The effect of vertical internal baffles on the particle mixing and graindrying characteristics in a batch fluidized bed column is investigated. Experimental work wascarried out in a 3m high rectangular fluidized bed d...The effect of vertical internal baffles on the particle mixing and graindrying characteristics in a batch fluidized bed column is investigated. Experimental work wascarried out in a 3m high rectangular fluidized bed dryer of cross sectional area of 0.15 m x 0.61 mat different operating conditions using paddy, a group D particle, as the fluidizing material. Theresults of the study showed that the fluidized bed dryer system with vertical internal baffles gavebetter particle mixing effect in the bed of particles than that without vertical internal baffles.This is due to the fact that the vertical internal baffle act as gas bubble breakers by breaking upthe large gas bubbles into smaller ones. The smaller bubbles cause a more vigorous mixing in the bedof particles before finally erupting at the bed surface. This improves the contacting efficiencyand enhanced the heat and mass transfer of the fluidized bed system. Thus a higher drying rate wasobtained in the falling rate period because the higher contacting efficiency increases theevaporation rate at the particle surface. However, the drying rate in the diffusion region showslittle improvement because the moisture diffusivity does not depend on the contacting efficiency.The fluidized bed dryer with vertical internal baffles could therefore be used in the initial rapiddrying stage in a two stage drying strategy for paddy. The insertion of vertical internal bafflesinto a fluidized bed system improves the processing of Group D particles in a fluidized bed systemespecially if the system is large in scale.展开更多
Purpose： To investigate the changes of cerebral hemodynamics pre- and post-ventricular drainage in patients with posttraumatic acute diffuse brain swelling. Methods： Twenty-four cases of traumatic diffuse brain swel...Purpose： To investigate the changes of cerebral hemodynamics pre- and post-ventricular drainage in patients with posttraumatic acute diffuse brain swelling. Methods： Twenty-four cases of traumatic diffuse brain swelling were analyzed retrospectively. Patients in nonsurgical group were treated by medicine therapy. Patients in surgical group were treated by external ventricular drainage plus medicine therapy. The first CT perfusion scan was completed within 4 -5 h after trauma and scanned again after 7 days. The changes of perfusion parameters in area-of- interest in two groups were analyzed and compared before and after treatment. Results： Compared with the nonsurgical group, the value of cerebral blood volume, cerebral blood flow and mean transit time in bilateral frontal temporoparietal grey matter, basal ganglia, cerebellum, and brain stem at pre- and post-therapy were increased significantly （p 〈 0.05） in surgical group, and consequently the prognosis of patients undergoing surgery was also better than that of nonsurgical group. Conclusion： External ventricular drainage can improve cerebral perfusion and increase survival quality for the patients with posttraumatic acute diffuse brain swelling.展开更多
Under hypersonic flight conditions,the sharp cowl-lip leading edges have to be blunted because of the severe aerodynamic heating.This paper proposes four cowl-lip blunting methods and studies the corresponding flow ch...Under hypersonic flight conditions,the sharp cowl-lip leading edges have to be blunted because of the severe aerodynamic heating.This paper proposes four cowl-lip blunting methods and studies the corresponding flow characteristics and performances of the generic hypersonic inlets by numerical simulation under the design conditions of a flight Mach number of 6 and an altitude of 26 km.The results show that the local shock interference patterns in the vicinity of the blunted cowl-lips have a substantial influence on the flow characteristics of the hypersonic inlets even though the blunting radius is very small,which contribute to a pronounced degradation of the inlet performance.The Equal Length blunting Manner(ELM)is the most optimal in that a nearly even reflection of the ramp shock produces an approximately straight and weak cowl reflection shock.The minimal total pressure loss,the lowest cowl drag,maximum mass-capture and the minimal aeroheating are achieved for the hypersonic inlet.For the other blunting manners,the ramp shock cannot reflect evenly and produces more curved cowl reflection shock.The Type V shock interference pattern occurs for the Cross Section Cutting blunting Manner(CSCM)and the strongest cowl reflection shock gives rise to the largest flow loss and drag.The cowl-lip blunted by the other two blunting manners is subjected to the shock interference pattern that transits with an increase in the blunting radius.Accordingly,the peak heat flux does not fall monotonously with the blunting radius increasing.Moreover,the cowl-lip surface suffers from severe aerothermal load when the shear layer or the supersonic jet impinges on the wall.展开更多
