Cole-Cole Model Research Articles

Магнитоимпеданс в сульфиде марганца, замещенного лютецием

The components of the impedance, the impedance of the LuxMn1-xS solid solution (x < 0.2) in the temperature range of 80-500 K and the frequency of 100-106 Hz were studied. A change in the sign of the magnetoimpedance in concentration and temperature is found. The contribution of the reactive and active components to the magnetoimpedance is determined. The correlation of magnetoimpedance temperatures with the temperatures of the maximum attenuation of ultrasound and electrosound has been established. The frequency dependences of the reactive part of the impedance are described in the Cole-Cole model.

Magnetoimpedance in manganese sulfide substituted with lutetium

The components of the impedance, the impedance of the LuxMn1-xS (x<0.2) solid solution in the temperature range of 80-500 K and the frequency of 100-106 Hz were studied. A change in the sign of the magnetoimpedance in concentration and temperature is found. The contribution of the reactive and active components to the magnetoimpedance is determined. The correlation of magnetoimpedance temperatures with the temperatures of the maximum attenuation of ultrasound and electrosound has been established. The frequency dependences of the reactive part of the impedance are described in the Cole-Cole model. Keywords: Semiconductors, impedance, magnetoimpedance, attenuation of ultrasound.

Li2SO4 doped Li2O + B2O3 glasses: Hopping mechanism, relaxation phenomena and conductivity behavior

This oxide glass system work reports a detailed of the hopping mechanism, electrical conductivity, and dielectric relaxation phenomena in Li2O + B2O3-based glass for various Li2SO4 mol%. The conductivity, impedance, and dielectric modulus were analyzed in a temperature range from 363 K to 563 K and in a frequency range from 100 Hz to 5 MHz. The conductivity of the glass sample was verified using Cole-Davidson, Jonscher’s power law, and Cole-Cole models and is found to be consistent with each other. Conductivity at the grain and grain boundary was also determined by fitting the impedance data using constant phase elements (CPE) in an equivalent circuit model. The equivalent circuit was used to interpret the impedance semicircles obtained from the ac measurements. Interpretation of the relaxation mechanism in the glass matrix is described by employing Kohlrausch-William-Watts (KWW) model and the modified KWW model, which discloses that the non-Debye type relaxation mechanism is followed by the charge carriers. Impedance spectroscopy has been discussed to distinguish between the contribution of grain boundaries and grains in the relaxation mechanism. The doping Li2SO4 effect can be explained by observing activation energy in the investigated samples. The power law exponent ‘S’ for glass matrix with temperature depicts CBH and NSPT hopping mechanism in AC conductivity. All the above results reveal the glass’s semiconducting nature and depend on the lithium sulphate content in the glass matrix.

A synthetic denoising algorithm for full-waveform induced polarization based on deep learning

Induced polarization (IP) is a widely used geophysical exploration technique. Continuous random noise is one of the most prevalent interferences that can seriously contaminate the IP signal and distort the apparent electrical characteristics. We develop a noise separation algorithm based on deep learning to overcome this issue. The standard IP signals are first produced by combining the Cole-Cole model and Fourier series decomposition, and then the mathematical simulation is used to generate various types of random noise interferences, which are subsequently added to the IP signals. Then, a denoising autoencoder deep neural network structure is built and trained by using noisy signals as input samples and pure signals as output samples. The resulting optimum network is capable of automatically reconstructing a clean IP signal from the noisy input. This network is tested using synthetic data sets. The trained neural network can perform the noise reduction of thousands of survey points in a matter of seconds and reduce signal distortion from approximately 25% to less than 5%. Deep learning-based denoising provides superior computation speed and precision compared with the wavelet denoising and smoothing filtering approach. The data for high-quality signals do not vary considerably before and after noise reduction. The noise interferences are successfully suppressed for low-quality signals. Based on the findings, the denoising autoencoder deep neural network has a promising future for suppressing random noise interferences, which can aid in improving the quality of IP data with high efficiency and precision.

