A high performance license plate recognition system (LPRS) is proposed in this work. The proposed LPRS is composed of the following three main stages: (i) plate region determination, (ii) character segmentation, and (iii) character recognition. During the plate region determination stage, the image is enhanced by image processing algorithms to increase system performance. The rectangular license plate region is obtained using edge‐based image processing methods on the binarized image. With the help of skew correction, the plate region is prepared for the character segmentation stage. Characters are separated from each other using vertical projections on the plate region. Segmented characters are prepared for the character recognition stage by a thinning process. At the character recognition stage, a three‐layer feedforward artificial neural network using a backpropagation learning algorithm is constructed and the characters are determined.
The separation of the laminar boundary layer from a convex corner on a rigid body
contour in transonic flow is studied based on the asymptotic analysis of the Navier–Stokes
equations at large values of the Reynolds number. It is shown that the flow
in a small vicinity of the separation point is governed, as usual, by strong interaction
between the boundary layer and the inviscid part of the flow. Outside the interaction
region the Kármán–Guderley equation describing transonic inviscid flow admits a
self-similar solution with the pressure on the body surface being proportional to
the cubic root of the distance from the separation point. Analysis of the boundary
layer driven by this pressure shows that as the interaction region is approached the
boundary layer splits into two parts: the near-wall viscous sublayer and the main
body of the boundary layer where the flow is locally inviscid. It is interesting that
contrary to what happens in subsonic and supersonic flows, the displacement effect
of the boundary layer is primarily due to the inviscid part. The contribution of the
viscous sublayer proves to be negligible to the leading order. Consequently, the flow in
the interaction region is governed by the inviscid–inviscid interaction. To describe this
flow one needs to solve the Kármán–Guderley equation for the potential flow region
outside the boundary layer; the solution in the main part of the boundary layer was
found in an analytical form, thanks to which the interaction between the boundary
layer and external flow can be expressed via the corresponding boundary condition for
the Kármán–Guderley equation. Formulation of the interaction problem involves one
similarity parameter which in essence is the Kármán–Guderley parameter suitably
modified for the flow at hand. The solution of the interaction problem has been
constructed numerically.
The incipient separation from a corner in steady two-dimensional transonic flow is studied based on viscous–inviscid interaction at high Reynolds number. Of particular interest is the investigation of the dependence of the critical deflection angle (when a well-attached flow turns into a separated flow) on the Kármán–Guderley parameter which characterizes the local flow field. In accordance with the procedure adopted, the analysis of the flow starts with the analysis of the boundary layer and then the solution of the Kármán–Guderley equation describing the inviscid part of the flow near the corner point is investigated. The analysis of the inviscid transonic flow is performed based on the hodograph method and new solutions are obtained corresponding to the present flow topologies. In these solutions, the transonic flow appears to be subsonic everywhere except at the sonic corner point. Then, the interaction problem is formulated using the triple-deck model. Lastly, a procedure based on a semi-direct solution of the governing equations using Newton iterations is developed to obtain the numerical solution of the interaction problem.
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