• 한국경영과학회:학술대회논문집
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• 대한산업공학회/한국경영과학회 1996년도 춘계공동학술대회논문집; 공군사관학교, 청주; 26-27 Apr. 1996
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• pp.290-293
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• 1996

This paper presents an EMQ model which determines an optimal production run length in a deteriorating machine. It is assumed that a machine is subject to a random deterioration from an in-control state to an out-of-control state with an arbitrary distribution and thus producing constant proportion of defective items. An average cost function and an optimal production run length are determined. A mistake in previous model is found and discussed. A mistake in previous model is found and discussed. Numerical experiments are carried out to see the behavior of the proposed model depending on the cost factors as well as machine parameters, and some interesting behaviors are observed.

• Journal of applied mathematics & informatics
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• 제42권3호
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• pp.709-723
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• 2024

We study the distributions of waiting times in variations of the geometric distribution of order k. Variation imposes length on the runs of successes and failures. We study two types of waiting time random variables. First, we consider the waiting time for a run of k consecutive successes the first time no sequence of consecutive k failures occurs prior, denoted by T^(k). Next, we consider the waiting time for a run of k consecutive failures the first time no sequence of k consecutive successes occurred prior, denoted by J^(k). In addition, we study the distribution of the weighted average. The exact formulae of the probability mass function, mean, and variance of distributions are also obtained.

• 대한의용생체공학회:학술대회논문집
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• 대한의용생체공학회 1991년도 추계학술대회
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• pp.57-60
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• 1991

A new approach to texture classification for ultrasound liver diagnosis using run difference matrix was developed. The run difference matrix consists of the gray level difference along with distance. From this run difference matrix, we defined several parameters such as LDE, LDEL, NUF, SMO, SMG, SHP etc. and three vectors namely DOD, DGD and DAD. Each parameter value calculated in fatty cirrhotic, chronic hepatitic and normal liver mage was plotted in two dimensional plane. We compared our results with run length method. There are several advantages of run difference matrix method over the run lengths. 1) It is more sensitive to small difference of gray level distribution. 2) The parameters provide more statistically significant value. Images were classified with the extracted parameters to each diseases using neural networks. In preliminary clinical exprements, this approach showed satisfying results.

• 한국통신학회논문지
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• 제18권10호
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• pp.1469-1482
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• 1993

본 논문에서 웨이브릿변환을 이용한 새로운 영상신호 부호화기법을 제안하였다. 웨이브릿 계수들을 시각체계의 민감도에 맞도록 제거하거나 양자화함으로써 영상의 우수한 화질을 유지하면서 높은 감축율을 얻도록 하였다. 웨이브릿 변환영역에서 각 부영상들을 블록으로 나누고 계수들의 통계적인 특성과 주파수특성들을 이용하여 중요하지 않은 계수들을 제거하였다. 제기된 블록들과 전송되는 블록들의 위치 정보는 지수 분포와 일치되는데 이를 run-length 부호화하였다. 양자화되는 계수들은 일반화된 가우시안 분포에 맞도록 가변길이 부호화되어 전송된다. 실험결과 기존의 영상코딩과 비교하여 1.0(b/p)이하의 낮은 전송 비트율에서 좋은 복원된 영상화질을 얻을 수 있었다.

• 경영과학
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• 제17권3호
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• pp.73-95
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• 2000

In Korea, the distribution channel for agricultural products is notorious for its complexity and ineffectiveness. In this sense, the Agricultural Cooperative has tried to clarify the distribution channel and reduce its length. However, there still exist much room for improvements. The Internet shopping mall specific for agricultural product, therefore, is drawing much attention because it can reduce the length of distribution channel drastically and improve effectiveness from the distribution perspective. To test the validity of such Internet-driven shopping mall, we gathered questionnaire data from the Internet based Hannaro Shopping Mall which is run directly by the Agricultural Cooperative. We performed experiments respectively for the two groups of operating personnel and consumers. Experimental results showed that several important factors can be identified which are significant statistically and deemed to have meaningful relationship with performance variables. Our results also showed that the Internet shopping mall has a great potential for improving the effectiveness of the distribution channel of the agricultural products.

