Explosion Energy Research Articles

In Ukrainian

Experimental methodology of the thermal vacuum process is that in order to obtain effective and economical production of nanomaterials, it is necessary to ensure a continuous flow of dispersed material inside the heating spiral element. This can done if the material enters the cavity of the heating element together with air. A two-phase system of gas-solid particles arises. The movement occurs in an ascending flow in a heated space with a constant decrease in pressure for 15 s. The results of the studies show that the velocity of material particles in the cavity of spiral heating element of the thermal vacuum unit depends on the thermal radiation of the heater walls, the energy of a local pulsed steam explosion with the appearance of a shock wave, which forms a significant number of nanodispersed and finely dispersed bodies. The greater the energy of the local explosion, the higher the velocity of the material particle, the greater the angle of incidence of the particle on the opposite wall of the heating element. Locally, the temperature of the external environment increases, the kinetic energy of material particles grows, and the flow of electrons, protons, and other charged particles accelerates significantly. A plasma clot is formed, a neutrino cloud is emitted. Nanoparticles take the form of nanotubes, fullerenes, thin films, crystals. It been established that the dispersed material in the thermal vacuum unit is successively affected by force, heat, deformation, ionization effects, which allows accelerating the process of obtaining nanodispersed materials. Each physical process in a thermal vacuum installation has its own space-time continuum and it is necessary to take into account only those characteristics that correspond to a specific interaction.

Gravitational collapse of white dwarfs to neutron stars: From initial conditions to explosions with neutrino-radiation hydrodynamics simulations

Abstract Using general relativistic neutrino-radiation hydrodynamics simulations with the multi-group M1 scheme in one dimension, we investigate the collapse of massive, fully convective, and non-rotating white dwarfs (WDs), which are formed by accretion-induced collapse or merger-induced collapse, and the subsequent explosion. We produce initial WDs in hydrostatic equilibrium, which have super-Chandrasekhar mass and are about to collapse. The WDs have masses of $1.6\, M_{\odot }$ with different initial central densities specifically at $1.0\times 10^{10}$, $4.0\times 10^{9}$, $2.0\times 10^{9}$, and $1.0\times 10^{9}\:\mbox{g}\:\mbox{cm}^{-3}$. First, we examine the stability of initial WD in case weak interactions are turned off. Secondly, we calculate the collapse of WDs with weak interactions. We employ hydrodynamics simulations with Newtonian gravity in the first and second steps. Thirdly, we calculate the formation of neutron stars and accompanying explosions with general relativistic simulations. As a result, WDs with the highest density of $10^{10}\:\mbox{g}\:\mbox{cm}^{-3}$ collapse not by weak interactions but by the photodissociation of the iron, and three WDs with low central densities collapse by the electron capture as expected at the second step and succeed in the explosion with a small explosion energy of $\sim\! 10^{48}\:$erg at the third step. By changing the surrounding environment of WDs, we find that there is a minimum value of ejecta masses, which is $\sim\! 10^{-5}\, M_{\odot }$. With the most elaborate simulations of this kind so far, this value is one to two orders of magnitude smaller than previously reported values and is compatible with the estimated ejecta mass from FRB 121102.

Study on the Influence of Notched Empty Hole Parameters on Directional Fracture Blasting Effect

Placing empty holes between charging holes is widely used in blasting engineering to achieve directional fracture blasting. Studies have shown that the presence of a notch along the empty hole wall enhances stress concentration and supports improved control over crack propagation. The notch angle and length are the two main parameters influencing the impact of notch holes. Therefore, in this study, we used numerical simulations to investigate how varying notch angles and lengths influence the directional fracture blasting effect. The findings suggest that, among the different types of holes used in directional fracture rock blasting, notched empty holes have the most significant guiding effect, followed by empty holes, while the absence of empty holes yields the least effective results. In the directional fracture blasting of a notched empty hole, stress concentration occurs at the notch tip following the explosion. This alters the stress field distribution around the empty hole, which shifts from a compressive to a tangential tensile state. Additionally, this concentration of stress causes the explosion energy to be focused on that location, resulting in a directional fracture blasting effect. In blasting construction, selecting the appropriate notch hole parameters is necessary to achieve optimal effects and reduce damage to surrounding rocks. Based on the notch parameters assessed in this study, the optimal effect of directional fracture blasting is achieved when the notch angle is 30°.

