• ETRI Journal
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• 제28권6호
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• pp.697-708
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• 2006

Various adaptive mesh refinement techniques are often employed in numerical simulations for increasing spatial and temporal resolution beyond the limits imposed by available CPU time and memory space. Recently, an octree-based adaptive mesh structure was successfully used in fluid animation to place more grid cells efficiently in visually interesting regions of fluids. In an attempt to optimize the use of computational resources further in fluid animation, this paper extends this adaptive technique by modifying the mesh refinement scheme so that the camera's viewing properties are dynamically exploited during the simulation. Based on a simple adaptive mesh structure, we show that the new meshing strategy can save a substantial amount of computation time and memory space by using a view-dependent adaptive approach. The experimental results reveal that the proposed technique provides a good compromise between the computational effort and the simulation's fidelity, and may be used quite effectively in 3D animation production.

• 한국시뮬레이션학회논문지
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• 제10권3호
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• pp.95-103
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• 2001

Rendering of 3D terrain data in real-time is difficult because of its large scale. So, it is necessary to use level-of-detail(LOD) that uses fewer data, but makes almost similar image to the original. We present an algorithm for real-time LOD generation and rendering of 3D terrain data. The algorithm applies wavelet transform to the terrain data, and then generates quadtree based view-dependent LOD using wavelet coefficients that are the output of wavelet transform. It also uses frame-to-frame coherence and view culling for high frame rates.

• 방송공학회논문지
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• 제21권2호
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• pp.237-251
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• 2016

본 논문에서는 High Efficiency Video Coding(HEVC)을 기반으로 구현된 3D 스케일러블 코덱에서 부호화 효율을 향상시킬 수 있는 기술을 제안한다. 기존의 3D-HEVC에서는 dependent view를 부호화 할 때, 자신의 깊이 영상이 존재하지 않아 이웃 view의 base view의 깊이 영상을 이용하여 텍스처를 부호화한다. 하지만 스케일러블 부호화를 지원하는 형태의 3D-HEVC에서는 자신의 하위 spatial layer의 깊이영상을 이용하여 부호화 할 수 있다. 본 논문에서는 3D 스케일러블 코덱에서 텍스처 정보를 부호화하기 위한 향상된 깊이영상 예측방법을 제안한다. 저자들이 구현한 3D 스케일러블 코덱을 이용하여 제안한 알고리즘으로 실험을 한 결과, 제안하는 알고리즘이 기존 기술 대비 효율적인 것을 확인 할 수 있었다.

• 천문학회보
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• 제37권2호
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• pp.211.1-211.1
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• 2012

The on-orbit test simulation for predicting the instrument directional responsivity was conducted by the Monte Carlo based integrated ray tracing (IRT) computation technique and analytic flux-to-signal conversion algorithms. For the on-orbit test simulation, the Sun model consists of the Lambertian scattering sphere and emitting spheroid rays, the Amon-Ra instrument is a two-channel including a broadband scanning radiometer (energy channel) and an imager with ${\pm}2^{\circ}$ FOV (visible channel). The solar radiation produced by the Sun model is directed to the instrument viewing port and traced through the dual channel optical train. The instrument model is rotated on its rotation axis and this gives a slow scan of the Sun model over the full field of view. The direction of the incident lights are fed with scanned images obtained from the visible channel instrument. The instrument responsivity was computed by the ratio of the incident radiation input to the instrument output. In the radiometric simulation, especially, measured BRDF of the 3D CPC was used for scattering effects on radiometry. With diamond turned 3D CPC inner surface, the anisotropic surface scattering model from the measured data was applied to ray tracing computation. The technical details of the on-orbit test simulation are presented together with field-of-view calibration plan.

• 방송공학회논문지
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• 제22권2호
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• pp.240-252
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• 2017

기존의 High Efficiency Video Coding(HEVC)기반의 다시점 비디오 부호화 기법은 종속 시점의 픽쳐를 부호화 할 때, disparity compensation prediction(DCP)을 위해 추가적인 참조 영상을 사용하기 때문에 높은 부호화 복잡도를 가지고 있다. 본 논문에서는 MV-HEVC에서 변위 움직임 벡터 탐색 복잡도를 줄이기 위한 빠른 변위 움직임 벡터 탐색 방법을 제안한다. 제안하는 방법은 어파인 변환을 이용한 초기 탐색 지점 결정 방법과 적응적인 탐색 영역 크기 결정 방법을 포함한다. 실험 결과는 제안하는 방법이 부호화 효율의 저하가 거의 없이 변위 움직임 탐색 복잡도를 90.78%까지 줄일 수 있는 것을 보여준다. 또한, 실험 결과는 제안하는 방법이 다른 복잡도 감소 기술들 보다 효과적으로 복잡도를 줄이는 것을 보여준다.

