• 한국지능시스템학회논문지
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• 제16권5호
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• pp.581-586
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• 2006

본 논문에서는 무인주행 차량의 자율주행에 사용되는 자계안내시스템에서 지자계를 제거하기 위한 새로운 방법으로 Ground 검출법을 제안한다. 자계안내시스템은 도로에 일정한 간격으로 자계표식을 매설하고 차량이 자계표식으로부터 떨어진 거리를 인식하여 주행하는 방법이다. 차량이 주행 중 측면이탈거리를 알기 위해서는 지자계가 제거된 자계표식의 자계만을 이용해야 한다. 그러나 자계센서는 자계를 검출할 때 자계표식의 자계와 지자계를 함께 계측한다. 지자계는 차량의 주행방향과 경사에 따라 다르게 검출되기 때문에 자계표식의 자계와 더해질 경우 측면이탈거리를 인식하는데 오차를 발생한다. 따라서 본 논문에서는 지자계를 제거하는 새로운 방법을 제안하고, 이를 검증하기 위한 실험 장치를 구성하였다. 그리고 실험을 통하여 제안한 방법의 타당성과 유용성을 입증한다.

• Journal of Positioning, Navigation, and Timing
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• 제12권4호
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• pp.335-342
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• 2023

Lunar Navigation Satellite System refers to a constellation of satellite providing PNT services on the moon. LNSS consists of main satellite and navigation satellites. Navigation satellites orbiting around the moon and a main satellite moves the area between the moon and the L2 point. The navigation satellite performs the same role as the Earth's GNSS satellite, and the main satellite communicates with the Earth for time synchronization. Due to the effect of the non-uniform shape of the moon, it is necessary to focus on the influence of the lunar gravitational field when designing the orbit simulation for navigation satellite. Since the main satellite is farther away from the moon than the navigation satellite, both the earth's gravity and the moon's gravity must be considered simultaneously when designing the orbit simulation for main satellite. Therefore, the main satellite orbit simulation must be designed through the three-body problem between the Earth, the moon, and the main satellite. In this paper, the orbit simulation tool for main satellite and navigation satellite required for LNSS was designed. The orbit simulation considers the environment characteristics of the moon. As a result of comparing long-term data (180 days) with the commercial program GMAT, it was confirmed that there was an error of about 1 m.

• 한국지구물리탐사학회:학술대회논문집
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• 한국지구물리탐사학회 2004년도 대한지구물리학회.한국지구물리탐사학회 공동학술대회 초록집
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• pp.3-17
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• 2004

Space-borne Earth observation technique is one of the most cost effective and rapidly advancing Earth science research tools today and the potential field and micro-wave radar applications have been leading the discipline. The traditional optical imaging systems including the well known Landsat, NOAA - AVHRR, SPOT, and IKONOS have steadily improved spatial imaging resolution but increasing cloud covers have the major deterrent. The new Earth observation satellites ENVISAT (launched on March 1 2002, specifically for Earth environment observation), ALOS (planned for launching in 2004 - 2005 period and ALOS stands for Advanced Land Observation Satellite), and RADARSAT-II (planned for launching in 2005) all have synthetic aperture radar (SAR) onboard, which all have partial or fully polarimetric imaging capabilities. These new types of polarimetric imaging radars with repeat orbit interferometric capabilities are opening up completely new possibilities in Earth system science research, in addition to the radar altimeter and scatterometer. The main advantage of a SAR system is the all weather imaging capability without Sun light and the newly developed interferometric capabilities, utilizing the phase information in SAR data further extends the observation capabilities of directional surface covers and neotectonic surface displacements. In addition, if one can utilize the newly available multiple frequency polarimetric information, the new generation of space-borne SAR systems is the future research tool for Earth observation and global environmental change monitoring. The potential field strength decreases as a function of the inverse square of the distance between the source and the observation point and geophysicists have traditionally been reluctant to make the potential field observation from any space-borne platforms. However, there have recently been a number of potential field missions such as ASTRID-2, Orsted, CHAMP, GRACE, GOCE. Of course these satellite sensors are most effective for low spatial resolution applications. For similar objects, AMPERE and NPOESS are being planned by the United States and France. The Earth science disciplines which utilize space-borne platforms most are the astronomy and atmospheric science. However in this talk we will focus our discussion on the solid Earth and physical oceanographic applications. The geodynamic applications actively being investigated from various space-borne platforms geological mapping, earthquake and volcano .elated tectonic deformation, generation of p.ecise digital elevation model (DEM), development of multi-temporal differential cross-track SAR interferometry, sea surface wind measurement, tidal flat geomorphology, sea surface wave dynamics, internal waves and high latitude cryogenics including sea ice problems.

