• Journal of computational fluids engineering
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• v.1 no.1
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• pp.19-25
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• 1996

A multiblock grid generation has been developed to be reliably used for a Navier-Stokes simulation of the turbomachinery flow-fields A multiblock structure simplifies the creation of structured H-grids about complex turbomachinery geometries and facilitate the creation of a grid in the tip flow region. The numerical algorithm adopts the combination of the algebraic and elliptic method to create the internal grids efficiently and quickly. The grid refinement process is enhanced by developing strategies to utilized Bezier curves and splines along with weighted transfinite interpolation technique and by formulating the grid-imbedding method for the viscous boundary-layer meshes. For purposes of illustration, the grid generator is applied to the high turning turbine rotor blades. Two different types of computational grids are provided to be compared with respect to the grid adaptation to the flow simulations. Extension to three-dimensions was done to show the possibility of its application to the tip-flow simulations. The grid quality of the multiblock structure is good in the passages, with gloval orthogonality and adequate smoothness.

• Journal of KIISE:Software and Applications
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• v.27 no.12
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• pp.1193-1201
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• 2000

본 논문에서는 탐색 영역과 특징의 가중치를 동적으로 조절하여 블록 단위의 움직임 벡터를 추출하는 활동적 블록 정합 알고리듬을 제안한다. 본 논문에서 제안하는 알고리듬은 탐색 영역의 중심 위치를 결정하기 위해 시간에 따른 블록의 동작 변화는 작다고 가정한다. 그리고 탐색 영역의 크기는 공간적으로 인접한 블록들의 신뢰도에 따라 조절된다. 또한 본 논문에서 제안하는 알고리듬은 다중 특징을 사용하는 블록 정합 알고리듬으로 블록 정합 시 특징의 기여 정도를 나타내는 가중치를 블록 안에서 각 특징이 가지는 구분력에 따라 자동으로 설정하는 정합 유사 함수를 사용한다. 실험 결과는 본 논문에서 제안한 블록 정합 알고리듬이 기존의 알고리듬 보다 정확하게 움직임 벡터를 추출함을 보여준다.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2010.05a
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• pp.798-801
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• 2010

This paper describes an efficient architecture for LDPC(Low-Density Parity Check) decoder, which supports three block lengths (648, 1,296, 1,944) of IEEE 802.11n standard. To minimize hardware complexity, the min-sum algorithm and block-serial layered structure are adopted in DFU(Decoding Function Unit) which is a main functional block in LDPC decoder. The optimized H-ROM structure for multi block lengths reduces the ROM size by 42% as compared to the conventional method. Also, pipelined memory read/write scheme for inter-layer DFU operations is proposed for an optimized operation of LDPC decoder.

• Journal of the Korean Society of Surveying, Geodesy, Photogrammetry and Cartography
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• v.33 no.1
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• pp.63-70
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• 2015

An Image fusion, or Pansharpening is a methodology of increasing the spatial resolution of image with low-spatial resolution using high-spatial resolution images. In this paper, we have performed an image fusion of hyperspectral imagery by using panchromatic image with high-spatial resolution, multispectral and hyperspectral images with low-spatial resolution, which had been acquired by ALI and Hyperion of EO-1 satellite sensors. The study has been mainly focused on evaluating performance of fusion process following to the image fusion methodology of the block association, which had applied to ALI and Hyperion dataset by considering spectral characteristics between multispectral and hyperspectral images. The results from experiments have been identified that the proposed algorithm efficiently improved the spatial resolution and minimized spectral distortion comparing with results from a fusion of the only panchromatic and hyperspectral images and the existing block-based fusion method. Through the study in a proposed algorithm, we could concluded in that those applications of airborne hyperspectral sensors and various hyperspectral satellite sensors will be launched at future by enlarge its usages.

• The Journal of the Acoustical Society of Korea
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• v.20 no.1
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• pp.56-61
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• 2001

This paper presents the real-time implementation of an AMR (Adaptive Multi Rate) vocoder which is included in the asynchronous International Mobile Telecommunication (IMT)-2000 mobile ASIC. The implemented AMR vocoder is a multi-rate coder with 8 modes operating at bit rates from 12.2kbps down to 4.75kbps. Not only the encoder and the decoder as basic functions of the vocoder are implemented, but VAD (Voice Activity Detection), SCR (Source Controlled Rate) operation and frame structuring blocks for the system interface are also implemented in this vocoder. The DSP for AMR vocoder implementation is a 16bit fixed-point DSP which is based on the TeakLite core and consists of memory block, serial interface block, register files for the parallel interface with CPU, and interrupt control logic. Through the implementation, we reduce the maximum operating complexity to 24MIPS by efficiently managing the memory structure. The AMR vocoder is verified throughout all the test vectors provided by 3GPP, and stable operation in the real-time testing board is also proved.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.33 no.1C
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• pp.79-85
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• 2008

