• 가족자원경영과 정책
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• 제21권3호
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• pp.141-159
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• 2017

The main purpose of this study is to investigate factors that influence sleep duration and sleep time poverty in terms of family characteristics, child characteristics, and time use. A series of data analyses were conducted on children's time use in two-parent families based on the 2013 Korean Children and Youth Panel Survey. One major finding is that children's sleep duration and the probability of having a sleep time poverty are related to their mothers' job classifications. The factors influencing the duration of sleep time and the sleep time poverty are similar in terms of family characteristics and children's time use. The mother's job classification, family income, number of younger siblings, number of older siblings, children's private tutoring hours, computer game hours, and TV hours are statistically significant factors affecting the duration of sleep time and the probability of having a sleep time poverty. However, the factor with greatest influence on sleep time duration is private tutoring hours and the factor most affecting sleep time poverty is computer game hours. The mother's job classification is a relatively powerful determinant for predicting her children's sleep duration and sleep time poverty.

• Smart Structures and Systems
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• 제4권6호
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• pp.809-828
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• 2008

Real-time hybrid testing is an attractive method to evaluate the response of structures under earthquake loads. The method is a variation of the pseudodynamic testing technique in which the experiment is executed in real time, thus allowing investigation of structural systems with time-dependent components. Real-time hybrid testing is challenging because it requires performance of all calculations, application of displacements, and acquisition of measured forces, within a very small increment of time. Furthermore, unless appropriate compensation for time delays and actuator time lag is implemented, stability problems are likely to occur during the experiment. This paper presents an approach for real-time hybrid testing in which time delay/lag compensation is implemented using model-based response prediction. The efficacy of the proposed strategy is verified by conducting substructure real-time hybrid testing of a steel frame under earthquake loads. For the initial set of experiments, a specimen with linear-elastic behavior is used. Experimental results agree well with the analytical solution and show that the proposed approach and testing system are capable of achieving a time-scale expansion factor of one (i.e., real time). Additionally, the proposed method allows accurate testing of structures with larger frequencies than when using conventional time delay compensation methods, thus extending the capabilities of the real-time hybrid testing technique. The method is then used to test a structure with a rate-dependent energy dissipation device, a magnetorheological damper. Results show good agreement with the predicted responses, demonstrating the effectiveness of the method to test rate-dependent components.

• 가족자원경영과 정책
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• 제24권3호
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• pp.19-33
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• 2020

The purpose of this study was to investigate whether paid work time desynchronization affected housework time desynchronization. Time slot data from the Korean Time Use Survey data from 2014 was analyzed. This study included 1,475 married couples aged 20 to 59. They were dual-earner couples, heterosexual couples, and both partners worked during the day, either durong the week or on the weekend. The data was analyzed by the following four groups: weekday-husband, weekday-wife, and weekend-husband, weekend-wife. The results demonstrated that as the desynchronization of paid work increased, the desynchronization of time spent on housework in the weekday-husband and weekend-husband groups also increased. Second, the amount of leisure time did not affect the desynchronization of time spent on housework. Lastly, the amount of time that one person spent on housework increased the housework time desynchronization level. In addition, if the family had children who attended primary, middle, or high school-mothers in the weekday-wife group completed more housework. These results demonstrated that paid work time desynchronization might be a way to decrease the amount of time that dual-earner wives' spent housework.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2004년도 학술대회 논문집 정보 및 제어부문
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• pp.82-85
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• 2004

This paper proposes the development of delay compensator to minimize performance degradation caused by time delays in network-based real-time control systems. The delay compensator uses the time-stamp method as a direct delay measuring method to measure time delays generated between network nodes. The delay compensator predicts the network time delays of next period in the views point of time delays and minimizes performance degradation from network through considering predicted time delays. Control output considering network time delays is generated by the defuzzification of probable time delays of next period. The time delays considered in the delay compensator are modeled by using a timed Petri net model. The proposed delay prediction mechanism for the delay compensator is evaluated through some simulation tests by measuring deviation of the predicted delays from simulated delays.

