Magnetic Field Intensity Research Articles

An induction curing technique for CFRP laminate via magnetic particle‐induced in situ heating

AbstractCuring high‐performance carbon fiber reinforced polymer (CFRP) structures with economical and energy‐efficient off‐oven techniques is important for the widespread application of the composite. In this work, we reported a magnetic particle‐induced in situ heating method to controllably cure CFRP laminates with stacking sequences of [0]8, [0/90]4s and [0/45/90/−45]2s. Results showed that all the laminates can undergo a consistent, layup‐independent two‐staged heating protocol via regulating the magnetic field intensity. Under the same curing protocol, the three stacking‐sequenced CFRP laminates can be cured more completely under induction heating than oven heating, in addition to a moderately improved tensile and flexural properties. However, the porosity of the laminates slightly increased under induction heating. The proposed new curing method provides a new avenue to the fabrication of advanced CFRP composite structures without oven or autoclave.Highlights A particle‐induced in situ heating method to controllably cure carbon fiber reinforced polymer (CFRP) laminates was proposed. This method was capable to cure CFRP laminates with different stacking sequences. Mechanical property of laminates was moderately improved under this method.

Study on the Characteristics of Turn-to-Turn Short Circuit Faults in the Primary Windings of the Generator Terminal Voltage Transformer

Turn-to-turn short circuit faults in the primary winding of generator terminal voltage transformers can lead to erroneous operation of stator grounding protection systems. This paper analyzes the fault characteristics associated with such failures and derives formulas for the fault phase current and zero-sequence voltage during a turn-to-turn short circuit in the primary winding. A 3D finite element model of the generator terminal voltage transformer is established by using Altair Flux 3D, and the accuracy of the model is verified. Based on this model, simulation tests were conducted to investigate turn-to-turn short circuits in the primary winding. The results reveal that as the number of shorted turns increases, the voltage of the fault phase decreases continuously while the voltages of the other two phases increase. The current in the short-circuited phase rises significantly, accompanied by an increase in zero-sequence voltage. Visualizations of magnetic field parameters indicate that as the number of shorted turns increases, the magnetic induction magnitude of the fault phase rises steadily and approaches saturation, resulting in heightened magnetic field intensity near the shorted turns. This analysis of fault characteristics through simulation contributes to the advancement of fault diagnosis systems for generator terminal voltage transformers.

Biological and physicochemical effects of magnetic field on <em>Artemia franciscana</em> exposed to cyanobacteria extract and treated with isotherapeutic 200cH

This study proposes an experimental model to analyze homeopathic potencies' biological and physicochemical effects on intense magnetic fields. The proposed model is based on the exposition of Artemia franciscana cysts to saxitoxin (cyanobacteria extract) and the treatment with R. raciborskii extract isotherapic 200cH (named saxitoxin 200cH), followed by the hatching and nauplii (larvae) vitality rate (live nauplii/total cysts), and the gene expression of heat shock proteins (HSP 26, 40, 90, and p26), as previously described ad bio-resilience indicators [1,2]. In a second experiment, pH, conductivity, and temperature temporal curves were built, and different treatments were compared before and after being poured into the seawater. The method details are as follows: Artemia franciscana cysts were seeded into artificial seawater in 96-well plates in triplicate, exposed immediately to 25ppm of R. raciborskii extract, and treated with sterile purified water (SPW), succussed SPW (vehicle controls), or saxitoxin 200cH prepared in SPW, submitted or not to a 2400 Gauss static magnetic field for 15 minutes. Plates were kept in a Faraday cage under stable lightening (300 mini-led lamps), temperature (26.5%), humidity (65%), and magnetic field (0.7 µT). The hatching and vitality rate were analyzed after 48 hours. In the second experiment, the physicochemical parameters were analyzed before and after one minute, two, and 24 hours after pouring the samples into seawater (100µL/100mL), kept at the same environmental conditions set for the first experiment. The statistical analysis was made by two-way ANOVA / Tukey, with α=0.05. Treatment of cysts with SPW alone reduced the hatching and nauplii vitality rate in relation to the other treatments (p≤0.05); however, the treatment with saxitoxin 200cH exhibited smaller variance and the highest statistical hatching (p=0.0009) and vitality (p=0.0007) levels. The previous submission of samples to the magnetic field reverted this result by canceling the statistical differences and increasing the variance of saxitoxin 200cH datapoints. The analyses of HSP gene expression are still in course. In the second experiment, there is no specific effect of saxitoxin 200cH on temperature, conductivity, and pH, independent of the exposition of samples to the magnetic field. The results corroborate the hypothesis that a possible interference on dipolar dynamics of saxitoxin 200cH caused by the intense magnetic field could negatively interfere with its biological effect independently of eventual changes in temperature, conductivity, and pH in the seawater, although its clear capacity to improve tracking homeopathic potencies in water when using the method of solvatochromic dyes, as previously shown [3].

