• 한국지반공학회논문집
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• 제35권12호
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• pp.45-58
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• 2019

본 연구에서는 강우의 침투에 따른 토사사면의 파괴에 대한 강우강도-지속시간의 강우기준을 평가하기 위하여 수치해석에 의한 파괴시간의 확률론적 해석 절차를 제안하였다. 취약도 곡선은 시간에 따른 강우의 침투해석 결과를 반영하며 지반의 역학적 특성의 불확실성을 고려한 MCS에 의한 확률론적 사면 안정해석의 결과로부터 강우강도-지속기간의 함수로 생성하였다. 확률론적 해석에서 한계상태함수를 계산하기 위하여 강우의 침투해석과 연동된 사면 안정해석을 수행하였다. 생성된 사면의 취약도 곡선들을 기반으로 확률론적 사면 파괴분포 분석을 수행하여 지반의 불확실성을 고려한 사면 파괴 유발 강우기준을 평가하였다. 제안된 사면 파괴분포 분석법은 강우의 침투로 인한 사면 파괴의 과정을 분석하고 사면 파괴가 발생할 수 있는 시간을 예측하는데 유용하게 사용될 수 있다.

• 콘크리트학회논문집
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• 제18권2호
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• pp.233-238
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• 2006

본 연구에서는 염해환경에 노출되어 있는 철근콘크리트 구조물의 수명예측에 있어서 철근덮개 파괴시간 예측을 위하여, 유한요소해석을 통한 방법을 제시하였다. 또한 본 연구에서는 인공세공용액중의 철근 부식속도로부터 콘크리트 중의 철근 부식속도를 유도하는 방법을 제시하였으며, 철근 부식의 분포에 따른 철근덮개의 파괴시간을 비교하여, 철근덮개 파괴시간을 합리적으로 예측하기 위한 방법을 제시하였다. 국부부식을 고려한 경우 균일한 부식을 가정한 경우보다 최대 약 40%정도 철근덮개 파괴시간이 짧아짐을 알 수 있다. 따라서, 철근덮개의 파괴시간 예측을 위한 유한요소해석에 있어서 국부부식을 고려하는 것이 합리적인 결과를 제시할 수 있을 것으로 사료된다.

• Journal of Information Technology Applications and Management
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• 제25권4호
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• pp.115-122
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• 2018

Software reliability has the greatest impact on computer system reliability and software quality. For this software reliability analysis, In this study, we compare and analyze the trends of the properties affecting the reliability according to the shape parameters of Erlang distribution based on the finite fault NHPP. Software failure time data were used to analyze software failure phenomena, the maximum likelihood estimation method was used for parameter estimation. As a result, it can be seen that the intensity function is effective because it shows a tendency to decrease with time when the shape parameters a = 1 and a = 3. However, the pattern of the mean value function showed an underestimation pattern for the true values when the shape parameters a = 1 and a = 2, but it was found to be more efficient when a = 3 because the error width from the true value was small. Also, in the reliability evaluation of the future mission time, the stable and high trend was shown when the shape parameters a = 1 and a = 3, but on the contrary, when a = 2, the reliability decreased with the failure time. Through this study, the property of finite fault NHPP Erlang model according to the change of shape parameter without existing research case was newly analyzed, and new research information that software developers can use as basic guideline was presented.

• 한국CDE학회논문집
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• 제18권4호
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• pp.250-257
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• 2013

This paper introduces a failure analysis procedure that underpins real-time fault prognosis. In the previous study, we developed a systematic eventization procedure which makes it possible to reduce the original data size into a manageable one in the form of event logs and eventually to extract failure patterns efficiently from the reduced data. Failure patterns are then extracted in the form of event sequences by sequence-mining algorithms, (e.g. FP-Tree algorithm). Extracted patterns are stored in a failure pattern library, and eventually, we use the stored failure pattern information to predict potential failures. The two practical case studies (marine diesel engine and SIRIUS-II car engine) provide empirical support for the performance of the proposed failure analysis procedure. This procedure can be easily extended for wide application fields of failure analysis such as vehicle and machine diagnostics. Furthermore, it can be applied to human health monitoring & prognosis, so that human body signals could be efficiently analyzed.

• Structural Engineering and Mechanics
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• 제52권1호
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• pp.137-147
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• 2014

The present paper deals with the first ply failure analysis of the laminated composite plates under various static and dynamic loading conditions. Static analysis has been carried out under patch load and triangular load. The dynamic failure analysis has been carried out under triangular pulse load. The formulation has been carried out using the finite element method and a computer code has been developed. The first order shear deformation theory has been applied in the present formulation. The displacement time history analysis of laminated composite plate has been carried out and the results are compared with those published in literature to validate the formulation. The first ply failure load for laminated composite plates with various lamination schemes under static and dynamic loading conditions has been calculated using various failure criteria. The failure index-time history analysis has also been carried out and presented in this paper.

