• 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.

• Annual Conference of KIPS
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• 2012.04a
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• pp.564-566
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• 2012

무선 센서 네트워크에서 관심지역이 배치된 센서들에 의하여 모두 관측되고 이의 데이터가 싱크노드까지 전달되는 동시에 네트워크의 수명을 최대화하도록 센서들을 배치하는 연구는 중요하다. 본 논문에서는 센서 에너지 소모의 균등화를 통해 네트워크 수명의 최대화를 이루기 위해 불균등 분포를 따르면서 네트워크의 기능이 올바르게 동작할 수 있도록 하는 센서의 배치 패턴을 제시한다.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.40 no.4
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• pp.336-345
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• 2012

In crack growth life, uncertainties are caused by variance of geometry, applied loads and material properties. Therefore, the reliability estimation for these uncertainties is required to keep the robustness of calculated life. The stress intensity factors are the most important variable in crack growth life calculation, but its equation is hard to know for complex geometry, therefore they are processed by the finite element analysis which takes long time. In this paper, the response surface is considered to increase efficiency of the reliability analysis for crack growth life of a turbine wheel. The approximation model of the stress intensity factors is obtained by the regression analysis for FEA data and the response surface of crack growth life is generated for selected factors. The reliability analysis is operated by the Monte Carlo Simulation for the response surface. The results indicate that the response surface could reduce computations that need for reliability analysis for the turbine wheel, which is hard to derive stress intensity factor equation, successfully.

• Korean Journal of Environmental Biology
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• v.36 no.4
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• pp.550-553
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• 2018

The lifespan of bats is longer compared to that of other similarly sized mammals, and it is recorded that some bats' lifespan is more than 30 years. However, it is known that the lifespan of Pipistrellus abramus using human residential areas as their habitats is less than five years. We have put aluminum rings on the forearms of 284 P. abramus starting from 2008. Interestingly, in June 2018, a female adult bat was recaptured ten years after the aluminum ring was attached. The results of this study on the lifespan of P. abramus is new and it's likely to form the baseline for lifespan studies and habitat management of P. abramus in the future.

• Journal of Digital Contents Society
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• v.16 no.1
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• pp.63-70
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• 2015

In this paper, we estimate the life cycle from acceleration life test about the hard disk of disk array of image storage of PACS. Webuil distribution was selected by the Anderson-Darling goodness-of-fit test with data of down time at $50^{\circ}C$ and $60^{\circ}C$. The equality test of shape parameter and scale parameter was conducted, so that the probability distribution estimated from data of down time at $50^{\circ}C$ and $60^{\circ}C$ was not statistically significant. The shape parameter was 1.0409, The characteristic life was 24603.5 hours at normal user condition($30^{\circ}C$) by the analysis of weibull-arrhenius modeling which included the acceleration factor of temperature, and The activation energy was 0.5011 eV through arrhenius modeling. The failure analysis of the failure samples of acceleration test and the samples of market return was conducted, so that the share percentage of failure mode was detail difference but the rank of share percentage was almost same. This study suggest the test procedure of acceleration test of hard disk drive in PACS using environment, and help the life estimation at manufacture and use.

• Journal of Digital Contents Society
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• v.15 no.1
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• pp.19-27
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• 2014

In order to estimate the life of 2,5 inch HDD which is adopted by PC environment, make the test plan which reflect the failure mode of market, make the test model of accelerated life test which reflect the stress of temperature. after an analysis of the environment of PC using, test procedure was decided that operation was write 50 % and read 50 %, and then access method was sequential 50 % and random 50%. The acceleration life test was executed on condition that temperature was $50^{\circ}C$ and $60^{\circ}C$, performance was 95 % in max performance, test time was 1000 hours. by the test of goodness of fit of anderson-darling of the failure data during test, it was confirmed that the distribution of failure fellow weibull. test for shape and scale was equal, and shape parameter was 0.7177, characteristic life was 429434 hours at normal user condition($30^{\circ}C$) by the analysis of weibull-arrhenius modeling. It made no difference about the statistics when equality test was executed. The activation energy was 0.2775eV. In analyzing between the failure samples of acceleration test and the samples of market return even though there is detail difference about the share of failure mode, the rank of share was almost same. This study suggest the test procedure of acceleration test of 2.5 inch HDD in PC using environment, and help the life estimation at manufacture and user.

• 한국도로학회:학술대회논문집
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• 2004.02a
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• pp.85-92
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• 2004

• Transactions of the Korean Society of Mechanical Engineers
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• v.18 no.12
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• pp.3149-3158
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• 1994

In this paper, using the formulation of dynamic equivalent load considering the effects of moment load and the equation to estimate the cage rotational speed, the new life equation of deep groove ball bearing under radial and moment loads was proposed. Fatigue life test apparatus with the measuring equipment of shaft and cage speed was designed and developed to be capable of subjecting combined radial and moment load. Fatigue life tests were executed by sudden death test method and the reliability of fatigue lives was evaluated by Weibull distribution analysis. From the results of fatigue tests and analysis, the relationships between film parameters and life adjustment factors were acquired. And it was turned out that so as to estimate the effect of moment load on fatigue life, the life adjustment factor as well as the dynamic equivalent load must be taken into account.

• The Korean Journal of Applied Statistics
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• v.29 no.5
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• pp.823-833
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• 2016

The lifetime is a key characteristic of product quality. It is best to obtain the lifetime data of all samples, but they are often censored due to time or expense limitations. In this paper, we propose a binomial cumulative sum (CUSUM) chart to monitor the mean of type I right-censored Weibull lifetime data, for a xed value of the Weibull shape parameter. We compare the performance of the proposed binomial CUSUM chart with CUSUM charts studied previously using the steady-state average run length (ARL). The results show that the performance of the binomial CUSUM chart is better when the censoring rate is high and/or the sample size is small.

• Composites Research
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• v.16 no.1
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• pp.13-18
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• 2003

Prediction of composite fatigue life is not a straightforward matter, depending on various failure modes and their interactions. In this paper, a methodology is presented to predict fatigue life and residual strength of composite materials based on Phenomenological Model(non-linear fatigue damage model). It is assumed that the residual strength is a monotonically decreasing function of the number of loading cycles and applied fatigue stress ratio and the model parameters(strength degradation parameter and fatigue shape parameter) are assumed as function of fatigue life. Then S-N curve is used to extract model parameters that are required to characterize the stress levels comprising a randomly-ordered load spectrum. Different stress ratios (${\sigma}_{min}/{\;}{\sigma}_{max}$) are handled with Goodman correction approach(fatigue envelope) and the residual strength after an arbitrary load cycles is represented by two parameter weibull functions.