With the increased penetration of non-conventionalrenewable energy resources, such as wind power plants (WPPs),into the power system, a lot of interest has been placed on studyingtheir impact for system protection, pl...With the increased penetration of non-conventionalrenewable energy resources, such as wind power plants (WPPs),into the power system, a lot of interest has been placed on studyingtheir impact for system protection, planning and operationsto ensure continued reliability of the electric grid. The impactof WPPs on the grid is typically identified during generationinterconnection studies. One of the challenges faced by protectionand planning engineers, at an early stage in this process, isthat many of the studies involving these power plants must beperformed without specific data available because the equipmentis not built yet. Among all the needed data, a particular interest inthis study is placed on the positive- and zero-sequence impedancesof the main power transformer (MPT) that interconnects a windpower plant to the transmission system due to its contribution toshort-circuit current during ground faults. The most commonlyfound in practice MPT winding configurations is a high-voltagewinding in wye with neutral bushing;a low-voltage windingin wye with neutral bushing without phase shift between thesewindings, and a stabilizing tertiary winding connected in deltathat is not designed for external loading designated as YNyn0+d.Thus, this paper proposes a methodology to estimate the sequenceimpedances of YNyn0+d transformers from a statistical point ofview applying clustering and regression analyses on existing MPTtest report data.展开更多
As the penetration rate of distributed energy increases,the transient power angle stability problem of the virtual synchronous generator(VSG)has gradually become prominent.In view of the situation that the grid impeda...As the penetration rate of distributed energy increases,the transient power angle stability problem of the virtual synchronous generator(VSG)has gradually become prominent.In view of the situation that the grid impedance ratio(R/X)is high and affects the transient power angle stability of VSG,this paper proposes a VSG transient power angle stability control strategy based on the combination of frequency difference feedback and virtual impedance.To improve the transient power angle stability of the VSG,a virtual impedance is adopted in the voltage loop to adjust the impedance ratio R/X;and the PI control feedback of the VSG frequency difference is introduced in the reactive powervoltage link of theVSGto enhance the damping effect.Thesecond-orderVSGdynamic nonlinearmodel considering the reactive power-voltage loop is established and the influence of different proportional integral(PI)control parameters on the system balance stability is analyzed.Moreover,the impact of the impedance ratio R/X on the transient power angle stability is presented using the equal area criterion.In the simulations,during the voltage dips with the reduction of R/X from 1.6 to 0.8,Δδ_(1)is reduced from 0.194 rad to 0.072 rad,Δf_(1)is reduced from 0.170 to 0.093 Hz,which shows better transient power angle stability.Simulation results verify that compared with traditional VSG,the proposedmethod can effectively improve the transient power angle stability of the system.展开更多
The active sound absorption technique excels in mitigating low-frequency sound waves,yet it falls short when dealing with medium and high-frequency sound waves.To enhance the sound-absorbing effect of medium and high-...The active sound absorption technique excels in mitigating low-frequency sound waves,yet it falls short when dealing with medium and high-frequency sound waves.To enhance the sound-absorbing effect of medium and high-frequency sound waves,a novel semi-active sound absorption method has been introduced.This method modulates the surface impedance of a loudspeaker positioned behind the sound-absorbing material,thereby altering the sound absorption coefficient.The theoretical sound absorption coefficient is calculated using MATLAB and compared with the experimental one.Results show that the method can effectively modulates the absorption coefficient in response to varying incident sound wave frequencies,ensuring that it remains at its peak value.展开更多
All-solid-state lithium batteries(ASSLBs)are strongly considered as the next-generation energy storage devices for their high energy density and intrinsic safety.The solid-solid contact between lithium metal and solid...All-solid-state lithium batteries(ASSLBs)are strongly considered as the next-generation energy storage devices for their high energy density and intrinsic safety.The solid-solid contact between lithium metal and solid electrolyte plays a vital role in the performance of working ASSLBs,which is challenging to investigate quantitatively by experimental approach.This work proposed a quantitative model based on the finite element method for electrochemical impedance spectroscopy simulation of different solid-solid contact states in ASSLBs.With the assistance of an equivalent circuit model and distribution of relaxation times,it is discovered that as the number of voids and the sharpness of cracks increase,the contact resistance Rcgrows and ultimately dominates the battery impedance.Through accurate fitting,inverse proportional relations between contact resistance Rcand(1-porosity)as well as crack angle was disclosed.This contribution affords a fresh insight into clarifying solid-solid contact states in ASSLBs.展开更多
Although previous studies have demonstrated that transcranial focused ultrasound stimulation protects the ischemic brain,clear criteria for the stimulation time window and intensity are lacking.Electrical impedance to...Although previous studies have demonstrated that transcranial focused ultrasound stimulation protects the ischemic brain,clear criteria for the stimulation time window and intensity are lacking.Electrical impedance tomography enables real-time monitoring of changes in cerebral blood perfusion within the ischemic brain,but investigating the feasibility of using this method to assess post-stroke rehabilitation in vivo remains critical.In this study,ischemic stroke was induced in rats through middle cerebral artery occlusion surgery.Transcranial focused ultrasound stimulation was used to treat the rat model of ischemia,and electrical impedance tomography was used to measure impedance during both the acute stage of ischemia and the rehabilitation stage following the stimulation.Electrical impedance tomography results indicated that cerebral impedance increased after the onset of ischemia and decreased following transcranial focused ultrasound stimulation.Furthermore,the stimulation promoted motor function recovery,reduced cerebral infarction volume in the rat model of ischemic stroke,and induced the expression of brain-derived neurotrophic factor in the ischemic brain.Our results also revealed a significant correlation between the impedance of the ischemic brain post-intervention and improvements in behavioral scores and infarct volume.This study shows that daily administration of transcranial focused ultrasound stimulation for 20 minutes to the ischemic hemisphere 24 hours after cerebral ischemia enhanced motor recovery in a rat model of ischemia.Additionally,our findings indicate that electrical impedance tomography can serve as a valuable tool for quantitatively evaluating rehabilitation after ischemic stroke in vivo.These findings suggest the feasibility of using impedance data collected via electrical impedance tomography to clinically assess the effects of rehabilitatory interventions for patients with ischemic stroke.展开更多
