Search

In this paper, an operator-based voltage control method for TENGs is investigated, achieving output voltage tracking without compensators and uncertainty suppression using robust right coprime factorization. Initially, a comprehensive simulation-capable circuit model for TENGs is developed, integrating their open-circuit voltage and variable capacitance characteristics. This model is implemented to simulate the behavior of TENGs with a rectifier bridge and capacitive load. To address the high-voltage, low-current pulsating nature of TENG outputs, a storage capacitor switching model is designed to effectively transfer the pulsating energy. This switching model is directly connected to a buck converter and operates under a unified control strategy. A complete TENG power management system was established based on this model, incorporating an operator theory-based control strategy. This strategy ensures steady output voltage under varying load conditions without using compensators, thereby reducing disturbances. Simulation results validate the feasibility of the proposed TENG system and the efficacy of the control strategy, providing a robust framework for optimizing TENG energy harvesting and management systems with significant potential for practical applications. [ABSTRACT FROM AUTHOR]

In this paper, the performance of a 5-level cascaded H-bridge inverter in unmanned aerial vehicle (UAV) applications is analized to identify, at the converter design stage, the better device choice depending on different UAV operation scenarios. Considering that regardless of the specific application there are some typical operations, such as take-off, climb, land, cruise, and potential recurring climbs and descents, the results can support the choice by considering the typical working conditions of the specific application where the UAV would be used. The results have been obtained by simulating the H-bridge inverter considering the circuit models of insulated-gate bipolar transistors (IGBTs), GaN high-electron-mobility transistors (HEMTs), and Si and SiC metal-oxide-semiconductor field-effect transistors (MOSFETs) provided by manufacturers. The study has highlighted that the choice of the device depends on the UAV usage, switching frequency, and load conditions. More specifically, considering the typical devices and systems costs in the case of a selective harmonic elimination procedure operating at the fundamental switching frequency, the Si devices should be used. Moreover, the preference for using IGBTs or Si MOSFETs depends on the typical working conditions of the UAV application. In the case of phase-shift carrier modulation technique, at 4 kHz the MOSFET is the best device and the choice between Si and SiC devices depends on the UAV application's main operation scenarios. At 20 kHz the SiC MOSFET is the best device, while at higher frequencies the GaN HEMT cost should be faced to take advantage of its best performance.

In this paper, a perfect absorber (PA) based on tungsten is proposed to include hexagonal‐shaped metasurface absorbers with varying hole sizes ranging from quadrangular to circular, allowing them to cover a wide wavelength spectrum. The study investigates the effects of various parameters, including the number of sides of the inner hole, on the absorber's performance and identifies the most suitable absorber by introducing an equivalent circuit. The outcomes of full‐wave numerical simulations primarily based on the finite element method (FEM) highly correspond to the final results of the circuit model. Additionally, the circuit model significantly reduces computation time and requires less storage compared with full‐wave simulations. The results show that the hexagonal‐square metasurface absorber achieves exceptional absorption rates, with an average of 99.9% in the 431 to 532 nm wavelength range and over 90% in the 300 to 915 nm range. The hexagonal‐hexagonal metasurface absorber also exhibits high absorption rates, with an average of over 99% in the 431 to 518 nm and 700 to 780 nm ranges, and over 90% in the 300 to 940 nm range. The absorption performance of the proposed hexagonal‐circle metasurface absorber is also remarkable, with an absorption value of over 99% in the 670 to 771 nm range and above 90% in the 365 to 991 nm range. These models can be utilized to design and simulate other subwavelength absorbers in a broad frequency range, including terahertz and visible light, making them suitable for various applications. [ABSTRACT FROM AUTHOR]

In this paper, the performance of a 5-level cascaded H-bridge inverter in unmanned aerial vehicle (UAV) applications is analized to identify, at the converter design stage, the better device choice depending on different UAV operation scenarios. Considering that regardless of the specific application there are some typical operations, such as take-off, climb, land, cruise, and potential recurring climbs and descents, the results can support the choice by considering the typical working conditions of the specific application where the UAV would be used. The results have been obtained by simulating the H-bridge inverter considering the circuit models of insulated-gate bipolar transistors (IGBTs), GaN high-electron-mobility transistors (HEMTs), and Si and SiC metal-oxide-semiconductor field-effect transistors (MOSFETs) provided by manufacturers. The study has highlighted that the choice of the device depends on the UAV usage, switching frequency, and load conditions. More specifically, considering the typical devices and systems costs in the case of a selective harmonic elimination procedure operating at the fundamental switching frequency, the Si devices should be used. Moreover, the preference for using IGBTs or Si MOSFETs depends on the typical working conditions of the UAV application. In the case of phase-shift carrier modulation technique, at 4 kHz the MOSFET is the best device and the choice between Si and SiC devices depends on the UAV application's main operation scenarios. At 20 kHz the SiC MOSFET is the best device, while at higher frequencies the GaN HEMT cost should be faced to take advantage of its best performance. [ABSTRACT FROM AUTHOR]

