Pressure Release Research Articles

Structural Transition Analysis of Bilayer Black Phosphorus under High Pressure via Ultralow-Frequency Raman Spectroscopy.

The unique anisotropic electron-photon and electron-phonon interactions of black phosphorus (BP) set it apart from other isotropic 2D materials. These anisotropic properties can be adjusted by varying the stacking thickness and sequence as well as by applying external pressure and strain. In contrast to multilayer or bulk BP, the effects of pressure on bilayer BP are still not fully elucidated. This study presents experimental evidence that explores the high-pressure response (0-20 GPa) of bilayer BP within the extreme low Raman shift region (5-150 cm-1), aiming at verifying structural phase transitions and stacking sequence variations. Notably, phase transitions were observed at ∼7 GPa for the orthorhombic to rhombohedral transition and at ∼14-16 GPa for a further transition to a simple cubic structure. The effects of pressure on bilayer BP with three distinct stacking sequences (AA, AB, and AC) were analyzed using angular-resolved polarized Raman spectroscopy (ARPR). The recovery of all characteristic Raman modes after the application of pressure substantiates the reversibility of the structural phase transitions in bilayer BP across all three stacking sequences. However, significant alterations in the stacking sequences were observed before and after the application of hydrostatic pressure. Specifically, AA and AC stacking sequences showed a tendency to relax into an optimized interlayer AB stacking structure upon the release of pressure from 20 to 0 GPa. This observed change in the stacking sequences of bilayer BP under pressure is detected for the first time in this work. The pressure-induced modifications in the stacking sequences, and consequently in the anisotropic properties of bilayer BP, highlight its potential as a promising material for pressure- (or strain-) sensitive optoelectronic nanodevices. Additionally, this study offers novel insights into the analysis of anisotropic interlayer interactions in other van der Waals-stacked 2D materials.

Synthesis and Characterization of Lithium Pyrocarbonate (Li2[C2O5]) and Lithium Hydrogen Pyrocarbonate (Li[HC2O5

AbstractThe anhydrous pyrocarbonate and the first hydrogen pyrocarbonate Li[HC2O5] have been synthesized in a laser‐heated diamond anvil cell at moderate pressures ( GPa). The structures of the two compounds have been obtained from single crystal X‐ray diffraction data. Raman spectroscopy and DFT calculations have been employed to further characterize their structure‐property relations. The present results significantly enlarge the group of inorganic pyrocarbonates by the discovery of the hydrogenated pyrocarbonate anion Li[HC2O5]−. In the structure of Li[HC2O5] there is a symmetric O−H−O arrangement at high pressures, which converts to a conventional O−H O hydrogen bond upon pressure release.

Synthesis and Characterization of Lithium Pyrocarbonate (Li2[C2O5]) and Lithium Hydrogen Pyrocarbonate (Li[HC2O5]).

The anhydrous pyrocarbonate and the first hydrogen pyrocarbonate Li[HC2O5] have been synthesized in a laser-heated diamond anvil cell at moderate pressures ( GPa). The structures of the two compounds have been obtained from single crystal X-ray diffraction data. Raman spectroscopy and DFT calculations have been employed to further characterize their structure-property relations. The present results significantly enlarge the group of inorganic pyrocarbonates by the discovery of the hydrogenated pyrocarbonate anion Li[HC2O5]-. In the structure of Li[HC2O5] there is a symmetric O-H-O arrangement at high pressures, which converts to a conventional O-H O hydrogen bond upon pressure release.

Synthesis of Laves phase hydrides YFe2H6 and YFe2H7 at high pressure: reaching a limit of interstitial hydrogen uptake

The C15 Laves phase compound YFe2 has been extensively studied for its significant hydrogen absorption in its tetrahedral interstitial sites. It can stably hold up to five hydrogen atoms per formula unit under ambient conditions. However, the maximum hydrogen capacity in such Laves phase materials remains an open question. The use of high pressure is a tool that facilitates the formation of polyhydrides with high hydrogen-to-metal ratios. By subjecting YFe2H4.2 to hydrogen pressures up to 50 GPa in a diamond anvil cell without any heating, two new interstitial compounds, YFe2H6 and YFe2H7, were synthesized. Synchrotron X-ray diffraction and ab initio calculations reveal that these new compounds have ordered hydrogen atoms occupying two types of tetrahedral interstitial sites, A2B2 and B4, and a new triangular interstitial site AB2, in an orthorhombic structure distorted from the C15 Laves phase. The magnetic properties of YFe2Hx hydrides have to be taken into account to reproduce experimental volumes, identify stable compounds on the convex hull of the YFe2-H system, and explain deviations from Vegard’s law regarding volume expansion with hydrogen concentration. These compounds cannot be retrieved at ambient pressure upon pressure release.

