Arbitrary Gas Research Articles

Method for Detecting Fire Indoors Based on Differences in Sample Averages of an Arbitrary Gas Environment Dangerous Parameter at Adjacent Observation Intervals

The object of the research is the series average of the dangerous parameters of the gas environment during the ignition of materials. The practical importance consists of using the difference between the average dangerous parameters of the gas environment on the intervals of absence and the presence of ignition to detect the ignition of materials. The theoretical substantiation of the method of detecting fires in premises is carried out based on sample averages fixed samples of current measurements of an arbitrary, dangerous parameter of the gas environment, which correspond to the general population of reliable absence and presence of fire. At a given significance level, the method determines the unbiased, uniformly most powerful fire detection rule. This allows you to determine how significant differences in sample means with a given significance level are due to ignition or are random. Laboratory experiments were conducted to verify the method of detecting the ignition of test materials. It was established, for example, that the maximum size of the effect ignition on the carbon monoxide concentration is typical for alcohol (exceeds the threshold by 8.9 times) and textiles (exceeds the threshold by 9.3 times). The size of the effect of the smoke density upon ignition of all materials is approximately the same and is determined by exceeding the corresponding thresholds from 4.62 to 3.9 times. The size of the effect on the temperature of the gaseous environment during ignition of all test materials is approximately the same order. It is characterized by exceeding the corresponding thresholds from 5.95 to 3.58 times. It is shown that the method of detecting fires allows to establish the extent to which the detected differences in sample means for samples from the general population of hazardous parameters of the gas environment are reliable with a given level of significance and are due to the ignition of materials or the action of random factors.

Caracal: A Versatile Ring Polymer Molecular Dynamics Simulation Package.

A new open-source program package named Caracal covering simulations of molecular systems with ring polymer molecular dynamics (RPMD) is presented. It combines a powerful RPMD implementation including chemical reaction rate calculations and biased periodic and nonperiodic samplings with a collection of easy to set up potential energy surface (PES) methodologies, thus delivering an all-inclusive approach. Most implemented PESs are based on the QMDFF and EVB-QMDFF methods. Where the quantum mechanically derived force field (QMDFF) can be set up for an arbitrary molecular system in a black-box fashion, the empirical valence bond (EVB)-QMDFF connects two QMDFFs and is able to represent the PES of a chemical reaction. With our previously published flavors of this composite method, PESs for almost arbitrary gas phase thermal ground state reactions can be set up. Given an optimized reaction path, the mechanism of the reaction can be classified and RPMD rate constants can be obtained via umbrella sampling and recrossing calculations on an EVB-QMDFF PES. Further, QMDFFs can be polymerized for the description of liquid systems. In this paper, the internal structure as well as the handling philosophy of Caracal are outlined. Further, examples of the different possible kinds of calculations are given.

Decomposition of Acoustic and Entropy Modes in a Non-Isothermal Gas Affected by a Mass Force

Diagnostics and decomposition of atmospheric disturbances in a planar flow are considered in this work. The study examines a situation in which the stationary equilibrium temperature of a gas may depend on the vertical coordinate due to external forces. The relations connecting perturbations are analytically established. These perturbations specify acoustic and entropy modes in an arbitrary stratified gas affected by a constant mass force. The diagnostic relations link acoustic and entropy modes, and are independent of time. Hence, they provide an ability to decompose the total vector of perturbations into acoustic and non-acoustic (entropy) parts, and to establish the distribution of energy between the sound and entropy modes, uniquely at any instant. The total energy of a flow is hence determined in its parts which are connected with acoustic and entropy modes. The examples presented in this work consider the equilibrium temperature of a gas, which linearly depends on the vertical coordinate. Individual profiles of acoustic and entropy parts for some impulses are illustrated with plots.

Similarity solution of subcritical pressure discharges from vessels for arbitrary gases

Based on the Bernoulli’s equation Fischer and Boettcher (2021) developed a model to predict the transient gas discharge from a vessel. Their dimensionless number was able to capture a variation of the molar mass, temperature, vessel volume and opening diameter and showed constant values for these. The influence of the gas, though, could not be completely captured. In this work we improve the model by optimizing the pressure loss coefficient, modifying the dimensionless number and solving the differential equation for determining the pressure over time using the 4th-order Runge-Kutta method. The model was extended to include the influence of the ambient pressure. These improvements lead to the first similarity correlation valid for arbitrary gases. Multiple numerical simulations are performed with ANSYS CFX to verify the similarity model. A grid independence study showed differences below 1 %. The mean deviation between the numerical simulation and the similarity-model is 1.939 %.

