城市道路网络OD估计模型及算法研究

考虑城市道路交通运行的复杂性,抽象出城市道路网络拓扑结构.通过布设检测器采集路段流量、转向比例等多源数据信息,在上述分析基础上,运用吸收马尔可夫理论对城市道路网络进行建模分析,将路段流量、转向比例、小区发生吸引量等参数联系起来,分别利用小区发生量和若干路段流量,得到交通流起讫点OD的不同估计模型,并给出相应算法.建立井字型路网仿真平台采集多源数据信息,求出马尔可夫转移概率矩阵,并用稀疏矩阵的形式导入Matlab编程仿真中进行一系列矩阵运算.数值算例表明,该模型能有效计算路段流量,进而提高OD估计精度.     

基于车道级基础路网的微观交通仿真数据建模与应用研究

从满足微观交通仿真需求角度分析了仿真数据模型建模的要点,建立了包括基础路网模型、信号控制方案描述模型和交通需求模型在内的微观交通仿真数据模型。信号控制方案描述模型中,信号灯分配通行时权,信号灯组描述交叉口的通行规则。交通需求模型由交通小区和OD矩阵组成,交通小区定义OD矩阵的起终点,OD矩阵定义路网上的出行量。以VISSIM为例,研究该模型与微观交通仿真模型要素之间的对应关系,提取数据转换生成VISSIM仿真模型,论证了其用于数据提取和交换的可行性。     

交通仿真在动态交通分配应用研究中的尝试

基于微观交通仿真模型CORSIM中交通仿真与交通分配相结合的特点,在仿真模型中将路网的OD流量通过按动态规律沿时间轴加以扩展,使之成为一个时变OD矩阵,再分析研究路段自由流车速与高峰时段路网流量的动态关系,从而进行动态交通分配的建模研究尝试.     

基于网络拓扑的子网络OD需求估计

为了对局部交通路网进行设计和评价,运用拓扑结构分析方法对子网络OD需求进行估计.根据子网络拓扑结构,分别对子网络边界点和内部点的OD量进行分析,每个与外界网络相连的边界点都为子网络的交通发生吸引点,内部点OD需求量与原来网络保持一致.进而建立了基于网络拓扑的子网络OD需求估计模型,其中目标函数同时考虑了交通需求的熵最大化及弹性化,约束条件为子网络OD量约束.将原问题分为求解交通需求和道路阻抗两部分,设计了启发式迭代算法反复求解,并运用凸组合算法计算交通需求.运用Sioux Falls网络对算法和模型进行了测试,结果表明考虑弹性需求的子网络OD估计模型在可靠性和计算精度上均优于考虑固定需求的子网络OD估计模型,算法能够快速收敛到所需精度,建立的模型可以用来对实际路网进行简化.     

城市道路网络动态OD矩阵预测模型

实时动态OD(Origin Destination)矩阵是动态交通分配系统的重要输入. 运用状态空间模型的有关概念,考虑交叉口进口道观测数据建立了相应的状态空间模型,提出了一步预测卡尔曼滤波方程实现估计和预测. 案例研究表明,将交叉口观测数据纳入测量方程能更好地对OD矩阵做出较精确的估计和预测,且基于仿真的分配矩阵估计方法能更准确地反映OD流量在检测设施上的比例分配.     

基于转弯比例的检测器布设与流量推算唯一性

基于交叉口转弯比例列出路网流量守恒的线性方程组,其系数矩阵表示路网中路段间交通流向的逻辑关系,采用"点线变换"的方法给出这种逻辑关系的有向图表示,从而使得流量守恒方程组的系数矩阵同时也是逻辑关系有向图的邻接矩阵.在对逻辑关系有向图进行分析的基础上,采用"回路组"的概念和Taussky定理,得到了系数矩阵的秩与方程数相等的结论,证明了"封闭环"式检测器布设方案可惟一地确定路网内所有路段的流量,并进一步指出检测器布设方案并不惟一.     

