Search Results (868)

The recent global energy crisis and the instability of the oil market have prompted scientists to explore innovative ways to produce alternative energy sources such as biodiesel. Current chemical processes for converting waste into biodiesel use catalyst-promoted conventional heating, ultrasonication, and magnetron-irradiated electromagnetic microwave irradiation, although developing more efficient, ecologically friendly methods remains challenging. The main goal of this research was to develop a novel, rapid, and efficient method for biodiesel production from waste cooking fats and oils (brown grease), using gyrotron-generated electromagnetic radiation. To achieve this goal, we investigated the effects of gyrotron radiation parameters, the heterogeneous catalyst WS₂, and the ratio of the reacting components on the efficiency of biodiesel production. Brown grease and its components, such as oleic acid, linoleic acid, triolein, and their mixtures, were explored as a source for biodiesel production. We selected promising conditions to develop a technological process for biodiesel production. As a result of our study, novel gyrotron-activated methods for biodiesel production using heterogeneous catalysts have been developed, and the production parameters have been improved. Full article

Vacuum induction melting (VIM) of recycled powder with bulk master alloy represents an industrialized approach for recycling metallic waste. However, the intrinsic mechanisms governing the co-melting behavior of materials with distinct melting characteristics, such as powder bed and bulk alloy, remain insufficiently understood. To address this, a coupled multiphysics model was developed to simulate the evolution of induction melting involving homogeneous alloys with different morphologies. This model integrates magnetic, electric, and phase-field dynamics while incorporating melt convective heat transfer, thereby establishing a fully coupled electromagnetic-thermo-hydrodynamic framework. Through this modeling approach, the entire VIM process of melting homogeneous alloy with different morphologies can be comprehensively analyzed. The validity of the model was verified via small-scale VIM experiments using FGH96 powder/bulk composite, supported by infrared temperature measurements. This simulation methodology is not only applicable to small-scale recycling but can also be extended to large-scale industrial production, providing a reliable theoretical foundation for the recycling of powder materials. Full article

Selective energy conversion in confined catalytic nanocavities is examined through a coupled reactive–photonic framework. The practical target is a combustor-integrated selective emitter for thermophotovoltaic (TPV) conversion and cascaded thermoelectric (TEG) recovery, in which Pt-coated anodic porous alumina (APA) functions simultaneously as a catalytic reactor, a cavity-modified electromagnetic environment and a heat-routing structure. Visible/near-infrared spectra (380–780 nm) show that Pt-coated APA exhibits a substantially stronger non-grey red-edge depression than a smooth zirconia reference. This observation establishes a spectral contrast in the measured window but is not used to identify an experimental cutoff wavelength, because a finite, open, lossy and array-coupled pore does not exhibit the abrupt edge predicted for an ideal cylindrical waveguide. For the mid-infrared, analytical scaling shows that the principal H₂O and CO₂ bands at 2.7, 4.3, 6.3 and 15.0 µm all lie deep in the evanescent regime relative to the ideal TE₁₁ cutoff wavelength λc ≈ 0.513 µm for a 300 nm pore. A converged finite-difference time-domain benchmark at the CO₂ 4.3 µm band yields a source-local Purcell factor F_p ≈ 0.38, indicating suppression of the total local density of optical states, while aperture flux is more than six orders of magnitude smaller than the near-field power budget. The specific contribution is therefore not the established fact of below-cutoff attenuation, but the co-design and separate quantification of a catalytic nanocavity as a reactive compartment, photonic environment and energy-branching element. The results provide a bounded mechanistic basis for combustor-integrated TPV and hybrid TPV/TEG architectures. Full article

Thermal energy storage using suitable materials is a strategic solution for integrating renewable energy and decarbonising industrial processes. Current Power-to-Heat systems using solar salt rely on electric heaters; however, the low thermal conductivity of molten solar salt promotes localised hot spots, leading to material degradation and reduced performance. Microwave heating is a promising alternative due to its volumetric heating capability and compatibility with renewable electricity. Nevertheless, dielectric characterisation shows that molten solar salt behaves as a highly conductive ionic medium with significant dielectric losses, limiting microwave penetration and resulting in predominantly surface-localised heating. To investigate this limitation, two cavity configurations were analysed using multiphysics simulations and parametric design studies: a single-mode elliptical cavity operating at 915 MHz with an iris, and a quasi-cylindrical multimode cavity operating at 2.45 GHz for scalable applications. The coupled electromagnetic, fluid-flow, and thermal behaviour was evaluated through the resulting field distributions and heating patterns. Complementary experiments assessed microwave-transparent container materials and determined the emissivity of molten solar salt from thermographic measurements, highlighting key engineering considerations for integrating microwave heating into next-generation Power-to-Heat technologies. The results demonstrate that microwave heating of highly conductive molten solar salt is fundamentally constrained by the limited electromagnetic penetration depth, defining practical design limits for its integration into next-generation Power-to-Heat systems. Full article

