• International Journal of Reliability and Applications
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• 제2권4호
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• pp.241-251
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• 2001

In this paper, optimal bum-in time to minimize the total mean cost, which is the sum of manufacturing cost with burn-in and cumulative warranty-related cost, is obtained. When the products with cumulative pro-rata warranty have high failure rate in the early period (infant mortality period), a burn-in procedure is adopted to eliminate early product failures. After burn-in, the posterior product life distribution and the warranty-related cost are dependent on burn-in time; long burn-in period may reduce the warranty-related cost, but it increases the manufacturing cost. The paper provides a methodology to obtain total mean cost under burn-in and cumulative pro-rata warranty. Property of the optimal burn-in time is analyzed, and numerical examples and sensitivity analysis are studied.

• Nuclear Engineering and Technology
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• 제55권7호
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• pp.2670-2677
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• 2023

In the nuclear safety studies, a new trend refers to the evaluation of uncertainties as a mandatory component of best-estimate safety analysis which is a modern and technically consistent approach being known as BEPU (Best Estimate Plus Uncertainty). The major objectives of this study consist in performing a study of uncertainties/sensitivities of the major analysis results for a generic CANDU 6 Nuclear Power Plant during Station Blackout (SBO) progression to understand and characterize the sources of uncertainties and their effects on the key figure-of-merits (FOMs) predictions in severe accidents (SA). The FOMs of interest are hydrogen mass generation and event timings such as the first fuel channel failure time, beginning of the core disassembly time, core collapse time and calandria vessel failure time. The outcomes of the study, will allow an improvement of capabilities and expertise to perform uncertainty and sensitivity analysis with severe accident codes for CANDU 6 Nuclear Power Plant.

• International Journal of Advanced Culture Technology
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• 제8권3호
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• pp.292-299
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• 2020

This paper presents an evaluation criteria of an information system availability for guaranteeing availability (service target level) from the perspective of the SLA contract and its technical point of view. In order to verify the effectiveness for information system failure and availability guarantee measures, three cases were examined. In summary, the failure time was reduced by 32% ~ 62% after applying the availability guarantee measure, verifying the excellence in the evaluation of an information system availability.

• 한국복합재료학회:학술대회논문집
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• 한국복합재료학회 1999년도 추계학술발표대회 논문집
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• pp.242-245
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• 1999

In aerospace industry improvement of structural performance of flight structure without increasing weight has great advantage. In this study, an innovative design method to increase the buckling load and tension failure load at the same time without increasing the weight was investigated by using the curvilinear fiber format in composite plates with central hole. It was investigated how much gain can be obtained with curvilinear fiber format for the plates with different hole size and different stacking sequence.

• 한국지진공학회:학술대회논문집
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• 한국지진공학회 1998년도 춘계 학술발표회 논문집 Proceedings of EESK Conference-Spring 1998
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• pp.123-130
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• 1998

The probability of unseating failure of the bridge spans under earthquakes is investigated. Seismic excitations are simulated as nonstationary processes by combining a stationary process and an intensity function. For computational convenience, a simplified single-degree-of-freedom model is adopted, which retains the dynamic characteristics of the original brige motion in concern. The time history analysis for the developed single degree-of-freedom model are carried out to evaluate the response processes, and the probabilistic characteristics of response displacements are evaluated. The reliability analysis of the bridge against the unseating failure is performed with the statistical information of the maximum displacements of responses.

• 한국방재학회:학술대회논문집
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• 한국방재학회 2008년도 정기총회 및 학술발표대회
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• pp.561-564
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• 2008

Rock slope had been slope failure due to geological and physical things over time. In this paper, it discusses rock slope stability analysis which was concerned about additional slope failure located near the Andong-si. Initially, achieved basic geological investigation and field test about rock slope, examine the stability of rock slope by doing limit equilibrium method and stereographic projection about 5 slopes.

