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A series of polymer dispersed liquid crystal devices using glass substrates have been fabricated and investigated focusing on their electrical properties. The devices have been studied in terms of impedance as a function of frequency. An electric equivalent circuit has been proposed, including the influence of the temperature on the elements into it. In addition, a relevant effect of temperature on electrical measurements has been observed.

We report a unique constant phase element (CPE) behavior ( 1 Z = Q 0 ( j ω ) α ) of the electrolyte−graphene interface with both Q 0 and α showing dependence on the gate voltage. The frequency response of the electrolyte−graphene interface was studied using electrochemical impedance spectroscopy (EIS). The result suggests that (1) the electrolyte−graphene interface should be characterized as a CPE ( α < 1), rather than an ideal capacitor; and (2) both Q 0 and α show ambipolar dependence on the applied voltage. We speculate that the CPE behavior of the electrolyte−graphene interface arises from the charged impurities on the substrate and the defects in the graphene lattice, which could introduce inhomogeneity of local density of states (DOS). The low density of states of graphene makes α sensitive to these local DOS near the Dirac point, and thus showing dependence on the gate voltage. Measurement of the electrolyte−graphene interface capacitance based on multi-frequency capacitance-voltage (CV) profiling was demonstrated, and the extraction of the carrier mobility was performed. The study could lead to a more accurate understanding of the capacitive behavior of the electrolyte−graphene interface, which is instructive for the design and analysis of devices involving the electrolyte−graphene interface for nanoelectronics and bioelectronics applications.

Cation ordering is the most common phenomenon detected in A 3 B′B″ 2 O 9 -based complex perovskites. Some important physical features of this system are due to the B-site ordering at long and short range. For microwave applications as filters and resonators, the 1:2 order is more appropriate. Otherwise, the oxygen vacancies and 1:1 order are considered the main factors behind the excellent performance of nonstoichiometric A 3 B′ 1+ x B″ 2- x O 9-δ -based ceramics as proton conductors. Until now, however, there are no available reports regarding the isolated effects of B-site ordering at long range on the electrical properties of stoichiometric systems. This work reports the preparation of 1:1 and 1:2 ordered Ba 3 CaNb 2 O 9 ceramics. Here, we combine the Raman scattering and group-theory calculations to distinguish the fingerprints of the 1:1 and 1:2 orders. The electrical properties of the ordered Ba 3 CaNb 2 O 9 are analyzed in terms of a phenomenological model based on the parallel combination of a resistor, constant phase element, and capacitor. In particular, the conductivity relaxation ascribed to the grains is due to the oxygen vacancies. Besides, we found that the 1:1 order increases the dc conductivity compared to the 1:2 order. [ABSTRACT FROM AUTHOR]

Poly(vinylidene fluoride)-based polymers and their blends are used to fabricate electrostatic fractional-order capacitors. This simple but effective method allows us to precisely tune the constant phase angle of the resulting fractional-order capacitor by changing the blend composition. Additionally, we have derived an empirical relationship between the ratio of the blend constituents and the constant phase angle to facilitate the design of a fractional-order capacitor with a desired constant phase angle. The structural composition of the fabricated blends is investigated by using Fourier transform infrared spectroscopy and X-ray diffraction techniques. [ABSTRACT FROM AUTHOR]

The influence of surface distributions on rates of heterogeneous reactions coupled by adsorbed intermediates was studied to determine whether this form of surface heterogeneity can provide a physical explanation for constant-phase-element behavior. Results obtained from finite-element simulations on disk and recessed disk electrodes show that there are two components that give rise to frequency dispersion. Frequency dispersion occurs due to geometry-induced nonuniform current distributions which leads to a complex ohmic impedance. The effects of geometry-induced frequency dispersion may be mitigated by use of small electrodes. Frequency dispersion also occurs due to the potential dependence of the faradaic impedance. The characteristic frequency associated with this form of frequency dispersion is not dependent on disk radius, but the contribution of frequency dispersion associated with reactions coupled by adsorbed intermediates may be reduced with the use of small electrodes. [ABSTRACT FROM AUTHOR]

Due to the dispersive porous nature of its material, carbon–carbon supercapacitors have a current–voltage relationship which is modeled by a fractional-order differential equation of the form i ( t ) = C α d α v ( t ) dt α where α ≤ 1 is a dispersion coefficient and C α is a pseudo-capacitance not measurable in Farads. Hence, the energy stored in a capacitor, known to equal CV 2 / 2 where C is the capacitance in Farad and V is the voltage applied, does not apply to a supercapacitor. In a recent work (Allagui et al., 2016), a fractional-order energy equation that enables the quantification of the energy stored in a supercapacitor when it is charged by a linear voltage ramp was derived. In addition, an effective capacitance (in proper Farad units) obtained from the time-domain analysis of the supercapacitor model under this type of charging was also derived. While some experimental results were given in Allagui et al. (2016), here we provide more experimental evidence of the applicability of the fractional-order energy equation using two commercial devices from two different vendors. We also show the effect of fast charging versus slow charging on the amount of energy stored in these supercapacitors. [ABSTRACT FROM AUTHOR]

