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Renewable energy generation is a manifestation of global economic and societal advancement and serves as a fundamental assurance for humanity's pursuit of sustainable development. However, recent years have witnessed several instances of high-frequency resonance events in high-voltage direct current (HVDC) transmission systems based on modular multilevel converters (MMC), which have resulted in converter station tripping and significant repercussions on the alternating current (AC) grid. This paper addresses the mid-to-high frequency resonance issues prevalent in flexible DC transmission systems employing modular multilevel converters (MMC-HVDC). To tackle these concerns, an impedance model for MMC's AC side is established. Utilizing impedance analysis, the essential factors contributing to the negative damping characteristics of MMC are identified as delay and voltage feedforward loops, predominantly causing negative damping in the frequency range exceeding 400 Hz. In response, a suppression strategy is proposed, involving the incorporation of a multi-band stop filter and virtual impedance. This strategy ensures that within the 0–2000 Hz frequency range, only the impedance phase within 230–430 Hz slightly surpasses 90°. Consequently, the phase difference between MMC's positive-sequence impedance and the AC system impedance is reduced from 222° to 174.7°, thus guaranteeing secure grid operation. Lastly, the accuracy and effectiveness of the theoretical analysis and suppression methodology are verified through the development of an electromagnetic transient model in MATLAB/Simulink, considering delay fluctuations of ±10%. [ABSTRACT FROM AUTHOR]

Sr1−xCaxFe12−xGdxO19 (x = 0, 0.04, 0.08, 0.12, 0.16, 0.20) hexaferrites were characterized by several techniques, such as X‐ray diffraction, scanning electron microscopy (SEM), energy‐dispersive X‐ray spectroscopy, and vibrating sample magnetometer. Structural results indicate the formation of a pure‐phase Sr1−xCaxFe12−xGdxO19 hexaferrite with space group P63/mmc. SEM photography confirms that there are a smaller number of defects due to the reduced porosity and surface area (increased particle size). Magnetic investigations showed a rise of the coercive force from 5069.8 to 5757.4 Oe and saturation magnetization from 79.25 to 80.68 emu/g. The maximum values appear to be for sample x = 0.16, which may be useful in such as permanent magnets, and high‐density media for magnetic storage devices. Dielectric parameters, such as conductivity, the real part of permittivity, dielectric loss, dielectric tangent loss, and complex modulus, were studied. Impedance analysis shows that the conduction process is mainly governed by the long‐range movement of the charge carriers based on the Debye model for x = 0.12. [ABSTRACT FROM AUTHOR]

Ethylene carbonate (EC) based plasticized solid polymer electrolyte (PSPE) systems have been prepared with PEO (polyethylene oxide) and PVdF (polyvinylidene fluoride) as copolymers, sodium nitrate as a salt by using solution casting technique. In this investigation the wt% of PEO, PVdF, NaNO3 maintain constant and EC wt% varies. The addition of small concentration of EC to PSPE systems facilitates fast ion conduction through it. As a result, the effective number of charge carriers mobility within the polymer matrix. The maximum conductivity has been observed for PPNE-5 system at ambient temperature. The characteristic studies (XRD, FTIR, SEM and DSC) have been carried out for all the systems. The electrical, dielectrical and complex impedance spectroscopic properties have been studied by using an impedance analyzer. Wagner’s polarization method has been used for the investigation of ion transference number. [ABSTRACT FROM AUTHOR]

Cupric-oxide-based thin films with various amounts of 0, 1, 2, 3, and 4 wt.% Ni doping were, in turn, deposited on ITO/glass substrates via a solution process. The 0.25 M concentrated solutions of copper (II) acetate monohydrate and nickel acetate tetrahydrate were used as starting materials mixed in ethanol solvent, in order to form the precursors. We obtained that the crystalline structure was not affected by the increase in Ni doping concentration as evidenced by X-ray diffraction patterns. The surface morphology observed by scanning electron microscope pointed out the presence of linked-structure nanoparticles. The influence of Ni doping on the optical bandgap width was evaluated by using ultravioletvisible spectrometry. We found that the optical bandgap should be direct, and it decreased from 2.69 to 2.38 eV for the range doped. Interestingly, we determined the relaxation time of the Ni-doped CuO/ITO/glass structure from measuring the electrochemical impedance spectroscopy, and it was 0.36 s for the undoped film, then gradually decreased to be 0.31, 0.11, 0.1, and 0.04 s with increasing the Ni doping concentration. This achievement result will serve as a foundation for the future photonic researches. [ABSTRACT FROM AUTHOR]

Silicon carbide fibers (SiC f) are promising materials for high-temperature applications, because of their excellent thermal and mechanical properties. Due to the inevitable oxidation of SiC f used at high-temperature, the surface and interfacial properties of SiC f can be changed. Impedance analysis is necessary to confirm the useful information for various properties. However, since single SiC f has a long length and a very small cross-section area, its capacitance is so small that impedance analysis is almost impossible. In this study, an in-situ analysis tool that can estimate the impedance of SiC f to confirm the resistance elements is proposed using bundled fiber specimens. It is confirmed that it is possible to measure the impedance of the SiC f under high-temperature and oxidation atmospheres by controlling the aspect ratio of the specimen. This tool provides a new pathway that can be applied in various systems by investigating the electrical properties according to the oxidation behavior. [ABSTRACT FROM AUTHOR]

