If no LVZ is detected in the model, any extrema of the dispersion curve is rejected and computation is restarted. On the other hand, if a LVZ takes place in the model (figure 3.7),
the dispersion curve may show one or more extrema. The validity of the preceding sample is checked by searching a hypothetical additional mode at a lower velocity (in the reverse direction of the initial search with the same step). If any additional mode is found, it proves that mode jumping occurred and computation is restarted. For those models with LVZ, the computation of dispersion curves may fail for all step sizes, even if the number of admitted restarts were infinite. Hence, some LVZs are tolerated in this implementation but not all of them. For some of them, the correct determination of the modal curve may require a denser frequency sampling (user input). In this latter case, a more refined technique should try to calculate the root at an intermediate frequency.
