• 한국측량학회지
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• 제27권2호
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• pp.129-138
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• 2009

달 중력장은 달의 내부구조와 이분성 및 마그마 바다의 분화 진화과정을 이해하고, 더 나아가 달의 기원과 진화를 규명하기 위한 중요한 자료이다. 본 연구에서는 달 탐사의 역사와 달의 중력장 탐지 및 중력장모델의 발전과정을 고찰하였으며, 최근에 임무를 종료한 일본의 SELENE위성의 관측방식을 소개하고, SELENE위성의 궤도추적자료를 처리하여 개발된 달 중력장모델 SGM90d(SELENE Gravity Model)를 이용해 달 전체의 중력이상을 결정하였으며, 기존의 달 중력장 모델인 LP165P모델과 비교분석을 수행하였다. SGM90d를 분석해 본 결과, SELENE위성의 4중 도플러 관측방식은 달 뒷면의 중력장 직접 관측에 매우 효과적이었으며, 달 뒷면 중력장의 최초 결정은 달의 메스콘과 같은 중력이상의 상세한 분포를 확인하고 달의 이분성을 이해하는데 큰 도움이 되었다.

• 한국측량학회:학술대회논문집
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• 한국측량학회 2006년도 춘계학술발표회 논문집
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• pp.99-104
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• 2006

The new gravity field combination models are expected to improve the knowledge of the Earth's global gravity field. This study evaluates eleven global gravity field models derived from gravimetry and altimetry surface data in a comparison with ground truth in South Korea. Geoid heights obtained from GPS and levelling in South Korea are compared with geoid heights from the models. The results show that the gravity satellites CHAMP, GRACE and LAGEOS plus gravimetry and altimetry surface data have led to an improvement in gravity field models. As expected, the new combination gravity field model which are EIGEN-CG03C and EIGEN-GL04C give better results than the predecessors widely used models(EGM96, OSU91A etc.).

• Earthquakes and Structures
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• 제9권1호
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• pp.111-126
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• 2015

In this study, the coupled effects of magnetic field, stress and thermal field on gravity waves propagating in a liquid layer over a solid surface are discussed. Due to change in temperature, initial hydrostatic stress and magnetic field, the gravity-sound Rayleigh waves can propagate in the liquid-solid interface. Dispersion properties of waves are derived by using classical dynamical theory of thermoelasticity. The phase velocity of gravity waves influenced quite remarkably in the presence of initial stress parameter, magneto-thermoelastic coupling parameter in the half space. Numerical solutions are also discussed for gravity-Rayleigh waves. In the absence of temperature, stress and magnetic field, the obtained results are in agreement with classical results.

• 대한원격탐사학회지
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• 제31권4호
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• pp.353-360
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• 2015

Earth's gravity field recovery was improved after the pre-processing upgrade of the Gravity Recovery And Climate Experiments (GRACE) satellite's star trackers. The star tracker measurements were filtered with a tighter low-pass filtering of 0.025Hz cutoff frequency, instead of a nominal filtering of 0.1Hz cutoff frequency. In addition, a jump removal algorithm was applied to remove discontinuities, due to direct Sun and/or Moon interventions, in the star tracker measurements. During the K-Band Ranging (KBR) calibration maneuvers, large attitude variations could be detected concurrently by both of the star trackers and the accelerometer. The misalignment angles of star trackers between the true frame and the normal frame could be determined by comparing measurements from these sensors. In this paper, new Earth' gravity field maps were obtained using above improvement. Based on comparisons to nominal Earth's gravity field maps, the new Earth's gravity field maps were found better than the nominal ones. Among the applied methods, the misalignment calibration of the star trackers had a major impact on the improvement of the new Earth's gravity field maps.

• 한국측량학회지
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• 제5권1호
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• pp.32-42
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• 1987

지구중력장의 대국적 변동과 국지적 불등성은 수평위치의 정확한 결정뿐만 아니라 수직위치의 정확한 결정에도 중요한 작용을 한다. 본 연구에서는 이러한 중요성에 비추어 정확한 높이결정에 있어서 중력장의 영향에 관제되는 중력포텐셜론과 각종 높이의 개념을 고찰하고, 실측중력자료와 수준측량자료를 이용하여 이들 높이를 산정하고 그 특성을 비교분석함으로써 정밀수직위치 결정에 있어서 중력장이 미치는 영향을 고찰하고자 한다. 부산~경주에 이르는 노선에 대하여 분석한 결과 중력장을 고려한 높이와 수준측량에 의한 높이차($\Delta$H)의 인접측점간의 비고 (dH)에 대한 비율($\Delta$H/dH)이, 보정식에 의한 값은 위도에 직선적으로 비례증가하고, 중력포텐셜에 의한 값은 위도보다 역지형의 영향을 크게 받음을 알 수 있었다.