Visualization of Flow-Induced Strain Using Structural Color in Channel-Free Polydimethylsiloxane Devices.

Measuring flow of gases is of fundamental importance yet is typically done with complex equipment. There is, therefore, a longstanding need for a simple and inexpensive means of flow measurement. Here, gas flow is measured using an extremely simple device that consists of an Ar plasma-treated polydimethylsiloxane (PDMS) slab adhered on a glass substrate with a tight seal. This device does not even have a channel, instead, gas can flow between the PDMS and the glass by deforming the PDMS wall, in other words, by making an interstice as a temporary path for the flow. The formation of the temporary path results in a compressive bending stress at the inner wall of the path, which leads to the formation of well-ordered wrinkles, and hence, the emergence of structural color that changes the optical transmittance of the device. Although it is very simple, this setup works sufficiently well to measure arbitrary gases and analyzes their flow rates, densities, and viscosities based on the change in color. It is also demonstrated that this technique is applicable to the flow-induced display of a pattern such as a logo for advanced applications.

Quantum edge plasmon excitations and electron spill-out effect

In this paper, by using the effective Schrödinger–Poisson model, we investigate quantum edge plasmon excitations and electron spill-out effect in an arbitrary degenerate electron gas in the presence of perpendicular electron drift momentum. It is found that the single-electron Schrödinger equation solution produces a nonoscillatory electron number density distribution on the interface showing characteristic surface-dipole and electron spill-out effects. However, the Schrödinger–Poisson model produces large amplitude dual-tone density distribution due to both wave-like and particle-like plasmon dispersion other than surface-dipole and electron spill-out effects. The variations in the density structure are investigated in terms of different parameters such as the chemical potential, temperature, quantum electron tunneling parameter, and perpendicular electron de Broglie's wavenumber. Furthermore, we extend our study to the case of collective electron tunneling and reveal that the interface potential energy significantly differs from the case of single-electron quantum tunneling and strongly depends on the electron gas parameters. The current study reveals interesting features of the transverse plasmon excitations and electron spill-out in a current carrying narrow metal slab or metal–dielectric quantum sandwich interfaces incorporating both single-electron and collective quantum tunneling.

Development of lower flammability limits testing apparatus for gasoline vapor – Air mixture using an internal vaporizer at ambient conditions

Fire accidents at public fuel stations in Indonesia have urged the need to characterize the causes of these fires. In the gas station area, the formation of gasoline vapor is the main concern of this research. Therefore, this study aims to analyze lower flammability limits (LFLs) of gasoline vapor-air mixtures of the selected gasoline samples. The LFL of gasoline vapor was characterized using a 1.2 L vertical tube integrated with an internal evaporator and a high voltage electric lighter with the energy of 10 J. The tube is made of glass with a diameter of 80 mm and a height of 300 mm with an open top end. This apparatus can run two test methods of upward and downward propagation. The experiment was conducted at the ambient condition with an evaporation temperature of the sample being 150 °C for the internal evaporator. Four gasoline samples were used with varying octane numbers (RON) obtained from arbitrary public gas stations. For validation, Iso-octane (IO) reference fluid with a purity level of 99.5% was tested for the assessment of LFL. The results with the upward propagation method showed that the LFL volume-based concentration were 1.62%, 1.61%, 1.64%, 1.60% and 1.05%, and downward propagation method were 2.48%, 2.39%, 2.30%, 2.11% and 1.57% for RON_88, RON_90, RON_92, RON_95 and IO_100 samples respectively. This study shows that a downward propagation flame has a higher gas temperature with lower velocity compared to an upward flame, which suggests that lower elevation fuel vapor sources at gas stations have a higher fire potential. This research topic is in an effort to provide input on the fire hazards at gas stations that are specific for tropical conditions with traffic practices such as in Indonesia and other countries that face similar hazards and threats. This study can provide input for further transportation safety policies and research.

