Circuit Model Research Articles

Circuit function is more robust to changes in synaptic than intrinsic conductances.

Circuit function results from both intrinsic conductances of network neurons and the synaptic conductances that connect them. In models of neural circuits, different combinations of maximal conductances can give rise to similar activity. We compared the robustness of a neural circuit to changes in their intrinsic versus synaptic conductances. To address this, we performed a sensitivity analysis on a population of conductance-based models of the pyloric network from the crustacean stomatogastric ganglion (STG). The model network consists of three neurons with nine currents: a sodium current (Na), three potassium currents (Kd, KCa, A-type), two calcium currents (CaS and CaT), a hyperpolarization-activated current (H), a non-voltage-gated leak current (leak), and a neuromodulatory current (MI). The model cells are connected by seven synapses of two types, glutamatergic and cholinergic. We produced one hundred models of the pyloric network that displayed similar activities with values of maximal conductances distributed over wide ranges. We evaluated the robustness of each model to changes in their maximal conductances. We found that individual models have different sensitivities to changes in their maximal conductances, both in their intrinsic and synaptic conductances. As expected the models become less robust as the extent of the changes increase. Despite quantitative differences in their robustness, we found that in all cases, the model networks are more sensitive to the perturbation of their intrinsic conductances than their synaptic conductances.

Robustly encoding certainty in a metastable neural circuit model.

Localized persistent neural activity can encode delayed estimates of continuous variables. Common experiments require that subjects store and report the feature value (e.g., orientation) of a particular cue (e.g., oriented bar on a screen) after a delay. Visualizing recorded activity of neurons along their feature tuning reveals activity bumps whose centers wander stochastically, degrading the estimate over time. Bump position therefore represents the remembered estimate. Recent work suggests bump amplitude may represent estimate certainty reflecting a probabilistic population code for a Bayesian posterior. Idealized models of this type are fragile due to the fine tuning common to constructed continuum attractors in dynamical systems. Here we propose an alternative metastable model for robustly supporting multiple bump amplitudes by extending neural circuit models to include quantized nonlinearities. Asymptotic projections of circuit activity produce low-dimensional evolution equationsfor the amplitude and position of bump solutions in response to external stimuli and noise perturbations. Analysis of reduced equationsaccurately characterizes phase variance and the dynamics of amplitude transitions between stable discrete values. More salient cues generate bumps of higher amplitude which wander less, consistent with experiments showing certainty correlates with more accurate memories.

Monitoring the Dilution of Buffer Solutions with Different pH Values above and below Physiological pH in Very Small Volumes.

The accurate determination of the post-dilution concentration of biological buffers is essential for retaining the necessary properties and effectiveness of the buffer to maintain stable cellular environments and optimal conditions for biochemical reactions. In this work, we introduce a silicon-based impedance chip, which offers a rapid and reagent-free approach for monitoring the buffer concentrations after dilution with deionized (DI) water. The impedance of the impedance chip is measured, and the impedance data are modeled using a multiparameter equivalent circuit model. We investigated six aqueous biological buffers with pH values above and below the physiological pH for most tissues (pH ~ 7.2-7.4) following dilution with DI water by factors of 2.0, 10.0, 20.0, 100.0, and 200.0. The impedance measurement is then performed for the frequency spectrum of 40 Hz to 1 MHz. From the interpretation of the impedance measurement using the multiparameter equivalent circuit model, we report a buffer-sensitive equivalent circuit parameter RAu/Si of the silicon-based impedance chip showing a linear trend on a logarithmic scale with the buffer concentration change after dilution. The parameter RAu/Si is independent of the buffer pH and the added volume. The results demonstrate the efficacy of the silicon-based impedance chip as a versatile tool for precise post-dilution concentration determination of diverse biologically relevant buffers. The presented impedance chip offers rapid, accurate, and reliable monitoring, making it highly suitable for integration into automated liquid-handling systems to enhance the efficiency and precision of biological and chemical processes.

