• 한국해양공학회:학술대회논문집
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• 한국해양공학회 2006년 창립20주년기념 정기학술대회 및 국제워크샵
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• pp.127-134
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• 2006

Based on a weakly non-Gaussian theory the occurrence probability of freak waves is formulated in terms of the number of waves in a time series and the surface elevation kurtosis. Finite kurtosis gives rise to a significant enhancement of freak wave generation in comparison with the linear narrow banded wave theory. For fixed number of waves, the estimated amplification ratio of freak wave occurrence due to the deviation from the Gaussian theory is 50% - 300%. The results of the theory are compared with laboratory and field data.

• 대한수학회보
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• 제37권1호
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• pp.135-152
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• 2000

For a linear operator Q from $R^{d}\; into\; R^{d},\; {\alpha}\;>0\; and\ 0-semi-stability and the operater semi-stability of probability measures on $R^{d}$ are defined. Characterization of $(Q,b,{\alpha})$-semi-stable Gaussian distribution is obtained and the relationship between the class of $(Q,b,{\alpha})$-semi-stable non-Gaussian distributions and that of operator semistable distributions is discussed.

• 한국인터넷방송통신학회논문지
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• 제17권6호
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• pp.59-68
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• 2017

무선 통신시스템에서 Random 과정을 해석적으로 표현할 수 있으며 적당한 확률분포를 구할 수 있다. 감쇄지수함수 확률분포에 의한 가우스, 레일레이, 나카가미 확률분포를 쉽게 유도했으며 시뮬레이션을 그림으로 보인다. 시간의 개념을 포함한 파형의 집합에 의한 확률적 표현이 Random과정(or Stochasic Process)인데 이를 무선환경의 조건에 따라 유도한다. 또한 가시거리 통신과 비가시거리 채널환경을 Rayleigh와 Rician 채널로 구체적인 예를 SISO, MIMO 환경에서 보인다. 또한, 본 논문에서 채널이 송신 블록 동안 일정하고 연속적인 송신 블록 사이에서 독립적으로 변하는 블록 페이딩 채널 모델을 가정함으로써 i.i.d 채널을 갖는 높은 SNR 영역에서 더 나은 성능을 얻을 수 있다는 동기를 부여한다. 이러한 변환을 실현하기 위한 알고리즘은 크로네 커 MIMO 채널에 적용 할 수 있다.

• 한국컴퓨터정보학회논문지
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• 제27권8호
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• pp.143-149
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• 2022

특허문서는 연구 개발된 기술에 대한 상세한 결과를 포함하고 있기 때문에 효과적인 기술분석을 위한 다양한 특허분석 방법에 대한 연구가 진행되고 있다. 특히 통계학과 머신러닝 알고리즘에 의한 정량적인 특허분석에 대한 연구가 최근 활발하게 이루어지고 있다. 정량적 특허분석에서 가장 많이 사용되는 특허 데이터는 기술 키워드이다. 기술 키워드 데이터를 분석하는 기존의 방법은 대부분 음의 무한대부터 양의 무한대까지 실수 공간 전체를 확률변수의 값으로 갖는 가우시안 확률분포에 기반한 모형이었다. 본 논문에서는 이론적으로 0부터 양의 무한대까지의 값을 갖는 특허 키워드의 빈도 데이터를 분석하기 위하여 감마 확률분포를 활용한 모형을 제안한다. 또한 감마 회귀모형의 회귀방정식을 결정하기 위하여 키워드 간의 기술 연관성을 시각화하는 2-모드 네트워크를 구축한다. 제안 방법과 기존의 가우시안 기반의 분석모형 간의 성능평가를 위하여 실제 특허 데이터를 수집하여 분석한다.

