• Journal of Korean Society for Quality Management
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• v.25 no.1
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• pp.100-115
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• 1997

Shewhart control chart is a basic technique to monitor the state of a process. We observe samples of size four or five and plot some statistic(e.g., mean or range) of each sample on the chart. When setting up the chart, we need to obtain u, pp.r and lower control limits. It is common practice that those limits are calculated from the preliminary 20-40 samples presumed to be homogeneous. However, it may ha, pp.n in practice that the samples are contaminated by outlying observations caused by various reasons. The presence of outlying observations make the control limits wider and hence decrease the sensitivity of the charts. In this paper, we introduce robust control charts with tighter control limits when outlying observations are present in the preliminary samples. Examples will be given via simulation study.

• Nutritional Sciences
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• v.9 no.3
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• pp.201-211
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• 2006

The purpose of this study was to provide dietitians with the guidance in forecasting meal counts for a university/college foodservice facility. The forecasting methods to be analyzed were the following: naive model 1, 2, and 3; moving average, double moving average, simple exponential smoothing, double exponential smoothing, Holt's, and Winters' methods, and simple linear regression. The accuracy of the forecasting methods was measured using mean squared error and Theil's U-statistic. This study showed how to project meal counts using 10 forecasting methods for dietitians. The results of this study showed that WES was the most accurate forecasting method, followed by $na\ddot{i}ve$ 2 and naive 3 models. However, naive model 2 and 3 were recommended for using by dietitians in university/college dining facilities because of the accuracy and ease of use. In addition, the 2000 spring semester data were better than the 2000 fall semester data to forecast 2001spring semester data.

• Proceedings of the Korean Vacuum Society Conference
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• 2014.02a
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• pp.355.1-355.1
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• 2014

Zirconium nitride (ZrN)는 높은 녹는점과 기계적 강도 그리고 내식성을 가져 부품 산업계에서 hard coating에 이용된다. 또한 금속과 같은 전기 전도성을 가지므로 초고집적소자의 확산방지막에 이르기까지 많은 응용이 되고 있다. 본 실험에서는 Si 기판 위에rf magnetron sputter를 사용하여 Zr박막을 증착 하였으며 질소 유량을 변화시키며 Zirconium nitride 박막을 증착하였다. 증착된 박막의 질소 유량변화에 따른 nano-electrotribology 특성변화를 관찰하기 위해 nano-indenter를 사용하였다. 또한 Weibull statistics을 사용하여 박막의 균일성을 검증하였다. 질소 유량이 각각 0, 0.5, 5 sccm으로 증가하는 동안 surface hardness는 12.37, 10.49, 12.14 GPa로 변화하였다. 이때, 박막의 elastic modulus는 175.27, 163.94, 172.18 GPa로 각각 변화하였다. 이러한 결과는 질소 유량에 따라zirconium nitride가 여러 상으로 생성되는 것으로 해석할 수 있다.

• Proceedings of the Korean Reliability Society Conference
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• 2000.04a
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• pp.123-129
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• 2000

SPC is the quality improvement technique of gathering since Motorola of U.S.A. have used SPC technique as a statistical process control method for promoting 6-sigma quality improvement strategy in 1988. In Korea, small and medium-sized enterprises are needed building of a system for statistical production control . In the present study, the methods of building SPC system with a moderate cost using a graphic programs of easy-to-use and high flexibility for small and medium-sized enterprises were inquired. The SPC system which enables statistic marking (maximum, minimum, mean, standard deviation, process capability index) and graph marking (X-Y coordinates and histogram) using LabVIEW 5.0, the graphic program by National Instrument Co., Ltd. was implemented in this study.

• International Journal of Reliability and Applications
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• v.15 no.1
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• pp.11-22
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• 2014

New classes of life distributions called new better (worse) than used at age $t_0$ in Laplace transform order, NBUL- $t_0$(NWUL - $t_0$) are introduced. For the classes NBUL - $t_0$(NWUL - $t_0$), preservation under convolution, mixture, mixing and the homogeneous Poisson shock model are studied. In the sequel, we obtain a test for $H_0$ : F is exponential versus $H_1$ : F is NBUL - $t_0$ and not exponential. The critical values and the powers of this test are calculated to assess the performance of the test. It is shown that the proposed test has high efficiencies for some commonly used distributions in reliability. Sets of real data are used as examples to elucidate the use of the proposed test for practical problems.

