Search Results (416)

Porous Ti-6Al-4V lattice implants combine high specific strength, osseointegrative porosity, and compatibility with additive manufacturing, but conventional stiffness tuning through porosity, pore size, or unit-cell topology compromises biological pore requirements. This study presents a computational design framework in which structural kurtosis, the normalized interlayer offset between neighboring layers of a periodic cubic lattice, regulates elastic response at fixed global porosity. Closed-form expressions for the effective modulus are derived from first principles: the aligned configuration from the axial load-bearing area fraction, and the interlayer-shifted configuration from Euler–Bernoulli beam theory for guided-end connecting members. The derivations reproduce the Gibson–Ashby exponents n = 1 and n = 2, replacing the previously asserted power law, and a calibrated one-parameter interpolation bridges intermediate offsets. At 65% porosity, the effective modulus falls from 16.5 GPa in the aligned lattice to 2.64 GPa in the shifted lattice. A local-yield analysis based on peak bending curvature gives recoverable elastic strains of 1.37% at 89% porosity and 0.68% at 65%; the compliance-based values of 20.5% and 5.12% are kinematic upper bounds that neglect plastic hinging. A prefactor-free benchmark shows that obtaining the same 6.25-fold reduction by increased porosity alone would require 85.9–94.4% porosity and 0.17–0.28 mm struts, outside the osseointegration window and the resolution of selective laser melting. A GAN-CAD-FEA workflow reproduced the analytical moduli to within 7% across six design cases. All results are analytical and numerical; no specimens were fabricated or tested, and experimental validation remains required. Full article

To enhance the seismic performance of existing reinforced concrete (RC) buildings during retrofitting, the study introduces a new type of joint connected by a T-shaped steel plate. Compared with previous similar strengthening methods, this novel structure incorporating a post-installed beam not only effectively improves the mechanical properties of RC columns, but the connectors also further enhance the integrity of the post-installed beam. Low-cycle reversed loading tests on one cast-in-place specimen (RC) and three T-shaped steel plate connection specimens (TRC1–TRC3) were conducted to evaluate failure modes, hysteresis and skeleton curves, and energy dissipation. Results show that the novel joint failure concentrates at beam-end–column steel jacket weld seams and column-side steel plate cracking, while the core-zone concrete remains intact. Compared with RC, the novel joints TRC1–TRC3 exhibit bearing capacity variations of −1.03%~+15.80% and significantly enhanced energy dissipation. The thickness of the beam’s wrapped steel improves the carrying capacity and energy dissipation, whereas the T-shaped connector thickness has limited influence on bearing capacity. ABAQUS parametric analysis indicates that bolt quantity, concrete strength, and connector thickness have limited influence and serve as secondary design factors. These findings provide a theoretical basis for retrofitting existing buildings. Full article

Based on the rotary bending loading principle, an experimental investigation into the fatigue properties of 6201 aluminum alloy individual wires is presented. Considering the long design service life, high-cycle fatigue (HCF) behavior, and slender geometry (high length-to-diameter ratio) of these wires, a high-speed rotary bending fatigue test platform is custom-designed and constructed. The design mechanically maximizes the probability of fracture at the midpoint of the constant-cross-section specimen, even when considering clamping damage at the ends. Through mechanical derivation for the test platform, based on the beam bending theory and the finite element method, a quantitative relationship is established between the bending stress amplitude and the deflection angle at the clamped end. Using this platform, the fatigue lives of 6201 aluminum alloy individual wires under various bending stress amplitudes are tested, and the stress–life (S-N) curve is obtained. The developed experimental method and the reported fatigue data in this study provide essential experimental and material data for fatigue life prediction and engineering design of 6201 aluminum alloy individual wires. Full article

