Accurate short-term traffic flow prediction plays a crucial role in intelligent transportation system (ITS), because it can assist both traffic authorities and individual travelers make better decisions. Previous rese...Accurate short-term traffic flow prediction plays a crucial role in intelligent transportation system (ITS), because it can assist both traffic authorities and individual travelers make better decisions. Previous researches mostly focus on shallow traffic prediction models, which performances were unsatisfying since short-term traffic flow exhibits the characteristics of high nonlinearity, complexity and chaos. Taking the spatial and temporal correlations into consideration, a new traffic flow prediction method is proposed with the basis on the road network topology and gated recurrent unit (GRU). This method can help researchers without professional traffic knowledge extracting generic traffic flow features effectively and efficiently. Experiments are conducted by using real traffic flow data collected from the Caltrans Performance Measurement System (PEMS) database in San Diego and Oakland from June 15, 2017 to September 27, 2017. The results demonstrate that our method outperforms other traditional approaches in terms of mean absolute percentage error (MAPE), symmetric mean absolute percentage error (SMAPE) and root mean square error (RMSE).展开更多
The Gorkha earthquake in Nepal led to many landslides and severe damage to the transportation infrastructure. After careful comparison of the aerial photographs and satellite images before and after the earthquake, pa...The Gorkha earthquake in Nepal led to many landslides and severe damage to the transportation infrastructure. After careful comparison of the aerial photographs and satellite images before and after the earthquake, partially verified by a field study, more than 2,064 landslides and many road failures were observed. Many bridges, especially steel-truss and suspension bridges, suffered little damage from inertia loads during the earthquake, but were severely damaged due to rockfalls. Potential geological hazards hindered the delivery of supplies in mountainous areas, and road closures impeded the overall speed of rehabilitation.展开更多
This study uses a simulation-based approach to investigate the impact of delivery delays due to constraints on transport capacity, transit speed, and routing efficiencies on an economy with various levels of interdepe...This study uses a simulation-based approach to investigate the impact of delivery delays due to constraints on transport capacity, transit speed, and routing efficiencies on an economy with various levels of interdependency among firms. The simulation uses object-oriented programming to create specialized production, consumption, and transportation classes. A set of objects from each class is distributed randomly on a 2D plane. A road network is then established between fixed objects using Prim’s MST (Minimum Spanning Tree) algorithm, followed by construction of an all-pair shortest path matrix using the Floyd Warshall algorithm. A genetic algorithm-based vehicle routing problem solver employs the all-pair shortest path matrix to best plan multiple pickup and delivery orders. Production units utilize economic order quantities (EOQ) and reorder points (ROP) to manage inventory levels. Hicksian and Marshallian demand functions are utilized by consumption units to maximize personal utility. The transport capacity, transit speed, routing efficiency, and level of interdependence serve as 4 factors in the simulation, each assigned 3 distinct levels. Federov’s exchange algorithm is used to generate an orthogonal array to reduce the number of combination replays from 3<sup>4</sup> to just 9. The simulation results of a 9-run orthogonal array on an economy with 6 mining facilities, 12 industries, 8 market centers, and 8 transport hubs show that the level of firm interdependence, followed by transit speed, has the most significant impact on economic productivity. The principal component analysis (PCA) indicates that interdependence and transit speed can explain 90.27% of the variance in the data. According to the findings of this research, a dependable and efficient regional transportation network among various types of industries is critical for regional economic development.展开更多
基于2010年,2015年和2019年中国30个省域物流公路运输碳排放数据和空间关系网,采用社会网络分析法(social network analysis,SNA)、地理信息系统(geographic information system,GIS)和地理探测器,从整体碳排放空间分布、整体网络结构...基于2010年,2015年和2019年中国30个省域物流公路运输碳排放数据和空间关系网,采用社会网络分析法(social network analysis,SNA)、地理信息系统(geographic information system,GIS)和地理探测器,从整体碳排放空间分布、整体网络结构演变、网络密度、凝聚子群、网络节点以及影响因素等角度分析我国30个省份公路运输碳排放空间分布和特征。结果表明:(1)从空间分布看,2010—2019年公路运输碳排放空间分布中部和南部排放量较多,西部和北部较少;(2)整体网络分析中,网络结构具有明显的核心-边缘结构,核心省份网络密度高且具有较发达的公路网络体系;(3)在不同的省份中,以广东省为例的中部和东部省份处于网络连接的核心,而甘肃省等较为偏远的省份处于网络的边缘;(4)产业结构、货运量和载货汽车拥有量对碳排放影响最大,而且交叉因子的影响作用大于单一因素的影响作用。展开更多
基金Supported by the Support Program of the National 12th Five Year-Plan of China(2015BAK25B03)
文摘Accurate short-term traffic flow prediction plays a crucial role in intelligent transportation system (ITS), because it can assist both traffic authorities and individual travelers make better decisions. Previous researches mostly focus on shallow traffic prediction models, which performances were unsatisfying since short-term traffic flow exhibits the characteristics of high nonlinearity, complexity and chaos. Taking the spatial and temporal correlations into consideration, a new traffic flow prediction method is proposed with the basis on the road network topology and gated recurrent unit (GRU). This method can help researchers without professional traffic knowledge extracting generic traffic flow features effectively and efficiently. Experiments are conducted by using real traffic flow data collected from the Caltrans Performance Measurement System (PEMS) database in San Diego and Oakland from June 15, 2017 to September 27, 2017. The results demonstrate that our method outperforms other traditional approaches in terms of mean absolute percentage error (MAPE), symmetric mean absolute percentage error (SMAPE) and root mean square error (RMSE).