• Wind and Structures
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• 제31권3호
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• pp.217-227
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• 2020

Based on translation models, both Gaussian and non-Gaussian wind fields are generated using spectral representation method for investigating the influence of non-Gaussian characteristics and directivity effect of wind load on fatigue damage of wind turbine. Using the blade aerodynamic model and multi-body dynamics, dynamic responses are calculated. Using linear damage accumulation theory and linear crack propagation theory, crack initiation life and crack propagation life are discussed with consideration of the joint probability density distribution of the wind direction and mean wind speed in detail. The result shows that non-Gaussian characteristics of wind load have less influence on fatigue life of wind turbine in the area with smaller annual mean wind speeds. Whereas, the influence becomes significant with the increase of the annual mean wind speed. When the annual mean wind speeds are 7 m/s and 9 m/s at hub height of 90 m, the crack initiation lives under softening non-Gaussian wind decrease by 10% compared with Gaussian wind fields or at higher hub height. The study indicates that the consideration of the influence of softening non-Gaussian characteristics of wind inflows can significantly decrease the fatigue life, and, if neglected, it can result in non-conservative fatigue life estimates for the areas with higher annual mean wind speeds.

• Wind and Structures
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• 제25권3호
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• pp.261-282
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• 2017

The probabilistic information of directional extreme wind speeds is important for precisely estimating the design wind loads on structures. A new joint probability distribution model of directional extreme wind speeds is established based on observed wind-speed data using multivariate extreme value theory with the t-Copula function in the present study. At first, the theoretical deficiencies of the Gaussian-Copula and Gumbel-Copula models proposed by previous researchers for the joint probability distribution of directional extreme wind speeds are analysed. Then, the t-Copula model is adopted to solve this deficiency. Next, these three types of Copula models are discussed and evaluated with Spearman's rho, the parametric bootstrap test and the selection criteria based on the empirical Copula. Finally, the extreme wind speeds for a given return period are predicted by the t-Copula model with observed wind-speed records from several areas and the influence of dependence among directional extreme wind speeds on the predicted results is discussed.

• 전자공학회논문지S
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• 제34S권11호
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• pp.9-15
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• 1997

The Nakagami m-distribution is used to model different fading environments and shown to fit experimental resutls more accurately than other distributions. In this paper, the probability of symbol error for M-ary QAM with square signal constellation in frequency-nonselective shlow Nakagami fading and additive white Gaussian noise is derived. When Nakagami fading index is integer, the derived resutls leads to the closed-form of a finite series.

• 한국정밀공학회지
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• 제12권12호
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• pp.130-138
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• 1995

Machined graphite/epoxy surfaces were studied by using SEM (Scanning Electron Microscopy), surface profilometry and its analysis to determine suitable surface describing parameters for machined unidirectional and multidirectional laminate composite. The surface roughness and profile are found to be highly depdndent on the fiber layup direction and the measurement direction. It was possible to machine 90 .deg. and -45 .deg. plies due to the adjacent plies, which were holding those plies. It was found that the microgeometrical variations in terms of roughness parameters $R_{a}$ without $D_{y}$(Maximum Damage Depth) region and $D_{y}$are better descriptors of the machined laminate composite surface than commonly used roughness parameters $R_{a}$and $R_{max}$ The characteristics of surface profiles in laminate composite are well represented in CPD (Cumulative Probability Distribution) plot and PPD (Percentage Probability Density) plot. Edge-trimmed multidirectional laminate surfaces are Gaussian and random for profiles measured along the tool movement direction, they are periodic and non-Gaussian in the direction perpendicular to the tool movement.t.ent.t.

• 수산해양기술연구
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• 제29권2호
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• pp.152-161
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• 1993

This paper deals with the effect of spatial distribution of material properties on its statistical characteristics and numerical estimation method of reliability of fatigue sensitive structures with respect to the fatigue crack growth. A method is proposed to determine experimentally the probability distribution functions of material parameters of Paris law. da/dN=C(ΔK/K sub(0) ) super(m), using stress intensity factor controlled fatigue tests. The result with a high tensile strength steel shows that the distribution of the parameter m is approximately normal and that of 1/C, is a 3-parameter Weibull. The main result obtained are : (1) The theoretical autocorrelation of the resistance, 1/C, to fatigue crack growth are almost same for different lengths. (2) The variance decreases with the increasing a averaging length. When spatial correlation length is very small. the variane decreases significantly were the averaging length. (3) The probability distribution of load cycles or the number for a crack to reach a certain length can be estimated using these functions by simulation of non-Gaussian(expecially Weibull) Stochastic Process.

• Korean Journal of Mathematics
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• 제6권2호
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• pp.231-242
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• 1998

On the basis of Heyer and Zeuner's results we will treat the central limit theorem for probability measures on hypergroup.