• KIISE Transactions on Computing Practices
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• v.21 no.1
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• pp.88-93
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• 2015

In modern computer systems, DRAM is commonly used as main memory due to its low read/write latency and high endurance. However, DRAM is volatile memory that requires periodic power supply (i.e., memory refresh) to sustain the data stored in it. On the other hand, PCM is a promising candidate for replacement of DRAM because it is non-volatile memory, which could sustain the stored data without memory refresh. PCM is also available for byte-addressable access and in-place update. However, PCM is unsuitable for using main memory of a computer system because it has two limitations: high read/write latency and low endurance. To take the advantage of both DRAM and PCM, a hybrid main memory, which consists of DRAM and PCM, has been suggested and actively studied. In this paper, we propose a novel page replacement algorithm for hybrid main memory. To cope with the weaknesses of PCM, our scheme focuses on reducing the number of PCM writes in the hybrid main memory. Experimental results shows that our proposed page replacement algorithm reduces the number of PCM writes by up to 80.5% compared with the other page replacement algorithms.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.38C no.2
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• pp.155-164
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• 2013

Two design techniques for more accurate and more convenient hybrid positioning system with visible light communication (VLC) and ad-hoc wireless network infrastructure are proposed, in order to overcome the problems of high estimation error, high cost, and limited service range of the conventional positioning techniques. First method is based on a non-carrier VLC based hybrid positioning technique for applications involving of low data rate optical sensing and narrow-range visible light reception from transmitter, and long-range positioning. The second method uses a 4 MHz carrier VLC-based hybrid positioning technique for a high data rate optical sensing and wide-range visible light receiving from transmitter, and mid-range positioning applications. In indoor environments with obstacles where there are long-range 7731.4cm and mid-range 2368cm distances between an observer and a target respectively, the hybrid positioning developed with two design techniques are tested, and the proposed system is verified and analyzed in this paper.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.15 no.8
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• pp.775-780
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• 2004

This paper describes the realization of the Ka-band group-delay equalized filter desisted with the help of a new hybrid method of Simulated Annealing(SA) and Conjugate Gradient(CG), to be employed by the multi-channel Input Multiplexer for a satellite use, each channel of which comprises a channel filter and a group-delay equalizer. The SA and CG find circuit parameters of an 8th order elliptic function filter and a 2-pole equalizer, respectively. Measurement results demonstrate that the performances of the designed component meet the specifications, and validate the design methods.

• Proceedings of the Korean Information Science Society Conference
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• 2004.10a
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• pp.40-42
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• 2004

Access Grid는 상호공동작업을 위하여 대용량의 컨텐츠 파일들을 주고받으며 공유한다. 특별히 중앙의 집중된 관리서버가 없는 Access Grid환경에서는 컨텐츠의 위치추적의 어려움, 부재, 병목 등의 현상이 발생하는데 이를 본 논문에서 1. 중앙 Hybrid서버의 구현 2. 집중컨텐츠의 거점노드복제 3. 중요컨텐츠의 24시간 공유보장 등의 기법으로 해결방안을 제안하였다. 그리고 이에 대한 효율성을 시뮬레이션 자료로 증명하였다.

• Journal of the Korean Society of Surveying, Geodesy, Photogrammetry and Cartography
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• v.29 no.2
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• pp.175-181
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• 2011

In remote sensing, it has been a difficult task to obtain a multispectral image with high spatial resolution because of the technical limitation of satellite sensors. In order to solve these problems, various pansharpening algorithms have been tried and proposed. However, most pansharpened images created by various approaches tend to distort the spectral characteristics of the original multispectral image or decrease the visual sharpness of the panchromatic image. To minimize the spectral distortion of pansharpened image while preserving spatial information of the panchromatic image, a hybrid pansharpening algorithm based on the spatial correlation was proposed. In this paper, we analyzed the spatial and spectral distortion of the hybrid pansharpened images generated by the various spatial correlation methods. In the experiments, we proved that the method by using Laplacian filtering was more efficient than other high frequency extraction algorithms in the viewpoint of spectral distortion and spatial sharpness.

• The KIPS Transactions:PartC
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• v.16C no.2
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• pp.223-228
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• 2009

Efficient service discovery mechanism is a crucial feature for a hybrid ad-hoc network supporting extension of a wireless ad-hoc network to the Internet. We propose an efficient cross-layer service discovery mechanism using non-disjoint multi-path source routing protocol for hybrid ad-hoc networks. Our scheme has advantages of multi-path routing protocol and cross-layer service discovery. Intuitively, it is not difficult to imagine that the cross-layer service discovery mechanism could result in a decreased number of messages compared to the traditional approach for handling routing independently from service discovery. By simulation, we show that faster route recovery is possible by maintaining multiple routing paths in each node, and the route maintenance overhead can be reduced by limiting the number of multiple routing paths and by maintaining link/node non-disjoint multi-path.

