• Proceedings of the KSR Conference
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• 2011.05a
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• pp.483-495
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• 2011

In modern society, the range of time and space in life is continually expanding due to increase of income and diversification of life. In order to respond to these changes and to satisfy needs and to secure the mobility of citizens, the construction of transport infrastructure and public transport services should be provided continually. In particular, to ensure mobility during late-night hours, providing metropolitan public transport services is urgently needed. Due to expansion of life zone, tension of time and space of metropolitan transportation is essential to construct transport infrastructure in preparation for entry into 24-hour community. This study was based on analysis of travel resource and survey data conducted by passengers of express trains, conventional trains, and metropolitan bus. This study is to investigate use characteristics of passengers and characteristics and problems of Gyeongin-line. Moreover, this study's purpose is to suggest plans in order to improve express train operation and extend hours of the midnight express. It is also important to vitalize public transportation.

• Journal of Environmental Health Sciences
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• v.26 no.3
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• pp.50-54
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• 2000

Ventilation rates can be measured directly by a tracer decay method, although little is known of the effects of different sampling intervals on decay rte calculations. This study determined variations in decay rates calculated by three techniques using residential ozone decay data. The calculation techniques were a regression technique, decay techniques using half-life and average-life, and finite difference techniques using two different time intervals. Variation associated with regression technique calculations for residential ozone decay rates based on data from both sample intervals were within 10% (2.81$\pm$1.88 hr-1). However, both half-life and finite difference technique calculations using a shorter-time interval were significantly different from those obtained with the regression technique(p<0.05). Therefore, the use of short sampling intervals in tracer decay may cause significant error in decay rate calculations.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.17 no.2
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• pp.495-502
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• 2013

In the mobile Ad hoc Network(MANET), improving technique for management and control of topology is recognized as an important part of the next generation network. In this paper, we proposed an efficient node life time management of ATICC(Adaptive Time Interval Clustering Control) in Ad-hoc Networks. Ad-hoc Network is a self-configuration network or wireless multi-hop network based on inference topology. This is a method of path routing management node for increasing the network life time through the periodical route alternation. The proposed ATICC algorithm is time interval control technique depended on the use of the battery energy while node management considering the attribute of node and network routing. This can reduce the network traffic of nodes consume energy cost effectively. As a result, it could be improving the network life time by using timing control method in ad-hoc networks.

• Research in Community and Public Health Nursing
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• v.26 no.2
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• pp.169-177
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• 2015

Purpose: Previous studies focused on the negative effects of Internet use such as obesity, depression, and addiction. However, few studies investigated whether the Internet use for an appropriate time has positive effects on adolescents' health. Thus, the purpose of the study was to examine the dose-response relationship between Internet use for non-academic purposes (NAP) and happiness/stress in adolescents. Methods: This study used data from the 2013 Korea Youth Risk Behavior Web-Based Survey. A total of 72,435 adolescents were included. Rao-Scott ${\chi}^2$ and multiple logistic regression were conducted. To test the dose-response relationship, this study examined how happiness/stress changed with increase in the time of Internet use for NAP. Results: After controlling for general characteristics, the odds ratios for being unhappy and stressful were lowest in adolescents using the Internet for NAP for more than 0 hour and less than an hour a day. Interestingly, students who did not use the Internet for NAP had a significantly higher risk of being unhappy/stressful than those using for more than 0 hour and less than an hour a day. Conclusion: Internet use for NAP for more than 0 hour and less than an hour a day has positive effects on happiness/stress in adolescents.

• The Journal of Korean Academy of Sensory Integration
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• v.18 no.1
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• pp.44-55
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• 2020

Objective : This study used the data of the National Statistical Office to analyze the time use of disabled youth and their self-satisfaction with it by their type of occupation. Methods : Using raw data extracted from Statistics Korea, 84 disabled youth from 10 to 24 years old were re-classified into six occupational areas based on Occupational Therapy Practice Framework (OTPF)-3. The occupational types were classified according to the time use by individuals based on data from Statistics Korea. Finally, according to the type of occupation, self-satisfaction with the use of time was identified. Results : The total amount of time spent by disabled youths was the largest in the rest and sleep categories, followed by daily living, education, leisure, social participation, and play. The analysis of occupational types showed that the groups were turned around (10.71% of participants), high activity group (50.00%), low activity (28.57%), and balanced (10.71%). There were significant differences between types in the first five of the aforementioned categories. There was no significant difference in the lack of time use, but there was a significant difference among their satisfaction with their use of time. The balanced type (21.53%) reported the most satisfaction. inadequacy Conclusion : The purpose of the project was to provide the raw data of intervention activities that can improve the quality of life and health of disabled youth. By analyzing their time use and occupations, deficiencies in time management and their satisfaction with their use of time can be noted.

