Small Explosions Research Articles

Introducing the Rebels’ Armament Dataset (RAD): Empirical Evidence on Rebel Military Capabilities

There is a scarcity of systematic data regarding the military equipment of rebel groups engaged in intrastate conflicts. This empirical gap has impeded the rigorous evaluation of (formal) theories concerning militarized interactions between governments and rebel groups. To address this deficiency, we have developed the Rebels' Armament Dataset (RAD). This dataset provides detailed information on the military arsenals of 270 groups over the period from 1989 to 2020, categorizing 15 different types of small arms, light weapons, explosives, and major weapons. In this article, we introduce RAD, compare it with existing datasets, elucidate the data collection process, present an initial overview of the information contained in it, and apply the data to examine civilian suffering in civil wars. Although this dataset is merely an initial step that can be expanded as additional public information becomes available, RAD offers the first organized compilation of data on the armament levels of rebels.

Unique seismic and eruption precursors to the 1996 and ongoing magmatic eruptions of Popocatépetl: Coupled and fluidized bed events

We describe three unique types of seismicity at Popocatépetl volcano that accompanied the initial vent-clearing eruptive activity in December 1994 through the eruption of the first two domes in 1996. We identify and describe two types of coupled events, 1) spasmodic burst coupled events, a burst of volcano tectonic (VT) events coupled with a large eruptive explosion (21 December 1994 and 5 March 1996), and 2) explosion-couplet coupled events, a pair of events with a deeper first event and whose second event correlates with a small gas emission or explosion. Explosion-couplets occurred with the onset of magmatic ash dominated eruptions and their properties are very useful for forecasting magmatic eruptions at Popocatépetl volcano. Measurable quantities including the time between the first and second phase, daily numbers of events, and the amplitude ratio between the second and first phase systematically changed as the first two domes approached the surface between March and June 1996. Interevent times decreased from many tens of seconds to a few seconds, while amplitude ratios increased from about 2 to 10 or more. Event numbers increased prior to and during initial dome extrusion. These changes were used to forecast the eruption of the first two domes. We also report on another unusual type of low frequency seismicity that accompanied emissions called fluidized bed events. Fluidized bed events occurred following the initial eruption on 21 December 1994, beginning mid-January 1995, when SO2 emissions were initially elevated, and the conduit was open. Fluidized bed events began to wane in late March through the end of May 1995 as did SO2 emissions. Consistent gas, visual and seismic observations by Centro Nacional de Prevención de Desastres (CENAPRED) enabled the direct correlation of the gas, magma, and seismic phenomena.

Risk Analysis of Small LPG Storage Tank Explosion in the School Cafeteria

This study aimed to determine the best safety measures in case of accidental gas leakage, fire, or explosion in the LPG storage tank of a domestic school kitchen by analyzing the ranges potentially affected by toxicity, overpressure, and radiant heat. Using the Areal Locations of Hazardous Atmospheres (ALOHA) program, the range of damage impact of gas leakage, toxicity owing to VCE and boiling liquid expanding vapor explosion (BLEVE), overpressure, and radiant heat were analyzed for a 1,000 kg-capacity small LPG storage tank installed in the kitchen. It was classified into worst-case and alternative (local weather) scenarios, depending upon the weather conditions, and analyzed by dividing into 50% and 100% storage, as per the difference in storage. The observed risk of toxicity placed the entire school area at risk of death or disability. The risk of overpressure posed a threat to buildings in the entire school area and around the school. The risk of blasts revealed a risk of death up to a distance of 135 m, and the farther regions were at risk of second-degree burns. Additionally, the risks of toxicity and overpressure are affected by weather conditions and LPG storage, whereas blasts are primarily affected by LPG storage with minimal impact from weather conditions.

Trainability issues in quantum policy gradients

Abstract This research explores the trainability of Parameterized Quantum Circuit-based policies in Reinforcement Learning, an area that has recently seen a surge in empirical exploration. While some studies suggest improved sample complexity using quantum gradient estimation, the efficient trainability of these policies remains an open question. Our findings reveal significant challenges, including standard Barren Plateaus with exponentially small gradients and gradient explosion. These phenomena depend on the type of basis-state partitioning and the mapping of these partitions onto actions. For a polynomial number of actions, a trainable window can be ensured with a polynomial number of measurements if a contiguous-like partitioning of basis-states is employed. These results are empirically validated in a multi-armed bandit environment.

