Search Results (5,645)

This study investigates heat transfer enhancement in the cooling channels of gas turbine blade turbulators using modified transverse baffles with isosceles triangular sawtooth perforations. The proposed baffle design aims to improve convective heat transfer by promoting flow mixing and disrupting the thermal boundary layer. Experiments were conducted in a rectangular channel with an aspect ratio of 3.75 under constant heat flux conditions using air (Pr = 0.7) as the working fluid. The effects of Reynolds number (Re = 6000–24,000), sawtooth width ratio (a/W = 0.0, 0.0625, 0.125, 0.25, and 0.5), and sawtooth height ratio (b/e = 0.0, 0.25, 0.5, 0.75, and 1.0) were systematically investigated. The blockage ratio (e/H) and pitch ratio (P/H) were maintained at 0.3 and 1.5, respectively. Heat transfer characteristics were evaluated using the thermochromic liquid crystal (TLC) technique, while thermal–hydraulic performance was assessed in terms of the Nusselt number (Nu), friction factor (f), and thermal performance factor (TPF). The results demonstrate that introducing sawtooth perforations significantly enhances heat transfer compared with a smooth channel, yielding Nusselt number ratios (Nu/Nu_s) between 1.6 and 2.6. The highest heat transfer enhancement was achieved at a/W = 0.0625 and b/e = 0.25, where the relatively small sawtooth openings generated stronger jet impingement, enhanced flow mixing, and more effective disruption of the thermal boundary layer. However, these geometric modifications also increased the pressure loss due to intensified flow blockage and recirculation, resulting in friction factor ratios (f/f_s) ranging from 8.9 to 14.9. The maximum pressure-drop penalty occurred at b/e = 0.25 because the smaller openings produced stronger turbulence and increased flow resistance. Despite the increased friction loss, the optimum configuration (a/W = 0.0625 and b/e = 0.25) achieved the highest thermal performance factor of 1.2 at Re = 6000. Full article

Physical treatment can improve the quality and overall characteristics of insoluble dietary fiber (IDF). This study investigated the effects of microjet homogenization treatment (MT), ultra-high-pressure treatment (HP), and ultrasonic treatment (UT) on the compositional profile, microstructure, basic properties, and bioactivity of IDF from okara. The modification processes increased IDF yield (unmodified IDF: 65.55%; MT-IDF: 70.51%; HP-IDF: 75.29%; UT-IDF: 79.09%). The mechanical action disrupted the compact structure, refined the particles, and increased the specific surface area (SSA). Compared with unmodified IDF (0.18 m²/g), the SSA values of MT-IDF, HP-IDF and UT-IDF increased by 83.33%, 50.00%, and 72.22%, respectively, thereby improving the overall hydration characteristics and adsorption performance of IDF. UT-IDF exhibited excellent water-holding capacity (8.11 g/g), yet its thermal stability ((mass loss: unmodified IDF (36.50%), MT-IDF (23.59%), HP-IDF (26.11%), and UT-IDF (33.74%)) and rheological properties (shear rate range of 35–40 s⁻¹: unmodified IDF (1.77 Pa·s), MT-IDF (15.86 Pa·s), HP-IDF (21.11 Pa·s), UT-IDF (5.36 Pa·s)) were relatively inferior to those of MT-IDF and HP-IDF. Notably, MT-IDF exhibited superior modification effects, including a loose, porous microstructure, enhanced adsorption performance, and favorable prebiotic potential (Lactobacillus acidophilus 36h-OD₆₀₀: 0.594; Bifidobacterium longum 36h-OD₆₀₀: 0.509). Among the three physical modification methods, MT offers significant advantages in enhancing the quality of IDF from okara, improving its processing suitability, and facilitating its high-value utilization. However, this study still has certain limitations: the evaluation of the correlation between fiber digestion rate and probiotic potential was based only on in vitro models and has not been systematically evaluated using real food matrices. Full article

