• Journal of Applied Reliability
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• v.14 no.1
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• pp.81-91
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• 2014

The IEC 61508 standard was established to specify the functional safety of E/E/PE safety-related systems. Safety life cycle to provide the framework and direction for the application of IEC 61508 is included in this standard. In this paper, we describe overviews, objects, scopes, requirements and activities of each phase in safety life cycle. In addition, we introduce safety integrity level(SIL) which is used for verifying the safety integrity requirements of E/E/PE system and perform a case study to estimate hardware SIL by FMEDA. The SIL is evaluated by two criteria. One of them is the architectural constraints which restrict the maximum SIL by combination of SFF and HFT. The other is the probability of failure which is classified into PFD and PFH based on frequency of demand and calculated by safe or dangerous failure rates.

• Journal of Chest Surgery
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• v.26 no.9
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• pp.686-695
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• 1993

A total of eighty one patients with resected stage II and IIIA non-small cell lung cancer treated with postoperative adjuvant radiation therapy between Jan. 1971 and Dec. 1990 were retrospectively analysed to evaluate whether postoperative radiation therapy improves survival. Patterns of failure and prognostic factors were also analysed. The 5 year overall and disease free survival rate were 40.5%, 43.4% and median survival 30 months. The 5 year actuarial survival rates by stage II and IIIA were 53.9% and 36.2%. Loco-regional failure rate was 14.7% and distant metastasis rate was 33.3% and both 4%. Statistically significant prognostic factor affecting survival was presence of mediastinal lymph node metastasis[N2]. This retrospective study suggests that postoperative radiation therapy in resected stage II and IIIA non-small cell lung cancer can reduce loco-regional recurrence and may improve survival rate as compared with other studies which were treated by surgery alone.

• Management Science and Financial Engineering
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• v.5 no.2
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• pp.43-53
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• 1999

In many situations, the system failures depend on the operating environmental conditions that vary on time, usually with periodical manners. We use nonhomogeneous Poisson processes whose rate functions exhibit cyclic behavior as well as a long-term evolutionary trend to model the stochastic process of the failures when the rate of occurrence of the failures varies periodically, for example from day to day or between seasons. In this study, we compare optimal policies under the nonho-mogeneous process with/without a cyclic component in the failure rate function. The analytical re-sults for various situations are presented along with numerical examples using simulated data.

• Journal of Korean Society of Industrial and Systems Engineering
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• v.35 no.1
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• pp.124-131
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• 2012

This paper presents a spreadsheet-based reliability prediction simulation framework for the conceptual product design stage to acquire system reliability information in timely manner. During early stage, reliability performance deals with both known and unknown failure rates and component-level and subsystem-level failure estimate to predict system reliability. A technique for performing life testing simulation using Excel spreadsheet has been developed under the such circumstances. This paper also discuss the results obtainable from this method such as reliability estimate, mean and variance of failures and confidence intervals. The resultant of this reliability prediction system is mainly benefitting small and medium-sized enterprise's field engineers.

• Journal of Chest Surgery
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• v.25 no.10
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• pp.1041-1047
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• 1992

The consecutive 35 patients underwent isolated aortic valve replacement with the low-profile model of the Ionescu-Shiley pericardial xenograft valve from 1984 to 1991. Operative mortality was 2.9%, and early survivors were followed up for a total 136.1 patient-years[Mean$\pm$SD, 4.00$\pm$2.14 years]. The linearized late mortality was 2.204% /pt-yr. Three patients required rereplacement of the valve with overall valve failure rate of 2.204% /pt-yr: two for endocarditis and one for paravalvular leak. There was no case of primary tissue failure. The linearized annual rates of complication were: thromboembolism 0.735% /pt-yr, bleeding 0.735%pt-yr, and endocarditis 2.204% /pt-yr. The actuarial survival at 8 years of follow-up was 90.4$\pm$5.3%, and the probabilities of freedom from thromboembolism and from rereplacement were 95.6$\pm$4.4% and 88.2$\pm$6.7% at 8 years respectively. Although the low profile Ionescu-Shiley pericardial valve provided favorable clinical performance comparable with the standard model up to 8 years, it needs prolonged follow-up to assess the pattern of its durability.

