Search Results (383)

The influence of ausforming temperature on the isothermal bainitic transformation behavior of 42CrMo steel was systematically investigated using thermo-mechanical simulation, dilatometric analysis, and electron backscatter diffraction (EBSD). The results show that ausforming significantly accelerates the bainitic transformation kinetics, whereas lower ausforming temperatures lead to a progressive reduction in the final bainite fraction. This apparently contradictory behavior originates from the competitive interaction between deformation-induced mechanical stabilization of austenite and dislocation-assisted heterogeneous nucleation of bainitic ferrite. Lower ausforming temperatures result in higher retained dislocation densities, which promote early-stage nucleation while simultaneously increasing resistance to transformation interface migration and hindering carbon redistribution. As a consequence, the bainitic ferrite microstructure is markedly refined, exhibiting reduced lath thickness and length. Crystallographic analysis reveals that the bainitic ferrite predominantly follows the Kurdjumov–Sachs orientation relationship with prior austenite, and that strong variant selection is induced by ausforming, particularly at lower deformation temperatures. The reduced variant multiplicity within individual prior austenite grains further contributes to the refinement and preferential orientation of the bainitic microstructure. These findings highlight the critical role of ausforming temperature in governing the coupled evolution of transformation kinetics, phase fraction, and crystallographic characteristics during bainitic transformation and provide guidance for microstructural control of bainitic steels through temperature-dependent thermo-mechanical processing. Full article

High-viscosity sodium alginate solutions (4.5% by mass, apparent viscosity 1 × 10⁴–2 × 10⁴ cP) are widely used in the preparation of hydrogels, wet spinning, and biomedical materials. Residual bubbles can cause internal voids in hydrogels, mechanical heterogeneity, fiber breakage during spinning, and reduced strength, and can severely affect the cell compatibility and clinical safety of biomaterials. Due to the difficulty of bubble migration, coalescence, and rupture in high-viscosity systems, traditional vacuum-standing degassing takes up to 24 h and is extremely inefficient, severely limiting the quality of subsequent processing. To address this issue, this study proposes a novel vacuum-assisted centrifugal recirculating degassing method for highly viscous sodium alginate solutions and aims to establish a kinetic framework for describing its overall degassing behavior. Using the number density of bubbles larger than 0.5 mm in diameter as an evaluation metric, we conducted vacuum-standing control experiments and univariate experiments with different screen mesh apertures (5, 1.5, 0.3, and 0.07 mm). We experimentally verified a continuous kinetic model of bubble number decay based on vacuum bubble expansion, centrifugally enhanced migration, and removal probability during the cycle. The results indicate that the bubble removal effect of 40 min of vacuum–centrifugal cyclic degassing is equivalent to that of 4 h of vacuum static settling, representing a 450% increase in degassing efficiency. There is an optimal range for a screen aperture, with the best degassing effect observed at 0.3 mm, achieving a bubble removal rate of 83.69%. The established kinetic model exhibits good fitting accuracy (RMSE = 0.17, MAPE = 5.9%) and can accurately predict degassing efficiency under different process conditions. This study provides a quantifiable, modelable, and optimizable process scheme for rapid degassing of high-viscosity sodium alginate solutions, and offers a theoretical reference for the development of degassing technologies for high-viscosity polysaccharide fluids. Full article

Temperature and pressure are critical controlling parameters in the in situ conversion process (ICP) of oil shale. Clarifying the mechanisms governing organic matter pyrolysis is essential for reliably extrapolating laboratory findings to geological conditions. This review systematically summarizes the effects of temperature and pressure on shale pyrolysis and on hydrocarbon generation kinetics. Temperature is the primary factor controlling pyrolysis rates and product distribution, with an optimal temperature window enhancing shale oil yield while suppressing secondary cracking. Low heating rates favor thorough pyrolysis, although their influence on reaction pathways is generally overlooked in current kinetic models. Pressure effects are stage-dependent: during organic matter conversion, they are minor, whereas, in the product expulsion stage, high pressure inhibits hydrocarbon expulsion, prolongs residence time, and promotes secondary cracking, thereby reducing overall oil yield while increasing light fractions. Discrepancies in reported pressure effects arise from variations in experimental systems, sample forms, and medium conditions. The coupling of temperature and pressure is synergistic rather than additive. Given that current kinetic models largely neglect pressure and heating-rate effects, and that temperature–pressure coupling mechanisms remain unclear, future research should focus on thermal simulation experiments across wide ranges of pressures and heating rates, complemented by ReaxFF molecular dynamics to elucidate reaction pathways and guide kinetic model development. Further in situ experiments under high-temperature and high-pressure conditions are needed to characterize coupled pore evolution and fluid migration. Ultimately, integrated thermo-hydro-mechanical-chemical (THMC) models should be developed to capture hydrocarbon generation, retention, and expulsion, providing a robust theoretical framework for optimizing ICP technology. Full article

