Hysteresis Research Articles

Effects of cavitation number and pitching frequency on hysteresis characteristics of a pitching hydrofoil

In this study, the effect of cavitation number σ and pitching frequency f* on hysteresis characteristics of a pitching hydrofoil, has been investigated. The angle of attack α changed from 5° to 15°, then from 15° to 5° at each pitching period. A pitching 2D(Two-dimensional) Clark-y hydrofoil is analyzed with high-speed video recording for the cavitation pattern. The hysteresis phenomenon is observed in increasing and decreasing of α, and the hysteresis effects changed with σ and f*. The cavitating flow around the pitching hydrofoil during different conditions are simulated by revised k-ω SST(Shear Stress Transfer) turbulence model and Merkle cavitation model. The calculation results of hysteresis characteristic parameters showed that the decrease of σ leads to the increase of hysteresis effect. As σ decreased, the evolution of cavity vortex is more complex. Especially in the downstroke, there are complex phenomena such as vortex decomposition and merging, which leads to the intensification of hydrodynamic hysteresis effect. There is a nonlinear relationship between the hysteresis characteristic parameters and f*. As f* increases, its influence on the cavitation flow in the downstroke becomes more and more serious. Besides, the evolution form of cavitation vortices also changes, which leads to the change of hysteresis characteristics.

Influence of Rotation on Magnetic Properties of Thin Film

Monte Carlo simulation based on the Metropolis algorithm is used to investigate the thermal and magnetic properties of the mixed spin-1/2 and spin-1 Ising model on a double-layer thin film one fixed. The upper layer rotates around the z-axis using the rotation matrix under the influence of different parameters such as the rotational angle, reduced exchange coupling constant, reduced anisotropy constant, and the applied external magnetic field. This study concentrated on examining the interactions between next-neighbor atoms, employing free boundary conditions. The critical and compensation behavior has been investigated by studying phase diagrams, and magnetic and thermodynamic properties such as magnetization, susceptibility, and specific heat. The system showed diverse types of Neel behaviors such as the N-, Q-, and P-type. Moreover, the hysteresis loops of the system have been examined for different values of the exchange interaction constant, temperature, crystal field, and the rotational angle. Finally, the system showed single and triple hysteresis loop behaviors and superparamagnetic behavior.

Synthesis, characterization, magnetic and morphological properties of poly(m-phenylenediamine)/ZnCoFe2O4 nanocomposites

In this work, poly(m-phenylenediamine) (PmPD)/ZnCoFe2O4 nanocomposites (NCs) were synthesised by in-situ chemical oxidative polymerisation method. The ZnCoFe2O4 nanoparticles (NPs) were prepared by auto-combustion method. The crystalline size of PmPD/ZnCoFe2O4 NCs and ZnCoFe2O4 NPs were calculated using the Powder X-ray diffraction (XRD) analysis. The functional group of the samples was analysed by Fourier transform infrared spectral (FTIR) analysis. The XRD and FTIR results were clearly indicated that the formation of ZnCoFe2O4 NPs and PmPD/ZnCoFe2O4 NCs. The spherical morphology of the PmPD/ZnCoFe2O4 NCs was confirmed through Field emission electron microscopy (FE-SEM). The magnetic hysteresis (M-H) loops of ZnCoFe2O4 NPs and PmPD/ZnCoFe2O4 NCs were revealed their ferromagnetic behaviour. Thermogravimetric analysis (TGA) was indicated that thermal stability of PmPD/ZnCoFe2O4 NCs and increases with increase in concentration of ZnCoFe2O4 NPs. The dielectric properties of PmPD/ZnCoFe2O4 NCs were also examined with different frequency.

