Standard Circuit Research Articles

A comparative evaluation of equivalent circuit and finite element electrical skin modelling techniques

Mathematical models are essential to our understanding of the electrical properties of the skin. In this paper, two types of simulation model, an equivalent circuit and a finite element simulation were investigated and compared to evaluate their accuracy. Impedance spectra were measured, between 100 Hz and 50 MHz, (the limits of the available spectrum analyser) of a pair of electrodes placed on skin and these spectra used to find the parameters of a standard equivalent circuit model. The resulting indicated that the components of the equivalent circuit may represent different parts of the skin physiology that indicated by the literature. A simulation model was constructed in COMSOL, with the dimensions, permittivity and conductivity of each skin layer taken from across the published literature. This model was tested for sensitivity to the thicknesses of tissue layers as well as the shape of the boundary between layers. It was found that changing the layer thicknesses only had a significant effect for the stratum corneum and dermis, and that changing the shape of the boundary between layers created an impedance change of up to two times at certain higher frequencies (>1 kHz). While the impedance curves generated by the two models had the same overall profile, there was a difference of up to 100 times in their DC impedance values. This indicated that the broad understanding of how electrical signals of different frequencies pass through the skin is correct, but that significant insufficiencies exist in the published properties of the skin layers, particularly the stratum corneum and that finding more accurate values for these properties is necessary for the development of better models.

Analysis of the pointwise completeness and the pointwise degeneracy of the standard and fractional descriptor linear systems and electrical circuits

The Drazin inverse of matrices is applied to analysis of the pointwise completeness and the pointwise degeneracy of the descriptor standard and fractional linear continuous-time and discrete-time systems. It is shown that: 1) The descriptor linear continuous-time system is pointwise complete if and only if the initial and final states belong to the same subspace. 2) The descriptor linear discrete-time system is not pointwise complete if its system matrix is singular. 3) System obtained by discretization of continuous-time system is always not pointwise complete. 4) The descriptor linear continuous-time system is not pointwise degenerated in any nonzero direction for all nonzero initial conditions. 5) The descriptor fractional system is pointwise complete if the matrix defined by (36) is invertible. 6) The descriptor fractional system is pointwise degenerated if and only if the condition (41) is satisfied. Considerations are illustrated by examples of descriptor linear electrical circuits.

Standardized circuit class group training versus individualized goal-directed group training to improve upper limb function in stroke survivors during in-patient rehabilitation: a pragmatic trial

Purpose To investigate the usability and effectiveness of standardized circuit class group training (CCT) compared to individualized goal-directed group training (GDT) in subacute stroke survivors. Materials and methods This study consists of three parts. Part 1 involved a pragmatic, non-randomized controlled trial with subacute participants and their therapists, who participated in four weeks either CCT or GDT. Superiority of the intervention was defined as significantly larger improvement on the Motor Activity Log for patients and lower workload for therapists. In Part 2, six additional workstations were developed for CCT. Part 3 replicated the study of Part 1 with the expanded CCT. Results Part 1 showed no difference in effectiveness between training methods. CCT did not match the rehabilitation goals of the patient sufficiently, however mental workload seemed lower for therapists. An expansion of CCT could improve the match between the patient’s goals and the training (Part 2). Results of Part 3 showed again no difference in effectiveness between methods. CCT was however perceived as less engaging compared to GDT, but mental load for therapists remained lower. Conclusions A standardized training could reduce the mental workload for therapists, but patients seemed less engaged. A combination of both might be most beneficial.Trial registration: Dutch Trial Register: NL8844 and NL9471 IMPLICATIONS FOR REHABILITATION Providing a standardized training program after stroke reduces therapists’ mental workload. Individualized goal-directed group training results in the best achievement of rehabilitation goals. A combination of standardized and individual training would use best of both intervention modalities. Patients should be involved in the co-creation developing process of training programs.

