• 한국산학기술학회논문지
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• 제16권7호
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• pp.4912-4917
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• 2015

연성 워터마킹은 인증이나 무결성 검증을 위한 목적으로 시각적인 화질저하 없이 워터마크를 영상에 삽입하는 기술로, 인증과 무결성 검증을 위한 워터마크는 필터링과 같은 영상 변형에 대하여 삽입된 워터마크가 쉽게 제거되어야한다. 본 논문에서는 디지털 서명을 이용하여 영상의 위변조 여부를 검출할 수 있는 블록기반 워터마킹 방법을 제안한다. 제안 방법에서는 초기화된 영상 블록의 해쉬 코드로부터 디지털 서명을 생성하고, 워터마킹 된 영상의 전체 블록을 검사하지 않고도 변형이 발생된 부분을 빠르게 검출할 수 있는 장점이 있다.

• 한국콘텐츠학회:학술대회논문집
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• 한국콘텐츠학회 2006년도 추계 종합학술대회 논문집
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• pp.499-502
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• 2006

H.264/MPEG4 Advanced Video coding joint standard 에서 복호기(디코더)의 디블럭킹 필터는 필요하다. 본 논문에서는 MPEG-4 비디오에서 낮은 비트율과 대역폭에서도 화질을 보장하는 개선된 디블럭킹 알고리즘을 제안한다. 제안된 디블럭킹 알고리즘은 간단한 shift, addition 그리고 comparison 만을 사용하기 때문에 복잡성이 줄어든다. 블록 왜곡의 유무를 판별하기 위해 마스크 블록의 경계강도를 구해 복잡영역, 중간영역 그리고 단순영역으로 분리해 처리한다 실험 결과, 본 논문에서 제안한 디블럭킹 알고리즘은 블록 왜곡이 줄어드는 것을 알 수 있다.

• KSII Transactions on Internet and Information Systems (TIIS)
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• 제7권2호
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• pp.366-385
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• 2013

In this paper, we propose a compressed sensing (CS) based Wyner-Ziv (WZ) codec using motion-aligned auto regressive model (MAAR) based side information (SI) extrapolation to improve the compression performance of low-delay distributed video coding (DVC). In the CS based WZ codec, the WZ frame is divided into small blocks and CS measurements of each block are acquired at the encoder, and a specific CS reconstruction algorithm is proposed to correct errors in the SI using CS measurements at the decoder. In order to generate high quality SI, a MAAR model is introduced to improve the inaccurate motion field in auto regressive (AR) model, and the Tikhonov regularization on MAAR coefficients and overlapped block based interpolation are performed to reduce block effects and errors from over-fitting. Simulation experiments show that our proposed CS based WZ codec associated with MAAR based SI generation achieves better results compared to other SI extrapolation methods.

• Journal of Hospice and Palliative Care
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• 제11권1호
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• pp.51-54
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• 2008

말기암 환자에서 암성통증 완화와 삶의 질 유지는 여전히 도전과제로 남아있다. 암성 통증 환자에게서 약물치료는 여전히 치료의 중심이 되고 있으나, 약물적 중재도 불구하고 많은 환자에서 적절한 통증 조절 효과를 얻지 못하거나 진통제와 관련된 부작용을 경험하고 있다. 이에 저자들은 복강신경총차단과 하장간막신경총차단 그리고 상하복신경 총차단의 다양한 교감신경차단을 시행하여 통증조절에 성공한 증례를 보고한다.

• 한국컴퓨터산업학회논문지
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• 제4권12호
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• pp.953-964
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• 2003

서로 다른 형태와 크기를 가지는 탐색패턴과 움직임 벡터의 분포는 블록 정합 알고리즘에서 탐색 속도와 화질을 좌우하는 중요한 요소이다. 본 논문에서는 크로스패턴과 납작한 육각패턴을 이용한 새로운 고속 블록 정합 알고리즘을 제안한다. 이 알고리즘은 초기에 크로스 패턴을 이용하여 탐색영역의 중심 주위에 분포 확률이 높은 움직임이 작은 벡터를 우선 찾은 다음에 움직임이 큰 벡터에 대해서는 납작한 육각패턴을 이용하여 고속으로 움직임 벡터를 찾게 하였다. 실험결과, 제안된 알고리즘은 육각패턴 탐색 알고리즘에 비하여 움직임 벡터 추정의 속도에 있어서 약 0.2-6.2% 의 성능 향상을 보였으며 화질 또한 PSNR 기준으로 약 0.02-0.3105 의 향상을 보였다.

