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The high-altitude areas of China are abundant in renewable energy and have a natural advantage in ammonia production. Based on this advantage, this paper proposes a co-combustion strategy for methane and ammonia to reduce carbon emissions in these areas. However, the NO emission characteristics associated with this strategy remain uncertain. A custom-designed combustion system capable of simulating high-altitude environments was used to investigate the effect of ammonia mixing ratio, equivalence ratio, and pressure on NO emission in methane/ammonia/air flames. Additionally, chemical kinetic calculations were conducted to explore the mechanisms of how sub-atmospheric pressure influences NO emission. The results indicate that for stoichiometric flames, NO increases with the ammonia mixing ratio. In fuel-rich flames, NO remains nearly constant once the ammonia mixing ratio exceeds 10 %. Sub-atmospheric pressure leads to higher NO, particularly in fuel-rich flames, where the increase can reach up to 24.4 %. Analysis of nitrogen reaction pathways and key radical concentrations reveals that sub-atmospheric pressure has a minimal effect on nitrogen conversion pathways. The variation in NO is achieved by altering the pathway contributions and the concentrations of H, NH, and N. This work provides direction and guidance for improving the application of methane and ammonia co-combustion in high-altitude areas., Competing Interests: Declaration of Competing Interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2024. Published by Elsevier B.V.)

Deionized water is replacing fluorinated liquids as the preferred choice for two-phase immersion cooling in data centers. Yet, insufficient bubble removal capability at low saturated pressure is a key challenge hindering the widespread application. To solve this issue, this study employs non-ionic surfactant (Tween 20) and asymmetric structures (expanding microchannel) to enhance the boiling performances of deionized water under sub-atmospheric pressure. The research examines the effects of pressure (8.8~38.5 kPa), surfactant concentration (0.1~0.5 mL/L), and heat flux density (10~180 W/cm 2 ) on the boiling heat transfer characteristics and analyzes the mechanism of unusual temperature oscillations induced by surfactants. It was found that the trade-off between the sub-atmospheric pressure, surface tension coefficient, and reduced static contact angle results in pronounced intermittent boiling on the heated surface. Even with the addition of surfactants, the improvement in heat transfer requires demanding conditions. Boiling enhancement throughout all heat flux conditions was achieved when the surfactant concentration was higher than 0.2 mL/L for the expanding microchanneled surface. The heat transfer coefficient reached 6.89 W·cm -2 ·K -1 under 8.8 kPa, which was 45% higher than without the surfactant. Under the same heat flux and sub-atmospheric pressure, as the concentration increased from 0.1 to 0.5 mL/L, the amplitudes of temperature fluctuation of the plane surface and expanding microchanneled surface decreased from 10 K to 2 K and 18 K to 1 K, respectively. The onset of nucleate boiling and wall superheat of the expanding microchanneled surface gradually decreased with the increase in surfactant concentration, where the onset of nucleate boiling decreased by 10.54 K. When the heat flux is 160 W/cm 2 , the wall superheat is reduced by 12.8 K.

The operation and performance of electrospray ionization (ESI) is affected by the surrounding environment. In this study, a compact sub-atmospheric pressure ESI (SAP-ESI) source was designed and fabricated using the 3D printing method. This source has a simple structure and is easy to operate, as the sample solution and auxiliary gas are continuously sucked into the source through the pressure difference. The compact and enclosed ionization chamber can reduce the fluctuation of the surrounding gas flow to ensure a remarkably stable (< 3%) electrospray. Moreover, the source can offer variable SAP conditions for ESI analysis. The yield of analyte ions increases with decreasing pressure, while the production of background ions is suppressed under these conditions. In the analysis of protein samples, SAP-ESI can increase the yield and charge state of ions, which may be due to the reduction of proton transfer between charged proteins and surrounding gas. The SAP-ESI source was then used to continuously monitor the extract aqueous solution of tea leaves, and to detect the carbendazim residues on the apple surface by coupling with the liquid extraction surface analysis technique. Experimental results demonstrate that the developed SAP-ESI is a stable, practical, and versatile ionization technique., (© 2023. The Author(s), under exclusive licence to Springer-Verlag GmbH, DE part of Springer Nature.)

