Search Results (10,294)

In this paper, we provide a new Riemann curvature formula in homogeneous Finsler geometry. Meanwhile, we prove that a homogeneous Finsler metric is Landsberg if and only if its connection operator induces Killing vector fields for a Hessian metric. As an application, we prove that any homogeneous Landsberg sphere with dimension bigger than 1 and constant flag curvature must be Riemannian. Full article

This study presented a comprehensive optimization of a piezoelectric injector specifically designed for pure methanol compression-ignition engines. As a fuel for compression-ignition engines, methanol exhibits broad application prospects. To overcome the challenges posed by methanol’s low cetane number and energy density, a co-optimization strategy was implemented, targeting the actuator, drive waveform, and internal flow geometry. The redesigned injector exhibited superior dynamic performance, featuring significantly faster response times and enhanced operational stability, which were critical for precise fuel delivery control. Furthermore, the optimized internal flow path increased the effective flow rate, ensuring sufficient fuel supply across all engine operating conditions. The upgraded injector was rigorously tested on an engine bench, demonstrating substantial performance gains. Brake thermal efficiency improved from 38.9% to 40.4% at low load and from 43.68% to 46.07% at high load. Emissions of CO, formaldehyde, acetaldehyde, and unburned methanol were consistently reduced, with the maximum reduction reaching 23.1%, confirming markedly enhanced combustion completeness. This improvement was directly attributed to the injector’s refined spray characteristics and precise control, although it led to a slight increase in NOx emissions due to higher peak combustion temperatures. Full article

The removal of spray paint vandalism from contemporary mural paintings and Street and Urban Art represents one of the most challenging operations in conservation practice, particularly when the unwanted layers are chemically similar to the original pictorial materials. Conventional cleaning methodologies often show limitations on rough and heterogeneous surfaces, where the risk of irreversible alteration of the original paint film increases. This study proposes tunable cleaning systems based on polyvinyl alcohol (PVA)–borax double-network hydrogels modified with biopolymers and loaded with nanostructured fluids for controlled and sustainable removal of spray-paint vandalism. Laboratory investigations, including solubility tests, qualitative assessment of mechanical properties and cleaning trials on representative mock-ups, were carried out to evaluate the stability, adaptability and cleaning performance of the most promising systems, including laboratory-prepared PVA-based formulations and commercial Peggy Nanorestore gels©. The optimized cleaning systems were successfully applied in situ on the mural Nido di Vespe in Rome, achieving a controlled reduction of the vandalism layer while preserving the integrity of the original surface and confirming the applicability of these systems under real conservation conditions. Full article

Octopus maya is a fast-growing species from the Yucatán Peninsula with high economic relevance, accounting for a major share of regional fishery production. However, a significant fraction of the organism, rich in type I collagen, is discarded as by-products, representing a promising and underutilized source for sustainable biomaterials. This study evaluated, through a 3² factorial design, the effect of two factors on the rheological and dynamic mechanical properties of film-forming solutions (FFS). The first factor was the type of food-grade polysaccharide: chitosan (Ch), hydroxypropyl methylcellulose (HPMC), or starch (S). The second factor was the proportion of each polysaccharide blended with ultrasound-extracted Octopus maya insoluble collagen (CIPM), using polysaccharide ratios of 30:70, 50:50, and 70:30 (w/w). This approach aims to valorize octopus by-products through the recovery and functional utilization of collagen. Rheological properties were determined by rotational and oscillatory rheometry at 25 °C, with flow curves fitted to the Carreau-Yasuda model. All formulations exhibited pseudoplastic behavior (n < 1), with viscosity decreasing as shear rate increased. Pure CIPM showed high viscosity (190.36 Pa·s at 1 s⁻¹), which decreased (0.3–10.44 Pa·s) in HPMC and chitosan systems, suggesting their potential suitability for applications requiring fluidity, such as spray coatings or film-forming solutions, based on their rheological properties. In contrast, starch-based systems exhibited higher viscosities (33.54–197.53 Pa·s) and a more structured viscoelastic profile (G′ > G″), suggesting potential suitability for thick coatings or gels requiring structural stability, although these applications were not experimentally validated. These results demonstrate that CIPM-polysaccharide systems enable tunable rheological properties, supporting the use of Octopus maya collagen as a sustainable functional material for advanced food and biomaterial design. Full article

