경시적 영과잉 가산자료와 생존자료의 결합모형

김동욱,천지훈,Kim, Donguk,Chun, Jihun 한국통계학회 2016 응용통계연구 Vol.29 No.7

시간의 흐름에 따라 관측되는 경시적(longitudinal) 자료의 경우, 경시적 자료와 생존(survival) 자료가 종종 동시에 수집된다. 이 때 경시적 자료에서 발생하는 결측이 생존자료와의 연관성으로 인해 발생한 무시할 수 없는 결측(non-ignorable missing)이라면, 경시적 자료분석 방법만으로는 두 자료 간의 연관성을 고려하지 않아 독립변수에 대한 효과는 편향된 결과를 얻게 된다. 이러한 문제를 해결하기 위해서 결측의 원인이 생존시간과 연관되어 있으므로 생존모형을 고려하여 불편추정량을 얻기 위해 경시적 자료와 생존자료의 결합모형에 대한 연구가 이루어져 왔다. 본 논문은 경시적 자료의 형태가 영이 많이 존재하는 영과잉 가산자료(zero-inflated count data)와 생존자료의 결합모형을 연구하였다. 경시적 영과잉 가산자료와 생존자료는 각각 허들모형(hurdle model)과 비례위험모형(proportional hazards model)의 부 모형을 적용하였고, 두 부 모형들의 변량효과가 다변량 정규분포를 따른다는 가정을 통하여 결합하였다. 모수의 최우추정법으로 EM 알고리즘을 활용하였고, 추정된 표준오차를 계산하기 위해 프로파일 우도(profile likelihood)를 이용하였다. 최종적으로 모의실험을 통해 두 부 모형의 변량효과 간 상관관계가 존재하는 경우 결합모형이 개별적 모형보다 편의와 포함확률(coverage probability)의 측면에서 더 우수함을 보였다. Both longitudinal data and survival data are collected simultaneously in longitudinal data which are observed throughout the passage of time. In this case, the effect of the independent variable becomes biased (provided that sole use of longitudinal data analysis does not consider the relation between both data used) if the missing that occurred in the longitudinal data is non-ignorable because it is caused by a correlation with the survival data. A joint model of longitudinal data and survival data was studied as a solution for such problem in order to obtain an unbiased result by considering the survival model for the cause of missing. In this paper, a joint model of the longitudinal zero-inflated count data and survival data is studied by replacing the longitudinal part with zero-inflated count data. A hurdle model and proportional hazards model were used for each longitudinal zero inflated count data and survival data; in addition, both sub-models were linked based on the assumption that the random effect of sub-models follow the multivariate normal distribution. We used the EM algorithm for the maximum likelihood estimator of parameters and estimated standard errors of parameters were calculated using the profile likelihood method. In simulation, we observed a better performance of the joint model in bias and coverage probability compared to the separate model.

AHP기법을 이용한 천연가스 발전소의 최적가용기술의 중요도 선정

김동욱 ( Donguk Kim ),권순길 ( Soongil Kwon ),황용우 ( Yongwoo Hwang ),김영운 ( Youngwoon Kim ) 한국전과정평가학회 2020 한국전과정평가학회지 Vol.21 No.1

최근 국내에서 환경오염시설의 통합관리에 관한 법률이 시행되었다. 통합관리에 따라 사업장의 환경인허가는 2017년 시행된 통합법에 따라 사업장 환경관리수준평가를 통하여 인허가 기간을 5∼8년까지 갱신하게 된다. 이 과정에서 최적가용기법의 적용률을 평가하게 되는데, 높은 평가점수를 받기 위해서 반드시 필요한 부분이다. 하지만 최적가용기법을 평가하는데 있어 사업장의 상황을 고려하지 않는 문제점이 있다. 적용 가능한 최적가용기법을 국내 기준서와 EU 기준서를 조사하여 사업장의 상황에 맞게 전문가들을 대상으로 AHP분석을 실시하여 우선적으로 적용할 기법을 선정하여 우선순위를 마련하였다. Recently, the Act on the Integrated Management of Environmental Pollution Facilities was implemented in Korea. Under the integrated management, the license period of the workplace will be renewed by five to eight years through the assessment of the level of environmental management of the workplace in accordance with the integrated law implemented in 2017. In this process, the application rate of the optimal use technique is evaluated, which is essential to obtain a high evaluation score. However, there is a problem in assessing optimal use techniques without considering the situation at the workplace. An AHP analysis was conducted on experts according to the situation of the workplace by examining the applicable optimal use techniques and the EU standards, and the priority was prepared by selecting the techniques to be applied first.

