The preparation of polymer nanocomposites combined with high strength, toughness, and high transparency remains a challenge. Aramid fibers are often used as fiber-reinforced materials for their superior mechanical and thermal properties, but the weak interfacial force between aramid fibers and matrix polymer limits the application in composite materials. In this work, aramid nanofibers were prepared by a two-step process, which included deprotonation and acid hydrothermal treatment to obtain better dispersions in general solvents. The hydrothermal aramid nanofibers (HANFs) were used as reinforcing materials and blended with polyacrylonitrile (PAN) to prepare polyacrylonitrile/aramid nanofibers (PAN/HANFs) composite films with different mass fractions of HANFs. The morphologies of HANFs and the thermal, optical, and mechanical properties of composite films were investigated. Interestingly, when the mass fraction of aramid nanofibers was less than 1.0%, the composite films were synchronously strengthened and toughened. When the mass fraction of HANFs was 0.5%, the tensile strength and toughness of the PAN/HANFs composite film reached 62.04 MPa and 22.56 MJ/m(3), which were 74.23% and 162.31% higher than the pure PAN film, respectively. Besides, its average transmittance in the visible light region remained 76.34%. This work may offer a novel and facile strategy for high transparent reinforced polymer composites, which have potential applications in high strength fiber or optical film.
In this article, the (2+1) - dimensional variable coefficients Broer-Kaup-Kupershmit equation is studied for the first time by Lie symmetry analysis. The derivation process of generating elements of vcBKK equation is given systematically, and the optimal system of the one-dimensional subalgebras is determined. Furthermore vcBKK equation is reduced based on the optimal system, and then the reduced equations are solved with the help of the (G’/G)-expansion method. The images of various kinds of exact solutions are drawn. Finally, according to the conservation theorem, the conservation laws of vcBKK equation is constructed.
Dynamical downscaling is conducted by MPAS-A v7.0 with a global variable resolution (MPAS-VR) and truncated regional (MPAS-RCM) configurations. Two sets of MPAS experiments are carried out to evaluate the simulation performance of summer precipitation in China. One is a global variable resolution run (VR) using 4 times grid refinement over the domain center (32oN, 100oE), and the grid spacing smoothly varies from ~25km to ~92km outside the refinement. The other is a regional configuration experiment (RCM) with the grid truncated according to an ellipse in the same center.
