Time Of Explosion Research Articles

3성분계 양극재의 고온에서 가스 발생에 따른 리튬이온 배터리 스웰링 거동 특성 및 열 폭주 위험성 분석

In this study, NCM cathode materials were mainly analyzed to confirm the fire risk of LIB. NCM cathode materials have poor surface stability and poor structural stability at high temperatures, so gas is generated and the cell swells, causing swelling. To confirm this phenomenon, a pouch full cell was manufactured and electrochemical output characteristics were tested, and it was confirmed that the cell surface temperature risen to 60°C. As a result of ICP-MS analysis, it was confirmed that the higher the ratio of Ni in the NCM cathode and the higher the temperature environment, the higher the solubility of Ni. In fact, the pouch full cell was stored in a high-temperature oven for a total of 4 weeks, and the swelling behavior was measured at intervals of 1 week, and the amount of gas generation was quantitatively measured through the internal pressure cell. As a result, the higher the Ni ratio, the more gas generated. In order to determine the correlation between these gas emissions and fire, harsh conditions were applied via a DC power supply. As a result, it was confirmed that the higher the ratio of Ni and the greater the number of charging and discharging, the more the cell swelled, the faster it exploded, and the higher the temperature at the time of explosion.

Dynamics of Pressure Variation in Closed Vessel Explosions of Diluted Fuel/Oxidant Mixtures

Nitrous oxide is widely used as oxidizer or nitriding agent in numerous industrial activities such as production of adipic acid and caprolactam and even for production of some semiconductors. Further, it is used as an additive in order to increase the power output of engines, and as an oxidizer in propulsion systems of rockets, because it has a large heat of formation (+81.6 kJ mol−1). N2O is highly exothermic, and during its decomposition a supplementary heat amount is released, so it needs special handling conditions. The combustion of fuels in nitrous oxide atmosphere can lead to high unstable and turbulent deflagrations that speedily self-accelerate and therefore a deflagration can change to a detonation. The peak explosion pressure and the maximum rate of pressure rise of explosions in confined spaces are key safety parameters to evaluate the hazard of processes running in closed vessels and for design of enclosures able to withstand explosions or of their vents used as relief devices. The present study reports some major explosion parameters such as the maximum (peak) explosion pressures pmax, explosion times θmax, maximum rates of pressure rise (dp/dt)max and severity factors KG for ethylene-nitrous oxide mixtures (lean and stoichiometric) diluted with various amounts of N2, at various initial pressures (p0 = 0.50–1.50 bar), in experiments performed in a spherical vessel centrally ignited by inductive-capacitive electric sparks. The influence of the initial pressure and composition on pmax, θmax and (dp/dt)max is discussed. The data are compared with similar values referring to ethylene-air mixtures measured in the same initial conditions. It was found that at identical C/O ratios with ethylene-air, ethylene-N2O-N2 mixtures develop higher explosion pressures and higher rates of pressure rise, due to the exothermic dissociation of N2O under flame conditions.

An explosion time characterization of asset price bubbles

AbstractIn a standard continuous time asset pricing model, this paper provides an explosion time characterization of asset price bubbles that extends the existing characterization theorems in the literature from diffusion processes to general semimartingales (which can include jumps). This characterization has a nice economic interpretation, not emphasized in the existing literature.

Flame behaviors and explosion characteristics of two‐phase propylene oxide/air mixture under different ambient pressures

AbstractPropylene oxide (PO) is widely used in fuel‐air explosives and pulse detonation engines. Based on computational fluid dynamics, the effects of ignition position, initial pressure, and mass concentration on the explosion characteristics of the PO/air mixture were studied by using a 20 L spherical container. The results showed that the ignition position had a significant effect on the flame structure. When the fuel cloud was ignited at the center, the flame structure experienced spherical, elliptical, and tulip shapes. The explosion time first decreased and then increased with the increase of ignition position, while the maximum explosion pressure decreased correspondingly. The maximum explosion pressure and the temperature had an inverted “U” correlation with concentration at normal pressure. However, the overpressure was insensitive to concentration in the negative pressure condition. The maximum flame temperature showed different flame behaviors under different initial negative pressures and cloud concentrations. This study provides a theoretical basis for understanding the explosion behaviors of PO/air mixture with different ignition positions and initial vacuum pressures, which is of great significance in preventing explosion accidents.

