Search Results (2,160)

A three-factor, four-level orthogonal design was employed to optimize the overall forming quality of powder bed fusion with a laser beam (PBF-LB)-fabricated TC4 alloy containing 0.3 wt.% YH₂. Sixteen process-parameter combinations were established, and two specimens were fabricated for each combination. Laser power, scanning speed, and hatch spacing were selected as the investigated variables. Relative density, surface roughness, and Vickers hardness were evaluated using the entropy weight method combined with the weighted-sum method. On this basis, the microstructure of the specimens produced under the optimal process parameters was systematically characterized. The results showed that the influence of the investigated factors on overall forming quality followed the order: hatch spacing > laser power > scanning speed. The optimal process parameters were a laser power of 200 W, a scanning speed of 1100 mm/s, and a hatch spacing of 0.10 mm, under which the specimens exhibited superior overall forming quality. The addition of 0.3 wt.% YH₂ did not significantly alter the dominant phase constitution of the alloy, but promoted α′ martensite refinement and weakened the texture through the in situ formation of Y₂O₃ nano-oxide particles. Full article

Steel–concrete composite components exhibit significant advantages, including reliable mechanical performance, rapid construction, cost efficiency, and low environmental impact. Existing studies on their seismic behavior have mainly focused on developing novel connection forms and enhancing joint zone strength, while systematic investigations into the post-earthquake axial compression behavior and failure mechanisms of composite joints remain limited. To address this gap, this study investigates the mechanical performance of steel–concrete composite components under strong seismic and post-earthquake conditions. Seismic damage characteristics are first analyzed based on representative case studies of conventional steel–concrete columns. Subsequently, low-cycle reversed loading tests followed by post-earthquake axial compression tests are conducted on seven beam–column joints with varying damage levels, and the damage evolution and seismic performance of joint zones under different structural configurations are systematically evaluated. In addition, the seismic performance of steel–concrete composite shear walls is further validated. The results provide a scientific basis for the seismic design, post-earthquake assessment, and repair of steel–concrete composite structures. Full article

The paper presents an optimisation workflow for modelling of a periodic mechanical structure in the form of a multi-material, axisymmetric beam. The optimisation objective is to prescribe the positions and widths of selected band gaps within a target frequency range for three basic types of structural vibrations: flexural, longitudinal and torsional. The decision variables were geometric parameters of the unit cell and material properties of selected thermoplastics assigned to successive segments of the cell. The frequency characteristics of the beam were determined using the time-domain spectral finite-element method (TD-SFEM). This model was used to perform a sensitivity analysis using the Morris method, which showed the dominant influence of the beam geometry on the position and width of band gaps, with a relatively smaller role of material variability. Due to high computational costs of the global optimisation based on a FEM solver, a surrogate regression model in the form of a residual MLP network was developed to predict the positions and widths of the first five band gaps for each vibration type. The global search was carried out using a genetic algorithm (GA) with the surrogate model and then the results were refined using a deterministic goal-attainment method with a high-fidelity model. Full article

Architected polymer composites use spatially organized phases to achieve targeted property combinations. Shape forming elements (SFEs) are modular coextrusion die inserts that impose internal architectures by reshaping multiple melt streams. This study evaluates three SFE designs (Jacks, I-Beam, and Barn Door) that position a liquid crystalline polymer (LCP) and an amorphous polyamide (APA) in distinct core–shell configurations. Polymer clay prototyping and ANSYS Polyflow simulations were used to screen flow behavior, followed by extrusion at two puller speeds and characterization via optical microscopy and tensile testing. Microscopy revealed that abrupt area transitions and viscosity contrast disrupt encapsulation and distort designed features. Regression analysis showed that LCP content governs stiffness and strength, while higher puller speed enhances reinforcement through molecular orientation. Cross sectional geometries were quantified using interfacial perimeter, moments of inertia, and polar dispersion ratios, and correlated to tensile performance. Increased interfacial length reduced modulus, strength, and ductility. Modulus improved with LCP orientation and confinement, strength increased when LCP was placed at vertical extremities, and elongation was maximized by horizontally distributing LCP within a thick APA shell. These results demonstrate that SFEs enable tunable tradeoffs between stiffness, strength, and ductility. Full article

