Search Results (114)

Mycelium-bonded composites (MBCs), or myco-composites, represent a novel engineered material that combines natural lignocellulosic substrates with a fungal matrix. As a sustainable alternative to plastics, MBCs are gaining increasing interest; however, their large-scale industrial adoption remains limited, partly due to low social acceptance resulting from their unattractive appearance. Laser engraving provides a promising method for fabricating intricate patterns and functional surfaces on MBCs, minimizing tool wear, material loss, and environmental impact, while enhancing esthetic and engineering properties. This study investigates the influence of CO₂ laser parameters on the material removal rate during the engraving of myco-composites, focusing on the effects of variable laser power, beam defocus, and head feed rate on engraving outcomes. The results demonstrate that laser power and beam focus significantly impact material removal in mycelium-bonded composites. Specifically, increasing the laser power results in greater material removal, which is more pronounced when the beam is focused due to higher energy density. In contrast, a beam defocused by 1 mm produces less intense material removal. These findings highlight the critical role of beam focus—surpassing the influence of power alone—in determining engraving quality, particularly on irregular or uneven surfaces. Moreover, reducing the laser head feed rate at a constant power level increases the material removal rate linearly; however, it also results in excessive charring and localized overheating, revealing the low thermal tolerance of myco-composites. These insights are essential for optimizing laser processing techniques to fully realize the potential of mycelium-bonded composites as sustainable engineering materials, simultaneously maintaining their appearance and functional properties. Full article

Overheating in miniaturized electronic devices can reduce their useful life, where conventional heat sinks are insufficient. The utilization of ionenes as solid–solid phase change materials is proposed to enhance thermal dissipation without the risk of leakage. In this work, a series of imidazolium ionenes with structural modifications in their aromatic core and aliphatic chain length were synthesized. The synthesis was carried out using the respective monomers diimidazole and alkyl dibromide, followed by counterion bromide exchange using lithium bis(trifluoromethanesulfonyl)imide, with yields over 90% in all cases. Thermal characterizations showed that all ionenes are heat-resistant, with degradation temperatures between 421 °C and 432 °C; moreover, they all presented only a solid–solid transition (Tg) as a phase change, between 59 °C and 28 °C, which varied depending on the aromatic core used and the length of the aliphatic chain. The obtained ionenes were introduced into an experimental device with an operating temperature of 40 °C, to be evaluated as solid–solid phase change materials in heat sinks. These demonstrated an average decrease in operating temperature of 9 °C compared to the device without ionenes. On the other hand, the stability of the ionenes was analyzed over 10 thermal cycles at 40 °C at a heating rate of 5 °C/min. This analysis demonstrated that the ionenes did not present changes or degradation during the evaluated cycles. These findings demonstrate that imidazolium ionenes are promising solid–solid phase change materials for use as efficient and self-repairing heat sinks in compact electronic devices. Full article

Overheating and overcharging are the core triggering conditions for the thermal runaway of lithium-ion batteries. Studying the behavioral differences of thermal runaway of lithium-ion batteries under these two conditions is crucial for the safety design and protection of lithium-ion batteries. In this study, we investigated the temperature, pressure, gas generation, and heat generation characteristics of lithium batteries under these two conditions. Under overheating conditions, the release of lattice oxygen in the cathode and the decomposition of the electrolyte trigger a self-catalytic reaction, generating CO₂ (54.7%) and H₂ (29.7%), with a total heat release of 17.6 kJ and a heat accumulation rate of 24.3 W, forming a local high-temperature core area. Under overcharging conditions, the voltage drop, capacity attenuation of 21.1% (2230→1762 mAh), and internal resistance surge (6→21 mΩ) reflect severe damage to the electrode. Accompanied by the oxygenation of the EC electrolyte (CO₃²⁻ + C₂H₄↑), the gas production rate is faster. The middle pressure was 0.601 MPa, and the proportion of CO₂ was 67.4%. However, the triggering of thermal runaway relies on the synergistic effect of internal electrochemical reactions and ohmic heat accumulation, resulting in a relatively low rate of energy accumulation. Full article

