• Structural Engineering and Mechanics
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• v.32 no.1
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• pp.55-69
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• 2009

A quasi ideal importance sampling simulation method combined in the conditional expectation is proposed for the structural reliability estimation. The quasi ideal importance sampling joint probability density function (p.d.f.) is so composed on the basis of the ideal importance sampling concept as to be proportional to the conditional failure probability multiplied by the p.d.f. of the sampling variables. The respective marginal p.d.f.s of the ideal importance sampling joint p.d.f. are determined numerically by the simulations and partly by the piecewise integrations. The quasi ideal importance sampling simulations combined in the conditional expectation are executed to estimate the failure probabilities of structures with multiple failure surfaces and it is shown that the proposed method gives accurate estimations efficiently.

• Proceedings of the Korean Reliability Society Conference
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• 2000.11a
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• pp.405-409
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• 2000

The flow network is considered to be in a functioning state if it can transmit a maximum flow which is greater than or equal to a specified amount of flow. In this paper we consider the measures of importance of a link in the flow network. We define the structural importance and reliability importance of link when the required amount of flow is given. Also, we present the performance importance of link in a flow network. The performance importance can be used to determine which links should be improved first in order to make the greatest improvement in performance of the network. Numerical examples are presented for illustrative purpose.

• Communications for Statistical Applications and Methods
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• v.14 no.3
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• pp.577-582
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• 2007

A continuum structure function (CSF) is a non-decreasing mapping from the unit hypercube to the unit interval. A B-type CSF, defined in the text, is a CSF whose behaviour is modeled by its underlying binary structures. As the measure of importance of a system component for a B-type CSF, the structural and reliability importance of a component at a system level ${\alpha}$(0 < ${\alpha}$ < 1) are defined and their properties are deduced.

• IE interfaces
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• v.6 no.2
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• pp.67-78
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• 1993

In this paper, we deal with the application of the fuzzy sets theory to evaluate and estimate the system reliability under the fault tree analysis. We formulate the uncertainty of component reliability to fuzzy sets, and propose a procedure for obtaining the system reliability in case the system structure is described by fault tree. An importance measure of each component is proposed. Computer program for fuzzy fault tree analysis(FFTA) is developed using C language to obtain the system reliability and the component‘s fuzzy importance.

• Journal of the Korea Safety Management & Science
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• v.14 no.1
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• pp.225-233
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• 2012

The research discusses interrelationship of structural and reliability importance measures which used in the probabilistic safety assessment. The most frequently used component importance measures, such as Birnbaum's Importance (BI), Risk Reduction (RR), Risk Reduction Worth (RRW), RA (Risk Achievement), Risk Achievement Worth (RAW), Fussel Vesely (FV) and Critically Importance (CI) can be derived from two structure importance measures that are developed based on the size and the number of Minimal Path Set (MPS) and Minimal Cut Set (MCS). In order to show an effectiveness of importance measures which is developed in this paper, the three representative functional structures, such as series-parallel, k out of n and bridge are used to compare with Birnbaum's Importance measure. In addition, the study presents the implementation examples of Total Productive Maintenance (TPM) metrics and alternating renewal process models with exponential distribution to calculate the availability and unavailability of component facility for improving system performances. System state structure functions in terms of component states can be converted into the system availability (unavailability) functions by substituting the component reliabilities (unavailabilities) for the component states. The applicable examples are presented in order to help the understanding of practitioners.

• Journal of the Korean Society of Manufacturing Process Engineers
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• v.19 no.12
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• pp.70-79
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• 2020

This paper describes a comparative study of characteristics of probabilistic design using various reliability analysis methods in the structure design of an automatic salt collector. The thickness sizing variables of the main structural member were considered to be random variables, including the uncertainty of corrosion, which would be an inevitable hazard in the work environment of the automatic salt collector. Probabilistic performance functions were selected from the strength performances of the automatic salt collector structure. First-order reliability method, second-order reliability method, mean value reliability method, and adaptive importance sampling method were applied during the reliability analyses. The probabilistic design performances such as reliability probability and numerical costs based on the reliability analysis methods were compared to the Monte Carlo simulation results. The adaptive importance sampling method showed the most rational results for the probabilistic structure design of the automatic salt collector.

