scholarly journals Longitudinal coupling impedance measurements of a bellow at low frequencies

1993 ◽  
Author(s):  
Alessandro Ratti
Author(s):  
Richard Galos ◽  
Xin Li

Electrical Impedance Measurement of PZT Nanofiber sensors are performed and material properties including resistivity and dielectric constant are derived from the measurements. Nanofibers formed by electro-spinning with diameters ranging from 10 to 150 nm were collected and integrated into sensors using microfabrication techniques. The nanosensor impedance was extremely high at low frequencies and special matching circuitry was fabricated to detect output. The resulting impedance measurements are also compared with those of individual nanofibers that were tested using Scanning Conductive Microscopy (SCM) and Conductive AFM.


2019 ◽  
Vol 26 (10) ◽  
pp. 1950067 ◽  
Author(s):  
AHMED MOUGARI ◽  
MOKHTAR ZABAT ◽  
SMAIL BOUDJADAR

From the defects-free self-assembled organic layers (SAMs) of CH3([Formula: see text]SH molecules with short chain lengths ([Formula: see text]) electrodeposited on the (111) surface of monocrystalline gold previously prepared, monitored defects (pinholes) were potential-induced from cyclic partial reduction of SAMs at an appropriate potential. Electrochemical impedance measurements were in-situ conducted and [Fe(CN)6][Formula: see text] ions were used as probes for mass and charge transfer. Interface evolution was modeled with an equivalent electrical circuit containing two distinct constant-phase elements (CPEs). One is a generalized semi-infinite Warburg element in series with a charge transfer resistance attributed to subdiffusion phenomenon through leaky sublayers at low frequencies; the other CPE is used for characterizing the interface heterogeneity at medium and high frequencies. At low frequencies, electrochemical impedance measurements show subdiffusion phenomenon, which depends on the remaining sublayer and its thickness. When the defect density increases, diffusion tends to be ordinary, obeying the Fick’s law.


2020 ◽  
Vol 10 (2) ◽  
pp. 127-140 ◽  
Author(s):  
Nicolas Murer ◽  
Jean-Paul Diard ◽  
Bogdan Petrescu

When performing electrochemical impedance spectroscopy (EIS) measurements on a system, we must make sure it fulfills certain conditions. One of them is that it should be stationary that is to say, steady-state and time-invariant. Commonly studied systems are time-variant, for example a corroding electrode or a battery under operation. A corroding electrode sees its polarization resistance decrease with time. A passivating electrode sees its polarization resistance increase with time. These phenomena cause a deformation of the Nyquist impedance at low frequencies. This result was first simulated and validated by experimental measurements on a corroding steel sample undergoing uniform cor­rosion. The effect of performing impedance measurements on a discharging battery was also shown. Several methods are available to check and correct time-variance. The non-stationary distortion (NSD) indicator is used to separate valid and invalid data samples and the so called “4D impedance” method can easily produce instantaneous impedance data.


1989 ◽  
Vol 153 ◽  
Author(s):  
Ken M. Takahashi

SummaryIn-situ interfacial impedance measurements were used to study the effects of moisture at 80 °C on the interface between oxidized silicon and a diglycidyl ether of bisphenol A (DGEBA) epoxy cured with diethylene triamine (DETA). Using two electrode configurations, admittances attributable to bulk and interfacial conduction processes were distinguished. Bulk impedance measurements followed Randles behavior; conduction in the bulk epoxy was ionic, and was diffusion controlled at low frequencies. Equivalent circuit models were used to demonstrate that an apparent interfacial conduction process was caused by distributed current leakage into the silicon subphase, not a true interfacial conduction path that would indicate water adsorption or interfacial aggregation. However, transitions in diffusivity and bulk epoxy permittivity behavior above a 70-80% relative humidity threshold were observed. Effective epoxy permittivity (∈c) jumped to values indicative of a water cluster induced Maxwell-Wagner relaxation. The humidity threshold corresponds to a level that has been associated with adhesion loss in epoxies. It appears that epoxy adhesion losses result from bulk epoxy property changes at high humidity rather than interfacial bond displacement or delamination.


2010 ◽  
Vol 88 (8) ◽  
pp. 597-605
Author(s):  
Sondos Okoor ◽  
A. M. Al-Khateeb ◽  
I. M. Odeh

The longitudinal coupling impedance is obtained analytically for a smooth and resistive cylindrical pipe of finite wall thickness. We assumed a particle beam with Gaussian charge distribution in the longitudinal and transverse directions. For wall thicknesses d less than the skin depth, the impedance increases because of coupling with the vacuum outside the pipe, while for thicknesses d nearly of the order of the skin depth, the impedance becomes independent of the wall thickness. The resistive wall impedance decreases with increasing wall conductivity and it has its maximum values at low frequencies. By increasing beam energies, the space charge impedance decreases while the resistive wall contribution increases. Gaussian and uniform beams have nearly the same impedance at low energy, independent of the wall thickness, while at higher energies obvious differences are observed at wall thicknesses below the skin penetration depth.


2002 ◽  
Author(s):  
D. Davino ◽  
H. Hahn ◽  
M. Blaskiewicz

Geophysics ◽  
1983 ◽  
Vol 48 (11) ◽  
pp. 1453-1467
Author(s):  
Geoffrey A. Dorn

The thickness and shear‐wave velocity of a surface layer can theoretically be determined from seismic radiation impedance measurements using a torsional vibrator. These studies also provide physical insight into vibrator‐earth interaction. The radiation impedance of a circular disk vibrating torsionally on an anelastic half‐space has resonance peaks with a spacing that is a function of the ratio between baseplate radius and seismic wavelength. At low frequencies the shape of the impedance function is nearly independent of the baseplate flexure, although the magnitude is affected. At high frequencies the impedance depends strongly on the flexibility of the baseplate. The mass of the baseplate introduces an additional resonant effect, the frequency of which is a function of the baseplate mass. The presence of a surface layer produces an impedance curve which oscillates around the half‐space response. The amplitude of the oscillations is a function of the acoustic impedance contrast and depends upon the radiation pattern of the source. The oscillations are resonances caused by reflections within the surface layer, and both the period and amplitude of the oscillations are inversely proportional to the layer thickness. The amplitude of the layer resonance decreases rapidly as material damping increases. With impedance measurements over a sufficiently broad frequency range (up to about 500 Hz), it may be feasible to use half‐space oscillations and the layer resonances to determine the shear velocity and thickness of the layer of material beneath the baseplate.


Sign in / Sign up

Export Citation Format

Share Document