• 산업경영시스템학회지
• /
• 제40권1호
• /
• pp.165-172
• /
• 2017

Machines are physically or chemically degenerated by continuous usage. One of the results of this degeneration is the process mean shift. Under the process mean shift, production cost, failure cost and quality loss function cost are increasing continuously. Therefore a periodic preventive resetting the process is necessary. We suppose that the wear level is observable. In this case, process mean shift problem has similar characteristics to the maintenance policy model. In the previous studies, process mean shift problem has been studied in several fields such as 'Tool wear limit', 'Canning Process' and 'Quality Loss Function' separately or partially integrated form. This paper proposes an integrated cost model which involves production cost by the material, failure cost by the nonconforming items, quality loss function cost by the deviation between the quality characteristics from the target value and resetting the process cost. We expand this process mean shift problem a little more by dealing the process variance as a function, not a constant value. We suggested a multiplier function model to the process variance according to the analysis result with practical data. We adopted two-side specification to our model. The initial process mean is generally set somewhat above the lower specification. The objective function is total integrated costs per unit wear and independent variables are wear limit and initial setting process mean. The optimum is derived from numerical analysis because the integral form of the objective function is not possible. A numerical example is presented.

• 응용통계연구
• /
• 제11권1호
• /
• pp.53-64
• /
• 1998

수리 가능한 시스템에 대한 고장시간을 표현하는 여러가지 형태의 통계적 모형이 최근 엔지니어들과 신뢰성분야 학자들의 많은 관심을 끌고 있다. 본 논문에서는 수리가능한 시스템의 신뢰성 증가를 나타내는데 유용하게 적용되는 power law process를 고려하고 특히 정시중단자료(time truncated data)인 경우 고장간격에 대한 신뢰구간을 붓스트랩 기법을 이용하여 구하고 이것을 Crow(1982)가 구한 기존의 신뢰구간과 비교 분석하였다.

• 약학회지
• /
• 제37권4호
• /
• pp.383-388
• /
• 1993

Pharmacokinetics of aucubin, an irdoid glucoside, was compared in rats of experimental hepatic failure(EHF). EHF was induced by CCI$_{4}$ or D-galactosamine pretreatment. This work was designed to find out any differences in the pharmacokinetics of aucubin that may explain the different protective effect of aucubin on CCI$_{4}$- and galactosamine-induced EHF : aucubin reportedly protected CCI$_{4}$-inducing hepatotoxicity effectively, but did not for galactosamine-hepatotoxicity. EHF was induced by intraperitoneal injection Of CCI$_{4}$(0.9ml/kg) or galactosamine(250 mg/kg) to Wistar rats 24 hr before the pharmacokinetic study. The rats were fasted during the 24 hr. Aucubin was iv injected at a dose of 15 mg/kg and the plasma aucubin was assayed by HPLC. There were no significant differences in the pathophysiologies(body weight, liver weight, GTP, hematocrit, blood cell distrbution and plasma protein binding of aucubin) between the two EHF models except GOP which was significantly (p<0.05) higher in CCI$_{4}$-than in galactosamine-EHF. On the other hand, pharmacokinetics of aucubin such as total cleatance(CL$_{t}$), distribution volume at steady-state(Vd$_{ss}$), and mean residence time(MRT) differed significantly(p<0.05) between the models : for example, CL$_{t}$ was increased two fold by CCI$_{4}$, but not by galaclosamine ; Vd$_{ss}$, in galactosamine-EHF was higher than that in CCI$_{4}$-EHF ; MRT was decreased by CCI$_{4}$, but increased conversely by galactosamine. The increase of CL$_{t}$(and decrease of MRT) in rats of CCI$_{4}$-EHF was contrary to the general expectation for the hepatic failure : most of the hepatic failures have been known to decrease CL$_{t}$ of the administered drugs. Whether the difference in the pharmacokinetics is responsible for the different protective effect of aucubin against the two EHF models is of interest. However, much more studies on biliary excretion, urinary excretion, and hepatic uptake in cellular level should be preceded before any conclusions are made on the role of different pharmacokinetics on the different pharmacology of aucubin.

• 한국군사과학기술학회지
• /
• 제23권2호
• /
• pp.168-175
• /
• 2020

Failure of essential avionic equipments have a significant impact on the operations and safety of P-3 maritime patrol aircraft. Therefore, avionic equipments of P-3 are required to have higher reliability. Based on the field failure data, this paper studies the reliability growth of essential avionic equipments in P-3 using Duane model. Additionally, a simulation model is built and implemented for identifying the operational availability according to the field failure data of avionic equipments.