Dynamic stall control of an offshore wind turbine airfoil using a leading-edge microcylinder

This study conducted a computational investigation to examine the impact of passive flow control using a microcylinder positioned near the leading edge of a dynamically stalled NACA0012 offshore wind turbine airfoil at a Reynolds number of 1×106. Unsteady Reynolds-Averaged Navier-Stokes (URANS) simulations were used for parametric analyses to determine optimal control parameters, while Delayed Detached Eddy Simulation (DDES) provided insights into the transient vortex structures on the airfoil's suction surface, elucidating the control mechanisms of the microcylinder. The results reveal a strong correlation between the microcylinder’s effectiveness and its geometric configuration, particularly its diameter and distance from the airfoil surface. The microcylinder effectively modifies the flow field by generating vortices that interact with the boundary layer, thereby enhancing its resistance to adverse pressure gradients and delaying flow separation. The optimal configuration—characterized by a microcylinder with a diameter of 1% of the chord length (D/c = 0.01) positioned 1.5% of the chord length (L/c = 0.015) away from the airfoil surface—resulted in a 62% reduction in peak drag coefficient and a 50% decrease in aerodynamic hysteresis loop area. These improvements significantly enhance the dynamic aerodynamic performance and stability of the oscillating NACA0012 airfoil, effectively mitigating the detrimental effects of dynamic stall.

Investigation of dynamic stall models on the aeroelastic responses of a floating offshore wind turbine

Dynamic stall effects significantly affect the aerodynamic load prediction of wind turbines. In order to investigate the dynamic stall effects on the loads and responses of a 15 MW floating offshore wind turbine (FOWT), a novel dynamic stall model, namely IAG, is implemented within the widely-used simulation software package OpenFAST in this study. The superiority and accuracy of the IAG model are verified by comparisons against experimental data and numerical results from the Beddoes-Leishman (B-L) model. The results have shown that the IAG model is able to more accurately capture edges of the hysteresis loops of aerodynamic coefficients corresponding to various airfoils and operation states. The aeroelastic responses of a 15MW floating offshore wind turbine under normal and extreme environmental conditions are calculated by employing the IAG model. The impact of dynamic stall models on blade loads and displacements has been analyzed. It is found that the B-L model produces larger loads and displacements under high wind speed and yaw error conditions, attributed to the insufficiently computational robustness of the B-L model under deep stall situations and the seriously dynamic stall circumstances. The 1st-order and 2nd-order bending modes of the blade are expected to be enhanced by the aerodynamic loads that are predicted using the B-L model. Consequently, the bending-torsional coupling effects would be enhanced, leading to an increase up to 64.7% on the in-plane bending moment. This study has confirmed that the dynamic stall model should be properly selected properly for the fully coupled analysis of FOWTs.

Structure patterns of one-step synthesis of CuNi nanopowders in air environment: Experiment and atomistic simulations

A possibility for one-step synthesis of bimetallic CuNi nanopowders in a different ratio of Ni to Cu by solution combustion synthesis technique under normal air atmosphere without any post reduction is reported. The effect of different types of fuels like citric acid and glycine on the combustion process and characteristics of resultant solid products were investigated. XRD results showed the existing of CuNi as a main phase and small amounts of CuO and (Ni,Cu)4N. Determined CuNi particle sizes were in the range of up to 50 nm. Computer simulation was performed using the molecular dynamics method for similar concentration compositions, but in size range of 4.5–5.5 nm, as a result of cooling the system from 1700 K to 300 K. In addition, two types of melting scenario of binary CuNi NPs were studied: 1) heterogeneous melting of monocrystalline Cu and Ni NPs; 2) melting of the crystallization products of binary NPs. Melting temperatures weakly depend on the choice of the above-mentioned melting scenario. However, the nature of subsequent crystallization can be influenced by the initial energy of the system, which is higher for case 1. The characteristic temperatures of phase transitions of melting and crystallization are determined based on the analysis of hysteresis loops of the specific potential part of the internal energy of NPs. The patterns of atomic and structural segregation in binary CuNi NPs were studied.

