Search Results (71)

This research investigates resonator width optimization for simultaneously enhancing electrical performance and mechanical reliability in wideband RF MEMS filters through systematic evaluation of three configurations: 0% (L1), 60% (L2), and 100% (L3) matching ratios between cap and bottom wafers using Au-Au thermocompression bonding. The study demonstrates that resonator width alignment significantly influences both electromagnetic field coupling and bonding interface integrity. The L3 configuration with complete width matching achieved optimal RF performance, demonstrating 3.34 dB insertion loss across 4.5 GHz bandwidth (25% fractional bandwidth), outperforming L2 (3.56 dB) and L1 (3.10 dB), while providing enhanced electromagnetic wave coupling and minimized contact resistance. Mechanical reliability testing revealed superior bonding strength for the L3 configuration, withstanding up to 7.14 Kgf in shear pull tests, significantly exceeding L1 (4.22 Kgf) and L2 (2.24 Kgf). SEM analysis confirmed uniform bonding interfaces with minimal void formation (~180 nm), while Q-factor measurements showed L3 achieved optimal loaded Q-factor (Q_L = 3.31) suitable for wideband operation. Comprehensive environmental testing, including thermal cycling (−50 °C to +145 °C) and humidity exposure per MIL-STD-810E standards, validated long-term stability across all configurations. This investigation establishes that complete resonator width matching between cap and bottom wafers optimizes both electromagnetic performance and mechanical bonding reliability, providing a validated framework for developing high-performance, reliable RF MEMS devices for next-generation communication, radar, and sensing applications. Full article

Magnetic levitation enables the confinement and melting of conductive metals using alternating magnetic fields, eliminating the need for a crucible or other contact supports. This makes the technology particularly suitable for applications where container use is impractical, such as preventing contamination between the melt and the crucible, handling high-purity materials, or facilitating in-orbit operations. For a given coil design and load, selecting the appropriate feeding parameters, such as the current and frequency, is crucial to ensure the correct operation of the device. This study investigates the optimal current and frequency values required to levitate an aluminum billet using a proposed longitudinal electromagnetic levitator, which represents an initial prototype of a more complex system for automated material manipulation. The analysis was conducted through 2D and 3D finite element method (FEM) simulations, assessing the equilibrium position and stability with respect to translations and rotations under various operating conditions. The study identifies an operating configuration that ensures vertical stability while minimizing excessive heating, in order to obtain a sufficiently long confinement time before the melting point is reached. A fully coupled 2D thermal simulation was then performed to assess the billet’s heating rate under the selected operating conditions. Finally, an experiment was conducted on a prototype to confirm billet levitation. Full article

Background: Glioblastoma (GBM) resists current therapies due to its rapid proliferation, diffuse invasion, and heterogeneous cell populations. We previously showed that a single cold atmospheric plasma discharge tube (DT) reduces GBM viability via broad-spectrum electromagnetic (EM) emissions. Here, we tested whether two DTs arranged in a helmet configuration could generate overlapping EM fields to amplify the anti-tumor effects without thermal injury. Methods: The physical outputs of the single- and dual-DT setups were characterized by infrared thermography, broadband EM field probes, and oscilloscope analysis. Human U87-MG cells were exposed under the single or dual configurations. The viability was quantified with WST-8 assays mapped across 96-well plates; the intracellular reactive oxygen species (ROS), membrane integrity, apoptosis, and mitochondrial potential were assessed by multiparametric flow cytometry. Our additivity models compared the predicted versus observed dual-DT cytotoxicity. Results: The dual-DT operation produced constructive EM interference, elevating electric and magnetic field amplitudes over a broader area than either tube alone, while temperatures remained <39 °C. The single-DT exposure lowered the cell viability by ~40%; the dual-DT treatment reduced the viability by ~60%, exceeding the additive predictions. The regions of greatest cytotoxicity co-localized with the zones of highest EM field overlap. The dual-DT exposure doubled the intracellular ROS compared with single-DT and Annexin V positivity, confirming oxidative stress-driven cell death. The out-of-phase operation of the discharge tubes enabled the localized control of the treatment regions, which can guide future treatment planning. Conclusions: Two synchronously operated plasma discharge tubes synergistically enhanced GBM cell killing through non-thermal mechanisms that coupled intensified overlapping EM fields with elevated oxidative stress. This positions modular multi-DT arrays as a potential non-invasive adjunct or alternative to existing electric-field-based therapies for glioblastoma. Full article