Shock-induced twinning/detwinning and spall failure in Cu–Ta nanolaminates at atomic scales

Abstract This study provides new insights into the role of interfaces on the deformation and failure mechanisms in shock-loaded Cu–Ta–Cu trilayer system. The thickness of the Ta layer, piston velocities, and shock pulse durations were varied to explore the impact of impedance mismatch and loading conditions on spallation behavior and twin formation. It was found that the interfaces play a crucial role in the dynamic response of these multilayered systems since secondary reflection waves generated at the interfaces significantly affected the peak stress and pressure profiles, influencing void nucleation and failure modes. In the trilayer systems, failure predominantly occurred at interfaces and within the Ta layer, with void nucleation sites and twinning behavior being markedly different compared to single-crystal Cu and Ta. Increasing the Ta layer thickness modified the wave interactions, leading to different failure locations. Higher piston velocities were associated with increased spall strength by enhancing wave interactions and void formation, particularly at the interfaces and within the Ta layer, under specific configurations. Additionally, shorter shock pulse durations facilitated earlier initiation of the release fan, reducing twin formation and altering the failure dynamics by accelerating twin annihilation and pressure release.

Spatiotemporal information propagation in confined supersonic reacting flows

The interplay between mass injection, heat release, and boundary layer development plays a key role in dictating the dynamics and stability of confined supersonic flows. The relative impacts of these factors and the timescales over which they influence the upstream and downstream flow can provide critical insights into how different operating modes develop. As such, this work presents a series of simulations of an experimental axisymmetric direct connect flowpath. The mass flow rates and chemical compositions of the injection stages are varied, and subsequent information propagation and mode transitions are analyzed using spatiotemporal correlations of cross-sectional-averaged quantities. Increasing the injection flow rate decreases the time lags and durations of positive correlations between pressure and heat release at various points along the flowpath. Meanwhile, in dual-mode cases with lower injection flow rates, these correlations develop after longer time delays and persist for a longer times, illustrating how information propagates more gradually in these scenarios. Over the full flowpath, positive correlations persist for comparatively long times between (1) the upstream isolator pressure and the pressure elsewhere, and (2) the pressure in the downstream diverging combustor section and the upstream pressure. As such, the influence of the pressure in the intermediate constant-area combustor section decays more rapidly. Conditional statistics suggest that flow blockage and pressurization from the injected mass reduce the local ignition delay, thereby facilitating increased pressurization via heat release in a positive feedback loop.

Severe postoperative negative pressure pulmonary edema: a case report

BackgroundPostoperative negative pressure pulmonary edema (NPPE) can occur in any patient undergoing general anesthesia. There are several risk factors for it, especially postoperative laryngospasm. The disease is usually benign and quickly reversible. In our case the severity and need for advanced critical care therapy was unusual.CaseWe report a severe case of postoperative negative pressure pulmonary edema in a 62-year-old male patient undergoing elective right-sided retroperitoneoscopic adrenalectomy. The patient developed a severe case of acute respiratory distress syndrome (ARDS) after postoperative laryngospasm, possibly in conjunction with a suspected anaphylactic reaction. The patient was consequently treated with a combination of invasive airway pressure release ventilation (APRV) and a prone positioning regimen. After drastic improvement in respiratory function, the patient was discharged from the intensive care unit after 10 days and from the hospital after 14 days.ConclusionNPPE is a rare but relevant complication of anesthesia and laryngospasm. The disease can basically occur in any patient undergoing general anesthesia and therefore should be considered.

Synthesis of Na3WH9 and Na3ReH8 Ternary Hydrides at High Pressures.

