Supercapacitors are typically used in applications requiring frequent and continuous charging/discharging cycles, but most of the models available in the literature are designed to predict their behavior for a single sequence. In this letter, we show first that the electrical response and metrics of supercapacitors under periodic voltage excitations can generally be obtained using Fourier series analysis and convolution operations of functions derived based on any suitable impedance model. We verified our analysis procedure with simulations using particle swarm optimization, and experiments

The power-energy performance of supercapacitors is usually visualized by the Ragone plot of (gravimetric or volumetric) energy density vs power density. The energy is commonly computed from E = CV2/2, and the power from P = E/Δt, which assume RCbased models. In this study, we investigate the energy-power profiles of two commercial supercapacitors discharged with three different types of loads: (i) constant current, (ii) constant power, and (iii) constant resistive load. The energy is computed as per the definition from the time-integral of its instantaneous power, i.e. E(t) = ò p(t)dt with p(t

Double-dispersion impedance models are important for the accurate fitting of spectral impedance measurements in Electrical Impedance Spectroscopy (EIS). While the Cole–Cole model is the most widely known, it is possible to define double-dispersion Cole–Davidson and Havriliak–Negami models as well. In this work, we show that more freedom can be exercised when these three models are combined together and that this combination can be done in various forms. Experimental results using a two-stage optimization algorithm applied on the suggested models are provided. © 2021, European Biophysical

The need for portable and low-cost bio-impedance analyzers that can be deployed in field studies has significantly increased. Due to size and power constraints, reducing the hardware in these devices is crucial and most importantly is removing the need for direct phase measurement. In this paper a new magnitude-only technique based on modified Kramers–Kronig transforms is proposed and tested. Comparison with impedance measurements of fresh and aging tomato samples using a precise industry standard impedance analyzer is carried out and explained. Error and noise analysis of the proposed

A novel non-uniform Kramers–Kronig Transform algorithm for bioimpedance phase extraction is proposed and tested in this work. The algorithm error is studied and compared with a previously proposed phase extraction technique, also based on the Kramers–Kronig transform. Results using simulated datasets and experimental datasets confirm the excellent performance of the algorithm. © 2020, European Biophysical Societies' Association.

Pinched hysteresis behavior is considered evidence of the existence of the memristive element. Recently, the multi-lobes (more than two) behavior has been discovered in some memristive devices. In this paper, a fractional-order flux/voltage-controlled memristive model is introduced that is able to develop multiple symmetric and asymmetric pinch-off points. Generalized closed-form expressions for the necessary conditions of multiple pinch-off points existence are derived in addition to the coordinates of the pinch-off points in the I-V plane. Closed-form expressions for the minimum and maximum

The focus in supercapacitor research typically falls into one of two categories: (i) the rational design and engineering of electrode materials and electrolyte formulation to achieve high performance devices at competitive costs, and (ii) the modeling of their resulting behavior in response to constant-current charging/discharging, cyclic voltammetry or impedance spectroscopy. However, less work has been dedicated to new ways for charging these devices. In this work we show that charging a supercapacitor, modeled as a constant phase element with a series resistor, using a linear voltage ramp

Supercapacitors, which are now widely used as power sources in various applications, are discharged with one of the following three basic discharge modes: a constant current load, a constant resistance load or a constant power load. A constant current load is one which varies its internal resistance to achieve a constant current regardless of the applied voltage. For the constant resistance case, it results in a change of power as the voltage level changes. And for a constant power load, the load varies its impedance as the input voltage changes in order to keep the power constant. However

Fractional-order models of supercapacitors are advantageous in that they have fewer terms, offering simpler expressions to accurately describe the transient characteristics of these devices than integer-order models. When evaluating the discharge characteristics of supercapacitors, a constant current is often considered which does necessarily represent real-world applications. In this work, the voltage discharging expressions of a fractional-order model of a supercapacitor to time-varying polynomial discharging currents are presented using simulations to highlight the different cases. In

In this paper, we present new approaches to study the co-existence of some types of synchronisation between hyperchaotic dynamical systems. The paper first analyses, based on stability theory of linear continuous-Time systems, the co-existence of the projective synchronisation (PS), the function projective synchronisation (FPS), the full state hybrid function projective synchronisation (FSHFPS) and the generalised synchronisation (GS) between general master and slave hyperchaotic systems. Successively, using Lyapunov stability theory, the coexistence of three different synchronisation types is