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The electron-impact ionization of water molecules at low impact energies is investigated using a theoretical approach named M3CWZ. In this model, which considers exchange effects and post-collision interaction, the continuum electrons (incident, scattered, and ejected) are all described by a Coulomb wave that corresponds to distance-dependent charges generated from the molecular target properties. Triple differential cross-sections for low impact energy ionization of either the 1b1 or 3a1 orbitals are calculated for several geometrical and kinematical configurations, all in the dipole regime. The M3CWZ model is thoroughly tested with an extensive comparison with available theoretical results and COLTRIMS measurements performed at projectile energies of Ei = 81 eV [Ren et al., Phys. Rev. A 95, 022701 (2017)] and Ei = 65 eV [Zhou et al., Phys. Rev. A 104, 012817 (2021)]. Similar to other theoretical models, an overall good agreement with both sets of measured data is observed for the angular distributions. Our calculated cross-sections' magnitudes are also satisfactory when compared to the other theoretical results, as well as to the cross-normalized relative scale data at 81 eV impact energy. The 65 eV set of data, measured on an absolute scale, offers a further challenging task for theoretical descriptions, and globally the M3CWZ performs fairly well and comparably to other theories. The proposed approach with variable charges somehow allows to capture the main multicenter distortion effects while avoiding high computational costs. [ABSTRACT FROM AUTHOR]

North Korea continues to modernize and grow its nuclear weapons arsenal. In this Nuclear Notebook, the authors cautiously estimate that North Korea may have produced enough fissile material to hypothetically build up to 90 nuclear warheads, but has likely assembled fewer than that—potentially around 50. To deliver the warheads, North Korea is enhancing and diversifying its missile force, most recently with new solid-fuel long-range strategic missiles, short-range tactical missiles, and sea-based missiles. The Nuclear Notebook is researched and written by the staff of the Federation of American Scientists' Nuclear Information Project: director Hans M. Kristensen, associate director Matt Korda, research associate Eliana Johns, and program associate Mackenzie Knight. To see all previous Nuclear Notebook columns in the Bulletin of the Atomic Scientists dating back to 1987, go to [ABSTRACT FROM AUTHOR]

Existing analytical models for energy dissipation in ceramic-aluminum composites focus on blunt and ogive-shaped projectiles, leaving a gap in the analysis of spherical projectiles. This research addresses that gap by developing an analytical model to assess energy dissipation in ceramic and ceramic-aluminum composites impacted by spherical projectiles. The model employs the fracture energy method to analyze energy dissipation, accounting for radial, circumferential, and cone cracks, as well as crushing energy. It includes equations for the impact energy dissipated by the ceramic plate, the front and back plates of the ceramic plate, and the projectile. Validation is achieved through ballistics tests on Al-T3, B 4 C, and Al 2 O 3 monolithic plates and their composites against spherical projectiles traveling up to 740 m/s. The spherical projectiles used are made of SS-304 and Al-T3. The model's equations, which account for cone, crushing, radial, and circumferential crack mechanisms, predict the residual velocity and ballistic limits of the targets. Maximum energy dissipation occurs due to projectile erosion and deformation, impacted with B 4 C and B 4 C-Al-T3 composites showing the highest erosion and deformation compared to other targets. B 4 C targets exhibit more extensive cracking than Al 2 O 3 ceramic plates. However, the ballistic performance of Al 2 O 3 is superior to that of B 4 C ceramic plates against SS-304 and Al-T3 projectiles due to higher crushing energy. Similarly, Composite Type CT-D outperforms Composite Type CT-C in terms of ballistic performance. [ABSTRACT FROM AUTHOR]

How many dollars would the United States need to spend on its ballistic missile defense (BMD) for each dollar the attacker spends to launch land-based intercontinental ballistic missiles (ICBMs) armed with nuclear warheads? A hypothetical scenario is analyzed in which the United States has a functioning BMD technology and enough interceptors to distribute them in a two-layer defense with the overall system efficiency of 90%, as targeted by U.S. war planners. It is assumed that the attacker has enough missiles to deliver a range between 500 and 6000 warheads to the continental United States. Results show that in the most optimistic case for the defender, with a very high individual interceptor kill effectiveness of 90% and with perfect decoy discrimination capability, the United States would need to spend on average 8 times more than the attacker, for a total cost between $60 billion and $500 billion. With a more realistic individual interceptor effectiveness of 50% and if the system is unable to discriminate against decoys, the United States would need to spend on average 70 times more, for a total cost between $430 billion and $5.3 trillion. [ABSTRACT FROM AUTHOR]

The three-electron atomic-orbital close-coupling method is applied to H–He collision. The cross sections are calculated for projectile excitations to H(2 s) and H(2p), ionizations of projectile H, single ionization of target He, and electron capture for incident energy of 0.5–30 keV. Some basis sets are adopted to see the convergence behavior of the cross section for each process. The electron-exchange effect is essential to obtain reasonable results. Although the results have not yet reached convergence, the agreement with the experimental data is as good as previous calculations or better. [ABSTRACT FROM AUTHOR]

