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Polyvinyl chloride (PVC) products are composite materials consisting of thermal stabilizers, plasticizers, fillers and other additives in order to enhance thermal & mechanical properties and maintain sustainability & durability of PVC products. PVC products are in great demand due to wide spectrum of applications and therefore efficient, cost effective and multifunctional addditives are always required for their commercial viability. In this study, pentaerythritol p-aminobenzoate ester (PAE), a precursor for Zinc metal alkoxide was prepared and used to synthesize low melting Zinc pentaerythritol p-aminobenzoate ester complexes (Zn-PAE), which have been investigated as thermal stabilizer, plasticizer and mechanical properties enhancer. X-ray Photoelectron Spectroscopy, Differential Scanning Calorimetry, Scanning Electron Microscope (SEM), 1HNMR, and 13CNMR techniques have been used to examine synthesized PAE and Zn-PAE complexes. Zn-PAE complexes were synthesized in 1:1, 1:2, 1:3, and 1:4 ratios and compared for thermal stability and mechanical performance in PVC formulations. A specific chemical structure was observed in the PAE-Zn molecule, demonstrating that R-O-Zn bonds have been formed. The initial degradation temperature was increased by 51 ℃ in presence of Zn-PAE complex (1:3). Zn-PAE (1:3) has shown excellent thermal stability with an increment of 77.4 and 111.4 min time for HCl evolution observed through Congo red test and conductivity measurements respectively. Further experiments of oven ageing results confirmed effective thermal stabilizing effect of Zn-PAE complexes. No effect on initial colour of PVC sheets was observed upto 90 min for Zn-PAE (1:3) complex in comparison to 40 min of control sample comprising dibasic leadphthalate (DBLP) at a temperature of 220 ℃ (4 phr). The complexes are acting as thermal stabilizers as well as plasticizer as Tg values were found to decrease for all complexes (15.12 ℃ for Zn-PAE (1:3) complex). Increased value of tensile strength and percentage elongation further confirms the participation of Zn-PAE complexes in PVC backbone. [ABSTRACT FROM AUTHOR]

Dye-Surfactant interactions in aqueous solution are important in industrial processes. Generally, dyes associate strongly with oppositely charged surfactants. But, similarly charged dye-surfactants are not preferred anticipating repulsion. To gain insight into the nature and extent of interaction between anionic dye Eosin Yellow (EY) and mixed anionic micellar system, this study was undertaken. Mixed micellar system comprised of anionic, Sodium dodecyl sulfate (SDS) and nonionic Pluronic L-35 (L-35). The characterizations employed were FTIR Spectroscopy, Conductivity, UV visible spectroscopy, Fluorescence spectroscopy and SEM studies. A red shift with enhancement of intensity was observed both in UV-absorption and emission spectra of EY when interacted with SDS + L-35 mixed micellar system. From the conductance measurements, the counter ion binding constant β was calculated. Subsequently, various thermodynamic parameters viz., ΔGm, ΔHm and ΔSm were evaluated using β. The Gibbs free energy of micellization, ΔGm was observed to be −4.56 kJ mol−1, −13.34 kJ mol−1 and −18.55 kJ mol−1 for SDS, SDS + L-35 and SDS + L-35 + EY respectively. The negative values of ΔGm are indicating the spontaneous binding occurring between EY and SDS + L-35. The SEM images revealed enlargement of grain size of the mixed micelle after encapsulation of EY. To the best of our knowledge this is the first report of anionic dye EY with an anionic mixed micellar system.

Heating elements in the automotive industry are currently produced by several thermal spray processes and materials. However, simpler spraying technologies such as arc spraying are investigated regarding technological suitability as a cost-effective alternative to plasma spraying in the production process of these components. Thus, several mixtures and combinations of alternative pressurizing gases and further modifications of an arc spray process were examined in this study. Consequently, coatings based on NiCr were produced, since this alloy is typical for heating elements. Coating properties were investigated by SEM, EDS, and resistivity measurements. The results demonstrate reduced oxygen content and improved morphology compared with the industrially used plasma-sprayed coatings. Additionally, the improved microstructure affects the surface quality and specific resistivity of the coatings positively. This allowed for laser texturing the arc-sprayed coatings successfully. It must be considered a drawback, though, that cracks partially appeared in the underlying coatings. In contrast, the temperature coefficients of resistance and the resistivities of the heating elements were superior to the conventional coatings, which can lay the foundation for a future industrial application. To further investigate this and to minimize the influence of potential sample preparation issues on the analysis results, different methods of cross-sectioning, i.e., in detail hot mounting, cold mounting, and ion beam polishing, were evaluated. [ABSTRACT FROM AUTHOR]

Eddy current testing (ECT) have been widely applied for electromagnetic parameters measurement and structural health monitoring due to the advantages of non-contact and high sensitivity. However, lift-off variation affects the measurement accuracy of ECT. In this paper, a novel strategy to handle this issue has been proposed for conductivity measurement of non-magnetic materials. First of all, a simplified analytical solution is derived from classical Dodd-Deeds analytical solution. According to the simplified analytical solution, the conductivity of sample is proved to be proportional to reciprocal of the crossover frequency with phase equaling to - 3 π / 4 . Hence, the conductivity of samples can be estimated based on the characteristics. Furthermore, compared with magnitude signal of ECT, the phase feature is demonstrated minimally affected by lift-off variation from aspects of theoretical derivation. Meanwhile, we have also analyzed the relationship between size of coil and lift-off suppression capability of phase measurement through simplified analytical solution. Specifically, as coil size increases, the influence of lift-off fluctuations can be ignored on phase measurement in ECT. In order to verify the prosed strategy, the experiments involving samples with different conductivities and coils with different sizes have been carried out. The results indicate the proposed method can achieve high precise conductivity measurement and suppress the interference caused by lift-off to some extent. [ABSTRACT FROM AUTHOR]

Carbon-fiber-reinforced plastics (CFRPs) are of increasing popularity in a wide range of applications, and microwave curing promises significant reduction in processing times. However, for the design of an efficient microwave curing system, the composites' effective material parameters must be known. This work presents a measurement system using a wall perturbation approach with a coaxial cavity to determine the effective conductivity of a CFRP along the fiber direction. [ABSTRACT FROM AUTHOR]

The possibility has been explored to control the photonic Tamm resonances (TRs) in the one-dimensional microwave photonic crystal (MPC) with the dielectric filling by changing the thickness of the MPC’s outer layer adjacent to the heavily doped layer of the semiconductor GaAs structure. The controlled photonic TRs have been used to measure the conductivity of the heavily doped semiconductor layer. It has been shown that depending on the conductivity of the layer the specific tuning of the TR frequency is necessary in order to achieve a high sensitivity of the TR to the change of the conductivity. The possibility of observing the plasma resonance in the infrared range has additionally allowed to determine the concentration and mobility of free charge carriers in the heavily doped layer of the GaAs structure.