Seismoacoustic Wavefield at Popocatépetl Volcano, Mexico, Captured by a Temporary Broadband Network from 2021 to 2022

Abstract Popocatépetl is a highly active stratovolcano in central Mexico with recurrent activity of Vulcanian-type explosions and frequent degassing. The proximity of Popocatépetl volcano to Mexico City, one of the most populated cities in the world, demands continuous monitoring to achieve an adequate volcano risk assessment. We present an overview of the first high-dynamic-range and high-broadband (0.01–200 Hz; 400 Hz sampling rate) seismoacoustic network (PoPiNet), which we operated around Popocatépetl volcano from August 2021 to May 2022. Here, we show preliminary results of the explosions recorded in September 2021. We deployed five seismoacoustic stations within 4–25 km horizontal distance (range) from the vent. We identify infrasonic waveforms associated with tremor and explosions, with pressures ranging from 16 to 134 Pa and dominant frequencies between 0.2 and 5.0 Hz. The frequency content of the recorded signals at the closest stations to the volcano spans the sub-bass (20–60 Hz) and bass (60–250 Hz) ranges. The associated seismic signals of moderate explosions exhibit air-to-ground coupled waves with maximum coherence values at frequencies up to 5 and 25 Hz for the farthest and closest stations to the volcano, respectively. Conversely, we observe infrasound signal amplitudes from relatively small explosions reaching maximum pressures of 10 Pa that do not couple into the ground, even at the closest stations. These infrasound signals are associated with type-I long-period events as reported in previous investigations. The waveform consistency suggests repetitive and nondestructive sources beneath the volcano.

CO2 Flushing Triggers Paroxysmal Eruptions at Open Conduit Basaltic Volcanoes

AbstractOpen conduit volcanoes erupt with the highest frequency on Earth. Their activity is characterized by an outgassing flux that largely exceeds the gas that could be released by the erupted magma; and by frequent small explosions intercalated by larger events that pose a significant risk to locals, tourists, and scientists. Thus, identifying the signs of an impending larger explosion is of utmost importance for the mitigation of volcanic hazard. Larger explosive events have been associated with the sudden ascent of volatile rich magmas, however, where and why magma accumulates within the plumbing system remains unclear. Here we show that the interaction between CO2‐rich fluids and magma spontaneously leads to the accumulation of volatile‐rich, low density and gravitationally unstable magma at depth, without the requirement of permeability barriers. CO2‐flushing forces the exsolution of water and the increase of magma viscosity, which proceeds from the bottom of the magma column upward. This rheological configuration unavoidably leads to the progressive thickening of a gas‐rich and low density (i.e., gravitationally unstable) layer at the bottom of the feeding system. Our calculations account for observations, gas monitoring and petrological data; moreover, they provide a basis to trace the approach to deeply triggered large or paroxysmal eruptions and estimate their size from monitoring data. Our model is finally applied to Stromboli volcano, an emblematic example of open conduit volcano, but can be applied to any other open conduit volcano globally and offers a framework to anticipate the occurrence of unexpectedly large eruptions.

Classification of Small Sample Nuclear Explosion Seismic Events based on MSSA–XGBoost

Classification of Small Sample Nuclear Explosion Seismic Events based on MSSA–XGBoost

IoT-controlled explosion

This paper delves into the study and implementation of IoT-controlled explosions, exploring their relevance in various industrial sectors such as quarrying, mining, and building demolition. Additionally, the paper examines the application of controlled explosions in domestic settings, such as the ignition of firecrackers and the use of small explosions to deter animals from farmlands and fields. The term "controlled explosion" in this context refers to the ability to manage detonations remotely, mitigating the risks associated with potential injuries or fatalities.

The Interwar Period International Trade in Arms: A New Dataset

International weapons transfers send military capabilities, make arms production economically feasible, and construct security relations. They influence buyers’ and sellers’ foreign policies, domestic politics, and military spending behavior. However, data availability has limited their study to the bipolar Cold War and unipolar post-Cold War periods. We thus introduce the Interwar Period International Trade in Arms (IPITA) data, covering dyadic transfers of small arms, light weapons, ammunition, explosives, and major conventional weapons in the years 1920–1939. The IPITA data will offer new avenues to study the drivers, dynamics, and consequences of arms transfers, both in past and future multipolar systems.