Electronic Fourier–Galois Spectrum Analyzer for the Field GF(31)

A scheme for the Fourier–Galois spectrum analyzer for the field GF(31) is proposed. It is shown that this analyzer allows for solving a wide enough range of problems related to image processing, in particular those arising in the course of experimental studies in the field of physical chemistry. Such images allow digital processing when divided into a relatively small number of pixels, which creates an opportunity to use Galois fields of relatively small size. The choice of field GF(31) is due to the fact that the number 31 is a Mersenne prime number, which considerably simplifies the algorithm of calculating the Fourier–Galois transform in this field. The proposed scheme of the spectrum analyzer is focused on the use of threshold sensors, at the output of which signals corresponding to binary logic are formed. Due to this fact, further simplification of the proposed analyzer scheme is achieved. The constructiveness of the proposed approach is proven using digital modeling of electronic circuits. It is concluded that when solving applied problems in which an image can be divided into a relatively small number of pixels, it is important to take into account the specificity of particular Galois fields used for their digital processing.

Modeling and Analysis of Wide Frequency Band Coaxial TSV Transmission Interconnect.

In this paper, we first build the 3D model of coaxial TSV(CTSV), RDL, and bump of the CTSV interconnect, and extract the equivalent circuit model of each part. Then, we get the S-parameters of the 3D and equivalent circuit model of the CTSV interconnect structure; the validity of the equivalent circuit model is verified by comparing the consistency of the S-parameters. The simulation results show that the maximum errors for the S11 and S21 parameters are 0.4% and 0.18%, respectively, which proves the validity of the equivalent circuit modeling in this paper. Finally, parametric analysis is performed to investigate the effect of different model parameters on the signal-transmission characteristics of the CTSV interconnect.

Uncovering accurate values of the polarization resistance in molten fluorides using electrochemical impedance spectroscopy

High-temperature operation and the presence of oxidizing impurities in molten chloride and fluoride salts pose significant corrosion risks to structural alloys in molten salt nuclear reactors. Electrochemical impedance spectroscopy (EIS) offers an operando, real-time method to study the instantaneous corrosion behavior of these materials non-destructively. However, signal noises may originate from sources extraneous to the electrochemical systems that limit the ability to perform quality impedance measurements in low-frequency regime where polarization resistance (Rp) dominates. Using the exposure of pure Cr in molten LiF-NaF-KF containing 1 wt% EuF3 at 600 °C as a model corrosion system, the extent of Non-Uniform Current and Potential (NUCP) distribution during an AC perturbation associate with the disk electrodes is evaluated in terms of two dimensionless correction factors kfRct(=Rct/Reff) and kfCdl(=Cdl/Ceff). Results show that a small area Cr disk electrode increases the transition frequency that marks the dominance of Rp to a conventional terminational frequency above 10−2 Hz, enabling a reliable charge-transfer resistance (Rct) value to be determined via circle fitting of an electrical equivalent circuit model (ECM) model. Experimental results were supported by EIS simulations considering commonly used ECM models that factor in the NUCP effect of disk geometries.

State of Charge Estimation of Lithium-Ion Batteries Based on Fractional-Order Model with Mul-ti-Innovations Dual Cubature Kalman Filter Method

An accurate estimation of the lithium battery’s state of charge (SOC) is critical. The article proposes a dual fractional order multi-innovations cubature Kalman filter (DFOMICKF) algorithm for estimating lithium battery SOC. The algorithm adopts the idea of multiple time scales, where one of the FOMICKF is used to identify the circuit model parameters online in the macro time scale. Another FOMICKF is used to estimate the SOC in the micro time scale, and the circuit parameters updated online in real-time are passed into the estimation of the SOC filter to form an online joint estimation method of SOC and circuit parameters. Finally, multiple algorithms of DFOMICKF, FOMICKF, FOCKF, and CKF are compared and experimented under different working conditions to compare and analyze the estimated SOC errors. It is verified that the proposed algorithm can solve the problems of inaccuracy, poor convergence, and poor robustness of the traditional Kalman filtering algorithm for estimating SOC, which has good research value.

