From the figure 6 (b) it is evident that there is some energy concentration in the S0 mode at a frequency of 410 kHz the

group velocity was cantered at 2.775 m/ms, while the highest energy concentration is in the A0 mode at a frequency of 150 kHz, but the

group velocity was found to be 1.871 m/ms which is far less when compared to 2.775 m/ms, therefore this should be an A0 mode.

Knowing the

group velocity of the modes [A.sub.0] and [S.sub.0]: Vg ([A.sub.0],300kHz)=1268 m/s, Vg ([S.sub.0],300kHz)=5649 m/s, we can calculate the delamination position from the sensor A noted [P.sub.D] by [DELTA][t.sub.1] (Delta 1) and delamination length noted [L.sub.D] by [DELTA][t.sub.2] (Delta 2) as presented in Table 2.

where [L.sub.max] and [L.sub.min] are the maximum and minimum grid size, respectively; [[lambda].sub.min] is the minimum wavelength; [n.sub.min] is the minimum number of elements within one wavelength (usually [n.sub.min] is in the range of 8~10); [c.sub.s] denotes the velocity of shear waves; and [c.sub.min] is the minimum

group velocity of elastic waves.

The results of the joint inversion of the Z and R

group velocity spectra and the RPM frequency curve are presented in Figures 10 and 11.

The

group velocity vg of the wave packet associated with the electron of rest mass [m.sub.0], coincides with its velocity v.

[v.sub.ph] is the phase velocity, and vg is the

group velocity. [r.sub.c] is the optimum radius of the integral surface in the process of U scattering [58].

In the case of first derivatives we consider the dispersion error, the error in phase velocity, and the error in

group velocity as objective functions.

The cause of this result is that the frequency of DW is determined by the phase-matched condition associated with the nature

group velocity, but SS increases the

group velocity at resonant frequency eventually because it affects the

group velocity in an intensity dependent fashion [30].

The saddle point method is used to determine the solution with zero

group velocity. In general, there are two distinct spatial branches of solutions of (4) on the complex k* plane.

In this paper, tapered core is used instead of cylindrical core so as to make the light travel with the lesser

group velocity and also to stop the light at the fixed position efficiently.

The Rayleigh-wave

group velocity for the trace of each event registered has been measured by means of the combination of digital filtering techniques: Multiple Filter Technique (Dziewonski et al., 1969) and Time Variable Filtering (Cara, 1973), as shown in the flow chart displayed in Figure 2.

The results focused on waveforms, fast Fourier transforms (FFT), and frequency/time analysis (with superimposed

group velocity curves) of the signals.