• 대한전자공학회:학술대회논문집
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• 대한전자공학회 2000년도 추계종합학술대회 논문집(1)
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• pp.85-88
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• 2000

In order to resolve problems according to the phase error in QPSK demodulator of the digital communication systems. The demodulator requires carrier recovery loop which searches for the frequency and phase of the carrier. In this paper the complexity of implementation is reduced by the reduction into half of the number of the multiplier in filter structure of the conventional carrier recovery loop, and as the drawback of NCO of the conventional carrier recovery loop wastes a amount of power for the structure of lookup table , We designed the structure of combinational logic without the lookup table. In the comparison with dynamic power of the proposed NCO, the power of NCO with the lookup table is 175㎼, NCO with the proposed structure is 24.65㎼. As the result, it is recognized that about one eight of loss power is reduced. In the simulation of carrier recovery loop designed QPSK demodulator, it is known that the carrier phase is compensated.

• 전자공학회논문지A
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• 제32A권10호
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• pp.51-63
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• 1995

In this paper, a new real-time optical image switching system based on the phase-typed BPEJTC is suggested. The phase filter mask which has the arbitrary position mapping function between input and output planes is constructed by using the modified JTPS of the BPEJTC. Then, the input image is convolved with this phase filter mask in the spatial frequency domain and through further Fourier transform the input image is switched to the new positions in the output correlation plane where the correlation peaks are occurred. And, based on the computer simulation results, the practical optical switched to the new positions in the output correlation plane where the correlation peaks are occurred. And, based on the computer simulation results, the practical optical switching system is opto-digitally constructed and through some experiments on image switching the possiblity of real-time implementation of the multiple optical image switching system by using the BPEJTC is suggeste.

• 전력전자학회:학술대회논문집
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• 전력전자학회 1998년도 Proceedings ICPE 98 1998 International Conference on Power Electronics
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• pp.575-580
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• 1998

A power meter is an instrument for measuring in watts the power flowing in a electric equipment. Since the value which a conventional power meter measures is analog, the power meter is hard to determine a phase difference between the voltage and current for a inductive load. The phase difference causes a loss of electric power and a increase of power-line load. In this paper, we propose a digital power meter using TI's DSP(Digital Singnal Processor) TMS320C5x, which is employed to calculate the phase difference and more accurate power consumption.

• Journal of Power Electronics
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• 제9권2호
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• pp.198-206
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• 2009

An algorithm is developed that enables a single-phase matrix converter (SPMC) to perform functions of a generalized single phase power electronics converter such as acting as a frequency changer, rectifier, inverter, and chopper. This reduces the need for new converter hardware. The algorithm is implemented first on computer simulation software Orcad Capture CIS version 9.1. Simulation results are presented for five types of converters with a control input variable that decides the 1) type of converter and 2) type of output waveform. The simulated results verify the working and operation of a generalized converter based on SPMC. Simulated results are verified with experimental results. Hardware design is obtained using readily available ICs and other components. The trigger circuit has been tested qualitatively by observing waveforms on CRO. The operation of the proposed system has been found to be satisfactory.

• 한국정보처리학회논문지
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• 제7권5호
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• pp.1409-1418
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• 2000

Auditing plays a very important role in the process of developing and managing good quality software. The software developing proces should be audited precisely especially in the test phase. Up to the present, because auditing has depended on the auditor's experience of developing and auditing software, it has been impossible to audit objectively. It is limited to audit systematically and objectively because auditing process isn't systematized. In this paper, the auditing model to solve several problems in present auditing is suggested, a test phase audit system is developed, and the system is applied to the actual auditing process. Consequently, software administrators can establish effective software management, software developers can be supported by a highly reliable and quality software development tool, and auditors can be offered an objective audit standard.

• 한국통신학회논문지
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• 제7권3호
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• pp.112-119
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• 1982

CCITT V.26에 의거한 4-위상 DPSK 2400bps 모뎀이 설계 구성되었다. 회로 전체가 집적회로소자를 이용해 구성되었으며 능동 여파기와 반도체 지연장치가 사용되었다. 동기신호의 재생에 있어서 새롭고 간단한 방법을 시도하여 그 타당성을 확인하였다. Gaussian 잡음에 대한 에러율은(error rate) 이론치와의 차이가 매우 근소함이 확인되었다.

• 대한전기학회논문지:전기물성ㆍ응용부문C
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• 제55권4호
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• pp.217-222
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• 2006

A distributed balun such as Marchand balun typically shows good phase and amplitude balances, but its size is somewhat large especially in lower frequency band. In contrast, a lumped balun has compact size but its performance is not good compared with that of a distributed one. In this paper the distributed-coupled line can be reduced effectively by using the lumped-distributed implementation. Designed balun has two coupled line of each ${\lambda}/72$ and shows magnitude balance of 0.05 dB, phase balance of $0.7^{\circ}$ in passband. Balanced-type filter is designed using balun and it has insertion loss of 8 dB, return loss of 7 dB, magnitude balance of 0.2 dB, and phase balance of $1.2^{\circ}$ in passband.

• 대한전기학회:학술대회논문집
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• 대한전기학회 1998년도 하계학술대회 논문집 F
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• pp.1960-1962
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• 1998

Reference/modulating waveform continuity is not a necessary condition for the implementation of switching patterns for three-phase pulse-width modulated(PWM) converters. This is based on the fact that the converter phase-voltages do not need to be sinusoidal and switching pattern discontinuities do not degrade the quality of output/input voltage/current waveforms by introducing low-order harmonics if certain parameters are optimized. This paper introduces the selected harmonic elimination to reduce the switching frequency and low-order harmonics compared with continuous PWM techniques and some discontinues switching patterns for PWM converter.

• 전력전자학회:학술대회논문집
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• 전력전자학회 2005년도 전력전자학술대회 논문집
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• pp.504-506
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• 2005

This paper proposes a new neutral current reduction method using PQR instantaneous power theory on the active power filter, unbalanced nonlinear load condition in three-phase four-wire systems. For reduction of neutral line current, the single phase active power filter is used and its performance is same with the three-phase four-wire active power filter. For fully-digital implementation, ramp comparison PWM method was adopted. Simulation results verify good performance of the proposed current control strategy on the shunt APFs.

• 한국철도학회논문집
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• 제7권3호
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• pp.173-179
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• 2004

This paper describes a low-cost single-phase active power filter, which consists of a half-bridge PWM inverter with a simple control circuit. In order to verify the performance of proposed active power filter, many computer simulations with EMTP codes and experimental works with a hardware prototype were done. Both results confirm that the proposed active power filter shows excellent performance to eliminate the harmonics generated in the single-phase non-linear load. The active power filter has advantage of low implementation cost and compact size, using a half-bridge inverter and a simple control circuit with only one current sensor. So, it can be fabricated as a plug-in type. This paper shows the necessity and a good possibility to apply such advantage to the electric railway system.