• Proceedings of the Korean Operations and Management Science Society Conference
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• 2005.05a
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• pp.678-685
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• 2005

Estimating parameters of the lifetime distribution is investigated when field failure data are not completely reported. To take into account the reality and the accuracy of the estimates in such a case, the failure reporting probability is incorporated in estimating parameters. Firstly, method of maximum likelihood estimate(MLE) is used to estimate parameters of the lifetime distribution when failure reporting probability is known. Secondly, Expectation and Maximization(EM) algorithm is used to estimate the failure reporting probability and parameters of the lifetime distribution simultaneously when failure reporting probability is unknown. For both case, procedures of estimation are illustrated for single Weibull distribution and mixed Weibull distribution. Simulation results show that MLE obtained by the proposed method is more accurate than the conventional MLE.

• Journal of the Korean Society for Aviation and Aeronautics
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• v.18 no.4
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• pp.38-43
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• 2010

A continuing challenge in the aviation industry is how to safely keep aircraft in service longer with limited maintenance budgets. Therefore, all the advanced countries in aircraft technologies put great efforts in prediction of failure rate in parts and system, but in the domestic aircraft industry is lack of theoretical and experimental research. Prediction of failure rate provides a rational basis for design decisions such as the choice of part quality levels and derating factors to be applied. For these reasons, analytic prediction of failure rate is essential process in developing aircraft structure. In this paper, a procedure for prediction of failure rate for aircraft structural parts is presented. Cargo door kinematic parts are taken to illustrate the process, in which the failure rate for Hook part is computed by using Monte Carlo Simulation along with Response Surface Model, and system failure rate is obtained afterwards.

• Journal of Environmental Science International
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• v.16 no.4
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• pp.487-493
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• 2007

In this study is analysis which dams breach shapes are effect on peak discharge of dam-failure. The dam breach shapes and failure time are important peak discharge when dam failure. When dam failure times are 1hr, 2hr and 3hr condition for the ECRD and 0.1hr and 0.2hr for the CG and CFRD that breach shapes changed base length $B_b=1Hd,\;B_b=2Hd\;and\;B_b=3Hd$. As the results from DAMBRK(Dam Break model) peak discharge are increase base widths lengthen. As failure time is longer then peak discharge is decrease. So peak discharge is increase more short of dam failure time. Also peak discharge is increase become larger dam breach shapes.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 1997.04a
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• pp.51-55
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• 1997

This study is devote to developing navigation filter for detecting sensor failure in multi-sensor navigation system. In multi-sensor navigation system, Kalman filter is generally used to fuse data of each sensors. Sensor failure is fatal in case that the sensor is used as external measurement of Kalman filter therefore detection and recovery of sensor failure is one the important feature of navigation filter. Generally each sensors have its specific feature in measuring navigational information. Fuzzy theory is proposed to detect external sensor failure and provide valid external measurement to Kalman filter avoiding filter divergence and instability. This idea is applied to Autonomous Underwater Vehicle(AUV) which has two navigation sensor i. e self contained inertial sensor and acoustic external sensor. 2 dimensional simulation result shows acceptable failure detection and recovery

• Structural Engineering and Mechanics
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• v.4 no.6
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• pp.601-612
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• 1996

To simulate the large-scale failure evolution with current computational facilities, a simple approach, that catches the essential feature of failure mechanisms, must be available so that the routine use of failure analysis is feasible. Based on the previous research results, a simple analysis procedure is described in this paper for failure simulation. In this procedure, the evolution of localization is represented by a moving surface of discontinuity, and the transition between continuous and discontinuous failure modes are described via the moving jump forms of conservation laws. As a result, local plasticity and damage models, that are formulated based on thermodynamic restrictions, are still valid without invoking higher order terms, and simple integration schemes can be designed for the rate forms of constitutive models. To resolve localized large deformations and subsequent cracking, an efficient structural solution scheme is given for Static and dynamic problems.

• Journal of Korean Institute of Industrial Engineers
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• v.25 no.2
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• pp.204-216
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• 1999

Failure physics and statistical lifetime analysis constitute the two extreme ends of the reliability engineering spectrum, and studies that relate failure mechanisms to failure distributions have been near non-existent. This paper is an attempt to stimulate interest to fill the gap between the two extremes and proposes an approach of combining them through i) developing a failure mechanism model, ii) generating failure times by Monte Carlo simulation with the model, iii) deriving the failure time distribution and evaluating the product reliability, and iv) improving the product reliability by the sensitivity analysis. An application of the proposed approach to the BGA(Ball Grid Array) surface mount package is also provided.

• Computers and Concrete
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• v.12 no.3
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• pp.351-375
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• 2013

Post-punching resistance of a flat slab can help redistribute the gravity loads and resist progressive collapse of a structure following initial damage. One important difficulty with accounting for the post-punching strength of a slab is the discontinuity that develops following punching shear. A numerical simulation technique is proposed here to model and evaluate post-punching resistance of flat slabs. It is demonstrated that the simulation results of punching shear and post-punching response of the model of a slab on a single column are in good agreement with corresponding experimental data. It is also shown that progressive collapse due to a column removal (explosion) can lead to punching failure over an adjacent column. Such failure can propagate throughout the structure leading to the progressive collapse of the structure. Through post-punching modeling of the slab and accounting for the associated discontinuity, it is also demonstrated that the presence of an adequate amount of integrity reinforcement can provide an alternative load path and help resist progressive collapse.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.28 no.6
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• pp.685-692
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• 2004

A stochastic approach has been presented for superplastic deformation of Ti-6Al-4V alloy, and probability functions are used to model the heterogeneous phase distributions. The experimentally observed spatial correlation functions are developed, and microstructural evolutions together with superplastic deformation behavior have been investigated by means of the two-point and three-point probability functions. The results have shown that the probability varies approximately linearly with separation distance, and deformation enhanced probability changes during the process. The stress-strain behavior with the evolutions of probability function can be correctly predicted by the model. The finite element implementation using Monte Carlo simulation associated with reconstructed microstructures shows that better agreement with experimental data of failure strain on the test specimen.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2003.05e
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• pp.104-107
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• 2003

The ageing cause in many porcelain suspension insulators which occur on transmission and distribution line with dead-end stings is mechanical stress in interface between porcelain and cement materials. It is known that the principal mechanical stress which give electrical failure is the results of the displacement is due to cement growth. We studied an analysing method to find out a deformation of brittle porcelain with a thermal expansion of cement for suspension insulator. These simulation analysis and experimental results show that cement volume growths affect severely to be mechanical failure ageing. These simulation analysis and experimental results show that axial loading affects of Porcelain insulators severely to be mechanical failure ageing.

• Journal of Electrical Engineering and Technology
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• v.6 no.6
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• pp.760-768
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• 2011

The performance of transmission lines and its shielding design during a lightning phenomenon are quite essential in the maintenance of a reliable power supply to consumers. The leader progression model, as an advanced approach, has been recently developed to calculate the shielding failure rate (SFR) of transmission lines using geometrical data and physical behavior of upward and downward lightning leaders. However, such method is quite time consuming. In the present paper, an effective method that utilizes artificial neural networks (ANNs) to create a metamodel for calculating the SFR of a transmission line based on shielding angle and height is introduced. The results of investigations on a real case study reveal that, through proper selection of an ANN structure and good training, the ANN prediction is very close to the result of the detailed simulation, whereas the Processing time is by far lower than that of the detailed model.