• Journal of the Korean Institute of Telematics and Electronics
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• v.19 no.5
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• pp.55-67
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• 1982

In this Paper new results relating to the acquisition behavior of a class of first-and secondorder digital phase-locked loops (DPLL) originally proposed by Reddy and Cupta are presented in the absence of noise. It has been found that the number of quantization levels L and the number of phase error states N play important roles in acquisition. For a given L-level quantizer, as N increases, the acquisition time increases, and the lock range decreases. However, the deviation of the steady state phase error decreases in this case. When L increases, the acquisition time decreases, and the lock range increases. However, variation of L affects little for the steady state phase error. In addition, the effects of a loop filter on acquisition have also been considered. One can get smaller acquisition time and larger lock range as the filter parameter value becomes larger. However, deviation of the steady state phase error increases in that case. Analytical results have been verified by computer simulation.

• Proceedings of the KIEE Conference
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• 2011.07a
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• pp.230-231
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• 2011

본 논문은 2011년 제주계통 한림변전소와 금악변환소 사이에 설치 예정인 ${\pm}80kV$ 60MW HVDC 시스템의 DC 가공선로를 기존의 AC 송전 철탑의 AC 선로와 병렬로 추가하여 운영할 때 선로 Coupling에 따른 정상상태 영향을 분석한 내용이다. 한림변전소와 금악변환소 사이 철탑 17개의 데이터를 기반으로 송전선로를 모델링함으로써 실제 데이터에 최대한 근접할 수 있도록 정확성을 도모하였으며, 모델링과 분석에 있어서 전자계과도현상 해석프로그램인 PSCAD를 이용하였다. 특히 AC 병렬 연계 유무에 따른 DC 전류 주파수를 비교함으로써 AC/DC Coupling의 영향을 분석하였으며 최종적으로 이에 따른 기본파 성분 제거에 필요한 DC 필터 설치 유무에 관한 결론을 도출하였다.

• Journal of Astronomy and Space Sciences
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• v.22 no.2
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• pp.175-186
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• 2005

In this paper, the development of the extended kalman filter(EKF) which is based on Koreasat-3 bus system is introduced and the design result is shown through the simulation. Especially to determine the filter gains for accurate estimation, there is assumed that initial estimated parameters are not changed. But although the satellite performs the attitude control by 2Hz, it is verified that the EKF is running rightly using the changed filter gains. Also some cases are considered using the simulation : with each bias for 4-axis gyro and with gyro each axis failure. It is verified that the designed filter can be used as the back-up about gyro failure.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.41 no.5
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• pp.401-407
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• 2017

This paper describes wavenumber filtering for damage detection using single-frequency standing wave excitation and laser scanning sensing. An embedded piezoelectric sensor generates ultrasonic standing waves, and the responses are measured using a laser Doppler vibrometer and mirror tilting device. After scanning, newly developed damage detection techniques based on wavenumber filtering are applied to the full standing wave field. To demonstrate the performance of the proposed techniques, several experiments were performed on composite plates with delamination and aluminum plates with corrosion damage. The results demonstrated that the developed techniques could be applied to various structures to localize the damage, with the potential to improve the damage detection capability at a high interrogation speed.

• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.12 no.1
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• pp.35-44
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• 1998

In this paper, input LC filter design of diode rectifiers considering filter V A rating reduction has been propoesd. It consisted of an input LC parallel resonent tank whose inductor and capacitor values are se$.$ lected so that the input filter presents an infinite impedance to harmonic input ac current component. The operation of proposed input filter has been analyzed in detail under steady state conditions. Performance evaluation and related design data have been provided on Per Unit basis for the proper implementation of diode rectification system. Finally, Detailed input and output current analysis has shown that the proposed input filter yield high quality input ac current waveforms, in particular, high input power factor values and more reliabilty which reducing the V A rating of passive components as compared to the standard type LC filter.filter.

• The Transactions of the Korean Institute of Power Electronics
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• v.9 no.4
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• pp.303-310
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• 2004

In this paper, for compensating dynamic voltage sag and harmonic current, 3-phase hybrid series active power filter based on the space vector detection is proposed. The Space vector algorithm for detecting the voltage sag and the harmonic current in compared with conventional theory is a simple method for calculating the compensating reference without any coordinated transformation. The effectiveness of the proposed system is verified by the PSIM simulation in the steady state and the transient state, which the proposed system is able to simultaneously compensate harmonics and source voltage unbalance / sag.

• The Journal of the Acoustical Society of Korea
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• v.26 no.2
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• pp.69-74
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• 2007

In signal processing applications with highly correlated input signals, subband affine projection algorithm and step size controlling is a good solution for improving the slow convergence rate and large computational complexity of LMS-type algorithms. This paper proposes a subband affine projection algorithm using a variable step size. The proposed method achieves fast convergence rate and small steady-state error with a small computational complexity by combining the SAP and step size controlling in a subband structure. Experimental results on highly correlated input signal show that the proposed method is superior to the conventional methods.

• Proceedings of the KIPE Conference
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• 2011.11a
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• pp.30-31
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• 2011

본 논문은 LCL필터를 이용한 분산전원용 계통연계형 PCS의 공진 억제 기법들을 비교 분석하였다. 주요 비교대상은 기존의 커패시터 전류를 읽어오는 가상 저항 기법과 커패시터 전압을 읽어오는 공진 억제 기법이며, 각 기법의 장단점과 정상상태 THD 분석을 모의 실험으로 비교하였다.

• Proceedings of the Korea Multimedia Society Conference
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• 2001.06a
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• pp.124-127
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• 2001

핸즈프리 음성 통신에 있어 음향 반향 제거 시스템은 필수적인 요소이다. 본 논문에서는 음향 반향을 효과적으로 제거하기 위한 새로운 시변 적응 상수를 갖는 적응 알고리즘을 제안한다. 제안하는 알고리즘은 최적 필터의 직교 원리를 이용하여 적응 알고리즘의 적응 상수를 시변한다. 직교 원리에 따라 적응 상수를 시변하면 적응 초기에는 적응 필터가 반향 경로를 추정하지 못해서 큰 값을 가지지만 수렴 후에는 적응 필터의 입력 신호와 추정 오차 신호간의 상호 상관도가 작아져서 정상 상태 오차가 작으며 근단화자 등 의 주변 잡음 신호에 적응필터 계수가 오조정되는 것을 줄일 수 있다. 본 논문에서 음향반향 시뮬레이션을 통해서 제안하는 적응 알고리즘이 기존의 방법에 비해서 우수함을 보인다.

• Journal of the Institute of Electronics Engineers of Korea TC
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• v.49 no.7
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• pp.32-38
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• 2012

In this paper, to eliminate intersymbol interference of the received signal due to multipath propagation, a parallel equalization algorithm using two error estimation functions is proposed. In the proposed algorithm, multilevel two-dimensional signals are considered as equivalent binary signals, then error signals are estimated using the sigmoid nonlinearity effective at the initial phase equalization and threshold nonlinearity with high steady-state performance. The two errors are scaled by a weight depending on the relative accuracy of the two error estimations, then two filters are updated differentially. As a result, the combined output of two filters was to be the optimum value, fast convergence at initial stage of equalization and low steady-state error level were achieved at the same time thanks to the combining effect of two operation modes smoothly. Usefulness of the proposed algorithm was verified and compared with the conventional method through computer simulations.