Search Results (12,133)

The safe service of tunnel inverted arch structures in high-altitude cold regions is heavily restricted by the performance of backfilling materials, which need to simultaneously adapt to low-temperature, low-pressure extreme environments and meet the long-term mechanical requirements of underground building structures. However, the strength development and preliminary mechanical applicability of foam concrete for tunnel inverted arch backfilling under reduced atmospheric pressure remain insufficiently understood. To this end, this paper carries out mix proportion optimization and mechanical performance testing of foam concrete, focusing on the strength behavior under different dry densities and simulated high-altitude low-pressure conditions. The test results show that the compressive strength of foam concrete is positively correlated with dry density, and the growth rate accelerates when the dry density is above 1000 kg·m⁻³. Specifically, the developed high-performance foam concrete with a dry density of 1200 kg·m⁻³ achieves a 28-day compressive strength of 27.1 ± 1.2 MPa under 60 kPa atmospheric pressure, indicating stable mechanical performance with low variability. The results indicate that, within the tested dry-density range and under the adopted curing and pressure conditions, the developed foam concrete can meet the basic compressive-strength requirement for tunnel inverted arch backfilling. This study provides a reference for material selection and structural design in high-altitude cold-region tunnel engineering and highlights the potential applicability of lightweight foam concrete in underground structures. Full article

This study systematically investigates the tensile anisotropic mechanical behavior of ferritic steel under different orientations through an integrated experimental, theoretical modeling, and simulation approach employing advanced characterization techniques including electron backscatter diffraction (EBSD), digital image correlation (DIC), scanning electron microscopy (SEM), and finite element analysis. The results demonstrate pronounced orientation dependence in mechanical response, with initial yield strengths of 391, 391, and 405 MPa and fracture strains of 0.237, 0.220, and 0.212 observed for 0°, 45°, and 90° orientations, respectively, corresponding to orientation-induced variations of 3.6% in yield strength and 11.8% in fracture strain. These anisotropic characteristics are primarily attributed to the predominant α-fiber texture <110>||RD, which accounts for 59.8% of the texture components. Furthermore, crystallographic texture significantly influences fracture behavior, as evidenced by the distinct orientation-dependent macroscopic contraction characteristics and morphological features of fracture surfaces. Full article

To address the technical challenges associated with complex connection configurations and excessively long lap zones in the industrialized and prefabricated construction of reinforcements, this study proposes a novel parallel-lap splice that incorporates a third overlapping reinforcement. This innovative design offers several advantages, including neat ends, ease of construction, and enhanced economic efficiency. An experimental investigation was conducted to evaluate the effects of this new splice on the flexural behavior of reinforced concrete (RC) beams, with lap length (l_l) as the key variable (l_l = 64d, 40d, and 25d). A total of nine simply supported RC beams (three groups of three specimens each), all incorporating parallel-lap splices, were tested under four-point bending. The key mechanical properties were analyzed, including the mechanical characteristics, failure modes, flexural capacity, bending stiffness, and maximum flexural crack width. The experimental and analytical results reveal that RC beams with the new parallel-lap splice exhibit a distinctive “one primary + two secondary” crack pattern, characterized by a dominant flexural crack at midspan and secondary cracks at the ends of the lap zone. At the ultimate limit state, specimens with l_l = 64d experienced concrete crushing at the top surface of the midspan while those with l_l = 40d and l_l = 25d did not. Additionally, the l_l = 64d and l_l = 40d beams showed slight strength hardening, whereas the l_l = 25d beams exhibited rapid strength degradation. In terms of load-bearing capacity, both the l_l = 64d and l_l = 40d beams met the requirements specified in current design codes, while the l_l = 25d specimens showed a reduction in capacity exceeding 20%. Under serviceability limit states, midspan deflections and maximum crack widths for the l_l = 64d, l_l = 40d, and l_l = 25d specimens were found to fully comply with, marginally satisfy, and fail to meet the requirements of the design code, respectively. Based on these findings, as well as regression analysis of the relationship between peak load and lap length, it is recommended that a reasonable lap length for the proposed parallel-lap splice be taken as 60d, with a lap length correction factor of 1.5. Full article