The Two Alternative Explosion Mechanisms of Core-Collapse Supernovae: 2024 Status Report

In comparing the two alternative explosion mechanisms of core-collapse supernovae (CCSNe), I examine recent three-dimensional (3D) hydrodynamical simulations of CCSNe in the frame of the delayed neutrino explosion mechanism (neutrino mechanism) and argue that these valuable simulations show that neutrino heating can supply a non-negligible fraction of the explosion energy but not the observed energies, and hence cannot be the primary explosion mechanism. In addition to the energy crisis, the neutrino mechanism predicts many failed supernovae that are not observed. The most challenging issue of the neutrino mechanism is that it cannot account for point-symmetric morphologies of CCSN remnants, many of which were identified in 2024. These contradictions with observations imply that the neutrino mechanism cannot be the primary explosion mechanism of CCSNe. The alternative jittering jets explosion mechanism (JJEM) seems to be the primary explosion mechanism of CCSNe; neutrino heating boosts the energy of the jittering jets. Even if some simulations show explosions of stellar models (but usually with energies below that observed), it does not mean that the neutrino mechanism is the explosion mechanism. Jittering jets, which simulations do not include, can explode the core before the neutrino heating process does. Morphological signatures of jets in many CCSN remnants suggest that jittering jets are the primary driving mechanism, as expected by the JJEM.

Numerical Analysis of Explosion-Induced Deformations on Steel Panels in Urban Environments

Explosion proof structures are designed to be very heavy and non-functional using conventional systems so that they can be resistant to blast effects. As a result, not only the emergence of non-economic structures, but also their operational performance decreases. To effectively mitigate these challenges, a substantial body of research has focused on the development and application of designs and materials specifically engineered to withstand explosive load impacts. In this study, the strength of steel plates under explosives with different energies was tested. Related tests were performed using Ls-Dyna finite element software. An experimental literature was used to calibrate the numerical model. When the results obtained as a result of the calibration were compared with the experimental data, a high level of agreement was obtained. The calibrated numerical model was subjected to burst loads by varying the panel thicknesses and its dynamic responses were simulated. The displacement values were analyzed by placing the explosives equidistant from the panel centers. By comparing the analysis results, explosive energies were compared. The most effective explosive types could be listed according to the amount of change that the evaluated explosives in the same amount caused on the panel surfaces. In line with these studies, information will be gained about what type of steel materials will be used against which type of explosives in areas that need to be protected in urban areas.

Impact of star formation models on the growth of simulated galaxies at high redshifts

Star formation is a key process that governs the baryon cycle within galaxies, however, the question of how it controls their growth remains elusive due to modeling uncertainties. To understand the impact of star formation models on galaxy evolution, we performed cosmological zoom-in radiation-hydrodynamic simulations of a dwarf dark matter halo, with a virial mass of $ at $z=6$. We compared two different star formation models: a multi-freefall model combined with a local gravo-thermo-turbulent condition and a more self-consistent model based on a sink particle algorithm, where gas accretion and star formation are directly controlled by the gas kinematics. As the first study in this series, we used cosmological zoom-in simulations with different spatial resolutions and found that star formation is more bursty in the runs with the sink algorithm, generating stronger outflows than in the runs with the gravo-thermo-turbulent model. The main reason for the increased burstiness is that the gas accretion rates on the sinks are high enough to form stars on very short timescales, leading to more clustered star formation. As a result, the star-forming clumps are disrupted more quickly in the sink run due to more coherent radiation and supernova feedback. The difference in burstiness between the two star formation models becomes even more pronounced when the supernova explosion energy is artificially increased. Our results suggest that improving the modeling of star formation on small, sub-molecular cloud scales can significantly impact the global properties of simulated galaxies.

