Unsteady dielectric barrier discharge（DBD） plasma aerodynamic actuation technology is employed to suppress airfoil stall separation and the technical parameters are explored with wind tunnel experiments on an NACA00...Unsteady dielectric barrier discharge（DBD） plasma aerodynamic actuation technology is employed to suppress airfoil stall separation and the technical parameters are explored with wind tunnel experiments on an NACA0015 airfoil by measuring the surface pressure distribution of the airfoil.The performance of the DBD aerodynamic actuation for airfoil stall separation suppression is evaluated under DBD voltages from 2000 V to 4000 V and the duty cycles varied in the range of 0.1 to 1.0.It is found that higher lift coefficients and lower threshold voltages are achieved under the unsteady DBD aerodynamic actuation with the duty cycles less than 0.5as compared to that of the steady plasma actuation at the same free-stream speeds and attack angles,indicating a better flow control performance.By comparing the lift coefficients and the threshold voltages,an optimum duty cycle is determined as 0.25 by which the maximum lift coefficient and the minimum threshold voltage are obtained at the same free-stream speed and attack angle.The non-uniform DBD discharge with stronger discharge in the positive half cycle due to electrons deposition on the dielectric slabs and the suppression of opposite momentum transfer due to the intermittent discharge with cutoff of the negative half cycle are responsible for the observed optimum duty cycle.展开更多
The distribution of heat duties among individual separation subsystems and other aspects of heat integration in such systems are reviewed. Heat integration for different separation processes is investigated, using the...The distribution of heat duties among individual separation subsystems and other aspects of heat integration in such systems are reviewed. Heat integration for different separation processes is investigated, using the pinch point method. Such a study will provide theoretical guide lines for the proper choice of a desirable separation process.展开更多
针对传统的RBAC模型不能表达复杂的工作流安全访问控制约束的缺点,提出了一个适合工作流系统的基于多权角色和规则的条件化安全访问控制模型CMWRRBSAC(conditioned multi-weighted role and rule based secure access control model)。...针对传统的RBAC模型不能表达复杂的工作流安全访问控制约束的缺点,提出了一个适合工作流系统的基于多权角色和规则的条件化安全访问控制模型CMWRRBSAC(conditioned multi-weighted role and rule based secure access control model)。该模型基于传统的RBAC模型,提出了基于动态角色分配的条件化RBAC方法,定义了基于多权角色的工作流系统访问授权新概念,并针对多个角色和多个用户协同激活任务的序约束问题,给出了基于令牌的序约束算法和基于加权角色综合的序约束算法,讨论了一个基于规则的职责分离约束建模方法,并给出了改进的规则一致性检验算法。展开更多
基金supported by National Natural Science Foundation of China(No.21276036)Liaoning Provincial Natural Science Foundation of China(No.2015020123)the Fundamental Research Funds for the Central Universities of China(No.3132015154)
文摘Unsteady dielectric barrier discharge（DBD） plasma aerodynamic actuation technology is employed to suppress airfoil stall separation and the technical parameters are explored with wind tunnel experiments on an NACA0015 airfoil by measuring the surface pressure distribution of the airfoil.The performance of the DBD aerodynamic actuation for airfoil stall separation suppression is evaluated under DBD voltages from 2000 V to 4000 V and the duty cycles varied in the range of 0.1 to 1.0.It is found that higher lift coefficients and lower threshold voltages are achieved under the unsteady DBD aerodynamic actuation with the duty cycles less than 0.5as compared to that of the steady plasma actuation at the same free-stream speeds and attack angles,indicating a better flow control performance.By comparing the lift coefficients and the threshold voltages,an optimum duty cycle is determined as 0.25 by which the maximum lift coefficient and the minimum threshold voltage are obtained at the same free-stream speed and attack angle.The non-uniform DBD discharge with stronger discharge in the positive half cycle due to electrons deposition on the dielectric slabs and the suppression of opposite momentum transfer due to the intermittent discharge with cutoff of the negative half cycle are responsible for the observed optimum duty cycle.
基金Supported by the Research Promotion Foundation for Returned Scholar of the China Education Commission.
文摘The distribution of heat duties among individual separation subsystems and other aspects of heat integration in such systems are reviewed. Heat integration for different separation processes is investigated, using the pinch point method. Such a study will provide theoretical guide lines for the proper choice of a desirable separation process.
文摘针对传统的RBAC模型不能表达复杂的工作流安全访问控制约束的缺点,提出了一个适合工作流系统的基于多权角色和规则的条件化安全访问控制模型CMWRRBSAC(conditioned multi-weighted role and rule based secure access control model)。该模型基于传统的RBAC模型,提出了基于动态角色分配的条件化RBAC方法,定义了基于多权角色的工作流系统访问授权新概念,并针对多个角色和多个用户协同激活任务的序约束问题,给出了基于令牌的序约束算法和基于加权角色综合的序约束算法,讨论了一个基于规则的职责分离约束建模方法,并给出了改进的规则一致性检验算法。