This study presents the optimization of a laser ablation process designed to achieve the precise removal of polyamide coatings from ultra-thin platinum wires. Removing polymer coatings is a critical challenge in high-reliability manufacturing processes such as aerospace thermocouple fabrication. The ablation process must not only ensure the complete removal of the polyamide insulation but also maintain the tensile strength of the wire to withstand mechanical handling in subsequent manufacturing stages. Additionally, the exposed platinum surface must exhibit low surface roughness to enable effective soldering and be free of thermal damage or residual debris to pass strict visual inspections. The wires have a total diameter of 65 µm, consisting of a 50 µm platinum core encased in a 15 µm polyamide coating. By utilizing a UV laser with a wavelength of 355 nm, average power of 3 W, a repetition rate range of 20 to 200 kHz, and a high-speed marking system, the process parameters were systematically refined. Initial attempts to perform the ablation in an air medium were unsuccessful due to inadequate thermal control and incomplete removal of the polyamide coating. Hence, a water-assisted ablation technique was explored to address these limitations. Experimental results demonstrated that a scanning speed of 1200 mm/s, coupled with a line spacing of 1 µm and a single ablation pass, resulted in complete coating removal while ensuring the integrity of the platinum substrate. The incorporation of a water layer above the ablation region was considered crucial for effective heat dissipation, preventing substrate overheating and ensuring uniform ablation. The laser’s spot diameter of 20 µm in air and a focal length of 130 mm introduced challenges related to overlap control between successive passes, requiring precise calibration to maintain consistency in coating removal. This research demonstrates the feasibility and reliability of water-assisted laser ablation as a method for a high-precision, non-contact coating material. Full article

The drilling machinability of glass fiber G₁₄, basalt fiber B₁₄, and two hybrid laminates (B₄G₆B₄, G₄B₆G₄) was evaluated through 36 full-factorial experiments employing an HSS-G drill, three spindle speeds (715, 1520, 3030 rpm), and three feed rates (0.1–0.3 mm rev⁻¹). Peak thrust force varied from 65.8 N for B14 at 0.1 mm rev⁻¹ to 174.3 N for G₁₄ at 0.3 mm rev⁻¹; hybrids occupied the intermediate range of 101–163 N. Infra-red thermography recorded maximum drill temperatures of 110–120 °C for G₁₄, almost double those of B₁₄, while both hybrids attenuated hotspots to below 90 °C. ANOVA attributed 73.4% of thrust force variance to feed rate, with material type and spindle speed contributing 15.5% and 1.7%, respectively; for temperature, material type governed 41.5% of variability versus 17.0% for speed. Dimensional quality tests revealed that the symmetric hybrid G₄B₆G₄ maintained entrance and exit diameters within ±2% of the nominal 6 mm, whereas B₄G₆B₄ over-expansion exceeded 8% at the lowest feed and G₁₄ exit diameters grew to 6.1 mm at 0.3 mm rev⁻¹. Integrating basalt compliance with glass stiffness, therefore, halves thrust force relative to G₁₄, suppresses delamination and overheating, and offers a practical strategy to prolong tool life and improve hole quality in multi-material composite structures. These insights guide parameter selection for lightweight hybrid composites in aerospace, renewable-energy installations, and marine components worldwide. Full article

COVID-19 restricted the number of employees. Operational data showed that traditional methods of modeling heat consumption are not correct anymore. The aim is to model the energy demand of an office building during COVID-19 limitations and showcase improvements after a new controller or suggested alternatives are applied. After an actual heat consumption profile was simulated, energy conservation scenarios were considered: the usage of thermostatic radiator valves (TRVs); accounting impacts of solar radiation and wind; changing mass flow rates based on the indoor temperature; adopting an additional control, changing the temperature setpoint; introducing night and day setbacks. After implementing new design and operational methods, the overheating of indoor spaces was alleviated, and the average indoor temperature was reduced from 23.5 °C to 20.4 °C. The annual specific heat consumption decreased to 174 kWh/m² (20.2% lower). The methodology ensured thermal comfort and high energy-saving potential. If operating parameters were adjusted, the total saving effect in energy demand was 119.8 MWh, with an energy-saving rate of 19.8%. Employing TRV-related savings and considering thermal inertia provided more stable indoor temperatures and higher energy performance. The minimum saving effect corresponded to the optimal operation and ensuring the indoor environment by considering wind and the maximum one-to-night setbacks. The fluctuations in indoor temperature became smoother. Full article

