Search Results (134)

This study is based on isotope (δ¹⁸O, δ²H, ¹⁴C), hydrochemical, and groundwater-level data from the past 47 years in the central North China Plain (NCP). It uses methods such as mathematical statistics, Piper diagrams, Gibbs models, and ion ratios to investigate the characteristics of changes in the groundwater flow field, hydrochemistry, and isotopes across various aquifers in the Hengshui funnel area before and after the implementation of groundwater exploitation reduction measures (GWER). Furthermore, it reveals the driving mechanisms of these measures’ effects on hydrochemical characteristics and isotopic variations. The results show the following: (1) The hydrochemical type of shallow groundwater (SG) before GWER was primarily Cl▪SO₄-Na▪Ca, which diversified to Cl▪SO₄-Na and SO₄▪Cl-Na types after GWER; the deep groundwater (DG) type changed from Cl▪SO₄-Na to Cl-Na. (2) Before GWER, the hydrochemical composition of SG and DG was primarily controlled by the dissolution of silicates, salt rocks, and evaporites. After GWER, the hydrochemical composition of DG primarily originated from the dissolution of evaporites and salt rocks, accompanied by enhanced cation exchange. (3) The δ¹⁸O of SG was affected by the recharge of irrigation return water, changing from enrichment to depletion before and after the GWER. The δ¹⁸O value in DG changed from depletion to enrichment, and the groundwater age changed from older to younger after the GWER. The GWER altered the hydrodynamics, weakened the hydraulic connectivity, and led to changes in the evolution of the hydrochemistry. The findings have direct implications for water quality and promoting the sustainable utilization of deep groundwater in the NCP’s central funnel area. Full article

The traditional Discrete Element Method (DEM) can track the motion details of individual particles, but its computational cost becomes excessively high when simulating large-scale systems involving millions or even billions of particles. In this study, a coarse-grained DEM approach was employed to analyze the flow behavior of mixed particles in a coal powder silo. This method maintains reasonable simulation accuracy while effectively reducing the total number of computational particles and significantly improving computational efficiency. After conducting investigations on the mesh-to-particle size ratio and model validation, this paper focuses on examining the effects of coal particle size distribution and mixing ratio on the characteristics of particle motion. The results indicate that during the discharge process of mixed particles, the downward velocity of particles in the central axis region near the outlet is significantly higher than that in the wall region, exhibiting typical funnel flow characteristics. The particle size distribution has a notable impact on the particle descent velocity. The uniform distribution case shows the highest descent velocity, the linear distribution case the lowest, while the normal distribution case falls between the two. Notably, in the normal distribution case, the descent velocity in the central axis region is similar to that of the uniform distribution, while the descent velocity in the wall region approaches that of the linear distribution. This presents a combined characteristic of the two extreme distributions rather than a simple transitional state. In contrast, the particle mixing ratio has a relatively minor influence on the overall motion characteristics. The mass flow rate of particles and the cross-sectional velocity distribution remain largely consistent, with only slight differences observed in the velocity within the central axis region. Full article

