PDH(Plesiochronous Digital Hierarchy)是窄带传输时代的一类传输系统.之所以命名为准同步是因为它复用的各支路信号不是来自于同一个时钟源,尽管各支路的速率标称值相同,但实际上却存在一定的容差,因此在复用之前必须对各支路信号进...PDH(Plesiochronous Digital Hierarchy)是窄带传输时代的一类传输系统.之所以命名为准同步是因为它复用的各支路信号不是来自于同一个时钟源,尽管各支路的速率标称值相同,但实际上却存在一定的容差,因此在复用之前必须对各支路信号进行码速调整,各支路在复用前具有相同的码速,通常采用脉冲插入法,即在各支路中人为地插入一些必要的脉冲,通过控制插入脉冲的多少使各支路的速率达到一致,从而实现码速统一.展开更多
Airway networks are the basic carriers of air traffic.Characterizing airway networks will significantly improve the operating efficiency of aviation.This study is targeted at the airway network composed of 1479 waypoi...Airway networks are the basic carriers of air traffic.Characterizing airway networks will significantly improve the operating efficiency of aviation.This study is targeted at the airway network composed of 1479 waypoints in 2018 of China.Together with spatial structures,traffic flow characteristics,and the dominating traffic flow,four airway network models are constructed from the perspective of complex networks,including physical airway network,airway traffic network,directed airway traffic network,and dominance-based directed airway traffic network.Then the topological characteristics of different networks are statistically analyzed by using typical network measure indices,and the differences of these indices among different networks are investigated.Thereby,composite indices are proposed.Statistical results show that the airway network under the influence of traffic flows exhibits richer heterogeneity and asymmetrical between-node relationship,and the distributions of indices among different networks are significantly different.Comparative analysis of composite indices and traffic flows show that some waypoints yield great results in multiple composite indices and traffic volumes;some waypoints display large results in multiple composite indices but low traffic flows,and other waypoints only perform well in certain composite indices.The importance levels of waypoints are divided,by the K-means method based on degree composite index,betweenness composite index and closeness composite index,into three levels,and the reasonableness of clustering results is validated by the statistical results of traffic flows,airport number,and flight delay.展开更多
This paper discussed the necessity of establishing a computer network in a mining railway transport management system. The network structure and the system security design, associated with the real development conditi...This paper discussed the necessity of establishing a computer network in a mining railway transport management system. The network structure and the system security design, associated with the real development condition of a mining area, were brought forward, and the system evaluation was given.展开更多
文摘PDH(Plesiochronous Digital Hierarchy)是窄带传输时代的一类传输系统.之所以命名为准同步是因为它复用的各支路信号不是来自于同一个时钟源,尽管各支路的速率标称值相同,但实际上却存在一定的容差,因此在复用之前必须对各支路信号进行码速调整,各支路在复用前具有相同的码速,通常采用脉冲插入法,即在各支路中人为地插入一些必要的脉冲,通过控制插入脉冲的多少使各支路的速率达到一致,从而实现码速统一.
基金This work was supported by the National Natural Science Foundations of China(Nos.U1833103,71801215,and U1933103)。
文摘Airway networks are the basic carriers of air traffic.Characterizing airway networks will significantly improve the operating efficiency of aviation.This study is targeted at the airway network composed of 1479 waypoints in 2018 of China.Together with spatial structures,traffic flow characteristics,and the dominating traffic flow,four airway network models are constructed from the perspective of complex networks,including physical airway network,airway traffic network,directed airway traffic network,and dominance-based directed airway traffic network.Then the topological characteristics of different networks are statistically analyzed by using typical network measure indices,and the differences of these indices among different networks are investigated.Thereby,composite indices are proposed.Statistical results show that the airway network under the influence of traffic flows exhibits richer heterogeneity and asymmetrical between-node relationship,and the distributions of indices among different networks are significantly different.Comparative analysis of composite indices and traffic flows show that some waypoints yield great results in multiple composite indices and traffic volumes;some waypoints display large results in multiple composite indices but low traffic flows,and other waypoints only perform well in certain composite indices.The importance levels of waypoints are divided,by the K-means method based on degree composite index,betweenness composite index and closeness composite index,into three levels,and the reasonableness of clustering results is validated by the statistical results of traffic flows,airport number,and flight delay.
文摘This paper discussed the necessity of establishing a computer network in a mining railway transport management system. The network structure and the system security design, associated with the real development condition of a mining area, were brought forward, and the system evaluation was given.
