Gaseous Medium Research Articles

Jetted Seyfert Galaxies at z = 0: Simulating Feedback Effects on Galactic Morphology and Beyond

Abstract We use high-resolution cosmological zoom-in simulations to model feedback from Seyfert-type supermassive black hole (SMBH) jets onto galaxies with identical dark matter (DM) halos of log M/M ⊙ ∼ 11.8. The low-mass, ∼106 M ⊙, seed SMBHs have been introduced when the parent DM halos have reached log M/M ⊙ ∼ 11. In a controlled experiment, we vary only the efficiency of the SMBH accretion and focus on galaxies and their immediate environment properties. Our results show that the active galactic nucleus jet feedback has a substantial effect on the basic properties of Seyfert-type galaxies, such as morphology, gas fraction and distribution, star formation rate and distribution, B/D ratio, DM halo baryon fraction, and properties of the circumgalactic medium and beyond. These have been compared to a galaxy with supernovae only feedback. We focus on the energy deposition by the jet in the interstellar medium (ISM) and intergalactic gas medium, and follow the expansion of the multiple jet cocoons to ∼2 Mpc. We find that the jet–ISM interaction gradually pushes the star formation to larger radii with increasing accretion efficiency, which results in increased mass of the outer stellar disk, which is best fit as a double-exponential disk. Furthermore, we compare our galaxies and their properties with the observed nearby Seyfert galaxies, including the scaling relations, and find a close agreement, although statistical analysis of observed Seyferts is currently missing. In a forthcoming paper, we focus on the evolution of these objects at z ≲ 10 and study the effect of the SMBH seeding redshift.

Suppression of Collision-Induced Dissociation in a Supersonically Expanding Gas.

In high-resolution mass spectrometry, an electrospray ionization source is often paired with an ion-funnel to enhance ion transmission. Although it is established that ions experience collision-induced dissociation as they pass through this device, the impact of gas-flow dynamics on ion fragmentation remains unexplored. The present work demonstrates that the gas-flow dynamics from the capillary interface of an electrospray ionization source into an ion-funnel significantly reduces ion fragmentation. This reduction stems from the substantial decrease in the rate of increase in the internal energy of the ions, resulting from the collisions with a supersonically expanding gas. The results of this study have significant consequences for systems that employ electrospray mass spectrometry and ion-mobility spectrometry as well as in interdisciplinary fields involving ion transport through a gaseous medium.

Synthesis and performance analysis of novel SiO2 Janus nanoparticles for enhancing gas foam injection in oil reservoirs

Gas foam injection offers a viable solution to challenges faced in oil reservoirs, yet ensuring optimal foamability and stability remains a pivotal hurdle in practical field operations. This study presents a novel synthesis procedure to create silica (SiO2) Janus nanoparticles (JNPs) and examines their potential to enhance gas foam stability for enhanced oil recovery (EOR) applications. Two variations of SiO2 JNPs were synthesized via a masking procedure, employing oleic acid and ascorbic acid within a Pickering emulsion, marking a pioneering approach. These nanoparticles underwent comprehensive analysis for a deeper understanding. The investigation sought to unravel the mechanisms behind these JNPs’ performance in the foam injection process, probing various operational parameters such as JNP type, concentration, and gas medium (air, CO2, and CH4) impact on surface tension reduction, foamability, and stability through static tests. Results uncovered remarkable efficiency in SiO2-oleic acid JNPs, showcasing a substantial edge in reducing surface tension compared to bare SiO2 nanoparticles. Specifically, at a concentration of 15,000 ppm, SiO2-oleic acid JNPs demonstrated a 25 mN/m greater reduction in surface tension than bare SiO2 within a CH4 medium. Notably, while the gas type had limited influence on surface tension under standard pressure, the synthesized JNPs showed superior foam stabilization in air compared to CO2 and CH4 environments. SiO2-oleic JNPs exhibited outstanding foamability, stabilizing 80% of the foam generator cell’s height and remaining stable for 122 min during the EOR process. Conversely, ascorbic acid-SiO2-oleic acid JNPs displayed elevated foamability but reduced stability compared to SiO2-oleic acid JNPs. Despite achieving full height in the foam generator cell, stability was limited to 26 min in the CO2 medium.

