Search Results (1,181)

Vertisols represent some of the most dynamic pedological systems due to the high content of smectitic clays and the intense shrinkage–swelling processes associated with seasonal variations in humidity. The present work analyzes the dynamics of pedoturbations and the rheological behavior of a smectitic Vertosol located in the Cheglevici experimental field (Aranca Plain, western Romania), continuously monitored for a period of over 50 years (1967–2020). In a stationary experiment, inert markers were buried at depths ranging from 25 to 150 cm to track the vertical displacement of the soil mass. Periodically collected samples were analyzed from a granulometric, mineralogical, chemical, and rheological point of view (plasticity limits, activity index, volumetric shrinkage, free swelling, deformation modulus, cohesion, conventional pressure). The results indicate a high smectite content (69–76%) and rheological indices specific to highly active soils (PI > 35%, A > 1.0, VS > 100%, FS > 140%). The progressive redistribution of the markers provides strong evidence of substantial profile-scale soil redistribution associated with long-term pedoturbation processes, supporting the hypothesis of a near-complete profile turnover over multidecadal timescales. A significant increase in apparent density and a tendency for granulometric homogenization across the profile, associated with structural reorganization, are also highlighted. The study provides long-term experimental evidence on the vertical dynamics of the soil mass in Smectitic Vertisols and reveals major implications for agricultural management, infrastructure stability, and water flow modeling in expansive soils. Full article

Monitoring the activation of concealed water-conducting structures and predicting the evolution of mining-induced floor failure above a confined aquifer are critical for ensuring the safety and sustainability of deep coal mining. The present study formulates an optimized hydrophobic similar material, improves the bidirectional four-face stress-adjustable loading test platform, integrates water pressure-flow and excitation current monitoring systems, and innovatively introduces the electric current change rate (K value) as a core analytical indicator to systematically conduct physical simulation experiments on floor failure during coal seam mining above a confined aquifer containing concealed water-conducting structures. The results demonstrate the successful development of similar materials with tunable properties (density: 1605–1994 kg·m⁻³; uniaxial compressive strength: 0.07–0.41 MPa; water absorption: 0.2–3%; permeability: 6.8 × 10⁻⁶–7.68 × 10⁻⁴ cm·s⁻¹), effectively replicating the mechanical and seepage characteristics of the prototypical rock strata. The spatiotemporal evolution of the mining-induced fracture field was identified to occur in two distinct stages: “horizontal–vertical evolution” followed by “horizontal periodic evolution”, with a failure depth stabilizing above the No. 9 lower coal seam and a horizontal lag of 4.3–10.1 cm behind the working face. The K value parameter proves highly sensitive in dynamically characterizing the multi-field coupling process of stress–damage–seepage, enabling the clear delineation of the floor’s “six horizontal zones” and “three vertical zones” structure. Crucially, the K value analysis revealed the underlying mechanism of confined water conduction, showing a significant upward migration in the concealed structure area that approached, but did not breach, the key aquifuge layer. The present study provides a novel geophysical perspective and an effective technical parameter (K value) for deciphering the failure mechanism of mining-disturbed coal seam floors, thereby offering a diagnostic framework and a theoretical basis for water hazard early warning and the promotion of green and safe mining practices. Full article

