• ETRI Journal
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• v.29 no.1
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• pp.27-35
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• 2007

Energy savings in orthogonal frequency division multiplexing (OFDM) systems is an active research area. In order to achieve a solution, we propose a new cooperative relaying scheme operated on a per subcarrier basis. This scheme improves the bit error rate (BER) performance of the conventional signal-to-noise ratio (SNR)-based selection relaying scheme by substituting SNR with symbol error probability (SEP) to evaluate the received signal quality at the relay more reliably. Since the cooperative relaying provides spatial diversity gain for each subcarrier, thus statistically enhancing the reliability of subcarriers at the destination, the total number of lost subcarriers due to deep fading is reduced. In other words, cooperative relaying can alleviate error symbols in a codeword so that the error correction capability of forward error correction codes can be fully exploited to improve the BER performance (or save transmission energy at a target BER). Monte-Carlo simulations validate the proposed approach.

• Journal of the Korean BIBLIA Society for library and Information Science
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• v.19 no.1
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• pp.89-111
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• 2008

This study intends to research model to nation-wide Library Cooperative System in Korea and to make legal and institutional devices. For this purpose, it analyzes and investigate theories, types and model of Library Cooperation; and current status and problems in operations of major Cooperative System in all library types. The results developed new model of national wide Cooperative System on the basis of region Cooperative System.

• Proceedings of the Microbiological Society of Korea Conference
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• 1991.04a
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• pp.173-174
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• 1991

• Proceedings of the Korea Society of Design Studies Conference
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• 2001.10a
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• pp.11.1-11
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• 2001

• Journal of the Korea Institute of Military Science and Technology
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• v.19 no.4
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• pp.517-525
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• 2016

In this research, the effect of the pressure control of cooperative control system with regenerative brake for a military series hybrid-electric vehicle was studied. A cooperative control system with regenerative brake was developed to maximize regenerative energy from electric traction motors of the vehicle. However, the pressure control method of the system was modified to solve a time delay problem and it deteriorates the performance of the system. A Simulink model including the hybrid-electric components, the cooperative control system with regenerative brake, and the vehicle dynamics was developed and used to find a solution. The regenerative energy ratio with respect to the whole brake energy was increased in this research from less than 60 % to over 80 %.

• Journal of Society of Preventive Korean Medicine
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• v.13 no.3
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• pp.29-41
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• 2009

Objectives : This study was performed to compare consciousness of doctors on cooperative practices of western medicine and traditional Korean medicine, and to provide policy implication for development of cooperative practices. Methods : The structured questionnaires were mailed to 132 doctors working in non-cooperative practicing university hospital and 77 doctors working in cooperative practicing hospitals in Busan metropolitan city. The response rate was 40.2% and 40.3% respectively. This survey was performed from 10 Oct. 2008 to 31 Oct. 2008. Results : The doctors working in general hospital had comparatively negative consciousness on basic concept, value and necessity for cooperative practices and traditional Korean medicine. In regards with disease treatment's effectiveness of cooperative practices, both groups evaluated musculoskeletal and immune disease were more effective than others. There were positive relationships between perception for cost-effectiveness and consciousness on intention to participate cooperative practices(p<0.05). Also doctors who experienced traditional medicine treatment had positive consciousness on cooperative practices(p=0.05). Conclusions : To activate cooperative practices of western medicine and traditional Korean medicine, some efforts should be carried out. These include promoting cooperative education programs in medical schools and traditional Korean medical schools, doing research on cost-effectiveness of cooperative practices, and trying to minimize legal and systemic restrictions for cooperative practices.

• The Mathematical Education
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• v.44 no.3 s.110
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• pp.397-408
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• 2005

This research developed self-directed teaming program for students who learn mathematics to improve their abilities for learning mathematics. A small-group cooperative teaming model was based on the self-directed loaming program which this research developed. The main target of this program was the second grade students of middle school. The program was consisted with three developing parts. The part 1 of program developing was consisted with analyzing and reconstructing mathematics curriculum, devising small-group cooperative learning program, and structuring teaching and teaming plans. The part 2 included the management of small-group cooperative Loaming and how to use the materials which this research developed. The part 3 provided various cooperative learning opportunities for students to improve their abilities for loaming mathematics.

• Proceedings of the Korean Society of Broadcast Engineers Conference
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• 1997.06a
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• pp.83-88
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• 1997

In this study, we focus on precise and natural cooperative object manipulation in a virtual space. We introduce two virtually expanded physical laws-virtual mechanical equilibrium on a rigid object and exclusive object arrangement-to create realistic cooperative manipulation. We have built a trial system according to our proposed design. The method is expected to allow users to exchange intended manipulation by haptic and visual channels.

• Journal of the military operations research society of Korea
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• v.27 no.1
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• pp.114-127
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• 2001

To support cooperative work in various scenes by computer systems, functions of sharing personalization, observation and control are needed. Especially, in advanced cooperative work, people have various position so that sometimes one person needs to restrict behavior of another. In this paper, we describe representation of access restriction of hypermedia system, which is framework of CSCW(Computer-Supported Cooperative Works) system we developed and propose a way to go on working cooperatively with people, restricting others.

• Journal of Communications and Networks
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• v.10 no.2
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• pp.148-155
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• 2008

In wireless data communication systems, retransmission of an erroneous packet is inevitable due to the harsh communication environment. In this paper, an efficient retransmission scheme using cooperation from neighboring nodes is investigated. In the cooperative retransmission scheme, an erroneous packet is transmitted to the destination by cooperative nodes which have favorable channels. This cooperative retransmission scheme requires no a priori information of neighboring nodes and has no limitation on the number of cooperating nodes. Distributed beamforming is used to accommodate multiple cooperating nodes. Phase and frequency offsets of cooperating signals are extracted from the NACK message and used to co-phase retransmitted data packets. The outage probability of the cooperative retransmission scheme is analyzed for the case of perfect synchronization and when the offsets are estimated. To reduce the impact of the residual phase and frequency offsets in cooperating signals, a low-rate feedback scheme is also investigated. It is shown that improved outage probability and reduced packet error rate (PER) performance can be achieved even for long data packets. The proposed cooperative retransmission scheme is found to outperform simple retransmission by the source as well as decode-and-forward cooperation.