• Journal of Satellite, Information and Communications
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• v.9 no.3
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• pp.59-63
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• 2014

This paper describes the basic principles of 3D broadcast system and proposes new 3D broadcast technology that reduces the amount of data by applying CS(Compressed Sensing). Differences between Sampling theory and the CS technology concept were described. Recently proposed CS algorithm AMP(Approximate Message Passing) and CoSaMP(Compressive Sampling Matched Pursuit) were described. This paper compared an accuracy between two algorithms and a calculation time that image data compressed and restored by these algorithms. As result determines a low complexity algorithm for 3D broadcast system.

• Journal of Korea Society of Industrial Information Systems
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• v.4 no.4
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• pp.32-39
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• 1999

Video-On-Demand servers have to provide timely processing guarantees and reduce the storage and reduce the storage and bandwidth requirements for continuous media However, compression techniques used in Video-On-Demand servers make the bit rates of compressed video data significantly variable from frame to frame Consequently, most pervious Video-On-Demand servers which use constant bit rate retrieval to guarantee deterministic service under-utilize the system resources and restrict the number of clients. In this paper, I propose a buffer management scheme called CAP(Caching And Prefetching) for Video-On-Demand server using variable bit rate continuous media. By caching and prefetching the data CAP reduces the variation of the compressed data and increases the number of clients simultaneously served and maximizes the utilization of system resources. Results of trace-driven simulations show the effectiveness of the scheme.

• Proceedings of the Korea Concrete Institute Conference
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• 1994.10a
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• pp.187-193
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• 1994

일반 콘크리트 (설계강도 $\sigma_{28}=210 kg/\textrm{cm}^2$)에 산업폐기물인 Fly Ash를 혼합하고 기포재 (Air Entrainment Agent) 첨가에 따른 Fly Ash-Concrete의 물성 변화를 시험하였다. Fly Ash-Concrete의 slump를 6, 8, 10cm로 고정시킨후, 각각의 slump 반죽상태에다 기포재, Neopor-400을 25,000cc/$\textrm{m}^3$, 50,000cc/$\textrm{m}^3$, 75,000cc/$\textrm{m}^3$으로 증가시켰다. 이때 기포재 증가에 따른 공기량 변화와 압축강도 $(\sigma_7 과 \sigma_{28})$ 를 측정하였다. 또한 기포재를 첨가한후, 60분과 90분까지 방치하고, 60분후와 90분후의 공기량과 압축강도 $(\sigma_7 과 \sigma_{28})$ 변화를 측정하였다. 시험결과에 의하면, 기포재가 첨가되는 시간에서부터 60분, 90분 동안 방치하면 공기량은 감소된다. 동시에 압축강도는 점진적으로 증가된다. KSF 5405가 요구하는 slump값이 90분 이내에 $12\pm0.5$의 범위에 들어 가기 위해서는 기포재는 50,000cc/$\textrm{m}^3$-75,000cc/$\textrm{m}^3$만큼 첨가되어야 한다. 이때의 7일 압축강도가 170-200kg/$\textrm{cm}^2$이고 28일 압축강도는 215-290kg/$\textrm{cm}^2$이다. 이 값은 설계강도 $\sigma$28=210kg/$\textrm{cm}^2$ 보다 최고 약 40%까지 증가율을 보여 주었다.

• Journal of KIISE:Software and Applications
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• v.30 no.7_8
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• pp.687-695
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• 2003

In this paper, we present a document image compression system based on segmentation, Quincunx downsampling, (5/3) wavelet lifting and subband-oriented SPIHT coding. We reduced the coding time by the adaptation of subband-oriented SPIHT coding and Quincunx downsampling. And to increase compression rate further, we applied arithmetic coding to the bitstream of SPIHT coding output. Finally, we present the reconstructed images for visual comparison and also present the compression rates and PSNR values under various scalar quantization methods.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.34 no.11B
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• pp.1296-1302
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• 2009

We propose an efficient coding method of digital holograms using MCTF and standard compression tools for video. The hologram is generated by a computer-generated hologram (CGH) algorithm with both an object image and its depth information. The proposed coding consists of localization by segmenting a hologram, frequency transform using $64\times64$ segment size, 2-D discrete cosine transform DCT for extracting redundancy, motion compensated temporal filtering (MCTF), segment scanning the segmented hologram to form a video sequence, and video coding, which uses H.264/AVC. The proposed algorithm illustrates that it has better properties for reconstruction, 10% higher compression rate than previous research in case of object.

