• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 1998.04a
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• pp.69-74
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• 1998

차량에서 인체가 노출되는 진동환경으로서 좌석과 바닥에서의 진동사이에 위상차가 존재하는 경우에 대한 인체의 반응을 주관평가 실험을 통해 분석하였다. 인체가 진동에 민감하게 반응할 뿐만 아니라 인체와 좌석으로 구성되는 진동시스템의 공진주파수와 관련된 2.5, 3.15, 4, 5, 6.3 Hz의 주파수에서, 진동의 크기를 각각 0.25, 0.4, 0.63, 1.0, 1.6m/s$^{2}$로 변화시켜 가며 위상차가 인체의 안락성에 어떻게 영향을 미치는 지를 분석하였다. 두 진동간의 위상차는 진동량이 적을수록, 또 주파수가 낮을수록 인체의 안락성에 악영향을 미쳤다. 진동의 진폭이 0.25m/s$^{2}$ 일 때 위상차가 180.deg.인 경우의 불편함은 0.deg.인 경우보다 2.5배 정도 큰 것으로 나타났다. 특히 현가장치가 장착된 의자의 경우에는 좌석과 바닥진동의 위상차이가 안락성에 미치는 영향을 정량적으로 파악하여 인체-좌석 시스템의 공진주파수를 선정해야 함을 알 수 있다.

• Korean Journal of Optics and Photonics
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• v.31 no.6
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• pp.247-258
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• 2020

In this paper, based on a stochastic parallel gradient descent (SPGD) algorithm we study phase control of a coherent-beam-combining system under turbulent atmospheric conditions. Based on the statistical theory of atmospheric turbulence, we carry out the analysis of the phase and wavefront distortion of a laser beam propagating through a turbulent atmospheric medium. We also conduct numerical simulations of a coherent-beam-combining system with 7- and 19-channel laser beams distorted by atmospheric turbulence. Through numerical simulations, we characterize the phase-control characteristics and efficiency of the coherent-beam-combining system under various degrees of atmospheric turbulence. It is verified that the SPGD algorithm is capable of realizing 7-channel coherent beam combining with a beam-combining efficiency of more than 90%, even under the turbulent atmospheric conditions up to cn2 of 10-13 m-2/3. In the case of 19-channel coherent beam combining, it is shown that the same turbulent atmospheric conditions result in a drastic reduction of the beam-combining efficiency down to 60%, due to the elevated impact of the corresponding refractive-index inhomogeneity. In addition, by putting together the number of iterations of the SPGD algorithm required for phase locking under atmospheric turbulence and the time intervals of atmospheric phenomena, which typically are of the order of ㎲, it is estimated that hundreds of MHz to a few GHz of computing bandwidth of SPGD-based phase control may be required for a coherent-beam-combining system to confront such turbulent atmospheric conditions. We expect the results of this paper to be useful for quantitatively analyzing and predicting the effects of atmospheric turbulence on the SPGD-based phase-control performance of a coherent-beam-combining system.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.10 no.2
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• pp.243-249
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• 2006

In this paper, the phase noise effects of OFDM transmission diversity systems were analyzed. Since OFDM communication system is very sensitive to phase noise, the system performance may degrade seriously due to the increase of subcarrier interferences and system noise. Therefore, The phase noise model was suggested and its distribution and power were varied to investigate the effects of phase noise on the system performance. The degree of the system performance degradation depends on the specific diversity structures of transmission systems. Here, the performances of OFDM systems with two and three antennas transmission diversity were analyzed and compared with that of systems without transmission diversity as the phase noise characteristics varied.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2014.05a
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• pp.679-681
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• 2014

The performance of M-ary APSK modulation system due to phase noise are analyzed in this paper. The effects for phase noise in the higher order modulation are simulated by using constellation of the higher order modulation signals. the simulated results are verified by comparing with the analytic results for lower order PSK modulation signals. Based on the evaluation of simulation method, the phase noise effects for higher order APSK modulation signals are suggested in this paper.

• Journal of the Korean Geotechnical Society
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• v.19 no.4
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• pp.299-310
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• 2003

In the evaluation of the subgrade stiffness structure by the SASW method, the calculation of the phase velocities is the important task controlling the reliability of the result. The interpretation of the phase spectrum should precede the phase-velocity calculation in the current practice of the SASW method. The difficulty involved in the interpretation prohibited the SASW method from being spread over to the industry. This study proposed a new method called the frequency-wave number technique, which is based on the frequency-wave number relationship of the surface wave in the multi-layered system. The frequency-wave number technique eliminates the expertise in the interpretation of the phase spectrum, automates the phase-velocity calculation and expedites the determination of the phase-velocity dispersion curve. To verify the validity of the proposed frequency-wave number method, the transfer function determined from the numerical simulation of the SASW measurements was used fir the calculation of the automatic calculation of the phase velocities and compared with the phase velocities by WinSASW employing the phase-unwrapping method. Also, the proposed method was applied to the real SASW measurements performed at$\bigcirc$$\bigcirc$area in GyeongGi-Do to see how the proposed method works with the real measurements.