Electrical impedance tomography(EIT)is a non-invasive imaging modality that generates real-time images by measuring tissue bioimpedance.It works by applying current and collecting voltage data to reconstruct images of...Electrical impedance tomography(EIT)is a non-invasive imaging modality that generates real-time images by measuring tissue bioimpedance.It works by applying current and collecting voltage data to reconstruct images of electrical conductivity,refl ecting tissue properties.[1]We aim to off er a comprehensive guide to the fundamental technology behind EIT and to explore its clinical applications across both pulmonary and extrapulmonary domains.展开更多
Impedance pneumography has a significant advantage for continuous and noninvasive monitoring of respiration,compared with conventional flowmeter-based ventilation measurement technologies.While thoracic impedance is s...Impedance pneumography has a significant advantage for continuous and noninvasive monitoring of respiration,compared with conventional flowmeter-based ventilation measurement technologies.While thoracic impedance is sensitive to pulmonary ventilation,it is also sensitive to physiological activities such as blood flow and cardiomotility,in addition,body movement/posture.This paper explores the possibility of simultaneously monitoring pulmonary ventilation,blood circulation and cardiomotility by bioimpedance measurement.Respiratory,blood perfusion and cardiomotility signals are extracted using the wavelet method from thoracic impedance data measured in breath-holding and tidal breathing statuses,to investigate signal strength and their dependency.This research provides a foundation for the development of bedside devices to monitor various physiological activities.展开更多
Electrochemical impedance spectroscopy(EIS)was used to examine the electrical properties of metakaolin(MK)cement-based materials at elevated temperatures.We utilized a new equivalent circuit to investigate the EIS res...Electrochemical impedance spectroscopy(EIS)was used to examine the electrical properties of metakaolin(MK)cement-based materials at elevated temperatures.We utilized a new equivalent circuit to investigate the EIS results of cementitious materials blended with MK at these temperatures.A new evaluation method to high temperature damage is proposed.The findings show that both elevated temperatures and MK contents in cement mortar can impact the impedance spectra’s form properties.However,the residual compressive strength of the MK-blended cementitious material at elevated temperatures does not improve with the addition of MK.A quantitative relationship between the electrochemical parameters of the new equivalent circuit and the residual compressive strength is determined.The degree of high-temperature damage to cementitious materials can be evaluated based on these electrochemical parameters,providing a new approach for evaluating the high-temperature damage of MK-blend cementitious materials.展开更多
One of the core works of analyzing Electrochemical Impedance Spectroscopy(EIS)data is to select an appropriate equivalent circuit model to quantify the parameters of the electrochemical reaction process.However,this p...One of the core works of analyzing Electrochemical Impedance Spectroscopy(EIS)data is to select an appropriate equivalent circuit model to quantify the parameters of the electrochemical reaction process.However,this process often relies on human experience and judgment,which will introduce subjectivity and error.In this paper,an intelligent approach is proposed for matching EIS data to their equivalent circuits based on the Random Forest algorithm.It can automatically select the most suitable equivalent circuit model based on the characteristics and patterns of EIS data.Addressing the typical scenario of metal corrosion,an atmospheric corrosion EIS dataset of low-carbon steel is constructed in this paper,which includes five different corrosion scenarios.This dataset was used to validate and evaluate the pro-posed method in this paper.The contributions of this paper can be summarized in three aspects:(1)This paper proposes a method for selecting equivalent circuit models for EIS data based on the Random Forest algorithm.(2)Using authentic EIS data collected from metal atmospheric corrosion,the paper es-tablishes a dataset encompassing five categories of metal corrosion scenarios.(3)The superiority of the proposed method is validated through the utilization of the established authentic EIS dataset.The ex-periment results demonstrate that,in terms of equivalent circuit matching,this method surpasses other machine learning algorithms in both precision and robustness.Furthermore,it shows strong applicability in the analysis of EIS data.展开更多
In the islanded operation of distribution networks,due to the mismatch of line impedance at the inverter output,conventional droop control leads to inaccurate power sharing according to capacity,resulting in voltage a...In the islanded operation of distribution networks,due to the mismatch of line impedance at the inverter output,conventional droop control leads to inaccurate power sharing according to capacity,resulting in voltage and frequency fluctuations under minor external disturbances.To address this issue,this paper introduces an enhanced scheme for power sharing and voltage-frequency control.First,to solve the power distribution problem,we propose an adaptive virtual impedance control based on multi-agent consensus,which allows for precise active and reactive power allocation without requiring feeder impedance knowledge.Moreover,a novel consensus-based voltage and frequency control is proposed to correct the voltage deviation inherent in droop control and virtual impedance methods.This strategy maintains voltage and frequency stability even during communication disruptions and enhances system robustness.Additionally,a small-signal model is established for system stability analysis,and the control parameters are optimized.Simulation results validate the effectiveness of the proposed control scheme.展开更多
Electrochemical impedance spectroscopy(EIS)offers valuable insights into the dynamic behaviors of lithium-ion batteries,making it a powerful and non-invasive tool for evaluating battery health.However,EIS falls short ...Electrochemical impedance spectroscopy(EIS)offers valuable insights into the dynamic behaviors of lithium-ion batteries,making it a powerful and non-invasive tool for evaluating battery health.However,EIS falls short in quantitatively determining the degree of specific degradation modes,which are essential for improving battery lifespan.This study introduces a novel approach employing deep neural networks enhanced by an attention mechanism to identify the degree of degradation modes.The proposed method can automatically determine the most relevant frequency ranges for each degradation mode,which can link impedance characteristics to battery degradation.To overcome the limitation of scarce labeled experimental data,simulation results derived from mechanistic models are incorporated into the model.Validation results demonstrate that the proposed method could achieve root mean square errors below 3%for estimating loss of lithium inventory and loss of active material of the positive electrode,and below 4%for estimating loss of active material of the negative electrode while requiring only 25%of early-stage experimental degradation data.By integrating simulation results,the proposed method achieves a reduction in maximum estimation error ranging from 42.92%to 66.30%across different temperatures and operating conditions compared to the baseline model trained solely on experimental data.展开更多
