• International Journal of Reliability and Applications
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• 제3권1호
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• pp.37-50
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• 2002

Simultaneous estimation of accuracy and probability corresponding to a prediction interval is considered in this study. Traditional application of confidence interval forecasting consists in evaluation of interval limits for a given significance level. The wider is this interval, the higher is probability and the lower is the forecast precision. In this paper a measure of stochastic forecast accuracy is introduced, and a procedure for balanced estimation of both the predicting accuracy and confidence probability is elaborated. Solution can be obtained in an optimizing approach. Suggested method is applied to constructing confidence intervals for parameters estimated by normal and t distributions

• Nuclear Engineering and Technology
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• 제49권2호
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• pp.313-326
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• 2017

The systematic management of plant risk is crucial for enhancing the safety of nuclear power plants and for designing new nuclear power plants. Accident sequence precursor (ASP) analysis may be able to provide risk significance of operational experience by using probabilistic risk assessment to evaluate an operational event quantitatively in terms of its impact on core damage. In this study, an ASP methodology for two operation mode, full power and low power/shutdown operation, has been developed and applied to significant accident precursors that may occur during the operation of nuclear power plants. Two operational events, loss of feedwater and steam generator tube rupture, are identified as ASPs. Therefore, the ASP methodology developed in this study may contribute to identifying plant risk significance as well as to enhancing the safety of nuclear power plants by applying this methodology systematically.

• Computational Structural Engineering : An International Journal
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• 제2권1호
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• pp.1-10
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• 2002

Information on the distribution of the basic random variables is essential for the accurate evaluation of structural reliability. The usual method for determining the distribution is to fit a candidate distribution to the histogram of available statistical data of the variable and perform appropriate goodness-of-fit tests. Generally, such candidate distributions would have two parameters that may be evaluated from the mean value and standard deviation of the statistical data. In the present paper, a-parameter Gamma distribution, whose parameters can be directly defined in terms of the mean value, standard deviation and skewness of available data, is suggested. The flexibility and advantages of the distribution in fitting statistical data and its significance in structural reliability evaluation are identified and discussed. Numerical examples are presented to demonstrate these advantages.

• 한국데이터정보과학회:학술대회논문집
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• 한국데이터정보과학회 2006년도 추계 학술발표회 논문집
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• pp.59-69
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• 2006

Pearson's correlation coefficient and Vector similarity are generally applied to The users' similarity weight of user based recommender system. This study is needed to find that the correlation coefficient of similarity weight is effected by the number of pair response and significance probability. From the classified correlation coefficient by the significance probability test on the correlation coefficient and pair of response, the change of MAE is studied by comparing the predicted precision of the two. The results are experimentally related with the change of MAE from the significant correlation coefficient and the number of pair response.

• 국제학술발표논문집
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• The 1th International Conference on Construction Engineering and Project Management
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• pp.1231-1236
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• 2005

Global construction projects manifest more risks than do other industries. Often, firms doing business in construction markets find these risks intimidating. To secure corresponding profits, many global contractors attempt to forecast the effects of risks and establish risk management strategies. However, one key problem with present-day risk management methods is that they are basically analytical or mathematical-oriented approaches which are not easy to adopt in real business. Based on preliminary investigations and evaluations of current tools, this research elicits more practical algorithms for risk checklist by constructing risk scenarios over the whole period of project execution. For the application of the algorithms, a "SE/RF" (Source-Event/Regular-Floating) checklist is suggested, which sorts out risk sources and their subsequent events, as well as dividing various risk factors into either regular or floating categories. In addition, the "PIS" (Probability-Impact-Significance) method is introduced, in place of traditional "PI" (Probability-Impact) methods, by adding the additional criterion of "risk significance" to determine the degree of risk exposure in a more realistic way. As a result, we draw the significant finding that the "PIS" method presents a closer evaluation regarding degree of risk exposure as compared to the level of expert judgments than those from traditional methods. Finally, we provide an integrated procedure for international project risk management with all of the research achievements being incorporated.

• 한국응급구조학회지
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• 제11권3호
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• pp.191-204
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• 2007

This study analyzes use and operation of silver ambulance with 110 patients who had used silver ambulance in Gwangju and Jeonnam regions from June of 2006 to June of 2007 and 53 paramedics who are involved directly in ambulance operation and the results of this analysis are as follows. 1. Users' health conditions, 69.1% of users answered as bad and 67.3% suffered from chronic diseases over 3 months and it was found that they used silver ambulance due to their bad health conditions. 2. Cronbach's alpha was 0.630 and family function index was generally reliable and solution was high as 1.60, but total points were low as 7.11 and it was considered that they had family troubles. 3. On the question of ambulance use, 44.5% answered they used it because it is free, 53.6% used it for appointed medical examination and treatment and 18.1% used it for emergency. 4. Degrees of satisfaction with ambulance and paramedics were 95.4% and 76.4% respectively and 80.0% of ambulance users answered ambulance arrived quickly within 15 min. 5. Correlation($x^2 $) between family or relative's residence and frequency of visits was 86.367 and its significance probability was 0.00 and it was found that it was significant in the level of 0.1%, but correlation($x^2 $) between visitors other than family or relatives and frequency of visits was 14.768 and its significance probability was 0.25 and it was found that it was not significant in the level of 5%. 6. Correlation($x^2 $) between transfer operation speed and mobilization time was found that it was not significant in the level of 5%. Correlation($x^2 $) between their own health condition purpose of ambulance use was 13.802 an 5.696 and its significance probability was 0.93 and it was found that it was not significant in the level of 1%, and it was considered because paramedics carried patients with safe operation.

