Impedance Parameters Research Articles

Machine induced dynamic field responses of group pile with different pile arrangements

AbstractThe main objective of the current investigation is to study the dynamic behaviour of a 3-pile group with different loading direction under coupled (horizontal and rocking) excitations. To accomplish this objective, machine-induced field excitation tests are conducted on small-scale hollow steel piles. The 3-pile group is driven into the ground in a triangular arrangement with 3d spacing. Two different soil-pile setups, i.e., Pile Group-I and Pile Group-II, are created based on dynamic force directions. In the case of Pile Group-I, the forces are applied to the direction of the median of the triangle, and for Pile Group-II, the forces are applied to other directional loads. From the test results, it is found that the resonant peaks of horizontal and rocking amplitudes for Pile Group-I are lower than Pile Group-II. In the case of resonant frequencies, the values of Pile Group-I are observed to be the same or a little bit higher as compared to Pile Group-II. It is found that the dynamic soil-pile-soil interaction effect is more prominent for Pile Group-II than for Pile Group-I. For numerical investigation, the continuum approach method is utilised with the inclusion of a dynamic group interaction factor to predict the dynamic coupled responses in terms of frequency and amplitude for these two soil-pile setups. To understand the behaviour of pile groups, boundary zone parameters and variations of impedance parameters (stiffness and damping) with operating frequencies are also measured using this theoretical approach.

Consensus-based secondary frequency control for parallel virtual synchronous generators

In off-grid operating modes, microgrids with Virtual Synchronous Generators (VSG) controlled inverters are limited to primary frequency control capabilities. When operating under the primary frequency control, if VSG's output frequency exceeds the safe operational range, it can adversely affect stable operation. Consequently, there is a need to implement a secondary frequency control strategy. This paper presents an analysis of the conventional secondary frequency regulation in VSGs. It reveals that when multiple VSGs in parallel to the Point of Common Coupling (PCC) with varied line impedances, the proportionate distribution of each VSG's active power output, post frequency control, does not align with predetermined ratios. In response to this challenge, the paper introduces a quasi-distributed secondary frequency control approach, tailored for systems with multiple feed-in points. This approach modifies the traditional method of compensating for frequency deviation through average ratio integral compensation, replacing it with a compensation based on a consensus algorithm. This negates the need for global communication and additional impedance measuring equipment. By facilitating information exchange between neighboring converters, it enables global control, effectively resolving the issue of line impedance parameters impacting the distribution of VSG's active power output. This decouples the previously strong correlation between line impedance and VSG's active power. The proposed method is characterized by its strong adaptability, scalability, and swift dynamic adjustments, significantly enhancing the fault tolerance of information exchange and the stability of microgrid operations. Finally, the correctness and effectiveness of the proposed improved control strategy are verified by simulation and HIL-based platform.

Modeling human transmissibility via nighttime light remote sensing for Hyphantria cunea propagation pattern prediction

Human mobility and goods transportation are essential processes that lead to pest propagation, and accurately characterizing spatial transmissibility has always been a popular research topic. Therefore, we propose a spatial modeling and quantification method based on nighttime light remote sensing to reflect human transmissibility and integrate this method with other variables to map the pest spreading risk. First, residential areas in China are extracted from annual NPP/VIIRS datasets. Then, the human transmissibility index is established based on GIS cost-distance analysis with impedance parameters related to geographical and land use features. Consequently, the propagation risk of the human-induced pest Hyphantria cuneas in China is assessed with a binary logistic model. The results show that the human transmissibility index obtained from nighttime light remote sensing images can be used to assess human accessibility in a continuous way in the field. When the Hyphantria cunea risk prediction index was adopted, the accuracy of pest range prediction improved by nearly 5% for occurrence and 3.3% overall, with a significant difference observed in a Wilcoxon signed-rank test compared with the effect of anthropogenic factors quantified considering basic geographic information and infrastructure features. In addition, all the model R2 values increased at different levels. The human transmissibility index can be used to effectively characterize the spatial pattern of human impacts and displays high accuracy in pest risk prediction. Understanding the human transmissibility mechanism of pests is important and provides a reference for achieving early warnings regarding pest spreading, performing potential host analyses for human infection caused by unknown pathogens, and modeling human ecological interference.

