Figure 14

Topological derivatives shown in Figure 13 plotted as surfaces. Left: topological derivative corresponding to six linearly spaced frequencies between 0.2 and 2 Hz and a 2-by-2 grid of lamps. Right: counterpart when a 3-by-3 grid of lamps is used. True defects appear as coherent mountain-like structures opposite to the random peaks of the spurious minima