This paper presents a comprehensive analytical framework for investigating loss mechanisms and thermal behavior in high-speed magnetic field-modulated motors for flywheel energy storage systems. Through systematic classification of electromagnetic, mechanical, and additional losses, we reveal that modulator components constitute approximately 45% of total system losses at rated speed. Finite element analysis demonstrates significant spatial non-uniformity in loss distribution, with peak loss densities of 5.5 × 10⁵ W/m³ occurring in the modulator region, while end-region losses exceed central-region values by 42% due to three-dimensional field effects. Our optimized design, implementing composite rotor structures, dual-material permanent magnets, and integrated thermal management solutions, achieves a 43.2% reduction in total electromagnetic losses, with permanent magnet eddy current losses decreasing by 68.7%. The maximum temperature hotspots decrease from 143 °C to 98 °C under identical operating conditions, with temperature gradients reduced by 58%. Peak efficiency increases from 92.3% to 95.8%, with the η > 90% region expanding by 42% in the speed–torque plane. Experimental validation confirms model accuracy with mean absolute percentage errors below 4.2%. The optimized design demonstrates 24.8% faster response times during charging transients while maintaining 41.7% smaller speed oscillations during sudden load changes. These quantitative improvements address critical limitations in existing systems, providing a viable pathway toward high-reliability, grid-scale energy storage solutions with extended operational lifetimes and improved round-trip efficiency. Full article

The power conversion system of a small micro-reactor has strict requirements on the compactness of the rotating mechanical support. Although the active magnetic bearing is an ideal choice, the thermally induced vibration caused by it may destroy the stability of the system. As such, this study proposes a multi-physics coupling simulation framework, which integrates electromagnetic, thermal, and mechanical multi-physics coupling mechanisms and quantifies the stability of the system under thermal-induced vibration in the frequency domain. Firstly, the equivalent magnetic circuit and electromagnetic finite element modeling and calculation of the compressor rotor are carried out. In the case of the maximum AC current of 10 A, the equivalent stiffness of the magnetic pole is 4.21 × 10⁸ N/m and 2.1 × 10⁸ N/m, and the eddy current loss of the rotor is 4.17496 W. Based on the eddy current loss, a magneto-thermal coupling model is established to reveal the temperature gradient distribution and the thermal sensitivity coefficient of the journal is 0.006. Subsequently, the thermal stress and equivalent stiffness are coupled to the rotor dynamics equation, and the maximum amplitude of the rotor is obtained at a value of 0.001 mm. Finally, the critical stability threshold of the system is determined by a Nyquist diagram, and the results show that the system is stable as a whole. In this paper, the quantitative analysis of the cross-scale coupling mechanism of electromagnetic, thermal, and mechanical multi-physical fields is realized, which provides a systematic analysis method for the thermally induced vibration of magnetically suspended rotors and has important engineering significance for high power density rotating mechanical systems in small micro-reactors. Full article

Owing to the distinct advantages of stator–permanent magnet (PM) motors over other PM machines, their prominence in high-power-density applications is surging dramatically, capturing growing interest across diverse applications. This article proposes an innovative design procedure for two primary stator–PM motor types, flux switching and biased flux, yielding 30 novel motor designs. The procedure involves splitting teeth, incorporating a flux reversal effect, and embedding flux barriers into the conventional structure. The analytical reasons behind the novel motors’ architecture are mathematically expressed and verified using finite element analysis (FEA). Through an effective optimisation based on a multi-objective genetic algorithm, various feasible stator/rotor pole combinations are explored, with over 36,000 samples evaluated using FEA coupled with the algorithm. The electromagnetic characteristics of promising motors are analysed, revealing that adding the flux reversal effect and flux barriers, which reduce PM volume while decreasing leakage flux and enhancing air gap flux, improves torque production by up to 68%. Beyond torque enhancement, other electromagnetic parameters, including torque ripple, core loss, and the power factor, are also improved. The proposed motors enhance the PM torque density significantly by about 115% compared to conventional motors and reduce the motor costs. A generalised decision-making process and thermal analysis are applied to the top-performing motors. Additionally, the prototyping measures and considerations are thoroughly discussed. Finally, a comprehensive conclusion is reached. Full article

