Direction Of Magnetic Field Research Articles

Dynamic Modeling and Guidance Analysis of a Ferromagnetic Continuum Robot with Geometric Discretization and Base Linear Motion

Abstract With the advancement of robotics in medicine in recent years, diverse and promising applications for ferromagnetic continuum robots (FCR)s have been introduced. These robots utilize an electromagnetic actuation system for movement and control, which leads to reduced tissue damage, significantly shorter surgery durations, and improved patient recovery times. Recent research in FCR modeling highlights the critical challenge of developing a dynamic model to assess system behavior in real-time, crucial for maximizing benefits in medical applications. In this paper, the geometric discretization method and Lagrange's principle are used to derive the dynamic equations of an FCR under the influence of an external magnetic field. Using the proposed method, the system's dynamic equation is formulated as a set of second-order differential equations solvable in real-time. This approach enables the examination of the system's behavior at any given moment, providing a suitable foundation for designing various controllers based on the model. Furthermore, to complete and develop the robot's steering system, an algorithm considering the base's linear motion is presented. Given the electromagnetic system used in steering the FCRs, an analysis of the magnetic field in both ideal and real conditions is conducted to enhance reliability for medical applications. Finally, to evaluate the performance of the proposed theoretical framework in dynamic modeling, the deformation of two robots under the influence of an external magnetic field will be analyzed. Simulation results indicate that the robots deform in a direction different from the magnetic field direction, demonstrating non-planar deformation characteristics. Furthermore, comparison with experimental data demonstrates that the theoretical framework accurately predicts the robot's deformation, with calculation errors less than 5%.

Effect of longitudinal direct current magnetic field and heat treatment composite process on microstructure and mechanical properties of 2319 aluminum alloy WAAM

Wire arc additive manufacturing (WAAM) had been proven to be viable for producing large metal components. However, its optimal performance had been limited by defects such as porosity, elemental segregation, and coarse grains. This study had introduced a composite process of applying a direct current magnetic field along with heat treatment to improve the microstructure and mechanical properties of the specimens, while also comparing changes under four different conditions. The results had indicated that applying a direct current magnetic field had expanded the arc and improved the macroscopic morphology. With a direct current of 2A, the specimen had the fewest macropores, making it the optimal parameter. After applying the magnetic field alone, porosity had significantly decreased, with a reduction of 0.43% compared to the blank specimen, and the average pore volume had decreased by 10.45mm³ compared to the blank specimen. After the composite application of the magnetic field and heat treatment, the proportion of recrystallization had increased, Cu element segregation had been notably improved, maximum texture strength had decreased, the proportion of high-angle grain boundaries had increased, and porosity improved by the magnetic field had increased. In terms of mechanical properties, the average microhardness had reached 206.2 HV, an increase of 104.36% compared to the blank specimen. The longitudinal average tensile strength had reached 387.9MPa, a 63.3% improvement over the blank specimen. Anisotropy had decreased, while elongation had been reduced.

The effect of hydrostatic pressure on electric transport properties of bulk black arsenic phosphorus single crystals

Black arsenic phosphorus AsxP1-x (b-AsxP1-x), as a novel two-dimensional material, has recently attracted great attention owing to their exotic physical properties. Here, we report a systematic study of the pressure dependence of electric transport properties in b-As0.75P0.25 single crystal. At ambient pressure, b-As0.75P0.25 shows an extrinsic semiconducting behavior, and the magnetoresistance (MR) has an obvious dependence on the magnetic field direction, resulting in an anisotropic MR effect. With the applied hydrostatic pressure, the crystal exhibits a tendency towards metallic behavior, whereas at pressures above 1.0-1.3GPa, the resistivity starts to increase at low temperatures. This picture is simultaneously supported by low temperature high-pressure MR measurements. Taking into account the negative and positive contributions to the MR, we have been able to propose a modified two-band model to describe the MR properties. The analysis of the MR data reveals the coexistence of high-mobility electrons and holes with nearly identical carrier densities. Above the critical pressure, the density of the electron that remains dominant increases with pressure while the electron mobility decreases significantly under pressure, leading to a transition in resistivity. This work has implications to both the fundamental understanding of bulk b-As0.75P0.25 and studies of two-carrier correlated materials.

