Search Results (4,464)

This study investigates Project-Based Learning (PBL) to boost student engagement in a Transport Phenomena course at the Federal University of Mato Grosso do Sul (UFMS). Through a hands-on project involving Floating Treatment Islands (FTIs) for water quality improvement, PBL was hypothesized to enhance student involvement and analytical skills. Students designed and optimized FTIs, experimenting with configurations like root length and plant type. Quantitative outcomes reveal a standard deviation of 1.5 in project scores among top performers (course average > 6), reflecting diverse problem-solving strategies, while a standard deviation of 0.8 near the passing threshold (course average ≈ 6) indicates consistent efforts to improve grades. Additionally, 80% of students rated their experience ≥ 4 on a 5-point scale, signaling high satisfaction, although 40% identified data interpretation as a challenge requiring targeted support. Outcomes were assessed by analyzing score variability, revealing higher standard deviations among top performers, indicating diverse problem-solving approaches, while lower deviations near the passing threshold suggested uniform efforts to improve grades. Despite general satisfaction, some students faced data interpretation challenges, highlighting areas for instructional refinement. The results affirm PBL’s effectiveness in fostering engagement and practical skills but suggest that adaptive teaching methods are essential to support comprehension and maintain engagement across different performance levels. Full article

As a novel type of ocean monitoring tool, unmanned sailboats exhibit significant application potential. In this study, a novel wing sail structure for offshore unmanned sailboats is proposed and its performance compared with that of the conventional NACA 0021 wing sail. The Reynolds-averaged Navier–Stokes (RANS) equations are employed for numerical analysis, and the aerodynamic performance is evaluated using ANSYS Fluent. The results indicate that the lift coefficient and lift-to-drag ratio of the HF-14-CE-01 wing sail are significantly superior to those of the NACA 0021 wing sail. Compared to the NACA 0021 wing sail, the HF-14-CE-01 wing sail has undergone structural optimization. The HF-14-CE-01 wing sail demonstrates improved wind direction efficiency, uniform force distribution, ease of adjustment, and extends the service life of the sail. Subsequent research examined the influence of aspect ratio on both the aerodynamic performance of the wing sail and the thrust generated by the unmanned sailboat, identifying an optimal aspect ratio of 4 for the HF-14-CE-01 wing sail. Analysis of the velocity and static pressure contour maps for the HF-14-CE-01 wing sail identified a critical angle of attack of 28°, providing a clear visual representation of its aerodynamic performance. Furthermore, compared with other rigid sail designs, the HF-14-CE-01 wing sail achieved a 30.9% increase in peak lift coefficient, indicating superior propulsion capability. Full article

In the context of green building development, the lighting design of campus living rooms in hot summer and cold winter areas faces the dual challenges of glare control in summer and insufficient daylight in winter. Based on BIM technology, this study uses Revit 2016 modeling and the HYBPA 2024 performance analysis platform to simulate and optimize the daylighting performance of the campus activity center of Hunan City College in multiple rounds of iterations. It is found that the traditional single large-area external window design leads to uneven lighting in 70% of the area, and the average value of the lighting coefficient is only 2.1%, which is lower than the national standard requirement of 3.3%. Through the introduction of the hybrid system of “side lighting + top light guide”, combined with adjustable inner louver shading, the optimized average value of the lighting coefficient is increased to 4.8%, the uniformity of indoor illuminance is increased from 0.35 to 0.68, the proportion of annual standard sunshine hours (≥300 lx) reaches 68.7%, and the energy consumption of the artificial lighting is reduced by 27.3%. Dynamic simulation shows that the uncomfortable glare index at noon on the summer solstice is reduced from 30.2 to 22.7, which meets the visual comfort requirements. The study confirms that the BIM-driven “static-dynamic” simulation coupling method can effectively address climate adaptability issues. However, it has limitations such as insufficient integration with international healthy building standards, insufficient accuracy of meteorological data, and simplification of indoor dynamic shading factors. Future research can focus on improving meteorological data accuracy, incorporating indoor dynamic factors, and exploring intelligent daylighting systems to deepen and expand the method, promote the integration of cross-standard evaluation systems, and provide a technical pathway for healthy lighting environment design in summer-hot and winter-cold regions. Full article

