Research on multi-factor regulation of expansion characteristics in upflow activated carbon filters.

To address the practical engineering challenges of compaction difficulty and low efficiency associated with traditional backfilling methods for narrow and confined urban foundation trenches, this study proposes an eco-friendly backfill material: sodium silicate-activated fly ash-cement composite fluidized stabilized soil, using in-situ loess from the Xiong'an New Area as raw material. Material components were optimized through curing agent ratio determination and single-factor tests. The development laws of mechanical properties, the micro-scale solidification mechanism, and the flow-filling characteristics within narrow trenches were systematically elucidated by integrating scanning electron microscopy and computational fluid dynamics (CFD) simulations. The results indicate that a fly ash-to-cement mass ratio of 1:1 serves as the critical benchmark for optimizing the composite curing agent proportion. This ratio effectively inhibits excessively rapid early water evaporation and provides a stable hydration environment for the later pozzolanic reaction of fly ash. The optimal mix proportion achieves a balance between high fluidity and high strength. A water content of 51.25% ensures sufficient cementitious reactions. A sodium silicate content of 2.0% strikes a balance between activating fly ash and avoiding excessive slurry viscosity. A curing agent content of 35% facilitates the formation of a continuous and dense cementitious network. Under the optimal proportion, the material exhibits a spread flow of 175mm and a 14-day compressive strength of 4.53MPa, meeting the requirements for pumping construction and strength. The compressive strength of fluidized stabilized soil results from the synergistic interaction of fluidity, molding compactness, and water loss behavior. This is manifested microscopically by the generation of cementitious products, pore filling, and particle cementation, and macroscopically reflected in the coupled effects of physical water migration and chemical water consumption. Adopting a single-pour length covering three utility tunnel Sect. (9m) and a pouring speed of 5m/s combined with a terminal speed reduction process can significantly enhance the compactness and construction quality of trench backfilling. This approach facilitates the formation of a stable flow field and reduces air bubble retention in corners. Field application demonstrates that this process can meet the dual requirements of construction efficiency and quality. The research findings provide a theoretical foundation and key technical guidance for the construction of underground comprehensive utility tunnels in the Xiong'an New Area.

Fencing is an intermittent combat sport in which performance depends on the interaction of neuromuscular qualities, aerobic support, and weapon-specific demands. However, evidence on sex-based differences in the physical capacity profiles of regional fencers remains limited. This study compared the physical capacity profiles of 27 fencers from the Liga Vallecaucana de Esgrima (13 women and 14 men; 14-31 years) in an observational, cross-sectional, comparative study. Field-based assessments included push-ups, sit-ups, squats, jump squats, pull-ups, terminal speed attained in the 20-m shuttle run test, and estimated VO2max. The analysis adopted an exploratory, estimation-oriented approach based on mean differences, 95% confidence intervals, Hedges' g, supplementary significance testing, false discovery rate adjustment, and a directed acyclic graph to clarify causal assumptions. The most robust sex-based difference was observed in pull-up performance, with men outperforming women by 5.43 repetitions (95% CI: 3.51 to 7.45; g = 1.88), and this was the only comparison retained after FDR correction. No conclusive sex-based differences were found for push-ups, sit-ups, squats, jump squats, terminal shuttle-run speed, or estimated VO2max. Mean estimated VO2max for the overall sample was 43.48 ± 9.12 mL·kg-1·min-1. These findings suggest that upper-limb pulling strength may be the main distinguishing physical quality in this cohort, although its implications for individualized conditioning remain to be established. Nevertheless, the results should be interpreted as observational associations rather than causal effects because of the cross-sectional design, the small sample, the field-based measurements, the imbalance in weapon distribution, and the lack of standardized measures of training exposure.

