Search Results (317)

To address the insufficient load-bearing capacity and overall stiffness of timber truss roofs in brick–timber and earth–timber structures in rural areas, as well as the requirements for preserving traditional architectural characteristics, a steel–timber composite roof system was proposed. The system was developed through rational integration of timber and steel components to enhance the overall mechanical performance of the structure. At the joint level, flexural performance tests were conducted on cramp-iron joint, gusset–plate joint, and steel–timber joint. The moment–rotation relationships, failure modes, and ductility characteristics of the three joint types were systematically investigated. Based on the experimental results, a trilinear moment–rotation model was established. Furthermore, a finite element model of the roof structure was established using SAP2000 (26.2.0), and the stress distribution and load–displacement responses under horizontal static loading were analyzed through numerical simulation. The influence of different joint configurations on the mechanical performance of the roof structure was evaluated from an overall structural perspective. The results demonstrated that the peak bending moment of the steel–timber joint was increased by approximately 163.50% and 3.74% compared with those of the cramp-iron joint and gusset–plate joint, respectively. The ductility coefficient was enhanced by approximately 9.33% and 62.91%, respectively. In the finite element model of the roof structure, the peak load of the roof system with the steel–timber joint was increased by approximately 114.96% and 9.54%, while the corresponding displacement capacity was improved by approximately 76.62% and 43.41%, compared with the other two roof systems, respectively. Future studies will focus on further evaluating the seismic performance of steel–timber composite roof systems through cyclic loading experiments, dynamic response analysis, and full-scale structural validation, thereby providing a more comprehensive understanding of their long-term applicability in earthquake-prone rural buildings. Full article

This study investigated the effect of the partial replacement of silica with carbon fillers, namely carbon black (CB), graphene, and carbon nanotubes (CNTs), on the curing behaviour, thermo-mechanical properties, ageing resistance, and degradation of styrene-butadiene rubber (SBR) vulcanizates. The aim was to determine whether small amounts of carbon fillers could improve the durability-related properties of silica-filled SBR compounds. Graphene and CNTs reduced the maximum curing torque compared with the CB-filled compound while maintaining satisfactory curing characteristics. Thermal conductivity increased with temperature for all materials and reached 0.126 W·m⁻¹·K⁻¹ for the graphene-filled vulcanizate at 40 °C, compared with 0.109 and 0.107 W·m⁻¹·K⁻¹ for the CNT- and CB-filled compounds, respectively. Dynamic ageing tests revealed significant differences in self-heating behaviour. After 10,000 De Mattia cycles, the graphene-filled compound exhibited the lowest temperature increase (1.5 °C), whereas the CB5/Sil15 formulation showed the highest value (4.5 °C). GC-IMS analysis confirmed the formation of volatile degradation products during cyclic ageing, while increasing carbon filler content reduced the intensity of the characteristic VOC signals. Analysis of the crosslink structure indicated that CNT-containing compounds exhibited the highest resistance to ageing-induced structural changes, whereas graphene promoted an increase in the proportion of monosulfidic and carbon–carbon crosslinks. Overall, the results demonstrate that partial replacement of silica with carbon nanofillers improves the thermo-mechanical stability of SBR vulcanizates. Graphene provided the greatest enhancement in thermal conductivity and the lowest heat build-up, while CNTs showed the highest resistance to structural changes during dynamic ageing. Full article

