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Ultrasonic gas flowmeters employ non-intrusive measurement techniques, characterized by rapid responsiveness and exceptional anti-interference capabilities. These attributes not only minimize disruption to the gas during measurement but also facilitate dynamic process control while ensuring robust performance under complex operational conditions. This paper provides an overview of the key components of ultrasonic gas measurement systems, briefly summarizing the fundamental principles of commonly used measurement methods. After focusing on the evolution of transducer structures and materials within ultrasonic probes, it categorizes different types of transducers and outlines the latest designs of excitation circuits in both hardware and software. The review also critically assesses the determination of echo signal reception characteristics and the accuracy and effectiveness of time-of-flight calculations. Based on innovative analyses of the critical nodes within the measurement system's components, a framework system is established for corresponding measurement scenarios. The measurement results show that the repeatability error of the new transducer remains below 0.3%. The optimized signal processing method expands the measurable flow range to 30–1200 m3/h, and the zero drift is reduced to approximately half of the system's original zero drift. This paper aims to provide clear guidance for researchers and professionals in related industries, enabling them to conduct more in-depth studies based on their research interest and enhancing their understanding of ultrasonic measurements. [ABSTRACT FROM AUTHOR]

The main problem considered here is how the obstacle embedded in a gas flow can organize self-protection, by means of surrounding gas, against the gas flow and fluctuations. We show that this is possible in the regime of the nonlinear dynamical screening, which is a result of the nonequilibrium transition that is accompanied by the emergence dense gas phase ahead of the obstacle due to blockade effect in a gas, the emergence of local invariants (invariant behavior of obstacle state that becomes insensitive to the main system parameters), spatial localization of induced gas fluctuations near gas domain wall. As a result, the domain wall in a gas, instead of obstacle, becomes the main scatterer of the flow and protects obstacle state against external driving noise and fluctuations. This can be associated with nonequilibrium protection effect. Considered effects are closely related with skin- and edge-correlation ones inherent to non-Hermitian systems. To demonstrate these phenomena, we resort to the limiting case of the two-component lattice gas in a narrow channel with ring geometry. To describe the nonlinear nonequilibrium steady-state gas structures and long-time gas fluctuations near them, the local equilibrium approach and the mean-field approximation are used. [ABSTRACT FROM AUTHOR]

In the production of castings, intrusive gas pore represents a kind of common defects which can lead to leakage in high gas-tightness requirement castings, such as cylinder blocks and cylinder heads for engines. It occurs due to the intrusion of gases generated during the resin burning of the sand core into castings during the casting process. Therefore, a gas generation and flow constitution model was established, in which the gas generation rate is a function of temperature and time, and the flow of gas is controlled by the gas release, conservation, and Darcy's law. The heat transfer and gas flow during casting process was numerically simulated. The dangerous point of cores is firstly identified by a virtual heat transfer method based on the similarity between heat transfer and gas flow in the sand core. The gas pores in castings are predicted by the gas pressure, the viscosity and state of the melt for these dangerous points. Three distinct sand core structures were designed and used for the production of iron castings, and the simulated gas pore results were validated by the obtained castings. [ABSTRACT FROM AUTHOR]

This study explores the low-temperature synthesis of graphene using plasma-enhanced chemical vapor deposition (PECVD), emphasizing the optimization of process parameters to achieve controlled growth of pristine and hydrogenated graphene. Graphene films were synthesized at temperatures ranging from 700 °C to as low as 400 °C by varying methane (25–100 sccm) and hydrogen (25–100 sccm) gas flow rates under 10–20 mBar pressures. Raman spectroscopy revealed structural transitions: pristine graphene grown at 700 °C exhibited strong 2D peaks with an I(2D)/I(G) ratio > 2, while hydrogenated graphene synthesized at 500 °C showed increased defect density with an I(D)/I(G) ratio of ~1.5 and reduced I(2D)/I(G) (~0.8). At 400 °C, the material transitioned to a highly hydrogenated amorphous carbon film, confirmed by photoluminescence (PL) in the Raman spectra. Atomic force microscopy (AFM) showed pristine graphene with a root mean square roughness (Rq) of 0.37 nm. By carefully adjusting PECVD synthesis parameters, it was possible to tune the surface roughness of hydrogenated graphene to levels close to that of pristine graphene or to achieve even smoother surfaces. Conductive AFM measurements revealed that hydrogenation could enhance graphene's contact current under specific conditions. The findings highlight the role of PECVD parameters in tailoring graphene's structural, morphological, and electronic properties for diverse applications. This work demonstrates a scalable, low-temperature approach to graphene synthesis, offering the potential for energy storage, sensing, and electronic devices requiring customized material properties. [ABSTRACT FROM AUTHOR]

Medical air-compression nebulizers deliver atomized medication to the lungs, providing rapid and painless treatment for respiratory diseases. However, the size of most atomized droplets is around 10 μm, limiting drug deposition in the lower airways and alveoli, with increasing the proportion of sub-5 μm droplets remaining challenging. In this work, finite element analysis was employed to model the effects of gas flow rate, liquid channel width, and broken baffle structure on droplet size distribution, aiming to optimize structure symmetrical parameters and operating conditions. A novel compression atomizer was developed and experimentally evaluated, incorporating an improved symmetrical structure for the crushing baffle. Following this modification, the proportion of sub-5 μm droplets increased from 54.6% to 59.25%, representing a 4.65% enhancement in the generation of sub-5 μm droplets. The effects of gas flow rate and liquid concentration on droplet size distribution were systematically investigated to further optimize the atomization performance. The results demonstrated a significant increase in the proportion of sub-5 μm droplets, thereby enhancing drug delivery efficiency to the lower respiratory tract and improving treatment efficacy for respiratory diseases. [ABSTRACT FROM AUTHOR]

Hydraulic fracturing changes the stress state of the coal body, and the residual water within the coal body after fracturing affects its permeability characteristics. To examine the impact of hydraulic measures on the permeability of coal under varying water contents and radial stress distributions, permeability tests were conducted using the improved LFTD1812 triaxial permeameter. The flow rate of coal under different water content combinations was measured, and the permeability, pressure gradient, and seepage velocity of the samples were calculated. The relationships among porosity, permeability, pressure gradient, and seepage velocity were analyzed. The effect of water content on permeability was evaluated, and the directional behavior of permeability was identified. The results showed that the porosity of the samples with water contents of 25%, 17.5%, and 10% decreased by 48.5%, 23.9%, and 17.6%, respectively, during the loading process. The permeability of all samples ranged from 1.91 × 10−13 m2 to 76.91 × 10−13 m2. As the absolute value of the pressure gradient increased, the downward trend of permeability was categorized into three stages: rapid, slow, and stable. Higher water content corresponded to lower initial permeability, with the permeability–pressure gradient curve shifting downward. Additionally, the slow decline zone moved to the right, and the absolute value of the pressure gradient required to enter this zone decreased. Seepage velocity consistently decreased with increasing water content across all osmotic pressure levels, although the rate of decline progressively weakened. The maximum permeability difference between the forward and reverse samples was 10.48 × 10−13 m2. Permeability directionality decreased with increasing equivalent water content and osmotic pressure, with water content identified as the primary influencing factor. Permeability variations caused by axial compression were divided into three phases: the weak influence of the polarization effect, the transition phase, and the strong influence phase. These findings confirm that water content has the most significant impact on permeability, demonstrating that gas flow primarily follows the principle of distance priority toward the nearest borehole. Boreholes closer to the source exhibit higher extraction volumes. These results provide theoretical support for improving coal permeability, enhancing gas drainage efficiency, and preventing gas accidents through hydraulic measures. [ABSTRACT FROM AUTHOR]