The Na-W-H and Na-Re-H ternary systems were studied in a diamond anvil cell through X-ray diffraction and Raman spectroscopy, supported by density functional theory and molecular dynamics calculations. Na3WH9 can be synthesized above 7.8 GPa and 1400 K, remaining stable between at least 0.1 and 42.1 GPa. The rhenium analogue Na3ReH8 can form at 10.1 GPa upon laser heating, being stable between at least 0.3 and 32.5 GPa. Na3WH9 and Na3ReH8 host [WH9]3- and [ReH8]3- anions, respectively, forming homoleptic 18-electron complexes in both cases. Both ternary hydrides show similar structural types and pressure dependent phase transitions. At the highest pressures they adopt a distorted fcc Heusler structure (Na3WH9-II' and Na3ReH8-II') while upon decompression the structure symmetrizes becoming fcc between ∼6.4 and 10 GPa for Na3WH9-II and at 17 GPa for Na3ReH8-II. On further pressure release, the fcc phases transform into variants of a (quasi-) hexagonal structure at ∼3 GPa, Na3WH9-I and Na3ReH8-I.

Investigation into the impact of acetylene on performance and emission characteristics of a compression ignition engine using a blended biodiesel of ethanol and tamanu oil.

Due to the significant increase in transportation, traditional fossil fuels utilised in internal combustion engines will only be accessible for a limited duration. Additionally, the harmful pollutants produced by these fuels, including CO, NOx, unburned hydrocarbons, smoke, and a small amount of particulate matter, have a severe negative impact on the environment. Although biodiesel proves efficient without necessitating engine modifications, its performance is hindered by its higher viscosity. Consequently, this research aims to enhance performance by introducing acetylene alongside tamanu methyl ester (biodiesel); however, this approach results in elevated NOx levels. To mitigate NOx emissions, a combination of ethanol and biodiesel is employed. This study investigates the performance and emission attributes of Acetylene + TME90E10 as the fuel. The combustion pressure and heat release rate of TME90E10 with 6 lpm, improved by 5.41% and 9.1% than diesel. When compared to regular diesel fuel, the introduction of 6l per minute of acetylene with TME90E10 yields a substantial 24.4% decrease in hydrocarbon (HC) emissions. Furthermore, employing TME90E10 at the same acetylene flow rate demonstrates the lowest carbon monoxide (CO) emissions, registering at 0.07%, in contrast to the 0.13% emissions observed throughout the exhaust cycle when using pure diesel fuel.

Reperfusion injury case following cervical fusion with OPLL: a case report and literature review

IntroductionSpinal cord ischemic reperfusion injury is characterized by an abrupt decline in neurological function and only a few cases have been published in literature. Herein, we present a white cord syndrome following anterior decompression cervical fusion.Case ReportA 54-year-old Jewish male patient was diagnosed with disc herniation among the intervertebral discs at C2, C3, C4, C6, and C7, along with ossification of the posterior longitudinal ligament, pressuring more to the right side of the spinal canal, ruling-out cervical myelopathy. Under general anesthesia and multimodal intraoperative monitoring, he underwent laminectomy surgery from C3 to C6 and cervical fixation from C3 to C7. No blood pressure fluctuations occurred during surgery, and complete pressure release was achieved on the spinal cord and the nerve roots. In addition, neuromonitoring did not indicate any nerve damage during the surgery. A neurologic exam in the post-anesthesia care unit revealed weakness in his right hand and leg. A brain computed tomography scan ruled out cerebrovascular accident, neck computed tomography revealed optimal implant position, and magnetic resonance imaging ruled out spinal cord distress or injury. We treated him with intravenous fluids, steroids, painkillers, and anticoagulants. Following surgery, we involved the occupational therapy department. After a few days, we observed a significant improvement in motor function in the right leg; however, there was no change in the right hand.ConclusionWhite cord syndrome likely arises from reperfusion injury subsequent to surgical decompression of a compressed spinal cord segment. Although infrequent, it is imperative for spine surgeons to recognize this potential complication and apprise patients of it prior to the procedure.

Comparison of intracompartment pressure changes in tibial plateau fractures and controlled people: A pilot study.

