Search Results (398)

This study investigates the porous structure of Royal Water Lily Leaf vein cross-sections, integrating macroscopic structural observations, quasi-static compression experiments, and finite element simulations to systematically explore the influence of gradient fractal characteristics on mechanical performance and energy absorption behavior. First, the geometric features of the vein cross-sections were extracted through macroscopic measurements, and a parametric model incorporating key variables-porosity, pore ellipticity, and distribution density coefficient-was established. Single-factor analysis reveals that porosity plays a dominant role in determining the overall load-bearing capacity and energy absorption capability; pore ellipticity primarily affects local deformation modes and plateau-stage stability; while the distribution density coefficient significantly regulates the progressive and uniform deformation behavior. Subsequently, a multi-factor coupling model based on the Box–Behnken response surface methodology was developed to investigate the interactions among structural parameters. The results showed that the three variables exhibited significant synergistic effects rather than simple monotonic relationships. Within the investigated range, the optimized configuration (porosity = 30%, ellipticity = 1.6, distribution density coefficient = 1.5) achieved excellent comprehensive performance, with SEA = 115.75 J/kg, MCF = 248.2 N, and CFE = 0.445. Further analysis revealed that the porous vein structure does not exhibit strict self-similar fractal geometry but instead presents a gradient fractal characteristic with hierarchical progression and regional heterogeneity. During compression, the structure undergoes progressive collapse from the inner region outward, enabling staged load-bearing and efficient energy dissipation. These findings provide theoretical support and engineering guidance for the design and optimization of lightweight bioinspired porous energy-absorbing structures. Full article

To explore the damage mitigation mechanism of steel fiber-reinforced cellular concrete (SFR-CC) under underwater explosion loading, this study systematically analyzes two key variables: steel fiber volume fraction (0.5%, 1.0%, 1.5%, and 2.0%) and protective layer thickness (100 mm, 125 mm, 150 mm, 175 mm, and 200 mm). Based on underwater explosion numerical simulation, the influences of different variable combinations on damage evolution process, structural failure characteristics, dynamic mechanical response behavior, and energy dissipation capacity are investigated. The research results reveal that SFR-CC can effectively mitigate the energy of explosion shock waves. Both the steel fiber volume fraction and protective layer thickness exert significant influences on its underwater anti-explosion performance. The SAP20S15 protective layer exhibits excellent underwater protection performance. Under this specific engineering configuration, it achieves a remarkable attenuation of shock wave pressure acting on the protected structure. Increasing the thickness of the protective layer can substantially enhance its energy absorption capacity and markedly reduce the shock wave energy imposed on the protected structure. In addition, the energy dissipation sharing ratio, structural spalling angle, and peak velocity vector sum (PVS) were employed to conduct a systematic evaluation on the protective performance of the structure under various protective schemes. When the volume fraction of steel fibers is 1.5%, the energy dissipation ratio of the protective layer accounts for 80.49%, with the corresponding structural spalling angle and PVS of the protected plate being 59.5° and 21.4 m/s, respectively. When the protective layer thickness increases to 200 mm, the energy dissipation sharing rate rises by 54.8%, while the spalling angle and PVS of the RC slab decrease by 33.1% and 33.6%, respectively. This further verifies the superior underwater protection performance of the SAP20S15 protective layer under the same parametric conditions. Prediction curves for the damage grade of protected structures with different steel fiber volume fractions and protective layer thicknesses were established. The predicted values of the curves are in good agreement with the numerical simulation results, which can provide a theoretical reference for the rapid evaluation of the underwater anti-explosion performance of SFR-CC protective layers. The research findings can offer theoretical support for the engineering application of SFR-CC protective layers under identical parameter conditions in underwater explosion scenarios. Full article

