Search Results (198)

This study investigates the influence of key parameters—vehicle speed, weight, loading lane, and pavement roughness—on the Dynamic Amplification Factor (DAF) and ride comfort of a beam–arch composite continuous rigid-frame bridge under vehicle–bridge coupling. A six-span bridge is analyzed using a spatial beam-element model in ANSYS and a typical three-axle vehicle model is adopted to conduct the coupled dynamic response analysis. Based on the modal and structural characteristics of this bridge, key response indices are selected, including vertical displacement and bending moment at midspan, longitudinal displacement and bending moment at pier top, arch crown displacement, and tensile force in the long hanger. Control sections are identified in Span 4 (midspan, arch crown, long hanger) and at the top of Pier 16. The results demonstrate that pavement roughness significantly influences ride comfort, with the root mean square (RMS) value varying up to 107%, whereas the loading lane shows a negligible effect. Vehicle speed effects are divided into two distinct regimes: at 60 km/h and within 70–90 km/h, with dynamic responses in the higher speed range approximately 22% greater. Increasing vehicle weight raises the peak dynamic response by up to 77.68%, but does not lead to a proportional increase in DAF. Transverse loading eccentricity has a more pronounced impact on vertical bridge responses (>20% change) than on longitudinal responses (<10% change). Deterioration in pavement roughness elevates both dynamic response and DAF, with maximum increases reaching 27.97% and 28%, respectively. Full article

Low-orbit thermal infrared bidirectional whisk-broom imaging offers wide-swath coverage and high spatial resolution for monitoring moving targets such as aircraft, but large scan angles and terrain undulation cause non-rigid geometric distortion and radiometric inconsistency between forward and backward scans. These effects generate strong clutter in difference images and degrade small and weak target detection. To address this problem, we propose an infrared small target detection method that fuses accurate registration and weighted difference. First, we propose a hybrid multi-scale registration algorithm that achieves coarse affine registration through sparse feature–point matching and then iteratively corrects nonlinear deformations by integrating a global grayscale-driven force with a local sparse-feature-guided force, yielding a registration error of 0.3281 pixels. On this basis, a multi-scale weighted convolutional morphological difference algorithm is proposed. A novel dual-structure hollow top-hat transform is constructed to accurately estimate the background, and a multi-directional convolution mechanism is introduced to effectively suppress anisotropic edge clutter and enhance target saliency. Experiments on SDGSAT-1 thermal infrared bidirectional whisk-broom data show an SCRG of 18.27, and a detection rate of 91.2% when the false alarm rate is below 0.15%. The method outperforms representative competing algorithms and provides a useful reference for space-based aerial moving target detection. Full article

A static load test, single-wheel load test, and cyclic-wheel load test were carried out on large-thickness flexible base-layer and semi-rigid base-layer asphalt pavement structures by a multifunctional wheel-load testing machine. A comparative analysis was conducted on the influence and mechanism factors, such as load strength, test temperature, and load rate, on the stress and strain at the top and bottom of two asphalt pavement structures. The results show that in the interval of 1.3 MPa ≥ load intensity ≥ 0.5 MPa, with the increase of static load, the transverse strain and vertical strain at the top and bottom of the base layer of large-thickness flexible base-layer asphalt pavements increase slowly with a slight increase; the transverse strain and vertical strain at the top of the base layer of large-thickness semi-rigid base-layer asphalt pavements are more sensitive to heavy traffic load; and the transverse strain and vertical strain generated at the bottom of the base layer increase uniformly with the enhancement of static load. Under the action of a single-wheel load, the transverse and vertical strain generated at the top and bottom of the base layer of large-thickness flexible base-layer and semi-rigid base-layer asphalt pavements are alternately tensile and compressive, mainly compressive strains, while large-thickness semi-rigid base-layer asphalt pavement exhibits more complex strain changes. Full article