Acute compartment syndrome (ACS) is a serious medical condition that can be encountered in tibial plateau fractures. However, no studies of compartment pressure changes in patients with tibial plateau fractures compared to patient without fractures have been reported. To obtain a comprehensive understanding of the pressure changes in patients with fractures, we monitored and recorded the compartment pressure and attempted to reveal the potential pressure release function of the human fascia. Cohorts of 43 normal individuals and 23 patients (initial 33, 10 were excluded due to inclusion criteria) and include the number of patients who completed the study with closed tibial fractures (the fracture group, FG, which comprised 6 men and 17 women) were included in this retrospective research. Compartment pressures were measured with Icare, a device that is traditionally used to measure intraocular pressure. Results of measurements at 6 different locations in the lower limb were recorded and compared for three days (days 2, 3, and 4 post fracture) between normal cohort (CG) and fracture cohort (FG) patients. The compartment pressures were comparable at each pressure measurement site (upper, middle and lower) in patients of the CG and the FG. Compared with the CG patients, there was a significant increase in compartment pressure at the upper lateral location in 18-45-year-old patients in the FG (P = 0.013) and at the upper lateral (P = 0.004) and medial locations (P = 0.005) in 46-69-year-old patients, and the values tended to normalize over time. Compared with the contralateral normal limb of patients in the FG, there was a significant increase in compartment pressure at the upper lateral location in 18-45-year-old patients (P = 0.009) and at the upper lateral (P = 0.015) and medial locations (P = 0.016) in 46-69-year-old patients on the fractured side. Based on different fracture classifications, there were no significant differences in compartment pressure at the medial (upper, middle and lower) locations when compared with pressures at the corresponding lateral sites of measurement. The results of this study revealed that the fascial compartment as a whole can release the increased intracompartment pressure after fracture to prevent complications such as acute compartment syndrome caused by a continued increase in pressure. The Icare as a portable device, is potentially useful in compartmental pressure measurement especially in emergency room.

Strong Enhancement of Magnetic Coercivity Induced by Uniaxial Stress.

The performance of permanent magnets is intricately tied to their magnetic hysteresis loop. In this study, we investigate the heavy-fermion ferromagnet CeAgSb_{2} through magnetization measurements under uniaxial stress. We observe a 2400% increase in magnetic coercivity with just a modest stress of approximately 1kbar. This effect persists even after pressure release, attributable to stress-induced defects that efficiently pin domain walls. Other magnetic properties such as ordering temperature and saturation moment exhibit only weak pressure dependencies and display full reversibility. Our findings offer a promising route for increasing coercive field strength and enhancing the energy product in ferromagnetic materials and are potentially applicable to a broad spectrum of commercial or emerging magnetic applications.

Influence of steam induction on the performance and hydrogen knock limit of a hydrogen-gasoline spark ignition engine

This study examines the effect of steam induction on the performance and hydrogen knock limit of a hydrogen-gasoline dual-fuel Spark Ignition (SI) engine. The experimental setup includes gasoline direct injection, along with steam and hydrogen port induction. Steam-to-fuel ratios of 7.5 %, 15 %, and 22.5 % were used, and hydrogen was introduced in step sizes of 2 LPM until knock onset. The extension of the hydrogen knock limit was achieved through steam induction and retarding spark timing. Under the default configuration, the maximum achievable hydrogen flow rate was 8 LPM, which increased to 20 LPM with retarded spark timing and 22.5 % steam proportion. Steam induction initially increased and then decreased brake thermal efficiency, brake mean effective pressure, in-cylinder pressure, and heat release rate. In contrast, advancing spark timing and hydrogen enrichment consistently improved performance and combustion characteristics. Cyclic variation showed a decreasing trend with the introduction of steam and hydrogen. Unlike hydrogen enrichment, steam addition reduced CO and NOX emissions.

Charge transfer behavior of triboelectric polymers and triboelectric sensors operated under ultrahigh pressure

AbstractThe energy generation performance of triboelectric materials under ultrahigh pressure remains to be investigated. Here, the variations in molecular structure and built‐in electric field of triboelectric polymers under ultrahigh pressure have been thoroughly studied. The attenuation of built‐in electric field and the escaping of triboelectric charges under ultrahigh pressure are observed in different triboelectric polymers, whereas the existence of deep traps allows the built‐in electric field to be recoverable with the release of pressure. Moreover, the macromolecular conformational changes, including twisting molecular chains and crystal structure changes, can also induce the redistribution of deep traps, leading to a sudden increase in built‐in electric field under specific pressure. Finally, a triboelectric sensor for ultrahigh pressure condition is fabricated with excellent cycle repeatability and a total thickness of 2 mm, which has a sensitivity of 0.07 V MPa−1 within a linear region of 1–100 MPa. This study offers in‐depth insight into the physical understanding of charge behavior both on interface and in bulk of triboelectric materials, whereas the proposed ultrahigh pressure sensors can promote various potential applications of triboelectric sensor in extreme environments.

