• KSII Transactions on Internet and Information Systems (TIIS)
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• 제10권5호
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• pp.2326-2345
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• 2016

For the compression of color images, a common bitmap usually is generated to replace the three individual bitmaps that originate from block truncation coding (BTC) of the R, G and B channels. However, common bitmaps generated by some traditional schemes are not the best possible because they do not consider the minimized distortion of the entire color image. In this paper, we propose a near-optimized common bitmap scheme for BTC using Binary Ant Colony Optimization (BACO), producing a BACO-BTC scheme. First, the color image is compressed by the BTC algorithm to get three individual bitmaps, and three pairs of quantization values for the R, G, and B channels. Second, a near-optimized common bitmap is generated with minimized distortion of the entire color image based on the idea of BACO. Finally, the color image is reconstructed easily by the corresponding quantization values according to the common bitmap. The experimental results confirmed that reconstructed image of the proposed scheme has better visual quality and less computational complexity than the referenced schemes.

• 대한의용생체공학회:의공학회지
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• 제20권3호
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• pp.265-274
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• 1999

본 논문에서는 3차원 의료 영상에 적합한 interframe 부호화 알고리즘을 제안하였다. 제안된 알고리즘은 움직임 추정/보상과 변환 부호화를 사용하는 동영상 압축 방법에 기초를 두고 있다. 이 알고리즘에서는 움직임 추정을 위해 와핑 방법이 채택되었다. 그리고, 부호화 효율을 향상시키기 위해 적응적 모드 선택을 사용하여 웨이블릿 변환 영역에서 움직임 조상된 오차 영상과 원 영상을 혼합한다. 이렇게 혼합된 영상은 제로트리 부호화 기법에 의해 압축된다. 본 논문은 제안된 방법이 3차원 의료 영상의 부호화에 매우 유용함을 증명하였다. 모의실험결과는 제안된 방법이 슬라이스 간의 간격과 무관하게 항상 좋은 결과를 얻을 수 있도록 하고, 그럼으로써 3차원 의료 영상 압축에 매우 바람직하다는 사실을 보여준다.

• Journal of Information Processing Systems
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• 제13권1호
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• pp.40-56
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• 2017

Since the progress of digital medical imaging techniques, it has been needed to compress the variety of medical images. In medical imaging, reversible compression of image's region of interest (ROI) which is diagnostically relevant is considered essential. Then, improving the global compression rate of the image can also be obtained by separately coding the ROI part and the remaining image (called background). For this purpose, the present work proposes an efficient reversible discrete cosine transform (RDCT) based embedded image coder designed for lossless ROI coding in very high compression ratio. Motivated by the wavelet structure of DCT, the proposed rearranged structure is well coupled with a lossless embedded zerotree wavelet coder (LEZW), while the background is highly compressed using the set partitioning in hierarchical trees (SPIHT) technique. Results coding shows that the performance of the proposed new coder is much superior to that of various state-of-art still image compression methods.

• 한국가시화정보학회지
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• 제6권1호
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• pp.41-46
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• 2008

In this paper, the recirculation flow motion and mixing characteristics driven by air bubble stream in a rectangular water tank is studied. The time-resolved PIV technique is adopted for the quantitative visualization and analysis. 488 nm Ar-ion CW laser is used for illumination and orange fluorescent ($\lambda_{ex}=540nm,\;\lambda_{em}=560nm$) particle images are acquired by a PCO 10bit high-speed CCD camera (1280$\times$1024). To obtain clean particle images, 545 nm long pass optical filter and an image intensifier are employed and the flow rates of compressed air is 3 l/min at 0.5 MPa. The recirculation and mixing flow field is further investigated by time-resolved POD analysis technique. It is observed that the large scale recirculation resulting from the interaction between rising bubble stream and side wall is the most dominant flow structure and there are small scale vortex structures moving along with large scale recirculation flow. It is also verified that the sum of 20 modes of velocity field has about 67.4% of total turbulent energy.

