Search Results (418)

Aerosol-generating procedures (AGPs) expose healthcare personnel to airborne pathogens and require portable engineering controls that can be integrated into routine clinical workflows. We developed a portable, foldable negative-pressure aerosol-containment system (FNPACS) combining adaptive fan control, an H14 high-efficiency particulate air (HEPA) filter, and a disposable metal-oxide prefilter in a mobile filtration module. Bench performance was evaluated using pressure-flow testing in accordance with National Environmental Balancing Bureau (NEBB) procedures and International Organization for Standardization (ISO) 14644-3, polyalphaolefin aerosol challenge testing, and smoke visualization, while an exploratory clinical study assessed environmental contamination via real-time reverse-transcription PCR (rRT-PCR) in 11 patients (31 assay analyses). Bench testing demonstrated HEPA filtration efficiencies of 99.994–99.997%, stable negative-pressure generation across fan duty cycles, no detectable downstream breakthrough beyond the HEPA filter under the tested conditions, and effective inward airflow on smoke testing. A Lagrangian discrete phase model (DPM) particle-tracking simulation further characterized size-dependent aerosol-surrogate transport. Under HEPA-ON active-extraction conditions, 73.0–86.1% of simulated 0.3–10 µm water-equivalent particles were transported to the HEPA suction pathway, while 13.9–27.0% were deposited on internal wall surfaces. In the clinical evaluation, SARS-CoV-2 RNA detection on environmental swabs was limited and predominantly low level. The clearest reproducible signal occurred on the top interior surface under HEPA-OFF conditions, whereas HEPA-ON detections were isolated or presumptive high-Ct signals without reproducible confirmation. These findings provide preliminary engineering and usability support for FNPACS as a feasible near-source aerosol-control platform for AGPs. The patient swab component should be interpreted as an exploratory, proof-of-concept assessment rather than confirmatory evidence of clinical containment efficiency because several clinical cases had non-supportive patient-related controls and were therefore not used in the primary containment interpretation. Full article

The energy consumed by thermal management systems strongly affects the driving range of battery electric vehicles. In this study, we develop an integrated control strategy that couples the Sparrow Search Algorithm (SSA) with Nonlinear Model Predictive Control (NMPC) to simultaneously reduce energy consumption and satisfy cabin comfort and battery safety requirements. We construct a multiloop coupled, heat pump-based integrated thermal management model, including a compressor, heat exchangers, expansion valves, and an electro-thermal battery sub-model. Bench and vehicle-level tests confirm that the model predicts the refrigerant mass flow rate and heating capacity with mean relative errors of 4.76% and 4.30%, respectively. The SSA is used to tune the NMPC weighting parameters offline, minimizing the mean absolute errors of the cabin temperature, battery temperature, and total system energy consumption. The resulting SSA-NMPC strategy is evaluated under NEDC and CLTC-P driving cycles. Under the investigated NEDC-based high-load assessment with representative operating conditions, the proposed strategy limits the cabin temperature overshoot to 0.35 °C and battery temperature fluctuation to 0.26 °C, while achieving a 6.31% energy saving under high-speed cruising. The proposed framework focuses on cabin and battery thermal regulation and considers motor waste heat recovery. These results demonstrate that the SSA-NMPC approach can improve thermal management performance under the investigated operating conditions. Full article

This study presents the hydraulic characterization of a direct-acting pressure-reducing valve (PRV) using a combined experimental and numerical approach. An experimental test bench was implemented to measure inlet, control port, and outlet pressures over a flow rate range from 0 to 4.0 m³/h, under a constant inlet pressure of 8 bar and a set pressure of 3 bar. In parallel, a three-dimensional steady-state CFD model was developed using a sequential force balance analysis between hydraulic and spring restoring forces. The results show good agreement between numerical predictions and experimental data, with a maximum error below 10% in outlet pressure. The pressure drop exhibited a nonlinear increasing trend with flow rate, reaching values close to 1.8 bar at 4.0 m³/h. The flow coefficient K_v remained within a range of 2.2–3.0, while the pressure regulation coefficient S remained below 0.05, indicating stable regulation performance. Additional simulations at 25 bar provided improved agreement with manufacturer data, suggesting that catalog curves may be based on nominal pressure conditions. The proposed methodology demonstrates that steady-state CFD coupled with force balance analysis is an effective and computationally efficient approach for predicting the hydraulic behavior of direct-acting PRVs. Full article

