• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.31 no.1
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• pp.113-119
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• 2003

During the mission operation time, it is very important to estimate the spacecraft propellant remaining as accurately as possible. This is because the quantity of propellant is related directly to how long the satellite can be operated ín orbit. There are two different methods for spacecraft propellant gauging; the PVT method and the book-keeping method. This paper describes the characteristics and applications of these methods using the flight operation data of KOMPSAT-1. Additionally, propellant consumption rates in delta-V maneuvering and each attitude control submode are analyzed according to spacecraft operation modes. The earth search submode shows the highest propellant consumption rate.

• Journal of the Korean Society for Nondestructive Testing
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• v.30 no.2
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• pp.126-131
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• 2010

The purpose of this study is to assess the condition of composites used in aircraft under varying temperature environment with ultrasound guided wave technique. Investigation of crucial influential factor on the composite health monitoring related to aircraft operational environments such as the number of thermal cycles and temperature deviation between ground level and flight altitude has been of a great concern for aircraft safety issue. In this study, ultrasonic guided wave health monitoring scheme is proposed to evaluate composite specimens damaged with the thermal fatigue simulating aircraft operational condition. Guided wave dispersion curves are used to select right modes which show a promising sensitivity to each different thermal fatigue damage level. The present approach can be also implemented as one of on-lines health monitoring tools for aircraft.

• The Journal of the Convergence on Culture Technology
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• v.8 no.6
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• pp.953-958
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• 2022

Holographic Stereogram can provide the depth perception without the visual fatigue and dizziness because it use multiple images acquired from the multiple viewpoints. In order to produce a holographic stereogram, it is necessary to obtain perspective images of a live object and record it on film using a digital hologram printer. when acquiring perspective images, the hologram without distortion can be produced only when the perspective images with a constant distance between the camera and the target is obtained. If the target is small, it is possible to keep the constant distance from the camera to object. but if it is large, this is difficult to keep the constant distance. In this study, we photograph the large object using the POI (Point of Interest) function which is one of the smart flight modes of drone to produce perspective images required for the hologram production. after that, problems such as the unexpected shakings and distance change between camera and object is corrected in post production. as a result, we produce the perspective images.

• Proceedings of the Korean Vacuum Society Conference
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• 1998.02a
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• pp.17-17
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• 1998

Synchrotron radiation is produced when charged particles moving with relativistic velocities a are accelerated - for example, deflected by the bending magnets which guide the electron or p positrons in circular accelerators or storage rings. By using special focusing magnetic lattices i in the particle accelerators it is possible to make the dimensions of the particle beam very small with a hi맹 charge density which results in a light source with high b디lIiance. Synchrotron light h has important properties which make it ideal for a wide range of investigations in surface s science. The fact that the spectrum of electromagnetic radiation emitted in a bending magnet e extends in a continuum from the 얹r infra red region to hard x-rays means that it is id않I for a v variety of spectroscopic studies. Since there are no convenient lasers, or other really bright l light sources, in the vacuum ultraviolet and soft x-ray re.밍ons the development of synchrotron r radiation has enabled enormous advances to be made in this di펌C비t spectr따 re밍on. P Polarization-dependent measurements, for ex없nple ellipsometry or circular dichroism studies a are possible because the radiation has a well-defined polarization - linear in the plane of orbit w with additional right-circular, or left-circular, components for emission an생es above, or below, t the horizontal, respectively. Since the synchrotron light is emitted from a bunch of charge c circulating in a ring the light is emitted with a well-defined time structure with a short flash of l light every time a bunch passes an exit port. The time structure depends on the size of the ring a and the number and sequence of filling of the bunches. A pulsed light source enables time¬r resolved studies to be performed which provide direct information on the lifetimes and decay m modes of excited states and in addition opens up the possibility of using time of flight t techniques for spectroscopic studies. The fact that synchrotron radiation is produced in a clean u ultrahi야 vacuum environment is of gr않t importance for surce science studies. The current t비rd generation synchrotron light sources provide exceptionally high baliance and stability a and open up possibilities for experiments which would have been inconceivable only a short time ago.

• Journal of Korean Society for Atmospheric Environment
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• v.32 no.6
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• pp.593-602
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• 2016

The physicochemical characteristics of particulate matter emissions from various vehicle's fuel types were studied at the facility of Transport Pollution Research Center(TPRC), National Institute of Environmental Research (NIER), Korea. Three different types of fuels such as gasoline, liquefied petroleum gas (LPG) and diesel were tested on the NIER driving mode and the constant speed modes(30, 70, and 110 km/h). Chemical composition of submicron particles from vehicle emissions was measured by the High Resolution Time of Flight Aerosol Mass Spectrometer (HR-ToF-AMS) during running cycles. Organics were dominant chemical species of particulate matter emissions for all three different vehicles' fuel types. Moreover, regardless of fuel types, emission rate of organics and inorganics decreased as the average speed of vehicle increased. The portion of fully oxidized fragment families of $C_xH_yO_z$ accounted for over 98% of organic aerosol(OA) in LPG and diesel vehicles, while the relatively high fraction of $C_xH_y$ in OA was observed in gasoline vehicle.

• Journal of Astronomy and Space Sciences
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• v.22 no.3
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• pp.329-352
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• 2005

Long term observations of full-disk Lyman-o irradiance have been made by the instruments on various satellites. In addition, several sounding rockets dating back to the 1950s and up through the present have measured the $Lyman-{\alpha}$ irradiance. Previous full disk $Lyman-{\alpha}$ images of the sun have been very interesting and useful scientifically, but have been only five-minute 'snapshots' obtained on sounding rocket flights. All of these observations to date have been snapshots, with no time resolution to observe changes in the chromospheric structure as a result of the evolving magnetic field, and its effect on the Lyman-o intensity. The $Lyman-{\alpha}$ Imaging Solar Telescope(LIST) can provide a unique opportunity for the study of the sun in the $Lyman-{\alpha}$ region with the high time and spatial resolution for the first time. Up to the 2nd year development, the preliminary design of the optics, mechanical structure and electronics system has been completed. Also the mechanical structure analysis, thermal analysis were performed and the material for the structure was chosen as a result of these analyses. And the test plan and the verification matrix were decided. The operation systems, technical and scientific operation, were studied and finally decided. Those are the technical operation, mechanical working modes for the observation and safety, the scientific operation and the process of the acquired data. The basic techniques acquired through the development of satellite based solar telescope are essential for the construction of space environment forecast system in the future. The techniques which we developed through this study, like mechanical, optical and data processing techniques, could be applied extensively not only to the process of the future production of flight models of this kind, but also to the related industries. Also, we can utilize the scientific achievements which are obtained throughout the project And these can be utilized to build a high resolution photometric detectors for military and commercial purposes. It is also believed that we will be able to apply several acquired techniques for the development of the Korean satellite projects in the future.