The present study provides a comprehensive investigation into the hydrodynamic performance of grooved rubber journal bearings (GRJBs) employed as shaft supports in various rotating systems, with particular emphasis on marine applications. These bearings are lubricated with non-Newtonian fluids such as modern oil containing additives and viscoelastic water-based lubricant, which—owing to its complex composition including hydrocarbon chains, metal oxides, and impurity particles and contaminants such as salts, organic substances, microalgae, biopolymers, and microorganisms—deviates from the ideal Newtonian fluid model and demonstrates non-Newtonian rheological behavior. By examining various theories used in the analysis of non-Newtonian fluid behavior, the power-law model, which has a high degree of generality, has been employed in the present study. Also, to improve modeling accuracy, the elastic deformation of the rubber bush in this study is characterized using the Winkler foundation approach and analyzed via the finite element method (FEM). This advanced mechanical formulation, integrated with non-Newtonian lubrication modeling of lubricant using the power-law fluid model, and the parametric assessment of groove number and dimensions on steady-state bearing performance parameters, constitutes the core of this research. The investigation focuses on groove configurations of 4, 6, 8, and 10 channels. The findings indicate that increasing the groove count partitions the convergent pressure film zone into discrete segments, thereby reducing the maximum hydrodynamic pressure while intensifying the overall energy dissipation within the bearing. Additionally, the influences of rheological properties of the fluid—namely the power-law index (n) and the consistency index (m)—on key performance characteristics are thoroughly examined. An increase in both parameters enhances the effective viscosity and load carrying capacity; however, the exponential amplification due to the power-law index exhibits a more pronounced effect on load capacity and peak pressure compared to the consistency index. Full article

Drought is a major environmental constraint that disrupts photosynthetic processes. This study investigated the effects of foliar-applied commercial humic acid (HA) at different concentrations (1, 3 and 5 mg/mL) on the photosynthetic apparatus of sweet basil (Ocimum basilicum L. Italiano classico) under PEG-induced stress. The responses of the photosynthetic machinery were evaluated using chlorophyll a fluorescence analyses (JIP-test and PAM), leaf pigment composition, and assessments of membrane integrity. Drought stress caused pronounced alterations on both the donor and acceptor sides of photosystem II (PSII), including impaired Q_A⁻ reoxidation, reduced open PSII reaction centers (qP), diminished electron transport (ETo/RC, REo/RC), and substantial declines in performance indices (PI_ABS, PItotal). Energy dissipation increased (DI₀/RC), with regulated energy losses (Φ_NPQ) rising more strongly than non-regulated losses (Φ_NO). Drought also elevated oxidative stress markers (MDA and H₂O₂), leading to enhanced membrane injury. Among the tested concentrations, 5 mg/mL HA provided the most effective protection against drought stress. This treatment mitigated PEG-induced damage on both PSII donor and acceptor sides and increased the proportion of open reaction centers (qP). Improved PSII photochemistry corresponded with more efficient Q_A⁻ reoxidation, facilitated its interaction with plastoquinone, and caused the overall stabilization of photosynthetic functions under drought. The protective effects of HA were also evident for both PSI subpopulations. The enhanced tolerance was associated with the activation of antioxidant enzymes (CAT, SOD, APX) and the increased levels of anthocyanins and total phenolic content (TPC). In contrast, lower HA concentrations (1 and 3 mg/mL) provided insufficient protection. This study clearly demonstrates that HA enhances drought tolerance in basil in a concentration-dependent manner by protecting the structural and functional integrity of the photosynthetic apparatus, supporting its potential use as a foliar treatment to improve crop resilience under water-limited conditions. Full article

Hulless barley (Hordeum vulgare L. var. nudum) on the Qinghai–Tibet Plateau is consistently exposed to intense solar irradiance, yet whether and how reproductive spikes and flag leaves partition photoprotection remains unclear. Here, we compared a pigmented black landrace (Cai Peng Zi, CPZ) with a white cultivar (Zang Qing 3000, ZQ3000) across early, middle, and late spike coloration stages under field conditions. By integrating measurements of anthocyanin and chlorophyll contents, chlorophyll fluorescence parameters, and rapid light-response curves, we dissected organ-specific strategies in photochemistry and energy dissipation in spikes and flag leaves. The results showed that anthocyanin accumulation in CPZ spikes increased significantly during spike coloration, while chlorophyll a and the chlorophyll a/b ratio declined, indicating a shift from light harvesting to photoprotection in reproductive tissues. This pigment transition coincided with reduced PSII performance (declines in QY_max, qP, and qL) but stable non-photochemical quenching (NPQ and qN), pointing to reduced photochemical capacity with relatively stable energy dissipation in the spike. In contrast, CPZ leaves maintained higher QY_max than ZQ3000 but exhibited a pronounced decline in NPQ and qN at late stages, reflecting CPZ’s attenuated regulated energy dissipation capacity. Rapid light-response analysis further supported differences between organs and cultivars. Under high PAR, ZQ3000 spikes exhibited steeper declines in Y(II) and stronger downregulation of ETR(II), whereas CPZ spikes showed more moderate decreases; in leaves, ZQ3000 maintained consistently lower Y(NO) and higher Y(NPQ), indicating greater reliance on regulated energy dissipation. Collectively, our results reveal how pigment-mediated screening in reproductive structures and dynamic regulation of energy dissipation in leaves are coordinated to optimize light-use efficiency in high-altitude environments, providing physiological insights for breeding resilient hulless barley varieties. Full article

