• 방송공학회논문지
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• 제19권2호
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• pp.250-256
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• 2014

현재 MPEG에서 무료(royalty-free) 비디오 코덱으로 표준화 중인 IVC(Internet Video Coding)에서는 저지연(low-delay) 모드 부호화 구조에서 비참조 P 프레임 부호화 기법을 사용하여 부호화 성능 이득을 얻고 있다. IVC 시험모델 ITM(IVC Test Model) 4.0에 채택되어 있던 기존의 비참조 P 프레임 기법은 움직임 벡터(MV)의 크기를 이용하여 적응적으로 고정된 부호화 구조의 비참조 P 프레임을 적용하였으나 시퀀스에 따라서 오히려 부호화 성능이 크게 떨어지는 단점이 있었다. 본 논문에서는 이러한 기존의 적응적 비참조 P 프레임 부호화 성능을 개선하기 위하여 기존의 고정된 비참조 P 프레임의 구조를 변경하는 기법과 MV와 함께 참조 프레임 대비 비참조 프레임의 발생 비트량 비를 함께 사용하는 적응적 기법을 제시한다. 실험결과 제안된 기법은 시퀀스에 따른 큰 성능 저하 없이 ITM 7.0 대비 6.6% 정도의 비트율 감소를 얻음을 확인하였다.

• 한국측량학회지
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• 제36권6호
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• pp.451-456
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• 2018

시설물의 유지 관리 및 모니터링에 UAVs (Unmanned Aerial Vehicles)의 활용이 확대되고 있다. 안전 점검을 위한 시설물의 외관 상태 평가를 위하여 고해상도 영상을 취득하는 것이 필요하며, 넓은 지역을 빠르게 취득하기 위하여 비디오 데이터로 취득할 필요가 있다. 일반적으로 비디오 데이터에는 위치 정보가 포함되지 않아, 검사 개체의 실제 크기에 대한 정량적 분석이 어렵다. 본 연구에서는 교량 시설물을 대상으로 비디오 프레임과 기준 사진의 정합을 이용하여 교량의 3차원 점군(point cloud) 데이터의 활용성을 평가하고자 한다. 드론을 이용하여 비디오와 사진을 취득하고, 기준 사진과의 특징점 정합을 통하여 비디오 프레임의 외부 표정 요소를 생성하였다. 실험 결과 비디오 프레임 데이터는 기준 사진과 유사한 표정 정확도를 얻었으며, 표정된 프레임 데이터를 이용하여 생성된 점군 데이터는 교량의 형상 및 크기를 잘 표현하였다. 향후 다양한 조건의 정합 실험을 통하여 결과물의 안정성이 확인되면, 비디오 기반의 시설물 모델링 및 점검에 효과적으로 적용될 것으로 기대된다.

• Earthquakes and Structures
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• 제13권5호
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• pp.443-454
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• 2017

When eccentrically braced steel frames (EBFs) are in the desired failure mode, links yield at each layer and column bases appear plastically hinged. Traditional design methods cannot accurately predict the inelastic behavior of structures owing to the use of capacity-based design theory. This paper proposes the use of performance-based seismic design (PBSD) method for planning eccentrically braced frames. PBSD can predict and control inelastic deformation of structures by target drift and failure mode. In buildings designed via this process, all links dissipate energy in the rare event of an earthquake, while other members remain in elastic state, and as the story drift is uniform along the structure height, weak layers will be avoided. In this condition, eccentrically braced frames may be more easily rehabilitated after the effects of an earthquake. The effectiveness of the proposed method is illustrated through a sample case study of ten-story K-type EBFs and Y- type EBFs buildings, and is validated by pushover analysis and dynamic analysis. The ultimate state of frames designed by the proposed method will fail in the desired failure mode. That is, inelastic deformation of structure mainly occurs in links; each layer of links involved dissipates energy, and weak layers do not exist in the structure. The PBSD method can provide a reference for structural design of eccentrically braced steel frames.

