Simulation of Electroosmotic and Pressure-Driven Mixed Flow of Viscoelastic Fluids in Converging-Diverging Tubes北大核心CSCD

The electroosmotic and pressure⁃driven mixed flow was widely used in various biochemical microflu⁃ idic fields, where the elastic instability of the viscoelastic fluid cannot be ignored. A viscoelastic fluid was used to numerically simulate electroosmotic and pressure⁃driven mixed flow in a 10 ∶ 1 ∶ 10 microchannel converging⁃ diverging tube. The effects of different pressures and different polymer concentrations on the fluid flow were studied, and the superposition principle for the velocity distributions of Newtonian fluids and viscoelastic fluids in converging⁃diverging tubes was analyzed. The results show that, the reverse pressure brings the viscoelastic fluid into higher instability, which makes the inlet vortex larger by 25 μm for every 1 Pa pressure increase. The positive pressure makes the eddy current smaller. For a relatively small reverse pressure, the inlet vortex in⁃ creases with the polymer concentration and tends to be stable gradually. For a relatively large reverse pressure, the vortex size first increases and then decreases with the polymer concentration. © 2023 Editorial Office of Applied Mathematics and Mechanics. All rights reserved.     

基于单颗粒NaYF4微米棒的上转换白光发射特性

上转换白光材料在固态照明、液晶显示器和生物成像等领域展现出其他光源无法比拟的优势,倍受研究者们广泛关注.为此,本文采用水热法合成了一系列掺杂不同离子浓度的NaYF₄∶Yb³⁺/Re³⁺/Tm³⁺(Re³⁺=Ho³⁺,Er³⁺)微米晶体.在980 nm近红外光激发下,通过调控掺杂离子的浓度,研究Ho³⁺/Tm³⁺及Er³⁺/Tm³⁺共掺杂单颗粒NaYF₄微米晶体的白光发射特性.研究表明:在NaYF₄∶Yb³⁺/Ho³⁺/Tm³⁺微米晶体中,通过调控Yb³⁺离子的掺杂浓度易于实现其白光发射;而在NaYF₄∶Yb³⁺/Er³⁺/Tm³⁺微...