Search Results (6,257)

Powder Bed Fusion-Laser Beam/Polymer (PBF-LB/P) is a key additive manufacturing technology widely used in aerospace, but its process parameters are difficult to optimize for thermoplastic composites due to poor powder flowability and unstable melting regions. To address this challenge, this paper develops discrete element and finite element models to systematically determine the PBF process window for both powder spreading and sintering stages, with verified reliability. In the spreading stage, the powder layer performance is evaluated through surface profile, density, and uniformity. The effects of reinforcement phase, spreading speed, and layer thickness are analyzed, establishing reasonable spreading parameter windows. It is found that the optimal layer thickness for PEEK powder is determined to be 0.13 mm, while that for PEEK/CF composite powder is 0.12 mm. At the optimal layer thickness, the powder bed exhibits desirable properties, which minimize its adverse influence on the sintering process and serve as a prerequisite for subsequently establishing the sintering process window. For the sintering stage, sufficient sintering constraint criteria are established, and a systematic determination method is proposed. By analyzing microscopic sintering mechanisms and characterizing the effects of laser power, scanning speed, and hatching space on melt pool dimensions and temperature, a reasonable sintering process window can be efficiently determined. It is found that within the process window, the PEEK specimens achieved a maximum relative density of 99.31% and exhibited a tensile strength 13.1% higher than that of specimens processed outside the window, demonstrating a clear superiority. Full article

The effects of practical parameters on the flexural behavior of reinforced concrete (RC) beams strengthened with steel strand mesh-reinforced engineered cementitious composite (ECC) were investigated, based on the finite element (FE) simulation. First, an FE model for strengthened RC beams was developed. The model was validated by comparing it with existing experimental data. Subsequently, the model was employed for parametric analysis on the flexural performance of the strengthened beams. The results showed that steel strand mesh-reinforced ECC significantly enhanced the flexural capacity, stiffness, and ductility of the RC beams, with improvements ranging from 7.81% to 61.84%, 6.35% to 40.90%, and 5.92% to 50.16%, respectively. As the reinforcement ratio of longitudinal steel strand, ECC thickness, and cracking strength increased, the flexural capacity increased. However, an increase in the reinforcement ratio of the longitudinal steel bars and the section height of the RC beam reduced the improvement in flexural capacity. The increase in the thickness of the strengthening layer and reinforcement ratio of the longitudinal steel strand enhanced the improvement of stiffness. Differently, an increase in the reinforcement ratio of longitudinal steel strand, concrete strength, and height of the RC beam diminished the improvement of stiffness. The enhancement of ductility increased with the concrete strength. Finally, formulas for calculating the bearing capacity and stiffness of RC beams strengthened with steel strand mesh-reinforced ECC and the limit of steel strand quantity were proposed. These formulas agreed well with experimental and numerical simulation FE results. Full article

Grounded in the principles of wave dynamics, this study employs the wave function expansion approach to mathematically describe how plane P- and SV-waves scatter around a composite tunnel lining embedded in an unbounded medium. To establish the transient analytical framework for the dual-layer structure subjected to blast excitations, we integrate Fourier integral transforms alongside the Heaviside step and Dirac delta functions. We systematically analyze how the tunnel’s transient dynamic stress concentration factor (DSCF) responds to variations in the shear modulus ratio, as well as the specific characteristics of the incoming waves (i.e., wave type and dimensionless pulse duration). Furthermore, a seismic mitigation strategy featuring a “soft-exterior, rigid-interior” configuration is theoretically explored. The analytical outcomes theoretically indicate that short-duration transient waves provoke severe dynamic stress concentrations within the lining, with SV-waves posing a markedly greater threat to structural integrity than P-waves. Analyses reveal that the peak dynamic stress concentration (DSCFmax) primarily localizes at the tunnel’s crown and invert. Interestingly, altering the pulse duration does not significantly shift this spatial distribution pattern. Ultimately, analytical results suggest that adopting the “soft-exterior, rigid-interior” design and optimizing the thickness of the primary support can substantially alleviate these stress concentrations, providing preliminary theoretical guidance for vibration attenuation. Full article