Hydraulic nozzles are widely utilized for dust removal, cooling, and waste heat recovery in mining production. Nevertheless, the influence of co-flow disturbance on the atomization characteristics within the downstream region of droplet fields remains inadequately understood. In this study, three typical hydraulic nozzles were selected, and the atomization characteristics of the downstream region under different co-flow disturbance intensities were experimentally investigated. The results reveal that increasing co-flow disturbance velocity does not intensify the reduction in sauter mean diameter (SMD), but markedly reduces the dispersed phase fraction (DPF). Under four co-flow disturbance velocities (1.5, 3.0, 4.5, and 6.0 m/s), the relative reduction rates of mean SMD are 6.77%, 3.27%, 4.42% and 2.60%, while those of mean DPF are 13.86%, 35.85%, 52.88%, and 61.86% (e.g., hollow-cone nozzle), respectively. The variation in SMD is achieved through the redistribution of cumulative volume among CV₁, CV₂, CV₃, and CV₄. As the velocity increases from 0 to 3 m/s, the mean SMD of the three hydraulic nozzles exhibits a decreasing trend, which can be directly attributed to the continuous increase in the total cumulative volume of CV₁ and CV₂, and the continuous decrease in those of CV₃ and CV₄. For the hollow-cone and solid square-cone nozzles, the SMD first decreases and then increases, with the turning point occurring at 3.0 m/s, consistent with the variation trend of cumulative volume fractions. In contrast, for the solid-cone nozzle, the SMD continues to decrease at velocities exceeding 3.0 m/s. This work provides both a fundamental understanding of atomization characteristics in the downstream region of hydraulic nozzles under co-flow disturbance and practical guidance for velocity control in mine spray systems. Full article

This paper proposes a trajectory planning method for a four-degree-of-freedom (4-DOF) spraying robotic arm based on a digital twin platform and an improved soft actor–critic (SAC) algorithm. The method addresses the complex environment of underground shotcrete spraying operations, the high cost and risk of physical robotic arm training, and the difficulty of incorporating spraying process constraints into traditional path planning methods. To enable unified modeling of the virtual prototype, operating scenario, reference trajectory, joint constraints, and spraying process proxy indicators, a digital twin platform for the spraying robotic arm was built using Unity Editor 2022.3.14f1c1.A composite reward function was designed to incorporate trajectory tracking, spray distance, nozzle normal, spraying speed, safety, and motion smoothness, and a prioritized experience replay (PER) mechanism based on double-critic temporal difference (TD) error was introduced to the conventional SAC algorithm. Simulation results show that, under the current digital twin environment and two-dimensional S-shaped reference trajectory, the Improved SAC algorithm reduces trajectory tracking root mean square error (RMSE) from 24.0 ± 2.0 mm to 8.0 ± 0.7 mm, corresponding to a 66.7% reduction compared with standard SAC. In addition, the spray distance error, nozzle normal error, spraying speed error, and motion smoothness index are reduced by 43.5%, 49.1%, 47.3%, and 48.7%, respectively. Full article

Severe air leakage in the goaf of gob-side entry retaining panels can intensify oxygen supply to residual coal and consequently increase the probability of coal spontaneous combustion. Taking the 3451S working face of a coal mine in Hebei Province as the engineering case, this study integrated in situ beam-tube monitoring with Fluent-based numerical simulation to characterize the evolution of the spontaneous-combustion three zones and to optimize prevention and control measures. The results demonstrate that the oxidation zone is characterized by an inclined, continuous band-like distribution penetrating the goaf. The simulated oxygen distribution is consistent with the field measurements, demonstrating the reliability of the established numerical model. The ventilation pattern markedly affects the air-leakage flow field and oxygen concentration distribution, and the Y-type ventilation mode exhibits a higher spontaneous-combustion risk. When the air-volume ratio between the 3451S haulage roadway and the gob-side retained entry is adjusted to 3:1, the oxidation-zone area decreases by approximately 11%. A combined control strategy involving cement-blanket and polymer-spraying leakage sealing, together with precise nitrogen injection, is then proposed to improve the goaf oxygen environment. At a nitrogen-injection rate of 600 m³/h, the oxidation-zone area is reduced by 11,160 m² and the CO concentration remains stable at approximately 4.9 ppm, providing field evidence for improved fire-prevention performance. These results support the design of targeted spontaneous-combustion control strategies for gob-side entry retaining goafs. Full article