To accurately reveal the mechanism of interlayer separation, crack propagation, and progressive instability of vault strata in underground cavities in gentle-dipping bedded rock masses, this paper systematically elucidates the entire mechanical behavior of separation evolution, crack penetration, structural transformation, and step-by-step caving of vault bedded rock masses under excavation disturbance through a comprehensive integration of excavation unloading mechanical analysis, the Griffith strength criterion, and the dynamic transformation theory of beam structures. The results show that excavation induces radial unloading and circumferential stress concentration in the surrounding rock, and the vault rock mass preferentially undergoes interlayer separation along near-horizontal gentle-dipping bedding planes, forming a spatial zoning feature of gradient attenuation from bottom to top: a strong separation zone at the lower part, a transition zone in the middle, and a closed zone at the upper part. The vault strata undergo a cyclic dynamic structural transformation of cantilever beam–fixed-end beam–simply supported beam, exhibiting stepped fracturing and layer-by-layer caving failure characteristics. The fracture and caving range follow a three-stage evolution law of initial increase–peak–subsequent convergence and stabilization. Based on the elastic mechanics stress transformation relationship, a Griffith initiation criterion for surrounding rock of circular cavities under non-axisymmetric loads is derived and established, and mechanical calculation models of single beam and composite beam suitable for stratified rock masses are constructed, which quantitatively reveal the controlling effects of tensile strength of strata, lateral pressure coefficient, tunnel diameter, stratification thickness, and burial depth on crack initiation and failure degree. Verified by a city-gate-shaped tunnel numerical test and an practical engineering case of a large-scale underground tunnel in western China, the theoretical calculation results are in good agreement with the on-site failure morphology and numerical analysis results. The established separation criterion and mechanical model can effectively predict the initiation risk and stability critical conditions of vault strata. The research results can provide a theoretical basis and technical support for the stability evaluation, early warning, and optimal design of support structures of surrounding rock in underground engineering in gentle-dipping bedded rock masses. Full article

The rapid expansion of unmanned aerial vehicles (UAVs) applications in logistics, surveillance, and defense highlights the need for scalable and reliable energy delivery solutions. Conventional charging approaches constrain operational endurance and scalability, requiring frequent returns to base. This paper presents a laser-based wireless power transmission system designed to enable safe, contactless and efficient power transfer from ground to air. The main innovation of the work lies in the integration of an end-to-end architecture combining a high-power optical source, a hierarchical beam pointing framework with coarse and fine steering stages, and a receiver composed of sensing and energy conversion module mounted onboard the UAV. A further contribution is the adoption of a hybrid control strategy in which the reference position, obtained via RTK positioning, facilitates the coarse acquisition of the beam, whilst optical feedback from the receiver side enables precise alignment corrections. An experimental campaign is conducted to validate the main system functions under representative operating conditions. Beam propagation, pointing accuracy, and control response are characterized through laboratory and outdoor tests, including long-range spot measurements and closed-loop steering validation. The results demonstrate the technical feasibility of laser-based wireless energy transfer for UAV applications and provide an experimentally grounded framework for the development of persistent aerial operations in civil and defense scenarios. Full article

