• Geophysics and Geophysical Exploration
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• v.25 no.1
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• pp.44-49
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• 2022

Closed-form expressions of vector gravity and gravity gradient tensor based on a line segment are derived. If a cylindrical object with axial symmetry is observed from a distance, it is possible to approximate it as a line segment; therefore, it is necessary to compute the gravity and the gravity gradient tensor due to a line source by using closed-form expressions. The gravitational potential for a line segment is defined as a one-dimensional integral, and this integral is differentiated with respect to the Cartesian coordinate system to derive the vector gravity. The expressions of the gravity gradient tensor are derived by differentiating the vector gravity once more in the same coordinate system.

• Economic and Environmental Geology
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• v.28 no.1
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• pp.79-88
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• 1995

The gravity measurment has been carried out at 48 gravity stations with intervals of 1.0~1.5 km along the survey line between Samcheog, Gosari and Taebaek to study subsurface geology and geologic structure in the northeastern part of the Ockchon zone. The Bouguer gravity anomaly values were obtained from the measured gravity values through the gravity corrections. The subsurface geology and geologic structure were interpreted quantitatively by means of the Fourier series method and Talwani method for 2.5 dimensional body. In the study area, the depth of Conrad discontinuity is about 10 km at Samcheog, northeastern end of the survey line, and it is increased rapidly to about 12.5 km at Miro, 15 km at Gosari and 15.5 km at Dongjeom, southwestern end of the survey line, respectively. The depth of the basement of the Ockchon zone exposed at Samcheog is increased smoothly to about 2 km at 5 km from Samcheog along the survey line, and is exposed again in the area between Singiry and Gosari. Beyond Gosari its depth is increased to about 1.7 km, and displaced 2.3 km downward by Osipcheon fault near Dogyeri and 0.5 km by Baeksan thrust near Cheolam, respectively. Many V-shaped low Bouguer gravity anomalies resulted from the fracture zone associated with faults imply the existence of Osipcheon fault and several inferred faults. The low Bouguer gravity anomaly zone between Tongdong and Dongjeom is caused by Jurassic gneissose granite. A local high Bouguer gravity anomaly at 35 km along the survey line from Samcheog is interpreted by the effect of iron deposit of high density existed at subsurface. The thickness of Great Limestone Group varies from 0.5 km to 1.4 km, that of Pyeongan Supergroup from 0.4 km to 0.9 km, and that of Yangdeog Group is about 0.3 km. The thickness of Jurassic gneissose granite varies from 1.5 to 3.0 km.

• Journal of the Korean earth science society
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• v.35 no.7
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• pp.529-536
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• 2014

In this paper, the automatic determination algorithm of strike and dip of a line source using gravity gradient on a single profile is proposed. In general, the gravity gradient tensor due to a line source has only two independent components because of its 2-Dimensional (2-D) characteristics. However, if the line source has the strike and dip regarding the observation profile, it comes to have five independent components. The proposed algorithm of the determination both strike and dip is based on the rotational transform that converts full gravity gradient tensor to reduced 2-D gravity gradient tensor. The least-square method is applied in order to find optimum rotational angles that make one of the row components minimalized simultaneously. The two synthetic cases of a line source are represented; one has strike only and the other has both strike and dip. This study finds that the automatic determination method using gravity gradient tensor can find directions of a line source in each case.

• The Journal of Korean Physical Therapy
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• v.11 no.1
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• pp.63-70
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• 1999

This study was for mathematical method of calculating the joint reaction force during on single - leg stance on a normal and hemiplegic patients. It is important to compare the distance of the line of gravity from the hip joint on hemiplegic patients with this on normal in this study. In earlier studies, there is no include the concept about biomechanical analysis on the shin of line of gravity of hemiplegic patients. Though this concept, we found the compensation make the line of gravity closer to the supporting hip joint and the trunk was toward the side of paralysis. The result of the Joint reaction force on hemiplegic patients is found to be approximately $31.33\%$ in the unaffected side by biomechanical analysis.