Battery health evaluation and management are vital for the long-term reliability and optimal performance of lithium-ion batteries in electric vehicles.Electrochemical impedance spectroscopy(EIS)offers valuable insight...Battery health evaluation and management are vital for the long-term reliability and optimal performance of lithium-ion batteries in electric vehicles.Electrochemical impedance spectroscopy(EIS)offers valuable insights into battery degradation analysis and modeling.However,previous studies have not adequately addressed the impedance uncertainties,particularly during battery operating conditions,which can substantially impact the robustness and accuracy of state of health(SOH)estimation.Motivated by this,this paper proposes a comprehensive feature optimization scheme that integrates impedance validity assessment with correlation analysis.By utilizing metrics such as impedance residuals and correlation coefficients,the proposed method effectively filters out invalid and insignificant impedance data,thereby enhancing the reliability of the input features.Subsequently,the extreme gradient boosting(XGBoost)modeling framework is constructed for estimating the battery degradation trajectories.The XGBoost model incorporates a diverse range of hyperparameters,optimized by a genetic algorithm to improve its adaptability and generalization performance.Experimental validation confirms the effectiveness of the proposed feature optimization scheme,demonstrating the superior estimation performance of the proposed method in comparison with four baseline techniques.展开更多
Electrochemical impedance spectroscopy(EIS)is a robust characterization method to probe prevalent(electro)chemical processes in an electrochemical system.Despite its extensive utilization in fuel cell research,the app...Electrochemical impedance spectroscopy(EIS)is a robust characterization method to probe prevalent(electro)chemical processes in an electrochemical system.Despite its extensive utilization in fuel cell research,the application of EIS in redox flow battery systems particularly for simplified two-electrode full-cell configurations is more limited.Herein we attempt to strengthen the understa nding of cha racteristic EIS data of vanadium redox flow batteries by a combination of equivalent circuit modeling with a validated Multiphysics model analyzed under hydrodynamic conditions in frequency domain.Following a highlight of system linearity and stability concerns for EIS in redox flow batteries,we specifically use our combinatory approach to investigate the effects of different cell component properties on observed galva nostatic EIS spectra and accompanying fitted equivalent circuit element parameters.For the investigated two-electrode full-cell flow battery configuration with the same electrode material on both sides,the EIS spectral data is observed to be dominated by different mass or cha rge transport processes at different ends of the spectrum.Sensitivity analyses of both obtained EIS spectral data and fitted circuit elements parameters show that electrode morphological properties,membrane porosity,and electrolyte inflow conditions predominantly define the EIS spectral data.Insights from the type of analyses performed herein can facilitate flow battery cell/stack diagnostics and targeted performance improvement efforts.展开更多
Bladder cancer(BC)is a common malignancy and among the leading causes of cancer death worldwide.Analysis of BC cells is of great significance for clinical diagnosis and disease treatment.Current approaches rely mainly...Bladder cancer(BC)is a common malignancy and among the leading causes of cancer death worldwide.Analysis of BC cells is of great significance for clinical diagnosis and disease treatment.Current approaches rely mainly on imaging-based technology,which requires complex staining and sophisticated instrumentation.In this work,we develop a label-free method based on artificial intelligence(AI)-assisted impedance-based flow cytometry(IFC)to differentiate between various BC cells and epithelial cells at single-cell resolution.By applying multiple-frequency excitations,the electrical characteristics of cells,including membrane and nuclear opacities,are extracted,allowing distinction to be made between epithelial cells,low-grade,and high-grade BC cells.Through the use of a constriction channel,the electro-mechanical properties associated with active deformation behavior of cells are investigated,and it is demonstrated that BC cells have a greater capability of shape recovery,an observation that further increases differentiation accuracy.With the assistance of a convolutional neural network-based AI algorithm,IFC is able to effectively differentiate various BC and epithelial cells with accuracies of over 95%.In addition,different grades of BC cells are successfully differentiated in both spiked mixed samples and bladder tumor tissues.展开更多
Reservoirs with a group of vertical fractures in a vertical transversely isotropic(VTI)background are considered as orthorhombic(ORT)medium.However,fracture detection in ORT medium using seismic inversion methods rema...Reservoirs with a group of vertical fractures in a vertical transversely isotropic(VTI)background are considered as orthorhombic(ORT)medium.However,fracture detection in ORT medium using seismic inversion methods remains challenging,as it requires the estimation of more than eight parameters.Assuming the reservoir to be a weakly anisotropic ORT medium with small contrasts in the background elastic parameters,a new azimuthal elastic impedance equation was first derived using parameter combinations and mathematical approximations.This equation exhibited almost the same accuracy as the original equation and contained only six model parameters:the compression modulus,anisotropic shear modulus,anisotropic compression modulus,density,normal fracture weakness,and tangential fracture weakness.Subsequently,a stepwise inversion method using second-order derivatives of the elastic impedance was developed to estimate these parameters.Moreover,the Thomsen anisotropy parameter,epsilon,was estimated from the inversion results using the ratio of the anisotropic compression modulus to the compression modulus.Synthetic examples with moderate noise and field data examples confirm the feasibility and effectiveness of the inversion method.The proposed method exhibited accuracy similar to that of previous inversion strategies and could predict richer vertical fracture information.Ultimately,the method was applied to a three-dimensional work area,and the predictions were consistent with logging and geological a priori information,confirming the effectiveness of this method.Summarily,the proposed stepwise inversion method can alleviate the uncertainty of multi-parameter inversion in ORT medium,thereby improving the reliability of fracture detection.展开更多
Accurate quantification of exercise interventions and changes in muscle function is essential for personalized health management.Electrical impedance myography(EIM)technology offers an innovative,noninvasive,painless,...Accurate quantification of exercise interventions and changes in muscle function is essential for personalized health management.Electrical impedance myography(EIM)technology offers an innovative,noninvasive,painless,and easy-to-perform solution for muscle health monitoring.However,current EIM platforms face a number of limitations,including large device size,wired connections,and instability of the electrode-skin interface,which limit their applicability for monitoring mus-cle movement.In this study,a miniature wireless EIM platform with a user-friendly smartphone app is proposed and devel-oped.The miniature,wireless,multi-frequency(20 kHz-1 MHz)EIM platform is equipped with flexible microneedle array elec-trodes(MAE).The advantages of MAEs over conventional electrodes were demonstrated by physical field modeling simula-tions and skin-electrode contact impedance comparison tests.The smartphone APP was developed to wirelessly operate the EIM platform,and to transmit and process real-time muscle impedance data.To validate its effectiveness,a seven-day adaptive fatigue training study was conducted,which demonstrated that the EIM platform was able to detect muscle adaptations and serve as a reliable indicator of fatigue.This study presents an innovative approach to applying EIM technology to muscle health monitoring and exercise testing,thereby advancing the development of personalized health management and athletic performance assessment.展开更多