Task decomposition is a fundamental challenge in multi-agent collaborative maintenance systems, where unstructured natural language instructions must be precisely translated into logically coherent, executable sub-task sequences. This paper formulates task decomposition as a constrained optimal path search problem on a heterogeneous knowledge graph that encodes coal mine equipment topology, fault causality, and maintenance procedures. We construct a composite cost function that systematically integrates semantic similarity from graph neural network embeddings, relation-type weights, and structural path length, transforming instruction parsing into a mathematically tractable combinatorial optimization. The cost function is derived from the principles of shortest-path reasoning in knowledge graphs: the relational weights capture domain-specific association strengths, the semantic similarity term promotes contextually coherent chains, and the path-length penalty prevents unnecessarily long derivations. A multi-hop reasoning algorithm coupling heterogeneous graph convolution with beam search is developed to solve this problem efficiently, achieving high-quality approximate solutions while ensuring computational tractability. The reasoning process is inherently interpretable, as the optimal path directly maps to a traceable atomic task sequence with explicit dependency relations. A formal complexity analysis shows the algorithm scales as $O$($b$·$K$·$d_{max}$), where b is the beam width and d_max is the maximum node degree. Several theoretical properties of the proposed framework are further derived: the cost function is non-negative and strictly monotonic, optimal paths satisfy the optimal substructure property, cycle-free optimal paths always exist, and beam search can yield globally optimal solutions given a sufficiently large beam width. These theoretical conclusions establish mathematical guarantees for the presented decomposition framework. Experiments on 200 composite maintenance instructions with gold-standard annotations (inter-annotator agreement Cohen’s $\kappa =0.88$) demonstrate that the proposed method achieves 94.3% task sequence accuracy (95% CI: 91.2–96.8%) and 96.4% dependency accuracy (95% CI: 93.5–98.1%), substantially outperforming both a rule-augmented baseline (58.6%, 62.1%) and a GPT-4o few-shot chain-of-thought baseline (73.2%, 70.5%); McNemar’s test yields p < 0.001 for both comparisons. The average inference time is 29.7 ms (SD 2.1 ms), meeting stringent industrial real-time constraints. Ablation studies quantify the contribution of each cost function component and confirm the robustness of the chosen beam width and hyperparameters. When integrated into a full multi-agent system, the framework delivers end-to-end response time within 3 s (P50: 1.87 s, P95: 2.83 s) and maintains an 86.7% task success rate even under dual agent failures, validating the robustness of the proposed mathematical formulation. This work establishes a rigorous graph-theoretic foundation for instruction decomposition in multi-agent systems, with direct applicability to safety-critical industrial environments. Full article

The use of Glass Fiber-Reinforced Polymer (GFRP) bars to reinforce concrete beams can provide high resistance to corrosion, high performance, high sustainability, and reasonable strength but with low ductility. This study focused on the structural behavior and indirect evaluation of the ductility index of hollow and solid beam specimens reinforced with GFRP bars, steel bars, or both (hybrid). Eight simply supported beam specimens with dimensions of 1200 mm (length), 150 mm (height), and 100 mm (width) were made using self-compacted concrete (SCC) and tested using two-point repeated loading. The tests results showed that the ultimate load capacity of the tested solid and hollow beams reinforced with GFRP bars were 78% and 67% higher than that of the corresponding solid and hollow beam specimens with steel-bar reinforcement. The measured energy absorption is “instantaneous” energy absorption because the residual stress disappears after the load is removed at the end of the test and any cracks will close due to the semi-linear response of the beam specimens reinforced with GFRP bars. Regarding the solid beam specimens, those containing GFRP bars showed an increase in energy absorption of 64–127% compared with the corresponding reference beams. The hollow beam specimens containing GFRP bars showed an increase in energy absorption of 21–68% compared with the corresponding reference beam containing three steel bars. Full article

To investigate the feasibility and effectiveness of seismic repair for prefabricated single-beam column joints in modern Chinese traditional-style buildings (MCTBs), low-cycle reversed loading tests were conducted on two original joints with different T-stub web thicknesses and one repaired joint. A repair strategy was proposed in which damaged T-stub connectors were removed and replaced with welded end-plate connections. The seismic behavior of the joints, including failure mode, hysteretic response, skeleton curve, stiffness degradation, ductility, energy dissipation capacity, and seismic performance comparison between the original and repaired joints, was systematically evaluated. In addition, a refined finite element model was established using ABAQUS and validated against the experimental results to investigate the stress distribution, deformation characteristics, and load-transfer mechanism of the joints. The results indicate that damage in the original joints was mainly concentrated in the T-stub connection region, while the beam and column members remained essentially intact, demonstrating an effective damage-control mechanism. Increasing the T-stub web thickness improved the load-carrying capacity, stiffness, and ductility of the joints. After repair, the load-transfer mechanism changed from a blind-bolted T-stub connection to a welded end-plate connection, resulting in a different damage evolution pattern and failure mode. Nevertheless, the repaired joint exhibited stable hysteretic behavior, satisfactory deformation capacity, and favorable energy dissipation performance. Compared with the original joint, the repaired specimen achieved a moment capacity comparison ratio of approximately 116%, stiffness comparison ratios exceeding 120%, and an energy dissipation comparison ratio of approximately 148%. The finite element results agreed well with the experimental observations and further revealed the evolution of stress concentration regions and load-transfer paths before and after repair. The present experimental results demonstrate the feasibility of the proposed repair method for rehabilitating damaged joints while maintaining satisfactory seismic performance without replacing the primary beam and column members. The proposed repair strategy therefore provides a practical and efficient solution for the post-earthquake rehabilitation of prefabricated joints in MCTBs. Full article