Flux jumps, cluster distribution model and vortex phase diagram of oxygenated YBa2Cu3-xAlxO6+δ single crystals for H|| ab

This work reports magnetic field direction dependent second magnetisation peak (SMP) anomaly in single crystals of oxygenated for ab. Detailed investigations on crystal A revealed the direction dependence of SMP anomaly at temperatures below 25 K, above which the direction dependence vanishes. The state of spatial order of the vortex lattice was found to be correlated to the vortex lattice symmetry that underwent a change at certain fields and was captured via single flux jumps observed in the third and fifth quadrant of magnetisation hysteresis loops. Bean’s critical state profiles drawn to explain the flux jumps required the presence of clusters of in the basal plane of with closely lying binding energies. Large full width at half maximum observed in Cu, O, Y and Ba photoelectron spectra confirmed the validity of the proposed cluster model. A vortex phase diagram incorporating all features in the magnetisation hysteresis loops has been made for oxygenated for || ab depicting various phases.

Magnetic Field-Induced Control of Crystal Orientation in Porous CuNi Films for Enhanced Electrocatalytic Hydrogen Evolution.

Porous CuNi films are promising candidates for electrocatalytic water splitting, with their catalytic performance largely influenced by the crystallographic structure and chemical state. In this study, by employing a magnetic field-controlled bubble template-assisted electrodeposition method, CuNi films with a preferred Ni(111) crystal orientation were synthesized. Moreover, adjusting the magnetic field direction during deposition can affect the degree of preferred orientation and, consequently, the electrochemical activity of the films. The deposited porous CuNi films under the up/down Lorentz force conditions show a preferred orientation along the Ni(111) direction, although the extent of this orientation varies. For the sake of comparison, porous CuNi films electrodeposited under the condition of magnetic stirring and undistributed were also synthesized. The electrochemical performance was evaluated using cyclic voltammetry and Tafel analysis, revealing that the preferred Ni(111) orientation enhances hydrogen atom migration, thereby improving the hydrogen evolution reaction (HER) efficiency. The porous CuNi film deposited with upward Lorentz force exhibits the highest HER activity, and the onset potential is as low as -3 mV vs a reversible hydrogen electrode (RHE). This work emphasizes the importance of the magnetic field in optimizing the crystal orientation and electrochemical performance of CuNi films for sustainable energy applications.

Effect of magnetic field on mass transfer at esa

The study analyzed the effect of magnetic field (value and direction) on mass transfer at electro-spark alloying (ESA). It was experimentally established the increase the productivity of ESA process by additional action of the magnetic field.

Modeling Magneto-Active Soft Robots in Vessels Based on Discrete Differential Geometry of Framed Curves

Abstract Cardiac arrhythmias, such as atrial fibrillation, pose significant health risks and are often treated using minimally invasive cardiac ablation. However, the limited maneuverability of mechanically driven catheters can undermine both the success and efficiency of the procedure. In contrast, magnetic soft continuum robots (MSCRs) offer a promising alternative by utilizing external magnetic fields to directly steer the catheter tip. This approach allows for precise control, simplifying navigation through intricate vascular systems, ensuring stable contact with lesions, and minimizing manual manipulation. To optimize the use of MSCRs in magnetically assisted cardiac ablation, it is crucial to model their behavior, focusing on contact with the vascular environment. This article establishes a theoretical model of MSCRs based on Cosserat beam theory and discrete differential geometry (DDG). The model is validated and subsequently used to simulate three scenarios: partially magnetized MSCRs, MSCRs with point contacts, and MSCRs with line contacts. The results reveal significant nonlinear behavior upon contact. By applying our model, we demonstrate how adjustments of the magnetic field's direction, magnitude, and MSCR length can guide navigation through bifurcated vessels and achieve precise contact with a lesion. These findings provide valuable insights into the design and control of MSCRs, enabling more efficient, simulation-driven guidance for minimally invasive procedures and advancing digital health care in endovascular applications.