Human wrist motion decoding with a biological-signal-based interface is a key technique in the upper-limb exoskeleton and prosthesis control. One critical issue in this field is achieving high recognition precision and fast time response while against external disturbances of sensor re-wearing. In this study, we proposed a high-framerate Electrical Impedance Tomography (EIT) system combined with an adaptive recognition algorithm for real-time wrist kinematics decoding. The high-framerate EIT system was developed by a parallel stimulation-measurement sequence, and the sampling rate was as high as 104 Hz. Compared to the most widely used myoelectric techniques, the EIT-based interface can provide extra deep muscular spatial information with similar surface electrodes. It greatly benefited the subsequent recognition algorithms, in which the key EIT regions indicating muscle morphology kept consistent after an arbitrary sensor re-donning. The designed adaptive algorithm achieved equally high performance with an automatic update of the classifier mean values with a fast self-operated calibration process. We validated the approach on 12 subjects with a 2-dimensional Fitts’ law test. The wrist gestures and joint angles were mapped to the direction and speed of the cursor movement, respectively. The average throughputs (TPs) of Fitts’ law tests were 1.0269 ± 0.0971 bits/s and 1.0095 ± 0.0931 bits/s without and with sensor re-donning, respectively, which were comparable to the TPs of sEMG-based studies. The results showed the promise of the EIT-based interface on real-time human motion intent recognition. Future endeavors are worth being paid in this direction for more complicated robotic tasks. [ABSTRACT FROM AUTHOR]

In rotating machines, the approach of applying nonlinear conductive stress grading tape (SGT) has been applied to reduce the electric field stress in the coil’s overhang region. To characterize and verify the electric field grading effect of SGT in electric machines, electric field analysis using the nonlinear conductivity of SGT as a boundary condition must be considered. However, previous studies have shown limitations in the characterization and application of SGT materials in insulation system design for various reasons, such as lack of conductivity measurement standards for nonlinear materials or not considering possible changes in material properties during the manufacturing procedure. In this study, the nonlinear conductivity of SGT was measured by considering the rotating machine’s manufacturing procedure. A finite element method (FEM) electric field analysis was performed using the measured nonlinear conductivity. Based on the improved conductivity measurement method of SGT and FEM analysis, the effects of changing several insulation design parameters in the field grading performance were studied on a 13.8 kV stator coil. Moreover, the effect of preheating on the SGT conductivity was also examined. Based on analysis results, we realized the possibility of more precise insulation design of the stator coil. Our findings supplement the insufficient insulation design guide on the SGT part and contribute to establishing a systematic approach for insulation design. Furthermore, the proposed methods enable design optimization and detection of the cause of insulation failure.

In this paper we deal with a simplified anisotropic rat head phantom development and the investigation of the influence of the anisotropic white matter on electroencephalogram source localization. The proposed phantom is based on the cubic cross cell composition combined with agar mixture to set desired electrical conductivity anisotropic ratio. For the fabrication of the phantom, the 3D printed technology is exploited. Starting from a real rat brain, we proposed a simplified brain model incorporating the actual dimensions, shape and conductivity parameters of both grey and white matter containing simultaneously relevant deep-brain electrical signal sources. Five testing dipoles were located in the areas corresponding to the active brain regions. A single dipole localization error was calculated by comparing an inverse solution with a dipole position obtained from a computer tomography image. Neglecting anisotropy had a rather weak effect on localization error of a single testing dipole in our model. The reliability map was computed and interpreted in terms of spatial similarity between distributed inverse solutions involving isotropic and anisotropic forward models. We found spatially specific error increases located close to the electrodes and in the vicinity of anisotropic compartment. Hence, areas to be most sensitive to neglecting anisotropy in our model were identified.

Massive hydraulic fracturing (MHF) is currently the most effective technology used to create fracture networks with sufficient conductivity and maximize the stimulated reservoir volume (SRV) in tight oil and gas reservoirs. The newly initiated fracture networks during MHF usually exhibit complex fracture morphology and contain intersected fractures and fracture branches. The conductivity of these fractures plays a pivotal role in determining long-term productivity. Due to the complex geometry, it is difficult to accurately evaluate intersected fracture conductivity through traditional conductivity measurement methods and devices which are designed for a single primary fracture. Unlike previous studies where fracture conductivity was measured using two rock slabs under single-direction (vertical) loading, we establish a novel conductivity measurement apparatus that can mimic different fracture intersection scenarios under both vertical and transverse loading to facilitate the evaluation of intersected fracture conductivity. Based on this apparatus, a standard conductivity measurement framework for intersected fractures under biaxial compaction conditions is also proposed, and stable and reliable conductivity testing data are obtained. Sensitivity analyses are performed to find out the controlling factors of intersected fracture conductivity and the corresponding conductivity evolution law. Results indicate that the overall intersected fracture conductivity of intersected fractures can be divided into three stages, with closure pressure increasing, videlicet, the conductivity rapid reduction stage at low closure pressure, the conductivity slow reduction stage, and the conductivity stabilization stage. Higher proppant concentration results in higher conductivity. However, the conductivity differences among cases with different proppant concentration are relatively small at high closure pressure (conductivity stabilization stage). The more complex the fracture intersecting pattern is, the higher the conductivity would be. The experimental results can provide guidance for the design of proppant placement procedure for intersected fractures. [ABSTRACT FROM AUTHOR]

This article presents the comparison of the dielectric properties of three different refrigerant fluids, HFE-7100, HFC-245fa, and HFO-1336mzz(E) (R-1336E Opteon ME), the latter having a global warming potential of two orders of magnitude lower than the other two. Refrigerant fluids are used, among others, in generator circuit breaker applications where good thermal and chemical properties must be coupled with excellent dielectric strength and low electric conductivity. This article describes in detail the applied measurement techniques and the results obtained, as well as comparisons to previous measurements and literature. The comparison includes dielectric breakdown in liquid and vapor phase, dc conductivity, real permittivity, and dissipation factor. [ABSTRACT FROM AUTHOR]