Floor Ordovician karst confined water inrush severely restricts safe exploitation of lower coal seams across North China-type coal basins. Surface directional drilling regional grouting serves as the dominant aquiclude reconstruction technology for water hazard mitigation, yet existing research lacks quantitative decoupling and hierarchical sensitivity quantification of medium intrinsic attributes and controllable grouting parameters. To resolve this knowledge gap, this work delineates five core governing variables: porous medium permeability, matrix porosity, injection pressure, slurry dynamic viscosity and slurry bulk density. A coupled Darcy–Bingham two-phase flow numerical framework based on the COMSOL Multiphysics fluid–solid interaction module is constructed—combined with L₂₅(5⁶) orthogonal experimental design to quantitatively characterize the gradient response law of slurry effective diffusion volume against multi-factor perturbation. Variance analysis (ANOVA) demonstrates a hierarchical control sequence: porous medium permeability > matrix porosity > grouting pressure > slurry dynamic viscosity > slurry bulk density. Medium permeability, porosity and injection pressure dominate slurry migration behavior with diffusion volume perturbation amplitudes ranging 2–191%; whereas, rheological and density parameters exert secondary marginal effects limited within 1–8%. Fracture hydraulic theoretical interpretation reveals permeability acts as the primary groutability discriminant index, and injection pressure exhibits prominent marginal diminishing effect with an efficiency threshold of 8 MPa. This study establishes a quantitative parameter optimization framework for Ordovician top aquiclude reconstruction engineering, providing theoretical support for targeted grouting parameter regulation and risk reduction in blind high-pressure injection. Full article

Conventional valorization of blast furnace slag commonly involves granulation, fine grinding, mechanical activation, or chemical activation, which increase energy demand and processing complexity. This study investigated a minimally processed blast furnace slag (MP-BFS), defined here as the fraction passing 64 µm obtained by sieving a 0–8 mm industrial material without grinding, additional granulation, thermal treatment, or chemical activation. MP-BFS replaced 10–50% of the cement by mass to reduce clinker in industrial mortars formulated at a constant flow spread of 23–24 cm and tested from 8 h to 90 d. Bulk density, water-accessible porosity, total and capillary water absorption, and compressive and flexural strengths were evaluated. Replacing 10% of the cement with slag improved compressive strength from the earliest test age and increased the 28-day compressive and flexural strengths by 5.1% and 9.5%, respectively, relative to the control mortar; this response coincided with a reduction in measured porosity from 8.95% to 8.01%. This improvement is consistent with a physical filling effect and improved particle packing, although these mechanisms were not directly verified by microstructural analyses. At higher replacement levels, water-accessible porosity increased, reaching 24.45% at 50% slag replacement, alongside greater water ingress and delayed strength development. Exploratory empirical regression analyses described associations among slag content, porosity, water transfer, and compressive strength within the investigated formulations. A simplified screening-level constituent-production-and-transport comparison per cubic meter, based on generic ICE factors and an assumed 50 km transport distance, estimated a maximum embodied carbon reduction of 44% at 50% replacement. Curing energy, use, carbonation, maintenance, and end-of-life stages were excluded. Overall, 10% MP-BFS replacement provided the most favorable performance–carbon content balance, whereas 30–50% achieved larger carbon reductions but showed early-age strength losses that limit their suitability for rapid-demolding applications under the investigated conditions. Full article

This study investigated density-driven mixing and stratified flow dynamics in Paldang Reservoir, a river-type reservoir formed at the confluence of the South Han River, North Han River, and Gyeongan Stream in South Korea. High-resolution field observations were conducted under varying hydrologic and hydraulic conditions using an Acoustic Doppler Current Profiler (ADCP) and multi-parameter water quality sensors (EXO2). Spatial distributions of flow velocity, water temperature, and electrical conductivity (EC) were analyzed to evaluate tributary interaction and mixing behavior within the reservoir. Distinct spatial mixing structures associated with tributary inflow heterogeneity and hydraulic operation conditions were identified. During flood-season conditions, highly turbid and high-conductivity inflow from the South Han River propagated beneath the North Han River inflow, generating density-driven lower-layer intrusion near the confluence region. Under intermittent discharge conditions at the Cheongpyeong Dam, unstable upper- and lower-layer separation structures and localized reverse-flow behavior developed. In contrast, continuous discharge conditions promoted stable tributary propagation and persistent stratified mixing structures. Case-based Richardson number (Ri) estimates further indicated localized shear-driven mixing at low-Ri inflow sections and relatively stable stratification at high-Ri sections, providing quantitative support for the observed spatial heterogeneity in density-driven mixing. Overall, spatial mixing in Paldang Reservoir was governed by tributary density contrasts and further shaped by hydraulic operation conditions. These findings improve understanding of density-driven mixing processes in river-type reservoirs under varying hydraulic conditions. Full article

