Showing papers on "Atmospheric pressure published in 2022"

Numerical Simulation of Atmospheric Lamb Waves Generated by the 2022 Hunga‐Tonga Volcanic Eruption

Abstract: On 15 January 2022, around 4:30 UTC the eruption of the Hunga-Tonga volcano, in the South Pacific Ocean, generated a violent underwater explosion. In addition to tsunami waves that affected the Pacific coasts, the eruption created atmospheric pressure disturbances that spread out in the form of Lamb waves. The associated atmospheric pressure oscillations were detected in high-frequency in-situ observations all over the globe. Here we take advantage of the similarities in the propagation and characteristics between atmospheric Lamb waves and long ocean waves and we use a 2DH ocean numerical model to simulate the phenomenon. We compare the outputs of the numerical simulation with in-situ atmospheric pressure records and with remote satellite observations. The signal in the model matches the observed atmospheric pressure perturbations and reveals an excellent agreement in the wave arrival time between model and observations at hundreds of locations at different distances from the origin.

Numerical simulation of atmospheric Lamb waves generated by the 2022 Hunga-Tonga volcanic eruption

Abstract: On January 15th, 2022, at 4:30 UTC the eruption of the Hunga-Tonga volcano, in the South Pacific Ocean, generated a violent underwater explosion. In addition to tsunami waves that affected the Pacific coasts, the eruption created atmospheric pressure disturbances that spread out in the form of Lamb waves. The associated atmospheric pressure oscillations were detected in high-frequency in-situ observations all over the globe. Here we take advantage of the similarities in the propagation and characteristics between atmospheric Lamb waves and long ocean waves and we use a 2DH ocean numerical model to simulate the phenomenon. We compare the outputs of the numerical simulation with in-situ atmospheric pressure records and with remote satellite observations. The signal in the model matches the observed atmospheric pressure perturbations and reveals an excellent agreement in the wave arrival time between model and observations at hundreds of locations at different distances from the origin.

Characteristics of the deep sea tsunami excited offshore Japan due to the air wave from the 2022 Tonga eruption

Abstract: Abstract A large eruption of the Hunga Tonga-Hunga Haʻapai volcano in Tonga on January 15, 2022 generated air–sea coupled tsunamis observed at the ocean-bottom pressure sensor network along the Japan Trench (S-net) in Japan. Initial tsunamis from the 2022 Tonga eruption, detected by 106 ocean-bottom pressure sensors, were well modeled by an air–sea coupled tsunami simulation, with a simple atmospheric pressure pulse as sine function, having a half-wavelength of 300 km and a peak amplitude of 2 hPa. A one-dimensional air–sea coupled tsunami simulation having a simple bathymetry shows that an input atmospheric pressure pulse with a short half-wavelength of 50 km, which is shorter than the length of the ocean bottom slopes, caused an amplitude increase via the Proudman resonance effect near the deep trench. The wavefront distortion due to the separation of the air–sea coupled wave propagating with a speed of 312 m/s and tsunami propagating with that of $$\sqrt{gd}$$ gd , where g is gravity acceleration and d is the ocean depth, is also significant near the shore. In contrast, these effects are not significant for the half-wavelength of the input atmospheric pressure pulse of 300 km. These results indicate that the air–sea coupled tsunami propagating through the trench is sensitive to the wavelength of an atmospheric pressure pulse. Graphical Abstract

Dry reforming of methane in an atmospheric pressure glow discharge: Confining the plasma to expand the performance

Abstract: • Confinement of APGD plasma reactor leads to excellent performance for DRM. • CO 2 and CH 4 conversion of 64 % and 94 % are reached, respectively. • Energy cost for majority of conditions stays below 4 eV/molecule. • High selectivity for syngas, with water and acetylene as main by-products. • Quasi-1D chemical kinetics model can reveal underlying chemical pathways. We present a confined atmospheric pressure glow discharge plasma reactor, with very good performance towards dry reforming of methane, i.e., CO 2 and CH 4 conversion of 64 % and 94 %, respectively, at an energy cost of 3.5–4 eV/molecule (or 14–16 kJ/L). This excellent performance is among the best reported up to now for all types of plasma reactors in literature, and is due to the confinement of the plasma, which maximizes the fraction of gas passing through the active plasma region. The main product formed is syngas, with H 2 O and C 2 H 2 as by-products. We developed a quasi-1D chemical kinetics model, showing good agreement with the experimental results, which provides a thorough insight in the reaction pathways underlying the conversion of CO 2 and CH 4 and the formation of the different products.