Curved prisms can serve as core components of dispersive spectroscopy and converge light paths, making them widely used in spectral imaging technology. Their positional stability, surface shape errors, and temperature stability in optical systems directly affect the performance of spectral imaging systems. On the basis of the analysis of design indicators and optimization of the support structure for curved prisms, a multipoint flexible adhesive support structure (MPPASS) of large rectangular curved prisms for space-based application is proposed. The novelty of the MPPASS lies in its ability to achieve micro-stress and high stability support for large-aperture rectangular optical elements through the bonding of peripheral small points and the introduction of flexible bonding rings. The design principles of the adhesive support structure were deeply studied, and on this basis, the engineering design, finite element analysis, adhesive testing, and mechanical testing of large curved prisms were completed. The designed curved prism assembly has a maximum deformation displacement of 0.0085 mm and a maximum tilt angle of 0.65” under gravity loading, a first-order frequency of 1003.5 Hz, and a maximum acceleration amplification factor of 3.12 in the X, Y, and Z directions. The root mean square (RMS) variation value of the mirror shape errors for the curved prism assembly was 5.26 nm under a uniform temperature load of 20 ± 1 °C, and the RMS value of the mirror shape errors was 0.019 λ after mechanical testing. The installation surface flatness of 0.02 mm did not significantly affect its mirror shape errors. The experimental results verified the rationality of the design, temperature stability, and mechanical stability of the MPPASS. Full article

This paper presents the preparation of Z-cut near-stoichiometric lithium niobate (NSLN) wafers using a combined process of the lithium-rich Czochralski growth and diffusion methods. The fabricated Z-cut NSLN wafers exhibited outstanding comprehensive performance, including a high Curie temperature of up to 1200 °C, a refractive index gradient in the diameter direction below 1.5 × 10⁻⁴ cm⁻¹, and a UV absorption edge shifted 14 nm toward the ultraviolet region compared to congruent lithium niobate crystals, with a coercive field of 1268 V/mm. Additionally, the wafers demonstrated excellent processing characteristics, with the bow of 4-inch wafers controlled within 55 μm, surpassing the machining standards of traditional lithium niobate wafers of the same size. These results indicated the highly uniform chemical stoichiometry and crystallization quality of the wafers. Leveraging the high uniformity and low coercive field of the wafers, periodic triangular domain structure arrays were successfully fabricated, laying the foundation for domain engineering design in electro-optic deflectors and switching devices. This study not only achieves the scalable preparation of NSLN wafers but also provides a reliable technical solution for their practical applications in high-performance electro-optic devices. Full article

Recent advancements in rice breeding have significantly increased production in China. However, high-yielding varieties require strong airflow for effective cleaning. Longitudinal-flow rice combine harvesters equipped with a centrifugal fan with four blades are widely used in China; however, these fans exhibit fluctuating cleaning performance and airflow maldistribution. To address these limitations, this study developed an innovative multi-blade cleaning fan design by incorporating the blade clocking effect, a concept not previously applied in centrifugal fans. To support the design process, the required airflow rates and reduction in static pressure were first analyzed. Based on these findings and fundamental fan design theory, three fan models were designed with blade clocking angles of 0°, 5.5°, and 10.5°, respectively. Three fan models were evaluated through computational fluid dynamics (CFD) simulations using a design of experiments approach based on Box–Behnken design response surface methodology to identify the optimal fan. The fan features a 10.5° clocking angle, meeting the airflow requirements for effective cleaning. In the test bench measurements, the setup with guide plate angles No. 1 and No. 2 at 32° and a fan speed of 1200 rpm was identified as optimal. The newly designed multi-blade cleaning fan overcomes the limitations of conventional four-blade designs, significantly enhancing airflow uniformity. Full article

The aim of this study was to address the issue of significant performance degradation in existing defogging algorithms under extreme fog conditions. Traditional Taylor series-based deformable convolutions are limited by local approximation errors, while the heavy-tailed characteristics of the Cauchy distribution can more successfully model outliers in fog images. The following improvements are made: (1) A displacement generator based on the inverse cumulative distribution function (ICDF) of the Cauchy distribution is designed to transform uniform noise into sampling points with a long-tailed distribution. A novel double-peak Cauchy ICDF is proposed to dynamically balance the heavy-tailed characteristics of the Cauchy ICDF, enhancing the modeling capability for sudden changes in fog concentration. (2) An innovative Cauchy–Gaussian fusion module is proposed to dynamically learn and generate hybrid coefficients, combining the complementary advantages of the two distributions to dynamically balance the representation of smooth regions and edge details. (3) Tree-based multi-path and cross-resolution feature aggregation is introduced, achieving local–global feature adaptive fusion through adjustable window sizes (3/5/7/11) for parallel paths. Experiments on the RESIDE dataset demonstrate that the proposed method achieves a 2.26 dB improvement in the peak signal-to-noise ratio compared to that obtained with the TaylorV2 expansion attention mechanism, with an improvement of 0.88 dB in heavily hazy regions (fog concentration > 0.8). Ablation studies validate the effectiveness of Cauchy distribution convolution in handling dense fog and conventional lighting conditions. This study provides a new theoretical perspective for modeling in computer vision tasks, introducing a novel attention mechanism and multi-path encoding approach. Full article

