Search Results (6,795)

Conventional air stripping for ammonia–nitrogen wastewater is often hampered by packing clogging and low mass transfer efficiency. To address these limitations, this study proposes a jet impact negative pressure reactor (JI-NPR) featuring an optimized scatter-pattern (D7) multi-orifice configuration. Computational Fluid Dynamics (CFD) simulations were employed to systematically investigate the effects of Reynolds number (Re = 5503.4~9651.0, corresponding to 2.76~4.84 m/s) on the hydrodynamic characteristics and deamination performance. Results indicate that increasing jet velocity significantly enhances the water volume fraction, resultant velocity, and pressure core intensity within the impact zone. Notably, these enhancements are maximized at the second row (z = 146 mm), attributed to reduced interference from the negative-pressure flash evaporation region. While a higher Re promotes interfacial renewal and vortex evolution, thereby enhancing mass transfer, it also intensifies energy dissipation and reduces the uniformity of the turbulent kinetic energy distribution. This work elucidates a critical trade-off between mass transfer enhancement and energy consumption, establishing a quantitative structure: the Re–flow field-performance relationship. The findings provide a theoretical foundation for the design and optimization of energy-efficient, high-performance wastewater treatment systems. Full article

Stable circulation and limited mechanical loading are key requirements in the fluidized-bed coating of small vegetable seeds. For Chinese cabbage seeds, their small mass, irregular geometry, and mechanical sensitivity make it difficult to evaluate operating conditions using only global indicators, such as mean particle velocity and bed expansion height. In this study, a two-way coupled computational fluid dynamics–discrete element method (CFD-DEM) model was developed for a draft-tube fluidized-bed seed coater. Chinese cabbage seeds were represented by seven-sphere clumps, and an L9(3³) orthogonal array was used as a screening design to examine inlet air velocity, initial bed height, and bottom circulation inlet gap. The evaluation combined cycle time distribution (CTD), the global low-speed particle fraction R_s, the 95th-percentile normal contact force F_95,n, and the normalized high-percentile contact-load ratio η_c,95. Because the L9 array cannot resolve interactions or support a full quadratic model, factor effects were interpreted descriptively within the investigated range rather than as a confirmatory global optimization. Initial bed height produced the largest descriptive contribution to the circulation period, R_s, and F_95,n. Increasing inlet air velocity shortened the circulation period and reduced Rs but increased high-percentile contact loading. Across the nine cases, F_95,n ranged from 7.50 to 14.50 mN and η_c,95 from 0.18% to 0.35%; η_c,95 is used only as a normalized load ratio and not as a validated probability of seed damage. Case 4 ranked first under equal weighting and contact-load-priority weighting, whereas Case 7 ranked first under circulation-priority weighting. Case 4 is therefore described as a weight-dependent balanced candidate within the tested parameter range. Prototype experiments reproduced the ordering of circulation periods for three dry operating conditions, supporting qualitative consistency between simulated and observed circulation behavior. Visible breakage remained below 0.5%, but this observation provides only preliminary qualitative correspondence with the simulated contact-load trend. The proposed framework is intended for dry-stage screening and does not directly predict wet-coating quality, adhesion, agglomeration, or germination performance. Full article

The primary cause of the scale effect in scaled models for flood discharge and energy dissipation lies in the dissimilarity of the air dispersion patterns of the ski-jump nappe. To uncover the scale-effect relationship governing the air dispersion patterns of ski-jump energy dissipation nappes in high dams, a series of scaled physical model tests were conducted at the Baihetan Hydropower Station. The air dispersion patterns were systematically observed, as well as the distribution characteristics of entrained air concentration in the ski-jump nappe across various scales. Based on the experimental observations, a two-dimensional stochastic diffusion numerical model was developed, successfully replicating the dispersion process of the nappe as it gradually transformed from a crescent shape to a circular one. Furthermore, by calibrating the concentration distribution curve, a quantitative relationship was established between the random displacement parameter σ and the Weber number. The study revealed that when the Weber number (We) is below 40,000, σ increases rapidly and approximately linearly with We, indicating a high sensitivity to dispersion degree. However, once We surpasses 40,000, the growth rate significantly decelerates, approaching saturation, suggesting that the dispersion degree closely approximates the prototype condition. Consequently, it is suggested that the Weber number control threshold for the physical model of ski-jump water–air two-phase flow in high dams be set above 40,000, providing a valuable reference for selecting large-scale models. Full article