高速公路动态OD矩阵估计

基于广义最小二乘法模型,建立了一种高速路动态OD矩阵估计算法,可通过对路段交通量和行程时间的检测来估计时变的OD矩阵。对任意估计时段的OD流,通过假定各车辆间的时头距均匀分布,且可按相同比例拉伸或压缩,得出了模型中关键的分配矩阵的解析算式。算法是一种递推的估计过程,仅需较少的先验信息。针对一个具有19个OD对的高速公路网,大量仿真实验表明,提出的方法对具有较大流量的OD对估计效果较好。     

基于路段流量相关性的检测器优化布设

根据路网中路段间流量的相关性,提出了一种路网交通检测器优化布设方法.通过路径-路段发生矩阵得到关键路段数量,并分析了网络规模、网络连通性、OD对数量及路径数量对关键路段数的影响;综合考虑路径覆盖率、道路等级、道路长度以及配套设施等因素,建立了最优关键路段组选择的多目标优化模型;提出了通过线性组合由关键路段流量推算其他路...     

交通网络中动态起点-迄点矩阵估计的一种实用算法

基于广义最小二乘模型建立了一种带滑动窗的动态起点-迄点(OD)矩阵估计算法，可通过对路段交通量和行程时问的检测来估计时变的OD数据．对任意估计时段的OD流，通过假定各车辆问的时头距均匀分布且可按相同比例拉伸或压缩，得出模型中关键的分配矩阵的解析算式．该算法是一种递推的估计过程，仅需较少的先验信息而估计过程不会发散．滑动窗的引入可充分利用量测信息，抑制量测噪声．大量仿真实验表明，所提出的方法在估计精度上明显优于Cascetta的递推估计法，但计算量并无显著增加．     

基于中观仿真的路网容量算法研究

中观仿真模型既能分析微观层面的排队长度和延误等详细交通状态指标,又能模拟宏观层面的交通量特性、路径选择行为,特别适用于大中型路网的交通仿真。本文提出了一种借助中观仿真软件通过逐步加载OD量来计算整个路网内所有的道路和交叉口能够容纳车辆数的计算方法,并采用实例分析的方法对提出的路网容量算法的可行性给予论证。     

Characterization of Ordovician carbonate reservoirs, southeastern Saskatchewan, Canada

The discovery of the prolific Ordovician Red River reservoirs in 1995 in southeastern Saskatchewan was the catalyst for extensive exploration activity which resulted in the discovery of more than 15 new Red River pools. The best yields of Red River production to date have been from dolomite reservoirs. Understanding the processes of dolomitization is, therefore, crucial for the prediction of the connectivity, spatial distribution and heterogeneity of dolomite reservoirs.The Red River reservoirs in the Midale area consist of 3～4 thin dolomitized zones, with a total thickness of about 20 m, which occur at the top of the Yeoman Formation. Two types of replacement dolomite were recognized in the Red River reservoir: dolomitized burrow infills and dolomitized host matrix. The spatial distribution of dolomite suggests that burrowing organisms played an important role in facilitating the fluid flow in the backfilled sediments. This resulted in penecontemporaneous dolomitization of burrow infills by normal seawater. The dolomite in the host matrix is interpreted as having occurred at shallow burial by evaporitic seawater during precipitation of Lake Almar anhydrite that immediately overlies the Yeoman Formation. However, the low δ18O values of dolomited burrow infills (-5.9‰～ -7.8‰, PDB) and matrix dolomites (-6.6‰～ -8.1‰, avg. -7.4‰ PDB) compared to the estimated values for the late Ordovician marine dolomite could be attributed to modification and alteration of dolomite at higher temperatures during deeper burial, which could also be responsible for its 87Sr/86Sr ratios (0.7084～0.7088) that are higher than suggested for the late Ordovician seawaters (0.7078～0.7080). The trace amounts of saddle dolomite cement in the Red River carbonates are probably related to "cannibalization" of earlier replacement dolomite during the chemical compaction.     

A computer generator for randomly layered structures

AcomputergeneratorforrandomlylayeredstructuresYUJia shun1,2,HEZhen hua2(1.TheInstituteofGeologicalandNuclearSciences,NewZealand;2.StateKeyLaboratoryofOilandGasReservoirGeologyandExploitation,ChengduUniversityofTechnology,China)Abstract:Analgorithmisintrod…     

