• The Bulletin of The Korean Astronomical Society
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• v.45 no.1
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• pp.52.2-52.2
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• 2020

At quasi-perpendicular shocks in the high-�� (��=Pgas/Pmag~100) intracluster medium (ICM), various microinstabilities occur by the temperature anisotropies and/or drift motions of plasma. In the downstream, the Alfvén ion cyclotron instability (AIC) due to the ion temperature anisotropy (Ti⊥>Ti║) is triggered by shock-reflected ions, the whistler instability (WI) is driven by the electron temperature anisotropy (Te⊥>Te║) as a consequence of the shock compression of magnetic fields, and the mirror instability is generated due to the ion and/or electron temperature anisotropy. At the shock foot, the modified two stream instability (MTSI) is possibly excited by the cross-field drift between ions and electrons. In the upstream, electron firehose instability (EFI) is driven by the electron temperature anisotropy or the relative drift between incoming and reflected electrons. These microinstabilities play important roles in the particle acceleration in ICM shocks, so understanding of the microinstabilities and the resultant plasma waves is essential. In this study, based on a linear stability analysis, the basic properties of the microinstabilities in ICM shocks and the ion/electron scale fluctuations are described. We then discuss the implication of our work on the electron pre-acceleration in ICM shocks.

• Journal of The Korean Association For Science Education
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• v.27 no.6
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• pp.497-509
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• 2007

Among many remedial approaches against the increasing unfavorableness toward school science, one of the prevalent findings studied by affective experts is that students' achievement in science and their attitude toward it has a relatively weak relationship. In contrast, cognitive experts assert that the conceptual change involves more than cognitive aspects, and may be influenced by affective factors such as beliefs, motivation, learning attitudes, and sociocultural contexts. The latter regards continuous conceptual change as leading to better student understanding of science with variables of students' attitude toward science. As an initial step toward illuminating the affective-cognitive learning aspects of science, the purpose of this study is to develop an instrument for analyzing the relationship between students' conceptual understanding and affective factors. Cognitive questionnaires from the database of distribution in students' misconceptions of physics (DMP project), and affective questionnaires from the Relevance of Science Education (ROSE project) are integrated into our instrument. The respondents are high school students in Okayama prefecture, Japan. Through the pilot test, the authors integrated attitude toward science (AS) and interest inventory (II) from ROSE into cognitive understanding (CD) from DMP. Statistical methodologies such as factor analysis and item total correlation theoretically discerned the effective sixty-three items from the two original item pools. Having discussed two validity issues, the authors suggest ongoing research associated with our affective-cognitive research perspective.

• The Bulletin of The Korean Astronomical Society
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• v.35 no.2
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• pp.36.2-36.2
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• 2010

CQUEAN (Camera fo QUasars in EArly uNiverse) is a newly developed camera by CEOU for the 2.1m telescope at the McDonald Observatory, Texas, USA. We report the early science results from the commissioning run of CQUEAN which include the observations of the gamma-ray burst (GRB) afterglows and quasars at z ~ 5.5. Although the data were originally taken to test the instrument performance, the results are already very encouraging. We uncovered GRB afterglows at z = 0.8 - 1.4, with our data being used for the international collaboration research to understand the nature of GRBs. The unique filter sets we employed are providing the data which are effective for selecting quasars at z ~ 5.5. The special aspects of CQUEAN - high sensitivity at 0.8-1.1 ${\mu}m$ and fast readouts - will allow us to produce many interesting through surveys of high redshift quasars and fast follow-up of transient objects such as GRBs and exoplanets in future.

• Journal of The Korean Association For Science Education
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• v.19 no.1
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• pp.78-90
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• 1999

This study investigated the high school students' and science teachers' understanding of idealization involved in the physics experiment. Major research questions are as follows: (1) what kind of ideal conditions do subjects identify from the presented experimental context? (2) do subjects think how well ideal conditions are satisfied with the experiment? (3) how well do subjects expect the effect of idealization on the experimental result? (3) what kind of view point do science teachers have about the ideal condition involved in the experiment? A total of 85 subjects were given 6 questions related with the research questions I. 2. and 3. with simple experiment about the brightness of the bulbs connected with parallel to the battery. And another 4 questions for the forth research question were given to 42 science teachers. Subjects' responses were summarized and used to draw the implications for the teaching of physics experiment.

• Journal of The Korean Association For Science Education
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• v.31 no.6
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• pp.848-863
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• 2011

The purpose of this study is to explore how high school physics teachers perceive and understand fundamental physical constants as well as how they explain them and what methods they currently use in class. This study developed a questionnaire survey to recognize physics teachers' level of understanding of fundamental physical constants, which were measured by many scientists and contributed the to generation and improvement of scientific theories. Those questionnaire surveys were conducted among 130 high school physics teachers in Seoul, Gyeonggi, and Incheon. Among them, 124 participated in the survey and six were interviewed. The content of the survey consists of three parts: (i) basic questions about teachers, (ii) questions to measure the teachers' understanding of fundamental physical constants, and (iii) questions about the educational use of fundamental physical constants. The survey was distributed via e-mail, and respondents submitted their responses via e-mail as well. Semi-structured interviews were conducted for 30 minutes each, and all interviews were recorded, transcribed and analyzed twice.