Shock Wave Boundary Layer Interactions represent a complex flow feature combining high-speed inertial force - dominated flows with low-speed viscous force dominated regions. In this research, planar oblique shock impingement on finned missile body (slender body) have been studied, involving a complex flow field of shocks and expansion waves. Computational studies are used to perform quantitative and qualitative analysis of multi body configurations and investigate the associated flow physics. There is change in induced forces and moments of finned body with change in location of shock impingement, due to the combined effect of enhanced compression, expansion and flow pitch angle on different regions of the missile. For fixed lateral separation between the bodies, changes in coefficient of forces and moments of missile body are very small for shock impingement locations close to fin leading edge. The fins contribute about 50-60% to coefficient of forces and moments of finned missile body. With change in angle of incidence, there is change in polarity of forces and moments illustrating extreme sensitivity of missile body to location of shock impingement, which is due to the combined effect of enhanced compression and expansion on different regions of the missile. [ABSTRACT FROM AUTHOR]

While existing US strategic missile defence systems are not designed for and cannot defend against peer and near-peer adversary threats, both Russia and China appear concerned about eventual technical breakthroughs and US overconfidence. Both Russia and China are developing long-range nuclear delivery systems that are designed to counter ballistic missile defences to assure their nuclear retaliatory capabilities. Advances in sensors, materials, and machine learning will afford improvements to missile defence in future decades. How will the offense/defence competition play out? This paper examines these technical trends and concludes that while technical advances are likely to improve the performance and cost-effectiveness of ballistic missile defences, peer and near-peer adversaries will also improve their ability to avoid, overwhelm, or defeat such defences and they will not play a decisive role in limiting nuclear retaliation by a responsive adversary. [ABSTRACT FROM AUTHOR]

This paper applies KOCOA terrain analysis to the study of the Iron Age hillfort of Burnswark Hill (SW Scotland) and its associated Roman military remains. The Roman camps and projectiles identified at Burnswark have sparked a long scholarly debate, with views ranging from authors that interpret the evidence as related to Roman military training at an already abandoned hillfort, and others who consider it representative of a brutal Roman military attack on an indigenous stronghold. This article presents the recently undertaken KOCOA analysis of the site, which assesses how the terrain influenced the conduct of the Roman intervention at Burnswark. The results are used in conjunction with the insights provided by the metal detector surveys and excavations from the last decade. The combined evidence strongly suggests that the events at Burnswark can best be described as a Roman oppugnatio longinqua obsidio, an active siege that ended in a storming assault. [ABSTRACT FROM AUTHOR]

The US has been constructing a security network in the Indo-Pacific, composed of US-led alliances and security partnerships. This network is less hierarchical than the hub-and-spoke alliance structure that the US maintained during the Cold War. The article suggests that, akin to the ‘connectivity strategy’ introduced in this special issue, the US, which once dominated a hierarchical hub-and-spoke system with unquestioned centrality, is now striving to enhance its centrality within the US-led security network. To achieve this, the US has been working to improve its ‘closeness’, ‘betweenness’, and ‘eigenvalue’ centrality, in addition to degree centrality. Furthermore, the article posits that the US adopts ‘the strategy of association,’ as introduced in this special issue. The US has been at the forefront of regional missile defense, maritime security, and dual-use technology development to foster like-mindedness and build trust among network members, viewing China (and North Korea) as the ‘other’. Lastly, the article conceptualises ‘security mutuality’ by building upon the concept of ‘alliance mutuality’ proposed by William Tow and Amitav Acharya. It asserts that fostering ‘security mutuality’ is essential for sustaining US coalitional hegemony. [ABSTRACT FROM AUTHOR]

Firearm violence is a pressing public health issue in the United States and becoming increasingly so worldwide. This concern has prompted researchers to examine the prevalence of such violence in media entertainment. Japanese manga have a large youth readership in the U.S., yet research on their depictions of firearms is presently lacking. We randomly selected 50 chapters from each of ten top-selling manga series worldwide (N = 500) to identify dialogue, action, and other illustrations involving handguns, rifles, machine guns, other projectile weapons, and bombs. Of the 500 chapters, 129 (25.8%) had at least one depiction of a firearm or other projectile weapon, with 684 instances of characters handling (e.g., carrying, holding, firing, reloading) such a weapon. Of the 384 unique characters so depicted, the vast majority were males (88.3%), adults (92.2%), and "good" characters (73.4%). Manga readers, especially male adolescents and preteens, are frequently exposed to storylines in which one or more characters are using a firearm or other projectile weapon. Working collaboratively, manga publishers and distributors should act to develop and implement a comprehensive rating system to flag content that may be harmful to youth so that parents can more easily monitor what their children are reading. [ABSTRACT FROM AUTHOR]

Considering an unpowered missile diving to intercept a maneuvering target, a novel fixed‐time guidance and attitude control algorithm is proposed. First, the second‐order derivatives of the aerodynamic angles are directly linked to the fin deflections, which can avoid the tracking of missile body angle rate instruction in the traditional methods. Second, a novel fixed‐time time‐varying parameter nonsingular terminal sliding mode guidance law is proposed, which can avoid control input singularity without switching to the polynomial form when the error approaches the origin. Third, a new global time‐varying sliding mode with a predefined convergence time and analytical solution is developed to design the attitude controller. The system states are proved to be fixed‐time convergence based on the Lyapunov stability theory. Six‐degree‐of‐freedom simulations are conducted to validate the superiority of the proposed algorithm in terms of miss distance, impact angle error, interception time and control energy. [ABSTRACT FROM AUTHOR]

