• Journal of Applied Reliability
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• v.16 no.3
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• pp.216-223
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• 2016

Purpose: This paper suggests the procedure to enhance the reliability of the software of the medical device that is to cure, treat, diagnose, and prevent a disease or an abnormal health conditions. Methods: After test requirements are classified by the software requirements specification for safety and backgrounds, reliability assessment methods are suggested. Results: Verification and validation for function and safety can be performed whether the medical device software are implemented as intended. Conclusion: Procedure on the static analysis, unit test, integration test, and system test are provided for the medical device software.

• Structural Engineering and Mechanics
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• v.3 no.2
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• pp.135-144
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• 1995

Since structural systems may fail in any one of several failure modes, computation of system reliability is always difficult. A method using numerical quadrature for computing structural system reliability with either one or more than one failure mode is presented in this paper. Statistically correlated safety margin equations are transformed into a group of uncorrelated variables and the joint density function of these uncorrelated variables can be generated by using the Maximum Entropy Method. Structural system reliability is then obtained by integrating the joint density function with the transformed safety domain enclosed within a set of linear equations. The Gaussian numerical integration method is introduced in order to improve computational accuracy. This method can be used to evaluate structural system reliability for Gaussian or non-Gaussian variables with either linear or nonlinear safety boundaries. It is also valid for implicit safety margins such as computer programs. Both the theory and the examples show that this method is simple in concept and easy to implement.

• Journal of the Korea Safety Management & Science
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• v.8 no.5
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• pp.243-251
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• 2006

This paper is to propose various quality and reliability sampling inspection methods to perform the competitive global outsourcing strategy while purchasing and subcontracting. The study also represents implementation strategy which can be efficiently and effectively used in the enterprise. Quality sampling inspection schemes extend reliability inspection techniques with a little change.

• Geomechanics and Engineering
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• v.33 no.6
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• pp.543-552
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• 2023

The design of foundations based on a deterministic approach may not be safe and reliable occasionally, since soils sometimes show considerable spatial variability, and thus, significant uncertainties in turn affect the estimation of footing bearing capacity. The design of footing on cohesionless stratums on the basis of reliability analysis has not received much attention. This paper performs two-dimensional random finite difference analyses of shallow strip footings on a spatially variable frictional soil considering correlation structure. Friction angle (ϕ) is considered as a log-normally distributed random variable and Monte Carlo Simulation is then performed to determine the statistical response based on the random fields. A new approach reliability-based safety factor is defined based on various reliability levels by considering the coefficient of variation of ϕ and correlation length in both the horizontal and vertical directions. The comparison of the probabilistic safety factor and the conventional one illustrates the limitations of the deterministic safety factor and provides insight into how the heterogeneity of soils properties affects the required safety factor. Results show that the conventional safety factor of 3 can be conservative in some cases, especially for soil with low values of mean ϕ and COV_ϕ.

• Journal of Korean Society of Coastal and Ocean Engineers
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• v.21 no.4
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• pp.278-289
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• 2009

In the present study, we evaluated the target reliability indices and partial safety factors for caisson sliding of a vertical breakwater. The average of the reliability indices of existing breakwaters was proposed as the target reliability index for the breakwater of normal safety level. The target reliability indices of high and low safety levels were also proposed based on the analysis of breakwaters in Korea and Japan. The partial safety factors were then proposed for each safety level by averaging the values calculated for 12 breakwater crosssections in Korea. The appropriateness of the proposed partial safety factors was partly verified by showing that the reliability index calculated by using the present partial safety factors is located between those of mild and steep bottom slopes of JPHA(2007). The proposed partial safety factors were inversely used to calculate the caisson width and reliability index of existing breakwaters. While the reliability indices of existing breakwaters designed by the deterministic method show a large variation, those designed by the partial safety factor method show a small variation. This indicates that the partial safety factor method allows a consistent design for given target probability of failure.

