• 대한기계학회논문집A
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• 제32권9호
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• pp.707-712
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• 2008

The fatigue characteristics of a material or a structure are generally derived from fatigue tests of standard specimens. However, test results of standard specimens are different from those of real structures or components. Therefore, to calculate more accurate fatigue life, the geometrical effect and surface condition must be considered by comparing test results of standard specimens with those of real structures or components. Thus the object of this paper is to evaluate the fatigue characteristics of a real waterwork pipe. Also, to evaluate fatigue characteristic based on life distribution, the statistical fatigue characteristics were analyzed by the normal distribution and related data of P-S-N curve.

• 한국해안·해양공학회논문집
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• 제22권4호
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• pp.279-285
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• 2010

해안 구조물의 신뢰성 설계과정에서 조위자료를 정규분포로 가정하여 설계를 수행하는 경우가 빈번하다. 그러나 조위 자료는 쌍봉형 정규 분포 형태를 따르기 때문에 설계과정에서 등가 정규분포 개념에 근거하여 등가평균 및 등가표준편차를 추정하게 되며, 이 과정에서 정규분포를 가정한 경우의 추정 평균 및 표준편차와는 다른 추정오차가 발생하게 된다. 본 연구에서는 쌍봉형 정규분포 형태를 따르는 조위에 대하여 등가평균 및 등가표준편차를 추정하고, 정규분포를 가정하여 추정한 평균과 표준편차와 비교하였다 그 결과, 등가 매개변수 추정오차는 조위조건과 조위의 크기에 따라 크게 변하고 있는 것으로 파악되었다. 인천의 경우, ${\pm}400cm$ 조건에서 등가평균 및 등 가표준편차 추정편차는 각각 100 cm 이상, 80~100 cm 정도로 파악되었으며, 조석이 약한 포항에서는 ${\pm}60cm$ 조건에서 모두 2~4 cm 정도의 작은 추정 편차를 보이고 있는 것으로 파악되었다.

• 한국지반공학회:학술대회논문집
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• 한국지반공학회 2004년도 춘계학술발표회
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• pp.319-326
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• 2004

Uncertainty is inevitably involved in rock slope engineering since the rock masses are formed by natural process and subsequently the geotechnical characteristics of rock masses cannot be exactly obtained. Therefore the reliability analysis method has been suggested to deal properly with uncertainty. The reliability analysis method can be divided into level I, II and III on the basis of the approach for consideration of random variable and probability density function of reliability function. The level II approach, which is focused in this study, assumes the probability density function of random variables as normal distribution and evaluates the probability of failure with statistical moments such as mean and standard deviation. This method has the advantage that can be used the problem which the Monte Carlo simulation approach cannot be applied since the complete information on the random variables are not available. In this study, the analysis results of level II reliability approach compared with the analysis results of level III approach to verify the appropriateness of the level II approach. In addition, the results are compared with the results of the deterministic analysis.

• 한국정밀공학회:학술대회논문집
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• 한국정밀공학회 2005년도 춘계학술대회 논문집
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• pp.1691-1694
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• 2005

The fatigue characteristic of a material or a structure is derived from fatigue tests of standard specimens. However test results of standard specimens are very different from those of real structures or components. Therefore, to calculate more accurate fatigue life, the geometrical effect and surface condition must be considered by comparing test results of standard specimens with those of real structures or components. Thus the object of this paper is to evaluate the fatigue characteristic of a real waterwork pipe by conducting fatigue tests with standard specimens and non-standard(plate-shaped) specimens of base metal and weld metal. Also, to evaluate fatigue characteristic based on life distribution, statistical fatigue characteristic was analyzed by the normal distribution and related data of P-S-N curve.

