Impedance Behavior Research Articles

Electrical impedance behaviour of carbon fibre reinforced cement-based sensors at different moisture contents

Carbon fibre reinforced cement-based sensors offer a potential low-cost and high-performance alternative to externally applied sensors for health monitoring of concrete structures. This paper focuses on the moisture dependence of bulk conductivity for carbon fibre reinforced cement-based sensors with fibre contents 0.1–1.5 vol%. Under two-point AC impedance spectroscopy at frequencies 1 Hz–10 MHz, the electrode polarization (EP) process, an electrical double layer polarization process (EDLP), and the bulk Maxwell-Wagner type interfacial polarization process (MWP) were identified. While reducing the saturation degree from 100 % to 0 %, the fractional change of bulk conductivity (FCS) underwent three different stages, which consists of a non-linear stage at 100–80 % saturation, a linear stage at 80–20 % saturation, and a final stage at 20–0 % saturation. The results gave insights into the stability of cement-based sensors under field conditions, and the underlying mechanisms of behaviour. From this, a route towards appropriate use of cement-based sensors in mechanical sensing and potentially moisture sensing without further external measures can be realised.

24 h movement behavior and metabolic syndrome study protocol: A prospective cohort study on lifestyle and risk of developing metabolic syndrome in undergraduate students from low-income regions during a pandemic.

Obesity and its comorbidities are increasingly prevalent in Latin America, with a more rapid growth in individuals with lower income. The composition of movement behaviors within a 24 h period may have important implications for obesity, metabolic and mental health in cross-sectional data. However, a longitudinal study is needed to confirm the findings from the primarily cross-sectional evidence. The COVID-19 pandemic has been associated with cardiometabolic outcomes and has impeded healthy behavior. The first objective is to evaluate the time elapsed since the diagnosis of not meeting 24 h movement guidelines and the potential subsequent onset of metabolic syndrome in undergraduate students from low-income regions within 4 years of follow up. The second objective is to test the association between 24 h movement, mental wellbeing, eating behaviors, and abdominal obesity in the period of this pandemic. The 24 h movement behavior and metabolic syndrome (24 h-MESYN) study is a multicentre cohort study that will include participants from two Brazilian cities within the 2022-2025 period to asses the first objective, and also a nested case-control study at the baseline will be carried out to evaluate the second objective. Previously, we conducted a feasibility study in the academic year of 2021 to assessing the psychometric properties of subjective tools, refine our study protocol, and adjust the epidemiological conditions of the cohort's subsequent phases (like as prevalence of exposure of interest, sampling process, and study adherence). Statistical tests as Cohen's kappa agreement; factorial analysis; logistic, Poisson and linear regression; and Kaplan-Meier analysis will be performed, in accordance with the objectives.

Research on Hybrid Force Control of Redundant Manipulator with Reverse Task Priority.

This paper presents the reverse priority impedance control of manipulators with reference to redundant robots of a given task. The reverse priority kinematic control of redundant manipulators is first expressed in detail. The motion in the joint space is derived following the opposite order compared with the classical task priority–based solution. Then the Cartesian impedance control is combined with the reverse priority impedance control to solve the reverse hierarchical impedance controlled, so that the Cartesian impedance behavior can be divided into the primary priority impedance control and the secondary priority impedance control. Furthermore, the secondary impedance control task will not disturb the primary impedance control task. The motion in the joint space is affected following the opposite order and working in the corresponding projection operators. The primary impedance control tasks are implemented at the end, so as to avoid the possible deformations caused by the singularities occurring in the secondary impedance control tasks. Hence, the proposed reverse priority impedance control of manipulator can achieve the desired impedance control tasks with proper hierarchy. In this paper, the simulation experiments of the manipulator will verify the proposed reverse priority control algorithm.

Electrical, magnetic and -optical -study of Gd3+ and Sm3+ ion doped at Fe-site in bismuth ferrite

The synthesis of two complex perovskites BiGd0.5Fe0.5O3 (BGFO) and BiSm0.5Fe0.5O3 (BSFO) was carried out by the doping of Gd3+ and Sm3+ions at the B-site of bismuth ferrite by applying solid state/mixed oxide reaction method. The Rietveld analysis and X-ray diffraction pattern show that both BGFO and BSFO perovskites stabilize in the cubic-Fm3m phase. The FE-SEM study suggests an average grain size of 236.88 nm (BGFO) nm and 285.56 nm (BSFO). FTIR study shows the existence of Bi–O stretching vibration (BiO6) and Fe–O–Fe bending-vibration for BGFO and BSFO. The dielectric and impedance behaviors of these materials were studied in a wide range of temperatures (25 °C–500 °C) and frequencies (1 kHz–1000 kHz). The P-E hysteresis loop study shows a small remnant polarization with an energy storage density of 0.6163 J/cm3 (BGFO) and 0.6053 J/cm3 (BSFO). The energy storage efficiency (η%) of 66.49% and 76.85% is estimated for BGFO and BSFO respectively.