The trade-off between mechanistic interpretability,operational convenience,and predictive accuracy is challenging for predicting the lifetime of lithium-ion batteries.To resolve this contradiction,we propose a damage ...The trade-off between mechanistic interpretability,operational convenience,and predictive accuracy is challenging for predicting the lifetime of lithium-ion batteries.To resolve this contradiction,we propose a damage model based on fatigue damage theory and electrochemical impedance spectroscopy.The causal relationship of“fatigue damage→resistance increase→capacity fading”is revealed to describe the underlying mechanism.Charge transfer resistance is chosen as the variable to ensure the convenience of data acquisition.To verify the accuracy of the model,the electrochemical impedance spectrum and capacity of a graphene-coated silicon electrode at two charging rates are collected and analyzed.50% and 75% of the measured data are utilized as inputs to compare the prediction capabilities of the proposed damage model and the existing empirical model.The particle filter algorithm is adopted to train the parameters of both models.The maximum prediction error of the damage model is less than 3%,showing better prediction accuracy and medium-term prediction stability than the empirical model.Our work demonstrates that the proposed damage model is an effective way to resolve contradictions in lifetime prediction.展开更多
As lithium-ion batteries become increasingly prevalent in electric scooters,vehicles,mobile devices,and energy storage systems,accurate estimation of remaining battery capacity is crucial for optimizing system perform...As lithium-ion batteries become increasingly prevalent in electric scooters,vehicles,mobile devices,and energy storage systems,accurate estimation of remaining battery capacity is crucial for optimizing system performance and reliability.Unlike traditional methods that rely on static alternating internal resistance(SAIR)measurements in an open-circuit state,this study presents a real-time state of charge(SOC)estimation method combining dynamic alternating internal resistance(DAIR)with artificial neural networks(ANN).The system simultaneously measures electrochemical impedance various frequencies,discharge C-rate,and battery surface temperature during the∣Z∣atdischarge process,using these parameters for ANN training.The ANN,leveraging its superior nonlinear system modeling capabilities,effectively captures the complex nonlinear relationships between AC impedance and SOC through iterative training.Compared to other machine learning approaches,the proposed ANN features a simpler architecture and lower computational overhead,making it more suitable for integration into battery management system(BMS)microcontrollers.In tests conducted with Samsung batteries using lithium cobalt oxide cathode material,the method achieved an overall average error of merely 0.42%in self-validation,with mean absolute errors(MAE)for individual SOCs not exceeding 1%.Secondary validation demonstrated an overall average error of 1.24%,with MAE for individual SOCs below 2.5%.This integrated DAIR-ANN approach not only provides enhanced estimation accuracy but also simplifies computational requirements,offering a more effective solution for battery management in practical applications.展开更多
A temperature and acoustic impedance simultaneous sensor based on forward stimulated Brillouin scattering(FSBS)in highly nonlinear fiber(HNLF)with high sensitivity and high accuracy is proposed and demonstrated in thi...A temperature and acoustic impedance simultaneous sensor based on forward stimulated Brillouin scattering(FSBS)in highly nonlinear fiber(HNLF)with high sensitivity and high accuracy is proposed and demonstrated in this paper.High-order acoustic modes(HOAMs)are used to achieve individual or simultaneous measurement of the two parameters.Transverse acoustic waves(TAWs)involved in the FSBS process can efficiently sense the mechanical or environmental changes outside the fiber cladding,which will be reflected in a linear shift of the acoustic resonance frequency.By analyzing the frequencies of specific scattering peaks,the temperature and acoustic impedance outside the fiber cladding can be obtained simultaneously.The highest measured temperature and acoustic impedance sensitivities are 184.93 k Hz/℃and444.56 k Hz/MRayl,and the measurement accuracies are 0.09℃and 0.009 MRayl,respectively,which are both at desirable levels.We believe this work can provide potential application solutions for sensing fields involving temperature or acoustic impedance measurements.展开更多
Quantum well infrared photodetectors(QWIPs) based on intersubband transitions hold significant potential for high bandwidth operation. In this work, we establish a carrier transport optimization model incorporating el...Quantum well infrared photodetectors(QWIPs) based on intersubband transitions hold significant potential for high bandwidth operation. In this work, we establish a carrier transport optimization model incorporating electron injection at the emitter to investigate the carrier dynamics time and impedance spectroscopy in GaAs/AlGaAs QWIPs. Our findings provide novel evidence that the escape time of electrons is the key limiting factor for the 3-dB bandwidth of QWIPs. Moreover, to characterize the impact of carrier dynamics time and non-equilibrium space charge region on impedance, we developed an equivalent circuit model where depletion region resistance and capacitance are employed to describe non-equilibrium space charge region. Using this model, we discovered that under illumination, both net charge accumulation caused by variations in carrier dynamics times within quantum wells and changes in width of non-equilibrium space charge region exert different dominant influences on depletion region capacitance at various doping concentrations.展开更多
文摘With the increased penetration of non-conventionalrenewable energy resources, such as wind power plants (WPPs),into the power system, a lot of interest has been placed on studyingtheir impact for system protection, planning and operationsto ensure continued reliability of the electric grid. The impactof WPPs on the grid is typically identified during generationinterconnection studies. One of the challenges faced by protectionand planning engineers, at an early stage in this process, isthat many of the studies involving these power plants must beperformed without specific data available because the equipmentis not built yet. Among all the needed data, a particular interest inthis study is placed on the positive- and zero-sequence impedancesof the main power transformer (MPT) that interconnects a windpower plant to the transmission system due to its contribution toshort-circuit current during ground faults. The most commonlyfound in practice MPT winding configurations is a high-voltagewinding in wye with neutral bushing;a low-voltage windingin wye with neutral bushing without phase shift between thesewindings, and a stabilizing tertiary winding connected in deltathat is not designed for external loading designated as YNyn0+d.Thus, this paper proposes a methodology to estimate the sequenceimpedances of YNyn0+d transformers from a statistical point ofview applying clustering and regression analyses on existing MPTtest report data.
