Search Results (111)

Aiming at the lightweight design of a bridge-shed integration structure, this paper presents a three-layered absorbing system in which a part of the sand cushion is replaced by expanded polystyrene (EPS) geofoam and the reinforced concrete (RC) protective slab is arranged above the sand cushion to enhance the composite system’s safety. A three-dimensional Smoothed Particle Hydrodynamics–Finite Element Method (SPH-FEM) coupled numerical model is developed in LS-DYNA (Livermore Software Technology Corporation, Livermore, CA, USA, version R13.1.1), with its validity rigorously verified. The dynamic response of rockfall impacts on the shed slab with composite cushions of various thicknesses is analyzed by varying the thickness of sand and EPS materials. To optimize the cushion design, a specific energy dissipation ratio (SEDR), defined as the energy dissipation rate per unit mass (η/M), is introduced as a key performance metric. Furthermore, the complicated interactional mechanism between the rockfall and the optimum-thickness composite system is rationally interpreted, and the energy dissipation mechanism of the composite cushion is revealed. Using logistic regression, the ultimate stress state of the reactive powder concrete (RPC) slab is methodically analyzed, accounting for the speed and mass of the rockfall. The results are indicative of the fact that the composite cushion not only has less dead weight but also exhibits superior impact resistance compared to the 90 cm sand cushions; the impact resistance performance index SEDR of the three-layered absorbing system reaches 2.5, showing a remarkable 55% enhancement compared to the sand cushion (SEDR = 1.61). Additionally, both the sand cushion and the RC protective slab effectively dissipate most of the impact energy, while the EPS material experiences relatively little internal energy build-up in comparison. This feature overcomes the traditional vulnerability of EPS subjected to impact loads. One of the highlights of the present investigation is the development of an identification model specifically designed to accurately assess the stress state of RPC slabs under various rockfall impact conditions. Full article

Internal fins are commonly utilized as a passive technique to enhance natural convection, but their efficiency depends on complex interplay between fin design, material properties, and convective strength. This study presents an extensive numerical analysis of buoyancy-driven flow in square cavities containing a single horizontal fin on the hot wall. Over 9000 simulations were conducted, methodically varying the Rayleigh number (Ra = 10 to 10⁵), Prandtl number (Pr = 0.1 to 10), and fin characteristics, such as length, vertical position, thickness, and the thermal conductivity ratio (up to 1000), to assess their overall impact on thermal efficiency. Thermal enhancements compared to scenarios without fins are quantified using local and average Nusselt numbers, as well as a Nusselt number ratio (NNR). The results reveal that, contrary to conventional beliefs, long fins positioned centrally can actually decrease heat transfer by up to 11.8% at high Ra and Pr due to the disruption of thermal plumes and diminished circulation. Conversely, shorter fins located near the cavity’s top and bottom wall edges can enhance the Nusselt numbers for the hot wall by up to 8.4%, thereby positively affecting the development of thermal boundary layers. A U-shaped Nusselt number distribution related to fin placement appears at Ra ≥ 10³, where edge-aligned fins consistently outperform those positioned mid-height. The benefits of high-conductivity fins become increasingly nonlinear at larger Ra, with advantages limited to designs that minimally disrupt core convective patterns. These findings challenge established notions regarding passive thermal enhancement and provide a predictive thermogeometric framework for designing enclosures. The results can be directly applied to passive cooling systems in electronics, battery packs, solar thermal collectors, and energy-efficient buildings, where optimizing heat transfer is vital without employing active control methods. Full article

This study employs Particle Image Velocimetry (PIV) technology to investigate the statistical properties and flow structures of the turbulent boundary layer over smooth walls and riblet walls with yaw angles of 0, ±30° in both clear water and liquid–solid two-phase flow fields. The results indicate that, compared to the smooth wall, streamwise riblet walls and 30° divergent riblet walls can reduce the boundary layer thickness, wall friction force, comprehensive turbulence intensity, and Reynolds stress, with the divergent riblet wall being more effective. In contrast, convergent riblet walls have the opposite effect. The addition of particles leads to an increase in boundary layer thickness and a reduction in wall friction resistance, primarily by reducing turbulence fluctuations and Reynolds stress in the logarithmic region of the turbulent boundary layer. Moreover, the two types of drag-reduction riblet walls can decrease the energy content ratio of near-wall streak structures and suppress their motion in the spanwise direction. Their impact on burst events is mainly characterized by a reduction in the number of ejection events and their contribution to Reynolds shear stress. In comparison, convergent riblet walls have the complete opposite effect and also enhance the intensity of burst events. The addition of particles can fragment streak structures and suppress the intensity and number of burst events, acting similarly on drag-reduction riblet walls and further strengthening their drag reduction characteristics. Full article

