• Journal of The Korean Association For Science Education
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• v.33 no.3
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• pp.664-678
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• 2013

This study aims to investigate gifted students' explanations for daily celestial motion from the Earth-based and heliocentric frames of reference. Eleven sixth-grade elementary school students were chosen for this study and data was collected through a questionnaire and an in-depth interview. The collected data was analyzed into celestial objects which are the Sun, the moon and the stars and analyzed based on the Earth-based and heliocentric perspectives again. As a result of the research, most gifted students were able to connect the Earth-based and heliocentric frames of reference with the Sun's daily apparent motion. However, they understood the daily apparent motion of the moon and the stars far less frequently compared to the Sun's motion and could not explain the Earth's rotation clearly. The result of the interview showed that the lack of understanding about the daily celestial motion was caused by inaccurate understanding of the Earth's rotation such as using memorized knowledge learned in school and guessing the answer.

• Journal of the Korean earth science society
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• v.31 no.3
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• pp.267-275
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• 2010

The purpose of this study is to investigate student's Acquisition about the conception of the Earth Rotation between difference of their Spatial Sensibility. In this study, four students were selected out of 83 9th graders in Gwangju, Korea. The spatial sensibility test instrument was developed by the Korean Testing Center, and the test instruments of 'the movement of celestial bodies' were developed by Kim (1997). The results were as follows: Students with higher spatial sensibility understood precisely about the Earth's rotation in stereoscopic space. However, those with lower spatial sensibility failed to grasp the Earth's rotation and memorized it as fragmentary concepts. As for gender effect, male student with higher spatial sensibility explained the concepts clearly, while that with lower spatial sensibility has difficulty with the Earth's rotation in relation to the diurnal motion of celestial bodies. On the other hand, female student with higher spatial sensibility explained the concepts correctly in detail, while that with lower spatial sensibility had difficulty explaining the concepts in stereoscopic space. Therefore, students with higher spatial sensibility should be presented with problems in which they form their own solution. Those with lower spatial sensibility should be allowed to understand the phenomena intuitively. In developing teaching methods, female students should interact with the concepts in stereoscopic space directly, while male students should consider the celestial objects from various viewpoints. Then spatial sensibility in relation to the movement of celestial bodies would be expected to improve.

• 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.

• Journal of The Korean Astronomical Society
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• v.33 no.2
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• pp.127-135
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• 2000

We investigate the effects of planetary rotation on the exospheres of the earth and Mars with simple collisionless models. We develope a numerical code that computes exospheric densities by integrating velocity functions at the exobase with a 10 point Gauss method. It is assumed in the model that atoms above the exobase altitude move collisionlessly on an orbit under the planet's gravity. Temperatures and densities at the exobase over the globe are adopted from MSIS-86 for the earth and from Bougher et al's MTGCM for Mars. For both the earth and Mars, the rotation affects the exospheric density distribution significantly in two ways: (1) the variation of the exospheric density distribution is shifted toward the rotational direction with respect to the variation at the exobase, (2) the exospheric densities in general increase over the non-rotating case. We find that the rotational effects are more significant for lower thermospheric temperatures. Both the enhancement of densities and shift of the exospheric distribution due to rotation have not been considered in previous models of Martian exosphere. Our non-spherical distribution with the rotational effects should contribute to refining the hot oxygen corona models of Mars which so far assume simple geometry. Our model will also help in analyzing exospheric data to be measured by the upcoming Nozomi mission to Mars.

• Journal of The Korean Association For Science Education
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• v.29 no.7
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• pp.759-766
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• 2009

This study was conducted to examine 10 Belizean teachers' conceptions about the causes of seasonal change. This research was conducted with an integrated method using a open ended written test and an interview which included a drawing. There are four categories, explained by the teachers, as the causes of seasonal changes. They are; climate, rotation of the earth on its axis, revolution of the earth around the sun, and the tilting of earth's axis as it revolves. Most teachers misunderstood that the first of three categories was responsible for seasonal change. Second, it is more effective to use the integrated method shown in this research than to use only a written test when seriously investigating the causes and understanding of seasonal change. Third, 8 out of 10 teachers could not correctly explain the causes of seasonal change. The reasons for seasonal change seemed to be hard for the informants to understand even though it was taught in elementary, middle, high school, and college elective classes.

