• Journal of Electrical Engineering and Technology
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• v.10 no.2
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• pp.465-473
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• 2015

The increasing need to improve transient security assessment of existing or forecasted operating conditions of networks by power system operators is major concern of the power system security monitoring problem at the Energy Management Systems. This paper proposes a preventive control of transient stability with generation rescheduling based on rotor trajectory index obtained using time domain simulations. This index may help power engineers in making operational decision and to obtain a generation configuration with better transient security dispatch. The effectiveness of the proposed methodology is demonstrated on IEEE 39-bus New England system for a three phase fault at different loading conditions with single and multiple line outage cases.

• Proceedings of the Korean Institute of IIIuminating and Electrical Installation Engineers Conference
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• 2007.05a
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• pp.328-333
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• 2007

Traditional maintenance planning is based on a constant maintenance interval for equipment life. In order to consider economic aspect for tm based preventive maintenance, preventive maintenance is desirable to be scheduled by RCM(Reliability-Centered Maintenance) evaluation. The main objective of RCM is to reduce the maintenance cost, by focusing on the most important functions of the system and avoiding or removing maintenance actions that are not strictly necessary. So, Markov state model is utilized considering stochastic state in RCM In this paper, a Markov state model much can be used for scheduling and optimization of maintenance is presented. The deterioration process of system condition is modeled by the stepwise Markov model in detail. Also, because the system is not continuously monitored, the inspection is considered. In case study, simulation results about RCM will be shown using the real historical data of combustion turbine generating unit in Korean power systems.

• Journal of Korean Society of Occupational and Environmental Hygiene
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• v.25 no.3
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• pp.346-354
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• 2015

Objectives: This study was conducted to evaluate the changes and regional differences of mortality and morbidity particularly respiratory system diseases in the area of exposure to coal dust(Ansim area, Dong-gu, Daegu). Methods: The authors analyzed secondary data(cancer registration data, mortality data, and health insurance data) for respiratory system diseases. We calculated age standardized incidence ratio(SIR), mortality ratio(SMR), and health care utilization ratio(SHR) using those data. Results: There were no significant differences between Ansim area(or Dong-gu, Daegu) and the control area for cancer registration data and mortality data. In the results for the health insurance data, significant increased SHR in asthma was observed compared to the control area. Conclusions: Although confounders such as selection bias were not clearly ruled out, our findings reveal increased asthma SHR in the area of exposure to coal dust. Further prospective studies are required to clarify the increasing respiratory disease due to exposure to coal dust.

• Journal of Korean Academy of Oral Health
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• v.41 no.2
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• pp.96-101
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• 2017

Objectives: The aim of this study was to investigate the relationship between cognitive function and occlusal status in elderly individuals. Methods: A total of 162 individuals aged 65 years and older, who attended the senior citizen center in Daegu city, were included after consent for participation in the study was obtained. The Korean version of the Mini-Mental State Examination (MMSE-K) was used to evaluate the level of cognitive function. Occlusal status was determined using the T-scan $III^{(R)}$ system. All collected data were analyzed by ${\chi}^2$ test, t-test, one way ANOVA, and linear regression analysis using SPSS version 23.0 for Windows. Results: There was a significant relationship between the cognitive function and the use of dentures. Individuals with posterior occlusal status had higher MMSE-K scores than those with anterior occlusal status. There was a positive correlation between the cognitive function and posterior occlusal force. Conclusions: These results suggest that occlusal status was associated with cognitive function in the elderly individuals. Active national policies to improve occlusal condition in the elderly population are needed.

• Journal of Preventive Medicine and Public Health
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• v.24 no.4 s.36
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• pp.473-484
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• 1991

Hospitals have been very susceptable to changes in external environment. Accordingly, they have been experiencing great financial difficulty due to low insurance rates and increasing competition. As a remedy, hospitals have attempted to use computer in a strategic manner. Such system is called strategic information system(SIS), and order communication system(OCS ) is an example of SIS in hospital setting. While OCS has known to be effective in reducing waiting time for outpatients, many hospitals are reluctant to introduce this system mainly because there are no real data or methods for justifying the cost of the system. Cost-benefit analysis has been traditionally used for such purpose, but this method deals with limited portion of benefits and therefore not very useful for analyzing the economic feasibility of SIS. In this paper, information economics tools which expand cost with value was used to analyze the economic feasibility of OCS. To assist the analysis, financial simulation model was developed using simulation package, called IFPS(Interactive Financial Planning System).