Prediction and Simulation of Biodiesel Combustion in Diesel Engines: Evaluating Physicochemical Properties, Performance, and Emissions

Environmental and energy sustainability concerns have catalyzed a global transition toward renewable biofuel alternatives. Among these, biodiesel stands out as a promising substitute for conventional diesel in compression-ignition engines, providing compatibility without requiring modifications to engine design. A comprehensive understanding of biodiesel’s physical properties is crucial for accurately modeling fuel spray, atomization, combustion, and emissions in diesel engines. This study focuses on predicting the physical properties of PODL20 and EB100, including liquid viscosity, density, vapor pressure, latent heat of vaporization, thermal conductivity, gas diffusion coefficients, and surface tension, all integrated into the CONVERGE CFD fuel library for improved combustion simulations. Subsequently, numerical simulations were conducted using the predicted properties of the biodiesels, validated by experimental in-cylinder pressure data. The prediction models demonstrated excellent alignment with the experimental results, confirming their accuracy in simulating spray dynamics, combustion processes, turbulence, ignition, and emissions. Notably, significant improvements in key combustion parameters, such as cylinder pressure and heat release rate, were recorded with the use of biodiesels. Specifically, the heat release rates for PODL20 and EB100 reached 165.74 J/CA and 140.08 J/CA, respectively, compared to 60.2 J/CA for conventional diesel fuel. Furthermore, when evaluating both soot and NOx emissions, EB100 displayed a more balanced performance, achieving a significant reduction in soot emissions of 34.21% alongside a moderate increase in NOx emissions of 45.5% compared to diesel fuel. In comparison to PODL20, reductions of 20.4% in soot emissions and 3% in NOx emissions were also noted.

Dynamical state and driving region of combustion instability in a turbulent combustor with a variable swirling flow system

We experimentally study the dynamical state and driving region of combustion instability in a turbulent combustor under low- and high-swirling flow conditions by the complex-systems approach. As the swirl number is increased, the combustion state undergoes a transition from stable combustion to complex combustion instability with large-amplitude modulations via low- and high-amplitude combustion instability. A chaotic state emerges during combustion instability with large-amplitude modulations. A symbolic dynamics-based thermoacoustic power network can identify the emergence of the thermoacoustic power source during combustion instability. The driving region of combustion instability can be clearly extracted from the symbolic dynamics-based synchronization index and the local node entropy in the Rayleigh index-based transition network. Reservoir computing has a potential use in clarifying the phase synchronized state between acoustic pressure and heat release rate fluctuations during the chaotic state in combustion instability with large-amplitude modulations.

Atelectrauma can be avoided if expiration is sufficiently brief: evidence from inverse modeling and oscillometry during airway pressure release ventilation

BackgroundAirway pressure release ventilation (APRV) has been shown to be protective against atelectrauma if expirations are brief. We hypothesize that this is protective because epithelial surfaces are not given enough time to come together and adhere during expiration, thereby avoiding their highly damaging forced separation during inspiration.MethodsWe investigated this hypothesis in a porcine model of ARDS induced by Tween lavage. Animals were ventilated with APRV in 4 groups based on whether inspiratory pressure was 28 or 40 cmH2O, and whether expiration was terminated when end-expiratory flow reached either 75% (a shorter expiration) or 25% (a longer expiration) of its initial peak value. A mathematical model of respiratory system mechanics that included a volume-dependent elastance term characterized by the parameter E2\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$${E}_{2}$$\\end{document} was fit to airway pressure-flow data obtained each hour for 6 h post-Tween injury during both expiration and inspiration. We also measured respiratory system impedance between 5 and 19 Hz continuously through inspiration at the same time points from which we derived a time-course for respiratory system resistance (Rrs\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$${R}_{rs}$$\\end{document}).ResultsE2\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$${E}_{2}$$\\end{document}during both expiration and inspiration was significantly different between the two longer expiration versus the two shorter expiration groups (ANOVA, p < 0.001). We found that E2\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$${E}_{2}$$\\end{document} was most depressed during inspiration in the higher-pressure group receiving the longer expiration, suggesting that E2\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$${E}_{2}$$\\end{document} reflects a balance between strain stiffening of the lung parenchyma and ongoing recruitment as lung volume increases. We also found in this group that Rrs\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$${R}_{rs}$$\\end{document} increased progressively during the first 0.5 s of inspiration and then began to decrease again as inspiration continued, which we interpret as corresponding to the point when continuing derecruitment was reversed by progressive lung inflation.ConclusionsThese findings support the hypothesis that sufficiently short expiratory durations protect against atelectrauma because they do not give derecruitment enough time to manifest. This suggests a means for the personalized adjustment of mechanical ventilation.

