为提高培养飞行员的效率和质量,节约费用,从整体上设计并实现了一种实时的、面向网络的飞行系统仿真模型。为了使其具有通用性及实时性,采用数据驱动方式,并通过使用稳定系数方式单独设计了一种适用的空气动力的数学模型。通过简单的配置用XML(extensib le M arkup Language)格式描述的配置文件,可以同时模拟各种类型的飞机飞行驾驶,为飞行员的飞行模拟训练提供了仿真平台,模型的建立方法可以为同类设计和研究提供借鉴。实践证明,本模型在通用性、实时性以及仿真度等方面基本符合要求,应用此模型实现了某种国产初级教练机的仪表飞行系统,并被应用于飞行员的仪表飞行训练中。测试结果表明,如果不加控制信号,飞机能保持平飞状态达30 s以上。
传统的RBAC访问控制模型已经不能表达复杂的工作流安全访问控制约束。基于传统的RBAC模型,提出了一个新的基于双权角色的条件化RBAC访问控制模型CRDWR(conditioned RBAC based on double-weightedroles)。阐述了基于动态角色分配的条件化RBAC策略,定义了基于双权角色的工作流系统访问授权新概念,并针对多个角色协同执行任务的序约束问题,给出了基于令牌的序约束算法。该模型能够表达复杂的工作流安全访问控制约束。
We propose an algorithm for learning hierarchical user interest models according to the Web pages users have browsed. In this algorithm, the interests of a user are represented into a tree which is called a user interest tree, the content and the structure of which can change simultaneously to adapt to the changes in a user＇s interests. This expression represents a user＇s specific and general interests as a continuurn. In some sense, specific interests correspond to shortterm interests, while general interests correspond to longterm interests. So this representation more really reflects the users＇ interests. The algorithm can automatically model a us er＇s multiple interest domains, dynamically generate the in terest models and prune a user interest tree when the number of the nodes in it exceeds given value. Finally, we show the experiment results in a Chinese Web Site.
