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Activity-Based Motion Estimation Scheme for H.264 Scalable Video Coding
Sangkwon Na,Chong-Min Kyung IEEE 2010 IEEE transactions on circuits and systems for vide Vol.20 No.11
<P>This paper proposes a motion estimation scheme to reduce the computational complexity of multilayer motion estimation for scalable video coding. Based on the result of the motion estimation of the lower resolution layer referred to as base layer, we developed a new approach for exploring the search range of the enhancement layer with high coding efficiency. This approach is based on the activity defined as the absolute difference between the motion vector predictor and the final motion vector. Based on the correlation of the activities between neighboring layers, an inter-layer activity model was developed using a curve-fitted linear equation to exploit the activity in the base layer for deciding the search center and the search range of the enhancement layer. Each activity pair in the neighboring layers is used to associate the relevant macroblock to one of two groups; boundary region and interior region. The base-layer motion vector predictor is basically selected over all the activity regions; for each activity region, the proposed motion estimation algorithm decides whether to include the median motion vector predictor or not. Minimal sufficient search range is also decided from the inter-layer activity prediction factor that is adjusted to the given sequence. The proposed scheme reduced the execution time of motion estimation by 99.26% at the cost of 1.56% bit-rate increase and 0.048 dB peak signal-to-noise ratio (PSNR) decrease on average compared with the conventional full-search algorithm. The fast full-search block matching algorithm can also be incorporated to obtain the extra CPU time reduction in the motion estimation process. By adopting the fast full-search block matching algorithm (FFSBMA) in JSVM reference software, the CPU time was reduced by up to 91.84% and the memory bandwidth was reduced by 90% at the sacrifice of 1.27% bit-rate increase and 0.041 dB PSNR decrease on average compared with the FFSBMA only.</P>
A Fast Rate Estimation For Rate-Distortion-Optimized H.264 Intra Encoder Design
Sangkwon Na(나상권),Jungho Do(도정호),Chong-Min Kyung(경종민) 대한전자공학회 2010 대한전자공학회 학술대회 Vol.2010 No.6
This paper presents a H.264/AVC intra encoder design with mode decision based on rate-distortion (R-D) optimization. Reducing the computational complexity of the R-D optimized mode decision is critical to successful application of H.264/AVC to real-time full high definition (HD) video applications. For that purpose we proposed a fast rate estimation, developed to quickly estimate the rate cost. To reduce the time for estimation of "rate", we proposed three simple, yet sufficiently accurate, models for three most time-consuming reference tables, i.e., coeff_token, total_zeros, and run_before tables, respectively. The rate estimation error obtained by the proposed simple model for the three tables were "zero" with about 80% probability. With fast rate estimation employed, we achieved R-D performance with only 0.001 dB increase of PSNR at 0.234% increase of the bit-rate. The total H.264 encoding with CAVLC using the proposed fast rate estimation scheme was reduced to 40% compared to that with actual CAVLC execution.
Low-Power Bus Architecture Compositionfor AMBA AXI
Sangkwon Na,Sung Yang,Chong-Min Kyung 대한전자공학회 2009 Journal of semiconductor technology and science Vol.9 No.2
A system-on-a-chip communication architecture has a significant impact on the performance and power consumption of modern multi-processors system-on-chips (MPSoCs). However, customization of such architecture for a specific application requires the exploration of a large design space. Thus, system designers need tools to rapidly explore and evaluate communication architectures. In this paper we present the method for application-specific low-power bus architecture synthesis at system-level. Our paper has two contributions. First, we build a bus power model of AMBA AXI bus communication architecture. Second, we incorporate this power model into a low-power architecture exploration algorithm that enables system designers to rapidly explore the target bus architecture. The proposed exploration algorithm reduces power consumption by 20.1% compared to a maximally connected reduced matrix, and the area is also reduced by 20.2% compared to the maximally connected reduced matrix.