Carrier-envelope-phase characterization of ultrafast mid-infrared laser pulses through harmonic generation and interference in argon

The propagation of an intense, femtosecond, mid-infrared laser pulse in a gaseous medium results in the efficient generation of spectrally overlapping low-order harmonics, whose optical carrier phases are linked to the carrier-envelope phase (CEP) of the mid-infrared driver pulse. Random peak-power fluctuations of the driver pulses, converted to the fluctuations of the nonlinear phases, acquired by the pulses on propagation, cause this phase correlation to smear out. We show that this seemingly irreversible loss of phase can be recovered, and that the complete information needed for the phase correction is contained in the harmonic spectra itself. The optical phases of the intense driver pulse and its harmonics, as fragile as they appear to be against even weak disturbances, evolve deterministically during highly nonlinear propagation through the extended ionization region.

Development of supported nickel-containing catalysts for methane tri-reforming: influence of pretreatment conditions

To improve the efficiency of catalysts for methane tri-reforming, the effect of pretreatment conditions of the Ce0.2Ni0.8O1.2/Al2O3 catalyst on its physicochemical and functional properties was studied. A set of methods (thermal analysis, low-temperature nitrogen adsorption, X-ray phase analysis, electron microscopy, temperature-programmed reduction with hydrogen) has established that varying the composition of the gaseous medium (oxidizing, inert, reducing) used during pretreatment at 800 °C allows one to adjust the textural, structural and redox characteristics of the catalyst and, as a consequence, its functional properties. It has been shown that in the series of compositions of the gas environment used in the pretreatment of the catalyst, oxidative → inert → reducing, an increase in the specific surface area and dispersion of the active component is observed, but a decrease in the resistance of the sample to reoxidation and coking. It has been established that the highest and most stable performance of the methane tri-reforming process (H2 yield – 86 % at CH4 conversion – 95 %) is provided by the catalyst after pretreatment in an inert environment due to the implementation of the optimal degree of metal-support interaction and an increase in the concentration of centers involved in CO2 activation.

A prediction model for electrical strength of gaseous medium based on molecular reactivity descriptors and machine learning method.

Ionization and adsorption in gas discharge are similar to electrophilic and nucleophilic reactions. The molecular descriptors characterizing reactions such as electrostatic potential descriptors are useful in predicting the electrical strength of environmentally friendly gases. In this study, descriptors of 73 molecules are employed for correlation analysis with electrical strength. These molecular descriptors are categorized into two types: area-related descriptors and reactivity-related descriptors. Furthermore, the predictive performance between statistical models and machine learning models is compared. The statistical models include multiple linear regression, and polynomial regression, while machine learning models consist of K-nearest neighbors, random forest, and gradient boosting decision trees. The results indicate that machine learning models are generally better than statistical models in terms of predictive accuracy and stability, with gradient boosting decision trees demonstrating the best performance. Specifically, the coefficient of determination and mean squared error on the testing set after 1000 training iterations are 0.864 and 0.105, respectively. Therefore, the application of molecular reactivity descriptors and machine learning methods can effectively predict the electrical strength of gaseous medium. The Gaussian 16 software is employed to optimize the molecular structure with the M06-2X functional and def2 series basis sets in this study. Then, the Multiwfn is utilized for wavefunction analysis to obtain molecular surface descriptors.

Analytical Solution and Energy Behavior to a Forced Shock Wave Problem Under Dusty Gas Regime

ABSTRACTIn the presented research work, we have solved a new kind of problem of forced shock waves in a compressible inviscid perfect gas having dirty (dust) particles of small size in a one‐dimensional unsteady adiabatic flow. The approach that we have used is referred to as the generalized geometry approach. Here, we investigated how the density of the zone, which is undisturbed, changes as a function of the position from the point of the source of explosion. In addition, we have obtained analytically a novel solution to the problem in the form of a new rule of power of time and distance. Further, we have investigated the energy behavior of forced shock waves and interaction within the environment containing dust particles. Also, the behavior of the entire energy of a forced shock wave is expounded at different Mach numbers, respectively, for planar geometry, cylindrically symmetric geometry, and spherically symmetric geometry under a dusty gas medium. Furthermore, the findings show that dust particles in a gas produce a more sophisticated representation rather than the standard gas dynamics.