Dirty Paper Coding(DPC) can achieve the sum capacity of a multiuser multiple-input multiple-output(MU MIMO) broadcast channels. However, due to the high computational complexity of the successive encoding and decoding, deploying DPC in real systems is impractical. As one of practical alternatives to DPC, Block Diagonalization(BD) was researched. BD is an extension of the zero-forcing preceding technique that eliminates interuser interference(IUI) in downlink MIMO systems. Though BD has lower complexity than DPC, BD shows poor sum capacity performance. We show that sum capacity performance of BD is degraded due to no IUI constraint. Then, we modify BD to improve its sum capacity performance with relaxing the constraint and sub optimal channel set searching. With simulation results, it can be verified that our modification in BD induces some improvement in sum capacity performance.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.26 no.9B
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• pp.1299-1307
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• 2001

고정된 패턴을 사용하는 기존의 고속 블록기반 움직임 추정법에서는 국소 최소해로 고립될 가능성이 있을 뿐만 아니라, 여러 움직임이 공존하는 움직임 경계에서 정확한 움직임의 추정이 어렵다는 문제점을 가지고 있다. 이러한 문제점을 극복하기 위하여 본 논문에서는 탐색점의 수를 줄이는 동시에 국소 최소해로의 고립을 피하기 위하여 탐색 후보영역을 적용한 다중 국소 탐색법(multiple local search method : MLSM)을 제안한다. 또한, 블록 내의 움직임 영역별 정합오차의 최소편차를 고려하는 새로운 정합함수를 제안함으로써 움직임 경계에서 움직임 벡터추정의 부정확성과 움직임 보상영상에서의 화질저하문제를 개선하고자 한다. 실험결과, 제안한 방법은 기존의 방법에 비해 움직임 경계에서의 추정에서 우수한 결과를 보였으며, PSNR에 대해서도 전역탐색법과 유사한 결과를 얻을 수 있었고, 움직임 보상결과, 움직임 경계부근에서의 향상된 화질을 얻을 수 있었다.

• Proceedings of the KIEE Conference
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• 2007.10a
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• pp.377-378
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• 2007

본 논문에서는 저전력 임베디드 시스템을 위한 효율적인 다중 NAND 플래쉬 파일 시스템을 제안한다. 기존에 제안되었던 하드디스크를 비롯한 저장 장치들과는 달리 NAND 플래쉬 메모리는 특정 블록에 쓰기 연산을 하기 전에 해당 블록은 이미 소거된 상태이어야 한다. 또한 이러한 소거의 횟수는 각 블록마다 제한적이다. 이러한 문제를 해결하기 위해서 소거 횟수 평준화 기법이 많이 사용되고 있고 관련하여 많은 연구가 진행되고 있다. 본 논문에서는 소거 횟수에 임계치를 설정하여 연산하는 방법을 제안한다. 또한 기존에는 단일 플래쉬 메모리만을 고려하고 있으나 본 논문에서는 다중 플래쉬 메모리 구조를 고려한다.

• Proceedings of the Korean Society of Broadcast Engineers Conference
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• 2003.11a
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• pp.47-50
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• 2003

본 논문에서는 동영상을 효율적으로 부호화하기 위한 새로운 다중해상도 움직임 보상 방법과 잉여 양자화 방법을 제안한다. 본 논문에서 제안하는 동영상 부호화기는 다단계 이산웨이브렛 분해 움직임 예측 및 움직임 보상 블록 Tree 의 구성 및 블록 분할. 적응적 산술 부호화기로 구성된다 제안된 동영상 부호화기는 단순하면서도 낮은 연산량을 필요로 하며, 임베디드 특성과 SNR 계위 부호화 특성과 같은 좋은 기능을 제공한다. 또한 기존에 제안되었던 이산웨이브렛변환을 이용하는 동영상 부호화 방법과 비교하여 우수한 성능을 제공한다.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.30 no.9A
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• pp.772-780
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• 2005

In this paper, an efficient pre-processing in space tine block coded-spatial multiplexing systems is presented. The pre-processing scheme is designed empirically with extending the diagonally weighted orthogonal space time-block coded diversity system to spatial multiplexing system. Simulation results show the proposed scheme outperforms both the precoder using the predefued codebooks and typical antenna selection scheme over moderate doppler frequency in limited feedback channel.