Enhanced Second-Order RC Equivalent Circuit Model with Hybrid Offline–Online Parameter Identification for Accurate SoC Estimation in Electric Vehicles under Varying Temperature Conditions

Accurate estimation of State-of-Charge (SoC) is essential for ensuring the safe and efficient operation of electric vehicles (EVs). Currently, second-order RC equivalent circuit models do not account for the influence of battery charging and discharging states on battery parameters. Additionally, offline parameter identification becomes inaccurate as the battery ages. Online identification requires real-time parameter updates during the SoC estimation process, which increases the computational complexity and reduces the computational efficiency of real vehicle Battery Management System (BMS) chips. To address these issues, this paper proposes a SoC estimation method that combines online and offline identification based on an optimized second-order RC equivalent circuit model, which distinguishes it from existing methods in the field. On the basis of the traditional second-order RC model, the Ohmic resistance (R0), polarization resistance (R1), polarization capacitance (C1), diffusion resistance (R2), and diffusion capacitance (C2) during the charging and discharging processes are discussed separately. R0, which does not change frequently, is identified offline, while R1, R2, C1, and C2, which dynamically change with time and current, are identified online. To thoroughly verify the feasibility of the proposed method, we construct an SoC estimation test bench, which allows us to adjust the battery’s surface temperature in real time using a temperature control chamber. Experimental validation under Federal Urban Driving Schedule (FUDS) (−10 °C to 45 °C, 80% battery capacity) and Dynamic Stress Test (DST) (−10 °C to 45 °C, 8% battery capacity) conditions demonstrate that our method improves SoC estimation accuracy by 16.28% under FUDS and 28.2% under DST compared to the improved GRU-based transfer learning method, while maintaining system SoC estimation efficiency.

Internal Electrostatic Discharge Modeling: Validation and Fitting Using Tests on Insulated Wires

Electron beam tests were conducted to observe the internal electrostatic discharge behavior of four wire samples arcing into three termination resistors. The charging environment during the test was also simulated using 3-D NUMIT to calculate the expected voltage development within each wire. The impedances of the wires and the test setup were measured and included in a circuit model of the discharging wire connected to the measurement circuit. The circuit model was fit to the largest discharge observed on a 50 Ω load. The circuit model was then used to simulate discharges into 5 kΩ and 10 MΩ terminations, and the simulated pulses were compared to observed pulses on those terminations. Simulated peak voltages agree with observed voltages to within a factor of 1.6 and simulated decay times agree with observed decay times to within a factor of 2.3. For large pulses, derived source voltages range from 3.7 to 15.5 kV, derived source capacitances range from 4 to 11 pF, and derived source resistances range from 1100 to 3500 Ω.

A novel high‐isolation dual‐polarized air‐patch antenna based on composite decoupling structure

AbstractThis paper presents a novel wideband dual‐polarized air‐patch antenna with enhanced port isolation. The proposed design consists of a suspended metal patch, two feeding slots, and novel composite decoupling structures (CDS). The CDS is composed of two reactive loads (RLs), an additional square slot (ASS), and two neutralizing lines (NLs). The reactive loads and one NL are connected to the feeding slots. The other NL is connected to the ASS. The CDS plays a critical role in achieving wideband high port isolation. The decoupling principles are illustrated by using a circuit model and through rigorous mathematical derivation. Design evolution of the proposed antenna (Ant 1–5) was carefully explained. Experimental results demonstrate that the proposed antenna has a −15 dB refection coefficient bandwidth covering the frequency range of 3.32–3.67 GHz. Additionally, it exhibits high port isolation (>35 dB), low cross polarization, high gain, and excellent total efficiency (>85%).

