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In this paper, a S-type memristor with tangent nonlinearity is proposed. The introduced memristor can generate two kinds of stable pinched hysteresis loops with initial conditions from two flanks of the initial critical point. The power-off plot verifies that the memristor is nonvolatile, and the DC V - I plot shows that the memristor is locally active with the locally active region symmetrical about the origin. The equivalent circuit of the memristor, derived by small-signal analysis method, is used to study the dynamics near the operating point in the locally active region. Owing to the bistable and locally active properties and S-type DC V - I curve, this memristor is called S-type BLAM for short. Then, a new Wien-bridge oscillator circuit is designed by substituting one of its resistances with S-type BLAM. It finds that the circuit system can produce chaotic oscillation and complex dynamic behavior, which is further confirmed by analog circuit experiment.

The exchange bias (EB) is an effect occurring in coupled ferromagnetic/antiferromagnetic materials of diverse shapes, from core–shell nanoparticles to stacked nanostructures and thin films. The interface coupling typically results in a horizontal—often also vertical—shift of the hysteresis loop, combined with an increased coercivity, as compared to the pure ferromagnet, and the possibility of asymmetric hysteresis loops. Several models have been developed since its discovery in 1956 which still have some drawbacks and some unexplained points, while exchange bias systems are at the same time being used in hard drive read heads and are part of highly important elements for spintronics applications. Here, we give an update of new theoretical models and experimental findings regarding exchange bias phenomena in thin films during the last years, including new material combinations in which an exchange bias was found.

We introduce a novel methodological advancement by clustering paired near-surface air temperature with the planetary boundary layer height to characterize intra-city clusters for analytics. To illustrate this approach, we analyze three heatwaves (HWs): the 2019 HW in Paris, the 2018 HW in Montreal, and the 2017 HW in Zurich. We assess cluster-based characteristics before, during, and after heatwave events. While the urban clusters identified by this clustering align well with built-up areas obtained from the Moderate Resolution Imaging Spectroradiometer (MODIS) land cover data, additional local hot spots spanning several kilometers can also be recognized, extending outside the built-up areas. Using the objective hysteresis model, we further determine the overall strength coefficient of the hysteresis loop between ground storage flux and all-wave downward radiative flux, ranging from 0.414 to 0.457 for urban clusters and from 0.126 to 0.157 for rural clusters during the heatwave periods. Across all cities, we observe a consistent refueling-restoration mode in the cumulative ground heat flux as the heatwaves progress. Future developments of this proposed two-component clustering approach, with the integration of more influential physics and advances in spatial and temporal resolutions, will offer a more comprehensive characterization of cities for urban climate analytics.

Various experimental methods are used to examine the effect of cooling rate on the magnetic properties of magnetic materials, such as melt spinning at different wheel speeds. To shed light on these experimental studies as a theoretical study, we used a mixed spin (1, 3/2) Ising system on a square lattice under an oscillating magnetic field within the path probability method. It is very advantageous to use the path probability method in such studies, because it explains the dynamic magnetic phase behaviors and dynamic hysteresis curves of the system depending on all system parameters, and one of the coupling parameters ( k 2 ) arising in this method corresponds to the wheel speed (rate constant) in the melt spinning method. In this study, dynamic hysteresis curves of a magnetic material were obtained for different k 2 parameters as well as other system parameters, namely reduced temperature, crystal field interaction, and angular frequency. In some magnetic materials, hard and soft magnetic hysteresis loop behaviors and single and multiple hysteresis loop behaviors have been obtained, which have been reported theoretically as well as experimentally. The results shed light on experimental workers who were unable to reach higher wheel speeds using the melt-spinning method.

In this paper, we studied the spin-3/2 Ising model of diluted graphene-like monolayer under a non-equilibrium state by using Monte Carlo (MC) simulation. We conducted a comprehensive analysis of the temperature-dependent magnetization curves, susceptibility, critical temperature, and hysteresis loops taking into account various factors such as the anisotropy, exchange coupling, external magnetic field, and shell atom concentration. We also compared our findings to various existing theoretical works and obtained a strong quantitative alignment with certain theoretical predictions and experimental outcomes.

