Abstract: In the current research structural health
monitoring is considered for addressing the critical issue of
post-earthquake damage detection. A non-standard approach
for damage detection via acoustic emission is presented -
acoustic emissions are monitored in the low frequency range
(up to 120 Hz). Such emissions are termed high-frequency
transients. Further a damage indicator defined as the
Time-Ratio Damage Indicator is introduced. The indicator
relies on time-instance measurements of damage initiation and
deformation peaks. Based on the time-instance measurements
a procedure for estimation of the maximum drift ratio is
proposed. Monitoring data is used from a shaking-table test
of a full-scale reinforced concrete bridge pier. Damage of the
experimental column is successfully detected and the proposed
damage indicator is calculated.
Abstract: An acoustic emission (AE) technique is useful for
detection of partial discharges (PDs) at a joint and a terminal section of
a cross-linked polyethylene (XLPE) cable. For AE technique, it is not
difficult to detect a PD using AE sensors. However, it is difficult to
grasp whether the detected AE signal is owing to a single discharge or
not. Additionally, when an AE technique is applied at a terminal
section of a XLPE cable in salt pollution district, for example, there is
possibility of detection of AE signals owing to creeping discharges on
the surface of electric power apparatus. In this study, we evaluated AE
signals in order to grasp what kind of information we can get from
detected AE signals. The results showed that envelop detection of AE
signal and a period which some AE signals were continuously detected
were good indexes for estimating state-of-discharge.
Abstract: In this paper, acoustic techniques are used to detect hidden insect infestations of date palm tress (Phoenix dactylifera L.). In particular, we use an acoustic instrument for early discovery of the presence of a destructive insect pest commonly known as the Red Date Palm Weevil (RDPW) and scientifically as Rhynchophorus ferrugineus (Olivier). This type of insect attacks date palm tress and causes irreversible damages at late stages. As a result, the infected trees must be destroyed. Therefore, early presence detection is a major part in controlling the spread and economic damage caused by this type of infestation. Furthermore monitoring and early detection of the disease can asses in taking appropriate measures such as isolating or treating the infected trees. The acoustic system is evaluated in terms of its ability for early discovery of hidden bests inside the tested tree. When signal acquisitions is completed for a number of date palms, a signal processing technique known as time-frequency analysis is evaluated in terms of providing an estimate that can be visually used to recognize the acoustic signature of the RDPW. The testing instrument was tested in the laboratory first then; it was used on suspected or infested tress in the field. The final results indicate that the acoustic monitoring approach along with signal processing techniques are very promising for the early detection of presence of the larva as well as the adult pest in the date palms.