• Journal of Korean Society for Quality Management
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• v.43 no.2
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• pp.169-184
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• 2015

Purpose: This paper is concerned with optimally designing accelerated degradation test (ADT) plans based on a gamma process for the degradation model. Methods: By minimizing the asymptotic variance of the MLE of the q-th quantile of the lifetime distribution at the use condition, the test stress levels and the proportion of test units allocated to each stress level are optimally determined. Results: The optimal plans of ADT are developed for various combination of parameters. In addition, a method for determining the sample size is developed, and sensitivity analysis procedures are illustrated with an example. Conclusion: It is important to optimally design ADT based on a gamma process under the condition that a degradation process should be always nonnegative and strictly increasing over time.

• Journal of Korean Society for Quality Management
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• v.27 no.3
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• pp.79-93
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• 1999

The common accelerated life test(ALT) consists of test methods applying a constant stress, higher than the use condition stress, to items. There we, however, situations for which a progressive stress ALT, in which the stress on a test item is continuously increased with time, Is more convenient to perform testing and simpler in analyzing data than a constant stress ALT. When a product under constant stress s follows a Weibull distribution with parameters $\theta$(5) and $\beta$, maximum likelihood(ML) estimators of parameters involved in the model are obtained and their asymptotic distributions are derived under stress bounded ramp tests in which the stress is increased linearly from use condition stress to the stress upper bound. The optimum test plans are also found which minimize the asymptotic variance of the ML estimator of the log mean life at design constant stress. For selected values of the design parameters, tables useful for finding optimal test plans are given. The effect of the pre-estimates of design parameters is studied.

• Journal of the Korean Graphic Arts Communication Society
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• v.15 no.2
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• pp.57-76
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• 1997

A color halftoning is the process of generating halftone images for the different color plans, for example, cyan, magenta, yellow, and black for a offset printing device. A conventional halftone technique, so called AM screening, is simple and easy to implement, but the halftoned dot patterns by using this method is not free for the moire` fringe. Moire` patterns are caused the power spectrum distribution on low spatial frequency domain. To avoid Moire` patterns, the conventional screen require the different screen angles for each color plans. Recently, Ultra-fine and 7 color printing methods are developed to expend the color gamut. In 7 color printing method must be used the halftone technique of random and blue noise characteristic to avoid Moire` fringe.

• Journal of Korean Society for Atmospheric Environment
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• v.2 no.2
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• pp.31-40
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• 1986

Motor vehicle related air pollution has become more serious because of rapid increase of number of cars, specially in the urban area. The increase trend seems to be accelerated, however, the fact is that road conditions, parking facilities and traffic control systems are far behind coping with this situation. In spite of the lack of related basic data, urban transportation planning (UPT) and air pollution dispersion models were applied to predict air pollution level. In standard UPT model, trip generation, distribution, modal split and network assignment were estimated by experimental equations and appropriate models. The air pollution level in the central business area was believed to be higher and it will increase continuously due to the increase of traffic demand. To meet this situation, air pollution problem should be considered as a part of integrated plannings of urban plans or transportation plans as well as more stringent motor vehicle emission standards, have to be enforced.

• Journal of Environmental Science International
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• v.12 no.2
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• pp.157-162
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• 2003

Boeun-gun is hard to develop, because of large numbers of mountains and vast distribution of limited development districts. However it is easy to access from the entire country, and there are large conservation area such as national park and dams. Short-term plans such as attraction of tourists can be established using these advantages. Long-term plans can be planed with stable establishment of continuous considerations and supports. These supports will be rewarded while it demands some time and costs. Private owned mountains can be converted from negligence upkeep of property to utilization of mountains with basic consideration of mountain conservation. This may contribute the essential function of mountain.

• Journal of the Speleological Society of Korea
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• no.95
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• pp.1-13
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• 2009

The problems of Ondal cave have been analyzed by the lack of academic names and explanations compared to other caves. To improve the problems, there needs to be various and balanced distribution of names, increase explanations, specializing in the form of academic explanations and the information format.

• Journal of Korean Society of Industrial and Systems Engineering
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• v.5 no.7
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• pp.29-32
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• 1982

On designing the rectifying inspection plans of double sampling, the relations of the sample sizes $n_1$, $n_2$ and the acceptance numbers $c_1$, $c_2$ are obtained by using the Chi-square distribution. As the average number of pieces inspected per lot is a function of $c_1$ and $c_2$, the optimal solution is the values of $c_1^*$ and $c_2^*$ for which the average amount of inspection is a minimum. Then the values of $n_1^*$ and $n_2^*$ are easily obtained from the equations given by ($n_1$, $n_2$) and ($c_1$, $c_2$).

• Journal of Korean Institute of Industrial Engineers
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• v.22 no.3
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• pp.459-471
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• 1996

This paper considers ramp tests for exponential lifetime distribution when there are limitations on test stress and test time. The inverse power law and a cumulative exposure model are assumed. Maximum likelihood (ML) estimators of model parameters and their asymptotic covariance matrix are obtained. The optimum ramp test plans are also found which minimize the asymptotic variance of the ML estimator of the log mean life at design constant stress. For selected values of the design parameters, tables useful for finding optimal test plans are given. The effect of the pre-estimates of design parameters is studied.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.8 no.4
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• pp.918-925
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• 2004

SCM means that production companies set up schedules for the purchase, manufacture and sales of production parts, go on smoothly the flow of products (added value and material flow) by systematically arranging the demand plans of customers and the distribution situation, thereby executing the management of them in an effective way. This article aims at analyzing the external flow between government and companies and presenting the problems and the improvement plans, which can make clear all the information flow of supply networks including the internal integration.

• Journal of the Korean Institute of Educational Facilities
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• v.18 no.4
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• pp.25-32
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• 2011

This study was carried out to obtain basic data for architectural plans about factors on the facilities relocation needed in management of variation type. For this, floor plans of thirteen middle schools located in Korea and Japan were compared. The results showed a successful conversion to block system according to each subject after remodeling in the schools of our country, however, a monotonous spacial composition excluded other spaces such as media space, teachers' station and preparation room was also shown. These mentioned spaces were important factors in the investigated schools of Japan. By the results of the spacial composition about each space required to the management of variation type, a space share of supplemental areas for learning activities and movement, had shown comparatively low share before remodeling, was improved to 6% and 11.6%, respectively. However, the spacial share of two areas were 16.8% and 12.9%, respectively, in the schools of Japan and it meant the distribution of area was more even than the cases of our country.