Search Results (3,263)

To address the critical challenges of geological hazards, such as water and mud inrush, encountered during the construction of deep-buried tunnels in China, this study investigates the hydraulic properties of remolded mud-infill materials. A multi-scale approach, integrating indoor variable-head permeability tests with scanning electron microscopy (SEM), was employed to characterize the evolutionary patterns of the permeability coefficient (k). Specifically, the research evaluates the independent influences of moisture content, dry density, and confining pressure, alongside the synergistic coupling between dry density and hydration state. The results demonstrate the following: Under independent variable conditions, k exhibits a monotonic decline with increasing dry density and confining pressure while showing a positive correlation with moisture content, with the sensitivity varying significantly across different parameter regimes; under coupled effects, the permeability in both low- and high-moisture ranges manifests a distinct “increase–decrease–increase” fluctuation as dry density rises, reaching a local peak at 2.20 g/cm³. Notably, a relative minimum k (6.12 × 10⁻⁷ cm/s) is achieved at the optimum moisture content (5.8%); micro-mechanistic analysis reveals that low-moisture samples are characterized by randomized angular particles and well-developed interconnected macropore networks, facilitating higher k values. Conversely, high-moisture samples exhibit preferential plate-like stacking dominated by occluded micropores, resulting in a substantial reduction in hydraulic conductivity. This study elucidates the multi-factor coupling mechanism governing the seepage behavior of remolded mud, providing essential theoretical benchmarks for the prediction and mitigation of water–mud outburst disasters in deep underground engineering, thereby ensuring the structural stability and operational safety of tunnel projects. Full article

Characterizing surface runoff and the transport process of non-point source pollutants (NSPs) carried by this runoff is crucial for identifying key source areas, estimating pollution loads entering water bodies, and implementing pollution control, which is particularly important in regions dominated by smallholder farming in China. Currently, most of the commonly used NSP models originated from international countries and have shortcomings such as high data requirements, high generalization degrees, and requiring the calibration of numerous parameters in the application process. Therefore, a distributed non-point source pollution model based on the time-varying gain and stormwater runoff response was constructed, designed for application at the watershed scale. This study describes the construction of the model, introducing its principles and structure through three key modules: a rainfall–runoff module, a soil erosion module, and a pollutant migration and transformation module. The proposed model was used to simulate the rainfall–runoff, soil erosion, and nutrient migration and transformation processes at different spatiotemporal scales. Although it achieved the best performance at the monthly and annual scales, its simulation results at the daily and hourly scales still met the relevant requirements, with relative errors within 20% and Nash–Sutcliffe Efficiency (NSE) coefficients of approximately 0.7. The annual sediment delivery ratios for the Yangliu Small Watershed and the basin above the Ankang section in 2022 were determined to be 0.445 and 0.36, respectively. The pollutant processes corresponding to different runoff events in the Yangliu Small Watershed were simulated, and the average NSE for total nitrogen (TN), ammonia nitrogen (NH₃-N), nitrate nitrogen (NO₃-N), total phosphorus (TP), and soluble reactive phosphorus (SRP) were determined to be 0.69, 0.74, 0.79, 0.71, and 0.71, respectively. For the basin above the Ankang section, the NSE coefficients for the simulation of NH₃-N and TP pollutant processes were 0.78 and 0.83, respectively. The model demonstrated robust applicability across various spatial (ranging from small to large watersheds) and temporal (hourly−daily−monthly−annual) scales, and exhibited stability across different basins in a semi-humid region of China. The model is characterized by a parsimonious parameter set, ease of calibration, and strong spatiotemporal versatility, thus providing an efficient and reliable tool for non-point source pollution simulation. Full article

