Search Results (385)

This article addresses the problem of finding the shortest route for Automated Guided Vehicles (AGVs) in a production environment with constrained battery state-of-charge (SoC) and time-dependent operating conditions. The route map is divided into a uniform grid containing stationary obstacles and two types of dynamic obstacles: human, for which AGV transportation is prohibited, and inanimate (moving objects), which impose a penalty function. A key contribution of the proposed methodology is the introduction of a battery residual charge matrix, which embeds cell-level energy feasibility directly into the grid-based environment representation by determining minimum admissible SoC constraints and accounting for transition-dependent energy costs. This matrix restricts the set of traversable cells under low-energy conditions, enabling energy-aware route feasibility evaluation during both initial planning and adaptive replanning. The proposed approach is based on the A* and D* Lite algorithms, providing shortest-path construction that explicitly integrates battery SoC into the spatio-temporal cost function. To avoid collisions in a multi-agent environment during routing, a simplified hybrid scheme with M* elements performs local coordination and adaptive trajectory replanning. The effectiveness of the proposed methodology was assessed using travel time, temporal complexity, and spatial complexity metrics. Simulation results on a $10\times 10$ grid showed that agents with sufficient battery completed routes of 8 and 11 cells with travel times of 7.2 to 10.7 conventional units. A critically low-energy agent was initially unable to move, but after adjusting the minimum SoC constraint, all agents completed their routes with travel times up to 11.4 conventional units, demonstrating the direct impact of energy constraints on system performance. Additional experiments with varying agent counts and SoC thresholds confirmed reliable balancing of route feasibility and energy constraints across configurations. Full article

This study investigates the transient wheel–rail contact mechanics of welded joints in heavy-haul rails via a validated 3D finite element model, and analyzes the stick-slip behavior, dynamic response and elastoplastic characteristics in the base material zone, heat-affected zone and weld bead zone. Results show a distinct contact state transition from stick-slip in the base material to predominant slip within the welded zones, indicating higher wear susceptibility. Dynamic response analysis reveals the highest and lowest contact-point acceleration amplitudes in the base material and heat-affected zone, respectively, due to material heterogeneity. Plastic deformation consistently initiates at the rail surface, where stress and strain concentrate, establishing it as the primary site for damage nucleation. A systematic parametric study shows that plastic deformation can be effectively mitigated by increasing the yield strength and elastic modulus of the welded joint material, or reducing the wheelset velocity, unsprung mass and wheel–rail friction coefficient. In contrast, adjusting the primary suspension and fastener parameters exerts a negligible influence on plastic deformation control. These findings provide a mechanistic basis for optimizing the performance and maintenance of welded joints in heavy-haul rail operations. This study reveals the coupling law of multiple mechanisms among contact behavior, dynamic response and material failure during the damage initiation process of rail welded joints from the mechanistic perspective, which provides a theoretical basis for the structural optimization, condition assessment and maintenance of rail welded joints in heavy-haul railways. Full article

Low-velocity impacts during manufacturing and maintenance (e.g., tool drops) can induce barely visible impact damage in composite aircraft structures, motivating sensing-assisted approaches for rapid post-event assessment. This study proposes and validates a strain-based structural health monitoring framework for carbon-fiber-reinforced polymer (CFRP) panels by combining surface-mounted strain gauges with explicit finite element analysis (FEA). Drop-weight tests were con-ducted in accordance with ASTM D7136 using a 1.0 kg hemispherical impactor at drop heights of 250–400 mm. Three strain gauges were positioned at 1.25 mm, 32.5 mm, and 52.5 mm from the impact point to quantify the spatial attenuation of peak surface strain. The measured peak strains exhibited clear-dependent decay and increased with impact energy up to 350 mm, whereas the 400 mm case showed a non-monotonic response and a pronounced deviation from an elastic energy-scaling baseline, consistent with a transition to damage-dominated energy dissipation. Dedicated MSC Apex/Nastran Implicit simulations reproduced experimental trends and provided a physics-based digital twin for interpreting strain signatures in elastic regions, correlating them with likely damage states. Full article

