Abstract In this paper, a dual concentric square-loop dual-polarized reconfigurable frequency selective surface with a high tuning ratio of 2.02 operating in the 1.53–3.10 GHz band is proposed. This high tuning ratio has been achieved by using four SMV1430-LF varactor diodes, which have been actuated using a simple biasing arrangement made of stubs and four metallic vias per unit-cell. The unit-cell has been rigorously analyzed, and an equivalent circuit (EC) model has been developed for the physical insight. The proposed EC model also demonstrates the reconfigurability of the unit-cell and thus predicts its behavior. The effect of the angular incidence of the impinging electromagnetic wave on the structure up to a 45º has been experimentally verified, which demonstrates its angular stability and polarization insensitive behavior. The structure may find applications in the electromagnetic spectrum’s L, S , and 2.45 GHz ISM bands.

Implantable antennas play a crucial role in advancing leadless pacemakers, facilitating seamless wireless communication in the restricted and lossy environment of the human body. This research presents the design, simulation, and performance assessment of a miniaturized robot-shaped implantable antenna with enhanced parameters for leadless cardiac pacemakers (LCPs), functioning at the Industrial, Scientific, and Medical (ISM- 2.4-2.48 GHz) band. The proposed implantable antenna is designed on a high dielectric Rogers RO/Duroid 3010, having a thickness of 0.635 mm, serving as a dielectric material for both the substrate and superstrate layers. To maintain the effectiveness of a small radiating patch and ensure optimal performance, the proposed antenna has been designed with a volume of 63.5 mm3(10 mm × 10 mm × 0.635 mm). Incorporating symmetric slots in the radiating patch and ground plane enables miniaturization, impedance matching, improved gain and bandwidth. To evaluate and enhance applicability in a practical scenario, the multilayer cubic phantom model and the human Gustav voxel model have been utilized at the required ISM band. The proposed antenna's equivalent circuit model was also analyzed at the desired band. A link margin analysis is conducted to ensure communication reliability, demonstrating that the antenna can effectively communicate up to 40 m. The proposed antenna exhibits a simulated impedance bandwidth of 380 MHz and a peak realized gain of -23.5 dBi. Additionally, to assess adherence to the IEEE C905.1-2005 safety standards, the specific absorption rate has been evaluated. Further,in-vitromeasurements were carried out in a human tissue-mimicking phantom. The measured results correlate with the simulated results, confirming that the proposed antenna is appropriate for implantation in LCPs.

Irreversible electroporation (IRE) is a minimally invasive, non-thermal, and cell-selective technique. When combined with the noninvasive nature of contact electrodes, they hold great promise for the treatment of cardiac conditions, gastrointestinal tumors, and superficial lesions. However, its broader clinical application is hindered by its reliance on a kilovolt-level, high-voltage pulse characteristics power supply and the lack of real-time postoperative assessment methods for evaluating ablation efficacy. To address these challenges, a contact electrode system with integrated IRE and impedance monitoring functions was developed. Numerical simulations were performed to optimize the anode, gap, and cathode widths in the concentric electrode design. This ensured efficient electric-field focusing under low-voltage conditions. The ablation performance was verified using a potato model. A four-electrode impedance measurement technique was used to capture the spectral characteristics of biological tissues. The impedance changes were analyzed using a double-shell equivalent circuit model. The system achieved a 2mm ablation depth at 125 V, which is suitable for the treatment of superficial lesions. This reduces the required voltage from the kilovolt level to the hundred-volt level. The four-electrode method reduced contact resistance interference, and the Nyquist plots showed a unique double-arc pattern. Changes in cell wall resistance correlated with ablation depth ( = 0.86) with a prediction error of <10%. This study presents an innovative approach for IRE therapy that combines low-voltage operation with real-time feedback through impedance spectroscopy, thereby offering improved safety and treatment monitoring.

