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In order to investigate the mechanical formation, the mechanical‐thermo coupling mesoscale mechanism and the corresponding energy release characteristics of PTFE/Al composite material reactive jet, a mesoscale discretization model of PTFE/Al reactive liner with a mass ratio of 73.5 %/26.5 % is developed on the basis of the random delivery principle. The mesoscale numerical simulation is used to perform PTFE/Al reactive jet formation, obtaining the relative distribution characteristics of material, pressure, and temperature. The overpressure experiments for the energy release of reactive jets are conducted. The results show that there is an increasing tendency in the amount of Al particles from the jet's tip to its tail due to the velocity variance between PTFE and Al. The high temperature zones are found to be concentrated on the tip and axis of the jet, with particle deformation, collision and friction in the reactive jet accounting for the temperature rise. Moreover, the Al particle size has a significantly influence on the particle distribution and the mechanical‐thermo coupling behavior in the reactive jet, and the decrease of particle size is beneficial to the chemical reaction among the components of the reactive jet. To be more specifically, under the conditions of Al particle size of 400 μm, 600 μm and 800 μm, the overpressure peaks of reactive jet in 13 L chamber are 3.32 MPa, 2.86 MPa and 2.61 MPa, respectively. The variation of the overpressure with Al particle size obtained by experiment is consistent with the analysis of the mechanical‐thermo coupling characteristics of mesoscale numerical simulation. [ABSTRACT FROM AUTHOR]

Reactive materials (RMs) are special type of impact-initiated energetic materials that have been widely studied with broad military application prospects. However, simulating the ignition and reaction of RMs using current numerical methods is difficult due to their complex mechanism related to high dynamic loads. In this work, based on a theoretical model consisting of impact ignition criteria and chemical reaction rate of polymer-based RMs, a numerical method with a unified equation of state was proposed and compiled as an executable program. Experiments consisting of typical polytetrafluoroethylene /Al RM projectiles impacting double-spaced plates were conducted and simulated using the user-compiled program, and the results verified the effectiveness of the numerical method. The simulation also qualitatively analyzed the second-collision induced reaction enhancement mechanism. In addition, the results revealed that the kinetic-chemical combined effect is a crucial factor that determined the damage enhancement effect on the rear plates. [ABSTRACT FROM AUTHOR]

Specular highlight removal is a challenging task in the field of image enhancement, while it can significantly improve the quality of image in highlight regions. Recently, deep learning-based methods have been widely adopted in this task, demonstrating excellent performance by training on either massive paired data, wherein both the highlighted and highlight-free versions of the same image are available, or unpaired datasets where the one-to-one correspondence is inapplicable. However, it is difficult to obtain the corresponding highlight-free version of a highlight image, as the latter has already been produced under specific lighting conditions. In this paper, we propose a method for weakly supervised specular highlight removal that only requires highlight images. This method involves generating highlight-free images from highlight images with the guidance of masks estimated using non-negative matrix factorization (NMF). These highlight-free images are then fed consecutively into a series of modules derived from a Cycle Generative Adversarial Network (Cycle-GAN)-style network, namely the highlight generation, highlight removal, and reconstruction modules in sequential order. These modules are trained jointly, resulting in a highly effective highlight removal module during the verification. On the specular highlight image quadruples (SHIQ) and the LIME datasets, our method achieves an accuracy of 0.90 and a balance error rate (BER) of 8.6 on SHIQ, and an accuracy of 0.89 and a BER of 9.1 on LIME, outperforming existing methods and demonstrating its potential for improving image quality in various applications. [ABSTRACT FROM AUTHOR]

