Search Results (1,281)

Large-scale and long-term hydrogen storage is a key requirement for a sustainable hydrogen-based energy system. Although underground hydrogen storage (UHS) in porous media has gained increasing attention, the behavior of hydrogen during cyclic injection and withdrawal remains poorly understood. This study experimentally investigates the effects of cyclic hydrogen injection cycles (3, 6, 9, and 12 cycles) on the physical and mechanical properties of both dry and brine-saturated Berea, which serves as a representative reservoir rock. Porosity, permeability, and mineral composition of the samples were measured before and after the injection cycles, while triaxial tests were conducted post-injection and compared with reference sister samples. Results show negligible and inconsistent mineralogical changes before and after hydrogen injection. Porosity remained nearly constant (<2 percentage variation), whereas permeability declined by more than 20% in samples, which can impact recovery efficiency. Mechanical properties remained largely unchanged, indicating stability. However, further experimental and modeling studies are required to better understand the observed permeability reduction and its implications for underground hydrogen storage (UHS). Full article

Predicting the fatigue lives of high-performance alloys, specifically aluminum 7075-T6 and Inconel 718, is essential for ensuring structural integrity in applications such as aerospace and energy. While Poisson’s ratio is typically treated as a constant within fracture mechanics and finite element analysis, it has been found to vary significantly with increased temperatures and substantial amounts of plastic deformation. Variations in Poisson’s ratio can, therefore, have a significant impact on local stress fields around cracks and the behavior at crack tips. This study introduces a novel approach by systematically isolating the effects of varying Poisson’s ratios on fatigue life cycles, stress distributions, and fatigue crack growth using finite element analysis with the robust ANSYS SMART crack growth feature. The results indicate a stark difference in the effects of Poisson’s ratio on the fatigue life of aluminum 7075-T6 compared to Inconel 718. A strong negative correlation exists between Poisson’s ratio and fatigue life cycle numbers for aluminum 7075-T6, whereas a more linear trend is observed for all fatigue life cycle numbers of Inconel 718. The underlying reasons for these trends lie in the differing sensitivities of elastic, shear, and bulk moduli between the two alloys. Overall, a higher Poisson’s ratio intensifies the maximum principal stress for both alloys. Additionally, an increase in Poisson’s ratio leads to a decrease in von Mises stress for both metals. Furthermore, these numerical results demonstrate that an increase in Poisson’s ratio corresponds to a decrease in the cyclic plastic zone size at the crack tip for both alloys, indicating enhanced hydrostatic constraint and reduced shear deformation. The findings presented herein underscore the necessity of eliminating the use of static values for Poisson’s ratio when evaluating the structural performance of high-performance alloys under extreme operational environments. Additionally, this research highlights several key areas where existing modeling approaches are lacking and establishes a framework for developing improved constitutive models for fatigue life prediction. Full article

Understanding the failure mechanism of soft rock roadways in high-humidity environments, as well as designing appropriate control measures, are critical for ensuring their stability. In this study, swelling and triaxial compression tests on argillaceous sandstone were first performed. Results show that the triaxial compressive strength (TCS), elastic modulus, cohesion, and internal friction angle of argillaceous sandstone are all decreased due to the water weakening effect. Then, a self-developed finite-element-based numerical code was employed to elucidate the role of humidity diffusion in the deformation and failure of soft rock roadways. Simulation results indicate that under the influence of humidity, high stress concentration zones develop, initiating microcracks within these regions. As humidity continues to diffuse, the high stress concentration zones expand and migrate deeper into the surrounding rock, causing microcracks to propagate and accelerating humidity diffusion. This cyclical process repeats, ultimately resulting in macroscopic fracturing. The failure of roadway exhibits a tensile–shear mixed mode during humidity diffusion. A comparative analysis of four control measures reveals that conventional non-waterproof shotcrete primary support is of limited effectiveness in ensuring the stability of high-humidity soft rock roadways. It is essential to promptly establish a closed waterproof support structure. Furthermore, localized support defects significantly impact control effectiveness. Full article

