• Magazine of the Korea Concrete Institute
• /
• v.9 no.1
• /
• pp.105-113
• /
• 1997

The reduction phenomena of concrete compressive strength with the size of cylinders have been very interested in, but till now the adequate. analysis technique is not fixed. Based on the existing research results. the bigger the member size is, the smaller the strengt.h is. However. the real test ~.csults reveal that the wduction rate becomes blunt and there are considerable differences between size offrct law and real results. The punposc. ofthis paper is to propose tho model equat.ion which covers the compressive strength of' cylinder specimens in case of general hight/dialnetcr ratio in terms of the size effect. he effect of maximum aggregate size on the microcrack zone was also studied, and the model equation was proposed by considering the concept of'the characteristic length. These results will also be used to predict the cornprcssivt. stxngth of various sized concrete cores sampled from existing structures.

• Proceedings of the Korean Society of Broadcast Engineers Conference
• /
• 2009.11a
• /
• pp.67-70
• /
• 2009

H.264/AVC 동영상 표준은 기존의 동영상 표준과 비교했을 때 뛰어난 압축률을 보인다. 특히 세밀한 움직임 예측을 통해 영상을 효율적으로 압축하지만 움직임 예측은 H.264/AVC 동영상 표준의 높은 복잡도의 원인 중 하나이다. 따라서 H.264/AVC의 부호화 시간을 단축하기 위해서는 고속 움직임 추정 기법이 필수적이다. 일반적으로 영상 신호는 인접한 화면과 매크로블록 사이에서 상관관계가 높고 부호화하고자 하는 매크로블록의 움직임벡터는 인접한 매크로블록에서 결정된 최적의 움직임 벡터와 유사한 방향성을 가진다. 그러므로 고정된 탐색 영역의 크기를 이용하면 불필요한 영역까지 움직임 예측 과정이 수행되어 계산량이 증가한다. 본 논문에서는 영상의 공간적, 시간적 상관도를 이용하여 탐색 영역의 크기를 결정하는 방법을 제안한다. 인접하는 블록들의 움직임 벡터의 표준편차를 이용하여 움직임이 작은 영역에서는 작은 탐색 영역을 이용하여 움직임 예측을 수행하고 반대로 움직임이 큰 영역에서는 큰 탐색 영역을 이용하여 움직임 예측을 수행한다. 또한 현재 화면과 참조 화면의 거리차가 클수록 참조 화면으로 선택되는 확률이 낮다는 사실을 이용하여 적응적으로 탐색 영역의 크기를 조절한다. 제안한 방법은 기존의 전 영역 탐색 방법과 유사한 부호화 성능을 보이면서 움직임 예측 시간이 평균 약 58.93% 감소하는 것을 확인할 수 있다.

• Korea Information Processing Society Review
• /
• v.14 no.2
• /
• pp.43-52
• /
• 2007

• Korea Multimedia Society
• /
• v.16 no.1
• /
• pp.9-16
• /
• 2012

• The Magazine of the IEIE
• /
• v.32 no.9 s.256
• /
• pp.54-60
• /
• 2005

• The Magazine of the IEIE
• /
• v.22 no.6
• /
• pp.17-26
• /
• 1995

• Broadcasting and Media Magazine
• /
• v.7 no.3
• /
• pp.35-43
• /
• 2002

• The Magazine of the IEIE
• /
• v.19 no.12
• /
• pp.44-58
• /
• 1992

• Journal of Broadcast Engineering
• /
• v.21 no.4
• /
• pp.484-492
• /
• 2016

The High efficiency video coding (HEVC) is the newest video coding standard that achieves coding efficiency higher than previous video coding standards such as H.264/AVC. In intra prediction, the prediction units (PUs) are derived from a large coding unit (LCU) which is partitioned into smaller coding units (CUs) sizing from 8x8 to 64x64 in a quad-tree structure. As they are divided until having the minimum depth, Optimum CU splitting is selected in RDO (Rate Distortion Optimization) process. In this process, HEVC demands high computational complexity. In this paper, to reduce the complexity of HEVC, we propose a fast CU mode decision (FCDD) for intra prediction by using FAST (Features from Accelerated Segment Test) corner detection. The proposed method reduces computational complexity with 53.73% of the computational time for the intra prediction while coding performance degradation with 0.7% BDBR is small compared to conventional HEVC.

• The KIPS Transactions:PartB
• /
• v.19B no.2
• /
• pp.83-92
• /
• 2012

Multimedia contents can be copied and manipulated without quality degradation. Therefore, they are vulnerable to digital forgery and illegal distribution. In these days, with increasing the importance of multimedia security, various multimedia security techniques are studied. In this paper, we propose a content authentication algorithm based on reversible watermarking which supports JPEG compression commonly used for multimedia contents. After splitting image blocks, a specific authentication code for each block is extracted and embedded into the quantized coefficients on JPEG compression which are preserved against lossy processing. At a decoding process, the watermarked JPEG image is authenticated by extracting the embedded code and restored to have the original image quality. To evaluate the performance of the proposed algorithm, we analyzed image quality and compression ratio on various test images. The average PSNR value and compression ratio of the watermarked JPEG image were 33.13dB and 90.65%, respectively, whose difference with the standard JPEG compression were 2.44dB and 1.63%.