An electrochemical reactions coupled multi-physics model is developed and applied to elucidate overall performance and thermal stress distributed in solid oxide electrolysis cells (SOECs) with graded fuel electrodes. Extending the conventional fuel electrode, the effects of various graded parameters are investigated and discussed in terms of porosity, pore size, and material composition, with the goal of identifying characteristics of the hydrogen production rate and maximum thermal stress. The results show that the application of the graded parameters is able to optimize the gas distribution and to improve reaction kinetics, avoiding local overheating. The generated hydrogen molar fraction is enhanced by 15.6% while the maximum thermal stress is decreased by 5.0% if the graded parameters are applied, while changing the material composition may increase the thermal stress under the same circumstances. These explorations elucidate the complex role of the graded fuel electrodes on the electrolysis and thermomechanical properties of SOECs. Full article

This study aims to improve the operational efficiency of district heating (DH) systems by introducing a novel control method based on variable flow rate control, without compromising indoor comfort. The novelty of this work lies in its integrated analysis of flow control and substation configurations in DH networks, linking real-world operational strategies with mathematical modeling to improve energy efficiency and infrastructure costs. Using a case study from Omsk, Russia, where supply temperatures and energy demand profiles are traditionally rigid, the proposed approach utilizes operational data, including outdoor temperature, supply/return temperature, and hourly consumption patterns, to optimize heat delivery. A combination of flow rate adjustments, bypass line implementation, and selective control strategies for transitional seasons (fall and spring) was modeled and analyzed. The methodology integrates heat meter data, indoor temperature tracking, and Supervisory Control and Data Acquisition (SCADA)-like system inputs to dynamically adapt supply temperatures while avoiding overheating and reducing distribution losses. The results show a significant reduction in excess heat supply during warm days, with improvements in heat demand prediction accuracy (17.3% average error) compared to standard models. Notably, the optimized configuration led to a 21% reduction in total greenhouse gas (GHG) emissions (including 6537 tons of CO₂ annually), a 55.3% decrease in annualized operational costs, and a positive net present value (NPV) by year nine, with an internal rate of return (IRR) of 25.4%. Compared to conventional scenarios, the proposed solution offers better economic performance without requiring extensive infrastructure upgrades. These findings demonstrate that flexible, data-driven DH control is a feasible and sustainable alternative for aging networks in cold-climate regions. Full article

This study analyzes biometeorological conditions during summer heat events in 11 cities located in different regions of Poland in the summer months from 2020 to 2024. Heat days (defined as days with a maximum temperature exceeding 30 °C) and heatwaves (defined as at least three consecutive days with a maximum temperature above 30 °C) were identified. Biometeorological conditions were assessed based on the Universal Thermal Climate Index (UTCI) and heart rate (HR), assuming a metabolic heat production of 135 W∙m⁻² for an adult human. The indices were calculated using the BioKlima 2.6 software. The findings reveal that all cities experienced significant thermal stress during heat events. The maximum UTCI values during heat days indicated strong and very strong heat stress. During the most intense heatwaves, assessed using the Heat Wave Severity (HWS) index, these categories of heat stress occurred 20–30% of the time. Simultaneously, the mean daily heart rates exceeded the warning threshold of 90 beats per minute. Differences in biometeorological conditions were found between urban centers and places located outside the center, where strong heat conditions occurred less frequently. The results indicate that biometeorological conditions imposing thermal stress on the human body were present in all Polish cities during the analyzed five-year period. In Warszawa, Wrocław, and Rzeszów, heatwaves and heat stress occurred annually. Full article