Background: This review aims to systematically summarize the lineage origins, subtype classification, and functional dynamics of endometrial macrophages, clarify their mechanisms of action in normal reproductive physiology (menstrual cycle, pregnancy) and common reproductive diseases, integrate cognitive breakthroughs brought by cutting-edge research technologies, and provide theoretical support for basic research and clinical translation in reproductive medicine. Methods: Recent basic and clinical research studies related to endometrial macrophages were retrieved, with a focus on incorporating findings from technologies such as single-cell sequencing and multi-omics. The reviewed content covers core aspects including macrophage origins (embryonic-derived, bone marrow-derived), subtype classification (M1/M2 and novel metabolism-related subtypes), cycle- and pregnancy-specific functions, and disease-associated mechanisms. A comprehensive analysis of the regulatory networks of endometrial macrophages under physiological and pathological conditions was conducted. Results: Endometrial macrophages, by virtue of their phenotypic plasticity and functional heterogeneity, play a central role in cyclical endometrial remodeling, pregnancy establishment, and the regulation of reproductive immune homeostasis. Dysregulation of their function is closely associated with various reproductive disorders such as recurrent spontaneous abortion and endometriosis. In-depth exploration of their biological characteristics and regulatory mechanisms holds great significance for filling knowledge gaps in the field of reproductive immunology and advancing precise prevention and treatment of related diseases. Conclusions: Endometrial macrophages are core regulators of the reproductive immune microenvironment, and their spatiotemporal dynamic functions are closely linked to reproductive health. The revelation of novel classification systems and regulatory mechanisms provides new perspectives for in-depth understanding of reproductive physiological and pathological processes, as well as important targets for immune-targeted therapy of reproductive-related diseases. This holds great clinical translational significance for promoting the precision development of reproductive medicine. Full article

A CFD-based constrained three-component aerodynamic-trim procedure is implemented to investigate the load balance and coupled flowfield response of a simplified shipborne helicopter hovering over a flight deck. During the unsteady CFD calculation, the collective and cyclic pitch controls are updated according to the period-averaged vertical force and the rolling and pitching moments of the helicopter center of gravity. A pre-trim initialization is introduced before the formal-trim process to avoid large pitch corrections from the initial fixed-pitch state. Under a 20 m/s headwind, the initial fixed-pitch case shows a vertical-force deficit and extra rolling and pitching moments. After dynamic trim, the pitch controls converge to ${\theta }_0=8.46°$, $A_1=-2.48°$, and $B_1=1.20°$. Over the final one-revolution interval of approximately t = 31.74–32.00 s, the period-averaged loads are $F_z=112.82 \mathrm{k}\mathrm{N}$, $M_x=-0.06 \mathrm{k}\mathrm{N}·\mathrm{m}$, and $M_y=-0.07 \mathrm{k}\mathrm{N}·\mathrm{m}$. Additional +30° and −30° oblique-wind calculations confirm convergence toward the prescribed three-component load targets under asymmetric inflow conditions. The instantaneous flowfield comparisons suggest local responses in the rotor-inflow and fuselage-pressure regions after trim. Frequency-domain analysis identifies a dominant blade-passing-frequency component together with additional low-frequency content characteristic of the coupled rotor–ship aerodynamic response. Full article

Lined rock caverns offer a promising option for underground hydrogen, helping to mitigate renewable intermittency and enhance system stability. Considering the geological characteristics of hard rock formations in Southern Ontario, Canada, this study establishes a thermo–gas–mechanical coupled framework that incorporates hydrogen mass and energy evolution in the cavern, gas–wall convective heat exchange, dynamic cavern-volume feedback, and the deformation behaviour of the sealing layer, concrete lining, and surrounding rock. The influences of cavern geometry, sealing material, and in situ stress on the short–term thermodynamic and mechanical responses are further examined. The results show that hydrogen temperature and pressure exhibit clear stage–dependent evolution during the charging–storage–discharging cycle. The comparison between the first and 20th operating cycles indicates that repeated operation mainly causes a moderate adjustment of the cyclic thermal state and temperature–pressure baseline, without changing the overall stage–dependent response pattern. During charging, temperature and pressure increase simultaneously; during storage, both gradually decrease as thermal energy is transferred to the cavern wall; and during discharging, expansion causes pronounced cooling and depressurization, followed by gradual recovery driven by heat transfer from the surrounding rock. Cavern geometry significantly affects stress redistribution around the cavern. The circular cavern shows a relatively uniform stress distribution, whereas the arched cavern is more prone to local stress concentration near the sidewall–floor transition zone. The sealing material mainly influences gas temperature fluctuations through its thermal conductivity. The fibre–reinforced plastic (FRP) sealing layer amplifies thermal fluctuations during cyclic operation, whereas the steel sealing layer promotes heat dissipation through the lining and surrounding rock, thereby moderating cavern–gas temperature variations. In situ stress difference further controls the directional distribution of stresses around the cavern. As the minimum horizontal principal stress increases, compressive stress concentration at the crown and invert becomes stronger, while relative stress release occurs near the sidewalls. These findings provide a thermo–mechanical basis for preliminary cavern–geometry design, comparison of sealing–layer thermal performance, and assessment of in situ stress adaptability for lined rock cavern hydrogen storage in Southern Ontario. 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