Spectral dependence of the millimeter wavelength extinction due to two fibrous aerosols were measured over a frequency range spanning the primary attenuation peak. For contrast, two conductivities were selected, one representing polyacrylonitrile (PAN) graphite and the other is a metal-coated version incorporating the PAN core. Aerosol densities were measured to determine the mass-specific values of extinction. Aerosol length and diameter distributions were measured to provide parameters for comparison with theory. Both measurements and theory show a much stronger attenuation resonance for the higher conductivity material. At the resonance frequency, for which the particle length is approximately one-half the wavelength, the extinction efficiencies differ by about a factor of 3. [ABSTRACT FROM AUTHOR]

Gas diffusion layers (GDL) play multi-roles in proton exchange membrane fuel cells, including gas-water transport, thermal-electron conduction and mechanical support. Mechanical strength and transport properties are essential for GDLs. In this work, high-density (paper-type) and low density (felt-type) GDLs are scanned and reconstructed using X-ray computed tomography. Porosities under different compression ratios are compared and discussed. Effective diffusivity and liquid water permeability are calculated using pore-scale modeling and lattice Boltzmann method. Mechanical strength, anisotropic thermal-electrical resistivity for two types of GDLs are obtained using compression tests and thermal-electrical conductivity measurements. Results show that the porosity, diffusivity, permeability, and through-plane thermal-electrical conductivity of felt-type GDL are significantly higher than that of paper-type GDL owing to the higher porosity and fiber-clusters oriented along the through-plane direction. The in-plane electrical resistivity of paper-type GDL is lower than that of felt-type GDL. The mechanical strength of felt-type GDL is much lower, but the fibers of paper-type GDL are more easily to be broken because of its lower elasticity. The results obtained may guide microstructure optimization and performance improvement of GDLs. [Display omitted] • XCT, LBM and PSM are combined to compute porosity, diffusivity and permeability. • SEM and compression tests are applied to investigate the mechanical strength. • Thermal conductivity and electrical resistivity under different compression ratios are measured. • Mechanical and transport properties of two types of GDL are comprehensively compared. [ABSTRACT FROM AUTHOR]

Due to lightning strikes, electric current with high power density flows through the ground grid or driven rod of power distribution line towers to the soil, which may threaten the safety of aquatic organisms in nearby ponds. In engineering practice, there is a lack of an effective risk assessment method for aquatic organisms around earthing devices of power distribution networks under impulse current dissipation caused by lightning strikes. To solve this problem, a method to assess the safety of grass carp is proposed. First, based on a method of equivalent conduction, the conductivity of a typical grass carp is measured, and current threshold values causing different reactions in grass carp are observed and recorded. Then, the steps for risk assessment are given, with consideration given to the probability distribution characteristics of lightning current amplitude. Finally, some protective measures to reduce the threat of lightning current are given. The performances of different protection methods are analyzed based on a case in Foshan city. The results show that implementing protective measures can effectively reduce adverse reactions of grass carp in thunderstorm weather. [ABSTRACT FROM AUTHOR]

Carbon-fiber-reinforced plastics (CFRPs) are of increasing popularity in a wide range of applications, and microwave curing promises significant reduction in processing times. However, for the design of an efficient microwave curing system, the composites’ effective material parameters must be known. This work presents a measurement system using a wall perturbation approach with a coaxial cavity to determine the effective conductivity of a CFRP along the fiber direction.

Conductive glucose sensor using glucose oxidase immobilized macro porous silicon has been studied in this paper. Macro porous silicon layer is grown on p-type silicon substrate by electrochemical etching process. Two electrodes have been made with silver on front side of the macro porous silicon layer. Then the macro porous silicon surface has been functionalized for efficient glucose sensing by physisorption of glucose oxidase. Current–voltage characteristics have been studied at different glucose concentrations. Current value initially increases due to adsorption of glucose molecules upto 1 mM glucose concentration, after that current value decreases with increasing glucose concentration. Sensor response has been analysed with the help of different types of conduction mechanisms like hopping, Poole–Frenkel, trap-assisted and Fowler–Nordheim tunneling. Different conduction mechanisms are dominating at different applied field ranges. The sensor shows good response, high sensitivity and excellent repetitive behavior. [ABSTRACT FROM AUTHOR]

The article presents an analysis of the influence of temperature on the electrical conductivity of composite polyacrylonitrile-polyaniline fibers (PAN/PANI). The fibers are obtained by synthesizing polyaniline directly in the spinning solution of fiber-forming polyacrylonitrile and characterized by X-Ray Diffraction (XRD), Differential Scanning Calorimetry (DSC), Scanning Electron Microscopy (SEM) methods. Electrical characterization of fibers is performed by current-voltage characteristic. The polarizing voltage of the electrodes in the range from -1 V to 1 V with a speed of 100 mV/sec is changed cyclically and linearly while simultaneously the current is measured. The current-voltage characteristic of the fibers is recorded at various temperatures in the range from -15 °C to 100 °C for 30 min. Based on the measurements, temperature changes in the conductance are determined in constant relative humidity. The current-voltage characteristics of the fibers in the ambient atmosphere with a relative humidity of 38 % are linear and symmetrical, which indicates the electron nature of the conductivity and the ohmic contact of the electrode-fiber. The characteristic of temperature conductance changes is not of a typical shape, it is parabolic. The conductance of the developed PAN/PANI fibers at 22 °C is about $1.50\cdot 10^{\mathrm {-4 { }}}\text{S}$ (6.7 $\text{k}\Omega$ ) and decreases below and above this temperature. The analysis of research results and literature data enables the determination of individual factors affecting changes in conductance of the tested composite fiber.

In this paper, the transport properties of discontinuous 4 nm copper layers obtained by dual-source non-reactive magnetron sputtering in the presence of argon are presented. The value of resistance and capacitance of the current parallel to the plane of these layers can be adjusted independently by changing the nominal thickness of the metallization. The influence of frequency on the conductivity of the obtained structures in the range from 4 Hz to 8 MHz was studied. Additionally, in order to compare the non-oxidized and oxidized layers, some of them were heated at 500 °C. Based on the results obtained, the mechanism of electric charge transfer was determined, the knowledge of which is essential for planning further experiments based on this sputtering method and potential selection of future application of the structures. Statistical measurements at room temperature will serve as a reference for the conductivity and resistivity values obtained by mathematical calculations from measurements of resistance, capacitance, phase shift angle, and dielectric loss tangent as a function of temperature from 20 K to 375 K, which are expected in further studies on the obtained structures. The work is an introduction to the technology of obtaining multi-layer metal-dielectric structures.