This study presents a comprehensive analysis and optimization methodology for bridge-connected modulators in coaxial magnetic gears. A novel harmonic modeling method incorporating magnetic saturation through permeability convolution matrices and multiple-layer radial subdivision is developed, achieving computational efficiency 20 times greater than finite element analysis with comparable accuracy (deviation < 3.2%). The research establishes an electromagnetic–structural coupling framework that captures the complex interactions between the magnetic field distribution and mechanical deformation, revealing critical trade-offs between electromagnetic performance and structural integrity. Multi-objective optimization using an improved NSGA-II algorithm identifies Pareto-optimal solutions balancing torque density, structural safety, efficiency, and thermal stability. Experimental testing validates that bridge width ratios between 0.05 and 0.07 provide optimal performance, delivering torque densities exceeding 80 kNm/m³ while maintaining stress ratios below 0.65 of material yield strength. Thermal analysis demonstrates that optimized configurations maintain operating temperatures below 70 °C with reduced thermal gradients. Vibration characteristics exhibit a strong correlation with bridge width, with wider bridges providing enhanced stability at higher speeds. The findings establish practical design guidelines for high-performance magnetic gears with improved reliability and manufacturability, advancing the fundamental understanding of electromagnetic–structural interactions in field-modulated magnetic gear systems. Full article

In this paper, a 96 V, 2.5 kW, 36-slot, and 32-pole brushless direct-current (BLDC) motor is designed, analyzed, and tested in the laboratory and on the prototype vehicle to provide the required output performance for an electric vehicle (EV) according to the rated operating conditions. Applications for in-wheel electric drivetrains have the potential to deliver high efficiency and high torque. Consequently, in-wheel motor topology is proposed for small EVs, and the sizing equations, including primary, stator, and rotor dimensions, are developed step by step for the preliminary design. Then, a multi-goal function is introduced to obtain optimum motor design. This motor has an outer-rotor-type construction. In addition, a concentrated winding arrangement is used, which ensures low-end winding and thus low copper loss. Then, multiphysics using the coupled electromagnetic–thermal analysis is carried out. Elective analysis using the finite element method, a motor prototype, and experimental studies verifies the design effectively. Full article

The torsion beam, integral to rear suspension systems in vehicles, is a critical component where strength and durability must be prioritized in specific regions. To enhance the strength of these regions, induction hardening, a localized heat treatment method, is employed. However, the application of this treatment introduces distortion, which compromises the precision of welding between components and raises significant concerns about product quality and safety. To address these challenges, the present study introduces a front-end analysis process for induction hardening aimed at predicting distortion following heat treatment. A three-dimensional model of the product was utilized to simulate the front-end process of induction hardening. A coupled analysis of electrical and thermal fields was conducted to replicate the heating effect induced by coils during the heat treatment process. Additionally, a thermo-structural coupled analysis was performed to predict the distortion occurring during the cooling phase. A comparative analysis with actual product measurements demonstrated that the proposed method achieved a distortion displacement prediction accuracy of 98%, thereby validating the efficacy of the proposed analysis process. Full article

Hydropower, with its high degree of flexibility, plays an important role in the transformation of the global energy mix. Generators are the core component of the hydropower units; their performance directly affects the efficiency and reliability of the hydroelectric units. The dynamic characteristics of a generator during operation are usually the result of the coupling and interaction of multiple physical fields. Therefore, the interactions among electromagnetic, thermal, structural, and fluid fields inside hydroelectric generators have become of great concern. This paper briefly reviews the hydroelectric generator multi-physics coupling investigations, which include research conducted through field measurements, theoretical analysis, and numerical simulations. The review covers electromagnetic vibrations of generators under the influence of electromagnetic and structural fields, heat generation of generators under the influence of electromagnetic and thermal fields, ventilation and heat dissipation of generators under the influence of flow and thermal fields, and physical field changes of generators under the influence of electromechanical signals. The review also highlights unresolved issues in the field of hydropower that could benefit from fundamental research using a multi-physics coupling approach. Full article

This study focuses on the effect of an induction heating device on the entry of a thin strip continuous casting and rolling line. A finite element model for the electromagnetic–thermal coupling of transverse magnetic flux induction heating was developed by adopting COMSOL software 6.1 to systematically investigate the effects of process parameters on the magnetic field, eddy current field, and the transverse temperature distribution of the strip. The results show that when the gap is between 20 mm and 40 mm, the maximum value of magnetic induction in the overheating region at the edges of the strip increases from 0.28 T to 0.35 T and 0.38. When the strip width is 1000 mm, there is an approximately 29% increase in magnetic induction in comparison to a strip with a width of 800 mm, and both eddy current density and temperature exhibit abnormal fluctuations. The maximum temperature difference in the temperature uniformity region at the center of the strip is only 3 °C at different frequencies, and the temperature-rise curves almost completely overlap. With increasing current, the temperature difference between the weak temperature region and the temperature uniformity region at the center widens, indicating a deterioration in temperature uniformity. Meanwhile, the field conditions are simulated using a simplified model of continuous heating. The results indicate that the maximum temperature deviation in the overheating region at the edges of the strip is 6 °C, while the deviation in the temperature uniformity region is 2 °C. Furthermore, the simulation data reveal an average temperature rise of 1156 °C across the width of the strip, with a deviation of 1.4 °C compared to the measured results, which verifies the validity of the proposed model. The analysis results provide a reference basis for designing transverse magnetic flux induction heating devices and optimizing process parameters. Full article