Abstract Waveform-selective metasurfaces offer unprecedented control over electromagnetic waves on the basis of pulse width. However, existing circuit models fail to capture the power-dependent behaviors of these metasurfaces, thereby limiting their use in practical applications. Here, for the first time, we present analytical equivalent circuit models that accurately predict both power- and time-dependent responses by incorporating voltage-dependent diode resistance through the Maclaurin series and Wright omega functions. As a result, the variations in the input power and time domain are effectively predicted theoretically. Moreover, our concept is successfully extended to different types of waveform-selective metasurfaces and increasingly complex scenarios, including repeated pulses and nonresonant frequencies. Thus, our equivalent circuit approach can readily explain and quantify the electromagnetic behaviors of waveform-selective metasurfaces. This strategy provides a high degree of control for addressing complex electromagnetic problems by leveraging pulse width as a tuning parameter, even at a fixed frequency.

Introduction . Methods for assessing the reliability of communication networks require simple and effective calculation tools. Although reduction methods allow the analysis of complex systems to be simplified, their application is limited by certain conditions. Aim . To investigate a reduction method based on the sequential transformation of networks with serial and parallel connections into equivalent circuits. Bipolar connectivity that implies a path between two dedicated nodes is considered, in contrast to multipolar connectivity that evaluates connectivity between several critical nodes and all-pole connectivity that requires paths between all nodes of the network. Materials and methods . Purely sequential and purely parallel structures, as well as their combinations, are considered. For sequential systems, the probability of operability is defined as the product of the serviceability probabilities of the elements, for parallel systems – through the probability of failure of all components. Results . For mixed structures, a reduction algorithm for calculating their reliability using simplified formulas is proposed. The reduction procedure and the final formulas for calculating network reliability are directly derived from the rules for serial and parallel connections. A communication network was used as an example to confirm the method accuracy provided that the failures of the elements are independent. Conclusion . The demonstrated reduction method is effective for analyzing the reliability of communication networks with series-parallel structures. The accuracy of calculations depends significantly on the assumption of the independence of failures. The advantages of the method include its simplicity and clarity; however, the method is inapplicable in cases of gradual failures and the interdependence of elements. In addition, this method processes correctly only loaded redundancy; for systems with unloaded or lightweight redundancy, the method needs to be modified. Computational difficulties for large-size networks and the possibility of information loss about the criticality of elements is noted. This is related to the loss of data on the contribution of individual components to the overall reliability of the system in the process of simplification, which impedes the analysis of weak links. The results obtained can be used in the design and optimization of communication networks, as well as for assessing their operational reliability.

This study introduces a novel hybrid model for an electromembrane stack, unifying an equivalent electrical circuit model incorporating specific resistance (RM,Rs) and capacitance (Cgs,Cdl) parameters with an empirical fouling model in a single framework. The model simplifies the traditional approach by serially connecting N (N=10) ion exchange membranes (anionic PC-SA and cationic PC-SK) and is validated using NaCl and Na2SO4 solutions in comparison with laboratory tests using various voltage signals, including direct current and electrically pulsed reversal operations at frequencies of 2000 and 4000 Hz. The model specifically accounts for the chemical stratification of the cell unit into bulk solution, diffusion, and Stern layers. We also included a calibration method using correction factors (αi) to fine-tune the electrical current signals induced by voltage stimulation. The empirical component of the model uses experimental data to simulate membrane fouling, ensuring consistency with laboratory-scale desalination processes performed under pulsed reversal operations and achieving a prediction error of less than 10%. In addition, a comparative analysis was used to assess the increase in electrical resistance due to fouling. By integrating electronic and empirical electrochemical data, this hybrid model opens the way to the construction of simple, practical, and reliable models that complement theoretical approaches, signifying an advance for a variety of electromembrane-based technologies.

Abstract Thermo-electrochemical modelling of a Lithium-ion battery pack having three prismatic cells connected in series has been carried out to evaluate the heat generation in a battery pack. An equivalent circuit model (ECM) based on a second-order resistive-capacitive Thevenin model is employed to solve the electrochemical reaction inside the battery cell. In such a model, all parameters, including battery voltage, heat generation rate, and temperature, vary with the battery state of charge as discharging continues, rather than being considered constant, thereby enhancing the accuracy of the results. The temperature rise of the battery pack is mitigated using parallel flow and cross flow induced by parallel/counterflow channels and novel Z-type channels, respectively. A significant reduction in the average battery temperature of over 40 K has been attained employing surface channels over the surface of the battery. Z-type with base cooling proves to be the most effective, among various configurations, resulting in a 2 K to 3 K reduction in temperature compared to counterflow, the worst-case scenario. The counterflow results in better spatial temperature homogeneity, followed by Z-type with base cooling, compared to other approaches. An insignificant effect of Reynolds number on temperature distribution, about 0.2 to 0.3 K, has been noticed, while increasing the discharge rate from 1C to 2C, results in approximately 2 to 3 K temperature rise when the cooling channel is in operation.

