• Proceedings of the KIEE Conference
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• 2006.10c
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• pp.223-225
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• 2006

A ball moving on a beam is a typical nonlnear dynamic system, which is often adopted to proof test diverse control schemes. Ball and plate system is the extension of the traditional ball and beam problem that moves a metal ball on a rigid plate. In this paper, a trajectory planning and tracking problem is proposed for ball and plate system, which is to control the ball from a point to another without hitting the obstacles. Our scheme is composed of three controllers, TS type optimal path tracking controller, mandani type obstacle avoidance controller and trajectory planning controller that determines the desired trajectory. But this type of construction can give rise to chattering executions. Because the difference of contributions from concurrent controllers can cause behaviors unsmoothly. We propose fuzzy pid supervision control1er to handle this problem.

• Journal of the Korean Society of Child Welfare
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• no.54
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• pp.173-197
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• 2016

This study aims to examine developmental trajectories and predictor variables of problem behaviors and school adjustment trajectories among children from low-income families using latent growth modeling. The data was collected from the 2nd year to the 4th year (2012-2014) of a community child center child panel survey conducted by the National Youth Policy Institute. The major findings are as follows. First, as the grade went up, the problem behaviors of children from low-income families increased while school adjustment decreased. Second, multi-level domains, such as individual, school, and family variables influenced school adjustment trajectory, while only individual variables, such as depression, isolation, and motivation for achievement influenced problem behavior trajectory. Third, common protective factors between problem behaviors and school adjustment trajectories were motivation for achievement in and satisfaction of the community child center. Common risk factors between problem behaviors and school adjustment trajectories were isolation and aggression. Based on the results, the implications for child welfare practices were discussed.

• Human Ecology Research
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• v.56 no.2
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• pp.157-165
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• 2018

Using data from the Panel Study on Korean Children, this study investigated whether children with high levels of problem behaviors adjusted more poorly on the $1^{st}-grade$ than children with low levels of problem behaviors, and whether there was evidence of intra-individual stability in behavior problems over time. Data were analyzed by use of the Latent Growth Model and group differences analyses. Three findings were noteworthy. First, there was evidence of intra-individual and inter-individual variability in behavior problems between poor- and non-poor household children. Second, children with higher initial levels of internalizing and externalizing behaviors at 4 years had lower school readiness scores at 6 years. Finally, children with lower levels of school readiness at 6 years had lower school adjustment scores in $1^{st}$ grade. The results discuss implications for future research and policies for preschool children. With mediating effect of school readiness, developmental trajectories of child's problem behavior have been found to be predictors of delayed achievements in school. The results show that intervention programs are necessary for children with high levels of problem behavior. This study also showed that children who experienced poverty at home could have more difficulties in school readiness and school adjustment.

• KSII Transactions on Internet and Information Systems (TIIS)
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• v.14 no.8
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• pp.3328-3349
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• 2020

With rapid development of ubiquitous computing and location-based services (LBSs), human trajectory data and associated activities are increasingly easily recorded. Inappropriately publishing trajectory data may leak users' privacy. Therefore, we study publishing trajectory data while preserving privacy, denoted privacy-preserving activity trajectories publishing (PPATP). We propose S-PPATP to solve this problem. S-PPATP comprises three steps: modeling, algorithm design and algorithm adjustment. During modeling, two user models describe users' behaviors: one based on a Markov chain and the other based on the hidden Markov model. We assume a potential adversary who intends to infer users' privacy, defined as a set of sensitive information. An adversary model is then proposed to define the adversary's background knowledge and inference method. Additionally, privacy requirements and a data quality metric are defined for assessment. During algorithm design, we propose two publishing algorithms corresponding to the user models and prove that both algorithms satisfy the privacy requirement. Then, we perform a comparative analysis on utility, efficiency and speedup techniques. Finally, we evaluate our algorithms through experiments on several datasets. The experiment results verify that our proposed algorithms preserve users' privay. We also test utility and discuss the privacy-utility tradeoff that real-world data publishers may face.

