• Journal of Korean Society of Coastal and Ocean Engineers
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• v.20 no.2
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• pp.137-147
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• 2008

A reliability analysis has been performed to investigate the systematic stability of multi-failure modes of rubble-mound breakwaters. The reliability functions of four different failure modes are established straightforwardly. AFDA(Approximate Full Distribution Approcah) reliability models for each failure modes are directly developed and satisfactorily calibrated through the comparison with CIAD's results. In the reliability analysis of single failure mode, the probabilities of failure are calculated and the influence coefficients of random variables in the failure modes are properly evaluated. Meanwhile, three different models such as uni-modal bounds, bimodal bounds, and PNET are applied to evaluate the probabilities of failure of multi-failure modes for rubble-mound breakwaters. It may be found that uni-modal bounds tend to overestimate the probability of failure of multi-failure modes. Therefore, for the systematic reliability analysis of multi-failure modes, it is recommended to use bi-modal bounds or PNET which consider the correlation between the failure modes for rubble-mound breakwaters. By introducing the reliability analysis of multi-failure modes, it could be possible to find out the additional probabilities of failure occurred by the multi-failure modes of a multi-component system such as rubble-mound breakwaters.

• The Journal of the Acoustical Society of Korea
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• v.17 no.4
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• pp.28-34
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• 1998

미래 개인 휴대통신에서는 고속의 데이터 서비스를 위하여 높은 대역폭 효율을 요 구하게 된다. 무선통신 서비스를 향상시키기 위하여 코딩기법, 변조기법, 다중화기법 등의 다양한 방법이 연구되고 있다. 이중에서 특히 변조기법은 시스템의 성능을 결정하는 중요한 요소가 된다. 본 논문에서는 PSK. OQPSK, π/4 DQPSK, MSK, GMSK의 다섯가지 변조기 법에대한 BER성능을 시뮬레이션하였다. 시뮬레이션을 위한 다중경로 페이딩채널로서 3가지 서로 다른 채널을 적용하였다. 이때 시뮬레이션을 위하여 1.544Mbps의 전송속도와 1.9GHz 의 반성주파수 환경을 고려하였다. 또한 fractional 선형 등화기를 적용하여 변조방식에 따른 성능향상 정도를 비교하였다. 채널 Ⅰ, Ⅱ, Ⅲ에 대해 각각 30dB, 20dB, 10dB 정도에서 error floor현상이 발생했으며 π/4 DQPSKS가 가장 낮은 BER 특성을 보인 반면 QPSK는 가장 높은 BER을 나타냈다. 등화기를 적용했을 때는 GMSK의 성능향상이 가장 크게 나타 났다.

• The Korean Journal of Applied Statistics
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• v.31 no.5
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• pp.599-610
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• 2018

The method of Mack and Skillings (Technometrics, 23, 171-177, 1981) is a nonparametric multiple comparison method in a randomized block design with replications. This method is likely to result in loss of information because each block is ranked using the average of observations instead of repeated observations. In this paper, we proposed a new nonparametric multiple comparison method in the randomized block model with replications using an alignment method proposed by Hodges and Lehmann (The Annals of Mathematical Statistics, 33, 482-497, 1962) that extend the joint placement method proposed by Chung and Kim (Communications for Statistical Applications and Methods, 14, 551-560, 2007). In addition, Monte Carlo simulation compared the family wise error rate and power with the parametric method and the nonparametric method.

• 한국신재생에너지학회:학술대회논문집
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• 2008.05a
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• pp.445-447
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• 2008

본 연구에서는 다중벽 탄소나노튜브용 표면개질제를 리빙라디칼중합법을 통하여 제조하고, 이를 이용하여 표면개질되고 분산제어된 다중벽탄소나노튜브를 제조하고 염료감응형 태양전지의 대전극 재료로 사용하였다. 우선 리빙라디칼중합법 중 nitroxide mediated polymerization (NMP) 기술을 이용하여 poly(maleic anhydride-co-p-acetoxystyrene)-block-poly(p-acetoxystyrene)를 합성하고, 공중합체중의 maleic anhydride기에 이미드화 반응을 통하여 pyrene기를 도입하였다. 공중합체 중의 p-acetoxystyrene 반복단위들은 가수분해 반응을 통하여 p-hydroxystyrene 반복단위로 변환하였으며, 제조된 공중합체의 구조와 열 특성 등을 GPC, GC, $^1H$-NMR, TGA을 통하여 분석하였다. 제조된 공중합체를 이용하여 다중벽 탄소나노튜브의 표면을 polymer wrapping법으로 처리하였고, 표면개질된 탄소나노튜브의 분산성을 다양한 용매에서 비교분석하였다. 표면이 개질되고 페이스트 내에의 분산성이 향상된 다중벽탄소나노튜브를 염료감응태양전지의 대전극 제조에 응용하였으며, 표면처리 및 분산제어 여부에 따른 제작 특성 및 동작특성 등을 평가하였다.

