• Journal of the Korean Society of Safety
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• v.32 no.5
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• pp.115-121
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• 2017

This paper is to introduce the main modeling assumptions and data structures associated with right-censored data to describe the successful methodological ideas for analyzing such a field-failure-data when components operating in different environments. The Kaplan - Meier method is the most popular method used for survival analysis. Together with the log-rank test, it may provide us with an opportunity to estimate survival probabilities and to compare survival between groups. An important advantage of the Kaplan - Meier curve is that the method can take into account some types of censored data, particularly right-censoring. The above non-parametric method was used to verify the equality of parts life used in different environments. After that, we performed the life distribution analysis using the parametric method. We simulated data from three distributions: exponential, normal, and Weibull. This allowed us to compare the results of the estimates to the known true values and to quantify the reliability indices. Here we used the Akaike information criterion to find a suitable life time distribution. If the Akaike information criterion is the smallest, the best model of failure data is presented. In this paper, no-nparametrics and parametrics methods are analyzed using R program which is a popular statistical program.

• Journal of the Korea Institute of Military Science and Technology
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• v.11 no.4
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• pp.59-67
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• 2008

In the next near future, the human would like to use the small unmanned ground vehicle(SUGV) on the diverse fields. Specially the world of today is tried to apply with operating the task on very difficult working environments such as some dangerous or unreachable area. To work this task, this vehicle should be guaranteed with the high level of reliability, safety, and performance. In this paper, we propose to focus on not only the functional requirements, but also the non-functional requirements based on software architecture at the design stage for developing the embedded system. Through focusing on the non-functional requirements on this software architecture, we can obtain the design goal of the target system and also show the enhancement of reliability, safety and performance with 'Vtune' performance analysis tool.

• Journal of the Society of Naval Architects of Korea
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• v.31 no.1
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• pp.142-154
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• 1994

In this paper, stochastic imperfection sensitivity analyses of stiffened cylindrical shells under static load are presented. Multimode formulation is performed for the buckling load calculation based on the Donnell's theory and Galerkin approximation. Random imperfection field theory and response surface method are combined with deterministic bucking analysis scheme to perform stochastic imperfection sensitivity analyses of stiffened cylindrical shells considering random geometric imperfection. From the characteristics of probabilistic bucking load, the relation between reliability index and safety parameter can be obtained in addition to the relation between load and reliability index. Those results can be used to determine the range of required safety parameter and acceptable imperfection.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.29 no.6C
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• pp.251-258
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• 2009

In this study, the optimum design conditions for embankment construction on soft clay layer improved by soil compaction pile (SCP) are discussed by comparing the practical design method to the reliability design which is based on the loss function and advanced first order second moment (AFOSM) method. The results are summarized as follows; 1) the relationship between safety factor and failure probability becomes heavy exponentially, failure probability decreases rapidly till 1% approximately until safety factor is smaller than 1.2 and after then, failure probability decrease gradually along the increase of the safety factor. The design safety factor of 1.2 may be the critical value that has been established on considering both relationships appropriately, 2) the safety factor of 1.15 at the minimum expected total cost is a little smaller than the design safety factor of 1.2 and the failure probability is about 1%, 3) the sensitivities of the ratio of stress share and the internal friction angle of sand is larger than the variables related the undrained shear strength of soft layer. This result means that the distribution characteristic of n and ${\phi}$ influences on the stability analysis considerably and they should be considered necessarily on stability analysis of embankment on soft layer improved by SCP, 4) new failure points of the input variables at the design safety factor of 1.2(below failure probability of 0.1~0.3%) is far 1~2 times of standard deviation from the initial design values of themselves.

