• Journal of the Korea Institute of Information and Communication Engineering
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• v.9 no.5
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• pp.1123-1131
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• 2005

In this paper, optimal position of optical phase conjugator (OPC) for best compensating distorted WDM channels due to both chromatic dispersion and self phase modulation (SPM) in $8{\times}40$ Gbps WDM systems is numerically investigated, and the eye opening penalty (EOP) and bit error rate (BER) characteristics of overall WDM channels at this position is investigated, comparing with that in case of OPC placed at mid-way of total transmission length. It is confirmed that the compensation extents in WDM system with OPC is more improved by the shifting OPC position from the mid-way of total transmission length, depending on the modulation format and fiber dispersion coefficient. Ant it is confirmed that, from a viewpoint of the reception performance, EOP of each channel is more or less different with one another, but the BER characteristics of overall channels are almost equal.

• 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.

• ETRI Journal
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• v.37 no.1
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• pp.26-31
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• 2015

Axial-ratio (AR) bandwidth enhancement is achieved for a circularly polarized (CP) cylindrical dielectric resonator antenna (DRA) using a wideband hybrid coupler (WHC) combined with dual probe feed. The presented WHC, comprised of a Wilkinson power divider and a wideband $90^{\circ}$ shifter, delivers good characteristics in terms of 3 dB power splitting and consistent $90^{\circ}$ (${\pm}5^{\circ}$) phase shifting over a wide bandwidth. In turn, the proposed CP DRA, for the employment of the WHC, in place of conventional designs, provides a significant enhancement on AR bandwidth and impedance matching. The antenna prototype with the WHC exhibits a 3 dB AR bandwidth of 48.66%, an impedance bandwidth of 52.5% for voltage standing wave ratio (VSWR) ${\leq}2$, and a bandwidth of 44.66% for a gain of no less than 3 dBi. Experiments demonstrate that the proposed WHC is suitable for broadband CP DRA design.

• Proceedings of the IEEK Conference
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• 1998.10a
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• pp.1231-1234
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• 1998

Many signal processing methods of widening the sound image for spatial impression have been studied. Most typical methods of widening the sound image are related to the phase shifting and precedence effect. However, these methods are not effective in center sound image. As listener's position moves from center to outside, the center sound image is shifted to the speaker. That is to say, the directional localization of center sound image is unstable. In this paper, we propose a television audio system including center speaker, and analyze the role of center speaker using theory of Makida and precedence effect. In experiments, we confirm the usefulness of the center speaker for the stability of center sound image.

• Journal of the Korean Solar Energy Society
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• v.21 no.4
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• pp.47-54
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• 2001

This study has been conducted to verify the possibility of adaptation of a latent storage type air-conditioning system, shifting the peak load of electronic power to a building. In this paper, an energy equation to evaluate performance of PEM(phase change material) has been suggested and solved, after discretization. As a result, it is confirmed that the results from the energy equation are correspond with those from present studies to analysis of one-dimensional solidification and to analysis of two-dimensional solidification.

• Proceedings of the KIEE Conference
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• 2009.07a
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• pp.1589_1590
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• 2009

본 논문에서는 구면 렌즈 검사를 위해 제작된 Fizeau형 위상 천이 간섭계(Fizeau-type Phase Shifting Interferometer : FPSI)에 비구면 해석 알고리즘을 적용한 소형 비구면 렌즈 해석 방법을 제안한다. 또한 본 논문에서 제안한 방법의 측정 결과와 기존 비구면 검사 시스템의 측정 결과를 비교하여 그 성능을 평가한다.

• Journal of Electrical Engineering and Technology
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• v.10 no.4
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• pp.1610-1620
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• 2015

A major problem in conventional multilevel inverter is that an increase in power semiconductor switches causes an increase in cost and switching losses of the inverter. The multicarrier strategy adopted for the multilevel inverters has become more popular due to reduced cost, lower harmonic distortion, and higher voltage capability than the conventional switching strategy applied to inverters. Various topologies and modulation strategies have been reported for utility and drive applications. Level shifted based pulse width modulation techniques are proposed to investigate the performance of the multilevel inverter. The proposed work focuses on reducing the utilized switches so that the cost and the switching losses of the inverter do not go up and the consistent efficiency could be achieved. This paper presents the detailed analysis of these topologies. The analysis is based on the number of switches, DC sources, output level, maximum voltage, and the efficiency. As an illustration, single phase cascaded multilevel inverter topologies are simulated using MATLAB/SIMULINK and the experimental results demonstrate the viability of these inverters.

• Journal of the Korean Society of Physical Medicine
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• v.3 no.2
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• pp.113-119
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• 2008

Purpose : In this case report, we demonstrated the improvement of gait ability on the child who has mental retardation with incomplete gait pattern. Methods : The subject was a 4 years old boy with mental retardation. We applied the Bobath approach to the subject. Treatments included to facilitate trunk alignment and stability, and to train weight bearing and shifting, to facilitate pelvis posterior-anterior movement, and to train walk especially stance phase and assist up-down stairs locomotion in environment similar to actual daily life. It was performed 24 sessions for 12 weeks. Results : With this treatment, he could accomplish dynamic standing stability and he could independent walk at the out door after 12 weeks. In gross motor function measure(GMFM), total motor function was improved to 85.6% from 75.7%. Conclusion : The gait ability of child with mental retardation was improved by using the bobath approach.

• The Journal of the Korea Contents Association
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• v.1 no.1
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• pp.24-31
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• 2001

In The AV system, to produce a realistic sound effect is very difficult because the distance between stereo speakers is very narrow. Many signal processing method of widening the sound image for spatial impression have been studied. Most of the typical methods of widening the sound image are related to the phase shifting. but this method was not effective in the concrete wall structure with high reflectivity. In this paper, we proposed an effective method of extending stereo sound image using Precedence Effect and reflected sound. In experiments we confirmed the usefulness of the method for extending stereo sound image of a conventional AV system in wider listening area of a room.

• Proceedings of the KIEE Conference
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• 2005.11b
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• pp.223-225
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• 2005

This paper presents a scheme to solve the congestion problem using hybrid control with phase-shifting transformer(PST) and power generation in power systems. A good design of PST and power generation control can improve total transfer capability(TTC) in interconnected systems. This paper deals with an application of optimization technique for TTC calculation. The optimization method is used to maximize power flow of tic line subject to security constraints such as voltage magnitude and real power flow. The proposed method is applied to 10 machines 39 buses model systems to show its effectiveness.