Polymers derived from nickel complexes of salicylaldimines are extensively studied due to their electrochemical, catalytic, and sensing properties. However, almost all studies are devoted to the polymers obtained from tetradentate bis(salicylidenaldiminato) complexes, in which the aromatic rings are bound via an imine bridge. Herein, we report a first systematic study focused on the polymerization of salicylaldimine nickel complexes without a bridge between the imine fragments. As a result, an impact of the ligand structure on the polymerization ability of the complexes and electrochemical behavior of the polymers obtained thereof was discovered and quantified. An observed phenomenon was rationalized both computationally and experimentally, involving the electrochemical and spectroelectrochemical techniques. [ABSTRACT FROM AUTHOR]

Milk adulteration by various impurities, such as water, whey, and urea, and some other harmful chemicals is an important issue in different countries in the world. Traditionally, analytical instruments are used for milk quality analysis. These instruments are accurate but these are complex, expensive, inconvenient for field use, and require laborious skilled procedures to get the reading. Portable sensors-based instruments working on direct/indirect transduction phenomena are also reported in the literature. Most commonly, the conductive sensors with selective sensing films are used for detecting the milk impurities but such sensors require calibration and show drift due to aging. There is a need to develop a rapid, accurate, sensitive, and cost-effective simple working detection system. This article presents the theory, design, fabrication, and test results of an accurate and simple working prototype model of an ac cross-conductance sensor for milk adulteration detection. The structure of the sensor has four conductive brass electrodes, arranged in the form of a concentric cylinder, with narrow gaps among them. The sensor was fabricated and tested in the laboratory environment to analyze the quality of 1) drinking water having different total dissolved solids (TDS) and 2) milk having different amounts of impurities, such as water, whey, and urea. The sensor can differentiate between pure and adulterated milk with significant resolution and precision. [ABSTRACT FROM AUTHOR]

This article presents a model-based eddy current (EC) testing method for the reconstruction of geometrical features, that may be hidden, through, or blind cavity in a large electrically conductive plate. Based on a distributed current source (DCS) modeling method, a perturbation model is formulated to convert the feature reconstruction problem into finding a possibility vector using a finite set of measured magnetic flux density (MFD) data and solved with the Tikhonov regularization method. The proposed method is numerically and experimentally validated and demonstrated by using the specimens with compound conductive/nonconductive geometrical features and comparing them with two published feature detection methods. Parametric studies are conducted to analyze the effects of feature shape, sensor configuration, and multi-coil excitation on reconstruction accuracy. [ABSTRACT FROM AUTHOR]

Paracetamol (PCM) is one of the most commonly employed drugs for the treatment of fever and pain. The activity of the drug is dependent on the excipients utilized during formulation as well as on physiological conditions. Herein, the conductivity measurements are implied to deduce the possible molecular interactions occurring between sodium dodecyl sulfate (SDS) and PCM in the presence of ZnSO4 at various temperatures. The critical micelle concentration (cmc) of SDS was found to be lowered with the augmentation of PCM concentration. The cmc values of the SDS + PCM mixture were found to be reduced with the increase of temperature and concentration of ZnSO4. The counterion binding values were found to be temperature and additives dependent. The estimated values of free energies of micellization ( Δ G m o ) signify the spontaneous aggregation of SDS + PCM mixture in all media studied. The spontaneity of self-assembly for SDS + PCM mixture augmented at a higher temperature. The estimated values of enthalpy of micellization ( Δ H m o ) and entropy of micellization ( Δ S m o ) were positive throughout. The values of Δ H m o and Δ S m o exhibit excellent linearity. The values of different transfer energies, intrinsic enthalpies, and compensation temperature were also calculated and explained properly. [ABSTRACT FROM AUTHOR]

This article presents a novel method for measuring the electrical conductivity of metallic materials using a cylindrical resonator. The theory and the process of measuring the electrical conductivity are explained. The cylindrical resonator is designed and proved using full-wave electromagnetic simulations. A prototype operating at 10.5 GHz is fabricated, and the scattering parameters are measured. The quality factor of the cylindrical resonator is calculated at the first step from the measured scattering parameters, and the electrical conductivity of the metallic material is derived using Maxwell's equations. By replacing the top cover of the cylindrical resonator with different materials or metallic sheets, the electrical conductivities can be measured easily. For validating the method, three top covers and six metallic sheets are fabricated and tested. The measured electrical conductivities are compared with other published results and typical values. Besides, by adjusting the operating frequency of the cylindrical resonator, the proposed method can be applied to determine the electrical conductivity at specific frequencies. [ABSTRACT FROM AUTHOR]

A study on the interaction of a fourth-generation antibiotic drug, moxifloxacin hydrochloride (MFH), with a cationic surfactant, such as cetyltrimethylammonium bromide (CTAB) in the aqueous solution of alcohol (1-propanol (1-PrOH)) and polyols (galactose/maltose), has been carried out using the conductivity measurement technique. The critical micelle concentration (cmc), micelle ionisation (α), counter ion binding (β), and thermodynamic properties ( Δ G m 0 , Δ H m 0 , and Δ S m 0 ) for the self-aggregation of MFH + CTAB mixture have been estimated in 1-PrOH/polyols solutions. The presence of 1-PrOH delays the MFH + CTAB micelle formation, whereas polyols create a congenial environment for the micelle formation. In 1-PrOH, the values of α experience a reduction with the increase of 1-PrOH concentration and temperature. The values of α were found to be dependent on the concentration of other additives. In all of the cases thoroughly studied, the values of Δ G m 0 were found negative, which experience an enhancement in polyols solutions and decreased in 1-PrOH solution. On the basis of Δ H m 0 and Δ S m 0 values, the suggested interaction forces between MFH and surfactant are hydrophobic, ion-dipole, and electrostatic in nature. The values of Δ H m 0 , ∗ reveal that the micelle is more stable in polyols media than that of the 1-PrOH medium. [ABSTRACT FROM AUTHOR]

Abstract Background Total hemoglobin (tHb) measurement is indispensable for determining the patient’s condition (hemorrhagic vs. ischemic) and need for blood transfusion. Conductivity- and absorbance-based measurement methods are used for blood gas analysis of tHb. For conductivity-based measurement, tHb is calculated after converting blood conductivity into a hematocrit value, whereas absorbance measurement is based on light absorbance after red blood cell hemolysis. Due to changes in plasma electrolytes and hemolysis, there is a possibility that conductivity- and absorbance-based measurement methods may cause a difference in tHb. Methods In this study, test samples with controlled electrolyte changes and hemolysis were created by adding sodium chloride, distilled water or hemolytic blood to blood samples collected from healthy volunteers, and tHb values were compared between both methods. Results Conductivity-based measurement revealed reduced tHb value (from 15.49 to 13.05 g/dl) following the addition of 10% sodium chloride, which was also reduced by the addition of hemolysate. Conversely, the addition of distilled water significantly increased tHb value than the expected value. In the absorbance method, there was no significant change in tHb value due to electrolyte change or hemolysis. Conclusions We have to recognize unexpected conductivity changes occur at all times when tHb is measured via conductivity- and absorbance-based measurement methods. The absorbance method should be used when measuring tHb in patients with expected blood conductivity changes. However, when using this method, the added contribution of hemoglobin from hemolytic erythrocytes lacking oxygen carrying capacity must be considered. We recognize that discrepancy can occur between conductivity- and absorbance-based measurement methods when tHb is measured.

