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Articles by Chunyan Li
Total Records ( 2 ) for Chunyan Li
  Yan Liang , Bin Fang , Jiye Qian , Lin Chen , Chunyan Li and Ying Liu
 

The identification of non-cell objects in biological images is not a trivial task largely due to the difficulty in describing their characteristics in recognition systems. In order to better reduce the false positive rate caused by the presence of non-cell particles, we propose a novel approach using a local jet context features scheme combined with a two-tier object classification system. The newly proposed feature scheme, namely local jet context feature, integrates part of global features with the “local jet” features. The scheme aims to effectively describe the particle characteristics that are invariant to shift and rotation, and hence help to retain the critical shape information. The proposed two-tier particle classification strategy consists of a pre-recognition stage first and later a further filtering phase. Using the local jet context features coupled with a multi-class SVM classifier, the pre-recognition stage intends to assign the particles to their corresponding classes as many as possible. To further reduce the false positive particles, next a decision tree classifier based on shape-centered features is applied. Our experimental study shows that through the proposed two-tier classification strategy, we are able to achieve 85% of identification accuracy and 80% of F1 value in urinary particle recognition. The experiment results demonstrate that the proposed local jet context features are capable to discriminate particles in terms of shape and texture characteristics. Overall, the two-tier classification stage is found to be effective in reducing the false positive rate caused by non-cell particles.

  Chunyan Li and Eddie Weeks
  An unmanned automated boat equipped with an acoustic Doppler current profiler was used in field surveys at a tidal inlet, the Southwest Pass of Vermillion Bay, Louisiana on Sept 6 and Oct 6, 2007. During the first survey, under calm weather conditions, a small scale eddy with a diameter of 300 m was discovered with strong upwelling and downwelling zones. A detailed analysis of this small eddy shows that the eddy’s velocity field is relatively uniform in the vertical and the eddy is formed by a flow convergence, tidal velocity shear induced relative vorticity, and the interaction between the horizontal flows and bathymetry. The major upwelling area is where an uphill flow occurs while the major downwelling area is where a downhill flow occurs. The vorticity of this eddy is on the order of 0.013 s– 1, which is two orders-of-magnitude larger than the planetary vorticity, and one-order-of magnitude larger than that in a typical tidal inlet without eddies. The Coriolis effect is thus insignificant and the generation of the eddy cannot be affected by the earth rotation. The maximum upwelling and downwelling velocities exceed 0.3 m/s. This high vertical velocity in a tidal inlet does not appear to have been reported before. The second survey, conducted under a thunder storm condition, did not reveal a similar eddy at the same location during roughly the same tidal phase. Though the measurements of 3-D flow structure under a thunder storm condition in a tidal channel does not appear to have been reported before, the second survey is of important value in providing support of the mechanism of the eddy formation during the first survey: the wind tends to produce downwind flow in shallow water than in deep water, producing a velocity shear counterproductive to the formation of the eddy. Therefore, the second survey under a thunder storm condition did not show an eddy. A scaling analysis of the non-hydrostatic flow shows that the uphill and downhill flows introduce a non-hydrostatic flow component proportional to the square of the bottom slope which leads to the conclusion that the non-hydrostatic flow component affects less than 10% of the vertical momentum balance.
 
 
 
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