• Korean Journal of Childcare and Education
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• v.16 no.1
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• pp.115-143
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• 2020

Objective: The purpose of this study was to examine underlying types of developmental trajectories of adaptation to child care among infants and toddlers. This study also aimed to identify latent classes in their child care adaptation types in order to find predictors that account for individual differences. Methods: Participants were 420 mothers of infants and toddlers and 123 teachers. The levels of child care adaptation of participating infants and toddlers were rated monthly from early April to June, 2019. The collected data were analyzed using growth mixture modeling, latent class analysis and multinominal logistic analysis. Results: The results of growth trajectories of child care adaptation showed there were two to four latent groups by dimension of child care adaptation. Also, the groups of individual dimensions of child care adaptation were classified into three latent classes, which were 'complying and positive group', 'negative group', and 'individualized group. Multinominal logistic analysis revealed that children's age, gender, and temperament differentiated the three latent classes of adaptation to child care. Conclusion/Implications: The results show individual characteristics that infants and toddlers possess should be prudently considered in order for successful adaptation to child care.

• Korean Journal of Culture and Social Issue
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• v.28 no.3
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• pp.331-352
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• 2022

This study used a latent growth curve models(LGCM) to examine longitudinal changes in youth's game usage, self-control and the longitudinal mediation effect of adaptive game use in the relationship between game usage and self-control. A four-year longitudinal data of 863 adolescents from the Game User Panel Survey, provided through participation in the 2019 Game User Panel Research Conference hosted by the Korea Creative Contents Agency, was used to verify the longitudinal mediation effect of adaptive game use. SPSS 21 was used to verify the normality of variables from each wave, and to conduct correlation analysis. Mplus 6.12 was used to verify the longitudinal mediation effect. The results are as follows. First, game usage, self-control and adaptive game yielded linear temporal growth. Second, latent growth curve models showed that the direct effect of game usage on self-control was insignificant, but game usage had a significant indirect effect on self-control through adaptive game use. Continuous adaptive gaming increased self-control. Third, sobel test results showed that both the initial value and change rate of adaptive game use had a full-mediation effect, confirming the longitudinal mediation effect. This study verified the longitudinal change of self-control affected by change in game usage and adaptive game use.

• Journal of The Korean Association of Information Education
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• v.23 no.6
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• pp.551-560
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• 2019

In the advanced information age, learning is an activity in which learners access information resources through computers and Internet to acquire and evaluate information on their own. The emergence of an online learning platform based on the fourth industrial revolution technology is developing into an environment in which elementary and secondary learners learn and study based on constructivism learning theory. In the online learning environment, the researches on the information retrieval ability of the elementary and secondary learners and the self-directed learning ability were found to be highly related. However, it is necessary to analyze the relation between information retrieval ability and self-directed learning ability through a cross-sectional study that is limited to specific curriculum and contents and expands the longitudinal research. In this study, the panel data of the Seoul Education Longitudinal Study collected over 8 years are used to find the difference in self-directed learning ability according to the longitudinal pattern of information retrieval ability and frequency.

• The Mathematical Education
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• v.58 no.1
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• pp.21-39
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• 2019

This study examines the longitudinal effect of goal perception, mathematics class factors(perceptions about mathematics teachers (PMT), mathematics classroom attitude), and mathematics academic achievement. This study consists of three research models. First, we examined the longitudinal change of goal perception, perceptions about mathematics teachers (PMT), mathematics classroom attitude, and mathematics academic achievement using latent growth curve modeling. Secondly, the slope of PMT is a critical mediator between the slope of goal perception and the slope of mathematics academic achievement. Finally, the slope of mathematics classroom attitude is a critical mediator between the slope of goal perception and the slope of mathematics academic achievement. Data were extracted from Seoul Education Longitudinal Study from 2010 to 2012 (in three waves), and the analysis used by middle school students, measured by 4163 students of the three-wave surveys. Latent growth modeling was applied to verify the research problems. The results of the research are as follows. First, the slope of goal perception had positive and significant effects on the slope of PMT and mathematics classroom attitude, respectively. Second, the slope of PMT and mathematics classroom attitude had positively significant effects on the slope of mathematics academic achievement. Finally, it was confirmed that the slopes of PMT and mathematics classroom attitude are critical mediators between the slope of goal perception and the slope of mathematics academic achievement.

• Structural Engineering and Mechanics
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• v.53 no.5
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• pp.939-956
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• 2015

In this study, in order to propose an efficient model to predict the torque capacity of steel fiber reinforced concrete (SFRC) beams, the existing experimental data related to torsional response of beams is reviewed. It is observed that existing data neglects the effects of some parameters on the variation of torque capacity. Thus, an experimental research was also conducted to obtain the effects of neglected parameters. In the experimental study, a total of seventeen SFRC beams are tested against torsion. The parameters considered in the experiments are concrete compressive strength, steel fiber aspect ratio, volumetric ratio of steel fibers and longitudinal reinforcement ratio. The effect of each parameter is discussed in terms of torque versus unit angle of twist graphs. The data obtained from this experimental research is also combined with the data got from previous studies and employed in artificial neural network (ANN) analysis to estimate the ultimate torque capacity of SFRC beams. In addition to parameters considered in the experiments, aspect ratio of beam cross-section, yield strengths of both transverse and longitudinal reinforcements, and transverse reinforcement ratio are also defined as parameters in ANN analysis due to their significant effects observed in previous studies. Assessment of the accuracy of ANN analysis in estimating the ultimate torque capacity of SFRC beams is performed by comparing the analytical and experimental results. Comparisons are conducted in terms of root mean square error (RMSE), mean absolute error (MAE) and coefficient of efficiency ($E_f$). The results of this study revealed that addition of steel fibers increases the ultimate torque capacity of reinforced concrete beams. It is also found that ANN is a powerful method and a feasible tool to estimate ultimate torque capacity of both normal and high strength concrete beams within the range of input parameters considered.

