• Current Optics and Photonics
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• v.7 no.4
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• pp.435-442
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• 2023

These days, the size of a reflective telescope has been increasing for astronomical observation. An additional optical system usually assists a large ground telescope for image analysis or the compensation of air turbulence. To guide collimated light to the external optical system through a designated path, a coudé mirror is usually adopted. Including a collimator, a coudé mirror of a ground telescope is affected by gravity, depending on the telescope's pointing direction. The mirror surface is deformed by the weight of the mirror itself and its mount, which deteriorates the optical performance. In this research, we propose an optimization method for the coudé mirror assembly for a 1-m class ground telescope that minimizes the gravitational surface error (SFE). Here the mirror support positions and the sizes of the mount structure are optimized using finite element analysis and the response surface optimization method in both the horizontal and vertical directions, considering the telescope's altitude angle. Throughout the whole design process, the coefficients of the Zernike polynomials are calculated and their amplitude changes are monitored to determine the optimal design parameters. At the same time, the design budgets for the thermal SFE and the mass and size of the mount are reflected in the study.

• Journal of The Korean Association For Science Education
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• v.39 no.2
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• pp.173-186
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• 2019

The purpose of this study is to design and apply a pilot inquiry experiment focusing on the epistemological issues of scientific activities, and derive educational implications by analyzing experimental activities and reflective discussions. Three graduate students who major in science education participated in the study voluntarily. Participants showed the characteristics of stable enquiry in Experiment 1. However, the small but continuous changes in Experiment 2 led the experiment to a phase of fluid enquiry seeking new theories. Participants mobilized various resources, proposed new hypotheses, and models and requested additional experiments to verify them. In the process of reflective discussions, the participants led to the following three epistemological issues. First, at the beginning of the experiment, their observations were theoretically dependent. Second, when the observations were no longer coherent with theory, they face a crisis, and the adjustment of observation and theory proceeds. Third, stable enquiry and fluid enquiry are performed according to the relationship between observation and theory. The educational implications of school science inquiry based on the above process and results are as follows: First, this study shows that fluid enquiry can follow stable enquiry naturally, and examples of the activities are presented together. Second, in this study, it was confirmed that participants could draw up epistemological issues based on their experiences through reflective discussions following inquiry.

• Korean Journal of Child Studies
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• v.33 no.3
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• pp.149-175
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• 2012

This study is designed to positively transform a teacher's emotional state whilst teaching their classes and be able to create happier lessons for preschool children. To do this, a teacher needs to reflect upon current problems and take steps to deal with them. The data for this study was collected from participatory observation and in-depth interviews, making use of photos, a reflective teacher's journal and interview records from Mar. 28, 2011 through Oct. 7, 2011. The problems identified were, (1) teacher centered classes, (2) a daily routine filled with large group activities, (3) disruptive students, and (4) repetitiveness. The routes to greater classroom "happiness" are (1) rearranging seats, (2) "story sharing activities" in small groups, (3) making a separate "story sharing activity" area, (4) using small groups instead of large groups, (5) changing the daily routine. The role of the teacher in finding greater "happiness" are (1) meaningful, 'real observation', (2) discovering genuine change from small points, (3) power sharing, and (4) growing and developing with children.

• Journal of the Korean School Mathematics Society
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• v.8 no.4
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• pp.495-508
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• 2005

This study focused on what philosophy of education based on theory of Dewey has to be involved in teacher professional development program. In this view, an attempt was made to identify characteristics and ultimate goal of professional development program. Finally, this paper also discussed the design and the process of the professional development program based on the principles of reflective thinking and psychological observation by Dewey in order to connect theory with practice as a model which is for conducting professional development program for a group of mathematics teachers.

• Journal of the Optical Society of Korea
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• v.9 no.2
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• pp.68-73
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• 2005

When aligning catoptric or catadioptric telescopes for space cameras, it is difficult to align precisely if the field of view is large or there are several reflective surfaces. The quantitative knowledge of mirror misalignments greatly helps align a misaligned telescope precisely, and also reduce the alignment time. This paper describes a generalized reverse-optimization alignment solution algorithm using Zernike sensitivity, and proposes the minimum number of fields to take interferograms. This method was successfully applied on a Cassegrain telescope design for Earth observation from space with arbitrary misalignments and a model including some primary mirror deformation.

• Journal of Science Education
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• v.39 no.3
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• pp.389-403
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• 2015

The goal of this study were to look into the elementary school teacher's experience in the self-review of science class and analyze the changes of reflection level revealed in it. This study was a qualitative example research where two elementary school teachers participated and performed self-review via reflective writings regarding their science classes. Both teachers showed changes in aspect and frequency of review to a certain extend by reflective writings based on their class experience and the educational settings they are at. They all revealed a high level of changes on reflection by the feedback from the class reviews. Affirmative changes of cognition on science class and the perception of factors affecting the practice of the class such as understanding students, class observation of the peer teachers et al. contributed to the elevation of reflection level by continuously adjusting and complementing the practical knowledge through the reflection during or after the class.