This paper presents a novel design strategy for outlier-robust, three-element non-uniform linear array (NULA) configurations optimized for multiple-input multiple-output (MIMO) radar systems aimed at target direction of arrival (DoA) estimation. The occurrence of outliers, i.e., ambiguous estimates, is a well-known issue in DoA estimation based on the maximum likelihood (ML), which is caused by the local maxima of the likelihood function. Specifically, we study how the positioning of both transmitters and receivers affects both presence of outliers and accuracy of ML DoA estimation. By leveraging a theoretical prediction of the DoA mean squared error (MSE), we propose a design strategy to jointly optimize the positions of NULA array of three transmitting and receiving elements, only inside a subspace which guarantees that the outlier probability remains below a specified threshold. Compared to NULA configurations with a single transmitter, the proposed designs achieve superior estimation accuracy due to two key factors: improved asymptotic performance resulting from a narrower mainlobe, and enhanced robustness against outliers due to reduced sidelobes. Furthermore, the proposed approach is well-suited for practical implementation in low-cost radars using only 3 × 3 or 2 × 3 MIMO configurations, as it also incorporates practical design constraints such as minimum inter-element spacing to account for the physical dimensions of the antennas, and tolerance in the installation accuracy. Full article

The heat exchanger in a hydropower unit plays a critical role in ensuring the stability of the unit and improving operational efficiency. This paper conducted a global flow-field/heat-transfer numerical analysis of multi-tube heat exchangers in hydropower units (with 98 tubes) and applied it to optimization research under actual operating conditions. Using a three-dimensional two-phase flow model, this work systematically analyzes the effects of different sand content and particle size on heat-transfer performance, revealing the impact of particle-flow and fluid-flow nonuniformity on heat-exchange efficiency. This research fills the gap in existing studies regarding the analysis of the impact of complex operating conditions on hydropower unit radiators. To address the issues of nonuniform flow fields and poor flow mixing in existing heat exchangers, an improved inlet/outlet structural-optimization plan is proposed. The original cylindrical inlet/outlet is replaced with a square structure, and its area is increased. The optimized structure improves flow uniformity, reduces flow losses, enhances heat-transfer performance by 7.7%, and achieves a significant reduction of 0.53 K in oil temperature. The findings of this study provide theoretical and engineering guidance for the design and optimization of heat exchangers in hydropower units and are of high value for practical applications. Full article

Electrospun nanofibrous mats from bovine, porcine, and fish gelatin were systematically fabricated at varying concentrations (15, 20, 25, and 30 wt.%) to investigate the influence of molecular characteristics on morphology, crystallinity, mechanical properties, thermal behavior, and solubility. Optimal ranges of viscosity (0.08–1.47 Pa·s), surface tension (35–50 mN·m⁻¹), and electrical conductivity (0.18–1.42 mS·cm⁻¹) were determined to successfully produce homogeneous fibers. Bovine and porcine gelatin, characterized by higher molecular weight and greater proline/hydroxyproline content, exhibited thicker (up to 725 ± 41 nm at 30 wt.%) and less uniform nanofibers due to higher viscosity and surface tension, restricting polymer jet stretching. Conversely, fish gelatin, with lower molecular weight and limited proline/hydroxyproline content, produced significantly thinner (as low as 205 ± 28 nm at 20 wt.%) and more uniform nanofibers. X-ray diffraction analysis revealed distinct crystallinity transitions associated with triple-helix and amorphous structures, dependent on gelatin type and concentration, including the emergence of peaks near 7.9° and 20.1° (2θ) for bovine gelatin. Mechanical tests demonstrated superior tensile strength for bovine gelatin (up to 2.9 MPa at 30 wt.%), balanced properties for porcine gelatin, and exceptional elasticity for fish gelatin. Thermal analysis indicated concentration-dependent shifts in viscoelastic behavior and damping performance. Solubility studies showed rapid dissolution of low-concentration fish gelatin fibers, moderate stability for intermediate-concentration porcine gelatin, and excellent structural retention for high-concentration bovine gelatin. These results demonstrate the potential for tailored gelatin nanofiber design to meet specific functional requirements in biomedical applications. Full article

This study presents a simulation-driven methodology for the design and optimization of a lightweight drone frame. Starting with a CAD model developed in SolidWorks, finite element analysis (FEA) and computational fluid dynamics (CFD) which are used to evaluate stress, deformation, fatigue behavior, and aerodynamic performance. Topology optimization is then applied to reduce non-critical material and enhance the stiffness-to-weight ratio. CFD-informed refinements further help to minimize drag and improve airflow uniformity. The final design is fabricated using fused deposition modeling (FDM) with PLA, enabling rapid prototyping and experimental validation. Future work will explore advanced materials to improve fatigue resistance and structural durability. Full article

