• Journal of Korean Society for Quality Management
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• v.42 no.1
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• pp.1-14
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• 2014

Purpose: In this paper, the minimal repair-replacement warranty policy is used to carry out a warranty cost analysis with warranty servicing times and failure times that are statistically correlated to bivariate distributions. Methods: Based on the developed approach by Park and Pham (2012a), we investigate the property of the Freund's bivariate exponential distribution and obtain the number of warranty services using the field data to conduct the warranty cost analysis. Results: Maximum likelihood estimates are presented to estimate the parameters and the warranty model is investigated using a Freund's bivariate exponential distribution. A numerical example is discussed to deal with the applicability of the developed approach in the paper. Conclusion: A novel approach of analyzing the warranty cost is proposed for a product in which failure times and warranty servicing times are used simultaneously to investigate the eligibility of a warranty claim.

• Proceedings of the Earthquake Engineering Society of Korea Conference
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• 2003.03a
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• pp.286-293
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• 2003

In this study a story-wise distribution of hysteretic energy in multi-story steel moment-resisting framse (MRE), buckling restrained braced frames (BRBF-R), and hinge-connected framed structures with buckling restrained braces (BRBF-H) subjected to various earthquake ground excitations was investigated. According to analysis results the hysteretic energy in MRF and BRBF-R turned out to be the maximum at the base and monotonically diminishes with increasing height. In top stories the plastic deformation of members is almost negligible. However the story-wise distribution of hysteretic energy in BRBF-H was relatively uniform over the height of the structure. This is considered to be more desirable because damage is not concentrated in a single story.

• The Transactions of the Korean Institute of Electrical Engineers A
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• v.51 no.5
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• pp.217-224
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• 2002

This paper presents an algorithm to obtain an approximate optimal solution for the service restoration and load balancing of large scale radial distribution system in a real-time operation environment. Since the problem is formulated as a combinatorial optimization problem, it is difficult to solve a large-scale combinatorial optimization problem accurately within the reasonable computation time. Therefore, in order to find an approximate optimal solution quickly, the authors proposed an algorithm which combines optimization technique called cyclic best-first search with heuristic based feeder loadings balance index for computational efficiency and robust performance. To demonstrate the validity of the proposed algorithm, numerical calculations are carried out the KEPCO's 108 bus distribution system.

• Journal of Korean Society for Quality Management
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• v.31 no.4
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• pp.164-175
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• 2003

This paper investigates bootstrap confidence intervals of the process capability index(PCI) based on the expected loss derived from the empirical distribution function(EDF). The PCI based on the expected loss is too complex to derive its confidence interval analytically, so the bootstrap method is a good alternative. We propose three types of the bootstrap confidence interval; the standard bootstrap(SB), the percentile bootstrap(PB), and the acceleration biased­corrected percentile bootstrap(ABC). We also perform a comprehensive simulation study under various process distributions, in order to compare the accuracy of the coverage probability of the bootstrap confidence intervals. In most cases, the coverage probabilities of the bootstrap confidence intervals from the EDF PCI turned out to be more accurate than those from the PCI based on the normal distribution. It is expected that the bootstrap confidence intervals from the EDF PCI can be utilized in real processes where the true distribution family may not be known.

• Transactions of Materials Processing
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• v.6 no.3
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• pp.250-256
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• 1997

Hammer forging was employed for Alloy 718 disk. The change in grain size during hot forging depends very much on dynamic recrystallization. The final grain size depends especially on the critical strain$($\varepsilon$_C)$/TEX> for dynamic recrystallization and Zener-Holloman parameter(Z). In this study, the critical strain$($\varepsilon$_C)$, the strain for 50 pct. recrystallization$($\varepsilon$_{0.5})$ and fraction of dynamic recrystallization(Xdyn) were measured by compression tests. FE simulation was also carried out ot predict the evolution of microstructure. The strain, strain rate and temperature distribution predicted by forging simulation can be effectively used to predict the distribution of grain sizes in the forged workpiece. The present model predictions showed an excellent agreement with the microstructural evolution of hammer-forged Alloy 718 disks.

• Electrical & Electronic Materials
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• v.10 no.9
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• pp.881-888
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• 1997

This study demonstrats the profiles of phosphorus ions in silicon by MeV implantation(1∼3 MeV). Implanted profiles could be measured by SIMS(Cameca 4f) and compared with simulation results(TRIM program and analytical description method only using on Pearson function). The experimental result in the peak concentration region has a little bit deviation from simulation data. By RBS and Channeling measurements the defect distribution of implanted samples could be measured and spectrum are calibrated depth with RUMP simulation By XTEM measurement the thickness of defect zone also could be measured. Finally thermal annealing for the electrical activation of implanted ions carried out by RTA(rapid thermal annealing). The concentration-depth profiles after heat treatment was measured by SR(spreading resistance)-method.

• Journal of the Korean Society for Precision Engineering
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• v.16 no.5 s.98
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• pp.175-185
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• 1999

Acoustic emission(AE) measurement was carried out to evaluate the fracture behavior of high tension steel. Fracture toughness $K_{AE}$ could be determined reasonably by using the load value corresponding to an abrupt change of the accumulated AE counts AE emitted from the test specimens. AE characteristics of the base metal, the weld metal and the heat-affected zone could be distinguished using a constant value b which represented the AE amplitude distribution, Consequently the structure integrity can be evaluated by variation of the constant b at the load level. In addition it was found that AE signals due to crack growth have high amplitude but low rise time and duration.

• Proceedings of the KIEE Conference
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• 2000.07c
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• pp.1548-1550
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• 2000

The effect of air pollution on the distribution facilities was investigated. In order to evaluate the pollution level in the metropolitan area, contaminated specimens were analyzed with various technique such as ICP-AES, EA, and so on. The contaminants on the surface of the distribution line or insulators were combined with approximately 10 percent of organic and 90 percent of inorganic materials. We found out that the electric facilities were affected by the contaminants on the surface of the facilities.

• Convergence Security Journal
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• v.8 no.4
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• pp.121-126
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• 2008

It is of great practical interest to decide when to stop testing a software system in development phase and transfer it to the user. This decision problem called an optimal release policies. In this paper discussed to specify an optimal release policies. In this paper, propose an optimal release policies of the life distribution applied Erlang distribution of special pattern of Gamma distribution. In this paper, discuss optimal software release policies which minimize a total average software cost of development and maintenance under the constraint of satisfying a software reliability requirement. From Sensitivity Analysis, make out estimating software optimal release time.

• Journal of the Korean Society of Manufacturing Technology Engineers
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• v.9 no.6
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• pp.111-117
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• 2000

The plastically deformed layer in a machined surface must be considered in precision machining process. Therefore the analysis of the machined surface, including the plastic deformation and strain distribution should be carried out quantitatively. The subsequent recrystallization technique was presented for analysis of the plastically deformed layer in the machined surface, and the technique was successfully applied to determine the plastic strain in the machined surface. This investigation is to evaluate the plastic strain in the distance 0.1mm from the machined surface, and in particular, to find the effect of shear angle, shear strain, cutting energy etc. on the plastic strain.