Interstellar Clouds Research Articles

Formation of complex organics by covalent and non-covalent interactions of the sequential reactions of 1-4 acrylonitrile molecules with the benzonitrile radical cation.

Benzonitrile molecules are present in ionizing environments including interstellar clouds and solar nebulae, where their ions can form adducts with neutral molecules such as acrylonitrile leading to the formation of a variety of nitrogen-containing complex organics. Herein, we report on the formation of complex organics by the sequential reactions of 1-4 acrylonitrile (C3NH3) molecules with the benzonitrile radical cation (C7NH5+˙). The results reveal the formation of the covalently bonded N-acrylonitrile-benzonitrile radical cation (C10N2H8+˙) with a rate coefficient of 2.2 (±0.4) × 10-11 cm3 s-1 at 423 K and a calculated collision cross-section of 73.8 Å2 in good agreement with the measured cross-section of 70.7 Å2 of the C10N2H8+˙ adduct. Subsequent reversible association of 1-3 acrylonitrile molecules with the N-acrylonitrile-benzonitrile radical cation (C10N2H8+˙) at lower temperatures (250-200 K) results in the formation of the N-rich clusters (C10N2H8+˙)(C3NH3)1-3 which can be enhanced in the very cold cores of the interstellar medium (ISM) and could offer unique potential candidates for the substantial amount of nitrogen carriers detected in the emission spectra of the ISM. The observed N-acrylonitrile-benzonitrile covalent adduct and its associated acrylonitrile clusters could have significant implications in the formation of different types of complex organics in different regions of outer space. It is anticipated that the current results would have direct implications in the search for nitrogen-containing complex organics in space.

BD+44°493: Chemo-dynamical Analysis and Constraints on Companion Planetary Masses from WIYN/NEID Spectroscopy* *The WIYN Observatory is a joint facility of the University of Wisconsin Madison, Indiana University, NSF NOIRLab, the Pennsylvania State University, Purdue University, and Princeton University. Based on data collected at the Subaru Telescope, which is operated by the National Astronomical Observatory of Japan. Based on observations made

In this work, we present high-resolution (R ∼ 100,000), high signal-to-noise ratio (S/N ∼ 800) spectroscopic observations for the well-known, bright, extremely metal-poor, carbon-enhanced star BD+44°493. We determined chemical abundances and upper limits for 17 elements from WIYN/NEID data, complemented with 11 abundances redetermined from Subaru and Hubble data, using the new, more accurate, stellar atmospheric parameters calculated in this work. Our analysis suggests that BD+44°493 is a low-mass (0.83 M ⊙), old (12.1–13.2 Gyr) second-generation star likely formed from a gas cloud enriched by a single metal-free 20.5 M ⊙ Population III star in the early Universe. With a disk-like orbit, BD+44°493 does not appear to be associated with any major merger event in the early history of the Milky Way. From the precision radial-velocity NEID measurements (median absolute deviation = 16 m s−1), we were able to constrain companion planetary masses around BD+44°493 and rule out the presence of planets as small as msini=2 M J out to periods of 100 days. This study opens a new avenue of exploration for the intersection between stellar archaeology and exoplanet science using NEID.

Kinetic Study of the Reactions of Ground State Atomic Carbon and Oxygen with Nitrogen Dioxide over the 50-296 K Temperature Range.