Semi-batch nitration processes involve substantial heat release, and local reactant enrichment may induce hot-spot formation and increase the risk of thermal runaway. However, global indicators such as the volume-averaged reactor temperature cannot adequately characterize local thermal hazards or quantitatively describe the redistribution of reaction heat under practical flow conditions. In this study, a three-dimensional transient computational fluid dynamics (CFD) model coupled with reaction kinetics, fluid flow and heat transfer was established for the semi-batch nitration of 4-chlorobenzotrifluoride (4-Cl-BTF). On this basis, a CFD-based quantitative framework was proposed to characterize local heat distribution and hot-spot evolution directly from the predicted temperature field. The roles of feed location, stirring speed, feeding time, and impeller type were then investigated. The results show that hot-spot evolution is dominated by the spatial mismatch between local heat generation and heat transport rather than by the global thermal response alone. Insufficient mixing and excessive instantaneous feed flux intensified local reactant enrichment, thereby promoting early hot spot formation. In contrast, feed location and impeller type mainly affected the migration and connectivity of hot spots by reshaping the internal circulation pathway. The present work provides an initial quantitative description of hot spot propagation under realistic impeller-driven flow conditions, and offers a spatially resolved basis for local thermal risk assessment and operating condition optimization in semi-batch nitration reactors. Full article

Lead sulfide quantum dots (PbS QDs), as a functional-layer coating, enable non-volatile integration and neuromorphic computing in memristive structures to address the von Neumann bottleneck. Herein, the dual-interface mechanism of PbS QDs in the memristor film structure is reviewed. First, the local electric field enhancement effect generates tip electrode-like structures in the coating film through QD-mediated spatial charge gradients, thereby enabling precise control over the nucleation and growth of conductive filaments (CFs). As a result, the consistency of switching voltages and the thermal stability at elevated temperatures are significantly improved. Conversely, the anion reservoir effect exploits surface dangling bonds on QDs to efficiently capture anions from the dielectric layer, thereby synergistically regulating vacancy migration kinetics. This process enables zero-initialization behavior and ultra-low-power operation. In addition, the spatial distribution design and density modulation of QDs further reinforce both mechanisms. The structural optimization of QD/dielectric interface engineering can simultaneously improve cycling endurance and resistive switching uniformity. Furthermore, modification of QD surface chemistry through ligand decoration and passivation suppresses the stochasticity of ionic diffusion while improving the linearity of synaptic weight updates. This interfacial engineering strategy utilizing QDs as coating films advances the development of high-performance photonic–electronic systems for memory–computing convergence. Full article

Aqueous zinc-ion batteries offer a safe and economical platform for large-scale energy storage, yet vanadium oxide cathodes remain hindered by sluggish Zn²⁺ migration, poor electronic conductivity, and structural degradation during cycling. Herein, a PEDOT regulated interfacial engineering strategy is proposed to construct surface modified sodium vanadium oxide nanostructures with coordinated ion and electron transport. The 1P-NaVO cathode retains the layered framework while introducing a PEDOT-derived surface component that strengthens interfacial charge transfer and preserves accessible Zn²⁺ diffusion pathways, delivering 655 mAh g⁻¹ at 0.1 A g⁻¹. Kinetic analyses further reveal accelerated charge storage behavior, including an increased pseudocapacitive contribution, a low charge transfer activation energy of 20.6 kJ mol⁻¹, and improved Zn²⁺ diffusion, with D_Zn²⁺ values of approximately 10^−10.8 to 10^−9.8 cm² s⁻¹. Ex situ XRD and SEM disclose a reversible structural response during Zn²⁺ insertion and extraction, involving interlayer perturbation, local framework relaxation, transient electrolyte-derived surface species, and partial morphology recovery after recharge. These findings show that controlled PEDOT-derived surface regulation promotes efficient coupling between interfacial electron transfer and Zn²⁺ diffusion, offering a practical design principle for durable vanadium-based cathodes in aqueous zinc-ion batteries. Full article