This paper presents an intelligent proportional-derivative adaptive global nonsingular fast-terminal sliding-mode control (IPDAGNFTSMC) for tracking temperature trajectories of a hypersonic missile in thermal structural tests. Firstly, the numerical analyses on a hypersonic missile's aerodynamic heating are based on three different external flow fields via the finite element calculation, which provides the data basis for the thermal structural test of hypersonic vehicles; secondly, due to temperature trajectory differences of a hypersonic missile and the thermal inertia and nonlinear characteristics of quartz lamps in thermal structural test, IPDAGNFTSMC is proposed, consisting of three components: (i) the mathematical model of the thermal structural test is established and further replaced via an intelligent proportional-derivative with a nonlinear extended state observer (NESO) for online unknown disturbances observation; (ii) compared with the traditional sliding-mode control method, the AGNFTSMC method eliminates the reaching phase and the initial control state is trapped on the sliding-mode surface. Therefore, it can alleviate chattering phenomenon, accelerate the convergence rate of the sliding mode, and ensure that there is no singular problem in the entire control process; (iii) the adaptive law is designed to effectively solve problems of convergence stagnation and chattering phenomenon. The Lyapunov stability theory is used to prove the stability of the proposed IPDAGNFTSMC-NESO. Finally, the advantages of the designed control method are verified by experimental simulation and comparison. [ABSTRACT FROM AUTHOR]

Copyright of Chinese Journal of High Pressure Physics is the property of Chinese Journal of High Pressure Physics Editorial Office and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

This research explores the ability of 60 mm thick reinforced concrete (RC) plates to resist impacts from ogive-nosed hard steel projectiles. The projectiles used in the present study have a diameter of 19 mm, a length of 200 mm, and a mass of 0.4 kg impacted on the RC plates with incident velocities ranging from 92 m/s to 161 m/s. Numerical simulations were conducted using ABAQUS/Explicit finite element software to validate the experimental results. The Holmquist–Johnson–Cook (HJC) material model was employed to simulate the constitutive behavior of concrete, while the Johnson–Cook (JC) material model was used to simulate the material response of reinforcing steel bars. The residual velocities obtained from the simulations closely matched the actual experimental results, showing a polynomial correlation with the incidence velocities of the projectiles. Moreover, the experimentally and numerically determined ballistic limit for the 60 mm thick RC plate was found to be 108 m/s and 109.5 m/s, respectively. In contrast, the ballistic limit calculated using empirical mathematical expressions was 107.4 m/s. This alignment between predicted, calculated, and actual ballistic limits underscores the reliability and accuracy of both numerical and empirical approaches. [ABSTRACT FROM AUTHOR]

Numerical investigations are conducted to examine the penetration depth of ellipsoid-shaped projectiles into semi-infinite aluminum targets under conditions of hypervelocity impact. These results are then compared against empirical equations developed by various researchers for spherical projectiles. The semi-infinite aluminum target, sized at 1 5 0 × 1 5 0 × 5 0 mm, is composed of Al7075-T651. The projectiles are fashioned from Al-7075-T651, steel, and boron carbide. The projectile's shape factor was determined using the L/d ratio, specifically for the symmetrical ellipsoidal shape. Employing Ansys Autodyn, a 3-dimensional finite element model (FEM) is created and calibrated using existing experimental findings from the literature. The validation utilized the Johnson–Cook (JC) and Johnson–Holmquist (JH-2) material models for both the targets and projectiles. These validated models are subsequently employed to analyze how the ellipsoid projectile's shape and density influenced their interaction with the semi-infinite targets. Furthermore, the investigation also encompassed an analysis of the resulting crater shapes generated by the hypervelocity impact of both metallic and nonmetallic projectiles. It is observed that for a definite SF, max m depth of penetration is observed due to steel project as compared to boron carbide and aluminum projectile. Both the diameter of the crater and the height of the bulge ( H c) are directly proportional to the impact velocity and density of projectiles, and inversely proportional to SF. However, for a particular material and impact velocity of the projectile, in the case of H c , there are no clear-cut observations displayed it seems like a mixed variation. [ABSTRACT FROM AUTHOR]

This article motivates the special issue, explaining the new debate over whether emerging technologies – including small satellites, machine learning, cyber weapons, and quantum technologies – will enable major powers to undermine each others’ nuclear retaliatory capabilities. The first article analyzes key relevant emerging technologies. Following articles explore how emerging technologies will influence the vulnerability of mobile missiles, ballistic missile submarines, and nuclear command-and-control; and the ability of missile defenses against intercontinental range missiles. The final article explores China’s views on the requirements of nuclear deterrence. Overall, the articles suggest that U.S. prospects for achieving a damage-limitation capability are poor and declining. [ABSTRACT FROM AUTHOR]

Technological spillover – the transfer and use of knowledge between defence and civilian sectors – is desired by many countries, and particularly salient under intensifying US-China competition. Yet to date, no systematic measure of spillover exists. This paper presents a novel measure of spillover using a dataset of over 116,000 defence-related patents, and argues that (1) concerns over China’s ‘authoritarian advantage’ should be moderated, and (2) the composition and structure of knowledge transfer networks in the US and China should inform the appropriate channels of managing competition, which I demonstrate through case studies of aerial drones and missile technology spillover networks. [ABSTRACT FROM AUTHOR]

Nuclear-armed states have sought to secure their nuclear arsenals from preemptive attack by deploying mobile ground-launched missiles. However, recent developments in remote-sensing technologies have spurred a debate about the survivability of ground-mobile missiles. Current scholarship implicitly assumes that mobile missiles will be operated sub-optimally, underestimating the difficulty of tracking mobile missiles and hence their survivability. In this paper, I analyze how a set of remote sensing technologies, including space-based radar, could track mobile missiles. I find that, today, ground-mobile missiles could defeat tracking through evasive operation and that technological countermeasures could allow them to remain survivable into the near future. [ABSTRACT FROM AUTHOR]

