Search Results (601)

The impact of sewage discharge on water quality in reversing rivers has rarely received attention. This study simulated water quality changes in Maoergang River (a water body with counter flow conditions) affected by effluent discharge from Yangjiabu Sewage Treatment Plant. The results revealed that the diffusion patterns of COD, NH₄⁺-N, and TP in the study area were largely consistent; however, different hydrological conditions and discharge scenarios resulted in obvious differences in pollutant distribution. During the dry season, regardless of normal or counter folow conditions, the Maoergang and Xitiaoxi downstream were the primary affected segments. Regulated by hydrodynamic forces, under normal flow conditions, the Xitiaoxi downstream received a higher pollutant load while the Xitiaoxi upstream received minimal inputs. In the wet season, pollutant concentrations were generally lower due to the dilution effect of increased runoff; notably, the primary affected segments shifted to the downstream reaches of Maoergang and Huanchenghe. Under accidental discharge scenarios, excessive sewage release expanded the scope of pollution impacts, with elevated pollutant concentrations causing water quality non-compliance in parts of the upstream and downstream Xitiaoxi—both of which are within the germplasm resource protection zone. Predictive analysis indicated that when the sewage treatment plant’s discharge was reduced to 1.0 × 10⁴ t·d⁻¹, the receiving water bodies could still meet local water quality standards, even under the counter flow hydrological conditions, which pose the greatest threat to water quality during the dry season. Full article

This numerical study demonstrates the existence of a critical injection momentum threshold necessary for stable liquid film formation, highlighting that either excessive or insufficient momentum degrades cooling performance. This optimization is critical for maximizing cooling effectiveness from short injection holes in high-performance propulsion systems. By comparing Smoothed Particle Hydrodynamics (SPH) and Volume of Fluid (VOF) methods, we find that the SPH method predicts a thicker, more continuous coolant film due to its superior mass conservation during interface breakup. A key design insight emerges: cooling performance peaks at a distinct, critical coolant momentum. Insufficient momentum leads to poor coverage, while excess momentum causes film separation and is counter-productive. The identified configuration—defined by a precise combination of flow rate, pressure, and geometry—promotes immediate and stable film formation. The robustness of this finding is confirmed by the agreement between the two numerical methods on film thickness and the captured physical evolution of the film from a pronounced wave to a damped state. Full article

This study employs computational fluid dynamics (CFD) to investigate the aerodynamic performance and static stability of hybrid wing aircraft, considering the interference of counter-rotating embedded propellers. Extensive numerical verification has been carried out, including comparisons with NASA’s high-lift propeller (HLP) data. Three configurations—no propeller, counter-rotating inboard-upwash (CNIU) and counter-rotating outboard-upwash (CNOU) are defined to analyze the aerodynamic force/moment characteristics and flow field structures over a range of angles of attack from −6° to 26°, in conjunction with crosswind velocities of 0, 5, 10, and 15 m/s. The propeller-induced slipstream alters the aircraft’s fundamental performance by modifying wing pressure distributions and vortex systems. Specifically, the CNIU configuration increases the low-pressure areas on both the fuselage and outer wing upper surfaces, enhancing the lift-to-drag ratio by 28.4% at low angles of attack. In contrast, the CNOU configuration improves longitudinal steady-static margin by 27.4% under typical conditions and demonstrates superior lateral static stability under 10 m/s leftward crosswind conditions. For engineering applications in the aerodynamic design of such aircraft, the CNIU configuration is recommended for high cruise efficiency, whereas the CNOU configuration is preferred for flight stability. Full article

To address the issue of climate change caused by greenhouse gases, extensive research has been conducted on technologies for separating and capturing carbon dioxide. This study aimed to investigate the internal flow behavior and relative spatial distribution of CO₂-related features inside a vortex tube using the Schlieren method. Due to the presence of numerous components in a typical counter-flow vortex tube that may cause optical refraction along the measurement path, a simplified tube with a single nozzle was designed and manufactured for the experiments. The experiments consisted of CO₂ single-phase flow and air–CO₂ mixture flow tests. Images captured during the experiments were processed using Gaussian filtering and background correction to enhance the visibility of boundary layers and internal flow structures. Based on the pixel intensity values of the processed Schlieren images, relative intensity distributions associated with CO₂-related flow behavior inside the tube were estimated and visualized. The experimental results revealed that, in both CO₂ single-phase and air–CO₂ mixture flows, regions of relatively high Schlieren intensity consistently appeared at specific locations within the tube. These observations indicate that the internal flow structure and relative distribution patterns are sensitive to the local flow features near the nozzle region under the tested conditions. The temporal evolution of the normalized Schlieren pixel intensity and its standard deviation was quantitatively evaluated, in a relative sense, to characterize the development of vortex flow structures under different operating conditions. The proposed visualization and analysis framework provides a systematic qualitative approach, supported by relative quantitative indicators, for investigating vortex-induced flow behavior. This framework may serve as a foundation for future studies that integrate complementary diagnostics and numerical analyses to further explore the vortex-based gas separation mechanism. Full article