With the changing demands of society, gears, as fundamental components of mechanical devices, are evolving towards higher reliability and longer service life. To address the issue of thermal scuffing at the gear meshing interface, we propose the introduction of micro/nano-textures to improve the thermal elastohydrodynamic lubrication characteristics of the meshing surfaces, thereby enhancing the lubrication performance and anti-scuffing load capacity of the gear surfaces. First, finite element models with different microstructural features were established. Then, numerical calculations were conducted using computational fluid dynamics (CFD) software to analyze the impact of various micro-texture configurations on the lubrication performance of the tooth surface. Finally, an orthogonal experiment was performed to optimize the groove length, groove width, and areal density of the micro-textures in order to obtain the best processing parameters. The results show that, compared with the triangular, rectangular and trapezoidal micro-textures, the wedge-shaped micro-texture produces the largest pressure difference at the meshing-in and meshing-out points of the texture grooves, which causes the dynamic pressure effect to be more obvious. Compared with the triangular, rectangular and trapezoidal micro-textures, the wedge-shaped micro-texture has the largest bearing capacity and the smallest friction coefficient, so it has better bearing capacity and anti-friction and wear performance. The process parameters were optimized through orthogonal experiments, and the optimal combination of process parameters was obtained as the areal density of 50%, the depth of micro-pits of 12 µm, and the width of micro-pits of 200 µm. Under these optimal parameters, the pressure difference at the meshing-in and meshing-out points of the wedge micro-texture increased significantly by 255.6% compared to the initial model, and the oil film friction coefficient decreased by 17.857% relative to the initial model. These results demonstrate that the micro-texture with optimal parameters significantly enhances the lubrication and anti-friction/wear performance of the tooth surface. Full article

Interannual variability of sea level anomalies (SLA) in the South China Sea (SCS) is significantly influenced by large-scale climate modes; however, their temporal evolution and interdecadal modulation mechanisms remain insufficiently understood. Based on observational records and ERA5 reanalysis data spanning 1980–2022, this study employs a Bayesian Dynamic Linear Model (DLM) to quantify the time-varying impacts of El Niño-Southern Oscillation (ENSO) on interannual SLA variability across different subregions of the SCS and further investigates the modulation effect of the Pacific Decadal Oscillation (PDO) background state. The results indicate that ENSO is a key climatic driver of interannual SLA variability in the SCS; nevertheless, its influence exhibits pronounced non-stationarity, with dynamic regression coefficients showing clear phase-dependent fluctuations throughout the study period. The northern and eastern subregions display stronger responses to ENSO forcing, whereas the southern and western subregions exhibit relatively weaker signals. The negative phase of the PDO enhances the ENSO-SLA relationship, while the positive phase weakens it, with sign reversals occurring in certain subregions. Correlation analyses further suggest that ENSO influences SLA primarily through wind stress anomalies induced by sea level pressure (SLP) gradients, which regulate Ekman transport, whereas the PDO exerts an indirect effect mainly by modifying the large-scale background circulation structure. Full article

To investigate the strength evolution of concrete structures operating in long-term service in humid environments while facing threats such as earthquakes, explosions, and impacts, this study utilized a Hopkinson pressure bar (SHPB) and an MTS testing system to conduct experiments on concrete with four different moisture contents (relative saturation of 0%, 50%, 80%, and 100%) across a strain rate range of approximately 10⁻⁵ to 2 × 10² s⁻¹. Based on these results, a relationship equation was established describing how the strength factor of wet concrete varies with strain rate. The study identified sensitive and non-sensitive regions for the strain rate effect in wet concrete. As the water content increases, the threshold for the sensitive region decreases. Specifically, the inflection strain rate for dried concrete is approximately 32 s⁻¹, whereas for saturated concrete, it drops below 5 s⁻¹. A functional equation describing the variation in the strain rate sensitivity coefficient with water content was derived, showing that the strain rate effect on strength becomes more pronounced as water content increases. The rate-wet coupling effect on concrete compressive strength was analyzed, and zones dominated by the strain rate strengthening effect and the water-weakening effect were identified. The mechanism of strength variation in wet concrete across different strain rate ranges was investigated. The analysis indicates that free water participates in the action processes of each mechanism from low to high strain rates. As the strain rate increases, the mechanisms of pore water interaction and thermal activation undergo a transition. At higher strain rates, the significant increase in the dynamic strength of wet concrete results from the combined and coupled effects of the material’s “true strain rate effect” and the stress wave effect in wet concrete, which are driven by the mutual coupling of pore water, thermal activation, and viscous drag mechanisms. This paper aims to provide a reference for the in-depth understanding of the strength evolution and control of hydraulic concrete structures. Full article

