Gas Pressure Research Articles

Interdisciplinary approaches to modeling extraction efficiency and safety for clean energy under coupled multi-field effects

Coal bed methane, a crucial clean energy source, has attracted extensive research attention. Characterized by intricate and rough fracture systems, coal seam is vital for gas migration, which will be influenced by the in situ stress, coal temperature, adsorption–desorption effect, solid deformation, and gas pressure. This paper introduces an innovative, interdisciplinary fractal model that addresses the limitations of current computational models in accurately representing the complex fractures under the coupled multi-field effects. Four novel fractal micro-parameters are introduced to capture the dynamics of rough networks. And rigorous validation against field extraction data reveals that the proposed micro-parameters outperform existing methods in analytical efficacy. Notably, those micro-parameters significantly influence fracture behavior and gas seepage. For instance, a DT increase from 1.2 to 1.8 and an ε rise from 0.06 to 0.18 lead to a respective 29.8% and 22.7% increase in gas pressure. Moreover, alterations in these fractal micro-parameters under coupled multi-field effects markedly impact coal bed stress, raising safety concerns in engineering projects, with a potential increase in coal stress by up to 2.62%. This research offers innovative insights into the complex coupled mechanisms governing rough fractures and significantly advances the understanding of the efficiency and safety in clean energy extraction processes.

Numerical simulation of streamer, pressure wave, and vortex induced by nanosecond pulsed surface dielectric barrier discharges

In this study, a two-dimensional fluid model is employed to simulate the streamer, pressure wave, and vortex in surface dielectric barrier discharge driven by nanosecond pulse voltage (ns-SDBD). It comprises a numerical model with two interconnected modules: discharge dynamics and gas flow dynamics. These modules are coupled through the physical variables including ‘EHD force’, ‘thermal source’, ‘velocity field’, ‘gas temperature’, and ‘gas pressure’. Our research primarily focuses on the underlying physical mechanisms of pressure waves and vortices for plasma-based flow control. The generation of pressure waves is attributed to the rapid gas heating by pulsed discharge, whereas the formation and development of the vortex are related to the ionic wind (EHD effect) provided by the plasma. To thoroughly understand and optimize flow control performance, an investigation into the effects of various discharge parameters, such as voltage amplitude and polarity, is conducted. Additionally, several SDBD modules are arranged in series, each featuring a dual three-electrode configuration. Subsequently, the dynamic behaviors of multiple streamers, pressure waves, and vortices, along with their interactions, are explored.

Intrinsic correlation between the generalized phase equilibrium condition and mechanical behaviors in hydrate-bearing sediments

The phase equilibrium and mechanical behaviors of natural gas hydrate-bearing sediment are essential for gas recovery from hydrate reservoirs. In heating closed systems, the temperature-pressure path of hydrate-bearing sediment deviates from that of pure bulk hydrate, reflecting the porous media effect in phase equilibrium. A generalized phase equilibrium equation was established for hydrate-bearing sediments, which indicates that both capillary and osmotic pressures cause the phase equilibrium curve to shift leftward on the temperature-pressure plane. In contrast to bulk hydrate, hydrate-bearing sediment always contains a certain amount of unhydrated water, which keeps phase equilibrium with the hydrate within the hydrate stability field. With changes in temperature and pressure, a portion of pore hydrate and unhydrated water may transform into each other, affecting the shear strength of hydrate-bearing sediment. A shear strength model is proposed to consider not only hydrate saturation but also the change in temperature and pressure of hydrate-bearing sediment. The model is validated by experimental data with various hydrate saturation, temperature and pressure conditions. The deformation induced by partial dissociation was studied through depressurization tests under constant effective stress. The reduction in gas pressure within the hydrate stability field indeed caused sediment deformation. The dissociation-induced deformation can be reasonably estimated as the difference in volume between hydrate-bearing and hydrate-free sediments from the compression curves.

