Magnetic Sheet Research Articles

Process Development of Screen-Printed Magnetic Sheets for Electric Machines via Statistical Design of Experiments

Electrical machines play a major role in achieving a more sustainable economy by driving the further electrification of industry and transportation. To enhance the electric motor productivity during production and the efficiency during operation, it is essential to maximize the material yield rate during the production of stator and rotor sheet stacks and reduce iron losses during operation. Screen-printing technology can help to achieve these goals by producing thin magnetic sheet laminations in near-net-shape geometry, resulting in minimum material waste during production. Moreover, reducing the sheet thickness decreases the eddy current losses and avoids mechanical stress during manufacturing, leading to improved motor efficiency. Additionally, screen printing facilitates the production of multi-material components and variable alloy compositions. This study aims to identify the relevant factors and printing parameters so that screen-printed magnetic sheets can achieve product specifications. A method involving the statistical design of experiments is performed in several iterations to investigate the target parameters of the print cycle time, green part weight, shape integrity and layer thickness, and to analyze the main interdependencies. The results of this study provide valuable insights into optimizing the screen-printing process for soft magnetic sheets, enabling the production of efficient electric motors while reducing material scrap.

Interplay of Three‐Dimensional Instabilities and Magnetic Reconnection in the Explosive Onset of Magnetospheric Substorms

AbstractMagnetospheric substorms are preceded by a slow growth phase of magnetic flux loading and current sheet thinning in the tail. Extensive data sets have provided evidence of the triggering of instabilities at substorm onset, including magnetic reconnection and ballooning instabilities. Using an exact kinetic magnetotail equilibrium we present particle‐in‐cell simulations which capture the explosive nature of substorms through a disruption of the dipolarization front by the ballooning instability. We use self‐consistent particle tracking to determine the nonthermal particle acceleration mechanisms.

Fabrication and applications of a novel and multi-feature spectroscope

A spectroscope is an optical device that can stimulate student’s interest in the visible light’s constituent colors. This educational tool is conventionally used to qualitatively observe the emission spectra of various light sources, which can serve as a springboard to understanding the fundamentals of spectroscopy, the wave nature of light, and the orbital theory of atoms and molecules. This research builds on the functionality and accessibility of a simple spectroscope through the utilization of low-cost readily available materials, and more importantly, improvisation via the inclusion of a magnetic sheet mounted on the entrance slit cover. The magnetic sheet was employed to vary the slit width, to add absorption filters, and to mount a cuvette containing liquid samples. Furthermore, this sheet allowed the simultaneous observation of the emission spectrum of a light source and the transmission or absorption spectrum of the samples. The breadth of data from a variety of activities involving spectra was also made possible by a mobile phone camera as a recording device. In this study, the novel features strengthen the interconnectedness of various concepts in introductory spectroscopy. This elucidates the experimental and theoretical base of STEM Education in domains such as optics and photonics, and molecular spectroscopy.

Motion of a current-vortex sheet in the magnetic Kelvin-Helmholtz instability.

In this paper, we consider the Kelvin-Helmholtz instability in the magnetohydrodynamic flow. The motion of the interface is described by a current-vortex sheet. We examine the linear stability of the current-vortex sheet model and determine the growth rate of the interface. The interface is linearly stable for M_{A}<2 where M_{A} represents the Alfvén Mach number. It is found that the interface is linearly unstable in the limit of the critical Alfvén Mach number M_{A}=2, due to resonance of eigenvalues. We perform numerical simulations for the current-vortex sheet for both regimes of M_{A}<2 and M_{A}>2. The numerical results show the stabilizing effects of the magnetic field on the evolution of the current-vortex sheet when the magnetic field is sufficiently large. For the regime M_{A}<2, the sheet oscillates both longitudinally and transversely and the transverse surface wave is pronounced for a large M_{A}. Remarkably, the interface is nonlinearly unstable for M_{A}≈2, for M_{A}<2, which may be due to the propagation of surface waves. For the regime M_{A}>2, the roll-up of the spiral is weakened and the spiral is more pinched and stretched for smaller M_{A}. A comparison of the unstable evolutions of large and small values of M_{A} shows significant differences of the magnetic field and vortex sheet strength.

