工况紧急程度对驾驶员避撞行为的影响

利用同济大学8自由度高仿真驾驶模拟器研究了临撞工况紧急程度对驾驶员避撞行为的影响.通过不同初始车头时距(1.0 s,[1.0 s,1.5 s),[1.5 s,2.5 s])和不同前车减速度(0.30g,0.50g,0.75g)的组合,建立了不同紧急程度的前车减速临撞工况,运用驾驶员感知反应时间、油门释放反应时间、制动转移时间、制动延误、最大刹车踏板压力、最大减速度等指标比较了不同紧急程度下避撞行为的差异.结果表明,①随着工况紧急程度的增加,驾驶员更快地释放油门及达到最大刹车踏板压力,并且施加更大的制动力度;②当初始车头时距为1.5 s左右时,驾驶员感知反应时间约为1.2s,而当初始车头时距增大到2.5 s以上时,感知反应时间变得非常大,甚至达到了3 s;③驾驶员开始释放油门与开始制动间的转移时间不受工况紧急程度影响,保持在0.8 s附近;④在低紧急程度下,驾驶员表现出多阶段刹车行为,使得驾驶员需要更多的时间才能达到最大刹车踏板压力.     

边缘标线影响跟车车距调节行为的结构方程模型

从驾驶员距离感知、速度感知以及碰撞估计等视知觉角度,研究了边缘标线对驾驶员跟车车距调节行为的影响.通过开展路上试验,采集真实车流数据,运用结构方程模型探索了多个因素影响跟车行为的交互因果关系.结果显示:边缘标线铺设角度、前车车型、时间频率以及碰撞时间均能显著增大跟车车头间距;这些因素引起的车头间距增大可能是由于它们会导致跟车减速度绝对值的增大(实际值减小);距离因素可以引起更强烈的危险性感知,并呈现为更显著的车头间距变化.本研究为减少追尾碰撞事故和提高道路交通安全水平提供了一种新的方法.     

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。     

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.     

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.     

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.     

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.     

跟驰行驶状态下的驾驶模拟有效性研究

为验证驾驶模拟技术在跟驰行为研究中的有效性,设计了实车实验与驾驶模拟实验。选取了跟驰距离、跟驰距离标准差、车头时距及驾驶员反应延迟时间作为分析指标,并采用Wilcox检验、生存分析方法分别验证了非时间数据、时间数据的有效性。结果表明跟驰距离、车头时距、驾驶员反应延迟时间具备绝对有效性,两种不同实验环境下跟驰距离标准差随跟驰速度变化趋势相同,具备相对有效性。实车实验中,前车加速度、前后车相对距离、前车加速度变化状态显著影响驾驶员反应延迟时间。有效性分析结果为基于驾驶模拟实验的跟驰行为研究提供前提条件,生存分析结果可用于驾驶员反应延迟时间建模及跟驰模型优化。     

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。     

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.     

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.     

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.