Magnetic Array Research Articles

Flexible Anisotropic Magnetic Micropillar Arrays for Precision Directional Recognition in Human–Machine Interactions

Flexible Anisotropic Magnetic Micropillar Arrays for Precision Directional Recognition in Human–Machine Interactions

Analysis of RF modes in an in-vacuum undulator

Electron storage rings commonly use in-vacuum undulators (IVUs) consisting of magnet arrays positioned closely above and below the electron beam to create a bright, tunable and broad spectral range with narrow peaks. These devices present several challenges to the electron beam dynamics since the magnets come within a few millimetres of the beam and a vacuum chamber around the magnets results in discontinuities in the otherwise smooth chamber. This paper analyzes the radio frequency (RF) eigenmodes that exist in the IVU chamber which have been observed at other facilities and may excite beam instabilities. An equivalent RF circuit for the IVU confirms the TEM-nature of the eigenmodes. To eliminate the problematic modes induced in IVU device that may lead to beam instabilities, a conceptual solution is proposed and initial simulations are presented.

Design and implementation of a nondestructive testing system for magnetic field imaging based on machine learning

This study presents the design of a nondestructive testing (NDT) system for detecting metal defects using a magnetic field sensor array. The system integrates a hardware-software detection framework that includes parallel computation and processing cores, along with multiple anisotropic magnetoresistance (AMR) sensors. These AMR sensors capture subtle variations in the magnetic field, which serve as the foundation for defect identification. The system enables synchronized data acquisition from multiple AMR sensors, achieving multi-axis data fusion and parallel signal processing. Furthermore, the detection system gathers defect features to train an NDT system based on machine learning (ML). Subsequently, ML-generated defect imaging features are processed through an imaging framework, producing magnetic field imaging (MFI) for precise defect localization. The study tested six different metal samples with various defect sizes and types to validate the system. The results demonstrate the system’s ability to accurately detect and identify different defects, highlighting the high precision of magnetic field detection and the overall effectiveness of the proposed system for NDT.

Fabrication of Ultrafine L10-FePt-Based Magnetic Patterns Enabled by Single-Step Nanoimprint-Assisted Block Copolymer Self-Assembly.

The bit islands in magnetic patterns play a crucial role in advancing magnetic recording density, but the trade-off issues between miniaturization and scalable production are still challenging. Here we present a two-in-one technique of nanoimprint lithography (NIL)-assisted self-assembly using a specially engineered FePt-containing block copolymer (BCP), offering a simple one-step fabrication for L10-FePt bit-patterned media with high throughput. This method combines top-down NIL with bottom-up self-assembly to precisely control the ultrafine magnetic bits in the nanoscale patterns. The FePt-derived BCPs, designed with an equal atomic ratio of Fe and Pt, ensure the preparation of homogeneously dispersed L10-FePt nanoparticles (NPs). Subsequent BCP pyrolysis results in NPs with enhanced magnetic properties, significantly advancing high-density data storage devices. This strategy offers a novel approach to drive the innovative creation of ordered magnetic metal alloy NPs arrays for practical applications.

Research on Magnetic Field of Permanent Magnet Rolls Arranged Periodically in Circumferential—Axial Direction

The separation of non-magnetic non-ferrous metals such as copper and aluminum from scrapped automobiles is a critical area of research due to the increasing number of end-of-life vehicles. Traditional eddy current separation methods have limitations, particularly in handling large-sized broken copper and aluminum parts. This paper proposes a novel magnetic roller model featuring a circumferential–axial periodic arrangement of permanent magnets. This study explores the external magnetic field distribution of this new roller design by constructing an equivalent current model, solving magnetic scalar potential equations, and employing simulation tools. The findings indicate that the new magnet array enhances both the magnetic field strength and the range of the external magnetic field, leading to improved separation efficiency of large-sized metal fragments. The results provide a theoretical basis for advancing the separation technology of large-sized broken copper and aluminum parts in scrapped automobiles, offering potential improvements in the recycling of non-ferrous metals from end-of-life vehicles.