Advanced facilities like GSI-FAIR in Germany or RIKEN in Japan are dedicated to the research of nuclei far from the stability line. In this paper, we study the fragmentation of relativistic projectiles as a production method for these nuclei, with particular emphasis on the role of secondary reactions. [ABSTRACT FROM AUTHOR]

Introduction/purpose: Rockets with high-explosive (HE) warheads are the most numerous type used for multiple launch rocket systems (MLRS). They are used for a wide range of combat tasks. Besides other design characteristics, the effect on the target depends on the position where detonation is initiated in their explosive charge. The study analyses the fragmentation effects of steel balls from the 128 mm M77 HE warhead with the standard point-detonating (PD) fuze and with a differently positioned detonating assembly. Methods: The study uses a simple numerical model for the assessment of the fragmentation effect, which requires modest resources. A numerical model of the fragmentation effect was used with Gurney’s model of explosive propulsion and Taylor’s and Shapiro’s method for the direction of the fragment velocity vector. The penetration ability of projected steel balls through hard homogenous steel was analysed using the Project Thor analytical model of kinetic energy projectile penetration. Introduction/purpose: Rockets with high-explosive (HE) warheads are the most numerous type used for multiple launch rocket systems (MLRS). They are used for a wide range of combat tasks. Besides other design characteristics, the effect on the target depends on the position where detonation is initiated in their explosive charge. The study analyses the fragmentation effects of steel balls from the 128 mm M77 HE warhead with the standard point-detonating (PD) fuze and with a differently positioned detonating assembly. Methods: The study uses a simple numerical model for the assessment of the fragmentation effect, which requires modest resources. A numerical model of the fragmentation effect was used with Gurney’s model of explosive propulsion and Taylor’s and Shapiro’s method for the direction of the fragment velocity vector. The penetration ability of projected steel balls through hard homogenous steel was analysed using the Project Thor analytical model of kinetic energy projectile penetration. [ABSTRACT FROM AUTHOR]

A cavitation flow can greatly impact a vehicle's attitude and stability when exiting water. This paper adopts an improved delayed detached eddy turbulence model and a Schnerr–Sauer cavitation model as well as the volume-of-fluid method and an overlapping grid technique to investigate this effect. In addition, the experimental system of the underwater launch is designed and built independently, which the numerical results are in good agreement with the experimental results. The transient cavitation flow structure and motion characteristics of the projectiles successively launched underwater are studied. When the axial spacing ranges from 0 to 1.0 times the diameter of the projectile, both projectiles are severely affected to various extents in cavitation pattern, vortex structure, and motion characteristics. It is worth noting that the internal cavity of the secondary projectile is disturbed by the wake of the primary projectile, resulting in large-scale fractures and detachment of the internal cavity, but its motion stability is good. [ABSTRACT FROM AUTHOR]

Three-dimensional density measurement around a Hayabusa re-entry capsule model using the background-oriented schlieren (BOS) technique is carried out in the ballistic range at the Institute of Fluid Science, Tohoku University. A Hayabusa re-entry capsule model with a diameter of 15 mm is used for a projectile, and the Mach number was 1.20. A method of model Position and Pose detection from BOS images was proposed for a capsule model, and unsteady flow field measurement around a free-flight test model was conducted. From the results, we succeeded in measuring the three-dimensional density distribution around a capsule model and visualizing the detailed structure in the wake region. [ABSTRACT FROM AUTHOR]

This study investigates the high-impact behaviour of auxetic materials, recognised for their negative Poisson’s ratio and exceptional energy absorption, when combined with shape memory alloys to enhance impact resistance. Using finite element analysis in Abaqus, 42 unique auxetic models were developed with variations in angles, thicknesses, heights, and lengths to examine structural response under high-velocity impacts. The findings reveal that modifications to the height-to-length ratio, thickness-to-length ratio, and cell design angle significantly affect residual projectile velocity – reducing it by up to 17%, fully eliminating it in some cases, or increasing it by 34% depending on the configuration. These adjustments also influence energy absorption rates and specific energy absorption during collision events. Poisson’s ratios, derived through both analytical and numerical methods, showed strong agreement, validating the accuracy of the models. Overall, the study ident ifies optimal design configurations that maximise energy absorption and minimise projectile velocity upon impact. These findings have practical implications for industries requiring durable materials in high-impact applications, and the integration of auxetic structures with shape memory alloys suggests promising directions for innovative material design. [ABSTRACT FROM AUTHOR]

Due to a short flight time, the dual-axis rotational inertial navigation system carried by some launch vehicles or missiles is often only used for self-calibration and self-alignment. It is generally in the strap-down state rather than the rotation modulation state during flight. This wastes the precision potential of the navigation system. Therefore, a mode-switching strategy is proposed in this paper to improve the orbit injection accuracy of a launch vehicle. The rotational navigation system of the launch vehicle is in the near-platform mode or strap-down mode at different periods. It is switched in a timely manner to take advantage of the various modes. Numerical simulation and turntable experiment results show that compared with the traditional strap-down inertial mode, the mode-switching strategy can effectively improve the orbit accuracy of the launch vehicle by about 12% to 13% and hardly increases any costs. [ABSTRACT FROM AUTHOR]