Optimization of Structural, Dielectric, and Electrical Properties in Lead-free Ba0.85Ca0.15Zr0.1Ti0.9O3 through site engineering for Biocompatible Energy Harvesting

Piezoelectric energy harvesting has recently gained attention due to its high power density and potential for self-powered sensor networks. This study investigates the effects of dopants on Ba0.85Ca0.15Zr0.1Ti0.9O3 (BCZT) ceramics, examining Strontium (Sr2+), Zinc (Zn2+), and praseodymium (Pr3+/4+) ions at different sites and their impact on structural, dielectric, and electrical properties. X-ray diffraction and Rietveld analysis reveal a coexistence of tetragonal and rhombohedral/orthorhombic phases, with a predominant tetragonal phase, confirmed by Raman analysis. Energy-dispersive X-ray spectroscopy ensures chemical homogeneity. The density measurements indicate a dense microstructure with a relative density of 90-95%. Dielectric analysis shows a relaxor-like behavior in AB-site doped BCZT ceramics, validated by polarization-electric field hysteresis loops. B-site doped BCZT ceramics exhibit ultra-low leakage currents, approximately 103 times lower than undoped BCZT. An optimized biocompatible flexible film-based energy harvester, incorporating A-site doped BCZT ceramic particles, demonstrated impressive energy harvesting capabilities. A simple finger tapping generated ~80.2V and ~18.2nA, with an average peak-to-peak power density of 7.6 µW-cm-3. These results highlight the significant potential of dopant inclusion in BCZT ceramics, marking a major advancement in doping strategies for piezoelectric energy harvesting in miniature electronics.

Design of superparamagnetic Fe3O4@SiO2@3,4-DABP nanocatalysts, fabrication by co-precipitation and sol-gel methods, characterization of detailed surface texture properties and investigation of solar cell performance

This research focuses on the synthesis, characterization, and evaluation of Fe3O4, Fe3O4@SiO2, and Fe3O4@SiO2@3,4-DABP magnetic nanocatalysts (MNCs) for their potential use as sensors within the intricate architectures of solar cell devices. Fourier transform infrared (FTIR) spectroscopy, scanning electron microscopy with energy dispersive X-ray spectroscopy (SEM-EDS), transmission electron microscopy (TEM), vibrating sample magnetometry (VSM), X-ray diffraction (XRD), thermogravimetric analysis (TGA) and Brunauer-Emmett-Teller (BET) surface area measurements were carried out to characterize the structural, morphological and magnetic properties of the MNCs. The MNCs exhibit an average particle size of approximately 10 nm. Fe3O4, Fe3O4@SiO2, and Fe3O4@SiO2@3,4-DABP MNCs have saturation magnetization values ​​of 61.64 emu/g, 37.31 emu/g, and 20.13 emu/g, respectively. Thermal analysis reveals mass change losses of 6.5%, 12% and 28.1%, respectively, indicating different thermal stability profiles. It confirms that their crystal structure is face-centered cubic spinel, with type IV hysteresis loops and H3 loops indicating a mesoporous structure according to the IUPAC classification. Efficiency tests of Fe3O4, Fe3O4@SiO2 and Fe3O4@SiO2@3,4-DABP MNCs in solar cell devices show efficiencies of 1.49%, 1.77% and 2.15%, respectively. As the hierarchical modification of the MNCs increases, the efficiency of the solar cell devices increases. These results highlight the potential of Fe3O4, Fe3O4@SiO2 and Fe3O4@SiO2@3,4-DABP as promising sensitizers in solar cell technology. Fe3O4@SiO2@3,4-DABP MNCs have high catalytic activity, chemical stability, electronic conductivity and low cost. This study also marks the first demonstration of the effectiveness of environmentally friendly Fe3O4@SiO2@3,4-DABP MNCs in enhancing solar cell performance, prepared via a cost-effective, simple and eco-friendly approach.

Numerical investigation of unsteady aerodynamics on a grooved NACA 4415 airfoil

Surface grooves have demonstrated the capability to mitigate laminar separation bubbles and enhance airfoil aerodynamic performance. However, wind turbine operation introduces dynamic effects that significantly impact airfoil behavior, leading to substantial deviations from static conditions. Numerical simulations were carried out to discuss the effectiveness of surface groove structures in controlling separation bubbles under dynamic conditions and their potential to enhance unsteady aerodynamics. The influence of groove parameters (depth, width, position) on the NACA 4415 airfoil’s boundary layer attributes and unsteady aerodynamic properties are analyzed across various pitching amplitudes and reduced frequencies. It is found that the position of groove structures under dynamic conditions is crucial, that groove structures located ahead of separation bubbles on the airfoil surface can effectively eliminate the separation bubbles, and their control effectiveness is superior to that under static conditions. Well-designed groove structures can reduce the airfoil’s maximum lift, drag, and moment coefficients under dynamic conditions. They also reduce the aerodynamic hysteresis effect and improve the aerodynamic damping characteristics. This comprehensive analysis sheds light on the critical interplay between dynamic wind conditions, airfoil behavior, and the potential of groove structures to optimize wind turbine performance.

