This paper reports the successful additive-free sintering of fine Nd-Fe-B powder prepared by reduction-diffusion (RD) and wet ball milling (WBM) washing. Fine Nd-Fe-B powder by RD poses difficulties in sintering without rare earth (RE) hydride additives due to oxidation or loss of the Nd-rich phase during the washing step. Here, the effect of different washing methods such as conventional water washing, acetic acid washing, and WBM washing on the Nd-rich phase and oxygen content of RD powders was examined. The WBM washing involves low energy milling in organic media, which simplifies the removal of impurities from the RD powder. Among all the samples, the magnet made by sintering with WBM powder showed the coercivity of 8.7 kOe and (BH)max of 33.7 MGOe, which are comparable to magnets made of acidic washed RD powder with the essential addition of NdH_x of 10 wt% reported in other studies. This is considered that in the powder after WBM washing, oxygen content was decreased compared to water washing and Nd-rich phase remained compared to acidic washing, which resulted in successful densification during sintering and the formation of Ndrich areas in sintered body. This finding makes an important step towards the production of Nd-Fe-B based magnets from sintering with RD powder without additive.

Both Mn₄C (=Mn₃MnC) and Mn₃GaC have been studied previously. However, the reports on Mn_3+xGa_1-xC (0 ≤ x ≤ 1) with intermediate compositions are very rare. In this work, the structure and magnetic properties of Mn_3+xGa_1-xC prepared by using solid state reaction were studied systematically. High purity anti-perovskitetype Mn_3+xGa_1-xC were obtained in the composition range of 0 ≤ x ≤ 0.5, above which Mn₂₃C₆ precipitates and the fraction of Mn₂₃C₆ in the samples increases with increasing x. The structural stability, lattice parameters, and room temperature saturation magnetization of ferromagnetic Mn_3+xGa_1-xC (0 ≤ x ≤ 1) decreases with increasing x. The Curie temperature of Mn_3+xGa_1-xC (0 ≤ x ≤ 1) increases with increasing x. Most Mn_3+xGa_1-xC with varied x exhibit near-zero coercivity and zero remanent magnetization. This work indicates that the temperature coefficient of magnetization of Mn_3+xGa_1-xC may be tuned by tuning the fraction of the Ga atoms.

We investigated the changes in the microstructures and magnetic properties of a grain boundary diffusion-processed (GBDP) anisotropic Nd-Fe-B powder. The powder was obtained via hydrogenation decomposition desorption recombination (HDDR) and diffused with heavy rare-earth elements (HREs), such as Dy and Tb fluorides, as well as metallic powders. The HREs diffused through the grain boundaries into the HDDR powder and were found primarily in the RE-rich triple junction regions. The HREs in the RE-rich regions formed the main phase (Nd₂Fe₁₄B), followed by a high-coercivity (Nd+Tb)₂Fe₁₄B shell. We also studied the GBDP powder with Tb and low-melting temperature elements such as Cu and Al. The addition of Cu to the GBDP source effectively improved the grain boundary structure and diffusion depth. The magnetic properties changed from remanence and coercivity of 12.5 kG and 15.7 kOe to 12.3 kG and 23.9 kOe, respectively, for GBD by Tb and Cu mixtures.

For nano-magnetic fluid(NMF), the magnetic nano-particle(MNP) kinematic behavior in a magnetic field and the chain-like microstructure evolution are important to study the NMF properties at the microscopic level. However, the chain structure formation mechanism and the effects of multiple environmental factors on microstructural morphology remain unclear. In this paper, the interaction of a two-particle system, chain structure formation process, microstructure evolution and response time simulation of NMF is investigated by the discrete element simulation method. The results show that the magnetic dipole and repulsive forces dominate the chain structure formation and evolution under a uniform magnetic field. MNPs assemble into chain-like structures and various complex structures along the magnetic field direction. The volume fraction, magnetization intensity and particle size significantly affect the microstructure and the response time. The above study can obtain the specific morphology of the microstructure at different working conditions and broaden the application of NMF in practical engineering.

This paper employs a genetic algorithm (GA) in conjunction with density functional theory (DFT) to explore a range of tri-transition metal (tri-TM) doped Si12 anti-hexagonal prism clusters, specifically TM₃Si₁₂ clusters featuring either single or dual types of TM atoms. The investigation encompasses neutral, cationic, and anionic states. Our findings reveal that most clusters exhibit remarkable stability and diverse magnetic properties. The HOMO-LUMO gap results for the cluster series are elucidated by an electron-counting rule, providing a more detailed explanation than previous theories.