文摘The effect of vertical internal baffles on the particle mixing and graindrying characteristics in a batch fluidized bed column is investigated. Experimental work wascarried out in a 3m high rectangular fluidized bed dryer of cross sectional area of 0.15 m x 0.61 mat different operating conditions using paddy, a group D particle, as the fluidizing material. Theresults of the study showed that the fluidized bed dryer system with vertical internal baffles gavebetter particle mixing effect in the bed of particles than that without vertical internal baffles.This is due to the fact that the vertical internal baffle act as gas bubble breakers by breaking upthe large gas bubbles into smaller ones. The smaller bubbles cause a more vigorous mixing in the bedof particles before finally erupting at the bed surface. This improves the contacting efficiencyand enhanced the heat and mass transfer of the fluidized bed system. Thus a higher drying rate wasobtained in the falling rate period because the higher contacting efficiency increases theevaporation rate at the particle surface. However, the drying rate in the diffusion region showslittle improvement because the moisture diffusivity does not depend on the contacting efficiency.The fluidized bed dryer with vertical internal baffles could therefore be used in the initial rapiddrying stage in a two stage drying strategy for paddy. The insertion of vertical internal bafflesinto a fluidized bed system improves the processing of Group D particles in a fluidized bed systemespecially if the system is large in scale.
文摘Purpose： To investigate the changes of cerebral hemodynamics pre- and post-ventricular drainage in patients with posttraumatic acute diffuse brain swelling. Methods： Twenty-four cases of traumatic diffuse brain swelling were analyzed retrospectively. Patients in nonsurgical group were treated by medicine therapy. Patients in surgical group were treated by external ventricular drainage plus medicine therapy. The first CT perfusion scan was completed within 4 -5 h after trauma and scanned again after 7 days. The changes of perfusion parameters in area-of- interest in two groups were analyzed and compared before and after treatment. Results： Compared with the nonsurgical group, the value of cerebral blood volume, cerebral blood flow and mean transit time in bilateral frontal temporoparietal grey matter, basal ganglia, cerebellum, and brain stem at pre- and post-therapy were increased significantly （p 〈 0.05） in surgical group, and consequently the prognosis of patients undergoing surgery was also better than that of nonsurgical group. Conclusion： External ventricular drainage can improve cerebral perfusion and increase survival quality for the patients with posttraumatic acute diffuse brain swelling.
基金supported by the National Natural Science Foundation of China(Grant Nos.90716014 and 91216115)
文摘Under hypersonic flight conditions,the sharp cowl-lip leading edges have to be blunted because of the severe aerodynamic heating.This paper proposes four cowl-lip blunting methods and studies the corresponding flow characteristics and performances of the generic hypersonic inlets by numerical simulation under the design conditions of a flight Mach number of 6 and an altitude of 26 km.The results show that the local shock interference patterns in the vicinity of the blunted cowl-lips have a substantial influence on the flow characteristics of the hypersonic inlets even though the blunting radius is very small,which contribute to a pronounced degradation of the inlet performance.The Equal Length blunting Manner(ELM)is the most optimal in that a nearly even reflection of the ramp shock produces an approximately straight and weak cowl reflection shock.The minimal total pressure loss,the lowest cowl drag,maximum mass-capture and the minimal aeroheating are achieved for the hypersonic inlet.For the other blunting manners,the ramp shock cannot reflect evenly and produces more curved cowl reflection shock.The Type V shock interference pattern occurs for the Cross Section Cutting blunting Manner(CSCM)and the strongest cowl reflection shock gives rise to the largest flow loss and drag.The cowl-lip blunted by the other two blunting manners is subjected to the shock interference pattern that transits with an increase in the blunting radius.Accordingly,the peak heat flux does not fall monotonously with the blunting radius increasing.Moreover,the cowl-lip surface suffers from severe aerothermal load when the shear layer or the supersonic jet impinges on the wall.