• Earthquakes and Structures
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• 제8권5호
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• pp.1215-1240
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• 2015

In this paper, the Theory of Plastic Mechanism Control (TPMC) is applied to the seismic design of dual systems composed by moment-resisting frames and Chevron braced frames. The application of TPMC is aimed at the design of dual systems able to guarantee, under seismic horizontal forces, the development of a collapse mechanism of global type. This design goal is of primary importance in seismic design of structures, because partial failure modes and soft-storey mechanisms have to be absolutely prevented due to the worsening of the energy dissipation capacity of structures and the resulting increase of the probability of failure during severe ground motions. With reference to the examined structural typology, diagonal and beam sections are assumed to be known quantities, because they are, respectively, designed to withstand the whole seismic actions and to withstand vertical loads and the net downward force resulting from the unbalanced axial forces acting in the diagonals. Conversely column sections are designed to assure the yielding of all the beam ends of moment-frames and the yielding and the buckling of tensile and compressed diagonals of the V-Braced part, respectively. In this work, a detailed designed example dealing with the application of TPMC to moment frame-chevron brace dual systems is provided with reference to an eight storey scheme and the design procedure is validated by means of non-linear static analyses aimed to check the actual pattern of yielding. The results of push-over analyses are compared with those obtained for the dual system designed according to Eurocode 8 provisions.

• International Journal of Fluid Machinery and Systems
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• 제4권1호
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• pp.161-171
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• 2011

The availability of a high quality open source CFD simulation platform like OpenFOAM offers new R&D opportunities by providing direct access to models and solver implementation details. Efforts have been made by Hydro-Qu$\'{e}$bec to adapt OpenFOAM to hydroturbines for the development of steady-state capabilities. This paper describes the developments that have been made to implement new turbomachinery related capabilities: multiple frames of reference solver, domain coupling interfaces (GGI, cyclicGGI and mixing plane) and specialized boundary conditions. Practical use of the new turbomachinery capabilities are demonstrated for the analysis of a 195-MW Francis turbine.

• International Journal of Concrete Structures and Materials
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• 제6권4호
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• pp.209-220
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• 2012

Post-earthquake fire (PEF) can lead to a rapid collapse of buildings that have been partially damaged as a result of a prior earthquake. Almost all standards and codes for the design of structures against earthquake ignore the risk of PEF, and thus buildings designed using those codes could be too weak when subjected to a fire after an earthquake. An investigation based on sequential analysis inspired by FEMA356 is performed here on the immediate occupancy (IO), life safety (LS) and collapse prevention (CP) performance levels of two portal frames, after they are pushed to arrive at a certain level of displacement corresponding to the mentioned performance level. This investigation is followed by a fire analysis of the damaged frames, examining the time taken for the damaged frames to collapse. As a point of reference, a fire analysis is also performed for undamaged frames and before the occurrence of earthquake. The results indicate that while there is minor difference between the fire resistances of the fire-alone situation and the frames pushed to the IO level of performance, a notable difference is observed between the fire-alone analysis and the frames pushed to arrive at LS and CP levels of performance and exposed to PEF. The results also show that exposing only the beams to fire results in a higher decline of the fire resistance, compared to exposing only the columns to fire. Furthermore, the results show that the frames pushed to arrive at LS and CP levels of performance collapse in a global collapse mode laterally, whereas at the IO level of performance and fire-alone situation, the collapse mechanism is mostly local through the collapse of beams. Whilst the investigation is conducted for a certain class of portal frames, the results confirm the need for the incorporation of PEF into the process of analysis and design, and provide some quantitative measures on the level of associated effects.