B-167 Quantification of Thyroglobulin in Serum for Clinical Research using SISCAPA Workflow Combined with LC-MS/MS

Abstract Background Accurate measurement of Thyroglobulin (Tg) using existing immunoassay-based techniques can be challenging in the presence of anti-Tg antibodies (TgAb), which can prevent the binding of Tg to assay antibodies thus leading to non-quantifiable Tg concentrations. The Stable Isotope Standards and Capture with Anti-Peptide Antibodies (SISCAPA™) Workflow combined with LC-MS/MS has been successfully employed to circumvent this problem by digesting the serum sample thus eliminating interfering TgAb and measuring a Tg-specific surrogate peptide instead. Methods Using a Andrew+™ Pipetting Robot, denaturation and reduction buffer was added to 250µL serum samples and incubated at 37°C. Internal standard and trypsin were added and samples incubated at 37°C. The samples were quenched with protease inhibitor and Anti-Tg FSP mAb SISCAPA was added to the serum samples and mixed for 60 minutes. Using a magnetic array plate, the beads were left to pull down, samples were discarded, and the beads were twice washed with PBS/CHAPS prior to elution with acetonitrile with formic acid. Using an ACQUITY™ UPLC™ I-Class PLUS FL System, samples were injected onto a Waters™ XSelect™ HSS T3 Column using a water/acetonitrile/formic acid gradient elution profile and the Tg FSP peptide was quantified using a Waters Xevo™ TQ Absolute Mass Spectrometer. Results The method demonstrated no significant carryover or matrix effects and was shown to be linear from 0.1 - 50 ng/mL. Analytical sensitivity investigations indicate the analytical sensitivity of this method would allow precise quantification (<20%) at 0.1 ng/mL with S/N (PtP) >10:1. Coefficients of variation (CV) for total precision and repeatability on 5 analytical runs for low, mid and high QCs were all < 9.5% (n = 25) for both automated and manual precision assessments. Comparison with samples from the UK NEQAS scheme demonstrated significant method bias of -40% for the developed LC-MS/MS method. Re-assignment of the calibrator concentrations using the EQA samples reduced the bias to -5.5%, indicating differences in the calibration materials used for these measurements. Conclusions A LC-MS/MS clinical research method for serum thyroglobulin was developed using SISCAPA, followed by analysis using ACQUITY UPLC I-Class PLUS FL System and the Xevo TQ Absolute Mass Spectrometer. The method provides analytical sensitivity down to 0.1 ng/mL from 250 µL serum, while providing sufficient sample for re-analysis. The method demonstrates excellent linearity across the calibration range, with no significant carryover, interferences, and matrix effects. Total reproducibility and repeatability of the method was ≤9.5% RSD for manual and automated sample preparation, using the Andrew+ Pipetting Robot. In addition, the Andrew+ Pipetting Robot can minimize user touch-time, allowing a full plate to be prepared within four hours without user intervention.

Study on the Accurate Magnetic Field Analytical Model of an Inertial Magnetic Levitation Actuator Considering End Effects

To address the demand for low noise and high stealthiness in ships and other vessels, this paper innovatively proposes an inertial magnetic levitation actuator based on non-uniform-sized Halbach permanent magnet arrays. To improve control accuracy, it is necessary to establish an accurate analytical model of the magnetic field and then obtain an accurate electromagnetic force model. However, the distortion of the magnetic field at the ends produces end effects, resulting in thrust fluctuations that affect the actuator’s control accuracy. Therefore, considering the end effects is necessary to establish an accurate analytical model of the magnetic field. To analyze the end leakage magnetic field of the Halbach array, the concept of a mechanical pseudo-cycle in the actuator is proposed, and the cycle of a Fourier series is redefined. A completed analytical expression of the Halbach array magnetic field distribution is derived by the new Fourier series, in which the end leakage magnetic field is contained. The accuracy of the proposed method is verified by solving the analytical model of the magnetic field, and the analytical results are compared with finite element simulations and experimental tests.

Elliptical Halbach magnet and gradient modules for low-field portable magnetic resonance imaging.

This study aims to develop methods to design the complete magnetic system for a truly portable MRI scanner for neurological and musculoskeletal (MSK) applications, optimized for field homogeneity, field of view (FoV), and gradient performance compared to existing low-weight configurations. We explore optimal elliptic-bore Halbach configurations based on discrete arrays of permanent magnets. In this way, we seek to improve the field homogeneity and remove constraints to the extent of the gradient coils typical of Halbach magnets. Specifically, we have optimized a tightly packed distribution of magnetic Nd2Fe14B cubes with differential evolution algorithms and a second array of shimming magnets with interior point and differential evolution methods. We have also designed and constructed an elliptical set of gradient coils that extend over the whole magnet length, maximizing the distance between the lobe centers. These are optimized with a target field method minimizing a cost function that considers also heat dissipation. We have employed the new toolbox to build the main magnet and gradient modules for a portable MRI scanner designed for point-of-care and residential use. The elliptical Halbach bore has semi-axes of 10 and 14& cm, and the magnet generates a field of 87& mT homogeneous down to 5700& ppm (parts per million) in a 20-cm diameter FoV; it weighs 216& kg and has a width of 65& cm and a height of 72& cm. Gradient efficiencies go up to around 0.8& mT/m/A, for a maximum of 12& mT/m within 0.5& ms with 15& A and 15& V amplifier. The distance between lobes is 28& cm, significantly increased with respect to other Halbach-based scanners. Heat dissipation is around 25& W at maximum power, and gradient deviations from linearity are below 20% in a 20-cm sphere. Elliptic-bore Halbach magnets enhance the ergonomicity and field distribution of low-cost portable MRI scanners, while allowing for full-length gradient support to increase the FoV. This geometry can be potentially adapted for a prospective low-cost whole-body technology.

