• Journal of Science Education
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• v.38 no.3
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• pp.569-584
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• 2014

The Purpose of this study was an analysis of high school student's understanding level about concepts of special relativity through in-depth interview. The 8 participants were 10th grade students in H high school in Ulsan city, who were interviewed and analyzed in the results of the interview about basic concepts of special relativity using achievement checklist in 6 situations(principle of constancy of light velocity, principle of relativity, relativity of simultaneity, garage paradox, rocket paradox). As results of the checklist, the participants showed high achievement in the content level of simple phenomena and simple concepts related to special relativity. But they showed low achievement in the concept level for fundamental understanding of special relativity. As results of the interview, it was found that the participants decided the order of events depending on their intuition and had a difficulty to apply the coordinate system to real situation, even though they mathematically understood it. In addition, some participants who could not understand the inertial coordinate system explained paradoxes of relativity depending on their intuition and had learner's chaos. Finally, though high school students usually being in formal operational stage, some students had difficulty to draw phenomena of space and time in two dimensional plane.

• Proceedings of the Korean Vacuum Society Conference
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• 2010.08a
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• pp.38-38
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• 2010

낮은 세기의 레이저와 정지한 전자가 반응하면 전자는 레이저 전기장 세기에 비례하여 가속되며 레이저의 파장과 같은 파장의 빛을 낸다. 반면, 레이저의 세기가 일정 수준을 넘으면 전자의 속도가 빛의 속도에 가까워지게 되어 가속이 둔화되는 현상이 나타나며, 더 이상 전기장의 세기와 가속도가 비례하지 않게 된다. 이러한 비선형적인 전자의 운동이 레이저 기본 파장의 조화파(harmonic)를 발생시키는데, 이를 상대론적 비선형 톰슨 산란(relativistic nonlinear Thomson scattering, RNTS)이라고 한다. 단일 전자를 가정한 경우 RNTS에 의해 아토초($10^{-18}$ 초) 길이의 X선 펄스가 발생하는 것이 시뮬레이션 연구를 통해 잘 알려졌다. [1] 그러나, 실제 실험에서 적용할 수 있는 것은 단일 전자가 아니라 고체, 플라즈마, 전자 빔 등의 전자 덩어리이다. 전자덩어리를 구성하는 각각의 전자가 아토초 펄스를 발생시더라도 각각의 펄스 간에 결맞음(coherence) 조건이 맞지 않으면 아토초 펄스는 발생되지 않는다. 또한, 강한 세기의 펄스를 얻는데도 결맞음은 중요하다. 이 연구에서는 결맞음 조건으로 얇은 타깃에 대한 거울 반사 조건, 즉 레이저가 얇은 타깃에 입사되며 거울의 반사 조건을 만족하는 위치에 검출기(detector)를 위치시키는 방법을 제안하였다. 박막이 충분히 얇을 경우 각각의 전자에 대하여 레이저가 발사되어 타깃에 맞고 검출되기까지의 시간이 거의 일치하게 된다. 거울 반사 조건에 의한 아토초 펄스 발생은 particle-in-cell 방법을 통한 시뮬레이션으로 검증되었다. 결맞음 조건을 위한 얇은 타깃으로는 박막과 나노선 배열(nanowire array)을 사용하였다. 전자들 간의 쿨롱(Coulomb) 힘은 결맞음이 유지되는 것을 방해하는데, 박막에 비해 나노선 배열이 쿨롱 힘의 영향을 적게 받기 때문에 결맞음이 더 잘 유지된다.

• Journal of the Korea Institute of Information Security & Cryptology
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• v.22 no.5
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• pp.1039-1055
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• 2012

It is required for us to enhance the national cyber capability as the worldwide countries have been doing effort to strengthen their cyber capabilities. However, we are encountering the difficulty in estimating national cyber capability due to the absence of any cyber capability assessment methodology. This paper presents the national cyber capability assessment methodology which is used for settle up national cyber policy. We also introduce the result of five major nations(US, China, Japan, Russia, Korea)' cyber capability assessment using the proposed methodology. The methodology is developed using open data and includes three areas; base capability, attack capability and defense capability. The assessment result shows the in the order of US, China, Korea, Russia, Japan. As the analysis of that result, in order to enhance the our cyber capability, we recommend that first, cyber budget and human resources for the base capability should be more invested, second, the strategy for attack capability enhancement is strongly required and lastly, the patch ratio and security monitoring level should be upgraded.