Mining coal seams with shallow, thick, and hard roofs often results in extensive roof suspension. This issue poses significant challenges regarding stratum control and mitigation of strong mining pressure, especially within the confined working space of a mining face. This study focuses on the 13101 working face of Shengfu Coal Mine. Through field observations, theoretical analysis, and numerical simulations, the characteristics of support resistance and microseismic activity were investigated. This research elucidates the mechanism behind the strong mining pressure driven by the structural coupling and synergistic breakage of two key strata, highlighting how their interaction dictates weighting intensity. A small-aperture hydraulic fracturing technology, specifically designed for inter-support spaces, was developed. The results indicate that the working face exhibits alternating “minor weighting” and “major weighting” events. Minor weighting occurs at an average interval of 12.38 m with a dynamic load factor of 1.14, while major weighting occurs at 41.07 m with a factor of 1.56. The roof structure was found to form a combination of an “inclined stepped rock beam” and a “voussoir beam.” Field applications demonstrate that the proposed technology reduces the major weighting interval by 41.46% and total microseismic energy release by 35.01%. This study provides a theoretical and technical basis for preventing roof disasters under similar geological conditions. Full article

The laser-induced lift-off of functional surface layers is a key process in micro- and nano-fabrication; however, optimization criteria for maximizing the lifted-off area remain insufficiently defined. In analogy to the well-established theory of efficient laser ablation, where the maximum ablated volume per pulse is achieved at a peak fluence of $F_0^{\mathrm{o}\mathrm{p}\mathrm{t}}=e^2{F}_{\mathrm{t}\mathrm{h}}$, we develop a theoretical framework for efficient laser lift-off driven by Gaussian beams. The main highlight of this work is the derivation of a new analytical equation for the maximum delaminated area, enabling the straightforward determination of optimal processing conditions. By analytically describing the lift-off area as a function of peak fluence, beam radius, and focus position, we demonstrate that the maximum lifted-off area is achieved at a substantially lower optimal fluence, namely $F_0^{\mathrm{o}\mathrm{p}\mathrm{t}}=e^1{F}_{\mathrm{t}\mathrm{h}}$. Closed-form expressions for the optimal beam radius, maximal lift-off area, and optimal focus position are derived and validated by numerical modeling. The theory is applied to the picosecond laser lift-off of copper oxide from copper, showing excellent agreement between experimental observations and model predictions. The results reveal fundamental differences between ablation- and lift-off-dominated material removal and provide practical guidelines for maximizing process efficiency in laser-assisted delamination, selective coating removal, and surface functionalization. Full article

This study scientifically assessed the safety of the Ming Dynasty official-style timber structure of Taiyuan Chongshan Temple’s Great Mercy Hall, a nationally protected cultural relic. An integrated framework was adopted, including form restoration via 3D laser scanning and manual surveying, damage detection using impedance meters, stress wave tomography and one-dimensional stress wave testing, mechanical analysis with a differentiated material finite element model, and short-term on-site monitoring at risk points. Results showed that the 303.3 mm construction ruler length was restored, with the column grid tilting northwestward; the main structure was hardwood pine, and critical columns had severe localized damage (24% internal damage rate, 13% cross-sectional damage ratio) with 42% residual strength in some members; and the structure remained elastically safe, with material degradation causing 6.3–13.3% linear displacement amplification. Two weak links (eave purlin deflection: 33–37 mm; double-eave golden column axial force concentration: 86.9–88.5 kN) and dougong’s outward inclination due to eccentric compression were identified. Short-term monitoring indicated temperature-driven elastic responses and an 8 mm cumulative residual displacement in the northern single-step beam, and a three-level early warning threshold system was proposed. This study clarified the hall’s state as “overall stable with localized weaknesses”, providing a methodological reference for the preventive protection of similar ancient timber structures. Full article

To improve the rutting resistance and low-temperature cracking performance of polymer-modified asphalt under extreme conditions, hierarchically structured ZnO-loaded porous activated carbon (ZnO/PAC) nanosheets were introduced as a synergistic reinforcing agent for SBS-modified asphalt. The ZnO/PAC hybrids were synthesized via template-assisted carbonization followed by hydrothermal growth, and their effects were evaluated by microscopic characterization and rheological tests, including temperature sweeps, multiple stress creep and recovery (MSCR), and bending beam rheometer (BBR) analyses. ZnO was successfully anchored onto the PAC, forming a three-dimensional flower-like nanostructure. Among the investigated samples, ZPS3 with 3 wt.% ZnO/PAC showed the best overall performance. At 64 °C, the rutting factor increased from 4.2 kPa for the SBS-modified asphalt to 6.8 kPa for ZPS3, representing a ~62% enhancement and indicating markedly improved high-temperature deformation resistance. MSCR results further confirmed the superior rutting resistance of ZPS3, which exhibited the highest recovery and the lowest non-recoverable creep compliance. In addition, BBR results showed that the low-temperature performance grade improved from −12 °C for conventional the SBS-modified asphalt to −18 °C for the ZnO/PAC-modified system. These results demonstrate that ZnO/PAC nanosheets can effectively enhance both the high-temperature rutting resistance and low-temperature cracking resistance of SBS-modified asphalt. Full article

