Hysteresis Research Articles

Using acetic acid as a preconditioner to optimize rheology of alkali-activated coal gasification slag based backfill pastes

The workability of alkali-activated coal gasification slag (CGS) based backfill materials is critical parameter in transportation processes, while the high water demand of CGS hinders its application due to its high specific surface area. This study utilizes acetic acid (AA) as a preconditioner to modify the surface characteristics of CGS, aiming to optimize the rheology of alkali-activated CGS backfill pastes (AAC). The shear stress, viscosity, thixotropic property, and zeta potential of AAC, and mineral composition and surface morphology of AA-modified CGS at various AA dosages were systematically investigated. It is found that the yield stress, plastic viscosity, and hysteresis loop area of AAC reaches the lowest value at 4 wt% AA dosage on the basis of the CGS, owing to AA reacts with the minerals on the surface of CGS particles, and then the AA is adsorbed on the CGS particles and acts as a surfactant, which increases the static electricity between CGS particles. However, the yield stress of AAC increases significantly when the AA dosage exceeds 4 wt%, attributing to the smaller particle size resulting from AA modification, which raises water demand. This investigation proposes a novel approach for optimizing the rheology of CGS based AAC and provides theoretical guidance for employing modified CGS as backfill materials.

Experimental Study on Water and Salt Migration and the Aggregate Insulating Effect in Coarse-Grained Saline Soil Subgrade under Freeze–Thaw Cycles

Understanding multiphase transformations and the migration of heat, water, vapor, and salt in coarse-grained saline soil under groundwater recharge and environmental freeze—thaw cycles is crucial for ensuring the stability of highway infrastructures. To clarify the water, heat, vapor, and salt migration patterns in coarse-grained saline soil, as well as the salt-insulating effect of the aggregate insulating layer, an experimental study was conducted in a soil column model under pressureless water replenishment with fluorescein-labeled liquid water under freeze—thaw cycles. The results showed that the temperature in the saline soil columns periodically changed and that hysteresis effects occurred during temperature transfer. External water replenishment and the content of liquid water inside the soil exhibited nonlinear changes with environmental temperatures. After multiple freeze—thaw cycles, two water and salt accumulation zones formed within the coarse-grained saline soil subgrade. The migration of liquid water resulted in a water and salt accumulation zone in the nonfrozen zone, whereas the migration of water vapor yielded a water and salt accumulation zone in the frozen zone. To prevent water and salt migration, a 20 cm thick gravel insulating layer could be laid at a distance of 10 cm from the bottom of the roadbed, which could provide a satisfactory salt-insulating effect. The research results provide a theoretical basis and guidance for regulating the stability of subgrades in saline soil areas.

Wind Tunnel Tests of a Two-Element Wingsail with Focus on Near-Stall Aerodynamics

_ Modern wind propulsion systems on ocean-going cargo vessels require automated trimming. Rigid wingsail designs often incorporate more than one degree of freedom enabling to trim for optimal performance in all sailing conditions. A profound understanding of the aerodynamic behavior is the basis for any trimming strategy. The region around stall is of particular importance as this is where the largest lift but also potential hysteresis effects are expected. In the present research, a two-element wingsail (main wing and flap) was tested in wind tunnel experiments investigating the two available degrees of freedom: the orientation of the main wing to the inflow and the deflection of the flap. Aerodynamic loads were measured in dynamic actuation sequences over both degrees of freedom capturing stall and reattachment. The consistent data reveals two stall stages. In the region between the first and the second stall, when changing the direction of rotation, the flow is found to be reversible. The hysteresis loop is in this case smaller and reattachment occurs at larger angles compared to when both stall stages occur. This smaller hysteresis loop could be exploited in trimming. The second stall stage, however, is identified as detrimental both in the forces and the amount of required actuation to allow the flow to reattach. A considerate flap trim, i.e. the adjustment of the wingsail curvature, is suggested to avoid the second stall. Keywords Wind propulsion; Wind tunnel tests; Stall hysteresis; Two-element wing; Rigid wingsail; Trimming; Automation

