Search Results (3,043)

In this paper, we introduce a new three-parameter lifetime distribution that is obtained via a power transformation of the modified bimodal exponential model. The inclusion of an additional shape parameter significantly enhances the flexibility of the baseline distribution, allowing it to capture a wide range of distributional characteristics, including skewness, heavy tails, and varying hazard rate shapes such as increasing, decreasing, and non-monotonic forms. Several important structural properties of the proposed model are derived, including explicit expressions for the probability density function, cumulative distribution function, moments, and moment generating function. Entropy measures such as Rényi entropy, Shannon entropy, and cumulative residual entropy are also obtained. Key reliability characteristics, including the survival function, hazard rate function, cumulative hazard function, reversed hazard rate, and mean residual life function, are investigated in detail. A theoretical result on the modality of the distribution is established, demonstrating its ability to exhibit both unimodal and bimodal shapes. Parameter estimation is carried out using maximum likelihood estimation along with several alternative methods. A comprehensive simulation study is conducted to evaluate the performance of the estimators under different parameter settings. Finally, the applicability and effectiveness of the proposed distribution are demonstrated through the analysis of real datasets from reliability and environmental studies. Comparative results based on goodness-of-fit measures indicate that the proposed model provides a superior fit compared to several existing competing distributions. Full article

Traditional petroleum coke-based porous carbons suffer from low specific surface area, insufficient surface active sites, and inferior rate and cycling performance. Herein, a series of sulfur/fluorine-co-doped hierarchical porous carbon (S+F-PC) cathode materials were synthesized controllably from industrial solid-waste petroleum coke via KOH high-temperature activation and heteroatom doping strategies. Polyaniline/carbon nanotube (PANI/CNTs) core–shell composites were fabricated as anodes through in situ oxidative polymerization, and S+F-PC//PANI/CNT asymmetric aqueous supercapacitors were assembled. The structural and chemical modulation mechanisms of dual heteroatom doping, as well as the electrochemical energy storage kinetics of electrodes and devices, were systematically investigated using SEM, TEM, XRD, XPS, BET, CV, GCD, EIS, and long-cycle tests. The results verify the synergistic modification effect of sulfur and fluorine co-doping. S-induced lattice distortion creates abundant mesopores and pseudocapacitive active sites, while F atoms stabilize the carbon skeleton to avoid high-temperature structural collapse and enhance the graphitization degree. The optimized S+F-PC exhibits an interconnected micropore–mesopore–macropore hierarchical network and a specific surface area of 172.2 m²/g, delivering a high specific capacitance of 477 F/g at 1 A/g, outperforming pure PC, and single-S-doped and -F-doped counterparts. The PANI/CNTs core–shell structure effectively alleviates the volume expansion of PANI during cycling, and the one-dimensional CNTs form a continuous conductive network. The PANI/CNT anode achieves a specific capacitance of 417 F/g, with a capacity retention of 91.4%, after 10,000 cycles. The assembled asymmetric supercapacitor realizes a stable voltage window of 1.6 V. It presents a specific capacitance of 117 F/g at 1 A/g, a maximum energy density of 41 Wh/kg at a power density of 2000 W/kg, and 87.2% capacity retention after 10,000 cycles. This work provides a feasible strategy for the high-value recycling of industrial-waste petroleum coke and the design of high-performance heteroatom-doped carbon electrodes and matched asymmetric aqueous supercapacitors. Full article

Ultra-thin metal bipolar plates are critical components of proton exchange membrane fuel cells (PEMFCs), and their forming characteristics decisively influence service performance. This study proposes a constitutive model incorporating size effects to elucidate how sheet thickness and grain size govern stress–strain responses and formability of ultra-thin plates. The verified model is employed in finite element analysis for formability of ultra-thin plates. Based on the results of simulation, key stamping die parameters were optimized using Random Forest and XGBoost surrogate models. Results indicate that increasing grain sizes reduces grain boundary density, leading to stress localization within coarse grains and promoting local thinning. This effect increases stored elastic energy and simultaneously raises the maximum stress, thinning rate, and springback angle. Conversely, the increasing sheet thickness strengthens triaxial constraint and raises forming stress, while suppressing thinning and springback through enhanced strain redistribution and plastic dissipation. Thus, grain coarsening degrades formability overall, whereas increasing thickness introduces a trade-off between higher forming stress and improved dimensional stability. Both surrogate models demonstrated high predictive accuracy on unseen data (maximum error is 2.01%), identifying a non-standard parameter combination (α = 16.0°, R = 0.30 mm, h = 0.48 mm, W = 1.46 mm, S = 0.73 mm) that yields a thinning rate of 4.43% and a springback angle of 0.151°, a level of precision that is difficult to achieve using conventional orthogonal experimental design. This result was verified by additional finite element simulations. The proposed constitutive model and optimization approach provide a theoretical framework and practical guideline for micro-scale bipolar plate die design. Full article

