• 한국우주과학회:학술대회논문집(한국우주과학회보)
• /
• 한국우주과학회 2004년도 한국우주과학회보 제13권2호
• /
• pp.61-61
• /
• 2004

• 한국전기전자재료학회논문지
• /
• 제21권1호
• /
• pp.29-34
• /
• 2008

In this paper, we investigated electrical and physical characteristics of nickel silicide using rare-earth metals(Er, Yb, Tb, Dy), Incorporated Ytterbium into Ni-silicide is proposed to reduce work function of Ni-silicide for nickel silicided schottky barrier diode (Ni-silicided SBD). Nickel silicide makes ohmic-contact or low schottky barrier height with p-type silicon because of similar work function (${\phi}_M$) in comparison with p-type silicon. However, high schottky barrier height is formed between Ni-silicide and p-type substrate by depositing thin ytterbium layer prior to Ni deposition. Even though the ytterbium is deposited below nickel, ternary phase $Yb_xN_{1-x}iSi$ is formed at the top and inner region of Ni-silicide, which is believed to result in reduction of work function about 0.15 - 0.38 eV.

• Journal of Astronomy and Space Sciences
• /
• 제31권1호
• /
• pp.41-50
• /
• 2014

The Earth is not perfectly spherical and its rotational axis is not fixed in space, and these geophysical and kinematic irregularities work as dominant perturbations in satellite orbit propagation. The International Earth Rotation Service (IERS) provides the Conventions as guidelines for using the Earth's model and the reference time and coordinate systems defined by the International Astronomical Union (IAU). These guidelines are directly applied to model orbital dynamics of Earth satellites. In the present work, the effects of the latest conventions released in 2010 on orbit propagation are investigated by comparison with cases of applying the previous guidelines, IERS Conventions (2003). All seven major updates are tested, i.e., for the models of the precession/nutation, the geopotential, the ocean tides, the ocean pole tides, the free core nutation, the polar motion, and the solar system ephemeris. The resultant position differences for one week of orbit propagation range from tens of meters for the geopotential model change from EGM96 to EGM2008 to a few mm for the precession/nutation model change from IAU2000 to IAU2006. The along-track differences vary secularly while the cross-track components show periodic variation. However, the radial-track position differences are very small compared with the other components in all cases. These phenomena reflect the variation of the ascending node and the argument of latitude. The reason is that the changed models tested in the current study can be regarded as small fluctuations of the geopotential model from the point of view of orbital dynamics. The ascending node and the argument of latitude are more sensitive to the geopotential than the other elements. This study contributes to understanding of the relation between the Earth's geophysical properties and orbital motion of satellites as well as satellite-based observations.

• 한국지구과학회지
• /
• 제27권3호
• /
• pp.289-301
• /
• 2006

이 연구의 목적은 초임 중등 과학 교사들이 과학 수업에서 학생들의 동기 유발과 학생 이해에 대해서 어떠한 지향을 하고 있으며, 그것이 실제 수업에서 어떻게 실행되고 있는지를 분석하는 것이다. 연구 참여자는 수도권 중 고등학교에서 근무하는 경력 1년 미만의 과학 교사 6명이다. 자료 수집은 수업 관찰 및 녹화, 구조화된 심층 면담과 우선순위 면담, 수업 자료를 통해 이루어졌다. 모든 수업과 면담 자료를 전사한 후, 분석틀에 맞추어 분석하였다. 연구 결과, 초임 과학 교사들은 동기 유발과 학생 이해에 관해 '관리 중심 과학 수업'에서부터 '전통적 과학 수업'까지 지향하고 있었으며, '구성주의적 과학 수업'은 지향하지 못하였다. 지향하는 바를 실행하는데 있어서 한명의 교사는 전문 단계의 실행 수준을 보여주었지만, 나머지 교사들은 초보 단계의 실행을 나타냈다. 본 연구를 통해 과학 교사들에게 동기 유발과 학생 이해에 관한 구성주의적 과학 수업의 방향을 제시해 줄 수 있을 것이다.

• 대한화학회지
• /
• 제24권6호
• /
• pp.434-443
• /
• 1980

이번 실험에서 1차 분리된 희토류 산화물로부터 column chromatography에 의하여 희토류 금속들을 분리해 내고 정량하였다. 희토류 산화물을 Amberlite IR-120 수지에 흡착시킨 다음 EDTA 암모니아 알칼리용액을 사용하여 용출시켰다. 각 분획물중의 희토류금속의 함량을 측정한 결과 Ce가 가장 효과적으로 분리되었고 Nd와 Sm도 부분적으로 분리되었으나 Pr은 전혀 분리되지 않았다.