Point-of-care (POC) technologies are promising tools to decentralize and accelerate the diagnosis of rare diseases. Among them, electrochemical immunosensors offer advantages such as high sensitivity, low cost, portability, low sample consumption, and suitability for use in resource-limited settings. However, the performance of these devices is dependent on electrode surface properties, which influence electron transfer, biomolecule immobilization, and analytical sensitivity. In this work, screen-printed carbon electrodes (SPCEs) were modified through two strategies: (i) gold electrodeposition and (ii) cold plasma treatment. The modified electrodes were functionalized with EDC/NHS, followed by the immobilization of anti-SMN antibodies and electrochemical characterization using cyclic voltammetry and differential pulse voltammetry. The impact of each modification approach on the electrochemical response and reproducibility of the sensor was evaluated. Gold electrodeposition resulted in higher and more reproducible electrochemical responses, demonstrating improved electron transfer properties and surface homogeneity. The primary objective of this study was to investigate how different surface modification strategies affect the electrochemical performance of SPCE-based immunosensors, employing the detection of Survival Motor Neuron (SMN) protein, a biomarker associated with Spinal Muscular Atrophy (SMA), as a proof-of-concept application. The resulting platform successfully differentiated specific and non-specific protein recognition events through distinct electrochemical patterns, demonstrating the suitability of gold-modified SPCEs for immunosensing applications. These findings provide insights into the influence of surface engineering strategies on sensor performance and support the future development of optimized electrochemical platforms for biomarker detection. Full article

Ground-motion intensity measures (IMs) are key parameters for seismic hazard and risk assessment. However, seismic hazard characterization and code-based design spectra commonly rely on a limited set of parameters, particularly peak ground acceleration (PGA), spectral acceleration, and control periods defining spectral shape. Such representations may not fully capture seismic input relevant to structural response, soil deformation, slope instability, and indirect environmental impacts. This study analyzes 220 horizontal accelerogram components recorded during the Vrancea earthquakes of 4 March 1977, 30 August 1986, 30 May 1990, and 31 May 1990. Twenty-three IMs were computed, covering peak and effective amplitudes, velocity-related measures, cumulative and energy-based indicators, spectral intensities, duration, cyclicity, and impulsivity, together with a set of frequency content-related parameters. Pearson and Spearman correlations were evaluated using both the geometric mean and the maximum of the two horizontal components. Hierarchical clustering, PGA-centered correlation profiles, event-specific comparisons, and spatial representations were used to assess redundancy, complementarity, and relationship stability. Results show that amplitude-, velocity-, and spectrum-related IMs form strongly correlated groups, whereas duration, cyclicity, and impulsivity remain more distinct. Spatial comparisons also show that different IMs may produce different station rankings and regional patterns for the same event. These findings support selecting complementary IM families for more comprehensive, risk-informed structural and geotechnical applications. Full article

Background and Objectives: This study aimed to investigate the biomechanical properties of different cephalomedullary fixation methods for osteoporotic femurs using a synthetic bone model. Materials and Methods: Lateral impact tests and axial cyclic loading tests were performed, and each test was divided into three groups: group 1 with one reconstruction screw, group 2 with two reconstruction screws, and group 3 without cephalomedullary fixation. To simulate a healed femoral shaft fracture, no osteotomy was performed on the specimens. Results: Groups 1 and 2 had significantly higher mean stiffness, ultimate failure load, and energy to failure in the lateral impact test compared to the native synthetic femur (p < 0.001 for all), while group 3 had significantly lower values in all outcomes (p < 0.05 for all). Groups 1 and 2 showed significantly higher average number of cycles, total load to failure, and initial axial stiffness in the axial cyclic incremental loading test compared to the native synthetic femur (p < 0.001 for all), whereas group 3 showed a significantly lower mean number of cycles and total load to failure (p < 0.001 for all). Conclusions: Under the specific test conditions of this intact synthetic bone model, cephalomedullary fixation with one or two reconstruction screws demonstrated superior relative mechanical stability compared to standard interlocking nails. Using two reconstruction screws provided the greatest biomechanical resistance to failure. In cases where inserting two reconstruction screws is technically challenging or infeasible, a single reconstruction screw may offer an acceptable biomechanical alternative to help prevent peri-implant fractures in healed or prophylactic settings. Intramedullary nailing without cephalomedullary fixation exhibited the lowest mechanical performance, suggesting a potential biomechanical vulnerability to peri-implant fractures under these test conditions. Full article