In order to avoid overheating of a BLDC permanent magnet (PM) motor at high speeds, this paper focuses on the loss reduction of a 90 W 47,000 r/min BLDC hollow-cup motor. It is proposed to provide an optimizing method for the series reactors and the parameterization of reactors in the motor system. The finite element method (FEM) is used to calculate and analyze the time harmonic of air-gap magnetic flux density, stator core loss, and rotor eddy current loss in two cases: with a series reactor and without a reactor. By parameterizing the inductance value, the optimal resistance value is determined to minimize motor loss. In addition, an electromagnetic–thermal coupling analysis is conducted, and the results show that the temperature distribution of the stator core, winding, and rotor are improved under reactor suppression. Finally, an experimental platform is built to verify the temperature increase and the efficiency of the motor load operation. A clear reference for the research and optimization analysis of motor loss reduction is provided. Full article

In this study, we present an exact solution to the Lindblad master equation describing the interaction of two quantized electromagnetic fields in a decaying cavity coupled to a thermal reservoir at a finite temperature. The solution is obtained using the superoperator technique, leveraging commutation relations to factorize the exponential of the Lindblad superoperators into a product of exponentials. To demonstrate the applicability of this approach, we analyze the dynamics of the system both analytically and numerically for two initial conditions: nonentangled and entangled coherent states, exploring their temporal evolution. Additionally, we employ entropy and quantum discord analysis to characterize quantum correlations and analyze the behavior of entanglement (or lack thereof) during the evolution. This comprehensive analysis provides valuable insights into the behavior of open quantum systems and their interaction with the environment. Full article

In this study, we investigate the properties of a thin accretion disk around a static spherically symmetric black hole in 4D Einstein–Gauss–Bonnet gravity, with an additional coupling constant, $\alpha$, appearing in the spacetime metric. Using the Novikov–Thorne accretion disk model, we examine the thermal properties of the disk, finding that increasing $\alpha$ reduces the energy, angular momentum, and effective potential of a test particle orbiting the black hole. We demonstrate that $\alpha$ can mimic the spin of a Kerr black hole in general relativity up to $a\simeq$ 0.23 M for the maximum value of $\alpha$. Our analysis of the thermal radiation flux shows that larger $\alpha$ values increase the flux and shift its maximum towards the central black hole, while far from the black hole, the solution recovers the Schwarzschild limit. The impact of $\alpha$ on the radiative efficiency of the disk is weak but can slightly alter it. Assuming black-body radiation, we observe that the disk’s temperature peaks near its inner edge and is higher for larger $\alpha$ values. Lastly, the electromagnetic spectra reveal that the disk’s luminosity is lower in Einstein–Gauss–Bonnet gravity compared to general relativity, with the peak luminosity shifting toward higher frequencies, corresponding to the soft X-ray band as $\alpha$ increases. Full article

This study aims to facilitate the assessment of the electromagnetic-electrical-thermal coupled response of a developed 30 kHz/12 kW silicon carbide (SiC)/silicon (Si) hybrid power-integrated module (hPIM) during load operation. To achieve this goal, an efficient electromagnetic-circuit-thermal coupling (ECTC) analysis methodology is introduced. This ECTC methodology incorporates a fully integrated electromagnetic-circuit coupling (EMCC) analysis model for parasitic extraction in order to addressing their effects on power losses, and a simplified electrothermal coupling (SETC) analysis model for temperature evaluation in order to consider the coupling influence of the instantaneous junction temperature on instantaneous power losses. The SETC model couples a simple lookup table that maps the power loss (P) in terms of the temperature (T) constructed using the developed EMCC model, and an equivalent Foster thermal network model established through three-dimensional (3D) computational fluid dynamics (CFD) thermal flow analysis. This PT lookup table, replacing the tedious and time-consuming EMCC simulation, is responsible for fast estimation of temperature-dependent power losses. The proposed analysis models, namely the CFD, EMCC, and SETC analysis models, are validated through thermal experiments and detailed modeling. Finally, the influence of various operation conditions on the power losses of the hPIM during the power conversion operation is explored through parametric analysis. Full article