This work aims to investigate the effect of a wide range of oblique impacts of the 7.62-mm-caliber projectile on the slim high-performance fiber-reinforced concrete (HPFRC) panels. The trajectory of the projectile, the depth of penetration, and the extent and type of plate damage are discussed in detail. The numerical models developed in commercially available software are also included in this work to support and supplement the experimental data. In the model, each fiber is modeled separately, leading to a more realistic prediction of the material behavior. The analyses identified four basic scenarios for projectile impact: total plate perforation by the projectile core, core penetration combined with or without rear HPFRC material detachment, and ricochet. The results show that the numerical model can effectively and accurately predict the impact response and damage morphologies of the slim HPFRC panel. [ABSTRACT FROM AUTHOR]

For early-stage non-small cell lung cancer, surgery is the preferred approach in operable patients, whereas SABR is preferred for patients who are medically inoperable. The combination of neoadjuvant SABR followed by surgery was tested in the Measuring the Integration of Stereotactic Ablative Radiotherapy Plus Surgery for Early-Stage Non-Small Cell Lung Cancer (MISSILE) phase 2 trial. We report long-term outcomes beyond 5 years of follow-up. Patients diagnosed with T1-2N0M0 non-small cell lung cancer with good performance status and adequate lung function were enrolled. Patients underwent neoadjuvant SABR followed by lobectomy/wedge resection. Forty enrolled patients received SABR, of which 36 patients proceeded to surgery. The pathologic and major complete response rates were 60% and 63%, respectively. Median follow-up was 6.6 years following surgery. Five-year overall, disease-free, and cancer-specific survival were 66.7% (95% CI, 48.8%-79.5%), 58.3% (95% CI, 40.7%-72.4%), and 76.4% (95% CI, 58.2%-87.4%), respectively. Five-year local, regional, and distant control were 93.5% (95% CI, 76.3%-98.4%), 80.1% (95% CI, 62.7%-90.0%), and 82.4% (95% CI, 64.9%-91.7%), respectively. After SABR and surgery, 16.7% (n = 6) of patients experienced related grade ≥3 adverse events, and there were no grade 5 events. The combined approach of SABR and surgery was safe and demonstrated reasonable long-term clinical outcomes, but similar to surgery alone. [ABSTRACT FROM AUTHOR]

Copyright of Journal of Dalian University of Technology / Dalian Ligong Daxue Xuebao is the property of Journal of Dalian University of Technology and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

This paper investigates three-dimensional pursuit problems in noncooperative stochastic differential games. By introducing a novel polynomial value function capable of addressing high-dimensional dynamic systems, the forward–backward stochastic differential equations (FBSDEs) for optimal strategies are derived. The uniqueness of the value function under bounded control inputs is rigorously established as a theoretical foundation. The proposed methodology constructs optimal closed-loop feedback strategies for both pursuers and evaders, ensuring state convergence and solution uniqueness. Furthermore, the Lebesgue measure of the barrier surface is computed, enabling the design of strategies for scenarios involving multiple pursuers and evaders. To validate its applicability, the method is applied to missile interception games. Simulations confirm that the optimal strategies enable pursuers to consistently intercept evaders under stochastic dynamics, demonstrating the robustness and practical relevance of the approach in pursuit–evasion problems. [ABSTRACT FROM AUTHOR]

Copyright of Journal of Shanghai Jiao Tong University (1006-2467) is the property of Journal of Shanghai Jiao Tong University Editorial Office and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Personal protective systems widely use aramid textile fabrics, whether in soft or rigid form, to protect against various types of ballistic threats. Ballistic impact refers to a high-velocity impact caused by a thrusting source, often involving a low-mass object. To use these materials effectively in structural applications, it is crucial to have a thorough understanding of their ballistic behavior when subjected to high-velocity impact. Upon contact of the projectile with the ballistic material, complex ballistic penetration processes take place, which require a comprehensive and quantitative examination for a better understanding. This study aims to analyze the damage mechanism of aramid fabric by altering the projectile impact trajectory based on numerical simulations. We aim to obtain a thorough understanding of the behavior of the aramid fabric by performing numerical simulations and examining the penetration process in detail. The obtained results are analyzed based on the von Mises stress distribution (panel and projectile, projectile only, and main wires), projectile deformation, projectile velocity during ballistic impact, and based on photographs obtained during the impact. [ABSTRACT FROM AUTHOR]

Aramid fibers, due to their relatively high inter-yarn friction, high strength, high modulus, and other characteristics, have become a typical representative of flexible anti-ballistic materials in modern warfare. Current research on the anti-penetration of aramid fabrics mostly focuses unilaterally on the structure and performance of aramid fabrics or the shape and size of projectiles, with fewer studies on the coupled effect of both on ballistic performance. This study analyzes how the coupling relationship (or size effect) between the projectile and fiber bundle dimensions affects the fabric ballistic performance from a mesoscopic scale perspective. Taking plain weave aramid fabric as the research object, considering different diameter projectiles, through a large number of ballistic impact tests and numerical simulations, parameters such as ballistic limit velocity, average energy absorption of fabric, and specific energy absorption ratio (average energy absorption of fabric divided by projectile cross-sectional area) are obtained for ballistic performance analysis. The influence law of projectile size on the ballistic performance of high-performance fabrics is as follows: The relative range of fitted ballistic limit velocity at different target positions gradually decreases and then stabilizes as the projectile diameter increases, indicating that the fabric structure effect gradually disappears at a projectile diameter of 12 mm; The average ballistic limit velocity at three impact positions, P1, P2, and P3, provides the corresponding ballistic limit velocity for 1000D aramid fabric, which increases with projectile diameter but the rate of increase slows down at an inflection point, which in this study occurs where the fabric structure effect nearly disappears at a projectile diameter of 12 mm; The energy absorption ratio increases and then decreases as the projectile diameter increases from 4 mm to 20 mm, reaching a peak at the diameter of 12 mm due to the gradual disappearance of the fabric structural effect. The projectile diameter of 12 mm corresponds to the coupling size of 11.159, which provides a size design reference for the macroscopic-based continuum models of aramid plain weave fabrics. [ABSTRACT FROM AUTHOR]