Background: Lipedema is a chronic disorder of subcutaneous adipose tissue characterized by symmetrical fat accumulation in the extremities, pain, and orthostatic edema. Objectives: This study aimed to assess whether high-resolution cutaneous ultrasound can detect measurable tissue-level changes in subcutaneous tissue over six months. Methods: A retrospective, single-center, real-world longitudinal observational cohort study was conducted in 60 women with lipedema followed at three timepoints (baseline, 3 months, 6 months). High-resolution ultrasound (18–20 MHz) measured subcutaneous and dermal thickness at standardized anatomical sites. Results: All primary ultrasound parameters decreased significantly over six months of conservative multicomponent management, which included individualized nutritional counseling and physical activity. Medial proximal thigh subcutaneous thickness declined by 18.7% (48.2 to 39.2 mm; p < 0.001). Edema prevalence fell from 100% to 55.0%. Echogenicity improved significantly between 3 and 6 months, suggesting a delayed structural remodelling effect distinct from early volumetric reduction. Ultrasound reductions were inversely correlated with weight loss, suggesting that ultrasound captures tissue-level information not fully reflected by anthropometric measures alone. Conclusions: Standardized cutaneous high-resolution ultrasound detected consistent tissue-level modifications over six months of routine clinical follow-up, capturing changes beyond anthropometric measures and representing a candidate monitoring tool warranting evaluation in controlled study designs. Full article

Piezoelectric pressure sensors for dynamic monitoring face a trade-off between charge output and measurement range, and existing high-sensitivity designs are largely confined to narrow ranges. This study presents a composite layered piezoelectric pressure sensor in which a 316L stainless-steel diaphragm drives a centrally suspended PZT-5H wafer supported by a perforated alumina gasket, with the wafer thickness and cavity radius optimized under a 10 MPa full-scale stress constraint. Over 0–10 MPa, quasi-static calibration gave a highly repeatable quadratic pressure–charge relationship ($R^2=0.99995$) with a maximum residual below 1% FS. The sensitivity is pressure-dependent: the secant sensitivity increased monotonically from 3.16 pC/kPa at 1 MPa to 5.36 pC/kPa at 10 MPa, reflecting a stress-stiffening response rather than a measurement tolerance band. The output deviation remained within 3% from 25 °C to 150 °C. Shock-tube testing yielded a resonance of ∼50 kHz and a mutually consistent 10–90% leading-edge interval of 10.12 $\mathsf{\mu }$s. Combining high charge sensitivity over a wide 0–10 MPa range with a fast transient response and stable operation up to 150 °C, the proposed sensor is suited to dynamic pressure-pulsation monitoring in fluid-power and thermal and power-plant fluid systems. Full article

Background/Objectives: Direct compression of cohesive powders is often challenged by poor flow, blend heterogeneity, and variable tablet quality. This study investigated how mixing time, fill level, and rotational speed affect the blending behavior and tablet properties of a sodium naproxen–calcium carbonate formulation and aimed to define a robust operating space for process optimization. Methods: Powder blends were prepared in a V-type mixer according to a central composite design and analyzed using response surface methodology. The effects of the three process parameters were evaluated through powder flow descriptors (angle of repose, angle of fall, and angle of difference) and tablet quality attributes, including thickness, mass, active pharmaceutical ingredient (API) content, and abrasiveness. Statistical significance was assessed by ANOVA, and a design space was established using predefined acceptance criteria. Results: Mixing time significantly affected the angle of difference, indicating changes in blend cohesiveness and flow uniformity, whereas fill level significantly influenced API content. Tablet thickness and mass remained relatively stable across the tested conditions. Abrasiveness showed the greatest numerical variability and tended to increase at high fill levels combined with short mixing times. Response surface analysis identified two acceptable operational regions that satisfied the quality criteria for blend homogeneity, API content, and abrasiveness. Conclusions: The studied process variables exerted selective, property-specific effects rather than uniform changes across all quality attributes. The results support QbD-based process design for cohesive direct-compression systems and show that robust tablet manufacture can be achieved within more than one operating window. Full article

Deep excavations in composite “soft upper-hard lower” strata present significant deformation control challenges due to strong stiffness contrasts. This study investigates the deformation characteristics of a deep metro foundation pit in Jinan under zoned excavation conditions. A three-dimensional finite element model was developed to simulate the staged excavation process, and the spatiotemporal evolution of diaphragm wall deflection and ground settlement was analyzed, with particular focus on the influence of soft soil thickness. The results show clear spatial variation, with maximum lateral wall displacements exhibiting a typical “bulging” profile along the longer sides of the pit. The normalized maximum wall displacement (δ_hm/H_e) ranges from 0.051% to 0.090%, while the ratio of maximum ground settlement to wall displacement is 0.35–0.57, indicating lower deformation levels compared to homogeneous soft soils. As the soft soil thickness increases, the wall displacement increases and the location of maximum displacement migrates downward and outward. Under the investigated conditions, a transition toward a “kick-out” deformation mode occurs when the soft soil thickness reaches the transition range identified in the parametric analysis. These findings provide a quantitative basis for deformation prediction and support design in composite strata. Full article