An equivalent circuit model (ECM) is a highly practical tool for simulating Li-ion battery behavior. There are many relevant studies which compare different ECM variants or suggest algorithms to extract model parameters from the experimental data. However, little attention has been given to the battery tests used for identification of the ECM parameters. Therefore, here the influence of experimental test pulse characteristics on the parameterized ECM accuracy was systematically studied. The test pulse duration was varied in a wide range from 9 s to about 2.5 min. The portion of the relaxation phase data used by the parameter optimization algorithm was also varied in an even wider range. Total 168 ECM parameter sets were obtained. Each parameter set was validated using nine diverse current profiles representing different battery operation conditions, including one based on Urban Dynamometer Driving Schedule (UDDS). The validation results prove that the impact of the test pulse choice on the parameterized ECM accuracy is great to the point that it can overshadow the use of a higher-order Thevenin model. By choosing the optimal parameter set, the simulated voltage root mean square error (RMSE) was reduced to as low as 3.0 mV and 1.2 mV for first- and second-order ECM, respectively, while the second-order model based on arbitrary chosen test pulse on average yields RMSE value above 5 mV.

This paper introduces the electrochemical equivalent circuit model for a carbon nanotube (CNT) coiled yarn subjected to external mechanical deformation. The mechanically coiled CNT yarn electrode, with average coil diameters of 83μm and 112μm, operates in an electrode-electrolyte configuration in which applied strain induces mechano-electrochemical energy conversion. Electrochemical impedance spectroscopy (EIS) was employed to characterize the impedance behavior of the coiled CNT electrode under various applied strain conditions, while the scaling behavior associated with different numbers of CNT sheets was anticipated based on physical and geometric considerations. The measured impedance spectrum was analyzed and fitted using ZView software (Scribner Associates) to extract lumped electrochemical parameters, including both fixed and strain-dependent elements grounded in the electrochemical characteristics of the mechano-electrochemical energy harvester. Analysis of the Nyquist spectra reveals that the output impedance increases as the coiled CNT electrode is stretched and decreases with scaling of the device through additional CNT sheets, while the peak-to-peak open-circuit voltage increases with increasing stretch of the yarn. Based on these observations, a lumped-element equivalent circuit with strain-dependent electrochemical parameters was developed. The proposed model enables SPICE-based circuit simulations and facilitates impedance matching between the MEEH and external loads, thereby maximizing power transfer to the load. The equivalent circuit accurately reproduces the measured electrical behavior with a minimum error below 5% for both 3-sheet and 6-sheet MEEH configurations. These results demonstrate that the proposed modeling approach effectively anticipates impedance and power performance as functions of mechanical strain and device scaling.

Abstract Two‐deimensional (2D) periodic structures such as frequency selective surfaces (FSS) are widely used for controlling the transmission, reflection, and scattering of electromagnetic waves. Applications including low‐emissivity (low‐E) glass for energy‐efficient buildings and metasurfaces for reducing radar cross section (RCS) and infrared signatures require both frequency selective and low‐E properties. This work presents a cost‐effective methodology for a single‐layer low‐E FSS (SLLE‐FSS) that satisfies these requirements. The design incorporates micro metal patches (MMPs), an array of metallic patches much smaller than the wavelength, which remain transparent in the RF band while reflecting most IR energy. By integrating MMPs within the same layer as the FSS, a high metal filling ratio is achieved without compromising RF characteristics. To address the computational cost caused by the scale difference between FSS and MMPs, equivalent circuit models (ECMs) are introduced for efficient design of both transmission‐ and reflection‐type structures. The proposed approach is validated through simulations and measurements of MMPs, SLLE‐FSS prototypes, and an SLLE‐based artificial magnetic conductor (SLLE‐AMC) for IR–radar bi‐stealth metasurfaces. Results confirm that the methodology enables single‐layer structures combining frequency selectivity and low‐E properties, offering broad applicability to multifunctional electromagnetic and optical systems.

