• Journal of The Korean Association For Science Education
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• v.24 no.5
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• pp.987-995
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• 2004

The purpose of this study was to analyze characteristics of problem solving process with proportional or compensational reasoning of the elementary school students. For this study, 85th grade students were selected and tested with Science Reasoning Task, information processing ability test and proportional and compensational reasoning tasks. This study revealed that students in mid concrete stage could solve the proportionality task and easy compensation task. But, most of the students could not solve difficult compensation task. And as the students got higher score in information processing test, it took them less time to solve the problem. The types of strategy used in solving proportional and compensational problem were categorized as the factor of change, building-up and the cross-product. Most of the students failed in problem solving used incorrect schema knowledge, procedure knowledge and strategy knowledge. Many students tended to use proportionality strategy to solve the difficult compensation task. Result of this study suggested that various task included different structure and the same schema knowledge can be effective for the advancement of students' proportional and compensational reasoning ability.

• Journal of Educational Research in Mathematics
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• v.23 no.1
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• pp.1-16
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• 2013

The primary purpose of this study is to survey multiplicative thinking levels and its characteristics of third graders in elementary school and to analyze how to use it when they solve the proportional problems. As results, the transition thinking ranked the highest among the four kinds of thinking levels when the $3^{rd}$ graders solved the multiplication problems. It means that the largest numbers of students still can not distinguish the additive and multiplicative situations completely and remain in the transition thinking, which thinks both additively and multiplicatively. In addition, the performance of solving proportional problems was distinguished from the levels of thinking. Through this study, we can give some implications of the importance of multiplicative thinking and instructional methods related to multiplication.

• 한국지형공간정보학회:학술대회논문집
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• 2002.03a
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• pp.27-33
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• 2002

최근 들어 다항식비례모형(RFM: Rational Function Model)은 비전문가에게 있어서 지형보정을 위한 정확도 문제를 해결함과 동시에 센서 종류에 상관없이 적용 가능한 범용적인 센서모델링 기법으로 각광을 받고 있다. 그러나 엄밀(physical) 모델이 없는 센서 혹은 위성의 궤도력 자료를 제공하지 않는 센서의 경우 다항식비례모형의 적용을 위해서는 다수의 매개변수 사용으로 인한 계수들 간의 상관성을 고려해야 한다. 이에 본 연구에서는 2차 다항식비례모형에 기초하여 전방 다항식비례모형(Forward RFM)과 상관도 분석을 통한 전방 다항식비례모형의 이른 및 위치정확도에 관한 연구를 수행하였다. 대상연구지역은 KOMPSAT(Korea Multi-Purpose Satellite)과 SPOT으로 촬영한 대전광역시와 그 주변지역으로 SPOT과 KOMPSAT 모두 상관성 분석 전에는 대략 50% 정도의 검사점에 대해 과대오차(>100m)가 얻어졌으며, 이 점들을 제외한 검사점에 대해서도 SPOT은 평균수평오차 20-24m, 평균표고오차 25m, KOMPSAT은 평균수평오차 15-24m, 평균표고오차 30m를 나타내었다. 전방 다항식비례모형에 대하여 상관성 분석을 수행한 후에는 검사점에 대한 모든 과대오차 조정결과가 소거되었고 검사점에 대해서 SPOT은 평균수평오차 8.8m, 평균표고오차 25.2m, KOMPSAT은 평균수평오차 8.4m, 평균표고오차 14.5m를 나타내었다. 최종적으로 연구지역에 대한 수치표고모형의 제작을 통해 상관도 분석을 통한 다항식비례모형의 실제 적용 가능성을 보여주었다.

• School Mathematics
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• v.16 no.4
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• pp.659-675
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• 2014

The purpose of this study is to investigate the effects of scheme based strategy Instruction on problem solving of word problems of ratio and proportion for students with under achievement or at risk for learning disabilities. Three $7^{th}$ graders of underachieving or at risk LD were participated in this study. Three steps of instructional experiment-testing baseline, intervention with schematic-based strategy, testing for the abilities of problem solving, generalization, & sustainability. The results showed that the schema-based strategy, FOPS was effective method for all three students enhancing problem solving abilities and for generalizing and sustaining the problem solving.

• Journal of Labour Economics
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• v.29 no.2
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• pp.67-116
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• 2006

This study directly analyzes the wage distributions rather than indirectly looking at a few of their moments. It also investigates wage distributions using various descriptive and semi-parametric methods. The wage distributions of Korean manufacturing industries can in general be represented by three distinct forms, underdeveloped, advanced and the medium of the two. The discrepancies in these distribution forms are explained by differences in the labor-type distributions and their weights in the composition of wage distribution forms, and further clarified through various descriptive statistics based on them. However, the descriptive statistical analysis has a limit in that it shows mixed outcomes of different categoric variables. Then, this problem is resolved by applying a semi-parametric estimation of hazard function and the marginal effect evaluations of variable changes on estimated distributions not on the function. As a result of this marginal analysis, the common features and differences of categoric variables and their intensities of effects on distributions are revealed.

