• Journal of the Korean Society of Industry Convergence
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• v.3 no.4
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• pp.293-296
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• 2000

We have accumulated the knowledge of the phenomena of external nature under the gravity fields of the earth, but have not the data of the natural phenomena under the high or low gravity fields. It is necessary to research the phenomena of the combustion, heat transfer and the behavior of the living animals under the high or low gravity fields. This paper introduces the mysterious universe in high and low gravity fields from the experimental study by Arai et al.

• International Journal of Aeronautical and Space Sciences
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• v.14 no.1
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• pp.11-18
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• 2013

Human spaceflight experience in extra-vehicular activity (EVA) is limited to two regimes: the micro-gravity environment of Earth orbit, and the lunar surface environment at one-sixth of Earth's gravity. Future human missions to low-gravity bodies, including asteroids, comets, and the moons of Mars, will require EVA techniques that are beyond the current experience base. In order to develop robust approaches for exploring these small bodies, the dynamics associated with human exploration on low-gravity surface must be characterized. This paper examines the translational and rotational motion of an astronaut on the surface of a small body, and it is shown that the low-gravity environment will pose challenges to the surface mobility of an astronaut, unless new tools and EVA techniques are developed. Possibilities for addressing these challenges are explored, and utilization of the International Space Station to test operational concepts and hardware in preparation for a low-gravity surface EVA is discussed.

• Advances in Computational Design
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• v.4 no.2
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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

• Journal of Korean Society of Occupational and Environmental Hygiene
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• v.22 no.3
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• pp.257-264
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• 2012

Objectives: This study's aims were to evaluate the effects of load center of gravity within an object lifted and feet placements on peak EMG amplitude acting on bilateral low back muscle groups, and to suggest adequate foot strategies with an aim to reducing low back pain incidence while lifting asymmetric load. Methods: The hypotheses that asymmetric load imposes more peak EMG amplitude on low back muscles contralateral to load center of gravity than symmetric load and maximum peak EMG amplitude out of bilateral ones can be relieved by locating one foot close to load center of gravity in front of the other were established based on biomechanics including safety margin model and previous researches. 11 male subjects were required to lift symmetrically a 15.8kg object during 2sec according to each conditions; symmetric load-parallel feet (SP), asymmetric load-parallel feet (AP), asymmetric load-one foot contralateral to load center of gravity in front of the other (AL), and asymmetric load-one foot ipsilateral to load center of gravity in front of the other (AR). Bilateral longissimus, iliocostalis, and multifidus on right and left low back area were selected as target muscles, and asymmetric load had load center of gravity 10cm deviated to the right from the center in the frontal plane. Results: Greater peak EMG amplitude in left muscle group than in right one was observed due to the effect of load center of gravity, and mean peak EMG amplitudes on both sides was not affected by load center of gravity because of EMG balancing effect. However, the difference of peak EMG amplitudes between both sides was significantly affected by it. Maximum peak EMG amplitude out of both sides and the difference of peak EMG amplitude between both sides could be reduced with keeping one foot ipsilateral to load center of gravity in front of the other while lifting asymmetric load. Conclusions: It was likely that asymmetric load lead to the elevated incidence of low back pain in comparison with symmetric load based on maximum peak EMG amplitude occurrence and greater imbalanced peak EMG amplitude between both sides. Changing feet positions according to the location of load center of gravity was suggested as one intervention able to reduce the low back pain incidence.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.31 no.8
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• pp.58-68
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• 2003

Accurate estimation of the Earth gravity field plays an important role in understanding the Earth geodynamic activities. After brief discussion on the objective of the gravity estimation, dedicated satellite missions for this purpose are described. Recently launched NASA/DLR Gravity Recovery and Climate Experiment (GRACE) mission, which consists of two co-orbiting low altitude satellites, is described. For the performance analysis, full numerical simulation was performed. The simulation procedure and its key instrument modelings are described. From the simulation results, a significant improvement on the Earth gravity field accuracy is expected.

• 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.

