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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]

When the lightweight quartz fiber-reinforced phenolic (LQFRP) composite is subjected to the combined effect of a local structural heat source and high-speed airflow, its ablation behavior exhibits significant localized characteristics and strong coupled effect. In this study, we have developed a bidirectional loosely coupled numerical model that integrates thermal, fluid, solid and ablation phenomena to solve the ablation-through problem of the LQFRP composite. The model takes into account the mechanisms of pyrolysis, oxidation, sublimation, and thermal mechanical erosion that occur during the ablation process of the LQFRP composite. The results suggest that the local structural heat source plays a crucial role in the erosion and retreat of the LQFRP composite. The morphology of the ablation pit shows a noticeable asymmetry, which is attributed to the aerodynamic heat and force. As a result of the local structural heat source, the fluid temperature downstream of the ablation pit is higher compared to that upstream of the ablation pit. The fluid that flows downstream of the ablation pit undergoes significant compression, leading to the formation of an oblique shock wave. The distribution of resin pyrolysis degree within the LQFRP composite is influenced by internal heat conduction. This study will offer valuable insights and guidance for the practical application of the LQFRP composite in the ultra-high temperature field. [ABSTRACT FROM AUTHOR]

The archerfish is unique in its ability to hunt by shooting a jet of water from its mouth that hits insects situated above the water's surface. To aim accurately, the fish needs to overcome physical factors including changes in light refraction at the air-water interface. Nevertheless, archerfish can still hit the target with a high success rate under changing conditions. One possible explanation for this extraordinary ability is that it is learned by trial and error through a motor adaptation process. We tested this possibility by characterizing the ability of the archerfish to adapt to perturbations in the environment to make appropriate adjustments to its shots. We introduced a perturbing airflow above the water tank of the archerfish trained to shoot at a target. For each trial shot, we measured the error, i.e., the distance between the center of the target and the center of the water jet produced by the fish. Immediately after the airflow perturbation, there was an increase in shot error. Then, over the course of several trials, the error was reduced and eventually plateaued. After the removal of the perturbation, there was an aftereffect, where the error was in the opposite direction but washed out after several trials. These results indicate that archerfish can adapt to the airflow perturbation. Testing the fish with two opposite airflow directions indicated that adaptation took place within an egocentric frame of reference. These results thus suggest that the archerfish is capable of motor adaptation, as indicated by data showing that the fish produced motor commands that anticipated the perturbation. [ABSTRACT FROM AUTHOR]

The efficiency and dynamic response of air compressors are crucial for stability and lifespan of hydrogen fuel cells. A predictive control scheme with surge‐ and choke‐constrained awareness is proposed to ensure safe and efficient operation of air compressors in this study. The proposed scheme consists of an efficiency enhancement model predictive control (EE‐MPC), and an improved active disturbance rejection control (IADRC). Surge‐ and choke‐constrained awareness is achieved by comparing predicted air flow with surge and choke limitations. Simultaneously, the EE‐MPC is constrained with oxygen excess ratio (OER) and obtains optimal solution by searching active set. The reference flow and supply manifold pressure trajectories for IADRC are generated by EE‐MPC. A designed piecewise differentiable nonlinear smoothing function is embedded in IADRC. The disturbances are estimated for coordinating flow and pressure control. Under China heavy‐duty commercial vehicle test cycle for bus conditions, root‐mean‐squared errors (RMSEs) of flow and pressure are 3.27 g s−1 and 1.88 × 103 Pa, respectively, and the mean efficiency can be enhanced by 13.4% compared to the MPC with fixed OER. Finally, a controller hardware‐in‐the‐loop test is conducted, with flow and pressure RMSEs of 2.48 g s−1 and 4.28 × 103 Pa between the test and simulation, respectively. [ABSTRACT FROM AUTHOR]