We present a new method to estimate terminal bubble velocities during first-order phase transitions in a plasma in local equilibrium. The method relies on calculating the extrema of a modified potential function for the scalar field undergoing the transition. The shape of this function, which we refer to as the “pseudopotential”, changes with the wall velocity, and if the dependence of the fluid temperature on scalar gradients is weak — which is confirmed to hold with high accuracy in concrete examples — the difference in pseudopotential between two appropriate extrema gives the net outward pressure acting on the bubble wall. It then follows that the correct terminal bubble velocities are those that lead to degenerate minima in the pseudopotential. This allows to compute bubble velocities without having to solve the equation of motion of the scalar field, and in contrast to other methods this can be done without relying on simplified equations of state for the plasma or without choosing a specific ansatz for the scalar field profile. We illustrate the method in a singlet extension of the Standard Model, computing the net outward pressure as a function of the wall velocity. We confirm the dip in outward pressure found in the literature for hybrid bubbles, which implies that stationary deflagrations are stable, while their detonation counterparts are unstable.

Background: Velocity loss (VL) is widely used in velocity-based training (VBT) to index mechanical fatigue, yet attentional focus cues may alter velocity profiles and their relationship with internal load. This study tested whether internal focus, external focus, or control modifies repetition-level velocity, lactate kinetics, and lactate–VL% coupling during bench press (BP) at 60% one-repetition maximum (1RM). Methods: Thirty-six trained men were randomized into three groups. Thirty-four participants completed the study and were included in the final analyses according to outcome-specific data availability. Participants completed two counterbalanced sessions on a Smith machine BP: (i) a single set to technical failure, and (ii) a conventional 3 sets × 10 repetitions at 60% 1RM. Concentric velocity was recorded via a linear position transducer and analyzed at the repetition level using linear mixed-effects models. Lactate was analyzed via Gaussian generalized estimating equations (GEEs). Results: Repetitions to failure and terminal velocity at failure did not differ between groups (Welch p = 0.328; ω2 = 0.045). During 3 sets × 10 repetitions, velocity decreased across sets and repetitions (both p < 0.001); adding group terms improved fit (LR χ2(12) = 42.26, p < 0.001), with additional improvement for group-dependent fatigue patterns (LR χ2(6) = 14.90, p = 0.021). Lactate increased over time (Wald χ2(4) = 244.56, p < 0.001) with convergence by post-lactate set 3 and post-lactate 30 s. Lactate–VL% coupling was strongly moderated by group (post-lactate × group: χ2(2) = 80.42, p < 0.001), with slopes (ΔVL% per 1 mmol·L−1) of 5.27 (internal focus), 13.60 (external focus), and 0.04 (control). After Holm correction across prespecified primary outcomes, only the post-session rating of perceived exertion differed (pHolm = 0.004; ω2 = 0.045), with higher values in the external focus group. Pairwise effects were calculated as comparator minus external focus; therefore, negative g values indicate a higher rate of perceived exertion (RPE) in the external focus group (gHedges ≈ −1.50 vs. control; −1.37 vs. internal focus). Conclusions: Attentional cueing did not consistently alter averaged VL% outcomes after multiplicity correction, but it was associated with differences in early lactate kinetics and modified the observed association between post-set lactate and VL% in the interaction-based coupling model. Cueing scripts should therefore be reported verbatim and standardized in VBT studies, particularly when VL-derived indices are interpreted alongside internal load markers.

This study investigates the dynamics of a single bubble rising in a quiescent liquid and impacting a fixed cylinder using a resolved two-fluid approach. The resolved two-fluid approach is validated against experimental data and compared with a one-fluid approach through 2D axisymmetric and 3D simulations across a wide range of Reynolds and Eötvos numbers, and density ratios. The two-fluid model accurately reproduces the bubble shape, terminal velocity, and impact dynamics, showing agreement with both experimental observations and the one-fluid approach. A detailed analysis on the impact force coefficient exerted by the bubble on the cylinder is conducted with the two-fluid approach by varying the bubble’s Reynolds and Eötvos numbers and the density, viscosity, and bubble-to-cylinder diameter ratios ( R e b ∈ [ 1 , 80 ] , E o ̈ ∈ [ 10 , 116 ] , ρ l / ρ g ∈ [ 25 , 1000 ] , μ l / μ g ∈ [ 10 , 100 ] , and d b / D c ∈ [ 0 . 5 , 1 . 0 ] ). This study reveals that, when varying one dimensionless number at a time, the bubble Reynolds number has the most significant influence on the impact force coefficient, followed by the bubble-to-cylinder diameter ratio and the Eötvös number, while the effects of viscosity and density ratios are weaker. A correlation on the impact force coefficient (associated to the force applied by the bubble on the cylinder at impact) is proposed and may be useful for Euler–Lagrange point-particle methods. • Numerical study of bubble impact on a cylinder across a wide range of dimensionless numbers. • Resolved two-fluid approach validated against experimental data and one-fluid simulations. • Two-fluid approach accurately capture bubble shape and terminal velocity. • Bubble Reynolds number found to have the strongest influence on the drag coefficient associated to the bubble impact on the cylinder. • Drag coefficient correlation proposed to improve impact predictions.

