Search Results (184)

Measuring weak magnetic fields proposes significant challenges to the sensing capabilities of magnetic field sensors. The magnetic field detection capacity of tunnel magnetoresistance (TMR) sensors is often insufficient for such applications, necessitating targeted optimization strategies to improve their performance in weak-field measurements. Utilizing magnetic flux concentrators (MFCs) offers an effective approach to enhance TMR sensitivity. In this study, the finite element method was employed to analyze the effects of different MFC geometric structures on the uniformity of the magnetic field in the air gap and the magnetic circuit gain (MCG). It was determined that the MCG of the MFC is not directly related to the absolute values of its parameters but rather to their ratios. Simulation analyses evaluated the impact of these parameter ratios on both the MCG and its spatial distribution uniformity, leading to the formulation of MFC design optimization principles. Building on these simulation-derived principles, several MFCs were fabricated using the 1J85 material, and an experimental platform was established to validate the simulation findings. The fabricated MFCs achieved an MCG of 7.325 times. Based on the previously developed TMR devices, a detection sensitivity of 2.46 nT/$\sqrt{\mathrm{Hz}}$ @1Hz was obtained. By optimizing parameter configurations, this work provides theoretical guidance for further enhancing the performance of TMR sensors in magnetic field measurements. Full article

Electric mountain bikes (eMTBs) demand compact, high-torque motors capable of handling steep terrain and variable load conditions. Surface-mounted permanent magnet synchronous motors (SPMSMs) are widely used in this application due to their simple construction, ease of manufacturing, and cost-effectiveness. However, SPMSMs inherently lack reluctance torque, limiting their torque density and performance at high speeds. While interior PMSMs (IPMSMs) can overcome this limitation via reluctance torque, they require complex rotor machining and may compromise mechanical robustness. This paper proposes a surface-inset PMSM topology as a compromise between both approaches—introducing reluctance torque while maintaining a structurally simple rotor. The proposed motor features inset magnets shaped with a tapered outer profile, allowing them to remain flush with the rotor surface. This geometric configuration eliminates the need for a retaining sleeve during high-speed operation while also enabling saliency-based torque contribution. A baseline SPMSM design is first analyzed through finite element analysis (FEA) to establish reference performance. Comparative simulations show that the proposed design achieves a 20% increase in peak torque and a 33% reduction in current density. Experimental validation confirms these findings, with the fabricated prototype achieving a torque density of 30.1 kNm/m³. The results demonstrate that reluctance-assisted torque enhancement can be achieved without compromising mechanical simplicity or manufacturability. This study provides a practical pathway for improving motor performance in eMTB systems while retaining the production advantages of surface-mounted designs. The surface-inset approach offers a scalable and cost-effective solution that bridges the gap between conventional SPMSMs and more complex IPMSMs in high-demand e-mobility applications. Full article

Compact toroid (CT) injection, with its characteristics of high plasma density and extremely high injection velocity, is considered a highly promising method for core fueling in fusion reactors. Previous studies have lacked investigation into the transport process of CT within drift tubes. To investigate the dynamic processes of CT in drift tubes, this study developed a compressible magnetohydrodynamics (MHD) solver and a magnetic diffusion solver based on the OpenFOAM platform. They were integrated into a multi-region coupling framework to create a multi-region coupled MHD solver, mhdMRF, for simulating the dynamic behavior of CT in drift tubes and its interaction with finite-resistivity walls. The solver demonstrated excellent performance in simulations of the Orszag–Tang MHD vortex problem, the Brio–Wu shock tube problem, analytical verification of magnetic diffusion, and validation of internal coupling boundary conditions. Additionally, this work innovatively explored the effects of the geometric structure at the end of the inner electrode and finite-resistivity walls on the transport processes of CT. The results indicate that optimizing the geometric structure at the end of the inner electrode can significantly enhance the confinement performance and stability of CT transport. The resistivity of the wall profoundly influences the magnetic field structure and density distribution of CT. Full article

