Based on the blasting theory and stress wave theory, stemming mechanism and movement of stemmed material in rock blasting were analyzed and the calculation expression of stemming lengths was deduced. The blasting expe...Based on the blasting theory and stress wave theory, stemming mechanism and movement of stemmed material in rock blasting were analyzed and the calculation expression of stemming lengths was deduced. The blasting experiment with different stemming lengths was carried out and the results show that the theoretical stemming length, which is 0.73 ~ 0.8 time of burden, is in the range of the experiential length, which is O. 63 - O. 88 time of burden. The blasting results of field experiments with theoretical stemming length are satisfactory, which shows the theoretical derivation and analysis are correct and reliable. The results will supply rock blasting with the theoretical gist of parameters design.展开更多
Optimum design of rider-bicycle mechanisms is very important for customizing bicycles and plays a crucial role in the improvement of athletes' performances and in protection of the riders.Since the birth of the fi...Optimum design of rider-bicycle mechanisms is very important for customizing bicycles and plays a crucial role in the improvement of athletes' performances and in protection of the riders.Since the birth of the first bicycle,people have been keeping optimizing bicycles with respect to physical conditions of human.In modern design,the basic structure of a bicycle has been formulized,while many geographic parameters remain uncertain.In this paper,the bicycle and the human body are considered as a kinematic mechanism,called rider-bicycle mechanism.The optimum design is implemented from the perspective of mechanism.Effort-saving and comfortableness are considered at the same time.The corresponding performance charts are drawn and the relationship between the performances and parameters of seat height,crank length and body parameters are discussed.By using these charts,the optimal design method of bicycle's parameters for a specified person is then founded.Optimum solutions to get suitable seat height and crank length for a person are obtained accordingly.The research is of significance for customizing bicycles and design of bicycle robot.展开更多
We calculated numerically the localization length of one-dimensional Anderson model with correlated diagonal disorder. For zero energy point in the weak disorder limit, we showed that the localization length changes c...We calculated numerically the localization length of one-dimensional Anderson model with correlated diagonal disorder. For zero energy point in the weak disorder limit, we showed that the localization length changes continuously as the correlation of the disorder increases. We found that higher order terms of the correlation must be included into the current perturbation result in order to give the correct localization length, arid to connect smoothly the anomaly at zero correlation with the perturbation result for large correlation.展开更多
文摘Based on the blasting theory and stress wave theory, stemming mechanism and movement of stemmed material in rock blasting were analyzed and the calculation expression of stemming lengths was deduced. The blasting experiment with different stemming lengths was carried out and the results show that the theoretical stemming length, which is 0.73 ~ 0.8 time of burden, is in the range of the experiential length, which is O. 63 - O. 88 time of burden. The blasting results of field experiments with theoretical stemming length are satisfactory, which shows the theoretical derivation and analysis are correct and reliable. The results will supply rock blasting with the theoretical gist of parameters design.
基金supported in part by Tsinghua University Student Research Training (Grant No. 102T0078)the National Natural Science Foundation of China (Grant Nos. 51075222 and 51135008)
文摘Optimum design of rider-bicycle mechanisms is very important for customizing bicycles and plays a crucial role in the improvement of athletes' performances and in protection of the riders.Since the birth of the first bicycle,people have been keeping optimizing bicycles with respect to physical conditions of human.In modern design,the basic structure of a bicycle has been formulized,while many geographic parameters remain uncertain.In this paper,the bicycle and the human body are considered as a kinematic mechanism,called rider-bicycle mechanism.The optimum design is implemented from the perspective of mechanism.Effort-saving and comfortableness are considered at the same time.The corresponding performance charts are drawn and the relationship between the performances and parameters of seat height,crank length and body parameters are discussed.By using these charts,the optimal design method of bicycle's parameters for a specified person is then founded.Optimum solutions to get suitable seat height and crank length for a person are obtained accordingly.The research is of significance for customizing bicycles and design of bicycle robot.
基金Supported by National Natural Science Foundation of China under Grant No.10374093the Knowledge Innovation Project of Chinese Academy of Sciences
文摘We calculated numerically the localization length of one-dimensional Anderson model with correlated diagonal disorder. For zero energy point in the weak disorder limit, we showed that the localization length changes continuously as the correlation of the disorder increases. We found that higher order terms of the correlation must be included into the current perturbation result in order to give the correct localization length, arid to connect smoothly the anomaly at zero correlation with the perturbation result for large correlation.