• 한국의류학회지
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• 제29권8호
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• pp.1102-1113
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• 2005

The propose of this study is to develop the optimal sizing system of ready-to-wear f3r elementary school girls using a newly invented statistical technique. The body measurements was classified by the method that equalizes the distribution of the subjects using the probability density function, to theoretically systemize a method to determine a size range of ready-to-wear for elementary school girls between 6 to 12 years old. The statistical method were 1) The total of 11 height groups, which size interval from one another is 6 cm that is an average height gap between each age. 2) In order to determine an approximate figure (m ${\times}$ n) to establish the appropriate sizes far each height group that fit to the combinations of bust and hip girth, which based on their means and standard deviations on the probability density curve to produce the standard normal distribution. 3) m and n were aligned by 4cm -the grading increments used for patterns making- and determined the size ranges by confirming the approximate figures of m and n. 4) The representative values were determined by an area ratio calculated by dividing the area determined from the range of bust and hip girth with the representative value. Considering the characteristics of subjects' distribution, the area ratios was used. 5) Weight was calculated by seeking a growth exponent for each age and multiplying it by the number of girls that fit to each size range. As sections that show the highest weight are more likely sought by the consumers, these sections were determined as the optimal size standards. 6) This optimal sizing system consists of sizes determined by the optimal size standards and its sizes are marked with height, bust and hip girth.

• 상하수도학회지
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• 제34권4호
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• pp.251-258
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• 2020

Sewer deterioration models are needed to forecast the remaining life expectancy of sewer networks by assessing their conditions. In this study, the serious defect (or condition state 3) occurrence probability, at which sewer rehabilitation program should be implemented, was evaluated using four probability distribution functions such as normal, lognormal, exponential, and Weibull distribution. A sample of 252 km of CCTV-inspected sewer pipe data in city Z was collected in the first place. Then the effective data (284 sewer sections of 8.15 km) with reliable information were extracted and classified into 3 groups considering the sub-catchment area, sewer material, and sewer pipe size. Anderson-Darling test was conducted to select the most fitted probability distribution of sewer defect occurrence as Weibull distribution. The shape parameters (β) and scale parameters (η) of Weibull distribution were estimated from the data set of 3 classified groups, including standard errors, 95% confidence intervals, and log-likelihood values. The plot of probability density function and cumulative distribution function were obtained using the estimated parameter values, which could be used to indicate the quantitative level of risk on occurrence of CS3. It was estimated that sewer data group 1, group 2, and group 3 has CS3 occurrence probability exceeding 50% at 13th-year, 11th-year, and 16th-year after the installation, respectively. For every data groups, the time exceeding the CS3 occurrence probability of 90% was also predicted to be 27th- to 30th-year after the installation.

• Structural Engineering and Mechanics
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• 제42권1호
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• pp.121-129
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• 2012

All contemporary seismic Codes have adopted smooth design acceleration response spectra, which have derived by statistical analysis of many elastic response spectra of natural accelerograms. The above smooth design spectra are characterized by two main branches, an horizontal branch that is 2.5 times higher than the peak ground acceleration, and a declining parabolic branch. According to Eurocode EN/1998, the period range of the horizontal, flat branch is extended from 0.1 s, for rock soils, up to 0.8 s for softer ones. However, from many natural recorded accelerograms of important earthquakes, the real spectral amplification factor appears to be much higher than 2.5 and this means that the spectrum leads to an unsafe seismic design of the structures. This point is an issue open to question and it is the object of the present study. In the present paper, the spectral amplification factor of the smooth design acceleration spectra is re-calculated on the grounds of a known "reliability index" for a desired probability of exceedance. As a pilot scheme, the seismic area of Greece is chosen, as it is the most seismically hazardous area in Europe. The accelerograms of the 82 most important earthquakes, which have occurred in Greece during the last 38 years, are used. The soil categories are taken into account according to EN/1998. The results that have been concluded from these data are compared with the results obtained from other strong earthquakes reported in the World literature.