Layered side-casting backfilling performed with a trailing suction hopper dredger (TSHD) is widely used in tidal waters, but its continuous moving release can generate a time-varying far-field sediment plume that complicates both backfilling control and environmental impact assessment. To investigate how construction parameters affect far-field sediment dispersion and deposition under side-casting conditions, this study develops a two-dimensional hydrodynamic–sediment coupled numerical model with a mass-conserving moving-source term for a tidally dominated coastal area. Model performance was evaluated against field observations, yielding NRMSE/MRAE values of 0.0787/6.03% for water level, 0.2249/18.30% for current speed, 0.2344/27.10% for suspended-sediment concentration (SSC), and 0.1230/11.10% for deposition thickness; the correlation coefficient for current speed was 0.904. Based on the validated model, scenario analyses were conducted for different combinations of sailing speed and sediment concentration. The results show that far-field plume evolution exhibits pronounced stage-dependent behavior, with the largest affected footprint generally occurring during the late operational period or shortly after source termination. Within the tested parameter space, sailing speed has a stronger influence on the dispersion scale and SSC recovery duration because it controls both the release duration and source sweeping rate. Sediment concentration more directly affects deposition-related responses, including deposited thickness, lateral coverage, and along-track continuity, although its incremental effects weaken in the high-concentration range and remain coupled with sailing speed. Dimensional analysis further suggests that the relative magnitudes of source duration, advection, and settling timescales help explain the differences among scenarios. These results provide a physically based reference for parameter selection and construction planning in layered side-casting backfilling under tidal forcing. Full article

The spatial assessment of soil erosion drivers provides essential information for prioritizing soil conservation areas. This study aims to compare the performance of the Ordinary Least Squares (OLS) regression model and the Geographically Weighted Regression (GWR) model in explaining and analyzing the spatial variations of soil erosion in the Qara-Su watershed (Ardabil Province, Iran) and identifying the relative roles of the driving factors affecting erosion. To determine the relative importance of factors influencing soil erosion in the Qara-Su watershed, potential soil erosion (A) data and RUSLE model factors, including R, K, LS, C, and P, were collected at 13,845 points within the watershed. Initially, general relationships between erosion and contributing factors were examined using the OLS regression model. Subsequently, to analyze the spatial variability of relationships and identify the relative importance of factors at different locations within the watershed, the GWR model with an adaptive kernel and optimal bandwidth selection based on AICc was employed. The performance of the OLS and GWR models was compared based on fit indices such as R² and Akaike Information Criterion corrected (AICc), and the relative importance of erosion factors was determined based on the mean local GWR coefficients. Results from the RUSLE model indicated an average annual soil erosion of approximately 7.64 tons per hectare, suggesting that the watershed falls into the moderate erosion risk category. According to the GWR model, significant improvements in explaining variations and reducing errors were observed, with higher R² and adjusted R² values (0.62 vs. 0.50) and lower AICc values (3687 vs. 97,848) compared to the OLS model. The local GWR coefficients confirmed spatial non-stationarity and revealed that LS (topography) has the highest importance in mountainous areas. The C factor showed a stronger protective effect in agricultural land-use areas. These results provide a basis for developing targeted strategies to mitigate and manage erosion drivers with higher relative importance and facilitate a better understanding of the causes and mechanisms of soil erosion across the watershed. Full article

Air-to-water heat pumps (ASHPs) are a key technology for residential heating decarbonization; however, their seasonal performance is highly sensitive to outdoor temperature variability. Although thermal energy storage (TES) is widely recognized as a means of improving system efficiency, reported performance gains vary due to differences in climatic datasets, control strategies, and modeling assumptions. This study presents a systematic multi-year assessment of the impact of a water-based TES tank on the seasonal performance of a residential ASHP under measured microclimatic conditions. Hourly simulations were conducted for a single-family house at three locations in eastern Croatia using eight years (2018–2025) of measured meteorological data. Building characteristics, system configuration, and operating strategy were kept identical to isolate the influence of storage volume. TES integration reduced annual electricity consumption by 4.8–9.1%, with a multi-year average reduction of 7.02%, and consistently increased the seasonal coefficient of performance (SCOP) across all analyzed years and locations. The highest relative improvements occurred under less favorable microclimatic conditions, emphasizing the importance of diurnal temperature distribution rather than seasonal averages alone. A parametric analysis identified an optimal storage volume of approximately 1000–1500 L when both energy and economic indicators are considered. The results demonstrate that stable and reproducible seasonal efficiency gains can be achieved through a simple, non-predictive operating strategy under continental climatic variability. Full article