A drain current formula for two-dimensional field-effect transistors with one-shot convergence algorithm

Two-dimensional material-based field-effect transistors (2DM-FETs) exhibit both ambipolar and unipolar carrier transports. To physically and compactly cover both cases, a quasi-Fermi-level phase space (QFLPS) approach was proposed, but it still involves complicated integration operations. This article aims at improving the numerical efficiency of the QFLPS model by several orders of magnitude so that it can readily be implemented in a standard circuit simulator. We first rigorously derive the integral-free formula for the drain-source current to achieve this goal. Besides computationally benign, it explicitly gives the correlation terms between the electron and hole components. Secondly, to work out the boundary values required by the new expressions, we develop an algorithm for the channel electrostatic potential based on the zero-temperature limit property of the 2DM-FET system. By calibrating the model with the realistic device data of black phosphorus and monolayer molybdenum disulfide FETs, the algorithm is tested against practical cases. Two orders of magnitude improvement in time consumption can be achieved compared with the integral-form QFLPS approach, and it is even four orders of magnitude faster than the traditional continuity-equation based approach.

The Observable Movement Quality scale for patients with low back pain (OMQ-LBP): validity and reliability in a primary care setting of physical therapy

BackgroundThe Observable Movement Quality scale for patients with low back pain (OMQ-LBP) is a newly developed measurement instrument for use in primary care settings of physical and exercise therapists to assess movement quality (MQ) of patients with low back pain (LBP).ObjectiveThis study aims to determine validity, reliability and feasibility of the OMQ-LBP. The OMQ-LBP consists of a standardized movement circuit (performed twice) consisting of five daily activities problematic for LBP patients, which are scored with an 11-item observation list.MethodsConstruct validity was determined by testing seven hypotheses on associations between constructs (n = 85 patients with LBP) and four hypotheses on known group differences (n = 85 patients with LBP and n = 63 healthy controls; n = 35 matched participant-patients having VAS-pain ≥ 20 mm during and/or after both circuits and healthy controls). Internal consistency was analyzed with Cronbach’s alpha (n = 85 patients with LBP). For inter- and intra-rater reliability Intraclass Correlation Coefficient (ICC) values were examined (n = 14 therapists: seven primary care physical therapists and seven exercise therapists). Additionally, content validity and feasibility were determined using thematic analysis of a brief interview with participants, patients (n = 38) and therapists (n = 14).ResultsAfter Bonferroni correction 2/7 associations between constructs and 2/4 significant group differences were confirmed. Cronbach’s alpha was 0,79. The ICC-values of interrater reliability of the OMQ-LBP total score and the duration score were 0.56 and 0.99 and intra-rater reliability 0.82 and 0,93, respectively. Thematic analysis revealed five themes. Three themes elucidate that both patients and therapists perceived the content of the OMQ-LBP as valid. The fourth theme exhibits that OMQ-LBP provides a clear and unambiguous language for MQ in patients with LBP. Theme 5 depicts that the OMQ-LBP seems feasible, but video recording is time-consuming.ConclusionsThe OMQ-LBP is a promising standardized observational assessment of MQ during the five most problematic daily activities in patients with LBP. It is expected that uniform and objective description and evaluation of MQ add value to clinical reasoning and facilitate uniform communication with patients and colleagues.

Bias-Voltage-SSHI Interface Circuit for Strong Coupling Piezoelectric Energy Systems

Compared with the standard extraction interface circuit (SEH), the harvested energy and harvested power of synchronized switching harvesting interface circuits (SSHI) and synchronous charge extraction interface circuit (SECE) cannot improve more effectively. This paper proposes a Bias-Voltage-SSHI Interface Circuit (BV-SSHI), consisting of a single peak voltage detection switch and a rectifier, to solve this problem. The proposed BV-SSHI improves the output voltage by biasing the voltage of the piezoelectric energy harvester and obtains similar harvested power as SSHI. Simulation results show that the BV-SSHI can obtain more harvested energy and harvested power than SEH under weak, medium, and strong coupling systems. Results show that the higher harvester's voltage and the larger phase difference cause the electrical restoring force (χV) to significantly weaken the vibration displacement, especially under strong coupling systems. Thus, the gain effect of the SSHI and SECE is weakened. The experimental results of the medium coupling systems show that the BV-SSHI can obtain 247.2% harvested energy and 121.2% maximum harvested power compared with SEH. The BV-SSHI can achieve at least 142.4% harvested energy and 100.3% maximum harvested power compared with what SSHI and SECE can achieve.