Monitoring electric power systems is essential for avoiding disruptions, improving efficiency, and detecting faults. Traditional methods involve interrupting the power lines and pose safety risks. On the contrary, non‐contact power meters allow for safe power measurement without touching the wires but designing them presents challenges related to battery life and sustainability. This paper introduces a novel battery‐less RF‐powered wireless circuit that overcomes these limitations and optimizes the performance of the sensing of the voltage. This circuit includes an efficient RF‐DC converter, a designed non‐contact flexible and curved AC voltage sensor, a signal conditioning circuit, a digital processing unit, and a passive UHF Radio‐Frequency Identification interface for wireless communication. It harnesses electromagnetic energy from the radio front end to power the entire system. The circuit has been properly conceptualized, developed, and analyzed through electrical modeling and SPICE simulations. Transient and steady‐state analyses have been carefully conducted on individual circuit blocks to analyze their electric characteristics. Finally, a proof‐of‐concept circuit has been realized and experimentally verified to validate the simulation outcomes. With a bandwidth of 3 kHz, an RF‐DC conversion sensitivity of −16 dBm, a current consumption of only 2.2 mA, and an efficient power management procedure, this energy‐autonomous, non‐contact metering circuit offers very high RF and sensing sensitivities and ultra‐low power consumption, making it ideal for monitoring AC electric systems, particularly in inaccessible environments where battery‐based solutions are impractical. [ABSTRACT FROM AUTHOR]

The streaming potential effect has a wide range of applications in geophysics. The core streaming potential experiment requires that there is no external circuit at both ends of the core, but a measurement circuit must be introduced to measure the voltage between both ends of the core which will cause an external circuit. In order to analyze the effect of measurement circuits on the streaming potential experiment, this paper proposes a core current source model, i.e., the core in the streaming potential experiment is regarded as a circuit composed of a current source whose output current is equal to the seepage current and the core resistance. By changing the resistance value of the external circuit, it is found that the seepage current is not affected by the external resistance but by the excitation pressure. Experiments on the streaming potential of 20 sandstone cores under distilled water, 0.01 mol/L, 0.02 mol/L, 0.05 mol/L, 0.1 mol/L, 0.2 mol/L, 0.4 mol/L, and 0.6 mol/L sodium chloride solutions revealed that the effect of the external circuit on the streaming potential signal increased with decreasing mineralization. For distilled water-saturated sandstone cores, the effect of the external circuit was about 2%. [ABSTRACT FROM AUTHOR]

Fast optical modulation of nanoplasmonics is fundamental for on-chip integration of all-optical devices. Although various strategies have been proposed for dynamic modulation of surface plasmons, critical issues of device compatibility and extremely low efficiency in the visible spectrum hamper the application of optoplasmonic nanochips. Here we establish an optoplasmonic system based on Au@Cu2–xS hybrid core–shell nanoparticles. The optical excitation of hot electrons and their charge transfer to the semiconductor coating (Cu2–xS) lead to lowered electron density of Au, which results in the red shift of the localized surface plasmon resonance. The hot electrons can also transport through the Cu2–xS layer to the metal substrate, which increases the conductance of the nanogap. As such, the coupled gap plasmon blue-shifts with a magnitude of up to ∼15 nm, depending on the excitation power and the thickness of the coatings, which agrees with numerical simulations. All of this optoelectronic tuning process is highly reversible, controllable and fast with a modulated laser beam, which is highly compatible and sufficiently useful for on-chip integration of nanophotonic devices. [ABSTRACT FROM AUTHOR]

In this paper, an optical chemical sensor is proposed to detect some toxic gases such as Methane (CH4), Nitrogen (N2), Nitrogen dioxide (NO2), and Carbon monoxide (CO). This type of chemical sensor consists of graphene ribbons and Kapton materials as sensing elements. Also, exploits electromagnetic properties such as absorption in terms of signal transducing. These kinds of small-scale, flexible architectures and advanced detection techniques are in demand to identify toxic gases as well. To develop the proposed chemical sensor, this study describes the structure in the aspect of an equivalent circuit model (ECM) mathematically, while the full-wave simulation (FEM) is performed as the reference. Acceptable agreement between the ECM and FEM simulations is shown while an interesting tuning capability against external stimulation is obtained. It should be noted that the ECM approach is performed in just a few seconds while the FEM simulation takes more than 3 h to produce results. In addition, the maximum error is around the second absorption peak and is less than 4%.The main contribution of this work is introducing a simple structure to distinguish several toxic gases in the sub-THz gap (0.1–2 THz). Additionally, ample simulations are performed to verify the sensor's reliability. According to the simulation results, the proposed meta-structure can appropriately show different peak frequencies and even different numbers of absorption peaks against different concentrations of toxic gases. Additionally, due to the ultra-thin nature of the graphene and the flexibility of the Kapton, the proposed sensor can be wearable while it is considered non-invasive testing.

