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• A novel side-aerated reactor for in-situ H 2 O 2 electrosynthesis was designed. • Side-aerated reactor coupled with a composite cathode greatly improved H 2 O 2 production. • Different aeration system and cathodes were evaluated for comparison. • Key factors for in-situ H 2 O 2 electrosynthesis were determined. The active graphite felt (GF) catalytic layer was effectively synthesized through a wet ultrasonic impregnation-calcination method, modified with CB and PTFE, and implemented in a pioneering side-aeration electrochemical in-situ H 2 O 2 reactor. The optimal mass ratio (CB: PTFE 1:4) for the modified cathode catalytic layer was determined using a single-factor method. Operating under optimum conditions of initial pH 5, 0.5 L/min air flow, and a current density of 9 mA/cm2, the system achieved a remarkable maximum H 2 O 2 accumulation of 560 mg/L, with the H 2 O 2 production capacity consistently exceeding 95 % over 6 usage cycles. The refined mesoporous structure and improved three-phase interface notably amplified oxygen transfer, utilization, and H 2 O 2 yield. Side aeration led to an oxygen concentration near the cathode reaching 20 mg/L, representing a five-fold increase compared to the 3.95 mg/L achieved with conventional bottom aeration. In the final application, the reaction system exhibited efficacy in the degradation of landfill leachate concentrate. After a 60-minute reaction, complete removal of chroma was attained, and the TOC degradation rate surpassed 60 %, marking a sixfold improvement over the conventional system. These results underscore the substantial potential of the system in H 2 O 2 synthesis and environmental remediation. [ABSTRACT FROM AUTHOR]

A number of bolt-microtubular anode supports (BMASs) are manufactured by winding the corresponding thin tapes on threaded rods of different thread pitches and depths, followed by co-lamination using isostatic press. Bolt-microtubular cells (BMCs) are also constructed on BMASs to investigate the effects of the created surface patterns on the cell performance and microstructure. The bolt-microtubular cell, whose anode support is patterned by using a threaded rod with 0.8 mm thread pitch and 0.4 mm thread depth, exhibits ∼92% higher maximum performance than that of the reference cell at 800 ºC under 0.3 NL/min hydrogen flow and stagnant air. The almost doubled performance is mainly due to the increase in anode-electrolyte and cathode-electrolyte interfacial areas by the surface patterns created. The cell is also subjected to a 200-h life test at 800 °C and 0.7 V and demonstrates a stable performance. [ABSTRACT FROM AUTHOR]

• Numerical modeling of an integrated refrigerated container. • Different cargo pallet arrangements and cargo packaging boxes are tested. • Airflow short-circuiting has both positive and negative effects on cargo cooling. • Improving vertical airflow in cargo pallets enhances cargo cooling than air gaps. Improving the performance of a refrigerated container is crucial in effectively preserving thermal-sensitive cargo. The combined effect of vertical airflow resistance and airflow short-circuiting in air gaps play a vital role in cargo cooling. This study numerically investigates the effects of cargo vertical airflow resistance and air gaps between cargo pallets using two commonly used apple packaging boxes, each stacked in six different cargo pallet arrangements. A heat transfer enhanced refrigerated container design and a numerical model developed from the present authors' previous studies are used. The numerical model uses the porous medium model to incorporate the refrigeration unit and cargo within the refrigerated container. Additionally, the numerical domain includes the T-bar floor in the refrigerated container. Initially, the airflow characteristics based on vertical airflow resistance and air gaps are discussed. Then, the corresponding effects on cargo cooling are addressed. Results show that the air gaps between the cargo pallets have positive and negative effects on cargo cooling. In cargos with lower vertical airflow resistance, an increase in air gaps leads to reduced cargo cooling and elevated temperature non-uniformity. Conversely, cargos with higher vertical airflow resistance experience increased cooling rates and reduced temperature non-uniformity with the increase in air gaps. However, avoiding airflow short-circuiting through the air gaps between the cargo pallets and improving the vertical airflow inside the cargo pallets can provide better cargo cooling, which outweighs the positive cooling effect of the air gap. [ABSTRACT FROM AUTHOR]

[Display omitted] • We proposed an SPA based on a Kresling-like pattern with a rigid skeleton by observing the cloning and moving behaviors from salps. • An extensible inserting structure is innovatively designed to replace the creases in traditional Kresling patterns. • The SPA can perform an axial contraction motion without twisting and a controllable bending motion. • The number of layers of Kresling-like patterns is changeable by adding or reducing skeleton components. • The elongation can reach to above 162% and the output force can reach to above 6.36 N. Biomimetic soft pneumatic actuators (SPA) with Kresling origami patterns have unique advantages over conventional rigid robots, owing to their adaptability and safety. Inspired by cloning and moving behaviors observed from salps, we proposed an SPA based on a Kresling-like pattern with a rigid skeleton. The elongation and output force were tested, and the effectiveness of the applications with the SPA was evaluated. The proposed SPA consists of rigid skeletons and a soft skin. The rigid skeletons are constructed using layers of Kresling-like patterns, while a novel extensible inserting structure is devised to replace the folds found in conventional Kresling patterns. This innovative approach ensures that the SPA exhibits axial contraction/expansion motion without any twisting movement. To mimic the bionic characteristics of swimming and ingesting progress of salps, the proposed SPA can perform an axial contraction motion without twisting and a controllable bending motion based on multi-layered Kresling-like patterns; to mimic the cloning and releasing life phenomena of salps, the number of layers of Kresling-like patterns is changeable by adding or reducing skeleton components according to the practical needs. The experimental elongation results on the SPA with multiple layers of Kresling-like patterns show that the elongation can increase to above 162% by adding layers; the experimental output force results show that the three-layer SPA can provide 6.36 N output force at an air flow rate of 10 L/min, and the output force will continue to increase as the number of layers of Kresling-like pattern increases or the air flow rate increases. Further, we demonstrate the applications of the SPA in soft grippers, scissor grippers, claw grippers and pipe crawlers. Our proposed SPA can avoid twisting in the radial contraction motion with high elongation and output force, and provide the practical guidance for bio-inspired soft robotic applications. [ABSTRACT FROM AUTHOR]

The oxidation kinetics and oxide scale morphology of the Si 2 BC 3 N/Ta 4 HfC 5 ceramics sintered by hot-pressing were explored at 1000 °C and 1500 °C in flowing air. Dense Si 2 BC 3 N/Ta 4 HfC 5 ceramic sintered at 1900 °C with fine grain sizes shows the optimal oxidation resistance both at 1000 °C and 1500 °C. When oxidized at 1000 °C, the formation of a porous oxide layer of Ta 2 O 5 , Hf 6 Ta 2 O 17 and HfO 2 containing amorphous SiO 2 are primarily responsible for the unsatisfying oxidation resistance of the composite. A highly oxidation resistance component like Si 2 BC 3 N can promote the oxidation resistance of Ta 4 HfC 5 at 1500 °C, thanks to the formation of a dense and continuous tantalum-hafnium silicate glass. The oxidation kinetic curve at 1500 °C can be described by a parabolic law whilst the oxidation process is controlled by the diffusion rate of oxygen through the oxide layer; however, the oxidation reaction rate governs the oxidation progress at 1000 °C via a linear oxidation kinetics. • Different oxide phases of Si 2 BC 3 N/Ta 4 HfC 5 ceramics form when oxidized at 1000 °C and 1500 °C, respectively. • Si 2 BC 3 N/Ta 4 HfC 5 ceramics has a better oxidation resistance than Ta 4 HfC 5 when oxidized at 1500 °C. • Si 2 BC 3 N/Ta 4 HfC 5 ceramic sintered at 1900 °C has the best oxidation resistance because of the fine grain size and good relative density. [ABSTRACT FROM AUTHOR]