The research investigates lubrication characteristics of a three-stage planetary transmission system under first and second gear conditions. A whole-system CFD model and a planetary carrier bearing CFD model are established. Oil distribution is simulated using a UDF dynamic mesh technique. A dedicated test bench is designed and built for a multi-stage planetary transmission system to measure oil flow data at the outlets of each planetary stage. By comparing the simulation and experimental results, the CFD model is confirmed. The oil distribution in the planetary transmission system is followed. In the first gear condition, the oil distribution within the second stage is significantly lower than that in the other two stages, and mainly converges onto the meshing surfaces of gears. In the second gear condition, the planetary carrier remained stationary, resulting in limited oil distribution in the first stage. Meanwhile, the third-stage planetary carrier bearings exhibit insufficient oil distribution across different gear conditions. To address this issue, several structural optimization structures for the numerical model of the third-stage planetary carrier bearings are compared in terms of theoretical oil supply rates and oil volume fraction distribution characteristics. Among these, constrained by the fixed positions between the oil inlet and oil holes, the structures with different numbers of oil holes in the planetary carrier lead to an oil flow rate reduction due to flow division and pressure loss induced by turbulence at high rotational speed, failing to meet the oil demand. Optimization of oil-hole diameter enlargement, the oil flow rate increases proportionally with the hole diameter. A diameter of 5 mm satisfies the theoretical oil flow rate demand, yet an asymmetric oil distribution is observed between the two inner bearings. Building upon the initial design with two oil holes, a 5 mm diameter design, a 1 mm axial leftward offset of the oil hole position, and a 20° oil-guiding inclination on the outer hub reduce the oil distribution asymmetry between the two inner bearings from 64.5% to 13%. The oil volume fraction increases from 0.005 to 0.069 in the inner bearing and from 0.001 to 0.013 in the outer bearing, resulting in a substantial improvement in overall bearing lubrication performance. Full article

PWM-based variable-rate spraying is an effective approach for improving pesticide application precision, but the coupling between nozzle actuation response, flow regulation, droplet size, and spray distribution under different operating parameters remains insufficiently clarified. This study aimed to evaluate the nozzle-level performance of a self-developed direct-acting PWM variable-rate nozzle and to identify suitable operating conditions for stable variable-rate spraying. An indoor integrated test bench was established to measure response time, PWM waveform retention, flow-rate characteristics, droplet-size distribution, and lateral spray distribution under pressures of 0.2–0.4 MPa, PWM frequencies of 5–30 Hz, and different duty cycles. The measured pull-in and release times were 8.00–9.50 ms and 12.00–13.00 ms, respectively, indicating rapid and stable actuation. The driving waveform was well retained, with an amplitude of 11.6–12.8 V and a measured frequency of 5.00–29.94 Hz. The flow rate increased monotonically with duty cycle, and the flow linearity ranged from 0.43% to 8.51%; better linearity was obtained at 5–25 Hz, whereas deterioration at 30 Hz was mainly associated with the shortened PWM period and increased switching-delay effect. The Dv50 ranged from 113.67 to 208.78 μm, and the relative span ranged from 1.173 to 1.323. The lateral distribution showed good symmetry, and the best uniformity was obtained at 20 Hz. Overall, the developed nozzle showed good potential for PWM variable-rate spraying and provides a reference for nozzle parameter matching and spray performance optimization. Full article

Multiple-fault events can initiate overload propagation and cascading outages, resulting in severe load loss and reduced system resilience. Therefore, beyond conventional protection concepts based on the (n − 1) criterion, there is also a need to address multiple-fault events to minimize loss of load. This paper presents an optimized overload tripping scheme to mitigate cascading outages in high-voltage grids under multiple-fault conditions, where selected line switches or circuit breakers are opened in a controlled manner to isolate limited grid sections, minimize interrupted load, and prevent further overload propagation. The method combines inverse definite minimum time relay modeling with a heuristic graph-search algorithm implemented in pandapower to identify feasible switching actions that minimize load loss while preventing overload propagation. The approach is demonstrated on SimBench high-voltage urban and mixed benchmark grids under double-line fault scenarios. In the urban grid, the proposed scheme reduces the maximum load loss from 34.0% to 2.4%, while in the mixed grid, the reduction is from 50.3% to 5.2%. A SAIFI-inspired resilience proxy is introduced to quantify the reduction in customer/load interruptions, showing a resilience improvement factor of about 3.6 for cascading scenarios. In addition, thermal inertia analysis indicates that corrective switching must be completed within approximately 5 min to remain within line-temperature limits. The analysis is based on quasi-steady-state power-flow and relay simulations; transient stability effects are outside the scope of this study. The results demonstrate that the optimized overload tripping scheme is a promising adaptive protection strategy for improving grid resilience under severe contingency conditions. Full article