• 대한수학회지
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• 제61권4호
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• pp.693-711
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• 2024

A Markov-modulated Bernoulli process is a generalization of a Bernoulli process in which the success probability evolves over time according to a Markov chain. It has been widely applied in various disciplines for modeling and analysis of systems in random environments. This paper focuses on providing analytical characterizations of the Markovmodulated Bernoulli process by introducing key metrics, including success period, failure period, and cycle. We derive expressions for the distributions and the moments of these metrics in terms of the model parameters.

• 한국신뢰성학회지:신뢰성응용연구
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• 제15권3호
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• pp.139-144
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• 2015

Track drive unit adopted in the small sized excavator generally have been used in the construction equipment under the 10 tons as the driving device with forwarding and reversing of excavator. It is required to study the accelerated life test applied by over torque and speed to test the durability life test reflected the many driving modes of small sized excavator and also need to equip the comprehensive performance and life test equipments to do the various performance tests. This study had analyzed the failure modes of the components, and calculated the equivalent loads investigated the used loads in the real field conditions and elicits the acceleration factor adopted in the inverse power model. Also, this study have considered the changes of the acceleration factor and the durability test time in the case of the rotary group and the bearing through analyzing the main failure modes. It was calculated the no failure test time about 2 samples and confidence level 90% and elicited the accelerated life time 720 hours.

• 한국화재소방학회논문지
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• 제30권3호
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• pp.79-85
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• 2016

원자력발전소의 방화지역에서 전기적인 단락, 지락, 전기회로 개방 등의 전기 문제로 화재가 발생할 수 있다. 전기 화재가 발생할 경우 안전계통 및 관련기기의 안전정지 기능이 상실된다. 이러한 사고를 예방하기 위하여 안전계통은 다중성, 독립성으로 설계되어 있다. 그러나 케이블 화재시 운전원은 오동작, 잘못된 지시 및 계측으로 발전소 상황을 잘 못 판단하여 적절한 조치를 하지 못할 수 있다. 따라서 주제어실 화재시 케이블 기능상실온도에서 최소 운전원 조치 요구시간인 5분은 매우 중요하다. 본 논문에서 주제어실 화재시 케이블의 기능상실온도 시간을 분석하여 운전원 조치시간이 충분한지 평가하여 주제어실 화재에 대한 안전성을 확인하였다.

• Journal of Korean Neurosurgical Society
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• 제49권4호
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• pp.217-221
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• 2011

Objective : This paper presents data from a retrospective study of endoscopic third ventriculostomy (ETV) in patients with shunt malfunction and proposes a simple and reasonable post-operative protocol that can detect ETV failure. Methods : We enrolled 19 consecutive hydrocephalus patients (11 male and 8 female) who were treated with ETV between April 2001 and July 2010 after failure of previously placed shunts. We evaluated for correlations between the success rate of ETV and the following parameters : age at the time of surgery, etiology of hydrocephalus, number of shunt revisions, interval between the initial diagnosis of hydrocephalus or the last shunt placement and ETV, and the indwelling time of external ventricular drainage. Results : At the time of ETV after shunt failure, 14 of the 19 patients were in the pediatric age group and 5 were adults, with ages ranging from 14 months to 42 years (median age, 12 years). The patients had initially been diagnosed with hydrocephalus between the ages of 1 month 24 days and 32 years (median age, 6 years 3 months). The etiology of hydrocephalus was neoplasm in 7 patients; infection in 5; malformation, such as aqueductal stenosis or megacisterna magna in 3; trauma in 1; and unknown in 3. The overall success rate during the median follow-up duration of 1.4 years (9 days to 8.7 years) after secondary ETV was 68.4%. None of the possible contributing factors for successful ETV, including age (p=0.97) and the etiology of hydrocephalus (p=0.79), were statistically correlated with outcomes in our series. Conclusion: The use of ETV in patients with shunt malfunction resulted in shunt independence in 68.4% of cases. Age, etiology of hydrocephalus, and other contributing factors were not statistically correlated with ETV success. External ventricular drainage management during the immediate post-ETV period is a good means of detecting ETV failure.