Lewis acid-catalyzed epoxide openings efficiently promote intramolecular cyclizations forming complex oxygenated frameworks. Herein, we investigated the reactivity of epoxyolefins under catalytic conditions using various metal triflates. The study focuses on the competition between epoxide isomerization and intramolecular cyclization involving a pendant olefin. Screening of several metal triflates revealed that Lewis superacids, particularly Bi(OTf)₃, promote efficient transformations at room temperature with low catalyst loadings (1 mol%). Structural variation in the substrates significantly influenced product distribution likely through coordination effects, impacting cyclization efficiency with higher yields observed for non-chelating epoxyolefins. Substrates derived from geraniol underwent selective cyclization to cis-cyclic alcohols and bicyclic ethers in good yields, with stereochemical outcomes consistent with the Eschenmoser model. Reaction conditions such as temperature and catalyst loading further modulated selectivity, allowing control over product distribution. These results highlight the potential of metal triflates as versatile and efficient catalysts for the stereoselective intramolecular cyclization of epoxyolefins, offering access to cyclic frameworks under mild conditions. Full article

To address the difficulty of extracting weak fault features of rolling bearings in wind turbines under strong background noise, a fault feature extraction method based on the collaborative filtering correlation spectrum, named CESIgram, is proposed. The collaborative filtering correlation spectrum (CFCS) based on Block Matching 3D is designed to suppress random noise while preserving cyclostationary structures, resulting in a clearer cyclic spectral representation. A projection method along the cyclic frequency axis is proposed to obtain the carrier-based enhanced envelope spectrum. An integrated envelope spectrum index combining harmonic significance and periodic impact is proposed to quantify fault feature enrichment in different enhanced envelope spectra. The method works in three stages: spectral representation via Fast-SC, reformulation of the spectral correlation via CFCS, and adaptive band selection via CESI. The method successfully extracted fault characteristic frequencies and their harmonics in simulation and experimental signals under various strong noise conditions, while Fast Kurtogram, Autogram, Infogram, and Fast Entrogram failed to detect any fault-related peaks. Comparative analysis shows that the proposed method has significant advantages in noise suppression and fault feature extraction. The effectiveness is verified using simulation and experimental signals of rolling bearing faults in wind power equipment. Full article

This study fabricated choline–acrylic acid deep eutectic solvent (DES) hydrogels via in situ free-radical polymerization and systematically investigated the individual and co-optimization effects of lignin dosage and water content on the chemical structure, micromorphology, compressive mechanical properties, swelling behavior, and thermal stability of the hydrogels. This work quantitatively uncovers the co-optimization mechanism between the two variables in modulating crosslink density and pore architecture, thereby filling a research gap in the dual-factor co-optimization of biomass-based DES hydrogels. The results reveal that a moderate lignin dosage (0.02 g) generates abundant dynamic hydrogen bonds, densifying the crosslinked network and raising the maximum compressive stress from 0.378 MPa to 0.426 MPa, whereas excessive lignin triggers molecular aggregation and deteriorates mechanical performance. Higher water content dilutes crosslinking sites, reduces network compactness, boosts the swelling ratio while lowering compressive strength, and exerts negligible impacts on thermal degradation characteristics. FTIR analysis confirms that lignin participates in network formation solely through non-covalent hydrogen bonds, without forming new covalent bonds. A comprehensive performance evaluation identifies the optimal formulation as 0.02 g lignin and 60 g water. Although this two-factor optimization strategy provides clear experimental and theoretical guidance for designing sustainable soft materials, the present work still has limitations, including the use of only static laboratory characterizations, with no cyclic mechanical measurements or aging assessments. This study advances the customized performance tuning of lignin-derived DES hydrogels and facilitates the high-value valorization of lignin, which is promising for multifunctional green-material applications, including adsorption, flexible electronics, and biological carriers. Full article