• Journal of the Korean Society of Propulsion Engineers
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• v.12 no.1
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• pp.23-28
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• 2008

Flow analysis in a turbine cascade by Euler or Navier-Stokes equation gives relatively accurate solution, however, those method require large computer memory or computing time. On contrast, the panel method, which is applied to incompressible and inviscid flow, provides fast and reasonal solution but the compressibility correction is required for a high air velocity case. In this paper, the compressibility corrected panel method was applied in order to find velocity distribution on turbine blades. Results showed that the calculated velocity in a turbine cascade by the compressibility corrected panel method gave good agreement with the solution by finite volume method for compressible flow.

• Journal of KIISE:Software and Applications
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• v.31 no.12
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• pp.1628-1636
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• 2004

Data compression techniques have been studied for decades because they saved space and time to reduce costs. The Lempel-Ziv 77 (LZ77) is a dictionary-based, lossless compression algorithm. The dictionary size of the LZ77 algorithm is fixed, and the performance of the algorithm is highly dependent on its dictionary size. In this paper, we suggest a dynamic LZ77 algorithm that changes its dictionary size during compression, and also we suggest a genetic algorithm to evolve the dictionary-resizing strategies. The suggested algorithm outperformed the original version up to about 16%.

• Journal of Internet Computing and Services
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• v.10 no.6
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• pp.219-228
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• 2009

The increased popularity of multimedia applications places a great demand on efficient data storage and transmission techniques. Some methods have been proposed to combine compression and encryption together to reduce the overall processing time, but they are either insecure or intensive computationally. specially, they are unsuitable to wireless communication of mobile device. We propose a novel solution called partial encryption, We introduce quadtree and zerotree wavelet image compression in this paper, it reduces computation for date transmission in mobile device, and does not reduce the compression rate. In conclusion, the proposed partial encryption schemes are fast, secure, and do not reduce the compression performance of underlying compression algorithm.

• Proceedings of the Korea Water Resources Association Conference
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• 2015.05a
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• pp.9-9
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• 2015

레이더 기술의 발전으로 말미암아, 현재의 기상 레이더는 그 관측 범위와 정밀성 뿐 아니라, 시공간 해상도의 월등한 향상을 이룩하였으며, 특히 이중편파 기술을 이용한 기상 관측을 통해 기존의 단일편파 레이더로 해석할 수 없었던 다양한 대기현상 분석을 가능케 하였다. 이처럼 기상레이더 관측 기술의 발전은 광범위한 관측반경과 높은 시공간해상도로 관측 정확성을 향상시킨 반면, 해상도 증가에 따른 기본적인 자료량이 증가되었으며 이중편파를 활용한 자료해석기법의 다양화로 인해 레이더 자료의 용량 또한 기하급수적으로 증가하게 되었다. 이러한 이유로 현재 도입이 진행중인 고성능의 기상레이더들로부터 광범위한 국토 범위에 대해 지속적으로 관측되는 방대한 양의 레이더 자료를 저장하고 분석하기 위해서는 많은 시간과 비용이 요구될 것으로 우려된다. 그러한 문제점을 해결하기 위해 레이더 자료의 유통 특성을 분석한 바, 기상레이더 자료는 자료의 획득시부터, 신호처리, 품질관리, 기상분석 등의 단계를 거치며, 각 단계의 사용자에 의해 각각 처리되고 가공되는 특성이 있음을 확인하였다. 따라서 제안 기법은 각 레이더 자료의 특성을 재해석하는 방법으로 압축함으로써 용량을 최소화시키는 동시에, 레이더 자료의 각 유통 단계의 여러 사용자들에게 서비스 될 수 있는 생성, 가공 및 단순화된 형태의 자료를 모두 포함하면서 각 단계의 사용자들에 적합한 자료의 형태로 제공할 수 있는 기법을 제안한다. 실험 결과, 기상레이더 자료의 특성과 기상 에코의 분포를 이용한 내용 기반 손실 압축 기법을 통해 다양한 사용자들을 위한 적응적이고, 효율적인 압축을 수행할 수 있음을 확인하였다.

• Journal of the Korean Society of Propulsion Engineers
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• v.4 no.4
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• pp.59-69
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• 2000

A numerical analysis based on two-dimensional, incompressible and compressible Navier-Stokes equations was carried out for double circular arc compressor cascade and the results are compared with available experimental data. The incompressible code based on SIMPLE algorithm adopts pressure weighted method and hybrid scheme for the convective terms. The compressible code with preconditioning method involves a upwind-biased scheme for the convective terms and LU-SGS scheme for temporal integration. Several turbulence models are evaluated by computing the turbulent viscous flows; Baldwin-Lomax, standard $\kappa$ -$\varepsilon$, $\kappa$ -$\varepsilon$ Lam. Bremhorst, standard $\kappa$-$\omega$, $\kappa$ -$\omega$ SST model.