With the goal of improving the performance of cooling systems of magnetic sensors, the effects of adding nanoparticles and employing ferrohydrodynamics (FHD) are studied with numerical simulations. To produce ferrohydrodynamics, a wire near the hot surface is used to produce a varying Kelvin force. To better describe the magnetic force, a ferrofluid consisting of iron oxide and water is used. In the velocity and temperature equations, new terms are added to represent ferrohydrodynamics and buoyancy. To apply such complex physics, the control volume finite element method (CVFEM) is applied, and the equations are written in vorticity form to help remove pressure terms. This modeling approach is validated against previously published work and the results show good agreement. An improvement of 11.65 % in the convection rate is achieved by adding nanoparticles. Considering a higher buoyancy force results in a 118.92 % increase in the Nusselt number Nu. As MnF increases up to 2 × 10³, Nu increases by about 81.88 % at the lowest Rayleigh number Ra. The influence of ferrohydrodynamics on Nu declines as the gravity force increases. The hot surface becomes cooler by about 10 % and 37.5 % when MnF and Ra are increased.

This paper presents a harmonic analytical method for modular permanent-magnet (PM) machines. By using the complex Fourier separation method, the magnetic field in all parts of machine regions is solved from system equations through the application of boundary conditions with take into account the permeability of iron parts. Three types of concentrated winding have been used, namely, single layer, double layer same phase and double layer between phase. Additionally, the performance results of these configurations are also compared. Finally, to validate the proposed analytical method, the results are verified with the finite-element method (FEM). Thus, the validation shows good results for the proposed model.

This study aimed to confirm the characteristics of deep-learning image reconstruction (DLIR) intensity in abdominopelvic computed tomography (CT) using noise level and blind quality evaluation parameters. The study was conducted using phantoms and patients, and CT images were obtained while adjusting the intensity of DLIR to low (DLIR-L), middle (DLIR-M), and high (DLIR-H). To quantitatively evaluate image quality, the coefficient of variation (COV) and contrast-to-noise ratio (CNR), as well as natural image quality evaluation (NIQE) and blind/referenceless image spatial quality evaluator (BRISQUE), were used. In both the noise level and blind quality evaluation results, a higher strength of DLIR resulted in better results derived from the phantom and patient studies. In particular, the results of the phantom study confirmed that NIQE and BRISQUE of CT images acquired using DLIR-H were improved by approximately 5 % and 1 %, respectively, compared to the corresponding the application of DLIR-L. Moreover, when high-strength deep-learning was applied to a real patient's CT image reconstruction method, the NIQE and BRISQUE results improved by approximately 6 % and 4 %, respectively, compared with their respective medium levels. In conclusion, we quantitatively analyzed the image quality according to the intensity of the recently developed deep-learning-based CT image reconstruction method.

When gearboxes have the same torque density, a higher gear ratio raises the overall system torque density of geared motors. Coaxial magnetic gears (CMGs) have a high torque density, which exceeds 100 kNm/m³, and are therefore expected to improve the overall torque density of the system. However, because the gear ratio and torque density are inversely proportional to those of a conventional CMG, conventional CMGs are not suitable for a gearbox. This study proposes a new CMG structure, which more than doubles the torque density compared with that of a conventional CMG. In addition, this structure improves the system efficiency.

In order to prevent the demagnetization of low coercivity permanent magnets, the pole-changing permanent magnet synchronous motor usually adopts I_d=0 control strategy, which has the problems that the reluctance torque of the motor cannot be utilized and the torque density is low. In order to solve this problem, a new type of rotor reverse salient pole structure of pole-changing permanent magnet synchronous motor is proposed in this paper. Based on the comparative analysis of the magnetic field distribution characteristics of the motor under different pole numbers, the common d-axis and q-axis magnetic path under 8-pole and 4-pole are planned, and then the winding inductance L_d>L_q under two pole numbers is realized by setting bar and arc magnetic barriers and non-uniform reduction of air gap length. On this basis, the Taguchi method is used to set the parameters of the proposed structure, and the motor torque ripple is reduced under the premise of increasing the motor torque amplitude as much as possible under the 8-pole and 4-pole, and the optimal parameter combination of the proposed structure is determined. Through the FEA, it is verified that the motor can produce the maximum torque at the negative current angle before and after the pole change, so as to effectively utilize the reluctance torque, avoid the permanent magnet demagnetization and improve the torque density.