• 기술발표회
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• 통권2006호
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• pp.342-355
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• 2006

The Tunnel portal is designed on temporary support system which is composed by 28m height H-Pile method and Ground Anchor method. The tunnel has excavated about 30m from the portal, but some deformation is found on the surface ground just above the tunnel face. It was investigated very carefully to find out the causes of deformation. By the observation and study, two main causes of deformation are found out. The one is earth pressure increase compared with classical earth pressure theory. That was due to the direction of ground rock mass's discontinuities. It causes the increase of earth pressure that are activated by the direction of discontinuity. The other one is that present design method neglect the transferred force by removal of temporary support members and ground anchor within the tunnel contour line as the tunnel excavation proceeds As the result of removals of the member and anchor, some force transferred from removed systems to remaining supporting systems. In designing the portal support systems, lt must be considered the discontiunity of ground mass and the transfered force due to excation.

• 한국지구과학회지
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• 제32권7호
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• pp.871-880
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• 2011

본 연구에서는 수정된 버전의 InVEST Volcanic Concept Survey 검사지를 통해 예비 지구과학교사들의 화산시스템에 대한 이해를 탐구하였다. 그 결과, 화산 과정을 이해하는 예비 지구과학교사들은 극히 제한적이라는 결과를 얻었다. 즉, 화산관련 용어의 단순개념을 묻는 질문들은 높은 점수의 응답들을 얻은 반면에 화산분출의 구조를 묻는 고도의 사고를 요구하는 깊은 개념적 연결의 질문들은 낮은 점수의 응답들을 얻었다. 특히, 환경과의 영향 및 위험 예측에 대한 문항에 대해서는 매우 낮은 이해를 나타내었다. VCS 결과는 개념구조의 틀 안에서 예비 지구과학교사들이 화산 개념을 잘 이해하고 있는지를 과학교육 연구자들에게 알려주는 측정 기준으로서의 교육적 가치를 향상시킬 것이다.

• Structural Engineering and Mechanics
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• 제87권3호
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• pp.255-272
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• 2023

Spatial cable systems can provide more transverse stiffness and torsional stiffness without sacrificing the vertical bearing capacity compared with conventional vertical cable systems, which is quite lucrative for long-span earth-anchored suspension bridges' development. Higher economy highlights the importance of refined form-finding analysis. Meanwhile, the internal connection between the lateral and vertical sags has not yet been specified. Given this, an analytic algorithm of form-finding for the earth-anchored suspension bridge with spatial cables is proposed in this paper. Through the geometric compatibility condition and mechanical equilibrium condition, the expressions for cable segment, the recurrence relationship between catenary parameters and control equations of spatial cable are established. Additionally, the nonlinear general reduced gradient method is introduced into fast and high-precision numerical analysis. Furthermore, the analytic expression of the lateral and vertical sags is deduced and discussed. This is very significant for the space design above the bridge deck and the optimization of the sag-to-span ratio in the preliminary design stage of the bridge. Finally, the proposed method is verified with the aid of two examples, one being an operational self-anchored suspension bridge (with spatial cables and a 260 m main span), and the other being an earth-anchored suspension bridge under design (with spatial cables and a 500 m main span). The necessity of an iterative calculation for hanger tensions on earth-anchored suspension bridges is confirmed. It is further concluded that the main cable and their connected hangers are in very close inclined planes.

