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Benzene and Toluene Levels Measured with DOAS During Vehicular Restrictions in Beijing 被引量:3
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作者 李素文 谢品华 +1 位作者 韦民红 王江涛 《Chinese Journal of Chemical Physics》 SCIE CAS CSCD 2015年第1期119-122,I0002,共5页
Measurements of atmospheric benzene and toluene were carried out continuously using dif- ferential optical absorption spectroscopy from August 7 to August 28 in Beijing during the period of vehicular restrictions. The... Measurements of atmospheric benzene and toluene were carried out continuously using dif- ferential optical absorption spectroscopy from August 7 to August 28 in Beijing during the period of vehicular restrictions. The correlations between traffic flows and totals of benzene and toluene were studied during the period of vehicular traffic restrictions from August 17 to August 20 and non-traffic restrictions on August 16 and August 21. The correlation coef- ficient was 0.8 between benzene and toluene. And the calculated daily mean value ratios of benzene to toluene were 0.43-0.50. During the period of vehicular restrictions, traffic flows were reduced about 11.8% and the levels of benzene and toluene were reduced by 11.4% and 12.8%, respectively. The vehicle emissions were recognized as the major sources for atmospheric benzene and toluene in Beijing. 展开更多
关键词 Differential optical absorption spectroscopy Benzene and toluene Vehicularrestrictions tramc emissions Traffic flows
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道路交通的流体物理模型与粒子仿真方法 被引量:1
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作者 崔曼 薛惠锋 +1 位作者 陈福振 卜凡彪 《物理学报》 SCIE EI CAS CSCD 北大核心 2017年第22期199-212,共14页
针对受多种因素影响的复杂道路交通系统问题,基于颗粒动力学理论,结合传统的Lighthill-WhithamRichards物理模型,建立道路交通系统的流体物理模型,采用无网格粒子与网格相结合的方法进行数值仿真,并应用于典型道路交通问题的求解.在新... 针对受多种因素影响的复杂道路交通系统问题,基于颗粒动力学理论,结合传统的Lighthill-WhithamRichards物理模型,建立道路交通系统的流体物理模型,采用无网格粒子与网格相结合的方法进行数值仿真,并应用于典型道路交通问题的求解.在新模型中,将车辆比拟为硬颗粒,车辆的跟车比拟为颗粒间的碰撞相互作用,已知道路情况对驾驶员操作车辆的影响比拟为流-粒两相系统中的外部流体驱动力作用,不同车道间车辆的影响比拟为颗粒间的黏性作用,从而在颗粒动力学理论的基础上,推导建立了道路交通系统拟流体模型;引入光滑离散颗粒流体动力学(SDPH)对车辆系统模型进行离散,建立"SDPH车辆"与真实车辆之间的一一对应关系,再结合有限体积方法,对道路交通构建的双流体模型进行求解,建立求解交通流体物理模型的新型仿真方法.最后,采用所建立的模型和方法对车辆汇入以及机非混合对交通系统的影响过程进行了数值仿真,所得结果与实测值符合较好,表明新的模型和方法有效性好、可靠性高,为道路交通问题的解决提供了一条全新的途径. 展开更多
关键词 道路交通问题 颗粒动力学 粒子法 流体物理模型
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Hopf bifurcation and uncontrolled stochastic trafficinduced chaos in an RED-AQM congestion control system 被引量:1
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作者 王俊松 袁睿翕 +1 位作者 高志伟 王德进 《Chinese Physics B》 SCIE EI CAS CSCD 2011年第9期92-97,共6页
We study the Hopf bifurcation and the chaos phenomena in a random early detection-based active queue man- agement (RED-AQM) congestion control system with a communication delay. We prove that there is a critical val... We study the Hopf bifurcation and the chaos phenomena in a random early detection-based active queue man- agement (RED-AQM) congestion control system with a communication delay. We prove that there is a critical value of the communication delay for the stability of the RED-AQM control system. Furthermore, we show that the system will lose its stability and Hopf bifurcations will occur when the delay exceeds the critical value. When the delay is close to its critical value, we demonstrate that typical chaos patterns may be induced by the uncontrolled stochastic traffic in the RED-AQM control system even if the system is still stable, which reveals a new route to the chaos besides the bifurcation in the network congestion control system. Numerical simulations are given to illustrate the theoretical results. 展开更多