Design of Planar Permanent Magnet Array for Remotely Actuated Magnetic Micro Robots

Design of Planar Permanent Magnet Array for Remotely Actuated Magnetic Micro Robots

Magnetic augmentation through multi-gradient coupling enables direct and programmable profiling of circulating biomarkers

Conventional magnetic biosensing technologies have reduced analytical capacity for magnetic field dimensionality and require extensive sample processing. To address these challenges, we spatially engineer 3D magnetic response gradients for direct and programmable molecular detection in native biofluids. Named magnetic augmentation through triple-gradient coupling for high-performance detection (MATCH), the technology comprises gradient-distributed magnetic nanoparticles encapsulated within responsive hydrogel pillars and suspended above a magnetic sensor array. This configuration enables multi-gradient matching to achieve optimal magnetic activation, response and transduction, respectively. Through focused activation by target biomarkers, the platform preferentially releases sensor-proximal nanoparticles, generating response gradients that complement the sensor’s intrinsic detection capability. By implementing an upstream module that recognizes different biomarkers and releases universal activation molecules, the technology achieves programmable detection of various circulating biomarkers in native plasma. It bypasses conventional magnetic labeling, completes in <60 minutes and achieves sensitive detection (down to 10 RNA and 1000 protein copies). We apply the MATCH to measure RNAs and proteins directly in patient plasma, achieving accurate cancer classification.

An analytical model for a coaxial electromagnetic recuperator considering end effect

A coaxial electromagnetic recuperator (CER), leveraging the principle of tubular permanent magnet linear synchronous motor, has been introduced to mitigate the shortcomings of the traditional recuperator, including low reliability and uncontrollable counter-recoil motion. Firstly, the layout and structural scheme of the CER are presented, with the maximum recuperator force determined through a force analysis of the recoil process. Subsequently, by incorporating a virtual permanent magnet area at both ends of the permanent magnet array, a precise CER analysis model is developed. This model adeptly accounts for the end effect due to magnet length limitations and formulates expressions for air gap flux density, back electromotive force, and electromagnetic thrust. The analytical model’s accuracy is then validated against a finite element model. Finally, the key parameters influencing CER performance were improved, and the overall structure of the CER was refined, significantly enhancing its thrust capabilities.

Large-scale magnetic target state estimation using model parameter optimization

Abstract Aiming at the problem of non-negligible target scale in the state estimation of magnetic targets, a state estimation method that requires only the measurement data of a single three-axis magnetic sensor and is insensitive to the initial value is proposed. Firstly, the state estimation model of a single three-component magnetic sensor is established based on a magnetic dipole array. A signal preprocessing method is designed to reject useless signals and keep the waveform intact. Five swarm intelligent optimization algorithms such as Particle Swarm Optimization (PSO), Artificial Hummingbird Algorithm (AHA), Artificial Rabbits Optimization (ARO), Grey Wolf Optimizer (GWO), and Improved GWO (IGWO) are introduced to perform state optimization, and two methods, such as Conjugate Gradient Least Squares (CGLS), and Stepwise Regression (SR), are introduced to calculate the magnetic moment parameters, and PSO-CGLS, AHA-CGLS, AHA-CGLS, ARO-CGLS, ARO-CGLS, ARO-CGLS, ARO-CGLS, ARO-CGLS, ARO-CGLS, ARO-CGLS, ARO-CGLS, and ARO-CGLS are designed in combination. CGLS, ARO-CGLS, GWO-CGLS, IGWO-SR, IGWO-CGLS, and six state estimation methods. In order to address the problem that the parameter optimization range is too large, the state to be estimated is adjusted from the initial state to the state at the moment of the maximum value of the magnetic field modulus, and the method of positive transverse distance estimation is used to narrow the range of positive transverse position optimization. Finally, numerical simulation tests and ship model tests are used for verification, and the results show that the proposed methods are accurate and can meet the needs of precise target state estimation.&amp;#xD;