This study aims to develop a green composite cementitious material (GCCM) by partially replacing cement with multiple industrial solid wastes and to further enhance its toughness by incorporating basalt fibers (BF) for the effective disposal of shield tunnel spoil (STS). The deterioration behavior of STS synergistically improved by GCCM and BF was systematically investigated under drying–wetting (D-W) cycles using unconfined compressive strength (UCS) tests, mass loss and P-wave velocity measurements, as well as industrial computed tomography (CT) and scanning electron microscopy (SEM). The results show that BF significantly improves the early-age strength and deformation toughness of STS, with an optimal UCS increase of about 13% at 0.45% BF. Although the mechanical properties of the specimens deteriorated with an increasing number of D-W cycles, the “bridging effect” of BF effectively inhibited the propagation and coalescence of cracks. Quantitative CT analysis further revealed that the addition of 1.00% BF reduced the pore volume (V_k) and crack volume (V_l) by 54.3% and 63.2%, respectively, after eight D-W cycles. The damage mechanism is primarily attributed to the loss of cementitious materials caused by water migration and the swelling–shrinkage stress of clay minerals. The three-dimensional (3D) network structure formed by BF, through its pull-out energy dissipation mechanism, effectively maintained the macro- and microstructural integrity of the material. This study highlights the novelty of combining GCCM with BF to enhance the long-term durability of STS, providing a theoretical basis and technical support for its green disposal and engineering application in complex environments. Full article

Against the backdrop of the global clean energy transition, this paper addresses the volatility of renewable energy like wind and PV power, focusing on magnetic suspended flywheel energy storage systems (FESS). It expounds FESS’s structure (flywheel body, magnetic suspension bearings, etc.) and working principles (charging, energy retention, discharging) and studies key technologies including rotor material selection, magnetic bearing classification/modeling, motor coordination, and heat dissipation. Challenges such as high material costs and magnetic bearing stability are pointed out, with prospects for developing FESS toward higher performance, lower cost, and multi-scenario integration to support the clean transformation of power systems. Full article

This study combines theoretical analysis with experimental investigation to examine the hysteretic behavior and seismic mechanisms of self-centering timber frames incorporating reinforced concrete slabs through tests on two full-scale comparative specimens. One specimen was constructed with a floor slab, while the other was designed without a slab, and both were subjected to low-cycle reversed loading under identical test conditions. The seismic performance of the two specimens was comparatively evaluated in terms of hysteresis curves, load-carrying capacity, stiffness degradation, and energy dissipation capacity. The experimental results indicate that, under the adopted test configuration, the presence of the slab increases the initial stiffness of the frame by 81.25% and enhances its load-carrying capacity. In addition, prior to concrete cracking, the slab improves the energy dissipation efficiency through composite action. The slab also reduces the rate of post-tensioning loss by approximately 12.5%, indicating its beneficial role in mitigating such loss. Overall, this study provides both theoretical and experimental support for the quantitative evaluation of slab effects in self-centering timber frames. Full article

To study the influence of polyoxymethylene (POM) fibers on the mechanical properties of shotcrete for tunnel support, this research conducted four-point bending tests on concrete with different POM fiber dosages (0, 5, 7, and 9 kg/m³) and lengths (30 mm, 36 mm, and 42 mm). The mechanical properties are analyzed in terms of failure modes, flexural strength, and the toughness index. The results show that, with the increase fiber length and dosage, the incorporation of POM fibers can enhance the toughness of concrete and significantly improve the flexural performance of shotcrete, with the peak flexural strength increasing by 15.31% to 89.46%. Additionally, through scanning electron microscopy (SEM) image analysis, the reinforcing mechanism of POM fibers is revealed: when shotcrete with POM fibers is subjected to flexural loading, it undergoes four stages: elastic, elastic–plastic, yield, and failure. The addition of POM fibers increases the density and uniformity of concrete, and the flexural strength is indirectly enhanced by increasing frictional energy dissipation through the formation of fiber–matrix interfaces between fibers and concrete. The research findings provide a theoretical basis and design reference for the application of POM fiber-reinforced shotcrete in tunnel support. Full article