基金supported by theMajor Science and Technology Projects of China Southern Power Grid(Grant number CGYKJXM20210328).
文摘As the penetration rate of distributed energy increases,the transient power angle stability problem of the virtual synchronous generator(VSG)has gradually become prominent.In view of the situation that the grid impedance ratio(R/X)is high and affects the transient power angle stability of VSG,this paper proposes a VSG transient power angle stability control strategy based on the combination of frequency difference feedback and virtual impedance.To improve the transient power angle stability of the VSG,a virtual impedance is adopted in the voltage loop to adjust the impedance ratio R/X;and the PI control feedback of the VSG frequency difference is introduced in the reactive powervoltage link of theVSGto enhance the damping effect.Thesecond-orderVSGdynamic nonlinearmodel considering the reactive power-voltage loop is established and the influence of different proportional integral(PI)control parameters on the system balance stability is analyzed.Moreover,the impact of the impedance ratio R/X on the transient power angle stability is presented using the equal area criterion.In the simulations,during the voltage dips with the reduction of R/X from 1.6 to 0.8,Δδ_(1)is reduced from 0.194 rad to 0.072 rad,Δf_(1)is reduced from 0.170 to 0.093 Hz,which shows better transient power angle stability.Simulation results verify that compared with traditional VSG,the proposedmethod can effectively improve the transient power angle stability of the system.
基金National Natural Science Foundation of China(No.51705545)。
文摘The active sound absorption technique excels in mitigating low-frequency sound waves,yet it falls short when dealing with medium and high-frequency sound waves.To enhance the sound-absorbing effect of medium and high-frequency sound waves,a novel semi-active sound absorption method has been introduced.This method modulates the surface impedance of a loudspeaker positioned behind the sound-absorbing material,thereby altering the sound absorption coefficient.The theoretical sound absorption coefficient is calculated using MATLAB and compared with the experimental one.Results show that the method can effectively modulates the absorption coefficient in response to varying incident sound wave frequencies,ensuring that it remains at its peak value.
基金supported by the Beijing Natural Science Foundation(Z200011,L233004)the National Key Research and Development Program(2021YFB2500300)+3 种基金the National Natural Science Foundation of China(52394170,52394171,22109011,22393900,and 22108151)the Tsinghua-Jiangyin Innovation Special Fund(TJISF)(2022JYTH0101)the S&T Program of Hebei(22344402D)the Tsinghua University Initiative Scientific Research Program.
文摘All-solid-state lithium batteries(ASSLBs)are strongly considered as the next-generation energy storage devices for their high energy density and intrinsic safety.The solid-solid contact between lithium metal and solid electrolyte plays a vital role in the performance of working ASSLBs,which is challenging to investigate quantitatively by experimental approach.This work proposed a quantitative model based on the finite element method for electrochemical impedance spectroscopy simulation of different solid-solid contact states in ASSLBs.With the assistance of an equivalent circuit model and distribution of relaxation times,it is discovered that as the number of voids and the sharpness of cracks increase,the contact resistance Rcgrows and ultimately dominates the battery impedance.Through accurate fitting,inverse proportional relations between contact resistance Rcand(1-porosity)as well as crack angle was disclosed.This contribution affords a fresh insight into clarifying solid-solid contact states in ASSLBs.
基金supported by the Fundamental Research Funds for the Central Universities,Nos.G2021KY05107,G2021KY05101the National Natural Science Foundation of China,Nos.32071316,32211530049+1 种基金the Natural Science Foundation of Shaanxi Province,No.2022-JM482the Education and Teaching Reform Funds for the Central Universities,No.23GZ230102(all to LL and HH).
文摘Although previous studies have demonstrated that transcranial focused ultrasound stimulation protects the ischemic brain,clear criteria for the stimulation time window and intensity are lacking.Electrical impedance tomography enables real-time monitoring of changes in cerebral blood perfusion within the ischemic brain,but investigating the feasibility of using this method to assess post-stroke rehabilitation in vivo remains critical.In this study,ischemic stroke was induced in rats through middle cerebral artery occlusion surgery.Transcranial focused ultrasound stimulation was used to treat the rat model of ischemia,and electrical impedance tomography was used to measure impedance during both the acute stage of ischemia and the rehabilitation stage following the stimulation.Electrical impedance tomography results indicated that cerebral impedance increased after the onset of ischemia and decreased following transcranial focused ultrasound stimulation.Furthermore,the stimulation promoted motor function recovery,reduced cerebral infarction volume in the rat model of ischemic stroke,and induced the expression of brain-derived neurotrophic factor in the ischemic brain.Our results also revealed a significant correlation between the impedance of the ischemic brain post-intervention and improvements in behavioral scores and infarct volume.This study shows that daily administration of transcranial focused ultrasound stimulation for 20 minutes to the ischemic hemisphere 24 hours after cerebral ischemia enhanced motor recovery in a rat model of ischemia.Additionally,our findings indicate that electrical impedance tomography can serve as a valuable tool for quantitatively evaluating rehabilitation after ischemic stroke in vivo.These findings suggest the feasibility of using impedance data collected via electrical impedance tomography to clinically assess the effects of rehabilitatory interventions for patients with ischemic stroke.