A large number of publications have been devoted to the study of aerosol atmospheric transport, but the low-temperature transfer of metals and metalloids as a part of gas flow remains poorly understood. The present work is devoted to the study of gas stream composition using an approach based on the collection of nascent condensate upon cooling of the air flow formed over the surface of contaminated sites. A special laboratory unit was designed to collect the condensate followed by the study of its composition using atomic emission and mass spectrometry. The main novelty of this work consists of the application of the single-particle ICP‒MS technique to obtain qualitative information concerning the state of the elements in the condensates. Gold and silver are most likely present in the samples as nanoparticles; arsenic, selenium, tin and lead are present both as nanoparticles and as soluble forms; and barium and mercury are present only in soluble forms. The condensed phase contains As, Hg, Au, Ag, Pb and Sn at the ppb level, while the main elements of the tailings material (Fe, Ba, Cu, Zn and others) are present at the ppm level, which exceeds the background concentration. [ABSTRACT FROM AUTHOR]

To investigate which breathing systems are available and why they are selected in dogs weighing 5–10 kg. Anonymous online voluntary open survey. An online survey, designed following CHERRIES guidelines, was advertised through the American College of Veterinary Anesthesiologists - List, Association of Veterinary Anaesthesia and European College of Veterinary Anaesthesia and Analgesia (February–March 2022). A convenience sample was taken. Of the 256 responses received, 138 were completed. This included (n responses received) veterinarians (107) and veterinary nurses or technicians (29) actively involved in the anaesthesia of dogs. The most prevalent breathing systems available to respondents were circle (99%), coaxial Bain (79%) and modified Ayre's T-piece (with adjustable pressure limiting valve) (72%). When recommending a dog weight range suitable for the use with these systems, respondents advised a median (interquartile range) from 5 (3–10) to 100 (100–100), 3 (0–8) to 20 (10–33) and 0 (0–0) to 10 (7–10) kg, respectively. Respondents agreed or strongly agreed that important factors in selecting a breathing system were the fresh gas flow requirement (92%), dog weight (91%), resistance (83%) and environmental pollution (79%). In clinical scenarios based on 5–10 kg dogs, the circle system was chosen by 58% for a thin and 77% for a keel-chested versus 44% for an obese and 66% for a barrel-chested dog, respectively. The circle system is the most commonly available breathing system. The minimum weight limit used for the circle system is less than that reported by previous surveys. Several factors influence the choice of breathing system other than dog weight. [ABSTRACT FROM AUTHOR]

This study investigates the structure and photodetector properties of MoO3-x/p-Si heterojunction grown by reactive DC magnetron sputtering in varying O2/Ar gas flow rates. The X-ray diffraction study revealed the presence of α-MoO3 and sub-oxide phases Mo5O14 with the predominance of α-MoO3 observed in all thin films. It was observed that the prepared samples showed high transmittance values of about 80%. The FESEM images showed that the prepared samples have flake-like structures. An increase in oxygen content resulted in a compact/dense morphology and a noticeable decrease in the size of the grains. The best performance of the photodiodes is achieved by the sample (O2/Ar = 3/12), which has better crystal quality and a low dark saturated current density (0.06 μA/cm2) compared to others. This sample shows the greatest photoresponse ratio (ILight/IDark) of 569 and 812 when exposed to UV and IR light. The MoO3/p-Si heterojunction device demonstrates rapid switching properties, with fast rise and decay times in the 7–32 ms range. [ABSTRACT FROM AUTHOR]

In the present work, heat transfer dynamics between the substrate and the deposited metal is investigated to assess its effect on the evolution of defects and the quality of the product. A series of experiments involving the deposition of Al4043 wire were conducted on Al4043 aluminum alloy substrate at a voltage range of 13–19 V. A one‐dimensional inverse computational model was adopted to estimate the heat flux transients. The metal/substrate interfacial heat flux was correlated with the microstructure evolution during the solidification of the metal. The experimental results clearly indicated that heat transfer plays a dominant role in the final finish and quality of the product and is controlled by variables, such as voltage, gas flow rate (GFR), wire feed rate (WFR), and forward traversal speed. At an integral heat flow (HF) in the range of 3000–5000 kJ/m2 corresponding to voltages between 13.8 and 14.5 V, argon GFR of 12–15 L/min, and a WFR of 4.1 mm/min, the porosity in the additively manufactured component was found to be minimum. The ultimate tensile strength was found to be 65 and 76 MPa, corresponding to the voltage of 13.5 and 14.5 V, respectively, and decreased to 25 MPa for a higher voltage of 19 V. At the GFR range of 8–10 L/min, the HF was in the range of 450–510 kJ/m2 with increased porosity (33%–42%). Porosity was found to decrease (15%–22%) with 12–15 L/min range of GFR and the corresponding HF was in the range of 700–950 kJ/m2. The specimens fabricated under these optimal parameters exhibited superior mechanical properties. [ABSTRACT FROM AUTHOR]

The Fourier's law of heat conduction becomes invalid in extreme conditions, such as the second sound in solids and anomalous heat conduction in nanosystems. The objective of the present analysis is to investigate the novel thermoelastic interaction for a homogeneous rod build up of a permeating material which is in contact with the boundary plane. In the context of nonlocal elasticity theory, the constitutive relations for the current problem have been framed on taking into account the mechanical damage. In order to address the non-Fourier heat conduction phenomena for thermomass gas flow, heat transport equation for the present problem has been constructed based on a new theory of generalized thermoelasticity for thermomass gas flow assimilating low velocity and linear resistance based on the generalized non-Fourier theory of heat conduction with memory responses. The left boundary of the rod is thermally shocked as directed and is traction-free. Laplace transform technique has been used to solve the governing equations while the inversion of the Laplace transform has been carried out using the method of Zakian. The numerical computations have been performed for various values of damage parameter to reveal significant effect of various parameters such as nonlocal parameter and time-delay parameter. Also, the rising of delay-time of the heat transport retains a longer history of past deformation of the system. Moreover, the nonlocal theory proposes more information about the medium in contrast with the macroscopic one, and consequently, magnitude of the thermophysical quantities reduces in such situation. [ABSTRACT FROM AUTHOR]

Condensation heat transfer enhancement technology is an important problem for heat exchangers. The air-steam condensation inside a vertically enhanced tube with concave and convex surfaces is analyzed numerically, and the effects of relevant parameters on thermohydraulic performance are discussed. The numerical results show that the drop in steam and temperature between the inlet and outlet is improved by 53.8% and 96.8%, respectively, compared with smooth tubes. In the condensation process, the noncondensable gas accumulates near the wall, which leads to the deterioration of condensation. The structures of concave and convex surfaces disrupt the boundary layer flow and noncondensable gas film and promote flow mixing, leading to enhanced condensation heat transfer. All the numerical results provide guidance values for heat transfer enhancement technology in the applications of condensers. [ABSTRACT FROM AUTHOR]