Oxygen excess ratio (OER), which is influenced by the air flow input to the cathode, is one of the important factors affecting the performance of fuel cell system. Insufficient oxygen supply will result in a sharp drop in output voltage, while an excessive supply will bring about a large parasitic power load on the air compressor, reducing the net output power of the system and operating efficiency. Both insufficient and excess oxygen supply can adversely affect the operating life of the proton exchange membrane fuel cell (PEMFC). Due to the serious nonlinear, hysteresis, uncertainty and interference in the process of OER control, this paper proposes an OER feedforward control based on extended state observer (ESO) for a PEMFC auxiliary system with the ESO to predict the total disturbance to improve the dynamic response of the system with large time delay utilizing terminal sliding mode control (TSMC). The control strategy is divided into two stages. The first stage constructs an ESO to realize real-time observation of the state variables required for the internal operation of the auxiliary machine system and the PEMFC, and yields the air compressor voltage control signal through terminal sliding mode control. In the second stage, combined with V/f control for the compressor, the transmitted air flow is adjusted, ultimately achieving the goal of changing the OER of the PEMFC and improving operating efficiency. The simulation results show that the proposed control strategy has good anti-interference capabilities, a faster response, and less overshoot. The gas flow transmission in the gas supply system is more robust, the PEMFC operation is safer, and its lifespan is extended. • The control difficulty caused by time delay characteristics of gas transmission in hydrogen production system considering gas-electric coupling is overcome. • The additional ESO can well observe the state variables and external disturbance that cannot be directly measured in the PEMFC system. The closed-loop control based on TSMC of the system is realized more accurately. • This paper considers the situation that when the energy storage system cannot meet the energy demand, PEMFC still wants to provide continuous power output. An adjusting strategy for OER in PEMFC through the electromagnetic effect of air compressor to extend the life span of the PEM fuel cell is proposed. • The proposed OER feedforward control strategy demonstrated superior robustness and fast response characteristics for oxygen excess ratio optimization. [ABSTRACT FROM AUTHOR]

Inferior meatus augmentation by injection or implants is one of the treatments for empty-nose syndrome (ENS), but levels of evidence of efficacy are low. We present the technique and evaluate our experience. The primary objective was to analyze changes in Empty Nose Syndrome 6-item Questionnaire (ENS6Q) scores after treating patients with ENS by autologous fat injection. Secondary objectives were the analysis of the evolution of each of the six ENS6Q items and identification of complications. Eleven patients underwent a minimally invasive approach to limit nasal airflow using fat injection between March 2021 and December 2022. Ten of the 11 patients showed a decrease in overall ENS6Q score (P = 0.0058); 6 had a final ENS6Q score < 11. Ten were satisfied with the procedure, but remained symptomatic. The procedure did not result in any complications. These encouraging results confirm the data in the literature suggesting that fat injection improves symptomatology in empty nose syndrome. However, like other minimally invasive approaches to limit nasal airflow, it does not eliminate all symptoms. These results need to be confirmed by studies on larger cohorts with longer follow-up, preferably in a multicenter setting. [ABSTRACT FROM AUTHOR]

• Three parallel compressors more efficient than two variable speed compressors. • R452B versus R410A led to better efficiencies and compatibility at high ambient. • Reliable oil return of three parallel compressors having multiple capacity levels. • Three parallel centrifugal blowers led to improved air flow distribution. This study delineates a meticulous exploration of technologies to enhance the energy efficiency of rooftop air conditioning units, employing the DOE/ORNL heat pump design model for comprehensive engineering design and optimization. A baseline rooftop air conditioning unit, featuring a 13 ton (45.7 kW) cooling capacity and a 17.9 integrated energy efficiency ratio, served as the point of departure for substantive efficiency enhancements. Key modifications included the consolidation of two refrigerant circuits into one, integrating three parallel 2-stage (dual-speed) compressors, fan replacements with high-efficiency substitutes. Notably, a lower global warming potential refrigerant, R452B, was evaluated as a substitute for R-410A, demonstrating better performance in the lab prototype. The achieved measured integrated energy efficiency ratio of 21.4 in the lab prototype surpassed the baseline integrated energy efficiency ratio. Comparative evaluations between R410A and R452B indicated heightened efficiency with the latter, showcasing a lab-demonstrated integrated energy efficiency ratio of 22.4 at the rated capacity of 13.8 ton (48.5 kW) and 23.9 integrated energy efficiency ratio at the rated capacity of 10 ton (35.2 kW). This research underscores the successful development of a rigorous, energy efficient rooftop air conditioning unit prototype with noteworthy environmental and economic implications. [ABSTRACT FROM AUTHOR]

An airlift pump is a vertical tube that utilizes the buoyant effects of a gas to lift a liquid. Unlike a standard mechanical pump, the liquid flow rate through the airlift pump is not directly controlled; rather, it depends on the supplied gas flow rate, the tube length and diameter, and the relative height of the liquid supply free surface (submergence ratio). The present study uses the commercial CFD code ANSYS CFX to model the isothermal, 3D, transient flow in an airlift pump using water and air. The model applies pressure boundary conditions at both ends of the tube and specifies the mass flow rate of air through multiple openings in the side of the tube. The bottom of the tube is an inlet of water only and the outlet is a two-phase flow opening. A time-dependent, homogeneous, VOF two-phase RANS CFD modelling approach is used with the air treated as an ideal gas. This work found that a complete 3D domain was necessary for consistent prediction of the airlift performance and physically realistic two-phase flow structures. Statistical analysis of the two-phase flow structures was applied to characterize airlift pump instability and better understand the physics of the airlift pump. [ABSTRACT FROM AUTHOR]

This study explores the use of air-fed atmospheric pressure plasma jets (APPJs) as a pre-joining treatment for 3D carbon fiber-reinforced carbon matrix composites (C/C) with the aim of both creating a textured surface that resembles a brush structure and improving the joint strength. The effects of various treatment time lengths on the mass loss, etching depth, and surface texture were investigated using SEM and confocal microscopy. An optimal process time of 30 s was selected, while keeping the other process parameters fixed (air flow of 1750 l/h and nozzle-sample distance of 5 mm). Wetting tests were conducted at 1000 °C, on both untreated and pre-treated C/C surfaces by means of liquid TiCuNi brazing alloy, and low contact angles of about 20° were measured. C/C–TiCuNi–C/C and C/C–TiCuNi–Cu joints were then produced, and their interfacial reactivity was evaluated. The apparent shear strength measured for the APPJ-treated C/C–Cu joints was 140 % higher than the value recorded for the untreated joints, thus confirming the effectiveness of the treatment. Even though a further investigation is needed in which an optimization of the process parameters should be included, this preliminary study has revealed the viability of APPJ as a promising technique to enhance the bonding of C/C composites in dissimilar assemblies and to improve the joint quality. [ABSTRACT FROM AUTHOR]

An experimental and numerical investigation is conducted on the thermo-acoustic stability of a bluff-body turbulent combustor, considering variations in airflow rate and fuel composition. The focus is on mapping the behavior of the combustor in terms of the Reynolds number (Re). The stability of the combustor is assessed for three different fuels: pure hydrogen (PH), synthesis natural gas (SNG), and syngas (SG). The experimental analysis was carried out for selected fuel compositions using simultaneous, unsteady pressure measurement and OH* chemiluminescence across the variation of Reynolds number, Re , over the 2289–8009 range. The numerical modelling of bluff body stabilized turbulent diffusion flames has been performed by the ANSYS-Fluent. The standard k-ɛ model of turbulent flow, and the PDF (Probability Density Function)/Mixture Fraction combustion model for non-premixed combustion have been used in the combustion modelling. The experimental results reveal at low Re and the fundamental duct acoustic mode, SNG shows stable combustion, while SG exhibits high amplitude oscillations. When the Re is increased, SNG experiences significant oscillations with high amplitude nearer to duct acoustic mode, whereas SG shows comparatively lower amplitude oscillations at the third harmonic. When studying PH, it is interesting to note the presence of significant oscillations at higher Re at the first harmonic and highest amplitude oscillations at fundamental mode at lower Re. The combustion dynamics of the fuels are affected by the global equivalence ratio (ϕ) and the momentum flux ratio (MFR) fuel to air. A clear distinction in flame anchoring has been observed among the selected fuels. The PH flame is anchored at the injection location, and SNG flame is found in the shear layer and wake of the bluff body, while SG flame is anchored near the walls of the combustor and shear layer of the bluff body. In addition, the average flow fields and temperature contours for the listed fuels are also presented in this study. • Stability of combustor is mapped for three hydrogen enriched fuels across the Re. • CH 4 in H 2 excites fundamental acoustic mode, while CO excites higher frequencies. • Equivalence ratio and momentum ratio dictates the flame anchoring mechanism. • Flame-driven vorticities and flow effect are responsible for the size of vortices. • Macro flame structures across fuels and flow conditions dictates spectral content. [ABSTRACT FROM AUTHOR]

