• 대한산업공학회지
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• 제32권1호
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• pp.51-60
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• 2006

When the nature of measuring a performance variable is destructive or very expensive, it is attractive to use a surrogate variable which is highly correlated with the performance variable and less expensive to measure. In this paper, we propose rectifying screening procedures using the performance and surrogate variables. Two screening procedures are considered; a statistically-based screening procedure to reduce the current proportion of nonconforming items to a specified lower value after screening, and an economically-based screening procedure where the screening limit is determined so that the expected cost is minimized. It is assumed that the surrogate variable given the performance variable is normally distributed with known mean and standard deviation. For two screening procedures, methods of finding the optimal solutions are presented and numerical examples are also given.

• 대한산업공학회지
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• 제24권2호
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• pp.279-285
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• 1998

A quality inspection procedure interchangeably using the performance and screening variables is proposed. At the start of the inspection, the performance variable is measured for all items. As soon as i consecutive items are found to be free of defects, the screening variable is measured instead of the performance variable. If an item is rejected, the inspection based on the performance variable is resumed. All nonconforming items found in the inspection are either reworked or replaced with conforming items. It is assumed that the performance variable is dichotomous, and the screening variable given the performance variable is normally distributed with known mean and variance. The average outgoing quality (AOQ) expression is derived, and the methods of finding the inspection procedure with a specified average outgoing quality limit (AOQL) are presented.

• 한국품질경영학회:학술대회논문집
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• 한국품질경영학회 2009년도 추계학술대회
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• pp.3-10
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• 2009

When the measurement method for a performance variable is destructive or expensive, it is profitable to replace the performance variable with a highly correlated surrogate variable. In this paper we propose screening procedures using a surrogate variable with specified producer's and consumer's risks. Blending the basic concepts of acceptance sampling plans and screening procedures, the proposed model can be used effectively by quality professionals. Two models are considered: the normal model with dichotomous performance and continuous surrogate variables, and the bivariate normal model with continuous performance and surrogate variables. It is assumed the surrogate variable given the performance variable is normally distributed in the normal model, and performance and surrogate variables are jointly normally distributed in the bivariate normal model. For the two models, Producer's and consumer's risks are derived, and methods of finding the optimal screening procedures are presented. Numerical examples are also given.

• 품질경영학회지
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• 제37권4호
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• pp.23-30
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• 2009

When the measurement method for a performance variable is destructive or expensive, it is profitable to replace the performance variable with a highly correlated surrogate variable. In this paper we propose screening procedures using a surrogate variable with specified producer's and consumer's risks. Blending the basic concepts of acceptance sampling plans and screening procedures, the proposed model can be used effectively by quality professionals. Two models are considered: the normal model with dichotomous performance and continuous surrogate variables, and the bivariate normal model with continuous performance and surrogate variables. It is assumed the surrogate variable given the performance variable is normally distributed in the normal model, and performance and surrogate variables are jointly normally distributed in the bivariate normal model. For the two models, producer's and consumer's risks are derived, and methods of finding the optimal screening procedures are presented. Numerical examples are also given.

• 한국경영과학회:학술대회논문집
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• 한국경영과학회 2006년도 추계학술대회
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• pp.365-368
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• 2006

The implementation of a screening procedure for removing non-conforming products has become a common practice especially in high-tech manufacturing industries. Screening procedures involve a measurement on the quality characteristic of interest since decisions regarding the conformance to specifications are usually made on the basis of the realization of measurement. A significant variability in measurement procedures may result in the misclassification of an outgoing product (that is, falsely accepting defectives or falsely rejecting conforming items), which may lead to wrong interpretation on product quality, It may thus be necessary to consider the impacts of misclassification errors due to measurement variability when designing screening procedures. Along this line, this article investigates the design of screening procedures based on the assessment of misclassification errors. The main objective is to determine the screening limits on measured values so that two types of misclassification errors may properly be compromised.

• 산업공학
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• 제16권spc호
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• pp.65-69
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• 2003

Process capability has long been viewed as a critical performance measure to indicate how well a process meet the specifications and customer requirements. Several indices, including $C_p$ and $C_{pk}$, have been proposed and widely implemented to quantify the process capability. However, these indices have been obtained without regard to inspection or screening procedures through which finished products will be truncated at the specifications. Consequently, only a fraction of outgoing products within the specifications will be passed into the customers. From the customer's point of view, it will thus be meaningful to assess the process capability with truncated samples. This article investigates how to estimate the process capability when only incomplete truncated data are available. On the basis of parameter estimation for truncated samples, the proposed methodology may be helpful to evaluate the process capability by examining a sample of items from the lots submitted.

