• The Journal of Korean Institute of Communications and Information Sciences
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• v.28 no.1C
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• pp.64-71
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• 2003

In this paper, we proposed an algorithm that shorten coding time maintaining image quality in JPEG2000, which is the standard, of still image compression. This method encodes only the bit plane selected as appropriate truncation point for output bitstream, obtained from estimation of frequency distribution for whole image. Wavelet characterized by multi-resolution has vertical, horizontal, and diagonal frequency components for each resolution. The frequency interrelation addressed above is maintained thorough whole level of resolution and represents the unique frequency characteristics for input image. Thus, using the frequency relation at highest level, we can pick the truncation point for the compression time decrease by estimating code bits at encoding each code block. Also, we reduced the encoding time using simply down sampling instead of low-pass filtering at low-levels which are not encoded in color component of lower energy than luminance component. From the proposed algorithm, we can reduce about 15~36% of encoding time maintaining PSNR 30$\pm$0.5㏈.

• Restorative Dentistry and Endodontics
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• v.25 no.4
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• pp.494-498
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• 2000

이 연구의 목적은 'Three-File' 방식에 의한 근관형성시 근관의 형태변화 및 전이정도를 분석하고 이를 기존의 근관형성방법과 비교하고자 하는 것이다. 만곡된 근관을 가진 투명한 레진블럭 상에서 'Three-File' 방식, crown-down방식 및 스테인레스강 화일에 의한 수동방식으로 근관형성을 시행하고 이를 똑같은 위치가 재현가능한 고정틀에 위치시킨 후 사진의 이중노출 기법을 이용하여 근관형성 전후의 근관의 형태변화 및 전이정도를 분석한 결과 다음과 같은 결과를 얻었다. 1. 스테인레스강 화일의 경우 근관확대가 가장 컸고 근관의 전이정도도 심하였으며, 형성된 근관이 taper하지 못하고 불규칙한 형태를 보였다. 2. Profile로 crown-down방식에 의해 형성한 경우 taper한 근관형태를 보였고, 근관의 전이 정도도 스테인레스강 화일의 경우보다 작았다(p<0.01). 3. Profile로 'Three-File'방식에 의해 형성한 경우 taper한 근관형태를 보였고 근관의 전이정도도 스테인레스강 화일의 경우보다 유의하게 작았으나(p<0.01), crown-down방식에 의해 형성한 경우와 유의할 만한 차이는 없었다(p>0.01).

• Journal of KIISE:Software and Applications
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• v.32 no.10
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• pp.949-955
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• 2005

In this Paper, we propose fast block matching algorithm by dividing complex areas based on complexity order of reference block and square sub-block to reduce an amount of computation of full starch(FS) algorithm for fast motion estimation, while keeping the same prediction quality compared with the full search algorithm. By using the fact that matching error is proportional to the gradient of reference block, we reduced unnecessary computations with square sub-block adaptive matching scan based image complexity instead of conventional sequential matching scan and row/column based matching scan. Our algorithm reduces about $30\%$ of computations for block matching error compared with the conventional partial distortion elimination(PDE) algorithm without any prediction quality, and our algorithm will be useful in real-time video coding applications using MPEG-4 AVC or MPEG-2.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.37C no.11
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• pp.1162-1169
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• 2012

One of the important operational requirements for mission critical Ethernet networked system is having the fault tolerant capability. Such capability can be obtained by equipping multiport Network Interface Card (NIC) in each node in the system. Conventional NIC uses two or more Media Access Controls (MACs) and a co-processor for the MAC switching whenever an active port fails. Since firmware is needed for the co-processor, longer fail-over switching and degraded throughput can be generally expected. Furthermore the system upgrading requiring the firmware revision in each tactical node demands high cost. In this paper we propose a novel single MAC based NIC that does not use a co-processor, but just use general discrete building blocks such as MAC chip and switching chip, which results in better performances than conventional method. Experimental results validate our scheme.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.37 no.1A
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• pp.1-7
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• 2012

The conventional Zhu's differential space-time modulation(DSTM) based on quasi-orthogonal design adopted a complex precoder in order to allow an independent joint detection of two complex symbols without any channel informations at a receiver. In this paper, by simply replacing the complex precoder used in Zhu's DSTM with a real precoder, a new DSTM is presented for four transmit antennas. The real precoder enables the receiver to decode two real symbols pair separately, and thus the new DSTM has greatly reduced decoding complexity compared to the Zhu's DSTM. By computer simulation results, the proposed scheme is shown to exhibit almost identical or improved error performance compared to the existing DSTMs.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.34 no.4C
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• pp.349-354
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• 2009