Modeling Femtosecond Beam Propagation in Dielectric Hollow-Core Waveguides

The propagation of femtosecond pulses in guided structures is a matter of both fundamental and practical interest in nonlinear optics. In particular, hollow-core waveguides (HCWs) filled with a gas medium are fabricated and used as devices for the generation of attosecond pulses from high-order harmonics. In this process, the configuration of the laser field (intensity and phase) inside the waveguide is of crucial importance for enhancing the (well-known, low) efficiency of high-order harmonic generation (HHG). Here, we present numerical calculations which demonstrate the main features of the propagation process in fabricated HCWs. We consider a variety of experimental parameters like gas pressure, waveguide size, laser wavelength, and pulse energy and duration. In particular, the beam profile at the fiber input is found to be a sensitive parameter which influences the whole evolution of the laser field along the propagation. Our model is based on a split-step method modified to account for propagation in ionized media and is validated against experimental and theoretical data from the literature. Our results contribute to the description of the main features of beam propagation in HCWs and provide guiding directions for designing efficient configurations for HHG.

ЕЛЕКТРОСТАТИЧНЕ ПОЛЕ В ПОВІТРЯНОМУ ПРОМІЖКУ СИСТЕМИ ПЛОСКО-ПАРАЛЕЛЬНИХ ЕЛЕКТРОДІВ ДЛЯ ОБРОБКИ КРАПЕЛЬ ВОДИ БАР’ЄРНИМ РОЗРЯДОМ

This study investigates the electrostatic field in a discharge chamber (DC) designed for water purification from organic pollutants using pulsed barrier discharge (PBD) technology. The DC consists of vertical plane-parallel electrodes, with an air gap containing water droplets between them, and one of the electrodes is insulated from the air gap by a dielectric (barrier). The research employs computer modeling in both two-dimensional and three-dimensional setups. Therefore, the aim of this work is to compare the distribution of the electrostatic field intensity of PBD in the air gap and the electrical capacitance of the DC to establish the optimal distance between droplets and to determine the calculation error using the two-dimensional DC model. Electrostatic field modeling was performed using the Poisson equation and the finite element method. Calculations were performed for two-dimensional and three-dimensional models with conditions of a droplet diameter of 1 mm, a gas gap length of 3.36 mm, and an applied voltage of 3 kV. The influence of droplet conductivity and the distance between them on the characteristics of the electrostatic field in the gas medium and in the droplets was investigated. A comparison of the calculated capacitance values of the DC in the two-dimensional and three-dimensional models depending on the distance between the droplets was conducted. The research results can be used in the application of electro-discharge technology based on pulsed barrier discharges in water treatment systems, specifically in selecting the parameters for the movement of the treated liquid in the plasma zone. References 10, figures 7.

Multiwire Position-Sensitive Neutron Detector with Two Layers of Boron-10

Multiwire position-sensitive neutron detector with two layers of boron-10 was developed to detect both thermal and fast neutrons. Sensitive dimensions of two coordinate neutron detector are 50 × 50 mm. New detector characteristics are compared with ones of 100 × 100 mm detector built earlier which we used in neutron flux spatial distribution measurement. Plane-parallel design of new detector has symmetrical structure with respect to wire anode and also includes two intermediate grids and two cathodes made of parallel wires with 2 mm pitch and two silicon substrates coated boron-10 layers of 0.003 mm thickness. Detector geometry, working gas mixture and pressure are chosen so as to ensure full absorption of secondary alpha particle from reaction with thermal neutron within detector gas medium half thickness. Neutron coordinates are determined from measured ionization loss pulse heights produced by secondary nucleus. Detector expected efficiency to thermal neutrons is about 5%. The detector can be used in small-angle and diffraction scattering setups in condensed matter physics.

