• Journal of The Korean Association For Science Education
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• v.36 no.6
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• pp.851-866
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• 2016

The purpose of this study is to investigate pre-service elementary teachers' views of the law of action-reaction by examining their degrees of understanding and Typically-Perceived-Situations (TPS). Data were collected from 177 Grade 3 pre-service elementary teachers. The results of analyzing these data show: First, the participants did not sufficiently understand about the law of action-reaction, and their degrees of understanding were different depending on the situation provided in the questionnaire. Second, in relation to the TPSs of the law of action-reaction, the participants thought of irrelevant situations to the law of action-reaction such as "a situation generated by inertia" as well as commonly relevant ones such as "a person pushing a wall", and had somewhat biased TPSs in terms of 'action type' and 'result motion type' of action-reaction. Finally, several suggestions on the science education for promotion of understanding about the law of action-reaction were given.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2009.10a
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• pp.671-677
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• 2009

A reaction wheel is commonly used, as an important actuator, to control the attitude of a satellite. Operation of the reaction wheel plays a role of an excitation source to loading equipment inside the satellite. As requirements for environmental vibration to manifest the performance of precision equipment are getting more stringent, the research for analysis or reduction of unwanted action force in high frequency range when operating the reaction wheel is necessary. In this paper, the procedure to extract input forces and damping of a rotor system of reaction wheel is suggested. The analysis for measured action forces of reaction wheel is accomplished and important higher harmonics of action forces are determined. The input forces and damping of the rotor system are, then, extracted by curve-fitting and a particular solution for input force.

• Transactions of the Korean Society for Noise and Vibration Engineering
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• v.20 no.3
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• pp.263-271
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• 2010

A reaction wheel is commonly used, as an important actuator, to control the attitude of a satellite. Operation of the reaction wheel plays a role of an excitation source to loading equipment inside the satellite. As requirements for environmental vibration to manifest the performance of precision equipment are getting more stringent, the research for analysis or reduction of unwanted action force in high frequency range when operating the reaction wheel is necessary. In this paper, the procedure to extract input forces and damping of a rotor system of reaction wheel is suggested. The analysis for measured action forces of reaction wheel is accomplished and important higher harmonics of action forces are determined. The input forces and damping of the rotor system are, then, extracted by curve-fitting and a particular solution for input force.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.30 no.8
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• pp.126-132
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• 2002

Jitter induced from several payloads on-board satellites degrade the performance of pointing accuracy and attenuate the resolving power of highly-precise camera image such as KOMPSAT II. In this paper, we introduce a micro-vibration measurement technique, analysis of dynamic characteristics, and modeling method for a reaction wheel assembly which is one of the major sources of jitter in satellites and an effective vibration reduction techniques are considered. Based on these techniques, vibration measurement and passive control were performed with an micro-vibration generator which was designed to have similar dynamic performances with an actual reaction wheel assembly above 50Hz.

• Proceedings of the KIPE Conference
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• 2000.07a
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• pp.657-660
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• 2000

전력연구원은 원자로 내부에 적용하기 위한 소형경량의 수중로봇을 개발하기 위한 준비작업으로 자이로를 이용한 수중로봇 조향장치를 개발하고 있다 이장치는 자이로 3개를 조합한 모듈을 서보가 회전시켜 일정한 방향으로 서보의 회전속도에 비례하는 회전토크를 발생하도록 고안되었다 발생된 토크는 작용/반작용의 원리에 의해 서보가 부착되어있는 로봇본체에 작용한다. 이장치를 이용하면 수중로봇의 중심에서 Yaw와 Pitch를 제어할 수 있는 토크가 발생하고 좁은 공간에서 신속한 자세변환이 가능하다 본 고에서는 자이로 조향장치의 구조와 이론적 배경 및 시뮬레이션 결과를 소개한다.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.46 no.9
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• pp.760-766
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• 2018

Due to external disturbances on the satellite, unwanted momentum is accumulated on reaction wheels. To remove this momentum, three magnetic torquers which are installed along the satellite's axes are used. The magnetic torquers generated torque indirectly by interactions with the earth's magnetic field. Thus, during momentum dumping, we should consider both the magnetic torquer and the earth's magnetic field generated on the magnetic torquers at the same time. When low earth orbit satellite with high inclination angle holds nadir pointing attitude, weak earth's magnetic field is generated along the satellite's pitch axis. In this case, one magnetic torquer is overloaded and momentum dumping performance is degraded. This research will review the method to improve the momentum dumping performance by adjusting magnetic torquers arrangement.