Enantioseparation of antihistamines using magneto-thin-layer chromatography: The effects of various orientations and intensities of magnetic fields

The effect of magnetic fields produced by magnet and solenoid was investigated for the first time in the enantioseparation of antihistamines using thin-layer chromatography. The racemic mixtures of cetirizine and hydroxyzine were selected as the model drugs for studying the magnetic field effect on enantioseparation. The magnets were fixed to a U-shape blade that rotated around the separation chamber by a motor to apply a magnetic field perpendicular to the direction of mobile phase movement. Also, the separation chamber was positioned within a solenoid, and an electric current was utilized to apply the magnetic field in a parallel direction to the mobile phase movement. L-arginine was added to the mobile phase as a chiral selector to perform the enantioseparation of drugs. When magnets generate the magnetic field, both in attraction and repulsion, the spots become broader and the peak height decreases as the magnetic field intensity and rotation speed of the magnets increase. An increase in peak height was observed in the presence of the magnetic field generated by + 3.25A current in the solenoid. Regardless of the type of applied magnetic field, the retention factor values exhibited slight reductions. It was observed that separated enantiomers were similarly affected by various magnetic fields. The distribution coefficient, mass transfer, equilibrium, and lipophilicity were all potentially influenced by the magnetic field, which could explain the alterations.

Juno Observations Set New Constraints on the Electrodynamic Interaction Between Io and Jupiter.

Juno's highly elliptical polar orbits provide unprecedented in-situ observations of the electrodynamic interaction between Jupiter and its volcanic moon Io. These observations occur in regions never sampled before both near Io's orbit and near Jupiter's ionosphere and at distances between the two. Magnetic field data obtained during multiple traversals of magnetic field lines mapping to Io's orbit reveal remarkably rich and complex magnetic signatures near flux tubes connected to Io's orbital position. Here we present a methodology to model the distribution of currents along Io's flux tube (IFT) and Alfvén wings in such a way as to match the magnetic field signature observed during Juno's traversals of the IFT and Alfvén wings downstream of Io. We obtain the location, size and morphology of the current-carrying region as well as the distribution of currents within the IFT and Alfvén wings. The observed field-aligned currents exhibit strong filamentation, with upward and downward currents splitting into secondary cells rather than forming uniform structures. Additionally, there is a strong correlation between total field-aligned current intensity, particle energy flux, and Poynting flux, indicating efficient energy transfer and coupling in the Jupiter-Io system. Using all of Juno's traversals up to perijove (PJ) pass 42, we estimate the strength of the interaction with regards to distance along Io's extended tail, Io's position in the plasma torus and the magnetic field intensity at the footprint in Jupiter's ionosphere, illuminating the interaction of Jovian magnetospheric plasma with Io and setting important constraints in the Io-Jupiter interaction.

