Synthesis of pyrazinyl compounds from glycerol and 1,2-propanediamine over Cu-TiO_2 catalysts supported on γ-Al_2O_3

Cu-TiO_2 catalysts supported onγ-Al_2O_3 are prepared and used in glycerol cyclization with 1,2-propanediamine to produce pyrazinyl compounds including 6-hydroxymethyl-2-methylpyrazine,5-hydroxymethyl -2-methyIpyrazine,2,6-dimethylpyrazine and 2,5-dimethylpyrazine in a fixed-bed system.It is found that glycerol cylclization with 1,2-propanediamine gave a high total yield of pyrazinyl compounds（〉80%） over Cu-Ti02/γ-Al_2O_3 catalyst,and cyclization was through the reactions between activated 1,2-propanediamine and the intermediates from glycerol dehydration and oxidation.In addition,the regioselectivity of the pyrazinyl compounds was mainly controlled by the steric hindrance of the substrates during the cyclization process.

Experiment on surface wake of internal waves generated by underwater vehicle in stratified fluids

The surface flow field of internal waves generated by the underwater vehicle is very weak.In order to study the characteristics of the surface wake of internal waves,a surface particle image velocimetry(PIV)technique which can be used to measure the flow field in the order of mm/s is developed.Breakthrough is made with respect to the key technique measuring the micro-velocity flow field of internal waves on the water surface in stratified fluids.The wake generated by SUBOFF model is measured in stratified fluid tank,and the surface flow field of internal waves is successfully measured for the first time.The experimental results are compared with predicted results by the classical Tuck’s internal wave theory.The results show the characteristics of the surface wake signature of internal waves and the variation of the angle between internal wave beams and the surface flow velocity of internal wave with the towing speed of the model are in good agreement.It provides support for further research on wake signature remote sensing of internal waves in laboratory.