Bubble wake visualization by using photochromic dye

Wake structure of a single “clean bubble”, rising in rectilinear, zigzagging or spiraling path, is experimentally investigated. A single nitrogen gas bubble was produced in a silicone oil pool and the wake structure development in the rear of the rising bubble was visualized by using photochromic dye. The flexibility of this visualization method enabled us to distinguish wake from drift easily. Both bubble motion and wake structure were recorded by using stereo high-speed video camera simultaneously. We present the first experimental support for the existence of the standing eddy at the rear of the clean bubble, as predicted by a previous numerical study by Ryskin and Leal [1984. Journal of Fluid Mechanics 148, 19-35], Dandy and Leal [1986. Physics of Fluids 29(5), 1360-1366] and Blanco and Magnaudet [1995. Physics of Fluids 7(6), 1265-1274]. We study motion of a pair of vortex filaments, which is called double-threaded type wake, in the case of bubble rising in an axi-asymmetric path. Visualization results of multiple formations of horse-shoe type vortices in one period of zigzag motion of rising bubble with shape oscillations, which has not been observed in previous studies are also presented.     

二苯基硫代卡巴腙汞基光致变色聚合物的研制

合成了侧链含有二苯基硫代卡巴腙汞基的丙烯酸酯共聚物，研究了它们的光致变色性能，探讨了共聚物结构及一苯基硫代卡巴腙汞基含量对光致变色性能的影响，变时间为5～10s，回复时间为40～120s，先致变色性能良好．     

Hydrothermal synthesis of WO3 films on the TiO2 substrates and their photochromic properties

Tungsten oxide (WO₃) films have been prepared on the synthesized TiO₂ substrates from a sodium tungsten precursor via a hydrothermal method. X-ray diffraction, scanning electron microscopy and transmission electron microscopy analyses were used to investigate the effect of precursor concentrations on the structures and morphologies of the films. Ordered WO₃ films were successfully synthesized on the as-grown TiO₂ substrates. With the concentrations increasing from 0.001 M to 0.024 M, the morphologies of the films changed from multi-layer laminated structure to ladder-shaped lamellar structure finally columnar structure. The results also showed that with an increase in precursor concentration, the observed absorptions at 365 nm of the films increased until precursor concentration of 0.016 M, and then decreased with higher concentration. The film obtained with precursor concentration of 0.016 M on the TiO₂ substrate had the best photochromic properties.     

Synthesis and characterization of a new photochromic alkylene sulfide derivative

A process has been developed for the synthesis of a new photochromic alkylene sulfide derivative. The process involves the synthesis of an alkylene sulfide with terminal free amino groups and a novel unsymmetrical photochromic diarylperfluorocyclopentene containing an aldehyde group, which coupled together to produce the corresponding Schiff base. The structures of the products were confirmed by a range of spectroscopic techniques.     

螺噁嗪类光致变色化合物的制备及其性能初探

通过萘并噁嗪环上引入不同类型的取代基,合成了三种螺噁嗪光致变色化合物。研究了其光致变色性能和抗疲劳性能,结果表明,在紫外灯照射下由无色变为蓝色,这种变化是可逆的,并且具有较高的抗疲劳性。