• Journal of The Korean Association For Science Education
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• v.27 no.4
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• pp.354-365
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• 2007

The purpose of this study was to understand the undergraduate students' response characteristics by their cognitive conflict levels and result predictions when they were confronted with the learning tasks of action & reaction and electric circuits. The 147 engineering college students who were enrolled at the introductory physics classes were selected as the subjects for this study. The students were grouped by cognitive levels and result predictions. First, in action and reaction task, the trend of suspecting experimental results and finding the reasons was dominant; however, in electric circuits, the trend of accepting the results was dominant. Second, the reasons for the responses on the subcategories of cognitive conflict were different by the level of cognitive conflict. The responses were influenced by students' preexisting knowledge, former experiences, learning habits, learning motivation, and epistemological beliefs, etc. The high conflict group recognized what they do not consider and was positive to reappraise their preconceptions, while the low conflict group showed the tendency of accepting the situation without doubt and low interest on learning physics. In conclusion, students responses showed differences in cognitive conflict levels, result predictions and presented conflict tasks. The research results, especially the response characteristics, suggest that more research on effective cognitive conflict strategies appropriate for different tasks and students' conflicts are necessary for effective physics teaching.

• Journal of The Korean Association For Science Education
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• v.24 no.3
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• pp.596-611
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• 2004

Based on conceptual change theory, cognitive conflict is known as an important factor for conceptual change even though there are still questions about its positive and negative effects on science learning. However there are little research which propose types of meaningful(constructive) cognitive conflict in learning science. The purpose of this study is to find out how are the anxiety types of cognitive conflict to which high school students respond in the action-reaction task, and to reveal what's the characteristic of the explanatory hypothesis according to the anxiety types. The result of this study indicated that first, the characteristics of the anxiety types of the cognitive conflict were classified as eight types. Especially the students who belong to the types of conviction of logical misconception and reasonable modification suggested explanatory hypothesis close to physical nature. On the other hand, the students who showed other types of anxiety except the two types of anxiety suggested temporary supported hypothesis or simple explanatory hypothesis based on students' observation and intuition. Finally we discussed the importance and the implication of the types of anxiety in applying the cognitive conflict strategy to science instruction.

• Journal of The Korean Association For Science Education
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• v.25 no.5
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• pp.571-582
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• 2005

In spite of the importance of cognitive conflict in conceptual change, there has been little research on the characteristics of cognitive conflict in students enrolled at vocational high schools. The purpose of this study was to expose these students' cognitive conflict types and investigate characteristics of cognitive conflict according to the type of cognitive conflict. This paper examined how vocational students' motivational beliefs and epistemological beliefs affect the process of cognitive conflict when students are confronted with an anomalous situation related to the action and reaction concept. Results indicated that many vocational students experienced low levels of cognitive conflict and remained passive during the explanation of anomalous phenomenon or easily desisted any attempt to resolve the conflict situation because of their epistemological belief to depend on the external absolute knowledge of teachers, an extrinsic motivation to choose easier tasks, or reliance on the teachers' reputations. Therefore, Instructors need to recognize these characteristics in order to facilitate vocational students' conceptual change when presenting cognitive conflict tasks.

• Journal of the Korean Institute of Landscape Architecture
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• v.20 no.2
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• pp.127-140
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• 1992

본 연구에서는 Schwartz의 Norm Activation 이론을 도입하여, 실 외휴양지에서 환경훼손행위 관리를 위한 Communicatin 정책의 이론적 배 경으로 도입되어 있는 Prosocial Behavior 이론의 적용성을 실험하였다. 본 연구는 실험실에서 자체개발한 설문지를 통하여 수행되었으며, 미국 Texas A&M 대학교의 남녀 대학생 340명이 참가하였다. 본 실험의 결과 실외휴 양 환경에 대한 훼손행위(Depreciative Behavior)의 인과응보적인 결과를 알려 주는 Information이 실외휴양지 관리에 바람직한 행동의사를 활성화 시키는데 효과적인 반면, 훼손행위에 대한 법적인 제재조치를 설명하는 위 협적 Information은 바람직한 행동의지를 활성화시키지는 못했다. 이용자의 개인적인 성향인자인 사회적 책임감(Social Responsibility)의 고저는 사회 에 바람직한 행동의지의 활성화와 직접적인 관계가 있었다. 그러나, 사회적 책임감의 고저가 환경훼손행위에 대한 인과응보적인 Information이나 제재 조치에 대한 위협적인 Information과의 교호작용은 없었다. 통계학적으로 유의성은 적으나 사회적 책임감이 높은 시험구의 경우 제재조치에 대한 위 협적인 Information에 대한 반작용이 컸으나, 사회적인 책임감이 높은 실험 구의 경우 제재조치에 대한 위협적인 Information이 효과적인 결과를 볼 때, 이용자의 바람직한 행동의지에 역으로 작용하는 Communication정책에 대한 체계적인 연구가 요구된다.