Proton exchange membrane fuel cells (PEMFCs), characterized by high efficiency, zero carbon emissions, and low-temperature start-up capability, are among the most promising clean energy technologies. The design of flow channels and flow fields is critical for enhancing fuel cell power density, mitigating water flooding, and reducing costs. This paper systematically reviews the effects of key geometric factors in PEMFC flow fields and channels, including structural geometry, cross-sectional shape, and baffle design, on cell performance, with the aim of improving water management and enhancing PEMFC performance. Furthermore, the optimization of flow fields such as parallel, serpentine, and interdigitated configurations is reviewed as well. Particularly, the structural features and enhancement mechanisms of biomimetic and novel flow fields, as well as the advantages of three-dimensional flow fields in promoting mass transfer and improving water and thermal management, are discussed, thereby laying a foundation for the innovation and development of future high-performance proton exchange membrane fuel cells. Full article

This study developed a Photovoltaic–Reservoir Water Quality Impact Model (PVRWQIM) based on triangular fuzzy number theory (TFN) to address data sparsity and measurement uncertainty in conventional water quality assessment. The model consists of two components: a TFN-based exceedance-risk module for quantifying the likelihood of water quality parameters exceeding predefined risk thresholds, and a transitional TFN module for evaluating changes in exceedance risk before and after floating photovoltaic (FPV) construction. The model was applied to Junshan Reservoir in Jiangxi Province, China, using 15 observations each from before and after FPV construction. The results indicate the following: (i) Before construction, the exceedance probabilities for water temperature (T), dissolved oxygen (DO), permanganate index (COD_Mn), total phosphorus (TP), total nitrogen (TN), chlorophyll a (Chla), and cyanobacterial density (CD) were 16.7%, 16.1%, 31.3%, 33.7%, 33.3%, 32.7%, and 31.3%, respectively. After construction, the exceedance probabilities for T, DO, COD_Mn, TP, and TN increased to 93.1%, 89.7%, 82.5%, 83.5%, and 83.3%, respectively (p < 0.01), while the probabilities of exceedance for Chla and CD decreased to 14.8% and 14.2%, respectively (p < 0.05). (ii) T and DO are the primary threat factors triggered by FPV construction, with a probability of increased ecological risk of approximately 90%. (iii) The model reveals a statistical correlation pattern: the probability of reduced ecological risk for CD and Chla is 62%, while the probability of increased ecological risk for COD_Mn, TP, and TN is 77%. The two sets of indicators exhibit opposite trends, suggesting that FPV shading may directly suppress algae growth while simultaneously weakening self-purification capacity indirectly through cooling and reduced water flow, thereby contributing to nutrient accumulation. It should be noted that, based on limited observational data, this study reveals correlations rather than proven causal mechanisms; the aforementioned causal interpretations require further validation through controlled experiments or mechanistic models in the future. (iv) The proposed PVRWQIM provides a practical tool for quantifying reservoir water quality risks under sparse data and measurement uncertainty and can support environmental assessment of similar FPV projects. Full article

With the rapid development of data centers, significant energy consumption challenges have emerged, with cooling system energy consumption accounting for over 30%. Traditional air cooling, limited by airflow organization issues, struggles to meet the cooling demands of high heat flux density chips. Although liquid cooling technology exhibits superior cooling performance, it often leads to high system power consumption due to design and flow matching factors. Therefore, conducting energy-saving optimization of liquid cooling systems holds significant importance. This paper establishes a piping network model for a cabinet-level indirect liquid cooling system, incorporating the heat flow method and piping network fluid dynamics–resistance balance relationships to establish overall system flow and heat transfer constraints. Based on this, optimization analyses are conducted for cabinet liquid cooling systems under centralized and distributed pump configurations. For centralized pump configurations with a constant thermal load, a Lagrangian function is established to minimize system power consumption, and the optimal pump operating frequency is determined using variational principles. When the cooling water temperature rises from 20 °C to 24 °C, the total power consumption increases by 1.55 times. Placing a server with a specific load of 1.2 kW at the bottom of the cabinet rather than the top results in a 34.4% energy savings. With a constant total pump power consumption, a Lagrangian function is established to maximize the system thermal load, and the optimal pump operating frequency is determined. When the cooling water inlet temperature increases by 2 °C, the total thermal load decreases by 4.9%. Servers with higher thermal loads should be placed nearby to make the cooling system more energy-efficient. Comparisons reveal that as the total system thermal load increases from 4.0 kW to 6.0 kW, the distributed pump configuration achieves an average energy savings of 2.5 W, with a maximum savings of 7.09 W, compared to the centralized pump configuration. Full article