2D patterned magnetic composite sheets for polarization-insensitive and wide-angle microwave attenuation

Magnetic composite sheets loaded with carbonyl iron powders (CIP) are widely used due to their high-efficiency microwave attenuation at very thin thickness because of their outstanding permeability and magnetic loss. However, their performance varies dramatically at various incident angles and polarization modes, namely transverse electric (TE) and transverse magnetic (TM) modes. In this study, it is demonstrated that two-dimensional (2D) patterning could offer an effective solution for achieving wide-angle performance in both TE and TM modes. Different shapes of the 2D patterns (circles, hexagons, and cross-holes) are investigated and their dimensions are optimized through full-wave simulation. The consistent results with the experiment reveal that these 2D patterns with optimized dimensions could improve TM mode performance significantly to above 20 dB attenuation for an oblique incident angle up to about 40°, thanks to the resulted field resonance revealed by simulation. Due to the improved TM mode performance, the patterned composite sheet could exhibit almost identical high-efficiency attenuation in both modes, becoming polarization-insensitive. The performance improvement also comes with a ∼16% reduction in weight. Given these merits and the ease of fabrication, the low-profile and robust 2D patterned magnetic composite sheets could attract great attenuation in practical applications for wide-angle and polarization-insensitive microwave attenuation.

Characterizing fragmentation and sub-Jovian clump properties in magnetized young protoplanetary discs

ABSTRACT We study the initial development, structure, and evolution of protoplanetary clumps formed in three-dimensional resistive magnetohydrodynamic (MHD) simulations of self-gravitating discs. The magnetic field grows by means of the recently identified gravitational instability dynamo. Clumps are identified and their evolution is tracked finely both backward and forward in time. Their properties and evolutionary path is compared with clumps in companion simulations without magnetic fields. We find that magnetic and rotational energy are important in the clumps’ outer regions, while in the cores, despite appreciable magnetic field amplification, thermal pressure is most important in counteracting gravity. Turbulent kinetic energy is of a smaller scale than magnetic energy in the clumps. Compared with non-magnetized clumps, rotation is less prominent, which results in lower angular momentum in much better agreement with observations. In order to understand the very low sub-Jovian masses of clumps forming in MHD simulations, we revisit the perturbation theory of magnetized sheets finding support for a previously proposed magnetic destabilization in low-shear regions. This can help explaining why fragmentation ensues on a scale more than an order of magnitude smaller than that of the Toomre mass. The smaller fragmentation scale and the high magnetic pressure in clumps’ envelopes explain why clumps in magnetized discs are typically in the super-Earth to Neptune mass regime rather than super-Jupiter as in conventional disc instability. Our findings put forward a viable alternative to core accretion to explain widespread formation of intermediate-mass planets.

Development of Student Magnetic Inquiry Project Results Sheet (SMIPRS) Integrated with Local Wisdom and Islamic Values

Development of Student Magnetic Inquiry Project Results Sheet (SMIPRS) Integrated with Local Wisdom and Islamic Values

LLC 공진형 컨버터를 위한 인덕터 집적 평면형 변압기의 설계 및 구현

The miniaturization of magnetic components is one of the most important issues in the design and fabrication of high-density switching power converters. In recent years, an integrated magnetics (IM) technique has been considered a possible solution for reducing the size and cost of the magnetic components. This paper deals with the design and implementation of an inductor integrated planar transformer for improving the power density of an LLC esonant converter. The proposed technique utilizes a leakage layer inserted between the primary and secondary printed circuit board (PCB) windings to implement a series resonant inductor in the transformer without any additional windings. The analysis and design method of the proposed inductor integrated transformer are discussed, and the implementation of the transformer using the PCB windings and magnetic sheets is presented. The implemented inductor integrated transformer is applied to the actual LLC resonant converter with a power rating of 750 W. The experiments are carried out for the actual converter, and the effectiveness of the proposed technique is verified from the experimental results.

Kirigami Makes a Soft Magnetic Sheet Crawl.

Limbless crawling on land requires breaking symmetry of the friction with the ground and exploiting an actuation mechanism to generate propulsive forces. Here, kirigami cuts are introduced into a soft magnetic sheet that allow to achieve effective crawling of untethered soft robots upon application of a rotating magnetic field. Bidirectional locomotion is achieved under clockwise and counterclockwise rotating magnetic fields with distinct locomotion patterns and crawling speed in forward and backward propulsions. The crawling and deformation profiles of the robot are experimentally characterized and combined with detailed multiphysics numerical simulations to extract locomotion mechanisms in both directions. It is shown that by changing the shape of the cuts and orientation of the magnet the robot can be steered, and if combined with translational motion of the magnet, complex crawling paths are programed. The proposed magnetic kirigami robot offers a simple approach to developing untethered soft robots with programmable motion.