To elucidate the damping mechanism of platform dry friction dampers for turbine blades and optimize their design parameters, this study establishes a two-dimensional global–local unified sliding dry friction damping model. This model comprehensively accounts for the blade’s bending-torsion coupling vibration characteristics and the dual-state behavior of the damper, encompassing both stick and slip phases. An iterative solution strategy combining finite element methods with in-house developed programs is employed to simulate the vibration response of turbine blades equipped with dampers under multiple loading conditions. The influence of normal pressure and dimensionless normal pressure on the blade’s vibration characteristics, equivalent stiffness, and equivalent damping is systematically analyzed. To validate the reliability of the simulation results, a dedicated test platform capable of independently simulating centrifugal force effects was constructed, and modal tests as well as vibration response tests were conducted. The results demonstrate that the proposed model accurately describes the nonlinear energy dissipation behavior of dry friction damping, providing a reliable theoretical basis for blade vibration response analysis. Dimensionless normal pressure is identified as a key parameter influencing vibration reduction effectiveness. The resonant amplitude of the blade exhibits a non-monotonic trend, initially decreasing and then increasing with rising dimensionless normal pressure. The optimal dimensionless normal pressure range is found to be 20–30, within which the blade vibration amplitude can be reduced by more than 50%. Experimental verification confirms that the vibration reduction and energy dissipation mechanism of the damping block aligns closely with simulation results, achieving a maximum vibration reduction of 72.6%. Moreover, the optimal dimensionless normal pressure values correspond well with simulation predictions. Based on the optimal dimensionless normal pressure, a forward design method for platform dampers is proposed, which can provide theoretical support and engineering guidance for the optimal design of vibration reduction structures in aero-engine turbine blades. Full article

This paper describes the thermal and energy performance of three roof configurations: a conventional concrete slab, a BIPV system, and a BIPV system equipped with passive aluminum fins. Three-dimensional transient finite element simulations were carried out under field-measured 24 h meteorological boundary conditions characteristic of hot climates. The objective of this study is to quantify the impact of PV integration and passive cooling strategies on heat transfer behavior and building energy performance. The BIPV roof achieved a 38.4% lower residual temperature than the concrete slab at 19:00, indicating superior heat dissipation. The addition of passive fins reduced module temperature by up to 10–12 °C and decreased peak roof temperature by up to 12%. This temperature reduction decreased electrical losses from 13.2% to 10.4%, resulting in a 21% relative reduction in temperature-induced losses. The predicted temperature ranges (≈60–75 °C under peak conditions) are consistent with values reported in experimental and numerical studies of BIPV systems in hot climates, supporting the physical realism of the model. Convective heat transfer was represented using effective coefficients, providing a computationally efficient engineering approximation of air-side heat exchange. Despite construction cost increases of up to 38%, PV integration achieved competitive payback periods of approximately 8.5–9 months under hot climate conditions. This economic assessment is based on a simple payback approach using an incremental cost formulation, where the photovoltaic system replaces the conventional concrete roof, reducing the effective investment. This study introduces a reproducible 3D transient FEM methodology for evaluating BIPV roofs under field-measured climatic boundary conditions. The framework explicitly couples geometry-resolved passive cooling, full-day thermal evolution, and temperature-dependent electrical losses, providing a physically consistent basis for assessing BIPV design alternatives in hot climates. Full article

Bird strike events on rotating jet engine fan blades pose significant risks to aviation safety, yet high-fidelity numerical simulations remain computationally expensive, limiting their use in parametric design studies. This study develops a physics-guided machine learning surrogate framework for predicting bird strike response on rotating Ti-6Al-4V fan blades, systematically comparing Lagrangian (gelatin-based, Mooney–Rivlin) and Smoothed Particle Hydrodynamics (SPH, water-like) formulations. A total of 100 explicit dynamic simulations were conducted in ANSYS LS-DYNA (R2) (50 per formulation), varying bird impact velocity and blade angular speed. Random Forest, Support Vector Regression, Polynomial Regression, and XGBoost regression models were trained and evaluated using five-fold cross-validation. Results demonstrate that SPH-based surrogates achieve superior predictive accuracy, with Random Forest yielding R² = 0.9938 for maximum deformation and R² = 0.9962 for total energy dissipation. In contrast, Lagrangian-based stress surrogates exhibited severe performance degradation (R² = 0.24) due to mesh-dependent numerical noise. The trained surrogates achieved computational speed-up factors of 10⁴–10⁵ relative to direct simulation. These findings establish that surrogate model reliability is fundamentally governed by the numerical quality of the training data, providing guidance for integrating machine learning with impact simulation workflows in aero-engine blade design. Full article