Sheep play a crucial role in strengthening food security in different regions, where climates are often variable and resources can be limited. The importance of these animals includes nutrition and income. For sustainable production, manipulating estrous cyclicity is a pivotal, particularly in tropical and dry climate regions. Given the variation in reproductive performance in various breeds with seasons, and management practices, it is difficult to select effective protocols at all times. There is a need for in-depth knowledge on efficiency of available protocols. This review critically synthesizes current estrus synchronization strategies in sheep, integrating physiological principles with comparative evaluation of hormonal molecules, protocol architectures, and reproductive performance data. Progesterone-based systems remain the cornerstone of synchronization, particularly when combined with equine chorionic gonadotropin (eCG), because they simulate luteal activity and promote follicular recruitment during seasonal anestrus. However, prolonged progestogen exposure may induce persistent follicles and compromise oocyte quality, whereas short-term protocols (5–7 days) frequently achieve comparable or improved fertility while reducing hormonal exposure. Gonadotropin-releasing hormone (GnRH)-based approaches improve control of ovulation timing and are particularly useful for fixed-time artificial insemination (FTAI), although their effectiveness declines during deep anestrus without exogenous gonadotropic support. Prostaglandin-only systems provide cost-effective synchronization in cyclic ewes, but their reliability is limited outside the breeding season. Emerging innovations, including recombinant gonadotropins and nano-formulated hormone delivery systems, aim to enhance endocrine precision while addressing welfare, immunogenicity, and regulatory concerns associated with conventional eCG use. Across studies, variation in outcomes reflects the complex interaction among endocrine regulation, follicular dynamics, luteal competence, breed-specific ovarian responsiveness, and seasonal neuroendocrine suppression. Therefore, current evidence suggests that synchronization success depends less on protocol complexity than on physiological compatibility with breed characteristics, seasonal reproductive status, and production objectives. Future research on precision endocrine modulation, reduced hormonal exposure, ethical standardized outcome reporting is warranted. Full article

Objectives: To compare the geometric design, metallurgical properties, mechanical performance, and irrigation dynamics of Reciproc Minima (M20 and M25) and Reciproc Blue R25 instruments. Methods: One hundred and eighty instruments (n = 60/group) were evaluated. Geometry was analyzed using stereomicroscopy, scanning electron microscopy, and 3D surface scanning. Metallurgical characteristics were assessed by energy-dispersive X-ray spectroscopy and differential scanning calorimetry. Mechanical performance tests (n = 10/group) included cyclic fatigue, torsional resistance, bending resistance, buckling resistance, and cutting efficiency. Irrigation dynamics were examined through computational fluid dynamics simulations based on a micro-CT-derived mandibular molar model prepared according to each system and combined with open-ended, side-vented, or double side-vented needles. Data were analyzed using one-way ANOVA or Kruskal–Wallis tests (α = 0.05). Results: The results showed that blade dimensions increased progressively from Minima M20 to Reciproc Blue R25. All instruments had S-shaped cross-sections and non-active tips. Energy-dispersive spectroscopy confirmed near-equiatomic NiTi composition, and similar phase transformation temperatures were observed across groups. Minima M20 showed the highest cyclic fatigue resistance (p < 0.0001), whereas Minima R25 exhibited greater angular deflection (p < 0.0001). Reciproc Blue R25 had the highest buckling resistance and lowest flexibility (p < 0.0001). M25 showed the lowest axial force, indicating the numerically highest cutting efficiency, but it did not differ significantly from Reciproc Blue R25 (p > 0.05). No needle delivered irrigant to working length. The open-ended needle achieved greater apical penetration, particularly with Reciproc Blue R25. Minima M20 generated the highest wall shear stress, and Reciproc Blue R25 the lowest apical pressure. Conclusions: Reciproc Minima and Reciproc Blue R25 showed similar metallurgical characteristics; however, differences in geometric design resulted in distinct mechanical behaviors and irrigation fluid dynamics. These findings suggest that low-taper reciprocating instruments may represent a conservative alternative in anatomically challenging canals, while clinicians should consider the associated differences in mechanical behavior and irrigation dynamics when selecting the most appropriate instrument. Full article