In this study, an eco-friendly geopolymer concrete (GPC) was synthesized using fly ash, slag, and rice husk ash as precursors, and glass fibers were incorporated to enhance its mechanical properties. And then this study investigates the residual mechanical properties and microstructure evolution of glass fiber-reinforced geopolymer concrete (GFGPC) following elevated temperature exposure and subsequent cooling. Specimens incorporating varying glass fiber volume fractions (0–2.5%) were subjected to temperatures ranging from 25 °C to 800 °C, followed by either natural cooling or water-spraying cooling. The uniaxial compressive strength, Brazilian splitting tensile strength, and three-point flexural strength of the glass fiber-reinforced GPC were experimentally determined. Furthermore, fracture performance indicators—including the energy absorption capacity at failure, characteristic length, and double-K fracture parameters—were systematically analyzed. Results indicate that a glass fiber content of 1.5% optimally enhances the composite’s mechanical performance. Under natural cooling, splitting tensile and flexural strengths exhibit a non-monotonic trend, peaking at 200 °C. Conversely, water-spraying cooling induced thermal shock generally degrades tensile and flexural properties. However, at extreme temperatures (600 °C and 800 °C), water-spray cooling facilitates matrix densification and secondary geopolymerization, resulting in a residual compressive strength increase of 12.16% and 20.77% compared to natural cooling. Furthermore, based on composite damage theory, a binary nonlinear prediction model was developed to accurately capture the coupled effects of temperature and fiber characteristics on the residual compressive strength (R² > 0.90). Coupled with scanning electron microscopy (SEM) observations, the profound effects of elevated temperatures and thermal shock on the GPC gel matrix were elucidated, and the microscopic mechanisms underlying the failure of the fiber-bridging effect at high temperatures were thoroughly investigated. The findings of this study provide a solid theoretical foundation and scientific reference for the performance assessment and repair decision-making of GPC structures post-fire exposure. Full article

Against the background of the global “dual carbon” strategic goal, low-carbon upgrading of road engineering and efficient recycling of waste plastics have become critical approaches to relieve the shortage of natural aggregates and control plastic pollution. Most existing studies only focus on the optimization of single mechanical indicators, while lacking collaborative analysis of mechanical performances and carbon reduction benefits, meaning they cannot provide sufficient scientific support for the design of low-carbon and sustainable road materials. In this study, recycled plastic aggregate (PA) was used to partially replace natural coarse aggregate, and its influence on the mechanical characteristics of cement-stabilized macadam (CSM) was systematically investigated. Combined with life cycle assessment (LCA), the carbon emission reduction potential was quantitatively evaluated, aiming to improve the toughness of road base materials and promote low-carbon sustainable development. The results demonstrate that when the PA content increases from 0% to 20%, the mechanical strength of CSM gradually decreases, while the toughness presents a steady upward trend, and the maximum carbon emission reduction rate reaches 50.8%. The optimal toughness improvement of 28.39% is obtained at the PA content of 16%. This study clarifies the internal correlation between mechanical behaviors and low-carbon benefits of recycled plastic aggregate, provides reliable technical support for the high-value utilization of waste plastics and the optimization of sustainable road materials, and offers important references for the green and low-carbon transformation of transportation infrastructure. Full article

The purpose of the present study was to examine whether countermovement vertical jump (CMJ) force-time metrics differ among teams with three ranking statuses competing within the same professional women’s handball league in Europe (i.e., SuperLeague). Following a standardized dynamic warm-up procedure, twenty-six professional female handball players (top-ranked: n = 8; mid-ranked: n = 8; bottom-ranked: n = 10) performed three CMJs on a uni-axial force plate sampling at 1000 Hz (VALD Performance). Nineteen force-time metrics were derived to characterize neuromuscular performance qualities during both the eccentric (i.e., braking) and concentric (i.e., propulsive) phases of the jumping motion. A one-way ANOVA revealed no statistically significant differences (p < 0.05) between the teams for any CMJ force-time metric of interest (i.e., peak and mean eccentric force and power, jump height, reactive strength index-modified, countermovement depth, eccentric and concentric duration) across ranking status in either phase of the movement, nor for anthropometric characteristics (i.e., height and body mass). Overall, the results indicate that CMJ force-time metrics did not differentiate team ranking status within this sample of professional female handball players. These findings suggest that, within a homogeneous cohort competing at the same level of play, CMJ-derived neuromuscular performance characteristics may have limited sensitivity for distinguishing between teams of different competitive rankings. While CMJ force-time analysis remains a useful tool for monitoring individual neuromuscular status, the present results do not allow conclusions regarding the role of other performance determinants (e.g., tactical or technical factors), which were not directly assessed in this study. Full article