• 전기전자학회논문지
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• 제23권3호
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• pp.925-933
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• 2019

본 논문에서는 Zynq Soc Platform의 부분 재구성 기능을 사용하여 영상 압축으로 생성된 blocking artifacts를 제거하는 후처리 시스템을 설계한다. 높은 연산량을 제공하고 실시간으로 1080p 영상을 처리하도록 부분 재구성이 가능한 FPGA(Field Programmable Gate Array) 영역에 디블로킹 필터를 구현한다. 또한 부분적으로 재구성 가능한 영역을 활용하여 제한된 환경의 임베디드 시스템에서 하드웨어 리소스를 보다 효율적으로 사용할 수 있다. 제안된 시스템의 실험결과는 디블로킹 필터처리 후 약 0.6dB의 PSNR 향상을 보여준다. Zynq SoC에서 구현된 필터가 동작할 때 68.33mW의 전력을 소모한다.

• 한국정보통신학회:학술대회논문집
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• 한국정보통신학회 2022년도 춘계학술대회
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• pp.104-107
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• 2022

오토인코더 딥러닝 모델은 이상 데이터도 정상 데이터로 복원하는 능력이 우수하여 이상탐지에 적절하지 못한 경우가 발생한다. 그리고 데이터의 일부를 가린(마스킹) 후 가린 데이터를 복원하는 방식인 Inpainting 방식은 잡음이 많은 이미지에 대해서는 복원능력이 떨어지는 문제점을 가지고 있다. 본 논문에서는 MLP-Mixer 모델을 수정·개선하여 이미지를 일정 비율로 마스킹하고 마스킹된 이미지의 압축된 정보를 모델에 전달해 이미지를 재구성하는 방식을 사용하였다. MVTec AD 데이터 셋의 정상 데이터로 학습한 모델을 구축한 뒤, 정상과 이상 이미지를 각각 입력하여 재구성 오류를 구하고 이를 통해 이상탐지를 수행하였다. 성능 평가 결과 제안된 방식이 기존의 방식에 비해 이상탐지 성능이 우수한 것으로 나타났다.

• 한국정보처리학회논문지
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• 제6권11호
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• pp.3150-3156
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• 1999

In this paper, VTQM(Variable Threshold Quantization Method) is proposed, which enhances PSNR by composing the advantages of round-off and truncation quantization methods. From vast experiments, PSNR's of JPEG images with the method are compared with that of standard JPEG methods. At the boundary which affects the compression ratio, VTQM quantizes with a new threshold to reduce the length of compressed data; otherwise, VTQM employs the round-off quantization method to preserve the original image information. As a result, VTQM reduces bit rate while preserving the image quanity. The experimental results show that VTQM enhances PSNR by 0.2-0.3dB., 0.4-0.5dB, with the same bit rate than those of the traditional truncation and round-off quantization methods, respectively.

• 대한전자공학회:학술대회논문집
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• 대한전자공학회 2003년도 하계종합학술대회 논문집 V
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• pp.2677-2680
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• 2003

This paper describes the implementation of a 4 channel embedded DVR system. It receives analog video from CCD cameras and converts to 640${\times}$480 CCIR-656 digital video by 30 frames/sec. These digital images are compressed to the wevelet transformed image using hardware codec which is capable of 350:1 real-time compression and decompression. The DVR is working on linux and it implemented on an embedded system which is based on StrongARM processor. For the interface between processor system module and image processing module, GPIO and memory control module are used, device drivers are developed. Linux kernel source is customized. This paper provides techniques of embedded system development and embedded linux porting.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2004년도 학술대회 논문집 정보 및 제어부문
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• pp.175-177
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• 2004

The current JPEG-2000 standard is a wavelet based scheme because wavelet transform have some advantages compare to DCT transform. In compressed images, there are some image degradation factors like contrast distortion by Quantization process. This factor is very important to HVS (Human Visual System). Therefore, In this paper, we propose a new algorithm for contrast enhancement using the properties of wavelet coefficients. This algorithm is processed in the wavelet domain and so it can be applied efficiently to JPEG-2000.

• 한국자동차공학회논문집
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• 제18권5호
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• pp.1-8
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• 2010

The introduction of mixture heterogeneity has been considered to be one of the ways to avoid knocking, as it reduces the pressure rise rate in HCCI Combustion. The purpose of this research was to investigate the effects of heterogeneity, in particular thermal stratification and fuel strength stratification, on HCCI Combustion fueled with DME and n-Butane. Thermal stratification is formed in the Combustion Chamber of a Rapid Compression Machine with three kinds of pre-mixture, each with different properties. The stratified charge mixture was adiabatically compressed, throughout which cylinder gas pressure and two-dimensional chemiluminescence images were measured and analyzed.