Information Technology Reference
In-Depth Information
(a)
(b)
2
2
4
4
6
6
8
8
10
10
12
12
0
1
2
3
4
5
6
7
8
9
0
0.5
1
1.5
2
2.5
3
3.5
4
4.5
5
x 10
-4
x 10
-4
Time (us)
Time (us)
Fig. 6.9 Recorded signals and recovered sources (the supposed ''interference'' is highlighted)
a Recorded signals b Recovered sources
the recovered sources by ICA; the sample numbers processed were from 600 to
6000.
Figures
6.10
a and b show two B-Scans obtained from the mixture matrix
x
¼
P
12
x
¼
P
12
corresponding
to
a
i
;
s
i
;
s
i
¼
0
ð
i
6¼
2
Þ
and
a
i
;
s
i
;
s
i
¼
0
ð
i
¼
2
Þ
,
i
¼
1
i
¼
1
respectively. The first B-Scan represents the sinusoidal phenomenon depicting the
non-consolidated zone. Thus, this phenomenon can be associated with the shape of
the material in the non-consolidated zone. The second B-Scan is the information
related to the consolidated zone. The diagrams obtained from the ICA information
depict the two different zones of the material more precisely than the B-Scan
obtained by non-stationary analysis.
6.2.4 Thickness Material Layer Profile
Figures
6.11
a and b show the recorded signals plus 1 MHz artificial
interference added and the corresponding B-Scan calculated by the evolution of
the centroid frequency [
33
]. The following information is represented in the dia-
gram: (i) the x axis, which is the transducer position from position 0 to 10; (ii) the
y axis, which is the depth axis; and (iii) the z axis, which is depicted by colours
that denote the parameter level at a given position in a given depth.
The depth is obtained by depth
¼
velocity
time
=
2 where factor 2 is due to the
round trip travel of the ultrasound pulse between the material surface and the layer.
The first two layers of the dome wall were composed of mortar and plaster,
respectively. For the calculation of depth, an average ultrasound propagation
velocity of 1600 m/s was calculated from lab probes. Due to the 1 MHz inter-
ference, the B-Scan is not clear enough to represent a profile of a layer.
Figures
6.12
a and b show the results obtained by applying ICA on the ultra-
sonic signals. To assess the sensitivity of ICA in detecting the interference, a
Search WWH ::
Custom Search