• Journal of KIISE:Computer Systems and Theory
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• v.33 no.5
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• pp.297-305
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• 2006

Trace-driven simulation is widely used for measuring the performance of a microprocessor in its initial design phase. However, since it requires much time and disk space, the statistical simulation has been studied as an alternative method. In this paper, statistical simulations are performed for a high performance superscalar microprocessor with a perceptron-based multiple branch predictor. For the verification, various hardware configurations are simulated using SPEC2000 benchmarks programs as input. As a result, we show that the statistical simulation is quite accurate and time saving for the evaluation of microprocessor architectures with multiple branch prediction.

• The Journal of the Acoustical Society of Korea
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• v.22 no.3
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• pp.224-232
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• 2003

In this paper, efficient deployment method of sensors and target positioning performance with respect to measurement error are dealt with. Active sonar can be categorized into Monostatic, Bistatic, Multistatic sonar, and characteristics of respective sonar are different. Assuming that each sensor can receive range and angular information, we compare the performance of Monostatic, Bistatic, and Multistatic systems. And we suggest Weighted least square (WLS) which gives the weight to former case, LS. In particular. adopting suggested method we investigate the target positioning performance according to number of sensor, distance from transmitter to receiver, and propose efficient arrangement rule for Multistatic sonar configurations. According to the experimental results, RMSE of Multistatic sonar is found to be superior to Monostatic and Bistatic by 35.98%. 37.45% respectively, and WLS is superior to LS approximately by 7.4% in average. Furthermore, as the difference of respective sensor's variance is large, it is observed that the improvement ratio of target positioning performance is increased.

• The Korean Journal of Applied Statistics
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• v.19 no.3
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• pp.447-460
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• 2006

This paper develops a multiple comparison method for finding an optimal ordering of K geometric means of exponential parameters. This is based on the paired comparison experimental arrangement whose results can naturally be represented by a completely oriented graph. Introducing posterior preference probabilities and stochastic transitivity conditions to the graph, we obtain a new graphical model that yields criteria for the optimal ordering in the multiple comparison. Necessary theories involved in the method and some computational aspects are provided. Some numerical examples are given to illustrate the efficiency of the suggested method.

• Journal of the Institute of Electronics and Information Engineers
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• v.50 no.8
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• pp.67-75
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• 2013

The advantages of the orthogonal frequency division multiplexing (OFDM) are high spectral efficiency, resiliency to RF interference, and lower multi-path distortion. To further utilize vast channel capacity of the multiuser OFDM, one has to find the efficient adaptive subchannel and bit allocation among users. In this paper, we compare the performance of the linear programming dual of the 0-1 integer programming formulation with the existing convex optimization approach for the optimal subchannel and bit allocation problem of the multiuser OFDM. Utilizing tight lower bound provided by the LP dual formulation, we develop a primal heurisitc algorithm based on the LP dual solution. The performance of the primal heuristic is compared with MAO, ESA heuristic solutions, and integer programming solution on MATLAB simulation on a system employing M-ary quadrature amplitude modulation (MQAM) assuming a frequency-selective channel consisting of three independent Rayleigh multi-paths.

• Communications for Statistical Applications and Methods
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• v.19 no.1
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• pp.33-45
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• 2012

The primary interest of drug development studies is to estimate the smallest dose that shows a significant difference from the zero-dose control. The smallest dose is called the Minimum Effective dose(MED). In this paper, we suggest a nonparametric procedure to simultaneously find the MED of each group based on placements. The Monte Carlo simulation is adapted to estimate the power and the family-wise error rate(FWE) of the new procedures with those of discussed nonparametric tests to find MED.

• Proceedings of the Korea Water Resources Association Conference
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• 2008.05a
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• pp.169-173
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• 2008

본 연구는 저수량 지역 빈도분석(regional low flow frequency analysis)을 수행하기 위하여 일반최소자승법(ordinary least squares method)을 이용한 Bayesian 다중회귀분석을 적용하였으며, 불확실성측면에서의 효과를 탐색하기 위하여 Bayesian 다중회귀분석에 의한 추정치와 t 분포를 이용하여 산정한 일반 다중회귀분석의 추정치의 신뢰구간을 비교분석하였다. 각 재현기간별 비교결과를 보면 t 분포를 이용하여 산정된 평균 추정치와 Bayesian 다중회귀분석에 의한 평균 추정치는 크게 다르지 않았다. 그러나 불확실성 측면에서 평가해볼 때 신뢰구간의 상한추정치와 하한추정치의 차이는 Bayesian 다중회귀분석을 사용한 경우가 기존 방법을 사용한 경우보다 훨씬 작은 것으로 나타났으며, 이로부터 저수량(low flow) 지역 빈도분석을 수행하는 경우 Bayesian 다중회귀분석이 일반 회귀분석보다 불확실성을 표현하는데 있어서 우수하다는 결과를 얻을 수 있었다. 또한 낙동강 유역에 2개의 미계측 유역을 선정하고 구축된 Bayesian 다중회귀모형을 적용하여 불확실성을 포함한 미계측 유역에서의 저수량(low flow)을 추정하였으며 이와 같은 방법이 미계측 유역에서의 저수(low flow) 특성을 나타내는 데 있어서 효과적일 수 있음을 입증하였다.