In this work, novel nanocomposites (NCs) were fabricated via in situ-chemical oxidative polymerization process. For the purpose of examining their physical and chemical properties, the synthesized samples were examined utilizing a variety of analytical techniques. XRD, TEM, SEM, electrical and dielectric studies confirm the presence of copolymer P(Py-co-OT) and reveal that MFe2O4@P(Py-co-OT)NCs exhibited a core–shell structure. The Poly (Pyrrole-co-o-toluidine) possessed the highest activation energy and the lowest conductivity. Moreover, the incorporation of MFe2O4 into copolymer enhances the conductivity. Impedance analysis emphasizes the contribution of grain boundaries on transport properties. A relationship between the polarization effect and the dielectric behavior was found. An enhancement on the dielectric constant εʹ and the dielectric loss ε″ was noticed with the embedding of spinel ferrites into copolymer. Results obtained suggest that this binary material has a promise for use in energy conversion applications. [ABSTRACT FROM AUTHOR]

The study examines the effects of metal salt doping on polyethylene oxide (PEO) solid polymer electrolyte films. Sodium Bromide (NaBr) doped PEO films are prepared using a solution casting technique. The study finds that Na+ rom NaBr interacts with PEO's ether group (C–O–C) through complexation, as confirmed by Fourier Transform Infrared (FTIR) Spectroscopy. X‐ray diffraction analysis reveals that NaBr reduces PEO's degree of crystallinity. The addition of NaBr improves PEO's thermal stability, as shown by thermogravimetric analysis (TGA). Scanning electron microscopy (SEM) images show smooth surface morphology of the polymer electrolyte films. The study also finds that the polymer electrolytes are non‐Debye in nature, based on dielectric studies. The highest ionic conductivity of 1.01 × 10−5 S/cm is observed for the 12.5 wt% NaBr doped PEO, with a low activation energy of 0.246 eV. Wagner's polarization technique is used to determine the charge carrier transport numbers, and the transient ionic current technique confirmed the presence of a single ionic species in the polymer electrolyte. Overall, the study suggests that 12.5 wt% NaBr doped PEO films have appropriate electrical properties for developing charge storage devices. [ABSTRACT FROM AUTHOR]

This study aims at the application of the prepared Polymer Nanocomposite in the field of solid-state optoelectronic devices. Polymer Nanocomposite was prepared by incorporating iron nanoparticles, synthesized random Copolyester (BCTP), and Polypyrrole by Insitu chemical polymerization method. The application of the synthesized random Copolyester with wide biological activity due to bis chalcone moiety can also be extended to the optoelectronics field. The Copolyester (BCTP) was subjected to spectral analysis such as Fourier Transform Infrared Spectroscopy (FTIR) to confirm the chemical structural orientation. The Iron nanoparticles, Polypyrrole, and polymer nanocomposite were characterized by Fourier Transform Infrared Spectroscopy (FTIR) and powder X-ray Diffraction (PXRD). The FTIR spectroscopy confirms the formation of polymer nanocomposite by the prominent shift in stretching frequency from the starting materials taken. Powder X-ray Diffraction was used to determine the Iron Nanoparticles' average crystallite size. The structural morphology of iron nanoparticles, Polypyrrole, and polymer nanocomposite were identified by Scanning electron Microscopy. The SEM images gave the view of Iron nanoparticles, Polypyrrole was seated in the Polymer matrix. The specific capacitance for the newly synthesized Polymer Nanocomposite was found to be 58.88 F/g by Cyclic Voltammetric analysis. The electrochemical behavior of the random copolyester (BCPT), Iron nanoparticles, Polypyrrole, and polymer nanocomposite was carried out by Impedance analysis. This confirms the Polymer Nanocomposites were conducting nature with good ionic conductance of 6.89 x 10-5 S cm-1. [ABSTRACT FROM AUTHOR]

Influence of manganese incorporation on structural, optical and electrical properties of cadmium sulfide (CdS) is presented in this work. Pure and different percentages of Mn-doped CdS thin films were synthesized via chemical bath deposition technique on microscope glass slide substrate. Rietveld refined X-ray diffraction (XRD) revealed the fabrication of cubic mono-phase CdS. Increase in grain size from ~ 12.17 to ~ 18.08 nm and decrease in average microstrain with increasing doping percentage of Mn were confirmed from XRD analysis. Doping was further found to reduce the value of optical bandgap. Electrical conductivity and dielectric properties were investigated using complex impedance spectroscopy technique. Impedance analysis shows enhancement of conductivity with increasing incorporation of manganese ion. Cole–Cole plot ensured the contribution of grain and grain boundary toward total resistance and capacitance value of the synthesized films. [ABSTRACT FROM AUTHOR]

The electrical impedance analysis of the ZnO films has been performed using complex impedance spectroscopy in the frequency range from 100 Hz to 1 MHz with temperature change from 70 to 175°C. Combined impedance and modulus plots have been used to analyse the sample behaviour as a function of frequency at different temperatures. Temperature dependence of ac conductivity indicates that the electrical conduction in the material is a thermally activated process. The frequency dependence of the ac conduction activation energy is found to obey a mathematical formula. It is concluded that the conductivity mechanism in the ZnO sensor is controlled by surface reaction. The operating temperature of the ZnO gas sensor is 175°C. The impedance spectrum also exhibited a decreased semicircle radius as the ammonia concentration is increased from 50 to 500 ppm. In addition, the impedance spectrum also exhibited a decreased semicircle radius with the exposure time increase from 0 to 20 min thereafter slightly increased. Impedance spectroscopy analysis has shown that the resistance variation due to grain boundaries significantly contributed to the gas sensor characteristics. [ABSTRACT FROM AUTHOR]

The fast slew rates of wide bandgap semiconductors can produce common-mode currents that flow through the baseplates of multi-chip power modules. These currents increase the electromagnetic signature of these devices and force designers to reduce edge rates or add additional filters in order to meet compliance standards. Parasitic baseplate capacitances that exist within power module packaging are known to be a primary path for the flow of these common-mode currents. Unfortunately, the measurement techniques currently available to characterize these capacitances are either challenging to perform or require the internal interconnects to be removed. This paper proposes a simple and non-destructive measurement technique to characterize the baseplate capacitances of multi-chip power modules on a per-terminal basis. The technique can be performed with an impedance analyzer and does not require any special fixturing or alterations to the module. The measurement technique described in this paper is applied to three fully populated commercial modules and is validated by comparisons to the standard destructive measurement technique and finite-element analysis simulation software.

