Fig. 1.

Illustration of the estimation of the damping capacity (a) with the nonlinear method on a clockwise pressure-luminal cross-sectional area (P-LCSA) loop obtained from a carotid artery at 10 Hz, and (b) with the linear method on an elliptical P-LCSA loop. Points A and B are the points corresponding to the maximum and minimum LCSA in the hysteresis loop, respectively. Point C is the point with the maximum LCSA value and the pressure value at point A. Here, W_D is the loop area and W_S is the area under the loading (upper) curve $\overrightarrow{AB}$ and above the straight line AC. Loading curves are indicated by the arrow. Note that the hysteresis loop in (a) shows a weak nonlinearity in that the loop deviates slightly from an elliptical shape.