Synchronized charge extraction circuit for electret‐based vibration energy harvester

AbstractImpedance matching is one outstanding issue for the electret‐based vibration energy harvester (eVEH) due to its small equivalent capacitance. In this paper, the authors developed a synchronized charge extraction (SCE) circuit for eVEH, to improve its performance in small load resistance conditions. An electromagnetic detector is embedded with the eVEH to detect its maximum vibration amplitude. The synchronized switch is controlled by a microcontroller unit. According to the authors’ simulation study, the power output of eVEH interfaced with the SCE circuit is three times larger than that of the standard circuit, which proved the effectiveness of our SCE circuit.

Single-Gate In-Transistor Readout of Current Superposition and Collapse Utilizing Quantum Tunneling and Ferroelectric Switching.

In nanostructure assemblies, the superposition of current paths forms microscopic electric circuits, and different circuit networks produce varying results, particularly when utilized as transistor channels for computing applications. However, the intricate nature of assembly networks and the winding paths of commensurate currents hinder standard circuit modeling. Inspired by the quantum collapse of superposition states for information decoding in quantum circuits, the implementation of analogous current path collapse to facilitate the detection of microscopic circuits by modifying their network topology is explored. Here, the superposition and collapse of current paths in gate-all-around polysilicon nanosheet arrays are demonstrated to enrich the computational resources within transistors by engineering the channel length and quantity. Switching the ferroelectric polarization of Hf0.5 Zr0.5 O2 gate dielectric, which drives these transistors out-of-equilibrium, decodes the output polymorphism through circuit topological modifications. Furthermore, a protocol for the single-electron readout of ferroelectric polarization is presented with tailoring the channel coherence. The introduction of lateral path superposition results into intriguing metal-to-insulator transitions due to transient behavior of ferroelectric switching. This ability to adjust the current networks within transistors and their interaction with ferroelectric polarization in polycrystalline nanostructures lays the groundwork for generating diverse current characteristics as potential physical databases for optimization-based computing.

Four-Phase Interleaved Boost Converter for Maximum Power Extraction in PV System

The use of renewable energy is increasing, thus affecting the rapid use of DC-DC converter technology. The use of a conventional boost converter has a weakness, namely high current ripple. This input current ripple will enter the voltage source, so that the switching noise will spread to other circuits. This problem can be overcome by using a multiphase converter topology that can suppress current ripple. But the conventional multiphase topology has large power losses, because the value of the inductor used tends to be large. Ripple currents will also reduce the efficiency of solar power plants. This study aims to design a four-phase interleaved boost converter that is applied to PV (photovoltaic) with maximum power extraction. The topology method of this circuit is to assemble a conventional boost converter in parallel up to 4 levels, so that it can suppress the input current ripple. This topology modification series also uses the interleaved scaling method in order to reduce heat distribution on each switch. The test method in this study uses a standard boost converter circuit as a comparison, and observes its characteristics and performance through simulation. The converter system is also operated as Maximum Power Point Tracking (MPPT) using the PSO and P&O algorithm controls as a comparison. Based on the simulation results, the MPPT tracking speed has the same speed, which is 2 ms, but the speed to achieve ripple stability in the standard circuit and four-phase interleaved boost converter is 4.5 ms and 6.1 ms, respectively.

