• International Journal of Aeronautical and Space Sciences
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• v.15 no.3
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• pp.267-280
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• 2014

A spacecraft placed in an Earth-Moon L2 quasi-halo orbit can maintain constant communication between the Earth and the far side of the Moon. This quasi-halo orbit could be used to establish a lunar space station and serve as a gateway to explore the solar system. For a mission in an Earth-Moon L2 quasi-halo orbit, a spacecraft would have to be transferred from the Earth to the vicinity of the Earth-Moon L2 point, then inserted into the Earth-Moon L2 quasi-halo orbit. Unlike the near Earth case, this orbit is essentially very unstable due to mutually perturbing gravitational attractions by the Earth, the Moon and the Sun. In this paper, an insertion maneuver of a spacecraft into an Earth-Moon L2 quasi-halo orbit was investigated using the global optimization algorithm, including simulated annealing, genetic algorithm and pattern search method with collision avoidance taken into consideration. The result shows that the spacecraft can maintain its own position in the Earth-Moon L2 quasi-halo orbit and avoid collisions with threatening objects.

• Proceedings of the Petrological Society of Korea Conference
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• 2001.06a
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• pp.45-47
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• 2001

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.38 no.7
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• pp.684-692
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• 2010

Based on the planar restricted three body problem formulation, optimized trajectories for the Earth-Moon transfer are obtained. Mixed impulsive and continuous thrust are assumed to be used, respectively, during the Earth departure and Earth-Moon transfer/Moon capture phases. The continuous, dynamic trajectory optimization problem is reformulated in the form of discrete optimization problem by using the method of direct transcription and collocation, and then is solved using the nonlinear programming software. Representative results show that the shape of optimized trajectory near the Earth departure and the Moon capture phases is dependent upon the relative weight between the impulsive and the continuous thrust.

• Journal of The Korean Association For Science Education
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• v.15 no.4
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• pp.379-393
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• 1995

In spite of school science learning, the students' conceptions have not been changed easily. Therefore, to make students overcome their non scientific conceptions has been an important issue in science education. The purpose of this study was to identify the conceptions of students and teachers on the motion of the earth and the moon. The instrument was developed for estimating students' understandings of the concepts related to the motion of the earth and the moon. The validity of the instrument was examined by the specialists in Science Educator and Astronomer. At the same time, the two field trials had been executed, and the items were modified. Also, it consists of 12 items including 9 two-tier multiple choice items and 3 multiple choice items. The population of this study consists of 250 eighth-, 299 tenth-, 292 eleventh-grade students, 134 science teachers in secondary school. SPSS/PC+ was adopted for the statistical analysis. The type of misconceptions possessed students were as follows: 1) At 12:00 noon, the sun is directly overhead. 2) First quarter moon is a half of overall surface of the moon. 3) Air don't rotate with the earth surface because it keeps apart from the earth surface. 4) Summer is warmer than winter, because the earth is nearer from the sun in summer. 5) Whenever season is changed, the direction of rotation axis of the earth is changed. 6) The moon is the brightest at the position of new moon, because the distance between the moon and the sun is the shortest and the moon is received strongest sunlight. 7) The moon is not seen at the position of real full moon, because it is covered with shadow of the earth. 8) When the moon is not seen in the earth, sunlight is not reached at the moon. The major findings were as follows : 1) The middle school students had more misconceptions than those of high school students. And female students had more misconceptions than those of male ones. 2) The rate of correct answer and the type of conception in the tenth grade students were very similar with eleventh grade students. 3) The higher cognitive level, the better development of scientific conception and the less misconception. Also, the correlation coefficient between scientific conception score and GALT score was 0.57. 4) The students in scientific part had higher the rate of correct answer than those of students in human part and the former had less misconception than the latter. 5) The rate of correct answer about model and figure items was lower than descriptive ones, because they did not understand about figures itselves. These types of misconceptions will be used for science instruction and studies of other conceptions need.

• Proceedings of the KSEEG Conference
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• 2000.04a
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• pp.83-83
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• 2000

• 한국석유지질학회:학술대회논문집
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• autumn
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• pp.40-40
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• 2000

• Journal of The Korean Astronomical Society
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• v.45 no.2
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• pp.49-57
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• 2012

In this study, I calculate the past and future dynamical states of the Earth-Moon system by using modified Lambeck's formulae. I find that the ocean tidal effect must have been smaller in the past compared to its present amount. Even though the Moon is already in the spin-orbit synchronous rotational state, my calculation suggest that it will not be in geostationary rotational state in the next billion years or so. This is due to the associated Earth's obliquity increase and slow retardation of Earth's spin and lunar orbital angular velocities. I also attempt to calculate the precessional period of the Earth in the future. To avoid uncertainties in the time scale, the future state is described by using the Earth-Moon distance ratio as independent parameter. Effects due to solar tidal dissipation are included in all calculations.

• Coupled systems mechanics
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• v.7 no.5
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• pp.611-626
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• 2018

We theoretically consider a possible influence of periodic oceanic tides on non-periodic changes in the dynamics of the Earth and Moon over a long time scale. A particular emphasis will be placed on the contribution from rotating tidal waves, which rotate along the inner edge of an oceanic basin surrounded by topographic boundary. We formulate the angular momentum and the mechanical energy of the rotating tidal wave in terms of celestial parameters with regard to the Earth and Moon. The obtained formula are used to discuss how the energy dissipation in the rotating tidal wave should be relevant to the secular variation in the Earth's spin rotation and the Earth-Moon distance. We also discuss the applicability of the formula to general oceanic binary planets subject to tidal coupling.

• Journal of the Korean earth science society
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• v.32 no.5
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• pp.514-520
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• 2011

As homework, a total of 32 seventh grade science-gifted students were asked to observe the moon at daily intervals for one month duration. They were also asked to take the photos and to record relevant variables in a given format. The purpose of the task was to investigate what students thought, as they observed the moon. The results show that students paid attention mainly to the position of the moon relative to other variables such as the date in the lunar calendar, the observer's position on the earth, and the position of the sun. Overall students' response implied that students did not observe the lunar phase in relation with relevant variables. Some reponses from students show common misconceptions such as the cause of the lunar phase to reflect the shadow of the earth. However, some responses reveal students' idea that has been rarely reported in the previous researches. For example, some students drew the moon to revolve in the opposite direction. Significant number of students drew the sun's position to be due west before the full moon and due east after the full moon. Few students recognized the relation between the time of observation and observer's position on the earth. The results of current research suggest that not only the education but also the research needs to be expanded to consider informal environment such as the actual field conditions.

• Proceedings of the KSEEG Conference
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• 2000.04a
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• pp.84-85
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• 2000