• Journal of the Korean Institute of Gas
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• v.22 no.6
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• pp.52-58
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• 2018

In reliability based design and assessment (RBDA) methodology, reliability targets are used to ensure that safety levels are met relevant limit states in the stage of design and maintenance. The target reliability for flammable gas pipelines have not been developed yet in Korea. Instead of the reliability targets, the tolerable criteria for risk measures such as societal and individual risk have been applied in pipeline risk management. This paper introduces the procedures to develop the target reliability using tolerable risk criteria for societal and individual risk which can be enforced for high pressure natural gas pipelines in quantitative risk assessment. In addition, we propose the target reliability for natural gas and hydrogen gas transmission pipelines by the procedures.

• Journal of the Korean Society of Safety
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• v.35 no.5
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• pp.39-48
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• 2020

This study proposes a fast estimation method of dynamic reliability indices or failure probability for SDOF structure subjected to earthquake excitations. The proposed estimation method attempts to derive coefficient function for correcting dynamic effects from static reliability analysis in order to estimate the dynamic reliability analysis results. For this purpose, a total of 60 cases of structures with various characteristics of natural frequency and damping ratio under various allowable limits were taken into account, and various types of approximation coefficient functions were considered as potential candidate models for dynamic effect correction. Each reliability index was computed by directly performing static and dynamic reliability analyses for the given 60 cases, and nonlinear curve fittings for potential candidate models were performed from the computed reliability index data. Then, the optimal estimation model was determined by evaluating the accuracy of the dynamic reliability analysis results estimated from each candidate model. Additional static and dynamic reliability analyses were performed for new models with different characteristics of natural frequency, damping ratio and allowable limit. From these results, the accuracy and numerical efficiency of the optimal estimation model were compared with the dynamic reliability analysis results. As a result, it was confirmed that the proposed model can be a very efficient tool of the dynamic reliability estimation for seismically excited SDOF structure since it can provide very fast and accurate reliability analysis results.

• Journal of the Korea Safety Management & Science
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• v.9 no.2
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• pp.149-159
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• 2007

This paper is to propose two computation procedures of reliability measures for large interval data. First method is efficient to verify the relationship among four reliability measures such as F(t), R(t), f(t) and $\lambda(t)$. Another method is effective to interpret the concept of various reliability measures. This study is also to reinterpret and recompute the errors of four reliability measures discovered in the reliability textbooks. Various numerical examples are presented to illustrate the application of two proposed procedures.

• Journal of the Korean Institute of Gas
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• v.18 no.6
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• pp.32-39
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• 2014

To ensure the reliability of the safety system so that handing large quantities of hazardous materials in chemical plant is considered basic information in chemical process design. However, the reliability of the production system may be reduced when the reliability of the safety system emphasized in order to ensure the safety of chemical process. It is necessary to balance the reliability of the production system and reliability of the safety. In this study, a quantitative risk assessment was performed by selecting the furnace process, which is widely used in the chemical plant in order to suggest a way to ensure the safety and productivity of chemical process, based on the quantitative data. Quantitative risk assessment methodology have been used directed graph analysis methodology. It is possible to evaluate the reliability of the safety system and the production system. In this study, the optimum system design requirement to improve the safety and the productivity of the furnace is two-out-of-three logic for TT and PT.

• Journal of Applied Reliability
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• v.12 no.2
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• pp.91-103
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• 2012

Tubular markers for road safety facilities are used to lead the driver's sight line and separate the lanes on the road. Such tubular markers are usually installed on the road and frequently hit by vehicles, they are accordingly requested to assure the product durability. The traditional evaluation method of tubular markers include only quality tests of the material properties. However, most of consuming agencies in charge of road management at fields have proposed problems on long-term performance of the products hit by vehicles under various weather conditions. Therefore, the objectives of this study are to develop the reliability test methods and equipments to simulate the product failures of tubular markers due to vehicle collision and wheel compression and the delamination and discoloration of reflection sheets attached on the surface of the products under high and low temperatures.