Search Results (441)

This work introduces ultrafast high-temperature graphitization (UHG) as an effective method to synthesize graphite with significantly reduced processing times of about 100 s and reduced consumed energy, as opposed to conventional methods that require several days at 2800 K. This novel process achieves graphitization of up to 90% within a few minutes due to the accelerated kinetics occurring at temperatures as high as 3400 K. Samples processed using UHG attained stable cyclic capacities of 350 mAh/g, which is fully comparable to commercially available graphite. Finite Element Simulations were also used to calculate the energy consumption for a scaled-up configuration, and it was found that the UHG approach reaches ultra-low energy consumption, requiring only 2.4 MJ/kg for the direct conversion of coke into graphite. By minimizing the duration of high-temperature processing and employing localized heating, UHG is envisioned to mitigate some of the challenges associated with traditional Acheson furnaces that have been in use for more than a century. Full article

Phosphorus is an essential resource for numerous industrial applications. However, its uneven global distribution makes Europe heavily dependent on imports. Recovering phosphorus from waste streams is therefore crucial for improving resource security. The FlashPhos project addresses this challenge by developing a process to recover phosphorus from sewage sludge, in which phosphorus-rich slag is produced in a flash reactor and subsequently reduced in a Submerged Arc Furnace (SAF). In this process, approximately 250 kg/h of sewage sludge is converted into slag, which is further processed in the SAF to recover about 8 kg/h of white phosphorus. This work focuses on the development of a computational model of the SAF, with particular emphasis on slag behaviour. Due to the extreme operating conditions, which severely limit experimental access, a numerically efficient three-dimensional CFD model was developed to investigate the internal flow of the three-phase, AC-powered SAF. The model accounts for multiphase interactions, dynamic bubble generation and energy sinks associated with the reduction reaction, and Joule heating. A temperature control loop adjusts electrode currents to reach and maintain a prescribed target temperature. To further reduce computational cost, a novel simulation approach is introduced, achieving a reduction in simulation time of up to 300%. This approach replaces the solution of the electric potential equation with time-averaged Joule-heating values obtained from a preceding simulation. The system requires transient simulation and reaches a pseudo-steady state after approximately 337 s. The results demonstrate effective slag mixing, with gas bubbles significantly enhancing flow velocities compared to natural convection alone, leading to maximum slag velocities of 0.9–1.0 m/s. The temperature field is largely uniform and closely matches the target temperature within ±2 K, indicating efficient mixing and control. A parameter study reveals a strong sensitivity of the flow behaviour to the slag viscosity, while electrode spacing shows no clear influence. Overall, the model provides a robust basis for further development and future coupling with the gas phase. Full article

The integration of mobile devices into aviation powering electronic flight bags, maintenance logs, and flight planning tools has created a critical and expanding cyber-attack surface. Security for these systems must be not only effective but also transparent, resource-efficient, and certifiable to meet stringent aviation safety standards. This paper presents AVI-SHIELD, a novel framework for developing high-assurance, on-device threat detection. Our methodology, grounded in the MITRE ATT&CK^® framework, models credible aviation-specific threats to generate the AviMal-TinyX dataset. We then design and optimize a set of compact, interpretable detection algorithms through quantization and pruning for deployment on resource-constrained hardware. Evaluation demonstrates that AVI-SHIELD achieves 97.2% detection accuracy on AviMal-TinyX while operating with strict resource efficiency (<1.5 MB model size, <35 ms inference time and <0.1 Joules per inference) on both Android and iOS. The framework provides crucial decision transparency through integrated, on-device analysis of detection results, adding a manageable overhead (~120 ms) only upon detection. Its successful deployment on both Android and iOS demonstrates that AVI-SHIELD can provide a uniform security posture across heterogeneous device fleets, a critical requirement for airline operations. This work provides a foundational approach for deploying certifiable, edge-based security that delivers the mandatory offline protection required for safety critical mobile aviation applications. Full article