To provide reference for the design of the air-suction tea sorting device, the coupled numerical simulation model was established by the coupling method of computational fluid dynamics (CFD) and discrete element method (DEM) with tea of different quality as test objects, and the model was verified experimentally. Regarding tea particles of different quality, when the test tea particle mass was 0.215, the test value was located in the simulation value with a minimum error of 9 mm, which an error rate of 3.33%, and maximum error of 19 mm, with an error rate of 7.03%. When the test tea particle mass was 0.145, the minimum error of the test value was 5 mm and the error rate was 1.54%, and the maximum error was 9 mm and the error rate was 3.33%. The verification results established the accuracy of the model. During the suspension test and simulation, tea particles were affected by the air flow field of the observation tube, and tea particles fluctuated. During suspension, tea particles were attached to the inner wall of the observation tube under the action of the air flow field. An in-depth study showed that the relationship between the different distances from the initial position of the particles during suspension and the simulation time was a peak function. The extreme function is used to fit the actual trajectory, and the fitting degree is good. The fitting degree of the particle closest to the initial position was 0.9455, and the fitting degree of the particle farthest from the initial position was 0.9981. [ABSTRACT FROM AUTHOR]

Excellent mechanical and electric properties enable the piezoelectric materials to be widely and dynamic aero-mechanical-electric coupling properties of the piezoelectric plate structures can significantly affect performance of aircrafts flying in high speed. This paper is focused on the flutter behaviors of the functionally graded piezoelectric material (FGPM) plate in supersonic airflow. The first-order shear deformation theory (FSDT) is employed to formulate the energy functional of the FGPM plate with general boundary conditions. The supersonic air flow is taken into account using the supersonic piston theory. The governing equations for the aero-mechanical-electric coupling system are deduced on basis of the Hamilton's principle. To address the limitation of intricate boundary conditions to the admissible functions, a modified Fourier series is introduced to yield the unified solutions of the FGPM plate subject to supersonic airflow and with arbitrary boundary conditions. Flutter properties of series of FGPM plates are investigated to demonstrate robust ability of the proposed method to accurately yet consistency include the aero-elastic-electric coupling, inhomogeneous material and arbitrary boundary conditions. The influences of the boundary condition, material constituent, external voltage and yawed flow angle on the vibration, and flutter behaviors of the FGPM plate are examined. Adjusting corresponding parameters accordingly can significantly improve the stability of the plate structures subject to supersonic airflow, which provides physical insights into dynamic optimal design of the plate structures. [ABSTRACT FROM AUTHOR]

The concept of e-mobility is gaining the utmost importance owing to stringent emission norms. However, the safety issues associated with propulsion batteries are posing a major threat to their success. The occurrences of accidents caused due to thermal runaway in electric two-wheelers grabbed global attention. In this research work, an effort is being taken to address this concern, by arranging the battery cells in a pentagonal arrangement and employing forced air convection. The influence of air velocity (0.15, 0.30, and 0.45 m/s) and air inlet position (60, 75, and 90 mm) and intermediate cell distance (4, 6, and 8 mm) on the thermal performance of the battery is investigated using a numerical approach. Maximum cell temperature, pressure drop across the channel, maximum air velocity, maximum turbulent kinetic energy, and maximum turbulence intensity are considered output responses. A grey relational analysis (GRA) is used to identify the optimum level for all input parameters considering all output responses. The optimal forced convection parameters for the proposed pentagonal cell arrangement are the intermediate cell distance of 6 mm, air velocity of 0.45 m/s, and air inlet position of 90 mm from the center of the cell arrangement. With this arrangement, the peak cell temperature is reduced from 48.32 to 36.83 °C (8%). The study is extended with an airflow improviser to examine the influence of its geometrical parameters (improviser angle, fillet angle, and its distance from the center of the battery module) on the battery cell temperature. At the optimal conditions, the presence of an airflow improviser increases the air velocity from 1.76 to 2.302 m/s (19%) and turbulence intensity from 196 to 0.350 m2/s2 (33%). Thus, the cell temperature could be reduced to the extent of 8.6% by adopting the pentagonal cell arrangement with airflow improviser and optimal operating parameters. [ABSTRACT FROM AUTHOR]

