Tidal current asymmetry due to existence of shallow water constituent current is studied. It is found that there is a relationship between the asymmetry and the reversion of tidal current rotating.The influence functi...Tidal current asymmetry due to existence of shallow water constituent current is studied. It is found that there is a relationship between the asymmetry and the reversion of tidal current rotating.The influence function for determining when the reversion occurs can be used for finding characteristics of tidal current asymmetry.For a shallow water area where semidiurnal current dominates, the current characteristic at extremum moment ~↑t of the influence function is discovered:if both M2 and M4 constituent currents are in the same direction at the moment ~↑t, then at t=~↑t+TM2/2 their directions are opposite. It is convenient to discuss the asymmetry by the use of a parameter α which is defined as a ratio:-WM4 (~↑t)/WM2 (~↑t).In most cases,if α is larger than zero，the reversion of tidal current rotating will be occurring about the moment ~↑t, and current magnitude be adifference of Mz and M4 current magnitudes at ~↑t. If α is smaller than zero,the reversion will not happen,and current magnitude is a sum of both constituent current magnitudes at ~↑t. For the case that|α| is larger than 1,the current directions at ~↑t and ~↑t +TM2/2 are the same, as to |α| which is smaller than 1,two directions at two moments are opposite. Especially when ~↑t happens to be close to moments of both M2 and M4 current maximums, influence of the asymmetry will be significant, the larger theM4 current maximum, the more asymmetric the current.The influence of the asymmetry on sand movement is also dealt with,such an asymmetry will lead to the transportation of sand towards certain direction.展开更多
采用广义梯度矢量流(G enera lized grad ien t vector flow,GGVF)作为势能函数的Snake算法在处理灰度图像分割时具有较好的性能。但当处理彩色图像时,GGVF模型往往将彩色图像转化为灰度图像进行处理,此过程造成颜色信息丢失,因而容易...采用广义梯度矢量流(G enera lized grad ien t vector flow,GGVF)作为势能函数的Snake算法在处理灰度图像分割时具有较好的性能。但当处理彩色图像时,GGVF模型往往将彩色图像转化为灰度图像进行处理,此过程造成颜色信息丢失,因而容易受到阴影等伪边界灰度变化的干扰。本文提出了基于HSV颜色模型的GGVF,充分利用了图像的色彩信息进行图像分割。实验结果表明,该方法能够有效地区分彩色图像的真实边界与由阴影产生的伪边界,并取得较好的分割结果。展开更多
文摘Tidal current asymmetry due to existence of shallow water constituent current is studied. It is found that there is a relationship between the asymmetry and the reversion of tidal current rotating.The influence function for determining when the reversion occurs can be used for finding characteristics of tidal current asymmetry.For a shallow water area where semidiurnal current dominates, the current characteristic at extremum moment ~↑t of the influence function is discovered:if both M2 and M4 constituent currents are in the same direction at the moment ~↑t, then at t=~↑t+TM2/2 their directions are opposite. It is convenient to discuss the asymmetry by the use of a parameter α which is defined as a ratio:-WM4 (~↑t)/WM2 (~↑t).In most cases,if α is larger than zero，the reversion of tidal current rotating will be occurring about the moment ~↑t, and current magnitude be adifference of Mz and M4 current magnitudes at ~↑t. If α is smaller than zero,the reversion will not happen,and current magnitude is a sum of both constituent current magnitudes at ~↑t. For the case that|α| is larger than 1,the current directions at ~↑t and ~↑t +TM2/2 are the same, as to |α| which is smaller than 1,two directions at two moments are opposite. Especially when ~↑t happens to be close to moments of both M2 and M4 current maximums, influence of the asymmetry will be significant, the larger theM4 current maximum, the more asymmetric the current.The influence of the asymmetry on sand movement is also dealt with,such an asymmetry will lead to the transportation of sand towards certain direction.
文摘采用广义梯度矢量流(G enera lized grad ien t vector flow,GGVF)作为势能函数的Snake算法在处理灰度图像分割时具有较好的性能。但当处理彩色图像时,GGVF模型往往将彩色图像转化为灰度图像进行处理,此过程造成颜色信息丢失,因而容易受到阴影等伪边界灰度变化的干扰。本文提出了基于HSV颜色模型的GGVF,充分利用了图像的色彩信息进行图像分割。实验结果表明,该方法能够有效地区分彩色图像的真实边界与由阴影产生的伪边界,并取得较好的分割结果。
