Search Results (17,231)

This study investigates unsteady magnetohydrodynamic free convection flow past a rotating vertical plate embedded in a Darcy–Forchheimer porous medium. The formulation incorporates Hall current, thermal radiation, viscous dissipation, Joule heating, and an Arrhenius-type chemical reaction with activation energy to represent thermo-reactive transport in an electrically conducting fluid. The coupled nonlinear equations governing momentum, thermal energy, and species concentration are transformed into dimensionless form and solved numerically using the Crank–Nicolson scheme. Grid independence and validation tests confirm the accuracy and stability of the numerical procedure. The results show that electromagnetic forces, rotation, porous resistance, and thermo-reactive effects significantly influence wall shear stress, heat transfer, and mass transport. In particular, the interaction between magnetic field strength and Hall current alters near-wall transport behavior, highlighting the role of electromagnetic coupling in rotating porous systems. The study provides physical insight relevant to the design and analysis of transport processes in high-temperature energy systems, rotating reactors, and porous thermal management devices. Full article

Developing specialized aluminum alloys for additive processes is a strategic approach to achieve both strength and mass reduction in high-performance products. The prospects of the new metallic powder composition of Al3Ca2La2Mn0.4Zr alloy for laser powder bed fusion (LPBF) have been studied. It has been found that the best printing mode, providing a more than 99.0% density of the specimens, includes substrate heating to 150 °C and printing with a 350 W laser power, a 1500 mm/s printing speed, a 0.08 mm hatch distance and a 0.03 mm layer thickness (energy density 97.2 J/mm²). The optimal printing mode provides for the following strength parameters: UTS 366 ± 5 MPa, yield strength 223 ± 8 MPa, and relative elongation 30 ± 3%. The alloy exhibits high thermal stability for the structure and its properties. Annealing temperatures below 300 °C have no critical effect on the alloy hardness: the hardness decreases by less than 10% of the initial 110 ± 3 HV. At 350 °C, the hardness decreases by 25.5% (82 ± 2 HV); 100 h exposure at 350 °C reduces the UTS to 265 ± 2 MPa and the yield strength to 178 ± 10 MPa, while maintaining the relative elongation of 29 ± 2%. Full article

The goal of laser polishing (LP) is to improve the surface quality of functional parts, components, and assemblies. LP is a complex nonlinear thermophysical process, in which laser radiation induces localized melting of a material with an initially rough surface topography. During LP, the thermodynamic state evolves dynamically due to transient melt flow, heat transfer, and rapid solidification within the laser–material interaction zone. A smooth surface is formed through the interplay between surface tension-driven flow, which promotes energy minimization, and nonequilibrium effects associated with melting and solidification. From the perspective of self-organization, LP can be interpreted as an open system driven by energy input, where complex material redistribution leads to the evolution of surface topography. In this work, the self-organization of molten material is analyzed using chaos-based descriptors, including the Lyapunov exponent, phase portrait, approximate entropy, and the Hurst exponent, calculated from measured surface topographies before and after laser polishing. The results show that LP acts as a spatial low-pass filter, reducing high-frequency surface components associated with micromilling marks, and exhibits a directional bias in material redistribution relative to the laser scanning direction. Among the evaluated descriptors, the Lyapunov and Hurst exponents demonstrate consistent behaviors, indicating their suitability as robust indicators of surface state in post-process analysis. For the investigated conditions (Inconel 718), a laser fluence of 158.3 mJ/cm² provided the best-achieved surface quality, corresponding to an improvement in surface roughness (Ra) of approximately 70% and the lowest Lyapunov exponent of 1.966 and highest Hurst exponent of 0.859. This study demonstrates that chaos-based analysis of surface topography provides a phenomenological framework for assessing process stability and surface evolution, offering a basis for thermophysics-informed development of LP in applications such as mold and die manufacturing. Full article