• International Journal of Aeronautical and Space Sciences
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• 제14권2호
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• pp.193-199
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• 2013

This work investigates the orbital perturbations of the cubesats that lie on LEO due to Earth albedo. The motivation for this paper originated in the investigation of the orbital perturbations for closed- Earth pico-satellites due to the sunlight reflected by the Earth (the albedo). Having assumed that the Sun lies on the equator, the albedo irradiance is calculated using a numerical model in which irradiance depends on the geographical latitude, longitude and altitude of the satellite. However, in the present work the longitude dependency is disregarded. Albedo force and acceleration components are formulated using a detailed model in a geocentric equatorial system in which the Earth is an oblate spheroid. Lagrange planetary equations in its Gaussian form are used to analyze the orbital changes when $e{\neq}0$ and $i{\neq}0$. Based on the Earth's reflectivity data measured by NASA Total Ozone Mapping Spectrometer (TOMS project), the orbital perturbations are calculated for some cubesats. The outcome of the numerical test shows that the albedo force has a significant contribution on the orbital perturbations of the pico-satellite which can affect the satellite life time.

• 대한원격탐사학회:학술대회논문집
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• 대한원격탐사학회 2005년도 Proceedings of ISRS 2005
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• pp.22-25
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• 2005

The 10 Year Implementation Plan for a Global Earth Observation System of Systems (GEOSS), which was endorsed at the Third Earth Observation Summit in Brussels in February, 2005, emphasizes the importance of data management facilities for diverse and large-volume Earth Observation data from inhomogeneous information sources. A three year research plan for addressing this key target of GEOSS has just approved as the first step by the Japanese government. The goals of this research are, (1) to develop a data management core system consisting of data integration and information fusion functions and interoperability and information service functions; (2) to establish data and information flows between data providers and users; (3) to promote application studies of data integration and information fusion, especially in the fields of weather forecasting, flood forecasting, agricultural management, and climate variability and changes. The research group involves leading scientists on information science and technology, who have been developing giant data archive servers, storage area networks, metadata models, ontology for the earth observations. They are closely cooperating with scientists on earth sciences, water resources management, and agriculture, and establishing an effective collaborative research framework.

• 대한화학회지
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• 제61권6호
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• pp.311-319
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• 2017

By using Density Functional Theory (DFT), we have performed alkali metal and alkaline earth metal inside fullerene-like BeO cluster (FLBeOC) in terms of energetic, geometric, charge transfer, work function and electronic properties. It has been found that encapsulated processes of the alkali metal are exothermic and thermodynamically more favorable than alkaline earth metal encapsulation, so that interaction energy ($E_{int}$) of the alkali metal encapsulation FLBeOC is in the range of -0.02 to -1.15 eV at level of theory. It is found that, the electronic properties of the pristine fullerene-like BeO cluster are much more sensitive to the alkali metal encapsulation in comparison to alkaline earth metal encapsulation. The alkali and alkaline earth metal encapsulated fullerene-like BeO cluster systems exhibit good sensitivity, promising electronic properties which may be useful for a wide variety of next-generation nano-sensor device components. The encapsulation of alkali and alkali earth metal may increase the electron emission current from the FLBeOC surface by reducing of the work function.

• Nuclear Engineering and Technology
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• 제50권6호
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• pp.915-922
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• 2018

Metallic fuel has been considered for sodium-cooled fast reactors because it can maximize the uranium resources. It generates rare earth elements as fission products, where it is reported by aggravating the fuel-cladding chemical interaction at the operating temperature. Rare earth elements form a multicomponent alloy (Ce-Nd-Pr-La-Sm-etc.) during reactor operation, where it shows a higher reaction thickness than a single element. Experiments have been carried out by simplifying multicomponent alloys for mono or binary systems because complex alloys have difficulty in the analysis. In previous experiments, xCe-yNd was fabricated with two elements, Ce and Nd, which have a major effect on the fuel-cladding chemical interaction, and the thickness of the reaction layer reached maximum when the rare earth elements ratio was 1:1. The objective of this study is to evaluate the effect and relationship of rare earth elements on such synergistic behavior. Single and binary rare earth model alloys were prepared by selecting five rare earth elements (Ce, Nd, Pr, La, and Sm). In the single system, Nd and Pr behaviors were close to diffusion, and Ce showed a eutectic reaction. In the binary system, Ce and Sm further increased the reaction layer, and La showed a non-synergy effect.