Suspension rheology of polyaniline coated manganese ferrite particles under electric/magnetic fields

Manganese ferrite (MnFe2O4) nanoparticles initially fabricated using a solvothermal process were coated with conducting polyaniline (PANI) to produce core/shell-structured MnFe2O4/PANI nanoparticles. An electro/magnetorheological (E/MR) fluid was prepared by suspending MnFe2O4/PANI particles in silicone oil, and the rheological properties under either electric or magnetic fields were investigated. Scanning electron microscope and transmission electron microscope provided the particle morphology and size information. X-ray diffraction and Fourier transform infrared spectroscopy were used to analyze the crystal structure and chemical composition of the particles. Chain formation in E/MR fluids under electric or magnetic fields was observed by optical microscopy, and the rheological properties were evaluated using a rheometer. Steady shear and dynamic oscillatory tests were conducted to confirm the effective E/MR characteristics while varying the electric/magnetic field strength. The dielectric properties of the particles measured using an LCR meter were analyzed based on the Cole-Cole model. The E/MR fluids composed of MnFe2O4/PANI showed a reversible and fast electro/magnetic response.

Characterization of a Thermoacoustic-based Pulsed High Power Microwave Detector Chain.

Detection of microwave-induced thermoacoustic (TA) wave generation was evaluated as a potential technique for detection of high power microwave (HPM) directed energy exposure. Even when HPM is employed for counter-materiel effects, incidental but still potentially harmful personnel exposure is possible. Real-time detection of ongoing exposure with potentially unknown time and frequency domain characteristics is a critical first step in preventing acute health effects by alerting and then enabling the timely use of electromagnetic frequency energy shielding, such as structures and vehicles. Leveraging the TA effect as a field interaction mechanism, a lossy dielectric polymer subjected to pulsed HPM was tested using a planar sample geometry with thin film piezoelectric sensors used to capture the resulting TA output. The piezoelectric signal was analyzed in both the time and frequency domain to determine empirical relationships between incident microwave beam properties and signal components. This analysis was coupled with an empirically-based single term Cole-Cole model approximation fit for the complex permittivity. The results were used to identify appropriate signal conditioning and processing techniques needed to convert the TA response into a useful form for personnel exposure applications. These results also served as a comparison point for multi-physics finite element method computational modeling of the electromagnetic response of a simplified three-layer tissue model.

Ambiguity in induced polarization time constants and the advantage of the Pelton model

The perceived differences between two popular relaxation models (referred to here as the “Cole-Cole model” and the “Pelton model”), along with their corresponding time constants, have been a source of confusion in recent spectral induced polarization (SIP) literature. These differences complicate comparisons among experimental results recorded by different researchers. A circuit model approach is adopted to better understand the differences among these relaxation models. Either relaxation model can fit SIP data sets equally well, the sole difference corresponds to the relaxation time that varies for the impedance and admittance formulations of the circuit models. The reporting of time constants from a common relaxation model will advance petrophysical investigations of the controls on SIP measurements when exploring databases compiled from previously published data sets.

Structural, complex dielectric, Ac conductivity and impedance properties of Mn3-xCrxTeO6 (x = 0.02, 0.04, 0.06 and 0.08) compounds

In this communication, the synthesis of polycrystalline Mn3-xCrxTeO6 (MCTO) (x = 0.02, 0.04, 0.06 and 0.08) compounds is carried out using the standard high-temperature solid-state reaction (SSR) method. The X-ray Diffraction (XRD) technique revealed the trigonal (hexagonal axes) crystal structure of MCTO compounds. The doping of Chromium (Cr) on the Mn site does not affect the structure of the compound. The compositional purity and morphological observations are also investigated. Dielectric parameters are examined throughout a wide frequency range. Detailed investigation obtained by theoretical fitting of the cole-cole model revealing a non-Debye type relaxation mechanism which is also evident from the complex modulus studies. An investigation on electrical conductivity is carried out by conceptually fitting experimental data using a power law and indicates a Correlated Barrier Hopping mechanism in MCTO compounds as the cause of conduction. The resistance and capacitance were validated by impedance analysis, and the effect of grains and grain boundaries was also studied accordingly. In-depth, this study demonstrates an effective synthesis approach and a thorough examination of Cr-doped Mn3TeO6 multiferroic compounds, potentially providing fundamental attributes to investigate their applications in various fields of multiferroics.