A major Chinese woody oil plant with unsaturated-fatty-acid-rich seeds for biodiesel and edible oil, Xanthoceras sorbifolium tolerates drought but not waterlogging; salicylic acid (SA), a key stress response signal, is inexpensive, safe, and effective for enhancing stress tolerance. Two-year-old saplings of Xanthoceras sorbifolium were used as materials. They were sprayed with 0.5 mmol·L⁻¹ SA for 3 days (based on prior studies), and then waterlogged for 10 days; physiological and transcriptomic data were collected. SA significantly increased height, diameter, and root dry weight by 392.6%, 450.0%, and 242.4% compared to water control; enhanced osmotic regulatory substances, antioxidant enzyme activities, secondary metabolites, and root activity; and reduced malondialdehyde content and relative electrical conductivity by 23.40% and 148.7%. SA-enhanced antioxidant defense correlated with synergistic transcriptional regulation. Transcriptome analysis showed that SA up-regulated key enzyme genes involved in flavonoid synthesis, such as PAL and 4CL, and regulated hormone signal transduction-related genes such as SAUR and DELLA. Key transcription factor genes were also screened, mainly including members of the MYB, bHLH, and ERF families. SA alleviated waterlogging damage. Meanwhile, this study provides valuable insights into the molecular basis of the response to waterlogging stress regulated by salicylic acid, and offers important theoretical and practical significance for the promotion and cultivation of Xanthoceras sorbifolium in rainy southern regions of China. Full article

Thermal/environmental barrier coatings (T/EBCs) have become a notable research field for the development of high-performance thermal protection coatings. The mechanical properties are essential for T/EBCs, which determine the functionality, reliability and durability of coatings. The Yb₄Hf₃O₁₂ TEBCs were prepared by atmospheric plasma spraying using nanostructured spherical feedstocks and the nanomechanical properties of the Yb₄Hf₃O₁₂ coatings were characterized by nano-indentation in this work. Results indicate the elastic indentation work (W_e) is 16.06 ± 1.45 nJ and the plastic indentation work is 28.62 ± 6.87 nJ for nanostructured Yb₄Hf₃O₁₂ coatings. The ratio of plastic work to total deformation work during indentation as the energy dissipation parameter (η) is 0.63 ± 0.05 for nanostructured Yb₄Hf₃O₁₂ coatings and it can be preliminarily inferred that the Yb₄Hf₃O₁₂ coating may possess favorable erosion resistance, although direct erosion testing is needed for confirmation. Full article

This study investigates the influence of barrel filling ratio on the microstructure, phase composition, and tribological performance of detonation-sprayed Cr₃C₂–NiCr coatings. Coatings were deposited at barrel filling ratios of 43% and 53% under identical spraying conditions. Microstructural characterization revealed the formation of dense lamellar coatings with low porosity and uniform distribution of Cr₃C₂ carbide particles within the NiCr metallic matrix. Compared with the coating deposited at a barrel filling ratio of 43%, the coating deposited at 53% exhibited a denser microstructure. X-ray diffraction analysis confirmed that Cr₃C₂ and NiCr remained the dominant phases after spraying, while a minor amount of Cr₇C₃ formed due to partial decarburization of chromium carbide during thermal exposure. Tribological performance was evaluated under dry sliding conditions using a ball-on-disc configuration at normal loads of 10 and 15 N and sliding speeds of 5 and 10 cm/s. Wear volume was determined from the geometry of the wear track after testing, and wear rate was calculated accordingly. The coating produced at a barrel filling ratio of 53% demonstrated improved wear resistance under elevated loads despite exhibiting a higher coefficient of friction. The minimum wear rate reached 1.23 × 10⁻⁴ mm³/(m·N), which was associated with reduced porosity and enhanced structural integrity of the coating. The obtained results demonstrate that optimization of detonation spraying parameters significantly affects coating structure and tribological behavior. The developed Cr₃C₂–NiCr coatings are promising protective materials for components operating under severe friction and wear conditions, including industrial and high-temperature engineering applications. Full article