Design of thiacalixarene linked triphenylene based room temperature columnar LCs with self-assembly and dielectric property: Impact of flexibility on molecular systems

New thiacalixarene based bi-substituted triphenylene derivatives exhibiting columnar hexagonal phase have been designed and synthesized. The mesophase study of newly synthesized compounds was investigated by using optical polarising microscopy, differential scanning calorimetry, thermal gravimetric analysis and further confirmed by X-ray diffraction study. The target compounds showed stabilized columnar hexagonal phase with self-assembly at room temperature with enantiotropy nature. The confirmation of the molecular structure of these triphenylene based compounds was achieved by different spectroscopic techniques. To establish the structure-properties relationships, four supramolecular materials based on thiacalixarene and parent triphenylene linked bromo alkyl chain were prepared. These supramolecular liquid crystalline materials displayed dielectric behaviour in the frequency range of 20 Hz-2 MHz from 20 °C to 50 °C temperature. Further, the complex and impedance behaviour of two selected derivatives was also studied with respect to temperature and frequency.

A Novel Method to Reduce Low-Frequency Output Current Ripple of PWM Inverters

The output current of PWM inverters may contain low-frequency harmonics due to nonidealities, such as fluctuating dc voltage and dead-time. Low-frequency harmonics are detrimental to the inverter's current controller performance as well as its operation. They increase losses, cause synchronization problems in a grid-connected inverter, and cause torque pulsations in motors. Reducing low-frequency harmonics through conventional means require a big and expensive filter. In this article, a method to reduce low-frequency current harmonics is proposed. This method uses a virtual impedance, which is a controller block that mimics the behavior of a real impedance. Because it is virtual, it does not have physical drawbacks to the system, such as volume, weight, and losses. It can be designed only to affect the disturbance signals and to assume characteristics unlike a real impedance. It can also be added as a plug-in block to an already existing controller, saving a significant amount of design effort. Simulation and experimental results show a decrease of current THD to almost 1/3 of the original THD when no virtual impedance is used, demonstrating the effectiveness of the proposed method.

Straightforward Modeling of Frequency Dispersive and Nonlinear Common Mode Chokes for Transient Simulations

The simulation and design process of electromagnetic compatibility (EMC) filters need accurate models for their used components. Common mode chokes, which are essential filter components, exhibit a complex behavior that is usually hard to model for the purpose of transient circuit simulation. This article gives an easy method of modeling such components as long as hysteretic effects can be neglected. The process presented produces an easy to setup and easy to use SPICE model. The incorporated effects are the frequency dependent impedance behavior as well as the nonlinear effect from saturation processes. Both effects are well separated in the model and require only data from the manufacturer, thereby circumventing data fitting methods and measurements on samples with their lead and shipping time efforts. The frequency dependent behavior is modeled via a discrete <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">RL</i> -ladder model whereas the nonlinear effects are integrated via treating the saturation as a phase transition. The choke modeling technique was verified for a typical current pulse shape. The comparison between the measurement and the simulation model showed a good match, especially for the maximum amplitude of the current pulse shape, which is essential to determine saturation.

Homogeneity Characterization of Textile-Integrated Wearable Sensors based on Impedance Spectroscopy.

One of the main challenges during the integration of a carbon/polymer-based nanocomposite sensor on textile substrates is the fabrication of a homogeneous surface of the nanocomposite-based thin films, which play a major role in the reproducibility of the sensor. Characterizations are therefore required in every fabrication step to control the quality of the material preparation, deposition, and curing. As a result, microcharacterization methods are more suitable for laboratory investigations, and electrical methods can be easily implemented for in situ characterization within the manufacturing process. In this paper, several textile-based pressure sensors are fabricated at an optimized concentration of 0.3 wt.% of multiwalledcarbon nanotubes (MWCNTs) composite material in PDMS. We propose to use impedance spectroscopy for the characterization of both of the resistive behavior and capacitive behavior of the sensor at several frequencies and under different loads from 50 g to 500 g. The impedance spectra are fitted to a model composed of a resistance in series with a parallel combination of resistance and a constant phase element (CPE). The results show that the printing parameters strongly influence the impedance behavior under different loads. The deviation of the model parameter of the CPE from the value 1 is strongly dependent on the nonhomogeneity of the sensor. Based on an impedance spectrum measurement followed by parameter extraction, the parameter can be determined to realize a novel method for homogeneity characterization and in-line quality control of textile-integrated wearable sensors during the manufacturing process.