The heat and mass transfer effects on steady two-dimensional magneto hydrodynamic flow of second-grade fluid is carried out in this study. Mathematical formulations for nonlinear flows over stretching surface in the presence of magnetic field, temperature dependent thermal conductivity, porous medium and convective boundary are carried out in Cartesian coordinate system. The model equations are determined by using fundamental laws of fluid mechanics. The governing PDEs for second-grade fluid have been derived and then transfigured into a system of nonlinear coupled ODEs via appropriate similarity transformation. The BVP is then solved by an efficient numerical scheme known as Runge Kutta Fehlberg method along with shooting technique. The outcomes are presented graphically and tabulated with the aim of illustrating the physical impacts of governing parameters on the temperature, concentration, and velocity profiles. Greater Prandtl numbers result in a decrease in temperature, while higher values of thermal conductivity and coefficient of internal heat absorption all result in an increase in temperature. Further, comparison of the results with published literature for limited cases show the validity of numerical technique.

A pulsed eddy current nondestructive testing (PECT) system with annular array probes is designed for inner defect detection of metal pipelines. Tunneling magnetoresistance (TMR) array probes are applied to detect the magnetic signal generated by the inner surface defect of the metal pipelines. Compared to single probe structure, the annular array probes have advantages of high sensitivity, large scanning area and internal realtime detection. However, since many probes are densely arranged in the array, signal interference may occur between adjacent probes. Therefore, two methods of anti-interference, magnetic shielding and time-sharing excitation, are proposed in this work. By modeling and simulation, the working principles of the two anti-interference modes are analyzed and compared respectively. The experimental results show that both methods can reduce the interference between adjacent TMR probes. Compared with the time-sharing excitation method, the magnetic shielding method exhibits better performance with stronger differential signal peak and smaller error, and proves to be a more effective method for the defect detection of the metal pipelines.

The purpose of this study was to investigate the effect of high- and low-frequency rTMS on the recovery of upper extremity function in acute stroke patients. This study was designed as a randomized, sham-controlled, double-blind, clinical trial. Experimental subjects were randomly divided into 10 Hz rTMS group (high frequency) and 1Hz group (low frequency). All subjects received 10 stimulation sessions, 5 days a week for 2 weeks. In the high frequency group (N=12), 10Hz rTMS was applied to the M1 area on the side of the brain lesion. The control group (N=13) applied 1Hz rTMS to the same brain area as the high-frequency group. In this study, the Modified Barthel Index (MBI) was used to evaluate independence in activities of daily living in stroke patients. To evaluate upper limb motor function, Fugl-Meyer motor assessment (FMA-UE) and Manual Function Test (MFT) were used. All subjects had motor function assessed before and 2 weeks after rTMS. There was no significant difference before and after intervention in both the high-frequency and low-frequency groups (p > 0.05). In the comparison between the two groups, there was no significant difference in all variables after the intervention (p > 0.05). There is still controversy as to whether high-frequency stimulation of the lesional M1 or low-frequency stimulation of the contralesional M1 is effective for stroke patients with mild and moderate functional impairment.

The purpose of this study was to investigate the effect of repetitive transcranial magnetic stimulation (rTMS) according to the brain stimulation site on cognition and upper extremity function in stroke patients. The 48 patients were randomly assigned to group 1 (n = 16), group 2 (n = 16) and sham control group (n = 16). Group 1 stimulated the ipsilateral dorsolateral prefrontal cortex (DLPFC) with 90 % of the resting motor threshold (RMT), and group 2 stimulated the ipsilateral primary motor cortex (M1) with 90 % of the RMT. For sham stimulation of group 3, the coil was placed perpendicular to the skull. All subjects received rTMS before traditional rehabilitation treatment, and rTMS sessions were conducted 5 times per week, for a total of 4 weeks. The subject's cognition was evaluated using Five-minute cognitive test (FCT) and Korean version of Alzheimer’s disease assessment scale-cognitive subscale (ADAS-K-cog), and the upper extremity function was evaluated using Wolf Motor Function Test (WMFT) and Jebsen-Taylor Hand Function Test (JTHFT). All evaluations were followed before and after intervention and 2 weeks after completion of the interventions. As a result of this study, the group that applied rTMS to DLPFC significantly improved both cognition and upper extremity functions, and the group that applied rTMS to M1 significantly improved motor functions. Additionally, because the long-term effects of rTMS were confirmed in both groups through follow-up tests, this study suggests that rTMS is an effective intervention method for long-term rehabilitation of stroke patients with permanent disabilities.

