• Journal of Korean Society for Quality Management
• /
• v.32 no.2
• /
• pp.201-211
• /
• 2004

Process adjustment is a complimentary tool to process monitoring in process control. Process adjustment directs on maintaining a process output close to a target value by manipulating another controllable variable, by which significant process improvement can be achieved. Therefore, this approach can be applied to the 'Improve' stage of Six Sigma strategy. Though the optimal control rule minimizes process variability in general, it may not properly function when special causes occur in underlying process, resulting in off-target bias and increased variability in the adjusted output process, possibly for long periods. In this paper, we consider a responsive feedback control system and the minimum mean square error control rule. The bias in the adjusted output process is investigated in a general framework, especially focussing on stationary underlying process and the special cause of level shift type. Illustrative examples are employed to illustrate the issues discussed.

• Proceedings of the Korean Society for Quality Management Conference
• /
• 2004.04a
• /
• pp.425-429
• /
• 2004

Process adjustment Is a complimentary tool to process monitoring in process control. Process adjustment directs on maintaining a process output close to a target value by manipulating another controllable variable, by which significant process improvement can be achieved. Therefore, this approach can be applied to the 'Improve' stage of Six Sigma strategy. Though the optimal control rule minimizes process variability in general, it may not properly function when special causes occur in underlying process, resulting in off-target bias and increased variability in the adjusted output process, possibly for long periods. In this paper, we consider a responsive feedback control system and the minimum mean square error control rule. The bias in the adjusted output process is investigated in a general framework, especially focussing on stationary underlying process and the special cause of level shift type. Illustrative examples are employed to illustrate the issues discussed.

• Proceedings of the Korean Society for Quality Management Conference
• /
• 2004.04a
• /
• pp.436-441
• /
• 2004

Knowing the time of the process change could lead to quicker identification of the responsible special cause and less process down time, and it could help to reduce the probability of incorrectly identifying the special cause. In this paper, we propose a generalized maximum likelihood estimate. (MLE) of the process change point when a control chart with variable sample size (VSS) scheme signals a change in the process mean, and evaluate the performance of this estimator when it mi used with a VSS EWMA chart.

• Proceedings of the Korean Statistical Society Conference
• /
• 2005.05a
• /
• pp.191-196
• /
• 2005

Knowing the time of the process change could lead to quicker identification of the responsible special cause and less process down time, and it could help to reduce the probability of incorrectly identifying the special cause. In this paper, we propose a MLE of the process change point when control charts with the fixed sampling rate (FSR) scheme or the variable sampling rate (VSR) scheme monitor a process to detect changes in the process mean and/or variance of a normal quality variable.

• Journal of the Korean Statistical Society
• /
• v.33 no.4
• /
• pp.381-399
• /
• 2004

Statistical process control (SPC) and engineering process control (EPC) are based on different strategies for process quality improvement. SPC re-duces process variability by detecting and eliminating special causes of process variation, while EPC reduces process variability by adjusting compensatory variables to keep the quality variable close to target. Recently there has been need for an integrated process control (IPC) procedure which combines the two strategies. This paper considers a scheme that simultaneously applies SPC and EPC techniques to reduce the variation of a process. The process model under consideration is an IMA(1,1) model with a step shift. The EPC part of the scheme adjusts the process, while the SPC part of the scheme detects the occurrence of a special cause. For adjusting the process repeated adjustment is applied according to the predicted deviation from target. For detecting special causes the exponentially weighted moving average control chart is applied to the observed deviations. It was assumed that the adjustment under the presence of a special cause may increase the process variability or change the system gain. Reasonable choices of parameters for the IPC procedure are considered in the context of the mean squared deviation as well as the average run length.

• Journal of Aerospace System Engineering
• /
• v.6 no.1
• /
• pp.7-12
• /
• 2012

Fuel tank design requires special care because tank explosion can cause catastrophic event with high possibility as shown in accident of TWA 800. In this study, cause of fuel tank explosion was reviewed and several design considerations to minimize explosion possibility were introduced.

• Aerospace Engineering and Technology
• /
• v.3 no.1
• /
• pp.272-276
• /
• 2004

Fuel tank design requires special care because tank explosion can cause critical event with high possibility and cause of recent explosion accidents haven't been found out definitely. In this study, cause of fuel tank explosion was reviewed and several design considerations to minimize explosion possibility were introduced.

• Journal of the Korean Data and Information Science Society
• /
• v.22 no.6
• /
• pp.1123-1135
• /
• 2011

This paper considers the multivariate integrated process control procedure for detecting special causes in a multivariate IMA(1, 1) process. When the multivariate control chart signals, the special cause will be detected and eliminated from the process. However, when the elimination of the special cause costs high or is not practically possible, an alternative action is to readjust the process with approximately modified adjustment scheme. In this paper, we propose the readjustment procedure after having a true signal, and show that the use of the readjustment can reduce the deviation of a process from the target.

• Journal of the Korean Data and Information Science Society
• /
• v.21 no.5
• /
• pp.841-852
• /
• 2010

An integrated process control (IPC) procedure is a scheme which simultaneously applies the engineering control procedure (EPC) and statistical control procedure (SPC) techniques to reduce the variation of a process. In the IPC procedure, the observed deviations are monitored during the process where adjustments are repeatedly done by its controller. Because the effects of the noise, the special cause, and the adjustment are mixed, the use and properties of the SPC procedure for the out-of-control process are complicated. This paper considers efficiency of EWMA charts for detecting special causes in an ARMA(1,1) noise model with a minimum mean squared error adjustment policy. And we propose the readjustment procedure after having a true signal. This procedure can be considered when the elimination of the special cause is not practically possible.

• Korean Journal of Acupuncture
• /
• v.17 no.1
• /
• pp.123-140
• /
• 2000

The purpose of this study is to understand the special character and the tendency of the movement change that 12 meridians possess. We studied about the incidental and fundamental rule of the six atmospheric influence that was presented by Pyobonjoong(the incidental, fundamental, intermediate) theory, and the Hwang won-uh's the Six Channel activity of the Qi theory that presented movement form of the meridian through the six atmospheric influence. Then we found the following substances. The Pyobonjoong(the incidental, fundamental, intermediate) theory is applicable to understand the special character and the tendency of the movement change that Meridians possess. But, because the Pyobonjoong(the incidental, fundamental, intermediate) theory can't classify the characteristic difference of the hand and foot meridians, then the principle that can devide the meridians of the hand and foot, must be supplied. The Jungwha(right changing)-Daewha(opposite changing) theory is able to concretely classify the special character of the hand and foot six meridians. And Hwang's Shawha(superintending change)-Jongwha(following change) theory that is base on Jungwha(right changing)-Daewha(opposite changing) theory, is able to classify the special character of the hand and foot six meridians, too. If the concept of the Meridians is understood by the Shawha(superintending change)-Jongwha(following change) theory, the special character of the hand and foot six meridians could be concretely classified and then the meridian of the Bowels and the six atmospheric influence corresponded to the meridians could be expansively explained as the point that take charge and control these special Qi in the human body The Bon-Qi(fundamental Qi) act on the special character of Shawha(superintending change) six meridians and the tendency of the movement change is cause by the insufficiency and excessiveness of the Bon-Qi(fundamental Qi). The Qi of the Shawha(superintending change) meridians act on the special character of Jongwha(following change) six meridians and the tendency of the movement change is cause by the exuberance of Yang and the deficiency of Yang.