A sparse digital signal model for ultrasonic nondestructive evaluation of layered materials

Signal modeling has been proven to be an useful tool to characterize damaged materials under ultrasonic nondestructive evaluation (NDE). In this paper, we introduce a novel digital signal model for ultrasonic NDE of multilayered materials. This model borrows concepts from lattice filter theory, and bridges them to the physics involved in the wave-material interactions. In particular, the proposed theoretical framework shows that any multilayered material can be characterized by a transfer function with sparse coefficients. The filter coefficients are linked to the physical properties of the material and are analytically obtained from them, whereas a sparse distribution naturally arises and does not rely on heuristic approaches. The developed model is first validated with experimental measurements obtained from multilayered media consisting of homogeneous solids. Then, the sparse structure of the obtained digital filter is exploited through a model-based inverse problem for damage identification in a carbon fiber-reinforced polymer (CFRP) plate.

[Oblique orientation of the accessory pathway demonstrated by radiofrequency application]

Activation mapping of atrial and ventricular insertion has suggested an oblique orientation of some accessory pathways. However, this aspect has not been demonstrated by radiofrequency application. This report presents two patients with Wolff-Parkinson-White syndrome and an accessory pathway with bidirectional conduction and oblique orientation. The accessory pathway oblique orientation was demonstrated by transient and permanent conduction abolition following radiofrequency application in two separate ventricular and atrial sites. These findings may explain the failure to ablate accessory pathway by radiofrequency application in the ventricular side of the mitral annulus guided by retrograde atrial activation occasionally observed in patients with a concealed accessory pathway.