본 연구에서는 지진에 대한 고층건물의 응답특성, 그리고 지진응답에 미치는 중력하중의 영향과 중력하중의 영향이 내진설계에 미치는 중요성을 산정하였다. 이를 위해서 예제 구조물에 대한 정적해석 및 지진하중에 대한 동적해석을 하였다. 지진에 대한 고층건물의 지진응답 특성을 파악하기 위하여 비탄성 변형의 건물 높이에 따른 분포를 알아보았다. 지진이 발생하면 휨모멘트 요구도가 건물의 상부층보다 하부층에서 상대적으로 더 많이 증가해서 설계모멘트와의 차이가 건물의 하부층으로 갈수록 더 커진다. 그 결과 현재 쓰이는 내진설계방법에 따라 설계된 예제 건물들은 지진에 대하여 비탄성 응답이 건물의 각 층마다 서로 다르게 발생하는데 주로 건물의 하부층에서 큰 비탄성 응답이 발생한다. 또한 설계시에 고려된 중력하중 때문에 구조적 손상이 건물의 꼭대기 층에서 아래로 갈수록 크게 증가한다. 구조물의 지진응답에 관하여 중력하중은 보의 항복시간을 앞당기며, 보의 양단의 소성힌지에 각기 다른 비탄성 거동을 유발시킨다. 그러나 중력하중에 의한 초기 휨모멘트의 영향은 보가 비탄성 거동을 계속함에 따라 재분배되어 보의 양단에서 그 영향이 감소되며 비탄성 변형이 계속되면 크게 감소한다. 중력하중에 의한 초기 휨모멘트의 영향이 감소는 고층건물의 내진설계에 있어서 중력하중의 영향이 주는 의미는 기둥과 보의 휨강도를 결정할 때 현재의 방법보다 중력하중의 영향을 줄이고 지진하중의 영향을 증가시켜야 한다는 것이다.

Several subjects related to gravity terrain correction, such as segmentation and geometric fitting of topography, methodology of gravity effect calculation, and difference between slab and spherical shell type corrections, are widely reviewed. Through the review, an effective terrain correction program in which accuracy in the correction is balanced with simplicity in excution is developed. The program written in microsoft Fortran for general use appears to be effective in the viewpoint of accuracy as well as simplicity. Topography data file which is convenient in management and retrieve is designed for the excution of the program. It is required for estimating terrain and Bouguer correction values to assume the mean density which should effectively be used over the area concerned. The preexisting methods for the density determination are examined and an alternative method modified the preexisting ones is proposed in the present study.

Gravity survey was conducted to investigate subsurface structure of the Bupyung caldera. Two profiles of about 23 ㎞ and 21㎞ length were chosen across the caldera and gravity values were measured at 333 points on those profiles. The regional gravity trend of the survey area is mainly attributed to isostasy. The maximum negative gravity anomaly over the caldera appears to be -8.5m gal. Gravity profiles were analyzed and interpreted by using power spectrum analysis, Marquardt-Levenberg inversion and ideal-body inversion methods. The result of 2-D inversion shows the existence of the low density structure of about 8km surface width and 3km depth under the caldera. Since the caldera has three dimensional, 2-D gravity inversion results in relatively large error as compared with 3-D modeling. Fortran subroutine was coded to calculate the gravity anomalies caused by 3-D subsurface bodies. The result of 3-D modeling shows the Bupyeong caldera can be approximated by basin-shaped low density body whose depth reaches to 3㎞. At this depth level we assume that there exist a nearly flat boundary between granite batholith and metamorphic rock out side of the caldera. The negative anomaly of Bupyeong caldera appears to be caused by density contrast between low-density granite inside the caldera and surrounding metamorphic complex. Relationship between the defect mass and the diameter of Bupyeong caldera satisfies general relationship observed in world-wide volcanic calderas.

The multiquadric terrain equation reproduces topography which is much closer to the real one than the digital terrain model. Also, terrain correction calculated by using the multiquadric terrain model shows a better result than that of digital terrain model. The accuracy of terrain correction depends on the accuracy of terrain data. Therefore, determination of the mean elevation of a terrain compartment by taking simple average of the maximum and minimum terrain height is not recommended. To obtain more accurate mean elevation of a compartment, a smaller scale topographic map such as 1:5,000 map is desirable for reading terrain data. But 1:25,000 map can be used for practical use. The pattern size of 250m×250m compartment is appeared to be suitable for near correction(D-F range), and 5㎞×5㎞ size for far correction. The computer program developed in this research can be used in all cases of surface and subsurface gravity surveys.

