Novel phase distributions for large electronically beam-scanning reflectarrays

In this paper, the hybrid combination of genetic algorithm and particle swarm optimization (GAPSO) is used to optimize the phase distribution (PD) of beam-scanning reflectarray. The GAPSO takes advantage of both conventional algorithms and it could cover their weaknesses. Two novel PDs are proposed in this paper which constant phase elements (CPEs) and ordinary elements (OEs) are two basic kinds of elements used in them. The phases of CPEs are fixed and it is not changed during beam scanning and only OEs’ phase could be adjusted to scan the main beam. In this work GAPSO and two novel PDs are applied to array factor’s PD of a 30 × 30 reflectarray antenna to displace the main beam electronically in the vertical plane from − 40° to 40°. Also, in these two novel PDs, 28.8% of total elements are selected as CPEs. In the first one with only CPEs, the phase of OEs (71.2% of total elements) could adjust, but in the second novel PD with CPEs and phase symmetry plane 35.5% of the total elements’ phase could be changed to scan the beam. Optimization results show that the novel PD and hybrid algorithm have appropriate performance in the electronically beam scanning of reflectarrays.

Novel Phase Distributions for Large Beam- Scanning Reflectarrays

In this paper, the hybrid combination of genetic algorithm and particle swarm optimization (GAPSO) is used to optimize the phase distribution (PD) of beam-scanning reflectarray. The GAPSO takes advantage of both conventional algorithms and it could cover their weaknesses. Two novels PDs are proposed in this paper. Constant phase elements (CPEs) and ordinary elements (OEs) are two basic kinds of elements used in these two novel PDs. The phases of CPEs are fixed and it is not changed during beam scanning and only OEs’ phase could be adjusted to scan the main beam. GAPSO and two novels PDs are applied to array factor PD of a 30*30 reflectarray antenna to displace the main beam electronically in the vertical plane from-40⁰ to 40⁰. In these two novel PDs, 28.8% of total elements are selected as CPEs. In the first one with only CPEs, the phase of OEs (71.2% of total elements) could adjust, but in the second novel PD with CPEs and phase symmetry plane 35.5% of the total elements’ phase could be changed to scan the beam. Optimization results show that the novel PD and hybrid algorithm have appropriate performance in the electronically beam scanning of reflectarrays.

Impedance and modulus studies of Na0.9Ba0.1Nb0.9(Sn0.5Ti0.5)0.1O3 ceramic

Polycrystalline Na[Formula: see text]Ba[Formula: see text]Nb[Formula: see text](Sn[Formula: see text]Ti[Formula: see text]O3is prepared by the solid-state reaction technique. The formation of single-phase material was confirmed by an X-ray diffraction study and it was found to be a tetragonal phase at room temperature. Nyquist plots ([Formula: see text]ˆ2 versus [Formula: see text] show that the conductivity behavior is accurately represented by an equivalent circuit model which consists of a parallel combination of bulk resistance and constant phase elements (CPE). The frequency dependence of the conductivity is interpreted in terms of Jonscher’s law. The conductivity [Formula: see text] follows the Arrhenius relation. The modulus plots can be characterized by the empirical Kohlrausch–Williams–Watts (KWW), [Formula: see text] = exp([Formula: see text]/[Formula: see text] function and the value of the stretched exponent ([Formula: see text] is found to be almost independent of temperature. The near value of activation energies obtained from the analyses of modulus and conductivity data confirms that the transport is through an ion hopping mechanism dominated by the motion of the (O[Formula: see text] ions in the structure of the investigated material.

Complex Impedance, Dielectric Properties and Electrical Conduction Mechanism of LaBa0.5Ag0.5FeMnO6 Double Perovskite Oxides

The double perovskite oxide with formula LaBa0.5Ag0.5FeMnO6 was prepared by the sol-gel method. The structural analysis at room temperature indicated that this sample is single phase and crystallize in the cubic system with the Pm-3m space group. The complex impedance spectroscopy has been measured in the range of temperature, 200–340 K, and frequency, 100 Hz–1MHz, respectively. Dielectric measurements by analysis of the impedance function, Z" as a function of Z' versus frequency curves, were mounted to an equivalent circuit consisting of series of combinations of resistor, capacity and constant phase elements. The study of ac conductivity as a function of frequency has been interpreted using the Joncher's law and determines the activation energy. The modulus analysis was also performed indicating the presence of a relaxation process accompanied by a conduction phenomenon.