Ultra-wideband absorber based on graphene surface with polarization insensitivity under large angles

In this paper, a frequency-selective absorber with large-angular stability under oblique incidence is present. The absorptivity of the structure can be reached to maximum by impedance matching and parameter optimization method under a specific angle (40°), which ensures an excellent absorption response within 60° oblique incidence. This method solves the problem that the absorptivity of traditional absorbers deteriorates with the increase of incident angle. The absorber consists of a three-layer structure: two lossy layers and a metal ground layer, the equivalent circuit model is discussed and the operating frequency band is widened by generating electric resonances and magnetic resonances. Due to the high symmetry of the structure, the absorber has good polarization insensitivity. Numerical simulation shows that from 4.4 to 20 GHz, the absorptivity of the structure is above 90% within 40° oblique angle of incidence. Finally, the design plays an important role in military stealth and preventing electromagnetic interference.

Synergetic gait prediction and compliant control of SEA-driven knee exoskeleton for gait rehabilitation.

In recent years, lower limb exoskeletons have achieved satisfactory clinical curative effects in rehabilitating stroke patients. Furthermore, generating individualized trajectories for each patient and avoiding secondary injury in rehabilitation training are important issues. This paper explores the utilization of series elastic actuator (SEA) to deliver compliant force and enhance impact resistance in human-robot interaction, and we present the design of novel knee exoskeleton driven by SEA. Subsequently, the novel gait trajectory prediction method and compliant control method are proposed. The attention-based CNN-LSTM model is established to generate personalized gait trajectories for affected limbs, in which the spatial-temporal attention mechanism is adopted to improve the prediction accuracy. The compliant control strategy is proposed to nonlinearly and adaptively tune impedance parameters based on artificial potential field (APF) method, and active rehabilitation training is carried out in the coordination space to guarantee patient safety. The experimental results based on four healthy subjects demonstrated that synergetic gait prediction model could satisfactorily characterize the coordination movement with higher accuracy. The compliant control could limit the patient's movement in the safe coordination tunnel while considering personalization and flexibility.

Fine characterization of interbedding sand-mudstone based on waveform indication inversion

Abstract Owing to the increasing challenges associated with coal mine exploration and development, extremely precise surveys with high-resolution images are required to support production. Conventional inversion methods cannot provide sufficiently precise images of the complex lithologies in coal measure strata. Accordingly, this study performed research in Qiyuan mining area, Shanxi Province, China, and predicted the complex lithology on the basis of facies control using waveform indication inversion and waveform indication simulation. Horizontal changes in seismic waveforms were used to reflect lithologic assemblage characteristics for facies-controlled constraints, and the vertical mapping the connection between seismic waveform and logging curves was shown. Moreover, high-resolution inversions of wave impedance and natural gamma parameters were conducted. Combined with lithologic shielding and accurate time–depth conversion, the inversions enabled the precise characterization of the lithological assemblage distribution in the study area. Our results showed that waveform indication inversion could distinguish between coal seams and limestone, whereas waveform indication simulation based on natural gamma could effectively distinguish between sandstone and mudstone. Furthermore, the horizontal resolution was improved and the vertical resolution extended to a thickness of 2–3 m. In addition, the inversion results were highly consistent with drilling results, with an error <0.1 m. Therefore, waveform indication inversion and simulation could be applied to coal mines for safe and efficient production.

Within-breath oscillometry for identifying exercise-induced bronchoconstriction in pediatric patients reporting symptoms with exercise.