This study aimed to evaluate the performance expression stability (PES) of sixteen alternative complex–contrast training (CCT) set strategies. Three separate cross-sectional studies (n = 14–17) evaluated the effects of different intra-contrast rest periods (ICRP; ≤300 s) and rest redistribution (RR) strategies (≤60 s) within CCT sets on the application of vertical jump propulsive force were examined using dual force platforms. To establish PES for propulsive force–time variables, repetitions one and two of the baseline set were analyzed using within-participant (coefficient of variation, CV; standard error of measurement; smallest worthwhile change; relative mean bias) and between-participant (intra-class correlation coefficient, ICC_3,1; Pearson’s correlation coefficient, r) stability metrics. Results showed that all CCT set strategies facilitate stable performance expression between participants and facilitated the detection of practically meaningful changes for propulsive impulse, peak force, mean force, and propulsion time (ICC_3,1 = 0.64–0.99, r = 0.80–0.99, CV = 1.12–9.98%), while rate of force development metrics demonstrated less consistent between- and within-participant stability (ICC_3,1 = 0.55–0.97, r = 0.46–0.96, CV = 7.52–27.66%). The findings indicate that alternative CCT set strategies facilitate the stable expression of propulsive force–time performance in vertical jumps, although individualized prescriptions are essential for optimizing rate of force development outcomes. Performance expression stability insights provide a practical tool for balancing the effectiveness and potential for performance enhancement of vertical jump propulsion across alternative CCT set strategies. Practitioners may use these results to improve the prescription and monitoring of CCT-based strength and power mesocycles. Full article

Underwater rock plug blasting involves a highly complex, transient gas–liquid–solid multiphase flow that is difficult to simulate accurately with conventional single-phase models. To address this gap, a novel three-phase three-layer mathematical model is presented in this study. This model represents the stratified flow behavior by decomposing the conduit into an upper gas layer, a middle gas–liquid–solid mixture layer, and a lower consolidated bed layer. Governing equations for mass, momentum, and energy conservation are derived and solved using the finite volume method. The model is validated against physical model tests, showing a maximum gate shaft surge deviation of only 0.27%, a Pearson correlation coefficient of 0.965, and a relative RMSE of 4.2%. A sensitivity analysis is performed to quantify the influence of key operational water levels, including the reservoir, gate shaft, and slag pit, on critical transient loads. The results demonstrate that a decrease in the reservoir water level from 106 m to 86 m concurrently reduces both surge height and impact pressure. A smaller reservoir–shaft water level difference (5–15 m) increases the initial cushion pressure and amplifies the surge. In contrast, a larger level difference (20–30 m) suppresses surge but increases impact pressure. Furthermore, an excessively high water level in the slag pit (exceeding 47.8 m) weakens the cushioning effect, thereby lowering the impact pressure. The proposed multiphase model provides an improved approach for predicting hydraulic transients during underwater rock plug blasting. Full article

This study develops and evaluates simultaneous confidence interval procedures for all pairwise differences of coefficients of variation under delta-inverse Gaussian distributions. The objective is to provide reliable comparative inference for relative variability in zero-inflated and highly skewed data, where standard normal-based methods may be unreliable. Five approaches were studied and compared in terms of coverage probabilities and average widths: generalized confidence interval, adjusted generalized confidence interval, fiducial confidence interval, method of variance estimates recovery, and normal approximation. A Monte Carlo simulation study was conducted under varying shape parameters, zero-inflation probabilities, sample sizes, and numbers of populations ($k$ = 3, 6, and 10). Although most methods produced CPs near the nominal 0.95 level, meaningful differences emerged when both coverage accuracy and interval efficiency were considered. The AGCI method consistently delivered stable coverage across parameter settings and remained robust as dimensionality increased. The MOVER approach achieved competitive coverage while frequently yielding narrower intervals. In contrast, GCI occasionally showed mild undercoverage, and FCI tended to produce overly wide intervals. An empirical application to zero-inflated mortality data supports the simulation findings. Overall, AGCI and MOVER provide reliable and practical tools for simultaneous inference on differences in CVs across delta-IG populations. Full article