Oxygen starvation in proton exchange membrane fuel cells (PEMFCs) could lead to uneven internal current distribution, which is unfavorable to the fuel cell performance and lifetime. As oxygen starvation could occur locally, investigating the internal dynamic characteristics of PEMFC is critical to understanding the performance degradation mechanism. In this paper, the self-designed segmented cell of 396 segments is used to measure the dynamic current distributions of the automotive PEMFC with active area of 406 cm2 during oxygen starvation operation by decreasing air flow rate. As the air stoichiometry decreases from 2.4 to 0.8, the cell voltage drops gradually to 0.005 V and the internal current distribution becomes extremely nonuniform. The local current density increases to 1.64 A/cm2 at the air inlet and decreases to 0.25 A/cm2 at air outlet under the load current density of 0.6 A/cm2, which is dominated by the localized oxygen starvation around air outlet. When air flow rate is decreased to 0, the cell voltage reverses with a negative value of −0.042 V and the current distribution uniformity recovers. Under the negative cell voltage condition without air supply, the current distribution is determined by the membrane water content rather than the oxygen concentration. It is also found that larger step variation of air flow rate leads to a more significant overshoot of local current at air inlet and undershoot at air outlet. The different mechanisms for the internal current evolution of PEMFC is analyzed under Rich-Oxygen, Lack-Oxygen and No-Oxygen conditions, which are beneficial to improve air supply control strategy and the fuel cell design. • Dynamic internal performance of PEMFC under oxygen starvation is studied. • Segmented cell with 396 segments is used to measure the dynamic current distributions. • Uneven oxygen distribution worsens the uniformity of the current distribution significantly. • Under No-Oxygen condition cell voltage reverses with recovered internal current uniformity. • Step variation of air flow rate leads to overshoot and undershoot of local currents. [ABSTRACT FROM AUTHOR]

Mixing characteristics play an important role on the operational process of rotating detonation combustor (RDC). In this paper, a series of numerical calculations were conducted to analyze the influence of injection diameter, injection position, reactant mass flow rate, and equivalence ratio on mixing characteristics. Mixing performance parameters and total pressure loss in combustor dome and ignition zone were analyzed in detail. The findings indicated that all four injection conditions had significant influence on mixing characteristics, among which injection position was the most significant factor. When injection position was in convergent section, the mixing characteristics were better than those in ignition section. Reducing the fuel diameter gradually improved mixing characteristics, but also increased total pressure loss. The change of reactant mass flow rate had a minimal effect on mixing characteristics. As equivalence ratio decreased, mixing characteristics decreased and total pressure loss decreased. In addition, the comparative analysis also showed that penetration depth of hydrogen had an impact on flow field disturbance and distribution of return region, which led to the difference in mixing characteristics. When hydrogen was injected into the convergent structure section where air flow velocity did not reach sonic speed and was in acceleration phase, total pressure loss would be effectively reduced in combustor dome. • A new rotating detonation combustor model with convergent inlet structure was built. • Mixing performance parameters and total pressure loss in combustor dome and ignition zone were analyzed using RANS and LES. • Mixing characteristics of RDC were significantly enhanced when the injection position was in convergent structure section. [ABSTRACT FROM AUTHOR]

• A modified evaporative condenser model with 4 characteristic parameters is proposed. • Data screening and supplementation methods are developed for on-site applications. • The average relative errors of the training and test sets are 2.10 % and 2.87 %. • Air–water mass transfer is the major factor in enhancing thermodynamic performance. Evaporative condensers (ECs) have been widely adopted in the fields of refrigeration, petrochemicals, etc. owing to the advantages of low water and energy consumption. However, due to the lack of a reliable mathematical model, the energy-saving potential of ECs remains unexplored. To realize thermodynamic performance predictions under on-site conditions, a generic model with 4 characteristic parameters, that could be identified specifically for different ECs, is innovatively proposed in this paper. Taking the refrigeration system of a food factory as a case study, a well-organized data processing method including filtering, screening, and supplementation is established. The processed real-operating data is used for characteristic parameters identification and model validation. Simulations indicate satisfactory transferability and a good agreement between the test and simulated results, with average relative errors of 2.10 % and 2.87 % for the training and test sets, respectively. Based on the proposed model, the overall performance and the working fluids' thermodynamic state of the EC during operation are investigated carefully. It could be concluded that the air–water mass transfer is the dominating factor in enhancing EC's thermodynamic performance, and air flow shows greater significance than water in improving heat exchange capacity. The heat exchange intensity of the superheating and two-phase zones is similar, while that of the subcooling zone is the lowest, averaging only 37.9 %. [ABSTRACT FROM AUTHOR]

This paper compares the performance of a vertical-finned microchannel heat exchanger (VMHX) and a 2-row fin-tube heat exchanger (FTHX) under wet and frosting conditions. The VMHX features vertically oriented fins with an extension at the windward side and parallel microchannel tubes, allowing for efficient water drainage and better performance than conventional microchannel heat exchangers with parallel serpentine fins. However, the performance of the VMHX has not been sufficiently compared to that of FTHX. After conducting experiments under specific operating conditions, the VMHX exhibits better water drainage performance than the FTHX at higher inlet air velocities, higher maximum heat flow, and time-integrating heat flow under certain operating conditions. Although the heating time is relatively shorter than the 2-row FTHX, these results suggest that the VMHX may be a more suitable option for applications requiring efficient water drainage and heat transfer. Additionally, the operating conditions significantly affect the heat exchanger's performance. The performance of VMHX is analyzed under different inlet air velocities, inlet air temperatures, and evaporation temperatures. The results indicate that frost itself had no effect on the heat exchanger performance and that the decrease of the inlet air flow rate was the main factor that decreased the heat exchanger performance. Overall, the results of this study provide valuable insights into the performance of VMHX and FTHX under wet and frosting conditions and the impact of various operating parameters on VMHX performance. These findings can inform the development of more efficient and reliable heat exchangers for various applications. [ABSTRACT FROM AUTHOR]

The reader will come to appreciate: • Many adults who were born extremely preterm in the 1980s and 1990s, and who did not develop bronchopulmonary dysplasia, have lung function in the low normal range. • Extremely preterm born infants with a history of bronchopulmonary dysplasia may be at increased risk of a chronic obstructive pulmonary disease in middle age and older years based on the trajectory of their lung function. • Despite improved neonatal care and the advent of surfactant therapy, the rate of bronchopulmonary dysplasia has not decreased. Extreme preterm (EP) birth, denoting delivery before the onset of the third trimester, interrupts intrauterine development and causes significant early-life pulmonary trauma, thereby posing a lifelong risk to respiratory health. We conducted a systematic review and meta -analysis to investigate adult lung function following EP birth (gestational age <28 weeks); comparing forced expiratory volume in first second (FEV 1), forced vital capacity (FVC), and FEV 1 /FVC to reference values. Subgroup differences were explored based on timing of birth relative to surfactant use (1991) and bronchopulmonary dysplasia (BPD) status. Systematic searches were performed in Medline, EMBASE, Web of Science and Cochrane Central. Quality assessments were carried out using a modified Newcastle-Ottawa Scale for cohort studies. Sixteen studies encompassing 1036 EP-born adults were included, with 14 studies (n = 787) reporting data as %predicted, and 11 (n = 879) as z-score (not mutually exclusive). Overall mean [95 % confidence interval (CI)] %FEV 1 was 85.30 (82.51; 88.09), %FVC was 94.33 (91.74; 96.91), and FEV 1 /FVC was 79.54 (77.71 to 81.38), all three with high heterogeneity. Overall mean (95 %CI) zFEV 1 was −1.05 (-1.21; −0.90) and zFVC was. −0.45 (-0.59; −0.31), both with moderate heterogeneity. Subgroup analyses revealed no difference in FEV 1 before versus after widespread use of surfactant, but more impairments after neonatal BPD. This meta -analysis revealed significant airflow limitation in EP-born adults, mostly explained by those with neonatal BPD. FEV 1 was more reduced than FVC, and FEV 1 /FVC was at the lower limit of normal. Although at a group level, most adult EP-born individuals do not meet COPD criteria, these findings are concerning. [ABSTRACT FROM AUTHOR]

[Display omitted] • The void fraction (41.31%) formed by large-particle size gravel was rapidly reduced. • High rate of gas flow in the pipeline made landfill gas diluted rapidly. • A larger void fraction (44.62%) led to formation of a smaller anaerobic zone. The main disposal method for municipal solid waste (MSW), including the growing worldwide volumes of kitchen waste, involves transport to landfills. Because kitchen waste is mainly composed of organic matter and has a high moisture content, large amounts of leachate and landfill gas are generated when it is sent to landfills. Therefore, rapid waste stabilization is essential. In this study, four semi-aerobic bioreactors (named NS, SS, MS, and LS) were established with void fractions of 33.76%, 39.84%, 44.62%, and 41.31%, respectively. The results showed that the void fractions of landfill directly affected the gas flow path. When the landfill void fraction was small (e.g., NS), most airflow traveled directly through the pipeline and minimal airflow entered the waste layer. When the landfill void fraction was large (e.g., MS), air easily entered the waste layer and some air flowed into the gas vent with the landfill gas. As the reaction proceeded, the void fraction gradually decreased due to gravity-induced sedimentation. During the water addition experiment, the voids were occupied by water, leading to formation of an anaerobic area. Among the four bioreactors, only MS had negligible formation of an anaerobic zone in the center. Methane (CH 4) generation was detected only at the connection between the gas vent and the leachate collection pipe. A larger void fraction led to formation of a smaller anaerobic zone. The ratio of air flowing in pipeline was lowest in MS. These results indicated that a large void fraction promotes the decomposition of organic matter. [ABSTRACT FROM AUTHOR]

