.6
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• pp.405-420
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• 2017

We investigated the H I, He II and O III emission lines of the symbiotic star AG Peg, using the spectroscopic data secured at different phases in three periods at the Lick Observatory. We measured FWHM and the intensity of six O III Bowen lines and studied the efficiency of fluorescence mechanism. The mean FWHM of O III normal and Bowen lines observed during three time periods did not make much difference, while Bowen line intensities are about 4.0 times higher than the normal lines. Comparing the predicted and the observed ratios, we found that the observed intensities are higher than predicted intensities, except for O III ${\lambda}$ 3759.87. The O III ${\lambda}$ 3791.26 and 3754.67 intensity ratios observed only in 2001 are in good agreement with the predictions by Saraph and Seaton (1980). We obtained the Bowen efficiency parameter (R)=0.47 for 2002, but we could not find R for the other two periods of time. Because of this, based on the 2002 efficiency result, we calculated the intensity ratio of O III normal and Bowen lines relative to He II ${\lambda}$ 4685.68 and derive the efficiency variation with time period. The result showed that the efficiency is the highest in 1998 and the lowest in 2001. We conclude that the efficiencies with phase are caused by the electron temperature changes in the ionized gas. The efficiencies of AG Peg are likely to increase along with electron temperature. Our analysis results may be useful in understanding the physical conditions of the ionized shell in symbiotic star and the intensity ratio and efficiency variation.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.25 no.11
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• pp.1759-1766
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• 2001

Vibration transient generated by developing localized fault in gear can be used as indicators in gear fault detection. In this paper, we propose the zoomed phase map for a fault signal using continuous wavelet transfers to detect this vibration transient. Local fault induces the abrupt fluctuation of load exciting tooth and phase lag in the vibration signal measured on the gearbox. The relatively large fault like "tip breakage" easily can be detected by the clear fluctuation of exciting load. However, minor fault like "initial pitting"cannot be detected using the load fluctuation. To defect this kind of minor fault, the phase map for a fault signal is taken into account. The phase lag by minor fault is observed well in the zoomed phase map.

• Journal of Korea Multimedia Society
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• v.5 no.1
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• pp.114-119
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• 2002

Realtime assignment of railways is an important component in the railway control systems. To solve this problem, we must exactly represent the track topology. Graph is a proper data structure for representing general network topologies, but not Proper for track topologies. In this paper, we define a new data structure, railway graph, which can exactly represent topologies of railway networks. And we describe a path search algorithm in the defined railway graph, and a top-down approach for designing railway network by the Proposed graph.