Evaluating oscillometry parameters separately for the inspiratory and expiratory breath phases and their within-breath differences can help to identify exercise-induced bronchoconstriction (EIB) in pediatric outpatients disclosing exercise-induced symptoms (EIS). To assess the response in impedance parameters following an exercise challenge in patients reporting EIS. Sixty-eight patients reporting EIS (34 asthmatics and 34 suspected of asthma, age mean = 10.8 years, range = 6.0-16.0) underwent an incremental treadmill exercise test. Spirometry was performed at baseline and 1, 5-, 10-, 15-, and 20-min post exercise. Oscillometry was performed at baseline and at 3- and 18-min post exercise. Bronchodilator response to 200 µg albuterol was then assessed. EIB was defined as a forced expiratory volume in 1 s (FEV1) fall ≥10% from baseline. Expiratory and inspiratory resistance (Rrs) and reactance (Xrs), their z-score (Ducharme et al. 2022), and their mean within-breath differences (ΔRrs = Rrsexp-Rrsinsp, ΔXrs = Xrsexp-Xrsinsp) were calculated. Receiver operating characteristic (ROC) curves and their areas (AUCs) were used to evaluate impedance parameters' performances in classifying EIB. Asthmatic patients developed EIB more frequently than those suspected of asthma [18/34 (52.9%) vs. 2/34 (5.9%), p < 0.001]. In the 20 subjects with EIB, Rrsinsp, Rrsexp, Xrsinsp, and Xrsexp peaked early (3'), and remained steady except for Xrsinsp, which recovered faster afterward. ΔXrs widened 18 min following the exercise and reversed sharply after bronchodilation (BD) (-1.81 ± 1.60 vs. -0.52 ± 0.80 cmH2O × s/L, p < 0.001). Cutoffs for EIB leading to the highest AUCs were a rise of 0.41 in z-score Rrsinsp (Se: 90.0%, Sp: 66.7%), and a fall of -0.64 in z-score Xrsinsp (Se: 90.0%, Sp: 75.0%). Accepting as having "positive" postexercise oscillometry changes those subjects who had both z-scores beyond respective cutoffs, sensitivity for EIB was 90.0% (18/20) and specificity, 83.3% (40/48). Oscillometry parameters and their within-breath differences changed markedly in pediatric patients presenting EIB and were restored after the bronchodilator. Strong agreement between z-scores of inspiratory oscillometry parameters and spirometry supports their clinical utility, though larger studies are required to validate these findings in a broader population.

Engineering 3D-interconnected graphene nanoplatelets and polyaniline nanocomposite for high energy density energy storage

A high-performance, seaweed-shaped 3D interconnected nanocomposite electrode comprising graphene nanoplatelets (GNP) and polyaniline (PANI) as an electrode material for supercapacitors is synthesized via conventional in-situ chemical oxidative polymerization. This research aims to enhance the electrochemical performance of the GNP/PANI nanocomposite electrode material by manipulating their shape and electroactive characteristics for greater optimization. While seaweed-shaped GNP/PANI nanocomposites have been reported previously, none have demonstrated high electrochemical performance with an optimized 40 wt% of GNP in GNP/PANI nanocomposite. This deficiency is attributed to the lack of 3D well-interconnected nanocomposite formation and the electroactivity of GNP/PANI when compared to individual PANI or GNP in H2SO4 electrolyte.The electrochemical study confirms an upward revision in specific capacitance, from 400 Fg−1 for GNP and 514 Fg−1 for PANI, to 1088 Fg−1 for the GNP/PANI electrode material in an aqueous 1 M H2SO4 electrolyte solution. It is envisioned that formation of such 3D interconnected GNP/PANI nanocomposite contributes in increasing the interplanar and interchain distances in the nanocomposite particularly in GNP layered structure. Additionally, it is observed that the electrochemical impedance parameters, such as charge transfer resistance Rct (0.12 Ω), high response frequency (1.367 Hz), and short relaxation time (τo ∼ 0.73 s) of the GNP/PANI nanocomposite electrode material, demonstrate excellent performance. The seaweed-shaped GNP/PANI nanocomposite exhibits promising potential as an electrode material for next-generation symmetric supercapacitors due to its high specific capacitance, low cost, and ease of fabrication.

Gold electrode modified with proteoliposome-derived bilayer for electrochemical studies of HMG‑CoA reductase and its inhibition

Electrochemical methods are used to characterize transport phenomena in the presence of membrane proteins to monitor changes in their catalytic properties or activity in the presence of activators or inhibitors. Because membrane proteins are fully active in their natural environment, the lipid membrane, electrochemical investigations of enzymes should be carried out when they are present in an appropriate lipid bilayer deposited on an electrode surface. Here, HMG-CoA reductase (HMGR), the membrane protein responsible for cholesterol synthesis, and its related coenzyme (HMG-CoA) were incorporated into a lipid bilayer obtained by spreading proteoliposomes on the surface of a gold electrode modified with a thioglucose. Nicotinamide adenine dinucleotide phosphate, NADPH was oxidized to NADP+ during the enzymatic reaction when HMG-CoA was reduced to the product, mevalonate, which is further transformed into cholesterol. The reconstitution of HMG-CoA reductase and its mechanism were investigated by following the NADP+ reduction on the electrode using cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS). The activity of HMGR was studied over time and in the presence of fluvastatin, an exemplary HMGR reductase inhibitor commonly used to treat hypercholesterolemia. The inhibitory effect of the statin was electrochemically evaluated by monitoring the decrease of NADP+ reduction current and changes in the impedance parameters of the HMGR-proteoliposome-derived bilayer.