Among all the operating parameters that control the cell culture environment inside bioreactors, appropriate mixing and aeration are crucial to ensure sufficient oxygen supply, homogeneous mixing, and CO 2 stripping. A model-based manufacturing facility fit approach was applied to define agitation and bottom air flow rates during the process scale-up from laboratory to manufacturing, of which computational fluid dynamics (CFD) was the core modeling tool. The realizable k -ε turbulent dispersed Eulerian gas-liquid flow model was established and validated using experimental values for the volumetric oxygen transfer coefficient (k L a). Model validation defined the process operating parameter ranges for application of the model, identified mixing issues (e.g., impeller flooding, dissolved oxygen gradients, etc.) and the impact of antifoam on k L a. Using the CFD simulation results as inputs to the models for oxygen demand, gas entrance velocity, and CO 2 stripping aided in the design of the agitation and bottom air flow rates needed to meet cellular oxygen demand, control CO 2 levels, mitigate risks for cell damage due to shear, foaming, as well as fire hazards due to high O 2 levels in the bioreactor gas outlet. The recommended operating conditions led to the completion of five manufacturing runs with a 100% success rate. This model-based approach achieved a seamless scale-up and reduced the required number of at-scale development batches, resulting in cost and time savings of a cell culture commercialization process. [Display omitted] • Appling a bioprocessing model package in manufacturing facility fit. • Predicting impeller flooding of a scale-up model by computational fluid dynamics. • Predicting pCO2 levels by CO 2 stripping model. • Evaluating cellular oxygen demand, foaming, and fire hazards. • Achieving seamless scale-up with reduced manufacturing scale development batches. [ABSTRACT FROM AUTHOR]

The flow of air inside a vertical slender long duct with a temperature difference between the horizontal walls characterized by the Rayleigh number R a and a pressure gradient in the horizontal direction characterized by the Reynolds number R e is studied using the lattice Boltzmann method. In this case, the longitudinal rolls found in ducts with a width larger than the height cannot develop and the flow remains quasi-two-dimensional. Therefore, a two-dimensional approach is used, considering periodic boundary conditions on the vertical walls. For R a c < R a ≤ 2. 0 × 1 0 5 with R a c the critical Rayleigh number for thermal convection, there are two transitions at R e 0 (R a) and R e C P (R a) , R e 0 < R e C P . The first transition at R e 0 has a sharp decrease in the average Nusselt number and for 0 < R e < R e 0 the temperature difference between the horizontal walls is more important than the pressure gradient. The second transition at R e C P marks the appearance of a conductive Poiseuille flow with no thermal convection. For 1. 0 × 1 0 5 ¡ R a there is a third transition at R e M , R e 0 < R e M < R e C P . For R a < 1. 0 × 1 0 5 and R e 0 < R e < R e C P , and for 1. 0 × 1 0 5 < R a and R e M < R e < R e C P , the pressure gradient dominates over the pressure gradient. Both the temperature difference and the pressure gradient are important for 1. 0 × 1 0 5 < R a and R e 0 < R e < R e M with an appreciable decrease of the average Nusselt number at R e 0 and R e M . [ABSTRACT FROM AUTHOR]

Human airways represent a complex flow system with a spatially and temporally variable character of air flow during respiration. In this paper, we experimentally studied the oscillatory flow of air with monodispersed micron-sized liquid particles in a transparent, anatomically realistic model of human upper airways and several bronchi generations using phase-Doppler anemometry (PDA). The PDA provided point-wise high-frequency measurements of axial velocities of individual aerosol particles in multiple positions of the airways (in the trachea and the upper bronchi) for three breathing regimes with a sinusoidal course. Typical time-resolved velocity plots at several positions within the model were documented and analysed using dimensionless criteria. Local mean air velocity and turbulence time-lines disclosed specific flow dynamic features in the multiple bifurcation system, namely the transit of vortical structures, oscillations induced by flow reversals, and inspiratory flow separations behind bifurcations. The results elucidated the laminar, transitional and turbulent flows during inspiratory and expiratory breathing phases. The character of the flow varies significantly with position in the airways, while the breathing regime has a generally low effect on the flow character. Inspection of the flow in the terminal branches indicated the need to add further branches for more realistic results there. [ABSTRACT FROM AUTHOR]

Nonequilibrium flows of air components behind reflected shock waves are systematically studied on the basis of several theoretical models for the rate coefficients of fully coupled vibrational energy exchanges and chemical reactions. Numerical simulations are performed in the frame of the state-to-state approach under initial conditions corresponding to recent shock-tube experiments in mixtures O 2 /Ar, NO/Ar, NO/N 2 /Ar. The model takes into account partial vibrational relaxation between the incident and reflected shock waves, state-resolved dissociation, recombination, exchange reactions with formation of NO in the vibrationally excited states, as well as vibrational–vibrational and vibrational–translational energy transitions. It is shown that for oxygen, relaxation between the incident and reflected shocks is not frozen, and taking it into account in the most test cases considerably improves the agreement of calculated and experimentally measured pressure. For NO-containing mixtures, the effect of intermediate relaxation is weaker. Average deviation of the number density of molecular species with respect to the experimental one is analyzed for several hundreds of numerical simulations; on the basis of these estimates, recommendations are given for the best choice of model parameters. These recommendations can be used for modeling high-temperature flows, in particular, under reentry conditions. • Recent shock-tube experiments in air species are simulated numerically. • State-to-state models of vibrational–chemical coupling are validated. • Good agreement with experimental data is shown. • Recommendations are given for the best choice of model parameters. [ABSTRACT FROM AUTHOR]

This present investigation unveils a novel insight into the dominant airmass flows originating from both continental and maritime sources, shaping the characteristics of the raindrop size distribution (DSD), atmospheric instabilities, and cloud effective radius over Delhi (28.62°N, 77.17°E), the capital city of India. The investigation employs the Hybrid Single-Particle Lagrangian Integrated Trajectory model to analyze airmass back trajectories corresponding to days featuring rain events within the study area. An observable pattern emerges: days with rainfall driven by continental (maritime) activities experience higher (lower) atmospheric instabilities, which is validated by radiosonde measurements. This enhanced atmospheric instability leads to the prevalence of larger raindrops during continental-influenced rain events, in contrast to days marked by maritime airflow, as estimated from surface-based disdrometer measurements. Furthermore, observations from the INSAT 3D/3DR satellite indicate a tendency towards a smaller cloud effective radius associated with continental airmass inflow, as opposed to maritime inflow. Notably, a category of rain events characterized by ambiguous airmass back trajectories, referred to as mixed types, is identified. These mixed events showcase intermediary variations in the investigated atmospheric parameters, positioning them between the continental and maritime scenarios. The discernible differences in DSD characteristics between rain events influenced by continental and maritime activities yield fluctuations in the radar reflectivity-rain rate (Z-R) power law relations, which bear significance for the application of rain radar remote sensing. Hence, this investigation underscores the critical implication of incorporating airmass source information while characterizing rain features and related atmospheric parameters over a capital metropolis like Delhi. [ABSTRACT FROM AUTHOR]

• A novel system is proposed to utilize LNG cold energy in cascade. • Thermodynamic and economic analyses are carried out for the proposed system. • The system is compared to other systems in the same field for performance evaluation. • The round-trip efficiency of the proposed energy storage system is 138.81 %. For cutting down the energy consumption and improving the cold energy conversion efficiency of the traditional liquefied air energy storage system (LAES), a novel energy system integration solution is proposed by combining the LAES with liquefied natural gas (LNG) regasification process. In this paper, the principal energy storage and energy release processes are simulated by Aspen Hysys. The influences of air mass flow rate and LNG regasification pressure on the performance are analyzed. The results indicate that the introducted system can attain 137.82 % round-trip efficiency, which is about 20 % higher than the conventional LAES system. Besides, the energy capacity reaches up to 10.87 MW and the exergy efficiency is 39.58 % during long-distance transportation. It's noteworthy that the power output in the liquefied air energy discharging period far exceeds the power generation from the organic Rankine cycle. The higher LNG transport pressure, the worse LNG-LAES system performance. When the air mass flow rate raises from 40,000 kg/h to 64,000 kg/h, the exergy efficiency is 3.4 % higher than the original, while the round-trip efficiency decreases by 29.79 %. Finally, through economic viability calculations, the dynamic recovery period of the LNG-LAES system is 5.41 years. [ABSTRACT FROM AUTHOR]