Hydraulic rock drill exhibits outstanding attributes of high power and high frequency, but there are some issues including unclear mechanisms governing impact dynamic behaviors and inaccurate evaluation of impact performance. In this study, a dynamic test platform for the hydraulic rock drill was established by employing the terminal velocity method, utilizing a high-frequency non-contact laser displacement sensor to precisely capture the transient kinematics of the impact piston. The quantitative results indicate that as the input pressure rises from 10 MPa to 23 MPa, the impact frequency increases from 50 Hz to 76.9 Hz, and the impact energy increases from 89.9 J to 275 J. A hydraulic rock drill AMESim simulation model incorporating the impact system, collision medium and buffer system was developed and validated. This reveals the operating mechanism of impact piston driven by the equivalent pressure difference between the front and rear chambers. And the stroke reversal interval governs the duration between the deceleration onset and collision of the impact piston. As a result, both excessively large and small stroke reversal intervals will lower the impact power. The 12 mm stroke reversal interval has been identified as the optimal setting for maximizing impact power, at which the impact power reaches 17,561.3 W, which presents an increase of 4.70% and 3.12% compared to the intervals of 7 mm and 17 mm, respectively. This study contributes a reliable theoretical basis and direct data support to the performance evaluation and optimized design of hydraulic shock systems.

Abstract We study outflow from an unmagnetized, shocked accretion disk&amp;#xD;around a non-rotating super-massive black hole using&amp;#xD;multidimensional hydrodynamics simulation with radiative cooling.&amp;#xD;We aim to investigate whether such shocked accretion flow can&amp;#xD;launch sustained collimated bipolar outflow reaching out to thousands&amp;#xD;of gravitational radii even in the absence of magnetic field&amp;#xD;and if yes, what terminal velocity&amp;#xD;can they achieve? We present the results of a few simulations of&amp;#xD;geometrically thick accretion flow with increasing specific angular momentum&amp;#xD;on a vertically elongated cylindrical domain. We show that&amp;#xD;bipolar outflow from a region very close to the black hole is&amp;#xD;originating and propagating vertically out to our simulation&amp;#xD;domain boundary at around $2651$ Schwarzschild&amp;#xD;radius. The outflow attains a terminal velocity with a maximum&amp;#xD;value found to be $0.14c$ and the outflow rate depends on&amp;#xD;the angular momentum value of the accreting material.&amp;#xD;We also compute the self-Comptonized bremsstrahlung spectra for&amp;#xD;all the disk-jet runs.

During the preliminary design of flight vehicles, i.e., missiles or guided rockets, propulsion system performance serves as a critical determinant of both maximum range and terminal velocity. However, complex grain configurations in solid rocket motors (SRMs) typically require geometric modeling software to obtain burning surface area, which severely constrains efficiency. To address this challenge, this study presents a neural network-enhanced rapid performance prediction and matching optimization framework for solid rocket motors (NN-SRM). In NN-SRM, neural networks are employed to simulate the evolution of key parameters during grain combustion, including burning surface area, grain volume, and moment of inertia. The zero-dimensional internal ballistics equations coupled with one-dimensional steady isentropic flow relations are incorporated into the framework to rapidly obtain thrust curves. A discrete–continuous mixed differential evolution algorithm is further employed to identify the optimal grain configuration that satisfies specific thrust requirements. Results demonstrate that, as for cylindrical, star, and finocyl grains, the neural network achieves R2 exceeding 0.95. Finally, thrust matching optimization is conducted on three grains and achieves promising thrust solutions for the conditions of large thrust with short time and small thrust with long time, which demonstrates the effectiveness and practicality of the constructed NN-SRM.

