Permeability is a vital property of rock mass, which is highly affected by tectonic stress and human engineering activities. A comprehensive monitoring of pore pressure and flow rate distributions inside the rock mass...Permeability is a vital property of rock mass, which is highly affected by tectonic stress and human engineering activities. A comprehensive monitoring of pore pressure and flow rate distributions inside the rock mass is very important to elucidate the permeability evolution mechanisms, which is difficult to realize in laboratory, but easy to be achieved in numerical simulations. Therefore, the particle flow code （PFC）, a discrete element method, is used to simulate permeability behaviors of rock materials in this study. Owe to the limitation of the existed solid-fluid coupling algorithm in PFC, an improved flow-coupling algorithm is presented to better reflect the preferential flow in rock fractures. The comparative analysis is conducted between original and improved algorithm when simulating rock permeability evolution during triaxial compression, showing that the improved algorithm can better describe the experimental phenomenon. Furthermore, the evolution of pore pressure and flow rate distribution during the flow process are analyzed by using the improved algorithm. It is concluded that during the steady flow process in the fractured specimen, the pore pressure and flow rate both prefer transmitting through the fractures rather than rock matrix. Based on the results, fractures are divided into the following three types： I） fractures link to both the inlet and outlet, II） fractures only link to the inlet, and III） fractures only link to the outlet. The type I fracture is always the preferential propagating path for both the pore pressure and flow rate. For type II fractures, the pore pressure increases and then becomes steady. However, the flow rate increases first and begins to decrease after the flow reaches the stop end of the fracture and finally vanishes. There is no obvious pore pressure or flow rate concentration within type III fractures.展开更多
The n-way combination testing is a specification-based testing criterion, which requires that for a system consisted of a few parameters, every combination of valid values of arbitrary n(n >_2) parameters be covere...The n-way combination testing is a specification-based testing criterion, which requires that for a system consisted of a few parameters, every combination of valid values of arbitrary n(n >_2) parameters be covered by at least one test. This letter proposed two different test generation algorithms based on combinatorial design for the n-way coverage criterion. The automatic test generators are implemented and some valuable empirical results are obtained.展开更多
In this paper an improved fog effect algorithm in VRML and X3 D is presented with respect to expressing density. The fundamental idea in the approach is to adapt local fog density having influence on Iocal regions wit...In this paper an improved fog effect algorithm in VRML and X3 D is presented with respect to expressing density. The fundamental idea in the approach is to adapt local fog density having influence on Iocal regions with various grades of fog density whereas existing VRML and X3 D only make use of global fog effect. Several filters for making different fog density are presented along with experiments showing the correctness of the proposed method.展开更多
It is scientifically important science value and engineering promising to develop the buoyancy-lift integrated hybrid airship for high attitude platform.Through the numerical method,a new tandem wings hybrid airship w...It is scientifically important science value and engineering promising to develop the buoyancy-lift integrated hybrid airship for high attitude platform.Through the numerical method,a new tandem wings hybrid airship with both higher utility value and economy efficiency was obtained and its total performance and technical parameters were analyzed in detail.In order to further improve the lift-drag characteristics,we implemented the optimization design for aerodynamic configuration of tandem wings hybrid airship via the response surface method.The results indicate that the tandem wings hybrid airship has considerable volume efficiency and higher aerodynamic characteristics.After optimization,the lift-drag ratio of this hybrid airship was increased by 6.08%.In a given gross lift condition,tandem wings hybrid airship may provide more payload and specific productivity.Furthermore,the size of tandem airship is smaller so the demand for skin flexible materials can be reduced.Results of this study could serve as a new approach to designing buoyancy-lifting integrated hybrid airship.展开更多
基金Project（BK20150005） supported by the Natural Science Foundation of Jiangsu Province for Distinguished Young Scholars, China Project（2015XKZD05） supported by the Fundamental Research Funds for the Central Universities, China
文摘Permeability is a vital property of rock mass, which is highly affected by tectonic stress and human engineering activities. A comprehensive monitoring of pore pressure and flow rate distributions inside the rock mass is very important to elucidate the permeability evolution mechanisms, which is difficult to realize in laboratory, but easy to be achieved in numerical simulations. Therefore, the particle flow code （PFC）, a discrete element method, is used to simulate permeability behaviors of rock materials in this study. Owe to the limitation of the existed solid-fluid coupling algorithm in PFC, an improved flow-coupling algorithm is presented to better reflect the preferential flow in rock fractures. The comparative analysis is conducted between original and improved algorithm when simulating rock permeability evolution during triaxial compression, showing that the improved algorithm can better describe the experimental phenomenon. Furthermore, the evolution of pore pressure and flow rate distribution during the flow process are analyzed by using the improved algorithm. It is concluded that during the steady flow process in the fractured specimen, the pore pressure and flow rate both prefer transmitting through the fractures rather than rock matrix. Based on the results, fractures are divided into the following three types： I） fractures link to both the inlet and outlet, II） fractures only link to the inlet, and III） fractures only link to the outlet. The type I fracture is always the preferential propagating path for both the pore pressure and flow rate. For type II fractures, the pore pressure increases and then becomes steady. However, the flow rate increases first and begins to decrease after the flow reaches the stop end of the fracture and finally vanishes. There is no obvious pore pressure or flow rate concentration within type III fractures.
文摘The n-way combination testing is a specification-based testing criterion, which requires that for a system consisted of a few parameters, every combination of valid values of arbitrary n(n >_2) parameters be covered by at least one test. This letter proposed two different test generation algorithms based on combinatorial design for the n-way coverage criterion. The automatic test generators are implemented and some valuable empirical results are obtained.
文摘In this paper an improved fog effect algorithm in VRML and X3 D is presented with respect to expressing density. The fundamental idea in the approach is to adapt local fog density having influence on Iocal regions with various grades of fog density whereas existing VRML and X3 D only make use of global fog effect. Several filters for making different fog density are presented along with experiments showing the correctness of the proposed method.
基金supported by the National High-Tech Research and Development Program of China (Grant No. 863-2007AA11Z243)Foundation for Basic Research of Northwestern Polytechnic University (Grant No.JC-201103)
文摘It is scientifically important science value and engineering promising to develop the buoyancy-lift integrated hybrid airship for high attitude platform.Through the numerical method,a new tandem wings hybrid airship with both higher utility value and economy efficiency was obtained and its total performance and technical parameters were analyzed in detail.In order to further improve the lift-drag characteristics,we implemented the optimization design for aerodynamic configuration of tandem wings hybrid airship via the response surface method.The results indicate that the tandem wings hybrid airship has considerable volume efficiency and higher aerodynamic characteristics.After optimization,the lift-drag ratio of this hybrid airship was increased by 6.08%.In a given gross lift condition,tandem wings hybrid airship may provide more payload and specific productivity.Furthermore,the size of tandem airship is smaller so the demand for skin flexible materials can be reduced.Results of this study could serve as a new approach to designing buoyancy-lifting integrated hybrid airship.