This study investigates the effects of kinetic energy and projectile size on particle emission from a phenylalanine overlayer adsorbed on a graphene bilayer during argon projectile bombardment. Projectiles of various sizes (1–1000 atoms) and kinetic energies (0.5–40 keV) are used to study their impact on the ejection efficiency, mass distribution, and kinetic and angular spectra of the emitted substances. Particle ejection mechanisms are discussed in scenarios with and without sample perforation. Additionally, this study investigated the potential use of graphene in secondary ion mass spectrometry or neutral secondary mass spectrometry analyses. [ABSTRACT FROM AUTHOR]

The three body fragmentation of methane dication has been studied using the technique of cold target recoil ion momentum spectroscopy. The process is initiated by impact of energetic Ar9+ ions on neutral methane and the data is subsequently collected in coincidence with Ar8+ projectile. By analysing the dissociation channels leading to (H + H+ + CH 2 + ) and (H + H 2 + + CH+) fragments, it is concluded that these fragments are formed in a sequential manner via formation of molecular intermediates CH 3 + and CH 2 + respectively. It is shown that these molecular intermediates carry a few eVs as their internal energies, part of which is released when they emit an H-atom with the open possibility that the final detected fragments may still be internally excited. This was accomplished by analysing the two-steps of the sequential process in their own native frames. For a molecular system having three-dimensional structure, our results prove to be an ideal example to highlight the importance of using native frames for correct interpretation of the obtained results. Our results indicate that the dissociation of methane dication can be a major source of production of H-atoms in addition to H+ fragments with the probability of the two being of similar order. [ABSTRACT FROM AUTHOR]

To study different working conditions on the impact resistance of ZK61m magnesium alloy thin plate, includes radius of curvature of the projectile (Caliber-radius-head, CRH) and number of layers in the target plate. The impact resistance of magnesium alloy plate by the shape of the projectile head was analyzed through experiments and simulations, the ballistic limit (BLV) of the target plate and the failure mode of the target plate under different CRH projectile impacts were obtained. The experimental results show that the BLV of the target plate decreases with the increase of CRH value and the failure mode changes from shear punch plug failure to tensile cracking failure. The numerical simulation results show that the Lode parameter dependent MMC fracture criterion is closer to the experimental results; the MMC fracture criterion was selected to analyze the effects of CRH and the number of target plate layers on the impact resistance of magnesium alloy thin plates. It was found that the impact resistance of the target plate changes slowly and then increases rapidly with the increase of the CRH value; its impact resistance showed a linear decrease with the number of target plate layers increase. [ABSTRACT FROM AUTHOR]

Armor steel is widely used for ballistic resistance in military infrastructures and vehicles. However, the high areal density of monolithic steel plates presents challenges in balancing protection and maneuverability. This study focuses on a novel armor design, invented by the authors: An N-shaped perforated armor plate (NPAP). The NPAP consists of a perforated plate, an inclined plate, and a back plate. A validated finite element (FE) model was used to analyze the dynamic damage behavior of the NPAP target and projectile under ballistic impact. Numerical simulation revealed that the NPAP target combined the edge and obliquity effects, resulting in asymmetric interaction and causing yaw and fracture of the projectile. The kinetic energy of the steel core after penetrating the NPAP target decreased by 84.7–88.0% compared to the initial kinetic energy. The NPAP target showed a 20.7–43.9% lower residual depth of penetration (RDOP) compared to the monolithic target. Furthermore, the effects of the dip angle of the inclined plate and plate thickness configurations on the ballistic performance of NPAP were examined. The results indicated that the NPAP target's ballistic performance is more susceptible to the impact location on the perforated plate with a larger dip angle of the inclined plate. Additionally, the NPAP target with a thin perforated plate and a thick back plate configuration exhibited better ballistic performance, given the constant thickness of the inclined plate. [ABSTRACT FROM AUTHOR]

The study of the penetration efficiency of formed charges with different liner structures has practical implications for optimizing combatant structure design. In this paper, a kind of toroidal explosively formed projectile (TEFP) is proposed and the influence of the cone angle and morphology of the liner on the formation mechanism and penetration performance of TEFP is analyzed by numerical simulation. The results showed that, with the same charge mass, the TEFP exhibited a better hole reaming performance than the shaped charge jet; as the liner cone angle increased from 90∘ to 150∘ in a stepwise manner, the axial velocity of the TEFP increased slightly, while the penetration cavity diameter tended to decrease. Compared with the straight cone liner structure, the curved cone liner TEFP significantly improved the penetration depth with a slightly lower penetration cavity diameter, realizing the large-diameter penetration breakout effect for concrete targets. [ABSTRACT FROM AUTHOR]