Fast and very fast transient overvoltages generally appear during switching operations within electrical substations. The oscillatory nature of such phenomena with frequencies that can reach several tens of megahertz tends to degrade the lifetime of high voltage equipment such as bushings and transformers, inducing partial discharges activity or breakdown of the insulation system. According to several case studies, bushings are one of the most sensitive parts to such overvoltages, indeed, a failure in a bushing will in most cases lead to a failure of the transformer, often catastrophically. Generating such overvoltages with a very high frequency character and considerable amplitude can be very difficult, moreover, studying the effect of such overvoltages on the insulated bushings is not easy, even experimentally. Therefore, a simulation of the fast transients in the system can be very useful to understand the consequences of such phenomena. In this context, this document aims to propose a model of high voltage capacitive graded oil impregnated paper (OIP) bushing based on a distributed electrical circuit. The equivalent circuit is constructed based on the geometric design and electrical properties of the materials. The model was developed and implemented using Matlab/SimulinkⓇ software, and was validated with experimental measurements based on impedance sweep frequency analysis. The modeling results are in a good agreement with the experimental ones.

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This study employs a simple and cost-effective technique to enhance the photoelectrochemical (PEC) water-splitting performance of melamine cyanaurate microrods (M), SnO2 nanostructures (S), and melamine cyanaurate microrods decorated with SnO2 quantum dots (MS) by optimizing NaOH and Na2SO3 electrolytes. Notably, the MS electrode demonstrates a remarkable improvement in PEC efficiency in Na2SO3 solution associated with NaOH solution. Specifically, the induced currents of the MS anode in the Na2SO3 electrolyte are approximately 6.28 mAcm−2 more than those observed in the NaOH electrolyte solution. It is revealed that SO32− anions effectively consume the holes, leading to improved separation of the generated charge pairs. This effective charge separation mechanism significantly contributes to the enhanced PEC performance observed in Na2SO3 electrolytes. The findings of this study suggest a capable approach for improving the PEC activity of the materials through the careful optimization of the supported electrolytes.

Blend polymer electrolytes have been produced with the use of poly (vinylidene fluoride) (PVDF)and Poly (vinylpyrrolidone) (PVP) mixed with NaClO4 by the method of solution cast technique. Characteristics of the Fourier transform infrared spectroscopy(FTIR), X-ray diffraction (XRD), and scanning electron microscopy are studied to authorize the complexation of sodium perchlorate salt with blend systems. AC and DC conductivity studies are carried out for all blend systems by changing PVP wt%, and PVDF wt% at fixed 4 weight percentage of NaClO4. Impedance spectroscopy has been used to examine the nonconducting (Dielectric) properties, and electric modulus (M*) from 10Hz to 30 MHz between 298 K and 343 K for all the systems. The maximum ionic conductivity is noticed for PVDF: PVP-NaClO4 (20:80-4) system at room temperature, that could be due to decrease in the crystalline nature and enlargement of amorphous region. The variation of ionic conductivity of the blend polymer electrolyte systems with temperature followed Arrhenius behaviour and the maximum ionic conductivity 4.332x10-5 S cm-1 was observed for PP-4 System at room temperature. [ABSTRACT FROM AUTHOR]

Aluminum doped cobalt ferrite nanoparticles(CoFe2–xAlxO4(x = 0.0 and 0.5)) were synthesized by wet chemical co-precipitation method. X-ray diffraction pattern confirmed the successful doping of the smaller cation of Al3+ and the single-phase cubic spinel structure of the prepared nanoparticles. The crystallite size of nanoparticles was examined ~25 nmusing X-ray diffraction data.The lattice parameter 'a ' also decreased by doping the Al3+cation. Two functional groups and fundamental peaks of calcined samples were identified byFourier-transform infrared spectroscopy in the range of 450–600 cm−1, these characteristic absorption bandsconfirmed the cubic spinel structure of prepared nanoparticles. Field emission electron microscopy images confirm the formation of nearly spherical ferrite nanoparticles with an average size ~25–30 nm that is in good agreement with XRD results. Magnetic hysteresis study at room temperature confirmed the ferrimagnetic nature of the prepared samples and the decrease in saturation magnetization (MS = 74–44 emu/g) and reduction in coercivity (HC = 627.8–539.4 Oe) due to doping the Al3+cation. Improved values of dielectric constant, low dielectric loss and resistivity were displayed by Al3+cation doped ferrite nanoparticles and has been measured at room temperature for frequency dependence in the range of 100 Hz–10 MHz using impedance analyzer. It is revealed strong dependence of dielectric parameters on frequency and Al3+ ion content. Doping the Al3+ cation was increasing the values of dielectric constant and dielectric loss for (CoFe2–xAlxO4(x = 0.0 and 0.5)) while decreases the electrical resistance of prepared nanoparticle. results explored the capability of the Al doped cobalt ferrite to be suitable for high frequency applications and magnetic memory devices. Highlights: Aluminum Cobalt ferrite nanoparticles are prepared by co precipitation method using sodium hydroxide as reactant agent. Crystal size of the prepared nanoparticles is calculated by the XRD data ~25 nm and confirmed by FESEM spectroscopy techniques. Magnetic hysteresis study confirmed the ferrimagnetic nature of Aluminum Cobalt ferrite nano particles. Impedance spectroscopy analysis indicates the material to be suitable for memory device applications. [ABSTRACT FROM AUTHOR]