The main aim of this paper is the investigation of practical aspects of synthesis of so-called active constant phase elements (CPE). The proposed synthesis is based on the multiplication of partial bilinear immittance segments with electronically adjustable locations of zero and pole. An overview of already known methods for the synthesis of active types of CPE is given and explained as the initial motivation of this work. This work introduces a solution of new simplified two-active-elements-based bilinear immittance and investigates its implementation in loop of operational-transconductance-amplifiers-based impedance converter operating as a general immittance multiplier of a theoretically infinite number of partial immittance segments. The presented results show practical consequences of applying these bilinear immittance segments in CPE synthesis. The most important advantages of the presented proposal are: simplified circuitry of a partial bilinear segment and mutually independent electronic and linear control of zero and pole frequencies allowing electronic reconfiguration of the order of CPE. The design is accompanied by a detailed analysis of real behavior and practical recommendations for design. Real non-ideal features of active elements have significant impact on CPE operation. Therefore, a detailed study of practical aspects has been prepared and supported by Matlab calculations. Conclusions resulting from analyses are supported by PSpice simulations and real experiments. [ABSTRACT FROM AUTHOR]

The electrochemical impedance of Geobacter sulfurreducens biofilms reflects the extracellular electron transfer mechanisms determining the rate of current output. Binned into two characteristic parameters, conductance and capacitance, biofilm impedance has received significant attention. The goal of this study was to evaluate a small overpotential approximation for extracellular electron transfer in G. sulfurreducens biofilms. Our motivation was to determine whether conductance over biofilm growth behaved linearly with respect to limiting current. Biofilm impedance was tracked during growth using electrochemical impedance spectroscopy (EIS) and electrochemical quartz crystal microbalance (eQCM). We showed that normalization of the biofilm impedance is useful for characterizing the changes during growth. When the conductance and capacitance were compared to the biofilm current, we found that: 1) conductance had a linear response and 2) constant phase elements (CPE) had a saturating response that coincided with the limiting current. We provided a framework using a simple iV relationship that predicted the conductance-current slope to be 9.57 V -1 . CPEs showed more variability across biofilm replicates than conductance values. Although G. sulfurreducens biofilms were used here, other electrochemically active biofilms exhibiting catalytic waves could be studied using the same methods. [ABSTRACT FROM AUTHOR]

A differential impedance analysis method considering constant phase element (CPE) was proposed for cement-based materials. Results indicated that the method is very accurate for the identification circuit of single capacitive loop. For series circuit of double capacitive loops, the method can accurately identify all impedance parameters when ratio ( q ) of the two time constants is large. For series and parallel circuits of double capacitive loops, even when q is close to 1, number of the capacitive loop can be identified accurately. The method can selectively identify the variation, frequency range and frequency dependence of the impedance parameters of cement-based materials; it can also explain why when two capacitive loops exist in a Nyquist plot of cement-based materials, only one can be observed by the naked eye. The method is beneficial for establishing a reasonable equivalent circuit of impedance spectroscopy with a CPE behavior, especially when q is very small. [ABSTRACT FROM AUTHOR]

Complex immittance (Impedance Z, Modulus M, Admittance Y, Permittivity ϵ) spectra for some equivalent circuit models involving resistances, capacitances and constant phase angle elements (CPE) are calculated for different ratios of the parameters. A comparison of experimentally obtained complex immittance plots with these diagrams greatly facilitates the search for the most appropriate equivalent circuit representing the electrical properties of electronic ceramics. An equivalent circuit for Ba1-xSrxTiO3(x = 0.35) ceramic system is developed by using these simulated plots. [ABSTRACT FROM AUTHOR]

A circular-route scanning method called α-β circular scanning is proposed and realized using sinusoidal signals with a constant phase difference of π/2. Experiments show that the circular scanning range of α-β circular scanning is 57% greater than the rectangular scanning range of raster scanning within an effective optical field of view. Moreover, the scanning speed is improved by 7.8% over raster scanning because the whole sine signal is utilized in α-β circular scanning whereas the flyback area of the saw-tooth signal needs to be discarded in raster scanning. The maximum scanning acceleration decreases by a factor of 44, drastically decreasing the high noise, which should considerably elongate the lifetime of the galvanometers while inhibiting internal vibration. The proposed α-β circular scanning technique could be used in scanning imaging, optical tweezers and laser-beam fabrication. [ABSTRACT FROM AUTHOR]

