Among the intrinsic properties of some materials,e.g.,foams,porous materials,and granular materials,are their ability to mitigate shock waves.This paper investigated shock wave mitigation by a sandwich panel with a gr...Among the intrinsic properties of some materials,e.g.,foams,porous materials,and granular materials,are their ability to mitigate shock waves.This paper investigated shock wave mitigation by a sandwich panel with a granular core.Numerical simulations and experimental tests were performed using Autodyn hydro-code software and a shock tube,respectively.The smoothed particle hydrodynamics(SPH)method was used to model granular materials.Sawdust and pumice,whose properties were determined by several compression tests,were used as granular materials in the sandwich panel core.These granular materials possess many mechanisms,including compacting(e.g.,sawdust)and crushing(e.g.,pumice)that mitigate shock/blast wave.The results indicated the ineffectiveness of using a core with low thickness,yet it was demonstrated to be effective with high thickness.Low-thickness pumice yielded better results for wave mitigation.The use of these materials with a core with appropriate core reduces up to 88%of the shock wave.The results of the experiments and numerical simulations were compared,suggesting a good agreement between the two.This indicates the accuracy of simulation and the ability of the SPH method to modeling granular material under shock loading.The effects of grain size and the coefficient of friction between grains have also been investigated using simulation,implying that increasing the grain size and coefficient of friction between grains both reduce overpressure.展开更多
A water distribution problem in the Mexican Valley is modeled first as a three-person noncooperative game. Each player has a five-dimensional strategy vector, the strategy sets are defined by 15 linear constraints, an...A water distribution problem in the Mexican Valley is modeled first as a three-person noncooperative game. Each player has a five-dimensional strategy vector, the strategy sets are defined by 15 linear constraints, and the three payoff functions are also linear. A nonlinear optimization problem is first formulated to obtain the Nash equilibrium based on the Kuhn-Tucker conditions, and then, duality theorem is used to develop a computational procedure. The problem can also be considered as a conflict between the three players. The non-symmetric Nash bargaining solution is suggested to find the solution. Multiobjective programming is an alternative solution concept, when the water supply of the three players are the objectives, and the water authority is considered to be the decision maker. The optimal water distribution strategies are determined by using these solution concepts and methods.展开更多
文摘Among the intrinsic properties of some materials,e.g.,foams,porous materials,and granular materials,are their ability to mitigate shock waves.This paper investigated shock wave mitigation by a sandwich panel with a granular core.Numerical simulations and experimental tests were performed using Autodyn hydro-code software and a shock tube,respectively.The smoothed particle hydrodynamics(SPH)method was used to model granular materials.Sawdust and pumice,whose properties were determined by several compression tests,were used as granular materials in the sandwich panel core.These granular materials possess many mechanisms,including compacting(e.g.,sawdust)and crushing(e.g.,pumice)that mitigate shock/blast wave.The results indicated the ineffectiveness of using a core with low thickness,yet it was demonstrated to be effective with high thickness.Low-thickness pumice yielded better results for wave mitigation.The use of these materials with a core with appropriate core reduces up to 88%of the shock wave.The results of the experiments and numerical simulations were compared,suggesting a good agreement between the two.This indicates the accuracy of simulation and the ability of the SPH method to modeling granular material under shock loading.The effects of grain size and the coefficient of friction between grains have also been investigated using simulation,implying that increasing the grain size and coefficient of friction between grains both reduce overpressure.
文摘A water distribution problem in the Mexican Valley is modeled first as a three-person noncooperative game. Each player has a five-dimensional strategy vector, the strategy sets are defined by 15 linear constraints, and the three payoff functions are also linear. A nonlinear optimization problem is first formulated to obtain the Nash equilibrium based on the Kuhn-Tucker conditions, and then, duality theorem is used to develop a computational procedure. The problem can also be considered as a conflict between the three players. The non-symmetric Nash bargaining solution is suggested to find the solution. Multiobjective programming is an alternative solution concept, when the water supply of the three players are the objectives, and the water authority is considered to be the decision maker. The optimal water distribution strategies are determined by using these solution concepts and methods.