In this study, we investigate the presence of the Griffiths-like anomaly in the geometrically frustrated antiferromagnet ${\mathrm{HoBaCo}}_4$${\mathrm{O}}_{7+\delta }$ and globally its absence in ${\mathrm{ErBaCo}}_4$${\mathrm{O}}_{7+\delta }$, despite only small differences in the ionic radii, f-electron occupancy, and the corresponding crystal structures of the ${\mathrm{Ho}}^{3+}$ and ${\mathrm{Er}}^{3+}$-members. Previous studies have identified the Griffiths phase in the Dy-analog, ${\mathrm{DyBaCo}}_4$${\mathrm{O}}_{7+\delta }$, suggesting certain inherent features of this class of materials that regularly give rise to such anomalies. To explore the curious disappearance of such an anomalous feature in ${\mathrm{ErBaCo}}_4$${\mathrm{O}}_{7+\delta }$, we prepared a series of compounds with varying compositions ${\mathrm{Ho}}_{1-x}$${\mathrm{Er}}_x$${\mathrm{BaCo}}_4$${\mathrm{O}}_{7+\delta }$ ($0\le x\le 1$) and systematically studied the evolution of various physical properties as a function of Er-doping. Our experimental studies, including X-ray diffraction (XRD), magnetic, X-ray absorption spectroscopy (XAS), X-ray photoelectron spectroscopy (XPS), heat capacity, and muon spin relaxation spectroscopy ($\mu$SR spectroscopy), revealed that while the Griffiths-like anomaly indeed disappears with doping at the macroscopic level, signatures of inhomogeneity are retained in ${\mathrm{ErBaCo}}_4$${\mathrm{O}}_{7+\delta }$ too, at least at the local level. Overall, our results highlight the significant role of ionic radius and local structural distortions in stabilizing the Griffiths phase in this class of systems. Full article

The strong heterogeneity of carbonate reservoirs poses significant technical challenges in reservoir classification and permeability evaluation. This study proposes a new method for reservoir classification based on nuclear magnetic resonance (NMR) logging data for the Asmari formation of the Middle East M Oilfield, a carbonate reservoir. By integrating NMR T₂ spectrum characteristic parameters (such as T₂ geometric mean, T_2R35/R50/R65, and pore volume fraction) with principal component analysis (PCA) for dimensionality reduction and an improved slope method, this study achieves fine reservoir type classification. The results are compared with core pressure curves and petrographic pore types. This study reveals that the Asmari reservoir can be divided into four categories (RT1 to RT4). RT1 reservoirs are characterized by large pore throats (maximum pore throat radius >3.8 μm), low displacement pressure (<0.2 MPa), and high permeability (average 22.16 mD), corresponding to a pore structure dominated by intergranular dissolution pores. RT4 reservoirs, on the other hand, exhibit small pore throats (<1 μm), high displacement pressure (>0.7 MPa), and low permeability (0.66 mD) and are primarily composed of dense dolostone or limestone. The classification results show good consistency with capillary pressure curves and petrographic pore types, and the pore–permeability relationships of each reservoir type have significantly higher fitting goodness (R² = 0.48~0.68) compared with the unclassified model (R² = 0.24). In the new well application, the root mean square error (RMSE) of permeability prediction decreased from 0.34 mD using traditional methods to 0.21 mD, demonstrating the method’s effectiveness. This approach does not rely on a large number of mercury injection experiments and can achieve reservoir classification solely through NMR logging. It provides a scalable technological paradigm for permeability prediction and development scheme optimization of highly heterogeneous carbonate reservoirs, offering valuable references for similar reservoirs worldwide. Full article

This review article provides an in-depth analysis of recent advancements in the fabrication, structural characterization, and magnetic properties of Heusler alloy glass-coated microwires, focusing on Co₂FeSi alloys. These microwires exhibit unique thermal stability, high Curie temperatures, and tunable magnetic properties, making them suitable for a wide range of applications in spintronics, magnetic sensing, and biomedical engineering. The review emphasizes the influence of geometric parameters, annealing conditions, and compositional variations on the microstructure and magnetic behavior of these materials. Detailed discussions on the Taylor–Ulitovsky fabrication technique, X-ray diffraction (XRD) analysis, and scanning electron microscopy (SEM) provide insights into the structural properties of the microwires. The magnetic properties, including room-temperature behavior, temperature dependence, and the effects of annealing, are thoroughly examined. The potential applications of these microwires in advanced spintronic devices, magnetic sensors, and biomedical technologies are explored. The review concludes with future research directions, highlighting the potential for further advancements in the field of Heusler alloy microwires. Full article