Abstract Abstract&amp;#xD;In this study, a novel modified Chua-like hyperchaotic circuit using the memcapacitor is presented. Since commercial memcapacitor production is currently unavailable, the previously designed equivalent circuit of the memcapacitor will be used in the chaotic circuit. The dynamic equations of the circuit are obtained, and therefore the effect of the memcapacitor is incorporated into the modified Chua circuit. The incorporation of both incremental and decremental configurations of the memcapacitor equivalent circuit into the chaotic system has enabled the successful realization of two distinct sets of chaotic attractors, demonstrating the versatility of the proposed design. Both experimental and simulation studies demonstrate that the newly designed hyperchaotic circuit driven by the memcapacitor generates the hyperchaotic complex oscillations and that the chaotic attractor is highly sensitive to the parameters and initial conditions. Dynamic analyses of the circuit such as Lyapunov exponents, bifurcation analyses, coexisting attractors, Fast Fourier Transform (FFT) spectra, complexity evaluation, and noise robustness analysis have also been successfully carried out. Additionally, the applicability of the proposed circuit in the field of secure communication has been verified through a chaos-based image encryption and decryption study, demonstrating strong performance in NPCR, UACI, and Shannon entropy tests. Compared to previously reported mem-element-based chaotic circuits, the proposed system distinguishes itself by exhibiting hyperchaotic behavior with coexisting attractors and by being verified through analog experimental implementation, demonstrating both its dynamical richness and practical hardware feasibility. The obtained results indicate that the proposed circuit possesses strong potential for use across a broad range of chaotic system applications.&amp;#xD;

This paper presents a compact bandpass filter (BPF) based on substrate-integrated suspended line (SISL) technology for 5G applications. The filter employs stepped-impedance resonators (SIRs) and edge-coupled open stubs to achieve a narrow passband from 4.04 GHz to 4.27 GHz, centered at 4.15 GHz, with a fractional bandwidth (FBW) of 5.54%. Enhanced out-of-band rejection is obtained through symmetrically placed open stubs near the input/output ports, extending the rejection band beyond 12 GHz with attenuation levels below −30 dB. The fabricated filter exhibited a low insertion loss (IL) of less than 0.35 dB and a return loss (RL) greater than 18 dB in the passband. The lumped-element equivalent circuit, even – odd mode analysis, and parametric studies validated the design, while measured results showed good agreement with simulations. The SISL platform offers self-packaging, low loss, and integration advantages, making the filter well suited for RF/microwave systems.

Abstract To address the insufficient reliability and state awareness in the battery-driven fail-safe shutdown stage of All-electric subsea control system, this paper proposes an accurate state-of-charge (SOC) estimation method suitable for deep-sea environments. The method tightly integrates a second-order RC equivalent circuit, variable forgetting factor recursive least squares (VFFRLS), and an unscented Kalman filter (UKF). By employing a dynamically adaptive forgetting factor and a sliding-window error evaluation mechanism, it achieves joint optimization of online parameter identification and state estimation, thereby maintaining high estimation accuracy and robustness under long-term service conditions. At the system level, a low-cycle-load operating strategy is adopted in which the battery remains in trickle-charging standby and discharges only during power loss, combined with a fast-switching mechanism that enables the battery to smoothly take over the power supply after external power failure, thus enhancing overall system reliability. Joint validation at both the battery level and with a full-scale subsea electric valve actuator prototype demonstrates that, compared with conventional covariance-matching methods, the proposed algorithm exhibits strong robustness to initial condition settings, maintains SOC estimation errors within 2%, and ensures that the valve can complete the fail-safe shutdown operation within 2 s after power loss. These results indicate that the proposed method not only improves the accuracy and stability of the battery management system, but also verifies the engineering feasibility of the battery-driven fail-safe shutdown scheme.