关键词 stability Hopf bifurcation CHAOS stochastic tramc
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Properties of train traffic flow in a moving block system 被引量:1
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作者 王敏 曾俊伟 +3 位作者 钱勇生 李文俊 杨芳 贾欣欣 《Chinese Physics B》 SCIE EI CAS CSCD 2012年第7期171-176,共6页
The development direction of railways is toward the improvement of capacity and service quality, where the service quality includes safety, schedule, high speed, and comfort. In light of the existing cellular automato... The development direction of railways is toward the improvement of capacity and service quality, where the service quality includes safety, schedule, high speed, and comfort. In light of the existing cellular automaton models, in this paper, we develop a model to analyze the mixed running processes of trains with maximal speeds of 500 km/h and 350 km/h respectively in the moving block system. In the proposed model, we establish some sound rules to control the running processes of a train, where the rules include the departure rules in the intermediate stations, the overtaking rules, and the conditions of speed limitation for a train stopping at a station or passing through a station. With the consideration of the mixed ratio and the distance between two adjacent stations, the properties of the train traffic flow (including capacity and average speed) are simulated. The numerical results show that the interactions among different trains will affect the capacity, and a proper increase of the spatial distance between two adjacent stations can enhance the capacity and the average speed under the moving block. 展开更多
关键词 train tramc flow moving block cellular automaton model SIMULATION
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基于复杂网络的Internet流量分析
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作者 路兰 杨洪勇 《计算机工程》 CAS CSCD 北大核心 2011年第2期91-93,共3页
基于复杂网络理论对Internet网络结构进行分析,模拟Internet网络中选择服务器的过程,建立一个基于距离和流量的Internet自组织网络结构模型(FDM)。通过仿真Internet网络数据传输过程,分析比较FDM与BBV模型的丢包率,研究Internet网络中... 基于复杂网络理论对Internet网络结构进行分析,模拟Internet网络中选择服务器的过程,建立一个基于距离和流量的Internet自组织网络结构模型(FDM)。通过仿真Internet网络数据传输过程,分析比较FDM与BBV模型的丢包率,研究Internet网络中心连接节点的缓存器容量、处理器速度对网络流量的影响。 展开更多
关键词 复杂网络 网络流量 丢包率 BBV模型
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A lattice traffic model with consideration of preceding mixture traffic information
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作者 李志鹏 刘富强 孙剑 《Chinese Physics B》 SCIE EI CAS CSCD 2011年第8期508-514,共7页
In this paper, the lattice model is presented, incorporating not only site information about preceding cars but also relative currents in front. We derive the stability condition of the extended model by considering a... In this paper, the lattice model is presented, incorporating not only site information about preceding cars but also relative currents in front. We derive the stability condition of the extended model by considering a small perturbation around the homogeneous flow solution and find that the improvement in the stability of traffic flow is obtained by taking into account preceding mixture traffic information. Direct simulations also confirm that the traffic jam can be suppressed efficiently by considering the relative currents ahead, just like incorporating site information in front. Moreover, from the nonlinear analysis of the extended models, the preceding mixture traffic information dependence of the propagating kink solutions for traffic jams is obtained by deriving the modified KdV equation near the critical point using the reductive perturbation method. 展开更多