• Proceedings of the Korea Association of Information Systems Conference
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• 2005.05a
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• pp.393-408
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• 2005

인터넷의 성장은 고객에게 많은 혜택을 주었지만, 방대한 양의 정보는 오히려 장시간의 상품 탐색과 제품 선택을 어렵게 만들었다. 이에 따라, 정보의 양을 줄여 줄 수 있는 서비스를 고객들은 요구를 하기 시작하였고, 이에 따라 다양한 방법들이 고객에게 제시 되어졌다. 제시되어진 방법 중의 하나가 개인화 추천 시스템이다. 추천 시스템은 고객의 취향과 관심에 적합한 상품을 추천 해 주는 서비스로서 상품 검색 노력을 줄여 주고, 고객의 취향에 적합한 제품을 제시 해 줌으로써 고객충성도 제고에도 많은 도움을 주고 있다. 이러한 추천 시스템에서 가장 많이 사용되어지고 있는 기법은 협업 필터링이다. 협업 필터링은 협업에서도유용한 기법으로 인정을 받았다. 하지만 희박성과 확장성이라는 문제점으로 인해 추천의 정확도가 다소 떨어진다는 것이 단점이다. 본 연구에서는 이러한 단점을 극복할 수 있는 방법으로써 Hybrid 협업 필터링 기법을제시하고, 이를 토대로 추천 기법이 혼합되어진 Hybrid 추천 시스템에 대한 개념을 제시하고자 한다.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2002.05a
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• pp.535-539
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• 2002

본 논문에서는 Hybrid SC/MRC-Lc/L 다이버시티 수신 기법과 콘볼루션 부호화 기법을 각각 또는 함께 이용할 때의 Multi-Carrier DS-CDMA 시스템의 성능 개선을 구하였다. 우선 다중경로 페이딩 및 다중접속간섭의 영향을 분석하고, 두 기법에 의한 성능 개선 정도를 구하여 비교, 분석하였다. Hybrid SC/MRC-Lc/L 수신에서는 각각의 반송파에 대하여 상관을 취하고 상관기 출력들 중에서 가장 큰 신호성분을 Lc개만큼 선택하여 최대비 합성하며, 콘볼루션 부호화는 다중경로 페이딩 및 다중접속간섭에 의하여 발생된 오류를 정정 및 검출한다. 분석 결과, 콘볼루션 부호화 기법을 채용함으로서 성능이 현저하게 개선되는데, 부호이득과 전력제한 사이에 trade off를 고려하여 부호화 율( r)을 선택할 필요가 있다는 것과 하이브리드 SC/MRC-L$^{c}$ /L 수신에서는 입력 다이버시티 가지의 수 (L)가 많을수록 선택의 폭이 넓어지며, 적절한 숫자의 다이버시티 가지의 선택이 시스템의 복잡성과 성능 대 비용 등을 결정한다는 것을 알 수 있었다.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.39 no.2
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• pp.191-197
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• 2015

The message passing interface (MPI) and hybrid programming models for the parallel computation of a pressure equation were compared in a distributed memory system. Both models were based on domain decomposition, and two numbers of the sub-domain were selected by considering the efficiency of the hybrid model. The parallel performances for various problem sizes were measured using up to 96 threads. It was found that in addition to the cache-memory size, the overhead of the MPI communication/OpenMP directives affected the parallel performance. For small problems, the parallel performance was low because the percentage of the overhead of the MPI communication/OpenMP directives increased as the number of threads increased, and MPI was better than the hybrid model because it had a smaller communication overhead. For large problems, the parallel performance was high because, in addition to the cache effect, the percentage of the communication overhead was relatively low compared to that for small problems, and the hybrid model was better than MPI because the communication overhead of MPI was more dominant than that of the OpenMP directives in the hybrid model.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.20 no.8
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• pp.791-796
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• 2009

A hybrid iterative physical optics-method of moments(IPO-MoM) technique is presented for the analysis of jet engine structures which are both electrically large and complex. In this technique, the IPO method is used to analyze smooth inlet region and the MoM method is used to analyze electrically complex region inclusive of blades and hub. It is efficient and accurate by virtue of combining the respective merits of both methods. Numerical results are presented and validated through comparison with Mode-FDTD and measured results.