A novel modeling and new irreversibility analysis of non-homogeneous charged gas flow is presented as an extension and further development of our previous article [J. Non-equilibrium. Thermodyne. 49 (2024), 1–21]. We study the non-equilibrium irreversible thermodynamics (NIT) properties of the exact solution to the dilute non-homogeneously charged gas problem with unsteady Rayleigh flow. In contrast to previous research, the charged gas is non-homogeneous under the influence of induced electromagnetic forces, the flat plate moving damping with time, and the effect of positive ions is considered, leading to significant advancements in understanding natural plasma dynamics. We are solving eight non-homogeneous partial differential equations (PDE). We used a Laplace transformation technique and small parameters methods. To the best of our knowledge, as two new scientific achievements, we introduced a new mathematical model for a mixture of charged gas to calculate the thermodynamic forces, kinetic coefficients, and fluxes variables, see Appendices. Second, we present a fantastic new technique by a flowchart to identify the equilibrium time of multi-component plasma step-by-step using the velocity distribution function (VDF). We indicate that electrons, which are faster lighter components, reach equilibrium faster than slower heavier components. A standard laboratory argon plasma model is used to apply the results. [ABSTRACT FROM AUTHOR]

This paper presents a study on the removal of CO2 gas from gas mixture (CO2/N2) of 14% CO2 using adsorption onto zeolite 13X in a fluidized bed at 298 K and 1 atm pressure. The effects of static bed height (5–25 cm) and rate of flow of the gas mixture (6–14 L/min) on the breakthrough time were studied. The desorption of CO2 was performed by absorbing the adsorbed CO2 molecules using NaOH solution (0.1 M). The absorption process which was accompanied with chemical reaction achieved two objectives. The first was converting CO2 gas into a valuable substance (Na2CO3) which could be used in many industries. The second was the storage of CO2 gas in what was called a chemical carrier which could emit the gas when it was needed. The effect of static bed height (5–25 cm) on the absorption process in the fluidized bed was also studied. For the adsorption process, the results showed that the breakthrough time increased with decreasing the flow rate but with increasing the static bed height. In the desorption process, the total amount of absorbed CO2 molecules was 396 mg, achieving a recovery of 90.8% at 5 cm static bed height. HIGHLIGHTS: Studying the adsorption in a fluidized bed. Using breakthrough curve to estimate the adsorbed amount of CO2. Studying the effects of operational parameters on the breakthrough time. Performing the desorption by absorption process. Recovering the adsorbed CO2 molecules. [ABSTRACT FROM AUTHOR]

The objective of this research is to examine the impact of welding parameters on the surface roughness, hardness, and tensile strength of welds produced by a single-pass TIG welding process in austenitic stainless-steel plates (AISI 316L). Furthermore, the optimal processing variable settings will be identified in order to provide the highest levels of hardness, lowest levels of surface roughness, and highest levels of tensile strength. This study focuses on three parameters: arc current, voltage, and shielding gas flow rate, which were altered across three levels. A large number of tests were carried out on 3-mm thick AISI 316L stainless steel plates in order to determine the efficient and realistic operating limits of TIG welding settings. The welding process parameters' operational limitations were determined by visual examination and bead shape. The values of current are taken as 100, 125, and 150 (A); voltage as 16, 18, and 20 (V); and gas flow rate as 6, 9, and 12 (L/min). Their impact on tensile strength, microhardness, and surface roughness was inspected. The experiments were conducted using Taguchi L9 orthogonal array (OA). Each input parameter was found to have an impact on the response. The optimized welding parameters for improved mechanical properties and surface roughness were identified. The results indicated an optimum tensile strength, 624.92 MPa, achieved at the parametric combination of 100 A current, voltage of 16 V, and gas flow of rate 6 L/min. The microhardness results indicated an optimum value, of 319.2 HV, achieved at the parametric combination of a current of 125 A, 16 V of voltage, and a gas flow rate of 9 L/min. A minimum surface roughness, 7.33 µm, was attained at 125 A current, voltage of 16 V, and gas flow rate of 9 L/min. These results highlight the significant impact of welding parameters on the mechanical properties and surface roughness of AISI 316L stainless steel welds. [ABSTRACT FROM AUTHOR]

Salt caverns are widely regarded as a suitable option for the underground storage of hydrogen. However, an accurate assessment of the hydrogen leakage through the walls of salt caverns into the surrounding formations remains crucial. In this work, the flow of hydrogen into the surrounding formation is evaluated by assuming that salt rock consists of bundles of tortuous nano-capillary tubes. A formulation was then proposed to model the flow in linear and radial domains. The formulations are based on a newly proposed unified gas flow model that is valid for the entire range of Knudsen numbers and accounts for gas slippage, bulk diffusion, and Knudsen diffusion. A finite-difference approximation with an iterative procedure was then used to treat the nonlinearity and solve the presented formulations. The formulations were validated against the experimental data reported in the literature. The results obtained indicated that for hydrogen flow over a wide range of pore radii and operating pressures and temperatures, the slippage flow regime must be considered. In a salt cavern with relevant dimensions and operating conditions, the cumulative hydrogen leakage after 30 years of cyclic storage was only 0.36% of the maximum storage capacity. It was also noticed that most of the leaked hydrogen would flow back into the salt cavern at times when the pressure in the salt cavern is lower than the surrounding pressure, e.g. during production and subsequent idle times. At low storage pressure and very tight salt rock, diffusion was the most important mechanism for hydrogen transport. At a high pressure though, viscous flow became the predominant leakage mechanism. The presence of a thin interlayer such as mudstone, carbonate, and anhydrite in the body of the salt rock can have a significant impact on the amount of leakage. It appeared that although increasing the maximum operating pressure from 120 to 135 bar only led to an 11.9% increase in the maximum storage capacity, the hydrogen loss increased significantly from 0.007% at 120 bar to 0.36% at 135 bar. Furthermore, although the absolute leakage rate for natural gas storage was higher than that for hydrogen storage, the relative leakage rate in relation to the maximum salt cavern capacity was much lower. The leakage range was also lower for natural gas storage compared to hydrogen storage. The formulations presented and the results obtained in this study can help to have a better understanding of the salt caverns when it comes to large-scale hydrogen storage. [ABSTRACT FROM AUTHOR]

In this study, Au nano-particles--CdS quantum dot was synthesized and introduced as a new nanocomposite adsorbent for extraction and pre--concentration of rabeprazole (RAB). The drug analyte was quantitatively retained by the adsorbent from the large volume of real samples. The desorbed RAB was determined using ion mobility spectrometry with a corona discharge ionization source. Under instrumental optimum conditions (drift voltage: 6700 V, corona voltage: 2200 V, drift gas flow rate: 600.0 ml min-1, carrier gas flow rate: 300.0 ml min-1, injection port temperature: 220 ºC, cell temperature: 180 ºC and pulse width: 100 µs) RAB was determined in the range of 0.1-25.0 ng including two linear segments. The limit of detection was 0.03 ng and also limit of quantitation was found to be 0.1 ng. The precision values (RSDs%) were 7.8% and 6.9% for 1.0 and 10.0 ng of RAB, respectively. Finally, the developed method was applied for the determination of RAB in biological (human urine and serum) and pharmaceutical (tablet) samples with satisfactory recovery results. [ABSTRACT FROM AUTHOR]