基金supported partially by grants from the National Natural Science Foundation of China(82470068,82270086,GS Zhang82372185,BP Tian)+2 种基金the Natural Science Foundation of Zhejiang Province(Key Project)(LZ25H150001,GS Zhang)the National Health Commission Scientifi c Research Fund Zhejiang Provincial Health Major Science and Technology Plan Project(co-construction project of National Health Commission Committee and Zhejiang Province)(WKJ-ZJ-2526,GS Zhang)the Medical and Health Research Program of Zhejiang Province(2023572679).
文摘Electrical impedance tomography(EIT)is a non-invasive imaging modality that generates real-time images by measuring tissue bioimpedance.It works by applying current and collecting voltage data to reconstruct images of electrical conductivity,refl ecting tissue properties.[1]We aim to off er a comprehensive guide to the fundamental technology behind EIT and to explore its clinical applications across both pulmonary and extrapulmonary domains.
基金the National Natural Science Foundation of China(No.61371017)the Interdisciplinary Program of Shanghai Jiao Tong University(No.YG2021QN37)。
文摘Impedance pneumography has a significant advantage for continuous and noninvasive monitoring of respiration,compared with conventional flowmeter-based ventilation measurement technologies.While thoracic impedance is sensitive to pulmonary ventilation,it is also sensitive to physiological activities such as blood flow and cardiomotility,in addition,body movement/posture.This paper explores the possibility of simultaneously monitoring pulmonary ventilation,blood circulation and cardiomotility by bioimpedance measurement.Respiratory,blood perfusion and cardiomotility signals are extracted using the wavelet method from thoracic impedance data measured in breath-holding and tidal breathing statuses,to investigate signal strength and their dependency.This research provides a foundation for the development of bedside devices to monitor various physiological activities.
基金Funded by the Natural Science Foundation of Inner Mongolia Autonomous Region(No.2024QN05023)High Level Talent Research Launch Foundation of Inner Mongolia University(No.10000-22311201/008)。
文摘Electrochemical impedance spectroscopy(EIS)was used to examine the electrical properties of metakaolin(MK)cement-based materials at elevated temperatures.We utilized a new equivalent circuit to investigate the EIS results of cementitious materials blended with MK at these temperatures.A new evaluation method to high temperature damage is proposed.The findings show that both elevated temperatures and MK contents in cement mortar can impact the impedance spectra’s form properties.However,the residual compressive strength of the MK-blended cementitious material at elevated temperatures does not improve with the addition of MK.A quantitative relationship between the electrochemical parameters of the new equivalent circuit and the residual compressive strength is determined.The degree of high-temperature damage to cementitious materials can be evaluated based on these electrochemical parameters,providing a new approach for evaluating the high-temperature damage of MK-blend cementitious materials.
基金support of the project from the National Key R&D Program of China,Research and Application of Sensing System for Cross-regional Complex Oil&Gas Pipeline Network Safe and Efficiency Operational Status Monitoring(Grant No.2022YFB3207603).
文摘One of the core works of analyzing Electrochemical Impedance Spectroscopy(EIS)data is to select an appropriate equivalent circuit model to quantify the parameters of the electrochemical reaction process.However,this process often relies on human experience and judgment,which will introduce subjectivity and error.In this paper,an intelligent approach is proposed for matching EIS data to their equivalent circuits based on the Random Forest algorithm.It can automatically select the most suitable equivalent circuit model based on the characteristics and patterns of EIS data.Addressing the typical scenario of metal corrosion,an atmospheric corrosion EIS dataset of low-carbon steel is constructed in this paper,which includes five different corrosion scenarios.This dataset was used to validate and evaluate the pro-posed method in this paper.The contributions of this paper can be summarized in three aspects:(1)This paper proposes a method for selecting equivalent circuit models for EIS data based on the Random Forest algorithm.(2)Using authentic EIS data collected from metal atmospheric corrosion,the paper es-tablishes a dataset encompassing five categories of metal corrosion scenarios.(3)The superiority of the proposed method is validated through the utilization of the established authentic EIS dataset.The ex-periment results demonstrate that,in terms of equivalent circuit matching,this method surpasses other machine learning algorithms in both precision and robustness.Furthermore,it shows strong applicability in the analysis of EIS data.
基金supported by the National Natural Science Foundation of China(52007009)Natural Science Foundation of Excellent Youth Project of Hunan Province of China(2023JJ20039)Science and Technology Projects of State Grid Hunan Provincial Electric Power Co.,Ltd.(5216A522001K,SGHNDK00PWJS2310173).
文摘In the islanded operation of distribution networks,due to the mismatch of line impedance at the inverter output,conventional droop control leads to inaccurate power sharing according to capacity,resulting in voltage and frequency fluctuations under minor external disturbances.To address this issue,this paper introduces an enhanced scheme for power sharing and voltage-frequency control.First,to solve the power distribution problem,we propose an adaptive virtual impedance control based on multi-agent consensus,which allows for precise active and reactive power allocation without requiring feeder impedance knowledge.Moreover,a novel consensus-based voltage and frequency control is proposed to correct the voltage deviation inherent in droop control and virtual impedance methods.This strategy maintains voltage and frequency stability even during communication disruptions and enhances system robustness.Additionally,a small-signal model is established for system stability analysis,and the control parameters are optimized.Simulation results validate the effectiveness of the proposed control scheme.
基金supported by the National Key R&D Program of China(2024YFB2505003).