To address severe strata pressure induced by large end-area hanging spans and poor caving of thick, hard roofs in western coal mines, this study takes the 1302 working face of Zhujiamao Coal Mine as a case study. A multiscale mechanical model is developed to describe the progressive evolution of a stratified hard roof from a continuous beam to a cantilever beam and finally to an arched triangular hanging roof. Limit criteria for the maximum hanging length under bending and shear failure are derived, indicating that bending governs end-area roof instability. The theoretical results show good agreement with field observations and numerical simulations, providing guidance for liquid nitrogen fracturing target selection. Coupled FLAC3D-3DEC simulations reveal the staged deformation of overlying strata and clarify the spatial correspondence between the “O-X” fracture pattern and the arched triangular hanging roof. Based on these findings, a collaborative weakening strategy integrating directional drilling, hydraulic pre-cracking, and deep liquid nitrogen fracturing is proposed. Field observations and comparative tests confirm that this method effectively forms a three-dimensional fracture network, reduces roof stiffness and strength, shortens the caving interval, lowers peak shield resistance, and promotes stable caving of the end-area hanging roof. Full article

The reservoir quality and gas-bearing properties of the Wufeng Formation–Longmaxi Formation shale vary significantly across different structural units in the Luzhou area of the Sichuan Basin. The mechanisms of shale gas enrichment, tectonic controls, and accumulation models are critical determinants of the potential for three-dimensional (3D) development. Integrating data from core analyses, logging interpretation, focused ion beam scanning electron microscopy (FIB-SEM), and high-resolution core scanning, this study investigates the control exerted by fracture development and tectonic activity on shale gas enrichment and preservation. A conceptual model for shale gas enrichment and accumulation is established, and the potential for 3D development of deep shale gas in the Luzhou block is evaluated. The results indicate that: (1) Reservoir heterogeneity in deep shale gas plays is jointly governed by reservoir space characteristics, diagenesis, structural position, tectonic evolution, and fracture-fluid activity. Organic-rich siliceous shales retain favorable reservoir properties, characterized by an organic matter (OM) pore-dominated pore structure, relatively high porosity and permeability, and good gas-bearing potential due to overpressure preservation. (2) Structural style exerts dominant control over the gas-bearing variability. Synclines are significantly more favorable than anticlines, with free gas migration governing the enrichment pattern. The cores and flanks of synclines form zones of high gas content due to structural integrity, whereas the gas content decreases in anticlinal areas near faults. (3) Shale gas enrichment relies on the synergistic configuration of “high organic carbon content + high-quality pore reservoir space + robust structural preservation conditions.” Well L213 in the syncline core, distant from faults, exhibits good structural integrity and preservation conditions. Free gas from structurally lower positions migrates laterally toward the flanking anticlines, with a portion preserved in the syncline flanks. Concurrently, microfractures enhance reservoir storage and permeability, rendering syncline structures more conducive to shale gas preservation. (4) The high-quality shale succession in the study area is thick and laterally continuous, characterized by “vertical stacked pay zones.” This provides an excellent geological foundation for 3D development. By optimizing the well trajectory design and employing efficient fracturing technologies, such as “intensive fracturing” combined with temporary plugging and diversion, full and balanced utilization of vertically stacked sweet spot reservoirs can be achieved, significantly enhancing the single-well productivity and estimated ultimate recovery (EUR). Full article

Fabry–Perot resonator (FPR) sensors are widely implemented in optical and microwave waveguides because their interference fringe spectra enable highly sensitive, stable, and calibration-free measurements. In contrast, despite the extensive use of beams and plates as waveguides in vibration- and ultrasound-based structural health monitoring (SHM), an explicit FPR framework for these mechanical waveguides has not been established. This paper demonstrates that flexural beams can be rigorously treated as FPRs despite their inherently dispersive nature. Through analytical derivation, wave-propagation analysis, and fringe-based group-velocity extraction, we show that flexural-beam resonances arise from multi-reflection interference analogous to Fabry–Perot interference. A closed-form relationship between the frequency-dependent group velocity and the FPR free spectral range (FSR) is established, enabling inverse determination of mechanical or environmental perturbance from the FPR fringe spectrum. By extending FPR-based fringe analysis to dispersive mechanical waveguides, this work introduces a theoretical framework for implementing dispersive mechanical waveguide-based FPR sensors. Full article

