• 대한산업공학회지
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• 제39권5호
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• pp.422-428
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• 2013

In many cases, an $\bar{X}$ control chart which is based on the performance variable is used in industrial fields. However, if the performance variable is too costly or impossible to measure and a less expensive surrogate variable is available, the process may be more efficiently controlled using surrogate variables. In this paper, we propose a model for the economic design of a VSI (Variable Sampling Interval) $\bar{X}$ control chart using a surrogate variable that is linearly correlated with the performance variable. The total average profit model is constructed, which involves the profit per cycle time, the cost of sampling and testing, the cost of detecting and eliminating an assignable cause, and the cost associated with production during out-of-control state. The VSI $\bar{X}$ control charts using surrogate variables are expected to be superior to the Shewhart FSI (Fixed Sampling Interval) $\bar{X}$ control charts using surrogate variables with respect to the expected profit per unit cycle time from economic viewpoint.

• 품질경영학회지
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• 제45권4호
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• pp.943-956
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• 2017

Purpose: This paper proposes a VSS(Variable Sample Size) ${\bar{X}}$ control chart using surrogate variable and shows its effectiveness compared with FSS(Fixed Sample Size) ${\bar{X}}$ control chart using either performance variable or surrogate variable. Methods: The expected cost function of VSS ${\bar{X}}$ control chart is derived. The optimal designs are then found for numerical examples using a GA(genetic algorithm) and compared to those of the FSS ${\bar{X}}$ control charts. Results: Computational results show that VSS ${\bar{X}}$ control chart using surrogate variables is superior to FSS ${\bar{X}}$ control chart using either performance variable or surrogate variable from the economic view points. Conclusion: The proposed VSS ${\bar{X}}$ control chart will be useful in industry fields where a performance variable is not avaliable or too costly.

• 품질경영학회지
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• 제32권1호
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• pp.92-101
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• 2004

Tris paper present an economic statistical design which have statistically constraints for the optimal design of an EWMA control charts with variable sampling interval. Cost function use that proposed by Lorenzen and Vance, and the optimal design parameters include the sample size, control limit width, sampling interval, EWMA weight value. Comparisons between VSI EWMA control charts optimal economic design and optimal economic statistical designs show the following fact. Although have demerits which are more costly than economic design, have merits which to detect shifts more efficiently and to improve statistical performance.

• 한국태양에너지학회 논문집
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• 제33권5호
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• pp.41-50
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• 2013

Economic feasibility study using weighted average variable Jeju System Marginal Price, SMP, was conducted for Gasiri wind farm of Jeju Island. To predict the variable Jeju SMP, generator share ratio for SMP was calculated from the real time wind power production and the power demand data for years. Also, sensitivity analysis on Net Present Value, NPV, and Benefit/Cost Ratio, B/C ratio, were performed to clarify which factors are more important in assessing economic feasibility. The result shows that the Gasiri wind farm has a minimum of 110 billion won and a maximum of 132 billion won difference between fixed and variable SMP. Also, Capacity Factor, C.F., had the highest sensitivity for NPV, followed by SMP. Accordingly, when economic analysis for a potential wind farm site is carried out, the variable SMP as well as C.F. should be considered for more accurate assessment of the wind farm.

• 대한가정학회지
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• 제32권1호
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• pp.1-18
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• 1994

The purpose of this study is to find the differences between the husband's and wife's satisfaction of home life. This study is also to compare and analyze some empirical influence on life satisfaction of husband and wife according to home socio-demographic variables and subjective evaluation of economic level including their perception levels of home economics circumstance. The major results are as follows; 1. The husband's score of life satisfaction shows signifcantly more than wife's score that is his score is 3.36 and her score is 3.19. 2. The variables which affect couple's life satisfaction are the perception of resource adequacy the perception of the adequacy of household income, the evaluation level of resource contribution and the perception of level of living relative to others. The most influential variable of the husband is the perception of resource adequacy, while the most influential variable of the sife is the evaluation level of resource contribution. 3. The result of the relative contribution for the variables of life satisfaction are as follows. The explanation of husband's sociodemographic variable is 11.5% if variable of subjective evaluation of economic level is added the explain power is 34.1%(increase, 22.6% (p<0.001)) The explanation of wife's socio-demographic variable is 9.8% If variable of subjective evaluation of economic level is added the explanation is 41.2% (increase 31.4% (p<0.001)).