The ballistic resistance behavior of double-layer steel plates incorporated with different materials is experimentally and numerically investigated by using blunt- and ogive-nosed projectiles of middle strength. These materials are Q235 steel (low strength and high ductility) and 45 steel (high strength and low ductility). Experimental results showed that the ballistic resistance is better for the double-layer plates with the front layer of low ductility and high strength and the back layer of high ductility and low strength material than that of the opposite layer order impacted by ogive-nosed projectiles, but the situation is opposite for blunt-nosed projectiles. The ballistic limit of H + A (753.85 m/s) is increased by 29.5% when compared to that of A + H (582.19 m/s) for ogive-nosed projectiles of 45 steel. In the case of blunt projectiles, a 2.8% decrease in the ballistic limit of middle-strength projectile. Ogive-nosed projectiles are more sensitive than blunt-nosed projectiles when it comes to the effect of the layer order of the double-layer plates. Moreover, the ballistic limit velocities of blunt-nosed projectiles are obviously bigger than that of ogive-nosed projectiles for the double-layer plates of the front layer of low strength, while the situation is opposite for the double-layer plates of the front layer of high strength. Furthermore, the projectiles lose some mass and length after impact. The deformation of projectiles is also concerning the nose shape and velocity of projectiles, as well as the layer order of the double-layer plates. Finally, numerical simulation results are obtained and compared using the ABAQUS subroutine VUMAT-modified Johnson-Cook material model. And these results fairly agree with the experiment. [ABSTRACT FROM AUTHOR]

Composite structures in the aerospace and railway industries frequently experience single or multiple low‐ or high‐velocity impacts. The dynamic behavior of composite structures under single impacts cannot be extrapolated to multiple impacts. This study investigates the influence of the distance between projectiles in simultaneous multiple impact scenarios using a finite element model for multiple impacts on carbon fiber‐reinforced polymer (CFRP) laminate plates. The critical distance between projectiles, where stress wave interaction becomes significant, was identified. Results indicate that a distance between the centres of the projectiles of approximately two to three times the projectile diameter is the most damaging for simultaneous multiple impacts. Highlights: A finite element model for multiple impacts on CFRP laminate plates was developed.Four different distances between projectiles were evaluated.The ballistic limit, out‐of‐plane displacements, energy absorption, and related parameters were studied.A distance of twice the projectile diameter was identified as the most critical.The distance between projectiles significantly affects the synergistic effects. [ABSTRACT FROM AUTHOR]

Studying ballistic impact on reinforced concrete (RC) structures is essential for enhancing the safety and cost‐effectiveness of these structures. The depth of penetration (DOP) and residual velocity (RV) of projectiles are critical design parameters requiring precise quantification to improve the ballistic‐resistant design. Traditional empirical models are available for quantifying these parameters but are deterministic and often yield inaccurate results due to the inherent uncertainties in ballistic impacts. This paper introduces a probabilistic approach to quantify DOP and RV accurately. Bayesian inference models are developed using dimensionless explanatory functions to estimate these parameters in RC panels under hard projectile impacts, accounting for associated uncertainties. Numerical modeling is performed using LS‐Dyna, and the model is validated against experimental data from past studies. Data from refined numerical simulations, along with available experiments from the literature, are utilized to develop the probabilistic models. The findings reveal the significant influence of projectile and concrete properties, as well as the projectile's incidence angle, on DOP and RV. The probabilistic models developed are validated with previous experimental results, demonstrating their reliability and accuracy. Consequently, robust design formulae are proposed for estimating DOP and RV for RC panels under hard projectile impacts, providing a valuable tool for precise impact assessments in engineering applications. [ABSTRACT FROM AUTHOR]

AbstractThis study investigates the impact response of bio-inspired helicoidal laminated composite plates under soft body impacts using the SPH methodology in ABAQUS. Impacts at velocities of 50 m/s, 100 m/s, and 200 m/s are analyzed for different helicoidal schemes. The model is validated against existing literature, and damage is evaluated using the Hashin failure model. Helicoidal laminates exhibit less damage than cross-ply and quasi-isotropic laminates. Damage increases with impact velocity, becoming severe at 200 m/s, with significant vibrations. The study highlights the superior performance of helicoidal laminates under high-velocity impacts. [ABSTRACT FROM AUTHOR]

As lightweight and load-bearing efficiency needs have grown, conventional metal has steadily given way to carbon fibre-reinforced polymer (CFRP) laminates. Also, CFRP laminates are more prone to localised damage due to impact loads like tool drop, runway debris and hail stone. This paper, investigated the penetration and perforation behaviour of CFRP laminate reinforced with 0.2 and 0.5 wt% MWCNTs. The projectile impact experiment was conducted using spherical and conical projectiles and the impact resistance was evaluated. The results revealed that 0.5 wt% MWCNTs embedded in CFRP laminate provided better impact resistance to both projectiles. The ballistic limit velocity was enhanced by 14.2% and 17.9% for spherical and conical projectiles, respectively, in the case of 0.5 wt% MWCNTs. Furthermore, numerical simulations were performed using an orthotropic model with Chang-Chang composite failure criteria. The results from numerical findings were consistent. It was concluded that MWCNTs reinforcement improves the projectile impact resistance and energy absorption. [ABSTRACT FROM AUTHOR]

The muzzle flow field of underwater guns involves the interaction and reflection of shock waves within the propellant gas jet. When underwater guns are fired in series, the evolution of the shock wave structure in the muzzle flow field becomes more complex due to the superposition effect of the propellant gas jets. This study establishes a transient two-dimensional axisymmetric muzzle flow field computational model to simulate the dynamics of the muzzle flow field as it evolves during series launch of an underwater gun. The results show that the initial propellant gas jet expands further due to the impelling effect of the subsequent projectile. In the strong coupling series launch mode, the axial size of the bottle-shaped shock structure of the initial propellant gas jet exhibits a dynamic change of "growth decay." However, in conventional coupling and weak coupling series launch conditions, the axial expansion of the bottle-shaped shock structure shows a single "growth" process. For the subsequent launch, in all three launch modes, the subsequent propellant gas jet will form two oblique shock waves under the compression of the gas–liquid interface and undergo several "shock reconstruction" processes at the axis, ultimately forming a stable bottle-shaped shock wave structure. [ABSTRACT FROM AUTHOR]

