Search Results (22,719)

Accurately determining the thermal transmittance (U-value) of glazing systems plays a pivotal role in building energy conservation. This study establishes an explicit analytical model and conducts a systematic parametric analysis to elucidate the heat transfer mechanisms and key influencing factors governing the U-values of both single-pane and insulating glass. Based on fundamental thermodynamic principles and blackbody radiation laws, numerical iterative models are developed and validated against WINDOW and Fluent software simulations, with deviations consistently below 3.8%. A comprehensive parametric analysis quantifies the effects of glass thickness, cavity width, surface emissivity, and indoor/outdoor heat transfer coefficients. The results reveal that: (1) while U-values decrease approximately linearly with increasing glass thickness, they exhibit a non-monotonic relationship with cavity width, identifying an optimal cavity width of approximately 16 mm for air-filled insulating glass units; (2) surface emissivity exerts the most significant influence on the U-value, with cavity-facing surfaces demonstrating the greatest sensitivity (up to 81% variation), whereas outdoor surface emissivity shows negligible impact; (3) the U-value displays greater sensitivity to variations in the indoor heat transfer coefficient compared to outdoor conditions. Based on the parametric analysis under standard winter conditions, a preliminary design hierarchy is proposed for energy optimization: prioritize Low-E coatings on cavity surfaces, followed by cavity width optimization near 16 mm, and finally consider increasing glass thickness. The validated models and quantitative insights establish a benchmark calculation method for U-value analysis. These findings offer theoretical guidance and a prioritized optimization pathway for the preliminary design of energy-efficient glazing systems, particularly under standard winter conditions. Full article

During the high-temperature deposition of tungsten thin films on alumina ceramic substrates, the inherent mismatch in thermal expansion coefficients frequently triggers interfacial delamination, where uncontrollable factors in stochastic surface topographies can exacerbate localized stress concentrations. To resolve these interfacial failures, the enhancement of interfacial adhesion through a deterministic surface microgroove design is identified as the general objective of the present research. Within this framework, the establishment of a robust quantitative mapping between the transverse scratching offset distances and the resultant periodic microgeometry is first pursued as a specific experimental objective. This methodological approach effectively transforms the stochastic nature of the substrate into deterministic geometric configurations. Second, a specific numerical objective is fulfilled by evaluating the interfacial stress redistribution and damage evolution utilizing refined thermomechanical coupled simulations based on the cohesive zone model. The integrated findings demonstrate that optimizing the microgroove spacing effectively governs the morphological transition and broadens stress diffusion pathways to mitigate thermal mismatch effects. Specifically, the structural optimization at a spacing of 28.8 μm facilitates an approximately 31.8% reduction in the maximum interfacial stress and a 10% decrease in the average film stress compared to the 13.6 μm spacing. Finally, this research clarifies the underlying mechanisms of stress buffering and provides a rigorous engineering methodology for the structural design of reliable high-performance ceramic–metal interfaces in extreme environments. Full article

Flood and flash flood events can generate severe hydraulic actions on civil structures, requiring modeling strategies able to link flow features to structural damage. This paper proposes a two-scale numerical framework based on advanced finite element modeling to assess the vulnerability of structures subjected to inundation and flood-driven impact. At the macroscale, the flood propagation and the interaction with the built environment are simulated through the depth-averaged Shallow Water Equations, adopting a time-explicit interface treatment to capture the evolution of the free surface. The macroscale model provides time-dependent water depth and flow velocity along the external surfaces of the structure, which are then used to derive hydrostatic and hydrodynamic actions, also in comparison with code-based formulations. At the mesoscale, these actions are transferred to a detailed structural model to investigate the nonlinear mechanical response of the building. Structural components are described through a coupled damage–plasticity constitutive law, enabling the prediction of stiffness degradation, cracking-driven damage patterns, and the identification of the most critical structural zones under flood loading. The proposed workflow is finally applied to a real structure located in the municipality of Cosenza (Italy), demonstrating the capability of the approach to combine hydraulic intensity measures with physics-based structural damage assessment, supporting scenario analyses and risk mitigation evaluations. Full article

