• The Korean Journal of Applied Statistics
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• v.31 no.1
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• pp.123-137
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• 2018

A nonlinear mixed effects model is mainly used to analyze repeated measurement data in various fields. A nonlinear mixed effects model consists of two stages: the first-stage individual-level model considers intra-individual variation and the second-stage population model considers inter-individual variation. The individual-level model, which is the first stage of the nonlinear mixed effects model, estimates the parameters of the nonlinear regression model. It is the same as the general nonlinear regression model, and usually estimates parameters using the least squares estimation method. However, the least squares estimation method may have a problem that the estimated value of the parameters and standard errors become extremely large if the assumed nonlinear function is not explicitly revealed by the data. In this paper, a new estimation method is proposed to solve this problem by introducing the ridge regression method recently proposed in the nonlinear regression model into the first-stage individual-level model of the nonlinear mixed effects model. The performance of the proposed estimator is compared with the performance with the standard estimator through a simulation study. The proposed methodology is also illustrated using quantitative high throughput screening data obtained from the US National Toxicology Program.

• Journal of the Korea Society of Computer and Information
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• v.18 no.7
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• pp.183-190
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• 2013

This study aims to analyze the relationships among factors which influence acceptance intention of smart education. Based on literature reviews related with previous technology acceptance models, a potential model and seven hypotheses were suggested. Questionnaire was carried out among 132 students from elementary and secondary schools. They have experiences of utilizing applications of mobile devices for instructional goal. Cronbach alpha of the questionnaire was .78. The collected data were analyzed through path analysis. The results of this research are as follows. Seven hypotheses were adopted: Interaction will affect on perceived usefulness, Interaction will affect on perceived ease of use, Interaction will affect on acceptance intention, Interaction will affect on social influence, Social influence will affect on perceived usefulness, Perceived usefulness will affect on acceptance intention, Perceived ease of use will affect on acceptance intention. The model revised through the results of path analysis had good-fitness. That is, overall fit measures (RMSEA, CFI, NNFI), indexes that show the suitability of the model were quite good.

• KDI Journal of Economic Policy
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• v.27 no.2
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• pp.123-154
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• 2005

Using Korean household data, this paper examines how consumption of durable goods is determined. Previous studies report that the standard Permanent Income Hypothesis (PIH), while being broadly consistent with non-durable goods consumption, provides little explanation for durable goods consumption. In this paper, we consider the (S, s) model as an alternative to the standard PIH. The (S, s) model predicts that, because of fixed adjustment costs, consumers make no adjustment to the durable goods stock until deviation from the optimal level becomes large. When the adjustments are made, the durable goods stock attains the optimal level. In order to test this prediction, we examine the intra-temporal relationship between non-durable goods and durable goods consumption and intertemporal changes in durable goods consumption, using data from the Korean Household Panel Study. The results show that, while the standard PIH is rejected by the data, the (S, s) model is not.

• Proceedings of the Korean Operations and Management Science Society Conference
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• 1997.10a
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• pp.149-152
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• 1997

'98년부터 통신시장이 전면 개방됨에 따라 국내외적으로 전환기를 맞이하고 있다. 이런 급변하는 시장환경에서 경쟁우위를 유지하기 위해서는 우수한 기술경쟁력과 가격경쟁력을 가지고 능동적으로 대처할수 있어야 한다. 본 연구에서는 시장측면의 기술활용정도와 기술측면의 기술수준 등 2가지의 변수를 바탕으로 기술경쟁력 분석모형을 설정하여 경쟁력 강화방안을 모색하였다. 또한 본 분석모형에 따라 ETRI(한국전자통신연구원)의 사례연구 결과도 제시하였으며, 이를 토대로 연구기관의 종합적인 기술경쟁력 강화방안을 마련하였다.

• Korean Journal of Childcare and Education
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• v.11 no.2
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• pp.59-85
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• 2015

The purpose of this study was to investigate the effects of child care teachers' emotional supports in individual classrooms on children's social skills, including self-control, assertion, cooperation, and responsibility that were related to their character development. Data were collected in a purposive sample involving 32 teachers working with 646 children at age five and 555 parents of the children. Hierarchical Linear Modeling (HLM) was used to analyze a two-level model. The results showed that there were significant differences among classes with data reported by teachers but characteristics such as teachers' education and work experiences, child-teacher ratio, and type of child care centers as well as teacher's emotional supports did not explain the differences. Children's age and gender, which were predictors at the individual level, significantly explained their level of social skills reported by parents as well as teachers. The findings implied that other predictors influencing differences among classes should be explored in future studies.