• 한국경영과학회:학술대회논문집
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• 한국경영과학회 2005년도 추계학술대회 및 정기총회
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• pp.189-206
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• 2005

Much of work on network externality assumed network effects are dependent on the network size. Therefore, very little consideration is given to the view that marginal benefits from joining the network may not increase with the network size if consumer benefits come from the direct interaction with neighbors, namely local network. In this study, we used the agent-based simulation method to reexamine the effectiveness of the traditional network market strategy under the presence of the local network where two incompatible technologies compete. We found that the strategy of growing an initial customer base is not effective under the presence of the local network. Our study also showed that targeting customers based on their technology Preference is not as effective as targeting customers within the same local network. As a result, the focus of a network market strategy should be directed to taking advantage of the customer network.

• 한국재료학회지
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• 제22권9호
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• pp.450-453
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• 2012

In crystalline solar cells, the substrate itself constitutes a large portion of the fabrication cost as it is derived from semiconductor ingots grown in costly high temperature processes. Thinner wafer substrates allow some cost saving as more wafers can be sliced from a given ingot, although technological limitations in slicing or sawing of wafers off an ingot, as well as the physical strength of the sliced wafers, put a lower limit on the substrate thickness. Complementary to these economical and techno-physical points of view, a device operation point of view of the substrate thickness would be useful. With this in mind, BC-BJ Si and GaAs solar cells are compared one to one by means of the Medici device simulation, with a particular emphasis on the substrate thickness. Under ideal conditions of 0.6 ${\mu}m$ photons entering the 10 ${\mu}m$-wide BC-BJ solar cells at the normal incident angle (${\theta}=90^{\circ}$), GaAs is about 2.3 times more efficient than Si in terms of peak cell power output: 42.3 $mW{\cdot}cm^{-2}$ vs. 18.2 $mW{\cdot}cm^{-2}$. This strong performance of GaAs, though only under ideal conditions, gives a strong indication that this material could stand competitively against Si, despite its known high material and process costs. Within the limitation of the minority carrier recombination lifetime value of $5{\times}10^{-5}$ sec used in the device simulation, the solar cell power is known to be only weakly dependent on the substrate thickness, particularly under about 100 ${\mu}m$, for both Si and GaAs. Though the optimum substrate thickness is about 100 ${\mu}m$ or less, the reduction in the power output is less than 10% from the peak values even when the substrate thickness is increased to 190 ${\mu}m$. Thus, for crystalline Si and GaAs with a relatively long recombination lifetime, extra efforts to be spent on thinning the substrate should be weighed against the expected actual gain in the solar cell output power.

• 한국소성가공학회:학술대회논문집
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• 한국소성가공학회 2008년도 춘계학술대회 논문집
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• pp.220-223
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• 2008

Large curved plate blocks are widely used to construct hull structure in shipbuilding industry. Most curved plates are manufactured by using manual method called as line heating that use deformation caused by residual stress after local heating along a line which is perpendicular to the curvature direction. However, its working environment is poor and its formability is totally dependent on an experienced technician. In view of that, multi-point dieless forming (MDF) technology that use reconfigurable punch arrays instead of one piece die is proposed in this study. The MDF process is based on a concept of equivalent die surface made by numbers of punches which has round tip at the end of it. In this study, numerical simulation for common curvature type such as saddle shape was carried out. In addition, experiments in the plate forming process were also conducted to compare with the numerical results in view of final configuration. Consequently, it was noted that the proposed dieless forming method has considerable feasibility to substitute the new process for conventional manual method.

• 한국콘텐츠학회:학술대회논문집
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• 한국콘텐츠학회 2006년도 춘계 종합학술대회 논문집
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• pp.132-135
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• 2006

최근 실내외에서 사용될 수 있는 무선 네트워크 기술의 발전에 따라 모바일 단말을 이용한 멀티미디어 데이터 서비스가 점차 증가하는 추세이다. 무선 네트워크는 채널을 공유하며 전송 매체의 특성으로 인해 높은 에러율을 가진다. 따라서 다양한 환경에서 QoS(Quality of Service)를 제공하는데 많은 문제점을 가지고 있다. 본 논문은 전송 마감시한을 고려하여 서비스율을 보상하는 CSD-WRR(Channel State Dependent-WRR) 기법을 제안한다. 시뮬레이션 결과는 제안한 기법이 기존의 WRR에 비하여 마감시한 실패율과 공평성에서 우수한 성능을 보였다.

• Journal of Electrical Engineering and Technology
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• 제1권4호
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• pp.427-434
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• 2006

This paper analyzes arc phenomena including the secondary arc's elongation in the Korean 765kV single transmission line (79km) between Sin-Ansung S/S and Sin-Gapyeong S/S, which will be installed in Korea in June 2006. In particular, both frequency independent and frequency dependent line models are compared to make our final decisions. As well, the significant simulation results are investigated by the EMTP program. As a result, there is no need of HSGS in the Korean 765kV single transmission line from both a practical and an economical point of view.