Background and Aims: Priming the breathing circuit with a volatile agent plays a major role in inhalational induction. It depends on the fresh gas flow rate (FGF), concentration setting of the volatile agent, and time taken to attain the desired end-tidal concentration. The aim of the study is to compare ventilator-assisted priming (VAP) and a passive priming technique using different fresh gas flows (FGFs) in neonatal, pediatric, and adult anesthetic circuits with sevoflurane vaporizer. Methodology: An exploratory study was conducted on a single Datex ohmeda GE Inc. workstation using three different circuits. In both techniques, FGF with 100% oxygen and 8% sevoflurane vaporizer concentration was set at 2 L/min, 4 L/min, and 8 L/min corresponding to their three groups FGF-2, FGF-4, and FGF-8, respectively. The time taken to achieve 6% sevoflurane concentration at the patient end of the circuit was measured. In this study, we have explored various combinations of tidal volumes, respiratory rates with three different fresh gas flows, and their priming time with sevoflurane consumption. Results: The minimum time required to prime neonate, pediatric, and adult circuits using the ventilator-assisted technique to attain end-tidal sevoflurane 6% is 29 seconds, 39 seconds, and 61 seconds with 2 L/min FGF. Their corresponding sevoflurane consumptions are 0.25 ml for the neonate circuit, 0.78 ml for the pediatric circuit, and 2 ml for the adult circuit. Conclusion: The ventilator-assisted priming technique is an effective and quick method to attain end-tidal sevoflurane 6% with low FGF (2 L/min), low tidal volume (100 ml), maximum respiratory rate (20), and minimal sevoflurane consumption when compared to the passive priming technique. [ABSTRACT FROM AUTHOR]

This study investigated the discharge voltage characteristics of an argon-fed lanthanum hexaboride heaterless hollow cathode to assess the influence of flow rate, discharge current, background pressure, and applied magnetic field strength. Decreasing the flow rate from 15 to 3 sccm led to a considerable increase in discharge voltage and peak-to-peak oscillation, particularly for flow rates below 5 sccm. Subsequently, variation in discharge current was tested at 4–7 A; this test revealed that the discharge voltage decreases from 53 to 48 V as the discharge current increases, while the peak-to-peak oscillation increases by approximately 2 V with the rise in discharge current. At high background pressures (8.1 × 10−4 Torr), the discharge voltage decreased by 15 V, and the peak-to-peak oscillation was maintained at 5 V. Furthermore, the spectral analysis of the discharge voltage indicated the occurrence of high-energy oscillations at 10–500 kHz owing to ionization instability. The discharge voltage decreased when the strength of an externally applied axial magnetic field increased from 0 to 118 G. Such a result can be attributed to increased ionization (caused by the applied magnetic field) in the emitter and cathode-keeper region, thereby decreasing sheath potential on the emitter surface. • Discharge voltage is used as an important parameter for analyzing the cathode performance. • When the gas flow rate decrease, the discharge voltage fluctuation increases. • High background pressure leads to the disappearance of voltage oscillation amplitude variation. • Applying a magnetic field causes a decrease in discharge voltage, and the oscillation of the discharge voltage is suppressed. • The magnetic field reduces discharge voltage by increasing the anode's surface area available for current reception. [ABSTRACT FROM AUTHOR]

One of the important tasks of space flight safety is the ability of a wing to maintain stability in an oncoming turbulent flow. In this case, the spacecraft must move the greatest distance. The paper studies the motion of a thin plate near a boundary in an oncoming flow of rarefied gas. At low Reynolds numbers, the effect of the boundary on the plate is studied, and the possibility of self-propulsion is shown. • The drag force of the plate increases sharply as the distance to the boundary decreases. • The lifting force and moment change from the center of the plate to the boundary decreases. • The point of application of the resultant force shifts to the rear edge of the plate. • Self-motion is possible for plates that have a common rib. [ABSTRACT FROM AUTHOR]

Low-temperature purge significantly impacts the performance of Proton Exchange Membrane Fuel Cell (PEMFC) under cold start condition. To explore the influence of gas blowing on PEMFC at low temperature, first of all, a three-dimensional and multiphase-physical model for a single cell is established. Secondly, the performance impacts of two factors, the water content in proton exchange membrane and the ambient temperature, on PEMFC are analyzed. Then, the influences of gas flow rate, blowing time and gas temperature on water content in membrane are conducted. The results indicate that a higher initial water content in the membrane at a lower start-up temperature shortens the duration of the cold start process. Consequently, it leads to increase cold starting failures. As the gas flow rate increases, the water content in the membrane decreases as the change rate decreases. The water content can be reduced by extending the purging time, but beyond a certain threshold no significant change is observed. Furthermore, the purge gas temperature shows minimal impact on the rate of change of water content. However, as it increases, the water content decreases. In order to balance both the purging effect and energy consumption, the purging flow rate of 1x10-5 kg.s-1 and the purging time of 56 seconds are recommended. [ABSTRACT FROM AUTHOR]

With the improvement of dry gas seal efficiency in high-parameter fields, the flow pattern of gas film lubrication is complicated. Based on gas lubrication theory, the Reynolds equation of compressible gas was established with a bidirectional T-groove dry gas seal as the research object. The Reynolds equation was solved to obtain a modified turbulent film pressure distribution law that affects gas lubrication. The effectiveness of the calculation program was verified by experimental tests. The results show that with an increase in operating parameters, the turbulence effect caused the gas film pressure fluctuation in the T-groove region to intensify, resulting in gas film flow instability. In addition, the inertia effect improved, which slowed down the leakage and affected the change law of stiffness and the rigid leakage ratio. When the fluid speed and gas pressure were low, the inertia effect could be ignored. When the groove depth was increased to 8 μm, the height difference between the trough and non-T-groove region became larger due to the combination of the turbulence and inertia effects. Further, when the gas film thickness was 3 μm, the opening force and gas film stiffness were high due to the dynamic pressure effect in the small film thickness groove. An increase in the gas film thickness weakened the turbulence effect and reduced the gas film pressure fluctuation. [ABSTRACT FROM AUTHOR]

The influence of quartz tube size on the surface distributions of reactive oxygen species (ROS) in model tissue treated with a He + O2 plasma jet was investigated. Gelatin gel was used to construct the model tissue, and a KI-starch color agent was mixed with the model tissue to visualize the distribution of ROS. With increasing quartz tube diameter, the uniformity of the ROS distribution on the model tissue decreased, and the change in the surface distribution area of the ROS on the model tissue over the irradiation distance was quite different for different quartz tube diameters. The surface distribution of ROS on the model tissue was affected mainly by the working gas flow; thus, the diffusion range of the working gas flow on the model tissue surface determined the surface distribution area of ROS on the model tissue. The working gas flow was accelerated, and the diffusion range of the working gas flow on the model tissue surface expanded when the plasma was ignited, resulting from the modification of the working gas flow by the electrohydrodynamic (EHD) effect. The EHD effect on the expansion of the diffusion range of working gas flow on the model tissue was different for different quartz tube diameters, and the effect was determined mainly by the discharge current density of the plasma jet and the plasma propagation length. [ABSTRACT FROM AUTHOR]

Four types of voids exist in shale, including inorganic pores, organic pores, natural fractures, and hydraulic fractures, where the gas flow within is affected by voids sizes, shapes, and the mineral composition surrounding them. It is still a challenge to build an effective multi-scale model for shale by now. A model classifying organic pores and inorganic pores with and without clay was proposed in our previous work by incorporating various testing methods. However, some improvements can be made, including wider the pore size of the model to full-scale and adding the fractures without being considered previously. Therefore, a new model is proposed by integrating an improved full-scale matrix pore network model (PNM) with fractures. That is, the effects of four types of voids, including organic pores, inorganic pores containing clay, inorganic pores without clay, and fractures, on gas flow are all considered in the model. Then, the factors affecting the permeability of the matrix (i.e., without fractures) and the whole model (i.e., with fractures) were analyzed. The results show that connectivity both in small- and large-scale PNM and total organic content facilitate the flow, while clay content and water film thickness hinder the flow, especially within small pores. Fractures along the pressure drop accelerate gas flow, and the fractures perpendicular to the pressure drop only channel the pressure when the fractures along the pressure drop both exist. The model can be applied to other mudstones and shales and studies the fluid migration within them through proper parameters adjustment. [ABSTRACT FROM AUTHOR]