Aimed at solving the problem of insulation failure caused by the local overheating of the oil-immersed converter transformer, this paper investigates the heat transfer characteristics of the 500 kV converter transformer based on the electromagnetic-flow-heat coupling model. Firstly, this paper used the finite element method to calculate the core and winding loss. Then, a two-dimensional fluid-heat coupling model was used to investigate the effects of the inlet flow rate and the radius of the oil pipe on the heat transfer characteristics. The results show that the larger the inlet flow rate, the smaller the specific gravity of high-temperature transformer oil at the upper end of the tank. Increasing the pipe radius can reduce the temperature of the heat dissipation of the transformer in relative equilibrium. Still, the pipe radius is too large to lead to the reflux of the transformer oil in the oil outlet. Increasing the central and sub-winding turn distance, the oil flow diffusion area and flow velocity increase. Thus, the temperature near the winding is reduced by about 9%, and the upper and lower wall temperature is also reduced by about 4%. Based on the analysis of the sensitivity weight indicators of the above indicators, it is found that the oil flow rate has the largest share of influence on the hot spot temperature of the transformer. Finally, the surface temperature of the oil tank when the converter transformer is at full load is measured. In the paper, the heat transfer characteristics of the converter transformer are investigated through simulation and measurement, which can provide a certain reference value for the study of the insulation performance of the converter transformer. Full article

An efficient Battery Management System (BMS) specifically for Electric Vehicles is crucial for improving battery run time performance. A primary function of an effective BMS is accurately determining the State of Charge (SOC) and State of Health (SOH) of lithium-ion batteries in Electric Vehicles (EVs). However, many existing studies have concentrated on examining sensor malfunctions in batteries to avert problems such as overcharging and overheating and are lacking in terms of effective handling of non-linear behaviors. To overcome these limitations, the proposed work introduces a hybrid approach for estimating the state of lithium-ion batteries. It employs an Extended Kalman Filter (EKF) for SOC estimation and modified Multi-Layer Perceptron (MLP) for SOH estimation in batteries. It can handle the non-linear characteristics often exhibited by sensor readings and fault behaviors. The EKF algorithm involves initialization, prediction, and correction phases, allowing for accurate state estimation based on measurements. For SOH estimation, the NASA battery dataset, which includes various battery conditions across different temperatures, is analyzed using a modified MLP regression process. This modified MLP employs a gradient shift bias adjustment technique to minimize error rates by refining the gradients and biases introduced during the training process. It also effectively adjusts the model’s weights for better SOH estimation. The results demonstrate improved accuracy in battery performance, as indicated by lower RMSE, MSE, MAE and R² values. Furthermore, the study highlights the effectiveness of this hybrid method for significant battery management at different temperatures, which emphasizes the potential of this model, with enhanced state estimation for EV applications. Full article

The rise of 3D heterogeneous packaging holds promise for increased performance in applications such as AI by bringing compute and memory modules into close proximity. This increased performance comes with increased thermal management challenges. This research explores the use of thermal sensing and load throttling combined with federated computation to manage localized internal heating in a multi-3D chip package. The overall concept is that individual chiplets may heat at different rates due to operational and geometric factors. Shifting computational loads from hot to cooler chiplets can prevent local overheating while maintaining overall computational output. This concept is verified with experiments in a low-cost test vehicle. The test vehicle mimics a 3D chiplet stack with a tightly stacked assembly of SoC devices. These devices can sense and report internal temperature and dynamically adjust frequency. The configuration is for ESP32-S3 microcontrollers to work on a federated computational task, while reporting internal temperature to a host controller. The tight packing of processors causes temperatures to rise, with those internal to the stack rising more quickly than external ones. With real-time temperature monitoring, when the temperatures exceed a threshold, the AI system reduces the processor frequency, i.e., throttles the processor, to save power and dynamically shifts part of the workload to other ESP32-S3s with lower temperatures. This approach maximizes overall efficiency while maintaining thermal safety without compromising computational power. Experimental results with up to six processors confirm the validity of the concept. Full article