In the context of sixth-generation (6G) wireless communications technology, advanced radio-frequency switches are required to accommodate high-frequency terahertz range and complex modulation techniques. This paper proposes a flexible charge-controlled memristor model specifically designed for ultra-high-frequency applications. It describes in detail the derivation of the behavior model of the proposed memristor circuit. The memristor circuit model is built around four inverters, two multipliers, one integrator, one adder, and one differentiator. Through PSPICE simulation, the typical hysteresis loop of the memristor is thoroughly analyzed, demonstrating its suitability for use in wireless communication systems. The model exhibits a good typical hysteresis loop that operates over a wide frequency range from 100 kHz to 20 THz, meeting the specific requirements of terahertz applications. Compared to existing memristor designs, it operates at a much higher frequency. However, the zero crossing of the typical hysteresis loop deviates when the operating frequency exceeds 20 THz. Furthermore, the proposed memristor model can be customized in terms of set/reset voltage, operating frequency and R off / R on , and has been verified for use in high speed switches with switching speeds of 19.5 ps. Furthermore, this research fills the gap in ultra-high-frequency memristor modeling, offering valuable insights and guidance for the utilization of memristors in the 6G technology and ultra-high frequency fields. [ABSTRACT FROM AUTHOR]

A new geometrical vision for a graphene-based THz wave absorber is investigated in this work. A high-performance THz absorber is proposed to exploit complementary conventional periodic arrays of graphene disks. The equivalent circuit model is modified to take account of the complement pattern. The absorber works in two different operational modes based on chemical potential values. One mode shows absorption around 1 THz while the other one expresses perfect absorption at 6 THz and 9 THz. Such a considerable shifting ability via gate stimulations makes the proposed absorber an ideal block for reconfigurable metasurface. The comparison between the circuit model and full-wave simulation verifies an excellent match while ample sensitivity analysis are reported to show the reliability of the proposed switchable THz absorber.

Via is an essential component in the design of an Electromagnetic Band Gap (EBG) structure. This paper investigates the effects of the via in a mushroom-like EBG structure and proposes an equivalent circuit model of the via. It is revealed that when the via in the mushroom-like structure is offset, the element reflection phase will vary within 720 degrees instead of 360 degrees phase range in a conventional design. This phenomenon can be explained by a new circuit model that introduces a mutual inductance, and the corresponding electromagnetic properties of mushroom-like EBG structure can be quantitatively analyzed by this model. In addition, the applicability and error analysis of the model are discussed in this paper. The theoretical modeling and analysis enable an efficient and in-depth exploration of the via functions in similar EBG structures, and also provide more theoretical guidance and assistance for the design of reflection and transmission units based on EBG structure.

In recent years, there has been a considerable increase in the use of DC power equipment in the industry, making it crucial for insulation materials to withstand high DC electric fields. The current integration method (Q(t) measurement) is one of the most useful and effective methods to measure the time dependency of charges. However, the mathematical/physical model of Q(t) measurement is not advanced because obtained data are not completely analyzed, particularly the methods in which delay parameters affect the charge saturation time of insulators. In this study, we analyze the delay property of Q(t) data by solving differential equations with some approximations. In addition, sample sheets of polyimide and polyethylene terephthalate are tested for experimental purposes. The results indicate that circuit properties can be estimated from the analysis of experimental Q(t) data based on the assumption of a circuit model. The proposed analysis method can be used for further discussions regarding the analytical estimation of timing of charge saturation, and the relationship between circuit models and the space charges phenomenon.

In this paper, an operator-based voltage control method for TENGs is investigated, achieving output voltage tracking without compensators and uncertainty suppression using robust right coprime factorization. Initially, a comprehensive simulation-capable circuit model for TENGs is developed, integrating their open-circuit voltage and variable capacitance characteristics. This model is implemented to simulate the behavior of TENGs with a rectifier bridge and capacitive load. To address the high-voltage, low-current pulsating nature of TENG outputs, a storage capacitor switching model is designed to effectively transfer the pulsating energy. This switching model is directly connected to a buck converter and operates under a unified control strategy. A complete TENG power management system was established based on this model, incorporating an operator theory-based control strategy. This strategy ensures steady output voltage under varying load conditions without using compensators, thereby reducing disturbances. Simulation results validate the feasibility of the proposed TENG system and the efficacy of the control strategy, providing a robust framework for optimizing TENG energy harvesting and management systems with significant potential for practical applications.

Signal propagation models play a fundamental role in radio frequency communication research. However, emerging communication methods, such as body-coupled communication (BCC), require the creation of new models. In this paper, we introduce mathematical models that approximate the human body as an electrical circuit, as well as linear regression- and random forest-based predictive models that infer the expected signal loss from its frequency, measurement point locations, and body parameters. The results demonstrate a close correspondence between the amplitude-frequency response (AFR) predicted by the electrical circuit models and the experimental data gathered from volunteers. The accuracy of our predictive models was assessed by using their root mean square errors (RMSE), ranging from 1.5 to 7 dB depending on the signal frequency within the 0.05 to 20 MHz range. These results allow researchers and engineers to simulate and forecast the expected signal loss within BCC systems during their design phase. [ABSTRACT FROM AUTHOR]

The streaming potential effect has a wide range of applications in geophysics. The core streaming potential experiment requires that there is no external circuit at both ends of the core, but a measurement circuit must be introduced to measure the voltage between both ends of the core which will cause an external circuit. In order to analyze the effect of measurement circuits on the streaming potential experiment, this paper proposes a core current source model, i.e., the core in the streaming potential experiment is regarded as a circuit composed of a current source whose output current is equal to the seepage current and the core resistance. By changing the resistance value of the external circuit, it is found that the seepage current is not affected by the external resistance but by the excitation pressure. Experiments on the streaming potential of 20 sandstone cores under distilled water, 0.01 mol/L, 0.02 mol/L, 0.05 mol/L, 0.1 mol/L, 0.2 mol/L, 0.4 mol/L, and 0.6 mol/L sodium chloride solutions revealed that the effect of the external circuit on the streaming potential signal increased with decreasing mineralization. For distilled water-saturated sandstone cores, the effect of the external circuit was about 2%.

