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用剪切波速估算土的原位干密度 被引量:3
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作者 仲济刚 魏迎奇 胡云进 《大坝观测与土工测试》 2000年第3期48-50,共3页
试验研究了剪切波速与上覆压力和团结比的关系,提出了一个由实际测定的剪切波速估算试验控制密度的方法,通过实际计算验证该法的可行性。
关键词 无粘性土 剪切波带 干密度 上覆压力
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基于三维带限剪切波变换的磁共振图像融合 被引量:3
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作者 段昶 汪学刚 +1 位作者 王洪 王帅 《生物医学工程学杂志》 EI CAS CSCD 北大核心 2015年第1期181-186,196,共7页
越来越多的医疗设备能采集人体不同特征数据并形成三维图像。在临床应用中,通常需要将多幅含有不同重要信息的源图像融合到一幅图像中以辅助治疗。而传统的图像融合方法主要针对二维图像,这些方法直接应用于三维数据会导致第三维信息的... 越来越多的医疗设备能采集人体不同特征数据并形成三维图像。在临床应用中,通常需要将多幅含有不同重要信息的源图像融合到一幅图像中以辅助治疗。而传统的图像融合方法主要针对二维图像,这些方法直接应用于三维数据会导致第三维信息的损失。本文结合近期出现的超小波变换——三维带限剪切波变换和四组传统融合准则,提出新的三维磁共振图像融合方法。最后通过四组人脑T2*和磁量图(QSM)源数据,将本文的方法分别与基于二维和三维的小波、双树复数小波的融合方法进行对比。实验显示基于三维变换的融合方法性能普遍优于基于二维变换的方法;三维方法中,剪切波克服了传统小波变换缺乏表达方向的缺陷,能有效地提高传统图像融合算法的性能,因此,本文的方法质量指标最高。 展开更多
关键词 磁共振图像融合 三维剪切变换 剪切变换 磁量图
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Measurement of the Variation of Shear Velocity on Bed during a Wave Cycle
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作者 Nelly Oldekop Toomas Liiv 《Journal of Earth Science and Engineering》 2013年第5期322-330,共9页
Almost all works in the field of boundary layer flow under the breaking wave consider the flow similar as the flow in an oscillating pressure tube. Although the two flows are similar, there are many differences. The r... Almost all works in the field of boundary layer flow under the breaking wave consider the flow similar as the flow in an oscillating pressure tube. Although the two flows are similar, there are many differences. The results achieved in such manner are therefore also only similar to the results that can be achieved during measurements in the surf zone. Present article deals with boundary layer measurements on an inclined bottom under breaking waves. The measurements over the whole wave cycle were carried out, and the shear velocity under the breaking wave was calculated based on the measurements. It was found that there is a considerable space and time variation of the term in the surf zone. The turbulence generated during the wave breaking changes the shape of the shear velocity profile in comparison to the profile measured before breaking. As the values of shear velocity are directly correlated with the description of the whole velocity field in the wave, it can be assumed that the enhanced description of the shear velocity results in better understanding of the whole velocity field under breaking waves. Therefore, the article brings a new insight into the field and aims to make a discussion about the need to rethink the way of describing the boundary layer flow in the surf zone. 展开更多
关键词 Breaking wave surf zone TURBULENCE shear velocity velocity distribution.
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