Construction and validation of C3F8 electron impact and heavy particle reaction scheme for modeling plasma discharges

This work presents the results of developing a set of electronic and chemical reactions for a plasma discharge in octafluoropropane (C3F8). Electronic reactions were obtained using the most relevant set of cross sections at the moment, taking into account experimentally known dissociation and ionization channels. Based on the dissociation products obtained during electronic reactions, a set of chemical reactions was adapted by analogy with the C4F8 reaction scheme from the literature. Next, the resulting complete set of reactions was tested against published experimental data on the concentration of electrons, negative ions, and electronegativity in a capacitive plasma discharge at different gas pressures and discharge input powers. For this purpose, a one-dimensional hydrodynamic drift-diffusion model was used. Reasonable agreement was obtained between the model and experimental data on electronegativity. Eventually, the resulting set of reactions was adapted for a two-dimensional hydrodynamic drift-diffusion model of an ICP discharge. The results of the calculations are two-dimensional distributions of radicals and ions, radical and ion composition of fluxes onto the substrate under conditions typical for industrial reactors.

Hollow microsphere probes formed by hollow core optical fiber discharging for monitoring gas pressure and temperature.

A hollow core fiber (HCF) is spliced with a single-mode fiber, and then, the end face of the HCF is etched to form a microsphere interferometer for measuring gas pressure and environmental temperature. The total length of each microsphere is less than 200μm. We fabricated two such structures and used femtosecond laser pulses to drill micro-holes on the HCF walls of both structures. One of the structures is directly used to measure air pressure, achieving a sensitivity of up to 2.857 nm/MPa while being almost insensitive to temperature. This structure is capable of assessing pressure down to 3.4kPa within the range of 0-0.5 MPa. Another structure is filled with thermally sensitive material dimethyl silicone oil through a micro-hole, and then, it is sealed with AB adhesive to form a harmonic Vernier effect temperature sensor, with a sensitivity of up to -5.16 nm/°C. This structure is capable of assessing temperature down to 0.38 °C within the range of 30-60 °C. Additionally, the sensors have good repeatability and stability and compact structure and simple manufacturing and can be used as a sensing probe for monitoring gas pressure and temperature under extreme environments.

Экспериментальное исследование гидравлических характеристик сферических насадок для массообменных аппаратов

A critical analysis of the trends in the development of nozzles for mass transfer devices is given, some designs are described in which the transfer of heat and mass is organized from the standpoint of today technically the most perfect. It is shown that the specific surface, the free specific volume of the nozzle and the hydraulic resistance of the layer are determined as the main characteristics of irregular type packing bodies. The scheme and description of an experimental setup for determining the hydrodynamic characteristics of nozzles in laboratory conditions are given. The results of studies of the hydrodynamic parameters of a layer consisting of a spherical hollow irregular nozzle for a dry and irrigated column are presented. The singular velocities of the gas flow corresponding to the transition points (points of deceleration, suspension, inversion or choking) to different hydrodynamic modes of operation of the filling mass transfer columns (film, intermediate, turbulent) and corresponding pressure drops have been experimentally determined. The dependences of the hydraulic resistance of the nozzle layer on the gas velocity in the column for dry and irrigated nozzles with a 1 m high layer are determined. The main reasons for the decrease in gas pressure in the layer of the irrigated nozzle are indicated. The singular gas flow velocities and their corresponding pressure drops are calculated using known empirical dependencies for dry and irrigated nozzles. The results of experimental studies and engineering calculations were compared, thereby proving the possibility of using computational equations with satisfactory accuracy (up to 15%). The study of the hydrodynamics of the layer and its hydraulic characteristics has shown that the spherical, hollow nozzle design with evenly spaced holes on the surface provides an effective redistribution of working phases in the mass transfer apparatus.

Optimizing unconventional gas extraction: The role of fracture roughness

In unconventional reservoir engineering, such as coalbed methane and shale gas extraction, fracture behavior is pivotal in gas accumulation, migration, and extraction, acting as a primary channel for gas flow. Current research inadequately addresses the quantitative impact of fracture roughness on gas extraction. In this study, we introduce a novel interdisciplinary model that quantitatively characterizes shale fracture roughness and correlates it with shale permeability. This model comprehensively considers factors affecting shale extraction, including fracture roughness, in situ stress, reservoir deformation, and adsorption-desorption dynamics. It provides a thorough analysis of how fracture roughness influences gas seepage, extraction efficiency, and reservoir stability under various physical conditions. Our validated findings reveal that fracture roughness significantly affects shale permeability, stress responses, and displacement. As the fracture roughness coefficient χ increases from 0.2 to 1.0, the maximum reduction in gas pressure within the hydraulically fractured region is 4.7%, while the maximum increase in reservoir stress is 2.8%. In shale reservoirs near extraction well, particularly in hydraulically fractured zones, the maximum decrease in shale gas pressure is 11.1%, and the maximum increase in stress is 3.2%, which offer a groundbreaking approach for optimizing extraction rates and ensuring project safety in the industry.