Longitudinal combustion instability in a hypergolic liquid bipropellant combustor with single dual-swirl coaxial injector

Self-excited longitudinal combustion instabilities were investigated in a hypergolic liquid bipropellant combustor, which applied single dual-swirl coaxial injector. Hot-fire tests were conducted for four different injector geometries, while extensive tests on injection conditions were carried out for each injector geometry. The synchronous measurement of the pressure and heat release rate was applied, successfully capturing the process of the pressure and heat release rate enhanced coupling and developing into in-phase oscillation. By calculating Rayleigh index at the head and middle section of the chamber, it is shown that Rayleigh index of the middle section is even higher than that of the head, indicating a long heat release zone. When the combustion instability occurs, the pressure in propellant manifolds also oscillates with the same frequency and lags behind the oscillation in the combustor. Compared to the oscillation in the outer injector manifold, the oscillation in the inner injector manifold shows a higher correlation with that in the chamber in amplitude and phase. Based on numerical simulations of the multiphase cold flow inside the injector and combustion process in the chamber, it is found that injector geometries affect longitudinal combustion instability by changing spray cone angle. The spray with small cone angle is more sensitive to the modulation of longitudinal pressure wave in combustion simulations, which is more likely to excite the longitudinal combustion instability. Meanwhile, the combustion instability may be related to the pulsating coherent structure generated by the spray fluctuation, which is determined by injection conditions. Besides, a positive feedback closed-loop system associated with the active fluctuation and passive oscillation of the spray is believed to excite and sustain the longitudinal combustion instability.

Microballistics in fungi and plants

Ballistic movements in biology are powered by muscle contraction, explosive chemical reactions, the formation and collapse of gas bubbles, merger of fluid droplets, and release of hydrostatic pressure. At the macroscopic end of this kinetic carnival we find jumping fleas, violent spider jaws, shrimp claw hammers, and squirting beetles and cucumbers. The speeds are startling, but the mechanisms seem familiar because they occur on a spatial scale that overlaps with our physical experiences. We jump, albeit more slowly than fleas, for example, and it does not seem strange that seeds will spurt from a swollen cucumber when it hits the ground. Ballistics in microscopic dimensions are very different, operating in a seemingly alien world of fluid mechanics where thin air becomes soup and gravity vanishes.

Study on the acoustic disturbance characteristics of the spray flame

The axial sound field was added to the ethanol spray flame as a perturbation element to study the dynamic response and combustion characteristics. A forced acoustic field is applied to a small oscillating flame. In cases where the frequency of the external sound field matches the eigenfrequency, even small amplitude self-excited flames demonstrate significant instability. As the intensity of the sound field increases, the amplitude of pressure oscillations sharply rises, and the pressure and flame heat release oscillations are in-phase. When the sound field operates at frequencies other than the eigenfrequency, it has an inhibitory effect on the evaporation and combustion process of ethanol droplets. Consequently, intensifying the sound field leads to a reduction in both the area of the evaporation combustion zone and the axial temperature of the flame. The CO formation is influenced by both temperature and the sound field, showing a pattern of increasing and then decreasing with the increase of sound intensity. Additionally, NOx generation exhibits higher emission concentrations in low-temperature and short flames, which is more likely to prompt NOx and is not closely related to frequency.