Short-term traffic flow prediction is one of the essential issues in intelligent transportation systems(ITS). A new two-stage traffic flow prediction method named AKNN-AVL method is presented, which combines an advanc...Short-term traffic flow prediction is one of the essential issues in intelligent transportation systems(ITS). A new two-stage traffic flow prediction method named AKNN-AVL method is presented, which combines an advanced k-nearest neighbor(AKNN)method and balanced binary tree(AVL) data structure to improve the prediction accuracy. The AKNN method uses pattern recognition two times in the searching process, which considers the previous sequences of traffic flow to forecast the future traffic state. Clustering method and balanced binary tree technique are introduced to build case database to reduce the searching time. To illustrate the effects of these developments, the accuracies performance of AKNN-AVL method, k-nearest neighbor(KNN) method and the auto-regressive and moving average(ARMA) method are compared. These methods are calibrated and evaluated by the real-time data from a freeway traffic detector near North 3rd Ring Road in Beijing under both normal and incident traffic conditions.The comparisons show that the AKNN-AVL method with the optimal neighbor and pattern size outperforms both KNN method and ARMA method under both normal and incident traffic conditions. In addition, the combinations of clustering method and balanced binary tree technique to the prediction method can increase the searching speed and respond rapidly to case database fluctuations.展开更多
Methods that can efficiently model the effects of rock joints on rock mass behavior can be beneficial in rock engineering. The suitability of equivalent rock mass(ERM) technique based upon particle methods is investig...Methods that can efficiently model the effects of rock joints on rock mass behavior can be beneficial in rock engineering. The suitability of equivalent rock mass(ERM) technique based upon particle methods is investigated. The ERM methodology is first validated by comparing calculated and experimental data of lab triaxial compression test on a set of cylindrical rock mass samples, each containing a single joint oriented in various dip angles. The simulated results are then used to study the stress-strain nonlinearity and failure mechanism as a function of the joint dip angle and confining stress. The anisotropy and size effects are also investigated by using multi-scale cubic ERM models subjected to triaxial compression test. The deformation and failure behavior are found to be influenced by joint degradation, the micro-crack formation in the intact rock, the interaction between two joints, and the interactions of micro-cracks and joints.展开更多
Mining operation, especially underground coal mining, always has the remarkable risks of ground control. Passive seismic velocity tomography based on simultaneous iterative reconstructive technique （SIRT） inversion ...Mining operation, especially underground coal mining, always has the remarkable risks of ground control. Passive seismic velocity tomography based on simultaneous iterative reconstructive technique （SIRT） inversion is used to deduce the stress redistribution around the longwall mining panel. The mining-induced microseismic events were recorded by mounting an array of receivers on the surface, above the active panel. After processing and filtering the seismic data, the three-dimensional tomography images of the p-wave velocity variations by SIRT passive seismic velocity tomography were provided. To display the velocity changes on coal seam level and subsequently to infer the stress redistribution, these three-dimensional tomograms into the coal seam level were sliced. In addition, the boundary element method （BEM） was used to simulate the stress redistribution. The results show that the inferred stresses from the passive seismic tomograms are conformed to numerical models and theoretical concept of the stress redistribution around the longwall panel. In velocity tomograms, the main zones of the stress redistribution arotmd the panel, including front and side abutment pressures, and gob stress are obvious and also the movement of stress zones along the face advancement is evident. Moreover, the effect of the advance rate of the face on the stress redistribution is demonstrated in tomography images. The research result proves that the SIRT passive seismic velocity tomography has an ultimate potential for monitoring the changes of stress redistribution around the longwall mining panel continuously and subsequently to improve safety of mining operations.展开更多