In this paper, a new motion compensation scheme to reduce external memory access frequency which is one of the major bottlenecks for real-time decoding is proposed. Most H.264/AVC decoders store reference pictures in external memories due to the large size and reference blocks are read into the decoder core as needed during decoding. If the reference data access is done for each reference block in decoding sequence, the memory bandwidth can be unacceptable for real-time decoding. This paper presents a memory access scheme for motion compensation to read as many reference data as possible with reduced memory access frequency by analyzing reference data access pattern for each macroblock. Experimental results show that the proposed motion compensation scheme leads to approximately 30% improvement in memory bandwidth requirement.

• Smart Media Journal
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• v.3 no.4
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• pp.16-21
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• 2014

HEVC is the latest joint video coding standard with ITU-T SG16 WP and ISO/IEC JTC1/SC29/WG11. Its coding efficiency is about two times compared to H.264 high profile. Intra prediction has 35 directional modes including dc and planer. However an accurate mode decision on lots of modes with SSE is too costly to implement it with hardware. The key idea of this paper is a DCT shared architecture to reduce the complexity of HEVC intra encoder. It is to use same DCT block to quantize as well as to calculate SSE in RDO. The proposed intra encoder uses two step mode decision to lighten complexity with simplified RDO blocks and shares the transform resources. Its BD-rate increase is negligible at 20% on hardware aspect and the operating clock frequency is 300MHz@60fps on FHD ($1920{\times}1080$) image.

• The Journal of the Korea Contents Association
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• v.6 no.1
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• pp.1-7
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• 2006

This paper proposes a new method that reduces the complexity of the combined system, which consists of the selective mapping(SLM) and the partial transmit sequence(PTS) in the Orthogonal Frequency Division Multiplexing(OFDM). In order to reduce the Peak-to-Average Power Ratio(PAPR), many techniques have been developed such as SLM and PTS. and their combined systems. However the method that simply combines PTS and SLM to improve the effectiveness of a system increases the complexity of calculation. The scheme employed in this research suggests a system that combines PTS and SLM reducing the complexity via the N($N=2^n$)-point inverse fast Fourier transforms(IFFT), which uses the decimation in time domain not only to improve PAPR but also to reduce the amount of calculation. The proposed method reduces the complexity by multiplying a phase sequence and a subblock index to the data sequences in the middle of IFFT, which yields an optimal sequence with minimal PAPR. The superiority of the proposed method is demonstrated by simulation results and analysis.

• Journal of Digital Convergence
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• v.15 no.3
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• pp.211-219
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• 2017

Among government projects for reduction of coastal disaster, coastal maintenance project stage 1(2000~2009) and stage 2(2010~2019) to reduce coastal erosion and sedimentation are currently under process. In performing the coastal maintenance projects, it is necessary to install artificial concrete armor units for coastal protection. Presently in Korea, products manufactured in Japan are applied to the site, or blocks self-developed by the construction firms are installed. However, there is a lack of technical reviews such as verification of hydraulic characteristics, securing the stability and design techniques. This study is intended to develop waterfront shore protection blocks with good accessibility of people and excellent coastal disaster reduction and protection capability. Through this study, hydraulic characteristics and stability coefficients of shore protection blocks could be drawn.

• Journal of Broadcast Engineering
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• v.4 no.2
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• pp.127-133
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• 1999

The conventional fractal image compression based on discrete wavelet transform uses the fixed block size in fractal coding and reduces PSNR at low bit rate. This paper proposes a fractal image coding based on discrete wavelet transform which improves PSNR by using variable block size in fractal coding. In the proposed method. the absolute values of discrete wavelet transform coefficients are computed. and the discrete wavelet transform coefficients of different highpass subbands corresponding to the same spatial block are assembled. and the fractal code for the range block of each range block level is assigned. and then a decision tree C. the set of choices among fractal coding. "0" encoding. and scalar quantization is generated and a set of scalar quantizers q is chosen. And then the wavelet coefficients. fractal codes. and the choice items in the decision tree are entropy coded by using an adaptive arithmetic coder. This proposed method improved PSNR at low bit rate and could achieve a blockless reconstructed image. As the results of experiment. the proposed method obtained better PSNR and higher compression ratio than the conventional fractal coding method and wavelet transform coding.rm coding.