This study investigated the frequency properties of an air-cored coil and applied it to inspect conductivity change. Theoretical analysis and experimental study showed that what we measured is not the coil's own resistance and inductance but the equivalent ones which change with frequency. Case studies on conductivity measurement using a coil probe showed that we can greatly enhance measurement sensitivity by making the best of the coil's frequency properties. By utilizing the coil at frequencies that the coil's resistance and inductance are `frequency-invariant', we were able to detect conductivity change with high sensitivity on the basis of `same product of conductivity and frequency, ωσ(product of angular frequency and conductivity), same impedance' principle. The study also showed that we can use the coil's resonant properties, e.g., resonant frequency, resistance at resonant, to sense conductivity change, regardless of change on thickness. A slight variation of conductivity could be perceived by fine frequency adjustment. The results strongly suggest using a coil in accordance with its frequency characteristics.

The inconsistent response to transcranial electric stimulation in the stroke population is attributed to, among other factors, unknown effects of stroke lesion conductivity on stimulation strength at the targeted brain areas. Volume conduction models are promising tools to determine optimal stimulation settings. However, stroke lesion conductivity is often not considered in these models as a source of inter-subject variability. The goal of this study is to propose a method that combines MRI, EEG, and transcranial stimulation to estimate the conductivity of cortical stroke lesions experimentally. In this simulation study, lesion conductivity was estimated from scalp potentials during transcranial electric stimulation in 12 chronic stroke patients. To do so, first, we determined the stimulation configuration where scalp potentials are maximally affected by the lesion. Then, we calculated scalp potentials in a model with a fixed lesion conductivity and a model with a randomly assigned conductivity. To estimate the lesion conductivity, we minimized the error between the two models by varying the conductivity in the second model. Finally, to reflect realistic experimental conditions, we test the effect rotation of measurement electrode orientation and the effect of the number of electrodes used. We found that the algorithm converged to the correct lesion conductivity value when noise on the electrode positions was absent for all lesions. Conductivity estimation error was below 5% with realistic electrode coregistration errors of 0.1° for lesions larger than 50 ml. Higher lesion conductivities and lesion volumes were associated with smaller estimation errors. In conclusion, this method can experimentally estimate stroke lesion conductivity, improving the accuracy of volume conductor models of stroke patients and potentially leading to more effective transcranial electric stimulation configurations for this population. [ABSTRACT FROM AUTHOR]

One of the most attractive types of novel nonvolatile memory concepts is resistive random access memory (ReRAM) based on a reversible (“soft”) dielectric breakdown effect. The interest is caused by combining simple architecture with promising performance: excellent scalability, nanosecond speed, long data retention, and low power consumption. However, the commercialization of this type of memory is retarded mainly due to serious drawbacks: high cell-to-cell variability of switching parameters and limited endurance related to the ionic origin of resistive switching effect coupled with the problem of voltage overshooting. In particular, these issues complicate the examination of test samples because during the lifespan of memory cells, and the permanent reselection of test switching parameters is required. This challenge can be overcome by developing a measurement technique that combines careful testing of every single structure and the ability to test a large number of test structures. As such a technique, we propose an automated testing algorithm that automatically avoids voltage overshooting and provides an effective way of characterization of cell-to-cell and cycle-to-cycle variability. It includes all stages of ReRAM cell operation, specifically electroforming, dc switching, and endurance testing in the pulsed mode. The developed technique allows on-the-fly restoring of the memory window in case of its degradation, making it possible to better understand the potential of the material stacks of the memory cell. [ABSTRACT FROM AUTHOR]

A new series of metal complexes were prepared by refluxing nickel chloride with hot methanolic solution mixture of 8-Hydroxyquinoline and Schiff bases(L1-L6). Schiff base ligands were synthesised by the condensation of 4-aminopheno, 4-aminosalicylic acid, 2-aminobenzthiazole with salicylaldehyde and vanillin. The metal complexes have been characterised by gravimetric metal analysis, magnetic moment, conductivity measurement, 1HNMR and IR analysis. [ABSTRACT FROM AUTHOR]

The basic principle of a noncontact method of measurement of conductivity of liquids, presented earlier, is analysed to evolve design rules to have minimal error in the measurement. In this method, the current is sent through the liquid whose conductivity is to be measured by induction and the voltage across the liquid column is measured using capacitive coupled electrodes and the conductivity computed therefrom. Hence, problems that arise due to contamination or corrosion of contacting electrodes are eliminated. The signal conditioning circuit is developed such that the measurement of the voltage-drop across the column of the liquid and hence the determination of the conductivity of the liquids unaffected by the coupling capacitances of the potential electrodes. Thus, small deviations that can creep in during manufacturing of the probe (manufacturing tolerances) do not affect the performance. An error analysis of the proposed system was carried out and the practicality of the scheme verified by developing and testing a prototype. The test results showed a worst-case error of 0.82% in conductivity measurements. The facts that the proposed method is unaffected by the coupling capacitors and the presence of materials kept outside of the probe were also verified. [ABSTRACT FROM AUTHOR]

This article compares two different techniques to assess the oil quality of new and aged transformers. It is shown that laboratory tan δ tests and measurements with a portable IEG 61620 square wave method result in comparable diagnostic classifications. [ABSTRACT FROM AUTHOR]

The inconsistent response to transcranial electric stimulation in the stroke population is attributed to, among other factors, unknown effects of stroke lesion conductivity on stimulation strength at the targeted brain areas. Volume conduction models are promising tools to determine optimal stimulation settings. However, stroke lesion conductivity is often not considered in these models as a source of inter-subject variability. The goal of this study is to propose a method that combines MRI, EEG, and transcranial stimulation to estimate the conductivity of cortical stroke lesions experimentally. In this simulation study, lesion conductivity was estimated from scalp potentials during transcranial electric stimulation in 12 chronic stroke patients. To do so, first, we determined the stimulation configuration where scalp potentials are maximally affected by the lesion. Then, we calculated scalp potentials in a model with a fixed lesion conductivity and a model with a randomly assigned conductivity. To estimate the lesion conductivity, we minimized the error between the two models by varying the conductivity in the second model. Finally, to reflect realistic experimental conditions, we test the effect rotation of measurement electrode orientation and the effect of the number of electrodes used. We found that the algorithm converged to the correct lesion conductivity value when noise on the electrode positions was absent for all lesions. Conductivity estimation error was below 5% with realistic electrode coregistration errors of 0.1° for lesions larger than 50 ml. Higher lesion conductivities and lesion volumes were associated with smaller estimation errors. In conclusion, this method can experimentally estimate stroke lesion conductivity, improving the accuracy of volume conductor models of stroke patients and potentially leading to more effective transcranial electric stimulation configurations for this population.

