• Journal of the Optical Society of Korea
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• 제11권1호
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• pp.10-17
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• 2007

We need two operation modes to obtain the complex hologram without bias and the conjugate image in the modified triangular interferometer (MTI). To solve the problem, we proposed the optimized MTI with one wave plate, which can obtain cosine and sine functions by the combination of one wave plate and one linear polarizer. In the extraction of phase term using the combination of polarization components, the phase error occurs, and we analyzed such potential phase errors in the optimized MTI.

• 한국조명전기설비학회:학술대회논문집
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• 한국조명전기설비학회 2005년도 학술대회 논문집
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• pp.185-188
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• 2005

We present the method to obtain four speckle patterns with relative phase shift of ${\pi}/2$ by passive devices such as wave plate and polarizer, and calculate the phase at each point of the speckle pattern in shearographic system using Wollaston prism. And, we analyzed the phase error caused using wave plates by Jones matrix.

• Journal of the Optical Society of Korea
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• 제9권4호
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• pp.145-150
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• 2005

The method to obtain four speckle patterns with relative phase shift of $\pi$/2 by passive devices such as two waveplates and a linear polarizer, and to calculate the phase at each point of the speckle pattern in shearography with a Wollaston prism is described. In this paper, we analyze its potential error sources caused by wave plates.

• 한국전자파학회논문지
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• 제13권8호
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• pp.797-803
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• 2002

본 논문에서는 라이시안(Rician) 감쇄가 존재하는 채널 환경에서 협대역 잡음이 더하여진 경우에 대역 여파기를 통과한 수신신호의 위상오류에 대한 확률 밀도 함수를 유도하고 0차 모먼트가 1이 됨을 보임으로써 확률밀도 함수로서의 타당성을 검증한다. 일반적으로 감쇄 환경에서 시스템의 오류 확률은 먼저 가산성 백색 가우시안 잡음(AWGN : Additive White Gaussian Noise)만이 존재할 때의 오류 확률을 구한 후, 그 결과 식을 해당 감쇄에 대한 확률 밀도 함수로 평균을 취하여 구한다. 하지만 본 논문에서는 감쇄 환경에서의 수신 신호에 대한 위상 오류식을 구한 다음, 그 식을 한번의 이중 적분을 취함으로써 오류 확률을 구하게 된다.

• Journal of Power Electronics
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• 제15권6호
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• pp.1593-1600
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• 2015

This paper proposes a novel compensation algorithm of current offset error for single-phase linear compressor in home appliances. In a half-bridge inverter, current offset error may cause unbalanced DC-link voltage when the DC-link is comprised of two serially connected capacitors. To compensate the current measurement error, the synchronous reference frame transformation is used for detecting the measurement error. When an offset error occurs in the output current of the half-bridge inverter, the d-axis current has a ripple with frequency equal to the fundamental frequency. With the use of a proportional-resonant controller, the ripple component can be removed, and offset error can be compensated. The proposed compensation method can easily be implemented without much computation and additional hardware circuit. The validity of the proposed algorithm is verified through experimental results.

• 대한전자공학회논문지
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• 제19권3호
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• pp.37-45
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• 1982

본 논문은 변형된 디지탈 Costas loop에 관한 논문으로서 제1부의 계속이다. 본 제2부 논문에서는 시스템에 잡음이 있을 경우 그의 성능을 해석하였다. 입력신호가 white Gaussian 잡음이 첨가되면 고려되는 DPLL의 noise process는 phase error detertor의 tan-1(·)함수에 의해서 Rician이 됨을 보였다. 이 경우 Chapman-Kolmogorov 방정식을 수치적으로 풀므로써 1차와 2차 loop phase error의 steady state probability density함수, mean 및 variance를 얻었으며 이 결과를 컴퓨터 시뮬레이tus에 의해서 입중하였다.

• 한국주조공학회지
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• 제20권2호
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• pp.129-140
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• 2000

This study aims at the phase-field modeling of the phase transformation in graphitization of the cast iron. As the first step, we constructed a phase-field model including the phases with negligible solubility. Under the dilute regular solution approximation, a simplified version of the phase-field model was obtained, which can be used for the phase transformation related with the stoichiometric phases. The results from the numerical calculation of the phase-field model was in good agreement with the exact analytic solution. The compositional shift due to Gibbs-Thomson effect can be reproduced within 0.5% error in the numerical calculation. The interface velocity, whereas, in numerical calculation of phase-field model appeared to be 15% larger than that from the analytic solution. This error is due to the shift of the interface position in phase-field model from the position with ${\phi}=0.5$.