This study explores temperature fields in ammonia-hydrogen laminar diffusion flames at atmospheric pressure, employing a two-color NO-PLIF method for experimental analysis of the two-dimensional temperature distribution. Various experiments are conducted, manipulating co-flow air flows and molar fractions of hydrogen to create distinct NO generation environments. The uncertainty of measurements along the flame centerline is systematically assessed through simulation repetition, providing valuable insights into the impact of two-dimensional temperature measurement. The findings reveal that in laminar diffusion flames, an increase in co-flow rate or a decrease in hydrogen content results in a more concentrated distribution of the NO tracer and lower uncertainty. The study emphasizes the influence of flame front contraction and expansion, along with the shift of the active reaction region characterized by high luminous intensity based on hydrogen, on the temperature field outside the flame front. • A 2D temperature field of NH 3 /H 2 flame is acquired. • The reaction structures under varying air co-flow rates and ammonia proportions are provided. • The direct effects of chemical luminescence on the temperature field are presented. [ABSTRACT FROM AUTHOR]

In this paper, image processing techniques are employed to investigate the growth and detachment characteristics of initial bubbles in vertical glass tubes. The study explores the effects of different continuous phases (water and Therminol®66), nozzle diameters, air flow rates, and continuous phase liquid levels on the detachment diameter and shape of bubbles. Furthermore, based on the detachment characteristics obtained under various experimental conditions, a novel predictive model for bubble detachment diameter is established in both water and Therminol®66. The results show that the bubble detachment diameter in the continuous phase therminol® 66 is larger than the bubble detachment diameter in water, and that the shape of the bubbles in therminol® 66 is close to spherical, with an ellipsoidal shape in water. With the increase in nozzle diameter and airflow, the bubble detachment diameter increases, and the shape is stretched in the vertical direction. With the increase in the continuous phase liquid level, the bubble detachment diameter decreases, and the shape change is not significant. In addition, the accuracy of the bubble detachment diameter prediction model was validated through experimental data. Compared with the experimental values, the average absolute errors were 5.04% and 5.11% in water and Therminol®66, respectively. This study aims to investigate the characteristics of initial bubble growth and detachment, providing valuable references for nozzle design. [Display omitted] • The growth characteristics of initial bubbles under different working fluids are studied • The shape and diameter of the bubble detachment process are studied under different operating conditions. • A new bubble detachment diameter prediction model is established [ABSTRACT FROM AUTHOR]

Increasing demands on efficient airslides conveying in the fields of construction, agriculture, pharmacy and power require deep understanding of the flow characteristics of materials being conveyed. This study designs a full-scaled airslide test rig, in conjunction with an experimental method, to investigate the flow behaviour of two different materials, namely sand and flyash under vent and non-vent conditions. The flow modes of the sand and flyash are predicted based on the measured material properties and fluidisation. Furthermore, tests are conducted using the designed airslide, from which the flow is characterised by analysing the variations of the key parameters, including the mass flow rate, the superficial air velocity, the pressure inside the airslide and the flowing material bed height. The work shows the developed test rig and method are capable of characterising fluidised flow for airslide systems. [Display omitted]. • Predict the flow modes of sand and flyash using different theoretical models. • Develop a full-scaled airslide test rig and experimental method. • Conduct airslide experiments under variable operation conditions. • Characterise the flow of sand and flyash during airslide conveying. [ABSTRACT FROM AUTHOR]

The work presented in this paper employed a resonant acoustic mixing (RAM) process to optimize the fine particle agglomeration process for dry powder inhalation to achieve efficient pulmonary delivery of melatonin. The formulation prepared by acoustic mixing with the double layer grids demonstrated superior agglomerate particle size distribution and approximately 90% of the metered dose in the dosing chamber was emitted from Turbuhaler® (90% emitted dose). Acceleration force during acoustic mixing significantly affected the packing fraction of mixtures and mechanical strength of agglomerates resulting in improved fine particle fraction. The particle agglomeration via RAM can improve the efficiency of agglomerate production by utilizing the internal space of the mixer to induce more particle collision. The agglomerates formulation exhibited ideal fine particle fraction of 47.65 ± 1.46% and 56.02 ± 2.55% at flow rates of 30 and 60 L/min, respectively. The fine particle deposition was only slightly affected at the lower air-flow rate, suggesting a reliable inhalation performance in vivo. [Display omitted] • Agglomeration was optimized via resonant acoustic mixing with double layer grids. • Emitted dose of about 90% was achieved by optimized agglomerate size distribution. • The superior dispersion contributed to a fine particle fraction of about 60%. • Aerosolization was only slightly affected by air flow rate to facilitate clinical trial. [ABSTRACT FROM AUTHOR]

This study establishes the performance requirements for an air-breathing electric propulsion device to operate in very low Earth orbit (< 450 km). We demonstrate that existing electric propulsion architectures, including electrostatic thrusters, fail to generate enough thrust while operating on flow rates of air that can be harvested in orbit. Instead, we develop and characterize a type of electromagnetic pulsed thruster that operates in a magneto-deflagration mode (i.e., forms an expansion wave during the acceleration process) that becomes more efficient as less propellant is used. We show this mode of operation can generate specific impulses up to 1 0 4 s, thrust per power > 2 mN/kW, thrust densities > 100 mN/m 2 , and thrust efficiencies up to 10% while consuming < 100 μ g of air per discharge. We map these performance metrics on a candidate spacecraft to show the deflagration thruster can enable fully air-breathing drag compensation at altitudes ranging from ∼ 200 km to 350 km depending on its geometry and is extendable to other altitudes if stored propellant is utilized. • Air-breathing electric propulsion (ABEP) systems use harvested air to compensate for drag. • ABEP devices cannot generate enough thrust for VLEO with harvestable amounts of air. • This study develops a deflagration thruster that operates efficiently in VLEO conditions. • The thruster achieves I sp up to 104 s and T/P above 2 mN/kW while operating on air. • The deflagration thruster enables air-breathing drag compensation from ∼ 200–350 km. [ABSTRACT FROM AUTHOR]

This study proposes a mixed-mode dryer with a semi-transparent photovoltaic thermal (PVT) collector for the assessment of drying and thermal performance using computational and experimental findings. The thermal behavior and fluid flow characteristics have been analyzed to optimize the air flow rate in the PVT solar dryer by considering three different inlet velocities of 0.048 m/s (Case 1), 0.096 m/s (Case 2), and 0.144 m/s (Case 3). The temperature distribution is obtained more uniformly for the PVT collector and dryer cabin in Case 2. The results of the investigation show that Case 3 has a positive impact on the PVT solar dryer performance. In numerical and experimental methods, the enhanced thermal efficiency is attained as 30.78% and 29.78% for Case 2, and 33.20% and 31.14% for Case 3, respectively, in comparison to Case 1. Case 3 has improved Reynolds and Nussselt numbers by 3.06 and 2.45 times, respectively compared to Case 1. Experimental results varied by 2.24 to 4.90% from simulated outcomes obtained from CFD. The machine learning approach of ANN has been implemented with different hidden layers network models to choose the best drying conditions by predicting the drying performance parameters. [Display omitted] [ABSTRACT FROM AUTHOR]

To effectively reduce the dust pollution in the fully mechanized face, this study proposes a large-scale dust-droplet coupling model based on LES-VOF and the dust-droplet probabilistic collision algorithm. Subsequently, the dispersion of droplets and dust under various spray pressures was analyzed. The accuracy of the model was verified through experiments and measurements, with a relative error of less than 15.0%. The analysis results indicated that the airflow on the air inlet side generated a vortex field, resulting in the accumulation of dust and droplets within 0–9.8 m from the heading face. The airflow on the air outlet side moved backward along the tunnel floor, causing the droplets and dust to disperse in a larger area. As the spray pressure increased, the droplet coverage distance showed a bimodal pattern, while the dust diffusion distance initially increased and then decreased. If the spray pressure exceeded 5 MPa, the covering distance of droplets and dust reached 23.0 m and 4.2 m, respectively, and the dust concentration in the area going beyond 15.0 m was below 20.0 mg/m3. The dust concentration at the driver's location was measured at 5.35 mg/m3, achieving a significant dust reduction rate of 90.60%. More importantly, the on-site application analysis has presented well-aligned data with the simulation results. [Display omitted] [ABSTRACT FROM AUTHOR]