Vertical prestressing is critical for shear resistance in long-span PC continuous rigid-frame bridges, yet existing design methods rely on the inaccurate superposition of single-tendon stress fields, neglecting mechanical interaction between adjacent tendons. This study derives the first closed-form elastic analytical solution for the vertical normal stress field under two interacting prestressing tendons, explicitly capturing the coupling term. Validated against high-fidelity Finite Element Analysis (FEA), the solution achieves a Mean Absolute Percentage Error (MAPE) below 6.8%, outperforming conventional superposition methods by 6.8–17.7 percentage points. The analysis reveals a transition from diffusion-dominated to superposition-dominated stress regimes and establishes a predictive linear relationship between tendon spacing and the depth of the prestressing blind zone. The section at one-fourth of the web height below the top edge is identified as the critical control section, leading to a proposed maximum spacing limit of 0.34 times the web height to ensure a stress uniformity coefficient greater than 0.95. This criterion represents a 13.3% increase over empirical rules and a 27.5% increase over the JTG 3362-2018 limit, enabling estimated savings of 52,000 CNY per typical four-span bridge while maintaining structural safety. This represents a 13.3% increase over empirical rules and a 27.5% increase over the limit in JTG 3362-2018, enabling estimated savings of 52,000 CNY per typical four-span bridge while maintaining structural safety. Full article

Turbulent structure and diffusion over different underlying surfaces are fundamental to understanding mass and momentum exchange in the atmospheric boundary layer. This study investigated these processes over six distinct surfaces—flat plate, sand, grass, small gravel, large gravel, and vegetation—through wind tunnel experiments combined with high-frequency velocity measurements. Quadrant analysis, Reynolds stress decomposition, and turbulence kinetic energy budget analysis were employed to elucidate the mechanisms driving variations in diffusion coefficients. The results reveal two distinct turbulence generation regimes: over rigid surfaces (flat plate, sand, gravel), turbulence is primarily generated by roughness elements, whereas over canopy surfaces (grass, vegetation), canopy-induced shear and wake dynamics dominate. Consequently, the vertical profiles of turbulent diffusion coefficients K_x and K_z exhibit markedly different patterns across surface types. For rigid surfaces, diffusion coefficients peak near the surface and decay monotonically with height. For canopy surfaces, diffusion coefficients reach their maximum at the canopy top, reflecting the dual influence of canopy-induced shear and energy dissipation within the canopy. These findings provide a mechanistic understanding of surface-induced variability in turbulent diffusion processes and offer quantitative parameterizations that can improve pollutant dispersion modeling over complex terrain. Full article

The steel frame-shear wall composite system has excellent lateral resistance performance in prefabricated steel structure buildings. However, the traditional steel plate concrete shear wall is prone to early buckling of the steel plate and concentrated interface damage under cyclic loading, which limits its energy dissipation capacity. This study presents a steel plate-enhanced reinforced concrete shear wall (SPRCSW) with an internal corrugated steel plate and double-layer steel mesh working together and conducts a selection study based on finite element analysis. Under the same design conditions, the peak bearing capacity in the positive and reverse directions of the SPRCSW is increased by approximately 55.4% and 46.9%, respectively, compared to the ordinary reinforced concrete shear wall, with a ductility coefficient reaching 6.08. The stiffness decline is mild, and the hysteretic curve is complete. Then, this paper forms an SR-SPRCSW composite structural system by combining the new shear wall with a steel frame using semi-rigid joints. Through the comparison of the finite element analysis and low-cycle reverse loading test results of the SR-SPRCSW structure, it is verified that the overall structural system shows good agreement in hysteretic response, skeleton curve characteristics, and failure mode under both research methods, with the peak shear bearing capacity error of less than 1% and the overall bearing capacity deviation controlled within 8%. On this basis, the key parameters of the semi-rigid joints in the SR-SPRCSW structure are analyzed. The results show that the strengthening of the “top and bottom + double web” angle steel joint can raise the peak bearing capacity of the SR-SPRCSW structure by approximately 26.1% and the yield displacement by approximately 29.5%; increasing the strength grade and diameter of high-strength bolts can heighten the initial stiffness and bearing capacity of the overall structure, but ductility slightly decreases; the thickness of the angle steel has a significant impact on the stiffness and deformation capacity of the structure, and a recommended range of values with better comprehensive performance is provided. The findings offer valuable insights for designing seismic-resistant semi-rigid steel frames with steel plate reinforced concrete shear walls and optimizing their parameters. Full article