Numerical simulations of MHD effect on convective heat transfer characteristics in bubbles coalescence process

In this numerical study, the coalescence characteristic of a coaxial bubble pair and its influence on the liquid-to-wall convection heat transfer are investigated under different magnetic field intensities, magnetic field directions, and wall confinement ratios by adopting the volume of fluid (VOF) method. The results reveal that in the direction of heat flow, the toroidal vortices around the bubbles are dampened and even vanish completely after applying the spanwise magnetic fields, while the toroidal vortices only get away from the hot wall in the presence of the transverse magnetic fields. Correspondingly, the convective heat transfer on the hot wall is suppressed to varying degrees under the magnetic fields in different directions. The inhibitory action of the magnetic field on the heat transfer becomes stronger with the decreasing separation distance (s*) between the coaxial bubbles. The total increment of heat transfer (Nu*) is a decreased function of Hartmann number (Ha) and that decreased amplitude of Nu* under the spanwise magnetic field is nearly twice that of the transverse magnetic field. Additionally, the variations of Nu* are independent of the wall confinement ratio (Cr) for Ha < 400, while the Cr has an obvious effect on Nu* for Ha > 400 and the values of Nu* are considerably smaller at a larger Cr. The results about the effect of the magnetic field and wall confinement on the two-phase heat transfer can be referenced in the cooling system design of fusion reactor.

Research on propagation characteristics of an electromagnetic wave in magnetized fully ionized dusty plasma

When some spacecraft fly at high speed in near-earth space, the dusty plasma is attached to the surface of the spacecraft due to the intense friction between the spacecraft and the space. The dusty plasma attached to the aircraft hinders the propagation of electromagnetic (EM) waves and affects the flight safety of the pilot. In this paper, we replace the collision term of the general Boltzmann equation with the Fokker-Planck-Landau collision term and obtain the general correlation expression of the electron distribution function in the fully ionized dusty plasma. The dielectric relation of EM waves in magnetized fully ionized dusty plasma is calculated considering the impact effect and charging effect of dust particles in the case of an external magnetic field. The reflection coefficient (R) and transmission coefficient (T) of the EM wave in magnetized fully ionized dusty plasma are calculated by a scattering matrix method. The effects of applied magnetic field intensity and dust particle parameters on the propagation characteristics of EM waves in magnetized fully ionized dusty plasma are discussed by simulation. In addition, the propagation characteristics of EM waves in ordinary plasma and magnetized fully ionized dusty plasma are compared. The results show that with the increase in the additional magnetic field, the reflection of the EM wave in the fully ionized dusty plasma decreases and the transmission increases. In the 0–100 GHz band, dust particles block EM waves from penetrating fully ionized dusty plasma. Other dusty plasma parameters also affect the propagation characteristics of EM waves to varying degrees. These results provide a theoretical reference for solving the communication related problems of high-speed aircraft.

The effect of magnetic field intensity on the tribological properties of PA6 and UHMWPE in pure water and seawater environments

The effect of magnetic field intensity on the tribological properties of PA6 and UHMWPE in pure water and seawater environments

Study on the Microstructure and Properties of Al Alloy/Steel CMT Welding–Brazing Joints Under Different Pulse Magnetic Field Intensities