This study aimed to assess the remineralization efficacy of NaF gel enriched with hydroxyapatite nanoparticles (HANPs) and bioactive glass nanoparticles (BAGNPs), with and without adjunctive Er, Cr: YSGG laser irradiation (ECL; 0.5 W, 5 Hz, 20 mJ/pulse, 60 µs pulse duration, water–air spray), on artificially demineralized enamel by evaluating enamel microhardness (MH), resin tag length (RTL), and shear bond strength (SBS) of pit and fissure sealants (PFSs). A total of 168 extracted human third molars free from cracks, fractures, erosion, enamel hypoplasia, surface irregularities, and any history of prior chemical or fluoride treatment were included in the study. All samples underwent continuous immersion in a demineralizing solution until specific DIAGNOdent values of 10-25 were achieved. Samples were randomly allocated into six groups (n = 28): Group 1 (untreated control), Group 2 (NaF gel), Group 3 (NaF + HANPs), Group 4 (NaF + BAGNPs), Group 5 (NaF + HANPs-ECL), and Group 6 (NaF + BAGNPs-ECL). Enamel MH was assessed using a Vickers MH tester (n = 8). RTL was evaluated using scanning electron microscopy (SEM) (n = 8). SBS was measured using a universal testing machine (n = 12), followed by failure mode analysis. Data were analyzed using ANOVA and Tukey’s post hoc test (p < 0.05). Group 5 (NaF + HANPs-ECL) exhibited the highest values for MH (366.20 ± 26.11 HV), RTL (70.34 ± 2.57 µm), and SBS (13.67 ± 0.35 MPa), whereas the untreated control group exhibited the lowest values for all the outcomes. Groups 1 and 2 demonstrated comparable RTL and SBS values (p > 0.05). The remaining groups exhibited significantly different MH, RTL, and SBS values (p < 0.05). The ECL-assisted nanoparticle-integrated NaF gel significantly enhanced enamel MH, RTL, and shear SBS of PFS compared to NaF gel alone. HANPs demonstrated superior remineralization outcomes compared to BAGNPs across all tested parameters. The present findings support the adjunctive use of laser activation with nanoparticle-modified NaF gel as a promising strategy for optimizing sealant performance on demineralized enamel. Full article

The increasing demand for materials with enhanced properties and high-performance devices has driven substantial research into nanomanufacturing, particularly using carbon nanotubes (CNTs), because of their exceptional properties and high sensitivity to chemical doping. In this way, this work summarizes nanomanufacturing methods for CNT-based devices developed in Brazil, covering the complete cycle from nanocomposite production to functional device assembly across cellulosic, polymeric, and metallic matrix systems. For cellulosic matrices, vacuum filtration enables the production of buckypaper, which is subsequently assembled into chemiresistive, thermoresistive, and thermoelectric devices. For polymeric matrices, 3D printing combined with surface functionalization techniques (spray coating, inverted immersion, and direct immersion) produces piezoresistive robotic sensors, metal-free thermal sensors, and biomedical scaffolds for tissue engineering. For metallic matrices, electrodeposition can produce Cu-CNT-coated aluminum comparable to traditional copper power transmission cables, while arc welding produces stainless steel composites with properties comparable to commercial high-grade steels. These devices have commercial and industrial applications, with low-cost and scalable production methods in comparison with conventional materials. Characterization results demonstrate that CNT integration into diverse matrices successfully bridges nanoscale properties to macroscopic functional devices. Current challenges include uniform CNT dispersion and structural defect control, laboratory to industry scale transition, and long-term device stability under environmental conditions. Future perspectives encompass lab-on-chip systems, wearable devices, 3D-printed smart structures, Internet of Things integration, and machine learning-enhanced analytics. Full article