Steel–concrete composite components exhibit significant advantages, including reliable mechanical performance, rapid construction, cost efficiency, and low environmental impact. Existing studies on their seismic behavior have mainly focused on developing novel connection forms and enhancing joint zone strength, while systematic investigations into the post-earthquake axial compression behavior and failure mechanisms of composite joints remain limited. To address this gap, this study investigates the mechanical performance of steel–concrete composite components under strong seismic and post-earthquake conditions. Seismic damage characteristics are first analyzed based on representative case studies of conventional steel–concrete columns. Subsequently, low-cycle reversed loading tests followed by post-earthquake axial compression tests are conducted on seven beam–column joints with varying damage levels, and the damage evolution and seismic performance of joint zones under different structural configurations are systematically evaluated. In addition, the seismic performance of steel–concrete composite shear walls is further validated. The results provide a scientific basis for the seismic design, post-earthquake assessment, and repair of steel–concrete composite structures. Full article

This study considers the potential of utilizing waste glass powder as a sustainable additive to improve the characteristics of clay subgrade soils. A comprehensive experimental program was designed, wherein a selected clay soil was amended with four distinct contents of glass powder that were finely ground: 0%, 3%, 6%, and 9% by weight. The primary objective was to evaluate the resultant improvements in soil strength and the enhanced interfacial bond between the treated subgrade and an overlying Type B granular subbase layer, which was further reinforced with an SS2 Geogrid. To characterize these effects, a suite of laboratory tests was performed, including the Modified Proctor Test, Atterberg Limits Test, California Bearing Ratio (CBR) test, and a large-scale direct shear test. A specially made large-scale instrument for direct shear was employed for the interface testing. The results demonstrate a clear positive correlation between the proportion of glass powder and the improvement in geotechnical properties. The most significant enhancement was observed at the 9% inclusion rate, which yielded a 6.6% increase in the maximum dry density and a substantial 49% improvement in the CBR value. Concurrently, this optimal mix design resulted in a 14% reduction in optimum moisture content, alongside notable decreases in the swelling and plasticity indices by 33% and 39%, respectively, confirming the efficacy of glass powder in stabilizing the clay subgrade. Full article

This study examines the relationship between firms’ financial adaptability and performance during periods of macroeconomic stress. Using panel data on companies listed on the Mongolian Stock Exchange from 2015 to 2024, the analysis measures financial adaptability through a Firm Adaptability Index (FAI) constructed from observable indicators of liquidity, coverage capacity, and asset-use efficiency. The index is constructed using principal component analysis (PCA) to avoid arbitrary equal-weighting assumptions, and the debt ratio is deliberately excluded to prevent multicollinearity with the leverage control variable used in the regression models. The empirical framework primarily relies on panel regression models with interaction terms, supplemented by a DID-style comparison and an event-study-based diagnostic. The validity of the quasi-experimental design is confirmed by a formal parallel-trend test and placebo checks using artificial shock dates. The findings do not support the view that financial adaptability exerts a uniformly strong and stable direct effect on firm performance across all conditions. Instead, its empirical relevance becomes more visible when macroeconomic conditions worsen. In particular, the interaction result related to interest rates suggests that firms with higher levels of financial adaptability tend to exhibit less pronounced profitability sensitivity to financing cost pressure. Additional analyses point to short-term liquidity buffers as a plausible channel and show that the strength of this relationship varies by firm size and sectoral characteristics. This study contributes to the literature by bringing together the related concepts of financial flexibility, organizational resilience, dynamic capabilities, and strategic adaptability within a firm-level empirical setting. It also proposes a practical way to measure financial adaptability not through a single proxy, but through a composite index that integrates several observable financial dimensions. Overall, the evidence suggests that financial adaptability is better understood not as a constant determinant of profitability, but as an internal capability whose relevance becomes more apparent under conditions of heightened uncertainty. Full article