• 품질경영학회지
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• 제37권2호
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• pp.46-57
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• 2009

The traditional approach to economic design of control charts is based on the assumption that a process is monitored using a performance variable. However, various types of automatic test equipments recently introduced as a part of factory automation usually measure surrogate variables instead of performance variables that are costly to measure. In this article we propose a model for economic design of a control chart which uses a surrogate variable that is highly correlated with the performance variable. The optimum values of the design parameters are determined by maximizing the total average income per cycle time. Numerical studies are performed to compare the proposed $\bar{X}$ control charts with the traditional model using the examples in Panagos et al. (1985).

• 대한산업공학회지
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• 제27권4호
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• pp.366-373
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• 2001

Economic component screening procedures for multi-component assembly products supplied with warranty are proposed. It is assumed that the screening variable is continuous and the performance variable is dichotomous. Logistic and normal models are considered; the proportion of conforming items is a logistic function of the screening variable in the logistic model and the screening variable given the performance variable is normally distributed in the normal model. Cost models are constructed which involve three cost components; screening inspection cost for each component, cost due to disposing a rejected component, and warranty cost for an assembly product. Methods of finding the optimal screening procedures are presented and numerical examples are given.

• 대한산업공학회지
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• 제21권3호
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• pp.387-396
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• 1995

For situations where there are several markets with different profit/cost structures, an economic two-sided screening procedure using a correlated variable is developed. It is assumed that the performance variable and the screening variable are jointly normally distributed. A profit model is constructed which involves selling price, cost incurred by imperfect quality, and screening inspection cost. Methods of finding the optimal screening procedure are presented and numerical examples are given.

• 대한지리학회지
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• 제40권2호
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• pp.187-201
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• 2005

경제 클러스터와 도시 고용중심지에 대한 연구는 최근 지리학 분야에서 매우 중요하게 다루어지고 있다. 그러나 경제 클러스터 탐색을 위한 기존 연구들은 탐색방법의 내재적 한계, 선형 클러스터 탐색의 비효율성, 경제적 유의성 검증의 부족등의 문제를 내포하고있다 본 연구의 목적은 경제 클러스터 탐색방법으로서 통계적, 경제적 유의성을 검증하는 VCEC(Variable Clumping method for Economic Clusters)를 제안하는 것이고, 이를 바탕으로 미국 뉴욕주 이리 카운티(Erie County)의 경제 중심지 탐색을 위한 실증적 경험 사례분석을 하는 것이다. 다양한 탐색 반경과 총 고용인구 한계치의 적용을 통해 통계적, 경제적인 유의성을 가진 경제중심지 탐색이 가능하였다.

• 대한산업공학회지
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• 제19권3호
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• pp.25-35
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• 1993

Economic screening procedures using a correlated variable are proposed to assure that the proportion of conforming items is above a desired level after screening. It is assumed that the performance variable and the screening variable are jointly normally distributed. Two screening procedures are considered. In the first screening procedure, all of the items are inspected on the screening variable. If an item fails to meet the screening specifications, it is rejected and excluded from shipment without inspection of the performance variable. In the second screening procedure, the item which fails to meet the screening specifications is inspected on the performance variable. If the value of the performance variable is within specifications the item is accepted, and the item is rejected otherwise. Cost models are constructed which involve cast from an accepted nonconforming item, cost from a rejected item, and quality inspection cost. Methods of finding optimal cutoff value on a screening variable are presented and numerical examples are given.