Butt welding experiments on 6061 Al alloy and Q235B steel of 2 mm thickness were conducted using an ER4047F flux-cored wire as the filler metal, after adding a pulsed magnetic field into the process of cold metal transfer (CMT) welding. The effect of the pulsed magnetic field intensity on the macro morphology, microstructure, tensile strength and corrosion resistance of the welding–brazing joint was analyzed. The results showed that when the pulsed magnetic field intensity increased from 0 to 60 mT, the wettability and spreadability of the liquid metal were improved. As a result, the appearance of the Al alloy/steel joint was nice. However, when the pulsed magnetic field intensity was 80 mT, the stability of the arc and the forming quality of the joint decreased, which resulted in a deterioration in the appearance of the joint. A pulsed magnetic field with different intensities did not alter the microstructure of the joint. All of the joint was composed of θ-Fe2(Al,Si)5 and τ5-Al7.2Fe1.8Si at the interface and Al-Si eutectic phase and α-Al solid solution at the weld seam zone. Actually, with the pulsed magnetic field intensity increasing from 0 mT to 60 mT, the IMC thickness in the interfacial layer gradually reduced under the action of electromagnetic stirring. Also, the grain in the weld seam was refined, and elements were distributed uniformly. But when the pulsed magnetic field intensity was 80 mT, the grain in the weld seam began to coarsen, and the intermetallic compound (IMC) thickness was too small, which was unfavorable for the metallurgical bonding of Al alloy and steel. Therefore, with the increase in pulsed magnetic field intensity, the tensile strength of the joints first increased and then decreased, and it reached its maximum of 187.7 MPa with a pulsed magnetic field intensity of 60 mT. Similarly, the corrosion resistance of the joint first increased and then decreased, and it was best when the pulse magnetic field intensity was 60 mT. The Nyquist plot and Bode plot confirmed this result. The addition of a pulsed magnetic field caused less fluctuation in the anode current density, resulting in less localized corrosion of the joint using the scanning vibrating electrode technique (SVET). The XPS analysis showed the Al-Fe-Si compounds replacing the Fe-Al compounds in the joint was the main reason for improving its corrosion resistance under the action of a pulsed magnetic field.

Bifurcation and chaos in axially moving ferromagnetic thin plates with imperfections under magnetic field and line load

This paper explores the complex dynamic behavior of axially moving ferromagnetic thin plates with initial geometric imperfection, subject to a magnetic field and a line load. The equation of motion for the imperfect plate is derived using Hamilton's variational principle, based on Kirchhoff's thin plate theory and the magnetoelastic theory of ferromagnetic materials, and discretized via the Galerkin method. When system stiffness becomes negative under specific parameters, leading to structural instability, the Melnikov method is used to predict chaos analytically and to establish the necessary conditions for its onset. Based on these predictions, a chaotic distribution map is generated in the parameter space to visualize chaotic regions. Numerical simulations are performed to produce bifurcation diagrams, maximum Lyapunov exponent plots, and system response curves, providing a dynamic analysis of the system's behavior under varying bifurcation parameters. The results indicate a complex nonlinear coupling between the plate's physical and geometric properties and the external magnetic field conditions. Variations in magnetic field intensity, axial velocity, and frequency ratio result in complex nonlinear dynamics, including bifurcations and transitions between periodic and chaotic states. This study offers critical insights into the dynamic characteristics and evolution of nonlinear systems, with significant implications for controlling and predicting chaotic vibrations in engineering applications.

MAGNETIC ACTIVATION OF ION EXCHANGE PROCESS DURING DEMINERALISATION OF NATURAL WATERS

The process of demineralizing natural water involves removing heavy metal ions and other pollutants from it. Given the current environmental trends, including environmental degradation and water pollution, there is a need to improve the efficiency of water treatment methods while minimizing the environmental impact. Reagent demineralization methods are widely used in water treatment systems, but they are often accompanied by high economic and resource costs, as well as additional pollution. A promising area is the combined use of reagent treatment with other demineralization methods, in particular the ion exchange method, which has been actively developing in recent years. This method is based on the stoichiometric exchange of ions between ion exchange materials and water. The article deals with the issue of magnetic activation of the ion exchange process in the demineralization of natural waters. The analysis of existing water treatment systems using the method of ion exchange is carried out and the parameters that need to be improved are determined. A mathematical model for evaluating the efficiency of magnetic activation of cationite KU-2x8 is proposed. The analysis confirms the relevance of research in the field of intensification of ion exchange processes to improve environmental safety and efficiency of water demineralization. The results demonstrate the influence of such parameters as the initial water hardness and magnetic field intensity on the total exchange capacity of the cationite.