• Terrestrial laser scanning of the column of Hera Lacinia Temple and its surroundings. • Polygonal modelling and survey of the column and basement. • CFD analysis of the column, subjected to the main winds in the area. The study presents the results of a multidisciplinary research that integrates terrestrial laser scanning (TLS) and computational fluid dynamics (CFD) to document and analyse an archaeological asset subject to natural hazards. The experimentation was conducted on the surviving column of the temple of Hera Lacinia, located in Capo Colonna near Crotone (Italy). The column, the fragments of the crepidoma and of the foundation constitute the most visible remains of the peripteral Doric temple (second quarter of the 5th century B.C.), belonging to the most important sanctuary of Magna Graecia. The temple, the sanctuary and the other ancient buildings, which are in the area of the Capo Colonna promontory, were destroyed over the centuries to obtain construction material. Today the column and the remains of the temple are located inside the National Archaeological Park of Capo Colonna, protected from human action, but subject to natural phenomena which are dangerous or potentially dangerous in the long term. The wind exerts a constant erosion of the surface of the column and wear of the lower part of the shaft due to the continuous oscillations to which it is subjected; moreover, the wind thrust could add up to a possible seismic action. On the other hand, the geomorphological evolution of the promontory (coastal erosion and subsidence) causes the coastline to recede, and is responsible for landslides affecting the column-basement system. Starting from the point cloud acquired by the TLS, a mesh of the column, basement and surrounding terrain was created, aimed both at documentation, graphic analysis and CFD. The survey enabled the description of the current state of the column-basement system, documenting and measuring the shapes of the column, as well as the different inclinations of the individual parts caused by instability of the ground. Furthermore, the CFD model of the Hera Lacinia column was developed. The model is based on the three-dimensional Reynolds-Averaged Navier-Stokes (RANS) equations with the k-ε closure turbulence model. The oncoming wind was modelled according to the results obtained from 70 years of statistics analysis (from 1950–2021) of wind hourly data (streamwise and spanwise components). The interaction between wind flow and the Hera Lacinia column geometry shows very complex phenomenona. The adopted numerical model was able to simulate correctly the main phenomena involved such as the flow separation occurring around the column as well as the wake behind it. Particular attention was paid to investigating the most damaged areas of the column, identified by analysing recent images of the column, where the values of the time-averaged drag and lift forces were obtained. In order to obtain the erosion-based damage prediction future research will focus on the analysis of air flow erosion of the Hera-Lacinia column, starting from the measurements in situ of the main air characteristics and using the latter as the fluid for the numerical simulation, and by also considering different values of wind speed and directions. [ABSTRACT FROM AUTHOR]

The present study investigated the Interval Starting Accessibility Drying (ISAD) process with the main objective to optimize the main processing parameters, i.e. the active time (toN) and the tempering time (toFF)> which ranged between 5 to 30 s and 1 to 3 min, respectively. ISAD performances were compared with continuous airflow drying for several quality parameters and energy consumption. The modulation of the time related operating conditions allowed rewetting the surface after each tempering time in a total way with toN= 5s-and toFF=2 or 3min. ISAD significantly affected (p<0.05) the effective drying time and the energy saving which reached as much as 87.26% compared to continuous drying when toN= 5s and toFF =3 min. The processes did not significantly impact the shrinkage, rehydration capacity or total color change. However, drying processes notably influenced the content of polyphenols and carotenoids. The optimal conditions of combined optimized responses were toN = 5 s of toFF = 2.52 min with a desirability D= 0.924. [ABSTRACT FROM AUTHOR]

This study analyses Compound Fins (CFs) in turbulent airflows using numerical and experimental methods. CFs combine Novel Plate Fin Heatsinks (NPFHSs) [1] and Slotted fins (S8 and S9) [2] and are compared to plain plate fins. Numerical modelling of turbulent airflow is conducted using Reynolds-Averaged Navier-Stokes equations, and ANSYS is used for the analysis. The CFs are manufactured using selective laser melting and validated experimentally. CF variations are categorized as CF18, CF19, CF28 and CF29 as described in Table 1. CFs outperform plain fins, with CF18, CF19, CF28, and CF29 showing higher Nu numbers by 52.7%, 51.2%, 44.8%, and 47.9%, respectively. CF18 and CF19 have 22.9% and 21.7% higher heat transfer coefficients than NPFHS1, respectively. CF28 and CF29 have 19.1% and 22.4% higher heat transfer coefficients than NPFHS2, respectively. CF18 and CF19 have higher air pressure drops than plain fins, while CF28 and CF29 have lesser pressure loss. The study concludes that CFs perform better than plain fins and are lighter. The methodology ensures the accuracy and reliability of the findings, making the study a valuable contribution to electronic cooling. [ABSTRACT FROM AUTHOR]

• Throughout cattle manure composting, average airflow resistance decreased by 40.1%. • All research parameters had the greatest variation at the thermophilic phase. • With the aerobic reaction, the total pressure ought to be adjusted to a lower level. • Ranks affecting airflow resistance were bulk density, particle size, specific gravity. Composting is widely adopted in livestock waste management, and the ventilation system control is essential for composting efficiency. For ventilation system, the airflow resistance is a major factor influencing the ventilation intensity and oxygen supply capacity. This study explored the variation law of airflow resistance, bulk density, specific gravity, particle size and total pressure throughout composting with cattle manure. The airflow resistance was calculated with Ergun equation, and contribution coefficients of different components were analyzed with principal component analysis (PCA). Results showed that the viscous airflow resistance was dominant throughout cattle manure composting. The average airflow resistance was 0.146 Pa/m, and resistance of pile at lower layer was higher than that at the upper layer by 18.1 %. For contribution coefficient affecting airflow resistance, the ranks were bulk density, average particle size and specific gravity. During composting process, the average airflow resistance decreased by 40.1 % and the total pressure reduced by 3.47 %. All parameters had the greatest variation at thermophilic phase, which accounted for more than 60 % of the total variation amplitude. Meanwhile, less than 10 % of the total pressure was used to overcome the airflow resistance. Therefore, reducing bulk density of pile should be considered preferentially to decrease the airflow resistance. During cattle manure composting process, the total pressure of ventilation system ought to be adjusted with the aerobic reaction to a lower level, especially at thermophilic phase with the most rapid descent rate. This study can provide support for reducing the energy consumption required for ventilation of composting. [ABSTRACT FROM AUTHOR]

In recent years, much attention has been paid to the development of plasma aerodynamics. Among the main tasks to be solved in this area are an increase in thrust force, induced velocity and efficiency of operation of multi-discharge actuator systems used to control air flows. This work presents the results of experimental studies of the dependencies of the characteristics (thrust force, speed of the created air flow, power consumption) of such systems on the parameters of the power mode (voltage, frequency, pulse front duration) with unipolar high-voltage pulses with a bias voltage and comparison of these characteristics when working with other power modes. • High-voltage power supply system provides DC bias voltage to MAS electrodes in combination with repeated unipolar pulses. • High-voltage power supply system with rectangular voltage pulses for multi-discharge actuator system is created. • Electric discharge and gas dynamic characteristics of MAS under various power supply modes were investigated. • At optimal actuator system power supply modes comparable values of thrust force and airflow rates are achieved. [ABSTRACT FROM AUTHOR]

The ventilation resistance coefficients of a mine is vital to ventilation system safety management, diagnosis, and intelligentization. Airflow typically serves as the basis for inverting ventilation resistance coefficients. However, the issue of non-uniqueness in conventional nonlinear optimization methods affects the accuracy of inversion. Therefore, this study introduces a novel optimization approach based on deep reinforcement learning (DRL) to invert resistance coefficients. In this methodology, inversion is regarded as a Markov decision process, with the ventilation network solving model (VNSM) embedded within the DRL environment. We design an agent utilizing deep neural networks, which dynamically adjusts the resistance coefficient state variables by interacting with the VNSM to enhance the consistency between theoretical and measured airflow. The consistency corresponds to the agent's reward. The proximal policy optimization is employed to optimize the agent's policy. In field experiment, the MAE between the airflow calculated and the measured airflow is 0.354, with MSE of 0.287, RMSE of 0.536, and MRE of 0.013. Compared with the standard genetic algorithm, differential evolution algorithm, and evolution strategy algorithm, the DRL method shows lower MRE, MAE, RMSE, and MSE values by 23.5%, 15.3%, 14.1%, and 26.4%, respectively. Additionally, DRL method exhibits smaller sensitivity differences for different roadways than others algorithm. [ABSTRACT FROM AUTHOR]