文摘Electrochemical impedance spectroscopy(EIS)offers valuable insights into the dynamic behaviors of lithium-ion batteries,making it a powerful and non-invasive tool for evaluating battery health.However,EIS falls short in quantitatively determining the degree of specific degradation modes,which are essential for improving battery lifespan.This study introduces a novel approach employing deep neural networks enhanced by an attention mechanism to identify the degree of degradation modes.The proposed method can automatically determine the most relevant frequency ranges for each degradation mode,which can link impedance characteristics to battery degradation.To overcome the limitation of scarce labeled experimental data,simulation results derived from mechanistic models are incorporated into the model.Validation results demonstrate that the proposed method could achieve root mean square errors below 3%for estimating loss of lithium inventory and loss of active material of the positive electrode,and below 4%for estimating loss of active material of the negative electrode while requiring only 25%of early-stage experimental degradation data.By integrating simulation results,the proposed method achieves a reduction in maximum estimation error ranging from 42.92%to 66.30%across different temperatures and operating conditions compared to the baseline model trained solely on experimental data.
文摘Battery health evaluation and management are vital for the long-term reliability and optimal performance of lithium-ion batteries in electric vehicles.Electrochemical impedance spectroscopy(EIS)offers valuable insights into battery degradation analysis and modeling.However,previous studies have not adequately addressed the impedance uncertainties,particularly during battery operating conditions,which can substantially impact the robustness and accuracy of state of health(SOH)estimation.Motivated by this,this paper proposes a comprehensive feature optimization scheme that integrates impedance validity assessment with correlation analysis.By utilizing metrics such as impedance residuals and correlation coefficients,the proposed method effectively filters out invalid and insignificant impedance data,thereby enhancing the reliability of the input features.Subsequently,the extreme gradient boosting(XGBoost)modeling framework is constructed for estimating the battery degradation trajectories.The XGBoost model incorporates a diverse range of hyperparameters,optimized by a genetic algorithm to improve its adaptability and generalization performance.Experimental validation confirms the effectiveness of the proposed feature optimization scheme,demonstrating the superior estimation performance of the proposed method in comparison with four baseline techniques.
基金sponsored by the Dubai Electricity and Water Authority(DEWA)R&D centre,Dubai,United Arab Emirates。
文摘Electrochemical impedance spectroscopy(EIS)is a robust characterization method to probe prevalent(electro)chemical processes in an electrochemical system.Despite its extensive utilization in fuel cell research,the application of EIS in redox flow battery systems particularly for simplified two-electrode full-cell configurations is more limited.Herein we attempt to strengthen the understa nding of cha racteristic EIS data of vanadium redox flow batteries by a combination of equivalent circuit modeling with a validated Multiphysics model analyzed under hydrodynamic conditions in frequency domain.Following a highlight of system linearity and stability concerns for EIS in redox flow batteries,we specifically use our combinatory approach to investigate the effects of different cell component properties on observed galva nostatic EIS spectra and accompanying fitted equivalent circuit element parameters.For the investigated two-electrode full-cell flow battery configuration with the same electrode material on both sides,the EIS spectral data is observed to be dominated by different mass or cha rge transport processes at different ends of the spectrum.Sensitivity analyses of both obtained EIS spectral data and fitted circuit elements parameters show that electrode morphological properties,membrane porosity,and electrolyte inflow conditions predominantly define the EIS spectral data.Insights from the type of analyses performed herein can facilitate flow battery cell/stack diagnostics and targeted performance improvement efforts.
基金financial support from the National Natural Science Foundation of China(NSFC Grant No.22076138)the National Natural Science Foundation of China(NSFC Grant No.62174119).
文摘Bladder cancer(BC)is a common malignancy and among the leading causes of cancer death worldwide.Analysis of BC cells is of great significance for clinical diagnosis and disease treatment.Current approaches rely mainly on imaging-based technology,which requires complex staining and sophisticated instrumentation.In this work,we develop a label-free method based on artificial intelligence(AI)-assisted impedance-based flow cytometry(IFC)to differentiate between various BC cells and epithelial cells at single-cell resolution.By applying multiple-frequency excitations,the electrical characteristics of cells,including membrane and nuclear opacities,are extracted,allowing distinction to be made between epithelial cells,low-grade,and high-grade BC cells.Through the use of a constriction channel,the electro-mechanical properties associated with active deformation behavior of cells are investigated,and it is demonstrated that BC cells have a greater capability of shape recovery,an observation that further increases differentiation accuracy.With the assistance of a convolutional neural network-based AI algorithm,IFC is able to effectively differentiate various BC and epithelial cells with accuracies of over 95%.In addition,different grades of BC cells are successfully differentiated in both spiked mixed samples and bladder tumor tissues.
基金sponsorship of the National Natural Science Foundation of China(42430809,42274157,42030103,42404132)the Fund of State Key Laboratory of Deep Oil and Gas,China University of Petroleum(East China)(SKLDOG2024-ZYTS-02)+5 种基金the Postdoctoral Fellowship Program of CPSF(GZB20240850)the Postdoctoral Project of Qingdao(QDBSH20240102082)the Fundamental Research Funds for the Central Universities(24CX07004A,24CX06036A)the CNPC Innovation Fund(2024DQ02-0505,2024DQ02-0136)the Innovation fund project for graduate student of China University of Petroleum(East China)the Fundamental Research Funds for the Central Universities(24CX04002A).
文摘Reservoirs with a group of vertical fractures in a vertical transversely isotropic(VTI)background are considered as orthorhombic(ORT)medium.However,fracture detection in ORT medium using seismic inversion methods remains challenging,as it requires the estimation of more than eight parameters.Assuming the reservoir to be a weakly anisotropic ORT medium with small contrasts in the background elastic parameters,a new azimuthal elastic impedance equation was first derived using parameter combinations and mathematical approximations.This equation exhibited almost the same accuracy as the original equation and contained only six model parameters:the compression modulus,anisotropic shear modulus,anisotropic compression modulus,density,normal fracture weakness,and tangential fracture weakness.Subsequently,a stepwise inversion method using second-order derivatives of the elastic impedance was developed to estimate these parameters.Moreover,the Thomsen anisotropy parameter,epsilon,was estimated from the inversion results using the ratio of the anisotropic compression modulus to the compression modulus.Synthetic examples with moderate noise and field data examples confirm the feasibility and effectiveness of the inversion method.The proposed method exhibited accuracy similar to that of previous inversion strategies and could predict richer vertical fracture information.Ultimately,the method was applied to a three-dimensional work area,and the predictions were consistent with logging and geological a priori information,confirming the effectiveness of this method.Summarily,the proposed stepwise inversion method can alleviate the uncertainty of multi-parameter inversion in ORT medium,thereby improving the reliability of fracture detection.