The IMF Clock Angle Effect on the Tail Cross Section of the Martian Magnetic Pileup Boundary and Bow Shock

Using a three-dimensional global magnetohydrodynamic (MHD) simulation model, we investigate the effects of different interplanetary magnetic field (IMF) clock angles on the tail configuration of the Martian magnetic pileup boundary (MPB) and bow shock (BS). The study reveals the following: (1) The cross sections of the tail MPB and BS are approximately elliptical. The MPB tail cross section generally elongates in the direction of the IMF clock angle, whereas the BS tail cross section is roughly elongated perpendicular to the IMF clock angle direction. (2) An IMF with a northward component can cause the tail cross section of the MPB to shift slightly to the south when the intense crustal magnetic fields are located on the dayside. (3) As the tail distance from Mars increases, the eccentricity of the cross section ellipses of both the MPB and BS tail increases, as well as the major and minor axes. Additionally, the major and minor axes of the tail MPB’s cross section ellipses begin to decrease at the far magnetotail, suggesting that the Martian MPB tail might be a closed structure on the nightside.

Interaction of the Prominence Plasma within the Magnetic Cloud of an Interplanetary Coronal Mass Ejection with the Earth’s Bow Shock

The magnetic cloud within an interplanetary coronal mass ejection (ICME) is characterized by high magnetic field intensities. In this study, we investigate the interaction of a magnetic cloud carrying a density structure with the Earth’s bow shock during the ICME event on 2023 April 24. Elevated abundances of cold protons and heavier ions, namely, alpha particles and singly charged helium ions, associated with the prominence plasma are observed within this structure. The plasma downstream of the bow shock exhibits an irregular compression pattern, which could be due to the presence of heavy ions. Heavy ions carry a significant fraction of the upstream flow energy; however, due to their different mass-per-charge ratio and rigidity, they are less scattered by the electromagnetic and electrostatic waves at the shock. We find that downstream of the shock, while the ion thermal energy is only a small fraction of the background magnetic energy, nevertheless increased ion fluxes reduce the characteristic wave speeds in that region. As such, we observe a transition state of an unstable bow shock in which the plasma flow is super Alfvénic both upstream and downstream of the bow shock. Our findings help with the understanding of the intense space weather impacts of such events.

Optimization of Reservoir Computing Utilizing Interfered Spin Waves

Reservoir computing is a learning model that enables low-cost and fast learning compared to conventional deep learning. It enables physical implementation by replacing the reservoir part with a physical device that possesses nonlinearity, short-term memory, and high dimensionality. In particular, it was theoretically predicted that spin wave interference can perform highly efficient reservoir computing in micromagnetic simulations,[1] and it was experimentally verified by the present authors.[2] Whereas the computational performance was suggested to vary significantly depending on the interval of input voltage pulses used for spin wave excitation and the applied magnetic field intensity, the details were unclear to date. Therefore, we expanded the measurement range to investigate detailed mechanism of the system and to explore untouched high performance in the study.We use a device fabricated on the surface of a single crystal, as shown in Fig. (a), then we performed one of the most important prediction benchmark tasks, the Nonlinear Autoregressive Moving Average (NARMA) model. Since it has been found that utilizing the nonlinear interference of spin waves through multi-detection demonstrates high performance, in this study, we utilized both Detection A and Detection B. We evaluated the prediction error of NARMA10, which requires short-term memory up to 10 steps, by varying the applied magnetic field and the interval of input voltage pulses under measurement conditions. As shown in Fig. (b), the comparison between the target waveform and the output waveform during training and testing under the conditions of a magnetic field of 182 mT and a pulse interval of 23.6 ns shows a good match, at that time, the error was 0.183 during the testing phase. Next, we examined the detailed condition dependence in NARMA10. As indicated in Fig. (c), high performance is obtained in the region where the pulse interval is between 20 and 30 ns, while the performance was low in the region below 19.3 ns, particularly in the strong magnetic field range from 188 mT to 200 mT. We will discuss the condition dependence with the other NARMA models like NARMA2. Additionally, we will discuss in detail the dependence on input pulse intervals, along with evaluations of short-term memory capacity and nonlinearity. This work was in part supported by Innovative Science and Technology Initiative for Security Grant Number JPJ004596, ATLA, Japan and JST PRESTO (JPMJPR23H4).【Reference】[1] Nakane et al., IEEE Access 6, 4462 (2018).[2] Namiki et al., Adv. Intell. Syst. 5, 2300228 (2023). Figure 1