This study numerically examined the anchorage mechanism of rebar hooks under varying straight development lengths, including high stress levels. A three-dimensional rigid body spring model (3D RBSM) was used for the investigation and successfully reproduced the experimental pullout test stress–slip relationships and inner–outer strain distributions for the rebar hook with and without a straight development length. A validated numerical model was used to assess local concrete stresses and internal crack propagation, enabling a clear interpretation of how straight development length influences the anchorage mechanism. The results revealed that increasing straight development length increases stiffness, reduces rebar strains and concrete stresses in the hook region, promotes crack formation around the rebar surface, and forms maximum tensile stresses closer to the top surface, ultimately resulting in earlier splitting failure at high rebar stress levels. A comparison of cases with and without hooks shows that combining the hook with straight development length improves stress distribution, delays crack propagation, and increases anchorage by reducing tensile stress concentrations near the top surface and side faces. These findings provide valuable insights into the role of straight development length in the anchorage performance of 180-degree rebar hooks. Full article

Smart textiles require conductive materials that maintain electrical stability under repeated mechanical deformation and laundering while preserving textile-like flexibility. In this work, an elastic–rigid copolymer elastomer was designed as a polymer binder for washable conductive pastes used in wearable textile electronics. The copolymer was synthesized using polytetramethylene ether glycol (PTMEG), 3,3′,4,4′-benzophenonetetracarboxylic dianhydride (BTDA), and m-xylylene diisocyanate (XDI), enabling the incorporation of thermally stable imide segments and elastic polyurethane domains within a single polymer framework. By adjusting the molar ratio between rigid and soft segments, the resulting copolymer exhibited balanced tensile strength, Young’s modulus, and elastic recovery, outperforming a commercial thermoplastic polyurethane in mechanical performance. Silver-filled conductive pastes were prepared by dispersing 62 wt% micrometer-sized silver flakes into the copolymer matrix, achieving a bulk resistivity of 3.5 × 10⁻⁵ Ω·cm. The printed conductive films showed stable electrical resistivity under cyclic tensile deformation up to 20% strain. Washing durability was further evaluated following the AATCC 135 top-loading laundering standard. After 50 laundering cycles, the resistance increase remained within 2.8–5.5 Ω for knitted fabrics and 2.0–5.1 Ω for woven fabrics, indicating satisfactory electrical stability and adhesion to textile substrates. These results suggest that elastic–rigid copolymer binders are suitable for the development of wash-durable conductive pastes for wearable textile applications. Full article

To investigate the bearing characteristics of super-long and large-diameter cast-in-place piles with combined pile-end and pile-side post-grouting, double-load-box self-balanced static-load tests were conducted on two such piles of the Yellow River Bridge Project on Jiaoping Expressway both before and after grouting. This study aims to provide technical insights for the design and construction of similar pile foundations. The test results indicate that, after grouting, the ultimate bearing capacities of test piles SZ1 and SZ2 increased by 123.1% and 72.8%, respectively, with a significant reduction in pile top settlement under the same load level. Under each load level, the axial force of the pile shaft reaches its maximum near the upper load box, presenting a triangular distribution curve. Furthermore, the side frictions of SZ1 and SZ2 enhanced by 87.73% and 83.59%, respectively, after grouting, while their ultimate end resistances are improved by 362.6% and 120.6%. These findings demonstrate that post-grouting effectively optimizes the mechanical properties of the pile–soil interface and enhances the structural stiffness of the surrounding soil. Specifically, the grout hardens at the pile end, solidifies the sediment there, increases the density of the pile-end soil layer, and improves the bearing rigidity of the bearing stratum. This research validates the effectiveness of the combined pile-end and pile-side post-grouting technology in improving the bearing performance of super-long and large-diameter cast-in-place piles, providing valuable technical support for the safe and efficient construction of the Yellow River Bridge on the Jiaoping Expressway and similar engineering projects. Full article

