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孔隙介质中快纵波的衰减特性和动力协调现象 被引量:10
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作者 胡恒山 王克协 刘家琦 《计算物理》 CSCD 北大核心 2002年第3期203-207,共5页
依据Biot理论并采用前人的骨架模量 孔隙度关系 ,计算了弹性波在孔隙介质中的衰减曲线 ,发现快纵波存在零衰减点 .为解释这种现象 ,分析了孔隙流体相对于骨架运动的特点 .结果表明 ,存在快纵波动力协调介质 ,快纵波在这种介质中传播时 ... 依据Biot理论并采用前人的骨架模量 孔隙度关系 ,计算了弹性波在孔隙介质中的衰减曲线 ,发现快纵波存在零衰减点 .为解释这种现象 ,分析了孔隙流体相对于骨架运动的特点 .结果表明 ,存在快纵波动力协调介质 ,快纵波在这种介质中传播时 ,流体和骨架之间无宏观相对位移 ,因此无论频率多高 ,流体粘滞系数多大 ,快纵波都不衰减 .一个引申的结论是 ,在动力协调的渗透性孔隙介质中 ,即使存在双电层 ,快纵波也不产生流动电势 . 展开更多
关键词 孔隙介质 衰减特性 BIOT理论 快纵波 动力协调 衰减系数 流动电势 声波 地下油气控测
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Real-time traffic information extraction based on compressed video with interframe motion vector
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作者 黄庆明 王聪 《Journal of Harbin Institute of Technology(New Series)》 EI CAS 2003年第3期284-289,共6页
Extraction of traffic information from image or video sequence is a hot research topic in intelligenttransportation system and computer vision. A real-time traffic information extraction method based on com-pressed vi... Extraction of traffic information from image or video sequence is a hot research topic in intelligenttransportation system and computer vision. A real-time traffic information extraction method based on com-pressed video with interframe motion vectors for speed, density and flow detection, has been proposed for ex-traction of traffic information under fixed camera setting and well-defined environment. The motion vectors arefirst separated from the compressed video streams, and then filtered to eliminate incorrect and noisy vectors u-sing the well-defined environmental knowledge. By applying the projective transform and using the filtered mo-tion vectors, speed can be calculated from motion vector statistics, density can be estimated using the motionvector occupancy, and flow can be detected using the combination of speed and density. The embodiment of aprototype system for sky camera traffic monitoring using the MPEG video has been implemented, and experi-mental results proved the effectiveness of the method proposed. 展开更多
关键词 extraction of traffic information Interframe motion vector compressed video stream
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