• Journal of Korean Society of Industrial and Systems Engineering
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• v.41 no.4
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• pp.203-212
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• 2018

Quality requirements of manufactured products or parts are given in the form of specification limits on the quality characteristics of individual units. If a product is to meet the customer's fitness for use criteria, it should be produced by a process which is stable or repeatable. In other words, it must be capable of operating with little variability around the target value or nominal value of the product's quality characteristic. In order to maintain and improve product quality, we need to apply statistical process control techniques such as histogram, check sheet, Pareto chart, cause and effect diagram, or control charts. Among those techniques, the most important one is control charting. The cumulative sum (CUSUM) control charts have been used in statistical process control (SPC) in industries for monitoring process shifts and supporting online measurement. The objective of this research is to apply Taguchi's quality loss function concept to cost based CUSUM control chart design. In this study, a modified quality loss function was developed to reflect quality loss situation where general quadratic loss curve is not appropriate. This research also provided a methodology for the design of CUSUM charts using Taguchi quality loss function concept based on the minimum cost per hour criterion. The new model differs from previous models in that the model assumes that quality loss is incurred even in the incontrol period. This model was compared with other cost based CUSUM models by Wu and Goel, According to numerical sensitivity analysis, the proposed model results in longer average run length in in-control period compared to the other two models.

• Geotechnical Engineering
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• v.13 no.4
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• pp.67-74
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• 1997

This paper presents the deterministic model to evaluate the two dimensional stability of geotextile-reinforced embankments on soft foundations. The potential failure surfaces in this study are assumed as the logarithmic spiral curves refracted at the boundary of layers. To facilitate the iterative calculations, we developed a program that determines the geotextile tensile force for an geoteztile-reinforced embankments. This program can be used for situations with a varying number of soil layers and soil types. A series of calculations have been made for a schematised situation. The results of these series are collected in stability charts, which are compared with those by circular potential failure surfaces. Using these charts in an early stage of the design provides a reasonable estimate of the stability of geotextile-reinforced embankments. In a later stage a more detailed calculation can be made by the developed programs.

• Journal of the Korean Data and Information Science Society
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• v.14 no.4
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• pp.939-950
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• 2003

Control charts are very useful tool for monitoring of process characteristics. This paper discusses the problem of design of control limits when the subgroups are composed by cluster sampling type. As an alternative method of design of control limits XbBar chart is proposed, which uses the control limits based on the variation between subgroups instead of using classical variation within subgroups. Two examples are presented for reasonable design of control limits and conditions of subgroups based on the cluster sampling. Through examples the guidelines for making proper control limits are proposed.

• Journal of Korean Institute of Industrial Engineers
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• v.39 no.5
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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.

• Structural Engineering and Mechanics
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• v.6 no.3
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• pp.245-257
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• 1998

This paper present an analysis which may be used to obtain a rational design of a system of inclined piles used in preventing downhill creep of unsaturated clay formations. It uses two simple and relatively easy to measure parameters (an estimate of the maximum downhill creep together with a knowledge of the depth of the so called active zone) to calculate the required section size and the optimal spacing (pitch) of the piles for a desired efficiency of the system as a whole. Design charts are provided to facilitate the process.

• IE interfaces
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• v.6 no.1
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• pp.19-30
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• 1993

Various types of control charts are available, but their full advantages are not being utilized due to the lack of experts who can select, design, implement, and interpret. An expert system is developed which would perform these functions as if each process had a resident expert.

• Journal of Korean Society of Industrial and Systems Engineering
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• v.24 no.66
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• pp.19-26
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• 2001

I propose the control chart pattern to provide a more comprehensive scheme for detecting process X and R shifts using individual observations in start-up process. It is important to automate the identification of special disturbances to facilitate real-time manufacturing. This papers formulates X-R charts for interpretation by artificial neural networks. In this papers, which uses the backpropagation algorithm, two samples are fed into the trained neural network to provide outputs ranging from 0 to 1. Simulation results sow that the performance of the proposed control chart using the neural network(NNCC) is quite promising. Using these NN charts, guidelines are given for detecting and classifying process X and R shifts.

• Journal of the Korean Home Economics Association
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• v.43 no.9 s.211
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• pp.175-191
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• 2005

This paper proposed a sizig system for men's jackets in order to improve the clothing fitness and rain the productivity. The sizing system was classified according to 3 age groups. Figure types were categorized by shoulder angle and body shape. The size interval of the basic dimensions was established at regular intervals centering around their means. Altogether, 15 size charts were developed based on the frequency distribution. Size designating measurements for jackets were height, chest girth and waist girth. Size intervals were 3cm for chest and waist girth, 5m for height, and 2cm for waist and hip girth. Considering the cover factor, charts with a limited number of sizes were suggested with necessary measurements for each figure type of each age group.

• Journal of Korean Society for Quality Management
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• v.32 no.4
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• pp.156-168
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• 2004

This research investigates the statistical efficiency of variable sampling size & sampling interval(VSSI) $\bar{X}$ charts under two assignable causes. Algorithms for calculating the average run length(ARL) and average time to signal(ATS) of the VSSI $\bar{X}$ chart are proposed by employing Markov chain method. States of the process are defined according to the process characteristics after the occurrence of an assignable cause. Transition probabilities are carefully derived from the state definition. Statistical properties of the proposed chart are also investigated. A simple procedure for designing the proposed chart is presented based on the properties. Extensive sensitivity analyses show that the VSSI $\bar{X}$ chart is superior to the VSS or VSI $\bar{X}$ chart as well as to the Shewhart $\bar{X}$ chart in statistical sense, even tinder two assignable causes.

• Journal of Korean Institute of Industrial Engineers
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• v.4 no.2
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• pp.59-66
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• 1978

This paper is a work scheduling for design of piping Department of chemical plant using accumulated curve. Accumulated curve prepared by analysis of performance data, collected executed manhours for chemical plant of "D" Company during the past two years. It compared scheduled manhours with actual used manhours up to six months, put into the form of figures and charts the results can he summarized as below; 1) It can he found an important factor of critical control thus piping department got 30% of total scheduled menhours. 2) A plan of manpower mobilization can be scheduled before work starting. 3) Project progress can he found easily as put into the form of figures and charts for schedule to actual.