To address the issue of uneven temperature distribution during the tire vulcanization process based on electromagnetic heating, this study focuses on the hot plate of a tire vulcanizing machine. An octagonal hot plate with dimensions of 1380 mm × 1380 mm × 60 mm was adopted, and temperature sensors were installed to monitor temperature changes in real time. Through electromagnetic simulation, the effects of current intensity, frequency, and coil-to-hot-plate distance on temperature uniformity were studied. The simulation results show that the temperature difference increases with current intensity and current frequency, while the temperature difference decreases with the increase in coil-to-hot-plate distance. To minimize the temperature gradient, the coil layout was structurally optimized based on the geometric features of the hot plate to improve magnetic field distribution. Several coil arrangements were designed and compared, including uniform, dual-ring, multi-ring, and the newly proposed flower-shaped configuration. It shows that the multi-ring circular coil has the best uniformity when heating a circular hot plate, and the flower-shaped coil has best temperature uniformity when heating an octagonal hot plate. Experimental validation using an industrial-scale prototype confirmed that the optimized design reduced temperature variation to within ±2 degrees Celsius. This work contributes a practical and geometrically informed coil design strategy for improving the temperature uniformity and energy efficiency of electromagnetic heating systems in industrial tire vulcanization. Full article

Developing advanced materials with enhanced performance through the doping of nanoclusters is a promising strategy. However, there remains an insufficient understanding of the specific effects induced by such doped nanoclusters, particularly regarding the structural evolution pattern after doping with rare-earth elements and their impact on performance. To solve this problem, we used first-principles calculation to study the structural evolution pattern and spectroscopic properties of anionic TbGe_n (n = 6–17) nanoclusters through the ABCluster global search technique coupled with the mPW2PLYP double-hybrid density functional theory. The results revealed that the geometrical evolution pattern is from the typical Tb-linked structures (for n = 10–13, in which Tb acts as a linker connecting two germanium sub-clusters) to Tb-centered cage configurations (for n = 14–17). The simulated photoelectron spectroscopy of anionic TbGe₁₆ agrees well with its experimental counterpart. Furthermore, we calculated properties such as infrared spectroscopy, Raman spectroscopy, ultraviolet–visible (UV–vis) spectra, magnetism, charge transfer, the HOMO-LUMO gap, and relative stability. The results suggest that TbGe₁₂⁻ and TbGe₁₆⁻ clusters, with their remarkable stability and tunable photothermal properties, can serve as ideal building blocks for developing novel functional nanomaterials. These clusters demonstrate promising applications in solar photothermal conversion, photoelectric conversion, and infrared imaging technologies through their distinct one- and three-dimensional architectures, respectively. Full article

We develop a unified analytical framework that systematically connects kinetic theory, optimal transport, and entropy dissipation through the novel integration of hypocoercivity methods with geometric structures. Building upon but distinctly extending classical hypocoercivity approaches, we demonstrate how geometric control, via commutators and curvature-like structures in probability spaces, resolves degeneracies inherent in kinetic operators. Centered around the Boltzmann and Fokker–Planck equations, we derive sharp exponential convergence estimates under minimal regularity assumptions, improving on prior methods by incorporating Wasserstein gradient flow techniques. Our framework is further applied to the study of hydrodynamic limits, collisional relaxation in magnetized plasmas, the Vlasov–Poisson system, and modern data-driven algorithms, highlighting the central role of entropy as both a physical and variational tool across disciplines. By bridging entropy dissipation, optimal transport, and geometric analysis, our work offers a new perspective on stability, convergence, and structure in high-dimensional kinetic models and applications. Full article

With global energy demand surging and traditional energy resources diminishing, the solar absorber featuring optimized design shows substantial potential in areas like power generation. This study proposes a solar absorber that is insensitive to wide-angle incidence and polarization. It has a cylindrical structure with square holes, which is constructed from titanium nitride (TiN). The calculation results indicate that, for plane waves, the average absorption of this solar absorber across the wavelength range of 300–2500 nm reaches 92.4%. Moreover, its absorption rate of the solar spectrum corresponding to AM1.5 reaches 94.8%. The analysis of the characteristics within the electric and magnetic field profiles indicates that the superior absorption properties arise from a cooperative resonance effect. This effect originates from the interaction among surface plasmon resonance, guided-mode resonance, and cavity resonance. In this study, the geometric parameters of the solar absorber’s structure significantly influence its absorption performance. Therefore, we optimized these parameters to obtain the optimal values. Even at a large incident angle, this absorber maintains high absorption performance and shows insensitivity to the polarization angle. The findings expected from this study are likely to be of considerable practical importance within the realm of solar photothermal conversion. Full article

