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소규모 역삼투 담수화 시설에서 에너지 회수장치의 필요성에 대한 연구
전종민 ( Jongmin Jeon ),곽경섭 ( Kyungsup Kwak ),김누리 ( Noori Kim ),정재학 ( Jaehak Jung ),손동민 ( Dong-min Son ),김수한 ( Suhan Kim ) 한국화학공학회 2017 Korean Chemical Engineering Research(HWAHAK KONGHA Vol.55 No.6
Energy recovery device (ERD) is used to save energy consumption in seawater reverse osmosis processes. However, small-scale ERDs (<100 m<sup>3</sup>/d) are hardly observed in seawater desalination market. In South Korea, most of seawater desalination plants for drinking water production are small-scaled and have been operated in island areas or on ships. Thus, the effect of ERDs for these small-scale SWRO processes should not be neglected. In this work, the small-scale SWRO processes are designed and analyzed in terms of energy consumption with/without ERD. The realistic effi-ciencies of high pressure pumps are considered for the energy analyses. The unit cost of electricity depending on the application place (e.g., inland and island areas, on ships) is investigated to calculate the energy cost for unit water pro-duction in various SWRO applications classified by plant capacity, application place, and the installation of ERD. As a result, the energy cost can be saved up to 1,640.4 KRW/m<sup>3</sup> when ERD is applied, and the saving effect increases at smaller plants on ships. In conclusion, the development of small-scale ERDs are necessary because small-scale SWRO pro-cesses are dominant in Korean seawater desalination market, and the electricity saving effect becomes higher at smaller-scaled system.
Performance of DF Protocol for Distributed Cooperative Spectrum Sensing in Cognitive Radio
Mingrui Zou(추명예),Sangjun Bae(배상준),Kyungsup Kwak(곽경섭) 한국통신학회 2009 韓國通信學會論文誌 Vol.34 No.2A
Cognitive radio has been proposed to mitigate the spectrum scarcity problem by allowing the secondary users to access the under-utilized frequency bands and opportunistically transmit. Spectrum sensing, as a key technology in cognitive radio, is required to reliably detect the presence of primary users to avoid the harmful interference. However, it would be very hard to reliably detect the presence of primary users due to the channel fading, shadowing. In this paper, we proposed a distributed cooperative spectrum sensing scheme based on conventional DF (decode-and-forward) cooperative diversity protocol. We first consider the cooperation between two secondary users to illustrate that cooperation among secondary users can obviously increase the detection performance. We then compare the performance of DF based scheme with another conventional AF (amplify-and-forward) protocol based scheme. And it is found that the proposed scheme based on DF has a better detection performance than the one based on AF. After that, we extend the number of cooperative secondary users, and demonstrate that increasing the cooperation number can significantly improve the detection performance.
전송 안테나 및 성상도 선택과 전력 할당을 적용한 MIMO 다중 사용자 시스템의 성능분석
유현,김진수,황현철,김백현,이형기,곽경섭,Yoo Hyun,Kim JinSu,Hwang HyeonChyeol,Kim BaekHyun,Lee HyungKi,Kwak KyungSup 대한전자공학회 2005 電子工學會論文誌-TC (Telecommunications) Vol.42 No.9
In this paper, we suggest the scheme combining long-term feedback and short-term feedback in MIMO multi-user system and analyze its system performance. At the beginning of communication, long-term feedback is fed back to transmitter such as the number of active antennas, constellations, and transmission powers which are determined to satisfy the given target symbol error and target data rate for each user. After this, short-term feedback of active antenna index is fed back periodically Simulation results show the proposed scheme outperforms better than long-term feedback or short-term feedback information scheme. 본 논문에서 장시간 귀환 기법과 단시간 귀환 기법을 결합하는 MIMO 다중 사용자 시스템을 제안하고 성능을 분석하였다 통화 초기에 목표 심볼 오류와 목표 전송를을 고려하여 활성 안테나 수, 성상도, 전송 전력과 같은 장시간 귀환 기법을 수신단에서 전송단에 귀환한다. 이 후에 수신단에서 단시간귀환기법으로서 활성안테나 인덱스를 주기적으로 전송단에 알려준다. 모의실험을 통해 장시간 귀환 기법 또는 단시간 귀환 기법만을 적용하였을 경우보다 장시간 귀환 기법 방법에 단시간 귀환 기법을 적용하였을 경우에 우수한 성능 개선이 있음을 확인할 수 있었다.