Real Part Of Admittance Research Articles

Structural Damage Detection through EMI and Wave Propagation Techniques Using Embedded PZT Smart Sensing Units.

Lead Zirconate Titanate (PZT) sensors have become popular in structural health monitoring (SHM) using the electromechanical impedance (EMI) technique for damage identification. The vibrations generated during the casting process in concrete structures substantially impact the conductance signature’s (real part of admittance) magnitude and sensitivity. The concept of smart sensing units (SSU) is presented, composed of a PZT patch, an adhesive layer, and a steel plate. It is embedded in the concrete structure to study the impact of damage since it has high sensitivity to detect any structural changes, resulting in a high electrical conductance signature. The conductance signatures are obtained from the EMI technique at the damage state in the 10–500 kHz high-frequency range. The wave propagation technique proposes implementing the novel embedded SSUs to detect damage in the host structure. The numerical simulation is carried out with COMSOL multiphysics, and the received voltage signal is compared between the damaged and undamaged concrete beam with the applied actuation signal. A five-cycle sine burst modulated by a Hanning window is employed as the transient excitation signal. For numerical investigation, six cases are explored to better understand how the wave travels when a structural discontinuity is accounted for. The changes in the received signal during actuator–receiver mode in the damage state of the host structure are quantified using time of flight (TOF). Furthermore, the numerical studies are carried out by combining the EMI-WP technique, which implies synchronous activation of EMI-based measurements and wave stimulation. The fundamental idea is to implement EMI-WP to improve the effectiveness of SSU patches in detecting both near-field and far-field damage in structures. One SSU is used as an EMI admittance sensor for local damage identification. Meanwhile, the same EMI admittance sensor is used to acquire elastic waves generated by another SSU to monitor damages outside the EMI admittance sensor’s sensing area. Finally, the experimental validation is carried out to verify the proposed methodology. The results show that combining both techniques is an effective SHM method for detecting damage in concrete structures.

Conductivity enhancement in polymer electrolytes on gamma irradiation

We expose PEO(1− x)–NH 4ClO 4( x) (with x = 0.16–0.26) to gamma irradiation with doses varying from 10 to 40 kGy. The change in ion-conductivity with irradiation is observed. The ion-conductivity goes through a maximum at 30 kGy. The enhancement is two orders of magnitude for the x=0.16 sample, but not significant for x higher than 0.20. An equivalent circuit is used to fit simultaneously the Cole–Cole plot and the real part of admittance vs. frequency plot. It is seen that the samples show an inductive loop at high frequency for low doses, where conductivity is low. This may be a result of the spiral coiling of the polymer molecules.

Performance of smart piezoceramic patches inhealth monitoring of a RC bridge

This paper presents the results of a health monitoring study, carried outduring the destructive load testing of a prototype reinforced concrete (RC)bridge. The bridge was made up of cement-concrete reinforced with steel rods,and represented a popular class of road bridges in which regular healthmonitoring is a very important issue during the service life. The bridge wasinstrumented with piezoceramic transducer (PZT) patches, which wereelectrically excited at high frequencies, of the order of kHz, and the realpart of admittance (conductance) was extracted as a function of the excitingfrequency. The patches were scanned for the acquisition of this signature atvarious stages during the loading process. The signatures of the patcheslocated in the vicinity of the damage were found to have undergone drasticchanges, while those farther away were less affected. Damage wasquantified in non-parametric terms using the root mean square of the deviationin signatures with respect to the baseline signature of the healthy state.This non-parametric index was found to correlate well with the damageprogression in the structure.

Frequency dependence of A.C. conductance of non-irradiated and neutron irradiated silicon detectors

The admittance-Y (real and imaginary) as a function of frequency (ω) and temperature (T) of silicon detectors, non-irradiated and neutron irradiated, were studied. An electric circuit model of Y(ω) was calculated. The experimentally measured data for real part of admittance G as a function of to have shown a quadratic dependence G∼ω 2 , for temperatures T≥40K. This experimental dependence was the same as resulted from the calculations based on the electric circuit model for the region of values T where G was proportional to the resistivity of the silicon detector (p). For temperatures T n (n a , a =2.3 for 170≤T≤ 270 K and a=1.8 for 50≤T≤ 150K). At T≤ 20K, due to the process of freeze-out of free carriers, the value G remains practically independent on to and on further decrease of T. Measurements on neutron irradiated samples at Φ >10 13 n/cm 2 , have shown important changes in the dependence of G as a function of co and T.

An analysis of light-induced admittance changes in rod outer segments.