In the context of increasing water scarcity, the new paradigm in efficient water management relies on the digitalisation of water infrastructure to optimise resource use. One of the key factors in addressing the new challenges facing urban water cycle companies is the shortage of qualified technical staff. This context highlights the new training needs of technical personnel required by companies in the urban water cycle sector due to the increasing digitalisation of tools and the new technological requirements of jobs which are not yet sufficiently reflected in the existing training offer. Companies express their dissatisfaction with how poorly existing training programs meet their current needs. Vocational training has a fundamental role to play in providing high-quality, technically up-to-date training that is aligned with the needs of water management companies. This mission involves the adoption of innovative teaching strategies and methods and the development of innovative teaching resources. This paper presents the design of a bench-scale plant specifically designed as a teaching resource at a Spanish vocational training centre that offers intermediate-level training in water networks and treatment plants and advanced-level training in water management. The plant, occupying a footprint of 4 × 5 m, simulates a drinking water distribution network, from the intake to the distribution network via a pumping station with two pumps (1 + 1) of 0.75 kW each that provide a flow range of 4–12 m³/h with a range of 22–10 m water column and a regulating reservoir of 1 m³ located above the water network. The plant is equipped with sensors that allow operational data to be monitored: pressures, flow rates, consumption and levels, enabling multiple operational scenarios to be simulated: leaks, sectorisation, pressure and flow management, etc. Its design has focused on facilitating the acquisition by students of the skills and learning outcomes required in the curricula of the different professional modules that make up the aforementioned studies, through learning based on multidisciplinary collaborative projects. Full article

Background: Endovascular aortic aneurysm repair (EVAR) is considered the gold standard for the treatment of abdominal aortic aneurysms. However, the performance of stent-grafts used during this procedure may be affected by their structural design, particularly in anatomically challenging, tortuous iliac arteries. This study aimed to evaluate the hemodynamic performance of different stent-graft limb designs in an in vitro EVAR simulation using compliant three-dimensional (3D)-printed iliac artery models with controlled angulations. Methods: Four commercially available stent-grafts (Anaconda^®, Endurant II^®, Treo^®, Zenith Spiral-Z^®) representing different stent-strut configurations (including O-ring, Z-stent, and spiral designs) were deployed in compliant 3D-printed vascular phantoms simulating severe iliac angulations of 75°, 90°, and 105°. The models were incorporated into a pulsatile flow circuit, and pressure and flow velocity were measured proximally and distally to the angulated segment. Results: Across all tested angulations, the O-ring-based design demonstrated the most favorable hemodynamic performance. In particular, the Anaconda stent-graft showed the smallest pressure loss and the lowest increase in distal flow velocity, especially in the 90° and 105° models. These findings suggest that O-ring-supported structures provide greater flexibility and conformability in severely angulated iliac segments. Conclusions: In this controlled in vitro setting, stent-grafts with O-ring strut morphology better preserved flow conditions than other tested configurations in tortuous anatomy. These results suggest that stent-graft structural design may influence device behavior in challenging iliac anatomy under controlled in vitro conditions. These findings should be considered hypothesis-generating bench data and do not represent direct evidence for clinical device selection. Full article

Bridging the gap between theoretical heat exchanger analysis and physical intuition remains a persistent challenge in engineering education, particularly when students are confronted with real-system effects such as pressure losses, measurement uncertainty, and deviations from simplified models. This work addresses this challenge through the coupled development of a pedagogical framework and an experimental platform. A modular heat exchanger test bench was conceived, designed, and constructed by graduate students within a structured project-based learning environment, in which competitive and cooperative phases were combined to emulate real engineering practice. This approach positions the test bench not only as a laboratory tool, but as the outcome of an active learning process that integrates system design, instrumentation, and modeling. The resulting platform enables the comparative study of multiple heat exchanger technologies—including three water-to-water heat exchangers (plate, shell-and-tube, and double-pipe) and one air-to-water fin-and-tube heat exchanger—under parallel, counterflow, and crossflow arrangements across a wide range of operating conditions. Comprehensive instrumentation (temperature, flow rate, and pressure measurements) supports rigorous energy balance analysis, effectiveness evaluation, and hydraulic performance assessment. Beyond undergraduate experimentation, the test bench provides a framework for advanced learning objectives, including uncertainty propagation, $\epsilon$-NTU analysis, model development, and experimental validation. The confrontation between model predictions and experimental data, including observed discrepancies, is shown to play a central role in developing critical engineering judgment. The proposed approach demonstrates how the integration of project-based learning with a reconfigurable experimental platform can create a sustainable and scalable environment for heat transfer education. Full article

