• 한국과학교육학회지
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• 제33권3호
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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.

• 한국지구과학회지
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• 제31권3호
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• pp.267-275
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• 2010

본 연구의 목적은 9학년 학생의 공간능력 차이에 따른 지구자전 개념을 알아보는 것이다. 광역시 소재 9학년 학생 83명중 천체의 공간운동 개념 평가(김기정, 1997)에서 개념 획득 정도가 비슷하면서 공간능력에 차이가 있는 남학생 2명과 여학생 2명을 각각 표집하여 질적 분석의 대상으로 삼았다. 연구 결과, 공간능력이 높은 학생일수록 개념이 올바르고 개념들을 입체적 공간으로 재구성하여 이해하였다. 공간능력이 낮을수록 개념이 불완전하고 단편적인 개념들을 암기하고 있었다. 성별에 따라서는 공간능력이 높은 남학생은 개념들을 간단 명료하게 표현하였고, 낮은 학생은 자전에 대한 방향을 일주운동과 연관시켜 해석하지 못했다. 반면에 여학생은 공간능력이 높을 때 개념들을 구체적으로 표현하였으며, 낮을수록 개념들을 입체적으로 표현하지 못하였다. 따라서 공간능력이 높은 학생은 문제 상황을 제시하여 스스로 해결할 수 있도록 하고, 낮은 학생은 현상들을 직접 관찰하여 쉽게 이해 할 수 있도록 학습 자료를 개발하여야겠다. 여학생은 공간을 입체적으로 조작해 볼 수 있도록 하고 남학생은 사물을 여러 관점으로 생각해 볼 수 있도록 교수 전략 및 학습 자료 등을 개발 한다면 천문단원의 공간능력이 향상되고, 개념 획득이 잘 될 수 있을 것이라 기대한다.

• 천문학회지
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• 제45권2호
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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.

• 천문학회지
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• 제33권2호
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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.

• 한국과학교육학회지
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• 제29권7호
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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.

• 한국지반공학회:학술대회논문집
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• 한국지반공학회 2008년도 추계 학술발표회
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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.

• 천문학회지
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• 제25권2호
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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.

• 대한원격탐사학회:학술대회논문집
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• 대한원격탐사학회 2003년도 Proceedings of ACRS 2003 ISRS
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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.

• 한국지반공학회논문집
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• 제25권1호
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• pp.55-64
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• 2009

수평하중에 대한 지지력의 발휘는 말뚝의 주요 용도 중 하나이며, 최근 초고층 건물, 송전탑, 풍력발전기 등 수평하중이 지배적인 구조물의 증가로 이에 대한 연구가 활발히 진행되고 있다. Broms(1964) 이후 많은 연구자들이 수평방향 지지력 산정을 위한 방법들을 제안하여 왔으나, 각 방법별로 서로 다른 토압분포와 수평토압계수를 가정하여 설계자로 하여금 혼란을 가져을 여지를 갖고 있다. 수평지지력 산정에 주요 요소가 되는 수평토압계수는 수평하증에 의한 말뚝의 회전 거동에 영향을 받는다. Prasad와 Chari(1999)는 말뚝의 회전점을 가정하여 극한지지력을 산정하는 식을 제안하였다. 본 연구에서는 균일지반과 다층지반의 모두에서 말뚝의 회전점을 측정하였으적, 기존의 연구 결과와 비교하였다. 실험 결과 회전점 측정값과Prasad와 Chari(1999)의 예측값이 잘 일치하였으며 다층지반은 회전점의 위치를 변하게 하는 요소로 작용하는 것으로 나타났다.

• 천문학회지
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• 제40권2호
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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.