Experimental investigation on fractal characteristics of pores in air-entrained concrete at low atmospheric pressure

Abstract: This study intends to investigate the characteristics of pore structure of air-entrained concrete at low atmospheric pressure (0.7P0 = 0.7 atm) and standard atmospheric pressure (P0 = 1 atm) through in situ experiments. By using the data obtained from mercury intrusion porosimetry (MIP) test, the surface fractal dimension in different pore size regions is computed and linear regressed based on thermodynamic model. The results show that low atmospheric pressure has great impact on the fractal properties of pores and pore volume. The surface fractal dimension of pores <10 nm prepared at 0.7P0 is 4.5%–27.6% smaller than that at P0; the surface fractal dimension of pores >1000 nm at 0.7P0 is 4.5%–13.6% bigger than that at P0. The volumes of pores <10 nm and >1000 nm at 0.7 P0 is respectively 9.4%–38.9% and 38.5%–66.7% lower than that at P0; and the volume of pores within 10–1000 nm at 0.7P0 is 19.8%–41.8% higher than that at P0. The mechanisms behind the abnormal structure of pores at 0.7P0 are discussed from perspectives of cement hydration and mechanical equilibrium of air bubble.

Enhancement of CO2 conversion in microwave plasmas using a nozzle in the effluent

Abstract: • Improvement of CO 2 conversion in microwave plasma towards and at atmospheric pressure is obtained by using a nozzle in the effluent. • Improving wall-plug efficiency–increase of CO 2 conversion at atm. pressure. • Achieving supersonic expansion requires nozzle diameters of 2.5 mm. Plasma conversion is an alternative approach to the electrochemical and photochemical technologies searching for most efficient way to convert CO 2 into carbon monoxide (CO). The CO 2 plasma conversion investigated in recent years demonstrated conversion and energy efficiencies up to 50%. Commonly, these values are obtained at pressures lower than atmospheric pressure at about 100 mbar. In this work we present an investigation of the CO 2 conversion and the energy efficiency in a microwave plasma torch equipped with a nozzle of different diameters installed downstream of the plasma at varying distances to the microwave discharge, in the pressure range 100–900 mbar. The results obtained using the nozzle demonstrate an enhancement of conversion and energy efficiency, particularly at pressures close to atmospheric pressure and for lower CO 2 flows (SEI above 2 eV/molecule), bringing the values of conversion and energy efficiency close to those obtained at lower pressures. It is assumed that the fast cooling of the hot plasma gas with surrounding colder gas leads to reduction of CO recombination into CO 2 thus preserving the maximum conversion obtained. With a 2.5 mm nozzle at sub-atmospheric pressures, conditions with large pressure difference in the resonator and in the effluent are observed, which is accompanied by an additional increase in conversion. A likely reason for this is reduction of the recombination rates due to lowering of the pressure in the effluent and possible temperature reduction resulting from the supersonic expansion. Using the nozzle it is possible to significantly increase the performance of the plasma torch at 900 mbar, both in conversion and energy efficiency towards values achieved at 200 mbar, which is an important step towards industrial applicability of this technology.

Aurora Borealis in dentistry: The applications of cold plasma in biomedicine

Abstract: Plasma is regularly alluded to as the fourth form of matter. Its bounty presence in nature along with its potential antibacterial properties has made it a widely utilized disinfectant in clinical sciences. Thermal plasma and non-thermal (or cold atmospheric) plasma (NTP) are two types of plasma. Atoms and heavy particles are both available at the same temperature in thermal plasma. Cold atmospheric plasma (CAP) is intended to be non-thermal since its electrons are hotter than the heavier particles at ambient temperature. Direct barrier discharge (DBD), atmospheric plasma pressure jet (APPJ), etc. methods can be used to produce plasma, however, all follow a basic concept in their generation. This review focuses on the anticipated uses of cold atmospheric plasma in dentistry, such as its effectiveness in sterilizing dental instruments by eradicating bacteria, its advantage in dental cavity decontamination over conventional methods, root canal disinfection, its effects on tooth whitening, the benefits of plasma treatment on the success of dental implant placement, and so forth. Moreover, the limitations and probable solutions has also been anticipated. These conceivable outcomes thus have proclaimed the improvement of more up-to-date gadgets, for example, the plasma needle and plasma pen, which are efficient in treating the small areas like root canal bleaching, biofilm disruption, requiring treatment in dentistry.