Shock cooling emission from explosions of massive stars – III. Blue supergiants

ABSTRACT Light emission in the first hours and days following core-collapse supernovae is dominated by the escape of photons from the expanding shock-heated envelope. In preceding papers, we provided a simple analytic description of the time-dependent luminosity, L, and colour temperature, $T_{\rm col}$, as well as of the small (${\simeq} 10 {{\, \rm per\, cent}}$) deviations of the spectrum from a blackbody at low frequencies, $h\nu \lt 3T_{\rm col}$, and of ‘line dampening’ at $h\nu \gt 3T_{\rm col}$, for explosions of red supergiants (RSGs) with convective polytropic envelopes (without significant circumstellar medium). Here, we extend our work to provide similar analytic formulae for explosions of blue supergiants with radiative polytropic envelopes. The analytic formulae are calibrated against a large set of spherically symmetric multigroup (frequency-dependent) calculations for a wide range of progenitor parameters (mass, radius, and core/envelope mass ratios) and explosion energies. In these calculations, we use the opacity tables we constructed (and made publicly available), which include the contributions of bound–bound and bound–free transitions. The analytic formulae reproduce the numeric L and $T_{\rm col}$ to within 10 and 5 per cent accuracy, and the spectral energy distribution to within ${\sim} 20\!-\!40 {{\, \rm per\, cent}}$. The accuracy is similar to that achieved for RSG explosions.

Shock Activation Mechanism of Aluminum Nano-Particles outside High Explosives

Abstract Adding aluminum nanoparticles (ANPs) to explosive charges can effectively increase the total explosion energy and work capacity. A novel explosive charge was researched where ANPs were placed outside the high explosive. And the shock activation mechanism for the ANPs was proposed. The proposed shock activation mechanism suggests that under shock loadings, ANPs ignite due to the combined effects of shock work and plastic work. To investigate this mechanism, four turns of explosion experiments were conducted with varying layer thicknesses of ANPs in an enclosed space. The quasi-static pressure was measured to characterize the activation efficiency of the ANPs. The experimental results revealed that the reaction degree of the ANPs ranged from 55.9% to 67.2%, indicating that ANPs reached a relatively high reaction degree despite being placed outside the high explosives. Furthermore, the reaction degree decreased monotonically from 67.2% to 55.9% as the Al layer thickness increased from 1.3% to 6.3% of the explosive diameter. This observation suggests that the activation efficiency of the ANPs decreased with increasing layer thickness. These experimental findings show that the shock activation mechanism can effectively explain the activation of ANPs placed outside of explosives. The proposed shock activation mechanism is indeed valid and provides a promising approach to enhance the explosion energy and work capacity by incorporating ANPs in the charge configuration.

Effect of modified coated aluminum powder on the explosive properties of emulsion explosive

Abstract In order to investigate the effect of aluminum powder content on the detonation properties of emulsion explosives and to reduce the emulsion of aluminum powder on the emulsion explosives to improve their service life, the paraffin-coated spherical micron aluminum powder is used to prepare the proportion of 0%, 5%, 7%, 9%, 11%, 15%, and 20% of the aluminum-containing emulsion explosives. Using the chronometer method to determine the detonation velocity, the lead column compression method to assess its brisance, and conducting underwater explosion tests to calculate parameters such as shock wave energy, bubble energy, and total energy of the aluminum-containing emulsion explosives. Additionally, high and low-temperature cyclic accelerated aging tests are performed to study the effect of aluminum powder on the service life of the emulsion explosives. The results show that aluminum powder mass fraction of 5%, containing aluminum emulsion explosive detonation velocity, is the largest, 5459m·s−1, with the increase of aluminum powder content, containing aluminum emulsion explosives detonation velocity of the overall trend of reducing. Briance first increased and then decreased, reaching a maximum value of 24.06mm in 15%. The total energy of the underwater explosion increases with the increase in aluminum powder content. In the aluminum powder mass fraction of 20% to reach the maximum, the shock wave energy increased by 26.7%, the bubble energy increased by 65.4%, and the total energy increased by 65.4%. The service life of paraffin-coated aluminum emulsion explosives is better than that of emulsion explosives containing ordinary aluminum powder service life.