Theoretical and Experimental Investigation of Explosion Characteristics of Hydrogen Explosion in a Closed Vessel

A simplified model that calculates the deflagration pressure–time curves of a hydrogen explosion was proposed. The deflagration parameters (pressure peak, duration, deflagration index, and impulse) of hydrogen–air mixtures with different hydrogen concentrations were experimentally investigated. The results show that the pressure curves calculated by the model are consistent with experimental data pertaining to a methane and hydrogen explosion. By comparison, the pressure peak and deflagration index are found to be influenced by the aspect ratio and surface area of vessels. The impulse and explosion times at fuel-lean hydrogen concentrations are greater than those at fuel-rich concentrations. When the hydrogen concentration is between 34 vol.% and 18 vol.%, the greatest explosion damage effect is formed by both the overpressure and the impulse, which should be considered for hydrogen explosion safety design in industrial production.

The origin and distribution of the main oxygen sensing mechanism across metazoans.

Oxygen sensing mechanisms are essential for metazoans, their origin and evolution in the context of oxygen in Earth history are of interest. To trace the evolution of a main oxygen sensing mechanism among metazoans, the hypoxia induced factor, HIF, we investigated the phylogenetic distribution and phylogeny of 11 of its components across 566 eukaryote genomes. The HIF based oxygen sensing machinery in eukaryotes can be traced as far back as 800million years (Ma) ago, likely to the last metazoan common ancestor (LMCA), and arose at a time when the atmospheric oxygen content corresponded roughly to the Pasteur point, or roughly 1% of present atmospheric level (PAL). By the time of the Cambrian explosion (541-485Ma) as oxygen levels started to approach those of the modern atmosphere, the HIF system with its key components HIF1α, HIF1β, PHD1, PHD4, FIH and VHL was well established across metazoan lineages. HIF1α is more widely distributed and therefore may have evolved earlier than HIF2α and HIF3α, and HIF1β and is more widely distributed than HIF2β in invertebrates. PHD1, PHD4, FIH, and VHL appear in all 13 metazoan phyla. The O2 consuming enzymes of the pathway, PHDs and FIH, have a lower substrate affinity, Km, for O2 than terminal oxidases in the mitochondrial respiratory chain, in line with their function as an environmental signal to switch to anaerobic energy metabolic pathways. The ancient HIF system has been conserved and widespread during the period when metazoans evolved and diversified together with O2 during Earth history.

A Study on the Effect of Hydrogen Gas Explosion in a Cylinder Cabinet for Semiconductors on the Protective Wall

In the semiconductor industry, hydrogen is used with many other hazardous and dangerous substances with flammable, toxic, and corrosive properties. In order to safely handle them, convenient-to-use gas cabinets are often required. As known well, hydrogen is highly flammable and explosive, and risk analysis needs to safely use the gas in the cabinets. In this study, overpressure and impact according to various gas cabinet conditions were measured when hydrogen leaks in the gas cabinet, and the effect of overpressure on the protective wall was simulated. For the research, a demonstration experiment was conducted by custom manufacturing a gas cylinder cabinet identical to the standard used in the field, and the protection performance analysis was performed by reverse-engineering it through 3D scanning. As a result of the demonstration experiment, the maximum pressure at the time of hydrogen gas explosion in the gas cylinder cabinet was measured at 0.3 bar. After calculating the detonation pressure propagation profile using the TNT equivalence method, the protective performance of the protective wall was confirmed using AUTODYN. The maximum stress of the concrete and the maximum stress of the reinforcing bar due to the explosion in the gas cylinder cabinet were calculated to be 30.211 MPa and 112.88 MPa, respectively, which do not exceed the tensile strength of concrete and the yield strength of the reinforcing bar. This result is expected to be of great help to the development of the semiconductor industry by suggesting the rationale for mitigating the firewall when changing the semiconductor layout.