The kinetics of the reactions of nitrogen dioxide, NO2, with atomic oxygen and atomic carbon in their ground triplet states (3P) have been studied at room temperature and below using a supersonic flow (Laval nozzle) reactor. O(3P) and C(3P) atoms (hereafter O and C respectively) were created in situ by the pulsed laser photolysis of the precursor molecules NO2 at 355 nm and CBr4 at 266 nm, respectively. While the progress of the O + NO2 reaction was followed by detecting O atoms by a chemiluminescent tracer method, progress of the C + NO2 reaction was followed by detecting C atoms directly by vacuum ultraviolet laser-induced fluorescence at 116 nm. The measured rate constants for the O + NO2 reaction are found to be in excellent agreement with earlier work at higher temperatures and extend the available kinetic data for this process down to 50 K. The present work represents the first kinetics study of the C + NO2 reaction. Although both reactions display rate constants that increase as the temperature falls, a more substantial rate increase is observed for the O + NO2 reaction. The effects of these reactions on the simulated abundances of interstellar NO2 and related compounds were tested using a gas-grain model of the dense interstellar medium, employing expressions for the rate constants of the form, k(T) = α(T/300)β, with α = 1 × 10-11 cm3 s-1 and β = -0.65 for the O + NO2 reaction and α = 2 × 10-10 cm3 s-1 and β = -0.11 for the C + NO2 reaction. Although these simulations predict that gas-phase NO2 abundances are low in dense interstellar clouds, NO2 abundances on interstellar dust grains are predicted to reach reasonably high levels, indicating the potential for detection of this species in warmer regions.

Global Thermal Instability in the Spherical Interstellar Clouds

Thermal instability (TI) is a trigger mechanism, which can explain the formation of small condensations through some regions of the interstellar clouds. The instability criterion for flat geometry approximations has been investigated in previous works. Here, we focus on spherical perturbations in the spherical clouds. Our goal here is to examine the conditions for the occurrence of TI through the thermally dominated (i.e., gravitationally stable) quasi-static spherical interstellar clouds. First, we obtain the profiles of density, temperature, pressure, and enclosed mass of a symmetric spherical cloud. Then, we use the perturbation method to investigate the linear regime of instability and find its growth rate. Considering spherical perturbations on the quasi-static spherical cloud, instead of a thermal and dynamical equilibrium flat cloud, changes the instability criterion so that we can conclude that sphericalness can increase the occurrence of TI. The results show that in the spherical clouds, perturbations with shorter wavelengths have more chance to grow via TI (i.e., greater growth rates).

Metallicity Mapping of the Ionized Diffuse Gas at the Milky Way Disk–Halo Interface

Metals in the diffuse, ionized gas at the boundary between the Milky Way’s interstellar medium (ISM) and circumgalactic medium, known as the disk–halo interface (DHI), are valuable tracers of the feedback processes that drive the Galactic fountain. However, metallicity measurements in this region are challenging due to obscuration by the Milky Way ISM and uncertain ionization corrections that affect the total hydrogen column density. In this work, we constrain ionization corrections to neutral hydrogen column densities using precisely measured electron column densities from the dispersion measures of pulsars that lie in the same globular clusters as UV-bright targets with high-resolution absorption spectroscopy. We address the blending of absorption lines with the ISM by jointly fitting Voigt profiles to all absorption components. We present our metallicity estimates for the DHI of the Milky Way based on detailed photoionization modeling of the absorption from ionized metal lines and ionization-corrected total hydrogen columns. Generally, the gas clouds show a large scatter in metallicity, ranging between 0.04 and 3.2 Z ⊙, implying that the DHI consists of a mixture of gaseous structures having multiple origins. We estimate the inflow and outflow timescales of the DHI ionized clouds to be 6–35 Myr. We report the detection of an infalling cloud with supersolar metallicity that suggests a Galactic fountain mechanism, whereas at least one low-metallicity outflowing cloud (Z < 0.1 Z ⊙) poses a challenge for Galactic fountain and feedback models.

Dynamic evolution of flame and overpressure of leakage and explosion of hydrogen-blended natural gas in utility tunnels