Modeling linear and nonlinear viscoelastic oscillatory rheometric stress-strain hysteresis of asphalt binders

AbstractUnderstanding the complex stress-strain hysteresis behavior of asphalt binders under varied conditions is critical for optimizing pavement performance. This study addresses the challenge by analyzing and modeling asphalt binder responses in oscillating shear mode across different aging states (unaged, short-term aged, and long-term aged), stretch amplitudes, frequencies, and temperatures. Fifty-three stress-strain hysteresis loops were meticulously analyzed, revealing distinct stress paths relative to applied stretch levels. A nine-parameter parallel rheological framework model was developed, integrating a four-parameter eight-chain (FEC) hyperelastic model in one network and a FEC hyperelastic model with a linear viscoelastic flow element in series in another. This constitutive model was implemented in LS-DYNA finite element simulations to predict experimentally-measured stress-strain hysteresis loops accurately. The research demonstrates the model’s capability to simulate both linear and nonlinear viscoelastic responses of asphalt binders across a wide range of environmental and loading conditions. This approach significantly enhances our ability to capture and understand the stress-strain behavior critical for asphalt pavement durability and performance optimization.

Numerical Study of Cone Penetration Tests in Lunar Regolith for Strength Index

The cohesive properties of lunar regolith, combined with a low-gravity environment, result in it having a distinct mechanical behavior from sandy soil on Earth. Consequently, empirical formulas derived from cone penetration tests (CPTs) for calculating the shear strength parameters of Earth’s sand cannot be directly applied to lunar regolith. This study utilized the three-dimensional discrete element method (DEM) to numerically simulate triaxial shear tests and cone penetration tests in a lunar environment. The particle contact model for lunar regolith in the discrete element method (DEM) simulation incorporated the hysteresis effect of van der Waals forces, thereby simulating the cohesive properties of lunar regolith in a lunar environment. We proposed a relationship for calculating the shear strength index of lunar regolith based on normalized cone tip resistance using the results from triaxial and CPT simulations and referencing empirical formulas derived from ground-based CPT data. The results of this study provide a valuable reference for future lunar CPTs.

A Progressive Loss Decomposition Method for Low-Frequency Shielding of Soft Magnetic Materials

Energy loss in shielding soft magnetic materials at low frequencies (1–100 Hz) can cause fluctuations in the material’s magnetic field, and the resulting magnetic noise can interfere with the measurement accuracy and basic precision physics of biomagnetic signals. This places higher demands on the credibility and accuracy of loss separation predictions. The current statistical loss theory (STL) method tends to ignore the high impact of the excitation dependence of quasi-static loss in the low-frequency band on the prediction accuracy. STL simultaneously fits and predicts multiple unknown quantities, causing its results to occasionally fall into the value boundary, and the credibility is low in the low-frequency band and with less data. This paper proposes a progressive loss decomposition (PLD) method. Through multi-step progressive predictions, the hysteresis loss simulation coefficients are first determined. The experimental data of the test ring verifies the credibility of PLD’s prediction of the two hysteresis coefficients, improving the inapplicability of the STL method. In addition, we use the proposed method to obtain the prediction results of the low-frequency characteristics of the loss of a variety of typical soft magnetic materials, providing a reference for analyzing the loss characteristics of materials.