Under China’s carbon peaking and carbon neutrality goals, its photovoltaic (PV) sector is transitioning from scale expansion to quality-oriented growth, where intelligent upgrading is essential to improve efficiency, safety, and O&M digitalization. However, its upgrade process in China is severely hampered by a wide range of complex influencing elements. The purpose of this study is to pinpoint and examine the main obstacles to the PV upgrading process as well as clarify their cause–effect relationships to support targeted interventions. Using a mixed-methods approach, we first analyzed interview data from thirty stakeholders using grounded theory to derive barrier categories and factors. The cause-and-effect linkages among these factors were then quantified using the gray-DEMATEL approach. The findings show that funding cost constraints and the lack of incentive mechanisms are the primary and secondary causal factors, respectively, while insufficient R&D capabilities are the most significant resultant factor. The lack of cooperation mechanisms and funding cost constraints were identified as the most comprehensive influencing factors. These findings provide a systematic decision-making framework for policymakers and industry stakeholders to formulate targeted strategies for accelerating PV intelligent upgrading in China. Full article

In this study, thermal deformation in non-planar, large-scale additive manufacturing (LSAM) was experimentally and numerically investigated. A Bézier-based non-planar build surface was fabricated by CNC machining, and a single layer of ABS was deposited using a hybrid LSAM system. Toolpaths with raster angles of 0° and 45° were generated for surface-conformal printing. Infrared thermography was employed to monitor the thermal history during deposition. A three-dimensional finite element model was developed to simulate transient heat transfer and thermally induced deformation. Experimental deformation was quantified by 3D scanning and compared with simulation results. The results show that the slope geometry strongly influences deformation direction: negative slopes promote contraction, whereas positive slopes lead to upward deflection. Maintaining the material temperature above the glass transition temperature significantly reduces skew deformation. The finite element method predictions demonstrate strong agreement with experimental measurements, with normalized root mean square errors (NRMSEs) of approximately 11% for thermal deformation and 10% for temperature history. The proposed framework enables prediction and mitigation of thermal warping in non-planar polymer additive manufacturing. Full article

The constituent elements of source-to-sink systems and their coupling relationships are key controls on the development of sedimentary systems and the spatial distribution of sand bodies. Taking the Paleogene strata in the southern Laizhouwan Sag of the Bohai Bay Basin as a case study, we integrate drilling, logging, core, thin-section, and high-resolution 3D seismic data to quantitatively characterize basement lithology and effective provenance area, drainage-unit subdivision, types and scales of sediment transport pathways, and geometric parameters of depositional fans, within a source-to-sink analytical framework. The results show that: (1) Two distinct provenance types are developed in the southern Laizhouwan Sag, including Proterozoic granitic–gneissic basement and Mesozoic volcanic–clastic basement. These provenance types exhibit pronounced differences in effective source area, vertical relief, and drainage-network configuration across different sequence stages. (2) Two main categories of sediment transport pathways are identified, namely paleo-valleys and fault-controlled troughs. V-shaped, U-shaped, and W-shaped paleo-valleys show systematic morphological transitions along topographic gradients. The width-to-depth ratio of transport channels exerts a significant control on depositional fan scale, with U-shaped valleys exhibiting the highest sediment transport efficiency. Finally, (3) the depositional domain is dominated by near-source fan-delta systems, whose scale shows a strong positive correlation with effective provenance area and transport-channel morphology. Overall, the southern Laizhouwan Sag is characterized by a typical fault-controlled, steep-slope source-to-sink system, in which sedimentary system distribution is jointly governed by effective provenance area, sediment transport pathway geometry, and fault-related slope-break zones. This study provides a quantitative example and methodological reference for source-to-sink system characterization and prediction of favorable sand body distribution in continental rift basins. Full article

