• Bulletin of the Korean Space Science Society
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• 1992.10a
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• pp.20-20
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• 1992

격변 변광성의 일종인 DQ Her형 별(Intermediate Polar Star; IP)이 자기장에서 방출하는 가시광선은 자전주기에 따라 그 강도가 변한다. 이러한 쌍성계에서 백색 왜성인 주성의 주번에 자기력 선을 따라 정도의 물질이 주계열성인 반성으로부터 accretion 된다. 이 물질은 주성 표면에서 충격파로 생긴 X-선원에 의해 reemission 되는 데, 이런 현상적인 모델을 만들어 관측적으로 나타나는 자전주기에 따른 가시광선의 강도 변화를 설명하였다. 이런 결과가 IP 에서 방출되는 가시광선 관측의 분석과 이런 종류의 쌍성계가 가지는 궤도기울기, accretion rate, 공전축에 대한 자전축의 기울기, interaction radius 등의 물리적 상수를 결정하는 데 응용될 수 있음을 보이려고 한다.

• Journal of Science Education
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• v.33 no.2
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• pp.193-206
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• 2009

The purpose of this study was to examine the effect of the consistent presentation of illustrations about the aligning direction of the Axis on the middle school students' acquisition and retention of astronomical concepts. This study was taken using the nonequivalent control-group pretest-posttest design on 116 7th middle school subjects. The same teaching and learning activities were given to both the experimental (n=59) and control groups (n=57) through three lessons. The experimental group was given a consistent presentation of the illustrations about the aligning direction of the Axis, while the control group was given an inconsistent presentation of the same illustrations about aligning direction. Two days after the three lessons, the 1st posttest was administered to compare the statistical difference of mean of both groups, using ANCOVA test. The result of ANCOVA test implicated that the consistent presentation of the illustrations about the aligning direction of the Axis had a positive influence on the experimental group's acquisition of the concepts. The 2nd posttest result for retention effect was given two month later by one-paired t-Test in each group and showed that the method had a positive effect on the experimental group, compared with control group. The results of this study implicated that paying careful attention to using the consistent illustration is highly beneficial for students' meaningful learning on astronomical concepts.

• Publications of The Korean Astronomical Society
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• v.4 no.1
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• pp.31-52
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• 1989

The rotational properties of late-type main sequence stars in the solar neighborhood have been investigated. So rotation periods and stellar radii are determined for 104 field stars, 8 Ursa Major Group stars, and 20 Hyades cluster stars. Most of the rotation periods are derived using the Noyes et al. (1984)'s relation between chromospheric activity and rotation period. Stellar radii are calculated by the Stefan law for the nearby stars within 25 pc from the sun. Rotational velocities at equator are determined by the above rotation periods and stellar radii. Their distribution along the (B-V) color shows an upper boundary and an abrupt drop for the stars in the range of 0.4<(B-V)<0.8, as found from the apparent rotational velocity data. Furthermore, it is apparent that there is an lower boundary of rotational velocity. The inclination of rotation axis to line-of-sight is obtained by comparing the rotational velocity at equator with the apparent rotational velocity given by the analysis of the line profiles. For the field stars, it is found that the inclination has no correlation with the galactic lattitude and follows random distribution.

• Journal of Astronomy and Space Sciences
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• v.16 no.1
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• pp.69-78
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• 1999

We have developed an attitude sensing S/W system, one of modules of Mission Analysis System(MAS), which simulates attitude sensing data as almost the same as the real sensor of a satellite in orbit. When attitude elements($alpha,delta$) of a satellite and positions of Earth, Moon, and Sun are given, the S/W system calculates look angles and dihedral angles of each celestial bodies relative to the rotations axis of the satellite. It consists of two sub-modules : One is ephemeris service module which consider the perturbations of four planets(Venus, Mars, Jupiter, Saturn) for positions of Sun and Moon and 4 $\times$4 earth gravitational potential terms for a satellite's position. The other is attitude simulation module which generates attitude sensing data. Varying the rotational axis of a satellite and it's orbital elements, we simulated the generating attitude sensing data with this S/W system and discussed their results.

• Journal of the Korean Society of Earth Science Education
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• v.10 no.3
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• pp.254-261
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• 2017

This study is to investigate preconception of elementary school students and Belizean elementary school teachers and to devise experiment to understand a cause of seasonal change. An open-ended questionnaire and interviews were conducted for 91 6th grade students who didn't learn seasonal change and 10 Belizean teachers to find out preconception of seasonal change and they were categorized by using inductive analysis. They thought that the Earth's rotation, the distance between the Sun and the Earth, the Earth's revolution, pollution and climate change cause seasonal change. And it found out that these misconceptions come from difficulty in awareness of space and impreciseness of textbooks and books and so on. The experiment was designed to correct inaccurate preconception and to improve lessons of seasonal change. It is to measure a meridian altitude and a length of daytime and nighttime and to compare them. This experiment can help to understand the cause of seasonal change by measuring natural phenomenons like the meridian altitude and the change of length of daytime by model.