Effect of 1800 MHz radiofrequency field exposure on cytokine and signal transduction protein expression in differentiated THP-1 cells

Purpose To evaluate the effects of 1800 MHz continuous wave (CW) and global system for mobile communications (GSM) modulated radiofrequency electromagnetic field (RFEMF) exposures on signal transduction (ST) protein and cytokine expression in differentiated human-derived monocytic THP-1 cells. Materials and methods THP-1 cells were differentiated into adherent macrophage-like cells using phorbol 12-myristate 13-acetate (PMA). Following differentiation, cells were exposed to 1800 MHz CW or GSM modulated RFEMF for 0.5, 4, or 24 h at a specific absorption rate (SAR) of 0 (sham) or 2.0 W/kg. Concurrent positive controls (lipopolysaccharide for cytokines; anisomycin for ST proteins) and negative controls were included in each experiment. The expression levels of cytokines (GM-CSF, IFN-γ, IL-1β, IL-6, IL-10, TNF-α) from culture media and phosphorylated and total ST proteins (CREB, JNK, NF-κB, p38, ERK1/2, Akt, p70S6k, STAT3, STAT5) from cell lysates were assessed using Milliplex magnetic bead array panels. Results No consistent effect of RFEMF exposure was observed in differentiated THP-1 cells. A statistically significant effect of overall exposure condition was observed for IL-6 with GSM modulation (P = 0.042), but no difference between RFEMF and sham for any exposure condition remained following adjustment for multiple comparisons (P ≥ 0.128). No statistically significant effect of exposure condition was detected for any other cytokine evaluated with either of the RFEMF modulations (P ≥ 0.078). There were no statistically significant changes in expression levels for any of the ST proteins under any studied exposure condition (P ≥ 0.320). Conclusions In this study, no evidence of changes were observed in differentiated human derived THP-1 cells following exposure of up to 24 h to 1800 MHz RFEMF at SARs of 0 and 2.0 W/kg on the expression of ST proteins or cytokines.

Magnetic Sensor Array for Electric Arc Reconstruction in Circuit Breakers.

Noninvasive imaging of circuit breakers under short-circuit testing is addressed by recording the magnetic field produced over an array of external sensors and by solving an inverse problem to identify the causing current distribution. The temporal and spatial resolution of the sensing chain are studied and implemented in a physical set-up. A wire model is adopted to describe electrical current distribution. Additionally, the simpler, more direct approach to evaluating the passage of electric current in front of sensors is proposed. The dynamics of suitable approximating models of the electric arc that forms across contacts is obtained and agrees with multi-physical simulations and with experimental time histories of current and voltage. The two methods are flexible and allow the analysis of different types of circuit breakers.

A Semi-Analytical Approach for the Optimization of High-Speed PMSM With Halbach Magnet Array

A Semi-Analytical Approach for the Optimization of High-Speed PMSM With Halbach Magnet Array

Design Considerations of High-Speed PMSM With Nonuniform Two-Segment Halbach Magnet Array

Design Considerations of High-Speed PMSM With Nonuniform Two-Segment Halbach Magnet Array

Performance enhanced magnetic negative stiffness eddy-current damper: Numerical simulation and experimental investigation

Passive negative stiffness dampers (NSDs) possess significant advantages and promising application prospects in the field of structural vibration control. NSDs with high energy dissipation capability are desired to satisfy the vibration mitigation requirements for large-scale engineering structures, such as high-rise buildings and long-span bridges. However, in practical applications, due to the constraints of mounting space and additional weight, the negative stiffness and damping coefficient of existing NSDs are generally not very large and with poor adjustability. To overcome these limitations, this study develops a novel magnetic negative stiffness eddy-current damper (MNSECD) with enhanced overall performance. This damper consists of a magnetic negative stiffness system (MNSS), a multi-layer-plate-type eddy-current damping system (ECDS) in parallel, and a bidirectional ball screw transmission system. Firstly, different magnetic arrays are designed to optimize the magnetic fields of the MNSECD, and to enhance its magnetic negative stiffness and eddy-current damping without adding extra dimensions and weight. Subsequently, the electromagnetic finite-element models (FEMs) of the MNSECD are established to precisely simulate its magnetic negative stiffness and eddy-current damping forces, and these models are further utilized to elucidate the enhancement mechanism of different magnetic arrays. Finally, based on the numerical simulation results, the best performing magnetic array is selected respectively for the ECDS and MNSS systems to carry out experimental studies on a small-scale prototype. Numerical and experimental results indicate that the selected magnetic array for the MNSS proves highly effective in enhancing the magnetic negative stiffness of the MNSECD, while the selected magnetic array for the ECDS also demonstrates superior effectiveness in enhancing the eddy-current damping of the damper. These findings suggest that the novel MNSECD can be readily used in the vibration control of large-scale engineering structures.