Effect of atmospheric pressure cold plasma (ACP) treatment on the technological characteristics of quinoa flour

Abstract: Atmospheric pressure cold plasma (ACP) is considered as non-thermal treatment with potential microbial inactivation efficiencies. This study is aimed to determine the effect of ACP treatment on technological characteristics of quinoa flour using Fourier Transform Infrared Spectroscopy, flour hydration characteristics, thermal properties, rheological measurement and morphological characterization. Whole quinoa grains were subjected to a dielectric barrier discharge plasma reactor for 5 min at 50 kV, 10 min at 50 kV, 5 min at 60 kV and 10 min at 60 kV known as S1, S2, S3 and S4 respectively. Untreated sample is named as control sample. Results indicated the significant impact of ACP treatment on rheological, thermal, hydration and morphological characteristics of quinoa flour depending on the exposed time and voltage. For example, while a voltage dependent decrease (p < 0.05) has been found in enthalpy with values equal to 743.6 ± 0.5, 1395 ± 1, 635.6 ± 0.6 and 804.3 ± 0.9 J/g for S1, S2, S3 and S4 respectively, it is positively influenced by increasing the exposure time at constant voltage. Consequently, it seems that the influence of ACP treatment on technological characteristics which is mainly induced by time- and/or voltage-dependent changes in proteins and starch structures needs to be optimized regarding the desired behavior characteristics.

Gas-discharge induced flash sintering of YSZ ceramics at room temperature

Abstract: Abstract This is the first study to conduct the flash sintering of 3 mol% yttria-stabilized zirconia (3YSZ) ceramics at room temperature (25 °C) under a strong electric field, larger than 1 kV/cm. At the standard atmospheric pressure (101 kPa), the probability of successful sintering is approximately half of that at low atmospheric pressure, lower than 80 kPa. The success of the proposed flash sintering process was determined based on the high electric arc performance at different atmospheric pressures ranging from 20 to 100 kPa. The 3YSZ samples achieved a maximum relative density of 99.5% with a grain size of ∼200 nm. The results showed that as the atmospheric pressure decreases, the onset electric field of flash sintering decreases, corresponding to the empirical formula of the flashover voltage. Moreover, flash sintering was found to be triggered by the surface flashover of ceramic samples, and the electric arc on the sample surfaces floated upward before complete flash sintering at overly high pressures, resulting in the failure of flash sintering. This study reveals a new method for the facile preparation of flash-sintered ceramics at room temperature, which will promote the application of flash sintering in the ceramic industry.

Numerical study on discharge characteristics and plasma chemistry in atmospheric CO2 discharges driven by pulsed voltages

Abstract: In recent years, plasma technology as a new approach for CO2 splitting has attracted growing interest. The understanding of discharge characteristics and plasma chemistry is particularly important to improve the conversion of CO2 in applications. In this paper, the dissociation of CO2 driven by short pulsed voltages at atmospheric pressure is numerically investigated with 24 species and 137 reactions considered in the fluid model, to explore the discharge characteristics and plasma chemistry. The key reaction pathways of CO2 conversion are unveiled according to the simulation, and the calculated conversion and energy efficiency relying on the specific energy input agrees well with the experimental measurements. The simulation shows that by increasing the pulse rising rate of pulsed voltage, the breakdown voltage is enhanced and the densities of CO and O2 are significantly improved with the increase in current density. From the simulation, a relatively strong electric field of 2.6 kV/cm always persists during the plateau phase to drive the heavy positive ( CO2+) and negative ions ( CO3−) to the electrodes, and the electric field induced by the surface charge significantly affects the discharge current during the pulse falling phase. As the duration of plateau phase increases from 200 to 1000 ns, the discharge current density during the pulse falling phase is enhanced from −20.9 to −116.0 mA/cm2, indicating a very different discharge behavior from the atmospheric helium plasmas. This study provides deep insight into the atmospheric CO2 discharges driven by pulsed voltages, and according to the computational data the production of CO and O2 can be effectively optimized by tailoring the waveforms of pulsed voltages in many applications.

Controlled growth of 3D assemblies of edge enriched multilayer MoS2 nanosheets for dually selective NH3 and NO2 gas sensors

Abstract: The successful controlled growth of edge enriched 3D assemblies of MoS2 nanosheets for the fabrication of dually selective NH3 and NO2 gas sensors using a single step atmospheric pressure CVD method.