To enhance critical infrastructure protection against low-cost UAV impacts, this study proposes a novel ring lattice sandwich structure (RLSS) fabricated via an economical interlocking-assembly-brazing method. Its quasi-static compressive behavior is systematically investigated through experiments, numerical simulations, and theoretical analysis. Theoretical models for relative density and initial yield stress are validated against experiments, with errors of 7.1% and 6.6%, respectively. Quasi-static tests show that the one-layer RLSS exhibits a specific energy absorption (SEA) of 8.67 J/g, while the two-layer structure drops to 5.66 J/g due to inter-layer torsional instability. SHPB impact tests at strain rates of 750–1369 s⁻¹ demonstrate a pronounced strain-rate effect, with dynamic increase factors ranging from 1.14 to 1.43. Numerical simulations accurately reproduce the experimental deformation modes and reveal that multi-layer (2–5 layers) RLSSs reduce SEA by 46.9% compared with the one-layer simulated value of 9.43 J/g. Adding a 0.3-mm inner panel in simulations restores the crushing mode and raises the SEA of the two-layer structure to 7.19 J/g, surpassing the non-panel counterpart (6.03 J/g). Hybrid core configurations provide additional advantages: Mode I (ring–pyramid with inner panel) enhances total energy absorption with a limited ring-layer count, while Mode II (alternating layers) achieves minimal plateau stress fluctuation (PSF = 0.09). These findings confirm that the proposed RLSS, especially when optimized with thin inner panels or hybrid designs, offers great potential as protective cladding against impact and blast threats. Full article

Spent automotive catalysts represent an important secondary resource for platinum group metals, offering environmental and economic advantages over primary mining. This review evaluates bioleaching-based recovery strategies of these metals as sustainable alternatives to conventional pyrometallurgical and hydrometallurgical processing. The cyanogenic bioleaching using Chromobacterium violaceum, Pseudomonas fluorescens, and Bacillus megaterium, and acidophilic bioleaching using Acidithiobacillus spp. for washcoat degradation and base-metal removal are discussed through the one-step, two-step, spent-medium, and decoupled systems. The analysis shows progressive improvement of recovery as process separation increases. Sequential pretreatment involving ultrasound-assisted acid leaching, thermal oxidation, and pressure-enhanced processing improved recovery by removing competing base metals and increasing PGM accessibility. Kinetic analyses indicate that diffusion through the porous catalyst support matrix becomes the dominant rate-controlling mechanism at high conversion, which impacts reactor design. Despite sustainability potential, industrial implementation remains constrained by low pulp density, cyanide stability, reactor productivity, and scale-up limitations. Routes to commercialisation require feasibility studies of process designs that integrate viable process flow diagrams combining pretreatment, biological lixiviant generation, intensified bioleaching, and downstream metal purification. Full article

