• School Mathematics
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• v.11 no.1
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• pp.17-37
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• 2009

Concept and model of multiplication is not single. Concepts of multiplication can be classified into three cases: repeated addition, times idea, pairs set. Models of multiplication can be classified into four cases: measurement, rectangular pattern, combinatorial problem, number line. Among diverse cases of multiplication's concept and model, which case does elementary mathematics education lay stress on? This question is a controvertible didactical point. In this thesis, (1) mathematical and didactical analysis of multiplication's concept and model is performed, (2) a concrete program of teaching multiplication which is based on times idea is contrived, (3) With this new program, the teaching experiment is performed and its result is analyzed. Through this study, I obtained the following results and suggestions. First, the degree of testee's understanding of times idea is not high. Secondly, a sort of test problem which asks the testee to find times value is more easy than the one to find multiplicative resulting value. Thirdly, combinatorial problem can be handled as an application of multiplication. Fourthly, the degree of testee's understanding of repeated addition is high. In conclusion, I observe the fact that this new program which is based on times idea could be a alternative program of teaching multiplication which could complement the traditional method.

• Journal of Science Education
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• v.44 no.3
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• pp.300-317
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• 2020

The purpose of this study is to suggest improvements in the science concepts and inquiry activities presented in the earth science section in the 2015 revised curriculum elementary science textbooks. For this study, two science educator and three elementary school teachers developed a survey questionnaire to investigate science concepts, inquiry activities, and suggest improvements. The survey was conducted two times, and 30 elementary school teachers and three earth science professors (geology, meteorology, astronomy) participated in the survey. As a result, it was investigated that eight concepts in the solid section, three concepts in the fluid section, and one concept in universe and integration section contained misconceptions. It was investigated that the content of inquiry activity needs to be supplemented, with seven elements in solid section, three elements in fluid section, and one in the universe and integration section. According to the research results, if the textbook is revised, it is necessary to accurately confirm the science concepts or content of inquiry activities. Also in the case of science concepts presented in textbooks, it will be necessary to consider not only the scope and sequence of contents but also the process of learning progression.

• The Journal of the Institute of Internet, Broadcasting and Communication
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• v.10 no.6
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• pp.195-200
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• 2010

This paper introduces a new mobile music service, private music on demand (PMOD), which is implemented by mobile DJ in wireless and wired networks. The newly introduced PMOD service is based on the concept that users can have music services at anytime and by any form they want. The mobile DJ implementing PMOD services, therefore, enables users to do more than simply listening music through networks.

• Bulletin of the Society of Naval Architects of Korea
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• v.32 no.1
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• pp.28-31
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• 1995

워터제트(Waterjet) 추진의 개념은 선박용 스크류 프로펠러 만큼이나 오래 되었지만, 1960년대 까지도 많은 이용이 없었다. 왜냐하면 스크류 프로펠러가 더 간단하고 가벼우면서 훨씬 더 효 율적인 추진도구로 간주되어 왔기 때문이었다. 그러나 최근 수년 사이에 워터제트로 추진되는 세계적인 선박들 및 제작회사들의 수가 괄목할만한 증가를 보이고 있고, 선진국의 초고속선 개 발과 관령하여 워터제트 추진방식에 대한 새로운 시각에서의 연구가 활발히 진행되어지고 있 다[1]. 21세기 해상교통수당을 선도할 수 있으리라 판단되고 있는 초고속선 개발 연구를 수행하고 있는 선박·해양공학연구센터에서도 초고속선용 추진 장치로서 워터제트 추진기를 선택하였었 다[2]. 이러한 대표적인 이유로서는 종래의 일반적인 선박용 스크류 프로펠러로서는 고속 추진에 한계를 가지고 있는 반면, 워터제트 추진방식은 각 요소들의 최적 설계를 통해 고속에서의 추 진효율 향상을 꾀할 수 있기 때문이었다. 선진국에서는 이미 이러한 워터제트 추진에 대한 성 능해석 기법이 정립되어 있고[3], 중.소형 워터제트 추진기 제작을 통한 경험을 바탕으로 대출력 워터제트 추진기 개발도 가능한 단계이다[4]. 그러나 국내에서는 이에 대한 연구가 거의 없어 외국의 기술에 의존하고 있는 실정이다. 본 고에서는 워터제트 추진기의 기본적인 개념과 당 연구센타에서 수행하고 있는 모형시험법 개발 연구의 일부를 소개하고자 한다.

