• 한국통신학회논문지
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• 제27권6B호
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• pp.569-578
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• 2002

This paper proposes a new multicarrier code division multiple access (CDMA) system. The proposed multicarrier CDMA system provides the advantages that the transmission bandwidth is more efficiently utilized by using divided spreading sequence, time and frequency diversity is achieved in frequency selective nultipath (acting channel, and inter-carrier interference (ICI) can be minimized by using specific data and code pattern. In this system, transmitted data bits are serial-to-parallel converted to some parallel branches. On each branch each bit is direct-sequence spread-spectrum modulated by divided spreading sequences and transmitted using orthogonal carriers. The receiver providers a Rake for each carrier, and the outputs of Rakes are combined to get time and frequency diversity. This multicarrier CDMA system allows additional flexibility in the choice of system parameters. Upon varying system parameters, bit error rate (BER) performance is examined for the proposed multicarrier CDMA system. Simulation results show that the proposed multicarrier CDMA scheme can achieve better performance than the other types of conventional multicarrier CDMA systems.

• 대한전기학회논문지:전기기기및에너지변환시스템부문B
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• 제50권3호
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• pp.122-129
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• 2001

Exact simulation of conducted EMI in switched mode power supplies is proposed. In order to achieve exact simulation, PSPICE active component ABM model and modified transformer model are proposed. Each model parameter is extracted from measurements and data-books. PSPICE simulation results with high frequency PCB pattern model are accordant with EMI measurements for a 50[W] isolated flyback converter. EMI relations of each component and EMI patterns are analyzed.

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 1996년도 추계학술대회 논문집
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• pp.265-269
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• 1996

In this paper, electric field interference was analyzed in the Printed Circuit Board to restrain the elcctromagnetic wave using Boundary Element Method and Finite Element Method. First, charge density distribution was simulated using Boundary Element Method and the characteristic impedance was caculated to restrain the reflex wave, and mutual capacitance was caculated in the multi-strip line PCB. Finally, electric field was simulated in the variable patterns using Finite Element Method. As a result, the optimal structure and characteristics of strip line was obtained and the imformations about the optimal design pattern could be obtained with the analysing the feild distribution.

• 대한기계학회논문집A
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• 제28권1호
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• pp.85-91
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• 2004

The sapphire wafers for blue light emitting devices were manufactured by the implementation of the surface machining technology based on micro-tribology. This process has been performed by chemical and mechanical polishing process. The sapphire crystalline wafers were characterized by double crystal X-ray diffraction. The sample quality of sapphire crystalline wafer at surfaces has a full width at half maximum of 89 arcsec. The surfaces of sapphire wafer were mechanically affected by residual stress during the polishing process. The wave pattern of optical interference of sapphire wafer implies higher abrasion rate in the edge of the wafer than its center from the Newton's ring.

• 한국철도학회:학술대회논문집
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• 한국철도학회 2004년도 추계학술대회 논문집
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• pp.1341-1346
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• 2004

Basic design for single-phase active power filter, which aims at railway applications provided with PWM-controlled converters, is comprehensively studided and its performance is presented in this paper, Active power filters are used to compensate railway signaling and public telecommunication interference due to the high-order harmonic currents generated in railway traction locomotives. A type of hybrid digital filter which is composed of low pass filter and high pass filter is proposed so that the desired harmonic reference current with accurate magnitude and phase shift can be extracted from catenary line current. A design criteria to determine input inductor L and output capacitor C is also described, considering voltage, current. PWM pattern, and switching frequency of the main converters, Finally, computer simulation and DSP-based experiments resulted from laboratory test are presented.

• 대한전자공학회논문지
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• 제19권4호
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• pp.6-14
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• 1982

난·시청지역 해소를 위한 소출력 방송국의 출력 증가시 동일 채널의 다른 방송국가의혼신을 막기 위하여 트정 방향의 전계 강도를 감소시켜야 할 경우 현재 안테나에 대한 배향성 조정이 불가피하게 된다. 본 연구는 이러한 경우 단지 급전선의 길이에 의한 급전점의 위상 조정에 의하여 임의의 방향에 대한 전계 강도를 조절하는 방법에 대하여 연구한 것이다.

• Annals of Clinical Neurophysiology
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• 제20권1호
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• pp.26-30
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• 2018

Background: The motor unit number index (MUNIX) and motor unit size index (MUSIX) refer to the electrophysiological measurement of the motor units using the surface electromyographic interference pattern (SIP) recorded during graded muscle contraction. In order to improve the reliability and reproducibility of MUNIX by the systematization of the graded muscle contractions, we applied a digital hand instrument to the procedure of recording SIP signals. Methods: We tested the applicability of the digital instrument in the MUNIX technique by assessing the mean values and the reproducibility of the MUNIX involving the abductor pollicis brevis (APB) and the abductor digiti minimi (ADM) muscles in 30 healthy adults. Results: The digital dynamometer was successfully applied to the MUNIX measurements of the APB and ADM muscles, and showed high reproducibility across trials. Conclusions: Application of the digital instrument would be useful in improving the reliability and reproducibility of MUNIX.

• 천문학회지
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• 제4권1호
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• pp.9-16
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• 1971

The asymmetry of received intensity pattern within the bandwidth is derived from the analogy of the intensity distribution of two-slit interference. This suggests that the length of $\frac{1}{2}{\lambda}$ delay line should be adjusted to the slightly upper frequency than the central frequency of the radio telescope with a wide bandwith. Some strange communication signals and man-made noises prevented us from obtaining the discernible information from the observed data for the sun. To overcome this difficulties, it is necessary to alter the operating frequency and site. It will be fo1lowed to measure the angular dimensions of the superposed radio sources by changing the distance between two antennas.

• 전자공학회논문지A
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• 제30A권3호
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• pp.43-51
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• 1993

Effects of incident beam position and intensity on self-pumped optical phase conjugation are presented using barium titanate as an optical phase conjugator. Depending on the position of incident beam, the crystal used consists of four major operating regions: irregular pulsing, regular pulsing, stable phase conjugation, and unstable oscillating regions. In the second region, the pulsing frequency and amplitude of phase conjugate beam are proportional to I$_{in}$ and I$_{in}^{0.85}$, respectively, where I$_{in}$ is the incident beam intensity. In the fouth region, the rising time and intensity of the first-generated pulse are proportional to I$_{in}^{0.92}$ and I$_{in}^{0.81}$, respectively. A frequency shift by beam fanning is also discussed by observing interference pattern from an interferometer.

• 전자공학회논문지D
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• 제35D권12호
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• pp.75-82
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• 1998

체적홀로그램의 저장용량을 향상시키기 위해서 여러 가지 다중화 기법이 제안되고 있는 가운데, 본 논문에서는 각다중화와 공간다중화를 병행한 복합 다중화 시스템을 구현하였다. 기준파의 각도 및 공간상의 위치를 변화시키는 방법으로 스텝 모터를 사용하여 다중 홀로그램을 기록할 수 있었다. 기록 시간 스케줄에 의하여 노출 시간을 조절하므로써 기준파와 물체파 간의 간섭 패턴을 홀로그램에 기록하였다. 3층 300개의 영상을 한 개의 LiNbO₃ :Fe에 기록하였으며 실험 결과를 보였다.