Purple celery (Apium graveolens L.) is a high-value functional vegetable rich in anthocyanins, but achieving a balanced optimization between biomass accumulation and nutritional quality in plant factories remains challenging due to species-specific spectral trade-offs, and current research lacks integrated light recipes that simultaneously optimize photosynthetic efficiency, antioxidant defenses, and functional quality while suppressing nitrate accumulation. This study evaluated five LED treatments over 30 days: white light (CK), monochromatic red (R), and red-to-blue photon flux density ratios of 5:5, 7:3, and 8:2. Red light induced stem elongation but suppressed root development. Conversely, 8R2B delivered the best performance, significantly elevating leaf, petiole, root, and total fresh biomass and increasing total dry weight by 68.8% over CK. It also markedly enhanced chlorophyll a, b, total chlorophyll, and carotenoids, as well as improved PSII quantum yield (YII), photochemical quenching (qP), and electron transport rate (ETR), while reducing non-photochemical heat dissipation (NPQ) by 61.0%, indicating superior light-use efficiency. Furthermore, 8R2B upregulated CAT and POD activities promoted soluble sugars (up 688.4% in leaves), soluble proteins, and ascorbic acid accumulation, yet reduced leaf nitrate by 28.5%. Principal component analysis confirmed 8R2B as the most effective formulation across all growth, photochemical, defense, and quality traits. These findings provide a novel, evidence-based 8:2 red-to-blue LED light recipe for high-yield, high-quality, and commercially viable purple celery production in controlled environment agriculture. Full article

Organic fertilization is a key strategy for improving soil structure and fertility in China’s Vertisols, yet the trade-offs among soil quality enhancement, grain yield performance, and nutrient use efficiency under different organic amendment regimes remain insufficiently elucidated. Based on a unique 43-year field fertilization experiment, this study systematically evaluated the effects of long-term chemical fertilization (NPK) alone, low-dose (NPKLS) and high-dose straw incorporation (NPKHS), combined chemical fertilizer with cattle manure (NPKCM), and pig manure (NPKPM) fertilization on soil physical, chemical properties, crop yields and plant nutrient utilization efficiency. The results showed that NPKCM and NPKPM significantly improved soil physical properties by reducing soil bulk density, improving soil pore structure, and enhancing soil water retention capacity and saturated hydraulic conductivity. Although long-term manure application led to slight soil salt accumulation, the rate of accumulation remained substantially lower than that associated with commercial organic fertilizers and did not approach the crop salinity damage threshold, suggesting low ecological risk. Compared with NPK treatment, manure amendment effectively counteracted soil acidification induced by prolonged chemical fertilization, while also significantly increasing soil total phosphorus and available phosphorus content, and elevated the proportion of active phosphorus (PAC). The improved soil phosphorus activation capacity and comprehensive soil quality further contributed to substantial increases in wheat grain yield under NPKCM and NPKPM treatments. Despite these agronomic benefits, the additional nitrogen and phosphorus inputs from manure resulted in soil nutrient surpluses, which considerably reduced nitrogen and phosphorus partial factor productivity as well as agronomic efficiency. In contrast, straw incorporation treatments (NPKLS, NPKHS) sustained stable crop yield without notable declines in nutrient efficiency, positioning them as a greener and more sustainable approach to balancing grain production with resource use efficiency. These findings highlight the need to integrate nutrient credits from manure into fertilization program. Given the 43-year evidence, fertilization strategy should consider not only the nutrients supplied by manure but also the quantities exported through harvested products, with adjustments based on annual soil fertility analyses. Such nutrient budgeting is essential to maximize fertilizer use efficiency, prevent excessive phosphorus accumulation, and maintain balanced soil fertility over time. Full article

Yb³⁺-containing glasses and glass-ceramics are attractive photonic materials because Yb³⁺ can act simultaneously as a near-infrared absorber, an energy-transfer sensitizer, a luminescent center, and a composition-dependent modifier of glass structure and crystallization. This brief review focuses on crystallization from parent glasses to glass-ceramics and examines glass-network chemistry, local Yb³⁺ coordination, phase separation, viscosity, heating rate, treatment temperature, holding time control nucleation, crystal growth, phase selection, rare-earth partitioning, transparency, and optical performance. Representative oxyfluoride, phosphate, oxyapatite, borosilicate, and aluminosilicate systems are compared using thermal analysis, X-ray diffraction, electron microscopy, vibrational spectroscopy, and optical spectroscopy. The available data show that Yb₂O₃ or YbF₃ does not have a universal effect on crystallization: low concentrations can promote fluoride-rich clustering or lower the apparent crystallization barrier, whereas higher concentrations can increase packing density, stabilize the residual glass, change the competitive phase assemblage, or suppress crystallization. Crystallization-enhanced luminescence is most consistently obtained when Yb³⁺ and the activator partition into low-phonon-energy nanocrystals while crystal size and refractive-index mismatch remain sufficiently small to preserve transparency. This review also identifies major reporting gaps, including limited quantification of crystalline fraction, partition coefficients, luminescence lifetime, quantum efficiency, and long-term thermal stability. Practical design guidelines and unresolved questions are proposed to support the rational development of transparent Yb³⁺-containing glass-ceramics for lasers, sensing, optical amplification, and related photonic applications. Full article