• 대한원격탐사학회지
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• 제21권1호
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• pp.51-57
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• 2005

The currently operating NASA/GFZ Gravity Recovery and Climate Experiment (GRACE) mission is designed to measure small mass changes over a large spatial scale, including the mapping of continental water storage changes and other geophysical signals in the form of monthly temporal gravity field. The European Space Agency's Gravity field and steady state Ocean Circulation Explorer (GOCE) space gravity gradiometer (SGG) mission is anticipated to determine the mean Earth gravity field with an unprecedented geoid accuracy of several cm (rms) with wavelength of 130km or longer. In this paper, we present a summary of present GRACE studies for the recovery of hydrological signals in the Amazon basin using alternative processing and filtering techniques, and local inversion to enhance the temporal and spatial resolutions by two-folds or better. Simulation studies for the potential GRACE detection of slow deformations due to Nazca-South America plate convergence and glacial isostatic adjustment (GIA) signals show that these signals are at present difficult to detect without long-term data averaging and further improvement of GRACE measurement accuracy.

• Structural Engineering and Mechanics
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• 제53권2호
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• pp.277-296
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• 2015

The objective of this paper is to investigate the surface waves in fibre-reinforced anisotropic thermoelastic medium subjected to gravity field. The theory of generalized surface waves has firstly developed and then it has been employed to investigate particular cases of waves, viz., Stoneley waves, Rayleigh waves and Love waves. The analytical expressions for displacement components, force stress and temperature distribution are obtained in the physical domain by using the harmonic vibrations. The wave velocity equations have been obtained in different cases. The numerical results are given and presented graphically in Green-Lindsay and Lord-Shulman theory of thermoelasticity. Comparison was made with the results obtained in the presence and absence of gravity, anisotropy, relaxation times and parameters for fibrereinforced of the material medium. The results indicate that the effect of gravity, anisotropy, relaxation times and parameters for fibre-reinforced of the material medium are very pronounced.

• 대한원격탐사학회지
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• 제17권4호
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• pp.297-305
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• 2001

Ocean satellite altimetry-implied free-air gravity anomalies have had the shortest wavelengths removed during the processing to generate the optimal solution between multiple radar altimeter missions. ERS-1 168day mission altimetry was residualized to a reference geoid surface generated by integrating Anderson & Knudsen’s free-air gravity anomalies for the Barents Sea. The altimetry tracks were reduced and filtered to extract the shortest wavelengths (between 4 and 111 km) from both ascending and descending tracks, respectively. These data were recombined using existing quadrant-swapping techniques in the wavenumber domain to generate a correlated, high frequency gravity field related to the local geologic sources. This added-value surface adjusted the reference free-air gravity anomalies to better reflect features in the gravity field at a wavelength related to the distance between altimetry ground tracks.

• Geomechanics and Engineering
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• 제37권3호
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• pp.243-251
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• 2024

In the current work, a poro-thermoelastic half-space issue with temperature-dependent characteristics and an inclined load is examined in the framework of the three-phase-lag model (3PHL) while taking into account the effects of magnetic and gravity fields. The resulting coupled governing equations are non-dimensional and are solved by normal mode analysis. To investigate the impacts of the gravitational field, magnetic field, inclined load, and an empirical material constant, numerical findings are graphically displayed. MATLAB software is used for numerical calculations. Graphs are used to visualize and analyze the computational findings. It is found that the physical quantities are affected by the magnetic field, gravity field, the nonlocal parameter, the inclined load, and the empirical material constant.

• 대한지구과학교육학회지
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• 제1권1호
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• pp.72-84
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• 2008

This study is focused on the main concepts of gravity and geomagnetics which are introduced in the earth science textbooks of high school in 7th curriculum. This study examines the validity and accuracy of the Earth Science textbooks and shows some effective teaching plans by using the latest materials. This study also illustrates the main concepts of gravity and geomagnetics through presenting some effective and practical teaching-learning methods. The results of the study were as follows: First of all, a number of main concepts of six textbooks of high school were selected; the field of gravity, the direction and dimension of gravity, the measurement of gravity, the main reason of gravity anomaly and geoid, earth terrestrial magnetic field, secular variation of goemagnetics. Secondly, most Earth Science textbooks of high school explains the main concepts of the gravity and geomagnetics in similar ways. Those textbooks, however, don't put an emphasis on the essential contents which has been regarded as important thing in terms of the current educational course of study. The high school textbooks also use the material which is too old-fashioned and has some problems of accuracy and validity. Especially, many main concepts of the textbooks and scientific data(such as the direction of gravity, the measurement of gravity, the main reason of gravity anomaly, the use of geoid, secular variation) are different with those of South Korea, In addition, some materials(graphs and diagrams) are very old ones and they don't have authentic information.Finally, Among the various main concepts, some important ideas (the direction of the gravity and the method of measuring gravity, the measurement and use of gravity anomaly, the definition of geoid and secular variation of geomagnetics) should be corrected by showing the latest and authentic materials.