An mmWave Sensor for Real-Time Monitoring of Gases Based on Real Refractive Index

We propose a millimeter-wave (mmWave) sensor to monitor gases and aerosols based on time-of-flight (ToF), thus, on the real refractive index. It utilizes an ultrawideband frequency-modulated continuous-wave (FMCW) radar operating from 72 to 92 GHz at a sampling rate of 500 Hz. Also, we introduce a model for simulation of the refractive index of arbitrary gases at mmWave frequencies using molecular spectroscopic data. Simulations then allow the identification of the respective gas under test. We characterized the performance of the sensor regarding the refractive index within various experiments. The precision is 0.027 ppm, and the 20-h long-term stability is better than 0.2 ppm. The linearity is at least 1.5 ppm. Due to sophisticated temperature compensation, the temperature drift is less than 10 ppm for 30 K. Since the sensor is accurate, precise, and robust, it is perfect for in-process real-time monitoring and classification of gases or aerosols in the industry.

General Drag Coefficient for Flow over Spherical Particles

A generalized physics-based expression for the drag coefficient of spherical particles moving in a fluid is developed. The proposed correlation incorporates essential rarefied effects, low-speed hydrodynamics, and shock-wave physics to accurately model the particle-drag force for a wide range of Mach and Knudsen numbers (and therefore Reynolds number). Owing to the basis of the derivation in physics-based scaling laws, the proposed correlation embeds gas-specific properties and has explicit dependence on the ratio of specific heat capacities. The correlation is applicable for arbitrary particle relative velocity, particle diameter, gas pressure, gas temperature, and surface temperature. Compared with existing drag models, the correlation is shown to more accurately reproduce a wide range of experimental data. Finally, the new correlation is applied to simulate particle trajectories in high-speed dusty flows, relevant to a spacecraft entering the Martian atmosphere. The enhanced surface heat flux due to particle impact is found to be sensitive to the particle drag model.

Diagnostic Relations between Pressure and Entropy Perturbations for Acoustic and Entropy Modes

Diagnostics and decomposition of atmospheric disturbances in a planar flow are considered and applied to numerical modelling with the direct possibility to use in atmosphere monitoring especially in such strong events which follow magnetic storms and other large scale atmospheric phenomena. The study examines a situation in which the stationary equilibrium temperature of a gas may depend on a vertical coordinate, which essentially complicates the diagnostics. The relations connecting perturbations for acoustic and entropy (stationary) modes are analytically established and led to the solvable diagnostic equations. These equations specify acoustic and entropy modes in an arbitrary stratified gas under the condition of stability. The diagnostic relations are independent of time and specify the acoustic and the entropy modes. They provide the ability to decompose the total vector of perturbations into acoustic and non-acoustic (entropy) parts uniquely at any instant within the total accessible heights range. As a prospective model, we consider the diagnostics at the height interval 120–180 km, where the equilibrium temperature of a gas depends linearly on the vertical coordinate. For such a heights range it is possible to proceed with analytical expressions for pressure and entropy perturbations of gas variables. Individual profiles of acoustic and entropy parts for some data are illustrated by the plots for the pure numerical data against those obtained by the model. The total energy of a flow is determined for both approaches and its vertical profiles are compared.

Streamer inception thresholds derived from a statistical electron transport model

The aim of this article is to review a statistical description of electron transport in gases based on transport parameter theory, and to derive expressions for streamer inception thresholds in quasi-homogeneous electrical fields within this description. The critical average number of electrons required to induce avalanche-to-streamer transition is derived for arbitrary gases as a function of the gap electric field and the relevant gas parameters. The model is then evaluated for synthetic air. Significant deviations from the traditional approximation are found for small gaps ( 1 mm). Moreover, the minimal necessary number of electrons for avalanche-to-streamer transition is found to scale approximately with the inverse of gas pressure. The application of the adapted streamer inception criterion to the calculation of the partial discharge inception voltage for twisted enamelled wires, where discharges are incepted in gaps with 1 mm, is discussed. Our results support the conclusion that space charges generated by sub-critical avalanche processes play a determining role for streamer onset in such configurations, i.e. that their partial discharge inception cannot be reliably quantified by applying the streamer criterion in the Laplacian electrode field. Finally, the streamer inception probability is compared to the deterministic streamer inception criterion. In particular, the problem of non-exponential growth in the early stages of the electron avalanche development is argued to be properly addressed within the applied statistical interpretation of transport parameters.