Thin, steeply dipping orebodies hosted in kaolinized altered fault zones are difficult to mine safely because of weak rock mass integrity, water sensitivity, and limited self-supporting capacity. This study investigates the F20 ore-bearing altered structural zone at Changtai Mining and develops an artificial floor design for downward drift-and-fill mining. Engineering geological characterization, rock mass quality evaluation, mechanical analysis, and three-dimensional numerical simulation were combined to assess floor-bearing requirements and regional recovery stability. The results show that the wall rocks are grade III, whereas the ore-bearing altered zone is grade IV and represents the controlling weak component. For the preferred 3.5 m × 3.5 m drift, an equivalent artificial floor bearing thickness of about 1.0 m is required. Numerical evaluation indicates that supported drifts remain stable, but crosscut–drift intersections are the main deformation and damage concentration zones. A representative 0.5 m drift offset significantly weakens the load-transfer path of the floor–rock system. The proposed vertically aligned, short drift, rapid backfill scheme with a reinforced composite artificial floor provides a practical basis for safe recovery of weak kaolinized altered orebodies. Full article

Patterned and multilayer materials used in advanced technologies exhibit complex three-dimensional compositional architectures in which buried interfaces and elemental gradients critically influence performance. However, most non-destructive analytical techniques remain largely surface-sensitive, limiting access to subsurface information in opaque systems. In this work, we present a novel framework for non-destructive three-dimensional elemental characterization based on the integration of artificial neural networks with ion beam analysis techniques, namely, Particle-Induced X-ray Emission (PIXE) and Elastic Backscattering Spectrometry (EBS). The proposed approach enables the reconstruction of depth-resolved 3D elemental distributions by combining complementary spectral information with data-driven analysis. The methodology is demonstrated on a GaSb thermophotovoltaic device featuring multilayer metallic contacts, where the elemental distribution beneath thick gold layers is revealed for the first time. The neural network approach overcomes limitations associated with low counting statistics in pixel-resolved spectra, enhancing sensitivity and enabling reliable classification of compositional features. The fusion of PIXE-derived lateral information with EBS-based depth profiling enables full three-dimensional visualization and quantitative and qualitative mapping of elemental distributions. Beyond the specific case study presented, this approach provides a general and scalable strategy for 3D compositional analysis of complex materials, including systems containing both heavy and light elements. The results highlight the potential of combining advanced data-driven methods with ion beam techniques to expand the capabilities of non-destructive characterization, with broad applicability in energy, electronics, and functional materials. Full article

This study investigated the rheological, structural, barrier, mechanical, optical, and thermal properties of composite edible films based on citrus pectin and vegetable purées derived from broccoli, cauliflower, pumpkin, carrot, and their blends. Film-forming formulations were characterized in terms of rheological behavior, thickness, microstructure, gas and water vapor permeability, optical and mechanical properties, water contact angle, and thermal stability. The incorporation of vegetable purées significantly modified the properties of the pectin-based matrices. All film-forming solutions exhibited non-Newtonian shear-thinning behavior, with flow behavior index values below unity. The addition of vegetable purées markedly increased viscosity and flow resistance, indicating the formation of more structured systems with stronger intermolecular interactions. Apparent viscosity increased from 0.19 Pa·s in the control sample to 1.41 Pa·s and 1.19 Pa·s in the broccoli (B) and broccoli–cauliflower (B-CF) formulations, respectively, while the consistency coefficient increased from 0.29 to 51.38 Pa·sⁿ. Composite films exhibited lower water contents (0.090–0.114 gH₂O·g_d.m.⁻¹) than the control film (0.179 gH₂O·g_d.m.⁻¹) and were thicker (170–282 μm) than the pure pectin film (125 μm). Barrier analysis revealed a reduction in water vapor permeability from 18.99·10⁻¹⁰ to 10.74–14.69·10⁻¹⁰ g·m⁻¹·s⁻¹·Pa⁻¹ and a decrease in carbon dioxide permeability from 21.95 to 10.47–17.91 GRT. The carrot-containing film exhibited the highest tensile strength (62.17 MPa), whereas the pumpkin–carrot film demonstrated the most favorable combination of barrier and mechanical properties, including the lowest oxygen permeability (6.95 GRT), low water vapor permeability (10.74·10⁻¹⁰ g·m⁻¹·s⁻¹·Pa⁻¹), and high tensile strength (51.02 MPa). Thermogravimetric analysis revealed similar three-stage degradation profiles for all samples, while vegetable incorporation modified moisture release and increased residual mass. The obtained results confirmed the research hypothesis that vegetable-processing by-products can serve as valuable structure-forming components of pectin-based composite films and that interactions between vegetable-derived biopolymers and citrus pectin improve the mechanical, barrier, and functional properties of the resulting materials. Among the tested formulations, the pumpkin–carrot film demonstrated the greatest potential for further development as a biodegradable packaging material. The utilization of vegetable by-products in pectin-based films represents a sustainable approach supporting circular economy principles and the development of environmentally friendly packaging systems. Full article