김상권(Sangkwon Kim),박준용(Joonyong Park),김가민(Gamin Kim),김소영(Soyeong Kim),나유승(Yuseung Na),송하민(Hamin Song),조지은(Jieun Cho),손영록(Youngrok Son),석지원(Jiwon Seok),조기춘(Kichun Jo) 한국자동차공학회 2021 한국자동차공학회 부문종합 학술대회 Vol.2021 No.6
자율주행은 스스로 주행환경을 인지하고, 최적의 주행 경로를 결정하여 차량을 안전하게 제어하여 목적지까지 도달하는 기술이다. 자율주행을 위한 핵심 기술은 인지, 판단, 제어 세 가지로 분류할 수 있으며 기술의 고도화를 위해 운전자의 인지능력과 동등한 고수준 주행환경인지 능력은 필수적이다. 주야간, 날씨와 같은 다양한 환경 변화조건에서 일정 수준 이상의 인식성능이 유지되어야 하기 때문에 이를 위해 다양한 주행 데이터셋을 기반으로 학습한 인공지능기술이 주목받고 있다. 하지만, 인공지능 학습용 데이터를 구축하기 위해선 고가의 센서 및 수집장비를 요구하며, 수집한 원천 데이터를 학습용 데이터셋으로 변환하기 위해 데이터 분류 및 주석 작업 인력에 의존하기 때문에 대량의 데이터셋을 구축하는 것은 천문학적인 인력과 비용을 필요로 한다. 본 논문에서는 도심, 지하차도 및 터널 등 GNSS 수신 상태 음영 지역에서 위치 및 주변환경을 인지하기 위한 데이터셋, 주행 중 갑자기 마주할 수 있는 표면 이상과 장애물을 촬영한 데이터셋, 자율버스 개발을 위해 버스전용도로 구간을 포함한 주행도로를 촬영한 데이터셋의 구축방법을 다룬다. 각 데이터셋 마다 원천 데이터의 요구사항을 도출하고, 요구사항에 기반하여 선정한 카메라, 라이다, 고정밀 GNSS/INS, 저가형 GNSS 등 필요한 센서를 장착한 수집 장치를 구축한다. 그리고 이미지 데이터와 포인트 클라우드 정밀지도 등 학습에 활용할 수 있는 데이터에 대해 학습 분류체계를 구성하였고, 각 학습 데이터마다 YOLOv3, ConvPoint 등 연관된 AI 모델 적용을 통해 데이터 유효성 품질에 대해 평가하고 이를 이용한 서비스를 시연함으로써 활용 가능성에 대해 평가한다.
Dynamic Analysis of Three-Dimensional Drivetrain System of Wind Turbine
Shi, Wei,Park, Hyun-Chul,Na, Sangkwon,Song, Jinseop,Ma, Sangjin,Kim, Chang-Wan Korean Society for Precision Engineering 2014 International Journal of Precision Engineering and Vol.15 No.7
In our previous study, a torsional model was used to perform a dynamic analysis of a wind turbine drivetrain. However, detailed characteristics could not be obtained with this torsional model. In this paper, the mathematical model of the wind turbine drivetrain is extended to a three-dimensional dynamic model. A typical arrangement with one low-speed planetary gear stage and two high-speed spur gear stages is used in this work. The governing equation of the drivetrain is derived by using Lagrange's equation. Lagrange's equation takes into account the kinetic energy of each component and potential energies from the shaft, bearing, and gear mesh. The governing equation is solved numerically using direct numerical integration. A dynamic analysis is carried out to investigate the transient response of the drivetrain system.
소형가스터빈용 인젝터의 분무 특성에 따른 반응 유동장 전산 해석
김세환(Seihwan Kim),정인석(In-Seuck Jeung),박희호(Hee-Ho Park),나상권(Sangkwon Na) 한국추진공학회 2010 한국추진공학회 학술대회논문집 Vol.2010 No.5
항공용 저출력 소형 가스터빈 엔진에 적용을 위한 연료 분사기의 분무 특성에 따른 반응 유동장에 대한 수치해석을 수행하였다. 인젝터의 개발에 있어 연료의 분무 상태가 엔진 성능에 큰 영향을 미치므로 다양한 변수에 대한 고려가 요구되고 있다. 본 연구에서는 정지 상태의 유동장에 분사기를 위치시키고 액적의 평균 직경, 분사 압력, 분사각을 변경하며 그에 따른 반응 특성을 살펴보았다. 해석 결과 분사압과 분사 각도가 클수록, 액적의 직경이 작을수록 활발한 반응이 일어나지만 분사압이 큰 경우 영역내에서 기화되는 연료량이 감소함을 확인할 수 있었다. This work shows the result of numerical simulation on a reacting flow by varying atomization properties which can be obtained from a injector for a small and low power aircraft gas turbine engine. Because the atomization properties mainly affect on the performance of the engine, a lot of efficiency tests are needed when a new injector is developed. Nowadays researches has been actively performed using computational analysis. Using commercial package CFD-ACE+, basic studies on the reacting flow field have been conducted. Those results show that the reaction rate is increased when higher pressure and wider angle spray condition are used. More smaller parcels can also enhance the fuel-air reaction.
Blends of Nylon 6/Wastc PET with Compatibilizer
Jun,Yoon,Kim, Junggyu,Hong, Wanhae,Jun, Hong,Na, Sangkwon,Song, Yonho CHOSUN UNIVERSITY 1997 Basic Science and Engineering Vol.1 No.2
Nylon 6 was blended up to 30% content of waste PET by using 5phr compatibilizers(EAA,SEBS) for packaging film. The mechanical properties of blends showed a decrease in tensile strength and % elongation with increasing PET content. The use of compatibilizers appears to enhance the tensile strength quite appreciably. One component of blend acted as a nucleating agent to the other at a certain composition. The water vapour permeability was drastically reduced without seriously affecting the oxygen permeability.