Stainless-steel bipolar plates (BPPs) are attractive for proton exchange membrane water electrolysis (PEMWE) due to their low cost and manufacturability, yet their use is limited by severe corrosion. Despite the advantages of plasma-enhanced atomic layer deposition (PEALD) in producing dense films, ion bombardment may induce surface damage and increase roughness. This paper describes a cross-flow PEALD strategy with a remote plasma source to deposit metallic tantalum (Ta) coatings on stainless steel. In a cross-flow reactor, plasma species reach the substrate primarily through diffusion across the boundary layer of the gas flow, providing a gentler plasma–surface interaction and enabling the formation of dense, smooth Ta coatings. The roughness of the Ta films is markedly reduced from 1.45 nm to 0.24 nm, which is favorable for interfacial electrical contact. The process exhibits self-limiting growth with a linear growth rate of ~0.49 Å cycle⁻¹. In a simulated PEMWE environment, Ta-coated stainless steel shows improved corrosion resistance, with the corrosion potential increasing from −0.27 to 0.07 V vs. Ag/AgCl (pH 0.3) and the corrosion current density decreasing to 2.05 × 10⁻⁷ A cm⁻². Overall, cross-flow PEALD enables high-quality metallic Ta coatings that enhance corrosion protection and interfacial electrical performance for BPPs. Full article

In the design of an experimental water tank equipped with a movable underwater shaking table featuring a large travel range, numerous auxiliary devices must be installed beneath the tank, resulting in substantial occupation of the available space. In this context, the optimal design of the water-supply passage within the flow-making system has emerged as a key engineering challenge. To investigate the optimal design of the flow-making system for an experimental water tank equipped with a movable underwater shaking table, this study uses the construction of the experimental water tank at the National Facility for Earthquake Engineering Simulation (NFEES) as a case study. Several candidate design schemes were proposed and evaluated using computational fluid dynamics (CFD) simulations to identify the optimal configuration. Following the selection of the flow circulation scheme, a flow-guiding device was further designed at the tank outlet to improve the flow pattern within the water tank. The results demonstrate that the horizontal–vertical combined layout is the optimal configuration for the water-supply passage. For the flow-guiding device, the optimal design consists of guide vanes arranged parallel to the guiding slope with a vane angle of 0°, a total of five vanes, and a vane density of 1.0. The flow-making system was constructed based on the optimal design identified through numerical simulations, and full-section flow-making experiments were subsequently conducted in the completed water tank under various water depth conditions. The experimental results show good agreement with the numerical predictions, confirming the feasibility and effectiveness of the proposed design. The findings of this study provide valuable guidance for the design and performance optimization of flow-making systems in experimental water tanks equipped with movable underwater shaking tables. Full article