Circular water distribution wells with an asymmetric inlet and outlet arrangement are susceptible to air-entraining vortices, which may threaten hydraulic structures and related equipment. To clarify vortex transitions and critical conditions under the combined effects of relative submergence S/D and outlet Froude number Fr, physical model experiments and numerical simulations were conducted. The experiments covered S/D values from 2.0 to 5.0 and Fr values from 1.03 to 2.06, while the simulations reproduced ten hydraulic measurement cases. Vortex morphology, air-entrainment intermittency, and hydraulic characteristics were examined. By combining quantitative experiment–simulation validation at multiple elevations with a systematic S/D–Fr regime analysis, the vortex transitions under the asymmetric layout were further characterized. Increasing S/D progressively weakens the vortex, causing a transition from a penetrating air-entraining vortex through intermittent air entrainment to a non-air-entraining surface vortex. Increasing Fr raises the air-entrainment intermittency and promotes the downward penetration of the air core. The critical relative submergence S_c/D increases linearly with Fr, and the fitted relation has a coefficient of determination of 0.9826. The resulting critical values are generally higher than those predicted by commonly used empirical relations, which may be associated with the asymmetric arrangement and the resulting persistent background circulation. The resulting critical relation and vortex regime map provide a quantitative basis for operating-water-level assessment and vortex-risk evaluation of circular water distribution wells with similar asymmetric layouts and within comparable hydraulic conditions. Full article

Accurate remaining useful life (RUL) prediction of air circuit breakers (ACBs) is crucial for condition-based maintenance. However, existing data-driven prognostic methods suffer from electromechanical feature fragmentation, cross-device domain shifts, and the inability to penalize safety-critical late predictions. This study proposes an explainable RUL prediction framework via physics-informed feature fusion. Through full-lifecycle monitoring, novel indicators, including the electromechanical coupled degradation index (EMCDI) and the contact spring over-travel consumption rate (CSOCR), are introduced to decode interactive degradation cycles. To eliminate the interferences of initial manufacturing tolerances, a phase-decoupled normalization strategy empowers a random forest (RF) model to achieve cross-device transferability in a two-device proof-of-concept experiment, requiring only 50 initial operations for target calibration. Additionally, a safety-oriented asymmetric penalty score (APS) is integrated into the evaluation framework to explicitly penalize hazardous life overestimations. Experimental results demonstrate a full-lifecycle R² of 0.9936 and a mean absolute error (MAE) of 38.5136. While the early-stage R² of 0.6880 objectively reflects the statistical flatness of the equipment’s healthy plateau, the framework maintains robust tracking capabilities across the entire lifespan, surpassing mainstream deep learning algorithms such as CNN, MLP, and LSTM. The proposed method consistently achieves a conservative, risk-averse predictive distribution for industrial reliability. Finally, model-level permutation importance analysis confirms that the RF model prioritizes physics-informed indicators rather than relying on spurious curve fitting. Full article

To promote carbon reduction in existing coal-fired power units while ensuring stable operation, ammonia–coal co-firing has attracted increasing attention as a promising low-carbon combustion technology. This study developed a three-dimensional numerical model for a single swirl-stabilized pulverized-coal burner to investigate ammonia–coal co-firing under a constant total fuel heating input. The model was validated against reference measurements, with relative deviations of 2.97% for nitrogen oxide concentration and 2.92% for burnout rate. The effects of ammonia co-firing on flame characteristics, combustion performance, and species distribution were then evaluated. As the ammonia blending ratio increased from 0% to 20%, the peak furnace temperature decreased from 1597.35 to 1389.82 K, while the high-temperature region contracted. At the centerline end, the carbon dioxide molar fraction decreased from 16.46% to 12.03%, corresponding to a 26.9% reduction. Nitrogen oxide concentrations were lower near the burner but increased downstream after secondary-air mixing; the highest downstream concentration was 544.86 mg/Nm³ under a 15% ammonia blending condition. The present study clarifies how co-firing of ammonia with pulverized coal affects in-furnace temperature and combustion-species distributions in a swirl pulverized-coal burner, providing an engineering basis for low-carbon retrofits of existing coal-fired power units. Full article

