• Current Industrial and Technological Trends in Aerospace
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• v.8 no.2
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• pp.76-85
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• 2010

This paper discusses recent development trends of fiber optic gyroscope (FOG) in space application. Fiber optic gyroscope utilizes Sagnac effect to measure the angular rate of a rotating object in space. Having a rather short development history compared to ring laser gyroscope (RLG), the fiber optic gyroscope, owing to the emerging technologies in fiber optic society and the digital signal processing technique, reveals itself as a noteworthy replacement of the ring laser gyroscope in the space mission. This paper summarizes the current trends of fiber optic gyroscope based on the actual products commercialized in the market over the last decades, while presenting the future development trends of the fiber optic gyroscope in the space exploration.

• The Transactions of the Korean Institute of Power Electronics
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• v.6 no.6
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• pp.525-537
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• 2001

In this paper a new space vector RPPWM(Random Position PWM) is proposed. In the propsed RPPWM each of three phase pulses is located randomly in each switching interval. Based on the Space vector modulation technique the duty ratio of the pulses is calculated Along with the randomization of the PWM pulses. we can obtain the effects of spread spectra of votlage, current as in the case of randomly changed switching frequency, To verify the validity of the proposed RPPWM simulation study was tried using Matlab/Simulink The main model described in Simulink block diagrams includes the space vector modulation block pulse position randomization block inverter block 3 phase induction motor block and so on By the simulation study, the harmonics of the output voltage and the current of inverter are predicted in different PWM methods- SVPWM, LLPWM proposed RPPWM.

• The Transactions of the Korean Institute of Power Electronics
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• v.23 no.1
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• pp.9-15
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• 2018

This study investigates a bidirectional quasi-Z-source inverter (Bq-ZSI) system with bidirectional power transfer capability and a modified space vector modulation scheme for reducing the ripple of the inductor current. By replacing the diode in the impedance network with an active switch, the power flow can be bidirectional. The average inductor current of the Bq-ZSI network is negative in the regenerative braking mode, thereby regenerating the power. In addition, modified space vector modulation scheme is applied to the Bq-ZSI to control shoot-through time effectively. A 5 kW prototype is built and tested to implement the proposed system. Experimental results show that the Bq-ZSI system is capable of regenerative braking of the induction motor and that the modified space vector modulation method is efficient.

• Journal of Astronomy and Space Sciences
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• v.36 no.3
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• pp.213-223
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• 2019

This paper analyzes delta-Vs to maintain an extremely low altitude on the Moon and investigates the possibilities of performing a CubeSat mission. To formulate the station-keeping (SK) problem at an extremely low altitude, current work has utilized real-flight performance proven software, the Systems Tool Kit Astrogator by Analytical Graphics Inc. With a high-fidelity force model, properties of SK maneuver delta-Vs to maintain an extremely low altitude are successfully derived with respect to different sets of reference orbits; of different altitudes as well as deadband limits. The effect of the degree and order selection of lunar gravitational harmonics on the overall SK maneuver strategy is also analyzed. Based on the derived SK maneuver delta-V costs, the possibilities of performing a CubeSat mission are analyzed with the expected mission lifetime by applying the current flight-proven miniaturized propulsion system performances. Moreover, the lunar surface coverage as well as the orbital characteristics of a candidate reference orbit are discussed. As a result, it is concluded that an approximately 15-kg class CubeSat could maintain an orbit (30-50 km reference altitude having ${\pm}10km$ deadband limits) around the Moon for 1-6 months and provide almost full coverage of the lunar surface.

• Korean Institute of Interior Design Journal
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• v.22 no.3
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• pp.108-116
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• 2013

This study has the purpose to review the way of experience element and property of space design appearing in vocational experience space and accumulate basic study material for children's vocational experience space and build systematic and specialized modules. Analysing the marketing elements of experience space through pilot research to arrange frame of analysis, and in a determined range, experimental marketing's property appearing in children's vocational experience center is analysed. This researcher analysed experimental displaying space's function of recognition, emotional, behavior, sense marketing and experimental marketing induced from pilot research on space design expressive elements of experimental marketing when it is applied to spaces through the frame of analysis with the combination of total 8 kind's experience display space function such as investigative, conceptional, aesthetic, entertaining, logical, relative, participating, and comprehensive experience based on 5 vocational experience spaces located in Seoul and Gyeonggi, opened after 2010, being operated at present with more than 500 pyeong (about 1,650 square meter) and targeted for children, after this researcher visited the site directly to make check list with the frame of analysis together with the staff and administrator in charge of vocational experience education. As a conclusion, vocational experience center is a space of edutainment helping children experience various profession more easily to find their interest and to bring up their dream. By analysing current vocational experience center through the element called experimental marketing, current status of vocational experience center could be known. the experience itself in vocational experience center becomes a merchandise. Instead of mere experience, so as to get professional experience and new information, new experiences should be provided by incessant variation and development. This study is to build basic research data for children's vocational experience space, however not only drawing specialty of vocational experience center through the connection of enterprises based on the contents arranged above but also systematic and specialized modules are expected to be built in next researches.

