• Journal of Korean Society for Quality Management
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• v.43 no.4
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• pp.471-488
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• 2015

Purpose: Double sampling $T^2$ chart is a useful tool for detecting a relatively small shift in process mean when the process is controlled by multiple variables. This paper finds the optimal design of the double sampling $T^2$ chart in both economical and statistical sense under Weibull failure model. Methods: The expected cost function is mathematically derived using recursive equation approach. The optimal designs are found using a genetic algorithm for numerical examples and compared to those of single sampling $T^2$ chart. Sensitivity analysis is performed to see the parameter effects. Results: The proposed design outperforms the optimal design of the single sampling $T^2$ chart in terms of the expected cost per unit time and Type-I error rate for all the numerical examples considered. Conclusion: Double sampling $T^2$ chart can be designed to satisfy both economic and statistical requirements under Weibull failure model and the resulting design is better than the single sampling counterpart.

• Korean Journal of Fisheries and Aquatic Sciences
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• v.36 no.4
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• pp.389-401
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• 2003

The changes in structure and abundance of taxon or species groups in the East Sea ecosystem were compared between pre- and post-Climatic Regime Shift (CRS) occurred in the mid 1970s using an ECOPATH model. Although the East Sea ecosystem consisted of primary producers, primary consumers, secondary consumers and terminal consumers most species groups were classified as secondary consumers. The mean trophic level between pre- and post-CRS increased from 3.09 during the pre-CRS period to 3.28 during the post-CRS period. Total biomass of the species groups in the East Sea ecosystem increased by $9\%$ due to the CRS, and total catch increased by $48\%.$ The most significant differences between pre- and post-CRS models occurred at the mid/high trophic levels occupied by fishes and cephalopods. Relative contribution of the different species groups to the total energy flow was calculated for the trophic level III. As a result, the status by the dominant species in the East Sea ecosystem shifted from cephalopods to walleye pollock due to the CRS. Relative contribution of 5 species, which were commercially important, such as Pacific saury, Pacific sardine, filefish, walleye pollock and sandfish in trophic level III, were also changed due to the CRS. Finally, the CRS turned out to cause large variations in biomass and catch of fisheries resources as well as the status and role of the major species.

• Journal of Korean Society on Water Environment
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• v.39 no.4
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• pp.302-315
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• 2023

Distribution characteristics and altitudinal gradient of four species (E. strigata, E. separigata, E. orientalis-sachalinensis group) of the mayfly genus Ephemera (Order Ephemeroptera) were analyzed with probability distribution models (exponential, normal, lognormal, logistic, Weibull, gamma, beta, Gumbel). Data was collected from 23,846 sampling units of 6,787 sites in Korea from 2010 to 2021. The beta distribution model showed the best fit for positively skewed E. orientalis-sachalinensis and little-skewed E. strigata along with altitudinal gradient. The reversed lognormal distribution model showed the best-fit for negatively skewed E. separigata. E. orientalis-sachalinensis distributed at the range of altitude 1~700 m (mean 251 m, median 226 m, mode 124 m, and standard deviation 161 m), E. strigata distributed at the range of altitude 5~871 m (mean 474 m, median 478 m, mode 492 m, and standard deviation 200 m), E. separigata distributed at the range of altitude 7~846 m (mean 620 m, median 659 m, mode 760 m, and standard deviation 181 m). Altitudinal habitat suitability ranges were estimated to be 42~257 m for E. orientalis-sachalinensis, 335~644 m for E. strigata, and 641~824 m for E. separigata. Based on the altitudinal spectrum of suitability and altitude-related temperature analysis results, E. orientalis-sachalinensis was estimated to be thermophilic, E. strigata to be mesophilic, and E. separigata to be thermophobic. This is the first national-scale evaluation of the altitudinal distribution of Ephemera in Korea. These results will be used in a further research study on altitudinal shift of the species of Ephemera under climate change.

• Korean Journal of Agricultural Science
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• v.38 no.2
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• pp.219-225
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• 2011

Changes in biota, species distribution range shift and catastrophic climate influence due to recent global warming have been observed during the last century. Since global warming affects various sectors, such as agriculture and vegetation, it is important to predict more accurate impact of future climate change. The purpose of this study is to examine the observed distribution of Abeliophyllum distichum in the Korean peninsula. For this purpose, two period (present and future) climate data were used. Mean data between 1950 and 2000, were used as the present value and the year 2050 and 2080 data from A1B senario in IPCC SRES were used for the future value. Potential habitation is analyzed by MaxEnt(Maximum Entropy model), and Abeliophyllum distichum's coordinates data were used as a dependent variable and independent variables are composed of environmental data such as BioClim, altitude, aspect and slope. The result of six types GCM mean calculation, the potential habitability decreased by 40-60% of the average existing distribution. The methodogies and results of this research can be applicable to the climate changing adaptation stratiegies for the biodiversity conservation.