Investigation of the effect of the angle of inclination of the receiving surface on the displacement of a single deposited layer during additive shaping by an electric arc in a protective gas medium

Purpose of research. The study is devoted to the study of the influence of the angle of inclination of the receiving surface with a convex and concave profile on the change in the displacement of a single deposited layer during additive shaping by an electric arc in a protective gas medium. Experimental studies on shaping on receiving surfaces with different angles of inclination have been carried out. Based on the samples obtained by electric arc welding in a protective gas medium, the displacement values of the individual deposited layers are determined. Since the angle of inclination of the receiving surface can affect the displacement of a single deposited layer during additive shaping by an electric arc in a protective environment, a one-factor dispersion analysis was performed. Methods. Methods of organization and planning of the experiment, mathematical processing of experimental results, single-factor analysis of variance. Results. As a result of the dispersion analysis, it was revealed that the angle of inclination of the receiving surface during additive shaping of products affects the displacement of a single deposited layer and is a significant parameter during additive shaping by an electric arc in a protective gas environment. In particular, it was found that the significance criterion for the slope angle is p < 0.01. In turn, for a convex surface it is p < 0.03, for a concave surface it is p < 0.004. Comparing the results, it can be seen that the criterion is more significant for a concave surface. Conclusion. It is determined that the angle of inclination of the receiving surface significantly affects the change in the displacement of a single deposited layer during additive shaping by an electric arc in the sphere of protective gas. Therefore, the angle of inclination of the receiving surface with a convex and concave profile is significant and should be taken into account when designing technological processes for additive shaping of products by an electric arc in a protective environment.

An Effective Method for Generating Isolated Attosecond Pulses from a Solid Crystal Film

Solids subjected to strong-field laser excitation can produce high harmonics, making high-order harmonic generation (HHG) one of the most effective methods for creating ultrafast coherent light sources, such as isolated attosecond pulses (IAPs). While extensive research has been conducted on generating IAPs through HHG in gaseous media, studies focusing on solid media are relatively limited. In crystals, the presence of numerous ionization and recombination sites, combined with high density and periodic structure, results in more complex interference dynamics. This complexity paves the way for unique applications in generating IAPs. Using an argon (Ar) crystal as a specific example, we have proposed and theoretically demonstrated an innovative approach for generating IAPs from a solid crystal film using a multi-cycle conventional driving laser pulse.

Variable Kerr nonlinearity and optical bistability of a four-level lambda atomic medium

Using perturbation theory we obtain expressions for the third-order nonlinear susceptibility and the Kerr nonlinear coefficient of a four-level lambda-type atomic system in the presence of Doppler broadening. The model is applied to the Rb atomic gas medium at room temperature; the investigations demonstrate the ability to enhance and control the Kerr nonlinear coefficient according to laser parameters in single-window and double-window EIT regimes. The amplitude and the sign of the Kerr nonlinear coefficient change sensitively to the driving laser parameters as well as ambient temperature. As a representative application, this Kerr nonlinear medium is applied to optical bistability (OB) and shows that the threshold intensity and the width of OB are also easily changed according to the laser parameters. In particular, in double-window EIT regime the emergence of nonlinear coefficient at different frequency domains that leads to the appearance of OB at multiple frequency domains simultaneously. This study is a good preparation for experimental observations of Kerr nonlinearity and optical bistability.

