Some depression cells with heights lower than their surrounding cells may often be found in Grid-based digital elevation models (DEM) dataset due to sampling errors.The depression-filling algorithm presented by Planch...Some depression cells with heights lower than their surrounding cells may often be found in Grid-based digital elevation models (DEM) dataset due to sampling errors.The depression-filling algorithm presented by Planchon and Darboux works very quickly compared to other published methods.Despite its simplicity and deli-cacy,this algorithm remains difficult to understand due to its three complex subroutines and its recursive execution.Another fast algorithm is presented in this article.The main idea of this new algorithm is as follows:first,the DEM dataset is viewed as an island and the outer space as an ocean;when the ocean level increases,the DEM cells on the island's boundary will be inundated;when a cell is inundated for the first time,its elevation is increased to the ocean level at that moment;after the ocean has inun-dated the entire DEM,all of the depressions are filled.The depression-removing processing is performed using a priority queue.Theoretically,this new algorithm is a fast algorithm despite the fact that it runs more slowly than Planchon and Darboux's method.Its time-complexity in both the worst case and in an average case is O(8nlog 2 (m)),which is close to O(n).The running speed of this algorithm depends mainly on the insertion operation of the priority queue.As shown by the tests,the depres-sion-filling effects of this algorithm are correct and valid,and the overall time consumption of this algorithm is less than twice the time consumed by Planchon & Darboux's method for handling a DEM smaller than 2500×2500 cells.More importantly,this new algorithm is simpler and easier to understand than Planchon and Darboux's method This advantage allows the correct program code to be written quickly.展开更多
研究AFDX(Avionics Full Duplex Switched Ethernet)端系统中的数据流调度问题,为解决数据流实时调度的问题,对保证速率的优先级实时调度算法(Priority Real Time scheduling algorithm based on Rate-Guaranteed,PRTRG)进行改进并分析...研究AFDX(Avionics Full Duplex Switched Ethernet)端系统中的数据流调度问题,为解决数据流实时调度的问题,对保证速率的优先级实时调度算法(Priority Real Time scheduling algorithm based on Rate-Guaranteed,PRTRG)进行改进并分析。改进后的PRTRG算法可以通过参数设置有效控制数据流在端系统中的延迟上界,满足数据流调度实时性的要求。在AFDX端系统数据流调度模型下,运用matlab进行仿真并与FIFO(First In First Out)结果进行比对分析,改进PRTRG算法可有效地降低高优先级数据流的调度延迟上界,在原算法基础上提出的数据流等待时间和缓冲区长度等参数,保证了低优先级数据流延迟的确定性要求,解决了数据流实时调度问题。展开更多
针对星载路由设备的发展趋势,即交互速率提升、带宽增加以及设计轻量化,本文提出了一种基于改进轮询的星载高速交换算法的设计方案。该方案采用基于改进RR(Round Robin,轮询)调度算法和PBPW(Priority-based Bandwidth Privilege with We...针对星载路由设备的发展趋势,即交互速率提升、带宽增加以及设计轻量化,本文提出了一种基于改进轮询的星载高速交换算法的设计方案。该方案采用基于改进RR(Round Robin,轮询)调度算法和PBPW(Priority-based Bandwidth Privilege with Weighting,基于优先级并带权重的带宽特权)算法相结合的二级队列调度算法。在第一级调度中,引入优先级轮询调度,确保高优先级的数据帧能够优先转发,同时开放了缓存共享机制,一定程度上避免了拥塞和资源的浪费;在第二级调度中,为每条链路分配了阈值,从而避免了某些链路因“饥饿”而无法得到服务,同时防止了其他链路的拥塞问题。与传统的基于FIFO(First In First Out,先进先出)的简单队列调度算法相比,这种改进的轮询调度机制显著提高了星载路由器的转发速率,并降低了转发时延。此外,通过轮询方式实现了对高优先级数据帧的优先转发,进一步优化了路由器的性能。展开更多
基金financially supported by the National Basic Research Program of China (Grant No.2006CB400502)the Promotion of 100 Young Talent Scientist Project of the Chinese Acad-emy of Sciences (8-057493)the Special Meteorology Project(GYHY(QX)2007-6-1)
文摘Some depression cells with heights lower than their surrounding cells may often be found in Grid-based digital elevation models (DEM) dataset due to sampling errors.The depression-filling algorithm presented by Planchon and Darboux works very quickly compared to other published methods.Despite its simplicity and deli-cacy,this algorithm remains difficult to understand due to its three complex subroutines and its recursive execution.Another fast algorithm is presented in this article.The main idea of this new algorithm is as follows:first,the DEM dataset is viewed as an island and the outer space as an ocean;when the ocean level increases,the DEM cells on the island's boundary will be inundated;when a cell is inundated for the first time,its elevation is increased to the ocean level at that moment;after the ocean has inun-dated the entire DEM,all of the depressions are filled.The depression-removing processing is performed using a priority queue.Theoretically,this new algorithm is a fast algorithm despite the fact that it runs more slowly than Planchon and Darboux's method.Its time-complexity in both the worst case and in an average case is O(8nlog 2 (m)),which is close to O(n).The running speed of this algorithm depends mainly on the insertion operation of the priority queue.As shown by the tests,the depres-sion-filling effects of this algorithm are correct and valid,and the overall time consumption of this algorithm is less than twice the time consumed by Planchon & Darboux's method for handling a DEM smaller than 2500×2500 cells.More importantly,this new algorithm is simpler and easier to understand than Planchon and Darboux's method This advantage allows the correct program code to be written quickly.
文摘研究AFDX(Avionics Full Duplex Switched Ethernet)端系统中的数据流调度问题,为解决数据流实时调度的问题,对保证速率的优先级实时调度算法(Priority Real Time scheduling algorithm based on Rate-Guaranteed,PRTRG)进行改进并分析。改进后的PRTRG算法可以通过参数设置有效控制数据流在端系统中的延迟上界,满足数据流调度实时性的要求。在AFDX端系统数据流调度模型下,运用matlab进行仿真并与FIFO(First In First Out)结果进行比对分析,改进PRTRG算法可有效地降低高优先级数据流的调度延迟上界,在原算法基础上提出的数据流等待时间和缓冲区长度等参数,保证了低优先级数据流延迟的确定性要求,解决了数据流实时调度问题。
文摘针对星载路由设备的发展趋势,即交互速率提升、带宽增加以及设计轻量化,本文提出了一种基于改进轮询的星载高速交换算法的设计方案。该方案采用基于改进RR(Round Robin,轮询)调度算法和PBPW(Priority-based Bandwidth Privilege with Weighting,基于优先级并带权重的带宽特权)算法相结合的二级队列调度算法。在第一级调度中,引入优先级轮询调度,确保高优先级的数据帧能够优先转发,同时开放了缓存共享机制,一定程度上避免了拥塞和资源的浪费;在第二级调度中,为每条链路分配了阈值,从而避免了某些链路因“饥饿”而无法得到服务,同时防止了其他链路的拥塞问题。与传统的基于FIFO(First In First Out,先进先出)的简单队列调度算法相比,这种改进的轮询调度机制显著提高了星载路由器的转发速率,并降低了转发时延。此外,通过轮询方式实现了对高优先级数据帧的优先转发,进一步优化了路由器的性能。
