• 한국전산구조공학회:학술대회논문집
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• 한국전산구조공학회 2003년도 가을 학술발표회 논문집
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• pp.495-502
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• 2003

This study proposed the Probability Density Function (PDF) interpolation technique to evaluate the seismic fragility curves as a function of the return period. Seismic fragility curves have been developed as a function of seismic intensities such as peak ground acceleration, peak pound velocity, and pseudo-velocity spectrum. The return period of design earthquakes, however, can be more useful among those seismic intensity measurements, because the seismic hazard curves are generally represented with a return period of design earthquakes and the seismic design codes also require to consider the return period of design earthquake spectrum for a specific site. In this respect the PDF interpolation technique is proposed to evaluate the seismic fragility curves as a function of return period. Seismic fragility curves based on the return period are compared with ones based on the peak ground acceleration for the bridge model.

• Communications for Statistical Applications and Methods
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• 제23권6호
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• pp.555-562
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• 2016

Interval censored data often occur in an observational study where the subject is followed periodically. Instead of observing an exact failure time, two inspection times that include it are available. There are several methods to analyze interval censored failure time data (Sun, 2006). However, in the presence of competing risks, few methods have been suggested to estimate covariate effect on interval censored competing risk data. A sub-distribution hazard model is a commonly used regression model because it has one-to-one correspondence with a cumulative incidence function. Alternatively, Klein and Andersen (2005) proposed a pseudo-value approach that directly uses the cumulative incidence function. In this paper, we consider an extension of the pseudo-value approach into the interval censored data to estimate regression coefficients. The pseudo-values generated from the estimated cumulative incidence function then become response variables in a generalized estimating equation. Simulation studies show that the suggested method performs well in several situations and an HIV-AIDS cohort study is analyzed as a real data example.

• 대한원격탐사학회:학술대회논문집
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• 대한원격탐사학회 2002년도 Proceedings of International Symposium on Remote Sensing
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• pp.123-127
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• 2002

In this paper, we propose spatial prediction model for landslide hazard mapping that can account for the fuzziness of boundaries in thematic maps showing the different environmental impacts, depending on the scales and the resolutions of them. The fuzziness or uncertainty of boundary is represented in favourability function based on fuzzy object concept and the effects of them are quantitatively evaluated with the help of cross validation procedures. To illustrate the proposed schemes, a case study from Boeun, Korea was carried out. As a result, the proposed schemes are helpful to account for intrinsic uncertainties in categorical maps and can be effectively adopted in spatial prediction models for other purposes.

• 시스템엔지니어링학술지
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• 제10권2호
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• pp.15-20
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• 2014

The river crossing is a very challenging operational function for the ground wheeled vehicle. In this study, the typical hazardous elements were identified by analysing the functional flow of river crossing operation and the survey on the similar operational experiences in real fields. The identified hazardous elements were reviewed on the basis of ALARP concept and reduction approaches were recommended for limited cases.

• 한국지진공학회:학술대회논문집
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• 한국지진공학회 2002년도 추계 학술발표회 논문집
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• pp.28-34
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• 2002

The b-value in the magnitude-frequency relationship logN(m) = $\alpha$ - bmwhere N(m) is the number of earthquakes exceeding magnitude m, is important seismicity parameter In hazard analysis. Estimation of the b-value for earthquake data observed on KSRS array network is done employing the maximum likelihood technique. Assuming the whole Korea Peninsula as a single seismic source area, the b-value is computed at 0.9. The estimation for KMA earthquake data is also similar to that. Since estimate is a function of minimum magnitude, we can inspect the completeness of earthquake catalog in the fitting process of b-value. KSRS and KMA data lists are probably incomplete for magnitudes less than 2.0 and 3.0, respectively. Examples from probabilistic seismic hazard assessment calculated for a range of b-value show that the small change of b-value has seriously effect on the prediction of ground motion.

• Communications for Statistical Applications and Methods
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• 제24권1호
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• pp.15-27
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• 2017

This paper introduces a two-parameter discrete distribution based on a continuous two-parameter bathtub distribution. It is the only two-parameter discrete distribution that shows a bathtub-shaped hazard function. Some statistical properties of the distribution are discussed. Three different methods are used to estimate its two unknown parameters. The point estimators of the parameters have no closed form. The bootstrap method is used to estimate the distributions of these point estimators. Different approximations of the interval estimations for the two-parameters are discussed. Real data sets are analyzed to show how this distribution works in practice. A simulation study is performed to investigate the properties of the estimations obtained and compare their performances.

• Journal of the Korean Data and Information Science Society
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• 제10권1호
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• pp.103-110
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• 1999

In this paper, we summarize some relative risk estimators under the two sample model with proportional hazard and examine the relative efficiencies of the nonparametric estimators relative to the maximum likelihood estimator of a parametric survival function under random censoring model by comparing their asymptotic variances.

• Wind and Structures
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• 제23권1호
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• pp.75-90
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• 2016

A probabilistic approach that combines structural demand hazard analysis with cumulative damage assessment is presented and applied to a steel tower of a wind turbine. The study presents the step by step procedure to compare the reliability over time of the structure subjected to fatigue, assuming: a) a binomial Weibull annual wind speed, and b) a traditional Weibull probability distribution function (PDF). The probabilistic analysis involves the calculation of force time simulated histories, fatigue analysis at the steel tower base, wind hazard curves and structural fragility curves. Differences in the structural reliability over time depending on the wind speed PDF assumed are found, and recommendations about selecting a real PDF are given.

• 한국신뢰성학회:학술대회논문집
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• 한국신뢰성학회 2005년도 학술발표대회 논문집
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• pp.131-137
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• 2005

In this paper, we propose a Bayesian approach to determine the adaptive preventive maintenance(PM) policy for a general sequential imperfect PM model proposed by Lin, Zuo and Yam(2000) that PM not only reduces the effective age of the system but also changes the hazard rate function. Assuming that the failure times follow Weibull distribution, we adopt a Bayesian approach to update unknown parameters and determine the Bayesian optimal sequential PM policies. Finally, numerical examples of the optimal adaptive PM policy are presented for illustrative purposes.

• 한국지진공학회논문집
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• 제14권4호
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• pp.17-22
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• 2010

본 연구에서는 지진해일에 의한 원자력발전소의 확률론적 안전성 평가를 위하여 필수적으로 도출해야 하는 지진해일 재해도 곡선을 도출하기 위한 연구를 수행하였다. 1900년도 이후에 기록된 동해안에서의 지진해일 기록과 1900년도 이전에 역사지진기록에서 찾을 수 있는 지진해일 기록을 이용하여 지진해일에 의한 최대파고에 대한 재현주기를 산정하고자 하였다. Power law, upper-truncated power law 그리고 지수함수에 의해서 추세선을 작성하였으며 그 결과를 비교하였다. 동해안에서 발생한 지진해일의 기록이 10건 내외에 불과하므로 기록에 의한 지진해일 재해도 곡선추정 연구에 제한이 있으나 국내에는 지진해일의 재해도곡선 추정에 관한 연구가 전무한 현실이므로 지진해일 확률론적 안전성 평가를 위한 초석을 놓은 것으로 판단된다.