• Journal of Korean Society for Quality Management
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• v.23 no.3
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• pp.20-32
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• 1995

This paper is concerned with the economic selection of both the lower limit and the process mean for a continuous production process. Consider a production process where items are produced continuously. All of the items are subject to acceptance inspection. The items for which the measured values of the quality characteristic are larger than the lower limit are accepted, and those smaller than the lower limit are rejected and excluded from shipment. The process mean may be set higher to reduce the costs incurred by imperfect quality. Using a higher process mean, however, results in a higher production cost when production cost is an increasing function of the quality characteristic. Assuming that the quality characteristic is normally distributed with known variability, cost models are constructed which involve production cost, cost incurred by imperfect quality, rejection cost, and inspection cost. Methods of finding optimal values of the lower limit and the process mean are presented and numerical examples are given.

• Proceedings of the Korean Society for Quality Management Conference
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• 2006.04a
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• pp.334-337
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• 2006

This paper considers the problem of selecting the most profitable process mean for production processes where measurement errors exist in inspection systems. For such situations, a sequential inspection procedure is proposed to reduce measurement errors. The decision to accept, reject, or take an additional inspection of an item is made at every measurement point until the number of repeated measurements reaches its upper bound. An expected profit model is constructed and the optimal process mean, the cut-off values, and the upper bound of the number of repeated measurements are obtained when accepted(rejected) items are sold at regular(reduced) price. A numerical study is performed to investigate the performance of the proposed procedure.

• The Pure and Applied Mathematics
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• v.18 no.2
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• pp.129-139
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• 2011

We consider an optimal trading rule in this paper. We assume that the underlying asset follows a mean-reverting process and the transaction consists of one buying and one selling. To maximize the profit, we find price levels to buy low and to sell high. Associated HJB equations are used to formulate the value function. A verification theorem is provided for sufficient conditions. We conclude the paper with a numerical example.

• Korean Journal of Construction Engineering and Management
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• v.19 no.3
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• pp.43-51
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• 2018

Facility Management (FM) phase in building lifecycle management is the most crucial phase concerning building value and life cycle cost management. Nevertheless, systematic and rational FM process is not yet constructed, leading to failure of facility value and cost management from accurate and proactive FM. This is because there has been minimal approach regarding construction of optimal FM process based on rational FM data analysis. The purpose of this study is to provide optimal FM process with quantitative FM data analysis method using spatial data. This study investigated existing FM data structure and derive the limitation of it from both expert interview and practical FM material analysis. As a solution for this limitation, this study provided optimal FM process with MTBF (Mean Time Between Failure), which is quantitative FM data analysis method. The effect of the provided process was validated with a case study. It is expected that this process allows rational and objective FM data analysis, resulting in accurate and proactive FM. And it is expected that it can be used as a useful basic data for developing an effective system for the FM process.

• International Journal of Quality Innovation
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• v.1 no.1
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• pp.32-37
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• 2000

In an industrial process, the proper objective is to find the optimal operating conditions with minimum process variability around the target. Vining and Myers(1990) suggest to use the separate model for the mean response and the process varian linear predictor ${\tau}_i={\log}\;{\sigma}^2_i$ is unknown and should be estimated. Noting that the variance of $\hat{{\tau}_i}$ is heterogeneous, another appropriate D-optimality criterion $D_3$ based on the method of generalized least squares is proposed in this paper.

• Korean Journal of Chemical Engineering
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• v.35 no.11
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• pp.2150-2156
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• 2018

We suggest a systematic method for obtaining the optimal compression ratio in the multi-stage closed-loop compression process of carbon dioxide. Instead of adopting the compression ratio of 3 to 4 by convention, we propose a novel approach based on mathematical analysis and simulation. The mathematical analysis prescribes that the geometric mean is a better initial value than the existing empirical value in identifying the optimal compression ratio. In addition, the optimization problem considers the initial installation cost as well as the energy required for the operation. We find that it is best to use the fifth stage in the general closed-loop type carbon dioxide multi-stage compression process.

• Journal of Korean Society for Quality Management
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• v.39 no.2
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• pp.170-178
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• 2011

In general, a software fault detection phenonenon is described by a software reliability model based on a nonhomogeneous Poisson process(NHPP). In this paper, we propose a software reliability growth model considering the differences of the software environments in both the testing phase and the operational phase. Also, we consider the problem of determining the optimal release time and the optimal warranty period that minimize the total expected software cost which takes account of periodic software maintenance(e.g. patch, update, etc). Finally, we analyze the sensitivity of the optimal release time and warranty period based on the fault data observed in the actual testing process.

• Journal of Korean Society for Quality Management
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• v.12 no.2
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• pp.6-10
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• 1984

A model for obtaining optimal resetting period and optimal target value of the process quality level is proposed when the quality characteristic is subject to a linear shift in mean. Different sales conditions are considered where good items can he sold at a regular price and bad items at a discounted one. Some numerical examples are also given.

• Journal of Korean Society of Industrial and Systems Engineering
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• v.10 no.15
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• pp.39-44
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• 1987

A model for obtaining optimal target value and optimal production quantity of the process is described when the mean quality characteristic decreases according to the increase of production quantity. Two different cases are considered where defective items can be either sold at a reduced unit price or discarded. Some numerical examples are also given.

• Journal of the Korean Data and Information Science Society
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• v.18 no.3
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• pp.773-782
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• 2007

The statistical process control charts are very extensively used for monitoring of process mean, deviation, defect rate or reject rate. In this paper we consider a control chart to monitor the process reject rate in the high yield process, which is based on the observed cumulative probability of the number of items inspected until r defective items are observed. We first propose selection of the optimal value of r in the CPC-r charts, and also consider the usefulness of the chart in high yield process such as semiconductor or TFT-LCD manufacturing process.