Early-age characterisation of Portland cement by impedance spectroscopy

Alternating current impedance spectroscopy (ACIS) was used to assess the effect of different sand, anhydrite and water contents on the electrochemical response of Portland cement paste in the early stages of hydration. Potential factors that may affect impedance measurements and data interpretation are also discussed, such as the complexity of the chemical composition of cement, its physical properties and hydration kinetics, and technique limitations. The impedance data obtained were benchmarked against different supporting techniques and literature data, showing a strong relationship among hydration rates as determined by thermochemistry, setting time measurements by physical approaches, pore fluid chemistry, electrical conductivity and the observed impedance behaviour. The results demonstrate that ACIS is a sensitive technique for assessing cement paste hydration, enabling differentiation of changes in the water and cement content, hydration degree and microstructural development during the first 24 h after mixing.

Superior dielectric behaviour and band gap tuning of Zn doped MgO nanoparticles

ABSTRACT The primary aim was to study the doping effect of Zn in MgO nanoparticles (NPs) prepared by the co-precipitation method. X-ray diffraction (XRD) results inferred the cubic structure of MgO with good crystallinity, which changed with dopant additions. Scanning electron microscope (SEM) images exposed the development of NPs with decreasing size and dimensions with little agglomeration on doping. Fourier transform infrared (FTIR) results revealed the Mg-O bond formation, which is associated with Zn-O bond on increasing dopant content. UV Vis studies showed the red shift in absorption edge and decreased band gap with percentage of Zn dopant additions. The dielectric results exposed the dielectric constant, dielectric loss and ac conductivity of Zn-doped MgO NPs. Dopant addition led to the higher dielectric constant and low dielectric loss at lower frequency due to oxygen vacancies generation. The impedance behaviour in different frequency regimes illustrated the effective contribution of conductive grains and insulating grain boundaries.

Skin-Induced Motion Artifact Removal for Ambulatory Electrocardiography

Skin-induced motion artifact (SIMA) is a troublesome problem for ambulatory electrocardiography (ECG) signal acquisition by e-skin dry sensor. Reference based algorithm is a promising way to tackle it. A highly correlated reference signal is the key for this solution. In this article, by using a new synthesized reference signal for LMS algorithm, which combines both skin induced impedance behavior and skin “slope” and recovery “time constant”, the SIMA related noise is greatly reduced. Firstly, we show the phenomenon that the SIMA “slope” and “recovery time constant” have some relationships with skin induced impedance, its derivatives and specific tissue characteristics. Secondly, We do the offline “slope” and “time constant” calibration work first, then measure the real time skin induced impedance, and then combine the above information together, to form a virtual reference signal, then we show the new reference has high correlation with actual SIMA noise. Finally, considering that SIMA potential consists of fast changing part and slow changing part, we use an improved LMS algorithm to handle the contradiction between speed and accuracy, which includes fast tracking part and low convergence error part. We set up the SIMA removal system in Matlab, and use actual motion artifact contaminated ECG signal as the input, and then do offline signal processing. Results show that SIMA is improved around <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$7\sim 15$ </tex-math></inline-formula> dB typically on average. Integrating skin-induced impedance with human body related “slope” and “time constant” as a reference signal seems a feasible method to remove skin-induced motion artifact.

Parylene C as an Insulating Polymer for Implantable Neural Interfaces: Acute Electrochemical Impedance Behaviors in Saline and Pig Brain In Vitro

Parylene is used as encapsulating material for medical devices due to its excellent biocompatibility and insulativity. Its performance as the insulating polymer of implantable neural interfaces has been studied in electrolyte solutions and in vivo. Biological tissue in vitro, as a potential environment for characterization and application, is convenient to access in the fabrication lab of polymer and neural electrodes, but there has been little study investigating the behaviors of Parylene in the tissue in vitro. Here, we investigated the electrochemical impedance behaviors of Parylene C polymer coating both in normal saline and in a chilled pig brain in vitro by performing electrochemical impedance spectroscopy (EIS) measurements of platinum (Pt) wire neural electrodes. The electrochemical impedance at the representative frequencies is discussed, which helps to construct the equivalent circuit model. Statistical analysis of fitted parameters of the equivalent circuit model showed good reliability of Parylene C as an insulating polymer in both electrolyte models. The electrochemical impedance measured in pig brain in vitro shows marked differences from that of saline.