Research on the surrounding rock stability and its control during gob-side entry driving with a narrow pillar (GSED-NP) is of critical importance for ensuring safe mining operations and efficient production in underground coal mines. This work proposed a thick anchored dual-layer locking (TADL) supporting technology by analyzing the big and small voussoir beam (BSVB) weighting characteristics in GSED-NP as well as engineering implementation and on-site validation. First, field surveys and numerical simulation show that the 9.60 m and 10.65 m thick medium grained sandstone in the overlying strata were fractured in the coal body of the next face, and formed BSVB structure after rotation, subsidence, and re-hinging. Under the effect of stress transfer of BSVB structure, the lateral abutment pressure distribution is characterized by internal and external stress field (IESF) distribution. Second, numerical calculation was carried out according to the above characteristics. Third, a supporting technical scheme was formulated and implemented, and the field monitoring data proved the ideal outcome. Finally, the influence of the critical fracture location of the main roof on the stress distribution was discussed, and it is thought that the stress distribution is mainly related to the main roof fracture location which has a critical range on the stress transfer. This research can provide a reference for the surrounding roadway control under similar conditions. Full article

Honeycomb composites are extensively utilized in critical applications where weight is a concern in a structure, due to their high efficiency in stiffness-to-weight ratio. In this study, the effective elastic orthotropic behavior of honeycomb composites is analytically expressed as a function of the elastic properties of the constituent sheet material and the geometric parameters of the representative unit cell. Closed-form expressions based on classical beam theory and plate theory are evaluated and systematically validated against a high-fidelity finite element analysis FE-based homogenization benchmark constructed from a representative unit cell with in-plane periodic kinematic constraints. The analytical predictions exhibit generally good agreement with the FE results, with plate-theory-based formulations capturing most elastic constants with higher accuracy. To further support the fidelity of the numerical benchmark, the predicted normalized in-plane moduli are additionally compared with published experimental measurements for aluminum honeycombs, demonstrating close agreement for representative specimens. To quantify the influence of the geometric parameters, a Taguchi-style design-of-experiments (DOE) study reveals that relative density and internal cell angle jointly govern the majority of elastic moduli and Poisson’s ratios, while cell height plays a minor role. Furthermore, dedicated parametric studies confirm the cubic thickness-scaling of in-plane moduli (E₁, E₂, G₁₂), demonstrating the dominant role of bending-controlled deformation. Together, these results establish a validated, high-fidelity FE homogenization benchmark for assessing analytical formulations and providing design-level constitutive data for optimizing honeycomb core sandwich structures. Full article

Objectives: Hidradenitis suppurativa (HS) is a chronic, inflammatory skin disease that significantly impairs patients’ quality of life, especially in its moderate to severe forms. Traditional treatments, including antibiotics, hormonal therapies, and surgery, often fail to provide long-term relief in such cases. This study aims to explore the role of radiotherapy, particularly with the use of 3D printing technology to create personalized boluses and applicators, as an adjunctive treatment for refractory HS. A systematic review of published studies was conducted to assess the efficacy of radiotherapy in managing HS, with a specific focus on studies using 3D printing technology to create customized boluses and applicators. Methods: Publications from databases such as PubMed, Scopus, and Google Scholar were analyzed for studies detailing radiotherapy techniques, dosing regimens, and the use of 3D-printed devices in HS treatment. The studies selected included those employing both external beam radiotherapy and brachytherapy, with particular emphasis on patient outcomes and adverse effects. Results: The reviewed studies highlighted a growing body of evidence supporting the use of radiotherapy for HS, especially in severe or treatment-resistant cases. The use of 3D-printed boluses and applicators in radiotherapy demonstrated significant improvements in treatment precision and patient comfort. Personalized treatment plans allowed for more accurate dose distribution, minimized air gaps, and reduced exposure of healthy tissue. No major long-term toxicity was reported across the majority of studies. Conclusions: Radiotherapy, particularly when combined with 3D printing technology, presents a promising treatment option for patients with severe or refractory HS. Customizable boluses and applicators enhance the precision of radiotherapy by conforming to irregular skin surfaces, thereby improving dose conformity and reducing side effects. Despite the positive results, further research is needed to assess the long-term safety and clinical feasibility of this approach. The integration of 3D printing in radiotherapy could significantly improve treatment outcomes, offering a more personalized and effective therapeutic option for HS patients. Full article

A hydroelastic theoretical model is formulated, and an analytical solution is obtained to investigate the interaction between wave-opposing current loading with compression and a moored floating flexible platform within the framework of Timoshenko–Mindlin beam theory based on the linearized wave and small structural response. By employing the matching technique and orthogonal mode-coupling relation, the closed-form analytical solutions for structural displacement, as well as shear force and bending moment, are obtained. The wave blocking and buckling limit in the presence of compressive force against an opposing current is determined via group and phase velocities from the dispersion relation in the context of the Timoshenko–Mindlin beam theory. Further, the combined influence of opposing current, compressive loading, and key structural design parameters on the hydroelastic response are examined. The results demonstrate that opposing currents and compressive forces can significantly alter the hydroelastic response, highlighting their critical role in structural engineering analysis. The current analysis provides a comprehensive analytical framework that can support the design and optimization of floating flexible platforms in the presence of opposing currents and compressive loads in complex marine environments. Full article