• Journal of the Korea Society of Computer and Information
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• v.27 no.8
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• pp.203-210
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• 2022

In this study, we tried to examine the longitudinal mediating effects of school violence damage experience and aggression in the relationship between child maltreatment experiences and school bullying experiences. For the analysis data for this purpose, the 3rd, 5th, 6th, and 7th data of the Korean Children and Youth panel data of the Korea Youth Policy Research Institute were used. A total of 1,813 data were analyzed using the statistical program SPSS 26.0 and Amos 26.0 version as a multivariate latent growth model. As a result of the analysis, it was possible to confirm the mediating effects of school violence victimization experiences and aggression. These results suggest that multilateral efforts are needed to lower the level of maltreatment, school violence victimization, and aggression that affect the school bullying experiences. Based on the results of this analysis, this study specifically suggested practical measures to prevent adolescents' maltreatment experiences from being reproduced as school bullying experiences.

• Ecology and Resilient Infrastructure
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• v.3 no.1
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• pp.1-7
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• 2016

River restoration has recently progressed in consideration of ecological functions along with flood controls and conservation. For river restorations that consider ecological health and diversity, it is important to contemplate the recovery of hydraulic and hydrologic connectivity in isolated spaces by longitudinal structures. In this study, as a first step for the provision of hydraulic and hydrologic data, which is necessary for the ecological connection analysis in isolated spaces, we developed a one-dimensional numerical model for rainfall runoff and channel routing and applied it to the Cheongmi watershed. The developed numerical model can simulate hydraulic and hydrologic analysis at the same time using the rainfall data. Numerical results were compared with observed data and other numerical results. As a result, a very reasonable agreement is observed. The results of this study will be improved so that the long-term hydrologic and hydraulic analysis is possible to predict ecological change.

• Journal of the Korean Society for Railway
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• v.9 no.1 s.32
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• pp.118-124
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• 2006

SThe rigidities of bridge substructures are the important data in the rail-bridge interaction analysis in Korean High -Speed Railway. This experimental study is being performed because of followings. 1) More correct longitudinal stiffness of the structure including substructure should be considered in the calculation of stresses in rails. 2) There are many uncertainties in the design and construction of the piers and foundations. 3) Actual guideline for the rigidities of piers and foundations in the design is necessary. 4) Measurement on the rigidity of pier according to the types of piers, foundations and soil-conditions is needed. Curve for estimating the total rigidity of substructure will be obtained through this and further experimental studies. It may be used in the analysis of Korean High-Speed Railway bridge and then, longitudinal stresses in the rails can be estimated more accurately. One pair of piers, which consist of pot-bearing for fixed support and pad-bearing for movable support, are loaded by steel frame devices with steel wire ropes and hydraulic jack. The responses which are measured at each loading stages in those field tests are displacements and tilted angles on the top and bottom of piers. This study is being performed testing and analysis about several piers in the construction field.

• Journal of the Korean Society of Manufacturing Process Engineers
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• v.21 no.4
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• pp.91-99
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• 2022

By applying METHOD 514.8 of the US military standard MIL-STD-810H, vibration analysis of the winding core automatic feeding device was performed during vehicle transportation. The contact point between the LM guide and main support frame was weak in the vertical axis, transverse axis, and longitudinal axis during the transportation of the automatic winding core feeder vehicle, and the maximum equivalent stress was 236.31 MPa in the longitudinal axis. When random vibration was applied, the safety margin in the longitudinal direction was 0.26, indicating low safety. The safety margin was changed by increasing the damage factor to 0.1. Finally, the safety margin was improved to 3.48 to secure safety. Resonance occurred with a Q factor of 9.34 in the harmonic response to which the RMS value of the ASD data was input, and the vertical axis safety margin was derived as 0.16. When the damping factor was 0.15, the Q factor was 3.37, and resonance was avoided with a safety margin of 6.62.

• Korean Journal of Childcare and Education
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• v.18 no.6
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• pp.21-36
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• 2022

Objective: The present study examined long-term effects of media use during early childhood on grit in middle childhood, focusing on the mediating role of attention problems. Methods: For statistical analysis, the 6th, 7th, and 11th data sets from the Panel Study on Korean Children were used. A total of 1,352 cases were finally selected. Descriptive statistics analysis, correlation analysis, path analysis, and bootstrapping were conducted. Results: The results showed that the use of media for educational purposes in early childhood did not have a significant effect on attention problems and grit. However, when the media use time for play in early childhood was longer, levels of attention problems in early childhood were higher and levels of grit in middle childhood were lower. The mediating effect of attention problems on the relationship between media use time for play of young children and grit of middle childhood was significant. Conclusion/Implications: Findings of the present study suggest that the use of media for play during early childhood needs to be carefully monitored because it can have a negative effect on attention and grit development.