Metal-free two-dimensional (2D) polymers built from open-shell π-conjugated units offer a promising platform for realizing correlation-driven magnetism without transition metal elements. Here, we present a systematic first-principles study of phenalenyl-based 2D polymers that elucidates how atomic-level chemical substitution controls magnetic order through the interplay of electronic correlation and sublattice symmetry. Combining density functional theory with an effective tight-binding and Hubbard model analysis, we show that atomic substitution with boron or nitrogen on phenalenyl building blocks acts as a sublattice-resolved tuning knob for both the ratio of on-site Coulomb interaction to inter-site hopping (U/t) and the relative on-site energies of the two sublattices. Sublattice-asymmetric substitution with boron or nitrogen breaks sublattice equivalence and drives the system from an antiferromagnetic Mott-insulating state into spin-polarized semiconducting phases with pronounced spin-dependent gaps. In contrast, uniform substitution on both sublattices preserves symmetry and yields nonmagnetic metallic states characterized by rigid band shifts rather than correlation-driven spin polarization. These results establish a unified microscopic framework in which electronic correlations and sublattice symmetry emerge as cooperative yet independently tunable parameters, providing general design principles for metal-free 2D π-conjugated materials with tailored magnetic and spintronic functionalities. Full article

Buried oil and gas pipelines, the critical arteries of global energy infrastructure, are increasingly vulnerable to severe geological hazards such as reverse faulting, yet their structural integrity is often pre-compromised by stochastic corrosion damage accumulated during service. However, quantifying the coupled impact of spatial corrosion heterogeneity and large ground deformation remains a formidable challenge due to the complex nonlinearities involved in soil–structure interactions and wall thinning. This study establishes a probabilistic assessment framework integrating random field theory, nonlinear finite element analysis, and a generative conditional diffusion model to characterize realistic 2D non-Gaussian corrosion morphologies. The numerical results reveal a significant geometric stiffening effect induced by internal pressure, where moderate operating levels effectively suppress cross-sectional distortion by counteracting the Brazier effect. Consequently, this mechanism facilitates a fundamental transition in failure modes from localized tensile rupture to ductile buckling, significantly extending the critical fault displacement threshold. Furthermore, probabilistic fragility analysis demonstrates that the spatial dispersion of pitting, rather than just average wall thinning, governs the initiation of premature failure. Mechanistic analysis indicates that high internal pressure, while providing pneumatic support, exacerbates tensile strain localization at corrosion pits, leading to a heightened probability of premature rupture under minor fault deformations, a critical hazard that traditional deterministic models significantly underestimate. These findings provide a quantitative theoretical foundation for the reliability-based design and maintenance of energy lifelines traversing active tectonic zones. Full article

The structural and electronic properties of the rare-earth-modified VOCl₂ monolayer (V_1−xX_xOCl₂, where X = Nd, Sm and Eu) are explored, by using the density functional theory calculations. In particular, the influence of the rare-earth (X) concentration on the physical properties is investigated for $x=0.166$, 0.083, and 0.062. The lattice parameters for all the optimized structures reveal an increase, while the crystal structure changes from rectangular (with Pmm2 space-group) to oblique for the $x=0.166$ concentration, preserving the original space-group for the other compositions. The structural analyses also revealed moderate changes in the VO₂Cl₄ distortions, after the inclusion of the rare-earth elements. On the other hand, the electronic properties have shown that the substitution of V by the Nd, Sm and Eu cations also preserves the semiconductor behavior of the studied system. The obtained results for the density of state reveal a non-zero total magnetization and show that the inclusion of the X cations promotes a transition from the antiferromagnetic to the ferrimagnetic state in the V_1−xX_xOCl₂ compositions. Furthermore, the modern theory of polarization reveals the ferroelectric character for the pure and modified system. These results show that the controlled substitution at the V-site with rare-earth elements simultaneously modifies the structural, electronic, magnetic and multiferroic properties of the VOCl₂ system, offering promising potential of the studied system for application in 2D-based materials and electronic devices with enhanced multifunctional properties. Full article