The high velocity of supercavitating projectiles in a wave environment alters the flow characteristics and water entry stability, which significantly impacts the development and application of supercavitating weapons. This paper, investigates the effects of waves on the oblique water entry of high-speed supercavitating projectiles using computational fluid dynamics, with Stokes' second-order wave theory as the foundation for wave simulations. The numerical simulation method is validated through high-speed water entry experiments. The analysis explores the impact of wave inclination on cavity formation and the forces acting on the projectile. The results reveal that variations in wave inclination change the actual water-entry angles, affecting the cavitation structure near the free surface, modifying the impact intensity on the tail fins during water contact, and ultimately influencing the hydrodynamic forces acting on the projectile. When the actual water-entry angles are similar, the forces on the projectile during entry remain consistent under different conditions, with the trajectory being determined by the entry angle. Additionally, a reduction in the actual water-entry angle improves the projectile's entry stability but increases the amplitude and frequency of tail slap, ultimately affecting the stability of the projectile's trajectory after water entry. [ABSTRACT FROM AUTHOR]

In modern battlefield, the requirements for long-range guidance and efficient damage of projectiles are increasing. The curved portion of projectiles is an important factor affecting the ballistic stability and aerodynamic characteristics. The optimization design of the curved portion of projectiles is of great significance for improving the guidance distance, accuracy, and the flight stability of projectiles. In this paper, a design method of the curved portion based on the exponential curve is proposed. The aerodynamic characteristics of projectiles of the curved portion based on the exponential curve and the existing typical curved portion under various Mach numbers (0.8, 1.5, and 3 Mach numbers) and various angles of attack (0, 10° and 20°) were numerically simulated by ANSYS Fluent software. The simulation results showed that when flying at various Mach numbers at zero attack angle, the projectile with logarithmic curve arc has the largest drag and drag coefficient, while the exponential curve arc has the smallest drag and drag coefficient. The drag coefficients between the two types of projectiles are 4.9, 14.5, and 13.7%, respectively, at various velocities. As compared with zero attack angle, the lift coefficient of exponential curve increases by 0.08 and 0.18 at the 10° attack angle and the 20° attack angle, and the change in the drag coefficient is only 0.008 and 0.077, which also indicates that the projectiles with the exponential curve arc have the better aerodynamic characteristics. [ABSTRACT FROM AUTHOR]

Given the significantly large deformation and high strain exhibited by explosively formed projectiles (EFP) in penetration, their penetration performance into multi-layer targets differs from that of ordinary bullets or rigid projectiles. Therefore, it is necessary to investigate the ballistic performance and the damage mechanism of target deformation when an EFP penetrates a multi-layer target. This study conducted high-velocity impact tests of EFPs on four types of multi-layer steel targets, analyzing the damage morphology and deformation characteristics of multi-layer steel targets subjected to EFP penetration from both macro and micro levels. To investigate the anti-penetration performance of more target combinations at different EFP velocities, an accurate symmetrical finite element model of EFP penetration into multi-layer targets was established using Autodyn 16.0 finite element software and the SPH-FEM algorithm based on the symmetrical characteristics of the EFP and target structure. The experimental and simulation results showed that for a three-layer composite target, when the thickness of the middle layer remained constant, using the target layers with a front–rear target thickness ratio of less than one was beneficial for enhancing the anti-penetration performance of the targets against EFPs; when the EFP velocity was low and the residual velocity for penetrating a single-layer target was no more than 200 m/s, the anti-penetration performance of the two-layer target was optimal. When the EFP velocity exceeded 1500 m/s, the single-layer target exhibited the best anti-penetration performance to the EFP, and the more layers, the smaller the ballistic resistance. When the number of layers was more than six, the ballistic resistance of the multi-layer targets gradually tended to remain constant. [ABSTRACT FROM AUTHOR]

Bird-strikes against aircrafts and against wind generator blades are urgent issues. In addition, their effects on flying cars are beginning to be highlighted. As it is assumed that birds vary in size, impact experiments using projectiles that take into account the characteristics and shapes of birds are unavoidable for material screening during their development stage. However, such kinds of experiments have not been sufficiently carried out. In this study, to elucidate the effect of the shape and the properties of projectiles on the impact behaviors of CFRPs, a fundamental study was done by three-dimensional measurement using various projectiles including a gelatin cylinder, rubber cylinders and rubber spheres for mainly two types of CFRPs with different laminate configurations (stackings) at the impact velocities below 370 m/s. The difference in the elapsed-time dependence of the largest displacement of deformation (vertex displacement) due to the stackings was slight, but the deformation behavior changed depending on the shape of the projectile, i.e. especially, large deformable or large-diameter projectiles resulted in a wider bottom area. To determine the penetration and delamination, the contacted area, related to the projectile's diameter, should be considered. The deformation of CFRPs by a spherical projectile just after the impact could be described by a quartic/quintic-function and after a certain period of time (30–50 μs) by a quadratic-function. Empirical equations for the kinetic energies of penetration and delamination for aircraft structural grade CFRP were proposed. [ABSTRACT FROM AUTHOR]