Cyclic high-pressure gas impact is a promising waterless stimulation method for enhancing permeability in deep low-permeability coal seams. However, the nonlinear fracture evolution, cumulative fatigue damage, and coupled fracturing mechanisms during repeated gas impacts remain insufficiently understood. In this study, cyclic high-pressure gas impact tests were conducted on unconfined synthetic rock-like specimens under gas pressures of 5 MPa and 7.5 MPa. The macroscopic crack networks induced by repeated impacts were quantitatively characterized using digital image processing and box-counting fractal analysis. Ultrasonic P-wave velocity measurements were used to reconstruct the spatial evolution of internal damage after each impact, and an empirical Weibull statistical damage model was established to describe the nonlinear fatigue degradation process. In addition, two-dimensional LS-DYNA numerical simulations were performed to reveal the transient stress wave propagation and stress-field evolution during cyclic impacts. The results show that fracture propagation under cyclic gas impacts exhibits a distinct nonlinear pattern, characterized by slow early-stage damage incubation followed by rapid late-stage crack coalescence. The fractal dimension of the surface crack network increased markedly after repeated impacts, reaching a maximum of 1.51 under the 7.5 MPa condition. Ultrasonic damage analysis further indicates that, based on path-averaged evaluations, apparent damage is more pronounced near boundaries at the lower pressure, whereas higher pressure induces severe structural degradation along the central measurement paths, with a maximum damage value of 0.47. The combined experimental and numerical results suggest that the initial impacts generate transient stress waves and cumulative microcracking, thereby progressively weakening the rock matrix. This progressive degradation subsequently enables quasi-static gas wedging to drive macroscopic crack propagation and coalescence. These findings provide a preliminary phenomenological baseline for understanding cyclic gas-induced cracking, providing a preliminary basis for understanding waterless reservoir stimulation by cyclic gas impacts. Full article

A critical research gap persists in modular steel construction regarding the seismic behavior of inter-module connections between square steel tubular columns and H-shaped steel beams. While numerous connection systems have been proposed, two fundamental challenges remain unresolved: the inherent conflict between construction efficiency and mechanical performance, and the insufficiency of restoring force models that systematically describe hysteretic characteristics and stiffness degradation under cyclic loading. To address these issues, a novel box-type modular connection between square steel tubular columns and H-shaped steel beams is proposed. A finite element model was established using ABAQUS, and the modeling methodology was validated against experimental results from the literature. The seismic behavior was systematically investigated, and a restoring force model with theoretical saturation and linear degradation was developed. Results show that the novel joint is a semi-rigid connection that satisfies the “strong column–weak beam” design principle. The outer ring plate shifts the plastic hinge away from the vulnerable beam end region, preventing failure at the beam–column connection. Among the detrimental factors identified, the insert-to-column gap has the most severe impact, causing up to a 49.5% reduction in energy dissipation and a 6.5% reduction in initial stiffness; the outer ring plate thickness below the beam flange thickness causes a 44.6% drop in energy dissipation. The proposed restoring force model, validated against nine calibration specimens and one independent specimen, predicts peak load with a deviation of only 1.14% and the equivalent viscous damping coefficient with a relative error of 14.7%, confirming its reliability in capturing the cyclic behavior of the joint. This study provides both design recommendations for engineering practice and a theoretical foundation for elasto-plastic analysis of modular frames with this connection type. Full article

Natural fibre-reinforced polymer biocomposites are increasingly considered for construction applications because of their renewable reinforcement, low density and potentially reduced environmental impact. Their durability, however, is strongly constrained by moisture, which promotes fibre swelling, weakens the fibre–matrix interphase and creates conditions favourable to fungal colonisation. This review examines the effects of moisture and biodeterioration on the structural and thermal performance of natural fibre-reinforced polymer composites used in construction. Across the reviewed studies, moisture and hygrothermal ageing produced tensile-strength reductions ranging from less than 10% to approximately 40%, while losses in stiffness or impact performance exceeded 40–70% in particularly susceptible systems. In contrast, directly comparable quantitative data linking fungal biodeterioration with changes in thermal conductivity remain scarce, representing a major research gap. Current durability standards, particularly ISO 846:2019, provide useful screening data but do not fully reproduce the cyclic hygrothermal conditions experienced by porous, hygroscopic construction biocomposites. More reliable durability assessment requires integrated microbiological, hygrothermal, mechanical and microstructural testing supported by advanced non-destructive diagnostics. Protection strategies should combine moisture control and biological resistance while considering long-term service performance, environmental impacts, recyclability and end-of-life constraints. Full article

