Search Results (892)

This study focuses on a novel lightweight technology for manufacturing variable-axial fiber-reinforced polymer components. In the presented approach, channels following the load flow are implemented in an additively manufactured basic structure and impregnated continuous fiber bundles are pulled through these component-integrated cavities. Improved channel cross-section geometries to enhance the mechanical performance are proposed and evaluated. The hypothesis posits that increasing the surface area of the internal channels significantly reduces shear stresses between the polymer basic structure and the integrated continuous fiber composite. A series of experiments, including analytical, numerical, and microscopic analyses, were conducted to evaluate the mechanical properties of the composites formed, focusing on Young’s modulus and tensile strength. In addition, an important insight into the failure mechanism of the novel fiber composite is provided. The results demonstrate a clear correlation between the channel geometry and mechanical performance, indicating that optimized designs can effectively reduce shear stress, thus improving load-bearing capacities. The findings reveal that while fiber volume content influences the impregnation quality, an optimal balance must be achieved to enhance mechanical properties. This research contributes to the advancement of production technologies for lightweight components through additive manufacturing and the development of new types of composite materials applicable in various engineering fields. Full article

Magnetohydrodynamic (MHD) flow and heat transfer in porous media are central to many engineering applications, including heat exchangers, MHD generators, and polymer processing. This study examines the boundary layer flow and thermal behavior of an electrically conducting viscous fluid over a porous stretching tube. The model accounts for nonlinear thermal radiation, internal heat generation/absorption, and Darcy–Forchheimer drag to capture porous medium resistance. Similarity transformations reduce the governing equations to a system of coupled nonlinear ordinary differential equations, which are solved numerically using the BVP4C technique with Response Surface Methodology (RSM) and sensitivity analysis. The effects of dimensionless parameters magnetic field strength (M), Reynolds number (Re), Darcy–Forchheimer parameter (Df), Brinkman number (Br), Prandtl number (Pr), nonlinear radiation parameter (Rd), wall-to-ambient temperature ratio (rw), and heat source/sink parameter (Q) are investigated. Results show that increasing M, Df, and Q suppresses velocity and enhances temperature due to Lorentz and porous drag effects. Higher Re raises pressure but reduces near-wall velocity, while rw, Rd, and internal heating intensify thermal layers. The entropy generation analysis highlights the competing roles of viscous, magnetic, and thermal irreversibility, while the Bejan number trends distinctly indicate which mechanism dominates under different parameter conditions. The RSM findings highlight that rw and Rd consistently reduce the Nusselt number (Nu), lowering thermal efficiency. These results provide practical guidance for optimizing energy efficiency and thermal management in MHD and porous media-based systems.: Full article

Global warming, driven by greenhouse gas (GHG) emissions, is accelerating globally and highlights the need for effective mitigation strategies. This study assesses the economic feasibility of rainbow trout aquaculture by incorporating GHG emissions into its analysis, thereby contributing to mitigation efforts in the fisheries sector. Focusing on two farming systems—recirculating aquaculture systems (RAS) and flow-through systems (FTS)—we estimated GHG emissions and conducted an economic evaluation using data collected through field surveys. The average GHG emission was 7.14 kg CO₂ eq per kilogram of trout produced, with RAS showing lower emissions than FTS. Electricity and feed were identified as the primary emission sources. The economic analysis revealed an average net present value (NPV) of USD 987,609 and an internal rate of return (IRR) of 18%, with RAS outperforming FTS in profitability. A sensitivity analysis under carbon pricing showed that economic feasibility was maintained, but the NPV declined by about 24% under the carbon tax scenario. Overall, these findings underscore the importance of balancing profitability and emission reduction for sustainable aquaculture management. Full article

This study investigates the development and application of the GDELT (Global Database of Events, Language, and Tone) news database. Through experiments, we conducted a quantitative statistical analysis of the GDELT event database to evaluate its practical characteristics. The results indicate that although the database achieves comprehensive coverage across all countries and regions and includes most major global media outlets, the accuracy rate of its key fields is only approximately 55%, with a data redundancy as high as 20%. Based on these findings, while the GDELT data demonstrates good coverage and data integrity, data correction and deduplication are recommended before its use in research contexts and industrial applications. Subsequently, a survey of the existing literature reveals that current studies using GDELT primarily focused on event-related metrics, such as event quantity, tone, and GoldsteinScale, for application in international relations analysis, crisis event prediction, policy effectiveness testing, and public opinion impact analysis. Nevertheless, news constitutes a fundamental channel of information dissemination in media networks, and the propagation of news events through these networks represents a critical area of study for information recommendation, public opinion guidance, and crisis intervention. Existing research has employed the Event, GKG, and Mentions tables to construct cross-national news flow network models. However, the informational correlations across different data table fields have not been fully leveraged in preliminary data selection, leading to substantial computational overhead. To advance research in this field, this study employs chained list queries on the Event and Mentions tables within GDELT. Using social network analysis, we constructed a media co-occurrence network of event reports, through which core hubs and associative relationships within the event dissemination network are identified. Full article