• International Journal of Reliability and Applications
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• v.17 no.2
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• pp.107-119
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• 2016

A new concept of aging classes namely new better (worse) than used at age $t_0$ in moment generating function order, $NBU_{mgf}-t_0$ ($NWU_{mgf}-t_0$) is introduced. For the classes $NBU_{mgf}-t_0$ ($NWU_{mgf}-t_0$), preservation under convolution, mixture, mixing and the homogeneous Poisson shock model are studied. In the sequel, nonparametric test is proposed, the asymptotic normality of the class is established and the asymptotic null variance is estimated. The percentiles and powers of this test are tabulated. The asymptotic efficiencies for some alternatives distributions are derived. Finally sets of real data are used as examples to elucidate the use of the proposed test in practical application.

• Journal of Preventive Medicine and Public Health
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• v.30 no.4 s.59
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• pp.884-892
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• 1997

Currently, there are 100 community emergency centers which expect to provide professional emergency care like Level 1 trauma centers in U.S.A. To evaluate perforance of emergency centers, most studies have been widely adopted death rate based methods such as Trauma and Injury Severity Score(TRISS) and A Severity Characterization of Trauma(ASCOT). However, these methods are only applicable in situation where registration process of trauma patients is well established. Therefore, an alternative method should be applied to evaluate performance of emergency centers in Korea which does not have well-developed registration scheme. This study aims to develop new performance measures which are applicable to Korea and evaluate performance of 35 community emergency centers through new measures. The new measures are included that 'W-statistic' ; death rate calculated on the basis of International Classification based Injury Severity Score(ICISS), and 'the degree of severity' ; rate of severe trauma patients of each emergency medical centers. The study results can be summarized as follows. First, about 34% of sample emergency centers show they provide proper care in terms of their function. Second, tertiary hospitals, university hospitals, and hospitals located in Seoul show higher severity degree of patients and lower severity-adjusted death rate.

• Journal of Korean Society for Atmospheric Environment
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• v.32 no.6
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• pp.559-574
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• 2016

Based on air quality monitoring data ('10~'14) of Suwon City provided by the Korean Department of Environment, a fundamental statistic for 5 criteria pollutants such as $SO_2$, CO, $NO_2$, $O_3$, and $PM_{10}$ was initially investigated. The purpose of this paper was to review the ambient air quality standards(AAQS) of Korea, the U.S.A. and the EU and further to assess the degree of standard strength by the achievability of the AAQS comparing each national standard. Since the level and the way of standards for each air pollutant are various among countries, it is difficult to determine the degree of relative attainment using the same set of data above. Further when all the areas having bad air quality for a specific pollutant are classified as non-attainment case, it is more difficult to assess the degree of standard strength. Thus we introduced a new concept called the average concentration distance (ACD) to quantitatively estimate the strength. As results, the Korean 1-hr $NO_2$ AAQS is slightly stronger than the US standard and weaker than the EU standard. The Korean $O_3$ standard is strongest; however, the Korean $PM_{10}$ standard is weakest. Furthermore the equivalent levels of 8-hr $O_3$ standards in the U.S.A. and the EU were respectively estimated as 97.5 and 95.7 percentiles of the Korean standard with maintaining the existing standard of 60 ppb.

• Korean Journal of Construction Engineering and Management
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• v.14 no.6
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• pp.70-77
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• 2013

Construction industry is broadly agreed as one of the most important sectors of any economy around the world. In this paper, time series data of Korean construction industry and Korean economy are examined. The Bon's proposition will be inspected for Korean context using both cross-sectional and longitudinal analyses. The analysis of the longer than four decades national account statistic of the Korean macro economy verify Bon's proposition of an inverted U-shaped relationships. The verified U-shaped relationships for Korean context exist not only in terms of the construction share in total GDP but also in terms of total construction volume as an economy develops from LDC to NIC and then to AIC eventually with time. The results of the thesis show that the contribution towards the macro economy has varied across different stages of development.

• Journal of the Korean Society of Fisheries and Ocean Technology
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• v.54 no.1
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• pp.38-53
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• 2018

The purpose of this study is to estimate potential yield (PY) for Korean west coast fisheries using the holistic production method (HPM). HPM involves the use of surplus production models to apply input data of catch and standardized fishing efforts. HPM compared the estimated parameters of the surplus production from four different models: the Fox model, CYP model, ASPIC model, and maximum entropy model. The PY estimates ranged from 174,232 metric tons (mt) using the CYP model to 238,088 mt using the maximum entropy model. The highest coefficient of determination ($R^2$), the lowest root mean square error (RMSE), and the lowest Theil's U statistic (U) for Korean west coast fisheries were obtained from the maximum entropy model. The maximum entropy model showed relatively better fits of data, indicating that the maximum entropy model is statistically more stable and accurate than other models. The estimate from the maximum entropy model is regarded as a more reasonable estimate of PY. The quality of input data should be improved for the future study of PY to obtain more reliable estimates.