Optical and near-infrared photometry of 94 type II supernovae from the Carnegie Supernova Project

Context. Type II supernovae (SNe II) mark the endpoint in the lives of hydrogen-rich massive stars. Their large explosion energies and luminosities allow us to measure distances, metallicities, and star formation rates into the distant Universe. To fully exploit their use in answering different astrophysical problems, high-quality low-redshift data sets are required. Such samples are vital to understand the physics of SNe II, but also to serve as calibrators for distinct – and often lower-quality – samples. Aims. We present uBgVri optical and YJH near-infrared (NIR) photometry for 94 low-redshift SNe II observed by the Carnegie Supernova Project (CSP). A total of 9817 optical and 1872 NIR photometric data points are released, leading to a sample of high-quality SN II light curves during the first ∼150 days post explosion on a well-calibrated photometric system. Methods. The sample is presented and its properties are analysed and discussed through comparison to literature events. We also focus on individual SNe II as examples of classically defined subtypes and outlier objects. Making a cut in the plateau decline rate of our sample (s2), a new subsample of fast-declining SNe II is presented. Results. The sample has a median redshift of 0.015, with the nearest event at 0.001 and the most distant at 0.07. At optical wavelengths (V), the sample has a median cadence of 4.7 days over the course of a median coverage of 80 days. In the NIR (J), the median cadence is 7.2 days over the course of 59 days. The fast-declining subsample is more luminous than the full sample and shows shorter plateau phases. Of the non-standard SNe II highlighted, SN 2009A particularly stands out with a steeply declining then rising light curve, together with what appears to be two superimposed P-Cygni profiles of Hα in its spectra. We outline the significant utility of these data, and finally provide an outlook of future SN II science.

Effect of aluminum powder particle size on quasi-static pressure and temperature in confined space explosion of aluminized explosives

Abstract Aluminum powder particle size is a crucial parameter concerning the energy release of aluminized explosives. This study aimed to examine the effect of single aluminum powder particle size and particle size gradation on the explosive energy release characteristics of aluminized explosives in confined spaces by using a self-developed confined explosion experimental device. Aluminized explosive samples having aluminum powder particle sizes of 6, 24, and 43 μm and particle size gradation of 6/24/43 μm were tested for explosion parameters generated by an internal explosion. The results indicate that the quasistatic pressure of the measured aluminum powder samples decreased gradually with the increase of the particle size. The quasi-static pressure of the particle size gradation explosive samples was the largest, and the quasi-static pressure increased by 5.0%, 9.9%, and 12.0%, respectively, compared with a single particle size. The highest peak temperature was observed for the 6 μm particle size sample. However, the highest equilibrium temperature was obtained for the particle size gradation sample, indicating that particle size gradation promotes the reaction of aluminum powder in the afterburning stage; this helps maintain the temperature of a confined space for a certain duration and increase the energy release of the aluminized explosives.

A Validation Study on Dynamic Response and Failure Analysis of Large Unconfined Pipes under Localized Blast Loading Using an Explicit Dynamic Approach

Abstract This study utilized an Explicit Dynamic Approach to analyze the dynamic behavior of large-diameter pipes subjected to localized blast loading. The objective of the validation study was to investigate the effects of the explosion's blast force on the dynamic response and material behaviors in large-diameter pipes. The existing experimental data was benchmarked with the numerical results to assess the prediction accuracy. The crucial factors include the amount of the explosive mass (0.2-5.0 kg), the contact regions, and the wall thickness of the pipe (1.46 cm and 2.62 cm). As a result, the contact area significantly influenced the deformation range in each case, ranging from 50-400 cm2. The amount of explosive energy was crucial in determining the material response. For instance, deformations like pitting and spallation were found from the case testing with less than 1.4 kg of TNT, and the completed tearing in the central area was found from the case of higher explosive mass. With modest explosive mass, the pipe material underwent inelastic deformation. However, the material became vulnerable to adiabatic shearing failure when the explosive energy exceeded 1.4 kg in penetrating the 2.62 cm-thick walls. The difference between the simulations and experimental deformation (1.46-mm-thickness) was average at 8.5 %, which presents an attractive tool. Therefore, this Explicit Dynamic tool will be used in subsequent research to study the responses of structural building systems to occasional explosion scenarios and capture the explosion fragments.