Positron emission tomography (PET) images in magnetic resonance (MR)/PET fusion imaging systems are corrected for parts attenuated by gamma-rays by various MR pulse sequences. We aimed to study the quality of MR/PET images using an attenuation correction method based on ultrashort echo-time (UTE) pulse sequences. The proposed image-quality improvement algorithm was modeled as a convergence of the median-modified Wiener filter (MMWF) for noise reduction and Prewitt operator for emphasizing the edge area. By applying the proposed algorithm to MR/PET images, superior contrast to noise ratio and coefficient of variation values were obtained compared to those in the original image. The edge rise distance data of the proposed algorithm exhibited a very small difference from that of the original MR/PET image (difference: 2.21 %). In conclusion, we confirmed the applicability and usefulness of MMWF and Prewitt operator in UTE-based MR/PET imaging.

In the ever-evolving field of Magnetic Resonance Imaging (MRI), an array of innovative techniques are emerging that incorporate the use of contrast agents, with a particular focus on their application in the diagnosis of cancer. These cutting-edge strategies commonly involve the integration of MRI with a biocompatible targeting entity and Magnetic Nanoparticles (MNPs), a combination that has demonstrated significant efficacy in the detection of cancerous cells. Among these pioneering approaches, one strategy that shows remarkable promise involves the coupling of MRI with a Nano-drone (NH2-PEGylated Hyaluronic Acid-Manganese ferrite). This novel nano-drone is fabricated using a thermal decomposition method, a process known for its precision and reliability. The resultant Nano-drone exhibits sensitivity to T2 weighted or T2 Turbo Spin Echo (TSE) MRI, paving the way for new diagnostic possibilities in the realm of cancer detection. To validate the efficacy of this innovative approach, we designed an experiment that involved the injection of a specific Gastric Cancer cell line, known as MKN-45, into murine gastric tissue. This strategic application allowed us to closely monitor the interaction of the Nano-drone with the cancer cells. In the subsequent stages of the experiment, we utilized T2 TSE magnetic resonance sequences to evaluate the imaging impact of the Nano-drone. This assessment was crucial in determining the targeting proficiency of the Nano-drone, and how effectively it could pinpoint the cancer cells within the gastric tissue. Our findings from this comprehensive study suggest the potential of the Nano-drone as a groundbreaking probe for the visualization of Gastric Cancer. Furthermore, they underscore the significance of TSE validation in unveiling new diagnostic possibilities. The results of our study offer a beacon of hope in the fight against cancer, demonstrating the potential of the Nano-drone to open new avenues in cancer diagnosis and treatment.

In response to climate change caused by carbon emissions, many studies and policy efforts have been implemented to reduce carbon emissions through various international agreements and policies. A policy for expanding the supply of eco-friendly vehicles is also a representative example. When an internal combustion engine vehicle is converted to an electric vehicle (xEV), the emission reduction effect is extremely high. However, xEV vehicles are difficult to distribute because of their shorter mileage compared with internal combustion engines. Recent studies have aimed to reduce the weight of a vehicle by improving the power density of the driving motor and securing a driving distance by improving the system efficiency accordingly. In this study, we aimed to improve the efficiency of the motor by improving the residual magnetic flux density and reducing iron loss by improving the performance of the iron core material. In addition, the power density of a vehicle motor was improved by applying a hairpin winding that maximized the fill factor of the stator. To verify the validity of the derived motor, efficiency and ripple maps for the entire driving range were extracted to confirm the output characteristics. The validity of this study was identified through manufacturing and testing.

Here, the investigation of the structural features, magnetic properties, and domain structure of multilayer superlattices prepared by molecular beam epitaxy and partial oxidation of magnetic layers is presented. The influence of the number of repetitions on the morphology of the interfaces is investigated. It is also shown that the epitaxial growth of the Pd and Cu layers is retained when growing over oxide layers. The paper presents the dependences of the coercive force and magnetic anisotropy energy and explains their behavior. The domain structure is studied by the magnetooptical Kerr effect and magnetic force microscopy. The possibilities of modifying the domain structure into skyrmion lattices by local action with a magnetic probe and without an external magnetic field are demonstrated.

The coercivity of a ferromagnetic material is highly dependent on the morphology and defects at the submicron scale. In this work, sub-micron grains of CoFe alloy were obtained by depositing them on the rough surface of diamagnetic MoS₂ thin films, which resulted in the coercivity being enhanced by 7 times compared to that deposited on smooth MoS₂ surface. The morphologies of the MoS₂ thin films were controlled by adjusting the growth temperature and deposition time. Surfaces of MoS₂ thin films with 200-nm-high nano standing walls spaced 100 nm and 250 nm apart, as well as a smooth surface with a roughness of 0.6 nm, were used. The CoFe alloys deposited on these varied surfaces exhibited significantly different ferromagnetic hysteresis behaviors. For spin valve applications, the enhanced coercivity in the soft magnet with a bilayer structure suggests a new approach to building pinned layers.