This work presents a numerical investigation of a direct oil cooling system for Axial Flux Permanent Magnet (AFPM) machines. Building upon the authors’ previous study, which established the fundamental fluid dynamic mechanisms governing oil jet impingement on curved coil surfaces, the present research extends the analysis by performing a systematic parametric optimization of nozzle diameter and axial position. A validated CFD model, benchmarked against experimental data from the literature, is employed to quantify the influence of jet momentum, stagnation pressure, and flow attachment on the resulting thermal performance. Nine configurations are simulated at constant coolant mass flow rate, revealing that the nozzle diameter is the dominant parameter: smaller diameters generate higher jet velocities, stronger stagnation regions, and larger jet-induced forces, leading to significantly enhanced heat transfer coefficients and Nusselt numbers. Nozzle height plays a secondary yet relevant role, as higher positions promote a more coherent jet core and improve impingement quality. Among the nine simulated cases, the configuration with D = 3 mm and L = 14 mm achieves the lowest hotspot temperature and the most efficient energetic behavior within the simulated set, with only a modest increase in pumping power. The results confirm that direct oil impingement is highly sensitive to jet momentum and angle of attack and demonstrate that optimized nozzle design can substantially improve the thermal management of high power density AFPM machines. This extended analysis provides quantitative references for nozzle sizing and placement within the simulated operating conditions with enhanced cooling efficiency. Full article

JP-10 is a pivotal high-density hydrocarbon fuel for advanced aerospace propulsion systems. Doping aluminum nanoparticles to prepare nanofluid fuels is a promising route to enhance its energy density and combustion performance, yet the droplet formation mechanism of such multiphase fuels remains poorly understood, hindering single-droplet combustion research and atomization system optimization. This work constructed a piezoelectric drop-on-demand (DOD) monodisperse droplet generation platform integrated with phase Doppler anemometry (PDA) and high-speed imaging. Using Al/JP-10/OA nanofluids with aluminum mass fractions of 0.1 wt. %, 0.5 wt. % and 1.0 wt. %, we systematically explored the effects of liquid flow rate, driving frequency and particle concentration on droplet size, size uniformity and ejection velocity. In this work, Al/JP-10/OA nanofluids with aluminum mass fractions of 0.1 wt. %, 0.5 wt. % and 1.0 wt. % were tested under liquid flow rates of 1.1–1.5 mL/min and driving frequencies of 10–50 kHz, with measured droplet diameter ranging from 241.04 μm to 292.26 μm and ejection velocity ranging from 1.65 m/s to 2.45 m/s. The results demonstrate that average droplet diameter increases linearly with flow rate and decreases monotonically with driving frequency. Compared with the 0.1 wt. % nanofluid, the 1.0 wt. % nanofluid shows a 4.4% larger droplet diameter and 12.1% lower ejection velocity, while the 0.1 wt. % sample retains excellent monodispersity with a size Span below 0.098. The multi-scale regulation mechanisms involving viscous variation, shear-thinning rheology and particle agglomeration are further clarified. This study provides fundamental data and theoretical support for atomization design of nanofluid aviation fuels. Full article