• Journal of the Korean Society of Surveying, Geodesy, Photogrammetry and Cartography
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• v.38 no.6
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• pp.717-723
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• 2020

Determination of local tie vectors between the space geodetic techniques such as VLBI (Very Long Baseline Interferometer), SLR (Satellite Laser Ranging), DORIS (Doppler Orbit determination and Radiopositioning Integrated on Satellite), GNSS (Global Navigation Satellite System) is essential for combination of ITRF (International Terrestrial Reference Frame). Therefore, it is required to compute IVP (Invariant Point) position of each space geodetic technique with high accuracy. In this study, we have computed Sejong VLBI IVP position by using updated mathematical model for adjustment computation so that the improvement on efficiency and reliability in computation are obtained. The measurements used for this study are the coordinates of reflective targets on the VLBI antenna and their accuracies are set to 1.5 mm for each component. The results show that the position of VLBI IVP together with its standard deviation is successfully estimated when they are compared with those of the results from previous study. However, it is notable that additional terrestrial surveying should be performed so that realistic measurement errors are incorporated in the adjustment computation process.

• Journal of Science Education
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• v.33 no.2
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• pp.184-192
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• 2009

Understanding about the Nature of Science (NOS) is element of scientific literacy. Its importance is emphasized, especially understanding about NOS was presented as goal of science education on the fifth curriculum in Korea. Attempt of teaching NOS has been continuous in school, that was limited by method of using History of Science. Except method of using History of Science, Experimenting is appropriate for method of teaching NOS. We expected that is effective to apply reflective approach method for understanding the NOS and composite lesson to emphasize reflection and discussion to general experiment class in the school. We applied experiment class to emphasize reflection and discussion to second grade students in the middle school and researched whether positive reflection and discussion is helpful understanding the NOS in science experiment class or not, through questionnaire about NOS and analysis of observation and interview. As a result, experiment class to emphasize reflection and discussion was effective for scientific inquiry skills and sociality of scientific inquiry, particularly for relation observation with deduction and possibility of variable analysis to experiment result. Therefore, experiment class to emphasize reflection and discussion is effective for understanding the NOS.

• Korean Journal of Optics and Photonics
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• v.33 no.2
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• pp.74-83
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• 2022

The entire process, from the raw material to the final system qualification test, has been developed to fabricate a large-diameter, lightweight reflective-telescope system for a satellite observation. The telescope with 3 anastigmatic mirrors has an aperture of 700 mm and a total mass of 66 kg. We baked a silicon carbide substrate body from a carbon preform using a reaction sintering method, and tested the structural and chemical properties, surface conditions, and crystal structure of the body. We developed the polishing and coating methods considering the mechanical and chemical properties of the silicon carbide (SiC) body, and we utilized a chemical-vapor-deposition method to deposit a dense SiC thin film more than 170 ㎛ thick on the mirror's surface, to preserve a highly reflective surface with excellent optical performance. After we made the SiC mirrors, we measured the wave-front error for various optical fields by assembling and aligning three mirrors and support structures. We conducted major space-environment tests for the components and final assembly by temperature-cycling tests and vibration-shock tests, in accordance with the qualifications for the space and launch environment. We confirmed that the final telescope achieves all of the target performance criteria.

• Journal of Information Display
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• v.2 no.2
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• pp.52-60
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• 2001

The electrical and mechanical properties in indium-tin-oxide films deposited on polymer substrate were examined. The materials of substrates were polyethersulfone (PES) which have gas barrier layer and anti-glare coating for plastic-based devices. The experiments were performed by rf-magnetron sputtering using a special instrument and buffer layers. Therefore, we obtained a very flat polymer substrate deposited ITO film and investigated the effects of buffer layers, and the instrument. Moreover, the influences of an oxygen partial pressure and post-deposition annealing in ITO films deposited on polymer substrates were clarified. X-ray diffraction observation, measurement of electrical property, and optical microscope observation were performed for the investigation of micro-structure and electro-mechanical properties, and they indicated that as-deposited ITO thin films are amorphous and become quasi-crystalline after adjusting oxygen partial pressure and thermal annealing above $180^{\circ}C$. As a result, we obtained 20-25 ${\Omega}/sq$ of ITO films with good transmittance (above 80 %) of oxygen contents with under 0.2 % and vacuum annealing. Furthermore, using organic buffer layer, we obtained ITO films which have a rather high electrical resistance (40-45 ${\Omega}/sq$) but have improved optical (more than 85 %) and mechanical characteristics compared to the counterparts. Consequently, a prototype reflective color plastic film LCD was fabricated using the PES polymer substrates to confirm whether the ITO films could be realized in accordance with our experimental results.