Effect of obstacle shape on the deflagration characteristics of premixed LPG-air mixtures in a closed tube

In the present research, the deflagration behaviors of premixed LPG-air mixtures with volume fractions from 4% to 8% and various obstacles at a block ratio of 0.6 were experimentally investigated in a closed tube with a length-diameter ratio of 20.4. The parameters such as explosion pressure, explosion time, pressure rise rate, and revised deflagration index were obtained. Moreover, the flame propagation behaviors were recorded, and the structural evolution of the flame front and the corresponding flame speed were identified and then analyzed. The obtained results showed that the net square and perforated disc obstacles increase the flame speed the most, and the peak value reaches 256.2 m/s. When the flame front reaches close to the end of the tube, the combined effects of the reflected deflagration wave and the vortex-induced by the turbulence drive the unburned mixture to propagate to the burned zone, resulting in a backward flame. The maximum explosion pressure and the revised gas deflagration index of the LPG-air mixture increased for six kinds of obstacles with different shapes. The time to peak pressure was greatly reduced. The mesh square and perforated disc obstacles enhanced the pressure parameters the most. The obtained results are of significance in providing fundamental data on the explosion of LPG-air mixtures, providing theoretical guidance for the design of LPG-related devices and structures, and being useful to develop the corresponding explosion mitigation technology.

High-Cadence TESS and Ground-based Data of SN 2019esa, the Less Energetic Sibling of SN 2006gy ∗ ∗ This paper includes data gathered with the 6.5 m Magellan Telescope at Las Campanas Observatory, Chile.

We present photometric and spectroscopic observations of the nearby (D ≈ 28 Mpc) interacting supernova (SN) 2019esa, discovered within hours of explosion and serendipitously observed by the Transiting Exoplanet Survey Satellite (TESS). Early, high-cadence light curves from both TESS and the DLT40 survey tightly constrain the time of explosion, and show a 30 day rise to maximum light followed by a near-constant linear decline in luminosity. Optical spectroscopy over the first 40 days revealed a reddened object with narrow Balmer emission lines seen in Type IIn SNe. The slow rise to maximum in the optical light curve combined with the lack of broad Hα emission suggest the presence of very optically thick and close circumstellar material (CSM) that quickly decelerated the SN ejecta. This CSM was likely created from a massive star progenitor with an ∼ 0.2 M ☉ yr−1 lost in a previous eruptive episode 3–4 yr before eruption, similar to giant eruptions of luminous blue variable stars. At late times, strong intermediate-width Ca ii, Fe i, and Fe ii lines are seen in the optical spectra, identical to those seen in the superluminous interacting SN 2006gy. The strong CSM interaction masks the underlying explosion mechanism in SN 2019esa, but the combination of the luminosity, strength of the Hα lines, and mass-loss rate of the progenitor seem to be inconsistent with a Type Ia CSM model and instead point to a core-collapse origin.

Explosion characteristics of n-decane/hydrogen/air mixtures

Hydrogen can be used in conjunction with aviation kerosene in aircraft engines. To this end, this study uses n-decane/hydrogen mixtures to investigate the explosion characteristics of aviation kerosene/hydrogen in a constant volume combustion chamber with different hydrogen addition ratios (0, 0.2, 0.4), wide effective equivalence ratios (0.7–1.7), an initial temperature of 470 K, and initial pressures of 1 and 2 bar. The results show that the explosion pressure and explosion time decrease linearly with increasing hydrogen addition ratio. The effect of initial pressure is also discussed. A comparison of the adiabatic explosion pressures indicates that the hydrogen addition effect varies at different initial pressures and effective equivalence ratios owing to heat loss. In addition, the maximum pressure rise rate and deflagration index increase with increasing hydrogen concentration, which is more obvious for rich mixtures and high hydrogen concentrations.

Orphan optical flare as SOSS emission afterglow, localization in time

ABSTRACT We report on MASTER optical observations of an afterglow-like optical and X-ray transient AT2021lfa/ZTF21aayokph. We detected the initial steady brightening of the transient at 7σ confidence level. This allowed us to use smooth optical self-similar emission of GRBs model to constrain the explosion time to better than 14 min as well as to estimate its initial Lorentz factor Γ0 = 20 ± 10. Taking into consideration the low Γ0 and non-detection in gamma-rays, we classify this transient as the first failed GRB afterglow.