With the rapid development of artificial intelligence technology in the field of intelligent manufacturing, convolutional neural networks (CNNs) have shown excellent performance and generalization capabilities in industrial applications. However, the huge computational and resource requirements of CNNs have brought great obstacles to their deployment on low-end hardware platforms. To address this issue, this paper proposes a scalable CNN accelerator that can operate on low-performance Field-Programmable Gate Arrays (FPGAs), which is aimed at tackling the challenge of efficiently running complex neural network models on resource-constrained hardware platforms. This study specifically optimizes depthwise separable convolution and the squeeze-and-excite module to improve their computational efficiency. The proposed accelerator allows for the flexible adjustment of hardware resource consumption and computational speed through configurable parameters, making it adaptable to FPGAs with varying performance and different application requirements. By fully exploiting the characteristics of depthwise separable convolution, the accelerator optimizes the convolution computation process, enabling flexible and independent module stackings at different stages of computation. This results in an optimized balance between hardware resource consumption and computation time. Compared to ARM CPUs, the proposed approach yields at least a 1.47× performance improvement, and compared to other FPGA solutions, it saves over 90% of Digital Signal Processors (DSPs). Additionally, the optimized computational flow significantly reduces the accelerator’s reliance on internal caches, minimizing data latency and further improving overall processing efficiency. Full article

A new quasi-one-dimensional ejector model for the prediction of ejector performance is carried out, which is based on the theory of ideal gas expansion and free layer development. The model is proposed for calculation of the variable area bypass injector (VABI) and ejector nozzle in the variable cycle engine (VCE), both at the design point and off-design point. The internal structure of ejector nozzle is determined based on an analysis of the flow field of the 2D ejector nozzle Computational Fluid Dynamics (CFD) result. The flow during the expansion section is divided into three parts: primary flow, secondary flow, and mixed layer flow. Combined with the growth rate of mixing layer thickness, the calculation methods of ejector nozzle exit parameters under critical working conditions and blocking working conditions are given, and the calculated results demonstrate a strong consistency with CFD results, maintaining relative errors below 3%. This method is used to evaluate the ejector nozzle capacity quickly in the overall design stage, which provides theoretical support for the design of the main bypass system of a variable cycle engine. Full article

To explore the influence of double-electrode regulation technology on the solidification microstructure and properties of GCr15 bearing steel, the double-electrode insertion process was employed in this study, combined with metallographic analysis, mechanical property testing, and electron probe composition characterization. We analyzed the mechanisms of solidification microstructure evolution and mechanical property improvement, as well as the composition segregation control effect, of GCr15 steel under double-electrode regulation. The results show that the double-electrode technology significantly refines the microstructure and improves the internal quality of the ingot by optimizing the temperature field and electromagnetic field distribution in the molten pool and enhancing the internal flow of the melt. The tensile strengths in the upper and middle parts were increased by 84.6% and 29.6%, respectively, which can be attributed to the uniform distribution of carbides at the grain boundaries and the reduction of segregation. Composition analysis indicates that the macroscopic segregation index of C element was decreased under the dual-electrode process. This research provides a theoretical basis and process optimization direction for the high-quality preparation of high-carbon chromium bearing steel. Full article

This study investigates the effects of air pressure, glue pressure, and viscosity on atomization characteristics through experimental and simulation methods, aiming to reveal gas–liquid interaction mechanisms and optimize process parameters. The rheological parameters of aqueous polyurethane adhesives with varying viscosities were characterized. Spray characteristics, including spray angle, cured film diameter, and thickness, were quantitatively measured under different operating conditions. The internal flow field and droplet dynamics were numerically analyzed. The results indicate the following: Increasing the air pressure (from 0.3 to 0.7 MPa) enlarges the spray angle and film diameter while reducing the film thickness. In contrast, increasing the glue pressure enlarges all three parameters: spray angle, film diameter, and film thickness. Furthermore, increasing the viscosity within the test range reduces the spray angle, film diameter, and film thickness. These effects stem from enhanced gas kinetic energy and shear intensity (promoting liquid film fragmentation), an increased fluid flow rate with glue pressure, and strengthened droplet resistance to breakup with suppressed spreading at higher viscosities. This research provides useful criteria for nozzle design and the optimization of industrial atomization processes involving non-Newtonian adhesives. Full article