Multi-rotor unmanned aircraft systems (UAS) are now pervasive, yet quantitative evidence on how and why they fail remains fragmented across heterogeneous national reporting systems. This study analyses 319 multi-rotor UAS occurrences (2016–2022) coded from three official sources: the U.S. SAFECOM system (122), the Australian Transport Safety Bureau database (159) and the U.K. Air Accidents Investigation Branch reports (38). Each occurrence was assigned a primary causal factor from a twelve-factor taxonomy and a flight phase (take-off, en route, landing). Analyses comprised distributional estimation with Wilson confidence intervals, chi-squared association tests with permutation p-values for sparse tables, Cochran–Armitage trend tests, and correspondence analysis. Human factors (23.2%, 95% CI 18.9–28.1) and data-link problems (21.0%, CI 16.9–25.8) dominated, and 74.6% of occurrences arose en route—a phase profile opposite to that of manned aviation. Cause and phase were significantly associated (permutation p < 0.001, Cramér’s V = 0.305): all take-off occurrences were technological, none human-related, and battery failures clustered in landing (42%). Causal profiles differed markedly between reporting systems (p < 0.0001, V = 0.338), cautioning against naive pooling, and data-link problems nearly tripled from 11.9% (2016–17) to 32.9% (2021–22). Findings inform operator training, link redundancy, battery management and reporting standardisation. Full article

This study presents SenseMat, a modular sensing infrastructure based on recycled end-of-life tire (ELT)-derived rubber flooring that integrates continuous body-weight (BW) estimation, environmental monitoring and Internet-of-Things (IoT) connectivity into a single structural livestock infrastructure. Designed as a modular engineering platform, SenseMat provides a structural framework that can be extended with additional sensing modules and adapted to different monitoring applications requiring resilient flooring and distributed sensing. The technical feasibility of the weighing module was evaluated through a 51-day proof-of-concept study conducted under commercial buffalo farming conditions, involving two buffalo calves and generating 4872 BW measurements acquired at 30 min intervals. Following a dedicated preprocessing workflow, continuous BW estimates showed good consistency with weekly reference measurements obtained using a professional livestock scale (R² = 0.975 and 0.948), with mean relative errors of 0.88% and 1.03% and root mean square errors of 2.15 and 3.09 kg for the two animals, respectively. Simultaneously, the integrated environmental module continuously monitored air temperature and relative humidity, suggesting the capability of the platform to provide synchronized environmental information alongside continuous BW acquisition within a unified monitoring framework. These findings demonstrate the technical feasibility of integrating sensing, environmental monitoring and IoT connectivity into recycled ELT-derived livestock flooring, supporting its development as a modular smart platform for continuous monitoring in precision livestock farming. Future validation under larger-scale commercial conditions will further assess its scalability and broader applicability. Full article

Under-race lubrication is an effective oil supply method for high-speed angular contact ball bearings, but the relationship between internal oil–air two-phase flow distribution and end oil return behavior remains insufficiently understood. In this study, a Volume of Fluid (VOF)-based oil–air two-phase flow model was developed for an under-race lubricated angular contact ball bearing and validated experimentally. The effects of oil flow rate, rotational speed, inlet-hole axial position, diameter, and number were investigated. The maximum relative error between the numerical and experimental oil return ratios was 3.17%. At 3000 rpm, increasing the oil flow rate from 65 to 140 L/h increased the average oil volume fraction on the rolling element surfaces from approximately 0.037 to 0.089. In contrast, increasing rotational speed reduced oil retention on bearing component surfaces and the oil return ratio at the large-clearance end. At 140 L/h, the oil return ratio decreased from approximately 97% at 3000 rpm to 86.5% at 6000 rpm. Shifting the inlet holes toward the small-clearance end enhanced cage wetting but reduced oil retention on the rolling elements and large-clearance-end oil return. Within the investigated range, a mid-plane inlet position, smaller inlet-hole diameter, and larger number of inlet holes were more favorable for oil delivery to the rolling elements while maintaining a relatively high oil return ratio. Full article

γ-TiAl-based alloys are promising lightweight materials for high-temperature applications, but their insufficient oxidation resistance near 800 °C remains a major limitation. This study aims to clarify the short-term oxidation behavior and associated scale/interface evolution of an as-cast Ti-44Al-4Nb-1.5Cr-0.5Mo-0.1B (at.%) alloy. This composition was selected because the Nb, Cr, and Mo containing TiAl system enables alloying-element redistribution to be examined together with oxide-scale evolution. Isothermal oxidation was conducted in static air at 800 °C for 1–48 h, followed by oxidation-kinetics measurements and multiscale characterization. The mass gain increased continuously with a kinetic exponent of n = 1.77, indicating deviation from ideal parabolic behavior. After 48 h, a porous and chemically heterogeneous multilayered scale formed, comprising a TiO₂-dominated outer region, locally distributed Al-rich oxides, and nitride-containing interfacial regions. TiN and Ti₂AlN were identified together with pronounced interfacial N enrichment and localized Nb/Cr enrichment. The results indicate that a continuous compact Al-rich protective layer was not established during short-term oxidation, highlighting the importance of scale continuity and compactness in limiting oxidation of TiAl alloys near 800 °C. Full article