Background: Acoustic cavitation plays an important role in the medical treatment using high-intensity focused ultrasound (HIFU), but unnecessarily strong cavitation also could deform the morphology and enlarge the size of lesions. It is known that the increase of ambient hydrostatic pressure (P stat ) can control the acoustic cavitation. But the question of how the decrease of P stat and dissolved oxygen concentration (DOC) influence the strength of cavitation has not been thoroughly answered. In this study, we aimed to investigate the relationship among the P stat , DOC and the strength of cavitation., Methods: Ex vivo bovine liver tissues were immersed in degassed water with different DOC of 1.0 mg/L, 1.5 mg/L and 2.0 mg/L. Ultrasound (US) of 1 MHz and the spatial and temporal average intensity (I sata ) of 6500 W/cm 2 was used to expose two groups of in vitro bovine livers for 2 s; one group was under atmospheric pressure (P stat  = 1 bar) and the other was under sub-atmospheric pressure (P stat  = 0.1 bar). Acoustic cavitation was detected by a passive cavitation detector (PCD) during the exposure process. Echo signals at the focal zone of HIFU were monitored by B-mode ultrasound imaging before and after exposure. The difference between two pressure groups was tested using paired sample t-test. The difference among different DOC groups was evaluated by one-way analysis of variance (ANOVA)., Results: The results demonstrated a significant difference of broadband acoustic emissions from the cavitation bubbles, echo signals on B-mode image, morphology of lesions under various conditions of ambient pressure and DOC. The lesion volume in tissue was increased with the increase of ambient pressure and DOC., Conclusion: Cavitation could be suppressed through sub-atmospheric pressure and low DOC level in liver tissue, which could provide a method of controlling cavitation in HIFU treatment to avoid unpredictable lesions., (© 2021. The Author(s).)

This study evaluates the vapor transportation by transmission pipelines during seawater desalination. This study seeks to reach a high rate of water transportation during desalination. Hence, the results obtained from this research are closer to reality than other analyses. Other benefits of this research include increasing efficiency, studying the element-to-element transmission, and considering flow as a compression case. The water desalination system comprises three parts of evaporation, transportation, and condensation. In the transportation part, equations of continuity, momentum, and energy are implemented, and the temperature of the vapor is calculated at the beginning of the condensation pipe. Other achievements of this study include the division of transportation lines to small elements and the implementation of vapor condensation in transportation lines. This study used pipelines with diameters of 1, 2, and 4 m to transmit vapor to Ramsar city and the heights of Takhte Soleiman, 16 km away from the city with the elevation of 2000 m. The results show that diameter, transportation length, and temperature differences are, respectively, the most influential factors on the efficiency of sub-atmospheric vapor transportation. The outcomes of this study were presented as the outflow of condensed water at the destination. Considering the margin of safety in calculations, it was scientifically proved that the results obtained in this study were approximately 10% more than results derived from other studies in the literature that are based on the incompressibility of fluids., (© 2020 Published by Elsevier Ltd.)

Background: This study examines the efficacy of hypobaric oxygenation as it relates to the elimination of gaseous microemboli (GME) at designated flow, pressure and temperature combinations., Methods: Hypobaric oxygenation was employed for experimental trials (n=60), but not for control trials (n=60), while circuit design, data measurements and testing conditions were maintained for both settings. Hypobaric oxygenation conditions were created by applying 100% oxygen at sub-atmospheric sweep gas pressures of 0.67 atmospheres to the gas phase of an integrated hollow-fiber microporous membrane oxygenator. GME were quantified using an Emboli Detection and Classification system (EDAC), while a continuous air infusion, at a rate of 100 ml/min, was applied to the circuit. Trials were conducted at 37°C, 28°C, and 18°C and at two flow and line pressure combinations of: 3.5 L/min & 150 mmHg and 5 L/min & 200 mmHg., Results: Sub-atmospheric sweep gas pressures allowed adequate oxygenation independent of carbon dioxide removal while significantly reducing the potential entrance of nitrogen into the blood. GME was reduced significantly across all temperatures and flows when compared to control trials; GME counts were reduced by 99.7% post-oxygenator and 99.99% at the arterial cannula., Conclusion: Correlation between the use of hypobaric oxygenation and GME counts suggests hypobaric oxygenation could play a significant role in the reduction of GME., (© The Author(s) 2016.)

The effect of O(3) on C(2)H(4)/synthetic-air flame propagation at sub-atmospheric pressure was investigated through detailed experiments and simulations. A Hencken burner provided an ideal platform to interrogate flame speed enhancement, producing a steady, laminar, nearly one-dimensional, minimally curved, weakly stretched, and nearly adiabatic flame that could be accurately compared with simulations. The experimental results showed enhancement of up to 7.5% in flame speed for 11 000 ppm of O(3) at stoichiometric conditions. Significantly, the axial stretch rate was also found to affect enhancement. Comparison of the flames for a given burner exit velocity resulted in the enhancement increasing almost 9% over the range of axial stretch rates that was investigated. Two-dimensional simulations agreed well with the experiments in terms of flame speed, as well as the trends of enhancement. Rate of production analysis showed that the primary pathway for O(3) consumption was through reaction with H, leading to early heat release and increased production of OH. Higher flame stretch rates resulted in increased flux through the H+O(3) reaction to provide increased enhancement, due to the thinning of the flame that accompanies higher stretch, and thus results in decreased distance for the H to diffuse before reacting with O(3)., (© 2015 The Author(s) Published by the Royal Society. All rights reserved.)