• The Journal of Korean Institute of Communications and Information Sciences
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• v.34 no.8C
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• pp.764-771
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• 2009

In this paper, we propose a fast multiple reference frame selection method using neighboring motion vectors and the correlation of inter-mode blocks in H.264 video coding. Using the property that an optimal reference frame has the statistical characteristics, the motion estimation of small Inter-block size is estimated from the motion estimation of the larger Inter-block size. Simulation results show that the proposal method decreased the computations about 91%. Without the sacrifice of coding performance, comparing to the H.264 multiple reference picture coding.

• 한국전산유체공학회:학술대회논문집
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• 1995.10a
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• pp.110-110
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• 1995

• The Korean Journal of Applied Statistics
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• v.31 no.5
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• pp.599-610
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• 2018

The method of Mack and Skillings (Technometrics, 23, 171-177, 1981) is a nonparametric multiple comparison method in a randomized block design with replications. This method is likely to result in loss of information because each block is ranked using the average of observations instead of repeated observations. In this paper, we proposed a new nonparametric multiple comparison method in the randomized block model with replications using an alignment method proposed by Hodges and Lehmann (The Annals of Mathematical Statistics, 33, 482-497, 1962) that extend the joint placement method proposed by Chung and Kim (Communications for Statistical Applications and Methods, 14, 551-560, 2007). In addition, Monte Carlo simulation compared the family wise error rate and power with the parametric method and the nonparametric method.

• Journal of Korea Society of Industrial Information Systems
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• v.25 no.5
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• pp.13-21
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• 2020

This paper proposes a sign reversal channel switching method in space-frequency block code for orthogonal frequency division multiplexing system. In case of sending source data on other antenna, it is necessary for the receiver to change combining method according to the channel variation. If one does not know the predefined channel switching sequence, it is not possible to decode the received data precisely. In transmit data symbols' exchanges for a channel switching, data symbols are exchanged according to a format of space-frequency block code. In this paper, we proposes a simple sign reversal method except exchanging data symbols between transmit antennas. It is shown that this method occurs another combining method for a simple encryption in the receiver.

• Proceedings of the IEEK Conference
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• 2005.11a
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• pp.307-310
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• 2005

우리는 레일리 페이딩 채널에서 다중 전송 안테나를 사용한 전송 방식을 택한 Alamouti 방식의 전송쌍 에러 확률(Pairwise error probability)을 사용해서 시스템의 성능을 분석해 보았다. 데이터는 시공간 블록 코딩을 사용해서 전송 안테나에 n 개의 배열로 전송되어졌다. 각각의 수신안테나의 수신 신호는 채널의 상태에 따라 변형된 n개의 송신 신호들의 선형결합으로 수신된다. 최대 가능도 복호 알고리즘(Maximum likelihood decoding algorithm)은 신호를 다시 재결합하는 간단한 방법을 사용하였다. 이러한 방식은 시공간 블록코드의 직교적인 성질을 이용한 것이고, 수신기에서의 수신신호가 선형결합이라는 것을 바탕으로 한 것이다. 모의실험을 통해서 시공간 블록 코딩을 사용하고, 다중 안테나를 사용한 시스템에서 우리가 분석한 결과를 확인했다.

• Proceedings of the Korean Information Science Society Conference
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• 2007.06c
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• pp.130-133
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• 2007