The current paper experimentally studied the performance of solar-driven internally cooled liquid desiccant system for hot and humid climates using CaCl2 as a liquid desiccant. The system is designed to investigate the input conditions of the room by adjusting various air and solution variables. This internally cooled liquid desiccant system consists of the dehumidifier and regenerator in a single module and the regeneration of the solution is done by solar energy. The present study analyzes the effect of solution concentration, air mass flow rate and solution volume flow rate using different performance indices such as humidity reduction, moisture effectiveness, enthalpy effectiveness, and COP. The results demonstrate that the maximum moisture reduction of 4.2 g/kg d.a. is found at an airflow rate of 0.03195 kg/s, a solution volume flow rate of 12.5 LPM, and a solution concentration of 37%, while the maximum COP of 0.274 is obtained at an airflow rate of 0.0715 kg/s, a solution volume flow rate of 12.5 LPM, and a solution concentration of 37%. The maximum moisture and enthalpy effectiveness are obtained as 24.1% and 26.2%, respectively. The paper also presents the correlations for moisture and enthalpy effectiveness based on findings from experiments. [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 airport line plays an important role in the airport landside traffic connection, which greatly relieves the urban road pressure. Studying the characteristics and laws of the time and space distribution of the airport line passenger flow will provide basic support for the airport line's capacity configuration, passenger flow control, and air‐track coordinated operation, and will also provide quantitative basis for the layout of urban terminal buildings. This paper proposes a method to analyse the temporal and spatial distribution characteristics of airport line passenger flow based on AFC card swiping data. By mining and extracting the travel behaviour data of subway airport line air passengers, the distribution characteristics of airport line passenger flow are analysed and visualized from two aspects of passenger travel time and space. Finally, a case study is carried out based on the actual data of Daxing airport express. The results show that: (1) the travel time of departure and return passengers is concentrated in 60–90 min; (2) The departure and arrival points of passengers are concentrated within the Fourth Ring Road, and a large number of air passenger flows are gathered and evacuated at hubs such as Beijing South Railway Station and Beijing West Railway Station. [ABSTRACT FROM AUTHOR]

This article presents a study on the capture velocity of local exhaust ventilation (LEV) using a specially designed workstation within a laboratory setting. The workstation featured a worktop with dimensions of 90 cm width and 45 cm depth, and the exhaust duct was positioned near the pollutant source, considering the intended operation of the LEV system. The worktop was divided into squares for precise documentation and remeasurement. A supply duct above the worktop provided controlled fresh airflow. Smoke was used to visualize airflow patterns. The measurements focused on air velocity and turbulence intensity, aiming to understand flow structures and vortices. Various capture rates were tested at specific measurement points. The study revealed that the central capture lines yielded the highest efficiency. To address air extraction from behind the exhaust duct, a back sheet panel was introduced. The results showed that installing a back sheet enhanced capture velocities. The findings contribute to understanding LEV efficiency and the importance of proper design and adjustments for effective containment of contaminants in the occupational environment. [ABSTRACT FROM AUTHOR]

The study described here analyzed natural ventilation techniques, operated in a real building in the United Arab Emirates (UAE), to assist passive cooling. The assessment has been conducted by comparing digital simulation results and field measurements. Computational fluid dynamics (CFD) was used to retrospectively understand and quantify the monitored contribution of natural ventilation toward cooling the building. After calibrating the model with the field monitored data, the CFD simulations showed that the predicted ventilation strategies (buoyancy and stack effect to remove indoor heat; "wind catcher" effect to provide indoor passive cooling) contribute to lower the indoor temperature by an average of 0.7°C throughout the day. The outcomes of the study contributes to assist early stage design, with special regard to passive cooling via natural ventilation, to achieve more sustainable buildings. Nevertheless, while it is quite reliable to plan for main air flow and direction, in a real building alternative behavior might occur that is difficult to control and might affect the ventilation purpose and efficiency. [ABSTRACT FROM AUTHOR]

Air cooling systems are widely used in current data centers owing to their low capital costs and high reliability. To satisfy the increasing rack power density, the optimal air-cooling technology and an economic analysis should be carefully discussed. Therefore, this study discusses four airflow management technologies: Case 1: raised floor and cold aisle containment supply/computer room air conditioning (CRAC) direct return; Case 2: CRAC direct supply/hot aisle containment (HAC) return; Case 3: overhead duct supply/CRAC direct return; and Case 4: overhead duct supply/HAC return. Using a validated model, the thermal and economic performances of each case were compared. Results showed that Case 4 exhibited the best thermal performance, followed by Cases 3, 2, and 1. Case 1 cannot satisfy the heat dissipation requirement when the rack power density is larger than 12.5 kW; whereas only Case 4 can be used when the power density is larger than 15 kW. Regarding location within China, owing to the high ambient temperature, Shenzhen showed the highest annual cost value and power usage effectiveness, followed by Shanghai, Xi'an, Beijing, and Harbin. Finally, Cases 3 and 4 are recommended for application when the rack power density is greater than 10 kW. [ABSTRACT FROM AUTHOR]