E-cargo bikes have emerged as a promising solution for sustainable urban mobility and last-mile logistics. However, their structural design must ensure durability and safety under demanding cargo transport and daily operating conditions. This study evaluates the structural performance of three single-track E-cargo bike frame typologies, Urban, Long John and Long Tail, using finite element analysis under fatigue and impact loading conditions derived from EN 15194:2020 and EN 17860-2:2024. Numerical models of aluminum 6061-T6 frames were developed to simulate cyclic pedaling, horizontal, seat-post and vertical cargo loading forces, together with falling-frame and falling-mass impact tests. Structural performance was assessed through fatigue life, stress distribution, damage initiation, plastic strain and permanent wheelbase deformation. The Urban and Long John frames satisfied the adopted fatigue-life requirements, whereas the Long Tail frame failed the vertical loading-area fatigue test with a predicted fatigue life of 5.22 × 10⁴ cycles, below the required 2 × 10⁵ cycles. The maximum von Mises stresses during the falling-frame impact test reached 384 MPa, 326 MPa and 356 MPa for the Urban, Long John and Long Tail frames, respectively, while the corresponding permanent wheelbase deformations remained limited to 2.07 mm, 1.97 mm, and 1.43 mm, all below the acceptance criterion. These results highlight the influence of frame geometry and cargo location on structural behavior and support future frame optimization. Full article

Power management of photovoltaic generation, flexible loads, e.g., electric vehicles and heat pumps, and battery energy storage systems (BESSs) have become important for energy arbitrage. This work develops a two-level power management model for day-ahead and real-time scheduling, where the contribution of flexible loads (e.g., vehicle-to-grid (V2G) use) and BESSs is compared, considering different load types, load sizes, seasons, and battery degradation. An empirical degradation model has been linearized and incorporated, including cyclic and calendar aging. The results showed that the seasonal effect significantly influences the grid power exchange and the V2G use. Moreover, the load type has a notable impact on the flexibility of the node since commercial grids import less grid power and use less V2G due to lower flexibility. Furthermore, a larger load size decreases the need for BESS use and increases the likelihood of V2G use. While degradation has a small effect on the total cost of small aggregated loads, the effect increases notably as the size of the load increases, while it also greatly reduces V2G and BESS use. Finally, the model has been validated against benchmark and control models, showing cost reductions of up to 5.81% and 30.6%, without and with BESS use, respectively. Full article

Aramid nanofibers (ANFs) inherit the exceptional properties of the bulk counterparts, while introducing a large specific surface area and excellent processability. However, the strong inter-fibrillar interactions and tendency to agglomerate hinder their high-content incorporation into polymer matrices. Here, we report a one-pot reprotonation–compounding strategy for fabricating aramid nanofiber-reinforced poly(vinyl alcohol) (ANF–PVA) composite films, where the ANF dispersion was mixed with polymers during the protonation process to form a continuous 3D network in the ANF-PVA film. The optimized film with a loading of 20 wt% ANFs exhibited a tensile strength of 122.2 MPa and a toughness of 28.36 J m⁻³. Furthermore, the high ANF loading enabled versatile applications. A robust ANF-PVA hydrogel, prepared via salt-induced gelation, delivered 132% enhancement in tear strength and 38.2% increase in cyclic compressive strength compared with the PVA hydrogel. Moreover, inspired by the “brick-and-mortar” architecture of natural nacre, the fully organic ANF-PVA film was incorporated into carbon fiber/epoxy laminates, with a configuration of one nacre-inspired film per five prepreg plies, achieving a 36.5% improvement in impact toughness and minimal loss in flexural strength. This scalable reprotonation–compounding approach provides a general route for producing high-loading ANF-based composites, paving the way for the broader utilization in advanced materials. Full article