Spin-torque transfer magnetic random access memory (STT-MRAM) is one potential candidate to replace the dynamic random access memory (DRAM) due to its superior features of nonvolatility, fast read/write speed, and high scalability. The error correction coding methods are applied to improve the reliability of STT-MRAM which is affected by the process variation and thermal fluctuation. In this paper, we investigate, for the first time, the design and optimization of the polarization-adjusted convolutional (PAC) code for the STT-MRAM channel. A crucial problem for the application of PAC codes to the STT-MRAM channel is the optimization of the index set of the non-frozen bits of the PAC codes. Hence, a rate-profile optimization method based on the genetic-algorithm-assisted bit-swapping is proposed. Simulation results show that the PAC code with the optimized rate-profile outperforms both the polar code and the PAC code with existing generic rate-profiles.
Ferrite material has non-negligible permeability, permittivity, and conductivity, so that the magnetic behaviour of ferrite cores is frequency dependent. This article presents a method to predict the complex permeance of ferrite E- and U-cores including electromagnetic resonance. The cores are decomposed into elementary segments, for which the Maxwell equations are solved analytically to obtain a network of frequency-dependent permeances or reluctances.
The eddy current testing (ECT) signals of a crack change with the crack's geometry and electromagnetic properties. The conductivity of the specimen and the conductivity inside or around the crack are generally unknown but play important roles in ECT responses. The objective of this study is to find characteristics features to determine the depth of cracks independently of the material conductivity and the partial conductivity of the cracks. Theoretical and numerical analysis showed that the amplitudes of the intrinsic impedance signal or the magnetic field density signal vary little with frequency. By identifying nearly conductivity-invariant features in the spectra of magnetic flux density signals and constructing a master curve that correlates the characteristic features with crack depth, we will be able to approximately estimate the depth of a crack by referring to the pre-constructed master curve.
Enjoying the merits of compact structure, less noise and high specific power, axial-flux magnetic-geared double-rotor machines (AMGDRMs) have been proved a promising candidate for the electrical-continuously variable transmission (e-CVT) in hybrid electric vehicles (HEVs). However, an additional permanent magnet synchronous machine (PMSM) is needed for torque compensation in the e-CVT system. In this paper, a novel integrated scheme which can realize the functional integration of a PMSM is proposed to improve compactness further. By carefully designing pole-pair number combination, the PMSM torque would be produced by the interaction between the armature fifth-harmonic and PM fundamental magnetic fields when injecting harmonic current. However, such combination would cause significant principled torque ripple. Hence, a suppression method based on the phase-shift structure is proposed to cancel the torque fluctuation out, thus the proposed machine can enable both the MGDRM and PMSM operations without significant torque ripple. Compared with existing dual-winding integrated schemes, an integrated winding configuration where only one set of conventional integral-slot winding is placed into one stator is adopted in the proposed machine, simplifying the manufacture process. First, the machine structure and operation principle are investigated. Second, the torque ripple suppression mechanism is analyzed. Finally, 3-D FEA simulations are carried out to validate the proposed machine and evaluate overall performances.
In this work, ball-milled iron (Fe)-based nanocrystalline alloy sheets and obtaining platelet particles are used to effectively utilize the end material and apply it to a soft magnetic composite. The instrumental analysis results reveal that, although a microstrain is introduced into the nanocrystalline α-Fe grains in the achieved alloy powder, the amorphous part filled among the grains experiences almost no change. The ball-milling treatment greatly increases the coercive force of the pulverized nanocrystalline sheet. Although the coercive force of the alloy powder decreases after the heat treatment, it remained approximately 10 times higher than that of the heat-treated alloy sheet without the ball-milling treatment, even after the heat treatment. The magnetic process of the ball-milled and post-annealed nanocrystalline alloy powder is discussed based on the results of the synchrotron radiation X-ray analysis and transmission electron microscopy with the Lorentz technique.
Tailoring details of thermal processing, including controlled heating rates and annealing time, plays a key role in the enhancement of soft magnetic properties of amorphous and nanocrystalline soft magnetic materials. In particular, rapid thermal processing also known as flash annealing has shown potential for grain size refinement, tailoring of phase identity, and tuning of magnetic properties. This work explores the differences between conventional furnace annealing and isothermal annealing with flash annealing techniques for a range of detailed thermal processing conditions (temperature, time, cooling method) in an FeNi-based alloy. As compared to conventional annealing, flash annealing results in dominant FCC γ FeNi phase with refined grains. Microstructural refinement due to flash annealing showed improved soft magnetic properties with reduced coercivity and improved ductility for improved core manufacturing at scale.