海南岛地体及其毗邻陆缘晚中生代—新生代古地磁研究和构造演化

本文叙述了对海南岛及其毗邻大陆边缘白垩纪到第四纪地层岩石进行古地磁研究的全部工作过程。通过分析岩石中剩余磁矢量的磁偏角及磁倾角的变化,提出海南岛白垩纪以来经历的构造演化模式如下:早期伴随顺时针旋转而向南迁移,后期伴随逆时针转动并向北运移。联系该地区及邻区的地质、地球物理资料,对海南岛上述的构造地体运动提出以下认识:北部湾内早期有一拉张作用,主要是该作用使湾内地壳显著伸长减薄,形成北部湾盆地。从而导致了海南岛的早期构造运动,而海南岛后期的构造运动则主要是受南海海底扩张的影响。海南地体运动规律的阐明对于了解北部湾油气盆地的形成演化有重要的理论和实际意义。     

Exciton Seebeck in Molecular Systems

Various applications relevant to the exciton dynamics,such as the organic solar cell,the large-area organic light-emitting diodes and the thermoelectricity,are operating under temperature gradient.The potential abnormal behavior of the exicton dynamics driven by the temperature difference may affect the efficiency and performance of the corresponding devices.In the above situations,the exciton dynamics under temperature difference is mixed with     

Achieving Unusual States of Matter Under High Pressure

The elongation method,originally proposed by Imamura was further developed for many years in our group.As a method towards O(N)with high efficiency and high accuracy for any dimensional systems.This treatment designed for one-dimensional(ID)polymers is now available for three-dimensional(3D)systems,but geometry optimization is now possible only for 1D-systems.As an approach toward post-Hartree-Fock,it was also extended to     

《Chinese Science Bulletin》SUBJECT INDEX TO VOLUME 59(2014)

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An on-line scaling method for improving scalability of a database cluster

The explosive growth of the Internet and database applications has driven database to be more scalable and available, and able to support on-line scaling without interrupting service. To support more client's queries without downtime and degrading the response time, more nodes have to be scaled up while the database is running. This paper presents the overview of scalable and available database that satisfies the above characteristics. And we propose a novel on-line scaling method. Our method improves the existing on-line scaling method for fast response time and higher throughputs. Our proposed method reduces unnecessary network use, i.e. , we decrease the number of data copy by reusing the backup data. Also, our on-line scaling operation can be processed parallel by selecting adequate nodes as new node. Our performance study shows that our method results in significant reduction in data copy time.     

An improved R-tree based on childnode''s probability

R-Tree is a good structure for spatial searching. But in this indexing structure,either the sequence of nodes in the same level or sequence of traveling these nodes when queries are made is random. Since the possibility that the object appears in different MBR which have the same parents node is different, if we make the subnode who has the most possibility be traveled first, the time cost will be decreased in most of the cases. In some case, the possibility of a point belong to a rectangle will shows direct proportion with the size of the rectangle. But this conclusion is based on an assumption that the objects are symmetrically distributing in the area and this assumption is not always coming into existence. Now we found a more direct parameter to scale the possibility and made a little change on the structure of R-tree, to increase the possibility of founding the satisfying answer in the front sub trees. We names this structure probability based arranged R-tree (PBAR-tree).     

Integrating GIS Web services based on mediating architecture

The geographic information service is enabled by the advancements in general Web service technology and the focused efforts of the OGC in defining XML-based Web GIS service. Based on these models, this paper addresses the issue of services chaining,the process of combining or pipelining results from several interoperable GIS Web Services to create a customized solution. This paper presents a mediated chaining architecture in which a specific service takes responsibility for performing the process that describes a service chain. We designed the Spatial Information Process Language (SIPL) for dynamic modeling and describing the service chain, also a prototype of the Spatial Information Process Execution Engine (SIPEE) is implemented for executing processes written in SIPL. Discussion of measures to improve the functionality and performance of such system will be included.     

Tracking data management using topology of moving object database system for moving object constrained trajectory in LBS application

Advances in wireless technologies and positioning technologies and spread of wireless devices, an interest in LBS (Location Based Service) is arising. To provide location based service, tracking data should have been stored in moving object database management system (called MODBMS) with proper policies and managed efficiently. So the methods which acquire the location information at regular time intervals then, store and manage have been studied. In this paper, we suggest tracking data management techniques using topology that is corresponding to the moving path of moving object. In our techniques, we update the MODBMS when moving object arrived at a street intersection or a curved road which is represented as the node in topology and predict the location at past and future with attribute of topology and linear function. In this technique, location data that are corresponding to the node in topology are stored, thus reduce the number of update and amount of data. Also in case predicting the location,because topology are used as well as existing location information, accuracy for prediction is increased than applying linear function or spline function.