Concept for a geometry-insensitive high-field magnetic resonance detector

AbstractWe introduce an inverse design methodology for a new class of eigenfrequency-invariant metamaterial-resonators, targeting nuclear magnetic resonance detection at ultra-high $$\mathbf {B_0}$$ B 0 field, and operating at two specified frequencies selected from within the 100-1500 MHz range. The primary optimisation goal is to maximise the magnetic field intensity and uniformity within a liquid sample, while the electric energy should be kept to a minimum level to reduce dielectric heating or quadrupolar moment excitation effects. Due to the symmetric geometry requirement of the cavity, a demultiplexer is also designed to direct each discrete resonant signal to another predetermined output port of the resonator. In order to reduce the geometrical dependency of the resonance frequency, a bespoke metamaterial is used for the cavity host. Therefore, an additional optimisation problem for a unit cell domain is defined to seek a proper material layout for the host region of the resonators. Given the sensitivity of the frequency domain, the optimisation process is effectively regulated through the utilisation of both a Helmholtz filter and a projection method. It is found that considerable improvements of the resonator quality factor can be obtained through this optimisation process.

Impacts of Double Rotating Cylinders on the Forced Convection of Nanoencapsulated Phase Change Material

ABSTRACTMany engineering and industrial applications rely on heat transfer (HT) as a basic and central process. Therefore, engineers and researchers place significant emphasis on optimizing HT rates. Here, we numerically attempt to maximize the heat transmission rate of mixed convection of nanoencapsulated phase change material in a square compartment. The compartment is differentially heated and incorporates two cold rotating cylinders. The Galerkin finite element approach is utilized for addressing the system governing equations. A range of various factors affecting the thermal activity in the compartment were considered. These factors include the speed of spinning cylinders (Re = 0–1000), the porousness of the compartment (Da = 10−5–10−2), the magnetic field intensity (Ha = 0–100), and the concentration of nanoadditives (ϕ = 0%–8%). The obtained numerical findings demonstrated that the thermal activity inside the compartment is positively correlated to the speed of the spinning cylinders, the concentration of nanoadditives, and the porousness of the compartment. In contrast, increasing the intensity of the magnetic field obstructs the heat transmission. It was noted that at the highest Re number, the average Nusselt number augmented by 257% and 13.6% when increasing Da and ϕ, respectively.

Three-dimensional simulation of film boiling on a horizontal surface with magnetic field

This study conducts a numerical investigation into the three-dimensional film boiling of liquid under the influence of external magnetic fields. The numerical method incorporates a sharp phase-change model based on the volume-of-fluid approach to track the liquid–vapour interface. Additionally, a consistent and conservative scheme is employed to calculate the induced current densities and electromagnetic forces. We investigate the magnetohydrodynamic effects on film boiling, particularly examining the pattern transition of the vapour bubble and the evolution of heat transfer characteristics, exposed to either a vertical or horizontal magnetic field. In single-mode scenarios, film boiling under a vertical magnetic field displays an isotropic flow structure, forming a columnar vapour jet at higher magnetic field intensities. In contrast, horizontal magnetic fields result in anisotropic flow, creating a two-dimensional vapour sheet as the magnetic strength increases. In multi-mode scenarios, the patterns observed in single-mode film boiling persist, with the interaction of vapour bubbles introducing additional complexity to the magnetohydrodynamic flow. More importantly, our comprehensive analysis reveals how and why distinct boiling effects are generated by various orientations of magnetic fields, which induce directional electromagnetic forces to suppress flow vortices within the cross-sectional plane.