The rising environmental burden of Portland cement production has intensified the demand for eco-friendly binders that support sustainable construction. This study investigates the development and performance of eco-friendly self-compacting geopolymer concrete (SCGC) produced from industrial by-products, including fly ash (FA), ground granulated blast furnace slag (GGBFS), silica fume (SF), metakaolin (MK), and glass waste powder (GWP). Twenty-one binder formulations were evaluated for fresh-state workability, mechanical performance, durability, and microstructural characteristics under different curing regimes. Fresh properties were assessed using slump flow, V-funnel, L-box, and J-ring tests, while hardened-state evaluations included compressive and flexural strength, Young’s modulus, and water absorption. Scanning electron microscopy (SEM) and X-ray diffraction (XRD) analysis were performed on selected mixes to examine microstructural features and crystalline phase development. Results highlight a strong dependency of SCGC performance on binder composition and curing conditions. Mixes rich in GGBFS and SF demonstrated superior mechanical and durability performance, achieving compressive strengths of up to 102.4 MPa under water curing and 107.6 MPa under heat curing, along with negligible water absorption, reflecting a dense and well-developed gel matrix. SEM micrographs confirmed homogeneous, compact microstructures in high-performing mixes, while XRD analysis revealed broad amorphous humps indicative of well-formed N-A-S-H and C-A-S-H gel phases with minimal crystalline residues. In contrast, FA-dominant mixes displayed delayed strength development, and MK-GWP-rich systems exhibited higher porosity and reduced strength. This study underscores the significance of precursor synergy, optimized curing strategies, and microstructural refinement in tailoring SCGC for high-performance, durable, and low-carbon applications in sustainable construction with values ranged from 38.64 GPa (Mix 21) to 25.04 GPa (Mix 19) at 28 days. Stiffer mixes corresponded to denser matrices containing GGBFS and silica fume, whereas lower values were linked to weaker bonding and higher porosity. Full article

This study investigates the synergistic influence of recycled concrete aggregate (RCA) and recycled steel fibers (RSF) on the fresh and hardened performance of eco-efficient fiber-reinforced self-compacting concrete (SCC). Twelve C30/37.5 mixtures were produced using demolition waste as coarse RCA at replacement levels of 25, 50, 75, and 100% by mass, combined with RSF recovered from scrap tires at volume fractions of 0.25, 0.50, and 0.75%. Fresh properties were assessed in accordance with EFNARC guidelines using slump-flow (T500), V-funnel, L-box, and J-ring tests, while hardened performance was evaluated through compressive, splitting tensile, and flexural strengths at 28 days, together with density and ultrasonic pulse velocity (UPV). Increasing RCA and RSF contents reduced workability, reflected in lower slump-flow diameters and higher T500 and V-funnel times, although most mixtures maintained satisfactory self-compacting behaviour. Compressive strength decreased with RCA content and, to a lesser extent, with higher RSF, with a maximum reduction of about 39% at 100% RCA relative to the control mix, yet values remained structurally acceptable. In contrast, RSF markedly enhanced tensile and flexural responses: at 25% RCA, 0.75% RSF increased splitting tensile and flexural strengths by approximately 41% and 29%, respectively, compared with the corresponding fiber-free mix. RCA reduced density and UPV by about 10–14%, but these reductions were partially mitigated by RSF addition. Overall, the results demonstrate that SCC with moderate RCA (25–50%) and RSF (0.50–0.75%) can achieve a favourable balance between rheological performance and enhanced tensile and flexural behaviour, offering a viable composite solution for sustainable structural applications. Full article

We review some aspects of accretion disks physics, spacetime photon shell and photon orbits, related to retrograde (counter-rotating) motion in Kerr black hole (BH) spacetimes. In this brief review, we examine the counter-rotating components of the Kerr BH shadow boundary, under the influence of counter-rotating accretion tori, accreting flows and proto-jets (open critical funnels of matter, associated with the tori) orbiting around the central BH. We also analyze the redshifted emission arising from counter-rotating structures. Regions of the shadows and photon shell are constrained in their dependence of the BH spin and observational angle. The effects of the counter-rotating structures on these are proven to be typical of the fast-spinning BHs, and accordingly can be observed only in the restricted classes of the Kerr BH spacetimes. This review is intended as a concise guide to the main properties of counter-rotating fluxes and counter-rotating disks in relation to the photon shell and the BH shadow boundary. Our findings may serve as the basis for different theoretical frameworks describing counter-rotating accretion flows with observable imprints manifesting at the BH shadow boundary. The results can eventually enable the distinction of counter-rotating fluxes through their observable imprints, contributing to constraints on both the BH spin and the structure of counter-rotating accretion disks. In particular, photon trajectories and their impact parameters can manifest in the morphology of the BH shadow. Such features, when accessible through high-resolution imaging and spectral or polarization measurements, could provide a direct avenue for testing different theoretical models on accretion disk dynamics and their BH attractors. Full article

