Stroboscopic two-dimensional ultrasonic velocity profiling for measuring flow transition in Taylor Couette systems

Flow characterization in a Taylor Couette system was made by investigating the radial velocity component with Ultrasonic Doppler Velocimetry based flow mapping. With the technique presented in this work, it is possible to measure the radial velocity components for variable axial position in a Couette cell within Taylor vortex flow (TVF), wavy vortex flow (WVF), modulated vortex flow (MVF) as well as spiral vortex domains in a conical shaped gap. The resulting maps for the different flow states show the location of vortices in the annular gap between the inner and outer cylinder. Cylindrical and conical concentrically rotating inner bodies were applied and respective flow patterns were analyzed. The method uses a stroboscopic triggering to synchronize flow measurements and rotational motion. The oscillation frequency f of unsteady motion in WVF, MVF, and spirals can be obtained from the power spectrum of velocity. The UVP transducer was preferably positioned in radial direction, perpendicular to the surface of the inner rotating body for measuring the radial velocity component. At the same time, the transducer was moved with constant velocity vertically along the outer cylinder height.     

UV吸收前体在热敏相纸中的应用研究

UV吸收前体(UVP)是应用于热敏相纸中的一类特殊的紫外吸收剂,它本身不能吸收紫外光,在一定条件下(紫外光和氢质子提供剂)可生成有效的紫外吸收剂,本文就其形成机理进行了简述,同时研究了3种UV吸收前体在热敏相纸中的应用情况。