Background/Objectives: Tuberculosis (TB), caused by Mycobacterium tuberculosis (MTB), remains a major global health problem. Drug resistance and the limitations of sputum-based diagnostic methods highlight the need for additional host-response biomarkers. Protein tyrosine phosphatase receptor type O (PTPRO) has been implicated in inflammatory signaling and macrophage immune regulation, but its relationship with TB-related host transcriptional responses remains unclear. This study aimed to identify and preliminarily evaluate a PTPRO-related blood transcriptional signature with potential relevance to TB discrimination and treatment-response assessment. Methods: Genes correlated with PTPRO expression were first screened using TCGA-LUSC as a large human transcriptomic discovery resource. The resulting candidate genes were then filtered in TB-related whole-blood datasets by intersecting genes upregulated in TB compared with healthy controls, pneumonia, and lung cancer. This strategy yielded a five-gene PTPRO-related signature, termed PO5. The signature was evaluated in independent GEO cohorts and further explored by RT-qPCR in H37Ra-infected THP-1-derived macrophages and in a small clinical blood cohort. A PO5-derived TB risk score was calculated for each sample, and receiver operating characteristic analysis was used to assess discriminatory performance. Changes in TB risk scores during anti-TB treatment were also examined. Results: PTPRO expression was increased in TB whole-blood transcriptomic data and in H37Ra-infected macrophages. In public datasets, PO5 showed potential for distinguishing TB from healthy controls, latent TB, pneumonia, and lung cancer. PO5-derived TB risk scores also decreased after anti-TB treatment. In the exploratory clinical cohort, several PO5 genes showed expression changes in the same general direction as those observed in the public datasets, although the small sample size limited the strength of this evidence. Conclusions: PO5 represents a preliminary PTPRO-related blood transcriptional signature with potential relevance to TB discrimination and treatment-response assessment. These findings remain exploratory and require validation in larger prospective multicenter cohorts, together with further mechanistic studies. Full article

The synergistic deformation and energy dissipation of backfill–surrounding rock composite structures under impact loading remain poorly understood, despite the frequent exposure of deep mine backfilled stopes to dynamic disturbances such as blasting and seismicity. In this study, Split Hopkinson Pressure Bar (SHPB) tests were conducted at a fixed impact pressure of 0.2 MPa on single-material specimens and bonded backfill–rock composite cylinders, with loading applied from both the backfill end and the surrounding rock end. Single backfill specimens exhibited dominant reflected energy (~90%) and low crushing energy consumption (<20%), whereas composite specimens displayed characteristic “double-peak” or “flat-peak” stress–strain signatures with peak strengths exceeding that of standalone backfill. When loading was directed from the high-strength surrounding rock into the backfill, the reflected energy ratio decreased to 60–80% and crushing energy consumption increased to 20–30%, demonstrating a loading-direction-dependent energy dissipation mechanism. These results provide a quantitative reference for optimizing blast sequence design in backfilled stopes. Full article

Geosynthetics-reinforced soil technology represents an innovative reinforcement method for calcareous sand foundations and revetment engineering in coral reef areas. The interaction response at the reinforced soil interface directly influences the safety and stability of reinforced soil structures. However, research on the interaction mechanisms between geosynthetics and calcareous sand interfaces remains insufficient. Therefore, this paper investigates the effects of different normal stresses and various interface types on the shear characteristics of the geosynthetics–calcareous sand interface through a series of large-scale monotonic direct shear tests. By integrating statistical damage theory and accounting for the influence of residual strength, we establish the constitutive relation for interface damage. The results indicate that the shear stress–displacement curves for both the geosynthetics–calcareous sand interface and the unreinforced calcareous sand exhibit softening behavior. Furthermore, the relationship between the interface shear modulus and horizontal displacement for the geogrid–calcareous sand and unreinforced calcareous sand adheres to a power function model, while the relationship for the geotextile–calcareous sand follows a logarithmic function model. In the structural design of geosynthetics-reinforced calcareous sand, it is crucial to consider the influence of residual shear strength on structural stability. This study proposes a statistical damage constitutive model that accounts for the strain-softening characteristics of the geosynthetics–calcareous sand interface, while also considering the impact of residual strength. The findings provide a theoretical basis for the stability analysis of geosynthetics-reinforced calcareous sand structures in coral reefs with significant engineering implications for island reef construction, coastal development, and bank slope protection projects. Full article