COMPLEX TECHNOLOGY OF THE CLEANING OF AGGLOMERATION GASES FROM DUST AND HARMFUL GASES WITH OBTAINING A GOOD PRODUCT

The purpose of the work is to improve the design of the dust-catching device of the sintering machine, to increase the efficiency of catching charged dust particles in laminar layers near the precipitating elements, the configuration and location of the elements of the precipitating elements, to establish the dependence of the effective (calculated) drift speed of charged dispersed particles on the speed of the medium being cleaned, with classical the process of electrogas purification and the combined flow of gases in electrofilters. It was established that the combined movement of gases in a modular unit ensures the charging of the entire population of dust particles to the limit values ​​by organizing a highly turbulent flow and keeping dust particles in the zones with the greatest tension in the corona charge covers, as well as effective trapping of charged dust particles in laminar layers near the precipitating elements . Mathematical modeling of the deposition block was carried out in order to optimize the configuration. The main dependences of the number and mutual location of precipitating elements to ensure maximum dust deposition were established. Studies of gas medium velocity spectra in models of new electrostatic precipitators have been carried out. The optimal live cross-sections of the aerodynamic partitions are determined to ensure favorable conditions for charging suspended particles and uniform distribution of the cleaned flow through the catching holes. The MV-2 modular type electric gas purification device with a capacity of 30 thousand nm3/h has been developed, based on innovative developments in the field of KEIT (combined electro-ion gas purification technology) in the field of conversion and control of cascade energy and aerodynamics of turbulent and laminar flows during inertial deposition dispersed suspension of flue gases. An apparatus for cleaning gases from a sinter machine with a capacity of up to 400,000 nm3/h is proposed. with an efficiency of 99 %, for replacing existing equipment (multicyclones). "MV-2JS" electric device was developed. This is a plasma-catalytic reactor, which allows you to produce the necessary amount of ozone in a low-cost way to oxidize the harmful components (SO2, NOx, CO) of the outgoing gases. The use of this device allows, in addition to the cleaning of flue gases from harmful gas impurities, to obtain commercial products (fertilizers, gypsum, sulfuric acid, etc.) at the output and to completely get rid of solid and liquid waste during gas desulfurization.

Spatial filtering and optimal generation of high-flux soft x-ray high harmonics using a Bessel–Gauss beam

In recent years, significant advancements in high-repetition-rate, high-average-power mid-infrared laser pulses have enabled the generation of tabletop high-flux coherent soft x-ray harmonics for photon-hungry experiments. However, for practical applications, it is crucial to effectively filter out the driving beam from the high harmonics. In this study, we leverage the distinctive properties of a Bessel–Gauss (BG) beam to introduce a novel approach for spatial filtering, specifically targeting soft x-ray harmonics, releasing with a high-photon flux simultaneously. Our simulations reveal that by finely adjusting the focus geometry and gas pressure, the BG beam naturally adopts an annular shape, emitting high harmonics with minimal divergence in the far field. To achieve complete spatial separation of the driving beam and harmonic emissions, we pinpoint the optimal gas pressure and focusing geometry, particularly under overdriven laser intensities, for achieving good phase matching of harmonic emissions from short-trajectory electrons within the gas medium when the exact ionization level is higher than the “critical” value. Additionally, we establish scaling relations for sustaining optimal phase-matching conditions crucial for spatially separating the driving laser and the high-harmonic field, especially as the wavelength of the driving laser increases. Furthermore, our analysis demonstrates a substantial enhancement of harmonic yields by at least one order of magnitude compared to a truncated Gaussian annular beam. We also show that under accessible experimental conditions, soft x-ray photon flux up to 1010 photons/s at 250 eV can be achieved. The utilization of the BG beam opens up a promising pathway for the development of high-flux attosecond soft x-ray light sources, poised to serve a wide range of applications.

Based on supercritical carbon dioxide projectile launch technology research

Abstract In order to expand the application of compact high-velocity gas cannons in the field and hazardous areas, this paper proposes a new type of one-stage gas cannon with supercritical carbon dioxide as the gas medium. FLUENT numerical simulation method was used to study the gun bore firing process. Based on the projectile force, projectile velocity and flow field cloud diagram, the firing characteristics of the gas gun were analysed. The effects of different structures, different initial pressures and projectile masses on the firing performance were investigated. In order to verify the accuracy of the simulation model, a supercritical carbon dioxide gas cannon experimental test platform was built. The results show that the pressure in the chamber of the gas cannon with stacked arrangement structure fluctuates. Increasing the initial pressure and reducing the mass of the projectile can increase the initial velocity of the projectile. The greater the initial pressure is, the greater the pressure loss is under the stacked arrangement. There is a certain matching relationship between the thickness of the diaphragm, the filling amount of liquid carbon dioxide and the amount of heating charge. The amount of heating charge and the remaining thickness of the diaphragm have a greater impact on the launch performance of the gas cannon than the mass of liquid carbon dioxide.