Neutrino driven explosions aided by axion cooling in multidimensional simulations of core-collapse supernovae

In this study, we present the first multidimensional core-collapse supernovae (CCSNe) simulations including QCD axions in order to assess the impact on the CCSN explosion mechanism. We include axions in our simulations through the nucleon-nucleon bremsstrahlung emission channel and as a pure energy-sink term under the assumption that the axions free-stream after being emitted. We perform both spherically symmetric (1D) and axisymmetric (2D) simulations. In 1D, we utilize a parameterized heating scheme to achieve explosions, whereas in 2D we self-consistently realize explosions through the neutrino heating mechanism. Our 2D results for a $20 M_\odot$ progenitor show an impact of the axion emission on the shock behavior and the explosion time when considering values of the Peccei-Quinn energy scale $f_a \leq 2 \times 10^8$ GeV. The strong cooling due to the axion emission accelerates the contraction of the core and leads to more efficient neutrino heating and earlier explosions. For the axion emission formalism utilized, the values of $f_a$ that impact the explosion are close to, but in tension with current limits based on the neutrinos detected from SN1987A. However, given the non-linear behavior of the emission and the multidimensional nature of CCSNe, we suggest that a self-consistent, multidimensional approach to simulating CCSNe, including any late time accretion and cooling, is needed to fully explore the axion bounds from supernovae and the impact on the CCSN explosion mechanism.

Dynamics of Pressure Evolution during Gaseous Ethane–Air Mixture Explosions in Enclosures: A Review

The study here presents data from the literature regarding the characteristic parameters of explosion propagation in gaseous ethane–air mixtures. The maximum explosion pressures, maximum explosion times, maximum rates of pressure increase, and deflagration indices from experimental measurements are discussed and analyzed against the initial pressure, initial temperature, and equivalence ratio, as well as the explosion vessel characteristics. Ethane is used for ethylene production, as a refrigerant in cryogenic systems, as an alternative clean fuel in the power generation industry and automotive propulsion, and for many other applications. Therefore, the explosion characteristics of its mixtures with air are of great interest for explosions occurring after accidentally forming flammable mixtures, as well as for the prediction of combustors’ performances and/or engines that work in different conditions.

Explosive source signature determination: Two unequal shots in the same hole

AbstractBuried explosive charges generate seismic waves with unrivalled bandwidth. The source time function is not always repeatable and is difficult to measure, but is required for subsequent data processing including reverse time migration and full waveform inversion. I present a new method for estimating the explosive seismic source time function for every shot, using two unequal shots in the same shot hole. The measured data for each charge are deconvolved for the modelled monopole seismic source time function to recover estimated earth impulse responses or Green's functions. The source model parameters are adjusted to maximize the likeness of the estimated Green's functions from the two shots, applying physical constraints to obtain the prior probability density functions for each parameter. Ten parameters specify the two source models, but only five of these are independent and a grid search is used to find them. The method is tested on an experimental data set, obtained for a different purpose, consisting of a line of single geophones and three in‐line shot holes, each with two unequal charges, the larger one at twice the depth of the smaller. The method works well where the charge size ratio is at least 2: the estimated source time functions are recovered and the estimated Green's functions are more similar than the seismograms before deconvolution. To apply the method in practice, the smaller charge should be deeper than the larger. If the small charge is small enough, the vertical separation between the charges can be reduced to less than 1 m. The Green's functions for the two charges would then be almost identical for frequencies up to 250 Hz, and the differences in the measured data from the two charges would be caused principally by the differences in the two source time functions.

Explosion behaviors of vapor–liquid propylene oxide/air mixture under high-temperature source ignition

Propylene oxide (PO) is widely used in fuel–air explosive (FAE) and pulse detonation engines (PDE). The explosion process of PO/air mixture in a 20 L spherical container under high-temperature source ignition was studied through experiment and numerical simulation. A good agreement was observed between the experimental and simulation results. The ignition temperature (1100–2500 K) and initial droplet size (10–200 μm) had no obvious effect on the maximum explosion pressure (Pmax) at a nominal concentration of 130 g/m3. Explosion time (te) and reaction time (tr) of PO aerosol explosion increased with the increase in initial droplet size. The flame propagation process in the direction of 90° was not the same as that of 45°. Explosion flame propagated from the center to the surrounding area, then sagged along wall facing the center and presented a U-shape. Explosion time at ignition temperature of 1600 K was 29.63 ms, which was the shortest compared with the temperature of 2000 K, 2500 K, and 1100 K. The influence of ignition temperature on te was more obvious than that of initial droplet size. The flame propagation mechanism of droplet sizes of 10 μm and 50 μm was different from that of 100 μm and 200 μm. The time to reach the maximum flame temperature(tf) increased with the increase in droplet size; the flame propagation speed decreased with the increasing droplet size, and the maximum flame velocity can reach 6.07 m/s.