• Korean Journal of Health Education and Promotion
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• v.32 no.5
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• pp.43-51
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• 2015

Objectives: Socioeconomic factors are one of the significant factors explaining drinking problems in our society. From the poverty and inequality perspective, not only absolute poverty but perceived level of poverty or inequality has a direct effect on one's health and health behaviors. The purpose of the study is to explore the growth trajectories of problem drinking in Korea in relation to poverty and perceived income. Methods: Data from 13,414 adults were analyzed using 4 years of data (2010 to 2014) from the Korea Welfare Panel. Main variables included poverty status, perceived income inequality, and problem drinking. A latent growth modeling was employed for the analysis. Results: The non-poverty group had higher initial level of problem drinking; however, the poverty group showed higher rate of increase in problem drinking rate. The perceived income inequality had no significant influence on the initial level, but over time, those with higher level of perceived income inequality showed higher rate of increase in problem drinking. Conclusions: Findings showed that poverty and inequality affect changes in problem drinking. Efforts to prevent and decrease problems related to alcohol should not only focus on changing individuals' behavior but also on decreasing the inequality gap.

• Korean Journal of Social Welfare Studies
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• no.39
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• pp.315-342
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• 2008

The aim of this study was to examine growth trajectories of delinquent behaviors during adolescence. In addition, the effects of protective and risk factors that might account for individual difference in the level of delinquent behaviors and in the rate of change were examined. Four waves of data in the Korea Youth Panel Survey(KYPS) were used to analyze the linear growth modeling. The sample consisted of 3346 adolescents who were assessed at 4 measurement waves with approximately 1-year intervals. The results showed significant individual differences in both final level of delinquent behaviors and in the rate of change across 3 measurement occasions. Adolescent gender, family's socioeconomic background predicted the final level and the rate of change of delinquent behaviors. The protective effects of positive parenting and self-control were significantly associated with problem behaviors and the risk effects of the association with deviant peers and negative stigma were significant on the final level of delinquency. Self-control and deviant peer affiliation had differential influences over time significantly. Practice and policy implications as well as further research topic were discussed in the light of searching for important factors in preventing adolescent problem behaviors.

• Journal of the Korean Data and Information Science Society
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• v.21 no.6
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• pp.1125-1136
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• 2010

Lately there exist increasing demands for online abnormality monitoring over trajectory stream, which are obtained from moving object tracking devices. This problem is challenging due to the requirement of high speed data processing within limited space cost. In this paper, we present a FADA (Fuzzy Anomaly Detection Algorithm) which constructs normal profile by computing mobility feature information from the GPS (Global Positioning System) logs of mobile devices in MANETs (Mobile Ad-hoc Networks), computes a fuzzy dissimilarity between the current mobility feature information of the mobile device and the mobility feature information in the normal profile, and detects effectively the anomaly behaviors of mobile devices on the basis of the computed fuzzy dissimilarity. The performance of proposed FADA is evaluated through simulation.

• Korean Journal of Culture and Social Issue
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• v.14 no.1_spc
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• pp.299-317
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• 2008

The school drop-out among the youth has grown to become a serious social problem since about 2000 and calls for an attention to its seriousness. Therefore, this study reviewed the statitistical reports and the previous empirical findings on the school drop-out and integrated to establish a comprehensive understanding of this social phenomenon. The main concepts and terminologies on school drop-out, the current statistics, the possible causal factors and the usual trajectory the youth take after dropping-out of school were discussed to conceptualize the issue. Analyses indicated 12 characteristics of the students who dropped out of school. Those 12 characteristics were restructured according to the ecological conceptual model. The social instability and the financial crisis in the 1990's has eroded the stability of the primary environments of adolescents such as family and school. The family breakdowns from divorce and other reasons weakened psychological and financial support for adolescents. The diminished authority of teachers and school over students exposed conflicts between teacher and students, students' loss of purpose and interest in academic attainment. The adolescents showed emotional reponses like increased level of depression, helplessness, aggression, indicated cognitive reponses such as the loss of purpose and interest in studying, a heightened sense of uncertainty of the future, and behavioral responses like sexual acting out behaviors, and bullying. The unmet psychological needs of adolescents result in run-away and school drop-out behaviors, which in turn progress into juvenile delinquency as the society fails to provide adequate and appropriate guidance and interventions. The intervention strategies at the national level were proposed and the limitations of the study were discussed.