Abstract. This study focuses on the reliability assessment of precipitation data calculated from drop size distribution (DSD) based on disdrometer data observations according to wet-bulb temperature (Tw). Three distinct quality control (QC) methods based on fall velocity were implemented and validated against measurements from tipping-buckets and weighing rain gauges collected from January 2020 to February 2024. The analysis indicated that all QC methods exhibited high reliability (correlation coefficient (CC)&gt;0.98) for rainfall conditions when Tw was above 5 °C, with a mean absolute percentage error (MAPE) of approximately 8.5 %. However, the precision of precipitation measurements exhibited a notable decline when Tw was below 2 °C, as indicated by a CC of less than 0.6 and MAPE exceeding 30 %. This reduction in accuracy can primarily be attributed to the outcomes of the QC methods, which rely on the falling velocity, given that raindrops and solid particles were observed within the specified Tw range. When considering the melting of snow particles at Tw ranging from 0 to 2 °C, the CC approached 0.9, suggesting enhanced measurement reliability. The findings of this study indicate that Tw is a more effective variable than air temperature (Tair) for differentiating the precipitation types. This conclusion arises from the observation that the fall velocity of hydrometeors does not reach the terminal velocity of raindrops, even within the Tair range of 1–5 °C, coupled with the broad distribution of fall velocities. The DSD shape demonstrated stability across multiple QC methods when Tw was equal to or greater than 2 °C. In contrast, considerable variations were observed at lower temperatures, where particles with diameters ranging from 1 to 2 mm exhibited irregular distribution patterns at temperatures below 1 °C. These results suggest that DSD parameters should be derived from disdrometer data obtained under conditions where Tw is above 2 °C to ensure the reliability of the findings. This study provides critical insights for improving precipitation measurement techniques and DSD analyses in regions with variable temperature conditions.

Using Atrial Cardiomyopathy Metrics to Characterize Atrial Fibrillation in Endurance Athletes.

It looks at how much movement there is of air coming from the back of a fast first car (Formula 1) and how this affects the speed of the second car going behind the first one. By incorporating the findings provided by CFD in combination with high-resolution telemetry of the 2023 F1 season, we evaluate the performance of varying distances followed for. and it's showing us really great and opposite impact whose results are absolutely negative. To a great degree, closing the gap (0.5 sec or less) brings about a considerable lap time penalty of 0.4 - 0.8 seconds, which is a strategic cost in a sport decided by tenths: The overall penalty results from a striking performance divide – straights give the wake some benefit, boosting terminal speed by 8-15km/h via drag reduction But however, this advantage is completely overshadowed by a huge extent in corners due to the loss of downforce, which causes drivers to travel slower by 8-15km/h in low-speed areas and make them to reduce braking point by 5 -10m. An extremely high level of aerodynamic disturbance that totally derails a car’s balance and stability and causes unpredictable understeer /overunder or increases tyre wear. Therefore despite the wake affording proximity on straights; the negative effects still limit the vehicles ability to corner and have control over the car. This means its fundamentally limiting the ability of the car to overtake as well. Therefore the study finds that the benefit is far less than the loss and that there is a central performance tradeoff that still challenges engineers and strategy experts today in modern Formula 1.

Abstract To address the challenges of lightweight requirements and the high cost and low efficiency of traditional experimental methods in the aerodynamic design of foldable micro-aircraft, this paper uses Comsol simulation software to study the terminal velocity characteristics of five foldable aerodynamic shapes: planar, V-shaped, inverted V-shaped, W-shaped, and M-shaped. A three-dimensional simulation model is established, and fluid flow, unidirectional flow, and laminar flow physical fields and steady-state studies are implemented to analyze the impact of different configurations and angle adjustments on terminal velocity. The mass-velocity ratio of each configuration is calculated to evaluate load capacity. Simulation results show that the planar configuration has the highest terminal velocity, and the closer the configuration is to a planar shape, the higher the terminal velocity is. The number of folds has a relatively small impact on terminal velocity. When adjusting the angle, the terminal velocity is optimal when the configuration is parallel to the wind speed field, and the more folds a configuration has, the less affected it is by the angle. The M-shaped and W-shaped configurations have the lowest mass-velocity ratios and the best overall efficiency. The research conclusions provide a theoretical basis for the selection of micro-aircraft configurations under different design requirements and offer technical support for the aerodynamic optimization design of foldable micro-aircraft.