Massive hydraulic fracturing (MHF) is currently the most effective technology used to create fracture networks with sufficient conductivity and maximize the stimulated reservoir volume (SRV) in tight oil and gas reservoirs. The newly initiated fracture networks during MHF usually exhibit complex fracture morphology and contain intersected fractures and fracture branches. The conductivity of these fractures plays a pivotal role in determining long-term productivity. Due to the complex geometry, it is difficult to accurately evaluate intersected fracture conductivity through traditional conductivity measurement methods and devices which are designed for a single primary fracture. Unlike previous studies where fracture conductivity was measured using two rock slabs under single-direction (vertical) loading, we establish a novel conductivity measurement apparatus that can mimic different fracture intersection scenarios under both vertical and transverse loading to facilitate the evaluation of intersected fracture conductivity. Based on this apparatus, a standard conductivity measurement framework for intersected fractures under biaxial compaction conditions is also proposed, and stable and reliable conductivity testing data are obtained. Sensitivity analyses are performed to find out the controlling factors of intersected fracture conductivity and the corresponding conductivity evolution law. Results indicate that the overall intersected fracture conductivity of intersected fractures can be divided into three stages, with closure pressure increasing, videlicet, the conductivity rapid reduction stage at low closure pressure, the conductivity slow reduction stage, and the conductivity stabilization stage. Higher proppant concentration results in higher conductivity. However, the conductivity differences among cases with different proppant concentration are relatively small at high closure pressure (conductivity stabilization stage). The more complex the fracture intersecting pattern is, the higher the conductivity would be. The experimental results can provide guidance for the design of proppant placement procedure for intersected fractures.

This paper discusses an artificial neural inversion approach for non-destructive testing of the graphite moderator bricks that make up the cores of Advanced Gas-Cooled Reactors (AGR). The study employed fully connected feedforward neural networks consisting of four hidden layers and trained with backpropagation approach using Levenberg-Marquardt optimisation algorithm. The approach is based on multi-frequency (MF) eddy current (EC) measurements, and combinations of simulated and measured datasets from a laboratory sample and one of the operating reactor core, along with different regularisation parameters were used to train and test the networks. Various types of artificially generated errors were added to the data during training procedures, which in turn allowed for error tolerance and improved the generalisation of the ANNs to unseen test datasets. First, the ANN was tested using unseen simulated data, followed by the measurements collected from laboratory sample and one of the operating reactor core. The first test from the unseen simulated data showed mean profile error ranging between 1.30% and 8.20%, whereas the profiles estimated from reactor core measurements showed mean profile error ranging between 1.84% and 17.80% when compared with the resistivity measurements from trepanned graphite sample taken out of the reactor core. Further comparison of the network outputs against the profiles estimated using traditional iterative inversion algorithm indicates reasonable agreement between the two approaches with the exception of one case, but the solution time for the ANN was found to be over three orders of magnitude faster than the iterative inversion algorithm. [ABSTRACT FROM AUTHOR]

Electrolytic conductivity (EC) sensors are widely used in diverse industries, including: pharmaceuticals, food, power, manufacturing, and environmental monitoring. This article presents an overview and analysis of EC sensors used in these industries from the lowest to the highest range of conductivities and in applications, where there are strong requirements for accurate and traceable conductivity measurements of water and electrolyte solutions. Included are reported sensor designs based on two- and four-electrodes with parallel plates, coaxial cylinders, van der Pauw configurations, planar and miniature configurations, and contactless inductive or capacitive coupling. A comprehensive list of exact analytical formulas for computation of cell constants for the configurations is provided. The advantages and disadvantages of using frequency domain or time domain measurement schemes in these sensors are discussed, and the reader is guided to select the suitable method of sensor calibration among the methods available, computing uncertainty budgets, ensuring traceability to the International System of Units (SI) and compliance with standards, such as Pharmacopeias. Finally, trends in the development of EC sensors and the related challenges in relation to calibration and compliance with standards are presented. This article also introduces the reader to the EC cell of a sensor, which can be modeled by solving the Poisson–Nernst–Planck equations or using appropriate equivalent circuit diagrams. It is stepwise described how the models can be extended to include effects such as electrode polarization and steric effects of ions, and it is illustrated by means of an ideal EC cell, where guards eliminate fringe fields, that the simplest equivalent circuit with a single resistor and a single capacitor models electrolytic sensor data very well in the lower range of electrolytic conductivities. [ABSTRACT FROM AUTHOR]

Additive manufacturing (AM) or 3-D printing of concrete allows for construction of arbitrary shape structures without a mold. Since reproducibility of 3-D printed concrete is lower than that of conventional fabrication, each 3-D printed structure should be monitored for proper curing. Conventional qualification of concrete is based on several tests, including destructive compressive strength measurements. Because a structure is 3-D printed layer-by-layer, the surfaces of AM concrete structures have significant surface roughness. This limits the applicability of conventional nondestructive testing methods. We investigated qualification of 3-D printed mortar by monitoring curing with nondestructive electrical conductivity measurements. Bulk resistance of concrete was extracted from electrochemical impedance spectroscopy (EIS) measurements made using custom flexible self-adhesive electrodes, which contour to rough surfaces. We show that bulk resistivity of concrete increases linearly with time. This allows for developing a calibration curve for compressive strength lookup from nondestructive electrical conductivity measurements. Conductivity measurements also allow for estimation of formation factor, which is an indicator of mortar permeability. [ABSTRACT FROM AUTHOR]