A novel method for calculating harmonic contribution based on difference recurrence estimation

AbstractDetermining the harmonic contribution of each harmonic source is conducive to improving the harmonic management of the power system. The main problem with harmonic contribution calculation is determining the equivalent system harmonic impedance. The previous harmonic impedance calculation method can only calculate the impedance value when the harmonic fluctuation is significant, and the calculation fails when the harmonic fluctuation is small. Therefore, a new method called difference recurrence estimation is proposed to construct the objective function from impedance parameters. The advantages of the proposed method are low data requirement, high estimation accuracy, and excellent tracking performance. An improved genetic algorithm (GA) is presented by integrating an adaptive crossover operator and population intervention into the standard GA to improve the global searching impedance parameter ability. Based on these parameters, harmonic impedance and harmonic contribution are calculated accurately. The superiority of the proposed model is verified through simulation and field cases.

Research on adaptive impedance control technology of upper limb rehabilitation robot based on impedance parameter prediction.

Introduction: With the aggravation of aging and the growing number of stroke patients suffering from hemiplegia in China, rehabilitation robots have become an integral part of rehabilitation training. However, traditional rehabilitation robots cannot modify the training parameters adaptively to match the upper limbs' rehabilitation status automatically and apply them in rehabilitation training effectively, which will improve the efficacy of rehabilitation training. Methods: In this study, a two-degree-of-freedom flexible drive joint rehabilitation robot platform was built. The forgetting factor recursive least squares method (FFRLS) was utilized to estimate the impedance parameters of human upper limb end. A reward function was established to select the optimal stiffness parameters of the rehabilitation robot. Results: The results confirmed the effectiveness of the adaptive impedance control strategy. The findings of the adaptive impedance control studies showed that the adaptive impedance control had a significantly greater reward than the constant impedance control, which was in line with the simulation results of the variable impedance control. Moreover, it was observed that the levels of robot assistance could be suitably modified based on the subject's different participation. Discussion: The results facilitated stroke patients' upper limb rehabilitation by enabling the rehabilitation robot to adaptively change the impedance parameters according to the functional status of the affected limb. In clinic therapy, the proposed control strategy may help to adjust the reward function for different patients to improve the rehabilitation efficacy eventually.

Time-domain versus frequency-domain system identification of lithium-ion batteries using fractional models

This study presents a comparison between time-domain and frequency-domain approaches for system identification of Lithium-ion batteries using fractional models. As reported in the literature, time-domain approaches have the advantage of collecting data on smaller time-intervals (few seconds) as compared to frequency-domain data (several minutes). The model is derived using a fractional-order equivalent circuit model (FO-ECM) which exhibit long memory diffusion phenomena, and its impedance parameters are determined through the application of Levenberg-Marquardt optimization algorithm both in time and frequency domains. Comparisons are conducted on experimental data generated from three commercial batterie cells with different chemistries and cross-validation results are shown between the obtained time-domain and frequency-domain models. Similar models found with both methods which affirm the reliability and applicability of the proposed identification methods both in time and frequency domains.

Characterizing MIMO Channels in Low-Voltage Electric Power Line Communication through Impedance and Scattering Parameters Analysis

Characterizing MIMO Channels in Low-Voltage Electric Power Line Communication through Impedance and Scattering Parameters Analysis

ERRATUM: Characterizing MIMO Channels in Low-Voltage Electric Power Line Communication through Impedance and Scattering Parameters Analysis

ERRATUM: Characterizing MIMO Channels in Low-Voltage Electric Power Line Communication through Impedance and Scattering Parameters Analysis

Impedance modeling, Parameters sensitivity and Stability analysis of hybrid DC ship microgrid

Impedance modeling, Parameters sensitivity and Stability analysis of hybrid DC ship microgrid

Li-ion cell impedance identification in the time domain as an alternative to identification in the frequency domain

Electrochemical Impedance Spectroscopy (EIS) is a widely used tool for selecting a pertinent Equivalent Circuit Model (ECM) of Li-ion cells which is characterized by non integer order operators. The main drawback of EIS is the long time required to scan a whole spectrum down to low frequencies. Thus, chronopotentiometry (CP) is an alternative method which consists in identifying impedance parameters using an excitation current sequence lasting a few seconds and the corresponding induced voltage variations. An impedance fractional model needs to be synthesized in order to allow simulation also in the time domain. The pertinence of CP is demonstrated using experimental results obtained with a Samsung 3.4 Ah Li-ion cell. Due to its inability to take into account the inductive behavior, fractional model used in the time domain exhibit limitations. Nevertherless, parameters identified in the time domain present similar results to the ones identified in the frequency domain under the condition of a restricted frequency range.