Low-Frequency Blast Detection Using a Large-N Dark Fiber in Noisy Environments: Template Matching and Optimal Channel Selection

Abstract Distributed acoustic sensing (DAS), deployed on dark telecom fiber, is well-positioned to play a significant role in seismic monitoring networks because of the combination of a large aperture, fine spatial resolution, broadband sensitivity, and the ubiquitous presence of unused telecommunication fibers in many areas of the world. In this study, we explore the feasibility of dark-fiber array deployed in a noisy environment for detecting small explosions. We test the effectiveness of template matching for the detection of low-frequency blasts generated by mining activities in the Imperial Valley, California. We first evaluate dark-fiber detection performance by analyzing the relationship between detection threshold (DT) and the number of DAS channels used. We find that although, as expected, increasing the number of channels yields higher detection significance and lowers DT, the gain in performance is far from linear, with local anomalies across the DAS cable associated with zones of higher noise. We focus on investigating the types of noise affecting template matching and practical approaches mitigating anthropogenic noise that lower detection performance. Using median absolute deviation, we identify two types of noise sources affecting detection performance. Next, we design a voting scheme that selects DAS channels contributing to lowering of the DT and ensures improvement in detection when adding sequential channels. Finally, we compare dark-fiber detection performance with nearby conventional seismometers and find that a single station can outperform up to ∼10 DAS channels. However, using the full aperture of our dark-fiber transect allows to obtain ∼10% lower DT and yields fewer false-positive detections than an array of four seismometers. Methodological solutions for noise assessment and channel selection allow us to fully benefit from the large aperture and dense sampling offered by dark fiber. The findings of this study are a step toward incorporating existing telecom fibers into novel explosion-monitoring workflows.

Impact load measurement of small multi-bubble explosions near solid wall

The interaction of multiple spark-generated bubbles near solid boundary is investigated experimentally. Qualitative study is done with high-speed imaging for bubble shape evolution and PVDF sensor for impact force measurement. Similar-sized bubbles are created synchronously and distance between bubbles or boundary is chosen to be as small as possible. The jet direction of two horizontally aligned bubbles is strongly influenced by proximity parameter (γ) near boundary. The role of inter bubble distance (η) between bubbles and its contribution to intensity of impulsive force is also presented. It is found that strongest impact is recorded for horizontal pair, compared to vertical pair and diagonal pair, for small η values. Three bubbles are arranged with middle one which is smaller, similar or bigger than left and right bubbles. Allocating bigger bubble in the center indeed produces the most destructive impact on boundary among all cases. Moreover, diverse bubble deformation features are witnessed for various combination of dimensionless parameter applied in this study.

Characteristics and variation laws of electromagnetic radiation generated during explosion

AbstractThe characteristics and laws of explosive electromagnetic radiation must be clarified to investigate its interference with electronic equipment. Currently, studies pertaining to explosive electromagnetic radiation are performed via small equivalent explosive explosion tests, and conclusions regarding the regularity of electromagnetic radiation from warhead explosions are not confirmed. This study analyzes the power laws of explosion electromagnetic radiation via numerical simulations, literature comparisons, experimental testing, and other methods. The results show that the duration of the explosion electromagnetic radiation is proportional to the 1/3 power of the equivalent. The delay time is between 44 and 53 μs and is inversely proportional to the detonation velocity. The peak time is positively correlated with the 1/2 power of the equivalent. The electric field intensity of an explosive explosion is directly proportional to the 1/3 power of the equivalent, whereas the electric field intensity of a warhead explosion is positively correlated but not linearly related with the equivalent power. The spectral distribution of the electromagnetic radiation caused by different types of explosives differ significantly. The electromagnetic radiation measurement results for explosive explosions can be predicted via numerical simulation. However, the simulation results do not match the measurement data of warhead explosions, thus highlighting the necessity of warhead explosion electromagnetic measurements.

Experimental research and finite element analysis on blast resistance of RRACFST columns

In order to research the dynamic response of rectangular recycled aggregate concrete-filled steel tubular (RRACFST) columns under blast loads, three contact blast experiments were carried out on three column models, and their different failure modes, dynamic strain rates and acceleration rates were determined. The numerical model was established using the arbitrary Lagrangian-Eulerian method and the fluid–solid coupling algorithm available in the explicit nonlinear finite element software LS-DYNA™, and the reliability and validity of the numerical model were verified by the experimental results. On this basis, the numerical model was used to analyze the parameters, as well as the effects of the replacement rate of recycled aggregate, column height, steel tube thickness and steel strength on the contact explosion resistance of RRACFST columns. Also, the advantages and disadvantages of overall refinement and local refinement are compared. The study results show that the RRACFST columns had basically no overall response to the action of contact blast loads, producing only a small explosion crater in the detonation area, without breaking the steel tube, and with no recycled aggregate concrete (RAC) overflows. The steel tube thickness was the decisive factor affecting the blast resistance performance of the RRACFST columns. In addition, for the numerical simulation of contact explosion, the local refinement was better than the overall refinement.