To clarify the poorly understood soil-structure interactions flanking the pile cap, this study systematically investigates the sensitivity of the New Type Concrete Expanded-Plate (NT-CEP) pile system to variations in sub-cap silt profiles, specifically moisture content (12%~16%) and dry density (80%~90% compaction degree). Mechanical results indicate that the pile cap and expanded bearing plates operate via a robust synergistic load-sharing mechanism, with plastic failure zones localized beneath these components. Within conventional physical limits, fluctuations in moisture and density trigger less than a 4% variance in the ultimate compressive capacity, demonstrating the remarkable structural resilience of the internal compensatory load-transfer path. Based on the evaluated boundary conditions, a site-specific operational envelope featuring a minimum compaction degree of 80% and a critical moisture threshold below 14% is recommended as a preliminary reference. Nevertheless, explicit mechanical limitations must be rigorously addressed: these quantitative thresholds are strictly benchmarked against the scaled model testing utilizing a specific silt thickness and pile geometric stiffness ratio. Significant deviations in these parameters are expected under three distinct boundary constraints: (1) altered multi-axial stress paths inherent to complex interbedded geologies; (2) catastrophic matric suction loss and pore pressure accumulation driven by elevated groundwater tables; and (3) severe skin friction degradation common in thixotropic soft clays. Consequently, these indicators constitute a context-specific design envelope rather than a rigid universal standard, providing a mechanics-driven baseline for the gradient optimization of advanced NT-CEP foundations while delineating required calibration paths for future full-scale field instrumentation. Full article

High-pressure processing (HPP) is a nonthermal method that has gained importance for producing minimally processed products. HPP has been adopted to improve the storage stability and retain the quality characteristics of the highly perishable seafood products. The main objective of this study was to investigate the quality and refrigerated storage stability of fresh Atlantic salmon (Salmo salar) achieved using HP treatments. Similar-sized fresh Atlantic salmon pieces were prepared, vacuum-packed into high-density polyethylene (HDPE) pouches, and subjected to HP treatments at 150, 250, and 350 MPa with holding times of 10, 20, and 30 min. The treated products and control (without treatment) were stored at 4 °C for up to 21 days and evaluated every week for microbial growth, texture, color, and protease activity. Applied pressure treatment demonstrated an immediate improvement in textural properties such as firmness and tenderness, while also resulting in some loss in color properties. During storage, the lightness (L* value) increased, and the redness (a* value) decreased. Texture degradation was more severe with control samples, while it was better preserved in HP-treated products. The microbial growth during refrigerated storage was more rapid, and the product spoiled, while the treated samples showed better microbial stability. The 20–30 min treatments at 150 MPa demonstrated good microbial stability and reduced color change, while treatment at 350 MPa provided better microbial and texture stability, resulting in a greater color loss. Overall, it was demonstrated that HP treatment can slow down the quality deterioration rate and hence extend the refrigerated shelf life of salmon. Full article

Oscillating water column wave energy converters require self-rectifying turbines capable of maintaining stable performance under bidirectional airflow. This study numerically investigates the aerodynamic performance and internal flow characteristics of an axial-flow impulse turbine using OpenFOAM under both uniform and reciprocating airflow conditions. Rotor motion was modeled using the Multiple Reference Frame approach, and the numerical model was validated against experimental data for one-way flow at an inlet velocity of 8.71 m s⁻¹ and rotational speeds ranging from 300 to 1300 rpm. The CFD results successfully reproduced the experimental efficiency trend, yielding a peak efficiency of η = 0.4269 at 700 rpm and ϕ ≈ 0.95, which closely aligns with the experimental peak efficiency of η = 0.4425. Validation metrics demonstrated a high degree of accuracy, with an RMSE of 0.0219, a mean absolute error of 0.0197, a maximum absolute error of 0.0399, a squared Pearson correlation coefficient of 0.826, and a peak-efficiency difference of 3.5%. Flow-field analysis revealed that low rotational speeds resulted in high outlet velocities and incomplete energy extraction, whereas excessive rotational speeds caused flow misalignment, downstream vortex formation, and additional aerodynamic losses. Under reciprocating flow conditions, characterized by a sinusoidal velocity amplitude of 8.71 m s⁻¹ and periods of 0.5–2.0 s at 700 rpm, both input and torque coefficients exhibited hysteresis, with the strongest loops observed at the shortest periods. Examinations of streamline, pressure, and velocity distributions indicated that residual flow during flow reversal alters the effective inlet direction in the subsequent half-cycle, resulting in flow memory and a phase-dependent turbine response. As the present computational domain excludes the OWC chamber, these findings characterize turbine-level aerodynamic performance rather than the complete system power coefficient. Full article