• Proceedings of the Korean Geotechical Society Conference
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• 2008.10a
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• pp.708-712
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• 2008

Piles and pile foundations have been in common use since very early times. Usually function of piles is to carry load to a depth at which adequate support is available. Another important use of piles is to furnish lateral support and nowadays it is getting highlighted due to the wind load, lateral action of earthquake, and so on. After Broms (1964), many researchers have been suggested methods for estimating lateral capacity of pile. But each method assumes different earth pressure distribution and lateral earth pressure coefficient and it gives confusion to pile designers. Lateral earth pressure, essential in lateral capacity estimation, influenced by pile's behavior under lateral load. Prasad and Chari (1999) assumed the rotation point of pile and suggested an equation of ultimate lateral load capacity. In this study, we investigate the depth of rotation point in both homogeneous soil and multi layered soil, and compare to the estimation value by previous research. To model the pile set up in the sand, we use the chamber and small scale steel pile, and rain drop method. Test results show the rotation point is formed where the Prasad and Chari's estimation value, and they also show multi layered condition affects to location of rotation point to be scattered.

• Journal of The Korean Astronomical Society
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• v.25 no.2
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• pp.67-78
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• 1992

Effects of cloud rotation 011 the profiles of CO J=$1{\rightarrow}0$ lines arc investigated by theoretically general ing line profiles under physical conditions similar to t he ones in large globules. The synthesized profiles are presented and their characteristics are discussed. It is found that when the Doppler shift of the observed CO lines is interpreted as the rotation velocity, the optically thin $^{13}CO$ lines underestimate the rotation velocity by up to 10 percents, while the self-reversed optically thick $^{12}CO$ lines overestimate the velocity up to 20 percents. The optically thin line is shown to be of use in probing the distribution of rotation velocity in dark globules.

• Proceedings of the KSRS Conference
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• 2003.11a
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• pp.369-371
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• 2003

This paper attempts to study the evolution of the Solar System including the earth through various existing hypotheses and the occurrence of earthquakes on the earth. From the analysis of the various theories it can be inferred that the Mystery regarding evolution of Solar System is a complex problem which requires continuos research. The occurrence of the earthquake is also affected by the earth's rotation, which produces Centrifugal Force, which together with convection current causes plate displacement resulting in earthquakes. The extent of displacement varies with the size and density of the plates.

• Journal of the Korean Geotechnical Society
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• v.25 no.1
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• pp.55-64
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• 2009

One of the important use of piles is to furnish lateral support and nowadays it is getting highlighted due to the increase of skyscrapers, transmission towers, wind turbines, and other lateral action dependent structures. After Broms (1964), many researchers have suggested methods for estimating lateral capacity of pile. But each method assumes different earth pressure distribution and lateral earth pressure coefficient causing confusion on the part of pile designers. Lateral earth pressure, essential in lateral capacity estimation, is influenced by pile's rotational behavior under lateral load. Prasad and Chari (1999) assumed the rotation point of pile and suggested an equation of ultimate lateral load capacity. In this study, we investigate the depth of rotation point in both homogeneous soil and multi layered soil, and compare with the estimation value by previous research. Test results show that measured rotation point and estimated value by Prasad and Chari's equation show good agreement and multi layered condition affects the location of rotation point to be changed.

• Journal of The Korean Astronomical Society
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• v.40 no.2
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• pp.49-60
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• 2007

This paper deals with the theory for rotational motion of a two-layer Earth model (an inelastic mantle and liquid core) including the dissipation in the mantle-core boundary(CMB) along with tidal effects produced by Moon and Sun. An analytical solution being derived using Hori's perturbation technique at a second order Hamiltonian. Numerical nutation series will be deduced from the theory.