• Journal of the Korean earth science society
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• v.28 no.4
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• pp.491-496
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• 2007

We performed R band time-series CCD photometric observations of the 55 Pandora for 2 nights using the 0.6 m telescope equipped with 2K CCD camera at SOAO (Sobaeksan Optical Astronomical Observatory). From the observation we determined its rotation period $P=0.^d2007=4.^h8168$, and maximum amplitude $0.281\;{\pm}\;0.001$. We also derived the pole position ${\lambda}_p(^o)=342$, ${\beta}_p(^o)=64$, and the shape parameter a/b = 1.27, b/c = 1.31 by applying Amplitude-Magnitude method.

• The Bulletin of The Korean Astronomical Society
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• v.35 no.1
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• pp.35.1-35.1
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• 2010

천체는 천구의 북극을 중심으로 지구자전에 의하여 반시계방향으로 일주 운동을 한다. 적도의식 망원경의 최대 장점은 극축이 정확히 맞추어졌다면 접안렌즈 중앙에 적위축 조정으로 정확히 원하는 천체를 위치시키고, 적경축을 지구자전축에 동기 시켜 회전시키면 어떠한 대상이라도 추적이 가능하다. 본 연구에서는 Hardware적으로 적경축 구동을 지구 자전속도에 동기 시키는 제어회로를 설계하였다.

• Journal of Science Education
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• v.44 no.1
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• pp.1-14
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• 2020

In this study, we analyzed the written and drawn explanations of thirty elementary school pre-service teachers in order to examine their perception on the seasonal length of day and night. The main findings are as follows: First, pre-service teachers used the most common term in the description of the texts, such as meridian altitude, axis of rotation, and revolution, and there were more misconceptions in the drawn explanation than in the written explanation. Second, by analyzing the pre-service teachers' perceptions by combining written and drawn explanations, it is possible to detect scientific errors that the distance between the Earth and the Sun is closer when the axis of rotation is tilted in relation to the revolution and seasonal changes due to changes in the orbital radius of the Earth. In addition, there have been types of explanations such as seasonally changing meridian altitudes related to the rotation of the Earth but no change in the location of the Sun. Based on the results of the analysis, we discussed the lack of experience in constructing an explanatory system of specific phenomena using scientific knowledge, lack of observational experiences about natural phenomena, and lack of exposure to other explanatory systems that cause cognitive conflicts. We hope that it will be concrete and practical help to improve the understanding of pre-service teachers in the science domain of primary teacher training program.

• Journal of Korean Elementary Science Education
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• v.41 no.4
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• pp.673-689
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• 2022

To understand seasonal changes it is necessary to understand the relationship between celestial bodies in a three-dimensional space, and to this end, modeling activities in which students directly construct, use, evaluate, and modify three-dimensional models are important. In this study, the process of elementary school students using globes and light bulbs to model Earth's motion in a three-dimensional space as a cause of seasonal changes was analyzed. Seventeen sixth graders participated in the modeling process. After exploring phenomena and concepts related to seasonal change, students constructed models using globes and bulbs and used them to explain seasonal changes. Video data recording students' modeling process, students' activity sheets, and transcripts of post-interview were used as research data, and data triangulation was conducted. The modeling level analysis framework was also developed based on previous studies. In particular, the framework was developed in detail in this study in consideration of the concept of Earth's motion as well as understanding model and implementing modeling. In the final analysis framework, the 3D modeling level was classified from level 1 to level 3, and student performance that may appear at each level was specified. As a result of the study, there were two main levels of modeling using globes for elementary school students to explain seasonal changes. The rotation and tilt of the axis of rotation and revolution of the earth were considered but the level at which empirical evidence was not used (level 2), the level at which empirical evidence was used to explain seasonal chages (level 3). However, even when students use empirical evidence, it did not lead to the construction of a scientific model. In this study, the cause was explored in relation to the characteristics of the tool used for modeling.

• Journal of the Korean Society of Earth Science Education
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• v.15 no.2
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• pp.249-262
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• 2022

This study was conducted on the alternative concept of elementary school pre-service teachers to seasonal changes. From May 2021 to June 2022, it was conducted with 60 pre-primary teachers at P National University of Education. The conclusion of this study is as follows. First, pre-primary teachers explained the cause of seasonal changes, and out of 60 pre-primary teachers, only 22 (36%) had scientific concepts, and the remaining 38 (64%) students had alternative concepts. Second, in explaining how the inclination of the Earth's axis of rotation is related to seasonal changes, only 16 (27%) of the 60 pre-primary teachers had a scientific concept, and the remaining 44 (73%) had alternative concepts. Third, pre-primary teachers explained the relationship between the change in the solar altitude and the seasonal change. Among 60 pre-primary teachers, 12 (20%) had a scientific concept, and the remaining 48 (80%) had alternative concepts. Fourth, looking at the comprehensive types of alternative concepts for seasonal changes, the aS-bS-cS type, which is classified as a type that explains the causes of seasonal changes using scientific concepts as a whole, was 8(13%) out of 60 pre-primary teachers. and the remaining 52 (87%) had at least one alternative concept to explain seasonal changes.