• Current Industrial and Technological Trends in Aerospace
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• v.9 no.1
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• pp.55-63
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• 2011

Space debris is the collection of objects in orbit around Earth that were created by humans but no longer serve any useful purpose. Since plenty of spacecrafts were launched in space after 1957, the number of space debris has been increased. According to USSTRATCOM, the number of space debris which are bigger than 10cm is more than 15,000. Recently two critical events were occurred. Which one was that China shot down their satellite using missile and the other was that t o satellite, Iridium 33 and Cosmos 2251, collided in space. Space debris environment in which KOMPSAT-2 is operating has been severe. This paper presents the status of space debris and international activity, and the comparison of conjunction assessment process between Korea Aerospace Research Institute and abroad satellite operation center.

• Journal of the Korean housing association
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• v.12 no.4
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• pp.93-104
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• 2001

This study has been performed to analyze size and deficit problem of residential space in later life. In this study, 216 Koreans aged 50 to 79 were surveyed for their current residential space ad family related items such as age, marital status, living arrangement, birth order, and housing status. The results are drawn as follows: 1. The space size significantly fluctuates by marital status, number of generations living together, tenure, and structure type; For example, use of indoor area per person ranges from 7.01 pyoung for three-generation households to 19.53 for one-generation households. 2. s for space deficit, very old widowed females, 60's living in rented or multi-family housing units, and those living in three generations are high risk groups of the space deficit below 7 young per person. In this study, further researches are recommended as follows; Regarding the highest risk group of space deficit, life styles causing space-related conflicts should be studied, and accordingly proper welfare services for the causal life styles be offered. Housing maintenance & utility costs be investigated and guidelines should be proposed for any surplus groups among the 60's, so that their space surplus can be reduced by suitable adjustment process.

• Bulletin of the Korean Space Science Society
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• 2008.10a
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• pp.32.2-32.2
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• 2008

A major solar radio burst can disturb many kinds of radio instruments, including cellular phone, GPS, and radar. Korea Astronomy and Space Science Institute (KASI) is developing Korean Solar Radio Burst Locator (KSRBL) in collaboration with New Jersey Institute of Technology. KSRBL is a single dish radio spectrograph, which records the spectra of microwave (0.5 - 18 GHz) bursts with 1 MHz spectral resolution and 1 s time cadence, and locates their positions on the solar disk within 2 arcmin. Hardware manufacturing is almost completed including 4-channel digitizer/FPGA. The system is currently installed at Owens Valley Radio Observatory (OVRO), and test of the operation is in progress. It will be installed at KASI in 2009. We report current status and test results of KSRBL.

• Journal of Astronomy and Space Sciences
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• v.11 no.1
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• pp.93-106
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• 1994

A three-dimensional box model has been developed to study the MHD wave coupling in the magnetosphere. In this model, the effects of the ring current are included by assuming the pressure gradients in the MHD equations. It is found that the axisymmetric ring current may play an important role in producing spectral noises in compressional waves, while field line resonances have no such disturbances. These results may explain the current observational characteristics that compressional cavity modes hardly appear in the satellite experiment, while field line resonances often occur. Our numerical resluts also suggest that any discrete spectral peaks such as the global cavity modes can hardly occur where the pressure distribution of the ring current becomes important. The continuous band of transverse waves is found to be unperturbed until the ring current becomes significantly asymmetric with respect to the dipole axis. In addition, our results in the absence of the pressure gradient are found to be consistent with the previous results from the box-like and dipole models.

• Bulletin of the Korean Space Science Society
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• 2008.10a
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• pp.32.1-32.1
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• 2008

It is well known that solar and space weather activities can influence the performance and reliability of modern technological system and can endanger human life. Since 2007, the Korea Astronomy and Space Science Institute (KASI) has initiated a research project for the construction of Korean Space Weather Prediction Center (K-SWPC) to make preparations for the next solar cycle maximum (~2012). In this talk, we briefly introduce the current progress of KASI activities for K-SWPC; extension of ground observation system, construction of space weather database and network, development of prediction models, and space weather effects. In addition, future plans for KSWPC will be discussed.