• 한국콘크리트학회:학술대회논문집
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• 한국콘크리트학회 2003년도 봄 학술발표회 논문집
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• pp.311-314
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• 2003

Concrete structures such as bridge, pavement, airfield, and offshore structure are normally subjected to repeated load. This paper proposes a failure probability models of concrete subjected to split tension repeated-loads, based on experimental results. The fatigue tests were performed at the stress ratio of 0.1, the loading shape of sine, the frequency of 20Hz, and the stress levels of 90, 80 and 70%. The fatigue test specimen was 150mm in diameter and 75mm in thickness. The fatigue analysis did not include which exceeded 0.9 of statistical coefficient of determination values or did not failure at 2$\times$$10^6$ cycles. The graphical method, the moment method, and maximum likelihood estimation method were used to obtain Weibull distribution parameters. The goodness-of-fit test by Kolmogorov-Smirnov test was acceptable 5% level of significance. As a result, the proposed failure probability model based on the two-parameter($\alpha and \mu$) Weibull distribution was good enough to estimate accurately the fatigue life subjected to tension mode.

• 한국건설관리학회논문집
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• 제6권1호
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• pp.73-79
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• 2005

This paper, introduces a Stochastic Project Scheduling Simulation system (SPSS III) developed by the author to predict a project completion probability in a certain time. The system integrates deterministic CPM, probabilistic PERT, and stochastic Discrete Event Simulation (DES) scheduling methods into one system. It implements automated statistical analysis methods for computing the minimum number of simulation runs, the significance of the difference between independent simulations, and the confidence interval for the mean project duration as well as sensitivity analysis method in What-if analyzer component. The SPSS 111 gives the several benefits to researchers in that it (1) complements PERT and Monte Carlo simulation by using stochastic activity durations via a web based JAVA simulation over the Internet, (2) provides a way to model a project network having different probability distribution functions, (3) implements statistical analyses method which enable to produce a reliable prediction of the probability of completing a project in a specified time, and (4) allows researchers to compare the outcome of CPM, PERT and DES under different variability or skewness in the activity duration data.

• International Journal of Reliability and Applications
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• 제2권1호
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• pp.27-36
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• 2001

This Paper proposes a new methodology for assessing the reliability of an accident management, which Is based on the reliability physics and the scheme to generate dynamic event tree. The methodology consists of 3 main steps: screening; uncertainty propagation; and probability estimation. Sensitivity analysis is used for screening the variables of significance. Latin Hypercube sampling technique and MAAP code are used for uncertainty propagation, and the dynamic event tree generation method is used for the estimation of non-success probability of implementing an accident management strategy. This approach is applied in assessing the non-success probability of implementing a cavity flooding strategy, which is to supply water into the reactor cavity using emergency fire systems during the sequence of station blackout at the reference plant.

• Earthquakes and Structures
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• 제10권2호
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• pp.429-450
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• 2016

An attempt has been made to incorporate the concept of collapse safety margin into the procedures proposed in the performance-based earthquake engineering (PBEE) framework for direct earthquake loss estimation, in which the collapse probability curve obtained from incremental dynamic analysis (IDA) is mathematically characterized with the S-type fitting model. The regressive collapse probability curve is then used to identify non-collapse cases and collapse cases. With the assumed lognormal probability distribution for non-collapse damage indexes, the expected direct earthquake loss ratio is calculated from the weighted average over several damage states for non-collapse cases. Collapse safety margin is shown to be strongly related with sustained damage endurance of structures. Such endurance exhibits a strong link with expected direct earthquake loss. The results from the case study on three concrete frames indicate that increase in cross section cannot always achieve a more desirable output of collapse safety margin and less direct earthquake loss. It is a more effective way to acquire wider collapse safety margin and less direct earthquake loss through proper enhancement of reinforcement in structural components. Interestingly, total expected direct earthquake loss ratio seems to be insensitive a change in cross section. It has demonstrated a consistent correlation with collapse safety margin. The results also indicates that, if direct economic loss is seriously concerned, it is of much significance to reduce the probability of occurrence of moderate and even severe damage, as well as the probability of structural collapse.