Ta₂AlC is an emerging ceramic material characterized by its high melting point, high hardness, excellent thermal stability, and superior mechanical properties, which allow for broad application prospects in aerospace and defense fields. This paper investigates the physical mechanisms underlying the modulation of the mechanical and photoelectric properties of Ta₂AlC through doping using the first-principles pseudopotential plane-wave method. We specifically calculated the geometric structure, mechanical properties, electronic structure, Mulliken population analysis, and optical properties of Ta₂AlC doped with V, Ga, or Si. The results indicate that doping induces significant changes in the structural parameters of Ta₂AlC. By applying the Born’s criterion as the standard for mechanical stability, we have calculated that the structures of Ta₂AlC, both before and after doping, are stable. The mechanical property calculations revealed that V and Si doping weaken the material’s resistance to deformation while enhancing its plasticity. In contrast, Ga doping increases the material’s resistance to lateral deformation and brittleness. Doping also increases the anisotropy of Ta₂AlC. Electronic structure calculations confirmed that Ta₂AlC is a conductor with excellent electrical conductivity, which is not diminished by doping. The symmetric distribution of spin-up and spin-down electronic state densities indicates that the Ta₂AlC system remains non-magnetic after doping. The partial density of states diagrams successfully elucidated the influence of dopant atoms on the band structure and electronic state density. Mulliken population analysis revealed that V and Ga doping enhance the covalent interactions between C-Ta and Al-Ta atoms, whereas Si doping weakens these interactions. Optical property calculations showed that V and Si doping significantly enhance the electromagnetic energy storage capacity and dielectric loss of Ta₂AlC, while Ga doping has minimal effect. The reflectivity of doped and undoped Ta₂AlC reaches over 90% in the ultraviolet region, indicating its potential as an anti-ultraviolet coating material. In the visible light region, both doped and undoped Ta₂AlC exhibit a similar metallic gray appearance, suggesting its potential as a temperature control coating material. The light loss of Ta₂AlC is limited to a narrow energy range, indicating that doping does not affect its use as a light storage material. These results demonstrate that different dopants can effectively modulate the mechanical and photoelectric properties of Ta₂AlC. Full article

Driven by technological advancements and accelerated infrastructure development, an increase in the need to monitor the performance of prominent structures such as bridges, metro-corridors, and sea-link bridges is being advocated by experts to predict and minimize any hazards resulting from the degradation of the structures over time. However, accessing and replacing the batteries becomes problematic and expensive when the sensors are instrumented in remote areas of the bridge structures, especially when the sensors are embedded. For these reasons, a strong case can be made for harvesting and storing ambient energy from the surroundings to drive the sensors for structural health monitoring (SHM). This study aims to introduce a new trapezoidal strain-amplifying sensor/energy harvester (TSAH) for civil engineering structures that uses flexural strain amplification to enhance energy harvesting from structural vibrations. TSAH also serves as a sensor for integrated energy harvesting and SHM. This article examines the influence of the geometric properties of TSAH on strain amplification via numerical investigations under a specific set of external loads. Based on numerical studies, the sensors are bonded to the trapezoidal strain-amplifying plate to develop and assess the TSAH. Experimental investigations were carried out first in the laboratory to evaluate the effectiveness of the TSAH over the directly bonded (DB) sensors with two different types of piezo-transducers for energy harvesting. The host structure was exposed to impact and shaker vibrations for the laboratory research. For the various scenarios taken into consideration in the study, the typical amplification factor for peak voltage is determined to be between 1.45 and 3.75, while for the power, it is between 1.09 and 6.08. Further, for field verification, the TSAH configuration was evaluated on a real-life bridge structure, viz the Chipiyana rail over-bridge (ROB), Asia’s heaviest steel ROB located on the Delhi–Meerut expressway. The field experiments also establish the superior performance of TSAH, with an amplification factor ranging from 1.75 to 3.75 for peak voltage and 3.75 to 5.53 for peak power. As compared to the previously proposed curved configuration in the literature, the TSAH configuration is suitable for brittle sensors as well. Its ability to be permanently bonded by epoxy/welding, or temporarily using magnets, bolts, or clamps, offers it versatility over other surface bonded/embedded configurations. As a result of this, it imparts reusability in case of any damage, which promotes the goal of sustainability. Full article