• Journal of the Korean Society of Surveying, Geodesy, Photogrammetry and Cartography
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• v.29 no.3
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• pp.319-325
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• 2011

It has been used not orthometric height but normal orthometric height for the official height in Korean benchmark because it has been used not observed gravity but normal gravity for the computation of orthometric correction. The purpose of this study is to propose height renewal method of Korean benchmark. For this purpose, we observed gravity by CG5 digital gravimeter in both the first benchmark line between Sokcho and Gangneung area and the second benchmark line between Soksa and Inje area. We calculated relative gravity value and orthometric correction in all benchmarks. So, the maximum orthometric correction shows -0.349mm in the first benchmark line, and the maximum orthometric correction shows -44.060mm in the second benchmark line. In conclusion, we can confirm that the orthometric correction based on observed gravity is necessary for more accurate official height computation in the Korean benchmark.

• Economic and Environmental Geology
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• v.32 no.6
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• pp.645-651
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• 1999

The gravity and magnetic measurements have been obtained from 34 stations with 50m intervals along the survey line positioned between Jangtanri and sindapri for studying subsurface geology and structures of the volcanic rocks in Yeoncheon area. The Bouguer gravity and magnetic anomaly values were evaluated from the reduction of the field observation, and then interpreted by Nettleton's method and maximum-pepth rules, are approximately 160m based on magnetic data and 135m based on gravity data. High Bouguer gravity anomaly zone between 0m in Jangtanri and 900m along the survery line, is caused by thick and high density, older dasalt which is positioned beneath jijangbong tuff breccia, and this result corresponds to the interpretation result based on magnetic anomly. Lower gravity and magnetic anomaly zones ariund 900m are caused by between 1300m and 1550m are caused by high density of Quarternary basalt exposed in the surface, and lower gravity and magnetic anomalies at 200m and 1250m are caused by faults.

• Journal of The Korean Astronomical Society
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• v.39 no.4
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• pp.125-128
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• 2006

In order to determine the precise effective temperature and surface gravity of warm stars, all synthetic spectral lines in the wavelength range of $4000-5700{\AA}$ with T=6000-7750 K, and log g=3.5, 4.0, and 4.5 for [M/H]=0.0, $V_{rot}$=10 km $s^{-1}$, and $V_{tubl}$=2 km $s^{-1}$ were calculated using the SYNSPEC package(Hubeny, et al., 1995) and the Kurucz(1995) model. Then, the depth-ratios for all line pairs were investigated and we selected two and six depth-ratios appropriate for the surface gravity and temperature indicators, respectively. We plotted six grids with X- and Y-axes for the depth-ratios of surface gravity and temperature, respectively, for the simultaneous estimation of these two atmospheric parameters. This method was applied to the spectum of $\delta$ Scu for the determination of its temperature and surface gravity simultaneously.

• The Journal of Churna Manual Medicine for Spine and Nerves
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• v.2 no.2
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• pp.17-32
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• 2007

Objectives : The lumbosacral joint is unstable area from an anatomical viewpoint, while it is also a very mobile area in ordinary life, so that clinically major causes of low back pain originate in this joint. The purpose of this study is to assess the difference of the Ferguson's angles, Lumbar gravity lines, Lumbar lordotic angles among Herniated of Intervertebral Disc(HIVD) patients. Methods : We analyzed the lateral view of lumbar spine checked at erect position on 88 patients who had been diagnosed as HIVD by Magnetic Resonance Imaging(MRI). We investigated the Ferguson's angle, Lumbar gravity line, Lumbar lordotic angle on X-ray film. Results and Conclusions : In the acute lumbago group the Ferguson's angle had a tendency to decrease, while in the chronic group it had a tendency to increase. In the acute lumbago group the Lumbar gravity line fell in front of the normal range(sacrum), while in the chronic group it fell behind the normal range(sacrum). In the acute lumbago group the Lumbar lordotic angle usually decreased, while in the chronic group it increased. The Ferguson's angle and the Lumbar gravity line, the Ferguson's angle and the Lumbar lordotic angle, the Lumbar gravity line and Lumbar lordotic angle each had a positive realtionship. The Ferguson's angle, the Lumbar gravity line and the Lumbar lordotic angle was less influenced by the level of HIVD and was more influenced by how long the patient had the pain. The correlationship between each factor was less in the chronic lumbago group than the acute group. In the chronic lumbago group the instability of the lumbosacral joint increased, while in the acute group the compression of the weight on the sacrum increased.