An investigation on structural, electrical, magnetic and impedance behaviour of (1-x)Pb(Zr0.30Ti0.70)O3-(x)SmFeO3 solid solution

A solid state reaction technique was used to synthesize solid solutions of (1-x)Pb(Zr0.30Ti0.70)O3-(x)SmFeO3 (denoted as (1-x)PZT-(x)SF) in the composition series 0.05 ≤ x ≤ 0.20. Refinement of X-ray diffraction data using the Rietveld method and the appearance of A˝ and Á modes at 450–550 cm−1 and 700–850 cm−1 respectively in the deconvoluted Raman spectrum proposed the existence of tetragonal phase (P4mm) and monoclinic phase (Cm) in the series. The P-E and M-H hysteresis curves show that all the samples have ferroelectric and magnetic characteristics at room temperature. The ferroelectric-paraelectric phase transition occurs at a temperature of 690 K. Electrical characteristics have been investigated using impedance plots with the variation of frequency 100 Hz - 1 MHz and temperature 513–593 K. From the impedance data the character of Nyquist plots ascribed the existence of bulk and grain boundary contributions in the samples. The superimposition of normalised curves of impedance spectra and modulus spectra points out that the conductivity relaxation has been seen in all the samples.

Preparation and characterization of CdO-ZnO core shell nano particles: Prepared by two step wet chemical method

CdO–ZnO core-shell nanoparticles (CSN) were successfully synthesized by two step assisted chemical sol gel method. The structural properties of synthesized CSN have been analyze by X-ray diffraction (XRD) method, XRD pattern shows a uniform, homogenous phase formation of nano crystals. Microstructural properties of prepared CSN have been analyze by FESEM and HRTEM methods, Surface morphology of the CSN was investigated using FESEM, which shows dense growth and thin layer of ZnO shell over CdO core where as crystallinity of the CSN have been observed from HRTEM images, HRTEM reassures the particle size as obtained from XRD analysis. The optical properties and optical band gap of CSN is obtained from UV–Visible spectroscopy. Raman modes obtained from Raman spectroscopy distinctly identify the CdO and ZnO phonon vibrational modes. The electrical properties have been investigated by temperature dependent dielectric measurement. Moreover, the impedance behavior at different temperature has been investigated by impedance spectroscopy.

Analysis of Interface Material Noise in Non-contact Capacitive Sensing.

The thermal noise due to the resistivity of insulation materials can become a significant noise source in non-contact capacitive sensing, especially when measuring micro-volt-level physiological signals. Since both the impedance and the resistivity of practical insulation materials may be strongly frequency dependent, their thermal noise is often frequency dependent. This paper studies the impedance and noise behavior of different interface materials as function of frequency, by means of modelling, simulations, and experimental measurements. The results show that the inherent resistive noise of some fabrics (e.g., cotton, polyester) could outweigh the typical noise level of circuits for physiological sensing; and as a result, the interface noise can limit the quality of low-amplitude signal detection. Clinical Relevance- This study gives a guideline for material selection from the noise perspective in case of capacitive electrode sensing.

Tele-Impedance Control Approach Using Wearable Sensors.

Tele-operational tasks often suffer from instability issues and limited reliability during unpredictable interactions. We propose a real-time control law reproducing the impedance and kinematic behaviour of a subject's arm (shoulder and elbow) on a remote avatar in a 2-DoF task. The human arm impedance and kinematics are estimated respectively from EMG and M-IMU data and then mapped into the avatar arm through an impedance control. Contrary to literature methods, our portable tele-impedance controller relies only on wearable sensors and enables an easy use in unstructured environments. The good performance (R2> 0.7) of the muscle model used to map on the robot the human stiffness of five healthy subjects indicates the possibility of applying the proposed algorithm for a tele-impedance control.