Hybrid desalination systems that combine osmotic and thermal driving forces offer a promising route to improve water recovery and energy efficiency for high-salinity feedwaters where conventional processes face limitations. This study presents a comprehensive mathematical modeling framework and performance analysis of a hybrid forward osmosis–membrane distillation (FO-MD) system for seawater desalination. The novel contributions include: (1) a coupled heat, mass, and solute transport model that explicitly accounts for concentration polarization, temperature polarization, reverse salt flux, and their dynamic interactions through the draw solution loop; (2) a quantitative assessment of the synergistic regeneration effect, showing how MD maintains draw solution concentration and stabilizes FO performance over time; (3) systematic evaluation of parameter sensitivity to polarization effects; and (4) comparative energy analysis quantifying specific energy consumption relative to standalone processes. Model predictions were validated against published experimental data, showing good agreement for both FO and MD fluxes (R² > 0.94). The MD flux increased from approximately 2–3 LMH at 30 °C to 17 LMH at 50 °C, confirming vapor pressure enhancement. FO water flux increased significantly with draw solution concentration from 0.2 to 1.1 M due to higher osmotic pressure differences. Time-dependent simulations of the integrated FO-MD system showed that MD regeneration reduces draw solution dilution by 60% compared to standalone FO, maintaining FO flux approximately 43% higher after 6 h of operation. Sensitivity analysis revealed that FO predictions are moderately sensitive to mass transfer coefficients (6–9% flux change for 20% parameter variation), while MD shows lower sensitivity to heat transfer coefficients (3–5%). Energy analysis indicates that FO-MD hybridization reduces thermal energy consumption by 15–40% compared to standalone MD, with specific energy consumption of 382 kWh/m³ (40.2 kWh/m³ primary energy equivalent) when using low-grade heat. The obtained results demonstrate that FO-MD hybridization enhances water recovery and operational stability compared to standalone processes, supporting its potential for energy-efficient desalination of high-salinity brines and industrial wastewaters where low-grade heat is available. Full article

Background/Objectives: Restoring lower-limb strength and symmetry is crucial after ACL injury and reconstruction. The limb symmetry index (LSI) is often used to assess strength symmetry for return-to-sport decisions, but various assessment methods can influence outcomes. This study aimed to compare LSI across common knee flexor testing methods in healthy male athletes and to examine associations between absolute strength outcomes, thereby establishing baseline reference values for LSI in a healthy population. Methods: Twenty-two healthy recreationally active males participated in this prospective cross-sectional study. Knee flexor strength was assessed bilaterally using three force plate isometric tests, a static dynamometer-based test (isometric), and isokinetic dynamometer-based tests. Absolute strength values were normalized to body mass. LSI values were calculated for each testing condition. Differences in LSI across modalities were analyzed with repeated-measures ANOVA, and associations between normalized strength outcomes were assessed using Pearson correlation coefficients. Results: LSI values ranged from 96.69 to 101.83 across the testing conditions, with no significant differences observed between measures. Normalized absolute strength outcomes demonstrated very strong correlations within the same measurement category (r = 0.86–0.94 for force plate tests and r = 0.88–0.96 for isokinetic tests). In contrast, correlations between isometric and isokinetic strength outcomes were moderate (r = 0.41–0.67). Conclusions: LSI values were consistent across knee flexor strength testing modalities, suggesting that symmetry assessment was relatively consistent across different measurement methods in the studied group. In contrast, normalized absolute strength outcomes showed only moderate and variable associations across modalities, indicating that different testing approaches assess related but not interchangeable aspects of muscle strength. Full article