During precast beam yard construction on soft ground, prestress tensioning-induced camber transforms the initially uniform load distribution into eccentric concentrated loads at the beam ends, thereby posing risks to foundation stability and geometric accuracy. This study investigates the mechanical responses of natural ground, single-pile reinforcement, and double-pile reinforcement under tension loading through field monitoring and numerical simulations based on a Hangzhou–Ningbo Expressway project. The results show that single-pile reinforcement exhibits a typical point-support behavior, characterized by significant stress concentration at the pile head, a pile–soil stress ratio ranging from 3.0 to 4.0, and a coefficient of variation in base pressure reaching 0.81. In contrast, the double-pile scheme enables load redistribution through a line-support mechanism along the beam length, improving stress uniformity and reducing the coefficient of variation to 0.62. Orthogonal test-based sensitivity analysis further identifies pile diameter and cushion thickness as the dominant factors influencing composite ground. performance. This study clarifies the differences in load-transfer mechanisms among various pile arrangements under tension loading and provides a theoretical basis for the optimized design of casting bed foundations for precast beam yards in soft soil regions. Full article

To clarify the bearing characteristics and load transfer mechanisms of long large-diameter pile foundations in dense silty fine sand strata within the middle and lower reaches of the Yellow River, a graded tension–compression anchor reaction loading test method was devised and implemented using a field-configured apparatus. This approach enables graded static load testing on large-tonnage long bored cast-in-place piles. Then, the relative displacement and settlement between pile and soil under vertical cyclic loading were analyzed. Finally, numerical simulations were adopted to study the settlement behavior of pile tops and ends under cyclic loads representative of beam yard operational conditions (20 cycles). Results indicate that, under vertical loading, the shaft friction resistance and tip resistance of large-diameter long bored cast-in-place piles are not mobilized simultaneously, but sequentially. The degree of shaft friction is related to the magnitude of pile top loading, soil properties, burial depth, and construction methods. The soil between piles generates vertical resistance to horizontal force-transfer rods, becoming part of the pile foundation’s bearing capacity and sharing the load. Moreover, in dense silty fine sand strata, long large-diameter pile foundations exhibit pure friction pile behavior. When calculating the bearing capacity of such piles, parameters from geotechnical reports based on code-specified values should be multiplied with corresponding correction coefficients. In addition, the shaft friction resistance in dense silty fine sand layers remains under-mobilized. Limited loading–unloading cycles in permanent–temporary integrated beam yard operations do not induce significant deformation in pile foundations, indicating minimal impact on their bearing performance. Full article