As mining operations progressively advance to greater depths to meet increasing mineral demand, there is a growing need to develop new or improved rockbolts capable of effectively dissipating energy under dynamic loading conditions. Impact laboratory tests provide valuable insights into the dynamic performance of rockbolts; however, such tests require considerable time and cost associated with specimen preparation and experimental validation. Numerical modeling represents a robust alternative which, when properly calibrated with laboratory results, can accurately simulate the deformation process and energy dissipation mechanisms of support elements. This paper presents the implementation and results of a numerical model developed to simulate the dynamic behavior of a threadbar subjected to impact loading. The model explicitly represents all components of a full-scale impact test configuration, including the impact mass, reaction frame, threadbar geometry, grout, and steel tube. The numerical model enables real-time analysis of the dynamic response and interaction among the test components (steel tube, grout, and bolt). The implemented numerical codes were calibrated and validated against published laboratory results of threadbar dynamic behavior. Subsequently, a comprehensive parametric analysis was conducted to evaluate the response of each component in terms of load, displacement, and dissipated energy. The results allowed identification of the primary factors governing the dynamic response of the rockbolt system. The proposed methodology can be extended to other reinforcement systems and provides relevant insights into the design of bolts under dynamic loading conditions. Full article

The quality factor (Q) and its circumferential non-uniformity are essential for the resolution and long-term stability of Coriolis vibratory gyroscopes (CVGs). In practice, packaging and mounting anchors introduce torque-dependent and circumferentially non-uniform anchor dissipation, resulting in harmonic damping anisotropy. This paper presents an energy-consistent framework that quantitatively relates the tightening torque to both the mean damping factor $\eta =1/Q$ and its circumferential harmonic components. A hemispherical resonator gyroscope (HRG) is used for validation, where the dominant component is the fourth harmonic. By decomposing the energy dissipated per cycle, anchor loss is separated into friction loss and radiation loss. The friction channel is modeled using a partial-slip contact energy loss formulation combined with an equivalent tangential impedance coupling description, leading to a torque power-law scaling suitable for parameter identification. The radiation channel is described by an impedance coupling model that captures torque-enhanced anchor stiffness and potential saturation leakage under strong coupling. Controlled torque experiments show that $\eta \left(\vartheta \right)$ exhibits an almost pure fourth-harmonic dependence on the standing wave orientation for all tested torques. Within the accessible torque range, the mean damping decreases slightly with torque, while the harmonic amplitude increases and the phase progressively converges, supporting a friction-dominated interpretation. The phase convergence further suggests progressive stabilization of the contact state. The proposed approach provides quantitative guidance for torque selection and anchor structure design in resonant gyroscopes. Full article

Hydrogen is a carbon-free energy carrier that can support decarbonization of the energy and transport systems. Its usage as a fuel in internal combustion engines can abate the pollutants and CO₂ emissions but also presents various challenges. Among these, the formation of under-expanded jets requires proper injector design and accurate control of the injection process. CFD can accelerate the development of hydrogen engine technologies towards market readiness. Low-dissipative density-based schemes are essential to accurately describe the complex flow structures, that affect mixture formation in under-expanded injections. In the present work, the AUSM scheme was implemented in the OpenFOAM library, and successfully used to simulate an experimental hydrogen-into-nitrogen injection. The numerical method, validated against experimental Schlieren images, was compared with the Kurganov–Noelle–Petrova scheme implemented in the current density-based OpenFOAM solver. The numerical results highlighted the reduced dissipation of the AUSM scheme, leading to improved jet penetration and gas mixing. The investigation demonstrated the superior performance of the AUSM scheme, suggesting it as an alternative OpenFOAM solver. Nevertheless, the study identified areas for improvement and critical issues associated with this type of simulations. Full article