Magnetic field quality conversion factors experimentally measured in clinical MR-linac beams for seven MR-compatible ionization chamber models.

The purpose of this work was to experimentally quantify MR-compatible ionization chamber response for 1.5T Elekta Unity and 0.35T ViewRay MRIdian MR-linac systems through the determination of the magnetic field quality conversion factor, kB,Q. Seven MR-compatible ionization chamber models from Standard Imaging and PTW were evaluated. Both the quality conversion factor kQ and the magnetic field quality conversion factor kB,Q were experimentally determined through a cross-calibration method. Specifically, the ratio of absorbed dose measured with a reference A1SL chamber under reference conditions to corrected output measured with each test chamber at the same point of measurement allowed for the determination of kB,Q. The angular dependence of the magnetic field quality conversion factor for MR-compatible chamber models was assessed for the 1.5T Elekta Unity system by measuring kB,Q with the chamber axis and magnetic field direction aligned at cardinal angles (0°, 90°, 180°, 270°). Beam quality conversion (kQ) factors for MR-compatible ionization chambers measured in a standard linac beam showed an average percent difference of -0.09±0.18% compared to computed kQ values for their conventional chamber versions. Similarly, magnetic field quality conversion (kB,Q) factors for corresponding MR and non-MR ionization chamber models measured using the same cross-calibration technique demonstrated average percent differences of -0.1±0.3% and 0.0±0.2% for the Elekta Unity and ViewRay MRIdian, respectively. Investigation of the angular dependence of this correction factor demonstrated identical chamber response for equivalent MR-compatible and conventional chamber models. This work provides critical experimental validation of MR-compatible ionization chamber performance, with a direct comparison of measured kB,Q values to corresponding conventional chamber models demonstrating nearly equivalent chamber response. kB,Q values determined using our experimental method will serve as an important reference for upcoming MR-linac reference dosimetry protocols and ultimately represent an important step towards accurate output calibration of MR-linac systems.

Magneto-Photonic Effect of Fe3O4@SiO2 Nanorods for Visualizing the Direction of Magnetic Fields with High Spatiotemporal Resolution.

In this work, we demonstrate the visualization of the complex magnetic fields by utilizing the magneto-photonic effect of Fe3O4@SiO2 nanorod suspension with one-to-one correspondence between the visible colors and magnetic field directions. The selected anisotropic nanorods possess appropriate saturated magnetization and high electrostatic repulsion, which is magnetically direction-responsive but strength-insensitive, accurately detecting the field direction while eliminating the influence from intensity. The combined experiment-simulation study validates the accuracy of the simulation, allowing us to further determine the intensity distribution of the magnetic field. The packed photonic device's high spatial (∼20 μm) and temporal (∼1 ms) resolutions were confirmed by time-resolved ultrasmall-angle X-ray scattering (USXAS) tests, as well as observations using an optical microscope and a high-speed camera. Our work provides a new technique for visualizing magnetic fields and opens an avenue toward further studying and utilizing complex magnetic fields for various purposes.

Incoherent scattering ion line spectra of vortex beams by magnetized ionospheric plasma with bi-Maxwellian distribution

Abstract Incoherent scattering theory is one of the important means of plasma parameter diagnosis. The incoherent scattering of vortex beams carrying orbital angular momentum can bring new incremental information to plasma diagnosis. Based on the angular spectrum theory of Bessel vortex beams and the theory of incoherent scattering, this paper studies the incoherent scattering of the ionospheric magnetized plasma to vortex electromagnetic waves under the bi-Maxwellian distribution along the magnetic field drift. The numerical results show that when the angle between the scattering wave vector and the magnetic field direction is small, the ion spectral lines have an obvious frequency shift. When the angle is close to 90°, the ion line spectra produce harmonic oscillation, and the drift speed restrains this oscillation phenomenon. The linear Doppler shift will shift the spectral line as a whole, while the rotating Doppler shift of the vortex beam will weaken the spectral line oscillation. This work may provide a possibility for further research on the scattering of vortex beams by magnetized plasma and the development of ionospheric plasma irregularities parameter inversion.