In this article, we present a simple and low-cost experimental setup for thermoelectric effect measurements of thin film materials near room temperature, which can be used to determine their conductivity types. Bi2Te3 and Sb2Te3 thin films grown by the molecular beam epitaxy technique were used as the tested samples. Their Seebeck coefficients were determined to be $(-141\pm 1)\,{\mathrm{\mu V/K}}$ and $(39\pm 2)\,{\mathrm{\mu V/K}}$ , respectively, confirming that the former is an n-type material and the latter is a p-type material. A heterostructure composed of Sb2Te3 and Bi2Te3 was characterized by electrical transport measurements. Data fitting was carried out for its current–voltage characteristics with the Shockley diode model and a real diode model proposed by Cataldo et al., and some physical parameters of the heterostructure were extracted, including its ideality factor and saturation current. Based on its rectifying current–voltage behavior, we confirm that the aforementioned heterostructure is a p-n junction, which echoes the contrast in the conductivity types of Sb2Te3 and Bi2Te3 as determined by the thermoelectric effect measurements. [ABSTRACT FROM AUTHOR]

In this study, a new method for gas holdup measurement in water continuous oil-gas-water multiphase flow based on conductance sensors is proposed. This method includes the use of the combined conductance sensors and the establishment of gas holdup model. A cross-sectional type conductance sensor is applied to acquire the conductivity of oil-gas-water mixture. For the purpose to derive gas holdup from the mixture conductivity, a novel liquid conductivity sensor which has shallow detection depth is proposed and it is flush-mounted on the inner wall of pipe to detect the liquid conductivity. The performances of the cross-sectional type conductance sensor combined with the liquid conductivity sensor are evaluated by experiments. And the results indicate that the liquid conductivity sensor can online detect the liquid conductivity in the multiphase mixture effectively. Based on the measured conductivity of multiphase mixture and the conductivity of liquid, the normalized conductivity which is related to the gas holdup is defined. The gas holdup model based on flow structures is investigated and established, and finally the measurement of gas holdup independently of salinity in oil-gas-water multiphase flow based on the conductance method is achieved for the first time. [ABSTRACT FROM AUTHOR]

Objective: Tissue electroporation is achieved by applying a series of electric pulses to destabilize cell membranes within the target tissue. The treatment volume is dictated by the electric field distribution, which depends on the pulse parameters and tissue type and can be readily predicted using numerical methods. These models require the relevant tissue properties to be known beforehand. This study aims to quantify electrical and thermal properties for three different tissue types relevant to current clinical electroporation. Methods: Pancreatic, brain, and liver tissue were harvested from pigs, then treated with IRE pulses in a parallel-plate configuration. Resulting current and temperature readings were used to calculate the conductivity and its temperature dependence for each tissue type. Finally, a computational model was constructed to examine the impact of differences between tissue types. Results: Baseline conductivity values (mean 0.11, 0.14, and 0.12 S/m) and temperature coefficients of conductivity (mean 2.0, 2.3, and 1.2 % per degree Celsius) were calculated for pancreas, brain, and liver, respectively. The accompanying computational models suggest field distribution and thermal damage volumes are dependent on tissue type. Conclusion: The three tissue types show similar electrical and thermal responses to IRE, though brain tissue exhibits the greatest differences. The results also show that tissue type plays a role in the expected ablation and thermal damage volumes. Significance: The conductivity and its changes due to heating are expected to have a marked impact on the ablation volume. Incorporating these tissue properties aids in the prediction and optimization of electroporation-based therapies. [ABSTRACT FROM AUTHOR]

Recently, there has been significant research focus on the design of high functional density electronic systems, especially for 5G applications. In parallel, to address accurate, high-quality, fine-resolution circuit geometry requirements, increased research into additive manufacturing (AM) printing techniques, such as aerosol jet printing (AJP), has emerged. The issues are complicated by low-loss flexible substrates, such as liquid crystal polymers (LCPs), which are commonly used in the design of high-frequency circuits and systems. These substrates cannot be taken through high sintering temperature processes that are commonly required for silver inks. To avoid permanent damage, it is essential that the sintering temperature remains below the glass transition temperature (${\text{T}}_{g}$) of the substrates. Recent work on LCP substrates has demonstrated 10%–20% bulk silver (Ag) conductivity by using low-temperature thermal sintering techniques. This article investigates the use of a rapid ultraviolet (UV) flash annealing technique to achieve high conductivity of Ag on LCP for use in high-frequency circuits while maintaining the integrity of the substrate. Results are compared against thermally sintered films. The resulting conductivity was studied as a function of UV exposure time and energy, printed film thickness, surface roughness of the substrate, and multilayer deposition. [ABSTRACT FROM AUTHOR]

Shape-driven approaches have been proposed as an effective strategy for the electrical impedance tomography (EIT) reconstruction problem in recent years. In order to augment the shape-driven approaches, we propose a new method that transforms the shape to be reconstructed as basic primitives directly modeled by using Fourier representations. To allow automatic topological changes between the basic primitives and surrounding objects simultaneously, Boolean operations are employed. The Boolean operations with direct representation of primitives can be utilized for dimensionality and ill-posedness reduction, enabling feasible shape and topology optimization with shape-driven approaches. As a proof of principle, we leverage the proposed method for two dimensional shape reconstruction in EIT with various conductivity distributions. We demonstrate that our method is able to improve EIT reconstructions by enabling accurate shape and topology optimization. [ABSTRACT FROM AUTHOR]

We propose a broadband conductivity measurement method in the millimeter-wave bands using a balanced-type circular disk resonator (BCDR). Because of the unique feature of the BCDR’s mode selective behavior over a wide band, the proposed technique can provide broadband conductivity measurements from less than 20 GHz up to over 100 GHz with a single closed-type resonator utilizing higher order mode resonances. We consider three measurement scenarios for the proposed BCDR-based broadband conductivity measurements. First, we discuss the absolute measurements of copper conductivity and then consider the relative conductivity measurements for metallic disks with reference to copper conductivity obtained in the first scenario. Finally, the second scenario is extended to the interface conductivity measurements of copper-clad substrates. The proposed measurement scenarios are demonstrated both numerically and experimentally in the millimeter-wave bands with uncertainty evaluations. The proposed technique can contribute to the development of advanced materials and implementation processes of planar circuits for various millimeter-wave applications, including 5G and 6G. [ABSTRACT FROM AUTHOR]

In this article, we present anisotropic conductivity measurements by using two kinds of multimode rectangular cavities. Plate-laminated waveguides are fabricated by diffusion bonding of etched thin metal plates and their sidewalls have anisotropic conductivity characteristics. The anisotropic conductivity is measured by two multimode rectangular cavities when polarization is vertical or horizontal to the lamination direction. Transmission characteristics of the cavities are measured and the conductivity is calculated by the measured resonant frequencies and unloaded quality factors. The anisotropic conductivities are derived by solving a linear equation. As an example, aluminum alloy (A6063) E-band (60.5–91.9 GHz) rectangular cavities are fabricated and the conductivity is characterized. [ABSTRACT FROM AUTHOR]