• 한국해안해양공학회지
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• 제18권2호
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• pp.112-123
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• 2006

우리나라 연안 비조석 성분자료의 확률밀도함수 형태로 쌍봉형 정규분포 함수 형태를 제안하였다. 비조석 성분 자료는 국립해양조사원에서 제공하는 인천, 군산, 목포, 제주, 여수, 마산, 가덕도, 부산, 포항, 속초 검조소의 1시간 간격 조위자료에서 64개 분조성분을 이용하여 합성된 성분을 제외한 잔차성분이다. 제안된 분포함수와 비조석 성분자료 분포함수의 RMS 오차 및 결정계수(R2) 값을 비교·분석한 결과, 비조석 성분자료의 확률밀 도함수로 본 연구에서 제안한 쌍봉형 함수가 기존에 사용하던 정규분포형 함수보다 더 적합한 함수로 파악되었다. 본 연구에서 제안된 확률밀도함수의 매개변수는 Newton 방법을 수정한 Levenberg-Marquardt 방법으로 추정 하였으며, 비조석 성분 자료의 표준편차 및 왜곡도 계수는 목포, 제주, 속초 지점을 제외하고는 분석지점 검조소 자료의 비조화 상수와 밀접한 관계가 있는 것으로 파악되었다.

• 한국산림과학회지
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• 제109권4호
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• pp.504-511
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• 2020

본 연구는 확률밀도함수를 이용한 목재수확예측기법으로 면적가중치법(AW), 면적비율가중치법(ARW), 표본면적변화율가중치법(SCRW)를 적용하여 전국 국유림의 산림경영계획 목표량 설정을 위한 벌채계획량을 추정하였다. 벌채계획량 추정을 위한 산림면적은 산림기본통계의 2010년, 2015년의 영급별 국유림면적을 이용하였으며, 5년간의 산림면적변화량을 벌채면적으로 가정하여 산출하였다. AW, ARW, SCRW를 이용한 벌기령의 평균은 각각 5.41, 5.56, 5.37로 V~VI영급수준으로 산출되었다. 벌채면적은 각각 594,462 ha, 586,704 ha, 580,852 ha로 SCRW가 실제 면적변화량과 가장 유사하였으며, Chi-square 검정도 SCRW이 가장 안정적으로 분석되었다. 산림경영계획의 목재수확예측을 위한 방법으로 SCRW가 AW와 ARW보다 적합한 것으로 판단된다.

• 한국농림기상학회지
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• 제19권3호
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• pp.130-139
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• 2017

기상청 동네예보 풍속으로부터 농작물의 강풍피해를 예측하기 위해, 방재기상관측지점 19곳의 2012년 풍속자료를 이용하여 기상청 동네예보의 3시간 간격과 동일한 0000, 0300 ${\cdots}$ 2100 시간대의 풍속과 직전 3시간 동안의 최대풍속 간의 관계를 직선회귀식으로 표현하였다. 매 3시간 마다 추정된 최대풍속 중 가장 큰 값을 일 최대풍속으로 간주하고, 이 때의 추정오차를 정규분포와 Weibull 분포 확률밀도함수로 표현하였다. 또한 일 최대풍속과 작물 피해 임계풍속 간의 편차를 추정오차 기반 확률 분포에 적용하여 확률누적값으로 풍해 '주의보'와 '경보' 단계를 설정하였다. 19지점별 최대풍속 추정 회귀계수(a, b)와 추정오차의 표준편차 및 Weibull 분포의 모수(${\alpha}$, ${\beta}$)는 공간내삽하여 분포도로 작성하고 종관기상관측지점 4곳(순천, 남원, 임실, 장수)의 격자값을 추출하였다. 이를 이용해 2012년의 일 최대풍속을 추정하고, 배 만삼길 품종의 낙과 발생 사례에서 제시된 풍속 10m/s를 낙과 임계풍속으로 간주, 풍해 주의보와 경보를 판정하였다. 그 결과, 최대풍속 추정오차를 Weibull 분포로 표현하여 풍해 위험 정도를 판정하는 것이 정규분포만을 이용하는 것보다 더 현장에 정확한 주의보를 발령할 수 있었다.