In order to ascertain the true characteristics of the leakage explosion loads of hydrogen-blended natural gas (HBNG) in utility tunnels, the influence of leakage location on the concentration field distribution of HBNG leakage in utility tunnels was studied through the CFD technique. Furthermore, the characteristics of explosion flame and overpressure load distribution of HBNG of inhomogeneous distribution under effect of different ignition delay times and ignition positions were also investigated. The results show that the greater the distance between the leakage location and the air outlet, the more readily HBNG can propagate throughout the utility tunnel. This, in turn, leads to more prominent downstream gas cloud stratification. The development of explosion flame is primarily seen in the direction of low resistance and ample space within the utility tunnel. With the increase in ignition delay time (tid) and the backward shift of the leakage location (Llk), the average flame velocity generally exhibits a decreasing trend. Overall, the peak overpressure exhibits a concave trend. Under circumstances where the leakage source is in the front or middle section of the tunnel, the average peak overpressure demonstrates a general tendency of increase followed by decline with the increase in tid. In comparison, in the case of a leakage source located at the back end, it decreases gradually as tid increases. The most severe explosion overpressure load is readily induced when the leakage source is located at the front end. In the case of a leakage source located in the front section of the tunnel, the overpressure load at each measuring point decreases continuously and then rises as the ignition position moves backward. However, in the case of a leakage source located in the rear section of the tunnel, the average value of peak overpressure induced by ignition in the middle of the tunnel is the greatest, while the average value of peak overpressure induced by ignition at the back end is the smallest. The maximum explosion overpressure load is found at the front-most leakage source under front-end ignition conditions. The findings of this study offer scientific substantiation for the structure of the utility tunnel, which is designed for explosion withstanding, prevention, and control as well as risk assessment.

Quantitative characterization method of point cloud distribution in tunnel for optimizing TLS scanning plan

A novel method for quantitatively describing the distribution of point clouds in tunnels is introduced to optimize tunnel scanning schemes. The method uses point cloud spacing and thickness to represent the density and unevenness of the point cloud, respectively. Point cloud spacing is categorized into point spacing and ring spacing based on the scanning trajectory, and these metrics are calculated using coordinates from a regularly distributed point cloud. Point cloud thickness is derived by combining the measurement error range in the laser incidence direction with the laser incidence angle. The above calculation method has been validated through tunnel field tests. The quantitative characterization method evaluates the effects of resolution, station spacing, and linearity error on point cloud spacing and thickness. It helps determine the necessary resolution, station spacing, and TLS scanner specifications to ensure that point cloud spacing and thickness meet the requirements for tunnel health assessment. By addressing the lack of comprehensive quantitative consideration of point cloud distribution in selecting scanning parameters, this method provides a robust framework for optimizing scanning schemes, ensuring accurate and reliable point cloud data for tunnel inspection.

Dimming events of evolved stars due to clouds of molecular gas. Scenarios based on 3D radiation-hydrodynamics simulations with CO5BOLD

The dramatic dimming episode of the red supergiant Betelgeuse in 2019 and 2020, caused by a partial darkening of the stellar disk, has highlighted gaps in the understanding of the evolution of massive stars. We analyzed numerical models to investigate the processes behind the formation of dark surface patches and the associated reduction in the disk-integrated stellar light. With the CO5BOLD code, we performed global 3D radiation-hydrodynamical simulations of evolved stars, including convection in the stellar interior, self-excited pulsations, and the resulting atmospheric dynamics with strong radiative shocks. We attribute dimming phenomena to obscuring clouds of cool gas in the lower atmosphere, forming according to three different scenarios. One process transports material outward in a strong shock, similar to what occurs in 1D simulations of radially pulsating asymptotic giant branch (AGB) stars. However, in 3D models, deviations from spherical symmetry of the shock front can lead to further local density enhancements. Another mechanism is triggered by a large convective upflow structure, in combination with exceptionally strong radial pulsations. This induces Rayleigh-Taylor instabilities, causing plumes of material to be sent outward into the atmosphere. The third and rarest scenario involves large-amplitude convective fluctuations, leading to enhanced flows in deep downdrafts, which rebound and send material outward. In all cases, the dense gas above the stellar surface cools and darkens rapidly in visible light. AGB stars show localized dark patches regularly during intermediate phases of their large-amplitude pulsations, while more massive stars will only intermittently form such patches during luminosity minima. The episodic levitation of dense gas clumps above the stellar surface, followed by the formation of complex molecules in the cooling gas and possibly dust grains at a later stage, can account for the dark patches and strong dimming events of supergiant stars such as Betelgeuse.