Replicable Patterns of Memory Impairments in Children With Autism and Their Links to Hyperconnected Brain Circuits

BackgroundMemory impairments have profound implications for social communication and educational outcomes in children with autism spectrum disorder (ASD). However, the precise nature of memory dysfunction in children with ASD and the underlying neural circuit mechanisms remain poorly understood. The default mode network (DMN) is a brain network that is associated with memory and cognitive function, and DMN dysfunction is among the most replicable and robust brain signatures of ASD. MethodsWe used a comprehensive battery of standardized episodic memory assessments and functional circuit analyses in 25 8- to 12-year-old children with ASD and 29 matched typically developing control children. ResultsMemory performance was reduced in children with ASD compared with control children. General and face memory emerged as distinct dimensions of memory difficulties in ASD. Importantly, findings of diminished episodic memory in children with ASD were replicated in 2 independent data sets. Analysis of intrinsic functional circuits associated with the DMN revealed that general and face memory deficits were associated with distinct, hyperconnected circuits: Aberrant hippocampal connectivity predicted diminished general memory while aberrant posterior cingulate cortex connectivity predicted diminished face memory. Notably, aberrant hippocampal-posterior cingulate cortex circuitry was a common feature of diminished general and face memory in ASD. ConclusionsOur results represent a comprehensive appraisal of episodic memory function in children with ASD and identify extensive and replicable patterns of memory reductions in children with ASD that are linked to dysfunction of distinct DMN-related circuits. These findings highlight a role for DMN dysfunction in ASD that extends beyond face memory to general memory function.

Realization of the TOW-THOMAS Biquad Active Filter

The Tow-Thomas Biquad Circuit provides the filter designers with a valuable building block for building higher order active filters. It is a flexible circuit structure in which the transfer function properties are easily manipulated by modifying the passive RC elements that connect the operational amplifiers. It can be easily defined in its low-pass and bandpass operations. Above all, we can easily fabricate the possible filters inside a single chip with very slight modification of the standard Tow-Thomas Circuit.

Electrical Transport Mechanisms in Graphene Nanoplatelet Doped Polydimethylsiloxane and Application to Ultrasensitive Temperature Sensors.

The temperature effect on electronic transport mechanisms in graphene nanoplatelet (GNP) doped polydimethylsiloxane (PDMS) for temperature sensing applications has been investigated under electrical impedance spectroscopy (EIS) analysis. AC measurements showed a very prevalent frequency-dependent behavior in low filled nanocomposites due to the lower charge density. In fact, 4 wt % GNP samples showed a nonideal capacitive behavior due to scattering effects. Therefore, the standard RC-LRC circuit varies with the substitution of capacitive elements by CPEs, where a CPE is a constant phase element which denotes energy dissipation. In this regard, the temperature promotes a prevalence of scattering effects, with an increase of resistance and inductance and a decrease of capacitance values in both RC (intrinsic and contact mechanisms) and LRC (tunneling mechanisms) elements and, even, a change from ideal to nonideal capacitive behavior as in the case of 6 wt % GNP samples. In this way, a deeper understanding of electronic mechanisms depending on GNP content and temperature is achieved in a very intuitive way. Finally, a proof-of-concept carried out as temperature sensors showed a huge sensitivity (from 0.05 to 11.7 °C-1) in comparison to most of the consulted studies (below 0.01 °C-1), proving, thus, excellent capabilities never seen before for this type of application.

Recent Progress and Applications of HfO2-Based Ferroelectric Memory

The discovery of ferroelectricity in hafnium oxide (HfO <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> ) based thin films in 2011 renewed the interest in ferroelectrics. These new ferroelectrics possess completely different crystal morphology with conventional perovskite ferroelectrics, and present more robust ferroelectric properties upon aggressive scaling and compatibility with standard integrated circuit fabrication processes. In this article, we give a brief introduction to the conventional ferroelectric memories, then review the basic properties, recent progress, and memory applications of these HfO <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> -based ferroelectrics.

Comparison of Four Mechanical Insufflation-Exsufflation Devices: Effect of Simulated Airway Collapse on Cough Peak Flow.