Effects of Stepdown Pressure and Wettability on Bubble Nucleation in Gas-Supersaturated Oil-Water Systems

Summary This study investigates the influences of wettability and stepdown pressure on pressure-driven bubble nucleation within a gas-supersaturated oil-water system. Two gases—carbon dioxide (CO2), which is highly soluble in water, and methane (CH4), which is sparingly soluble in water—were used individually for the bubble nucleation experiments. Equal heights of oil (n-decane) and water, in a wettability-controlled glass vial placed in a saturation cell, were saturated with either of the gases at 6000-mbar pressure, followed by applying a stepdown pressure of either 6000 mbar, 500 mbar, or 100 mbar to start the bubble nucleation process. The average bubble nucleation pressures for CO2 and CH4 gases on a hydrophobic vial surface with 500-mbar stepdown pressure were 4333 ± 289 mbar and 3833 ± 289 mbar, respectively. It is important to note that the bubble nucleation took place exclusively on the portion of the solid surface submerged in water. However, bubble nucleation did not take place with 100-mbar stepdown pressure for either gas in the hydrophobic vial despite the pressure being brought down to atmospheric pressure. As expected, bubble nucleation did not take place in the hydrophilic vial for the gases despite the pressure being brought down to atmospheric pressure from the saturation pressure, regardless of the stepdown pressure. In addition, bubble nucleation did not take place in CO2-supersaturated water in the oil-wetted hydrophilic and hydrophobic vials, even at maximum supersaturation.

Centralized design and production of the ultra-high vacuum and laser-stabilization systems for the AION ultra-cold strontium laboratories

This paper outlines the centralized design and production of the ultra-high-vacuum sidearm and laser-stabilization systems for the AION Ultra-Cold Strontium Laboratories. Commissioning data on the residual gas and steady-state pressures in the sidearm chambers, on magnetic field quality, on laser stabilization, and on the loading rate for the 3D magneto-optical trap are presented. Streamlining the design and production of the sidearm and laser stabilization systems enabled the AION Collaboration to build and equip in parallel five state-of-the-art Ultra-Cold Strontium Laboratories within 24 months by leveraging key expertise in the collaboration. This approach could serve as a model for the development and construction of other cold atom experiments, such as atomic clock experiments and neutral atom quantum computing systems, by establishing dedicated design and production units at national laboratories.

Topological signatures of Mo2TiC2O2

Mo2TiC2 is the Ordered Double Transitional Metal Layered Carbides (ODTMLC) derived from its parent MAX phases Mo2TiAlC2 by a wet chemical etching. Its oxidation was done by a new ablated plasma thrust method in which the MXenes were at 750 °C under an oxygen background in the pulsed laser deposition chamber. The reflective high electron energy diffraction technique assures the oxidation at the ambient gas pressure p = 0.1 mbar, which was described in the previous paper. The obtained Mo2TiC2O2 was transferred for their topological test under angle-resolved photoemission spectroscopy, circular dichroism test, and Chemical Potential (CP) analysis. An indirect energy bandgap of 125 meV was obtained. The sine function of α along with period π and β with period 2π shows that there is a possibility of helical spin textures in both α (electron-like pocket around Γ̄) and β (elliptical electron-like pocket around M̄). The CP analysis shows the possibility of at least 100 meV bandgap creation on a single surface so that the surface charges will flow without any effect of bulk. The Mo2TiC2O2 can be used as topological insulating material.

Preparation and thermal responsiveness of microencapsulated fluorinated liquids for automatic fire extinguishing