Liquid delivery systems have been commercialized to supply precursors to the atomic layer deposition (ALD) reactor at high flow rates. However, the complicated internal structure of the conventional vaporizer causes a problem of slow flow and temperature deviation. In this paper, we propose a cyclone-type vaporizer with a simple structure to supply ALD precursors in large quantities. We investigated the effect of key design parameters on the gas flow and temperature distribution inside the vaporizer by computational fluid dynamics analysis. The design parameters were optimized by considering the flow velocity distribution, residence time at the bottom, and temperature uniformity inside the vaporizer. In the optimized model, a swirling flow was actively formed to reach the bottom of the vaporizer with high flow velocity. The cyclone vaporizer with optimized design parameters was constructed to test its vaporization performance. The cyclone vaporizer vaporized all the injected CpZr(NMe2)3 at a constant feed rate of 4 g/min. [ABSTRACT FROM AUTHOR]

The prerequisite for rapid and steady development of TMDC-based optoelectronic devices is high efficiency in materials preparation, which relies on a mature synthesis technique and optimized production conditions. Visualization based on numerical simulation, which illustrates the impact of growth parameters on deposited products, is helpful to understand formation mechanisms and modify growth conditions. In this work, we construct two models with two different substrate placements, where the substrate is parallel or perpendicular to gas flow direction. The simulation results show more velocity distribution uniformity across a wider range from −1.4 cm to 1.4 cm for vertically placed (VP) compared to horizontally placed (HP) substrates. The calculated average velocities of 0.048, 0.053, 0.078, 0.137, and 0.391 cm/s along five different positions on the VP substrate are greater than the values of 0.027, 0.026, 0.025, 0.023, and 0.036 cm/s on the HP substrate. Comparing the precursor concentration distributions on both substrates, it is observed that the S molar concentration gradient on both substrates is negligible and the uniform Mo molar concentrations from z = −1.4 cm to 2.0 cm on the VP substrate ensure minimal change in the S/Mo ratio, which contributes to forming single-morphology domains. Furthermore, increasing the distance between the precursor inlets and the VP substrate decreases the amount of molecules on the substrate surface, achieving near-stoichiometry and promoting monolayer deposition. This is verified by the experimental result, which showed gentle morphological transformation on the VP substrate from a truncated triangle to a hexagon, and then back to a truncated triangle. By contrast, the multi-morphology and thickness of MoS2 on the HP substrate result from the complex Mo concentration along the flow direction. Moreover, PL intensities of the MoS2 domains deposited on the VP substrate are enhanced by 11.9-fold compared to the average intensity on the HP substrate. This result indicates the MoS2 grown on the VP substrate has less intrinsic defects than that grown on the HP substrate. The combination of numerical simulation with experimental methods facilitates the visualization of invisible growth conditions, which provides effective guidance for using simulation results for other TMDC materials. [ABSTRACT FROM AUTHOR]

Investigating the imbibition characteristics of coals can yield profound insights for advancing coalbed methane extraction and utilization strategies. However, there has been little exploration of the micro-pore imbibition phenomenon during the two-phase flow of gas and water, as research has focused more on the process of static imbibition. In this study, we used an independently developed low-field nuclear magnetic resonance (NMR) displacement experimental device to conduct a systematic study on the dynamic imbibition phenomenon of low-permeability coals under conditions in which gas and water coexist. The experimental results show that the imbibition process under conditions of gas–water coexistence was significantly influenced by the physical properties of the coal samples, such as the wetting contact angle, porosity, and permeability. A smaller wetting contact angle and lower porosity and permeability values were indicative of a stronger imbibition effect. Meanwhile, changes in effective stress and pore pressure had a significant effect on the imbibition process. Changes in effective stress were observed to elastically compress (or expand) the coal pores, leading to intensified (or weakened) imbibition. Greater pore pressure led to a more violent imbibition reaction. These findings provide a new theoretical basis for understanding and predicting imbibition phenomena in the two-phase flow of gas and water in coalbed methane engineering, offering the potential to illuminate the intricate self-absorption phenomena occurring during CO2 geological sequestration processes. [ABSTRACT FROM AUTHOR]

Aiming at the problem of the cement hydration shrinkage phenomenon, which occurs when cement seals downhole casing in the process of Carbon Capture, Utilization, and Storage (CCUS) technology, this paper proposes a method of sealing the casing by combining threaded casing with bismuth–tin alloy. The effect of different types of grooves (square-, trapezoidal-, and screw-threaded grooves) set on the inner surface of the casing on the gas sealing performance of the alloy plug was analyzed. And the effect of the overlay pressure on the gas sealing performance of the alloy plug during the molding process was analyzed. The experimental results show that under 0.2 MPa overlay pressure, the gas breakthrough pressure values of alloy plugs in square-threaded, screw-threaded, trapezoidal-threaded, and smooth hole casings are 5, 3.7, 2.9, and 1 MPa, respectively. When the pitch in the screw-threaded casing is half of the original, the gas breakthrough pressure value of the alloy plugs in the casing is 4.7 MPa. And after the application of 0.2 MPa overlay pressure, the gas sealing performance of the alloy plugs in the screw-threaded, trapezoidal-threaded, and light hole casings was improved by 220%, 230%, and 100%, respectively. The experimental results show that when the grooves are set on the inner surface of the casing, the gas flow path per unit length of the alloy plug-casing interface is prolonged, and the grooves increase the degree of zigzagging on the inner surface of the casing. The gas sealing performance of the alloy plugs is greatly enhanced. This research can provide theoretical support for the application of downhole Carbon Storage using Sn58Bi in casing. [ABSTRACT FROM AUTHOR]

The design of industrial installations using digital design techniques (digital twin), aligned with the concept of Industry 4.0, provides a tool to optimize maintenance costs, process gas emissions, energy consumption and to reduce the risks associated with production testing. Modern manufacturing plants conduct chemical processes by combining production experience with model-based research. Analyzing processes using advanced digital techniques can replace traditional methods of technological process balancing. The methodology based on the digital twin already serves as a holistic system of process connections, supporting production, research and development, production planning, and quality control. This paper presents the digital design, optimization, and comparison of process data obtained through simulations for two different types of ammonia recovery units in soda ash production using the ammonia–soda process. Using specialized modeling software and relying on historical data, engineering assumptions, and new concepts, virtual models were created in which the material and thermal balances of the process were simulated. This research is divided into two stages. In the first stage, a model-based approach and model optimization techniques are presented, while in the second stage, the preparation of models of the distillation installation is presented, and the influence of various structural parameters of the equipment on the temperature profile and gas flow rate in the ammonia recovery section is discussed. The process of the research method, based on simulations in a virtual environment, allows for evaluating the implementation potential of the proposed concepts, optimizing process parameters, and redefining the approach to conducting chemical processes. A series of simulations conducted in studies on ammonia recovery indicated a potential increase in gaseous ammonia recovery by up to 14.09%, taking into account the type of distillation apparatus or the height of the packing section. [ABSTRACT FROM AUTHOR]