Magnetic properties of CCTO doped with GeO2

The high dielectric constant presented by CaCu3Ti4O12 (CCTO) makes this material promising for industrial applications, in particular for electronic devices. Nevertheless, the preparation method and the doping by oxides has a great influence on the microstructure, and consequently in the dielectric properties. In this work we prepared and studied CCTO doped by germanium oxide, in concentrations up to 10% by weight. X-ray diffraction shows the presence of nanocristals. The grains and the grain boundaries compositions have been characterized by scanning electron microscopy with energy dispersive X-ray spectrometry mapping. The magnetization measurements show an antiferromagnetic behaviour with a Néel temperature TN=25 K, independent of the GeO2 doping (up to 6%). Analyses of the high temperature dependence of the magnetic susceptibility show that the increase of the GeO2 doping decreases the paramagnetic temperature. Dielectric spectroscopy measurements, in the frequency range from 75 kHz to 30 MHz, at room temperature, have been carried out. Cole-Cole model of dielectric relaxation adjusts correctly the data. The results, obtained with the different techniques, indicate that there is the increase of samples grain size up to 6% of germanium oxide, which causes an increase of the real and imaginary parts of complex permittivity.

The synthesis of a liver tissue mimicking solution for microwave medical applications

This paper presents the synthesis of a mixture solution that is equivalent to ex-vivo liver tissue dielectric characteristics between 500 MHz and 5 GHz. The mimicking solution was synthesized using concentrations of two chemicals, the solute which is referred to as the inclusion phase and the solvent, referred to as the host phase. The inclusion phase consisted of bovine serum albumin (BSA) powder and the host phase consisted of a phosphate-buffered saline (PBS) solution with a concentration of Triton X-100 (TX-100). The dielectric properties of these two phases were substituted into Bruggeman's two-phase mixture equation to estimate the dielectric properties of excised liver. Furthermore, the study exploits Bruggeman’s equation to investigate the impact of tissue dehydration levels on the dielectric properties of an excised tissue. The effect of dehydration has been characterised as a function of time based on the loss-on-drying technique (a substance is heated until it is completely dry). Dielectric parameters were measured as a function of frequency using the Slim Form open-ended coaxial probe at a constant room temperature of circa 25 °C. Measured dielectic data were fitted to the Cole-Cole model and good agreement with the mimicking solutions was obtained. These results indicate that these solutions can be used to model the human body phantoms for microwave medical applications.

Extended RC Impedance and Relaxation Models for Dissipative Electrochemical Capacitors

Electrochemical capacitors are a class of energy devices in which complex mechanisms of accumulation and dissipation of electric energy take place when connected to a charging or discharging power system. Reliably modeling their frequency-domain and time-domain behaviors is crucial for their proper design and integration in engineering applications, knowing that electrochemical capacitors in general exhibit anomalous tendency that cannot be adequately captured with traditional integer-order-based models. In this study we first review some of the widely used fractional-oder models for the description of impedance and relaxation functions of dissipative resistive-capacitive system, namely the Cole-Cole, Davidson-Cole, and Havriliak-Negami models. We then propose and derive new q-deformed models based on modified evolution equations for the charge or voltage when the device is discharged into a parallel resistive load. We verify our results on anomalous spectral impedance response and time-domain relaxation data for voltage and charge obtained from a commercial supercapacitor.