Effect of square-hole obstacle in a long pipe on methane/air premixed explosion characteristics

ABSTRACT This paper primarily studies the impact of the obstacle blocking ratios (BR) on the explosion characteristics of CH4 and Air premixed gases in cuboid pipes, a small plexiglass CH4 explosion pipe test platform of 50 mm × 50 mm × 600 mm was built independently. In this study, square-hole obstacles with different blocking ratios pressure peak set in a horizontal cuboid pipe to analyze the evolution of the explosion pressure, the shape and speed of the flame of propagation of the pre-mixed CH4/air in the pipeline. According to the results, the obstacle has a negligible impact on the initial and secondary pressure peaks, P1 and P2, However, it has a substantial impact on the P3, and the P3 only exists when there is an obstacle. As the BR increases, the time taken for the third pressure peak P3 to appear becomes shorter, the greater the pressure value. When BR = 0.75, the highest P3 recorded was 12.5 kPa and 30 kPa for methane equivalent ratios of 0.8 and 1, respectively. Compared with the non-obstacle, the square-hole obstacle in the pipe has a significant influence on the evolution of the flame shape. When there is an obstacle, after the hemispherical flame, the center position of the flame front is deformed and convex, and then the bundle flame is formed, and there is no tulip flame. Simultaneously, the presence of an obstruction results in a rise in the mean flame propagation velocity, the flame is the first to reach the location of the obstacle, when BR = 0.5. As the flame moves through the obstacle, its propagation velocity escalates with the blockage ratio’s progression.

The post-2016 long-lasting Vulcanian activity of Sabancaya volcano (Peru) and associated aeolian remobilisation of volcanic ash

The characterisation of tephra deposits resulting from almost simultaneous sedimentation and wind remobilisation is complex, and multidisciplinary strategies are required in order to accurately constrain associated processes and eruptive parameters. We present a multifaceted study that aims to characterise the recent eruptive activity and the subsequent aeolian remobilisation of tephra deposits at Sabancaya volcano (Peru), which started erupting in November 2016 with frequent and relatively small explosions (plume heights <6 km above the vent). First, we estimated the bulk volume of tephra deposit produced between November 2016 and August 2018 at 0.04 ± 0.02 km3, and the dense rock equivalent (DRE) volume at 0.02 ± 0.01 km3. This corresponds to a tephra production rate of 1.1 ± 0.5 × 10−3 km3 DRE per month. Second, continuous sampling in a dedicated tephra collector network between April 2018 and November 2019 allowed estimation of the tephra volume at 2.3 ± 1.1 × 10−5 km3 DRE per month, indicating a significant decrease in the mass eruption rate since 2018. Third, by characterising the pulsatory activity through the repose interval between explosions and magma characteristics, Sabancaya's activity was classified as Vulcanian. Finally, aeolian remobilisation phenomena were studied using high-resolution videos, measurements of the airborne concentration of particulate matter with a diameter of ≤10 μm (PM10) and particle physical characterisation. Subtle morphological differences are identified between remobilised particles and those in primary deposits, and we found that particles moving at ground level and above 1.5 m have grainsizes transportable by saltation and suspension, respectively.

Self-Acceleration and global pulsation of unstable laminar Hydrogen-Air flames

The self-acceleration and global pulsation of spherically expanding laminar hydrogen-air flames were studied in a spherical explosion vessel, over a wide range of equivalence ratios (0.4–2.0), initial temperatures (300–400 K), and initial pressures (0.1–0.7 MPa). Comprehensive quantitative data on the self-acceleration propagation of unstable laminar hydrogen-air flames were obtained. The results show that the self-similarity appears after the onset of instability, and the previous assertion of acceleration exponent α = 1.5 is not valid for hydrogen-air flames. The derived values of α for such flames vary from 1.125 and 1.39 in the present work. For the self-accelerating flame, the temporal evolution of the flame radius is described by ru=Atα, and temporal flame propagation speed is described by Sn=Aαtα-1. A modified theoretical expression of the constant A is proposed and validated against the present experimentally derived results. The acceleration phase after flame instability presents a global pulsating acceleration pattern. The frequency of global pulsation rises as the pressure or temperature of the flame increases. A pulsing flame speed equation can be used to reliably estimate flame speed after the onset of cellular instability. Self-acceleration observed in small laboratory explosions can serve as a predictive indicator for flame behaviour on a larger atmospheric scale.

