• 한국초전도ㆍ저온공학회논문지
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• 제16권2호
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• pp.64-69
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• 2014

Measuring an exact amount of remaining cryogenic liquid propellant under microgravity condition is one of the important issues of rocket vehicle. A Pressure-Volume-Temperature (PVT) gauging method is attractive due to its minimal additional hardware and simple gauging process. In this paper, PVT gauging method using liquid nitrogen is investigated under microgravity condition with parabolic flight. A 9.2 litre metal cryogenic liquid storage tank containing approximately 30% of liquid nitrogen is pressurized by ambient temperature helium gas. During microgravity condition, the inside of the liquid tank becomes near-isothermal condition within 1 K difference indicated by 6 silicon diode sensors vertically distributed in the middle of the liquid tank. Helium injection with higher mass flow rate after 10 seconds of the waiting time results in successful measurements of helium partial pressure in the tank. Average liquid volume measurement error is within 11% of the whole liquid tank volume and standard deviation of errors is 11.9. As a result, the applicability of PVT gauging method to liquid propellant stored in space is proven with good measurement accuracy.

• 한국연소학회지
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• 제2권1호
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• pp.29-38
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• 1997

In this study, the experimental and numerical investigations of the ignition of methane-air mixtures by a electrically heated wire have been carried out. In order to define the initial condition and make the analysis simple, the following control unit was developed; which heats the wire to the setting temperature in a very short time, and maintains the wire temperature constant until ignition. Experiments with the feedback control have been performed using nickel and platinum wires in normal gravity and microgravity. From experimental results, ignition temperatures in normal gravity are higher than those in microgravity, however, the dependences of ignition temperature on equivalence ratio are not affected by natural convection. Numerical calculations, including catalytic reaction for platinum, have been performed to analyze the experimental results in microgravity. Numerical results show that reactants near platinum wire are consumed by catalytic reaction, therefore, the higher temperature is needed to ignite the mixture with platinum wire.

• 한국지구물리탐사학회:학술대회논문집
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• 한국지구물리탐사학회 2007년도 공동학술대회 논문집
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• pp.101-106
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• 2007

A time-lapse microgravity survey on a newly widen road at Muan, where limestone cavities are developed, for monitoring the change of the subsurface density distribution before and after grouting. Microgravity monitoring is identified as a quick, easy and cost effective. But, it requires strict data acquisition and quality control due to the differences of conditions at measurements. The survey was carried out two times, that is, October 2005 and September 2006. The data were adjusted for reducing the effects due to the different condition of each survey. The processed data acquired in 2005 and 2006 were inverted into the subsurface density distributions. They show the change and development of density structure during the lapsed time, which implies the effects of grouting.

• Animal cells and systems
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• 제4권3호
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• pp.215-221
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• 2000

Our anatomical and behavioral studies of embryonic rats that developed in microgravity suggest that the vestibular sensory system, like the visual system, has genetically mediated precesses of development that establish crude connections between the periphery and the brain. Environmental stimuli also regulate connection formation including terminal branch formation and fine-tuning of synaptic contacts. Axons of vestibular sensory neurons from grabistatic as well as linear acceleration receptors reach their targets in both microgravity and norm81 gravity, suggesting that this is a genetically regulated component of development. However, microgravity exposure delays the development of terminal branches and synapses in gravistatic but not linear acceleration-sensitive neurons and also produces behavioral changes. These latter changes reflect environmentally controlled processes of development.

• 항공우주의학회지
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• 제30권1호
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• pp.25-29
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• 2020

Space exploration is one of the dreams of humankind. However, the intriguing environment was a challenge for the human body, where we must counter with many extreme conditions such as thermal support, radiation, microgravity. Life, as well as the human body, developed and evolved in the continuous presence of gravity, especially when living creatures transfer from the ocean to the land. Once this gravitational force doesn't impact on the body, the drastic changes occur. Some of these changes were observed immediately, while others progress only slowly. Since the first orbital flight was performed, several hazards for the organs of the human body were identified [1]. These changes in human physiology can reverse when astronauts return to Earth. This article will review the published findings of the effects of microgravity exposure on the human body.