In the quest to design reactors with a higher productivity, their mixing efficiency should be highly improved. The mass transfer coefficient is a parameter that measures the rate of the refining rates and has been extensively investigated in the past; however, most of the correlations developed in steelmaking are based on the effect of the gas flow rate or its alternative form, stirring energy. The gas flow rate can play a big role in mass transfer but there are many more variables involved. This work has investigated the combined effect of five variables on the mass transfer coefficient due to bottom gas injection with two injection devices: the gas flow rate, the radial position and the separation angle of the porous plugs, the slag thickness, and the ladle aspect ratio. A novel expression in a dimensionless form has been developed, which accurately predicts the mass transfer coefficient. The expression proposed indicates that increasing the gas flow rate, the slag thickness, the ladle aspect ratio, and the separation angle also increases the mass transfer coefficient. On the contrary, increasing the radial position away from the center affects mass transfer, especially at high gas flow rates. Based on the experimental data and their practical application, an optimum layout for the injection of gas is suggested to optimize both mass transfer and the mixing intensity of liquid steel. [ABSTRACT FROM AUTHOR]

Silicon tetrafluoride (SiF4), being a toxic gas, contains abundant fluorine and silicon resources. However, at present, the extraction of these resources from SiF4 remains a significant challenge for current technologies. Microwave plasma emerges as a promising technology with considerable potential in this area. Nevertheless, the majority of research endeavors concentrate on the silicon production through microwave plasma treatment of SiF4, while the resultant tail gas, rich in fluorine resources, is neglected and subsequently wasted. In this paper, a low-pressure microwave plasma is employed to process SiF4 and H2 for the one-step synthesis of hydrogen fluoride (HF). The microwave power reflection ratio, electron density, SF4 conversion rate, and produced HF concentration in varying microwave power levels and gas flow rates are obtained. The results demonstrate that all the processing parameters have a direct impact on the HF concentration. The maximum HF concentration of 11,200 ppm is achieved under the specific condition: an H2 flow rate of 2.5 sccm, a SiF4 flow rate of 2 sccm, and a microwave power level of 1100 W. Notably, this condition also results in the lowest energy cost. Moreover, the underlying reaction mechanism of the conversion from SiF4 to HF is thoroughly analyzed. This work presents fundamental process guidance for the production of HF using microwave plasma, facilitating the scalability of this technology in industry. [ABSTRACT FROM AUTHOR]

To reasonably divide the types of flow units along the latticework subchannel, one must prepare for the establishment of a one-dimensional fluid network model of the latticework in the middle region of the turbine blade. The characteristics of the flow structure along the latticework subchannel were studied by numerical simulation. The effects of rib angle (15–45°), the ratio of rib width to rib spacing (0.3–1.0), and inlet Reynolds umber (21,000–80,000) on the flow structure along the subchannel are summarized. The results indicated that the ratio of rib width to rib spacing and inlet Reynolds number had no effect on the distribution position of each flow unit in the subchannel. The change of rib angle did not change the flow structure type along the subchannel. The longitudinal vortex was mainly formed by one turning vortex and two detached vortices. The narrowing of the turning channel will cause the turning vortex to induce a secondary longitudinal vortex. There were five kinds of flow structures along the subchannel: transverse vortex zone (entrance of the inlet section), uniform flow zone (inlet section), longitudinal vortex generation zone (turning channel section), longitudinal vortex zone (turning channel section), and longitudinal vortex free development zone (outlet section). This finding provides support for the selection of empirical formulas for each module in the one-dimensional modeling of subchannels. Finally, the boundary prediction equations of each flow structure in the subchannel were established, and the average prediction error was less than 10%. The rationality of the flow structure division along the latticework subchannel was improved, and the modeling efficiency of the latticework one-dimensional model was optimized. [ABSTRACT FROM AUTHOR]

Gas-liquid flow (GLF), especially slug and annular flows in oil and gas gathering and transportation pipelines, become particularly complex inside elbows and can easily exacerbate pipeline corrosion and damage. In this study, FLUENT was used to conduct 3D simulations of slug and annular flow in elbows for different velocities to assess the ensuing changes in terms of pressure. In particular, the multifluid VOF (Volume of Fraction) model was chosen. The results indicate that under both slug and annular flow conditions, the pressure inside the elbow is lower than the outside. As the superficial velocity of liquid and gas increase, the pressure and liquid flow velocity at different positions of the elbow also increase, while the secondary flow weakens. Under annular flow conditions, the liquid film on the outer side of the elbow is thicker than that on the inner side, and the liquid velocity in the main liquid film zone is the lowest. [ABSTRACT FROM AUTHOR]

The Hudson Oilfield's Donghe sandstone reservoir has multiple independent oil–water systems. The complex oil–water relationship is mainly due to reservoir heterogeneity, especially the sealing and shielding effects of interlayers. This paper uses methods like well logging and test well data interpretation, seismic impedance inversion, and the simulation of oil and gas preferential migration paths. It analyzes and quantifies parameters related to sand layer oil content, physical properties, and the development degree of interbedded layers using small layers as units. Sandstone horizontal transportability has three types. Type I matches structural forms to form preferential migration paths. Type II transportability has enclosed sand bodies that obstruct oil and gas flow and change their migration paths. Unevenly distributed calcareous interbedded layers are the main controlling factor for vertical sand body transportability. Locally continuous cemented calcareous interbedded layers can form the base of a dome-shaped pinch-out lithologic trap in sandstone. The closure area of the trap is controlled by the pinch-out line of sandstone and the distribution of continuous interbedded layers together. [ABSTRACT FROM AUTHOR]

BACKGROUND: This target is to decide power input and gas hold‐up for gas–liquid mixing aqueous CMC solutions. The analysis considers the impact by varying the impeller speed and gas flow rates in a stirred tank bioreactor of three kinds of multiple impellers. The effects of the impeller type, rheology, and operating conditions were investigated on power drawn, relative power demand (RPD), gas holdup, and volumetric mass transfer coefficient. RESULT: Compared to the Rushton turbine (6RT) and 4‐pitch blade (4PBT) impeller, the propeller (3PP) impeller presented a minimal event of the gassing on the RPD. 4PBT impeller has shown a higher gas hold‐up compared to the Rushton turbine and propeller impellers. The aerated agitated tank was established a dimensionless correlation for the RPD as a function of flow number and web number. Besides, the gas–liquid agitated system was also introduced a dimensionless correlation to compute the overall gas hold‐up as a function of specific power consumption. For the maximum dispersion mixing intensity, the impeller structure with low RPD looks to be more adequate. Further, maximizing gas holdup in the structures with high RPD is advantageous. The effects of impeller speed, gas superficial velocity, and rheology on the volumetric mass transfer coefficient were examined. CONCLUSION: The volumetric mass transfer coefficient increased with an increase in impeller speed, gas superficial velocity, and power consumption per unit volume and decreased as rheology increased. The averaged kLa for each multiple‐impeller was correlated well with the specific gassed power consumption and gas superficial velocity. © 2024 Society of Chemical Industry (SCI). [ABSTRACT FROM AUTHOR]