• Journal of Elementary Mathematics Education in Korea
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• v.21 no.1
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• pp.115-134
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• 2017

It is necessary to understand the characteristics of each type of division problems in other to help students develop a rich understanding when they learn each type of division problems. This study focuses on a specific type of division problems; a quotitive division as finding a scale factor in enlargement context. First, this study investigated via survey how 4th-6th graders and preservice and inservice elementary teachers solved a quotitive division relating to scaling problem. And semi-structured interviews with preservice and inservice elementary teachers were conducted to explore what knowledge they brought when they tried to solve enlargement quotitive division problems. Most of participants solved the given quotitive division problem in the same way. Only a few preservice and inservice teachers interpreted it as a proportion problem and solved in a different way. From the interviews, it was found that different conceptions of context and decontextualization, and different conceptions of times (as repeated addition or as a multiplicative operator) were connected to different solutions. Finally, three issues relating to teaching enlargement quotitive division were discussed; visual representation of two solutions, conceptions connected each solution, and integrating quotitive division and proportion in math textbooks.

• School Mathematics
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• v.10 no.4
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• pp.603-623
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• 2008

The purpose of this research was to gain a better understanding of the characteristics of students' mathematical representations using additive strategy in ratio and proportion tasks. The additive strategy is the erroneous one used most often among the strategies reported in solving ratio and proportion tasks. It is a problem solving strategy that preserves the difference from one ratio to another. Students' additive strategies were categorized into four parts: subtracting without considering units of quantities, comparing the numbers that represent the whole subtracted from the part and same part, adding the difference, and subtracting the difference. In order to change from additive strategy to multiplicative strategy, the researcher asked to find out the unit quantity and found the characteristics of students' mathematical notations in the following: Firstly, the students made the number which they wanted by multiplying and adding same numbers. Secondly, they represented the mid-points between natural numbers. Thirdly, they related $a{\div}b$ to decimal number, not $\frac{a}{b}$. Fourthly, they were inclined to divide the larger number with the smaller number without understanding the context of the problem. These results are interpreted as showing that lower level of performance in the dividing operation with the notations of fraction hinders the transformation from additive strategy to multiplicative strategy.

• 한국노년학
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• v.38 no.4
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• pp.963-979
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• 2018

The purpose of this study was to identify frailty profiles based on physical, psychological, and social domains of functioning and to examine the associated factors showing the differences among frailty profiles. Respondents were 70 years and older(n=403) and latent class analysis was applied to determine the optimal subgroups based on Tilberg Frailty Indicators which comprised of three domains(the physical, psychological, and social domain). Also, we performed multinominal logistic regression analysis to find out factors making differences among frailty profiles. Latent class analysis(LCA) identified three distinct types: multi-frail type(27.0%), psychologically frail type(26.8%), inadequate support type(46.2%). All three types had common difficulties in dealing with daily life problems and did not receive enough help with theses difficulties. Based on the results of the LCA three-class models, people in multi-frail type accumulated problems in physical and psychological domains and had partially social domain. On the other hands, psychologically frail type showed a relatively high anxiety disorder and depression. Lastly, people in inadequate support type reported the lack of helps, but they were relatively healthy. Comparing these groups with inadequate support type, people with multi-frail had lower educational level, poor nutritional management status and were less likely to participate in labor market. People in psychologically frail type were more likely to be male, to live in big cities rather than middle and small cities, and less likely to smoke. Based on these results, our results showed the multifaceted concept of frailty among Korean elderly people and we suggested several implications for preventing frail process.

• Journal of the korean Society of Automotive Engineers
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• v.5 no.4
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• pp.34-40
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• 1983

점탄성유체 유동에 대하여 일반적으로 U.C맥스웰 모델 또는 올드로이드 B모델이 사용되지만 이러한 모델들은-매우 큰 전단율 영역인 윤활문제에서 믿기 힘든-수직응력의 크기가 전단율의 제곱에 비례함을 나타내므로, 본 연구에서는 수직응력 계수들 (.psi.,.psi.$_{2}$)이 가정될 수 있는 Criminale-Ericksen-Filbey모델이 사용되었다. 2차 수직응력계수는 다른 문제들에서와 같이 무시되었으며 Weissenberg수가 포함된 특수레이놀즈식이 유도되었다. 이 모델의 속도분포는 -2차원 약한 점탄성 유체에 대하여 증명된 바와 같이-뉴우톤 유체와 같이 가정되었다. 유도된 특수레이놀즈 식은 Weissenberg수를 1까지 계산되었으며 그 결과 점탄성유체가 유한저어널 베 어링에서 유리한 것으로 나타났지만 그 차가 미소하여 일반베어링에서 점탄성 윤활유의 영향이 무시됨을 보였다.

• Journal of the Korean Chemical Society
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• v.46 no.6
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• pp.569-580
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• 2002

The purpose of this study was to analyze the problem-solving process of student's compensation con-cept.For this purpose, verbal interactions during activities were audio-taped, transcribed, and analyzed. And classroom observation and interview with students were carried out. Students who were superior in mathematical operations tended to explain compensation concept using proportionality. On the other hand, students who had low level of conservation concept can not connect 'relation of two variables' with 'conservation of equilibrium' at the formation process of com-pensation concept. Students who succeed in the formation of compensation concept showed high level of conservation concept. To promote the formation of compensation concept, it is necessary that how to develop proportional concept and conservation concept as closely related with compensation concept should be studied.