The establishment of an internal flowfield inside a single water droplet subjected to shock-wave impact is numerically and theoretically investigated. The main focus is on the description of the droplet internal flow pattern, which is believed to be one of the dominant factors in initial droplet deformation. The droplet internal flow pattern holds steady for quite a long time after the incident shock passage, and a saddle point is observed for the first time. Accordingly, the saddle point inside the droplet flow is used as a characteristic point to describe the internal flow. Cases of different incident shock strengths are tested, and a theoretical prediction is proposed to delineate the correlation between the saddle point steady position and the strength of the incident shock wave. The numerical cases are found to be in good agreement with the prediction. The present study helps to complete the understanding of the overall droplet aerobreakup phenomenon.

Owing to its good air stability and high refractive index, two-dimensional (2D) noble metal dichalcogenide shows intriguing potential for versatile flat optics applications. However, light field manipulation at the atomic scale is conventionally considered unattainable because the small thickness and intrinsic losses of 2D materials completely suppress both resonances and phase accumulation effects. Here, we demonstrate that losses of structured atomically thick PtSe2 films integrated on top of a uniform substrate can be utilized to create the spots of critical coupling, enabling singular phase behaviors with a remarkable π phase jump. This finding enables the experimental demonstration of atomically thick binary meta-optics that allows an angle-robust and high unit thickness diffraction efficiency of 0.96%/nm in visible frequencies (given its thickness of merely 4.3 nm). Our results unlock the potential of a new class of 2D flat optics for light field manipulation at an atomic thickness.

Missing data recovery using data fusion of incomplete complementary data sets: A particle image velocimetry application

This article describes an investigation into interface bonding research of 316L/Q345R stainless clad plate. A threedimensional thermal-elastic-plastic model has been established using finite element analysis to model the multi-pass hot rolling process. Results of the model have been compared with those obtained from a rolling experiment of stainless clad plate. The comparisons of temperature and profile of the rolled stainless clad plate have indicated a satisfactory accuracy of finite element analysis simulation. Effects on interface bonding by different parameters including pre-heating temperature, multi-pass thickness reduction rules, rolling speed, covering rate, and different assemble patterns were analyzed systematically. The results show that higher temperature and larger thickness reduction are beneficial to achieve the bonding in vacuum hot rolling process. The critical reduction in the bond at the temperature of 1200°C is 28%, and the critical thickness reduction reduces by about 2% when the temperature increases by 50°C during the range from 1000°C to 1250°C. And the relationship between the minimum pass number and thickness reduction has been suggested. The results also indicate that large covering rate in the assemble pattern of outer soft and inner hard is beneficial to achieve the bond of stainless clad plate.

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