Ecological resilience is a critical indicator of forest ecosystem stability and the capacity to respond to disturbance. Under intensifying climate change and human activities, accurately evaluating forest ecological resilience is important for ecosystem restoration and sustainable management. This study developed a satellite time−series−based framework for assessing ecological resilience from the complementary perspectives of resistance and recovery. Taking the Qianshan region, a typical forest area in the northeastern forest belt, as a case study, MODIS Normalized Difference Vegetation Index (NDVI) time−series data from 2005 to 2024 were analyzed. The Breaks For Additive Season and Trend (BFAST) algorithm was used to detect vegetation breakpoints, after which ecological resistance and recovery were quantified using breakpoint magnitude and post−disturbance NDVI growth rate. The optimal−parameter−based geographical detector (OPGD) was further applied to identify the spatial drivers of resistance and recovery and their interaction effects. Approximately 21% of the pixels in the Qianshan region experienced at least one breakpoint during the study period, and more than 80% of the disturbed pixels contained only one detected breakpoint. More than 70% of the disturbed pixels subsequently exhibited vegetation recovery, and most recovered pixels had normalized recovery values between 0.40 and 1.00. In contrast, ecological resistance was generally low and varied substantially among land−cover types. Forests exhibited higher resistance but lower recovery, whereas grasslands and croplands showed lower resistance but stronger post−disturbance recovery. Among the individual factors, precipitation and slope had relatively high explanatory power for the spatial differentiation of recovery. Factor interactions substantially enhanced explanatory power, with the interaction between precipitation and elevation exerting the strongest influence on resistance and the interaction between precipitation and slope exerting the strongest influence on recovery. Although mining density had relatively limited explanatory power at the regional scale, mining activities caused non−negligible localized impacts, particularly in open−pit mining areas. The proposed framework provides a practical basis for long−term monitoring, ecological restoration, and differentiated forest management in disturbance−prone regions. Full article

This study examined the effects of dietary ellagic acid (EA) on growth performance, survival, immune responses, and oxidative status of common carp (Cyprinus carpio) exposed to high stocking density (HSD). A 2 × 3 factorial design was used, with two stocking densities (25 and 100 kg/m³) and three EA levels (0, 50, and 100 mg/kg diet). HSD significantly reduced growth performance, as indicated by lower weight gain and specific growth rate (SGR), increased feed conversion ratio (FCR), and decreased survival (p < 0.05). It also suppressed immune responses, including white blood cell count (WBC), nitroblue tetrazolium activity (NBT), phagocytic activity (PA), lysozyme activity (LYZ), and bactericidal activity (BA). Furthermore, HSD increased malondialdehyde High stocking density caused (MDA) levels and decreased superoxide dismutase (SOD), catalase (CAT), and glutathione peroxidase (GSH-Px) activities in liver, head kidney, and spleen tissues (p < 0.05). Fish were challenged by intraperitoneal injection of Aeromonas salmonicida subsp. achromogenes. Dietary EA supplementation significantly improved survival under both stocking densities, with the highest survival observed in fish receiving 100 mg/kg EA. Kaplan–Meier survival analysis and log-rank tests confirmed significant differences among treatment groups (p < 0.05). Pairwise comparisons further demonstrated that EA, particularly at 100 mg/kg, enhanced survival under high-density conditions. EA supplementation also improved growth performance, antioxidant status, and immune responses in a dose-dependent manner. Polynomial contrast analysis revealed significant linear trends: increasing EA levels enhanced weight gain, antioxidant enzyme activities, and immune parameters, while reducing MDA levels (p < 0.05). Significant SD × EA interactions indicated that EA alleviated the adverse effects of crowding stress. In silico analyses showed higher binding affinity of EA toward SOD, CAT, and GSH-Px. Overall, dietary EA effectively mitigated density-induced oxidative stress and immunosuppression, supporting its potential as a functional feed additive in intensive aquaculture. Full article

This study examines the evolution of microstructure, the metastability of retained austenite (RA), and the corresponding mechanical behavior exhibited by a nanostructured bainitic bearing steel subjected to prolonged austempering within a transformation stasis regime. The results indicate that following the completion of nanostructured bainitic formation at 300 °C for 3 h, a prolonged austempering time does not alter the microstructure, but reduces the dislocation density in BF while increasing the carbon content in RA. For the 4 h and 6 h specimens, a reduction in the overall RA mechanical stability is observed, accompanied by different transformation rates of stress-induced martensite during tensile deformation. This behavior is largely due to the weakened constraint effect of the BF matrix and the evolution of a carbon concentration gradient within the RA. During the transformation stasis, prolonged austempering elevates the yield strength while maintaining an unchanged ultimate tensile strength, albeit with a marginal reduction in microhardness. Relative to the baseline elongation recorded for the 3 h specimen, both the 4 h and 6 h specimens exhibit enhanced ductility, with the 4 h specimen yielding a peak value of 16.8%, which is 1.66 times that of the 3 h specimen. This improvement stems largely from the greater RA volume fraction that transforms into stress-induced martensite in the 4 h specimen, as well as its continuous and stable transformation rate during tensile deformation. Therefore, it can be concluded that an appropriately prolonged austempering time within nanostructured bainitic transformation stasis is essential for optimizing mechanical performance. This study provides a low-cost, energy-saving isothermal heat treatment technical scheme for mass industrial production of high-performance bearing steel. Full article