Mechanical insufflation-exsufflation (MI-E) devices are used to improve airway clearance in individuals with acute respiratory failure. Some MI-E devices measure cough peak flow (CPF) during MI-E to optimize pressure adjustments. The aim was to compare CPF and effective cough volume (ECV: volume expired/coughed > 3 L/s) measurements between 4 MI-E devices under simulated conditions of stable versus collapsed airway. Four MI-E devices were tested on the bench. Each device was connected via a standard circuit to a collapsible tube placed in an airtight chamber that was attached to a lung model with adjustable compliance and resistance. Pressure was measured upstream and downstream the collapsing tube; air flow was measured between the chamber and the lung model. Each device was tested in 2 conditions: collapse condition (0 cm H2O) and no-collapse condition (-70 cm H2O). For each condition, 6 combinations of inspiratory/expiratory pressures were applied. CPF was measured at the "mouth level" by the device built-in flow meter and at the "tracheal level" by a dedicated pneumotachograph. Comparisons were performed with non-parametric tests. CPF values measured at the tracheal level and ECV values differed between devices for each inspiratory/expiratory pressure in the collapse and no-collapse conditions (P < .001). CPF values were significantly lower at the tracheal level in the collapse as compared with the no-collapse condition (P < .001 for each device), whereas they were higher at the mouth level (P < .05) for 3 of the 4 devices. CPF values differed significantly across MI-E devices, highlighting limitation(s) of using only CPF values to determine cough effectiveness. In simulated of airway collapse, CPF increased at the mouth, whereas it decreased at the tracheal level.

Analytical solutions using special trans functions theory for current–voltage expressions of perovskite solar cells and their approximate equivalent circuits

Perovskite solar cells (PSC) have been recognized as devices with a constant increase in power conversion efficiency, confirming this promising technology’s upward trend. This paper deals with the mathematical modeling of current voltage and inverse voltage-current relationships of PSCs, in which standard equivalent circuits, as well as approximate equivalent circuits where series or parallel resistance is neglected, are investigated. Analytical solutions for voltage-current and current–voltage dependencies are derived for all investigated circuits. Furthermore, analytical solutions for short-circuit current and open-circuit voltage are derived. All nonlinear formulations of these dependencies are solved by applying special trans function theory. This paper proposes an enhanced algorithm called the Chaotic African Vultures Optimization Algorithm (Ch-AVOA) for PSC’s parameter estimation. The proposed algorithm is compared with other algorithms in terms of the convergence speed to the global solution and other statistical test measures to validate the algorithm’s efficiency.

Wideband H-Plane T-Junction Power Divider With Compensation Elements Using Double Ridged Empty Substrate Integrated Waveguide

The empty substrate integrated waveguide (ESIW) presents the same advantages as the substrate integrated waveguide (SIW): low cost, low profile, and easy integration, but with lower insertion losses because the dielectric is removed. In order to increase the operational usable bandwidth, one or two ridge layers can be added to the ESIW, leading to the single ridge ESIW (RESIW) or the double ridge ESIW (DRESIW). A transition from microstrip to DRESIW has already been presented, but no other passive components have been implemented in this technology yet. This letter presents a broadband 3-dB DRESIW power divider based on an <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$H$ </tex-math></inline-formula> -plane T-junction with compensation elements, which can be easily manufactured using standard planar circuit manufacturing techniques. The manufactured prototype presents measured return losses greater than 12 dB from 6.9 to 20.4 GHz, representing a 99% fractional bandwidth (FBW), whereas the power division is rather symmetric since the maximum <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$S_{21}$ </tex-math></inline-formula> and <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$S_{31}$ </tex-math></inline-formula> parameters are −3.98 and −3.78 dB, respectively.