With the increasing functional and geometric complexity of modern steel buildings, irregular beam-to-column joints are becoming increasingly common in engineering practice, while their seismic performance and force transfer mechanisms remain insufficiently understood. Based on previous full-scale cyclic loading tests on unequal-depth steel beam (UDSB) and staggered steel beam (SSB) joints incorporating inclined internal diaphragms, this study presents numerical simulations and parametric analyses of irregular steel beam to concrete-filled steel tube (CFST) column joints. Three-dimensional nonlinear finite element models were developed using ABAQUS and validated against experimental results. The strengthening effects of internal diaphragms and concrete infill were then comparatively investigated. The results indicate that internal diaphragms increase the initial stiffness and load-carrying capacity of the joints to approximately 2.0–2.3 times and 1.16–1.8 times, respectively, compared with joints without diaphragms, whereas concrete infill provides smaller enhancements of about 1.3 times in stiffness and 1.2–1.3 times in strength. In addition, the hysteretic response of joints without diaphragms shows good agreement with the post-fracture behavior observed in the experiments, validating the diaphragm fracture mechanism. A parametric study further demonstrates that, under cyclic loading, the beam depth ratio, staggered floor ratio, column wall thickness, column width, diaphragm thickness, and diaphragm opening diameter have significant influences on joint strength and stress distribution, while the effect of axial load ratio is relatively minor. Finally, a strength prediction method applicable to inclined-diaphragm UDSB and SSB joints is proposed, and corresponding fitted expressions are derived based on the parametric results. The findings provide useful guidance for the seismic design of irregular steel beam–CFST column joints incorporating internal diaphragms. Full article

To address the difficulty of directionally cutting thick, hard key strata in gob-side entry retaining using conventional blasting or hydraulic fracturing, this paper proposes a high-pressure water-jet slotting-induced pre-cracked weakening belt (PCWB) roof-cutting technology. Several finite-length PCWBs are arranged within the key stratum and designed to coalesce into a plane, inducing through-going roof failure along a pre-determined path. A fixed–fixed key strata beam model combined with linear elastic fracture mechanics shows that the double-belt configuration forces the bending moment and shear force to concentrate in a thin rock bridge, where bending and shear stresses are amplified by about 1.5–2.8 times and 1.2–1.7 times, respectively, for 2–4 m thick key strata, providing a mechanical basis for preferential tensile–shear failure. Two-dimensional RFPA2D simulations reveal “width-dominated, length-assisted” control of cutting performance and identify an optimal weakening belt geometry of about 400 mm in width and 200 mm in length. Three-dimensional numerical modeling of parallel slot pairs indicates that intra-pair spacing of about 40 mm produces a continuous, directional weakening belt, whereas smaller or larger spacing causes, respectively, destructive interference or loss of connectivity. High-pressure water-jet tests (320 MPa, 0.33 mm nozzle, 1.30 mm/s traverse speed) on limestone blocks confirm that single slots can penetrate the full thickness and that cracks from adjacent slots coalesce through the rock bridge, forming a wide, straight fracture band. Field application in the Dongjiang Mine (3.5 m limestone key stratum, ~400 m depth) shows that the first weighting is advanced from the 7th to the 3rd day, peak support resistance is reduced from 8.8 to 7.4 MPa, and periodic weighting becomes more frequent and smoother. The PCWB technology is therefore suitable for panels with 2–4 m thick hard key strata at similar depths, offering precise key stratum severance, active stress relief, and safe, controllable construction. Full article

This paper presents a methodology enabling the use of a Pitot probe for static pressure measurement in supersonic flow under severely confined spatial conditions where standard design guidelines cannot be satisfied. In particular, the recommended placement of a static pressure tapping at a distance of 10–20 tube diameters is not feasible; the proposed approach allows for the tapping to be located immediately downstream of the static tube cone. The methodology combines theoretical analysis, experimental measurements, and Computational Fluid Dynamics (CFD) simulations. Experiments were performed using appropriately selected pressure sensors, while detailed simulations in Ansys Fluent (Ansys 2024 R2) included both a high-fidelity probe model and free-stream flow analysis. By comparing experimental and numerical results, a correction coefficient was established based on the free-stream dynamic pressure obtained from CFD. This enables the accurate estimation of static pressure even in non-ideal probe configurations. The measurement error did not exceed 20%, while in most cases, very good agreement between experimental and CFD results was achieved. The main contribution of this paper is the validated methodology, which extends the applicability of Pitot probes to geometrically constrained environments where conventional static pressure measurement techniques cannot be implemented. Full article

