@@ -14,7 +14,7 @@ Most experiments study a model 2 dimensional (2D) granular system composed of ci
* Finally a circular Hough transform is applied to the gray scale image in Fig.~\ref{fig-diskpos}(b) to find centers and diameters of the discs \cite{peng07jcise}. The transform is an algorithm computing the curvature at each pixel point based on the image gray scale gradient. The curvature will automatically give the center and radius. Then a voting process rules out fake circles and combines circles with close enough centers and similar radii. The final result of particle identification is shown in Fig.~\ref{fig-diskpos}(c), where blue circles indicate particle centers and radii given by the algorithm with errors smaller than $0.02$ times the particle diameter.
The procedure described above with results at each step is illustrated in the figure below.