• Journal of the Society of Naval Architects of Korea
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• v.48 no.1
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• pp.84-92
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• 2011

This paper presents the primary conceptual design results of Smart Harbor. As the world trade becomes active, so container cargo volume is increasing constantly. Since the coming of very large container ships, It's necessary that a harbor handles many containers more than before. Therefore, we designed the new concept of SMART HARBOR which overcomes land site problem for port expansion and geographic constraints of very large container ships in harbor.

• The Transactions of the Korea Information Processing Society
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• v.3 no.3
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• pp.471-477
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• 1996

An image edge detection method based on the toll set concept is proposed. Initially the edge structure is established for an image following human perception n model. Then toll set membership values are computed and the toll set intersection and union operators are applied to them. The final toll set membership values are normalized to get the vagueness degrees and the thresholding operation based on entropy concept is performed on them to determine the edge of an image.

• Journal of the Korean Institute of Landscape Architecture
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• v.38 no.5
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• pp.53-63
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• 2010

The purposes of this study are to classify the characteristics of parks by park use patterns and the understanding of design concepts and to analyze the difference of cognition of design concept between designers and park users. The literature studies and surveys were performed to analyze park use patterns and understanding of design concepts for Seoul Forest Park, Yeouido Park and Seonyudo Park. Several statistical methods have been used such as descriptive analysis and importance-performance analysis. The results of this research are as follows. As the results of an analysis of park use patterns, Seonyudo Park may he qualified as an urban landmark park, while Yeouido Park can he classified as a neighborhood park. Seoul Forest Park bas characteristics of both. Second, the higher frequency of visits generally leads higher preference. Third, the overall cognition of the design concepts of parks shows 3.51 on average, which is comparatively high. The functional concepts are better transmitted to the users compared to abstract concepts. The cognition of the design concepts of each park are evaluated in the higher order of Seonyudo Park, Seoul Forest Park and Yeouido Park. Fourth, the cognition levels of detailed design concepts for each place are lower than the overall design concepts. On the other hand, levels of satisfaction are increased after the design concepts are noticed. It would he necessary make the effort to give information about the design concept of each space. The results of this study are limited in that it covers only three parks in Seoul, and did not consider seasonal variables. Nevertheless, this study may he significant in that it dealt with the cognition of design concepts for urban parks, focusing on the difference between designers and visitors.

• Journal of The Korean Association For Science Education
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• v.21 no.4
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• pp.648-657
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• 2001

Using the concepts on the need of existence of living things, we investigate students' concepts on interdependence concepts between living things. The purposes of this study are to identify components of conceptual ecologies influencing on students' concepts and to describe the relations between those components and their concepts. The subjects of this study are 4 boys, 2 girls in the 3rd grade of middle school. The sources of data used in this study include a questionnaire, interviews and observation of the discussion class. Then, all data collected through each methods are compared and summarized in the relation to the questions of research. As a conclusion, it reveals that students' concepts are connected with several cognitive or affective components. Especially, the major components influencing on students' concepts are their metaphysical beliefs, conceptions includes other fields. These components function as constraints. Given these results, a teacher who want to teach a new concept to students should consider their characteristics and the components of conceptual ecology.

• Tunnel and Underground Space
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• v.15 no.4 s.57
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• pp.305-315
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• 2005

DDA (Discontinuous Deformation Anlaysis) is one of the latest numerical analysis which has merits of both FEM and DEM. In this research a new edge-to-edge contact algorithm was applied on DDA. With adoption of new edge-to-edge contact state definition, sub-algorithm was improved about open-close iteration, contact state judge, contact detecting, and friction forces acting on joints. Newly applied DDA was verified based on two different cases. The DDA results show good agreement with numerically predicted one.

• Journal of the Korean Chemical Society
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• v.52 no.1
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• pp.84-95
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• 2008

In this study, preconceptions held by chemistry major secondary school science teachers were searched in relation to explanations of water evaporation phenomena with phase equilibrium diagrams. 25 chemistry major science teachers were selected to complete questionnaires developed in this study and 6 among of them were selected to participate in follow-up interviews. Among these, 10 participants were selected for an evaluation of the change of their preconceptions through lessons developed in this study. From the results, it was found that many teachers believed that the phase equilibrium diagram could not explain water evaporation phenomena. They also thought that there was no relation between vapor pressure and the vertical axis of the phase equilibrium diagram. However, after the lessons in earth science, they recognized that the vapor pressure curve of the phase equilibrium diagram could be explained by adopting a saturated vapor curve. Because they had known the process of application the conceptions of saturated situation, nonsaturated situation, process of equilibrium movement in saturated vapor curve. They could understand natural phenomena such as evaporation with the phase equilibrium diagram through a change in their conceptions as guided from science lessons integrating earth science and chemistry.