Chaotic behavior in power systems that are integrated with permanent-magnet synchronous generators (PMSGs) poses a significant threat to stability and security. Existing control methods often suffer from slow convergence, reliance on precise system models, or the inability to guarantee convergence within a predefined time. To address these issues, this paper develops a predefined-time synchronization control scheme for chaotic PMSG systems under unknown nonlinearities and external disturbances. First, an adaptive neural network with variable exponent coefficients is constructed to approximate unknown system dynamics online. Second, a predefined-time stability criterion is established, ensuring global convergence of synchronization errors within a user-specified time, independently of initial conditions. Third, the proposed controller achieves superior disturbance rejection without requiring prior knowledge of disturbance bounds. Numerical simulations demonstrate that the proposed method outperforms conventional finite-time control in convergence speed, control smoothness, and robustness to parameter variations—offering a practical and theoretically guaranteed solution for enhancing the stability of PMSG-based power systems. Full article

This paper presents a systematic investigation into the design and performance of layered polymer gradient refractive index (GRIN) lenses. A material-driven optimization algorithm is proposed, which uses physical volume fractions of the constituent polymers to parameterize the refractive index distribution. By integrating effective medium theory with Sellmeier-based dispersion data, the algorithm ensures that the gradients remain within physically realizable material limits while better aligning with actual refractive index profiles. First, refractive index distribution models for first-order radial GRIN lenses and linear spherical radial GRIN lenses were derived based on material properties, establishing manufacturable lens parameterization expressions. Subsequently, simulation software was employed to model and compare a first-order GRIN doublet, a cemented doublet, a linear spherical radial GRIN lens, and a first-order GRIN aspheric lens. Numerical results demonstrate that the proposed GRIN structures exhibit superior performance in both monochromatic aberration suppression and chromatic control, particularly under large aperture conditions. For a lens system with a 50 mm focal length and a 25 mm entrance pupil diameter, the spherically symmetric GRIN lens achieves diffraction-limited chromatic performance, with its secondary spectrum reduced by over 70% compared to conventional cemented doublets. Furthermore, the first-order GRIN doublet maintains the smallest RMS spot size across multiple fields of view and exhibits the most stable aberration growth rate as the aperture increases. These results validate the feasibility of the material-driven GRIN modeling approach and provide theoretical support for high-performance, short-focal-length optical systems. Full article

Folic acid, an essential vitamin for human health, plays a crucial role in maintaining intestinal homeostasis and functional stability, and its absorption is frequently impaired in Crohn’s disease, where it is closely associated with clinical complications and nutritional management. Nevertheless, the quantitative relationship between the complex multiscale architecture of intestinal villi, their morphological dynamics, and the efficiency of folic acid absorption remains insufficiently understood, primarily because existing studies rely on oversimplified representations of villous geometry and neglect the internal vascular structure, thereby limiting their ability to capture the coupled transport processes within individual villi. While existing studies have considered the influence of villous morphology on intestinal absorption, they generally rely on oversimplified representations and do not account for the internal structural organization of villi. This study aims to elucidate the quantitative relationship between villous multiscale architecture and folic acid absorption efficiency under pathological conditions of Crohn’s disease. Herein, a two-dimensional multiphysics numerical model is developed that integrates the external environment of intestinal villi with their internal microstructure, simulating folic acid transport via diffusion and Michaelis–Menten kinetics, coupled with convection–diffusion in the microvascular network under Stokes flow conditions. We find a reduction in villus height to 400 μm or local blood flow velocity to 0.01 mm/s leads to a marked decrease in folic acid absorption capacity, by approximately 57% and 50%, respectively. These changes are primarily attributed to inflammation-induced villus atrophy, which reduces the effective absorptive surface area. Furthermore, reduced blood flow velocity lowers the Peclet number, facilitating the accumulation of folic acid within the villi, which in turn further reduces the efficiency of folic acid absorption. This work contributes to a deeper understanding of how diseases affect the absorptive function of intestinal villi and provides a theoretical basis for the pathological mechanisms of the gut. Full article