In the global energy sector, water-bearing reservoir-typed gas storage accounts for about 30% of underground gas storage (UGS) reservoirs and is vital for natural gas storage, balancing gas consumption, and ensuring energy supply stability. However, when constructing the UGS in the M gas reservoir, selecting suitable areas poses a challenge due to the complicated gas–water distribution in the multi-layered water-bearing gas reservoir with a long production history. To address this issue and enhance energy storage efficiency, this study presents an integrated geomechanical-hydraulic assessment framework for choosing optimal UGS construction horizons in multi-layered water-bearing gas reservoirs. The horizons and sub-layers of the gas reservoir have been quantitatively assessed to filter out the favorable areas, considering both aspects of geological characteristics and production dynamics. Geologically, caprock-sealing capacity was assessed via rock properties, Shale Gouge Ratio (SGR), and transect breakthrough pressure. Dynamically, water invasion characteristics and the water–gas distribution pattern were analyzed. Based on both geological and dynamic assessment results, the favorable layers for UGS construction were selected. Then, a compositional numerical model was established to digitally simulate and validate the feasibility of constructing and operating the M UGS in the target layers. The results indicated the following: (1) The selected area has an SGR greater than 50%, and the caprock has a continuous lateral distribution with a thickness range from 53 to 78 m and a permeability of less than 0.05 mD. Within the operational pressure ranging from 8 MPa to 12.8 MPa, the mechanical properties of the caprock shale had no obvious changes after 1000 fatigue cycles, which demonstrated the good sealing capacity of the caprock. (2) The main water-producing formations were identified, and the sub-layers with inactive edge water and low levels of water intrusion were selected. After the comprehensive analysis, the I-2 and I-6 sub-layer in the M 8 block and M 14 block were selected as the target layers. The numerical simulation results indicated an effective working gas volume of 263 million cubic meters, demonstrating the significant potential of these layers for UGS construction and their positive impact on energy storage capacity and supply stability. Full article

Under the impetus of achieving global sustainable development goals, the civil construction industry is accelerating its transition towards high-quality, green, and low-carbon practices. Prefabricated, modular building technology has become a key tool due to its advantages in energy conservation, emission reduction, and shortened construction periods. However, existing research on the seismic performance of prefabricated, modular, reinforced concrete column–beam (RCS) composite structures often focuses on the construction form of beam–column joints, paying less attention to the impact of floor slabs on the seismic performance of joints during earthquakes. This may make joints a weak link in structural systems’ seismic performance. To address this issue, this paper designs a prefabricated, modular RCS composite joint considering the effect of floor slabs and uses the finite element software ABAQUS 2023 to perform a quasi-static analysis of the joint. The reliability of the method is verified through comparisons with the experimental data. This study examines various aspects, including the joint design and the material’s constitutive relationship settings, focusing on the influence of parameters, such as the axial compression ratio and floor slab concrete strength, on the joint seismic performance. It concludes that the seismic performance of the prefabricated, modular RCS composite joints considering the effect of floor slabs is significantly improved. Considering the composite effect of the slabs, the yield loads in the positive and negative directions for node FJD-0 increased by 78.9% and 70.0%, respectively, compared to that of the slab-free node RCSJ3. The ultimate bearing capacities improved by 13.2% and 9.98%, respectively, and the energy dissipation capacity increased by 23%. Additionally, the variation in the axial load ratio has multiple effects on the seismic performance of the joints. Increasing the slab thickness significantly enhances the seismic performance of the joints under positive loading. The bolt pre-tensioning force has a crucial impact on improving the bearing capacity and overall stiffness of the joints. The reinforcement ratio of the slabs has a notable effect on the seismic performance of the joints under negative loading, while the concrete strength of the slabs has a relatively minor impact on the seismic performance of the joints. Therefore, the reasonable design of these parameters can optimize the seismic performance of joints, providing a theoretical basis and recommendations for engineering application and optimization. Full article

