驾驶员前向避撞行为特征的降维及多元方差分析

驾驶员在追尾临撞工况下的避撞过程可以分为多个阶段(如制动前、制动后),而在每一阶段中,又存在多个分析角度(如制动快慢、制动力度)及不同的关键时刻与特征值,因此系统描述驾驶员的避撞行为需要多种参数.对多种避撞行为参数进行降维处理,并探究工况紧急程度对每类参数的综合影响.利用同济大学8自由度高仿真驾驶模拟器,研究驾驶员在不同前车减速度(0.30g,0.50g,0.75g)和不同初始车头时距(1.5s,2.5s)下的避撞行为,全面记录了驾驶员危险感知、油门释放和刹车制动等避撞行为参数.利用主成分分析对众多参数进行降维处理,将避撞行为特征划分为感知反应、制动延误、制动力度3个方面,并通过多元方差分析探究车头时距、前车减速度及二者交互项对这3个方面的影响.结果表明,驾驶员感知反应受到车头时距和前车减速度同时影响,制动延误受到车头时距、前车减速度以及二者交互项的影响,制动力度则仅受到前车减速度的影响.在变化趋势上,随着工况紧急程度的增加,驾驶员的感知反应越快,制动延误越短,而制动力度越大.     

基于自然驾驶数据的驾驶员紧急制动行为特征

基于中国自然驾驶数据,建立了紧急工况下制动避撞的驾驶员模型,分析了驾驶员的紧急制动反应时间和紧急制动输入特性的规律特征.结果表明:驾驶员的紧急制动反应时间与驾驶工况的紧急程度相关,以碰撞时刻倒数的临界值0.2s~(-1)作为危险触发阈值,驾驶员的紧急制动反应时间分布为均值0.5s的正态分布;最大制动减速度随驾驶工况紧急程度变化不明显,最大制动减速度梯度随驾驶工况紧急程度的增加而增加.     

基于自然驾驶数据的避撞预警对跟车行为影响

基于60 689 km车辆运行数据提取了1 613个跟车行为片段,并分析了前向避撞预警(FCW)系统对跟车行为2个重要参数——车头时距和反应时间的影响.结果表明,FCW系统对跟车车头时距影响不显著,但显著降低了跟车中的反应时间.白天状态下,反应时间减少了0.13 s;后车逼近前车时,反应时间减少了0.09 s.     

基于纵向避撞时间的预警/制动算法

针对汽车纵向避撞系统的要求,提出了一种基于纵向避撞时间的纵向碰撞预警/避撞(FCW/FCA)算法。通过分析纵向避撞时间与驾驶员反应时间之间的关系,建立了前车不同行驶工况条件下的安全车距模型,并在3种不同行驶工况下,与Berkeley模型进行制动/预警距离的对比。研究结果表明:该算法确定的制动距离与Berkeley模型确定的距离相差很小,并且考虑了前车的运行工况;该算法还能够根据前车行驶工况的不同,确定出合理的预警距离。对比分析结果验证了该算法的有效性和可行性,能够提高车辆行驶的安全性。     

基于纵向避撞时间的预警／制动算法

针对汽车纵向避撞系统的要求,提出了一种基于纵向避撞时间的纵向碰撞预警／避撞（FCW／FCA）算法。通过分析纵向避撞时间与驾驶员反应时间之间的关系,建立了前车不同行驶工况条件下的安全车距模型,并在3种不同行驶工况下,与 Berkeley 模型进行制动／预警距离的对比。研究结果表明：该算法确定的制动距离与 Berkeley 模型确定的距离相差很小,并且考虑了前车的运行工况;该算法还能够根据前车行驶工况的不同,确定出合理的预警距离。对比分析结果验证了该算法的有效性和可行性,能够提高车辆行驶的安全性。     

智能汽车自动紧急控制策略

结合驾驶员在紧急工况下的驾驶行为以及不同避撞方式的避撞效能,对以自动紧急制动系统(Autonomous Emergency Braking,AEB)为代表的控制策略进行分析,发现当前的紧急制动控制策略并不能很好地适应驾驶员行为和满足避撞效能的需要.为此,提出了一种融合制动控制和转向控制的自动紧急控制(Autonomous Emergency Control,AEC)策略.在该策略中驾驶员始终在环,系统通过集成驾驶员模型、车辆模型和道路环境模型信息判断驾驶员的行为是否正确,并将控制输入与驾驶员输入叠加在一起作为车辆的输入对驾驶员不当驾驶行为进行纠正.     