Stretchable semiconductors capable of maintaining electrical performance under large mechanical deformation are essential for reliable wearable electronic devices. However, polymer semiconductors often suffer from electrical degradation when subjected to tensile strain. In this study, electrical stability under strain was achieved by using a rubber-blended poly(2,5-bis(2-octyldodecyl)-3,6-di(thiophen-2-yl)diketopyrrolo[3,4-c]pyrrole-1,4-dione-alt-thieno[3,2-b]thiophene) (DPPT-TT) polymer semiconductor based on a conjugated polymer/elastomer phase separation-induced elasticity (CONPHINE) structure. Unlike most previous studies on fully stretchable thin-film transistors (TFTs), which primarily report overall performance changes under mechanical strain, this work systematically identifies the dominant origin of electrical performance degradation through a stepwise electrical analysis encompassing the gate insulating layer, the semiconductor layer, and complete devices. Bottom-gate top-contact (BGTC) and bottom-gate bottom-contact (BGBC) devices were fabricated on rigid Si/SiO₂ substrates to examine the intrinsic properties of the DPPT-TT/styrene-ethylene-butylene-styrene (SEBS) CONPHINE film. As a result, the device exhibits 90% mobility retention even at 100% tensile strain applied parallel to the charge transport direction. Quantitative resistance analysis using the Y-function method reveals that variations in channel resistance play a dominant role in strain-induced performance degradation, whereas changes in contact resistance contribute only marginally. These findings demonstrate that stabilizing channel resistance, rather than contact resistance, is important for achieving high mobility retention under large mechanical deformation, thereby providing concrete and quantitative design guidelines for reliable stretchable TFTs. Full article

Unlike classical multi-layered micro-perforated panels (MPPs), which rely on sub-millimeter orifices for sound dissipation, we propose a multi-layered porous Helmholtz resonators absorber. It consists of alternately layered perforated porous material panels and perforated rigid panels with millimeter- to centimeter-scale orifices, primarily relying on porous materials for sound energy dissipation. Theoretically, perforated porous material panels are modeled as homogeneous fluid layers using double porosity theory, and the total surface impedance is derived through bottom-to-top impedance translation. A double-layered prototype was tested to validate the theoretical and numerical models, achieving near-perfect absorption peaks at 262 Hz and 774 Hz, with a subwavelength total thickness of 11 cm and a broadband absorption above an absorption coefficient of 0.7 from 202 Hz to 1076 Hz. Simulations of sound pressure, particle velocity, power dissipation, and sound intensity flow confirm that Helmholtz resonances in each layer enhance sound entry into resistive porous materials, causing absorption peaks. Parameter studies show this absorber maintains high absorption peaks across wide ranges of orifice diameters and panel thicknesses. Finally, an optimized triple-layer porous Helmholtz resonators absorber achieves an ultra-broadband absorption above a coefficient of 0.95 from 280 Hz to 1349 Hz with only 16.5 mm thickness. Compared with conventional MPPs, this design features significantly larger orifices that are easier to fabricate and less susceptible to blockage in harsh environments, offering an alternative solution for low-frequency and broadband sound absorption. Full article

The performance of metaheuristic algorithms in solving high-dimensional, non-convex optimization problems is intricately linked to the balance between global exploration and local exploitation. Inspired by biomimetic principles of swarm intelligence, this study evaluates the Educational Competition Optimizer (ECO), a human learning-inspired metaheuristic, and addresses its vulnerability to rapid population homogenization and premature convergence in complex landscapes. To bridge the gap between rigid hierarchical competition and flexible biological cooperation, we propose the Comprehensive Learning-Enhanced Educational Competition Optimizer (CL-ECO), which introduces a dimension-wise multi-exemplar social learning mechanism to the ECO framework. Analogous to cooperative information sharing in animal swarms, CL-ECO reconstructs search trajectories by learning from different peers across decision variables, thereby promoting population diversity and adaptive exploration. Rigorous validation on the CEC 2017 benchmark suite demonstrates that CL-ECO achieves statistically superior convergence accuracy and robustness compared to seven state-of-the-art algorithms, securing the top Friedman rank (1.5862). Furthermore, the practical utility of CL-ECO is substantiated through a complex reservoir production optimization case study, where it outperforms the baseline algorithm in NPV maximization, proving its capability in managing complex, real-world engineering constraints. Full article