The rapid growth of the construction sector has substantially increased the demand for natural resources, resulting in growing pressures on ecosystem services and resource sustainability. This study presents a dynamic emergy-based assessment of construction material consumption in Kerala, India, for the period 2009–2023, focusing on four major construction materials: steel, cement, river sand, and brick clay. Emergy accounting was employed to quantify annual material consumption, emergy per unit cost, ecosystem service deficits, economic losses associated with ecological degradation, and the contribution of recycling and material substitution. Temporal trends were evaluated using the non-parametric Mann–Kendall test and Sen’s slope estimator, while logistic (sigmoid) functions were fitted to characterize resource-use transitions and identify growth, transition, saturation, and overshoot phases. Steel and cement exhibited significant positive consumption trends (τ = 0.752 and 0.790, respectively), whereas river sand and brick clay displayed strong declining trends (τ = −0.891 and −0.638, respectively). Logistic modelling revealed that steel and cement remain in growth phases supported by recycling and material substitution, whereas river sand and brick clay exhibit characteristics of transition and ecological overshoot. Carrying-capacity assessments indicate that river sand and brick clay extraction exceeded sustainable ecosystem-support capacities, resulting in persistent ecosystem service deficits. The study demonstrates that recyclability plays a critical role in reducing transformity, delaying resource scarcity, and moderating ecological overshoot. Full article

Accurate characterization and prediction of drilling fluid rheological properties under high-temperature and high-pressure (HTHP) conditions are core prerequisites for safe and efficient deep well drilling operations. To systematically clarify the thermobaric rheological laws and intrinsic coupling mechanism of high-density drilling fluids, this study takes 2.0 g/cm³ oil-based drilling fluid (OBDF) and water-based drilling fluid (WBDF) as research objects, and carries out full-scale rheological tests via a Fann iX77 HTHP rheometer under temperatures ranging from room temperature to 200 °C and pressures from atmospheric pressure to 200 MPa. The results show that the shear stress of both fluids is positively correlated with pressure and shear rate and negatively correlated with temperature. 150 °C is identified as the critical thermal thickening temperature for WBDF: above this temperature, polymer degradation and solid precipitation cause abnormal viscosity growth, and high shear rates can effectively alleviate this thickening effect by promoting the dispersion of precipitates. There are significant differences in rheological sensitivity between the two systems: WBDF rheology is dominated by temperature dependence, while OBDF exhibits high sensitivity to both temperature and pressure due to the compressibility of the oil continuous phase; temperature and pressure exert a mutual inhibitory effect on fluid rheology. The proposed Arrhenius–Powell one-step global coupled prediction model achieves favorable prediction accuracy for both OBDF and non-thickened WBDF, with the coefficient of determination (R²) no less than 0.96. The model can provide reliable basic parameters for HTHP wellbore hydraulic calculation and pressure loss prediction, fully meeting the accuracy requirements of field engineering applications. Full article

Pneumatic flexible elements are widely used in mechanical systems for vibration damping, noise reduction, and improvement of dynamic properties. During cyclic loading, periodic compression and expansion of the enclosed air cause pressure fluctuations, airflow between interconnected chambers, pressure losses, and the conversion of mechanical energy into heat. This thermal loading may influence the stiffness, damping properties, durability, and operational reliability of elastomeric pneumatic elements. This study investigates the influence of the number of connecting openings on the thermal behaviour of two pneumatically coupled flexible elements under dynamic loading. Experimental measurements were carried out using a specially designed test rig at different charging pressures and with different numbers of active connecting openings. Three temperatures were monitored: the air temperature inside the pneumatic element T_air, the inner surface temperature T_in, and the outer surface temperature T_out. The results showed that increasing the number of connecting openings reduced all monitored temperatures and led to a more uniform temperature distribution within the pneumatic system. The thermal response also depended on the charging pressure, with a gradual transition from air-dominated heating at lower pressures to inner-surface-dominated heating at higher pressures. A simplified theoretical model was used to identify the main physical quantities influencing temperature development, including pressure, volume variation, airflow resistance, heat transfer, and energy dissipation. In addition, the interpretation of the observed temperature reduction was supported by a simplified analytical assessment based on the orifice–flow relationship, which showed that increasing the total flow area reduces the pressure difference required for cyclic airflow and consequently decreases pressure-loss-related heat generation. The findings demonstrate that the number of connecting openings is an important design parameter for controlling the thermal response of pneumatic flexible elements. Full article