Geosynthetic-reinforced and pile-supported （GRPS） embankment has been increasingly constructed in a large number of regions and for a wide range of projects in the past decades. However, many disadvantages are expos...Geosynthetic-reinforced and pile-supported （GRPS） embankment has been increasingly constructed in a large number of regions and for a wide range of projects in the past decades. However, many disadvantages are exposed through a lot of applications on conventional technique of GRPS embankment （called CT embankment）, i.e., intolerable settlement and lateral displacement, low geosynthetic efficiency, etc. In view of these disadvantages, the fixed geosynthetic technique of GRPS embankment （called FGT embankment） is developed in this work. In this system, the geosynthetic is fixed on the pile head by the steel bar fulcrum and concrete fixed top. The principles and construction techniques involved in the FGT embankment are described firstly. Then, the numerical analysis method and two-stage analysis method are used to study the performance of FGT embankment, respectively. It is shown that the FGT embankment can provide a better improvement technique to construct a high embankment over soft ground.展开更多
为克服单一赋权法的局限性,结合山区干线公路交通特征及交通安全评价指标的选取原则,从社会因素、驾驶因素、环境因素、管理因素和道路因素五个维度出发,选取18个综合评价指标,运用序关系分析法(Order Relation Analysis Method,G1)-指...为克服单一赋权法的局限性,结合山区干线公路交通特征及交通安全评价指标的选取原则,从社会因素、驾驶因素、环境因素、管理因素和道路因素五个维度出发,选取18个综合评价指标,运用序关系分析法(Order Relation Analysis Method,G1)-指标相关性权重确定法(Criteria Importance Through Intercriteria Correlation,CRITIC)确定各评价指标的权重,并结合折中妥协多属性决策法(VlseKriterijumska Optimizacija I Kompromisno Resenje,VIKOR)对山区干线公路交通安全进行综合评价,提出了基于G1-CRITIC-VIKOR模型的山区干线公路交通安全综合评价及比选方法。以中国西部6条山区干线公路为例进行实证研究,结果表明,G1-CRITIC-VIKOR模型的评价效果与传统的秩和比(Rank-Sum Ratio,RSR)综合评价法及加权逼近理想解排序法(Technique for Order Preference by Similarity to Ideal Solution,TOPSIS)的评价结果基本一致,且评价效果明显优于后者,具有更好的辨识性,验证了该模型的可行性和科学性。展开更多
产业开发区内多发环境污染导致的邻避(not in my backyard,NIMBY)问题对经济发展和社会稳定造成了一定的阻碍,其中工业企业是主要的邻避设施,目前对该类邻避效应的研究及对邻避效应大小的定量评价方法尚不完善。文章以合肥市高新区为例...产业开发区内多发环境污染导致的邻避(not in my backyard,NIMBY)问题对经济发展和社会稳定造成了一定的阻碍,其中工业企业是主要的邻避设施,目前对该类邻避效应的研究及对邻避效应大小的定量评价方法尚不完善。文章以合肥市高新区为例,以区域内的工业企业为研究对象,提出新的邻避效应评价方法。在评价体系中,将企业规划布局的合理性和大气防护距离也作为邻避效应评价指标,采用模糊最优最劣决策法(best-worst method,BWM)计算指标权重,并通过逼近理想解对不同工业企业的邻避效应大小进行排序。研究结果表明,风险感知和大气防护距离是影响邻避效应的最主要因素,通过敏感性分析确定该评价方法有较好的可靠性和鲁棒性,为决策者解决产业开发区的邻避问题提供思路和依据。展开更多
基金Project(2012CB725403)supported by the National Basic Research Program of ChinaProjects(71210001,51338008)supported by the National Natural Science Foundation of ChinaProject supported by World Capital Cities Smooth Traffic Collaborative Innovation Center and Singapore National Research Foundation Under Its Campus for Research Excellence and Technology Enterprise(CREATE)Programme
文摘Short-term traffic flow prediction is one of the essential issues in intelligent transportation systems(ITS). A new two-stage traffic flow prediction method named AKNN-AVL method is presented, which combines an advanced k-nearest neighbor(AKNN)method and balanced binary tree(AVL) data structure to improve the prediction accuracy. The AKNN method uses pattern recognition two times in the searching process, which considers the previous sequences of traffic flow to forecast the future traffic state. Clustering method and balanced binary tree technique are introduced to build case database to reduce the searching time. To illustrate the effects of these developments, the accuracies performance of AKNN-AVL method, k-nearest neighbor(KNN) method and the auto-regressive and moving average(ARMA) method are compared. These methods are calibrated and evaluated by the real-time data from a freeway traffic detector near North 3rd Ring Road in Beijing under both normal and incident traffic conditions.The comparisons show that the AKNN-AVL method with the optimal neighbor and pattern size outperforms both KNN method and ARMA method under both normal and incident traffic conditions. In addition, the combinations of clustering method and balanced binary tree technique to the prediction method can increase the searching speed and respond rapidly to case database fluctuations.
基金Projects(51074014,51174014) supported by the National Natural Science Foundation of China
文摘Methods that can efficiently model the effects of rock joints on rock mass behavior can be beneficial in rock engineering. The suitability of equivalent rock mass(ERM) technique based upon particle methods is investigated. The ERM methodology is first validated by comparing calculated and experimental data of lab triaxial compression test on a set of cylindrical rock mass samples, each containing a single joint oriented in various dip angles. The simulated results are then used to study the stress-strain nonlinearity and failure mechanism as a function of the joint dip angle and confining stress. The anisotropy and size effects are also investigated by using multi-scale cubic ERM models subjected to triaxial compression test. The deformation and failure behavior are found to be influenced by joint degradation, the micro-crack formation in the intact rock, the interaction between two joints, and the interactions of micro-cracks and joints.