Magnetic properties and magnetocaloric effect of chromium-based high-entropy perovskite oxides

High-entropy oxides (HEOs) represent a significant advancement in the field of high-entropy ceramics and have received considerable attention in magnetism research. This study systematically investigated the magnetic and magnetocaloric properties of HEOs at low temperatures. To this end, three high-entropy perovskites metal oxides were designed using rare-earth transition metals ((R0.2Gd0.2Eu0.2Dy0.2Tb0.2)CrO3, R = Pr, Nd and Sm) because of their remarkable performance in magnetic refrigeration. The samples were prepared using solid-state sintering method and had a single-phase orthogonal distortion structure. All prepared samples exhibited weak antiferromagnetic properties and an antiferromagnetic–paramagnetic transition at lower temperatures. Further, the samples exhibited maximum magnetic entropy changes of 12.8, 13.1, and 13.6 J/kg K under a magnetic field intensity of 50 kOe with relative cooling powers of 153.05, 143.71, and 149.15 J/kg, respectively. An Arrott diagram indicated that all samples exhibited second-order phase transitions. The changes in the degree of spin ordering and the transition trends of the magnetic exchange interaction for each sample were analyzed at the phase transition temperature. The calculated magnetocaloric performance data indicate that these compounds exhibit excellent magnetocaloric properties and can be used as low-temperature magnetic refrigeration materials.

Pulsed and Polarized X‐Ray Emission From Neutron Star Surfaces

ABSTRACTThe intense magnetic fields of neutron stars naturally lead to strong anisotropy and polarization of radiation emanating from their surfaces, both being sensitive to the hot spot position on the surface. Accordingly, pulse phase‐resolved intensities and polarizations depend on the angle between the magnetic and spin axes and the observer's viewing direction. In this paper, results are presented from a Monte Carlo simulation of neutron star atmospheres that uses a complex electric field vector formalism to treat polarized radiative transfer due to magnetic Thomson scattering. General relativistic influences on the propagation of light from the stellar surface to a distant observer are taken into account. The paper outlines a range of theoretical predictions for pulse profiles at different X‐ray energies, focusing on magnetars and also neutron stars of lower magnetization. By comparing these models with observed intensity and polarization pulse profiles for the magnetar 1RXS J1708‐40, and the light curve for the pulsar PSR J0821‐4300, constraints on the stellar geometry angles and the size of putative polar cap hot spots are obtained.

Morphologic transformation of ferrofluid during micropump driving under field control.

The superiority of ferrofluid pumps in the fields of biomedical, life science, energy, and power research has been experimentally demonstrated. However, the mechanisms underlying the morphological transformations of ferrofluid fusion and separation during pump driving are not completely understood. To bridge the gap between the theory and practical applications of ferrofluid pumps, we employed optical methods to record the dynamic morphological transformation of rotating and fixed ferrofluids under different magnetic field polarities, magnetic field distributions, and ferrofluid mass fractions. The magnetic field polarity causes dynamic differences in the fusion-separation process of the ferrofluid but does not affect the volume segmentation of the ferrofluid, which depends on the ratio of the magnetic field intensities. When this ratio deviates from one, the morphology of ferrofluid changes, reducing the pumping efficiency. Compared to external environmental factors, the mass fraction does not change the morphology of the ferrofluid. However, high mass fractions lead to wall-clinging of the ferrofluid, and low mass fractions induce bubbles, both of which detrimentally affect the pumping performance. This study reveals the properties of ferrofluid and the effects of external environmental conditions on the morphological transformation of ferrofluid, providing references for optimizing ferrofluid pumps.