Industrial tunnel pasteurizers are widely used for bottled liquid products because they provide a robust and continuous thermal treatment. However, operating conditions are often conservatively selected to ensure microbiological safety, which may result in excessive energy consumption and limited thermal efficiency. This study experimentally investigates the thermal behavior and energy performance of an industrial tunnel pasteurizer used for a sealed bottled herbal-based high-viscosity liquid formulation under both nominal and modified operating conditions. An instrumented bottle was developed to measure temperature evolution at different locations inside the bottle, including the product core. In parallel, the overall heat capacity of the bottle–product system was determined by differential scanning calorimetry, enabling the estimation of the thermal energy absorbed by the bottles. Mass and energy balances were applied to quantify the heat exchanged in each process stage and to estimate phase-specific and overall heat-transfer efficiencies. Under nominal conditions, the pasteurization requirement, defined as a temperature above 72 °C for at least 12 min at the coldest point, was fully satisfied, with the temperature remaining above 72 °C for approximately 22 min near the bottle wall and 17–18 min at the product core. The energy analysis showed that overall process efficiency was limited, indicating room for improvement. Three additional experimental tests were therefore carried out under modified temperature and flow-rate conditions. In all cases, the pasteurization target was maintained. The results demonstrate that the process complies with the prescribed pasteurization target while offering significant opportunities for energy savings through optimization of the operating parameters. Full article

Understanding the rapid non-isothermal crystallization behavior of polymers is crucial for tailoring and optimizing their performance. However, conventional techniques are limited in achieving rapid heating and cooling rates, which hinders in-depth investigation of the crystallization kinetics of fast-crystallizing polymers. In this study, a high-scan-rate MEMS thermopile DSC chip is employed to systematically investigate the non-isothermal crystallization kinetics of polyamide 66 (PA66) under rapid temperature variations. The results show that PA66 forms a lamellar α phase under slow cooling (1 °C/s) and a cauliflower-like γ phase under rapid cooling (300 °C/s), and becomes completely amorphous under ultrafast cooling (quenching). Furthermore, the technique enables quantitative analysis of the cold crystallization kinetics of fully amorphous PA66 during rapid heating. The results indicate that PA66 exhibits a higher apparent activation energy for homogeneous nucleation cold crystallization at low heating rates (≤10 °C/s), reaching 172.3 kJ·mol⁻¹, which is approximately 3.2 times that at high heating rates (≥25 °C/s). The results of this study demonstrate that the developed fast-scanning chip-based DSC provides a powerful tool for analyzing the processing heating and cooling rate conditions of rapidly crystallizing polymers. Full article

This study investigates the phenomenon of supratransmission in three-dimensional crystals with a B2 (CsCl) structure, employing classical molecular dynamics with β-Fermi–Pasta–Ulam–Tsingou potentials up to fourth-nearest neighbors. We analyze energy transfer from a harmonically driven surface into the crystal bulk across various frequency regimes relative to the phonon spectrum. While low-amplitude excitation results in energy transmission only within the phononic bands, high-amplitude driving triggers supratransmission in the phononic gap and above the optical band. Our results demonstrate that in these nonlinear regimes, energy is transported not by linear phonon waves but by discrete breathers (DBs) emitted quasi-periodically from the surface. A key finding is the distinct sublattice selectivity of these excitations: gap DBs propagate primarily along the heavy atom sublattice, whereas above-spectrum DBs travel along the light atom sublattice. We quantify the velocities and oscillation periods of these localized modes, revealing their critical role in bypassing linear spectral restrictions. These findings provide new insights into nonlinear energy transport in binary alloys and suggest potential applications for controlling heat flow and signal processing in crystals. Full article