• Journal of the Korean Geophysical Society
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• v.2 no.1
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• pp.27-38
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• 1999

The errors between track segments or at the cross-over points of shipborne gravity were successfully reduced by applying a cross-over error adjustment technique using satellite gravity. The integration of shipborne and satellite altimeter-implied free-air gravity anomalies after the cross-over error adjustment resulted in a high resolution gravity map which contains both short and long wavelength components. The successful adjustment of the cross-over errors in the shipborne gravity using the satellite gravity suggests that the shipborne gravity can be combined with the satellite anomalies characterized by a stable and long wavelength component. The resulting free-air anomaly map is evenly harmonized with both short and long wavelength anomalies. Thus the corrected anomaly map can be better used for the geological interpretation. Free-air anomalies with more than 140 mGal in total variations generally correspond to the seafloor topographic changes in their regional patterns. A series of gravity highs are aligned from the Korea Plateau to the Oki Island, which are interpreted to be caused by seamounts or volcanic topographies. The gravity minima along the western and southern shelf edge are associated not only with the local basement morphology and thick sediment fill at the continental margin, but also possibly with the crustal edge effect known for passive continental margins. Series of NE-trending linear anomalies are possibly caused by a swarm of volcanic intrusions followed the initial opening of the Ulleung Basin. The linear high anomalies in the Ulleung Plateau are terminated by the straightly NNW-trending anomalies with a sharp gradient in its western boundary which indicates a fault-line scarp. The opposite side adjoined with the fault-line scarp shows no correlation with the fault-line scarp in geometry indicating that the block might be horizontally slided from the north. A gravity high in contrast to the deepening in seafloor toward the northeastern central Ulleung Basin is probably responsible for the thin crust and shallow seated mantle. The gravity minima along the western and southern shelf edge are associated not only with the local basement morphology and thick sediment fill at the continental margin, but also possibly with the crustal edge effect known for passive continental margins. Series of NE-trending linear anomalies are possibly caused by a swarm of volcanic intrusions followed the initial opening of the Ulleung Basin. The linear high anomalies in the Ulleung Plateau are terminated by the straightly NNW-trending anomalies with a sharp gradient in its western boundary which indicates a fault-line scarp. The opposite side adjoined with the fault-line scarp shows no correlation with the fault-line scarp in geometry indicating that the block might be horizontally slided from the north. A gravity high in contrast to the deepening in seafloor toward the northeastern central Ulleung Basin is probably suggestive of a thin crust and shallow seated mantle.

• Journal of Acupuncture Research
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• v.27 no.3
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• pp.93-104
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• 2010

Objectives : The purpose of this study is to observe the effects of work environment and low back pain on the structural and muscle strength changes in lumbar spine to helpful for preventation and cure of low back pain. Methods : Through measuring of lumbosacral angle, lumbar lordotic angle, lumbar gravity line ratio analyzed structure of lumbar spine and using Trunk Extension Flexion Program of CYBEX NORM System(cybex770+TMC, USA) analyzed Flex. PT, Ext. PT, E/F ratio of lumbar spine of company employees given a medical examination. Results : According to work environment, lumbar gravity line ratio is higher in white collar group than in blue collar group, Ext. PT is significantly lower in white collar group than in blue collar group. According to low back pain or not, lumbar gravity line ratio, Ext. PT is lower in low back pain group than in non-low back pain group. Conclusions : Work environment and low back pain effects on the structural and muscle strength changes in lumbar spine.