Uncertainty Quantification and Sensitivity Analysis for the Electrical Impedance Spectroscopy of Changes to Intercellular Junctions Induced by Cold Atmospheric Plasma.

The influence of pertinent parameters of a Cole-Cole model in the impedimetric assessment of cell-monolayers was investigated with respect to the significance of their individual contribution. The analysis enables conclusions on characteristics, such as intercellular junctions. Especially cold atmospheric plasma (CAP) has been proven to influence intercellular junctions which may become a key factor in CAP-related biological effects. Therefore, the response of rat liver epithelial cells (WB-F344) and their malignant counterpart (WB-ras) was studied by electrical impedance spectroscopy (EIS). Cell monolayers before and after CAP treatment were analyzed. An uncertainty quantification (UQ) of Cole parameters revealed the frequency cut-off point between low and high frequency resistances. A sensitivity analysis (SA) showed that the Cole parameters, R0 and α were the most sensitive, while Rinf and τ were the least sensitive. The temporal development of major Cole parameters indicates that CAP induced reversible changes in intercellular junctions, but not significant changes in membrane permeability. Sustained changes of τ suggested that long-lived ROS, such as H2O2, might play an important role. The proposed analysis confirms that an inherent advantage of EIS is the real time observation for CAP-induced changes on intercellular junctions, with a label-free and in situ method manner.

Application of induced polarization imaging across different scales to understand surface and groundwater flow at the Hofermuehle landslide

Understanding changes in hydraulic properties of the subsurface is critical to delineate areas susceptible for groundwater accumulation and the triggering of landslides. Laboratory studies have demonstrated the possibility to estimate the hydraulic conductivity from induced polarization (IP) measurements. However, to-date only rare studies have been applied at the field scale and none has evaluated the frequency-dependence in field IP imaging data. We show that the application of petrophysical models linking hydraulic conductivity (K) and IP at 1 Hz, resolves for the same estimations from frequency-domain measurements as well as from time-domain IP. Moreover, our IP images reveal an evident frequency-dependence between 0.1 and 240 Hz in the electrical properties, which is also observed in lab measurements conducted in soil samples. To account for this, we fit a Cole-Cole model to our multi-frequency IP results and evaluate models linking K and the normalized chargeability, gaining a subsurface model of the hydraulic conductivity with enhanced resolution. Our results reveal clear variations at depth in the electrical conductivity and polarization associated with the presence of a plane of instability and the sliding plane. We also resolve lateral changes delineating areas with K below 10-6 m/s, which may act as barriers for groundwater flow. To evaluate our results we also estimate the hydraulic conductivity using a joint inversion algorithm that directly solves for porosity and saturation through the simultaneous inversion of seismic refraction and electrical resistivity tomography data. We observed consistent hydraulic conductivity images obtained through the inversion of the IP data and the joint inversion, with such model being in agreement with existing information of the site. We resolve a 3D model of the hydraulic conductivity at the Hofermuehle landslide from IP data that reveals the geometry of areas with poor drainage that may lead to land sliding.

Capturing In Situ Glyphosate (De)sorption Kinetics in Floodplain Aquifer Sediment Columns: Geophysical Measurements and Reactive Transport Modeling.

Glyphosate, an ionizable organic herbicide, is frequently detected in soils and groundwater globally despite its strong retention via sorption. Understanding its apparent mobility hinges on our ability to quantify its system-specific sorption behavior, hindered by its affinity to adsorb onto sediments, yielding very low aqueous concentrations. Here, we present findings from a saturated flow-through column experiment in which we monitored glyphosate sorption onto a natural calcareous aquifer sediment, using the noninvasive geophysical method spectral induced polarization (SIP). Our kinetic sorption reactive transport model predicted the strong nonlinear reversible retention of glyphosate and reproduced the spatial profile of retained glyphosate in the sediment, with a measured maximum of 0.06 mg g-1. The strong contribution of sorption to pore fluid conduction masked the expected variations in imaginary conductivity, σ″. However, time constants derived from a Cole-Cole model matched the timing and spatial distribution of model-predicted sorbed concentration changes, increasing from 0.8 × 10-3 to 1.7 × 10-3 s with an increase in sorbed glyphosate of 0.1 mg g-1. Thus, glyphosate sorption modified the surface charging properties of the sediment proportional to the solid-bound concentrations. Our findings link SIP signal variations to sorption dynamics and provide a framework for improved monitoring of charged organic contaminants in natural sediments.