[Display omitted] • Tune Synthesis of Graphene oxide. • Annealing of Graphene Oxide with different temperature. • Optimizing Dielectric and Electrical Properties of Graphene Oxide Thin Film. • Cole-Cole plot and Nyquist plot at different temperatures. • Insulator to semiconductor transition. The study focused on exploring the impact of annealing temperatures on dielectric and electrical, and conductivity properties of Graphene Oxide (GO) thin films. The investigation involved measuring impedance spectra across a temperature range spanning from room temperature (T=300 K) to high temperature (T=560 K). The findings revealed intriguing trends in the behavior of GO thin films under varying annealing temperatures. Firstly, it was observed that the dielectric constant of the GO thin film exhibited an upward trend with increasing temperature within the specified range. This indicates a temperature-dependent response in the dielectric properties of the material. Secondly, the electrical conductance of the film was found to be influenced by both frequency and annealing temperature. Specifically, the AC conductance showcased semiconductor behavior across a broad temperature spectrum, with a notable increase in conductance as the annealing temperature rose. This suggests a correlation between electrical properties and the annealing temperature of the GO thin film. Furthermore, the impedance analysis of the GO films revealed distinct relaxation processes at different temperatures, indicating varying dynamics within the material under thermal conditions. Additionally, the study highlighted a direct relationship between dielectric behavior and factors such as dielectric loss, polarization effects, and enhancements in the dielectric constant. These findings underscore the intricate interplay between thermal treatment, dielectric properties, and conductivity in GO thin films. Hence, the research elucidates the complex nature of GO thin films' electrical, dielectric, and conductivity characteristics under annealing temperature variations, shedding light on potential applications and further avenues for exploration in this field. [ABSTRACT FROM AUTHOR]

PVC gel actuator possesses the advantages including low driving voltage, substantial deformation, and high output force, making it ideal for applications in micro-lenses, assistive rehabilitation, and soft robotics. However, there remains a lack of in-situ characterization and quantitative analysis of plasticizer migration and charge transfer within PVC gel, resulting in an unclear understanding of changes in the plasticizer content, mechanical and electrical properties of the enrichment layer. In this study, we conducted in-situ characterization of plasticizer migration and charge transfer within PVC gel, and analyzed the change of plasticizer content, mechanical and electrical properties. In-situ Raman spectroscopy results revealed that plasticizer migration takes time to reach equilibrium, resulting in a gradient distribution of plasticizer content within the enrichment layer. Furthermore, in-situ broadband impedance analysis demonstrated that stimulation voltage induces changes in the material's electrical properties, transitioning from uniform electrical characteristics to distinct properties between the gel layer and the enrichment layer. Notably, we established a mathematical relationship between modulus and plasticizer content, revealing a gradient distribution of modulus within the enrichment layer. This study not only contributes to understanding the underlying mechanisms of mechanical and electrical properties variations within PVC gel, but also provides valuable insights for optimizing the actuation performance of PVC gel actuators. [Display omitted] • Plasticizer migration of PVC gel at stimulation is quantitatively characterized. • Voltage and plasticizer content are proportional to migration equilibrium time. • Plasticizer content and modulus exhibit gradients across thickness direction. • PVC gel layer and enrichment layer differed significantly in electrical properties. [ABSTRACT FROM AUTHOR]

This paper details the successful fabrication of Cu-doped TiO 2 nanostructures using a co-precipitation method. A thorough analysis of the structural and electrical characteristics of the nanostructure samples was carried out. It was found that all synthesized samples exhibited an anatase TiO 2 structure. The XRD pattern indicated an average crystalline size of 23.19 nm for Cu-doped TiO 2 nanostructures, whereas TiO 2 nanostructures showed a size of 11.78 nm. The UV-Visible spectrum indicated a noticeable absorption band shift towards longer wavelengths, coupled with an increased absorption rate of light. Analysis of electrical conductivity showcased temperature-dependent variations in conductivity at high frequencies. Impedance spectroscopy unveiled improved conductivity upon the integration of Cu into TiO 2 nanostructures. Nonetheless, at 300 K, copper doping resulted in a decline in electrical conductivity, whereas at elevated temperatures, Cu doping showed a increase in conductivity for the nanostructures samples. These findings underscore the potential and applicability of the nanostructures, showcasing improved AC conductivity and electrical characteristics, making them promising for various electrical applications. • Simple co-precipitation method were applied to synthesize Cu doped TiO 2 nanoparticles. • The XRD models show that weak X-ray reflections from Cu doped TiO 2 nanoparticles confirm the presence of the TiO 2 phase. • The average diameter of Cu doped TiO 2 nanoparticles between 12 and 25 nm. • The optical gap of Cu doped TiO 2 nanoparticles is estimated at around 3.3 eV. • Electrical conductivity analysis demonstrated temperature-dependent changes in conductivity at high frequencies. [ABSTRACT FROM AUTHOR]

• LiNbO 3 crystal fibers were obtained by Laser Heated Pedestal Growth (LHPG) technique. • Resonance method was validated through numerical simulations with COMSOL software. • LiNbO 3 crystal fibers could be employed as piezoelectric temperature sensor. This study focuses on the growth and characterization of crystalline LiNbO 3 (LN) piezoelectric fibers pulled by the Laser Heated Pedestal Growth (LHPG) technique. The electrical properties of the fibers were investigated using an impedance analyzer, which yielded values for resonance frequency, anti-resonance frequency, and phase angle. Subsequently, elastic constants and coupling factor were determined through calculations based on thickness resonance modes. The accuracy of the resonance method was validated through numerical simulations utilizing COMSOL software, demonstrating a close agreement between experimental and simulated results. Additionally, a temperature sensing was conducted, subjecting the fibers to a wide temperature range from 30 °C to 236 °C to assess their sensitivity to temperature variations. The coupling factors of K = 0.37 for LN-1 and K = 0.35 for LN-2 demonstrated efficient performance of the crystalline fibers. Furthermore, the numerical simulations exhibited strong correlation between simulated and experimental data. The sensitivity analysis revealed the potential of LN fibers for temperature sensor applications, exhibiting a sensitivity of −87 Hz.°C−1. These findings underscore the promise of LN piezoelectric fibers in advanced sensing technologies. [ABSTRACT FROM AUTHOR]