Polytetrafluoroethylene/aluminum (PTFE/Al) reactive material is a pivotal research object in the aerospace, military, and mechanical engineering fields and can release chemical energy (CE) under shock or impact. However, its relatively low mechanical strength limits its applications. The present paper proposes a Cu-PTFE/Al (73.5wt. %/26.5wt. %) double-layer liner that can form tandem explosive formed projectiles (EFPs) under the shock of shaped charges, which not only retains the strong penetration ability but also shows a more significant lateral enhancement effect through the deflagration reaction. Here, the preparation process of the PTFE/Al liner is given, and an analytical model for the Cu-PTFE/Al tandem EFP of the damage process against multi-spaced plates is established, revealing the penetration and deflagration-enhanced mechanisms. Subsequently, a two-step segmented numerical simulation for the penetration–deflagration coupling effects is conducted, and the time-space interaction process and damage results between kinetic energy penetration and CE deflagration are obtained. A series of experiments of tandem EFPs against spaced plates are conducted, including the different materials, thickness ratio, and standoff. Experimental results show that compared with Cu–Cu tandem EFP with the same condition, the penetration ability of Cu-PTFE/Al composite EFP is reduced, but the damage enhancement effect is greatly improved; the maximum damage area of a single plate is increased by 220.1%, and the average damage area of a single plate is increased by 76.2%. This study provides important reference data and a theoretical basis for the design of metal-reactive tandem EFPs. [ABSTRACT FROM AUTHOR]

This document is an editorial for a special issue of the journal "Materials" focused on the topic of "Materials under High Pressure." It emphasizes the interdisciplinary nature of studying materials under extreme high pressure and mentions various scientific disciplines involved in this field. The special issue includes fourteen peer-reviewed research articles covering topics such as processing technology, characterization, testing, theoretical modeling, and simulation. The document provides a brief summary of some of the research findings presented in the special issue, including investigations on the dynamic mechanical properties of materials, dispersion characteristics driven by explosion, detonation-driven deformation and jet formation, and shock-induced chemical reactions in reactive materials. The document also discusses various studies on materials under high pressure, including the strain-softening effect of THV-based reactive materials and the strain-strengthening effect of PTFE-based reactive materials. It explores the control of shock-induced energy release characteristics in PTFE/Al-based energetic materials through experimentation and theoretical analysis. The mechanical properties, constitutive behaviors, and failure criteria of aluminum-polytetrafluoroethylene-tungsten reactive materials are investigated. Additionally, an impact-initiated chemical reaction model is proposed to describe the ignition and energy release behavior of Al/PTFE reactive materials. The document also includes studies on structural damage and material failure caused by high-velocity impact, such as the vibration features and fault mechanism of electronic components under shock load and the dynamics of a space harpoon impacting a target plate. The authors hope that this collection of case studies [Extracted from the article]

Although deep learning-based approaches for video processing have been extensively investigated, the lack of generality in network construction makes it challenging for practical applications, particularly in video restoration. As a result, this paper presents a universal video restoration model that can simultaneously tackle video inpainting and super-resolution tasks. The network, called Video-Restoration-Net (VRN), consists of four components: (1) an encoder to extract features from each frame, (2) a non-local network that recombines features from adjacent frames or different locations of a given frame, (3) a decoder to restore the coarse video from the output of a non-local block, and (4) a refinement network to refine the coarse video on the frame level. The framework is trained in a three-step pipeline to improve training stability for both tasks. Specifically, we first suggest an automated technique to generate full video datasets for super-resolution reconstruction and another complete-incomplete video dataset for inpainting, respectively. A VRN is then trained to inpaint the incomplete videos. Meanwhile, the full video datasets are adopted to train another VRN frame-wisely and validate it against authoritative datasets. We show quantitative comparisons with several baseline models, achieving 40.5042 dB/0.99473 on PSNR/SSIM in the inpainting task, while during the SR task we obtained 28.41 dB/0.7953 and 27.25/0.8152 on BSD100 and Urban100, respectively. The qualitative comparisons demonstrate that our proposed model is able to complete masked regions and implement super-resolution reconstruction in videos of high quality. Furthermore, the above results show that our method has greater versatility both in video inpainting and super-resolution tasks compared to recent models. [ABSTRACT FROM AUTHOR]