초등학생용 수업의 질 평가 척도 개발 및 타당화

김동욱(Donguk Kim),손원숙(Wonsook Sohn) 한국교육평가학회 2020 교육평가연구 Vol.33 No.3

본 연구의 목적은 초등학생이 지각한 수업의 질적 수준을 측정하기 위하여 학생용 수업의 질 평가 척도(Student Evaluations of Instruction Quality Scale: SEIQs)를 개발하고 타당화하는 것이다. 수업의 질은 학생이 능동적으로 사고하고 동기를 형성하는 데 필요한 교사와 학생 간 상호작용과 교실의 환경적 맥락으로 정의되었다. 이를 위해 D와 K지역 초등 5, 6학년 학생 1,512명을 연구대상으로 하였다. 먼저 선행연구를 탐색하여 수업의 질 평가 영역을 학생중심수업, 교사지지 및 학급경영으로 개념화한 후 관련 문항을 수집하여 문항풀을 구성하였다. 다음으로 예비 및 본 검사를 실시하여 척도 타당화 절차를 시행하였고, 최종 문항은 총 27개로 구성되었다. Rasch 모형 분석 결과 척도 및 문항의 신뢰도는 적절한 수준을 보였고, 척도의 요인구조는 학생중심수업(학생참여수업, 참여수업지원, 참여수업조정), 교사지지 및 학급경영으로 구성된 위계적 3요인이 파악되었다. 마지막으로 수업의 질을 판단하는 CLASS 척도(Pianta et al., 2008), 수업흥미 및 학업참여와의 상관관계를 살펴본 결과, SEIQ 척도의 하위요인은 학습지원, 정서적 지원, 학급조직 뿐 아니라 정의적 성취와도 정적 상관을 보였다. 마지막으로 수업의 질 평가 척도의 활용방안 및 추후 연구에 대한 시사점을 제안하였다. This paper describes the development and psychometric evaluation of the Student Evaluations of Instruction Quality Scale(SEIQs), for assessing students’ perception of instruction quality and focusing on students’ cognitive activation and classroom environment. The SEIQs comprises three dimensions based on the triarchic quality of instruction model(Klieme et al., 2009). Three dimensions composed of (a) student-oriented instruction as teaching practices for supporting cognitive activation, (b) teacher support and (c) classroom management as environments for supporting motivation and preventing student problem behaviors. The survey was conducted with a total of 1,512 Korean students ranging from Primary 5 to 6 sampled from 19 schools located in ten different regions. The results are summarized as follows: First, the structural aspect of validity of the SEIQs was verified by analyzing Rasch rating scale and confirmatory factor analysis based on the final 27 items. Hierarchical three factor model showed a good fit. Second, the criterion-related validity of the questionnaire was verified by analyzing its correlations with the CLASS(Pianta et al., 2008) scale, students’ classroom instruction interest and academic engagement. The five sub-factors such as student participation instruction, student participation support, student participation adjustment, teacher support and classroom management had positive correlations with the instructional supports, emotional supports and classroom organization domain of the CLASS(Pianta et al., 2008) scale. In addition, students’ classroom instruction interest and academic engagement had positive correlations with the five sub-factors. Finally implications for research and limitations are discussed.