Coexistence of ferroelectricity and antiferroelectricity in 2D van der Waals multiferroic

Multiferroic materials have been intensively pursued to achieve the mutual control of electric and magnetic properties. The breakthrough progress in 2D magnets and ferroelectrics encourages the exploration of low-dimensional multiferroics, which holds the promise of understanding inscrutable magnetoelectric coupling and inventing advanced spintronic devices. However, confirming ferroelectricity with optical techniques is challenging in 2D materials, particularly in conjunction with antiferromagnetic orders in single- and few-layer multiferroics. Here, we report the discovery of 2D vdW multiferroic with out-of-plane ferroelectric polarization in trilayer NiI2 device, as revealed by scanning reflective magnetic circular dichroism microscopy and ferroelectric hysteresis loops. The evolution between ferroelectric and antiferroelectric phases has been unambiguously observed. Moreover, the magnetoelectric interaction is directly probed by magnetic control of the multiferroic domain switching. This work opens up opportunities for exploring multiferroic orders and multiferroic physics at the limit of single or few atomic layers, and for creating advanced magnetoelectronic devices.

On the excess loss in FeSiAl soft magnetic composites

Aiming at the issue of inconsistent theoretical expression of excess loss in soft magnetic composites, the irrational linear frequency dependence of excess loss W ex is analyzed. By comparing and analyzing the experimental data of magnetic loss of FeSiAl core under different transverse magnetic fields with the theoretical results, it is determined that the excess loss of FeSiAl composite is proportional to the 1/2th power of the frequency. Meanwhile, it is experimentally discovered that there is a positive correlation between the hysteresis loss and the excess loss of FeSiAl magnetic core, which might provide an effective approach to reduce the excess loss of FeSiAl magnetic core.

Modelling the effect of excitation frequency on the shape of hysteresis loop in permalloy

Modelling the effect of excitation frequency on the shape of hysteresis loop in permalloy

Optimal Design and Analysis of High-Frequency Isolation Transformer for Switched-Mode Power Converters

High-frequency (HF) transformers have gained great interest in recent years due to the advent of powerful soft magnetic materials with low core loss in semiconductor power switches. Also, the optimal design of the HF transformer is a significant issue for high-performance energy conversion systems. In this paper, a 40W 50/12.5/25 V universal input and two output discontinuous-conduction mode (DCM) flyback transformer is designed by using mathematical calculations and analyzed via 3D ANSYS/Maxwell simulation including electromagnetic and loss analysis. It is shown that the simulation results accounting for hysteresis losses, eddy current losses, copper losses, and magnetic flux density determine the accuracy of the mathematical model calculation. Analyzes are performed at 100 kHz frequency levels. Results obtained will include core magnetic flux density, core/copper losses, leakage/magnetizing inductances, windings parasitic capacitances, input/output voltage, current values, and all design parameters. Finally, the proposed HF transformer's overall efficiency is calculated and presented. Significantly, the HF transformer achieves 97.8% efficiency thanks to the transformer's core and coil selection, B-H and B-P characteristics, one-to-one dimension design, and mesh operation. The dynamic and mathematical results of the designed transformer demonstrate the design and efficiency success

Nonlinear Modeling of a Piezoelectric Actuator-Driven High-Speed Atomic Force Microscope Scanner Using a Variant DenseNet-Type Neural Network

Piezoelectric actuators (PEAs) are extensively used for scanning and positioning in scanning probe microscopy (SPM) due to their high precision, simple construction, and fast response. However, there are significant challenges for instrument designers due to their nonlinear properties. Nonlinear properties make precise and accurate control difficult in cases where position feedback sensors cannot be employed. However, the performance of PEA-driven scanners can be significantly improved without position feedback sensors if an accurate mathematical model with low computational costs is applied to reduce hysteresis and other nonlinear effects. Various methods have been proposed for modeling PEAs, but most of them have limitations in terms of their accuracy and computational efficiencies. In this research, we propose a variant DenseNet-type neural network (NN) model for modeling PEAs in an AFM scanner where position feedback sensors are not available. To improve the performance of this model, the mapping of the forward and backward directions is carried out separately. The experimental results successfully demonstrate the efficacy of the proposed model by reducing the relative root-mean-square (RMS) error to less than 0.1%.