• Journal of Korean Society of Water and Wastewater
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• v.23 no.3
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• pp.305-313
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• 2009

This paper provides a method for evaluating a residual life of water mains using a proportional hazard model(PHM). The survival time of individual pipe is defined as the elapsed time since installation until a break rate of individual pipe exceeds the Threshold Break Rate. A break rate of an individual pipe is estimated by using the General Pipe Break Model(GPBM). In order to use the GPBM effectively, improvement of the GPBM is presented in this paper by utilizing additional break data that is the cumulative number of pipe break of 0 for the time of installation and adjusting a value of weighting factor(WF). The residual lives and hazard ratios of the case study pipes of which the cumulative number of pipe breaks is more than one is estimated by using the estimated survival function. It is found that the average residual lives of the steel and cast iron pipes are about 25.1 and 21 years, respectively. The hazard rate of the cast iron pipes is found to be higher than the steel pipes until 20 years since installation. However, the hazard rate of the cast iron pipes become lower than the hazard rates of the steel pipes after 20 years since installation.

• Journal of Family Resource Management and Policy Review
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• v.21 no.3
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• pp.43-59
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• 2017

This study aimed to analyze time allocation for men who work long hours and their wives. Using 2014 time-use survey data (provided by Statistics Korea), we analyzed the amount of time spent in four areas-paid work, housework, leisure, and life essentials-of male workers who work more than 52 hours a week and of their wives. Descriptive statistics and a paired t-test were conducted using SPSS version 18.0. The results were as follows: First, the time allocation of men who worked long hours differed from their wives with the exception of personal maintenance time. Second, the working time of wives who work long hours was longer than their husbands who work long. Third, men who worked long hours did less housework when their wives were employed than when they were not employed. All the results showed gender differences in terms of time allocation. Equal role-sharing between spouses is needed for the work-life balance of both husbands and wives.

• Journal of Korean Society for Quality Management
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• v.35 no.4
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• pp.61-66
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• 2007

The performance of a building material degrades as time goes by and the failure of the material is often defined as the point at which the performance of the material reaches a pre-specified degraded level. Based on a stochastic deterioration model, a performance based service life prediction method for building materials and components is developed. As a stochastic degradation model, a gamma process is considered and lifetime distribution and service life of a material are predicted using the degradation model. A numerical example is provided to illustrate the use of the proposed service life prediction method.

• Journal of the Korean Society of Safety
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• v.27 no.4
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• pp.115-120
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• 2012

In order to establish preventive maintenance standards through analysis & reliability prediction of about 60,000pcs of 20kindsof relays and contractors used for Seoul subway trains, several life prediction methodologies were applied. Firstly, Occurrence, Severity, Detection were defined and predicted by applying operation characteristic of EMU to the number of actions of relays & contactors which the manufacturers generally offer as the life cycle data. Secondly, failure distribution and average life of parts were analyzed through interpretation of field data based on a lot of experience which had built up in the field for a long time. Finally, using the 217PLUS standard as a reliability prediction program, comparative analysis of use reliability and inherent reliability was done through reliability prediction at the part level and system level.

• Journal of Applied Reliability
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• v.4 no.1
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• pp.1-14
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• 2004

Accelerated life test models and procedures are developed to assess the reliability of typical power relays. The main function of relays is to control high voltage circuits by operating low voltage circuits. The accelerated life test method and test equipments are developed using the relationship between stresses and life characteristics of the products. Using the developed accelerated life test method, the parameters of the ALT model and lifetime distribution are estimated and the reliability of the relays at use condition is assessed. The proposed accelerated life test method and procedure may be extended and applied to testing similar kinds of products to reduce test time and costs of the tests remarkably.