基金Scientific Research Fund of Institute of Engineering Mechanics,China Earthquake Administration under Grant No.2014B02China postdoctoral Science Foundation under Grant No.2013M531083+1 种基金National Natural Science Foundation of China under Grant No.51508535Natural Science Foundation of Hei Longjiang Province of China under Grant No.LC2012C32
文摘The Gorkha earthquake in Nepal led to many landslides and severe damage to the transportation infrastructure. After careful comparison of the aerial photographs and satellite images before and after the earthquake, partially verified by a field study, more than 2,064 landslides and many road failures were observed. Many bridges, especially steel-truss and suspension bridges, suffered little damage from inertia loads during the earthquake, but were severely damaged due to rockfalls. Potential geological hazards hindered the delivery of supplies in mountainous areas, and road closures impeded the overall speed of rehabilitation.
文摘This study uses a simulation-based approach to investigate the impact of delivery delays due to constraints on transport capacity, transit speed, and routing efficiencies on an economy with various levels of interdependency among firms. The simulation uses object-oriented programming to create specialized production, consumption, and transportation classes. A set of objects from each class is distributed randomly on a 2D plane. A road network is then established between fixed objects using Prim’s MST (Minimum Spanning Tree) algorithm, followed by construction of an all-pair shortest path matrix using the Floyd Warshall algorithm. A genetic algorithm-based vehicle routing problem solver employs the all-pair shortest path matrix to best plan multiple pickup and delivery orders. Production units utilize economic order quantities (EOQ) and reorder points (ROP) to manage inventory levels. Hicksian and Marshallian demand functions are utilized by consumption units to maximize personal utility. The transport capacity, transit speed, routing efficiency, and level of interdependence serve as 4 factors in the simulation, each assigned 3 distinct levels. Federov’s exchange algorithm is used to generate an orthogonal array to reduce the number of combination replays from 3<sup>4</sup> to just 9. The simulation results of a 9-run orthogonal array on an economy with 6 mining facilities, 12 industries, 8 market centers, and 8 transport hubs show that the level of firm interdependence, followed by transit speed, has the most significant impact on economic productivity. The principal component analysis (PCA) indicates that interdependence and transit speed can explain 90.27% of the variance in the data. According to the findings of this research, a dependable and efficient regional transportation network among various types of industries is critical for regional economic development.
文摘基于2010年,2015年和2019年中国30个省域物流公路运输碳排放数据和空间关系网,采用社会网络分析法(social network analysis,SNA)、地理信息系统(geographic information system,GIS)和地理探测器,从整体碳排放空间分布、整体网络结构演变、网络密度、凝聚子群、网络节点以及影响因素等角度分析我国30个省份公路运输碳排放空间分布和特征。结果表明:(1)从空间分布看,2010—2019年公路运输碳排放空间分布中部和南部排放量较多,西部和北部较少;(2)整体网络分析中,网络结构具有明显的核心-边缘结构,核心省份网络密度高且具有较发达的公路网络体系;(3)在不同的省份中,以广东省为例的中部和东部省份处于网络连接的核心,而甘肃省等较为偏远的省份处于网络的边缘;(4)产业结构、货运量和载货汽车拥有量对碳排放影响最大,而且交叉因子的影响作用大于单一因素的影响作用。