The ongoing digitalization of processes and products in mechanical engineering is accompanied by an increasing demand for data. In order to provide this data, technical systems are being extended with sensory functions. To supply those sensory functions on rotating elements—such as shafts—with electrical energy, and to be able to transmit signals out of the system, sliding contacts can be used as a cost-effective and established solution. However, if electrical properties of machine elements are utilized for sensing purposes, such as condition monitoring of rolling element bearings by means of impedance measurement, sliding contacts are directly in the measurement path and can thus influence the measured impedance. The aim of this paper is to analyze the impedance of graphite and silver graphite carbon brushes under different rotational speeds, in different positions, and with different carrier frequencies. The material of the carbon brushes as well as the position have significant effects on the impedance behavior. Furthermore, carbon brushes show a significant running-in behavior. The results are discussed, and indications for use in impedance measurements are given. Silver graphite carbon brushes in axial positioning are particularly suitable for impedance measurements of sensory utilizable machine elements. Sufficient running-in time must be considered.

Alumina nanofiller of 20 nm size has been dispersed with different weight percentages in succinonitrile (SN) plasticized PEO/PVdF/KNO3/SN polymer electrolyte system, and the samples have been prepared by solution cast. The ionic conductivity, dielectric properties are studied using impedance spectroscopy from 1 Hz to 10 MHz at various temperatures. The dielectric response of the samples is examined through dielectric constant (ε'), dielectric loss (ε''), modulus (M' and M'') and relaxation time (τ). The thermal properties of composite polymer electrolytes dispersed with nano alumina are changed remarkably. The ionic conductivity of composite polymer electrolytes has been enhanced by one order of magnitude with the addition of nanofiller, and the maximum ionic conductivity (0.207 × 10−3 S cm−1) is noticed for 2 wt% of Al2O3. The rise in conductivity is attributed to an increase in dissociation of ions and creation of a large number of free conducting paths for ion movement by the addition of nano-sized Al2O3.

OBJECTIVE:Characteristic impedance (Zc) is an important component in the theory of hemodynamics. It is a commonly used metric of proximal arterial stiffness and pulse wave velocity. Calculated using simultaneously measured dynamic pressure and flow data, estimates of characteristic impedance can be obtained using methods based on frequency or time domain analysis. Applications of these methods under different physiological and pathological conditions in species with different body sizes and heart rates show that the two approaches do not always agree. In this study, we have investigated the discrepancies between frequency and time domain estimates accounting for uncertainties associated with experimental processes and physiological conditions. APPROACH:We have used published data measured in different species including humans, dogs, and mice to investigate: (a) the effects of time delay and signal noise in the pressure-flow data, (b) uncertainties about the blood flow conditions, (c) periodicity of the cardiac cycle versus the breathing cycle, on the frequency and time domain estimates of Zc, and (d) if discrepancies observed under different hemodynamic conditions can be eliminated. Main results and Significance: We have shown that the frequency and time domain estimates are not equally sensitive to certain characteristics of hemodynamic signals including phase lag between pressure and flow, signal to noise ratio and the end of systole retrograde flow. The discrepancies between two types of estimates are inherent due to their intrinsically different mathematical expressions and therefore it is impossible to define a criterion to resolve such discrepancies. Considering the interpretation and role of Zc as an important hemodynamic parameter, we suggest that the frequency and time domain estimates should be further assessed as two different hemodynamic parameters in a future study.

In the present work, the Sr(Fe0.5Nb0.5)1-xMnxO3 powders were synthesized via a molten salt technique. Pure phase perovskite was obtained at 800 °C which was very low compared to previous works prepared by solid state reaction technique (> 1200 °C). XRD analysis for the Sr(Fe0.5Nb0.5)1-xMnxO3 ceramics revealed that the unit cell had an orthorhombic symmetry. Examination of dielectric measurement showed that all ceramic samples exhibited very high dielectric constants (εr,max > 200,000 at 1 kHz). The dielectric data showed that all ceramics exhibited a relaxor like behavior. Loss tangent value tended to decrease with increasing Mn, especially at low temperature range. The obtained loss tangent values were found to be lower than those reported in previous works. Impedance spectroscopy analysis revealed that the relaxor like behavior could be related with bulk grain, grain boundaries and electrode responses, where the samples had a heterogeneous conduction. Type of electrode and applied voltage had strong effects on the dielectric behavior. [ABSTRACT FROM AUTHOR]

Background: Pancreatic cancer has an increasing incidence and prevalence trend. Its prognosis is negatively affected by poor/altered nutritional status. Therefore, nutritional interventions play a critical/pivotal role at any stage. Despite being included in the prehabilitation items of Enhanced Recovery After Surgery (ERAS) protocols for pancreatic surgery, nutritional recommendations concerning early post-discharge period are lacking. Aim: To assess the acceptability and feasibility of a personalized and standardized food plan for patients following pancreatic surgery. A secondary aim is to determine if adherence to a personalized food plan is linked to improved postoperative outcomes. Methods: A prospective monocentric cohort study will be performed, including 180 patients undergoing pancreatic surgery. Body composition, nutritional, muscular, and hydro-electrolyte status will be assessed with bio-impedance analysis (BIA). Patients will receive a personalized nutritional plan after discharge for the following 45 days. Summary: Detailed nutritional indications have been formulated with broad consensus for the pre-operative (prehabilitation) and postoperative period. No previous study has specifically formulated or validated a nutritional intervention focused on the early post-discharge period. The results of this study might contribute to paving the way for future research and to broaden nutritional recommendations within the ERAS protocol., Competing Interests: Declaration of conflicting interestsThe authors declared no potential conflicts of interest with respect to the research, authorship, and/or publication of this article.