The oxygen reduction reaction (ORR) remains a major bottleneck in terms of kinetics and durability in fuel cells and zinc–air batteries (ZABs). Metal–organic frameworks (MOFs) are versatile precursors for platinum-group metal (PGM)-free ORR electrocatalysts because their metal distribution, ligand chemistry, guest confinement, morphology, and porosity can be controlled before pyrolysis. This review examines how these precursor characteristics and subsequent thermal conversion govern metal migration; heteroatom retention; carbon ordering; pore evolution; and, ultimately, the nuclearity, coordination environment, and accessibility of the resulting active sites. Recent advances in conventional and asymmetric M–N_x single-atom sites, dual- and multi-atom sites, and single-atom–cluster or nanophase interfaces are critically evaluated, with particular attention to the evidence supporting structural assignments, activity, selectivity, and durability. Half-cell performance is further related to practical fuel-cell and ZAB operation by considering catalyst loading, ionomer or electrolyte contact, gas and water transport, and catalyst-layer degradation. Further progress will require simultaneous optimization of active-site structure, accessible-site density, hierarchical porosity, carbon stability, and electrode architecture, together with standardized testing protocols for reliable translation from rotating disk electrode measurements to working cathodes. Full article

This paper presents the application of a novel methodology to build a comprehensive Measurement-Informed Inventory (MII) by integrating unreported emissions into government inventories. These emissions are often excluded from current regulatory requirements or associated with upset conditions, and are identified through aerial surveys and confirmed by oil and gas (O&G) operators. This methodology utilizes the Mechanistic Air Emissions Simulator (MAES) tool to generate spatially and temporally resolved emission estimates for O&G sites, using annual inventory data submitted to the Greenhouse Gas Reporting Program (GHGRP) and quarterly aerial surveys conducted in 2023 by Bridger Photonics at partner-operated sites in the Appalachian Basin. The analysis is part of the Appalachian Methane Initiative (AMI) coalition efforts to improve methane emissions characterization and mitigation efforts in the Appalachian Basin. On average, results show that emissions from the MII models are 58.9% higher than the emissions reported to the GHGRP for reporting year 2022 (submitted in 2023) for these facilities, which was the most recent inventory available at the time of the 2023 surveys, when the reported total is restricted to normal operation. Measured against the total reported inventory, which includes 479.2 mt/year of operator-reported fugitive emissions, the increase is 40.0%. Site-level methane emission rates exceeding 15 kg/h are estimated to account for 94.9% of total emissions across all midstream sites, while rates above the 95th percentile of the site-level distribution (105 kg/h) contribute 33.4%, highlighting the disproportionate influence of large emitters. These results are based on 19 partner-operated facilities from two operators and are not a representative sample of the Appalachian midstream sector. The simulated average loss rate for the participating companies under analysis was 6.45 × 10⁻⁴, lower than the loss rate values reported in the literature for this sector, which span different supply chain scopes. The principal contribution of this work is methodological: it shows how aerial observations, operator-provided information, and a stochastic facility model can be combined to account for the tail end of the emissions distribution that is often absent from conventional bottom-up (BU) estimates, and it indicates that aerial campaigns optimized to detect events from upset conditions can support more accurate MIIs. Full article