Most early-stage fires originating in small confined spaces may not be effectively mitigated by automatic fire-extinguishing systems. Leveraging the unique controlled release capability and barrier properties of microcapsules presents a promising avenue for developing multifunctional and intelligent fire-extinguishing agents tailored for early-stage fire suppression. This paper introduces two types of microcapsules that integrate automatic detection and fire extinguishing functions, utilizing fluorinated liquids specifically perfluoro(2-methyl-3-pentanone) and 1,1,1,2,2,3,4,5,5,5 decafluoro-3-methoxy-4(trifluoromethyl)-pentane as core materials. The preparation process was optimized, and the thermal response of the microcapsules was evaluated by directly incorporating them into combustible materials. The results indicated a correlation between the preparation method, coating efficiency, and thermal stability of microcapsules with the core-wall materials. When the fluoride solution in the core material reaches the thermal response threshold temperature, the gas pressure generated during vaporization and phase change can break through the shell, enabling early active fire protection. Beyond a specific threshold of additive microcapsules in the material, the material exhibits self-extinguishing potential during combustion. In cases where the additive amount falls short of achieving self-extinguishing, the fire-resistant performance of materials can be enhanced through various measures. For instance, reducing the amount of fire-extinguishing agents, delaying the ignition time of fuel, and lowering the heat release rate during combustion are effective strategies. Moreover, the degree of improvement is related to the additional amount and the type of core-wall materials. The thermal-response mechanism of microcapsules constitutes a comprehensive mechanism with physical and chemical effects. The finding of this research offer a new technical approach for microencapsulating high-boiling-point gas extinguishing agents, facilitating intelligent and precise prevention of early fires resulting from combustible materials.

Usage of Energy Storage Capacitors in TE Gas Laser Pulsers

An energy storage capacitor is crucial for both electrically pumped and optically pumped pulsed lasers. In electrically pumped lasers, the energy stored in the capacitors is directly deposited into the lasing medium, while in optically pumped lasers, it energizes the flash lamp that, in turn, pumps the lasing medium. We discuss here the application of energy storage capacitors in the operation of electrically pumped pulsed gas lasers. Increasing the operating pressure of the gain medium, a prerequisite for obtaining higher energy from the laser, has resulted in great advancements in the gas laser pulse technology. This progress has led to the development of transverse electric discharge pumping, enabling easy scalability of gas pressure and achievable output power. An ideal TE pulser efficiently charges the capacitor to an appropriate voltage with minimal energy dissipation on the charging element and facilitates a rapid and uniform transfer of this stored energy into the lasing medium before a glow-to-arc transition can set in. Various types of pulser circuits employed to energize pulsed gas lasers are described in this paper.

Compact Hybrid Interferometer Based on Twin- Core Side Hole Fiber and Harmonic Vernier Effect for Gas Pressure Measurement

Compact Hybrid Interferometer Based on Twin- Core Side Hole Fiber and Harmonic Vernier Effect for Gas Pressure Measurement

Study of synchronous RF pulsing in dual frequency capacitively coupled plasma

Low-pressure multi-frequency capacitively coupled plasmas (CCPs) are used for numerous etch and deposition applications in the semiconductor industry. Pulsing of the radio-frequency (RF) sources enables control of neutral and charged species in the plasma on a millisecond timescale. The synchronous (i.e. simultaneous, in-phase) pulsing of both power sources in a dual frequency CCP is examined in this article. Due to the low gas pressure, modeling has been done using the electrostatic particle-in-cell/Monte Carlo collision method. The objective of this work is to investigate the sensitivity of the plasma properties to small changes in timing during synchronous pulsing of the two RF sources. It is demonstrated that small deviations in the on and off times of the two RF sources can lead to major changes in the plasma characteristics. This high sensitivity is of concern for process repeatability but can be utilized to enable better control of the dynamics of plasma-surface interaction. In the simulations, the pulsing parameters (on and off times and ramp rates) are varied and the temporal evolution of plasma characteristics such as electron density (ne ), species current at the electrode, and electron temperature are examined. It is demonstrated that if the low-frequency (LF) source is turned off a few μs before (or after) the high-frequency source, ne during the off-state is significantly higher (or lower) due to the frequency coupling effect. Similarly, turning on the LF source with a small delay results in a sharp increase in the plasma density when the RF sources are turned on.

Formation and Stability of Salty Soil Seals in Mars‐Like Conditions. Implications for Methane Variability on Mars

AbstractMethane spikes observed in the Martian atmosphere require the abrupt release of large amounts of methane from the Martian subsurface. The mechanism for such release has not been identified. We tested whether gas traps can form under Mars‐like conditions in the shallow Martian regolith due to salt migration in the icy soil. Experiments were performed on various soil samples in a Mars Simulation Chamber comprising different perchlorate salts and water concentrations mixed with JSC Mars‐1A. Inside the chamber, the samples were exposed to a range of temperatures from −20°C to 10°C and maintained CO2 gaseous pressure between 8 and 10 mbars. As a methane analog, Neon was injected periodically underneath the soil sample. It was found that over a wide range of Mars‐like soil parameters, a gas impermeable soil seal can form over a relatively short period (3–13 days) but requires 5%–10% of perchlorate salt content in the soil. It was determined that such a seal could sustain several mbars of neon above the Martian atmospheric pressure in the soil. Based on our experiments, substantial amounts of gaseous methane may accumulate under the soil seal and get released abruptly into the atmosphere upon seal cracking. An abrupt release of methane from the shallow subsurface may help explain methane variability at the Martian surface, as the Mars Science Laboratory detected.