• Journal of Industrial Technology
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• v.28 no.B
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• pp.227-234
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• 2008

Reliability predictions for selected electronic parts using 217-Plus have been performed in this study. 217-Plus has recently developed and may be applied for electronics failure prediction as a surrogate of MIL-HDBK-217. We first briefly reviewed 217-Plus component models. Based on three selected components, predictions using both MIL-HDBK-217 and 217-Plus have been made and the results were compared. Even though the comprehensive conclusion may be drawn from extensive component and system level analyses, the results in this study may provide general insights towards reliability through two specifications.

• The Transactions of the Korean Institute of Electrical Engineers A
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• v.48 no.10
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• pp.1198-1205
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• 1999

This study is focused on the reliability evaluation for distribution system based on deterministic evaluation technique. Average failure rates, average outage time, and average annual outage time of electrical parts and load points are calculated through network reduction method and failure mode & effective analysis method. And reliability indices of distribution system are calculated. Finally, by employing analytic hierarchy process method, unique index which evaluates and improves the distribution system is calculated. As a result, finding weak points and expansion schedule of the system is possible. The usefulness of this method is verified by applying it to the Inchon International Airport.

• Journal of Advanced Marine Engineering and Technology
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• v.23 no.6
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• pp.785-793
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• 1999

There are two kinds of method in ship maintenance. One is the corrective maintenance and the other is the preventive maintenance. For these maintenances recently the stochastic techniques are widely used to keep the maximum availibility and the optimal maintenance period minimizing a given cost function. Thus this paper suggest a method to decide the optimal policy of ship's maintenances by using dynamic programming and the effectiveness of the method is verified through several examples in which failure rates and maintenance data of ship's machineries and parts are given.

• Proceedings of the KSR Conference
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• 2007.05a
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• pp.993-999
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• 2007

With the introduction of the RAMS(Reliability, Availability, Maintainability, Safety), the interest of the system assurance has been increased. First of all, fast-growing electronic circuit requires analyzing the failure rates, by dividing the signalling system more specifically. Since 2005, the K.N.R (Korean National Railway) has incorporated ERP(Enterprise Resource Planning) in order to establish the complete status as the top international comprise, therefore while ordering the project, it has established the classification system and then has been applying to ERP system in 2007. Due to the complex of the classification system, the reliability analysis of the signalling system was assessed with the limit of IXL ATP with On-board and wayside equipment. This paper assumed MTBF(Mean Time Between Failure), MTTR((Mean Time Between Repair) of total signalling system, by using the classification of ERP program.

• Journal of Chest Surgery
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• v.25 no.11
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• pp.1337-1345
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• 1992

One hundred and fourty-one Bjork-Shiley Monostrut valves were implanted in 105 consecutive patients from November 1983 to February 1990. There were 61 male and 44 female patients with a mean age of 33.6 years at the surgery. The cummurative follow-up was 370.3 patient-years with a mean of 44.0 months per patient. The operative mortality rate was 3.8%, and the linealized late mortality was 1.18%/patient-year. The incidence of major complications were 4.59%/patient-year, and the actuarial rate of freedom from valve-related morbidity was 80.2$\pm$4.4% at 7 years. The 7-year survival rate was 90.5$\pm$4.1%, and the actuarial rate of freedom from thromboembolism at 7 years was 93.3$\pm$2.3%. The linealized annual rates of complication were ; structural valve failure 0.27% /patient-year, non-structural valve failure 0.54% /patient-year, thromboembolism 1.62% /patient-year; bleeding 1.62% /patient-year; endocarditis 0.54% /patient-year. On the basis of our experience, we judged the Bjork-Shiley Monostrut valve reliable, with similar incidence of valve-related morbidity of other mechanical prosthetic valves.