This study employs a multi-method, high-precision research approach to evaluate the thermal comfort performance of a window-based direct evaporative cooling (DEC) air conditioning system installed in a university dormitory building (50 rooms) in Beijing. To compensate for the insufficiency of single-day test data, the study was conducted continuously for 30 days from 1 June to 30 June 2026 (00:00–23:59 daily). Eight calibrated sensor sets were deployed in each of the 50 rooms (that is, eight fixed sensor sets per room × 50 rooms = 400 synchronously logged spatial measurement points, each integrating a fixed SHT35 temperature/humidity sensor with a matched hot-wire anemometer probe; this unusually dense, building-scale simultaneous deployment is uncommon in previous dormitory studies), recording data simultaneously across all rooms throughout the test period with the DEC units continuously operating. The research integrates field physical measurement data, standardized subjective questionnaire surveys (200 within-person paired questionnaires, each pairing a student’s retrospective recall of the pre-DEC condition with an in situ vote collected during DEC operation), and advanced computational thermophysiological modeling results based on the frameworks of ISO 7730–2021 and ASHRAE Standard 55–2023. Environmental parameters, including dry-bulb temperature (Ta), relative humidity (RH), and air velocity (Va), were monitored at eight spatially distributed points per room with a 10 Hz sampling frequency and a one-hour median resolution. The mean radiant temperature (Tr) was approximated as equal to Ta due to the absence of globe temperature measurements, and this simplification is discussed as a limitation. Simultaneously, through a single-session questionnaire (June 24–30) compliant with ISO 10551 and the Appendix B requirements of ANSI/ASHRAE Standard 55, which paired each respondent’s retrospective recall of the early-June pre-DEC (non-cooled) condition with a concurrent vote collected during DEC operation—a recalled-pre/concurrent-post design rather than two separate real-time pre-/post-intervention surveys—data on clothing ensembles, activity levels, and subjective thermal sensation votes (TSV) were collected. The acquired data were input into a customized simulation platform developed in the Fortran language (which was debugged and cross-validated against the ISO 7730/ASHRAE Standard 55 reference implementation to within 0.01 PMV scale units), which employs the Fanger two-node thermoregulation model to accurately calculate and predict the predicted mean vote (PMV), predicted percentage of dissatisfied (PPD) occupants, new effective temperature (ET*), and standard effective temperature (SET*). The results indicate that the DEC unit achieved a stable outlet temperature reduction of Δt = 3.87 °C (inlet temperature 31.72 °C, outlet temperature 27.85 °C), with an average wet-bulb air temperature of 18.66 °C and an average outlet relative humidity of 58.3% (inlet RH: 42.1%), confirming the expected humidifying effect of direct evaporative cooling while maintaining an average indoor relative humidity of 42.07%—a result particularly relevant to Beijing’s dry-to-semi-humid summer environment, where evaporative cooling is thermodynamically favorable. Because no DEC-off baseline period was monitored, the measured indoor conditions are reported as observational associations with DEC operation rather than as effects attributable exclusively to the unit; the pre-DEC satisfaction level was recalled retrospectively within the same single session and is therefore subject to recall/contrast bias; and all energy-saving figures are theoretical nameplate estimates rather than metered energy consumption. Full article

This paper presents a wideband circularly polarized (CP) stacked patch antenna for 5G Sub-6 GHz applications. A major challenge in wideband dual-feed antennas is the fabrication limit caused by standard chemical etching and mechanical milling processes for extremely narrow high-impedance microstrip lines in two-stage branch-line couplers. To overcome this bottleneck, a Defected Ground Structure (DGS) is utilized. By etching the ground plane, the distributed inductance is increased, allowing the highly sensitive narrow traces to be physically widened while strictly maintaining the 50 Ω impedance. The antenna features an aperture-coupled mechanism via an H-shaped slot to excite the driven and parasitic patches, which are separated by an air gap to maximize bandwidth. The fabricated prototype demonstrates an impedance bandwidth (|S₁₁| < −10 dB) of 41.6% (2.92–4.37 GHz) and a simulated 3 dB axial ratio bandwidth of 23.14% (3.26–4.07 GHz) with a peak realized gain of 7.54 dBi. Excellent agreement between simulated and measured results validates the robustness of the proposed DGS technique against fabrication tolerances. Full article

In the complex problem of air-to-ground mission planning, multi-UAV systems face significant challenges such as system complexity and heterogeneity, insufficient target observability, and difficulties in collaborating information sharing. To address these issues, this paper proposes a novel learnable sparse attention graph architecture (SAGA). This architecture deeply integrates graph reasoning and policy optimization within the MAPPO framework and includes three innovative mechanisms: (i) a GATv2-based graph neural network encoder that performs multi-round distributed consensus on the communication graph among UAVs via a multi-head attention mechanism, enabling selective aggregation of tactical information; (ii) an edge predictor that learns to prune low-value communication links, generating a sparse and mission-adaptive communication topology; and (iii) an L1 sparsity penalty term that further enhances communication efficiency. In a self-developed simulation environment for heterogeneous multi-UAV mission planning, comprehensive comparative experiments were conducted against the following baseline reinforcement learning algorithms: MADDPG, MATD3, QMIX, MAPPO, TarMAC, DGN, and G2ANet. The experimental results show that SAGA achieves reward values of 390 and 1100 in small-scale and large-scale scenarios, and outperforms the best-performing baseline algorithm by more than 20% across all operational performance metrics. Generalization experiments validate the model’s robust transfer capability under unknown defense deployment modes. Ablation experiments further confirmed the individual contributions of the three components. This study provides an innovative and effective method for mission planning of heterogeneous multi-UAV systems in partially observable adversarial environments. Full article