• Communications for Statistical Applications and Methods
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• v.23 no.1
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• pp.1-20
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• 2016

Causal inference methodologies have been developed for the past decade to estimate the unconfounded effect of an exposure under several key assumptions. These assumptions include, but are not limited to, the stable unit treatment value assumption, the strong ignorability of treatment assignment assumption, and the assumption that propensity scores be bounded away from zero and one (the positivity assumption). Of these assumptions, the first two have received much attention in the literature. Yet the positivity assumption has been recently discussed in only a few papers. Propensity scores of zero or one are indicative of deterministic exposure so that causal effects cannot be defined for these subjects. Therefore, these subjects need to be removed because no comparable comparison groups can be found for such subjects. In this paper, using currently available causal inference methods, we evaluate the effect of arbitrary cutoffs in the distribution of propensity scores and the impact of those decisions on bias and efficiency. We propose a tree-based method that performs well in terms of bias reduction when the definition of positivity is based on a single confounder. This tree-based method can be easily implemented using the statistical software program, R. R code for the studies is available online.

• Hwankyungkyoyuk
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• v.18 no.2 s.27
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• pp.90-100
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• 2005

This study was intended to investigate effects of building school forests on elementary school students, including changes in mental image of school, attitude toward nature and forest, and awareness of their relationship with school forest. The total number of 770 drawings and 1,124 writings were collected to be analyzed from three elementary schools. The results showed that there were significant differences between two student groups, respectively forest school group versus non-forest school group, in their mental image of school. For instance, more often observed in the drawings of forest school group students than their counterparts were natural and human elements, activities associated with nature, and natural or human elements located at central area. Also, more frequently found in the writings of forest school group students than their counterparts were letter-style sentences, stories about school forests, inherent values on nature and forest, and curiosity regarding the nature. These results seem to indicate that in order to materialize educational value of school forests, practical workshops for teachers need to be held as soon as possible and new activity models for students should be developed. In addition to that, long-term research on effectiveness of school forest have to be conducted to a number of schools.

• Korean Journal of Childcare and Education
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• v.16 no.3
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• pp.39-58
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• 2020

Objective: The purpose of this study is to investigate the effects of parents' perception of infant's use of digital devices on language development. Methods: For this study, a survey was conducted on 285 parents of 1-2year old infants attending childcare centers in Jeollanam-do. Results: First, the digital devices that infants were exposed to the most was the television, and their first exposure to digital devices was at 13~17 months. The most time spent using digital devices was 30 minutes and they most frequently used them at home. Second, parents perceived the educational value of digital devices as low. Third, language development was high when the initial use of digital devices for infants was late, when the daily use time of digital devices was less than 30 minutes, when digital devices were used with parents, and when parents always managed digital devices and usage time. Fourth, Parents' perception of the use of digital devices has a significant influence on their infants' language development. Conclusion/Implications: Language development due to the use of digital devices and parents' perception of the use of digital devices has a significant impact on infants language development.

• Trans-
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• v.6
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• pp.17-33
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• 2019

The core of Laban Movement Analysis, which is used for academic research purposes, is that the individual's psychological or emotional state through movement is expressed in external motion by internal intention, which is symbolic of internal emotions. In addition, the Laban motion analysis focuses on analyzing the structure of the object of movement and its structure comparatively and analytically with the past or other structures, and the analyzed grammars of the dance ultimately influence each other in psychological, social and cultural aspects 'Relationality' provides clues to be found. It also provides a resource of records in terms of the system implied from the 'momentary nature' of dance, which has educational value as a multidisciplinary research material.

• Human Ecology Research
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• v.54 no.4
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• pp.351-363
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• 2016

This study examined in depth what teachers experience in a practical problem-based home economics class. This study established the research question, "What do teachers experience in the practical problem-based home economics class?" and selected three teacher participants who had steadily performed a practical problem-based home economics class to directly observe classes and conducted intensive interviews with the class performing teachers. The three research participants performed the practical problem-based class as a method of practicing their educational beliefs and based on a problem consciousness that textbook centered classes focusing on concepts cannot manage. They also tried to make efforts to reconstruct the textbook centered with practical problems to promote the critical thinking abilities of students. In practicing the practical problem-based class, the research participants recognized that it was important to show the present problems in reality to the students, teach broad value concepts, and establish rapport with students. They tried to make class content correspond to class evaluation. They felt awarded in how they influenced the development of students and the perception of home economics subjects in a positive way as well as experienced various actual difficulties in performing the practical problem-based class. The three research participants examined themselves through the agony and reflection of the class, and integrated the class with daily activities by applying problem solving methods of practical problem-based classes to their lives.