Summary Revil asserted in the comment that none of Macnae’s paper is novel. The paper however introduced a novel method of chargeability prediction as the fraction of pores blocked by metallic particles rather than the prediction using limiting Maxwell effective medium estimates based on volume fractions. This reply presents an analysis of two cases where the novel chargeability prediction proves to be significantly better than earlier methods when applied to laboratory pyrite-clay mixtures and to published petrophysical data from a Co-Cu disseminated mineral deposit. Another item of novelty in the paper was emphasis that the resistivity and conductivity time-constants can differ by orders of magnitude for the high chargeabilities of economic sulphide deposits, a fact not commonly recognised in the literature. Revil asserts in the comment that the term Induced Polarization (IP) should explicitly exclude dielectric effects and analogies as discussed in the paper, an assertion inconsistent with the early literature on IP and the fact that both diffusive and dielectric effects can affect low-frequency data. The reply provides detail on the physical nature of equivalent circuits, and how they can mechanistically model the IP phenomenon and the topology of conductive paths in materials, an issue that I did not emphasize in the paper as I thought it would have been obvious to most readers.

In the current study, solid polymer electrolytes (SPEs) based on chitosan and dextran biopolymers incorporated with various amounts of ammonium trifluoromethanesulfonate (NH4CF3SO3) were prepared employing a casting approach. NH4CF3SO3 is an ammonium-based salt that has been chosen in this study as a proton provider because it has low lattice energy (540.59 KJ/mol), delocalization, and low mobility of the anion part of the salt due to the large size of the triflate anion (-CF3SO3), which causes good ionic dissociation and provides more free ions by involving both NH+ and H+. Consequently, ionic conductivity will be improved. Fourier transform infrared spectroscopy (FTIR) and X-ray diffraction (XRD) have been performed for structural analysis, ensuring the dissociation of dopant salt in a polymer blend and investigating the interaction and complexation between polymers and salt. The degree of crystallinity (Xc) of the prepared SPE samples was determined via deconvoluted XRD spectra. Electrochemical impedance spectroscopy (EIS) has been utilized to measure the ionic conductivity and to analyze electrical properties of SPE samples. The Nyquist plots were fitted with the proposed electric equivalent circuits (EECs); furthermore, the electrolyte sample with the highest DC conductivity has been selected, which is equal to 6.24 × 10−6 S/cm, which corresponds to the CDATF5 sample. Dielectric properties analysis, including dielectric constant (ε′) and loss (εʺ), electric modulus (M’ and M”), tanδ, and AC conductivity (𝜎AC) of the electrolyte films, has been studied. SPEs made of the CS:DX-ATF system demonstrate enhanced structural flexibility and electrochemical efficiency, positioning them as a viable alternative for sustainable applications of solid-state energy storage devices, e.g., rechargeable batteries, electrochemical double-layer capacitors (EDLCs), fuel cells, sensors, actuators, and dye-synthesized solar cells.

Combined prompt cancer diagnosis and treatment is a key pursuit of the scientific community. Since the 20th century, a variety of early cancer detection methods (screening tests) have been developed. Histopathological examination of cancerous tissues is the "gold standard" in establishing the final diagnosis, as well as documenting the adequacy of the therapeutic intervention, although unable to detect neoplastic/malignant cells in real-time. In the current experimental research, we present a novel, innovative medical diagnostic device and demonstrate its potential utilization as a screening test for the early detection of neoplastic/malignant lesions in real-time. A group of 215 patients were enrolled in the study. The innovative medical diagnostic device was used to collect a sufficient number of measurements from head and neck neoplastic -including skin - lesions. Using special software algorithms, the cell membrane was simulated with an equivalent electric circuit. The excitation response of the biological tissues was calculated by applying a dielectric spectroscopy method. The presence of neoplastic cells was detected as a significantly increased contribution of the capacitive reactance to the total impedance of the tissues under examination (θ angle). The θ angle extracted measurements were compared to the respective histopathologic reports. θ angle values were found to be statistically different between normal, non-neoplastic, and malignant tissues (p<0.001). In terms of physics, the unknown complex impedance of the tissue under assessment as well as the capacitive reactance can be experimentally measured and therefore cancerous cells can be distinguished from healthy cells by the changes in the measured capacity reactance contribution (θ angle differences). The described innovative medical device leads reliable results for the early detection of neoplastic/malignant cells in real-time.