This study develops a comprehensive analytical framework to predict the flexural behavior of externally prestressed steel–concrete composite I-girders (EPCIBs) subjected to positive bending. The analytical model is formulated using strain compatibility and internal force equilibrium and accounts for elastic–plastic behavior of concrete, structural steel, and external tendons. Validation against three independent experimental programs demonstrated strong accuracy, with differences in ultimate moment within 5–8%, mid-span deflection within 6–10%, and tendon stress increments within less than 6% compared with measured results. Additional validation against nonlinear ABAQUS finite element (FE) models confirmed similar accuracy, with ultimate moment discrepancies generally below 8%. A comprehensive parametric study quantified the sensitivity of EPCIB behavior to span length, shear-span ratio, prestressing level, concrete slab properties, and steel-section geometry. Increasing the initial prestressing force from 160 kN to 300 kN increased the ultimate moment capacity by 10–15% and reduced service-level deflection by 18%. Increasing slab thickness from 60 mm to 120 mm enhanced capacity from 230 kN·m to 380 kN·m (a 65% increase), while increasing slab width from 600 mm to 1200 mm produced a moderate 10–12% capacity gain. Enhancing steel section dimensions showed the highest influence: increasing bottom-flange width from 200 mm to 300 mm increased strength by 30–35%, increasing bottom-flange thickness from 8 mm to 14 mm improved capacity by 55–60%, and increasing web depth from 200 mm to 400 mm more than doubled the flexural capacity (up to 150% increase, reaching 780–800 kN·m). Web-thickness variations (4–8 mm) produced smaller gains of 25–30%. Full article

Here, we report a facile, reproducible, fully aqueous route to fabricate citric acid–crosslinked poly(vinyl alcohol) (PVA) composite hydrogels incorporating polyaniline nanoparticles (PANI-NP) of ca. 200 nm mean diameter and polydispersity index (PDI) below 0.2, synthesized directly in water. Nanocomposites incorporating 2, 3, and 5% w/w PANI-NP were thoroughly characterized in terms of thickness (obtaining materials of approximately 500 µm), morphology, spectroscopic and thermal properties, surface properties, swelling behavior, and nanomechanical behavior assessed by atomic force microscopy (AFM) operating in Peak Force Quantitative Nanomechanical Mapping (PF-QNM) mode. Incorporation of PANI-NP progressively increased the elastic modulus of the composites (from 794 MPa for neat PVA to values exceeding several GPa at 3–5% w/w loading) and modified swelling capacity to values as low as 140% (from 247% for neat PVA), reflecting nanoscale interfacial interactions. Notably, the hydrogel composites exhibited significant photothermal activity under low-power near-infrared (NIR) LED irradiation (850 nm, 90 mW cm⁻²), achieving temperature increases of up to 13.7 °C even at low PANI-NP loadings, with a stable and reproducible response across multiple heating–cooling cycles. Overall, this work establishes a straightforward, water-based fabrication platform for structurally stable, photothermally active nanocomposites with promising potential in light-responsive smart material applications. Full article