• 한국농공학회논문집
• /
• 제46권2호
• /
• pp.93-103
• /
• 2004

In trench excavation, essential factor of earth-retaining temporary work structure should be easy taking to pieces and movement, and dead weight must be less. This paper studies about the light weight material and application as earth-retaining structure to prevent the slope failure of sand soil ground caused by the variation of groundwater level in trench excavation. That is, light weight earth-retaining structural is proposed and a simulation with FEM on application of proposed structural in sandy soil is presented. The results are summarized as follows; (1) The study proposed FRP H-shaped pannel for the light weight member, and also presented estimation method about stability. (2) Mechanical property (bending moment, shear force, axial force, displacement) were changed according to groundwater level, but these values had been within enough safety rate and allowable stress. Therefore, proposed light weight pannel with FRP is available for bracing structure in trench excavation.

• 터널과지하공간
• /
• 제18권2호
• /
• pp.118-124
• /
• 2008

흙막이 구조물에 대한 발파진동 허용기준을 설정하고 10 m 이내 근거리 발파를 실측하여 흙막이 구조물에 전달되는 진동규모를 확인하였다. 또 시험발파 계측데이터로부터 발파작업이 흙막이 구조물과 배면지반에 미치는 영향을 평가하였다. 연구결과 $0.5{\sim}2.0kg$ 범위의 발파작업은 흙막이 구조물과 배면지반에 거의 영향을 미치지 않는 것으로 분석되었으나 발파압력에 의한 암반블록의 이동 영향을 고려하여 최소저항선의 2배 정도를 이격하여 발파할 것을 추천한다.

• 한국측량학회:학술대회논문집
• /
• 한국측량학회 2003년도 추계학술발표회 논문집
• /
• pp.169-174
• /
• 2003

Design of a rational earth volume conversion coefficient is required as the earth volume conversion coefficient may give great influence on construction work volume and construction costs in the civil engineering works where large-scaled earth volume is excavated. However, there are a great deal of difficulties in the calculation of the exact spoil surface earth and Insufficient earth volume by adopting the figures presented on the generally used design specifications which are not the results obtained from the selection tests in calculating the earth volume conversion coefficient. In this connection, it would be desirable to calculate the earth volume conversion coefficient by carrying out large-scaled site test adequate for the relevant environment. In consequence, this study aims at calculating the exact earth volume conversion coefficient of cutting and banking areas of weathering rocks in large-scaled construction sites where land is being developed into home lots. For this, we have excavated the respective 20 sites of the cutting and banking areas in the said site and then calculated the volume after the excavation. As a result, the relative exactness degree of the crossing was calculated at 0.5% in average. The relative exactness degree of 0.5% in the volume may be judged as an exact measurement as it corresponds to 0.17% of the relative exactness degree in the length measurement. We have calculated the exact earth volume conversion coefficient by the use of function ratio as per the wet unit weight and the indoor soil quality test as per volume calculated. And then we have found out minor differences as a result of the comparison and analysis with the earth volume conversion coefficient determined by the dry unit weight test as per sand replacement method. This may be judged as a rational design method for the calculation of earth volume conversion coefficient, as well as high reliability of site test as a precision photogrammetry is adopted for volume measurement of the irregular excavating areas.

• 지구물리와물리탐사
• /
• 제11권4호
• /
• pp.373-378
• /
• 2008

현재 전세계적으로 지구과학 분야의 지도제작은 Generic Mapping Tools (GMT) 소프트웨어가 사용되고 있으나, 사용자가 그 내용을 이해하기 쉽지 않고, 마이크로소프트 (MS) 윈도우 PC에서의 구동이 잘 되지 않은 단점이 있다. R언어는 패키지 'GEOmap'을 사용하면 MS윈도우상에서 GMT와 같은 지도작업이 잘 될 뿐 아니라, GMT에 비해 명령어가 이해하기 쉬우며, 명령에 대한 Help 기능이 컴퓨터 상에서 대화형으로 잘 구비되어 있다. 여기서는 'GEOmap'을 이용한 지도제작의 대강을 설명하고, 본 연구팀이 최근 발표한 토모그라피 지도제작에대한 적용례를 소개하였다.

• Journal of Astronomy and Space Sciences
• /
• 제31권1호
• /
• pp.51-61
• /
• 2014

In this work, the preliminary analysis on both the tracking schedule and measurements characteristics for the spacecraft on the phase of lunar transfer and capture is performed. To analyze both the tracking schedule and measurements characteristics, lunar transfer and capture phases' optimized trajectories are directly adapted from former research, and eleven ground tracking facilities (three Deep Space Network sties, seven Near Earth Network sites, one Daejeon site) are assumed to support the mission. Under these conceptual mission scenarios, detailed tracking schedules and expected measurement characteristics during critical maneuvers (Trans Lunar Injection, Lunar Orbit Insertion and Apoapsis Adjustment Maneuver), especially for the Deajeon station, are successfully analyzed. The orders of predicted measurements' variances during lunar capture phase according to critical maneuvers are found to be within the order of mm/s for the range and micro-deg/s for the angular measurements rates which are in good agreement with the recommended values of typical measurement modeling accuracies for Deep Space Networks. Although preliminary navigation accuracy guidelines are provided through this work, it is expected to give more practical insights into preparing the Korea's future lunar mission, especially for developing flight dynamics subsystem.