In this paper, we used 2,2’-azobis(isobutyronitrile) (AIBN) as a radical pair-forming agent to investigate whether magnetic fields can control a liposomal drug release through differences in the physical properties of biomembranes. Exposure to a static magnetic field of 0.25 T was performed using a pair of commercially available permanent magnets. Irradiations of ß-carotene-containing liposomal nanocarriers modified with AIBN were performed using an original air-cooled UV -LED irradiation system. Under exposure to the static field, the AIBN in the membrane was excited by a UV -LED emission wavelength of 365 nm. According to the overall result of seven kinds of prepared nanocarriers, the drug release potentials with magnetic field effects obtained using a static field of 0.25 T were more extensive on the order of 16-32%, than those obtained at geomagnetic fields. Conclusively, we strongly propose a novel photomagnetic controlled drug-release technology using these liposomal nanocarriers equipped with magnetic controls.
The present study investigates the impact of a non-magnetic improvement treatment on the bridge of the rotor core sheet, with an emphasis on the effects of the length and position of the treatment on magnetic properties. A prototype rotor core was fabricated by laminating 60 rotor core sheets. The effect of the non-magnetic improvement length on the magnetic flux at the relative improved position of 0% was evaluated, and the rotor core improved with an improvment ratio of 70%, showing a 38.0% magnetic flux increment. The effect of the relative improvement position on the magngetic flux with the improvement ratio of 70%-76 % was evaluated. Findings demonstrate that the rotor core with a relative improvement position of −27% exhibits a significant magnetic flux increment of 40.1%.
The rotation of an electrodynamic wheel (EDW) above a flat conductive, non-magnetic, track induces currents in the track that can create lift and thrust/braking force. This paper presents a new type of dual-EDW that consists of two EDWs in series that can also create a controllable lateral force. The magnitude and direction of the lateral force can be changed via the relative phase angle shifting of the two rotors. The changes in the lateral force magnitude as well as direction are shown to not affect the lift and thrust force magnitude. The geometric analysis of the design is presented and the practical difficulty of implementing the design is also discussed.
The detailed energy dynamics of transcranial magnetic stimulation of the cerebral cortex remain unclear. The present study therefore examined the energy distribution of transcranial magnetic stimulation. Magnetic energy was assessed in terms of the magnetic flux density, and the stimulation resolution was evaluated. The magnetic flux density measuring device comprised a pickup probe and simple electronic circuits (e.g., an integrator and buffer amplifier). The pickup probe comprised a sensor coil (with an inner diameter of 8 mm), twisted pair line, and lead-out cable. Magnetic stimulation was applied using a Rapid2 stimulator and a figure-8 flat coil (with a diameter of 70 mm). The brain model made from an acrylic plate was based on a subject with a 62%–63% motor threshold and a scalp-primary motor cortex distance (i.e., distance from the scalp to the center of the sensor coil) of 15 mm. The highest magnetic flux density after the removal of background noise was approximately 180 mT at the center of the stimulus coil, whereas the resolution of the transcranial magnetic stimulation was approximately 6 mm (i.e., from the center to within ± 3 mm). The stimulation area estimated from the measurements was 12 mm 2 around the location of highest magnetic flux density. Relative to the magnetic flux density at the center of the stimulation coil, the stimulus area in which the magnetic flux density decreased by less than 1% was approximately 50.27 mm 2 and the stimulus area in which the magnetic flux density decreased by less than 5% was 254.47 mm 2 . This study showed that the distribution of the magnetic stimulation energy supplied to the target cortex may be evaluated using a simple measurement device and brain model.
The slip ring solution for power transfer between rotating structures has adverse impacts on the maintenance of offshore wind turbines. Rotary transformer systems transfer electric energy based on the electromagnetic induction through the air-gap without mechanical contact. The rotary transformer can be integrated into dual active bridge converters (DAB) to utilize leakage inductance instead of the cumbersome inductor used typically in the system. The X-rotor wind turbine concept uses this idea to eliminate the need for slip rings and transfer bulk power to the AC network from generators mounted in a rotating structure. In this paper the design, performance, efficiency, and manufacturing details of a 1 MW wireless power transfer system for the novel X-rotor offshore wind turbine concept is presented. The results show that this design methodology that includes rotary transformers and dual active bridge converters is suitable for high-efficiency high-power wireless transfer systems.
In this study, we investigated an Fe-B-P-Cu system nanocrystalline alloy with both high saturation magnetic flux density and low coercivity. In particular, we manufactured as-quenched Fe 84.3 B 6 P 9 Cu 0.7 alloy powder with a smooth and spherical surface. After annealing, this powder showed a nanocrystalline structure, low coercivity, and saturation magnetic flux density of 1.68 T. These magnetic properties are excellent compared to those of conventional powders. Thus, Fe 84.3 B 6 P 9 Cu 0.7 nanocrystalline alloy powder can be used to produce superior inductors with high saturation magnetic flux density as well as low coercivity.
To address potential electromagnetic interference (EMI) issues in highly dense electronic circuits, where electric components and interconnections are integrated in proximity, we investigated the effectiveness of integrating a noise suppression sheet (NSS) inside printed circuit boards (PCBs). We fabricated NSSs compatible with PCB embedding and systematically evaluated their noise suppression performance. Using a newly proposed measurement jig to simulate the embedding of NSSs in PCBs, we confirmed the suppression effect of conduction and radiation noise. We also embedded NSSs in PCBs used in actual products and confirmed the validity of PCB-integrated NSS for suppressing radiation noise in the frequency range of 700MHz to 1GHz, which is widely used for telecommunications.