5 cm OH Masers in Northern Star Formation Regions

We present a 6.0 GHz excited-state OH maser survey toward 155 northern star formation regions utilizing the Shanghai Tianma Radio Telescope. In total, we detect 44 6.0 GHz OH masers, 8 of which are new detections (one at 6016 MHz, two at 6030 MHz, and five at 6035 MHz). Of these 44 detected 6.0 GHz OH masers, 13 sites exhibit 6030 MHz OH masers, all 44 sites show the 6035 MHz transition, one site (G009.620+0.194) has the only 6016 MHz OH maser, and one site (W3(OH)) shows the only 6049 MHz OH maser. The 6016 MHz OH maser is the first OH maser of this transition detected in star formation regions. Investigations of the association between 6030/6035 MHz OH masers with 1665 MHz ground-state OH, 6.7 GHz methanol, and 22 GHz water masers show that 1665 MHz OH masers are good indicators of 6.0 GHz OH masers (29% detection rate), which is consistent with previous results. The majority (more than 77%) of 6030 and 6035 MHz OH masers are associated with 6.7 GHz methanol and/or 22 GHz water masers. Comparison between our spectra with previous spectra, we find that only two sources remain fairly stable since their discoveries. We identify 80 Zeeman pairs in 32 6.0 GHz OH maser sites with typical magnetic field strengths of less than 10 mG. The magnetic field directions derived from these 32 maser sites with Zeeman pairs are consistent with previous work, which indicates that the 6.0 GHz OH masers may be potential tracers of the large-scale Galactic magnetic field.

Magnetic field induced anomalous shift of plasmon resonance peak in Al-based plasmon-polariton photodetectors

The influence of magnetic field on Ψ(λ) and Δ(λ) dependences of Al-based plasmon-polariton photodetectors (PPPD) at different magnetic flux densities (100 and 300 mT) and magnetic field directions was investigated. It was obtained that the action of the magnetic field results in the shift of the surface plasmon resonance peak (SPR) position and a change in its intensity. Particularly, in the configuration ( and are collinear) the noted effects were the most pronounced. Additionally, it was found that the magnetic-induced effects are sensitive to the angle of incidence, particularly they enhance with decreasing the angle of incidence. Therefore, they were the most pronounced at the smallest angle in our experiment (20°). The possible physical mechanisms of observed phenomena are discussed. The obtained results can open up new opportunities in the design of optoelectronic sensors of the magnetic field or high-speed optical modulators.

Spatial magnetic force and magnetic energy density analysis of microsphere medium in high gradient magnetic fields: a 3D simulation

Abstract High gradient magnetic separation technology is the key technology for green and efficient separation and purification of mineral resources. Existing studies are vague about the division of the attraction and repulsion zones of the medium, and there are fewer explorations of the effect of various conditions on the attraction zones. In this work, a novel method for calculating the magnetic force is derived, which provides an accurate calculation of the 3D magnetic force. The attraction and repulsion zones are divided clearly by analyzing the relationship between the spatial angle of the spherical medium and the magnetic force density per unit volume, with the magnetic force density per unit volume tangent to the spherical surface as the dividing line. The attraction and repulsion zones are divided by β = 30°~35°, and the attraction region accounts for 45%~50% of the total space volume. Furthermore, the influence of different conditions on the attraction zone is studied. It was found that the zone of attraction decreases as one moves away from the spherical medium, which results in an ellipsoid with the effective zone of attraction of the spherical medium having the magnetic field direction as its long axis. The attraction region increases from 45.49% to 49.87% of the space occupied with increasing the relative permeability of the spherical medium. It does not affect the proportion of the attraction zone in space by changing the background magnetic field and the size of the spherical medium, but it will change the depth of the magnetic force. It provides a theoretical basis for the design of high-efficiency magnetic media, and gives a reference for further improving the selection effect of high gradient magnetic separation technology on fine and weak magnetic particles.

