Typical Gas Mixture Research Articles

Pattern-based colorimetric sensor array chip for discrimination of Baijiu aromas

Gas mixtures are comprised of numerous complex components, making the accurate identification a continuing challenge due to the significant limitations of existing detection methods. Herein, we developed a low-cost and sensitive pattern-based colorimetric sensor array chip for the identification of typical gas mixtures - Baijiu aroma. Specifically, three nanomaterials (AuNPs, MoS2 and ZIF-8) were prepared to adsorb gas molecules and enhance the reaction of trace gases with sensor arrays. The colorimetric sensor array chip took only 5 min to complete the recognition of Baijiu aromas and effectively avoided recognition errors caused by sommelier olfactory fatigue. Notably, the hierarchical cluster analysis (HCA) revealed no confusion or errors in the results of 80 tests across the five trials involving 16 commercial Baijius. Even fake Baijius with similar ingredients could be easily identified, demonstrating the excellent analytical capabilities of the system in Baijiu identification and its significant potential for quality control of Baijius.

Coupled heat pulse propagation in two-fluid plasmas.

Because of the large mass differences between electrons and ions, the heat diffusion in electron-ion plasmas exhibits more complex behavior than simple heat diffusion found in typical gas mixtures. In particular, heat is diffused in two distinct, but coupled, channels. Conventional single fluid models neglect the resulting complexity, and can often inaccurately interpret the results of heat pulse experiments. However, by recognizing the sensitivity of the electron temperature evolution to the ion diffusivity, not only can previous experiments be interpreted correctly, but informative simultaneous measurements can be made of both ion and electron heat channels.

Impact of twisting tapes with various pitch lengths on the exergy and entropy performances of line heaters

Water bath fire tube heaters, so-called line heaters, are commonly used for industrial applications from small scales to large scales. The main problem of such heaters is the very low effectiveness of the heater due to the inefficient heat transfer within the heater (mainly between the fire tube and gas flow). The effects of using a specific type of twisting tape on the performance of these heaters, a typical heater used in natural gas pressure reductions points, were recently investigated. This study assesses the impacts of twisting tapes with different styles placed in the gas coil of the heater on the entropy generation and exergy performance of these heaters via computational fluid dynamic methods. For this, a typical gas mixture and typical line heater were considered. The results show that twisting tapes with larger numbers of twists and shorter twist pitch better enhance the exergy efficiency of the heater and decrease the rate of entropy generation over the gas heating process. Based on the obtained results, twisting tapes with the 17 and 68 twists decrease the rate of entropy generation by 16.8% and 27.1% and decrease the Bejan number for, respectively, over 36% and 77%.

Vacuum ultraviolet spectroscopy of cold atmospheric pressure plasma jets

AbstractDue to elevated pressure, cold atmospheric pressure plasmas generate excimer species, which can emit highly energetic photons, thus transferring energy inside the discharge and to treated substrates. However, they are difficult to assess, as they are absorbed by air or window material. Here, we present a method to measure vacuum ultraviolet photons using a monochromator with an aerodynamic window. The emission spectra of a radiofrequency‐excited atmospheric plasma jet were analyzed for typical gas mixtures. The data indicate that helium excimers contribute notably to the excitation of molecular and atomic species. The emission intensities do not follow densities of ground‐state species, underlining the variety of excitation channels and the change of the electron energy distribution function under changing gas composition.

Study of the ecological gas for MRPCs

The Multigap Resistive Plate Chamber (MRPC) is a gaseous detector; the performance depends very much on the gas mixture as well as the design. MRPCs are used as a timing device in several collider experiments and cosmic ray experiments thanks to the excellent timing performance. The typical gas mixtures of RPC-type detectors at current experiments are based on the gases $\rm C_2F_4H_2$ and $\rm SF_6$. These gases have very high Global Warming Potential (GWP) values of 1430 and 23900 respectively. The present contribution has been performed as a part of efforts to reduce the amount of greenhouse gases used in high energy experiments. The performance of MRPC has been measured with two different gas mixtures; $\rm C_2F_4H_2$ based gas mixtures and the ecological $\rm C_3F_4H_2$ (HFO-1234ze). A small MRPC was used for the tests. It has an sensitive area of 20 $\times$ 20 $\rm cm^2$; it was been built with 6 gaps of 220 $\mu$m. In normal operation, the strong space charge created within the gas avalanche limits the avalanche's growth. $\rm SF_6$ plays an important part in the process due to its high attachment coefficient at low electric fields. It is thus necessary to find another gas that has a similar attachment coefficient. $\rm CF_{3}I$ is a possible candidate. Tests were performed with this gas added to $\rm C_3F_4H_2$.