The response of a commercial super‐capacitor to an applied periodic current excitation in the form of a triangular waveform is investigated in this study. This waveform has a linear‐with‐time variation which enables linear charging and discharging of the device. A model consisting of a linear resistance Rs and a constant phase element is used to describe the super‐capacitor impedance and expressions for the voltage across the device, the power, and stored energy are derived using concepts from fractional calculus. Experimental results are shown and an application of the study to super‐capacitor parameter extraction is described. [ABSTRACT FROM AUTHOR]

The coulostatic method has been successfully used in the study of electrode processes. In the literature, the technique is explained on the premise that the step-charge is transferred to an ideal interfacial capacitance. Here, for the first time, we have generalized the coulostatic test method by considering a non-ideal interfacial capacitance modeled by a constant phase element (CPE), which agrees with the relaxation processes observed experimentally. The methodology proposed allows one to determine the parameters of a modified Randles circuit consisting of a resistor in series with the parallel combination of a CPE and another resistor. A set of useful expressions for the transient response to a rectangular current pulse is derived using fractional calculus and circuit theory. In addition, we analyze the width of the pulse required to guarantee an efficient coulostatic approach, that is, the total charge associated with the current pulse is transferred to the CPE. Both the method proposed and the impedance spectroscopy (IS) technique (for comparative purposes) are used to study a two-electrode setup consisting of two platinum (Pt) electrodes in contact with a phosphate-buffered saline (PBS) solution. [ABSTRACT FROM AUTHOR]

Fractional-order capacitors are the core building blocks for implementing fractional-order circuits. Due to the absence of their commercial availability, they can be approximated through appropriately configured passive or active integer-order element topologies. Such a topology, constructed using Operational Transconductance Amplifiers (OTAs) and capacitors has been implemented in monolithic form through the AMS 0.35 μm CMOS process, and the fabricated chips are employed here for the experimental evaluation of the behavior of networks constructed from fractional-order capacitors connected in series or in parallel. [ABSTRACT FROM AUTHOR]

The surface area and fractal dimensions of the surface of loose copper and zinc deposits obtained within 30 and 300 s at direct current sixfold exceeding limiting diffusion current on a smooth electrode were in situ determined by impedance spectroscopy. Impedance measurements were performed in 0.5 M NaSO solution. A constant phase element taking into account the distribution of double-layer capacitance over the fractal surface of the electrode was used in the equivalent impedance scheme. Specific surface calculated with regard to the weight of the released metal slightly varied within 300 s (from 6.16 to 6.55 and from 7.12 to 5.89 m/g for copper and zinc deposits, respectively). Fractal dimensions estimated by chronopotentiometry were given for comparison. Fractal dimensions found by two methods for loose copper and zinc deposits agree with each other; their values (2.19-2.75) testify that the surface of the deposits densely fills the space. [ABSTRACT FROM AUTHOR]

ABSTRACT The seismic industry is increasingly acquiring broadband data in order to reap the benefits of extra low- and high-frequency contents. At the low end, as the sharp low-cut decay gets closer to zero frequency, it becomes harder for a well tie to estimate the low-frequency response correctly. The fundamental difficulty is that well logs are too short to allow accurate estimation of the long-period content of the data. Three distinctive techniques, namely parametric constant phase, frequency-domain least squares with multi-tapering, and Bayesian time domain with broadband priors, are introduced in this paper to provide a robust solution to the wavelet estimation problem for broadband seismic data. Each of these techniques has a different mathematical foundation that would enable one to explore a wide range of solutions that could be used on a case-by-case basis depending on the problem at hand. A case study from the North West Shelf Australia is used to analyse the performance of the proposed techniques. Cross-validation is proposed as a robust quality control measure for evaluating well-tie applications. It is observed that when the seismic data are carefully processed, then the constant phase approach would likely offer a good solution. The frequency-domain method does not assume a constant phase. This flexibility makes it prone to over-fitting when the phase is approximately constant. Broadband priors for the time-domain least-squares method are found to perform well in defining low-frequency side lobes to the wavelet. [ABSTRACT FROM AUTHOR]

We introduce ordered rings and fields following Artin-Schreier's approach using positive cones. We show that such orderings coincide with total order relations and give examples of ordered (and non ordered) rings and fields. In particular we show that polynomial rings can be ordered in (at least) two different ways [8, 5, 4, 9]. This is the continuation of the development of algebraic hierarchy in Mizar [2, 3]. [ABSTRACT FROM AUTHOR]

