针对目前城市轨道交通路网乘客出行路径估计准确率不足及直接监测方式受限的问题,提出基于多源监测数据的出行路径估计方法.首先,利用自动售检票(Automatic Fare Collection,AFC)数据、车站换乘断面监测量、区间断面监测量等多源监测数...针对目前城市轨道交通路网乘客出行路径估计准确率不足及直接监测方式受限的问题,提出基于多源监测数据的出行路径估计方法.首先,利用自动售检票(Automatic Fare Collection,AFC)数据、车站换乘断面监测量、区间断面监测量等多源监测数据,基于路网客流时空作用关系,构建符合实际监测情况和乘客出行总体规律的乘客出行路径估计模型.然后,运用计算图结构将模型抽象成一种分层网络,并提出基于正向传播和反向传播技术的模型求解算法.最后,以广州局部地铁路网为例进行分析.研究结果表明:所提出的方法可以实现路网乘客出行路径以及车站换乘客流的估计;在路网监测断面占比为75%时,估计结果的均方误差、均方根误差以及平均绝对百分比误差分别为1.67%、1.83%、1.27%,且误差会随着监测断面占比的增加而降低.展开更多
近年来,低轨卫星星座快速发展,其在军事和民用领域也将发挥越来越重要的作用.如何提高低轨卫星网络的带宽利用率成为保障低轨卫星星座发挥价值的重要研究方向.而传统TCP(Transmission Control Protocol)协议及其变种主要针对地面网络设...近年来,低轨卫星星座快速发展,其在军事和民用领域也将发挥越来越重要的作用.如何提高低轨卫星网络的带宽利用率成为保障低轨卫星星座发挥价值的重要研究方向.而传统TCP(Transmission Control Protocol)协议及其变种主要针对地面网络设计,难以适应长往返时延、高误码率、高动态变化的低轨卫星网络.因此,为了充分利用低轨卫星网络的带宽资源,承载高速率业务,需要针对卫星网络的特点设计新型传输控制协议.首先,分析了低轨卫星网络的特点以及现有传输控制协议在卫星网络中存在的问题;然后,提出了基于路径信息估计和时延区分的新型拥塞控制DDTCP(delay-differentiated TCP)算法.低轨卫星网络端到端时延可能由多种因素引起,DDTCP在源端会保存过去一段时间内的时延信息,进而通过路径时延区分机制对拥塞窗口演化进行分类处理,可以在网络状况发生突变后,快速设置合理的拥塞窗口,避免链路缓存溢出或吞吐下降.实验结果表明,新的传输控制协议DDTCP可以在低轨卫星网络中实现更高、更稳定的吞吐量,与传统拥塞控制算法相比,吞吐量提升19%以上.展开更多
The article is devoted to the evaluation of fractal properties of routing data in computer large scale networks. Implemented the study of percolation network topological structures of large dimension and made their tr...The article is devoted to the evaluation of fractal properties of routing data in computer large scale networks. Implemented the study of percolation network topological structures of large dimension and made their transformation into fractal macrostructure. An example of calculating the fractal dimension of the data path for the boundary of the phase transition between the states of network connectivity. The dependence of the fractal dimension of the percolation cluster on the size of the square δ-cover and conductivity value network of large dimension. It is shown that for the value of the fractal dimension of the route dc ≈ 1.5, network has a stable dynamics of development and size of clusters are optimized with respect to the current load on the network.展开更多
The authors integrate two well-known systems, the Rssler and Lorentz systems,to introduce a new chaotic system, called the Lorentz-Rssler system. Then, taking into account the effect of environmental noise, the author...The authors integrate two well-known systems, the Rssler and Lorentz systems,to introduce a new chaotic system, called the Lorentz-Rssler system. Then, taking into account the effect of environmental noise, the authors incorporate white noise in both Rssler and Lorentz systems to have a corresponding stochastic system. By deriving the uniform a priori estimates for an approximate system and then taking them to the limit,the authors prove the global existence, uniqueness and the pathwise property of solutions to the Lorentz-Rssler system. Moreover, the authors carried out a number of numerical experiments, and the numerical results demonstrate their theoretic analysis and show some new qualitative properties of solutions which reveal that the Lorentz-Ro¨ssler system could be used to design more complex and more secure nonlinear hop-frequence time series.展开更多