STUDY OF THE STRUCTURAL AND ELECTROMAGNETIC CHARACTERISTICS OF FERROMAGNETIC-DIAMAGNETIC COMPOSITES OBTAINED BY THE METHOD OF MODIFIED CHEMICAL CO PRECIPITATION

The microwave electromagnetic properties of ferromagnetic-paramagnetic and ferromagnetic-diamagnetic composites can be changed by varying the concentration of diamagnetic (paramagnetic) and ferromagnetic components. To implement the task of introducing such composites into production, research is required to find effective and simple synthesis technologies that make it possible to vary the content of components with different magnetic characteristics. This work demonstrates a simple method for the synthesis of ferromagnetic ((NiZn)Fe2 O4 )- diamagnetic (ZnO) composites by modified chemical deposition followed by annealing. Also, a comprehensive study of the structural and electromagnetic characteristics of experimental samples was carried out. Using the powder X-ray diffraction method, it was revealed that the phase composition of the final samples is represented exclusively by diamagnetic and ferromagnetic phases. Using scanning electron microscopy, it was found that after thermal annealing the powders have submicron sizes with an average size of 100–137 nm. Using vibration magnetometry, magnetic hysteresis loops were measured, the analysis of which showed that an increase in the concentration of the diamagnetic phase leads to an increase in the coercive force of the composites. The measured microwave spectra of complex magnetic permeability show that by changing the ratio between the ferromagnetic and paramagnetic phases, it is possible to realize a frequency shift of natural ferromagnetic resonance. Also, through the calculation of the reflection coefficient on a metal plate, it is shown that the resulting composites can be used as the basis for new radio-absorbing materials. In addition, the synthesized powders can also be used to create microwave devices and microwave antennas.

Non-exchange bias hysteresis loop shifts in dense composites of soft-hard magnetic nanoparticles: New possibilities for simple reference layers in magnetic devices

Exchange bias has been extensively studied in both exchange-coupled thin films and nanoparticle composite systems. However, the role of non-exchange mechanisms in the overall hysteresis loop bias is far from being understood. Here, dense soft-hard binary nanoparticle composites are used not only as a novel tool to unravel the effect of dipolar interactions on the hysteresis loop shift but also as a new strategy to enhance the bias of any magnet exhibiting an asymmetric magnetization reversal. Mixtures of equally sized, 6.8 nm, soft maghemite (γ-Fe2O3) nanoparticles (no bias—symmetric reversal) and hard cobalt doped γ-Fe2O3 nanoparticles (large exchange bias—asymmetric reversal) reveal that, for certain fractions of soft particles, the loop shift of the composite can be significantly larger than the exchange-bias field of the hard particles in the mixture. Simple calculations indicate how this emerging phenomenon can be further enhanced by optimizing the parameters of the hard particles (coercivity and loop asymmetry). In addition, the existence of a dipolar-induced loop shift (“dipolar bias”) is demonstrated both experimentally and theoretically, where, for example, a bias is induced in the initially unbiased γ-Fe2O3 nanoparticles due to the dipolar interaction with the exchange-biased hard nanoparticles. These results open a new paradigm in the large field of hysteresis bias and pave the way for novel approaches to tune loop shifts in magnetic hybrid systems beyond interface exchange coupling.