Hierarchically nitrogen-doped carbon hollow microspheres assembled with loose and porous magnetic carbon sheets for enhanced microwave absorption

Combining hollow materials with magnetic particles to construct hierarchical structures favors enhancement of microwave absorption properties. However, the fabrication of the well-defined materials possessing both hollow and hierarchical features still faces a huge challenge. Herein, a facile two-step method is developed to synthesize hierarchically nitrogen-doped carbon hollow microspheres assembled with loose and porous magnetic carbon sheets. Especially, many magnetic Fe/Fe3C NPs covered with N-doped graphitic layers are embedded in the mesoporous N-doped carbon sheets layers. Benefited from the special structure, the optimal nitrogen-doped carbon hollow microspheres exhibit an excellent microwave absorption property with an EAB of ∼4.00 GHz at a thickness of 2.5 mm and the minimal reflection loss of −39.87 dB at a frequency of 7.76 GHz, while the filler ratio is only 10 wt% in the paraffin wax. Electromagnetic parameters analysis reveals that unique hierarchical structure and rich heterogeneous interfaces result in the enhancement of dielectric and magnetic losses as well as optimized the impedance matching. The computer simulation technology (CST) simulation further verifies the practical applicability of the optimal nitrogen-doped carbon hollow microspheres. This work provides an effective way for the efficient synthesis of hierarchical and hollow materials for microwave absorption.

Recycling Potential in the European Union (EU) of Low Voltage Three-Phase Induction Motors Up to 75 kW of Power: Quantitative Analysis

This article quantifies the recycling potential of the metallic materials that make up three-phase induction motors. The data on the use of electric motors by type and power determines that the most significant recycling potential lies in this low-voltage motor which powers up to 75 kW. The work aims to show the possibility of such recycling in the European Union (EU). The metals used to make the various parts of the induction motor and the main recycling methods that allow their reuse are listed. It evaluates which part of the motor can apply these recycling methods relatively easily (stator) and which part is more complex (rotor). A calculation process is used to exhaustively quantify the metals that incorporate different motors selected for other powers to determine the amounts of material that can be recycled and reused to manufacture new equipment. The recycling potential is quantifies by parts (stator and rotor) employing approximate equations obtained from the study and by materials (copper, aluminum, magnetic sheet, steel). The data calculated, the economic volume, the possibilities of energy-saving, and the environmental advantages of dedicating efforts and resources for collecting, recycling, and reusing the materials in three-phase induction motors for industrial applications show. The withdrawal of electric motors in industrial applications, due to causes related to the restructuring of production processes, manufacturing systems, breakdowns, or directly due to aging, generates considerable possibilities of reusing the metals used in their manufacture.

Merged magnetic resonance and light sheet microscopy of the whole mouse brain

We have developed workflows to align 3D magnetic resonance histology (MRH) of the mouse brain with light sheet microscopy (LSM) and 3D delineations of the same specimen. We start with MRH of the brain in the skull with gradient echo and diffusion tensor imaging (DTI) at 15 μm isotropic resolution which is ~ 1,000 times higher than that of most preclinical MRI. Connectomes are generated with superresolution tract density images of ~5 μm. Brains are cleared, stained for selected proteins, and imaged by LSM at 1.8 μm/pixel. LSM data are registered into the reference MRH space with labels derived from the ABA common coordinate framework. The result is ahigh-dimensionalintegratedvolumewithregistration (HiDiver) with alignment precision better than 50µm. Throughput is sufficiently high that HiDiver is being used in quantitative studies of the impact of gene variants and aging on mouse brain cytoarchitecture and connectomics.

Low-frequency magnetic microwave absorber using reactive ground for extended bandwidth

A design method to extend the operating bandwidth of a low-frequency magnetic microwave absorber is presented. According to the mapped impedance distribution from the design objective, a synthesized reactive ground consisting of a triple-ring array, instead of the perfect electric conductor (PEC), is conveniently placed at the back of a commercially available magnetic sheet to realize impedance matching. Compared with the conventional PEC, the reactive ground extends the operating bandwidth of reflection coefficient being less than −10 dB by introducing four consecutive absorption peaks so that the optimized structure achieves broadband absorption from 2.3 to 4.3 GHz with a thickness of 0.027 times the free-space wavelength at the lowest operating frequency and a 60.6% fractional bandwidth which is nearly two times that of the conventional structure. The physical mechanism is further investigated through the distributions of current flow and power loss. Finally, a prototype is fabricated and measured. The good agreement between the simulated and measured results verifies the effectiveness of the presented design method.