Empirical plot of gas generation from oil-prone marine shales at different maturity stages and its application to assess gas preservation in organic-rich shale system

Abstract Determining the degree of gas preservation and loss in shale gas system is critical to evaluate unconventional shale gas potential, particularly in the tectonically faults developed areas. In this study, an empirical plot of gas yields from marine shales at different stages of maturity and residual TOC content is derived from pyrolysis results and applied to evaluate the extent of shale gas loss. Miniature core plugs drilled from immature Barnett mudstone, Eagle Ford limestone, Woodford chert and mudstone samples were isothermally heated at 130 °C, 300 °C, 310 °C, 333 °C, 367 °C, 400 °C, and 425 °C for 72 h under a confining pressure of 68.0 MPa, corresponding to immature, early stage of oil window, main stage of oil window, late stage of oil window, main stage of oil cracking to wet gas, and late stage of oil cracking, respectively. The generated gas yields from marine shales with increasing thermal maturity are evaluated quantitatively by anhydrous closed-system pyrolysis. Experimental results show that gaseous hydrocarbon yields (C1 C5) from type II kerogen-dominated marine shales are linearly proportional to their residual TOC content at each stage of petroleum formation. The regression lines in the plot of generated gas yield and residual TOC content thus represent different gas-generation stages of type II kerogen-dominated marine shales. In the application to three geologic cases, the measured total gas content and present-day TOC content from a variety of shale gas wells with varying thermal maturity levels were incorporated into the empirical plot. And the comparative results show that, the gas contents of these core samples investigated for the low thermal maturity New Albany Shale in the Illinois Basin are somewhat higher than the estimated yield of generated gas from type II kerogen-dominated marine shales at the early stage of oil window, suggesting that microbial gas made contribution to the excess gas content in the New Albany shale gas system and it represents a typical gas mixture containing both early thermogenic gas and biogenic gas. In contrast, significant gas loss was observed in both the high thermal maturity Barnett Shale in the Fort Worth Basin and the overmature Silurian Longmaxi Shale in the Sichuan Basin as compared to each the estimated yield of generated gas. This phenomenon is probably caused by either petroleum expulsion or tectonic dissipation, or coupling of two processes. As for the Silurian Longmaxi Shale, it is estimated that approximately 60%–90% of total generated gas in quantities has been lost in the overmature Silurian Longmaxi shale gas system where industrial gas flow had been achieved. This provides an upper-limit measure to shale gas loss caused by petroleum expulsion and tectonic dissipation throughout geological time.

A reduced model for the evaporation and decomposition of urea–water solution droplets

Selective catalytic reduction with urea–water-solution is commonly used in the automotive sector to reduce nitric oxide emissions. Detailed modelling of the exhaust gas system in front of the catalyst can help in optimizing this process. Such simulations include many different physical effects and chemistry on strongly differing spatial and time scales, thus require a high amount of computational reserves. Therefore, simplified or reduced models are needed to describe some of the processes which can then be added in the overall simulation. To develop reduced models the evaporation and decomposition of a droplet of urea–water-solution and the corresponding gas phase chemistry in hot exhaust gas are analysed using detailed simulations. It is shown that the process can be separated into three main phases, namely water evaporation, urea decomposition and reactions in the gas phase, which, for the conditions considered, do not significantly couple with each other. For the first two phases a simple model is developed, which calculates the mass and energy source term for a droplet evaporation process depending only on temperature and water content of the surrounding exhaust gas and the initial diameter of the droplet. The time scales and entropy production of the gas phase chemistry are determined for typical gas mixture compositions and initial conditions and based on these results a skeletal mechanism for chemical kinetics is generated. It can describe the gas phase chemistry for temperatures up to 800 K. In addition, it is found that gas phase chemistry at temperatures up to 1000 K can be modelled without the need to resolve the boundary layer of the small droplets.

