• 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.

• 천문학회보
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• 제35권2호
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• pp.53.1-53.1
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• 2010

Earth's polar motion has been known for more than one century, and it has been monitored by astrometric observation and recently by space geodetic technique. The Chandler and the annual wobbles are two dominant parts of Earth's polar motion. But according to our recent analysis on a relevant and accurate dataset, another polar motion component, of which period is about 500 days, exists with an amplitude of 20 milliarcseconds in average. This third largest component of polar motion should be caused by resonance of unidentified oscillating mode of Earth, possibly Earth's inner core wobble.

• 지구물리와물리탐사
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• 제19권2호
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• pp.91-96
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• 2016

지구의 극운동 자료(IERS 08 C04, 1981년 이후)로부터 1 년 주기 성분을 제거한 뒤 얻어진 시계열에 대하여 최소제곱법을 적용하여 지구의 자유-오일러 운동(찬들러 워블) 시계열을 얻었으며, 이의 진폭과 위상 등의 변화를 조사하였다. 한편 대지진 발생 전의 전조현상으로서의 극의 움직임을 찾아보았으나 발견하지 못하였다. 스마일리의 추측과는 달리, 규모 8.5 이상의 최근 지진 여섯 개의 발생시점 부근에서 극운동의 특별한 징후가 없었다.

• 대한지구과학교육학회지
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• 제13권1호
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• pp.29-39
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• 2020

본 연구에서는 지구 자전과 태양의 겉보기 운동을 학습하기 위한 역할놀이 활동의 학습 효과 및 어려움을 알아보기 위해서 역할 놀이 활동을 통한 개념 이해정도, 면담으로 수집한 활동에서 나타나는 어려움, 활동 중 시선이동을 분석하였다. 연구 참여자는 초등학교 5학년 학생 22명이며, 역할 놀이 중 실험 행동과 사후 면담, 시선이동자료를 수집하여 분석하였다. 연구결과, 학생들은 역할 놀이 활동을 통해 지구의 자전과 자전방향은 설명할 수 있지만 태양의 겉보기 운동을 설명하는 것은 어려워했다. 학생들은 역할 놀이 활동을 통해 태양의 겉보기 운동을 지각하기 어려워하기 때문에, 자전에 의해 나타나는 태양의 겉보기 운동 개념을 학습하기 위한 역할 놀이 활동은 학습 효과가 낮다.

• Journal of Astronomy and Space Sciences
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• 제20권4호
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• pp.319-326
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• 2003

The motion of each satellite in a tethered satellite system is non-Keplerian in the Earth's gravitational field. In this paper, the tether perturbation force is formulated and compared with the perturbation force due to the Earth's oblateness. Also, the center of mass motion of the tethered satellite system is analyzed. The tether perturbing force on the one of satellites in a tethered satellite system is much bigger than the Earth's oblateness perturbation. The two-body motion approximation of the center of mass is acceptable to describe the motion of the system, when the libration is small.

• Journal of Astronomy and Space Sciences
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• 제30권1호
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• pp.33-41
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• 2013

Various features of the existing perturbations in the Earth's spin rotation are investigated for the recent and most reliable data by spectral analysis, filtering, and comparison with idealized model. First, theory of Earth's spin rotational perturbation is briefly re-derived in the Earth-fixed coordinate frame. By spectral windowings, different periodic components of the length of day perturbation are separated, and their characters and excitations are discussed. Different periodic components of polar motion are acquired similarly and described with further discussion of their excitations. Causes of the long time trends of both the length of day and polar motion are discussed. Three possible causes are considered for the newly discovered 490-day period component in the polar motion.

• 대한지구과학교육학회지
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• 제13권3호
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• pp.297-304
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• 2020

이 연구의 목적은 지구의 공전 실험에 대해 알아보고, 학교 급별로 효과적인 지구의 공전 실험이 무엇인지 알아보는데 있다. 연구자는 지구의 공전을 학습할 수 있는 8가지의 실험 방법을 조사 또는 개발하였다. 초등 예비교사 26명에게 이 실험을 실시하고 토의하도록 한 후, 학교 급별로 효과적인 지구의 공전 실험을 선택하고 이유를 쓰도록 하였다. 그 결과 초등학교에서는 계절별 별자리가 달라지는 실험, 중·고등학교에서는 계절별 별의 스펙트럼을 비교하는 실험, 대학교에서 외행성의 역행운동이 효과적이라고 선택하였다. 예비교사는 직접 체험의 가능 여부, 교과 내용과 연계되는 정도, 배경지식과 고차원적인 사고의 정도를 실험 선택의 이유로 제시하였다.

• 한국지진공학회논문집
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• 제24권6호
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• pp.277-283
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• 2020

In order to improve the ground-motion prediction equation, which is an important factor in seismic hazard assessment, it is essential to obtain good quality seismic data for a region. The Korean Peninsula has an environment in which it is difficult to obtain strong ground motion data. However, because digital seismic observation networks have become denser since the mid-2000s and moderate earthquake events such as the Odaesan earthquake (Jan. 20, 2007, M_L 4.8), the 9.12 Gyeongju earthquake (Sep. 12, 2016, M_L 5.8), and the Pohang earthquake (Nov. 15, 2017, M_L 5.4) have occurred, some good empirical data on ground motion could have been accumulated. In this study, we tried to build a ground motion database that can be used for the development of the ground motion attenuation equation by collecting seismic data accumulated since the 2000s. The database was constructed in the form of a flat file with RotD50 peak ground acceleration, 5% damped pseudo-spectral acceleration, and meta information related to hypocenter, path, site, and data processing. The seismic data used were the velocity and accelerogram data for events over M_L 3.0 observed between 2003 and 2019 by the Korean National Seismic Network administered by the Korea Meteorological Administration. The final flat file contains 10,795 ground motion data items for 141 events. Although this study focuses mainly on organizing earthquake ground-motion waveforms and their data processing, it is thought that the study will contribute to reducing uncertainty in evaluating seismic hazard in the Korean Peninsula if detailed information about epicenters and stations is supplemented in the future.

• 한국항해항만학회지
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• 제30권9호
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• pp.729-734
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• 2006

The authors aim to establish the theory necessary for developing the free gyroscopic compass and focus on mainly two points. One is to suggest north-finding principle by the angular velocity of the earth's rotation, and the other is to suggest orthogonal coordinate transformations of the motion rate of the spin axis, which transforms the components of motion rate in the free gyro frame into those in the platform frame and that this transformed rate is, in turn, transformed into the NED(north-east-down) navigation frame. Subsequently, ship's heading is obtained by using the fore-aft and athwartship components of the motion rate of the spin axis in the NED frame. In addition it was found how to solve the transformation matrix necessary for transforming each frame.

• Journal of Astronomy and Space Sciences
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• 제36권1호
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• pp.11-20
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• 2019

Being a torque free motion of the rotating Earth, Chandler wobble is the major component in the Earth's polar motion with amplitude about 0.05-0.2 arcsec and period about 430-435 days. Free core nutation, also called nearly diurnal free wobble, exists due to the elliptical core-mantle boundary in the Earth and takes almost the whole part of un-modelled variation of the Earth's pole in the celestial sphere beside precession and nutation. We hereby present a brief summary of their theories and report their recent features acquired from updated datasets (EOP C04 and ECMWF) by using Fourier transform, modelling, and wavelet analysis. Our new findings include (1) period-instability of free core nutation between 420 and 450 days as well as its large amplitude-variation, (2) re-determined Chandler period and its quality factor, (3) fast decrease in Chandler amplitude after 2010.