As an attempt to pave the way for developing the lithium polymer batteries, (PVA/PVP) blend filled with different weight percentages of lithium perchlorate (LiClO4) was prepared using solution casting technique. Morphological and microstructural properties of the SPE were studied via SEM, XRD and FT-IR spectroscopy, where its semicrystalline nature was confirmed. Thermal stability, dielectric properties, the relaxation dynamics inside the current system and electrical conduction behavior of the synthesized films were prudently studied. The electrical conduction mechanism inside the samples was interpreted using the Jonscher's double power law. Activation energy was calculated using Coats-Redfern and Broido models. The oblate semicircular arc observed in Nyquist curves indicated the non-Debye behavior of ions relaxation in the present SPE samples. This behavior was assured by the evident decrease in intensity of the M'' relaxation peak. The complex impedance analysis not only verified the dominance of the resistive nature over the capacitance but also demonstrated that the conduction in the SPE was only produced by the induced ions. Mixing LiClO4 filler at 8 wt.% with the PVA/PVP host matrix had a fruitful effect on amelioration in the structural, thermal and dielectric properties of the prepared composite sample. This beneficial enhancement recommends the (PVA/PVP)/LiClO4 composite to be used in fabricating lithium polymer batteries and energy storage devices with high performance.

Bioimpedance analysis is a label-free and easy approach to obtain information on cellular barrier integrity and cell viability more broadly. In this work, we introduce a small, low-cost, portable in vitro impedance measurement system for studies where a shadow-free exposure of the cells is a requirement. It can be controlled by a user-friendly web interface and can perform measurements automated and autonomously at short intervals. The system can be integrated into an existing IoT network for remote monitoring and indepth analyses. A single-board computer (SBC) serves as the central unit, to control, analyze, store and forward the measurement data from the single-chip impedance analyzer. Various materials and manufacturing methods were used to produce a purpose-built lid on top of a modified 24-well microtiter plate in a “do it yourself” fashion. Furthermore, three different sensor designs were developed utilizing anodic aluminum oxide (AAO) membranes and gold-plated electrodes. Preliminary tests with potassium chloride (KCl) showed first promising results.

This paper highlights the development of graphene nanoplatelets polyvinyl alcohol(GNP@PVA) nanocomposite electrode to acquire real time Electrocardiogram(ECG) signal. In order to create GNP@PVA nanocomposite, solution casting was used. By drop casting the GNP@PVA nanocomposite onto a commercial silver/silver chloride (Ag/AgCl) electrode with different GNP concentrations, namely 0, 0.5, 0.75, and 1 wt/wt% are created. The 3-lead ECG system is designed using Arduino microcontroller, GNP@PVA electrode and AD8232 sensor. To investigate the physical, spectral, and microcrystalline characteristics of the prepared nanocomposites, the prepared GNP@PVA electrode is subjected to various analyses, including scanning electron microscope (SEM) analysis, X-ray diffraction (XRD), Fourier Transform Infrared Spectroscopy (FTIR) and Raman spectroscopy. The results demonstrated that ECG signals acquired by GNP@PVA (1%) has increased R peak value along with high sensitivity. To validate the performance and efficiency of designed GNP@PVA electrode, the acquired real time ECG signal is compared with commercial Ag/AgCl electrode. In contrast to commercial Ag/AgCl electrode, the designed GNP@PVA dry electrode has high signal to noise ratio of 21 due to high conductivity.

The use of piezoelectric transducers for internal dynamic pressure measurements in ammunition testing provides a significant advantage in the development and performance analysis of weapons and ammunition. Knowledge of the electrical characteristics of the dynamic pressure measurement chain, which includes the piezoelectric transducer and the charge amplifier, is a relevant condition for the design of interior ballistics pressure measurement systems. Thus, this study aims to characterize and model a piezoelectric transducer and its associated charge amplifier. First, the piezoelectric transducer was characterized using impedance analysis and modeled using a least squares curve-fitting tool, according to the Butterworth–Van Dyke model. Next, the charge amplifier was characterized through response analysis based on known inputs and modeled using LTSpice simulation techniques and the least squares curve-fit tool. Consequently, a measurement chain model is presented and simulated for two cases with different impulse signals. The first impulse signal was obtained from an interior ballistics computer simulation, and in the second case, it was considered the negative step signal characteristic of the calibration of piezoelectric transducers by means of dead weight. From the simulations, it was possible to verify the effectiveness of the model, which provided results with a low error in relation to the original pressure curve, and its applicability is demonstrated by the result of the simulation of the pressure variation in the calibration, where the attenuation of the signal can be visualized as the characteristic of the input curve changes.

This work investigates an electrochemical impedance analysis based on synthesized TiO2 nanofibers (NFs) photoanodes, which were fabricated via electrospinning and calcination. The investigated photoanode substrate NFs were studied in terms of physicochemical tools to investigate their morphological character, crystallinity, and chemical contents via scanning electron microscope (SEM), X-ray photoelectron spectroscopy (XPS), and X-ray diffraction (XRD) analyses. As a result, the studied photoanode substrate NFs were applied to fabricate dye-sensitized solar cells (DSCs), and the electrochemical impedance analysis (EIS) was studied in terms of equivalent circuit fitting and impacts of N-doping, the latter of which was approved via XPS analysis. N-doping has a considerable role in the enhancement of charge transfers, which could be due to the strong interactions between active-site N atoms and the used photosensitizer. [ABSTRACT FROM AUTHOR]

