• Journal of The Korean Society of Agricultural Engineers
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• v.57 no.3
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• pp.101-108
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• 2015

The purpose of this study was to evaluate the safety of the small reservoir, which is distributed in a rural area, based on systemic reliability. It has been estimated that safety of respective reservoir the calculation of failure probability for individual reservoirs can evaluate the safety of the reservoir of the study area. The change of safety for watershed could be figured out as that result. Probability of failure was increased from $3.90{\times}10^{-5}$ to $1.35{\times}10^{-4}$ in Naesu-inpyung reservoir, from $1.33{\times}10^{-5}$ to $4.77{\times}10^{-5}$ in Buyeon reservoir and from $4.24{\times}10^{-5}$ to $2.55{\times}10^{-2}$ in Dalakmal respectively. From the results, the collapse of the upper stream reservoir was analyzed qualitatively that may affect the safety of the reservoir on the downstream area.

• International journal of advanced smart convergence
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• v.11 no.4
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• pp.104-119
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• 2022

Life safety awareness level diagnosis is necessary for customized safety education and continuous safety awareness. As the starting stage of safety education for each life cycle, a scale that has verified the reliability and validity of high school students' life safety awareness has not yet been developed. In this context, the purpose of this study is to develop and validate the life safety awareness scale of high school students and to analyze interindividual differences. Questionnaire data was collected from April to June 2022 from 834 students in the first, second, and third grades of high schools in △△ city in Jeollabuk-do. A final 25-item scale was developed using the preliminary survey, preliminary test, the main test, descriptive statistical analysis, and exploratory and confirmatory factor analysis. This scale consists of four sub-factors: 'safety prevention', 'safety knowledge', 'safety preparation', and 'safety protection'. Good reliability and validity were verified by analysis of content validity and construct validity. The generalizability of the scale was verified by crossover validation between the search group and the crossover group. Based on the interindividual differences analysis, although there was a difference between genders in life safety awareness, there was no difference by grade level and academic achievement. This study is significant in developing the first valid scale that can measure high school students' life safety awareness and providing the necessity and rationale for life safety education by life cycle considering individual gender differences.

• Journal of the Korean Society of Safety
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• v.35 no.3
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• pp.49-57
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• 2020

In comparison with the existing static reliability analysis methods, the dynamic reliability analysis(DyRA) method is more suitable for estimating the failure probability of a structure subjected to earthquake excitations because it can take into account the frequency characteristics and damping capacity of the structure. However, the DyRA is known to have an issue of numerical stability due to the uncertainty in random sampling of the earthquake excitations. In order to solve this numerical stability issue in the DyRA approach, this study proposed two earthquake-scale factors. The first factor is defined as the ratio of the first earthquake excitation over the maximum value of the remaining excitations, and the second factor is defined as the condition number of the matrix consisting of the earthquake excitations. Then, we have performed parametric studies of two factors on numerical stability of the DyRA method. In illustrative example, it was clearly confirmed that the two factors can be used to verify the numerical stability of the proposed DyRA method. However, there exists a difference between the two factors. The first factor showed some overlapping region between the stable results and the unstable results so that it requires some additional reliability analysis to guarantee the stability of the DyRA method. On the contrary, the second factor clearly distinguished the stable and unstable results of the DyRA method without any overlapping region. Therefore, the second factor can be said to be better than the first factor as the criterion to determine whether or not the proposed DyRA method guarantees its numerical stability. In addition, the accuracy of the numerical analysis results of the proposed DyRA has been verified in comparison with those of the existing first-order reliability method(FORM), Monte Carlo simulation(MCS) method and subset simulation method(SSM). The comparative results confirmed that the proposed DyRA method can provide accurate and reliable estimation of the structural failure probability while maintaining the superior numerical efficiency over the existing methods.

• Proceedings of the Safety Management and Science Conference
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• 2007.11a
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• pp.275-298
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• 2007

Recently, all kind of 21C-typed electronic goods show the tendency of hightechnology and digital convergence rapidly. Also, failure mechanism which differs from original goods concept presents. Today, failure mechanism which differs from one that was happened by restricted harmful environment material before adapted the raw of environment material is changing the paradigm of reliability engineering. Thus, when applied the environment matter of original and secondary material at the electronic goods were removed, reliability assessment method and prediction stay into low level. This study suggests as solution to overcome these phenomenon. The study on the management method of environmental restriction substances which is recognized as important element in the reliability assessment about environment material of electronic goods and the study on reliability assessment method of PWB without environment material are progressed.

• The Transactions of the Korean Institute of Electrical Engineers P
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• v.57 no.4
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• pp.417-423
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• 2008

For the evaluation in the safety of outdoor insulator, there are various methods such as: visual observation; voltage measurement; use of ultrasonic wave due to partial discharge; electric field measurement; use of infrared/ultraviolet sensor-type camera. However, many problems have been issued regrading the reliability of the evaluation test and safety of testing operation. Accordingly, the present study has investigated and analyzed the characteristics and mechanisms of the insulator deterioration, in order to obtain an optimal method for detecting poor insulator so that the reliability of power facilities can be enhanced. Besides, based on theoretical analysis of domestic and international detection methods for poor insulator, the reliability has been compared and evaluated quantitatively. As a result, it was shown that the corona camera would be the best choice for domestic workplace application in detecting poor insulator for enhancing the reliability of power transmission line.