• The Bulletin of The Korean Astronomical Society
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• v.38 no.2
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• pp.68.2-68.2
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• 2013

Camera for QUasars in EArly uNiverse (CQUEAN) is an optical CCD camera system made by Center for Exploration of the Origin of the Universe (CEOU). CQUEAN is developed for follow-up observation of red sources such as high-redshift quasar candidates ($z{\geq}5$), gamma-ray bursts (GRB), brown dwarfs and young stellar objects. The CQUEAN is composed of a science camera with deep-depletion CCD chip which is sensitive at around $1{\mu}m$, a set of custom-made wide-band filters for detection of quasar candidates at z~5, and a guide camera. A focal reducer was developed to secure $4.8^{\prime}{\times}4.8^{\prime}$ field of view, and an in-house user software for efficient data acquisition. CQUEAN was attached to 2.1m Otto Struve Telescope in McDonald Observatory, USA, in August 2010. About 1000 quasar candidates including 3 confirmed with follow-up spectroscopy, have been observed so far, and many high-z galaxy cluster candidates, GRBs and supernovae were also observed. And monitoring of HBC 722, a young stellar object, is under way since 2011. Further enhancement of CQUEAN including the introduction of narrow-band filters is planned.

• Journal of the Korean Society of Fisheries and Ocean Technology
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• v.43 no.2
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• pp.87-100
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• 2007

This study was carried out to offer fundamental data for improving the fishing efficiency of the Danish seine. The net height and the shape in the water was measured to analyze the efficiency of the existing Danish seine. And then, an improved fishing gear was developed based on the results and was tested in the field. Measuring devices were attached on center of a ground rope and a head rope. The net height is the spread distance between the ground rope and the head rope, which was measured on the different ratio of buoyancy. The results are obtained as follows. The net height estimated from the design plan of horizontal hanging ratio 0.40 in the existing Danish seine A and B estimated both 4.94m. The net height of the existing Danish seine A and B was respectively 1.8m and 2.3m, which form 36.4% and 46.2% of the net height estimated from the design plan. Buoyancy was changed as 79.5% and 96.2% relative to the sinking force in the existing Danish seine. The net height of 79.5% was 3.95m which increased to 80% of the estimated net height. The other shows the same result with the first case. It is not necessarily that the high buoyancy/sinking force ratio make the high net height, 80% is adequate as the buoyancy/sinking force ratio. In case of the improved Danish seine, the mean net height was about 5.0m, means 58.3% of estimated net height 8.58m.

• The Bulletin of The Korean Astronomical Society
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• v.43 no.1
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• pp.68.4-69
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• 2018

GMACS is one of the instruments for the Giant Magellan Telescope (GMT) which will provide wide field, multi-object, moderate resolution spectroscopy of faint targets. KHU (Kyung Hee University) is in charge of control software of GMACS. As a first step, the Slit Mask Exchange Mechanism Prototype (SMEM-P) will be used as a preliminary example to make development process between electronics and high level software. Recently, we have developed a sample program to communicate with low level devices via EtherCAT. It is expected to be a mockup design for software and control system of GMACS. In this poster, we show the development process and test operation results of control software for SMEM-P.

• Proceedings of the Korean Vacuum Society Conference
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• 2013.08a
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• pp.132.2-132.2
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• 2013

Electrons in graphene make ballistic transport with very high mobility (${\sim}2{\times}105 $cm2V-1s-1), which holds promises for applications in fast electronic devices. However, such expectations have been hampered by the semi-metallicity or zero bandgap of graphene, which makes it impossible to completely turn off graphene transistor devices. Here, we report the observations of local bandgap modulations in Moir$\acute{e}$ patterned graphene on metal substrates using scanning tunneling microscopy and spectroscopy. The Moir$\acute{e}$ patterned graphene was made by combinations of self-assembly processes, and they showed additional electronic states that could be interpreted as sub-band states. Our experimental observations could be explained with orbital transitions of carbon atoms from sp2 to sp3, as supported by our density functional theory calculation results. Our findings will add new poweful components for device applications.

• Nuclear Engineering and Technology
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• v.52 no.11
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• pp.2535-2542
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• 2020

To understand the fundamental parameters of Alvand tokamak, A Rogowski coil with an active integrator was designed and constructed. Considering the characteristics of the Alvand tokamak, the structural and electrical parameters affecting the sensor function, were designed. Calibration was performed directly in the presence of plasma. The sensor has a high resistance against interference of external magnetic fields. Plasma current was measured in various experiments. Based on the plasma current profile and loop voltage signal, the time evolution of plasma discharge was investigated and plasma behavior was analyzed. Alvand tokamak discharge was divided into several regions that represents different physical phenomena in the plasma. During the plasma discharge time, plasma had significant changes and its characteristic was not uniform. To understand the plasma behavior in each of the phases, the Rogowski sensor should have sufficient time resolution. The Rogowski sensor with a frequency up to 15 kHz was appropriate for this purpose.