• Journal of the Earthquake Engineering Society of Korea
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• v.23 no.1
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• pp.55-70
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• 2019

The phase properties of ground acceleration records from Mw 5.5~6.5 earthquakes are analyzed. The interrelationships between phase properties and significant durations, as well as PGA, are clarified through both of theoretical and empirical approaches. The probabilistic characteristics of phase information is also discussed based on previous studies and it is shown that circular normal distribution is the most appropriate probability distribution for the phase angle and phase difference. Whereas those variates can be modeled by Gaussian random variables. From the survey results on the frequency dependency of the phase statistics, a simple model is introduced, which is possible to express the frequency dependency of phase information. It is also shown that the significant duration can be controlled by appropriately chosen standard deviation of phase difference for 4~8Hz frequency band and additional consideration of phase scattering in higher frequency band through a series of Monte Carlo simulations. The source of phase scattering effect is also pointed out and discussed.

• Journal of the military operations research society of Korea
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• v.24 no.2
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• pp.57-74
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• 1998

This paper is aimed to propose an testing and evaluation strategy and plan in Military Information Systems, especially focusing on development an“New-generation Wargame Model”. Through this research, we concluded that the effective and efficient testing/evaluation strategy/plan can aid the productivity, maintainability, availability, etc., of the Militray Information Systems. Highlights of the proposed testing and evaluation strategy and plan for Military Information Systems are as follows. First, in the unit and module integration testing phase, hybrid of black-box and white-box testing techniques are available for Military Information Systems and progressive approach for module integration phase should be considered because of the complexity. Second, in the system testing phase, integrated module should be tested with respect to the function and performance that should be satisfied with the user requirements, specifications, risk analysis, etc., Third, in the acceptance testing phase, reliability, interoperability, maintainability, availability, integrity, etc., must be considered in the actual or mini-operational environments for testing efficiently and effectively.

• Journal of the Institute of Electronics and Information Engineers
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• v.53 no.6
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• pp.15-20
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• 2016

In this paper, we consider selective mapping (SLM) based OFDM systems without side information, where SLM is one of the promising peak-to-average power ratio (PAPR) reduction techniques due to its simplicity and no distortion in the transmitted signal. First, we construct a new phase sequence where a part of phase sequence is replaced by an orthogonal sequence. Based on the proposed phase sequence, we propose a new scheme for detecting coherently the index of the phase sequence used in transmitter without side information. Computer simulation shows that the proposed detection scheme performs well in SLM-based OFDM systems, and specifically outperforms the existing ones when channel variation is relatively small between sub-carriers used in phase sequence detection.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.20 no.7
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• pp.1229-1236
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• 2016

In underwater acoustic multipath channel, a performance of underwater acoustic (UWA) communication systems is affected by dynamic variation of boundary and high temporal and spatial variability of the channel conditions. Time and spatial variations of UWA channel induce a carrier frequency offset (CFO) since a phase and a frequency of received signal mismatch with a transmitting signal. Therefore, a performance of a phase shift keying underwater acoustic communication system is degraded. In this study, we have analyzed a performance of CFO estimation and compensation using a phase code in time and spatial variation channel. A constant amplitude zero autocorrelation (CAZAC) signal is applied as a phase code signal and its performance is evaluated in water tank. The bit error rate of a quadrature phase shift keying (QPSK) system with a phase code is improved about 4 to 10 times better than that without a phase code.

• Proceedings of the IEEK Conference
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• 2004.06a
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• pp.43-46
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• 2004

In this paper, we present a carrier phase estimation algorithm for LDPC coded systems. LDPC coded system can not achieve the ideal performance if phase offset is introduced by channel. However, the estimation of phase offset is very hard since the operating point of LDPC is very low SNR. To solve this problem, the algorithm using the tentative soft decision value and based on Maximum Likelihood (ML), was proposed in [2]. But this algorithm has problem which works only under constant phase offset. If phase offset is time variant, it has a severe degradation in performance. To solve this problem. we propose two types of estimators. symbol by symbol estimator: Unidirectional estimator (UDE) and hi-directional estimator (BDE), and sub-block estimator (SBE).

• Proceeding of EDISON Challenge
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• 2017.03a
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• pp.417-423
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• 2017

Monolayer $MoS_2$의 metastable phase인 T' phase가 stable한 H phase보다 안정해지는 조건을 모색하기 위해 substitutional doping을 했을 때와 strain을 걸어주었을 때의 에너지 차이를 DFT 방법으로 계산하였다. Doping을 했을 때와 strain이 있을 때 T' phase와 H phase의 에너지 차이가 감소함을 확인하였으나 H phase보다 T' phase가 안정해지는 조건을 찾지는 못하였다. 하지만 이 방법을 기존의 alkali adsorption 방법과 병행하여 기존 방법의 단점을 보완할 수 있을 것을 기대해 볼 수 있다. 또한 전자구조 분석 중 얻은 dopant의 주기와 족에 따른 경향성은 다른 TMD 물질의 phase engineering을 design할 때 universal한 design rule로서 응용할 수 있음을 기대해 볼 수 있다.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.6 no.2
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• pp.151-158
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• 2002

In this paper, Phase locked microwave oscillator having the low phase noise and high stability for digital MMDS down converter was designed. we have been analyzed the low phase noise properties by the active device nonlinear equivalent circuits and derived the necessary and sufficient conditions for high stable voltage control oscillator. And it is applied to phase locked loop, we design the phase locked microwave oscillator of frequency synthesizer. Experimental results of designed phase locked oscillator shows -85dBc/Hz @ 10KHz phase noise properties and simulation result is -90Bc/Hz @ 10kHz respectively we shows that proposed low phase noise and stable conditions of phase locked microwave oscillator can be applied to design the high stable digital MMDS frequency synthesizer.

• Journal of Power Electronics
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• v.11 no.6
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• pp.837-845
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• 2011

This paper proposes phase current reconstruction techniques for two-phase two-leg and two-phase four-leg inverters using a single current sensor. In the proposed methods, one phase current is sampled simultaneously with a particular branch current by using only one current sensor, and then current reconstruction algorithms are applied to extract the information on two phase currents from the sensor output. The sampled current information is periodically updated at the peak and the valley of the triangular carrier waveform in each switching cycle of pulse-width modulation (PWM). The voltage vector spaces where the phase currents can be reconstructed are evaluated. Compared to the existing method using two individual current sensors in two phases, the proposed schemes can save implementation cost since it is possible to remove one current sensor. In addition, the proposed methods are free from gain discrepancy issues between two current sensors. Simulations and experiments show excellent current reconstruction performance of the proposed methods.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.12 no.7
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• pp.1180-1186
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• 2008

The LNB phase noise of user terminal for high data rate satellite transmission was analyzed in this paper. The phase noise severely affects the service performance in low data rate transmission as well as multi-mode signal for high data rate. As the satellite link frequency is increased, the effects of phase noise for multi-mode signal is increased. The phase noise of LNB, which is operated in high frequency band, is about equal to the transmission system phase noise and have an major effects on service performance degradation. The available transmission mode was analyzed in presence of phase noise of LNB and analysis method for LNB phase noise spectrum distribution was proposed in multi-mode signal.

• Journal of applied mathematics & informatics
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• v.24 no.1_2
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• pp.505-511
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• 2007

In this paper, we examine the Markov chain $\{X_k,\;N_k;\;k=0,\;1,...$. We show that the marginal steady state distribution of Xk is discrete phase type. The implication of this result is that the queue length distribution of phase type for large number of examples where this Markov chain is applicable and shows a queueing application by matrix geometric methods.