Electrical impedance based biosensing is a label-free technique that is gaining momentum in biology/medicine. The electrical impedance, typically measured using an array of micro-fabricated interdigitated electrode array (IDE), is a byproduct of the interaction between electric fields and target bio-molecules/cells. In current impedance based biosensing, it has been focused on utilizing the magnitude of the impedance (|Z|) to detect/quantify bio-molecules. There were no reports on designing IDE electrodes, sensitivity analysis and detailed impedance data analysis. To address this issue, we have designed and fabricated IDE array and performed model experiments. We have found that depending on the frequency of the external electric potential, there is a variation of electric field across the array of IDEs from first pair to last pair. We then developed impedance data analysis technique (using (|Z|) and its phase (φ)) to analyze the complex impedance data, and finally, we have utilized Warburg theoretical circuit model to calculate the capacitance and resistance of the individual IDE pairs in the constant phase impedance region. Using the capacitance values, we have developed a procedure to determine the sensitivity of the IDE array. We have found that sensitivity of the IDE array does not depend on the sample conductivity. [ABSTRACT FROM AUTHOR]

Several issues concerning constant-phase element (CPE) behavior in the impedance response of films with a distributed resistivity are addressed here. To carry it out we consider two theoretical distributed models that account for exact CPE behavior and which provided us with the phenomenology of power-law frequency responses usually found in the literature. We focus on the derivation of the relationship between CPE parameters and the physical properties of the film, which remains a challenging problem of paramount importance in impedance data interpretation. Results are compared to existing expressions widely used to extract film properties from CPE behavior, in particular to those derived by Hsu and Mansfeld [1] and by Hirschorn et al. [2]. A mathematical basis for the agreements or deviations observed in previous experimental works as well as for some conjectures formulated in related literature is provided. We also address some possible ambiguities that can arise when the experimental frequency range does not allow the recognition of the overall behavior. [ABSTRACT FROM AUTHOR]

A better characterization of the rich variety of anomalous ionic-electronic mechanisms in organic-inorganic metal halide perovskite solar cells is essential to obtain a stable and physically robust interpretation of the dynamic responses obtained. Therefore, new approaches towards light intensity-induced effects understanding are intensively searched for. Among all the mechanisms whose elucidation is locked and still under live debate, the apparent inductance phenomena stand out, which are visible not only in photovoltaic devices and optoelectronic elements, but also, for instance, in electrochemical and biological systems. Usually, the negative loops in impedance spectra are modeled through ideal elements (negative capacitance or inductance) although the results show systematic deviations (constant-phase-element behavior). In most scenarios, the influence of chemical inductance dispersion is somehow neglected, that is, ideal conditions are mimicked, omitting the practical device operation. Here we reformulate the theory that captures the slow (non-electromagnetic) inductive effects in the current-voltage curves of perovskite solar cells, deciphering the microscale behavior, consisting essentially of defects associated with deep trap states, from macroscale observations and experimental measurements. The audience is potentially huge, since many authors of multidisciplinary backgrounds are genuinely interested in adequately interpreting this behavior of general character. [Display omitted] • The fractional-order chemical inductor • Impedance analysis of dispersive and negative arcs in perovskites • Review of a transversal phenomenon to multitude of disciplines • Generalization of a part of the fast-slow dynamical systems theory • Study of highly stable and efficient devices by using the proposed model [ABSTRACT FROM AUTHOR]

As it results from many research works, the majority of real dynamical objects are fractional-order systems, although in some types of systems the order is very close to integer order. Application of fractional-order models is more adequate for the description and analysis of real dynamical systems than integer-order models, because their total entropy is greater than in integer-order models with the same number of parameters. A great deal of modern methods for investigation, monitoring and control of the dynamical processes in different areas utilize approaches based upon modeling of these processes using not only mathematical models, but also physical models. This paper is devoted to the design and analogue electronic realization of the fractional-order model of a fractional-order system, e.g., of the controlled object and/or controller, whose mathematical model is a fractional-order differential equation. The electronic realization is based on fractional-order differentiator and integrator where operational amplifiers are connected with appropriate impedance, with so called Fractional Order Element or Constant Phase Element. Presented network model approximates quite well the properties of the ideal fractional-order system compared with e.g., domino ladder networks. Along with the mathematical description, circuit diagrams and design procedure, simulation and measured results are also presented.

The paper presents a coaxial-like sensor operating in the 20 Hz–2 MHz frequency range used to determine the electrical properties of selected liquids of low electrical conductivity. Examined materials included low-concentrated aqueous solutions of potassium chloride, sodium chloride and trisodium citrate, which are common food additives. Impedance spectra of the measurement cell filled with particular liquids were obtained and analyzed using the electrical equivalent circuit approach. The values of physical quantities and parameters describing the equivalent circuit components, including a constant phase element, were calculated for each sample. The applied sensor was also calibrated for electrical conductivity measurements up to 8 mS/m. The constant phase element parameters differed among the studied solutions and concentrations. This may provide a basis for a detection method of small amounts of compounds, such as food additives in low-concentrated aqueous solutions. To demonstrate the potential of the presented method, samples of purchased mineral water and a flavored drink containing various additives were tested.