Multiresonant metasurfaces for arbitrarily broad bandwidth pulse chirping and dispersion compensation

We show that ultrathin metasurfaces with a specific multiresonant response can enable simultaneously arbitrarily strong and arbitrarily broadband dispersion compensation, pulse (de)chirping, and compression or broadening. This breakthrough overcomes the fundamental limitations of both conventional nonresonant approaches (bulky) and modern singly resonant metasurfaces (narrowband) for quadratic phase manipulations of electromagnetic signals. The required nonuniform trains of resonances in the electric and magnetic sheet conductivities that completely control phase delay, group delay, and chirp are rigorously derived and the limitations imposed by fundamental physical constraints are thoroughly discussed. Subsequently, a practical, truncated approximation by finite sequences of physically realizable linear resonances is constructed and the associated error is quantified. By appropriate spectral ordering of the resonances, operation can be achieved either in transmission or reflection mode, enabling full space coverage. The proposed concept is not limited to dispersion compensation, but introduces a generic and powerful ultrathin platform for the spatiotemporal control of broadband real-world signals with a myriad of applications in modern optics, microwave photonics, radar, and communication systems.

Machine Learning Empowered Magnetic Substrate Coupled Broadband and Miniaturized Frequency Selective Surface

This works offers a polarization-insensitive, wide angular stable, and wideband electromagnetic interference shielding structure using an integration of frequency selective surface (FSS) with magnetic substrates. The equivalent circuit model (ECM) together with the analytical model is derived to figure out the physics of the shielding structure. The overall inductance of the shielding structure is increased using a magnetic ferrite sheet and magnetic silicon rubber sheet as substrates. Further, four different deep neural network configurations are investigated with inverse modeling to predict the shielding structure parameters within a fraction of seconds. The mse between expected and predicted output is only 2.92 × <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$10^{-8}$</tex-math></inline-formula> . The entire X-band is shielded with a minimum 10-dB shielding effectiveness (SE) and with SE of 56 dB at resonance. The FSS unit cell size is only 0.21 <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$\lambda$</tex-math></inline-formula> × 0.21 <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$\lambda$</tex-math></inline-formula> . Furthermore, the proposed shielding structure shows stable transmission performance up to <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$75^{\circ}$</tex-math></inline-formula> angle of incidence for both perpendicular and parallel polarization. Finally, a prototype is fabricated and measured using nondestructive free space measurement. Good agreement among the simulated, ECM, analytical model, and measured results demonstrate the efficacy of the proposed technique for building an effective shielding structure.

Peeling behaviour of a hard magnetic soft sheet driven by the magnetic field: Geometric nonlinearity analyses

Magneto-responsive smart structures can produce large deformation and realize the remote non-contact control driven by the magnetic field, which are widely applied in a lot of engineering areas. In the present study, the peeling behavior of a hard-magnetic soft sheet driven by the magnetic field is comprehensively investigated both experimentally and theoretically. Firstly, the peeling experiments of two identical magnetic sheets under the control of a cylindrical magnet are performed, where one is adhered by the liquid film and the other takes a cantilever configuration. In addition, we build the expression of the total energy functional of the sheet-liquid-magnet system, and then derive the approximate solutions on the beam deflection and the adhered length during the peeling process based on the Rayleigh-Ritz method. The numerical result is in excellent agreement with the experimental data. The effects of the external magnetic field and work of adhesion on the maximum deflection and adhered length are fully explored, and more results are predicted via calculation. These findings can provide some inspirations on engineering of many new devices, such as smart structures, micro-sensors and intelligent robots, etc.

An alarm device for mechanical compression device displacement at femoral artery puncture sites

Objective To develop an alarm device for the mechanical compression device displacement (MCD), and further evaluate its effectiveness in clinical use. Material and methods The alarm device is mainly composed of buzzer, indicator light, magnetic sheet. This is a prospective randomized and controlled study. Four hundred patients who met the inclusion/exclusion criteria were included and randomly assigned to two groups (MCD group vs alarm + MCD group). The primary outcome measures were the sensitivity and specificity of the alarm device to detect MCD displacement, time to hemostasis (TTH), time to ambulation (TTA), time to hospital discharge (TTHD), hospital costs (HC), complication rates, and patient satisfaction. Results The sensitivity and specificity of the alarm device in detecting MCD displacement were 94.44% and 88.46%, respectively. The study group achieved shorter TTH (p = .034), shorter TTA (p = .021), lower complication rates (p = .025), and better patients’ satisfaction (p < .001) compared to the control group. However, no significant difference was observed in TTHD (p = .361) and HC (p = .583). Conclusion The alarm device is highly sensitive in detecting MCD displacement, while achieving better clinical outcomes compared with artificial monitoring.