• Journal of the Korean Society of Safety
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• v.21 no.6 s.78
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• pp.74-81
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• 2006

Probabilistic Risk Assessment considering statistically random variables is performed for the preliminary design of a Arch Bridge. Component reliabilities of girders have been evaluated using the response surfaces of the design variables at the selected critical sections based on the maximum shear and negative moment locations. Response Surface Method(RSM) is successfully applied for reliability analyses for this relatively small probability of failure of the complex structure, which is hard to be obtained by Monte-Carlo Simulations or by First Order Second Moment Method that can not easily calculate the derivative terms of implicit limit state functions. For the analysis of system reliability, parallel resistance system composed of girders is changed into parallel series connection system. The upper and lower probabilities of failure for the structural system have been evaluated and compared with the suggested prediction method for the combination of failure modes. The suggested prediction method for the combination of failure modes reveals the unexpected combinations of element failures in significantly reduced time and efforts compared with the previous permutation method or system reliability analysis method.

• International Journal of Reliability and Applications
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• v.3 no.1
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• pp.1-16
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• 2002

In reliability engineering, the bathtub-shaped hazard rates play an important role in survival analysis and many other applications as well. For the bathtub-shaped, initially the hazard rate decreases from a relatively high value due to manufacturing defects or infant mortality to a relatively stable middle useful life value and then slowly increases with the onset of old age or wear out. In this paper, we present a new two-parameter lifetime distribution function, called the Loglog distribution, with Vtub-shaped hazard rate function. We illustrate the usefulness of the new Vtub-shaped hazard rate function by evaluating the reliability of several helicopter parts based on the data obtained in the maintenance malfunction information reporting system database collected from October 1995 to September 1999. We develop the S-Plus add-in software tool, called Reliability and Safety Assessment (RSA), to calculate reliability measures include mean time to failure, mean residual function, and confidence Intervals of the two helicopter critical parts. We use the mean squared error to compare relative goodness of fit test of the distribution models include normal, lognormal, and Weibull within the two data sets. This research indicates that the result of the new Vtub-shaped hazard rate function is worth the extra function-complexity for a better relative fit. More application in broader validation of this conclusion is needed using other data sets for reliability modeling in a general industrial setting.

• Proceedings of the Computational Structural Engineering Institute Conference
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• 2004.04a
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• pp.267-274
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• 2004

Since there is a large variation in measurements of the thickness of corroded elements, the thickness of corroded elements are considered as imprecise elements. There is also a considerable degree of uncertainty in a visual assessment of thickness loss. The remaining thickness of a severly corroded element may be represented by an imprecise which expresses the range over which there is uncertainty about the thickness. Therefore, the objective of this paper is to propose a new methodology to safety assessment using imprecise reliability into conventional safety assessment frameworks. For this purpose, this study presents a safety assessment model using Imprecise reliability for large civil structures and demonstrates the applicability of the approach to cable-stayed bridge projects.

• Transactions of the Korean Society of Automotive Engineers
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• v.20 no.2
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• pp.1-7
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• 2012

A Failure data from operating condition includes various failures. Reliability evaluation by operating condition is more correct than test condition. Additional, the evaluation result by operating condition is widely used for quality assurance, forecasting amount of manufacturing at EOL. To discover valuable things from the failure data, arrangement of the failure data and information technique to handle data is needed among many failure data. This paper introduces a reliability prediction program to solve this problem based on the failure. And new technologies for parameters estimation with method of Graphic-Wizard-Parameters-Estimation and Genetic Algorithm are introduced.

• Structural Engineering and Mechanics
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• v.62 no.3
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• pp.365-372
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• 2017

Reliability analysis is a probabilistic approach to determine a safety level of a system. Reliability is defined as a probability of a system (or a structure, in structural engineering) to functionally perform under given conditions. In the 1960s, Basler defined the reliability index as a measure to elucidate the safety level of the system, which until today is a commonly used parameter. However, the reliability index has been formulated based on the pivotal assumption which assumed that the considered limit state function is normally distributed. Nevertheless, it is not guaranteed that the limit state function of systems follow as normal distributions; therefore, there is a need to define a new reliability index for no-normal distributions. The main contribution of this paper is to define a sophisticated reliability index for limit state functions which their distributions are non-normal. To do so, the new definition of reliability index is introduced for non-normal limit state functions according to the probability functions which are calculated based on the convolution theory. Eventually, as the state of the art, this paper introduces a simplified method to calculate the reliability index for non-normal distributions. The simplified method is developed to generate non-normal limit state in terms of normal distributions using series of Gaussian functions.