Reinforced concrete beams with a fiber-reinforced polymer (FRP) plate bonded to their soffit, known as FRP-plated RC beams, commonly fail due to premature debonding of the FRP plate, limiting the utilization of the FRP strength. Inclined U-jacketing has been demonstrated to be effective as the end anchorage for mitigating debonding failures. The mechanism by which the inclined U-jacketing mitigates debonding failure remains unclear, and no design approach has been developed. Therefore, the present study has been conducted to investigate the mitigating effects of the key parameters of the inclined U-jacket through a series of four-point bending tests and systematic modeling. The test results indicate that both the inclination angle and the chamfer radius significantly affected the bond behavior of inclined U-jacket-to-concrete joints. Compared with the 45° configuration, reducing the inclination angle to 30° increased the peak load and peak displacement by 85.4% and 81.6%, respectively. In contrast, the effect of U-jacket side height became negligible once an effective bonded height had been reached, as increasing the side height from 75 mm to 120 mm changed the peak load by only 2.17%. In addition, a pre-peak parameter identification framework based on a power-function-type cohesive element constitutive relationship was proposed and validated. By analyzing the power-function parameters, namely the coefficient a and exponent b, the influences of U-jacket geometric variables on interfacial mechanical behavior were quantitatively characterized. The proposed approach provides experimentally verifiable parameterization to support the optimized design of inclined U-jacket anchorage systems. Full article

Countermovement jump (CMJ) analysis is widely used to assess lower limb neuromuscular function, but commercial force plates often suffer from high cost, closed algorithms, and lack of bilateral independent measurement. This study developed and evaluated a dual channel strain gauge force plate system featuring open architecture and hardware-triggered video synchronization. The system consists of two physically isolated plates, each with four full bridge strain beams, a precision analog front end, and a 2000 Hz acquisition unit. A microcontroller-based hardware trigger synchronizes force data with video capture. Custom host software implements adaptive jump phase recognition and calculates peak force (PF), concentric impulse, jump height, rate of force development (RFD), and asymmetry index (ASI). Validation included static mass measurements in 14 participants, low-load static calibration (5.0–30.0 kg), free-fall impulse validation (7.00 to 31.32 N·s), 240 fps high-speed video cross validation of flight time, ecological-validity comparison with published AMTI-based force-plate data, and 48 h test–retest reliability assessment. Static mass measurement showed a mean absolute percentage error (MAPE) of 1.01% and a coefficient of determination (${\mathrm{R}}^2$) of 0.9992, while low-load testing confirmed excellent linearity (${\mathrm{R}}^2>0.996$) and minimal absolute error (mean absolute error = 0.34 kg) at lighter weights. Dynamic impulse validation yielded ${\mathrm{R}}^2>0.997$ and MAPE < 3%. Flight time agreement with high-speed video was within ±10 ms. Test–retest reliability was excellent for concentric impulse (intraclass correlation coefficient (ICC) = 0.997) and jump height (ICC = 0.987), and good for PF (ICC = 0.962) and rate of force development at 100 ms (RFD_100ms) (ICC = 0.883). The physically isolated dual-plate architecture effectively captured bilateral force differences, although the ASI demonstrated moderate reliability (ICC = 0.748), likely reflecting the inherent biological variability in bilateral coordination. The ecological-validity comparison further indicated that the macroscopic kinetic outputs of the proposed system fell within the expected physiological and biomechanical ranges reported for adult CMJ testing. Overall, these findings support the study hypothesis that the proposed dual-channel force plate system provides a valid, reliable, and cost-effective solution for synchronized bilateral CMJ kinetic assessment in sports performance monitoring and biomechanical research, while offering improved accessibility through an open-source and transparent analysis framework with a hardware cost below 500 USD. Full article

This review synthesizes findings from more than 100 journal articles, reports, and design standards on the design, simulation, and testing of steel beam-to-column connections, with emphasis on semi-rigid bolted extended end-plate (EEP) joints. The core objective of this study is to highlight the critical importance of accurately capturing this semi-rigid behavior, given the significant implications of improper modeling for the global response, safety, and design reliability of steel frames. While connections are often idealized as fully rigid or pinned, EEP connections typically exhibit a semi-rigid response governed by nonlinear moment–rotation (M–θ) behavior. The reviewed literature is organized around: (i) mechanical response and key failure mechanisms (end-plate yielding, bolt fracture, and prying action); (ii) analytical and numerical prediction methods, including component-based models and finite-element approaches capable of representing contact, bolt pretension, and cyclic degradation; and (iii) system-level implications for steel frames. Approaches used in major standards (AISC and Eurocode 3) for classifying connection stiffness and strength are compared, and experimental programs are summarized to identify the dominant parameters controlling resistance, ductility, and failure mode. Translating these component-level findings to the structural-system level, the review highlights how appropriately detailed semi-rigid EEP connections can enable moment redistribution, reduce member demands, and support stable inelastic deformation under seismic actions. Key research gaps include three-dimensional and multiaxial loading, impact and other high-rate actions, and the performance of alternative materials such as stainless steel. Full article