Background: Postoperative macular edema may limit visual recovery following cataract surgery. Although smoking is recognized as a risk factor for ocular inflammation, its impact on early postoperative macular morphology following cataract surgery has not been investigated. Methods: This prospective cohort study enrolled 88 elderly patients undergoing elective cataract surgery in a single university teaching hospital. The patients were divided into long-term smokers and lifelong non-smokers. Spectral-domain optical coherence tomography (OCT) was used to assess the central subfoveal thickness (CST), cube volume (CV), cube average thickness (CAT), retinal nerve fiber layer (RNFL), and cup-to-disk ratio (CDR) preoperatively and on the 1st, 7th, and 14th postoperative days (PODs). The phacoemulsification time and cumulative dissipated energy were recorded. Linear mixed-effects models were used to assess group-by-time interactions, and multivariable regression, adjusted for baseline covariates, was employed for analyses. Results: Eighty patients were included in the final analysis. Smokers had significantly thinner baseline CST than non-smokers. Both groups showed early postoperative CST increases, but only smokers exhibited sustained and significantly greater increases in CV and CAT on POD 14 (CV Δ +0.30 mm³ vs. +0.04 mm³; p = 0.026; CAT Δ +6.5 µm vs. +1.2 µm; p = 0.037). The RNFL and CDR changes did not differ significantly at earlier timepoints. However, smokers showed a notably greater RNFL thickening on POD 14 (Δ +4.2 µm; p = 0.001). Smoking status remained the strongest independent predictor of these changes (p < 0.001), while phacoemulsification parameters showed no significant interaction effects. Conclusions: Cigarette consumption independently predicts pronounced postoperative macular and RNFL thickening after uncomplicated elective cataract surgery. These transient structural changes could complicate early glaucoma assessment and should be considered when interpreting postoperative OCT findings in smokers. Full article

Helmets are crucial for protecting motorcycle riders from head injuries in accidents. This study proposes a helmet pad design based on a negative-Poisson’s-ratio (NPR) structure and comprehensively evaluates its protective effect on head injuries. A concave hexagonal honeycomb structure was embedded into the energy-absorbing lining of a motorcycle helmet, and finite element collision simulations were conducted according to the ECE R22.05 standard. These simulations compared and analyzed the differences in protective performance between concave hexagonal honeycomb helmets with different parameter configurations and traditional expanded polystyrene (EPS) helmets under flat anvil impact scenarios. Using biomechanical parameters, including peak linear acceleration (PLA), head injury criterion (HIC), intracranial pressure (ICP), maximum principal strain (MPS), and the probability of AIS2+ traumatic brain injury, the protective effect of the helmets on traumatic brain injury was evaluated. The results showed that when the wall angle of the honeycomb structure was 60°, honeycomb helmets with wall thicknesses of 0.8 mm and 1.0 mm significantly reduced PLA and HIC values. In particular, the honeycomb helmet with a wall thickness of 1.0 mm reduced ICP by 25.7%, while the honeycomb helmet with a wall thickness of 1.2 mm exhibited the lowest maximum principal strain in the skull compared to EPS helmets and reduced the probability of AIS2+ brain injury by 7.2%. Concave hexagonal honeycomb helmets demonstrated an excellent protective performance in reducing the risk of traumatic brain injury. These findings provide important theoretical foundations and engineering references for the design and optimization of new protective helmets. Full article

In recent decades, the application of composite materials in aerostructures has significantly increased, with modern commercial aircraft progressively replacing aluminum alloys with composite components. This shift is exemplified by comparing the material compositions of the Boeing 777 and the Boeing 787 (Dreamliner). The Boeing 777 incorporates approximately 50% aluminum alloy and 12% composite materials, whereas the Dreamliner reverses this ratio, utilizing around 50% composites and 12% aluminum alloy. While metals remain advantageous due to their availability and ease of machining, composites offer greater potential for property tailoring to meet specific performance requirements. They also provide superior strength-to-weight ratios and enhanced resistance to corrosion and fatigue. To ensure the reliability of composites in aerospace applications, comprehensive testing under various loading conditions, particularly impact, is essential. Impacts were performed on quasi-isotropic (QIT) carbon-fiber reinforced epoxy panels with stainless steel, round-nosed and flat-ended impactors with rubber discs of 1-, 1.5- and 2 mm thickness, adhered to the flat-ended impactor to simulate the transition between hard and soft impact loading conditions. QIT composite panels were tested in this research employing similar lay-ups often being implemented in aircraft wings and other structures. The rubber discs were applied in the flat-ended impactor case but not for the round-nosed impactor due to the limited adhesion between the rubber and the rounded stainless-steel surface. Impact energies of 7.5, 15 and 30 J were investigated, and the performance of the panels was evaluated using force-time and force-displacement data alongside post-impact ultrasonic C-scan imaging to assess the damaged area. Damage was observed at all three energy values for the round-nosed impacts but only at the highest impact energy when using the flat-ended impactor, leading to the hardness study with adhered rubber discs being performed at 30 J. The most noticeable difference with the addition of rubber discs was the reduction in the damage in the plies nearest the top (impacted) surface. This suggests that the rubber reduces the severity of the impact, but increasing the thickness of the rubber from 1 to 2 mm does not notably increase this effect. Indentation clearly plays a significant role in promoting delamination at low-impact energies for the round-nosed impactors. Full article

