• Journal of Power System Engineering
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• v.14 no.6
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• pp.61-66
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• 2010

Engineering asset management (EAM) requires the accurate assessment of current and the prediction of future asset health condition. Suitable mathematical models that are capable of predicting time-to-failure and the probability of failure in future time are essential. In general reliability models, lifetime of component and system is estimated using failure time data. This paper deals with the reliability assessment of elevators using life of main components. Especially this work is concerned with the stochastic nature of life of elevator components. First, we investigate the Weibull statistical analysis of lifetime data for the components. The final goal is to establish the mathematical model for reliability assessment. This work provides more perspectives to future research in the fields of reliability and maintainability.

• The Korean Journal of Applied Statistics
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• v.8 no.2
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• pp.121-132
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• 1995

In this paper we consider optimal designs of partially step-stress life testing which is deviced for k-component series systems with the considerably long life time. Test items are first run simultaneously at use condition for a specified time, and the surviving items are then run at accelerated condition until a predetermined censoring time. The optimal criterion for the change time to accelerated condition is to minimized either the generalized asymptotic variance of maximum likelihood estimators of the hazard rates at use condition and the acceleration factors or the asymptotic variance of the maximum likelihood estimators of the acceleration factors.

• Journal of Korean Society of Rural Planning
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• v.18 no.4
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• pp.91-101
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• 2012

The time management and allotments for various activities of daily life is much different by age groups. This study analyzes time allotments of different age groups for various activities of daily life to figure out the change of main activity by aging through 2009 time use survey by National Statistical Office. Especially we focus on time allotments of rural elderly population and intangible factors for life quality of people instead of physical and environmental elements. The results show that there is a large gap of time allotments for paid and unpaid working time of rural and urban elderly population. Whereas the time for leisure of elderly women in rural areas is much shorter than that of urban elderly women and rural elderly men spend more time to provide community services and help to other households. However, the percentage leisure time of rural elderly people for passive activities such as TV, radio, magazine etc. is longer than that of urban elderly people. We hope that our analysis data could be used for developing new policies and project to improve the life quality of rural elderly population.

• Journal of Family Resource Management and Policy Review
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• v.8 no.1
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• pp.101-116
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• 2004

This study analyze using pattern of the Korean elderly leisure time to know their leisure lifestyle. In order to do this study, we analysed the time use dairy which were collected by Korean National Statistical Office in 1999 and analysis of data was done through mean of time, percentage of acting people hourly. The result of this study were as follows : 1) The elderly spend leisure time average 6 hours 34 minute in a day and enjoy leisure activities from A.M. 11:00 to P.M. 12:00 and from P.M. 8:00 to P.M:. 10:00 mainly. 2) The elderly spend leisure time for acquaintance, using mass media, sports leisure activity and dilettante life. Especially the elderly associate with more others than their family, use more TV than others and spend time for break and amusement as dilettante life.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.16 no.4
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• pp.2401-2406
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• 2015

Pipelines are used by large heavy industries to deliver various types of fluids. Since this is important to maintain the performance of large systems, it is necessary to accurately predict remaining life of the corroded pipeline. However, predicting the remaining life is difficult due to uncertainties in the associated variables, such as geometries, material properties, corrosion rate, etc. In this paper, a statistical method for predicting corrosion remaining life is proposed using Bayesian inference. To accomplish this, pipeline failure probability was calculated using prior information about pipeline failure pressure according to elapsed time, and the given experimental data based on Bayes' rule. The corrosion remaining life was calculated as the elapsed time with 10 % failure probability. Using 10 and 50 samples generated from random variables affecting the corrosion of the pipe, the pipeline failure probability was estimated, after which the estimated remaining useful life was compared with the assumed true remaining useful life.

• Journal of the Korean Home Economics Association
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• v.46 no.1
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• pp.103-116
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• 2008

The purpose of this study was to empirically describe the everyday life of middle-aged adults in terms of their time-use activities. From the original '2004 Time dairy' Data, developed by the Korean National Statistical Office (KNOS), 17,684 respondents aged between 35-59 were selected. In order to categorize their activity patterns, work/labour, domestic labour, and spare leisure time were classified according to the action classification system. As a result, four dominant types were found: namely work-leisure, work-oriented, family-oriented, and leisure-oriented activities. Results of multinomial logistic analysis revealed that gender, age, socioeconomic status, job characteristic, and family structure were the major determinants on time-use. Compared with work-leisure, young middle aged women holding a part-time job with less income tended to be involved in a family-centered time use. Dual earners with lower SES status were likely to have work-oriented time schedules. Older men with relatively lower income were more likely to be involved in leisure-oriented activities rather than work-leisure activities. Multitasking behavior was a significant variable in explaining the four different types of time-use. Work-oriented group showed the highest level of time pressure as well as fatigue. Group differences in these measures, however, was not as large as expected.