Construction of a scalable RF power supply for small CO2 waveguide lasers

This paper presents the design, construction and test of a radio frequency self-oscillator-amplifier (SOA). The main goal is to develop a small reliable and non-expensive RF circuit generator capable to deliver up to 180W of RF power to sustain ionization in waveguide-like electrodes in CO2 laser amplifying media. The laser media amplifier (LMA) is a specific designed (or homemade) setup that can be coupled to our RF SOA circuit. The LMA was built as a simple inductive-capacitive (LC) component which has the capability to efficiently absorb above the 95% of the RF energy delivered by the SOA. RF energy between the SOA and the laser head is achieved by the use of a matching circuit (MC) in order to assess the LMA transient ionization stability. In this work we complete our study by adding a 5-pass (WI) optical resonator to have laser light output. The proposed circuit was designed to oscillate in a frequency within the range of 60MHz to 80MHz and a center frequency of 70MHz and its components were fine tuned to optimize its signal output power in the range from 120W to 180W (2–3 times the manufacturer output power specification at 70MHz). Before we interconnect the RF SOA into the laser head we test its performance by using a dummy load with 50W termination. The next step is to measure the complex impedance of our laser head. The LMA is a capacitive-like discharge that has several parallel-distributed inductors along the laser electrodes to create a steady and uniform plasma discharge. The complex impedance of our laser head is measured in two modes by using a Vector Impedance Analyzer (VIA) AEA-Via Echo 1000SF; in high vacuum and at the final gas mixture pressure. Once we know the complex impedance we input this value in the ADS software to find the best matching circuit (MC) between the SOA and the LMA. From this stage, we are able to perform an overall evaluation of the complete setup: SOA-MC-LMA. We proceed to test the ionization state of our laser performance using a typical gas mixture of CO2-N2-He with proportion of 1:1.2:3.7 correspondingly and at a final pressure of 70Torr a maximum optical output power better than 20W was obtained at a maximum RF feed power of 173W.

Velocity of deflagration combustion at high pressures and temperatures

The article presents additional calculated data on combustion velocity for typical gas mixtures at pressures up to 6000 atm and temperatures up to 4000 K. It was determined that combustion velocity is mainly influenced by initial temperature, and the dependence on pressure is rather low. For fuel-oxygen and air-fuel mixtures in three-dimensional space (pressure-temperature-velocity of deflagration combustion), we have found a single surface of combustion velocities and continuous dependence of flame velocity on initial conditions.

POWER RADIO FREQUENCY CIRCUIT DESIGN FOR A SMALL CO2 SLAB WAVEGUIDE LASER

The design, construction, and test of a radio frequency oscillator-amplifier is presented in this paper. The RF circuit is inserted as part of the electrodes of an in-house-built compact CO2 waveguide laser. Our circuit was designed to have a frequency at 81 MHz and its signal output between 90 W and 150 W. Capacitive discharge is evaluated over a period of time and, after a correct positioning of several inductors parallel-distributed along the laser electrodes, a steady and uniform plasma discharge was created. The overall RF circuit-laser test is done with a typical gas mixture of CO2-N2-He with proportion of 1:1:3, correspondingly, and at a final pressure of 40 Torr. Under these conditions, a maximum optical output power greater than 10.7 W was obtained for an input feed RF power of 147 W.

Two-Stage Radio Frequency Power Generator-Amplifier Design for a TEM00 CO2 Slab Waveguide Laser

This letter presents the results of the research conducted on the design, construction and test of a two stage ra- dio frequency power generator-amplifier directed adapted to an in-house-built compact CO2 waveguide laser. The main characteristic of this power supply lies in the fact its design is based on MOSFET technology for both the oscillator and the amplifier stages. RF output power is centered at 81MHz frequency signal between 100W to 150W. The two-stage sys- tem device has a minimum electric conversion efficiency of 64%. Consequently, the laser head and RF excitation design must have an electrical termination of 50� impedance and the whole system may include a proper matching circuit. The overall test, for the entire system: RF excitation along with our CO2 laser head, is made with a typical gas mixture of CO2- N2-He with proportion of 1:1:3 correspondingly and at a final pressure of 40Torr. Under these specific conditions, a maximum optical output power of 10.7W was obtained for an input feed RF power of 147W. Regarding the optical qual- ity we measured the transverse mode of propagation TEM00 which indicate the entire system work very near the diffrac- tion limit specifications for similar laser systems.