The finite-element model was developed using ABAQUS to investigate the hysteretic properties of space joints. This study examined the effects of axial compression ratio, T-plate stiffness, column wall thickness, and bolt-preload on the joint’s hysteretic behavior. The model was verified by comparing the failure modes, hysteresis curves, and skeleton curves of the specimens with the test results of the relevant literature, ensuring the reliability of the research. The results reveal three primary failure modes: beam flange buckling, T-plate buckling, and column-wall buckling; increasing the thickness of the T-plate web or column wall significantly enhances joint stiffness and mitigates brittle failure. Specifically, the stiffness of T-plate 1 has a substantial impact on joint performance, and it is recommended that its web thickness be no less than 18 mm. In contrast, variations in the thickness of T-plate 2 have negligible effects on seismic performance. Increasing the column wall thickness improves the bearing capacity and stiffness of the joint, with a recommended minimum thickness of 12 mm, which should not be less than the flange thickness of the steel beam. While an increase in the axial compression ratio reduces the bearing capacity and stiffness, it enhances the energy dissipation capacity and ductility of the joint. Notably, variations in bolt-preload were found to have minimal influence on joint performance. These findings provide valuable insights for optimizing the design of unilateral bolted joints in steel structures to improve seismic resilience. Full article

In this work, we present results on the impact of electron beam surface modification on the phase composition, microstructure, chemical composition, and mechanical properties of Fe-Ni-Cr-Mo-W high-entropy alloy. During the experiments, the beam power was 600 and 1200 W. The phase composition was studied using XRD measurements. Scanning electron microscopy (SEM) and energy-dispersive X-ray spectroscopy (EDS) were used to analyze the microstructure and chemical composition, respectively. The results showed that at the lower value of the power of the electron beam, a distinguished modified zone cannot be observed. With an increase in the discussed technological parameter, a treated zone with a thickness of about 30 μm can be seen on the top of the sample. The modulus of elasticity on the surface of the unprocessed alloy was measured to be 130 GPa and increased to 156 GPa in the case of both technological regimes of the electron beam surface modification process. The hardness on the top of the untreated alloy was about 4.5 GPa and reduced to about 3 GPa in the case of electron beam treatment on the alloy with a beam power of 600 W. The application of the modification process with a higher value of beam power, 1200 W, led to an even further decrease in the hardness, to about 2.8 GPa. The resistance to plastic deformation of the surface of the considered specimens was also analyzed via the H³/E² ratio, and the results show that the application of the treatment procedure leads to a decrease in the resistance to plastic deformation in both cases. This decrease is more pronounced in the case of the treatment with the higher value of power of the electron beam. Full article

Corrugated steel plate shear walls (CSPSWs) exhibit excellent energy dissipation capacity and lateral resistance performance due to their unique “accordion structure”, making them a highly promising seismic component in prefabricated buildings. The assembled CSPSWs utilize bolted connections on both sides, which align with the energy-saving and emission-reduction trends of prefabricated construction. Compared to traditional welded connections, this method reduces the impact on frame columns during seismic deformation and allows for easier post-damage replacement. Through experimental and finite element analysis, this study systematically investigates the lateral mechanical behavior of assembled CSPSWs and compares them with flat steel plate shear walls (FSPSWs), revealing the stress mechanisms and failure modes of corrugated structures. Additionally, parametric analysis quantifies the influence of plate thickness, width/height ratio, and wave height on structural performance. Experimental results demonstrate that CSPSWs significantly outperform FSPSWs in out-of-plane displacement resistance and energy dissipation efficiency. Parametric analysis indicates that increasing plate thickness and width/height ratio enhances energy dissipation, while increasing wave height negatively affects energy dissipation capacity. This research provides theoretical support for the optimal design and engineering application of assembled corrugated steel plate shear walls. Full article