• Journal of Families and Better Life
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• v.30 no.4
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• pp.119-132
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• 2012

The purpose of this study was to investigate the differences in time use between Korean and American high school students. The data sources were the '2009 Time Use Survey' conducted by Korea National Statistical Office and the '2009 ATUS (American Time Use Survey)' conducted by Labor Statistics Division in the U.S.. 1,734 Korean diaries (1,311 on weekdays and 423 on Sundays) and 321 American diaries (208 on weekdays and 113 on Sundays) from high school students of 15 to 18 years of age were analyzed. Descriptive statistics and t-test were used for the statistical analysis. The time use patterns of Korean students on weekdays and Sundays were different than those of their American counterparts. On weekdays and Sundays, the sleeping time of Korean students was 2 hours less than the time of their American counterparts. Koreans studied more, nearly double the time of their American counterparts on weekdays and five times more on Sundays. The study-oriented time allocation of Korean students resulted in less leisure time than the American students. Korean students spent their leisure time of more than 30 minutes participating in social activities, media, and hobbies, and their time allocation to volunteer work and religious activities were nil. On Sundays, the time for studying by Korean students was more than five times longer than that spending by their American counterparts. Koreans used their leisure time of 6 hours and 47 minutes mainly for media, hobbies and social activities. The participation rate of volunteering by Korean students was only 0.5%, though it was 31.0% for the Americans. For a study-life balance for Korean students, it was recommended that trends toward time management and social policy should increase the time allocation to sleeping, housework, work, sports, and volunteering and decrease the time use in studying and hobbies.

• Communications for Statistical Applications and Methods
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• v.26 no.2
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• pp.191-203
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• 2019

The problem of examining how well an assumed distribution fits the data of a sample is of significant and must be examined prior to any inferential process. The observed failure time data of items are often not wholly available in reliability and life-testing studies. Lowering the expense and period associated with tests is important in statistical tests with censored data. Goodness-of-fit tests for perfect data can no longer be used when the observed failure time data are progressive Type II censored (PC) data. Therefore, we propose goodness-of-fit test statistics and a graphical method based on generalized Lorenz curve for PC data from a location-scale distribution. The power of the proposed tests is then assessed through Monte Carlo simulations. Finally, we analyzed two real data set for illustrative purposes.

• Journal of the Korean Home Economics Association
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• v.40 no.8
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• pp.23-36
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• 2002

The purpose of this study is to analyze the actual condition of labor during the marriage by estimating the total labor-time of husband and wife and to prove the contribution of labor-time to household. The statistical life-time research data of Bureau of Statistics were used to prove the overwork of wives compared with husbands during the marriage. The result of the study can help to prove the wife's contribution of labor-time to household.

• Journal of the Korean Institute of Navigation
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• v.16 no.1
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• pp.94-97
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• 1992

In this paper, the individual number of the future has depended not only upon the present individual number but upon the present individual age, considering the stochastic process model of individual number when the life span of each individual number and the individual age as a set, this becomes a Markovian. Therefore, in this paper the individual is treated as invariable, without depending upon the whole record of each individual since its birth. As a result, suppose {N(t), t>0} be a counting process and also suppose $Z_n$ denote the life span between the (n-1)st and the nth event of this process, (n{$geq}1$) : that is, when the first individual is established at n=1(time, 0), the Z$Z_n$ at time nth individual breaks, down. Random walk $Z_n$ is $Z_n=X_1+X_2+{\cdots}{\cdots}+X_A, Z_0=0$ So, fixed time t, the stochastic model is made up as follows ; A) Recurrence (Regeneration)number between(0.t) $N_t=max{n ; Z_n{\leq}t}$ B) Forwardrecurrence time(Excess life) $T^-I_t=Z_{Nt+1}-t$ C) Backward recurrence time(Current life) $T^-_t=t-Z_{Nt}$