An analytical formula for the electromagnetic field generated by a current-carrying cylindrical coil above a half-infinite conductive plate has been studied. The theoretical analysis showed that when the radius of the coil was much larger than the penetration depth, the electromagnetic wave at the plate surface could be approximated as a plane wave, and the real part of the plane wave impedance would not be affected by lift-off changes. Using normalized plane wave impedances as theoretical values and normalized coil impedances measured by swept-frequency eddy current technique as experimental values, a novel approach is proposed to rapidly and simultaneously solve the coating thickness, coating conductivity and substrate conductivity of a conductive plate with ultra-thin metallic coatings by Levenberg−Marquardt algorithm. The experimental results show that the maximum relative measurement errors of the proposed method for single- and double-coated plates are less than 8% and 18%, respectively, and the measurement time is less than 1 s, which is suitable for fast parameter detection. [ABSTRACT FROM AUTHOR]

This work proposes a novel shape-driven reconstruction approach for difference electrical impedance tomography (EIT). In the proposed approach, the reconstruction problem is formulated as a shape reconstruction problem and solved via an explicit and geometrical methodology, where the geometry of the embedded inclusions is represented by a shape and topology description function (STDF). To incorporate more geometry and prior information directly into the reconstruction and to provide better flexibility in the solution process, the concept of a moving morphable component (MMC) is applied here implying that MMC is treated as the basic building block of the embedded inclusions. Simulations, phantom studies, and in vivo pig data are used to test the proposed approach for the most popular biomedical application of EIT – lung imaging – and the performance is compared with the conventional linear approach. In addition, the modality’s robustness is studied in cases where (i) modeling errors are caused by inhomogeneity in the background conductivity, and (ii) uncertainties in the contact impedances and reference state are present. The results of this work indicate that the proposed approach is tolerant to modeling errors and is fairly robust to typical EIT uncertainties, producing greatly improved image quality compared to the conventional linear approach. [ABSTRACT FROM AUTHOR]

The appearance of Tamm resonances in forbidden bands of 1-D microwave photonic crystal with dielectric filling adjacent to monolithic metal nanolayer or to a nanolayer in the form of parallel metal strips has been investigated. The reflection and transmission coefficients in the microwave range were calculated using the transfer matrix method and the finite element method in the ANSYS HFSS software. The experimental data confirmed the calculation results and demonstrated the appearance of Tamm resonances in the $X$ -band at certain thicknesses and electrical conductivities of metal nanolayers. It has been established that the amplitude in the antinodes of the standing electromagnetic wave at the Tamm resonance frequency in the first forbidden band increases monotonically with the distance from the depth of the photonic crystal to its boundary with conducting layer almost linearly. At the frequency of Tamm resonances in the higher-order forbidden bands the amplitude increases stepwise. The method for measuring the electrical conductivity of metal nanolayers contacting the photonic crystal has been theoretically justified and experimentally confirmed. The measurement technique is based on the fitting procedure to minimize by the least squares method the difference between the experimental and calculated frequency dependences of the reflection and transmission coefficients in the vicinity of the Tamm resonance. [ABSTRACT FROM AUTHOR]

The flashover performance of contaminated insulators highly depends on the type of pollutant and its present concentration. In this paper, important agricultural salts (NaCl, K2SO4, NaHCO3, CaSO4, KHCO3, MgSO4, NH4), 2Fe(SO4)2, and 6H2O (ferrous ammonium sulphate, dust, and urea) at different concentrations, and biological contaminants, such as algae and fungi, were taken as pollutants, and the AC flashover behavior of a porcelain-cap-and-pin-type insulator polluted with these two different pollutants was investigated. The experiment was carried out by a semi-natural method, wherein the insulator was first polluted artificially; thereafter, natural fog was applied to measure the wet flashover voltage. Test results indicated that the flashover voltages were affected by both soluble salts and non-soluble components deposited on the insulator surface. In the case of the thickly contaminated layers, non-soluble deposits greatly reduced the flashover voltage. Moreover, by using regression analysis, four empirical models based on different variables were developed. The empirical models developed in the present work represented a good degree of relation in predicting the flashover voltage of naturally contaminated insulators.

Herein, the conductivity measurement technique is used to determine the interactions that may occur between polyvinyl pyrrolidone (PVP) polymer and cetylpyridinium chloride (CPC) surfactant in the presence of NaCl and Na2SO4 of fixed concentration at variable temperatures (298.15–323.15 K) with an interval of 5 K. In the absence or presence of salts, we observed three critical micelle concentrations (CMC) for the CPC + PVP mixture. In all situations, CMC1 values of CPC + PVP system were found to be higher in water than in attendance of salts (NaCl and Na2SO4). Temperature and additives have the tendency to affect counterion binding values. Various physico-chemical parameters were analyzed and demonstrated smoothly, including free energy (ΔG0m), enthalpy (ΔH0m) and entropy change (ΔS0m). The micellization process is achieved to be spontaneous based on the obtained negative ΔG0m values. The linearity of the ΔHmo and ΔSmo values is excellent. The intrinsic enthalpy gain (ΔH0*m) and compensation temperature (Tc) were calculated and discussed with logical points. Interactions of polymer hydrophobic chains or the polymer + surfactant associated with amphiphilic surface-active drugs can employ a strong impact on the behavior of the gels.

Conductivity is an important parameter which has definite correlation with the amount of moisture present within the transformer insulation. However, in existing methods conductivity is usually estimated from time domain (PDC) measurement, which is inadvertently noise prone and time consuming. Considering this issue, in this article presents a novel technique for conductivity estimation for moisture sensing of oil-paper insulation using frequency domain spectroscopy measurement (FDS). To this end, FDS measurement of oil-paper insulation was performed from 50mHz to 1kHz to obtain the imaginary complex permittivity $\varepsilon ''$ ($\omega$), which is a function of conductivity ($\sigma$) as well as imaginary complex susceptibility $\chi ''$ ($\omega$). From the knowledge of frequency variation of both $\sigma $ and $\chi ''$ ($\omega$), we developed an electrical equivalent model of the insulation. The equivalent model parameters were optimized until $\varepsilon ''$ ($\omega$) computed from the proposed model and that obtained from original FDS measurement were almost identical. The conductivity values obtained from the equivalent model showed good agreement when compared with PDC measurement. To validate the practicability of the proposed method, experiments were conducted on various test samples and also on a few real life transformers. Most importantly, the measurement time was found to be reduced by 78.5%, enabling diagnosis of transformer insulation at a significantly reduced time. [ABSTRACT FROM AUTHOR]