Background: Craniofacial growth is regulated by a complex interaction of genetic, functional, and systemic metabolic factors. Mechanical loading generated during mastication plays a fundamental role in mandibular development through bone modeling and remodeling mechanisms. In contrast, Type I diabetes mellitus is associated with impaired bone metabolism, which may compromise skeletal growth. Although the independent effects of functional loading and metabolic disorders on bone tissue have been widely investigated, their combined influence on mandibular development remains insufficiently understood. Objective: This study primarily aimed to evaluate the effect of Type I diabetes mellitus on mandibular growth in growing rats and, secondarily, to assess the impact of dietary consistency (hard versus soft food) on mandibular development under diabetic and non-diabetic conditions, as well as determine whether diabetes modifies the mandibular adaptive response to increased masticatory loading. Materials and Methods: An experimental animal study was conducted using twenty-four male Wistar rats aged one month. The animals were randomly allocated into four groups according to metabolic status (control or diabetic) and dietary consistency (hard or soft diet). Type I diabetes mellitus was experimentally induced in the relevant groups using streptozotocin. All animals underwent cone beam computed tomography (CBCT) scanning at baseline (Day 1) and at the end of the experimental period (Day 28). Linear measurements were obtained using specialized software following euthanasia. Two-way ANOVA was used to evaluate the effects of diabetes, diet, and their interaction, using appropriate post hoc tests for multiple comparisons. Categorical variables were analyzed using the chi-square test. A p-value < 0.05 was considered statistically significant. Results: Longitudinal morphometric analysis demonstrated that Type I diabetes mellitus significantly impaired mandibular growth. Diabetic animals exhibited reduced growth rates and smaller final mandibular dimensions compared with controls. Hard diet intake significantly enhanced mandibular development in control animals, reflecting a strong adaptive response to increased functional loading. However, this osteogenic response was markedly attenuated in diabetic rats. Under soft-diet conditions, differences between control and diabetic groups were diminished, indicating that reduced mechanical stimulation limits adaptive growth responses. Significant interaction effects between diabetes and dietary consistency were observed in several morphometric parameters, particularly those related to mandibular body length, ramus height, and condylar position. Conclusions: Type I diabetes mellitus exerts a detrimental effect on mandibular growth in growing rats and compromises the adaptive response of craniofacial structures to mechanical loading. Although a hard diet functions as a potent osteogenic stimulus, its growth-promoting effect is substantially reduced in the presence of metabolic dysfunction. Full article

This study experimentally investigated the structural behavior of reinforced concrete beams with circular openings created by core drilling in the midspan and shear span regions under fixed-ended boundary conditions. A total of 21 full-scale beams with shear span-to-effective depth ratios (a/d) of 1.25, 1.75, and 2.25 were tested under a four-point bending setup. After concrete hardening, 100, 200, and 300 mm diameter openings were introduced by core drilling. The results showed that the effect of opening location on load-carrying capacity varied with the a/d ratio. In the a/d = 1.25 and 1.75 series, openings in the shear span caused more pronounced reductions, whereas in the a/d = 2.25 series, midspan openings became more influential. Increasing the opening diameter reduced both load-carrying capacity and energy dissipation capacity, and this reduction varied with opening location and a/d ratio. Openings in the shear span led to shear failure in the a/d = 1.25 and 1.75 series, whereas flexural effects became more pronounced in the a/d = 2.25 series. Nevertheless, 300 mm openings caused shear failure even in beams expected to exhibit more flexure-dominated behavior. Full article