• Investigative Magnetic Resonance Imaging
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• 제22권1호
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• pp.37-49
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• 2018

Purpose: The effect of global inhomogeneity on quantitative susceptibility mapping (QSM) was investigated. A technique referred to as Simultaneous Unwrapping Phase with Error Recovery from inhomogeneity (SUPER) is suggested as a preprocessing to QSM to remove global field inhomogeneity-induced phase by polynomial fitting. Materials and Methods: The effect of global inhomogeneity on QSM was investigated by numerical simulations. Three types of global inhomogeneity were added to the tissue susceptibility phase, and the root mean square error (RMSE) in the susceptibility map was evaluated. In-vivo QSM imaging with volunteers was carried out for 3.0T and 7.0T MRI systems to demonstrate the efficacy of the proposed method. Results: The SUPER technique removed harmonic and non-harmonic global phases. Previously only the harmonic phase was removed by the background phase removal method. The global phase contained a non-harmonic phase due to various experimental and physiological causes, which degraded a susceptibility map. The RMSE in the susceptibility map increased under the influence of global inhomogeneity; while the error was consistent, irrespective of the global inhomogeneity, if the inhomogeneity was corrected by the SUPER technique. In-vivo QSM imaging with volunteers at 3.0T and 7.0T MRI systems showed better definition in small vascular structures and reduced fluctuation and non-uniformity in the frontal lobes, where field inhomogeneity was more severe. Conclusion: Correcting global inhomogeneity using the SUPER technique is an effective way to obtain an accurate susceptibility map on QSM method. Since the susceptibility variations are small quantities in the brain tissue, correction of the inhomogeneity is an essential element for obtaining an accurate QSM.

• 수산해양기술연구
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• 제35권3호
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• pp.215-226
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• 1999

The experimented rangefinder consist of sets of V/A-Code GPS and sets of L1 C/A-code & carrier phase receivers connected by two spread spectrum radio modems in order to measure relative range and bearing between two ship antennas by real time, comparing and analyzing accuracy of both GPS receivers at the fix point on the land by means of executing zero baseline test by C/A code and by carrier phase as well as measuring distance range 5m, 10m, 15m between each other receivers. The results from the measurement of relative range and bearing are as follows as ;1. According to the results from zero baseline test, the average error by C/A-code receiver is less than 0.1m, which proves theories from published books but when each GPS receivers track different satellites, the range accuracy error becomes up to 100m by means of S/A. Because of this sudden wide range error, rangefinder is not appropriate at relative range measurement without additional modification of the algorism of the GPS receiver itself.2. According to relative range measurement by Carrier Phase and zero baseline test at static condition, the range error is less than 3.5cm in case that it passes more than 5 minutes after GPS sets can track simultaneously more than 6 satellites. Its main reason is understood that the phase center of antenna is bigger than geodetic antenna.3. When range measurement of two receivers from 5m, to 10m to 15m, the each range error is 0.340m, 0.190m, 0.011m and each standard variation is 0.0973m, 0.0884m, 0.0790m. The range error and standard variation are in inverse proportion to distance between two receivers. 4. L1 Carrier Phase GPS generally needs 5 minutes to fix and during this ambiguity search, the relative range and bearing angle is shown to be various.

• 한국전자파학회논문지
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• 제20권4호
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• pp.375-380
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• 2009

계층적 M진 위상 편이 변조(hierarchical M-ary phase shift keying) 방식은 설정된 위상 파라미터에 따라 각 비트의 오류 성능이 변하기 때문에 각 시스템의 요구에 맞은 위상 파라미터 값을 구할 수 있는 방법을 필요로 한다. 따라서 본 논문에서는 계층적 M-PSK 변조 방식에 대한 BER의 근사적 접근을 통해 원하는 각 비트의 오류 성능에 따라 중요 위상 파라미터를 찾을 수 있는 방법을 제안하고, 이전에 제시된 계층적 M-PSK 변조 방식에 대한 정확한 오류 성능 분석 방법을 통하여 제안한 방법의 정당성을 검증한다.