• 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.

• 한국지구과학회지
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• 제32권1호
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• pp.12-20
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• 2011

변성암복합체, 옥천층군, 조선누층군 및 화성암류에서 지하 지질분포 및 밀도 불연속면을 파악하기 위해 충주호 주변에 있는 256개 지점에서 중력측정을 실시하였다. 부게 중력이상은 옥천층군에서 높은 값을 가지며 조선누층군으로 갈수록 상대적으로 낮은 값의 분포를 보였다. 지하 밀도 불연속면의 평균심도는 약 2.0 km이며, 전반적으로 문주리층과 황강리층이 서창리층보다 중력기반 심도가 상대적으로 얇으며, 옥천계 동측에 위치한 조선누층군이 옥천층군보다 비교적 두꺼운 기반 심도로 분포된 것으로 파악되었다.

• 한국수산과학회지
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• 제51권3호
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• pp.332-337
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• 2018

The Pacific cod Gadus macrocepahlus, lays demersal eggs and the hatching larvae rise toward the surface layer of the ocean to feed. The change in the specific gravity of eggs and larvae was investigated to examine their vertical distribution and movement in the water column. The specific gravities of fertilized eggs and various size classes of larvae were measured using a density gradient apparatus. In total, the instantaneous specific gravity of 146 eggs and 225 larvae were measured. To prevent any disturbance in the gradient water column due to larval movement, 0.004% MS222 was used for anesthesia. Due to their high specific gravity, eggs spawned were deposited over the sea-bed of the spawning ground. The specific gravity of hatching larvae decreased abruptly. However, Pacific cod larvae still had a comparatively high specific gravity at hatching ($1.03655{\pm}0.00146g/cm3$, n=4, mean SL=3.62 mm) and their specific gravities tended to decrease as they grew. The specific gravity stabilized 6 days after hatching ($1.02590{\pm}0.00212g/cm3$, n=15, mean SL=4.67 mm) and the cod larvae were eventually able to float in the water column.

• 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.

• 한국정밀공학회지
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• 제28권4호
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• pp.455-462
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• 2011

This paper is about the design of a new gravity compensator for the lower body exo-skeleton device. The exo-skeleton devices is for increasing the torque of the human body joint for the purpose of helping the disabled, workers in the industry, and military soldiers. So far, most of studied exo-skeleton devices are actuated by the motors, but motors are limited in energy such that a short durability is always a big problem. In this paper, a new gravity compensator is proposed to reduce the torque load applied to human body joints due to gravity. The gravity compensator is designed using a tortional bar spring, and its structure and characteristics are studied through the test and computer simulation. A design concept on the exo-skeleton device using the gravity compensator is presented. An analysis and computer simulation on the torque reduction of the proposed exo-skeleton device that applies and non-applies the gravity compensator are performed.

• 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.

• Advances in Computational Design
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• 제4권2호
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• pp.141-153
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• 2019

This research is comprised of virtually simulating behavior while experiencing low gravity effects in advance of real world testing in low gravity aboard Zero Gravity Corporation's (Zero-G) research aircraft (727-200F). The experiment simulated a drill rig penetrating a regolith simulant. Regolith is a layer of loose, heterogeneous superficial deposits covering solid rock on surfaces of the Earth' moon, asteroids and Mars. The behavior and propagation of space debris when drilled in low gravity was tested through simulations and visualization in a leading dynamic simulation software as well as discrete element modeling software and in preparation for comparing to real world results from flying the experiment aboard Zero-G. The study of outer space regolith could lead to deeper scientific knowledge of extra-terrestrial surfaces, which could lead us to breakthroughs with respect to space mining or in-situ resource utilization (ISRU). These studies aimed to test and evaluate the drilling process in low to zero gravity environments and to determine static stress analysis on the drill when tested in low gravity environments. These tests and simulations were conducted by a team from Texas A&M University's Department of Construction Science, the United States Air Force Academy's Department of Astronautical Engineering, and Crow Industries

• 한국군사과학기술학회지
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• 제27권2호
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• pp.127-139
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• 2024

This paper discusses a gravity compensation technique designed to reduce wavefront error caused by gravity during the assembly and alignment of satellite multi-band optical sensor. For this study, the wavefront error caused by gravity was analyzed for the opto-mechanical structure of multi-band optical sensor. Wavefront error, an indicator of optical performance, was computed by using the displacements of optics calculated through structural analysis and optical sensitivity calculated through optical analysis. Since the calculated wavefront error caused by gravity exceeded the allocated budget, the gravity compensation technique was required. This compensation technique reduces wavefront error effectively by applying the compensation load to the appropriate position of the housing tube. This method successfully meets the wavefront error budget for all bands. In the future, a gravity compensation equipment applying this technique will be manufactured and used for assembly and alignment of multi-band optical sensor.

• 한국지구과학회지
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• 제31권1호
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• pp.1-7
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• 2010

그 동안 많은 연구에서 지형보정을 위한 프로그램들이 개발되어왔으며, 매우 효과적으로 지형보정을 수행하는 것으로 인정받아왔다. 특히, 한반도 뿐만이 아니라 세계적으로도 수치 지형자료가 보편적으로 보급되어 지형보정을 위한 기반 자료는 충분히 확보되고 있다. 이번 연구는 일반적인 광역탐사가 아닌 소규모 광체나 지질구조에 대한 정밀한 중력탐사에 대한 자동지형보정을 수행할 수 있도록 하는 프로그램을 개발하였다. 소규모 지하자원이나 지하공동 등의 소규모 지질현상에 대한 중력탐사에는 기존의 광역탐사에 적합한 지형보정프로그램보다 더욱 정밀한 지형보정프로그램이 필요하다. 따라서 본 연구를 통해서 개발된 자동정밀지형보정프로그램으로 정밀중력탐사를 보다 효율적으로 수행할 수 있게되었다. 본 연구에서 개발된 정밀지형보정프로그램에서는 multiquadric equation을 이용한 지형구현을 통해 보다 정밀한 지형 생성이 가능하게 설계하였으며, 연구자의 설정에 따라 중력측정점 주변에 자세한 지형값을 넣어 정밀한 지형보정이 가능하도록 하였다. 또한 기존의 광역중력탐사에서 무시되던 지형과 중력계 사이의 거리 차에 따른 옵션을 설정하여 정밀한 지형보정 수치를 산출하도록 하였다.

• 한국잠사곤충학회지
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• 제20권2호
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• pp.6-9
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• 1978

잠 103$\times$잠 104 와 그 역교, 잠107$\times$잠108 및 그 역교를 공시하여 6개 업자의 잠종비중별 부화율 및 실용부화율 시험에서 얻은 결과는 1. 난비중을 세분하여 부화율 실용부화율을 보면 경비중에 비하여 중비중 및 중비중의 난이 부화율 및 실용부화율이 높았다. 2. 일모체는 중모체에 비하여 경비중 및 중비중난에서 부화률이 높았고 실용부화율은 경비중난에서만 높았다. 3. 중모체는 비중별 실용부화율 및 부화율의 차이가 컸으며 이에 비하여 일모체는 부화율에는 차이가 없으나 실용부화율에서 비중별 차이를 인정할 수 있었다. 4. 제조업자별 중비중난의 부화율 및 실용부화율의 차이는 없으나 경비중, 중비중난에서는 현저한 차이를 나타내었다.