연안해역에 저밀도 Froude수의 액체를 방류할 때 인근해역에 미치는 영향을 저감하기 위해서, 중력분류의 혼합\ulcorner희석특성을 알아보았다. 연직방향방류시 밀도 Froude수가 작은 것이 분류의 퍼짐폭이 증대하여 방류수의 혼합\ulcorner희석이 활발해진다. 수평방향방류시 밀도 Froude수가 클수록 혼합\ulcorner희석효과가 증대된다. 수평방향방류가 연직수평방류보다 혼합희석효과가 뛰어나다. 수평방향방류시 다공관으로 방류하는 것이 단공관의 경우 보다 효과적이다. 이는 방류수를 분산시켜 방류함으로서 주위수와 접하는 표면적이 증대되기 때문이다.

In order to investigate the relationship between the distribution pattern of subsurface geological features and the Bouguer anomaly in the Eumseong area, Chungbuk Province, gravity values were measured from 290sites using Worden gravity meter. The study area consists of (1) Pre-Cambrian metamorphic rocks which were intruded by the Jurassic igneous rocks, (2) the Mesozoic Chopyeong and Baegyari Formation, and (3) the Basalt and Andesite which intruded the Cfiopyeong Formation. Terrain correction value using 0.5km X 0.5km blocks is an average of 0.9mgal (max. 1.8mgal, min. 0.1mgal). The depth of density boundary in the study area were calculated by power spectrum analysis with double Fourier transform and FFT. Downward continuation of gravity was performed using the sinχ/χ convolution method. To minimize the Gibbs phenomenon associated with the downward continuation, Hamming filter was used. The value of Bouguer anomaly is-8mgal to 4mga1. Direction of the regional anomaly is the NEW whose trend is parallel with regional structural features. Residual anomaly is low in sedimentary rocks of middle part and igneous rocks regions of eastern and western parts of the study area, whereas it is high in metamophic rocks and andesite vein of middle part. Mean depth of the density boundary is 1420m, and undulation aspect of the subterrain was highest in andesite region. The boundary depth is increasing from Chopyeong Formation to Baegyari Formation.

The purpose of this study is to investigate basic parameters which are essential for tidal correction of gravity data. This study involves computation of the theoretical values and laboratory measurements of tidal force of gravity. The theoretical variation of tidal force was computed according to the relative position of moon and sun on the celestial sphere by using a computer program Gravity measurements were carried out in Seoul University for 120 operation-hours, and also in coastal area in Incheon for 48 operation-hours. The gravimetric factor (δ) and phase delay were determined by comparing theoretical values with measured gravity data. Summarized results of this study are as follows ; (1) The gravimetric factor in Seoul is in the range of 1.22∼1.36(avg.=1.28) and the phase delay is in the range of 0.1∼0.3 hours (avg.=0.16 hours). (2) The mean garvimetric factor in Incheon is 1.31 and mean phase delay is 0.025 hours (3) The difference of mean gravimetric factor between in Seoul and in Incheon is 0.03 and that of phase delay is 8 minutes.

The gravity anomaly of the southern part of the Gyeongsang basin and the adjacent sea is analyzed. According to the power spectrum analysis method, calculated the mean depth of the moho and the boundary between the sedimentary layer and the basements is 32㎞ and 61㎞ respectively. With these values, regional and residual anomalies of the gravity for each depth are calculated by the running average method and interpreted. By the sin X/X method, the crustal thickness and the depth of the boundary of the sedimentary layer in the southern part of the Gyeongsang basin turns out to vary from 34㎞ to 28㎞ and from 8.5㎞ to 0.5㎞ respectively.