• Journal of Distribution Science
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• v.12 no.10
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• pp.85-97
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• 2014

Purpose - This study aims to clarify through which process asset specificity and supplier development project (SDP) affect performance. Cooperation, partnership, the level of information exchange, and the importance of information sharing are considered significant variables as mediators related to the process. Finally, the performance formation model of the supply chain through asset specificity and supplier development project would be suggested as being a result of this study. Research design, data, and methodology - Data collection was as follows: questionnaires were distributed to 250 companies that have business ties with H Company. The empirical study to test our hypothesis was based on statistical analysis (using SPSS 19.0 and AMOS 19.0). The hypothesis of this paper is that the asset specificity and supplier development project variables have positive effects on the following variables: mediators such as cooperation and partnership (reliability and dependence); and the cooperation and partnership variables have a positive effect on the following variables: level of information sharing, the importance of information sharing, and level of information sharing; the importance of information sharing has a positive effect on supply chain performance. We tested our hypothesized model utilizing path analysis with latent variables. Results - First, it was found that asset specificity has significant positive effects on cooperation (H1), reliability (H2), and dependability (H3). Second, it was proved that the level of comprehension on the purpose of SDP has positive effects significantly on cooperation (H4), reliability (H5), and dependability (H6). Third, the hypotheses related to cooperation were all significantly accepted. The relationships of cooperation with the level (H7) and importance (H8) of information sharing were significant. Fourth, the hypotheses related to reliability were all significantly accepted. The relationships of reliability with the level (H9) and importance (H10) of information sharing were significant. In terms of dependability, however, the hypotheses were partially accepted. The effect of dependability was significant on the importance of information sharing (H12), but insignificant on the level of information sharing (H11). Finally, the causal relationships from the level of information sharing to SCM performance (H13) and from the importance of information sharing to SCM performance (H14) were both significantly accepted. Conclusion - First, with rapid changes in the business environment, enterprises should acquire the right information to properly implement SCM. For successful SCM, firms should understand the supplier development project. Second, asset specificity and the level of comprehension on SDP have significant effects both on cooperation and partnership (reliability and dependability). Third, mediators such as cooperation, reliability, and dependability significantly affect the level and importance of information sharing. Fourth, the level and importance of information sharing have significant impacts on SCM performance. This paper makes a meaningful contribution to further the understanding of how SDP affects SCM performance. Finally, successful SCM performance is achieved by information sharing through a collaborative environment and partnership (confidence & dependence) rather than by investing only in setting up an information system.

• Journal of Korean Society of Coastal and Ocean Engineers
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• v.21 no.5
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• pp.405-409
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• 2009

Reliability analysis of coastal structure using importance sampling was shown. When Monte Carlo simulation is used to evaluate overturng failure probability of coastal structure, very low failure probability leads to drastic increase in simulation time. However, importance sampling which uses randomly chosen design candidates around the failure surface makes it possible to analyze very low failure probability efficiently. In the numerical example, failure probability of caisson type quay wall was analyzed by using importance sampling and performance according to the level of failure probability was shown.

• Proceedings of the KSR Conference
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• 2009.05a
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• pp.483-494
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• 2009

Since the embedded system is more intelligent, the importance of the reliability in the embedded system is a lot more visible. Especially the reliability of the embedded system in the train control system is even better important. As the special quality of the embedded system, the hardware of the system is directly controlled by the software in the embedded system. As the expansion of complexity, the expense amd the time for verification is required more and more. This paper is presented the verification of the reliability as the method with background of failure Embedded system is gradually, the importance of 'A built-in on the system embedded system's reliability is focused. In particular, in the train control system built-in of the embedded system, reliability is even more important. The embedded system of the system controls over hardware, software with built-in directly. The more complex system is, the more increasable of depending on the reliability of the time verification and expensive is. This paper is about he characteristics of the reliability and verification of embedded system under the failure mechanisms, based on the verification methodology suggested by in the train control system.

• Journal of the Korea Safety Management & Science
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• v.2 no.4
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• pp.91-102
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• 2000

Nowadays, every kind of system is changed so complex and enormous, it is necessary to assure system reliability, product liability and safety. Fault tree analysis(FTA) is a reliability/safety design analysis technique which starts from consideration of system failure effect, referred to as “top event”, and proceeds by determining how these can be caused by single or combined lower level failures or events. So in fault tree analysis, it is important to find the combination of events which affect system failure. Minimal cut sets(MCS) and minimal path sets(MPS) are used in this process. FTA-I computer program is developed which calculates MCS and MPS in terms of Gw-Basic computer language considering Fussell's algorithm. FTA-II computer program which analyzes importance and function cost of VE consists. of five programs as follows : (l) Structural importance of basic event, (2) Structural probability importance of basic event, (3) Structural criticality importance of basic event, (4) Cost-Failure importance of basic event, (5) VE function cost analysis for importance of basic event. In this study, a method of initiation such as failure, function and cost in FTA is suggested, and especially the priority rank which is calculated by computer-aided decision analysis program developed in this study can be used in decision making determining the most important basic event under various conditions. Also the priority rank can be available for the case which selects system component in FMEA analysis.