Statistical Investigations on Relationship of Intraocular Pressure with Environmental Factors

Clinical relevance: Intraocular pressure (IOP) has a significant role in glaucoma pathophysiology. There are factors that influence in the IOP value, such as central corneal thickness or the biomechanical properties of the cornea. However, other less studied factors may influence the IOP, such as environmental pollution.
 Background: The increase in air pollution is related to acute respiratory pathologies. Regarding the eyes, is related to conjunctivitis or dry eye disease. The purpose was to analyse the correlation of environmental factors (atmospheric pressure, temperature, O3, NO2, PM10 and PM2.5 concentrations) with intraocular pressure in young healthy patients.
 Methods: A cross-sectional study was carried out on patients treated at General Optica centres in Spain and Portugal in collaboration with the University of Valladolid. This study included healthy patients (between 18 and 40 years old). IOP measurements were taken with different air tonometers (CT-80, CT-800, NCT-200, NT-510 and NT-530) for one week and correlated with environmental factors (atmospheric pressure, temperature, O3, NO2, PM10 and PM2.5 concentrations). Correlation (Spearman’s Rho) analyses were performed between IOP and the different environmental parameters. Moreover, groupings were performed as a function of the values for healthy exposure levels recommended by the WHO. Different comparisons were performed using the Mann‒Whitney U test.
 Results: Statistically significant correlations were found (p < .04) between IOP and temperature (r = 0.37), atmospheric pressure (r = 0.20), NO2 (r = 0.14), PM10 (r = 0.21), O3 (r = 0.16) and PM2.5 concentrations (r = 0.16). Regarding the IOP values of people who were exposed to unhealthy concentrations (AQI > 20) versus those who were not, higher IOP values were only found in people exposed to PM2.5.
 Conclusion: Slight correlations were found between higher temperature, atmospheric pressure and concentrations of pollutant gases and increased IOP. More clinical studies are needed to understand the role that these environmental factors play in the aqueous humour flow and the value of IOP to know if and to what extent these factors may be risk of glaucoma.

The Four-Sinker Densimeter: A New Instrument for the Combined Investigation of Accurate Densities and Sorption Phenomena of Pure Gases and Gas Mixtures

An apparatus for high-accuracy gas density and adsorption measurements over the range of temperature from (193 to 423) K and pressure from (0 to 15) MPa is described. This instrument is based on the two-sinker densimetry principle and incorporates a magnetic suspension balance. In addition to the two “density sinkers”, two “sorption sinkers” are weighed to investigate density and adsorption of a gas sample simultaneously. The design of the sinkers increases the resolution of density and adsorption investigations and enables the correction of sorption effects on density measurements. The complete apparatus, including the sinkers, the temperature and pressure measuring systems, and the measurement procedure, is described. For the density range investigated, the uncertainty (k = 2) is between (0.0034 to 0.019) kg·\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$\\cdot$$\\end{document}m−3, corresponding to (0.060 to 0.011)%. The uncertainty (k = 2) in adsorption load is (0.16 to 0.26) μ\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$\\upmu$$\\end{document}g·\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$\\cdot$$\\end{document}cm−2. Density measurements at T = (283 and 293) K and pressures up to 10 MPa of high-purity argon and nitrogen validate the instrument for density. Adsorption measurements of high-purity carbon dioxide and propane on a gold surface validate the instrument for adsorption investigation at T = (283 and 293) K and up to the saturation pressure of the investigated gas. The apparatus was used to measure the binary mixture (0.75 CO2\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$\ ext{CO}_2$$\\end{document} + 0.25 C3H8\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$${\ ext{C}_3\ ext{H}_8}$$\\end{document}). In the future, the apparatus will also be used to accurately determine dew-point densities and pressures of pure gases and gas mixtures.