• Safety and Health at Work
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• v.6 no.4
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• pp.305-311
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• 2015

Background: The purpose of this study was to examine the relationship nursing personal and workplace system factors (work disability) and work ability index scores in Ontario, Canada. Methods: A total of 111 registered nurses were randomly selected from the total number of registered nurses on staff in the labor, delivery, recovery, and postpartum areas of four northeastern Ontario hospitals. Using a stratified random design approach, 51 participants were randomly selected in four northeastern Ontario cities. Results: A total of 51 (45.9% response rate) online questionnaires were returned and another 60 (54.1% response rate) were completed using the paper format. The obstetric workforce in northeastern Ontario was predominately female (94.6%) with a mean age of 41.9 (standard deviation = 10.2). In the personal systems model, three variables: marital status (p = 0.025), respondent ethnicity (p = 0.026), and mean number of patients per shift (p = 0.049) were significantly contributed to the variance in work ability scores. In the workplace system model, job and career satisfaction (p = 0.026) had a positive influence on work ability scores, while work absenteeism (p = 0.023) demonstrated an inverse relationship with work ability scores. In the combined model, all the predictors were significantly related to work ability scores. Conclusion: Work ability is closely related to job and career satisfaction, and perceived control at work among obstetric nursing. In order to improve work ability, nurses need to work in environments that support them and allow them to be engaged in the decision-making processes.

• KIPS Transactions on Software and Data Engineering
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• v.1 no.3
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• pp.177-186
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• 2012

In this paper, we propose a real-time approach for detecting and tracking a hand region by analyzing depth images. We build a hand model in advance. The model has the shape information of a hand. The detecting process extracts out moving areas in an image, which are possibly caused by moving a hand in front of a camera. The moving areas can be identified by analyzing accumulated difference images and applying the region growing technique. The extracted moving areas are compared against a hand model to get justified as a hand region. The tracking process keeps the track of center points of hand regions of successive frames. For this purpose, it involves three steps. The first step is to determine a seed point that is the closest point to the center point of a previous frame. The second step is to perform region growing to form a candidate region of a hand. The third step is to determine the center point of a hand to be tracked. This point is searched by the mean-shift algorithm within a confined area whose size varies adaptively according to the depth information. To verify the effectiveness of our approach, we have evaluated the performance of our approach while changing the shape and position of a hand as well as the velocity of hand movement.

• The Journal of Korea Institute of Information, Electronics, and Communication Technology
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• v.2 no.1
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• pp.23-28
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• 2009

Recently, the research which concerns the object class recognition has been done. Although an object tracking based on most of histograms employs a colored model to improve robustness, the system is not reliable enough yet. In this paper, we presents a method to express and track an object by using the histograms which are composed with visual features through succesive frames. The experimental results shows that this method is reliable to track a car within 80m distance from camera.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.34 no.3C
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• pp.274-278
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• 2009

Recently, the research which concerns the object class recognition has been done. Although an object tracking based on most of histograms employs a colored model to improve robustness, the system is not reliable enough yet. In this paper, we presents a method to express and track an object by using the histograms which are composed with visual features through successive frames. The experimental results shows that this method is reliable to track a car within 80m distance from camera.

• Journal of the Korean Statistical Society
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• v.36 no.4
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• pp.457-469
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• 2007

Many procedures are available to identify a single outlier or an isolated influential point in linear regression and logistic regression. But the detection of influential points or multiple outliers is more difficult, owing to masking and swamping problems. The multiple outlier detection methods for logistic regression have not been studied from the points of direct procedure yet. In this paper we consider the direct methods for logistic regression by extending the $Pe\tilde{n}a$ and Yohai (1995) influence matrix algorithm. We define the influence matrix in logistic regression by using Cook's distance in logistic regression, and test multiple outliers by using the mean shift model. To show accuracy of the proposed multiple outlier detection algorithm, we simulate artificial data including multiple outliers with masking and swamping.

• Journal of Ubiquitous Convergence Technology
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• v.1 no.1
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• pp.3-8
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• 2007

This paper presents a set of techniques used in a real-time visual surveillance system. The system is implemented on a low-cost embedded DSP platform that is designed to work with stationary video sources. It consists of detection, a tracking and a classification module. The detector uses a statistical method to establish the background model and extract the foreground pixels. These pixels are grouped into blobs which are classified into single person, people in a group and other objects by the dynamic periodicity analysis. The tracking module uses mean shift algorithm to locate the target position. The system aims to control the human density in the surveilled scene and detect what happens abnormally. The major advantage of this system is the real-time capability and it only requires a video stream without other additional sensors. We evaluate the system in the real application, for example monitoring the subway entrance and the building hall, and the results prove the system's superior performance.