In simulating Quantum Computing by using the circuit model the size of the matrices to deal with, together with the number of products and additions required to apply every quantum gate becomes a really hard computational restriction. This paper presents a data structure, called Functional Matrices, which is the most representative feature of QSimov quantum computing simulator which is also provided and tested. A comparative study of the performance of Functional Matrices with respect to the other two most commonly used matrix data structures, dense and sparse ones, is also performed and summarized within this work. [ABSTRACT FROM AUTHOR]

The results of computer and physical simulation of discharge processes in a new type of pulseplasma ignition systems of gas turbine engines with a controlled switching spark gap are presented. A circuit design model of a pulse-plasma ignition system has been developed, which makes it possible to evaluate the regularities of discharge processes in a semiconductor spark plug depending on the parameters of the discharge circuits - the capacities of the high-voltage and low-voltage storage capacitors, the inductance of the main discharge circuit. The results of computer simulation are confirmed experimentally, the increased efficiency of the ignition system with a controlled spark gap compared to the known circuit solutions containing two switching spark gaps is substantiated. [ABSTRACT FROM AUTHOR]

A new metamaterial refractive index sensor based on the impedance matching idea is suggested to provide an ultra-narrowband absorption response at terahertz frequencies. In order to accomplish this, the graphene layer has been modeled as circuit components using the recently developed transmission line method and the recently proposed circuit model of Periodic Arrays of Graphene Disks. The given research gives a flowchart and equations for designing a sensor, greatly simplifying the sensor design approach. This study only explores Periodic Arrays of Graphene Disks but we think the offered technique is extensible to any available graphene forms that past designers supplied with a circuit model. We compare and contrast the full-wave simulation results with the suggested circuit model. The metallic ground prohibited the transmission of the episode wave, and all occurrence electromagnetic waves are restricted in the basic design between the graphene disk. As a consequence, a perfect narrowband absorption peak is obtained. Disk absorption spectra have been discovered for a variety of refractive lists. The findings of the circuit model and full-wave simulations appear to be balanced. This RI sensor is suitable for biomedical sensing because of the combination of its features. The proposed sensor's performance as a cancer early detection sensor was evaluated among biomedical sensors, and the findings indicated that the proposed sensor is an excellent candidate for this application. [ABSTRACT FROM AUTHOR]

Abstract In this paper, we present a GST‐based wideband plasmonic switch. With the excitation of localised surface plasmons and concentration of electric field in the structure, a near‐perfect and wideband absorption is achieved. The switch consists of a GST layer, which acts as a Fabry–Perot cavity. Increasing the temperature and changing the state of GST lead to a high difference between the absorption spectra in amorphous and crystalline states in a wide range of wavelength. Therefore, the switch has a high extinction ratio of 13.71 dB at the wavelength of 1343 nm. Also, the response time of the switch is obtained as 46 fs. The structure has near‐perfect absorption up to the incident angle of about 20°. Moreover, due to the symmetry of structure, the absorption spectrum is independent of polarisation. To show the validity of simulation results, the analytical method of equivalent circuit model is presented. The proposed polarisation‐insensitive switch with high extinction ratio, fast response time and wide bandwidth can be used in photodetectors, plasmonic modulators and logic gates.

The tower model is very important for the assessment of lightning protection for transmission line. The parameters of tower model mainly rely on the impulse experiments of tower. There is a difference between the current channel of the experiments and the lightning strikes, which will result in different impulse responses of the towers. Based on FDTD method, the insulator voltage and current distribution of the tower were calculated when impulse current injected into tower along the lightning strike channel. The parameters of the equivalent model of the tower were determined which can reproduce the insulator voltage, the current flowing into the tower and the current flowing into ground wire.

This paper outlines the detailed study on the imperfections, which are commonly associated with the realization of Radiofrequency Micro-Electro-Mechanical System (RF-MEMS) devices. It also includes empirical modeling of each phenomenon. These imperfections have been broadly categorized into two major classes: fabrication related and another is linked with IC assembly/packaging method. The thorough study deciphers the insight device physics embedded with all those fabrication and packaging issues in MEMS devices. Individual modeling of these issues gives a clear picture of their impacts on device performances. [ABSTRACT FROM AUTHOR]

The plasmonic response of C-shaped nano-apertures is investigated. Full-field numerical simulations are presented that show how the resonance condition depends on the wavelength and polarization of the incident light. Effects of dimension scaling are also discussed. A circuit model is proposed that relates geometrical and material parameters to equivalent inductive and capacitive circuit elements. The topological profile of the induced surface currents is used to find the representative inductance and capacitance values. The equivalent impedance of the circuit model is found to be correlated to the resonance behavior of the actual C-aperture. Comparison between the numerical simulations and the circuit model analysis shows agreement in predicting the resonant wavelength and bandwidth variations with C-aperture dimensions. The presented analysis can be useful in designing C-apertures for applications such as photonic metasurfaces, optical trapping, and fluorescence microscopy. [ABSTRACT FROM AUTHOR]