• We studied bacterial respiratory infections and pneumonia in people with HIV (PWH). • The cumulative incidence of pneumonia was highest in PWH with airflow limitation. • PWH with active smoking had a higher risk of bacterial infections and pneumonia. • PWH with previous AIDS had a higher risk of bacterial respiratory infections. We aimed to determine the incidence rate, pathogen composition, and risk factors, particularly airflow limitation, associated with bacterial respiratory infection and pneumonia in a prospective cohort of well-treated people with HIV (PWH) between 2015-2021. We included 1007 PWH from the Copenhagen Comorbidity in HIV infection (COCOMO) study. Spirometry was performed at inclusion. Microbiology samples were collected prospectively. Cumulative incidence was determined by the Aalen-Johansen estimator. Cox proportional hazard models were used to calculate risk factors, adjusted for traditional and HIV-specific variables. The incidence rates of first bacterial respiratory infection and pneumonia were 12.4 (95% CI 9.7-15.5) and 5.5 (95% CI: 3.8-7.7) per 1000 person-years, respectively. The cumulative incidence of pneumonia was four times higher in PWH with airflow limitation (11.8% vs 3.2%, P <0.001). Risk factors for bacterial respiratory infection were airflow limitation (hazard ratio [HR] 2.9, [95% CI: 1.7-5.1], P <0.001), smoking (HR 2.3, [95% CI: 1.4-3.8], P <0.001), and previous AIDS-defining event (HR 2.0, [95% CI: 1.2-3.3], P = 0.009). For pneumonia, airflow limitation (HR 2.7, [95% CI: 1.2-6.3], P = 0.016), smoking (HR 2.5, [95% CI: 1.2-5.4], P = 0.016), and older age (HR 1.5, [95% CI: 1.1-2.1], P = 0.015) were identified as risk factors. Increased emphasis on airflow limitation prevention, including smoking cessation, may reduce the burden of bacterial respiratory infection and pneumonia in PWH. [Display omitted] [ABSTRACT FROM AUTHOR]

In this paper, the diffusion characteristics and laws of hydrogen leakage in confined spaces are investigated using a combination of numerical simulations and experiments, and a small-scale cube model (dimensions: 0.47 m×0.33 m × 0.20 m) is used. The effects of leak source location, obstacles, leak hole size and shape on hydrogen diffusion and concentration evolution were investigated. The results show that the top funnel is sprayed vertically downward, the diffusion velocity decreases rapidly under the blocking effect of air and buoyancy force, and the momentum of the airflow is exchanged. During the injection phase, the leaking gas is mainly subjected to strong buoyancy forces and the hydrogen concentration shows a stratification effect. When the injection stops, the concentration difference decreases and eventually the hydrogen concentration reaches a steady state. The obstacle model in turbulence (4.3%) increases the concentration difference by a factor of about three compared to the empty room model (1.7%), which seriously affects the diffusive behavior of hydrogen. The obstacle in laminar flow model (10.4%) has almost the same concentration difference as the empty room model (10.2%). Rectangular leakage holes have a greater initial kinetic energy and diffuse more widely and faster. • Effects of obstacles, leakage hole size and shape on concentration were studied. • The rate of diffusion is reduced due to the blocking effect of air and buoyancy. • Hydrogen concentration shows a stratification effect in the presence of buoyancy. • Obstacles cause loss of gas kinetic energy and delay the averaging time. • Rectangular leakage holes have a large gas diffusion range and fast diffusion rate. [ABSTRACT FROM AUTHOR]

The performance, cost, and durability of proton exchange membrane fuel cells (PEMFCs) can be impacted by the bipolar plate's (BPP's) configuration, especially in an air-cooled PEMFC. An air-cooled PEMFC stack with concave-convex dual flow channel metallic BPPs are designed and the heat dissipation effect of the proposed BPP structure is investigated. To investigate the heat transfer and airflow processes of various concave-convex dual flow channel structures, a three-dimensional multi-physical field model with two PEMFC units is built. The results show that the heat dissipation effect can be enhanced by lengthening both sides of the BPP, and installing fans before the heat sink ribs on both sides can further enhance the heat dissipation effect. The largest temperature drop rate is 16.5% in the original BPP and air velocity increased from 1 m/s to 1.5 m/s with the current density of 400 mA/cm2. The uniformity of the MEA temperature can reach over 0.9 with the concave-convex dual channel BPPs. The heat dissipation effect can be enhanced by lengthening both sides of BPPs, shortening the cathode flow path will cause a more uniform temperature distribution. • A novel design of adding heat sink ribs on non-main flow field of the metallic BPP. • The heat dissipation efficiency of BPP C increased by 13.28% than BPP B. • Short cathode flow channel results in temperature distribution uniformity over 0.96. • The novel BPP has 6.01% thermal management efficiency improvement than BPP C. [ABSTRACT FROM AUTHOR]

This study demonstrates the applicability of an explicit model predictive controller (ExMPC) to the air mass flow control in a fuel cell electric vehicle. The two control tasks comprise the supply of air to the fuel cell stack for the electrochemical reaction as well as the dilution of hydrogen in the outlet gas flow of the cathode subsystem. With the aim of achieving zero control deviation for steady states, the linear model in the state observer is extended with two perturbations. During the experimental validation of the proposed controller, fast dynamics are achieved with the ExMPC, which generally exploits the limits of the control variables. After the calibration of the ExMPC, the final comparison to a set of reference PI controllers reveals a significant improvement in the closed-loop behavior of the cathode subsystem during step changes in the controller setpoints. • An explicit model predictive controller is applied to a fuel cell electric vehicle. • Delays for control and controlled variables are considered. • The operating limits of the control variables are exploited during dynamic operation. • Improved closed-loop behavior is achieved in comparison to reference PI controllers. [ABSTRACT FROM AUTHOR]

In this study, a novel air blower by applying the DBD plasma actuator for a PEM fuel cell is proposed for reducing power consumption and air flow saving. For this purpose, the DBD plasma actuators are installed on the bottom surface of the cathode channel of a PEMFC. The impact of the application of DBD plasma and the number of DBDs on the air mass flow rate and performance of PEMFC were numerically investigated. Results show that in comparison to the conventional air blower model, using the DBD plasma air blower at the cathode channel of a PEMFC results in a reduction of velocity magnitude and uniform velocity distribution of airflow within the cathode channel. Also, results indicate that the DBD plasma air blower model with less air flow consumption provides almost the same current density and performance as the conventional model. Results illustrate that the DBD plasma air blower with 3 DBDs can be a suitable candidate to obtain the best design for the DBD plasma air blower. The robust advantages of using the DBD plasma air blower become more underscored when the findings present the 90.31% reduction in the average power consumption. • DBD actuator as air blower for a PEM fuel cell is numerically investigated. • Using DBD actuator air blower PEMFC significantly decreased air consumption. • Using DBD actuator air blower decreased the 90.31% average power consumption. [ABSTRACT FROM AUTHOR]

Reducing NO x emissions from industrial burners is a significant concern due to their harmful environmental and human health impact. A computationally efficient numerical model was developed and validated using a detailed GRI 3.0 chemistry mechanism to simulate the combustion process and precisely predict the NO x emissions from industrial burners. The numerical model was implemented to reduce NO x emissions by varying the burner's primary to secondary air mass flow ratio. An optimum nozzle diameter was proposed to abate NO x emissions by a factor of 0.845. A feasibility study on the optimised burner was conducted by blending up to 50% hydrogen by volume with natural gas by maintaining the same burner power output. Results showed that the burner exhibited similar flame characteristics until 40% hydrogen was added to natural gas. A 41.8% increase in NO and a 76.8% decrease in CO emissions were observed by enriching natural gas with 50% hydrogen. • Implementation of a two-step numerical model to analyse an Industrial Burner. • Validation with Sandia Flame D experiments and Industrial burners. • Computational optimisation techniques to reduce the computation time. • Modification of primary to secondary air mass flow ratio to reduce NO x emissions by a factor of 0.845. • 76.8% reduction in CO and 41.8% increase in NO when enriching Natural Gas with 50% of Hydrogen. [ABSTRACT FROM AUTHOR]

