Research on dynamic response characteristics of CFRP/Al HC SPs subjected to high-velocity impact

CFRP/Al HC SPs(Carbon Fiber Reinforced Plastic/Aluminum Honeycomb Sandwich Panels)composite structures are widely used in the aerospace and many other fields due to their excellent performances. In order to reveal profoundly the dynamic response characteristics of CFRP/Al HC SPs composite structure under high-velocity impact loading, the experiments about aluminum honeycomb core and CFRP/Al HC SPs composite structure impacted by high-velocity projectiles have been performed by using a one-stage light gas gun loading and a high-speed camera systems, respectively. The whole physical process of collision is analyzed by using TEMA software which is provided by high-speed camera's manufacturer,and the pictures and related physical parameters of the projectile passing through the different layers at the key moments are extracted based on the set frame rate of the video. Meanwhile, the ABAQUS/Explicit module was used to conduct numerical simulation under the same conditions as the experiments, and extracting the pictures and related physical parameters during the projectile penetrating through aluminum honeycomb core and the sandwich panels at the different key moments. The results show that the durations of action for the projectile impacting the Al HC core and the CFRP/Al HC SPs at the velocity about 280 m/s were 86 μs and 240 μs in experiments, respectively, and the durations of action were 90.7μs and 236.2 μs at the same experimental conditions in numerical simulation, which were basically consistent comparing the experimental to simulated results. Moreover, more than 70% for the kinetic energy of the projectile consumed by the sandwich panels was attributed to the front panel and the aluminum honeycomb core during the entire impact process, and all these have verified the reliability of the numerical simulation.

Alleviating hysteresis and improving device stability of perovskite solar cells via alternate voltage sweeps

The anomalous hysteresis in a perovskite solar cell induced by an asymmetric field is confirmed by a capacitance–voltage measurement. By applying several cycles of alternating reverse and forward scans, this hysteresis phenomenon is obviously alleviated, resulting in a hysteresis-less state in the perovskite solar cell. Meanwhile, the open-circuit voltage and power conversion efficiency of the perovskite solar cell are enhanced by 55.74% and 61.30%, respectively, while the current density and fill factor keep almost invariable. The operation of alleviating hysteresis is essential for further research and is likely to bring in performance gains.

Evidence for the Late Pliocene Aridification in the Eastern Tarim Basin,Northwest China

INTRODUCTION The vast arid regions in mid-latitude Asia(MLA)are among the most prominent landscapes on Earth’s surface and have been thought to provide a key source of global atmospheric dust(Hovan et al.,1989).Over the past decades,research on aridification of MLA have made tremendous progress and pointed large-scale aridity has prevailed in this region since the Late Pliocene despite long-term stepwise drying(Fang et al.,2020;Liu et al.,2014).However,direct sedimentary records for the late Pliocene aridification is still lack,hindering our understanding of regional comparison and the behind drive mechanism.The Tarim Basin in northwest China is one of the driest and largest inland basins and is considered as an ideal candidate for aridity records of MLA(Sun et al.,2013).Although considerable studies of environmental variations have been conducted(Liu et al.,2020;Zheng et al.,2015),a comprehensive picture of climatic change of the basin during the Late Pliocene is still unavailable,due to fragmentary sedimentary records,especially in the eastern Tarim Basin.In this contribution,we report the Late Pliocene lacustrine sediments found in Lop Nur of the east of Tarim Basin.The occurrence of abundant magnesite,their related crystal morphology and C-O isotopic signature suggested a typical brackish or even saline lake environment and arid climatic condition in eastern Tarim Basin during this interval.

Protecting-group-free ortho-C–H borylation of anilines enabled by mesoionic carbene-Ir complex

We describe an iridium-catalyzed ortho-selective C–H borylation of unprotected anilines.The employing strongσ-donating cyclometalated mesoionic carbene as C^C bidentate ligand is crucial for the high ortho-selectivity.Computational studies support outer-sphere X–H⋅⋅⋅O_(boryl) hydrogen bond interactions,which are strengthened by bidentate C^C ligand introduction.The method shows broad substrate scope and high functional group tolerance.