• Journal of Digital Convergence
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• v.17 no.2
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• pp.9-18
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• 2019

This study investigates the factors affecting the educational satisfaction and the transfer of learning of cyber crime prevention education students in order to confirm the effectiveness of the current education. Based on the CIPP model, we confirmed whether the level of social demand and the level of knowledge in the context evaluation, recency of subjects in the input evaluation and interaction in the process evaluation affect the educational satisfaction and the transfer of learning of the students by conducting the survey for the students. As a result of analysis, it was proved that the level of knowledge, recency of subjects and interaction had a significant relationship with the educational satisfaction and recency of subjects, interaction and educational satisfaction significantly affect transfer of learning. Based on the findings, this study provides a few constructive suggestions to improve the effectiveness of the cyber crime prevention education program.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.26 no.2D
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• pp.251-258
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• 2006

This study is to develop an estimation method of freeway design capacity through the analysis of time headway distribution in continuum flow. Traffic flow-speed diagram and time headway distribution plotted from individual vehicle data shows: a) a road capacity is not deterministic but stochastic, b) time headway distribution for each vehicle speed group follows pearson type V distribution. The freeway design capacity estimation model is developed by determining a minimum time headway for capacity with stochastic method. The estimated capacity values for each design speed are lower when design speed ${\leq}80km/h$, and higher when design speed ${\geq}106km/h$ in comparison with HCM(2000)'s values. In addition, The distinguish difference is that this model leads flexible application in planning level by defining the capacity as stochastic distribution. In detail, this model could prevent a disutility to add a lane for only one excess demand in a road planning level.

• Journal of Korean Society for Quality Management
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• v.45 no.1
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• pp.55-64
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• 2017

Purpose: A large number of attributes with mixed levels are often considered in the conjoint analysis. The respondents may have difficulty with scoring their preferences accurately because of many attribute items involved in each survey question. We research on the technique for reducing the number of attribute items. Methods: In order to reduce the number of attribute items in a survey question, we make a new attribute by merging two original attributes. A 'No question' option is also included as a new level in a merged attribute. Results: We propose BIB $6^4$ design in the case where we have four attributes with 2 levels and 3 levels, respectively and then analyze all the respondents survey data generated by the repeated simulation study in order to compare various model selection methods. Conclusion: How to reduce the number of attribute items is proposed and how to design and analyze the survey data are illustrated.

• Korean Journal of Social Welfare
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• v.63 no.1
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• pp.187-215
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• 2011

This study examined the longitudinal relationship between depressive symptoms and alcohol use based on the tension reduction hypothesis and the intoxication hypothesis considering for path of depressive symptoms on alcohol use and vice versa simultaneously. And this study examined the effect of psychosocial behavior factors (i.e. smoking level, self-esteem, satisfaction with family relationships, and satisfaction with social relationships) on depressive symptoms and alcohol use. Using the data on the Korea Welfare Panel Study for the 1st, 2nd, and 3rd years, this study were estimated using the Latent Growth Curve Model which is helpful for examining differences between the two. The results are as follows: the initial level of alcohol use had a positive impact on the rate of change in depressive symptoms, thereby supporting the intoxication hypothesis. Second, self-esteem and satisfaction with family relationships act as variables with the biggest effect on the initial level and the rate of change in depressive symptoms, whereas other psychosocial behavior factors such as smoking level and satisfaction with social relationship exert the largest influence over the initial level and the rate of change in alcohol use. This study has implications in that it clarified the confused relationship mechanism between alcohol use and depressive symptoms the two. Based on the finding of the study, political and practical implications were discussed.

• Proceedings of the Korean Society of Computer Information Conference
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• 2011.06a
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• pp.253-256
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• 2011

이 연구는 국내 초등학교에서 실시되고 있는 방과후 컴퓨터교육의 운영을 조사하고 문제점을 체계적으로 분석하고 파악함으로써 방과후 컴퓨터교육의 개선방안을 제안하는데 목적이 있다. 이를 위해, 방과후 컴퓨터교육에 관련한 문헌조사 및 컴퓨터교육의 운영에 대한 CIPP평가모형을 적용한 설문조사, 지도교사 집단면담 등을 토대로 방과후 컴퓨터교육의 운영성과를 분석했다. 연구결과, 현행 방과후 컴퓨터교육은 대체로 바람직하게 운영되고 있다고 인식하고 있었다. 각 평가항목별 구체적인 분석결과 수준별 고려여부(학생:M=2.35, 교사:M=2.70), 시설 및 기자재(학생:M=2.25, 교사:M=2.20), 복리후생 여건(학생:M=2.28, 교사:M=2.50), 교재구성(학생:M=2.51, 교사:M=2.65), 맞춤형 수준별 전략(학생:M=2.90,교사: M=2.45) 등의 분야는 미흡하다고 인식하는 것으로 조사되었다. 또한 집단면담 결과를 토대로 교육현장 요구 반영, 과정별 차이를 고려한 목표 제시, 새로운 교육 과정의 개발이 필요, 강사 전문성 기준의 재정립, 교재 구성 및 유용성 제고, 래포(rapport) 형성과 개인별 맞춤형 수업 가능성, 성찰과정을 강조하는 평가, 통합 커뮤니티 구축 가능성 모색, 방과후 컴퓨터 수업 개선을 위한 연계 방안 필요성 등을 고려해야 하며, 각종 방과후 컴퓨터교육 운영에의 저해요인(컴퓨터관련 각종 규정, 학생들의 참여의지 부족, 예산 및 인력부족 등)등을 개선하는 것이 중요하다. 초등학교 방과후 컴퓨터교육에 대한 양적 질적 성과분석 결과를 바탕으로 차세대 방과후 컴퓨터 교육의 개발을 위한 총론적 개선방안 제시는 물론, 구체적인 차세대 방과후 컴퓨터교육의 개발연구가 필요하다.