• Proceedings of the KIEE Conference
• /
• 1998.07f
• /
• pp.1944-1946
• /
• 1998

This paper presents a novel current control system to eliminate the steady state control error for PWM AC-DC converter. A general mathematical model of the converter which is represented as a state-space model is established. The state-space model is used for the simulation of converter with the proposed tracking control system of sinusoidal current. In this system, a novel current control which do not require coordinate transformations using internal principle of PI controller is described. It is proved that the steady state deviation reduce to zero through a transfer function of source current control system. Finally, simulations show good source current control characteristics by means of a simplified control system which do not require coordinate transformations.

• The Bulletin of The Korean Astronomical Society
• /
• v.38 no.1
• /
• pp.66.1-66.1
• /
• 2013

Six universities, four institutes and agencies, and two vendors are working for space weather in South Korea. Along with education and research activities, they have been extending ground-based observation system and upgrading space weather service, and participating in international space weather programs. Recently, several space missions for space weather have been proposed in accordance with the national space program of Korea. Here, we report and discuss the current status and future perspective of Korean community for space weather.

• Bulletin of the Korean Space Science Society
• /
• 1994.04a
• /
• pp.13-13
• /
• 1994

No Abstract. See Full-text

• The Bulletin of The Korean Astronomical Society
• /
• v.38 no.2
• /
• pp.81.2-81.2
• /
• 2013

K-GMT Science Group (KGSG) is in charge of overall science operations with an aim to promote scientific activities of Korean Astronomical Community for the GMT era in 2020. KGSG is currently running and/or promoting K-GMT Science Program, K-GMT Science White Paper Initiative, and K-GMT Summer School for Young Researchers. KGSG is also planning to join several international survey projects such as SDSS IV and LSST. We will introduce the current status on various operations and the future plan for KGSG to the community members.

• Bulletin of the Korean Space Science Society
• /
• 2001.04a
• /
• pp.33-33
• /
• 2001

No Abstract, See Full Text

• Bulletin of the Korean Space Science Society
• /
• 2004.10b
• /
• pp.53-53
• /
• 2004

• Journal of Astronomy and Space Sciences
• /
• v.28 no.1
• /
• pp.27-36
• /
• 2011

The present study examines the morning-afternoon asymmetry of the geosynchronous magnetic field strength on the dayside (magnetic local time [MLT] = 06:00~18:00) using observations by the Geostationary Operational Environmental Satellites (GOES) over a period of 9 years from February 1998 to January 2007. During geomagnetically quiet time (Kp < 3), we observed that a peak of the magnetic field strength is skewed toward the earlier local times (11:07~11:37 MLT) with respect to local noon and that the geosynchronous field strength is larger in the morning sector than in the afternoon sector. That is, there is the morning-afternoon asymmetry of the geosynchronous magnetic field strength. Using solar wind data, it is confirmed that the morning-afternoon asymmetry is not associated with the aberration effect due to the orbital motion of the Earth about the Sun. We found that the peak location of the magnetic field strength is shifted toward the earlier local times as the ratio of the magnetic field strength at MLT = 18 (B-dusk) to the magnetic field strength at MLT = 06 (B-dawn) is decreasing. It is also found that the dawn-dusk magnetic field median ratio, B-dusk/B-dawn, is decreasing as the solar wind dynamic pressure is increasing. The morning-afternoon asymmetry of the magnetic field strength appears in Tsyganenko geomagnetic field model (TS-04 model) when the partial ring current is included in TS-04 model. Unlike our observations, however, TS-04 model shows that the peak location of the magnetic field strength is shifted toward local noon as the solar wind dynamic pressure grows in magnitude. This may be due to that the symmetric magnetic field associated with the magnetopause current, strongly affected by the solar wind dynamic pressure, increases. However, the partial ring current is not affected as much as the magnetopause current by the solar wind dynamic pressure in TS-04 model. Thus, our observations suggest that the contribution of the partial ring current at geosynchronous orbit is much larger than that expected from TS-04 model as the solar wind dynamic pressure increases.

• Journal of the Korean Institute of Educational Facilities
• /
• v.15 no.1
• /
• pp.34-43
• /
• 2008

The purpose of the study is to provide design guidelines and space structure of health rooms for elementary and middle schools. In order to do that, with the subject of health teachers from 96 schools in Seoul city, which remodeled the health rooms in 2005 and 2006, the research was carried out. Through the research, we organized the collected opinions and current situation about the procedures of the promotion, size, location and space formation. Based on that, we could acquire a better grasp of a type of space structure for the guidelines. From the research, we realized that in terms of location, size, and internal space structure, it has been improved compared to the past. However, we also saw more rooms for improvements in the coming future. We believe that such result will be utilized as the basic information for the roadmap of new space structure of health rooms at current schools and new schools.

• Journal of the Korean Society for Aeronautical & Space Sciences
• /
• v.39 no.12
• /
• pp.1133-1140
• /
• 2011

Current design process for the Hall effect thruster has relied on expensive experimental method based on the limited historical data. In this study, a proper design space for the Hall effect thruster is chosen and associated design space exploration is conducted based on a recently proposed numerical method in order to improve current design process. According to the results of the design space exploration, performance envelope is determined for the given design space and the correlations between performance metrics are analyzed. Further analysis shows that main factors in performances for the Hall effect thruster are the anode mass flow rate and the discharge voltage.

• Journal of the Korean Institute of Rural Architecture
• /
• v.8 no.2
• /
• pp.80-93
• /
• 2006

This purpose was to explore various directions of elderly service welfare space in village community center. Data were collected 3 types that floor plans of village community centers from 24 villages, interview data of these centers use and needs from 24 aged leaders or 96 elderly. The results were as followed: 1) The floor plans of more than 50% was type IV that was composed a basic spaces(entrance, living room, two rooms, kitchen), a toilet space, a heating system space and a storage space. This type was a current basis of the rural village community centers for elderlies. 2) Elderlies used the centers at winter or out of agricultural season, and visited these to pass the time and to promote friendship among them. 3) Also they went these to take a meal together and to save down personal heating expenses. Their needs for centers were a temporary share dwelling space at winter, a maintain social relationship throughout a health, a education and a side work activity, supplying health or sports facilities, and setting up toilet space. Therefore the current centers were needed to add functions of a temporary share dwelling, a energy saving heat system and a social promoting relationship, and so these could be represented to a elderly welfare service center in rural villages.