Research on magnetic field distribution characteristics of 2G-HTS dynamo in superconducting wireless power supply applications

Abstract The high-temperature superconducting (HTS) dynamo injects direct current (DC) into the winging of superconducting machines through non-electrical contact, solving issues such as thermal leakage in traditional current leads and current decay due to flux motion, joint resistance and AC losses. However, it has been observed that the DC output voltage decreases with an increasing air gap between the rotor magnet and HTS stator. To increase the output of the HTS dynamo at a fixed gap, this study employs an efficient numerical model based on the equivalent current method to investigate the magnetic field distribution of the magnets with different structural parameters. The relationship between the magnetic field distribution of the rotor magnet and the open-circuit voltage of the stator is established and extensively validated against simulation modeling and experimental data. Experimental results indicate that the rotor’s magnetic field distribution and the stator’s magnetic field penetration influence the open circuit voltage of the HTS dynamo. Specifically, when the distance between adjacent magnets is large, the magnetic field penetration occurs only on both sides of the stator, causing circuit voltage to increase initially and then decrease with the magnet distance decreases. A reverse point opposite to the magnetic field direction on both sides is generated at the center of the stator when the distance decreases further, which increases the average induced current density, and suppresses the downward trend. By optimizing the magnetic field distribution of the rotor magnets on the stator, the DC output power of the dynamo can be effectively improved. This model and the results contained in this article provide a comprehensive theoretical basis for researchers to compare and optimize their own modeling and experiment of the HTS dynamo.

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.

A Special Kind of Interplanetary Coronal Mass Ejection

Abstract It is generally believed that Coronal mass ejections (CMEs) have magnetic flux rope structures because of their helical shapes. However, only about 30-40% of interplanetary CMEs (ICMEs) have a local magnetic flux rope structure. The usually explanations are that the spacecraft only crossed the flank of the ropes and failed to detect the complete magnetic flux rope structure, or some processes destruct these magnetic flux rope structure. Several studies suggest that some ICMEs inherently possess disordered magnetic fields and consequently exhibit no magnetic flux-rope structures. We introduce a special kind of ICMEs. They have low magnetic field magnitude and stable magnetic field direction, relatively fast expansion speed, lower proton temperature and density. Their all three measured magnetic field components are relatively stable. We want to know whether these ICMEs also have magnetic flux rope structures or not. We identified 20 special ICMEs and analyzed their evolution based on their observed characteristics. We took a special ICME as example, which had apparent rope configuration at 1 AU but evolved to a special ICME at 5.4 AU, to illustrated that this kind of ICMEs may come from magnetic clouds (MCs) whose rope structure had been being stretched due to expansion. We inferred that the missing of obvious flux rope structure may be due to the expansion of MCs, not the flank crossing effect. However, more than 50% of the events were associated with dominant x-component of the magnetic filed, which indicates a leg crossing. Therefore, the detection of part of these special ICMEs may also be results of leg crossing effect.

Comparative Analysis of Higher‐Order Ionospheric Delay on PPP Long‐Term Coordinate Time Series and Residual Modeling Using Horizontal Gradients and RINEX Data

AbstractHigher‐order ionospheric corrections, including second‐ and third‐order effects and signal bending, are essential for improving Global Navigation Satellite System (GNSS) time series accuracy. However, their influence on long‐term Precise Point Positioning (PPP) time series, particularly signal bending, remains underexplored. Most studies rely on Global Ionosphere Maps (GIMs) for second‐order delay corrections due to the complexity of RINEX‐based inversions. Analyzing data from 37 International GNSS Service stations (2009–2020), we found that higher‐order ionospheric effects predominantly impact the North component of mid‐ and low‐latitude stations. Second‐ and third‐order delays contribute 50% and 20% to annual and semi‐annual amplitudes, respectively, while signal bending accounts for 5% and 2%. Additionally, signals traveling along the magnetic field direction induce phase delays, with equatorial regions experiencing more frequent and intense ionospheric activity. This leads to maximum horizontal velocity impacts of 0.45 mm/yr at the equator and a distinct southern trend at mid‐ and low‐latitudes. GIM‐based corrections increase seasonal signal amplitudes and root mean square error (RMSE) at some stations due to discrepancies with RINEX‐based corrections, which generate higher‐order ionospheric residuals. These residuals contribute 48.6% of the RMSE in RINEX‐based corrections, surpassing the 39.8% from second‐ and third‐order delays. To address this, we propose a GIM‐based residual model incorporating horizontal gradients, reducing RMSE by 48%, 26%, and 52% for the East, North, and Up components, respectively. Monthly or quarterly gradient updates during quiet ionospheric periods ensure precise corrections, enhancing GNSS time series and coordinate system accuracy.

