The laser Doppler velocimeter (LDV) and hydrogen bubble ow visualization techniques have been used to measure the characteristics of turbulent boundary layer ow over riblets surface and to observe its coherent structure in the near wall region. The experimental results indicate that, in comparison with the turbulent boundary layer ow over a smooth surface, greater values are obtained for the thickness of viscous sublayer, the thickness of bu er region and the integral constant C in the log-law. Moreover, the maximum value of turbulent intensity u =U * is increased by 6.7%, but its position is decreased by 6.4%, the skewness factor and the atness factor are hardly a ected by the riblets surface. The non-dimensional value of low-speed streak spacing is reduced by 20%, this is also an indication of turbulent drag reduction.
An efficient method for the "one-pot" preparation of aryl Schiff bases is reported. In the presence of a selenium catalyst, the aryl Schiff bases have been prepared by a one-stage condensation of nitroarenes and aryl aldehydes using carbon monoxide as reducing agent at atmospheric pressure. The reductive condensation occurs with high selectivity regardless of the substituent groups on the aromatic ring without affecting other reducible functional groups.
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