보은군 회남면 조곡리에는 옥천계 누층군내에 감람암의 노두가 발견되며 이 암석의 밀도는 2.9∼3.1 g/㎤로서 주변암석 보다 0.3g/㎤ 이상 크기 때문에 중력 탐사에 의한 감람암의 지하연장 규모를 추정할 만 하다. 본 지역과 주변지역에서 정밀측정을 실시한 결과 중력 이상치는 서측에서 18mgal, 동측에서는 8mgal 정도로 지역적 경향을 보이며 이로부터 분리한 국지적 중력이상은 감람암 노두지역 부근에서 4,3mgal 정도이다. 이를 분석 연구하여 감람암체가 약 3㎞ 이내의 뿌리를 갖고 있으며 지하로 들어갈수록 서측으로 경사되어 있음을 알 수 있었다. 따라서 감람암체는 현 위치에서 맨틀로부터 상승 분출했다기 보다 이미 분출된 후에 지각변동을 받아 이동된 듯하다.

선박용 강판(KR Grad A-3)과 라임티타니아계 피복 아아크 용접봉(E4303)을 이용하여 대기중용접 및 습식 수중 용접하여 TRC 임계응력치, 열 사이클, 경도분포, 확산성 수소량, micro조직 등을 실험적으로 조사한 결과를 요약하면 다음과 같다. 1. TRC 시험에 의한 초기 임계응력치 Σ 하(cr) 은 대기중 용접 및 수중용접의 어느 쪽에서도 Y groove 형상의 경우가 각각 71kg/mm 상(2), 51kg/mm 상(2) 로서 가장 높고, 반대로 45˚r 형 groove의 경우가 각각 52kg/mm 상(2), 41kg/mm 상(2)로서 최저이며, 수중용접부의 냉파괴 감수성이 대기중용접보다 높다. 2. 용접부의 경도는 조립 열영향부에서 가장 높고 대기중용접에서 약 H 하(k) 365, 수중용접에서는 급격한 냉각속도 때문에 약 H 상(k) 670으로 높게 되어 후자의 경우 파괴 감수성의 증가에 의한 낮은 임계응력치를 갖게 된다. 3. 48시간 동안의 확산성 수소량은 대기중용접에서 약 18cc/100g-weld-metal, 수중용접의 경우 약 48cc/100g-weld-metal로서 수중용접의 경우가 약 3배 정도 더 침입하고 있으므로 이의 방지책이 필요하다.

The computation of the undulation of the Moho discontinuity from gravity data has frequently been carried out by the application of the Fourier series and the Sinc function (sin x/x), However, no serious effort has been attempted to examine the suitability of data and the adaptability of implicit assumptions required in such methods. This paper deals with model studies for comparison of the Fourier series and Sinc function methods, and examinations of several criteria for obtaining meaningful results. Also, an inversion method based on mass plane concept has been devised to complement the weakness of the above two methods. This method has been appeared as an effective scheme for increasing depth computation points so that a more detailed undulation is obtained.

The national wide gravity survey to establish gravity values for the base reference stations in Korea was initiated by the U.S. Army. The Division of Geodesy, U.S. Army Map Service Far East (DG, USAMSFE) conducted two base station surveys in 1961 and 1964, and measured gravity values at 15 stations throughout Korea. Professor Woollard also observed 3 gravity base stations in 1964 as a part of the International Gravity Measurements. All of these surveys were tied directly to DG Base of USAMSFE in Tokyo and Tachikawa Air Force Base stations. GMIK (presently Korea Institute of Energy and Resources) also made 10 base station measurements in 1971, which are tied to USAMSFE base stations established in the previous survey. In a broader sense, all of these measurements are related to Potsdam system whose value is now recognized to be too large by about 14 mgals. In accordance with the International Gravity Standardization Net 1971 (IGSN 71), adopted and recommended by the International Union of Geodesy and Geophysics, GMIK, in cooperation with Institute of Geological Sciences of England, measured gravity values at 15 base reference stations which are tied to IGSN 71 primary base stations in London and Kyoto. The results of this survey are generally lower by about 13.8 mgals than previous values. On the other hand, the National Geography Institute established a fundamental national gravity base reference station in the back yard of the Institute's building and determined the gravity value, which is tied to the IGSN 71 value of the base reference station located in Tokyo. The measurements were made twice in 1975 and 1980 with the cooperation of Japan Geophysical Survey Institute. NGI also established four auxilliary gravity base reference stations in 1980. The author recently measured the gravity difference between two base reference stations located in Korea Institute of Energy and Resources and National Geography Institute and found the measured value is different by more than 1 mgal to that computed from the gravity values adopted by two Institutes. Therefore it is recommended to conduct a more detailed crosscheck to establish consistent base reference values throughout the country.