CO₂ is a promising fracturing fluid for tight reservoirs because it avoids water-phase damage and offers low viscosity, high diffusivity, and strong penetration into fine pore throats, but its pore-scale flow in pore-fracture systems remains difficult to evaluate because thermodynamic state, fractures, and mass transfer act together. In this study, a radial microfluidic model containing randomly distributed microfractures was used with a temperature- and pressure-controlled visualization platform to compare CO₂–oil and water–oil flow. Image segmentation and areal-fraction statistics quantified swept area and final fluid distribution. Gaseous CO₂ at ambient pressure and compressed-liquid CO₂ below the critical temperature differ substantially in density and viscosity, but both retain a discernible CO₂–oil interface and exhibit pressure-driven preferential-path flow. The gaseous case shows strong fracture guidance and fingering, whereas the compressed-liquid velocity series demonstrates increasingly rapid advancement and stronger channeling at excessive velocity. Under near-critical supercritical conditions (35 °C, 8 MPa), progressive oil-color fading ahead of the displacement front shows that dissolution participates while flow expands through matrix pores. Under higher-temperature supercritical conditions, disappearance of the sharp interface and continuous color attenuation identify dissolution-assisted diffusion as a significant transport mechanism and produce diffuse redistribution across the pore space. Water undergoes immiscible channelized displacement and remains capillary-trapped in small throats and low-permeability regions. The results identify three flow regimes: distinct-interface pressure-driven displacement, near-critical convection–dissolution coupling, and higher-temperature supercritical dissolution-assisted diffuse redistribution. Full article

Cross-flow micro heat exchangers enable compact thermal management for high-density electronics, but their design is traditionally constrained by a strict trade-off between heat transfer and hydraulic resistance. To mitigate this limitation, we investigate the influence of mixed-geometry channel designs on the coupled thermal and hydraulic performance using a three-dimensional conjugate heat transfer model of water flowing through a stainless-steel micro-matrix with a 40-micrometer hydraulic diameter. Numerical simulations show that at low Reynolds numbers (100 to 200), corner-induced steady three-dimensional flow redistribution modifies the thermal boundary layer, causing convective and hydraulic performance to deviate from standard macroscale predictions. By expanding the transverse microchannel spacing from 10 to 60 μm, the Nusselt number increases from 1.15 to 2.07 while maintaining a nearly constant pressure gradient. These results provide geometric guidelines for designing high-efficiency microfluidic cooling systems by mitigating the traditional trade-off between heat-transfer enhancement and hydraulic resistance. Among the geometries evaluated, pure square channels maximize heat transfer, hybrid circular-square configurations optimize hydraulic efficiency, and triangular designs perform poorly due to high viscous drag. These results provide geometric guidelines for mitigating the traditional trade-off between heat-transfer enhancement and hydraulic resistance in microfluidic cooling systems. Full article

To study the soil moisture dynamics and rainfall infiltration characteristics of karst sloping farmland and their driving factors, an abandoned farmland was selected for this study, and five monitoring points (from the foot, S1, of the slope to the top, S5) were set along the terrain gradient. The volumetric water content data of the 0–40 cm soil layer was obtained through in situ monitoring for one year. The infiltration characteristics were quantified in combination with a staining tracer test, and the soil properties were determined. The results showed that the soil moisture content increased with the deepening of the soil layer, and there was significant slope differentiation. The moisture content in the downhill slopes (S1, S2) was significantly higher than that in the uphill slopes (S4, S5), and the annual average value of S5 was 27.4% lower than that of S1. The moisture difference (Δθ, the difference in moisture content between hillslope and flatland) changed from positive to negative from the foot of the slope to the top, indicating that moisture was transported downward along the slope surface. A dye tracer showed that from S1 to S5, the water transport pathway gradually shifted from exhibiting deeper vertical penetration and narrower lateral spread to showing shallower vertical penetration and wider lateral spread. The preferential flow index decreased from 46.6 ± 2.3% to 34.7 ± 2.1%, indicating a progressive reduction in rapid vertical channeling, while the lateral flow index reached its peak (21.4 ± 2.7%) in the middle of the slope (S3), suggesting enhanced horizontal water redistribution at this position. Correlation analysis indicated that soil bulk density was extremely significantly negatively associated with infiltration capacity, while capillary porosity, non-capillary porosity, total porosity, organic matter, and high aggregate content were extremely significantly positively associated with infiltration capacity. These results revealed that the topographic gradient affected soil moisture and water infiltration paths by regulating soil physical properties in this karst forest ecosystem. It should be noted that the research results are only applicable to one slope and should not be directly extended to all karst slope agricultural landscapes. Full article