In heating processes using superheated steam, a practical heat transfer model for predicting the change in the material temperature taking condensation/evaporation into consideration is required. This study observed the behavior of condensed water and verified a simple but practical heat transfer model to predict the heating time of materials. The one-dimensional model, which comprehensively includes the conductive, convective, radiative, and latent heat fluxes, was utilized. For simplicity, film condensation was assumed. To conduct experiments covering a wide humidity range, the humidity of the airflow was regulated by mixing superheated steam with high-temperature air. The sample material having 50 mm of length, 50 mm of width, and 10 mm of thickness was placed under this airflow, and the change in temperature over time was measured. During the initial stages of heating via superheated steam, condensation, and subsequent evaporation were observed. The time required for the evaporation of condensed water increased with the humidity, owing to the large amount of condensed water. The ending time of evaporation was successfully estimated within about −30% error. Although some modifications will be required in the future, the model is expected to be a powerful tool in various industries where superheated steam is applied. [ABSTRACT FROM AUTHOR]

Dust resuspension from four typical fabrics (cotton, linen, silk, and polyester) exposed to airflow with common velocities within 0–10 m/s, including a moving fabric case and a fixed fabric case, was experimentally studied in this article. A set of empirical correlations, involving air velocity, fabric motion mode, fabric type, and airflow duration was developed to describe and predict the moving fabric case. It was found that a stronger-than-expected resuspension was triggered by short-term accelerating airflow. The resuspension enhancement of over 90% was reported for the moving fabrics compared with the fixed ones. Fabric motion induced by airflow was proposed to account for these resuspension findings. Fabric acceleration was then demonstrated to be a key factor in evaluating the resuspension for such a scenario. This article not only reveals an inconspicuous phenomenon of dust resuspension from fabrics under the impact of airflow and consequent fabric motion, but also provides a theoretical basis for particulate matter assessment and regulation. Copyright © 2024 American Association for Aerosol Research [ABSTRACT FROM AUTHOR]

Assessing patients with complaints of nasal obstruction has traditionally been done by evaluation of the nasal airway looking for fixed or dynamic obstructive locations that could impair nasal airflow. Not infrequently, however, symptoms of nasal obstruction do not match the clinical examination of the nasal airway. Addressing this subset of patients may be a challenge to the surgeon. Evaluation of patients with symptoms of nasal obstruction should include a combination of a patient-reported assessment of nasal breathing and at least one objective method for measuring nasal airflow or nasal airway resistance or dimensions. This will allow distinction between patients with symptoms of nasal obstruction and low airflow or high nasal airway resistance and patients with similar symptoms but whose objective evaluation demonstrates normal nasal airflow or normal airway dimensions or resistance. Patients with low nasal airflow or high nasal airway resistance will require treatment to increase nasal airflow as a necessary step to improve symptoms, whereas patients with normal nasal airflow or nasal airway resistance will require a multidimensional assessment looking for less obvious causes of impaired nasal breathing sensation. [ABSTRACT FROM AUTHOR]

Measuring nasal airflow and nasal breathing has been a major goal of rhinology. Many objective methods for measuring nasal airflow or nasal airway resistance or dimensions provide valuable data but are time-consuming and require expensive equipment and trained technicians, thus making these methods less practical for clinical practice. Peak nasal inspiratory flow (PNIF) measurement is fast, unexpensive, noninvasive, and able to provide an objective evaluation of nasal airflow in real-time. Unilateral PNIF measurements allow separated evaluation of each side of the nasal airway and may prove particularly useful when clinical assessment detects significant asymmetry between both nasal cavities. PNIF measurements are most useful for assessing changes in nasal airflow achieved by any form of therapy, including surgical treatment of the nasal airway. These measurements generally correlate with other objective methods for nasal airway evaluation, but not unequivocally with patient-reported evaluation of nasal breathing. Nevertheless, as low PNIF values prevent the sensation of a suitable nasal breathing, PNIF measurement may also prove useful to optimize the decision of how to best address patients with complaints of nasal airway obstruction. [ABSTRACT FROM AUTHOR]

