불확정 모형하에서 가속수명시험의 최적 설계

서순근,하천수,김갑석 한국품질경영학회 2001 품질경영학회지 Vol.29 No.3

This paper presents new compromise ALT plan which is applied to situations that true relationship between stress and parameters is not known exactly. The assumed failure distribution of this study is one of location-scale family, i. e., exponential, Weibull, and lognormal distributions which have been ones of the popular choices of failure distributions. The method of applying the stress is constant, and the censoring mechanism is Type I censoring. Compared with existing compromise plans under true simple linear model in terms of statistical efficiency, the efficiency of new compromise plan is better than the corresponding other compromise ones in most cases. For case when true model is quadratic, this plan can be used without any severe loss in statistical efficiency. The proposed new compromise ALT plan is illustrated with a numerical example and sensitivity analyses are conducted to study effects of pre-estimates of design parameters.

붓스트랩방법을 이용한 피로모형의 설계곡선 설정

서순근,조유희 한국품질경영학회 2002 품질경영학회지 Vol.30 No.4

The fatigue curve with estimated parameters represents the estimate of the median or mean life at a given applied stress. But, in order to assist a designer in making decisions regarding the fatigue failure mode, it is common practice to construct a design curve on the lower or safe side of data. In this study, to overcome the limitations(i.e., no runout, equal variance, and quality of the approximation, etc) of Shen, Wirsching, and Cashman's method which suggested the approximate design curve for nonlinear models using tolerance interval constructed by Owen's method, an algorithm to find design curves under the fatigue model using a parametric bootstrap method, is proposed and illustrated with multiple fatigue data sets.

投資決定時 學習現象을 反映한 費用推定에 관한 硏究

徐洵根 동아대학교 공과대학 부설 한국자원개발연구소 1982 硏究報告 Vol.6 No.1

This paper deals with cost projections and net cash flow estimations adjusted for learning relating to financial plannings. A model is developed for investment decisions which incorporates a labor cost function to express the effects of employee learning during the start-up phase and is extended during the steady-state phase of production. The accounting treatment for a cost allocation based on the learning curve phenomenon is discussed and sensitivity analysis to asses the impacts of estimation errors in the learning rate and steady-state production time is explored. Finally an example to demonstrate the feasibility of proposed model and its methodology is illustrated.

피로곡선 모형의 통계적 분석 및 비교

서순근,조유희 한국품질경영학회 2003 품질경영학회지 Vol.31 No.2

The fatigue has been considered to the most important failure mode where optimal design or reliability prediction of the machinery in aircraft, atomic reactors, and structure systems, etc.. is required. When the statistical analysis of fatigue life data is performed, some difficulties are present because of the following facts : nonlinear relationship, heteroscedastic data, large scatter in the data, censored data (runouts), and existence of fatigue limit. To find the S-N curve models that characterize fatigue strength better, this research compares existing fatigue curve models developed recently in terms of the residual mean square and the estimate of fatigue limit, etc. for various fatigue data sets.

강건 실험계획법을 이용한 열화자료의 분석

서순근,하천수 한국품질경영학회 2004 품질경영학회지 Vol.32 No.1

The reliability of the product can be improved by making the product less sensitive to noises. Especially, it is important to make products robust against various noise factors encountered in production and field environments. In this paper, the phenomenon of degradation assumes a simple random coefficient degradation model to present analysis procedures of degradation data for robust experimental design. To alleviate weak points of previous studies, such as Taguchi's, Wasserman's, and pseudo failure time methods, novel techniques for analysis of degradation data using the cross array that regards amount of degradation as a dynamic characteristic for time are proposed. Analysis approach for degradation data using robust experimental design are classified by assumptions on parametric or nonparametric degradation rate(or slope). Also, a simulation study demonstrates the superiority of proposed methods over some previous works.

수명이 지수분포를 따를 때 정기검사 및 정시종결하에서 신뢰성 샘플링검사계획의 개발

서순근,김갑석 한국경영과학회 1996 한국경영과학회지 Vol.21 No.1

A Reliability Acceptance Sampling Plan(RASP) is developed for testing the exponential mean lifetime under the periodic(i. e., equally-spaced) inspection and Type I censoring. Under the periodic inspection, the exact sampling distribution of maximum likelihood(ML) estimator of mean can not be derived. Hence sample size and acceptance criterion are determined by the algorithm proposed on the basis of Monte Carlo simulation such that the producer's and consumer's risks are satisfied for given censoring time and number of inspections. In addition, the developed RASP is compared to other RASP's designed under the continuous inspection and under the periodic inspection in terms of sampling size, OC curve, and expected completion time, The effects for the RASP by the chosen inspection scheme are also discussed.

자동시각검사환경하에서 공정 목표치의 설정

서순근,이성재 한국품질경영학회 2001 품질경영학회지 Vol.29 No.3

This paper deals with problem of determining process target value under automated visual inspection(AVI) system. Three independent error sources - digitizing error, illumination error, and positional error - which have a close relationship with the performance of the AVI system, are considered. Assuming that digitizing error is uniformly or normally distributed and illumination and positional errors are normally distributed, respectively, the distribution function for the error of measured lengths is derived when the length of a product is measured by the AVI system. Then, Optimal target values under two error models of AVI system are obtained by minimizing the total expected cost function which consists of give away, rework and penalty cost. To validate two process setting models, AVI system for drinks filling process is made up and test results are discussed.

100% 선별검사를 고려한 허용차의 결정

徐洵根,鄭原基 동아대학교 공과대학 부설 한국자원개발연구소 1994 硏究報告 Vol.18 No.2

This paper presents an economic model to determine producer's tolerance factor of a quality characteristic with 100% screening inspection on the assumptions of continuous quadratic loss function and linear inspection cost. A solution procedure for the optimum tolerance is developed and illustrated with a numerical example. Taguchi's tolerance determining procedure have been analyzed in the framework of western statistical quality control although Taguchi has derived tolerances with the consideration of quadratic loss function and deterministic quality characteristic.

라인내 품질관리의 정기점검방식에 관한 연구

서순근,김갑석,배봉수 동아대학교 공과대학부설 생산기술연구소 1996 生産技術硏究所硏究論文集 Vol.1 No.2

The assumptions of period checking policy for On-Line Quality Control presented by Taguchi are examined and his loss function and formulae are evaluated by simulation. New iterative procedures are proposed under Taguchi's loss and improved loss functions, respectively. Computational experiments are conducted for various combinations of parameter values and their results are discussed. Sensitivity analysis for assumption of random walk model is also illustrated with an example.

순 방사형 물류체계에서 수송장비의 보유대수 결정과 분배정책 : 복합포아송과정을 따를 경우 The Case of Compound Poisson Process

서순근,이병호 한국경영과학회 1999 韓國經營科學會誌 Vol.24 No.3

Fleet sizing and empty equipment redistribution are two of the most critical problems in managing a fleet of equipment over a transportation network. Where the demand pattern followed the compound Poission process(CPP) which can be generated one or more at a time under homogeneous Poissio process(HPP), this paper presented a mathematical model to determine control parameters of a decentralized distribution policy and fleet size. In case of the pure hub-and-spoke system, a popular form of a logistics system, and validated this model by simulation. That is, where the number of demanded equipments followed geometric and binomial distribution, respectively, cost models on the pure hub-and-spoke logistics system with deterministic transportation time, which could be solved analytically, were established and analyzed. We also compared the deterministic case with stochastic one that the transportation time follows some probability distributions.