• The Korean Journal of Applied Statistics
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• v.35 no.6
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• pp.725-737
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• 2022

In the standard assumption of statistical process monitoring (SPM) under consideration, the in-control region of the control parameter of quality characteristic consists of a single point. However, if small deviations from the ideal situation may not be of practical importance, the parametric space can consist of three regions: In-control, indifference, and out-of-control. In this paper, we propose two exponentially weighted moving average (EWMA) charting procedures applicable to the situation with three parameter regions, and compare the efficiency of the proposed procedures with the Shewhart chart and the cumulative sum (CUSUM) chart.

• Journal of The Korean Society of Agricultural Engineers
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• v.56 no.4
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• pp.53-58
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• 2014

The objective of this study is to suggest rainfall threshold for landslide forecasting and warning. For this study, we chose the research area where landslide have occurred. And we performed infiltration-stability analysis with rainfall intensity-duration. As the results of this study, slope stability variation chart with rainfall intensity-duration are established. This kind of chart is believed to be able to be used for forecasting and warning the landslide caused by rainfall.

• The Korean Journal of Applied Statistics
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• v.22 no.6
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• pp.1131-1142
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• 2009

We suggest a fast and accurate algorithm to compute ARLs of CUSUM chart for controling process variance. The algorithm solves the characteristic integral equations of CUSUM chart (for controling variance). The algorithm is directly applicable for the cases of odd sample sizes. When the sample size is even, by using well-known approximation algorithm combinedly with the new algorithm for neighboring odd sample sizes, we can also evaluate the ARLs of CUSUM charts efficiently and accurately. Based on the new algorithm we consider the optimal design of upward and downward CUSUM charts for controling process variance.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.28 no.4A
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• pp.232-237
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• 2003

We present the derivation of the loci of the reflection coefficient of a loaded transmission line on the Smith chart as the length of the transmission line is varied. The results show that the loci constitute a circle when the characteristic impedance of the transmission line differs from the normalizing one, whose center and radius are determined by the impedances of the load and the transmission line. The results can be used in the matching circuit design using microstriplines when line width and length should be compromised.

• Journal of Advanced Marine Engineering and Technology
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• v.16 no.5
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• pp.67-76
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• 1992

This paper describes the vibration characteristic of second-order nonlinear systems subjected to parametric excitation. Emphasis is put on the examination of the hydrodynamic nonlinear damping effect on limiting the response amplitudes of parametric vibration. Since the parametric vibration is described by the Mathieu equation, the Mathieu stability chart is examined in this paper. In addition, the steady-state solutions of the nonlinear Mathieu equation in the first instability region are obtained by using a perturbation technique and are compared with those by a numerical integration method. It is shown that the response amplitudes of parametric vibration are limited even in unstable conditions by hydrodynamic nonlinear damping force. The largest reponse amplitude of parametric vibration occurs in the first instability region of Mathieu stability chart. The parametric excitation induces the response of a dynamic system to be subharmonic, superharmonic or chaotic according to their dynamic conditions.

• Journal of the Korean Society of Manufacturing Technology Engineers
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• v.19 no.6
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• pp.746-752
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• 2010

Rib structure has been used to bed and column of machine tool to heighten weight stiffness ratio, cost performance and weight saving. In this paper the bed rib structure was estimated with thermal characteristics. Using superposition principle, machine tool designer can describe every complicated heat generation in the machine tool thermal source. As thermal characteristics, thermal deformation of guide rail and column and Maximum-minimum temperature variation were selected. The size, configuration and direction against the thermal loading surface operated to the thermal characteristics. The DB chart was made following rib structure estimating thermal characteristics. With superposition principle and DB chart, machine tool designer can prognosticate the thermal characteristics without FEM analysis to every bed rib structure.

• Proceedings of the Safety Management and Science Conference
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• 1999.11a
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• pp.247-257
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• 1999

There are several models for process quality assurance by quality system(ISO 9000), process capability analysis, acceptance control chart and so on. When a high level process capability has been achieved, it takes a long time to monitor the process shift, so it is sometimes necessary to develop a quicker monitoring system. To achieve a quicker quality assurance model for high-reliability process, this paper presents a model for process quality assurance when the fraction nonconforming is very small. We design an acceptance control chart based on variable quality characteristic and time-censored accelerated testing. The distribution of the characteristics is assumed to be normal of lognormal with a location parameter of the distribution that is a linear function of a stress. The design parameters are sample size, control limits and sample proportions allocated to low stress. These parameters are obtained under minimization of the relative variance of the MLE of location parameter subject to APL and RPL constraints.

• Journal of the Korean Data and Information Science Society
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• v.28 no.4
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• pp.937-945
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• 2017

The purpose of using a control chart is to detect any change that occurs in the process. When control charts are used to monitor processes, we want to identify this changes as quickly as possible. Many problems in quality control involve a vector of observations of several characteristics rather than a single characteristic. Multivariate CUSUM or EWMA charts have been developed to address the problem of monitoring covariance matrix or the joint monitoring of mean vector and covariance matrix. However, control charts tend to work poorly when we use the highly correlatted variables. In order to overcome it, Hawkins (1991) proposed the use of regression adjustment variables. In this paper, to monitor covariance matrix, we investigate the performance of MEWMA-type control charts with and without the use of regression adjusted variables.

• Journal of the Korean Society of Marine Environment & Safety
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• v.24 no.2
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• pp.146-156
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• 2018

The ship's chart system was changed from the use of paper chart to the ENC (Electronic Navigational Chart) using ECDIS (Electronic Chart Display and Information System). The introduction of ENC in ships is necessary for ship automation and for the digitalizing of data and integration of information, but unexpected various problems have occurred and are posing a great threat to safe navigation in the transitional period when the new system has been applied to the sea. In this paper, to assess whether ECDIS contributes to the safety of navigation for its intended purposes as new navigation equipment, a usability test of ECDIS was conducted on masters and crew who have used ECDIS on ocean-going vessels. The result was verified with a paired sample T-test, and it was significantly analyzed with the effectiveness of a simplified task; cost efficiency was decreased since ECDIS was used. By analyzing 'MSC.1/Circ.1503 ECDIS - Guidance for good practice', we found that the effects of the maintenance of ECDIS software, operating anomalies identified within ECDIS, differences between raster chart display system (RCDS) and ECDIS, and matters of identification were compounded by the overlapping information on the safety of ships. The anomalies were also grouped according to their characteristics, and we proposed suitable improvements accordingly. The reason for the reduction in efficiency in the usability test was that the problems with ECDIS were intended to be solved only with the careful use of navigational officers who did not have systematic solutions. To solve these problems, the maintenance of software, the improvement of ECDIS anomalies, the reliable ENC issuance including the global oceans, and S-mode development are a priority.

• Proceedings of the KSR Conference
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• 2007.05a
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• pp.1861-1863
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• 2007

In rock mass, great many discontinuity exists that is caused to various factors of formation. But these are parted to some groups by specific category, so called these as discontinuity set. This discontinuity set has unique special characteristics in original rock mass, but for the moment, differ the special quality if external force such as digging etc. acts, specially, change of stress condition. Also, geometrical relation change between discontinuity orientation and direction of excavation various characteristic is seen. Therefore, we introduce here the useful chart that can do specification these relation.