This study numerically investigates the critical fuel concentration and flammable regions of methane–air and methane oxy-fuel counterflow diffusion flames. The goal is to determine the effects of strain rate, oxidizer composition, and radiative heat transfer models on flame extinction. Calculations were performed using the counterflow diffusion flame with the adiabatic (ADI), optically thin (OTM), and statistical narrow-band (SNB) radiation models at strain rates of 10 s⁻¹, 80 s⁻¹, and 200 s⁻¹. The key findings are as follows: For methane–air flames, radiation reabsorption has a negligible impact. The flammable region decreases with increasing strain rate (S_Low > S_Mid > S_High) across all models. In O₂/CO₂ flames, radiation plays a significant role. While the ADI and SNB models maintain the same trend as in air flames, the OTM yields a different order (S_Mid > S_High > S_Low). Reducing oxygen concentration increases the critical fuel concentration and shrinks the flammable region. When the oxygen concentration is between 0.35 and 0.40, the combustion characteristics of O₂/CO₂ flames resemble those of conventional air flames. In conclusion, this work highlights the critical influence of radiation modeling and oxidizer composition on oxy-fuel flame extinction limits, providing insights for combustion system design under CO₂ dilution. Full article

This scoping review examines public health communication across nine Eastern European and Central Asian states—Armenia, Azerbaijan, Belarus, Kazakhstan, Kyrgyzstan, Russia, Tajikistan, Turkmenistan, and Uzbekistan—highlighting how these systems have transitioned from Soviet-era legacies to contemporary practices. Eligibility criteria included the English- and Russian-language literature published from 1998 onwards, focusing on nine post-Soviet states. Sources of evidence comprised searches in Google Scholar, ScienceDirect, SSRN, Heliyon, MEDLINE/PubMed, and official government websites. Data were charted by three independent reviewers using a standardized form, with discrepancies resolved by senior reviewers. The review identifies persistent gaps in communication during health crises, with a particular focus on the COVID-19 pandemic, where centralized and hierarchical information flows often undermine transparency and responsiveness, as well as further increased health inequalities between rural and urban health outcomes. Despite ongoing reforms, the communication dimension of healthcare systems remains underdeveloped. Findings reveal that centralized and top-down communication remains a dominant feature across the region, hindering timely dissemination of information and limiting the capacity to counter misinformation, as both misinformation and disinformation sometimes emerge from the government. Ultimately, this review contributes a critical analysis of these systematic communication failures and underscores the need to strengthen public health communication and reduce health inequalities. To do it, governments must prioritize transparency, disclose decision-making processes, and rely on evidence-based messaging to build trust. Effective crisis response requires not only government leadership but also the active engagement of the medical and patient communities, supported by civil society and independent media. This review points out the need for more inclusive, transparent, and trust-oriented communication strategies to enhance public health preparedness and resilience in nine Eastern European and Central Asian contexts. Full article

As an active flow-control technology, the counterflowing jet can reduce drag by reconstructing the flow field structure during the re-entry of a vehicle, thereby mitigating the adverse effects of high overload on personnel. However, variations in the angle of attack (AoA) and nozzle mass flow rate tend to induce transitions in its flow field modes and fluctuations in drag reduction performance. To further investigate the aerodynamic interference characteristics of the counterflowing jet during the re-entry process, this study focused on a 2.6% subscale model of the Apollo return capsule. The Reynolds-averaged Navier–Stokes (RANS) equations turbulence model was employed to numerically analyze the effects of different mass flow rates and freestream AoAs on the flow field modes and the drag behavior. The results indicate that with an increase in AoA, the flow field structure of the long penetration mode (LPM) is likely to be destroyed, and the shock wave shape exhibits significant asymmetric distortion. In contrast, the flow field structure of the short penetration mode (SPM) remains relatively stable; however, the bow shock and Mach disk exhibit two typical offset patterns, whose offset characteristics are jointly regulated by the mass flow rate and AoA. In terms of drag characteristics, the AoA significantly weakens the drag reduction effect of the LPM. In contrast, the SPM can maintain a stable drag reduction efficiency of approximately 50% within a certain AoA range. Nevertheless, as the AoA further increases, the drag reduction effect of the SPM gradually diminishes. Full article

