Journal of The Japanese Society for Quality Control
Online ISSN : 2432-1044
Print ISSN : 0386-8230
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Volume 25, Issue 2
Displaying 1-31 of 31 articles from this issue
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Features
Activity Report of Research Section
Research Papers
Contributed Paper
  • Experimental Design for System Identification of Continuous Processes
    Tomomichi SUZUKI, Hitoshi KUME
    Article type: Contributed Paper
    1995 Volume 25 Issue 2 Pages 63-69
    Published: April 15, 1995
    Released on J-STAGE: February 06, 2019
    DOIhttps://doi.org/10.20684/quality.25.2_63
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    To control countinuous process properly, it is very important to grasp process dynamics accurately. But that is not done satisfactorily. As a result, process control has not been executed properly. Experimental design that enables accurate grasping of process dynamics is proposed. Gaps between system theory and practice in system identification are invested. As a result, we have found that there are needs for experiment that is capable of producing high quality data for system identification. Experiment patterns under practical restricts of manipulated variable are proposed, and the condition that estimates parameters in the process model most accurately is derived. The best condition is then compared with what Box and Jenkins had given, and it is shown that the former can estimate as accurately as the latter with smaller range of manipulated variable.
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  • Estimation of the change-point in a Fraction Defective Based on Minimum Description Length Criterion
    Hideo SUZUKI, Takao ENKAWA
    Article type: Contributed Paper
    1995 Volume 25 Issue 2 Pages 71-80
    Published: April 15, 1995
    Released on J-STAGE: February 06, 2019
    DOIhttps://doi.org/10.20684/quality.25.2_71
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    This paper presents a method using Minimum Description Length Criterion (MDL) that can effectively detect the change in a fraction defective and simultaneously estimate its change-point in a sequence of samples. A promising model selection criterion, MDL minimizes the total umber of binary digits needed to reproduce the observed data including the code length of the parameters themselves. The change-point estimated by the proposed method is expected to provide valuable information for real-time process control. First, an approximate MDL expression customized for a binomial distribution is derived. Second, an algorithm is proposed in which the detection and estimation are conducted on the basis of the derived MDL each time a sequential sample is given. Finally, simulation experiments are provided provided to verify the performance of the proposed method by comparison with asymptotic MDL and Cumulative Sum charts.
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Technical Note
  • Optimal Thresholds of Two Monitors in Condition Monitoring Maintenance
    Kazuyuki SUZUKI, Kan TACHIKAWA
    Article type: Technical Note
    1995 Volume 25 Issue 2 Pages 81-87
    Published: April 15, 1995
    Released on J-STAGE: February 06, 2019
    DOIhttps://doi.org/10.20684/quality.25.2_81
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    It is sometimes difficult to comprehend the exact internal state of a large system because of its complexity and preciseness. Under these circumstances, a monitoring system which indirectly gives information on true state plays an important role. However,a monitor might have two kinds of errors; "no alarm (fail to operate)" when the system is in a bad state, and "raising alarm (fail to idle)" when in a good state. Using combinations of two monitors having different thresholds, Tanaka^<[12]> has derived an optimal design of monitoring system which minimizes the expected risk. In this research, assuming that thresholds of the monitors can take arbitrary values, optimal thresholds are investigated. A sufficient condition is given that two thresholds of the monitors become equal.
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