The rare combination of ferroelectricity, low band gap and high carrier mobility in a material can facilitate exceptional photovoltaic efficiency. In this paper, we attempted to reduce the band gap and improve the conductivity of ferroelectric solid solution BiY (1-x) Mn x O 3 by varying composition. The BiY (1-x) Mn x O 3 (x = 0.0, 0.10, 0.25, 0.50, 0.75) samples were prepared by high energy ball milling method and structural, dielectric, optical, electrical and ferroelectric properties were analyzed systematically. Herein, we show that band gap of the material is drastically reduced from 3.0 eV (BiYO 3) to 1.76 eV (x = 0.50) and the samples exhibit ferroelectric behavior with significant polarization. Compound resistance of grain and grain boundaries were also found to reduce with increase in Mn concentration in the BiY (1-x) Mn x O 3 solid solution, demonstrating improvement in semiconducting behaviour of the material. Thus, solid solution formation of BiMnO 3 with BiYO 3 , tunes band gap in useful region, improves electrical conduction and enhances ferroelectric polarization showing good potential for high performance solar cell and thermoelectric applications. [ABSTRACT FROM AUTHOR]

The polyvinylidene fluoride (PVDF)-0.05Ba0.8Sr0.2TiO3 (BST) nanocomposite (0.05 is the fractional weight of BST) facile thick films of thickness ~100 μm have been synthesized by tape-casting. The synthesized films are exposed to an electric field of 22 kV/mm (for different time durations, 0 min, 40 min, 50 min, and 60 min) to investigate the electric field-induced effects on dielectric and structural properties of nanocomposite thick films. Structural studies have shown that the electric field increases the β phase of PVDF in PVDF-BST nanocomposites. The most prominent effect of the applied electric field is observed in the dielectric behavior of the nanocomposite thick films. The film exposed to the electric field for 60 min has the highest dielectric constant (~25) and very low tangent loss (~0.02) at 1 kHz, whereas the unexposed film of nanocomposite has a dielectric constant of ~15 and tangent loss (~0.03). The approximated Debye relaxation theory has been used to understand the correlation between dielectric and structural observations. Analysis confirms the duration of exposure to the electric field enhances the β-phase, which causes the increase in the density of dipoles. The enhanced dielectric performance is attributed to the increased dipolar density due to modification in the structural and interfacial behavior as well as molecular motion of the dipoles in the polymeric chain. [ABSTRACT FROM AUTHOR]

The attention to a stable and ionic conductive electrolyte is driven by the limitations of liquid electrolytes, particularly evaporation and leakage, which restrain their widespread use for electrochemical device applications. Solid polymer electrolyte (SPE) is considered to be a potential alternative since it possesses high safety compared to its counterparts. However, it still suffers from low device efficiency due to an incomplete understanding of the mechanism of ion transport parameters. Here, we present a simple in situ solution casting method for the production of polymer-based electrolytes using abundantly available methylcellulose (MC) doped at different weight percentages of potassium thiocyanate (KSCN) salt. Fourier transform infrared (FTIR), and electrochemical impedance spectroscopy (EIS) methods were used to characterize the prepared samples. Based on EIS simulation and FTIR deconvolution associated with the SCN anion peak, various ion transport parameters were determined. The host MC medium and KSCN salt have a strong interaction, which was evident from both peak shifting and intensity alteration of FTIR spectra. From the EIS modeling, desired electric circuits correlated with ion movement and chain polarization were drawn. The highest ionic conductivity of 1.54 × 10−7 S cm−1 is determined from the fitted EIS curve for the film doped with 30 wt.% of KSCN salt. From the FTIR deconvoluted peak, free ions, ions in contact with one another, and ion aggregates were separated. The extracted ion transport parameters from the EIS method and FTIR spectra of the SCN anion band confirm that both increased carrier concentration and their mobility were crucial in improving the overall conductivity of the electrolyte. The dielectric investigations were further used to understand the conductivity of the films. High dielectric constants were observed at low frequencies for all MC:KSCN systems. The dispersion with a high dielectric constant in the low-frequency band is ascribed to the dielectric polarization. The wide shift of M″ peak towards the high frequency was evidenced by the MC-based electrolyte impregnated with 30 wt.% of KSCN salt, revealing the improved ionic movement assisted with chain segmental motion. The AC conductivity pattern was influenced by salt concentration. [ABSTRACT FROM AUTHOR]

Differing from a two-level voltage source converter (TL-VSC), the internal dynamics of a modular multilevel converter (MMC) are much more complicated. Since the fluctuation of submodule capacitor voltage is unavoidable when transmitting power, the MMCs output voltages cannot track the references perfectly. The interaction between the time-varying capacitor dynamics and controllers may lead to self-instability of the MMCs. In order to address this self-instability issue, this paper first establishes the small-signal closed loop transfer function matrices (TFMs) of the external and internal control loop by the harmonic linearization method. Further, a novel design principle of MMC controllers is proposed. Then, the critical impact factors on the stability of circulating current controller and AC voltage controller are investigated based on the generalized Nyquist criterion(GNC). The proposed models and analysis methods are validated by time-domain simulations in PSCAD/EMTDC. [ABSTRACT FROM AUTHOR]

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Polyaniline-WO3 nanocomposite was synthesized through in-situ chemical polymerization. The structural properties are studied by using XRD and FESEM characterization. The XRD results confirmed the presence of crystalline WO3 nanoparticles in the polymer nanocomposite structure. FESEM images confirmed the sheet-like structure with heterojunction of WO3 nanoparticles and polyaniline matrix. The transport properties of the synthesized nanocomposites are studied using impedance spectroscopy analysis. The complex impedance analysis conducted using the Nyquist plot and equivalent circuit model of the nanocomposites are simulated using ZSimpWin software. The major conduction mechanism in the material is found to be grain boundary effect and the grain boundary conduction parameters are calculated. The polyaniline-WO3 nanocomposite with WO3 doping concentration of 15% has exhibited better sensing characteristics towards the target VOC (Volatile Organic Compound) 3-Carene, a breath-based biomarker for malaria. The memristor sensor model of the polyaniline nanocomposite with 15% of WO3 is simulated using MATLAB-Simulink. The pinched hysteresis loop obtained confirmed the memristor properties of the material. [ABSTRACT FROM AUTHOR]