The Influence of Filler Particle Size on the Strength Properties and Mechanical Energy Dissipation Capacity of Biopoly(Ethylene Terephthalate) BioPET/Eggshell Biocomposites

This work aims to evaluate how the particle size of a waste filler in the form of eggshells changes the mechanical properties of biopoly(ethylene terephthalate) (bioPET). BioPET was modified with three different waste fractions: 1.60–3 mm—large particles; 1.60–1 mm—medium particles; 1 mm–200 μm—small particles. Waste filler was added to the biopolymer matrix in the amount of 10 wt.%. Static tensile tests, as well as bending and impact tests, were carried out to assess the strength properties of the waste-enriched materials. Dissipation energy changes and relaxation processes were observed and evaluated by means of a low-cycle dynamic test. Waste particles were shown to be an effective modifier of bioPET by increasing its stiffness (all particle sizes) and strength (the smallest ones). Studies of the wetting angle and mechanical energy dissipation in the first hysteresis loops indicate the better adhesion of small particles to the biopolymer and their greater ability to dissipate mechanical energy.

Perpendicular magnetic anisotropy and Gilbert damping of MgO/Co100–x Fe x /Pt trilayers

Perpendicular magnetic anisotropy and Gilbert damping of MgO/Co100–x Fe x /Pt (x = 20, 50) trilayers before and after annealing at 200–400 °C were evaluated by hysteresis loop and time-resolved magneto-optical Kerr effect (TRMOKE) measurements. The anisotropy field of the trilayers increased with reducing the CoFe thickness, which reflects the anisotropy is originated from the interface. The annealing around 300 °C was effective to increase the anisotropy because the roughness of the MgO/CoFe interface was reduced by annealing. The effective Gilbert damping α eff also increased with reducing CoFe thickness and increasing annealing temperature. The increase of α eff was considered to be promoted by the interdiffusion between CoFe and Pt after annealing. Small α eff and large perpendicular anisotropy were confirmed to be obtained using Co50Fe50 compared to using Co80Fe20.

Analysis of Structural, Optical, Morphological and Magnetic Behaviour of Lead Nanoferrite by Two Different Methods

Sol gel and the hydrothermal approach are two distinct techniques that have been successfully used to synthesise lead nanoferrite (PbFe2O4). To determine which of the two approaches is superior, the features of the sample prepared by each have been examined. Vibration Sample Magnetometer (VSM), Fourier Transform Infrared Spectroscopy, UV-VIS Spectral investigations, Scanning Electron Microscopy (SEM), X-Ray Diffraction, and Size, Band Gap Energies, Morphology, and Magnetic Properties of Nanostructures were used to determine and compare its various aspects. The mean diameters of the synthesised lead ferrite nanocrystalline were found to be 33 nm for the sol gel method and 20 nm for the hydrothermal method, respectively, based on X-Ray Diffraction analysis using Debye-Scherer’s formula with the peak. FTIR spectra are used to analyse the vibration characteristics of nanomaterials. The optical characteristics of the synthesised nanomaterials, such as their Energy Band Gap, were determined using UV-VIS Spectral investigations. SEM is used for surface morphological investigations, allowing the structure of the synthesised nanomaterials to be studied. Using VSM, the magnetisation of the produced nanomaterials was examined, and the hysteresis loops were used to calculate the saturation magnetisation (Ms), coercivity (Hc), and retainivity (Mr).

Interactions between soil and other environmental variables modulate forest expansion and ecotone dynamics in humid savannas of Central Africa.

Forest expansion into savanna is a pervasive phenomenon in West and Central Africa, warranting comparative studies under diverse environmental conditions. We collected vegetation data from the woody and grassy components within 73 plots of 0.16 ha distributed along a successional gradient from humid savanna to forest in Central Africa. We associated spatially collocated edaphic parameters and fire frequency derived from remote sensing to investigate their combined influence on the vegetation. Soil texture was more influential in shaping savanna structure and species distribution than soil fertility, with clay-rich soils promoting higher grass productivity and fire frequency. Savanna featuring woody aboveground biomass surpassing 40 Mg ha-1 could escape the grass-fire feedback loop, by depressing grass biomass below 4 Mg ha-1. This thicker woody layer also favoured the establishment of fire-tolerant forest pioneers, which synergically contributed to the expansion of forests. Conversely, savannas below this fire suppression threshold sustained a balance between trees and grasses through the grass-fire feedback mechanism. This hysteresis loop, particularly pronounced on clayey soils, suggests that the contrast between grassy savanna and young forests might represent alternative ecosystem states, although savannas with low woody biomass remained vulnerable to forest edge encroachment.