Financial systems are highly nonlinear and often influenced by investment cycles, market fluctuations, and external financing activities, which can generate complex dynamic behaviors. This paper proposes a new three-dimensional chaotic financial firm model by extending the classical Bouali financial system through the inclusion of a cyclic reinvestment perturbation represented by a sinusoidal nonlinear term. The proposed modification aims to capture state-dependent nonlinear reinvestment feedback in reinvestment decisions caused by changing economic conditions and business cycles. The dynamical characteristics of the model are investigated using equilibrium analysis, local stability theory, Lyapunov exponents, the Kaplan–Yorke dimension, bifurcation analysis, and multistability analysis. Numerical results show that the system possesses three equilibrium points, all of which are unstable under the selected parameter setting. The system exhibits chaotic dynamics confirmed by a positive maximum Lyapunov exponent and a fractal attractor characterized by a Kaplan–Yorke dimension greater than two. Comparative results indicate that the new model demonstrates richer nonlinear dynamical behavior than existing financial firm systems reported in the literature. Furthermore, bifurcation and Lyapunov spectrum analyses disclose multiple transitions between periodic and chaotic states as system parameters vary, while multistability analysis reveals the coexistence of symmetric periodic and chaotic attractors under identical parameter values but different initial conditions. Finally, total amplitude control and offset boosting techniques are implemented to regulate attractor size and position while preserving the underlying chaotic behavior. These findings demonstrate that cyclic reinvestment perturbations significantly enrich the nonlinear dynamics and symmetry properties of financial firm systems, providing a useful framework for studying complex financial behaviors and chaos control. Full article

Graded aggregates used in high-speed railway subgrades often undergo micro breakage (i.e., corner and edge spalling) under cyclic loading, whereas the mechanism linking local particle spalling to contact-network evolution and permanent deformation remains unclear. To address the lack of a physically based micro breakage criterion and a continuous local shape-updating scheme in existing DEM approaches, this study proposes an energy-driven micro breakage method. The method uses the relationship between contact elastic energy and fracture energy for newly created free surfaces as the breakage criterion. It also employs a radial function representation to simulate local particle shape evolution. The proposed method is subsequently validated through multilevel tests and shows reasonable agreement with the experimental results for particle micro breakage and the associated mechanical responses. Furthermore, dynamic triaxial simulation results show that micro breakage exhibits a distinct cumulative characteristic and increases with loading frequency and amplitude. Meanwhile, micro breakage drives particle rearrangement and new contact formation, leading to skeleton densification and weakening of the strong force-chain network, which in turn accelerates plastic deformation accumulation. These coupled processes constitute an important mechanism governing the progressive degradation of graded aggregates under cyclic loading. This study clarifies the associated particle-scale mechanism and provides a reference for performance optimization. Full article

