In desert areas in Hexi region,11 barchan dunes,6 chains of barchan dunes,6 pyramid dunes,6 parabolic dunes and 6 accumulated sand-belts were chosen to study their movement speed based on images obtained by Google Ear...In desert areas in Hexi region,11 barchan dunes,6 chains of barchan dunes,6 pyramid dunes,6 parabolic dunes and 6 accumulated sand-belts were chosen to study their movement speed based on images obtained by Google Earth in various periods.The results show that among the dunes,the movement of the barchan dunes was the fastest,followed by the chains of barchan dunes,and only the tops of the pyramid dunes swayed,while the parabolic dunes and accumulated sand-belts hardly moved forward.The higher the barchan dunes(or the chains of barchan dunes) were,the slower the movement was.On the contrary,the higher the pyramid dunes were,the faster the swing was.There was a positive correlation between the movement speed of the barchan dunes and the average wind speed of sandstorms.展开更多
[ Objective ] The paper was to study the particle size characteristics of barchan dune and its formation mechanism in Hexi desert area d Gansu. [ Method] Through particle size measurement and wind speed flow field obs...[ Objective ] The paper was to study the particle size characteristics of barchan dune and its formation mechanism in Hexi desert area d Gansu. [ Method] Through particle size measurement and wind speed flow field observation d dune, the particle size differences of various sampling plots and various parts of dune were analyzed using analysis of variance, and the relationship between particle size and wind speed was analyzed using correlation coefficient method. [ Result] （ 1 ） Barehan dune and barehan chains in Hexi desert area of Gansu were mainly consisted of fine sands and medium sands at the depth of 0 -5 cm： the sand particle in Gulang desert area was fine, which had significant difference with that in Jinchang, Linze, Jinta and Minqin desert areas. （2） Medium sands gradually increased from the bottom of windward slope to the dune peak in both barchan dune and barchan chain. On the windward slope of barehan dune, fine sands gradual- ly increased from the middle to both sides, while coarse sands and medium sands gradually decreased. On the windward slope of barehan chain, fine sands first de- creased then increased from the middle to NE side, but first increased then decreased from the middle to SW side. （3） In terma of particle size, there were great variations between fine sands and coarse sands ; for dune parts, there were great variations between dune peak and leewant slope toe; for dune types, the variation of fine sands in various parts of barchan chain was greater than that of barchan dune, while differentiation degree of medium sands and fine sands was greater than that of barchan dune. The particle size of fine sands was positively correlated with wind speed, and that of medium sands was negatively correlated with wind speed. [ Conclusion] The formation environment of particle size of berehan dune mainly included sand source and dynmnic source, and wind speed was the dynamic source for particle size distribution of barchan dune.展开更多
In this study, the mean droplet diameter in the cavity zone and the total mass transfer area of a multi-stage highspeed disperser(HSD) reactor with different packing combinations were measured and evaluated. The effec...In this study, the mean droplet diameter in the cavity zone and the total mass transfer area of a multi-stage highspeed disperser(HSD) reactor with different packing combinations were measured and evaluated. The effects of rotational speed and packing radius, as well as the packing ring radius and numbers, on the mean droplet diameter and the total mass transfer area were evaluated. A model was established to calculate the mass transfer area in the cavity zone in the HSD reactor, and it was found that the packings contribute 61%–82% of the total mass transfer area. A correlation for predicting the mass transfer area in the packing zone was regressed by the dimensionless analysis method. An enhancement factor based on the mass transfer area in the packing zone was proposed to evaluate the effect of packing combination on mass transfer area. Two optimum packing combinations were proposed in consideration of the mean droplet diameter and the enhancement factor.展开更多
基金Sponsored by Major State Basic Research Development Program(973 Program)(2014CB460611)National Natural Science Foundation of China(41261102)
文摘In desert areas in Hexi region,11 barchan dunes,6 chains of barchan dunes,6 pyramid dunes,6 parabolic dunes and 6 accumulated sand-belts were chosen to study their movement speed based on images obtained by Google Earth in various periods.The results show that among the dunes,the movement of the barchan dunes was the fastest,followed by the chains of barchan dunes,and only the tops of the pyramid dunes swayed,while the parabolic dunes and accumulated sand-belts hardly moved forward.The higher the barchan dunes(or the chains of barchan dunes) were,the slower the movement was.On the contrary,the higher the pyramid dunes were,the faster the swing was.There was a positive correlation between the movement speed of the barchan dunes and the average wind speed of sandstorms.
基金Supported by Special Project for Preceding Study of 973 Program "Stability Research of Tall Barchan Dune at Oasis Fringe(2014CB460611)National Natural Science Foundation of China "Climate Factors and Their Ecological Effects on Formation of Accumulation Sand-belt at Oasis Edge of Minqin(41261102)
文摘[ Objective ] The paper was to study the particle size characteristics of barchan dune and its formation mechanism in Hexi desert area d Gansu. [ Method] Through particle size measurement and wind speed flow field observation d dune, the particle size differences of various sampling plots and various parts of dune were analyzed using analysis of variance, and the relationship between particle size and wind speed was analyzed using correlation coefficient method. [ Result] （ 1 ） Barehan dune and barehan chains in Hexi desert area of Gansu were mainly consisted of fine sands and medium sands at the depth of 0 -5 cm： the sand particle in Gulang desert area was fine, which had significant difference with that in Jinchang, Linze, Jinta and Minqin desert areas. （2） Medium sands gradually increased from the bottom of windward slope to the dune peak in both barchan dune and barchan chain. On the windward slope of barehan dune, fine sands gradual- ly increased from the middle to both sides, while coarse sands and medium sands gradually decreased. On the windward slope of barehan chain, fine sands first de- creased then increased from the middle to NE side, but first increased then decreased from the middle to SW side. （3） In terma of particle size, there were great variations between fine sands and coarse sands ; for dune parts, there were great variations between dune peak and leewant slope toe; for dune types, the variation of fine sands in various parts of barchan chain was greater than that of barchan dune, while differentiation degree of medium sands and fine sands was greater than that of barchan dune. The particle size of fine sands was positively correlated with wind speed, and that of medium sands was negatively correlated with wind speed. [ Conclusion] The formation environment of particle size of berehan dune mainly included sand source and dynmnic source, and wind speed was the dynamic source for particle size distribution of barchan dune.
基金Supported by the National Natural Science Foundation of China(21676007,21506005)
文摘In this study, the mean droplet diameter in the cavity zone and the total mass transfer area of a multi-stage highspeed disperser(HSD) reactor with different packing combinations were measured and evaluated. The effects of rotational speed and packing radius, as well as the packing ring radius and numbers, on the mean droplet diameter and the total mass transfer area were evaluated. A model was established to calculate the mass transfer area in the cavity zone in the HSD reactor, and it was found that the packings contribute 61%–82% of the total mass transfer area. A correlation for predicting the mass transfer area in the packing zone was regressed by the dimensionless analysis method. An enhancement factor based on the mass transfer area in the packing zone was proposed to evaluate the effect of packing combination on mass transfer area. Two optimum packing combinations were proposed in consideration of the mean droplet diameter and the enhancement factor.