• Animal cells and systems
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• 제4권3호
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• pp.231-237
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• 2000

The effects of microgravity and hypergravity on aging are still poorly documented, particularly in mammals. However, there is a growing interest for the use of the fruit fly, Drosophila melanogaster, and this species may be now considered as a model organism in gravitational biology studies dealing with aging.

• Journal of Advanced Marine Engineering and Technology
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• 제29권8호
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• pp.907-914
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• 2005

Experiments at the Japan Microgravity Center (JAMIC) have investigated the interaction between diffusion flames and solid surfaces Placed neat flames The fuel for the flames was $C_{2} H_{4}$ The surrounding oxygen concentration was 35$\%$ with surrounding air temperatures of $T_{a}$ : 300K. Especially, the effect of wall temperature on soot deposition from a diffusion flame Placed near the wall has been studied by utilizing microgravity environment, which can attain very stable flame along the wall. Cylindrical burner with fuel injection was adopted to obtain two dimensional soot distributions by laser extinction method. In the experiment two different wall temperatures. $T_{w}$=300, 800 K, were selected as test conditions The results showed that the soot distribution between flame and burner wall was strong1y affected by the wall temperature and soot deposition increases with decrease in wall temperature. The comparison among the values lot two different wall temperatures suggests that the change in thermophoretic effect is the most dominant factor to give the change in soot deposition characteristics.

• 한국연소학회:학술대회논문집
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• 한국연소학회 2007년도 제34회 KOSCO SYMPOSIUM 논문집
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• pp.19-24
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• 2007

The deposition behavior of soot particles in a diffusion flame along a solid wall was examined experimentally by getting rid of the effect of natural convection utilizing microgravity environment. The microgravity environment was realized by using a drop tower facility. The fuel for the flame was an ethylene ($C_2H_4$) and the surrounding oxygen concentration 35% with the surrounding air velocity of $V_a$=2.5, 5, and 10 cm/s. Laser extinction method was adopted to measure the soot volume fraction distribution between the flame and burner wall. The results show that observation of soot deposition in normal flame was difficult from buoyancy and the relative position of flame and solid surface changes with time. The soot particle distribution region moves closer to the surface of the wall as the surrounding air velocity is increased. And the experiments determined the trace of the maximum soot concentration line. It was found that the distance between soot line and flame line is around 5 mm. That is, the soot particle near the flame zone tends to move away from flame zone because of thermophoretic force and to concentrate at a certain narrow area inside of the flame, finally, to adhere the solid wall.

• 한국지구물리탐사학회:학술대회논문집
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• 한국지구물리탐사학회 2005년도 공동학술대회 논문집
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• pp.251-254
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• 2005

인공 지하공동에 해당하는 폐갱도 탐지를 위한 고정밀중력탐사를 수행하였다. 수치모델링으로 중력탐사로서 폐갱도 탐지가 가능한지를 실험하였고, 전남 화순 탄광지역 인근에서 도로건설 예정지에 존재 가능성이 있는 폐갱도 탐지에 적용하였다. 탐사자료에 정밀지형보정과 비평활화 역산을 적용하여 지하공동에 해당하는 반응을 유추할 수 있었다.

• 한국지구물리탐사학회:학술대회논문집
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• 한국지구물리탐사학회 2005년도 공동학술대회 논문집
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• pp.181-186
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• 2005

중력탐사는 지하의 밀도 분포를 구하는 탐사법이므로 지하의 빈 공간의 탐지나 기반암의 견고성을 파악하는 데 직접적인 정보를 제공하므로, 고정밀 중력탐사는 지하공동, 터널, 채굴적 등의 탐지에 효과적으로 적용될 수 있다. 이 논문은 석회암 공동 탐지, 폐갱도 탐지 그리고 사력댐의 밀도 구조 등 3가지 실제 탐사 사례를 통하여 고정밀 중력탐사가 천부 토목 조사와 구조물 안정성 조사에 유용하게 활용됨을 보여주고자 한다.