Iron wool as a heating agent for magnetic catalysis: Experiments and analysis of heating properties under a high-frequency magnetic field

Magnetically induced heterogeneous catalysis has been attracting attention due to its high energy efficiency and flexibility for dynamic reactor control. Iron wool is a commercial, low-cost, and versatile heating agent, which has been used in several magnetic catalysis studies, but its heating properties have never been investigated. Here, the properties of three types of Fe wool were studied using optical and electronic microscopy, x-ray diffraction, and measurements of both heating power and high-frequency hysteresis loops. The effects of strand width, packing, and magnetic field amplitude and frequency were studied. A maximum specific absorption rate (SAR) around 700 W/g under a rms field of 47.4 mT at 93 kHz was measured for the larger width Fe wool. High-frequency hysteresis loops were used to quantify the contribution of hysteresis losses and eddy currents to total heating. Eddy currents contribute 65%–90% to the global heating depending on the strand width. Coating the wool with SiO2 and Ni has negative effects on the SAR but none on hysteresis losses. It is interpreted as originating from the cut-off of inter-wire eddy currents due to the insulating (SiO2, oxidized Ni) nature of the coating. Last, it was found that adding more Fe wool in a given volume mostly decreases the SAR. This effect could be not only due to the absorption and/or screening of the field by surface strands but also due to magnetic interactions. The results described in this work give insights into the magnetic heating of microscale magnetic materials and optimize their use for heterogeneous catalysis.

Elucidating the hysteresis effect in printed flexible perovskite solar cells with SnO2 quantum dot- and PCBM-based electron transport layers

Recently, flexible perovskite solar cells (FPSCs) fabricated using solution-processed printing techniques have garnered significant attention. However, challenges remain in achieving cost-effective, scalable manufacturing under ambient conditions and ensuring stable, efficient devices. This study focuses on fabricating printed FPSCs using the slot-die coating technique and examines the impact of SnO2 quantum dot (QD) and (6,6)-Phenyl C61 butyric acid methyl ester (PCBM) based electron transport layers (ETLs) on device performance and hysteresis. Experimentally results show that SnO2 QD-based devices exhibited favorable photovoltaic properties but significant hysteresis compared to PCBM-based devices. Numerical simulations have shown that the hysteresis effect in devices is influenced not only by the higher concentration of mobile ions in the perovskite layer of PCBM-based devices compared to SnO2 QD-based devices, but also by the more effective redistribution of these ions during forward and reverse J-V scans. The results provide insights into the behavior of printed FPSCs with different ETLs, contributing to the development of high-performance, hysteresis-free printed FPSCs.

Swirl-induced hysteresis in a sudden expansion flow

Swirling sudden expansion flows are complex flow fields containing several coherent structures that depend on the swirl number and can exhibit hysteresis behavior between increasing and subsequently decreasing swirl levels. While these flows have extensively been studied in simple geometries, results involving special designed nozzles are scarce. Therefore, this paper aims to provide insights into a more complex geometry, specifically a two-step conical expansion with a converging outlet. Experimental data is acquired for changing swirl numbers at a Reynolds number in the range of 35, 000. Stereoscopic Particle Image Velocimetry is employed to characterize downstream flow structures, while Laser Doppler Velocimetry is used to characterize upstream structures and to determine the inlet swirl number. Several distinct flow patterns are found as a function of the swirl number and the identified flow patterns include, in order of increasing swirl, a Closed Jet Flow, an Open Jet Flow (OJF), and a Coandã Jet Flow (CoJF). A central positive axial velocity is noted for both OJF and CoJF downstream of the expansion due to the converging outlet geometry. At higher swirl numbers, Vortex Breakdown moves upstream into the nozzle until a negative axial velocity is noted in the inlet tube. For these higher swirl numbers, no hysteresis is observed in the inlet tube between increasing and subsequently decreasing swirl. However, downstream of the nozzle, it is observed that the CoJF detaches at a lower swirl number than the swirl number required for attachment, indicating a hysteresis effect between in- and decreasing swirl.