• 응용통계연구
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• 제37권2호
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• pp.177-189
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• 2024

관리도에서 런길이는 관리 통계량이 관리한계를 벗어날 때까지 관측한 표본의 수로 정의한다. 일반적으로 런길이의 분포는 비대칭이 심하고 변동성이 크기 때문에 평균 런길이만 사용하여 관리도를 설계하고 성능을 평가하는 것은 적절하지 않을 수도 있다. 평균 런길이 기반 설계에 대한 대안으로 이 논문에서는 백분위수를 기반으로 한 관리도의 설계를 소개하고, 이를 지수가중이동평균 관리도의 설계에 적용하는 절차를 제안하고 있다. 이 절차는 백분위수 모수들이 주어진 경우, 모의실험을 통하여 적합된 함수를 사용하여 관리한계의 계수를 설정하는 것이다. 또한 모의실험을 수행하여 제안된 설계 절차를 평균 런길이 기반 설계와 비교하고 평가하였다. 모의실험 결과, 제안된 절차는 이상상태에서 탐지 능력은 거의 유지하면서 관리상태에서의 성능을 향상시킨다는 사실을 확인할 수 있었다.

• Journal of the Korean Data and Information Science Society
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• 제26권4호
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• pp.1027-1034
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• 2015

A control chart is very useful in monitoring various production process. There are many situations in which the simultaneous control of two or more related quality variables is necessary. When the joint distribution of the process variables is multivariate normal, multivariate Shewhart control charts using the function of the maximum likelihood estimator for monitoring the dispersion matrix are considered for the simultaneous monitoring of the dispersion matrix. The performances of the multivariate Shewhart control charts based on the proposed control statistic are evaluated in term of average run length (ARL). The performance is investigated in three cases, where the variances, covariances, and variances and covariances are changed respectively. The numerical results show that the performances of the proposed multivariate Shewhart control charts are not better than the control charts using the trace of the covariance matrix in the Jeong and Cho (2012) in terms of the ARLs.

• Journal of the Korean Data and Information Science Society
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• 제23권4호
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• pp.807-814
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• 2012

We know that the exponentially weighted moving average (EWMA) control charts are sensitive to detecting relatively small shifts. Multivariate EWMA control charts are considered for monitoring of variance-covariance matrix when the distribution of process variables is multivariate normal. The performances of the proposed EWMA control charts are evaluated in term of average run length (ARL). The performance is investigated in three types of shifts in the variance-covariance matrix, that is, the variances, covariances, and variances and covariances are changed respectively. Numerical results show that all multivariate EWMA control charts considered in this paper are effective in detecting several kinds of shifts in the variance-covariance matrix.

• Journal of the Korean Data and Information Science Society
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• 제23권3호
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• pp.617-626
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• 2012

Multivariate Shewhart control charts are considered for the simultaneous monitoring the variance-covariance matrix when the joint distribution of process variables is multivariate normal. The performances of the multivariate Shewhart control charts based on control statistic proposed by Hotelling (1947) are evaluated in term of average run length (ARL) for 2 or 4 correlated variables, 2 or 4 samples at each sampling point. The performance is investigated in three cases, that is, the variances, covariances, and variances and covariances are changed respectively.

• Communications for Statistical Applications and Methods
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• 제23권6호
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• pp.497-515
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• 2016

Modern processes often monitor more than one quality characteristic that are referred to as multivariate statistical process control (MSPC) procedures. The MSPC is the most rapidly developing sector of statistical process control and increases interest in the simultaneous inspection of several related quality characteristics. Most multivariate detection procedures based on a multi-normality assumptions are independent, but there are many processes that assume non-normality and correlation. Many multivariate control charts have a lack of related joint distribution. Copulas are tool to construct multivariate modelling and formalizing the dependence structure between random variables and applied in several fields. From copula literature review, there are a few copula to apply in MSPC that have multivariate control charts, and represent a successful tool to identify an out-of-control process. This paper presents various types of copulas modelling for the multivariate control chart. The performance measures of the control chart are the average run length (ARL) and the average number of observations to signal (ANOS). Furthermore, a Monte Carlo simulation is shown when the observations were from an exponential distribution.