文摘Mining operation, especially underground coal mining, always has the remarkable risks of ground control. Passive seismic velocity tomography based on simultaneous iterative reconstructive technique （SIRT） inversion is used to deduce the stress redistribution around the longwall mining panel. The mining-induced microseismic events were recorded by mounting an array of receivers on the surface, above the active panel. After processing and filtering the seismic data, the three-dimensional tomography images of the p-wave velocity variations by SIRT passive seismic velocity tomography were provided. To display the velocity changes on coal seam level and subsequently to infer the stress redistribution, these three-dimensional tomograms into the coal seam level were sliced. In addition, the boundary element method （BEM） was used to simulate the stress redistribution. The results show that the inferred stresses from the passive seismic tomograms are conformed to numerical models and theoretical concept of the stress redistribution around the longwall panel. In velocity tomograms, the main zones of the stress redistribution arotmd the panel, including front and side abutment pressures, and gob stress are obvious and also the movement of stress zones along the face advancement is evident. Moreover, the effect of the advance rate of the face on the stress redistribution is demonstrated in tomography images. The research result proves that the SIRT passive seismic velocity tomography has an ultimate potential for monitoring the changes of stress redistribution around the longwall mining panel continuously and subsequently to improve safety of mining operations.
基金Foundation item： Project（51278216） supported by the National Natural Science Foundation of China Project（11-2-05） supported by the Scientific and Technological Project for Shanxi Communication Construction, China Project（HF-08-01-2011-240） supported by the Graduates＇ Innovation Fund of Huazhong University of Science and Technology, China
文摘Geosynthetic-reinforced and pile-supported （GRPS） embankment has been increasingly constructed in a large number of regions and for a wide range of projects in the past decades. However, many disadvantages are exposed through a lot of applications on conventional technique of GRPS embankment （called CT embankment）, i.e., intolerable settlement and lateral displacement, low geosynthetic efficiency, etc. In view of these disadvantages, the fixed geosynthetic technique of GRPS embankment （called FGT embankment） is developed in this work. In this system, the geosynthetic is fixed on the pile head by the steel bar fulcrum and concrete fixed top. The principles and construction techniques involved in the FGT embankment are described firstly. Then, the numerical analysis method and two-stage analysis method are used to study the performance of FGT embankment, respectively. It is shown that the FGT embankment can provide a better improvement technique to construct a high embankment over soft ground.
文摘为克服单一赋权法的局限性,结合山区干线公路交通特征及交通安全评价指标的选取原则,从社会因素、驾驶因素、环境因素、管理因素和道路因素五个维度出发,选取18个综合评价指标,运用序关系分析法(Order Relation Analysis Method,G1)-指标相关性权重确定法(Criteria Importance Through Intercriteria Correlation,CRITIC)确定各评价指标的权重,并结合折中妥协多属性决策法(VlseKriterijumska Optimizacija I Kompromisno Resenje,VIKOR)对山区干线公路交通安全进行综合评价,提出了基于G1-CRITIC-VIKOR模型的山区干线公路交通安全综合评价及比选方法。以中国西部6条山区干线公路为例进行实证研究,结果表明,G1-CRITIC-VIKOR模型的评价效果与传统的秩和比(Rank-Sum Ratio,RSR)综合评价法及加权逼近理想解排序法(Technique for Order Preference by Similarity to Ideal Solution,TOPSIS)的评价结果基本一致,且评价效果明显优于后者,具有更好的辨识性,验证了该模型的可行性和科学性。
文摘产业开发区内多发环境污染导致的邻避(not in my backyard,NIMBY)问题对经济发展和社会稳定造成了一定的阻碍,其中工业企业是主要的邻避设施,目前对该类邻避效应的研究及对邻避效应大小的定量评价方法尚不完善。文章以合肥市高新区为例,以区域内的工业企业为研究对象,提出新的邻避效应评价方法。在评价体系中,将企业规划布局的合理性和大气防护距离也作为邻避效应评价指标,采用模糊最优最劣决策法(best-worst method,BWM)计算指标权重,并通过逼近理想解对不同工业企业的邻避效应大小进行排序。研究结果表明,风险感知和大气防护距离是影响邻避效应的最主要因素,通过敏感性分析确定该评价方法有较好的可靠性和鲁棒性,为决策者解决产业开发区的邻避问题提供思路和依据。