A two-layers, multi-band super absorber with the capability of being tuned is proposed in this paper. The idea behind the design is to realize periodic arrays of graphene disks via graphene ribbons with different lengths. Then circuit modeling is developed to be used alongside the impedance matching concept to achieve more than ten absorption peaks. The exploited spacer is a lossless polymer in the THz frequency range while the bottom of the device is occupied by a relatively thick golden plate. The developed circuit model description is verified by full-wave simulation. According to the simulation results, the proposed absorber shows more than ten peaks with absorption over 90%. The peak frequencies are interestingly able to be shifted via exploited single chemical potential variations. Additionally, deviations of absorber response against graphene electron relaxation time and device geometry are shown to be marginal which makes the presented meta-absorber, a reliable optical device.

A Germanium (Ge) metastructure with switching features from broadband plasmon‐induced transparency (PIT) and electromagnetically induced absorption (EIA) is presented, which forms a broadband PIT through the near‐field coupling between the localized plasmon resonance and the Mie resonance employing four gold cut wires as bright plasmon resonators and four C‐shaped dielectric rings as dark plasmon resonators. A wide transparent window above 0.9 is achieved covering from 0.622 to 0.823 THz with a relative bandwidth of 27.8%. In addition, through phase modulation, a magnetic dipole is generated by the constructive interference of the near‐field coupling of the three resonators to realize the PIT to EIA conversion. In addition, a grid‐like metastructure is introduced to realize the PIT to EIA conversion by phase modulation. To enhance the EIA bandwidth, another layer of C‐shaped reflection plate resonator is introduced to increase the dark mode loss, and a layer of frequency selective surface composed of cross‐shaped resonators is also used. Thus under the dual effect, a wide absorption window above 0.75 is achieved covering from 0.647 to 0.756 THz with a relative bandwidth of 15.5%. [ABSTRACT FROM AUTHOR]

Copyright of Journal of Ordnance Equipment Engineering is the property of Chongqing University of Technology and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

The present paper addresses the theoretical design and circuit model details of a square- and circle-shaped broadband perfect ring absorber in a wide wavelength range. This absorber has a three-layered structure, which is respectively made up of tungsten, silica, and tungsten. The optimal design is related to tungsten since its impedance matches the free area of the visible spectrum. It records a more desirable response at significant temperatures that can be attributed to the significantly high melting point of tungsten (3422°C). The effects of structure-related parameters and different metals on absorption-related performance are also detailed. The results suggest that the circular ring absorber registers an ultra-broadband absorption response in the range of 550–676 nm, as absorptivity rises above 99%. Comparatively, the square ring absorber records the maximum possible absorption rate of 96.61% at 482 nm and the minimum absorption rate of 94.40% at 642 nm in the visible light regime (400–800 nm). Finally, an exact circuit model is used to obtain the analytical expressions for the proposed absorber. We contrast the findings for this circuit model with the results of full-wave simulation, which shows a good match. The proposed circuit model is basic, as it suggests the physical results of the design along with the operation of a wide range of subwavelength structures over an extensive frequency range. [ABSTRACT FROM AUTHOR]

Long electromagnetic transients occur in electrical systems because of switching and impulse actions As a result, the simulation time of such processes can be long, which is undesirable. Simulation time is significantly increased if the circuit in the study is complex, and also if this circuit is described by a rigid system of state equations. Modern requests of design engineers require an increase in the speed of calculations for realizing a real-time simulation. This work is devoted to the development of a unified spectral method for calculating electromagnetic transients in electrical circuits based on the representation of solution functions by series in algebraic and orthogonal polynomials. The purpose of the work is to offer electrical engineers a method that can significantly reduce the time for modeling transients in electrical circuits. Research methods. Approximation of functions by orthogonal polynomials, numerical methods for integrating differential equations, matrix methods, programming and theory of electrical circuits. Obtained results. Methods for calculating transients in electrical circuits based on the approximation of solution functions by series in algebraic polynomials as well as in the Chebyshev, Hermite and Legendre polynomials, have been developed and investigated. The proposed method made it possible to convert integro-differential equations of state into linear algebraic equations for images of time-dependent functions. The developed circuit model simplifies the calculation method. The images of true current functions are interpreted as direct currents in the proposed equivalent circuit. A computer program for simulating the transient process in an electrical circuit was developed on the basis of the described methods. The performed comparison of methods made it possible to choose the best method and a way to use it. The advantages of the presented method over other known methods are to reduce the simulation time of electromagnetic transients (for the considered examples by more than 6 times) while ensuring the required accuracy. The calculation of the process in the circuit over a long time interval showed a decrease and stabilization of errors, which indicates the prospects for using research methods for calculating complex electrical circuits. [ABSTRACT FROM AUTHOR]

This paper investigates the electrical performance of graphene-based on-chip spiral inductors by virtue of a physics-based equivalent circuit model. The skin and proximity effects, as well as the substrate loss effect, are considered and treated appropriately. The graphene resistance and inductance are combined into the circuit model. It is demonstrated that the electrical characteristics of the on-chip square spiral inductor can be improved by replacing copper with graphene. Moreover, graphene exhibits more effectiveness in improving the inductance in tapered inductors than uniform ones. [ABSTRACT FROM AUTHOR]