Synchrotron signatures of cosmic ray transport physics in galaxies

ABSTRACT Cosmic rays (CRs) may drive outflows and alter the phase structure of the circumgalactic medium, with potentially important implications on galaxy formation. However, these effects ultimately depend on the dominant mode of transport of CRs within and around galaxies, which remains highly uncertain. To explore potential observable constraints on CR transport, we investigate a set of cosmological fire-2 CR-magnetohydrodynamic simulations of L* galaxies which evolve CRs with transport models motivated by self-confinement (SC) and extrinsic turbulence (ET) paradigms. To first order, the synchrotron properties diverge between SC and ET models due to a CR physics-driven hysteresis. SC models show a higher tendency to undergo ‘ejective’ feedback events due to a runaway buildup of CR pressure in dense gas due to the behaviour of SC transport scalings at extremal CR energy densities. The corresponding CR wind-driven hysteresis results in brighter, smoother, and more extended synchrotron emission in SC runs relative to ET and constant diffusion runs. The differences in synchrotron arise from different morphology, interstellar medium gas, and B properties, potentially ruling out SC as the dominant mode of CR transport in typical star-forming L* galaxies, and indicating the prospect for non-thermal radio continuum observations to constrain CR transport physics.

The effect of winds on atmospheric layers of red supergiants II. Modelling VLTI/GRAVITY and MATISSE observations of AH Sco, KW Sgr, V602 Car, CK Car, and V460 Car

Context. Mass loss plays a crucial role in the lives of massive stars, especially as the star leaves the main sequence and evolves to the red supergiant (RSG) phase. Despite its importance, the physical processes that trigger mass-loss events in RSGs are still not well understood. Recently, we showed that adding a semi-empirical wind to atmosphere models can accurately reproduce observed extensions in the atmospheres of RSGs, where the mass-loss events are taking place, particularly in the CO and water lines. Aims. By adding a static wind to a MARCS atmospheric model, we computed synthetic observables that match new interferometric data of the RSGs AH Sco, KW Sgr, V602 Car, CK Car, and V460 Car obtained with the VLTI/MATISSE and VLTI/GRAVITY instruments between August 2022 and February 2023. We also used archival VLTI/AMBER data of KW Sgr and VLTI/GRAVITY data of AH Sco. The MATISSE wavelength range includes the SiO molecule at 4.0 μm with a spectral resolution of R ~ 500. Methods. The model intensities with respect to the line-of-sight angle (μ) as well as the spectra and visibilities were computed using the stellar radiative transfer code TURBOSPECTRUM. We found the best-fit model, mass-loss rate, and best-fit angular Rosseland diameter for the observations. We simultaneously matched our model to the data, covering a wavelength range of 1.8–5.0 μm, which corresponds to the K, L, and M bands. Results. Our models reproduce the spectro-interferometric data over this wide wavelength range, including extended atmospheric layers of CO, H2O, and SiO. We obtain a range of Rosseland angular diameters between 3.0 < θRoss < 5.5 mas and a range of mass-loss rates of −6.5 < log Ṁ/M⊙ yr−1 < −4 for our five targets. In our best-fit models, the partial pressure of SiO relative to the gas pressure, PSiO/Pg, and the SiO 4.0 μm line intensity increase between 2 and 3 stellar radii. The relative intensity depends on the luminosity used for our models, since the more luminous models have a higher mass-loss rate. Conclusions. This work further demonstrates that our MARCS+wind model can reproduce the observed physical extension of RSG atmospheres for several spectral diagnostics spanning a broad wavelength range. We reproduce both spectra and visibilities of newly obtained data as well as provide temperature and density stratifications that are consistent with the observations. With the MATISSE data, we newly include the extension of SiO layers as a precursor of silicate dust.

Determination of Non-ionizing Radiation and Shielding Studies of a New DC Plasma Device

In the present work, the determination of the electromagnetic radiation and shielding studies of a new designed and constructed portative plasma device have been reported. For this aim, the electromagnetic interference (EMI) measurements are performed. The device works with high voltage up to 2 kV depending on its filling gas pressure and contains a couple of terminals in the low pressurized chamber to form plasma structures confined in terms of electrical and magnetic confinement. The chamber as a simple torus geometry has been operated with He gas for the plasma stability explorations. The EMI measurements have been practiced for different distances from the setup and used different shielding materials to prevent the non-ionizing radiation. According to detailed tests with different shielding materials (Swatter, Square, Honeycomb) it is observed that the shape of the shielding material is very important for the optimum shielding results.