On the Influence of the Ionization–Recombination Processes on the Hydrogen Plasma Polytropic Index

Abstract An analytical approximation for the polytropic index of a hydrogen gas has been derived. The derived expressions can be useful for theoretical work and numerical calculations. These results open the possibility of direct computation of these thermodynamic quantities, rather than interpolating from tables. Additionally, the polytropic index is graphically represented as a function of temperature and density. It is concluded that the partially ionized hydrogen plasma cannot be exactly polytropic. The calculated deviations from the monoatomic value 5/3 are significant and measurable. The present theory supposes that hydrogen molecules are completely dissociated, and this analytical result for pure hydrogen plasma can be applied for the solar chromosphere, where He ionization is negligible and H2 dissociation is almost complete. These two conditions define the ranges of applicability of temperatures and densities. The analytical result for pure hydrogen plasma is a test example of how this approach can be extended for an arbitrary gas cocktail.

Betaboltz: A Monte-Carlo simulation tool for gas scattering processes

We present an open-source code for the simulation of electron and ion transport for user-defined gas mixtures with static uniform electric and magnetic fields. The program provides microscopic interaction simulation and is interfaced with cross-section tables published by LXCat[1]. The framework was validated against drift velocity tables available in literature obtaining an acceptable match for atomic and non-polar molecular gases with spherical symmetry. The code is written in C++17 and is available as a shared library for easy integration into other simulation applications. Program summaryProgram Title: BetaboltzCPC Library link to program files:https://doi.org/10.17632/hjhx8bj45c.1Licensing provisions: LGPL v3Programming language: C++17Nature of problem: Simulations of electron and ion transport in arbitrary gas mixture under static uniform electric and magnetic fields.Solution method: Particle motion using classical and relativistic equation via interaction sampling using Monte-Carlo techniques.Additional comments including restrictions and unusual features: At the time of writing only static uniform electromagnetic fields are supported. However, the implementation of arbitrary fields can be added given an analytical solution is available. A custom XML format for cross-section was developed, because full compatibility with LXCat [1] XML format was not possible. Cross-section databases in the new format are available in the download section of the LXCat site [2].

A free-running dual-comb spectrometer with intelligent temporal alignment algorithm

Dual-comb spectrometer is demonstrated as a promising tool in atmospheric composition detection with extremely-high spectral resolution and fast scanning capability. In this paper, an intelligent temporal alignment (ITA) algorithm is proposed into signal processing of a free-running dual-comb spectrometer around 1.5 μm. The signal processing in the algorithm only relies on the original interference sequence to complete the signal alignment without reference signal. As a result, the alignment of 12CO gas absorption line in the wavelength range of 1564-1570 nm is well retrieved in good agreement with HITRAN database. To the best of our knowledge, this paper proposes and implements for the first time the combination of the ITA algorithm and free-running dual-comb spectroscopy. It lays a technical foundation for the intelligent analysis of arbitrary gas absorption spectral lines.

Gas Damping in Capacitive MEMS Transducers in the Free Molecular Flow Regime.

We present a novel analysis of gas damping in capacitive MEMS transducers that is based on a simple analytical model, assisted by Monte-Carlo simulations performed in Molflow+ to obtain an estimate for the geometry dependent gas diffusion time. This combination provides results with minimal computational expense and through freely available software, as well as insight into how the gas damping depends on the transducer geometry in the molecular flow regime. The results can be used to predict damping for arbitrary gas mixtures. The analysis was verified by experimental results for both air and helium atmospheres and matches these data to within 15% over a wide range of pressures.

Modeling femtosecond pulse propagation and high harmonics generation in hollow core fibers

One way to increase the well known low efficiency of high order harmonics generation is to place the gas medium in a hollow core waveguide. The numerical model used to obtain driving and harmonics field configuration along and across the waveguide was developed for an arbitrary gas density profile and arbitrary fiber diameter modulation. The model was tested against experimental measurements and excellent agreement was obtained for the fluorescence emission along the waveguide. We analyse the influence of the diameter modulation which result from the fabrication process on both pulse propagation and on harmonic generation.