Oil condition monitoring is an important way to achieve mechanical equipment health assessment, condition early warning, fault diagnosis, and intelligent maintenance. A microsensor integrated with inductance-resistance and capacitance sensing units is presented, which can comprehensively detect metal debris, air bubbles, and moisture in oil based on impedance analysis. The inductance-resistance sensing unit not only detects traditional inductance parameter, but also proposes a resistance detection method based on coil to further improve the detection sensitivity for nonferromagnetic metal debris. The capacitance sensing unit can detect air bubbles, and a new moisture measurement method is also proposed. Based on the signal characteristics of inductance, resistance and capacitance detection results, the microsensor can effectively distinguish 16–500 μm iron debris, 60–500 μm copper debris, >170 μm air bubbles and moisture in oil. The ultrasensitive microsensor can obtain more oil status information, which has important value and wide engineering application prospect for modern fault diagnosis and prediction theory based on information fusion. [ABSTRACT FROM AUTHOR]

This research presents a straightforward and cost-effective sensor design for the detection of harmful chemical adulterants in raw milk, with a focus on formaldehyde, a common preservative. The proposed sensor design involves a minimal sample volume of 4 ml and utilizes a low-cost assembly with two nickel electrodes within a plastic cuvette. Electrochemical Impedance Spectroscopy (EIS) was conducted with an LCR meter to record three key electrical parameters: impedance (Z), phase angle (θ), and parallel plate capacitance (C p). Testing was conducted in a controlled laboratory environment at temperatures between 25 to 27 °C for both unadulterated and adulterated milk samples. The results reveal that Z is the most sensitive parameter, capable of detecting formaldehyde adulteration as low as 0.5%. Conversely, θ and C p effectively detected adulteration levels exceeding 3%. A noteworthy finding is a consistent and proportional increase in Z ranging from 2.2% to 26.4% as the formaldehyde concentration increases from 0.5% to 10% across a wide frequency range from 10 kHz to 200 kHz. This method offers a dependable and efficient approach to quality control, ensuring the safety and integrity of milk products. • Novel sensor design comprising two identical Ni sheets and a plastic cuvette for detecting formaldehyde adulteration in milk. • Unique benefits include non-corrosiveness, easy cleaning, and extended lifespan without the need for coating, distinguishing it from previous research. • Measures key electrical parameters to assess sensor effectiveness, including capacitance, phase angle, and impedance. • Ability to detect formaldehyde in milk at concentrations as low as 0.5%, highlighting its sensitivity and reliability. [Display omitted] [ABSTRACT FROM AUTHOR]

Lead-free all-inorganic perovskite single crystals (SCs) are currently the subject of a lot of research because of their enhanced material stability and lower biological toxicity. These advancements are essential for removing major obstacles to the real-world implementation of device applications. The lead-free hybrid organic-inorganic compound (CH 3 NH 3) 2 MnCl 4 was synthesized in this work at room temperature employing the slow evaporation solution growth approach. Investigating its structural, optical, and electric characteristics was the key objective of the study. The (CH 3 NH 3) 2 MnCl 4 compound crystallises in the orthorhombic system (Pccn space group). For the compound under study, the UV–visible spectroscopy spectrum shows the direct band-gap value of ∼3.6 eV, indicating that it is a semiconductor material. The electric studies were conducted in a wide frequency range from 10−1 Hz–106 Hz and a temperature range from 348 to 388 K. Nyquist plots revealed only a semicircle in the whole impedance spectra due to the effect of interior grains. The obtained results were analyzed by fitting the experimental data to an equivalent circuit model R//C//CPE. The Alternating current conductivity (σ AC) follows Jonscher's power law. The fitting of σ AC curves reveals that the activation energy is equal to 0.706 eV. The dominant transport mechanism is the CBH model in the temperature range from 348 to 388 K. Studies of the dielectric constant permittivity ε *( ω ) confirmed that the relaxation process was thermally activated. • This work presents the following findings: • The (CH 3 NH 3) 2 MnCl 4 compound crystallises in the Orthorhombic system. • The UV–visible spectroscopy indicating that it is a semiconductor material. • Nyquist plots indicating the dominant to the effect of interior grains. • The dominant transport mechanism is the CBH model. [ABSTRACT FROM AUTHOR]

Electrochemical impedance spectroscopy (EIS) is the golden tool for many emerging biomedical applications that describes the behavior, stability, and long-term durability of physical interfaces in a specific range of frequency. Impedance measurements of any biointerface during in vivo and clinical applications could be used for assessing long-term biopotential measurements and diagnostic purposes. In this paper, a novel approach to predicting impedance behavior is presented and consists of a dimensional reduction procedure by converting EIS data over many days of an experiment into a one-dimensional sequence of values using a novel formula called day factor (DF) and then using a long short-term memory (LSTM) network to predict the future behavior of the DF. Three neural interfaces of different material compositions with long-term in vitro aging tests were used to validate the proposed approach. The results showed good accuracy in predicting the quantitative change in the impedance behavior (i.e., higher than 75%), in addition to good prediction of the similarity between the actual and the predicted DF signals, which expresses the impedance fluctuations among soaking days. The DF approach showed a lower computational time and algorithmic complexity compared with principal component analysis (PCA) and provided the ability to involve or emphasize several important frequencies or impedance range in a more flexible way. [ABSTRACT FROM AUTHOR]