Wireless Glucose Sensing System Based on Dual-Tag RFID Technology

Glucose sensing is an important way to improve the efficiency of diagnosis and treatment of diabetic patients. A glucose sensing system with low-cost, penetrability and safety is necessary. In this paper, a wireless sensing system for continuous glucose monitoring based on dual-tag radio frequency identification (RFID) technology was proposed. A modified system model incorporating Cole-Cole dielectric model is built to describe the relationship among glucose concentration, matching capacitance of tags and operating frequency, and the related parameters were determined by particle swarm optimization based on linear descending weights (LDW-PSO). The experiments were performed in the frequency range from 902 MHz to 928 MHz, and the results show that the maximum relative error between measured glucose concentration and estimated one is 4.15%, and all the measured glucose concentration lie in the reasonable region in Clarke’s error grid, indicating that our proposed monitoring method has a great potential in the healthcare field.

Estimation of Moisture Content in XLPE Cable Insulation Using Electric Modulus

In this article, a novel approach is proposed for accurate moisture content (MC) estimation of cross-linked polyethylene (XLPE) insulation employing electric modulus. Additionally, the variation of real and imaginary part of electric modulus in the argand plane is fitted using Cole-Cole (C-C) model for understanding of distributed relaxation behavior of XLPE insulation. Based on the frequency variation of dielectric parameters, five moisture sensitive parameters are identified and using these parameters, five empirical relationships are proposed for quantitative assessment of MC in XLPE insulation. It is observed that parameters obtained from the complex modulus spectrum yields better accuracy in estimation of MC compared to the parameters obtained from traditional frequency domain spectroscopy (FDS).

Inversion of induced polarization-affected towed-transient electromagnetic data in a lateritic regolith geology: A case study from western Tanzania

For several decades, induced polarization (IP) effects on transient electromagnetic (TEM) responses have been observed. These effects can manifest as late-time negative transients or as rapidly decaying curves and are usually associated with highly polarizable bodies. If neglected, IP effects can lead to erroneous resistivity models. Recent work allows IP effects to be incorporated into the inversion of TEM data on a more routine basis. In a recent field survey in western Tanzania, strongly IP-affected TEM signals are observed using a towed-transient electromagnetic (tTEM) system. The survey have been carried out to locate drinking water resources in a weathered regolith setting. In these settings, an inversion of tTEM data using a resistivity-only forward model (i.e., IP neglected) cannot fit the data and severely limits the value of the TEM data for hydrogeologic interpretation. To account for IP effects, we have applied a modified version of the Cole-Cole model called the maximum phase angle (MPA) model to invert IP-affected tTEM data. The MPA model incorporates four inversion model parameters: resistivity ([Formula: see text]), MPA ([Formula: see text]), relaxation time ([Formula: see text]), and frequency exponent ([Formula: see text]). The MPA model fits the data well and improves the reliability of the resistivity model. In much of the surveyed region, the inverted models using MPA display a three-layer system consisting of an upper resistive laterite layer of varying thickness and an intermediate polarizable conductive unit overlying more resistive weathered basement rocks. The conductive polarizable layer is interpreted as a chemically weathered saprolite separating the surficial and deeper aquifers. Overall, tTEM inversion results provide a local understanding of groundwater systems, especially in such regions with very limited subsurface knowledge.