In this study, a fully coupled three-dimensional multiphysics CFD model of a photoelectrochemical (PEC) water splitting cell incorporating a ZnO/BiVO₄ photoanode was developed using COMSOL Multiphysics^® 6.1. The model integrates semiconductor charge transport, ionic transport (diffusion, migration, and convection), electrochemical kinetics, and fluid dynamics within a widely adopted experimental configuration. This work focuses on coupling the dominant transport phenomena governing macro-scale PEC behavior under realistic operating conditions, allowing the overall PEC behavior to be captured without resolving microscopic interfacial complexities. The simulation results show good agreement with previously reported experimental data in terms of photocurrent density, demonstrating the capability of the model to reproduce photocurrent behavior. The developed framework provides insight into the interplay between photogenerated charge transport and electrochemical reactions and can serve as a predictive tool for analyzing and optimizing PEC system performance prior to experimental implementation. Full article

Understanding the spatiotemporal variability of nanoplastics (NPs) in porous media is vital for environmental risk assessment, yet quantitative in-media analysis of NP distributions during transport remains limited. To address this, we innovatively applied low-field nuclear magnetic resonance (LF-NMR) as a non-invasive approach to dynamically monitor magnetic polystyrene nanoplastic (MPSNP) transport in saturated quartz sand. By establishing the relationship between LF-NMR transverse relaxation rate [1/T_2,I − 1/T_2,0] and MPSNP concentrations, we reconstructed spatiotemporal concentration profiles via T₂ inversion. This methodology enabled systematic evaluation of the effects of ionic strength (IS), flow velocity, initial concentration, and flow direction. Three mathematical models were further applied to analyze MPSNP transport behavior. Results revealed IS as the dominant factor; increasing IS (0.001 to 1 mM) dropped mass recovery from 85.7% to 0%, the migration front no longer advanced at IS > 5 mM. Lower flow rates, higher initial concentrations, and horizontal flow also enhanced retention. The two types of two-site kinetic models provide a better fit for the features of the breakthrough curves. This novel use of LF-NMR demonstrates its robust capability to resolve spatial transport heterogeneity, underscoring that flow velocity, flow direction, and ionic strength are critical regulatory parameters that should be carefully accounted for when evaluating nanoplastic transport in porous media. Full article

In this work, an amide extractant was employed to purify Mo(VI) from chloride media, with particular emphasis on the extraction behavior of impurities and their migration during the extraction and scrubbing stages. The effects of hydrochloric acid concentration, extractant concentration, phase ratio, and temperature on Mo(VI) extraction were examined to clarify the extraction equilibrium and kinetics. Under the optimized conditions, a high extraction efficiency of 93.13% was achieved in a single stage. The loaded organic phase was subsequently purified by hydrochloric acid scrubbing, effectively removing co-extracted impurities while maintaining minimal Mo loss. Efficient stripping of Mo(VI) was realized using an ammonia solution with a stripping efficiency of 98.47%. FT-IR and ESI-MS analyses revealed that Mo(VI) was extracted as a protonated molybdenum oxychloride species interacting with the amide extractant through hydrogen bonding. Density functional theory calculations further confirmed the favorable interaction between the protonated molybdenum species and the carbonyl oxygen of the amide extractant. Thermodynamic analysis indicated that the extraction process was exothermic, with an enthalpy change of −22.17 kJ/mol. These findings provide mechanistic insight into the amide extraction of molybdenum from chloride systems and offer practical guidance for the purification of low-purity molybdenum products. Full article