The development of sustainable flame-retardant polymer composites is important for expanding the practical use of bio-based plastics while reducing reliance on petroleum-derived and halogenated materials. In this work, biodegradable polylactic acid (PLA) composites were prepared using raw wood-derived biochar as a degradable carbon-based filler and magnesium hydroxide (MH) as a halogen-free flame-retardant additive. PLA/Biochar/MH composites were prepared by melt compounding and compression molding, followed by systematic evaluation of their structural, thermal, flame-retardant, mechanical, and stability-related properties. The flame-retardant performance, evaluated by limiting oxygen index (LOI) and UL-94 (UL: Underwriters Laboratories) vertical burning tests, was significantly enhanced by the combined biochar/MH system. Biochar alone slightly increased the LOI of PLA, while MH-containing composites exceeded the practical 21% LOI threshold, with PLA/Biochar20/MH20 achieving the highest LOI value of 26.2%. This improvement was attributed to char formation, heat absorption, gas dilution, and magnesium oxide-supported barrier formation. The composites also maintained reasonable dimensional stability after accelerated aging with thickness changes below 1%. Overall, this study demonstrates that combining biodegradable PLA with degradable biochar and halogen-free MH provides a promising sustainable strategy for developing flame-retardant PLA-based composites with improved residue formation and dimensional stability. Full article

We show that halide evaporation during melt growth of ${\mathrm{CsPbBr}}_3$ on polycrystalline FTO under partially open conditions drives discrete phase selection between the line compounds of the CsBr–PbBr₂ system, producing a sharp ${\mathrm{CsPbBr}}_3/{\mathrm{CsPb}}_2{\mathrm{Br}}_5$ bilayer instead of compositional grading. In situ optical imaging shows that solidification begins with nucleation and lateral growth of a planar ${\mathrm{CsPbBr}}_3$ single crystal while the melt layer is still thick enough to average over the FTO relief. As the crystal thickens, the residual melt then becomes inhomogeneous and unstable, producing a buried porous layer of faceted ${\mathrm{CsPb}}_2{\mathrm{Br}}_5$ grains with a characteristic in-plane spacing of 1–10$\mathsf{\mu }\mathrm{m}$). This morphology is consistent with a faceted Mullins–Sekerka-type instability under a non-conservative evaporative boundary condition. Beneath the single-crystal cap, the first-formed faceted islands are large and become progressively smaller as the advancing front approaches the FTO pyramids, while elevated ambient halide partial pressure suppresses the instability, consistent with diffusion–capillarity selection under decreasing residual melt thickness and steepening local gradients, modified by evaporative flux. Oxygen associated with microvoids or the oxide substrate enables a secondary reaction–diffusion pathway forming Pb–Br–O crystallites without altering the primary length scale. These results identify evaporation as an active control parameter coupling phase equilibria and interfacial stability in volatile halide melts. In the buried, porous bilayer morphology observed here, the secondary phases and porosity reduce the active ${\mathrm{CsPbBr}}_3$ volume and are expected to degrade scintillation through increased trapping, nonradiative recombination, and light scattering. Full article

Background: Universal-shade resin composites (USRCs) have gained popularity for their simplified shade-matching and reduced chairside time. However, their long-term performance under oral environmental stresses remains uncertain. This study aimed to compare the mechanical and esthetic properties of five commercially available single-shade resin composites and one conventional micro-hybrid resin composite (MHRC) after simulated aging. Methods: A total of 18 disc-shaped specimens (10 mm circular × 3 mm thick) were prepared from five USRCs (Omnichroma, Zenchroma, A-Uno, TRANSCEND, and Ecosite One) and one MHRC (Clearfil AP-X). The polymerized specimen disk was polished using 2500 grit SIC paper. The mechanical properties, Vickers microhardness (HV), elastic modulus (EM) and creep (CR), and the esthetic properties, color and gloss, were measured after 24 h water storage and after 1-year stimulated aging. The data was analyzed using SPSS 27.0 software. A significance level of α = 0.05 was used for all statistical analyses. Results: Both the aging and types of material showed a significant effect on the mechanical and esthetic properties of the tested resin composite materials. The MHRC showed a significantly higher HV and EM compared to the USRC (p < 0.05). The MHRC showed significantly lower CR compared to USRC (p < 0.05). The color retention of USRCs was comparable to the MHRC (p > 0.05) and some USRCs showed superior gloss values compared with MHRC (p < 0.05). The solubility of USREs were comparable to MHRC (p > 0.05) except A-Uno which showed significantly higher solubility compared to MHRC (p < 0.05). Conclusions: Within the limitations of this in vitro study, it concludes that the USRC possesses inferior mechanical properties compared with the convention MHRC. Thus, their use should be limited when strong and durable mechanical properties are required under heavy occlusal stress. The use of USRCs could be beneficial for achieving a highly esthetic outcome of the restoration that does not includes the area that comes under heavy occlusal stress. Full article