Magnetic fluid seals use magnetic field gradients generated by permanent magnets, pole pieces, and rotating shafts to confine ferrofluid in the sealing gap and form multiple liquid sealing rings. Compared with mechanical and labyrinth seals, they exhibit low wear, high cleanliness, low friction loss, and near-zero leakage, making them suitable for high-vacuum equipment, semiconductor devices, clean robotic joints, and rotary feedthrough systems. This review summarizes the development, theoretical basis, experimental methods, structural design, performance characteristics, failure mechanisms, numerical modeling approaches, and engineering applications of magnetic fluid sealing technology. Quantitative comparisons show that ferrofluid seals generally provide a single-stage pressure-bearing capacity of approximately 10–20 kPa with near-zero leakage and good self-replenishment, whereas magnetic powder seals can reach approximately 50–100 kPa per stage but suffer from higher leakage and poor self-recovery. Under high-speed conditions, centrifugal depletion, viscous heating, carrier-liquid volatilization, and interfacial instability become the dominant causes of performance degradation. The reviewed literature indicates that pole-tooth geometry, magnetic-circuit topology, saturation magnetization, thermal transport, and medium compatibility jointly determine sealing reliability. Future research should focus on high-saturation and low-vapor-pressure ferrofluids, optimized pole-tooth and magnetic-circuit structures, magnetic–flow–thermal coupling, integrated cooling, online monitoring, life prediction, and standardized reliability evaluation. Full article

In slurry shield tunneling, inefficient control of slurry permeability in sandy formations can cause excessive slurry loss, increased material consumption, reduced bentonite reuse, and compromised tunnel-face stability. To address these challenges and enhance material efficiency, this study investigates slurry infiltration and bentonite particle deposition mechanisms in saturated sandy soils. Based on deposited-particle mass conservation and slurry volume conservation coupled with excess pore-water pressure, a mathematical model is established to capture the evolution of slurry rheological properties and soil pore characteristics during infiltration. Through multilayer infiltration column experiments, a multiple regression formula for the filtration coefficient is established, considering the spatiotemporal variability of slurry and soil properties. Furthermore, a dynamic penetration criterion for slurry particles is proposed and verified through single-soil infiltration tests. Results demonstrate that most bentonite particles deposit on the soil surface, with only a minimal fraction migrating into deeper pores until reaching shear stress equilibrium. The maximum infiltration distance is positively correlated with soil particle size but negatively correlated with slurry mass concentration. Increasing the slurry mass concentration or shear strength promotes the development of a well-structured filter cake and infiltration zone. These findings provide a theoretical framework for precisely regulating slurry permeability, thereby minimizing material waste and supporting sustainable shield tunneling operations. Full article

Aiming at the industrial problems of traditional sulfonated drilling fluids in high-temperature drilling of deep oil and gas reservoirs at 180°C, including high-temperature degradation, poor environmental protection, and severe reservoir damage, this paper adopts a function-oriented research idea to construct a set of non-sulfonated water-based drilling fluid systems with excellent comprehensive performance and temperature resistance up to 180 °C. Strict screening criteria for single agents were established, and six core non-sulfonated treatment agents were selected from 18 candidate agents in four categories: viscosifiers, fluid loss reducers, inhibitors, and high-temperature stabilizers. The compounding synergistic effects of cross-category treatment agents were studied, and four core action mechanisms were revealed. The optimal formula was obtained through optimization. Tests show that after hot rolling at 180 °C for 16 h, the system has an apparent viscosity retention rate of ≥81%, a yield point retention rate of ≥76%, and a high-temperature and high-pressure filtration loss of ≤12.8 mL. It can resist 15% salt, 1.0% calcium, and 15% drill cuttings, and maintains stable performance under composite pollution. At 180 °C, the shale linear expansion rate is only 8.6%, and the cuttings rolling recovery rate reaches 92.4%. The core permeability recovery value is ≥90.2%, the biotoxicity EC₅₀ value is 42,600 mg/L, and the 28-day biodegradation rate is 68.3%. This system can replace traditional sulfonated drilling fluids and provide a green and feasible technical solution for safe and efficient drilling in deep high-temperature formations. Full article

Tesla valves are passive hydraulic devices capable of producing directional flow resistance without moving components, making them attractive for applications in microfluidics, thermal systems, and high-reliability hydraulic circuits. Despite extensive experimental and numerical studies, an analytical formulation capable of describing the hydrodynamic behavior of Tesla valves under varying operating and geometric conditions remains limited. In this work, a comprehensive analytical model is developed to describe the pressure losses, flow redistribution, and diodicity behavior of Tesla valves through a physics-based formulation derived from conservation laws, dimensional analysis, and inertial scaling principles. The proposed model incorporates the influence of Reynolds number, flow partition, geometric ratios, branch inclination angle, and number of diode stages within a unified nonlinear framework. A closed structural equation is obtained that relates hydraulic losses and directional asymmetry to the internal geometry of the valve. The formulation reveals the existence of geometric and energetic constraints governing rectification efficiency, including bounds associated with stage number, channel scaling, and angular momentum exchange. The results show that Tesla valve performance emerges from a delicate balance between inertial amplification and dissipative mechanisms, providing an analytical framework for the design and optimization of Tesla-type hydraulic systems across multiple scales. Full article