Building information modeling (BIM)-based interior design automation remains constrained by a semantic mismatch: engineering constraints are explicit and categorical, whereas aesthetic style is implicit, contextual, and difficult to formalize. As a result, existing systems often overfit local visual similarity or rely on rigid rules, producing recommendations that drift stylistically at the scene level or conflict with professional design logic. This paper proposes KsDesign, a neuro-symbolic framework for interpretable, retrieval-based BIM scene completion that unifies visual style perception with explicit design knowledge. Offline, KsDesign mines category-level co-occurrence and compatibility patterns from curated designer-quality interiors and encodes them as a weighted Furniture-Matching Knowledge Graph (FMKG). Online, it learns style representations exclusively from BIM-derived 2D renderings/projections of 3D family models and BIM scenes, and applies a knowledge-guided attention mechanism to weight contextual furniture cues, synthesizing a global scene-style representation for candidate ranking and retrieval. In a Top-3 (K = 3) evaluation on 10 BIM test scenes with a 20-expert consensus ground truth, KsDesign consistently outperforms single-modal baselines, achieving 86.7% precision in complex scenes and improving average precision by 23.5% (up to 40%), with a 15.5% average recall increase. These results suggest that global semantic constraints can serve as a logical regularizer, mitigating the local biases of purely visual matching and yielding configurations that are both aesthetically coherent and logically valid. We further implement in-authoring explainability within Revit, exposing KG-derived influence weights and evidence paths to support rationale inspection and immediate family insertion. Finally, the knowledge priors and traceable intermediate representations provide a robust substrate for integration with LLM-driven conversational design agents, enabling constraint-aware, verifiable generation and interactive iteration. Full article

In the rapidly urbanizing Global South, megacities face a perplexing “paradox of idleness”: acute land scarcity in the urban core coexisting with inefficient rural homesteads in the hinterland. Using Shanghai as a representative case, this study integrates spatial autocorrelation analysis with Geographical Detector modeling to quantify the spatial differentiation patterns and driving mechanisms of this phenomenon. The results reveal a distinct core-periphery gradient, with vacancy density increasing from the inner suburbs to the remote hinterland. Four regional typologies were identified: dispersed-inefficient, high-density accumulation, sparse-stable, and intensive-efficient. Quantitative analysis identifies demographic aging and low agricultural efficiency as dominant drivers. Counter-intuitively, the study finds that top-down institutional pilots alone exert a negligible direct impact. Instead, interaction analysis confirms a significant policy-bundling effect, in which institutional tools promote revitalization only when coupled with economic and locational incentives. These findings expose a mechanism of “involuntary vacancy” trapped by institutional rigidity, distinct from the market-driven abandonment seen in shrinking or remote Western contexts. Consequently, a gradient-based governance framework is proposed to transition from “one-size-fits-all” regulation to targeted spatial restructuring pathways. Full article

A well-structured urban park system (UPS) is crucial for optimizing urban spatial layout and improving the quality of the human living environment. In response to the tendency of current planning to prioritize quantitative indicators while overlooking the relational structure arising from the collective spatial configuration of parks, this study introduces Social Network Analysis (SNA) to evaluate the spatial structure of Shanghai’s park system by constructing a service-coverage overlap network. The findings reveal the following: (1) Parks with high degree centrality are concentrated in high-density urban core areas due to service overlap, whereas large suburban parks with high betweenness centrality function as critical bridging hubs, reflecting a polycentric structure. (2) There is a discernible discrepancy between these emergent network tiers and the statutory park hierarchy, highlighting a tension between bottom-up spatial patterns and top-down planning frameworks. (3) Stability simulations indicate a dual character of the system, where the network topology is vulnerable to attacks yet functionally resilient to failures due to spatial redundancy, suggesting that a decline in service quality may precede the loss of basic accessibility. This study demonstrates the value of SNA in diagnosing park system structure, identifying key nodes, and assessing system resilience. The insights advocate for planning approaches that transcend rigid hierarchical frameworks, integrate the actual functional roles of parks, and protect structural hubs, thereby enhancing systemic resilience and promoting equitable service provision. Full article