Room‐temperature Magnetocapacitance Spanning 97K Hysteresis in Molecular Material

AbstractMagnetic capacitor, as a new type of device, has broad application prospects in fields such as magnetic field sensing, magnetic storage, magnetic field control, power electronics and so on. Traditional magnetic capacitors are mostly assembled by magnetic and capacitive materials. Magnetic capacitor made of a single material with intrinsic properties is very rare. This intrinsic property is magnetocapacitance (MC). The studies on MC effect have mainly focused on metal oxides so far. No study was reported in molecular materials. Herein, two complexes: (CETAB)2[CuCl4] (1) and (CETAB)2[CuBr4] (2) (CETAB=(2‐chloroethyl)trimethylammonium) are reported. There exist strong H−Br and Br−Br interactions and other weak interactions in complex 2, so the phase transition energy barrier is high, resulting in the widest thermal hysteresis loop on a molecular level to date. Furthermore, complexes 1 and 2 show large MC parameters of 0.247 and 1.614, respectively, which is the first time to observe MC effect in molecular material.

Enhanced energy storage performance of lead-free Sr0.7Bi0.2TiO3 ceramics via tape casting

Abstract The development of pulsed power technology demands high energy storage density dielectric materials. In this study, Sr0.7Bi0.2TiO3 relaxor ferroelectric (rFE) ceramic thick films were prepared using a tape-casting process. The ceramics exhibit a dense structure and typical rFE hysteresis curves, achieving an energy storage density of 4.77 J cm−3 and efficiency of 94.4%, attributed to the high polarization intensity, low remnant polarization, and low hysteresis loss of rFE. Additionally, the material demonstrates good temperature stability. Moreover, the Sr0.7Bi0.2TiO3 ceramic thick films show advantages in charge-discharge performance, capable of discharging within hundreds of nanoseconds and achieving a power density of 137 MW cm−3. Overall, the Sr0.7Bi0.2TiO3 ceramic thick film exhibits a comprehensive performance advantage in terms of energy storage density, efficiency, and power density. Additionally, the material was fabricated using the tape-casting process, which is compatible with subsequent multilayer ceramic capacitor production, indicating potential for further performance enhancement.

Unveiling Frequency-Dependent Electromechanical Dynamics in Ferroelectric BaTiO3 Nanofilm with a Core-Shell Structure

Diverse domain patterns significantly influence the nonlinear electromechanical behaviors of ferroelectric nanomaterials, with polarization switching under strong electric fields being inherently a frequency-dependent phenomenon. Nevertheless, research in this area remains limited. In this study, we present a phase-field investigation of frequency-dependent electromechanical dynamics of a polycrystalline BaTiO3 nanofilm with a core-shell structure, subjected to applied frequencies ranging from 1 to 80 kHz. Our findings elucidate the microstructural mechanisms underlying the electromechanical behaviors observed in these materials. The effect of the grain size and the strains effect are also taken into account. Hysteresis and butterfly loops exhibit a marked change in shape as the frequency changes. We discuss the underlying domain-switching dynamics as a basis for evaluating such frequency-dependent properties. In addition, we examine the scaling behaviors of the dynamic hysteresis and the influence of grain boundaries on the domain structure. We can also observe from hysteresis loops that the remnant polarization and coercive field significantly diminish when grain sizes decrease from 60 to 5 nm. A smaller grain size of the nanofilm yields a larger percentage of the dielectric grain boundary, which “dilutes” the overall ferroelectricity of the film. A vortex domain structure is more likely to form at low frequency and a small grain size.

Hysteresis loop variations induced by nitrogen flow rate in solution-based VO2 films

Hysteresis loop variations induced by nitrogen flow rate in solution-based VO2 films

Effects of Natural Disasters on West Africa Sahel’s Economy: The Case of Burkina Faso, Mali and Niger

The Sahel region is facing the adverse effects of the natural disasters due to the drought and floods which are the most frequent events. These effects can be spread and affected the all the Sahel States economy. Therefore, this study attempts to analyze the effects of these natural disasters on the macroeconomic variables such as production, consumption, investment and inflation in the three (3) the northern central Sahel States. To do so, the panel vector autoregressive model (PVAR) is run on the World Bank and the International Emergency Disasters Database (EM-DAT) data from 1990 to 2021. The results revealed that the occurrence of drought shock generates significantly a negative impact on the GDP per capita at 5% level across the northern central Sahel countries (Burkina Faso, Mali, and Niger). Also, the lagged of the macroeconomic variables such as production, investment and inflation have respectively a significant and positive impact on consumption at 5% level, production at 5% level and consumption at 10% level. Furthermore, the results show an asymmetry of natural disaster shocks at the scale of the northern central Sahel States but these shocks are symmetrical in pairs. As a result, the appropriate policies must make to absorb these shocks and avoid any hysteresis effect.