An Advanced High Power Electromagnetic Pulse Generator with High Repetition Frequency

Abstract In this paper, an electromechanical pulse power source with repetitive frequency based on piezoelectric ceramic array and miniature plasma diode is introduced, which drives the piezoelectric ceramic array with an electromechanical system to generate a high-voltage pulse, which can generate strong electromagnetic radiation power after interacting with the gaseous medium plasma in the miniature plasma diode. This pulse power source can produce high output energy gain by using low-power DC power supply, and the pulse repetition frequency can be electronically adjusted by adjusting the motor speed. This pulse power source also has the advantages of compact structure and low cost, with a wide range of application prospects.

Exploration of the potential energy surfaces of the [formula omitted] clusters: Solvent phase vs gas phase

In the present work, we investigated the potential energy surfaces (PESs) of the structures of the Cu2+ ion in methanol clusters in two different media: gas and solvent phases. The effects of medium polarization by the integral equation formalism polarized continuum model (IEF-PCM) on structural and energetic parameters were examined on the conformers of the Cu2+(MeOH)n=9,10 clusters using the M06-2X/6-31++G(d,p) level of theory. Thus, in the solvent phase, the cluster structures are hexa-coordinated in the global minimum isomer. The study of the temperature dependency shows that the hexa-, and penta-coordinated structures compete with a large predominance of the hexa-coordinate structures with two solvation shells in the solvent phase. The Wiberg bond indices (WBI) analysis of the ionic bond confirms the structural study. In the IEF-PCM solvent compared to the gas medium, Wiberg bond indices of the tetra-, and penta-coordinate conformers are weaker, and the hexa-coordinate conformers in both media are nearly identical. This proves that compared to the solvent phase, the dative bond is stronger in the gas phase. This is supported by the significant difference in the electronic binding energies at saturation found with a single fitting function which are -88.6 and -146.6 kJmol−1 in the solvent and gas phases, respectively.

Utilizing Tetradesmus obliquus for Phycoremediation Enhanced Nitrogen and Phosphorus Removal in Urban Wastewater Treatment

Microalgae can scavenge pollutants through a process called phycoremediation, which involves the removal or biotransformation of pollutants in wastewater and gaseous media. Algae must grow rapidly, tolerate seasonal and diurnal variations, and form aggregates easily. In this study, the phosphorus and nitrogen removal capacity of the microalga Tetradesmus obliquus, isolated from urban water bodies, was evaluated and its cultivation was proposed as an alternative for tertiary treatment of urban effluents. The inoculum was placed in a bioreactor at 25 ºC with natural lighting for 21 days in modified Bold Basal Medium (BBM). The experiment included a control group (BBM) and a treatment with distilled water (AD) and increasing concentrations of urban effluent (12.5%, 25%, 50%, and 100%), inoculated with 8.8x105 cells/ml of biomass. The treatments were carried out in triplicate for 15 days. pH, dissolved oxygen (DO), conductivity, NO3- and PO4-3 concentrations, and biological variables such as cell count and optical density were determined. Tetradesmus obliquus showed efficiency in removing phosphates and nitrates. Maximum efficiency was shown after 15 days of treatment with 100% effluent, removing 22.92% of phosphates and 65.66% of nitrates.

Fully Integrated MEMS Micropump and Miniaturized Mass Flow Sensor as Basic Components for a Microdosing System.

Despite major advances in the field of actuator technology for microsystems, miniaturized microfluidic actuation systems for mobile devices are still not common in the market. We present a micropump concept and an associated mass flow sensor design, which, in combination, have the potential to form the basis for an integrated microfluidic development platform for microfluidic systems in general and microdosing systems in particular. The micropump combines the use of active valves with an electrostatic drive principle for the pump membrane and the valves, respectively. With a size of only 1.86 mm × 1.86 mm × 0.3 mm, the first prototypes are capable of pumping gaseous media at flow rates of up to 110 μL/min. A specific feature of the presented micropump is that the pumping direction is perpendicular to the chip surface. The corresponding flow sensor combines the principle of hot-wire anemometry with a very small footprint of only 1.4 mm × 1.4 mm × 0.4 mm. The main innovation is that the hot wires are fixed inside a through-hole in the substrate of the microchip, so that the flow direction of the fluid to be measured is perpendicular to the chip surface, which enables direct integration with the presented micropump. Detection thresholds of around 10 μL/min and measuring ranges of up to 20 mL/min can be achieved with the first prototypes, without dedicated evaluation electronics.