Modeling Study of Commercial NCA Cylindrical Battery Cells’ Impedance Behavior Under Different Operation Conditions

The classic 18650 and 21700 format cylindrical Li-ion batteries have been widely used today to power electric vehicles (EVs). Their wound jelly-roll structure (in a form of an Archimedean spiral) can provide a relatively higher energy density in the limited EV given space comparing with the battery cells using stacked electrodes. As the rapid development and deployment of EV technology require high performance and reliable Li-ion batteries, it is critical to understand the mechanism and process behind battery cell behaviors under various driving conditions. In this study, a series of impedance experiments is designed to explore the impact of battery state of charge (SOC), temperature, C-rates and other operating conditions. Then, an impedance mathematical model is developed to explore the potential mechanisms behind experimental observations. Our obtained results show that the impedance response of cylindrical NCA battery cells varies with the state of charge in both charge and discharge operation, and the SOC dependent impedance existed in different operating temperatures and C-rates. Through modeling analysis, results indicate the operating temperature and charge-discharge rate could significantly influence the impedance response of the battery cell but could not directly cause the variation of the impedance response at different SOC conditions. Besides, modeling results also show that the contact resistance variation, resulted from the expansion and contraction of cell electrodes during charge and discharge, could lead to a SOC dependent impedance behavior of the commercial cell and influence battery output performance.

Human-Robot Variable Impedance Skills Transfer Learning Based on Dynamic Movement Primitives

Endowing robots with human-like abilities to perform motor skills smoothly and naturally is one of the important goals of robotics. Learning from demonstration (LfD) has been successfully applied for learning tasks on robots, for which the human tutor can demonstrate a successful execution. Learning human stiffness schedule strategy is one of the promising approaches for lightweight collaborative robots to execute physical in-contact tasks while remaining compliant when possible, as it enables robots to show human-like adaptive impedance behavior in an effective and efficient manner. In this letter, we develop a robot skill learning framework considering both movement and impedance features. Electromyography (EMG)-based method is used to estimate human upper limb stiffness such that the information of impedance can be obtained. Dynamic movement primitives (DMPs) model is employed to model movement and impedance features simultaneously. Throughout this procedure, the robot skills learning from a human tutor can be achieved. Besides, the learned skills can be generalized. An impedance controller imitating the human impedance mechanism is utilized in the task reproduction phase to achieve both task successful execution and safe physical interaction. The effectiveness of the proposed methods is verified in a water pumping task on a Kinova robot.

Studies of structure, dielectric and conduction mechanism of Bi3+/Yb3+ modified BaTiO3

The present communication aims at the study of the structural, dielectric, electrical and conduction properties of Bi3+/Yb3+ substituted BaTiO3 with a chemical composition of Ba0.5Bi0.5Yb0.5Ti0.5O3. The modified BaTiO3, could be synthesized by a solid state reaction technique. The X-ray diffraction data and pattern revealed the formation of the above compound with tetragonal crystal system. The material's molecular structure (Ba–Ti–O bond, O–Ti–O stretching-mode, metal-oxygen bond, optical band gap, and so on) was determined using room temperature Fourier transform infrared (FTIR) and UV–visible spectroscopic spectra. Detailed investigations of the material's electrical (dielectric/leakage current and impedance) behavior over a wide temperature (250C–5000C) and frequency (1 kHz–1000 kHz) range revealed the presence of capacitive, resistive, and conductive mechanisms. On the investigation of the polarization-electric field (P-E) hysteresis loop on multiple substitution, the change of ferroelectric polarization (spontaneous and residual) and storage density of BaTiO3 was observed. Defect chemistry of the modified barium compound has been discussed in the details.

Salt Solution Concentration Effects on the Electrochemical Impedance Spectroscopy of Poly(3,4‐ethylenedioxythiophene) (PEDOT)

AbstractPoly(3,4‐ethylenedioxythiophene) (PEDOT) has become a widely used modifier for biomedical electrodes because of its ability to significantly decrease the impedance at low frequencies (below 1 kHz). However, in past studies the role of the solution concentration (ionic conductivity) on the electrochemical impedance behavior has not been well established. Here we describe the electrochemical impedance spectroscopy of the conjugated polymer (PEDOT) using standard screen‐printed electrodes and various standard salt (NaCl) solutions with known conductivities from 1.0E‐2 S/cm to 3.1E‐6 S/cm. Changing the conductivity of the salt solution used for impedance measurements had a dramatic influence on the experimentally obtained spectra. An equivalent circuit consisting of a constant phase element in series with a parallel resistor and second constant phase element was used to match and describe these systems. Our results make it possible to better elucidate the influence of electrode, solution, and polymer coating on the resulting impedance response.