Indoor environmental quality significantly affects occupant health, making stress-reduction interventions in built environments important. Aroma, a key sensory element, requires validation for stress relief. This study induced stress in 24 participants using a difficult arithmetic task in a controlled lab. EEG was recorded during exposure to lavender essential oil, a blended essential oil, or no aroma. Analyses focused on EEG microstates and functional connectivity. Stress reduced microstate C frequency, increased A-D transition probability, and weakened functional connectivity. Both aromas reversed these neural abnormalities toward baseline. The blended essential oil significantly enhanced theta-band functional connectivity, indicating a superior stress-relief effect compared with lavender. Integrating specific aromas indoors can thus promote user stress recovery, supporting aroma-based biophilic design for mental health. Full article

This study comprehensively evaluates the elemental composition of soil and Pinus species needle samples across 25 distinct plots established along the D825 highway in Kahramanmaraş, Türkiye. Located at the confluence of the Mediterranean, East Anatolian, and Central Anatolian regions, this area represents a critical ecological transition zone. A total of 75 soil and 75 needle samples were analyzed in triplicate to assess heavy metal contamination and potential toxicity risks across these elevation gradients. According to the results, the Geoaccumulation Index (I_geo) values for all examined metals remained below zero, categorizing the study area as “unpolluted.” Enrichment Factor (EF) analyses confirmed the lithogenic origin of Cr, Mn, and Ni; however, Lead (Pb) and Cadmium (Cd) exhibited an EF of 1.34. This ‘minimal enrichment’ could potentially be associated with anthropogenic pressures, possibly stemming from traffic emissions on the highway. Although current metal levels fall below global toxicity thresholds (WHO/FAO), the positive skewness and high variation in Pb and Cd distributions suggest a likelihood of localized accumulation, which may warrant systematic monitoring. The original contribution of this study lies in its integrated assessment of plant–soil barrier mechanisms within this unique transition zone, demonstrating how forest ecosystems maintain resilience capacity despite ophiolitic parent material contributions. While soil Cr and Ni levels were elevated due to the geological structure, plant tissue concentrations remained within safe physiological limits, suggesting effective stabilization within the soil-biomass matrix. The findings suggest that these forest ecosystems play a key role in maintaining ecological health and environmental sustainability against potential anthropogenic encroachment in this strategic intersection. Full article

Progressive collapse is characterized by disproportionate structural failure triggered by localized damage, such as column loss under extreme loading conditions. The objective of this study is to develop a simplified analytical model that is applicable in engineering practice without the need for high-fidelity nonlinear finite element analysis. Although current design guidelines (GSA and DoD) provide analytical procedures and acceptance criteria, they do not explicitly address the tensile resistance of girders after the acceptance criteria are satisfied, particularly under large deformation and connection failure. To address this limitation, this study proposes a simplified theoretical load–displacement model for a fixed-end girder subjected to three concentrated loads, considering the effects of secondary beams and focusing on the local girder response under a column-removal scenario. The proposed model incorporates moment–axial force interactions at plastic sections in the large-deformation range. Based on one-dimensional finite element analysis results, an early-developed axial force of 0.15F_p at the onset of the transition stage and a residual bending moment of 0.3M_p during the catenary action stage are explicitly introduced to better represent actual structural behavior. The girder response is idealized using five characteristic points: yielding (Y), full plasticity (P), transition initiation (T), pure catenary action initiation (C), and collapse governed by connection failure (F_conn). Stress distributions at plastic sections are analyzed using three-dimensional finite element models to establish stress-based formulations and a rational procedure for estimating axial force at collapse. The validity of the proposed model is verified through comparisons with finite element analysis results for girders with different span-to-depth ratios. The results demonstrate reasonable agreement in terms of collapse load and displacement, particularly for slender girders, confirming the applicability of the proposed model for progressive collapse assessment. Full article

