• Bulletin of the Korean Space Science Society
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• 2006.10a
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• pp.118-118
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• 2006

• Journal of Astronomy and Space Sciences
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• v.17 no.2
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• pp.249-256
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• 2000

It has been developed to calculate fuel budget for a geostationary communication and broadcasting satellite. It is quite essential that the pre-launch fuel budget estimation must account for the deterministic transfer and drift orbit maneuver requirements. After on-station, the calculation of satellite lifetime should be based on the estimation of remaining fuel and assessment of actual performance. These estimations step from the proper algorithms to produce the prediction of satellite lifetime. This paper concentrates on the fuel estimation method that was studied for calculation of the propellant budget by using the given algorithms. Applications of this method are discussed for a communication and broadcasting satellite.

• Journal of the Korea Institute of Military Science and Technology
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• v.27 no.2
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• pp.238-246
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• 2024

Modern military operations rely heavily on broadband communication and data transmission. Recently, the rising use of intelligent unmanned technology necessitates more frequencies. Free-space optical(FSO) communication can offer high-data-rate communications with high security and no need for licensing. Therefore, the FSO communication holds significant interest and potential in the defense industry. In this paper, we present design of a FSO communication terminal taking Korean domestic weather conditions into account. The domestic atmospheric attenuation is analyzed using several models and two-year meteorological information for a city in Korea, and this analysis is utilized to design the FSO communication terminal. The design results were verified using an FSO communication test bed, and we achieved an Ethernet bandwidth of approximately 1.86 Gbps at a distance of 1.3 km with the optical amplifier output power of the test bed set to about 20 dBm.

• Aerospace Engineering and Technology
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• v.13 no.1
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• pp.120-128
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• 2014

Adventure of human race for space exploration is toward outer region of solar system. Recently the main targets of space explorations are becoming mainly the Mars, Venus and asteroids instead of the Moon which was the popular place human wants to explore. There are several technical challenges as spacecraft goes far and far away from the Earth, and among them communication protocol is one of the most challenging problems. In this paper, several international technical trends regarding deep space communication protocol technologies in an aspect of software implementation is presented. It is expected that these references are helpful for the development of the lunar orbiter pathfinder which is planned to be launched in 2017.

• Journal of Power Electronics
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• v.16 no.2
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• pp.455-463
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• 2016

This paper proposes a compensation method to improve the distorted space vectors when a 3-level Neutral Point Clamped (NPC) inverter has an unbalanced neutral point voltage. Since both the neutral point voltage of the DC link and the space vector of a 3-level NPC inverter are closely related depending on the output load connecting state, a distorted space vector can occur when the neutral point voltage of a 3-level NPC inverter is unbalanced. The proposed method can improve the distorted space vectors by adjusting the injection time of the small and medium vectors and by modulating the amplitude of the carrier waveforms. In this paper, the proposed method is verified by both simulation and experimental results based on a 3-level NPC inverter.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.16 no.4
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• pp.2851-2859
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• 2015

The objective of the research lays at proposing user centered communication space. System of transformable space composition and characteristic of communication space is analyzed in order to achieve the objective. Based on analyzed case, it chose space method made through bellows method, and based on chosen method, it is trying to propose possibility of communicative space which suggests program with rotation. In addition to this, it will have function to selectively accommodate various programs and will widen the range of expandability which can be used for various places.

• Journal of Environmental Science International
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• v.22 no.4
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• pp.397-406
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• 2013

With the methodology of AHP, this paper focuses on communication activities and their constituents in city parks, selecting 11 constituents, natural or artificial, and establishes an evaluation model on the basis of the analysis of the characteristics of tourists' communication activities in order to obtain the weight and order of importance of the constituents of communication activities space. First-grade indicators influence weight and the order of the constituents of communication activities space are: artificial constituents (0.6614) > natural constituents (0.3386). The weight and order of five secondary indicators attached to natural constituents: private space (0.1538) > shade tree (0.0955) > gentle slope mound (0.0474) > beautiful waterscape (0.0270) > sunshine lawn (0.0149); the weight and order of six secondary indicators attached to artificial constituents: field boundary (0.2865) > Leisure chairs (0.1843) > resting areas (0.0795) > appropriate square (0.0533) > tree-lined road (0.0352) > landscape sketch (0.0227).Using modern decision analysis methodology to research the relationship of environment constituent elements has great theoretical and practical significance for the scientific design and construction of suitable environment for human needs.

• Proceedings of the Korea Society of Information Technology Applications Conference
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• 2005.11a
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• pp.73-76
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• 2005

The advanced information and communication technology gives vehicles another role of the third digital space, merging a physical space with a virtual space in a ubiquitous society. In the ubiquitous environment, the vehicle becomes a sensor node, which has a computing and communication capability in the digital space of wired and wireless network. An intelligent vehicle information system with a remote control and diagnosis is one of the future vehicle systems that we can expect in the ubiquitous environment. However, for the intelligent vehicle system, many issues such as vehicle mobility, in-vehicle communication, service platform and network convergence should be resolved. In this paper, an in-vehicle gateway is presented for an intelligent vehicle information system to make an access to heterogeneous networks. It gives an access to the server systems on the internet via CDMA-based hierarchical module architecture. Some experiments was made to find out how long it takes to communicate between a vehicle's intelligent information system and an external server in the various environment. The results show that the average response time amounts to 776ms at fixec place, 707ms at rural area and 910ms at urban area.

• Bulletin of the Korean Space Science Society
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• 2006.10a
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• pp.154-154
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• 2006

• Bulletin of the Korean Space Science Society
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• 2006.10a
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• pp.155-155
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• 2006