• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.39 no.12
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• pp.1174-1180
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• 2011

Field Programmable Gate Array(FPGA)s are replacing traditional integrated circuits for space applications due to their lower development cost as well as reconfigurability. However, they are very sensitive to single event upset (SEU) caused by space radiation environment. In order to mitigate the SEU, on-board computer of STSAT-3 employed a triple modular redundancy(TMR) and scrubbing scheme. Experimental results showed that upset threshold energy was improved from 10.6 MeV to 20.3 MeV when the TMR and the scrubbing were applied to the on-board computer. Combining the experimental results with the orbit simulation results, calculated bit-flip rate of on-board computer is 1.23 bit-flips/day assuming in the worst case of STSAT-3 orbit.

• Transactions of the Korean Society of Machine Tool Engineers
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• v.17 no.4
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• pp.42-50
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• 2008

Various researches to reduce weight of a vehicle are achieving. One of these researches is tendencious to manufacture the hollow piston rod using friction welding instead of solid one of the vehicle shock absorber. This study deals with the friction welding of SM45C to SM20C-pipe that is used normally in the vehicle shock absorber. The friction time was variable conditions under the conditions of spindle revolution of 2,000rpm, friction pressure of 55MPa, upset pressure of 75MPa, and upset time of 2.0seconds. Under these conditions, the microstructure of weld interface, tensile fracture surface and mechanical tests of friction weld were studied and so the results were as follows. When the friction time was l.5seconds under the conditions, the maximum tensile strength of the friction weld happened to be 837MPa, which is 113% of SM20C's tensile strength and 97% of SM45C's. The optimal welding conditions were n=2,000rpm, $P_1=55MPa$, $P_2=75MPa$, $t_1=1.5sec$, $t_2=2.0sec$ when the total upset length is 1.7mm.

• Journal of the Institute of Electronics Engineers of Korea SD
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• v.45 no.3
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• pp.1-5
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• 2008

This paper analyzes on the radiation effect of silicon solar cells in a low Earth orbit satellite by using high energy electron beams. Generally, the satellite circling round in a low orbit go through Van Allen belt, in which electronic components are easily damaged and shortened by charged particles moving in a cycle between the South Pole and the North Pole. For example, Single Event Upset (SEU) by radiation could cause electronic devices on satellite to malfunction. From the ground experiment in which we used the high energy electron beam facility at Knrea Atomic Energy Research Institute (KAERI), we tried to explain sun sensor degradations on orbit could he caused by high energy electrons. While we focused on the solar cells used for light detectors, We convince our research also contributes to understand the radiation effect of solar cells generating electric powers on satellites.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2013.05a
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• pp.1173-1174
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• 2013

• Bulletin of the Korean Space Science Society
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• 2002.10a
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• pp.82-82
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• 2002

• 제어로봇시스템학회:학술대회논문집
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• 1986.10a
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• pp.248-250
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• 1986

This paper explain application of expert system techniques from the latest theories of artificial intelligence to industrial process control. This controller continuously monitors a loop's response to disturbances and adapts the tuning parameters (P.I.D) to provide the best response to load upset or set-point change.

• Proceedings of the Korean Magnestics Society Conference
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• 2015.11a
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• pp.179-179
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• 2015

• Proceedings of the Korean Magnestics Society Conference
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• 2016.05a
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• pp.47-47
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• 2016

• Transactions of the Korean Society of Machine Tool Engineers
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• v.16 no.3
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• pp.109-116
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• 2007

The present study examined mechanical properties according to the change of outer circumference in the friction welding of A2024-T4 stock, which is used much as aircraft structure, truck wheel, stainless materials and A2024-T4 stock with 10 hollow at the center. Welding conditions were fixed at RPM 2,000rpm, friction pressure of 50MPa, friction time of 1.5sec, upset pressure of 120MPa and upset time of 2.0 seconds. From the result of this study were drawn conclusions as follows : According to the result of a tensile strength test, the solid shaft showed linear increase of tensile strength with the change of outer circumference, the hollow shaft showed maximum tensile stength when the length (L) was 2mm and decrease of tensile strength with the change of outer circumference, hardness appeared to increase and then decrease for welding interface, and it showed maximum hardness 155Hv at L=5mm of the solid shaft. Bending strength increased linearly far change of the distance (L) of outer circumference in the solid shaft and then decreased linearly in the hollow shaft. the result of examining tissue, the tissue grew finer around the welding interface and divided the basic material and the welding surface.

• Journal of Astronomy and Space Sciences
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• v.18 no.2
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• pp.109-118
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• 2001

KITSAT-1, launched in 1992, passes through Inner Van Allen Radiation Belt in which high energy Protons cause single event upsets(SBUs) in the main memory of KITSAT-1 OBC(On-Board Computer) 186. The present paper compares SEU data from the OBC186 with the AP-8 model of NASA/NSSDC using the Chi-Square method to estimate the SEU threshold energy. Shielding effect by the satellite body has been taken into account to model the proton fluxes at the position of OBC186, and SEUs recorded during the high solar activities have been removed to avoid the spurious result. The result shows that the SEU threshold energy of the main memory of KITSAT-1 OBC186 is estimated to be about $110{pm}10MeV$.