As one of the most serious challenges in the 21st century, climate change poses a major threat to global grain production, especially in agricultural and populous countries such as China. This study employs the Vegetation Photosynthesis Model (VPM) and Geographically and Temporally Weighted Regression (GTWR) model to systematically quantify and analyze the spatio-temporal heterogeneous responses of three major crop yields (rice, maize, and wheat) to climate change from 2000 to 2018 in China. The results are as follows. (1) During 2000–2018, all climate factors showed significant inter-annual fluctuations and regional variations. Specifically, both mean maximum and minimum temperatures rose by approximately 1 °C overall; total precipitation initially decreased before increasing, with 2011 being the turning point; total sunshine hours fluctuated sharply before stabilizing; mean wind speed increased slowly at first and then more rapidly; and mean relative humidity decreased first and then increased, turning around in 2009. (2) The VPM-based crop yield estimates were well-verified against the statistics from the China Statistical Yearbook, with the coefficient of determination (R²) ranging from 0.77 to 0.84 for the three crops (all p < 0.01), confirming the high reliability of the yield data used in this study. (3) The national mean yields of three crops based on the VPM showed a fluctuating upward trend from 2000 to 2018. Spatially, the yield changes in three crops showed significant regional differences. (4) From 2000 to 2018, crop yields based on the VPM model exhibited distinct responses to climate change: rice yields were mainly positively affected by mean maximum temperature, maize yields were mainly negatively affected by total precipitation, while wheat yields benefited most significantly from mean relative humidity. The Northeast Plain (the major production region for rice and maize) and the Huang-Huai-Hai Plain (the key region for wheat) proved most sensitive to climate change, and the impacts on all three crops intensified over time. The study suggests that in the future, attention should be focused on the adaptive management of major crop production regions under climate change, and multiple approaches such as optimizing the planting structure and layout, improving crop varieties, perfecting the risk management system, and establishing a policy support and guarantee system should be adopted to enhance the climate resilience of the agricultural system. Full article

Objective: The classic excitation/inhibition dichotomy may be insufficient to describe rTMS mechanisms in the aging brain. This study investigated immediate whole-brain resting-state functional connectivity effects of 10 Hz (high-frequency) and 1 Hz (low-frequency) rTMS over the left dorsolateral prefrontal cortex (DLPFC) in healthy older adults. Methods: Thirty healthy older adults (aged 60–75 years) participated in a randomized, single-blind, crossover study, and underwent 20-min 10 Hz and 1 Hz rTMS in separate visits. A 106-channel fNIRS system was used to record resting-state activity before and immediately after each intervention. Functional connectivity was analyzed at the channel, region-of-interest (ROI) and network summary levels, including graph-theoretic metrics and distance-stratified connectivity summaries. Results: At the network summary level, 10 Hz stimulation was associated with relatively more positive changes in global topology and spatially distributed connectivity summaries, whereas 1 Hz stimulation showed the opposite overall trend. In the graph-theoretic analyses, stimulation frequency × time interaction effects were observed for global efficiency, local efficiency, clustering coefficient, and mean node strength. At the edge level, only a small number of effects survived FDR correction, and the broader connection-wise patterns were therefore interpreted as exploratory. Uncorrected analyses suggested widespread enhancement after 10 Hz stimulation and widespread reduction after 1 Hz stimulation, together with localized paradoxical effects, including selective decreases after 10 Hz and selective increases after 1 Hz (e.g., bilateral primary motor cortex connectivity). Conclusions: These findings suggest that 10 Hz and 1 Hz rTMS over the left DLPFC are associated with different patterns of immediate whole-brain network reconfiguration in healthy older adults. The presence of localized paradoxical effects further suggests that rTMS responses in the aging brain may involve more complex forms of reorganization than a simple excitatory/inhibitory dichotomy would predict. Significance: The present study provides preliminary support for a network-level perspective on neuromodulation in older adults and highlights the value of whole-brain fNIRS for characterizing distributed responses to rTMS. Larger, sham-controlled, behavior-linked, and longitudinal studies are needed to determine the robustness and functional significance of these effects. Full article