Based on the Nagel-Schreckenberg model, an improved cellular automaton traffic flow model is proposed, in which the random deceleration probability of each vehicle is no longer fixed, but is adaptively adjusted accord...Based on the Nagel-Schreckenberg model, an improved cellular automaton traffic flow model is proposed, in which the random deceleration probability of each vehicle is no longer fixed, but is adaptively adjusted according to the local traffic density in its vision and its current velocity. The numerical simulation results show that the maximum traffic capacity of the improved model under the same parameters is greater than that of the Nagel-Schreckenberg model, and is closer to the measured data. In addition, the traffic flow and vehicle velocity under different meteorological conditions are simulated by using the improved model, and the synchronized flow phenomenon consistent with the actual traffic is reproduced. Meanwhile, the results show that under the same parameters, when the traffic density is equal to 0.3, the traffic flow of the improved model increases by about 11% compared with the original model, and when the traffic density increases to 0.6, the traffic flow increases by about 27%. .展开更多
A wind-vehicle-bridge system can be regarded as an interaction result of wind-bridge interaction, wind-vehicle interaction and vehicle-bridge interaction, which is determined by nature wind, dynamic characteristics of...A wind-vehicle-bridge system can be regarded as an interaction result of wind-bridge interaction, wind-vehicle interaction and vehicle-bridge interaction, which is determined by nature wind, dynamic characteristics of vehicle and bridge structures, interrelationship between bridge and vehicle dynamic properties and so on. Firstly, based on the traffic loading investigation on the expressway bridge within 24 hours a day, all the critical parameters of traffic flow, such as the vehicle type, weight, separation space and speed are all recorded and analyzed to extract its statistical characteristics, which are used to work out random traffic flow simulation program RTF. This RTF program can be embedded with the other general FEM software. Secondly, a dynamic analysis module RTFWVB of the wind-vehicle-bridge coupling vibration under random traffic flow is presented, which can consider arbitrary number of vehicles, multi-lanes and traffic flow direction. Finally, Hangzhou Bay Bridge in China is selected as a numerical example to demonstrate dynamic interaction of the RTFWVB system. The results indicate that the traffic flow direction has just a little influence on bridge dynamic response, that the mean responses are mainly determined by the moving vehicle loads, and that the fluctuating components will increase with the increase of wind speed.展开更多
Conservation tillage is proven to be a useful agricultural practice for reducing the concentration of CO_(2) released to the atmosphere,but there is currently only limited information regarding the influences of contr...Conservation tillage is proven to be a useful agricultural practice for reducing the concentration of CO_(2) released to the atmosphere,but there is currently only limited information regarding the influences of controlled traffic on soil CO_(2) fluxes.Therefore,this study investigated the effects of controlled traffic on soil CO_(2) flux and on fuel consumption in winter wheat(Triticum aestivum L.)and maize(Zea mays L.)croplands of northern China.CO_(2) samples were collected from various compacted areas in the fields,including the crop zone,the inter-row zone and the traffic zone.CO_(2) flux from the soil surface was measured with a GXH-3010E1 CO_(2) infrared analyzer during the crop grain filling stage.CO_(2) fluxes were considerably larger for controlled traffic field(95.04±6.79)g/(m2·d)than that for random traffic field(50.91±7.57)g/(m2·d)in the crop zone,but there were no significant differences between random and controlled traffic fields in the inter-row zone.In contrast,in the traffic zone,all fluxes were lower than those in the other areas.Total CO_(2) fluxes were not significantly different between controlled traffic and random traffic fields.Controlled traffic can reduce fuel consumption by 9.7 L/hm2 compared to random traffic,which implies that it can also reduce the total annual amount of CO_(2) released from agricultural activities.展开更多
Research on the stochastic behavior of traffic flow is important to understand the intrinsic evolution rules of a traffic system. By introducing an interactional potential of vehicles into the randomization step, an i...Research on the stochastic behavior of traffic flow is important to understand the intrinsic evolution rules of a traffic system. By introducing an interactional potential of vehicles into the randomization step, an improved cellular automata traffic flow model with variable probability of randomization is proposed in this paper. In the proposed model, the driver is affected by the interactional potential of vehicles before him, and his decision-making process is related to the interactional potential. Compared with the traditional cellular automata model, the modeling is more suitable for the driver＇s random decision-making process based on the vehicle and traffic situations in front of him in actual traffic. From the improved model, the fundamental diagram （flow^tensity relationship） is obtained, and the detailed high-density traffic phenomenon is reproduced through numerical simulation.展开更多
随着信息技术的发展,用户和组织对网络安全的关注度不断提高,数据加密传输逐渐成为主流,推动互联网中加密流量的比例不断攀升。然而,数据加密在保障隐私和安全的同时也成为非法内容逃避网络监管的手段。为实现加密流量的检测与分析,需...随着信息技术的发展,用户和组织对网络安全的关注度不断提高,数据加密传输逐渐成为主流,推动互联网中加密流量的比例不断攀升。然而,数据加密在保障隐私和安全的同时也成为非法内容逃避网络监管的手段。为实现加密流量的检测与分析,需要高效地识别出加密流量。但是,压缩流量的存在会严重干扰对加密流量的识别。针对上述问题,设计了基于滑动窗口和随机性特征的加密流量识别方案,以高效且准确地识别加密流量。具体来说,所提方案根据滑动窗口机制对会话中数据传输报文的有效载荷进行采样,获取能够反映原始流量信息模式的数据块序列,针对每个数据块使用随机性测度算法进行样本特征提取,为原始载荷构建随机性特征。此外,通过设计基于CART(classification and reqression tree)算法的决策树模型,在提高加密和压缩流量识别的准确率的同时,极大降低了针对加密流量识别的漏报率。基于对多个权威网站数据的随机抽样,构建均衡的数据集,并通过实验证明了所提方案的可行性和高效性。展开更多
文摘Based on the Nagel-Schreckenberg model, an improved cellular automaton traffic flow model is proposed, in which the random deceleration probability of each vehicle is no longer fixed, but is adaptively adjusted according to the local traffic density in its vision and its current velocity. The numerical simulation results show that the maximum traffic capacity of the improved model under the same parameters is greater than that of the Nagel-Schreckenberg model, and is closer to the measured data. In addition, the traffic flow and vehicle velocity under different meteorological conditions are simulated by using the improved model, and the synchronized flow phenomenon consistent with the actual traffic is reproduced. Meanwhile, the results show that under the same parameters, when the traffic density is equal to 0.3, the traffic flow of the improved model increases by about 11% compared with the original model, and when the traffic density increases to 0.6, the traffic flow increases by about 27%. .