Planetesimal gravitational collapse in a gaseous environment: Thermal and dynamic evolution

Planetesimal formation models often invoke the gravitational collapse of pebble clouds to overcome various barriers to grain growth and propose processes to concentrate particles sufficiently to trigger this collapse. On the other hand, the geochemical approach for planet formation constrains the conditions for planetesimal formation and evolution by providing temperatures that should be reached to explain the final composition of planetesimals, the building blocks of planets. To elucidate the thermal evolution during gravitational collapse, we used numerical simulations of a self-gravitating cloud of particles and gas coupled with gas drag. Our goal is to determine how the gravitational energy relaxed during the contraction is distributed among the different energy components of the system, and how this constrains a thermal and dynamical planetesimal's history. We identify the conditions necessary to achieve a temperature increase of several hundred kelvins, and as much as 1600 K. Our results emphasise the key role of the gas during the collapse.

The Discovery and Evolution of a Radio Continuum and Excited-OH Spectral-line Outburst in the Nearby Galaxy NGC 660

Arecibo 305 m Telescope observations between 2008 and 2018 detected a radio continuum and spectral-line outburst in the nearby galaxy, NGC 660. Excited-OH maser emission/absorption lines near 4.7 GHz, and H2CO absorption at 4.83 GHz varied on timescales of months. Simultaneously, a continuum outburst occurred in which a new compact component appeared, with a GHz-peaked spectrum and a 5 GHz flux density that rose to a peak value of about 500 mJy from 2008.0 to 2012.0. Follow-up interferometric continuum images from the Very Large Array at 10 GHz of this new continuum component determined it to be located at the nucleus of NGC 660. Subsequent High Sensitivity Array line and continuum very long baseline interferometry observations of the NGC 660 nucleus revealed a morphology that appears to be consistent with rapidly precessing, mildly relativistic jets from the central black hole. While requiring detailed modeling, this strongly suggests that the outburst is due to nuclear activity. From its timescale, the shape of the continuum light curve, and the milliarcsec radio structure, the most likely cause of the outburst is active galactic nuclei-type activity of accretion of a gas cloud onto the central black hole.

Testing kinematic distances under a realistic Galactic potential. Investigating systematic errors in the kinematic distance method arising from a non-axisymmetric potential

Obtaining reliable distance estimates to gas clouds within the Milky Way is challenging in the absence of certain tracers. The kinematic distance approach has been used as an alternative, and it is derived from the assumption of circular trajectories around the Galactic centre. Consequently, significant errors are expected in regions where gas flow deviates from purely circular motions. We aim to quantify the systematic errors that arise from the kinematic distance method in the presence of a Galactic potential that is non-axisymmetric. We investigated how these errors differ in certain regions of the Galaxy and how they relate to the underlying dynamics. We performed 2D isothermal hydrodynamical simulation of the gas disk with the moving-mesh code Arepo adding the capability of using an external potential provided by the Agama library for galactic dynamics. We introduced a new analytic potential of the Milky Way, taking elements from existing models and adjusting parameters to match recent observational constraints. In line with results of previous studies, we report significant errors in the kinematic distance estimate for gas close to the Sun along sight lines towards the Galactic centre and anti-centre and associated with the Galactic bar. Kinematic distance errors are low within the spiral arms, as gas resides close to local potential minima and the resulting line-of-sight velocity is similar to what is expected for an axisymmetric potential. Interarm regions exhibit large deviations at any given Galactic radius, and this is caused by the gas being sped up or slowed down as it travels into or out of spiral arms. In addition, we identify ‘zones of avoidance’ in the $lv$-diagram, where the kinematic distance method is particularly unreliable and should only be used with caution and we find a power-law relation between the kinematic distance error and the deviation of the projected line-of-sight velocity from circular motion.