文摘针对目前城市轨道交通路网乘客出行路径估计准确率不足及直接监测方式受限的问题,提出基于多源监测数据的出行路径估计方法.首先,利用自动售检票(Automatic Fare Collection,AFC)数据、车站换乘断面监测量、区间断面监测量等多源监测数据,基于路网客流时空作用关系,构建符合实际监测情况和乘客出行总体规律的乘客出行路径估计模型.然后,运用计算图结构将模型抽象成一种分层网络,并提出基于正向传播和反向传播技术的模型求解算法.最后,以广州局部地铁路网为例进行分析.研究结果表明:所提出的方法可以实现路网乘客出行路径以及车站换乘客流的估计;在路网监测断面占比为75%时,估计结果的均方误差、均方根误差以及平均绝对百分比误差分别为1.67%、1.83%、1.27%,且误差会随着监测断面占比的增加而降低.
文摘近年来,低轨卫星星座快速发展,其在军事和民用领域也将发挥越来越重要的作用.如何提高低轨卫星网络的带宽利用率成为保障低轨卫星星座发挥价值的重要研究方向.而传统TCP(Transmission Control Protocol)协议及其变种主要针对地面网络设计,难以适应长往返时延、高误码率、高动态变化的低轨卫星网络.因此,为了充分利用低轨卫星网络的带宽资源,承载高速率业务,需要针对卫星网络的特点设计新型传输控制协议.首先,分析了低轨卫星网络的特点以及现有传输控制协议在卫星网络中存在的问题;然后,提出了基于路径信息估计和时延区分的新型拥塞控制DDTCP(delay-differentiated TCP)算法.低轨卫星网络端到端时延可能由多种因素引起,DDTCP在源端会保存过去一段时间内的时延信息,进而通过路径时延区分机制对拥塞窗口演化进行分类处理,可以在网络状况发生突变后,快速设置合理的拥塞窗口,避免链路缓存溢出或吞吐下降.实验结果表明,新的传输控制协议DDTCP可以在低轨卫星网络中实现更高、更稳定的吞吐量,与传统拥塞控制算法相比,吞吐量提升19%以上.
文摘The article is devoted to the evaluation of fractal properties of routing data in computer large scale networks. Implemented the study of percolation network topological structures of large dimension and made their transformation into fractal macrostructure. An example of calculating the fractal dimension of the data path for the boundary of the phase transition between the states of network connectivity. The dependence of the fractal dimension of the percolation cluster on the size of the square δ-cover and conductivity value network of large dimension. It is shown that for the value of the fractal dimension of the route dc ≈ 1.5, network has a stable dynamics of development and size of clusters are optimized with respect to the current load on the network.
基金supported by the National Natural Science Foundation of China(Nos.11101044,11371065)the Beijing Center for Mathematics and Information Interdisciplinary Sciences
文摘The authors integrate two well-known systems, the Rssler and Lorentz systems,to introduce a new chaotic system, called the Lorentz-Rssler system. Then, taking into account the effect of environmental noise, the authors incorporate white noise in both Rssler and Lorentz systems to have a corresponding stochastic system. By deriving the uniform a priori estimates for an approximate system and then taking them to the limit,the authors prove the global existence, uniqueness and the pathwise property of solutions to the Lorentz-Rssler system. Moreover, the authors carried out a number of numerical experiments, and the numerical results demonstrate their theoretic analysis and show some new qualitative properties of solutions which reveal that the Lorentz-Ro¨ssler system could be used to design more complex and more secure nonlinear hop-frequence time series.