The present studies focus on the analysis of the inherent differences between temperature- and pyrolysis-based models and foster a rational and comprehensive understanding of numerical models for lightning strike damage in laminated composites. A systematic methodology combining numerical simulation and pyrolysis kinetics analysis has been developed to examine the inherent differences in damage area and depth, damage threshold, electrical conductivity characteristics, and Joule energy between temperature- and pyrolysis-based models. The results indicate that the pyrolysis-based model demonstrates closer agreement with experimental data in terms of both damage area and damage depth predictions compared to the temperature-based model. The two damage thresholds (500 °C and pyrolysis degree of 0.1) yield equivalent predictions of overall damage, but the temperature-based criterion neglects localized heating rate effects. The pyrolysis-based model exhibits significantly delayed through-thickness conductivity development during initial current conduction compared to the temperature-based model due to the influence of heating rate. This lag results in the pyrolysis-based model predicting larger damage areas and shallower penetration depths. Joule heating analysis further confirms that the pyrolysis-based model exhibits higher overall electrical resistance than the temperature-based model. Through a systematic comparison of temperature- and pyrolysis-based models, this research holds the significance of enhancing the understanding of lightning strike damage mechanisms and advancing the development of high-fidelity numerical models for predicting lightning strike damage in laminated composite. Full article

Electromigration (EM) presents a major reliability challenge in advanced electronic packaging as device scaling and rising power demands lead to higher current densities in solder joints. While eutectic Sn-58Bi solder is widely adopted as a low-temperature alternative for its energy efficiency and compatibility with heat-sensitive substrates, its heterogeneous microstructure renders it vulnerable to EM-induced degradation. This review summarizes recent progress in understanding the EM behavior of Sn-Bi solder joints. We first introduce lifetime prediction models based on Black’s law, emphasizing the influences of current density, Joule heating, and thermomigration. Subsequently, the microstructural mechanisms accelerating degradation, including phase segregation and the coarsening of intermetallic compounds (IMCs), are examined. Various alloying strategies are evaluated for their effectiveness in strengthening the solder matrix and suppressing atomic diffusion to improve EM resistance. The critical role of substrate metallization is also discussed, comparing how different surface finishes affect interfacial reactions and joint lifetimes. Additionally, operational methods such as current polarity reversal are explored as potential pathways to mitigate degradation. Finally, we conclude that the EM reliability of Sn-Bi solder joints depends on the combined effects of alloy chemistry, interfacial reactions, and operating conditions, and we suggest future research directions in advanced modeling and material design for next-generation electronic applications. Full article

As the hydrogen economy rapidly expands, carbon-fiber-reinforced polymer composites (Towpreg) have become key materials for next-generation hydrogen pressure vessels, offering superior processability, reproducibility, and storage stability compared to conventional wet-winding composites. Since hydrogen storage vessels are evaluated at three representative service temperatures (−40, 25, and 85 °C), Towpreg materials must maintain consistent mechanical performance across this range to meet certification standards. This study establishes an integrated methodology combining Towpreg panel fabrication, temperature-controlled tensile and fatigue testing, and quantitative assessment of thermo-mechanical stability using DM epoxy resin as the matrix. To address artifacts such as tab slippage at high temperatures and inefficiency at low temperatures, a “Localized Thermal Control” approach was developed. The HY-Mini Heater System enables localized heating at 85 °C, while the HY-Cooler System applies a Joule–Thomson-based Stirling cooler for efficient localized cooling at −40 °C. Quantitative evaluation showed tensile strengths of 2973.3 MPa (RT), 2767.3 MPa (HT, ~7% decrease), and 2907.7 MPa (LT, ~2% decrease). Under R = 0.1 fatigue testing, the Basquin slope (m) was 11.97 (RT), 9.98 (HT), and 10.6 (LT), while the intercept (log b ≈ 3.7) remained nearly constant. These results confirm the excellent thermo-mechanical stability of the carbon-fiber-reinforced polymer composites (Towpreg) for hydrogen tank applications. Full article

Acoustofluidic devices use Surface Acoustic Waves (SAWs) to handle small fluid volumes and manipulate nanoparticles and biological cells with high precision. However, SAWs can cause significant heat generation and temperature rises in acoustofluidic systems, posing a critical challenge for biological and other applications. In this work, we studied temperature distribution in a Standing Surface Acoustic Wave (SSAW)-based PDMS microfluidic device both experimentally and numerically. We investigated the relative contribution of Joule and acoustic dissipation heat sources. We investigated the acoustofluidic device in two heat dissipation configurations—with and without the heat sink—and demonstrated that, without the heat sink the temperatures inside the microchannel increased by 43 °C at 15 V. Adding the metallic heat sink significantly reduced the temperature rise to only 3 °C or less at lower voltages. This approach enabled the effective manipulation and alignment of nanoparticles at applied voltages up to 15 V while maintaining low temperatures, which is crucial for temperature-sensitive biological applications. Our findings provide new insights for understanding the heat generation mechanisms and temperature distribution in acoustofluidic devices and offer a straightforward strategy for the thermal management of devices. Full article