This study develops a systematic framework for assessing the temporal dynamics of tropical cyclone (TC) risk in the Guangdong–Hong Kong–Macao Greater Bay Area (GBA) from 2013 to 2023. A unified composite index was constructed by integrating hazard, vulnerability, and mitigation capacity, allowing for the quantification of the interannual evolution of TC risk. The analysis showed that maximum storm surge and extreme precipitation drove hazard variability, with distinct peaks during the super typhoons of 2017 and 2018. In the vulnerability dimension, GDP and population density together accounted for over 50% of the total weight, and the vulnerability index shows an upward trend, though its growth slowed in 2020. Mitigation capacity improved steadily, accelerating after 2020 and partly offsetting the risk pressure from growing vulnerability. The risk index broadly mirrored the hazard index, peaking in 2018. Notably, in the two TC-free years (2014 and 2019), the risk index was higher in 2019 than in 2014, reflecting an increased vulnerability-to-mitigation ratio over the intervening period. A coherence check against three disaster loss indicators (2018–2023) yielded a correlation of r = 0.8, indicating broad consistency in the interannual patterns of the risk index and observed losses. This study provides a temporally explicit baseline for understanding recent TC risk dynamics and offers methodological support for resilience planning in coastal megaregions facing climate-related hazards. Full article

The corrosion behavior of ferritic–martensitic 17Cr stainless steel in CO₂-saturated brine was investigated using static autoclave immersion tests in 4.12 wt% NaCl solution at 230 °C under CO₂ partial pressures of 6.36, 18.28, and 24.57 MPa. The calculated in situ pH values obtained using the OLI System were 3.79, 3.55, and 3.49, respectively. Corrosion morphology, microstructural evolution, and corrosion products were characterized by SEM, EDS, EBSD, and Raman spectroscopy. The average mass-loss corrosion rate increased from 0.138 ± 0.0221 mm/year at 6.36 MPa pCO₂ to 0.326 ± 0.0142 mm/year at 24.57 MPa pCO₂. Although the specimens did not show severe macroscopic pitting, localized attack preferentially occurred in fine-grained martensitic banded regions. EBSD analysis revealed that these regions exhibited higher local misorientation and defect density, which may reduce the stability of Cr-rich surface films. Raman spectra identified Cr(OH)₃ in the corrosion products, and the Cr(OH)₃ signal became more evident with increasing CO₂ partial pressure. The results indicate that, under fixed temperature and salinity, the corrosion behavior of 17Cr stainless steel is governed by CO₂ partial pressure and microstructural heterogeneity. Full article

Introduction: This study presents the first systematic review and meta-analysis of randomized controlled trials (RCTs) evaluating the efficacy and safety of oral clonidine in spinal surgery to guide clinical practice and inform future research. Methods: RCTs were identified through four databases (PubMed, Scopus, Web of Science, Cochrane Central) up to August 2025. Risk of bias was assessed, and intraoperative and postoperative outcomes were extracted. Data were pooled using mean differences (MD) or risk ratios (RR) with 95% confidence intervals. Results: Eight RCTs with 474 patients (237 clonidine, 237 control) were included. Four studies had a low risk of bias, while two had some concerns, and two had a high risk. Clonidine had no impact on surgery duration but significantly reduced blood loss (MD = −177.76 mL), mean arterial pressure (MD = −11.33 mmHg), and heart rate (MD = −21.18 bpm). Regarding postoperative outcomes, clonidine was associated with improved analgesia, including lower pain scores up to 12 h and a longer time to first analgesic request, with no significant difference in pain scores at 24 h or total postoperative opioid consumption. No significant increase in postoperative complications, including bradycardia, dizziness, headache, or visual disturbances, was observed. Surgeon satisfaction was higher in the clonidine group. Despite high heterogeneity in some outcomes, sensitivity analyses confirmed the robustness of most findings. Conclusions: Prophylactic oral clonidine in spinal surgery significantly reduces blood loss, heart rate, and mean arterial pressure, with added analgesic benefits and good tolerability. Further high-quality RCTs are needed to confirm these results in broader patient populations. Full article