The ignition, reaction ratio, pressure, and temperature distribution of an Al/Teflon projectile impacting multilayer targets were analyzed. It was observed that the reactive Al/PTFE composite reacted during jet formation, which can be divided into a local reaction stage and an overall reaction stage. Moreover, the Al particle size led to a large difference in the jet formation process, showing that the jet formed from liners with larger Al particles was more condensed due to a slower chemical reaction. 10.3390/cryst12040471 7 Du C.X., Fu H.M., Zhu Z.W., Wang K.H., Gao G.F., Zhou F., Xu L.Z., Du Z.H. Penetration Failure Mechanism of Multi-Diameter Tungsten Fiber Reinforced Zr-Based Bulk Metallic Glasses Matrix Composite Rod. [Extracted from the article]

Reactive material fragment is an extremely efficient damage enhancement technology that incorporates the defeat mechanisms of kinetic energy and chemical energy. In this paper, the polymer-based reactive material fragment/target interactions are investigated. Related dynamic testing techniques for energy release characteristics of reactive material fragments are presented, and a series of ballistic experiments is conducted. The results show the reactive material fragment, which perforates the closed test chamber, undergoes a violent chemical reaction under highly dynamic loads and releases great amounts of thermo-chemical energy on the interior. The impact-initiated process and energy release behavior are markedly influenced by the impact velocity, indicating the material's fracture is of importance to the reaction. A relationship between the maximum pressure inside the chamber and the reaction efficiency is derived to analyze the influence quantitatively, and the venting effects are also considered. [ABSTRACT FROM AUTHOR]

Drop-weight tests were conducted to investigate the impact-initiation sensitivity of high-temperature PTFE-Al-W reactive materials. The test results show that the impact-initiation sensitivity of the materials more than doubles with increasing the sample temperature from 25 to 350 °C. Combined with the impact-induced initiation process recorded by high-speed video and the difference between reacted and unreacted residues, the crack-induced initiation mechanism was revealed. The rapid propagation of crack provides a high-temperature and aerobic environment where Al reacts violently to PTFE, which induces the initiation. Moreover, the influence of sample temperature on the sensitivity was discussed and analyzed. The analysis results indicate that the sensitivity shows a temperature interval effect, and 127 and 327 °C are the interval boundaries where the sensitivity changes significantly. The sensitivity may leaps at 127 °C and increases more rapidly in the temperature interval from 127 to 327 °C, but hardly changes after the temperature reaches 327 °C. [ABSTRACT FROM AUTHOR]

The traditional polytetrafluoroethylene (PTFE)/Al reactive material liner shaped charge generally produces insufficient penetration depth, although it enlarges the penetration hole diameter by chemical energy release inside the penetration crater. As such, a novel high-density reactive material liner based on the PTFE matrix was fabricated, and the corresponding penetration performance was investigated. Firstly, the PTFE/W/Cu/Pb high-density reactive material liner was fabricated via a cold pressing/sintering process. Then, jet formation and penetration behaviors at different standoffs were studied by pulse X-ray and static experiments, respectively. The X-ray results showed that the PTFE/W/Cu/Pb high-density reactive material liner forms an excellent reactive jet penetrator, and the static experimental results demonstrated that the penetration depth of this high-density reactive jet increased firstly and then decreased by increasing the standoff. When the standoff was 1.5 CD (charge diameter), the penetration depth of this reactive jet reached 2.82 CD, which was significantly higher than that of the traditional PTFE/Al reactive jet. Moreover, compared with the conventional metal copper jet penetrating steel plates, the entrance hole diameter caused by this high-density reactive jet improved 29.2% at the same standoff. Lastly, the chemical reaction characteristics of PTFE/W/Cu/Pb reactive materials were analyzed, and a semi-empirical penetration model of the high-density reactive jet was established based on the quasi-steady ideal incompressible fluid dynamics theory. [ABSTRACT FROM AUTHOR]