Photocatalytic Magnetic Microgyroscopes with Activity-Tunable Precessional Dynamics.

Magnetic nano/microrotors are passive elements spinning around an axis due to an external rotating field while remaining confined to a plane. They have been used to date in different applications related to fluid mixing, drug delivery, or biomedicine. Here we realize an active version of a magnetic microgyroscope which is simultaneously driven by a photoactivated catalytic reaction and a rotating magnetic field. We investigate the uplift dynamics of this colloidal spinner when it precesses around its long axis while self-propelling due to the light induced decomposition of hydrogen peroxide in water. By combining experiments with theory, we show that activity emerging from the cooperative action of phoretic and osmotic forces effectively increases the gravitational torque, which counteracts the magnetic and viscous ones, and carefully measure its contribution. Finally, we demonstrate that by modulating the field amplitude, one can induce hysteresis loops in the uplift dynamics of the spinners.

Predicting Potential Distribution of Teinopalpus aureus Integrated Multiple Factors and Its Threatened Status Assessment

The accurate prediction of the niche and the potential distribution of a species is a fundamental and key content for biodiversity related research in ecology and biogeography, especially for protected species. Biotic interactions have a significant impact on species distribution but are often overlooked by SDMs. Therefore, it is crucial to incorporate biotic interaction factors into SDMs to improve their predictive performance. The Teinopalpus aureus Mell, 1923 is endemic to high altitudes in southern East Asia, renowned for its exceptional beauty and rarity. Despite the significant conservation value, its spatial distribution remains unclear. This study integrated climate data, host plants, and empirical expert maps to predict its potential distribution. The results indicated that utilizing the species richness of host plants as a surrogate for biotic interactions was a simple and effective way to significantly improve the predictive performance of the SDMs. The current suitable distribution of T. aureus and its host plants is highly fragmented, primarily concentrated in the Nanling and Wuyi Mountains, and consisting of numerous isolated small populations. Given climate change, their distribution is significantly shrinking, increasing the threatened level in the future. Especially for the population of T. aureus hainani Lee, the likelihood of extinction is extremely high. Abiotic factors not only directly affect the distribution of T. aureus but also indirectly impact it through the host plants. This was evident in the delayed response of T. aureus to climate change compared to its host plants, which is called the “hysteresis effect” caused by biotic interactions. Overall, we tentatively suggest regarding T. aureus as a vulnerable species. In the future, multiple measures could be taken to indirectly protect the feeding and habitat resources of T. aureus by conserving host plants, thereby enhancing its survival prospects.

Coexistence of Superconductivity and Magnetic Ordering in the In–Ag Alloy Under Nanoconfinement

The impact of the interface phenomena on the properties of nanostructured materials is the focus of modern physics. We studied the magnetic properties of the nanostructured In–Ag alloy confined within a porous glass. The alloy composition was close to the eutectic point in the indium-rich range of the phase diagram. Temperature dependences of DC magnetization evidenced two superconducting transitions at 4.05 and 3.38 K. The magnetization isotherms demonstrated the superposition of two hysteresis loops with low and high critical fields below the second transition, a single hysteresis between the transitions and ferromagnetism with weak remanence in the normal state of the alloy. The shape of the loop seen below the second transition, which closes at a low magnetic field, corresponded to the intermediate state of the type-I superconductor. It was ascribed to strongly linked indium segregates. The loop observed below the first transition is referred to as type-II superconductivity. The secondary and tertiary magnetization branches measured at decreasing and increasing fields were shifted relative to each other, revealing the proximity of superconducting and ferromagnetic phases at the nanometer scale. This phenomenon was observed for the first time in the alloy, whose components were not magnetic in bulk. The sign of the shift shows the dominant role of the stray fields of ferromagnetic regions. Ferromagnetism was suggested to emerge at the interface between the In and AgIn2 segregates.