New high-field side magnetic probe array system for three-dimensional magnetic fluctuation measurements on EAST

To better study the magnetic fluctuations in the high-field side of EAST tokamak, a new high-field side magnetic probe array (HFS-MPA) has been developed on EAST recently. The HFS-MPA consists of 12 identical three-dimensional (3D) magnetic probes, which are mounted on the HFS wall with carefully designed arrangement. The HFS-MPA magnetic probes bring additional toroidal magnetic fluctuation measurements compared with the HFS regular magnetic probes which can only provide poloidal and radial magnetic fluctuation measurements. The upper limits of frequency and toroidal mode number (n) measurements of the magnetic fluctuations have been improved by comparing HFS-MPA with the HFS regular magnetic probes, i.e., 650 kHz vs 100 kHz and n = 23 vs n = 1. In developing the HFS-MPA diagnostic system, many practical challenges have been overcome and many special designs have been developed. These will be mentioned in the main subsystem description of the HFS-MPA diagnostic in this paper, which might be useful for developing new magnetic probe diagnostics in the future on EAST or other magnetically confined fusion devices. The calibration of the effective area and frequency response of the HFS-MPA is also described. The preliminary application in studying the frequency and propagation characteristics of the magnetic fluctuations with HFS-MPA compared with EAST regular magnetic probes shows that the HFS-MPA is well developed for plasma physics studies.

Experimental study of DC excitation effect on the performance of moving coil linear compressor

In this paper, a novel Multi-loop Moving Coil Linear Compressor (M-MC-LC) is studied, in which the piston is driven by the Co-core Bilateral Reverse Coil (CBRC) in a reciprocating motion within the magnetic array. The DC excitation technique is introduced to address the phenomenon that the piston is axially offset under the influence of gas force. In order to clarify the effect of DC excitation on the performance of the moving-coil linear compressor, the compressor prototype is developed, and the dynamic performance testing test-bed and the refrigeration performance test-bed are built to qualitatively and quantitatively analyze the relevant performance parameters of the compressor from theoretical and experimental aspects. The results show that when the DC excitation accounts for less than 20% of the total input voltage, the pressure ratio increases with the increase of DC excitation; when the percentage is at 22.9%, a sudden drop in the volumetric efficiency of compressor occurs. Mass flow and COP increases first and then decreases with the increase of DC voltage excitation. The study results provide a guideline for the stable and reliable operation of the system and provide a valuable reference for the linear compressor piston offset adjustment.

Forward modeling of single-sided magnetic resonance and evaluation of [formula omitted] fitting error based on geometric analytical method

Single-sided magnetic resonance (SSMR) offers advantages of portability and noninvasive measurement for water detection, with significant potential applications in groundwater exploration, petroleum well logging, and soil moisture monitoring. However, the inherent highly inhomogeneous static magnetic field and radiofrequency (RF) field in SSMR necessitate the utilization of the Carr–Purcell–Meiboom–Gill (CPMG) sequence measurement scheme. To accelerate forward modeling during pulse excitation, we introduce a Geometric Analysis Method (GAM) and assess T2 error using its primary parameters. The GAM involves applying spatial geometric rotations on the magnetization vector, leading to an analytical solution to the Bloch equation that disregards relaxation effects. Compared with the rotation matrix (RM) method, the GAM demonstrates high accuracy and reduces computational time by approximately 20.9%. By analyzing the primary parameters governing the magnetization vector in the analytical formula, we evaluated their impact on the transverse relaxation time (T2) obtained through fitting the SE signal. Ultimately, the forward modeling results of the CPMG sequence within the region of interest (ROI) of a single-sided Halbach magnet array are validated. The T2 fitting error increases as the primary parameters deviate from the ideal values, highlighting their significant role in the T2 fitting results. This study provides a theoretical foundation for optimizing the design of SSMR magnets and RF coils.