Water and sand inrush is frequently accompanied by surface subsidence, which severely constrains the sustainable development of coordinated coal mining and ecological environment. This study investigated four key influencing factors based on a water and sand inrush test system: fracture width, aquifer thickness, sand particle size composition and stratigraphic sedimentary structure. It obtained the morphological evolution characteristics of collapse funnels and revealed the evolution mechanism of collapse funnels induced by water and sand inrush. The results indicate that fracture width and aquifer thickness mainly affect the range of collapse funnel, and both show a positive correlation with the radius of collapse funnels. Sandy particle size composition plays a dominant role in the morphology of collapse funnels induced by disasters: as the size of the soil skeleton particles increases, the morphology of collapse funnels changes sequentially from a bowl shape to an inverted cone shape and then to a funnel shape with a sunken center and raised slopes. The stratigraphic sedimentary structure has a significant impact on the morphology and damage induced by disasters in collapse funnels. The upper clay layer of the underlying aquifer inhibits the water and sand inrush processes to some extent. An increase in the thickness and number of clay layers effectively prevents the water and sand mixture from flowing into the fracture channel from the lateral direction. This reduces the damage range of collapse funnels and decreases the rate of water and sand inrush. This study clarifies the formation mechanism of surface collapse funnels under the influence of the disaster-causing factors of water and sand inrush, and provides theoretical guidance for the prevention and control of such disasters. Full article

To better understand the relationship between meniscus instabilities and the high levels of turbulence in the fluid dynamics of a continuous medium slab mold, this study investigates the magnitudes of meniscus dynamics distortions and their fluid dynamic origin using a full-scale water modeling experiment and mathematical simulations. The three-dimensional mathematical model is composed of the continuity and momentum equations, together with the standard k-ε turbulence model and the volume of fluid model, to track the dynamics of the steel interface. The results show that the medium slab mold shares flow patterns common to both conventional slab molds and funnel thin slab molds, making its fluid dynamics more complex. Despite this, the fluid dynamics within the mold do not develop a dynamic distortion phenomenon but induce upward stream flows with instability and high velocities, which generate an unstable meniscus behavior characterized by significant surface oscillations, variations in velocity, and high deformations. These latter flow characteristics are the origin of meniscus dynamic distortion (MDD), which shows a constant frequency with non-constant periodicity and different median lifecycle ranges. Full article

Hydrogen-based direct reduction of iron ore is a promising route to reduce CO₂ emissions in steelmaking, where uniform particle flow inside shaft furnaces is essential for efficient operation. In this study, a full-scale three-dimensional Discrete Element Method (DEM) model of a shaft furnace was developed to investigate the effects of a diverter device on granular flow. By systematically varying the radial width and top/bottom diameters of the diverter, particle descent velocity, residence time, compressive force distribution, and collision energy dissipation were analyzed. The results demonstrate that introducing a diverter effectively suppresses funnel flow, prolongs residence time, and improves radial flow uniformity. Among the tested configurations, the smaller central diameter diverter showed the most favorable performance, achieving a faster and more uniform descent, reduced compressive force concentration, and lower collision energy dissipation. These findings highlight the critical role of diverter design in regulating particle dynamics and provide theoretical guidance for optimizing shaft furnace structures to enhance the efficiency of hydrogen-based direct reduction processes. Full article