The mechanisms underlying bat and bird activity peaks (attraction) or losses (avoidance) near wind turbines remain unknown. Yet, understanding them would be a major lever to limit the resulting habitat loss and fatalities. Given that bat activity is strongly related to airflows, we hypothesized that airflow disturbances generated leeward (downwind) of operating wind turbines–via the so-called wake effect–make this area less favorable for bats, due to increased flight costs, decreased maneuverability and possibly lower prey abundance. To test this hypothesis, we quantified Pipistrellus pipistrellus activity acoustically at 361 site-nights in western France in June on a longitudinal distance gradient from the wind turbine and on a circular azimuth gradient of wind incidence angle, calculated from the prevailing wind direction of the night. We show that P. pipistrellus avoid the wake area, as less activity was detected leeward of turbines than windward (upwind) at relatively moderate and high wind speeds. Furthermore, we found that P. pipistrellus response to wind turbine (attraction and avoidance) depended on the angle from the wake area. These findings are consistent with the hypothesis that changes in airflows around operating wind turbines can strongly impact the way bats use habitats up to at least 1500 m from the turbines, and thus should prompt the consideration of prevailing winds in wind energy planning. Based on the evidence we present here, we strongly recommend avoiding configurations involving the installation of a turbine between the origin of prevailing winds and important habitats for bats, such as hedgerows, water or woodlands. [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]

To study the characteristics of nasal airflow in the presence of nasal cycle by computational fluid dynamics. CT scan data of a healthy Chinese individual was used to construct a three-dimensional model of the nasal cavity to be used as simulation domain. A sinusoidal airflow velocity is set at the nasal cavity entrance to reproduce the breathing pattern of a healthy human. There was a significant difference in the cross-sectional area between the two sides of the nasal cavity. Particularly, the decongested side is characterized by a larger cross-section area, and consequently, by a larger volume with respect to the congested side. The airflow velocity, pressure, and nasal resistance were higher on the congested narrow side. The temperature regulation ability on the congested narrow side was stronger than that on the decongested wider side. During the nasal cycle, there are differences in the nasal cavity function between the congested and decongested sides. Therefore, when evaluating the impact of various factors on nasal cavity function, the nasal cycle should be considered. [ABSTRACT FROM AUTHOR]

Mycotoxin production by aflatoxin B1 (AFB1) -producing Aspergillus flavus Zt41 and sterigmatocystin (ST) -hyperproducer Aspergillus creber 2663 mold strains on corn and rice starch, both of high purity and nearly identical amylose-amylopectin composition, as the only source of carbon, was studied. Scanning electron microscopy revealed average starch particle sizes of 4.54 ± 0.635 µm and 10.9 ± 2.78 µm, corresponding to surface area to volume ratios of 127 1/µm for rice starch and 0.49 1/µm for corn starch. Thus, a 2.5-fold difference in particle size correlated to a larger, 259-fold difference in surface area. To allow starch, a water-absorbing powder, to be used as a sole food source for Aspergillus strains, a special glass bead system was applied. AFB1 production of A. flavus Zt41 was determined to be 437.6 ± 128.4 ng/g and 90.0 ± 44.8 ng/g on rice and corn starch, respectively, while corresponding ST production levels by A. creber 2663 were 72.8 ± 10.0 µg/g and 26.8 ± 11.6 µg/g, indicating 3–fivefold higher mycotoxin levels on rice starch than on corn starch as sole carbon and energy sources. Key points: • A glass bead system ensuring the flow of air when studying powders was developed. • AFB1 and ST production of A. flavus and A. creber on rice and corn starches were studied. • 3–fivefold higher mycotoxin levels on rice starch than on corn starch were detected. [ABSTRACT FROM AUTHOR]