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This study investigates the impact of incorporating an Inner Ring Groove (IRG) on the leakage characteristics of dry gas seals, commonly used in turbomachinery such as gas turbines and compressors. The primary objective is to enhance sealing performance and reduce gas leakage, which is critical for improving the efficiency of these machines. The research focuses on various groove shapes, including spiral grooves for single-direction rotation and T-grooves and tree grooves for bi-directional rotation. The experimental setup involved measuring air leakage rates across different seal configurations, both with and without the IRG. The results indicated that while the IRG increased leakage in spiral groove seals, it significantly reduced leakage in T-groove and tree groove seals. Specifically, the IRG reduced leakage by approximately 26% in T-groove seals and 15.8% in tree groove seals, compared to their standard configurations. Additionally, the study employed Particle Image Velocimetry (PIV) to visualize gas flow within the seal gaps. The visualization revealed that the IRG altered the flow dynamics, particularly in T-groove seals, where it redirected the gas flow from a radial to a circumferential direction, thereby reducing leakage. In contrast, the IRG in spiral groove seals promoted radial flow, leading to increased leakage. These findings suggest that the application of IRGs can be particularly effective in bi-directional rotation seals, offering a potential design modification to enhance sealing performance. The study concludes that while IRGs may not be suitable for all groove types, their strategic application can lead to significant improvements in leakage reduction and overall efficiency of dry gas seals. [ABSTRACT FROM AUTHOR]

ABSTRACT In this study, we employed a nanosecond‐pulsed gear‐cylinder dielectric barrier discharge (DBD) assisted by a perpendicular magnetic field (MF) for toluene degradation. The effects of key discharge and gas parameters, as well as their optimal combinations with the perpendicular MF, on toluene degradation were systematically investigated. The results indicated that the maximum toluene degradation efficiency was achieved under conditions of short pulse rising times and widths, low gas flow velocities, and minimal oxygen concentrations. This optimal performance was attributed to three main factors: high mean electron energy, the generation of appropriate active oxygen species, and an extended residence time for plasma‐toluene molecule interactions. Furthermore, by meticulously adjusting the operational parameters, augmenting the number of magnetized energetic electrons in the perpendicular MF, and intensifying the ionization process, we observed a notable enhancement in both discharge intensity and toluene degradation efficiency. [ABSTRACT FROM AUTHOR]

Respiratory interventions including noninvasive ventilation, continuous positive airway pressure and high-flow nasal oxygen generated infectious aerosols may increase risk of airborne disease (SARS-CoV-2, influenza virus) transmission to healthcare workers. We developed and tested a prototype portable UV-C254 device to sterilize high flows of viral-contaminated air from a simulated patient source at airflow rates of up to 100 l/m. Our device consisted of a central quartz tube surrounded 6 high-output UV-C254 lamps, within a larger cylinder allowing recirculation past the UV-C254 lamps a second time before exiting the device. Testing was with nebulized A/PR/8/34 (H1N1) influenza virus. RNA extraction and qRT-PCR showed virus transited through the prototype. Turning on varying numbers of lamps controlled the dose of UVC. Viability experiments at low, medium and high (100 l/min) flows of contaminated gas were conducted with 6, 4, 2 and 1 lamp activated (single-pass and recirculation were tested). Our data show 5-log reduction in plaque forming units from a single lamp (single- pass and recirculated conditions) at high and low flows. UVC dose at 100 l/m was calculated at 11.6 mJ/cm2 single pass and 104 mJ/cm2 recirculated. The protype device shows high efficacy in killing nebulized influenza virus in a high flow of contaminated air. [ABSTRACT FROM AUTHOR]

The article presents a kinetic model for rarefied gas mixtures with disparate mass, focusing on transport properties and relaxation rates in various flow scenarios. The model is validated against Direct Simulation Monte Carlo (DSMC) simulations, showing accurate predictions of flow characteristics. The research offers valuable insights into the behavior of gas mixtures at the molecular level and provides a reliable approach for studying rarefied gas flows with diverse mass components. [Extracted from the article]

Interference removal in inductively coupled plasma tandem mass spectrometry (ICP-MS/MS) is strongly dependent on the gas selected for use within the collision/reaction cell. There has been little investigation on the effects that reaction gas impurities may have on the resulting spectra. The reactivity of 60 elements was evaluated using nitric oxide (NO 99.5%) with and without a gas purifier to reduce H2O impurities to <100 pptV. Experiments were performed using V, Ce, Tl and Th to investigate the effects of purified NO at various flowrates (0.22–1.49 mL min−1). Purified NO was shown to significantly mitigate oxy-hydride interferences, improve total ion sensitivity (notable at high gas flows), and shift product distributions advantageously. The reduction in oxy-hydride species results in a product distribution favoring the major expected products, where signals were shown to increase by an order of magnitude. Reduced background and increased signal for the major expected products provides avenues for improving various analytical applications of ICP-MS/MS. [ABSTRACT FROM AUTHOR]

The parameters of a glow discharge in helium with a nonuniform distribution of the density of neutral particles along the discharge gap have been calculated for a one-dimensional axisymmetric geometry. This formulation of the problem corresponds to the condition of generating a discharge between a Laval nozzle with a central body, which is the anode, and a ring cathode located coaxially to the central body at low pressures. In this case, a supersonic gas flow is generated through the Laval nozzle, which creates an increased gas pressure near the central body (anode), and high vacuum is maintained outside the supersonic jet. Thus, the internal structure of this discharge will depend on the density of gas particles in different regions of the interelectrode space. It has been established that this method of organizing a glow discharge in a supersonic gas flow makes it possible to control the spatial distribution of the internal characteristics of the discharge. [ABSTRACT FROM AUTHOR]

As an unconventional oil and gas resource, shale gas plays a very important role in global energy supply. A breakthrough in efficient exploitation of shale gas is how to accurately describe the percolation mechanism of shale gas in nano-pores. In this article, a new shale gas apparent permeability model is established on the basis of advection diffusion model and considering adsorption stress effect and gas viscosity correction. On this basis, the influence factors of apparent permeability, the comparative difference between stress effect or not and viscosity correction or not, and the contribution of gas flow mechanism are studied. The results show that: the apparent permeability decreases with the increase of pressure, increases with the increase of pore radius, and increases with the increase of temperature; when the pore radius increases, the difference caused by stress correction becomes obvious; when the pressure decreases, the difference caused by viscosity correction becomes obvious. The results can provide some new ideas and methods for the study of gas flow mechanism in microscopic nano-pores. [ABSTRACT FROM AUTHOR]

It is widely established that the electroreduction of carbon dioxide on a copper surface yields a spectrum of alcohols and hydrocarbons. But the selectivity of Cu toward a certain product is extremely poor as it forms a variety of reduced products concurrently. Controlling selectivity and overall performance depends on the modification of the Cu site and local environment. This study depicts how the product selectivity can be switched from C1 to C2 and multicarbon products by systematic incorporation of secondary metal (Pd) into the Cu lattice. Upon releasing the structural ordering from intermetallic to alloy and then to bimetallic, a systematic enhancement on the formation of C2 products from CO2 has been observed. Real‐time in situ X‐ray absorption spectroscopy (XAS) study showed the potential dependent evolution of Pd─Cu and Cu─Cu bonds in different Pd‐Cu‐based catalysts. The detailed analysis of in situ IR and Raman also determined the adsorbed intermediate species and helped to identify the mechanism. Computational studies show the feasibility of multicarbon product formation on bimetallic catalysts compared to alloy and intermetallic catalysts. The current density and the activity of the CO2 electroreduction have been enhanced by the utilization of the flow cell in the gas diffusion electrode configuration. [ABSTRACT FROM AUTHOR]