데이터베이스 시스템은 전통적으로 트랜잭션의 동시 접근 시 발생할 수 있는 문제들을 해결하고 동시성 향상을 위해 다양한 연구를 진행해 왔다. 다중 버전 기반의 동시성 제어 기법은 데이터 레코드에 대한 여러 버전을 전용 공간에 유지하고 이것을 통해 트랜잭션들의 동시 접근 시 블로킹 없이 원하는 데이터를 읽고 쓸 수 있게 된다. 그러나 데이터 레코드가 포함된 데이터 블록에 대해 여러 개의 트랜잭션이 동시에 데이터를 덮어쓰기 했을 경우 다수의 버전이 생성된다. 그래서 트랜잭션 별로 적합한 데이터 버전을 찾기 위해 버전들이 저장되어 있는 전용공간을 랜덤하게 검색해 데이터 블록을 찾아내야 하므로 많은 시간이 소모된다. 따라서 다중 버전 읽기의 부하를 줄이기 위해 차세대 저장 매체로 부상하고 있는 플래시 메모리를 이용할 경우 랜덤 읽기에 의한 데이터베이스 시스템의 성능저하를 줄일 수 있다. 플래시 메모리는 디스크와 달리 기계적인 파트가 존재하지 않기 때문에 저장된 모든 블록에 대해 빠른 랜덤 읽기를 가능하게 한다. 본 논문에서는 플래시 메모리를 다중 버전 기반의 동시성 기법에 적용했을 경우의 성능 평가를 통해 하드 디스크에 비해 3.5배 이상의 높은 성능을 보임을 증명한다.

• The Transactions of the Korea Information Processing Society
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• v.7 no.12
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• pp.3964-3975
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• 2000

There are two policies for maintaining consistency among the multiple processor caches in a multiprocessor system: Write invalidate and Write update. In the write invalidate policy, whenever a processor attempt to write its cached block, it has to invalidate all the same copies of the updated block in the system. As a results of this frequent invalidations, this policy results in high cache miss ratio. On the other hand, the write update policy renew them, instead of invalidating all the same copies. This policy has to transfer the updated contents through interconnection network, whether the updated block is ptivate or not. Therefore the network suffer from heavy transaction traffic. In this paper we present an efficient cache coherence protocol for shared memory multiprocessor system connected by slotted ring. This protocol is based on the write update policy, but the updated contents are transferred only in case of updating the shared block. Otherwise, if the updated block is private, the updated contents are not transferred. We analyze the proposed protocol and enforce simulation to compare it with previous version.

• Journal of the Institute of Electronics Engineers of Korea SP
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• v.45 no.6
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• pp.1-8
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• 2008

This paper introduces three efficient frame selection schemes to reduce the computation complexity for the multi-reference and variable block size Motion Estimation (ME). The proposed RSP (Reference Selection Pass) scheme can minimize the overhead of frame selection. The MFS (Modified Frame Selection) scheme can reduce the number of search points about 18% compared with existing schemes considering the motion of image during the reference frame selection process. In addition, the TPRFS (Two Pass Reference frame Selection) scheme can minimize the frame selection operation for the variable block size ME in H.264/AVC using the character of selected reference frame according to the block size. The simulation results show the proposed schemes can save up to 50% of the ME computation without degradation of image Qualify. Because the proposed schemes can be separated from the block matching process, they can be used with any existing single reference fast search algorithms.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.21 no.7
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• pp.900-910
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• 1997

Multiblock structured grids are, to a large extent, capable of filling up topologically complex flow domains in an efficient way. The proposed approach enables to use different flow models in each different block and the easy incorporation of different grid refinement strategies for different blocks. Furthermore, it may be expected that this multiblock structured approach will naturally lead to the parallel executions of calculations per block on different vector processors. In this paper, the hypercube + + structure is proposed for topological informations on multiblock grids and the B-spline volume for geometrical informations. Three samples of the-three dimensional results are presented to demonstrate the capabilities of the present approach.

• The KSFM Journal of Fluid Machinery
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• v.1 no.1 s.1
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• pp.72-80
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• 1998

Computational analysis of incompressible flows by numerically solving Navier-Stokes equations using multi-block finite volume method is conducted on a parallel computing system. Numerical algorithms adopted in this study $include^{(1)}$ QUICK upwinding scheme for convective $terms,^{(2)}$ central differencing for other terms $and^{(3)}$ the second-order Euler differencing for time-marching procedure. Structured grids are used on the body-fitted coordinate with multi-block concept which uses overlaid grids on the block-interfacing boundaries. Computational code is parallelized on the MPI environment. Numerical accuracy of the computational method is verified by solving a benchmark test case of the flow inside two-dimensional rectangular cavity. Computation in the axial compressor cascade is conducted by using 4 PE's md, as results, no numerical instabilities are observed and it is expected that the present computational method can be applied to the turbomachinery flow problems without major difficulties.