A nonlinear hysteresis compensation control of hydro-viscous drive in air transport operations

The Hydro-Viscous Drive (HVD) speed regulating system finds extensive application in air transport transmission systems to regulate the stepless speed or conduct overload protection. However, its intrinsic hysteretic behaviors, such as the asymmetric hysteretic and dead zone, could introduce inaccuracy and delay in control applications, posing challenges to system regulation. This paper investigates a Nonlinear Hysteresis Compensation Control (NHCC) that consists of two parts to control the HVD output speed by operating the valve under different engine operating conditions. In the first part, the Inverse Hysteresis Compensator (IHC) based on major loop data is introduced for the asymmetric hysteresis characterization and compensation of the HVD speed control system of the power generation and distribution, which aims to reduce the hysteresis and dead zone effect and expand the effective input range. In the second part, the Active Disturbance Rejection Controller (ADRC) is employed to mitigate the hysteresis effects of the compensated system and remove the steady-state error, which allows real-time compensation of the estimated perturbations as state feedback to achieve the required performance. An experimental laboratory station has been fabricated to evaluate the proposed method. The test results show that the NHCC method can regulate the fan speed to the desired value (|e|< 45 r/min at steady state) and broaden the effective input range to the full range under different engine conditions. Besides, the proposed control method can reduce the non-linearity of the input and output curves (from 18% to 4%) and compensate for the asymmetric hysteresis (from 38% to 5%).

Rapid and Accurate Calculation of PWM-Induced Harmonic Currents in IPMSMs Considering Hysteresis and Eddy Current Reaction Effects

Rapid and Accurate Calculation of PWM-Induced Harmonic Currents in IPMSMs Considering Hysteresis and Eddy Current Reaction Effects

Comprehensive magnetic properties of grain-oriented silicon steel sheet considering anisotropy under mechanical stress

The cores of transformers and reactors are subjected to mechanical stresses during both manufacturing and operation, these stresses exert an influence on the magnetic properties of the cores. Additionally, there exists rotating magnetic flux within the cores during operation. Therefore, it is necessary to further consider the magnetic properties of grain-oriented silicon steel sheet in the direction perpendicular to the rolling direction. To delve deeply into the comprehensive magnetic properties of grain-oriented silicon steel sheet under mechanical stress, with a particular focus on both the rolling direction and the direction perpendicular to it, this paper presents the establishment of a comprehensive magnetic properties measurement platform for grain-oriented silicon steel sheet that possesses stress adjustment capabilities. Through meticulous measurements, the impacts of tensile and compressive stresses on the magnetic hysteresis loops, B-H curves, relative permeability, magnetostriction, and iron loss characteristics of grain-oriented silicon steel sheet in both the rolling direction and the perpendicular direction were obtained and analyzed. The measurement results and subsequent analysis indicate that tensile and compressive stresses exert an influence on the magnetization characteristics of grain-oriented silicon steel sheet. Moreover, the extent of this influence varies between the rolling direction and the direction perpendicular to rolling for both tensile and compressive stresses; In the rolling direction, compressive stress promotes the magnetostriction of the grain-oriented silicon steels, while tensile stress inhibits it. In the direction perpendicular to rolling, both tensile and compressive stresses inhibit the magnetostriction of the grain-oriented silicon steels, with tensile stress exerting a greater inhibitory effect; Tensile stress acts to reduce the iron loss of grain-oriented silicon steels, whereas compressive stress increases it, this pattern is consistently observed in both the rolling direction and the direction perpendicular to rolling.