Despite the success of artificial neural networks in solving numerous tasks, they face significant challenges, including difficulties in online adaptation and rapidly increasing energy consumption. As a biologically plausible alternative, spiking neural networks offer promising capabilities for efficient cognitive computing. Recently, a three-element spiking neuron model consisting of a threshold selector, a tunnel diode, and a capacitor was proposed. In this work, we experimentally validate this model using a threshold selector hardware emulator and demonstrate its dynamical equivalence to the biologically plausible Izhikevich neuron model. To evaluate the novel neuron’s applicability for cognitive computing, we implement a liquid state machine (LSM) reservoir architecture with spatially dependent random topology for synaptic weight distribution. Our simulations on the MNIST and Fashion-MNIST benchmarks demonstrate competitive classification accuracy (97.9% and 89.5%, respectively) while offering estimated energy efficiency and processing speed enhancements compared to existing FPGA-based and memristor-based spiking reservoir implementations. The developed reservoir is feasible for processing neuromorphic sensors output, including visual perception tasks. Full article

This study introduces a hybrid framework that integrates transient numerical simulations with artificial neural networks (ANNs) to analyze and predict heat transfer in building walls. The framework is applied to ten different material–insulation combinations. Using the Leapfrog–Hopscotch (LH) finite difference scheme, we evaluated dynamic heat transfer and identified optimal insulation thicknesses for buildings in the cold continental climate of Bukhara. An ANN model was trained and validated on a dataset generated from 410 simulated wall configurations. The model achieved high predictive accuracy, with a mean squared error below 0.005. The thickness of the outer material layer ranged from 20 cm to 35 cm, while the inner layer thickness varied from 1 cm to 3 cm. Among the materials analyzed, glass wool + steel and gypsum + brick demonstrated superior insulation performance by minimizing heat loss most effectively, with values as low as 361,234 W/m² and 4,983,441 W/m², respectively, at 35 cm wall thickness. These findings underscore the potential of combining ANN-based predictions with physics-based simulations to design energy-efficient building envelopes in cold climates. Full article

This study develops a reduced-order predictive model of the Sit-To-Stand (STS) task to examine whether a simplified biomechanical representation can reproduce key STS patterns reported in the literature and to investigate the role played in movement by a flexible trunk. The model represents the human body as a planar multibody system and formulates STS as an optimization problem within a discrete mechanics framework. This formulation combines reduced model complexity, explicit torso flexibility, and a structure-preserving numerical approach for trajectory generation. Simulations were used to evaluate the effects of movement duration, reduced joint strength, and seat height on joint torques, kinematics, trunk motion, and ground reaction forces (GRFs). The results reproduced several qualitative trends reported in previous experimental studies, including increased peak joint torques and GRFs with shorter movement duration, lower joint strength, and reduced seat height, as well as greater compensatory trunk motion under more demanding conditions. These findings suggest that the proposed framework captures key adaptive features of STS mechanics and may provide useful insights for rehabilitation analysis and the design of assistive technologies such as lower-limb exoskeletons and rehabilitation devices. At the same time, the present work should be regarded as an initial methodological study, since validation is currently qualitative and further experimental calibration, quantitative validation, and sensitivity analysis remain part of ongoing work. Full article