This work investigates the impact of load-dump stress on p-GaN HEMTs under floating gate condition. The experiments show that preconditioning the device with a small load-dump stress (150 V, @t_d = 100 ms and t_r = 8 ms) enhances its robustness against a larger stress (190 V, @t_d = 100 ms and t_r = 8 ms). If a large load-dump stress (≥160 V, @t_d = 100 ms and t_r = 8 ms) is applied directly to the device’s drain, the device will burn out. This occurs because the rapidly changing drain voltage during a load-dump event can generate a capacitive coupling current, leading to transient positive charge accumulation in the gate region. Consequently, the channel under the gate is turned on, allowing a large current to flow through it. The coexistence of high current and high voltage leads to substantial Joule heating within the device, resulting in eventual burnout. When a small load-dump stress is initially applied, the resulting charging of electron traps in the gate region increases the threshold voltage. As a result, the device can withstand a larger load-dump stress before the channel turns on, which explains the device’s enhanced robustness. This work clarifies the failure threshold of p-GaN HEMTs under the load-dump stress, providing key support for improving the devices’ reliability in the practical applications. It can provide a basis for adding necessary protective measures in device circuit design, and clarify the triggering voltage threshold of protective measures to ensure that they can effectively avoid device damage due to the load-dump stress. Full article

Predictive current control of variable speed drives by direct command of inverter states allows fast control. Its application to multiphase system constitutes a flexible solution that tackles several objectives by means of a cost function with several terms. Weighting factors are used to give relative importance of each term. They have a remarkable effect on figures of merit. In particular, secondary plane content and average switching frequency are usually considered as figures of merit. However, weighting factor effect on global energy efficiency has not been studied before because losses have different sources (commutations, Joule effect, etc.) that do not have a clear link with weighting factors and because trade-offs might appear. The present work uses an experimental setup with a five-phase induction machine connected to a mechanical load. By measuring the power balance, it is possible to show the effect of weighting factor tuning on losses. By tuning ${\lambda }_{xy}$, efficiency increases by up to 25%. In parallel, optimizing ${\lambda }_{nc}$ reduces the average switching frequency by 9% and 18% across the evaluated configurations. This enables the selection of the most adequate values of the weighting factors. The results show that for each speed and load combination, the drive exhibits improved efficiency for some tuning. Full article

To address the degradation of O-ring material properties and reduced dynamic seal reliability caused by excessive hydrogen temperature rise in a Type IV hydrogen cylinder due to constant-flow filling strategies, this study systematically investigates the coupled mechanism by which a linearly decreasing flow filling strategy maintains sealing performance through temperature rise regulation. By establishing a fluid–thermal–solid coupled mathematical model that comprehensively considers the Joule–Thomson effect, compression heat, gas swelling, and material nonlinear behavior, combined with numerical simulation methods, the sealing performance of the linear decreasing and constant-flow filling strategies was systematically compared across three key dimensions: temperature field distribution, evolution of seal ring material properties, and contact stress at the sealing interface. Results demonstrate that the linear decrease filling strategy effectively suppresses hydrogen temperature rise, achieving a 4.6% lower temperature increase at completion compared to the constant-flow strategy. Concurrently, this strategy mitigates thermally induced degradation of seal material properties, reducing contact stress fluctuations by 5% and significantly enhancing dynamic seal reliability. This research provides theoretical foundations and design support for optimizing filling protocols in high-performance hydrogen storage vessels. Full article

The development of electro-thermal textiles has attracted growing interest as a promising approach for active thermal management in wearable systems. Metallic-coated fabrics can efficiently generate heat through the Joule effect; however, their long-term performance and safety are severely limited under perspiration due to metal ion release and corrosion. To overcome these challenges, this study introduces a Parylene-C encapsulation strategy for copper-coated polyethylene terephthalate nonwovens (CuPET) using a chemical vapor deposition (CVD) process. The conformal, biocompatible Parylene-C films (thickness 4–16 μm) act as effective protective barriers while preserving the porous textile structure. Morphological and comfort analyses demonstrate a controlled reduction in air permeability from 3100 to 1100 L·m⁻²·s⁻¹, maintaining acceptable breathability. Electro-thermal measurements reveal rapid and uniform heating, reaching 40–45 °C within 2 min at 2 V, and the addition of a thermal insulation layer further enhances the Joule heating efficiency, increasing the steady-state temperature by approximately 6 °C. ICP–OES results show an ≈80% reduction in copper ion release (from 28.34 mg·L⁻¹ to 5.80 mg·L⁻¹) after artificial sweat exposure. This work demonstrates a scalable encapsulation route that effectively balances sweat protection, electrical stability, and thermal performance, paving the way for safe, durable, and actively heated smart textiles for advanced thermal insulation applications. Full article