Coercivity enhancement of Ga-containing Nd-Fe-B as-sintered magnets driven by the microstructural changes occurring during postsinter annealing was studied via feature extraction and selection based on several data science methods. These data science methods reveal the correlation between the coercivity and the intensity and shape change of the specific structures in the X-ray diffraction pattern. Principal component analysis, a linear model with least absolute shrinkage and selection operator regression, and nonlinear random forest regression modeling of coercivity based on X-ray diffraction patterns objectively identified the microstructural changes correlating with coercivity enhancement. Further, quantitative evaluation of the correlation magnitude of microstructural changes to the coercivity of the magnet revealed a preferred direction of the correlation magnitude even in an identical phase. The validity of our findings was qualitatively confirmed based on the results of previous studies, indicating that sparse modeling accelerates materials research and development via automated decision-making.
Linear voice coil motor (VCM) has the advantages of high precision and high dynamic response, which fulfills the requirements of linear dynamic loading platform. In this article, a high thrust double layer series magnetic circuit linear voice coil motor is analyzed and designed. Based on 2-D FEM, the thrust and thrust ripple are optimized. Moreover, the damping force on coil support plate is analyzed and reduced by optimization of material and structure. Finally, a linear VCM prototype with a thrust rating of 2000 N is manufactured and tested, the thrust results have good consistency with FEM results.
To improve the shielding performance of magnetically shielded rooms (MSRs) used in biomagnetism measurements and to ensure their stability, we evaluated the electrical conduction properties at contact parts of conductor plates. These conductor plates are used as the conductive shield layer and form an integral part of the MSRs along with the magnetic shield layer. Although the conductive shield layer prevents magnetic noises with wide frequencies using the eddy current effect, poor electrical contact between the conductor plates causes increased electric resistance at that particular part. Consequently, this diminishes the effectiveness of the eddy current, thus lowering the shielding performance of the conductive shield layer. Therefore, cases of poor electrical contact should be detected and rectified to ensure high shielding performance and maintain stability. In this study, we develop resistance sensors to detect areas of poor contact. By establishing a quantitative relationship between poor contact and shielding performance, we can better understand the significance of these processes in improving and maintaining optimal performance. Moreover, we describe an application example of these resistance sensors on an actual construction site of an MSR.
In this paper, the influence of additional air gaps between stator tooth and back-iron on the acoustic performance of spoke-type permanent magnet synchronous motor (STPMSM) is studied. It is found that the existence of these gaps can reduce the electromagnetic vibration noise, and its sound pressure level decreases by 2.3dB. By comparing radial electromagnetic forces acting on the stator, it is found that the additional air gap will weaken the 2-order radial electromagnetic force in space, which leads to the reduction of electromagnetic vibration noise. In order to further consider the influence of non-uniform additional air gap, the electromagnetic force is decomposed by two-dimensional fast Fourier transform (2D-FFT). The results of space-time spectrum show that the non-uniform air gap will introduce new space-time components of electromagnetic force, but it will not have a great impact on the acoustic performance of STPMSM. In addition, several commonly used stator tooth segments and back-iron segments are compared, which have different shapes of additional air gaps. The results show that the structure with triangular separated stator tooth and back-iron has better acoustic performance.
The demagnetization process of exchange-coupled Sm(Fe 0.8 Co 0.2 ) 12 /α-Fe nanocomposite magnet particles with α-Fe phase coated on the sides of rectangular Sm(Fe 0.8 Co 0.2 ) 12 nanoparticles and the effect of Fe phase arrangement on their (BH) max are systematically investigated from micromagnetics calculations. The (BH) max of the reference model Sm(Fe 0.8 Co 0.2 ) 12 particles without Fe layer was 630 kJ/m 3 . On the other hand, the (BH) max of the nanocomposite magnet particle model, in which the four sides of the hard phase are coated with a soft phase, was found to have the highest (BH) max of 678 kJ/m3. This result may provide a guideline for designing high-performance magnet particle materials while reducing the use of rare metals.
ON BEHALF of the organizing committee, it is our pleasure to present selected papers from the INTERMAG 2023 Conference, which was held in Sendai, Japan, during May 15–19, 2023. The outstanding quality of the conference is reflected by the scientific and technical quality of the papers in this Conference Proceedings. The Publications Committee received 560 manuscripts, which were submitted for peer review and possible publication in either IEEE TRANSACTIONS ON MAGNETICS or this Conference Proceedings. In order to be considered for publication, the manuscripts were required to meet rigorous criteria for novelty in applied and basic magnetism. Following the standard IEEE review process, each paper published in IEEE TRANSACTIONS ON MAGNETICS and in the Conference Proceedings was reviewed by at least two anonymous referees. In the end, 279 papers were accepted for publication in IEEE TRANSACTIONS ON MAGNETICS and 55 papers in this Conference Proceedings.