1. Measurements were made of the time course and amplitude of the change in real part of admittance, DeltaG, of a suspension of frog rod outer segments, following a flash of light bleaching about 1% of the rhodopsin content of the rods. The measurements, based on the use of a specially designed marginal oscillator, covered the frequency range between 500 Hz and 17 MHz.2. The components of response, previously described for rods prepared by a method involving exposure to strongly hypertonic sucrose solutions, are present in similar form when rods are isolated and maintained in isotonic solutions made up with equi-osmotic concentrations of NaCl and sucrose or with Na(2)SO(4).3. Component I, identified as a slowly developing positive DeltaG apparent at very low frequencies, is frequency-independent up to the characteristic frequency of admittance for the suspension, f(Y) (about 2 MHz for rods suspended in a solution having the conductivity of Ringer solution), but decreases at still higher frequencies.4. Component II, identified as a rapidly developing positive DeltaG which appears only above a critical frequency about 2.5 decades below f(Y), increases approximately logarithmically with frequency to reach a limiting amplitude in the region of f(Y).5. The amplitude of component II, DeltaG(II), measured in the region of f(Y), varies linearly with the conductivity of the suspending medium, G(o), under conditions in which the conductivity of the rod interior is also a linear function of the external conductivity. The relation for a flash bleaching 1% of the rhodopsin content of the dark-adapted rod is [Formula: see text]6. Measurements made on rods suspended in a low-conductivity solution, which has the effect of reducing the conductivity of the rod interior to about one ninth its value for rods suspended in Ringer solution, reveal a decline in component II for frequencies above 8 MHz.7. To explain the frequency dependence of component II and its dependence on conductivity, it is proposed that component II arises from a light-induced increase in conductance of the disk membranes which obstruct the longitudinal flow of current through the rod interior except at very high frequencies.8. The disk-membrane conductance increase for rods suspended in a solution having the conductivity of Ringer solution is calculated to be 4.3 x 10(-11) mho/rhodpsin molecule bleached, a value which is similar to what has been found for ionic channels operated by membrane potential change in the nerve membrane and by synaptic transmitter in the postjunctional membrane.9. No component of response has been observed which could be reliably attributed to a surface membrane conductance decrease of the type observed in receptor cells in the retina.

Light-induced conductance changes in rod outer segments.

Alternating current measurements have been made on packed suspensions of rod outer segments. Since it is suspected that any changes that occur in the passive electrical properties of this experimental material will have their origin in conductive (i.e. dissipative) elements, attention has been directed to the detection of changes in the real part of admittance (Δ G) representing the change in amplitude of current through the material inphase with an applied sinusoidal voltage of unit amplitude). Owing to the presence of capacitative elements arising from membranes, Δ G will, in general, vary with the frequency of the applied voltage. Information can thus be derived about the position, relative to known structural features, of conductive elements that change on illumination. In particular, an increase of Δ G with frequency may be an indication that one is probing beyond the surface membrane to observe changes taking place in the interior of rod outer segments.KeywordsConductivity CellCarrier WaveDisc MembraneLongitudinal ConductancePlatinum BlackThese keywords were added by machine and not by the authors. This process is experimental and the keywords may be updated as the learning algorithm improves.

Conductance changes produced by light in rod outer segments.

1. Changes in the admittance of rod outer segments produced by illumination with brief flashes were studied by two methods: one, in which maintained changes in real and imaginary parts of admittance were observed in the frequency range 15 c/s-60 kc/s; the other, in which the time course of change in absolute value of admittance (Delta|Y|) was observed at frequencies of 100 kc/s-1.0 Mc/s.2. The response to light absorbed by rhodopsin was resolved into components. One of these components was a transient increase in conductance which arose from a rapid degradation into heat of the light energy. Another component, prominent at high frequencies where the conductivity of the rod interior was accessible to measurement, was produced by the uptake of H(+) by visual pigment in its conversion from metarhodopsin I to metarhodopsin II, causing a change in ionization of buffer.3. Two other components, designated I and II, appeared as maintained changes of admittance involving the organized structure of the rod. Component I appeared as a frequency-independent increase in the real part of admittance (DeltaG), the amplitude of which varied in proportion to the conductivity of the medium, without specificity as to ion species. Component II appeared as a DeltaG which rose linearly with log frequency over the range 1-60 kc/s, while the imaginary part of admittance change (DeltaB) rose to a plateau which was maintained for more than a tenfold frequency range. This component was unaffected by variations in conductivity in the region of low conductivities.4. When rods were suspended in a solution containing 100 mM hydroxylamine, component II no longer appeared as a maintained admittance change while component I was unaffected. Examination of the time course of response showed component II to appear transiently, decaying over the course of 2 sec following a flash.5. Measurements of Delta|Y| for rods in solutions of widely different conductivities showed component II to have a more rapid time course of development than component I and to be only slightly delayed in its early part relative to the buffer component.6. The amplitude of component I varied with temperature to the extent of 4.1%/ degrees C (Q(10) of 1.5) over the range -2-25 degrees C. The amplitude of component II was nearly constant over the range 15-27 degrees C, but fell steeply at temperatures below 10 degrees C, the Q(10) at low temperatures being about 2.4. The effect of temperature on amplitude and time course of component II is consistent with its dependence on the formation and continued presence of metarhodopsin II. The failure of component I to decrease steeply at temperatures below 10 degrees C indicates a dependence on an earlier stage in the thermal conversion of rhodopsin photoproducts.7. With light flashes each bleaching less than 1% of the rhodopsin content of the rod, all components of response were proportional to the amount of rhodopsin bleached (which would be proportional to the light absorbed). For brighter flashes components I and II failed to increase in proportion to the amount of rhodopsin bleached, the deviation from proportionality being greater for component I than for component II. The failure of summation of response extended to successive responses separated by up to 5 min.8. It is suggested that component I arises from a non-selective increase in ionic permeability of the surface membrane of the rod or from a change in rod volume, while component II arises from a change in conduction along the surface membrane.