Cyclone separators are important equipment for biomass transportation and separation. At present, the separation mechanism of particles with special shapes is rarely explored. A mutable filamentous particle was established to simulate the separation process of biomass materials. Firstly, comparing the simulateded results with the experimental images. Further comparison of the simulation results with the experimental airflow tangential velocity to verify the calculation model. This study explores the separation characteristics and forces acting on filamentous biomass particles through computational fluid dynamics (CFD) and discrete element method (DEM). The distribution characteristics of airflow are also described in detail. The research results indicate that after 0.8 s, the filamentous biomass particles are separated stably in the cyclone separator and form a particle vortex line on the conical wall. The higher the inlet gas velocity, the lower the separation efficiency of filamentous biomass particles. The inlet gas velocity is 4.9 m/s, and the separation efficiency of filamentous biomass particles reaches 98.7%. The total force acting on the filamentous biomass particles gradually decreases after a sharply increase at 0.2 s, and it no longer changes after 0.5 s. The airflow vortex in a cyclone separator is composed of an internal vortex and an external vortex. The tangential velocity of the internal vortex varies approximately linearly. The internal vortex of the cyclone separator has a negative pressure area, which can lead to a decrease in the separation efficiency of filamentous biomass particles. These conclusions provide valuable theoretical guidance for the process and separation of biomass materials. ● A novel flexible particle can accurately simulate the biomass particle. ● The separation mechanism of biomass particles was numerically studied. ● Increasing gas velocity will reduces separation efficiency. ● The tangential velocity of the internal vortex varies approximately linearly. [ABSTRACT FROM AUTHOR]

A large-eddy simulation (LES) was performed on two different supersonic combustors based on a high-temperature CO/H 2 jet, and the flame-stabilization mechanism was analyzed. The results showed that for a strut-cavity-based combustor with the high-temperature jet turned on, the jet ignited, and the strut promoted the mixing of the supersonic airflow and fuel. The cavity recirculation zone realized the exchange of energy and momentum between the high-temperature gas and fuel in the shear layer, resulting in a decrease in the chemical timescale—referred to as the flame-stabilization mode of the high-temperature jet and cavity shear-layer ignition. Moreover, in a strut-cavity-based combustor with the high-temperature jet turned off, the strut promoted the mixing process, and the cavity improved the residence time of the fuel, resulting in the flow timescale being larger than that of the reaction—referred to as the flame-stabilization mode of the strut-cavity recirculation-zone flame stabilization. In the strut-based combustor with the high-temperature jet turned on, the rocket jet performed an ignition role in the flame stabilization process— referred to as the flame-stabilization mode for high-temperature jet ignition. When the jet was turned off, the chemical timescale increased rapidly and continued to be larger than the flow timescale, resulting in flameout. • The flame-stabilization mechanism was analyzed on two different supersonic combustors based on a high-temperature CO/H2 jet. • The supersonic combustors can be divided into three regions with the high-temperature CO/H2 jet. • There are three flame stabilization mechanisms in the supersonic combustor. [ABSTRACT FROM AUTHOR]

Recently, there has been growing interest in utilizing ammonia through its decomposition process for on-site hydrogen production, primarily due to technical problems in hydrogen generation and storage. As ammonia decomposition is an endothermic reaction, an external heat source is required to facilitate the reaction. To address this, an ammonia autothermal reforming process that directly integrates ammonia decomposition and oxidation using air as the source of oxygen within a single reactor vessel was proposed. This process eliminates the need for additional external heat sources and simplifies the process. The design of the reactor incorporates an air distribution structure that allows for achieving a specified temperature range for the desired reaction. Thermodynamic analysis of the autothermal system revealed that high feed temperature, high reaction temperature, and low pressure are the most beneficial conditions for generating a high yield of hydrogen. The proposed process was simulated to assess its feasibility using kinetic parameters obtained from experimental data in the literature [27]. An optimization problem to minimize the reactor length in designing the proposed reactor was developed. The reactor design produces a high yield of hydrogen while maintaining the reaction temperature within the desired range. Adjusting the air flow rate at distribution points along the reactor to maintain peak temperatures at predetermined levels was shown to provide good load flexibility for variations in ammonia flow rate. • Hydrogen production from ammonia by integrating ammonia decomposition and ammonia oxidation was proposed. • Thermodynamic analysis of the ammonia autothermal reforming process was performed. • A new ammonia autothermal reformer with an air side stream distribution was proposed and optimized. • The reactor has good load flexibility for variations in ammonia flow rate. [ABSTRACT FROM AUTHOR]

Single-crystal and fine-grained polycrystalline samples of Cr 2 AlC were oxidized under dry air flow at temperature in the 1000–1400 °C range during 100 h. A continuous alumina layer forms on top of the Cr 2 AlC surface whereas a Cr 7 C 3 sublayer also appears. In-lab characterization of oxidized Cr 2 AlC samples shows strong damaging at the free surface, resulting from the buckling of the alumina scale. In-situ X-ray diffraction measurements under synchrotron radiations were performed to measure the lattice strain during the first hours of oxidation process and further calculate the internal stress in the Al 2 O 3 layers. Alumina layers undergo tensile stress during isothermal oxidation, showing that the buckling of the alumina scale does not result from the oxide growth. Such a tensile stress likely results from the Cr 2 AlC to Cr 7 C 3 phase transformation. During cooling, the tensile stress decreases down to compressive values, due to the thermal expansion coefficient mismatch between the film and the substrate, leading to buckling of the alumina layer. It is demonstrated that the dimensions of the buckles cannot be explained either by gas pressure or by the magnitude of the internal compressive stress in the alumina scale after cooling. The discrepancy between the experimental maximum deflection and the one predicted by the elastic theory can only be explained by a significant plastic deformation occurring in the alumina scale. [ABSTRACT FROM AUTHOR]

Top-submerged nozzles with lateral holes find applications as passive mixing devices in radiochemical/hazardous industries. We report the mechanism of bubble formation and detachment at a lateral hole in such a nozzle for the first time. Three distinct phases – a growth phase, an elongation phase and finally a rise/detachment phase – could be observed during bubble formation. Effect of gas flow rate, diameter of lateral hole (1, 2 and 3 mm) and physical properties of liquid-liquid system on bubble detachment time and bubble equivalent diameter are reported. Three different liquid-liquid systems (DM water, 2 N and 4 N nitric acid) have been considered. Bubble diameter first reduced, reached a minimum and then started to increase in an oscillatory manner with increase in air flow rate. Before the onset of oscillatory behaviour an increase in hole diameter was seen to reduce bubble diameter. Such a behaviour is typical to bubble formation at lateral hole and is not seen for top-submerged nozzles with central opening. A detailed analysis of the results was carried out and it was observed that inertial forces played a major role. The work also reports a fundamental criterion which must be achieved for onset of oscillations in bubble diameter with flow rate. We also report a 2D CFD model that can simulate bubble formation dynamics at a lateral hole. The model was validated qualitatively as well as quantitatively against the experimental data. • Mechanistic picture of bubble detachment form a top-submerged nozzle with lateral hole. • Bubble diameter reduces to a minima, then increases in an oscillatory manner with air flow. • A fundamental criterion for onset of oscillations determined. • 2D CFD model reveals presence of asymmetric re-circulatory patterns in liquid phase. [ABSTRACT FROM AUTHOR]

Ammonia-fueled operation of solid oxide fuel cells is a promising alternative to their hydrogen-fueled operation. However, high ammonia decomposition rates at elevated operating temperatures of the solid oxide cells lead to a significant temperature drop at the stack inlet, causing increased thermal stresses. A multi-scale model is used in this study to investigate stack performance under direct feed and external pre-cracking of ammonia. Additionally, the effects of co- and counter-flow configurations, gas inflow temperatures, current density, and air flow rate on the stack performance under direct ammonia feed are examined. The simulation results show that for gas inlet temperatures above 750 °C, the power densities with direct feed and external cracking of ammonia differ by less than 5%. Moreover, it is indicated that the thermal stresses are lowest for the co-flow case, which decrease with decreasing gas inlet temperature and current density and with increasing air flow. Finally, this study shows that under practically applicable operating conditions, the risk of mechanical failure of the cells under direct ammonia feed operation is small. • Ammonia cools down the stack but leads to high tensile stresses. • Stack performs closely under direct and pre-reformed ammonia at higher temperatures. • Counter-flow configuration and higher inflow temperatures increase tensile stresses. • Lower load current density and higher air mass flow rate decrease tensile stresses. • Mechanical failure is not expected for operating condition considered in this study. [ABSTRACT FROM AUTHOR]

The ablation resistance and ablation mechanism of C/C-SiC-HfC (CSH) and mullite modified C/C-SiC-HfC (MCSH) composites were explored under 30 s × 2 cyclic ablations with oxyacetylene flame at a heat flux of 2.38 MW/m2. The results showed that MCSH exhibits better ablation resistance. During ablation, the introduction of mullite promoted the formation of HfSiO 4 and inhibited the consumption of SiO 2 and the appearance of porous HfO 2. HfSiO 4 , island-like structures, and flower-like oxide structures were tightly bound on the surface of composites to form a stable and dense Hf-Si-Al-O composite oxide layer, which can effectively resist high-velocity airflow erosion while limiting oxygen diffusion. [ABSTRACT FROM AUTHOR]