In the digitally saturated hospitality environment, research on digital transformation remains dominated by macro-level adoption trends and user-generated content, while the potential of micro-level web-behavioural data remains largely untapped. Recent systematic reviews highlight a fragmented body of literature and note that hospitality studies seldom address first-party behavioural data or big-data analytics capabilities. To address this gap, we collected clickstream, navigation and booking-funnel data from five luxury hotels in the Mediterranean and employed big-data analytics integrated with simulation modelling—specifically fuzzy cognitive mapping (FCM)—to model causal relationships among digital touchpoints, managerial actions and customer outcomes. FCM is a robust simulation tool that captures stakeholder knowledge and causal influences across complex systems. Using a case-study methodology, we show that first-party behavioural data enable real-time insights, support knowledge-based decision-making and drive digital service innovation. Across a 12-month panel, visitor volume was strongly associated with search traffic and social traffic, with the total-visitors model explaining 99.8% of variance. Our findings extend digital-transformation models by embedding micro-level behavioural data flows and simulation modelling. Practically, this study offers a replicable framework that helps managers integrate web-analytics into decision-making and customer-centric innovation. Overall, embedding micro-level web-behavioural analytics within an FCM framework yields a decision-ready, replicable pipeline that translates behavioural evidence into high-leverage managerial interventions. Full article

Background/Objectives: Optimizing drug deposition to the olfactory region is key in Nose-to-brain drug delivery strategies. However, findings from computational fluid dynamics (CFD) studies remain inconsistent concerning the parameters influencing olfactory deposition, limiting clinical translation and device optimization. This systematic review aims to identify robust CFD parameters for optimizing drug delivery to the olfactory region. Methods: A systematic review and meta-analysis were conducted following PRISMA guidelines, selecting studies reporting CFD simulations of nasal drug delivery with evaluation of olfactory deposition efficiency. The primary outcome was the correlation between each CFD parameter and olfactory deposition rate. Parameters included particle size, impaction parameter, flow rate, spray cone angle, insertion angle, injection velocity, head position, release position, and breathing pattern. Data were extracted and standardized, and statistical methods were used to assess correlations, heterogeneity, and potential biases in study results. Results: Smaller particle size (pooled r = −0.42) and lower impaction parameter (r = −0.39) were significantly associated with higher olfactory deposition. No consistent correlation was observed with breathing flow rate. Heterogeneity across studies was high (I² > 90%). Funnel plots asymmetry suggested potential publication bias in particle-related outcomes. Conclusions: Particle characteristics, especially size and inertia, are the most critical determinants of olfactory deposition in CFD simulations. These findings support design optimization of nasal delivery devices targeting the olfactory region and underscore the need for standardized reporting and validation across CFD studies. Full article

This study presents a novel approach to the development of self-compacting concrete (SCC) by partially replacing both cement and fine aggregate (sand) with waste marble sludge (WMS), a byproduct of the marble industry. The research aims to evaluate the feasibility of incorporating this industrial waste into SCC to enhance sustainability without compromising performance. To assess the fresh and hardened properties of the proposed mixtures, a comprehensive experimental program was conducted. Tests included slump flow, T₅₀, and V-funnel for evaluating workability, as well as measurements of specific gravity, compressive strength, flexural strength, Brazilian tensile strength, and water absorption at 28 days of curing. The results demonstrated that the mix containing 5% cement replacement and 20% sand replacement with marble sludge exhibited the highest mechanical performance, achieving a compressive strength of 48.2 MPa, tensile strength of 3.9 MPa, and flexural strength of 4.4 MPa. Furthermore, increasing the percentage of cement replacement led to enhanced flowability, as evidenced by an increase in slump flow diameter and a reduction in V-funnel flow time, indicating improved workability. Overall, the findings suggest that controlled incorporation of WMS can produce SCC with desirable mechanical and rheological properties, offering a promising pathway for sustainable concrete production. In addition to the technical performance, a carbon footprint analysis was conducted to examine the environmental benefits of marble sludge utilization. The mixture with 10% cement and 20% sand replacement exhibited the lowest carbon footprint, while the 7.5% replacement level provided the best balance between strength and sustainability. Full article