Thermotropic liquid crystal polymers comprise rigid chain segments called mesogens. This study presents a modeling approach to simulate the orientation of these mesogens in a flow channel with a rectangular cross section under no slip and wall slip boundary conditions. Rigid rods with finite length and an initial orientation are proposed. The interactions between the velocity field in the flow channel and these rods are modeled to simulate orientation. Moreover, a highly oriented boundary layer can be simulated. Orientation occurs in the flow direction close to the die wall under the no slip condition due to the high shear rate. As the distance from the die wall increases, the orientation decreases. Wall slip effectuates a more uniform orientation and causes a delay in the development of the highly oriented boundary layer. The thickness profile of this layer exhibits a shape that is analogous to that of a root function. To ensure products with high mechanical properties, it is essential to orient the mesogens at a high level in the die during manufacturing. The presented model enables the prediction of orientation in the flow channel. Therefore, this model is a useful tool to design the process in the right way to reach this goal. Full article

This study investigates the thermal performance of an oil-jet-cooled permanent magnet synchronous motor (PMSM), with a particular focus on end-winding heat dissipation. A high-fidelity numerical model that preserves the full geometric complexity of the end-winding is developed and validated against experimental temperature data, achieving average deviations below 7%. To facilitate efficient parametric analysis, a simplified equivalent model is constructed by replacing the complex geometry with a thermally equivalent annular region characterized by calibrated radial conductivity. Based on this model, the effects of key spray ring parameters—including orifice diameter, number of nozzles, inlet oil temperature, and flow rate—are systematically evaluated. The results indicate that reducing the orifice diameter from 4 mm to 2 mm lowers the maximum winding temperature from 162 °C to 153 °C but increases the pressure drop from 205 Pa to 913 Pa. An optimal nozzle number of 12 decreases the peak winding temperature to 155 °C compared with 162 °C for 8 nozzles, while increasing the oil flow rate from 2 L/min to 6 L/min reduces the peak winding temperature from 162 °C to 142 °C. Furthermore, a non-uniform spray ring configuration decreases maximum stator, winding, spray ring, and shaft temperatures by 5.6–9.2% relative to the baseline, albeit with a pressure drop increase from 907 Pa to 1410 Pa. These findings provide quantitative guidance for optimizing oil-jet cooling designs for PMSMs under engineering constraints. Full article

The practical application of powdered photocatalysts is significantly hindered by challenges in recyclability and structural instability. This work proposes a sustainable immobilization strategy by integrating BiVO₄ nanoparticles into a sodium alginate (SA) aerogel scaffold through a facile freeze-drying approach. The abundant hydroxyl/carboxyl groups of SA enable uniform dispersion of BiVO₄ within the porous network, while the aerogel architecture enhances light-harvesting efficiency and mass transfer kinetics. Innovatively, peroxymonosulfate (PMS) was introduced to synergistically couple photocatalysis with sulfate radical-based advanced oxidation processes (SR-AOPs), where the photogenerated electrons from BiVO₄ effectively activate PMS to yield high-activity ·SO₄⁻ radicals. The optimized BiVO₄/SA aerogel achieves nearly complete removal of Rhodamine B within 2 h under visible light, which is competitive to pure BiVO₄ powders. In addition, the mechanically robust aerogel exhibits exceptional reusability, retaining ~90% efficiency after five cycles without structural collapse. This work provides a paradigm for designing recyclable photocatalyst carriers with dual oxidation pathways, demonstrating significant potential for industrial wastewater treatment. Full article

To mitigate flood damage caused by overflow from a levee, it is essential to prevent the levee failure or extend the time to breaching. Although turfgrass on a levee slope is effective in suppressing erosion, insufficient maintenance can reduce its coverage. When overtopping occurs under such non-uniform turfgrass conditions, the flow tends to entrain air. In spillways, air entrainment is known to reduce friction loss; therefore, it may also contribute to lowering shear stress and erosion depth. This study conducted flume experiments with artificial turf arranged in various patterns on levee slopes to investigate flow patterns, air entrainment, and erosion. The flow pattern changed depending on the turf arrangement and overflow depth, and air entrainment occurred due to water surface fluctuations around the turfgrass. The inception point of air entrainment was found to be similar to or shorter than that observed in stepped spillways. Furthermore, the experiments showed a tendency for erosion depth to decrease once air entrainment is fully developed. This finding is significant because it suggests that erosion can potentially be minimized not only by reinforcing the levee structure itself but also by modifying flow characteristics through designs that promote air entrainment. Full article