Numerical harmonic modelling of low wattage LED lamps based on parameter estimation algorithms

This paper presents a numerical harmonic modeling approach for 18 low-wattage Light-Emitting Diode (LED) lamps. The proposed methodology utilizes meta-heuristic algorithms, namely Multi-Stage Ant Colony Optimization (MSACO) and Harris Hawk Optimization (HHO), to estimate optimal parameters for the equivalent circuits. Additionally, the study examines eight different configurations of Electromagnetic Interference (EMI) Filter circuits, including their respective parameters, which function as front-end circuits for the Full Bridge Rectifier (FBR) of the LED drivers. Through extensive investigations, the primary objective is to establish generalized and accurate models for various EMI filter circuits that can be universally applied, with validation through comparison against experimental results. Under both MSACO and HHO, the lowest average total error ranges were observed in the LC-Filter and CL-Filter configurations, with errors ranging from 21.302 % and 22.769 %, respectively. On the other hand, the L-Filter and R-only configurations exhibited the highest average total error ranges, with errors of 42.376 % and 44.648 %, respectively. Notably, this paper introduces a non-intrusive, non-invasive method for estimating optimal parameters based solely on measurements obtained from the input terminals of the LED lamps.

Evaluation of the power loss in IGBT single transistor device under the condition of pulse duration of 100 ns

The improvement in the reliability and lifespan of insulated gate bipolar transistor (IGBT) devices and the enhancement of system efficiency under high-frequency pulse conditions are receiving increasingly wide attention, and all of these are closely related to the evaluation of the power loss of the IGBT. The traditional method for assessing the power loss of the IGBT is through curve fitting of the dual-pulse experimental results, without delving into the conduction process of the IGBT and without considering the IGBT model itself and the parasitic parameters present in the test circuit. In response to the condition of a pulse duration of 100 ns for IGBT single devices, a universal test circuit has been designed to measure the collector-emitter voltage waveform and the collector current waveform. A method based on Computer Simulation Technology for field-circuit co-simulation to evaluate the power loss of the IGBT has been proposed, which takes into account the parasitic parameters in the actual circuit. In this method, the 3D model of the IGBT device, as well as the circuit model of the test circuit, is established. The power loss curve of the IGBT was obtained from the evaluation model, and the results agree well with the power loss curve obtained from experiments. This method provides guidance for seeking lower power loss in order to improve the reliability and lifespan of the IGBT, as well as enhance system efficiency. It also provides theoretical guidance for further research on the thermal damage mechanism of the IGBT.

A unified global model accompanied with a voltage and current sensor for low-pressure capacitively coupled RF discharge

A global model (GM) assumes ion energy ( ε ) on the electrode equals the time-averaged sheath voltage ( Vshtt ). However, using particle-in-cell simulation, we found that ε differs from Vshtt. We propose a unified global model (UGM) that calculates ε and collisional energy losses of ions by employing plasma circuit and sheath models, accompanied by a voltage and current sensor. We compared the results of the UGM with the experimental measurements and the results revealed that UGM is closer to the experiment than GM. UGM shows a linear relationship with the experiment, indicating that the UGM is applicable for plasma monitoring.

Open-slit circular tube piezoelectric ultrasonic transducer with longitudinal bending mode conversion

Abstract A new type of longitudinal bending mode conversion ultrasonic transducer is designed by compounding a sandwich type piezoelectric ultrasonic transducer, amplitude transformer and Open-slit circular tube radiator. The radiator is made of a circular tube cut into a number of curved plates along the axis, and the two ends are thin disc end caps. The electromechanical equivalent circuit model of the transducer is established and its frequency equation is derived. The vibration performance of the transducer is studied by using the equivalent circuit method and the finite element method. The results show that: the new structure design and the longitudinal vibration sandwich piezoelectric ultrasonic transducer can effectively stimulate the two ends of the slit circular tube radiator to produce first-order bending vibration, and the curved plate to produce high-order bending vibration, so as to achieve high efficiency, uniform and all-round ultrasonic radiation. The research results are expected to be applied in ultrasonic treatment of large volume liquid such as ultrasonic wastewater treatment, ultrasonic algae removal and ultrasonic chemical reaction.