Wafer-level fabrication of alkali vapor cells using in-situ atomic deposition

We demonstrate a new technique for filling mm-scale microfabricated silicon and glass cavities with alkali vapors at the wafer-scale. A single etched silicon wafer contains an array of cavities containing alkali precursor materials offset laterally from the cell array. The wafer is heated to create an array of alkali droplets on an upper glass wafer, which is then translated laterally under vacuum and bonded to create the cells. This technique can be implemented in a commercially available bonding tool, allows the fabrication of cells with arbitrary buffer gas contents and pressures and can potentially produce cells with dimensions below 100 µm.

Heat capacity and electrical conductivity of plasmon excitations

In this research, we calculate the heat capacity and electrical conductivity of plasmon excitations in an arbitrary degenerate electron gas by using the linearized Schrödinger-Poisson model. It is shown that the large heat capacity of electron fluid such as in metals can be attributed to the collective excitations. These excitations unlike those for low energy fermion excitations dominant at low temperatures follow the Bose-Einstein statistics and contribute significantly at higher temperatures where a significant number of electrons excite to energy levels beyond twice the plasmon energy of electron fluid. The current density and electrical conductivity of plasmon excitations in the current model show unique features for characteristic current-voltage and their temperature dependence. It is found that a single electron fermion excitation model such as the one used in free electron assumption is not appropriate for a full description of electron contribution to the physical properties of metals and plasmas at very high temperatures. The coupled pseudoforce system with a periodic density structure in the presence of a uniform electric field is also considered with appropriate boundary conditions to evaluate the characteristic aspects of collective excitations in a one dimensional plasmonic crystal. The application of the lattice periodicity on the wavefunction and the electrostatic potential results in singularities for the probability current due to plasmon excitations. It is shown that such an effect persists with an arbitrary ion core potential function which obeys the lattice periodicity. The current model clearly demonstrates the importance of collective electronic excitation in the physical properties of electron gas with an arbitrary degree of degeneracy.

Acoustic Funnel and Buncher for Nanoparticle Injection

Acoustics-based techniques are investigated to focus and bunch nanoparticle beams. This allows to overcome the prominent problem of the longitudinal and transverse mismatch of particle stream and x-ray beam in single-particle/single molecule imaging at x-ray free-electron lasers (XFEL). It will also enable synchronised injection of particle streams at kHz repetition rates. Transverse focusing concentrates the particle flux to the (sub)micrometer x-ray focus. In the longitudinal direction, focused acoustic waves can be used to bunch the particle to the same repetition rate as the x-ray pulses. The acoustic manipulation is based on simple mechanical recoil effects and could be advantageous over light-pressure-based methods, which rely on absorption. The acoustic equipment is easy to implement and can be conveniently inserted into current XFEL endstations. With the proposed method, data collection times could be reduced by a factor of $10^4$. This work does not just provide an efficient method for acoustic manipulation of streams of arbitrary gas phase particles, but also opens up wide avenues for acoustics-based particle optics.

Quantum interference of three dimensional plasmon excitations

In this paper, the quantum interference of plasmon excitations in the presence of charges or multipolar sources/sinks is investigated. The effective Schrödinger-Poisson system for dynamical description of the arbitrary degenerate fermi gas is reduced to a set of coupled linear pseudoforce system, and it is shown that this system admits a general multipolar solution in the 3D Cartesian coordinate. The obtained solution is then used to study well-known problems such as the double and quadruple charge interference effects. The double source interference produces patterns quite reminiscent of that of the double slit interference with the corresponding matter-wavelength matching that of the de Broglie wavelength of the electrons. It is found that the collective electrostatic interactions of quantum electron gas leads to the electrostatic energy depletion around the pole which causes electrostatic polar binding in the electron fluid. The later effect which has also been previously reported in some research seems to be an appropriate description of attractive metallic bindings. The current model is then extended to electronic interference effects in a crystal lattice with the quasiperiodic electronic states. The periodic arrangement of ionic cores in a crystal is shown to produce different density and electrostatic potential patterns for given energy eigenvalues of the fermi gas. Moreover, a generalized expression is obtained for electron probability current in the Schrödinger-Poisson model. The current model may provide a better platform for studying the quantum interference phenomenon in complex environments such as nanocompounds and plasmonic crystals.