特征基函数的构造是特征基函数方法(characteristic basis function method,CBFM)的关键步骤之一,传统的CBF构造方法(construction of characteristic basis functions,CBFs)是在子区域上应用矩量法(methodof moment,MoM),因此需要消耗...特征基函数的构造是特征基函数方法(characteristic basis function method,CBFM)的关键步骤之一,传统的CBF构造方法(construction of characteristic basis functions,CBFs)是在子区域上应用矩量法(methodof moment,MoM),因此需要消耗大量的计算时间。为降低构造过程的计算量,提高电大目标电磁散射的计算效率,提出了基于高频近似方法的特征基函数快速构造方法,针对边缘效应引入了等效边缘流(equivalent edge currents,EEC)修正,可以在保持算法通用性的同时显著提高包含边缘结构的目标散射计算精度。数值结果验证了方法的正确性及高效性。展开更多
In order to avoid internal attacks during data aggregation in wireless sensor networks, a grid-based network architecture fit for monitoring is designed and the algorithms for network division, initialization and grid...In order to avoid internal attacks during data aggregation in wireless sensor networks, a grid-based network architecture fit for monitoring is designed and the algorithms for network division, initialization and grid tree construction are presented. The characteristics of on-off attacks are first studied and monitoring mechanisms are then designed for sensor nodes. A Fast Detection and Slow Recovery (FDSR) algorithm is proposed to prevent on-off attacks by observing the behaviors of the nodes and computing reputations. A recovery mechanism is designed to isolate malicious nodes by identifying the new roles of nodes and updating the grid tree. In the experiments, some situations of on-off attacks are simulated and the results are compared with other approaches. The experimental results indicate that our approach can detect malicious nodes effectively and guarantee secure data aggregation with acceptable energy consumption.展开更多
Coastal erosion is an island-wide problem in Taiwan; about 80% of the island＇s sandy coastline had suffered from erosion over the past few decades. Historically, with the specific tectonic environment and rapid uplif...Coastal erosion is an island-wide problem in Taiwan; about 80% of the island＇s sandy coastline had suffered from erosion over the past few decades. Historically, with the specific tectonic environment and rapid uplifting rate, lots of sediment had been yielded and transported to the coastal area that resulted in an advancing shoreline. Taiwan economically moved from a developing country to a developed one; a lot of human intervention had been made along the island coast. These are the major factors on recent coastal erosion. Even actions such as building of stabilization structures may inadvertently increase erosion. Some intervention examples are chosen to address how human-induced change made the profound impact on coastal erosion in Taiwan. All the information serves to provide a better understanding of the coastal processes, and a better response to the erosion problem.展开更多
基金This work was supported by the National Natural Science Foundation of China under Grant No. 60873199.
文摘In order to avoid internal attacks during data aggregation in wireless sensor networks, a grid-based network architecture fit for monitoring is designed and the algorithms for network division, initialization and grid tree construction are presented. The characteristics of on-off attacks are first studied and monitoring mechanisms are then designed for sensor nodes. A Fast Detection and Slow Recovery (FDSR) algorithm is proposed to prevent on-off attacks by observing the behaviors of the nodes and computing reputations. A recovery mechanism is designed to isolate malicious nodes by identifying the new roles of nodes and updating the grid tree. In the experiments, some situations of on-off attacks are simulated and the results are compared with other approaches. The experimental results indicate that our approach can detect malicious nodes effectively and guarantee secure data aggregation with acceptable energy consumption.
文摘Coastal erosion is an island-wide problem in Taiwan; about 80% of the island＇s sandy coastline had suffered from erosion over the past few decades. Historically, with the specific tectonic environment and rapid uplifting rate, lots of sediment had been yielded and transported to the coastal area that resulted in an advancing shoreline. Taiwan economically moved from a developing country to a developed one; a lot of human intervention had been made along the island coast. These are the major factors on recent coastal erosion. Even actions such as building of stabilization structures may inadvertently increase erosion. Some intervention examples are chosen to address how human-induced change made the profound impact on coastal erosion in Taiwan. All the information serves to provide a better understanding of the coastal processes, and a better response to the erosion problem.
