• Convergence Security Journal
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• v.13 no.1
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• pp.71-78
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• 2013

In this study, software products developed in the course of testing, software managers in the process of testing software test and test tools for effective learning effects perspective has been studied using the NHPP software. The doubly bounded power law distribution model makeup Weibull distribution applied to distribution was based on finite failure NHPP. Software error detection techniques known in advance, but influencing factors for considering the errors found automatically and learning factors, by prior experience, to find precisely the error factor setting up the testing manager are presented comparing the problem. As a result, the learning factor is greater than automatic error that is generally efficient model could be confirmed. This paper, a numerical example of applying using time between failures and parameter estimation using maximum likelihood estimation method, after the efficiency of the data through trend analysis model selection were efficient using the mean square error and $R^2$.

• Proceedings of the Computational Structural Engineering Institute Conference
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• 1989.04a
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• pp.11-16
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• 1989

This paper presents a fatigue reliability model for the reliability-based evaluation of remaining fatigue life of existing rail-road bridges. It is demonstrated that the simple fatigue reliability model based on the Weibull distribution of fatigue life can be extended by incorporating various effects due to the rate of the train-traffic increase and in-service Inspections. The paper also suggests the system fatigue reliability analysis using an approximate formulation and 2nd-order bound solutions. The application of the proposed model to existing rail-road brdiges based on field load tests shows that it may be practically used for the assessment of fatigue reliability, remaining life, and in-service inspection scheduling of existing rail-road bridges.

• Journal of the Korean Data and Information Science Society
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• v.9 no.2
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• pp.149-158
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• 1998

In this paper we suggest the joint model of death times and counts with covariates. We assume that the death times follow a Weibull distribution with rate that depends on covariates. For the counts, a Poisson process is assumed with the intensity depending on time and the covariates. We obtain the maximum likelihood estimators of model parameters. This model is applied to data set of patients with breast cancer who received a bone marrow transplant.

• Transactions of the Korean Society of Automotive Engineers
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• v.18 no.1
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• pp.31-36
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• 2010

Collecting all failures during life cycle of vehicle is not easy way because its life cycle is normally over 10 years. Warranty period can help gathering failures data because most customers try to repair its failures during warranty period even though small failures. This warranty data, which means failures during warranty period, can be a good resource to predict initial reliability and permanence reliability. However uncertainty regarding reliability prediction remains because this data is censored. University of Wuppertal and major auto supplier developed the reliability prognosis model considering censored data and this model introduce to predict reliability estimate further "failure candidate". This paper predicts reliability of telecommunications system in vehicle using the model and describes data structure for reliability prediction.

• Proceedings of the Korean Operations and Management Science Society Conference
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• 1996.10a
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• pp.53-56
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• 1996

The conventional inventory models are concerned with the items of which utilities and amount of numbers are constant over time. But in practice the items in inventory systems are increasing or decreasing. This study is concerned with the development of ameliorating inventory models. The ameliorating inventory is the inventory of goods whose utility increases over the time by ameliorating activation. The term ameliorating inventory is used in this paper at least, since the terminology is not standard well known. This study is performed according to areas; one is an economic order quantity(EOQ) model for the items whose utility is ameliorating in accordance with Weibull distribution, and the other is a partial selling quantity(PSQ) model developed for selling surplus inventory accumulated by ameliorating activation. Computer programs are developed to obtain the optimal ordering and selling quantity. Numerical examples to illustrate the effect of ameliorating rate on inventory polices are shown at the end of this paper.

• Journal of the Korean Data and Information Science Society
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• v.23 no.6
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• pp.1195-1202
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• 2012

In this paper, we determine the expected total cost from the user's perspective for the replacement model with the extended warranty when minimal repair cost is a function of failure time. To do so, we define the extended warranty and assume the replacement model following the expiration of extended warranty from the user's perspective. Especially, we propose the criterion to buy the extended warranty and the numerical examples are presented to illustrate the purpose when the failure time of the system has a Weibull distribution.

• Journal of Korea Society of Digital Industry and Information Management
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• v.6 no.2
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• pp.183-191
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• 2010

Decision problem called an optimal release policies, after testing a software system in development phase and transfer it to the user, is studied. The applied model of release time exploited infinite non-homogeneous Poisson process. This infinite non-homogeneous Poisson process is a model which reflects the possibility of introducing new faults when correcting or modifying the software. The failure life-cycle distribution used mixture which has various intensity, if the system is complicated. Thus, software release policies which minimize a total average software cost of development and maintenance under the constraint of satisfying a software reliability requirement becomes an optimal release policies. In a numerical example, after trend test applied and estimated the parameters using maximum likelihood estimation of inter-failure time data, estimated software optimal release time.

• Proceedings of the Korean Reliability Society Conference
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• 2005.06a
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• pp.121-129
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• 2005

In this paper, we consider a periodic preventive maintenance(PM) policy in which each PM reduces the hazard rate of amount proportional to the failure intensity, which increases since the last PM and slows down the wear-out speed to that of new one. And the proportion of reduction in hazard rate decreases with the number of PMs. Our model is similar to $ARI_1$ proposed by Doyen and Gaudoin(2004) in the sense of reduction of hazard rate. Our model has totally different wear-out pattern of hazard rate after PM's, however, and the proportion of reduction depends on the number of PM's. Assuming that the system undergoes only minimal repairs at failures between PM's, the expected cost rate per unit time is obtained. The optimal number N of PM and the optimal period x, which minimize the expected cost rate per unit time are discussed. Explicit solutions for the optimal periodic PM are given for the Weibull distribution case.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.28 no.6
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• pp.739-746
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• 2004

The plastic deformation behavior of an aluminum alloy containing a particle and porosities was investigated at room temperature during equal channel angular pressing (ECAP). Finite element analysis by using ABAQUS shows that ECAP is a useful tool for eliminating residual porosity in the specimen, and more effective under friction condition. The simulation, however, shows considerably low density distributions for matrix near a particle at which many defects may occur during severe deformation. Finite element results of effective strains and deformed shapes for matrix with a particle were compared with theoretical calculations under simple shear stress. Also, based on the distribution of the maximum principal stress in the specimen, Weibull fracture probability was obtained for particle sizes and particle-coating layer materials. The probability was useful to predict the trend of more susceptible failure of a brittle coating layer than a particle without an interphase in metal matrix composites.

• Proceedings of the Korean Society For Composite Materials Conference
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• 2002.10a
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• pp.75-78
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• 2002

A simplified methodology is presented to predict fatigue life and residual strength of composite structures. To avoid excessive amount of tests that are required for model characterization, strength degradation parameter is assumed as function of fatigue life. S-N curve is used to extract fatigue life that is required to characterize the stress levels comprising a randomly-ordered load spectrum. And different stress ratios are handled with Goodman correction approach(fatigue envelope). It is assumed that the residual strength is a function of the number of loading cycles and applied fatigue stress amplitude. And the residual strength distribution after an arbitrary load cycles is represented by two parameter Weibull functions.