In this work, a defective commercial module with a rounded IV characteristic is analyzed in detail to identify the sources of its malfunction. The analysis of the module includes thermography images taken under diverse conditions, the IV response of the module obtained without any shadow, and shadowing one cell at a time, as recommended by the IEC 61215 Standard. Additionally, a direct measurement of the IV characteristic and resistance of single cells in the panel has been conducted to verify the isolation between the p and n areas. In parallel, theoretical cell and module behaviors are presented. In this frame, simulations show how cell mismatch can be the explanation to the rounded IV output of the solar panel under study. From the thermal images of the module, several localized hot spots related to failing cells have been revealed. During the present study, thermal breakdown is seen before avalanche breakdown in one of the cells, evidencing a hot spot. Not many papers have dealt with this problem, whereas we believe it is important to analyze the relationship between thermal breakdown and hot spotting in order to prevent it in the future, since hot spots are the main defects related to degradation of modern modules.

An energy harvesting system requires a power converter with its compact size and high power efficiency. Following the trend, this study suggests a new switched capacitor converter (SCC). The proposed converter is designed by a parallel- and cross-connecting two Fibonacci topologies. This connection leads the proposed SCC to generate its multilevel outputs as well. The proposed SCC has the lowest output resistors under five times conversion ratios from the theoretical analysis and comparison of two different SCC topologies. Simulation results confirm that the proposed SCC can be operated over 90% power efficiencies under 100 mW.

In simulating Quantum Computing by using the circuit model the size of the matrices to deal with, together with the number of products and additions required to apply every quantum gate becomes a really hard computational restriction. This paper presents a data structure, called Functional Matrices, which is the most representative feature of QSimov quantum computing simulator which is also provided and tested. A comparative study of the performance of Functional Matrices with respect to the other two most commonly used matrix data structures, dense and sparse ones, is also performed and summarized within this work.

The theoretical foundations of a metamaterial (MM) liner for the MRI bore that facilitates the propagation of reduced-cutoff cylindrical waveguide modes are presented in the Part 1 companion paper to this work. Here, in Part 2, the practical design and modelling of the novel MM liner is applied to a body MRI radio-frequency (RF) transmitter for 4.7T. An equivalent network mesh model is developed to reduce the distributed structure of the MM to one that uses lumped discrete tuning elements. The close match between full-wave simulation and the network model is demonstrated by comparison of the longitudinal propagation dispersion curves and input impedance. The application of the methods developed for analysis of the MM liner behavior are demonstrated in the design of a practical MM liner as an effective MRI RF transmitter. The liner’s simulated performance was evaluated using three key metrics of MR radio-frequency (RF) coil performance: transmit efficiency, the variation of the transmit field (a measure of homogeneity), and the 10g averaged local specific absorption rate (SAR). These metrics are compared to those of the commonly used birdcage (BC) coil. The main advantage of the MM liner is the 29.6% reduction in maximum SAR normalized to transmit field relative to the BC coil, with comparable transmit efficiency and homogeneity. Thus, the liner can potentially replace the BC coil as an RF transmitter and provide an enhanced safety margin, or allow the use of faster, more SAR-aggressive imaging sequences.

In this paper, we present a GST‐based wideband plasmonic switch. With the excitation of localised surface plasmons and concentration of electric field in the structure, a near‐perfect and wideband absorption is achieved. The switch consists of a GST layer, which acts as a Fabry–Perot cavity. Increasing the temperature and changing the state of GST lead to a high difference between the absorption spectra in amorphous and crystalline states in a wide range of wavelength. Therefore, the switch has a high extinction ratio of 13.71 dB at the wavelength of 1343 nm. Also, the response time of the switch is obtained as 46 fs. The structure has near‐perfect absorption up to the incident angle of about 20°. Moreover, due to the symmetry of structure, the absorption spectrum is independent of polarisation. To show the validity of simulation results, the analytical method of equivalent circuit model is presented. The proposed polarisation‐insensitive switch with high extinction ratio, fast response time and wide bandwidth can be used in photodetectors, plasmonic modulators and logic gates. [ABSTRACT FROM AUTHOR]

In this paper, we show that an additional inductor–capacitor–inductor filter can increase the oscillation amplitude of the enhanced swing Colpitts oscillator (ESCO), and call this topology the more enhanced swing Colpitts oscillator (mESCO). When it is connected with a rectifier, the DC–DC boost conversion ratio can be increased, especially for low-voltage sensor ICs or energy harvesting. This paper focuses on the electrical characteristics of mESCO. The oscillation frequency was modeled as a function of the circuit parameters of mESCO. The common gate voltage gain (ACG), defined by the ratio of the drain voltage amplitude to the source voltage amplitude of the switching MOSFET of mESCO, was also modeled under the assumption that all the circuit elements are ideal. The model was validated with a SPICE simulation. For ACG < 1.5, the model was in good agreement with the SPICE results within 10%. In addition, the drain voltage amplitude vda was modeled by assuming that the average transconductance of the MOSFET in a half cycle is null when the long-channel Shockley model is used. vda needs to be sufficiently high to have a large DC–DC boost conversion ratio. The model can predict the tendency that vda increases as ACG approaches unity. We found that the voltage difference of the drain voltage amplitude to the source voltage amplitude is a constant even when the circuit parameters, and thereby ACG are varied. [ABSTRACT FROM AUTHOR]