Mechanochemical Synthesis of Ammonia Employing H2O as the Proton Source Under Room Temperature and Atmospheric Pressure

Abstract: Realizing nitrogen fixation under mild conditions is of great significance to modern industry, agriculture, and society. Several approaches have been attempted to replace the conventional Haber–Bosch process to avoid high temperature and pressure reaction conditions, including photocatalysis, electrochemical catalysis, biomimetic catalysis, and so forth. This work demonstrates a conceptually novel, more cost-effective, and environment-friendly approach to nitrogen fixation by mechanical ball milling of nitrogen gas in water under room temperature and atmospheric pressure. Without extra catalysts, the stainless steel texture of the container and grinding balls has a crucial catalytic effect on direct nitrogen fixation. The presence of the ammonium ion (NH4+) in the solution is verified by both Nessler’s reagent method and ion chromatography. The process is demonstrated to be a zero-order reaction as CNH4+=2.432t(mg·L−1) (t: hour), and the optimized NH4+ selectivity reaches as high as 99.2%. Water is employed as a proton source instead of hydrogen, preventing the environmental pollution that originated from hydrogen production. Moreover, the characterizations of the resulted powders and theoretical calculations illustrate the superiority of H2O as the proton source, which lowers the energy requirement of the rate-determining step. This work provides a feasible aqueous-phase mechanochemical nitrogen fixation by ball milling N2 and H2O under mild conditions.

Highly precise measurement of atmospheric N2O and CO using improved White cell and RF current perturbation

Abstract: A highly precise dual gas sensor for measurement of atmospheric nitrous oxide (N2O) and carbon monoxide (CO) was developed and evaluated. A room temperature interband cascade laser emitting at 4.54 μm was used as a laser source to cover the absorption lines of N2O and CO simultaneously. Sensitivity and precision were enhanced by using an improved White cell with 76 m effective optical path length and radio frequency noise perturbation technique to reduce optical interference noise. A method was proposed to correct the laser frequency by calculating the correlation coefficient between the absorption signal with the reference signal, which effectively reduced the long-term drift of the absorption line center to less than 4 × 10−5 cm−1. By further precisely control the temperature and pressure of the absorption cell, a continuous 24 h measurement precision of 65 ppt N2O and 133 ppt CO at 0.1 Hz was demonstrated, with a daily drift less than 1.5 ppt. Finally, the repeatability and reliability of the sensor system were validated by real atmospheric measurements for two consecutive days.

Electric Transport in Few-Layer ReSe2 Transistors Modulated by Air Pressure and Light

Abstract: We report the fabrication and optoelectronic characterization of field-effect transistors (FETs) based on few-layer ReSe2. The devices show n-type conduction due to the Cr contacts that form low Schottky barriers with the ReSe2 nanosheet. We show that the optoelectronic performance of these FETs is strongly affected by air pressure, and it undergoes a dramatic increase in conductivity when the pressure is lowered below the atmospheric one. Surface-adsorbed oxygen and water molecules are very effective in doping ReSe2; hence, FETs based on this two-dimensional (2D) semiconductor can be used as an effective air pressure gauge. Finally, we report negative photoconductivity in the ReSe2 channel that we attribute to a back-gate-dependent trapping of the photo-excited charges.

Ammonia Synthesis at Room Temperature and Atmospheric Pressure from N2: A Boron‐Radical Approach

Abstract: Abstract Ammonia, NH3, is an essential molecule, being part of fertilizers. It is currently synthesized via the Haber–Bosch process, from the very stable dinitrogen molecule, N2 and dihydrogen, H2. This process requires high temperatures and pressures, thereby generating ca 1.6 % of the global CO2 emissions. Alternative strategies are needed to realize the functionalization of N2 to NH3 under mild conditions. Here, we show that boron‐centered radicals provide a means of activating N2 at room temperature and atmospheric pressure whilst allowing a radical process to occur, leading to the production of borylamines. Subsequent hydrolysis released NH4 +, the acidic form of NH3. EPR spectroscopy supported the intermediacy of radicals in the process, corroborated by DFT calculations, which rationalized the mechanism of the N2 functionalization by R2B radicals.

Highly precise measurement of atmospheric N2O and CO using improved White cell and RF current perturbation

Abstract: A highly precise dual gas sensor for measurement of atmospheric nitrous oxide (N2O) and carbon monoxide (CO) was developed and evaluated. A room temperature interband cascade laser emitting at 4.54 μm was used as a laser source to cover the absorption lines of N2O and CO simultaneously. Sensitivity and precision were enhanced by using an improved White cell with 76 m effective optical path length and radio frequency noise perturbation technique to reduce optical interference noise. A method was proposed to correct the laser frequency by calculating the correlation coefficient between the absorption signal with the reference signal, which effectively reduced the long-term drift of the absorption line center to less than 4 × 10−5 cm−1. By further precisely control the temperature and pressure of the absorption cell, a continuous 24 h measurement precision of 65 ppt N2O and 133 ppt CO at 0.1 Hz was demonstrated, with a daily drift less than 1.5 ppt. Finally, the repeatability and reliability of the sensor system were validated by real atmospheric measurements for two consecutive days.