• ETRI Journal
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• 제29권6호
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• pp.736-744
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• 2007

We propose a fast macroblock (MB) mode prediction and decision algorithm based on temporal correlation for P-slices in the H.264/AVC video standard. There are eight block types for temporal decorrelation, including SKIP mode based on rate-distortion (RD) optimization. This scheme gives rise to exhaustive computations (search) in the coding procedure. To overcome this problem, a thresholding method for fast inter mode decision using a MB tracking scheme to find the most correlated block and RD cost of the correlated block is suggested for early stop of the inter mode determination. We propose a two-step inter mode candidate selection method using statistical analysis. In the first step, a mode is selected based on the mode information of the co-located MB from the previous frame. Then, an adaptive thresholding scheme is applied using the RD cost of the most correlated MB. Secondly, additional candidate modes are considered to determine the best mode of the initial candidate modes that does not satisfy the designed thresholding rule. Comparative analysis shows that a speed-up factor of up to 70.59% is obtained when compared with the full mode search method with a negligible bit increment and a minimal loss of image quality.

• 제어로봇시스템학회논문지
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• 제8권8호
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• pp.625-632
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• 2002

We propose an outsole measurement/inspection system to improve the quality of the shoe product. It uses the Divide-and-Conquer technique to measure the length of shoes'outsole. First, it detects edge positions of outsole's toe and heel from each image frame using an unique scale block we defined and calculates the outsole's length as the distance of two edge positions. Then it compensates the total length of outsole using the side image of outsole. Next, it classifies the outsole as inferior goods if the measurement error is bigger than 5.8mm. As a result of testing with the various kinds of outsoles, it was shown that the 95% accuracy was acquired within 1mm allowable error range. In conclusion, the proposed inspection system is effective and useful in the measurement/inspection process of shoe product and any material object as well.

• 전자공학회논문지B
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• 제32B권1호
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• pp.64-72
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• 1995

We propose a new image coding method which takes into account both statistical redundancy and perceptual irrelevancy of the DCT coefficients so as to provide a high quality of the reconstructed images with a reduced transmission bit rate First, a block of DCT coefficients are decomposed into 16 subvectors so as for a subvector to convey key information about one of the low-pass or the dirctional filtered images. Then, the most significant subvector is selected as the principal edge of the block and then vector quantized. After that, the residuals of the block are computed and then sequentially quantized through aforementioned procedure until the quantization distortion is smaller than the target distortion. The proposed scheme is good at encoding images with a variety of transmission bit rates, especially at very low bit rate coding. In addition, it is another benifit of the proposed scheme that an image can be quantized with a wide range of the transmission bit rates by simply adapting the stopping criterion of the sequential vector quantizer according to the target distortion of the reconstructed image.

• 한국통신학회논문지
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• 제18권5호
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• pp.685-694
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• 1993

LOT(Lapped Transform)와 HVS(Human Visual System) 가중치를 이용하여 분류벡타 양자화기에 근거한 점진적 영상부호화 방법을 제안하였다. DCT변환을 이용한 기존의 블럭변환 영상부호화는 낮은 전송율에서 블럭화 현상이 심하게 나타난다. 본 논문에서는 영상블럭을 LOT로 변환하고 그 블럭들의 구조적 특성에 따라 네 부류로 분류한 다음 적응비트배정으로 재생 영상화질을 개선하기위해 HVS가중치를 갖는 LOT계수특성에 의해 서브벡타들로 나눈다. 이 서브벡타들을 벡타양자화하여 점진적으로 전송한다. 컴퓨터 시뮬레이션을 통한 부호화시험을 하여 점진적 전송에 의한 LOT/CVQ가 효율적인 전송임을 보이고 PIT/DCTVQ를 이용한 결과와 비교하였다.

• Journal of Mechanical Science and Technology
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• 제17권2호
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• pp.181-186
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• 2003

In order to assure the quality of the bent axis design axial piston pumps driven by tapered pistons, it is necessary to know the characteristics of force applied to tapered pistons and the mechanism for driving the tapered pistons. Since they are able to perform both reciprocating and spinning motions in cylinder block, it is difficult to understand the driving mechanismand-tomeasure the forces applied to tapered pistons experimentally In the present study, the theoretical mechanism for driving the tapered pistons is studied by use of the geometric method. The driving area of the tapered pistons is measured by measuring the strain of a cylinder forced against a tapered piston using an electric strain gauge and a slip ring. The forces applied to tapered pistons is also investigated with the change of discharge pressure and the rotational speed. As a results of this investigation, it is concluded that the cylinder block is driven by one tapered piston in a limited area and the driving area is changed due to space angle of the tapered pistons and the swivel angle of the cylinder block. It is also observed that the force applied to tapered pistons increases as the discharge pressure and the rotational speed increase.