To address the issue of insufficient accuracy in wind power forecasting arising from intermittency and volatility, this paper proposes a short-term wind power prediction model integrating MIC (Maximal Information Coefficient) feature selection with adaptive noise-complete set empirical mode decomposition, convolutional neural networks, and a bidirectional long short-term memory network hybrid architecture. The main innovations of this work lie in the following: Firstly, MIC quantifies the strength of the nonlinear correlation between meteorological features and the MAE (Mean Absolute Error) in power generation, thereby enabling the identification of highly correlated features to reduce the input dimensionality. Secondly, CEEMDAN (Complete Ensemble Empirical Mode Decomposition with Adaptive Noise) performs adaptive modal decomposition on raw power sequences. Combining sample entropy with K-means clustering reconstructs IMFs (Intrinsic Mode Functions), while the introduction of VMD (Variational Mode Decomposition) for quadratic optimisation significantly improves the quality of signal decomposition, enabling a more refined separation of fluctuation characteristics across different time scales. Finally, the optimised meteorological features and reconstructed components are input into a CNN (Convolutional Neural Network)-BiLSTM (Bidirectional Long Short-Term Memory) module. Power regression prediction is achieved through the synergistic effect of spatial feature extraction and bidirectional temporal dependency modelling. Case study results demonstrate that compared to the TCN (Temporal Convolutional Network)-Transformer, the proposed method achieves a 0.4022 improvement in the coefficient of determination R², a 13.2598 reduction in MAE, a 19.864 decrease in RMSE (Root Mean Square Error). At the same time, it maintains stable performance even when faced with unreliable data scenarios involving random missing features, demonstrating excellent generalisation ability. Furthermore, the model training time has been reduced to 77.6469 s, with a single prediction response time of just 0.0659 s. Full article

Soft story irregularity poses a critical seismic risk to existing building stocks. While current seismic codes define stiffness irregularity factors to detect this vulnerability, they are typically evaluated based solely on initial elastic properties. This study investigates the evolution of these code-defined factors (ASCE/SEI-7, UBC, NBC, TBEC-2018, and BSL) within the post-elastic range to examine how structural damage affects soft story irregularity. The methodology comprises two phases: a low-strength RC plane frame (Case A) and a parametric study on a 3D RC building with incrementally increased ground story heights (Case B). Nonlinear pushover analyses were conducted to track the variation in irregularity factors at each pushover step and examined graphically. Results demonstrate that soft story behavior is not a static characteristic; irregularity factors deteriorate significantly as plastic hinges form. Crucially, several models that initially satisfied code limits in the elastic range eventually exceeded irregularity thresholds under inelastic behavior. This indicates that relying solely on initial stiffness may mask latent irregularities emerging during seismic actions. Consequently, to capture the true severity of soft story mechanisms, it is recommended that stiffness irregularity factors be evaluated at target displacement levels corresponding to the design earthquake. Full article

Selective laser melting (SLM) offers a promising route for fabricating high-performance Cu–Sn alloys; however, the extremely transient thermal behavior of the molten pool and its influence on microstructural evolution and mechanical properties remain insufficiently understood. In this study, a finite element model based on ABAQUS was developed to simulate the transient temperature field and molten pool dynamics of Cu–10Sn alloy during the SLM process. By systematically varying the volumetric energy density (VED), the interplay among molten pool geometry, thermal characteristics, microstructure, and mechanical performance was investigated through a combination of numerical simulation and experimental investigation. The results reveal that increasing VED significantly enlarges the molten pool dimensions, elevates the peak temperature, and intensifies the maximum heating and cooling rates, thereby altering solidification conditions. At a VED of 208.33 J/mm³, the molten pool reached its maximum dimensions, with a length of 230 μm, a width of 161 μm, and a depth of 85 μm, resulting in the highest relative density within the investigated range (98.33%). Under this processing condition, the Cu–10 wt.% Sn (Cu–10Sn) alloy exhibited microhardness values of 190 HV near the solidified areas of melt pool interior and 208.4 HV near the solidified areas of melt pool boundary, accompanied by an ultimate tensile strength of 494 MPa. These findings elucidate the critical role of molten pool thermal behavior in governing microstructural refinement and mechanical properties of SLM-fabricated Cu–10Sn alloys and provide a mechanistic basis for understanding the effect of process parameters. Full article