• Journal of the Korea Safety Management & Science
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• v.10 no.4
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• pp.73-81
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• 2008

The current electrical safety plan developed for the national electricity system has been playing an important role in handling a variety of electrical accidents. However, it can be more effective to prevent or reduce those accidents if a preventive electrical safety plan is available. In this paper, an approach to developing the safety plan is described. We first discuss the contents that should be included in the plan. Noting that an effective plan requires the system level consideration of all the factors affecting the safety issues, an operation concept document (OCD) is considered. The OCD can allow us to understand the behavior of the safety system based on the operation environment, the system functions, the performance requirements, all at the system level of the safety system. Thus, the OCD can be useful in developing the safety plan. A detailed description then follows on how the OCD is developed for the electrical safety system under study. Finally, we discuss how the developed OCD can be used in deriving the preventive electrical safety plan.

• Journal of Preventive Medicine and Public Health
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• v.30 no.4 s.59
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• pp.840-851
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• 1997

To perform voluntary occupational health program in worksites, regulational supports are necessary. The regulational supports include assessment of current occupational health program and appropriate incentives. The purpose of this study is to find out the requirements of voluntary occupational health program and conditions to be improved. Study population was industrial health managers of both industries with less than 300 workers and over 300 workers, and the member of labor union who is responsible for safety and health in worksite. Two different questionnaire were used to find out the requirements and conditions to be improved respectively, The results were; 1. The category which prevalence rate of occupational injuries and occupational disease should be lower than national average was most important in health managers employed in industries over 300 workers and followed by reporting system, education, worksite policy, work environment assessment, protective equipment, consequently. But those employed in industries less than 300 workers showed high importance in prevalence rate of occupational injuries and disease, reporting system, worksite policy, work environment assessment, protective equipment, education, consequently 2. The members of labor union thought that worksite policy was most important and the next is education, reporting system, work environment assessment, protective equipment, prevalence rate of occupational injuries and disease. 3. There were difference in importance of education and worksite policy according to the size of industries. Reporting system, prevalence rate of occupational injuries and disease, and worksite policy had different importance between members of labor union and health managers. 4. In the results of quiestionnaire for conditions to be improved, the most important condition was top manager's willingness except personal protective equipments, and followed by financial support, legal support. The limitations of this study were the problems of representativeness of study population. but voluntary health program should be performed in worksites which have relatively good occupational health system. So, this selection bias could not disrupt our results.

• Journal of Pharmacopuncture
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• v.21 no.2
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• pp.98-103
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• 2018

Objective: DIt is need to evaluate he changes of the bio-signals through the hot-cold stimulation in the CV4. Methods: The 30 healthy participants were enrolled and randomly allocated, to one of three groups(10 participants for each group): the hot stone therapy(HST) group, or the cold stone therapy(CST) group or no treatment group(NT). All the participants took a rest for 10 minutes for stability before the test. And additional 10 minute rest after measurements of skin test and sEMG. After that two group received hot or cold stone therapy for 30 minutes and one group treated nothing with HRV test. Results: HRV LF value showed a significant increase over time in all three groups, but there was no significant difference between groups but HRV HF value did not show any significant difference with time in all three groups and there was no significant difference between groups. sEMG value showed a significant increase in the left side of the masseter muscle of the HST group and sebum levels was a significant decreased in HST group but no significant meaning was found. Conclusion: There was no objective evidence that hot-cold stimulation produced bio-signals changes in comparison to the control group, but additional studies are needed as the subjects were limited.

• Journal of Korean society of Dental Hygiene
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• v.19 no.3
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• pp.343-350
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• 2019

This study focused on the status of dental care development for children and adolescents. In contrast to the chronic disease management project, this research intended to provide basic data for the expansion of the system. We summarized the status of the system's expansion since 2012. It analyzed research reports, papers, related literature and books on the system of children and adolescent dental care service. The literature analysis classifies year, publication, title and published location. The current state of the system is listed as location, target, support funds, etc. Implementation of the project was first discussed in 2007. Initial planning focused on the Oral Health Policy Research Society of the Gunchi. Effective measures were formulated in 2008 under the center of the Gunchi. It is time to discuss the dental care system's direction and development, as well as future aims based on a beneficial program of preventive care. A system of dentistry should be introduced to benefit the entire population.

• Journal of the Korean Data and Information Science Society
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• v.22 no.4
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• pp.775-784
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• 2011

In this paper, we consider the periodic preventive maintenance model for repairable system following the expiration of non-renewing free replacement-repair warranty (NFRRW). Under this preventive maintenance model, we derive the expressions for the expected cycle length, the expected total cost and the expected cost rate per unit time. Also, we determine the optimal preventive maintenance period and the optimal preventive maintenance number by minimizing the expected cost rate per unit time. Finally, the optimal periodic preventive maintenance policy is given for Weibull distribution case.