基金supported by the Fundamental Research Funds for the Central Universities of China (No.CHD2011JC012)the National Natural Science Foundation of China(No.51278064)
文摘A wind-vehicle-bridge system can be regarded as an interaction result of wind-bridge interaction, wind-vehicle interaction and vehicle-bridge interaction, which is determined by nature wind, dynamic characteristics of vehicle and bridge structures, interrelationship between bridge and vehicle dynamic properties and so on. Firstly, based on the traffic loading investigation on the expressway bridge within 24 hours a day, all the critical parameters of traffic flow, such as the vehicle type, weight, separation space and speed are all recorded and analyzed to extract its statistical characteristics, which are used to work out random traffic flow simulation program RTF. This RTF program can be embedded with the other general FEM software. Secondly, a dynamic analysis module RTFWVB of the wind-vehicle-bridge coupling vibration under random traffic flow is presented, which can consider arbitrary number of vehicles, multi-lanes and traffic flow direction. Finally, Hangzhou Bay Bridge in China is selected as a numerical example to demonstrate dynamic interaction of the RTFWVB system. The results indicate that the traffic flow direction has just a little influence on bridge dynamic response, that the mean responses are mainly determined by the moving vehicle loads, and that the fluctuating components will increase with the increase of wind speed.
文摘Conservation tillage is proven to be a useful agricultural practice for reducing the concentration of CO_(2) released to the atmosphere,but there is currently only limited information regarding the influences of controlled traffic on soil CO_(2) fluxes.Therefore,this study investigated the effects of controlled traffic on soil CO_(2) flux and on fuel consumption in winter wheat(Triticum aestivum L.)and maize(Zea mays L.)croplands of northern China.CO_(2) samples were collected from various compacted areas in the fields,including the crop zone,the inter-row zone and the traffic zone.CO_(2) flux from the soil surface was measured with a GXH-3010E1 CO_(2) infrared analyzer during the crop grain filling stage.CO_(2) fluxes were considerably larger for controlled traffic field(95.04±6.79)g/(m2·d)than that for random traffic field(50.91±7.57)g/(m2·d)in the crop zone,but there were no significant differences between random and controlled traffic fields in the inter-row zone.In contrast,in the traffic zone,all fluxes were lower than those in the other areas.Total CO_(2) fluxes were not significantly different between controlled traffic and random traffic fields.Controlled traffic can reduce fuel consumption by 9.7 L/hm2 compared to random traffic,which implies that it can also reduce the total annual amount of CO_(2) released from agricultural activities.
基金supported by the National Natural Science Foundation of China(Grant Nos.11172247,61273021,61373009,and 61100118)
文摘Research on the stochastic behavior of traffic flow is important to understand the intrinsic evolution rules of a traffic system. By introducing an interactional potential of vehicles into the randomization step, an improved cellular automata traffic flow model with variable probability of randomization is proposed in this paper. In the proposed model, the driver is affected by the interactional potential of vehicles before him, and his decision-making process is related to the interactional potential. Compared with the traditional cellular automata model, the modeling is more suitable for the driver＇s random decision-making process based on the vehicle and traffic situations in front of him in actual traffic. From the improved model, the fundamental diagram （flow^tensity relationship） is obtained, and the detailed high-density traffic phenomenon is reproduced through numerical simulation.
文摘随着信息技术的发展,用户和组织对网络安全的关注度不断提高,数据加密传输逐渐成为主流,推动互联网中加密流量的比例不断攀升。然而,数据加密在保障隐私和安全的同时也成为非法内容逃避网络监管的手段。为实现加密流量的检测与分析,需要高效地识别出加密流量。但是,压缩流量的存在会严重干扰对加密流量的识别。针对上述问题,设计了基于滑动窗口和随机性特征的加密流量识别方案,以高效且准确地识别加密流量。具体来说,所提方案根据滑动窗口机制对会话中数据传输报文的有效载荷进行采样,获取能够反映原始流量信息模式的数据块序列,针对每个数据块使用随机性测度算法进行样本特征提取,为原始载荷构建随机性特征。此外,通过设计基于CART(classification and reqression tree)算法的决策树模型,在提高加密和压缩流量识别的准确率的同时,极大降低了针对加密流量识别的漏报率。基于对多个权威网站数据的随机抽样,构建均衡的数据集,并通过实验证明了所提方案的可行性和高效性。