• Progress in Medical Physics
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• v.3 no.2
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• pp.43-57
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• 1992

Phase detector techique provides a unique probe to membrane recycling phenomenon by enabling dynamic monitoring of cell membrane capacitance. However, it has inherent errors due to constant changes in measurement environments. The present study analyzed several error sources to develope application criteria of this technique. and the following was found based on a theoretical analysis. The initial phase angle has to be appropriately selected to minimize the error due to perturbation of access and membrane conductances. Excitation frequency is also important to determine the initial phase angle. However. deviation of the phase angle from a predetermined initial value during the measurement period does not affect capacitance estimation to a significant degree. Despite an appropriate initial phase selection an error in scaling factor is expected for a large increase in capacitance during exocytosis. which may be overcome by iteratively correcting the scaling factor over the measurement period. These results will provide a useful guideline in practical application of this technique.

• Proceedings of the Korean Information Science Society Conference
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• 1998.10b
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• pp.158-160
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• 1998

지도 제작에 있어서, 기존의 구축된 대축척의 원천 데이터로부터 소축척의 목적 데이터를 추출해 냄으로 데이터 구축을 중복되지 않고 효율적으로 할 수 있게 하는 것을 지도 일반화라고 한다. 초기의 선을 단순화하는 알고리즘 개발과 향상에 대한 연구로부터, 최근에는 자동화를 위한 지식 기반 일반화 및 데이터 품질에 대한 많은 관심과 연구가 진행되고 있다. 최근에 지리 정보 시스템의 발전으로 다양한 공간 분석이 필요하고, 그 성능 향상을 위하여 위상 정보를 구축하게 된다. 그러므로, 본 논문에서는 위상 정보를 가진 원천 데이터 베이스에서, 일반화 연산자가 적용됨으로 발생하게 되는 위상 데이터의 손실과 불일치를 해결하기 위하여 일반화 연산자들이 위상 정보에 미치는 영향과 이를 해결하기 위한 규칙들을 제시한다. 그리고, 지도 일반화 과정에서 위상 정보의 일관성을 유지한 목적 데이터 베이스를 구축하는 시스템을 구현하는 것이 본 논문의 목적이다.

• Proceedings of the Acoustical Society of Korea Conference
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• autumn
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• pp.93-96
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• 2000

수중 폭발성 음원(SUS)을 이용한 천해 저주파 잔향음 실험을 97년 제주 해역에서 실시하였다 측정된 신호를 고유음선 정보를 이용하여 시간영역에서 잡음, 반사, 산란 영역으로 구분하고 각 영역에 대해서 주파수별 스펙트럼 분석을 실시하였으며 각 영역이 갖는 확률적 특성을 분석하였다. 실험해역은 안정된 해저 형태를 갖는 천해였으므로 산란 신호는 일정한 크기를 갖고 지속적으로 수신되었다. 스펙트럼 분석 결과, 시간에 따른 안정성을 갖는 주파수 대역을 확인할 수 있었으며 구분된 영역별 위상은 반사영역과 산란영역의 위상 특성을 잘 반영하고 있었다. 구분된 각 영역에 대해 1/3 옥타브 벤드로 필터링 하여 확률 특성을 분석한 결과 주파수영역의 실수부와 허수부는 각각 정규 분포를 보였으며 그것의 진폭(envelope)은 레일리 분포를 나타냈다. 또한 산란신호의 위상은 저주파 대역에서 유니폼 분포 특성을 나타내어 잔향음의 기본적인 확률 특성을 잘 반영하고 있었다.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.28 no.1C
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• pp.1-8
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• 2003

In this paper, performance of the CPC(complex phase code) which is recently proposed as a practical phase encoding method for phase-code multiplexes holographic memory system is comparatively analyzed with those of the conventional phase codes such as PR(pure random code), RCE(random code with equality), WHM(Walsh Hadamard Matrix). In computer simulation, the size of an address bean is fixed at 32$\times$32 pixels and 0%-25% phase-error ratio in a pixel are intentionally added to the real phase values to consider the nonlinear phase-modulation characteristics of the practical spatial light modulator. From comparative analysis of crosstalks and signal-to-noise ratios for these phase codes by calculating auto-correlation and cross-correlation, it is found that the CPC have the lowest cross-correlation mean value of 0.021, the lowest standard deviation of 0.0113 and the highest signal-to-noise ratio(SNR) of 27.4 among the four types of phase code. In addition, from the calculation of the number of all possible address beams for these four types of phase code as the size of the address beam is fixed to 3232 pixels, the CPC is found to have 6.334$\times$10$^{49}$ address beams, which are relatively higher number than that of the conventional phase codes.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.20 no.4
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• pp.375-380
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• 2009

Bit error rate(BER) performance of each bit for hierarchical M-ary phase shift keying(H-MPSK) modulation scheme is changed according to the phase parameters. Thus, a method to find the phase parameters appropriate to the requests of the system is needed. In this paper, we propose a method to obtain the phase parameters from an approximate approach of BER for H-MPSK and verify a validity of the proposed method through the previously provided expression for analyzing an exact error probability of H-MPSK.