• Journal of The Korean Association of Information Education
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• v.11 no.2
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• pp.205-218
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• 2007

This study investigates the reasons of dropout in a survey of 348 dropouts from a cyber university located in Seoul, Korea. Most common reasons are time constraints due to work or family-related needs. Difficulties in adjusting to online learning environment and uncertainties regarding the value of a cyber university degree also played important roles. Drop-out students who pointed to these two reasons also suffered from lack of communication and interaction with other students and professors. Efforts to address these issues are in order as well as the development of time-efficient learning strategies and financial aids.

• English Language & Literature Teaching
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• v.12 no.4
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• pp.1-29
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• 2006

The purpose of this paper is to present a qualitative case study on teaching English as an international language in Korean context. The researcher investigated the implementation process of the new elementary English program from the government to local schools to find out to what extent the symbolic value of English as an international language affect the implementation process of the elementary English program. The research result showed that the elementary teachers shared the different views of the status of English from those of government and the parents, and their differing perception of the role of English constantly affected their implementation efforts. The research findings also revealed that the public's concern of English dominance in Korean educational system resulted in the government's 'comprised curriculum' by lowering the learning goals of the English program. The findings also indicated that the introduction of the elementary English program accelerated English dominance in both teacher and student culture. The question of how to resolve the conflict between acquiring English proficiency and its negative influence on Korean culture remains a complex issue in implementing the new elementary English program.

• Journal of the Korean Society of School Health
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• v.20 no.2
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• pp.69-80
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• 2007

Purpose: The present study purposed to investigate the current state of harmful business places around schools and to survey and analyze how much middle school students know about school environment hygiene purification zones, which have not been much effective. Methods: In addition, this study clarified the problem of harmful environment around schools by inquiring into students' value and perception on worsening harmful environment around schools and provided basic materials necessary for making policies on school education and the protection of educational environment. For these purposes, we conducted a questionnaire survey of 1,000 middle school students in Gyeonggi-do on their perception on harmful environment around their schools, and drew conclusions as follows. Result: Students' knowledge about the School Health Act was low, and they generally thought that the law does not play its role substantially and efficiently in purifying and regulating harmful environment and regulations are superficial and temporary. To the question of whether harmful businesses observe laws for purifying environment around schools, most of the students replied negatively. In actuality, as most of harmful businesses running at school environment hygiene purification zones are stationeries with game rooms, comic book stores, PC rooms, etc., which are highly accessible to students, they become serious problems in school environment. Conclusion: As it is required to make continuous and systematic surveys and researches on the school environment hygiene purification zones, we need to manage school environment efficiently through cooperation among the government, education offices and individual schools.

• Research in Community and Public Health Nursing
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• v.25 no.2
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• pp.75-84
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• 2014

Purpose: This study aimed to identify the level of knowledge on preventing cardiovascular disease (CVD) and nicotine dependency among smoking male college students, and to examine the predicting factors of nicotine dependency. Methods: This study was conducted as cross-sectional descriptive research using structured questionnaires. Data were collected from 411 smoking male college students ($22.5{\pm}2.59$ yr) at two universities located in two cities in Korea from September 2012 to April 2013. Logistic regression analysis was performed to estimate age-adjusted odds ratios of nicotine dependency. Results: The mean value of nicotine dependency was $4.2{\pm}1.96$ and the percentage of participants who had strong nicotine dependency (${\geq}7$) was 10.7%. Logistic regression analysis showed that, when adjustment was made for age, nicotine dependency was predicted by the frequency of alcohol drinking (${\geq}3$ times/week), knowledge on CVD prevention, the age starting drinking, and the total length of smoking. Conclusion: Nicotine dependency was strongly related to the frequency of drinking alcohol and lower knowledge on CVD prevention. Therefore, male college students who have a dependent smoking habit and drink alcohol frequently need to take more interest in health through educational counseling to modify their lifestyle behaviors and to have preventive knowledge related to CVD.

• Journal of the Institute of Electronics and Information Engineers
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• v.54 no.7
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• pp.127-132
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• 2017

In this paper, we propose a controller gain based on model based design and implement the two-wheel inverted pendulum type robot using NXT Lego and RobotC language. Two-wheel inverted pendulum robot consists of NXT mindstorm, servo DC motor with encoder, gyro sensor, and accelerometer sensor. We measurement wheel angle using bulit-in encoder and calculate wheel angle speed using moving average method. Gyro measures body angular velocity and accelerometer measures body pitch angle. We calculate body angle with complementary filter using gyro and accelerometer sensor. The control gain is a weighted value for wheel angle, wheel angular velocity, body pitch angle, and body pich angular velocity, respectively. We experiment and observe the effect of two-wheel inverted pendulum with respect to change of control gains.