Wind turbine (WT) drivetrains are exposed to high dynamic loads, especially caused by grid and converter faults. Those loads increase the frictional energy in the contact zone of the gearbox bearings and gear wheels and, thus, theoretically, the probability of failure of the gearbox before the WTs reach their service lifetime. To increase the robustness against grid and converter faults, gearboxes can be designed to include these as special load cases. The critical parts of gearboxes regarding the influence of grid and converter faults are the components of the fast-rotating gearbox side. This paper introduces an optimization procedure for the high-speed shaft (HSS) components of a WT gearbox, considering several electrical faults as special load cases. The basis for data collection in this work is a validated multi-body simulation (MBS) model of a WT drivetrain. Initially, a test plan is formulated using Latin hypercube sampling (LHS). Based on the simulation results generated with the detailed MBS model according to the defined test plan, computationally efficient surrogate models are derived that link the design parameters with the objectives of the optimization. The surrogate models are employed to optimize the microgeometry of the gearbox. The process is done for several electrical faults. With the optimization, the risk of damage to the gear wheels can be reduced by 28% with a reduced or equal risk of damage to the HSS bearing, depending on the load case. It is also shown via comparison that the optimal design for one critical fault simultaneously leads to a sufficient improvement for other electrical faults (max. 4% reduction in improvement of objectives). Thus, it is sufficient to do the optimization regarding electrical faults only for one critical fault, reducing the necessary computational effort significantly. Full article

Although amine-based post-combustion carbon capture is among the most established routes for CO₂ capture, it suffers from the high energy demand associated with amine regeneration. Recent research proposals suggest that microwave or frequency-tuned infrared heating may lead to more efficient amine regeneration processes. However, such approaches inherently introduce oscillating electromagnetic fields whose non-thermal effects on reaction pathways and energetics remain poorly understood. In this series paper, we employ high-accuracy quantum computational chemistry calculations to quantify the non-thermal effects of external electric fields on CO₂ absorption and desorption in monoethanolamine (MEA) and triethanolamine (TEA) under both aqueous and non-aqueous conditions. In this first part, we focus on static electric fields in order to establish a mechanistic reference framework helpful for interpreting non-thermal effects arising from frequency-tuned infrared laser excitation, which are addressed in Part II of this series. Our results show that static electric fields stabilize CO₂–amine reaction products, lowering absorption barriers, while consistently increasing both activation energies and reaction enthalpies associated with the amine regeneration process. This effect is particularly pronounced for MEA, where carbamate species become progressively more resistant to conversion to zwitterion as the field strength increases. These findings demonstrate that non-thermal static electric field effects counter the fundamental requirement for low-energy amine regeneration. By defining this intrinsic mechanistic limitation, the present study provides a useful baseline for assessing infrared laser-assisted carbon capture and underscores the importance of carefully selecting excitation frequencies to avoid adverse non-thermal stabilization effects. Full article

Quadrotor motion planning in cluttered environments presents significant challenges in achieving both computational efficiency and trajectory smoothness, particularly in low-altitude economy and intelligent energy system applications where autonomous aerial vehicles perform infrastructure inspection and power line monitoring. Many existing methods either rely on sampling-based algorithms that suffer from long computation times and suboptimal paths, or employ trajectory representations that produce high-order derivative discontinuities unsuitable for agile flight. In this work, we propose an efficient hierarchical motion planning framework that integrates a JPS–Bresenham-based path search with safe flight corridor construction and Bézier curve optimization. Our approach addresses trajectory generation through a two-stage process: a front-end path search that efficiently identifies collision-free paths with reduced waypoints, followed by a back-end optimization that leverages convex safe corridors with overlapping regions to expand the solution space. Through comprehensive benchmark experiments across six different map scenarios, we demonstrate that our method outperforms RRT* and PRM in both path quality and computational efficiency. Monte Carlo experiments across varying map sizes and obstacle densities confirm robustness and scalability advantages. Comparative studies with state-of-the-art planners demonstrate superior success rates and cost efficiency while maintaining strict kinodynamic feasibility. The Bézier-based optimization reduces snap integral by up to 55% compared to ordinary polynomial approaches, demonstrating its superiority for fast quadrotor trajectory planning in complex environments. Full article