In modern agriculture, reducing the internal moisture content of crop seeds is essential to enhance the activity and mobility of seed oil molecules, thereby increasing oil yield while minimizing the risk of mold and deterioration. However, traditional drying methods often result in uneven heating, leading to seed scorching and diminished drying efficiency and economic returns. To address these limitations, this study proposes a novel thin-layer seed drying system incorporating a redesigned drying tray structure. Specifically, the system places the seed-bearing tray beneath a vibration module operating at a predetermined frequency. The vibration mechanism induces the uniform motion of the seeds, thereby preventing localized overheating (scalding) and enabling automatic weighing for the real-time monitoring of moisture reduction during the drying process. The advancement of wireless sensor technologies in agriculture has enabled the deployment of more refined, large-scale monitoring networks. In this work, a commercial chip-based piezoelectric vibration detection device was integrated into the experimental setup to collect time-domain response signals resulting from interactions among seeds, impurities, and the drying tray. These signals were used to construct a comprehensive database of seed collision signatures. To mitigate discontinuities in signal transmission caused by vibration and potential equipment failure, the shortest routing protocol (SRP) was implemented. Additionally, the system outage probability (OP) and a refined closed-form solution for signal transmission reliability were derived under a Rayleigh fading channel model. To validate the proposed method, a series of experiments were conducted to determine the optimal vibration frequencies for various seed types. The results demonstrated a reduction in seed scalding rate to 1.5%, a decrease in seed loss rate to 0.4%, and an increase in moisture monitoring accuracy to 97.0%. Compared to traditional drying approaches, the vibrating drying tray substantially reduced seed loss and effectively distinguished between seeds and impurities. Furthermore, the approach shows strong potential for broader applications in seed classification and moisture detection across different crop types. Full article

Arresters on electric multiple units (EMUs) usually experience premature aging under a high-frequency voltage and impulse current. In addition, they lead to overheating faults when subjected to the high-frequency overvoltage of electric railways. This research investigates the aging behavior of arresters when subjected to overvoltage and an impact current. An analysis was conducted on the impact of the aging duration at 1 mA and the frequency of overvoltage on a lightning arrester’s outer-layer components. The results show that the 1 mA DC reference voltage of the MOA sheet decreased, and the leakage current significantly increased at a 0.75 DC reference voltage through the aging of high-frequency voltage, and the duration of the applied voltage and the voltage bearing rate had similar effects on the two parameters. After aging, the Co and Bi elements on the surface of zinc oxide decreased and migrated to the depletion layer, resulting in a decrease in the dispersion characteristics of the zinc oxide agglomerate surface. Under the impulse voltage, the thermal stress on the surface of the zinc oxide increased, resulting in the damage to the zinc oxide grains, which aggravated the thermal stress concentration and reduced the performance of the zinc oxide. This study reveals the deterioration mechanism of high-frequency voltage- and impulse current gap-modulated MOA materials and provides a theoretical basis and data support for the development of and monitoring methods for new lightning arresters. Full article

The presence of a bright spot structure in the divertor region during the discharge process, indicative of localized overheating, has been observed through multi-band and high-speed endoscope diagnostic on the Experimental Advanced Superconducting Tokamak (EAST). This localized deposition of hyperthermal heat flux can lead to erosion and melting of the target plate material, thereby posing a significant risk to the safe operation of the device. Moreover, it may introduce impurities into the main plasma, negatively impacting plasma performance. Therefore, real-time monitoring of the divertor and rapid identification of localized overheating regions during experiments are crucial. In this context, this paper proposes an improved DeepLabv3+-based highlight structure image-segmentation algorithm, which uses minimum value, image difference method, and Prewitt operator for dataset preprocessing. In order to realize the rapid identification of local overheated regions, this paper introduces the application of the improved DeepLabv3+ neural network algorithm based on MobileNetV2 as the backbone network in the bright spot structure segmentation task for the first time. The results show that the algorithm achieves a 65.36% average crosslinking rate (mIoU), 78.75% accuracy, 0.78 s per-iteration processing time, and 22.4 MB parameter size. This provides substantial advantages in terms of reduced computing and memory resources and real-time detection performance. Ultimately, the method proposed in this paper enables the rapid identification of the bright spot structure in the localized overheating region of the divertor on the EAST; it identifies areas of overheating and prevents damage to the divertor or other critical components due to overheating, ensuring safe operation of the device. Full article