For people with respiratory disorders who need additional oxygen therapy, oxygen concentrators are vital medical equipment. By concentrating oxygen from the ambient air, they function to give the user a greater flow of oxygen-enriched air. The application of lithium zeolite for oxygen concentration in POCs is the most intense part of this work. One kind of zeolite material that may selectively absorb nitrogen from the air to increase oxygen concentration is lithium zeolite. The capacity, effectiveness, and dependability of a POC fitted with lithium zeolite are all examined in this study, along with its overall performance. The findings show that lithium zeolite, which has benefits including high oxygen purity and low energy consumption, is a potential material for use in POCs. The results of this study aid in the creation of POCs for oxygen therapy that are more effective and efficient. This study suggests utilizing an Arduino microcontroller and an HX710B air pressure sensor to measure the oxygen flow rate in a POC. The POC's oxygen flow channel incorporates the HX710B sensor to monitor pressure variations, which the Arduino uses to translate into flow rate readings. To verify the accuracy and dependability of the system, its performance is assessed under different flow rate scenarios. Lithium zeolites are well-known for having a high selectivity for nitrogen adsorption, which can enhance the concentrator's oxygen separation process's effectiveness. Lithium-zeolite-based oxygen concentrators may have a lower environmental effect than standard concentrators. [ABSTRACT FROM AUTHOR]

Leaf gas-exchange measurements are useful in assessing plant environmental responses. However, uncertainties in the leaf gas-exchange model potentially limit its application. The main challenge in the model-dependent calculations is to detect violations of assumptions. Here, we developed a system that integrates into one instrument the direct measurement of leaf intercellular CO2 concentration and the standard open-flow (OF) and novel open-diffusion (OD) systems for flux measurement. In the OD system, a gas-permeable membrane between the leaf ambient air and outside air creates CO2 and H2O differentials, rather than the air flow in the OF chamber. We measured hypostomatous and amphistomatous leaves of several species with different photosynthetic capacities [sunflower (Helianthus annuus), grape (Vitis vinifera), lemon (Citrus limon), and cherry (Prunus avium)]. The CO2 and H2O differentials in the OD system strictly depend on the flux measured by the OF system. The lower permeability of the membrane resulted in a larger differential per flux, indicating that the OD system can increase the resolution for a small flux. An analysis of the conductance model along with observations suggested that cuticle and leaf intercellular conductances and the unsaturation of leaf humidity contributed to discrepancies between the direct measurement and standard calculation. The combined system developed here provides an opportunity to address these overlooked concepts in leaf gas exchange. [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]

Formaldehyde (HCHO) is a widespread air pollutant in the indoor environment. Previous studies have shown that some bacteria have potential application to remove indoor HCHO. The purpose of this study is to evaluate the effectiveness of Methylobacterium sp. strain R1 (S-R1) in removing formaldehyde (HCHO) from indoor air using biofilters. Three experiments confirmed S-R1's ability to degrade HCHO in the air, with 13C-NMR analysis revealing its involvement in the metabolic process. Optimal biofilter parameters, including 35 sponge layers, 30% humidity, and 9.50 m3/min air flow, resulted in a removal efficiency of up to 90% and an elimination capability of 24111-27000 μg/(m3 ∗ h) during a 60-minute test period. Long-term (31-day) operation of the biofilter with the optimal parameters effectively reduced HCHO levels from 1.60 mg/m3 to 0.02-0.03 mg/m3, below China's national standard, and maintained this level. Fluorescence microscope observation and downstream gas detection revealed stable S-R1 cell numbers and no bacterial leakage, respectively. Two conclusions can be drawn: (1) S-R1 is effective in removing HCHO in polluted air and (2) with optimum parameters, the S-R1 biofilter is engineering effective in purifying the indoor air environment. [ABSTRACT FROM AUTHOR]