TRIDYN simulation of target poisoning in reactive sputtering

During reactive sputter deposition, target “poisoning”, i.e. the formation of a compound layer at the target surface, may reduce the sputter erosion rate substantially and thereby represent a major limitation to achieve high deposition rates. In order to investigate the formation of the poisoned layer, the TRIDYN program has been employed to simulate the processes that take place at the target surface during sputtering at ion energies which are typical for a magnetron discharge, in a typical gas mixture of Ar with a small (<10%) addition of a reactive gas (e.g. oxygen). The bulk of the sputtering results from Ar ion bombardment, while the reactive gas ions contribute to compound formation due to implantation into the subsurface layer. In addition, reactive gas molecules are adsorbed on the surface and react with target metal atoms to add to the formation of the compound layer. Thus, both chemisorption and ion implantation of energetic reactive ions are the two main mechanisms for the formation of the poisoned layer.TRIDYN simulations have been performed at varying reactive ion to total ion flux ratio, and at varying ion to reactive neutral flux ratio, for fluences which are sufficiently large to achieve a stationary deposition/erosion balance. The results illustrate that the two mechanisms will generate almost identical shapes of the poisoned layer. They also demonstrate the significance of recoil implantation from the chemisorbed layer for the formation of the compound layer. In agreement with experimental findings, the calculated sputter erosion rate of the target is predicted to decrease monotonically as the partial pressure of the reactive gas increases. The shape of the sputter erosion curve hardly changes between conditions dominated by ion implantation or chemisorption. We therefore conclude that ion implantation basically acts as an additional source of reactive atoms to the target surface.

Diamond deposition in a microwave electrode discharge at reduced pressures

Abstract Diamond deposition on heated Si-substrates was studied under microwave discharge generated by an electrode-antenna either in a “point-to-plane” arrangement or in a “parallel-plane” arrangement at gas pressures of 1–15 Torr in a mixture of hydrogen with methane and oxygen. Diamond growth of 1 μm h −1 was obtained on surfaces up to 2 cm in diameter at microwave power of 150–200 W. No metal impurities from the electrode were detected in the diamond films. Typical gas mixture was 4% methane and 0.5% oxygen in hydrogen at a total pressure of 15 Torr. The role of additional r.f. potential during the film deposition was studied in the case of “point-to-plane” electrode arrangement. Correlation of the power absorbed in the plasma and the optical emission of H atoms have been observed.

Boltzmann equation analysis of electron-molecule collision cross sections in water vapor and ammonia

Sets of electron-molecule collision cross sections for H2O and NH3 have been determined from a classical technique of electron swarm parameter unfolding. This deconvolution method is based on a simplex algorithm using a powerful multiterm Boltzmann equation analysis established in the framework of the classical hydrodynamic approximation. It is well adapted for the simulation of the different classes of swarm experiments (i.e., time resolved, time of flight, and steady state experiments). The sets of collision cross sections that exist in the literature are reviewed and analyzed. Fitted sets of cross sections are determined for H2O and NH3 which exhibit features characteristic of polar molecules such as high rotational excitation collision cross sections. The hydrodynamic swarm parameters (i.e., drift velocity, longitudinal and transverse diffusion coefficients, ionization and attachment coefficients) calculated from the fitted sets are in excellent agreement with the measured ones. These sets are finally used to calculate the transport and reaction coefficients needed for discharge modeling in two cases of typical gas mixtures for which experimental swarm data are very sparse or nonexistent (i.e., flue gas mixtures and gas mixtures for rf plasma surface treatment).

Hydrates in the ocean and evidence for the location of hydrate formation

There is substantial evidence that the oceans of the world will pose the most important challenges in the area of hydrate formation. This work indicates three areas of concern for hydrate formation in the ocean: (1) deposits of natural gas in ocean hydrates, which will serve as an energy resource and environmental concern in the next tnillenium, (2) a recent proposal for the ocean storage of carbon dioxide in the form of hydrates, and (3) the prevention of hydrate formation in ocean pipelines. To address such applications, fundamental knowledge on the site of hydrate formation was determined. Results are presented for quiescent, high-pressure experiments done in a sapphire tube to determine the site of hydrate formation in deionized water and in mixtures with amorphous silica and sodium dodecyl sulfate. Visual (microscope aided) results are presented for formation with a typical gas mixture and with carbon dioxide.

