Introduction - Broadband Reflectometry for Enhanced Diagnostics and Monitoring Applications - page 5

Additionally, in [36] a TDR-based system for sensing crack/strain in reinforced
concrete structures was presented; fault location on concrete anchors was investi-
gated in [9]; a TDR-based solution for monitoring cement hydration was described
in [11], and so on.

1.2.4 Dielectric Spectroscopy Measurements

BMR has also been extensively used for dielectric spectroscopy of materials, which
involves measuring the frequency-dependent dielectric permittivity of the consid-
ered material. Typically, this kind of measurements relies on the combination of
reflectometric measurements and mathematical models that describe the expected
dielectric behavior of the considered material. Dielectric properties are of paramount
importance because they can be related to other non-electric properties of the SUT,
thus obtaining useful information.
It would be impossible to list all the specific materials for whose characteriza-
tion BMR has proven useful; however, some of the materials investigated through
this technique include alcohol mixtures [2], mixtures of ester with alcohol [30, 31],
poly(propylene glycol)water mixtures [29], chlorobenzene with n-methylformamide
[22], Nylon-11 with phenol derivatives [13], powders (e.g., zeolite powders [35]).
Dielectric characterization through BMR has also been extensively used for food
analysis [16] and for application on biological materials (e.g., for breast tissue anal-
ysis [25], for diagnosing skin cancer [15], for cerebral edema-related studies [10],
etc.).

1.2.5 Applications in Industrial Monitoring

Typical applications of BMR for industrial use include measurement of liquid lev-
els in tanks or containers. Basically, the level of the liquid is inferred from the
travel time of the EM signal along the probe immersed in the monitored liquid [19].
Thanks to the capability of discriminating interfaces between materials with dif-
ferent permittivity, TDR can be used for the localization of multiple interfaces in
layered media [4, 24].
Other applications of BMR include monitoring of levels in dykes and rivers;
moisture evaluation of agrofoods (such as cereals and coffee [5]); monitoring of
the osmotic dehydration process for fruit and vegetables; and other quality-control
applications that resort to measurement of dielectric characteristics.

1.3 Organization and Content of the Topic

The topic comprises two main parts: one is more theory-oriented, whereas the other
is more practice-oriented. The first part (from chapter two through chapter three) re-
calls the theoretical background of BMR measurements and presents the strategies