The low-pressure edge of a pump-turbine runner blade is more prone to cavitation than other parts. The installation angle of the blade’s low-pressure edge is one of the key parameters affecting the cavitation performance of the pump-turbine. Based on the installation angle of the blade’s low-pressure edge obtained by the principle of normal outflow of the turbine runner, two other installation angles of the low-pressure edge are constructed by increasing the installation angle of the low-pressure edge toward the band direction. Three types of blades are designed based on the parametric design program of the pump-turbine runner. The Zwart cavitation model is adopted to carry out full-channel steady numerical simulations for the three runners. The efficiencies and internal flow fields of the draft tube under turbine operating conditions are compared. The cavitation characteristics in pump mode, the distribution of the turbulent flow field, and the pressure distribution on the blade surface are analyzed. The influence laws of the installation angle of the blade’s low-pressure edge on pump-turbine performance is summarized. A design method for anti-cavitation of Francis pump-turbine runners has been explored. The results show that the LP1 blade can achieve normal outflow under the turbine’s rated operating condition, but due to the large inflow attack angle under pump operating conditions, the cavitation performance in pump mode is very poor. By increasing the installation angle of the blade’s low-pressure edge toward the band direction, the efficiencies and cavitation performances of the pump mode can be improved. The LP3 blade reduces the inflow attack angle while optimizing the pressure distribution on the blade’s suction surface, thereby reducing the superimposed effect of two phenomena under large-discharge pump operating conditions with low cavitation numbers: flow separations on the pressure surface caused by inflow impact, and flow separations on the suction surface of adjacent blades caused by cavitation. As a result, the cavitation performance of the LP3 blade is significantly better than that of the LP1 and LP2 blades. The proposed anti-cavitation design method is simple and effective and can be applied to the research and modification design of Francis pump-turbine runners. Full article

Extreme weather events, such as typhoons, induce strong wave–current interactions that significantly alter nearshore hydrodynamic conditions, particularly in shallow intertidal zones. This study investigates the influence of wind speed and water depth on wave–current coupling under typhoon conditions in Shenhu Bay, southeastern China—a semi-enclosed bay that hosts multiple ancient forest relics within its intertidal zone. A two-tier numerical modeling framework was developed, comprising a regional-scale hydrodynamic model and a localized high-resolution model centered on a protective structure. Validation data were obtained from in situ field observations. Three structural scenarios were tested: fully intact, bottom-blocked, and damaged. Results indicate that wave-induced radiation stress plays a dominant role in enhancing flow velocities when wind speeds exceed 6 m/s, with wave contributions approaching 100% across all water depths. However, the linear relationship between water depth and wave contribution observed under non-typhoon conditions breaks down under typhoon forcing. A critical depth range was identified, within which wave contribution peaked before declining with further increases in depth—highlighting its potential sensitivity to storm energy. Moreover, structural simulations revealed that bottom-blocked devices, although seemingly more enclosed, may be vulnerable to vertical pressure loading due to insufficient water exchange. In contrast, perforated designs facilitate an internal–external hydrodynamic balance, thereby enhancing protective effect. This study provides both theoretical and practical insights into intertidal structure design and paleo-heritage conservation under extreme hydrodynamic stress. Full article

This study presents an experimental analysis of high-pressure liquid and gas gate valve leakage under multiple operating conditions, based on the variation patterns of ultrasonic signals. Focusing on a multi-physics field analysis of gate valve internal leakage and corresponding experiments, this research illustrates the acoustic wave characteristics of gate valves across diverse working media, pressures, internal leakage defect sizes, and valve diameters. By drawing upon both fluid mechanics and acoustics theory, an analytical approach suited to high-pressure gate valve leakage issues is devised. Separate high-pressure gate valve leakage test platforms for liquid and gas environments were designed and constructed, enabling 126 groups of tests under varying conditions, which include one measurement per condition of the valve size, defect size, and pressure value. These experiments examine the quantitative correlation of internal leakage flow rates and ultrasonic signal measurements under different situations. In addition, the distinct behaviors and principles exhibited by high-pressure liquid gate valves and gas gate valves are compared. The findings provide theoretical and technical support for quantifying high-pressure gate valve leakage. The study analyzes the theoretical basis for the generation of ultrasonic signals from valve internal leakage, providing specific experimental data under various operating conditions. It explains the various observations during the experiments and their principles. The conclusions of this research have practical engineering value and provide important references for future studies. Full article