• 한국통신학회논문지
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• 제37권2A호
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• pp.113-118
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• 2012

본 논문에서는 움직임 벡터의 상관도와 참조 화면의 거리를 이용한 H.264/AVC 움직임 탐색 지점 제거 방법을 제안한다. 결정된 탐색 영역을 이용하여 전 영역 탐색 방법에서 정화소 단위의 탐색 지점을 제거하고 향상된 예측 지역 탐색 방법에서는 불필요한 예측 움직임 벡터를 제거한다. 또한, 현재 화면에서 멀리 있는 참조 화면은 최적의 참조 화면으로 선택되는 빈도가 낮다는 특성을 이용하여 현재 화면과 참조 화면 사이의 거리를 이용한 가중평균을 적용하여 거리가 멀어질수록 전 영역 탐색 방법의 탐색 영역의 크기를 줄여 움직임 예측에 소요되는 시간을 줄인다. 향상된 예측 지역 탐색 방법의 경우, 멀리 있는 참조 화면에서 개선 과정을 적응적으로 생략하여 움직임 예측 시간을 줄인다. 제안한 방법을 통해 전 영역 탐색 방법은 평균 57.13%의 움직임 예측 시간이 감소되었고, 향상된 예측 지역 탐색 방법은 평균 14.71%의 움직임 예측 시간이 감소되었다.

• 한국운동역학회지
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• 제14권2호
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• pp.139-152
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• 2004

Two subjects, an expert and a novice, were carefully selected based upon their foot speed. Three dimensional videography was used in the assessment of roundhouse kicking of the Tae-kwon-Do. The local reference frames were imbedded at the trunk, pelvis, thigh and shank. Anatomical angular displacement at the joints were measured by projecting the upper segment's local axes to the lower segment's local reference planes. The local axes again projected to the global reference frames and absolved each segment's movement. The peaks of the anatomical angular displacement curve assessed as the countermovements and the angular movements of the segments in the global space absolved in light of the occurrence of the countermovements. The expert showed larger and more countermovements than the novice at the all segments. The counterrnovement occured more clearly at the trunk than the hip and knee joint and during the preparative movement phase. These countermovements occurrence were due to either by turning upper or lower segments and controlled by the turning direction and sequence of the two nearby segments. It was revealed that the countermovements of the trunk during the preparative movement phase was the important factor of the power kicking.

• IEIE Transactions on Smart Processing and Computing
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• 제2권5호
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• pp.255-265
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• 2013

3DTV is expected to be a promising next-generation broadcasting service. On the other hand, the visual discomfort/fatigue problems caused by viewing 3D videos have become an important issue. This paper proposes a perceptual quality assessment metric for a stereoscopic video (SV-PQAM). To model the SV-PQAM, this paper presents the following features: temporal variance, disparity variation in intra-frames, disparity variation in inter-frames and disparity distribution of frame boundary areas, which affect the human perception of depth and visual discomfort for stereoscopic views. The four features were combined into the SV-PQAM, which then becomes a no-reference stereoscopic video quality perception model, as an objective quality assessment metric. The proposed SV-PQAM does not require a depth map but instead uses the disparity information by a simple estimation. The model parameters were estimated based on linear regression from the mean score opinion values obtained from the subjective perception quality assessments. The experimental results showed that the proposed SV-PQAM exhibits high consistency with subjective perception quality assessment results in terms of the Pearson correlation coefficient value of 0.808, and the prediction performance exhibited good consistency with a zero outlier ratio value.

• 한국방송∙미디어공학회:학술대회논문집
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• 한국방송공학회 2009년도 IWAIT
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• pp.258-262
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• 2009

In this paper, we propose an effective memory reduction algorithm to reduce the amount of reference frame buffer and memory bandwidth in video encoder and decoder. In general video codecs, decoded previous frames should be stored and referred to reduce temporal redundancy. Recently, reference frames are recompressed for memory efficiency and bandwidth reduction between a main processor and external memory. However, these algorithms could hurt coding efficiency. Several algorithms have been proposed to reduce the amount of reference memory with minimum quality degradation. They still suffer from quality degradation with fixed-bit allocation. In this paper, we propose an adaptive block-based min-max quantization that considers local characteristics of image. In the proposed algorithm, basic process unit is $8{\times}8$ for memory alignment and apply an adaptive quantization to each $4{\times}4$ block for minimizing quality degradation. We found that the proposed algorithm could improve approximately 37.5% in coding efficiency, compared with an existing memory reduction algorithm, at the same memory reduction rate.