To address the issues of high energy consumption and unstable construction quality caused by high-temperature heating during the preparation of traditional hot-mixed/grouted semi-flexible pavement (SFP) mixtures, a cold-mixed integrated (CMI) process was proposed. In addition, the material composition of the mixtures was optimized. The effects of the preparation process and binder type on the high- and low-temperature performance, water stability, and fatigue performance were then analyzed. Furthermore, the microstructural characteristics of the semi-flexible mixture were also investigated. The results indicated that the CMI process facilitated the formation and uniform distribution of calcium silicate hydrate (C-S-H), enhanced the binder’s ability to encapsulate aggregates and fill skeletal voids, significantly reduced the mixture’s void ratio, and improved its pavement performance. The proposed procedure was a means of enhancing high-temperature stability and fatigue life (an increase of 80% and 200 times compared to the hot-mixed/grouted (HMG) process, and 5 times and 300 times compared to AC-13, respectively). Compared with the HMG process, the CMI process offered greater advantages in enhancing the high-temperature stability and fatigue resistance of the mixture, particularly when using SBS-modified asphalt, where fatigue performance exhibited an order-of-magnitude improvement. Furthermore, while SBS modification could improve the road performance of SFP materials, mixtures prepared with SBS-modified emulsified asphalt demonstrated more significant enhancements in high-temperature stability and fatigue resistance, approximately 2 times and 10 times higher than SBS-modified mixtures, respectively. The addition of styrene–acrylic emulsion (SAE) could further enhance the low-temperature crack resistance by approximately 7%. The research results can provide a reference for the development and application of preparation processes for semi-flexible mixtures. Full article

Photosynthesis, the main energy source for life on Earth, confronts escalating challenges of high-light–high-temperature stress (HLHT). Our previous study identified a mutation in ATP synthase, F₁-α-C252Y, that significantly enhances the HLHT tolerance of Synechococcus elongatus PCC 7942 (Sye7942), although the underlying mechanism remains obscure. In this study, we found that this mutation led to elevated levels of the b subunit of F_o, F₁ subunits, and the ATP synthase within cells, without affecting ATP synthetic activity, indicating improved intracellular ATP synthesis activity. Additionally, the mutation altered the transcriptome of Sye7942, impacting the expression of genes involved in crucial processes, such as the electron transport chain, carbon fixation, and regulatory factors, which are crucial for cyanobacteria’s adaptation to stresses. Correspondingly, the mutant exhibited enhanced photosynthesis, accelerated growth, and increased glycogen under HLHT conditions, showing improved adaptation. The higher intracellular ATP synthesis activity, along with enhanced photosynthetic activity, suggests increased ATP production in the mutant under HLHT. Enhancing ATP production and remodeling the cellular transcriptome appear to be key strategies employed by the C252Y mutation for Sye7942 acclimating to HLHT. These findings provide valuable insights for enhancing photosynthetic efficiency and stress resilience in cyanobacteria and other photosynthetic organisms facing HLHT challenges. Full article

Large-diameter axial ventilation fans are widely used in poultry houses to regulate ai flow, temperature, and air quality. However, conventional induction motors driving these fans typically operate at fixed speed and suffer efficiency degradation under low-speed, high-torque conditions due to slip-induced rotor copper losses. This study presents an experimental investigation of a manufacturing constrained conversion of a commercial induction motor platform into a direct-drive surface permanent magnet synchronous motor (PMSM). Instead of developing a completely new motor design, the proposed approach reuses the existing stator lamination, housing structure, and winding production process while redesigning the rotor electromagnetic structure to incorporate surface-mounted permanent magnets. Experimental testing was conducted using a dynamo meter-based measurement system to evaluate the performance of both the commercial induction motor and the converted PMSM prototype. The results show that the commercial induction motor exhibits significant efficiency degradation at high torque due to increased slip, whereas the PMSM eliminates slip-dependent rotor copper losses and maintains efficiencies above 88% within the typical ventilation operating range of 650–750 rpm. This study further relates airflow demand to rotational speed using fan affinity laws, highlighting the cubic relationship between speed and input power and demonstrating the energy-saving potential of variable-speed PMSM drives. The proposed conversion framework therefore provides a practical pathway for improving the energy efficiency of agricultural ventilation systems while maintaining compatibility with existing motor manufacturing infrastructure. Full article