Accurate canopy thickness measurement is vital for advancing smart orchard sprayers and reducing pesticide use. We present three FMCW radar-based algorithms to estimate canopy thickness and assess their accuracy through experiments. Laboratory tests on simulated canopies showed a strong correlation between estimated and actual thickness. However, stability and relative error were significantly affected by leaf area density (LAD) and detection distance. When distance was 40.0–110.0 cm, LAD 1.5–4.2 m²/m³, and actual thickness 30.0–120.0 cm, the coefficient of variation and relative error remained within ±14%. Preliminary outdoor trials on three isolated tree canopies served strictly as an early proof-of-concept, not a full orchard evaluation. The Db algorithm performed poorly, with relative error up to 74.9%, whereas the Da and Dc methods proved robust, with maximum relative errors of 11.93% and −15.19%, respectively. These findings highlight that, with further refinement, Da and Dc algorithms are highly promising for precision variable-rate spraying systems in orchards. Full article

Andrographolide-loaded microparticles with an aqueous-based carrier system were developed with the aim of pulmonary drug delivery. Five formulations of andrographolide (0.6–5.8% w/w) loaded on mixed-polymer carriers containing chitosan (CHS), hydroxyethyl cellulose (HEC), Poloxamer 188, and PEG 20,000, with various ratios were produced under various spray-drying parameters: solution viscosity (5–20 cP), atomization air pressure (0.8–1.5 bar) and solution feed rate (3–6 mL/min). The physiochemical properties of the microparticles were strongly affected by carrier composition and atomization air pressure. The optimal formulation: andrographolide 0.6% w/w, CHS 62.2% w/w, HEC 15.5% w/w and Poloxamer 188 21.7% w/w, spray dried using solution viscosity 15 cP, atomization air pressure 1.1 bar and feed rate 3 mL/min, was selected according to its particle sizes (3–5 µm) with rough morphology, encapsulation efficiency (54.47%) and release behaviors (22.31%/h and 89.23% within 4 h). Good physical, chemical, and thermal stabilities under room storage condition (28 ± 2 °C, 50% relative humidity) were also proven. Importantly, it demonstrated potent antiviral activity against Influenza A/H1N1, achieving a 3.3-log₁₀ reduction in viral titer with 99.95% inhibition. Overall, this aqueous-based carrier approach and spray-drying technique offer a stable and effective inhalable formulation for localized treatment of influenza infections. Full article

Facing the stringent demands of ultra-high pressure fuel injection systems on atomization quality and mixing efficiency, non-circular nozzle geometries have shown significant potential. Biodiesel, as a renewable alternative fuel, suffers from poor atomization due to its high viscosity, low volatility, and large surface tension, posing greater challenges for injector design. Among non-circular designs, the equilateral triangular orifice offers distinct advantages in promoting atomization of high-viscosity fuels and inducing jet axis-switching. This study demonstrates that such triangular nozzles under ultra-high pressure conditions exhibit intense turbulent vorticity at the outlet and distinctive cavitation development, which significantly affect the primary breakup of biodiesel. During spray development, a pronounced axis-switching behavior is observed, characterized by alternating spray cone angles between the major and minor axes. This phenomenon intensifies with higher injection pressure but is mitigated by increased ambient backpressure. The comparative analysis quantitatively establishes these macro–micro coupling characteristics over ultra-high injection pressures of 160–200 MPa, using fixed orifice lengths of 1.5 mm across exit cross-sectional areas ranging from 24,942 to 29,272 μm². The axis-switching process is accompanied by vigorous air entrainment, which significantly enlarges the spray projected area, accelerates liquid breakup, and shortens penetration distance, collectively enhancing the mixing rate and uniformity of biodiesel with air. This work systematically investigates the atomization characteristics and axis-switching behavior of equilateral triangular orifices with varying side lengths when injecting biodiesel under ultra-high pressure conditions, providing an effective technical pathway for the active control of spray morphology and atomization enhancement of biodiesel. Full article