Figure 1
From: Homogeneous material based acoustic concentrators and rotators with linear coordinate transformation
Schematic diagram of coordinate transformation for the case of square acoustic concentrator. A big square \({\text{ABCD}}\) wraps a small square \({\text{A}}_{1} {\text{B}}_{1} {\text{C}}_{1} {\text{D}}_{1}\). The annular area around the small square is split into segment I and segment II. The external diameter of big square is \(L\). (a) Virtual space. The size of internal square is \(L_{0}\). (b) Physical space. The size of internal square is \(L_{1}\). With the shrinkage of inner small square, segment I and segment II should be transformed accordingly.