Air entrainment in self-compacting concrete (SCC) is governed by coupled interactions between chemical admixtures, empirical workability behaviour, aggregate-skeleton geometry and early air-bubble stability. In highly flowable mixtures, the hardened air-void system cannot be assessed reliably from total air content alone because bubble escape, redistribution and coalescence in the fresh state may change the final pore structure. This study evaluates the link between early fresh-air retention and hardened air-void characteristics in 25 SCC mixtures arranged according to a five-level Graeco-Latin square design. The analysed factors were air-entraining admixture (AEA) dosage (0.00–0.20% by mass of cement), binder type, water-to-binder ratio (0.29–0.41) and the volumetric paste-to-aggregate filling parameter φ (1.1–1.5). The aggregate skeleton was kept constant to separate paste-composition and volumetric-filling effects from aggregate grading. Fresh concrete was characterised by slump-flow diameter, T₅₀ flow time, density and air content after 5 and 15 min; these quantities were treated as empirical workability and early-retention indicators, not as direct rheological parameters. Hardened concrete was examined after 28 days according to EN 480-11 using total hardened air content A, spacing factor L, micropore content A₃₀₀ and specific surface α. The slump-flow diameter ranged from 50 to 79 cm, fresh air content after 5 min from 1.6% to 8.6%, air loss between 5 and 15 min from 0.41 to 1.12 percentage points, hardened air content from 1.20% to 8.59%, and spacing factor from 0.13 to 0.44 mm. Strong correlations were obtained between fresh and hardened air contents (A₅ vs. A: r = 0.920, R² = 0.846, p < 0.001, 95% CI for r: 0.824–0.964; A₁₅ vs. A: r = 0.922, R² = 0.849, p < 0.001, 95% CI for r: 0.828–0.965), while hardened air content was strongly and inversely related to spacing factor (A vs. L: r = −0.907, R² = 0.822, p < 0.001, 95% CI for r: −0.958 to −0.797). The recalculated ANOVA showed that statistical significance was response-dependent: w/b was significant for early air loss ΔA (F = 4.190, p = 0.040, partial η² = 0.677) and micropore content A₃₀₀ (F = 4.058, p = 0.044, partial η² = 0.670), whereas binder type showed near-threshold tendencies for fresh and hardened air contents. No single factor was statistically significant for all air-void descriptors. The SDI-based approach is therefore presented as a bounded explanatory framework, not as an externally validated prediction model. Direct durability claims, including freeze–thaw resistance, require separate experimental verification. Full article

Brachymystax lenok tsinlingensis is an endangered salmonid endemic to China. Traditional trapping methods frequently fail to detect this rare fish in low-density mountain streams, hampering evidence-based conservation. Here, we employed environmental DNA quantitative PCR (eDNA-qPCR) with species-specific primers to assess the spatial biomass distribution of this species in the Zhouzhi Heihe River. Concurrently, we surveyed plankton, benthic macroinvertebrates, and physicochemical water parameters. eDNA detected the target species at 12 of 14 sites, with reliable quantification achieved at 9 sites, suggesting that the method may be more effective than conventional trapping for detecting this species under the studied low-density conditions. eDNA-derived relative biomass exhibited pronounced spatial heterogeneity, ranging from 6.0 × 10⁻⁴ to 1.5 × 10⁻² g/cm³. Water depth showed a significant positive association with biomass (r = 0.5347), whereas phytoplankton Shannon diversity (a measure of species richness and evenness) was significantly negatively correlated (r = −0.5447). Flow velocity displayed a negative trend that did not reach statistical significance (r = −0.5009). Plankton and benthic communities indicated overall ecological conditions but did not directly explain the observed spatial variation in fish biomass. These findings indicate that the spatial pattern of B. lenok tsinlingensis is primarily shaped by local physical habitat structure, with deeper, hydraulically more complex channel units serving as key microhabitats. eDNA-qPCR thus represents an effective, low-disturbance monitoring tool for this endangered cold-water fish and provides a scientific basis for targeted habitat protection and restoration. Full article