Comparison of Direct Magnetic Field Measurements in a Sunspot by Ten Spectral Lines of Fe I, Fe II, Ti I, and Ti II

Comparison of Direct Magnetic Field Measurements in a Sunspot by Ten Spectral Lines of Fe I, Fe II, Ti I, and Ti II

High sensitivity direct magnetic field detection based metrology for ultra-thin magnetic films and Li-ion cells.

Ultra-low magnetic field sensing is emerging as a tool for materials' diagnostics, particularly for the operando studies of electrochemical systems. A magnetic metrology system having the capability of sensing fields as low as ∼1.88 pT has been setup for such studies using a commercial atomic magnetometer. The magnetometer setup is isolated from environmental perturbations, such as mechanical vibrations, electrical noises, and ambient magnetic fields, in order to measure small signals from the samples under study. Magnetic field measurements on ferromagnetic (permalloy, Ni0.8Fe0.2) thin films, monolayers of MoS2, vanadium doped MoS2, and lithium electro-deposited copper electrodes are performed to demonstrate the sensitivity of the setup. Magnetic field scanning of commercial Li-ion cells has also been performed using this magnetic metrology method, indicating the scope of the setup for operando diagnostics.

Assessment of fiber alignment through combined driven oscillatory and directional magnetic fields in matrix with similar rheological behavior to cementitious materials

In this paper a novel method to improve the effectiveness of the aligning of fibers used as reinforcement in Fiber Reinforced Cementitious Composites (FRCC) through directional homogeneous magnetic fields is proposed. A combination of homogeneous magnetic fields, oscillatory and directional, are assessed as a new method for fiber aligning which increase the aligning index and mechanical efficiency index of the fiber in cementitious composites. Fresh cementitious materials present a Static Yield Stress (T0s), which must be overpassed to allow the rotation of the fiber immersed in the matrix. To reduce the T0s of the matrix, oscillatory magnetic fields (OMF) are applied firstly, as they generate a vibrational strain of the fiber. Later, fibers are aligned through a directional magnetic field which finds a lower opposition of the rheological torque. The fibers are subjected to an orientation rotation caused by the magnetic field, which is caused by a magnetic torque. This torque is opposed by two torques, one of rheological origin (Yield stress and viscosity) and another of inertial type (geometry and mass distribution of the fiber). The rheological torque is the torque that opposes to the rotation of the fiber and is a function of the rheological properties of the matrix. Two pairs of Helmholt coils have been used in this research, to be able to generate orthogonal magnetic fields to directional magnetic fields. When the OMF was generated, one of the pair of coils were connected to the net, with a frequency of 50 Hz. OMF was performed in 0.64mT-1.25mT-2.18mT. To evaluate its effectiveness each of them was applied in periods of time of 2–5–7–10 seconds before the directional magnetic field of 30 mT. To assess the method steel fibers has been submerged in a metaphor fluid to reproduce the rheological properties of cement materials. The initial and final angles of the batch of fibers have been determined through photography and Computer-aided design. The results obtained shown that the use of OMF increases the alignment index up to 35 % and the mechanical efficiency rate up to 24.35 % in the batches studied. The research followed also showed that previous vibration can be applied during periods of 5 seconds, with the same pair of coils that for aligning but also the use of the two pair of coils can be used simultaneously.