• 한국산학기술학회논문지
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• 제21권7호
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• pp.428-434
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• 2020

일회성 무기체계는 대기 상태로 있다가 단 한 번의 임무를 수행한 이 후 폐기되는 특성에 따라 높은 신뢰도를 요구받는다. 유도탄은 일회성 무기체계로써 특성상 저장 상태로 수명의 대부분을 보내고, 임무수행을 위한 운용시간은 짧기때문에 임무성공률이 아닌 저장 신뢰도로 분석해야 한다. 유도탄의 신뢰도를 분석할 때에 어떠한 방법을 사용하는지에 따라 그 결과는 달라질 수 있으며, 고장자료와 함께 포함되는 우측 관측중단자료의 비율에 따라서도 차이가 발생할 수 있다. 본 연구는 공군의 OO유도탄을 대상으로 미래의 고장률을 보다 정확하게 예측하기 위한 방법을 제시하고자 작성하였다. 제시하는 방법은 먼저 평균 고장시간(MTTF: Mean Time To Failure, 이하 MTTF)을 적용한 모델과 고장 간 평균시간(MTBF: Mean Time Between Failure, 이하 MTBF)을 적용한 모델로 고장률을 예측하고, 두 모델 중 실제 고장률과 차이가 작은 모델을 선택한다. 선택한 모델로 고장자료와 함께 포함되는 우측 관측중단자료의 비율을 달리하여 고장률을 예측하고, 실제 고장률과의 차이가 최소화되는 비율을 찾는다. 실제 자료를 바탕으로 제안한 비율과 현재 검사 비율의 비교를 통해 제안한 비율이 미래 고장률을 예측하기에 더 적합함을 보였다.

• 한국콘크리트학회:학술대회논문집
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• 한국콘크리트학회 2003년도 가을 학술발표회 논문집
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• pp.234-237
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• 2003

Previous researches about headed reinforcement have not been concerned about bond failure which is quite important is some cases. In this paper, failure mechanism including bond failure was presented in order to define the contribution of bond stress at the time failure occurs. Examined with design codes and test results, it is proved to be rational to consider the contribution of bond stress in determining the ultimate pull-out capacity of headed reinforcement. Direct adaptation of design code for anchor bolt without modification for the contribution of bond stress will lead to underestimate the capacity of headed reinforcement.

• 한국기계가공학회지
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• 제12권4호
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• pp.22-28
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• 2013

It is important to begin left ventricular assist device (LVAD) treatment at appropriate time for heart failure patients who expect cardiac recovery after the therapy. In order to predict the optimal timing of LVAD implantation, we predicted pumping efficacy of LVAD according to the severity of heart failure theoretically. We used LVAD-implanted cardiovascular system model which consist of 8 Windkessel compartments for the simulation study. The time-varying compliance theory was used to simulate ventricular pumping function in the model. The ventricular systolic dysfunction was implemented by increasing the end-systolic ventricular compliance. Using the mathematical model, we predicted cardiac responses such as left ventricular peak pressure, cardiac output, ejection fraction, and stroke work according to the severity of ventricular systolic dysfunction under the treatments of continuous and pulsatile LVAD. Left ventricular peak pressure, which indicates the ventricular loading condition, decreased maximally at the 1st level heart-failure under pulsatile LVAD therapy and 2nd level heart-failure under continuous LVAD therapy. We conclude that optimal timing for pulsatile LVAD treatment is 1st level heart-failure and for continuous LVAD treatment is 2nd level heart-failure when considering LVAD treatment as "bridge to recovery".

• 대한기계학회논문집A
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• 제28권5호
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• pp.586-592
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• 2004

In this study, the failure analysis of a decanter is carried out and the methods of performance improvement are presented. The decanter is a centrifugal separator that is used to separate water and solids from municipal and industrial sludge. Therefore, the decanter should be designed to improve the dewatering of sludge. Besides high performance, the decanter should guarantee its life time under a severe using condition. For theses reasons, the failure analysis and performance improvement of the decanter are studied. It is found from this study that the failure is caused by mass unbalance, wear, clogging or crack. If these failure causes are prevented, the life time as well as the performance is expected to be improved.

• 한국신뢰성학회지:신뢰성응용연구
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• 제18권1호
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• pp.1-7
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• 2018

Purpose: Maintaining appropriate operational availability (Ao) is a key element of combat victory, but estimates vary according to estimation methods. The purpose of this study is to improve the accuracy of estimating operational availability by tracing the changes of the weapon system's failure rate, repair rate, and the level of logistic support. Methods: In order to track the change in the operating availability, the MDT (mean down time) is modeled by adding the repair time and the ALDT (administration and logistic delay time) to the service time. Results: Using the field data of the weapon system A operated by the ROKAF, the failure rate follows a non-homogeneous Poisson process that changes with time, and it is modeled considering the changing repair rate and the logistic support time. Conclusion: The accuracy of the analytical results was verified by comparing the actual operating data with the estimated availability. The results of this study can be used to track and evaluate the availability in a realistic situation where the failure rate and maintenance rate continuously change in operating environment.