Characterized by its low melting temperature of 138 °C, the eutectic Sn-58Bi solder expands the melting temperature range of interconnect joints in electronic packaging, making it widely used in multi-level packaging processes. However, its reliability at higher current densities poses a challenge. This paper employs a hybrid process combining laser soldering and hot-air reflow to fabricate Cu/Sn-58Bi/Cu solder joints in ball grid array (BGA) structures. Through mechanical testing under current loading, the effects of increasing current density (0 A/cm², 0.85 × 10³ A/cm², 1.70 × 10³ A/cm², 2.55 × 10³ A/cm², 3.40 × 10³ A/cm², 4.25 × 10³ A/cm²) were studied systematically. Results indicate that the shear strength decreases markedly with increasing current density, exhibiting a reduction of approximately 5.63% to 95.75%. This degradation is initiated by the overall temperature increase and material softening due to Joule heating. It is further exacerbated by the loss of the non-thermal electron wind’s strengthening contribution, which weakens as the dominant thermal impact escalates with current density. Fracture mode transitions from ductile failure within the solder matrix to a ductile-brittle mixture at the solder/IMC interface, with the transition initiating at 3.40 × 10³ A/cm². Finite element simulations reveal that current crowding in Sn-rich regions and at the solder/IMC interface induces localized Joule heating and thermomechanical strain, which jointly drive the degradation in shear strength and the shift in fracture path. Full article

Applying thin electrically conductive coatings to Liquid Crystalline Elastomers (LCEs) is an effective way of functionalizing two-way shape memory polymers with the ability to respond to electrical currents. However, achieving robust adhesion between a given electrically conductive coating and the surface of LCEs can be challenging. This can limit the functionality, performance, and potential applications of these materials. This work describes a facile method to develop electrically responsive Liquid Crystalline Elastomer polymeric artificial muscles with strain-sensing, self-actuation-sensing, and joule-heating features. In this work, the effect of treating LCEs with polydopamine (PDA) prior to functionalizing the LCE with an electrically conductive gold-sputtered coating was explored. The findings confirmed that the PDA treatment considerably improved the adhesion of the gold sputter coating to the LCEs, thereby leading to the fabrication of multi-functional strain-sensing, electrically conductive, and electro-responsive LCEs. Full article

The field of 4D printing has seen rapid advancement in recent years, making it a highly dynamic research domain. This new technology is promising for the development of brand-new lightweight, smart and reliable devices. This article is a literature review of the latest research in 4D printing, focusing on electroconductive thermosensitive Shape Memory Polymers. They are promising thanks to their high strength-to-weight ratio and their large deformability. However, devices made of such materials are difficult to embed into larger systems because of the triggering mechanism needed to actuate them. Electroconductive Shape Memory Polymers can be stimulated by the Joule effect, but the intricacies and interdependence of their properties make them a great scientific challenge. The first part of this article provides a clear explanation of the main concepts of 4D printing. Afterwards, it focuses on Fused Filament Fabrication due to its high customisability and ease of use. A description of the properties of thermosensitive 4D printed specimens is provided in the third part. Finally, their main challenges and intricacies are discussed. Full article

In scaled laser-driven magnetized liner inertial fusion (MagLIF), externally applied magnetic fields improve energy coupling by suppressing electron thermal conduction, enhancing Joule heating, and increasing $\alpha$-particle energy deposition. However, confinement can be significantly degraded by magnetic flux transport, dominated by resistive diffusion, and more critically, the Nernst effect. One-dimensional magnetohydrodynamic simulations demonstrate that increasing the applied field generally enhances neutron yield, but when the Nernst effect is included, the benefit of stronger magnetization diminishes. Stagnation is achieved at 2.72 ns, yielding a peak temperature of 2.17 keV and a neutron production of $1.2\times {10}^{12}$. When the Nernst effect is taken into account, the neutron yield decreases by 57.3% compared with the case without it under an initial magnetic field of 10 T. During the implosion, the magnetic field in the fuel gradually diffuses outward into the outer liner. By stagnation, the magnetic flux of fuel has decreased by 33.8%. Based on the characteristics of the Nernst effect, an optimized initial magnetic field of approximately 6 T is identified, which yields an about 2.5 times higher neutron yield than the unmagnetized case. These findings emphasize the key role of magnetic–energy coupling in target performance and provide guidance for the design and scaling of magnetized targets. Full article