• 대한가정학회지
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• 제35권1호
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• pp.319-338
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• 1997

This study examined the time allocation pattern of husbands and wives. This study investigated i)the pattern of time allocation in the light of the extent of time spent in housework child care and leisure among husbands and wives living in urban area ii) the differences in extent of time spent in such activities between wives and husbands and iii) the determinants of time spent in such activities. A system of time allocation equations based on household production theory and several hypotheses explaining the distribution of domestic work among couples were employed. According to the results the pattern of time allocation was different between wives and husbands. Regardless of women's employment status wives were more likely to have dual responsibilities than were husbands. The time equation employed in this study had more explanatory power in the pattern of time allocation of wives than of husbands and of employed wives than of non-employed wives. The sex-role ideology hypothesis was supported for non-employed wives but not for employed wives. The time availability hypothesis was supported for the time allocation of employed wives and husbands. The economic efficiency hypothesis was supported for employed wives' time allocation.

• Communications for Statistical Applications and Methods
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• 제22권3호
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• pp.209-222
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• 2015

Time series are used in many studies for model building and analysis. We must be very careful to understand the kind of time series data used in the analysis. In this review article, we will begin with some issues related to the use of aggregate and systematic sampling time series. Since several time series are often used in a study of the relationship of variables, we will also consider vector time series modeling and analysis. Although the basic procedures of model building between univariate time series and vector time series are the same, there are some important phenomena which are unique to vector time series. Therefore, we will also discuss some issues related to vector time models. Understanding these issues is important when we use time series data in modeling and analysis, regardless of whether it is a univariate or multivariate time series.

• 제어로봇시스템학회논문지
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• 제18권4호
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• pp.337-342
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• 2012

This paper presents performance evaluation of real-time mechanisms for real-time embedded linux. First, we presents process for implementing open-source real-time embedded linux namely RTAI and Xenomai. These are real-time extensions to linux kernel and we implemented real-time embedded linux over the latest linux kernel. Measurements of executions of real-time mechanisms for each distribution are performed to give a quantitative comparison. Performance evaluations are conducted in kernel space about repeatability of periodic task, response time of Semaphore, FIFO, Mailbox and Message queue in terms of inter-task communication for each distribution. These rules can be helpful for deciding which real-time linux extension should be used with respect to the requirements of the real-time applications.

• Journal of Advanced Marine Engineering and Technology
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• 제28권4호
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• pp.603-610
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• 2004

Time delays are included in most of actual systems, and some of which are shown as time varying. To analyze the time varying time delay system in the time domain. a useful delay module to express the function as a tool is much helpful to get corresponding outputs under given conditions. A method is proposed here to design the algorithm of time delay module for simulation or control purposes, including the problems of initializing and reallocating data in buffer. After classifying the time varying time delay into the distributed mode and lumped mode, an object to describe delay module is configured and tested under the defined input signal and given time delay variation. The simulation results show that the output of module matches reasonably with the case of real system.

• 가족자원경영과 정책
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• 제19권4호
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• pp.141-161
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• 2015

The purpose of this study was to explore the differences in time perspective by socio-demographic variables and to investigate the effect of time perspective on time management and life satisfaction for college students. Questionnaires including time perspective, time management, and life satisfaction scales were used for this study. The survey data from 382 college students were analyzed by frequency, percentage, mean, standard deviation, t-test, ANOVA, Duncan test, Pearson's correlation analysis, and stepwise regression. The time perspective, composed of four factors future insensibility and present, past, and future orientation, differed according to the sex, academic grade, and specialty of the college students. The time perspective of the college students and the socioeconomic status of their households were investigated as effective variables on time management and life satisfaction. Based on these results, the implications for research and policy on the time perspective of college students were discussed.

• 제어로봇시스템학회논문지
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• 제22권6호
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• pp.424-428
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• 2016

A simple new sufficient condition for asymptotic stability of the positive linear time-varying discrete-time systems, with unstructured time-varying uncertainty in delayed states, is established in this paper Compared with previous results that cannot be applied to time-varying systems; the time-varying system and delay time are considered simultaneously in this paper. The proposed conditions are compared with suitable conditions for the typical discrete-time systems. The considerations are illustrated by numerical examples of previous work.