To investigate the molecular structure characteristics and chemical reaction mechanisms of gas coal from the Hong II coal mine of the Ningxia Hongdunzi Coal Industry, this study explores its elemental composition, structural features, and methods for constructing and optimizing molecular models. The basic properties of the coal were determined through proximate and elemental analyses. The carbon structure was characterized using ¹³C-NMR nuclear magnetic resonance, the N and S chemical states were analyzed with XPS, and the distribution of hydroxyl, aliphatic hydrocarbons, aromatic rings, and oxygen-containing functional groups was characterized by FT-IR. Based on the analysis results, a molecular structure model of Hongdunzi gas coal was constructed with the molecular formula C₂₀₄H₁₁₇O₁₇NS, and the calculated results of the model showed high consistency with the experimental spectra of ¹³C-NMR. The macromolecular model of gas coal was constructed using the Materials Studio 2020 software, and its structure was optimized through geometric optimization and dynamic simulations. After optimization, the total energy of the model was significantly reduced from 8525.12 kcal·mol⁻¹ to 3966.16 kcal·mol⁻¹, highlighting the enhanced stability of the coal molecular structure. This optimization indicates that torsional energy plays a dominant role in molecular stability, while van der Waals forces and electrostatic interactions were significantly improved during the optimization process. Full article

Background: We aimed to measure the pacemaker- and defibrillator-induced distortion at 0.35T and 3.0T magnetic fields. Methods: The pacemaker/defibrillator was placed at the top center of a water-filled/MagPhan phantom, followed by a T1 scan at 3T and a TrueFISP scan at 0.35T. The extent of distortion (i.e., the distance from the device to the furthest signal loss/void/rings) in the water-filled phantom was measured in MIM. For geometrical distortion (i.e., dislocation of geometrical structures), the spheres in the MagPhan phantom were contoured and their distortion was calculated based on their manufacturing coordinate positions. Results: The maximum extent of distortion caused by the defibrillator was 18.8 cm at 0.35T and 5.8 cm at 3.0T. Similarly, the maximum extent of distortion caused by the pacemaker was 9.28 cm at 0.35T and 2.8 cm at 3.0T. Geometrical distortion measurements using the MagPhan phantom showed that the maximum distortion caused by the defibrillator was 12.8 mm at 0.35T and 13.2 mm at 3.0T. Likewise, the maximum distortion caused by the pacemaker was 8.7 mm at 0.35T and 6.0 mm at 3.0T. Conclusions: Defibrillators cause larger distortions/signal voids than pacemakers, and require careful consideration when performing MRI-based treatment planning. To minimize distortion, sequences with lower sensitivity to magnetic field inhomogeneity should be used. Full article

In the field of material manufacturing, torsional vibration has some benefits for cutting or forming processing. In principle, torsional vibration can be caused by the torque ripples of a motor. Flux-switching permanent magnet (FSPM) motors are doubly salient and generate torque ripples, making them an option for manufacturing. However, the amplitude of the torque ripples is related to the motor structure, and frequency has a linear relationship with running speed. The torque ripples cannot be controlled separately from the motor running speed at conventional current excitations. Thus, a novel FSPM machine with an auxiliary rotor (AR-FSPM) is proposed to adjust the torque ripples. The main rotor (m-rotor) outputs the power, and the auxiliary rotor (a-rotor) adjusts the ripple frequency. When the speed difference between two rotors is six times the m-rotor speed, the torque ripple waveforms overlap. In this case, by controlling the phase difference between the two rotors, the amplitudes of the torque ripples can be adjusted. In this study, the principle of this novel machine is introduced, and the relationship between the torque ripple performance and the geometric parameters of the auxiliary rotor is studied. Then, the torque ripple amplitude adjustment method for this machine is discussed. Finally, the prototype of this novel machine is presented to verify its feasibility. Full article