AT 2021hdr: A candidate tidal disruption of a gas cloud by a binary super massive black hole system

With a growing number of facilities able to monitor the entire sky and produce light curves with a cadence of days, in recent years there has been an increased rate of detection of sources whose variability deviates from standard behavior, revealing a variety of exotic nuclear transients. The aim of the present study is to disentangle the nature of the transient AT\,2021hdr, whose optical light curve used to be consistent with a classic Seyfert 1 nucleus, which was also confirmed by its optical spectrum and high-energy properties. From late 2021, AT\,2021hdr started to present sudden brightening episodes in the form of oscillating peaks in the Zwicky Transient Facility (ZTF) alert stream, and the same shape is observed in X-rays and UV from Swift data. The oscillations occur every sim 60-90 days with amplitudes of sim 0.2 mag in the g and r bands. Very Long Baseline Array (VLBA) observations show no radio emission at milliarcseconds scale. It is argued that these findings are inconsistent with a standard tidal disruption event (TDE), a binary supermassive black hole (BSMBH), or a changing-look active galactic nucleus (AGN); neither does this object resemble previous observed AGN flares, and disk or jet instabilities are an unlikely scenario. Here, we propose that the behavior of AT\,2021hdr might be due to the tidal disruption of a gas cloud by a BSMBH. In this scenario, we estimate that the putative binary has a separation of sim 0.83 mpc and would merge in sim 7times 10$^4$ years. This galaxy is located at 9 kpc from a companion galaxy, and in this work we report this merger for the first time. The oscillations are not related to the companion galaxy.

Discovery of a Bow-shock Nebula Around the Z Cam-type Cataclysmic Variable SY Cancri

We report the serendipitous discovery of a bow-shock nebula around the cataclysmic variable (CV) SY Cancri. In addition, SY Cnc lies near the edge of a faint Hα-emitting nebula with a diameter of about 15′ . The orientation of the bow shock is consistent with the direction of SY Cnc’s proper motion. Nebulae are extremely rare around CVs, apart from those known to have undergone classical-nova (CN) outbursts; bow shocks and off-center nebulae are even more unusual. Nevertheless, the properties of SY Cnc and its nebulosity are strikingly similar to those of V341 Ara, another CV that is also associated with a bow shock and is likewise off-center with respect to its faint Hα nebula. Both stars are binaries with optically thick accretion disks, belonging to the classes of Z Cam CVs or nova-like variables. We discuss three scenarios to explain their properties. They may have resulted from chance encounters with interstellar gas clouds, with the stars leaving in their wakes material that is recombining after being photoionized by ultraviolet radiation from the CVs. Alternatively, the large nebulae could be ejecta from unobserved CN outbursts in the recent past, which have been decelerated through collisions with the interstellar medium (ISM), while the stars continue to snowplow through the gas. Or the faint Hα nebulae may be ambient ISM that was flash-ionized by a CN outburst in the past and is now recombining.

Carbon sources spotted in cold interstellar clouds

Carbon sources spotted in cold interstellar clouds

Sulfur-bearing molecules in a sample of early star-forming cores

The sulfur content in dense molecular regions is highly depleted in comparison to diffuse clouds. The reason for this phenomenon is unclear, and it is therefore necessary to carry out observational studies of sulfur-bearing species toward dense regions, mainly in early evolution stages. In this context, the analysis of sulfur-bearing molecules in a large sample of dense starless molecular cores is of great importance to help us uncover the early sulfur chemistry in these regions. From the Atacama Large Millimeter Array (ALMA) data archive, we selected a project in Band 7 (275--373 GHz), which contains the emission of several sulfur-bearing species. The observations were performed toward a sample of 37 dense cores that are embedded in the most massive infrared-quiet molecular clumps from the ATLASGAL survey. The lines of 34SO, SO$_ $, NS, SO, SO$^ $, and H$_ $CS were analyzed, and the column densities of each molecular species were obtained. Based on the continuum emission and two CH$_ $OH lines, the 37 cores were characterized in density and temperature, and the corresponding H$_ $ column densities were derived. The abundances of these sulfur-bearing species were derived and studied. We find that the abundances of the analyzed sulfur-bearing species increase with increasing gas temperature. Based on the correlation between abundances and temperature, we suggest that the chemistry involved in the formation of each of the analyzed molecules may similarly depend on T$_ k $ in the range 20 to 100 K. Additionally, we find that the comparisons among abundances are highly correlated in general. Taking into account that this correlation decreases in more evolved sources, we suggest that the sulfur-bearing species we analyzed have a similar chemical origin. Our observational results show that the X(SO$_ $)/X(SO) ratio can be used as a chemical clock of molecular cores. Based on the line widths of the molecular lines, we point out that molecules with an oxygen content (34SO, SO$_ $, SO, and SO$^ $) may be associated with warmer and more turbulent gas than the other molecules. H$_ $CS and NS are associated with more quiescent gas, probably in the external envelopes of the cores, which trace similar physical and chemical conditions. We complement recent similar works done toward more evolved sources with a large sample of sources, but also provide quantitative information about abundances that might be useful in chemical models for explaining the sulfur chemistry in the interstellar medium.