A sub-wavelength Si LED integrated in a CMOS platform

A nanoscale on-chip light source with high intensity is desired for various applications in integrated photonics systems. However, it is challenging to realize such an emitter using materials and fabrication processes compatible with the standard integrated circuit technology. In this letter, we report an electrically driven Si light-emitting diode with sub-wavelength emission area fabricated in an open-foundry microelectronics complementary metal-oxide-semiconductor platform. The light-emitting diode emission spectrum is centered around 1100 nm and the emission area is smaller than 0.14 μm2 (~varnothing 400 nm). This light-emitting diode has high spatial intensity of >50 mW/cm2 which is comparable with state-of-the-art Si-based emitters with much larger emission areas. Due to sub-wavelength confinement, the emission exhibits a high degree of spatial coherence, which is demonstrated by incorporating the light-emitting diode into a compact lensless in-line holographic microscope. This centimeter-scale, all-silicon microscope utilizes a single emitter to simultaneously illuminate ~9.5 million pixels of a complementary metal-oxide-semiconductor imager.

Compact Modeling of Two-Dimensional Field-Effect Biosensors.

A compact model able to predict the electrical read-out of field-effect biosensors based on two-dimensional (2D) semiconductors is introduced. It comprises the analytical description of the electrostatics including the charge density in the 2D semiconductor, the site-binding modeling of the barrier oxide surface charge, and the Stern layer plus an ion-permeable membrane, all coupled with the carrier transport inside the biosensor and solved by making use of the Donnan potential inside the ion-permeable membrane formed by charged macromolecules. This electrostatics and transport description account for the main surface-related physical and chemical processes that impact the biosensor electrical performance, including the transport along the low-dimensional channel in the diffusive regime, electrolyte screening, and the impact of biological charges. The model is implemented in Verilog-A and can be employed on standard circuit design tools. The theoretical predictions obtained with the model are validated against measurements of a MoS2 field-effect biosensor for streptavidin detection showing excellent agreement in all operation regimes and leading the way for the circuit-level simulation of biosensors based on 2D semiconductors.

Non-Linear Analysis of Novel Equivalent Circuits of Single-Diode Solar Cell Models with Voltage-Dependent Resistance

The most commonly used model of solar cells is the single-diode model, with five unknown parameters. First, this paper proposes three variants of the single-diode model, which imply the voltage dependence of the series resistance, parallel resistance, and both resistors. Second, analytical relationships between the current and the voltage expressed were derived using the Lambert W function for each proposed model. Third, the paper presents a hybrid algorithm, Chaotic Snake Optimization (Chaotic SO), combining chaotic sequences with the snake optimization algorithm. The application of the proposed models and algorithm was justified on two well-known solar photovoltaic (PV) cells—RTC France solar cell and Photowatt-PWP201 module. The results showed that the root-mean-square-error (RMSE) values calculated by applying the proposed equivalent circuit with voltage dependence of both resistors are reduced by 20% for the RTC France solar cell and 40% for the Photowatt-PWP201 module compared to the standard single-diode equivalent circuit. Finally, an experimental investigation was conducted into the applicability of the proposed models to a solar laboratory module, and the results obtained proved the relevance and effectiveness of the proposed models.

Numerical Optimization of a Nonlinear Nonideal Piezoelectric Energy Harvester Using Deep Learning

This contribution addresses the numerical optimization of the harvested energy of a mechanically and electrically nonlinear and nonideal piezoelectric energy harvester (PEH) under triangular shock-like excitation, taking into account a nonlinear stress constraint. In the optimization problem, a bimorph electromechanical structure equipped with the Greinacher circuit or the standard circuit is considered and different electrical and mechanical design variables are introduced. Using a very accurate coupled finite element-electronic circuit simulator method, deep neural network (DNN) training data are generated, allowing for a computationally efficient evaluation of the objective function. Subsequently, a genetic algorithm using the DNNs is applied to find the electrical and mechanical design variables that optimize the harvested energy. It is found that the maximum harvested energy is obtained at the maximum possible mechanical stresses and that the optimum storage capacitor for the Greinacher circuit is much smaller than that for the standard circuit, while the total harvested energy by both configurations is similar.