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Enhanced antireflective and laser damage resistance of refractive-index gradient SiO2 nanostructured films at 1064 nm

Wan Lili, Yang Jie, Liu Xiaoru, Zhu Jiayi, Xu Gang, Hao Chenchun, Chen Xuecheng, Xiong Zhengwei

Polish Journal of Chemical Technology

2024

Vol. 26, nr 2

25--30

A facile sol-gel procedure was employed to create refractive-index gradient SiO2 antireflective (AR) films. A monolayer film, characterized by the porous crosslinking framework, was fabricated with a designed volume ratio mixture both with colloidal silica suspension and soluble organic polysiloxane. The upper layer for the bilayer film was a hexamethylisilazane (HMDS) modified colloidal silica suspension, leading to the film surface transfer to hydrophobic. The strategic design of nanostructures in the bottom and upper layers resulted in a refractive-index gradient SiO2 film with enhanced AR properties. The bilayer film demonstrated a transmittance of 99.5% at 1064 nm, accompanied by a notable reduction in refectivity. Moreover, the laser-induced damage threshold of the bilayer film was increased by 30%, rising to as high as 24.7 J/cm2 . The SiO2 nanostructured film both showed a refractive-index gradient structure with excellent AR properties and exhibited good laser damage resistance.

Grain-size characteristics and net transport patterns of surficial sediments in the Zhejiang nearshore area, East China Sea

Liang Juan, Liu Jian, Xu Gang, Chen Bin

Oceanologia

2020

No. 62 (1)

12--22

Spatial variations in grain-size parameters can reflect sediment transport patterns and depositional dynamic environments. Therefore, 616 surficial sediment samples taken from the Zhejiang nearshore area in the East China Sea were analyzed to better understand the net sediment transport pattern in this region. The study area is generally dominated by clayey silt and has relatively coarse mud sediment in the southeast. The sorting coefficient of surface sediment is higher than 1.4, and sediment is poorly sorted throughout the study area. The skewness has a strong correlation with the mean grain-size diameter. The net sediment transport pathways obtained by the grain-size trend analysis indicate several distinct characteristics of the surficial sediment transport. The sediment is transported southward under the action of the stronger southward Zhejiang-Fujian Coastal Current (ZMCC) in winter in the upper part of the nearshore area. Influenced by the obstruction of the Taiwan Warm Current (TWC) and the tidal current, surficial sediment transport vectors display two areas of grain-size trend convergence and indicate the net deposition environment has a high sedimentation rate. However, the transport is mainly toward the north under the control of the prevailing northward ZMCC and the strong TWC in the summer. The sedimentary rate is closely related to the processes of the sediment transport. On the one hand, sediment transportation affects the depositional rate in a different environment. On the other hand, the modern sedimentary rate can reflect indirectly the sediment source and sediment transportation.

Water entry of a wedge into waves in three degrees of freedom

Sun Shi Yan, Chen Hai Long, Xu Gang

Polish Maritime Research

2019

nr 1

117--124

The hydrodynamic problem of a two-dimensional wedge entering into a nonlinear wave in three degrees of freedom is investigated based on the incompressible velocity potential theory. The problem is solved through the boundary element method in the time domain. To avoid numerical difficulties due to an extremely small contact area at the initial stage, a stretched coordinate system is used based on the ratio of the Cartesian system in the physical space to the distance travelled by the wedge in the vertical direction. The mutual dependence of body motion and wave loading is decoupled by using the auxiliary function method. Detailed results about body accelerations, velocities and displacements at different Froude numbers or different waves are provided, and the mutual effect between body motion and wave loading is analysed in depth.