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Precise adjustment of the metal site structure in single-atom catalysts (SACs) plays a key role in addressing the oxygen evolution reaction (OER). Herein, we report the synthesis of O-doped Ni SACs anchored on porous graphene-like carbon (Ni–O–G) using molten salts (ZnCl2 and NaCl) as templates, in which the unique Ni–O4 structure serves as the active sites. Ni–O–G, with an overpotential of only 238 mV (@ 10 mA cm–2), is one of the more advanced catalysts. An array of characterizations and density functional theory calculations show that the Ni–O4 coordination enables Ni to be closer to the Fermi level compared to traditional Ni–N4, enhancing the electronic metal–support interaction to facilitate OER kinetics. Thus, this work offers an alternative strategy for the structural modulation of Ni SACs and the effect of different coordination elements with the same atomic coordination structure on the intrinsic OER activity.

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Dynamic spatial distribution and killing characteristics of warhead fragments are important topics in the field of weapon effectiveness and protection. However, there is little research on the fragment distribution formed by continuous dynamic attacks of multiple projectiles that explode above the ground. This study analyzes spatial distributions of warhead fragments using witness boards in a rectangular target test. The results show that the fragment distribution of multiple projectiles in continuous dynamic attacks demonstrates a spatial superposition characteristic. The superimposed distribution is the sum of the distributions of two independent fragment distributions. The distribution characteristics are consistent with fragment scattering behavior. Therefore, they can be used to analyze the killing effects of multiple projectiles conveniently. The effects of falling speed, falling angle, and explosion height on the damage range of fragments were explored by a fragment spatial distribution model obtained from experiments. Analysis indicates that the prefabricated fragment distribution conformed to a spatial superposition relationship under dynamic multiprojectile continuous attacks, and the superposition obeyed fragment scattering characteristics. As the projectile falling angle increased at the explosion center, or as the falling height decreased, the positive pressure duration increased gradually. The falling speed had the greatest impact on the specific impulse of overpressure. The falling angle had the greatest impact on the peak value of overpressure. Both the falling angle and the explosion height had the greatest impact on the positive pressure acting time.