Dynamic wireless power transfer (DWPT) systems for in-motion electric vehicle (EV) charging often suffer from unstable power delivery due to spatial variations in magnetic coupling caused by vehicle misalignment. This study presents a stabilization-oriented DWPT design methodology that prioritizes minimizing spatial variations of mutual inductance rather than maximizing peak coupling under perfect alignment. A ferrite-backed double-D coil configuration is analyzed and refined using three-dimensional finite-element electromagnetic modeling integrated with circuit-level co-simulation to evaluate coupling behavior, magnetic field homogeneity, and power transfer efficiency under realistic dynamic misalignment conditions. The proposed design achieves a coupling coefficient of 0.50–0.55 under aligned conditions and exhibits smooth, predictable degradation for lateral offsets up to 40–50 mm. Quantitative analysis demonstrates a low spatial coupling gradient of approximately 0.001 mm⁻¹, indicating that abrupt coupling transitions are effectively suppressed during vehicle motion. The system attains a maximum power transfer efficiency of 84.37% at an 80 mm air gap, while maintaining stable performance under both lateral and vertical displacement. Comparative evaluation shows improved misalignment tolerance and coupling stability relative to conventional double-D configurations. The results demonstrate that electromagnetic field shaping focused on coupling smoothness is an effective and practical strategy for reliable dynamic wireless charging of electric vehicles. Full article

The expansion of urban rail transit has exacerbated environmental issues related to low-frequency noise (LFN), yet the impact of geometric symmetry breaking on structure-borne noise remains underexplored. This study aims to quantify the mechanism by which cross-sectional asymmetry influences the vibro-acoustic coupling of viaducts. A 2.5D Hybrid Finite Element-Boundary Element Method (FEM-BEM) was employed to model a parametric box girder under eccentric track loading, and the numerical framework was validated against analytical benchmarks. The “Modal Symmetry Index” (MSI) and “Acoustic Asymmetry Indicator” (AAI) were defined to evaluate the effects of the asymmetry parameter ($\alpha$) on sound field distribution. Numerical results reveal a nonlinear “V-shaped” relationship between geometric asymmetry and acoustic directivity. While severe asymmetry ($\alpha >0.15$) exacerbates noise deflection via flexural–torsional coupling, a critical “self-balance zone” exists. Specifically, moderate asymmetry ($\alpha \approx 0.07$) effectively neutralizes load eccentricity, reducing the AAI from 1.5 dB (in strictly symmetric designs) to nearly 0 dB. Robustness analysis under right-side loading conditions further confirms a “reverse deflection” phenomenon, verifying that the proposed self-balance design minimizes directional sensitivity. These findings challenge the traditional assumption that geometric symmetry is acoustically optimal. A “competition–compensation” mechanism is identified, suggesting that deliberate, slight geometric asymmetry can serve as an effective passive noise control strategy for viaducts. Full article

To elucidate how pre-crack inclination affects the dynamic mechanical response, failure modes, and energy evolution of rocks, uniaxial impact compression tests were conducted on Φ50 mm Baima Iron Mine magnetite specimens with varying pre-crack angles using a split Hopkinson pressure bar (SHPB) system. The experiments were integrated with PFC2D discrete element simulations to investigate crack propagation and stress field characteristics. The results demonstrate that all specimens maintained dynamic stress equilibrium under impact loading. Crack inclination significantly influenced the dynamic stress–strain response: specimens with 0°~30°cracks exhibited gradual post-peak stress decay, indicating ductile behavior, while specimens with larger inclinations (≥45°) displayed pronounced brittle failure. Dynamic compressive strength followed a “U-shaped” trend with crack angle, reaching a minimum at 45°, whereas 0°and 90°specimens exhibited similar strength. Failure modes transitioned from axial splitting to wing-crack dominance, while anti-wing and shear cracks decreased significantly with increasing crack angle. Energy analysis indicated that reflected energy decreased and transmitted energy increased with increasing crack angle. Numerical simulations reproduced the experimental macroscopic failure patterns accurately, revealing the underlying mechanisms of crack-tip coalescence and stress concentration shifts as a function of crack inclination. These findings offer insights into the dynamic failure mechanisms of jointed rocks and provide guidance for engineering safety assessments. Full article