The reliability assessment problem for products subject to degradation and random shocks is investigated. Two kinds of probabilistic models are constructed, in which the dependent competing failure process is consider...The reliability assessment problem for products subject to degradation and random shocks is investigated. Two kinds of probabilistic models are constructed, in which the dependent competing failure process is considered. First, based on the assumption of cumulative shock, the probabilistic models for hard failure and soft failure are built respectively. On this basis, the dependent competing failure model involving degradation and shock processes is established. Furthermore, the situation of the shifting-threshold is also considered, in which the hard failure threshold value decreases to a lower level after the arrival of a certain number of shocks. A case study of fatigue crack growth is given to illustrate the proposed models. Numerical results show that shock has a significant effect on the failure process; meanwhile, the effect will be magnified when the value of the hard threshold shifts to a lower level.展开更多
In the commercial utilization of rigid ceramic filters, the performance of pulse cleaning has crucial effects on the long-term stable operation. In order to get a clear insight into the nature of this cleaning process...In the commercial utilization of rigid ceramic filters, the performance of pulse cleaning has crucial effects on the long-term stable operation. In order to get a clear insight into the nature of this cleaning process and provide a solid basis for industrial applications, the flow in ceramic candle filter was investigated. The flow in the pulse-jetspace and inside the ceramic candle is regarded as two- dimensional, unsteady, compressible flow, and numerical simulation is carried out by computational fluid dynamics. The numerical predictions of flow field are in good agreement with the experimental measurements. Effects of the candle diameter, the separation distance between the nozzle and the candle injector and the length of the candle on the flowfield have been numerically analyzed to provide the basis for the optimum design of the pulse cleaning system.展开更多
Resuspension of bed materials absorbing pollutants potentially poses unpredictable challenges to water management in alluvial rivers and its mechanism of transport has not been widely recognized.In this study,a transp...Resuspension of bed materials absorbing pollutants potentially poses unpredictable challenges to water management in alluvial rivers and its mechanism of transport has not been widely recognized.In this study,a transport equation that defines the movement of pollutants adsorbed on the bed materials in the active bed layer is established,on the basis of mass conservation law and continuum theory.The transport equation is coupled into the 1-D mathematical model to numerically investigate water pollution process due to the scour of the bed sediment adsorbing pollutants.Comparisons with the situation in which the dynamics of the active bed layer is not considered indicate that the periodical evolution of the bed layer plays an innegligible role in the pollution process due to sediment re-suspension.Furthermore,comparisons of the results with available experimental observations are presented,and fairly good agreement is obtained.展开更多
基金The National Natural Science Foundation of China(No.50405021)Graduate Training Innovative Projects Foundation of Jiangsu Province(No.CXLX12_0081)
文摘The reliability assessment problem for products subject to degradation and random shocks is investigated. Two kinds of probabilistic models are constructed, in which the dependent competing failure process is considered. First, based on the assumption of cumulative shock, the probabilistic models for hard failure and soft failure are built respectively. On this basis, the dependent competing failure model involving degradation and shock processes is established. Furthermore, the situation of the shifting-threshold is also considered, in which the hard failure threshold value decreases to a lower level after the arrival of a certain number of shocks. A case study of fatigue crack growth is given to illustrate the proposed models. Numerical results show that shock has a significant effect on the failure process; meanwhile, the effect will be magnified when the value of the hard threshold shifts to a lower level.
基金Supported by the National Natural Science Foundation of China(No.59976023)
文摘In the commercial utilization of rigid ceramic filters, the performance of pulse cleaning has crucial effects on the long-term stable operation. In order to get a clear insight into the nature of this cleaning process and provide a solid basis for industrial applications, the flow in ceramic candle filter was investigated. The flow in the pulse-jetspace and inside the ceramic candle is regarded as two- dimensional, unsteady, compressible flow, and numerical simulation is carried out by computational fluid dynamics. The numerical predictions of flow field are in good agreement with the experimental measurements. Effects of the candle diameter, the separation distance between the nozzle and the candle injector and the length of the candle on the flowfield have been numerically analyzed to provide the basis for the optimum design of the pulse cleaning system.
基金supported by the National Natural Science Foundation of China(Grant No.51109064)the State Key Program of National Science Foundation of China(Grant No.51239003)the National Basic Research Program of China("973"Project)(Grant No.2011CB403303)
文摘Resuspension of bed materials absorbing pollutants potentially poses unpredictable challenges to water management in alluvial rivers and its mechanism of transport has not been widely recognized.In this study,a transport equation that defines the movement of pollutants adsorbed on the bed materials in the active bed layer is established,on the basis of mass conservation law and continuum theory.The transport equation is coupled into the 1-D mathematical model to numerically investigate water pollution process due to the scour of the bed sediment adsorbing pollutants.Comparisons with the situation in which the dynamics of the active bed layer is not considered indicate that the periodical evolution of the bed layer plays an innegligible role in the pollution process due to sediment re-suspension.Furthermore,comparisons of the results with available experimental observations are presented,and fairly good agreement is obtained.