KORA 프로그램을 이용한 N-메틸피를리디논 누출에 따른 피해영향범위 분석에 관한 연구

김동욱(DongUk Kim),천영우(YoungWoo Chon),황용우(YongWoo Hwang) 한국가스학회 2016 한국가스학회 학술대회논문집 Vol.2016 No.11

영어 사교육비 및 참여 경감에 대한 방과후학교 및 EBS 효과

김동욱(Donguk Kim),현수영(Suyoung Hyun),윤유진(Eugene Yoon) 한국중원언어학회 2015 언어학연구 Vol.0 No.36

This study is to examine of the effects economic advantage from the participation of afterschool programs and EBS. For this study, samples were collected twice in a year through an internet survey from a total of 78,000 subjects, including parents and students in elementary, middle or high schools nationwide by Statistics Korea. The impact of variables deemed influential on private tutoring fee was analyzed first. In order to investigate the impact afterschool programs and EBS on private tutoring fee, the Hierarchical Linear Models and logistic regression model were used to figure out variables that influence private tutoring costs and participation in private tutoring. In this study, SAS(Ver. 9.3) was used for analysis. The results show that the participation of afterschool program and EBS could be the main factors leading to lessen the private tutoring of English. And also the results reveal that main factors to affect the participation of English private tutoring are family income, student’s school record, location of school.

총 에너지 방정식을 이용한 비압축성 지배방정식의 Roe 평균

김동욱(Donguk Kim),김민수(Minsoo Kim),이승수(Seungsoo Lee) 한국항공우주학회 2020 한국항공우주학회 학술발표회 논문집 Vol.2020 No.11

프로톤 전도성 페로브스카이트 산화물 기반 전기화학전지 개발

김동욱(Donguk Kim),이태경(Tae Kyeong Lee),한승우(Seungwoo Han),최민기(Mingi Choi),이원영(Wonyoung Lee) 한국세라믹학회 2023 세라미스트 Vol.26 No.1

Protonic ceramic cells (PCCs) are environmentally friendly energy conversion devices that operate in the intermediate temperatures due to their high ionic conductivity. This can resolve the drawbacks of solid oxide cells, such as thermochemical, physical, and thermal degradation caused by high operating temperatures. To effectively utilize PCCs as a next generation energy source, the development and optimization of PCC electrolyte materials and manufacturing process of electrochemical device are essential. This review summarizes the current progress, approaches, and challenges of PCCs and offers guidance on material design and manufacturing processes to overcome these difficulties.

γ-Re<SUB>θ</SUB> 천이 모델을 이용한 저 레이놀즈수 익형 주위 유동 해석

김동욱(Donguk Kim),백청(Chung Baek),이승수(Seungsoo Lee),공효준(Hyojoon Gong) 한국항공우주학회 2019 한국항공우주학회 학술발표회 논문집 Vol.2019 No.11

영어사교육 참여 및 영어사교육비 지출에 영향을 주는 변인분석

김동욱(Kim, Donguk),윤유진(Yoon, Eugene),남진현(Nam, Jin-hyun) 한국외국어교육학회 2012 Foreign languages education Vol.19 No.3

Private tutoring or shadow education is considered as a serious social problem in Korea. Furthermore, the average expense of English private tutoring per student is 81,000 won which comprises 33.8% of total tutoring expense. Total amount that all families spend in 2011 is 6.7685 trillion won. Most Korean households are suffering an ever-growing burden from private education. This study is to examine the main factors leading to overgrown private tutoring of English in Korea. English private supplementary instruction is differently influenced according to levels of public school system, elementary school, middle school and high school. Many other factors, such as economic situation, location of school, parental educational background, student’s school record also affect the expense and the participation of English private tutoring. The data are collected by the Korean Statistical Information Service(KOSIS) in 2011 and released by the Ministry of Education, Science and Technology and KOSIS in 2012. Statistical methods used in this study are CART, Logistic Regression, and Hierarchical Linear Model. The results show that main factors to affect the participation of English private tutoring are family income, student’s school record, location of school. Also, main factors affecting the expense of English private tutoring are family income, location of school and parental educational background.

XLPE 및 LSR 계면의 부분방전 발생가스 성분 분석

김동욱(Donguk Kim),남기진(Gijin Nam),김정태(Jeongtae Kim),장태인(Taein Jang) 대한전기학회 2013 대한전기학회 학술대회 논문집 Vol.2013 No.4