Home robot arms require a payload of 2 kg to perform various household tasks; at the same time, they should be operated by low-capacity motors and low-cost speed reducers to ensure reasonable product cost. Furthermore, as robot arms on mobile platforms are battery-driven, their energy efficiency should be very high. To satisfy these requirements, we designed a lightweight counterbalance mechanism (CBM) based on a spring and a wire and developed a home robot arm with five degrees of freedom (DOF) based on this CBM. The CBM compensates for gravitational torques applied to the two pitch joints that are most affected by the robot’s weight. The developed counterbalance robot adopts a belt-pulley based parallelogram mechanism for 2-DOF gravity compensation. Experiments using this robot demonstrate that the CBM allows the robot to meet the above-mentioned requirements, even with low-capacity motors and speed reducers.

Failure risk investigation of any structure in a seismic zone can be done by the seismic probabilistic risk assessment (SPRA), which became a very attractive area of research in terms of safety measurement. This paper introduces such kind of concept to identify which magnitude in a specific seismic zone will contribute more vulnerable failure point in a structure. Here, for implement this idea a case study on a concrete gravity dam has been carried out. In order to make a correlation between the magnitude and failure risk contribution based on different damage stage, a combination of seismic hazard analysis and the probability of structural collapse is adopted. Therefore, the deaggregation of the mean annual frequency of failure risk by magnitude is used in this study to quantify four different limit stages of failure identification criteria. Consequently, from analyzing the result, in case of concrete gravity dam, this deaggregation approach shows the tensile crack in the base looks more vulnerable damage stage for the specific seismic zone.

Technegas를 사용한 검사는 단순 확산 누적을 통해 폐 영상을 이미지화하기 때문에 검사를 마친 후에 검 사실이 오염될 수 있다. 따라서 방사선 작업 종사자와 검사를 기다리는 환자는 technegas 흡입으로 인한 내 부 피폭의 영향을 받게 된다. 이에 중력환기 전후의 시간경과에 따른 공간선량율 분포를 비교, 분석함에 따 라 방사선사, 의료진, 대기 환자의 피폭선량 저감화 방법을 모색하고자 한다. 중력환기 전후 환자의 호흡기 위치에서 거리별, 각도별로 공간선량율을 10분 동안 측정하고 평균값, 표준 편차 및 감소율을 계산하였다. 실험 결과, 중력 환기 전후 감소율은 최고 95.31%였고 가장 높은 감소율은 1 ∼ 3분 사이에서 나타났다. 중 력환기를 통해서 방사선 작업종사자, 대기환자, 환자 보호자 및 간호사의 피폭선량을 감소시킬 수 있다. 결 론적으로 중력환기를 통한 피폭선량 감소 결과는 방호 최적화를 이루는 역할을 할 것이며 ICRP 103에서 권고한 의료 피폭 저감화에 부합된다.

In this study, perfectly matched discrete layers with analytical wavelengths is applied to concrete gravity dam analyses. The validation of the proposed procedure is made by comparing the results with a previous study and the results obtained from SASSI,

All over the world, concrete gravity dams have to withstand lots of environmental hazards and time-varying external loading during an earthquake. Therefore, the risk assessment of this structure with time may become an important study for the dam structure, which is related to the chemo-mechanical effect on the aging concrete. The focusing point of this study is to propose an earthquake assessment procedure to determine the failure probability with time of any concrete gravity dam for the future if we consider the material deterioration. This material decay is mainly associated with the modulus of elasticity of the concrete and it is explained briefly in the manuscript.

In this study, the development of gravity type collecting device for nuclear dismantling through CFD simulation is shown as follows. As a result of investigating the dust removal efficiency according to the treatment air velocity of 5 m/s (low speed) ～ 30 m/s (high speed), large dusts (80 ～ 100 ㎛) As the wind speed increases, the damping efficiency decreases and the particle size of the dust behavior increases with the increase of the wind speed. As a result, the wind speed (wind speed) 5 m/s is considered to be suitable for improving the vibration damping efficiency.