Distribution patterns and corresponding dispersal outcomes of seeds following secondary wind dispersal

Spreading and entrainment characteristics of continuously released microplastic suspensions in water.

Distributional invariance and proportional scaling in axonal conduction.

Objective:This study evaluates risk factors influencing fall probability in the elderly based on the analysis of daily activity simulation characteristics on a Linear Static Platform. The findings aim to provide a reference for fall prevention and balance rehabilitation strategies in older adults. Methods:A total of 30 participants aged over 60years who met the inclusion and exclusion criteria were enrolled. Six gait balance tests simulating daily activities were administered using a Linear Static Platform. Subjects were divided into fall and non-fall groups, and regression analysis was used to predict fall risk intensity. Results:The walking test, the rapid turn while walking test, and the forward lunge squat test demonstrated higher accuracy in assessing fall risk. Increased step width（P=0.027, OR=1.99, 95%CI 1.08-3.66）, slower walking speed（P=0.020, OR=0.82, 95%CI 0.70-0.97）, increased endpoint sway velocity（P=0.031, OR=2.85, 95%CI 1.10-7.39）, and higher sway velocity during left and right turns（P=0.040, OR=1.16, 95%CI 1.01-1.30; P=0.037, OR=1.35, 95%CI 1.02-1.80） elevated left and right lunge impact index（P=0.010, OR=1.07, 95%CI 1.02-1.12; P=0.015, OR=1.05, 95%CI 1.01-1.09）were significantly associated with increased fall risk.. Conclusion:Among the six gait balance parameters reflecting daily activities in the elderly, step width, step length, walking speed, and terminal sway velocity may serve as effective indicators for assessing fall risk.

Modeling terminal velocity and aspect ratio of a single bubble in distorted-particle and cap bubble regimes for pool scrubbing simulation

Abstract Orbit transfer design is a key link in aerospace mission planning, and its accurate solution is of great significance for saving fuel and mission feasibility analysis. The Lambert problem, a classic problem in orbital mechanics, studies how to solve for the required initial and terminal velocity increments to pass through two given positions within a certain time. However, various transfer scenarios often need to be considered in practical missions, including the number of revolutions, transfer direction (short-path and long-path), and branch selection (left and right branches). Based on the classical Lambert algorithm, this paper proposes a comprehensive solving method that can automatically traverse and optimally select the number of revolutions, transfer direction, and branch to obtain the fuel-optimal transfer orbit. Through numerical simulation, we verify the effectiveness and robustness of this method in different transfer scenarios and compare it with methods from existing literature. The research results show that this method can efficiently and accurately solve multi-revolution orbit transfer problems, providing a reliable tool for orbit design in complex aerospace missions.

Rainfall simulators are typically categorised as either pressurised or drop-forming systems, each offering distinct advantages depending on the research application. This study presents a comparative experimental analysis of a pressurised nozzle-based rainfall simulator and a drop-forming needle-based rainfall simulator, assessing their suitability for urban stormwater management research. Both setups were constructed indoors with a 1.5 × 1.5 m rainfall area and a 2.3 m raindrop fall height. The simulators were evaluated based on rainfall intensity, spatial uniformity, drop size distribution and drop velocity. The pressurised system produced intensities from 23.9 to 109.7 mm/h, while the drop-forming system achieved 4.5-21.0 mm/h. Uniformity coefficients ranged from 81.2 to 93.3% (cups) and 86.6 to 96.4% (trays) for the pressurised system, and 85.7% (cups) and 94.8% (trays) for the drop-forming system. D50 raindrop sizes ranged from 0.8 to 1.2 mm for the pressurised system and 1.7 mm for the drop-forming system. Estimated median drop velocities ranged from 82.5 to 98.5% of terminal velocity. While both systems replicated key rainfall characteristics, the pressurised simulator was limited to high-intensity events. The drop-forming simulator offered finer control and broader applicability, supporting its use in urban hydrology and stormwater management research.