As a key component of the Tempcore process, the Tempcore cooler plays a critical role in enhancing the cooling efficiency of steel bars. A cylindrical corrugated tube designed specifically for the Tempcore cooling process of large diameter steel bars, where the corrugated surface induces turbulence to enhance cooling efficiency. The influence of its structural parameters on the cooling performance was investigated through a combination of numerical simulations and experimental validation. First, based on the law of mass conservation, the influence of structural parameters of the corrugated tube on their internal flow field was analyzed. Then, a simulation model of the Tempcore cooler was developed to explore the variation in steel bar cooling efficiency under different structural parameters. The results show that increasing the maximum inner diameter of the corrugated tube enhances cooling efficiency, which subsequently tends to stabilize. With increasing minimum inner diameter and pitch, the cooling efficiency of the bars first increases and then decreases. And based on the influence of individual parameters, an orthogonal simulation was performed to identify the optimal corrugated tube structural configuration for achieving maximum cooling efficiency. The minimum inner diameter was identified as a critical factor influencing the heat transfer efficiency of the steel bar. Finally, based on the results of orthogonal simulations, five corrugated tubes were fabricated and integrated into the Tempcore cooler for experimental validation. The accuracy of the simulation was verified through microstructural analysis of the produced steel bars, which exhibited a 38% increase in martensite volume fraction. The designed corrugated tubes significantly improve the cooling efficiency of the Tempcore process without requiring an upgrade to the water supply system capacity. Full article

Hydraulic fracturing is a critical technical means for enhancing production in gas fields, and post-fracturing flow-back constitutes a crucial phase of fracturing operations. Proppant backflow during the flow-back process significantly impacts both the effectiveness of stimulation and subsequent production. Particularly for tight gas reservoirs, achieving rapid post-fracturing flow-back while preventing proppant re-flux is essential. To date, domestic and international scholars have conducted extensive research on proppant backflow during flow-back operations, with laboratory experimental studies serving as a vital investigative approach. However, due to limitations in experimental apparatuses, further investigation is required regarding the migration mechanisms of proppants during flow-back, proppant backflow prevention techniques, and associated operational parameters. This paper developed a novel visualized flow chamber capable of simulating proppant migration in vertical fractures under closure stress conditions. Extensive proppant backflow experiments conducted using this device revealed that (1) proppant backflow initiates at weak structural zones near the two-phase interface boundaries; (2) proppant backflow occurs in three distinct stages, with varying fluid erosive capacities on proppant particles at each phase; (3) a multi-stage fiber injection sand control process was optimized; (4) at low proppant concentrations (<10 kg/m²), the fiber concentration should be 0.8%; at high proppant concentrations (>10 kg/m²), the fiber concentration should be 1.2%. The recommended fiber length is 6 mm. Full article

This study proposes a novel variable-radius arc rotor, developed based on the conventional arc rotor, for application in a hydrogen circulation pump. Numerical simulations are conducted to analyze and compare the flow characteristics of the optimized rotor with those of the baseline rotor. Results show that the optimized rotor increases outlet mass flow rates by over 15%; however, it has little effect on pressure pulsation, indicating limited influence on flow stability. Flow field analysis reveals that the optimized rotor promotes a more stable and streamlined internal velocity distribution, suppressing localized disturbances and vortices that are prevalent with the baseline rotor. Furthermore, assessments of turbulent kinetic energy (TKE) and three-dimensional vortex structures show that the optimized rotor confines high-energy zones to essential areas and facilitates controlled vortex evolution. These effects collectively lead to lower turbulence intensity, reduced energy loss, improved operational efficiency, and enhanced mechanical reliability of the pump. Full article

Severe pressure pulsations caused by complex flow fields in pumped-storage power stations significantly threaten operational safety and stability. With advances in computational technology, fully three-dimensional simulations coupling pipelines and pump-turbine units have become feasible. In this study, a fully three-dimensional analysis model was developed, coupling the water conveyance system and a finely modeled prototype-scale pump-turbine with splitter blades, to numerically simulate the compressible flow field under the maximum head pump mode. The study reveals a strong bidirectional coupling between the flow in the long outlet pipe and the internal flow within the pump-turbine unit. Influenced by structural features such as bifurcations and flow impingement at the T-junction, complex three-dimensional vortices arise and cannot be neglected. Based on the flow field, the study further investigates the time-domain, frequency-domain, and spatial characteristics of pressure pulsations at various downstream hydraulic components, ranging from the vaneless space to the outlet of the long outlet pipe. The pressure pulsation frequencies are shown to be affected by both rotor–stator interactions and the complex vortical structures in the flow. These findings clearly demonstrate the necessity of fully three-dimensional simulations that incorporate both the water conveyance system and the pump-turbine unit. Full article