This paper presents a side-by-side study of CFD predictions and experimental measurements for a novel counter-flow heat exchanger installed in the sidewall of a dishwasher (HEBS). The work aims to improve appliance efficiency by transferring heat from discharged hot wastewater to the incoming cold supply. Motivated by sustainability goals and tightening EU energy rules, the research targets the high losses typical of conventional machines. This approach combines detailed ANSYS Fluent 2022R2 simulations with controlled laboratory tests on a bespoke test rig. The measured data show a repeatable rise in the cold-water temperature of roughly 8 K, corresponding to an approximate 15% gain in thermal performance for the heat-recovery stage. While the simulations and experiments efficiently agree based on trends and qualitative behavior, there are noticeable quantitative differences in the total energy transfer, indicating the models need further refinement. The validation carried out here forms a solid basis for design optimization and for reducing energy consumption in household dishwashers. This work overcomes the limitations of previous studies which typically rely on external storage tanks or static heat recovery analysis. The primary novelty of this paper lies in the empirical validation of a high-efficiency heat exchanger integrated into the extremely constrained sidewall volume of the appliance, tested under transient, on-the-fly flow conditions, providing a verified methodology for constrained industrial applications. Full article

A combined flow control method, integrating nanosecond pulsed surface dielectric barrier discharge (NS-SDBD) with pulsed jets, is proposed to address the challenge of low mixing efficiency in supersonic combustion. Numerical validation and mechanism analysis were conducted by solving the three-dimensional unsteady Reynolds-averaged Navier–Stokes (RANS) equations, coupled with the shear stress transport (SST) k–ω turbulence model. The simulations were carried out under a Mach 2.8 inflow condition with a 50 kHz pulsed frequency for H₂ jets. The results demonstrate that, compared to the steady jet case, the combined control scheme increases the combustion product mass flow rate by 27.1% and enhances combustion efficiency by 26.8%. The average temperature in the wake region increases by 65 K, while the total pressure recovery coefficient shows only a marginal change. The pressure disturbance center evolves along the outer edge of the counter-rotating vortex pair (CVP) and is eventually absorbed by the vortex core. This process generates favorable velocity and vorticity perturbations, which enhance O₂ entrainment into the CVP and increase the average wake temperature. Meanwhile, the strengthened reflected shock induces favorable velocity perturbations in the upper shear layer of the wake and further elevates the local temperature. 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

The injection compression molding using dynamic mold control (ICM-DT) represents a promising technological approach to the manufacturing of highly filled, modified thermoplastic components with tight geometric tolerances. While the numerical prediction of flow states is, to date, predominantly based on the Cross–WLF modeling of viscoelastic characteristics of the melt, new material-related developments necessitate the assessment of process- and material-related boundaries. The present paper employs a highly filled graphite–polypropylene system, exhibiting a graphite mass fraction of 80%, for the quantitative comparison of Cross–WLF predictions and experimentally derived flow states. Based on coupled counter pressure-chamber high-pressure capillary rheometry (CPC-HCR) and counterpressurized viscometry (CPV) alongside the ICM-DT of thin-walled specimens, pressure-induced crystallization was identified to induce significant deviations from Cross–WLF predictions. Cross–WLF modeling strongly overestimates the processability of the applied graphite–polypropylene system under both injection molding (IM) and ICM regimes. We therefore observe a predominant influence of pressure-induced crystallization mechanisms in dynamic mold temperature process domains, in which the pressure-induced, crystallization-related exponential viscosity increase cannot be adequately modeled through both pressure-dependent and pressure-agnostic Cross–WLF models. The numerical approximation of flow states under dynamic mold temperature regimes hence necessitates the consideration of solidification-induced, self-intensifying pressure excursions. Full article

Water quality has traditionally been measured via in situ sensors and satellites. The latter has limited applicability for smaller inland water bodies, while the former requires significant logistics, labor, and expense for routine sampling, and reactive/spurious sampling is often not feasible as a result (e.g., sampling pre-/post-storm). Consequently, small uncrewed aircraft system-based (sUAS-based) sampling has emerged as a potential solution to bridge these sampling gaps and challenges. But sampling from an sUAS is complicated by the need to pump water from depth, rather than suspending a sensor from the sUAS, due to concern over sampling sUAS-impacted waters. Here, we measure the water flow below a hovering sUAS in a laboratory by applying the particle image velocimetry flow measurement technique. Observations suggest the development of two counter-rotating vortices under the sUAS, where, in the center of the vortex pair, water is upwelled to the surface, which would, therefore, be a sampling location relatively free of contamination by the sUAS. This location coincides with the still spot on the water surface underneath the sUAS; thus, if one wanted to sample water by suspending a sensor underneath an sUAS, then the optimal sampling location would be within this still spot. Full article