During the growth and development of tomato plants, its different cells or tissues would store external environmental information and express it in the form of ion transportation. In order to better examine the storage model of tomato plants, the tomato individual tissue and whole plant biological circuit models were closely examined based on the idea of modal theory. According to the parameter inversion theory, in the frequency range of 0.1Hz - 1MHz, the impedance spectrum measurement and dielectric properties of tomato plants in four modal periods of germination stage were carried out. The stages were namely the seedling stage, flowering and fruit setting stage, and fruiting stage respectively. Impedance spectrum fitting was performed with the ZSimpWin software. Then, the biological circuit model of each tissue of tomato plant was obtained. Next, the parameter inversion was used to calculate the value of each element of the biological circuit model. Lastly, the biological circuit model of the tomato plant body in each period was obtained. Through the charging and discharging test of the model of the tomato plant body at each stage, the corresponding parameter value relationship was obtained according to the capacitance characteristics. This would be compared with the component values obtained from the parameter inversion in the model. Results showed that the errors were all less than 4.8%, which verified the rationality of the model. This system acted as a theoretical guidance for the research on the growth and development of tomato and other plants. [ABSTRACT FROM AUTHOR]

Wide-bandgap (WBG) power devices have better dynamic characteristics and higher working temperatures compared to traditional Si devices and are more suitable for high-frequency and high-voltage applications because of fast turn-on and turn-off speeds. The main obstacle for the use of WBG devices is the high-frequency oscillation (HF-Osc) in voltage and current during the switching process. In this article, a new method of predicting the SiC mosfet switching behavior (including HF-Osc and slow switching) is proposed. First, the models of nonlinear capacitances are improved and parasitic elements are taken into account for improving the RLC equivalent circuit of the mosfet switching transient. On this basis, the LC equivalent frequency is obtained. Then, a new method is proposed to obtain the SiC mosfet instantaneous frequency. The comparison between them in the time domain makes it possible to analyze the SiC mosfet switching behavior. The prediction method is verified using a CREE SiC mosfet via a double pulse test. Experimental and simulation results show that the prediction method is effective in describing the HF-Osc characteristics. The proposed method can be used to effectively improve the mosfet HF-Osc, which provides guidance for the application of SiC mosfets. [ABSTRACT FROM AUTHOR]

A method of measuring the impedance of a microstrip transmission line using a vector network analyzer is proposed. The problem of determining the frequency dependence of the impedance of a microstrip line is very important in order to create circuit models of the electronic components and touchstone-files in the virtual strip channel with a reference impedance of 50 Ω. Circuit models of the components and files are used in computer-aided design systems of integrated microwave devices. It is proposed to solve the problem of measurement by a vector network analyzer in the entire frequency range of operation, by the LTR method. From the measurement results, for a network analyzer in the coaxial channel, of the S-parameters and coefficients of reflection of two segments, short and electrically long microstrip transmission lines, the phase velocity and a damping factor of an electromagnetic wave propagating in the strip line transmission were determined, as well as the converted S-parameters of two distorting adapters modeling contact fields of the coaxial and strip lines. Over the range 0.02–2.00 GHz, the impedance was found from the coefficients of reflection from the coaxial ports of the distorting adapters at two fixed frequency points, at which the reactive capacitive component of the complex impedance is compensated by the inductance of the contact fields of the coaxial and strip lines. The frequency dependence of the real part of the impedance, passing through these frequency points, is determined over the range of frequencies of operation of the network analyzer, by means of the circuit model of the microstrip Beatty standard in the NI AWR Design Environment computer-aided design system. The model of this standard of a line with an air section between two segments of strip lines with an insulation foundation was derived by means of an MLIN circuit analog, suitable for the physical prototype of the line. The importance of the measurement of impedance of the microstrip line is shown by a vector network analyzer on the example of identifying the characteristic parameters of the chip resistors. [ABSTRACT FROM AUTHOR]

A voltage mode capacitance multiplier for ultra-low frequency physiological signal processing is designed with a circuit model. With the proposed multiplier, a filter can achieve a cutoff frequency of 12 mHz with a 1 pF basic capacitance and a 10 kΩ resistor. The corresponding multiplication factor will be 1.35 × 10 9 . By changing the controlling terminal, the multiplication factor can be widely tuned from 1950 to 1.35 × 10 9 and the corresponding filter cutoff frequency will be from 12 mHz to 8.15 kHz. According to the circuit model, to further increase the multiplication factor to decrease the chip area, more multiplication stages can be added to the feedback loop., Competing Interests: Declaration of conflicting interestsThe author declared no potential conflicts of interest with respect to the research, authorship, and/or publication of this article.