Hairpin windings are increasingly adopted in permanent magnet (PM) traction machines owing to their high slot fill factor, compact end-winding structure, and suitability for automated manufacturing. However, limited heat dissipation and high copper losses under peak loading and high-frequency operation result in severe thermal constraints, which restrict the power rating of the machine. This paper presents a multi-physics comparison of different winding cooling topologies for a PM machine with hairpin winding, including hollow conductor cooling, end-winding cooling, and cooling channel insertion at slot-bottom, slot-middle, and slot-opening regions. A coupled electromagnetic–thermal model based on the finite element method (FEM), which accounts the heat transfer between different components, is used to analyze temperature distribution, losses, efficiency, loading capacity, and hydraulic requirements. The results show that the position of the cooling channel has great influence on the thermal behavior and electromagnetic performance of the machine under different working conditions. The study emphasizes the strong coupling between cooling design, conductor geometry, AC loss behavior, and efficiency and provides practical design guidelines for selecting appropriate cooling techniques in high-power-density traction machines. Consequently, an improved cooling system results in a reduced amount of PM for the same output power range. Full article

The photothermal response of plasmonic nanomaterials is strongly affected by the electromagnetic and thermal interactions between neighboring particles. In this work, the finite element method was employed to investigate the distance-dependent photothermal behavior of Ag@TiO₂ core–shell nanorods under 808 nm laser irradiation. A single-nanorod model was first used to analyze the optical absorption and temperature distribution of an isolated nanorod, and an idealized two-nanorod model was then established to examine the coupled electromagnetic and thermal fields at different inter-particle spacings. The results show that reducing the inter-particle distance induces two competing effects: thermal-field superposition enhances local heat accumulation, whereas strong near-field plasmonic coupling at small separations modifies the electromagnetic field distribution, induces resonance shifts, and reduces the effective absorption cross-section, thereby weakening heat generation. Consequently, the temperature response exhibits a non-monotonic dependence on inter-particle distance, reflecting the competition between thermal-field overlap and plasmonic coupling. This work helps clarify the electromagnetic–thermal coupling mechanism of Ag@TiO₂ core–shell nanorods under near-infrared irradiation and provides a theoretical reference for understanding their distance-dependent photothermal response. Full article

Partial differential equations (PDEs) play a central role in scientific and engineering analysis, with applications spanning fluid dynamics, heat and mass transfer, electromagnetism, quantum mechanics, and financial modeling, where they are used to describe diffusion processes, wave propagation, and the evolution of complex systems over space and time. Solving multidimensional partial differential equations (PDEs) is a computationally challenging problem, even for the most advanced classical systems. Over the past decade, quantum computing has attracted significant interest as a potential approach for solving complex computational problems, including multidimensional PDEs. Although a variety of approaches have been proposed for solving PDEs, most of the existing techniques are based on variational quantum algorithms (VQAs). Despite being promising, these VQA-based approaches suffer from low accuracy, long execution times, and limited scalability. In this work, we propose a scalable and efficient quantum algorithm for solving multidimensional PDEs. Our algorithm has two variants. One variant is based on the finite difference method (FDM), classical-to-quantum (C2Q) encoding, and numerical instantiation, whereas the other is based on FDM, C2Q, and column-by-column decomposition (CCD). We have also evaluated our algorithm using several practical case studies; namely, Poisson, heat, Black–Scholes, and Navier–Stokes equations. The results show that our proposed approach achieves higher accuracy, greater scalability, and faster execution time than the VQA-based approaches. We validated these findings on both noise-free and noisy simulators, as well as on a hardware emulator and real IBM quantum hardware. Full article

The accurate detection and quantification of electromagnetic radiation in the infrared (IR) and terahertz (THz) regions are critical for modern applications, yet they remain challenging due to the “THz gap” and the limitations of current room-temperature technologies. This paper proposes a novel uncooled IR–THz power sensor based on a hybrid graphene oxide (GO) and polydimethylsiloxane (PDMS) bilayer integrated into a surface plasmon resonance (SPR) architecture in the Kretschmann configuration. The device exploits the broadband optical absorption of GO to efficiently convert incident radiation into heat, while the high thermo-optic coefficient of the PDMS layer translates these thermal variations into measurable refractive index shifts. Finite Element Method (FEM) modeling was employed to optimize the sensor design, predicting a linear angular shift of 0.093 deg/mW. Experimental results confirm the theoretical expectations, demonstrating a high sensitivity of 0.083 deg/mW and an exceptionally low limit of detection and resolution on the order of 15 nW. By eliminating the need for cryogenic cooling or vacuum packaging, this platform offers a compact, low-cost, and high-performance solution for next-generation IR–THz metrology. Full article