This study investigated the influence of spatial orientation on bead morphology and molten pool dynamics during cold metal transfer wire arc additive manufacturing (CMT-WAAM). Experiments in horizontal, transverse, vertical-down, and vertical-up orientations under varying wire feed speeds revealed that increasing the feed rate improved bead uniformity and reduced defects in horizontal deposition, while gravity-induced asymmetry dominated non-horizontal orientations. Transverse cladding produced tilted, uneven beads with reduced penetration; vertical-down enhanced lateral spreading but resulted in the shallowest weld depth; vertical-up limited spreading, yielding narrow beads with higher reinforcement. Optimal cladding quality was achieved at a wire feed speed of 6.7 m/min for the first layer, with a reduced heat input applied for subsequent layers to minimize residual stress and deformation. Numerical simulations further elucidated transient temperature and flow fields. Heat accumulation and dissipation varied with orientation and layer sequence: horizontal deposition formed deep, symmetric pools; transverse deposition generated asymmetric vortices and uneven solidification; vertical-up deposition caused upward counterflow with restricted spreading; vertical-down promoted rapid spreading and faster solidification. A detailed comparison between simulated and experimental temperature distributions and cross-sectional profiles demonstrated excellent agreement, thereby validating the accuracy and predictive capability of the developed model. This integrated experimental-numerical approach provided a comprehensive understanding of orientation-dependent molten pool behavior and offered a robust framework for optimizing process parameters, enhancing dimensional accuracy, and controlling defects in CMT additive manufacturing. Full article

Background: Human adenovirus type 4 (HAdV-4), the sole member of species Human mastadenovirus E (HAdV-E), is of zoonotic origin and has established stable human transmission through recombination, conferring distinctive host adaptation and pathogenicity. It causes respiratory and ocular diseases, with a significant risk of severe pneumonia in children. No targeted antivirals are approved for routine use, leaving supportive care as the primary management. China bears a relatively high HAdV-4 disease burden in Asia. Methods: To generate neutralizing nanobodies (Nbs) against HAdV-4, we employed an alpaca immunization strategy using hexon protein from Ad4-RI67 strain, followed by the isolation of hexon-specific nanobodies. The epitope competition and molecular docking was employed to analysis the binding site of the Nbs’. We engineered VHH-Fc fusions by conjugating VHH domains to human IgG1 Fc. The lead candidate, NVA17, showed efficacy in both in vitro and in vivo (Stat1^+/− mouse model). Flow cytometric analysis was employed to assess the downstream immune effects of NVA17 in vivo. Its intracellular neutralization mechanism was further investigated through confocal microscopy by examining co-localization in TRIM21-overexpressing and knockdown cells. Results: The isolated nanobodies revealed epitopes distinct from those targeted by known antibodies. The lead candidate NVA17 demonstrated potent neutralizing activity in vitro (IC₅₀ < 10 ng/mL). In the Stat1^+/− mouse model, NVA17 provided complete protection against lethal challenge, significantly reduced viral load in the lungs, and ameliorated pathological damage. NVA17 treatment dose-dependently reversed the virus-induced reduction in immune cell counts and enhanced cytotoxicity, suggesting a systemic immunomodulatory effect. Mechanistic studies indicated that the antiviral activity of NVA17 partly depends on the TRIM21-mediated antibody-dependent intracellular neutralization (ADIN) pathway, whereby TRIM21 terminates the viral life cycle by promoting viral degradation via K48-linked ubiquitination. Conclusions: We have identified multiple antibody candidates, particularly NVA17, with significant therapeutic potential for developing antibody-based treatments against HAdV-4. This offers a targeted intervention strategy to counter the current lack of specific antiviral therapies. Full article

This study investigates water–air coupled transport characteristics during ponded water infiltration in unsaturated sand columns through systematic laboratory experiments. The experiments considered three soil textures, two initial dry densities (1.50 and 1.60 g/cm³), and four initial saturations (0% to 41%), with synchronous monitoring of pore pressure and volumetric water content using pressure sensors (P1–P7) and moisture sensors (W1–W5) to track dynamic changes in wetting front, pressure, and saturation. The results reveal four distinct stages of pore pressure variation during ponded water infiltration: pressure soars (Stage I), pressure ascends with air compression (Stage II), pressure surges due to air breakthrough (Stage III), and pressure stabilization (Stage IV). The duration, intensity of these stages, and wetting front migration rates are significantly influenced by soil texture, initial dry density, and initial saturation. Specifically, lower dry density and clay content shorten the time for the wetting front to reach the column bottom, while higher initial saturation promotes entrapped air bubble breakthrough, triggering Stage III. This study enhances understanding of water–air coupled transport in unsaturated sandy soils, providing insights for optimizing irrigation and soil-water conservation strategies. Full article