A transparent composite sample containing BaTiO 3 was synthesized by using the melting quenching method. The presence of a glassy phase in this composite sample was detected through XRD analysis, and this was further confirmed by DSC study. TEM and SAED analyses provided evidence that the BaTiO 3 nanoparticles/clusters are embedded within the borate glass matrix, establishing the composite nature of this sample. FTIR spectrum of the present sample revealed that the glass matrix is composed of two structural groups (BO 3 with NBO’s, and BO 4 ), along with the distinct groups for BaTiO 3 . XPS spectra of the present composite sample indicated the presence of more than one type of boron, barium, titanium and oxygen. DSC and dielectric studies of the present composite sample revealed the presence of the phase transition temperature (T c ). Dielectric constant (ɛ r ) and dielectric loss (tan δ) curves of the present composite sample displayed an anomaly peak in the vicinity of T C . The optical transmission spectrum of the present composite sample exhibit two transmission bands of Ti 3+ (3d 1 ) ions in tetragonal distorted sites. At room temperature, the present transparent composite sample exhibited double hysteresis loops for BaTiO 3 at low electric fields. The results obtained can be used for the development of lead-free ferroelectric material.

Many studies have proved that the fractional-order system is more accurate than the integer-order system. The theory of fractional calculus has received extensive attention in many fields. The research on flux-controlled memristor has been carried out for several years; however, fractional-order flux-controlled memristor has not received widespread attention. In light of the theory of fractional calculus, a generalized fractional-order dynamic model of flux-controlled memristor is proposed for the first time in this paper. The mathematical model is established and its characteristics of the pinched hysteresis loops are analyzed by changing the order and the frequency. The specific computational formulas of areas of pinched hysteresis loops are given. The equivalent circuit of the fractional-order flux-controlled memristor is constructed, and circuit simulations are given to illustrate the effectiveness of theoretical analysis and numerical calculation. In this study, the flux-controlled memristor model is extended to the fractional-order model that is closer to the real device, and the analysis method of areas of pinched hysteresis loops is further expanded.

Influence of Gd substitution on the structural, microstructure, dielectric, elastic and magnetic properties of Mg–Cu–Zn ferrites with the compositions Mg 0.3 Cu 0.2 Zn 0.4 Gd x Fe 2.1 - x O 4 (where x = 0.0, 0.01, 0.02 and 0.04) have been reported in this study. The structural property has been performed with an X-ray diffraction technique. It shows a single-phase cubic spinel structure for x ≤ 0.01, while a small peak of GdFeO 3 is seen with the spinel structure for x > 0.01. The surface morphology study indicates that the grain growth of Mg–Cu–Zn ferrites depends on the Gd content. It reveals that the average grain size is found to be larger for x = 0.01, which could be attributed to the densification of the sample. The magnetic hysteresis loop has been investigated for all the prepared samples. It shows that the saturation magnetization is found to be larger for x = 0.01, which is also correlated to the grain size. The dielectric constant of the prepared samples has been studied at 300 K as a function of frequency. An enhancement of the dielectric constant is observed for Gd-substituted Mg–Cu–Zn ferrites. The Cole–Cole plots have displayed a single semicircular arc, which indicates that the conduction mechanism occurred through a grain effect. The elastic constants such as bulk modulus, Young’s modulus, rigidity modulus and Poisson’s ratio have been calculated for all the studied samples. It reveals that all the synthesized samples are in ductile nature. It is expected that Gd substituted Mg–Cu–Zn ferrites with the composition Mg 0.3 Cu 0.2 Zn 0.4 Gd 0.01 Fe 2.09 O 4 is a potential material for high-frequency operation.

Exchange bias (EB) is a unidirectional anisotropy occurring in exchange-coupled ferromagnetic/antiferromagnetic systems, such as thin films, core–shell particles, or nanostructures. In addition to a horizontal shift of the hysteresis loop, defining the exchange bias, asymmetric loops and even vertical shifts can often be found. While the effect is used in hard disk read heads and several spintronics applications, its origin is still not fully understood. Especially in nanostructures with their additional shape anisotropies, interesting and often unexpected effects can occur. Here, we provide an overview of the most recent experimental findings and theoretical models of exchange bias in nanostructures from different materials.

Kapok is a natural fiber with an extremely high degree of hollowness. Numerous pores in its cell wall form the pathways for gas molecules. The delamination of the cell wall in scanning electron microscopy images and the hysteresis loop in nitrogen adsorption–desorption isotherms are interpreted to indicate that the kapok fiber has slit-shaped pores. Nitrogen adsorption method based on Brunauer–Emmett–Teller theory was used to analyze the mesopore. The specific surface area of kapok fiber is evaluated as 2.99 m 2 /g in the relative pressure range (0.05–0.35). The pore size of the fiber is distributed in 4–40 nm and mainly concentrated on 3–4 nm. The volume of the pores with diameters of 2–40 nm accounted for about 80% of the total pore volume, and those with diameters over 40 nm accounted for about 20%. By the V a  ~  α s micropore evaluating method, it is found that the micropore volume of the fiber is about 7.0399×10 −11  ml/g.