Thermal Vacuum Synthesis: Physical Processes in Nanomaterial Production

The thermovacuum process offers an efficient and cost-effective method for producing nanomaterials by ensuring the continuous flow of dispersed material inside a spiral heating element. This is achieved by introducing the material into the heating element's cavity along with air, forming a two-phase gas-solid particle system. The material moves upward through the heated space, where pressure gradually decreases. Experimental studies on materials like carbon, brown coal, and zirconium dioxide indicate specific conditions are necessary for the system's continuous operation. One key requirement is that the mass of solid particles should not exceed 1.0 to 1.2 grams per liter of air entering the heating element. This limit ensures that nanodispersed and finely dispersed particles can move freely, avoiding collisions and allowing faster-moving particles to overtake slower ones. These particles increase in velocity and temperature as they pass through the heating element, with changes in heat capacity and particle motion contributing to wave motion and pulsed heat loads. The velocity at which the material particles travel depends on the thermal radiation from the heater walls and the energy generated by local pulse steam explosions, which create shock waves. Higher explosion energy results in increased particle velocity, greater impact angles against the heater walls, and higher environmental temperatures. These conditions lead to accelerated electron, proton, and other charged particle flows, forming plasma clots and neutrino clouds. The nanoparticles take various forms, including nanotubes, fullerenes, thin films, and crystals, reaching velocities up to a thousand kilometers per second and heating temperatures of up to 17 million degrees during pulses. This process consistently subjects the material to force, heat, deformation, and ionization, expediting the creation of nanodispersed materials with enhanced physicochemical and mechanical properties. The thermovacuum process not only improves the efficiency of thermotechnological equipment but also reduces energy consumption, production time, and costs. The research findings support its use in the continuous and effective production of high-quality nanomaterials.

Three-dimensional magnetohydrodynamic simulations of core-collapse supernovae – I. Hydrodynamic evolution and protoneutron star properties

ABSTRACT We present results from three-dimensional, magnetohydrodynamic, core-collapse simulations of 16 progenitors following until 0.5 s after bounce. We use non-rotating solar-metallicity progenitor models with zero-age main-sequence mass between 9 and 24 ${\rm M}_{\odot }$. The examined progenitors cover a wide range of the compactness parameter including a peak around $23 \, {\rm M}_{\odot }$. We find that neutrino-driven explosions occur for all models within 0.3 s after bounce. We also find that the properties of the explosions and the central remnants are well correlated with the compactness. Early shock evolution is sensitive to the mass accretion rate on to the central core, reflecting the density profile of the progenitor stars. The most powerful explosions with diagnostic explosion energy $E_{\rm dia} \sim 0.75 \times 10^{51}$ erg are obtained by 23 and 24 ${\rm M}_{\odot }$ models, which have the highest compactness among the examined models. These two models exhibit spiral standing-accretion-shock-instability motions during 150–230 ms after bounce preceding a runaway shock expansion and leave a rapidly rotating neutron star with spin periods $\sim 50$ ms. Our models predict the gravitational masses of the neutron star ranging between $1.22$ and $1.67 {\rm M}_{\odot }$ and their spin periods 0.04 – 4 s. The number distribution of these values roughly matches observation. On the other hand, our models predict small hydrodynamic kick velocity (15–260 ${\rm km \, s}^{-1}$), although they are still growing at the end of our simulations. Further systematic studies, including rotation and binary effects, as well as long-term simulations up to several seconds, will enable us to explore the origin of various core-collapse supernova explosions.

