• Communications for Statistical Applications and Methods
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• 제20권3호
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• pp.235-240
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• 2013

Generalized linear mixed models(GLMMs) are frequently used for the analysis of longitudinal categorical data when the subject-specific effects is of interest. In GLMMs, the structure of the random effects covariance matrix is important for the estimation of fixed effects and to explain subject and time variations. The estimation of the matrix is not simple because of the high dimension and the positive definiteness; subsequently, we practically use the simple structure of the covariance matrix such as AR(1). However, this strong assumption can result in biased estimates of the fixed effects. In this paper, we introduce Bayesian modeling approaches for the random effects covariance matrix using a modified Cholesky decomposition. The modified Cholesky decomposition approach has been used to explain a heterogenous random effects covariance matrix and the subsequent estimated covariance matrix will be positive definite. We analyze metabolic syndrome data from a Korean Genomic Epidemiology Study using these methods.

• Journal of the Korean Data and Information Science Society
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• 제27권4호
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• pp.1083-1090
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• 2016

In clinical studies, different types of outcomes (e.g. repeated measures data and time-to-event data) for the same subject tend to be observed, and these data can be correlated. For example, a response variable of interest can be measured repeatedly over time on the same subject and at the same time, an event time representing a terminating event is also obtained. Joint modelling using a shared random effect is useful for analyzing these data. Inferences based on marginal likelihood may involve the evaluation of analytically intractable integrations over the random-effect distributions. In this paper we propose a joint HGLM approach for analyzing such outcomes using the HGLM (hierarchical generalized linear model) method based on h-likelihood (i.e. hierarchical likelihood), which avoids these integration itself. The proposed method has been demonstrated using various numerical studies.

• 한국과학교육학회지
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• 제10권1호
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• pp.119-125
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• 1990

The results of the analyses of 431 doctoral disserations of science education (Dissertation Abstracts International. 1980-1984) are as follows : 1. It was recognized that many countries as well as USA(e.g. Canada, Nigeria, Saudi Arabia, South Africa, Taiwan, Thailand, The Netherlands etc.) have deep interest in science education. 2. About 60% of dissertations had been focused on middle school (junior and senior)and college students as the subject of investigation. 3. Disciplines of science concerning the subject showed general science (35.6%), biology (18.3%), physics (11.4%), chemistry (11.4%), earth science (4.6%), and others (18.7%). 4. The number of dissertations belonging to experimental research was over 60 more than that of dissertations belonging to theoretical research. 5. In methodology of research, examination, test, questionaire were general method, and the field of research was focused mainly on the academic achievement.

• Communications for Statistical Applications and Methods
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• 제27권2호
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• pp.201-210
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• 2020

Baseline-category logit random effects models have been used to analyze longitudinal nominal data. The models account for subject-specific variations using random effects. However, the random effects covariance matrix in the models needs to explain subject-specific variations as well as serial correlations for nominal outcomes. In order to satisfy them, the covariance matrix must be heterogeneous and high-dimensional. However, it is difficult to estimate the random effects covariance matrix due to its high dimensionality and positive-definiteness. In this paper, we exploit the modified Cholesky decomposition to estimate the high-dimensional heterogeneous random effects covariance matrix. Bayesian methodology is proposed to estimate parameters of interest. The proposed methods are illustrated with real data from the McKinney Homeless Research Project.

• International Journal of Reliability and Applications
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• 제14권2호
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• pp.55-70
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• 2013

This paper deals with the Bayesian analysis of the failure data of a repairable mechanical system subject to minimal repairs and periodic overhauls. The effect of overhauls on the reliability of the system is modeled by a proportional age reduction model and the failure process between two successive overhauls is assumed to be 2-parameter Engelhardt-Bain process (2-EBP). Power Law Process (PLP) model has a disadvantage which 2-EBP can overcome. On the basis of the observed data and of a number of suitable prior densities, point and interval estimation of model parameters, as well as quantities of relevant interest are found. Also hypothesis tests on the effectiveness of performed overhauls have been developed using Bayes factor. Sensitivity analysis of improvement parameter is carried out. Finally, a numerical application is used to illustrate the proposed method.

• 한국가정과교육학회지
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• 제20권4호
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• pp.125-137
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• 2008