Magnetic actuation is a fundamental enabling technology for micro/nanorobotics and biomedical manipulation. However, the trade-off between magnetic field gradient, usable workspace, and efficient heat dissipation often conflicts and constrains its performance. Here, we present an enhanced electromagnetic manipulation system (EEMS) based on a compact, high-efficiency magnetic circuit and an optimized six-electromagnet configuration. By integrating high-permeability structural components and employing finite-element-based optimization, the system achieves a spherical workspace of 106 mm in diameter while maintaining strong and spatially controllable magnetic fields. Experimental results demonstrate magnetic flux densities up to 300 mT and a magnetic field gradient up to 9.5 T/m within the workspace, with a central magnetic field gradient of approximately 2 T/m under continuous operation at 3 A. Thermal simulations and measurements confirm safe operation below human body temperature without active cooling. Magnetic manipulation experiments in viscous environments further validate precise motion control and force balancing, highlighting the system’s potential for advanced magnetic manipulation and intelligent microrobotic applications. Full article

Here we describe a compact radiofrequency (RF) magnetic field generator designed to generate fields within millimeter-scale volumes. The device consists of printed multilayer circuit board (PCB) coils stacked in a paired parallel configuration. Compared to conventional solenoidal systems, this architecture significantly reduces device size, sample volume, and power requirements. We characterize the RF response of the system, including impedance and scattering parameters, and describe the behavior near ~330 kHz, which overlaps with frequencies common in magnetic nanoparticle heating, magnetic actuation, and other applications requiring localized fields. Electromagnetic modeling is used to evaluate magnetic field amplitude and spatial homogeneity (finding a maximum local deviation from the mean field of 5.5%). The mean B_z field across a 5 mm × 5 mm ROI centered between paired PCBs was 6.3 ± 0.1 mT/A (compared to 6.1 ± 1.0 mT/A measured experimentally). These results demonstrate operating parameters consistent with nanoparticle heating applications for PCB-based coil pairs. Full article

Crack defects are prone to occur during MAG overlay remanufacturing of TBM cutter rings, thereby affecting the repair quality and service reliability of the remanufactured layer. In this study, longitudinal alternating magnetic field (LAMF) stirring was introduced into the MAG overlay remanufacturing process of H13 steel cutter rings to regulate molten-pool behavior and suppress crack defects. A molten-pool-scale sequentially coupled thermo-fluid-electromagnetic model was developed to compare the relative changes in the temperature and velocity fields with and without LAMF under identical MAG process parameters, heat-source input, material properties, and boundary conditions. In the model, the effect of LAMF was introduced through a Lorentz-force source term acting on the electrically conductive molten metal. The simulation results show that LAMF promoted heat redistribution within the molten pool, smoothed the thermal transition near the rear region of the molten pool, and reduced local heat accumulation. Meanwhile, LAMF modified the molten-pool flow pattern by weakening excessive flow along the welding direction and enhancing transverse circulation and vortex-induced mixing. Comparative overlay remanufacturing experiments were then conducted using a self-built magnetic-field stirring platform. Penetrant testing, X-ray inspection, metallographic observation, and industrial CT reconstruction were combined to characterize surface cracks, internal defects, and post-solidification microstructure. Compared with the non-LAMF condition, the maximum internal crack length decreased from 29.41 mm to 20.30 mm, corresponding to a reduction of 30.98%, and the crack-defect volume fraction decreased from 0.93% to 0.28%, corresponding to a decrease of 0.65 percentage points. The combined simulation and characterization results indicate that Lorentz-force-driven electromagnetic stirring improves the thermal-fluid conditions near the solidification front, thereby effectively reducing the formation tendency of solidification-related crack defects during MAG overlay remanufacturing. Full article

Localized optical absorption by nanoscale inclusions can profoundly alter energy deposition in optical traps, giving rise to nonlinear and long-timescale dynamics. Recent experiments have reported the formation of expanding optically darkened regions and episodic plasma-like emission during pulsed near-infrared optical trapping of magnetic beads interacting with biological cells. Here, we develop a reduced-order mechanistic model to investigate whether absorber-driven optical–thermal feedback associated with Fe₃O₄ inclusions is sufficient to reproduce the observed pre-plasma darkening dynamics. The model is constructed progressively from first-principles electromagnetic absorption and pulse-scale thermal diffusion to nonlinear feedback mediated by an evolving optically modified region. Single-pulse and multi-pulse simulations demonstrate that isolated iron-oxide absorbers cool too rapidly to sustain long-timescale thermal accumulation through linear heating alone. However, incorporation of a bubble-mediated optical feedback channel produces bounded growth, partial optical darkening, and slow relaxation dynamics consistent with experimentally observed minute-scale evolution. Electromagnetic absorption was computed using full core–shell Mie theory, yielding absorption cross-sections sufficient to support strong localized optical attenuation under experimentally relevant trapping conditions. The resulting reduced-order feedback framework reproduces stable growth–relaxation cycles, finite transmission plateaus, and self-limited optical darkening without requiring runaway heating or catastrophic cavitation. To evaluate the model quantitatively, simulated transmission dynamics were compared against experimentally measured normalized transmission traces digitized from previously reported optical trapping experiments. The fitted model reproduced the observed finite transmission plateau and slow post-activation relaxation with good agreement ($R^2\approx 0.86$, RMSE $\approx 1.3\times {10}^{-2}$). These results support the interpretation that experimentally observed optical darkening arises from a feedback-regulated optical–thermal process involving slowly evolving structural modification of the trapping region rather than cumulative thermal storage within isolated absorbers. The present framework provides a quantitatively constrained reduced-order description of feedback-mediated optical darkening under pulsed optical trapping conditions and establishes iron-oxide absorption as a physically plausible ignition mechanism for dark-state formation in the pre-plasma regime. Full article