Effect of turbulent flow on the oxide properties of carbon steel in alkaline water

The purpose of this study is to investigate the changes in the morphology, chemical state, defect density, and impedance of oxides formed on SA 106 Gr.B carbon steel by turbulent water flow at the micro and atomic levels. A compact magnetite layer composed of multi-faceted particles is formed in stagnant water, while a porous magnetite layer composed of particles without a certain shape is formed in turbulent water. Ferrous ions are preferentially dissolved from the oxide in turbulent water, which increases the vacancies in the oxide lattice. An increase in the concentration of point defects is shown to be comparable to an increase in the corrosion rate of carbon steel. The flow-accelerated corrosion behavior is also well correlated with the electrochemical impedance parameters including the charge transfer resistance and capacitance. Our study provides a further understanding of carbon steel corrosion under turbulent water flow conditions.

Adaptive nonlinear control of the Single-Phase Grid-Connected Photovoltaic System

This paper addresses the problem of controlling the single-phase grid connected to the photovoltaic (PV) system through a three-level boost converter (TLBC) and half-bridge inverter (HBI) with LCL-filter. This study aims to achieve four main objectives: (i) ensure that the output voltage of PV panel track a reference given by the MPPT block based on the perturb and observe (P&O) algorithm; (ii) regulate DC bus voltage to ensure injection of photovoltaic power into the grid; (iii) guarantee power factor correction (PFC); (iv) ensure a balance between TLBC output voltages. The problem is dealt with using a nonlinear controller based on the backstepping and lyapunov approaches, a filtered-PI regulator to ensure the power balance between the grid and the PV panel. An adaptive observer is designed in order to estimate the voltage and the impedance parameters of power grid, by measuring only the grid current. The proposed controller and observer performances are confirmed by simulation in MATLAB\\Simulink.

Bioelectrical impedance parameters add incremental value to waist-to-hip ratio for prediction of metabolic dysfunction associated steatotic liver disease in youth with overweight and obesity.

Metabolic dysfunction-associated steatotic liver disease (MASLD) presents a growing health concern in pediatric populations due to its association with obesity and metabolic syndrome. Bioelectrical impedance analysis (BIA) offers a non-invasive and potentially effective alternative for identifying MASLD risk in youth with overweight or obesity. Therefore, this study aimed to assess the utility of BIA for screening for MASLD in the youth. This retrospective, cross-sectional study included 206 children and adolescents aged <20 years who were overweight and obese. The correlations between anthropometric measurements and BIA parameters and alanine aminotransferase (ALT) levels were assessed using Pearson's correlation analysis. Logistic regression analysis was performed to examine the associations between these parameters and ALT level elevation and MASLD score. Receiver operating characteristic (ROC) curves were generated to assess the predictive ability of the parameters for MASLD. Pearson's correlation analysis revealed that waist-to-hip ratio (WHR), percentage body fat (PBF), and BIA parameters combined with anthropometric measurements were correlated with ALT level. Logistic regression revealed that WHR, skeletal muscle mass/WHR, PBF-WHR, fat-free mass/WHR, and appendicular skeletal muscle mass/WHR were correlated with ALT level elevation after adjusting for age, sex, and puberty. WHR, PBF-WHR, and visceral fat area (VFA)-WHR were positively correlated with the MASLD score in the total population after adjusting for age, sex, and puberty. PBF-WHR and VFA-WHR were correlated with the MASLD score even in youth with a normal ALT level. The cutoff points and area under the ROC curves were 34.6 and 0.69 for PBF-WHR, respectively, and 86.6 and 0.79 for VFA-WHR, respectively. This study highlights the utility of combining BIA parameters and WHR in identifying the risk of MASLD in overweight and obese youth, even in those with a normal ALT level. BIA-based screening offers a less burdensome and more efficient alternative to conventional MASLD screening methods, facilitating early detection and intervention in youth at risk of MASLD.

Effect of biofouling on electrochemical impedance parameters and sensitivity of polyvinyl alcohol coated Iridium oxide based pH biosensors

Effect of biofouling on electrochemical impedance parameters and sensitivity of polyvinyl alcohol coated Iridium oxide based pH biosensors