Mass spectrometry of fusion-plasma gases

In a D–T fusion plasma, not only the components of primary interest (D2, T2, 4He), but also H2 and reaction products like HD, HT, and DT have to be considered. Even traces of 3He may be found in the system. For mass-spectrometric analyses of these eight gas species, at most six data are usable out of the mass range 1 to 6. Moreover, also taking into account water and hydrocarbon molecules, the unknowns outnumber by far the available data, making the underlying equation system unsolvable. This problem is overcome by repeatedly measuring the spectrum, but with stepwise changes in the settings of selected parameters of the instrument. Of particular interest are parameters like electron energy E (offering chemical separation of helium and hydrogen) and−in case of quadrupoles−field axis potential V (allowing to distinguish between molecular ions and fragment ions). By choosing 2 parameters each of E and V, we can get up to 24 linear independent equations out of the mass range 1 to 6, good enough for spectrum decomposition by means of established fit procedures. Details of this method and results from analyzing typical gas mixtures are presented.

Analysis of fusion-plasma gases by low-resolution mass spectrometry

For the analysis of DT fusion-plasma gases, not only the primary components D 2, T 2, 4He, but also H 2 and reaction products like HD, HT and DT have to be considered, and even traces of 3He may be in the system. For mass spectrometric analyses of these eight gas species, at most six data are usable out of the mass range 1 to 6. Moreover, by also taking into account water and hydrocarbon molecules, the unknowns outnumber by far the available data, making the underlying equation system unsolvable. This problem is overcome by repeatedly measuring the spectrum, but with stepwise changing of the settings of selected parameters of the instrument. Of particular interest are parameters like electron energy E (offering chemical separation of helium and hydrogen) and—in the case of quadrupoles—field axis potential V (allowing us to distinguish between molecular and fragment ions). By choosing two parameters each of E and V, we can get up to 24 linear independent equations out of the mass range 1 to 6, good enough for spectrum decomposition by means of established fit procedures. Details of this method and results from analysing typical gas mixtures are presented.

Numerical Investigations of Electron Beam Energy Deposition into the Gas Medium of an Excimer Laser

Electron beam propagation in a dense gas medium is numerically investigated. All the main phenomena that determine electron beam behavior in a gas (scattering and energy losses of the electrons on the gas atom molecules, ionization and excitation, electron thermalization, beam pinching, and influence of a magnetic guide field) are taken into account. The initial beam energy and the gas chamber dimensions are varied in a wide range: typical gas mixtures for the excimer lasers are considered. Graphs are given that allow the choice of the optimal electron beam energy that provides the maximum efficiency of the beam energy deposition into the gas, depending on the gas chamber dimensions.

Dynamics of the CO&amp;lt;inf&amp;gt;2&amp;lt;/inf&amp;gt;upper laser level as measured with a tunable diode laser

A tunable diode laser (TDL) operating in the 2140-2310 cm <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">-1</sup> wavenumber region is used to probe a conventional CW CO <inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</inf> laser discharge. Detailed vibrational populations in CO <inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</inf> are measured under lasing conditions, i.e., in the presence of an intense 10 μm field. The TDL is also used to investigate the rate of recovery of the populations in a variety of vibrational levels after the passage of an intense 10 μm pulse. This paper deals mainly with the behavior of the upper laser level, and the associated ν <inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</inf> mode. We show that electron deex-citation of the ν <inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</inf> mode is very important, and is responsible for the limitation of the ν <inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</inf> mode temperature observed previously. In typical gas mixtures, the ratio of the ν <inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</inf> mode electron deexcitation rate constant to the electron excitation rate constant is <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">\sim 3.5:1</tex> .

Specie concentration measurements utilizing Raman scattering of a laser beam

Abstract : The feasibility of utilizing Raman scattering as a diagnostic technique to measure individual specie concentrations in typical gas mixtures found in gas dynamic applications has been investigated and demonstrated. Utilizing this technique, either the local density of a pure gas or the concentration of individual diatomic (or polyatomic) species in a gas mixture can be uniquely determined. The range and limitations of this technique were investigated and evaluated under controlled static conditions. A Q-switched ruby laser, which has a pulse duration of approximately 10 nanoseconds, was used as a radiation source. The scattered radiation was monitored utilizing a high gain, wide spectral range photomultiplier tube in conjunction with a spectrograph. Measurements were also made utilizing narrow bandpass filters in place of the spectrograph. The species which were investigated include O2, N2, CO2, and CH4. Quantitative results are given for these gases in their pure state as well as in various mixture proportions. The relative and absolute intensity of the scattered radiation from the species investigated were compared with that predicted by theory. Measurements were also made of the vibrational temperature of O2. A description of the pertinent theory and concepts of Raman scattering is also included as well as a discussion of the limitations of the technique.