气体分离用MOF基混合基质膜的界面构建策略

混合基质膜结合多孔填料优异的气体分离性能和聚合物材料良好的加工性能,被认为是最具有应用前景的一种气体分离膜材料。金属-有机框架材料(MOF)由于具有高比表面积和孔隙率、可调节的孔径以及可修饰的表面性能,成为制备混合基质膜的重要多孔材料。本文针对MOF基混合基质膜制备中所面临的主要挑战,聚焦于MOF和聚合物界面缺陷问题,分析了界面缺陷的产生原因及其对性能的影响,重点阐述了改善MOF填料和聚合物基质界面相容性的策略,以期为制备具有良好的界面形态和优异的气体分离性能的混合基质膜提供借鉴思路。     

超音速等离子体点火过程的三维数值模拟

为了研究等离子体点燃超音速混合气流的过程,设计并验证了超音速燃烧室的三维计算模型,计算出了燃烧室等离子体点火时的流场参数和化学反应规律,分析了等离子体点火对燃烧室内燃烧的影响。计算结果表明:高温等离子体射流的滞止作用通过增加混合气在燃烧室内的停留时间提高了点火效率; 等离子体点火时燃烧区域的压力扩散比较充分,内部为压力相对平衡的低速流动; 高温等离子体射流高速射向混合气流时产生的速度矢量偏移扩大了点火面积,从而使点火效率得到提高; 氢气、空气燃烧的燃烧产物主要是水,燃烧区域局部温度主要受局部放热反应的影响。     

Fabrication of functional waterborne polyurethane/montmorillonite composites by click chemistry method

"Click" chemistry method was used to fabricate novel waterborne polyurethane (WPU)/montmorillonite (MMT) composites based on alkyne-containing WPU and azide-modified montmorillonite. The morphology of these composites was characterized by x-ray diffractometer, scanning electron microscope. The mechanical properties, thermal stability, and flame resistance of the composites were investigated by tensile, thermogravimetry and cone calorimetric experiments, etc. The experimental results show that the tensile strength, water resistance and flame retardancy of the WPU/MMT composites have been reinforced efficiently owing to the linking of MMT by click reaction.     

An improved diffuse interface method for three-dimensional multiphase flows with complex interface deformation

An improved diffuse interface (DI) method is proposed for accurately capturing complex interface deformation in simulations of three-dimensional (3D) multiphase flows. In original DI methods, the unphysical phenomenon of interface thickening or blurring can affect the accuracy of numerical simulations, especially for flows with large density ratio and high Reynolds number. To remove this drawback, in this article, an interface-compression term is introduced into the Cahn-Hilliard equation to suppress the interface dispersion. The additional term only takes effect in the interface region and works normal to the interface. The difference of the current method from the previous work is that the compression rate can be adjusted synchronously according to the magnitude of local vorticity, which is strongly correlated to the interface dispersion and changes with the computational time and interface position. Numerical validations of the proposed method are implemented by simulating problems of Laplace law, Rayleigh-Taylor instability, bubble rising in a channel, and binary droplet collision. The obtained results agree well with the analytical solutions and published data. The numerical results show that the phenomenon of interface dispersion is suppressed effectively and the tiny interfacial structures in flow field can be captured accurately.     

Vibration isolation with passive linkage mechanisms

Nonlinear Dynamics - This study is to present a novel way to achieve superior passive vibration isolation by employing a specially designed and compact linkage mechanism. The proposed...     

A mesh-free radial basis function–based semi-Lagrangian lattice Boltzmann method for incompressible flows

In this paper, a local radial basis function–based semi-Lagrangian lattice Boltzmann method (RBF-SL-LBM) is proposed. This is a mesh-free method that can be used for the simulation of incompressible flows. In this method, the collision step is performed locally, which is the same as in the standard LBM. In the meanwhile, the steaming step is solved in a semi-Lagrangian framework. The distribution functions at the departure points, which may be not the grid points in general, are computed by the local radial basis function interpolation. Several numerical tests are conducted to validate the present method, including the lid-driven cavity flow, the steady and unsteady flow past a circular cylinder, and the flow past an NACA0012 airfoil. The present results are in good agreement with those published in the previous literature, which demonstrates the capability of RBF-SL-LBM for the simulation of incompressible flows.     

Low-frequency multi-direction vibration isolation via a new arrangement of the X-shaped linkage mechanism

Nonlinear Dynamics - Most existing quasi-zero stiffness (QZS) isolators with excellent vibration isolation performance in the low-frequency range are designed to attenuate vibration transmission...