The honeycomb configuration has been widely adopted in numerous sectors owing to its superior strength-to-weight ratio, rigidity, and outstanding energy absorption properties, attracting substantial academic attention and research interest. This study introduces a biomimetic modular honeycomb configuration inspired by the variable-density biological enhancement characteristics of tree stem tissues. This study examined the out-of-plane compressive behavior and mechanical characteristics of modular honeycomb structures. A numerical model of the modular honeycomb was constructed utilizing finite element technology, enabling simulation studies at varying impact velocities. The improved weight-bearing and impact-absorbing properties of modular honeycomb structures are investigated using theoretical analysis and computer simulations. It also scrutinizes the effects of boundary and matching conditions on the honeycomb’s performance. The results indicate that adjusting the thickness of the walls in both the matrix honeycomb and sub-honeycomb structures can substantially improve their resistance to low-velocity out-of-plane compression impacts. Furthermore, the energy absorption capacity of modular honeycombs during high-velocity impacts is significantly influenced by multiple factors: the impact velocity, the density of the honeycomb structure, and the distribution of wall thickness within the sub-honeycomb and the primary honeycomb matrix. Notably, the modular honeycomb with an optimally designed structure demonstrates superior high-speed impact resistance compared to conventional honeycombs of equivalent density. These insights underscore the potential for advanced honeycomb designs to further advance material performance in structural applications. Full article

High-voltage underground cables inevitably experience frequency-dependent electromagnetic (EM) losses, driven primarily by skin and proximity effects. These losses become more severe at higher harmonic frequencies, which are increasingly common in modern power networks. In traditional multi-segment cable designs, uninsulated conductor bundles enable large circular eddy current loops that elevate AC resistance and exacerbate both skin and proximity phenomena. This paper investigates the impact of introducing a thin insulating layer between individual conductor strings in a five-segment high-voltage cable model. Two insulation thicknesses, 75 µm and 100 µm, are examined via two-dimensional finite element (FE) harmonic analysis at 0, 50, 150, and 250 Hz. By confining eddy currents to smaller loops within each conductor, the insulating layer achieves up to a 60% reduction in AC losses compared to the baseline uninsulated model, lowering the ratio of AC to DC resistance from about 3.66 down to 1.47–1.49 at 250 Hz. The findings confirm that adding even a modest inter-strand insulation is highly effective at mitigating skin and proximity effects, with only marginal additional benefit from thicker insulation. Such designs offer improved energy efficiency and reduced thermal stress in underground cables, making them attractive for modern power distribution systems where harmonic content is pervasive. Full article

Amidst global warming and energy crises, low-carbon building design is essential. China, the largest carbon emitter, commits to peaking emissions by 2030 and achieving carbon neutrality by 2060. This study focuses on low-carbon strategies for industrial buildings in cold regions, aiming to develop optimization designs centered on carbon emissions. Using ENERGYPLUS and the “standard coal method”, it quantifies operational carbon emissions and analyzes the impact of design methods on energy consumption across architectural layout, materials, and photovoltaic technology. This study, set in Xi’an and Yulin, assesses low-carbon techniques in cold and severely cold climate zones. It demonstrates that, for the architectural layout, the orientation of the building has a relatively small impact on carbon emissions, while an increase in the window-to-wall ratio significantly increases the carbon emissions of the building. For the building materials, the form of window glass, the reflectivity of roofs and walls, and the thickness of roof and wall insulation significantly affect carbon emissions. For the photovoltaic technology, the angle of photovoltaic roofs has no significant impact on carbon emissions. By further comparing the effectiveness of various low-carbon design technologies in reducing building carbon emissions, it was found that choosing more appropriate wall insulation boards can provide more significant carbon reduction effects at the same cost. Full article

To investigate the dynamic characteristics, energy dissipation patterns, and failure modes of granite with filled joints of varying thicknesses under impact loading, we utilized the Split Hopkinson Pressure Bar (SHPB) test setup for impact tests on both unfilled and filled granite samples. Additionally, a high-speed camera was used to capture the dynamic failure and crack propagation processes of the rock samples in real time. The results indicate that the thickness of the filling material significantly affects the stress–strain behavior of jointed rock masses, particularly in terms of characteristics of stress variation and post-peak morphology. In comparison to unfilled jointed rock samples, a distinct “stress bimodal” phenomenon is present, and the rebound of strain following the peak gradually decreases. The fracture patterns observed in the jointed rock samples are primarily characterized by tensile failure. Damage is notably more pronounced on the left side of the samples (near the incident bar), the lower side, and in the areas filled with gypsum. The most severe degree of damage occurs when the filling thickness is 7.56 mm. As the thickness of the filling increases, the dynamic compressive strength of the rock mass diminishes, and the peak strain first increases and then decreases. Concurrently, the energy reflection coefficient of the rock mass increases linearly, while the energy transmission coefficient declines linearly. Furthermore, the energy dissipation ratio first increases and then decreases. The test data reveal that the critical filling thickness influencing the dynamic properties, energy absorption characteristics, and damage degree of jointed rock samples falls within 4.91 mm to 7.56 mm. Full article