• Proceedings of the KIEE Conference
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• summer
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• pp.449-451
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• 2004

In the building, there are a lot of electricity, electrodes, and communication equipment. Many of those equipment needs to earthing. Naturally, the earth electrodes are constructed in the site of a building. In such a situation, when electric current flows into a certain earthing system the potential of other earthing systems rises. That is, the potential interference will take place between the earth electrodes. The conventional study has been considered by only the relation of the distance between the earth electrodes using the potential distribution formula of earth surface. However, it is necessary to inquire strictly, taking the surface potential of electrodes by electrode form into consideration. In this paper, basic formula is deduced on the basis of both electrodes surface potential of earth electrode as a source of the potential interference and earth electrode which receives the potential interference.

• Journal of the Korean earth science society
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• v.27 no.7
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• pp.723-729
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• 2006

The purpose of this study was to develop a program based on the Earth system based program to help students achieve science literacy. This program was designed to be connected across grade levels, and contents of the program were constructed to have meaningful interdisciplinary context. All the activities in the program were inquiry-based, and understanding of the nature of science was considered essential throughout the program. In addition, appreciation and stewardship for the Earth system were systematically emphasized on any grade level. Design of the program applied U.S. National Science Education Standards for the quality of and conditions for school science programs.

• 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 Geotechnical Society
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• v.36 no.11
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• pp.51-60
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• 2020

Estimation of passive earth pressure is an important factor in anchor block, temporary retaining wall and support block of raker that resist lateral earth pressure. In practice, due to ease of use, it is common to estimate the earth pressure using the theory of Coulomb and Rankine, which assumes the failure plane as a straight line. However, the passive failure plane generated by friction between the wall surface and the soil forms a complex failure plane: a curve near the wall and a flat plane near the ground surface. In addition, the limit displacement where passive earth pressure is generated is larger compared to where the active earth pressure is generated. Thus, it is essential to calculate the passive earth pressure that occurs at the allowable displacement range in order to apply the passive earth pressure to the design for structural stability reasons. This study analyzed the mobilized passive earth pressured to various displacement ranges within the passive limit displacement range using the semi-empirical method considering the complex failure plane.

• Journal of the Korean earth science society
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• v.35 no.7
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• pp.537-542
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• 2014

The Gravity Recovery and Climate Experiment (GRACE) has observed the Earth's mass redistribution mainly caused by the variations of groundwater, ice sheet, and sea level since its launch in April 2002. The global gravity model estimated by the GRACE observation is corrected by barometric pressure, and thus represents the change of Earth mass on the Earth's surface and below Earth's surface excluding air mass. However, the total air mass varies due to the water exchange between the Earth's surface and the atmosphere. As a result, the nominal GRACE gravity model should include the Earth's gravity spectrum associated with the total air mass variations, degree 0 and order 0 coefficients of spherical harmonics ($C_{00}$). Because the water vapor content varies mainly on a seasonal time scale, a change of $C_{00}$ (${\delta}C_{00}$) is particularly important to seasonal variations of sea level, and mass balance between northern and southern hemisphere. This result implies that ${\delta}C_{00}$ coefficients should be accounted for the examination of continental scale mass change possibly associated with the climate variations.

• Journal of the Korean earth science society
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• v.26 no.4
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• pp.329-335
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• 2005

The purpose of this study is to suggest the modification of activities to introduce the nature of science in earth science classrooms. A small modification can turn ordinary textbook activities into the nature of science activities. Since earth science could provide a good basis for the tentative, creative, and socially and culturally embedded nature of science, as well as appropriate understanding about scientific methods, careful modification of earth science activities could be effective for students to understand the nature of science. Considering which aspects of the nature of science are appropriate, along with the possible change in the activity, teachers will be able to modify textbook activities effectively. An example modification of H-R diagram activity was also suggested.

• Land and Housing Review
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• v.7 no.4
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• pp.271-279
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• 2016

Recently developed trenchless construction methods ensure stability for the ground settlement by inserting steel pipes along the underpass section and integrating steel pipes before ground excavation to form pipe-roof. This study is to confirm the reinforcing effect of pipe-roof by measuring lateral earth pressure acting on the underpass constructed by the STS (Steel Tube Slab) construction method. For this purpose, lateral earth pressure was measured at the left and right side of the pipe-roof after installing earth pressure cells. As a result, lateral earth pressure was measured with considerable reduction because the integrated pipe-roof shared surcharge. Therefore, economic design for the underpass could be expected by sharing design load by pipe-roof. In addition, construction cost was analyzed according to the design-load sharing ratio by pipe-roof. As pipe-roof shares design load by 40%, the total construction cost can decrease by almost 10% in the case of four-lane underpass.

• 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.

• KIEAE Journal
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• v.16 no.3
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• pp.83-88
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• 2016

Purpose : This study aimed to verify the surface hardness and water repellency of earth paint manufactured with earth, a natural material, and provide the results as basic data for paint made with natural materials. Method : After presenting the accurate manufacturing methods for basic materials for paint, the authors conducted and analyzed experiments to evaluate surface hardness and water repellency, fundamental performance indicators for paint, based on different mixture ratios. From the results of the experiment to assess the surface hardness of flour-based earth paint, we observed high surface hardness only after painting the specimen three times. Since potato starch-based earth paint has higher viscosity than its flour-based counterpart, the former did not paint well on the first occasion, resulting in low surface hardness. After painting two or more times, however, it was observed to have higher surface hardness than flour-based earth paint. Result : It was found that at least three iterations of painting was required to obtain high surface hardness of potato starch-based earth paint. Furthermore, the results of the water resistance experiment of earth paint suggest that the use of environment-friendly finishing materials coupled with boiled linseed oil will mitigate the drawbacks of earth paint. The experiment with one-year-old specimens also demonstrated similar water repellent characteristics, which indicates that the performance will improve once the paint has dried for a sufficient period of time.

• Journal of the Korea Institute of Building Construction
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• v.13 no.1
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• pp.1-9
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• 2013

There has recently been a great deal of research into the appropriate building materials for eco-friendly construction. In the field of earth architecture, there have been walls made of pure earth or with rammed earth including a small amount of cement. The purpose of the study is to investigate the possibility increasing compressive strength through a more eco-friendly composition by using Hwangtoh binder rather than cement to increase the strength performance of rammed earth. It was found that the more the ratio of binder was increased, the more the strength was increased, but enhancement did not increase noticeably in the lower part that did not compact completely, and proper height to pour earth is 200 mm. When stone dust was added, compressive strength was lower than when adding fine aggregate and coarse aggregate, but a finer surface texture was provided.