Acrylic resin based dielectric composite with a novel hybrid composed of carbon nanotube grafted with graphene oxide

With the continuous miniaturization and integration of electronic devices, polymeric composites with high dielectric constant and low loss have received more and more attention from the field of research. In this work, a novel chemical modification method to fabricate a three-dimensional filler structure consisting of graphene oxide and carbon nanotube (CNT-g-GO) was proposed. Then this filler was introduced into acrylic resin elastomer (AE), and an approach of solution casting combined with hot pressing was used to fabricate the composite films, besides the physical blending composite films of graphene oxide, carbon nanotube and acrylic resin (CNT/GO/AE) were also prepared for a comparison. Results show that the composite containing a volume fraction of 6.72 vol% CNT-g-GO exhibits a dielectric constant of 204.3 and a dielectric loss of 0.16 at 100HZ. The hybrid filler of CNT grafted GO further improves the breakdown strength of composites below the 4.5 vol% filler addition. Furthermore, the origin of the dependence of dielectric loss factor on the frequency at the low frequency was studied with a theoretical model, additionally the mechanism on that enhanced interfacial interaction can more effectively influence the dielectric relaxation behaviors of composites was investigated according to Cole-Cole theoretical model.

Investigation of the structural, optical, electrical and dielectric proprieties of LiCd0.5Fe2O4 spinel ferrite

The spinel ferrite material families are subjected to diverse studies according to their wide field application. In this work, the LiCd0.5Fe2O4 ferrite was successfully synthesized by a conventional solid-state method. The structural, optical, electrical and dielectric characterizations were treated. The Rietveld refinement method explored cubic spinel structure (Fd3‾m space group) with a lattice parameter: a = 8.628 Å, α = 90°. Besides, the surface micrograph shows a strong agglomeration of the grains. Optical results were calculated using diffuse reflectance data and Kubelka Munk theory. They show the semiconductor nature with a band gap around 2.9 eV and Urbach energy around 0.14 eV.The electrical measurements were studied over a range of frequency (40 Hz–1 MHz) and through large temperature scale (200 K–380 K) using the complex impedance spectroscopy technique. The AC conductivity behavior was described by the jump relaxation model, which obeys to the Jonscher's law. The complex impedance analysis has suggested the presence of the contribution of the grains, the grain boundaries and interface in the conduction mechanism. A reduction in real part Z′ was observed as a function of temperature and frequency, which indicates an increase in ac conductivity and a negative temperature coefficient of resistance. Hence, the complex modulus plots have affirmed the presence of grain boundaries contribution in the material. Both the complex modulus and impedance investigations have confirmed that the synthesized material exhibits a non-Debye type of relaxation. Finally, the dielectric behavior of the studied sample shows a polarization effect and the permittivity graphs are fitted theoretically with the Cole-Cole model.

Data-driven modeling of time-domain induced polarization

Induced polarization (IP) measurements are affected by various types of noise, which should be removed prior to data interpretation. However, existing data processing methods often rely on empirical assumptions about the standard shape of IP decay curves. Our goal is to introduce a data-driven approach for modeling and processing time-domain IP measurements. To reach this goal, we train a variational autoencoder (VAE) on 1,600,319 IP decays collected in Canada, the United States, and Kazakhstan. The proposed deep learning approach is unsupervised and avoids the pitfalls of IP parameterization with empirical Cole-Cole and Debye decomposition models, simple power-law models, or mechanistic models. Four applications of VAEs are key to modeling and processing IP data: (1) synthetic data generation, (2) Bayesian denoising, (3) evaluation of signal-to-noise ratio, and (4) outlier detection. Furthermore, we interpret the IP data compilation’s latent representation and reveal a correlation between its first dimension and the average chargeability. Finally, we determine that a single real-valued scalar parameter contains sufficient information to encode IP data. This new finding suggests that modeling time-domain IP data using mathematical models governed by more than one free parameter is ambiguous, whereas modeling only the average chargeability is justified. A pretrained implementation of the VAE model is available as open-source Python code.