본 연구는 독서를 활용한 기술 가정 수업의 효과를 알아보기 위해서 식생활 단원을 중심으로 독서교육의 교수-학습 지도안을 개발 적용하여, 학생들의 기술 가정 수업에 대한 흥미를 높이고 식생활 문제에 대한 관심도를 증가시켜 안전한 식품을 선택할 수 있는 능력을 길러주는 데 목적을 두었다. 본 연구에서는 경기도 부천시의 중학교 3학년을 대상으로 사전의 영양 성취도 점수를 비교하여 실험집단과 통제집단을 선정하였다. 통제집단은 전통적 강의식 수업으로, 실험집단은 독서교육을 활용하여 4주간, 총 8차시의 수업을 실시한 후 두 집단의 실험 처치 전 후의 차이를 SPSS 프로그램을 이용하여 paired t-test로 분석하였다. 본 연구 결과는 다음과 같다. 첫째, 독서교육을 위한 교수-학습 방법을 개발하여 이를 실제 수업에 적용하였다. 독서 활동 후에 개발된 독서 기록 카드와 학습지를 작성하면서 식생활과 관련된 용어를 명확히 이해하고 식생활 문제의 심각성을 깨달아 스스로 해결 방안을 모색할 수 있도록 교수-학습 방법을 개발하고 독서를 활용한 토론 학습을 통해 기술 가정 수업의 흥미를 높이고 의사소통 능력을 기를 수 있도록 하였다. 둘째, 위에서 개발한 교수-학습 방법을 활용한 실험집단과 전통적 강의식 수업을 진행한 통제집단의 사전 사후 검사를 실시하여 비교 분석하였다. 그 결과 전통적 강의식 수업을 진행한 통제집단에 비해 독서교육 교수-학습 방법을 적용한 실험집단 학생들의 기술 가정 수업과 교사에 대한 인식이 긍정적으로 변화한 것으로 나타났다. 또한 실험집단의 경우 실험 처치 후에 식품 선택 태도가 긍정적인 방향으로 변화하였다. 그러나, 실험 처치가 실험집단과 통제집단의 식생활 단원과 독서에 대한 관심도, 식습관에는 영향을 미치지 못한 것으로 나타났다. 이상의 결과에서 독서교육이 기술 가정과 수업의 흥미를 높이고 교사에 대한 인식을 긍정적으로 바꾸는 것으로 나타났으며, 식품 선택의 태도를 향상시키는 것으로 나타났다. 따라서, 학생들이 올바른 식습관을 형성하여 건강한 삶을 영위할 수 있도록 돕기 위해 독서교육을 활용한 다양한 교수-학습 지도안을 개발하고 지속적으로 수업에 활용하여야 할 것으로 사료된다.

• Journal of applied mathematics & informatics
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• 제9권2호
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• pp.879-890
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• 2002

In this paper we consider open queueing system with a Poisson arrival process which have a finite upper bound on the arrival rate for which the system is stable. Interpolation approximations for quantities of interest, such as moments of the sojourn time distribution, have previously been developed for such systems, utilizing exact light and heavy traffic limits. These limits cannot always be easily computed for complex systems. Thus we consider an interpolation approximation where all of the relevant information is estimated via simulation. We show that all the relevant information can in fact be simultaneously estimated in a single regenerative simulation at any arrival rate. In addition to light and heavy traffic limits, both the quantity of interest and its derivative (with respect to the arrival rate) are estimated at the arrival rate of the simulation. All of the estimates are then combined, using a least squares procedure, to provide an interpolation approximation.

• 한국의류학회지
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• 제14권2호
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• pp.73-84
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• 1990

The present research investigated perceptions of persons wearing Korean and Western clothing with reference to judgement of appropriateness of style in a variety of socially interacting contexts and relationship to social schemata and to general clothing interest. 180 male and 180 female students responded to open-ended and Likert-type questionnaires. The stimuli were 9 line drawings of male and female figures in traditional Korean and Western formal and informal attire. Data were analyzed by content analysis, frequency, percentage, and mean. Traditional Korean clothing was judged as inappropriate on the campus and in the office but appropriate in the ambiguous context. Korean traditional styles were related to person schemata, but Western styles were related to role schemata. Furthermore, Korean styles were considered to be 'impractical' and 'inactive.' A newly emerging perception of persons wearing Korean attire as 'individualistic' and 'radical activist' was discovered. Impressions of persons wearing traditional Korean clothing were partially related to subject's own clothing interest.

• 공학교육연구
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• 제22권6호
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• pp.21-27
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• 2019

In the last few years, interest in computer science education has increased significantly. The curriculum is being revised to introduce computer science. Although interest has focused on coding as the main subject, in fact the computer science includes much more than coding. It engages people in being creative with technology as well as understanding the fundamental principles of computer science. Therefore, it is important to consider the curriculum to provide a foundation by teaching and learning computer science. The curriculum is required the development of courses to teach computer science for non-majors in general education. To think like a computer scientist on the knowledge of computer science is computational thinking. In order to maximize the effectiveness of teaching and learning for computational thinking, various teaching methods and supplementary learning materials, and activities should be developed and provided.

• 공학교육연구
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• 제18권2호
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• pp.77-88
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• 2015

Recently, there has been an increasing interest in 'Flipped Learning,' an IT-based learner-centered teaching-learning method corresponding to meet the paradigm of the future education. For smooth Flipped Learning, there are three steps in total: a pre-class should precede; then, in the structure of classes in the classroom, in-class learning among peer learners should be done; and lastly, the operation of a post-class should be done. For successful Flipped Learning, class elements in each step should be designed with a time difference, interconnected so as to achieve a single educational objective. However, it was found that there was a limitation in that the teaching-learning model of the preceding Flipped Learning consisted of the order of analysis, design, development, implementation and evaluation as general procedures, so it would not sufficiently consider the situations of Flipped Learning only. On this background, this thesis proposes a differentiated Flipped Learning model for mastery learning in a subject of an institute of technology as a model of systematic instructional design and presents a case of a class applied to an actual subject of computer engineering.