Soil samples with clay content ranging from 15% to 31%, were taken from three debris flow gullies in Southwest China. Three debris flow slurry samples were prepared and tested with four measuring systems of an Anton P...Soil samples with clay content ranging from 15% to 31%, were taken from three debris flow gullies in Southwest China. Three debris flow slurry samples were prepared and tested with four measuring systems of an Anton Paar Physica MCR301 rheometer, including the concentric cylinder system,the parallel-plate system, the vane geometry, and the ball measuring system. All systems were smoothwalled. Flow curves were plotted and yield stress was determined using the Herschel-Bulkley model,showing differences among the different systems.Flow curves from the concentric cylinder and parallelplate systems involved two distinct regions, the low shear and the high shear regions. Yield stresses determined by data fitting in the low shear region were significantly lower than the values from the inclined channel test which is a practical method for determining yield stress. Flow curves in the high shear region are close to those from the vane geometry and the ball measuring system. The fitted values of yield stress are comparable to the values from the inclined channel test. The differences are caused by wall-slip effects in the low shear region.Vane geometry can capture the stress overshoot phenomenon caused by the destruction of slurry structure, whereas end effects should be considered in the determination of yield stress. The ball measuring system can give reasonable results, and it is applicable for rheological testing of debris flow slurries.展开更多
Force closure and stability problems exist in heavy gripping devices.Based on a typical gripping device for forging operations, the workpiece and the gripping device are innovatively considered as a single mechanism i...Force closure and stability problems exist in heavy gripping devices.Based on a typical gripping device for forging operations, the workpiece and the gripping device are innovatively considered as a single mechanism in this paper,and its global topological configuration is obtained.The changing element method is used to establish the optimized topology geometry of the gripping device by decreasing the degrees of freedom of the gripping mechanism and improving the force closure performance. Therefore,a new idea for the innovative design of heavy-duty forging gripping devices is provided.As the effect of revolute joint friction on loading capacity of the gripping device cannot be ignored,a unified mechanical equation including friction in terms of the topological adjacency matrix is established to analyze the force closure performance and calculate the loading capacity.The conclusions are provided by experiments.展开更多
A method to generate Airy beam by combining the Fresnel holographic lens and the cubic phase of Airy beam is proposed. The detailed theoretical derivation to express the optical transform principle of the proposed met...A method to generate Airy beam by combining the Fresnel holographic lens and the cubic phase of Airy beam is proposed. The detailed theoretical derivation to express the optical transform principle of the proposed method is presented. And excellent experimental results are demonstrated. It is shown that this approach works well and simplifies the experimental facility effectively, especially reducing the optical system length to half of that of the conventional method. In addition, the proposed method can realize the beam propagation trajectory control of Airy beam and generate Airy beam array.展开更多
基金financially supported by the Key Research Program of the Chinese Academy of Sciences (CAS) (Grant No. KZZD-EW-05-01)the Youth Talent Team Program of Institute of Mountain Hazards and Environment, CAS (Grant No. SDSQB-2013-01)the National Natural Science Foundation of China (Grant No. 41201011)
文摘Soil samples with clay content ranging from 15% to 31%, were taken from three debris flow gullies in Southwest China. Three debris flow slurry samples were prepared and tested with four measuring systems of an Anton Paar Physica MCR301 rheometer, including the concentric cylinder system,the parallel-plate system, the vane geometry, and the ball measuring system. All systems were smoothwalled. Flow curves were plotted and yield stress was determined using the Herschel-Bulkley model,showing differences among the different systems.Flow curves from the concentric cylinder and parallelplate systems involved two distinct regions, the low shear and the high shear regions. Yield stresses determined by data fitting in the low shear region were significantly lower than the values from the inclined channel test which is a practical method for determining yield stress. Flow curves in the high shear region are close to those from the vane geometry and the ball measuring system. The fitted values of yield stress are comparable to the values from the inclined channel test. The differences are caused by wall-slip effects in the low shear region.Vane geometry can capture the stress overshoot phenomenon caused by the destruction of slurry structure, whereas end effects should be considered in the determination of yield stress. The ball measuring system can give reasonable results, and it is applicable for rheological testing of debris flow slurries.
文摘Force closure and stability problems exist in heavy gripping devices.Based on a typical gripping device for forging operations, the workpiece and the gripping device are innovatively considered as a single mechanism in this paper,and its global topological configuration is obtained.The changing element method is used to establish the optimized topology geometry of the gripping device by decreasing the degrees of freedom of the gripping mechanism and improving the force closure performance. Therefore,a new idea for the innovative design of heavy-duty forging gripping devices is provided.As the effect of revolute joint friction on loading capacity of the gripping device cannot be ignored,a unified mechanical equation including friction in terms of the topological adjacency matrix is established to analyze the force closure performance and calculate the loading capacity.The conclusions are provided by experiments.
文摘A method to generate Airy beam by combining the Fresnel holographic lens and the cubic phase of Airy beam is proposed. The detailed theoretical derivation to express the optical transform principle of the proposed method is presented. And excellent experimental results are demonstrated. It is shown that this approach works well and simplifies the experimental facility effectively, especially reducing the optical system length to half of that of the conventional method. In addition, the proposed method can realize the beam propagation trajectory control of Airy beam and generate Airy beam array.