Due to the high content of alkali and alkaline earth metals (AAEMs) in Zhundong coal, serious ash-related problems such as slagging and fouling occurred in the process of utilization, which has attracted wide attention. In this work, the ash deposition characteristics in a new type circulating fluidized bed boiler burning Zhundong coal was studied. The effect of steam cooled flue on alleviating slagging problems was evaluated, and the influence of flue gas temperature and wall temperature on ash deposition characteristics were studied. The results showed that the mass of ash deposition and the concentration of submicron particles decrease gradually along the direction of flue gas flow in the steam cooled flue. The deposited ash changed from tightly bound to wall to loosely deposited, which indicated that the arrangement of the steam cooled flue greatly alleviated the slagging problems. Compared with flue gas temperature, the wall temperature had a greater impact on ash deposition characteristics. Mineral elements such as Na, S, Fe and Mg were more likely to enrich on the high temperature wall, while the Ca showed the opposite trend. On the low temperature wall, Na existed in the form of Na2SO4 and Na2Si2O5, while on the high temperature wall, the direct condensation of alkali metal vapor was prevented and the thermophoresis disappeared, so Na mainly existed in the form of Na2Si2O5. [ABSTRACT FROM AUTHOR]

This study investigates the effect of welding parameters on the microstructural evolution and mechanical properties, such as tensile strength and hardness, in mild steel plates welded using gas metal arc welding (GMAW). The welding parameters examined include welding current, arc voltage, and gas flow rate, with ER K-71 T filler wire as the consumable material. Results indicate that a higher welding current and reduced gas flow rate result in a maximum tensile strength of approximately 533 MPa. However, discrepancies were noted in the microhardness data across different zones, with the heat-affected zone (HAZ) exhibiting a hardness of 115.8 HV, while the weld zone and base metal showed values of 76.7 HV and 112.9 HV, respectively. Microstructural analysis revealed the presence of bainite and ferrite with a tempered martensitic structure in the welded area, demonstrating that the combination of welding parameters plays a critical role in controlling phase transformations and mechanical behavior. It is essential to reconcile the observed hardness values with the conclusions drawn to ensure accurate interpretation of the data. Highlights: The study investigates how different welding process parameters, including current, voltage, and gas flow, affect the internal structure and mechanical characteristics of weld metal. It was found that the highest tensile strength is achieved with a combination of high welding current and low gas flow rate. The welded joint shows greater hardness in the heat-affected zone compared to the original metal, with the fusion zone being less hard. Analysis of the weld area reveals the presence of bainite, ferrite, and tempered martensite, which are responsible for the mechanical properties observed. [ABSTRACT FROM AUTHOR]

Yttria-stabilized zirconia (YSZ) coatings are widely utilized thermal protective layers for metal and superalloy surfaces. These coatings are employed as thermal barrier coating (TBCs) to insulate metallic parts from higher thermal energy, thereby minimizing the cooling need for the topcoat ceramic layer. The choice of material is 7 wt% YSZ due to its exceptional capability to withstand challenging conditions characterized by extremely high temperatures and pressures, typically employed by the atmospheric plasma spraying (APS) in gas turbines, effectively extending their lifespan and improving performance. The deposition process of TBCs is significantly influenced by various spraying parameters, including gas flow rate and current (amp). These key parameters mutually play a significant role in controlling thermal stability, phase composition, and improved mechanical and microstructure properties. The aim of this research is to evaluate and contrast the impact of various spraying parameters on YSZ TBC performance. Accordingly, the influence of Hydrogen (H 2), Argon (Ar) flow rate, and Current (amp) was investigated. Microstructure and elemental mapping studying was conducted using Field Emission Scanning Electron Microscopy FESEM/EDS and phase studying was examined with X-ray diffraction (XRD). Porosity was measured by IMAGE J software while hardness measurement was calculated by Vickers hardness tester. Additionally, thermal cycling tests were conducted between 700 °C and 1200 °C. The porous coatings exhibited poor performance, delaminating early during the tests. In contrast, dense coatings performed significantly better, enduring up to 140 cycles before failure. [ABSTRACT FROM AUTHOR]

Gas‐quenching of perovskite wet films is widely used in upscaling perovskite solar cells (PSCs). However, due to uneven and turbulent gas stream generated by traditional approaches through air knife or air gun, it is a challenge to induce homogeneous nucleation and produce high‐quality perovskite films suitable for large‐area PSCs. Here this work presents a semi‐sealed gas quenching (SSGQ) strategy that produces homogeneous low‐velocity large‐area high‐pressure gas flow to extract low‐boiling‐point solvents effectively, while leaving behind perovskite intermediates undisturbed that then turn into large crystalline grains. As a result, the SSGQ‐processed perovskite films exhibit improved crystallinity and reproducibility, suppressed defect density and residual stress, as well as compact buried interface and large‐scale uniformity. Such blade‐coated large‐area (1.0 cm2) PSCs with carbon and metal electrodes achieve high power conversion efficiencies (PCEs) of 19.5% and 23.3% (20.5% and 24.2% for 0.04 cm2), both with the lowest PCE loss of ≤1.0% among reported works. This work presents a scalable and affordable approach for fabricating high‐quality perovskite films and high‐performance perovskite photovoltaics, paving the way to PSC commercialization. [ABSTRACT FROM AUTHOR]

This paper investigates the effect of porosity on the burning and flame spread characteristics of the wood grille. Five pore side lengths (1–9 cm, 5 porosities φ, 38.25%−85%) of the grilles are studied and compared, which are widely used in Chinese historical buildings. The results show that both peak mass loss rate and peak heat release rate decrease with increasing porosity, while the grille with 65% porosity is the first to experience significant mass loss. The flame height and pyrolysis height have a clear power-law relationship. When the side length is less than 5 cm (φ ≤75.5%), the flames are merged and this relationship is similar to continuous fuels. While for the side length higher than 5 cm (φ > 75.5%), the main part of the flame mostly stays on the vertical strips in a discrete state, rather than continuous fuels. This phenomenon can be explained that the flow rate of the gas flowing through the pores increases with the increase of the porosity, which effectively enhances convective heat transfer. As the porosity increases further, the effective heating length on the wood samples is reduced, resulting in a smaller total heat input and a slower burning process. [ABSTRACT FROM AUTHOR]

The simulation of gas flow in the bronchial tree using computational fluid dynamics (CFD) has become a useful tool for the analysis of gas flow mechanics, structural deformation, ventilation, and particle deposition for drug delivery during spontaneous and assisted breathing. CFD allows for new hypotheses to be tested in silico, and detailed results generated without performing expensive experimental procedures that could be potentially harmful to patients. Such computational techniques are also useful for analyzing structure–function relationships in healthy and diseased lungs, assessing regional ventilation at various time points over the course of clinical treatment, or elucidating the changes in airflow patterns over the life span. CFD has also allowed for the development and use of image-based (i.e., patient-specific) models of three-dimensional (3D) airway trees with realistic boundary conditions to achieve more meaningful and personalized data that may be useful for planning effective treatment protocols. This focused review will present a summary of the techniques used in generating realistic 3D airway tree models, the limitations of such models, and the methodologies used for CFD airflow simulation. We will discuss mathematical and image-based geometric models, as well as the various boundary conditions that may be imposed on these geometric models. The results from simulations utilizing mathematical and image-based geometric models of the airway tree will also be discussed in terms of similarities to actual gas flow in the human lung. [ABSTRACT FROM AUTHOR]