Continuous monitoring of impurity content and breakage rate in combine harvester grain flow remains challenging because representative samples are difficult to acquire online, and the visual targets are small, dense, and imbalanced. In this study, a prototype monitoring system integrating sample collection, controlled conveying, image acquisition, and embedded processing was developed for online grain-quality sensing during harvesting. To satisfy the requirement for sidewall sampling from the vertical grain conveying auger, centrifugal sampling and screw conveying were used to extract and transport grain-flow samples, and a stable imaging environment was established using an industrial camera and dedicated illumination. Pixel-area-to-mass mapping models were established for broken grains and impurity targets, with coefficients of determination higher than 0.93. In addition, a lightweight improved YOLOv8-Seg model was developed to recognize and segment broken grains and impurity targets under dense small-target conditions. Bench-scale validation showed that the relative error of impurity content ranged from 1.02% to 13.04%, with an average of 6.09%, while the absolute error of breakage rate ranged from 0.01 to 0.02 percentage points. These results demonstrate the feasibility of the proposed method for online estimation of impurity content and breakage rate under bench-scale conditions and provide a basis for future machine integration and field validation. Full article

Closed-circuit axial piston pumps in the travel hydraulic systems of heavy-duty engineering vehicles are highly vulnerable to severe transient cavitation during emergency braking. Rapid pressure reversal at the interface between the cylinder bore and the valve plate causes volumetric efficiency loss, intensified pressure pulsation, and erosion damage; however, the coupled mechanism by which throttling, vortex formation, and cavitation interact in this region, together with its structural regulation pathway, remains insufficiently understood. To address this gap, a closed-circuit axial piston pump for cotton pickers was investigated under emergency braking as a representative extreme loading scenario. A full-passage transient CFD model was established and validated against steady-state volumetric efficiency tests on a heavy-load test bench, as well as against PIV internal flow visualization on a Reynolds-scaled transparent model. Parametric transient CFD sweeps were then performed, and a multi-objective optimization model was developed and solved using a Kriging-assisted NSGA-II algorithm with entropy-weighted TOPSIS decision-making. The results identify the interface between the cylinder bore and the valve plate as the primary cavitation zone, with cavitation driven by local throttling and wall-attached vortices rather than by global low pressure. The optimized cylinder bore configuration reduces the peak gas volume fraction by 34.7% in the total flow domain and by 15.7% in the valve plate region, while maintaining volumetric efficiency above 97.8%; the port plate pressure pulsation increases by 12.97%. The key takeaway is that targeted optimization of the cylinder bore alone, without altering the overall valve plate or piston block architecture, can effectively suppress transient cavitation, while revealing an inherent trade-off with pressure pulsation control. In conclusion, this work clarifies the cavitation mechanism, provides a validated numerical and experimental framework, and offers an implementable design pathway for transient cavitation control of closed-circuit piston pumps under extreme loading conditions. Full article

As software systems continue to grow in scale and complexity, fuzzing has become an indispensable automated technique for vulnerability discovery. Compared with coverage-guided fuzzing, directed greybox fuzzing (DGF) focuses execution toward specific basic blocks or functions, making it widely used in scenarios such as patch testing and vulnerability reproduction. Recent studies have combined fuzzing with symbolic execution (SE) to generate inputs that are difficult to obtain through mutation alone. However, applying SE to all branch conditions along an execution path may explore many paths unrelated to the target, leading to substantial overhead in directed fuzzing. Meanwhile, existing distance metrics still have limitations in guiding seeds toward targets: AFLGo relies on structural control-flow distances, which may not precisely reflect target reachability, while existing probability-based metrics often simplify complex control-flow structures such as loops and back-edges. To address these limitations, we propose TriFuzz, a probabilistic distance-guided hybrid directed fuzzing framework that integrates a loop-aware reachability distance model, target-related selective symbolic instrumentation, and a tightly coupled AFLGo–SymCC coordination mechanism. TriFuzz uses the probability-based distance model as the primary guidance signal and applies selective symbolic instrumentation to prune irrelevant basic blocks and concentrate exploration on target-relevant code regions. Our evaluation on the AFLGo testsuite and UniBench shows that TriFuzz improves both time-to-target and time-to-exposure on most evaluated benchmarks, demonstrating the effectiveness of combining fine-grained probabilistic distance guidance with selective symbolic reasoning and tightly integrated hybrid execution. Full article