Application of Composite Distributed Electrodes in Cardiographic Sensors

Background: An analysis of equivalent circuits used to interpret the impedance of bio-electrode for electrocardiography shows that the best description is achieved using a double-time constant model of the skin-electrode interface. However, for the measurements it is necessary to use equipment with high input impedance, which leads to the loss of information about the real change in the bio-potential. Objective: The aim of the study is to comprehensively investigate and select the equivalent model that are used to interpret the impedance of a composite bioelectrode with distributed parameters. Method: We used theoretical and experimental research methods. Results: It is proposed for measuring bio-potential to use Ag/AgI/Al2O3 electrodes with distributed parameters. Such electrodes are characterized by a higher contact area and their impedance is described in terms of equivalent circuits with constant phase elements (CPE). It was shown that the electrode impedance is well described over a wide frequency range by an equivalent circuit typical for distributed electrodes including two CPE elements. Conclusion: It is experimentally shown that the distributed Ag/AgI/Al2O3 electrode has at least 6 times smaller polarization contribution than a commercial Ag/AgCl cardiographic electrode. It may enable more accurate measurements of bio-potentials providing less pulse shape distortion caused by polarization of electrochemical biosensors.

BENDING DETECTION OF LI-ION POUCH CELLS USING IMPEDANCE SPECTRA

Li-ion batteries are the preferred choice of energy storage in many applications. However, the potential for fire and explosion due to mechanical damage remains a safety concern. Currently, there are no criteria for the extent of the mechanical damage under which the batteries are safe to use. Here, we investigate the effects of bending damage to Li-ion cells on their impedance spectra. After the initial characterization of four Li-ion pouch cells, one of the cells underwent a three-point bending load. We measured the impedance spectra of this cell after each increment of loading. The impedance data of the control group cells were collected at the same intervals as the damaged cell. A distributed equivalent circuit model (dECM) was developed using the data from the electrochemical impedance spectroscopy (EIS) procedure. We observed that several model parameters such as the magnitude of constant phase elements had similar trends in the control cells and the bent cell. However, some model parameters such as resistances in parallel with constant phase elements, and the inductor showed dependency on the extent of the damage. These results suggest the potential for use of such parameters as an indicator of mechanical damage when visual inspection of cells is not possible in a battery pack setup. Future steps include investigation of similar trends for other commercial batteries,chemistries, and form factors to verify the applicability of the current findings in a broader context.

The origin of constant phase element in equivalent circuit of MIS (n) GaAs structures

The Au/Pd/Ti–SiO2-(n) GaAs properties have been analyzed via impedance spectroscopy (IS), as well as DLTS and ICTS, to identify the origin of electron processes responsible for existence of constant phase elements (CPE) in an equivalent circuits of that structure. We showed that CPEs connected in series with resistance represents the electron processes associated with deep levels in GaAs and/or interface states at SiO2-(n) GaAs interface, depending on the value of n of CPE parameter. CPE with n close to 1 characterize the electron processes associated with EL2 deep level, and CPE with n = 0.5–0.65 the complex electron processes associated with EL3 deep level and interface states together. We stated that constant phase elements in equivalent circuits of MIS-GaAs structures with large frequency dispersion of electrical characteristics can be the result of more than one electron process.

Fractional-Order Chaotic Memory with Wideband Constant Phase Elements

This paper provides readers with three partial results that are mutually connected. Firstly, the gallery of the so-called constant phase elements (CPE) dedicated for the wideband applications is presented. CPEs are calculated for 9° (decimal orders) and 10° phase steps including ¼, ½, and ¾ orders, which are the most used mathematical orders between zero and one in practice. For each phase shift, all necessary numerical values to design fully passive RC ladder two-terminal circuits are provided. Individual CPEs are easily distinguishable because of a very high accuracy; maximal phase error is less than 1.5° in wide frequency range beginning with 3 Hz and ending with 1 MHz. Secondly, dynamics of ternary memory composed by a series connection of two resonant tunneling diodes is investigated and, consequently, a robust chaotic behavior is discovered and reported. Finally, CPEs are directly used for realization of fractional-order (FO) ternary memory as lumped chaotic oscillator. Existence of structurally stable strange attractors for different orders is proved, both by numerical analyzed and experimental measurement.

Mathematical Model of Self-Discharge for Supercapacitors

Self-discharge is one of the most important considerations in manufacturing supercapacitors. This paper discussed two dynamic mathematical models of self-discharge behavior of supercapacitor from the concept of regular capacitor mechanisms and impedance of an R-C circuit, and constant phase elements (CPE), impedance of R-CPE, and fractional- order derivatives. The mathematical model was derived from each other to show their equality and relationships.