Biological cells, characterized by complex and dynamic structures, demand precise models for comprehensive understanding, especially when subjected to external factors such as electric fields (EF) for manipulation or treatment. This interaction is integral to technologies like pulsed electric fields (PEF), inducing reversible and irreversible structural variations. Our study explores both simplified and sophisticated equivalent circuit models for biological cells under the influence of an external EF, covering diverse cell structures from single- to double-shell configurations. The paper highlights challenges in circuit modeling, specifically addressing the incorporation of reversible or irreversible pores in the membrane during external EF interactions, emphasizing the need for further research to refine technical aspects in this field. Additionally, we review a comparative analysis of the performance and applicability of the proposed circuit models, providing insights into their strengths and limitations. This contributes to a deeper insight of the complexities associated with modeling biological cells under external EF influences, paving the way for enhanced applications in medical and technological domains in future.&#xD., (Creative Commons Attribution license.)

In this study, a biosensing scenario is developed for monitoring blood quality based on the detection of blood hemoglobin concentration. The procedure involves considering the blood sample as the dielectric with different refractive indexes for different concentrations of hemoglobin. Usually, the sensitivity to design parameters is the major issue with the metasurface-based detection. To address this issue, a three-layer graphene-based wave absorber is designed and modeled using passive circuit elements. The major idea behind this work is to maximize the device sensitivity against the blood sample. The research methodology involves impedance matching between the device and the surrounding environment, while full-wave simulation is also performed and compared to ensure circuit view accuracy. The findings suggest that the proposed graphene-based absorber can efficiently monitor blood quality via dual absorption peaks. The simulation results extracted from impedance matching and the full-wave method indicate frequency shifts of the second absorption peak. These shift values are interpreted based on hemoglobin concentration. Additionally, ample analyses are provided to show the reliability of the proposed absorber against geometrical aspects, incident angle, external stimulation, and the graphene electron relaxation time.

We explore the source of nonlinearities in Aluminum Nitride (AlN) Contour Mode Resonators (CMRs) operating in the Very High Frequency (VHF) range. We demonstrate that the red-shift of the resonance frequency found in VHF CMRs when the input RF power increases is due to nonlinear stiffness appearing from self-heating, and variable damping due to geometric nonlinearities. Moreover, we find a linear relationship between the variable damping coefficient and the resonator quality factor (Q). Such nonlinear mechanisms are modeled using a spring-mass-damper physical system and, in the electrical domain, a modified Butterworth-Van Dyke (MBVD) circuit where the nonlinear stiffness and variable damping are captured by a charge-dependent motional capacitor and a charge-dependent motional resistor, respectively. Detailed guidelines are provided to accurately analyze nonlinear CMRs using full-wave numerical simulations based on a finite-element method. Such simulations allow us to isolate the influence of each independent nonlinear mechanism and establish a relation between variable damping and geometric nonlinearities. Circuit and full-wave numerical simulations are in good agreement with measured data from fabricated 225 MHz CMRs exhibiting different Q. Finally, we exploit nonlinearities in high-Q CMRs to generate frequency combs at the MHz range opening the door to new exciting applications in telecommunication and sensing., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2024 Elsevier B.V. All rights reserved.)

This article investigates the possibility to develop time-domain immunity tests using electric near-field probes, for flexible customization of broadband input waveforms injected into specific pins of PCBs. For this purpose, a test design methodology is proposed, which is based on circuit modeling of the injection mechanism on the one hand, and on pulse design and equalization on the other hand. Two circuit models are developed. The former employs measurement/simulation data along with port-reduction techniques to model noise injection through near-field probes by means of internal induced sources. Conversely, the latter model only includes passive components and is derived starting from physical observation of the involved phenomena. Both models are compatible with circuit solvers and can be easily adapted for different traces under test. Since pulse-like noise is usually broadband, suitable stress waveforms are utilized to obtain different noise spectra. Also, in order to precisely control the shape of the waveform reaching the targeted pin, an equalization procedure is employed. These models and techniques can be easily applied to amplification systems originally designed for frequency-domain tests, thus providing a comprehensive solution for the design of broadband immunity tests in the time domain. The feasibility and accuracy of the proposed methodology are proved by full-wave simulations and measurements. [ABSTRACT FROM AUTHOR]

The center-surround receptive field of retinal ganglion cells represents a fundamental concept for how the retina processes and encodes visual information. Yet, traditional approaches of using the receptive field as a linear filter to integrate light intensity over space often do not capture the responses of a ganglion cell to complex visual stimuli. Thus, models with local nonlinearities in subunits of the receptive field or with local temporal dynamics are emerging to better reflect relevant aspects of retinal circuitry and capture stimulus encoding. Here, we review recent efforts to identify such receptive-field substructure and evaluate its role in visual stimulus encoding. The concomitant development of new computational tools may pave the way toward a model-based, functional approach to retinal circuit analysis. Visual stimulus encoding by the retina is not fully captured by the center-surround receptive fields of retinal ganglion cells. Mounting evidence of nonlinear spatial signal integration under natural stimuli and of specific visual functions solved by distinct ganglion cell types indicates the need to better understand receptive-field substructure. Nonlinear spatial integration can be captured by subdividing ganglion cell receptive fields into subunits, which are thought to correspond to presynaptic bipolar cells. Several statistical and model-based methods have recently been developed to identify the subunit layout from spiking responses of ganglion cells to visual stimuli. The subunits provide scaffolding for retinal computations, which may act through local adaptation and inhibition to shape responses to dynamic stimulation and to extract specific visual features. [ABSTRACT FROM AUTHOR]