Induction heating is widely used in industrial processes such as forging, hardening, and additive manufacturing, but its accurate numerical simulation requires coupled electromagnetic and thermal finite element analyses with nonlinear, temperature-dependent material properties. This work proposes a deep learning surrogate model based on a convolu-tional neural network for TEAM Workshop Problem 36, a reference benchmark for nonlinear magneto-thermal induction heating. A database of more than 40,000 finite element solutions was generated by varying the supply current from 2 to 6 kA and the frequency from 2 to 6 kHz, while accounting for transient nonlinear effects, including the Curie transition. The network, composed of 24 layers with transposed convolutions, batch normalization, and dropout, maps current, frequency, and time to radial temperature distributions in the steel billet. For most operating conditions, the model achieves mean absolute percentage errors of about 6–7% for radial line in the middle of the billet and about 10% for radial line close to the billet end. Larger discrepancies occur during the early heating stage and near the Curie temperature. Prediction times are reduced by three to four orders of magnitude with respect to a single finite element analysis. The results indicate that the proposed surrogate enables fast temperature estimation for optimization, digital twins, and closed-loop control of induction heating systems. Full article

Ultrastrong magnetic fields, ranging from 100 T to 1000 T, are generated exclusively by destructive pulsed magnets. While various generation methods exist, this review focuses on the Single-Turn Coil (STC) and Electromagnetic Flux Compression (EMFC) techniques, which provide optimal environments for high-precision measurements in materials science. First, we present recent technological breakthroughs in the EMFC method that have successfully achieved fields exceeding 1000 T. We then describe specialized measurement infrastructures for magneto-optics, magnetization, and magneto-transport, highlighting the development of miniaturized all-plastic cryostats and custom sample holders designed for the dual extremes of cryogenic temperatures and megagauss fields. Representative physical phenomena revealed through these techniques are discussed, including quantum phase transitions in frustrated magnets, Aharonov–Bohm effects in carbon nanotubes, and semiconductor-to-metal transitions in strongly correlated systems. Furthermore, we address emerging measurement platforms such as magnetostriction, specific heat, and ultrasound velocity. Throughout this review, we emphasize the instrumentation and experimental refinements that ensure reliable data acquisition in the ultrastrong pulsed field regime. Full article

Non-thermal millimeter-wave (MMW) irradiation represents a promising non-invasive strategy for cancer therapy, yet its effects in physiologically relevant 3D systems remain poorly defined. Here, we evaluated the biological impact of MMW exposure in 3D non-small-cell lung cancer (NSCLC) spheroids (NCI-H1299, A549) and normal WI-38 fibroblasts under active cooling to suppress bulk heating. We demonstrate that cellular responses are governed primarily by power density (PD), irradiation geometry, and genotype-dependent susceptibility. High-PD pyramidal horn (PH) irradiation (~4.9 mW/cm²) induced rapid apoptosis, metabolic collapse, and near-complete loss of clonogenic survival, whereas lower-PD waveguide (WG) irradiation (~0.6 mW/cm²) produced depth-limited, cumulative cytotoxicity. Surviving cancer cells exhibited robust senescence-associated growth arrest, particularly in p53-deficient NCI-H1299 cells, indicating a dual apoptotic–senescent anti-proliferative response. In contrast, WI-38 fibroblasts showed minimal apoptosis and only transient stress-associated senescence, confirming selective tumor vulnerability. Mechanistic modeling suggests that MMW energy couples to glycan-rich membrane domains, generating localized electromagnetic hotspots that trigger calcium influx, mitochondrial dysfunction, and depth-dependent apoptosis. These findings establish a mechanistic basis for selective, non-thermal MMW-induced cytotoxicity in 3D NSCLC models and support further preclinical development of MMW-based therapeutic strategies. Full article