Pressure‐Dependent Chemical Decomposition of an HMX‐Based PBX During Low‐Velocity Impacts

AbstractHMX decomposition kinetics are usually calibrated in the temperature range around 200 °C. This leads to an underestimation of several orders of magnitude of the thermal explosion times during impacts compared to measurements collected in Henson and Smilowitz, in Non‐shock initiation of explosives, Shock wave science and technology reference library, 2010. It highlights the incomplete physics used in the single‐ or multi‐stage decomposition kinetics to model the solid‐to‐gas transformation of HMX. The experimental device proposed in this work allows the observation of sample pressure and size during heating tests and thus allows the phase transition and thermal explosion of the samples to be observed in real time. The Henson and Smilowitz model is revisited by integrating (1) the mechanical resistance of the molecular network to the phase change and (2) a dependence of the vaporization and sublimation rates on the pressure. The latter describes the pressure‐dependence on the virtual melting mechanism and consequently on the presence or absence of δ‐HMX in the solid and liquid states. Good correlations between the numerical results and data are obtained. The modified model is then extrapolated to the low velocity impact range.

Explosion inhibition of coal dust clouds under coal gasification atmosphere by talc powder

During coal gasification, the explosion intensity of coal dust was enhanced and more difficult to inhibit due to the presence of CO and H2. To mitigate the risk of dust explosion under a coal gasification atmosphere, the inhibition performance of talc powder (TP) on coal dust explosion was investigated by using a 20 L spherical explosive vessel. The results showed that the explosion intensity of dust clouds was attenuated with the inhibition of TP. As the particle size of TP decreased, the explosion pressure gradually was reduced and the explosion time was extended. The maximum explosion pressure of dust clouds decreased from 0.845 to 0.270 MPa after the addition of 8000 mesh TP, representing a reduction of 68 %. And the flame propagation velocity was consequently dropped from 1.22 to 0.17 m/s. Moreover, the explosion of higher rank coal dust was more easily inhibited by TP. XPS analysis demonstrated that the C–C and C–O–C in coal dust were effectively protected under the effect of TP. And the inhibition mechanism of TP on coal dust explosion was elaborated thoroughly in combination with the analysis of explosion products.

Type IIP Supernova IV. Shock Breakout from Progenitor Stars Modeled with Convective Overshoot and Mass Loss

Red supergiant stars lose a lot of mass in slow winds that forms a circumstellar medium (CSM) around the star. When the star retains a substantial hydrogen envelope at the time of explosion, it displays characteristic light curves and spectra of a Type II plateau supernova (SN), e.g., the nearby SN 2013ej. When the shock wave launched deep inside the star exits the surface, it probes the CSM and scripts the history of mass loss from the star. We simulate with the STELLA code the SN radiative display resulting from shock breakout (SBO) for a set of progenitor stars. We evolved these stars with the MESA code from their main-sequence to core-collapse phase using diverse evolutionary inputs. We explore the SN display for different internal convective overshoot and compositional mixing inside the progenitor stars and two sets of mass-loss schemes, one the standard “Dutch” scheme and the other an enhanced, episodic and late mass loss. The SBO from the star shows closely time-separated double-peaked bolometric light curves for the Dutch case, as well as high-velocity ejecta with minuscule mass accelerated during SBO. The earlier of the peaks, which we call the precursor peaks, are compared with analytical expressions for SBO of stars. We also contrast the breakout flash from an optically thick CSM with that of the rarefied medium established by Dutch wind. We describe how the multigroup photon spectra of the breakout flashes differ between these cases.

Play Time: Gender, Anti-Semitism and Temporality in Medieval Biblical Drama

Play Time: Gender, Anti-Semitism and Temporality in Medieval Biblical Drama

MARTINGALE REPRESENTATIONS IN PROGRESSIVE ENLARGEMENT BY MULTIVARIATE POINT PROCESSES

In this paper, we show that all local martingales with respect to the initially enlarged natural filtration of a vector of multivariate point processes can be weakly represented up to the minimum among the explosion times of the components. We also prove that a strong representation holds if any multivariate point process of the vector has almost surely infinite explosion time and discrete marks space. Then we provide a condition under which the components of the multidimensional local martingale driving the strong representation are pairwise orthogonal.