Nonequilibrium Ionization Modeling of Petschek-type Shocks in Reconnecting Current Sheets in Solar Eruptions

Nonequilibrium ionization (NEI) is essentially required for astrophysical plasma diagnostics once the plasma status departs from the assumption of ionization equilibrium. In this work, we perform fast NEI calculations combined with magnetohydrodynamic (MHD) simulations and analyze the ionization properties of a Petschek-type magnetic reconnection current sheet during solar eruptions. Our simulation reveals Petschek-type slow-mode shocks in the classical Spitzer thermal conduction models and conduction flux-limitation situations. The results show that under-ionized features can be commonly found in shocked reconnection outflows and thermal halo regions outside the shocks. The departure from equilibrium ionization strongly depends on plasma density. In addition, this departure is sensitive to the observable target temperature: the high-temperature iron ions are strongly affected by the effects of NEI. The under-ionization also affects the synthetic SDO/AIA intensities, which indicates that the reconstructed hot reconnection current sheet structure may be significantly underestimated either for temperature or apparent width. We also perform an MHD-NEI analysis on the reconnection current sheet in the classical solar flare geometry. Finally, we show the potential reversal between the under-ionized and over-ionized states at the lower tip of reconnection current sheets where the downward outflow collides with closed magnetic loops, which can strongly affect multiple SDO/AIA band ratios along the reconnection current sheet.

Iodine‐Functionalized Magnetic Reduced Graphene Oxide as an Efficient Nanocatalyst for Acetylation of Phenol, Alcohol, and Sugar Derivatives

AbstractHere in this study, a new iodine‐modified magnetic nanocomposite (I@rGO@CoFe2O4) has been described. FT‐IR, XRD, SEM, TEM, EDX, TGA, and VSM techniques confirm the construction of I@rGO@CoFe2O4 nanocomposite and show ferromagnetic properties with a significant magnetization saturation (35.9 emu g−1). A deep eutectic solvent (DES) potassium triiodide‐choline chloride (KI3 : ChCl) has been used as a reducing agent and for modification of magnetic graphene oxide sheets. In addition, the applicability of the nanocomposite has been well demonstrated for acetylation of some phenol, alcohol, and sugar derivatives in solvent‐free conditions at room temperature. Increasing catalytic activity, high selectivity, reducing environmental hazards, and reusing the catalyst without significantly reducing activity are among the advantages of this method.

Composite magnetic sheet as sorbent for oil spill Clean-up

Water is the most vital resource required for the survival. But the cleanliness of this resource has been compromised in the form of oil spills which occurs due to the tanker disaster, transportation and storage of oil. It is extremely urgent to find the effective counter measure for oil spill treatment which aims oil spill-recovery strategy. Out of all the measures, development of a good biodegradable sorbent for spillage has sustained interest. To solve this environmental problem of oil spill, magnetic Sheet was synthesised by using lumen loading procedure using alkali treated bamboo fibers and cobalt ferrite nanoparticles (CoFe 2 O 4 ). Lumen loading permits the ferrite particles to be introduced solely into the lumens of bamboo fibres. For aiming this, CoFe 2 O 4 nanoparticles were first prepared by the sol–gel method and fibers were pre-treated with 6 % NaOH. Then synthesised ferrites were merged with the fibers. The samples were characterized by employing Scanning Electron Microscopy (SEM-EDS), Fourier transform infrared (FTIR), X-ray Diffraction (XRD). SEM confirms the deposition of cobalt ferrites nano particles on the surface and into the macropores of fibers. The sorption capacity for raw bamboo fibers, alkali treated bamboo fibers and composite sheet was calculated for three different type of oil such as mustard oil, coconut oil and olive oil. The sorption capacity shown by the raw bamboo fiber, 6 % NaOH treated bamboo fiber and composite magnetic sheet was in the range 1.8–2.2 g, 16.2–18.8 g and 1.8–2.4 g of oil per gram of sample respectively. The outcomes propose that the prepared magnetic sheet can be used as absorbent for oil-spill clean-up.