• Journal of the Korean earth science society
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• v.23 no.4
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• pp.309-323
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• 2002

This qualitative study investigated preservice teachers' understandings of the ontology and epistemology underlying constructivist notions of learning through four in-depth interviews. Of the sixteen participants in a larger study, five significantly changed ontological and epistemological beliefs and eleven did not. This study focused on these eleven teachers who have hardly changed their philosophical beliefs throughout the teacher education program. Ten teachers who consistently maintained the scientific realist beliefs were presented as a composite case (Young's case). Among the eleven teachers, there was one outlier who had consistently maintained an idealist and relativist epistemological position from the beginning of the study and was subjected to another case analysis (Ben's case). These cases corroborated the assertion that each individual's deeply entrenched ontological and epistemological beliefs are very hard to change. For researchers, this study offers insights into the reasons that preservice teachers give for non-changes in their thinking about learning to teach. The study also examines preservice teachers' perceived constraints in implementing their ideal pedagogies and the influence of the teacher education program on their pedagogical beliefs changes. The benefits and influences of the M.Ed. program's theoretical coursework and the field experiences on these teachers' learning-to-teach experiences are addressed with rich data. The implications for teacher educators as well as for the instructional practices of preservice teacher education programs are discussed. This research emphasize necessity of the field-based teacher education program and the need of empowering experienced school teachers as teacher educators in teacher preparation and professional development.

• KIPS Transactions on Computer and Communication Systems
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• v.9 no.11
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• pp.265-272
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• 2020

In the research of brain computer interface (BCI) technology, one of the big problems encountered is how to deal with some people as called the BCI-illiteracy group who could not control the BCI system. To approach this problem efficiently, we investigated a kind of spectral EEG characteristics in the prior resting state in association with BCI performance in the following BCI tasks. First, spectral powers of EEG signals in the resting state with both eyes-open and eyes-closed conditions were respectively extracted. Second, a convolution neural network (CNN) based binary classifier discriminated the binary motor imagery intention in the BCI task. Both the linear correlation and binary prediction methods confirmed that the spectral EEG characteristics in the prior resting state were highly related to the BCI performance in the following BCI task. Linear regression analysis demonstrated that the relative ratio of the 13 Hz below and above the spectral power in the resting state with only eyes-open, not eyes-closed condition, were significantly correlated with the quantified metrics of the BCI performance (r=0.544). A binary classifier based on the linear regression with L1 regularization method was able to discriminate the high-performance group and low-performance group in the following BCI task by using the spectral-based EEG features in the precedent resting state (AUC=0.817). These results strongly support that the spectral EEG characteristics in the frontal regions during the resting state with eyes-open condition should be used as a good predictor of the following BCI task performance.

• Journal of the Korean Institute of Traditional Landscape Architecture
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• v.33 no.4
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• pp.166-175
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• 2015

Nowadays, in the European countries, landscape is spoken of its importance as often as environment, by those who are engaged in such fields as politics, administration, research and civil society. In Korea, while recognizing such an international trend, academics and administrators have made a series of efforts to reflect landscape concept on a variety of policies. However, it is recognized that the effects of these policies have not been satisfactory. Under these circumstances, this paper aims to examine the complex values and multiple meanings in the landscape, which have been discussed by landscape experts in the European countries. Then, it aims to the explore the future direction of policy and research on the landscape to be pursued in Korea, where there is relatively less interest in the issues of landscape. It is argued that landscape should be approached and understood from a holistic perspective, because it is a very complex concept with multiple meanings that have been coined differently depending on the situation. All the academic fields, involved in the landscape research, should try in co-operation to develop the comprehensive approach rather than the inter- and multi-disciplinary approach to the landscape study. In Korea, moreover, it is also necessary in the legislation to recognize the fact that degradation and retreat in the quality of landscape would make a negative effect on the quality of human daily life. Natural and cultural heritages contained in the rural landscape are also now in danger of disappearing. These heritages, therefore, should become an important subject for research and policy on landscape before the countryside is completely evacuated after the aging population die out. To make this happen, it is very urgent that evaluation and classification of landscape character should be undertaken from the holistic perspective, which is equipped with a methodology overcoming as well as encompassing the boundaries of academic fields. It is also equally very urgent that education on landscape should be provided to the politicians, citizens and students as well as the officials dealing with landscape matters. Finally, government should strive to make the landscape concept penetrate deeply as well as widely into the spatial planning and legislation process while designing and implementing a comprehensive landscape policy at the national level.