• 품질경영학회지
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• 제22권4호
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• pp.28-39
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• 1994

This study is concerned with determination of an optimal target value in a filling process. Complete inspection procedures are widely used to improve outgoing quality of products. In many cases, however, it may be impossible or noneconomical to measure the quality characteristic, performance variable, directly. In such cases, it is a common practice to select an easily measurable variable which is highly correlated with the performance variable and perform screening products for the variable. This study proposes a model to determine the target value and the inspection rule based on the screening variable. This, study deals with the cases in which rejected products would be scrapped and sold at a reduced price in secondary markets.

• 품질경영학회지
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• 제28권2호
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• pp.1-16
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• 2000

This paper considers the problem of determining the optimal process mean and screening specification limits of a surrogate variable associated with product quality under two-stage screening procedure. In two-stage screening, the surrogate variable is inspected first to decide whether an item should be accepted, rejected or additional observations should be taken. If additional observations are required, the performance variable of interest is then observed to classify the undecided items. Assuming that the performance variable and the surrogate variable are jointly normally distributed, the optimal process mean and the screening limits are obtained by maximizing the expected profit which includes selling price, production, reprocessing, inspection and penalty costs. A numerical example is presented and numerical studies are performed to compare the proposed two-stage screening procedure with single-stage screening procedures.

• Nuclear Engineering and Technology
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• 제55권4호
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• pp.1485-1494
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• 2023

The bow of the nuclear fuel assembly is a well-known phenomenon. One of the vital criteria during the history of nuclear fuel development has been fuel assembly's mechanical stability. Once present, the fuel assembly bow can lead to safety issues like excessive water gap and power redistribution or even incomplete rod insertion (IRI). The extensive bow can result in assembly handling and loading problems. This is why the fuel assembly's bow is one of the most often controlled geometrical factors during periodic fuel inspections for VVER when compared e.g. to on-site fuel rod gap measurements or other instrumental measurements performed on-site. Our proposed screening method uses existing video records for fuel inspection. We establish video frames normalization and aggregation for the purposes of bow measurement. The whole process is done by digital image processing algorithms which analyze rotations of video frames, extract angles whose source is the fuel set torsion, and reconstruct torsion schema. This approach provides results comparable to the commonly utilized method. We tested this new approach in real operation on 19 fuel assemblies with different campaign numbers and designs, where the average deviation from other methods was less than 2 % on average. Due to the fact, that the method has not yet been validated during full scale measurements of the fuel inspection, the preliminary results stand for that we recommend this method as a complementary part of standard bow measurement procedures to increase measurement robustness, lower time consumption and preserve or increase accuracy. After completed validation it is expected that the proposed method allows standalone fuel assembly bow measurements.

• 한국산학기술학회논문지
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• 제22권6호
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• pp.314-320
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• 2021

최근 사회적으로 결혼연령이 높아짐에 따라 고령산모가 증가하면서 생화학적 표지물질을 이용한 다운증후군 선별검사는 산모들에게 필수적인 검사가 되었다. 다운증후군 임신을 진단하는 과정은 선별검사에서 고위험군으로 보고 되면 융모막 융모생검이나 양수검사 같은 침습적 검사를 통해 염색체 분석을 하는 단계로 진행이 되는데 이러한 확진검사는 비용이 많이 들고 태아손실의 위험도가 높다. 따라서 위험도는 낮고 다운증후군 발견율이 높은 선별검사를 선택하여 불필요한 침습적 검사를 줄여 산모와 태아의 위험도를 낮추는 것이 중요하다. 본 연구는 2018년 용인의 임상검사기관에 산전선별검사를 의뢰한 17세부터 46세까지 총 36,436명을 대상으로 triple test(185명), quad test(3,629명), integrated test(18,932명), sequential test(13,690명) 4가지 검사를 direct sandwich, indirect sandwich 기술을 이용한 Time-resolved fluoroimmunoassay 방법과 sandwich 방법을 이용한 면역측정 방법을 사용하여 35세 미만과 35세 이상 산모의 다운증후군 위험도를 분석하여 산모 연령이 증가함에 따른 양성률의 차이를 확인하였다. 검사결과 전체 산모의 다운증후군 고위험군은 triple test 36명, quad test 408명, integrated tset 1,441명, sequential test 924명 이었다. 이중 35세미만 산모의 고위험군은 triple test 7명(3.8%), quad test 141명(3.9%), integrated tset 644명(3.4%), sequential test 430명(3.4%)이었고, 35세이상 산모의 고위험군은 29명(15.7%), 267명(7.4%), 797명(4.2%), 494명(3.6%)으로 나타나 35세이상 산모가 훨씬 높은 고위험군을 나타내었다. 임상에 있어서 35세 미만과 35세 이상 산모의 위험도 분석을 한 연구는 국내외에 거의 희박하므로 본 연구는 향후 국내외의 많은 검사기관들과 예비 산모들에게 다운증후군 위험의 예방과 치료를 위한 매우 유용한 기초 자료가 될 것으로 생각된다.