Carnitine plays an essential role in fatty acid metabolism, and its biosynthesis is tightly regulated by γ-butyrobetaine hydroxylase (BBOX), an Fe(II)/α-ketoglutarate-dependent dioxygenase. BBOX is the target of mildronate (THP), a clinically used drug for treating ischemic heart diseases. However, the detailed mechanisms of BBOX-catalyzed hydroxylation and the atypical oxidative rearrangement underlying THP inhibition remain elusive. In this study, we employed combined quantum mechanics/molecular mechanics (QM/MM) methods to systematically elucidate these mechanisms at the atomic level. Our calculations reveal that the hydroxylation of γBB proceeds via a classical three-step mechanism in the quintet state, with hydrogen atom abstraction as the rate-determining step. Remarkably, substitution of the C4 methylene group in γBB with an amino group in THP redirects the reaction pathway, as the lone pair electrons on the adjacent nitrogen atom render N-N bond cleavage kinetically favored over hydroxyl rebound, thereby blocking carnitine synthesis. Through systematic evaluation of possible rearrangement pathways, we rule out the previously proposed direct 1,2-H migration and suggest a revised mechanism featuring imine-mediated hydrogen transfer, hydroxyl rebound preceding C-C bond formation, and final radical coupling. This work provides a detailed atomic-level understanding of both the catalytic and inhibitory mechanisms of BBOX, revealing how substrate electronic effects dictate reaction outcomes. The elucidated mechanistic insights offer a theoretical foundation for understanding the catalytic versatility of the αKG-dependent dioxygenase family and provide valuable guidance for the rational design of novel BBOX inhibitors. Full article

The development of precise quantitative metrics is essential for characterizing the response of biological systems to external perturbations, enabling a transition from qualitative observation to predictive modeling. In this context, mathematical frameworks can provide insight into the dynamic behavior of cell populations under external stimuli. In this study, a logistic-type growth model was employed to describe wound healing dynamics. A scratch assay protocol was applied to lung cancer cells, and a perturbation-based analytical framework was developed to quantify the influence of external factors. Novel metrics were introduced, including the percentage difference in wound closure at specific time points, the shift in inflection time, and the Average Difference in Wound Closure (ADWC). A pilot experimental study was conducted to evaluate the effect of Low-Level Laser Therapy (LLLT) on cell migration. The proposed model successfully captured the nonlinear dynamics of wound closure and enabled quantitative comparison between control and treated groups. The analysis demonstrated that LLLT enhances cellular activity, leading to a shift in the inflection time by approximately 7.6 h and an increase of 25.4% in wound closure at 24 h compared to the control group. The ADWC metric further confirmed a systematic difference in the overall healing dynamics between conditions. The presented perturbation-based framework provides a rigorous and interpretable tool for quantifying the effects of external stimuli on biological systems. These findings suggest a light-dependent modulation of tumor cell migration in an in vitro model, indicating that light exposure may influence cellular behavior under certain conditions. This observation may be relevant for clinical applications involving light, such as photodynamic therapy, particularly in cases of incomplete drug delivery. Full article

This study investigated the effects of freeze–thaw pretreatment on the solar hot-air drying behavior, moisture migration, and microstructure of Mongolian Astragalus (Astragalus membranaceus var. mongholicus) slices. An L9 orthogonal design with slice thickness, diameter, air velocity, and drying temperature was used; drying kinetics, water-state distribution, and surface morphology were assessed by thin-layer models, apparent effective moisture diffusivity, LF-NMR, and SEM. The drying process showed no obvious constant-rate period and was mainly characterized by a falling-rate stage, indicating that dehydration was controlled by internal moisture migration. Freeze–thaw pretreatment redistributed the initial water fractions but did not uniformly accelerate drying; the longest drying time decreased from 130 to 100 min, showing a condition-dependent effect. Slice thickness was the dominant factor affecting the average drying rate. The preferred conditions were 1–3 mm thickness, 8–11 mm diameter, 1.0 m·s⁻¹ air velocity, and 50 °C for the control group, and 1–3 mm thickness, 11–14 mm diameter, 1.5 m·s⁻¹ air velocity, and 50 °C after freeze–thaw pretreatment. The Midilli model best fit the moisture-ratio data, and the apparent effective moisture diffusivity remained on the order of 10⁻⁹ m²·s⁻¹. LF-NMR showed that endpoint residual moisture was mainly bound water, with free water almost completely removed. SEM observations showed a looser surface with more visible pores and cracks after freeze–thaw pretreatment. Overall, freeze–thaw pretreatment mainly affected solar hot-air drying by regulating moisture migration, with effects depending on process conditions. Full article