The diverse properties and applications of chitosan materials require a broad spectrum of characterization techniques. In the meantime, due to chitosan’s high gel-forming capability, the rheological properties of chitosan solutions vary significantly depending on their state, i.e., solution or gel. To elucidate the solution and gel-based characteristics of chitosan, the present study was conducted to thoroughly investigate its rheological characteristics at different concentrations (1.25%, 2.5%, and 4% w/v), using various steady and dynamic rheological measurements and different mathematical models. The results showed that the concentration of chitosan solutions strongly affects their rheological properties in terms of shear stress, viscosity, and various dynamic rheological characteristics, through strain, angular frequency, and temperature sweep tests. In this regard, an elastic behavior was observed for low concentrations of chitosan solutions at lower shear strains, while the higher concentrations and higher shear strains exhibited predominantly viscous behavior. In frequency sweep measurements, the 1.25% and 2.5% w/v chitosan solutions showed viscous-like behavior and the 4% w/v solution exhibited solid-like behavior with almost constant storage and loss modulus profiles over the studied frequency range. According to temperature sweep measurements, viscous-like behavior was dominant at lower temperatures, which resulted in elastic gel structures at higher temperatures. Investigating the recoverability of prepared solutions by cyclic strain measurements revealed that the higher-concentration solutions of chitosan possess the desired capability to recover their structure. The results of this study provide detailed rheological insights into chitosan solutions suitable for designing and developing various chitosan-based products for different applications. Full article

To accurately reveal the mechanism of interlayer separation, crack propagation, and progressive instability of vault strata in underground cavities in gentle-dipping bedded rock masses, this paper systematically elucidates the entire mechanical behavior of separation evolution, crack penetration, structural transformation, and step-by-step caving of vault bedded rock masses under excavation disturbance through a comprehensive integration of excavation unloading mechanical analysis, the Griffith strength criterion, and the dynamic transformation theory of beam structures. The results show that excavation induces radial unloading and circumferential stress concentration in the surrounding rock, and the vault rock mass preferentially undergoes interlayer separation along near-horizontal gentle-dipping bedding planes, forming a spatial zoning feature of gradient attenuation from bottom to top: a strong separation zone at the lower part, a transition zone in the middle, and a closed zone at the upper part. The vault strata undergo a cyclic dynamic structural transformation of cantilever beam–fixed-end beam–simply supported beam, exhibiting stepped fracturing and layer-by-layer caving failure characteristics. The fracture and caving range follow a three-stage evolution law of initial increase–peak–subsequent convergence and stabilization. Based on the elastic mechanics stress transformation relationship, a Griffith initiation criterion for surrounding rock of circular cavities under non-axisymmetric loads is derived and established, and mechanical calculation models of single beam and composite beam suitable for stratified rock masses are constructed, which quantitatively reveal the controlling effects of tensile strength of strata, lateral pressure coefficient, tunnel diameter, stratification thickness, and burial depth on crack initiation and failure degree. Verified by a city-gate-shaped tunnel numerical test and an practical engineering case of a large-scale underground tunnel in western China, the theoretical calculation results are in good agreement with the on-site failure morphology and numerical analysis results. The established separation criterion and mechanical model can effectively predict the initiation risk and stability critical conditions of vault strata. The research results can provide a theoretical basis and technical support for the stability evaluation, early warning, and optimal design of support structures of surrounding rock in underground engineering in gentle-dipping bedded rock masses. Full article