Subsurface contamination at low-permeability petrochemical sites necessitates long-term multi-phase extraction (MPE), yet operational sustainability is frequently compromised by well-bore clogging. This study develops a “prevent–identify–remediate” strategy through integrated laboratory and field-based investigations. Laboratory bench tests identified a critical packing density threshold of 70%, above which permeability loss escalates rapidly. Furthermore, rounded quartz sand maintained a significantly higher permeability ratio (0.4) compared to irregular zeolite (0.1). These findings were validated through a longitudinal two-year field pilot study in a silty-clay formation. Innovative large-diameter wells (200 mm) utilising optimised quartz sand showed high resilience, with only a 20% reduction in discharge capacity over 24 months. In contrast, conventional wells using local yellow sand exhibited severe physical clogging, resulting in a 57% decrease in stable flow. The study also characterised a diameter effect, where small-diameter wells (63 mm) proved inherently more vulnerable to rapid performance degradation regardless of filter media. To address existing impairment, high-pressure water jetting and dilute hydrochloric acid washing restored flow capacity by 50% and 40%, respectively. By coupling mechanistic insights with field evidence, this research provides a comprehensive platform for the sustainable design and maintenance of subsurface remediation infrastructure, ensuring long-term operational efficiency and reduced resource consumption. Full article

To determine the optimal operating parameters of the single-longitudinal-axial-flow threshing device for wheat harvesters under high feed rate conditions and lay a theoretical and methodological foundation for the subsequent development of a specialist system for threshing device parameter optimization, this study constructed a discrete element model (DEM) of wheat plants at harvest stage in EDEM software based on the Hertz–Mindlin with bonding contact model, combined with the discrete element parameters of wheat plants calibrated by a texturometer. Simulation experiments were designed and conducted to optimize the operating parameters of the threshing device, and a methodology that employs simulation experiments to obtain optimal parameter combinations under different operating environments was proposed, which was applied to the development of a specialist system for threshing device parameter optimization. Taking cylinder speed, cylinder inclination and threshing gap as experimental factors, and unthreshed rate, separation loss rate and breakage rate as evaluation indexes, single-factor and Box–Behnken simulation experiments were carried out. Mathematical models were established to reveal the correlation between evaluation indexes and influencing parameters, and then the optimal parameter combination was solved. The results showed that the threshing device achieved the optimal comprehensive operating performance at a cylinder speed of 850 r/min, a cylinder inclination of 6° and a threshing gap of 20 mm, with an unthreshed rate of 1.575%, a separation loss rate of 0.158% and a breakage rate of 0.509%. Bench validation tests indicated that the relative errors between simulated and measured indexes were all less than 5%, verifying the reliability of the established DEM. Compared with bench tests, the simulation experiment method in this study ensured high accuracy while significantly reducing the time and labor costs of tests. The obtained optimal operating parameters and the proposed simulation optimization methodology provide core data support and technical reference for the development of a specialist system for parameter optimization of the threshing device of wheat harvesters. Full article

Aircraft emergency hydraulic pumps are safety-critical units whose intermittent operation complicates condition assessment and reduces the diagnostic value of conventional bulk physicochemical oil properties. This study evaluates the applicability of tribotechnical oil analysis for monitoring degradation of the NP-27T emergency hydraulic pump under controlled bench conditions. Four NP-27T units were tested on a dedicated hydraulic bench, and oil samples were collected at defined intervals during operation and after test completion. The diagnostic methodology combined elemental spectrometry (ICP-OES), particle counting interpreted with reference to ISO 4406, and analytical ferrography. The results showed that flow performance deterioration was accompanied by measurable changes in oil-borne wear indicators, although the sensitivity of the individual diagnostic channels varied among the tested units. In several cases, the coarse particle fraction (>15 μm) exhibited the clearest response to degradation, while Fe and Cu concentrations provided useful but not uniformly monotonic trends across all pumps. Using a pragmatic early warning criterion based on the first exceedance of 100 particles/mL in the >15 μm fraction, the coarse particle signal provided lead times of approximately 13–345 min before the flow-based rejection limit was reached in the four tested units. Ferrographic analysis identified cutting and fatigue debris, together with larger wear particles, in units approaching or reaching the flow-based rejection limit. Overall, the findings demonstrate that the combined use of elemental analysis, particle counting, and ferrography provides a practical multi-indicator framework for relating oil-diagnostic signals to functional degradation of the NP-27T hydrogenerator. Under the present bench conditions, flow proved to be a more sensitive degradation indicator than pressure. The proposed approach therefore represents a useful complementary tool for maintenance decision-making and for integration with vibration-based condition monitoring of aircraft hydraulic systems. Full article