驾驶员制动和转向避撞极限

结合驾驶员避撞行为特征和车辆动力学特性,对驾驶员的制动和转向避撞极限进行了研究,得到了制动避撞和转向避撞的临界TTC(time-to-collision)值,并对比分析了两种避撞方式的适用性以及道路摩擦系数、重叠率等因素的影响.结果表明,转向避撞在高相对速度、低附着系数、低重叠率等工况下相比于制动避撞更有优势.     

汽车主动避撞系统安全报警算法

针对汽车主动避撞系统的安全报警要求,在比较固定车距报警、车头时距报警和驾驶员预估模型报警算法,并结合汽车制动过程运动学分析的基础上,提出了一种新的基于驾驶员模型的安全报警算法。该方法具有贴近驾驶习惯且易于工程实现的特点,该文通过仿真分析验证了其合理性。实车实验结果表明:车速为20km/h时,驾驶员模型算法优于车头时距算法,而两种驾驶员模型算法之间则相差不大;车速增加至30km/h时,驾驶员预估模型算法与车头时距算法结果接近,而该文提出的算法的报警时刻更好。     

基于驾驶倾向性辨识的避撞-报警算法

为了研究适应驾驶员个性需求的避撞-报警算法,将驾驶倾向性作为驾驶员的个性评价指标引入。以实车实验所得驾驶行为数据为基础,提出了一种驾驶倾向性的实时辨识方法。通过驾驶模拟实验,获取了不同驾驶倾向性驾驶员的反应时间和制动减速度数据;并据此提出了一种基于驾驶行为的避撞-报警算法;最后将该算法与典型安全距离算法进行仿真对比。结果表明:本文提出的避撞-报警算法具有较高的可信度,而且体现了各类型驾驶员报警触发时机差异。     

紧急避撞路径规划及其跟踪驾驶员转向模型

针对紧急避撞工况,提出并设计了一种紧急避撞路径规划方法和路径跟踪反馈预瞄驾驶员模型。首先,提出了一种基于Sigmoid曲线与物理约束的避撞路径规划方法,并建立融合最优曲率预瞄与闭环反馈转向修正的驾驶员模型以对所规划路径实现快速和精确跟踪。之后,搭建了CarSim+Simulink离线联合仿真平台,对避撞路径规划和路径跟踪反馈预瞄驾驶员模型的有效性进行了验证。最后,基于自主改装的试验车辆,进行实车试验以验证所提出的路径规划方法及驾驶员模型的可行性与实时性。仿真及实车试验结果均表明,所规划的避撞路径和驾驶员模型可以控制车辆快速、安全地避让障碍物。     

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).     

An Index mechanism for multi-scale view in spatial databases

There are numerous geometric objects stored in the spatial databases. An importance function in a spatial database is that users can browse the geometric objects as a map efficiently. Thus the spatial database should display the geometric objects users concern about swiftly onto the display window. This process includes two operations:retrieve data from database and then draw them onto screen. Accordingly, to improve the efficiency, we should try to reduce time of both retrieving object and displaying them. The former can be achieved with the aid of spatial index such as R-tree, the latter require to simplify the objects. Simplification means that objects are shown with sufficient but not with unnecessary detail which depend on the scale of browse. So the major problem is how to retrieve data at different detail level efficiently. This paper introduces the implementation of a multi-scale index in the spatial database SISP (Spatial Information Shared Platform) which is generalized from R-tree. The difference between the generalization and the R-tree lies on two facets: One is that every node and geometric object in the generalization is assigned with a importance value which denote the importance of them, and every vertex in the objects are assigned with a importance value,too. The importance value can be use to decide which data should be retrieve from disk in a query. The other difference is that geometric objects in the generalization are divided into one or more sub-blocks, and vertexes are total ordered by their importance value. With the help of the generalized R-tree, one can easily retrieve data at different detail levels.Some experiments are performed on real-life data to evaluate the performance of solutions that separately use normal spatial index and multi-scale spatial index. The results show that the solution using multi-scale index in SISP is satisfying.     

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.