关键词 traffic flow lattice model mixture tramc information numerical simulation
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学校周边道路交通管理设施设置研究 被引量:2
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作者 韦佼 赵龙 韩凤春 《西部交通科技》 2013年第12期63-66,共4页
文章分析了学校周边道路交通特性和学生过街交通行为特性,并结合学校周边交通管理设施设计原则,提出了一套人性化、完善的设施设置方法,为提高学生上下学过街安全性,引导过往车辆顺畅通行,完善交通管理设施设置方法提供参考。
关键词 学校周边道路交通特性 学生过街交通特性 交通管理设施
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《PLC》项目式教学应用研究——以交通信号灯制作为例 被引量:3
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作者 王滨 《湖南工业职业技术学院学报》 2018年第1期79-82,共4页
本文采用西门子S7-200可编程控制器PLC对十字路口交通信号灯控制系统进行了具体设计,并将PLC设备与实物教学模型相结合,进行模拟组装和调试,实现了十字路口交通信号灯的模拟自动化控制。此教学模式激发了学生的学习兴趣,提高了他们的学... 本文采用西门子S7-200可编程控制器PLC对十字路口交通信号灯控制系统进行了具体设计,并将PLC设备与实物教学模型相结合,进行模拟组装和调试,实现了十字路口交通信号灯的模拟自动化控制。此教学模式激发了学生的学习兴趣,提高了他们的学习积极性和主动性,活跃了课堂气氛~[1]。 展开更多
关键词 PLC 交通灯控制 程序设计 项目教学
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基于多重分形去趋势波动分析法的交通流多重分形无标度区间自动识别方法 被引量:9
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作者 熊杰 陈绍宽 +2 位作者 韦伟 刘爽 关伟 《物理学报》 SCIE EI CAS CSCD 北大核心 2014年第20期99-106,共8页
无标度区间是时间序列在统计意义上存在分形自相似性的尺度范围,是交通流多重分形特征研究中的重要组成部分.为解决交通流多重分形研究中多重分形去趋势波动分析法(multi-fractal detrended fluctuation analysis,MF-DFA)缺乏有效识别... 无标度区间是时间序列在统计意义上存在分形自相似性的尺度范围,是交通流多重分形特征研究中的重要组成部分.为解决交通流多重分形研究中多重分形去趋势波动分析法(multi-fractal detrended fluctuation analysis,MF-DFA)缺乏有效识别无标度区间方法的问题,本文在分析算法过程中交通流波动函数对数曲线突变点性质的基础上,结合传统无标度区间识别方法的构建思想,建立基于MF-DFA算法的无标度区间自动识别方法.以北京市二环快速路外环方向的部分道路为例开展实例研究,通过与传统无标度区间识别方法的结果对比,验证新方法的有效性.研究结果表明:本文方法能自动识别交通流多重分形无标度区间,且稳定性好;案例研究可知交通流短时间内波动较小、自相似性较强,随着研究时间段变长、交通流波动逐渐变大,自相似性逐渐消失,进一步解释了交通流无标度区间的有限性. 展开更多
关键词 交通流 多重分形 无标度区间 多重分形去趋势波动分析法
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Lead and Cadmium Contamination of Different Roadside Soils and Plants in Peshawar City, Pakistan 被引量:6
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作者 S.KHAN M.A.KHAN S.REHMAN 《Pedosphere》 SCIE CAS CSCD 2011年第3期351-357,共7页
Soil and plant samples were collected from roadside sites (along with primary, secondary and tertiary roads) and reference site to investigate the contamination of soils and old common plant species with lead (Pb) and... Soil and plant samples were collected from roadside sites (along with primary, secondary and tertiary roads) and reference site to investigate the contamination of soils and old common plant species with lead (Pb) and cadmium (Cd) in Peshawar City, Pakistan. All the data were analyzed using ANOVA analysis that showed a significant (P ≤ 0.01) variation in Pb and Cd concentrations in the roadside soils and plants as compared to the reference site. The mean concentrations of Pb and Cd were 53.9 and 6.0 mg kg-1 in soils and 49.1 and 10.9 mg kg-1 in plants, respectively. Significant variation (P ≤ 0.01) in concentrations of Pb and Cd in soil and plant samples along with primary, secondary and tertiary roads might be due to different traffic densities. The highest value (9.4) of metal accumulation index (MAI) was observed for Eucalyptus camaldulensis. In selected plant species, the Pb and Cd accumulation was found in the order of E. camaldulensis > Ficus elastica > Dalbergia sissoo > Alstonia scholaris. The roadside soils and plants were highly contaminated with Pb and Cd as compared to the reference site. 展开更多
关键词 electrical conductivity heavy metals metal accumulation index tramc density
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