• International Journal of Naval Architecture and Ocean Engineering
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• v.11 no.2
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• pp.782-795
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• 2019

Safety is always acritical focus of exploration of ocean resources, and it is well recognized that human factor is one of the major causes of accidents and breakdowns. Our research developed a dynamic human reliability assessment approach, Predicted Mean Vote-Cognitive Reliability and Error Analysis Method (PMV-CREAM), that is applicable to monitoring the cognitive reliability of oceanauts during deep-sea missions. Taking into account the difficult and variable operating environment of manned submersibles, this paper analyzed the cognitive actions of oceanauts during the various procedures required by deep-sea missions, and calculated the PMV index using human factors and dynamic environmental data. The Cognitive Failure Probabilities (CFP) were calculated using the extended CREAM approach. Finally, the CFP were corrected using the PMV index. This PMV-CREAM hybrid model can be utilized to avoid human error in deep-sea research, thereby preventing injury and loss of life during undersea work. This paper verified the method with "Jiaolong" manned submersible 7,000 m dive test. The"Jiaolong" oceanauts CR(Corrected CFP) is dynamic from 3.0615E-3 to 4.2948E-3, the CR caused by the environment is 1.2333E-3. The result shown the PMV-CREAM method could describe the dynamic human reliability of manned submersible caused by thermal environment.

• Journal of the Korean Society for Railway
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• v.10 no.6
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• pp.730-734
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• 2007

In this paper, we suggest the criticality of Hidden Failure with regard to the design of watch dog timer, used to detect HALT on railway signaling embedded controller, via FMEA and FTA. Hidden Failure means reliability and safety degradation of the system due to any failure occurred on elements added for fault tolerance. In this paper, therefore, we design vital watch dog timer to prevent the system from operating in low SIL conditions and assess the safety of circuit on failure occurrence to demonstrate that safety degradation problems owing to existing design are supplemented.

• Computational Structural Engineering
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• v.6 no.1
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• pp.107-115
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• 1993

This study is directed for the development of a computer aided safety assessment system for agricultural irrigation structures. The developed system is composed of four subsystems that incorporate database, structural analysis, safety assessment, and postprocess, which are made to be interfaced systematically. It is developed in the user-friendly menu driving form with pull-down type interaction on a personal computer. The main algorithm for safety assessment of deteriorated structures utilizes a rational rating system based on the reliability method. From this study, it may be stated that the proposed rating and safety assessment system provide an effective tool and thus it can be widely used in practice for the assessment of safety and load carrying capacity of existing deteriorated or damaged agricultural irrigation structures.

• Journal of the Korean Institute of Gas
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• v.23 no.5
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• pp.8-14
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• 2019

Although the rate of city gas supply in South Korea has grown significantly, the fields related to gas meters have not yet escaped from the initial method of service (e.g. measurement, safety checks, billing, etc). As smart gas meters are actively developed and researched, the introduction of smart gas meters requires rational performance evaluation methods and standards to verify reliability and safety. The purpose of this paper is to make a prototype of the performance evaluation to test the performance of the smart gas meter and to derive the performance evaluation method by conducting the demonstration operation so that the smart gas meter can be smoothly distributed in South Korea.

• Proceedings of the Korean Nuclear Society Conference
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• 2003.05a
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• pp.62-62
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• 2003

• Journal of Korean Society of Occupational and Environmental Hygiene
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• v.9 no.2
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• pp.79-89
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• 1999

A quantitative fit test, condensation nuclei counting (Portacount 8025, TSI), was performed concurrently with a banana oil (isoamyl acetate: IAA) qualitative fit test (MSA) to evaluate reliability on IAA QLFT and correlation between two methods. One brands of quarter mask (3M model 7500 medium) was prepared for QLFT with HEPA filter and gas & vapor removing media, i.e., combination cartridge. 110 subjects (65 male, 45 female) were fit tested QNFT and QLFT each three times. For a wearer combination having a FF<10, as determined by CNC QNFT, the point es timate (${\beta}$-error) of the probability of that combination not being rejected by the banana oil QLFT was found to be 0.0 with 95% confidence that this statistic is not expected to exceed 0.15. For a wearer combination having a FF<100, as determined by CNC QNFT, the point estimate of the probability of that combination not being rejected by the banana oil QLFT was found to be 0.07 with 95% confidence that this statistic is not expected to exceed 0.13. The uncertainty associated with each estimate, however, is large due to the small number of study subjects with inadequately fitting respirators.