Uranium is a resource with exceptionally high energy density, releasing substantially more energy per unit mass than conventional fossil fuels. In uranium mining, in situ leaching offers significant advantages over open-pit and underground mining, including reduced environmental impact, lower operational costs, enhanced safety, and improved controllability. Within the in situ leaching framework, acid leaching faces limitations in high-carbonate ore bodies, while alkaline leaching is unsuitable for deposits rich in pyrite and other sulfide minerals due to side reactions and precipitate formation that hinder leaching efficiency. In contrast, CO₂-O₂ leaching, as a neutral leaching approach, exhibits broader applicability across diverse ore types and geological settings. Incorporating CO₂ into the leaching process also enables carbon utilization, offering a potential pathway to cleaner uranium extraction aligned with carbon reduction and sustainable energy goals. This review systematically examines the geochemical principles, as well as hydrological and transport phenomena governing CO₂-O₂ in situ leaching. Recent technological advances are summarized, including progress in reaction kinetics and leaching efficiency, leaching solution design and control, and reservoir modification. Furthermore, the techno-economic implications of CO₂-O₂ in situ leaching are critically assessed, with particular emphasis on operational cost structures and the evolution of techno-economic analysis methodologies. On this basis, key challenges and future directions are identified. This work aims to support the future large-scale and economically efficient deployment of CO₂-O₂ in situ leaching for uranium resource development. Full article

Rare-earth elements including the fifteen lanthanides, from lanthanum (La) to lutetium (Lu), together with scandium (Sc) and yttrium (Y), can act either as matrix cations or as active luminescent centers when incorporated into host lattices. Owing to their relatively large ionic radii, high coordination numbers, and structural stability, ions such as La, Lu, Sc, Y, and gadolinium (Gd) typically serve as matrix cations in rare-earth vanadate (REVO₄)-based phosphors, while other trivalent lanthanide (Ln³⁺) ions act as active luminescent centers. These REVO₄ phosphors have proved to be good host lattices for optically active Ln³⁺ ions giving strong luminescence assigned to absorption of the vanadate (VO₄³⁻) groups, and the efficient energy transfer between host lattice and Ln³⁺ ions. The unique electronic configuration of Ln³⁺ ions, particularly their unpaired 4f electrons, makes them ideal for applications in luminescence, magnetism, electronic and magnetic relaxation, and catalysis. Due to their complementary luminescent characteristics, Ln³⁺-doped REVO₄ phosphors have attracted significant attention in recent years. Their unique optical properties make them highly valuable across a broad spectrum of applications. This paper provides a comprehensive review of the state of the art in Ln³⁺ (Eu³⁺, Sm³⁺, Tm³⁺, Er³⁺, Ho³⁺, Tb³⁺, Nd³⁺, and Yb³⁺)-doped REVO₄ (RE = Y, Gd, Lu, La) phosphors. It examines current synthesis approaches, alongside the development of advanced strategies, and explores structural characteristics, innovative designs, and luminescent behavior, including both downconversion and upconversion processes and sensing applications, of the Ln³⁺-doped REVO₄ phosphors. Full article

Improving the prediction accuracy of renewable energy power generation units is an important goal of the “source-storage integration” approach. However, the abundance of anomalous data and indistinct features in renewable energy station data seriously affects the health status prediction of these generator sets. To effectively enhance the performance of renewable energy generation prediction, this paper proposes an efficient data cleaning method for renewable energy stations based on anomaly detection and feature enhancement. First, anomaly detection is achieved by calculating a baseline power curve and partitioning data, utilizing the Density-Based Spatial Clustering of Applications with Noise (DBSCAN). Subsequently, considering that current models often learn low-frequency features while ignoring high-frequency features when processing time-series data, a data feature enhancement method is proposed. The proposed method integrates high-/low-frequency data decomposition, time–frequency domain conversion, and an improved attention mechanism to effectively enhance the high-frequency features of renewable energy station data, and reduces the RMSE of mainstream forecasting models significantly. Finally, using data from a renewable energy station in a region of China, the effectiveness and superiority of the anomaly detection and feature enhancement methods are analyzed. The results show that for renewable energy generation data, the proposed method reduces the RMSE of LSTM and Transformer models by 15.12%, 16.67% and 16.24%, 18.32% respectively, significantly improving prediction accuracy. Full article