文摘Accurate quantification of exercise interventions and changes in muscle function is essential for personalized health management.Electrical impedance myography(EIM)technology offers an innovative,noninvasive,painless,and easy-to-perform solution for muscle health monitoring.However,current EIM platforms face a number of limitations,including large device size,wired connections,and instability of the electrode-skin interface,which limit their applicability for monitoring mus-cle movement.In this study,a miniature wireless EIM platform with a user-friendly smartphone app is proposed and devel-oped.The miniature,wireless,multi-frequency(20 kHz-1 MHz)EIM platform is equipped with flexible microneedle array elec-trodes(MAE).The advantages of MAEs over conventional electrodes were demonstrated by physical field modeling simula-tions and skin-electrode contact impedance comparison tests.The smartphone APP was developed to wirelessly operate the EIM platform,and to transmit and process real-time muscle impedance data.To validate its effectiveness,a seven-day adaptive fatigue training study was conducted,which demonstrated that the EIM platform was able to detect muscle adaptations and serve as a reliable indicator of fatigue.This study presents an innovative approach to applying EIM technology to muscle health monitoring and exercise testing,thereby advancing the development of personalized health management and athletic performance assessment.
基金supported by the National Natural Science Foundation of China(12021002,12472183,and 12041201).
文摘The trade-off between mechanistic interpretability,operational convenience,and predictive accuracy is challenging for predicting the lifetime of lithium-ion batteries.To resolve this contradiction,we propose a damage model based on fatigue damage theory and electrochemical impedance spectroscopy.The causal relationship of“fatigue damage→resistance increase→capacity fading”is revealed to describe the underlying mechanism.Charge transfer resistance is chosen as the variable to ensure the convenience of data acquisition.To verify the accuracy of the model,the electrochemical impedance spectrum and capacity of a graphene-coated silicon electrode at two charging rates are collected and analyzed.50% and 75% of the measured data are utilized as inputs to compare the prediction capabilities of the proposed damage model and the existing empirical model.The particle filter algorithm is adopted to train the parameters of both models.The maximum prediction error of the damage model is less than 3%,showing better prediction accuracy and medium-term prediction stability than the empirical model.Our work demonstrates that the proposed damage model is an effective way to resolve contradictions in lifetime prediction.
文摘As lithium-ion batteries become increasingly prevalent in electric scooters,vehicles,mobile devices,and energy storage systems,accurate estimation of remaining battery capacity is crucial for optimizing system performance and reliability.Unlike traditional methods that rely on static alternating internal resistance(SAIR)measurements in an open-circuit state,this study presents a real-time state of charge(SOC)estimation method combining dynamic alternating internal resistance(DAIR)with artificial neural networks(ANN).The system simultaneously measures electrochemical impedance various frequencies,discharge C-rate,and battery surface temperature during the∣Z∣atdischarge process,using these parameters for ANN training.The ANN,leveraging its superior nonlinear system modeling capabilities,effectively captures the complex nonlinear relationships between AC impedance and SOC through iterative training.Compared to other machine learning approaches,the proposed ANN features a simpler architecture and lower computational overhead,making it more suitable for integration into battery management system(BMS)microcontrollers.In tests conducted with Samsung batteries using lithium cobalt oxide cathode material,the method achieved an overall average error of merely 0.42%in self-validation,with mean absolute errors(MAE)for individual SOCs not exceeding 1%.Secondary validation demonstrated an overall average error of 1.24%,with MAE for individual SOCs below 2.5%.This integrated DAIR-ANN approach not only provides enhanced estimation accuracy but also simplifies computational requirements,offering a more effective solution for battery management in practical applications.
文摘A temperature and acoustic impedance simultaneous sensor based on forward stimulated Brillouin scattering(FSBS)in highly nonlinear fiber(HNLF)with high sensitivity and high accuracy is proposed and demonstrated in this paper.High-order acoustic modes(HOAMs)are used to achieve individual or simultaneous measurement of the two parameters.Transverse acoustic waves(TAWs)involved in the FSBS process can efficiently sense the mechanical or environmental changes outside the fiber cladding,which will be reflected in a linear shift of the acoustic resonance frequency.By analyzing the frequencies of specific scattering peaks,the temperature and acoustic impedance outside the fiber cladding can be obtained simultaneously.The highest measured temperature and acoustic impedance sensitivities are 184.93 k Hz/℃and444.56 k Hz/MRayl,and the measurement accuracies are 0.09℃and 0.009 MRayl,respectively,which are both at desirable levels.We believe this work can provide potential application solutions for sensing fields involving temperature or acoustic impedance measurements.
基金financially supported by the National Natural Science Foundation of China (Grant No. 61991442)。
文摘Quantum well infrared photodetectors(QWIPs) based on intersubband transitions hold significant potential for high bandwidth operation. In this work, we establish a carrier transport optimization model incorporating electron injection at the emitter to investigate the carrier dynamics time and impedance spectroscopy in GaAs/AlGaAs QWIPs. Our findings provide novel evidence that the escape time of electrons is the key limiting factor for the 3-dB bandwidth of QWIPs. Moreover, to characterize the impact of carrier dynamics time and non-equilibrium space charge region on impedance, we developed an equivalent circuit model where depletion region resistance and capacitance are employed to describe non-equilibrium space charge region. Using this model, we discovered that under illumination, both net charge accumulation caused by variations in carrier dynamics times within quantum wells and changes in width of non-equilibrium space charge region exert different dominant influences on depletion region capacitance at various doping concentrations.