Dust accumulation on photovoltaic (PV) modules reduces power generation efficiency, and traditional water-based cleaning is impractical in arid regions. Inspired by the classical acoustic phenomenon of Chladni figures—specifically the mechanism where an acoustic standing wave field drives the regular migration and accumulation of particles—this study proposes a waterless dust removal method using low-frequency ultrasonic vibration via piezoelectric excitation. Impedance analysis identifies optimal electromechanical coupling at 28 kHz. Experiments demonstrate that higher driving voltages accelerate cleaning, with recovery rates saturating beyond 125 V. Notably, intense friction and collisions between particles within high-density dust layers consume substantial kinetic energy, significantly multiplying the required cleaning time. Macroscopic transport analysis reveals that dust removal relies on the synergy of vibration-induced adhesion decoupling and gravity-driven transport. Sufficient tangential gravity is crucial for macroscopic particle removal, and tilt angles above 30° provide the necessary downward driving force to ensure smooth particle sliding. Under optimal conditions, the system achieves an over 97% short-circuit current recovery at a low power consumption of ~10 W, providing a theoretical basis for waterless PV self-cleaning systems. Full article

This study develops an end-to-end workflow, from laboratory measurements to Eulerian–Eulerian two-phase simulations with SedFoam, to investigate bed erosion in free-surface open-channel flow over a deformable granular bed. Experiments were conducted with a calibrated non-cohesive deposit of epoxy-coated spherical beads under steady, fully turbulent, subcritical conditions. Particle Image Velocimetry provided mean-flow and turbulence data, while a 3D camera workflow supplied bed-elevation fields and time-resolved maps of sediment rearrangement. These datasets were used to constrain a staged numerical strategy in which single-phase hydrodynamics were first reproduced and then extended to live-bed morphodynamics. Validation over a rigid bed showed that the 2006 k–$\omega$ closure, combined with a rough-wall treatment, reproduced the measured mean-velocity profiles and provided acceptable turbulent kinetic energy levels, yielding dynamically consistent near-bed shear conditions. In live-bed conditions, the simulations reproduced the streamwise organization of scour and deposition, predicted cumulative erosion rates of the correct order of magnitude, and captured bedform migration consistent with time-resolved bed reconstructions. The numerical results were compared with repeated experiments while accounting for run-to-run variability and the metrological limits of the 3D camera. This work proposes a transferable experimental–numerical methodology for assessing the predictive capability of live-bed morphodynamic simulations, in which hydraulic characterization, three-dimensional bed monitoring, erosion/deposition metrics, and repeated experiments are combined within a common comparison procedure. Full article

Polymer microsphere flooding is an effective enhanced oil recovery (EOR) technology. Its primary mechanism is characterized by a dynamic cycle of “migration, plugging, breakthrough, and remigration”, which enables effective in-depth profile control and selective plugging. However, constructing accurate mathematical models and obtaining stable numerical solutions for this process remain challenging. Based on the black-oil framework, a three-phase, five-component mathematical model is developed for water-microsphere dispersed system, including oil, gas, water phases and two microsphere components (pre-swollen and post-swollen), and accounting for swelling kinetics, adsorption, and water phase permeability reduction. The model is numerically solved using a fully implicit finite-difference scheme, and validated by numerical tests and a field-scale application. The numerical simulation results demonstrated an overall agreement rate of approximately 85% with experimental data. Mechanistic comparisons indicated that polymer microsphere flooding significantly improves sweep efficiency and oil recovery. Field-scale application further showed that polymer microsphere flooding, compared with conventional water flooding, increases the recovery factor by 3.49 percentage points, reduces the maximum water cut by about 9.34 percentage points, and raises the average daily oil production rate over the entire development period by 7.5 m³. The proposed model can provide theoretical basis for the field application of polymer microsphere flooding for in-depth profile control. Full article