This study investigates the residual stresses developed during the curing process of polymer fiber-reinforced composites and their influence on fracture behavior, particularly the initiation and propagation of interlaminar cracks. The main objective is to quantify how different curing histories, including incomplete cure, alter the spatial distribution of residual stresses and, in turn, affect the mode-I fracture response of carbon-fiber/epoxy laminates. A transient thermal–structural finite element framework incorporating an autocatalytic cure kinetics model was used to simulate the curing process and predict residual stress development in a unidirectional carbon-fiber/epoxy laminate with an edge crack, considering thermal, chemical, and geometric effects. The cure model was calibrated using isothermal differential scanning calorimetry data to determine the degree of cure under different thermal conditions. The key novelty of this work is the integration of a validated cure-kinetics-based curing simulation with fracture analysis, enabling direct correlation of thermal history and degree of cure with spatially varying residual stresses at the crack front and their effect on fracture toughness. Numerical load–displacement predictions were compared with double cantilever beam experimental results and showed good agreement for the curing profiles examined. The results demonstrate that residual stresses generated by different cure cycles, including hold conditions and incomplete curing, significantly influence fracture toughness. In particular, the incomplete-cure profile produced an approximately 40% reduction in toughness compared with profiles that achieved complete cure, highlighting the importance of cure history in determining final structural performance. Full article

This study proposes an innovative structural wall system and evaluates its compressive performance. The wall consists of GLPB manufactured using laminated bonding (along the grain direction) and assembled using a staggered interlocking masonry method. Two key geometric parameters controlling the mechanical response of the GLPB wall—the slenderness ratio (β) and the eccentricity (e)—were selected as the primary design variables. Using a combined experimental and numerical approach, the study systematically investigated the compressive mechanical behavior and performance evolution of the wall, including compressive strength and deformation behavior. Through axial and eccentric compression tests, six sets of specimens with varying geometric parameters β and e were analyzed, yielding relevant data and characteristics regarding failure modes, ultimate load-carrying capacity, load–displacement response, crack resistance, and wall deformation. To further characterize the compressive mechanical performance of GLPB walls, a refined nonlinear finite element model was developed in ABAQUS (version 2020). This model incorporates the anisotropic constitutive behavior of wood, the Hill yield criterion, and the mechanical interactions at the interlocking and bonding interfaces. The study indicates that the average compressive strength of GLPB walls is 2.63 MPa, with a crack-to-failure load ratio ranging from 0.68 to 0.83. GLPB walls demonstrate comparable load-bearing capacity. The total axial vertical strain ranges from 0.033 to 0.041, indicating that the walls possess good deformation capacity. Based on Chinese masonry design standards and experimental evidence, a preliminary predictive formula for the load-bearing capacity of this wall was derived. A comparison of the aforementioned experimental measurements with simulation results showed errors of less than 10%, verifying the model’s validity and accuracy. Numerical simulation can, to a certain extent, compensate for the limitations of experimental methods in capturing internal mechanical states. Full article

Large-scale surface subsidence induced by extra-thick seam longwall top-coal caving (LTCC) is strongly amplified by thick unconsolidated overburden, posing serious serviceability risks to overlying linear infrastructure. Taking the S103 Provincial Highway above Panel 6118 in Inner Mongolia, China, as the engineering background, this study integrates theoretical analysis, numerical simulation, and in situ monitoring to investigate the subsidence-control mechanism of directional presplitting roof cutting. The results show that roof cutting mitigates surface subsidence by reconstructing the overburden structural system and weakening the stress-transfer chain, thereby transforming key-stratum deformation from integral bending to segmented block movement and narrowing the subsidence-affected zone. An equivalent mining-depth model for subsidence-boundary convergence is proposed to characterize the inward migration of the subsidence-basin boundary under thick unconsolidated cover, and a segmented probability-integral model is developed to explain the kink-like high-gradient feature in the post-cut subsidence profile. Parametric simulations of roof-cutting positions (p = 0, 2, 4, …, 32 m) show that the most effective mitigation occurs in the range p = 4–12 m; using minimum–maximum highway subsidence together with profile flattening as the optimization criteria, the representative optimum is identified at p ≈ 10 m, for which the maximum highway subsidence is approximately 57 mm, about 76% lower than that in the non-cutting case. The results further indicate that, although roof cutting significantly reduces subsidence and deformation gradients, fissure localization and possible discontinuous deformation near the pre-split weak plane still require careful field monitoring. Full article