SN 1054 as a pulsar-driven supernova: implications for the crab pulsar and remnant evolution

ABSTRACT One of the most studied objects in astronomy, the Crab Nebula, is the remnant of the historical supernova SN 1054. Historical observations of the supernova imply a typical supernova luminosity, but contemporary observations of the remnant imply a low explosion energy and low ejecta kinetic energy. These observations are incompatible with a standard $^{56}$Ni-powered supernova, hinting at an an alternate power source such as circumstellar interaction or a central engine. We examine SN 1054 using a pulsar-driven supernova model, similar to those used for superluminous supernovae. The model can reproduce the luminosity and velocity of SN 1054 for an initial spin period of $\sim$14 ms and an initial dipole magnetic field of 10$^{14-15}$ G. We discuss the implications of these results, including the evolution of the Crab pulsar, the evolution of the remnant structure, formation of filaments, and limits on freely expanding ejecta. We discuss how our model could be tested further through potential light echo photometry and spectroscopy, as well as the modern analogues of SN 1054.

Research on combined damage characteristics of underwater armor-piercing and explosion based on supercavitating projectile

Recent studies of supercavitating projectiles primarily focus on the formation and evolution of the cavity, as well as its underwater ballistic characteristics, while neglecting the terminal damage effects. Little attention has been given to exploring the combined damage effects of armor-piercing-explosion supercavitating projectiles (APESP). Therefore, this study comparatively analyzes the response processes and failure modes of an underwater aluminum alloy cylindrical shell target under the action of three different types of loads: armor piercing, explosion, and combined armor-piercing and explosion. This study investigates the underwater combined damage mechanisms of the APESP, clarifies each damage phase under the combined effect, discusses the advantages of damage resulting from the combined armor-piercing and explosion effect based on the target responses and damage modes, and explores the reasons for dissipation of explosion energy. The results show that: the APESP combines localized point damage characteristics of armor piercing with overall surface damage features of underwater explosion. Depending on load stages and target responses, the target response process under the action of the APESP can be divided into the hydrodynamic ram phase, penetration phase, shock wave phase, stable vibration phase, and bubble pulsation phase. The entire physical system can be abstracted as a low-frequency series spring system (equivalent to bubble pulsation frequency) with high-frequency external energy input, based on the energy relationship of the medium and the structure. The concept of the 'blower effect' is proposed based on target behavior during the stable vibration phase. Following the application of different loads, the plastic deformation of the target in a stable state is ranked as: underwater explosion > combined armor-piercing and explosion > underwater armor piercing. Supercavity, shell casing and penetration hole will cause the dissipation of explosion energy.

A Modified Initial Mass Function of the First Stars with Explodability Theory under Different Enrichment Scenarios

The most metal-poor stars record the earliest metal enrichment triggered by Population III stars. By comparing observed abundance patterns with theoretical yields of metal-free stars, physical properties of their first star progenitors can be inferred, including zero-age main-sequence mass and explosion energy. In this work, the initial mass distribution of the first stars is obtained from the largest analysis to date of 406 very metal-poor stars with the newest LAMOST/Subaru high-resolution spectroscopic observations. However, the mass distribution fails to be consistent with the Salpeter initial mass function, which is also reported by previous studies. Here, we modify the standard power-law function with explodability theory. The mass distribution of Population III stars could be well explained by ensuring that the initial metal enrichment originates from successful supernova explosions. Based on the modified power-law function, we suggest an extremely top-heavy or nearly flat initial mass function with a large exponent for the explosion energy. This indicates that supernova explodability should be considered in the earliest metal enrichment process in the Universe.

Multidimensional Radiation Hydrodynamics Simulations of SN 1987A Shock Breakout

Shock breakout is the first electromagnetic signal from supernovae (SNe), which contains important information on the explosion energy and the size and chemical composition of the progenitor star. This paper presents the first two-dimensional (2D) multiwavelength radiation hydrodynamics simulations of SN 1987A shock breakout by using the CASTRO code with the OPAL opacity table considering eight photon groups from infrared to X-ray. To investigate the impact of the pre-SN environment of SN 1987A, we consider three possible circumstellar medium environments: a steady wind, an eruptive mass loss, and the existence of a companion star. In sum, the resulting breakout light curve has an hour-long duration and a peak luminosity of ∼4 × 1046 erg s−1, with a decay rate of ∼3.5 mag hr−1 in X-ray. The dominant band transits to UV around 3 hr after the initial breakout, and its luminosity has a decay rate of ∼1.5 mag hr−1 that agrees well with the observed shock breakout tail. The detailed features of breakout emission are sensitive to the pre-explosion environment. Furthermore, our 2D simulations demonstrate the importance of multidimensional mixing and its impacts on shock dynamics and radiation emission. The mixing emerging from the shock breakout may lead to a global asymmetry of SN ejecta and affect its later SN remnant formation.