• Journal of Chest Surgery
• /
• 제28권3호
• /
• pp.287-292
• /
• 1995

From March 1989 to June 1994, 24 casesof esophageal cancer were treated surgically. Among 24, male was 22 cases, female was 2 cases, and the age ranged from 46 to 75, the mean was 59.8. Symptoms were dysphagia[86.9% , weight loss[65.2% and retrosternal pain or discomfort[47.8% . The tumor was located cervical esophagus in two, upper esophagus in three, middle esophagus in 12 and lower esophagus in 7. Among 24 patients, 22 were curative resection, partial esophagectomy with esophagogastrostomy[18 cases or colon interposition [3 cases , with total esophagectomy with musculocutaneous flap[1 case , with feeding jejunostomy or gastrostomy in two cases.Postoperative complications revealed 10 patients[45.4% , as followed ; pleural effusion and pneumonia in 5, passage disturbance in 4, empyema and wound infection in 3, esophagopleural fistula and sepsis in 2, anastomotic site leakage and respiratory failure in each 1. The operative mortality was 13.6 % [3/22 and causes of death were respiratory failure in 1 case and sepsis in 2 cases.During follow-up work, 8 cases died during follow-up period, mean survival time was 15.2 months in curative resection group. One year survival rate was 55.3% in resected group. Also, cancer recurrence revealed in 1 cases.

• Journal of the Korean Data and Information Science Society
• /
• 제17권3호
• /
• pp.945-952
• /
• 2006

Several accelerated life test plans use tests at only two levels of stress and thus, have practical limitations. They highly depend upon the assumption of a linear relationship between stress and time-to-failure and use only two extreme stresses that can cause irrelevant failure modes. Thus 3-level stress plans are preferable. When the lifetime distribution of test unit is exponential with mean lifetime $\theta_i$ at stress $x_i$, i=0, 1, 2, 3, we derive the optimum quadratic plan under the assumption that a quadratic relationship exists between stress and log(mean lifetime), and propose the compound linear plans, as an alternative to the optimum quadratic plan. The proposed compound linear plan is better than two other compromise plans for constant stress testing and nearly as good as the optimum quadratic plan, and has the advantage of simplicity.

• Journal of the Korean Data and Information Science Society
• /
• 제25권4호
• /
• pp.921-929
• /
• 2014

A bivariate exponential distribution with a location parameter is proposed as a model for a two-component shared load system with a guarantee time. Some statistical properties of the proposed model are investigated. The maximum likelihood estimators and uniformly minimum variance unbiased estimators of the parameters, mean time to failure, and the reliability function of system are obtained with unknown guarantee time. Simulation studies are given to illustrate the results.

• 산업공학
• /
• 제23권2호
• /
• pp.176-181
• /
• 2010

Warranty claim data analysis is a useful tool for the manufacturer because it contains many useful informations regarding reliability of the product in the real-world environments. Because of the nature of uncertainty and the incompleteness of data, some bias patterns are observed on warranty claim rate known as 'spikes'. Two types of spikes are considered. One is due to manufacturing-related failures. The other is caused by customer's behavior. This paper proposes a model by considering two types of spikes. Warranty claim data is analyzed with the proposed model. To represent spikes observed on the early warranty period, we classify failures into manufacturing-related failures and usage-related failures. Uniform distribution is assumed for the time delayed to diagnose and report by customers. By reducing maximum value of the delayed time by customers, the proposed model characterizes customer's rush in the vicinity of the warranty expiration limit. Experimental results by using the real warranty claim data show that the proposed model is better than the existing one in respect to MSE(Mean Squared Error). Moreover it is expected to estimate the failure rate more realistically with proposed model because it considers the delayed time to diagnose and report by customers.

• Communications for Statistical Applications and Methods
• /
• 제30권4호
• /
• pp.389-402
• /
• 2023

Multivariate or clustered failure time data often occur in many medical, epidemiological, and socio-economic studies when survival data are collected from several research centers. If the data are periodically observed as in a longitudinal study, survival times are often subject to various types of interval-censoring, creating multivariate interval-censored data. Then, the event times of interest may be correlated among individuals who come from the same cluster. In this article, we propose a unified linear regression method for analyzing multivariate interval-censored data. We consider a semiparametric multivariate accelerated failure time model as a statistical analysis tool and develop a generalized Buckley-James method to make inferences by imputing interval-censored observations with their conditional mean values. Since the study population consists of several heterogeneous clusters, where the subjects in the same cluster may be related, we propose a generalized estimating equations approach to accommodate potential dependence in clusters. Our simulation results confirm that the proposed estimator is robust to misspecification of working covariance matrix and statistical efficiency can increase when the working covariance structure is close to the truth. The proposed method is applied to the dataset from a diabetic retinopathy study.

• 디지털산업정보학회논문지
• /
• 제10권2호
• /
• pp.1-11
• /
• 2014

Software reliability in the software development process is an important issue. Software process improvement helps in finishing with reliable software product. In this field, SPC (Statistical process control) is a method of process management through application of statistical analysis, which involves and includes the defining, measuring, controlling, and improving of the processes. The proposed process involves evaluation of the parameter of the mean value function and hence the values of the mean value function at various inter failure times to develop relevant time control chart. In this paper, was proposed a control mechanism, based on time between failures observations using Rayleigh and Burr distribution property, which is based on Non Homogeneous Poisson Process (NHPP). In this study, the proposed model is reliable in terms of hazard function, because it is more efficient in this area can be used as an alternative to the existing model. Through this study, software developers are considered by the various intended functions, prior knowledge of the software to identify failure modes to feed to some extent shall be able to help.