This research investigates the feasibility of producing eco-friendly self-compacting concrete (SCC) by partially replacing both fine and coarse natural aggregates with waste marble sludge (WMS), a byproduct of the marble industry. The objective is to evaluate whether this substitution enhances or compromises the concrete’s performance while contributing to sustainability. A comprehensive experimental program was conducted to assess fresh and hardened properties of SCC with varying WMS content. Fresh-state tests—including slump flow, T₅₀ time, and V-funnel flow time—were used to evaluate workability, flowability, and viscosity. Hardened properties were measured through compressive, flexural, and Brazilian tensile strengths, along with water absorption after 28 days of curing. The mix with 10% replacement of both sand and coarse aggregate showed the most balanced performance, achieving a slump flow of 690 mm and a V-funnel time of 6 s, alongside enhanced mechanical properties—compressive strength 48.6 MPa, tensile strength 3.9 MPa, and flexural strength 4.5 MPa—and reduced water absorption (4.9%). A complementary cost model quantified direct material cost per cubic meter and a performance-normalized efficiency metric (compressive strength per cost). The cost decreased monotonically from 99.1 $/m³ for the base mix to $90.7 $/m³ at 20% + 20% WMS (−8.4% overall), while the strength-per-cost peaked at the 10% + 10% mix (0.51 MPa/USD; +12% vs. base). Results demonstrate that WMS can simultaneously improve rheology and mechanical performance and reduce material cost, offering a practical pathway for resource conservation and circular economy concrete production. Full article

The integration of recycled materials into cementitious systems presents a sustainable path to reducing environmental impact in construction. This study investigates the mechanical and durability performance of self-compacting mortars (SCMs) incorporating finely ground mortar waste powder (MWP) as a partial cement substitute, reinforced with aluminum oxide (Al₂O₃) and iron oxide (Fe₂O₃). Eleven mixes were designed with MWP replacing cement at 0–50% by volume. Fresh-state tests showed that slump flow decreased moderately (from 259 mm to 240 mm), while V-funnel times improved (from 10.51 s to 7.01 s), indicating acceptable flowability. The optimum performance was observed in SCM2 (5% MWP + oxides), which achieved 75.62 MPa compressive and 13.74 MPa flexural strength at 28 days, outperforming the control mix. Durability under high temperature and freeze–thaw cycling revealed that oxide-reinforced mixes exhibited superior strength retention, with SCM2 maintaining over 87 MPa after 300 °C exposure and minimal degradation after 100 freeze–thaw cycles. Porosity remained low (16.1%) at optimal replacement levels but increased significantly beyond 25% MWP. The results confirm that low-level MWP replacement, when reinforced with reactive oxides, provides a viable strategy for producing durable, high-performance, and eco-efficient SCMs. Full article

This study addresses the challenge of solid pollutant collection in seawater pond recirculating aquaculture by designing a novel funnel-shaped sewage collection device and evaluating its performance through Computational Fluid Dynamics (CFD) simulations and experimental validation. The results reveal that the device forms a rotating flow field, effectively concentrating solid particles in a central low-velocity zone with a diameter of approximately 2 m when the sewage pump is inactive. The optimal bottom dip angle for efficient sewage discharge is determined to be 21 degrees, with flow velocities near the outlet ranging between 0.031 and 0.062 m per second, sufficient to mobilize particles smaller than 5 mm. Prototype testing demonstrates a solid pollutant collection efficiency of 75.7 percent, confirming the device’s practical effectiveness in improving water quality and operational performance. This research offers a validated and efficient solution for solid waste management in aquaculture systems. Full article

In developing spacecraft dust environment testing equipment, cyclone separators serve as critical particulate separation devices. To optimize cyclone performance, this study investigates the impact of inlet configurations on internal flow fields. We propose a novel helical-baffle inlet design and comparatively analyze it against volute baffle inlets and conventional single-channel inlets using Eulerian–Lagrangian multiphase simulations. Three-dimensional streamline visualization reveals internal flow patterns, while the Q-criterion identifies vortical structures. Results demonstrate that both volute and helical configurations effectively eliminate inlet gas funneling effects. The flow-splitting baffles mitigate flow field asymmetry, with the helical-baffle design exhibiting optimal performance: it maintains vortex stability, enhances fluid dynamic equilibrium, reduces pressure drop and improves separation efficiency to 95.92% for 4 μm particles. Full article