Machine learning approaches for predicting impact sensitivity and detonation performances of energetic materials

Excellent detonation performances and low sensitivity are prerequisites for the deployment of energetic materials. Exploring the underlying factors that affect impact sensitivity and detonation performances as well as exploring how to obtain materials with desired properties remains a long-term challenge. Machine learning with its ability to solve complex tasks and perform robust data processing can reveal the relationship between performance and descriptive indicators, potentially accelerating the development process of energetic materials. In this background, impact sensitivity, detonation performances, and 28 physicochemical parameters for 222 energetic materials from density functional theory calculations and published literature were sorted out. Four machine learning algorithms were employed to predict various properties of energetic materials, including impact sensitivity, detonation velocity, detonation pressure, and Gurney energy. Analysis of Pearson coefficients and feature importance showed that the heat of explosion, oxygen balance, decomposition products, and HOMO energy levels have a strong correlation with the impact sensitivity of energetic materials. Oxygen balance, decomposition products, and density have a strong correlation with detonation performances. Utilizing impact sensitivity of 2,3,4-trinitrotoluene and the detonation performances of 2,4,6-trinitrobenzene-1,3,5-triamine as the benchmark, the analysis of feature importance rankings and statistical data revealed the optimal range of key features balancing impact sensitivity and detonation performances: oxygen balance values should be between −40% and −30%, density should range from 1.66 to 1.72 g/cm3, HOMO energy levels should be between −6.34 and −6.31 eV, and lipophilicity should be between −1.0 and 0.1, 4.49 and 5.59. These findings not only offer important insights into the impact sensitivity and detonation performances of energetic materials, but also provide a theoretical guidance paradigm for the design and development of new energetic materials with optimal detonation performances and reduced sensitivity.

A survey of extremely metal-poor gas at cosmic noon

Aims. We aim to study the high-precision chemical abundances of metal-poor gas clouds at cosmic noon (2 < z < 4) and investigate the associated enrichment histories. Methods. We analyze the abundances of four newly discovered metal-poor gas clouds utilizing observations conducted with Keck/HIRES and VLT/UVES. These systems are classified as very metal-poor (VMP), with [Fe/H] < −2.57, and one system qualifies as an extremely metal-poor (EMP) Damped Lyman-α (DLA) system with [Fe/H] = −3.13 ± 0.06. In combination with new high-resolution data of two previously known EMP DLAs and 2 systems reported in the literature, we conduct a comprehensive analysis of eight of the most metal-poor gas clouds currently known. We focus on high-precision abundance measurements using the elements: C, N, O, Al, Si, and Fe. Results. Our findings indicate increasing evidence of elevated [O/Fe] abundances when [Fe/H] < −3. EMP DLAs are well-modeled with a mean value of [O/Fe]cen = +0.50 ± 0.04 and an intrinsic scatter of σint[O/Fe] = 0.13-0.04+0.06. While VMP DLAs are well-modeled with [O/Fe]cen = +0.40 ± 0.02 and σint, [O/Fe] = 0.06 ± 0.02. We further find tentative evidence of a redshift evolution of [C/O] across these most metal-poor DLAs with lower redshift systems showing elevated [C/O] ratios. Using the measured abundances, combined with a stochastic chemical enrichment model, we investigate the properties of the stellar population responsible for enriching EMP gas at cosmic noon. We find that the chemistry of these systems is best explained via the enrichment of just two massive progenitors, N⋆ = 2 ± 1, that ended their lives as core collapse SNe with a typical explosion energy Eexp = (1.6 ± 0.6)×1051 erg. These progenitors formed obeying a Salpeter-like power-law IMF, where all stars of mass greater than Mmax = 32-4+10M⊙ collapse directly to black holes and do not contribute to the metal enrichment.