The cooler past of the intracluster medium in TNG-Cluster

Abstract The intracluster medium (ICM) today is comprised largely of hot gas with clouds of cooler gas of unknown origin and lifespan. We analyze the evolution of cool gas (temperatures ≲ 104.5 K) in the ICM of 352 galaxy clusters from the TNG-Cluster simulations, with present-day mass ∼1014.3 − 15.4 M⊙. We follow the main progenitors of these clusters over the past ∼13 billion years (since z ≲ 7) and find that, according to TNG-Cluster, the cool ICM mass increases with redshift at fixed cluster mass, implying that this cooler past of the ICM is due to more than just halo growth. The cool cluster gas at z ≲ 0.5 is mostly located in and around satellite galaxies, while at z ≳ 2 cool gas can also accrete via filaments from the intergalactic medium. Lower-mass and higher-redshift clusters are more susceptible to cooling. The cool ICM mass correlates with the number of gaseous satellites and inversely with the central supermassive black hole (SMBH) mass. The average number of gaseous satellites decreases since z = 2, correlating with the decline in the cool ICM mass over cosmic time, suggesting a link between the two. Concurrently, kinetic SMBH feedback shifts the ICM temperature distribution, decreasing the cool ICM mass inside-out. At z ≈ 0.5, the predicted Mg ii column densities are in the ballpark of recent observations, where satellites and other halos contribute significantly to the total Mg ii column density. Suggestively, a non-negligible amount of the ICM cool gas forms stars in-situ at early times, reaching ∼102 M⊙ yr−1 and an Hα surface brightness of ∼10−17 erg s−1 cm−2 arcsec−2 at z ≈ 2, detectable with Euclid and JWST.

Rate coefficients for C and O2 reactive collisions relevant to interstellar clouds from QCT and machine learning.

The chemical reactions between certain interstellar molecules are exothermic in nature and barrierless in the entrance channel, allowing these reactions to occur rapidly even at low astronomical temperatures, e.g., C and O2 interaction. Obtaining detailed rovibrational transition parameters for the reaction between C and O2, such as state-selected rate coefficients, is crucial for studying the associated atmospheric and astronomical environments. Hence, this work presents an approach that combines quasi-classical trajectory calculations with machine learning techniques based on Neural Network (NN) and Gaussian Process Regression (GPR) to determine state-selected rate coefficients. Employing this approach, we significantly reduced the computational requirements while simultaneously obtaining the accurate state-selected reaction cross sections and rate coefficients for the collision of C and O2. Both the NN-based and GPR-based models established in this work accurately predict the results calculated from explicit numerical calculations in the explored temperature range of 50-1500K, achieving a coefficient of determination R2 > 0.96. Most importantly, the current work provides the most comprehensive dataset of rovibrational rate coefficients of v = 0-4, j = 0-70 → v' = 0-15 for the astrophysical modeling of the C-O2 collision system.

Enhancing Open-Space Gas Detection Limit: A Novel Environmentally Adaptive Infrared Temperature Prediction Method for Uncooled Spectroscopy.