High-performance humidity sensors have received widespread attention for their wide use in healthcare, archaeology, electronic device manufacturing, etc., thus developing humidity sensors with wide sensing range, high response, narrow humidity hysteresis, fast response/recovery, and excellent stability are urgently needed. Humidity-sensitive materials are the core of humidity sensors. To obtain high-performance humidity sensors, humidity-sensitive materials should have high hydrophilicity, conductivity, and stability. Metal organic frameworks (MOFs) are promising humidity-sensitive materials due to their special characteristics, but often limited by the poor conductivity and hydrophilicity. Herein, a proton conduction enhanced CMC-Na/MOF-801/PPY (CMP) humidity-sensitive material was prepared through in-situ polymerization, and the corresponding humidity sensor was fabricated via drop-casting. The structure, functional groups, specific surface area, and element distribution of the CMP material were investigated by powder X-ray diffraction (XRD), fourier transform infrared spectroscopy (FT-IR), X-ray photoelectron spectroscopy (XPS), N&lt;sub&gt;2&lt;/sub&gt; sorption isotherm, transmission electron microscopy (TEM), and energy-dispersive X-ray spectroscopy (EDS). The abundant hydrophilic groups and continuous hydrogen bond network lead to tight dependence of the proton conductivity and impedance of the sensing material on the humidity. The results show that the optimized CMP sensor is highly sensitive to humidity change with high response of 516.7 at 43% RH and 1.24×10&lt;sup&gt;5&lt;/sup&gt; at 85% RH, narrow hysteresis of 1.9% RH, and short response/recovery time of 2.8 s and 1.2 s in the humidity range of 7–85% RH. Compared to reported MOFs-based humidity sensors, the CMP sensor exhibits unique technical characteristics. Further, the humidity sensing mechanism of the CMP sensor was investigated through a combination of material characterization, water adsorption kinetics, carrier concentration, complex impedance spectroscopy (CIS) plot, and equivalent circuit (EC). As proof of concept, by monitoring the humidity on the finger surface, we evaluated the potential applications of the CMP sensor in noncontact sensing. Moreover, a palmar hyperhidrosis diagnosis system based on the CMP sensor was assembled, realizing quick, intuitive, and accurate diagnosis the severity of palmar hyperhidrosis. It is believed that this work provides a reasonable strategy for constructing high-performance humidity sensors.

Abstract This study presents a comprehensive impedance spectroscopy (IS) analysis of Au/Ti/AlN/n-Si metal–oxide semiconductor (MOS) structures, with the aim of elucidating their dielectric and interfacial properties under different bias and frequency conditions. The real ( $${Z}{\prime}$$ Z ′ ) and imaginary ( $${Z}^{{\prime}{\prime}}$$ Z ′ ′ ) components of impedance were measured across 100 Hz–1 MHz and DC biases between 1 and 4 V, and the data were modeled using an equivalent circuit composed of a series resistance ( $${R}_{s}$$ R s ), a parallel resistance ( $${R}_{p}$$ R p ), and a parallel capacitance ( $${C}_{p}$$ C p ). The impedance spectra revealed a clear capacitive-to-resistive transition, while Cole–Cole plots consistently exhibited a single semicircle, confirming the presence of a unique relaxation mechanism. Relaxation times ( τ ), extracted both from $${Z}^{{\prime}{\prime}}$$ Z ′ ′ –f peaks and $${R}_{p}\bullet {C}_{p}$$ R p ∙ C p fitting, showed excellent agreement and demonstrated bias-dependent evolution, with accelerated relaxation at moderate bias and slower dynamics at higher bias due to trap saturation. Notably, $${C}_{p}$$ C p remained nearly constant across all biases, while $${R}_{p}$$ R p varied systematically, reflecting the influence of interfacial states. The analysis of normalized interface trap density further indicated progressive trap passivation with increasing bias, underscoring the stability of the AlN/Si interface. These findings validate the equivalent circuit model and highlight AlN as a promising dielectric material for high-frequency, low-leakage MOS applications, offering predictable relaxation behavior and reduced trap activity compared to conventional high-k dielectrics.

A magnetic equivalent circuit based electromechanical modelling method for propulsion shaft system drive by permanent magnet synchronous machine

Reduced Order Equivalent Circuit Model of Series Resonant Converter Considering the Interaction between Resonant Elements