Due to its superior insulating qualities, SF6 gas is extensively used in the power sector. However, because of its poor environmental protection properties, finding ecologically acceptable insulating gas has become a critical challenge in the power sector in the context of pursuing green electricity. This work simulates the arc-quenching performance of a gas mixture of CF3I and CO2, which is thought to be a workable substitute for SF6 gas. The COMSOL software is used to build a two-dimensional model of a single-pipe arc-quenching chamber based on the concepts of magnetohydrodynamics (MHD) theory. The lightning impulse current is made by applying electrical stimulation to pure CO2 gas, gas mixtures with 10% CF3I and 90% CO2, and gas mixtures with 30% CF3I and 70% CO2 in the single-pipe arc-quenching chamber. During the first stage of arc formation, the results show that CF3I/CO2 gas mixtures with 10% and 30% CF3I have lower electrical conductivity than pure CO2 gas. An 8/20 μs lightning impulse current waveform with a magnitude of 4 kA is used for this observation. The highest airflow velocity for pure CO2 is 1744 m/s, but the mixture of 10%/90% CF3I/CO2 has a maximum airflow velocity of 1593 m/s. The 30%/70% CF3I/CO2 mixture has the highest maximum airflow velocity at 1840 m/s. Airflow velocity increases and the overpressure in the arc-quenching chamber is prolonged when there is a greater concentration of CF3I gas in the gas mixture. Consequently, these factors greatly reduce the duration of the arc-extinguishing time. The arc-quenching chamber's overpressure is extended when the amount of CF3I gas in the gas mixture is increased, which increases the velocity of the airflow. As a result, these factors significantly decrease the duration of the arc-extinguishing time. [ABSTRACT FROM AUTHOR]

The COVID-19 pandemic brought to the surface the critical qualities of air – airflow, ventilation, particulates etc. – in relation to the well-being of people living in high-rise. Engineering and architectural research has burgeoned in response. However, in focusing on models of airflow, ventilation and particulates as discrete variables, engineering and architectural discourse fails to capture the diverse ways that air enters into and shapes the everyday lived experience of high-rise dwelling. Drawing on research in Sydney's Southwestern suburbs, we reveal high-rise as an assemblage that links apartment dwelling with air, via car-dependent suburbanisation, pollution and climate-change induced temperature extremes in the Anthropocene. In addition to viruses, air teems with carbon, insects, noise and pollutants, while viscerally mediating human encounters with fluctuating temperatures. Multiple relations between people, buildings and air unfold simultaneously, confounding attempts to account for air's elemental milieu through single variables like greenhouse gas or COVID-19. While embedded in relations of power, high-rise assemblages unleash vernacular adaptation that through low-tech and low-cost technologies work to connect suburban high-rise with evolving ecological systems. Recognising the pharmacological quality of air, as both 'poison' and 'cure', we contrast models of high-rise as encapsulated environments with resident (and other) experiments that orient high-rise to the elements, and the interlinked challenges of urban living in the Anthropocene. [ABSTRACT FROM AUTHOR]

Accurate air traffic flow prediction assists controllers formulate control strategies in advance and alleviate air traffic congestion, which is important to flight safety. While existing works have made significant efforts in exploring the high dynamics and heterogeneous interactions of historical air traffic flow, two key challenges still remain. (1) The transfer patterns of air traffic are intricate, subject to numerous constraints and limitations such as controllers, flight regulations, and other regulatory factors. Relying solely on mining historical traffic evolution patterns makes it difficult to accurately predict the constrained air traffic flow. (2) Weather conditions exert a substantial influence on air traffic, making it exceptionally difficult to simulate the impact of external factors (such as thunderstorms) on the evolution of air traffic flow patterns. To address these two challenges, we propose a Spatiotemporal Knowledge Distillation Network (ST-KDN) for air traffic flow prediction. Firstly, recognizing the inherent future insights embedded within flight plans, we develop a "teacher-student" distillation model. This model leverages the prior knowledge of upstream-downstream migration patterns and future air traffic trends inherent in flight plans. Subsequently, to model the influence of external factors and predict air traffic flow disturbed by thunderstorm weather, we propose a student network based on the "parallel-fusion" structure. Finally, employing a feature-based knowledge distillation approach to integrate prior knowledge from flight plans and extract meteorological features, our method can accurately capture complex and constrained spatiotemporal dependencies in air traffic and explicitly model the impact of weather on air traffic flow. Experimental results on real-world flight data demonstrate that our method can achieve better prediction performance than other state-of-the-art comparison methods, and the advantages of the proposed method are particularly prominent in modeling the complicated transfer pattern of air traffic and inferring nonrecurrent flow patterns. [ABSTRACT FROM AUTHOR]