Understanding the dynamic evolution of pore and fracture structure (PFS) in coal under mining disturbance is essential for safe coal extraction. In this study, coal specimens collected from the Dongqu Mine, Taiyuan, Shanxi Province, China, were subjected to stepwise cyclic confining pressure loading–unloading tests using a triaxial in situ nuclear magnetic resonance (NMR) system. Based on T₂ spectrum measurements, the real-time evolution of PFS, stress–strain response, permeability-related behavior, average pore diameter, and fractal characteristics were systematically investigated. The results show that irreversible damage developed in the coal specimens during cyclic confining pressure loading–unloading. With increasing cycle number, the load-bearing capacity gradually decreased, internal damage intensified, and pore expansion and coalescence became more pronounced. Seepage pore porosity showed an overall increasing trend, indicating a gradual enhancement of inferred permeability. Therefore, seepage pore porosity can be used as an effective indicator for evaluating permeability-related evolution in coal. During both loading and unloading stages, the relative volumes of small pores (SP), medium pores (MP), and large pores and fractures (LPF) continued to increase, whereas their average pore diameters fluctuated. This indicates that pore volume growth was controlled not only by the enlargement or shrinkage of pre-existing pores but also by new PFS generation. Fractal analysis showed that the fractal dimensions of MP, LPF, and total pores exhibited clear scale-dependent evolution, whereas the calculated SP fractal dimensions were lower than 2 and were therefore not suitable for pore-surface fractal interpretation. Among the valid pore systems, LPF exhibited the highest fractal dimension, indicating that LPF dominate the structural complexity of coal. These findings provide new insight into the fractal evolution of unloading-induced PFS damage and offer theoretical support for mitigating gas outburst and water inrush hazards during coal mining. Full article

Underground gas storage converted from depleted oil and gas reservoirs requires reliable long-term sealing of caprocks, faults, and other geological barriers during cyclic injection and withdrawal. Conventional evaluations mainly focus on static geological parameters, whereas the effects of stress evolution during operation are often insufficiently addressed. In contrast, four-dimensional geomechanical simulations based on fluid–solid coupling can capture the dynamic evolution of geological sealing behavior under injection and withdrawal conditions. The review summarizes progress in heterogeneous geomechanical model construction, stress-field evolution under cyclic loading, dynamic sealing assessment of caprocks and faults, and determination of safe operating pressure limits. Geological sealing evaluation has evolved from a static assessment based on geological characteristics to a dynamic assessment controlled by mechanical criteria. Geostress inversion has developed from three-dimensional heterogeneous mechanical models to four-dimensional geomechanical dynamic coupling analyses that account for seepage, stress, temperature, and other factors. Safe pressure evaluation has also progressed from conventional gravity-driven storage construction to the assessment of critical pressure evolution during the safe operation stage. Existing studies indicate that heterogeneous parameter characterization, coupled flow-stress simulation, and dynamic pressure management strongly affect the reliability of sealing evaluation in reservoir-type UGS. The results further show that pressure history, stress redistribution, and creep effects should be considered together when assessing long-term storage safety. The engineering cases listed at the end of this paper verify some of the research findings. The results presented above are of great significance for the construction and safe operation of reservoir-type gas storage facilities. Full article

To address the limitations of traditional Voltage-Current (VI) trajectory features in appliance load identification—such as the difficulty in distinguishing similar appliances, weakened amplitude information, and the absence of dynamic characteristics—this paper proposes a dual-stage cyclic training method for load identification that integrates multi-feature reconstruction with Particle Swarm Optimization (PSO). First, to overcome the high similarity of original VI trajectories, a PSO-based threshold optimization algorithm is designed to reconstruct VI trajectories through reflection operations and normalization, thereby enhancing the geometric morphological differences among similar appliances. Second, to supplement dynamic impedance information and energy level features, conductance-time trajectories and mean-square current color-block maps are introduced to characterize dynamic impedance variations and energy level differences, respectively. Finally, a three-channel classification network based on ResNet18 is constructed, where the reconstructed VI trajectories, conductance-time trajectories, and mean-square current color-block maps are fused via RGB channels as inputs, forming a closed-loop “threshold optimization—feature reconstruction—cyclic training” framework. Experimental results on the PLAID dataset demonstrate that the proposed method achieves an identification accuracy of 98.29% and a macro-averaged F1-score of 97.93%. Comparative experiments verify the effectiveness of the reconstructed VI trajectories, the complementarity of multi-feature fusion, and the superiority of the combinatorial optimization network, significantly improving the identification of multi-state and similar-condition appliances. Full article