Cover crops have been recognized as a sustainable practice to improve soil structure and fertility in intensive agroecosystems, yet quantitative evidence on their effects and underlying mechanisms remains limited in high-altitude cereal cropping systems. This study investigated the effects of diverse cover crops on soil physicochemical properties during fallow in southern Tibetan cereal cropping systems, quantified their effect sizes relative to bare fallow, and explored the associations among key soil properties. Results showed significant variations in 0–20 cm soil physicochemical properties among cover crop species. Specifically, the oat (Avena sativa)–common vetch (Vicia sativa) mixture significantly reduced soil pH and increased water-stable aggregate rate (WSAR), total carbon (TC), and C/N ratio compared with turnip (Brassica rapa var. L.) and common vetch monocultures, whereas bulk density, total nitrogen, and soil organic matter (SOM) did not differ among cover crop treatments. Effect size analysis indicated that cover crops significantly reduced soil pH by 3.39% and increased WSAR by 32.85%. Principal component analysis and the piecewise structural equation model revealed that soil pH, WSAR, TC, and SOM collectively explained 86.18% of the observed variation in soil physicochemical properties, with pH significantly and positively affecting TC but negatively influencing WSAR, which in turn strongly promoted TC and thereby greatly enhanced SOM. These findings demonstrate that cover crops substantially improve selected soil physicochemical properties, providing critical evidence for their integration into bare fallow to enhance soil health in high-altitude cereal cropping systems. Full article

Active flow control actuators are critical for improving aerodynamic performance in applications such as aircraft lift enhancement, drag reduction, and maneuverability improvement. However, the plasma synthesis jet actuator (PSJA) is limited by the constraints of electric energy deposition, making it difficult to further improve the jet velocity and mass flow rate. Meanwhile, the jet velocity driven by combustion needs to be further increased. This study preliminarily investigated the characteristics of a combustion-driven SparkJet actuator through experiments; a combustion-driven SparkJet actuator integrates the advantages of plasma actuators and combustion-driven actuators. The actuator employs a continuous methane–air mixture supply ignited by spark discharge. High-speed shadowgraph imaging is used to characterize the jet flow field evolution. The effects of the cavity volume, normalized outlet diameter (d* = d/h), and equivalence ratio on jet performance are systematically examined. As the normalized outlet diameter increases from 0.666 to 1, the jet penetration distance and jet width increase with an increasing normalized outlet diameter, owing to the reduced boundary layer blockage effect at the orifice. However, when the normalized outlet diameter equals 1, both the jet penetration distance and jet width first increase and then decrease with increasing cavity volume; hence, the outlet diameter and cavity have an optimal size. At an equivalence ratio of mixture ≤1, increasing the methane flow rate enhances the volumetric chemical heat release rate, thereby monotonically improving the jet width and penetration distance. The combustion-driven actuator demonstrates a significantly higher jet velocity compared to a conventional plasma actuator under identical geometric parameters; the combustion reaction can effectively amplify the jet energy and velocity of the actuator. Moreover, the combustion-driven SparkJet actuator also has the same working frequency when the actuator volume is the same, indicating that the combustion process does not significantly extend the cycle time. The maximum jet velocity first increases and then decreases with increasing cavity volume; the reason that the maximum jet velocity first increases is that a larger volume results in a greater mixture mass and more released heat; it then decreases due to incomplete combustion occurring in large chambers. These results show that the design standards for the combustion-driven actuator are fundamentally different from those for the plasma actuator, and their optimal performance is related to not only electrical energy density but also combustion performance. The design parameters of the combustion-driven actuator can be optimized to maximize the jet front velocity. The experimental data in this article provides a reference for optimizing the performance of combustion-driven actuators. Full article