Assessing Barrier Function in Psoriasis and Cornification Models of Artificial Skin Using Non-Invasive Impedance Spectroscopy.

Reconstructed epidermal equivalents (REEs) consist of two distinct cell layers - the stratum corneum (SC) and the keratinocyte layer (KL). The interplay of these layers is particularly crucial in pruritic inflammatory disorders, like psoriasis, where a defective SC barrier is associated with immune dysregulation. However, independent evaluation of the skin barrier function of the SC and KL in REEs is highly challenging because of the lack of quantitative methodologies that do not disrupt the counter layer. Here, a non-invasive impedance spectroscopy technique is introduced for dissecting the distinct contributions of the SC and KL to overall skin barrier function without disrupting the structure. These findings, inferred from the impedance spectra, highlight the individual barrier resistances and maturation levels of each layer. Using an equivalent circuit model, a correlation between impedance parameters and specific skin layers, offering insights beyond traditional impedance methods that address full-thickness skin only is established. This approach successfully detects subtle changes, such as increased paracellular permeability due to mild irritants and the characterization of an immature SC in psoriatic models. This research has significant implications, paving the way for detailed mechanistic investigations and fostering the development of therapies for skin irritation and inflammatory disorders.

Comprehensive Analysis on Rotor Vibration Characteristics Based on a Novel Dynamic Stator Interturn Short Circuit Model of Synchronous Generator

Comprehensive Analysis on Rotor Vibration Characteristics Based on a Novel Dynamic Stator Interturn Short Circuit Model of Synchronous Generator

Analysis of electromechanical equivalent circuit model for the functionally graded tubular piezoelectric transducer

Abstract In this paper, a functionally graded tubular piezoelectric transducer (FG-tPET) is proposed. Based on the constitutive equation and wave equation, the electromechanical equivalent circuit model (EECM) of FG-tPET is obtained. When the non-uniformity coefficient tends to zero, the EECM can be simplified as the EECM of the traditional single-tube piezoelectric ceramic transducer. The correctness of the theoretical model is verified in comparison with the experimental results in the literature. Based on the theoretical model, the influence of the geometric size and the non-uniform coefficient of the transducer on the resonance/anti-resonance frequency is analyzed. The results show that the geometric size and the non-uniform coefficient can realize the coordinated adjustment of the resonance/anti-resonance frequency.

Small-Signal Equivalent Circuit Model as a Tool for Optimizing Millimeter-Wave Detection With FETs

Small-Signal Equivalent Circuit Model as a Tool for Optimizing Millimeter-Wave Detection With FETs

Vibration Harvesters with Mechanical Weak Coupling and Their Equivalent Circuit Model

Vibration Harvesters with Mechanical Weak Coupling and Their Equivalent Circuit Model

Ultrasonic scalpel based on fusiform phononic crystal structure

Abstract In response to the ultrasonic scalpels with the vibrational modal coupling which leads to a decrease in efficiency, an ultrasonic scalpel based on fusiform phononic crystals (PnCs) is proposed. An accurate theoretical model is constructed, which is mainly composed of electromechanical equivalent circuit models to analyze the frequency response function and the frequency response curves of the admittance. Bragg band gaps exist in the fusiform PnCs owing to the periodic constraint, which can suppress the corresponding vibrational modes. The vibration characteristics (vibration mode, frequency, and displacement distribution) of the ultrasonic scalpel are analyzed, and the validity of the electromechanical equivalent circuit method is verified. The results indicate that other vibration modes near the working frequency can be isolated. In addition, blades based on fusiform PnCs have a function akin to that of the horn, which enables displacement amplification.