Gas cloud imaging with uncooled infrared spectroscopy is influenced by ambient temperature, complicating the quantitative detection of gas concentrations in open environments. To solve the aforementioned challenges, the paper analyzes the main factors influencing detection errors in uncooled infrared spectroscopy gas cloud imaging and proposes a temperature correction method to address them. Firstly, to mitigate the environmental effects on the radiative temperature output of uncooled infrared detectors, a snapshot-based, multi-band infrared temperature compensation algorithm incorporating environmental awareness was developed. This algorithm enables precise infrared radiation prediction across a wide operating temperature range. Validation tests conducted over the full temperature range of 0 °C to 80 °C demonstrated that the prediction error was maintained within ±0.96 °C. Subsequently, temperature compensation techniques were integrated, resulting in the development of a comprehensive uncooled infrared spectroscopy gas cloud imaging detection method. Ultimately, the detection limits for SF6, ethylene, cyclohexane, and ammonia were enhanced by 50%, 33%, 25%, and 67%, respectively.

Research on the Calculation Method and Diffusion Pattern of VCE Injury Probability in Oil Tank Group Based on SLAB-TNO Method

Accidental leakage from oil–gas storage tanks can lead to the formation of liquid pools. These pools can result in vapor cloud explosions (VCEs) if combustible vapors encounter ignition energy. Conducting accurate and comprehensive consequence analyses of such explosions is crucial for quantitative risk assessments (QRAs) in industrial safety. In this study, a methodology based on the SLAB-TNO model to calculate the overpressure resulting from a VCE is presented. Based on this method, the consequences of the VCE accident considering the gas cloud concentration diffusion are studied. The probit model is employed to evaluate casualty probabilities under varying environmental and operational conditions. The effects of key parameters, including gas diffusion time, wind speed, lower flammability limit (LFL), and environment temperature, on casualty diffusion are systematically investigated. The results indicate that when the diffusion time is less than 100 s, the VCE consequences are significantly more severe due to the rapid spread of the gas cloud. Furthermore, increasing wind speed accelerates gas dispersion, reducing the spatial extent of casualty isopleths. The LFL is shown to have a direct impact on both the mass and diffusion of the flammable gas cloud, with higher LFL values shifting the explosion’s epicenter upward. The environmental temperature promotes gas diffusion in the core area and increases the mass of the combustible gas cloud. These findings provide critical insights for improving the safety protocols in oil and gas storage facilities and can serve as a valuable reference for consequence assessment and emergency response planning in similar industrial scenarios.

Research on single-point fast three-dimensional concentration reconstruction of a smoke plume based on the static interference infrared imaging spectroscopy system

To meet the requirements of real-time and effectiveness of three-dimensional concentration telemetry of gas clouds and address the difficulty of fast three-dimensional concentration reconstruction of single instrument smoke plumes, the paper proposes a single-point fast three-dimensional concentration reconstruction of the smoke plume based on a static interference infrared Fourier transform imaging spectrometer (ISIFTS) by using the advantages of high throughput, large field of view, high stability, and rapid detection. Based on the scanning field switching characteristics of ISIFTS, a single instrument quickly scans the dual-field map data to obtain the three-dimensional point cloud of the target scene. Combined with the three-dimensional spatial parameters of the scene, a multi-dimensional re-projection algorithm is constructed based on the Gaussian plume continuous diffusion model to simulate the concentration-path-length product (CL) image, and the measured CL image is solved by analyzing the smoke plume image spectra data. The normalized cross-correlation fitting algorithm is used to perform the optimal matching of simulated-measured CL images, and then the three-dimensional concentration distribution of the plume scene is reconstructed based on the dimension mapping relationship. The field smoke plume telemetry experiment was designed and carried out, and the three-dimensional concentration distribution of plume gas at three emission points in the scene was obtained. The CO2 emission rates were calculated to be 13.572 kg / s, 12.225 kg / s, and 14.114 kg / s, respectively. The data are consistent with the emission rate of the coal-fired thermal power plant, which verifies the effectiveness of the single-point fast three-dimensional concentration reconstruction of the smoke plume method based on the ISIFTS system.