• KOREAN JOURNAL OF CROP SCIENCE
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• v.53 no.4
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• pp.434-439
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• 2008

The amount of salt to make seed sorting solution of the specific gravity of 1.13 was reconsidered and determined as 3.8 kg salt in 18 L water, which is lower amount than currently used. Five rice cultivars were examined. Percent germination and seedling emergence were not similar. Seedling emergence rate of Japonica varieties, Nampyungbyeo and Daerypbyeo-1 were 87% and 95% under specific gravity of 1.13, respectively. Seedling emergence rate of Tongil type variety, Dasanbyeo was as high as 67% in specific gravity of 1.06. Seedling emergence rate of waxy rice, Hwasunchalbyeo and Aranghangchalbyeo were examined. Seedling emergence rate was 94% in both cultivars in specific gravity of 1.04. Seedling emergence rate was same in specific gravity of 1.08 which is generally used for selecting seed currently. Early growth (plant height, leaf number, and dry weight) were not significantly different by specific gravity within species. In all cultivars except waxy rice, highest seedling emergence rate was observed in specific gravity of 1.13 which is currently used for selection and decreased as specific gravity is lowed. However, considering total amount of seeds in each group of specific gravity, amount of seed in lower specific gravity group is relatively small and total seedling emergence rate within variety dose not show big difference. However, if seeds with low speicific gravity are produced due to the bad grain filling condition and consequently total seed content of low specific gravity increases, results will be differnt. Reduction in total growth and yield could occur. It will be important to comply with the seed sorting criterion of 1.13 for Japonica, 1.06 for Tongil, and 1.04 for waxy rice variety to ensure the maximum rice growth and yield.

• The Bulletin of The Korean Astronomical Society
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• v.42 no.2
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• pp.55.4-55.4
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• 2017

For modified gravity models with screening mechanisms, the signal of modified gravity is larger at low density areas. We could add a density weighted mark to galaxy correlation function and increase the signal to noise of modified gravity detection. Based on mock galaxy catalogs from modified gravity simulations, we try different mark functions and parameters to find the best choices for discreminating modified gravity from GR. In this talk I will present our marked correlation funciton results and discuss its advantages and disadvantages.

• Journal of the Korean Society of Propulsion Engineers
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• v.25 no.4
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• pp.78-87
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• 2021

Understanding the liquid propellant transport phenomena in low gravity is essential for developing Korea Space Launch Vehicle (KSLV) upper-stage for the diversity of space missions. A low-gravity environment can be simulated via the free-fall method on the ground; however, the air drag is inevitable. To reduce air resistance during free fall, air-drag shield is usually adopted. In this study, the free-fall method was performed with an air-drag shield from a 7-m height tower. The acceleration of a falling object was measured and analyzed. Low gravity below 0.01 g was achieved during 1.2-s free fall with the air-drag shield. The minimum gravitational acceleration value at 1.2-s after free fall was ±0.005 g, which is comparable to the value obtained from Bremen drop tower experiments, ±0.002 g. A prolonged free-fall duration may enhance the low-gravity quality during the drop tower experiments.

• Economic and Environmental Geology
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• v.32 no.3
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• pp.281-291
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• 1999

This study presents the gravity data with GPS survrying and the geophysical profiles at the Choogaryeong Rift Valley. And in determing geoid by GPS measurement, survey control points (SCP) whoch built by the Republic of Korean Army are used. Seventy nine SCP and the two triangulation stations are reviewd by GPS. Digital terain model is under for terrain analysis. The analyses of the gravity surveying with GPS are as follows. The low values of the negative Bouguer anomalies represent the high elevation terrain. The Bouguer anomalies show the decrrasing trend toward the eastern part of the study area. Characteristics of free-air anomalies are related with terrain elevation. The regional gravity anomalies decreas toward the eastern part of the study area. The trends of variations are associated with the thermotectonic and geologic structure beneath the Choogaryeong Rift Valley. The most parts of the study area represent negative residual gravity anomalies due to the low dencity of sedimentary cover in the Rift Valley. There are three valleys and four mountains in the direction of NE-SW or NNE-SSW which are structured by the geological features.