A refined numerical investigation of a large equivalent shallow-depth underwater explosion

The large equivalent shallow-depth explosion problem is very significant in the field of naval architecture and ocean engineering, as such explosions can be used to attack and demolish ships and anti-ship missiles. In the current work, a refined numerical study of the flow-field characteristics of a large equivalent shallow-depth explosion is carried out using a self-developed Eulerian finite element solver. First, the numerical model is validated against theoretical results and a small equivalent explosion test in a tank. The numerical results are found to agree well with the theoretical and experimental results. In the next step, the cavitation cut-off effect is added to the underwater explosion model, and the cavitation phenomenon is quantitatively analyzed through the flow-field pressure. In addition, the dynamic characteristics of the bubble and water hump under various initial conditions for different stand-off parameters are analyzed. The effect of gravity on these physical processes is also discussed. The bubble pulsation period, taking into account the free surface effect, is then quantitatively studied and compared with Cole’s experimental formula for an underwater explosion. Overall, when the stand-off parameter γ &amp;gt; 2, the influence of the free surface on the empirical period of the bubble is not significant. Our investigation provides broad insights into shallow-depth underwater explosions from theoretical, experimental, and numerical perspectives.

Small black hole explosions

Small black holes are a powerful tool to explore infinite distances in moduli spaces. However, we show that in 4d theories with a scalar potential growing fast enough at infinity, it is energetically too costly for scalars to diverge at the core, and the small black hole puffs up into a regular black hole, or follows a runaway behaviour.We derive a critical exponent characterizing the occurrence or not of such small black hole explosions, both from a 4d perspective, and in the 2d theory after an S2 truncation. The latter setup allows a unified discussion of fluxes, domain walls and black holes, solving an apparent puzzle in the expression of their potentials in the 4d mathcal{N} = 2 gauged supergravity context.We discuss the realization of these ideas in 4d mathcal{N} = 2 gauged supergravities. Along the way we show that many regular black hole supergravity solutions in the literature in the latter context are incomplete, due to Freed-Witten anomalies (or duals thereof), and require the emission of strings by the black hole.From the 2d perspective, small black hole solutions correspond to dynamical cobordisms, with the core describing an end of the world brane. Small black hole explosions represent obstructions to completing the dynamical cobordism. We study the implications for the Cobordism Distance Conjecture, which states that in any theory there should exist dynamical cobordisms accessing all possible infinite distance limits in scalar field space. The realization of this principle using small black holes leads to non-trivial constraints on the 4d scalar potential of any consistent theory; in the 4d mathcal{N} = 2 context, they allow to recover from a purely bottom-up perspective, several non-trivial properties of vector moduli spaces near infinity familiar from CY3 compactifications.

Research on the Attenuation of Blast Wave by Groups of Filled Cracks in Surrounding Rock of Cavern

This study introduces an approach for constructing groups of filled cracks in the surrounding rock to achieve anti-blasting and wave elimination protection for underground caverns. To verify the attenuation effect of the explosion wave by the filled cracks, two models, a no-crack model, and a filled-crack model, were constructed using a certain proportion of analogue materials based on the similarity theory. With the implementation of small equivalent explosion conditions, the peak pressure of the surrounding rock of the cavern and the vibration acceleration of the cavern wall under different explosion conditions were measured. To accurately judge the attenuation efficiency of the filled cracks, the peak pressure attenuation percentages between different measuring points were calculated. Furthermore, the corresponding numerical simulation analysis process was performed according to the test conditions. The results show that not only the peak pressure attenuation percentages, but also the value of vibration acceleration, were significantly reduced due to the existence of filled cracks in the model. This indicates that filled cracks in the surrounding rock of the cavern can effectively attenuate the peak pressure and vibration acceleration caused by the explosion wave, thereby achieving the protection engineering goal of anti-explosion and wave elimination.

Remote Sensing Small Explosives With an Ionospheric Radar

AbstractEarth's ionosphere has long been targeted as a medium for remote sensing of explosive terrestrial events such as earthquakes, volcanic eruptions, and nuclear/conventional weapon detonations. Until now, the only confirmed ionospheric detections have been of very large events that were easily detectable through other traditional global sensor systems (e.g., seismic). We present the first clear, confirmed detections of relatively low yield 1‐ton TNT‐equivalent chemical explosions using pulsed Doppler radar observations of isodensity layers in the ionospheric E region. The shape and spectra of the detected waveforms closely match predictions from the acoustic ray tracing and weakly nonlinear waveform propagation models. The explosions were roughly three orders of magnitude lower yield than any previous confirmed ionospheric detection and represent the first conclusive evidence that explosions of this size can have clear impacts on the ionosphere. This technique could improve the remote detection of both anthropogenic and natural explosive events.